Hormone Secretion Rate Research Articles

Maintaining and Assessing Various Tissue and Cell Types of the Eye Using a Novel Pumpless Fluidics System.

Many in vitro models used to investigate tissue function and cell biology require a flow of media to provide adequate oxygenation and optimal cell conditions required for the maintenance of function and viability. Toward this end, we have developed a multi-channel flow culture system to maintain tissue and cells in culture and continuously assess function and viability by either in-line sensors and/or collection of outflow fractions. The system combines 8-channel, continuous optical sensing of oxygen consumption rate with a built-in fraction collector to simultaneously measure production rates of metabolites and hormone secretion. Although it is able to maintain and assess a wide range of tissue and cell models, including islets, muscle, and hypothalamus, here we describe its operating principles and the experimental preparations/protocols that we have used to investigate bioenergetic regulation of isolated mouse retina, mouse retinal pigment epithelium (RPE)-choroid-sclera, and cultured human RPE cells. Innovations in the design of the system, such as pumpless fluid flow, have produced a greatly simplified operation of a multi-channel flow system. Videos and images are shown that illustrate how to assemble, prepare the instrument for an experiment, and load the different tissue/cell models into the perifusion chambers. In addition, guidelines for selecting conditions for protocol- and tissue-specific experiments are delineated and discussed, including setting the correct flow rate to tissue ratio to obtain consistent and stable culture conditions and accurate determinations of consumption and production rates. The combination of optimal tissue maintenance and real-time assessment of multiple parameters yields highly informative data sets that will have great utility for research in the physiology of the eye and drug discovery for the treatment of impaired vision.

Mouse ovarian follicle growth in an amniotic membrane-based hydrogel.

Three-dimensional cultures of follicles on ECM-based scaffolds can be an approach for women who become infertile after cancer treatments. Human amniotic membrane (HAM) is extensively employed in tissue engineering because of its unique properties. We cultured mouse pre-antral follicles in a hydrogel derived from decellularized amniotic membrane (DAM) combined with alginate (ALG) to improve ovarian follicle culture. HAM was decellularized. Quantitative (nuclear contents, collagen, glycosaminoglycan [GAG]) and qualitative (DAPI, H&E, Masson's trichrome, Alcian blue, scanning electron microscopy assessments were performed. Then, we created an amniotic membrane-based hydrogel (AMBH) and conducted AMBH characterization assays (rheology, MTS, degradation rate). Isolated mouse pre-antral follicles were cultured in 15mg/mL AMBH (AMBH15), 30mg/mL AMBH (AMBH30), or 45mg/mL AMBH (AMBH45). ALG hydrogel was the control group. Follicular diameters, estradiol hormone secretion rate, follicular morphology, and the follicle antral and degeneration rate were examined. Quantitative and qualitative assays indicated successful decellularization. AMBH characterization assays showed that the ALG hydrogel had more appropriate gelation and slower degradation than AMBH. There was a statistically higher antral follicle formation rate in the AMBH45 group (p < .05) compared to the AMBH30 and AMBH15 groups and less (p < .05) degenerated follicles. There was no significant difference with the ALG group. Diameter and estradiol hormone secretion in the AMBH45 group were not significantly higher than the ALG group. Although decellularization was confirmed and the viscoelastic parameters of AMBH support follicle culture, there was no significant effect on ovarian follicle maturation compared to the ALG control group.

Comparison of thyroid function in different emotional states of drug-na\xefve patients with bipolar disorder

