Natural Remedies for Food Cravings

Sugar Crush Detox

This program was designed by Jane who had the same problems with sugar. Throughout her life, she was addicted to sugar and she thought she needs swift intervention before that habit develops into something else. She had an experience that helped her beat sugar addiction with the rest of the world. Her program helps you cut all the roots of majority of the health problems you usually gets. It attacks the weight loss problem at its source which is the biological craving for sugar. This product was specifically created to help people with sugar cravings beat this addiction and lead a healthy life. This program contains a couple of guides available in PDF, MP3 and video formats. The author used simple language in all the formats to ensure that everybody will be able to handle sugar addiction. If you are one of them and you want to get the full support required to quit sugar and lead a heathy life, then Sugar Crush Detox is for you. Read more...

Sugar Crush Detox Summary


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Sucrose Density Gradient Ultracentrifugation

Sucrose density gradient ultracentrifugation has historically been the workhorse of SV40 and polyomavirus DNA replication studies, and it may still have advantages under certain circumstances. For the major SV40 intermediates, the sedimentation coefficients are form I (superhelical SV40 DNA circles), 21S form II (relaxed circles),16S form III (double strand linear DNA),12-14S intermediate Cairns structures (replicating circular DNAs with growing replication bubbles), 25S.9 Alkaline sucrose gradients have been used to separate single stranded DNAs derived from dena-turation of viral replication intermediates. Under alkaline conditions, full SV40 genome-length linear single strand DNA has a sedimentation coefficient of 16S, and single strand SV40 circular DNA has a sedimentation coefficient of 18S. Alkaline denatur-ation of form I DNA gives a very compact form with a high sedimentation coefficient.10 Thus, alkaline sucrose gradients can be used to obtain good separation of form I SV40...

Sucrose Biosynthesis

Sucrose is a major product of photosynthesis. In many plants it is the main form in which carbon is translocated through the phloem of the vascular system from the leaf to other parts of the plant, but sucrose and other sugars may also be isolated and stored in vacuoles in the mesophyll cells. Sucrose is not merely a crucial sugar of vascular plants but is preeminently the sugar of vascular plants 86 . The rate of sucrose synthesis is a function of the carbon fixation rate, chemical partitioning of carbon between starch and sucrose, and the rate of sucrose export from the leaf 87 . Several processes may be involved in regulating the movement of carbon from the chloroplast to the vascular tissue 88 . It is Sucrose formation occurs exclusively in the cytoplasm 89 . Substantial progress has been made in elucidating the biochemical mechanisms that control sucrose formation in leaves 9,10,86,90,91 . The cyto-solic sucrose formation pathway starts with triose-P exported from the...

Sucrose Density Gradients

Compared to nondenaturing gel elec-trophoresis, ultracentrifugation through sucrose density gradients is a more gentle method for isolating labile LHC. Moreover, this method allows the isolation of sufficient material for further analyses and has the advantage that the green band collected from the centrifuge tube can be used immediately without the need to extract it from a gel. Sucrose gradients can be formed either by means of a gradient mixer in combination with a peristaltic pump or, more conveniently, by the freeze-thaw method described by Bassi and Simpson (6). For the latter method, a solution with 0.5 M sucrose, 5 mM Tricine-NaOH (pH 7.8), and 0.1 (wt vol) LM is filled in the centrifuge tubes. The tubes are placed in a -20 C freezer. Three hours before sample application, the tubes are transferred to a refrigerator and kept there until completely thawed. Subsequently, the upper tenth of the gradient solution is carefully removed, which results in gradients with a sucrose...


Sucrose is a disaccharide that is composed of a unit of glucose (acetal form) and a unit of fructose (ketal form) linked through C-1 of glucose and C-2 of fructose, i.e. a 1,2' link. In sucrose, neither glucose nor fructose can exist in open chain form because of the formation of acetal and ketal as shown below. As a result, sucrose is not a reducing sugar, and does now exhibit mutarotation. The specific rotation a D of sucrose is +66 . Hydrolysis of sucrose yields glucose and fructose with specific rotations Md + 52.5 and 92 , respectively, and makes the resulting mixture laevorotatory ( ). This phenomenon of sucrose is called the inversion of sucrose, and the resulting mixture is known as invert sugar, which is the main component of honey, and is sweeter than sucrose itself.

Development Of Enzyme Kinetics

The idea that an enzyme first combines with its substrate was suggested by Wurtz (1880), who found that papain appeared to form an insoluble compound with fibrin prior to hydrolysis of the latter. O'Sullivan and Tompson (1890) reached a similar conclusion, based on their observation that invertase is protected by its substrate sucrose against thermal denaturation. The theoretical basis of enzyme kinetics was consolidated through the work of Adrian Brown (1892, 1902) and Victor Henri (1903), whose work on enzyme-substrate complex formation foreshadowed ( adumbrated , as J. B. S. Haldane (1930) put it) the monumental paper by Leonor Michaelis and Maude Menten (1913). Their famous relationship (Eqn. 1.2) explains the kinetic behavior of literally thousands of enzyme-catalyzed reactions.

Control of Leaf Amino Acid Contents

It is clear that leaf amino acid contents increase with enhanced supply of N during growth (Khamis et al., 1990 Scheible et al., 1997a). Short-term changes have also been demonstrated. Leaf amino acid contents were markedly increased by supplying nitrate or ammonia to excised maize leaves (Foyer et al., 1994a). Short-term effects probably mainly reflect increased substrate supply and or enzyme activation while longer-term changes are also due to modified expression of enzymes such as NR (Scheible et al., 1997a). Interestingly, unlike phosphoenolpyruvate carboxylase (PEPc) and sucrose phosphate synthase (SPS), the NR activation state (Chapters 3-5) does not respond to nitrate (Huber et al., 1992 Ferrario et al., 1996). In the short-term at least, increases in amino acid contents are not general. In maize, enhancement of leaf amino acids on feeding N was almost entirely due to accumulation of Gln (Foyer et al., 1994a). The key response of the Gln pool has also been demonstrated in...

The Carbon Nitrogen Signal Transduction Network Interactions Between Nitrate Sugars and Abscisic Acid

Concentrations of glucose, sucrose or mannose that inhibit wild-type A. thaliana seedling development (Jang et al., 1997). These 'metabolic arrest' screens have yielded mutants that are glucose insensitive (gin) (Areanas-Huertero et al., 2000), glucose oversensitive (glo), carbohydrate insensitive (cai), sucrose insensitive (sis) and the mannose insensitive germination (mig) type (Smeekens and Rook, 1997). Other mutants that have proved useful in elucidating the sugar signaling process are a) reduced sucrose response (rsr) (Martin et al., 1997), b) sucrose uncoupled (sun) mutants, (Dijkwel et al., 1996,1997 Van Oosten et al., 1997) c) low and high -amylase (Iba and hba) (Mita et al., 1997a,b) mutants. The molecular and metabolic analysis of these mutants has revealed the existence of a signal transduction network that co-ordinates information from carbohydrate and N assimilation via the phytohormone, abscisic acid (ABA). ABA regulates plant development, seed dormancy, germination,...

Selecting a suitable preparation

Branded oral liquid preparations that do not contain fructose, glucose, or sucrose are described as 'sugar-free' in the BNF. Preparations containing hydrogenated glucose syrup, mannitol, maltitol, sorbitol, or xylitol are also marked 'sugar-free' since there is evidence that they do not cause dental caries. Patients receiving medicines containing cariogenic sugars should be advised of appropriate dental hygiene measures to prevent caries. Sugar-free preparations should be used whenever possible.

Nitrogen in the Photosynthetic Apparatus

The N-containing components responsible for photosynthesis are (i) the light harvesting Chl-protein complexes (LHC) (ii) the electron transport and photophosphorylation membrane complexes (iii) the enzymes of the RPP pathway and carbohydrate synthesis. The last category notably includes Rubisco. Nitrogen associated with proteins of the photo-synthetic apparatus can be divided into two major pools, representing components associated with the 'light' and 'dark' reactions. The first encompasses thylakoid membrane-bound proteins associated with light harvesting, electron transport and photo-phosphorylation. The second pool consists of soluble proteins, and includes those involved in C02 assimilation, photorespiration, RuBP regeneration, and starch and sucrose synthesis.

On the Possible Role of Inflammation in Obesity and Type 2 Diabetes in Schizophrenia

It is well known that genetic and environmental factors interact to favor weight gain, changes which disrupt metabolism. The body fat stores are normally maintained within a narrow range by energy homeostasis. This process is controlled by the brain regions, such as hypothalamus, that control appetite and energy balance in addition to peripheral signaling systems that monitor energy stores. Glucose, free fatty acids, insulin and leptin are examples of the signaling molecules that activate the hypothalamus thereby controlling the metabolic rate and the desire to eat. Obesity does not simply arise from the passive accumulation of excess body weight but is an active adaptation to the elevation of body fat. Clearly, the genetic background of the individual contributes to the variation in the response to elevated body fat which helps to explain why some individuals are protected against weight gain while the majority is not despite the fact that they live in the same environment and eat...

