Biomedical subjects

S V Shah

Publications and source records attributed to S V Shah.

At least 91 records · Page 5Linked to original sources

PubMed1987

Trypsin- and chymotrypsin-induced chemiluminescence by isolated rat glomeruli.

We examined whether the generation of reactive oxygen metabolites (as quantified by measuring luminol-amplified chemiluminescence) by isolated rat glomeruli could be triggered enzymatically. No response was observed with thrombin (1 or 10 U/ml), collagenase (100, 200, or 400 U/ml), or plasmin (0.1 or 1 U/ml). In contrast, chymotrypsin and trypsin caused a dose-dependent (10-200 micrograms/ml) increase in chemiluminescence from glomeruli. The peak response with chymotrypsin (100 micrograms/ml) and trypsin (50 micrograms/ml) was as follows: resting, 16 +/- 2 X 10(3) cpm/mg protein, n = 17; chymotrypsin, 233 +/- 58 X 10(3) cpm/mg protein, n = 17; and trypsin, 221 +/- 38 X 10(3) cpm/mg protein, n = 10. Tubules had only a minor response. Soybean trypsin inhibitor and aprotinin caused marked inhibition, indicating the dependency of the chemiluminescence response on the protease enzyme activity. The chemiluminescence response was by glomeruli rather than by "contaminating" leukocytes, since a similar marked response (n = 6) was observed in glomeruli isolated from cyclophosphamide-treated leukopenic (leukocyte less than 1,000/mm3) rats. Superoxide dismutase, a scavenger of superoxide, and free-radical scavengers benzoate and tryptophan inhibited the glomerular chemiluminescence response to trypsin and chymotrypsin. Neutral proteases from infiltrating leukocytes and/or renal tissue have been shown to be released in glomerular diseases; our results, which show the generation of chemiluminescence in response to neutral proteases, suggest a potential mechanism for the production of reactive oxygen metabolites in glomerular diseases.

Animals↗

PubMed1987

Gentamicin enhanced production of hydrogen peroxide by renal cortical mitochondria.

Agents that affect mitochondrial respiration have been shown to enhance the generation of reactive oxygen metabolites. On the basis of the well-demonstrated ability of gentamicin to alter mitochondrial respiration (stimulation of state 4 and inhibition of state 3), it was postulated that gentamicin may enhance the generation of reactive oxygen metabolites by renal cortical mitochondria. The aim of this study was to examine the effect of gentamicin on the production of hydrogen peroxide (measured as the decrease in scopoletin fluorescence) in rat renal cortical mitochondria. The hydrogen peroxide generation by mitochondria was enhanced from 0.17 +/- 0.02 nmol . mg-1 . min-1 (n = 14) in the absence of gentamicin to 6.21 +/- 0.67 nmol . mg-1 . min-1 (n = 14) in the presence of 4 mM gentamicin. This response was dose dependent with a significant increase observed at even the lowest concentration of gentamicin tested, 0.01 mM. Production of hydrogen peroxide was not increased when gentamicin was added to incubation media in which mitochondria or substrate was omitted or heat-inactivated mitochondria were used. The gentamicin-induced change in fluorescence was completely inhibited by catalase (but not by heat-inactivated catalase), indicating that the decrease in fluorescence was due to hydrogen peroxide. Thus this study demonstrates that gentamicin enhances the production of hydrogen peroxide by mitochondria. Because of their well-documented cytotoxicity, reactive oxygen metabolites may play a critical role in gentamicin nephrotoxicity.

Animals↗

PubMed1987

Effect of stimulated neutrophils on cyclic nucleotide content in isolated rat glomeruli.

