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Biomedical subjects

A Mishra

Publications and source records attributed to A Mishra.

At least 145 records · Page 8Linked to original sources
PubMed1989

Protein A protects mice from depletion of biotransformation enzymes and mortality induced by Salmonella typhimurium endotoxin.

Changes in hepatic microsomal mixed-function oxidase enzyme levels (aniline hydroxylase, aminopyrine demethylase, glutathione S-transferase), glutathione content, total sulphydryl content, and plasma enzyme levels of aspartate transaminase, alanine transaminase and alkaline phosphatase were studied in male Swiss albino mice exposed to Salmonella typhimurium endotoxin (50-150 micrograms per mouse, LC50 141.82 micrograms). Animals exposed to the same dose of endotoxin but pretreated with protein A of Staphylococcus aureus (5 micrograms/per mouse) protected the animals from both mortality and depletion of biotransformation enzymes.

Alanine Transaminase↗
PubMed1987

Cyclotron production of no-carrier-added 206Bi (6.24 d) and 205Bi (15.31 d) as tracers for biological studies and for the development of alpha-emitting radiotherapeutic agents.

The production and radiochemical purification of no-carrier-added (NCA) bismuth isotopes (i.e. 6.24 d 206Bi and 15.31 d 205Bi) was studied. The Bi isotopes are intended for use as tracers in biodistribution studies and in the design and testing of alpha-emitting radiotherapeutic agents. The total cross sections and yields for the production of 206Bi and 205Bi from the proton bombardment of natural Pb targets were measured using the stacked-foils technique. A radiochemical method for the separation and purification of NCA Bi radioactivities from a multi-gram Pb target was also tested, modified, and improved to provide aqueous solutions of chemically and biologically useful amounts of NCA 206,205Bi for measuring tissue and subcellular-distributions, and for studies covering several chemical aspects of the development of Pb/Bi radiotherapeutic agents.

Alpha Particles↗
PubMed1982

Replication in Drosophila chromosomes. VII. Influence of prolonged larval life on patterns of replication in polytene chromosomes of Drosophila melanogaster.

Prolongation of larval life in Drosophila melanogaster, by growing wild type larvae at lower temperature, or in animals carrying the X-linked mutation giant is known to result in a greater proportion of nuclei in salivary glands showing the highest level of polyteny. We have examined by autoradiography the patterns of 3H-thymidine incorporation during 10 min or 1 min pulses in salivary gland polytene chromosomes of older giant larvae and of wild type late third instar larvae of D. melanogaster grown since hatching either at 24 degrees C or at 10 degrees C. The various patterns of labelling and their relative frequencies are generally similar in glands from the warm- (24 degrees C) or cold (10 degrees C)-reared wild type larvae, except the interband (IB) labelling patterns which are very frequent in the later group but rare in the former. The IB type labelled nuclei in cold-reared wild type larvae show labelling ranging from only a few puffs/interbands labelled to nearly all puffs/interbands labelled. In warm-reared wild type larvae, very low labelled IB patterns are not seen. In older giant larvae, the 3H-thymidine labelling patterns are in most respects similar to those seen in cold-reared wild type larvae. In 1 min pulsed preparations from all larvae, the IB patterns are relatively more frequent than in corresponding 10 min pulsed preparations. No nuclei with the continuous (2C or 3C) type of labelling pattern, with all bands and interbands/puffs labelled, were seen in 1 min pulsed preparations from cold-reared wild type or in giant larvae, and only a few nuclei in 1 min pulsed preparations from warm-reared wild type larvae exhibited the 2C labelling pattern. Analysis of silver grain density on specific late replicating sites in late discontinuous (ID) type labelled nuclei suggests that the rate of DNA synthesis per chromosomal site is not different at the two developmental temperatures. It is suggested that correlated with the prolongation of larval life under cold-rearing conditions or in giant larvae, the polytene replication cycles are also prolonged. It is further suggested that the polytene S-period in these larvae is longer de to a considerable asynchrony in the initiation and termination of replication of different sites during a replication cycle.

Acclimatization↗
PubMed1981

Dosage compensation of x-chromosome activity in interspecific hybrids of Drosophila melanogaster and D. simulans.

We have used the unstable ring X-chromosome of D. melanogaster to generate XX/X0 mosaics in the hybrid progeny from crosses between D. melanogaster females and D. simulans males. The functional properties of the polytene X-chromosome(s) in salivary glands of such X0/XX mosaic hybrid larvae have been analysed by autoradiography after 3H-uridine or 3H-thymidine labelling of the glands. The simulans X-chromosome in the hybrid X0 nuclei displays typical pale staining, enlarged diameter, higher rate of transcription (nearly two times higher than each of the Xs in the XX nuclei in the same gland) and a faster completion of replication as would be the case in the original parental X0 or XY nuclei. In the hybrid XX polytene nuclei, the melanogaster as well as the simulans X functions in the same manner as in female cells of the parents. The nucleolar transcription is also equal in the hybrid XX and X0 nuclei. Thus is seems that despite the evolutionary diversification between these two species, the regulator system which brings about the dosage compensation of X-chromosome activity has been conserved.

