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S Patel

Publications and source records attributed to S Patel.

At least 307 records · Page 17Linked to original sources
PubMed1998

Chemokine receptor-ligand interactions measured using time-resolved fluorescence.

Two G protein-coupled receptor subtypes (CXCR1 and CXCR2) mediate Interleukin-8 (IL8) action in cells. A nonradioactive lanthanide-chelate derivatized IL8 ligand was developed to measure the binding activity of the chemokine receptors, CXCR1 and CXCR2. Site-specific mutagenesis of the carboxyl-terminal serine of IL8 to cysteine resulted in a mutant IL8 (IL8-S72C) having a single free sulfhydryl. Using an iodoacetamide derivative of the Eu3+-chelate of N-(p-benzoic acid)diethylenetriamine-N,N',N"-tetraacetic acid (DTTA), incorporation of one Eu3+ per IL8 molecule ([Eu3+]IL8-S72C) was achieved. The dissociation constant for this conjugate was similar to that measured for [125I]IL8 ( approximately 2 nM) when measured by time-resolved fluorometry using CHO cell lines stably expressing CXCR1 or CXCR2 receptors. The sensitivity, stability, and high specific activity of europium-labeled IL8 demonstrate the usefulness of lanthanide-labeled proteins in the measurement of receptor-ligand interactions and may be extended to other peptide ligands.

Animals↗
PubMed1998

Decorin activates the epidermal growth factor receptor and elevates cytosolic Ca2+ in A431 carcinoma cells.

Several independent lines of evidence have implicated decorin, a small leucine-rich proteoglycan, in the inhibition of cell proliferation. However, the mechanism by which decorin mediates its effect on cell proliferation is unclear. Here we report, for the first time, decorin-mediated increases in intracellular Ca2+ levels of single A431 cells. The effects of decorin persisted in the absence of extracellular Ca2+ but were blocked by AG1478, an epidermal growth factor (EGF)-specific tyrosine kinase inhibitor, and by down-regulation of the EGF receptor. The effects of decorin were not mimicked by the structurally homologous protein, biglycan. Our results indicate a novel action of decorin on the EGF receptor, which results in mobilization of intracellular Ca2+ providing a possible mechanism by which decorin causes growth suppression.

Calcium↗
PubMed1998

Site-directed mutagenesis of bacterial hemoglobin: the role of glutamine (E7) in oxygen-binding in the distal heme pocket.

The bacterial and yeast hemoglobins have a glutamine instead of histidine in the E7 position of the distal heme pocket. The recently determined crystal structure of Vitreoscilla hemoglobin (VHb) indicates that this residue is oriented out of the heme pocket and may not ligand the bound oxygen. This is in contrast to elephant myoglobin which also has a Gln(E7) but which does ligand the bound oxygen. This residue was changed in VHb using site-directed mutagenesis to leucine (VHbL) or to histidine (VHbH). Spectral and kinetic studies of the binding of oxygen and CO to VHbL showed that this substitution had little effect on the ligand-binding properties of this protein, evidence that Gln(E7) does not H-bond the bound ligand, in agreement with the findings of the crystallographic study of VHb. In contrast, the functional properties of VHbH were drastically altered in a way suggesting that the E7His may itself be liganded to the heme iron. These studies are further evidence that the distal heme pocket in VHb and related microbial hemoglobins differs from that in mammalian hemoglobins and may resemble in some ways the heme pocket in cytochrome b5.

Bacteria↗
PubMed1998

Foveal outer retinal function in eyes with unexplained visual symptoms or acuity loss.

OBJECTIVE: To determine whether foveal outer retinal dysfunction is common in eyes with unexplained visual symptoms or acuity loss. DESIGN: Prospective study. PARTICIPANTS: Seventy-three eyes of 44 consecutive patients with unexplained visual symptoms or acuity loss, 39 eyes of 39 control subjects, and 12 eyes of 7 patients with known maculopathy. INTERVENTION: Foveal cone electroretinography (ERG) and letter recognition perimetry. MAIN OUTCOME MEASURES: Foveal cone ERG data. RESULTS: Abnormal foveal cone ERG data were recorded in 35 (48%) of 73 eyes (23 [52%] of 44 patients). Among these 35 eyes, amplitude was lower than in normal controls (P<.001) and was correlated with visual acuity and the number of letter recognition perimetry errors (P<.05 for both). The latter was higher in eyes with abnormal retinal responses than in symptomatic eyes with normal responses (P<.01). However, initial symptoms, visual acuity, and macular appearance did not differentiate between these 2 groups. Foveal cone ERG test vs retest data showed consistent results. CONCLUSION: Foveal outer retinal dysfunction is a common underlying mechanism of previously unexplained visual symptoms or acuity loss. Foveal cone ERG testing should be considered early in the evaluation of eyes with this presentation.

