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Biomedical subjects

M Das

Publications and source records attributed to M Das.

At least 307 records · Page 17Linked to original sources
PubMed1979

Internalization and processing of the EGF receptor in the induction of DNA synthesis in cultured fibroblasts: the endocytic activation hypothesis.

The addition of EGF to cultured murine 3T3 cells produces a decrease in EGF binding activity with concomitant internalization and degradation of the initially bound EGF. When the EGF receptor on cultured 3T3 cells is affinity labeled with high specific activity 125I-EGF, and the fate of the affinity labeled EGF-receptor complex determined, the loss in binding activity was accounted for by receptor internalization and subsequent proteolytic processing of the EGF receptor molecules in the lysosomes. Studies of the effects of EGF concentration on EGF binding by cells, EGF-induced receptor internalization and EGF-induced stimulation of 3H-thymidine uptake into cellular DNA show that there is a direct correlation between EGF-induced receptor internalization and EGF-induced stimulation of DNA synthesis, but not between EGF binding and EGF-induced stimulation of DNA synthesis. This correlation is lost at high EGF concentrations, where stimulation of DNA synthesis is suboptimal. Optimal stimulation of DNA synthesis requires a minimum of 6 h of incubation of EGF with cells, and the suboptimal stimulation of DNA synthesis at high EGF concentration is intensified when the period of incubation of EGF with cells is less than 6 h. These data are consistent with a model of hormone signal transmission by Endocytic Activation, wherein the activation of EGF-induced processes requires constant EGF-induced internalization of receptor for a requisite 6-8 h period as an obligatory step in production of "second messenger" in the action of this hormone.

Animals↗
PubMed1979

Neonatal mononuclear cell metabolism: further evidence for diminished monocyte function in the neonate.

The metabolic capacity of neonatal monocytes was compared to the metabolic capacity of adult monocytes by two entirely different methods: the selective diminution of monocyte contamination of whole mononuclear cells and the isolation of relatively purified populations of monocytes. Monocyte removal from whole mononuclear cells produced a diminution in the pyruvate kinase (PK) activity (from 28.6 +/- 1.1 to 15.6 +/- 1.2 nmoles/min/10(7) cells) and an increase in adenosine triphosphate (ATP) content (from 7.9 +/- 1.0 to 9.5 +/- 0.8 nmoles/10(7) cells) in adult cells. No change in PK activity (from 13.5 +/- 1.3 to 14.0 +/- 1.3) was observed in cord cells, but the ATP content of cord cells was higher after monocytes depletion (from 4.7 +/- 0.5 to 6.2 +- 0.7). The suggestion of metabolic vulnerability was confirmed by metabolic analysis of isolated adult and cord monocytes. The PK activity of adult monocytes was greater than that of cord monocytes (57 +/- 9 and 25 +/- 0.3, respectively) and the ATP content of adult monocytes (5.7 +/- 0.2) was greater than that of cord monocytes (2.3 +/- 0.1). The data confirm prior observations of diminished energy metabolism in neonatal mononucler cells and suggest that the metabolic perturbations may, in part, correlate with functional immaturity of the neonatal monocyte.

Adenosine Triphosphate↗
PubMed1979

Serratus anterior paralysis in the young athlete.

Ten cases of isolated, complete paralysis of the serratus anterior muscle were diagnosed in young athletes during a three-year period. One patient had recurrent partial paralysis of the serratus anterior muscle, the first such case reported. From studies on cadavera and clinical observations, we concluded that paralysis of the serratus anterior muscle results from a traction injury to the long thoracic nerve of Bell. Since full recovery usually occurs in an average of nine months, surgical methods of treatment should be reserved for patients in whom function fails to return after a two-year period. Non-strenuous use of the involved extremity with avoidance of the precipitating activity, followed by exercises designed to maintain the range of motion of the shoulder and to increase the strength of associated muscles, is advocated for treatment of acute or repetitive injuries to the long thoracic nerve of Bell.

Adult↗
PubMed1978

Metal chelates as anti-cancer agents. II cytotoxic action of palladium and platinum complexes of 6-mercaptopurine and thioguanine.

The metal complexes Pd(MP)2.2H2O, Pt(MP)2H2O (MPH=6-mercaptopurine), Pt(AMP2.3H2O and Pd3(AMP)4Cl2(AMPH).4H2O (AMPH=thioguanine) have been isolated. They were screened for anti-tumour activity in the L-1210 lymphoid leukaemia test system in mice. All 4 show marked anti-tumour activity, the complex Pt(AMP)2.3H2O giving a T/C of 185 at the optimum dosage. However, the anti-tumour activity of the metal complexes is somewhat less than that shown by the parent purines under the same conditions.

Animals↗
PubMed1978

Molecular mechanism of mitogen action: processing of receptor induced by epidermal growth factor.

