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Biomedical subjects

P Sharma

Publications and source records attributed to P Sharma.

At least 199 records · Page 11Linked to original sources
PubMed1999

An open study to evaluate the efficacy of artemether in severe falciparum malaria.

An open clinical trial was conducted in 30 patients of severe falciparum malaria with heavy parasitaemia (parasitized erythrocytes above 5%). Artemether (methyl ether of dihydroartemisinin-active principle isolated from Chinese plant Qinghaosu) was administered as 80 mg intramuscular injection twice on first day and then single dose of 80 mg intramuscular on 2nd to 5th day. The trial could be completed in 28 patients and two patients expired. In our observation falciparum malaria affected the young adults in their most productive period of life i.e. 25-44 yrs. All patients became afebrile by the 4th day with fever clearance time approximately 31.92 +/- 15.30 hr. Twenty-five patients (83.33%) became parasite free by 5th day with mean parasite clearance time approximately 47.04 +/- 19.95 hr. Deranged liver function and renal profile was observed in 63% and 50% patients respectively. Two patients, who died had very high degree of parasitaemia (50% and 16%) with cerebral malaria. One died due to multiorgan failure and other due to massive hematemesis and shock. The type of response achieved by artemether therapy was analysed as per WHO criteria suggested for chloroquine resistance. S response was observed in 25 patients (cure rate 83.33%). Two patients (6.66%) patients showed R II response, one patient (3.33%) showed R III response and R I response was not observed in any patient. No significant side effects were noted. This pilot study demonstrated that intramuscular artemether is a useful addition to antimalarial drugs in this era of multidrug resistant P. falciparum malaria showing high clinical potency with virtually no side effect.

Adult↗
PubMed1999

Antihypertensive efficacy and tolerability of once-daily sustained-release diltiazem alone and in combination with ramipril in hypertension.

This study assessed once-daily (OD), sustained-release (SR) diltiazem alone and in combination with ramipril in essential hypertension. Fifty patients with supine diastolic blood pressure (DBP) > or = 95-< or = 114 mm Hg were entered into the active treatment phase of the study after 2 weeks of placebo run-in. Sustained-release diltiazem 180 mg OD was administered for 2 weeks, then optimally titrated, at 2 week intervals, to SR diltiazem 240 mg OD and then SR diltiazem 180 mg + ramipril 2.5 mg OD to achieve supine DBP < or = 90 mm Hg. After 4 weeks of diltiazem monotherapy (SR diltiazem 180 mg or 240 mg OD) mean supine DBP was reduced from 102.84 +/- 3.81 mm Hg to 90.15 +/- 5.02 mm Hg (P < 0.01) and mean supine heart rate was reduced from 85.15 +/- 11.02 bpm to 77.62 +/- 11.45 bpm (p < 0.01). Diltiazem monotherapy reduced supine DBP to < or = 90 mm Hg in 35/45 (77.77%) patients. Combination therapy (SR diltiazem 180 mg + ramipril 2.5 mg OD), received by non-responders to diltiazem monotherapy, reduced supine DBP to < or = 90 mm Hg in 3/10 (30%) patients. Sinus bradycardia was observed in one patient. Sustained-release diltiazem alone and in combination with ramipril reduce blood pressure in a dose related manner and is well tolerated.

Adult↗
PubMed1998

Mechanism of allosteric regulation of the rod cGMP phosphodiesterase activity by the helical domain of transducin alpha subunit.

The G protein alpha subunit (Galpha) is composed of two distinct folding domains: a GTP-binding Ras-like domain and an alpha helical domain (HD). We have recently reported that the helical domain (HDt) of the vertebrate visual transducin alpha subunit (Galphat) synergizes activation of retinal cyclic GMP phosphodiesterase (PDE) by activated Galphat (Liu, W., and Northup, J. K., (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 12878-12883). Here, we examine the molecular basis for this HD-based signaling regulation, and we provide a new model for the activation of the target effector. The HD proteins derived from visual transducin or taste gustducin alpha subunits, but no other Galpha HD proteins, each attenuate the PDE catalytic core (Palphabeta) and synergize Galphat stimulation of the holoPDE (Palphabetagamma2) with similar apparent affinities. The data from studies of both HDt-mediated attenuation and stimulation indicate that the HDt and the PDE inhibitory subunit (Pgamma) interact with PDE at independent sites and that Palphabeta contains the binding sites for HD. The saturation of both processes by HDt displays positive cooperativity with Hill coefficients of 1.5 for the attenuation of Palphabeta activity and 2.1 for synergism of holoPDE activation. Our data suggest the that Galphat-HDt regulates PDE by allosterically decreasing the affinity of Palphabeta for Pgamma and thus simultaneously facilitating the interaction of the activated Galphat-Ras-like domain with Pgamma. Thus, we propose a new model for the high efficiency of PDE activation as well as deactivation, and, overall, a novel mechanism for controlling fidelity, sensitivity, and efficacy of G protein signaling.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1998

