Mammalian clock output mechanisms

2011 ◽  
Vol 49 ◽  
pp. 137-151 ◽  
Author(s):  
Andries Kalsbeek ◽  
Chun-Xia Yi ◽  
Cathy Cailotto ◽  
Susanne E. la Fleur ◽  
Eric Fliers ◽  
...  
Keyword(s):  
Biological Clock ◽  
Endocrine System ◽  
Plasma Corticosterone ◽  
The Body ◽  
Hormone Release ◽  
Corticosterone Concentration ◽  
Timing System ◽  
Endogenous Rhythmicity ◽  
Peripheral Clocks ◽  
Specialized Organization

In mammals many behaviours (e.g. sleep–wake, feeding) as well as physiological (e.g. body temperature, blood pressure) and endocrine (e.g. plasma corticosterone concentration) events display a 24 h rhythmicity. These 24 h rhythms are induced by a timing system that is composed of central and peripheral clocks. The highly co-ordinated output of the hypothalamic biological clock not only controls the daily rhythm in sleep–wake (or feeding–fasting) behaviour, but also exerts a direct control over many aspects of hormone release and energy metabolism. First, we present the anatomical connections used by the mammalian biological clock to enforce its endogenous rhythmicity on the rest of the body, especially the neuro-endocrine and energy homoeostatic systems. Subsequently, we review a number of physiological experiments investigating the functional significance of this neuro-anatomical substrate. Together, this overview of experimental data reveals a highly specialized organization of connections between the hypothalamic pacemaker and neuro-endocrine system as well as the pre-sympathetic and pre-parasympathetic branches of the autonomic nervous system.

scholarly journals Mechanisms of Communication in the Mammalian Circadian Timing System

2019 ◽  
Vol 20 (2) ◽  
pp. 343 ◽  
Author(s):  
Mariana Astiz ◽  
Isabel Heyde ◽  
Henrik Oster
Keyword(s):  
Current Knowledge ◽  
The Body ◽  
Dark Cycle ◽  
Timing System ◽  
Circadian Timing System ◽  
Neuroendocrine Mechanisms ◽  
Peripheral Clocks ◽  
Central Pacemaker ◽  
And Function ◽  
Therapeutic Settings

24-hour rhythms in physiology and behaviour are organized by a body-wide network of endogenous circadian clocks. In mammals, a central pacemaker in the hypothalamic suprachiasmatic nucleus (SCN) integrates external light information to adapt cellular clocks in all tissues and organs to the external light-dark cycle. Together, central and peripheral clocks co-regulate physiological rhythms and functions. In this review, we outline the current knowledge about the routes of communication between the environment, the main pacemakers and the downstream clocks in the body, focusing on what we currently know and what we still need to understand about the communication mechanisms by which centrally and peripherally controlled timing signals coordinate physiological functions and behaviour. We highlight recent findings that shed new light on the internal organization and function of the SCN and neuroendocrine mechanisms mediating clock-to-clock coupling. These findings have implications for our understanding of circadian network entrainment and for potential manipulations of the circadian clock system in therapeutic settings.

Effects of progesterone induced postmaturity on CBG and pituitary-adrenal activities in the rat foetus

1986 ◽  
Vol 112 (3) ◽  
pp. 396-403 ◽  
Author(s):  
Jean Paul Dupouy ◽  
Alain Chatelain
Keyword(s):  
Binding Capacity ◽  
Sharp Decrease ◽  
Plasma Corticosterone ◽  
Corticosterone Concentration ◽  
Rat Pups ◽  
Body Weights ◽  
Normal Rat ◽  
Severe Jaundice ◽  
High Level ◽  
Subsequent Rise

