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Biomedical subjects

R Tandon

Publications and source records attributed to R Tandon.

At least 181 records · Page 10Linked to original sources
PubMed1991

A simple, sensitive liquid chromatographic assay of cis-thiothixene in plasma with coulometric detection.

A novel, simple, and very sensitive liquid-chromatographic assay with a coulometric detector has been developed for quantitating cis-thiothixene (CTX) in human plasma. A reverse phase, 5-microns cyano column (25 x 0.46 cm), a mobile phase of phosphate buffer (pH 2.5) and acetonitrile (40/60 by vol), and a coulometric detector are used for the separation of CTX, and the internal standard, trifluoperazine. CTX and trifluoperazine are extracted from alkalinized plasma into n-pentane-isopropanol (95/5 by vol) and purified by back extraction into perchloric acid. The optimum oxidation potential for the analytes is +0.8 V versus an Ag/AgCl electrode. The detection limit for CTX is 200 pg using 1 mL of plasma and CTX concentrations are linear from 0 to 40 micrograms/L. The average interassay CV is 9%, and the mean recovery is 99% relative to the internal standard. Possible interferences from various psychiatric and common drugs in the assay have been studied. The assay method was validated by determining the concentration of CTX in the plasma of 100 schizophrenic patients.

Antipsychotic Agents↗
PubMed1991

Potentiation of gastric toxicity of ibuprofen by paracetamol in the rat.

A fixed dose combination of ibuprofen (400 mg) and paracetamol (325 mg) is by far the most extensively prescribed medicament for a variety of musculoskeletal disorders in India. Following clinical observations that this drug combination induces significant adverse effects, its gastric toxicity was investigated in rats. Ibuprofen (25 mg kg-1 p.o., twice daily x 5 days), paracetamol (20 mg kg-1 p.o, twice daily x 5 days), and a combination of the two, had no significant effect on free and total gastric acidity in pylorus-ligated rats. Ibuprofen induced visible gastric ulceration whereas paracetamol did not. However, the combination of these two drugs had an additive effect inducing severe gastric erosions, ulcerations and bleeding. The augmented toxicity of this drug combination appeared to be a consequence of attenuated gastric mucin activity and reduction in the gastric muco-protective barrier. This investigation indicates the likely hazard of an irrational fixed dose drug combination.

Acetaminophen↗
PubMed1991

Stability of positive and negative symptom constructs during neuroleptic treatment in schizophrenia.

To assess the structural stability of positive and negative symptom ratings, we rated 40 schizophrenic inpatients on the Brief Psychiatric Rating Scale (BPRS) and the Scale for the Assessment of Negative Symptoms (SANS) at medication-free baseline and after 4 weeks of neuroleptic treatment. Positive symptom variables consisted of six BPRS items, and the negative symptom variables consisted of the five SANS subscale global scores. On principal components analysis, a three-factor, oblique-rotated solution resulted, with a negative symptom factor, a positive symptom factor, and an unstable behavioral agitation factor. The pre- and posttreatment factor loading patterns were similar. The findings suggest that BPRS-positive symptom items and the SANS measure distinct clinical dimensions and that the construct is stable, as demonstrated by minimal structural change with time.

Adult↗
PubMed1991

Effect of in utero exposure to di(2-ethylhexyl)phthalate on rat testes.

In utero exposure to di(2-ethylhexyl)phthalate (DEHP; 1000 mg/kg body weight) significantly decreased activities of testicular sorbitol dehydrogenase and acid phosphatase and increased gamma-glutamyl transpeptidase, lactate dehydrogenase and beta-glucuronidase activities at early ages. A decrease in the sperm count of the epididymal spermatozoa was also observed in the sexually matured animals of DEHP exposed group. The data suggest that in utero exposure to DEHP may affect the normal development of testes.

Animals↗
PubMed1990

Effect of anticholinergic medication on positive and negative symptoms in medication-free schizophrenic patients.

