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Biomedical subjects

M Pines

Publications and source records attributed to M Pines.

At least 91 records · Page 5Linked to original sources
PubMed1989

Inhibition of aldosterone secretion by atrial natriuretic peptide in chicken adrenocortical cells.

Dispersed chicken adrenocortical cells were preincubated with atrial natriuretic peptide (rANP), sodium nitroprusside (SNP) or 8-bromo cyclic GMP, followed by incubations with ACTH, chicken PTH, cholera toxin or various steroid intermediates of aldosterone production. Cyclic AMP production and aldosterone secretion were evaluated, in order to determine the sites of ANP inhibition in the sequence of events leading to aldosterone secretion. Dose-dependent inhibitory effects on ACTH-stimulated aldosterone secretion by rANP and SNP were observed. Both agents appeared to stimulate cGMP production by the particulate fraction of the avian adrenocortical cells. Aldosterone production, stimulated by cyclic AMP agonists such as ACTH, chicken PTH and cholera toxin, was significantly inhibited by ANP. On the other hand, ANP did not interfere with production or degradation of cAMP. Each of the aldosterone intermediates--pregnenolone, progesterone, 11-deoxycorticosterone and corticosterone--promoted aldosterone production when included in the incubation media. Atrial natriuretic peptide and SNP inhibited aldosterone secretion when enhanced by the intermediates, by about 40-60%, but the ACTH-stimulated secretion was inhibited by over 90%. The results suggest two sites of inhibition by ANP in the pathway of aldosterone synthesis and secretion: synthesis of cholesterol or pregnenolone, and conversion of corticosterone to aldosterone. The inhibition by 8-bromo cGMP of aldosterone secretion and the similar sites of inhibition for ANP and SNP suggest that cyclic GMP mediates the inhibition in both cases.

Adrenal Cortex↗
PubMed1989

Modulation of responsiveness of the adenylate cyclase system in avian chondroprogenitor cells by pertussis toxin, PTH, and PGE2.

Chondroprogenitor cells, derived from avian tibia epiphyseal growth plate, were cultured in vitro. Incubation of these cells with pertussis toxin augmented their cAMP response to parathyroid hormone (PTH), attenuated the response to forskolin, but did not modify the response to PGE2. Pertussis toxin modulation of the cAMP response was accompanied by ADP ribosylation of two proteins with molecular weights of 39 and 40 kD. Using specific antibodies, the 39 kD protein was identified as the inhibitory guanine nucleotide binding protein (Gi) of the adenylate cyclase system. The other ADP-ribosylated protein has not been identified. Preincubation of the chondroprogenitor cells with PTH or PGE2 resulted in time-dependent heterologous desensitization of the cAMP response to a second challenge of either hormone. The cells did not recover from the densitization for at least 18 h after removal of the hormones. PTH and PGE2 treatment did not affect the cAMP response to forskolin and cholera toxin. The PTH-dependent cAMP production was also not altered by forskolin treatment. PTH homologous desensitization was not affected by pertussis toxin treatment, but the heterologous desensitization due to PGE2 was significantly attenuated. These results suggest that exposure of chondroprogenitor cells to PTH and PGE2 results in heterologous desensitization of the cAMP response. The desensitization is not due to changes in the adenylate cyclase activity. The pertussis toxin-sensitive G proteins are involved in the PTH heterologous rather than homologous desensitization of the cAMP response.

Adenosine Diphosphate Ribose↗
PubMed1989

Renal and adrenal adenosine 3',5'-monophosphate production and corticosteroid secretion in response to synthetic chicken parathyroid hormone-(1-34).

The activity of synthetic chicken (c) PTH-(1-34) amide was tested in dispersed chicken and rat kidney and adrenocortical cells. In the adrenal cells the effect of intact cPTH was also evaluated. In chicken kidney cells, the time- and dose-response patterns of cAMP production were similar for cPTH-(1-34) amide and human (h) PTH-(1-34), whereas rat kidney cells were considerably more sensitive to hPTH-(1-34) than to cPTH-(1-34) amide. The agonist effects of both hPTH-(1-34) and cPTH-(1-34) amide in kidney cells were inhibited by the bovine PTH-(3-34) analog. In chicken adrenocortical cells, cPTH-(1-34) amide stimulated cAMP production and steroid secretion. This action of the peptide was inhibited by bovine PTH-(3-34) and hPTH-(1-34), which by themselves showed no agonist effects. The maximal response of steroid secretion to cPTH-(1-34) amide was significantly lower than that to ACTH, but intact cPTH (supplied as a semipurified parathyroid extract) stimulated steriodogenesis to the same extent as ACTH. In rat adrenocortical cells, intact cPTH stimulated both cAMP formation and steriodogenesis, but cPTH-(1-34) amine showed no agonist effect. The action of the intact hormone in the rat adrenal could be inhibited by cPTH-(1-34) amide. The present results demonstrate the interaction of cPTH-(1-34) with kidney and adrenocortical cells of either chicken or rat. The cAMP and steroidogenic responses of the adrenocortical cells to PTH appear to be dependent (completely in the rat and partially in the chicken) on some sequence beyond the 1-34 region.