Abstract. CBG and pituitary-adrenal activities were investigated in intact rat foetuses, in newborns spontaneously delivered by vaginal way and in postmature foetuses from mothers with delayed parturition caused by daily progesterone injection from day 20 of gestation. The postmature foetuses had lower body weights and higher adrenal weights on day 22, 23 and 24 of gestation than newborns of the same conceptional age. The corticosterone binding capacity of the plasma as well as the binding capacity of CBG for corticosterone decreased in intact foetuses for the last 3 days of gestation and stayed very low in pups from day 0 to day 8 postpartum. These parameters decreased more slowly in postmature foetuses; however, the differences between the latter and intact foetuses or newborns were not statistically significant. Similar evolution occurred in intact pregnant and suckling females as well as in females with prolonged gestation. The fall in CBG activity in normal rat pups and the subsequent rise in free steroids could explain a sharp decrease in plasma ACTH levels as well as the drop in adrenal and plasma corticosterone concentration. In foetuses with prolonged gestation, the same phenomenon did not occur. Stress conditions produced by maintaining growing foetuses in utero and the development of severe jaundice maintained high ACTH levels. In contrast, the fall in adrenal and plasma corticosterone concentrations in spite of the high level of circulating ACTH could be mainly due to the progesterone inhibition of the steroidogenic activity of the foetal adrenals.

Melatonin Modulates Lactation by Regulating Prolactin Secretion Via Tuberoinfundibular Dopaminergic Neurons in the Hypothalamus- Pituitary System

2020 ◽  
Vol 21 (8) ◽  
pp. 744-750 ◽  
Author(s):  
Hongyang Li ◽  
JingyaWei ◽  
Fengtao Ma ◽  
Qiang Shan ◽  
Duo Gao ◽  
...  
Keyword(s):  
Pineal Gland ◽  
Pituitary Gland ◽  
Antioxidant Capacity ◽  
Dopaminergic Neurons ◽  
Growth And Development ◽  
Endocrine System ◽  
Mammary Glands ◽  
Prolactin Secretion ◽  
The Body ◽  
Stimulation Of

In-depth studies have identified many hormones important for controlling mammary growth and maintaining lactation. One of these is melatonin, which is synthesized and secreted by the pineal gland to regulate circadian rhythms, improve antioxidant capacity, and enhance immunity. Prolactin is secreted by the pituitary gland and is associated with the growth and development of mammary glands as well as initiation and maintenance of lactation. The hypothalamus-pituitary system, the most important endocrine system in the body, regulates prolactin secretion mainly through dopamine released from tuberoinfundibular dopaminergic neurons. This review provides a reference for further study and describes the regulation of lactation and prolactin secretion by melatonin, primarily via the protection and stimulation of tuberoinfundibular dopaminergic neurons.

Dissociation of adrenal corticosteroid production from ACTH in water-restricted female rats

1981 ◽  
Vol 241 (1) ◽  
pp. R21-R24 ◽  
Author(s):  
R. G. Doell ◽  
M. F. Dallman ◽  
R. B. Clayton ◽  
G. D. Gray ◽  
S. Levine
Keyword(s):  
Corticosterone Level ◽  
Plasma Corticosterone ◽  
Female Rats ◽  
Adrenocorticotrophic Hormone ◽  
Corticosterone Concentration ◽  
Acth Concentration

These experiments were undertaken to investigate the mechanism whereby a precipitous drop in plasma corticosterone concentration is brought about following drinking in rats on a restricted water schedule. No alteration in adrenocorticotrophic hormone (ACTH) output was found, nor was catabolism of corticosterone sufficient to account for the drop. It is concluded that corticosterone level is controlled under these conditions by a mechanism independent of ACTH concentration.

INTERRELATIONSHIPS OF PITUITARY AND PLASMA CORTICOTROPHIN AND PLASMA CORTICOSTERONE IN ADRENALECTOMIZED AND STRESSED, ADRENALECTOMIZED RATS

1974 ◽  
Vol 63 (1) ◽  
pp. 213-222 ◽  
Author(s):  
JULIA C. BUCKINGHAM ◽  
J. R. HODGES
Keyword(s):  
Plasma Corticosterone ◽  
Prolonged Treatment ◽  
Delayed Effect ◽  
Plasma Acth ◽  
Corticosterone Concentration ◽  
Before And After ◽  
Small Rise ◽  
Acth Concentration ◽  
Corticosterone Treatment ◽  
Adrenalectomized Rats

