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Biomedical subjects

V Prakash

Publications and source records attributed to V Prakash.

At least 73 records · Page 4Linked to original sources
PubMed1992

Association of proteins in acidic solutions--a case study with beta-globulin.

The investigation of the effect of acid pH on the structure of beta-globulin indicated several transitions as a function of pH. Upon reducing the pH from 7.0, the beta-globulin molecule underwent an expansion due to hydration up to pH 5.0, and a further increase in H+ concentration resulted in unfolding. This is a single step cooperative denaturation as indicated by the viscosity profile. At extreme acid pH values (below pH 2.0) the protein associates or folds to a different conformational motif as shown by blue shift of ultraviolet fluorescence emission maximum and decrease in reduced viscosity values by more than 30% due to an entropically driven hydrophobic interaction. The conformational analysis of beta-globulin showed a decrease up to pH 3.0, followed by an increase in the ordered structure at low pH values indicating that the low pH values stabilized this new conformation. These results are discussed in view of the molten globule structure of proteins.

Beta-Globulins↗
PubMed1992

The nature of the unhydrolysed fraction of alpha-globulin, the major protein component of Sesamum indicum L. hydrolysed by alpha-chymotrypsin.

Alpha-globulin, the high molecular weight protein fraction from sesame (Sesamum indicum L.) seed, was hydrolysed by alpha-chymotrypsin. The hydrolysate was resolved into two fractions, the hydrolysed part and the unhydrolysed part of alpha-globulin using gel filtration on Sepharose 6B-100. The unhydrolysed alpha-globulin residue was characterized for its sedimentation coefficient, subunit composition, fluorescence emission spectrum, secondary structure, and other biophysical properties. The results indicated a decrease in the size of the protein molecule upon hydrolysis to a very small extent. The effect of hydrolysis products on hydrolysis of native alpha-globulin as well as on a standard substrate, casein, was also investigated. The results indicated that the hydrolysis products contribute to the resistance of alpha-globulin to proteolysis by alpha-chymotrypsin to the extent of 40%.

Alpha-Globulins↗
PubMed1992

Effect of different proteolytic enzymes on the nature of subunit composition of arachins from groundnut (Arachis hypogaea L.).

Arachin, the major protein from groundnut, was isolated from three varieties of groundnut (Spanish Improved, TMV-2 and DH-3-30) using a modified procedure involving precipitation with 18% ammonium sulphate to obtain homogeneous protein. The homogeneity was judged by polyacrylamide gel electrophoresis, gel filtration and sedimentation velocity techniques as well as correlation with amino acid composition. Rates of hydrolysis of arachins by trypsin (pH 7.6) and alpha-chymotrypsin (pH 7.8) were significantly different between the three varieties. Arachin from the Spanish Improved variety contained higher amounts of alanine and phenylalanine and lower amounts of carbohydrate and phosphorus as compared to TMV-2 and DH-3-30. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis pattern of arachin from TMV-2 showed only seven bands of which the ones with low molecular weight were more intense than those of the other two varieties. The far-ultraviolet circular dichroic spectra showed no significant differences among the three varieties in respect of alpha-helix content (5 +/- 2%), beta-structure (19 +/- 2%) and the aperiodic structure. The observed differences in hydrolysis rates have been explained as due to the differences in the acidic and basic subunits of arachins.

Amino Acids↗
PubMed1991

Mechanism of interaction of vinca alkaloids with tubulin: catharanthine and vindoline.

The interactions of the vinca alkaloid drugs catharanthine and vindoline with tubulin have been investigated and compared with those of vinblastine and vincristine. Both drugs were found to be less effective in bringing about the inhibition of tubulin self-assembly into microtubules than vincristine and vinblastine, the drug to protein molar ratio required being 3 orders of magnitude greater. An analytical ultracentrifuge study has shown that catharanthine can induce the self-association of tubulin into linear indefinite polymers with an efficacy that is 75% that of vinblastine or vincristine, the intrinsic dimerization constant for the liganded protein being K2 congruent to 1 x 10(5) M-1. The effect of vindoline was marginally detectable. Binding studies of catharanthine using the gel batch and fluorescence perturbation techniques showed a polymerization-linked binding of one catharanthine molecule per tubulin alpha-beta dimer with a binding constant of (2.8 +/- 0.4) x 10(3) M-1. For vindoline, binding to tubulin was marginally detectable by fluorescence spectroscopy, although addition of vindoline to tubulin did generate a difference spectrum. It was concluded that the binding of vinblastine/vincristine to tubulin and its consequences are determined by the interaction of the indole part of catharanthine with tubulin, the role of vindoline being that of an anchor.