In this study we examined the effect of cell-free supernatants from stimulated neutrophils on the adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) content in isolated rat glomeruli. Cell-free supernatants obtained from unstimulated and stimulated (with opsonized zymosan for 30 min at 37 degrees C) cells were incubated for 5 min with glomeruli and tubules. Cell-free supernatants from stimulated neutrophils significantly increased the cAMP content in the glomeruli from 34.7 +/- 2.3 to 99.7 +/- 7.0 pmol/mg protein (n = 23; P less than 0.001). The cAMP content in the tubules and the cGMP content in the glomeruli or tubules was not altered by the cell-free supernatants from stimulated neutrophils. The cAMP response of the glomeruli was not modified when supernatants were obtained from neutrophils stimulated in the presence of superoxide dismutase, a scavenger of superoxide anion. In contrast, the glomerular response to supernatants obtained from neutrophils stimulated in the presence of catalase, a scavenger of hydrogen peroxide, or in the presence of methionine or taurine, scavengers of hypochlorous acid, was significantly reduced (P less than 0.001). Additional experiments that used prostaglandin synthesis inhibitors (meclofenamate and ibuprofen) and phospholipase inhibitor (quinacrine) suggested that the reactive oxygen metabolites increase the cAMP content in glomeruli by stimulating phospholipase activity and thus enhancing prostaglandin synthesis. These data show that reactive oxygen metabolites generated by stimulated neutrophils increase cAMP content in glomeruli and suggest that neutrophils may modulate the glomerular function and the inflammatory response in glomerular disease by altering the cAMP content.

1-Methyl-3-isobutylxanthine↗

PubMed1987

Degradation of human glomerular basement membrane by stimulated neutrophils. Activation of a metalloproteinase(s) by reactive oxygen metabolites.

We examined the role of reactive oxygen metabolites in the degradation of human glomerular basement membrane (GBM) by stimulated human neutrophils. Neutrophils stimulated with phorbol myristate acetate (PMA) caused a significant degradation of GBM over 3 h resulting in 11.4 +/- 0.9% (SEM), n = 11 release of hydroxyproline compared with 0.3 +/- 0.09%, n = 11 release by unstimulated neutrophils. Superoxide dismutase, a scavenger of superoxide, did not inhibit the GBM degradation, whereas catalase, a scavenger of hydrogen peroxide, caused a marked inhibition (-60 +/- 7%, n = 4, P less than 0.001) of hydroxyproline release. Neither alpha-1 proteinase inhibitor, an inhibitor of elastase, nor soya bean trypsin inhibitor, an inhibitor of cathepsin G, caused any significant inhibition of GBM degradation. GBM degradation by cell-free supernatants obtained from stimulated neutrophils was markedly impaired in the presence of metal chelators EDTA (-72 +/- 7, n = 6, P less than 0.001) and 1,10,phenanthroline (-85 +/- 5%, n = 3, P less than 0.001). Considering these results, we postulated that reactive oxygen metabolites generated by the stimulated neutrophils activate a latent GBM degrading metalloproteinase(s). GBM degradation by supernatants obtained from incubations with catalase, azide, an inhibitor of myeloperoxidase, and methionine and taurine, scavengers of hypochlorous acid, was markedly reduced. Our data thus indicate that degradation of the GBM by PMA-stimulated neutrophils is due to activation of a latent metalloproteinase by hypochlorous acid or a similar oxidant generated by the myeloperoxidase-hydrogen peroxide-halide system.

Basement Membrane↗

PubMed1987

Beta-adrenergic blocking agents in the treatment of hypertension. Choices based on pharmacological properties and patient characteristics.

Drugs that block beta-adrenergic receptors have become one of the most widely used classes of drugs to treat hypertension. This review puts the use of beta-blockers as monotherapy for hypertension in perspective and provides reasons for choosing among the several beta-blockers available. The major reasons for discriminating within this class of drugs are related to differences in concomitant clinical conditions, differences in patient responses, and intrinsic differences among the beta-blockers. These differences relate to special properties such as beta-agonist activity (intrinsic sympathomimetic activity), beta 1-selectivity, and concomitant alpha-blockade, as well as differences in side effect profiles, excretion characteristics, and length of action of the various drugs.

Adrenergic alpha-Antagonists↗

PubMed1986

Degradation of glomerular basement membrane by a neutral metalloproteinase(s) present in glomeruli isolated from normal rat kidney.

