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V Lakshmi

Publications and source records attributed to V Lakshmi.

At least 73 records · Page 4Linked to original sources
PubMed1991

Kinetic studies on rat liver 11 beta-hydroxysteroid dehydrogenase.

The kinetic behavior of homogeneous rat liver 11 beta-hydroxysteroid dehydrogenase (11-HSD) was investigated. The purified enzyme catalyzed oxidation of the 11 beta-hydroxy steroids, cortisol and corticosterone, to their 11-oxo products. The reverse 11-oxoreductase was not detected. Initial velocity studies of 11 beta-dehydrogenase were consistent with a sequential bireactant mechanism. Glycyrrhetinic acid, a competitive inhibitor of corticosterone oxidation, was uncompetitive with respect to NADP+. The observed inhibition patterns were consistent with an ordered sequential mechanism with NADP+ adding to the enzyme first. Analogs of NADP+ and NAD+ did not inhibit steroid oxidation by 11-HSD, nor did the products of the 11 beta-dehydrogenase reaction slow oxidation, or catalyze reduction. Ligand binding studies generated patterns that supported the ordered sequential mechanism derived from kinetic studies. The kinetic behavior of 11-HSD is therefore similar to other alcohol dehydrogenases. The basis for the apparent inability of homogeneous 11-HSD to catalyze reduction remains to be established.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1991

Regional distribution of 11 beta-hydroxysteroid dehydrogenase in rat brain.

The activity and distribution of 11 beta-hydroxysteroid dehydrogenase in rat brain is described. Oxidation of corticosterone to 11-dehydrocorticosterone was significantly increased by NADP; the reverse reaction was increased by NADPH. Cortisol was a poor substrate. Both 11-dehydrogenase (11-DH) and 11-oxoreductase (11-OR) activities were found in brains of rats from 6 days to adult, and 11-DH and 11-OR activities were positively correlated with each other. Highest enzyme activities were found in pituitary, cerebellum, hippocampus, and cortex. Lower levels were found in the olfactory region, hypothalamus, brain stem, preoptic nucleus, and amygdala. Two antisera to 11-DH, designated 56-125 and 56-126, reacted with a 34K component corresponding in mass to rat liver 11-DH on Western blots. The dominant species of protein in all brain regions reacting with rat liver 11-DH antibody 56-125, was at 26K mol wt. Antiserum 56-126 did not cross-react with the 26K protein. The 26K component was not a 34K degradation product. In each region of the brain, Western blot analysis showed that the 26K band intensity was directly proportional to enzyme activity. However, the 26K protein was devoid of 11-DH activity. All 11-DH and 11-OR activities were associated with the 34K antigen. The data demonstrate the nonuniform distribution of 11-DH in brain tissue. They are consistent with the notion that 11-DH may confer upon brain the ability to control intracellular levels of active glucocorticoids and in this way mediate steroid function within the cell.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1991

Hepatitis B surface antigen--3 years experience.

Epidemiological surveillance of Hepatitis B surface antigen in the city of Hyderabad at our Institute shows that the incidence of HBsAg is considerably high among the general population. In a comparative evaluation of the two techniques used, RPHA and ELISA, the latter emerged as a reliable one with high specificity and sensitivity. Screening of all blood samples by ELISA is imperative for uniform reporting of the incidence. Non risk groups like voluntary blood donors, cardiac patients serve as potential reservoirs of HBV infection.

Carrier State↗
PubMed1990

Corticosteroid 11 beta-dehydrogenase of rat tissues: immunological studies.

Monospecific polyclonal antibodies to purified homogeneous rat liver corticosteroid 11 beta-dehydrogenase were generated in rabbits. The antibodies were immunoprecipitins, but enzyme activity was not completely suppressed in the antigen-antibody complex. Two antibody preparations, 56-125 and 56-126, used to detect 11 beta-dehydrogenase antigen in Western blots, generated different staining patterns for kidney, liver, brain, and heart. Using the two antibodies together, the total number of antibody-reacting components in kidney was three, and that in liver was two. Based on rates of digestion with proteases, the two prominent immunoreactive proteins in kidney appeared to be structurally or conformationally different. A prominent immunostaining component was present in stomach. Tissues that showed immunochemical evidence of 11 beta-dehydrogenase antigen showed corresponding levels of 11 beta-dehydrogenase activity. Most active were liver, testis, kidney, and lung. Lower levels of activity were found in prostate and epididymis, brain, and reproductive tract. We conclude that 11 beta-dehydrogenase is widely distributed in rat organs and is present at low levels with significant exceptions. The data indicate that 11 beta-dehydrogenase may occur in several enzyme forms, and that the distribution of these forms is to some extent tissue specific.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

A study on nutrition, growth and development of a high-risk group of children of urban leprosy patients.

