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pulsatile hormone secretion

M A Hannan, N Kawate, Y Fukami, W W P N Weerakoon, E E Büllesbach, T Inaba, H Tamada
We recently reported that plasma insulin-like peptide 3 (INSL3) concentrations increased soon after endogenous and exogenous stimulations of LH in male goats and bulls. However, the effects of LH suppression on INSL3 secretion are unknown in domestic animals. Here, we examined the effects of a long-acting GnRH antagonist (degarelix acetate; 4 mg/kg) on the secretions of plasma INSL3 and testosterone in two phases, an immediate and a long-term phase in male goats (n = 6; aged, 13-16 months). During the immediate phase, blood was taken at 15-minute intervals for 8 hours on Days -5, 0, and 3...
January 15, 2017: Theriogenology
Chrysanthi Fergani, Victor Navarro
Reproductive function is driven by the hormonal interplay between the gonads and brain-pituitary axis. Gonadotropin-releasing hormone (GnRH) is released in a pulsatile manner, which is critical for the attainment and maintenance of fertility, however, GnRH neurons lack the ability to directly respond to most regulatory factors, and a hierarchical upstream neuronal network governs its secretion. We and others proposed a model in which Kiss1 neurons in the arcuate nucleus (ARC), so called KNDy neurons, release kisspeptin (a potent GnRH secretagogue) in a pulsatile manner to drive GnRH pulses under the coordinated autosynaptic action of its cotransmitters, the tachykinin neurokinin B (NKB, stimulatory) and dynorphin (inhibitory)...
October 17, 2016: Reproduction: the Official Journal of the Society for the Study of Fertility
Katja Czieselsky, Mel Prescott, Robert Porteous, Pauline Campos, Jenny Clarkson, Frederik J Steyn, Rebecca E Campbell, Allan E Herbison
Using a new tail-tip bleeding procedure and a sensitive ELISA, we describe here the patterns of LH secretion throughout the mouse estrous cycle; in ovariectomized mice; in ovariectomized, estradiol-treated mice that model estrogen-negative and -positive feedback; and in transgenic GNR23 mice that exhibit allele-dependent reductions in GnRH neuron number. Pulsatile LH secretion was evident at all stages of the estrous cycle, with LH pulse frequency being approximately one pulse per hour in metestrous, diestrous, and proestrous mice but much less frequent at estrus (less than one pulse per 4 h)...
December 2016: Endocrinology
P Schüssler, M Kluge, W Gamringer, T C Wetter, A Yassouridis, M Uhr, R Rupprecht, A Steiger
We reported previously that repetitive intravenous injections of corticotropin-releasing hormone (CRH) around sleep onset prompt depression-like changes in certain sleep and endocrine activity parameters (e.g. decrease of slow-wave sleep during the second half of the night, blunted growth hormone peak, elevated cortisol concentration during the first half of the night). Furthermore a sexual dimorphism of the sleep-endocrine effects of the hormones growth hormone-releasing hormone and ghrelin was observed. In the present placebo-controlled study we investigated the effect of pulsatile administration of 4×50μg CRH on sleep electroencephalogram (EEG) and nocturnal cortisol and GH concentration in young healthy women...
September 28, 2016: Psychoneuroendocrinology
Manish Putteeraj, Tomoko Soga, Takayoshi Ubuka, Ishwar S Parhar
Reproduction is associated with the circadian system, primarily as a result of the connectivity between the biological clock in the suprachiasmatic nucleus (SCN) and reproduction-regulating brain regions, such as preoptic area (POA), anteroventral periventricular nucleus (AVPV), and arcuate nucleus (ARC). Networking of the central pacemaker to these hypothalamic brain regions is partly represented by close fiber appositions to specialized neurons, such as kisspeptin and gonadotropin-releasing hormone (GnRH) neurons; accounting for rhythmic release of gonadotropins and sex steroids...
2016: Frontiers in Endocrinology
Amitesh Pratap, Kathryn L Garner, Margaritis Voliotis, Krasimira Tsaneva-Atanasova, Craig A McArdle
Gonadotropin-releasing hormone (GnRH) acts via G-protein coupled receptors on pituitary gonadotropes to control of reproduction. These are Gq-coupled receptors that mediate acute effects of GnRH on the exocytotic secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as the chronic regulation of their synthesis. GnRH is secreted in short pulses and GnRH effects on its target cells are dependent upon the dynamics of these pulses. Here we overview GnRH receptors and their signaling network, placing emphasis on pulsatile signaling, and how mechanistic mathematical models and an information theoretic approach have helped further this field...
