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S Reichlin

Publications and source records attributed to S Reichlin.

At least 55 records · Page 3Linked to original sources
PubMed1991

Regulation of cholecystokinin octapeptide secretion by rat cerebral cortical cells in primary culture.

The regulation of cholecystokinin octapeptide (CCK-8) secretion was studied using a fetal cerebral cortical cell culture system. After 2-3 weeks in culture, the cells were utilized for short-term release experiments. CCK-8 was measured by RIA and its identity was confirmed by HPLC. Depolarization of the cells with K+ (6 x 10(-2) M) evoked CCK-8 release and this response was blocked by the Ca++ channel blocker verapamil (2 x 10(-5) M) and by Ca++ free medium. The Na+ channel opener veratridine (10(-4) M) stimulated CCK-8 release and was blocked by the Na+ channel blocker tetrodotoxin (10(-6) M) and by Ca++ free medium. The adenylate cyclase activator forskolin (10(-5) M) markedly increased CCK-8 secretion. No changes in CCK-8 release were induced by epinephrine, norepinephrine, dopamine, acetylcholine, or 5-hydroxytryptamine at 10(-5) and 10(-4) M, but gamma-aminobutyric acid (GABA) at 10(-4) M inhibited CCK-8 release. GABA inhibition was reversed by the GABA antagonist picrotoxin (10(-4) M). Both picrotoxin (10(-4) M) and bicuculline (10(-3) M), another GABA receptor antagonist, alone stimulated CCK-8 secretion. These data show that CCK-8 secretion by cerebral cortical cells 1) is stimulated by cell membrane depolarization in a calcium-dependent fashion, 2) is regulated by cAMP, 3) is unaffected by the neurotransmitters characteristic of corticopetal systems, 4) is tonically inhibited by GABA.

Animals↗
PubMed1990

Gomori-positive astrocytes in primary culture: effects of in vitro age and cysteamine exposure.

Gomori-positive astrocytes have been identified in the periventricular brain in situ and in diencephalic explants on the basis of their endogenous peroxidase activity, affinity for chrom alum hematoxylin, and orange-red autofluorescence. To facilitate analyses of their functional properties, we sought to identify these cells in dissociated fetal rat brain cultures. Astrocytes containing cytoplasmic inclusions with the above tinctorial and fluorescent properties represented less than 1% of cultured astrocytes at day 10 in vitro (DIV). There was a marked increase in the fraction of Gomori-positive astrocytes and their granule content between 10 and 46 DIV. As in situ, the peroxidase activity appeared to be non-enzyme-mediated insofar as it catalyzed diaminobenzidine oxidation over a wide range of pH (3-11) and could not be inhibited by tissue preheating or the catalase inhibitor, aminotriazole. Metalloporphyrins probably mediate both the pseudoperoxidase activity and autofluorescence in these cells. Cysteamine and cystamine, but not ethanolamine or L-cysteine, induced a massive accumulation of Gomori-positive astrocytes when administered from DIV 6-18. Alterations of the redox microenvironment or induction of porphyrin/heme biosynthetic enzymes may be the mechanisms responsible for this cyst(e)amine effect. Dissociated rat brain culture enriched for Gomori astroglia should provide ample opportunity to investigate the functional properties of these cells.

Animals↗
PubMed1990

Immunoreactive interleukin-1 beta localization in the rat forebrain.

To determine whether the cytokine, interleukin-1 beta, is present in the rat brain as has been reported in human brain, immunocytochemical studies were performed using an antiserum that recognizes recombinant, rat IL-1 beta. Immunoreaction product was present in the periventricular and medial hypothalamus, mossy fiber distribution in the hippocampus and olfactory tubercle. These studies demonstrate that IL-1 beta is part of a diffuse intrinsic neural system in the rat central nervous system, associated with regions involved with hypophysiotropic, autonomic, limbic and extrapyramidal functions.

Animals↗
PubMed1990

Melanotropin receptors of murine melanoma characterized in cultured cells and demonstrated in experimental tumors in situ.