This paper describes a cross-sectional study of the physical development of a high-risk group of 182 socially deprived healthy children of leprosy patients ranging from preschool age to early teens. They were rescued at the age of 4 years from the distress of leprosy colonies where they were born, and brought up in Government Homes (Preventorium) under better environmental conditions. Of them 135 children could be followed clinically for 10 years for the development of childhood leprosy. Another 94 children of leprosy patients living with their parents were included for comparison. A group of 158 normal children of similar economic status and age group were included as controls. It was observed that, although better environment, food and training were provided in the Preventorium, so that the children could be brought into the national mainstream, nevertheless 5 children developed an indeterminate type of leprosy during the course of 10 years. This is the first report of growth and development of children of leprosy patients from the Indian sub-continent.

Adolescent↗
PubMed1989

Evidence for kinetically distinct forms of corticosteroid 11 beta-dehydrogenase in rat liver microsomes.

In this paper we have characterized the 11 beta-dehydrogenase component of the 11 beta-hydroxysteroid dehydrogenase complex in rat liver microsomes. This enzyme oxidized cortisol and corticosterone to cortisone and 11-dehydrocorticosterone, respectively. Corticosterone was oxidized 10-20 times faster than cortisol to its 11-oxo product. In freshly isolated microsomes enzyme activity was partially suppressed. Exposure of the microsomes to detergent or to prolonged incubation (24 h) released latent enzyme activity. Latency release was dependent on steroid concentration. The pH-activity profiles of latent and stimulated enzymes differed in shape (concave vs convex) and in pH optimum (pH 10 vs pH 8.5-9.5). Magnitude of latency release was greatest at pH 7. Corticosterone was a potent inhibitor of cortisol oxidation, but cortisol inhibited corticosterone oxidation poorly. With cortisol or corticosterone as substrates, low and high Km species were found. The high Km form represented about 90% of total enzyme activity in untreated microsomes. When latency was released, the low Km form was not detected. Our results suggest that at least two isozymic forms of corticosterone 11 beta-dehydrogenase reside in rat liver microsomes, or that a single enzyme coexists in two kinetically distinguishable forms.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1989

Synthesis of tritium labeled cortoic acids.

A procedure is described for the microsynthesis and purification of the high specific activity tritium labeled cortisol metabolites, 20 alpha- and 20 beta-cortolic acids and 20 alpha- and 20 beta-cortolonic acids.

Cortisone↗
PubMed1989

Corticosteroid 11 beta-dehydrogenase in rat testis.

Corticosteroid 11 beta-dehydrogenase, the enzyme that catalyzes the oxidation of the biologically active steroid cortisol to its inactive metabolite cortisone, is present in testis. Since excess cortisol in men and other mammals and excess corticosterone in rodents cause physiological abnormalities including abnormal testicular function, it was pertinent to study the cellular distribution of 11 beta-dehydrogenase in the testis. Purified antiserum directed against homogeneous rat 11 beta-dehydrogenase was used to localize the enzyme in the developing rat testis. With immunofluorescence, the enzyme was not detectable in fetal testis or in the testis of young male rats until the 26th day of development. A few interstitial cells were stained in the testis of 26-day-old animals. In the testis of 31-day-old rats many cells in the interstitium were positive. In adult animals the entire interstitial region displayed bright fluorescence. Depleting animals of germ cells did not abolish the fluorescence. The appearance of this enzyme correlates temporally with the postnatal increase in Leydig cell number and the developmental rise in serum testosterone. We suggest that 11 beta-dehydrogenase of Leydig cells protects the testis from the deleterious effects of cortisol.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1989

Licorice inhibits corticosteroid 11 beta-dehydrogenase of rat kidney and liver: in vivo and in vitro studies.

