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Biomedical subjects

J Ginsberg

Publications and source records attributed to J Ginsberg.

At least 55 records · Page 3Linked to original sources
PubMed1993

Downregulation of protein kinase C levels leads to inhibition of GnRH-stimulated gonadotropin secretion from dispersed pituitary cells of goldfish.

We have previously shown that the abilities of the two native goldfish GnRHs, salmon GnRH (sGnRH) and chicken GnRH II (cGnRH II), to stimulate gonadotropin (GtH) secretion and elevate intracellular Ca2+ levels are mimicked by the protein kinase C (PKC) stimulators, 1,2-dioctanoylglycerol (DiC8) and 12-O-tetradecanoyl phorbol-13-acetate (TPA). The ability of PKC inhibitors to attenuate GnRH-stimulated GtH secretion was also demonstrated. In the present study, the involvement of PKC was examined through the reduction of cellular PKC levels by prolonged preincubation of the cells with TPA (TPA desensitization). TPA pretreatment reduced the levels of PKC in fish pituitary cells as measured by immunoblotting (Western blot). Pretreatment of dispersed goldfish pituitary cells in static culture with TPA abolished the GtH responses to sGnRH, cGnRH II and ionomycin, and drastically reduced TPA- and DiC8-stimulated GtH release, but had no major effect on forskolin-induced GtH release. TPA pretreatment also reduces the cell content of GtH in goldfish pituitary cells. Interestingly, treatment with all of the pharmacological secretagogues tested led to a decrease in cellular contents of GtH, however, the two native GnRHs had no such effect. In rapid column perifusion experiments (1-min fractions), the GtH responses induced by both native GnRHs were characterized by an initial acute increase in hormone secretion followed by a 'plateau' phase which is smaller in magnitude relative to the initial phase. TPA pretreatment of perifused cells greatly reduced both the peak and plateau phases of sGnRH- and cGnRHII-stimulated GtH secretion;TPA-induced GtH release is also greatly attenuated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Enhancement of thyrotropin-stimulated iodide organification in porcine thyroid cells after protein kinase-C inhibition.

We and others have previously shown that 12-O-tetracanoylphorbol-13-acetate (TPA), a protein kinase-C (PKC) activator, inhibits TSH-stimulated iodide organification in porcine thyroid cells. However, TPA action may be independent of PKC. To further explore the role of PKC in the regulation of differentiated thyroid function, we studied the effects of the PKC inhibitors 1-O-hexadecyl-2-O-methylglycerol (AMG-C16), 1-(5-isoquinolinesulfonyl)2-methylpiperazine (H7), and staurosporine on TSH-stimulated iodide organification in porcine thyroid cells in the presence and absence of TPA. AMG-C16 increased basal iodide organification in concentrations ranging from 15-240 microM (P < 0.01, by analysis of variance). Such stimulation by AMG-C16 (30-120 microM) persisted in the presence of submaximal (10 microU) and maximal (1 mU) concentrations of TSH. However, in the presence of TPA (> 10 nM), the effects of AMG-C16 were abolished. H7 (50 microM) and staurosporine (100 nM) also enhanced TSH-stimulated iodide organification. In the presence of staurosporine and TPA, no inhibition of TSH-stimulated iodide organification was observed. However, H7 could not reverse the effects of TPA. In summary, these studies indicate that in porcine thyroid cells, three distinct PKC inhibitors all enhanced TSH-stimulated iodide organification and that staurosporine reversed the effects of TPA on TSH-stimulated iodide organification. These findings are consistent with the concept that PKC acts as an endogenous negative modulator of iodide organification in vitro.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Human leukocyte antigen-DRB1*1104 in the chronic iridocyclitis of pauciarticular juvenile rheumatoid arthritis.

