Showing papers by "Jawaharlal Nehru University published in 1990"

Effects of calmodulin antagonists on radiation-induced lipid peroxidation in microsomes.

Abstract: Rat liver microsomes were irradiated with gamma-rays at a dose rate of 1.31 Gys-1. The extent of lipid peroxidation, measured in terms of malondialdehyde (MDA) formed, increased with radiation dose. The presence of calmodulin antagonists during irradiation decreased lipid peroxidation. The order of their protective efficiency was: chlorpromazine (CPZ) greater than promethazine (PMZ) greater than trimeprazine (TMZ). Their protective effect was diminished in the presence of ferrous (Fe2+) ions and was restored on addition of EDTA. However, calmodulin antagonists considerably inhibited radiation-induced lipid peroxidation in the presence of ferric (Fe3+) ions. Calmodulin antagonists also decreased the cytochrome P-450 content of microsomes. These results are discussed with respect to their applicability to radiotherapy. A possible mechanism for the inhibition of radiation-induced lipid peroxidation is suggested.

Lipid peroxidation and glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase, and glucose-6-phosphate dehydrogenase activities in FeCl3-induced epileptogenic foci in the rat brain.

Abstract: This study investigated the relationship between lipid peroxidation, subsequent activation of antioxidative enzymes, and development of iron-induced epilepsy in the rat. Epileptic foci were produced in rat cerebral cortex by intracortical injection of ferric chloride (FeCl3). The epileptic foci were identified by electrocorticography (ECoG). Epileptiform ECoG activity was shown to occur in the contralateral homotopic cerebral cortex as well. We measured levels of lipid peroxides and changes in the activities of the enzymes: superoxide dismutase (SOD), glutathione peroxidase (GP), glutathione reductase (GR), catalase (CA), and glucose-6-phosphate dehydrogenase (G6P) in the epileptogenic focus (both ipsilateral and contralateral) at days 3, 8, 15, and 23 after FeCl3 injection. Biochemical estimations were made in subcellular fractions, and changes in the ipsilateral site were compared with those in the contralateral site. The results of this study showed that large increases in lipid peroxidation were associated with development and buildup of the ECoG epileptiform discharges. Lipid peroxides increased in the ipsilateral focus by approximately 100% as compared with control. In the contralateral site, however, the increase in lipid peroxides was marginal only. The increase in lipid peroxidation was concomitant with development of the high level of epileptiform activity. The time course of changes in lipid peroxidation paralleled the time course of development and persistence of the epileptiform activity. Regarding changes in the enzyme activities accompanying development of iron epilepsy, the data showed that although SOD and G6P increased by approximately 60% and GR increased by approximately 40%, the increases in the enzyme GP and CA were much lower, less than 20%. Thus, comparatively less increase in CA and GP activities produces a deficiency of these two enzymes in the iron (ipsilateral) focus. Among the various biochemical disturbances that have been identified as involved in epileptogenesis, peroxidative injury resulting from lipid peroxidation in neural plasma membrane may be causally related to development of paroxysmal epileptiform activity in the iron focus. Since GP is an enzyme of major importance in detoxification of lipid peroxides in the brain, based on the results presented in this article, it appears reasonable to suggest that GP deficiency causes lipid peroxidation to increase tremendously during iron epileptogenesis.

Analysis of chlorophyll a fluoresence changes in weak light in heat treated Amaranthus chloroplasts.

Abstract: After preheating of Amaranthus chloroplasts at elevated temperatures (up to 45°C), the chlorophyll a fluorescence level under low excitation light rises as compared to control (unheated) as observed earlier in other chloroplasts (Schreiber U and Armond PA (1978) Biochim Biophys Acta 502: 138–151). This elevation of heat induced fluorescence yield is quenched by addition of 0.1 mM potassium ferricyanide, suggesting that with mild heat stress the primary electron acceptor of photosystem II is more easily reduced than the unheated samples. Furthermore, the level of fluorescence attained after illumination of dithionite-treated samples is independent of preheating (up to 45°C). Thus, these experiments indicate that the heat induced rise of fluorescence level at low light can not be due to changes in the elevation in the true constant F0 level, that must by definition, be independent of the concentration of QA. It is supposed that the increase in the fluorescence level by weak modulated light is either partly associated with dark reduction of QA due to exposure of chloroplasts to elevated temperature or due to temperature induced fluorescence rise in the so called inactive photosystem II centre where QA are not connected to plastoquinone pool. In the presence of dichlorophenyldimethylurea the fluorescence level triggered by weak modulated light increases at alkaline pH, both in control and heat stressed chloroplasts. This result suggests that the alkaline pH accelerates electron donation from secondary electron donor of photosystem II to QA both in control and heat stressed samples. Thus the increase in fluorescence level probed by weak modulated light due to preheating is not solely linked to increase in true F0 level, but largely associated with the shift in the redox state of QA, the primary stable electron acceptor of photosystem II.

