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Biomedical subjects

R Singh

Publications and source records attributed to R Singh.

At least 505 records · Page 28Linked to original sources
PubMed1991

Antifertility activity of volatile fraction of neem oil.

NIM-76, the odorous and volatile fraction of neem oil, was investigated for its antifertility activity in vivo in rats, rabbits and rhesus monkeys. The drug is effective when applied before coitus but not so when applied during post-coital stages. It, therefore, appears to act mainly by its spermicidal effect. No alteration in the estradiol (E2) and progesterone (P) values was observed after the application of the drug in monkeys.

Animals↗
PubMed1991

Potential anti-AIDS agents. Synthesis and antiviral activity of naphthalenesulfonic acid derivatives against HIV-1 and HIV-2.

Certain naphthalenesulfonic acid analogues have been synthesized and evaluated for their inhibitory effects on HIV-1- and HIV-2-induced cytopathogenicity, HIV-1 giant cell formation, and HIV-1 reverse transcriptase (RT) activity. A bis(naphthalenedisulfonic acid) derivative having a biphenyl spacer emerged as the most potent and selective inhibitor of virus-induced cytopathogenicity in MT-4 cells. The ED50 values for this compound were 7.6 and 36 microM for HIV-1 and HIV-2, respectively. No toxicity to the host cells was detected at 98 microM. This compound also inhibited giant cell formation and was superseded in potency by a bis(naphthalenedisulfonic acid) derivative having a flexible decamethylene spacer. In the cell-free RT assay, a long-chain amide derivative exhibited the most inhibition of RT. All the compounds that achieved complete inhibition of virus-induced cytopathogenicity at concentrations not toxic to host cells were derivatives of 4-amino-5-hydroxy-2,7- naphthalenedisulfonic acid. These analogues represent new leads for the development of anti-HIV agents.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Antibacterial activity and penicillin-binding protein affinity of new cephalosporin derivatives in Staphylococcus aureus and Escherichia coli.

A series of C3-substituted cephalosporins with different levels of oxidation was synthesized and the activities of eight compounds, including affinity for penicillin-binding proteins (PBPs), in Staphylococcus aureus and Escherichia coli were studied. The more hydrophobic cephalosporins, with a thiophene moiety at the C7 position, were more active than C7-methoxyiminoaminothiazole derivatives against S. aureus H (beta-lactam-susceptible), and compounds with a thioether function at C3 were more active than those with a sulphonyl function at this position. In contrast, the most active compounds against E. coli were hydrophilic, zwitterionic C7-methoxyimino-aminothiazole C3-thioether cephalosporins. The physicochemical properties of the most active compounds were in accord with those predicted for rapid outer membrane penetration. However, among the thiophene cephalosporins the dianionic sulphonyl compounds were more active than the monoanionic thioether derivatives. There was a reasonably good correlation between MICs and PBP affinities for S. aureus H. The compounds had most affinity for PBP 1 and least for PBP 4. The two most potent compounds had high affinities for PBPs 1, 2 and 3. The compounds had low affinities for the beta-lactam-insensitive PBP 2a of methicillin-resistant S. aureus strain DU4916-K7. The novel cephalosporins had the highest affinities for PBPs 1a/1b and 3 of E. coli DCO. The major morphological response of E. coli to the compounds was cell elongation.

Bacterial Proteins↗
PubMed1991

Dietary omega-3 fatty acids decrease mortality and Kupffer cell prostaglandin E2 production in a rat model of chronic sepsis.

We tested the hypothesis that substitution of omega-3 fat for dietary omega-6 fat would reduce mortality and decrease Kupffer cell prostaglandin E2 (PGE2) production in a rat model of chronic sepsis. Rats were fed via gastrostomy for 12 days with isonitrogenous, isocaloric diets containing 15% of calories as either safflower oil (omega-6) or a 10:1 mixture of menhaden oil (omega-3) and safflower oil. After five days of feeding, animals received an intra-abdominal abscess of defined bacterial content. Survivors were killed on post-laparotomy day 6 in conjunction with liver perfusion and protease liver digestion for Kupffer cell isolation. Kupffer cell PGE2 production was measured by radioimmunoassay after 18 hours of cell culture and again after stimulation with 0 LPS, 10 ng/ml LPS, and 10 micrograms/LPS. Mortality was decreased in menhaden oil-fed animals compared with safflower oil-fed animals (16% vs. 35%). Kupffer cell PGE2 production was decreased in menhaden oil-fed animals at 18 hours (354 +/- 54 vs. 570 +/- 95 pg/0.1 ml; p = 0.09) and after stimulation with 10 micrograms/ml LPS (140 +/- 41 vs. 288 +/- 45 pg/0.1 ml; p = 0.03) compared with safflower oil-fed animals.

Animals↗
PubMed1991

Carcinoma of the esophagus presenting with esophagocutaneous fistula--a case report.