Cultured melanoma cells are known targets for the pigment-inducing actions of melanotropins such as alpha-melanocyte-stimulating hormone (alpha-MSH). The objectives of the present studies were to determine the binding properties and functional relevance of MSH binding sites in a mouse melanoma cell line and to determine whether MSH receptors are expressed in situ. The binding properties of MSH receptors in intact cells of a highly metastatic, highly MSH-responsive mouse melanoma cell subline (B16-F10C23) were determined using a radiolabeled, biologically active preparation of the superpotent alpha-MSH analogue, [Nle4,D-Phe7]-alpha-MSH (125I-NDP-MSH). A single high-affinity class of binding site was detected (Kd for NDP-MSH, 5.6 x 10(-11) M; Kd for alpha-MSH, 2.6 x 10(-9) M as determined by Scatchard analysis and heterologous inhibition assays, respectively). alpha-MSH showed nearly identical concentration-response relationships in the radioreceptor assay (inhibition of 125I-NDP-MSH binding) and a bioassay (stimulation of intracellular cyclic AMP accumulation). Furthermore, the respective potencies of three melanotropins, NDP-MSH, alpha-MSH, and adrenocorticotropic hormone, in binding and biological assays were highly correlated. These results indicate that the 125I-NDP-MSH binding site represents the functional MSH receptor. Tumors were induced by inoculation of C57BL/6 mice with B16-F10C23 cells, and the presence of 125I-NDP-MSH binding sites was determined by in situ radiolabeling of frozen tissue sections followed by autoradiography. Specific MSH binding sites were distributed throughout the tumor tissue, but not in associated fibrovascular elements or in neighboring nonmelanoma tissues. As in cultured B16-F10C23 cells, melanotropins inhibited 125I-NDP-MSH binding to tissue sections in a concentration-dependent manner. These results support the hypothesis that functional MSH receptors are expressed in melanoma in situ, suggesting that the activities of melanoma cells in vivo may be subject to modulation by endogenous melanotropins. The methods described will be applicable for studies of the expression and regulation of MSH receptors in human melanoma and other target tissues.

Animals↗
PubMed1990

Glial peroxidase activity in the hypothalamic arcuate nucleus: effects of estradiol valerate-induced persistent estrus.

To test the hypothesis that stimulation of glial peroxidase activity by estrogens may play a role in the pathogenesis of the previously reported degenerative changes in the hypothalamic arcuate nucleus that occur in female rats treated with a long-acting estrogen preparation, the cellular localization and number of peroxidase-positive granules in the hypothalamus were determined in adult female rats treated with a single intramuscular injection of 2 mg of estradiol valerate. The persistent estrus state, manifested as persistent vaginal cornification and polycystic ovaries, was induced in 80% of the animals. In comparison with normally cycling controls, the arcuate nuclei of persistent estrus rats exhibited a 3- and 2.8-fold increase in numbers of diaminobenzidine-positive granules and granule clusters, respectively (P less than 0.01 for both comparisons). These peroxidase-positive granules were identified in astrocytes by double-label immunohistochemistry utilizing antiserum to glial fibrillary acidic protein. Diaminobenzidine staining occurred over a pH range of 4-10.5 and was resistant to the catalase inhibitor, aminotriazole, and to tissue pre-heating, indicating that the histochemical reaction was not due to tissue enzyme activity. Rather, these findings indicate that a non-enzymatic, pseudoperoxidation reaction has been induced in these cells by estrogen administration. Possible mediators of this reaction are metallo-porphyrins known to be present in rodent hypothalamus. The mechanisms by which astrocyte peroxidase activity may play a role in estrogen-related neural damage are discussed.

Animals↗
PubMed1990

Acetylcholine stimulates the secretion of corticotropin-releasing factor from primary dissociated cell cultures of the rat telencephalon and diencephalon.