Incubation of glomerular homogenates (200 micrograms protein) with glomerular basement membrane (GBM, 30-35 micrograms hydroxyproline) at pH 7.5 for 36 h at 37 degrees C resulted in significant GBM degradation as measured by hydroxyproline release (40 +/- 6%, n = 17). GBM degradation increased with increasing incubation time (12-48 h) and glomerular protein concentration (50-250 micrograms). GBM degradation was not significantly decreased by inhibitors of serine or cysteine proteinases or the inhibitor of bacterial metalloproteinases, phosphoramidon. In contrast GBM degradation by glomerular homogenates was markedly inhibited by the metal chelators 10mM EDTA (-95 +/- 3%, n = 7) and 2mM 1,10-phenanthroline (-96 +/- 2%, n = 4). Preincubation of glomerular homogenates with trypsin (followed by soya bean trypsin inhibitor) markedly stimulated GBM degradation (+103 +/- 20%, n = 11). These results document the presence of a GBM-degrading, neutral metalloproteinase(s) in glomeruli suggesting an important role for this enzyme in glomerular pathophysiology.

Animals↗

PubMed1986

Renal neuraminidase. Characterization in normal rat kidney and measurement in experimentally induced nephrotic syndrome.

Several lines of evidence suggest that increased neuraminidase activity may be responsible for the loss of glomerular N-acetylneuraminic acid (AcNeu) observed in various glomerular diseases. However, virtually no information is available on the activity of neuraminidase in glomeruli or the potential role of this enzyme in glomerular pathophysiology. Utilizing 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid (4MU-AcNeu) as substrate, we defined optimal assay conditions and characterized neuraminidase activity in glomeruli and, for comparison, in other renal fractions and liver. Neuraminidase activity in glomeruli, cortex and tubules was maximal at pH 4.4. The Km for 4MU-AcNeu was estimated to be 195 microM for glomeruli and 226 microM for cortex. Glomerular neuraminidase was inhibited by AcNeu (90% at 25 mM) and high concentrations of Triton X-100 (26% at 0.5%), but unaffected by CaCl2, EDTA or N-ethylmaleimide (each 1 mM). Neuraminidase activity (nmol/h per mg of protein; mean +/- S.E.M.) in normal rat kidney was: cortex, 14.47 +/- 0.76; medulla, 7.85 +/- 0.64; papilla, 2.64 +/- 0.11; tubules, 13.79 +/- 0.70; glomeruli, 5.57 +/- 0.28. In comparison, neuraminidase activity in rat liver was 2.58 +/- 0.14. Puromycin aminonucleoside (PAN)-induced nephrotic syndrome is a model of glomerular disease in which the loss of glomerular AcNeu is well documented. In two separate studies, we observed no change in the specific activity of neuraminidase in either glomeruli or cortex isolated from rats treated with PAN (15 mg/100 g, intraperitoneally) and killed at either the onset or the peak of proteinuria. Results were similar whether neuraminidase activity was expressed per mg of protein or per microgram of DNA.

Animals↗

PubMed1985

Hypokalemia secondary to primary hyperaldosteronism in a renal transplant recipient.

We describe a patient who developed persistant hypokalemia after renal transplantation that was initially attributed to diuretics and/or steroids. However after stopping the diuretic, the patient continued to have urinary losses of potassium (less than 30 mEq/day) at a time when the serum potassium was only 2.4 mEq/l and high urinary chloride (33 mEq/day) suggesting that the diuretics were not responsible for the hypokalemia and the metabolic alkalosis. The results of these simple laboratory tests and the presence of persistent severe hypokalemia prompted additional studies (peripheral renin activity; plasma aldosterone levels; and CT scan) that led to the diagnosis of left adrenal gland adenoma. Surgical removal of the adrenal adenoma led to the normalization of the serum potassium and a fall in the total CO2 content in plasma. To our knowledge this is the first report of a case of hypokalemia secondary to primary hyperaldosteronism in a renal transplant recipient.