An interesting manifestation of carcinoma of the esophagus, hitherto undescribed is reported. The patient at the time of diagnosis had presented with an esophagocutaneous fistula. He was treated by feeding jejunostomy and local palliative radiotherapy and showed good clinical improvement. The extreme rarity of such a presentation is highlighted.

Adult↗
PubMed1991

Novel naphthalenedisulfonic acid anti-HIV-1 agents. Synthesis and activity against reverse transcriptase, virus replication and syncytia formation.

Several naphthalenedisulfonic acid derivatives have been synthesized and evaluated in four anti-HIV-1 screens. Antiviral activity was evaluated in the assays that measure inhibition of HIV-1 reverse transcriptase (RT), HIV-1 induced giant cell (syncytia) formation, and HIV-1 induced cytopathogenicity in both a laboratory and clinical strain of HIV-1. 4-acetylamino-5-hydroxy-2,7- naphthalenedisulfonic and a bis naphthalenedisulfonic acid derivative emerged as the most active compounds exhibiting activity in all assays at concentrations non-toxic to the host cells. The bis 3-amino-1,5-naphthalenedisulfonic acid derivative was the most active compound, but less active than the bis 4-amino-5-hydroxynaphthalenedisulfonic acid analog in the assays that measure RT and syncytia inhibition. However, in the assay that measured inhibition of cytopathogenicity in a clinical HIV-1 isolate, 4-acetylamino-5-hydroxy-2,7-naphthalenedisulfonic acid was the most potent analog, demonstrating an in vitro therapeutic index greater than 54. This study shows that for certain naphthalenedisulfonic acid moieties a bis derivative is not a requirement for significant anti-HIV-1 activity. These agents represent a new class of lead non-nucleoside anti-HIV-1 compounds worthy of further development for potential anti-AIDS therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Pretreatment postural blood pressure drop as a possible predictor of response to the cholinesterase inhibitor velnacrine (HP 029) in Alzheimer's disease.

The failure of cholinesterase inhibitors to produce noticeable improvement in about half of patients with Alzheimer's disease (AD) may result from heterogeneity of neurotransmitter abnormalities in this disorder. This study examined whether pretreatment postural blood pressure (BP) drop, which presumably reflects sympathetic response, differed in patients who were responders or nonresponders to the cholinesterase inhibitor, HP 029. Twenty-three AD patients completed a double-blind dose-finding phase of a clinical trial in which four doses of HP 029 and placebo were administered. Evaluation for efficacy occurred after 7 days of treatment at each dose. Of the 23 patients, 12 were classified as responders in the dose-ranging phase of the study. Nonresponders demonstrated significantly greater decreases in pretreatment systolic postural BPs when going from a supine to sitting position than did responders. The greater postural BP drop in nonresponders may identify a subgroup of AD patients that responds poorly to cholinesterase inhibitors.

Aged↗
PubMed1991

Effects of NIDDM on the glucose transport system in human skeletal muscle.

The purpose of this study was to investigate cellular changes in the glucose transport system in skeletal muscle of lean non-insulin-dependent diabetes mellitus (NIDDM) compared to lean nondiabetic control patients. NIDDM patients had significantly elevated fasting levels (means +/- SE) of serum glucose (10.1 +/- 1.3 vs. 5.4 +/- 0.4 mM, P less than 0.001) and serum insulin (110.8 +/- 31.1 vs. 35.9 +/- 3.6 pM, P less than 0.0025). Basal glucose transport (35.1 +/- 5.5 vs. 30.8 +/- 8.0 pM/mg protein) and cytochalasin-beta binding (3.5 +/- 1.2 vs 3.8 +/- 1.0 pM/mg protein) in isolated sarcolemmal vesicles were not significantly different between NIDDM and control groups. Insulin binding was reduced in NIDDM (0.82 +/- 0.03 vs. 1.63 +/- 0.18 pM/mg protein) as was the Kd (0.93 +/- 0.03 vs. 1.38 + 0.12 nM). Tyrosine kinase activity, as assessed from incorporation of [32P]ATP into Glu 4:Tyr 1, was significantly (P less than 0.005) reduced in NIDDM at insulin concentrations from 1-100 nM. Maximum kinase activity was depressed (1.88 +/- 0.04 vs. 2.97 +/- 0.07 fM 32P/fM insulin binding at 100 nM insulin). The number of glucose transporters in the low-density microsomes was not significantly different between NIDDM and control groups (7.01 +/- 1.40 vs. 7.65 +/- 0.90 pM cytochalasin-beta bound/mg protein). These results suggest that decreased insulin binding and diminished receptor tyrosine kinase activity play a substantial role in the development of skeletal muscle insulin resistance associated with NIDDM.

Adenosine Triphosphate↗
PubMed1991

Levels of copper and zinc in depression.

