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PubMed1987

[Contribution of immunocytochemistry to the study of the development of neuroglandular peptidergic systems in the human fetal hypothalamus].

Immunohistochemistry makes possible the in situ detection of neuropeptides in the cell bodies were they are synthesized, in the fibers that carry them, and in endings. Immunohistochemistry appears necessary to identify and map peptidergic neurons and to study their ontogeny. From 1975, we have carried the immunohistochemical study of several hypothalamic neuronal populations in the human fetus: LH-RH (1976), somatostatin (1977), pro-opiocortin (1978), vasopressin and oxytocin (1979), corticoliberin (1982), somatocrinin (1983), and hypothalamic neurons containing an unidentified peptide (1984). Comparative ontogenetical studies have also been performed in rats.

Animals↗
PubMed1988

[Monoclonal antibodies to alpha-endorphin effective in immunohistochemistry and immunoblotting].

Four mouse monoclonal antibodies (E11, A8, F8, H5) to alpha-endorphin have been produced. The antibodies bind 12.5, 20.6, 9.6, 6.6% of 125I-beta-endorphin and 35.5, 15.1, 12.8, 12.2% of 125I-gamma-endorphin; the binding of 125I-alpha-endorphin being taken for 100%. The binding of antibodies E11, A8, F8 and H5 to 125I-alpha-endorphin was 50% inhibited by unlabeled ligand in concentrations 5, 50, 30 and 35 nM respectively. Using tissue sections of rat pituitary it was shown that antibody E11 can be used for the localization of endorphin producing cells by immunofluorescence. The antibodies F8 and H5 effectively detected endorphin precursor proopiomelanocortin by immunoblotting.

Animals↗
PubMed1988

Expression and dexamethasone regulation of the human corticotropin-releasing hormone gene in a mouse anterior pituitary cell line.

The factors controlling the expression of corticotropin-releasing hormone (CRH), a hypothalamic neuropeptide involved in the regulation of ACTH secretion, are poorly understood partly because a suitable in vitro model is lacking. To study the regulation of CRH gene expression, an 8-kilobase (kb) DNA fragment containing the entire human CRH gene as well as approximately 6 kb of 5' sequence and 0.8 kb of 3' sequence was isolated from a lambda Charon 4A human genomic library and introduced into a mouse anterior pituitary cell line, AtT-20, by CaPO4 transfection with a neomycin-selectable marker. Approximately 10% of the neomycin-resistant lines stably expressed the CRH gene and secreted radioimmunoassay-detectable CRH into culture media at levels greater than 100 pg/ml. By Southern blot analysis the 8-kb DNA fragment containing the CRH gene had been incorporated intact into the AtT-20 genome. In each CRH-producing strain, but not in the parent AtT-20 cell line, we detected by Northern blot analysis an RNA species that hybridized to two radioactive cRNA probes specific for either the 5' or 3' portion of CRH mRNA, and that co-migrated with placental CRH mRNA. Dexamethasone treatment for 24-96 h caused a specific decrease in CRH mRNA and peptide levels of 40-50% in the five CRH-producing cell lines with half-maximal suppression at approximately 10(-9) M dexamethasone, indicating that CRH gene expression is negatively regulated by glucocorticoids. Thus, we have established an in vitro model suitable for studying in detail those cis- and trans-acting factors which regulate CRH gene expression.

Animals↗
PubMed1985

Endorphins and exercise in females: possible connection with reproductive dysfunction.

Currently available measurements of beta-endorphin and beta-lipotropin in exercising women are in excellent agreement and indicate a 2-3 fold increase over basal levels. Possible effects of exercise upon the transfer of endorphins from the peripheral circulation to the brain are examined, and evidence is presented that suggests the occurrence of a concomitant exercise-related increase of endorphins in both humoral and central nervous system compartments. Steady-state measurements of circulating luteinizing hormone and follicle-stimulating hormone levels in oligo-amenorrheic athletes, on the other hand, do not agree. It is felt that the lack of consensus may be attributable partly to technical inadequacies and partly to lack of awareness of the need for frequent sampling. The bulk of the findings suggest a tendency for luteinizing hormone levels to be low and follicle-stimulating hormone levels to be normal or low, a pattern compatible with repeated activation of the CRH-ACTH-POMC system as a result of exercise.

Adrenocorticotropic Hormone↗
PubMed1985

DNA restriction fragment analysis of the proopiomelanocortin gene in schizophrenia and bipolar disorders.

The method of DNA restriction fragment analysis using gene probes for the proopiomelanocortin (POMC) gene was employed to detect possible molecular variation in the POMC gene in schizophrenia and bipolar illness. No gross structural abnormalities in restriction fragments were observed with the set of restriction enzymes used. Two allelic restriction sites were observed giving rise to fragment length polymorphisms. One of these is a new polymorphism, not previously reported, which will be of value as a linkage marker. The associations between the two DNA polymorphisms that are closely linked to the POMC gene and both schizophrenia and bipolar disorder were investigated. No association was found, thus adding weight to the evidence that there are no alterations in the POMC gene in schizophrenia and bipolar illness.

