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Biomedical subjects

M Das

Publications and source records attributed to M Das.

At least 343 records · Page 19Linked to original sources
PubMed1968

Red drop in the quantum yield of fluorescence of sonicated algae.

The change of the quantum yield of fluorescence, Phi, with the frequency of exciting light, was investigated in Chlorella, Anacystis, and Porphyridium suspensions, and in sonicates from these cells prepared under aerobic and anaerobic conditions. In case of Chlorella, sonicates were made in acid and in alkaline media (pH 4.65 and 7.80). In the alkaline medium, a drop of Phi towards the longer waves was found to begin at 1.466 x 10(4) cm(-1) (682 nm) in sonicates, and in suspension. In the acid medium, the drop began at 1.471 x 10(4) cm(-1) (680 nm), 1.418 x 10(4) cm(-1) (705 nm), and 1.389 x 10(4) cm(-1) (720 nm) in suspension, anaerobic sonicate, and aerobic sonicate, respectively. The results indicate that the cause of the change in the red drop is preferential destruction of a long-wave component of chlorophyll a (such as Chl a 693). The amount of this component remaining after sonication is larger in alkaline than in acid sonicates. With Anacystis and Porphyridium, only alkaline suspensions (pH 7.80) could be used for sonication, because in acid medium, the phycobilin-chlorophyll complex is rapidly broken and phycobilin extracted from the cell. In Anacystis, the red drop begins at 1.562 x 10(4) cm(-1) (640 nm) and 1.538 x 10(4) cm(-1) (650 nm) in suspension and sonicate, respectively; in Porphyridium, it starts at 1.550 x 10(4) cm(-1) (645 nm) in both cases. These results suggest that sonication in alkaline medium (pH 7.80) destroys some Chl a 693 in Anacystis, but not in Porphyridium.

Eukaryota↗
PubMed1967

Sterilization of Culex pipiens fatigans Wiedemann by apholate.

The use of alkylating agents has been found to be a promising way of chemosterilizing mosquitos for control purposes. The investigation discussed in the present paper has shown that apholate (2,2,4,4,6,6-hexahydro-2,2,4,4,6,6-hexakis (1-aziridinyl)-1,3,5,2,4,6-triazatriphosphorine) can induce sterility rates of from 43% to 95% in Culex pipiens fatigans Wiedemann treated in the larval stage, and from 80% to 100% in C. fatigans treated in the adult stage; treatment in the pupal stage produced no significant sterility.Of the methods of application of the apholate tested (immersion of larvae and pupae in water containing apholate, exposure of anaesthetized adults to residual deposits of apholate and dusting of anaesthetized adults with apholate powder), the dusting method was found to be effective.Apholate induces sterility in both sexes. Females were affected much more when they were treated in the adult stage. The average number of eggs laid by a treated female was found to be reduced no matter whether the treatment was during the larval or the adult phase.Male mosquitos chemosterilized by dusting were more competitive than normal males.

Alkylating Agents↗
PubMedDate not supplied

Effect of oral and parenteral administration of metanil yellow on some hepatic and intestinal biochemical parameters.

Metanil yellow, a non-permitted colour for food commodities, is used in the leather, paper and textile industries. In this paper the effect of oral and parenteral administration of Metanil yellow on hepatic and intestinal biochemical parameters was investigated. Oral administration of Metanil yellow (430 mg kg-1 body wt.) for 7 days caused significant depletion of hepatic and intestinal glutathione levels (33-52%) with a concomitant increase in lipid peroxidation (49-121%). Metanil yellow treatment for 7 days also led to a significant increase in cytochrome P-450 (P-450)-dependent aryl hydrocarbon hydroxylase (AHH) activity (99-223%) in the liver and intestine. Cytosolic glutathione-S-transferase (GST) (32-136%) and quinone reductase (QR) (20-92%) activities were also found to be substantially induced in hepatic and intestinal tissues following oral treatment of Metanil yellow. It is interesting to note that oral treatment of Metanil yellow showed a greater response in cytosolic enzymes of hepatic tissue as compared to intestine. Single parenteral administration of Metanil yellow (80 mg kg-1 body wt.) caused significant induction of P-450 and its dependent monooxygenases. Even after 5 days of single parenteral administration of Metanil yellow, hepatic AHH activity showed an elevation of 48% while other monooxygenases were marginally increased. Cytosolic GST and QR showed respective peak inductions of 92% and 60% after 2 and 3 days of parenteral administration of Metanil yellow, which levels off after the 5th day. It can be concluded that Metanil yellow acts as an inducer of a specific form of microsomal P-450 and cytosolic GST and QR, which may involve a cytosolic Ah receptor.

Administration, Oral↗
PubMedDate not supplied

A sensitive neutron dosimeter using superheated liquid.

The present work relates to a sensitive neutron dosimeter, a device for monitoring neutron dose in some accelerator and reactor sites. This device is capable of measuring a neutron dose as small as 0.1 microSv using superheated liquid as a sensitive liquid. The nucleation was measured by the volumetric method developed in our laboratory. The dose response of superheated drops of four liquids having boiling points of 8.92, -29.79, -40.75 and -45.6 degrees C, irradiated by a 3 Ci Am-Be neutron source has also been presented in this article.

Chlorofluorocarbons, Methane↗
PubMedDate not supplied

42,000-molecular weight EGF receptor has protein kinase activity.

The epidermal growth factor (EGF) receptor and other growth factor receptors have been shown to possess tyrosine-specific protein kinase activity. Before the demonstration of kinase activity in growth factor receptors, tyrosine kinases of molecular weight (MW) 60,000 (60K) were found to be encoded by the src oncogene and other oncogenes related to src. Our earlier work on intracellular processing of the EGF receptor, a 170,000-MW polypeptide, provided evidence for proteolytic separation of well defined structural domains, and suggested to us the possibility of separating functional domains by limited proteolysis. The isolation of such kinase domains should facilitate comparison of the receptor/kinase with other well characterized kinases including those of oncogene origin. We report here the identification of a catalytically functional 42K kinase derived proteolytically from the isolated human EGF receptor. This fragment, comparable in size to pp60src, carries the kinase ATP-binding site, and functions catalytically even after detachment from the EGF-binding site and the major autophosphorylation region.

Adenosine Triphosphate↗
PubMedDate not supplied

EGF receptor-associated DNA-nicking activity is due to a Mr-100,000 dissociable protein.

The receptor for epidermal growth factor (EGF) is a single-chain transmembrane polypeptide of relative molecular mass (Mr) 170,000 (170K) which has been implicated in the regulation of both normal and abnormal cell proliferation. It has an externally facing EGF-binding domain and a cytoplasmically facing tyrosine-specific protein kinase site. Although the receptor has been well characterized, the mechanism by which it transmits the growth stimulatory signal from the plasma membrane to the nucleus is unclear. EGF binding to cells has been shown to enhance topoisomerase activity within the cells. Topoisomerases catalyse the interconversion of topological isomers of DNA and thus may influence replication and transcription. Mroczkowski et al. reported that purified EGF receptors of both human and murine origin can nick supercoiled double-stranded (ds) DNA in an ATP-dependent fashion, an activity related to those of topoisomerases. Another related tyrosine kinase, pp60src, has also been reported to have a similar DNA-nicking activity. We have now characterized the EGF receptor-associated DNA-nicking activity by sucrose gradient centrifugation. Our results, presented here, indicate that the DNA-nicking activity is not intrinsic to the EGF receptor, but is found in a distinct molecular species.

DNA Topoisomerases, Type I↗