Adrenal Cortex Hormones↗
PubMed1989

Atrial natriuretic peptide and sodium nitroprusside stimulate cyclic GMP accumulation by avian skin fibroblasts and epiphyseal growth-plate chondroprogenitor cells.

Chondroprogenitor cells derived from avian tibia epiphyseal growth plate, and skin fibroblasts were cultured in vitro. In the fibroblasts, human (1-28) and rat (5-28) atrial natriuretic peptide (ANP) stimulated cyclic GMP (cGMP) production in a dose-dependent manner without affecting cAMP. Sodium nitroprusside also stimulated cGMP accumulation by chondroprogenitor cells and fibroblasts, but the maximum cGMP accumulation elicited by sodium nitroprusside was much lower than that obtained with ANP. The effects of ANP and sodium nitroprusside on chondroprogenitor cells and skin fibroblasts were additive. Human ANP increased cGMP production by the particulate fraction prepared either from chondroprogenitor cells or fibroblasts. Sodium nitroprusside, at concentrations of up to 1 mmol/l, did not affect cGMP production by the particulate fraction prepared from either cell type. The present study provides additional evidence that avian growth-plate chondroprogenitor cells and skin fibroblasts are targets for ANP. ANP and nitroprusside activate different guanylate cyclase isoenzymes--the particulate and soluble forms of the enzyme respectively. The data suggest that most of the guanylate cyclase activity in these cells is localized in the particulate fraction.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Nucleotide sequence of cloned cDNAs encoding chicken preproparathyroid hormone.

In order to characterize an avian parathyroid hormone gene, a lambda gt10 cDNA library constructed from chicken parathyroid gland mRNA was screened with a human preproparathyroid hormone (preproPTH) cDNA probe. Nucleotide sequence analysis of three independent clones confirmed that they encoded chicken preproPTH. This analysis, complemented by primer extension and Northern blot analysis of mRNA, demonstrated a 5'-untranslated region for chicken preproPTH of 127 nucleotides, a coding region of 357 nucleotides, and a 3'-untranslated region of approximately 2500 nucleotides. The coding sequence predicts a mature chicken PTH of 88 amino acids in contrast to the 84 amino acids of the mammalian hormones. Comparison of the avian and the mammalian hormones shows striking homology in the region of amino acids 1-32. The middle and carboxyl-terminal portions of chicken PTH, however, differ considerably from the mammalian hormones and include deletions of sequences conserved in mammalian PTH and insertions of novel peptide sequences. Comparison of the avian and mammalian structures suggests potential alterations of the mammalian sequences that may lead to altered bioactivity and/or hormone metabolism.

Amino Acid Sequence↗
PubMed1988

Inhibition of the proliferation of Nb2 cells by femtomolar concentrations of cholera toxin and partial reversal of the effect by 12-O-tetradecanoyl-phorbol-13-acetate.

One hour of exposure to cholera toxin is sufficient to elicit a significant delay in the initiation of DNA synthesis and cell division in lactogenic hormone-dependent Nb2-11C lymphoma cells. The inhibitory effect occurs already at very low concentrations of cholera toxin (5-50 fM), at which it is not accompanied by a detectable increase in intracellular cAMP, or ADP-ribosylation of the alpha subunit of Gs, the stimulatory guanine nucleotide binding protein of adenylate cyclase; IBMX, the phosphodiesterase inhibitor, acts synergistically to cholera toxin, indicating that a minute increase in cAMP may be sufficient for the inhibition. This indication is substantiated by the finding that dibutyryl cAMP also inhibits cell proliferation. Phorbol diester reverses partially the inhibitory activity of cholera toxin. It is most likely that this effect does not result from blocking the increase in cAMP, but rather from some subsequent, yet unidentified, events. The inhibitory effect of cholera toxin is not dependent on the concentration of the proliferation-stimulating lactogenic hormone and cannot be abolished or reduced by excess of the hormone. Cholera toxin also inhibits the autonomous proliferation of a lactogenic hormone-independent cell line (Nb2-SP); however, in this case the inhibition is not affected by TPA.