Adolescent↗
PubMed1998

Foveal dysfunction and central visual field loss in glaucoma.

OBJECTIVE: To determine whether foveal function distal to the ganglion cell layer is an independent predictor of central visual field function in glaucoma. SETTING: University affiliated hospital and private practice. PARTICIPANTS: Twenty-seven eyes (27 patients) with normal-pressure glaucoma, 10 eyes (10 patients) with primary open-angle glaucoma, and 47 eyes of 47 matched normal volunteers. INTERVENTION AND MAIN OUTCOME MEASURES: Foveal cone electroretinogram (ERG) amplitude, relative optic cup to disc area and their relations to Humphrey full-threshold 30-2 visual field central 4-point mean total deviation (C4MTD) and pattern deviation (C4MPD). RESULTS: Foveal cone ERG amplitude was subnormal in 14 (37.8%) of the 37 glaucomatous eyes and lower in the glaucoma group compared with normal eyes (P<.01). The C4MTD and C4MPD were lower in glaucomatous eyes with subnormal amplitudes compared with those with normal amplitudes (P<.01 and P<.05, respectively). Amplitude was directly correlated with C4MTD (P<.01) and C4MPD (P<.01). Relative optic cup to disc area was inversely correlated with C4MTD (P<.001) and C4MPD (P<.001). Partial correlation analysis revealed that amplitude and relative optic cup to disc area were independent predictors of C4MTD and C4MPD. CONCLUSION: Foveal function distal to the ganglion cell layer and optic disc cupping independently predict central visual field function in glaucoma.

Adult↗
PubMed1998

Soluble factor(s) released from neutrophils activates endothelial cell matrix metalloproteinase-2.

OBJECTIVE: Polymorphonuclear leukocyte (PMN) infiltration and microvascular injury are hallmarks of the tissue remodeling associated with multiple organ failure. These processes require the concerted action of various proteolytic enzymes, including serine and matrix metalloproteinases (MMPs). Matrix metalloproteinase-2 (MMP-2) plays an important role in the turnover of various ECM components, including type IV collagen, fibronectin, and gelatins. Like all MMPs, MMP-2 is secreted as an inactive zymogen (proMMP-2) and activated extracellularly by limited proteolytic cleavage. The physiologic mechanism(s) of proMMP-2 activation remains unclear. This study was designed to characterize the effect of PMNs on the activation of proMMP-2 produced by endothelial cells. METHODS: PMNs and human umbilical vein endothelial cells (HUVECs) were grown either separately or together for 2-16 h. To evaluate the role of cell-cell contact, cocultures were also established in which the two cell types were separated by a semipermeable polycarbonate membrane. Alternatively, PMN-conditioned medium was added to HUVEC cultures with or without various proteinase inhibitors (aprotinin, 1,10-phenanthroline, Batimastat, E-64, eglin c peptide, or pepstatin A). After incubation, the culture supernatants were analyzed by gelatin zymography to characterize the gelatinases. RESULTS: HUVECs produce MMP-2 in its inactive (72 kDa) form. PMNs produce high levels of MMP-9 (gelatinase B, 92 kDa) but no MMP-2. Coculture of PMNs with or addition of PMN-conditioned medium to HUVECs results in the production of active (62 kDa) MMP-2. ProMMP-2 activation by PMN-conditioned medium is not blocked by inhibitors of plasmin, cysteine-, acid-, or metalloproteinases. CONCLUSION: PMNs release a soluble factor that activates endothelial cell MMP-2 through a novel mechanism independent of cell-cell contact and not attributable to the activities of plasmin, cysteine-, acid-, or metalloproteinases. These findings may provide insight into the tissue remodeling that accompanies PMN-mediated microvascular injury.

Aprotinin↗
PubMed1998

Purification and biochemical properties of soluble recombinant human Bax.

Bax is a member of the Bcl-2 protein family with proapoptotic properties. The proteins of this family contain three highly conserved regions termed BH1, BH2, and BH3 as well as a hydrophobic COOH-terminal domain, which is responsible for the membrane attachment of the proteins. We have expressed human Bax truncated of the 20 amino acid COOH-terminal hydrophobic domain to obtain large amounts of soluble protein suitable for biochemical and structural studies. The truncated protein was expressed as a glutathione S-transferase (GST) fusion protein in Escherichia coli. The GST-Bax fusion protein was bound to glutathione-Sepharose, and Bax was released by thrombin cleavage and further purified by sequential chromatography on heparin-Sepharose and DEAE-Sepharose. The purified protein was present in solution as a heptamer and multimers of the heptamer complex. Limited tryptic digestion cleaved the protein in the region preceding the BH3 domain and produced a specific stable protein fragment of 15 kDa. Phosphorylation has been proposed as a possible regulatory mechanism of the bcl-2 proteins. The Bax protein was an in vitro substrate for specific serine/threonine protein kinases.

