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Biomedical subjects

G Krishna

Publications and source records attributed to G Krishna.

At least 127 records · Page 7Linked to original sources
PubMed1983

Mutagenicity studies of ambient airborne particles. I. Comparison of solvent systems.

Organic materials were extracted from airborne particles by shaking with different solvent systems including acetone, benzene, cyclohexane, dichloromethane (DCM), methanol, a mixture of acetone and DCM and a combination of benzene, cyclohexane and methanol. The solvent-extracted materials were tested for mutagenic activity with the Ames Salmonella/microsomal assay system. Acetone- and cyclohexane-extracted materials gave the highest and lowest mutagenic activities, respectively. Re-extraction experiments confirmed that most of the mutagenic material from air particles cannot be extracted by cyclohexane. The sequential extraction with acetone followed by DCM gave a better mutagenic response than acetone alone or acetone in combination with DCM. Extraction with varying amounts of solvent indicated that 1 ml of acetone per mg of airborne particles reached the maximum recovery of mutagenic material.

Air Pollutants↗
PubMed1983

Mutagenicity studies of ambient airborne particles. II. Comparison of extraction methods.

Organic materials were extracted with acetone from airborne particles by shaking, soxhletion and sonication for varying durations. 4-h, 1-h and 1/8-min extractions by shaking, soxhletion and sonication, respectively gave maximum his+ revertants with the Ames Salmonella/microsome assay. In a comparative study of extraction methods, sonication gave the highest and soxhletion the lowest mutagenic response. It appears that sonication with acetone is the best procedure for the extraction of mutagens from airborne particles as shown by Ames assay and Arar assay systems in Salmonella typhimurium.

Air Pollutants↗
PubMed1983

Neonatal lung abscess: resection using one-lung anesthesia.

Three neonates with lung abscess unresponsive to antibiotic therapy underwent successful resection of infected lobes with the aid of one-lung anesthesia. This was accomplished by selective endobronchial intubation of the opposite lung and obstruction of the ipsilateral main bronchus with a Fogarty balloon-tipped catheter. This valuable technique provides protection against tracheobronchial spillage of purulent material and results in the rapid recovery of these seriously ill neonates.

Catheterization↗
PubMed1983

Comparison of cardiovascular effects of thiopental and pentobarbital at equivalent levels of CNS depression.

Thiopental and pentobarbital have been used in high doses to protect the brain from injury following hypoxia or to reduce intracranial pressure. This study was performed to determine whether these barbiturates differ in cardiovascular effects when present in plasma concentrations that produce equivalent CNS effects. The effects of thiopental and pentobarbital on heart rate, stroke volume/kg, cardiac output/kg, systemic vascular resistance, mean arterial pressure, and central venous pressure were statistically indistinguishable at plasma concentrations of each barbiturate ranging from 50% to 100% of their concentration producing EEG silence. Three of the seven dogs given thiopental developed ventricular bigeminy at plasma concentrations ranging from 45% to 65% of their concentration producing EEG silence. Lidocaine (1.4-2.0 mg/kg intravenously) reversed the bigeminy to sinus rhythm. When given more than the amount needed to produce a flat EEG, five of the seven dogs given thiopental died, but all dogs given pentobarbital survived. Pentobarbital may be a better choice than thiopental when large doses are indicated.

Animals↗
PubMed1982

Membrane bound guanylate cyclase in rat fat cell plasma membranes: influence of divalent cations on calcium activation.

Rat fat cell plasma membrane preparations were used to study the effect of Mn2+, Mg2+, Ca2+ on guanylate cyclase activity. Among these three cations, Mn2+ was the most effective in activating the enzyme; Mg2+ and Ca2+ were 23% and 10% respectively as effective as Mn2+ in activating the enzyme. Low concentrations of Ca2+ (1 microM) increased the rate of cGMP formation at MgGTP concentrations ranging from 0.3 to 2 mM. This effect was less at higher concentrations of Ca2+ and was independent of the presence of excess Mg2+. Ca2+ (100 microM) had only a marginal stimulatory effect on the MnGTP-dependent enzyme.

Adipose Tissue↗
PubMed1982

Anaesthetic implications of neonatal necrotizing enterocolitis.

A retrospective analysis of infants with necrotizing enterocolitis was done to evaluate the effects of preoperative abnormalities upon anaesthesia and mortality. Mortality was significantly increased in infants weighing less than 1500 grams (p less than .001). Sixty-nine per cent of the infants had hyaline membrane disease and 35 per cent had platelet counts less than 50 X 10(9) cells/litre (50,000/mm3). Perioperative problems include peritonitis, sepsis, hypovolaemia, acidosis, and prematurity. Other ramifications of prematurity and anaesthesia are discussed.

Anesthesia↗
PubMed1980

Gametocytogenesis by malaria parasites in continuous culture.

Asexual proliferation of malaria parasites proceeds by multiplication of the parasites within red cells. Following rupture of the host cells the released merozoites re-invade other red cells. On re-invasion, a proportion of merozoites become, not asexual parasites but gametocytes, the sexual stages infective to the mosquito vectors. Conversion of asexual parasites to gametocytes occurs not only during natural infections but also in continuous in vitro culture as reported first by Trager and Jensen and by others. We showed previously that the proportion of early intra-erythrocytic stages (ring stages) of Plasmodium falciparum which developed into gametocytes in culture was influenced by culture conditions. Gametocyte formation was rare in conditions supporting rapid proliferation but frequent when parasite densisites were static. We now show that nearly 100% of ring stages develop into gametocytes in response to 1mM cyclic AMP in static cultures whereas in rapidly growing cultures few rings become gametocytes in response to cyclic AMP.

Animals↗
PubMed1980

Differential control of protein kinase activities of the retinal photoreceptor. Cation effects on phosphorylation by adenosine and guanosine 5'-triphosphates.

ATP-kinase activity in photoreceptor membranes is maximal at equimolar amounts of ATP and Mg2+. GTP-kinase activity is maximal with high concentrations of Mn2+. Under these conditions, calcium ion markedly inhibits phosphorylation with ATP but not with GTP. GTP-kinase activity is maximal at pH 6.5 and decreases at higher pH; little change is seen in ATP-kinase activity over the pH range of 6.0-7.5. GTP-kinase activity is inhibited by ATP and other adenine compounds; ATP-kinase activity is less sensitive, although I mM adenosine decreases activity by about threefold. No marked differences in the protein moieties phosphorylated by ATP or GTP were seen in bovine or frog outer segment membranes. Fluxes in cation and metabolite concentrations as well as availability of ATP and GTP could thus exert a major influence on protein kinase activity in the photoreceptor unit, affording the possibility of differential phosphorylation under various physiological conditions.

Adenosine↗