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Biomedical subjects

V Prakash

Publications and source records attributed to V Prakash.

At least 37 records · Page 2Linked to original sources
PubMed2000

Influence of metal ions on structure and catalytic activity of papain.

Papain is an endoprotease belonging to cysteine protease family. The catalytic activity of papain in presence of two different metal ions namely zinc and cadmium has been investigated. Both the metal ions are potent inhibitors of the enzyme activity in a concentration dependent manner. The enzyme loses 50% of its activity at 2 x 10(-4) M of CdCl2 and 4 x 10(-4) M of ZnCl2. It is completely inactivated above 1 x 10(-3) M concentration of either ZnCl2 or CdCl2. Of the two metal ions zinc with a ki value of 5 x 10(-5) M is a more potent inhibitor than cadmium which has a ki value of 8 x 10(-5) M. Both the metal ions have higher affinity for active site than the substrate. At concentrations above 1 x 10(-2) M of metal ions the inhibition is not reversible. Calorimetric studies showed decreased thermal stability of papain upon binding of these metal ions. Far UV circular dichroic spectral data showed only small changes in the beta-structure content upon binding of these metal ions. These data are also supported by decrease in the apparent thermal transition temperature of papain by 5 degrees C upon binding of metal ions indicating destabilization of the papain molecule. The mechanism of both partial and complete inactivation of papain in presence of these two metal ions both at lower and higher concentration has been explained.

Cadmium↗
PubMed1999

Profound thrombocytopenia in Plasmodium vivax malaria.

In India, malaria is endemic and commonly caused by Plasmodium vivax and P. falciparum. Thrombocytopenia is a common finding in falciparum infection but is rare in P. vivax infection. We report profound thrombocytopenia in a 43-year-old female patient due to P. vivax infection. The platelet count was as low as 5 x 10(9)/liter, such severe thrombocytopenia has never been reported in vivax malaria.

Adult↗
PubMed1999

Affinity properties of phosvitin: interaction of phosvitin with serine hydroxymethyl transferase.

The affinity of phosvitin with serine hydroxymethyl transferase (SHMT), an acidic multi-subunit protein, was evaluated by measurements of enzyme activity, sedimentation velocity, steady-state fluorescence, circular dichroism and kinetic thermal stability. While the presence of phosvitin had no effect on the SHMT activity, the sedimentation coefficient of SHMT increased from 8.7 S to 12.5 S suggesting the formation of a complex at a SHMT:phosvitin molar ratio of 2:1. Based on steady-state fluorescence quenching measurements an association constant of 2.4 +/- 0.2 x 10(5) M-1 at 25 degrees C was obtained for the interaction of phosvitin with SHMT. The temperature dependency of the association constant in the range 15-35 degrees C suggests the involvement of ionic forces in the interaction. The thermal inactivation of SHMT followed first order kinetics. In the presence of phosvitin the rate constant decreased and half time increased. The circular dichroism measurements suggest that phosvitin interaction does not involve pyridoxal phosphate binding domain of the enzyme. Although minor changes in the secondary structure of the enzyme were observed, the environment around aromatic amino acids did not change significantly.

Fluorescence↗
PubMed1999

Elevation of serum riboflavin carrier protein in breast cancer.

Presently available tumor markers have had a limited clinical impact. Riboflavin carrier protein (RCP) is an estrogen inducible protein that occupies a key position in riboflavin metabolism. Because other vitamin carrier proteins (VCP) have been shown to be overexpressed in patients with malignant disease, we evaluated serum RCP levels in patients with adenocarcinoma of the breast. In this prospective blinded study, patients with breast cancer, benign breast disease, and healthy controls were analyzed for RCP levels. Using a highly sensitive RIA, we observed that serum RCP levels were significantly elevated in women with breast cancer (n = 52) as compared with control subjects [n = 50; 6.06 +/- 7.27 ng/ml versus 0.70 +/- 0.19 ng/ml (mean +/- SD), respectively; P < 0.0001]. A serum RCP level of > or = 1.0 ng/ml was highly predictive of the presence of breast cancer, detecting 88% of tumors in stages I-II and 100% of tumors in stages III-IV. Overall, this RCP assay has a sensitivity of 92.3%, a specificity of 88%, a positive predictive value of 88.9%, and a negative predictive value of 91.7%. These results show increased serum levels of RCP in breast adenocarcinoma patients and suggest that RCP levels may be useful as a new marker for breast cancer. The positive predictive value in early-stage breast cancer suggests that the RCP assay may be a useful adjunct to present screening technology.

