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J S Davis

Publications and source records attributed to J S Davis.

At least 19 recordsLinked to original sources
PubMed1992

Greater importance of Ca(2+)-calmodulin in maintenance of ang II- and K(+)-mediated aldosterone secretion: lesser role of protein kinase C.

In this study we have investigated various components of the stimulus-secretion coupling process leading to aldosterone secretion from the calf adrenal glomerulosa cells as evoked by angiotensin II (AII) and potassium (K+). The roles of Ca2+, calmodulin and protein kinase C in the sustained phase rather than initiation of aldosterone secretion were of special interest. Our investigations revealed that the reduction of extracellular Ca2+ by EGTA or interruption of Ca2+ influx by nitrendipine at various time points after stimulation with either AII or K+ markedly compromised aldosterone secretion. Calmodulin inhibitors, calmidazolium and W-7 reduced aldosterone secretion profoundly. Agonists of protein kinase C, phorbol ester or diacylglycerol analogues failed to stimulate aldosterone secretion while the protein kinase C inhibitor, H-7, only partially inhibited aldosterone secretion at a concentration which completely inhibited protein kinase C activity. Calmodulin inhibitors produced significantly greater inhibition of aldosterone secretion than inhibitors of protein kinase C.

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

Modulation of luteinizing hormone-stimulated inositol phosphate accumulation by phorbol esters in bovine luteal cells.

The present studies were conducted to evaluate the effects of protein kinase C activators on the inositol phospholipid-phospholipase C second messenger system in isolated bovine luteal cells. This report describes the effects of phorbol esters on inositol phosphate accumulation in LH- and prostaglandin F2 alpha (PGF2 alpha)-stimulated bovine luteal cells. Corpora lutea of early pregnancy were dispersed with collagenase and luteal cells were prelabelled for 3 h with [3H]inositol. Inositol phosphates produced in response to LH or PGF2 alpha were analyzed by ion exchange column chromatography. The tumor promoter and protein kinase C activator 12-O-tetradecanolyphorbol 13-acetate (TPA) had no effect on basal levels of inositol phosphates but inhibited LH-stimulated accumulation of inositol mono-, bis-, and trisphosphates by 72%, 68%, and 65%, respectively. TPA reduced the response to maximally effective concentrations of LH and tripled the concentrations of LH required to evoke half-maximal accumulation of inositol mono-, bis-, trisphosphates. The inhibitory effects of TPA were rapid (5 min) whether added before or after treatment with LH. Treatment with TPA also reduced (58%) the initial phase of intracellular calcium mobilization in LH-treated cells. The inhibitory effects of TPA were not associated with acute reductions in [3H]inositol incorporation, [3H]inositol phospholipid levels, cAMP levels, or progesterone accumulation in control or LH-stimulated luteal cells. The effects of phorbol esters were concentration dependent and specific for active tumor promoters with 10-50 nM TPA producing maximal inhibitory effects. A synthetic diacylglycerol, 1-oleyl-2-acetylglycerol, mimicked the inhibitory effects of TPA. In contrast, pretreatment with a physiological activator of protein kinase C, PGF2 alpha, had no effect on LH-stimulated inositol phosphate accumulation. The inhibitory effects of TPA could not be explained by a generalized inhibition of phospholipase C or G-proteins since the accumulation of inositol phosphates in PGF2 alpha- and NaF-treated cells was not inhibited by TPA. These results demonstrate that tumor promoting phorbol esters modulate the inositol phospholipid-phospholipase C transmembrane signaling system in LH-stimulated bovine luteal cells. The results suggest that phorbol esters may alter the coupling of the LH-receptor complex to phospholipase C. These findings implicate protein kinase C in the regulation of transmembrane signaling in the bovine corpus luteum.

Animals↗
PubMed1991

Autoantibodies to human stress proteins. A survey of various rheumatic and other inflammatory diseases.

