Erythrocyte volume in man and various animals after the addition of glucose]

The optimal transmission of very diluted blood samples from 11 vertebrate species and man were measured. The red cells of 10 species reduced their volume when glucose or equi-osmotic amounts of sodium chloride were added. Only the erythrocytes of man and monkey (Japanese macaques) did not reduce their volume after addition of glucose or renormalized or overcompensated minor transitory changes. This increase of the volume of human red cells is, however, too low for noticeable viscosity changes of whole blood to be caused, if any. The different response of red cells to glucose makes a simple differentiation between animal and human blood samples possible, provided that primates other than man are excluded.     

Survival of irradiated animals and the preservation of CFUs after the administration of various radioprotectors

The comparative data are presented concerning the 30-day restoration of the bone marrow cellularity and the number of endogenous colonies in the spleen of the control animals and of those treated with the radioprotective agents after irradiation with doses from 4.5 to 8.1 Gy. There was a good agreement between the results of studies in the integrity of the haemopoietic system on day 9 after irradiation and the 30-day survival of animals.     

DNA strand breaks in pancreatic islets by in vivo administration of alloxan or streptozotocin

Administration of diabetogenic doses of alloxan or streptozotocin to rats caused extensive DNA strand breaks in pancreatic islets. DNA of pancreatic exocrine cells was not affected by either alloxan or streptozotocin. hepatocyte DNA was fragmented by streptozotocin but not by alloxan. Intracellular NAD level was decreased in tissues whose DNA was fragmented. The results may raise a novel aspect concerning the mechanisms of action of the diabetogenic agents as well as concerning the organotropisms of the agents.     

Presence of fructokinase in pancreatic islets

Homogenates of rat pancreatic islets that had been heated for 5 min at 70 degrees C to inactive hexokinases, catalyzed the ATP-dependent phosphorylation of D-fructose. This reaction was dependent on the presence of K+ and was inhibited by D-tagatose although not by D-glucose or D-glucose 6-phosphate. The phosphorylation product was identified as fructose 1-phosphate through its conversion to a bisphosphate ester by Clostridium difficile fructose 1-phosphate kinase. These findings allowed the conclusion that fructokinase (ketohexokinase) was responsible for this process. Similar results were observed with tumoral insulin-producing cells (RINm5F line). Fructokinase may account for a large share of fructose phosphorylation in intact islets, particularly in the presence of D-glucose.     

Glucose-induced, calcium-mediated protein phosphorylation in intact pancreatic islets

Conditions for studying protein phosphorylation in intact pancreatic islets were developed in order to study the effects of glucose and other effectors. Islets were incubated in Krebs-Ringer bicarbonate buffer containing 5 mM malate and 5 mM pyruvate (metabolic fuels that are not insulin secretagogues) for 150 min to permit incorporation of 32Pi into islet phosphate pools. Glucose or other effectors were then added, and the incubation was terminated after 10 to 30 min. Glucose increased phosphorylation of four islet peptides with molecular weights of 20,000, 33,000, 43,000 and 57,000. The calcium channel blockers, verapamil and D-600, inhibited phosphorylation of each of the four proteins, and trifluoperazine inhibited phosphorylation of the proteins with molecular weights of 20,000 and 57,000. The results indicate that glucose-induced insulin release may be mediated in part by protein phosphorylation, and that calcium may act as an intracellular messenger in coupling the glucose stimulus to the secretory process.     

Lymphokine release from human lymphomononuclear cells after co-culture with isolated pancreatic islets: effects of islet species, long-term culture, and monocyte-macrophage cell removal

This study evaluated the release of Th1 and Th2 cytokines from human lymphomononuclear cells (LMC) in response to purified human (HI) or bovine (BI) islets, and the role of long-term (3-4 weeks) islet culture and removal of monocyte-macrophage cells. The results showed that HI and BI caused a similar increase of the release of gamma interferon (IFN), IL-2 and IL-6 from LMC, whereas BI had a more marked effect than HI on IL-10 release. Culturing the islets had possible positive effects (reduction of IFN and IL-2), but also potentially negative effects (increase of TNF). Removal of monocyte-macrophage cells determined a significant reduction of IL-6, IL-10 and TNF production in response to xeno-islets.     

Liver gangliosides of various animals ranging from fish to mammalian species

Liver gangliosides of different animal species were analyzed. Bony fish liver contained a major ganglioside that migrated faster than GM3 on thin-layer chromatography (TLC). This ganglioside was identified to be GM4 (NeuAc) by methods including product analysis after sialidase treatment and negative-ion electrospray ionization (ESI)-mass spectrometry (MS). The presence of GM4 (NeuGc) in fish liver was also demonstrated. The main ganglioside band of bovine liver consisted of two different molecular species, i.e. GD1a (NeuAc/NeuAc) and GD1a (NeuAc/NeuGc). Major gangliosides of liver tissue exhibited a distinct phylogenetic profile; GM4 was expressed mainly in lower animals such as bony fish and frog liver, whereas mammalian liver showed ganglioside patterns with smaller proportions of monosialo ganglioside species. While c-series gangliosides were consistently expressed in lower animals, they were found only in mammalian liver of particular species. No apparent trend was observed between the concentration of liver gangliosides and the phylogenetic stage of animals. The present study demonstrates the species-specific expression of liver gangliosides.