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Biomedical subjects

K P Ray

Publications and source records attributed to K P Ray.

At least 37 records · Page 2Linked to original sources
PubMed1988

A local network for sharing resources and technical support: BACS/PHILNET.

Within the framework of large regional and national networks, local libraries can benefit by working together. We report the establishment of an online health sciences library network to share resources and technical support in the greater St. Louis area. BACS/PHILNET has evolved beyond a local automated interlibrary loan network to pilot off-site integrated library and information management systems in hospitals.

Computer Communication Networks↗
PubMed1987

Monoclonal antibodies to bovine growth hormone potentiate effects of the hormone on somatomedin C levels and growth of hypophysectomized rats.

Bovine growth hormone (50 micrograms/day) elevated somatomedin C levels in plasma of hypophysectomized rats: the effect was seen 12 h after the first injection and was sustained throughout a 7-day treatment period. When monoclonal antibodies to bovine growth hormone were administered with the hormone the stimulation of somatomedin C levels was markedly enhanced, as were effects on body weight. Each one of a panel of 7 monoclonal antibodies potentiated the actions of the hormone on growth and somatomedin C levels, though the extent and pattern of potentiation varied considerably from one antibody to another. Effects on growth and somatomedin C levels correlated fairly well, though there were some discrepancies.

Animals↗
PubMed1987

Purification of ovine somatotrophs using a combination of density gradient centrifugation and short-term culture.

Freshly dispersed or cultured (18 h) ovine anterior pituitary cells were fractionated on 55% sigmoidal Percoll gradients. This resulted in the separation of two sub-populations of cells at densities of 1.075 g/ml (peak I) and 1.055 g/ml (peak II). Radioimmunoassay of fractions from a gradient on which cells were separated before culture showed the profiles of GH and prolactin to be virtually superimposable. After culture, however, the lactotroph population exhibited an apparent shift in its density profile, the lighter population increasing at the expense of the denser one. Immunocytochemistry of the cells remaining in the denser peak (peak I) showed that it consisted of about 65% somatotrophs which was approximately a three-fold enrichment over the proportion of somatotrophs present in the original cell preparation (24%). Refractionation studies indicated that the change in the density profile of the lactotrophs was due to an actual reduction in their density rather than a loss of viability of the denser sub-population. Secretion data showed the purified somatotrophs to be more responsive than the crude cell preparation to the regulatory factors, GH-releasing hormone and somatostatin. This enriched cell population should prove useful in the detailed study of GH secretion.

Animals↗
PubMed1986

Use of quin 2 to measure calcium concentrations in ovine anterior pituitary cells and the effects of quin 2 on secretion of growth hormone and prolactin.

Intracellular free Ca2+ concentrations [Ca2+]i were measured in ovine anterior pituitary cells using the quin 2 technique. Thyrotropin-releasing hormone (TRH) increased, dopamine decreased and growth hormone-releasing hormone (GHRH) had no detectable effect on [Ca2+]i. Loading the cells with quin 2, at an intracellular concentration less than that used during calcium determination, reduced both basal growth hormone (GH) and (to a small extent) prolactin secretion. Loading cells with quin 2 also markedly reduced GHRH-stimulated GH secretion. However, TRH-stimulated prolactin secretion was 3-times basal irrespective of quin 2 loading. The results indicate that the use of quin 2 to measure [Ca2+]i in some cell types may be complicated by actions of quin 2 on cellular function.

Aminoquinolines↗
PubMed1986

Effects of dopamine and somatostatin on phorbol ester-stimulated prolactin and growth hormone secretion.

