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Biomedical subjects

V May

Publications and source records attributed to V May.

At least 37 records · Page 2Linked to original sources
PubMed1997

Anesthetic activity of novel water-soluble 2 beta-morpholinyl steroids and their modulatory effects at GABAA receptors.

(3 alpha,5 alpha)-3-Hydroxypregnan-20-ones and (3 alpha,5 alpha)-3-hydroxypregnane-11,20-diones bearing a 2 beta-morpholinyl substituent were synthesized, and the utility of these steroids as anesthetic agents was evaluated through determination of their potency and duration of hypnotic activity in mice after intravenous administration. Alkylation of the morpholinyl substituent or chlorination at C-21 afforded the novel amino steroids (2 beta,3 alpha,5 alpha)-3-hydroxy-2-(2,2-dimethyl-4-morpholinyl)-pregnane-11,20-dione (19) and (2 beta,3 alpha,5 alpha)-21-chloro-3-hydroxy-2-(4-morpholinyl)pregnan-20-one (37) that were more potent and advantageously produced shorter sleep times than related compounds which were previously reported. Furthermore, salts of these and other amino steroids generally retained good aqueous solubility. In a radioligand binding assay the compounds inhibited the specific binding of [35S]-tert-butyl bicyclophosphorothionate to rat whole brain membranes, and in an electrophysiological assay they potentiated GABAA receptor-mediated currents recorded from voltage-clamped bovine chromaffin cells. These in vitro results are consistent with the anesthetic activity of the amino steroids being related to their modulatory effects at GABAA receptors.

Anesthesia↗
PubMed1997

Pregnancy augments uteroplacental vascular endothelial growth factor gene expression and vasodilator effects.

This study examined a potential role for vascular endothelial growth factor (VEGF) in uterine artery remodeling and vasodilation during pregnancy. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect VEGF mRNA in uterine tissues from nonpregnant (NP), midpregnant (MP, 15-16 days), and late-pregnant (LP, 19-21 days) rats and in placentas from MP and LP rats. VEGF mRNA levels in uteri and placentas were determined by Northern blotting, and the vasorelaxant activity of recombinant human VEGF (rh-VEGF) was tested and compared in isolated uterine arteries from LP and NP animals. VEGF120 and VEGF164 were the major isoforms detected in uterine tissues; all members of the VEGF family (VEGF120, VEGF164, VEGF188, and VEGF205) were expressed in LP placentas. VEGF mRNA levels increased 60% in MP and 80% in LP above those in NP (P < 0.05) in uterine tissues; VEGF mRNA levels were also detectable in placentas and elevated approximately fivefold in LP vs. MP tissues (P < 0.01). Phenylephrine-preconstricted uterine arcuate arteries (NP and LP) dilated in response to rhVEGF, an effect that was completely abolished by endothelial denudation or pretreatment with genistein, a tyrosine kinase inhibitor. The magnitude of dilation to an intermediate concentration of rhVEGF (1 nM) was greater in LP than in NP vessels (55 +/- 8 vs. 24 +/- 11%; P < 0.05), and this effect was diminished comparably in both groups (approximately 60% by N omega-nitro-L-arginine, an inhibitor of nitric oxide synthesis. These results suggest that VEGF may play a role in the vascular remodeling and vasodilation that lead to decreased uterine vascular resistance and increased uterine blood flow during pregnancy.

Animals↗
PubMed1996

Pituitary adenylate cyclase-activating polypeptides, PACAP-38 and PACAP-27, regulation of sympathetic neuron catecholamine, and neuropeptide Y expression through activation of type I PACAP/VIP receptor isoforms.

The current studies have implicated a prominent role for PACAP peptides in modulating the physiological function of cells derived from the sympathoadrenal lineage. Compared to VIP, both PACAP-27 and PACAP-38 demonstrated potent, efficacious, and sustained stimulatory effects on sympathetic neuronal NPY and catecholamine production. The differential effects of PACAP peptides on SCG NPY and catecholamine content and secretion coincided with previous studies that activated directly the sympathetic intracellular cyclic AMP-protein kinase A signaling pathway. These effects appear to be mediated primarily by PACAP1 receptor splice variants coupled to both adenylyl cyclase and phospholipase C in SCG neurons. The actions of PACAP peptides in the SCG shared many parallels with adrenal medullary chromaffin cells, suggesting diverse roles for the PACAP peptidergic system in sympathoadrenal cell development and function. Rather than solutions, these results pose additional questions for the future. What are the endogenous sources of PACAP that regulate sympathetic and adrenal function? Do PACAP peptides, like VIP, have dual roles and also act as sympathetic postganglionic neuromodulators? Are VIP/PACAP receptors expressed during SCG development? What regulates sympathetic PACAP1 receptor isoform expression and how are they differentially coupled to neuronal intracellular signaling cascades? What defines the tissue-specific responses to PACAP-27 and PACAP-38? While many of these questions are not easily approached, future studies of these issues will certainly illuminate the function of PACAP and PACAP receptors in the nervous and endocrine systems.

