Volume 13, Issue 3
September 1988, pages 215-351
pp 215-222 September 1988
The concentration-dependent self-association of α-chymotrypsin is known to be influenced by various factors including the presence of small molecules and autolysis products. In this connection the effect of various amino acids on the self-association of α-chymotrypsin has been studied, as a point of interest, by measuring the sedimentation coefficient of α-chymotrypsin. The influence of an amino acid is seen to be governed by the nature of its side chain. Some amino acids do not affect the self-association of α-chymotrypsin at all while some affect it moderately and some others considerably. Functional groups such as the - OH group of Ser or the phenolic ring of Tyr do not seem to influence self-association behaviour. Based on these effects, amino acids could be categorized into 3 groups. Activity studies in the presence of amino acids indicate that the site of self-association and the active-site are probably mutually exclusive.
pp 223-228 September 1988
Using DNA clones, the physical distance between the linked genesnov andstr inHaemophilus influenzae was estimated. Although none of the cloned inserts contained both the markers, pJ1-8StrR 13 (insert of 18·7 kb) includedstr gene at one end and part ofnov gene at the other end of the insert. By EcoRI restriction analysis and by Southern hybridization, the distance between the two EcoRI sites, cutting at which inactivates the two genes, was estimated to be 17·7 kb. A single continuous EcoRI fragment (containing 4EcoRI sites within it) carrying both the genes intact would need to be 20·4 kb in size. These estimates were confirmed independently using different clones ofnovr andstrr alleles as probes for hybridization with BamHI-digested chromosomal DNA.
pp 229-233 September 1988
Detection of filarial antigen in different groups of sera was carried out by sandwich as well as inhibition enzyme-linked immunosorbent assays using antibody-coated sticks. Both systems were found to be equally sensitive in detecting antigen in 90% of microfilariae carriers. Incorporation of avidin-biotin in the sandwich assay system increased the sensitivity of antigen detection from 10−6 to 10−16 pg. A 67% decrease in the number of false negative results was observed when the sensitive avidin-biotin inhibition enzyme-linked immunosorbent assay system was used for analysis of filaria blood samples.
pp 235-241 September 1988
Ergosterol and cholesterol supplementation resulted in a significant increase (1·5-fold) in the sterol content while phospholipid remained unaffected inMicrosporum gypseum. The levels of phosphatidylethanolamine and phosphatidylcholine increased in ergosterol supplemented cells. However, a decrease in phosphatidylcholine and an increase in phosphatidylethanolamine was observed in cholesterol grown cells. The ratio of unsaturated to saturated fatty acids decreased on ergosterol/cholesterol supplementation. The uptake of amino acids (lysine, glycine and aspartic acid) decreased in sterol supplemented cells. Studies with fluorescent probe l-anilinonaphthalene-8-sulfonate showed structural changes in membrane organisation as evident by increased number of binding sites in such cells.
pp 243-248 September 1988
The composition, subcellular distribution and rate of synthesis of phospholipids were compared in ethambutol susceptible and resistant strains ofMycobacterium smegmatis. Significant quantitative alterations in phospholipids accompanied the acquisition of resistance, whereas fatty acyl group composition of total phospholipid remained the same in ethambutol resistant and susceptible strains. Cell wall of resistant strain exhibited an accumulation of phospholipids and a decrease in the degree of unsaturation of phospholipid fatty acyl groups. Changes in the cell wall phospholipid composition may contribute to resistance ofMycobacterium smegmatis to ethambutol.
pp 249-256 September 1988
Nick translation of intact rat heart nuclei has shown that the incorporation of [3H]-dATP is greater in hypertrophic heart nuclei than in normal heart nuclei suggesting that hypertrophic heart nuclei have more DNase I sensitive regions than normal heart nuclei. DNase I sensitivity analysis has shown that the rate and extent of digestion of myosin heavy chain genes are greater in hypertrophic than in normal heart nuclei. Dot blot hybridization analysis of myosin heavy chain transcripts from hypertrophic heart nuclei using myosin heavy chain cDNA as probe has shown that the sensitivity of myosin heavy chain genes to DNase I in hypertrophic heart nuclei correlates with myosin heavy chain gene activation and increased number of transcripts.
pp 257-262 September 1988
The effect of carnitine administration on levels of lipid peroxide and activities of superoxide dismutase and catalase was studied in rats administered isoproterenol to induce myocardial infarction. Levels of fatty acid were lower in rats pretreated with carnitine at the peak period and given isoproterenol than the levels in isoproterenoltreated control rats. Lipid peroxides were decreased in the heart at peak infarction in carnitine-treated rats compared to the levels in isoproterenol-treated controls. Activities of superoxide dismutase and catalase showed no change in carnitine-treated animals given isoproterenol compared to those in normal control rats, while they decreased in animals treated with isoproterenol alone.
