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Biomedical subjects

B Das

Publications and source records attributed to B Das.

At least 181 records · Page 10Linked to original sources
PubMed1983

Biochemical mechanisms in asbestos toxicity.

The alarming hazardous nature of asbestos makes it the foremost among toxic fugitive dusts. The biochemical mechanisms responsible for the diverse biological effects of asbestos, such as fibrosis, asbestos bodies, pleural plaques, respiratory difficulty, cancer, and cytotoxicity, are being studied in this laboratory. As asbestosis progresses in guinea pigs, along with reticulum formation, lysosomal enzymes are released from membrane-bound latent state to active free form, initiating degradative changes. Considerable alterations take place in the pulmonary metabolic machinery. Mitochondria in lung cells were found to be important loci for the toxic effect of asbestos. A profile of mitochondrial activity, in control and asbestotic animals, revealed specific enzymic changes such as increased cytochrome c oxidase during the disease. The functional organization of mitochondria was also altered, since the organelles from asbestotic lungs were swollen as measured by spectrophotometry. Glutamate dehydrogenase activity of mitochondria became exposed in asbestosis. The maleate dehydrogenase shunt which is involved in transport of the redox potential across the membrane was enhanced in cytosol and mitochondria. The involvement of microsomal enzymes in asbestosis was indicated by alterations in glucose-6-phosphatase and tyrosine transaminase and aniline hydroxylase. Changes in the biotransformational capacity of lung, due to asbestos, could be an important aspect in toxicity, especially the carcinogenic effect. Considerable alterations were encountered in the levels of different phospholipids and in mucopolysaccharide constituents. On the basis of the above, the molecular mechanisms in asbestos toxicity are explained as an integrated model. Interactions of dust constituents with those of membranes and the ensuing metabolic adjustments are thus important in the etiology of asbestosis.

Acid Phosphatase↗
PubMed1978

Pesticide (hexachlorocyclohexane) inhibition of growth and nitrogen fixation in blue-green algae Anabaenopsis raciborskii and Anabaena aphanizomenoides.

The effects of the pesticide hexachlorocyclohexane (HCH) on the nitrogen fixing blue-green algae Anabaenopsis raciborskii and Anabaena aphanizomenoides commonly found as blooms in fish ponds were studied. These algae were very sensitive to HCH, and a distinct decrease in growth rate was observed on prolonged incubation. Lower concentrations (10 microgram/ml) were algistatic and higher concentrations (60 microgram/ml) were algicidal. The inhibition of nitrogen fixation indicated that the presence of HCH might affect overall nitrogen economy of inland waters.

Cyanobacteria↗
PubMed1977

[Determination of the primary structure of alfalfa mosaic virus (strain S) coat protein. II. Complete sequence of the protein (author's transl)].

The alfalfa mosaic virus protein was submitted to the action of cyanogen bromide. Four peptides were isolated. Study of these peptides allowed us to determine the order. Then protein was submitted, after S-carboxymethylation or S-aminoethylation, to the action of different proteolytic enzymes: trypsin, chymotrypsin, thermolysin and papain. The peptides issued from these different hydrolysis were separated on Dowex 50 X4 and Dowex 1 X2, and their amino acid composition was determined. The use of classical methods of sequence determination, of mass spectrometry and for one case the use of a sequencer, lead to the obtention of the primary structure of all the tryptic peptides. The studies of chymotryptic, thermolytic and papainic hydrolysates, and of cyanogen bromide rupture, allowed us to isolate the overlapping peptides which were necessary for the reconstitution of the complete proteic chain.

Amino Acid Sequence↗
PubMed1977

Intrahepatic arterial infusion of combination of mitomycin-C and 5-fluorouracil in treatment of primary and metastatic liver carcinoma.

