M. V. Usha Rani

Polarity and temporality of high-resolution y-chromosome distributions in India identify both indigenous and exogenous expansions and reveal minor genetic influence of Central Asian pastoralists.

Although considerable cultural impact on social hierarchy and language in South Asia is attributable to the arrival of nomadic Central Asian pastoralists, genetic data (mitochondrial and Y chromosomal) have yielded dramatically conflicting inferences on the genetic origins of tribes and castes of South Asia. We sought to resolve this conflict, using high-resolution data on 69 informative Y-chromosome binary markers and 10 microsatellite markers from a large set of geographically, socially, and linguistically representative ethnic groups of South Asia. We found that the influence of Central Asia on the pre-existing gene pool was minor. The ages of accumulated microsatellite variation in the majority of Indian haplogroups exceed 10,000-15,000 years, which attests to the antiquity of regional differentiation. Therefore, our data do not support models that invoke a pronounced recent genetic input from Central Asia to explain the observed genetic variation in South Asia. R1a1 and R2 haplogroups indicate demographic complexity that is inconsistent with a recent single history. Associated microsatellite analyses of the high-frequency R1a1 haplogroup chromosomes indicate independent recent histories of the Indus Valley and the peninsular Indian region. Our data are also more consistent with a peninsular origin of Dravidian speakers than a source with proximity to the Indus and with significant genetic input resulting from demic diffusion associated with agriculture. Our results underscore the importance of marker ascertainment for distinguishing phylogenetic terminal branches from basal nodes when attributing ancestral composition and temporality to either indigenous or exogenous sources. Our reappraisal indicates that pre-Holocene and Holocene-era--not Indo-European--expansions have shaped the distinctive South Asian Y-chromosome landscape.

Genetic structure and affinities among tribal populations of southern India: a study of 24 autosomal DNA markers

We describe the genetic structure and affinities of five Dravidian‐speaking tribal populations inhabiting the Nilgiri hills of Tamil Nadu, in south India, using 24 autosomal DNA markers. Our goals were: (i) to examine what evolutionary forces have most significantly impacted south Indian tribal genetic variation, and (ii) to test whether the phenotypic similarities of some south Indian tribal groups to Africans represent a signature of close relationship to Africans or are due to convergence. All loci were polymorphic and average heterozygosities were substantial (range: 0.347–0.423). Genetic differentiation was high (Gst= 6.7%) and genetic distances were not significantly correlated with geographic distances. Genetic drift therefore probably played a significant role in shaping the patterns of genetic variation observed in southern Indian tribal populations. Otherwise, analyses of population relationships showed that Indian populations are closely related to one another, regardless of phenotypic characteristics, and do not show particular affinities to Africans. We conclude that the phenotypic similarities of some Indian groups to Africans do not reflect a close relationship between these groups, but are better explained by convergence.

DNA Sequence Variation and Haplotype Structure of the ICAM1 and TNF Genes in 12 Ethnic Groups of India Reveal Patterns of Importance in Designing Association Studies

We have examined the patterns of DNA sequence variation in and around the genes coding for ICAM1 and TNF, which play functional and correlated roles in inflammatory processes and immune cell responses, in 12 diverse ethnic groups of India. We aimed to (a) quantify the nature and extent of the variation, and (b) analyse the observed patterns of variation in relation to population history and ethnic background. At the ICAM1 and TNF loci, respectively, the total numbers of SNPs that were detected were 28 and 12. Many of these SNPs are not shared across ethnic groups and are unreported in the dbSNP or TSC databases, including two fairly common non‐synonymous SNPs at positions 13487 and 13542 in the ICAM1 gene. Conversely, the TNF‐376A SNP that is reported to be associated with susceptibility to malaria was not found in our study populations, even though some of the populations inhabit malaria endemic areas. Wide between‐population variation in the frequencies of shared SNPs and coefficients of linkage disequilibrium have been observed. These findings have profound implications in case‐control association studies.

In vitro effect of fenthion on human lymphocytes

Fenthion is an organophosphorus insecticide which is extensively used in control of leaf hoppers, cutworms, mites on vegetable crops. It has been reported that organophosphorus pesticides cause a significant increase in sister chromatid exchanges in mammalian cell lines. A significant increase of chromosomal aberrations has been reported in rural population exposed to pesticides. Organosphosphorus pesticides malathion, diazinon, dimethoate, phosdrin and dursban induced sister chromatid exchanges in human lymphoid cells. Exchange type of aberration has been reported in fluoriculturist who were exposed to organophosphorus, organochlorine pesticides. In the present investigation an attempt has been made to evaluate the cytogenetic effect of fenthion in human lymphocyte cultures in vitro.

Cytogenetic monitoring of men occupationally exposed to airborne pollutants.

A study of structural chromosomal aberration frequencies in peripheral blood lymphocytes was performed in a group of 20 professional drivers exposed to airborne pollutants and 20 matching controls. The subjects in the latter group were of the same sex (males) and of similar age as the exposed ones, and also had similar habits of smoking and alcohol. A statistically significant increase of chromosomal aberration was observed in the exposed subjects over the control group. An increasing trend of aberrations was observed with the duration of service (exposure) in the exposed individuals. This study clearly indicates the effect of occupational exposure to airborne pollutants.

Demographic Variations Influence Obesity in a Semi-urban Cohort of Tamil Nadu, South India

Abstract This case control study identified certain definite factors influencing obesity and dyslipidemia in semiurban subjects aged between 20 and 44 years of age. Obese cases (n= 177,) and controls (n = 166) were recruited by random sampling method and categorised into three age groups. The mean BMI, WHR and TGL were highest in obese subjects aged between 37 to 44 years. The mean TC levels (181.43 mg/dl) and mean TGL levels (180.29 mg/dl) were higher in vegetarians than in non-vegetarians. Further, the mean TGL levels (183.86 mg/dl) were highest in subjects who used hydrogenated vegetable oil as a cooking medium. TGL was derived as the most significant variable for dyslipidemia in the study cohort (r2 = 0.838,) with WHR, alcoholism, smoking, TC, LDL, HDL, FBG, and LDL/ HDL ratio as predictor variables.