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Biomedical subjects

K Prakash

Publications and source records attributed to K Prakash.

At least 55 records · Page 3Linked to original sources
PubMed1991

Antibodies to streptococcal opacity factor in a selected Indian population.

Antibody to at least one type of streptococcal opacity factor (OF) was present in 39.0% of 235 selected subjects and, in 47.8% of these, to more than one type. Only 21.6% of children less than 4 years old had antibody to OF; these were to one type in 62.5% or to more than one in 37.5%. In the study group as a whole, the commonest antibodies were those to OF from M-serotype 25 followed, in descending order, by serotypes 4, 22, 2, 9, 48, 49, 28, 61 and 75. Patients with rheumatic fever or rheumatic heart disease most often had antibodies to OF from M-types 25, 22, 4 and 9, whereas in patients with acute glomerulonephritis, antibodies to OF from M-types 48, 49 and 61 were commonest. The limitations of the OF-inhibition test as an epidemiological marker for prevalent M-types of group A streptococci are discussed.

Adolescent↗
PubMed1991

Synthetic oligonucleotides recreate Drosophila fushi tarazu zebra-stripe expression.

A complex array of activator and repressor elements located within 669 bp proximal to the fushi tarazu (ftz) transcriptional start site is sufficient to generate the "zebra-stripe" expression pattern characteristic of the ftz gene. P-element-mediated transformation and ftz promoter/lacZ fusion genes were used to characterize, in detail, several of these transcriptional control elements. By reconstructing promoters with synthetic oligonucleotides containing cis-regulators of stripe expression, we show that these regulatory sites can function as independent units to direct position-specific transcription in the Drosophila embryo. In particular, we demonstrate that multiple copies of a positive regulatory site can mediate expression in both the odd- and even-numbered parasegments throughout most of the germ band and that negative regulatory sites can transform a continuous pattern of gene expression into discrete stripes. The reconstructed promoter system presented provides an effective means of studying molecular mechanisms governing spatially restricted transcription in the early embryo.

Animals↗
PubMed1991

In vitro infection of natural killer cells with different human immunodeficiency virus type 1 isolates.

Natural killer (NK) cells are a discrete subset of leukocytes, distinct from T and B lymphocytes. NK cells mediate spontaneous non-MHC-restricted killing of a wide variety of target cells without prior sensitization and appear to be involved in initial protection against certain viral infections. Depressed NK cell-mediated cytotoxicity, one of the many immunological defects observed in AIDS patients, may contribute to secondary virus infections. Here we report that clonal and purified polyclonal populations of NK cells, which expressed neither surface CD4 nor CD4 mRNA, were susceptible to infection with various isolates of human immunodeficiency virus type 1 (HIV-1). Viral replication was demonstrated by detection of p24 antigen intracellularly and in culture supernatants, by the presence of HIV DNA within infected cells, and by the ability of supernatants derived from HIV-infected NK cells to infect peripheral blood mononuclear cells or CD4+ cell lines. Infection of NK cells was not blocked by anti-CD4 or anti-Fc gamma RIII monoclonal antibodies. NK cells from HIV-infected and uninfected cultures were similar in their ability to lyse three different target cells. Considerable numbers of cells died in HIV-infected NK cell cultures. These results suggest that loss of NK cells in AIDS patients is a direct effect of HIV infection but that reduced NK cell function involves another mechanism. The possibility that NK cells serve as a potential reservoir for HIV-1 must be considered.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Differentiation of human embryonal carcinoma cells induces human immunodeficiency virus permissiveness which is stimulated by human cytomegalovirus coinfection.

Human immunodeficiency virus (HIV) replicates in differentiated but not undifferentiated NTERA-2 human embryonal carcinoma cells; neither cell type expresses CD4. Susceptibility of the differentiated cells is enhanced by coinfection with cytomegalovirus. HIV infection induces lactoseries glycolipids, suggesting a mechanism whereby HIV might interfere with normal embryogenesis.

Antibodies, Monoclonal↗
PubMed1991

Comparison of enzyme linked immunosorbent assay and indirect haemagglutination test in serologic diagnosis of toxoplasmosis.