Spectrofluorometric Determinations of Tetrapyrroles at Room Temperature

In situ emission and excitation spectra were recorded on tissue homogenates or isolated plastids as described in Ref. 9 . At the end of dark incubation, the tissue was blotted dry, and homogenized with mortar and pestle in 5ml of 0.2M Tris-HCl 0.5M sucrose (v v), pH 8.0, under low irradiance green light. The homogenate was squeezed through two layers of cheesecloth, and 0.3 ml of the filtrate was mixed with 0.6 ml of glycerol. The filtrate-glycerol solutions were diluted with Tris-HCl-sucrose buffer glycerol (1 2 v v) to similar Chl concentrations, and subjected to spectrofluorometric analysis at 77 K 13 . Essentially, aliquots were introduced into 2.5-mm diameter glass tubes at room temperature in the darkroom with a Pasteur pipette. This was followed by repeated shaking of the tubes to drive the aliquot to the bottom of the narrow tubes. The tubes were frozen in liquid N2, and subjected to spectrofluorometric emission and excitation analysis at 77 K. Emission spectra between 580 and...

Post Translational Control of Nitrogen Metabolism Enzymes

The overall implications for the regulation of NR activity by 14-3-3 are quite substantial. It has been found that 14-3-3 is involved in regulation of many cellular processes including the cell cycle, metabolism, cell signaling and cell survival (Moorhead et al., 1999). In Arabidopsis cells, 14-3-3 was found to bind to NR, glyceraldehyde-3-phosphate dehy-drogenase, a calcium-dependent protein kinase, sucrose-phosphate synthase and glutamyl-tRNA synthetase. When the cells were starved for sugars, the binding of 14-3-3 was lost and the proteins were proteolytically degraded. These findings and the results of others suggest that 14-3-3 is involved in global regulation of not only N metabolism but also C metabolism in plants (Cotelle et al., 2000). When this concept is combined with the recent finding that polyamines may be involved with activating 14-3-3 for binding to NR (Provan et al., 2000), one begins to recognize 14-3-3 as a link between cell growth and development and the basic...

Protein Kinases and Control of Carbon and Nitrogen Metabolism

Originally, phosphorylation of NR was found to be catalyzed by Or'-dependent protein kinases (McMichael et al., 1995 Douglas et al., 1996). CDPK are a large group of enzymes with different structures and responses to Ca (Harmon et al., 2000). The CDPK are probably the best characterized of all plant protein kinases and are known to be involved in regulation of a number of different plant processes including growth and development. CDPK forms which are more or less specific for NR, sucrose phosphate synthase, 3-hydroxy-3-methylglutaryl-CoA reductase, and sucrose synthase, have been identified, purified and cloned in many cases (Harmon et al., 2000). Thus, a clear regulatory linkage between environmental and developmental signals via cellular Ca2+ concentration and CDPK and the regulation of these enzymes has been established (Fig. 4).

Polyacrylamide Rod Gel Electrophoresis

The solutions should usually be degassed before polymerisation and the gels used immediately after preparation. Prepare the gel mixture as prescribed and pour into suitable glass tubes, stoppered at the bottom, to an equal height in each tube and to about 1 cm from the top, taking care to ensure that no air bubbles are trapped in the tubes. Cover the gel mixture with a layer of water R to exclude air and allow to set. Gel formation usually takes about 30 min and is complete when a sharp interface appears between the gel and the water layer. Remove the water layer. Fill the lower reservoir with the prescribed buffer solution and remove the stoppers from the tubes. Fit the tubes into the holders of the upper reservoir and adjust so that the bottom of the tubes are immersed in the buffer solution in the lower reservoir. Carefully fill the tubes with the prescribed buffer solution. Prepare the test and reference solutions containing the prescribed marker dye and make them dense by...

Strategies For Characterizing Sugar Transporterhomologous Sequences

Replica plated on media with different concentrations (0.1-5 ) of glucose, fructose, man-nose, galactose, and even sucrose (as sucrose can be metabolized by intracellular inver-tase activities but is not taken up by the fc-null strain, it is even possible to select for sucrose transporters). If most of the transformants can grow on one or all of the various hexose media plates, the heterologous gene most likely encodes a sugar transporter. If all the transformants do not grow on hexoses, it is still possible that the transporter is not functional in yeast, such as GLUT1. In this case, several transformants should be mixed and subject to a sublethal mutagenic dose of UV-light and selected for the occurrence of suppressor colonies on the various hexose media (see below Fig. 2.4).

Alterations in Physiological Function Circardian Rhythms Sleep Pain Perception and Appetite

Depressed patients also frequently complain about altered appetite. Both the endocrine systems and neurotransmitters are involved in appetite control. The mono-amines that are often perturbed during depression also have effects on appetite. DA modulates sensory feedback and appetite (198, 199). NE in the hypothalamus increases meal size and stimulates carbohydrate intake through a2-adrenergic receptors (200). This effect shows rapid tolerance. Corticosterone upregulates a2-adrenoreceptors. 5-HT acts through the 5-HT2C receptor to affect eating rate and through the 5-HT1B receptor to affect meal size (198). CRF is a potent anorectic when injected in cerebral ventricles or paraventricular nucleus. Thus, when present, elevated CRF associated with depression may contribute to anorexia.

Handling Increased Seizures

It is also important to ascertain whether new medications or different foods have been introduced. In some children, the diet is so carefully titrated for seizure control that even small amounts of carbohydrate can induce seizures. One child had an increase in seizures when the family changed to a different luncheon meat. Several others experienced increased seizures after using suntan lotion, which may contain so much sor-bitol that some is absorbed through the skin. Hair gels, lotions, and ointments also often contain enough sorbitol to negate ketosis and cause seizures in susceptible patients. Many food additives described as sugar free contain carbohydrate-containing chemicals such as maltodextrin, sorbitol, starch, and fructose. Seven macadamia nuts rather than the three allowed in one child's diet caused a recurrence of seizures.

Nicotinestimulated Dopamine Release From Mesolimbic Neurons

Using the technique of in vitro superfusion, a comparison can be made of the activity and concentration-effect relationship of nicotine-evoked release in several brain areas. Male Sprague Dawley rats are anesthetized, decapitated, and their brains rapidly removed. The striatum and frontal cortex are removed by free-hand dissection with punches of NAc and amygdala taken from coronal slices. In order to prepare synaptosomes, tissue from the respective brain areas is homogenized in ice-cold 0.32 M sucrose (10 w v) at 450 rpm with a glass-Teflon homogenizer for 15 seconds. The homogenate is centrifuged at 1000 x g for 10 min followed by centrifugation of the resulting supernatant at 16,000 x g for 20 min. The resulting pellet is resuspended in Krebs-HEPES buffer and preincubated at 37 C for 10 min whereupon 2 to 4 Ci of 3H DA ( 40 Ci mmol) is added and incubated for an additional 10 min. Fifty to 100 l of the synaptosomal suspension is then transferred onto 25 mm GF-A glass-fiber filters...

Formulations for Dry Powder Inhalers

Staniforth and co-workers managed to reduce the effect of the lactose surface by co-processing the carrier (e.g. co-milling, mixing or surface modification) with up to 2 L-leucine. This process is called corrasion. This approach significantly increased the release of be-clomethasone diproprionate from the carrier 14,53,61 . Another approach to modifying the surface properties of carrier and drug could be the use of super critical fluid crystallization. This technique gives precise control over the particle size, shape and crystallinity of the particles produced 71,72 . Lactose, trehalose and mannitol were also found to be suitable as drug carriers for the pulmonary delivery of proteins. Sucrose was less suitable due to its hy-groscopicity 73 .

D Regulation of Nitrite Reductase Gene Expression

Exogenous nitrate (Faure et al., 1991) which suggests that nitrate is the actual inducing molecule. However, as shown in the first part of this chapter, NR activities not linked to the Nia gene may exist in plants and result in the production of nitrite in nia mutants. Nevertheless, the Nii gene was found as one of the genes that were most induced by nitrate in a survey of nitrate-regulated genes in Arabidopsis (Wang et al., 2000). Ammonium and amides (Gln and Asn) inhibit the expression of NiR in detached leaves and roots while sucrose induces NiR expression (Vincentz et al., 1993 Sivasankar et al., 1997). These are also well-known responses of NR expression and, in fact, NiR is often found to be coregulated with NR in response to N- and C-metabolites or light, at least at the transcriptional level (Fig. 3). There are, however, some differences the NiR mRNA was less induced than that of NR by exogenous sugars in dark-adapted N.plumbaginifolia leaves (Vincentz et al., 1993). In maize...

Nature Of Oxidative Damage

Secondary oxidative damage results from reaction of proteins with products of oxidation of small molecules, including lipids, carbohydrates, and amino acids. The intermediates in this process are reactive carbonyl and dicar-bonyl compounds, such as malondialdehyde, a, -unsaturated and hydroxy-aldehydes, glyoxal, and methylglyoxal (MGO), which react with nucleophilic groups on protein to form lipoxidation (9) and glycoxidation (I0,l l) products (Table 1). Lipoxidation products require oxidation (peroxidation) for their formation from lipids, whereas glycoxidation products are a subclass of advanced glycation end products (AGEs), requiring autoxidation chemistry (oxidation by molecular oxygen) for their formation from reducing sugars or ascorbate. Some AGEs (e.g., pyrraline and imidazolones formed by reaction of 3-deoxy-glucosone 3DG with lysine and arginine residues in protein) do not require oxidation for their formation from reducing sugars. These AGEs are useful indicators of...

