Human liver afferent and efferent nerves revealed by 3-D/Airyscan super-resolution imaging.

Neural regulation of hepatic metabolism has long been recognized. However, the detailed afferent and efferent innervation of the human liver has not been systematically characterized. This is largely due to the liver's high lipid and pigment contents, causing false-negative (light scattering and absorption) and false-positive (autofluorescence) results in in-depth fluorescence imaging. Here, to avoid the artifacts in three-dimensional (3-D) liver neurohistology, we embed the bleached human liver in the high-refractive-index polymer for tissue clearing and antifade 3-D/Airyscan super-resolution imaging. Importantly, using the paired substance P (SP, sensory marker) and PGP9.5 (pan-neuronal marker) labeling, we detect the sensory nerves in the portal space, featuring the SP+ varicosities in the PGP9.5+ nerve bundles/fibers, confirming the afferent liver innervation. Also, using the tyrosine hydroxylase (TH, sympathetic marker) labeling, we identify 1) condensed TH+ sympathetic nerves in the portal space, 2) extension of sympathetic nerves from the portal to the intralobular space, in which the TH+ nerve density is 2.6 ± 0.7-fold higher than that of the intralobular space in the human pancreas, and 3) the TH+ nerve fibers and varicosities contacting the ballooning cells, implicating potential sympathetic influence on hepatocytes with macrovesicular fatty change. Finally, using the vesicular acetylcholine transporter (VAChT, parasympathetic marker), PGP9.5, and CK19 (epithelial marker) labeling with panoramic-to-Airyscan super-resolution imaging, we detect and confirm the parasympathetic innervation of the septal bile duct. Overall, our labeling and 3-D/Airyscan imaging approach reveal the hepatic sensory (afferent) and sympathetic and parasympathetic (efferent) innervation, establishing a clinically related setting for high-resolution 3-D liver neurohistology.NEW & NOTEWORTHY We embed the human liver (vs. pancreas, positive control) in the high-refractive-index polymer for tissue clearing and antifade 3-D/Airyscan super-resolution neurohistology. The pancreas-liver comparison reveals: 1) sensory nerves in the hepatoportal space; 2) intralobular sympathetic innervation, including the nerve fibers and varicosities contacting the ballooning hepatocytes; and 3) parasympathetic innervation of the septal bile duct. Our results highlight the sensitivity and resolving power of 3-D/Airyscan super-resolution imaging in human liver neurohistology.

Site-specific autonomic vasomotor responses and their interactions in rat gingiva.

Blood flow in the gingiva, comprising the interdental papilla as well as attached and marginal gingiva, is important for maintaining of gingival function and is modulated by risk factors such as stress that may lead to periodontal disease. Marked blood flow changes mediated by the autonomic (parasympathetic and sympathetic) nervous system may be essential for gingival hemodynamics. However, differences in autonomic vasomotor responses and their functional significance in different parts of the gingiva are unclear. We examined the differences in autonomic vasomotor responses and their interactions in the gingiva of anesthetized rats. Parasympathetic vasodilation evoked by the trigeminal (lingual nerve)-mediated reflex elicited frequency-dependent blood flow increases in gingivae, with the increases being greatest in the interdental papilla. Parasympathetic blood flow increases were significantly reduced by intravenous administration of the atropine and VIP antagonist. The blood flow increase evoked by acetylcholine administration was higher in the interdental papilla than in the attached gingiva, whereas that evoked by VIP agonist administration was greater in the attached gingiva than in the interdental papilla. Activation of the cervical sympathetic nerves decreased gingival blood flow and inhibited parasympathetically induced blood flow increases. Our results suggest that trigeminal-parasympathetic reflex vasodilation 1) is more involved in the regulation of blood flow in the interdental papilla than in the other parts of the gingiva, 2) is mediated by cholinergic (interdental papilla) and VIPergic systems (attached gingiva), and 3) is inhibited by excess sympathetic activity. These results suggest a role in the etiology of periodontal diseases during mental stress.

Cold pressor stress effects on cardiac repolarization.

