PubMed Health⌕ Search

Biomedical subjects

R N Gupta

Publications and source records attributed to R N Gupta.

At least 19 recordsLinked to original sources
PubMed2001

Biosynthesis of vitamin B(6) in yeast: incorporation pattern of glucose.

Two yeasts, Saccharomyces cerevisiae ATCC 7752 and Candida utilis ATCC 9256, were incubated in the presence of variously multiply (13)C-labeled samples of D-glucose. The (13)C incorporation pattern within pyridoxamine dihydrochloride, established by (13)C NMR spectroscopy, differed from that which had previously been found within pyridoxine, isolated from Escherichia coli. Thus, the origin of the carbon skeleton of vitamin B(6) in yeast differs substantially from its origin in E. coli. In particular, in yeast the distribution of (13)C within the C(5) chain C-2',2,3,4,4' of pyridoxamine corresponds to the distribution of (13)C within the C(5) chain C-1,2,3,4,5 of the ribose component of cytidine. It follows that the C(5) chains of pyridoxamine and of ribose originate from a common glucose-derived pentulose or pentose intermediate. By contrast, in E. coli the C(5) chain of pyridoxine is derived from 1-deoxy-D-xylulose 5-phosphate which, in turn, originates by condensation of pyruvic acid with glyceraldehyde 3-phosphate.

Candida↗
PubMed2000

Evaluating contraceptive choice through the method-mix approach. An Indian Council of Medical Research (ICMR) task force study.

The method-mix approach was used to evaluate informed contraceptive choices in the present study. A total of 8,077 potential clients were given a balanced presentation of all available contraceptive methods in the national program, ie, the CuT 200 intrauterine device (IUD), low-dose combined oral pills (OC), condom, and sterilization (female/male) along with a new method, Norplant(R).(1) The majority of women opted for spacing methods; among them, the IUD was preferred by about 60% of clients, followed by condoms (9%), OC (6%), and Norplant (5%). Sterilization, mainly female, was accepted by about 17% of the women making an informed choice. The economic status of couples did not influence the contraceptive choices, as all the methods were offered free of cost in the present study, which is the current practice in the national program. Illiterate women more often accepted sterilization (about 25%) than did literate women (15%). This is because illiterate women had more children; about 30% of illiterate women had three or more children, as opposed to 16.2% of literate women. However, literacy status did not influence the choice of any specific spacing method. The study also revealed that, by encouraging potential clients to make an informed choice, they could override the provider's bias while accepting a particular type of spacing method. This is evident from the observation that Norplant was the first choice of the provider for 35% of the women, whereas only 5% of women preferred and accepted Norplant. The present study stresses an urgent need to promote the practice of informed choices in the national program with a variety of contraceptive options-especially, spacing methods for improving contraceptive prevalence and reproductive health in the country.

Adolescent↗
PubMed1997

Serum bupivacaine concentrations during continuous extrapleural infusion.

PURPOSE: To determine the rate of increase in serum bupivacaine concentration during continuous extrapleural infusion. METHODS: After thoracotomy for lobectomy under general anaesthesia, nine patients had an extrapleural catheter inserted, before chest closure, in a costovertebral gutter constructed surgically by lifting the parietal pleural. Bupivacaine 0.5% with epinephrine 1:200.000 was injected through the catheter as 0.3 ml.kg-1 bolus followed by 0.1 ml.kg-1.hr-1 for five days. Serum bupivacaine (free and total), albumin, alpha-1 acid glycoprotein concentrations were measured 15 min after injection and at 24 hr intervals for five days. Bupivacaine concentrations were determined by column liquid chromatography using solid phase extraction. Serum alpha-1 acid glycoprotein concentration was determined by nephelometry on QM 300 protein analyzer. Serum albumin concentration was determined by bromocresol green dye binding procedure on Hitachi 717 Autoanalyzer. RESULTS: A continuous elevation in total serum bupivacaine was observed, with an average value of 0.75 microgram.ml-1 on day 1 to 2.77 micrograms.ml-1 on day 4 (P < 0.05). There was no increase in postoperative free serum bupivacaine concentration; average value of 177 pcg.ml-1 on day 1 and 249 pcg.ml-1 on day 4 (P = 0.92). Postoperative serum alpha-1 acid glycoprotein concentration showed a steady rise with an average value of 0.94 microgram.ml-1 on day 1 and 1.47 micrograms.ml-1 on day 4 (P < 0.05). No change was observed in post-operative serum albumin with an average value of 31.4 g.l-1 on day 1 and 31.3 g.l-1 on day 4. CONCLUSION: Continuous extrapleural infusion of bupivacaine over five days after thoracotomy is associated with a steady increase in total serum bupivacaine concentration and no elevation in free serum bupivacaine concentration.

