Volume 3, Issue 3
September 1981, pages 215-320
pp 215-219 September 1981
Administration of aflatoxin B1 (3 mg/kg body wt) to rats leads to strong inhibition of the acceptor activity of liver tRNA as measured by charging with [14C]-chorella protein hydrolysate. The maximum inhibition occurs 2 h after treatment. At increasing intervals after treatment, the inhibition appears to be gradually relieved, till control values are restored by 72 h. The charging experiment using several [14C]-amino acids separately shows pronounced inhibition of acceptor activity of all tRNA species, although the degree of inhibition varies with individual species. Preliminary results seem to rule out the possibility of hypermethylation of tRNA or damage to the CCA terminus as probable causes. The resultant functional changes may be attributed to a covalent interaction of aflatoxin B1-metabolite with tRNA.
pp 221-226 September 1981
The single side chain amino group of the D-ornithine residue in bacitracin seems to be important for the antibacterial activity of the molecule, since, acetylation, formylation, carbamylation and deamination of the antibiotic caused 90–92% loss of antibacterial activity. In contrast, nearly 80–91% of the antibacterial activity of the parent antibiotic was retained after the esterification, amide formation and acid-chloride formation of the α—and Y -carboxyl groups of D-asparagine and D-glutamic acid residues of the antibiotic, respectively.
pp 227-230 September 1981
Adult rats were subjected to the combined stress of low atmospheric pressure and temperature at a simulated altitude of 7620 metres and at 5‡C for 5 hours. A significant increase in the influx of rubidium-86 and the efflux of sodium-22 was observed in erythrocytes of experimental ratsin vitro. Blood 2,3-diphosphoglycerate was appreciably enhanced while blood sodium and reduced glutathione contents in the experimental animals remained unchanged.
pp 231-238 September 1981
The adenosine triphosphatase activity of the avian myeloblastosis virus obtained from the blood of the virus-infected chicken was compared with that of the host cell myeloblasts. The specific activity of the viral enzyme is unusually higher than that of the myeloblasts. A significant difference in inhibitor sensitivity was observed with quercetin. When the virus was grown in chicken embryonic fibroblasts in culture, the resulting virus showed very little adenosine triphosphatase activity, comparable to that of the fibroblasts and similar sensitivity to inhibitors. Antibody raised against the purified enzyme of avian myeloblastosis virus inhibits the enzyme activity of the myeloblasts while the activity of the fibroblasts enzyme as well as that of fibroblast-grown virus remains unaffected.
pp 239-248 September 1981
Cell-free extracts of submaxillary glands from rat and goat iodinate exogenously added 3,5-diiodothyronine to form 3,5,3’-triidothyronine and thyroxine. This capacity was elevated after either thyroidectomy or exposure of rats to cold (3 ±1 ‡C) for 5 h. However, there was no further increase of iodination of 3,5-diiodothyronine when the thyroidectomized rats were exposed to cold stress. The submaxillary extracts have the ability to incorporate radioactive iodide into 3,5-diiodothyronine, 3,5,3’-triiodothyronine and thyroxine. The presence of 3,5-diiodothyronine was also detected in the soluble supernatant of submaxillary extract.
pp 249-257 September 1981
Nitrogen, phosphorus and potassium deficiency reduced the uptake of32P-phosphate,35S-sulphate,24Na-,42K-,45Ca-,54Mn-,59Fe- and65Zn- byCicer arietinum (Bengal gram) cv B-75. Root length, leaf area and dry weight of the tissues were also reduced. Since in several cases, the total contents of the radio nucleides both on per plant and per unit dry weight basis were curtailed, the decrease in uptake of several ions cannot be entirely due to reduced growth rate. The reduction in32P-phosphate uptake was more severe with nitrogen deficient plants than that in phosphate deficient ones; potassium deficient plants, however, took up42K- as avidly as the control plants. Simultaneously the uptake of35SO42- and other cations was affected particularly by nitrogen deficiency. The distribution of radionucleides between the root and shoot portions was also disturbed in several cases by deficiency conditions. The radionucleides taken up accumulated in the young regions as in the case of pea and other dicotyledonous plants. Mobilization of32P and35S in the reproductive plants was most markedly affected by nitrogen and potassium-deficiency.