Adenoma↗

PubMed1984

Increased cathepsin D-like activity in cortex, tubules, and glomeruli isolated from rats with experimental nephrotic syndrome.

We have examined the activity and distribution of cathepsin D (EC 3.4.23.5), a major renal lysosomal endoproteinase, in the various anatomical and functional areas of normal rat kidney. Cathepsin D-like activities (delta A280/h per mg of protein) in normal rat tissues were: cortex, 0.78 +/- 0.05, n = 37; medulla, 0.62 +/- 0.03, n = 12; papilla, 0.63 +/- 0.04, n = 12; tubules, 0.74 +/- 0.04, n = 28; glomeruli, 0.59 +/- 0.03, n = 28; and liver, 0.41 +/- 0.02, n = 28. Enzyme activity was maximal at pH 3.0-3.5 and inhibited more than 90% by pepstatin (6.7 micrograms/ml), suggesting that the enzyme is cathepsin D. In subsequent experiments we measured cathepsin D-like activity in cortex, tubules and glomeruli isolated from rats with puromycin aminonucleoside (PAN)-induced nephrotic syndrome. Treated animals (15 mg of PAN/100g body wt., intraperitoneally) developed proteinuria beginning 4 days after injection and exceeding 900 mg/24h on day 9. In two separate experiments involving 52 animals we observed a significant increase in cathepsin D-like activity in cortex (+82.7%), tubules (+109.6%) and glomeruli (+54.7%) isolated from PAN-treated rats killed during marked proteinuria (day 9, mean total urinary protein excretion: 937 +/- 94 mg/24h). This increase was observed whether the activity was expressed per mg of DNA or per mg of protein. Increased cathepsin D-like activity was first observed in cortex and tubules coincident with the onset of proteinurea (day 4, mean total urinary protein excretion: 112 +/- 23 mg/24h). In contrast with the significant elevation of renal cathepsin D-like activity, the activity (nmol/h per mg of protein) of alpha-L-fucosidase (EC 3.2.1.51), a non-proteolytic enzyme, was markedly decreased in the identical samples used for the measurement of cathepsin D-like activity: cortex (-46.4%); tubules (-46.1%); and glomeruli (-38.5%). In addition to changes in renal enzyme activities, PAN-treated rats excreted large amounts of cathepsin D-like activity in their urine (beginning on day 3) compared with nearly undetectable cathepsin D-like activity in the urine from control rats. The significant increases in glomerular and tubular cathepsin D activity may reflect an important role for this enzyme in the pathophysiology associated with PAN-induced nephrotic syndrome.

Animals↗

PubMed1984

Effect of enzymatically generated reactive oxygen metabolites on the cyclic nucleotide content in isolated rat glomeruli.

In the present study we examined the effect of reactive oxygen metabolites (generated by the xanthine-xanthine oxidase system), on adenosine-3',5'-cyclic monophosphate (cyclic AMP) and guanosine-3',5'-cyclic monophosphate (cyclic GMP) content in glomeruli and tubules that were isolated from rat renal cortex. Xanthine (0.1 mM)-xanthine oxidase (0.025 U/ml) significantly increased (P less than 0.001) the cyclic AMP content in glomeruli from 18 +/- 1 to 50 +/- 4 pmol/mg protein (n = 13). The response was dose dependent and was markedly inhibited (delta %-74 +/- 9, n = 3) by allopurinol (10(-3), a specific inhibitor of xanthine oxidase. Cyclic AMP content in the tubules, and the cyclic GMP content in glomeruli and tubules, were not altered by the xanthine-xanthine oxidase system. This lack of response was not due to lack of responsiveness of the tissues because parathyroid hormone caused a marked increase in the cyclic AMP content in tubules, and nitroprusside markedly increased the cyclic GMP content in glomeruli. The increase in cyclic AMP in glomeruli was due to generation of reactive oxygen metabolites rather than of other products (e.g. uric acid) of the xanthine-xanthine oxidase reaction--addition of uric acid to incubations had no effect; using another substrate for xanthine oxidase, acetaldehyde significantly increased (delta % 112 +/- 7, n = 4, P less than 0.001) the cyclic AMP content; and catalase that destroys hydrogen peroxide caused a marked inhibition (delta % -90 +/- 5, n = 4) of the response to xanthine-xanthine oxidase. The marked inhibition by catalase, and the lack of effect of superoxide dismutase (in a concentration that completely scavenged superoxide) suggested hydrogen peroxide as the responsible oxygen metabolite for the observed effect. Glucose-glucose oxidase (a system that directly generates hydrogen peroxide), and direct addition of hydrogen peroxide caused a dose-dependent increase in the cyclic AMP content in glomeruli, which further supports the role of hydrogen peroxide as the responsible species for the observed effect. Additional experiments that used prostaglandin synthesis inhibitors and antagonists of serotonin and histamine suggested that hydrogen peroxide increases cyclic AMP content in glomeruli by enhancing prostaglandin synthesis.

