PubMed Health⌕ Search

Biomedical subjects

M Khullar

Publications and source records attributed to M Khullar.

34 records · Page 2Linked to original sources
PubMed1995

Duodenal ulcer. Calcium status in isolated parietal cells.

Although the etiology of duodenal ulcer is not known, its treatment with drugs that reduce acid secretion is well accepted. The central role of calcium in stimulus-secretion coupling resulting in acid secretion by gastric parietal cells is documented. However, the status of intracellular calcium in gastric parietal cells in the basal state in patients with duodenal ulcer is not known. Multiple endoscopic gastric mucosal biopsies from the corpus of the stomach of 52 patients were processed and isolated parietal cells were studied. Intracellular calcium was estimated using fura-2-acetoxymethyl ester. Influx and efflux were determined by using radioactive calcium. Acridine orange retention was used to assess acid production. Only calcium influx at 20 min was significantly (P < 0.01) more in patients with duodenal ulcer as compared to the control group. There was no difference between the groups in calcium influx at 0 and 60 min; calcium efflux at 0, 20, and 60 min; intracellular free calcium and acid secretion. We conclude that in the unstimulated state calcium homeostasis in isolated parietal cells of patients with duodenal ulcer shows only a minimal difference as compared to controls.

Adult↗
PubMed1995

Digalactosylceramide is the receptor for staphylococcal enterotoxin-B in human kidney proximal tubular cells.

We have characterized a glycosphingolipid (GSL) receptor for Staphylococcus enterotoxin-B (SEB) in cultured human kidney proximal tubular (PT) cells. Solid-phase binding of [125I]SEB to the GSL receptor was concentration dependent and was not displaceable by two structurally related toxins, such as staphylococcal enterotoxin-A and toxic shock syndrome toxin-1. Rat kidney cells did not bind [125I]SEB. However, when the rat kidney cells were pre-incubated with digalactosylceramide, there was a concentration-dependent binding of [125I]SEB. Trimethylsilyl derivatization of methyl glycosides, followed by gas-liquid chromatography-mass spectrometry (GC-MS), revealed that galactose was the major sugar component of this putative receptor GSL. The sphingosines present in this GSL were d18:2, d22:2 and d23:0; the fatty acids present were palmitate, oleate and stearate. Permethylation of alditol acetates and GC-MS revealed two predominant sugars, namely 2, 3, 4 and 6 tetramethylgalactital and 2, 3 and 6 trimethylgalactital. The GSL receptor for SEB was sensitive to alpha-galactosidase, and resistant to beta-galactosidase and beta-glucosidase. Taken together, our studies reveal that the tentative structure of the receptor for SEB in human kidney PT cells is CerGal alpha 1-->4Gal. In summary, we have identified a GSL as one of the binding sites of SEB, a food-borne toxin. We believe that our finding may open up rational approaches for the therapy of SEB-induced glycopathology in man.

Animals↗
PubMed1995

Role of reactive oxygen species in renal damage in experimental leprosy.

Renal involvement is known to occur in leprosy. In the present study the possible role of reactive oxygen species (ROS) in causation of renal damage in mice infected with Mycobacterium leprae has been investigated. At least six animals from each group (control and infected) were killed at 0 day, 3, 6 and 9 months postinfection. The results showed a significant increase in the chemiluminescence (CL) response of peritoneal macrophages which was maximum between 3 and 6 months. No significant increase was observed in CL response of blood neutrophils. A significant increase in lipid peroxidation was observed at 3 and 6 months as evident by an increase in malondialdehyde levels. The increased ROS production might be the cause of lipid peroxidation. The renal damage is alos evident by decrease in the activity of renal brush border membrane enzymes, namely, alkaline phosphatase, leucine aminopeptidase and r-glutamyl transpeptidase. Thus ROS might play a role during early stages of M. leprae infection but in the later stages other immunological mechanisms may overpower the effect of ROS.

Alkaline Phosphatase↗
PubMed1992

Ca2+ transport in unstimulated platelets of essential hypertensives and their blood relatives.