BackgroundPrevious studies have shown that bipolar disorder is closely related to thyroid dysfunction. Psychiatric drugs have a large or small effect on thyroid function, and thyroid hormone levels can also affect the effect of drug treatment. Therefore, the purpose of this study is assessment the thyroid function of drug-naive bipolar disorder across different mood states, with the expectation of providing support for treatment options.MethodsThe present study is a cross-sectional study. Patients diagnosed with bipolar disorder according to the International Classification of Diseases diagnostic Criteria, Edition 10 (ICD 10) and who had never received medication were included in the study. The Montgomery Depression Scale (MADRS) was used to assess depressive symptoms and the Young Mania Rating Scale (YMRS) for manic symptoms. Thyroid function indicators include thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), total triiodothyronine (TT3), free thyroxine (FT4), and total thyroxine (TT4). Levels of TSH, TT4, FT4, TT3, and FT3 were measured within 48 h of hospitalization, between 06:00 and 08:00.ResultsThe data analysis finally covered the data of 291 subjects (136 in a bipolar manic group, 128 in a bipolar depressive group, and 27 in a bipolar mixed group), including 140 males and 151 females, with an average age of 27.38 ± 8.01. There was no significant difference in age, sex, marital status, work status, family history, and course of illness among the manic group, depressive group, and mixed group. The level of FT3, the rate of thyroid hormone increased secretion, and the total abnormality rate of thyroid hormone secretion in the manic group were significantly higher than those in the depressive group.ConclusionThese findings indicate that thyroid functions were significantly different between depressive and manic episodes in BD patients. In clinical practice, it is necessary to take into account the differences in thyroid hormone levels in patients with BD across different emotional states in choosing drug.

Korean-specific biokinetic model for iodine in radiological protection

The International Commission on Radiological Protection (ICRP) recently adopted a detailed biokinetic model for systemic iodine with reference transfer coefficients based on typical worldwide dietary intakes of stable iodine. The regional data provided demonstrate that the ICRP reference thyroidal biokinetics may differ substantially across regions with atypically low or high dietary intakes of stable iodine. Importantly, the design of the ICRP model facilitates modifications of reference thyroidal kinetics based on regional dietary iodine intake. The present study extended the ICRP model to the South Korean population, whose dietary iodine intake is much higher than the global mean. The following three transfer coefficients were selected as targets for Korean-specific values: thyroidal uptake rate (λ 1), hormonal secretion rate (λ 4) and leakage rate of thyroidal organic iodine as inorganic iodide (λ 5). The Korean-specific values for λ 1, λ 4 and λ 5 were determined to be 4.48, 0.0086 and 0.0171 d−1, respectively, to yield the measurements of thyroidal iodine and physiological status of Korean adults. The determined λ 1 and λ 5 values differed noticeably from the ICRP values, whereas the λ 4 value was comparable to that of the ICRP. Compared with the ICRP reference model, the Korean model, in which the Korean-specific transfer coefficients were adopted, predicted noticeably lower thyroidal uptake and faster decrease of thyroidal iodine. In addition, the predicted cumulative activities of radioiodine in the thyroid were substantially lower (40–80%) than those predicted by the ICRP model. The Korean model developed in this study demonstrates that the iodine biokinetics for Koreans (i.e. a population with a high iodine consumption) obviously differ from the prediction of the ICRP model. Hence, the Korean model may serve to improve the accuracy of thyroid dose estimation for Koreans and will lead to practical changes in matters concerned with radiological protection.

A computational model for gonadotropin releasing cells in the teleost fish medaka.

Pituitary endocrine cells fire action potentials (APs) to regulate their cytosolic Ca2+ concentration and hormone secretion rate. Depending on animal species, cell type, and biological conditions, pituitary APs are generated either by TTX-sensitive Na+ currents (INa), high-voltage activated Ca2+ currents (ICa), or by a combination of the two. Previous computational models of pituitary cells have mainly been based on data from rats, where INa is largely inactivated at the resting potential, and spontaneous APs are predominantly mediated by ICa. Unlike in rats, spontaneous INa-mediated APs are consistently seen in pituitary cells of several other animal species, including several species of fish. In the current work we develop a computational model of gonadotropin releasing cells in the teleost fish medaka (Oryzias latipes). The model stands out from previous modeling efforts by being (1) the first model of a pituitary cell in teleosts, (2) the first pituitary cell model that fires sponateous APs that are predominantly mediated by INa, and (3) the first pituitary cell model where the kinetics of the depolarizing currents, INa and ICa, are directly fitted to voltage-clamp data. We explore the firing properties of the model, and compare it to the properties of previous models that fire ICa-based APs. We put a particular focus on how the big conductance K+ current (IBK) modulates the AP shape. Interestingly, we find that IBK can prolong AP duration in models that fire ICa-based APs, while it consistently shortens the duration of the predominantly INa-mediated APs in the medaka gonadotroph model. Although the model is constrained to experimental data from gonadotroph cells in medaka, it may likely provide insights also into other pituitary cell types that fire INa-mediated APs.

