Volume 4, Issue 3
September 1982, pages 245-390
pp 245-255 September 1982
Severe destructive changes in the intestine of rats following whole body exposure to gamma rays (832 rads) were observed by light microscope, scanning and transmission electron microscope studies. Hypothermia (15‡C rectal temperature) induced prior to irradiation protected the intestinal mucosa from destruction. A simultaneous study showed that glucose absorption decreased significantly in irradiated rats, whereas it was increased in hypothermic irradiated animals.
pp 257-261 September 1982
An α-D-galactose-specific lectin from the seeds of jack fruit (Artocarpus integra) has been isolated in pure form by affinity chromatography on immobilised guar gum (a galactomannan). The lectin is shown to be a glycoprotein containing 3% carbohydrate and having a molecular weight of 39,500 as determined by gel filtration. Sodium dodecyl sulphate gel electrophoresis revealed a single polypeptide of 10,500 dalton, indicating that the native lectin is a tetrarner of identical subunits. The hemagglutinating activity of the lectin towards erythrocytes of all blood groups is found to be the same.
pp 263-268 September 1982
Pretreatment of male Wistar rats with L-ascorbic acid results in a decrease in thein vivo covalent binding of benzo(a)pyrene to hepatic nuclear DNA.In vitro formation of this adduct is also found to be low in liver slices and in liver nuclei of pretreated rats. No inhibition of the adduct formation is, however, observed when benzo (a) pyrene and exogenous DNA are incubated with liver microsomes isolated from ascorbic acid treated rats.It appears that the presence of ascorbate in the cellular or subcellular environment is essential for its inhibitory action.
pp 269-274 September 1982
Restraint-induced stress in rats was found to enhance steady state concentrations of whole brain and hypothalamic serotonin, at 1,2 and 4 h after immobilization. The increase was maximal at 1 h and tended to decline thereafter. The rate of accumulation of rat brain serotonin, in pargyline pretreated animals, was significantly enhanced after restraint stress. Bilateral adrenalectomy and metyrapone, an endogenous corticoid synthesis inhibitor, failed to affect restraint stress (1h)-induced increase in rat brain serotonin levels. Thus restraint stress-induced autoanalgesia and potentiation of the pharmacological actions of several centrally acting drugs, in rats, are serotonin-mediated responses. The results also indicate that restraint stress-induced effects on rat brain serotonin are not dependent on endogenous corticoid activity.
pp 275-279 September 1982
Neurospora crassa Em 5297a can utilize sodium Β-glycerophosphate as a sole phosphorous source (in the place of KH2PO4). Under these conditions a repressible alkaline phosphatase is elaborated which has different pH optimum towards Β-glycerophosphate (10.2) and pyrophosphate (9.0) as substrates. This enzyme does not require any metal ion for its activity and could be assayed in the presence of EDTA. However, under conditions of cobalt toxicity, the activity of this enzyme is high and is decreased in copper and nickel toxicities.
pp 281-286 September 1982
The pattern of release of extracellular cellulase during the germination ofTrichoderma reesei spores has been examined. The four enzymes namely, filter paper degrading enzyme, Β-1,4 endoglucanase, Β-glucosidase and xylanase appear sequentially in the culture broth during germination of the spores. The order of enzyme appearance is not altered by the type of carbon source in the germination medium. Measureable quantities of filter paper degrading enzyme is detected only after the outgrowth has occurred. A possible mechanism of spore germination and induction of the enzymes by insoluble cellulose is suggested.
pp 287-294 September 1982
Both the high molecular weight and the low molecular weight variants of urinary Y-glutamyl transpeptidase, displayed transpeptidase (pH optimum 8.6) and autotrans-peptidase (pH optimum 9.4) activities. Iodoacetamide inhibited the transpeptidase activity more efficiently than the autotranspeptidase activity with respect to both variants of Y-glutamyl transpeptidase. The high molecular weight form utilized L-glutamine as a better acceptor than L-cystine during the transpeptidation reaction whereas the reverse was the case with the low molecular weight variant. While phenylmethylsulphonyl fluoride-treated enzymes retained full activitiesper se, addition of maleic acid to the modified enzyme was found to inhibit the catalytic activities indicating a maleic acid-induced conformational change of the modified enzyme.
pp 295-306 September 1982
An inhibitor of trypsin and chymotrypsin was purified from horse gram (Dolichos biflorus) beans. The concentration of the inhibitor which provided total inhibition was 0.27 Μg/Μg tryptic enzyme and 0.46 Μg/Μg chymotryptic enzyme. The inhibitor was stable at 37‡C between pH of 3 to 11 and at 97‡C, upto pH 5.0 only. While the activities were rapidly lost in 0.1N NaO H the loss was only 5 0% in 0.1N HCl when kept for 2 h at 97‡C. On heating at pH 7.8, it remained stable upto 80‡C with a gradual loss in activities at 97‡C and a total loss occurring by autoclaving at 15 psi for 10 min. Reduction of disulphide bonds by 2-mercapto-ethanol, pronase digestion and boiling in the presence of 1 M NaCl led to reduction in the activities. However, the inhibitor was resistant to the action of pepsin and subtilisin and to urea at 37‡C.
pp 307-316 September 1982
Macrophages phagocytoseMycobacterium leprae and live bacilli inside such macrophages alter the lipid metabolism. There is increased accumulation of cholesterol ester in the bacteria infected cells. This increase appears to be due to the decreased level of esterase enzyme that could hydrolyse cholesterol esters. Associated with decreased level of this enzyme is the reduced amount of protein synthesis. Increased cholesterol ester may be responsible for conversion of macrophages into foamy cells in the presence ofM. leprae.