The cold pressor test (CPT) elicits strong cardiovascular reactions via activation of the sympathetic nervous system (SNS), yielding subsequent increases in heart rate (HR) and blood pressure (BP). However, little is known on how exposure to the CPT affects cardiac ventricular repolarization. Twenty-eight healthy males underwent both a bilateral feet CPT and a warm water (WW) control condition on two separate days, one week apart. During pre-stress baseline and stress induction cardiovascular signals (ECG lead II, Finometer BP) were monitored continuously. Salivary cortisol and subjective stress ratings were assessed intermittently. Corrected QT (QTc) interval length and T-wave amplitude (TWA) were assessed for each heartbeat and subsequently aggregated individually over baseline and stress phases, respectively. CPT increases QTc interval length and elevates the TWA. Stress-induced changes in cardiac repolarization are only in part and weakly correlated with cardiovascular and cortisol stress-reactivity. Besides its already well-established effects on cardiovascular, endocrine, and subjective responses, CPT also impacts on cardiac repolarization by elongation of QTc interval length and elevation of TWA. CPT effects on cardiac repolarization share little variance with the other indices of stress reactivity, suggesting a potentially incremental value of this parameter for understanding psychobiological adaptation to acute CPT stress.

Stress system dysfunction revealed by integrating reactivity of stress pathways to psychological stress in lean and overweight/obese men.

Although the patterns of response within the sympathoadrenal medullary (SAM) system and hypothalamo-pituitary adrenal (HPA) axis are interesting and important in their own accord, the overall response to acute psychological stress involves reactivity of both pathways. We tested the hypothesis that consideration of the integrated response of these pathways may reveal dysregulation of the stress systems, which is not evident when considering either system alone. Age-matched lean and overweight/obese men were subjected to a Trier Social Stress Test and reactivity of the SAM system (salivary α-amylase, systolic blood pressure, diastolic blood pressure, and heart rate) and the HPA axis (salivary cortisol) were measured. Relative reactivity of SAM system and HPA axis was calculated as the ratio between the measures from each pathway. Although analysis of reactivity of individual stress pathways showed no evidence of dysfunction in overweight/obese compared with lean men, analysis of HPA/SAM reactivity revealed significantly lower cortisol over systolic blood pressure (CoSBP) and cortisol over diastolic blood pressure (CoDBP) reactivity in overweight/obese compared with lean men. Other measures of HPA/SAM reactivity and all measures of SAM/HPA reactivity were unaltered in overweight/obese compared with lean men. These findings suggest that the cortisol response per unit of blood pressure response is blunted in men with elevated adiposity. Furthermore, these findings support a notion of a coordinated overall approach to activation of the stress pathways with the degree of activation in one pathway being related to the degree of activation in the other.

Orthodontic tooth movement-activated sensory neurons contribute to enhancing osteoclast activity and tooth movement through sympathetic nervous signalling.

OBJECTIVES: Orthodontic tooth movement (OTM) increases sympathetic and sensory neurological markers in periodontal tissue. However, the relationship between the sympathetic and sensory nervous systems during OTM remains unclear. Therefore, the present study investigated the relationship between the sympathetic and sensory nervous systems activated by OTM using pharmacological methods. MATERIALS AND METHODS: We compared the effects of sympathectomy and sensory nerve injury during OTM in C57BL6/J mice. Capsaicin (CAP) was used to induce sensory nerve injury. Sympathectomy was performed using 6-hydroxydopamine. To investigate the effects of a ß-agonist on sensory nerve injury, isoproterenol (ISO) was administered to CAP-treated mice. Furthermore, to examine the role of the central nervous system in OTM, the ventromedial hypothalamic nucleus (VMH) was ablated using gold thioglucose. RESULTS: Sensory nerve injury and sympathectomy both suppressed OTM and decreased the percent of the alveolar socket covered with osteoclasts (Oc.S/AS) in periodontal tissue. Sensory nerve injury inhibited increases in OTM-induced calcitonin gene-related peptide (CGRP) immunoreactivity (IR), a marker of sensory neurons, and tyrosine hydroxylase (TH) IR, a marker of sympathetic neurons, in periodontal tissue. Although sympathectomy did not decrease the number of CGRP-IR neurons in periodontal tissue, OTM-induced increases in the number of TH-IR neurons were suppressed. The ISO treatment restored sensory nerve injury-inhibited tooth movement and Oc.S/AS. Furthermore, the ablation of VMH, the centre of the sympathetic nervous system, suppressed OTM-induced increases in tooth movement and Oc.S/AS. CONCLUSIONS: The present results suggest that OTM-activated sensory neurons contribute to enhancements in osteoclast activity and tooth movement through sympathetic nervous signalling.

