Evaluation of Role of Heavy Metals in Causation of Colorectal Cancer

Over last two decades, there is increasing incidence and high prevalence of colorectal cancer in young Indians, who are mostly from rural environment with a very low socio-economic condition, consuming a diet low in meat, fat, but rich in carbohydrate and fiber with a normal or less than normal body weight. These facts have clearly indicated a completely separate epidemiological profile of this cancer in our country and so may be caused by some different and unknown etiological factors. West Bengal and Bangladesh (the Gangetic belt) are quite developed in agriculture and to some extent in industry as well. This implies a significant contamination of drinking water for this large population with industrial wastes containing heavy metals. As many of the heavy metals (lead, chromium, cadmium) have proved to be associated with gall bladder cancer in our country and heavy metal poisoning (arsenic) is common in this geographical region, we searched for the effect of some heavy metals in causation of colorectal cancer here.METHODSOur case-control study compared the tissue levels of two heavy metals namely arsenic and lead. In a city government hospital of Kolkata (eastern India), 50 sporadic colorectal cancer patients were compared with 100 age and sex matched benign colorectal cases over a period of one and half years. Quantitative estimation of arsenic and lead in colonic tissues by atomic absorption spectrophotometry was done to detect any significant difference between these two groups.RESULTSOur study did not find any statistically significant difference in the tissue levels of arsenic and lead between the cases and controls (p value >0.05).CONCLUSIONSOur study does not show any association of heavy metals with colorectal cancer, although this remains a possibility. We do not have any population-based reference data on levels of heavy metals in tissues of normal population in this geographic region, which made the comparison difficult.

Bilaterally symmetric Fourier approximations of the skull outlines of temnospondyl amphibians and their bearing on shape comparison.

Present work illustrates a scheme of quantitative description of the shape of the skull outlines of temnospondyl amphibians using bilaterally symmetric closed Fourier curves. Some special points have been identified on the Fourier fits of the skull outlines, which are the local maxima, or minima of the distances from the centroid of the points at the skull outline. These points denotes break in curvature of the outline and their positions can be compared to differentiate the skull shapes. The ratios of arc-lengths of the posterior and lateral outline of 58 temnospondyl skulls have been plotted to generate a triaguarity series of the skulls. This series grades different families, some of their genera and species as well as some individuals according to their posterior and lateral skull length ratios. This model while comparing different taxa, takes into account the entire arc-length of the outline of the temnospondyl skulls, and does not depend on few geometric or biological points used by earlier workers for comparing skull shapes.