Improvement in drug response and reduction of toxicity were observed after continuous intrahepatic arterial infusion of mytomycin-C (MMC) and 5-fluorouracil (5-FU) in 15 of 26 patients with primary or metastatic carcinoma of the liver. Serum bilirubin values of 10 mg/100 ml absence of ascites, extreme cachexia and impending hepatic failure were used as the criteria for admission of these patients into the study. The patients were given MMC in a dose of 0.08 mg/kg on day 1,5-FU in a dose of 8-10 mg/kg on days 2-5, and MMC on day 6. This schedule was reinitiated on days 8 and 15 for total mean duration of 18 days. Maintenance therapy was carried out by the administration of these drugs at induction dosage alternated each week as a single 24 hourly intravenous infusion. Objective response to combination therapy was defined as decrease of at least 50% in the liver size and in the abnormal levels of serum alkaline phosphatase and glutamic oxaloacetic transaminase (SGOT), and near normal levels of serum bilirubin for a minimum period of 2 months. The duration of objective response ranged from 3-16 months with a median of 8.2 months. The median survival time for the responders was 7.2 months for patients with primary carcinoma and 9.4 months for patients with metastatic carcinoma of the liver as compared to 2 months for patients who failed to respond to the treatment. Five out of 12 patients who were refractory to MMC or 5-FU by intravenous infusion responded to the present combination drug therapy. Of four patients who died during induction therapy, three had liver failure and the fourth suffered pulmonary embolism. These studies provide evidence that combination therapy with MMC and 5-FU increases the survival time of patients with hepatic cancer, presumably due to the synergistic action of these drugs which permits the use of a low dosage schedule and has less toxic effects.

Adult↗
PubMed1977

The effect of 2,4-dichlorophenoxyacetic acid on growth and nitrogen-fixation of blue-green alga Anabaenopsis raciborskii.

Sodium salt of 2,4-dichlorophenoxyacetic acid (80% active ingredient), commonly applied for the control of aquatic weeds, was used to observe its effect on the growth and nitrogen fixation of a heterocystous bloom forming blue-green alga Anabaenopsis raciborskii. A concentration of 10 microgram per ml of 2,4-D showed stimulation of growth and nitrogen fixation and these were almost unaffected in presence of its 100 microgram per ml in the medium. The alga could tolerate up to 800 microgram per ml in liquid culture media with and without nitrate nitrogen and up to 90 microgram per ml on to agar plates. Nitrogen fixation was inhibited in presence of its higher concentrations.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1977

Controlled trial of the effect of cycloalliin on the fibrinolytic activity of venous blood.

Cycloalliin is a natural constituent of onion, sulphur-containing but odourless. It was synthesised for this randomised double-blind study; its effect on fibribolytic activity and platelet aggregability was tested in venous blood from 18 male volunteers. It increased the former to a highly significant degree but had no effect on the latter. It was well tolerated and harmless in the single oral dosage used.

Adult↗
PubMed1976

Carbon dioxide homeostasis during laparoscopy.

Arterial blood gases were monitored in ten patients undergoing laparoscopy for diagnostic or sterilization procedure. During constant volume of ventilation, mean arterial co2 tension rose approximately 5 torr following insufflation of the peritoneal cavity with carbon dioxide. Arterial pH changes correlated well with arterial Pco2 changes. There was no significant change of oxygen tension in these patients.

Adult↗
PubMed1976

Isolation, growth and nitrogen fixation of a gas vacuole-less mutant of the blue-green alga Anabaena aphanizomenoides.

Mutants with loss of gas vacuoles (GVL-) were isolated from a clonal population of the gas vacuole containing (GVL+) blue-green alga Anabaena aphanizomenoides with a spontaneous mutation frequency of 1.7 x 10(-3) in nitrogen-free media. Growth and nitrogen fixation of the mutant were slow when compared to the GVL+ parent. Both the parent and mutant filaments tolerated 0.02 microgram/ml of streptomycin, and higher concentrations were lethal. The reversion of the mutant towards the parent did not occur.

Cyanobacteria↗
PubMed1975

Variability in structural carbohydrates and in vitro digestibility of forages. 3. Guar (Cyamopsis tetragonoloba).

Thirteen genotypes of guar (Cyamopsis tetragonoloba) were compared with the local variety for structural carbohydrates and in vitro digestibility. Neutral detergent fiber, acid detergent fiber, lignin, and acid insoluble ash varied 31.2 to 44.4, 26.1 to 37.4, 6.8 to 11.1, and .30 to 1.11%. Cellulose varied from 16.6 to 28.1% whereas hemicellulose content ranged between 3.6 and 9.2%. In vitro digestibility of dry matter ranged between 62.8 to 71.2% Variation in protein, mineral matter, and percentage of dry matter was from 12.7 to 19.7, 9.4 to 12.3, and 23.0 to 26.7. Neutral detergent fiber and lignin plus silica were correlated negatively with in vitro digestibility of dry matter. A genetic manipulation of breeding material can bring about a highly nutritive genotype of guar.

Animal Feed↗