An improved neuroendocrine–proportional–integral–derivative controller with sigmoid-based secretion rate for nonlinear multi-input–multi-output crane systems

This paper proposes an improved neuroendocrine–proportional–integral–derivative controller for nonlinear multi-input–multi-output crane systems using a sigmoid-based secretion rate of the hormone regulation. The main advantage of the sigmoid-based secretion rate neuroendocrine–proportional–integral–derivative is that the hormone secretion rate of neuroendocrine–proportional–integral–derivative can be varied according to the change of error. As a result, it can provide high accuracy control performance, especially in nonlinear multi-input–multi-output crane systems. In particular, the hormone secretion rate is designed to adapt with the changes of error using a sigmoid function, thus contributing to enhanced control accuracy. The parameters of the sigmoid-based secretion rate neuroendocrine–proportional–integral–derivative controller are tuned using the safe experimentation dynamics algorithm. The performance of the proposed sigmoid-based secretion rate neuroendocrine–proportional–integral–derivative controller-based safe experimentation dynamics algorithm is evaluated by tracking the error and the control input. In addition, the performances of proportional–integral–derivative and neuroendocrine–proportional–integral–derivative controllers are compared with the proposed sigmoid-based secretion rate neuroendocrine–proportional–integral–derivative performance. From the simulation work, it is discovered that the sigmoid-based secretion rate neuroendocrine–proportional–integral–derivative design provides better control performances in terms of the objective function, the total norm of error and the total norm of input compared to proportional–integral–derivative and neuroendocrine–proportional–integral–derivative controllers. In particular, it is shown the proposed sigmoid-based secretion rate neuroendocrine–proportional–integral–derivative controller contributes 5.12% of control accuracy improvement by changing the fixed hormone secretion rate into a variable hormone secretion rate based on the change of error.

Steroid hormone concentrations and body mass are differently affected by polyunsaturated fatty acids during the oestrous cycle in guinea pigs.

Reproductive functions in female mammals can be significantly affected by the actions of dietary polyunsaturated fatty acids (PUFAs) on steroid hormone secretion rates. Nevertheless, the effects of plasma free PUFAs on the oestrous cycle have seldom been considered. Therefore, in the present study, the diet of domestic guinea pigs was supplemented with high concentrations of different PUFAs and the effects of altered plasma PUFA patterns on steroid hormone concentrations, measured non-invasively, and body mass during oestrus and dioestrus were analysed. The oestrous cycle was characterised by increased oestrogen and cortisol concentrations in oestrus, corroborated by lowest bodyweight, whereas progesterone concentrations were highest in dioestrus. Plasma concentrations of the long-chain PUFAs docosahexaenoic acid (DHA; 22:6 ω3) and arachidonic acid (AA; 20:5 ω6) affected steroid hormone concentrations differently in oestrus and dioestrus. DHA positively affected oestrogen and progesterone concentrations and diminished cortisol concentrations only in oestrus. In contrast, AA negatively affected oestrogen and stimulated cortisol concentrations in oestrus and reduced progesterone concentrations in general. These findings imply selective and opposite contributions of DHA and AA to ovarian functions during different stages of the oestrous cycle, indicating a high biological relevance of plasma free PUFAs in female reproductive function.

The insensitive dormouse: reproduction skipping is not caused by chronic stress in Glis glis.

