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Biomedical subjects

L Singh

Publications and source records attributed to L Singh.

At least 19 recordsLinked to original sources
PubMed2006

Coat protein gene diversity among Chrysanthemum virus B isolates from India.

The complete coat protein (CP) sequences from 29 Indian isolates of Chrysanthemum virus B (CVB) were determined and analysed in relation to other previously characterized carlaviruses. The CP genes of the Indian CVB isolates were highly heterogeneous, sharing nucleotide sequence identities of 74-98%. Based on phylogenetic analyses, the isolates formed three groups potentially representing either two or three major CVB strain groupings. Recombination analysis revealed at least one definite recombination event involving the exchange of sequences between members of different groups. To our knowledge this is the first reported evidence of homologous recombination in carlaviruses.

Amino Acid Sequence↗
PubMed2006

Unique origin of Andaman Islanders: insight from autosomal loci.

Our mtDNA and Y chromosome studies lead to the conclusion that the Andamanese "Negrito" mtDNA lineages have survived in the Andaman Islands in complete genetic isolation from other South and Southeast Asian populations since the initial settlement of the region by the out-of-Africa migration. In order to obtain a robust reconstruction of the evolutionary history of the Andamanese, we carried out a study on the three aboriginal populations, namely, the Great Andamanese, Onge and Nicobarese, using autosomal microsatellite markers. The range of alleles (7-31.2) observed in the studied population and heterozygosity values (0.392-0.857) indicate that the selected STR markers are highly polymorphic in all the three populations, and genetic variability within the populations is significantly high, with a mean gene diversity of 77%. The Andaman "Negrito" populations do not show particular affinities either with the African populations or with the Indian populations, confirming their unique origin. In contrast, Nicobarese show close affinities with the Southeast Asian populations, suggesting their recent entry in the Islands.

Alleles↗
PubMed2006

Autosomal STR data on the enigmatic Andaman Islanders.

We have analyzed nine autosomal STR loci (D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, and D7S820) in 97 samples of enigmatic Andaman islanders including: 15 Great Andamanese, 46 Onge and 36 Nicobarese. Data was compared with the available data on Indian and South East Asian populations. Heterozygosity (H), power of discrimination (PD), probability exclusion (PE), typical paternity index (TPI), polymorphism information content (PIC), AMOVA and Arlequin analysis were carried out. Average heterozygosity observed was high and almost equal in all the populations. Similarly, PD, PE, TPI and PIC have been almost equal in all the populations.

DNA Fingerprinting↗
PubMed2006

Mutational analysis of the betaglycan gene-coding region in susceptibility for ovarian failure.

BACKGROUND: Elevation of FSH is frequently a consequence of impaired ovarian follicle growth. Down-regulation of the FSH levels by inhibins is mediated through its receptor betaglycan in the gonadotrophs. Understanding of germline status of the betaglycan gene (TGFBR3) is essential for ovarian failure pathophysiology. METHODS: Sequence analysis was performed for the coding region of TGFBR3 gene in a cohort of 196 ovarian failure cases that include 133 premature ovarian failure (POF) cases, 63 primary amenorrhoea (PA) cases compared with 200 controls. RESULTS: Forty-six variants including six novel exonic variants and 16 novel intronic variants were revealed. Two variants were missense: (i) p.Iso184Val in a control and (ii) p.Pro775Ser in a POF case. Genotypic distribution of three variants (c.382-81C>T, c.382-77T>C and c.1200G>A) was significantly different in the patients as compared with the controls. Five variants c.382-81C>T, c.382-77T>C, c.566-216G>A, c.1200G>A and c.2022T>C were chosen for haplotyping. The CCAAT haplotype was significantly higher in the patient population as compared with the controls (P = 0.00007). CONCLUSION: This study establishes the first mutational report of the TGFBR3 gene in correlation with ovarian failure. Significant diversity of genotype distribution and haplotype analysis suggested susceptibility of the TGFBR3 gene for ovarian failure aetiology.

Adult↗
PubMed2006

Association of cathepsin B gene polymorphisms with tropical calcific pancreatitis.

