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Biomedical subjects

S Gurnani

Publications and source records attributed to S Gurnani.

At least 19 recordsLinked to original sources
PubMed1989

Mechanism of interaction of the antileukemic drug cytosine arabinoside with aromatic peptides: role of sugar conformation and peptide backbone.

Interaction of the antileukemic drugs, cytosine-arabinoside (Ara-C) and adenosine-arabinoside (Ara-A) and a structural analogue, cytidine, with aromatic dipeptides has been studied by fluorescence and NMR spectroscopy. Ara-C and cytidine bind tryptophanyl and histidyl dipeptides but not tyrosyl dipeptides, while Ara-A does not bind to any of them. Both studies indicate association involving stacking of aromatic moieties. NMR spectra also indicate a protonation of the histidine moiety by Ara-C. In case of cytidine, the chemical shifts observed on binding to His-Phe imply that the backbone protons of the dipeptide participate in the binding. The conformation of the sugar and the base seem to play a very important role in the binding phenomenon as three similar molecules, Ara-C, Ara-A and cytidine bind in totally different ways.

Amino Acid Sequence↗
PubMed1986

Inhibition of microtubule assembly by actinomycin D, an anti-tumour drug.

Effect of actinomycin D, an antibiotic, was investigated on the biological function of tubulin from bovine brain. The microtubule assembly was inhibited nearly completely when an equal molar ratio of actinomycin D and tubulin was used. The depolymerisation of the same, however, was not altered under the same conditions. The competence of tubulin to bind colchicine and GTP was also not affected. Chromatographic and the spectrophotometric studies showed that 0.94 mol of actinomycin D binds per mole of tubulin.

Animals↗
PubMed1985

Effect of rifampicin on the biological activity of tubulin.

The effect of rifampicin on the biological properties of bovine brain tubulin was investigated. Assembly of microtubules was almost completely blocked by rifampicin, whereas the depolymerization was not affected. The drug was found to inhibit both colchicine and GTP binding to tubulin. Association of rifampicin with tubulin was confirmed by spectrophotometric method. Binding of rifampicin was found to be dependent both on temperature and time. At 0 degrees for 1 hr 0.84 moles of rifampicin were bound per mole of tubulin.

Animals↗
PubMed1985

Chemical characterization of the dapsone binding site of lysozyme.

The binding of dapsone to hen egg white lysozyme has been studied using fluorescence spectroscopy. At low concentrations the drug binds lysozyme with a Ka = 3.3 X 10(4) M-1 forming a 1:1 complex. At high concentrations the protein was found to bind the drug in a cooperative manner at two sites with an average association constant of 6.3 X 10(4) M-1. Both Trp-108 and Trp-62 of lysozyme are involved in the association process. Acetylation of the lysine residues increased the affinity of the drug to the protein. However, drug association showed no effect on the enzymatic activity of the protein.

Animals↗
PubMed1984

Involvement of tryptophan residues of lysozyme in its binding with cytosine arabinoside.

Cytosine-1-beta-D-arabinofuronaside, an antileukemic drug and hen egg white lysozyme (E.C. 3.2.1.17) form a 1:1 complex with Ka 1.2 X 10(4) M-1 at low drug concentrations. However, association was cooperative in nature at high concentrations with values of Ka = 1.8 X 10(4) M-1 and N = 2. Involvement of tryptophan in the drug protein complex was evident from fluorescence quenching and from the association of the drug with free tryptophan with a Ka = 1.5 X 10(4) M-1. Modification of tryptophan 108 reduced the binding by 89% suggesting a major role for this residue in the binding process. Oxidation of tryptophan 62 and acetylation of lysine residues also decreased the affinity of the drug to the protein by 55 and 66% respectively. Binding improved with increase in temperature and positive values for change in enthalpy and entropy were obtained. Ara-C inhibited lysozyme activity noncompetitively.

Cytarabine↗
PubMed1983

Inhibition of tubulin assembly by antileprosy drug dapsone.

The effect of dapsone on assembly-disassembly process of bovine brain tubulin was examined. The drug was found to readily bind tubulin dimer and that in its presence colchicine binding to tubulin was enhanced. Although dapsone associated with tubulin at a site other than the colchicine binding site, distinct inhibition of microtubule assembly was detected.

Animals↗
PubMed1983

Involvement of colchicine binding site of tubulin in the polymerisation process.

Role of lysine residues in the colchicine binding site and in the assembly-disassembly process was examined. It was observed that at 4 degrees C (pH 7.5-8, 8 +/- 1) lysine residues and the N-terminal methionine residue of tubulin were all buried within the molecule. Evidence indicates that epsilon-amino groups of lysine residues of tubulin are shared by both the colchicine binding site and the polymerisation process.

Acetylation↗
PubMed1983

An attempt to influence nerve degeneration and regeneration by using macrophage cell homogenate.

The effect of the contents of activated macrophages on the degenerative/regenerative process in the mouse sciatic nerve was investigated as a possible model for leprosy. The whole cellular homogenate or saline was injected every week around physically impaired (to bypass the perineurial barrier) and normal nerves. Recovery of the nerve function was monitored clinically and electromyographically. After 14 weeks animals were sacrificed and nerves were processed for histology. The data obtained from 134 experimental and control nerves were rated and analysed statistically. The course of the nerve regeneration in the physically impaired nerve with and without homogenate was found to be similar. One of the reasons for this could be insufficient concentration of the homogenate in the endoneurial space.

Animals↗
PubMed1980

Serum lysozyme in leprosy.

Serum lysozyme was assessed in 43 healthy subjects and 183 leprosy patients. Significantly elevated level of lysozyme was observed in sera of leprosy patients as compared to normal individuals. The enzyme levels in leprosy of different types showed elevations in following order, Erythema Nodosum Leprosum (ENL) greater than Lepromatous greater than Borderline greater than Tuberculoid. Enzyme levels in patients with inactive stage were lower than in untreated patients. The serum lysozyme level correlated well with the activity disease in leprosy--clinically and bacteriologically. Thus the estimation of serum lysozyme can be used as one of the parameters of activity of the disease.

Adolescent↗