Guanabenz inhibits alveolar bone resorption in a rat model of periodontitis.

Increase of sympathetic activity has been known to exacerbate osteoporosis through promotion of bone resorption. However, it is largely unknown about involvement of sympathetic activity in exacerbation of periodontitis. In this study, we investigated whether α2-adrenergic receptor (α2-AR) agonist guanabenz which decreases sympathetic activity, attenuates alveolar bone resorption in rats having high sympathetic activity with periodontitis. Volumes of residual alveolar bone and attachment levels in periodontium were examined using micro-computed tomography and hematoxylin-eosin staining, respectively. Furthermore, osteoclast numbers per bone surface and osteoclast surface per bone surface were measured using tartrate-resistant acid phosphatase staining. To examine the suppressive effects of guanabenz on pro-inflammatory cytokines, expression levels of tyrosine hydroxylase (TH), TNF-α, IL1-ß, and IL-6 in periodontium were measured using immunohistostaining. Administration of guanabenz attenuated loss of alveolar bone and attachment levels in rats having high sympathetic activity. Furthermore, its administration suppressed osteoclast numbers in rats having high sympathetic activity. TH, TNF-α, IL-1ß, and IL-6 positive cells in periodontium in rats treated with guanabenz for 12 weeks, were lower than those in control rats having high sympathetic activity. This study demonstrated administration of α2-AR agonist guanabenz attenuates alveolar bone resorption through decrease of sympathetic activity in rats.

Sympathetic Nerve Activity During Tooth Extraction in Women Is Related to Dental Anxiety Immediately After Surgery.

PURPOSE: This study assessed the relationship between changes in autonomic nervous system activity during impacted mandibular third molar extraction and a patient's postoperative psychological status, with the overarching aim of informing the development of interventions to reduce dental phobia and anxiety. We hypothesized that changes in autonomic nervous system activity during tooth extraction are related to postoperative psychology. METHODS: In our prospective cohort study, heart rate variability, heart rate (HR), and systolic blood pressure (SBP) were recorded during impacted mandibular third molar extraction. Heart rate variability values were dichotomized as either low frequency (LF 0.04-0.15 Hz) or high frequency (HF >0.15 Hz). The relative ratios (intraoperative vs baseline) of LF/HF, HF, HR, and SBP were divided into high and low groups based on their median values; the State Anxiety Inventory (STAI-S) results were compared between the groups with high and low relative ratios. RESULTS: Data of 34 female patients (age, 28.23 ± 1.05 years) were analyzed. Postoperative STAI-S values were significantly lower than preoperative values. Patients in the high LF/HF group had a significantly lower change in STAI-S values than those in the low LF/HF group (P < .05). There were no significant differences in the change in STAI-S values between the groups with high and low HF, HR, or SBP. CONCLUSIONS: Patients with low sympathetic nervous system activity had lower anxiety; the LF/HF index was the most sensitive indicator for changes in stress. Additional studies are required to develop optimal interventions for reducing sympathetic nerve activity in patients with dental phobia.

Comparison of the Effects of Septoplasty and Sinus Lifting Simulation in Rats on Changes in Heart Rate Variability.

The effects of septoplasty and sinus lifting simulation in rats on changes in the frequency domain of heart rate variability were compared. In the early postoperative period, the low-frequency component increases, and the high-frequency component decreases. The VLF range also increased. This indicates an increase in the activity of the sympathetic nervous system and a shift in metabolism under the influence of post-surgical inflammation.

Neural responses to social evaluative threat in the absence of negative investigator feedback and provoked performance failures.