BACKGROUND AND AIMS: Tropical calcific pancreatitis (TCP) is a type of chronic pancreatitis unique to countries in the tropics. Mutations in pancreatic secretory trypsin inhibitor (SPINK1) rather than cationic trypsinogen (PRSS1) explain the disease in only 50% of TCP patients. As cathepsin B (CTSB) is known to activate cationic trypsinogen, we attempted to understand the role of CTSB mutations in TCP. Evidence of epistatic interaction was investigated with the previously associated N34S SPINK1 allele, a variant considered to be a modifier rather than a true susceptibility allele. SUBJECTS AND METHODS: We sequenced the coding region of CTSB gene in 51 TCP patients and 25 controls and further genotyped 89 patients and 130 controls from the same cohort for Leu26Val, C595T, T663C, and Ser53Gly polymorphisms. The positive findings observed in the earlier cohort were re-examined in an ethnically matched replication cohort comprising 166 patients and 175 controls. Appropriate statistical analyses were performed and Bonferroni correction for multiple testing was applied. RESULTS: We found a statistically significant association of the Val26 allele at Leu26Val polymorphism with an odds ratio (OR) of 2.15 (95% confidence interval (CI) 1.60-2.90 (p = 0.009)), after Bonferroni correction (corrected p value = 0.025). This significant association of Leu26Val with TCP was replicated in another cohort (OR 2.10 (95% CI 1.56-2.84); p = 0.013). Val26 allele also showed significantly higher frequency in N34S positive and N34S negative patients than in controls (p = 0.019 and 0.013, respectively). We also found significant differences in the mutant allele frequencies at Ser53Gly and C595T single nucleotide polymorphisms between N34S positive patients and controls (p = 0.008 and 0.001, respectively). Although haplotype analysis did not complement the results of allelic association, it did uncover a unique haplotype protective for TCP (p = 0.0035). CONCLUSION: Our study suggests for the first time that CTSB polymorphisms are associated with TCP. As PRSS1 mutations are absent in TCP and the N34S SPINK1 mutation is proposed to play a modifier role, these variants may be critical as a trigger for cationic trypsinogen activation.

Calcinosis↗
PubMed2006

A to G transitions at 260, 386 and 437 in DAZL gene are not associated with spermatogenic failure in Indian population.

The autosomal DAZL (Deleted-in-Azoospermic-Like) gene, mapped to the short arm of the human chromosome 3, is the precursor for the Y-chromosomal DAZ cluster, which encodes for putative RNA-binding proteins. Mutations in the DAZL have been reported to be associated with spermatogenic failure in Taiwanese population but not in Caucasians. As there was no study on Indian populations, we have analysed the entire coding sequences of exons 2 and 3 of DAZL in a total of 1010 men from Indian subcontinent, including 660 infertile men with 598 non-obstructive azoospermia, 62 severe oligozoospermia and 350 normozoospermic fertile control men, to investigate whether mutation(s) in the DAZL is associated with male infertility. Interestingly, none of our samples (1010) showed A386G (T54A) mutation, which was found to be associated with spermatogenic failure in Taiwanese population. In contrast, A260G (T12A) mutation was observed in both infertile and normozoospermic fertile control men, without any significant association with infertile groups (chi2= 0.342; p = 0.556). Similarly, we have found a novel A437G (I71V) mutation, which is also present in both infertile and normozoospermic fertile control men without any significant difference (chi2 = 0.476; p = 0.490). Our study clearly demonstrates the complete absence of the A386G (T54A) mutation in Indian subcontinent and the other two mutations --A260G (T12A) and A437G (I71V)--observed are polymorpic. Therefore, we conclude that these mutations in the DAZL gene are not associated with male infertility in Indian subcontinent.

Adenine↗
PubMed2006

Novel mitochondrial mutation in the ND4 gene associated with Leigh syndrome.

We analyzed the complete mitochondrial genome of a 3-month-old female child with basal ganglionic lesions and other clinical features suggestive of Leigh syndrome, which is caused by variations in mitochondrial and nuclear genes. Our study revealed a novel, homoplasmic T11984C missense mutation in ND4 gene, which replaces a highly conserved amino acid tyrosine with histidine. Computational analysis showed that this mutation alters the secondary structure of ND4 subunit. As the mutation observed in this study was novel and homoplasmic, we speculate that there could be interplay of this mitochondrial mutation along with nuclear gene(s) in the pathogenesis.

Amino Acid Sequence↗
PubMed2005

STR data for the Amp FlSTR Profiler Plus loci among 27 populations of different social hierarchy from southern part of Andhra Pradesh, India.

Allele frequency for the 9 STR loci (D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820) were estimated from a total of 1096 individuals belonging to 27 endogamous populations from the state of Andhra Pradesh, India, covering the entire gamut of socio-economic variation of the linguistic region. These loci are found to be highly polymorphic within the populations with high levels of average heterozygosity (>0.80). However, the allele frequency distributions are fairly uniform across the populations in case of these loci suggesting relatively greater homogeneity among the populations. Regrouping populations into five broad socio-economic categories further reiterated the homogenous pattern of genetic diversity.

DNA Fingerprinting↗
PubMed2005

Direct immunofluorescence assay for rapid environmental detection of Vibrio cholerae O1.

