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Biomedical subjects

M Singh

Publications and source records attributed to M Singh.

At least 397 records · Page 22Linked to original sources
PubMed1998

Effect of angiotensin converting enzyme inhibitors on ischaemia-reperfusion-induced renal injury in rats.

The present study was designed to investigate the effect of captopril, a sulfhydryl (-SH) containing ACE inhibitor and lisinopril, a non-SH containing ACE inhibitor, on ischaemia-reperfusion-induced renal injury in rats and to study the involvement of the free radical scavenging property of captopril in its renoprotective effect. Bilateral renal artery occlusion was induced for 30 min followed by reperfusion for 24 h. Blood samples were taken from retro orbital sinus before surgery and at 24 h after reperfusion for blood urea and blood creatinine estimation. After completion of 24 h of renal reperfusion the carotid artery was cannulated and the mean arterial blood pressure (MABP) was recorded. The left kidney was used for histological examination. The right kidney was utilised for estimation of mitochondrial thiobarbituric acid reactive substances (TBARS). Renal ischaemia, followed by reperfusion, significantly increased blood urea nitrogen (BUN) and blood creatinine. However, creatinine clearance decreased markedly. Captopril administered before renal artery occlusion or immediately after reperfusion and lisinopril pre-treatment significantly attenuated the increase in BUN and blood creatinine. Creatinine clearance was markedly better in captopril-treated animals as compared to lisinopril-treated rats. Captopril significantly decreased the degree of tubular necrosis, haemorrhagic streaks and urinary casts. Lisinopril treatment decreased tubular necrosis and urinary casts but no marked effect on haemorrhagic streaks was noted. Administration of captopril before ischaemia or just after reperfusion significantly reduced the elevated concentration of mitochondrial TBARS but no such decrease was noted in lisinopril-treated rats. Based on these results it may be concluded that captopril and lisinopril markedly protected against ischaemia-reperfusion-induced renal injury and any additional renoprotective effect of captopril may be ascribed to its free radical scavenging properties.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Renal cell carcinoma containing fat mimicking angiomyolipoma: demonstration with CT scan and histopathology.

We report a case of a large renal tumour containing small amounts of fat and some calcification that proved to be a renal cell carcinoma. The CT appearance of the tumour was suggestive of an angiomyolipoma. Although the overwhelming majority of renal masses containing fat are angiomyolipomas, in the presence of calcification the diagnosis of renal cell carcinoma should be entertained.

Adipose Tissue↗
PubMed1998

Cytopathic effect of Blastocystis hominis after intramuscular inoculation into laboratory mice.

The present study investigated the pathogenesis of Blastocystis hominis by intramuscular injection of the organism into experimental mice. A total of 27 naïve BALB/c mice aged 6-8 weeks were injected in the leg muscle with axenic culture isolate B of B. hominis. Histological examination at different times revealed that B. hominis could produce a severe inflammatory reaction and myonecrosis. Most changes were observed at 6 h after injection and for up to 2-3 days. By 2 weeks the muscle had regained normal histology. There was infiltration of polymorphonuclear leukocytes (PML) into the injection site, indicating that B. hominis had a strong chemoattractant activity for PML.

Animals↗
PubMed1998

Autonomic functions in restrictive cardiomyopathy and constrictive pericarditis: a comparison.

BACKGROUND: This study was undertaken to analyze autonomic functions in restrictive cardiomyopathies. Restrictive cardiomyopathies have clinical and hemodynamic similarity with chronic constrictive pericarditis. Autonomic dysfunction has been described in the latter. METHODS AND RESULTS: Autonomic function analysis has not been reported in restrictive cardiomyopathy. Six consecutive patients with restrictive cardiomyopathy were included in this study (5 men, 1 woman, mean age 35+/-5.4 years). The tests performed were designed to test the sympathetic efferent pathway, that is, by cold hand immersion and loud noise tests, parasympathetic efferent pathway by Valsalva ratio and expiration/inspiration ratio and the baroreceptor function by testing their sensitivity slope. The results were compared with 20 patients with chronic constrictive pericarditis and with 10 healthy age- and sex-matched control subjects previously studied. The rise of systolic blood pressure after cold hand immersion and sudden loud noise was not significantly different compared with control subjects. The expiration/inspiration ratio was 1.1+/-0.01 compared with 1.57+/-0.1 in the control group (p < 0.01). The Valsalva ratio was significantly lower (1.1+/-0.04) compared with control subjects (1.83+/-0.1, p < 0.01). The baroreceptor sensitivity was not reduced compared with that in control subjects. In comparison to constrictive pericarditis, sympathetic efferent pathway is preserved in restrictive cardiomyopathy (p < 0.0001). The parasympathetic efferent pathway is borderline abnormal in restrictive cardiomyopathy but not significantly as compared with constrictive pericarditis (p=not significant). The baroreceptor sensitivity slope is normal in patients with restrictive cardiomyopathy as compared with significant depression seen in constrictive pericarditis (p < 0.05). Autonomic functions are better preserved in patients with restrictive cardiomyopathies compared with chronic constrictive pericarditis. CONCLUSIONS: Autonomic dysfunction is localized to parasympathetic efferent pathway. This is in comparison to constrictive pericarditis, in which severe autonomic dysfunction is a universal feature and includes all segments of autonomic nervous system.