It is generally assumed that anticholinergic drugs have no effects on schizophrenic symptomatology. A few studies, however, indicate that anticholinergic agents aggravate psychotic symptoms and antagonize therapeutic effects of neuroleptics in schizophrenic patients; more recently, some investigators have observed that these agents appear to benefit negative symptoms. In an effort to resolve this issue, we studied the effects of 2 days of treatment with biperiden on positive and negative symptoms in 15 medication-free schizophrenic patients. Positive symptoms increased significantly, while there was a trend toward a decrease in negative symptoms. The implications of these findings for the role of the cholinergic system in schizophrenia are discussed.

Adult↗
PubMed1990

Human equivalent doses of platelet inhibitors and experimental atherosclerosis.

The effects of aspirin, dipyridamole and sulfinpyrazone on the development of atherosclerotic lesions in the aorta were studied in cholesterol-fed rabbits. Aspirin and sulfinpyrazone prevented the development of atherosclerosis, whereas dipyridamole-treated animals developed advanced atherosclerotic lesions. As all the three drugs inhibit platelet function, some non-platelet effects are probably responsible for the differences in results. It is felt that dipyridamole should be avoided in hypercholesterolemic individuals.

Animals↗
PubMed1990

Biliobiliary fistula: preoperative diagnosis and management implications.

Experience with cholecystohepaticodochal and cholecystocholedochal fistulas as a result of an erosion of gallstones from the gallbladder into the adjacent common duct in five patients is presented. The incidence was 1.4% in a population of 350 patients undergoing cholecystectomy. The condition was indicated clinically on the basis of a symptom triad of jaundice, fever, and pain with cholelithiasis in a small contracted gallbladder. In addition, proximal intra- and extrahepatic ductal dilatation, calculus in the common duct, and normal-caliber (or unprofiled) distal common duct on ultrasound scan were present in all the patients. Endoscopic retrograde cholangiopancreatography proved to be the most useful means of investigation, and it confirmed the diagnosis in four patients before surgery. A modified antegrade cholecystectomy was performed with the gallbladder opened inferiorly at the fundus, and the stones were evacuated. A partial cholecystectomy and choledochoplasty were accomplished with gallbladder flaps whenever feasible. Other useful operative procedures are side-to-side hepaticodochojejunostomy and hepaticodochoduodenostomy. In the presence of high benign bile duct stricture, an approach to the left hepatic duct is now preferred for biliary bypass.

Adult↗
PubMed1989

Cholinergic hyperactivity and negative schizophrenic symptoms. A model of cholinergic/dopaminergic interactions in schizophrenia.

Despite renewed interest in negative schizophrenic symptoms, the pathophysiological mechanisms involved in their development remain obscure. Although the cholinergic system has been implicated in schizophrenia, it has not been accorded a major role in current theories of pathophysiology. We present evidence from several lines of research that suggests that muscarinic hyperactivity may be implicated in the pathogenesis of negative schizophrenic symptoms. Specifically, cholinergic overdrive leads to a behavioral syndrome strikingly similar to the negative schizophrenic syndrome, anticholinergic agents may alleviate negative symptoms, schizophrenic patients with negative symptoms tend to "abuse" anticholinergics, and polysomnographic, neuroendocrine, and other pharmacological findings appear to be generally consistent with this hypothesis. The hypothesis is testable and is presented as a heuristic model that focuses on the dynamic interplay between cholinergic and dopaminergic systems in schizophrenia.

Acetylcholine↗
PubMed1989

Lymphocyte subsets in acute rheumatic fever and rheumatic heart disease.

