Decreased monosaccharide transport in renal brush-border membrane vesicles of spontaneously hypertensive rats

Na(+)-dependent D-glucose and D-galactose transport were studied in brush-border membrane vesicles (BBMVs) from kidney cortex isolated from both spontaneously hypertensive rats (SHR) and their normotensive genetic control Wistar-Kyoto (WKY) rats. Initial rates and accumulation ratios of Na(+)-dependent D-glucose and D-galactose transport were significantly lower in SHR compared with WKY, the observed decreases being similar for both substrates. To explain the reduction in sugar transport by renal BBMVs, the density of Na(+)-dependent sugar cotransporters was studied in BBMVs from kidney cortex isolated from SHR and WKY rats. Phlorizin-specific binding and Western blot analysis indicated a reduction in the density of the cotransporters in SHR relative to WKY rats. This reduction was similar to those found for the initial rates and accumulation ratios for D-glucose and D-galactose in SHR. Na+ uptake, studied using 22Na+, was significantly increased in SHR, so the observed reduction in sugar transport could be due to disruption of the Na+ gradient between renal BBMVs in SHR. Furthermore, a significant decrease in the activity of Na(+)-K(+)-ATPase was observed in SHR. In conclusion, changes in the density of the Na(+)-dependent sugar cotransporter and in the Na+ gradient across the brush-border membranes might be involved in the observed reduction in sugar transport by renal BBMVs from SHR.     

Raffinose as reserve sugar inDysdercus koenigii—a biosynthesis confirmation by14C glucose

Summary Dysdercus koenigii, studied for its sugar spectrum, showed consistent absence of trehalose in its blood and body muscles. Instead of this known reserve sugar, raffinose has been shown to fulfil this need. The biosynthesis confirmation has been made by¹⁴C glucose.     

Sugar-mimicking glycosidase inhibitors: bioactivity and application

A large number of compounds mimicking the structures of monosaccharides or oligosaccharides have been discovered from natural sources. Such sugar mimics inhibit carbohydrate-degrading enzymes because of a structural resemblance to the sugar moiety of the natural substrate. Carbohydrate-degrading enzymes are involved in a wide range of important biological processes, such as intestinal digestion, posttranslational processing of the sugar chain of glycoproteins, their quality control mechanisms, lysosomal catabolism of glycoconjugates, and some viral infections. It has now been realized that inhibitors of the enzymes have enormous therapeutic potential in diabetes and lysosomal storage disorders. In this review, the general bioactivity, current applications, and the prospects for new therapeutic applications are described. Received 27 August 2008; received after revision 08 November 2008; accepted 03 December 2008     

Uptake of glusose-C14 and fructose-C14 by buffalo spermatozoa in extenders during cold storage

Buffalo spermatozoa exhibit insignificant uptake of glucose-C14 and fructose-C14 when semen samples were preserved in cold for 96 h in 2 extenders. Incorporation of C14 in spermatozoa, TCA precipitable proteins and soluble sugar phosphates was either equal or less in semen samples preserved in cold. CAW appeared to be a better extender than SKMEY as revealed by sugar uptake in cold.     

N-acetylmuramic acid 6-phosphate lyases (MurNAc etherases): role in cell wall metabolism, distribution, structure, and mechanism

MurNAc etherases cleave the uniqued-lactyl ether bond of the bacterial cell wall sugar N-acetylmuramic acid (MurNAc). Members of this newly discovered family of enzymes are widely distributed among bacteria and are required to utilize peptidoglycan fragments obtained either from the environment or from the endogenous cell wall (i.e., recycling). MurNAc etherases are strictly dependent on the substrate MurNAc possessing a free reducing end and a phosphoryl group at C6. They carry a single conserved sugar phosphate isomerase/sugar phosphate- binding (SIS) domain to which MurNAc 6-phosphate is bound. Two subunits form an enzymatically active homodimer that structurally resembles the isomerase module of the double-SIS domain protein GlmS, the glucosamine 6-phosphate synthase. Structural comparison provides insights into the two-step lyase-type reaction mechanism of MurNAc etherases: β-elimination of the D-lactic acid substituent proceeds through a 2,3-unsaturated sugar intermediate to which water is subsequently added. Received 31 August 2007; received after revision 12 October 2007; accepted 1 November 2007     

Shock induces a long-lasting elevation of blood glucose in Aplysia.