Adolescent↗
PubMed1998

Association of genital mycoplasma colonization with low birth weight.

OBJECTIVE: This study was conducted to document the prevalence of maternal genital tract colonization by Ureaplasma urealyticum and Mycoplasma hominis, and to assess its association with low birth weight (LBW) and prematurity. METHODS: The high vaginal swabs of pregnant women in spontaneous labor after 26 weeks of gestation were cultured for U. urealyticum and M. hominis. Clinical details and perinatal outcomes including birth weight and gestation were documented. RESULTS: Of a total of 303 women enrolled, 148 (48.8%) had positive vaginal cultures for U. urealyticum, while only five (1.6%) grew M. hominis. The mean birth weight and the incidences of LBW and preterm neonates among ureaplasma positive and ureaplasma negative mothers were statistically comparable. CONCLUSIONS: U. urealyticum emerged as a common inhabitant of the lower genital tract of women in labor, being present in nearly half of them. Its presence was not a risk factor of LBW or prematurity. Maternal colonization with M. hominis was uncommon.

Adult↗
PubMed1998

Characterization of a second calcium-dependent protein kinase from winged bean.

In plants, Ca2+ has emerged as the predominant second messenger for signal transduction, as cyclic nucleotides are not known to play any significant role in this system. Earlier, we characterized an interesting Ca(2+)-dependent protein kinase, WbCDPK (winged bean calmodulin-like domain protein kinase), from the soluble fraction of winged bean (Psophocarpus tetragonolobus) shoot extract. Here an isoform of WbCDPK is purified to apparent homogeneity from the same winged bean shoot extract. It is a single polypeptide chain protein-serine kinase, having an M(r) of about 70,000 and like WbCDPK, its preferred substrates are histone H1, syntide 2 and MLC-peptide (a synthetic myosin light chain related peptide) and it is totally dependent on Ca2+ for its activity, but exogenous calmodulin (CaM) does not stimulate it. However, it is strongly inhibited by CaM antagonists, indicating the presence of a CaM-like domain, as in WbCDPK. The two enzymes do not cross react immunologically and the isoform differs significantly from WbCDPK in its apparent inability to catalyse the autophosphorylation reaction, which is known to cause down-regulation of substrate phosphorylation in the case of WbCDPK.

Blotting, Western↗
PubMed1998

Diffuse leptomeningeal gliomatosis associated with multifocal CNS infarcts.

BACKGROUND: Widespread dissemination of astrocytoma throughout the cerebrospinal fluid is unusual, especially as the initial presentation in a patient, and association with cerebral infarcts is rare. CASE DESCRIPTION A 47-year-old man subacutely developed progressive headache and backache, vomiting, altered consciousness, and numbness in both arms. Brain computerized axial tomography showed calcification in the fourth ventricle and magnetic resonance imaging demonstrated diffuse meningeal enhancement, a lesion in the canal of Magendie, and T2-weighted hyperintense lesions in several locations. Angiography showed vasospasm/vasculopathy involving multiple cerebral vessels. Biopsy of the fourth ventricular mass revealed a subependymoma with an overlying leptomeningeal anaplastic astrocytoma with numerous Rosenthal fibers. The patient was treated with three doses of intrathecal methotrexate via lumbar puncture but suddenly became unresponsive and died 6 days later, 8 weeks after initial symptoms. Autopsy demonstrated the subependymoma and a widespread leptomeningeal anaplastic astrocytoma, which showed no clear-cut origin from the subependymoma, but microscopically infiltrated the left medial temporal lobe. Multiple subacute and acute infarcts of the brain, brain stem, and upper spinal cord were seen only in areas with leptomeningeal tumor. CONCLUSION Glioma cells surrounding and focally permeating central nervous system vessels without lumenal occlusion can lead to vasospasm and widespread infarcts.

Arachnoid↗
PubMed1998

Use of citric acid for neutralizing polymerase chain reaction inhibition by chlorogenic acid in potato extracts.

Polyphenolics are a widely distributed class of plant constituents implicated in the inhibition of the polymerase chain reaction (PCR). Since chlorogenic acid forms the bulk of phenolics in the potato tuber, a range of chlorogenic acid concentrations were tested for inhibition of reverse transcription (RT) and PCR steps. The RT step was inhibited at chlorogenic acid concentrations of 6.0 to 7.5 microg, while the PCR step was inhibited at much lower concentrations of 1.2 to 1.8 microg. Incorporation of 1.2% citric acid at the nucleic acid extraction step prevented darkening of the extract and neutralized the inhibitory effect of chlorogenic acid.