Adenocarcinoma↗
PubMed1998

Results of surgical decompression of ulnar nerve in leprosy.

Ulnar neurolysis in 279 cases of leprosy was performed with objectives of relief in neuritic pain and impending/ existing sensory motor loss of varying extent. Of the above, 193 could be followed between 3-10 years. Neuritic pain was first to disappear. 48.7% of the 193 cases showed sensory recovery. Motor power gain and/or further fall in muscle power was prevented as a result of preventive neurolysis in 173 (89.6%) cases. In this series benefits of appropriate and timely surgical intervention have been observed.

Adolescent↗
PubMed1998

Thermal stabilization of multimeric proteins: a case study with alpha-globulin.

Preferential interaction parameters of multisubunit protein, alpha-globulin and monomeric protein human serum albumin (HSA) were determined in different cosolvents using precision densitymetry. The apparent partial specific volumes were determined under both isomolal and isopotential conditions for alpha-globulin in 0.02 M glycine-NaOH buffer at pH 10 and the values were 0.692+/-0.002 and 0.688+/-0.001, ml/g, respectively, at 20.00+/-0.01 degrees C. From the partial specific volume data with cosolvents the preferential interaction parameter (xi3) and other thermodynamic parameters were calculated at different solvent concentrations. The (xi3) values increased with an increase in the solvent concentration up to 30% and reached a maximum with the values of-0.111+/-0.018 g/g and -0.076+/-0.012 g/g in sucrose and sorbitol, respectively. In glycerol the (xi3) values decreased with an increase in solvent concentration. The above data is further supported by thermal denaturation profiles in which the apparent thermal denaturation temperature (apparent Tm) of alpha-globulin shows an increase from 63 degrees C to higher temperatures in the order of sucrose, sorbitol and glycerol. Alpha-globulin showed coagulation due to protein interaction at temperatures above 50 degree C. The apparent Tm of 63 degrees C for control protein was increased significantly up to 75 degrees C in 40% sorbitol with two fold increase in the delta(S) values showing the increased structural stability of alpha-globulin. At high solvent concentration the protein gets dissociated and the resultant monomers are hydrated which was evident by fluorescence data and the difference spectral results with a 6nm red shift in the emission maximum and 2 nm blue shift in UV-absorption maximum arising out of perturbation of aromatic chromophores. The studies were performed both at native pH of 7.9 where the protein is in its oligomeric form and at pH of 10 where it is dissociated form and the results compared. The data showed that the solvent is excluded more from the protein vicinity in the dissociated state.

Densitometry↗
PubMed1997

Syringomyelia--a complication of meningitis--case report.

Syringomyelia following meningitis is a rare condition. This report summarizes the history of a 43 year old Indian male who developed arachnoiditis as a sequalae of tubercular meningitis. This later progressed to syringomyelia. The patient was treated with a syringo-subarachnoid shunt.

Adult↗
PubMed1997

The role of lysine-256 in the structure and function of sheep liver recombinant serine hydroxymethyltransferase.

The active site lysine residue, K256, involved in Schiff's base linkage with pyridoxal-5'-phosphate (PLP) in sheep liver recombinant serine hydroxymethyltransferase (rSHMT) was changed to glutamine or arginine by site-directed mutagenesis. The purified K256Q and K256R SHMTs had less than 0.1% of catalytic activity with serine and H4folate as substrates compared to rSHMT. The mutant enzymes also failed to exhibit the characteristic visible absorbance spectrum (lambda(max) 425 nm) and did not produce the quinonoid intermediate (lambda(max) 495 nm) upon the addition of glycine and H4folate. The mutant enzymes were unable to catalyze aldol cleavage of beta-phenylserine and transamination of D-alanine. These results suggested that the mutation of the lysine had resulted in the inability of the enzyme to bind to the cofactor. Therefore, the K256Q SHMT was isolated as a dimer and the K256R SHMT as a mixture of dimers and tetramers which were converted to dimers slowly. On the other hand, rSHMT was stable as a tetramer for several months, further confirming the role of PLP in maintenance of oligomeric structure. The mutant enzymes also failed to exhibit the increased thermal stability upon the addition of serine, normally observed with rSHMT. The enhanced thermal stability has been attributed to a change in conformation of the enzyme from open to closed form leading to reaction specificity. The mutant enzymes were unable to undergo this conformational change probably because of the absence of bound cofactor.

Animals↗