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Biomedical subjects

J Patel

Publications and source records attributed to J Patel.

At least 181 records · Page 10Linked to original sources
PubMed1989

Interaction of antibodies with human glomerular epithelial cells.

We tested the hypothesis that the pathogenesis of human idiopathic membranous glomerulonephritis is similar to that of Heymann glomerulonephritis, a model of membranous glomerulonephritis induced in rats by immunization with renal brush border preparations; the characteristic subepithelial deposits result from interaction of antibodies with a brush border antigen (gp330) expressed on the plasma membrane of glomerular visceral epithelial cells (GEC), followed by redistribution and shedding of gp330 immune complexes. The experiments were performed in cultured glomerular visceral epithelial cells, in living monkeys and rats, and in isolated perfused human, monkey, and rat kidneys. Antigens from plasma membranes of human renal brush border vesicles (HBBV) and GEC vesicles (HGECV) and their corresponding polyclonal and monoclonal antibodies reactive with human and monkey GEC were prepared. First, polyclonal antibodies to HGECV bound diffusely to cultured GEC; monoclonal antibody 8G5, recognizing a 60-kDa protein, mainly bound to the coated pits and apical invaginations; both polyclonal HGECV and 8G5 monoclonal antibodies induced antigen redistribution (capping) at 37 degrees C. Second, monkeys were actively or passively immunized, and isolated human and monkey kidneys were perfused with the antibodies. Active immunization with HBBV induced tubular immune deposits, whereas active immunization with HGECV did not provoke renal lesions. After passive immunization HBBV and HGECV antibodies bound diffusely to glomerular cells, and subepithelial deposits were observed during the autologous phase; in contrast, 8G5 induced early (day 3) granular deposits. Third, fine granular deposits developed in glomeruli of human and monkey kidneys perfused for 4 hours at 37 degrees C with 8G5; these deposits were more difficult to detect by electron microscopy than those occurring in kidneys of Lewis rats perfused with sheep antiHBBV. The results show that some antibodies redistribute antigens at the surface of human and monkey GEC in vitro, in vivo, and ex vivo and induce formation of granular deposits in human glomerular capillary walls. Failure to induce more severe lesions in human and monkey kidneys may be ascribed to lack of GEC antigens comparable to rat gp330, insufficient cross linking by monoclonal antibody, lack or insufficient concentration of epitope-specific antibodies, insufficient time of kidney perfusion, or a combination of these factors.

Animals↗
PubMed1988

Use of a narcotic antagonist (nalmefene) to suppress self-mutilative behavior in a stallion.

Nalmefene, an opioid antagonist, caused a decrease in self-mutilative behavior in a 500-kg stallion. Self-mutilative attempts were counted during a control period and on 4 subsequent occasions after the IM administration of 100 mg, 200 mg, 400 mg, or 800 mg of nalmefene. The frequency of self-mutilation decreased with increasing doses of nalmefene and was virtually abolished with the 800-mg dose.

Animals↗
PubMed1988

Magnetic resonance imaging in an unusual presentation of herpes encephalitis.

We report a patient with herpes simplex virus encephalitis who presented with left hemiparesis and progressed to aphasia and generalized spasticity. Computerized axial brain tomography with and without infusion of contrast medium was normal, as were the cerebrospinal fluid findings. However, magnetic resonance imaging scan and brain biopsy, were diagnostic of herpes simplex encephalitis.

Child↗
PubMed1988

Phorbol esters induce multidrug resistance in human breast cancer cells.

Mechanisms responsible for broad-based resistance to antitumor drugs derived from natural products (multidrug resistance) are incompletely understood. Agents known to reverse the multidrug-resistant phenotype (verapamil and trifluoperazine) can also inhibit the activity of protein kinase C. When we assayed human breast cancer cell lines for protein kinase C activity, we found that enzyme activity was 7-fold higher in the multidrug-resistant cancer cells compared with the control, sensitive parent cells. Exposure of drug-sensitive cells to the phorbol ester phorbol 12,13-dibutyrate [P(BtO)2] led to an increase in protein kinase C activity and induced a drug-resistance phenotype, whereas exposure of drug-resistant cells to P(BtO)2 further increased drug resistance. In sensitive cells, this increased resistance was accompanied by a 3.5-fold increased phosphorylation of a 20-kDa particulate protein and a 35-40% decreased intracellular accumulation of doxorubicin and vincristine. P(BtO)2 induced resistance to agents involved in the multidrug-resistant phenotype (doxorubicin and vincristine) but did not affect sensitivity to an unrelated alkylating agent (melphalan). The increased resistance was partially or fully reversible by the calcium channel blocker verapamil and by the calmodulin-antagonist trifluoperazine. These data suggest that stimulation of protein kinase C plays a role in the drug-transport changes in multidrug-resistant cells. This may occur through modulation of an efflux pump by protein phosphorylation.