An affinity labeling technique used previously for identification of a membrane receptor for epidermal growth factor (EGF) was exploited to investigate the physiological fate of receptor after binding of EGF. Incubation of affinity-labeled cells at 37 degrees resulted in a time-dependent loss of radioactivity from the EGF-receptor covalent complex (M(r) 190,000). Ninety percent of the radioactivity lost from the band of M(r) 190,000 during a 1-hr incubation at 37 degrees appeared in three bands of M(r) 62,000, 47,000, and 37,000. The crosslinked EGF-receptor complex (M(r) 190,000) on intact cells was accessible to the action of trypsin at 4 degrees and cofractionated with the plasmalemmal fraction. The proteolytic processing products of receptor were inaccessible to trypsin and banded with the lysosomal fraction upon subcellular fractionation. The rate of internalization and proteolytic processing of radiolabeled receptor was the same as the rate of reduction of binding activity induced by EGF. A study of the relationship between EGF-induced receptor internalization and processing, and stimulation of DNA synthesis, showed that both these processes were half-maximally stimulated at approximately 0.1 nM EGF, a concentration at which only 10% of the receptor sites are occupied. These data indicate that at concentrations of EGF subsaturating for binding but optimal for biological activity, there is a slow, continuous process of receptor internalization and degradation which could be limiting for EGF-induced mitogenesis.

Cell Line↗
PubMed1978

Enhancement by oxotremorine of acetylcholine release from the rat phrenic nerve.

Oxotremorine (10.5 micron) produced a paralytic effect on twitch responses of rat diaphragm in vitro to direct and indirect stimulation. 2 The paralytic effect of oxotremorine was absent when the diaphragm was stimulated directly in the presence of hemicholinium-3 (0.42 mM), at a time when twitch responses to indirect stimulation ceased completely. 3 Oxotremorine, at two different pharmacologically active doses, strikingly increased the resting as well as electrically evoked release of acetylcholine into the bathing fluid from the phrenic nerve-diaphragm preparation. 4 This presynaptic effect of oxotremorine may explain its pharmacological effects at the cholinergic synapses studied so far.

Acetylcholine↗
PubMed1978

Affinity labeling of a cell surface receptor for epidermal growth factor.

The membrane receptor for epidermal growth factor (EGF) on 3T3 cells has been identified and specifically labeled radiochemically using a photoreactive derivative of EGF. Photoreactive EGF, labeled with 125I, was incubated with 3T3 cells and then photolyzed in situ to generate a nitrene capable of reacting with a wide variety of chemical bonds. Analysis of the system by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed, besides the band of EGF, only 1 other major radioactive band which migrated at approximately 190,000 daltons. This band was absent when a nonresponsive and nonbinding variant of 3T3 was used. A direct proportionality between binding activity and crosslinked complex formation was demonstrated using a variety of binding conditions. The crosslinked complex in intact cells is accessible to the action of a macromolecule like trypsin at 4 degrees, suggesting a cell surface location for this complex. Upon incubation of cells at 37 degrees, radioactivity from previously formed EGF-receptor crosslinked complex is converted by cellular action to 3 forms of mol wt less than or equal to 58,000 daltons. These are not accessible to trypsin action upon intact cells.

Affinity Labels↗
PubMed1978

Levamisole and mebendazole in the treatment of bancroftian infection.

Levamisole and mebendazole, broad spectrum anthelminthic compounds were tested against microfilaria of Wuchereria bancrofti, and the results were compared with similarly treated diethylcarbamazine and untreated group. Levamisole at a dosage of 3 mg/kg daily for 8 days showed marked reduction in both microfilaria rate and microfilaria density and immediately thereafter mf-rate steadily increased almost up to pre-treatment level, the mf-density however showed only marginal increase. Mebendazole at dosage of 6 mg/kg daily for 10 days following 8 days treatment of levamisole also showed marginal increase of mf-rate but no increase of mf-density. Treatment with DEC at a dosage of 6 mg/kg daily for 12 days showed comparatively better results both in respect of reduction in mf-rate and mf-density. The reactions - severity and duration were more among levamisole treated groups as compared to DEC treated group. Thus with the dosages tried, DEC could be considered as a better drug than levamisole and mebendazole. Both the latter compounds had no or very limited effect on the adult worms of W. bancrofti.

Benzimidazoles↗
PubMed1978

Shy-Drager syndrome.

Explore the source record for details and available documents.

Autonomic Nervous System↗
PubMed1977

Serum angiotensin-converting enzyme. Isolation and relationship to the pulmonary enzyme.

Angiotensin-converting enzyme from rabbit serum was purified almost 60,000-fold to apparent homogeneity by a procedure exploiting its affinity for antibodies prepared against the enzyme from lung. The pure serum and pulmonary enzymes exhibited identical behavior during gel filtration, sucrose gradient centrifugation, and disc gel electrophoresis in the reduced, denatured state. Their catalytic properties with hippurylhistidylleucine, angiotensin I, and bradykinin as substrates were similar and their reactivity with antilung enzyme antibody was indistinguishable as examined by immunodiffusion, inhibition dose-response curves, and radioimmunoassay. Their content of fucose, mannose, galactose, and N-acetylglucosamine was also comparable; however, N-acetylneuraminic acid was much more abundant in the serum glycoprotein. This difference may reflect selective removal of sialic acid-deficient enzyme molecules from the circulation by the hepatic lectin which has been postulated to initiate the catabolic phase for plasma glycoproteins (Ashwell, G., and Morell, A.G. (1974) Adv. Enzymol. Relat. Areas Mol. Biol. 41, 91-128).

Animals↗