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At least 1,441 records · Page 80Linked to original sources
PubMed1988

Hexose metabolism in pancreatic islets stimulation by D-glucose of [2-3H]glycerol detritiation.

1. In pancreatic islets, a rise in glucose concentration is known to increase the ratio between D-[6-14C]glucose oxidation and D-[5-3H]glucose utilization. The opposite situation was found to prevail in parotid cells. 2. In rat pancreatic islets, D-glucose caused a concentration-related stimulation of 3H2O production from [2-3H]glycerol, but failed to affect 3H2O production from [1(3)-3H]glycerol or 14CO2 production from [U-14C]glycerol. At the low concentration used in most of these experiments (i.e. 1.0 mM), glycerol failed to affect D-[U-14C]glucose oxidation. 3. These findings suggest that the preferential stimulation by D-glucose of mitochondrial oxidative events in pancreatic islets represents an unusual situation in secretory cells and involves an accelerated circulation in the glycerol phosphate shuttle.

Anaerobiosis↗
PubMed1984

Enhancement of base hexose-monophosphate shunt activity of human polymorphonuclear leucocytes by human beta-interferon.

The effect of human fibroblast interferon (HuIFN-beta) on the HMP shunt activity of human polymorphonuclear leucocytes (PMNLs) was examined. HuIFN-beta caused an increase in the base level of the HMP shunt activity. No significant increase was observed in the same PMNLs stimulated with opsonized zymosan. The augmentation of this property, generally associated with antimicrobial and cytotoxic properties of the PMNLs, may be of potential importance in host defences against microbial and malignant diseases.

Humans↗
PubMed1989

Phosphoglucoisomerase-catalyzed interconversion of hexose phosphates; comparison with phosphomannoisomerase.

The isotopic discrimination, diastereotopic specificity and intramolecular hydrogen transfer characterizing the reaction catalyzed by phosphomannoisomerase are examined. During the monodirectional conversion of D-[2-3H]mannose 6-phosphate to D-fructose 6-phosphate and D-fructose 1,6-bisphosphate, the reaction velocity is one order of magnitude lower than with D-[U-14C]mannose 6-phosphate and little tritium (less than 6%) is transferred intramolecularly. Inorganic phosphate decreases the reaction velocity but favours the intramolecular transfer of tritium. Likewise, when D-[1-3H]fructose 6-phosphate prepared from D-[1-3H]glucose is exposed solely to phosphomannoisomerase, the generation of tritiated metabolites is virtually restricted to 3H2O and occurs at a much lower rate than the production of D-[U-14C]mannose 6-phosphate from D-[U-14C]fructose 6-phosphate. However, no 3H2O is formed when D-[1-3H]fructose 6-phosphate generated from D-[2-3H]glucose is exposed to phosphomannoisomerase, indicating that the diastereotopic specificity of the latter enzyme represents a mirror image of that of phosphoglucoisomerase. Advantage is taken of such a contrasting enzymic behaviour to assess the back-and-forth flow through the reaction catalyzed by phosphomannoisomerase in intact cells exposed to D-[1-3H]glucose, D-[5-3H]glucose or D-[6-3H]glucose. Relative to the rate of glycolysis, this back-and-forth flow amounted to approx. 4% in human erythrocytes and rat parotid cells, 9% in tumoral cells of the RINm5F line and 47% in rat pancreatic islets.

Animals↗
PubMed1988

Uncoupling of hexose transport and phosphorylation in human gliomas demonstrated by PET.

Tumor uptake of [18F]2-fluoro-2-deoxy-glucose (FDG) was studied in 20 patients with histologically classified gliomas, using dynamic positron emission tomography (PET). Parametric images of local blood volume, glucose metabolic rate, transport and phosphorylation rate constants were generated by weighted non-linear least-squares fits on a pixel-by-pixel basis. Tumor metabolism, i.e. ratios of tumor peak metabolism to contralateral brain metabolism, corresponded with histological grade. Approximately half of the tumors showed considerable metabolic heterogeneity, and metabolically active areas were found in the periphery of seven tumors. Rate constants of FDG transport and phosphorylation were significantly correlated and were inversely coupled to plasma glucose levels in contralateral brain. In contrast, tumor transport and phosphorylation rate constants varied independently of each other and of plasma glucose concentration. In some tumors large alterations of FDG phosphorylation were observed in presence of nearly normal FDG transport.

Adolescent↗
PubMed1985

Insulin and islet cell transplantation in streptozotocin-diabetic rats: effect on intestinal uptake of hexoses.

A previously validated in vitro technique was used to determine the effect of once daily injections of NPH insulin (NPH) and/or islet cell transplantation on the jejunal uptake of 0.5-40 mM glucose and galactose into the jejunum of streptozotocin-diabetic rats. Glucose uptake was greater in untreated diabetic rats than in control animals due to a higher maximal transport rate and a higher passive permeability of the jejunum, and a lower value of the apparent Michaelis constant. Galactose uptake was greater in diabetic rats due to a higher maximal transport rate, but there was also a higher value of the apparent Michaelis constant. This enhanced uptake of glucose and galactose was reduced and normalized by daily injections of NPH insulin or by islet cell transplantation. It is concluded: the jejunal uptake of glucose and galactose is increased in diabetic rats, but the kinetic basis for this change was different for the two sugars; insulin therapy may correct the enhanced uptake of some nutrients in diabetic rats and islet cell transplantation may be at least as effective as exogenous insulin in modifying the intestinal adaptation to diabetes.

Animals↗