Protective mechanism of glucose against alloxan-induced beta-cell damage: pivotal role of ATP

Glucose prevents the development of diabetes induced by alloxan. In the present study, the protective mechanism of glucose against alloxan-induced beta-cell damage was investigated using HIT-T 15 cell, a Syrian hamster transformed beta-cell line. Alloxan caused beta-cell damages with DNA fragmentation, inhibition of glucose-stimulated insulin release, and decrease of cellular ATP level, but all of these beta-cell damages by alloxan were prevented by the presence of 20 mM glucose. Oligomycin, a specific inhibitor of ATP synthase, completely abolished the protective effects of glucose against alloxan-induced cell damage. Furthermore, treatment of nuclei isolated from HIT-T15 cells with ATP significantly prevented the DNA fragmentation induced by Ca2+. The results indicate that ATP produced during glucose metabolism plays a pivotal role in the protection of glucose against alloxan-induced beta-cell damage.

Histopathologic study on the Toxicity of Cytolysin Produced by Vibrio vulnificus / 대한해부학회지

Vibrio vulnificus is an estuarine bacterium which causes septicemia and serious wound infection. But the pathogenesis of Vibrio vulnificus infection is unknown. Among the exotoxins secreted by Vibrio vulnificus, cytolysin has been incriminated as one of the potent virulence determinants. In order to clarify the toxicity of cytolysin in mice, the morphological changes of various organs after the intravenous injection of cytolysin were observed. The pathological changes of mouse due to a single intravenous injection of Vibrio vulnificus cytolysin (8 hemolytic units) were as follows : Blood volume was decreased, and pleural effusion, vascular permeability of lungs, wet weight and volume of lungs were increased. And cytolysin was lead to patchy hemorrhage of pulmonary surface. The microscopic findings of mouse lung in experimental group were characterized by (1) extensive perivascular edema; (2) accumulation of intraalveolar fluid with electron dense particles; (3) narrowing of alveolar space; (4) leukocyte infiltration in perivascular and intraalveolar space; (5) vasodilatation of capillary; (6) damaged capillary endothelial cells and alveolar epithelial cells; (7) interstitial edema of interalveolar septa; (8) disorganization of collagen bundles. These results indicate that the lung may be an important target organ of cytolysin in the pathologenesis and lethal activity of Vibrio vulnificus infections.

A variant of ornithine aminotransferase from mouse small intestine

The ornithine aminotransferase (OAT) activity of mouse was found to be highest in the small intestine. The mitochondrial OAT from mouse small intestine was purified to homogeneity by the procedures including heart treatment, ammonium sulfate fractionation, octyl-Sepharose chromatography, and Sephadex G-150 gel filtration. Comparing to the amino acid sequence of mouse hepatic OAT, six N-terminal amino acid residues have been deleted in intestinal OAT. However, the subsequent sequence was identical with that of hepatic OAT. The molecular weights of both intestinal and hepatic OAT were estimated as 46 kDa by SDS-gel electrophoresis and as 92 kDa by gel filtration, indicating that both native OATs are dimeric. Biochemical properties of intestinal OAT, such as molecular weight, pH optimum and K(m) values for L-ornithine and alpha-ketoglutarate, were similar to those of hepatic OAT. However, intestinal OAT was more labile than hepatic OAT to tryptic digestion.

Mechanism for Toxicity of Cytolysin Produced by Vibrio vulnificus / 대한피부과학회지

The extracellular cytolysin produced by V. ulnificus has gained great attention as a causative factor for the pathogenesis of V. vulnificus-infected disease. In this study, an attempt was made to elucidated the mechanism for the toxity of cytolysin. 1. Cytolysin given to mouse showed lethal activity with LD of 3.7 HU and produced hemoconcentration, suggesting that its lethal activitis attributable to the increased vascular permeability. 2. The lethal activity of cytolysin for mouse was prevented by intraperitoneal administration of clemastin or verapamil one hour before intravenous injection of cytolysin. 3. Treatment of peritoneal mast cells from rats with cytolysin stimulated histamine relesse irrespective of the prescence of extracellular Ca and the stimulatory effect of cytolysin was not affected by the pretreatment of mast cells with per tussis toxin. 4. The hemolytic activity and stimulatory effect of cytolysin on histamine release from mast cell were inhibited by cholesterol. The results suggest that the lethal activity of cytolysin is attributable to the increased vascular permeability which is resulted from the stimulation of histsmine release from mast cells and/or basophils by cytolysin.

Developmental Changes of Membrane Proteins from Human Erythrocytes

To investigate the developmental changes of human erythrocytes, adult and fetal erythrocyte membranes prepared from adult and cord blood were analyzed in regard to their proteins, glycoproteins, enzyme activities and glucose transport systems. 1. Adult and fetal erythrocyte membranes appeared to have the same major proteins and gl-ycoproteins in the electrophoretic pattern. 2. ATPase activity in adult erythrocyte membranes was lower than that of fetal erythrocyte membranes, whereas adult cholinesterase was higher. No significant change was observed in the activities of alkaline and acid phosphatases during development. 3. Glucose uptake was higher in fetal erythrocytes than in adult erythrocytes, suggesting some loss of glucose carrier system during devlopment. The results suggest that the major structural proteins in human erythrocyte membrane relatively unchanged while some functional proteins such as membrane enzymes and carrier proteins in transport systems are markedly changed during development.