Histopathological Alterations Induced by Naja naja Crude Venom on Renal, Pulmonary and Intestinal Tissues of Mice Model.

Aim: Snake bite causes a significant number of mortality and morbidity throughout the world. So, the current study was carried out to estimate the extinct of damage caused by intraperitoneal introduction of cobra venom on kidney, lung and intestinal tissues of mice model using histological technique. Place and Duration of Study: The entire study including the treatment along with preparing histological slide was conducted in protein science laboratory, Department of Genetic Engineering and Biotechnology, University of Rajshahi, Bangladesh between December 2013 to July 2014. Methods: Twenty five mature female albino mice were divided mainly into two groups as control and envenomated group. Lyophilized Naja naja venom was dissolved in 0.9% NaCl solution and injected intraperitoneally into the mice of the envenomated group at dosages equivalent to LD50 (0.25 mg/kg). Whereas the animals from control group were not received any venomous component. Both groups of animal were sacrificed for histological study and visualized under light microscope. Results: Injection of cobra venom induced a range of histological changes in all envenomated mice comparing with their control. Results from the histopathological examination showed mainly inflammatory cellular infiltration, vacuolation in renal tubules, shrinking of glomeruli, raising space between the walls of Bowman’s capsule in renal tissue and alveolar haemorrhage, inflammatory cellular infiltration and edema in pulmonary tissue. No significant histopathological alterations in intestinal tissue were observed without infiltration and mild hemorrhage. Conclusion: The findings from the current study revealed that, cobra venom at lethal dose causes multiple organ failure in experimental animal which could be considered among the factors that lead to death. By observing the site and the mode of action on tissue level, these findings may help to allay the severity of damage by discovering novel anti venom drug.

Rise in free intracellular calcium in HeLa cells infected with aggregative Klebsiella pneumoniae strains isolated from cases of diarrhoea.

BACKGROUND & OBJECTIVES: Klebsiella pneumoniae strains occasionally cause diarrhoea in humans. This study was done to determine the involvement of calcium in the pathogenesis of aggregative K. pneumoniae strains. METHODS: A total of nine strains of K. pneumoniae were tested for adherence assay in HeLa cell line. A representative strain CO-1215 was used for [Ca2+]i study using Fura-2 fluorescence. RESULTS: Infection of cultured HeLa cells with aggregative K. pneumoniae strain resulted in five-fold elevation of intracellular level of free calcium ([Ca2+]i) with maximum Ca2+ influx at 3 h after bacterial infection. Chelation of extracellular Ca2+ with [ethylenebis(oxyethylenenitrile)] tetraacetic acid and suspension of cells in Ca2+ free buffer suggested that the rise of Ca2+ in aggregative K. pneumoniae infected HeLa cells was due to influx of Ca2+ from extracellular medium. INTERPRETATION & CONCLUSIONS: This study showed aggregative adherence in HeLa cells and this adherence leads to influx of extracellular Ca2+. The unrestricted passage of calcium ions across cell membranes could cause phosphorylation of proteins involved in ion transport across the membrane, which could result in secretory diarrhoea. Further work is in progress to study the enterotoxicity of these strains in an in vitro rabbit intestinal model.

Escherichia coli heat stable enterotoxin receptors & guanylyl cyclase activity in the intestinal brush border membrane of hamsters & guinea pigs.

BACKGROUND & OBJECTIVES: Although Escherichia coli heat stable enterotoxin (STa) causes diarrhoea in laboratory animals, no studies were done to find out the species specific variation of distribution of the STa receptors in laboratory animals. The present investigation evaluates the density of STa receptors and the guanylyl cyclase (GC) activity in the small intestinal epithelial cells of hamsters and guinea pigs. METHODS: Brush border membrane (BBM) was prepared from the small intestines of hamsters and guinea pigs. Receptor binding assay, GC assay and autoradiography were performed to determine the density of STa receptors, the GC activity and molecular weights of the STa binding proteins respectively. RESULTS: The receptor densities, per mg BBM protein at equilibrium, were found to be 4.1 x 10(9) and 1.5 x 10(12) in hamsters and guinea pigs respectively. The GC activity was found to be lower in STa treated hamster BBM compared to that of guinea pig. Scatchard analysis of the stoichiometric data showed a linear plot, and STa bound with association constants of 0.31 x 10(12) M-1 and 1.04 x 10(12) M-1 in hamsters and guinea pigs respectively. Autoradiographic analysis of the SDS-PAGE, revealed that 125I-STa bound apparently to a 45 kDa membrane protein in hamster and a 115 kDa membrane protein in guinea pig. INTERPRETATION & CONCLUSIONS: It appears that a lower density of STa receptor exists in hamsters compared to that in guinea pigs. STa binds with a single population of STa receptors in each species with different ligand binding affinities. Also, the molecular weights of the STa binding proteins differ in these species. Moreover, the GC activity was found to be lower in hamsters than in guinea pigs.