PubMed Health⌕ Search

Biomedical subjects

S S Singh

Publications and source records attributed to S S Singh.

At least 19 recordsLinked to original sources
PubMed2005

The Duffy blood groups of Jarawas - the primitive and vanishing tribe of Andaman and Nicobar Islands of India.

Andaman and Nicobar Islands, union territory of India were inhabited by 14 aboriginal tribes. Some of these tribal populations have already become extinct, and the numbers of the existing ones are also dwindling. This group of islands being highly endemic for malaria, it was considered worthwhile to study the hunter-gatherer primitive tribe, Jarawas, for their Duffy blood group phenotype. Jarawas, the primitive tribe of Andaman Islands, inhabit the three jungle areas of South and one jungle area of Middle Andaman. Blood samples of 116 Jarawas were collected and tested for Duffy blood group and malarial parasite infectivity. The Duffy blood grouping was performed as per standard serological techniques, and peripheral smears were screened for malarial parasite and if present parasite density count was performed and the species identified. The results showed a total absence of both Fy(a) and Fy(b) antigens in two areas (Kadamtala and R.K. Nallah) and low prevalence of Fy(a) antigen in another two areas (Jirkatang and Tirur). There was absence of malarial parasite Plasmodium vivax infection though Plasmodium falciparum infection was present in 27.59% of cases. A very high frequency of Fy (a-b-) in the Jarawa tribe from all the four jungle areas of Andaman Islands along with total absence of P. vivax infections suggests the selective advantage offered to Fy (a-b-) individuals against P vivax infection.

Duffy Blood-Group System↗
PubMed2005

Malaria among the Jarawas, a primitive and isolated tribe on the Andaman islands, India.

The Jarawas are a primitive Negrito tribe of the Andaman islands, India. The members of this tribe have been geographically and socially isolated from the other inhabitants of the islands. None had attended a hospital or health unit until 1997, when a Jarawa boy with a fractured leg was taken to a hospital in Port Blair, and successfully treated. Since then, increasing numbers of Jarawas have sought treatment at the hospital and/or begun to make other contact with non-Jarawas on the islands. No malaria had ever been reported in the tribe until 2001, when an outbreak of febrile illness triggered a malariological survey. Malarial parasites, all identified microscopically as Plasmodium falciparum, were detected in the bloodsmears of 30 of the 179 Jarawas investigated. Although most malaria among the non-Jarawa inhabitants of the islands is caused by P. vivax, only P. falciparum was detected when blood samples from 26 of the subjects were investigated in PCR-based assays. Genetic-diversity studies, based on the msp(1) and msp(2) polymorphic markers, also revealed a relatively low level of polymorphism in the P. falciparum parasites infecting the Jarawas, compared with that seen in other areas of India. It seems possible that malarial parasites have only recently reached the Jarawas, as the result of the weakening of the tribe's isolation from other humans on the Andaman islands.

Adolescent↗
PubMed2004

Evaluation of inheritance to leaf rust in wheat using area under disease progress curve.

Six varieties, Kundan (K), Galvez-87 (G), Trap (T), Chris (C), Mango (M) and PBW-348 (P) along with fast ruster, Agra Local (AL), were screened for seedling reaction and adult pant response to leaf rust. Seedlings of all six varieties were susceptible while adult plants showed lower susceptability response than Agra Local. The F1s among the varieties, and also with Agra Local, showed the values lesser than the respective mid parental values for AUDPC suggesting a polygenic mode of inheritance. ANOVA for combining ability effects indicated variation due to the GCA and SCA effects, which indicated that both additive as well as non-additive type of genetic variances, govern AUDPC. The higher values for the GCA variance over the SCA variance indicated the predominance of an additive component over the dominance component for AUDPC. Significant values for GCA effects indicated that Kundan, Galvez-87 and Trap can be used as good general combiners for AUDPC. The crosses, KxAL, GxAL and TxAL showed significant sca effects for AUDPC, which indicated the predominance of non-additive gene effects in these crosses. Additive x additive and dominance x dominance components of the 5- parameter model were highly significant and contributed maximum extent compared to the additive and dominance components in the cross KxG, while dominance and dominance x dominance components contributed maximum in the remaining crosses. Under such a situation, improvement in the character may be expected through standard selection procedure, which may first exploit the additive gene effects and simultaneously care should be taken to see that the dominance effects are not dissipated, but rather they should be concentrated.