Entire populations of edible dormice (Glis glis) can skip reproduction in years without mast seeding of deciduous trees (particularly beech or oak seed), because juveniles require high-calorie seeds for growth and fattening prior to hibernation. We hypothesized that, in mast failure years, female dormice may be forced to spend larger amounts of time foraging for low-quality food, which would increase their exposure to predators, mainly owls. This may lead to chronic stress, i.e. long-term increased secretion of glucocorticoids (GC), which can have inhibitory effects on reproductive function in both female and male mammals. We monitored reproduction in free-living female dormice over 3years with varying levels of food availability, and performed a supplemental feeding experiment. To measure stress hormone levels, we determined fecal GC metabolite (GCM) concentrations collected during the day, which reflect hormone secretion rates in the previous nocturnal activity phase. We found that year-to-year differences in beech mast significantly affected fecal GCM levels and reproduction. However, contrary to our hypothesis, GCM levels were lowest in a non-mast year without reproduction, and significantly elevated in full-mast and intermediate years, as well as under supplemental feeding. Variation in owl density in our study area had no influence on GCM levels. Consequently, we conclude that down-regulation of gonads and reproduction skipping in mast failure years in this species is not caused by chronic stress. Thus, in edible dormice, delayed reproduction apparently is profitable in response to the absence of energy-rich food in non-mast years, but not in response to chronic stress.

Effects of substances on plants' active compounds on changes in the hormone levels of the pituitary–Thyroid axis in hyperthyroidism and hypothyroidism

The roles of thyroid glands in different functions of the body have been well explained such that hypothyroidism and hyperthyroidism can impair the metabolism and normal functions of the body's tissues. Recently, using medicinal plants and their active compounds in treating diseases has attracted attention, and the people's tendency to use these compounds, which are considered to be low risk and to cause no side effect, is increasing. Because changes in the levels of thyroid hormones have considerable effects on body physiology and play a substantial role in the pathogenesis of different diseases, it is necessary to conduct further studies on hyperthyroidism and hypothyroidism and also the effects of plants and their compounds on thyroid hormone secretion rates. This review was conducted to present the information on thyroid hormones, as metabolism-regulating agents, and their association with different diseases as well as the effects of plant-based active compounds on changes in the hormone levels of the pituitary–thyroid axis in hyperthyroidism and hypothyroidism. Results indicated that disrupted serum levels of the thyroid hormones lead to increased incidence of cardiovascular disease, diabetes, depression, menstrual disorders, and kidney disease. The most important effective compounds on these hormones include flavonoids, coumarins, alkaloids, minerals, essential oil components, such as terpinene, gamma-terpinene, and limonene, and antioxidant compounds that directly influence thyroid and change serum levels of the thyroid hormones through inhibiting thyroid peroxidase. Other mechanisms of change in thyroid hormone levels by plant-based compounds are related to decrease in lipoxygenase activity and increase in the activities of catalase and dismutase. It can therefore be argued that using medicinal plants and their compounds can be a novel and efficient approach to develop drugs for thyroid diseases.

Incretion of Insulin by Pancreas and Its Inactivation in Women during Long-Term Head-down Tilt Bed Rest

An increase in insular activity in response to hyperglycemia when performing a glucose tolerance test (GTT) during normal physical activity in eight women volunteers was found to be associated with increased blood concentrations of insulin provided by an increase in secretion rate and a decrease in inactivation rate. After 81 days of stay in long-term –6° head-down tilt bed rest (bed rest), flattened glycemic curves (with low hyperglycemic lifting) observed during the GTT, what was indicated high insular activity. An increase in the insular activity was evidencing also by a smaller peak of the blood concentration of glucose from 5 min after intravenous nfusion of 20 mL of 40% glucose solution at 120 minute of the GTT. In bed rest on empty stomach no significant changes in the concentrations of insulin and C-peptide were observed. The dynamics of hormone during the GTT was showed that the appearance of flattened glycemic curves when performing GTT during bed rest was associated with more pronounced, than under the usual conditions, an increase in insulin concentration in response to hyperglycemia. An increase in the blood insulin concentration when performing GTT in bed rest was mainly provided by increased hormone secretion rate in the pancreas, but not by a decrease in its inactivation rate. If you use regular exercises for prevention of hypokinesia under conditions of bed rest, an increase in insulin concentration during GTT was mainly provided by a decrease in its inactivation rate and not by an increase in secretion rate.

