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(physical chemistry) a sample of matter in which substances in different phases are in equilibrium; "in a static system oil cannot be replaced by water on a surface"; "a system generating hydrogen peroxide"
instrumentality that combines interrelated interacting artifacts designed to work as a coherent entity; "he bought a new stereo system"; "the system consists of a motor and a small computer"
a group of independent but interrelated elements comprising a unified whole; "a vast system of production and distribution and consumption keep the country going" (同)scheme
a complex of methods or rules governing behavior; "they have to operate under a system they oppose"; "that language has a complex system for indicating gender" (同)system of rules
a group of physiologically or anatomically related organs or parts; "the body has a system of organs for digestion"
a procedure or process for obtaining an objective; "they had to devise a system that did not depend on cooperation"
the living body considered as made up of interdependent components forming a unified whole; "exercise helped him get the alcohol out of his system"
of or relating to the hypophysis (同)hypophysial

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〈C〉(関連した部分から成る)『体系』,系統,組織[網],装置 / 〈C〉(教育・政治などの)『制度』,機構;《the~》体制 / 〈C〉(思想・学問などの)『体系』,学説 / 〈C〉(…の)『方法』,方式,やり方《+of doing》 / 〈U〉正しい方針(筋道,順序) / 〈U〉《the~》(身体の)組織,系統 / 〈U〉《the~,one's~》身体,全身

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/09/15 19:57:15」(JST)

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The hypophyseal portal system is a system of blood vessels in the brain that connects the hypothalamus with the anterior pituitary. Its main function is the transport and exchange of hormones to allow a fast communication between both glands. The fenestrated structure of capillaries in the hypophyseal portal system facilitates a rapid exchange between the hypothalamus and the pituitary, with only a small amount of hormones needed to stimulate an accurate effect in the respective target organs in the body.

Peptides released near the median eminence from hypothalamic nuclei are transported to the anterior pituitary, where they apply their effects. Branches from the internal carotid artery provide the blood supply to the pituitary. The superior hypophyseal arteries form the primary capillary plexus that supplies blood to the median eminence. From this capillary system, the blood is drained in hypophyseal portal veins into the secondary plexus. The peptides released at the median eminence enter the primary plexus capillaries. From there, they are transported to the anterior pituitary via hypophyseal portal veins to the secondary plexus. The secondary plexus is a network of fenestrated sinusoid capillaries that provide blood to the anterior pituitary. The cells of the anterior pituitary express specific G protein-coupled receptors that bind to the neuropeptides, activating intracellular second messenger cascades that produce the release of anterior pituitary hormones.^[1]

Structure

The blood supply and direction of flow in the hypophyseal portal system has been studied over several years on human cadaver specimens with injection methods. Results of these studies have shown that the neural hypophyseal stalk receives arterial blood from ascending and descending infundibular branches, coming from the arteries of the superior hypophyseal arterial system. Small ascending vessels arising from the anastomoses that connect the upper with the lower hypophyseal arterial system also supply blood to hypophyseal vessels. The majority of these branches penetrate into the neural tissue to break up into capillaries for rapid hormone exchange.^[1]

Development

Proper hormone secretion in the developing fetus is crucial for its growth in the womb of the mother. In order to allow a controlled hormone secretion in the developing organs of the fetus, stimulating hormones must be exchanged in the regulating structures in the brain in early stages of the development. Hormone-exchanging blood vessels between the hypothalamus and the pituitary gland, similar to those of the hypophyseal portal system, can be observed in early developmental stages of the fetus. A study performed on ovine fetuses, about 48-67 days of gestation, showed extensive and very well-developed capillary connections between the median eminence, the pituitary stalk, and the pituitary gland. In some of the fetuses, portal capillary loops had penetrated into the median eminence. These findings suggest that, in the ovine fetus, hypothalamic releasing hormones can be transported directly via a portal vascular way to the pituitary gland that develops as early as 45 days of gestation. These experimental results give evidence for an early development of what is later the fully developed hypophysial portal system. 4,5,6

Clinical significance

Over- or under-function as well as insufficiencies of the hypothalamus or the pituitary gland can cause a negative effect on the ability of the hypophyseal portal system to exchange hormones between both structures rapidly. This can have major effects on the respective target glands, making it impossible for them to carry out their functions properly. Occlusions and other issues in the blood vessels of the hypophysial portal system can also cause complications in the exchange of hormones between the hypothalamus and the pituitary gland.

References

^ ^a ^b Molina, Patricia.E. (2010). Endocrine Physiology. Lange. (3, p. 31). ISBN 978-0-07-161301-9.

External links

http://www.llu.edu/llu/medicine/anatomy/glossary/ans102_109.html#Q103
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/anatomy.html

UpToDate Contents

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English Journal

P2X7 receptors in neurohypophysial terminals: evidence for their role in arginine-vasopressin secretion.

