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Biomedical subjects

S Sinha

Publications and source records attributed to S Sinha.

At least 469 records · Page 26Linked to original sources
PubMed1984

A four-variable model for the pattern-forming mechanism in Hydra.

A generalized Gierer-Meinhardt model has been used to account for the transplantation experiments in Hydra. In this model, a cross inhibition between the two organizing centres (namely, head and foot) are assumed to be the only mode of interaction in setting up a stable morphogen distribution for the pattern formation in Hydra.

Animals↗
PubMed1984

Purification and comparative characterization of an enolase from spinach.

An enolase has been purified to apparent homogeneity, as measured by gel electrophoresis, some 400-fold from spinach (Spinacia oleracea). This is the first plant enolase that has been purified to homogeneity. At moderate ionic strengths, the 5,5-dithio-bis-2-(nitrobenzoate) (DTNB)-or parachloromercuribenzoate-reacted enzyme elutes from a Bio-Gel P-200 column with somewhat greater volumes than the yeast enzyme (M(r) = 93,000) indicating a greater size. Its elution volume from Ultrogel in 50% ammonium sulfate, however, suggests it exists as an active monomer (M(r) = 47,000). Sodium dodecyl sulfate-gel electrophoresis indicates the subunit molecular weight is 50,000 +/- 3,000, like that of yeast enolase.The enzyme contains 23 +/- 4 half-cystines per mole of subunit. Titrations with DTNB in guanidine hydrochloride or nondenaturing media indicate that most of these, if not all, are in the reduced state. Reaction of one or more of the sulfhydryls with DTNB or parachloromercuribenzoate stabilizes the enzyme.The kinetic parameters of the reaction catalyzed by spinach enolase, as well as the inhibitions by transition metal ions and fluoride, are similar to those properties of the yeast and rabbit muscle enzymes.

Journal Article↗
PubMed1983

Are circadian oscillators structurally unstable?

The common belief is that all biological oscillations are of limit cycle type. It is shown in this article that the phase response curves simulated on a two-species Lotka-Volterra linear (i.e. non-limit cycle type) oscillator, do look similar to those obtained by experimental methods by different workers. The form of the phase response curves, the existence of singularities and the mirror-image symmetry of opposite perturbations are modelled on the Lotka-Volterra system. The study, which is strongly indicative of the possibility that the underlying oscillator (or oscillators) is (are) not structurally stable, also indicates the necessity of designing critical experiments, capable of distinguishing between limit cycle and non-limit cycle oscillators, since the single-pulse phase resetting does nothing to distinguish between them.

Animals↗
PubMed1983

A serological test for leprosy based on competitive inhibition of monoclonal antibody binding to the MY2a determinant of Mycobacterium leprae.

A novel serological assay for leprosy has been devised on the basis of serum inhibition of binding of 125I-labelled ML04 monoclonal antibody to Mycobacterium leprae sonicate-coated microtitre plates. Antibodies were detected in 93% of lepromatous leprosy patients, whereas controls from the endemic area, including leprosy contacts and patients with tuberculosis, were serologically negative. The specificity and efficacy of the test may offer an advantage over previously used techniques.

Antibodies, Bacterial↗
PubMed1983

Definition of species specific and cross-reactive antigenic determinants of Mycobacterium leprae using monoclonal antibodies.

Four soluble antigens of Mycobacterium leprae have been identified using 12 murine monoclonal antibodies. Their specificity, taxonomic distribution and molecular nature were analysed by radioimmunoassays and by immunoblotting from polyacrylamide electrophoresis gels. A protein antigen MY1 (12K) reacted with one antibody (ML06) without demonstrable cross-reactivity for any of the other 20 tested species of mycobacteria. Another four antibodies which identified antigen MY2 revealed only a marginal degree of cross-reactivity with three other species of mycobacteria. Two antigens shared by several other mycobacteria species were: MY3 represented by five protein bands (35-70K) and a subtilisin resistant molecule MY4 (40-50K) with two distinct determinants and presumably of polysaccharide nature. The described monoclonal antibodies may represent novel valuable diagnostic reagents as well as tools for the purification of antigens which could be explored towards prophylactic or therapeutic immunization against leprosy.

Antibodies, Monoclonal↗
PubMed1982

Immune status of subsided cases of tuberculoid (TT) and borderline tuberculoid (BT) leprosy.

A comparative study of lepromin reactions (early and late), M. leprae induced lymphocyte blastogenesis, per cent T Cell number in peripheral blood and immunoglobulin (IgG, IgA and IgM) levels have been made in TT-active, TT-subsided, BT-active and BT-subsided leprosy cases. No significant difference has been noted amongst these groups in the above mentioned investigations except in subsided BT cases where 9 out of 11 cases failed to evoke any late skin reaction to Dharmendra antigen. In addition, BT subsided cases also showed significantly raised levels of IgG. The significance of these findings with respect to their immunity and reinfection has been discussed.

Adolescent↗