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"Endocrine System physiology."
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Existence of long-lasting experience-dependent plasticity in endocrine cell networks
Experience-dependent plasticity of cell and tissue function is critical for survival by allowing organisms to dynamically adjust physiological processes in response to changing or harsh environmental conditions. Despite the conferred evolutionary advantage, it remains unknown whether emergent experience-dependent properties are present in cell populations organized as networks within endocrine tissues involved in regulating body-wide homeostasis. Here we show, using lactation to repeatedly activate a specific endocrine cell network
in situ
in the mammalian pituitary, that templates of prior demand are permanently stored through stimulus-evoked alterations to the extent and strength of cell–cell connectivity. Strikingly, following repeat stimulation, evolved population behaviour leads to improved tissue output. As such, long-lasting experience-dependent plasticity is an important feature of endocrine cell networks and underlies functional adaptation of hormone release.
Experience-dependent plasticity and functional adaptation are thought to be restricted to the central nervous and immune systems. This study shows that long-lasting experience-dependent plasticity is a key feature of endocrine cell networks, allowing improved tissue function and hormone output following repeat demand.
Journal Article
Single Osteopathic Manipulative Therapy Session Dampens Acute Autonomic and Neuroendocrine Responses to Mental Stress in Healthy Male Participants
The efficacy of osteopathic manipulative therapy (OMTh; manipulative care provided by foreign-trained osteopaths) is supported by observational data and patient feedback, but there is still a need for objective, quantitative biomarkers that allow measurement of the underlying mechanisms. No study exploring the protective potential of OMTh for mental stress has been published, to the authors’ knowledge.To explore the modulating effect of OMTh on autonomic neural regulation of the heart and verifiy its ability to influence the activity of the hypothalmic-pituitary-adrenocortical axis.Healthy young adult men who had never received OMTh were exposed to either a brief protocol using craniosacral techniques or sham therapy (control) involving the same anatomical areas. A laboratory stress episode consisting of a 5-minute arithmetic task participants were required to perform in front of a committee preceded the therapy sessions. Continuous electrocardiograph recordings were done before, during, and after the stress episode. Heart rate and frequency-domain parameters of heart rate variability (specifically, high-frequency component power in normalized units and the ratio of low-frequency to high-frequency power) were measured to quantify the activity of the parasympathetic nervous system and the state of sympathovagal balance at the level of the heart, respectively. Saliva samples were also collected at points throughout the study to determine cortisol levels.Osteopathic manipulative therapy reduced the overall chronotropic effect of the stressor (t=−2.9, P<.05) and counteracted the vagal withdrawal and the shift of autonomic balance toward sympathetic prevalence (t=−2.8, P<.05) that were observed in control participants. Moreover, OMTh participants had a much lower overall cortisol level during the mental stressor compared with control participants (t=−2.3, P<.05). Participants in the OMTh group did not show the statistically significant reduction in the amplitude of the cortisol awakening response observed in their control counterparts after the stress episode (control: t=2.7, P<.05; OMT: P=.83).The application of a single OMTh session to healthy participants induced a faster recovery of heart rate and sympathovagal balance after an acute mental stressor by substantially dampening parasympathetic withdrawal and sympathetic prevalence. The OMTh session also prevented the typical increase in cortisol levels observed immediately after a brief mental challenge.
Journal Article
Individual variation and the endocrine regulation of behaviour and physiology in birds: a cellular/molecular perspective
Investigations of the cellular and molecular mechanisms of physiology and behaviour have generally avoided attempts to explain individual differences. The goal has rather been to discover general processes. However, understanding the causes of individual variation in many phenomena of interest to avian eco-physiologists will require a consideration of such mechanisms. For example, in birds, changes in plasma concentrations of steroid hormones are important in the activation of social behaviours related to reproduction and aggression. Attempts to explain individual variation in these behaviours as a function of variation in plasma hormone concentrations have generally failed. Cellular variables related to the effectiveness of steroid hormone have been useful in some cases. Steroid hormone target sensitivity can be affected by variables such as metabolizing enzyme activity, hormone receptor expression as well as receptor cofactor expression. At present, no general theory has emerged that might provide a clear guidance when trying to explain individual variability in birds or in any other group of vertebrates. One strategy is to learn from studies of large units of intraspecific variation such as population or sex differences to provide ideas about variables that might be important in explaining individual variation. This approach along with the use of newly developed molecular genetic tools represents a promising avenue for avian eco-physiologists to pursue.
