Biomedical subjects
Publications and source records attributed to L Singh.
Explore the source record for details and available documents.
As part of a larger epidemiological survey to study the prevalence of dementia in a suburb of Mumbai, Western India, we identified 78 cases with a Clinical Dementia Rating (CDR) > or = 1.0. Of these, 49 Alzheimer's disease (AD) cases were analyzed for risk association with APOE E*4 allele at apolipoprotein E gene (APOE) and presenilin-1 (PS-1) intron-8 polymorphism and were compared with 100 age- and sex-matched nondemented controls. Genotype analysis confirmed the association of APOE E*4 allele with AD as has been reported by various studies. We report a low frequency of APOE E*4 allele, consistent with a low prevalence of AD in this study. Comparisons with other similar studies on APOE from India suggest common risk factors for AD in the Indian population, which is diverse in its ethnic and racial characteristics. The frequency for allele 1 at PS-1 intron-8 polymorphism is the highest among all studies reported. This first report of PS-1 intron-8 polymorphism and AD from India demonstrates no significant association.
A strain of Clostridium botulinum type E has been isolated from soil samples of Gwalior, India. The isolated strain shows curved vegetative cells with oval, bulging, and terminal spores. The production of toxin was detected by immunodiffusion test, symptomatic death of mice and mouse protection assay with trivalent antitoxin (A+B+E). The culture supernatant gave 10(3) MLD (minimum lethal dose) per ml without any protease treatment. Group specific and serotype specific primers amplified the DNA fragments of 260 bp and 445 bp, respectively, indicating Clostridium botulinum type 'E.'
This paper describes the synthesis and physical and biological effects of introducing different substituents at the alpha-position of the tryptophan containing neurokinin-1 receptor antagonist [(R)-2-(1H-indol-3-yl)-1-methyl-1-((S)-1-phenyl-ethylcarbamoyl)-ethyl]-carbamic acid benzofuran-2-ylmethyl ester (CI 1021). The described compounds all exhibit less than 5 nM binding affinities for the human neurokinin-1 receptor and selectivity over the tachykinin NK(2) and NK(3) receptor subtypes. Application of variable temperature nuclear magnetic resonance spectroscopy studies of the amide and urethane protons was utilized to determine the existence of an intramolecular hydrogen bond. This intramolecular hydrogen bond increases the apparent lipophilicity to allow increased central nervous system penetration and pharmacological activity (gerbil foot tap test) in the case of the highest affinity compound [(S)-1-dimethylaminomethyl-2-(1H-indol-3-yl)-1-((S)-1-phenyl-ethylcarbamoyl)-ethyl]-carbamic acid benzofuran-2-ylmethyl ester (PD 174424) over those analogues that could not form an intramolecular hydrogen bond.
Amongst twenty five proteolytic bacteria isolated from lake sediment samples of Antarctica, six isolates were selected based on SDS PAGE protein profile and zone of hydrolysis on casein agar at 10 degrees C. Most of the cultures were rod shaped and motile with two showing terminal bulging spores. Isolates grew between 5 degrees C to 37 degrees C and protease was induced in the late log, stationary or death phase. Isolate SPA-3 grew maximally at 10 degrees C and SPA-6 at 37 degrees C while others preferred 20 degrees C-30 degrees C for growth. The growth and protease production on casein, skimmed milk, bovine serum albumin and gelatin varied with the isolates. Acetate was the dominant volatile fatty acid (24-66% of total VFA) produced during hydrolysis of protein substrate.
Polymorphic allelic variants of chemokine receptors CCR2 and CCR5, as well as of stromal-derived factor-1 SDF-1, the ligand for the chemokine receptor CXCR4, are known to have protective effects against HIV-1 infection and to be involved with delay in disease progression. We have studied the DNA polymorphisms at the loci that encode these proteins in 525 healthy individuals without any history of HIV-1 infection from 11 diverse populations of Andhra Pradesh, South India. The two protective alleles SDF-1-3'A and CCR2-64I at the SDF-1 and CCR2 loci, respectively, are present in all populations studied, although their frequencies differ considerably across populations (from 17% to 35% for the SDF-1-3'A allele, and from 3% to 17% for CCR2-64I). In contrast the CCR5-Delta32 allele is observed only in three populations (Yamani, Pathan and Kamma), all in low frequencies (i.e. 1% to 3%). The mean number of mutant alleles (for the three loci together) carried by each individual varies from 0.475 (in Vizag Brahmins) to 0.959 (in Bohra Muslims). The estimated relative hazard values for the populations, computed from the three-locus genotype data, are comparable to those from Africa and Southeast Asia, where AIDS is known to be widespread.