The antibody response against Toxoplasma gondii was evaluated by ELISA and indirect haemagglutination test (IHA) in 100 antenatal cases with bad obstetric history. 30 per cent of the cases were found to be positive by the IgM ELISA test and 22 per cent were positive by the IHA test. ELISA was found to be a more specific, reliable and easy test for screening of antenatal cases.

Acute Disease↗
PubMed1991

Application of serum opacity factor in subtyping of group A streptococci & identification of new M-types.

Out of 742 isolates of group A streptococci (GAS), 34.0 per cent were positive for production of serum opacity factor (SOF). The T and M typability of these GAS strains was 93.3 and 10.8 per cent respectively. Clustering of the strains under the T patterns 5/12/27, 8/25/Imp. 19 and 3/13/B3264 and low M typability indicated the utility of SOF testing as an additional marker in epidemiological characterisation of GAS. SOF was further found to be useful in identification of new M type and simplified M typing by saving time, labour and sera.

Antigens, Bacterial↗
PubMed1991

Clinical ventilatory functions and immunological studies in bronchial asthma.

Clinical characteristics, ventilatory functions and serum immunoglobulins (IgG, IgM and IgA) were assessed in 30 asthmatic patients. Sixty per cent patients belonged to early onset group ie, had onset of disease before 30 years of age. Seasonal asthmatics formed the largest group (56.6%) followed by perennial (26.6%) and irregular (16.6%) type. On the basis of ventilatory function tests, maximum number of cases (15) had asthma of moderate severity, followed by mild (12 patients) and severe forms (3 patients). Mean serum levels (mg%) of IgG (1631.93 +/- 270.71) and IgM (233.82 +/- 86.93) were significantly elevated in asthmatics as compared to controls. Higher serum IgA levels were observed in bronchial asthma patients (257.58 +/- 81.06) as compared to controls (225.69 +/- 49.75), but this rise was not statistically significant. Duration, periodicity of asthmatic attacks and the severity had no influence on the levels of the above three mentioned immunoglobulins, but it was observed that patients who had associated other allergies and positive family history of atopic disorders exhibited higher serum IgA and IgM levels, compared to those who had no such history. This difference was however not seen in serum IgG levels.

Adult↗
PubMed1990

Structure and chromosomal location of the rat ribophorin I gene.

Ribophorin I is a type I transmembrane glycoprotein characteristic of the rough portions of the endoplasmic reticulum where it is thought to play a role in the cotranslational insertion of nascent polypeptides. A rat ribophorin I cDNA was used to isolate four overlapping genomic clones from a rat EMBL3 genomic library. Restriction mapping, Southern blotting, and DNA sequencing showed that these clones, spanning approximately 21 kilobases of chromosomal DNA, include the entire ribophorin I gene, as well as 15 kilobases (kb) of upstream sequences. Southern blotting analysis of DNA from a panel of mouse-Chinese hamster cell hybrids demonstrated that the ribophorin I gene is located on mouse chromosome six. The ribophorin I gene contains 10 exons, seven of which encode the luminal domain of the polypeptide. Exon 8 encodes the trans-membrane domain and small portions of the flanking luminal and cytoplasmic domains. Exons 9 and 10 encode the remainder of the cytoplasmic domain, and the latter includes the 3'-untranslated portion of the mRNA. Six closely spaced transcription start sites located 3 to 24 base pairs upstream from the initiation codon were identified by primer extension analysis and S1 mapping. The sequence of a 1.3-kb region upstream of the cap sites was determined and found to contain three GC-rich potential Sp1-binding sites beginning at -14, -24, and -91 base pairs (bp), two octamer-like sequences at -233 and -1248 bp, and a CAAT-like box at -41 bp. The possible roles of these elements in regulating expression of the ribophorin gene in all cells and in differentiated cell types characterized by a well developed rough endoplasmic reticulum is discussed.

Animals↗
PubMed1990

Sandwich enzyme immunoassays for detection of Salmonella typhi.