Functional neuroimaging of social stress induction has considerably furthered our understanding of the neural risk architecture of stress-related mental disorders. However, broad application of existing neuroimaging stress paradigms is challenging, among others due to the relatively high intensity of the employed stressors, which limits applications in patients and longitudinal study designs. Here, we introduce a less intense neuroimaging stress paradigm in which subjects anticipate, prepare, and give speeches under simulated social evaluation without harsh investigator feedback or provoked performance failures (IMaging Paradigm for Evaluative Social Stress, IMPRESS). We show that IMPRESS significantly increases perceived arousal as well as adrenergic (heart rate, pupil diameter, and blood pressure) and hormonal (cortisol) responses. Amygdala and perigenual anterior cingulate cortex (pACC), two key regions of the emotion and stress regulatory circuitry, are significantly engaged by IMPRESS. We further report associations of amygdala and pACC responses with measures of adrenergic arousal (heart rate, pupil diameter) and social environmental risk factors (adverse childhood experiences, urban living). Our data indicate that IMPRESS induces benchmark psychological and endocrinological responses to social evaluative stress, taps into core neural circuits related to stress processing and mental health risk, and is promising for application in mental illness and in longitudinal study designs.

Neuroendocrine coordination and youth behavior problems: A review of studies assessing sympathetic nervous system and hypothalamic-pituitary adrenal axis activity using salivary alpha amylase and salivary cortisol.

Externalizing and internalizing behavior problems can have deleterious psychosocial consequences for youth. Both sympathetic nervous system (SNS) and hypothalamic-pituitary adrenal (HPA) axis activity and reactivity may contribute to behavior problems but have largely been studied separately, with inconsistent findings. Because the SNS and HPA axis interact to carry out physiological processes (e.g., responding to stressors), considering SNS and HPA axis activity jointly may elucidate disparate findings. This review discusses studies that simultaneously assessed SNS and HPA axis (re)activity and youth behavior problems using measures of salivary alpha amylase (sAA) and salivary cortisol. Multiple patterns of SNS and HPA axis coordination were associated with problem behaviors, especially when considering individual differences and youth's psychosocial context. Importantly, many study findings may be artifacts of widespread methodological differences. The reviewed studies lay the foundation for future research on neuroendocrine coordination as a contributing factor to youth problem behaviors and some recommendations for future research are discussed.

Neuroendocrine responses to a psychosocial stress test for larger groups of participants: comparison of two test exposures.

Objective. Individual stress tests characterized by social evaluative threat and uncontrollability are known to elicit strong neuroendocrine responses. We tested whether a psychosocial stressor submitted to a larger group of participants (up to 60) may elicit comparable stress responses.Methods. A total of 59 adult subjects (33 women, 26 men) participated in the study, whereas 24 of them suffered from allergy and 35 were healthy. The stress test consisted of a distraction stress task followed by a speech task, in which the participants were randomly subjected to questions related to a topic that they had to prepare as well as arithmetic questions in front of their peers and a committee that responded in standardized and non-supporting manner. State and trait anxiety inventory (STAI) for anxiety state was administrated before and after the test and salivary samples taking. The test was repeated after five months.Results. The results showed that the shared psychosocial stress application in a larger group of subjects was prosperous. The larger group test (LGST) resulted in an enhanced subjectively experienced stress and an intensive sympathetic nervous system activation, reflected by elevated salivary alpha-amylase activity and the heart rate. The cortisol increment after exposure to the stress test was not significant. Repeated exposure to the test failed to reproduce the original stress responses with exception of the heart rate rise.Conclusions. In a larger group of subjects, the psychosocial stress test did elicit stress responses similar to the individual stress tests. Our data indicate that the above-mentioned stress test is apparently not an appropriate approach for the repeated use.

Effect of increased inspiratory muscle work on blood flow to inactive and active limbs during submaximal dynamic exercise.