Animals↗
PubMed1988

The effect of parathyroid hormone and atrial natriuretic peptide on cyclic nucleotides production and proliferation of avian epiphyseal growth plate chondroprogenitor cells.

Cells derived from avian tibia epiphyseal growth plate were cultured in vitro. The cells which exhibited a polygonal phenotype and are termed chondroprogenitor cells, developed in culture as a monolayer with a doubling time of 40-48 h in 5% fetal calf serum. Production of cAMP by the chondroprogenitor cells was stimulated by human and bovine native (1-84) PTH. The effect of PTH on cAMP production could be blocked by the (3-34) PTH analog, suggesting interaction with specific receptors. cAMP production by avian chondroprogenitor cells was also stimulated by cholera toxin, forskolin, and prostaglandin E2 but not by ACTH or prostaglandin F2 alpha. PTH, cholera toxin, and forskolin also stimulated proliferation of the chondroprogenitor cells. In contrast, neither cAMP production nor proliferation of avian skin fibroblasts was affected by PTH. Human (1-28) and rat (5-28) atrial natriuretic peptide stimulated cGMP production by avian chondroprogenitor cells and also by skin fibroblasts. Atrial natriuretic peptide inhibited the basal and PTH-stimulated [3H]thymidine incorporation into DNA of chondroprogenitor cells, but did not affect avian skin fibroblast proliferation. These results suggest that the proliferation of avian epiphyseal growth plate chondroprogenitor cells is modulated by opposing mechanisms induced by PTH and ANP, probably mediated by cAMP and cGMP, respectively.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Stimulation of chick adrenal steroidogenesis by avian parathyroid hormone.

Dispersed chick adrenocortical cells were incubated with avian parathyroid hormone (aPTH) or ACTH. Accumulation of cyclic AMP (cAMP), activity of cAMP-dependent protein kinase and the secretion of corticosterone and aldosterone, in response to these hormones, were measured. Accumulation of cAMP and activity of cAMP-dependent protein kinase were stimulated by both aPTH and ACTH as well as by cholera toxin. Cyclic AMP production followed a similar time-course when stimulated by either peptide hormone. Stimulation of steroid hormone secretion was detectable after 20 min of incubation with ACTH, but only after 40 min with aPTH. The maximal steroid hormone secretion by adrenocortical cells was similar when induced by either peptide hormone. The aPTH concentrations needed for half-maximal response of corticosterone and aldosterone secretion were higher than those for ACTH (2.5- and 2-fold respectively), but still within the physiological range. The 11 beta-hydroxylase inhibitor metyrapone inhibited the secretion of both corticosterone and aldosterone when induced by either aPTH or ACTH. The results suggest that aPTH is almost as potent as ACTH in stimulating the secretion of corticosterone and aldosterone from chick adrenocortical cells and utilizes a cAMP-dependent pathway similar to that of ACTH.

Adrenal Cortex↗
PubMed1988

Regulation of aldosterone secretion by avian adrenocortical cells.

Dispersed chick adrenocortical cells were incubated with mammalian and avian angiotensin-II, Ca2+, K+, verapamil, nifedipine, Ca2+ ionophore (A23187), protein kinase-C activator (phorbol 12-myristate 13-acetate; TPA), atrial natriuretic peptide (ANP), sodium nitroprusside (SNP) and ACTH. Secretion of aldosterone and corticosterone, and accumulation of cyclic nucleotides were assessed. Secretion of aldosterone was not affected by angiotensin-II, Ca2+ channel blockers, Ca2+ ionophore or TPA. ANP stimulated production of cyclic GMP (cGMP), and inhibited aldosterone secretion with a similar dose-response relationship. SNP also stimulated cGMP production and inhibited the ACTH-stimulated aldosterone secretion. The results indicate that ANP is an inhibitor of aldosterone secretion in birds and suggest that this inhibition is mediated by cGMP. In contrast to mammalian glomerulosa cells, angiotensin-II and the calcium-inositol phosphate-protein kinase C pathway appear not to be involved in the regulation of aldosterone secretion by avian adrenal cells.

Adrenal Cortex↗
PubMed1988

Feed restriction in broiler breeder pullets: skip-a-day versus skip-two-days.