Antineoplastic Agents↗
PubMed1988

Identification, characterization, and functional correlation of calmodulin-dependent protein phosphatase in sperm.

Preliminary data demonstrated that the inhibition of reactivated sperm motility by calcium was correlated with inhibited protein phosphorylation. The inhibition of phosphorylation by Ca2+ was found to be catalyzed by the calmodulin-dependent protein phosphatase (calcineurin). Sperm from dog, pig, and sea urchin contain both the Ca2+-binding B subunit of the enzyme (Mr 15,000) and the calmodulin-binding A subunit with an Mr of 63,000. The sperm A subunit is slightly higher in Mr than reported for other tissues. Inhibition of endogenous calmodulin-dependent protein phosphatase activity with a monospecific antibody revealed the presence of 14 phosphoprotein substrates in sperm for this enzyme. The enzyme was localized to both the flagellum and the postacrosomal region of the sperm head. The flagellar phosphatase activity was quantitatively extracted with 0.6 M KCl from isolated flagella from dog, pig, and sea urchin sperm. All salt-extractable phosphatase activity was inhibited with antibodies against the authentic enzyme. Preincubation of sperm models with the purified phosphatase stimulated curvolinear velocity and lateral head amplitude (important components of hyperactivated swimming patterns) and inhibited beat cross frequency suggesting a role for this enzyme in axonemal function. Our results suggest that calmodulin-dependent protein phosphatase plays a major role in the calcium-dependent regulation of flagellar motility.

Animals↗
PubMed1987

Characterization of [3H]Ro 5-4864 binding to calmodulin using a rapid filtration technique.

The benzodiazepine [3H]Ro 5-4864 bound specifically and saturably to an apparently homogenous, univalent species of binding site on the calmodulin molecule with an associated equilibrium dissociation rate constant (Kd) of 644 +/- 121 nM. The rates of association (K1) and dissociation (K-1) governing this interaction were estimated to be 7.66 x 10(3) M-1 sec-1 and 2.9 x 10(-3) sec-1, respectively, yielding a non-equilibrium determination of the Kd to be 379 nM. Such binding of [3H]Ro 5-4864 was protein-, pH-, and temperature-dependent and demonstrated pharmacological selectivity. Only benzodiazepine compounds (chlordiazepoxide, diazepam and Ro 5-4864) inhibited [3H]Ro 5-4864 binding to calmodulin with inhibitory equilibrium dissociation constants (Ki) less than 10 microM. The benzodiazepine compounds Ro 15-1788 and flunitrazepam did not displace [3H]Ro 5-4864 binding to calmodulin nor did a number of pharmacologically active non-benzodiazepine compounds (Ki values greater than 10 microM). Consideration of the stoichiometry yielded an approximate mole ratio of 0.90:1.0 (Ro 5-4864: calmodulin), suggesting that there is one binding site for Ro 5-4864 per molecule of calmodulin. The data reveal that the binding of [3H]Ro 5-4864 to calmodulin fulfills the major criteria of a ligand binding to a receptor. Such an interaction may underlie some of the pharmacological actions of Ro 5-4864-like compounds.

Benzodiazepinones↗
PubMed1987

Purification and characterization of an Mr 87,000 protein kinase C substrate from rat brain.

We (Kligman, D., and Patel, J. (1986) J. Neurochem. 47, 298-303) and others have previously identified a major protein kinase C substrate of apparent molecular weight 87,000 (Mr 87,000). To gain insight into the function of this potentially important phosphoprotein, we have undertaken its purification and characterization from rat brain. We now report a purification scheme involving heat treatment, ammonium sulfate precipitation, anion ion-exchange and reversed-phase chromatography. This procedure gave a Mr 87,000 that was homogeneous (based on silver staining), 1,600-fold enriched relative to heat-treated material and at a yield of approximately 58 micrograms/kg wet weight. We also report the amino acid composition to be high in acidic residues and in alanine and show the protein to be phosphorylated on serine residues with a stoichiometry of 2 mol of phosphate/mol of substrate. The subcellular distribution indicates Mr 87,000 is present in two forms, membrane-bound and soluble. The membrane-bound Mr 87,000 represents 45% of the total phosphoprotein content and is enriched in microsomal and synaptic membranes. Ontogenic study has revealed this protein to be developmentally regulated, with the highest concentrations of Mr 87,000 found in prenatal animals. The availability of a purification procedure should greatly facilitate further structural characterization and elucidation of the function of Mr 87,000.

