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Biomedical subjects

A Patel

Publications and source records attributed to A Patel.

At least 19 recordsLinked to original sources
PubMed1992

Microheterogeneity of dopamine transporters in rat striatum and nucleus accumbens.

Previously we have shown that the [125I]DEEP-labeled dopamine transporter from the rat nucleus accumbens has a higher apparent molecular weight than that from striatum. The present study confirms and extends these observations. Experiments with nucleus accumbens showed [125I]-DEEP to specifically bind to a protein with an apparent molecular weight of 76 kDa and with the pharmacological properties of the dopamine transporter. In exoglycosidase studies, treatment with neuraminidase, but not alpha-mannosidase, reduced the apparent molecular weight of the dopamine transporter from both the striatum and nucleus accumbens; however, a difference in the apparent molecular weight was still observed. N-Glycanase treatment, on the other hand, did reduce the apparent molecular weight of the dopamine transporters from the two regions to a similar value, approximately 56 kDa. In radioligand binding studies examining the effect of partial deglycosylation on striatal dopamine transporters, neuraminidase did not affect specific [3H]WIN 35,428 binding at 4 and 40 nM concentrations. In conclusion, the present study demonstrates that the difference in the apparent molecular weight of the dopamine transporter from these two regions is due to a difference in glycosylation and that the dopamine transporter from both regions contains similar amounts of sialic acid in their carbohydrate structure. Furthermore, the present data also indicate that the polypeptide portion of the dopamine transporter from both regions could be the same gene product.

Animals↗
PubMed1992

Calcitonin gene-related peptide in inflammatory bowel disease and experimentally induced colitis.

Pronounced changes in gut neuropeptide content have been observed in colonic tissues from animals with acute experimental colitis and in some patients with inflammatory bowel disease. The early decrease of CGRP in the colon during colitis in the animal studies suggest that CGRP is released during the inflammatory process. No data are available showing the biological action of released CGRP during inflammation. The sensory neurotoxin capsaicin was used in animal studies to examine the effect of sensory nerves on inflammation and healing in experimental animal models. The severity of colitis was enhanced after capsaicin pretreatment in acute and chronic animal models of colitis. These data support the hypothesis that sensory nerves exert a protective and healing-promoting function in the gut. CGRP is a good candidate for this action of sensory nerves because it is a major component in sensory nerve fibers. How CGRP exerts its protective function in the intestine is unknown. Data from gastric ulcer models support the hypothesis that a main action of CGRP is regulation of mesenteric and mucosal blood flow resulting in enhanced protection and tissue healing. Other effector roles of CGRP afferent nerve endings could also be considered.

Animals↗
PubMed1992

Probes for the cocaine receptor. Potentially irreversible ligands for the dopamine transporter.

Several potentially irreversible ligands (i.e., wash-resistant binding inhibitors) for the cocaine receptor site on the dopamine transporter, derived from (-)-cocaine or 3 beta-phenyltropan-2 beta-carboxylic acid methyl ester (WIN 35,065-2), were prepared and shown to produce wash-resistant inhibition of [3H]-3 beta-(p-fluorophenyl)tropan-2 beta-carboxylic acid methyl ester ([3H]WIN 35,428) binding. All the compounds prepared had the same absolute configuration as cocaine; they include analogues possessing chemically reactive groups such as the isothiocyanato and bromoacetamido as well as photoactive azido groups. The potentially irreversible ligands, as well as all the intermediates prepared in this study, were evaluated for their ability to inhibit the binding of [3H]WIN 35,428 in coincubation experiments. Of the potentially irreversible ligands, 3 beta-(p-chlorophenyl)tropan-2 beta-carboxylic acid 2-[p-(bromoacetamido)phenyl]ethyl ester (6c) had the highest apparent potency. The potentially irreversible ligands were also preincubated, and inhibition of [3H]WIN 35,428 binding was determined both before and after washing the ligand-exposed tissues. The most effective ligands in this regard were 3 beta-(3-iodo-4-azidophenyl)tropan-2 beta-carboxylic acid methyl ester (5) and 3 beta-(p-chlorophenyl)tropan-2 beta-carboxylic acid 2-(3-iodo-4-azidophenyl)ethyl ester (6d). The structure-activity relationships of these data are discussed.