The study was undertaken to estimate plasma copper and zinc in thirty-five depressed patients. Two blood samples were drawn from each patient, one before starting treatment and the second after recovery from depression. The results were compared with the thirty-five normal healthy individuals. The mean plasma copper in controls, depressed patients and in patients after recovery were 106.82, 122.14 and 104.22 micrograms/dl, respectively. The copper levels in patients when depressed were significantly higher as compared to controls and after recovery from depression. The mean plasma zinc levels in controls, depressed patients and after recovery were 115.80, 107.62 and 125.68 micrograms/dl, respectively. No significant difference could be obtained between control and depressed patients. However, the values were significantly higher in recovered patients compared to patients with depression.

Copper↗
PubMed1991

Hypophosphatasia.

Explore the source record for details and available documents.

Child, Preschool↗
PubMed1991

The variability of blood pressure following repeated measurements.

Two series of Blood Pressure (BP) measurements were carried out to assess the variability in BP following repeated measurements in normotensive individuals. In one series, measurement of BP on three occasions three and seven days apart revealed a significant drop in BP in unaccustomed subjects ('untrained'). In a second series assessing the significance of time-interval between measurements or the number of measurements, it was found that a significant fall in BP occurred over the first four days in 'untrained' individuals, whose blood pressure was measured repeatedly for five consecutive days. A significant positive correlation was evident between the falls in systolic and diastolic pressures and the pressure at first screening. Assessment of the anxiety status revealed a significantly lower state anxiety in 'trained' subjects. It therefore appears that (a) BP in normotensive individuals previously unaccustomed to BP measurements, drops significantly with repeated measurements, (b) the number of measurements seem more important than the time-interval between measurements, (c) the largest falls occur in individuals with high initial pressures and (d) the fall upon repeated measurements may be due to reduced anxiety as familiarity with the procedure makes the subjects comparatively relaxed and less state anxious.

Adult↗
PubMed1991

Glycosylated hemoglobin and diabetic retinopathy.

Estimation of glycosylated hemoglobin (HbA1c) levels by modified Fluckinger and Winterhalter's method was done in 25 normal persons, 25 diabetic patients without retinopathy, and 25 diabetic patients with retinopathy. The HbA1c values were significantly higher in diabetic patients with or without retinopathy than in the control group (P less than .001). In diabetic patients with retinopathy, the mean value of HbA1c was higher in proliferative retinopathy than in background retinopathy, but statistical analysis showed this was not significant (P greater than .6).

Adult↗
PubMed1990

Characterization of U6 small nuclear RNA cap-specific antibodies. Identification of gamma-monomethyl-GTP cap structure in 7SK and several other human small RNAs.

The cap structure in human U6 small nuclear (sn)RNA, gamma-monomethylguanosine triphosphate (meGTP), was conjugated to human serum albumin and used as antigen to raise polyclonal antibodies in rabbits. The resulting antibodies reacted specifically with meGTP but not with GTP, GDP, GMP, meGMP, meATP, meCTP, meUTP, or with methyl phosphate in enzyme-linked immunosorbent assay and/or in radioimmunoassays. Although less efficiently, meGDP was also recognized by these antibodies. Indirect immunofluorescence studies with anti-meGTP antibodies showed predominantly nuclear immunofluorescence. Anti-meGTP antibodies immunoprecipitated intact U6 snRNA from a mixture of HeLa cell RNAs. In addition to the U6 snRNA, anti-meGTP antibodies immunoprecipitated several additional small RNAs that varied in length from approximately 50 to 330 nucleotides. These RNAs contained the meGTP cap structure and are structurally distinct from U6 snRNA. One of these meGTP-containing RNAs was found to be previously characterized 7SK RNA; human 7SK RNA synthesized in vitro also contained the same cap structure. Results obtained in this study provide evidence for the presence of gamma-monomethyl-GTP cap structure in a wide spectrum of human cellular RNAs. These antibodies will be useful in studying the structure and function of this new family of small RNAs.

Antibodies↗
PubMed1990

Clozapine fails to prevent the development of haloperidol-induced behavioral hypersensitivity in a cotreatment paradigm.

We have previously established that chronic cotreatments involving antimuscarinic agents and haloperidol attenuate the development of behavioral hypersensitivity without affecting dopamine receptor proliferation. The antipsychotic agent clozapine also has significant antimuscarinic activity and was coadministered with haloperidol in rats for 2 months to determine if it would similarly attenuate the development of hypersensitivity. Clozapine or chlorpromazine cotreatment, unlike thioridazine cotreatment, did not attenuate the development of haloperidol-induced behavioral hypersensitivity. Clozapine or thioridazine cotreatment also failed to prevent the development of haloperidol-induced D2 receptor proliferation, whereas chlorpromazine cotreatment enhanced D2 receptor proliferation relative to haloperidol-treated animals. Alterations in dopamine biochemistry in the striatum or nucleus accumbens could not explain this dissociation between behavioral hypersensitivity and dopamine receptor proliferation. It is therefore hypothesized that dopamine receptor proliferation is permissive for behavioral hypersensitivity and that factors in addition to alterations in dopamine function contribute to the expression of dopamine hypersensitivity states.

Animals↗