Molecular Size Of Native Aspnat

Whether or not the large molecular size of native Asp-NAT was an artifact of the enzyme preparation methods was tested by using different homogenization and solubilization conditions. A buffer that is commonly used in mitochondrial protein purification (Tris-sucrose medium Tris-HCl, 50 mM 1 mM EDTA 0.32 M sucrose 1 mM DTT protease inhibitor cock-tail added according to the quantity of processed tissue pH adjusted to 7.4) was employed to obtain a crude mitochondrial pellet from rat brains. Various detergents were tested to solubilize the pellet deoxycholate (DC) (negatively charged and one of the most commonly used detergents in mitochondrial studies), hexadecyl trimethyl ammonium bromide (positively charged, commonly called CTAB), Triton X-100 (non-ionic), laurylmaltoside (LM) (non-ionic, commonly used in mitochondrial protein reconstitution experiments) and CHAPS. Crude mitochondrial pellets were obtained by homogenizing frozen rat brain tissue in the Tris-sucrose medium using a...

Total Organic Carbon In Water For Pharmaceutical

A variety of acceptable methods is available for determining TOC. Rather than prescribing a given method to be used, this general chapter describes the procedures used to qualify the chosen method and the interpretation of results in limit tests. A standard solution is analysed at suitable intervals, depending on the frequency of measurements the solution is prepared with a substance that is expected to be easily oxidisable (for example, sucrose) at a concentration adjusted to give an instrument response corresponding to the TOC limit to be measured. The suitability of the system is determined by analysis of a solution prepared with a substance expected to be oxidisable with difficulty (for example, 1,4-benzoquinone). Glassware preparation. Use glassware that has been scrupulously cleaned by a method that will remove organic matter. Use TOC water for the final rinse of glassware. Standard solution. Dissolve sucrose R, dried at 105 C for 3 h in TOC water to obtain a solution containing...

Ketogenic Diet Snacks

A free snack may be given once daily if needed to help curtail hunger. Snacks include three small black (ripe) olives, one English walnut, two butternuts, one Brazil nut, two macadamia nuts, two pecan halves, or three filberts. These foods are high in fat and low in carbohydrate. It may become necessary to calculate a snack, i.e., 50-100 cal, into the diet if the child is always hungry at a given time each day. The snack must be ketogenically balanced, using the same ratio as the diet prescription. Typical ketogenic snacks include whipped cream with fruit or sugar-free gelatin and frozen eggnog.

Impact of Psychoactive Drugs

Examination of drug effects on Pavlovian conditioning has employed only a limited number of target responses with the conditioned eyeblink response being the most widely used. Eyeblink conditioning is carried out by presenting a tone or light CS just prior to delivery of an airpuff US to the cornea or a shock US to the cheek. These USs elicit a spectrum of responses but the eyeblink UR elicited by the airpuff or shock is the identified target response. Various components of the eyeblink can be measured including external eyelid closure in humans, rabbits, and rodents retraction of the eyeball and the associated passive extension of the nictitating membrane in the rabbit and the electrical signal generated by the muscles involved in the eyeblink. Three other target responses have also been employed. Acquisition of the conditioned skin conductance CR in humans is accomplished by the pairing of a tone CS and an aversive white noise US. Appetitive conditioning of the rabbit's jaw movement...

Incorporating Creativity into Ketogenic Diet Meals

Several ketogenic meals should be calculated for each child initially to provide variety. A protein-rich food paired with a fruit or vegetable provides the foundation of the ketogenic meal. Cream, butter, margarine, vegetable oils, and mayonnaise complete the requirement for fat. For variations of the ketogenic meals, families can incorporate combinations of protein-rich foods such as bacon and eggs or small amounts of low-carbohydrate food items such as avocado, nuts, sugar-free gelatin, and cheese.

Biological Properties Medicinal Applications Of Laminaria

Dietary use of Laminaria dates back to the days of the First World War when it was used in raw form as a feed supplement for horses. It is used as a food, principally in Asian countries, where it is valued for its flavor, mineral content, and health giving benefits. The most important components with a medicinal point of view are Laminaria's polysaccharides. It contains alginates, laminarin, laminine, and fucoidan as well as a number of other polysaccharides and simple sugars.

Supplementing The Ketogenic Diet Vitamins Minerals And Essential Fatty Acids

Vitamin and mineral supplementation is essential for all ketogenic diet candidates in efforts to provide optimal nutrition and to prevent micronutrient deficiencies. Supplements should be in sugar-free form. The Recommended Dietary Intakes published by the Food and Nutrition Board (2002) provide a guide for daily level of intakes of vitamins, minerals, and trace minerals based on age (5). A typical supplementation profile for a child on the oral ketogenic diet includes a multivitamin with minerals supplement plus a calcium and a phosphorus and potassium supplement. A multivitamin-with-min-erals supplement and individual mineral supplements should be given to the child at separate times throughout the day for optimal absorption.

Shortterm In Vitro Effects Of Pi Deprivation

Optimal photosynthesis of isolated chloroplasts requires a finely balanced concentration of Pi in the cytosol 42 . This optimal concentration may be maintained by transport to and from the vacuole and by metabolic processes causing changes in the rate of sucrose synthesis 18,42 . Over the short term, low Pi in the cytosol decreases the export of triose-P from the chloroplast, which leads to the inhibition of sucrose synthesis in the cytosol 9,34,43,44 .

Organic Anion Transport

Betz and Goldstein (10) demonstrated that -aminohippuric acid (PAH) uptake by isolated retinal capillaries is slightly greater than that of the extracellular marker sucrose, and is inhibited by fluorescein and penicillin. Organic anion transporter polypeptide does not transport PAH, though organic anion transporters (OATs Slc22a) prefer PAH as a substrate. Therefore, in addition to Oatp, OAT is also involved in the organic anion transport at the inner BRB. Nevertheless, further investigations regarding organic anion transporters at the inner BRB are needed, since their expression and function at the inner BRB remain largely unknown, including the function of Oatp1c1 and the expression of OAT.

Phosphate Translocators

The synthesis of sucrose from triose-P is believed to make the major contribution to the recycling of Pi (Figure 7.1). Sucrose synthesis releases Pi due to the action of a phosphatase and rapid export of sucrose from the cytoplasm will make Pi available as fast as the plant can synthesize triose-P little or none will be available for storage within the stroma as starch. If the demand for sucrose by growing sinks is less however, excess triose-P would be stored as starch and the rate of photosynthesis possibly diminished. Gerhardt et al. 54 observed asymmetric distribution of DHAP and 3-PGA across the chloroplast envelope in spinach leaves and suggested that the Pi translocator may be kinetically limiting in vivo. The reduction of TPT activity in vivo by antisense repression of chloroplast TPT resembles the situation of chloroplasts performing photosynthesis under Pi limitation 39 . To examine more specifically the role of the Pi translocator in assimilate partitioning in...

Starch Biosynthesis

A specific effect of Pi ions is exerted through the control of the distribution of newly fixed carbon between starch synthesis in the chloroplasts and the transfer of triose-P to the cytoplasm followed by synthesis of sucrose 48 . In isolated chloroplasts, low Pi slows photosynthesis and shifts the flow of carbon toward starch 48 . In some leaves mannose feeding produces the same effect by sequestering Pi as an abnormal hexokinase reaction becomes linked to oxidative phosphorylation 64,76 . Low levels of phosphate and high levels of sugars in phosphate-limited plants will lead to increased levels of ADP-glucose pyrophosphorylase transcript, which could contribute to increase in starch accumulation 77 .

Longterm In Vivo Effects Of Pi Deprivation

The view that Pi is an important regulator of the rate of photosynthesis and of the partitioning of triose phosphates between starch biosynthesis and sucrose biosynthesis is to a large extent based on research carried out with in in vitro systems involving the use of isolated chloroplasts, enzyme systems, protoplasts, and with detached leaves or leaf disks fed with man-nose to induce Pi deprivation. All of these studies point to the fact that the concentration of Pi in the cytosol versus that in the chloroplast is what Studies of long-term limitations of Pi on photosynthesis and carbon partitioning based on in vivo experiments using low phosphate (low P) plants have shown that the inhibition of photosynthesis was to a large extent due to limitations imposed on the PCR cycle in terms of RuBP regeneration 7,19,123-134 while the changes in carbon partitioning could be influenced in part by the relative capacities of the enzymes involved in starch and sucrose metabolism 134 . Recently, it...

Intracellular Pi Compartmentation

Methods have been developed for the assay of subcellular metabolite levels using leaf protoplasts. The protoplasts were ruptured by passage through a nylon net or a capillary tube. This was followed by immediate filtration of the particles (formed after rupture of the protoplasts) through a layer of silicone oil 72,185,186 or a combination of membrane filters 187 . Unfortunately, it has proved experimentally difficult to accurately determine chloroplastic and cytosolic Pi concentrations. Part of the problem relates to the presence, in the leaf cell vacuole, of a comparatively large amount of Pi 188 , which masks the much smaller amount present in the cyto-sol. Furthermore, protoplasts are of limited value since their carbohydrate metabolism is almost certainly affected by the lack of sucrose export to the phloem.