Adult↗
PubMed1996

Optimization of the determination of 4-aminopyridine in human serum and urine by column liquid chromatography.

Two convenient reversed-phase column liquid chromatographic procedures are described for the determination of 4-aminopyridine in human serum and urine. A 0.5-ml aliquot of serum after the addition of a 0.5-ml solution of 4-(aminomethyl)pyridine in 0.1 M Na2HPO4 as the internal standard is passed through a 1-ml BondElut C18 silica extraction column. The column is selectively washed to remove acidic, neutral and weakly basic compounds. The desired compounds are eluted with a 0.3-ml aliquot of 35% perchloric acid-methanol (1:100, v/v). A 10-microliters aliquot of the eluate is injected onto a 150 x 4.6 mm I.D. column packed with 5-microns C18 silica particles that is eluted at ambient temperature with a mobile phase containing octanesulfonic acid as the ion-pairing agent. The peaks are monitored at 263 nm. A. 0.25-ml aliquot of urine or 0.5 ml of serum is mixed with N-propionylprocainamide as the internal standard and subjected to benzoylation by Schotten Baumann reaction. The reaction mixture is adjusted to pH 5.5-6 and extracted with a BondElut C18 extraction column. An aliquot of the eluate is chromatographed at ambient temperature with a mobile phase containing tetramethylammonium perchlorate. The peaks are monitored at 278 nm.

4-Aminopyridine↗
PubMed1995

Column liquid chromatographic determination of clozapine and N-desmethylclozapine in human serum using solid-phase extraction.

A 0.5-ml aliquot of a serum sample, after the addition of a 50-microliters aliquot of a 5 microgram/ml solution of amoxapine as the internal standard, is vortex-mixed with 0.5 ml of acetonitrile and centrifuged. The supernatant is applied to a 1-ml BondElut C18 silica extraction column-conditioned with subsequent washings with 1 M HCL, methanol and water. After passing the sample at a slow rate, the column is washed twice with water and once with acetonitrile. The desired compounds are then eluted with a 0.25-ml aliquot of 35% perchloric acid-methanol (1:100, v/v). A 15 microliters aliquot of the eluate is injected onto a 150 x 4.6 mm I.D. column packed with 5-microns C8 silica particles and eluted at ambient temperature with a mobile phase of 0.1% tetramethylammonium perchlorate-acetonitrile (73:27, v/v) adjusted to pH 4.2 with 10% perchloric acid. The peaks are detected with an absorbance detector at 245 nm.

Antipsychotic Agents↗
PubMed1994

Column liquid chromatographic determination of paroxetine in human serum using solid-phase extraction.

A 0.5-ml aliquot of a serum sample, after the addition of a 100-microliters aliquot of a 5 micrograms/ml solution of dibucaine as the internal standard, is vortex-mixed with 0.5 ml of acetonitrile and centrifuged. The supernatant is applied to a 1-ml BondElut C18 silica extraction column conditioned with subsequent washings with 1 M HCl, methanol and water. After passing the sample at a slow rate, the column is washed twice with water and once with acetonitrile. The desired compounds are then eluted with a 0.25-ml aliquot of 35% perchloric acid-methanol (1:40, v/v). A 7-microliters aliquot of the eluate is injected onto a 150 x 4.6 mm I.D. column packed with 5-microns C8 silica particles and eluted at ambient temperature with a mobile phase of 10 mM phosphate buffer-acetonitrile (2:1, v/v) (pH 3.2). The peaks are detected with a fluorescence detector (excitation at 295 nm, emission at 365 nm). The resulting chromatogram is clean with no extraneous peaks. Paroxetine and dibucaine give sharp peaks which are well separated from each other and from the solvent peaks. The extraction recovery of the drug and the internal standard is in the range of 90% which allows a highly sensitive determination of paroxetine.