Adrenal Glands↗
PubMed1995

Pituitary adenylate cyclase-activating polypeptide (PACAP) regulation of sympathetic neuron neuropeptide Y and catecholamine expression.

Two forms of pituitary adenylate cyclase-activating polypeptide (PACAP), the 38- and 27-amino-acid forms (PACAP38 and PACAP27, respectively), which share amino acid sequence homology with vasoactive intestinal peptide (VIP), were evaluated for their abilities to regulate sympathetic neuron catecholamine and neuropeptide Y (NPY) expression. PACAP38 and PACAP27 potently and efficaciously stimulated NPY and catecholamine secretion in primary cultured superior cervical ganglion (SCG) neurons; 100- to 1,000-fold higher concentrations of VIP were required to modulate secretion, suggesting that SCG neurons express the PACAP-selective type I receptor. PACAP38 elicited a sustained seven- to ninefold increase in the rate of NPY secretion and threefold stimulation in the rate of catecholamine release. PACAP38 and PACAP27 produced parallel neuronal NPY and catecholamine release, but cellular levels of NPY and catecholamines were differentially regulated. Sympathetic neuron NPY content was decreased, whereas cellular total catecholamine levels were elevated by the PACAP peptides; total NPY and catecholamine levels (secreted plus cellular content) were increased. In concert with the increased total peptide and transmitter production, pro-NPY and tyrosine hydroxylase mRNA levels were elevated. Furthermore, PACAP38 was more efficacious than PACAP27 in regulating pro-NPY and tyrosine hydroxylase mRNA. SCG neuronal expression of mRNA encoding the type I PACAP receptor further supported the studies demonstrating that sympathetic neuronal levels of NPY and catecholamine content and secretion and mRNA are differentially regulated by the PACAP peptides.

Animals↗
PubMed1995

Differential regulation of sympathetic neuron neuropeptide Y and catecholamine content and secretion.

Cultured principal neurons of the superior cervical ganglion (SCG), which coexpress high levels of catecholamines and neuropeptide Y (NPY), were used as a model to simultaneously examine whether sympathetic neuronal peptide and transmitter content or secretion are differentially regulated. Accumulation of NPY immunoreactivity and the dopamine metabolites DOPAC and HVA in SCG neuronal conditioned culture medium was used as an index of NPY and catecholamine secretion, respectively. Release of NPY and catecholamines was linear with time; SCG neurons exhibited a basal NPY secretory rate of approximately 0.9-3 fmol NPY immunoreactivity/10(4) cells/hr, and basal DOPAC plus HVA accumulation was about 10-20 pmol total metabolites/10(4) cells/hr. While sympathetic neuronal NPY and total catecholamine cell content increased more than 6-10-fold by 14 d of culture, secretion remained constant. Depolarization stimulated the rate of NPY secretion 18-fold, whereas medium catecholamine metabolite levels increased 3-fold. Activation of intracellular signaling pathways was shown to be an important point of regulation of sympathetic neuron peptide and transmitter content and secretion. Differential regulation of SCG neuron NPY and catecholamine expression was second messenger system specific. Activation of the protein kinase A pathway with the cAMP analog dibutyryl cAMP, or the adenylyl cyclase activator forskolin, produced a concentration-dependent, sustained stimulation of NPY secretion; maximal stimulation resulted in decreased cellular NPY content. Parallel stimulated neuronal catecholamine release was observed, but in contrast to NPY, total cellular catecholamine content was also increased. Regulation of the protein kinase C pathway with phorbol myristate acetate (PMA) stimulated SCG neuronal NPY secretion to a lesser degree than activation of protein kinase A, but did not alter cellular NPY levels. PMA minimally stimulated catecholamine release and content. NPY secretion induced by the calcium ionophore A23187 was paralleled by a concomitant decrease in cellular NPY. A23187 decreased catecholamine release, but did not change cellular total catecholamine levels. The magnitude of the secretory responses of sympathetic neurons to these regulators was far greater than changes in NPY or catecholamine content, biosynthesis or mRNA levels, suggesting that release is a primary site of regulation. The independent regulation of sympathetic neuronal NPY and catecholamine content and release is consistent with the fundamental differences in the biosynthetic pathways, vesicular compartmentalization, uptake and metabolism of neuropeptides and neurotransmitters.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Pituitary adenylate cyclase-activating polypeptide regulation of AtT-20/D16v corticotrope cell proopiomelanocortin expression and secretion.