An immunofluorescence assay for direct detection of V. cholerae O1 was developed using polyclonal antibodies raised against outer membrane proteins (OMPs) of V. cholerae O1. Production of OMPs varied with growth media used; maximum production was found in tryptic soy broth. The detection system was specific because no cross-reactivity was observed with other bacteria including V. cholerae O139, E. coli, S. dysenteriae and Salmonella enterica subsp. enterica serovar Typhi. The technique was able to detect 240 CFU/mL of V. cholerae O1 suspended in phosphate-buffered saline. The assay coupled with bacterial enrichment in APW for 6 h detected as few as 5 CFU of V. cholerae in spiked samples. Moreover, a 2-h incubation of enriched bacterial cells in 0.1% yeast extract with 10 ppm nalidixic acid enhanced the bacterial size and helped in morphological identification of V. cholerae. Among 32 potable water samples from afflicted hand pumps and wells collected from a cholera-plagued area 12 were found to be contaminated with V. cholerae by immunofluorescence assay as well as by conventional culture methods. The proposed method could thus be employed in environmental surveillance of V. cholerae O1.

Antibodies, Bacterial↗
PubMed2005

Major histocompatibility complex class I polymorphism in Asiatic lions.

Asiatic lions (Panthera leo persica), whose only natural habitat in the world is the Gir forest sanctuary of Gujarat State in India, are highly endangered and are considered to be highly inbred with narrow genetic diversity. An objective assessment of genetic diversity in their immune loci will help in assessing their survivability and may provide vital clues in designing strategies for their scientific management and conservation. We analyzed the comparative sequence polymorphism at exon 2 and exon 3 of major histocompatibility complex (MHC) class I in three groups of lions, i.e. wild Asiatic (from Gir forest), captive-bred Asiatic (from zoological parks in India), and Afro-Asiatic hybrid groups (from zoological parks in India) through polymorphism chain reaction-assisted sequence-based typing. The two exons were amplified, cloned, sequenced, and analyzed for polymorphism at nucleotide and putative translated product level. The analysis revealed extensive sequence polymorphism not only between clones derived from different lions but also the clones derived from a single lion. Furthermore, the wild Asiatic lions of Gir forest exhibited abundant sequence polymorphism at MHC class I comparable with that of Afro-Asiatic hybrid lions and significantly higher than that of captive-bred Asiatic lions. We hypothesize that Asiatic lions of Gir forest are not highly inbred as thought earlier and they possess abundant sequence polymorphism at MHC class I loci. During this study, 52 new sequences of the multigene MHC class I family were also identified among Asiatic lions.

Amino Acid Sequence↗
PubMed2004

Mutational analysis of the mature peptide region of inhibin genes in Indian women with ovarian failure.

BACKGROUND: Clinically, premature ovarian failure (POF) is defined as unexplained amenorrhoea (> 6 months) with a high FSH level (> 40 IU) before the age of 40 years. POF is a heterogeneous genetic disease with unknown aetiology. Inhibin and activin regulate the FSH level by their opposing actions and thus have been considered as strong candidate genes in the aetiology of POF. METHODS: We have screened inhibin genes in patients with POF (n = 80), primary amenorrhoea (n = 33) and secondary amenorrhoea (n = 4). RESULTS: INHbetaB and INHbetaA genes do not show any association with ovarian failure. We found the Ala257Thr missense mutation in INHalpha gene with high statistical significance in POF (nine out of 80, 11.2%) (Fisher's exact test, P = 0.0005), primary amenorrhoea (three out of 33, 9.1%) (Fisher's exact test, P = 0.014) and secondary amenorrhoea (two out of four, 50%) (Fisher's exact test, P = 0.001) with complete absence of this mutation in controls (none out of 100). CONCLUSION: The INHalpha gene is a strong candidate gene for ovarian failure. Mutations in INHbetaB and INHbetaA genes are not associated with ovarian failure.

Adolescent↗
PubMed2004

Phylogeography of olive ridley turtles (Lepidochelys olivacea) on the east coast of India: implications for conservation theory.

Orissa, on the east coast of India, is one of the three mass nesting sites in the world for olive ridley turtles (Lepidochelys olivacea). This population is currently under threat as a result of fishery-related mortality; more than 100 000 olive ridleys have been counted dead in the last 10 years in Orissa. In general, the globally distributed olive ridley turtle has received significantly less conservation attention than its congener, the Kemp's ridley turtle (L. kempi), because the latter is recognized as a distinct species consisting of a single endangered population. Our study of mitochondrial DNA haplotypes suggests that the ridley population on the east coast of India is panmictic, but distinct from all other populations including Sri Lanka. About 96% of the Indian population consisted of a distinct 'K' clade with haplotypes not found in any other population. Nested clade analysis and conventional analysis both supported range expansions and/or long-distance colonization from the Indian Ocean clades to other oceanic basins, which suggested that these are the ancestral source for contemporary global populations of olive ridley turtles. These data support the distinctiveness of the Indian Ocean ridleys, suggesting that conservation prioritization should be based on appropriate data and not solely on species designations.

