Hypoprolactinemic Action of Calcitonin and the Tuberoinfundibular Dopaminergic System

Abstract: The effects of calcitonin on neurochemical parameters related to the tuberoinfundibular dopaminergic system have been investigated in an attempt to elucidate how calcitonin decreases serum prolactin levels. Intracerebroventricular human or salmon calcitonin injection decreases serum prolactin, medial basal hypothalamic dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) and hypophysial DA and increases hypophysial DOPAC. Results suggest that calcitonin may decrease prolactin secretion via the tuberoinfundibular dopaminergic system.     

The vascularization of the neural stalk and the pars nervosa of the hypophysis in the toad,Bufo bufo (L.) (amphibia,anura)

The angioarchitecture of the neural stalk and the encephaloposthypophysial portal system of the hypophysis of the toad, Bufo bufo (L.), was studied using three different methods. The neural stalk is mainly supplied by branches of the arteria infundibularis superficialis which form a widemeshed vascular network. Dorsally this network continues into the plexus of the pars nervosa. The vascularization of the pars nervosa is made up of the encephalo-posthypophysial portal system. This portal system consists of a hypothalamic branch (=portion), a mesencephalic and a mesencephalicbulbar branch (=portion). The hypothalamic branch was found to drain the pars ventralis of the tuber cinereum as well as more dorsal regions of the diencephalon. The mesencephalic-bulbar trunk enters the hypothalamic branch. The resulting common stem of the encephalo-posthypophysial portal vein the curves around the retroinfundibular communicating artery, crosses its ventral side and runs caudally. The secondary capillary plexus of the pars nervosa is characterized by well defined capillary plexus of the pars nervosa is characterized by well defined capillary networks which are located at the periphery of the parenchyma of the pars nervosa, thus forming a rostral, dorsal and ventro-caudal net. The central region of the parenchyma of the pars nervosa is supplied only by main branches of the encephalo-postpophysial portal vein. The venous drainage of the pars nervosa is via the vena hypophysea transversa.     

Types cellulaires et étapes de la différenciation de l'adénohypophyse chez l'embryon de roussette (Scyllium canicula,chondrichthyens)

Résumé L'identification et la répartition des cellules endocrines dans l'ébauche adénohypophysaire de Scyllium canicula, et la chronologie de la différenciation cellulaire et de l'histogenèse de cette glande ont fait l'objet de ce travail.Plus nettement encore que chez l'adulte on démontre qu'il y a quatre populations de cellules hormonogènes, localisées chacune dans un lobe différent. Les grains de sécrétion des cellules du lobe rostral sont glycoprotidiques et ont un diamètre modal, de 170 nm, ceux du lobe médian, de la même taille, sont protidiques ou polypeptidiques. Les gros granules du lobe neuro-intermédiaire (diamètre modal 260 nm) sont glycoprotidiques, les petits granules du lobe ventral (diamètre modal 120 nm), protidiques au polypeptidiques.Au stade 10 mm, les cellules de la poche de Rathke sont différenciées de celles de l'épithélium stomodéal par la présence d'inclusions énigmatiques, les godd bodies de Schechter.Au stade 35 mm les cellules des noyaux préoptiques et du tuber comportent des grains de neurosécrétion, de même diamètre, variant autour de 100 nm. A ce même stade, des granules apparaissent simultanément dans les quatre lobes de l'hypophyse, notamment dans le lobe neuro-intermédiaire où aucune fibre neurosécrétrice n'est encore décelée. L'innervation directe des cellules endocrines de ce lobe ne s'effectue qu'au stade 45 mm et s'accompagne de modifications de la taille des granules.La fin du développement embryonnaire se caractérise par une charge de plus en plus importante des cellules endocrines, en granules.

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Cellular types and differentiation of Scyllium canicula embryo adenohypophysis (chondrichthyes)Electron microscopical investigation

Summary The identification and distribution of endocrine cells in embryonic adenohypophysis of Seyllium canicula, and chronology of cellular differentiation and histogenesis of this gland have been investigated in this work.More clearly than in the adult, the presence of four populations of endocrine cells, each one located in a different lobe, is demonstrated. Secretion granules of rostral lobe cells are glycoprotidic, their modal diameter is 170 nm; median lobe ones, of same dimensions, are protidic or polypeptidic. The nemo-intermediate lobe big granules (modal diameter: 260 nm) are glycoprotidic, the ventral lobe small granules (modal diameter: 120 nm), protidic or polypeptidic.At stage 10 mm, Rathke's pouch cells are recognized from stomodeal epithelium by enigmatic inclusions, the odd bodies of Schechter.At stage 35 mm, preoptic and tuberal nucleus cells include neurosecretory granules of same diameter varying about 100 nm. At this same stage, granules appear simultaneously in the four hypophyseal lobes, including the neuro-intermediate lobe where no neurosecretory fiber is present. Direct innervation of endocrine cells of this lobe is accomplished at stage 45 mm and is accompanied by changes of granules dimensions. The end of embryonic development is characterized by increasing granular load of endocrine cells.

Travail effectué avec l'aide du C.N.R.S. (Bénéficiaire: J. Mellinger). Collaborateurs techniques: Meile F. Wrisez et Mme P. Iglesias.     

The rostral zone of the intermediate lobe of the mouse hypophysis,a zone of particular concentration of corticotrophic cells

Summary The rostral zone of the intermediate lobe of the mouse hypophysis can clearly be distinguished from the other lobes of the adenohypophysis, especially from the pars tuberalis and the remainder of the intermediate lobe. It consists almost exclusively of corticotrophic cells which show reactive changes after adrenalectomy. The hypophysial stalk is entirely surrounded by this zone; laterally it forms large cell aggregations which extend dorsally as thin cell strands. The corticotrophs are also found within the hypophysial stalk which they invade along the blood vessels; frequently they are dispersed among the typical cells of the intermediate lobe, especially along the neural lobe and the hypophysial cleft.On leave from the Department of Veterinary Anatomy, University of Missouri, Columbia, Mo., U.S.A.     