Base Sequence↗
PubMed1985

[Endogenous opioids].

The discovery of the opioid receptors and their corresponding ligands, the opioid peptides, is of fundamental importance as regards our understanding of a variety of functional mechanisms in the central and peripheral nervous system. This review considers the distribution of the multiple opioid peptides within the organism as well as their tissue-specific enzymatic processing. These parameters differ considerably between species. The multiple opioid peptides are paralleled by multiple opioid receptors. These opioid systems affect a broad spectrum of functions, such as behaviour, pain perception, the cardiovascular system, respiration, appetite, gut motility and secretion, water- and electrolyte balance and the complex field of endocrine mechanisms. The task of future pharmacological research is to study these functions by means of more selective opioid agonists and antagonists. An awareness of our present knowledge and of probable findings to come suggests novel therapeutic possibilities in the field of veterinary science.

Animals↗
PubMed1985

Reflex responses to reductions in functioning renal mass.

Both acute unilateral nephrectomy (AUN) and unilateral ureteral obstruction (UUO) result in an acute increase in cation excretion from the contralateral kidney. AUN results in reflex changes in systemic hemodynamics owing to an acute and transient increase in arterial pressure that activates carotid sinus baroreceptors and constitutes an afferent limb in the reflex; hemodynamic adjustments and increased cation excretion result. The reflex involves participation of the endogenous opioid system, with receptors located primarily in the central nervous system, and requires intact pituitary function because both hypophysectomy and pretreatment with large doses of dexamethasone prevent the postnephrectomy natriuresis. The natriuresis is closely correlated with an increase in the plasma concentration of the NH2-terminal fragment of the pituitary peptide precursor molecule proopiomelanocortin, which suggests that such a peptide could participate directly or indirectly in the postnephrectomy natriuresis. Surgical denervation of either the ipsilateral or the contralateral kidney markedly alters the response to AUN, which prevents the natriuresis and blunts the kaliuresis, and indicates a role for renal neural reflexes. Renorenal reflex pathways also mediate the response of the contralateral kidney to UUO, because denervation of either the ipsilateral (obstructed) or the contralateral kidney abolishes both the natriuresis and kaliuresis usually seen after UUO. This reflex also involves the endogenous opioid system, for it does not occur in rats receiving an i.v. infusion of the opiate receptor antagonist naloxone.

Adaptation, Physiological↗
PubMed1985

Hyperpigmentation, vitiligo, and Addison's disease.

Addison's disease is an uncommon disorder whose dermatologic manifestations range from vitiligo to hyperpigmentation. The association of adrenal autoantibodies and vitiligo has made the latter a possible cutaneous marker for an autoimmune cause. The other cutaneous marker, hyperpigmentation, is now more clearly understood on the basis of a prohormone common to both adrenocorticotrophic hormone (ACTH) and melanocyte-stimulating hormone (MSH).

Addison Disease↗
PubMedDate not supplied

Progress in chronophysiology of peptide hormones with emphasis on clinical application of analogues.

It is now established that peptide hormones are among the most versatile substances involved in intercellular communications. By substitution of one or more natural aminoacids, numerous peptide analogues have been synthesized with increased duration of action and potency with respect to endogenous hormones. Most of these effects are programmable as a function of dose and timing of administration. Not surprisingly, the chronobiological use of hormone-related peptides may represent a valuable tool providing new approaches to diagnosis and therapy of different disease states. One pertinent example of the applicability of peptide analogues refers to a new short chain ACTH analogue (ACTH 1-17; Synchrodyn) that has been proved useful to reset or preset the rhythmic ordering of a number of functions and to provide, furthermore, information about specific pathogenetic mechanisms and/or subtle alterations of the adrenal function. A large body of evidence indicates that the same concepts apply to most actions of the gonadotropin-releasing hormone (LH-RH) related analogues. The efficacy of the so-called low-dose pulsatile LH-RH therapy in the management of hypogonadotropic hypogonadism and of some forms of infertility seems now established. The use of potent analogues is providing new approaches to the heretofore unsuccessful therapies in a number of disease conditions. In this light, chronoendocrinology and biotechnology have to be mutually supporting. Novel clinical applications are expected from the emerging use of portable instrumentation designed to record endogenous data and/or to deliver drugs according to a temporal program.

Adrenocorticotropic Hormone↗
PubMed1985

Corticotropin releasing factor increases proopiomelanocortin messenger RNA in mouse anterior pituitary tumor cells.