SUMMARY Changes in pituitary and plasma corticotrophin (ACTH), estimated by redox bioassay, were correlated with changes in plasma corticosterone in adrenalectomized rats, with and without corticosterone treatment, before and after exposure to stress. After adrenalectomy, the plasma ACTH concentration was persistently increased. The pituitary ACTH content declined and then increased markedly. These changes were prevented by physiological doses of corticosteroids. Stress caused only a small rise in the plasma ACTH concentration in intact and sham-operated rats but a marked increase in adrenalectomized animals. This exaggerated response was reduced to normal by physiological doses of corticosterone. Prolonged treatment with higher doses of corticosterone was necessary to abolish completely the adrenocorticotrophic response to stress. However, one injection of the steroid, in a dose sufficient to raise the plasma corticosterone concentration to a similar level, did not impair the stress-induced release of ACTH. The results suggest that the synthesis and the basal release of ACTH are directly controlled by the concentration of corticosteroid in the blood, but the corticosteroids exert only a delayed effect in modulating the stress-induced release of the hormone.

Staphylococcal infection and pathomurfological characteristic of the pituitary-adrenal-thyroid system

2020 ◽  
Vol 03 (04) ◽  
pp. 69-73
Author(s):  
Samira Mammadhasan Yagubova ◽  
◽  
Elchin Chingiz Akbarov ◽  
Tarana Nadir Mirzayeva ◽  
◽  
...  
Keyword(s):  
Structural Changes ◽  
Adrenal Glands ◽  
Early Stage ◽  
Morphological Changes ◽  
Endocrine System ◽  
Staphylococcal Infection ◽  
The Body ◽  
Glandular Cells ◽  
Exogenous Factors ◽  
Specific Symptoms

During the staphylococcal infection, changes in the interaction of glandular cells, dystrophic and disorganizing pathologies in tissues, especially acute structural and hemodynamic changes in the stroma of the glands in the pituitary-adrenal-thyroid system, develop from the first day of the experiment. At the end of the experiment, on the background of a decrease in exudative processes, fibroplastic reactions are significantly activated, resulting in signs of incomplete regeneration – mainly sclerotic processes and cystic-atrophic changes in the parenchyma. Structural changes in tissues in the early stages of staphylococcal infection and the dynamics of development are characterized by specific symptoms in each of the glands. Since the pituitary gland is exposed to endogenous and exogenous factors earlier and more often than the adrenal glands, and the adrenal glands are earlier than the thyroid gland, dystrophic and destructive changes in the pituitary and adrenal glands are more pronounced at the early stage of the experiment. These morphological changes can change the hormonal status of the body and lead to dysfunction of the endocrine system as a whole – a decrease in the functional activity of the glands to some extent, and even inhibition of adenohypophyseal cells. Key words: staphylococcal infection, peritonitis, pituitary, adrenal and thyroid glands

Adrenocortical function in aging exercise-trained rats

1977 ◽  
Vol 43 (5) ◽  
pp. 839-843 ◽  
Author(s):  
J. A. Severson ◽  
R. D. Fell ◽  
J. G. Tuig ◽  
D. R. Griffith
Keyword(s):  
Age Groups ◽  
Plasma Corticosterone ◽  
Treadmill Running ◽  
Adrenocortical Function ◽  
Elevated Plasma ◽  
Corticosterone Concentration ◽  
Relationship Of ◽  
The Relationship

Plasma corticosterone concentrations and in vitro adrenal secretion of corticosterone were determined in exercise-trained rats. Rats, 100, 200, and 300 days of age, were trained for a 10-wk period by treadmill running. Following the training program, rats were subjected to an acute bout of swimming. Acute swimming elevated plasma corticosterone concentrations in all age groups. At 170 days of age, the plasma corticosterone concentration following swimming was higher in exercise-trained rats than in controls. The opposite was true of acutely swum rats at 270 and 370 days of age. Acute swimming elevated the in vitro adrenal gland response to adrenocorticotropic hormone stimulation in control rats at all ages and in trained rats at 170 days of age. The in vivo relationship of epinephrine and the pituitary adrenal system is suggested as a mechanism which could have caused this response. The relationship of secretion rates to plasma corticosterone concentrations indicated that extra-adrenal mechanisms, such as decreased turnover, were also responsible for the elevated plasma corticosterone levels observed in response to acute swimming.