Effects were compared of two methods of feed restriction (skip-a-day, SAD, vs. skip-two-days, STD) during 4 to 22 wk of age on the development, uniformity, and subsequent performance of White Rock pullets. The pullets, housed in cages, consumed the same amount of feed in both treatments. Nevertheless, body weights of birds kept under the STD feeding regimen were significantly (P less than .01) lower. This difference was still significant (P less than .05) at 35 wk of age. Flock uniformity at 11 wk of age was significantly (P less than .05) higher in pullets kept on the STD feeding program. Plasma glucose and corticosterone levels in fasted pullets and corticosterone levels in fed birds at the age of 21 wk were not affected by feeding regimen. However, the increase in plasma glucose after feeding was significantly (P less than .05) higher in pullets on the STD feeding program. Plasma corticosterone levels were consistently, and at times significantly (P less than .05), higher in fasted birds. Laying of the first egg was significantly (P less than .05) delayed in hens previously kept on the STD feeding regimen. Rate of egg production and egg weights up to 35 wk of age were not affected by the method of feed restriction.

Animal Husbandry↗
PubMed1988

Immunochemical studies of the 36-kDa common beta subunit of guanine nucleotide-binding proteins: identification of a major epitope.

Twenty-four of 24 rabbits immunized with the beta subunit common to guanine nucleotide binding proteins developed antibodies reactive on immunoblots with the 15-kDa (amino-terminal) tryptic fragment of beta. Only 2 of 24 developed antibodies reactive with the 26-kDa (carboxy-terminal) tryptic fragment. The 15-kDa fragment-reactive antibodies were also detected in several nonimmune sera. Antibodies reactive with the 15-kDa fragment could be affinity-purified from all beta-immune sera by adsorption to a fusion protein encoded by a cDNA clone identified by expression vector screening. The 15-kDa fragment antibodies in nonimmune sera did not bind to the fusion protein. Limited amino acid sequence homology between the 36-kDa beta subunit and the protein encoded by the cDNA clone suggested that the amino-terminal decapeptide of beta contains a major epitope. A synthetic decapeptide, corresponding to the amino terminus of the 36-kDa beta subunit, effectively and specifically blocked binding of antibodies in beta-immune sera (but not in beta-reactive nonimmune sera) to nitrocellulose-bound 15-kDa fragment. The 15-kDa fragment-reactive antibodies could be affinity-purified from beta-immune sera on a matrix containing bound decapeptide; affinity-purified antibodies reacted equally well with the 36- and 35-kDa forms of the beta subunit. Native transducin beta/gamma complexes readily blocked binding of 15-kDa fragment-reactive antibodies in immune but not nonimmune sera from binding to the nitrocellulose-bound fragment. The results show that nonimmune sera may contain antibodies directed against an epitope of the 15-kDa fragment that is buried in the native beta/gamma complex. In contrast, the amino terminal decapeptide of the beta subunit is exposed on the surface of the native protein and contains a major antigenic site in both the 35- and 36-kDa forms.

Amino Acid Sequence↗
PubMed1987

A set of monozygotic twins with Rett syndrome.

The case history of a set of twins with Rett syndrome is presented. The twins test as monozygotic by both blood groups and HLA titers. In a previous generation, the family had three females who died of an unknown degenerative disease on the paternal side of this family. The discussion includes a hypothesis about female genetic disease occurring in a recessive pattern on the X chromosome.

Brain Diseases↗
PubMed1987

Response of adrenal cells to parathyroid hormone stimulation.

Dispersed adrenal cells of avian and bovine origin were incubated with human (h) 1-34 parathyroid hormone (PTH(1-34)), bovine (b) PTH(1-84), bPTH(3-34), avian (a) PTH, and with ACTH. Kidney tubular cells, the established target cells for PTH, were used for comparison. Cyclic AMP (cAMP) accumulation and steroid hormone (aldosterone and corticosterone) secretion were measured in response to the hormones. In the bovine adrenocortical cells PTH of both bovine and avian origin stimulated cAMP production, but the aPTH action was more pronounced. The maximal cAMP response of avian adrenocortical cells to aPTH was 15-fold greater than that of ACTH, but a 20-times higher concentration of aPTH was required to reach half-maximal response. Avian PTH stimulated steroid hormone secretion in the chick adrenocortical cells, but the induced secretion was similar to that induced by ACTH, despite the difference in cAMP accumulation. Human PTH(1-34) and bPTH(1-84), which stimulated cAMP production in kidney cells, and the conventional antagonist bPTH(3-34) inhibited aPTH stimulation of cAMP accumulation in avian adrenocortical cells, but did not interfere with ACTH action. Furthermore, cAMP stimulation by aPTH and ACTH in avian adrenal cells was additive. The results establish the adrenal as a target organ for PTH, and suggest that the PTH acts through specific receptors, distinct from those for ACTH.