Enzyme immunoassays were developed using monoclonal antibodies raised against somatic (O), flagellar (H) and capsular (Vi) antigens of Salmonella typhi. The assay based on anti-O monoclonal antibodies could specifically detect S. typhi and soluble lipopolysaccharide (LPS) isolated from S. typhi. Anti-H MoAbs detected motile S. typhi and soluble flagellar antigen. Monoclonal antibodies against capsular polysaccharide could detect Vi-containing S. typhi as well as soluble Vi antigen. The three assays reported here detected S. typhi with 100% sensitivity in blood culture broths obtained from bacteriologically confirmed typhoid patients and were negative with blood specimens containing Salmonella senftenberg, E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis or Streptococcus (alpha-hemolytic) derived from patients with pyrexia. The assays, however, did not demonstrate the presence of soluble antigens in sera and urine samples obtained from typhoid patients.

Animals↗
PubMed1990

Comparison of alkaline phosphatase-conjugated oligonucleotide DNA probe with the Sereny test for identification of Shigella strains.

We compared an alkaline phosphatase-conjugated oligonucleotide DNA probe with the Sereny test to determine the sensitivity and specificity of the probe in detecting virulent Shigella strains. The probe hybridized with all 52 Sereny-test-positive strains (sensitivity, 100%) and 4 of 21 Sereny-test-negative strains (specificity, 81%). The probe did not hybridize with any of the Sereny-test-negative S. dysenteriae type 1 strains. This nonradioactive, synthetic probe provides a simple, rapid way to test a large number of strains simultaneously in a field setting, which will contribute to an improved understanding of the epidemiologic patterns of shigellosis in developing countries.

Alkaline Phosphatase↗
PubMed1989

Spot CAMP test for the prompt presumptive identification of group B streptococci.

Spot and conventional CAMP tests done on 200 strains (120 human and 80 bovine) of group B streptococci showed 96 per cent of human and 90 per cent of bovine strains positive by both tests, indicating 100 per cent agreement. None of the 20 non-group B streptococci strains was positive for CAMP test for group B streptococci. The advantage of spot CAMP test is that it can be performed on a single isolated colony, easy to perform, inexpensive and can presumptively identify group-B streptococci within 30 min on primary sheep blood agar plate.

Animals↗
PubMed1988

A temporally expressed gene from Schwanniomyces alluvius and detection of homologous sequences in other yeasts.

The boundaries of a temporally expressed gene (EG1) located on a 6.5-kb HindIII chromosomal DNA fragment of the yeast Schwanniomyces alluvius have been defined by cDNA hybridization and S1 nuclease mapping. The sequence of this gene reveals a 474-bp open reading frame (158 aa) and a TATA-like sequence 100 bp upstream from the first start codon. The encoded protein bears little resemblance with other known yeast structural proteins, including histones. A portion of the 3' untranslated region shows 50% identity with a consensus repetitive sequence (B2) found in the mouse genome. Repetitive sequences are also located in both 5' and 3' untranslated regions. Genomic DNA analysis indicated that related sequences were detected at two loci in Schw. alluvius and one locus in Saccharomyces cerevisiae. In contrast to the continuous transcription pattern of the ADE1 genes of Schw. alluvius and S. cerevisiae, the 0.8-kb transcripts of EG1 in these yeasts were most abundant in cells in early-log phase of growth and absent in cells of late-log phase, suggesting discontinuous synthesis.

Amino Acid Sequence↗
PubMed1988

Genetic and molecular characterization of an epidemic plasmid coding for multidrug resistance in Salmonella typhimurium of human origin.

All 201 multidrug resistant Salmonella typhimurium strains isolated from epidemics in India contained nonconjugative (157 strains) or conjugative (44 strains) Inc F1me multiresistance plasmids. Two small R-plasmids of 7 MDa which coded for resistance to either ampicillin or streptomycin and sulfamethoxazole were also detected along with other plasmids. The small plasmids were members of group 1 and group 2 incompatibility groups. Restriction endonuclease analysis of conjugative (96 MDa) and nonconjugative (88 MDa) Inc F1me plasmids showed considerable similarity except for the presence of unique fragments among both the groups and the loss of fragments corresponding to the smaller size of the nonconjugative plasmid. A single Inc F1me plasmid appears responsible for various outbreaks of multiresistant S. typhimurium in different parts of India.

Conjugation, Genetic↗