Volume 13, Issue 4
December 1988, pages 353-438
pp 353-358 December 1988
The oriVRK2 does not need the function of either trfA+ ortrfA Operon for replication and maintenance of an oriVRK2-containing plasmid inAzotobacter vinelandii.
pp 359-365 December 1988
The influence of Ca2+ mediators (nifedipine, verapamil and prostaglandin F2α) on fluorescence polarization of l-anilino-8-napthalene-sulphonate in dipalmitoyl phosphatidylcholine and dimyristoyl phosphatidylcholine liposomes was studied at various temperatures to understand the dynamic behaviour of membrane lipids. We also studied the effect of change in calcium concentration on the fluorescence polarization of the dye in the liposomes. Our results show increase in polarization (indicative of stiffening of the membrane) in the presence of Ca2+ ions. In the case of dimyristoyl phosphatidylcholine liposomes, all 3 drugs caused decrease in fluorescence polarization (increase in fluidity of the membrane) with or without Ca2+ ions in the medium. Contrary to this, in the case of dipalmitoyl phosphatidylcholine liposomes, the fluidization effect is observed for all the 3 drugs in the absence of Ca2+ ions; in the presence of Ca2+ ions stiffening is observed upon addition of nifedipine and verapamil which are antagonists, and fluidization is observed upon addition of prostaglandin F2α. The role of drug-induced fluidity changes in membranes in therapy planning is discussed in the paper.
pp 367-378 December 1988
The effect of light on nucleotide modifications in the tRNA of cucumber (Cucumis sativus L. var. Guntur) cotyledons was studied by chromatographic, electrophoretic and immunological methods. The tRNA from light-grown tissue showed the absence of 2-methylguanosine and a decrease in the relative proportions of ribothymidine and cytokinin-active ribonucleosides when compared to those produced from dark-grown tissue. On the other hand, a significant amount of one species of 2′-O-methyldinucleotide was observed in the tRNA of light-grown tissue which was not detected in the dark-grown tissue. Also, tRNA from light-grown tissue had higher levels of another species of 2′-O-methyldinucleotide. The results showed no difference in the amounts of other modified nucleosides in tRNA between tissues grown under the two conditions. 2′-O-Methyl-l-methyladenosine, a nucleotide modified both in the base and the ribose, apparently specific to plant tRNAs, has been found to be present in the RNA of both light- and dark-grown tissues. These results on the variation in modified nucleotides suggest that light has some role in nucleotide modification and, consequently, in cellular functions.
pp 379-391 December 1988
A gentle method for the isolation of nuclei from developing silk glands ofBombyx mori has been standardized. The nuclei, whether isolated or directly visualizedin situ within the silk glands, exhibit complex morphology. The nuclei occupy almost the entire volume of the gigantic silk gland cells. Although the isolated nuclei still retain their ramified morphology, being polyploid they are fragile and often become fragmented. The histone and low-salt-extractable proteins from nuclei isolated from the middle and posterior silk glands on different days of the fourth and fifth instars of larval development have been analysed. The histones did not show any stage- or tissue-specific variations whereas the low-salt-extractable proteins showed some developmental stage specific variation. Using the antibody raised against one such protein, its absence in the early stage of development has been confirmed by Western blotting techniques. This developmental stage specific protein may be functionally linked to some activities responsible for boosting up the production of silk or silk-related proteins during the fifth instar of larval development.
pp 393-399 December 1988
The effect of biotin deficiency on the metabolism of cholesterol was studied in rats fed cholesterol-free and cholesterol-containing diet. Biotin deficiency induced by feeding raw egg-white resulted in higher cholesterol in the serum and aorta, and higher high density lipoprotein cholesterol and low density lipoprotein + very low density lipoprotein cholesterol. In the liver, cholesterol increased only in the cholesterol diet group but not in the cholesterol-free diet group. Levels of triglycerides were lower in the biotindeficient, cholesterol-free diet group, but triglycerides were elevated in the cholesterol diet group. Concentration of bile acids in the liver and activity of lipoprotein lipase in the heart and adipose tissue were significantly decreased in the biotin-deficient rats. Release of lipoproteins into the circulation, incorporation of [1,2-14C] acetate into cholesterol, and activity of plasma lecithin: cholesterol acyl transferase were higher.
pp 401-408 December 1988
Calcium-dependent transglutaminase activity was found to be present in vaginal homogenates from adult cycling rats. Treatment of immature or adult ovariectomized rats with oestradiol (0.1 μg/g body weight) resulted in 1.5–2-fold enhancement in the enzyme activity. Progesterone treatment (0.1 μg/g body weight) decreased the enzyme activity. Analysis of amino acids produced by proteolytic enzyme digestion of insoluble keratins from rat vaginal tissue indicated the presence of γ-glutamyl-ε-⥿sine dipeptide (4 μmol/g protein) in this protein. These results suggest that oestradiol acts on vaginal tissue and induces the activity of transglutaminase. This enzyme catalyses the formation of γ-glutamyl-ε-lysine crosslinks between keratin polypeptides and thus leads to kerartization of the tissue.
pp 409-414 December 1988
Five cultures isolated from soil samples collected in Schirmacher oasis, Antarctica, have been identified as members of the familyMicrococcaceae, with 3 belonging to the genusMicrococcus and two toPlanococcus. The 3Micrococcus isolates (37R, 45R and 49R) were red-pigmented and h a d ∼ 75 mol% G + C in their DNA; they were identified asMicrococcus roseus. The twoPlanococcus isolates (30Y and Lz3OR) were yellow and orange in colour, and had 43.5 and 40.9 mol % G + C in their DNA respectively; they were identified asPlanococcus sp.
pp 415-418 December 1988
A stable pyridoxine-deficient pea mutant was obtained by screening the M2 progeny of azide-treatedPisum sativum cv Pusa Harbhajan. The mutation is visible lethal. The isolation of pyridoxine-deficient mutant demonstrates directly that pea plants synthesize their own pyridoxine and that pyridoxine is an essential growth factor for pea plants. The mutant character is determined by homozygous recessive alleles, designatedpdx-1, at a single locus. Pyridoxine-deficient plants are fertile and indistinguishable from the wild type if supplied exogenously with 2 mg of pyridoxine.
pp 419-424 December 1988
Jacalin has been found to agglutinate Ehrlich ascites cells. The agglutination was inhibited by α-glycosides of D-Gal and β -D-Gal(1 → 3)-D-GalNAc suggesting that the lectin-ascites interaction was carbohydrate-specific. There was 21.8% inhibition of tumour (ascites) cell growthin vivo in mice administered 50μg of jacalin by injection for 6 days following intraperitoneal injection of ascites cells. Administration of 100, 150 and 200μg jacalin resulted in 40.2, 57.5 and 83% inhibition respectively. Thein vivo inhibition of tumour cells growth by jacalin was due to its preferential binding with D-Gal-α -(1 → 6) present as terminal residues in the glycoprotein on tumour cell surface.
pp 437-438 December 1988