Corticotropin-releasing factor (CRF-41) immunoreactive neurones in the CNS are widely distributed; although the major concentration is in the parvocellular division of the paraventricular nucleus, there are also large clusters of CRF-containing neurones in the brainstem, limbic system and cerebral cortex. In this study, we sought to determine whether dispersed rat brain cells cultured in vitro are capable of secreting CRF immunoreactivity. In both telencephalic and diencephalic cultures CRF content of the cells increased from day 7 to 28. This effect was greatest in cells raised in media containing 10% fetal calf serum and 10% heat inactivated horse serum as compared with media containing 10% fetal calf serum and 10% NuSerum. Exposure of the cells to 56 mM K+ or to 10(-9) M acetylcholine caused a release of CRF which was calcium dependent. The effect of acetylcholine was antagonised by atropine (10(-6) M). The CRF immunoreactivity in both types of cell produced two peaks on gel chromatography; one of which eluted with the void volume and the other of which co-eluted with standard CRF-41. However, only the mature peptide was detected in media from cells stimulated with potassium. We conclude that cell cultures of the rat diencephalon and telencephalon produce immunoreactive CRF-41 and that immunoreactive CRF-41 secretion in both diencephalic and telencephalic cells is regulated by acetylcholine.

Acetylcholine↗
PubMed1990

Cysteamine induces cholecystokinin release from the duodenum. Evidence for somatostatin as an inhibitory paracrine regulator of cholecystokinin secretion in the rat.

To determine whether cholecystokinin secretion is regulated by endogenous somatostatin, somatostatin deficiency was induced in vivo with cysteamine (250 mg/kg body wt, IV) or anti-somatostatin antiserum in anaesthetized rats and in vitro with cysteamine (30 micrograms/mL) in a rat duodenum-incubation system. Cholecystokinin secretion was assessed in vivo by measuring amylase in duodenal perfusates collected at 10-minute intervals for 1 hour and in vitro by a carboxy-terminal radioimmunoassay. Cysteamine induced a marked decrease in duodenal immunoreactive somatostatin both in vivo (50%) and in vitro (60%). The rate of amylase secretion increased from 9.7 +/- 2.1 U (mean +/- SE) to 28.0 +/- 4.8 U at 20 minutes (P less than 0.001). The cholecystokinin-receptor antagonist CR-1392 abolished amylase response for 30 minutes, whereas the more potent antagonists Asperlicin (18.0 mg/kg body wt, IV) and L-364,718 (0.25 mg/kg body wt, IV) caused prolonged blockade. The rate of amylase secretion in gastrectomized animals increased from 7.2 +/- 2.0 U to 15.0 +/- 2.2 U 20 minutes after cysteamine administration (P less than 0.01), indicating that the effect was not due to the presence of gastrin. In vitro, cysteamine caused a nearly fourfold increase in cholecystokinin secretion compared with controls (63.1 +/- 4.9 vs. 15.2 +/- 3.7, respectively; P less than 0.001). In vivo immunoneutralization of circulating somatostatin with a high-affinity and high-capacity antiserum produced no significant change in the rate of amylase secretion. These results suggest that cholecystokinin secretion is tonically inhibited by somatostatin and that this effect is mediated by locally secreted (paracrine) but not by circulating somatostatin.

Amylases↗
PubMed1990

Somatostatin mediates bombesin inhibition of chloride secretion by rectal gland.

The function of bombesin-like peptide, a neurotransmitter present in nerve fibers of elasmobranch rectal glands, is unknown. Since the principal activity of the rectal gland is to secrete chloride, the effects of bombesin on chloride secretion and the role of somatostatin in this response was studied. Bombesin failed to stimulate secretion in rectal glands perfused in the basal state. When added to glands stimulated by a constant infusion of vasoactive intestinal peptide (VIP), bombesin (8 x 10(-7) M) reversibly inhibited chloride secretion by 56 +/- 9.7% and at the same time evoked a 10-fold increase in the liberation of somatostatin into the venous effluent. Inactivation of somatostatin by the addition of cysteamine partially suppressed the inhibitory effect of bombesin on glandular secretion. The effect of bombesin to reduce chloride secretion was completely prevented by the calcium channel blocker nifedipine, which inhibits neurotransmitter release. These results suggest that bombesin inhibits the effect of VIP to stimulate chloride secretion by releasing somatostatin from neurosecretory nerve terminals within the rectal gland.