Chromatography, High Pressure Liquid↗
PubMed1994

Column liquid chromatographic determination of bupivacaine in human serum using solid-phase extraction.

A convenient and economical procedure for the extraction of bupivacaine and its major metabolites, desbutylbupivacaine and 4'-hydroxybupivacaine, from serum is described. A 0.25-ml aliquot of 4 micrograms/ml solution of N-pentyl-2,6-pipecoloxylidide used as the internal standard and an equal volume of the serum sample are applied to a 1-ml BondElut C18 silica extraction column which has been conditioned by subsequent washing once with 1 M HCl, twice with methanol and once with water. After passing the sample at a slow rate, the column is washed twice with water and once with acetonitrile. The desired compounds are then eluted with a 0.25-ml aliquot of a mixture of 35% perchloric acid-methanol (1:40, v/v). A 5-microliters aliquot of the eluate is injected onto a 150 x 4.6 mm I.D. column packed with 5-microns C8 silica particles, which is eluted at ambient temperature with a mobile phase of acetonitrile-10 mM KH2PO4 (25:80, v/v) at a flow-rate of 1.5 ml/min. The peaks are detected at 205 nm. The extraction recovery of all the compounds is in the range of 90%. The chromatogram is clean and the desired peaks are well separated from each other and from the extraneous peaks.

Acetonitriles↗
PubMed1994

Optimization of a column liquid chromatographic procedure for the determination of plasma salbutamol concentration.

A reversed-phase column liquid chromatographic procedure with fluorescence detection for the determination of salbutamol in plasma is described. A l-ml aliquot of the sample, after the addition of bamethan as the internal standard, is passed through a Bond Elut silica extraction column. The column is selectively washed to remove neutral, acidic, and weakly basic compounds. The desired compounds are eluted with a l-ml aliquot of methanol. The eluate is evaporated under vacuum at ambient temperature and the residue is reconstituted in 40 microliters of the mobile phase which contains octanesulfonic acid as the ion-pairing reagent. The entire extract is injected onto a 150 x 4.6 mm I.D. column packed with 5-micron octylsilica particles. Peaks are detected with a fluorescence detector (excitation wavelength = 275 nm, emission wavelength = 310 nm). In the resulting chromatogram, salbutamol and the internal standard give sharp peaks that are well resolved from the extraneous peaks. The procedure allows the quantitation of salbutamol down to 0.2 ng/ml.

Albuterol↗
PubMed1993

Influence of renal clearance on peripheral homovanillic acid measurements in healthy subjects and schizophrenic patients.

In order to investigate the effect of renal clearance on plasma homovanillic acid (HVA) concentrations, we examined plasma concentration and urinary excretion of HVA and creatinine per 4 h over 24 h in eight male schizophrenic patients and eight healthy male subjects. Renal clearances of HVA and of creatinine were determined per 4 h period. No significant differences were found between groups in the total 24 h excretion of either HVA or creatinine. Although differences between groups in plasma HVA concentrations and urinary HVA excretion per 4 h did not reach statistical significance, the renal clearance of HVA was significantly lower in the patient group than in the control group. There was no difference between groups in creatinine clearance. Diurnal changes were seen in the renal clearance of HVA and creatinine in both groups. Renal HVA clearance decreased from 23.00-07.00 h, with a coincident decrease in urinary HVA excretion and an increase in plasma HVA concentration. We provide evidence that renal clearance is an important determinant of plasma HVA concentration, and should be considered when interpreting plasma HVA data.

Adult↗
PubMed1992

Determination of plasma homovanillic acid by liquid chromatography with electrochemical detection.