Modulation of Calcitonin, Parathyroid Hormone, and Thyroid Hormone Secretion by Electrical Stimulation of Sympathetic and Parasympathetic Nerves in Anesthetized Rats.

The thyroid and parathyroid glands are dually innervated by sympathetic (cervical sympathetic trunk [CST]) and parasympathetic (superior laryngeal nerve [SLN]) nerve fibers. We examined the effects of electrical stimulation of efferent or afferent nerve fibers innervating the thyroid and parathyroid glands on the secretion of immunoreactive calcitonin (iCT), parathyroid hormone (iPTH), 3,3′,5-triiodothyronine (iT3), and thyroxine (iT4) from the thyroid and parathyroid glands. In anesthetized and artificially ventilated rats, thyroid venous blood was collected. The rate of hormone secretion from the glands was calculated from plasma hormone levels, measured by ELISA, and the flow rate of thyroid venous plasma. SLNs or CSTs were stimulated bilaterally with rectangular pulses with a 0.5-ms width. To define the role of unmyelinated nerve fibers (typically efferent), the cut peripheral segments were stimulated at various frequencies (up to 40 Hz) with a supramaximal intensity to excite all nerve fibers. The secretion of iCT, iT3, and iT4 increased during SLN stimulation and decreased during CST stimulation. iPTH secretion increased during CST stimulation, but was not affected by SLN stimulation. To examine the effects of selective stimulation of myelinated nerve fibers (typically afferent) in the SLN, intact SLNs were stimulated with a subthreshold intensity for unmyelinated nerve fibers. iCT, iT3, and iT4 secretion increased during stimulation of intact SLNs at 40 Hz. These results suggest that excitation of myelinated afferents induced by low intensity and high frequency stimulation of intact SLNs promotes secretion of CT and thyroid hormones from the thyroid gland, potentially via reflex activation of parasympathetic efferent nerve fibers in the SLN.

A 3D microfluidic perfusion system made from glass for multiparametric analysis of stimulus-secretioncoupling in pancreatic islets.

Microfluidic perfusion systems (MPS) are well suited to perform multiparametric measurements with small amounts of tissue to function as an Organ on Chip device (OOC). Such microphysiolgical characterization is particularly valuable in research on the stimulus-secretion-coupling of pancreatic islets. Pancreatic islets are fully functional competent mini-organs, which serve as fuel sensors and transduce metabolic activity into rates of hormone secretion. To enable the simultaneous measurement of fluorescence and oxygen consumption we designed a microfluidic perfusion system from borosilicate glass by 3D femtosecond laser ablation. Retention of islets was accomplished by a plain well design. The characteristics of flow and shear force in the microchannels and wells were simulated and compared with the measured exchange of the perfusion media. Distribution of latex beads, MIN6 cell pseudo islets and isolated mouse islets in the MPS was characterized in dependence of flow rate and well depth. Overall, the observations suggested that a sufficient retention of the islets at low shear stress, together with sufficient exchange of test medium, was achieved at a well depth of 300μm and perfusion rates between 40 and 240μl/min. This enabled multiparametric measurement of oxygen consumption, NAD(P)H autofluorescence, cytosolic Ca2+ concentration, and insulin secretion by isolated mouse islets. After appropriate correction for different lag times, kinetics of these processes could be compared. Such measurements permit a more precise insight into metabolic changes underlying the regulation of insulin secretion. Thus, rapid prototyping using laser ablation enables flexible adaption of borosilicate MPS designs to different demands of biomedical research.

Measurement of GPCR-G protein activity in living cells.

