Inhibition of calmodulin-dependent enzymes in rat-brain by hexachlorocyclohexane

Ca2+ homeostasis is one of the major regulatory mechanisms operating in the nervous system, with calmodulin translating the Ca2+ message into cellular response. To check if hexachlorocyclohexane (HCH) acts as a calmodulin antagonist in the nervous system of rats, the in‐vitro effect of HCH on calmodulin‐dependent Ca2+‐ATPase and cAMP‐phosphodiesterase (PDE) in rat brain has been studied. In the membrane fraction from rat brain, a basal activity of Ca2+‐ATPase was obtained in the absence of Ca2+. Inclusion of Ca2+ (1 mM) increased the enzyme activity by 70%. Further, addition of fluphenazine, a potent calmodulin antagonist, inhibited the Ca2+‐dependent enzyme activity (IC50 = 85 μM), demonstrating the calmodulin dependence of the enzyme activity. The Ca2+‐ and calmodulin‐dependent Ca2+‐ATPase was inhibited by HCH in a dose‐dependent manner (IC50 = 80–90 μM). Ca2+‐ and calmodulin‐dependent cAMP‐PDE from the cytosolic fraction of rat brain was inhibited by HCH (340 μM) by 79%. Addition of excess calmodulin reversed the inhibitory effects of HCH or fluphenazine on Ca2+‐ATPase and cAMP‐PDE, suggesting their direct interaction with calmodulin. By fluorescence interaction studies it has been shown that HCH interacts directly with calmodulin. These studies show that HCH may modulate the intracellular concentration of Ca2+ and cAMP, by decreasing the effectiveness of calmodulin towards its effector enzymes, resulting in an altered signal transduction in the nervous syste

Comparative characterization of two toxic phospholipases A2 from Indian cobra (Naja naja naja) venom

Indian cobra venom contains many phospholipase A2 (PLA2) toxins. In the present study two toxic PLA2s have been purified from the Indian cobra (Naja naja naja) venom by column chromatography. The NN-XIa-and NN-XIb-PLA2s have mol. wts between 10,700 and 15,000. The NN-XIa-PLA2 induces myotoxic effects, oedema and neurotoxicity in mice and has an i.p. LD50 of 8.5 mg/kg body weight. The NN-XIa-PLA2 is also cytotoxic to Ehrlich ascites tumour cells. The other PLA2, NN-XIb, in contrast has an i.p. LD, of 0.22 mg/kg body weight, and it induces acute neurotoxicity. The NN-XIb-PLA2 is devoid of the other biological activities which are exhibited by NN-XIa-PLA2

Membrane deterioration and other biochemical changes, associated with accelerated ageing of maize seeds

Different biochemical assays were conducted to investigate the changes occurring during accelerated ageing of maize seeds. Decreases in the level of phospholipids and ascorbate and in the activity of peroxidase and increases in the activity of phospholipase A, the level of total free fatty acids and malonaldehyde, along with the formation of conjugated lipids like trienes and tetraenes all indicate probable integral membrane lipid peroxidation in seeds subjected to accelerated ageing. A reduction in the total content of food reserves like carbohydrate, reducing sugar and protein was found in aged seeds. A decreased activity of the enzymes acid phosphatase, phosphomonoesterase and dehydrogenase was noticed during accelerated ageing. A substantial increase in total free amino acids and in the activity of amylase and protease confirm the degradation of stored biomolecules in the seeds during ageing. The effect of these biochemical changes in relation to membrane deterioration and the breakdown of larger biomolecules is also discussed

Episode of coexisting infections with multiple dengue virus serotypes in central Karnataka, India

Summary: Background: The co-circulation of multiple dengue virus serotypes has been reported in many parts of the world, including India; however, concurrent infection with more than one serotype of dengue virus in the same individual is rarely documented. Method: An outbreak of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) occurred in and around Davangere, Karnataka, from June 2011–March 2012. This is the first report from India with a high percentage of concurrent infections with different dengue virus serotypes circulating during one outbreak. Acute phase sera from patients were tested for the presence of dengue virus RNA by RT-PCR. Results: Of the 72 samples tested for dengue virus RNA, 42 (58.3%) were positive. All four dengue virus serotypes were found to be co-circulating in this outbreak, and DENV-2 was the predominant serotype. In addition, concurrent infection with more than one dengue virus serotype was identified in 18 (42.9%) dengue virus-positive samples. Conclusion: Our study showed that serotype DEN-2 was dominant in the positive dengue virus-infected samples; the other serotype present was DEN-3. This is the first report of concurrent infections with different dengue virus serotypes in this part of the world. Keywords: Dengue fever, Concurrent infection, RT-PC