Production and characterization of xylanase from Bacillus thermoalkalophilus grown on agricultural wastes

Abstract: Bacillus thermoalkalophilus isolated from termite-infested mound soils of the semi-arid zones of India had the ability to produce good amounts of xylanase(s) from cheap agricultural wastes. Of the two hemicellulosic substrates tested, bagasse was found to be the better inducer for xylanase production. Alkali treatment of bagasse and rice husk had varied effects on enzyme production. The enzyme preparation had activity optima at 60° C and 70° C and a half-life of 60 min at 65° C. The enzyme was stable for 24 h over a pH range of 4.0–6.0, while maximum activity was observed at pH 6.0–7.0. Enzyme production and activity were inhibited by the end-product of xylan hydrolysis, xylose.

Free radical scavengers inhibit light-dependent degradation of the 32 kDa photosystem II reaction center protein.

Abstract: Abstract Involvement of oxygen-free radicals in the rapid, light-dependent degradation of the 32 kDa photosystem II reaction center protein was investigated. The free radical scavengers propyl-gallate and uric acid inhibited 32 kDa protein degradation without affecting linear electron flow. The involvement of singlet oxygen was excluded. Protection from degradation was also afforded under ultra-violet and far-red radiations. These data implicate free-radical damage as a common step in the degradation process, and emphasize the oxygen environment as a causative factor in destabilization of the 32 kDa protein.

Heavy metal distribution in sediments of Krishna River basin, India

Abstract: Suspended and bed sediments collected from the entire region of the Krishna River and its major tributaries were analyzed for heavy metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb) by the thin-film energy dispersive x-ray fluorescence technique. There is considerable variation in the concentration of elements towards downstream, which may be due to the variation in the subbasin geology and various degrees of human impact. Suspended particles are enriched in heavy metals throughout the basin relative to bed sediments. The heavy metals are enriched in coarse size fractions (10–90 µm) throughout the Krishna River except its tributary Bhima, where finer fractions (2 µm) dominate. Transition elements correlate very well with each other. There is a striking similarity between the bed sediments of Krishna River and the Indian average. When the annual heavy metal flux carried by the Krishna River was estimated, and viewed in relation to the other major riverine transport, the Krishna is seen to be a minor contributor of heavy metals to the Bay of Bengal.

Cloning and sequence analysis of gyrA gene of Klebsiella pneumoniae

Abstract: The gene gyrA encoding the DNA gyrase A subunit of Klebsiella pneumoniae has been cloned in the plasmid pBR322. Bases of about 3.5 Kb DNA have been sequenced to locate the gyrA gene. An open reading frame of 2628 nucleotides coding for a 97 KD protein has been identified. Homology to the extent of about 85% was detected at the nucleotide level and about 90% at the amino acid level, when the sequences were compared with that of Escherichia coli gyrA. Some very interesting differences have, however, been found in the promoter region.

Involvement of calcium, calmodulin and protein phosphorylation in morphogenesis of Candida albicans.

Abstract: SUMMARY: N-Acetyl-d-glucosamine-induced germ tube formation in Candida albicans at 37 °C was accompanied by an increase in the rate of protein phosphorylation. The calmodulin antagonist trifluoperazine and the Ca2+ ionophore A23187, which inhibited germ tube formation, also reduced the rate of phosphorylation. The rate of phosphorylation was also reduced when cells were incubated at 25 °C, which favoured yeast-phase growth. Two-dimensional SDS-PAGE analysis of phosphoproteins from germ-tube-forming and yeast cells revealed two germ-tube-specific and three yeast-specific phosphoproteins. Germ tubes and hyphae had more calmodulin activity than yeast cells, irrespective of the germ-tube-inducing condition used. As a first step towards understanding the inhibitory effect of trifluoperazine on germ tube formation, calmodulin from C. albicans was purified to homogeneity. It was heat stable, and displayed a pronounced Ca2+-induced shift in electrophoretic mobility.