Animals↗
PubMed1990

Prolactin circadian rhythm persists throughout lactation in women.

To determine whether the prolactin (PRL) circadian rhythm, with its characteristic nocturnal rise, persists during the hyperprolactinemia of lactation, PRL levels were analyzed in blood samples collected hourly for 24 h from 20 mothers, 4-46 months postpartum. The circadian rhythm of PRL persisted throughout lactation as manifested by: (1) significantly higher mean nighttime than daytime PRL levels in the whole sample, despite higher daytime nursing durations; (2) the distribution of zenith levels which most frequently occur between 23.00 and 07.00 h, when nursing duration is lowest, and which are almost absent between 07.00 and 23.00 h, when nursing duration is highest, and of nadir levels, which have an opposite pattern; (3) spontaneous PRL surges that are more frequent, longer, and of higher magnitude at night than during the day, and (4) the larger magnitude of suckling-induced PRL release from late afternoon through the night compared to the morning in some women. Our data suggest that the mechanisms responsible for the circadian rhythm in PRL secretion are relatively independent of the mechanisms of suckling-induced release. We propose that the nocturnal rise in PRL during lactation functions to ensure a robust milk supply during an extensive nonsuckling interval.

Circadian Rhythm↗
PubMed1990

Estrogen regulates the gene expression of vasoactive intestinal peptide in the anterior pituitary.

Vasoactive intestinal peptide (VIP), a prolactin (PRL)-releasing factor, has been shown to be synthesized within the anterior pituitary. To test the hypothesis that estrogens increase PRL secretion, at least in part, by stimulating VIP secretion, the concentrations of VIP, peptide histidine isoleucine (PHI) and prepro VIP mRNA were measured in the anterior pituitaries of oophorectomized rats treated with 17 beta-estradiol benzoate 25 micrograms/kg/day s.c. for 5 days. For comparison, changes in the hypothalamus were also measured. Estrogen treatment resulted in a marked increase in pituitary VIP content without detectable changes in PHI content, suggesting that estrogen may regulate differentially the enzymes involved in the posttranslational processing of the VIP prohormone. A VIP mRNA-transcript of about 1.7 kilobases was detected in all tissues studied, being most abundant in the cortex, less abundant in the hypothalamus and barely detectable in the untreated pituitary. Estrogen treatment resulted in an increase in VIP gene expression in the pituitary but not in the hypothalamus or cerebral cortex. This marked increase in prepro VIP mRNA rendered possible the demonstration in the estrogen-treated pituitary of a second VIP transcript of about 1.0 kilobase which was present in only very low quantities in the cortex and hypothalamus. We conclude that estrogen regulates the gene expression of VIP in the anterior pituitary. Changes in VIP secretion may contribute to the stimulatory effect of estrogen on PRL secretion.

Animals↗
PubMed1990

Melanotropin receptors demonstrated in situ in human melanoma.

Although some cultured human melanoma cell lines are responsive to melanotropins (melanocyte-stimulating hormones [MSH]), the prevalence and tissue distribution of MSH receptors in melanoma are unknown. We report here the use of an in situ binding technique to demonstrate specific MSH receptors in surgical specimens of human melanoma. The distribution and binding properties of specific MSH binding sites were determined by autoradiography and image analysis after incubation of frozen tumor tissue sections with a biologically active, radiolabeled analogue of alpha-MSH, [125I]iodo-Nle4, D-Phe7-alpha-MSH ([125I]NDP-MSH). In melanoma specimens from 11 patients, 3 showed high levels of specific binding, 5 showed low levels, and in 3 patients specific binding of [125I]NDP-MSH was not detectable. Specific MSH binding sites were present in melanoma cells, but not in adjacent connective or inflammatory tissues. Melanotropins, including alpha-MSH, NDP-MSH, and ACTH, inhibited [125I]NDP-MSH binding in a concentration-dependent manner, whereas unrelated peptides (somatostatin and substance P) did not. The apparent affinity of alpha-MSH for this binding site was in the nanomolar range (EC50 = 2 X 10(-9) M for inhibition of [125I]NDP-MSH binding in situ), similar to that recently described for the murine melanoma receptor. In one patient, analysis of multiple intratumor samples and tumors excised on three separate occasions revealed high levels of specific MSH binding in all samples. These results suggest that endogenous melanotropins may modulate the activities of human melanoma cells in vivo.