Incubation of cultured ovine pituitary cells with the tumor-promoting phorbol ester, 12-O-tetradecanoylphorbol 13-acetate (TPA) (0.1-100 nM), caused a dose-related stimulation of both growth hormone (ED50 approximately 4 nM) and prolactin (ED50 approximately 14 nM) secretion. Stimulation by TPA (100 nM) produced a substantial 10-fold increase in growth hormone with a smaller, 2-fold rise in prolactin secretion over 30 min; significant effects on the release of both hormones occurred within 2 min. Treatment with TPA also produced a small, time- and concentration-dependent rise in cellular cyclic AMP content which reached, at maximum, a level 20-30% over basal values. Non-tumor-promoting phorbol esters did not stimulate the secretion of either growth hormone or prolactin. In the presence of TPA (10 nM), dopamine (1-1000 nM) suppressed prolactin secretion to a level close to that observed for maximal inhibition of unstimulated cells. At high concentrations (0.1-1.0 microM) dopamine also partially attenuated (by 43%) the TPA-induced stimulation of growth hormone secretion. Somatostatin (0.01-1.0 microM) completely inhibited the substantial (approximately 9-fold) TPA-induced stimulation of growth hormone secretion (inhibitory ED50 approximately 47 nM), and also suppressed TPA-stimulated prolactin secretion to the control level. Our results suggest that activation of protein kinase-C may be involved in the stimulatory regulation of both growth hormone and prolactin secretion in sheep pituitary cells. Failure of TPA to attenuate the inhibitory activity of dopamine and somatostatin suggests that inhibitory regulation occurs at, or beyond, the point in the secretory process regulated by protein kinase-C.

Animals↗
PubMed1986

Dopamine and somatostatin inhibit forskolin-stimulated prolactin and growth hormone secretion but not stimulated cyclic AMP levels in sheep anterior pituitary cell cultures.

Forskolin, an activator of adenylate cyclase, has been used to investigate the effects of raising pituitary cell cyclic AMP concentrations on prolactin and growth hormone secretion and to examine the role of cyclic AMP in the inhibitory actions of dopamine and somatostatin. Incubation of cultured ovine pituitary cells with forskolin (0.1-10 microM; 30 min) produced a modest dose-related increase in prolactin release (120-140% of basal) but a much greater stimulation of growth hormone secretion (170-420% of basal). Cellular cyclic AMP concentrations were only increased in the presence of 1 and 10 microM forskolin (2-5.5 times basal). A study of the time course for forskolin (10 microM) action showed that stimulation of prolactin (1.5-fold) and growth hormone (4.7-fold) secretion occurred over 15 min; subsequently (15-60 min) the rate of prolactin secretion from forskolin-treated cells was equivalent to that measured in controls, while growth hormone release remained elevated. Cellular cyclic AMP concentrations were also rapidly stimulated by forskolin (10 microM); they reached a maximum (12 times control) within 15 min, and then declined (15-60 min) but remained elevated relative to those in untreated cells (4.9 times control at 60 min). Dopamine (0.1 microM) inhibited basal secretion of both prolactin and growth hormone. In the presence of forskolin (0.1-10 microM), dopamine (0.1 microM) inhibited prolactin secretion to below the basal level and considerably attenuated the stimulation of growth hormone secretion. Similarly, somatostatin suppressed both basal and forskolin-induced prolactin and growth hormone secretion. However, neither dopamine nor somatostatin significantly decreased the stimulatory effect of forskolin on cellular cyclic AMP accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Somatomedin C/insulin-like growth factor I: simplified purification procedure and biological activities of the purified growth factor.

Human somatomedin C has been purified from Cohn fraction IV paste by a simplified procedure using chromatofocusing, hydroxylapatite chromatography and reverse-phase high performance chromatography. The purified material has a specific activity by somatomedin C radioimmunoassay of 9160 units/mg (1 unit is defined as the amount of somatomedin present in 1 ml normal adult male human serum), representing a 650,000-fold purification, and possesses sulphation, mitogenic and insulin-like activities (specific activities of 3388 units/mg, 832 units insulin equivalents/mg and 1122 units/mg respectively). Somatomedin C is shown to be a potent stimulator of DNA synthesis (50% maximum stimulation at 150 fmol/ml) in isolated chondrocytes derived from costal cartilage, a major physiological target tissue.

Amino Acids↗
PubMed1985

Effects of growth hormone-releasing factor and somatostatin on growth hormone secretion and cellular cyclic AMP levels. Cultured ovine and rat anterior pituitary cells show markedly different responses.