Amino Acids↗
PubMed1987

Synovial sarcomas. True carcinosarcomas?

The histogenesis of synovial sarcomas remains controversial. An origin from epithelium, synovium, or synovial-related cells and neural tissue has been advanced. Using a combination of a cytokeratin (epithelial marker) antibody and a vimentin (mesenchymal marker) antibody, this study suggests that a synovial sarcoma might be regarded as a carcinosarcoma. It also highlights the diagnostic utility of those antibodies in the diagnosis of synovial sarcomas.

Carcinosarcoma↗
PubMed1987

Concanavalin A prevents phorbol-mediated redistribution of protein kinase C and beta-adrenergic receptors in rat glioma C6 cells.

Exposure of rat glioma C6 cells to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) caused an activation of protein kinase C wherein the enzyme rapidly became membrane-bound (T 1/2 of 15 min). This translocation of protein kinase C from cytosol to membrane was followed by a sequestration of cell surface beta-adrenergic receptors and a loss of isoproterenol-stimulated adenylate cyclase activity. We had reported previously that prior exposure of rat glioma cells to concanavalin A prevents the TPA-mediated sequestration of receptors and desensitization of adenylate cyclase (Kassis et al., 1985). We now show that the concanavalin A treatment also prevents the translocation and activation of protein kinase C. These results are further evidence that in the TPA-treated cells, sequestration of beta-adrenergic receptors is mediated by membrane-bound protein kinase C.

Animals↗
PubMed1987

Down-regulation of protein kinase C in rat glioma C6 cells: effects on the beta-adrenergic receptor-coupled adenylate cyclase.

Continuous exposure of rat glioma C6 cells to 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in a time and dose dependent loss of [3H]phorbol dibutyrate binding sites and protein kinase C activity. Thus, by 24 h, the cells were essentially depleted of protein kinase C activity. In agreement with previous studies, TPA treatment caused a reduction in isoproterenol-stimulated adenylate cyclase activity and a sequestration of beta-adrenergic receptors. Cells were treated with TPA for 24-48 h to completely down-regulate protein kinase C and then exposed to isoproterenol. Agonist-mediated desensitization of adenylate cyclase and sequestration of beta-adrenergic receptors occurred at similar rates in control and TPA-treated cells. In addition, agonist-mediated down-regulation of beta-adrenergic receptors was not impaired by the absence of protein kinase C activity. Although both agonists and phorbol esters cause desensitization of the beta-adrenergic receptor-coupled adenylate cyclase, agonist-mediated events can occur independently of protein kinase C.

Adenylyl Cyclases↗
PubMed1987

Chronic lithium treatment increases the phosphorylation of a 64-kDa protein in rat brains.

Despite the wide clinical use of lithium in the treatment of manic depressive illness there is no adequate explanation for its mechanism of action. In the light of lithium's suggestive effects on the second messenger system in the brain, we studied the effects of chronic dietary lithium treatment (achieving blood levels in the therapeutic range) on protein phosphorylation in different areas of rat brain. An increase in the phosphorylation of a 64-kDa membrane-associated protein was evident in the lithium-treated rats compared to controls. This increase was observed only under basal phosphorylating conditions and was abolished when the phosphorylation was performed in the presence of Ca2+ or Ca2+ and calmodulin. The possibility that this 64-kDa protein affected by lithium is the beta-subunit of the calmodulin-dependent protein kinase or a different protein which co-migrates with it is discussed.

Animals↗
PubMed1987

Desmin: its value as a marker of muscle derived tumours using a commercial antibody.