Corticotrophic cells in the rostral zone of the pars intermedia and in the adjacent neurohypophysis of the rat and mouse

Summary In the mouse, the rostral zone of the pars intermedia is almost exclusively composed of typical corticotrophic cells. They are located around and even within the neural stalk, at the level of transition between stalk and neural lobe. In the rat, the corticotrophic cells of the rostral zone are found in scattered islets among the MSH producing cells, and also in the neural lobe. In both the rat and mouse, these cells are in direct contact with various types of nerve terminals. Synaptoid contacts with aminergic and neurosecretory nerve fibers are observed. Furthermore they are also closely related to the hypophysial portal vessels. Following adrenalectomy, the cells located in the neurohypophysis always react more intensely than tose in the rostral zone. The functional significance of these corticotrophic cells which are subject to both humoral and neural regulation remains as yet hypothetical. Their participation in neurogenic stress response seems probable.     

Fine structure of pars neuro-intermedia of the loach,Misgurnus fossilis L.

Summary Two types of glandular cells are present in the pars intermedia of the loach, Misgurnus fossilis. Basophils are characterized by the presence in their cytoplasm of numerous secretory granules containing electron-dense and homogeneous material and by scarce endoplasmic reticulum. Weak acidophils contain in their cytoplasm abundant endoplasmic reticulum and numerous granules of different electron densities.The distal part of the neurohypophysis is composed of several types of neurosecretory axons, strongly branched pituicytes, numerous capillaries, and connective tissue elements. The axon terminals form the neuroglandular, neurovascular and neurointerstitial contacts. Some axon terminals are closely apposed to the basement membrane separating neurohypophysis from meta-adenohypophysis. At points of absence of continuity of this membrane, some neurosecretory axons become directly contiguous with cytoplasmic membranes of the intermedia cells.The investigation was partly supported by a research grant from the Zoological Committee of the Polish Academy of Sciences.     

Détection par immunofluorescence des cellules corticotropes et mélanotropes dans l'hypophyse de la grenouille,Rana temporaria L., au cours du développément

Summary During the embryonic and larval developmental stages of the frog, Rana temporaria L, anti- 1–24, 17–39 corticotropine, and MSH antibodies were used to define, with immunofluorescence technique, the appearence of corticotropic and melanotropic cells.A very small number of fluorescent corticotropic cells appears for the first time during the embryonic stage (10 mm), just before the differentiation of the pars intermedia. The cells are small, their large nucleus is surrounded by a fine rim of fluorescent cytoplasm.During premetamorphic stage, the anti-ACTH antibodies (anti- 1–24 and anti- 17–39 corticotropine) reveal more fluorescent cells in the whole pars distalis. The pars intermedia cells can also be visualized by both antisera.At the end of prometamorphosis and during climax the corticotropic cells show a more precise localization. As in adult frog pars distalis, they are concentrated in the rostral half of the lobe. With the same technique anti- and MSH antibodies reveal only the cells of the pars intermedia. No other cell type of the pars distalis reacts with these antibodies. This technique has the advantage to show that the ACTH and the MSH cells appear very early during the embryonic life.

     

Mise en évidence par immunofluorescence des cellules à hormones glycoprotidiques dans l'hypophyse d'un Rongeur d'Iran,Ellobius lutescens (Th): cellules gonadotropes et cellules thyréotropes

Résumé Les cellules à hormones glycoprotidiques (thyréotropes et gonadotropes) ont pu être indentifiées grâce aux réactions d'immunofluorescence qu'elles donnent avec des anticorps préparés à partir de LH et FSH ovine, de HCG et de PMSG, ainsi que de TSH bovine. Tandis que l'anticorps anti TSH brut révèle la totalité des cellules à hormones glycoprotidiques tout comme l'anticorps anti HCG, l'anticorps anti TSH saturé par LH ne laisse subsister la fluorescence qu'au niveau des grandes cellules anguleuses (Bleu Alcian et AF positives) qui fixent l'anticorps rendu ainsi spécifique pour TSH. Les deux autres types de cellules glycoprotidiques (PAS positives), qui présentent un dimorphisme très accentué, réagissent positivement avec l'anticorps anti LH ainsi qu'avec l'anticorps anti FSH: nous pouvons donc attribuer la fonction gonadotrope à ces deux catégories cellulaires sans qu'il soit cependant possible d'y distinguer les secrétions de type LH ou FSH.

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Immunofluorescent demonstration of gonadotrophic and thyrotrophic cells in the hypophysis of Ellobius lutescens (Th.), an iranian rodent

Summary Glycoprotein-containing cells (thyrotrophic and gonadotrophic cells) have been identified by immunofluorescence reactions, with antibodies to ovine LH and FSH, HCG, PMSG, and bovine TSH, in the hypophysis of the rodent Ellobius lutescens. Whereas raw anti-TSH antibody (as well as anti-HCG antibody) gives a positive reaction with all glycoprotein-containing cells, LH- saturated anti-TSH antibody fluoresces only at the site of large, angular cells (Alcian Blue- and Aldehyde Fuchsin-positive) which retain the antibody thus rendered TSH-specific. The two other types of glycoprotein (PAS-positive) cells, which exhibit a marked dimorphism, give a positive reaction with anti-LH and anti-FSH antibodies; thus we can attribute gonadotrophic functions of these two cell-types although we cannot discriminate between LH or FSH secretion.