Physiological changes in rats after exposure to low levels of microwaves.

Abstract: The effects of exposure to sublethal levels of microwaves were studied. Young albino rats of both sexes were exposed for 60 days to 7.5-GHz microwaves (1.0-KHz square wave modulation, average power 0.6 mW/cm2) for 3 h daily. During and after microwave exposure several physiological parameters were measured in both control and exposed animals. It was found that the animals exposed to microwaves tended to eat and drink less and thus showed a smaller gain in body weight. Some of the hematological parameters and organ weights were also significantly different. It is proposed that a nonspecific stress response due to microwave exposure and mediated through the central nervous system is responsible for the observed physiological changes.

Current trends in Candida albicans research.

Abstract: Publisher Summary This chapter discusses the current developments in Candida albicans research. C.albicans is a human pathogen and it can exist in different cellular morphologies. The objectives envisaged in C. albicans research are: (1) to understand the basis of pathogenicity and work out a specific therapy and (2) to study cellular differentiation. The chapter reviews articles covering C. albicans morphogenesis, genetics, antigenic variation, pathogenicity, and also host-defense mechanism. There are some exciting developments in C.albicans research. Some of them concern high-frequency switching of colony morphology, surface antigens, and genetic transformation systems. It exists in different cellular forms and can change from one form to another, depending on growth conditions. Thus, it is being used as a model system to study cellular differentiation. There are difficulties in studying C. albicans . As it is naturally diploid and a sexual cycle is absent, genetic analysis by conventional techniques cannot be applied. The other problem is the inherent strain differences.

Inhibition of photosystem II activity by Cu(++) ion. Choice of buffer and reagent is critical.

Abstract: Cupric ion (Cu++) inhibits the rate of photosystem II electron transport and the intensity of the variable part of chl a fluorescence in isolated chloroplast thylakoids. The inhibition is markedly dependent on the nature of the buffer used in the assay medium. In MES and HEPES buffers, complete inhibition of photosystem II occurs at 30 μM of Cu++, while in Tricine no inhibition occurred even at 200 μM Cu++. In other buffers used (TES, Phosphate, Tris), the efficacy of Cu++ inhibition is intermediate. The calculated binding constants are found to correspond to the observed I50 values for the six buffers used. It is concluded that the previous reports on copper inhibition, where buffers have been used indiscriminately should be reconsidered. Certain reagents such as hydroxylamine, ascorbate and diphenyl carbazide, which react with Cu++, should be avoided.

Crash of the immunization program: consequences of a totalitarian approach.

Abstract: India's Universal Immunization Program, which was to cover a population of more than 90 million pregnant mothers and 83 million infants living in more than 575,000 villages during 1986-90, has failed dismally. The coverage has been less than one-fifth of the requirement in more than half of the population. The situation in most third world countries, which have even weaker political clout and weaker health service infrastructures, is even more catastrophic. From a purely public health standpoint, the disaster was inevitable. No efforts were made even to define the problem of the six immunizable diseases; there was no question of understanding their natural history; the efficacy of the vaccines used was not well-known; the cold chain, which is meant to retain the potency of the vaccines at the time of inoculation, frequently broke down; there was confusion about the dosage; and even where the program is most successful, ecological conditions will erode much of the benefits from immunization. That such a technocentric program was imposed on the peoples of the third world by their governments was bad enough; even more frightening is that these countries were persuaded to follow the line developed in affluent countries by influential agencies such as UNICEF, WHO, the World Bank, the Rockefeller Foundation, and Rotary International. This is an awe-inspiring manifestation of the power of the affluent countries to impose their will on the weak and helpless peoples of the world. It is a bitter irony that UNICEF and WHO, which sponsored the famous global conference at Alma-Ata, should have lent their weight to a program that is the very antithesis of the Declaration. To embark on such a venture, the exponents had to ignore weighty scientific evidence that raised serious doubts about the program. They had to stoop to suppression of information, disinformation, and distortion of information. What is even worse, efforts will be made to erase this experience from memory, and similar efforts will again be made to launch such ill-conceived programs in the name of the welfare of the oppressed peoples of the world. Scholars who have concern for the oppressed must remain vigilant.

