Phloridzin AND Beta cells

In hepatocellular carcinoma HepG2 cells, free polymannose-type oligosaccharides appearing in the cytosol during the biosynthesis and quality control of glycoproteins are rapidly translocated into lysosomes by an as yet poorly defined process (Saint-Pol, A., Bauvy, C., Codogno, P., and Moore, S. E. H. (1997) J. Cell Biol. 136, 45-59). Here, we demonstrate an ATP-dependent association of [2-3H]mannose-labeled Man5GlcNAc with isolated rat liver lysosomes. This association was only observed in the presence of swainsonine, a mannosidase inhibitor, which was required for the protection of sedimentable, but not nonsedimentable, Man5GlcNAc from degradation, indicating that oligosaccharides were transported into lysosomes...

The mechanism(s) by which insulin enhance prematurely the activity of brush border membrane (BBM) hydrolases in rat immature intestine is unknown. Therefore, we have compared the responses of four BBM enzymes [sucrase-isomaltase (SI), maltase, lactase-phloridzine hydrolase (LPH), and aminopeptidase] with exogenous insulin, the analog B-Asp10, IGF-I, and antireceptor MAb [insulin-receptor (IR) MAb] given to preweaning pups. Low doses of insulin caused a precocious induction of SI and of SI mRNA and stimulated maltase activity without effect on LPH nor on aminopeptidase activities...

Although urea transport is receiving increased attention in mammalian systems, very little is known about urea transport in fish tissues. This study examined mechanisms of urea transport in red blood cells and hepatocytes from the lesser spotted dogfish (Scyliorhinus canicula), Atlantic stingray (Dasyatis sabina), turbot (Scopthalmus maximus), redfish (Scianops ocellatus), gulf toadfish (Opsanus beta) and oyster toadfish (Opsanus tau). Urea appeared to be passively distributed in both tissues (i.e. there was no difference between plasma and tissue urea concentrations)...

1. In this study, the mechanisms involved in the release of neurotensin-like immunoreactivity (NTLI) by glucose were investigated with the isolated, vascularly perfused rat jejunoileum preparation. 2. Luminal infusion of glucose (1-250 mM) produced a sharp and sustained release of NTLI in the intestinal venous effluent. The first significant response was observed with 5 mM glucose and the release reached a maximum under 250 mM glucose with a plateau secretion at 500% of basal. 3. There was no significant difference in the ability of galactose and 3-O-methylglucose to release NTLI when compared to glucose, but alpha-methylglucose, mannose, 2-deoxyglucose and fructose did not stimulate NTLI release...

Erwinia herbicola Y46 degrades phloridzin to yield phloretin, phloroglucinol, and phloretic acid, when grown on defined medium containing phloridzin as the sole source of carbon. The identities of the intermediates isolated from culture filtrates were established by co-chromatography and by ultraviolet absorption spectra. Only 3 of 11 strains of this species, and none of the 12 species of bacterial phytopathogens tested could effect this breakdown. Some of the latter organisms possessed beta-glucosidase activity which liberated d-glucose from phloridzin...

The hemerythrin-containing blood cells, or hemocytes, of the sipunculan worm Themiste dyscrita were found to have a stereospecific and nonconcentrative monosaccharide transport system. The transport system transferred both D-glucose and 3-O-methyl-D-glucose (3-OMG), and transport into cells by this system was rapid, reaching 50% equilibrium in approximately 20 s at 10 degrees C with an initial concentration gradient of 0.1 mM; the contribution to total uptake by simple diffusion was very small. 3-OMG uptake showed saturation kinetics with a low half-saturation constant (Km less than or equal to 0...

In insulin-deprived alloxan-induced diabetic dogs with severe hyperglycemia and marked hyperglucagonemia, glucagon was not suppressed by intravenous infusion of glucose at a progressively increasing rate up to 24 mg/kg of body weight per min. However, when the hyperglycemia was corrected by phloridzin, a blocker of renal tubular glucose reabsorption, the hyperglucagonemia was readily suppressed by as little as 2 mg of glucose per kg/min. Direct perfusion of phloridzin into the isolated pancreas of nondiabetic dogs had no effect on the in vitro glucagon response to increments in glucose...

We have previously demonstrated impaired glucose influence on insulin secretion in normal rats made overtly hyperglycemic with glucose infusions for 48 h. We examined the effects of a 96-h infusion period. Rats received 30, 35, or 50% glucose or 0.45% NaCl at 2 ml/h. The plasma glucose in the 30 and 35% rats peaked at 24 h but then returned to normal by 72 h. A peak followed by a gradual fall also occurred in the 50% rats, but significant hyperglycemia was maintained throughout. beta-Cell responsiveness to glucose was assessed with the perfused pancreas by examining the effect of altering the perfusate glucose concentration on insulin release...

Glucose influx into bovine erythrocytes was found to be significantly increased upon infection with the parasite, Babesia bovis. The influx of glucose into the infected cells over 4 min was not saturable at high concentrations of glucose (240 mM), nor was it affected by established inhibitors of mammalian glucose transport, such as cytochalasin B and phloretin (0.1-100 microM). Glucose uptake into the parasitized cells was, however, inhibited by phloridzin (phloretin-2-beta-glucoside) at concentrations over the range of 10-500 microM...

Studies are presented which support the concept that a cell membrane localized glucoreceptor system is involved in the insulin secretory response to glucose and that the specific stimulation of insulin synthesis by glucose reflects effects at both the transcriptional and posttranscriptional level. After 48 hours of fasting the insulin secretory response to glucose is markedly reduced. This reduction is overcome by 24 hours of refeeding carbohydrate, but notprotein or fat, and is blocked by refeeding in the presence of an inhibitor of RNA synthesis...

A constitutive beta-glucosidase of Erwinia herbicola Y46 was studied as a prerequisite to an assessment of its significance in the release of bacteriotoxic aglycones from plant beta-glucosides, and the possible effects of the aglycones on the course of such plant diseases as "fire-blight". The enzyme was purified 86.5-fold from crude extracts of cells grown on yeast beef broth. Ammonium sulfate precipitation, DEAE-cellulose fractionation, and gel filtration through Sephadex G-100 resulted in a preparation having one peak of activity on isoelectrofocussing, on gel filtration through Sephadex G-200, and on polyacrylamide gel electrophoresis...