Carbon Partitioning and Export

The partitioning of photosynthate between starch and sucrose appears to be strictly regulated at both genetic and biochemical levels 5 . There is a distinct interspecific variation in the ratio of starch sucrose synthesized in leaves of different species 92,118 . This genetically determined predisposition allows classification of plants as high (e.g., soybean), intermediate (e.g., spinach), or low (e.g., barley) starch formers. P deficiency increased the starch synthesis relative to sucrose in soybean, spinach, and barley leaves although the accompanying limitation on photosyn-thetic capacity varied considerably between the species 18 . Usuda and Shimogawara 204 measured carbon fixation, carbon export, and carbon partitioning in maize seedlings in the early morning and at noon in P-adequate and P-deficient leaves (Table 7.6). P deficiency caused marked reductions in carbon fixation and carbon export and changed the partitioning of fixed carbon between starch and sucrose. Long-term P...

Glutamate Dehydrogenase

Invariably causes an increase in measurable GDH activity (Srivastava and Singh, 1987 Ireland and Lea, 1999), and similar effects have also been observed following carbohydrate starvation (Robinson et al., 1992 Athwal et al., 1997). GDH activity has also been shown to increase following the onset of senescence (Srivastava and Singh, 1987 Bechtold et al., 1998), a time when carbohydrate concentrations fall and ammonia increases. In grapevine, Loulakakis and Roubelakis-Angelakis (1992) demonstrated that the ammonia-induced increase in GDH activity was due to the synthesis of the 43kDa subunit. In A. thaliana, the expression of both GDH1 and GDH2 was stimulated by darkening and ammonia, and the synthesis of GDH1 mRNA was repressed by light or sucrose (Melo-Oliveria et al., 1996). Turano et al. (1997) carried out a more detailed study on GDH gene expression in A. thaliana, in which enzyme activity, subunit composition and mRNA accumulation were determined following changes of N source in...

Recovery Of Plants From Phosphate Deficiency

Rao and Terry 134 monitored changes in photosynthesis, carbon partitioning, and plant growth in sugar beet by increasing the Pi supply to low-P plants. Within 72 h of increased Pi supply, low-P plants developed very high leaf blade Pi concentrations (up to sixfold of control levels). This dramatic increase in leaf blade Pi concentration was associated with a rapid increase in leaf sugar phosphates (especially RuBP), ATP, and total adenylates, which led to the rapid recovery (within 4h) of the rate of photosynthesis. Increased Pi supply to low-P plants also decreased the amount of carbon accumulation in leaf blades in the form of starch, sucrose, and glucose, but this decrease was found to be slower than the recovery of photosynthesis. These results suggest that the effects of low P on photosynthetic machinery and the partitioning of fixed carbon are reversible. The rapid recovery of photosynthesis may be attributed to the lack of marked effects of low P on the structure and function...

Acclimation And Adaptation Of Plants To phosphate Deficiency

The pioneering work of Walker and colleagues demonstrated that the isolated chloroplast requires a continuous supply of Pi in order to sustain photosynthesis. The Pi imported into the chloroplasts from the cytosol in exchange for triose-P and the Pi released from metabolic intermediates in the chloroplast stroma is available for photophosphorylation, which generates ATP for utilization in the PCR cycle. Thus, an adequate supply and internal cycling of Pi in the cell are essential for the regeneration of RuBP in the PCR cycle, which is a major limitation to maintain the rate of photosynthesis under Pi deprivation. The view that Pi supply is maintained in vivo by sucrose synthesis within the cytosol has been strengthened by substantial experimental evidence. The subcellular compartmentation of reactions and the resulting conservation of stromal and cytosolic Pi play an important role in the regulation of photosynthesis and carbon partitioning in leaves. Further, the rapid recovery of...

Alternative Substrates

While isozymes are apt to have different energies of activation, even under the same assay conditions, an enzyme acting on different substrates can in some circumstances exhibit the same energy of activa-tion10,11. Yeast sucrase, for example, has an energy of activation of 46 kJ-mol 1 (or 11.0 kcal-mol-1) for both sucrose and raffinose11-13. The rate-determining step in the enzyme-catalyzed reaction may differ with alternative substrates, and this may be reflected in the observed energy of activation. Likewise, if the rate-determining step changes with protein modification, assay conditions, or through site-directed mutagenesis, Arrhenius plots should reflect those changes. An example is the myosin ATPase which exhibits biphasicity in the Arrhenius plot with ITP as a substrate, but a typical linear Arrhenius plot with ATP as the substrate. Levy, Sharon, and Kosh-land14 suggested that this may be the result of the 6-amino group on ATP interacting with some functional moiety...

Michaelismenten Treatment

Late in the 19th century, the English chemist Adrian Brown first observed that the rate1 of sucrose fermentation in yeast was independent of sucrose concentration (Brown, 1892). Brown (1902) later suggested, however, that this apparent independence could be explained by assuming that invertase, the key enzyme for sucrose hydrolysis in the yeast, formed a binary complex with its substrate and that, under the conditions observed by Brown, the sucrose concentration was high enough to be saturating. Despite a similar contentious claim by French chemist Victor Henri (1903), Brown's concept2 was the first to provide a clear physical chemical

Chelates and complexes

Sucralfate may act by protecting the mucosa from acid-pepsin attack in gastric and duodenal ulcers. It is a complex of aluminium hydroxide and sulphated sucrose but has minimal antacid properties. It should be used with caution in patients under intensive care (important reports of bezoar formation, see Bezoar Formation below)

Pharmacological Interventions

Rimonabant is a cannabinoid antagonist that acts to control appetite and can lead to weight reduction. The proposed indication was to be weight management in people with a BMI of 30, or with a BMI of 27 and at least one comorbid medical condition. However, the manufacturer withdrew its application to sell this agent in the USA amid concerns that it may increase suicidal thinking and depression 73 . There are no published reports of its use in patients with schizophrenia receiving antipsychotics.

Evidence of Increased Mitochondrial Permeability MP

When isolated mitochondria are re-suspended in a buffer solution, the increase in MP causes colloidosmotic swelling of the mitochondria. The large extent of the swelling leads to changes in optical density at 540nm. MP can also be measured with the use of radioactive markers (sucrose, Ca2+). Patch-clamp techniques recognize the so-called mitochondrial mega-channels, which are possibly similar to the pores of mitochondrial transitional permeability.

Antiapoptotic Properties Of Antioxidants

These results suggest that the intracellular level of GSH may play a critical role in the regulation of cytokine-induced generation of ceramide, leading to apoptosis of brain cells (Singh et al., 1998). 2-Deoxy-D-ribose, the most reducing sugar, has been shown to induce apoptosis in normal human fibroblasts by a mechanism involving glutathione metabolism. 2-Deoxy-D-ribose was found to provoke disruption of the actin filament network and detachment from the substratum, while at the same time increasing the expression of several integrins and cell adhesion molecules. N-Acetyl-L-cysteine fully blocked 2-deoxy-D-ribose-induced apoptosis by preventing GSH depletion, while it also inhibited actin filament network disruption and mitochondrial depolarization (Kletsas et al., 1998).

Permeation Is Enhanced By Membrane Proteins

Many molecules do not diffuse through lipid bilayers (see Figure 5.6 and notice that sucrose and ions do not permeate). One of the most important functions of accessory molecules in the membrane is regulation of transport of molecules that do not pass freely through the lipid bilayer. Several classes of accessory molecules are engaged in membrane transport, as described in the sections that follow.

Postseizure Care and Animal Behavior

Different approaches are currently being used to care for rats with pilocarpine-induced SE. Each approach is an attempt to increase the survival rate of the rats. Obenaus et al.85 administer lactated Ringer's (2 ml d, s.c.) and feed the rat moist rat chow for up to 1 week after SE. Other investigators offer each rat sliced apples or peaches (personal observation), oral sports drink mixed with sucrose,86 or an oral mixture of powdered milk and sucrose for several days after SE.78 These procedures are labor intensive and the individual investigator has to find a balance between the amount of postseizure care and the improvement in the survival rate of pilocarpine-treated rats. Similar to kainic acid-treated rats, pilocarpine-treated rats exhibit an increase in aggressive behavior after recovery from SE.

Mutants Lacking Hydroxypyruvate Reductase

Clearly this enzyme has a low control coefficient in air, although it is likely to increase under more photorespiratory conditions. The most notable effects of the mutation were decreased conversion of Ser added to the leaf to sucrose, an increased accumulation of l4C in Ser following photosynthesis in air containing and decreased synthesis of glycerate 3-P. After 5 min in air containing MC02, following 60 min in 1 O, and 340 ppm C02, l4C in Ser was 30 of the total assimilated compared to 7.7 in the wild-type barley. This difference is less than would be expected if the flux of C into glycolate were equal to net photosynthesis. Because some 25 of the added l4C Ser was still converted to sucrose by leaves of the mutant, it is concluded that alternative enzymes are responsible for reduction of some hydroxypyruvate. There is an NADPH-dependent hydroxypyruvate reductase (Givan and Kleczkowski, 1992) that probably converts glyoxylate to glycolate, perhaps counteracting...