Cloning and functional expression of the guinea pig neuropeptide Y Y2 receptor.

Five neuropeptide Y (NPY) receptor subtypes have been cloned in mammals. The degree of sequence conservation differs considerably between subtypes as well as between evolutionary lineages. To shed further light on this, we have cloned the five NPY receptors in the guinea pig. Here, we report the cloning of the guinea pig Y2 receptor. The Y2 receptor is generally highly conserved, with 90-95% identity between different orders of mammals, including the guinea pig. The guinea pig receptor has a divergent cytoplasmic tail, indicating possible differences in regulation of signalling and/or down regulation. COS-7 cells transiently transfected with the gpY2 receptor show saturable 125I-PYY binding with a Kd = 6 pM. In displacement experiments, the gpY2 receptor was similar to the human and rat receptors with the following rank order of potencies: pNPY > pPYY > pNPY13-36 = pNPY22-36 >> [Leu31Pro34]NPY > BIBP3226. Thus, the guinea pig Y2 receptor is well conserved in comparison with human and rat with regard to both amino acid sequence and pharmacological profile.

Amino Acid Sequence↗
PubMed1998

Role of opioidergic and monoaminergic neurotransmission in the GnRH release mechanism of EBP-primed OVX rats.

We examined the effect of intracerebroventricular (i.c.v.) administration of mu-opioid agonist, morphine, and its antagonist naloxone followed by morphine on the activities of monoamine-metabolizing enzymes, namely tyrosine hydroxylase (TH) and monoamine oxidase (MAO) along with adenosinetriphosphatase (Na+, K+ -ATPase), the enzyme responsible for the maintenance of ionic gradients across the membrane, in seven discrete regions of brain from estrogen- and progesterone-primed ovariectomized rats. TH activity decreased after morphine treatment in some areas such as the median eminence-arcuate region (ME-ARC), the amygdala, and the thalamus, showing statistically significant change. MAO activity increased in all the areas studied, but more appreciable change was observed in medial preoptic area (mPOA), the ME-ARC region, and the cortex. Pronounced increase in Na+, K+ -ATPase enzyme activity was observed after the drug treatment. Naloxone given prior to morphine injection resulted in recovery of the enzyme activities in most of the areas studied. Our study may provide insights into the precise opioidergic modulation of gonadotropin releasing hormone (GnRH) release mechanisms through the involvement of monoaminergic system, elucidating the basis of various neuronal dysfunctions and their management in opioid addicts.

Analgesics, Opioid↗
PubMed1998

Structure of human endothelin-2 gene and demonstration of common expression in human right atrial tissue.

The endothelins (ET) are a group of three vasoactive peptides also known to be involved in vascular remodeling. ET1 is the most extensively studied, but recent evidence has highlighted the role of the little investigated ET2 gene as a potential candidate gene in regulating blood pressure. To allow the future role of this gene to be studied the structure of human ET2 was characterized and intron/exon boundaries were determined. With this structural information and using reverse-transcriptase PCR technology we show that the ET2 gene is commonly expressed in human right atrial tissue. This work will allow a more detailed assessment of the role of this physiologically important gene in human essential hypertension.

Base Sequence↗
PubMed1998

Site-specific phosphorylation of Lys-Ser-Pro repeat peptides from neurofilament H by cyclin-dependent kinase 5: structural basis for substrate recognition.