Animals↗
PubMed1992

A cocaine analog and a GBR analog label the same protein in rat striatal membranes.

Because some evidence suggests that cocaine and GBR12935 bind to different sites, we utilized photoaffinity probes from both classes of compounds to see if they label the same protein. [125I]RTI-82 a cocaine analog, and [125I]DEEP, a GBR analog, labeled protein(s) showing the same molecular weight, a similar pharmacological profile and a similar sensitivity to neuraminidase.

Animals↗
PubMed1992

Identification of a major growth factor for AIDS-Kaposi's sarcoma cells as oncostatin M.

Conditioned medium from human T cell leukemia virus type 2 (HTLV-II)-infected T cells supports the growth and long-term culture of cells derived from acquired immunodeficiency syndrome (AIDS)-associated Kaposi's sarcoma lesions (AIDS-KS cells). A protein of 30 kilodaltons was purified from conditioned medium that supports the growth of AIDS-KS cells. The amino-terminal sequence of this protein was identical to the amino-terminal sequence of Oncostatin M, a glycoprotein that inhibits the growth of a variety of cancer cells. Oncostatin M from conditioned medium stimulated a twofold increase in the growth of AIDS-KS cells at a concentration of less than 1 nanogram of the protein per milliliter of medium.

Acquired Immunodeficiency Syndrome↗
PubMed1992

High-affinity binding of [125I]RTI-55 to dopamine and serotonin transporters in rat brain.

RTI-55 (3 beta-(4-iodophenyl)tropan-2 beta-carboxylic acid methyl ester), one of the most potent inhibitors of dopamine uptake reported to date, was radioiodinated and tested as a probe for the cocaine receptor in Sprague-Dawley rat brain. Saturation and kinetic studies in the striatum revealed that [125I]RTI-55 bound to both a high- and low-affinity site. The Kd for the high-affinity site was 0.2 nM, while the Kd for the low-affinity site was 5.8 nM. The corresponding number of binding sites in the striatum was 37 and 415 pmol/g protein. The pharmacological profile of specific [125I]RTI-55 binding in the striatum was consistent with that of the dopamine transporter. Additionally, [125I]RTI-55 was found to bind with high affinity to the cerebral cortex. Scatchard analysis revealed a single high-affinity component of 0.2 nM with a density of 2.5 pmol/g protein. The pharmacological profile demonstrated by [125I]RTI-55 in the cerebral cortex matched that of the serotonin transporter. Autoradiographic analysis of sagittal brain sections with [125I]RTI-55 binding was consistent with these findings. Specific binding of [125I]RTI-55 was blocked by dopamine uptake inhibitors in areas rich in dopaminergic nerve terminals. Conversely, serotonin uptake inhibitors blocked the binding of [125I]RTI-55 in brain areas rich in serotonergic neurons. These results demonstrate that [125I]RTI-55 may be a very useful ligand for the dopamine and serotonin transporters.

Animals↗
PubMed1992

Effect of mixture of surfactants and adsorbents on anaerobic digestion of water hyacinth-cattle dung.

In an effort to improve the anaerobic digestion of water hyacinth-cattle dung with enriched methane content, the effects of mixtures of surfactant-surfactant, adsorbent-adsorbent and surfactant-adsorbent have been studied in various combinations. Among the combinations tested, bentonite and gelatin, gelatin and Tegoprens 43, sodium lauryl sulfate and Tegoprens 42, and Tegoprens 47 and Tegoprens 63 showed more than a 100% increase in gas production with higher methane yield.

Adsorption↗
PubMed1992

Effector-assisted refolding of recombinant tissue-plasminogen activator produced in Escherichia coli.