RATIONALE: Psychological dependence to the opioid analgesic morphine is attributable to the rewarding properties of the drug, and its evolution can be divided into two distinct phases: development and maintenance. Both phases can be studied using conditioned place preference (CPP). OBJECTIVES: To determine whether the two phases can be influenced by pre-treatment with gabapentin-like compounds. METHODS: CPP to morphine was used to demonstrate the rewarding properties of morphine in the presence or absence of gabapentin-like compounds. In-vivo microdialysis in the nucleus accumbens was used to determine the effects of gabapentin or pregabalin on morphine-induced dopamine release. RESULTS: Pretreatment with either gabapentin (10-100 mg/kg p.o.) or pregabalin (3-30 mg/kg p.o.) attenuated CPP induced by a submaximal dose of morphine (0.75 mg/kg). Neither gabapentin nor pregabalin had any effect alone in the CPP test. Both gabapentin-like compounds blocked the effect of morphine (0.75 mg/kg s.c.) to increase the release of dopamine in the nucleus accumbens. Studies of the maintenance of CPP to morphine showed CPP was maintained for at least 4 days after the initial test. In a second experiment, it was found that pregabalin (injected once, 24 h after CPP had been demonstrated) was able to reverse morphine-induced CPP. CONCLUSIONS: Neither gabapentin nor pregabalin induced CPP, but both compounds blocked the development of CPP to morphine and also blocked morphine's effects on dopamine release. Furthermore, pregabalin blocked the maintenance of morphine-induced CPP. It is concluded that gabapentin-like compounds, which have no intrinsic rewarding properties, may have some therapeutic use in the treatment of opioid dependence.
OBJECTIVES: To explore the feasibility of applying a dorsal free graft to treat urethral stricture by the ventral sagittal urethrotomy approach without mobilizing the urethra. METHODS: Twelve patients with long or multiple strictures of the anterior urethra were treated by a dorsal free full-thickness preputial or buccal mucosa graft. The urethra was not separated from the corporal bodies and was opened in the midline over the stricture. The floor of the urethra was incised, and an elliptical raw area was created over the tunica on which a free full-thickness graft of preputial or buccal mucosa was secured. The urethra was retubularized in one stage. RESULTS: After a follow-up of 8 to 40 months, one recurrence developed and required dilation. CONCLUSIONS: The ventral sagittal urethrotomy approach for dorsal free graft urethroplasty is not only feasible and successful, but is easy to perform.
The present study examines the effect of pregabalin (previously S-Isobutylgaba and CI-1008) in two distinct rat models of anxiety. Pregabalin binds with high affinity and selectivity to the alpha(2)delta subunit of voltage dependent calcium channels (VDCC). Its corresponding R-enantiomer (R-isobutylgaba) is approximately 10 fold weaker. Pregabalin dose-dependently induced anxiolytic-like effects in both the rat conflict test and elevated X-maze with respective minimum effective doses (MED) of 3 and 10 mg kg(-1). In contrast, R-isobutylgaba only showed activity at the highest dose of 100 mg kg(-1) in the conflict test. These data indicate that pregabalin may possess clinical utility as a novel anxiolytic agent and demonstrates the importance of the alpha(2)delta subunit of VDCC in the mediation of anxiety related behaviours.
From observations of lack of haplotype sharing based on Y-chromosome specific short tandem repeat (STR) loci, previous reports suggested negligible gene flow among different geographic populations of India. Using Single Nucleotide Polymorphism (SNP) sites in combination with STRs, we observed evidence of haplotype sharing across caste-tribe boundaries in South India. We examined 27 SNPs in the non-recombining region of the Y chromosome to investigate gene flow in 204 individuals belonging to three caste groups (Vizag Brahmins, Peruru Brahmins, Kammas), three tribes (Bagata, Poroja, Valmiki) and an additional group (the Siddis) of African ancestry. Principal component and AMOVA analyses show that the between group component of variation is non-significant (P>0.05), while that among populations within the caste and tribal groups is significant (P<0.001). In particular, the Valmikis and Siddis are close to the caste groups. Of a total of 11 distinct SNP-haplotypes observed, the two tribal groups (Bagata and Poroja) lack the haplotypes H4, H4A, H5A and H16, which are seen in the caste groups. In contrast, all three tribal groups exhibit the Southeast Asian haplotype H11 that is absent in the caste populations. The presence of haplotypes H4, H5, H14, and H16 in the Siddis indicate that they have assimilated considerable non-African admixture. The evidence of haplotype sharing between castes and tribes is also found when the H14 lineage was further subdivided by five STR loci. We conclude that even though these SNP-based Y-haplotypes are able to distinguish the populations, gene flow in these South Indian populations is not as negligible as that inferred from other studies based on Y-specific short tandem repeat markers.
