Search PubMed⌕ Search

Biomedical subjects

R Rajagopalan

Publications and source records attributed to R Rajagopalan.

At least 73 records · Page 4Linked to original sources
PubMed1988

Cardiovascular effects of new water-soluble derivatives of forskolin.

A series of 6- and 7-aminoacyl derivatives of 7-deacetylforskolin was prepared to provide water-soluble derivatives of the potent cardioactive diterpenoid forskolin. The compounds were evaluated for positive inotropic and blood pressure lowering properties in pharmacological models. Several derivatives displayed potent positive inotropic activity in guinea pig atria (EC50 = 0.16-3.0 micrograms/mL). In the most active compounds, the amino moiety of the aminoacyl chain corresponded to a cyclic amine, and the acyl moiety to a C2-C4 alkanoyl group. In vivo biological evaluation led to the selection of 6-(piperidinoacetyl)-7-deacetylforskolin hydrochloride (49) as a candidate for clinical development.

Animals↗
PubMed1987

[Interactions between macrophages and anti-infective agents].

Direct effects of antimicrobial agents on macrophages functions are not well precised. However, antimicrobials can enhance phagocytosis of bacteria by macrophages in vitro, at subinhibitory concentrations. This enhancement is related to the antibiotic effect. It is dependent of the nature of the antimicrobial agent, of the experimental procedure and some discrepancies appeared in the results. The precise mechanism, effect on the bacterial wall, or on the bacterial protein synthesis is uncertain. The third type of interaction concerns the intracellular penetration and activity of antimicrobial agents within macrophages. In a human monocyte-derived macrophage model, the intracellular growth of Legionella pneumophila was inhibited by erythromycin, rifampicin and fluoroquinolones at concentrations clearly lower than their MICs; doxycycline and cotrimoxazole were inhibitory at concentrations closed to their MICs. Cefoxitin was not inhibitory even at high concentrations despite a low MIC value. This confirms the good intracellular activity of macrolides and fluoroquinolones and the low intracellular activity of beta-lactams.

Anti-Bacterial Agents↗
PubMed1986

Generation of an auto-anti-idiotypic antibody that binds to glucocorticoid receptor.

A monoclonal antibody (8G11-C6) that is directed to a region near the ligand-binding site of the glucocorticoid receptor was obtained by an auto-anti-idiotypic route, using a derivative of triamcinolone coupled to thyroglobulin to immunize a mouse. The resulting hybridomas were screened for anti-idiotypic antibody (anti-antisteroid) with Fab fragments of affinity-purified polyclonal rabbit anti-triamcinolone antibody. The anti-idiotypes were then screened for binding to rat cytosol glucocorticoid receptor by a depletion procedure, yielding a clone, 8G11-C6, whose specificity for receptor was verified by sucrose density and Western blot analyses. Depletion was not significantly reduced by prelabeling the cytosol with [3H]triamcinolone acetonide. The anti-idiotype (8G11-C6) bound to Fab fragments of antisteroid and to partially purified receptor in a concentration-dependent manner. Both binding reactions were inhibited only by rabbit serum albumin conjugates of steroids known to bind to the glucocorticoid receptors. Triamcinolone derivatives of lysine and of oligopeptides containing up to six amino acids inhibited the binding of the anti-idiotype to the Fab fragments but not to the receptor, implying that the target epitope of the antisteroid antibody may be closer to its glucocorticoid-binding site than the cross-reacting epitope of the receptor. Our findings demonstrate further the versatility of the auto-anti-idiotypic route for the preparation of anti-receptor antibodies.

Animals↗
PubMed1986

Inhibition of microtubule assembly by actinomycin D, an anti-tumour drug.

Effect of actinomycin D, an antibiotic, was investigated on the biological function of tubulin from bovine brain. The microtubule assembly was inhibited nearly completely when an equal molar ratio of actinomycin D and tubulin was used. The depolymerisation of the same, however, was not altered under the same conditions. The competence of tubulin to bind colchicine and GTP was also not affected. Chromatographic and the spectrophotometric studies showed that 0.94 mol of actinomycin D binds per mole of tubulin.

Animals↗
PubMed1986

Decision analysis computer program for use in the labor room.

A decision analytic model (a decision tree) was constructed for use in the labor room. Probabilities and (dis)utilities were estimated by obstetricians and computerized. A sensitivity analysis on six branches of the decision tree uses estimates of four obstetricians and proves that the decisions resulting from the model are stable and insensitive to differences in probability estimates within reasonable limits. Therefore it is concluded that we can construct a decision tree that is a practical, valuable, and stable tool for consistent decision making.

Blood↗
PubMed1986

New amiloride analogue as hapten to raise anti-amiloride antibodies.

A new amiloride analogue, "amiloride-caproic acid," was synthesized, coupled to albumin, and used as a hapten to raise anti-amiloride antibodies in rabbits. The antibodies were affinity purified with an amiloride affinity column and characterized. Binding studies using [3H]benzamil showed a dissociation constant of 0.8 nM. Amiloride and amiloride-caproate inhibited [3H]benzamil binding; epsilon-guanidinocaproic acid showed no inhibition. Anti-amiloride antibodies reversed the inhibition by amiloride of sodium transport across toad urinary bladder. Anti-amiloride antibodies and an amiloride affinity column should provide useful tools for the characterization of the epithelial sodium channel.

Albumins↗
PubMed1985

Effect of rifampicin on the biological activity of tubulin.