Other Pharmacological Effects

Further pharmacological effects of deltorphins have been demonstrated under various experimental conditions. D-Ala-deltorphin improves memory consolidation in a passive avoidance apparatus in mice this effect is abolished by naltrindole 75 . D-Ala-deltorphin-II caused hypothermia in cold-adapted animals 76 . In contrast to mu opiate agonists, D-Ala-deltorphin-I, at low doses, stimulates respiratory activity in fetal lambs, and this effect is blocked by simultaneous administration of naltrindole 77 . The peptide D-Ala-deltorphin-II inhibits diarrhea induced by castor oil and colonic bead expulsion, but it leaves the rate of transit through the small intestine unchanged 78,79 . By the SC route D-Ala-deltorphin-I inhibits acidified alcohol-induced gastric mucosal lesions 80 , but by the ICV route, it fails to affect gastric secretion 81 . The peptide is involved also in the control of ingestive behavior. It stimulates the intake of food 82 and of sucrose 83 ,

Advanced Glycation End Products

Advanced glycation end products (AGEs) are a heterogeneous group of irreversible adducts resulting from nonenzymatic glycation and oxidation of proteins, lipids, and nucleic acids. Glucose and other reducing sugars react in a nonenzymatic reaction (Maillard reaction) with the N-terminal residues and or e-amino groups of proteins initially forming a Schiff base. Rearrangement of this aldimine leads after a short time to the formation of more stable but still reversible Amadori adducts. The open chain of the resulting ketoamin can react with other amino groups. Oxidation, dehydration, and condensation reactions finally lead to the production of irreversible crosslinks, which are proteinase resistant.

Multicolumn Chromatography Development of Route

The use of continuous counter-current chromatography was first proposed and demonstrated in 1940 and subsequently introduced as a production tool in the petrochemical and sugar industries as Simulated Moving Bed (SMB) chromatography in the late 1950s. As SMB is a continuous process, the production rate is generally very high, with the system requiring minimal supervision and intervention once the unit has achieved steady-state operating conditions. This technique is now more commonly referred to as Multi Column Chromatography (MCC), and the two largest-volume applications are the separation of the xylene isomers ( 1000 000 t y per system) and the purification ofbeet molasses to give fructose and sucrose ( 150000t y per system) 21 .

Principles and Role in Psychopharmacology

Liquid diet mixtures with or without alcohol provide 1,000 kcal L. The liquid diet method for administration of alcohol involves pair-feeding of control and treated animals with identical amounts ofthe same diet to control exposure to putative nutritional deficits. Control rats are pair-fed with an isocaloric liquid diet containing a carbohydrate such as sucrose or dextrin maltose as a caloric substitute for ethanol. It is highly recommend to have a second control group with continuous access to standard laboratory diet and water. If the alcohol-treated group differs from both control groups and the control groups do not differ from each other, effects seen will not be due to limitations in dietary intake or the liquid diet but rather to alcohol per se (Driscoll et al. 1990). To prevent decrease in diet intake and weight loss, ethanol (96.5 , v v) should be gradually presented in progressively increasing concentrations during a habitu-ation phase. After almost a week's feeding with...

Preparation of Synaptosomes

Synaptosomes were isolated for the first time from guinea pig forebrains by differential and sucrose density gradient centrifugation (Gray and Whittaker, 1962, Whittaker et a ., 1964). Small changes have been introduced into the original protocol in order to increase purity and responsiveness of the synaptosomal fractions (Nicholls, 1978, 1989). For most purposes, synaptosomes can be simply prepared by differential centrifugation, but it should be kept in mind that this fraction (P2-fraction) is heavily contaminated with mitochondria and myelin. For these reasons, further purification by Ficoll gradient centrifugation is recommended. The protocol described below is based on the procedure of Nicholls and coworkers (see e.g., Nicholls, 1978 McMahon eta ., 1992).

Products of Glycolysis in the Light

Furthermore, PEPc is activated by Gly, which increases its affinity for the activator glucose-6-phosphate and decreases sensitivity to the inhibitor, malate. This may be important, especially in photorespiratory conditions (Tovar-Mendez et al., 1998, 2000). The importance of PEPc in respiration was also shown in potato plants overexpressing the enzyme. PEPc overexpression led to enhanced respiration both in the dark and the light, and to accumulation of malate and increased sucrose biosynthesis (H usler et al., 1999). Whereas Glu is inhibitory to both PK and PEPc, Asp inhibits PEPc and activates PK (Moraes and Plaxton, 2000). Photorespiratory ammonia may exert

Further purification by Ficoll gradient centrifugation

Prepare Ficoll step-gradients in two centrifuge tubes by adding sequentially e.g., 4 ml of 12 , 1 ml of 9 and 4 ml of the 6 Ficoll solutions in 0.32 M sucrose (solutions 3). Leave enough room in the tube (3-4 ml) to load the resuspended synaptosomal pellet (P2). We use a Beckman SW41 rotor but other swing-out rotors with similar geometries are also acceptable.

Isolation and characterization of calvin cycle multienzyme complexes

Served that some enzymes of photosynthetic carbon reduction cycle remain associated even after isolation 24,25 . Muller 26 had suggested in 1972 that some of the CO2 fixing enzymes might be associated in the form of a labile complex. However, with the advances in protein purification techniques, several publications on purified enzymes accumulated and these initial observations and hypotheses were pushed into oblivion. Regardless of the ever increasing knowledge about several purified enzymes of Calvin-Benson cycle, the answer to the key question in plant biology What controls rates of photosynthesis '' remained elusive 27 . Considering the discrepancies in the in vitro and in vivo conditions, several laboratories sought to revive the investigations in multienzyme organization among stromal enzymes of chloroplasts. Since the interactions among the soluble enzymes can be generally weak and transient, the study of their supramolecular organization is often tricky and at times...

Photosynthesis and Mitochondrial Electron Transport

Mitochondrial respiration is essential for optimal photosynthesis. Low concentrations of oligomycin, which strongly inhibit mitochondrial oxidative phosphorylation but do not affect chloroplast photophosphorylation, caused an inhibition of photosynthesis by 30-40 in barley leaf protoplasts, but not in isolated chloroplasts (Kromer et al., 1988). Oligomycin caused a decrease in the ATP ADP ratio and an increase in the content ofglucose-6-phosphate and F6P. Subcellular analysis ofprotoplasts revealed that oligomycin caused a larger decrease in the cytosolic ATP ADP ratio than in the stromal ratio. Moreover, the increase in hexose monophosphates was restricted to the cytosol, whereas the stromal hexose monophosphates decreased upon the addition of oligomycin (Kromer et al., 1993). Oligomycin caused an increase in the TP PGA ratio (Kromer and Heldt, 1991b). Thus, during photosynthesis, mitochondrial oxidative phosphorylation contributes to the ATP supply of the cell and prevents...

The Role of Mitochondria in Photosynthetic Induction

Following a period of darkness, photosynthesis does not begin immediately but takes minutes to hours to attain the rate set by the prevailing conditions. This effect is known as induction, and is associated with the activation of enzymes and readjustment of metabolite pools involved in the RPP pathway and sucrose synthesis (Gardestrom, 1993). During this

Mitochondrial Respiration and Photoinhibition

Mitochondrial respiration optimizes chloroplast function, particularly in the prevention of overener-gization and overreduction ofchloroplasts. This may occur in four ways (i) integration and maintenance of metabolite movement, facilitating the export of excess energy and or reductant from the chloroplasts, (ii) Promotion of sucrose biosynthesis (a carbon sink) and feed-forward enhancement of photosyn-thetic rate, (iii) Minimization of the photosynthetic induction period, and (iv) Maintenance of enzyme activation in the chloroplast. These effects can be due to either direct intervention or through feedback or feed-forward regulation. Such interactions involve extensive metabolite traffic between subcellular compartments, including peroxisomes as well as chloroplasts, cytosol, and mitochondria.

Concluding Remarks

Nitrogen itself is an important signal for modulating C metabolism and subsequently the functioning of cellular organelles (Champigny, 1995 Stitt, 1999 Lewis et al., 2000). The effects of nitrate or ammonia on leaf tissue are phenomenonal, particularly in the modulation of gene expression and the diversion of C skeletons from carbohydrate into amino acid metabolism. Supply of nitrate or ammonia to N-starved leaves upregulates the biosynthesis not only of nitrate reductase, but also PEPc and carbonic anhydrase. At the same time nitrate down-regulates the activity of sucrose phosphate synthase. Reciprocal changes in the activity of PEPc and sucrose phosphate synthase are linked to the increase in the phos-phorylation status of these two enzymes (Champigny, 1995 Toroser and Huber, 2000).

Metabolic Pathways The Roads to Energy

The smaller end products of digestion also make up the metabolic stores, which include a pool of simple sugars, like glucose fatty acids, which come from the breakdown of lipids or fats and amino acids, produced by the breakdown of proteins. All the The carbohydrates, proteins, and lipids in foods are mostly in complex forms. For example, the carbohydrates are present as disaccharides, such as sucrose, or polysaccharides, such as starch. The first step in digestion is the breakdown of the larger, insoluble molecules into smaller, soluble forms that can be transported across the intestinal wall into the blood for delivery to the tissues.

Appetite Regulation Episodic and Tonic Signals

To understand the role of 5-HT in appetite control, it is essential to understand the nature of appetite regulation and the episodic and tonic signals critical to appetite expression. Episodic signals are a crucial in the meal-by-meal regulation of energy intake and are critical to both the appetite fluctuations and patterns of eating behavior we undertake throughout the day (Halford and Blundell 2000). They are generated by the anticipation and ingestion of food and the digestion, absorption, and initial metabolism of nutrients. In contrasts, tonic inhibitory signals are generated by the storage and general metabolism of energy. Whilst episodic and tonic factors are composed of distinct processes, they both act to inhibit food intake via common hypothalamic circuitry (Halford and Blundell 2000). Serotonin plays an important part in the episodic regulation of appetite linking peripheral generated signals to hypothalamic circuitry essential to long-term energy balance.