Autoradiography↗
PubMed1990

Intrinsic pituitary interleukin-1 beta is induced by bacterial lipopolysaccharide.

Using a specific antiserum recognizing recombinant rat interleukin-1 beta (IL-1 beta), immunoreactive material was localized to cytoplasmic granules in anterior pituitary endocrine cells and colocalized with TSH in thyrotropes. Authenticity was established by Northern blot hybridization using a specific rat IL-1 beta cRNA probe, revealing a 1.8-kilobase mRNA identical to that in the spleen. The marked increase in anterior pituitary IL-1 beta message after the administration of bacterial lipopolysaccharide, raises the possibility that IL-1 beta may be involved in paracrine or autocrine regulation of pituitary function during infectious challenge.

Animals↗
PubMed1989

Pantethine, a somatostatin depleting agent, increases food intake in rats.

During the course of studies of the effects of pantethine, a cysteamine precursor known to deplete tissue concentration of immunoreactive somatostatin, we observed that the subject rats continued to eat despite marked distension of the stomach. To determine whether this effect was caused by drug-altered food intake, we have measured food and water intake in pantethine-injected rats in the fed and fasting state. In three separate experiments, rats allowed free access to food until the morning of study showed significant increased food intake accompanied by an increased stomach content (at 4 hr) of both food and water following the IP injection of pantethine. In one experiment, intake at 3 hours was 0.60 g/100 g b.wt. (pantethine dose 0.74 g/kg b.wt.) and 0.64 g/100 g b.wt. (pantethine dose 1.47 g/kg b.wt.) compared with 0.24 g/100 g b.wt. in saline-treated animals (p less than 0.05). In contrast, pantethine, 1.47 g/kg b.wt., when administered to overnight-fasted rats, significantly inhibited food intake (3-hr intake 1.54 +/- 0.16 g/100 g b.wt. in rats injected with pantethine 1.47 g/kg b.wt. as compared with 3.3 +/- 0.21 g/100 g b.wt. in saline-injected controls). The intake-stimulating effect of pantethine in ad lib-fed rats was not demonstrable when the drug was administered shortly before the "lights out"-induced feeding at night. These findings indicate that pantethine, a cysteamine precursor, stimulates food intake in satiated rats, depending upon the stage of circadian rhythm, but is inhibitory to intake in fasted animals. We postulate that the effects are mediated directly or indirectly through the disinhibition of central appetite-regulating somatostatinergic pathways but, since cysteamine also inhibits dopamine-beta-hydroxylase, an effect on depletion of appetite-regulating central catecholamines cannot be excluded.

Animals↗
PubMed1989

Pituitary vasoactive intestinal peptide regulates prolactin secretion in the hypothyroid rat.

In this study, we demonstrated that the cell content and basal secretion of vasoactive intestinal peptide (VIP) in primary rat pituitary cell cultures were increased in hypothyroidism. VIP release from hypothyroid pituitary cells in vitro was stimulated by thyrotropin releasing hormone (TRH 10(-8) to 10(-6) M) and growth hormone (GH)-releasing hormone (GHRH 10(-9) to 10(-8) M) but not by corticotropin-releasing hormone or luteinizing hormone-releasing hormone in concentrations up to 10(-6) M. In the presence of anti-VIP antisera, there was a significant decrease in basal prolactin secretion from cultured hypothyroid pituitary cells (p less than 0.005) indicating that VIP exerts a tonic stimulatory effect on prolactin (PRL) secretion. The increment in PRL secretion following TRH was not affected by exposure to anti-VIP indicating that PRL release after TRH is not mediated by VIP at the pituitary level. In contrast to changes in PRL, exposure to anti-VIP had no effect on basal GH secretion, indicating that the PRL changes are hormone specific. Similarly, GHRH-induced GH release was unaffected by VIP immunoneutralization.

Animals↗