August 17, 2016: Molecular and Cellular Endocrinology
Nikolay Zernov, Mikhail Skoblov, Ancha Baranova, Konstantin Boyarsky
BACKGROUND: Anomalous levels of gonadotropin-releasing hormone (GnRH) secretion result in a variety of reproductive phenotypes associated with infertility or subfertility. The normosmic isolated hypogonadotropic hypogonadism (nIHH) is due to a failure of either GnRH pulsatile secretion in hypothalamus or its reception in pituitary. The spectrum of nIHH-associated alterations continues to expand, especially when additional ethnic populations are investigated. The aim of this study was to uncover genetic causes for nIHH in patients of Russian origin...
2016: Reproductive Biology and Endocrinology: RB&E
Mary R Richards, Lacey Plummer, Yee-Ming Chan, Margaret F Lippincott, Richard Quinton, Philip Kumanov, Stephanie B Seminara
BACKGROUND: A constellation of neurodegenerative disorders exists (Gordon Holmes syndrome, 4H leucodystrophy, Boucher-Neuhauser syndrome) in which patients suffer from both neurological disease (typically manifested by ataxia) and reproductive failure (idiopathic hypogonadotropic hypogonadism (IHH)). POLR3B, which encodes the second largest subunit of RNA polymerase III (pol III), and POLR3A, which forms the pol III catalytic centre, are associated with 4H leucodystrophy. METHODS: Whole exome sequencing was performed on a large cohort of subjects with IHH (n=565)...
August 10, 2016: Journal of Medical Genetics
Soon Gang Choi, Qian Wang, Jingjing Jia, Maria Chikina, Hanna Pincas, Georgia Dolios, Kazuki Sasaki, Rong Wang, Naoto Minamino, Stephen R J Salton, Stuart C Sealfon
Reproductive function is controlled by the pulsatile release of hypothalamic gonadotropin-releasing hormone (GnRH), which regulates the expression of the gonadotropins luteinizing hormone and FSH in pituitary gonadotropes. Paradoxically, Fshb gene expression is maximally induced at lower frequency GnRH pulses, which provide a very low average concentration of GnRH stimulation. We studied the role of secreted factors in modulating gonadotropin gene expression. Inhibition of secretion specifically disrupted gonadotropin subunit gene regulation but left early gene induction intact...
September 30, 2016: Journal of Biological Chemistry
Young-Lim Shin
Central precocious puberty (CPP) is caused by the premature reactivation of the hypothalamic-pituitary-gonadal axis. Genetic, nutritional, and environmental factors play a crucial role in determining pubertal timing. Recently mutations in kisspeptin (KISS1), kisspeptin receptor (KISS1R), and makorin RING finger protein 3 (MKRN3) genes have been identified as genetic causes of CPP. In particular, the MKRN3 gene is known to affect pubertal initiation. The MKRN3 gene is located on chromosome 15q11-q13 in the Prader-Willi syndrome (PWS) critical region...
June 2016: Annals of Pediatric Endocrinology & Metabolism
Calen P Ryan, Thomas W McDade, Lee T Gettler, Dan T A Eisenberg, Margarita Rzhetskaya, M Geoffey Hayes, Christopher W Kuzawa
OBJECTIVES: Testosterone (T), the primary androgenic hormone in males, is stimulated through pulsatile secretion of LH and regulated through negative feedback inhibition at the hypothalamus and pituitary. The hypothalamic-pituitary-gonadal (HPG) axis also controls sperm production through the secretion of follicle-stimulating hormone (FSH). Negative feedback in the HPG axis is achieved in part through the binding of T to the androgen receptor (AR), which contains a highly variable trinucleotide repeat polymorphism (AR-CAGn)...
July 15, 2016: American Journal of Human Biology: the Official Journal of the Human Biology Council
Kevin C J Yuen, Nicholas A Tritos, Susan L Samson, Andrew R Hoffman, Laurence Katznelson
INTRODUCTION: The clinical features of adult GH deficiency (GHD) are nonspecific, and GH stimulation testing is often required to confirm the diagnosis. However, diagnosing adult GHD can be challenging due to the episodic and pulsatile GH secretion, concurrently modified by age, gender, and body mass index (BMI). METHODS: PubMed searches were conducted to identify published data since 2009 on GH stimulation tests used to diagnose adult GHD. Relevant articles in English language were identified and considered for inclusion in the present document...
