Environmental cancer in the Indian context

There is increasing global concern on the upward trend of cancer attributable to environmental causes. This has found articulate expression in the intensive action programme initiated in developed countries to carry out systematic epidemiological surveillance studies on environmental based cancer, to conduct both short-term and long-term studies on experimental animals on the mechanism of induction and to search for preventive measures. Of all environmental agents, chemicals which have been introduced by man have received the maximum attention on account of the fact that besides functioning per se as carcinogens, many chemicals can play roles of synergists, promotors, or procarcinogens. The total number of chemicals in wide use today will be more than a million but hardly a thousand of them has been subjected to the vigorous three animal safety evaluation according to Brigg. Developmental programmes initiated in post-independence India in the last three decades include industrialisation and modernisation of agriculture. So far as industrialisation is concerned, the major units have grown round certain urban centres or in settlements which have become identifiable pockets of high levels of air and water pollution. Data on air pollution inventory provided by NEERI and other agencies indicate a high content of polycyclic hydrocarbons, including 3,4-benzpyrenes especially in Bombay and Calcutta. The marginal health surveys conducted in these metropolitan cities have attempted only correlation between high incidence of respiratory disorders to particulate or gaseous pollutants. The modernisation of agriculture, particularly boosting of farm productivity, involves greater and greater use of past control chemicals and synthetic fertilisers. Chlorinated pesticides are also being used in massive quantities for controlling vector-borne epidemics. The evidence for an unusually high body burden of organochlorine pesticide residues in Indians has been documented. Many of them have been shown to be carcinogenic to experimental animals. Relatively high levels of residues of organochlorine have been detected in placentae, cord blood, and breast milk. The presence of high levels of suspected particulate matter (SPM) made up of industrially released pollutant in industrial areas, or air-borne pollens and microbial or fungal spores or the minute fugitive dust particles is also a problem of concern to us in this country. Besides health effects caused by them per se, they can act as nuclei for absorption of NO2 released from industrial activity or from bacterial reduction of nitrate fertilisers. Ideal matrices are formed for chain photochemical reaction triggered by solar or other cosmic irradiation giving rise to nitrosamines, free radicals, etc. Water used for potable purposes in some rural areas has been shown to contain relatively high nitrate and nitrite content. Occupational exposure to carcinogenic chemicals has also received some attention. Sporadic surveys have been conducted for the ulceration of the nose and septum in workers handling chromate salts (valency vi) or bladder tumors in anthracene dyes. Detailed analysis of environment related morbidity and mortality data has not yet been attempted to build models for the purpose of predictive epidemiology. Welders are exposed to fumes of heavy metals including those of chromium and nickel. The intake of nickel through leafy vegetables and hydrogenated vegetable oils has been considered as one possible source of bioaccumulation of this carcinogenic metal. In the absence of data banks or registry of reliable morbidity/mortality data in humans, the Industrial Toxicology Research Centre has made a partial survey of the dust load of lungs of food animals killed in abbatoirs in the industrial and mining areas of Bihar and West Bengal. Blocking of lymph nodes by dust has been observed in most of the animals and analysis of the dust collected from lung by X-ray fluorescence spectroscopy has revealed the presence of many toxic metals. The Outdoor Occupational Clinic run by the Industrial Toxicology Research Centre in ESI Hospital at Kanpur has recorded cases of skin allergy due to chromium

Differentiation of pathogenic amoebae: encystation and excystation ofacanthamoeba 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 amoebaAcanthamoeba 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 enzymesviz. 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

Determination of leucine metabolism and protein turnover in sheep, using gas-liquid chromatography-mass spectrometry