G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors in eukaryotic genomes. They control a variety of cellular and physiological processes such as hormone secretion and heart rate, and therefore are associated with a majority of pathological conditions including cancer and heart diseases. Currently established assays to measure ligand-induced activation of GPCRs and G proteins possess limitations such as being time consuming, indirect, and expensive. Thus, an efficient method to measure GPCR-G protein activation is required to identify novel pharmacological modulators to control them and gain insights about molecular underpinnings of the associated pathways. Activation of GPCRs induces dissociation of G protein heterotrimers to form GαGTP and free Gβγ. Free Gβγ subunits have been shown to translocate reversibly from the plasma membrane to internal membranes. Gβγ translocation therefore represents the GPCR-G protein activation, and thus, imaging of this process can be used to quantify the kinetics and magnitude of the pathway activation-deactivation in real time in living cells. The objective of this chapter is to elaborate the protocols of (i) generation and optimization of the required sensor constructs; (ii) development of cell culture, transient transfection, imaging, and optogenetic procedures; (iii) imaging and data analysis methods; and (iv) stable cell line generation, pertaining to this assay to measure GPCR-G protein activation.

The surgical treatment of acromegaly.

Surgical extraction of as much tumour mass as possible is considered the first step of treatment in acromegaly in many centers. In this article the potential benefits, disadvantages and limitations of operative acromegaly treatment are reviewed. Pertinent literature was selected to provide a review covering current indications, techniques and results of operations for acromegaly. The rapid reduction of tumour volume is an asset of surgery. To date, in almost all patients, minimally invasive, transsphenoidal microscopic or endoscopic approaches are employed. Whether a curative approach is feasible or a debulking procedure is planned, can be anticipated on the basis of preoperative magnetic resonance imaging. The radicality of adenoma resection essentially depends on localization, size and invasive character of the tumour. The normalization rates of growth hormone and IGF-1 secretion, respectively, depend on tumour-related factors such as size, extension, the presence or absence of invasion and the magnitude of IGF-1 and growth hormone oversecretion. However, also surgeon-related factors such as experience and patient load of the centers have been shown to strongly affect surgical results and the rate of complications. As compared to most medical treatments, surgery is relatively cheap since the costs occur only once and not repeatedly. There are several new technical gadgets which aid in the surgical procedure: navigation and variants of intraoperative imaging. For the mentioned reasons, current algorithms of acromegaly management suggest an initial operation, unless the patients are unfit for surgery, refuse an operation or only an unsatisfactory resection is anticipated. A few suggestions are made when a re-operation could be considered.

Biological Rhythms in the Skin.

Circadian rhythms, ≈24 h oscillations in behavior and physiology, are reflected in all cells of the body and function to optimize cellular functions and meet environmental challenges associated with the solar day. This multi-oscillatory network is entrained by the master pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus, which directs an organism’s rhythmic expression of physiological functions and behavior via a hierarchical system. This system has been highly conserved throughout evolution and uses transcriptional–translational autoregulatory loops. This master clock, following environmental cues, regulates an organism’s sleep pattern, body temperature, cardiac activity and blood pressure, hormone secretion, oxygen consumption and metabolic rate. Mammalian peripheral clocks and clock gene expression have recently been discovered and are present in all nucleated cells in our body. Like other essential organ of the body, the skin also has cycles that are informed by this master regulator. In addition, skin cells have peripheral clocks that can function autonomously. First described in 2000 for skin, this review summarizes some important aspects of a rapidly growing body of research in circadian and ultradian (an oscillation that repeats multiple times during a 24 h period) cutaneous rhythms, including clock mechanisms, functional manifestations, and stimuli that entrain or disrupt normal cycling. Some specific relationships between disrupted clock signaling and consequences to skin health are discussed in more depth in the other invited articles in this IJMS issue on Sleep, Circadian Rhythm and Skin.

