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Biomedical subjects

H K Sharma

Publications and source records attributed to H K Sharma.

At least 37 records · Page 2Linked to original sources
PubMed1980

Altered phosphoglycerate kinase in aging rats.

Pure phosphoglycerate kinase from young and old rat muscle shows substantial differences in properties. Compared to the "young" enzyme, phosphoglycerate kinase isolated from old animals possesses a greater stability to heat and storage, a slower reacting -SH group, an altered UV spectrum, and requires more antiserum prepared to "young" enzyme for 50% inactivation. Km and specific activity are unchanged. Immunotitration experiments show evidence for an age-related alteration of the enzyme in liver and brain, but not in kidney, lung, or heart. Loss of NH2- or COOH-terminal amino acids is not responsible for the observed differences in the properties of "young" and "old" muscle phosphoglycerate kinase. Both forms of the enzyme contain a blocked (presumably acylated) NH2-terminal residue and the sequence of the three COOH-terminal residues (Ala-Val-Leu-COOH) is identical. Moreover, isoelectric focusing of the two enzyme forms of both acrylamide gels and in a sucrose gradient failed to detect evidence of deamidation or other charge-altering differences. We conclude that, like enolase from aged nematodes, muscle phosphoglycerate kinase becomes altered in conformation in old rats.

Aging↗
PubMed1980

Altered enolase in aged Turbatrix aceti results from conformational changes in the enzyme.

Young- and old-type enolases (2-phospho-D-glycerate hydrolyase, EC 4.2.1.11) from the free-living nematode Turbatrix aceti can be unfolded in 1.25 M guanidine hydrochloride and subsequently refolded with essentially a quantitative recovery. After refolding, both enolases form an identical or near-identical third type of the enzyme as determined by spectral criteria, sensitivity to heat, immunotitration, and rate of inactivation by bacterial protease. By the same criteria, the refolded enolase is closer in conformation to the native old form of the enzyme than to the young form. The results prove that young and old enolases are conformational isomers and that an in vivo transformation from young to old enzyme takes place by conformational changes without covalent modification. The process may be related to the previously demonstrated slowing of enolase turnover in T. aceti. Errors in sequence cannot be involved in the age-related alteration of the enzyme.

Aging↗
PubMed1980

Identifying drug-dependent persons in a survey: a note on methodological issues.

A survey of 2,064 male persons in a rural area revealed that 423 (20.5 per cent) expressed craving for one or more abused substances. Close relationships were found between self-expressed craving and daily use of a drug. These data also suggest that in a large-scale survey, self-expressed craving and frequency of drug use could be used for fairly reliable estimates of the state of dependence on a drug.

Epidemiologic Methods↗
PubMed1978

Altered enzymes in the free-living nematode, Turbatrix aceti, aged in the absence of fluorodeoxyuridine.

Aging of the free-living nematode, Turbatrix aceti, has been accomplished by a procedure based upon screening of the cultures every 3--4 days to remove newborn organisms. In this system, the enzymes, isocitrate lyase, phosphoglycerate kinase and enolase all show reduced specific activities with age in crude homogenates. More critically, pure enolase shows a reduced specific activity when isolated from old compared with young organisms (958 units/mg vs. 1340 units/mg, respectively). Immunotitration experiments confirm these results. Enolase from old T. aceti requires more antiserum per unit of enzyme activity than does enolase from young organisms. This relationship holds true for both crude homogenates and pure enzyme. The above results closely parallel previous results obtained using fluorodeoxyuridine to prevent reproduction of T. aceti during aging of the organisms. Therefore, use of fluorodeoxyuridine in the aging of nematodes is perfectly safe, at least with respect to results obtained with altered enzymes.

Aging↗
PubMed1978

Serological evidence for the alteration of enolase during aging.

Pure enolase isolated from young and old Turbatrix aceti has been compared using immunologic techniques. Antiserum prepared to "young" and "old" enolase, respectively, will completely precipitate either enzyme. However, antiserum prepared to "young" enolase reacts more efficiency with "young" than with "old" than with "old" enzyme and vice versa. A third form of enolase (inactive enolase) is found in homogenates of old organisms. This material yields a pattern of identity with "young" enolase and partial identity with "old" enolase. It also gives rise to specific antibodies which do not react with "young" or "old" enolase. The material appears to accumulate with age. The results indicate a close structural relationship between "young", "old" and inactive enolase.

Aging↗
PubMed1975

A new mode of ring cleavage of 2,3-dihydroxybenzoic acid in Tecoma stans (L.). Partial purification and properties of 2,3-dihydroxybenzoate 2,3-oxygenase.

2,3-Dihydroxybenzoic acid has been shown to be oxidized via the 3-oxoadipate pathway in the leaves of Tecoma stans. The formation of 2-carboxy-cis,cis-muconic acid, a muconolactone, 3-oxoadipic acid and carbon dioxide during its metabolism has been demonstrated using an extract of Tecoma leaves. The first reaction of the pathway, viz., the conversion of 2,3-dihydroxybenzoate to 2-carboxy-cis,cis-muconic acid has been shown to be catalysed by an enzyme designated as 2,3-dihydroxybenzoate 2,3-oxygenase. The enzyme has been partially purified and a few of its properties studied. The enzyme is very labile with a half-life of 3--4 h. It is maximally active with 2,3-dihydroxybenzoate as the substrate and does not exhibit any activity with catechol, 4-methyl catechol, 3,4-dihydroxybenzoic acid, etc. However, 2,3-dihydroxy-p-toluate and 2,3-dihydroxy-p-cumate are also oxidized by the enzyme by about 38% and 28% respectively, compared to 2,3-dihydroxybenzoate. Sulfhydryl reagents inhibit the enzyme reaction and the inhibition can be prevented by preincubation of the enzyme with the substrate. Substrate also affords protection to the enzyme against thermal inactivation. Sulfhydryl compounds strongly inhibit the reaction and the inhibition cannot be prevented by preincubation of the enzyme with its substrates. Data on the effect of metal ions as well as metal chelating agents suggest that copper is the metal cofactor of the enzyme. Evidence is presented which suggests that iron may not be participating in the overall catalytic mechanism.

Cations, Divalent↗
PubMedDate not supplied

Sociocultural perspective of substance use in India.

The present communication focuses on a sociocultural perspective of substance use in a pluralistic and diverse culture. India has a history of use of plant products, viz., cannabis, opium, and home-brewed alcoholic beverages, within a defined sociocultural framework over five millennium. Cross sectional epidemiological studies in the field of substance use in different parts of India show that certain social groups are more "vulnerable" to substance use. Caste, religion, and local customs and traditions play a significant role in the choice of drugs, their consumption, and their control in rural/semiurban populations. The intercultural barriers are diminishing in urban populations, and even alien drugs like heroin have been introduced. The social and cultural implications of the traditional vis-a-vis the altering drug use scene are discussed at length.

Adolescent↗