NEW FINDINGS: What is the central question of this study? Increased respiratory muscle activation is associated with neural and cardiovascular consequences via the respiratory muscle metaboreflex. Does increased sympathetic vasoconstriction originating from the respiratory musculature elicit a reduction in blood flow to an inactive limb in order to maintain blood flow to an active limb? What is the main finding and its importance? Arm blood flow was reduced whereas leg blood flow was preserved during mild leg exercise with inspiratory resistance. Blood flow to the active limb is maintained via sympathetic control of blood flow redistribution when the respiratory muscle-induced metaboreflex is activated. ABSTRACT: The purpose of this study was to elucidate the effect of increasing inspiratory muscle work on blood flow to inactive and active limbs. Healthy young men (n = 10, 20 ± 2 years of age) performed two bilateral dynamic knee-extension and knee-flexion exercise tests at 40% peak oxygen uptake for 10 min. The trials consisted of spontaneous breathing for 5 min followed by voluntary hyperventilation either with or without inspiratory resistance for 5 min (40% of maximal inspiratory mouth pressure, inspiratory duty cycle of 50% and a breathing frequency of 40 breaths min-1 ). Mean arterial blood pressure was acquired using finger photoplethysmography. Blood flow in the brachial artery (inactive limb) and in the femoral artery (active limb) were monitored using Doppler ultrasound. Mean arterial blood pressure during exercise was higher (P < 0.05) with inspiratory resistance (121 ± 7 mmHg) than without resistance (99 ± 5 mmHg). Brachial artery blood flow increased during exercise without inspiratory resistance (120 ± 31 ml min-1 ) compared with the resting level, whereas it was attenuated with inspiratory resistance (65 ± 43 ml min-1 ). Femoral artery blood flow increased at the onset of exercise and was maintained throughout exercise without inspiratory resistance (2576 ± 640 ml min-1 ) and was unchanged when inspiratory resistance was added (2634 ± 659 ml min-1 ; P > 0.05). These results suggest that sympathetic control of blood redistribution to active limbs is facilitated, in part, by the respiratory muscle-induced metaboreflex.

Gonadal hormones modulate the HPA-axis and the SNS in response to psychosocial stress.

Exposure to stress activates both the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS). A growing body of research points to the contribution of sex hormones (testosterone, estrogen, and progesterone), the end products of the hypothalamus-pituitary-gonadal (HPG) axis, in modulating stress reactivity. The present study aimed at investigating the potential modulating role of sex hormones on HPA and SNS reactivity to psychosocial stress. The reactivity, induced by the Trier Social Stress Test, was analyzed by measuring the levels of cortisol and alpha-amylase (markers for SNS activity) in four saliva samples each of 21 men and 37 women (17 not using oral contraceptives and in their luteal phase, and 20 women using oral contraceptives). In addition, basal sex hormones were sampled prior to the psychosocial stress exposure. Results revealed that controlling for testosterone, estrogen, and progesterone diminished the impact of stress on cortisol reactivity and on alpha-amylase reactivity. Moreover, controlling for sex hormones also diminished the differential pattern of cortisol reactivity in each experimental group among responders. Furthermore, correlation analyses revealed differences between groups in the association between sex hormones and alpha-amylase. The present findings indicate a modulatory role for sex hormones in HPA and SNS reactivity and emphasize the need for control of sex hormone fluctuations when examining cortisol and alpha-amylase reactivity to stress.

[Occupational stress among care workers: evaluation by a novel physiological method].

Objectives　In this report, I studied the occupational stress response in care workers using a novel physiological method. Specifically, I evaluated the individual level of stress response in these care workers and further examined the relationship between the stress responses and various types of jobs.Methods　This study included 35 care workers working at different geriatric health facilities. During working hours, the stress response levels of these care workers were evaluated based on the changes in their sympathetic functions as measured by frequency analysis of an electrocardiogram and recorded using Holter electrocardiography. Additionally, workers were asked to maintain a diary to record the types of work they performed throughout the day. Based on the collected data, I examined the stress response values and determined their associations with different types of work. Levels of salivary chromogranin A (CgA) protein were also measured in the participating care workers.Results　The maximum job stress index (i.e., the strongest job-related stress response exhibited during the day) and CgA concentrations were significantly higher in the shift-change group than the regular-shift group (maximum job stress index: 26.2±12.0 vs. 16.1±6.5, CgA protein: 10.8±14.6 vs. 2.3±1.2 pmol/mg; P<0.05 for both measurements). For the day-shift group, the job stress index (i.e., stress response while performing a job) and job stress peak value (i.e., peak value of stress response while performing a job) were significantly higher for the worker groups performing inter-professional tasks (148.9±27.0, 29.8±9.1, respectively) and oral care (82.4±16.7, 15.4±8.7, respectively) than the groups involved in other jobs. The job stress peak value was also significantly high (20.5±9.6) for the bathing care worker group. For the night-shift worker groups, the job stress index and job stress peak value were significantly higher for oral care and clothing care groups than the groups performing other jobs (oral care: 100.1±23.1, 17.6±8.6; clothing care: 102.8±22.8, 19.8±11.7). Interestingly, for the sheet-changing group, the job stress index and job stress peak value were significantly higher for the night-shift group than the day-shift group (night: 120.6±23.3, 25.7±10.9; day: 65.0±10.6, 16.4±10.9).Conclusions　In this study, I present a novel method for analyzing the occupational stress responses in care workers; this method employs frequency analysis of an electrocardiogram and measurement of the salivary concentration of CgA protein. Further, the stress response in these workers appeared to be enhanced by changing their shift schedules. In conclusion, inter-professional tasks, oral care, and tasks requiring the caregivers to touch patients were found to be stressful jobs. Interestingly, the stress response among sheet-changing workers seemed to differ between night and day shifts.