Adrenal Glands↗
PubMed1987

Down-regulation of lactogenic hormone receptors in Nb2 lymphoma cells by cholera toxin.

Exposure of lactogen-dependent (Nb2-11C) and lactogen independent (Nb2-SP) lymphoma cells to cholera toxin (0.05-50 pM) resulted within 18-28 h in a 50% decrease in the binding capacity of the intact cells to iodinated human growth hormone, and 40% decrease in cell-homogenates. Scatchard analysis revealed that the reduction in binding resulted from loss of cell-surface receptors accompanied by degradation of intracellular receptors. No alterations in receptor binding affinity were observed. One to 3 h of exposure to the toxin was sufficient to reduce the binding to the level obtained after continuous incubation with the toxin for 28 h. Addition of dibutyryl cAMP (0.1mM) to the medium resulted in similar down-regulation of lactogenic receptors.

Animals↗
PubMed1986

Immunochemical evidence for a novel pertussis toxin substrate in human neutrophils.

Pertussis toxin catalyzes incorporation of 20.2 pmol of ADP-ribose/mg of protein into approximately 40-kDa protein(s) in human neutrophil membranes compared with 14.1 pmol/mg in bovine brain membranes. Based on these measurements we estimate that pertussis toxin substrate(s) should represent at least 0.085% of total membrane protein in neutrophils. Both brain and neutrophil membranes show high concentrations (0.34 versus 0.16% of total membrane protein, respectively) of the common beta subunit of guanine nucleotide binding proteins. Affinity purified antibodies specific for Go-alpha fail to detect any protein in immunoblots of neutrophil membranes (150 micrograms) under conditions where as little as 10 ng of purified Go-alpha is detectable, and Go-alpha is readily detected in brain membranes (100 micrograms). An antiserum against transducin that cross-reacts strongly with Gi-alpha, detects as little as 5 ng of purified Gi-alpha and readily detects Gi-alpha in brain membranes, but in neutrophil membranes, the antiserum detects an approximately 40-kDa band that corresponds to less than 10% of the expected amount of pertussis toxin substrate(s). The results show that human neutrophil membranes contain relatively large amounts of pertussis toxin substrate(s), but that the predominant pertussis toxin substrate is immunochemically distinct from previously identified substrates, transducin, Gi, and Go.

Adenosine Diphosphate Ribose↗
PubMed1986

Relationship between endogenous cyclic AMP production and steroid hormone secretion in chick adrenal cells.

Dispersed chick adrenal cells were incubated with either ACTH, cholera toxin or forskolin. All three agents stimulated cyclic AMP accumulation and secretion of corticosterone and aldosterone by the dispersed cells. The dose-response to ACTH was similar for cyclic AMP and corticosterone but aldosterone secretion appeared to be more sensitive to ACTH stimulation. Concentrations higher than 10(-8) M of ACTH caused suppression of corticosterone output but not of cyclic AMP accumulation or aldosterone secretion. A significant cyclic AMP accumulation occurred within 30 min of exposure to ACTH whereas significant increases in steroid secretion were observed only after 30 min. An early increase (within 30 min) in cyclic AMP accumulation with both cholera toxin and forskolin was not accompanied by any significant stimulation of steroid secretion, which occurred only after 120 min. The results with the avian adrenal cells are consistent with the thesis that steroid production in the adrenocortical cells is stimulated by cyclic AMP-dependent pathways, whereas steroid release may be modulated by others.

Adrenal Glands↗
PubMed1986

Multisite phosphorylation of the alpha subunit of transducin by the insulin receptor kinase and protein kinase C.

The GDP-bound alpha subunit of transducin, but not the guanosine 5'-[gamma-thio]triphosphate-bound one, undergoes phosphorylation on tyrosine residues by the insulin receptor kinase and on serine residues by protein kinase C. Holotransducin is poorly phosphorylated by the insulin receptor kinase and is not phosphorylated by protein kinase C. Neither holotransducin nor any of its subunits were phosphorylated by the cAMP-dependent protein kinase. That a given subunit of transducin undergoes multisite phosphorylation depending on the type of nucleotide bound to it or the nature of the kinase suggests that hormone-dependent phosphorylation could provide a versatile mode for regulation of guanine nucleotide-binding protein (G protein) function. In particular, the findings that certain G proteins serve as substrates for both the insulin receptor kinase and protein kinase C implicate G proteins in playing a key role in mediating the action of insulin and ligands that act to activate protein kinase C.

Animals↗