The Relationship between Thyrotropin Receptor Antibody Levels and Intrathyroid Vascularity in Patients with Graves’ Disease

Thyroid stimulating hormone receptor antibodies (TSHRAbs) are specific autoantibodies of Graves' disease (GD). They activate adenylate cyclase, induce thyroid growth, and cause an increased rate of thyroid hormone production and secretion. TSHRAbs levels are decreased by treatment and may predict recurrence when they persist. Theoretically, TSHRAbs levels should be related to intrathyroid vascularity (ITV) due to the autoimmunity and inflammation. We aimed to analyze the relationship between TSHRAbs represented by thyrotropin-binding inhibitory immunoglobulin (TBII) levels and ITV measured by thyroid duplex sonography (TDS). 56 GD patients were prospectively recruited. ITV, measured using TDS, was defined as follows: (average color-flow area in the right and left sides of the thyroid/total thyroid area in transverse view)×100. The average TBII level was 47.1% and average ITV was 27.24. ITV positively and significantly correlated with TBII (p<0.001). TSHRAbs show significant correlation with ITV. This may help doctors to estimate thyroid autoimmune activity when they performing sonography at clinics.

Comparison of whole body circadian phase evaluated from melatonin and cortisol secretion profiles in healthy humans

Knowledge of whole body circadian phase is important for the evaluation of physiological processes and for planning time-qualified therapy. The nightly peak in melatonin secretion and the morning peak in cortisol secretion are well-known, prominent circadian rhythmic phenomena in health. Due to their high-amplitude oscillation and relative stability of phase under standardized light-dark conditions, both hormones, either by frequent, dense sampling for melatonin near the onset and/or offset of sleep, morning vs. evening sampling for cortisol, or around-the-clock dense sampling of either, have been suggested for use as a 24 h marker rhythm. Our study evaluated a feasible sampling protocol of collecting six blood samples over 24 h to individually determine whole body circadian phase (i.e., the acrophase, aØ) from each hormone and therein establish synchronization to the light-dark schedule. Cortisol and melatonin serum levels were measured in peripheral blood samples collected every 4 h for 24 h from 11 healthy men, ages 35–53 years, with the sleep/dark span from 23:00–07:00 h. Circadian changes were evaluated by ANOVA and 24 h cosine fitting for original serum levels and also for the fractional variation (FV) that was calculated to evaluate the dynamics (percentage change) of the rise and fall in serum levels between 4 h sampling times. A significant time-effect and 24 h rhythm was detected for both serum melatonin (aØ = 01:35 h) and cortisol (aØ = 07:48 h), confirming synchronization by the subjects as a group to their 24 h environmental light-dark (sleep-wake) schedule, with the anticipated peak for melatonin during darkness and for cortisol in the morning. Overall 4 h FV levels for melatonin and cortisol also showed prominent 24 h rhythms, with highest values prior to darkness onset for melatonin (aØ = 22:29 h) and near mid-dark for cortisol (aØ = 02:12 h), which preceded maximal serum levels by ∼3 h for melatonin and ∼5 h for cortisol. On an individual basis, all 11 subjects showed an unmistakable peak in serum melatonin levels at 02:00 h, while eight subjects showed a clear peak in serum cortisol levels at 06:00 h, one subject showed a delayed peak at 10:00 h, and two subjects showed a broad peak between 02:00 h and 14:00 h. The aØ spread was 5 h 18 min for melatonin (23:54 h to 05:12 h) and 7 h 11 min for cortisol (04:54 h to 12:05 h). These results show that 4 h sampling over 24 h, in lieu of more frequent sampling, can be useful for determining whole body circadian phase and light-dark synchronization, especially when using melatonin, since cortisol can be more easily influenced by external factors involving stress, thereby resulting in a larger spread in peak times. Calculating fractional variations over 4 h intervals also helps to describe the complex dynamics of hormone secretion rates over 24 h. It is thus possible to describe circadian characteristics of hormone secretion with a sampling and data analysis protocol that allows the definition of both temporal characteristics (by cosine fitting) and dynamics (percentage change) using samples obtained every 4 h over 24 h. This protocol may be useful in the study of hormone secretion levels and dynamics in disease and to guide therapeutic and other interventions by defining whole body circadian phase on an individual basis using melatonin or cortisol.