Amino Acid Sequence↗
PubMed1998

Is there a correlation between taurine levels and xenobiotic-induced perturbations in protein synthesis?: a study with tetracycline in rats.

Changes in urinary levels of taurine have been reported in rats following treatment with various xenobiotics including those which alter protein synthesis and/or are hepatotoxic. This paper reports on the time course of the urinary elevation of taurine following treatment of rats with tetracycline (50, 150 and 200 mg.kg-1). Maximum taurine excretion occurred 8-12 h following dosing. Serum albumin and total protein were significantly lower after 24 h (200 mg.kg-1). The increase in urinary taurine was dose-related and reflected in the raised serum levels of taurine 24 h after dosing. Serum and urinary protein and [3H]-leucine incorporation into acid precipitable protein in liver and muscle were reduced by tetracycline (100, 150 and 200 mg.kg-1) 10 h after dosing. The reduction in protein synthesis was correlated with increased urinary and serum levels of taurine at 10 h. The use of taurine as a non-invasive marker of protein synthesis is discussed.

Animals↗
PubMed1998

Discriminative stimulus properties of the putative dopamine D3 receptor agonist, (+)-PD 128907: role of presynaptic dopamine D2 autoreceptors.

The putative D3 receptor agonist, (+)-PD 128907, is widely used to study the functional relevance of D3 receptors in vivo. Given that non-selective D2/3/4 receptor agonists serve as effective discriminative stimuli in rats we have trained animals to discriminate (+)-PD 128907 (30 microg kg(-1), s.c.) from saline and examined the pharmacological specificity of the response. Consistent with a D3 receptor mediated response, the non-selective D2/3 receptor agonist apomorphine and the D3 preferring agonists 7-OH-DPAT and (-) quinpirole generalised to the cue whilst the D2/3 receptor antagonists haloperidol, raclopride, spiperone and (+)-butaclamol antagonised drug lever responding. In contrast, the D1 selective agonist (+/-)-SKF 81297 and D1/5 selective antagonist, R-(+)-SCH 23390 had no effect. Results also suggest that presynaptic dopamine receptors are involved. Thus the dopamine depleting agent alpha-methyl-p-tyrosine potentiated the effects of a submaximal dose of (+)-PD 128907 whereas amphetamine failed to generalise per se and blocked (+)-PD 128907 lever selection. However, studies using subtype selective antagonists argue against a role for the D3 receptor. Thus the 10-fold selective D2 receptor antagonist L-741,626 blocked the (+)-PD 128907 discriminative stimulus whereas L-745,829 and GR 103,691, antagonists > 40 and > 100-fold selective for D3 receptors, failed to modify the response. These results suggest that presynaptic D2 receptors mediate the discriminative stimulus properties of (+)-PD 128907 and highlight the lack of selectivity of (+)-PD 128907 for D3 receptors in vivo.

Animals↗
PubMed1998

Development of an ED teaching program aimed at reducing prehospital delays for patients with chest pain.

OBJECTIVE: Delays in providing thrombolytic agents to patients with chest pain occur mainly in the prehospital arena. To reduce prehospital delay in treating patients with chest pain, we created a discharge teaching video that emphasized calling 911 in the event of a possible heart attack and a written action plan to be posted near the telephone. We also gave patients their EKG readings to bring with them on their next visit to the emergency department. SETTING AND SAMPLE: All patients with chest pain admitted to the Chest Pain Observation Unit at Baystate Medical Center, Springfield, Mass, were eligible for this teaching effort. We tracked 127 nonconsecutive patients from January 1997 to May 1997. Of these patients, 108 were included in the study. RESULTS: We interviewed 102 patients (94%) 3 days after they were discharged from the Chest Pain Observation Unit. Within this group, 92% were able to describe what a heart attack might feel like, and 81.4% said they would call 911 or go to the hospital if they had symptoms of a heart attack. If they thought that their symptoms might be indigestion, 69% said they would take an antacid, then go to the hospital if they did not feel better. Fifty-one percent remembered what to do with their EKG readings, and 60.7% knew how to take their nitroglycerin correctly. CONCLUSION: We concluded that patients understood the message they were given and retained some of the material 3 days after discharge from the Chest Pain Observation Unit. The follow-up telephone calls revealed areas for improvement in the discharge teaching tools.