We describe a simple method for extracting homovanillic acid (HVA) from plasma. An aliquot of 0.5 ml of the internal standard solution (3-hydroxy-4-methoxycinnamic acid in 0.2 mol/l phosphoric acid) and 0.5 ml of the sample are applied to a 1-ml Bond Elut C18 column prewashed with methanol and 0.2 mol/l phosphoric acid. The sample is drawn through the column at low speed. The column is washed with water and eluted with dichloromethane. The eluate is evaporated under vacuum at ambient temperature and the residue reconstituted with 250 microliters of the mobile phase. A 10-microliters aliquot of the resulting solution is injected onto a 150 mm x 4.6 mm I.D. column packed with 5-microns octadecylsilyl silica particles (Beckman). Peaks are detected coulometrically in the screening-oxidation mode with E1 = +0.25 V and E2 = +0.38 V. In the resulting chromatogram, HVA and the internal standard give sharp peaks and are well separated from solvent and other endogenous electroactive acids. The extraction recovery is 90-95% which allows the determination of 0.5 microgram/l analyte.

Chromatography, Liquid↗
PubMed1992

Drug level monitoring: antidepressants.

The determination of antidepressant drugs which act by blocking neuronal uptake of biogenic amines, because of their widespread use and high toxicity, remains one of the most commonly requested drug assays in clinical laboratories. Easy to use immunoassay reagents for the estimation of these drugs are commercially available. However, immunoassays have not been universally accepted because of high probability of these reagents producing false negative and false positive results. At present, column liquid chromatography with absorbance detection and coupled with solid-phase extraction is the most viable technique for a general procedure for the identification and determination of these drugs. The technique of liquid chromatography is economical, environmental friendly since water-miscible and biodegradable solvents can be used for extraction of drugs and their chromatographic separation, and amenable to full automation. New techniques of separation, such as supercritical fluid chromatography and capillary zone electrophoresis, have not yet been applied for the determination of therapeutic concentrations of antidepressants.

Antidepressive Agents↗
PubMed1992

Platelet alpha 2-adrenergic receptors in depressed patients and healthy volunteers: the effects of desipramine.

Binding parameters (Bmax and Kd) of alpha 2-adrenergic receptors were studied in platelets from 14 depressed patients and 18 control subjects. Using 3H-clonidine (a partial alpha 2-adrenergic agonist) as the ligand and membranes, prepared from platelets isolated under physiological conditions, we found no significant differences in Bmax and Kd between medication free patients and control subjects. Platelet binding parameters in the depressed patients did not correlate with plasma levels of norepinephrine, epinephrine or MHPG. Age had a significant positive effect on platelet alpha 2-adrenergic receptor Bmax in both groups, and may have masked the patient-control differences. Treatment with desipramine for 28 days had no effect on the binding parameters in depressed patients when compared to pretreatment values. Adding desipramine to platelets of control subjects 'in vitro' did also not affect binding parameters. Our findings suggest that receptor binding studies with a partial alpha 2-adrenergic agonist in platelet membranes are not a useful model to test the hypothesis of a central supersensitive adrenergic system in depression.

Analysis of Variance↗
PubMed1990

Improved sample preparation in determination of urinary metanephrines by liquid chromatography with electrochemical detection.

In this relatively simple procedure for extracting metanephrines from urine, after an internal standard (4-hydroxy-3-methoxybenzylamine in 1 mmol/L HCl) is added, the sample is hydrolyzed in a boiling water bath, then treated with ammonia and alumina. Excess ammonia is removed under reduced pressure and the sample is applied to a 1-mL Bond Elut SCX column, which is washed, and metanephrines and internal standard are eluted with 0.5 mmol/L sodium acetate/acetonitrile (3/1 by vol). Of this elute, 5 microL is injected into a 15 cm x 4.6 mm (i.d.) column packed with 5-microns octadecylsilyl silica particles, which is eluted with a mobile phase containing tetramethylammonium perchlorate. Peaks are detected coulometrically at +0.28 V. In the resulting chromatogram, metanephrines give sharp peaks, well resolved from peaks for solvent and internal standard. There are no extraneous peaks for catechols or mono-oxygenated phenylethylamines. Results correlated well (r = 0.999, n = 13) with those by earlier described liquid-chromatography.

Aluminum Oxide↗