Recent work has shown that high molecular weight neurofilament (NF) proteins are phosphorylated in their carboxy-terminal tail portion by the enzyme cyclin-dependent kinase 5 (CDK-5). The tail domain of neurofilaments contains 52 tripeptide repeats, viz. Lys-Ser-Pro, which mainly exist as KSPXK and KSPXXX motifs (X = amino acid). CDK-5 specifically phosphorylates the serine residues within the KSPXK sites. We probed the structural basis for this type of substrate selectivity by studying the conformation of synthetic peptides containing either KSPXK or KSPXXX repeats designed from native neurofilament sequences. Synthetic peptides with KSPXK repeats were phosphorylated on serine with a recombinant CDK-5/p25 complex whereas those with KSPXXX repeats were unreactive in this system. Circular dichroism (CD) studies in 50% TFE/H2O revealed a predominantly helical conformation for the KSPXXX-containing peptides, whereas the CD spectra for KSPXK-containing peptides indicated the presence of a high population of extended structures in water and 50% TFE solutions. However, detailed NMR analysis of one such peptide which included two such KSPXK repeats suggested a turn-like conformation encompassing the first KSPXK repeat. Restrained molecular dynamics calculations yielded an unusually stable, folded structure with a double "S"-like bend incorporating the central residues of the peptide. The data suggest that a transient reverse turn or loop-type structure may be a requirement for CDK-5-promoted phosphate transfer to neurofilament-specific peptide segments.

Amino Acid Sequence↗
PubMed1998

Morphine enhances macrophage apoptosis.

Laboratory data indicate that morphine decreases the numbier of peritoneal and alveolar macrophages (Mphi) and compromises their phagocytic capability for immune complexes and bacteria. We hypothesize that morphine decreases the number of, as well as compromises the phagocytic capability of, Mphi by programming their death. We studied the effect of morphine on Mphi apoptosis in vivo as well as in vitro. Peritoneal Mphi harvested from morphine-treated rats showed DNA fragmentation. Morphine enhanced murine Mphi (J 774.16) apoptosis in a dose-dependent manner. Human monocytes treated with morphine showed a classic ladder pattern in gel electrophoretic and end-labeling studies. Morphine promoted nitric oxide (NO) production both under basal and LPS-activated states. N(G)-nitro-L-arginine methyl ester (L-NAME) and N(G)-monomethyl-L-arginine monoacetate (L-NMMA), inhibitors of NO synthase, attenuated the morphine-induced generation of NO by Mphi. Morphine also enhanced Mphi mRNA expression of inducible NO synthase (iNOS). Since morphine-induced Mphi apoptosis was inhibited by L-NAME and L-NMMA, it appears that morphine-induced Mphi apoptosis may be mediated through the generation of NO. Morphine promoted the synthesis of Bax and p53 proteins by Mphi. Moreover, IL-converting enzyme (ICE)-1 inhibitor attenuated morphine-induced Mphi apoptosis. These studies suggest that morphine activates the induction phase of the apoptotic pathway through accumulation of p53. The effector phase of morphine-induced apoptosis appears to proceed through the accumulation of Bax and activation of ICE-1. The present study provides a basis for a hypothesis that morphine may be directly compromising immune function by promoting Mphi apoptosis in patients with opiate addiction.

Animals↗
PubMed1998

Calcitropic peptides: neural perspectives.

In mammals and higher vertebrates, calcitropic peptides are produced by peripheral endocrine glands: the parathyroid gland (PTH), thyroid or ultimobranchial gland (calcitonin) and the anterior pituitary gland (growth hormone and prolactin). These hormones are, however, also found in the neural tissues of lower vertebrates and invertebrates that lack these endocrine organs, suggesting that neural tissue may be an ancestral site of calcitropic peptide synthesis. Indeed, the demonstration of CNS receptors for these calcitropic peptides and their induction of neurological actions suggest that these hormones arose as neuropeptides. Neural and neuroendocrine roles of some of these calcitropic hormones (calcitonin and parathyroid hormone) and related peptides (calcitonin gene related peptide, stanniocalcin and parathyroid hormone related peptide) are thus the focus of this review.

Animals↗
PubMed1998

Growth hormone: a paracrine growth factor in embryonic development?