Sympathetic neural and hemodynamic responses to head-up tilt during isoosmotic and hyperosmotic hypovolemia.

We hypothesized that muscle sympathetic nerve activity (MSNA) during head-up tilt (HUT) would be augmented during exercise-induced (hyperosmotic) dehydration but not isoosmotic dehydration via an oral diuretic. We studied 26 young healthy subjects (7 female, 19 male) divided into three groups: euhydrated (EUH, n = 7), previously exercised in 40°C while maintaining hydration; dehydrated (DEH, n = 10), previously exercised in 40°C during which ~3% of body weight was lost via sweat loss; and diuretic (DIUR, n = 9), a group that did not exercise but lost ~3% of body weight via diuresis (furosemide, 80 mg by mouth). We measured MSNA, heart rate (HR), and blood pressure (BP) during supine rest and 30° and 45° HUT. Plasma volume (PV) decreased similarly in DEH (-8.5 ± 3.3%) and DIUR (-11.4 ± 5.7%) (P > 0.05). Plasma osmolality was similar between DIUR and EUH (288 ± 4 vs. 284 ± 5 mmol/kg, respectively) but was significantly higher in DEH (299 ± 5 mmol/kg) (P < 0.05). Mixed-model ANOVA was used with repeated measures on position (HUT) and between-group analysis on condition. HR and MSNA increased in all subjects during HUT (main effect of position; P < 0.05). There was also a significant main effect of group, such that MSNA and HR were higher in DEH compared with DIUR (P < 0.05). Changes in HR with HUT were larger in both hypovolemic groups compared with EUH (P < 0.05). The differential HUT response "strategies" in each group suggest a greater role for hypovolemia per se in controlling HR responses during dehydration, and a stronger role for osmolality in control of SNA.NEW & NOTEWORTHY Interactions of volume regulation with control of vascular sympathetic nerve activity (SNA) have important implications for blood pressure regulation. Here, we demonstrate that SNA and heart rate (HR) during hyperosmotic hypovolemia (exercise-induced) were augmented during supine and tilt compared with isoosmotic hypovolemia (diuretic), which primarily augmented the HR response. Our data suggest that hypovolemia per se had a larger role in controlling HR responses, whereas osmolality had a stronger role in control of SNA.

Detection and measurement of alpha-amylase in canine saliva and changes after an experimentally induced sympathetic activation.

BACKGROUND: Salivary alpha-amylase (sAA) is considered a biomarker of sympathetic activation in humans, but there is controversy regarding the existence of sAA in dogs. The hypothesis of this study was that sAA exists in dogs and it could change in situations of sympathetic stimulation. Therefore, the aims of this study were: 1) to demonstrate the presence of alpha-amylase in saliva of dogs by Western-Blot, 2) to validate an spectrophotometric method for the measurement of sAA activity and 3) to evaluate the possible changes in sAA activity after the induction of an ejaculation in dogs which is known to produce a sympathetic activation. RESULTS: Western-Blot demonstrated a band in dog saliva specimens between 60 kDa and 50 kDa, similar to purified sAA. The spectrophotometric assay validated showed an adequate inter- and intra-assay precision, and a high correlation coefficient (r = 0.999) in the linearity under dilution study. sAA median activity significantly increased just after ejaculation compared with just before the ejaculation (2.06-fold, P = 0.005). CONCLUSIONS: This study demonstrated the existence of alpha-amylase in saliva of dogs and that this enzyme can be measured by a spectrophotometric assay. In addition, results showed that sAA increase after a sympathetic activation and could be potentially used as non-invasive biomarker of sympathetic activity in this species.