This study examined the staining reactions of a commercially available anti desmin antibody in 192 soft tissue sarcomas, 30 carcinomas and 22 malignant melanomas. Only 63% of rhabdomyosarcomas and 50% of leiomyosarcomas showed a positive reaction. Three non muscle sarcomas also reacted with the antibody. No positivity was seen amongst the carcinomas or the melanomas. These results do not compare favourably with the documented results of non commercial desmin antibodies in the literature. The most likely cause of the discrepancy in the varying results is the differing source of the antibody.

Adolescent↗
PubMed1987

Interactions between calcium channel compounds and adenosine systems in brain of rat.

A number of organic ligands of calcium channels were investigated for possible actions on several aspects of adenosine systems in the cerebral cortex of rat. The principle findings of the present study were that a number of antagonists of calcium channels and the agonist compound Bay K 8644 inhibited binding to adenosine receptors, binding to nucleoside transporters, and the accumulation of [3H]adenosine with a low microM potency. 2-Nitrophenyl dihydropyridine derivatives were more potent than 3-nitrophenyl dihydropyridine or non-dihydropyridine ligands of calcium channels at inhibiting binding to adenosine receptors. Dihydropyridine ligands of calcium channels were more potent than non-dihydropyridine ligands of calcium channel in inhibiting the binding of [3H]nitrobenzylthioinosine to cortical membranes or inhibiting the accumulation of [3H]adenosine into synaptoneurosomes. However, unlike the case of adenosine receptors, no distinction between 2-nitrophenyl and 3-nitrophenyl dihydropyridine derivatives was observed. In addition, the non-dihydropyridine ligand of calcium channels, diltiazem was a weak inhibitor of the accumulation of [3H]adenosine. These results demonstrate that organic ligands of calcium channels, particularly dihydropyridine compounds, can interact with several aspects of adenosine systems.

Adenosine↗
PubMed1987

Activation of distinct second messenger systems in anterior pituitary corticotrophic tumor cells alters the phosphorylation states of both shared and distinct cytosolic proteins.

The purpose of the present study was to investigate the effects of activation of different second messenger systems on protein phosphorylation in pituitary corticotrophic tumor cells (AtT-20/D16-16). Using two-dimensional gel analysis of cytosolic extracts from AtT-20 cells, several phosphoproteins exhibited alterations in 32P incorporation in response to stimulation of the cells with either forskolin--an activator of adenylate cyclase--or 12-O-tetradecanoyl phorbol-13-acetate (TPA)--a tumor promoting phorbol ester linked to protein kinase C activation. Alterations in phosphorylation levels were seen for phosphoproteins of the following apparent molecular weights and pIs: 87 kDa (pI 4.4-4.6), 67 kDa (pI 4.7-4.9), 43 kDa (pI 4.8-5.0), 39 kDa (pI 4.9-5.1), 33 kDa (pI 4.8-5.0), 19.5 kDa (pI 5.7-5.9), 19 kDa (pI 5.8-6.0), 16 kDa (pI 5.2-5.4) and 14 kDa (pI 5.1-5.3). For individual phosphoproteins, 32P incorporation varied over time and was also modulated by concentrations of Ca2+ and Mg2+ in the incubation medium. Treatment of the cells with forskolin led to statistically significant changes in the phosphorylation states of the 19.5 and 14 kDa proteins. Treatment of the cells with TPA also produced statistically significant changes in the 19.5 and 14 kDa proteins but, in addition, the 87 kDa, the 39 kDa and the 16 kDa phosphoproteins also exhibited significant changes. Alterations in the phosphorylation states of the 19.5 and the 14 kDa proteins were significantly correlated with alterations in beta-endorphin release from the cells. The primary finding of the present study was that activation of distinct second messenger systems can lead to alterations in the phosphorylation states of both shared and distinct phosphoproteins.

Adenylyl Cyclases↗
PubMed1987

Measurement of serum glycosylated proteins and glycosylated low density lipoprotein fraction in diabetes mellitus.

A simple method was developed for estimating serum glycosylated protein levels using gel filtration with Bio-Gel P6 by determining the protein and sugar content in the void volume fraction. The glycosylated protein levels (GSP) correlated well with fasting blood sugar levels and glycosylated albumin level (G-ALB) determined by affinity chromatography with Blue Sepharose CL6B. The glycosylation level of heparin-citrate precipitable fraction of serum which predominantly contained low density lipoprotein (G-LDL) also correlated well with GSP and LDL-cholesterol levels. Significantly different values were obtained for GSP, G-ALB, and G-LDL between normals and diabetics.

Adult↗