• Volume 15, Issue 2

      June 1990,   pages  59-115

    • Effect of king cobra venom on α2-macroglobulin and proteases in human blood plasma

      Maya Roche T N Pattabiraman

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      Normal human blood plasma showed hydrolytic activities on several synthetic substrates for proteases, the most effective being H-D-Ile-Pro-Arg-p-nitroanilide, H-D-Pro-Phe-Arg-p-nitroanilide and H-D-Val-Leu-Arg-p-nitroanilide. When plasma was preincubated for 12 h at 37°C, there was no significant alteration of the hydrolytic activities. On incubation for 12 h with king cobra venom (2 μg for 0.1 ml plasma), there was considerable decrease in the activities and complete abolition of the protease binding capacity of α2-macroglobulin. On chromatography on Sephadex G-200, α2-macroglobulin activity and bulk of the protease activity of normal plasma were eluted in the void volume region. A minor protease peak was eluted with aVe/Vo value of 2.5. With venom treated plasma, there was no decrease with this peak. The major protease peak and α2-macroglobulin activity were drastically reduced. Chromatography on red Sepharose showed that all the α2 acroglobulin activity and bulk of the protease activity in normal plasma were bound to the column. In venom treated plasma there was marked reduction in the bound fraction. The data suggest that cobra venom proteases directly or through proteases generated in plasmain situ causes limited cleavage of α2-macroglobulin as well as α2-macroglobulin bound proteases, inactivating them.

    • Optimization of sodium orthovanadate to treat streptozotocin-induced diabetic rats

      N Sekar S William N Balasubramaniyam P Kamarajan S Govindasamy

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      Oral administration of sodium orthovanadate restored blood glucose to normal levels in streptozotocin-induced diabetic rats. To establish the safety dose and to evaluate the side effects of over dose, if any, different doses of vanadium were used in the present study. Low concentrations of vanadium (0.1 and 0.3 mg/ml in drinking water) restored blood glucose, urea, cholesterol and the status of liver pathophysiological enzymes to normal levels in experimental rats. High vanadate treatment proved to be toxic not only to diabetic but also to normal rats as evidenced from the observations on the blood urea, plasma and liver glutamate oxaloacetate transaminase and glutamate pyruvate transaminase. Low vanadate treatment restored body homeostasis of diabetic rats and was found to be nontoxic to normals.

    • Enzyme activities associated with developing wheat(Triticum aestivum L.) grain amyloplasts

      R Mahajan Randhir Singh

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      Intact amyloplasts from endosperm of developing wheat grains have been isolated by first preparing the protoplasts and then fractionating the lysate of the protoplasts on percoll and ficoll gradients, respectively. Amyloplasts isolated as above were functional and not contaminated by cytosol or by organelles likely to be involved in carbohydrate metabolism. The enzyme distribution studies indicated that ADP-glucose pyrophosphorylase and starch synthase were confined to amyloplasts, whereas invertase, sucrose synthase, UDP-glucose pyrophosphorylase, hexokinase, phosphofructokinase-2 and fructose-2,6-P2ase were absent fro the amyloplast and mainly confined to the cytosol. Triose-P isomerase, glyceraldehyde-3-P dehydrogenase, phosphohexose isomerase, phosphoglucomutase, phosphofructokinase, aldolase, PPi-fructose-6-P-1 phosphotransferase, and fructose-l,6-P2ase, though predominantly cytosolic, were also present in the amyloplast. Based on distribution of enzymes, a probable pathway for starch biosynthesis in amyloplasts of developing wheat grains has been proposed.

    • Control of ornithine decarboxylase activity in jute seeds by antizyme

      Malabika Pandit Bharati Ghosh

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      The control of ornithine decarboxylase activity by antizyme was studied during early germination of jute seeds(Corchorus olitorius). When 2 mM of putrescine and spermidine were applied to the germinating medium, the enzyme activity was markedly inhibited (1.7-fold) during 16 h imbibition. This inhibition could be attributed to the formation of an inhibitory protein termed antizyme. The antizyme was partially purified from jute and barley seedlings. The activity of jute ornithine decarboxylase antizyme was weaker than that of barley.

    • Lamellar dispersion and phase separation of chloroplast membrane lipids by negative staining electron microscopy

      R C Yashroy

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      Aqueous dispersions of lipids isolated from spinach chloroplast membranes were studied by electron microscopy after negative staining with phosphotungstic acid. Influence of low temperature (5°C for 24 h) was also investigated. It was observed that when contacted with water, these lipids, as such, formed multilamellar structures. Upon sonication, these multilamellar structures gave rise to a clear suspension of unilamellar vesicles varying in size (diameter) between 250 and 750 Å. When samples of sonicated unilamellar vesicles were stored at 5°C for 24 h or more, they revealed a variety of lipid aggregates including liposomes, cylindrical rods (about 100 Å wide and up to 3600 Å long), and spherical micellar structures (100–200 Å in diameter)—thus indicating phase separation of lipids.

    • In situ study of chorion gene amplification in ovarian follicle cells ofDrosophila nasuta

      P K Tiwapi S C Lakhotia

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      The temporal and spatial pattern of replication of chorion gene clusters in follicle cells during oogenesis inDrosophila melanogaster andDrosophila nasuta was examined by [3H thymidine autoradiography and byin situ hybridization with chorion gene probes. When pulse labelled with [3H] thymidine, the follicle cells from stage 10–12 ovarian follicles of bothDrosophila melanogaster and,Drosophila nasuta often showed intense labelling at only one or two sites per nucleus.In situ hybridization of chorion gene probes derived fromDrosophila melanogaster with follicle cell nuclei ofDrosophila melanogaster andDrosophila nasuta revealed these discrete [3H] thymidine labelled sites to correspond to the two amplifying chorion gene clusters. It appears, therefore, that in spite of evolutionary divergence, the organization and programme of selective amplification of chorion genes in ovarian follicle cells have remained generally similar in these two species. The endoreplicated and amplified copies of each chorion gene cluster remain closely associated but the two clusters occupy separate sites in follicle cell nucleus.

    • Developmental regulation of cytochrome P-450 (b+e) and glutathione transferase (Ya+Yc) gene expression in rat liver

      V J Dwarki V S N K Francis G Padmanaban

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      The expression of cytochrome P-450 (b+e) and glutathione transferase (Ya+Yc) genes has been studied as a function of development in rat liver. The levels of cytochrome P-450 (b+e) mRNAs and their transcription rates are too low for detection in the 19-day old fetal liver before or after phenobarbitone treatment. However, glutathione transferase (Ya+Yc) mRNAs can be detected in the fetal liver as well as their induction after phenobarbitone treatment can be demonstrated. These mRNAs contents as well as their inducibility with phenobarbitone are lower in maternal liver than that of adult nonpregnant female rat liver. Steroid hormone administration to immature rats blocks substantially the phenobarbitone mediated induction of the two mRNA families as well as their transcription. It is suggested that steroid hormones constitute one of the factors responsible for the repression of the cytochrome P-450 (b+e) and glutathione transferase (Ya+Yc) genes in fetal liver.

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