To determine whether genetic markers for chronic iridocyclitis could be identified, we used both serologic and oligonucleotide dot blot techniques to characterize immunogenetically 164 children with early-onset pauciarticular juvenile rheumatoid arthritis. Seventy-eight children (47.6%) had chronic iridocyclitis and 86 (52.4%) had not had evidence of eye disease during a mean follow-up period after the onset of arthritis of 15.8 years (minimum of 5.5 years). Control subjects were 218 healthy, unrelated individuals. The analysis was limited to alleles known to be associated with an increased or decreased risk of early-onset pauciarticular juvenile rheumatoid arthritis or of chronic iridocyclitis in this form of juvenile rheumatoid arthritis. Only one split of human leukocyte antigen (HLA)-DR5, HLA-DRB1* 1104, showed a statistically significant association with a risk of chronic iridocyclitis (chi-square value = 7.52; p = 0.036 adjusted; odds ratio 3.45); HLA-DQA1* 0501 and HLA-DQB1* 0301, both in linkage disequilibrium with HLA-DRB1* 1104, also were significantly associated with eye disease. Patients with both the DRB1* 1104 and DPB1* 0201 genes had a 7.7-fold increased risk for chronic iridocyclitis compared with that for other patients. The presence of HLA-DRB1* 1104 was about four times as specific, but only about one third as sensitive, as antinuclear antibodies in identifying patients at risk for eye disease. Although all children with early-onset pauciarticular juvenile rheumatoid arthritis should undergo periodic slit-lamp examinations, those with the HLA class II gene DRB1* 1104 are at particularly high risk for eye disease, and we recommend that they be monitored carefully for its evolution.

Adult↗
PubMed1992

Protein kinase C as a mediator of TSH and thyroid autoantibody action.

Although it is well-established that TSH activates a cAMP-dependent pathway in the thyroid follicular cell leading to thyroid hormone synthesis and release, the present review provides new evidence that TSH also activates a non-cAMP-dependent signal transduction system. This cascade involves phosphoinositide (PI) turnover, diacylglycerol accumulation and protein kinase C (PKC) activation. Activation of this pathway leads to an inhibition of differentiated thyroid function in vitro. Recent evidence suggests that TSH can activate both pathways via a single transcription unit. Unlike TSH, TSH-receptor antibodies may selectively activate cAMP with no effects on PI turnover. In contrast, preliminary studies suggest TSH-blocking antibodies may activate PKC. PKC may be an important mediator of TSH and, possibly, thyroid autoantibody action.

Autoantibodies↗
PubMed1992

The iridocyclitis of early onset pauciarticular juvenile rheumatoid arthritis: outcome in immunogenetically characterized patients.

In a cohort of 72 patients with iridocyclitis (iritis) and early onset pauciarticular juvenile rheumatoid arthritis (EOPA-JRA) the course of the eye disease was matched with ocular outcome. Chronicity of inflammation (greater than 6 months/episode) was correlated with complications of eye disease that caused impairment of vision. HLA antigens in these patients were compared with the HLA antigens in a cohort of 77 patients with EOPA-JRA in whom iridocyclitis had failed to develop over a followup of 5 years or longer. HLA-DR5 (11) was correlated with the presence of eye disease, and HLA-DR1 with its absence; HLA-DRw8, which strongly predisposes to EOPA-JRA, was neutral with respect to eye disease.

Arthritis, Juvenile↗
PubMed1991

Painless thyrotoxic thyroiditis in association with ovarian and adrenal failure.

Polyglandular autoimmune syndrome (PGAS) type II is a disorder characterized by Addison's disease, autoimmune thyroid disease, and diabetes mellitus. In this report, a 19-year-old woman having Addison's disease, ovarian failure, painless thyroiditis, and an HLA type characteristic of PGAS II is described. Painless thyroiditis has been considered recently to have an autoimmune basis and has been reported previously in another patient with Addison's disease. The otherwise characteristic features of the patient in this case allow her to be classified as having PGAS II, thereby expanding the scope of reported autoimmune thyroid disorders in PGAS II.

Adrenal Gland Diseases↗
PubMed1991

Phorbol ester and phospholipase C-mediated differentiated thyroid function in vitro: the effects of protein kinase C inhibition and downregulation.