Cuadra AE1, Custer EE, Bosworth EL, Lemos JR.Author information 1Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts.AbstractArginine-vasopressin (AVP) plays a major role in maintaining cardiovascular function and related pathologies. The mechanism involved in its release into the circulation is complex and highly regulated. Recent work has implicated the purinergic receptor, P2X7R, in a role for catecholamine-enhanced AVP release in the rat hypothalamic-neurohypophysial (NH) system. However, the site of P2X7R action in this endocrine system, and whether or not it directly mediates release in secretory neurons have not been determined. We hypothesized that the P2X7R is expressed and mediates AVP release in NH terminals. P2X7R function was first examined by patch-clamp recordings in isolated NH terminals. Results revealed that subpopulations of isolated terminals displayed either high ATP-sensitivity or low ATP-sensitivity, the latter of which was characteristic of the rat P2X7R. Additional recordings showed that terminals showing sensitivity to the P2X7R-selective agonist, BzATP, were further inhibited by P2X7R selective antagonists, AZ10606120 and brilliant blue-G. In confocal micrographs from tissue sections and isolated terminals of the NH P2X7R-immunoreactivity was found to be localized in plasma membranes. Lastly, the role of P2X7R on AVP release was tested. Our results showed that BzATP evoked sustained AVP release in NH terminals, which was inhibited by AZ10606120. Taken together, our data lead us to conclude that the P2X7R is expressed in NH terminals and corroborates its role in AVP secretion.
Journal of cellular physiology.J Cell Physiol.2014 Mar;229(3):333-42. doi: 10.1002/jcp.24453.
Arginine-vasopressin (AVP) plays a major role in maintaining cardiovascular function and related pathologies. The mechanism involved in its release into the circulation is complex and highly regulated. Recent work has implicated the purinergic receptor, P2X7R, in a role for catecholamine-enhanced AV
PMID 24037803

Brain Endothelial Cells Control Fertility through Ovarian-Steroid-Dependent Release of Semaphorin 3A.

Giacobini P1, Parkash J1, Campagne C1, Messina A1, Casoni F1, Vanacker C1, Langlet F1, Hobo B2, Cagnoni G3, Gallet S1, Hanchate NK1, Mazur D1, Taniguchi M4, Mazzone M5, Verhaagen J2, Ciofi P6, Bouret SG7, Tamagnone L3, Prevot V1.Author information 1INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France; UDSL, School of Medicine, Place de Verdun, Lille, France; Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France.2Netherlands institute for Neuroscience, Amsterdam, The Netherlands; Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.3Candiolo Cancer Institute - FPO (IRCCS) and University of Torino, Department of Oncology, Candiolo, Italy.4Research Institute for Frontier Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan.5Versalius Research Center, VIB, Laboratory of Molecular Oncology and Angiogenesis, Leuven, Belgium; KU Keuven, Versalius Research Center, Leuven, Belgium.6INSERM, Neurocentre Magendie, U862, Université de Bordeaux, Bordeaux, France.7INSERM, Jean-Pierre Aubert Research Center, U837, Development and Plasticity of the Postnatal Brain, Lille, France; UDSL, School of Medicine, Place de Verdun, Lille, France; Institut de Médecine Prédictive et de Recherche Thérapeutique, IFR114, Lille, France; The Saban Research Institute, Childrens Hospital Los Angeles, University of Southern California, Los Angeles, California, United States of America.AbstractNeuropilin-1 (Nrp1) guides the development of the nervous and vascular systems, but its role in the mature brain remains to be explored. Here we report that the expression of the 65 kDa isoform of Sema3A, the ligand of Nrp1, by adult vascular endothelial cells, is regulated during the ovarian cycle and promotes axonal sprouting in hypothalamic neurons secreting gonadotropin-releasing hormone (GnRH), the neuropeptide controlling reproduction. Both the inhibition of Sema3A/Nrp1 signaling and the conditional deletion of Nrp1 in GnRH neurons counteract Sema3A-induced axonal sprouting. Furthermore, the localized intracerebral infusion of Nrp1- or Sema3A-neutralizing antibodies in vivo disrupts the ovarian cycle. Finally, the selective neutralization of endothelial-cell Sema3A signaling in adult Sema3aloxP/loxP mice by the intravenous injection of the recombinant TAT-Cre protein alters the amplitude of the preovulatory luteinizing hormone surge, likely by perturbing GnRH release into the hypothalamo-hypophyseal portal system. Our results identify a previously unknown function for 65 kDa Sema3A-Nrp1 signaling in the induction of axonal growth, and raise the possibility that endothelial cells actively participate in synaptic plasticity in specific functional domains of the adult central nervous system, thus controlling key physiological functions such as reproduction.
PLoS biology.PLoS Biol.2014 Mar 11;12(3):e1001808. doi: 10.1371/journal.pbio.1001808. eCollection 2014.
Neuropilin-1 (Nrp1) guides the development of the nervous and vascular systems, but its role in the mature brain remains to be explored. Here we report that the expression of the 65 kDa isoform of Sema3A, the ligand of Nrp1, by adult vascular endothelial cells, is regulated during the ovarian cycle
PMID 24618750

Role of cortactin in dynamic actin remodeling events in gonadotrope cells.