Recent analyses have identified a number of binding partners for E6, including E6AP, ERC55, paxillin, hDlg, p300, interferon regulatory factor 3, hMCM7, Bak, and E6TP1. Notably, association with E6 targets p53, E6TP1, myc, hMCM7, and Bak for degradation. However, the relative importance of the various E6 targets in cellular transformation remains unclear. E6 alone can dominantly immortalize normal human mammary epithelial cells (MECs), permitting an assessment of the importance of various E6 targets in cellular transformation. Studies in this system indicate that E6-induced degradation of p53 and E6 binding to ERC55 or hDlg do not correlate with efficient immortalization. Here, we have examined the role of E6TP1, a Rap GTPase-activating protein, in E6-induced immortalization of MECs. We tested a large set of human papillomavirus type 16 E6 mutants for their ability to bind and target E6TP1 for degradation in vitro and in vivo. We observed a strict correlation between the ability of E6 protein to target E6TP1 for degradation and its ability to immortalize MECs. Recent studies have identified telomerase as a target of E6 protein. Previous analyses of E6 mutants have revealed this trait to closely correlate with MEC immortalization. We examined our entire panel of E6 mutants for rapid induction of telomerase activity and found in general a strong correlation with immortalizing ability. The tight correlation between E6TP1 degradation and MEC immortalization strongly supports a critical role of functional inactivation of E6TP1 in E6-induced cellular immortalization.
Haplotype determination based on three Y-linked polymorphic sites, 92R7 (C/T), SRY-1532 (A/G), and YAP (-/+), in 127 males belonging to three caste Hindu populations of South India (Vizag Brahmins, Peruru Brahmins, and Kammas) and 13 males belonging to a migrant group (the Siddis) showed the existence of all four haplotypes (CA-, CG-, TG-, and TA-) under the YAP- background. This finding suggests that the reverse mutation (G-->A) at the SRY-1532 site, described earlier in the literature, is present in South Indian populations as well. The YAP+ mutation was seen in only five Siddi individuals. Four of these were of the CG+ haplotype structure, but a novel haplotype (CA+) was found in one male. To explain the occurrence of the six haplotypes found within these three sites, a haplotype tree is constructed that introduces a new reverse mutation at the SRY-1532 site (G-->A), occurring under the CG+ background after the migrant Siddi population arrived in India.
The high risk human papillomaviruses (HPVs) are associated with carcinomas of cervix and other genital tumors. Previous studies have identified two viral oncoproteins E6 and E7, which are expressed in the majority of HPV-associated carcinomas. The ability of high risk HPV E6 protein to immortalize human mammary epithelial cells has provided a single gene model to study the mechanisms of E6-induced oncogenic transformation. In recent years, it has become clear that in addition to E6-induced degradation of p53 tumor suppressor protein, other targets of E6 are required for mammary epithelial cells immortalization. Using the yeast two-hybrid system, we have identified a novel interaction of HPV16 E6 with protein kinase PKN, a fatty acid- and Rho small G protein-activated serine/threonine kinase with a catalytic domain highly homologous to protein kinase C. We demonstrate direct binding of high risk HPV E6 proteins to PKN in wheat-germ lysate in vitro and in 293T cells in vivo. Importantly, E6 proteins of high risk HPVs but not low risk HPVs were able to bind PKN. Furthermore, all the immortalization-competent and many immortalization-non-competent E6 mutants bind PKN. These data suggest that binding to PKN may be required but not sufficient for immortalizing normal mammary epithelial cells. Finally, we show that PKN phosphorylates E6, demonstrating for the first time that HPV E6 is a phosphoprotein. Our finding suggests a novel link between HPV E6 mediated oncogenesis and regulation of a well known phosphorylation cascade.