Unselected sera from patients with various rheumatic, inflammatory bowel, and autoimmune skin diseases (n = 268) were examined against human cell lysate by immunoblotting procedures, to determine the prevalence of autoantibodies to stress proteins (heat-shock proteins) hsp60 (homolog of Escherichia coli groEL and mycobacterial 65K antigens), hsp73, and hsp90. Using standard, sensitive and specific assay conditions, IgG and IgM autoantibodies to these stress proteins were not demonstrable, or were detected infrequently, in sera from control subjects (n = 36) and from patients with rheumatoid arthritis, Sjögren's syndrome, ankylosing spondylitis, Reiter's syndrome, systemic lupus erythematosus, and systemic sclerosis. Autoantibodies to hsp60 were relatively more common (greater than or equal to 20% of sera) in patients with mixed connective tissue disease, polymyositis/dermatomyositis, psoriatic arthritis, inflammatory bowel disease, epidermolysis bullosa acquisita, and bullous pemphigoid. Anti-hsp73 autoantibodies were detected in 20% or more of the sera from patients with Lyme disease and ulcerative colitis. Taken together, these data extend the spectrum of autoimmune and inflammatory diseases in which humoral anti-stress protein autoreactivity develops. However, the paucity of humoral autoreactivity to stress proteins in patients with systemic lupus erythematosus and rheumatoid arthritis argues against a direct role of anti-stress protein autoantibodies in the pathogenesis of these disorders.

Autoantibodies↗
PubMed1991

Prostaglandin F2 alpha stimulates inositol 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate formation in bovine luteal cells.

The present studies were conducted to further evaluate inositol phosphate formation and metabolism in prostaglandin F2 alpha (PGF2 alpha)-stimulated bovine luteal cells. Corpora lutea were dispersed with collagenase, and luteal cells were prelabeled for 3 h with [3H]inositol. Inositol phosphates produced in response to PGF2 alpha were analyzed by ion exchange column chromatography and HPLC. Time-course experiments revealed that significant increases in inositol trisphosphate (InsP3) were apparent within 5 sec of incubation with PGF2 alpha. Increases in inositol bisphosphate (InsP2) were also apparent within 5 sec. InsP1 and InsP4 were observed after a short (5-sec) lag period. HPLC revealed that PGF2 alpha provoked rapid (5 sec) increases in inositol 1,4,5-trisphosphate (Ins 1,4,5-P3), which was rapidly converted to inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5-P4) and inositol 1,3,4-trisphosphate (Ins 1,3,4-P3). The primary inositol bisphosphate isomer present in PGF2 alpha-stimulated bovine luteal cells was inositol 1,4-bisphosphate (Ins 1,4-P2), with lesser amounts of Ins 1,3-P2. Inositol monophosphates were also increased. These findings were confirmed in studies in which the metabolism of purified [3H]Ins 1,4,5-P3 was followed temporally in saponin-permeabilized bovine luteal cells. Additional studies demonstrated the presence of an enzyme, InsP3-3-kinase, in the cytosolic fraction of bovine corpora lutea. InsP3-3-kinase phosphorylated Ins 1,4,5-P3 to form Ins 1,3,4,5-P4. The activity of InsP3-3-kinase was calcium dependent and was enhanced by calmodulin at low calcium concentrations. Calmidazolium, a calmodulin inhibitor, reduced InsP3-3-kinase activity in a concentration-dependent manner. These results demonstrate the presence of multiple polyphosphorylated inositol phosphates in PGF2 alpha-stimulated bovine luteal cells. The isomers were formed via the action of a specific calcium/calmodulin-regulated kinase (InsP3-3-kinase), which phosphorylated Ins 1,4,5-P3 during agonist-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate. These data suggest that the inositol tris/tetrakisphosphate pathway is an important sequelae to PGF2 alpha-stimulated inositol phospholipid hydrolysis, and that the pathway may be activated during agonist-mediated calcium mobilization.

Animals↗
PubMed1991

A novel mechanism for the induction of aromatase in ovarian cells in vitro: role of transforming growth factor alpha-induced protein tyrosine kinase.

In the developing follicle, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are the primary stimulators of steroidogenesis in granulosa and theca cells. The steroidogenic actions of both these gonadotropins are largely if not exclusively mediated through cAMP. Previous studies have shown that EGF and TGF alpha do not affect basal estrogen production but attenuate FSH-stimulated estrogen production in vitro in rat granulosa cells. Here we present evidence that TGF alpha stimulates basal estrogen production in prepubertal porcine ovarian granulosa and theca cells in culture under defined conditions. In granulosa cells, TGF alpha is more potent than FSH in stimulating estrogen production. LH does not stimulate estrogen production in prepubertal porcine theca cells but rather attenuates that stimulated by TGF alpha. Treatment of follicular cells with genistein (inhibitor of protein tyrosine kinase) attenuates TGF alpha-induced estrogen biosynthesis suggesting that the action of TGF alpha is mediated through protein tyrosine kinase. These studies provide evidence for an alternative cAMP-independent and TGF alpha-induced tyrosine kinase-dependent mechanism for the induction of ovarian aromatase.