The three-dimensional dilute Ising magnet

Abstract: The dilute Ising model with a p = 0.8 fraction of the sites occupied by spins is simulated on L3 systems for L up to 300, using a single-cluster algorithm of Wolff. In the range of reduced temperature 0.002<(T − Tc)/Tc<0.03 the susceptibility appears to fit a simple power with an effective exponent γeff≈1.36.

Inhibition of skin tumors in DMBA-induced complete carcinogenesis system in mice by garlic (Allium sativum).

Abstract: The chemopreventive action of garlic extract on DMBA-induced complete skin carcinogenesis system was studied in random bred, 6-7 weeks old, male Swiss albino mice. Topical weekly application of DMBA for 25 weeks at two dose levels, i.e. 200 nmol during the first week followed by 100 nmol during subsequent weeks, or 400 nmol during the first week followed by 200 nmol during subsequent weeks, resulted in 73.9% and 100% tumor incidences respectively. When garlic extract was topically applied twice daily for 3 days every week prior to above-stated dose schedules of DMBA, the incidences of tumors were reduced to 31.8% (P less than 0.01) and 43.4% (P less than 0.01) respectively.

Energy flow through an Apatani village ecosystem of Arunachal Pradesh in northeast India.

Abstract: The energy flow through the ecosystem of a typical Apatani village in Arunachal Pradesh in northeastern India was studied. The energy and economic efficiency of the rice agro-ecosystem of this region is exceptionally high, and rice is exported after meeting local needs. The cropping pattern varies depending upon the amount of organic residues recycled into the system. Where recycling is more efficient and substantial, pisciculture is integrated with rice cultivation. Dry land cultivation of millet and mixed cropping in home gardens contribute toward meeting the diverse needs of the people. Swine and poultry husbandry is an important link with agro-ecosystems through the detritus food chain. Mithun (Bos frontalis)husbandry, which is dependent upon large forested grazing lands, is important for social and religious reasons, as well as being a source of food. Fuelwood is extracted from the natural forest and from the cultivated bamboo gardens; the latter also provide construction materials. This village ecosystem with high overall energy efficiency is based on tight recycling of resources.

Mercury-induced alterations of chlorophyll a fluorescence kinetics in cyanobacteria: Multiple effects of mercury on electron transport

Abstract: Changes in the fluorescence yield of chlorophyll were monitored to investigate the effect of HgCl2 on the cyanobacteria Spirulina platensis and Anacystis nidulans; weak modulated light, high intensity actinic light and additional strong sources of illumination were used. Depending on the concentration of HgCl2, three distinct types of change in the fluorescence yield of chlorophyll a were observed. At low concentrations (1.5 μM), HgCl2 behaves in a similar manner to diuron in that it increases the fluorescence intensity F0 in weak modulated light. This increase may be due to blockage of electron flow on the reducing side of photosystem II. At slightly increased levels of mercury (3 μM), the quenching of the variable fluorescence of chlorophyll suggests a decrease in electron flow on the donor side of photosystem II. This effect becomes much more evident in the presence of diuron. At sufficiently high concentrations (18 μM), a pronounced quenching of the chlorophyll fluorescence is observed, which may be due to both the blocking of photosystem II on the donor side and structural changes in the antenna pigments. These multiple effects of mercury are also observed in intact cells of Anacystis and in spheroplasts prepared from Anacystis. In the latter, the effects of mercury saturate at lower concentrations than those observed in intact cells. The effect of mercury cannot be reversed by ethylenediaminetetraacetic acid, suggesting that mercury binds with the pigment—protein complexes of the cyanobacteria.

A Dynamic Model of Domestic Political Conflict Process

Abstract: The dynamical behavior of domestic political hostility is modeled in terms of the interaction between hostile (challenger) and ruling (regime) groups. The conditions under which the conflict situat...

Influence of sugars on endoglucanase and β-xylanase activities of a Bacillus strain.

Abstract: ABacillus sp. screened from termite infested soils produced significant amount of endoglucanase and xylanase enzymes when grown on a lignocellulosic substrate, rice husk. Biosynthesis of these enzymes was significantly enhanced by the addition of 0.2% cellobiose or glucose for endoglucanase and xylose for β-xylanase activities. In the actual hydrolyses, glucose and cellobiose at low concentrations acted as activitors of endoglucanase activity whereas cellobiose and xylose acted as inhibitors of β-xylanase activity.