pp 263-268 September 1988
β-Alanine, though producing a deficiency of taurine in the tissues, had a similar effect on cholesterol metabolism as taurine. Both caused increased activity of hepatic hydroxymethylglutaryl coenzyme A reductase and increased incorporation of 1, 2 of [14C]-acetate into liver cholesterol. Both caused increased concentration of biliary cholesterol and bile acids. There was increased activity of lipoprotein lipase in heart, but decreased activity in the adipose tissue in both cases. Release of lipoproteins into circulation was decreased in both cases.
pp 269-274 September 1988
The levels of lipid peroxides in circulatory lipoproteins increased with chronic administration of ethanol or acetaldehyde. Low density lipoprotein showed a greater increase in its content of lipid peroxides than very low density lipoprotein or high density lipoprotein. However, very low density lipoprotein was more prone to lipid peroxidationin vitro than low density lipoprotein or high density lipoprotein. The effect of acetaldehyde was more marked than that of ethanol. Lipoproteins of control and hyperlipemic groups were partially protected against peroxidation by butyrated hydroxytoluene and serum high density lipoprotein of normal rats.
pp 275-283 September 1988
Luteinizing hormone is known to stimulate the enzyme ornithine decarboxylase in the ovary. Highly purified human follicle stimulating hormone that is devoid of significant biologically active luteinizing hormone can also induce ornithine decarboxylase activity in intact immature rats with a time course of induction similar to that reported for luteinizing hormone. A maximum of 8–10-fold stimulation above controls was observed 4 h following intravenous administration of human follicle stimulating hormone. This stimulation followed a strict dose response relationship. Ovine luteinizing hormone and human chorionic gonadotropin always induced more ovarian ornithine decarboxylase activity than that achieved by maximally effective doses of follicle stimulating hormone. This could not be attributed solely to the ability of specific cell population to respond to the respective gonadotropins. Although granulosa cells contained little receptor for luteinizing hormone/human chorionic gonadotropin and the residual tissue contained little receptor for follicle stimulating hormone, each tissue responded to these gonadotropins in a manner suggestive of the mediation by one or more diffusable factors. A relationship between gonadotropin induced 3’5’-cyclic adenosine monophosphate (cyclic adenosine monophosphate) concentration and ornithine decarboxylase activity suggests that the mediation of gonadotropin stimulated ovarian ornithine decarboxylase is not solely through cyclic adenosine monophosphate, indicating the presence of other factors in the induction of gonadotropin increased ornithine decarboxylase activity.
pp 285-293 September 1988
The mechanism of ‘down regulation’ of luteinizing hormone receptors was investigated in pseudopregnant rats using a modified radioimmunoassay capable of measuring endogenous tissue-bound hormone. Treatment of pseudopregnant animals with a desensitizing dose (desensitization treatment) of human chorionic gonadotropin resulted in a decrease in receptor concentration. This decrease was prevented if the animals were treated prior to the desensitization treatment with indomethacin, an inhibitor of prostaglandin biosynthesis, suggesting a role for prostaglandins in down regulation. The desensitization treatment resulted in a time-dependent decrease in subsequent responsiveness of the tissue to luteinizing hormone. Basal progesterone production rate was also decreased following desensitization. Total tissue cholesterol was found to be decreased following desensitization treatment, without any change in the ratio of free to esterified cholesterol. Mitochondrial cholesterol was significantly reduced and pregnenolone production by the mitochondria of desensitized corpora lutea was also markedly reduced. However, when cholesterol was added to the mitochondria of desensitized corpora lutea, pregnenolone production was increased, reaching values almost equal to that shown by the control mitochondria. These results show that decrease in the responsiveness following desensitization treatment is due to, besides receptor loss, decrease in tissue cholesterol, in particular mitochondrial cholesterol. The cholesterol side chain cleavage activity, although low, appears to be functionally intact; the low activity could be attributed to low levels of mitochondrial cholesterol.