Temporal phasing of locomotor activity, heart rate rhythmicity, and core body temperature is disrupted in VIP receptor 2-deficient mice

Neurons of the brain's biological clock located in the hypothalamic suprachiasmatic nucleus (SCN) generate circadian rhythms of physiology (core body temperature, hormone secretion, locomotor activity, sleep/wake, and heart rate) with distinct temporal phasing when entrained by the light/dark (LD) cycle. The neuropeptide vasoactive intestinal polypetide (VIP) and its receptor (VPAC2) are highly expressed in the SCN. Recent studies indicate that VIPergic signaling plays an essential role in the maintenance of ongoing circadian rhythmicity by synchronizing SCN cells and by maintaining rhythmicity within individual neurons. To further increase the understanding of the role of VPAC2 signaling in circadian regulation, we implanted telemetric devices and simultaneously measured core body temperature, spontaneous activity, and heart rate in a strain of VPAC2-deficient mice and compared these observations with observations made from mice examined by wheel-running activity. The study demonstrates that VPAC2 signaling is necessary for a functional circadian clock driving locomotor activity, core body temperature, and heart rate rhythmicity, since VPAC2-deficient mice lose the rhythms in all three parameters when placed under constant conditions (of either light or darkness). Furthermore, although 24-h rhythms for three parameters are retained in VPAC2-deficient mice during the LD cycle, the temperature rhythm displays markedly altered time course and profile, rising earlier and peaking ∼4-6 h prior to that of wild-type mice. The use of telemetric devices to measure circadian locomotor activity, temperature, and heart rate, together with the classical determination of circadian rhythms of wheel-running activity, raises questions about how representative wheel-running activity may be of other behavioral parameters, especially when animals have altered circadian phenotype.

Hypothesis: Role for the circadian Clock system and sleep in the pathogenesis of adhesions and chronic pelvic pain?

Intra-peritoneal adhesions ensuing from surgery or infection may lead to chronic pelvic pain, bowel obstruction, infertility and additional invasive surgery to resolve adhesion-related complications. As a result adhesions are a major clinical, social and economic concern. The cumulative year-on-year direct costs of adhesion-related readmissions for a 10-year period are more than £569 million. The degree of intra-abdominal adhesion formation in an individual patient after a surgical or infective insult remains difficult to predict. This reflects a lack of understanding as to the underlying aetiologies. Several different mechanisms leading to adhesion formation and re-formation have been proposed. These include abnormal modulations in inflammatory status, fibrinolytic pathways and matrix remodelling. A number of preventative strategies have been designed accordingly. However, although each individual model offers specific insights into the aetiology of adhesion formation, none have been shown to provide the basis for a highly effective clinical intervention. A unifying fundamental mechanism remains elusive. In this article we propose that such a mechanism can be found within the molecular control of circadian rhythms and “Clock” gene biology. A number of physiological processes demonstrating circadian variation have been shown to involve ‘Clock genes’ in the suprachiasmatic nucleus (SCN), which then entrains a similar set of Clock genes in peripheral tissues such as the heart, brain, spleen, lung, liver, skeletal muscle and kidney. The intrinsic time-keeping system influences activity, such as sleep, temperature regulation, rates of metabolism, immune responses, blood pressure and hormone secretion. The function and availability of mediators involved in the inflammatory response, fibrinolytic and anti-coagulation pathways are all under the tight control of the molecular Clock system. These include IL-6, PAI-1, fibrinogen, fibroblasts and TNF-α. We hypothesise that disruptions in the ‘Clock system’ are central to the causal pathway of adhesion formation. Our hypothesis takes into consideration and utilises current understanding in the field uniting individual principles. Moreover; this hypothesis suggests strategies for optimising existing therapeutic interventions.

The comparison of effects of three types of resistance, endurance and concurrent training on amount of growth hormone secretion in active males

The main purpose of the present study was to compare the effects of three types of endurance (E), resistance (R) and combined (C) exercise on the rate of growth hormone...