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Biomedical subjects

J Patel

Publications and source records attributed to J Patel.

At least 145 records · Page 8Linked to original sources
PubMed1992

Surgical techniques for endoscopic resection of bladder cancer.

Accompanying the advances in surgical techniques and new intravesical and systemic therapeutic agents for the treatment of individuals with bladder cancer has been the development of greatly improved instrumentation for viewing the interior of the urinary tract and removing neoplasms. Fiberoptic lenses can now be combined with a video system, which enables the urologist to examine the lower urinary tract, not only more easily but with greater magnification. Training is obviously accelerated with the use of video endoscopy. The system also provides the opportunity for documentation and transmittal of the operative findings using either still or motion photography. The endoscopic procedure should be carried out in an orderly fashion. Sufficient lenses and cautery loops must be available to visualize the entire lower urinary tract and to biopsy or resect any abnormality and ensure hemostasis. The urologist should work closely with the pathologist to obtain sufficient cytologic and pathologic material to be confident of the presence or absence of tumor.

Anesthesia, Spinal↗
PubMed1991

Development of an electrically stimulated neoanal sphincter.

In early surgical attempts to create a neoanal sphincter for patients who are faecally incontinent, skeletal muscle (usually the gracilis) has been transposed around the anal canal. Despite modifications, such as intermittent electrical stimulation, this procedure is likely to fail because the fast-twitch gracilis muscle is incapable of prolonged contraction without fatigue. Long-term electrical stimulation to convert such a muscle to a slow-twitch, fatigue-resistant muscle, though practicable, has yielded inconsistent results. We describe further modifications of this technique. A neoanal sphincter was constructed with an electrically stimulated transposed gracilis muscle in 20 incontinent patients with a deficient anal sphincter, and as part of a reconstruction in 12 patients in whom the anorectum had been excised or was congenitally absent. A totally implanted stimulator was used to convert the muscle from a fast-twitch to a slow-twitch muscle. Other modifications included vascular delay 4-6 weeks before transposition of the muscle, stimulation of the main nerve to the gracilis rather than its peripheral branches, and intermittent higher frequency stimulation. 2-4 of these modifications gave significantly fewer failures than did 0-1. With the new technique, continence has been restored in patients whose only other treatment option was a permanent stoma.

Adolescent↗
PubMed1991

Serological markers of sexually transmitted diseases associated with HIV-1 infection in pregnant black women.

While the prevalence of HIV-1 is increased in women attending sexually transmitted diseases (STD) clinics, in South Africa little is known about STD risk factors in women infected with HIV-1 in the general population. Serological markers of STDs were investigated in a cohort of 21 pregnant women, who were found to be carriers of HIV-1, and in 42 age- and residentially matched uninfected pregnant women. The rapid plasma reagin test (RPR) was positive in 33% of the HIV-1- infected women (P less than 0.05 compared with controls). The specific treponemal fluorescent antibody absorbed test (FTA-abs) was positive in 43% of the HIV-1-infected women (P less than 0.05 compared with controls). Similarly the prevalence of chlamydial IgG antibodies as measured by enzyme-linked immunosorbent assay was 95% (P = 0.026 compared with controls). Markers of hepatitis B infection were similar to both groups. Pregnant women with HIV-1 infection in the Johannesburg area have an increased seroprevalence of markers of STDs and more data are required on the attitudes and sexual activity of these women in order to target AIDS and education information.

Adult↗
PubMed1991

Beneficial effect of atrial pacing in severe acute aortic regurgitation and role of M-mode echocardiography in determining the optimal pacing interval.

The effect of atrial pacing on cardiac performance was assessed in 11 men (aged 20 to 64 years) with recent-onset severe aortic regurgitation (AR), all of whom had diastolic closure of the mitral valve on the echocardiogram. Thermodilution cardiac outputs were determined, and aortic, left ventricular and pulmonary arterial wedge pressures recorded. Once baseline recordings were completed, the pacing rate was increased by increments of 10 beats/min (70, 80, 90...) to a maximal rate of 140 beats/min. The optimal pacing interval, obtained from hemodynamic data, was defined as that at which the lowest filling pressure was associated with the highest cardiac index. This was then compared with a pacing interval derived from the R wave of the electrocardiogram to the diastolic mitral closing point on the M-mode echocardiogram. Such an interval would shorten diastole without affecting forward mitral flow. Atrial pacing improved the overall hemodynamic state in all patients; the most favorable hemodynamics were achieved at heart rates between 110 and 130 beats/min (mean: 120 +/- 8). At the optimal rate, left ventricular end-diastolic pressure decreased from 46 +/- 7 to 23 +/- 12 mm Hg (p less than 0.001), and the pulmonary arterial wedge pressure from 28 +/- 8 to 16 +/- 7 mm Hg (p less than 0.001), while the cardiac index increased from 2.34 +/- 0.46 to 2.63 +/- 0.49 liters/min/m2 (p less than 0.01). The mean difference between the optimal pacing interval determined from the hemodynamic data and the interval derived from the echocardiogram was 18 +/- 21 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1991