Animals↗
PubMed1991

Rheumatoid factor, cryoglobulinemia, anti-DNA, and renal disease in patients with systemic lupus erythematosus.

We retrospectively analyzed the relationship between rheumatoid factor (RF) and renal disease in 102 patients with systemic lupus erythematosus (SLE). We found a significant negative association between detectable RF at any time in a patient's course and clinically significant renal diseases. Multivariate analysis indicates that RF and cryoglobulins, operating independently, have a significant and opposite association with the development of renal disease in patients with SLE. These associations appear to be unrelated to the presence or absence of anti-ds-DNA (anti-DNA). Patients with SLE who are RF negative and cryoglobulin positive are likely to develop renal disease whereas those who are RF positive and cryoglobulin negative are very unlikely to do so. The addition of RF and cryoglobulin determinations to the data base of patients with SLE appears to be clinically useful.

Antibodies, Antinuclear↗
PubMed1990

Differential effects of calcium on progesterone production in small and large bovine luteal cells.

We studied the effects of calcium (Ca2+) ions in progesterone (P) production by separated small and large luteal cells. Corpora lutea were collected from 31 heifers between days 10 and 12 of the estrous cycle. Purified small and large cells were obtained by unit gravity sedimentation and flow cytometry. P accumulation in cells plus media was determined after incubating 1 x 10(5) small and 5 x 10(3) large cells for 2 and 4 h respectively. Removal of Ca2+ from the medium did not influence basal P production in the small cells (P greater than 0.05). However, stimulation of P by luteinizing hormone (LH), prostaglandin E2 (PGE2), 8-bromo-cyclic 3',5' adenosine monophosphate (8-Br-cAMP) and prostaglandin F2 alpha (PGF2 alpha) was impaired (P less than 0.05) by low Ca2+ concentrations. LH and PGE2-stimulated cAMP production was not altered by low extracellular Ca2+ concentrations, and PGF2 alpha had no effect on cAMP. In contrast, basal as well as LH and forskolin-stimulated P production were attenuated (P less than 0.05) in Ca2(+)-deficient medium in the large cells. However, P production stimulated by 8-Br-cAMP was not altered in Ca2(+)-deficient medium. Steroidogenesis in large cells was also dependent on intracellular Ca2+, since 8-N, N-diethylamineocytyl-3,4,5-trimethoxybenzoate (TMB-8), an inhibitor of intracellular Ca2+ release and/or action, suppressed (P less than 0.05) basal, LH and 8-Br-cAMP stimulated P. In contrast, basal P in small cells was not altered by TMB-8; whereas LH-stimulated P was reduced 2-fold (P less than 0.05). The calcium ionophore, A23187, inhibited LH-stimulated P in small cells and both basal and agonist-stimulated P in large cells. These studies show that basal P production in small cells does not require Ca2+ ions, while hormone-stimulated P production in small cells and both basal and hormone-stimulated P in large cells do require Ca2+. The inhibitory effect of Ca2+ ion removal was exerted prior to the generation of cAMP in the large cells, but distal to cAMP generation in hormone-stimulated small cells. The calmodulin/protein kinase C antagonist, W-7, also inhibited both basal and hormone-stimulated P production in both small and large luteal cells, indicating that P production in luteal cells also involves Ca2(+)-calmodulin/protein kinase C-dependent mechanisms.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

External calcium is required for activation of phospholipase C by angiotensin II in adrenal glomerulosa cells.

Previous studies have shown that external calcium (Ca2+) is required for the effects of angiotensin II (AII) on aldosterone secretion in adrenal glomerulosa zone. Using bovine adrenal glomerulosa cells prepared by collagenase dispersion, we examined whether external Ca2+ is required for the activation of phospholipase C by AII. Adrenal glomerulosa cells were exposed to Ca-EGTA buffered media to provide accurate estimates of external free Ca2+ concentrations. Phospholipase C activation was evaluated by measurement of inositol phosphates production. At 0.1 microM Ca2+ and less, sustained AII effects on inositol monophosphate (IP), inositol bisphosphate (IP2) and inositol trisphosphate (IP3) were markedly inhibited. Increasing the Ca2+ concentration to 50 microM or greater fully restored AII-induced inositol phosphates production. AII-induced increases in cytosolic Ca2+ measured by Quin-2 fluorescence, were diminished at lower external Ca2+ concentrations. Treating adrenal glomerulosa cells with Chelex-100, a strong Ca2+ binding resin, blocked early activation of phospholipase C by AII. Inhibition of IP3 production was also observed when inhibitors of Ca2+ movement across the plasma membrane were used, viz., La2+, TMB-8 and nifedipine. The requirement for Ca2+ during AII-induced activation of phospholipase C may be explained, at least partly by a requirement for Ca2+ at a site between the AII receptor and Phospholipase C.