scholarly journals The Morpho-Functional Parameters of Rat Pituitary Hormone Producing Cells After Genistein Treatment

2018 ◽  
Vol 41 (1) ◽  
pp. 5-19 ◽  
Author(s):  
Svetlana Trifunović ◽  
Verica Milošević
Keyword(s):  
Replacement Therapy ◽  
Estrogen Replacement Therapy ◽  
Target Genes ◽  
Kinase Inhibitor ◽  
Endocrine System ◽  
The Body ◽  
Pituitary Hormone ◽  
Estrogen Replacement ◽  
Genistein Treatment ◽  
Rat Pituitary

AbstractPhytoestrogens are a diverse group of steroid–like compounds that occur naturally in many plants. There are various types of phytoestrogens, including the best-researched isoflavones which are commonly found in soy. The consumption of soy products has many health benefits, including protection against breast cancer, prostate cancer, menopausal symptoms, heart disease and osteoporosis. In contrast, use of hormonally active compounds-isoflavones may unfortunately interfere with the endocrine system and can have far-reaching consequences. Genistein, the most abundant soy-bean derived isoflavone, possesses a ring system similar to estrogens and acts through an estrogen receptor (ER)-mediated mechanism, by increasing or decreasing the transcription of ER-dependent target genes. Also, genistein can act on cells through ER non-dependent mechanisms, such as tyrosine kinase inhibitor. The neuroendocrine systems are responsible for the control of homeostatic processes in the body, including reproduction, growth, metabolism and energy balance, and stress responsiveness. It is well known, that estrogen is important for development of the neuroendocrine system in both sexes. At the pituitary level, estrogen is known to affect the regulation of all hormone producing (HP) cells, by direct and/or indirect mechanisms. Due to structural and functional resemblance to estrogen, the question may arise of whether and how genistein affects the morphofunctional features of pituitary HP cells. This review deals with the consequences of genistein’s effects on morphological, stereological and hormonal features of HP cells within the anterior pituitary gland. Transparency on this issue is needed because isoflavones are presently highly consumed. Inter alia, genistein as well as other isoflavones, are present in various dietary supplements and generally promoted as an accepted alternative to estrogen replacement therapy. Potential isoflavone biomedical exploitation is not only limited to estrogen replacement therapy, so it should be treated in a wider context of different ageing symptoms remediation.

scholarly journals SAT-249 Polyarticular Osteoarthritis: A Disabling Manifestation of Acromegaly

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Azkia Khan ◽  
Hashim Ejaz ◽  
Vijaykumar Sekar ◽  
Sofia Syed
Keyword(s):  
Pituitary Adenoma ◽  
Endocrine System ◽  
Mass Effect ◽  
Free Testosterone ◽  
The Body ◽  
Medical Attention ◽  
Serum Prolactin ◽  
Oral Glucose ◽  
Patient Reported ◽  
Hands And Feet