Linking Between 5HT and Control of Both Food Intake and of Feeding Behavior

Significant advances in the identification and classification of numerous novel 5-HT receptors occurred (Hoyer and Martin 1997). The main focus for appetite research became the 5-HT1 and 5-HT2 receptor families, and eventually, postsynaptic 5-HT1B and the 5-HT2C receptors were established to be those criticial to satiety (see later and Chap. 4) (Blundell and Halford 1998). 5-HT neurons involved in appetite control project up towards the hypothalamic region, an area rich in orexigenic and anorexigenic systems critical in energy regulation. These systems include the hypo-thalamic anorexigenic neuropeptide melanocortin (MC) system.

Leaf Photosynthesis Acclimation To Elevated [co2

Of sucrose metabolism enzymes, including sucrose phosphate synthase and acid invertase 58,59 . Reduced expression of the Rubisco genes and differential response of other photosynthetic genes, including chlorophyll binding protein Cab and Rubisco activase Rca, have been also reported for a variety of C3 crops grown at elevated CO2 28,58,6066 . The expression of several genes coding for key C3 photosynthetic enzymes has been shown to be influenced by the levels of soluble sugars 67-69 . Particularly for Rubisco, transcription of the small subunit (rbcS), and to a lesser extent the large subunit (rbcL), has been shown to be strongly repressed by sucrose and glucose 60,70 . The buildup in carbohydrates at elevated growth CO2 , however, may signal the repression, but does not directly inhibit the expression, of Rubisco and other proteins that are required for photosynthesis 52,53,71-73 . Although the signal transduction pathway for regulation of the sugar-sensing genes may involve...

Cellulose acetate phthalate

A modified method based on the work of Kitajima etal. (1971) to prepare enteric coated microspheres using cellulose acetate phthalate was developed by Maharaj etal. (1984). Several pharmaceuticals such as loperamide and trifluoperazine-isopropamide and also rabies antigen were encapsulated by suspending the active compound, diluted with sucrose containing cornstarch if necessary, in paraffin oil. Then a solution of the polymer in acetone-ethanol 95 was added. Shortly thereafter the chloroform was added to harden the microspheres which were then decanted, washed and collected. The size of the microspheres increased as the time for formation increased from 0.5 min to lOmin and the encapsulation method had no appreciable effect on the activity of the biologically active substance.

Classification Of Surfactants

This subgroup of nonionic surfactants has polyhydroxyl (polyol) polar groups and includes the sorbitan esters, alkyl glucosides, sucrose esters, and polyglycerol esters. Widely used examples of this group are the fatty acid esters of sorbitan and the corresponding ethoxylated sorbitans or polysorbates (Tweens). The commercial sorbitan esters (marketed under the trade name Spans) are mixtures of the partial esters of sorbitol

Classification General classification

Di-, tri- and tetrasaccharides These carbohydrates are dimers, trimers and tetramers of monosaccharides, and are formed from two, three or four monosaccharide molecules, with the elimination of one, two or three molecules of water. For example, sucrose is a disaccharide composed of two monosaccharides, glucose and fructose.

The Search For Genetic Determinants Of Aging

The ongoing search for genetic determinants of aging and longevity has been one of the main features of recent biomedical research. This search starts from different theories proposed to explain why aging occurs. Among them, the ''network theory'' and '' remodeling theory'' of aging received particular attention in recent years 2 . The first theory suggests that aging is indirectly controlled by a network of cellular and molecular defense mechanisms that protect cells from a variety of internal and external stressors potentially dangerous for the maintenance of cell functional integrity 3 . Such stressors can be extremely diverse and include different physical (UV and gamma radiation, heat), chemical (components of the body and products of metabolism, e.g., oxygen free radicals and reducing sugars), and biological agents (viruses). The mechanisms that may play a critical role in the aging process at the cellular level can be summarized as follows

Enzymes of the Calvin Cycle

The ATP and NADPH generated by the photosyn-thetic light reactions are used in green plants to drive CO2 fixation into sugars by a chain of reactions known as the photosynthetic carbon reduction cycle (Calvin cycle). The ribulose 1,5-bisphosphate carbox-ylase oxygenase performs the role of initial acceptor of atmospheric carbon dioxide to give two molecules of three carbon compounds that are metabolized by a subsequent ten reactions resulting in both regeneration of the acceptor molecule and translocation of three molecules of trioses to the cytosol for synthesis of sucrose and starch. For detailed information on the various enzymes of the Calvin cycle including Rubisco, readers are advised to refer to some excellent reviews by Raines et al. 24 on all enzymes in general and by Hartman and coworkers 25,26 for Rubisco in particular.

The Distribution of G Proteins in the Plasma Membrane

Measurements of the absolute levels of expression of GPCRs and G proteins invariably conclude that the G proteins are in considerable molar excess with regard to any specific GPCR 17-18 . This poses certain problems in pharmacology, because models of GPCR-G protein function that are both robust and predictive in nature derive from the premise that GPCR G protein . Furthermore, the distribution of GPCRs and G proteins in the plasma membrane is non-random. Although the literature on the distribution of GPCRs is both large and complex, the equivalent literature for G proteins is relatively straightforward. Rather than being equally and randomly distributed, a substantial proportion of cellular G protein is targeted to, and located in, lipid 'rafts'. These are specialized structures enriched in cholesterol and sphingolipids that are both relatively resistant to dissolution by treatment with detergents and have low buoyant density 19 . This has allowed enrichment of such fractions on...

Regulation of C3 Photosynthesis

Electron transport, and Rubisco is extremely important. Conservation of phosphate is of great importance because it requires that a change in the level of any phosphorylated intermediate be compensated by an equal and opposite charge (in terms of phosphate elsewhere in the cycle). Therefore, changes in the activity of any of the PCR enzymes can affect both the substrate concentration and activities of other enzymes in the chloroplast regardless of whether they are adjacent on a metabolic scheme or are connected by the classical mechanism. Studies on the effect of various chloroplastic metabolites on Rubisco activity under suboptimal CO2 concentrations have shown that both phosphoglycolate and inorganic phosphate activate the enzyme 31,32 . The effectors elicit their response by stabilizing reversibly the binding of a CO2 and Me2+ in much the same manner that CABP does, but unlike CABP these effectors readily dissociate on dilution, yielding an activated ternary complex. The activation...

Classes of Mucoadhesive Polymers

The term polyacrylates includes synthetic, high molecular weight polymers of acrylic acid (polyacrylic acid or PAA) (Fig. 6.3a) that are also known as Car-bomers. They are either linear or (weakly) crosslinked (either by allyl sucrose (Carbomers) or divinyl glycol (Polycarbophils)) polymers that are broadly applied in pharmaceutical and cosmetic industry (mostly as excipient for controlled drug release for oral dosage forms and as stabilizers for gels). Crosslinked Carbomers, manufactured by the Performance Materials Segment of the BF Goodrich company under the commercial name Carbopols and Polycarbophils (PCPs), are also used as mucoadhesive platforms for drug delivery. Carbopols and PCPs have

Regulation of Decarboxylation

In well irrigated CAM plants the stomata open in the afternoon following malic acid consumption. The CO2 fixation involves conventional photosynthesis and assimilation of atmospheric carbon. The initial product of CO2 fixation is 3-PGA and is subsequently converted to sucrose as in C3 and C-4 plants. Similarly the CO2 fixation is also stimulated by reducing the oxygen concentration in CAM plants.

Miscellaneous carbohydrates Sugar phosphates

These sugars are formed by phosphorylation with ATP, e.g. glucose 6-phosphate. They are extremely important in carbohydrate metabolism. We have already seen that nucleotides contain sugar phosphates. Glycosylamines In these sugars, the anomeric -OH group (of common sugars) is replaced by an amino (-NH2) group for example, adenosine.

Ser Protein Kinases Phosphatases

Profound in the case of N-regulated metabolism. Phosphorylation dephosphorylation processes in plants post-transcriptionally regulate NR, PEPc, and sucrose phosphate synthase (SPS). This regulation occurs in response to changes in light dark conditions (or in photosynthetic activity). While a role for the N status of the plant has been described in the post-transcriptional modulation of NR, PEPc and SPS, the nature of the mechanisms involved in this control are far from clear. Kinases that specifically modulate NR, SPS or PEPc have been purified and partially characterized. Recently, a Ca2+ independent PEPc protein kinase was described. This is a novel member of the Ca2+ calmodulin-regulated group of protein kinases (Hartwell et al., 1999). This PEPc kinase is regulated by transcription controls that are modulated by light (Hartwell et al., 1999).

The Case of E canadensis

Photosynthetic active radiation showed label in malic acid, glucose, asparagine, proline, and hexose phosphates, while sucrose appeared only slightly labeled, indicating that bicarbonate was used for photosynthesis, while gaseous 14CO2 was not incorporated 58 . 14C was taken by penetrating the epidermis of the stem and the lower side of the leaves. In the symplast, label was accumulated in the chloroplasts of both epidermal layers and in the plastid envelope of the chloroplasts of cortex cells.

Regulation of Nitrogen Responsive Genes for Assimilation and Subsequent Metabolism of Nitrogen

Nit, nitrate Am, ammonia CK, cytokinin Sue, sucrose Glc, glucose Frc, fructose ABA, abscisic acid Nod, nodulation. References are shown in the text. Nit, nitrate Am, ammonia CK, cytokinin Sue, sucrose Glc, glucose Frc, fructose ABA, abscisic acid Nod, nodulation.