Recombinant tissue-plasminogen activator (r-tPA), expressed in Escherichia coli cells in an aggregated form, was solubilized with a strong chaotrope in the absence of any reducing agent. The solubilized molecule was reactivated by a procedure that was developed to mimic the physiological conditions optimal for the functional folding and activity of the native protein. The use of partially purified fibrinogen, as a source of fibrin (the effector), is shown to facilitate the reactivation process and increase its yield by at least a factor of two. The yield of the process is also shown to be particularly dependent on the recombinant protein concentration. At a concentration level of 3-3.7 mg r-tPA/L in the reactivation mixture, up to a 90% yield of activity was obtained. Purification of the activated form of r-tPA was achieved with a two-step column-chromatography scheme. This included a gel filtration step on a Sephadex G-50 column followed by an affinity chromatography step on a lysine-sepharose column. The product was composed of roughly equal amounts of one-chain and two-chain t-PA. The feasibility of using a two water-soluble polymeric phase system, with a centrifugal partition chromatography (CPC), in scaling up the reactivation process or the purification step was also evaluated.

Chromatography, Affinity↗
PubMed1992

The precise radioimmunoassay of adenosine: minimization of sample collection artifacts and immunocrossreactivity.

Anti-adenosine antibodies were produced in rabbits immunized with N6-carboxymethyladenosine conjugated to methyl albumin. 125I-N6-Aminobenzyladenosine was synthesized and used as a high-specific-activity, high-affinity ligand. A radioimmunoassay (RIA) was developed that can detect 6.25 nM (312.5 fmol) of underivatized adenosine and cross-reacts less than 0.02% with adenine nucleotides and guanosine and not at all with 1 mM inosine. The sensitivity of the RIA can be increased to a detection limit of 0.125 nM (6.25 fmol) by derivitizing samples with benzyl bromide to form N6-benzyladenosine. The assay was adapted to an automated RIA procedure. Assay precision was increased by: (i) inhibiting slight adenosine deaminase activity present in anti-sera; (ii) treating buffers and albumin used in the RIA with charcoal to remove contaminating adenosine; and (iii) correcting for a small but variable component of immunoreactivity not attributable to adenosine. A second antibody prepared with a 2',3'-disuccinyladenosine-albumin conjugate was also found to detect some non-adenosine-mediated immunoreactivity in plasma samples. Immunointerference in human plasma was eliminated in samples treated with ZnSO4/Ba(OH)2 or partially purified over C18 Sep Paks to remove nucleotides and assayed after sample benzylation or succinylation. Human blood was mixed with a novel "stop" solution that was optimized to inhibit adenosine formation from AMP by greater than 99% and to inhibit adenosine uptake into red cells and degradation by greater than 94%. Human plasma/stop solution was assayed by RIA and HPLC with equivalent results.

Adenine↗
PubMed1992

The nonrandom regional distribution of uterine leiomyomas: a clue to histogenesis?

Although uterine leiomyomas are a major public health problem, very little is known about their etiology or histogenesis. To seek clues as to why the myometrium so frequently gives rise to these tumors, we attempted to determine if the regional distribution of leiomyomas was uniform. It appears that the proportion of leiomyomas in the premenopausal (0.8%) and postmenopausal (3.7%) cervix may be substantially less than the proportion of smooth muscle in the premenopausal (7.3%) and postmenopausal (17%) cervix. These data suggest that the smooth muscle cells of the corpus uteri may be at higher risk for neoplastic transformation than those of the cervix. Within the corpus there appeared to be a relative excess of fundic leiomyomas (premenopausal, 89%; postmenopausal, 86%) as compared with fundic smooth muscle (premenopausal, 79%; postmenopausal, 61%). No such excess was apparent in the isthmus or cornu. Immunohistochemical studies of estrogen and progesterone receptors in premenopausal and postmenopausal myometrium were uniformly positive, with no regional differences to suggest a hormonal basis for regional susceptibility to leiomyomas. It may be fruitful to search for precursor lesions and other factors predisposing to neoplastic development in fundic myometrium.

Female↗
PubMed1992

Polycystic ovaries as a relative protective factor for bone mineral loss in young women with amenorrhea.