The hypothalamic peptides pituitary adenylate cyclase-activating polypeptides (PACAPs) may play central roles in the regulation of anterior pituitary gland function. The two pro-PACAP-derived peptides, PACAP38 and PACAP27, are posttranslationally processed from a common precursor molecule and share amino acid sequence homology with vasoactive intestinal peptide (VIP). To further evaluate and compare the physiological roles of these peptides, we have examined the short and long term effects of PACAP38, PACAP27, and VIP on POMC-related peptide production in the mouse AtT-20/D16v corticotrope cell line. Short term (0.5- to 5-h) treatment of AtT-20/D16v cells with PACAP38, PACAP27, or VIP elicited similar concentration-dependent and biphasic stimulation of ACTH release. Half-maximal stimulation of the higher potency phase was attained with 1-2 nM peptide; maximal secretion was observed at peptide concentrations greater than 100 nM. Similar 2- to 3-fold maximal stimulation of ACTH secretion was elicited by all three bioactive peptides; linear sustained ACTH secretion was observed. Long term (12- to 72-h) treatment of AtT-20/D16v cultures with these peptides resulted in substantially decreased rates of cellular division, with a concomitant increase in cell size and formation of cell processes characteristic of cellular differentiation. These morphological changes coincided with a sustained 2-fold increase in AtT-20 corticotrope intracellular hormone content and secretion. Northern blot analysis demonstrated a parallel induction of POMC mRNA expression by the PACAP38, PACAP27, and VIP peptides. These results suggest that AtT-20/D16v cells possess primarily the type II PACAP receptor subtype, which binds PACAP38, PACAP27, and VIP with apparent equal affinity. Furthermore, the long term effects of these peptides implicate a potentially significant role for PACAP and VIP peptides in the mediation of altered pituitary gland functions. In this vein, the PACAPs may prove to be unique regulators of neuroendocrine function and development.

Animals↗
PubMed1992

Galanin-like innervation of rat submandibular and sublingual salivary glands: origin and effect on acinar cell membranes.

The distribution and source of a galanin-like innervation of rat salivary glands has been examined. Additionally, submandibular and sublingual acinar cell membrane responses to galanin or a cholinergic agonist were studied. Galanin-immunoreactive fibers were observed throughout the submandibular and sublingual glands in association with ducts and acini. A subset of submandibular ganglion cells expresses galanin immunoreactivity. Parasympathectomy resulted in a marked decrease in galanin immunoreactivity in the glands. Sympathectomy resulted in marked reduction of dopamine beta-hydroxylase immunoreactivity with no appreciable change in galanin immunoreactivity. Retrograde labeling experiments demonstrated that galanin-immunoreactive sensory neurons in the trigeminal ganglion do not innervate the submandibular or sublingual gland. These results indicate that the galanin-like innervation of rat salivary glands is derived from parasympathetic nerves to the glands. Since rat sublingual glands contain largely mucous acini while rat submandibular gland acini are seromucous, electrophysiological responses to galanin and the muscarinic agonist, bethanechol, were compared. Agonist-induced voltage shifts varied between the two glands. The galanin-induced response at the level of the resting membrane potential in submandibular acinar cells was a hyperpolarization, while that in sublingual acinar cells was a depolarization. There was also a greater voltage dependence to the galanin-induced submandibular response than to the sublingual response. Differences were also noted in the acinar cell response to cholinergic stimulation between these glands. These results demonstrate the existence of a galanin-like innervation to salivary glands that may be functionally relevant. Moreover, the results challenge the idea that agonist-induced membrane responses are similar among acinar cells of different glands.

Animals↗
PubMed1992

Expression of peptidylglycine alpha-amidating monooxygenase: an in situ hybridization and immunocytochemical study.