Tumor-promoting phorbol esters, e.g., 12-O-tetradecanoylphorbol 13-acetate (TPA), inhibit TSH-stimulated iodide organification in vitro implying a role for protein kinase C (PKC) in the regulation of differentiated thyroid function. To further explore the PKC dependence of this action of TPA, we studied the effects of PKC inhibition and downregulation on phorbol-mediated differentiated thyroid function in vitro. In addition, the effects of the nonphorbol PKC activator, phospholipase C (PLC) were studied. TPA (100 nM) inhibited TSH-stimulated iodide organification in cultured porcine thyroid cells by over 95% and caused PKC translocation in vitro. Exogenous PLC (1 U/mL) could mimic these effects of TPA. The PKC inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) inhibited TSH-stimulated iodide organification at concentrations exceeding 10 microM. However, partial recovery of phorbol- and PLC-inhibited iodide organification was seen in the presence of identical concentrations of H7. H7 had no effect on PKC translocation in porcine thyroid cell extracts. After 24 h of TPA treatment to induce PKC downregulation, no recovery of TSH-stimulated iodide organification was observed, suggesting that the effects of TPA were irreversible. These studies indicate that the effects of TPA and PLC on differentiated thyroid function are mediated, at least in part, by PKC. These findings provide further evidence for a role for PKC in the regulation of differentiated thyroid function.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Soluble fibrin degradation products potentiate tissue plasminogen activator-induced fibrinogen proteolysis.

Despite its affinity for fibrin, tissue plasminogen activator (t-PA) administration causes systemic fibrinogenolysis. To investigate the mechanism, t-PA was incubated with plasma in the presence or absence of a fibrin clot, and the extent of fibrinogenolysis was determined by measuring B beta 1-42. In the presence of fibrin, there is a 21-fold increase in B beta 1-42 levels. The potentiation of fibrinogenolysis in the presence of fibrin is mediated by soluble fibrin degradation products because (a) the extent of t-PA induced fibrinogenolysis and clot lysis are directly related, (b) once clot lysis has been initiated, fibrinogenolysis continues even after the clot is removed, and (c) lysates of cross-linked fibrin clots potentiate t-PA-mediated fibrinogenolysis. Fibrin degradation products stimulate fibrinogenolysis by binding t-PA and plasminogen because approximately 70% of the labeled material in the clot lysates binds to both t-PA- and plasminogen-Sepharose, and only the bound fractions have potentiating activity. The binding site for t-PA and plasminogen is on the E domain because characterization of the potentiating fragments using gel filtration followed by PAGE and immunoblotting indicates that the major species is (DD)E complex, whereas minor components include high-molecular weight derivatives containing the (DD)E complex and fragment E. In contrast, D-dimer is the predominant species found in the fractions that do not bind to the adsorbants, and it has no potentiating activity. Thus, soluble products of t-PA-induced lysis of cross-linked fibrin potentiate t-PA-mediated fibrinogenolysis by providing a surface for t-PA and plasminogen binding thereby promoting plasmin generation. The occurrence of this phenomenon after therapeutic thrombolysis may explain the limited clot selectivity of t-PA.

Enzyme Activation↗
PubMed1991

Longitudinal analysis of HLA associated risks for iridocyclitis in juvenile rheumatoid arthritis.

The risk of iridocyclitis in children with early onset pauciarticular juvenile rheumatoid arthritis (EOPA-JRA) has been shown to be associated with certain HLA haplotypes. Our report contains an actuarial analysis, using one-year intervals, of 161 subjects and estimates haplotype specific risks. Individuals who possess the major susceptibility haplotype HLA-DR5 (11) developed eye disease earlier and with a greater frequency than did those with the protective HLA-DR1 haplotype. Highly significant differences were found between the resulting life-table curves for HLA-DR5 and HLA-DR1 positive subjects (p = 0.00003). These time oriented risk estimates may aid clinicians in determining more precisely the probability of iridocyclitis throughout the course of the disease in children with EOPA-JRA.

Adolescent↗
PubMed1990

Androgen receptor defects in patients with minimal and partial androgen resistance classified according to a model of androgen-receptor complex energy states.

