Volume 9, Issue 3-4
December 1985, pages 129-236
pp 129-135 December 1985
Uptake of89Sr and45Ca by 15 soft tissues of adult rat was studiedin vitro to assess the extent of discrimination between Sr and Ca. While brain, kidney, placenta and uterus have lower uptake of89Sr and 45 Ca that of diaphragm, lactating mammary gland, skeletal muscle, skin, spleen and testes is higher. Tissues with medium range uptake are heart, small intestine, liver, lung, non-lactating mammary gland and ovary. The 6 tissues displaying discriminating ability, as expressed by89Sr/45Ca (tissue/medium), in the decreasing order are: small intestine, kidney, lactating mammary gland, placenta, diaphragm and heart. Non-lactating mammary gland and the other tissues did not differentiate between Sr and Ca. The efect of several enzyme inhibitors, compounds influencing Sr-Ca metabolism and other factors was studied in terms of the nature and mechanism of Sr-Ca discrimination.
pp 137-144 December 1985
Biogas production has been shown to be inhibited by branched chain fatty acids (isobutyric, isovaleric) produced in the digester by cellulolytic organisms. Performance of these mixed cellulolytic cultures isolated at 25°C (C25) and at 35° (C35) in a batch digester using cattle manure confirmed that C35, which forms mainly straight chain fatty acids from cellulose was more suitable for use as an inoculum than C25 which formed predominantly branched chain fatty acids. Reconstitution of cellulolytic culture C35 and mixed methanogens M35 almost doubled both the amount and rate of methane production. Cellulolytic culture was useful in pretreatment of water hyacinth prior to its use as a substrate for methane generation A method for preservation and transportation of mixed cellulolytic culture for use as an inoculum in the digester is described.
pp 145-157 December 1985
Studies on the thermal inactivation of adenylate cyclase from neuroblastoma x glioma hybrid cells have been carried out. Inactivation curves show marked deviation from first-order kinetics, and as a first approximation can be adequately described as a sum of two negative exponentials. Half-lives of the rapidly decaying component have been estimated to be 5, 3.4,1.2 and 0.5 min at 37, 40, 44 and 48°C, respectively. The corresponding values for the slow-decaying component are found to be 90, 30, 11 and 5 min. Plausible inactivation pathways responsible for multi-exponential decay curves are discussed. Kinetic curves describing fractional loss of stimulatory response of adenylate cyclase to prostaglandin E1 are shifted downwards with reference to basal activity. In contrast, an upward shift is observed for the inhibitory response of the enzyme to etorphine. A quantitative analysis of the inactivation curves for prostaglandin and etorphine-responsiveness has led to definitive predictions regarding the heat-sensitivity of the ‘hypothetical’ temperature-labile component responsible for the observed shifts.
pp 159-163 December 1985
The ontogeny of hexokinase, phosphofructokinase, phosphoglucoisornerase, aldolase, pyruvate kinase and lactate dehydrogenase activities which are associated with glycolysis, an important energy yielding process, has been studied in human fetal heart for periods ranging from 13 weeks to above 33 weeks of gestation. Hexokinase, phosphoglucoisomerase and pyruvate kinase activities show similar developmental profiles exhibiting maximum activity at 25–28 weeks ofgestation. Phosphofructokinase activity, on the other hand, shows a minimum at this period and exhibits a peak value at early stages (13–16 weeks of gestation). Though considerable activity for aldolase is observed at an early period, it declines thereafter, but again increases in the later period. The probable role and correlations of these glycolytic enzymes with energy demand and general functional development in human fetal heart in ontogeny are evaluated.
pp 165-175 December 1985
The protein α-globulin fromSesamum indicum L. has been characterised for its size and shape using αarious chemical, physico-chemical and hydrodynamic properties. The protein has an S20,w0 of 12.8, D20,w °f 4.9 × 10-7 cm2/sec and a partial specific αolume of 0.725 ml/g in the natiαe state. The intrinsic αiscosity of the protein was determined to be 3 0 ml/g indicating it to be globular in shape. The molecular weight of the protein as determined by αarious approaches in analytical ultracentrifugation αaries from 2.6–2.74 × 105. The molecular weight from sedimentation equilibrium yields a αalue of 2.74 × 105 in the natiαe state and a αalue of 19000 in the dissociated and denatured state in 6 M guanidine hydrochloride. The eαaluation of frictional ratios using Stokes radius and results from electron microscopy confirms the protein to be globular in shape. The protein consists of at least 12–14 subunits. The eαaluation of hydrophobic parameters and energetics of interaction of subunits indicate that the protein is stabilized predominantly by hydrophobic interactions.
pp 177-184 December 1985
The effect of urea, guanidine hydrochloride and sodium dodecyl sulphate on glycinin, the high molecular weight protein fraction from soybean has been investigated by analytical ultracentrifugation. Urea and guanidine hydrochloride dissociate the protein to a ‘2S’ protein through the intermediary 7S and 4S proteins. Howeαer, in sodium dodecyl sulphate the protein directly dissociates to a 2S protein. Analysis of the data by calculation of per cent fraction and S20,w value indicates that dissociation and denaturation of glycinin occur simultaneously in the presence of the aboαe reagents but to different extents.