Inhibition of K(+)-evoked [3H]D-aspartate release and neuronal calcium influx by verapamil, diltiazem and dextromethorphan: evidence for non-L/non-N voltage-sensitive calcium channels.

The effects of inhibitors of voltage-sensitive calcium channels (VSCC) on K(+)-evoked [3H]D-aspartate release from rat hippocampal slices and the K(+)-evoked increase in intracellular calcium in neocortical neurons in primary culture were examined. K+ caused a concentration-dependent release of [3H]D-aspartate that was approximately 85% dependent on the presence of extracellular calcium. Neither the marine snail toxin, omega-conotoxin GVIA, nor the dihydropyridine VSCC antagonist, nitrendipine, had any effect on K(+)-evoked release of [3H]D-aspartate. omega-Conotoxin GVIA and nitrendipine caused a relatively small (20-30%) inhibition of K(+)-evoked increase in intracellular calcium in neocortical neurons in primary culture. This suggests that K(+)-evoked [3H]D-aspartate release is not dependent on L- or N-type VSCC, whereas K(+)-evoked neuronal calcium influx was only partially dependent on L- and N-type VSCC. Verapamil, dextromethorphan and diltiazem caused a concentration-dependent inhibition of K(+)-evoked release of [3H]D-aspartate with IC50 values of 30, 100 and 120 microM, respectively. The K(+)-evoked increase in intracellular calcium was inhibited with essentially the same rank order of potency, but with slightly greater potencies (IC50 values for verapamil, diltiazem and dextromethorphan were 20, 50 and 50 microM, respectively). At 300 microM, neither verapamil, diltiazem nor dextromethorphan inhibited [3H]D-aspartate release evoked by the calcium ionophore ionomycin, suggesting that these compounds are not acting intracellularly to inhibit the ability of free cytosolic calcium to evoke release.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Comparative performance of ion exchange and ion-paired reversed phase high performance liquid chromatography for the determination of nucleotides in biological samples.

We have compared anion exchange chromatography on APS-Hypersil (4.6 x 100 mm) eluted with a phosphate gradient with reversed phase chromatography on ODS-Hypersil (4.6 x 100 mm) in the presence of either tetrabutylammonium (TBA) or triethylammonium (TEA) ions with a methanol gradient. The systems have been compared both for ease of operation and for their resolving power with standard mixtures and acid extracts of both normal red cells (RBC) and ischaemic tissues. The two chromatographic modes exhibited similar separating efficiencies for standard mixtures of nucleotides but retention times were most stable using reversed phase liquid chromatography (RPLC) with TEA. Anion exchange columns slowly lost ion exchange capacity but selectivity was unchanged. RPLC in the presence of TBA gave reproducibile capacity factors only when operated isocratically due to irreversible changes to the silica surface. For RBCs the RPLC with TEA and anion exchange systems resolved 17 and 15 peaks, respectively, and for the ischaemic samples 22 and 14 peaks, respectively. However, nucleosides and bases were also resolved by the ODS column causing chromatographic crowding and uncertain peak identification.

Animals↗
PubMed1991

Voltammetric evidence that subsensitivity to reward following chronic mild stress is associated with increased release of mesolimbic dopamine.

Chronic exposure to mild unpredictable stress caused a decrease in rats' consumption of a palatable weak sucrose solution, which was reversed by chronic (5 weeks) administration of imipramine (5 mg/kg/day). Dopamine (DA) release in the nucleus accumbens (NAc) and caudate putamen (CPu) was measured in vivo using fast cyclic voltammetry, following electrical stimulation of the medial forebrain bundle. Experiments were performed under chloral hydrate anaesthesia 48 h after the termination of stress and the final imipramine injection. DA release was increased in the NAc of both stressed and imipramine-treated animals; imipramine did not normalize the increased DA release in stressed animals. In a further experiment, brain slices from stressed animals tended to be subsensitive to the inhibition of DA release in the NAc by quinpirole. No changes were observed in the CPu in any experiment. We discuss the relationship of these effects to stress-induced anhedonia.