Human pancreatic growth hormone-releasing factor (GRF-44-NH2) stimulated growth hormone (GH) secretion and intracellular cyclic AMP levels in cultured pituitary cells from both sheep and rat. Somatostatin (SRIF), over a wide range of doses and time, showed no significant effect on the elevated cyclic AMP levels in sheep cells, but did block the GH release in a dose-dependent manner. In rat cells, however, SRIF inhibited GRF-stimulated cyclic AMP levels by 75% maximum (still 8-fold greater than the basal levels) and GH release to almost half the basal value. We conclude that somatostatin inhibits GRF-elevated cyclic AMP levels in rat pituitary cells but not in sheep cells.

Animals↗
PubMed1984

Effects of growth hormone-releasing factor, somatostatin and dopamine on growth hormone and prolactin secretion from cultured ovine pituitary cells.

A synthetic form of human pancreatic growth hormone releasing factor (GRF-44-NH2) was shown to be a potent stimulator of growth hormone (GH) secretion and cellular cyclic AMP levels in cultured sheep pituitary cells. A small dose-dependent stimulation of prolactin secretion was also observed. Somatostatin (0.5 microM) completely blocked the maximal GRF (1 nM)-stimulated secretion without a significant effect on cyclic AMP levels. Dopamine (0.1 microM) inhibited the GRF-elevated GH secretion by 50% and lowered cyclic AMP levels by 30%. Dopamine (0.1 microM) inhibition of basal prolactin secretion was not affected by GRF (1 nM). The data support the hypothesis that cyclic AMP is involved in the action of GRF but suggest that somatostatin can inhibit GRF-induced secretion of GH independently of cyclic AMP.

Animals↗
PubMed1984

Studies of TRH-induced prolactin secretion and its inhibition by dopamine, using ovine pituitary cells.

Prolactin secretion from ovine pituitary cell cultures was stimulated by thyrotropin-releasing hormone (TRH) (10(-10)-10(-7) M) with a half-maximal effect at approximately 2.5 X 10(-9) M. A maximally effective concentration of TRH produced a peak secretory response, 5-10-fold stimulation over basal release, within 15 min. Dopamine (10(-10)-10(-7) M) but not somatostatin caused a dose-related inhibition of TRH (10(-8) M) stimulated prolactin release. Both dopamine (10(-7) M) and somatostatin (10(-7) M) inhibited basal secretion from the cells. TRH did not significantly increase pituitary cell cyclic AMP levels under any of the conditions tested. Stimulation of prolactin secretion by TRH was not prevented when Ca2+ was omitted from the incubation medium. Dopamine inhibited secretion induced by TRH under low Ca2+ conditions. Our results are consistent with a hypothesis that TRH may stimulate prolactin secretion via release of intracellular Ca2+ rather than increased cellular Ca2+ uptake, and imply that dopamine inhibition involves a lowering of intracellular Ca2+ levels.

Animals↗
PubMed1982

Actions of dopamine on prolactin secretion and cyclic AMP metabolism in ovine pituitary cells.

Prolactin secretion from cultured sheep pituitary cells was inhibited by low concentrations of dopamine (0.1 nM-0.1 microM) with a half-maximal effect at 3 nM. At a maximally effective dose (0.1 microM) dopamine significantly inhibited prolactin secretion within 5 min. with an 80% inhibition of basal secretion over 2 h. Basal prolactin secretion was stimulated by the addition of methylisobutylxanthine (MIX) (0.3-1.0 mM) and 8-bromo-cyclic AMP (2 mM), but cholera toxin (3 micrograms/ml) and prostaglandin E2 (0.1-1.0 microM), which also raised cellular cyclic AMP levels, had no effect on prolactin release. The inhibition of prolactin release by dopamine (0.1 microM) was not affected by any of these compounds. Dopamine inhibited MIX-induced cyclic AMP accumulation over a similar concentration range to the inhibition of secretion, but had no effect on the changes in cyclic AMP concentration produced by cholera toxin and prostaglandin E2. Overall the results with sheep pituitary cells suggest that lowered cyclic AMP levels do not mediate the inhibitory effects of dopamine on basal prolactin secretion, but that changes in cellular cyclic AMP levels may alter the secretion of this hormone, and dopamine may affect pituitary cell cyclic AMP concentrations in some circumstances.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Effects of dopamine on prolactin secretion and cyclic AMP accumulation in the rat anterior pituitary gland.