OBJECTIVE: To examine the impact of polycystic ovaries (PCO) on bone mineral density in amenorrheic women of reproductive age. DESIGN: A retrospective analysis and comparison of polycystic ovarian syndrome (PCOS) with non-PCOS amenorrheic women. A subgroup of patients with ultrasound (US)-diagnosed PCO was also investigated. SETTING: Specialist clinic in reproductive endocrinology. PATIENTS, PARTICIPANTS: Six hundred ten consecutive cases, mean age of 29.8 +/- 7.5 years, with current history of amenorrhea of various causes. MAIN OUTCOME MEASURE: Bone mineral density in the lumbar spine (L1 to L4) as measured by dual energy x ray absorptiometry, in relation to PCOS, US-diagnosed PCO, and US findings of normal ovaries. RESULTS: Amenorrheic patients with PCOS were found to be younger (P less than 0.001), with higher body mass index (P less than 0.001), were more estrogenized, as measured by endometrial thickness and uterine cross-sectional area (P less than 0.001), and had higher bone mineral density (P less than 0.001) compared with non-PCOS amenorrheic patients. CONCLUSIONS: Patients with amenorrhea because of PCOS and those with US-diagnosed PCO have a higher bone density compared with amenorrheic patients with normal ovaries as detected by US scan.

Adult↗
PubMed1992

Polycystic ovaries in patients with hypogonadotropic hypogonadism: similarity of ovarian response to gonadotropin stimulation in patients with polycystic ovarian syndrome.

OBJECTIVE: To characterize the ovarian response in patients with isolated hypogonadotropic hypogonadism with ultrasound (US) findings of polycystic ovaries (PCO). DESIGN: Twenty-seven treatment cycles in patients with hypogonadotropic hypogonadism and US findings of normal ovaries were compared with 31 cycles in patients with hypogonadotropic hypogonadism and US-diagnosed PCO. Forty-one cycles in the hypogonadotropic hypogonadism and US-diagnosed PCO were compared with 59 cycles of patients with polycystic ovarian syndrome (PCOS) to examine pattern of response after ovulation induction. SETTING: Specialist Reproductive Endocrine Unit. PATIENTS, PARTICIPANTS: Twenty hypogonadotropic patients in whom 10 had US findings of PCO and 13 patients with PCOS. MAIN OUTCOME MEASURE: Serum estradiol (E2) concentration, number of leading follicles on US, cancellation, and pregnancy rate. RESULTS: Hypogonadotropic patients with US-diagnosed PCO had higher baseline ovarian volume (P less than 0.02) compared with patients with hypogonadotropic hypogonadism with normal ovaries. After ovarian stimulation, a higher mean serum E2 concentration (P less than 0.001), endometrial thickness (P less than 0.001), and increased number of leading follicles (P less than 0.0001) were found in hypogonadotropic patients with US-diagnosed PCO, compared with hypogonadotropic patients with US findings of normal ovaries. Patients with PCOS had a higher serum E2 concentration (P less than 0.008), although they were treated for fewer days (P less than 0.0001) and with fewer ampules of gonadotropin (P less than 0.001) compared with patients with hypogonadotropic hypogonadism with US-diagnosed PCO. CONCLUSIONS: We have characterized a group of hypogonadotropic patients with US findings of PCO, in which the ovarian response to ovulation induction was similar to patients with PCOS. The results have practical and theoretical implications for the etiology and treatment of patients with PCO.

Adult↗
PubMed1992

Pathophysiology of mesenteric ischemia.

Intestinal ischemia can result from a host of pathophysiologic disturbances and, in turn, may produce a variety of adverse local and systemic consequences. Mechanisms of ischemic injury and the central role of vasoconstriction are discussed.

Animals↗
PubMed1992

Expression of a single dopamine transporter cDNA can confer two cocaine binding sites.

Radiolabeled cocaine analogs can bind to low and high affinity sites on striatal dopamine transporters (DAT). Recently, a cDNA encoding a rat brain dopamine transporter pDAT1 has been cloned. COS cells transfected with the pDAT1 in a eukaryotic expression vector express both a high (KD = 3.4 nM) and low affinity (KD = 163.6 nM) cocaine binding sites, suggesting that both sites are provided by a single gene product.

Animals↗
PubMed1992

Endometriosis of the ureter.

Five patients with ureteric endometriosis are described. Extensive pre-operative investigation failed to reveal the aetiology of the unilateral upper urinary tract obstruction seen in all of these patients. Due to the dense fibrosis that invariably accompanies ureteric endometriosis, early surgical excision of the ureteric stricture permits effective resolution of upper tract dilatation and improved renal salvage.

Adult↗