Animals↗
PubMed1991

Structural stability of lipase from wheat germ in alkaline pH.

The present investigation shows the effect of alkaline pH on the structure-function relationship of lipase from wheat germ. There is a 70% decrease in lipase activity at pH 10.0, which decreases to 93% at pH 12.0 as compared to neutral pH activity (Rajendran et al. 1990). This change is shown to be as a result of loss of alpha-helical structure with a concomitant increase in aperiodic structure. The results with fluorescence spectra and tyrosyl ionization indicate gradual exposure of aromatic side chains of tyrosine and tryptophan to the bulk solvent along with the structural changes. The enzyme is in an extended form at alkaline pH with a volume change of - 1300 ml mol as also indicated by increase in reduced viscosity to 12.5 ml g and significant decrease in sedimentation coefficient. The kinetics of the reaction points to a cooperative pseudo first-order reaction as determined by stopped-flow kinetic analysis in the ultraviolet region. The inactivation mechanism appears to follow a two-step mechanism of a fast and a slow reaction.

Chemical Phenomena↗
PubMed1991

Japanese encephalitis virus latency in peripheral blood lymphocytes and recurrence of infection in children.

In a study group of 40 children who had been admitted to hospital with acute encephalitis, the disease was due to infection with Japanese encephalitis virus (JEV). Three children developed recurrence of disease 8-9 months later. No virus had been isolated from these three patients during the acute stage of their illness, but virus was recovered from all during the recurrence phase by co-cultivation of their peripheral blood mononuclear cells in primary mouse embryo fibroblast cultures. Virus was also recovered by co-cultivation of peripheral blood mononuclear cells collected 8 months after their acute disease from three out of eight randomly selected asymptomatic children within the study group but not from similar cultures set up from JEV-seronegative children used as controls. Virus was also isolated by co-cultivation of T lymphocytes of asymptomatic children as detected by indirect immunofluorescence or by inoculation in mice.

Cells, Cultured↗
PubMed1991

Protective immunity to entamoeba histolytica infection in subjects with antiamoebic antibodies residing in a hyperendemic zone.

To investigate the relationship between amoebic gut infection and the presence of serum antiamoebic antibodies in a community where amoebiasis is highly endemic, a cross-sectional population survey was conducted covering 982 subjects in 2 adjacent villages in rural India. E. histolytica was detected in fecal smears in 18.1% (88/487) and antiamoebic antibodies by micro-ELISA in 28.7% (251/874) subjects. In 450 subjects in whom there was no clinical evidence of invasive amoebic disease or history of ingestion of antiamoebic drugs in the previous year and from whom both stool and matched serum samples were obtained, correlation of gut infection with seropositivity was attempted. Seropositivity in 80 cyst passers (23.8%) was significantly lower than in 370 non-cyst passers (35.1%; p less than 0.05). Conversely the rate of gut infection with E. histolytica was lower in seropositive subjects (19/149; 12.8%) as compared to seronegative subjects (61/301; 23%, p less than 0.05). In the population where E. histolytica infection was highly endemic, the rate of gut infection with the parasite was inversely related to seropositivity. Our data suggests that invasive E. histolytica infection (mostly asymptomatic) evokes good gut immunity in the host with clearing of the parasite from the colon and/or resistance to reinfection. High prevalence rate of amoebic antibodies indicates good "herd" immunity.

Adolescent↗
PubMed1991

Glycosylated hemoglobin and diabetic retinopathy.