Glucose, and not trehalose, was found to be the main blood sugar in Aplysia californica. Changes in blood glucose in response to stress produced by electric shock were measured in blood obtained both from animals dissected within ten minutes of shocking and from catheterized animals at various intervals, up to two and a half hours after the shock. Electric shock increased blood glucose levels. The rise in blood sugar continued as long as two and a half hours after shock.     

How Sweet It Is: Sugar,Science, and the State

Americans import large amounts of sugar, levy a stiff tariff on it, and base this tariff on the saccharine content of each sample, and thus the assessment of sugar quality for tax purposes was enormously important. It was also among the most difficult challenges of a scientific or technical nature facing the federal government in the nineteenth century, and the issues it raised would often recur as science-based quality control became an essential feature of industry.     

Studies on the biochemical effects of glibenclamide on alloxan diabetic rabbits

Treatment of alloxan diabetic rabbits with glibenclamide, the most potent of the sulfonylureas, for a period of 2 months, significantly ameliorated the diabetic condition. It produced a decrease in serum and liver lipids, amino acids, serum urea, blood sugar and urine sugar; increase in body weight, serum and liver proteins, liver glycogen, glucose tolerance and serum and liver acid labile phosphates. The possible mechanism of action of this hypoglycemic agent is discussed.     

Studies on the biochemical effects of glibenclamide on alloxan diabetic rabbits

Summary Treatment of alloxan diabetic rabbits with glibenclamide, the most potent of the sulfonylureas, for a period of 2 months, significantly ameliorated the diabetic condition. It produced a decrease in serum and liver lipids, amino acids, serum urea, blood sugar and urine sugar; increase in body weight, serum and liver proteins, liver glycogen, glucose tolerance and serum and liver acid labile phosphates. The possible mechanism of action of this hypoglycemic agent is discussed.     

Shock induces a long-lasting elevation of blood glucose inAplysia

Glucose, and not trehalose, was found to be the main blood sugar inAplysia californica. Changes in blood glucose in response to stress produced by electric shock were measured in blood obtained both from animals dissected within ten minutes of shocking and from catheterized animals at various intervals, up to two and a half hours after the shock. Electric shock increased blood glucose levels. The rise in blood sugar continued as long as two and a half hours after shock.     

Gastrointestinal transit and digestibility of maltitol,sucrose and sorbitol in rats: A multicompartmental model and recovery study

Using data obtained with a dye marker and the gavage technique, the kinetics of gastrointestinal transit of different loads of sugar substitutes (maltitol, sorbitol) and sugar (sucrose) in the rat were analysed using a linear multicompartmental model over a range from the realistic to the non-physiologic high, of carbohydrate intake levels and using only a few experimental time points. The model gave detailed insight into intestinal propulsion and gastrocecal transit time. Rate constants of transport between the compartments investigated were determined; they showed characteristics which could be related to the substance and the dosage administered. Analyses of the gastrointestinal content and calculations of the intestinal net water movement showed that the digestibility and absorption of the disaccharide sugar alcohol, maltitol, in the small gut depended inversely on the dose ingested. For all substances tested, caloric availability in the small intestine was calculated. At a physiological low level of maltitol intake, the results also indicated an insignificant calorie-saving effect in comparison to sucrose, an effect based mainly on the slow absorption rate of the maltitol cleavage product sorbitol.     

Gastrointestinal transit and digestibility of maltitol, sucrose and sorbitol in rats: a multicompartmental model and recovery study.

Using data obtained with a dye marker and the gavage technique, the kinetics of gastrointestinal transit of different loads of sugar substitutes (maltitol, sorbitol) and sugar (sucrose) in the rat were analysed using a linear multicompartmental model over a range from the realistic to the non-physiologic high, of carbohydrate intake levels and using only a few experimental time points. The model gave detailed insight into intestinal propulsion and gastrocecal transit time. Rate constants of transport between the compartments investigated were determined; they showed characteristics which could be related to the substance and the dosage administered. Analyses of the gastrointestinal content and calculations of the intestinal net water movement showed that the digestibility and absorption of the disaccharide sugar alcohol, maltitol, in the small gut depended inversely on the dose ingested. For all substances tested, caloric availability in the small intestine was calculated. At a physiological low level of maltitol intake, the results also indicated an insignificant calorie-saving effect in comparison to sucrose, an effect based mainly on the slow absorption rate of the maltitol cleavage product sorbitol.     