Area Under Curve↗
PubMed2002

Detection of pulsatile blood flow cycle in frog microvessels by image velocimetry.

The detection of pulsatile blood flow velocity through one section of a curved branching frog mesenteric microvessel during a flow cycle, by analysis of a sequence of videomicroscopic images recorded at a frame rate 25 frames s-1, is presented. From these data, 64 sequential digitized frames of 128 x 128 pixels and 256 grey level were selected. By processing sequential pairs of frames by image velocimetry, the corresponding displacement vector was calculated. Dividing this by the frame rate gave the vector velocity. The same procedure was repeated for all frames, and the corresponding maximum (0.36-0.38 mm s-1), minimum (0.0-0.025 mm s-1) and other velocity values were obtained and plotted. The preliminary data analysis showed that the separation between two velocity maxima was about 20 video frames, which corresponded to one cardiac cycle of time interval 0.8 s.

Animals↗
PubMed2001

Protein kinase C isozyme-specific phosphorylation of profilin.

Profilin, a cytoskeletal protein, is emerging as an important link between signal transduction pathways and cytoskeletal dynamics. Profilin is phosphorylated on its C-terminal serine by protein kinase C (PKC). The protein kinase used for the in vitro phosphorylation studies reported earlier was a mixture of isozymes, and therefore, attempts were made to address the isozyme specificity on profilin phosphorylation under in vitro conditions. Profilin was subjected to phosphorylation by PKCalpha, PKCepsilon, and PKCzeta isozymes individually, and it was observed that profilin phosphorylation is cofactor-independent. PKCzeta phosphorylates profilin to a higher extent, but exhibits cofactor dependency with respect to phosphoinositides. The stoichiometry of phosphorylation was measured in the presence of these different isozymes, and a maximum stoichiometry of 0.8 (mole phosphate incorporated/mole profilin) was obtained in the presence of PKCzeta. Phosphorylation of profilin by PKCzeta was maximal in the presence of phosphatidylinositol4,5-bisphosphate (PI4,5-P2) when compared to the other phosphoinositides studied.

Animals↗
PubMed2001

Mapping of hiv-1 Gag epitopes recognized by polyclonal antibodies using gene-fragment phage display system.

Phage display has emerged as a powerful technique for mapping epitopes recognised by monoclonal and polyclonal antibodies. We have recently developed a simple gene-fragment phage display system and have shown its utility in mapping epitope recognised by a monoclonal antibody. In the present study, we have employed this system in mapping epitopes recognised by polyclonal antibodies raised against HIV-1 capsid protein, p24 which is derived from proteolytic cleavage of Gag polyprotein. HIV-1 gag DNA was fragmented by DNase I and the fragments (50-250 bp) were cloned into gene-fragment phage display vector to construct a library of phages displaying peptides. This phage library was used for affinity selection of phages displaying epitopes recognised by rabbit anti-p24 polyclonal antibodies. Selected phages contained sequences from two discrete regions of p24, demonstrating the presence of two antigenic regions. The DNA sequences encoding these regions were also cloned and expressed as GST fusion proteins. The immunoreactivity of these epitopes as GST fusion proteins, or as phage-displayed peptides, was comparable in ELISA system using same anti-p24 polyclonal antibodies. The results indicate that the gene-fragment based phage display system can be used efficiently to identify epitopes recognised by polyclonal antibodies, and phage displayed epitopes can be directly employed in ELISA to detect antibodies.

Animals↗
PubMed1999

Leptospiral infection among primitive tribes of Andaman and Nicobar Islands.