The effect of rifampicin on the biological properties of bovine brain tubulin was investigated. Assembly of microtubules was almost completely blocked by rifampicin, whereas the depolymerization was not affected. The drug was found to inhibit both colchicine and GTP binding to tubulin. Association of rifampicin with tubulin was confirmed by spectrophotometric method. Binding of rifampicin was found to be dependent both on temperature and time. At 0 degrees for 1 hr 0.84 moles of rifampicin were bound per mole of tubulin.

Animals↗
PubMed1984

Properties of antibodies to thymine glycol, a product of the radiolysis of DNA.

Anti-thymine glycol antibodies were elicited by immunizing rabbits with thymine glycol monophosphate (TMP-glycol) conjugated by carbodiimide to BSA. The antibodies produced are specific for thymine glycol as measured by immunoprecipitation of TMP-glycol-RSA conjugates and hapten inhibition of reactivity with OsO4-treated DNA in an enzyme immunoassay. Using the enzyme immunoassay, the antibody is capable of detecting femtomole and picomole levels of thymine glycol in direct and competitive assays, respectively. This immunochemical assay is potentially suitable for measuring the production and repair of thymine glycol damage in cellular DNA.

Animals↗
PubMed1983

Inhibition of tubulin assembly by antileprosy drug dapsone.

The effect of dapsone on assembly-disassembly process of bovine brain tubulin was examined. The drug was found to readily bind tubulin dimer and that in its presence colchicine binding to tubulin was enhanced. Although dapsone associated with tubulin at a site other than the colchicine binding site, distinct inhibition of microtubule assembly was detected.

Animals↗
PubMed1983

Studies on oxidation of benzo [a] pyrene by sunlight and ozone.

The destruction of the carcinogen benzo[alpha]pyrene (BaP) by light is well known; laboratory workers are routinely advised to cover fluorescent lamps with yellow filters while treating samples containing BaP. However until recently the mechanism of oxidation by sunlight and ozone had not been studied in detail. Concentrations of benzo[a]pyrene in urban air are in the range of 5-10 micrograms/1000 m3. Oxidant concentrations (predominantly in the form of ozone) are reported to be in the range of 0.01 ppm (22 micrograms per m3). Thus a sampling system with a filter paper would filter about 22,000 micrograms of ozone passing through and collect about 5 micrograms of BaP for analysis. The effect of interactions of such large ozone concentrations with BaP deposited on the filter paper is reported; data for the oxidation rates for benzo[a]pyrene coated on quartz surface and exposed to ozone or sunlight are presented. The oxidation products were analysed by thin-layer chromatography and high-pressure liquid chromatography. From about eight products detected in these experiments, three have been identified as quinones based on UV-absorption spectrometry and mass spectrometry. Oxidation rates as high as 100% per hour of exposure are observed when less than 0.1 micrograms of BaP is coated inside the quartz tubes and exposed to ozone or sunlight. Oxidation rates for benzo[a]pyrene (using tritiated BaP) were determined for two types of experimental conditions. In the first set, tritiated BaP was spotted onto a glass fibre paper and sampling continued for 24 h; the loss of BaP was found to be 88%. In the second set tritiated BaP was spotted at intervals of one hour, for eight hours, while sampling is being carried out and the loss of BaP during the period was estimated to be 50%.

Benzo(a)pyrene↗
PubMed1982

Measurements of benzo(a)pyrene in the city of Bombay for the evaluation of carcinogenic risk.

Cigarette smoking, environmental chemicals and ionizing radiations are the three factors known to cause cancer in human beings. The relative importance of each of these is being constantly evaluated. There is an urgent need to monitor the environmental carcinogens on a large scale to assess the role of environmental chemicals in the incidence of cancer in human populations. Polycyclic aromatic hydrocarbons (PAH) are released into the atmosphere as a result of fossil fuel combustion and some of the PAH (e.g. benzo(a)pyrene) are recognised carcinogens. Measurement of benzo(a)pyrene in urban, suburban and rural regions of Bombay is carried out in order to evaluate the possible correlation with lung cancer incidence among different population groups. The variations in the concentration at the three sampling locations are discussed. The wide differences in the concentration at different locations seem to be very suitable for epidemiological investigations.

Air Pollutants↗
PubMed1978

A comparative assessment of alfathesin for use in outpatient anaesthesia.

Alfathesin and thiopentone were compared in a double blind study where each drug was given by intravenous infusion supplemented with fentanyl and nitrous oxide, in 54 healthy female patients under-going therapeutic abortion. The two drugs were similar in terms of changes in cardiorespiratory variables, side effects, clinical efficacy, and patient acceptability. Alfathesin produced a significantly more rapid recovery from anaesthesia, without the high incidence of dreams found with thiopentone in this study. Alfathesin would seem to be the preferable drug for use in outpatients undergoing minor surgical operations.

Abortion, Therapeutic↗
PubMed1978

The influence of fentanyl on an alfathesin infusion technique.

The effects of fentanyl (1 microgram/kg) supplementing an alfathesin infusion technique were assessed in a double blind study in 53 healthy unpremedicated female patients undergoing therapeutic abortion as outpatients. The addition of fentanyl reduced the tachycardia, tachypnoea and hyperventilation seen in those patients receiving alfathesin alone, without unduly prolonging recovery time. Two patients receiving alfathesin alone developed marked coughing or laryngospasm. Fentanyl would seem to be a desirable addition to an alfathesin infusion technique in unpremedicated patients presenting for outpatient anaesthesia.

Adult↗