Lymphocyte subsets in 53 patients with acute rheumatic fever and 78 patients with chronic rheumatic heart disease were compared with 20 normal control subjects and 39 patients suffering from uncomplicated streptococcal pharyngitis to obtain information about the pathogenesis of the disease. Twenty patients with rheumatic fever were followed for 24 weeks to evaluate changes occurring over the course of the disease. Total leukocyte and lymphocyte counts were increased in patients with rheumatic fever and to a lesser extent in those with rheumatic heart disease, when compared with controls. The difference between the two groups was significant. Patients with acute rheumatic fever had an increased number of B cells and a smaller increase in total T and T-helper-inducer (CD-4) cells. The proportion of B cells increased, while that of T-suppressor-cytotoxic (CD-8) cells fell. An increased number and proportion of B cells was also seen in patients with rheumatic heart disease. Total T and T-helper lymphocyte percentages and numbers were significantly higher in patients with rheumatic fever compared with those of patients with rheumatic heart disease. Follow-up studies at 6, 12, and 24 weeks revealed no significant differences from the entry point studies, although there was a trend toward reduction in the degree of derangement from normal values. Patients with uncomplicated streptococcal pharyngitis, however, did not show perturbations in the T-cell and T-subset counts. Our study suggests that the immunoregulatory defect in acute rheumatic fever is characterized by a relative reduction of suppressor T cells with an absolute increase in helper T cells and B cells, resulting in an increased cellular as well as humoral immune response.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1989

Angiographic abnormalities of the morphologically left ventricle in the presence of Ebstein's malformation.

Cineangiography of the morphologically left ventricle was performed in 10 patients with Ebstein's malformation. The angiographic findings included left ventricular contour abnormalities (8), mitral valve prolapse (7) and global hypokinesia (5). Left ventricular abnormalities were present whether the left ventricle was normally placed or in mirror-image position in congenitally corrected transposition. Abnormalities of the morphologically left ventricle in Ebstein's malformation have received little attention in the past. Frequent occurrence of these abnormalities should make careful evaluation of the morphologically left ventricle mandatory in all patients with Ebstein's malformation.

Adolescent↗
PubMed1989

Pulmonary arterial anatomy in tetralogy of Fallot.

We have searched for any abnormalities of the pulmonary arteries visualized by angiography in 200 consecutive patients with tetralogy of Fallot. All the patients were studied by conventional right ventricular angiography in the right and left anterior oblique views. Thirty six patients (18%) showed a total of 61 pulmonary artery stenoses, 32 being severe (52%), 17 moderate (28%) and 12 mild (20%). Bifurcational stenoses were the most common (31), followed by stenosis of the main pulmonary trunk, the right or the left pulmonary arteries (22), combined central and peripheral stenosis (6), and isolated peripheral pulmonary artery stenosis (2). Nine patients showed segmental stenosis involving both the right and left pulmonary arteries and three of them had atresia of the left pulmonary artery. The detailed preoperative evaluation of obstruction within the pulmonary arterial pathways is essential in tetralogy of Fallot to ensure normalisation of the right ventricular pressure following total correction.

Adolescent↗
PubMed1989

An improved sensitive assay for simultaneous determination of plasma haloperidol and reduced haloperidol levels by liquid chromatography using a coulometric detector.

A simple, highly sensitive and specific high-performance liquid chromatographic method that uses a coulometric detector for the simultaneous assay of haloperidol and reduced haloperidol in human plasma has been developed, using bromoperidol as the internal standard. A reversed phase C8 5-microns column (25 x 0.46 cm) and a mobile phase of phosphate buffer (pH 7.0), acetonitrile, and methanol (40:20:40 vol/vol) are used for separating the analytes. The analytes are extracted from alkalinized plasma using a mixture of pentane and isopropanol (95:5 vol/vol) and purified by back extraction into a perchloric acid solution. Teflon tubes with screw caps are used throughout the extraction work. The compounds are oxidized at a potential of +0.90 V against a Ag/AgCl reference electrode. The detection limit of the assay is 50 ng/L using 1 mL of plasma. The average interassay coefficient of variation for samples of concentration 1-40 micrograms/L is approximately 8%. Possible drug interferences in the assay have been studied. The absolute recovery of the method is approximately 80%. The assay has been validated by quantitating 150 schizophrenic patients' samples.

Chromatography, High Pressure Liquid↗