Environmental cancer in the Indian context--an overview.

Problems related to environmental carcinogenesis have begun to surface with increased industrial activity and diffusion of hazardous chemicals. Cancer Registries maintained in some of our cities can help in retrospectively analysing incidence and related aetiology. Even a casual analysis of the existing data related aetiology. Even a casual analysis of the existing data belies the oversimplicity of the WHO model used in developing countries to asign lower priority to cancer prevention and control than to communicable diseases. Exposure data to environmental inducers of cancer, radiations, chemicals and other stresses is urgently needed. Prevention strategy should be more and more on a scientific base for an early detection and risk estimates of chemical exposures. Sustained environmental monitoring for inducers and cofactors are required. The Factory Act must make provision for appropriate health surveillance of workers over a long period.

Differentiation of pathogenic amoebae: encystation and excystation of Acanthamoeba culbertsoni —A model.

Differentiation into dormant cysts and vegetative trophozoites is an inherent character intimately associated with the life cycle and infectivity of pathogenic amoebae. In the case of human intestinal amoebiasis encystation and excystation are of immediate relevance to the process of transmission of the disease from healthy carriers to susceptible individuals. Using a pathogenic free living amoeba Acanthamoeba culbertsoni as a model, considerable progress has been achieved in understanding the mechanism and control of the process of differentiation. The turnover of the regulatory molecule cyclic 3: ‘5’ adenosine monophosphate is responsible for triggering the process of encystation. Amoebae bind effector molecules such as biogenic amines to a membrane localized receptor which itself resembles the β- adrenergic receptor of mammalian organisms. The activation of adenylate cyclase or inhibition of cyclic AMP phosphodiesterase maintain the dynamic intracellular cyclic AMP. The cytosol fraction of amoebae has a cyclic AMP binding protein. During encystation, enzymes needed for synthesis of cellulose and glycoproteins are induced. Control is exercised at transcriptional level and the process is subject to catabolic repression. Excystation of mature amoebic cysts is mediated by glutamic acid and certain other amino acids by an as yet unelucidated mechanism. During excystation there is dormancy break, induction of deploymerizing enzymes viz. two proteases, a cellulase and a chitinase. The empty cysts or cyst walls are digested by these enzymes and their break down products are used for cellular growth. By invoking a flip-flop mechanism of repression and derepression some plausible explanation can be offered for the cascade of biochemical events that sets in when amoeba is ‘turned on’ to encystation or excystation.

Suppression of auxin stimulated growth of barley coleoptile sections by endosulfan.

Endosulfan, a cyclic sulphurous acid ester commonly used as a broad spectrum insecticide, suppressed the elongation of barley coleoptiles. Indoleacetic acid at optimum concentration overcame the inhibition of growth of coleoptiles treated with 10 ppm endosulfan. However, perfusion of the coleoptile sections with endosulfan and subsequent treatment with indoleacetic acid could not stimulate cell elongation to the extent observed in the control.

Studies on the uptake of benzanthrone by rat skin and its efflux through serum.

The uptake of benzanthrone by rat skin showed saturation kinetics and was dependent upon the weight of skin and time, temperature and pH of the incubation medium. Heating of segments above 50°C caused significant lowering of the uptake. The uptake was irreversibly inhibited by HgCl2 and not by sodium arsenate, KCN, NaF, p-chloromercuriben zoate, N-ethyl-maleimide, cycloheximide, iodoacetic acid and 2,4-dinitrophenol suggesting that the uptake was not energy-dependent. Lipid micelles of the skin accounted for a part of the binding. Most of the benzanthrone taken up by the skin was effluxed through serum proteins.

A rapid method for preparation of sarcolemma from frog skeletal muscle.

A rapid method for the preparation of sarcolema from frog skeletal muscle has been described. The purified cell segments were transparent and devoid of contractile material. The Na+, Κ+ -ATPase and 5'-nucleotidase activities in sarcolemma purified by this method were comparable to those reported for sarcolemmal preparations purified by density gradient centrifugation. The preparation also possessed acid phosphatase, alkaline phosphatase and Κ+-activated, ouabain-sensitive p-nitrophenyl phosphatase activities. The cholesterol to phospholipid ratio of the sarcolemma was 0.33, indicating its high purity; further, the preparation was free from mitochondria and contractile proteins.

Hepatic and extra-hepatic glutathione-S-transferase activity in wild pigeons (Columba livia).

Glutathione-S-transferase (EC 2.5.1.18) activity was assayed in hepatic and extrahepatic tissues of pigeons using l-chloro-2,4-dinitrobenzene and l,2-dichloro-4-nitrobenzene as substrates. Gluthathione-S-transferase activity towards l-chloro-2,4-dinitrobenzene in pigeon was in the order: kidney >liver >testes >brain >lung>heart. The enzyme activity with 1- chloro-2,4-dinitrobenzene as substrate was 40-44 times higher in pigeon liver and kidney than that observed with l,2-dichloro-4-dinitrobenzene as substrate. Km values of hepatic and renal glutathione transferase with l-chloro-2,4-dinitrobenzene as substrate were 2.5 and 3 mM respectively. Double reciprocal plots with varying reduced gluthathione concentrations resulted in biphasic curves with two Km values (liver 0.31 mM and 4mM; kidney 0.36 mM and 1.3 mM). The enzyme activity was inhibited by oxidized gluthathione in a dose-dependent pattern. 3-Methylcholanthrene elicited about 50% induction of hepatic glutathione transferase activity whereas phenobarbital was ineffective.

Evidence for the possible involvement of the Superoxide radicals in the photodegradation of bilirubin.

The photodecomposition of bilirubin follows first order kinetics with a kB value of 12·5 × 10-3 min–1. In the presence of a model system generating superoxide anions, such as xanthine-xanthine oxidase, the kB value was 103 × 10-3 min-1 This ten-fold enhancement of kB value by xanthine-xanthine oxidase was abolished when the reaction mixture was supplemented with a superoxide ion scavenger___ superoxide dismustase. Further, known singlet oxygen quenchers like ß–carotene and bistidine did not prevent the enhancement of bilirubin oxidation by xanthinexanthine oxidase, thereby ruling out the obligatory conversion of superoxide anion to singlet oxygen. It is concluded that radical oxygen mediated bilirubin degradation might be a natural catabolic route for the bile pigment degradation during oxygen stress.