In humans, glycyrrhetinic acid (GE), the active pharmacological ingredient of licorice, produces symptoms resembling those caused by excess mineralocorticoid secretion. We are proposing that 11 beta-dehydrogenase inhibition, and not intrinsic mineralocorticoid activity, is the primary mechanism of licorice induced pseudoaldosteronism. Glycyrrhizic acid (glycyrrhetinic acid glucuronide), when given orally to rats, partially inhibited renal 11 beta-dehydrogenase. In rats treated with dexamethasone before glycyrrhizic acid administration there was similar enzyme inhibition, suggesting that antimineralocorticoid effects of dexamethasone in licorice excess states are not mediated through a direct effect on 11 beta-dehydrogenase activity. Dispersed renal proximal tubular preparations, kidney homogenates, and microsomes readily converted corticosterone to 11-dehydrocorticosterone. GE and its synthetic analog carbenoxolone inhibited the conversion in these systems in a dose-dependent manner. Corticosteroid 11-oxoreductase, which was present in kidney homogenates at a level 10-20% that of 11 beta-dehydrogenase was not inhibited by any of the agents. With homogenate and microsomes, the Ki of GE was about 10(-9)-10(-8) M; with intact tubules, the Ki of GE was about 10(-5)-10(-6) M. It is suggested that a permeability barrier slows the entry of GE into the tubule cells. We conclude that the effects of licorice on corticosteroid metabolism in the kidney are based on its inhibition of 11 beta-dehydrogenase. Our data, supplemented by published evidence, is inconsistent with the conclusion that interaction with mineralocorticoid receptors accounts for the pharmacological effects of GE.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1989

The intrarenal localization of mineralocorticoid receptors and 11 beta-dehydrogenase: immunocytochemical studies.

The 11 beta-dehydrogenase (11-DH) component of the microsomal enzyme complex, 11 beta-hydroxysteroid dehydrogenase, has been postulated to be the specificity-conferring mechanism for the renal type I receptor. To this end, the distribution of 11-DH and the type I receptor was studied in rat kidney by immunocytochemistry. 11-DH-like immunostaining (LI) was found in Bouin's fixed tissue, in both nuclear and cytoplasmic components of some cells of the juxtamedullary proximal convoluted tubules, and in interstitial cells of the papillary medulla. In addition, weak staining was seen in superficial proximal convoluted tubules in paraformaldehyde-fixed tissue. Type I receptor-LI was found in distal convoluted tubules, connecting pieces, and initial cortical collecting tubules of the superficial cortex. Since colocalization of the enzyme and receptor was not demonstrated, the action of 11-DH on type I receptor specificity would, thus, appear to be paracrine rather than autocrine.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1988

Purification and characterization of the corticosteroid 11 beta-dehydrogenase component of the rat liver 11 beta-hydroxysteroid dehydrogenase complex.

We have proposed that 11 beta-hydroxysteroid dehydrogenase is composed of structurally independent units with 11 beta-dehydrogenase and 11-reductase activities. We now report the purification of rat liver 11 beta-dehydrogenase to apparent homogeneity. Starting with microsomes, 800-fold purification was achieved with agarose-NADP affinity chromatography. No 11-reductase accompanied the purification. Homogeneity of 11 beta-dehydrogenase was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino acid end-group analysis and immunoprecipitation. The terminal amino acid was methionine. Monomer mol wt was 34,000. The enzyme was found to be a glycoprotein. A sequence of 40 amino acid units was identified from the amino end. The amino-terminal region was found to be highly nonpolar. Unlike unpurified microsomal 11 beta-dehydrogenase, which showed curvilinear Eadie plots, homogeneous enzyme gave rectilinear plots. Michaelis constants were 1.83 +/- 0.06 microM for corticosterone and 17.3 +/- 2.24 microM for cortisol. First order rate constants were 10 times greater for corticosterone than cortisol, and maximum velocities were similar.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1986

Benzydamine HCl, a new agent for the treatment of radiation mucositis of the oropharynx.

Benzydamine HCl is a new nonsteroidal analgesic and anti-inflammatory compound which is not chemically related to local anesthetics such as procaine and xylocaine. A double-blind, randomized clinical investigation was carried out to determine the analgesic and anti-inflammatory effectiveness of benzydamine HCl in patients with radiation-induced mucositis of the oropharynx. Of the 67 patients in the study, 37 were on benzydamine and 30 on placebo. Patients developed radiation mucositis, hyperemia, and throat pain when the total radiation dose reached above 2,000 rad over 2 weeks (200 rad per fraction, five treatments per week). Analysis of the data showed that benzydamine HCl used as a rinse/gargle provided a statistically significant and clinically meaningful alleviation of the symptoms of oropharyngeal mucositis. There was also significant improvement in terms of reduction in hyperemia and mucositis in benzydamine group. No systemic side effects associated with benzydamine medication were noted. In view of the relative ineffectiveness of systemic analgesics and topical anesthetics for these conditions, benzydamine HCl promises to be a useful addition to the therapeutic armamentarium.