OBJECTIVE: Intracellular free Ca2+ concentration has been shown to be elevated in platelets from essential hypertensive patients. This study was designed to characterize Ca2+ homeostasis in platelets of essential hypertensives. DESIGN: A double-blind study was carried out. Untreated and treated (propranolol therapy) essential hypertensives were studied in comparison with normotensive control subjects. First-degree blood relatives of essential hypertensives were also studied. The various procedures used in the study were already standardized and well-established methods. METHOD: For Ca2+ uptake and efflux studies, 45Ca was used. For intracellular free Ca2+ concentration studies the fluorescent Ca2+ chelator dye fura-2/acetoxymethyl ester (fura-2/AM) was used. RESULTS: The uptake of 45Ca by unstimulated platelets of untreated essential hypertensives and their relatives was significantly higher than for controls. However, essential hypertensives treated with a beta-blocker drug showed no significant difference in Ca2+ uptake compared with controls. A significantly decreased Ca2+ efflux was observed in essential hypertensives (both untreated and treated) compared with controls. Relatives also showed a depressed Ca2+ efflux compared with controls. CONCLUSIONS: It appears that the elevated intracellular free Ca2+ concentration levels in platelets (also observed by us) may be due to both an enhanced uptake into, and decreased efflux of Ca2+ from, the cell. Beta-blocker therapy may help to normalize the elevated intracellular free Ca2+ concentration levels observed in essential hypertensives. Relatives exhibit a state predisposed towards the development of hypertension.

Adolescent↗
PubMed1992

Effect of exogenous copper on lipid peroxidation in rat hepatocytes. Possible involvement of protein kinase C.

We have investigated the direct effect of copper on malondialdehyde formation in rat isolated hepatocytes. Copper was found to decrease the cell viability with concomitant production of malondialdehyde in a time related manner. In addition the protein kinase C activator, PMA, was found to have a synergistic effect with copper on rat hepatocytes. These results indicate that protein kinase C may be important in mediating hepatotoxicity after exposure to copper.

Animals↗
PubMed1992

Salmonella typhimurium enterotoxin mediated fluid secretion.

Unidirectional Na+ and Cl- fluxes were studied in rats treated with S. typhimurium enterotoxin (S-LT). There was net absorption of Na+ and Cl- in the control group, while in the toxin treated animals there was net secretion of Na+ and Cl- (P less than 0.001). There was no change in the transport of D-glucose in the toxin treated group as compared to the control animals. The Na+, K(+)-ATPase pump was unaltered in the S-LT treated animals (198.67 +/- 11.23 nmoles Pi/mg protein/min) as compared to the control group (189.93 +/- 10.09 nmoles Pi/mg protein/min). There was no change in the unidirectional fluxes of Ca+2 in the S-LT treated animals as compared to the control animals, suggesting no change in the permeability of the S-LT treated intestinal membrane to Ca+2.

Animals↗
PubMed1991

Studies on the mechanism of Salmonella typhimurium enterotoxin-induced diarrhoea.

The unidirectional fluxes of Na+ and Cl- were studied in Salmonella typhimurium enterotoxin-treated rats. There was net secretion of Na+ and Cl- in toxin-treated animals, while in control animals there was net absorption of these ions. In the presence of the Ca(2+)-ionophore, there was net secretion of Na+ and Cl- in the control group, while the ionophore enhanced the secretion of these ions in experimental animals. The calcium channel blocker, verapamil, decreased the secretion induced by salmonella toxin, but could not reverse the secretion to absorption. There was no difference in the net absorption of Ca2+ in both the control and experimental animals. There was a significant increase in the intracellular free calcium concentrations in enterocytes isolated from toxin-treated rat intestines as compared to that in enterocytes isolated from control animals. In the presence of PMA (phorbol-12-myristated-13-acetate) there was net secretion of Na+ and Cl- in the control group, while in the experimental group there was no change in the fluxes of these ions. The selective, potent inhibitor of protein kinase C, H-7 (1-(5-isoquinolinylsulphonyl)-2-methylpiperazine) reversed the secretion of Na+ and Cl- in the toxin-treated group to absorption. The addition of indomethacin also inhibited the secretion induced by salmonella toxin, but failed to reverse it to absorption. However, the addition both H-7 and indomethacin to the experimental group had a partial additive effect. These studies demonstrate that the Salmonella enterotoxin-mediated fluid secretion involves protein kinase C and the arachidonic acid metabolites and perhaps does not involve the extracellular calcium pools.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

The correlation of biochemical virulence factors and enterotoxin production with LD50 of Salmonella typhimurium in mice.

Five strains of Salmonella typhimurium were examined to determine the parameters of virulence. The virulent species significantly resisted the macrophage bactericidal activity (p less than 0.05). The chemiluminescent (CL) response was studied to determine the level of Oxygen-free radicals (OFR) generated and the antioxidant enzymes superoxidase dismutase (SOD), catalase and glutathione peroxidase were assayed to determine the antioxidant mechanism of S. typhimurium to subvert these microbicidal pathways. The levels of the various enzymes were correlated with the virulence (as determined by LD50) and the ability of the microorganisms to induce diarrhoea. Oxygen free radical (OFR) generation elicited by macrophages, in the presence of virulent and avirulent salmonellae was not statistically significant (p greater than 0.05). No correlation was found between the levels of the antioxidant enzymes and the LD50 values. Thus the oxygen-dependent pathways do not appear to play a role in the pathogenesis of salmonellosis, and do not specify the virulence of the microorganism. Immunological and biological assays revealed the virulent strain to be more toxigenic than the avirulent strain. Therefore, the basis of differing virulence in S. typhimurium may be the ability to make and release more toxin in vivo.