Uptake of glucose-C14 and fructose-C14 by buffalo spermatozoa in extenders during cold storage

Summary Buffalo spermatozoa exhibit insignificant uptake of glucose-C¹⁴ and fructose-C¹⁴ when semen samples were preserved in cold for 96 h in 2 extenders. Incorporation of C¹⁴ in spermatozoa, TCA precipitable proteins and soluble sugar phosphates was either equal or less in semen samples preserved in cold. CAW appeared to be a better extender than SKMEY as revealed by sugar uptake in cold.Acknowledgment. We are indebted to Dr D. Sundaresan, Director, for his kind encouragement in this study.     

Frederick Pavy (1829-1911) and his opposition to the glycogenic theory of Claude Bernard

For more than 50 years the Guy's Hospital physician Frederick Pavy (1829-1911) attempted to discredit the theory of his erstwhile teacher, Claude Bernard, that liver glycogen was broken down to supply sugar to the systemic circulation. His opposition was driven by his clinical perceptions and was based on two assumptions: the first was that the kidney was a simple filter through which small molecules would diffuse, so that sugar had to be prevented from reaching the systemic circulation. For Pavy, the liver was the barrier. The second was teleological: he could not believe that nature would operate in what he saw as a defective way, i.e. converting sugar into glycogen and then back again. At the beginning of his long working life Pavy regarded himself as a physiologist and was critical of the stagnancy of English physiology which was kept afloat by amateurs like himself in whatever time they could spare from busy private practice. At the end he came to see his own view of carbohydrate metabolism as symbolic of the schism between responsible clinicians (himself) and irresponsible daydreaming physiologists (his opponents).     

Coupling of fructose-1,6-P2 to aminated agarose by Schiff base reduction. Affinity chromatography of yeast aldolase.

Fructose-1,6-P2 was immobilized by sodium borohydride reduction of the Schiff base formed with aminated agarose (AH-Sepharose 4B). The coupling occurs with high yield (25 mumoles immobilized fructose-1,6-P2 per ml packed gel) at neutral pH and room temperature. Schiff base reduction thus provides a convenient and mild coupling prodecure for sugar phosphates preserving their labile phospho ester bonds. As exemplified by a new isolation procedure for fructose-1,6-P2 aldolase from yeast, sugar phosphates insolubilized in this manner may be used for affinity chromatography of the corresponding enzymes, provided that contaminating unspecific phosphatases are removed in a preceding fractionation step.     

Über den enzymatischen Zuckerumbau in Nektarien

Summary The nectaries ofEuphorbia pulcherrima secrete small quantities of invertase. This secretion is more independent of environmental factors than the production of sugar sap. Floating on C¹⁴-glucose the nectaries transform this sugar into fructose and saccharose. From these statements it is concluded that the nectaries are not merely valvelike organs for the exsudation of phloem sap, but that they represent real glands with a characteristic active metabolism.

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Die vorliegende Arbeit wurde durch Mittel der Fritz-Hoffmann-La-Roche-Stiftung zur Förderung wissenschaftlicher Arbeitsgemeinschaften in der Schweiz ermöglicht. Wir danken bestens für die Unterstützung.     

Effects of long-term feeding of glibenclamide on normal rats

Summary Prolonged administration of glibenclamide decreased blood sugar, liver glycogen and protein and increased liver and serum lipids and organic phosphates of liver in normal rats. A significant weight increase observed in glibenclamide group of rats is attributed to lipid accumulation.     

Positive alliesthesia after insulin.

Volunteers experienced sucrose solution as more pleasant 36-48 min after insulin, than after saline control. These changes in affective estimates correlate negatively with blood sugar at 30 min and positively at 50 min after the insulin injection.     

Auslösende Faktoren beim Duftmarkieren von Sammelbienen

Summary Scent marking behaviour (exposure of the Nasonov gland) of foraging honeybees (Apis mellifica) depends on the flux of sugar per unit-time in the food source.     

Studies on the effect of allicin (diallyl disulphide-oxide) on alloxan diabetes.

On oral administration to alloxan diabetic rabbits, allicin produces an increase in its hypoglycemic action with relation to dose. A short-term treatment with allicin, as well as with tolbutamide, significantly reduced the blood sugar levels and glucose nitrogen ratio of the above animals.