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Captopril renography is used for the non-invasive diagnosis of renovascular hypertension, but suffers from the drawbacks of lower sensitivity and false-positive tests due to a fall in blood pressure. Aspirin renography has been proposed as a useful test for evaluation of unilateral renal artery stenoses of moderate degree. We studied the clinical usefulness of aspirin renography in 12 patients with a clinical suspicion of renovascular hypertension and compared it with captopril renography using 99Tcm-DTPA. The test was considered positive if there were changes in the time-activity curve according to the criteria specified by the American Society of Hypertension Working Group. Four patients with discordant results between captopril and aspirin underwent intra-arterial digital subtraction angiography. In two patients, the renal arteries were normal; captopril was false-positive in both these patients. Bilateral stenosis was noted in the third patient, with captopril being false-negative on the right side with moderate stenosis, whereas aspirin was true-positive. There was unilateral stenosis in the fourth patient; captopril was false-positive on the contralateral side. Our results suggest that aspirin renography is superior to captopril renography in the assessment of patients with a suspicion of both unilateral and bilateral renovascular hypertension.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10845220&dopt=Abstract

Invest Ophthalmol Vis Sci. 2000 Jun;41(7):1861-70.
Mechanisms mediating substance P-induced contraction in the rat iris in vitro.

Grumann-Junior A, Dias MA, Alves RV, Boteon JE, Calixto JB.

Department of Pharmcology, Centre of Biological Sciences, Universidade Federal de Santa Catarina, Florianopolis, Brazil.

PURPOSE: To determine some of the mechanisms by which substance P (SP) induces contraction in the isolated rat iris. METHODS: Rings of rat iris were mounted in a 5-ml organ chamber containing Krebs solution at 37 degrees C under basal tension of 75 mg, and isometric tension was recorded. RESULTS: Substance P produced graded contraction in the rat iris, being approximately 40-fold more potent than carbachol. Peptidase inhibitors (captopril, phosphoramidon, thiorphan) did not affect the SP response. The SP contraction was dependent on external Ca2+ by a mechanism resistant to both nifedipine and omega-conotoxin GVIA. Atropine and tetrodotoxin significantly shifted the SP response to the right (three- and fivefold, respectively). Neither phorbol nor genistein altered the SP-induced contraction, whereas staurosporine caused a weak inhibition. Indomethacin, pyrilamine, guanethidine, 8-37 calcitonin gene-related peptide (CGRP) fragment, and NG-nitro-L-arginine methyl ester had no effect on SP response. All the natural tachykinin agonists caused concentration-dependent contraction in rat iris with similar maximal responses. The NK3 selective agonist senktide caused graded contraction, being approximately 150-fold more active than the NK2 selective agonist [beta-ala] NKA. The NK1 selective agonist SP methyl ester induced a small contraction. The NK3 and NK2 antagonists SR 142801 and SR 48968 shifted the SP response to the right. Schilds plots gave pA2 (negative logarithm of the molar concentration of antagonist causing a twofold rightward displacement of the concentration response curves) values of 9.37 and 7.97 and slopes of 0.70 and 1.02, respectively. CONCLUSIONS: Substance P produces a potent contraction in the isolated rat iris that seems to depend on the neural release of acetylcholine by tetrodotoxin-sensitive mechanisms. Its response relies largely on external Ca2+, through mechanisms independent of activation of L- or N-type Ca2+ channels, and is probably mediated via activation of NK3 and NK2 receptors.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10845610&dopt=Abstract

J Virol. 2000 Jul;74(13):5949-56.
Characterization of the zinc binding activity of the rubella virus nonstructural protease.

Liu X, Yang J, Ghazi AM, Frey TK.

Department of Biology, Georgia State University, Atlanta 30303, USA.

The rubella virus (RUB) nonstructural (NS) protein (NSP) ORF encodes a protease that cleaves the NSP precursor (240 kDa) at a single site to produce two products. A cleavage site mutation was introduced into a RUB infectious cDNA clone and found to be lethal, demonstrating that cleavage of the NSP precursor is necessary for RUB replication. Based on computer alignments, the RUB NS protease was predicted to be a papain-like cysteine protease (PCP) with the residues Cys1152 and His1273 as the catalytic dyad; however, the RUB NS protease was recently found to require divalent cations such as Zn, Co, and Cd for activity (X. Liu, S. L. Ropp, R. J. Jackson, and T. K. Frey, J. Virol. 72:4463-4466, 1998). To analyze the function of metal cation binding in protease activity, Zn binding studies were performed using the minimal NS protease domain within the NSP ORF. When expressed as a maltose binding protein (MBP) fusion protein by bacteria, the NS protease exhibited activity both in the bacteria and in vitro following purification when denatured and refolded in the presence of Zn. Atomic absorption analysis detected 1.6 mol of Zn bound per mol of protein refolded in this manner. Expression of individual domains within the protease as MBP fusions and analysis by a Zn(65) binding assay revealed two Zn binding domains: one located at a predicted metal binding motif beginning at Cys1175 and the other one close to the cleavage site. Mutagenesis studies showed that Cys1175 and Cys1178 in the first domain and Cys1227 and His1273, the His in the predicted catalytic site, in the second domain are essential for zinc binding. All of these residues are also necessary for the protease activity, as were several other Cys residues not involved in Zn binding. Far-UV circular dichroism (CD) analysis of the MBP-NS protease fusion protein showed that the protease domain contained a large amount of alpha-helical structure, which is consistent with the results of secondary-structural prediction. Both far-UV-CD and fluorescence studies suggested that Zn did not exert a major effect on the overall structure of the fusion protein. Finally, protease inhibitor assays found that the protease activity can be blocked by both metal ion chelators and the metalloprotease inhibitor captopril. In conjunction with the finding that the previously predicted catalytic site, His1273, is essential for zinc binding, this suggests that the RUB NS protease is actually a novel virus metalloprotease rather than a PCP.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10846076&dopt=Abstract

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