The effects of dopamine on pituitary prolactin secretion and pituitary cyclic AMP accumulation were studied by using anterior pituitary glands from adult female rats, incubated in vitro. During 2h incubations, significant inhibition of prolactin secretion was achieved at concentrations between 1 and 10nm-dopamine. However, 0.1-1mum-dopamine was required before a significant decrease in pituitary cyclic AMP content was observed. In the presence of 1mum-dopamine, pituitary cyclic AMP content decreased rapidly to reach about 75% of the control value within 20min and there was no further decrease for at least 2h. Incubation with the phosphodiesterase inhibitors theophylline (8mm) or isobutylmethylxanthine (2mm) increased pituitary cyclic AMP concentrations 3- and 6-fold respectively. Dopamine (1mum) had no effect on the cyclic AMP accumulation measured in the presence of theophylline, but inhibited the isobutylmethylxanthine-induced increase by 50%. The dopamine inhibition of prolactin secretion was not affected by either inhibitor. Two derivatives of cyclic AMP (dibutyryl cyclic AMP and 8-bromo cyclic AMP) were unable to block the dopamine (1mum) inhibition of prolactin secretion, although 8-bromo cyclic AMP (2mm) significantly stimulated prolactin secretion and both compounds increased somatotropin (growth hormone) release. Cholera toxin (3mug/ml for 4h) increased pituitary cyclic AMP concentrations 4-5-fold, but had no effect on prolactin secretion. The inhibition of prolactin secretion by dopamine was unaffected by cholera toxin, despite the fact that dopamine had no effect on the raised pituitary cyclic AMP concentration caused by this factor. Dopamine had no significant effect on either basal or stimulated somatotropin secretion under any of the conditions tested. We conclude that the inhibitory effects of dopamine on prolactin secretion are probably not mediated by lowering of cyclic AMP concentration, although modulation of the concentration of this nucleotide in some other circumstances may alter the secretion of the hormone.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Temperature effects on cyclic AMP accumulation in cultured fibroblasts.

The kinetic parameters that determine the accumulation of cAMP in WI-38 cells stimulated with prostaglandin E1 have been determined at 37 degrees C and at lower temperatures. For desensitized cells, a reduction of temperatures from 37 degrees to 25 degrees C reduced both rate of synthesis and rate of elimination of cAMP by about 40%. The steady-state accumulation was, therefore, about the same at both temperatures. The extent of desensitization was also shown to be comparable at the two temperatures. It can be inferred that there was appreciable desensitization at 4 degrees C after a period of stimulation of less than one hour. This is contrasted with the behavior of C6-2B glioma cells at the same temperature. Escape of cAMP through the plasma membrane showed a greater temperature dependence than any of the other processes concerned with cAMP accumulation.

Cell Line↗
PubMed1979

Adenosine 3',5'-monophosphate-dependent protein kinase(s) in diploid and SV40 transformed human fibroblasts.

Cyclic AMP-dependent protein kinases (EC 2.7.1.37; ATP:protein phosphotransferase) in the human diploid fibroblast WI-38 and an SV40-transformant WI-38-VA13-2RA (VA13) have been compared on the basis of their concentrations in cells, isoenzyme composition and susceptibility to hormonal activation. In high population density cultures, total soluble cyclic AMP-dependent kinase activities measured with histone were essentially the same in WI-38 and VA13. Two soluble protein kinase forms separated by chromatography on DEAE-cellulose were present in both cell lines. The concentration of cyclic AMP required for half-maximal activation of both enzyme forms was 10-30 nM. Overall kinase stimulation was greater for the Peak I enzymes. Kinase activation induced in the presence of 0.5 M KCl was more rapid and complete for the Peak I enzymes. Under conditions which elevated the concentration of cyclic AMP in WI-38 and VA13 cells the activities of the soluble histone kinases were increased. Incubation of the cells with either of 5.7 micronM prostaglandin E1 or 1 micronM isopropylnorepinephrine induced complete activation of the cyclic AMP-dependent histone kinases within 5 min and maintained the effect for 20 min. When intracellular cyclic AMP levels were raised by prostaglandin E1, activation of glycogen phosphorylase (assayed-AMP) suggested that this enzyme cascade involving cyclic AMP-dependent protein kinase(s) was intact and responsive in both cell lines.