Animals↗
PubMed1991

Role of oxygen dependent mechanisms in virulence of Salmonella typhimurium.

Catalase and superoxide dismutase (SOD) activities of five strains of S. typhimurium, namely SF 1546 LT2 71, SF 1835 C5 50, 386 SF 1591 Ra 20, SF 1567 Rd1, and an Indian strain were determined and correlated with their virulence profile. All five Salmonella strains exhibited catalase and SOD activities. No correlation was observed between either SOD and/or catalase activity and LD50 values of the isolates. Oxygen free radical generation elicited by macrophages, in the presence of virulent and avirulent salmonellae was also not statistically significant (P greater than 0.05), although the virulent species significantly resisted the macrophage bactericidal activity (P less than 0.05). It appears, therefore, that oxygen-dependent bactericidal mechanisms may not be important in phagocytic killing of S. typhimurium.

Catalase↗
PubMed1986

Purification and characterization of a serine protease (esterase B) from rat submandibular glands.

A new protease has been purified to homogeneity from rat submandibular gland homogenate by using DEAE-Sephadex chromatography, chromatofocusing, aprotinin-Sepharose affinity chromatography, and high-performance liquid chromatography. The enzyme has been named esterase B, since it represents the second major esterolytic peak on DEAE-Sephadex chromatography of submandibular gland homogenate. It is an acidic protein (pI = 4.45) with an apparent molecular weight of 27 000. It is heat-stable and has an optimum pH of 9.5. Esterase B hydrolyzed the synthetic substrates tosyl-L-arginine methyl ester and Val-Leu-Arg-p-nitroanilide (S2266). It also cleaved dog plasma kininogen to produce a kinin, identified as bradykinin on reverse-phase high-performance liquid chromatography. Esterase B, however, is only a weak kininogenase, since it had only 5% of the kininogenase activity of equimolar concentrations of glandular kallikrein and had no effect on rat mean blood pressure or on the isolated rat uterus. Esterase B activated plasminogen and had caseinolytic activity. It was inhibited by aprotinin, soybean trypsin inhibitor, lima bean trypsin inhibitor, phenylmethanesulfonyl fluoride, antipain, leupeptin, and p-tosyl-L-lysine chloromethyl ketone. On double immunodiffusion, when reacted with kallikrein and tonin antisera, esterase B showed partial identity with kallikrein but not with tonin. On immunoelectrophoresis against kallikrein antisera, esterase B formed a precipitin arc at a position different from that of kallikrein. Esterase B appears to be a trypsin-like serine protease having some homology with glandular kallikrein.

Amino Acids↗
PubMed1986

Characterization of monoclonal antibodies against rat glandular kallikrein.

Monoclonal antibodies can be produced in large amounts, are homogenous and can be highly purified. A specific monoclonal antibody against glandular kallikrein could be very useful in studies of the kallikrein-kinin system, both in vivo and in vitro. Two monoclonal antibodies against rat glandular kallikrein (rgKK) were produced by immunized mouse spleen and lymph node fusion with myeloma Ag8.653. Both antibodies, named 2E9.8 and 2E9.9, bound active 125I-kallikrein and phenylmethylsulfonyl fluoride (PMSF)-inactivated 125I-kallikrein. A radioimmunoassay (RIA) was developed with each of the antibodies using rabbit anti-mouse gamma globulin to separate bound from free 125I-rgKK. The standard curve (range 10-1000 ng/tube) was curved even when subjected to logit-log transformation. Using 3% polyethylene glycol (PEG) to assist separation of bound from free, the standard curve became straight for 2E9.8 and the RIA was more sensitive, with a binding range of 0.35-2.4 ng/tube. Both antibodies were specific for rgKK since they had negligible cross-reaction with purified proteases from the submandibular gland of the rat (tonin, esterases B and E). They did not cross-react with mouse nerve growth factor, epidermal growth factor, nor with pig pancreatic kallikrein. Antibody 2E9.9 did appear to bind some human kallikrein when tested with high concentrations of this enzyme, while 2E9.8 did not. When preincubated with purified rgKK, both antibodies prevented the enzyme from releasing kinins from semi-purified dog kininogen and from cleaving [3H]-L-arginine methyl ester (3H-TAME). These results suggested that both antibodies bind an epitope near to, and maybe including, the active site of the enzyme. Monoclonal antibody 2E9.8 appears to be specific for rgKK, can be used in a sensitive RIA, and is capable of inhibiting the enzymatic activity of kallikrein. It should prove to be useful in vivo for examining the role of kallikrein in physiological processes.