pp 185-190 December 1985
The biosynthesis of nucleic acids and proteins was studied in rat uterus by following the incorporation of [3H]-thymidine, [3H]-uridineand[14C]-leucinein control and pregnant rats in the presence and absence of two anti-implantation drugs. One of the drugs, 78/224 caused a significant increase in incorporation whereas the other drug, Centchroman, caused an inhibition in incorporation of all the three precursors. The implications of these changes in the light of estrogenicity, agonist and antagonist actions of anti-estrogens have been analysed. The importance of homeostatic mechanisms involved in nucleic acids and proteins for the maintenance of constant internal milieu for blastocyst attachment has been discussed.
pp 191-196 December 1985
Antisera raised in albino rats against microfilariae ofLitomosoides carinii, Brugia pahangi, Brugia malayi and sera fromBancroftian elephantiasis patients promoted rat neutrophil-mediated adherence and cytotoxicity to the microfilariae. Pre-treatment of the immune sera, with microfilarial antigen at a final concentration of 5 and 25μg per ml blocked cellular adherence and cytotoxicity to the microfilariae indicating the presence of cross-reactive antibodies. The heterologous immune sera were effective in eliminating the circulatingLitomosoides carinii microfilariae inMastomys natalensis.
pp 197-201 December 1985
Cladosporium sphaerospermum, isolated from salt pans was halotolerant. When grown in the presence of salt, the activities of invertase, isocitrate lyase, fructose-1,6 diphosphate aldolase and malate dehydrogenase were found to be increased and that of amylase decreased. Both, enzyme activation as well as an increase inde novo synthesis of enzymes were found to be some of the mechanisms of salt mediated changes. This may be one of the adaptive mechanisms, in halotolerantCladosporium sphaerospermum.
pp 203-212 December 1985
Secondary structure prediction for the 4 legume lectins: Concanavalin A, soybean agglutinin, favabean lectin and lentil lectin, was done by the method of Chou and Fasman. This prediction shows that these four lectins fall into a structurally distinct class of proteins, containing high amounts of β-sheet and β-turns. There is a notable similarity in the gross structure of these proteins; all four of them contain about 40–50% of β-sheet, 35–45 % β-turn and 0–10% of α-helix. When the secondary structure of corresponding residues in each pair of these lectins was compared, there was a striking similarity in the Concanavalin A-soybean agglutinin and favabean lectin-lentil lectin pairs, and considerably less similarity in the other pairs, suggesting that these legume lectins have probably evolved in a divergent manner from a common ancestor. A comparison of the predicted potential β-turn sites also supports the hypothesis of divergent evolution in this class of lectins.
pp 213-221 December 1985
Arif mutantof Escherichia coli that exhibits medium and temperature-dependent sensitivity to rifampicin is described. In the absence of rifampicin, this strain grows in minimal and rich media at 30°C and 42°C. In its presence it is viable in rich medium at both temperatures, but in minimal medium only at 30°C. In minimal-rifampicin medium at the higher temperature, RNA synthesis is decreased. The addition of certain divalent salts (MgSO4, CaCl2, BaCl2) in excess, or chelators (EDTA, EGTA, o-phenanthrolein) greatly increase viability in minimal-rifampicin medium at 42°C. Excess MgSO4 (10 mM) also increases the rate of RNA synthesis in the same medium. A model is proposed wherein therif mutation is suggested to cause a structural change in RNA polymerase that allows the binding of rifampicin and other ligands at 42°C. Rifampicin-binding is suggested to alter the conformation of RNA polymerase, impairing its ability to express genes required for growth in minimal medium. Implicit in this view is the assumption that these genes are structurally different from those expressed in rich medium in respect of certain template features recognized by RNA polymerase.
pp 223-229 December 1985
Alkylation of DNA is an important step in the biological efects of alkylating agents. In an attempt to determine the effect of alkylation at N 1 and N 3-positions in adenine, diploid yeast auxotrophic to adenine was cultured in synthetic medium in which adenine was replaced by N 1 or N 3-methyladenines. The expectation was that, the cells will incorporate methyladenines to the DNA newly synthesised by the salvage pathway and thus facilitate the expression of their biological effects, if any. The biological end points monitored were cell killing, gene conversion and reverse mutation. Contrary to expectation, no growth occurred in the cultures even after 48 h of incubation. The cells retained viability, but were only arrested in growth. When subcultured in the presence of sub-optimum levels of both adenine and N 1-methyladenine complete growth occurred. However, no enhancement in the induction of gene conversion or back mutation was observed in these cultures.
Experiments with tritium labelled N 1-methyladenine showed that it is taken up by the cells. Hence, it is speculated that the ineffectiveness of methyladenines is due to their not being utilised as substrates in the synthesis of DNA by the salvage pathway. This is important for the assessment of the biological effects of DNA precursor pool alkylation
pp 231-236 December 1985 Short Communication
A DNA polymerase activity associated with the detergent insoluble cytoskeletal fraction has been identified in dividing and non-dividing rat hepatocytes and a hepatoma (the Zajdela Ascitic Hepatoma). About 35 % of the enzyme is found associated with the cytoskeletal fraction of non-dividing cells as compared to about 3–6 % of the enzyme in dividing cells even though the dividing cells contain larger amounts of the extranuclear enzyme. The properties of the enzyme are similar to those of DNA polymerase-v. It is suggested that the association of the enzyme with the cytoskeletal fraction has functional significance.