Chest Pain↗
PubMed1998

CD40L activation of dendritic cells down-regulates DORA, a novel member of the immunoglobulin superfamily.

Using a cDNA subtraction technique, a novel member of the immunoglobulin superfamily was isolated from human Dendritic cells (DC). This cDNA which we named DORA, for DOwn-Regulated by Activation encodes a protein belonging to the CD8 family of receptors containing a single V type loop domain with an associated J chain region, a transmembrane region containing an atypical tyrosine residue and a cytoplasmic domain containing three putative tyrosine phosphorylation sites. The hDORA gene has been localised to chromosome 16. From database searches a rat cDNA was identified that encoded a polypeptide with 63% identity to hDORA. The expression of the human cDNA was studied in detail. Northern blot analysis revealed 1.0 kb and 2.5 kb mRNAs in peripheral blood lymphocytes, spleen and lymph node, while low levels were observed in thymus, appendix, bone marrow and fetal liver. No signal was noted in non-immune system tissues. By RT-PCR analysis of hDORA revealed expression in cells committed to the myeloid lineage but not in CD34+ precursors or B cells and low expression in T cells. Expression was also observed in DC, purified ex vivo or generated in vitro from either monocytes or CD34+ progenitors. This was down-regulated following activation both by PMA and Ionomycin treatment and also by CD40L engagement. In situ hybridisation performed on tonsil sections showed the presence of hDORA in cells within Germinal Centers. This structure and expression suggests a function as a co-receptor, perhaps in an antigen uptake complex, or in homing or recirculation of DC.

Amino Acid Sequence↗
PubMed1998

Analysis of intrapulmonary right to left shunt in the hepatopulmonary syndrome.

BACKGROUND/AIMS: Severe hypoxaemia in patients with chronic liver disease in the absence of intrinsic lung disease, the hepatopulmonary syndrome, is associated with pulmonary vascular dilatation and may be an indication for liver transplantation. Divergence between two methods of measuring right to left shunt (radiolabelled albumin macroaggregates and 100% oxygen breathing) has been described, but the mechanism and reason for the inter-patient variability for this shunt difference are not well understood. METHODS: Eight hepatopulmonary syndrome patients were studied, with characteristic pulmonary diffusion abnormalities (carbon monoxide transfer factor 41+/-5 (mean+/-SE)% predicted) and significant decreases in arterial oxygen saturation (%) on standing vs. supine (-10%+/-3) and on exercise vs. rest (-15%+/-2). All had hypoxaemia at rest (arterial oxygen tension 8.2+/-0.6 kPa), partially corrected by breathing 100% oxygen (48.2+/-8.8 kPa). Pulmonary angiography was performed and right to left shunt measured by two independent methods: (a) 100% oxygen breathing and (b) i.v. injection of radiolabelled microspheres. RESULTS: Measurement of right to left shunt with 99mTc-labelled albumin macroaggregates confirmed significant intrapulmonary microvascular dilatation, i.e. an "anatomical" shunt equalling 32+/-4% of cardiac output. Shunt measurements made simultaneously by the classical 100% oxygen technique were significantly smaller (19+/-3%, p=0.01). For individuals, the difference between the 99mTc-albumin macroaggregate shunt and the 100% oxygen shunt ranged from 2% to 30% absolute, convergence suggesting larger shunt channels (pure anatomical shunt) and divergence representing a combination of anatomical shunt and alveolar-capillary diffusion limitation (smaller microvascular channels). CONCLUSIONS: Hypoxaemia in the hepatopulmonary syndrome may be due functionally either to right to left shunting or to diffusion limitation, depending upon the degree of dilatation of the pulmonary microvessels.

Adult↗
PubMed1998

Selective neurokinin-1 receptor antagonists are anti-hyperalgesic in a model of neuropathic pain in the guinea-pig.

Neuropathic pain is poorly managed by conventional analgesic therapy, such as non-steroidal anti-inflammatory drugs and opiates. The development of animal models of peripheral neural damage has aided in our understanding of the pathology and pharmacology of neuropathic pain. This report is the first clear demonstration using selective neurokinin-1 receptor antagonists of a potentially novel therapeutic approach to the treatment of neuropathic pain resulting from peripheral nerve damage in a guinea-pig model. The neurokinin-1 receptor antagonists, SDZ NKT 343 and LY 303,870 significantly reduced mechanical hyperalgesia following oral and intrathecal administration. (R,R)-SDZ NK T343, the enantiomer of SDZ NKT 343 did not show anti-hyperalgesic activity. RPR 100,893 showed significant anti-hyperalgesic activity only following intrathecal administration suggesting poor absorption or low level penetration of the blood-brain barrier. These results imply that neurokinin-1 receptor antagonists offer a new class of anti-hyperalgesic drugs with a largely central site of action in neuropathic pain.