The ability of corticotropin releasing factor (CRF) to stimulate adrenocorticotropin (ACTH) synthesis in corticotrophs was assessed by measuring total cell content of ACTH and the levels of proopiomelanocortin (POMC) mRNA in a cloned tumor cell line of the mouse anterior pituitary (AtT-20/D16-16). CRF treatment caused a time-dependent increase in POMC mRNA levels (measured using a hybridization technique) as well as elevating total ACTH content in AtT-20 cells. The increase in POMC mRNA levels preceded changes in ACTH content and slowly returned toward control levels after CRF withdrawal. The rise in POMC mRNA levels following CRF stimulation appeared to be specific since beta-actin mRNA levels were not affected by CRF treatment. Both 8-bromo-cAMP and phorbol ester increased POMC mRNA levels in AtT-20 cells, suggesting that CRF may act through different protein kinases to regulate the POMC gene. CRF appears to activate the POMC gene since treatment of the AtT-20 cells with the peptide increased the levels of an RNA species in the nuclei having the expected molecular weight of the transcript of the POMC gene. The results indicate that continued exposure of corticotrophs to CRF induces long term increases in the ACTH synthetic capacity of those cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1985

Natriuretic peptides derived from pro-opiocortin.

Natriuresis in response to hypertonicity, volume loads, or high sodium diets has been proposed to be mediated by the release of a humoral factor(s), and controlled by the central nervous system. We have determined that the natriuretic activity of ACTH or alpha MSH resides in a common sequence, ACTH(4-10)/alpha MSH(4-10). Steric restriction of this peptide by replacement of an L-Phe residue with a D-Phe produced a superagonist. Gamma-2 MSH is a peptide derived from the 16K N-terminus of pro-opiocortin, which contains an ACTH(4-10)-like sequence. The natriuretic effect of gamma-2 MSH was maximal between 0.64 pmole to 64 pmole. Doses greater than 128 pmole produced no significant effects on renal sodium excretion. The regulated release of gamma MSH peptides may contribute to CNS regulation of renal sodium excretion.

Adrenocorticotropic Hormone↗
PubMed1986

Characterization of pro-ACTH/endorphin-derived peptides in rat hypothalamus.

The proteolytic processing pattern of pro-ACTH/endorphin in rat hypothalamus is similar to the pattern in the pars intermedia; peptides the size of beta-endorphin, gamma-lipotropin (gamma-LPH), corticotropin-like intermediate lobe peptide (CLIP), alpha-melanotropin (gamma-MSH), joining peptide, and glycosylated gamma 3-MSH all represent predominant end products. Equimolar amounts of beta-endorphin-, alpha-MSH-, CLIP-, gamma-LPH-, and joining peptide-related immunoreactivity are found in hypothalamic extracts (approximately 3 pmol per hypothalamus). Although the proteolytic processing pattern in the hypothalamus is similar to that in the pars intermedia, a tissue-specific posttranslational processing pattern was detected. Ion-exchange analysis of beta-endorphin-sized immunoreactive material from hypothalamic extracts resolves three major forms, corresponding to beta-endorphin(1-31), beta-endorphin(1-27), and beta-endorphin(1-26). The alpha-N-acetylated forms of endorphin represent less than 10% of the total beta-endorphin immunoreactivity. Analyses of hypothalamic alpha-MSH-sized molecules with acetyl- and amide-directed alpha-MSH antisera suggest that hypothalamic alpha-MSH is fully amidated, but largely not alpha-N-acetylated. Fractionation by reverse-phase high-performance liquid chromatography (HPLC) confirms that greater than 85% of the alpha-MSH immunoreactivity corresponds to ACTH(1-13)NH2 or its sulfoxide, and less than 10% corresponds to alpha-MSH [alpha-N-acetyl-ACTH(1-13)NH2] or its sulfoxide. Isoelectric focusing demonstrates that 83-93% of hypothalamic CLIP is phosphorylated. Isoelectric focusing suggests that the majority of the hypothalamic gamma-LPH-sized immunoreactive material is indistinguishable from gamma-LPH synthesized by pituitary melanotropes. The minor extent of alpha-N-acetylation of alpha-MSH and beta-endorphin, the limited carboxyl-terminal proteolysis of beta-endorphin, and the extensive phosphorylation of CLIP represent major differences between the posttranslational processing patterns of pro-ACTH/endorphin in the hypothalamus and pars intermedia.

Acetylation↗
PubMed1986

[Neurochemical characteristics of opioid peptides].

Opioid peptides seem to be involved in an increasing number of cerebral functions. It appears from the most recent studies that these peptides are divided into three families: pro-opio-melanocortin, pro-enkephalin and prodynorphin. Unlike conventional neurotransmitters, these substances are fraught with extremely complex problems of specific biosynthesis and degradation. Finally, the multiplicity of opiate receptors and the search for specific endogenous or synthetic ligands raise major fundamental questions concerning the clinical relevance of studies performed on opioid peptides.

Aminopeptidases↗