Journal Article
Acute and cumulative effects of focused high-frequency vibrations on the endocrine system and muscle strength
The purpose of this study was to evaluate the acute and long-term effects of local high-intensity vibration (HLV,
f
=
300 Hz) on muscle performance and blood hormone concentrations in healthy young men. Totally 18 subjects (cV group) were studied in two sessions, either without (control) or with HLV treatment. The protocol was the same on both control and test days, except that, in the second session, subjects underwent HLV treatment. Counter-movement jumping (CMJ), maximal isometric voluntary contraction (MVC) test, and hormonal levels were measured before the procedure, immediately thereafter, and 1 h later. To assess the long-term effects of HLV, the cV group was subjected to HLV on the leg muscles for 4 weeks, and a second group (cR group,
n
= 18) embarked upon a resistance training program. All subjects underwent an MVC test and an isokinetic (100 deg/s) test before training, 4 weeks after training, and 2 months after the end of training. The HLV protocol significantly increased the serum level of growth hormone (GH,
P
< 0.05) and creatine phosphokinase (CPK,
P
< 0.05), and decreased the level of cortisol (
P
< 0.05). None of GH, CPK or testosterone levels were altered in controls. There was a significant improvement in MVC (
P
< 0.05). After 4 weeks, both the cV and cR groups demonstrated significant improvement in MVC and isokinetic tests (
P
< 0.05). This increase persisted for at least 2 months. Our results indicate that HLV influences the levels of particular hormones and improves neuromuscular performance. Our results indicate that HLV has a long-term beneficial effect comparable to that of resistance training.
Journal Article
Endocrine and metabolic link to coronavirus infection
Type 2 diabetes mellitus and hypertension are the most common comorbidities in patients with coronavirus infections. Emerging evidence demonstrates an important direct metabolic and endocrine mechanistic link to the viral disease process. Clinicians need to ensure early and thorough metabolic control for all patients affected by COVID-19.
Journal Article
Circadian clock control of endocrine factors
Key Points
Various endocrine factors are known to exhibit time-of-day-dependent oscillations in both humans and animals
Endocrine factor rhythms are driven not only by environmental and behavioural influences, but also by intrinsic circadian clocks
Circadian dyssynchrony is associated with multiple pathologic states, including cardiometabolic diseases and cancer
Reinstatement of circadian synchrony through time-of-day-restricted feeding and pharmacologic strategies improves metabolic homeostasis
Adequate circadian oscillation of endocrine factors is essential in the maintenance of metabolic homeostasis. The authors of this Review explain the influence of extrinsic and intrinsic factors on endocrine circadian rhythms and how dysregulation of these rhythms can lead to disease in animals and humans. They also discuss therapeutic strategies to restore circadian rhythmicity and improve metabolism.
Organisms experience dramatic fluctuations in demands and stresses over the course of the day. In order to maintain biological processes within physiological boundaries, mechanisms have evolved for anticipation of, and adaptation to, these daily fluctuations. Endocrine factors have an integral role in homeostasis. Not only do circulating levels of various endocrine factors oscillate over the 24 h period, but so too does responsiveness of target tissues to these signals or stimuli. Emerging evidence suggests that these daily endocrine oscillations do not occur solely in response to behavioural fluctuations associated with sleep–wake and feeding–fasting cycles, but are orchestrated by an intrinsic timekeeping mechanism known as the circadian clock. Disruption of circadian clocks by genetic and/or environmental factors seems to precipitate numerous common disorders, including the metabolic syndrome and cancer. Collectively, these observations suggest that strategies designed to realign normal circadian rhythmicities hold potential for the treatment of various endocrine-related disorders.