The total synthesis of the threonine-linked core 2 class disialylated hexasaccharide in a completely protected form was accomplished for the first time. The L-threonine conjugate, N-(9-fluorenylmethoxycarbonyl)-O-[(5-acetamido-4,7,8,9-tetra-O-ben zyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid)-(2-->3)-(2,6-di-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-2-acetam ido-2-deoxy-3,6-di-O-benzyl-beta-D-glucopyranosyl-(1-->6)-[(5-acetamido- 4,7,8,9-tetra-O-benzyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulo pyranosylonic acid)-(2-->3)-2,6-di-O-benzyl-beta-D-galactopyranosyl-(1-->3)]-2-acetami do-2-deoxy-alpha-D-galactopyranosyl-(1d-->4c:1f-->4e)-dilactone ]-L-threonine allyl ester was synthesized via stereocontrolled glycosylations employing readily accessible monosaccharidic blocks; t-butyl-diphenylsilyl-2-azido-2-deoxy-3,6-di-O-benzyl-beta-D-gluco pyranose, N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-6-O-t-butyldimethylsilyl -2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester, 8, 9 and N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-4,6-O-benzylidene-3-O-ch loroacetyl-2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester. For the introduction of the amino acid, the azide group was used to temporarily mask the amino group of GalNAc so as to obtain an alpha-glycosidic linkage without participation from the C-2 substituent. The threonine was attached to the sugar unit at the monosaccharide stage to avoid loss of oligosaccharide at a later stage. The Fmoc and allyl ester protected amino acid at the reducing end facilitates efficient glycopeptide synthesis on solid-phase support.
Gastrin-releasing peptide (GRP), a selective agonist for the BB(2) subtype of bombesin receptor, is reported to depolarise GABAergic interneurons in the stratum oriens layer of the hippocampus. Such an action might lead to increased extracellular levels of GABA in the hippocampus, and result in an anti-convulsant effect with this peptide. We have tested this hypothesis by determining the effect of GRP on extracellular levels of GABA in the ventral hippocampus of the freely moving rat using in vivo microdialysis, and by intracerebroventricular (i.c.v.) administration of GRP to audiogenic seizure-prone DBA/2 mice prior to exposure to the noise of an electric bell. Following local perfusion in the ventral hippocampus by reverse dialysis GRP (10 microM) significantly raised levels of GABA in the recovered dialysates by approximately 40%. In the seizure studies, GRP (30-300 ng) increased the latency to tonic seizure, the number of mice convulsing and reduced the incidence of lethality. In both dialysis and seizure studies, the effects of GRP were blocked by the selective BB(2) receptor antagonist, [D-Phe(6), Leu-NHEt(13)]bombesin (6-13). These experiments provide further functional evidence that activation of the BB(2) receptor may modulate neurotransmission in the hippocampus, and that this action may confer anti-convulsant properties on agonists acting at the BB(2) receptor in the brain.
We have identified a novel polymorphic L1 retroposon insertion, designated LY1, in the centromeric alphoid array of the human Y chromosome. The element belongs to the transpositionally active Ta subset and its presence is compatible with normal centromere function. It was found at highest frequency in China, where it accounts for 23% of the Han sample, and was present at low frequencies in the surrounding areas, but was not found at all outside Asia. Chromosomes carrying LY1 show considerable microsatellite diversity, suggesting an ancient origin for the lineage at approximately 10 000 years ago (with wide confidence limits), but only limited subsequent migration.
Explore the source record for details and available documents.
Vocabulary growth from 2;0 to 3;0 was studied in 28 late talkers using expressive vocabulary inventories reported bimonthly on the Language Development Survey (LDS). Group milestones were 18 words at 2;0, 89 words at 2;6, and 195 words at 3;0. A sub-group of 11 children (Group 1) showed a rapid vocabulary spurt between 2;2 and 2;8, reached the 150-180 word mark by 2;6, and attained the LDS ceiling of about 300 words by 2;10. In contrast, the 17 children in Group 2 still had a mean vocabulary of fewer than 30 words at 2;6, had less of a vocabulary spurt when they did start acquiring words, and attained the 150-180 vocabulary mark at 3;0. All 3;0 language outcome measures were significantly predicted by LDS vocabulary size from 2;2 to 2;4.