Allopurinol↗

PubMed1984

Impaired oxidative metabolism by leukocytes from renal transplant recipients: a potential mechanism for the increased susceptibility to infection.

Adolescent↗

PubMed1984

Paraplegia.

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Adult↗

PubMed1984

Arthroscopy.

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Arthroscopy↗

PubMed1984

Non-healing ulcers in the foot.

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Adult↗

PubMed1983

NADPH-induced chemiluminescence and lipid peroxidation in kidney microsomes.

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Animals↗

PubMed1983

Chemiluminescence and superoxide anion production by leukocytes from diabetic patients.

Stimulated neutrophils exhibit a burst of oxidative metabolism which results in the formation of superoxide anion and other oxygen species that participate in bacterial killing. Chemiluminescence is also produced and is a sensitive measure of oxidative metabolism and correlates well with antimicrobial activity. Since infection is an important cause of morbidity and mortality in diabetic patients we examined chemiluminescence and superoxide production by leukocytes from diabetics in the resting state and in response to a soluble (phorbol myristate acetate) and to a particulate stimulus (opsonized zymosan). No significant difference in the resting chemiluminescence was observed. However, the resting superoxide anion production by patients' leukocytes was significantly higher in autologous serum; when patients' leukocytes were placed in normal serum, a significant reduction in the resting superoxide anion production was observed. Using phorbol myristate acetate as a stimulus, leukocytes from diabetic patients had a markedly reduced chemiluminescence response [controls 388 +/- 48, n = 22, patient 220 +/- 37, peak cpm X 10(3)/10(6)P leukocytes, n = 22, (P less than 0.01)] and reduced superoxide anion response [controls 30.1 +/- 3.8, n = 16, patients 13.3 +/- 2.6 nmol/15 min/10(6)P leukocytes, n = 16 (P less than 0.001)]. Significantly reduced chemiluminescence response (P less than 0.05) and superoxide production (P less than 0.05) by leukocytes from diabetic patients were also observed using opsonized zymosan as a stimulus. No significant effects on chemiluminescence or superoxide response to phorbol myristate acetate were observed with cross-incubation studies in which patients' leukocytes were placed in normal serum or control leukocytes in patient serum. In vitro addition of insulin (25 microU; 100 microU/ml) had no significant effect on patient cell response; similarly increasing the glucose concentration from 100 mg/dl to 200 mg/dl and 400 mg/dl had no significant effect on control cell response. Glucagon in a lower concentration (200 pg/ml) had no significant effect; only at a higher concentration (400 pg/ml), it caused an inhibition of the phorbol stimulated chemiluminescence and superoxide response of control leukocytes. These results show an impaired oxidative burst by leukocytes from diabetic patients which may contribute to impaired bacterial killing and may explain, in part, the morbidity and mortality in diabetic patients suffering from infection.

Adult↗

PubMed1982

Dynamics of renal histamine in normal rat kidney and in nephrosis induced by aminonucleoside of puromycin.