Although pituitary growth hormone is obligatory for normal postnatal growth and development, early embryonic and fetal growth is generally considered to be independent of pituitary GH. Indeed, in chickens, somatotrophs and serum GH are not detectable until late in embryogenesis, and neither partial decapitation nor pre-hatch GH administration greatly affects embryonic growth. However, since it is now known that GH can be produced and act in many extra-pituitary tissues, early embryonic growth may be independent of pituitary GH but dependent upon the paracrine actions of extra-pituitary GH. The possibility that growth hormone may be a paracrine growth factor during early development will therefore be considered in this brief review, which is based on the embryogenesis of the domestic fowl.

Animals↗
PubMed1998

Vaccination of langur monkeys (Presbytis entellus) against Leishmania donovani with autoclaved L. major plus BCG.

The protective potential of killed Leishmania major (ALM) along with BCG was evaluated against L. donovani in Indian langur monkeys in single and triple dose schedules. A delayed protection was observed in monkeys after a single dose schedule of ALM (3 mg)+BCG (3 mg) given intradermally 2 months before intravenous challenge with L. donovani. Triple dose schedule each of 1 mg ALM + 1 mg BCG was more effective. The status remained unchanged until the end of the experiment (approximately 8 months). The study indicates that a combination of ALM + BCG may be a good candidate vaccine for exploiting against human Kala-azar.

Adjuvants, Immunologic↗
PubMed1998

Oxidation of the mesangial matrix metalloproteinase-2 impairs gelatinolytic activity.

Glomerulosclerosis is characterized by an accumulation of mesangial extracellular matrix. Oxygen radicals are strongly implicated in glomerular injury but it is unclear by what mechanism they could modulate matrix turnover dynamics. We evaluated whether oxidation of the 72 kD mesangial matrix metalloproteinase-2 (MMP-2), the major mesangial matrix-degrading enzyme, could alter its gelatinolytic activity. Oxidation of the MMP-2 using a FeCl3/ascorbate system resulted in impaired ability to degrade [3H]gelatin compared to control. Samples were also subjected to SDS-PAGE gelatin substrate zymography. At the 72 kD position a significant impairment of gelatinolytic activity of oxidized samples was observed, a decrease attenuated by coincubation of samples with the FeCl3/ascorbate system plus the radical spin trap N-tert-butyl-alpha-phenylnitrone suggesting specificity of oxidative changes in the decrease in enzymatic activity. These data represent the first report demonstrating that oxidation of the MMP-2 diminishes its activity and suggest a previously undescribed mechanism by which oxygen radicals may contribute to altered turnover of extracellular matrix.

Animals↗
PubMed1998

Morphine modulates proliferation of kidney fibroblasts.

Renal interstitial scarring is an important component of heroin-associated nephropathy. Kidney fibroblasts have been demonstrated to play a role in the development of renal scarring in a variety of renal diseases. We studied the effect of morphine, an active metabolite of heroin, on the proliferation of kidney fibroblasts. Morphine at a concentration of 10(-12) M enhanced (P < 0.001) the proliferation of kidney fibroblasts (control, 67.5 +/- 2.0 vs. morphine, 112.2 +/- 10.1 x 10(4) cells/well). [3H]thymidine incorporation studies further confirmed these results. Morphine at concentrations of 10(-12) M to 10(-10) M also modulated mRNA expression of early growth related genes (c-fos, c-jun and c-myc). Morphine at concentrations of 10(-8) to 10(-4) M promoted apoptosis of kidney fibroblasts and also enhanced the synthesis of p53 by kidney fibroblasts. We speculate that morphine-induced kidney fibroblast proliferation may be mediated through the activation of early growth related genes, whereas morphine induced kidney fibroblast apoptosis may be mediated through the generation of p53. The present in vitro study provides a hypothetical basis for the role of morphine in the development of renal interstitial scarring in patients with heroin-associated nephropathy.

Animals↗
PubMed1998

Short segment Barrett's esophagus--the need for standardization of the definition and of endoscopic criteria.

There has been a recent increase in abstracts and publications reporting intestinal metaplasia in the distal esophagus and cardia. The terms "short segment Barrett's esophagus," "intestinal metaplasia of the esophagogastric junction," and "intestinal metaplasia of the cardia" are being used to describe either similar or different entities. This review article deals with the current data on these issues, the definition of short segment Barrett's esophagus including the endoscopic and histologic criteria, the rationale for separating short segment Barrett's esophagus from intestinal metaplasia of the cardia, and a simple classification of intestinal metaplasia.

Barrett Esophagus↗