pp 317-325 September 1982
The analgesic, dipyrone (l,phenyl-2,3-dimethyl-5-pyrazolone-4-methylamino methane sulphonate sodium), at 20 mM concentration, inhibited the rejoining of single-strand scissions in DNA ofEscherichia coli B/r cells induced by 20 krad gamma-radiation. The chemical altered the cell membrane structure as evidenced from the uptake of acriflavin, the efflux of potassium ions from the bacterial cells and the inhibition of alkaline phosphatase-a cell membrane associated enzyme.
pp 327-330 September 1982
An attempt has been made to determine the correlation between liver damage and the virulence of mildly pathogenicMycobacterium avium in thioacetamide treated rabbits. Liver damage increased the susceptibility of rabbits to infection even with a moderately virulent organism.
pp 331-345 September 1982
The circular dichroic spectra of α-globulin fromSesamum indicum L. was recorded in the presence of cetyltrimethyl ammonium bromide, Triton X-100 and Brij-36T. The protein in 0.2 M phosphate buffer pH 7.4 had about 25% Β-structure and 5% α-helix, the rest being aperiodic or irregular structure and a-helix, structure was increased by cationic detergent cetyl trimethyl ammonium bromide. But, the increase in α-helix content was much less than that induced by an anionic detergent, sodium dodecyl sulphate. In non-ionic detergent like Brij-36T and Triton X-100, specific Β-structures like II-Β and I-Β were formed along with changes in α-helical and aperiodic structures. These results suggest that the protein has a fairly labile quaternary structure.
pp 347-359 September 1982
The interaction of α-globulin with urea/guanidine hydrochloride was investigated by determining the apparent partial specific volumes of the protein in these solvents. The apparent partial specific volumes were determined both under isomolal and isopotential conditions. The preferential interaction parameter with solvent components calculated were 0.08 and 0.1 g of urea and guanidine hydrochloride respectively per g protein. In both the cases the interaction was not preferential with water. The total binding of denaturant to α-globulin was calculated both for urea and guanidine hydrochloride and the correlation between experimentally determined number of mol of denaturant bound per mol of protein and the total number of peptide bonds and aromatic amino acids were found to be in excellent agreement with each other. The changes in volume upon transferring α-globulin from a salt solution to 8 M urea and 6 M guanidine hydrochloride were also calculated.
pp 361-368 September 1982
Studies with the induced lysogens of λS+R+, λS-R+, λS+R- and λS-R- phages have shown that while theS gene product is essential for the action of intracellularR gene product to release the periplasmic alkaline phosphatase in the presence of EDTA, the latter gene product can bring about this effect while acting onEscherichiacoli cells from outside, in the absence of functionalS gene product; chloroform, could help the intracellularR gene product in effecting bacterial lysis in the absence ofS gene product. These result support the premise that theS gene product facilitates theR gene product in crossing the cytoplasmic membrane into the periplasmic space such that the latter can act on the peptidoglycan layer of the host cell thus causing both the release of alkaline phosphatase and cell lysis.
pp 369-376 September 1982
Mice immunized against DS5-hCG-Β and DS6-hCG-Β, chemical analogs of Β-subunit of human choriogonadotropin (hCG-Β) in which 5 and 6 disulphide bonds respectively were reduced and alkylated, were found to produce antibodies specific to hCG without significant crossreactivity with human lutropin (hLH) as tested in a radioimmunoassay. In contrast, mice immunized against the native hCG-Β subunit produced hLH crossreacting antibodies. While the anti-DS5, DS6-hCG-Β serum was capable of selectively blocking the binding of [125I]-hCG to rat testicular LH/hCG receptors, it failed to inhibit the binding of [125I]-hLH to the same receptors. The radioimmunoassay for hCG using the mouse anti-DS5, DS6-hCG-Β serum was not as sensitive as that employing rabbit anti-DS5, DS6-hCG-Β serum. The minimal detection limit was 5 ng/ml for the mouse antibody as compared to 1 ng/ml for the rabbit antibody.
pp 377-390 September 1982
We propose a molecular mechanism for the intra-cellular measurement of the ratio of the number of X chromosomes to the number of sets of autosomes, a process central to both sex determination and dosage compensation inDrosophila melanogaster. In addition to the two loci,da andSxl, which have been shown by Cline(Genetics, 90, 683, 1978)and others to be involved in these processes, we postulate two other loci, one autosomal (Ω) and the other, X-linked (π). The product of the autosomal locusda stimulates Ω and initiates synthesis of a limited quantity of repressor.Sxl and π ,both of which are X-linked, compete for this repressor as well as for RNA polymerase. It is assumed thatSxl has lower affinity than π for repressor as well as polymerase and that the binding of polymerase to one of these sites modulates the binding affinity of the other site for the enzyme. It can be shown that as a result of these postulated interactions transcription from theSxl site is proportional to the X/A ratio such that the levels ofSxl+ product are low in males, high in females and intermediate in the intersexes. If, as proposed by Cline, theSxl- product is an inhibitor of X chromosome activity, this would result in dosage compensation. The model leads to the conclusion that high levels ofSxl+ product promote a female phenotype and low levels, a male phenotype. One interesting consequence of the assumptions on which the model is based is that the level ofSxl+ product in the cell, when examined as a function of increasing repressor concentration, first goes up and then decreases, yielding a bell-shaped curve. This feature of the model provides an explanation for some of the remarkable interactions among mutants at theSxl, da andmle loci and leads to several predictions. The proposed mechanism may also have relevance to certain other problems, such as size regulation during development, which seem to involve measurement of ratios at the cellular level.
Volume 44 | Issue 5
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