Acetylglucosamine↗
PubMed1991

Role of calcium in regulation of phosphoinositide signaling pathway.

Using primary neuronal cultures we have examined the role of extracellular Ca2+ in a receptor-regulated phosphoinositide turnover. We report that receptor (glutamic acid and acetylcholine)-activated phosphoinositide turnover requires the presence of extracellular Ca2+ (EC50 = 21.1 microM). The requirement for Ca2+ appears to be at an intracellular level and is highly selective for Ca2+. We also found that several inorganic and organic Ca2+ channel blockers, including La3+ and verapamil, inhibit phosphoinositide turnover. However, the pharmacological profile of these agents in this regard was distinct from their actions at the voltage-sensitive Ca2+ channels. To explain the above requirement for extracellular Ca2+ in agonist-stimulated phosphoinositide turnover and its sensitivity to Ca(2+)-channel blockers, we propose a hypothetical model suggesting that Ca2+, following IP-3-mediated mobilization, exerts a facilitatory action on the activity of receptor-phospholipase C complex. We further propose that in the absence of extracellular Ca2+ or in the presence of certain Ca(2+)-channel blockers, refilling of calciosomes is ineffectual or inhibited, causing its depletion and subsequent inactivation of agonist-stimulated phosphoinositide turnover.

Animals↗
PubMed1991

Molecular analysis of microtubule-associated protein-2 kinase cDNA from mouse and rat brain.

We have isolated and characterized brain cDNA clones encoding microtubule-associated protein-2 (MAP-2) kinase for rat (rMNK1) and mouse (mMNK1). The nucleotide sequences diverged by only 5% whereas the amino acid sequences were identical except for one conservative residue change. Conservation of the expressed sequence extended into other mammalian species. These findings constitute the first demonstration of a strict evolutionary conservation of MAP-2 kinase. Genomic restriction patterns revealed a single MAP-2 kinase gene that shares homology with other genomic sequences. The 3' terminal half of the gene appears to be encoded by four exons. rMNK1 and mMNK1 differed from a recently reported MAP-2 kinase cDNA, termed ERK1, because of a nonconservative change in position 82, from Gly in ERK1 to Arg in rMNK1. The rMNK1 gene was found to be expressed mainly as a 1.8-kb transcript that was highest in brain and in lung. In contrast to ERK1, rMNK1 showed two equally prominent mRNA species in liver, at 1.8 kb and 5 kb, which imply differential processing of the primary transcript. Results derived from the immunological screening of an expression library showed that MAP-2 kinase might share epitopes with two prominent protein kinase C substrates, MARCKS (an 80-kD protein kinase C substrate) and GAP-43, suggesting the possibility that MAP-2 kinase could interact with kinase C.

Amino Acid Sequence↗
PubMed1991

Calcium mobilization and entry by thapsigargin in neuronal tumor cell line, SK-N-SH.

Using fura-2 loaded neural tumour cells, SK-N-SH, we demonstrate that receptor-mediated activation of phosphoinositide hydrolysis not only causes the release of Ca2+ from intracellular stores but also causes a concomitant influx of extracellular Ca2+. Thapsigargin (TG), a sesquiterpene lactone, causes a sustained elevation of intracellular Ca2+ and depletion of the inositol 1, 4, 5-trisphosphate-sensitive intracellular Ca2+ stores. In the absence of extracellular Ca2+, the increase in intracellular Ca2+ concentration ([Ca2+]i) was transient, suggesting that thapsigargin activates both intracellular mobilization and the influx of Ca2+ from extracellular space. These results are consistent with the proposal that the depletion of the inositol 1, 4, 5-trisphosphate-sensitive intracellular Ca2+ pool serves as a signal for Ca2+ influx.

Calcium↗
PubMed1991

Williams syndrome: masseter spasm during anaesthesia.

A 4-year-old boy with Williams syndrome developed masseter spasm after halothane and suxamethonium. He did not develop malignant hyperthermia; the surgery was accomplished with a nontriggering anaesthetic and no further problems.

Anesthesia, Inhalation↗
PubMed1990

Comparison of intravenous amrinone and dobutamine in congestive heart failure due to idiopathic dilated cardiomyopathy.