Analgesics↗
PubMed1986

The syndrome of apparent mineralocorticoid excess: its association with 11 beta-dehydrogenase and 5 beta-reductase deficiency and some consequences for corticosteroid metabolism.

We describe the metabolism of cortisol (F) in three children, two of them siblings, with apparent mineralocorticoid excess (AME). As with prior patients with AME, oxidation of F to cortisone (E) was impaired, but reduction of E to F was not. We propose that this metabolic defect is caused by deficient 11-dehydrogenase associated with unimpaired 11-reductase. The following supporting observations were made: urinary C21 11-hydroxy metabolites exceeded C21 11-oxo metabolites: ratio of urinary cortols to cortolones, 6.6 +/- 2.8 (+/- SD; normal, 0.47); tetrahydrocortisol (THF) and alloTHF to tetrahydrocortisone, 14.6 +/- 5.6 (normal, approximately 1); normal subjects oxidized [11 alpha-3H]F with transfer of 3H to water; the patients did not; 11-hydroxy, but not 11-oxo, C19 steroids were excreted into the urine; and fibroblasts from patients had 5 times more 11-reductase activity than normal subjects, though fibroblasts from neither group had 11-dehydrogenase activity. Other defects of cortisol metabolism not directly associated with 11-dehydrogenase deficiency were found: impaired conversion of tetrahydro to hexahydro neutral steroids, indicating defective reductive metabolism of the side chain; depressed F production rate and increased half-life of circulating F, resulting in normal blood levels of F; increased excretion of unconjugated F metabolites; and decreased excretion of THF relative to alloTHF, consistent with a 5 beta-reductase defect. Excretion of acidic metabolites of F (cortoic acids) was within the normal range. However, little or no 20 beta-hydroxy acids were excreted, while the level of urinary 20 alpha-hydroxy acids was increased. The 11-hydroxy to 11-oxo ratio of acid metabolites was similar to values in normal subjects. The proportion of cortoic acids relative to neutral hexahydro metabolites was increased (0.37 to 1.27 in patients; 22 in normal subjects). We conclude that children with AME have multiple defects in the conversion of F to neutral metabolites, while metabolism to cortoic acids was less extensively affected. How the defects in cortisol metabolism and the symptoms of AME are related remains to be determined.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1985

Extraction of 11 beta-hydroxysteroid dehydrogenase from rat liver microsomes by detergents.

In these studies our goal was to solubilize the microsomal enzyme, 11 beta-hydroxysteroid dehydrogenase (11-HSD) as the first step in its purification. Enzyme was extracted from rat liver microsomes with representative detergents (Zwittergents, Tritons, modified sterols). Oxidation-reduction (O-R) ratios of extracts varied with detergent used and ranged from 0.18 (CHAPS) to 3.8 (Zwittergent 3-14) relative to a ratio of 1.7 in intact microsomes. All detergents solubilized 11-HSD using lack of sedimentation during high speed centrifugation as criterion. With Triton DF-18 and Triton X-100, optimum extraction of 11-HSD occurred in the detergent-protein ratio range of 0.1 to 0.2 O-R ratios decreased with increased Triton X-100, but were constant as Triton DF-18 was varied. The pH optimum of enzyme extraction was 9 at a detergent-protein ratio of 0.05 and 7.5-8.0 at a ratio of 0.2. Sodium chloride increased enzyme extraction by detergents; in the absence of detergent, salt extracted protein, but not enzyme. In aqueous solution at 0 degrees C or -15 degrees C, microsomal 11-oxidation activity rose within 24 h, then decreased; reductase activity consistently decreased. Oxidation and reduction activities were inversely related in the microsomal bound enzyme. No relationship between these activities appeared in detergent-solubilized enzymes. Possible mechanisms to account for the unexpected behavior of this enzyme are discussed.

11-beta-Hydroxysteroid Dehydrogenases↗