pp 259-268 September 1981
The correlative effects of the two sulphydryl inhibitors viz., the mono-and dithiol reagent, alloxan and cobalt chloride, were studied in the fresh water air breathing catfish,Clarias batrachus. Alloxan induced a typical mammalian-like triphasic response and necrobiotic changes in the islet Β-cells. Cobalt chloride elicited a discontinuous hyperglycemia with cytopathological changes in Β-cells following nearly the same sequence as those induced by alloxan. However, the α-cells of cobalt-treated fish showed, unlike those after alloxanization, specific degranulation, vacuolization and nuclear enlargement. The changes in the hepatic glycogen content of two experimental groups were observed to be equal. Both the drugs appeared to be detrimental to the normal islet function and were, thus, overtly or potentially diabetogenic agents to the fish.
pp 269-274 September 1981
A cytokinin-binding protein fraction was isolated from normal rabbit sera by affinity chromatography. The protein fraction bound tritium labelled N6- (δ2-risopentenyl) adenosine and the order of inhibition of this binding by competing non-radioactive compounds was, N6-(δ2-isopentenyl) adenosine < N6-benzyIadenosine < zeatin-riboside > N6-(δ2-isopentenyl) adenine < kinetin riboside > adenosine. The protein fraction showed broad specificity, the prefered cytokinin being N6-(δ2-isopentenyl) adenosine. This is the first report of the isolation of cytokinin binding proteins from mammalian sources.
pp 275-283 September 1981
Fifty-two isochromosomal lines ofDrosophila melanogaster were examined for the existence of additional genetic variations in ADH activity subsequent to treatment With guanidine hydrochloride, urea and heat. A wealth of hidden variation was discovered among and within the Mexican populations of the insect after treatment with the denaturants.
pp 285-291 September 1981
Binding of arylsulphatase B to isolated rat liver lysosomal membrane has been studied at 37‡C. The binding is strongly pH-dependent and is governed by ionic strength of the medium. Experimental evidence is given for the ability of the enzyme to dissociate from the firmly formed membrane-enzyme complex. The dissociation rate is greatly accelerated by raising the buffer molarity. Neuraminidase-treatment of the membrane causes significant reduction in its binding ability to the enzyme. This suggests that sialic acid groups participate, presumably by maintaining surface negativity of the membrane, at a stage of enzymemembrane interaction process which precedes the internalization of the lysosomal enzymes in the lysocomes.
pp 293-302 September 1981
A rapid method for the preparation of sarcolema from frog skeletal muscle has been described. The purified cell segments were transparent and devoid of contractile material. The Na+, K+ -ATPase and 5'-nucleotidase activities in sarcolemma purified by this method were comparable to those reported for sarcolemmal preparations purified by density gradient centrifugation. The preparation also possessed acid phosphatase, alkaline phosphatase and K+ -activated, ouabain-sensitive p-nitrophenyl phosphatase activities. The cholesterol to phospholipid ratio of the sarcolemma was 0.33, indicating its high purity; further, the preparation was free from mitochondria and contractile proteins.
pp 303-309 September 1981
The tensile properties and mode of fracture of elastoidin, a collagenous protein fibre from the fins of sharks, were compared with those of rat tail tendon fibres, considered to be a pure form of collagen. Elastoidin fibres were stronger than tendon in the dry state whereas the opposite was observed for fibres tested in the wet state. However, elastoidin was stiffer than tendon whether dry or wet. Scanning electron micrographs of the crosssections and fractured surfaces revealed that elastoidin fibres consisted of fibrils of varying diameter arranged in a lamellar fashion. From the nature of the fractured surfaces, it could be deduced that the primary failure mechanism for elastoidin was probably through a fissuring of the structure.
pp 311-320 September 1981
The interactions of flavin mononucleotide (riboflavin-5'-monophosphate) with two polypeptides, poly-(α-L-lysine) and poly-(α-L-histidine) in water and 0.05 M phosphate buffer were studied by measuring circular dichroism in the pH range 3 to 11. The interation of flavin mononucleotide with the two polypeptides was due to hydrophobic as well as ionic associations and was further influenced by the involvement of the ribityl side chain. The results of the present study have shown that small changes in the environmental conditions of the interacting molecules could modify their mode of interaction considerably.