Animals↗
PubMedDate not supplied

Biochemical and molecular markers in renal cell carcinoma: an update and future prospects.

Cancer is a big problem in the developed world as well as in developing countries. Renal cell carcinoma (RCC) accounts for approximately 3% of adult malignancies and 90-95% of neoplasms arising from the kidney. RCC is more common in men than in women (2:1), and it most often occurs in patients between the ages of 50-70 years. In all cancers the cancerous cells release particular kind of proteins (called tumour markers) and blood tests are used to detect the presence of these markers. These tumour markers nowadays are an area of interest for oncologists who search for a possible solution in the detection and treatment of RCC. Different kinds of biochemical and molecular markers such as ferritin, MN/CA9, apoptotic index, p53, IL-2, gamma-enolase, CD44, CD95, chromosome instability and loss of heterozygosity have been tested in RCC, but so far no marker fulfils one or the other criteria to be considered as an ideal marker for RCC. This review gives basic and updated information about the different kinds of biomarkers studied in RCC and about the role implementation of genomics and proteomics in RCC.

Adult↗
PubMedDate not supplied

Catecholamine-induced experimental cardiomyopathy--a histopathological, histochemical and ultrastructural study.

An experimental model of myocardiopathy was induced in rhesus monkeys following noradrenaline (NA) infusion (20 ug/kg body wt/minute), for a period of 2 hours daily for three consecutive days. The animals were sacrificed after two hours (acute phase), forty-eight hours (sub-acute phase) and twenty-one days (chronic phase). Focal depletion of succinic dehydrogenase, increase in adenosine triphosphatase, acid phosphatase and appearance of large fat droplets in myocardial muscle was noted in the acute phase. Histopathological examination revealed focal edema, opacity and fuchsinorrhagia of the muscle fibres distributed in both the ventricles. Myofibrillar degeneration, myocytolysis and vacuolization with aggregation of lymphomononuclear cells were the significant features in the acute phase. During sub-acute and chronic phases, these features became less prominent and reparative changes with proliferation of fibroblasts became more marked. By the twenty-first day, irregular, focal scars replaced the necrosed myocardium. Ultrastructurally, heart muscle showed myofibrillar disorganisation, distortion of Z and A bands, dilatation of sarcoplasmic reticulum and swelling and rupture of mitochondria. Altered membrane permeability was evidenced by the presence of reaction products of horseradish peroxidase within the cardiac cells. In the reparative phase, however, myocytolytic changes regressed and collagen deposition was the prominent feature. This experimental study has several histological features simulating human cases of myocardial infarction without coronary occlusion.

Animals↗
PubMedDate not supplied

Clonidine suppression test--an evaluation of its diagnostic significance in hypertensive patients.

The Clonidine Suppression Test (CST) was performed in 8 patients with Labile hypertension (Group I), 8 patients with mild and moderate Essential hypertension (Group IIa), 8 patients with severe Essential hypertension (Group IIb) and 6 patients with pheochromocytoma (Group III). The mean plasma catecholamine (CA) levels as estimated by a Spectrofluorimetric method were significantly reduced 3-4 hours after administration of clonidine (5 micrograms/kg) by mouth in Group I, IIa & IIb patients. Plasma norepinephrine levels fell from 1.82 +/- SEM 0.35 ng/ml to 1.03 +/- 0.11 ng/ml (p less than 0.05) in Group I, 1.64 +/- 0.36 ng/ml to 0.88 +/- 0.12 ng/ml (p less than 0.025) in Group IIa, 1.23 +/- 0.16 ng/ml to 0.86 +/- 0.12 ng/ml (p less than 0.005) in Group IIb patients. Plasma epinephrine levels fell from 0.35 +/- 0.06 ng/ml to 0.16 +/- 0.03 ng/ml (p less than 0.05) in Group I, 0.34 +/- 0.04 ng/ml to 0.22 +/- 0.03 ng/ml (p less than 0.01) in Group IIa, 0.33 +/- 0.06 ng/ml to 0.18 +/- 0.03 ng/ml (p less than 0.025) in Group IIb patients. The blood pressure and heart rate showed a similar response. By contrast, in patients with pheochromocytoma, the mean plasma CA levels did not show any significant fall, and even rose during the CST, but, when repeated post-operatively, showed normal suppression. No serious side effects were noticed. We conclude that the CST is a safe and reliable test for the diagnosis of pheochromocytoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