Estimation of glycosylated hemoglobin (HbA1c) levels by modified Fluckinger and Winterhalter's method was done in 25 normal persons, 25 diabetic patients without retinopathy, and 25 diabetic patients with retinopathy. The HbA1c values were significantly higher in diabetic patients with or without retinopathy than in the control group (P less than .001). In diabetic patients with retinopathy, the mean value of HbA1c was higher in proliferative retinopathy than in background retinopathy, but statistical analysis showed this was not significant (P greater than .6).

Adult↗
PubMed1990

Studies on buffalo pituitary lutropin (LH): physicochemical and immunological properties.

Physicochemical and immunological properties of buffalo pituitary lutropin (buffalo LH) are reported here. The preparation was shown to be homogeneous by several physicochemical criteria. The molecular weight was found to be 30,000-40,000 by SDS-PAGE, GP-HPLC, and ultracentrifugation analyses. It showed certain interesting features, such as anomalous sedimentation behavior, microheterogeneity due to sugar-linked sulfate, and weak immunogenicity in rabbits. The subunit nature of the hormone has been confirmed. Sugar composition showed similarities as well as differences with LH of other species. Preliminary data on the homologous and heterologous RIAs, using iodinated sheep LH and buffalo LH and the respective antisera, have also been given.

Animals↗
PubMed1990

ABO blood group differences in bone mineral density of recovering alcoholic males.

Since ABO blood group differences are associated with varying responses to many diseases, ABO blood type and bone density were studied in 39 recovering male alcoholics, comparing those with blood type O and non-O. The type O subjects had significantly higher bone densities as measured by quantitative computed tomography of the vertebrae than the non-O subjects (175.4 +/- 8.5 and 140.7 +/- 7.6, respectively, p = 0.004). There were no differences in age and indices of their alcoholism. Using multiple stepwise regression analysis, neither race nor maximal amount of alcohol consumed appeared to contribute to the differences in bone density. Only age, number of years of regular alcohol use and ABO blood type were determinants of the bone density differences. The ABO blood type contributed 20.3% to the differences in bone density (p = 0.001). The patients with non-O blood type lost a significant amount of bone with advancing age (r = -0.76, p = 0.0001) while those with blood type O did not (r = -0.37, p = 0.11). We conclude that, although alcoholism is a factor in the development of osteopenia, in males the ABO blood group status plays a significant role in the maximal mineralization of the skeleton and the amount of bone resorption during ageing, independent of alcohol abuse.

ABO Blood-Group System↗
PubMed1990

Determination of molecular weight and related hydrodynamic parameters of high molecular weight protein fraction from a few oilseeds.

The hydrodynamic parameters of the major protein fraction, viz. arachin from groundnut, alpha-globulin from sesame seed, brassin (M) from mustard seed and helianthinin from sunflower seed, have been determined in a single solvent system (0.05 M Tris-HCl buffer, pH 7.5 containing 0.5 M sodium chloride): sedimentation coefficient (s0(20,w)) and diffusion coefficient (D0(20,w)) by analytical ultracentrifugation, intrinsic viscosity [eta] by Ostwald viscometry and partial specific volume (V) by densimetry. The molecular weights (M) of the four proteins, calculated using the sedimentation-viscosity and sedimentation-diffusion coefficient methods, were found close to each other. The values have been compared with those in the literature and the reasons for discrepancies have been discussed.

Chemical Phenomena↗
PubMed1990

Effect of pH in the acidic region on the structural integrity of lipase from wheat germ.

To understand the structure-function relationship of the enzyme lipase the effect of acid pH on the activity of lipase has been followed using a number of physico-chemical techniques. Lipase from wheat/germ has S20,w value of 2.2 S and a molecular weight of 42,000 +/- 1,000. The enzyme has an intrinsic viscosity of 4.72 ml/g indicating it to be elongated in shape. With decrease in pH below 7.0 microenvironmental changes occur in the neighborhood of active site accompanied by minor conformational changes without any gross change in the hydrodynamic properties of the protein, as monitored with ultraviolet difference spectra, fluorescence spectra, viscosity and circular dichroism. The kinetics of the inactivation process has been established as consisting of a fast step and a slow step with a k value of 73/sec and 7.2/sec respectively. At extreme acid pH the enzyme reaggregates to a polymer arising out of hydrophobic interaction and the polymer has no activity.

Hydrogen-Ion Concentration↗