July 13, 2016: Endocrine Practice
Sarantis Livadas, George P Chrousos
PURPOSE OF REVIEW: The mechanism of puberty initiation remains an enigma, despite extensive research in the field. Pulsatile pituitary gonadotropin secretion under the guidance of hypothalamic gonadotropin-releasing hormone (GnRH) constitutes a sine qua non for pubertal onset. In turn, the secretion of GnRH in the human hypothalamus is regulated by kisspeptin and its receptor as well as by permissive or opposing signals mediated by neurokinin B and dynorphin acting on their respective receptors...
August 2016: Current Opinion in Pediatrics
A S Thakur, G P Littaru, I Funahashi, U S Painkara, N S Dange, P Chauhan
In neuroendocrine system the increase in oxidative status is produced by a glucocorticoid-dependent and transcriptional increase in pro-oxidative drive, with concurrent inhibition of the antioxidant defense system, ultimately leading to increased neuronal cell death. Functional hypothalamic disturbances and neuroendocirne aberrations have both short and long term consequences for reproductive health. Understandably, an impaired or diminished hypothalamic-pituitary-ovarian axis leads to anovulation and hypoestrogenism...
July 2016: Indian Journal of Clinical Biochemistry: IJCB
I J Clarke, L Arbabi
Gonadotropin releasing hormone is the primary driver of reproductive function and pulsatile GnRH secretion from the brain causes the synthesis and secretion of LH and FSH from the pituitary gland. Recent work has revealed that the secretion of GnRH is controlled at the level of the GnRH secretory terminals in the median eminence. At this level, projections of kisspeptin cells from the arcuate nucleus of the hypothalamus are seen to be closely associated with fibers and terminals of GnRH cells. Direct application of kisspeptin into the median eminence causes release of GnRH...
July 2016: Domestic Animal Endocrinology
Shinya Oishi, Nobutaka Fujii
Recent research has indicated pivotal roles for neuropeptides and their cognate receptors in reproductive physiology. Kisspeptins are RF-amide neuropeptides that stimulate gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus. Neurokinin B (NKB) is a member of the tachykinin family of neuropeptides and positively regulates pulsatile GnRH secretion. These peptides are coexpressed in kisspeptin/NKB/Dyn (KNDy) neurons of the arcuate nucleus, where they contribute to the regulation of puberty onset and other reproductive functions...
November 4, 2016: Biopolymers
Giacomo Cappon, Morten Gram Pedersen
Many multicellular systems consist of coupled cells that work as a syncytium. The pancreatic islet of Langerhans is a well-studied example of such a microorgan. The islets are responsible for secretion of glucose-regulating hormones, mainly glucagon and insulin, which are released in distinct pulses. In order to observe pulsatile insulin secretion from the β-cells within the islets, the cellular responses must be synchronized. It is now well established that gap junctions provide the electrical nearest-neighbor coupling that allows excitation waves to spread across islets to synchronize the β-cell population...
May 2016: Chaos
Allan E Herbison
The gonadotropin-releasing hormone (GnRH) neuronal network generates pulse and surge modes of gonadotropin secretion critical for puberty and fertility. The arcuate nucleus kisspeptin neurons that innervate the projections of GnRH neurons in and around their neurosecretory zone are key components of the pulse generator in all mammals. By contrast, kisspeptin neurons located in the preoptic area project to GnRH neuron cell bodies and proximal dendrites and are involved in surge generation in female rodents (and possibly other species)...
August 2016: Nature Reviews. Endocrinology
E Ullmann, A Barthel, K Petrowski, T Stalder, C Kirschbaum, S R Bornstein
Currently, the quantitative analysis of moderators affecting the function of the hypothalamus-pituitary-adrenal (HPA)-axis in health and sickness is still unreliable. This is, in particular, due to physiological factors such as pulsatile ultradian and circadian glucocorticoid secretion as well as to methodological limitations of the current techniques for steroid hormone determination. Based on this background, the determination of long-term hair steroid concentrations is an important methodological improvement allowing for the quantitative analysis of chronic HPA axis-activation...
2016: Scientific Reports
Frederik J Steyn, Virginie Tolle, Chen Chen, Jacques Epelbaum
This article reviews the main findings that emerged in the intervening years since the previous volume on hormonal control of growth in the section on the endocrine system of the Handbook of Physiology concerning the intra- and extrahypothalamic neuronal networks connecting growth hormone releasing hormone (GHRH) and somatostatin hypophysiotropic neurons and the integration between regulators of food intake/metabolism and GH release. Among these findings, the discovery of ghrelin still raises many unanswered questions...
April 2016: Comprehensive Physiology
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