Chlorogenic Acid↗
PubMed1998

Controlled release microparticles as a single dose diphtheria toxoid vaccine: immunogenicity in small animal models.

Diphtheria toxoid (DT) was encapsulated in microparticles prepared from polylactide-co-glycolide (PLG) polymers using a solvent evaporation technique. Combinations of small and large sized microparticles with controlled release characteristics were used to immunize Sprague Dawley rats and the antibody responses were monitored for one year. For comparison, control groups of rats were immunized at 0, 1 and 2 months with DT adsorbed to alum. The antibody responses generated by the microparticles were comparable to the alum immunized control groups from 32 weeks. Microparticles with a single entrapped antigen (DT) induced better antibody responses than microparticles with two antigens entrapped simultaneously (DT + TT). Microparticles prepared from a single polymer were less effective for long term antibody induction than a combination of microparticles prepared from three different polymers. A combination vaccine consisting of antigen absorbed to alum and also entrapped in microparticles gave the best response. In an inhibition assay designed to determine the relative binding of antisera to the antigen, the sera from the microparticle and the alum immunized animals showed comparable binding. An intradermal challenge study was performed in rabbits, which showed similar levels for the alum and the microparticle immunized animals at 4, 12 and 32 weeks after immunization.

Animals↗
PubMed1998

A comparison of biodegradable microparticles and MF59 as systemic adjuvants for recombinant gD from HSV-2.

A recombinant form of glycoprotein D from herpes simplex virus type-2 (gD2) was encapsulated into polylactide-co-glycolide (PLG) microparticles using a previously established solvent evaporation technique. The mean size of the microparticles was about 1 micron and high encapsulation efficiency of the antigen was achieved (70-80%). The microparticles were administered intramuscularly to Balb/C mice and the immune responses were compared with those obtained with the oil in water adjuvant MF59. The serum IgG response to gD2 induced by the microparticles was comparable with that induced by MF59. The serum neutralization titres were also comparable for microparticles and the emulsion. However, the microparticles induced a higher IgG2a isotype response and a more potent serum IFN-gamma response than MF59, suggesting a more Th1 type of response. The MF59 induced higher levels of serum IL-4 and IL-5 cytokines, suggesting a more Th2 type of response.

Adjuvants, Immunologic↗
PubMed1998

Oxidative transformations of 1-nitropyrene under simulated environmental conditions.

The oxidation of 1-nitropyrene (1-NP), adsorbed on silica gel, with dimethyldioxirane (DMD) leads to the formation of 1-nitropyrene 4,5-oxide and 1-nitropyrene 9,10-oxide in a ratio of 74/26 (4,5-oxide/9,10-oxide). When the adsorbed 1-NP is exposed to the products of the gas-phase reaction of tetramethylethylene (TME) with ozone at -40 degrees C, the same oxides are produced in a ratio of 72/28. The fact that the ratio of the oxides is essentially the same in these two different types of experiments is highly significant. We have speculated that the gas-phase ozonolysis of TME produces an energy-rich form of the carbonyl oxide, acetone oxide. Some of this carbonyl oxide may cyclize to the isomeric DMD which, we propose, is responsible for oxide formation in the TME/ozone experiment. This proposal is supported by the observation that using ozone alone to oxidize 1-NP does not lead to oxide formation. Thus the oxidant responsible for oxide formation in the TME/ozone experiment must be produced in the ozonolysis. We suggest that this oxidant is DMD.

Adsorption↗
PubMed1998

Possible mechanism of captopril induced endothelium-dependent relaxation in isolated rabbit aorta.

The mechanism of captopril, an angiotensin converting enzyme (ACE) inhibitor with sulfhydryl group (SH) in its structure, to produce an endothelium-dependent vasorelaxation was studied. In rabbit aorta with intact endothelium and precontracted with phenylephrine, captopril and superoxide dismutase (SOD) produced dose-dependent relaxation. Lisinopril, an ACE inhibitor without a -SH group in its structure, did not produce endothelium-dependent relaxation. It was observed that captopril, like SOD, produced the relaxation by protecting the EDRF from getting inactivated by superoxide anions as pyrogallol and methylene blue inhibited both the captopril and SOD-mediated relaxation. The free radical scavenging action of captopril is further substantiated by the observation that captopril, but not lisinopril, inhibited FeCl3/ascorbic acid-induced lipid peroxidation in whole tissue homogenates of rabbit aorta to a level comparable to that of SOD. These results suggest that endothelium-dependent vasodilation produced by captopril may be due to its ability to scavenge superoxide anion and this property may be ascribed to the -SH group present in its structure.

Angiotensin-Converting Enzyme Inhibitors↗