1. Whole-body protein synthetic rates in non-pregnant ewes were determined by the continuous infusion of L-[15N]- and [1-13C]leucine and measuring the plasma enrichment of leucine, α-ketoisocaproate (α-KIC) and expired carbon dioxide by gas-liquid chromatography-mass spectrometry. 2. The mean whole-body protein synthesis estimated from plasma leucine flux corrected for oxidation was 5.38 (SE 0.54) g/kg per d. 3. Under the conditions of the present study leucine oxidation was 0.323 (SE 0.067) mmol/kg per d and accounted for 10.71 (SE 2.26) % of plasma [13C]leucine flux. Deamination of leucine was 0.55 (SE 0.035) mmol/kg per d and accounted for approximately 17% of plasma [15N]leucine flux. 4. The rate of a-KIC reamination to leucine, calculated by subtracting 13C flux from 15N flux, was 0.228 (SE 0.101) mmol/kg per d. 5. The rate of whole-body protein degradation was 4.49 (SE 0.54) g/kg per d and there was a net protein gain of 0.89 (SE 0.21) g/kg per d

A systems approach to the control of chemical disasters

A systems approach is suggested for interlinking the three main components of a chemical accident: the event, the target and the effects. Such an approach helps in identifying information gaps vitally needed for establishing cause-effect relationship, forassessing risks from continuing or long term effects and for developing preventive measures for reducing injury from chemical accidents. Feasible classification modes of accidents such as during production, processing, distribution, transport and dismissal can be conveniently incorporated. Contingency and rehabilitation plans can be put in proper perspective so that the support infrastructure needed can be established and updated. Areas of research to be pursued on proirity basis to get feedback on methods for assessing risks can be delineated along with programmes for the development of the required technical manpower

An alternate pathway for bilirubin catabolism

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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

Growth inhibitory action of saccharin and cyclamate on rats receiving a poor rice diet

1. The effect of saccharin and cyclamate on growth of young rats fed on a poor rice diet or a balanced diet was investigated. 2. Saccharin and cyclamate retarded the growth of rats on the multi-deficient diet but not of those on the well-balanced diet during an 8-week feeding period. 3. The sweeteners did not produce any macroscopic or microscopic changes in the liver, kidneys, intestines, spleen or lungs of the animals receiving the poor rice diet other than the changes resulting from the nutritional deficiency of the diet. 4. The sweeteners did not inhibit the liver xanthine oxidase activity of rats receiving the poor rice diet to an extent greater than the inhibition brought about by the deficiency of protein in the diet. 5. When given by intubation to healthy rats, the sweeteners inhibited the induction of liver tryptophan oxygenase; given in vitro, they inhibited the succinate dehydrogenase activity of rat liver mitochondria

Evidence for the possible involvement of the superoxide radicals in the photodegradation of bilirubin

The photodecomposition of bilirubin follows first order kinetics with ak B value of 12.5 × 10-3 min-1. In the presence of a model system generating superoxide anions, such as xanthine-xanthine oxidase, the k B value was 103 × 10-3 min-1 This ten-fold enhancement ofk B 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 β -carotene and bistidine did not prevent the enhancement of bilirubin oxidation by xanthine-xanthine 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

Setaria cervi: enzymes of glycolysis and PEP-succinate pathway

Setaria cervi, the filarial parasite inhabiting the Indian water buffalo (Bubalus bubalis Linn.) contained almost all the enzymes involved in glycogen degradation. Significant activities of glycogen phosphorylase, glucokinase, phosphoglucomutase, phosphoglucose isomerase, phosphofructokinase, FDP-aldolase, glyceraldehyde-3-phosphate dehydrogenase, phosphopyruvate hydratase, pyruvate kinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were detected in cell-free extracts of whole worms. The presence of PEP-carboxykinase, malate dehydrogenase, fumarase and fumarate reductase revealed the functioning of the PEP-succinate pathway in addition to phosphorylating glycolysis and pentose phosphate pathway in the parasite. Excepting fumarate reductase all other enzymes were localized in the particulate-free cytosol fraction, although small amounts of glycogen phosphorylase, aldolase and lactate dehydrogenase were also detected in the mitochondrial fraction