Journal Article
An osteocalcin-deficient mouse strain without endocrine abnormalities
Osteocalcin (OCN), the most abundant noncollagenous protein in the bone matrix, is reported to be a bone-derived endocrine hormone with wide-ranging effects on many aspects of physiology, including glucose metabolism and male fertility. Many of these observations were made using an OCN-deficient mouse allele (Osc-) in which the 2 OCN-encoding genes in mice, Bglap and Bglap2, were deleted in ES cells by homologous recombination. Here we describe mice with a new Bglap and Bglap2 double-knockout (dko) allele (Bglap/2p.Pro25fs17Ter) that was generated by CRISPR/Cas9-mediated gene editing. Mice homozygous for this new allele do not express full-length Bglap or Bglap2 mRNA and have no immunodetectable OCN in their serum. FTIR imaging of cortical bone in these homozygous knockout animals finds alterations in the collagen maturity and carbonate to phosphate ratio in the cortical bone, compared with wild-type littermates. However, μCT and 3-point bending tests do not find differences from wild-type littermates with respect to bone mass and strength. In contrast to the previously reported OCN-deficient mice with the Osc-allele, serum glucose levels and male fertility in the OCN-deficient mice with the Bglap/2pPro25fs17Ter allele did not have significant differences from wild-type littermates. We cannot explain the absence of endocrine effects in mice with this new knockout allele. Possible explanations include the effects of each mutated allele on the transcription of neighboring genes, or differences in genetic background and environment. So that our findings can be confirmed and extended by other interested investigators, we are donating this new Bglap and Bglap2 double-knockout strain to the Jackson Laboratories for academic distribution.
Journal Article
Unifying regulatory motifs in endocrine circuits
Hormone systems, which control diverse physiological functions, have been extensively studied, yet consistent rules underlying these systems remain elusive. Here we identify unifying design principles in human endocrine systems. Available data was found for 43 of 63 systems, and all 43 fall into five classes of circuits. Each class uses distinct regulation circuitry to perform specific dynamical functions: homeostasis, acute input-output response, or adjustable set points. The circuits involve interactions across multiple timescales — minutes to hours for hormone secretion, ultradian and diurnal rhythms, and weeks for changes in endocrine gland mass. The weeks-timescale for gland mass occurs in several circuit classes, including the most complex, which features an intermediate gland, the pituitary. We analyze this circuit in detail and identify tradeoffs between endocrine amplification, buffering of hypersecreting tumors, and response times. These unifying principles reveal how circuit structure maps to function and contribute to the emerging field of systems endocrinology.
Hormone systems control diverse physiological functions but consistent rules to model these circuits remain incompletely understood. Here the authors use mathematical modelling to report that 43 hormone circuits can be divided into five classes based on regulatory motifs and that the circuit structure relates to function.
Journal Article
Neural regulation of endocrine and autonomic stress responses
Key Points
The response of mammals to external or internal challenge involves engagement of multiple physiological systems, prominently including the hypothalamic-pituitary-adrenocortical (HPA) axis and the autonomic nervous system (ANS).
Autonomic and HPA axis responses to systemic stressors are initiated by brainstem and hypothalamic structures that receive direct and indirect homeostatic feedback.
Psychological stress responses are activated and inhibited by limbic system structures, such as the medial prefrontal cortex, the hippocampus and the amygdala, which send multisynaptic input to brainstem and hypothalamic activators of the HPA axis and the ANS.
'Psychological' information and homeostatic information are integrated by telencephalic and diencephalic relays prior to the elaboration of HPA axis or ANS responses.
HPA axis and ANS components of the stress response are probably encoded in distinct yet highly interconnected limbic subregions.
Chronic stress induces neuroplasticity in central stress-processing networks, causing sensitization as well as habituation of HPA axis and ANS responses.
Limbic stress response networks overlap extensively with memory and reward circuitry, allowing stress responses to be coloured by prior experience and expected outcomes.
The physiological response to stress is regulated by a complex neurocircuitry that integrates and interprets stress-related and homeostatic information. Ulrich-Lai and Herman describe this circuitry, including its adaptation to chronic stress and its overlap with circuits that underlie memory and reward.
The survival and well-being of all species requires appropriate physiological responses to environmental and homeostatic challenges. The re-establishment and maintenance of homeostasis entails the coordinated activation and control of neuroendocrine and autonomic stress systems. These collective stress responses are mediated by largely overlapping circuits in the limbic forebrain, the hypothalamus and the brainstem, so that the respective contributions of the neuroendocrine and autonomic systems are tuned in accordance with stressor modality and intensity. Limbic regions that are responsible for regulating stress responses intersect with circuits that are responsible for memory and reward, providing a means to tailor the stress response with respect to prior experience and anticipated outcomes.
Journal Article