A prospective randomized study was performed in 46 consecutive patients with refractory congestive heart failure (CHF) due to idiopathic dilated cardiomyopathy to compare the hemodynamic responses to 48-hour infusions of amrinone and dobutamine. Both drugs substantially reduced pulmonary arterial wedge pressure, right atrial pressure and systemic vascular resistance and increased cardiac index. Amrinone caused a greater decrease in right atrial pressure than dobutamine (p less than 0.02) and had a positive chronotropic effect not observed with dobutamine (p less than 0.01). The increase in heart rate produced by amrinone correlated inversely with the changes in right atrial and pulmonary arterial wedge pressures, suggesting a baroreceptor response to reduced preload. Dobutamine produced a larger increase in stroke volume index than amrinone (p less than 0.01). Ninety-one percent of patients receiving amrinone and only 65% receiving dobutamine had reduction of greater than or equal to 30% in pulmonary arterial wedge pressure (p less than 0.05). Cardiac index increased greater than or equal to 30% in similar numbers of patients given amrinone (74%) and dobutamine (65%). Negative fluid balance was recorded in all patients receiving amrinone and in 78% of patients receiving dobutamine (p less than 0.05). Target hemodynamic criteria were achieved in 83% of patients receiving 10 micrograms/kg/min of amrinone. The effective maintenance dose of dobutamine was extremely variable. No clinically important adverse effects were observed with either drug regimen. Both amrinone and dobutamine are effective and safe agents for short-term parenteral therapy of patients with dilated cardiomyopathy in severe CHF that is unresponsive to oral medication.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Beckwith-Wiedemann syndrome: development of nephroblastoma during the surveillance period.

Two children, with Beckwith-Wiedemann syndrome and hemihypertrophy who were followed by ultrasonography, developed a large nephroblastoma in the interval between two abdominal ultrasound examinations. The customarily suggested bi-annual examinations are not frequent enough and may give physicians and parents a false sense of security.

Beckwith-Wiedemann Syndrome↗
PubMed1990

Color flow Doppler--a useful instrument in the diagnosis of vasa previa.

Vasa previa is associated with an increased perinatal mortality rate and rarely is diagnosed in the antepartum period. We present a case in which vasa previa was correctly diagnosed by use of color flow Doppler imaging. This modality is a valuable adjunct in the evaluation of patients suspected to have vasa previa.

Blood Vessels↗
PubMed1990

Influences of glutathione and sulfhydryl containing compounds on aqueous humor outflow function.

Several sulfhydryl reactive compounds have previously been shown to influence aqueous humor outflow facility. The purpose of the current study was to investigate the effect of glutathione depletion on certain of these sulfhydryl actions. Enucleated calf, monkey, and human eyes were perfused via the anterior chamber by the constant pressure (15 mmHg) technique. In calf eyes, perfusion of 10 mM cysteamine produced a small (-23%, P = 0.03) decrease in outflow facility that was also observed after hyaluronidase pretreatment. In contrast, following pretreatment with 1 mM BCNU [1,3 bis(2 chlorethyl)-1-nitrosourea], an inhibitor of glutathione reductase, and 10 mM diamide, a glutathione oxidant, which did not by themselves significantly affect outflow facility, perfusion of cysteamine resulted in an opposite effect--a remarkably large (+90%, P less than 0.001) increase in outflow facility. Other reduced and oxidized sulfhydryl-containing compounds such as cysteine, beta-mercaptoethanol, and glutathione, itself, as well as the non-sulfhydryl reducing agent, ascorbic acid, were substituted for cysteamine in this protocol and found to produce similar effects of varying magnitudes. In general, the reduced sulfhydryl containing compounds and ascorbic acid were the most effective. Pretreatment with BCNU alone without diamide did not produce this effect. Treatment with BCNU and diamide resulted in a greater than 75% decrease in reduced glutathione levels and a concomitant tenfold increase in glutathione mixed disulfide levels (0.229 vs. 0.030 mumol g-1 wet weight) in the calf trabecular meshwork. The subsequent perfusion with cysteamine reversed this mixed disulfide formation.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Chloromercuribenzenesulfonate↗
PubMed1990

Late results of combined iodine-125 and external beam radiotherapy in carcinoma of prostate.

A total of 96 patients were treated for localized carcinoma of the prostate using combined Iodine-125 (125I) implantation and external beam radiotherapy. The implant was tailored to deliver 10,000 rad to the periphery of the prostate. A significant incidence of serious late rectal complications was observed. Positive pelvic nodes were found in 28 percent of the patients. Disease-free survival at seven years was 76 percent for those with negative nodes and 46 percent for patients with positive nodes.

Fistula↗