Aldosterone↗
PubMed1990

Intracellular mediators of potassium-induced aldosterone secretion.

We have investigated the intracellular messengers of potassium in eliciting aldosterone secretion in calf adrenal glomerulosa cells since there were unresolved issues relating to the role of phosphoinositides, cAMP and protein kinases. We observed no evidence of hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) in 3H-inositol labeled alf adrenal cells or increase of cAMP in response to potassium. Addition of calcium channel blocker, nitrendipine after stimulating adrenal glomerulosa cells with potassium, markedly inhibited aldosterone secretion. A calmodulin inhibitor (W-7) produced greater reduction of aldosterone secretion than an inhibitor of protein kinase C (H-7). These results suggest that a rise in cytosolic free calcium concentration through voltage-dependent calcium channel and calmodulin are the critical determinants of aldosterone secretion stimulated by potassium.

Aldosterone↗
PubMed1990

Plasma DNA. A simple, rapid test for aiding the diagnosis of pulmonary embolism.

Previously, we reported that the sensitivity of plasma DNA for patients with pulmonary emboli was 83 to 88 percent. To confirm these findings in a more comprehensive study, we collected plasma samples from 137 consecutive patients undergoing 148 ventilation-perfusion lung scans for pulmonary embolism. DNA was measured using a counter-immunoelectrophoresis technique that used high titer precipitating double-stranded DNA antibody from a patient with systemic lupus erythematosus. In addition to 17 patients (17 lung scans) excluded for not having plasma collected, 32 patients (37 lung scans) were excluded for having either a condition other than pulmonary embolism that could be associated with plasma DNA or for having nonacute symptoms. Eighteen of 22 patients with a diagnosis of pulmonary embolism (defined by either a high probability lung scan or abnormal pulmonary angiogram) had detectable plasma DNA. Only four of 27 patients without pulmonary embolism (defined by either a normal lung scan or normal pulmonary angiogram) had plasma DNA detected. Based on these results, plasma DNA had a sensitivity of 82 percent and a specificity of 85 percent for this condition. Plasma DNA is a promising test for pulmonary embolism and could help physicians interpret equivocal lung scan findings and thereby clarify difficult decisions such as the need for pulmonary angiography.

Counterimmunoelectrophoresis↗
PubMed1989

Atrial natriuretic factor inhibits angiotensin-induced aldosterone secretion: not through cGMP or interference with phospholipase C.

ANF did not prevent the formation of [3H] inositol trisphosphate in response to AII but inhibited aldosterone secretion in calf adrenal glomerulosa cells. 8-bromo cGMP did not affect either inositol phosphate formation or aldosterone secretion. Changes in cytosolic Ca++ concentration induced by AII, as measured by Quin 2 fluorescence, were also unaffected by ANF. No difference in adrenal cell protein phosphorylation with AII or AII + ANF was observed. The results suggest that ANF may inhibit aldosterone secretion through a non-guanyl cyclase linked receptor system not involving the formation of phosphoinositide-derived second messengers. Interference with protein kinase C activity cannot be ruled out.

Aldosterone↗
PubMed1989

Proopiomelanocortin-derived peptides, phosphoinositides, cAMP, and aldosterone secretion.

Since the intracellular messengers of various proopiomelanocortin-derived peptides remain ambiguous at best, we have investigated the possible involvement of phosphoinositide metabolism in aldosterone secretion evoked by alpha-MSH, beta-LPH, as well as ACTH in rat and calf adrenal glomerulosa cells. We have also examined the cAMP responses in the adrenal glomerulosa cells to alpha-MSH comparing it with those of ACTH. Our results showed that neither alpha-MSH, beta-LPH, nor ACTH increased inositol triphosphate (IP3) or other inositol phosphates in adrenal glomerulosa cells while increasing aldosterone secretion from the same cells. Angiotensin II, known to cause hydrolysis of the phosphoinositides, increased IP3 in these adrenal cells in a dose-dependent manner. Both ACTH and alpha-MSH raised the cAMP levels in the calf adrenal glomerulosa cells, although the magnitude of the increase of cAMP in response to ACTH was greater. These findings suggest that IP3 as a mediator of alpha-MSH- and beta-LPH-induced aldosterone secretion is not likely and other mediator(s) may be involved.