pp 295-303 September 1988
Macrophages cultured from the peripheral blood of normal individuals, tuberculoid leprosy patients and long-term-treated, bacteriologically negative lepromatous leprosy patients are able to release hydrogen peroxide on stimulation withMycobacterium leprae. Macrophages from lepromatous leprosy patients who are bacteriologically positive produce considerably lower levels of hydrogen peroxide, even though stimulation of these cells withMycobacterium leprae is definitely demonstrable. This differential stimulation of macrophages appears to be largely specific toMycobacterium leprae. There is also a good indication that decreased stimulation of macrophages from positive patients could be due to an after-effect of infection. It is possible that while other factors aid survival ofMycobacterium leprae in the macrophages, hydrogen peroxide may not be as effective in the killing of the bacteria in infected patients as it would be, perhaps, in other infections.
pp 305-315 September 1988
Convenient assays for superoxide dismutase have necessarily been of the indirect type. It was observed that among the different methods used for the assay of superoxide dismutase in rat liver homogenate, namely the xanthine-xanthine oxidase ferricytochromec, xanthine-xanthine oxidase nitroblue tetrazolium, and pyrogallol autoxidation methods, a modified pyrogallol autoxidation method appeared to be simple, rapid and reproducible. The xanthine-xanthine oxidase ferricytochromec method was applicable only to dialysed crude tissue homogenates. The xanthine-xanthine oxidase nitroblue tetrazolium method, either with sodium carbonate solution, pH 10.2, or potassium phosphate buffer, pH 7·8, was not applicable to rat liver homogenate even after extensive dialysis. Using the modified pyrogallol autoxidation method, data have been obtained for superoxide dismutase activity in different tissues of rat. The effect of age, including neonatal and postnatal development on the activity, as well as activity in normal and cancerous human tissues were also studied. The pyrogallol method has also been used for the assay of iron-containing superoxide dismutase inEscherichia coli and for the identification of superoxide dismutase on polyacrylamide gels after electrophoresis.
pp 317-321 September 1988
InRhizobium meliloti, the promoter P1 of thenif HDK operon, and also the promoter P2, have earlier been shown to be active in the bacteria present in alfalfa root nodules, but not in the bacteria grown aerobically in culture. Here we have looked at the expression from P1 and P2 in two non-symbiotic nitrogen-fixing bacteria,Azotobacter vinelandii andAzospirillum brasilense, using constructions in which the promoters are fused upstream of theβ-galactosidase gene. The promoter P1, but not P2, is active inA. vinelandii, while neither P1 nor P2 is active inAzospirillum brasilense.
pp 323-327 September 1988
Two synthetic oligonucleotide probe mixtures, whose sequences were inferred from two separate stretches of amino acids, one closer to the carboxy terminal and the other closer to the amino terminal, of ferredoxin I protein ofAzotobacter vinelandii, were used to select ferredoxin I gene clones from a cosmid gene library ofAzotobacter vinelandii. Restriction analysis revealed that 7 out of 10 selected clones were of the same type. All these clones were found to hybridize withfixABCX genes ofRhizobium meliloti.
pp 329-342 September 1988
Ribosomal proteins S7, S9 and S 19 fromEscherichia coli have been studied by the sedimentation equilibrium technique for possible intermolecular interaction between pairs of proteins as well as in a mixture of 3 proteins. The proteins were isolated to a purity greater than 95% and were characterized in the reconstitution buffer. It was observed that none of the proteins has a tendency to self-associate in the concentration range studied in the temperature range 3–6°C. Protein S9 behaves differently in the presence of other proteins. Analysis of the sedimentation equilibrium data for S7-S9, S9-S19 and S7-S9-S19 complexes revealed the need for considering the presence of a component of higher molecular weight in the system along with the monomers and their complexes to provide a meaningful curve-fitting of the data. Proteins S7 and S19 were found to interact with an equilibrium constant of association of 3 ± 2 × 104 M−1 at 3°C with a Gibbs free energy of interaction ΔG° of −5·7 kcal/mol. These data are useful for the consideration of the stabilization of the 3 0S subunit through protein-protein interactions and also help in building a topographical model of the proteins of the small subunit from an energetics point of view.
pp 343-350 September 1988
The genetic characteristic such as ‘fermentability’ of a tea cultivar could be utilised to obtain maximum colour/bloom during manufacture of black tea. Pigment profile analysis has been used as a tool to assess the characteristic of a black tea brew. Fine plucking and optimum processing conditions are two basic requirements in producing good quality black tea. The assamica variety is characterised by linalool content while geraniol is specific in chinary clones. The higher amounts of terpenoids improved the flavour characteristic of second flush tea of north east India in general and Darjeeling in particular. Further, the surplus fatty acid degradation products lower the quality of black tea during monsoon flush.
pp 351-351 September 1988 Erratum
Volume 44 | Issue 5
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