Second Chloroquine Dimension

Replication is inhibited by aphidicolin. Of course, the equivalent torsionally stressed circular oligomer replication intermediates would not have a sedimentation coefficient of 40S. Since it is not possible to demonstrate circular oligomer replication intermediates by sucrose gradient ultracentrifugation, no sedimentation coefficient can be determined either for their normal intermediate Cairns structures or for torsionally stressed forms. For convenience, the torsionally stressed replication intermediates of circular oligomers will be called circular oligomer 40S forms. Demonstration of similar circular oligomer 40S intermediates was difficult because of the complexity of two-dimensional gel patterns in the higher molecular weight regions. Modifications of our standard two-dimensional gel systems gave indications of circular oligomer 40S intermediates, but they were not clear and unambiguous. An unusual approach was taken to simplify the gel pattern and demonstrated 40S...

Avoiding Drug Diversion from Medical to Illicit

There are a number of new and upcoming ways to avoid the potential for abuse. One problem is that sustained release opioid drugs can be crushed or rapidly extracted with alcohol. The sucrose acetate isobutyrate extended release (SABER) technology overcomes this problem because the viscous gel locks the drug into the matrix (i.e. RemoxyRM), despite attempts to crush, melt, or extract it with alcohol.

Periodontal diseases

Periodontal diseases are perhaps the most common chronic inflammatory diseases in humans. It is an inflammatory destruction of the tooth-supporting (periodontal) tissues, as a result of oral bacteria colonizing the tooth surfaces in the form of polymicrobial biofilm communities (Marsh, 2005). Depending on the localization of the biofilm in relation to the gingival margin, this can be either supragingival or ''subgingival.'' Biofilms or their released products can cause an inflammatory response by the periodontal tissues, aiming to eliminate this bacterial challenge (Feng and Weinberg, 2006). Human dental plaque has been exposed to 5 sucrose for 5 min, after which Gram's iodine (0.33 iodine in 0.66 KI) was applied. The sucrose solution was applied to the left central incisor (which appear on the right), while the right central incisor served as a control. Iodine selectively binds to alpha-1,4 glucans (iodophilic

Export of Fixed Carbon from Chloroplasts

The first product of ( (.) fixation in C, plants is 3-phosphoglycerate (3-PGA) that is reduced to triose phosphates (TPs) in the stroma. TPs serve as substrates for starch and fatty acid synthesis, both exclusively located in the chloroplasts. They are also the substrates for cytosolic sucrose biosynthesis and provide the C skeletons for amino acid biosynthesis. Part ofthe TPs has to be transported from the stroma to the cytosol. Initially, Baldry et al. (1966) and later Cockburn et al. (1967) and Bassham et al. (1968) demonstrated with isolated spinach chloroplasts that TPs and 3-PGA are released from the organelles and that photosynthesis depends on exogenous Following these observations, the transport processes between isolated chloroplasts and the surrounding medium were measured directly, showing that the above mentioned substrates are transported by the same protein (Heldt and Rapley, 1970 Fliege et al., 1978). This protein, known as the triose phosphate phosphate translocator...

Import of Carbon into Starch Storing Plastids

In contrast to chloroplasts, plastids from heterorrophic tissues, e.g. amyloplasts and leukoplasts, rely on the supply of photosynthates synthesized in source tissues. In most plant species, assimilated C is translocated to sink tissues as sucrose (Section III. A), then cleaved by apoplastic invertase and or by cyto-solic sucrose synthase (Sturm and Tang, 1999 and

Transport from the Mesophyll to the Vicinity of the Phloem

The transport of sucrose, amino acids, sugar alcohols or other solutes from the mesophyll to the vicinity of the sieve element companion cell complex are expected to be the same in all plant species, independent of the type of phloem loading. Mesophyll cells are highly interconnected with each other and with bundle sheath and vascular parenchyma cells by plasmodesmata, allowing the passage of assimilates along this route. The importance of plasmodesmata for assimilate export is reflected in the formation of secondary plasmodesmata upon the transition of maize leaves from importing sink tissues to exporting source tissues (Evert et al., 1996). These findings were supported by the study of Russin et al. (1996), who described a mutant maize, termed sucrose export deficient 1 (sxdl), in which tissue sucrose was increased and phloem export was decreased. An ultrastructural examination of wild-type and mutant leaf tissues revealed that in the mutant line the plasmodesmata interconnecting...

Studies made on collodion membrane

He also found that dilution of the ether alcohol Collodion with ether gives a thinner and less permeable membrane, whereas thickness and permeability increases with addition of amyl alcohol. Bauer6 found that the addition or 1 ml of glacial acetic acid to 200 ml of diluted collodion solution would reduce average pore size to 200m . The addition of2 ml reduce the pore size to l00 m , and the addition of 3 ml reduces pore size further to 15 m . Field made collodion membranes which held back potassium chloride and sucrose. Kistler9 found that collodion membrane can be made as dense as desired by filtering through them solution of cellulose or of collodion.

Composition and Concentrations of the Exported Carbon and Nitrogen Compounds

The concentrations of the C and N compounds in the phloem sap of several important crop plants collected from aphid (or planthopper) stylet exudation are shown in Table 1. Sucrose is the exclusive sugar present in the phloem of most plant species studied so far, being found at concentrations in the range of 200-1500 mM. Sucrose allows high translocation rates (up to 1 mh ') because it creates a high osmotic potential per C atom and, in solutions with high concentrations, its viscosity is relatively low. Reducing sugars like glucose or fructose were found in the phloem sap only in very low concentrations or were not detectable (Table 1 Ziegler, 1975). The nature of sugars transported in the phloem can be different from the predominant carbohydrates in source and sink tissues. In Alonsoa meridionalis sucrose, glucose and fructose are the predominant sugars in the leaves, whereas stachyose and raffinose are the main transport sugars (Knop et al., 2001). Pertinent questions therefore...

The Comet Assay Singlecell Gel Electrophoresis

Cells are embedded in agarose on microscope slides and lysed with Triton X-100 and 2.5 mol l_1 NaCl, which leaves the DNA, stripped of most protein, as nucleoids. The slides are placed in alkaline solution prior to electrophoresis. The still supercoiled loops of DNA resist electrophoresis however, breaks in the DNA relax supercoils, and loops are then free to migrate. They form a 'tail' to the nucleoid 'head' (hence the designation of 'comet'), and the percentage of DNA that moves into the tail reflects quantitatively the frequency of DNA breaks, over a range from a few hundred per cell up to several thousand (Collins et al., 1996). An assay for DNA breaks is of limited use in looking for endogenous oxidative damage to DNA since breaks can arise in a variety of ways unrelated to oxidation and, furthermore, breaks are quite rapidly repaired by cells. We have therefore modified the assay by incorporating a step, between lysis and electrophoresis, at which the DNA is digested with a...

Models of Phloem Loading

Phloem loading proceeds by at least two different mechanisms (1) the apoplastic way, in which sucrose and amino acids are first exported into the apoplast and then taken up into the SE-CCC by energy-dependent transport systems and (2) the symplastic way in which the assimilates are transferred from the source cells into the SE-CCC via plasmodesmata. Several features have been used to categorize plant species as apoplastic or symplastic phloem loaders, (i) According to Gamalei (1989) the mechanism of phloem loading in various plants depends on the minor vein configuration, describing the type of the companion cells (Turgeon et al., 1993) and the symplastic connections between the mesophyll cells and the SE-CCC. (ii) The mode of phloem loading may also depend on the type of carbohydrate being loaded (Zimmermann and Ziegler, 1975 Turgeon, 1996). (iii) As a physiological criterion for apoplastic or symplastic phloem loading the sensitivity or insensitivity toward thiol group-modifying...

Apoplastic Phloem Loading

In several plant species, there are relatively few plasmodesmata connecting the SE-CCC to surrounding cells. Gamalei (1989) classified these plant groups as 'type 2 (closed).' Some ofthem show a modification in either companion cells or parenchyma cells relative to transfer cells. Transfer cells are characterized by numerous cell wall invaginations, resulting in an increase in the plasma membrane surface area (Pate and Gunning, 1972). In plant species with such morphology apoplastic phloem loading is expected to be predominant. In apoplastic assimilate export at least two crossings ofthe membrane are required for solutes to reach the SE-CCC from the cytosol of bundle sheath cells or minor vein parenchyma cells to the apoplastic space and subsequently from the apoplast to the SE-CCC (Fig. 5). It is still unknown how sucrose and amino acids are transported from the cytosol ofsource cells into the apoplast. For both sucrose and amino acids, the apoplastic concentrations are much lower...

Symplastic Phloem Loading

Cucurbitaceae, Lamiaceae, Oleaceae, and Scrophu-lariaceae (Turgeon et al., 1975 Flora and Madore, 1993 Turgeon et al., 1993). This companion cell type is correlated with the translocation of considerable amounts of raffinose and stachyose in addition to sucrose (Table 2). The 'polymer trapping' model of phloem loading has been proposed to explain the coincidence of intermediary cell structure and stachyose transport (Turgeon, 1991). It is based on a size discrimination function of the plasmodesmata connecting the intermediary cells with the bundle sheath. Sucrose, which is synthesized in the mesophyll, diffuses through the plasmodesmata between mesophyll cells to the bundle sheath cells and thereafter into the intermediary cells (Fig. 6). Galactinol is synthesized from myo-inositol and UDP-galactose in the cytosol of the intermediary cells. It can also be produced in the mesophyll cells of certain plants (Sprenger and Keller, 2000). Inside the intermediary cells sucrose and galactinol...