Animals↗
PubMed2004

Absence of PRSS1 mutations and association of SPINK1 trypsin inhibitor mutations in hereditary and non-hereditary chronic pancreatitis.

BACKGROUND AND AIMS: Mutations in the cationic trypsinogen (protease, serine, 1 (trypsin 1); PRSS1) gene are causally associated with recurrent acute and chronic pancreatitis. We investigated whether mutations in the PRSS1 gene are associated with hereditary and non-hereditary pancreatitis. As a modifier role has been proposed for trypsin inhibitor (serine protease inhibitor, Kazal type I; SPINK1) mutations, the role of SPINK1 mutations in these patients was also analysed. SUBJECTS AND METHODS: The coding regions of PRSS1 and SPINK1 genes were sequenced in 290 controls and 198 patients, of whom 120 were diagnosed as idiopathic (ICP), 41 as alcoholic (ACP), and 37 as hereditary pancreatitis (HP). Twenty four unaffected relatives of HP probands were also analysed and genotype-phenotype correlations and statistical analyses were performed. RESULTS: No mutations in the PRSS1 gene were detected in any of the patients, including HP patients, while the N34S mutation was observed in the SPINK1 gene in the majority of HP patients (73%). Similarly, 26.8% of ACP (11 of 41) and 32.5% (39 of 120) of ICP patients also had SPINK1 mutations. The N34S mutation was observed in both homozygous and heterozygous conditions. In comparison, only 2.76% of the control population had the N34S allele (p<0.001). The P55S mutation was observed in one ICP and one ACP patient, and in three normal individuals. Genotype-phenotype correlations did not suggest any significant difference in the age of onset, severity of disease, or pancreatic endocrine insufficiency in patients with or without mutated SPINK1 and irrespective of the allelic status of N34S SPINK1. CONCLUSIONS: Irrespective of the aetiology, mutations in the PRSS1 gene are not associated with chronic pancreatitis, including HP. In contrast, the N34S mutation in the SPINK1 gene shows a significant correlation in these patients. A comparable phenotype in terms of age of onset, diabetes mellitus, and other phenotypic features in patients with or without SPINK1 mutations and N34S homozygotes and heterozygotes suggests that there may still be involvement of other genetic or environmental factors.

Adult↗
PubMed2003

A GATA-binding protein expressed predominantly in the pupal ovary of the silkworm, Bombyx mori.

Preferential localization of Bkm (Banded krait minor-satellite) DNA sequences on Y/W chromosomes of higher eukaryotes, which remain highly condensed in somatic cells but undergo extensive decondensation in the germ cells during early stages of development, led to the postulation for the existence of a sex- and tissue-specific Bkm-binding protein (BBP). Accordingly, we purified and characterized a BmBBP expressed predominantly in pupal ovary of the silkworm (Bombyx mori). 2D-PAGE revealed BmBBP as moderately basic (pI 7.8-8, in the range expected for DNA-binding proteins) and Matrix Assisted Laser Desorption/Ionization Time of Flight exhibited a value of 37.5-kDa. BmBBP neither contains nor requires divalent metal ions for its DNA-binding activity, suggesting that it does not belong to the well-studied GATA-family of transcription factors. BmBBP is unusually strong in its DNA-binding characteristics to Bkm (GATA-repeats), which suggests its probable role in bringing about coordinated chromatin conformational changes to activate genes present in associated chromosomal domains. Fluorescence immuno-localization studies employing specific anti-BmBBP antibodies revealed its presence in the follicle cells and in the ooplasm, as well as the nucleus of different developmental stages of oocytes.

Animals↗
PubMed2002

Is the amelogenin gene reliable for gender identification in forensic casework and prenatal diagnosis?

In humans, the amelogenin gene is present on both the X and the Y chromosomes. However, there are size differences in this gene between these chromosomes, which have been utilised for sexing in forensic casework and prenatal diagnosis. Our study using the AmpFl STR Profiler Plus kit, showed a deletion of Y chromosome-specific amelogenin in five Indian males (1.85%). We propose to call them "deleted-amelogenin males" (DAMs), who but for the detection of the presence of other Y-specific markers (e.g. SRY, STR and 50f2) would have been identified as females. Considering the consequences of the result obtained only using the amelogenin marker, we suggest the use of additional Y chromosome markers for unambiguous gender identification.

Amelogenin↗