Peptide alpha-amidation, an essential posttranslational modification that confers bioactivity to many neuroendocrine peptides, is catalyzed by peptidylglycine alpha-amidating monooxygenase (PAM; EC 1.14.17.3). To complement our previous studies on the distribution of PAM in neuroendocrine organs, we have examined expression of the PAM gene in several endocrine tissues by in situ hybridization and immunocytochemistry. In all instances, the autoradiographic densities for PAM mRNA correlated with staining patterns for PAM immunoreactivity. Very high levels of PAM mRNA were found in all heart atrial cardiomyocytes, while much lower levels were present in ventricular cells. In the sublingual gland, PAM was expressed diffusely in both acinar and tubule cells. In contrast, expression of PAM was confined to granular convoluted tubule cells in the submaxillary gland. PAM was expressed at high levels in a subset of adrenal medullary chromaffin cells, and low levels of PAM mRNA and immunoreactivity were also detected in the adrenal cortex. PAM was found predominantly in the calcitonin-producing parafollicular C-cells in the thyroid gland and in the glucagon-containing A-cells in the endocrine pancreas. Collecting and distal tubule cells of the kidney expressed both PAM mRNA and immunoreactivity. The basal cells in testicular seminiferous tubules containing PAM may represent developing germ and Sertoli cells. The cellular localization of PAM within the thyroid gland, adrenal gland, testis, and pancreas correlated with known peptidergic systems, and some of the observed cellular heterogeneity in PAM mRNA expression and immunoreactivity may reflect differences in the levels of amidated peptide production. The expression of PAM in cells not known to produce high levels of alpha-amidated peptides may indicate the production of yet unidentified alpha-amidated bioactive peptides or alternative functions of the PAM protein.

Adrenal Medulla↗
PubMed1990

Immunocytochemical and in situ hybridization studies of peptidylglycine alpha-amidating monooxygenase in pituitary gland.

The pituitary gland contains high levels of peptidylglycine alpha-amidating monooxygenase (PAM) activity and mRNA. Using affinity-purified rabbit polyclonal antisera generated to synthetic PAM peptides and PAM RNA probes, immunocytochemical and in situ hybridization studies were conducted to determine the tissue disposition and cell types expressing PAM in the adult male rat pituitary gland. PAM immunoreactivity was present at varying levels in nearly all of the anterior pituitary cells; one cell population stained intensely, while others stained moderately or weakly. These results correlated well with in situ hybridization studies that demonstrated high levels of PAM mRNA in a subpopulation comprising approximately 10-15% of the anterior pituitary cells. Based upon immunocytochemistry, intermediate pituitary lobe cells were divided into an intensely stained and a moderately stained group. PAM staining was also present in neural lobe fibers. Immunocytochemical staining of serial pituitary tissue sections for PAM and other pituitary hormones demonstrated that the anterior pituitary cells intensely stained for PAM represented a subpopulation of the gonadotropes. PAM was also identified at moderate levels in corticotropes and at lower levels in sommatotropes and lactotropes. These results suggest that many anterior pituitary cells are capable of producing amidated peptides along with their major peptide hormone.

Adrenocorticotropic Hormone↗
PubMed1990

Thyroid hormone regulation of peptidylglycine alpha-amidating monooxygenase expression in anterior pituitary gland.

Peptidylglycine alpha-amidating monooxygenase (PAM; EC 1.14.17.3) is a copper-, molecular oxygen-, and ascorbate-dependent enzyme which catalyzes the COOH-terminal amidation of bioactive peptides. Expression of PAM in the adult male rat anterior pituitary was evaluated after experimental manipulation of thyroid status. Levels of PAM mRNA increased 4- to 7-fold in animals made hypothyroid by treatment with 6-n-propyl-2-thiouracil or thyroidectomy and were not diminished below control levels in animals made hyperthyroid by treatment with T4. Treatment of thyroidectomized animals with T4 prevented the increase in PAM mRNA levels; similar doses of T4 returned serum TSH and anterior pituitary PAM mRNA to euthyroid values. Based on Northern blot analysis and amplification of fragments derived from rat PAM-1 by reverse transcription and the polymerase chain reaction, thyroid status did not affect the distribution of PAM mRNA among its various alternatively spliced forms. The specific activity of PAM in the anterior pituitary was increased slightly in both the soluble and particulate fractions from chemically hypothyroid rats; the majority of the PAM activity in the rat anterior pituitary was soluble, and increased secretion of enzyme may account for the lesser effect of chemical thyroidectomy on specific activity compared to mRNA levels. Western blot analysis demonstrated a 104-kDa PAM protein in particulate fractions prepared from control, PTU-treated, and T4-treated animals. The soluble fraction contained major PAM proteins of 95 and 75 kDa, and PTU treatment brought about an increase in the prevalence of the 75-kDa form of PAM protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