Alleles↗
PubMed1980

Fluorescence patterns of heterochromatin in mitotic and polytene chromosomes in seven members of three sub-groups of the melanogaster species group of Drosophila.

A comparative study of fluorescence patterns of heterochromatin in mitotic and polytene chromosomes of seven species belonging to 3 subgroups (melanogaster sub-group: D. melanogaster and D. simulans; montium sub-group: D. kikkawai and D. jambulina; ananassae sub-group: D. ananassae. D. malerkotliana and D. bipectinata) of the melanogaster species group of Drosophila (Sophophora) has been made. Hoechst 33258 (H) fluorescence patterns of mitotic chromosomes reveal differences correlated to the taxonomic groupings of these species. The melanogaster sub-group species have H-bright regions on heterochromatin of all chromosomes; the montium subgroup species have H-bright regions mainly on the 4th and Y-chromosomes; in the ananassae sub-group, while D. ananassae chromosomes do not show any H-bright regions. D. malerkotliana and D. bipectinata have small H-bright segments only on their 4th chromosomes. The H- and quinacrine mustard (QM) fluorescence patterns of larval salivary gland polytene chromocentre in these species, however, do not show the same taxonomic correlation. While D. ananassae and D. kikkawai polytene nuclei lack any H- or QM-bright region in the chromocentre, the remaining species have prominent H- and/or QM-bright region(s). In D. jambulina, the QM-bright regions are generally bigger than H-bright regions, while in D. malerkotliana and D. bipectinata the situation is reversed. Actinomycin D counterstaining prior to H-staining of polytene preparations of each species confirms that the H-bright region/s in the chromocentre are composed of A-T rich sequences. In vivo labelling of salivary gland polytene nuclei with 5-bromo-deoxyuridine for 24 to 48 h and subsequent H-staining reveals that in all the species, the H-bright regions do not replicate in 3rd instar stage and presumably represent the non-replicating alpha heterochromatin. Significantly, in all the species (excepting D. kikkawai and D. ananassae), the size, location and the number of H- and/or QM-bright regions were seen to vary in different polytene nuclei in the same gland. It seems that the organization and the extent of under-replication of alpha heterochromatin varies in different polytene nuclei. Present studies also show that even closely related species differ in the content and organization of H-bright heterochromatin. The 81F band at the base of 3R in D. melanogaster, but not in D. simulans, appears to contain non-replicating H-bright sequences in addition to replicating chromatin.

Animals↗
PubMedDate not supplied

Effect of sulphite on the oxidative metabolism of human neutrophils: studies with lucigenin- and luminol-dependent chemiluminescence.

To assess the effect of sulphite on the oxidative metabolism of human neutrophils, chemiluminescence (CL) measurements were performed using lucigenin and luminol as chemiluminigenic probes. Lucigenin-dependent CL was used for measuring superoxide anion (O2-) production, and luminol-dependent CL was used for determination of myeloperoxidase (MPO)-connected processes. With sulphite concentrations of 0.01 to 1 mmol/L, resting neutrophils showed an up to sixfold increase of lucigenin-dependent CL, but only a 1.9-fold increase of luminol-dependent CL. Subsequent stimulation of sulphite-treated neutrophils with phorbol myristate acetate (PMA) (soluble stimulant) or zymosan (particulate stimulant) resulted in an additional significant increase of lucigenin-dependent CL compared to stimulated control cells, whereas luminol-dependent CL increased slightly by 0.01 mmol/L sulphite and decreased then continuously. Sulphite concentrations above 1 mmol/L decreased both lucigenin- and luminol-dependent CL of resting and PMA- or zymosan-stimulated neutrophils. Lucigenin-dependent CL of sulphite-treated and subsequently stimulated neutrophils was strongly inhibited by extracellularly added superoxide dismutase, whereas luminol-dependent CL was markedly reduced by the MPO inhibitor azide. The intracellular activity of MPO in neutrophils stimulated with PMA in the presence of sulphite (2 mmol/L) was reduced by 55%. Sulphite (0.1 mmol/L) also inhibited strongly the activity of MPO in a cell-free system. These results indicate that micromolar concentrations of sulphite exert a stimulating effect on the O2- production of neutrophils extracellularly, but have an inhibitory effect on MPO-catalysed reactions intracellularly.

Acridines↗