Abstract Background Acromegaly is a slow-onset rare endocrinopathy that is characterized by chronic overproduction of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Excess GH and IGF-1 levels lead to insulin resistance, which is implicated in most of the complications associated with acromegaly. We present a case of acromegaly, wherein the patient presented with worsening polyarthralgia and decreasing mobility. As the patient was undergoing workup for rapidly progressing osteoarthritis, the internist became suspicious of patient’s changing physical appearance. Case A 53-year-old man with medical history of diabetes mellitus and hypertension was referred to endocrine clinic on account of high IGF-1 levels, 909 ng/ml (normal: 37-245 ng/ml). He was seeking medical attention because of rapidly progressing polyarthralgia and stiffness for the last two years. His symptoms were intensifying despite use of non-steroidal anti-inflammatory drugs and intra-articular steroid injections. Imaging revealed severe degenerative changes and narrowing of joint space in bilateral hip, knee and glenohumeral joints. Internist observed that the patient was exhibiting stigmata of acromegaly such as enlargement of hands and feet, prognathism and dental space widening. Patient reported headaches, blurry vision, sleep apnea, dysphagia and right ear exostosis. Colonoscopy revealed hyperplastic polyps. Repeat IGF- 1 levels were 910 ng/ml (Normal: 37-245 ng/ml). Oral glucose tolerance test showed failure of suppression of GH. Serial GH levels were 4.50, 5.08, 6.74, 5.81 and 5.21 ng/ml (Normal: 0.01- 0.97 ng/ml). Tests for other endocrinopathies revealed the following results: serum prolactin 4 ng/ml (Normal <18 ng/ml), serum cortisol 7.9 ug/dl (Normal: 6-27 ug/dl), 24 hour urine cortisol 23mcg/24 hours (Normal: 3.5-45 mcg/24 hours), serum TSH 2.25 uIU/ml (Normal: 0.34- 3 uIU/ml), serum T4 level 0.7 ng/dl (Normal: 0.6-1.6 ng/dl) and serum T3 level 144.9ng/dl (Normal: 87-178 ng/dl). Serum total and free testosterone levels were 111 ng/dl (Normal: 240-950 ng/dl) and 3.89 ng/dl (Normal: 4.06-15.6 ng/dl) respectively and were suggestive of hypogonadism. MRI Brain showed 12x10x8mm pituitary adenoma. He was referred for transsphenoidal surgery for resection of pituitary adenoma. Conclusion Polyarticular osteoarthritis is an early manifestation of acromegaly. Systemic diseases associated with acromegaly are the primary reason for which most patients seek medical attention. It is important to look for coexisting endocrinopathies whenever the diagnosis of acromegaly is established, since mass effect of pituitary adenoma can wreak havoc on the endocrine system of the body. High index of suspicion, early diagnosis and prompt treatment are the key to reverse some but not all comorbid conditions associated with acromegaly.

Effect of melittin on pituitary-adrenal responsiveness to stress

1988 ◽  
Vol 119 (3) ◽  
pp. 339-344 ◽  
Author(s):  
Jon D. Dunn ◽  
Jerald J. Killion
Keyword(s):  
Significant Influence ◽  
Restraint Stress ◽  
Surgical Stress ◽  
Plasma Corticosterone ◽  
Adrenocortical Function ◽  
Female Rat ◽  
Corticosterone Concentration ◽  
Initial Exposure ◽  
Adrenal Response ◽  
Sustained Increase

Abstract. We previously have shown that melittin evokes a sustained increase in plasma corticosterone levels of the female rat. Significant increases occurred only during the morning and the duration of the response was increased from 48 h to 8 days by a second milittin injection 3 days after initial exposure to melittin. To further evaluate the effect of melittin on adrenocortical function, rats were given melittin at 09.00 h on days 1 and 4 and on day 8 rats were subjected to a variety of different stresses. Saline-injected rats served as controls. Blood for determining non-stress and stress levels of corticosterone concentration (RIA) was collected by decapitation. In all cases morning but not afternoon non-stress plasma corticosterone levels of melittin-injected rats were higher than those of saline-injected controls; afternoon non-stress corticosterone levels did not differ between groups. Melittin- and saline-treated rats showed comparable corticosterone responses to a morning 2-min restraint stress. In contrast, melittin treatment facilitated the pituitary-adrenal response to rotational and surgical stress as well as the stress of removing one rat from a cage of two. Fifteen min after removal of the first rat of a cage of two, plasma corticosterone levels of the melittin-injected rat were significantly higher than those of saline-injected rats. Likewise, plasma corticosterone levels of melittin-treated rats were higher (P < 0.05) than those of saline-injected rats 15 min after rotational (10 rpm) and surgical (jugular cutdown and blood withdrawal) stress. Collectively these data indicate that exposure to melittin (and/or the resulting increase in morning corticosterone levels) may have a significant influence on the pituitary-adrenal responsiveness to stress.

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