Administration, Oral↗
PubMed1998

Separation of the S(+) and R(-)-enantiomers of tiagabine.HCl and its two chiral precursors by chiral chromatography: application to chiral inversion studies.

Chiral HPLC methods were developed and validated for tiagabine.HCl and its two chiral precursors to determine the chiral purity of the three compounds to ensure the quality of the final product which is used as a new antiepileptic drug. Tiagabine.HCl was derivatized with 1-napthalenemethylamine and was chromatographed on a Pirkle type phenyl glycine column with a mobile phase of 69:31, 0.1 M ammonium acetateacetonitrile (v/v). The two chiral precursors were chromatographed on a Chiralcel-OG column with a mobile phase of hexane, isopropanol etc. Each of the three HPLC methods have a selectivity factor (alpha) of 1-2 or higher. The validation of the methods was done by conducting standard addition and recovery studies of the S(+)-enantiomers in the samples. The %RSD of all three methods were < 5 with a limit of quantification of 0.05% (peak area) or lower. By using these methods, a study was conducted to investigate the effect of pH, temperature, and trace levels of transition metals such as Fe3+, Co2+, and Ni2+ on the conversion of R(-)-enantiomer to the S(+)-enantiomer of tiagabine.HCl and its two chiral precursors. The results of this study demonstrated that the two chiral precursors of tiagabine.HCl under reflux conditions are more sensitive to chiral inversion than tiagabine.HCl. Under reflux conditions, in the presence of trace metal ions and different pH, approximately 10, 11, and 1% of the R(-)-enantiomer was converted to the S(+)-enantiomer for ethyl nipecotate, ethylester of tiagabine, and tiagabine.HCl, respectively. However, at room temperature, tiagabine.HCl appears to be less chirally stable than its two chiral precursors. Approximately 0.4% R(-)-enantiomer of tiagabine.HCl was converted to the S(+)-enantiomer at room temerature and acidic conditions. Under similar conditions, the S(+)-enantiomer of ethyl nipecotate and ethylester of tiagabine.HCl was < 0.05%. The initial S(+)-enantiomer content for all three compounds was < 0.1%.

Anticonvulsants↗
PubMed1998

Binding of 2,4-disubstituted morpholines at human D4 dopamine receptors.

The synthesis of a series of 2,4-disubstituted morpholines is described and their affinities at human dopamine receptors reported. The orally bioavailable 7-azaindole compound 11 has nanomolar affinity at the hD4 receptor with > 1000-fold selectivity over the hD2 receptor.

Administration, Oral↗
PubMed1998

3-(1-piperazinyl)-4,5-dihydro-1H-benzo[g]indazoles: high affinity ligands for the human dopamine D4 receptor with improved selectivity over ion channels.

3-(4-Piperidinyl)-5-arylpyrazoles, such as 1, were selective for the cloned human dopamine D4 receptor (hD4), but also showed affinity at voltage sensitive calcium, sodium and potassium ion channels. A combination of substituent changes to reduce the basicity of the piperidine nitrogen and conformational restriction to give 4,5-dihydro-1H-benzo[g]indazoles reduced this ion channel affinity at the expense of selectivity for hD4 over other dopamine receptors. Incorporation of piperazine into the 4,5-dihydro-1H-benzo[g]indazoles in place of piperidine gave a novel series of high affinity, selective, orally bioavailable hD4 ligands, such as 16, with improved selectivity over ion channels.

Administration, Oral↗
PubMed1998

Substituted pyrazoles as novel selective ligands for the human dopamine D4 receptor.

Two novel series of 3-(heterocyclylmethyl)pyrazoles have been synthesised and evaluated as ligands for the human dopamine D4 receptor. Compounds in series I (exemplified by 8k) have a phenyl ring joined to the 4-position of the pyrazole while those in series II (exemplified by 15j) have a 5-phenyl ring linked by a saturated chain to the 4-position of the pyrazole. Both series supplied compounds with excellent affinity for the human D4 and good selectivity over other dopamine receptors. Excellent selectivity over calcium, sodium, and potassium ion channels was also achieved.

Antipsychotic Agents↗