We have characterized intracellularly the androgen-receptor (A-R) complexes formed by genital skin fibroblasts from 2 unrelated males with qualitative defects of the androgen receptor: one has a small nonhypospadic penis as part of a syndrome of mild androgen resistance; the other was born with ambiguous external genitalia. The dissociation rate constants of testosterone, methyltrienolone (MT), dihydrotestosterone (DHT) and mibolerone (MB) from normal androgen receptors were determined at various temperatures: when plotted by the method of Arrhenius, they yielded a linear hierarchy of dissociation states with energies of state IV greater than III greater than II greater than I, respectively. Relative to this hierarchy, patient A-R complexes were displaced to higher, androgen-inappropriate energies in a mutant-distinctive pattern. MB- or MT-R complexes of both patients were thermolabile; however, both up-regulated normally in response to prolonged incubation with either hormone. Apparent equilibrium affinity constants (Kd) of the DHT- and MB-R complexes formed by both patients were normal; however, the binding capacity (Bmax) for MB in 1 case was subnormal. The distinctive biochemical phenotypes of A-R complexes in these 2 patients with androgen resistance will facilitate the definition of structure-function relations in the androgen receptor, a classical DNA-binding, transcription-regulating protein.

Adolescent↗
PubMed1988

Translocation of protein kinase C in porcine thyroid cells following exposure to thyrotropin.

We have previously shown that protein kinase C activators modulate differentiated thyroid function in vitro; however, how protein kinase C may be activated physiologically is unknown. The present studies were undertaken in order to determine whether TSH could activate protein kinase C in vitro. Following exposure of porcine thyroid cells to TSH, translocation of protein kinase C from the cytosol to its membrane-bound form was observed. Maximal translocation occurred at the lowest TSH concentration able to trigger this response (10 mU/ml) but persisted at higher concentrations (20-100 mU/ml). Time-course studies revealed that translocation of protein kinase C was seen only after 40 min. TSH could also produce a similar translocation in human neutrophils (known to have TSH receptors). In thyroid cells pre-treated with TSH, modulation of phorbol-mediated protein kinase C translocation was noted. These results indicate that TSH causes the translocation of protein kinase C in porcine thyroid cells (and possibly other TSH receptor-containing cells) and therefore may regulate the action of protein kinase C on differentiated thyroid function.

Animals↗
PubMed1988

Human tissue-type plasminogen activator releases fibrinopeptides A and B from fibrinogen.

In five patients with venous thromboembolic disease treated with recombinant tissue-type plasminogen activator (rt-PA), there was a marked increase in the mean concentrations of fibrinopeptide A (from 0.6 to 5.9 nM; P less than 0.0001) and desarginine fibrinopeptide B (from 5.6 nM to 24.1 nM; P less than 0.01) 30 min after a bolus of rt-PA (0.6 mg/kg). Thrombin was unlikely to be responsible because the levels of desarginine fibrinopeptide B exceeded those of fibrinopeptide A and the changes occurred despite concomitant heparin therapy. The purpose of this study therefore, was to determine whether rt-PA directly releases the fibrinopeptides from fibrinogen. Incubation of rt-PA with heparinized plasma or purified fibrinogen resulted in time and dose-dependent release of both fibrinopeptide A and B. Contaminating thrombin was not responsible for this activity by the following criteria: the rate of rt-PA mediated fibrinopeptide B release was considerably faster than that of fibrinopeptide A, and fibrinopeptide release was unaffected by heparin, hirudin, or a monospecific antithrombin IgG. Aprotinin also had no effect on fibrinopeptide release, indicating that this activity was not plasmin mediated. Fibrinopeptide release was shown to be due to rt-PA because this activity was completely blocked by a monoclonal antibody against the enzyme. Further, the specificity of rt-PA for the thrombin cleavage sites on fibrinogen was confirmed by the demonstration that rt-PA released fibrinopeptide A or fibrinopeptide B from fibrinopeptide A or B-containing substrates, respectively. These studies thus demonstrate that (a) rt-PA releases fibrinopeptides A and B from fibrinogen thereby indicating that this enzyme is not specific for plasminogen, and (b) plasma fibrinopeptide A and desarginine fibrinopeptide B levels are not specific markers of thrombin action on fibrinogen in patients receiving rt-PA.

Chromatography, High Pressure Liquid↗