Histamine is known to have a profound effect on capillary permeability in nonrenal tissues and this effect is presumably mediated by cyclic (c)AMP. Because in our previous experiments we found that histamine stimulates cAMP accumulation in glomeruli (Torres, V. E., T. E. Northryn, R. M. Edwards, S. V. Shah, and T. P. Dousa. 1978. Modulation of cyclic nucleotides in isolated rat glomeruli. J. Clin. Invest.62: 1334.), we now explored whether this amine is formed in renal tissue, namely in glomeruli, and whether its renal metabolism is altered in experimental nephrosis induced by puromycin aminonucleoside (PA) in rats. In normal rats, histamine content was higher (Delta + 240%) in cortex than in medulla. In glomeruli isolated from renal cortex, histamine content was significantly higher (Delta + 260%) than in tubules. Incubation of isolated glomeruli with l-histidine resulted in a time-dependent increase of histamine content in glomeruli, but no change was found in tubules. The increase in glomerular histamine was blocked by the histidine decarboxylase inhibitor bromocresine. In rats with PA nephrosis induced by a single intraperitoneal injection of PA (15 mg/100 g body wt) urinary excretion of histamine was markedly increased (>Delta + 200%), but control rats did not differ from rats with PA nephrosis in urinary excretions of l-histidine and of creatinine. At the peak of proteinuria (day 9 after injection of PA) the plasma level of histamine was slightly elevated, and plasma histidine slightly decreased in animals that developed PA nephrosis. The content of histamine was markedly higher and the level of histidine was significantly lower in the renal cortex of PA-nephrotic rats as compared with controls; PA-nephrotic and control rats did not differ in the content of histidine and histamine in the liver. In addition, the content of histamine was higher in glomeruli isolated from PA-nephrotic rats; lesser difference was found in cortical tubules. The results further indicate that PA-nephrotic rats have higher content of histamine in the renal cortex, predominently in glomeruli with increased urinary histamine excretion. The elevated renal cortical histamine is not due to higher availability of histamine precursor l-histidine. Results thus show that glomeruli are a major site of intrarenal histamine synthesis and accumulation, and also suggest that abnormal renal metabolism of this amine in PA nephrosis may be related, as a cause or as a consequence, to the pathogenesis of this disease.

Animals↗

PubMed1981

Chemiluminescence and superoxide anion production by leukocytes from chronic hemodialysis patients.

During phagocytosis or in response to a soluble stimulus, polymorphonuclear leukocytes (PMN) undergo a burst of oxidative metabolism involved intimately in antimicrobial activity. Superoxide anion produced during the burst is bactericidal either directly or as an intermediate metabolite. In addition, stimulated PMN's emit light or chemiluminescence (CL). CL is a sensitive measure of PMN oxidative potential and correlates with antimicrobial activity. Because of the increased susceptibility to infection observed in patients on chronic hemodialysis (CHD), we studied superoxide anion production and luminol-amplified CL in PMN's from CHD patients and in age-matched controls in the resting state and in response to phorbol myristate acetate (PMA). Studies in autologous serum showed higher CL resting values in PMN's from CHD patients, and crossincubation studies indicated that this is a result of factor(s) in the patients' serum. In response to PMA, PMN's from patients on CHD in autologous serum had significantly (P less than 0.05) less of an increase (phorbol-stimulated minus resting values) in CL as compared with controls (peak time values, 60 +/- 5 x 10(3) cpm for patients vs. 76 +/- 5 x 10(3) cpm for controls). With crossincubation studies, these differences persisted, suggesting that there is a defect intrinsic to the patient PMN. Studies done after dialysis showed a significant reduction in resting values. The decreased response to PMA stimulation remained, however. No difference in superoxide anion production (superoxide-dismutase-inhibitable ferricytochrome c reduction) was seen in PMN's from patients on CHD compared with controls. This along with other studies indicating normal nitroblue tetrazolium (NBT) reduction in PMN's from CHD patients indicates that the decreased CL is due to superoxide-anion-independent mechanisms. Because CL correlates well with antimicrobial activity, the reduced response to PMA observed in neutrophils from patients on CHD may explain, at least in part, the increased susceptibility to infection in these patients.

Adult↗