The Andaman islands were known to be endemic for leptospirosis during the early part of the century. Later, for about six decades no information about the status of the disease in these islands was available. In the late 1980s leptospirosis reappeared among the settler population and several outbreaks have been reported with high case fatality rates. Besides settlers, these islands are the home of six primitive tribes of which two are still hostile. These tribes have ample exposure to environment conducive for transmission of leptospirosis. Since no information about the level of endemicity of the disease among the tribes is available, a seroprevalence study was carried out among all the accessible tribes of the islands. A total of 1557 serum samples from four of the tribes were collected and examined for presence of antileptospiral antibodies using Microscopic Agglutination Test (MAT) employing 10 serogroups as antigens. An overall seropositivity rate of 191% was observed with the highest rate of 53.5% among the Shompens. The seropositivity rates in the other tribes were 16.4% among Nicobarese, 222% among the Onges and 14.8% among the Great Andamanese. All of the tribes except the Onges showed a similar pattern of change in the seroprevalence rates with age. The prevalence rates were rising from low values among children to reach a peak in those aged 2140 years and then declined. Among Onges the seroprevalence rates continued to rise beyond 40 years. In all the tribes, seroprevalence rates were found to be significantly higher among the males. The commonest serogroups encountered were Australis followed by Grippotyphosa, Icterohaemorrhagiae, Pomona and Canicola.

Adolescent↗
PubMed1999

Simplified gene-fragment phage display system for epitope mapping.

We describe a simple and efficient system for epitope mapping by cloning random gene fragments into a specially designed gIIIp-based phage display vector. DNA encoding the antigen of interest is PCR-amplified and partially digested with DNaseI to generate 50-150-bp-long fragments, which are polished with T4 DNA polymerase and dephosphorylated. These fragments are cloned at the 5' end of the gIII after linearizing the vector with SmaI/SrfI, and the ligation is carried out in the presence of restriction enzyme SrfI. The restriction enzyme in the ligation reaction recuts the self-ligated vector but not the recombinants, since ligation with foreign fragments destroys the enzyme recognition site. Dephosphorylation of inserts prevents their chimerization and ensures ligation of single insert per vector molecule. Thus, using the above strategy, which prevents self-ligation of both the insert and the vector, the overall cloning efficiency and, thereby the library size, is improved more than 10-fold compared to the standard blunt-end, ligation-based methods for making similar libraries. The library is further enriched by a single-step infection of E. coli by phages obtained from primary transformants. This step eliminates all the phages that carry insert that are not in-frame with gIIIp and therefore do not display gIIIp. We have shown the utility of the above system in constructing a glutathione-S-transferase (GST) gene-fragment library in phages and identifying the epitope recognized by a monoclonal antibody against GST.

Amino Acid Sequence↗
PubMed1999

Clinico-epidemiological study of hospitalized cases of severe leptospirosis.

In an attempt to understand the clinical spectrum and pathological and biochemical abnormalities and their prognostic importance in leptospirosis, a prospective study was carried out in Port Blair during September 1996 to August 1997. Out of 80 patients suspected to have leptospirosis, 58 were proved to have current leptospiral infection using serological tests and among these, 14 died giving a case fatality rate of 24.1 per cent. The incidence of the disease showed two separate peaks roughly coinciding with the paddy sowing and harvesting season and the majority of the patients had history of exposure to wet and water logged environment prior to the attack of the disease. The disease presented as two separate clinical syndromes--the hepato-renal form and the pulmonary form though some degree of overlap was present. Hepatic and renal complications occurred in 30 patients each with 26 of them having both. These generally occurred late in the course of the disease and the mortality rate was relatively low. In contrast pulmonary complication occurred quite early and the case fatality rate in those patients was very high (6.7% vs 42.9%). The other complications encountered in the current series of cases were refractory hypotension probably due to myocarditis in 40 per cent and neck stiffness and altered sensorium due to central nervous involvement in 12.1 per cent of the patients. The chances of the patients developing complications were considerably low if treated early and very few of them developed any complications after 2 days of hospitalized treatment. The early occurrence of pulmonary complications indicates a pathogenesis totally different from that responsible for the other complications.