Navratil AM1, Dozier MG, Whitesell JD, Clay CM, Roberson MS.Author information 1College of Arts and Sciences, Department of Zoology and Physiology (A.M.N., M.G.D.), University of Wyoming, Laramie, Wyoming 82071; College of Veterinary Medicine and Biomedical Science, Departments of Microbiology, Immunology, and Pathology (J.D.W.) and Biomedical Sciences (C.M.C.), Colorado State University, Ft Collins, Colorado, 80523; and College of Veterinary Medicine, Department of Biomedical Sciences (M.S.R.), Cornell University, Ithaca, New York 14853.AbstractGnRH induces marked activation of the actin cytoskeleton in gonadotropes; however, the physiological consequences and cellular mechanisms responsible have yet to be fully elucidated. The current studies focus on the actin scaffolding protein cortactin. Using the gonadotrope-derived αT3-1 cell line, we found that cortactin is phosphorylated at Y(421), S(405), and S(418) in a time-dependent manner in response to the GnRH agonist buserelin (GnRHa). GnRHa induced translocation of cortactin to the leading edge of the plasma membrane where it colocalizes with actin and actin-related protein 3 (Arp3). Incubation of αT3-1 cells with the c-src inhibitor phosphoprotein phosphatase 1, blocked tyrosine phosphorylation of cortactin, reduced cortactin association with Arp3, and blunted actin reorganization in response to GnRHa. Additionally, we used RNA silencing strategies to knock down cortactin in αT3-1 cells. Knockdown of cortactin blocked the ability of αT3-1 cells to generate filopodia, lamellipodia, and membrane ruffles in response to GnRHa. We show that lamellipodia and filopodia are capable of LHβ mobilization in primary pituitary culture after GnRHa treatment, and disruption of these structures using jasplakinolide reduces LH secretion. Collectively, our findings suggest that after GnRHa activation, src activity leads to tyrosine phosphorylation of cortactin, which facilitates its association with Arp3 to engage the actin cytoskeleton. The reorganization of actin by cortactin potentially underlies GnRHa-induced secretory events within αT3-1 cells.
Endocrinology.Endocrinology.2014 Feb;155(2):548-57. doi: 10.1210/en.2012-1924. Epub 2013 Nov 25.
GnRH induces marked activation of the actin cytoskeleton in gonadotropes; however, the physiological consequences and cellular mechanisms responsible have yet to be fully elucidated. The current studies focus on the actin scaffolding protein cortactin. Using the gonadotrope-derived αT3-1 cell line,
PMID 24274984

Japanese Journal

Endocrine Mechanisms Responsible for Different Follicular Development During the Estrous Cycle in Hatano High- and Low-avoidance Rats

JAROENPORN Sukanya,HORII Yasuyuki,AKIEDA-ASAI Sayaka [他],WANG KaiMing,NAGAOKA Kentaro,OHTA Ryo,SHIROTA Mariko,WATANABE Gen,TAYA Kazuyoshi
The Journal of reproduction and development 57(6), 690-699, 2011-12-01
… These results strongly suggest that the strain difference in ovarian function of these two Hatano rats is due to the difference in the regulation of hypothalamo-hypophyseal system for gonadotropins secretion. …
NAID 10030406140

Age-related Changes in Astrocytes and Microvasculature in the Median Eminence of the Rat

Ike Hiromi,Tamada Yoshitaka,Uemura Mamoru,Ishihara Akihiko,Suwa Fumihiko,Ibata Yasuhiko
Acta histochemica et cytochemica 37(2), 129-138, 2004-00-00
… Age-related changes in astrocytes, tanycytes and the microvasculature were investigated in the median eminence (ME) of the anterior hypothalamo-hypophyseal system of 2- and 24-month old rats by means of immunocytochemistry and scanning electron microscopy. …
NAID 110003144374

高齢者の免疫機能に及ぼす運動の影響

赤間高雄,木村文律,秋本崇之 [他],河野一郎
体力科學 52(Supplement), 65-71, 2003-08-01
… Components of a non-specific immune system are neutrophils, macrophages and NK cells. … A specific immune system is composed of T lymphocytes and B lymphocytes. … It is essential in aging of the immune system. … Exercise influences the autonomic nervous system, hypothalamo-hypophyseal system, and immune system. …
NAID 110001914982