Loading of Sugar Alcohols

Current knowledge of the mechanism of phloem loading for sugar alcohols is limited. Export of both sorbitol and mannitol is often related to the synthetic capacity of the source and the resulting concentrations in the mesophyll cells (Moing et al., 1994). Based on studies of proton gradient dependent uptake of mannitol in plasma membrane vesicles isolated from celery phloem tissues, Salmon et al. (1995) concluded that a mannitol carrier exists. Recently, a putative mannitol transporter gene, AgMa T1, has been cloned in celery (Noiraud et al., 2001). These findings suggest that apoplastic transport might be involved in this type of phloem loading. The finding that PCMBS inhibited sorbitol and sucrose phloem transport in peach, a sorbitol transporting plant (Moing et al., 1997) supports this view. On the other hand, in Prunus species the minor vein configuration could allow symplastic phloem loading according to Gamalei (1989). Up to now, no sorbitol transporter has been identified in...

Water Soluble Polymers

Because of their structural diversity, and the opportunity to create a variety of linkages between monomer units, polysaccharides are among the most diverse and important polymers in nature. Consider, for example, the structural similarities and differences in the disaccharides sucrose and lactose

Shortterm Control Of Photosynthesis

FIGURE 24.1 Schematic of fine and coarse control points of carbon partitioning in a source leaf cell. CO2 is fixed by Rubisco to form triose phosphate (TP), which can either be converted to starch in the chloroplast, or exit the chloroplast via the TP translocator. In the cytosol, TP is converted to sucrose involving several steps, with controlling reactions catalyzed by FBPase and SPS. The sucrose is then exported to sink tissues. If sucrose accumulates, it is hydrolyzed by the cell wall or vacuole form of acid invertase and re-enters the cytosol where it is phosphorylated by hexokinase. The phosphorylation of hexoses by hexokinase sends a signal which results in downregulation of genes involved in photosynthesis 5,12,14,15 . Abbreviations RuBP, ribulose-1,5-bisphosphate TP, triose-phosphate ADP-Glc, adenine-5-diphosphate glucose AGPase, adenine-5-diphosphate glucose pyrophosphorylase Pi, inorganic phosphate PPi, Pyrophosphate F-1,5-BP, fruc-tose-1,5-bisphosphate FBPase,...

Longterm Control Of Photosynthesis

Invertase, Sucrose Cycling, and a Possible Control Point of Photosynthesis Invertase is an enzyme that catalyzes the irreversible reaction converting sucrose to glucose and fructose. In plants there are two forms of the enzyme, an acid and a neutral alkaline form, each reflecting the pH optimum of the enzyme 37,38 . The neutral form exists in the cytosol while the acid form is located in both the apoplast and the vacuole. The acid invertases are encoded by a small gene family, with separate and multiple genes for both the apoplastic and vacuolar forms. Both forms of invertase, along with sucrose synthase, are associated with sink tissues that require a constant influx of sucrose for metabolism 39 . Invertase maintains this flux by hydrolyzing sucrose and thus maintaining a gradient of sucrose from source to sink. A perplexing observation is that source leaves have acid invertase activity 40 . This would seem to confound the ability of the source leaf to export sucrose if it is...

Ray Diffraction of OGlycosides

One of the pioneering studies about sugar X-ray analysis was presented by Levy and Brown5 reporting the structure of sucrose and sucrose NaBr.H2O. Through these studies it was observed that although they were energetically equivalent, the chair conformation was different, due to slight hydrogen bridge interactions on the furanoside moiety (Figure 9.2). Figure 9.2. X-ray diffraction of sucrose and sucrose NaBr.H2O. Figure 9.2. X-ray diffraction of sucrose and sucrose NaBr.H2O.

Ultrastructure And Biogenesis

In fully green and redarkened plants the crystalline structures found are re-formed PLBs 236,237, 246,260,261 . In our investigations we showed that all the original PLBs in etiolated wheat leaves disappeared after 4h of irradiation and new, re-formed PLBs appeared after redarkening of the plants for 16h 104,105 . We have applied a method for isolating PLBs from re-etiolated wheat leaves by differential centrifugation, and PLBs were separated on a 10 to 50 continuous sucrose density gradient. The isolated re-formed PLBs were found at the same density (1.17 g ml) as the PLBs from dark-grown material 60 . Electron microscopy showed a large similarity between re-formed PLBs and PLBs from dark-grown material even the re-formed PLBs were mainly of the narrow type (Figure 25.3) and offered the possibility of controlling the cross-contamination of PLBs and thylakoids during isolation.

Use Of Fluorescence Probes For Investigating Pigmentprotein Complexes In Plastid Membranes

FIGURE 25.3 Electron micrographs of re-formed PLBs from 7-day-old wheat seedlings irradiated for 4h with white light with intensity of 4 W m2 and redarkened by keeping in darkness for 16 h. (A) Scanning micrograph of isolated re-formed PLBs. A bottom-loaded 1 to 50 sucrose gradient was used for isolation. (B) Transmission micrographs of a cross-section of isolated re-formed PLBs. FIGURE 25.3 Electron micrographs of re-formed PLBs from 7-day-old wheat seedlings irradiated for 4h with white light with intensity of 4 W m2 and redarkened by keeping in darkness for 16 h. (A) Scanning micrograph of isolated re-formed PLBs. A bottom-loaded 1 to 50 sucrose gradient was used for isolation. (B) Transmission micrographs of a cross-section of isolated re-formed PLBs.

Single Molecule Fluorescence Facilitates Observation of Dextran Binding to Bacterial Glucosyltransferase

Of the oral Streptococcal glucosyl transferases (GTFs) catalyzing glucosyl transfer from sucrose to growing glucan chains, GTF-I produces water-insoluble glucans by synthesizing a-1,3-glucans. As noted by Kaseda et al. (2000), the presence of a-1,6-glucans greatly accelerates

Bio Distribution Studies of the Carrier

The hepatocellular distribution can also be assessed at various time points after injection of a radiolabeled carrier by the isolation of the different cell types 24 . Rat and human liver cells can be isolated after perfusion of the liver with collagenase and or pronase 219-221 . Separation of the different cell types is performed by centrifugal elutriation, by density gradients (using Percoll, nyco-denz, stractan, or sucrose), or by magnetic retention of the cells that are selectively recognized by antibodies attached to nonsoluble magnetic beads 222 . However, most of the obtained cell fractions are not 100 pure after isolation 220 , and accurate determination of the uptake of ligands by a particular cell type may therefore be troublesome. In addition, isolation of liver cells from diseased rats, such as rats with liver fibrosis, is even more difficult with respect to purity and viability of cell fractions compared with normal rats. Another drawback in this method is that because...

Preparation Of Porphyrins And Chlorins By Degradation Of Natural Pigments

It is truly fortunate that massive amounts of natural products containing both hemin 11 and chlorophylls a and b 12,13 can be accessed. Fischer's three volumes (20,22,24), Die Chemie des Pyrrols, report an astonishing array of procedures for obtaining tetrapyrrole compounds from natural sources. Thus, large volumes of blood can be processed to provide hemin in kilogram quantities. From hemin, a large number of porphyrins and derivatives can be obtained (see later). Similarly, chlorophyll derivatives in the a and b series can be obtained by extraction of leaves, usually spinach. But if only chlorophyll a derivatives are desired, one can take advantage of the fact that certain algae, such as Spirulina, produce only chlorophyll a thus, a laborious separation of the chlorophyll a and b series can be avoided. If chlorophyll b derivatives are required, there used to be no option but to extract plant chlorophylls and perform the chromatographic separation, either by preparative scale...

Biosynthesis Of Oligomers Of Gpcrs

Several methods have been used to determine where receptor oligomers are formed in the biosynthetic pathway. Sucrose density gradient fractionation has provided a reliable means of isolating various subcellular compartments. Immunoblot analysis of these fractions has provided information regarding where GPCR oligomers are formed and how they are processed as they make their way to the plasma membrane. The advent of biophysical techniques in the study of GPCR oligomerization has provided a unique strategy for assessing the proximity of two receptors in the cell. Bioluminescence resonance energy transfer (BRET) and fluorescence resonance energy transfer (FRET) have enabled the measurement of receptor-receptor proximity within a range of 50 to 100 angstroms, a distance that would permit receptor oligomerization. The combination of BRET or FRET and subcellular fractionation has provided a powerful tool for determining the presence of GPCR oligomers in specific organelles. BRET signals...

Marine Algal Fucoidans As Potential Mmpis

Marine algae are reported to produce different polysaccharides including alginates, laminarans, and fucoidans. They usually contain large proportions of l-fucose and sulfate, together with minor amounts of other sugars such as xylose, galactose, mannose, and glucuronic acid. These algal

The Sugar Solution

The Sugar Solution

Curb Sugar Cravings Once And For All With These Powerful Techniques. Sugar sensitive people might be low in specific neurochemicals that help us feel calm, centered, confident, and optimistic. Sugar is a drug that temporarily makes the sugar sensitive feel better, but with damaging consequences.

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