Adolescent↗
PubMed1999

A study of serum bilirubin in neonates in relation to the maternal age.

A comparative study of neonatal serum bilirubin levels was done in neonates of different age groups of mothers. A total 122 healthy, new borns were selected for the study, born at Queen Mary's Hospital, Lucknow. Mothers were divided into two groups i.e. < 30 years and > 30 years of age. Samples of blood were collected thrice, first on day 1 from cord blood, 2nd and 3rd on days three and five of life from neonates by heel prick method, using small bore capillaries for blood collection, serum bilirubin estimation were done by the method of Malloy & Evelyn and Mean +/- SD were calculated. P-Value was observed between different age groups. In both the groups of mothers i.e. < 30 years and > 30 years serum bilirubin levels in their neonates raised to highly significant levels on day 3 (P-Value < 0.001) as compared to their cord blood serum bilirubin levels. On comparing serum bilirubin levels in neonates of both the maternal groups, it was observed that there is no significant difference between two groups on day of birth and day day 5 but statistically significant difference was observed on day 3 (P < 0.05), serum bilirubin levels were higher in neonates of younger age group mothers.

Adolescent↗
PubMed1998

Phosphatidylinositol 3-kinase binds to profilin through the p85 alpha subunit and regulates cytoskeletal assembly.

Phosphatidylinositol 3-kinase (PI3-K), endowed with catalytic (110kDa) and regulatory (85kDa) subunits co-precipitates with anti-tyrosine antibodies in mitogen-activated cells. Association of PI3-K with cytoskeleton activates its catalytic activity through undeciphered mechanisms. Recently Singh et al., (Biochemistry, 35, 16544-16549, 1996) have shown that profilin activates PI3-K activity in a concentration-dependent manner. Consequently, we investigated the interaction between the PI3-K and profilin employing the GSTp85 alpha fusion protein and the results indicate a specific interaction between profilin and p85 alpha. The effect of p85 alpha/profilin complex on polymerization of actin monomers was monitored fluorimetrically employing pyrene-labelled actin monomers. It was noted that p85 alpha/profilin complex inhibits actin polymerization suggesting that profilin can simultaneously bind to actin as well as to p85 alpha. The affinity of p85 alpha/profilin complex to actin increases in the presence of p85 alpha subunit of PI3-K as compared to profilin itself.

Actins↗
PubMed1997

The Ah receptor is a sensitive target of geldanamycin-induced protein turnover.

Geldanamycin (GA) binds directly to hsp90 and apparently disrupts certain hsp90 heterocomplexes. We have investigated the GA-hsp90 interaction and its effect on other associated proteins. Incubation of 2-[125I]-iodo-3-azido-7,8-dibromo-p-dioxin-labeled Hepa 1c1c7 cytosol with GA-coupled beads revealed a stable association of Ah receptor (AhR)/hsp90 complex with GA. In addition, sucrose gradient sedimentation analysis demonstrated that GA does not disrupt the 9S Ah receptor complex in vitro. HeLa and Hepa 1c1c7 cells were subjected to a dose-response and time-course treatment with GA and the level of the AhR was determined. A 75% depletion in AhR levels was observed within an hour of exposure to 100 nM GA. The relative stability of other proteins that associate with hsp90 was determined with the following rank order of sensitivity to GA exposure: AhR >> c-Raf-1 > glucocorticoid receptor > CDK4 >> p50. A series of hsp90 deletion mutants were used to map the domain that interacts with GA. Deletion of the first 221 amino acids in NH2-terminal domain resulted in loss of binding to solid-phase GA. Epitopes of monoclonal antibodies specific for hsp90 were also determined by direct immunoprecipitation with hsp90 mutants. Results indicated that monoclonal antibodies 8D3 and 3G3 interact with hsp90 via the first 221 amino acids in NH2-terminal region, whereas AC88 requires a COOH-terminal region between amino acids 661-677.

Affinity Labels↗