Adrenocorticotropic Hormone↗
PubMed1989

Second messenger systems and progesterone secretion in the small cells of the bovine corpus luteum: effects of gonadotropins and prostaglandin F2a.

The present studies were conducted to determine the effects of gonadotropins (LH and hCG) and prostaglandin F2a (PGF2a) on the production of "second messengers" and progesterone synthesis in purified preparations of bovine small luteal cells. Corpora lutea were removed from heifers during the luteal phase of the normal estrous cycle. Small luteal cells were isolated by unit-gravity sedimentation and were 95-99% pure. LH provoked rapid and sustained increases in the levels of [3H]inositol mono-, bis-, and trisphosphates (IP, IP2, IP3, respectively), cAMP and progesterone in small luteal cells. LiCl (10 mM) enhanced inositol phosphate accumulation in response to LH but had no effect on LH-stimulated cAMP or progesterone accumulation. Time course studies revealed that LH-induced increases in IP3 and cAMP occurred simultaneously and preceded the increases in progesterone secretion. Similar dose-response relationships were observed for inositol phosphate and cAMP accumulation with maximal increases observed with 1-10 micrograms/ml of LH. Progesterone accumulation was maximal at 1-10 ng/ml of LH. LH (1 microgram/ml) and hCG (20 IU/ml) provoked similar increases in inositol phosphate, cAMP and progesterone accumulation in small luteal cells. 8-Bromo-cAMP (2.5 mM) and forskolin (1 microM) increased progesterone synthesis but did not increase inositol phosphate accumulation in 30 min incubations. PGF2a (1 microM) was more effective than LH (1 microgram/ml) at stimulating increases in inositol phosphate accumulation (4.4-fold vs 2.2-fold increase for PGF2a and LH, respectively). The combined effects of LH and PGF2a on accumulation of inositol phosphates were slightly greater than the effects of PGF2a alone. In 30 min incubations, PGF2a had no effect on cAMP accumulation and provoked small increases in progesterone secretion. Additionally, PGF2a treatment had no significant effect on LH-induced cAMP or progesterone accumulation in 30 min incubations of small luteal cells. These findings provide the first evidence that gonadotropins stimulate the cAMP and IP3-diacylglycerol transmembrane signalling systems in bovine small luteal cells. PGF2a stimulated phospholipase C activity in small cells but did not reduce LH-stimulated cAMP or progesterone accumulation. These results also demonstrate that induction of functional luteolysis in vitro requires more than the activation of the phospholipase C-IP3/calcium and -diacylglycerol/protein kinase C transmembrane signalling system.

Animals↗
PubMed1989

Effects of human chorionic gonadotropin, prostaglandin F2 alpha and protein kinase C activators on the cyclic AMP and inositol phosphate second messenger systems in cultured human granulosa-luteal cells.

The effects of human chorionic gonadotropin (hCG) and prostaglandin F2 alpha (PGF2 alpha) on the adenylate cyclase-cAMP and inositol phospholipid-phospholipase C-inositol trisphosphate and diacylglycerol transmembrane signalling systems were evaluated in cultured human granulosa-luteal cells. Granulosa-luteal cells obtained from patients undergoing in vitro fertilization were cultured for 72 h prior to addition of hormones. During the last 24 h of culture granulosa-luteal cells were incubated with [3H]inositol. Neither hCG nor gonadotropin-releasing hormone (GnRH) stimulated the inositol phospholipid-phospholipase C signalling system. PGF2 alpha stimulated increases in inositol mono-, bis-, and trisphosphate accumulation in 30 min incubations. NaF (20 mM) mimicked the stimulatory effect of PGF2 alpha on inositol phosphate accumulation suggesting the involvement of a guanine nucleotide regulatory protein in the activation of phospholipase C. In contrast, hCG but not PGF2 alpha or NaF stimulated cAMP accumulation in 30 min incubations. Simultaneous treatment with hCG and PGF2 alpha did not alter the stimulatory effect of PGF2 alpha on inositol phosphate accumulation but reduced (37%) the stimulatory effect of hCG on cAMP accumulation. The protein kinase C activator, 12-O-tetradecanoylphorbol 13-acetate (TPA) inhibited the stimulatory effects of hCG (76%) and PGF2 alpha (62%) on cAMP and inositol phosphate accumulation, respectively. Thus, cultures of human granulosa-luteal cells possess multiple transmembrane signalling systems which may be modulated by the activation of protein kinase C.

Chorionic Gonadotropin↗