Cell Line↗
PubMed1979

Inhibition of cyclic nucleotide phosphodiesterase during exposure to WI-38 cells to prostaglandin E1.

Short term incubation of WI-38 cultures with 5.7 micron prostaglandin E1 (PGE1) caused cyclic AMP phosphodiesterase activity in fibroblast homogenates to fall by 25 to 35% as compared to controls. The PGE1-induced decline in phosphodiesterase activity coincided with a rapid increase in intracellular cyclic AMP levels in response to the hormone and was rapidly reversed by washing the cultures free of the prostaglandin before homogenizing the cells. The effect of PGE1 on WI-38 phosphodiesterase activity was localized to the enzyme form(s) present in 27,000 times g supernatant fractions of cell homogenates. These data suggest that the pattern of cyclic AMP accumulation in WI-38 fibroblasts exposed to PGE1 may be related, at least in part, to decreased phosphodiesterase activity during hormone stimulation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1978

Prolonged prostaglandin E1 stimulation of cyclic AMP production in transformed and normal WI-38 fibroblasts.

Long-term (48-hr) incubations of either the fibroblast strain WI-38 or its SV40-transformed counterpart, WI-38-VA13-2RA, in growth medium containing 1 micron prostaglandin E1 (PGE1) resulted in a sustained production and release of cyclic AMP from the cells into the medium. Despite the steady production, intracellular levels of the nucleotide decreased, reaching steady-state values within 4 hr of the initial exposure to PGE1. These values were maintained for the remainder of the 48-hr experimental period. The steady-state levels of intracellular cyclic AMP were higher than those observed in unstimulated cells, and cyclic AMP-dependent protein phosphokinase was in a highly activated state as compared to controls. Under these conditions little change in the growth or morphology of either the normal or transformed cells was observed. In contrast, inhibition of growth, apparent cell death, and unusual morphological changes were observed in both normal and transformed cells when high concentrations of either PGE1 (10 micron) or the phosphodiesterase inhibitor 1-methyl, 3-isobutylxanthine (0.5 mM to 2 mM) were used, which was indicative of toxic effects of the drugs. It was concluded that cyclic AMP-mediated activation of protein phosphokinase does not completely inhibit growth in WI-38 cells or restore normal growth and morphology to the SV40-transformed cells.

Cell Division↗
PubMed1976

The identification and properties of phosphatases in skeletal muscle with activity towards the inhibitory subunit of troponin, and their relationship to other phosphoprotein phosphatases.

1. Phosphoprotein phosphatases with activity towards the inhibitory subunit of troponin (troponin I), phosphorylase a and lysine-rich histone (fraction F1) have been fractionated from rat skeletal muscle by chromatography on Sephadex G-200 and polylysine-Sepharose. Six separate fractions were identified on the basis of substrate specificity and behaviour during chromatography. 2. All fractions showed similar Km values for any given protein substrate. The Km for troponin I (5 muM) was significantly lower than that previously reported. 3. Phosphatase activities towards troponin I and hosphorylase a did not show a requirement for bivalent-metal ions. Two of the fractions with only minor activity towards histone were activated by Mn2+. 4. Discontinuous polyacrylamide-gel-electrophoresis studies indicated that several of the fractions contained more than one phosphatase activity, and additionally showed that several of the activities could exist in different aggregation states. On the basis of these studies at least two phosphatases with activity only towards troponin I were identified. In addition, phosphorylase phosphatase (which has considerable activity towards troponin I) and a general phosphatase with activity towards all three substrates were found. 5. A fraction with mol.wt. of 150000 could be activated by freezing with 2-mercaptoethanol or by heating to 55 degrees C. This activation was accompanied by a decrease in mol.wt. to 25000. 6. The total amount of phosphatase with activity towards troponin I which was extracted would be sufficient to dephosphorylate all the troponin I present in skeletal muscle in approximately 10s.

Animals↗