Sex differences in the cardiovascular consequences of the inspiratory muscle metaboreflex.

It is currently unknown whether sex differences exist in the cardiovascular consequences of the inspiratory muscle metaboreflex. We hypothesized that the activation of the inspiratory muscle metaboreflex will lead to less of an increase in mean arterial pressure (MAP) and limb vascular resistance (LVR) and less of a decrease in limb blood flow (Q̇L) in women compared with men. Twenty healthy men (n = 10, 23 ± 2 yr) and women (n = 10, 22 ± 3 yr) were recruited for this study. Subjects performed inspiratory resistive breathing tasks (IRBTs) at 2% or 65% of their maximal inspiratory mouth pressure (PIMAX). During the IRBTs, the breathing frequency was 20 breaths/min with a 50% duty cycle. At rest and during the IRBTs, MAP was measured via automated oscillometry, Q̇L was measured via Doppler ultrasound, and LVR was calculated. EMG was recorded on the leg to ensure no muscle contraction occurred. The 65% IRBT led to attenuated increases (P < 0.01) from baseline in women compared with men for MAP (W: 7.3 ± 2.0 mmHg; M: 11.1 ± 5.0 mmHg) and LVR (W: 17.7% ± 14.0%; M: 47.9 ± 21.0%), as well as less of a decrease (P < 0.01) in Q̇L (W: -7.5 ± 9.9%; M: -23.3 ± 10.2%). These sex differences in MAP, Q̇L, and LVR were still present in a subset of subjects matched for PIMAX The 2% IRBT resulted in no significant changes in MAP, Q̇L, or LVR across time or between men and women. These data indicate premenopausal women exhibit an attenuated inspiratory muscle metaboreflex compared with age-matched men.

Effects of early life adversity on cortisol/salivary alpha-amylase symmetry in free-ranging juvenile rhesus macaques.

Early life adversity (ELA) affects physiological and behavioral development. One key component is the relationship between the developing Hypothalamic-Pituitary-Adrenal (HPA) axis and the Sympathetic Nervous System (SNS). Recent studies suggest a relationship between early life adversity and asymmetry in cortisol (a measure of HPA activation) and salivary alpha-amylase (sAA: a correlate of SNS activation) responses to stress among human children, but to our knowledge there have been no comparable studies in nonhumans. Here, we investigate the responses of these two analytes in "low stress" and "high stress" situations in free-ranging juvenile rhesus macaques (Macaca mulatta) on Cayo Santiago, Puerto Rico. Behavioral data on maternal maltreatment were collected during the first 3months of life to determine individual rates of ELA, and saliva samples were collected from subjects noninvasively during juvenility. Irrespective of ELA, salivary alpha-amylase levels were lower in low stress situations and higher in high stress situations. For cortisol however, high ELA subjects exhibited higher low stress concentrations and blunted acute responses during high stress situations compared to moderate and low ELA subjects. Cortisol and sAA values were positively correlated among low ELA subjects, suggesting symmetry, but were uncorrelated or negatively correlated among moderate and high ELA subjects, suggesting asymmetry in these individuals. These findings indicate dysregulation of the stress response among juveniles maltreated during infancy: specifically, attenuated cortisol reactivity coupled with typical sAA reactivity characterize the stress response profiles of juveniles exposed to higher rates of ELA during the first 3months of life.

Endocrine stress responses and risk of type 2 diabetes mellitus.

This study was carried to ascertain whether stress responses are associated with abnormalities in glucose tolerance, insulin sensitivity and pancreatic beta cell function and risk of type 2 Diabetes Mellitus. Salivary cortisol, a marker of hypothalamic-pituitary-adrenal (HPA) axis and salivary α-amylase, a marker of sympathetic nervous system (SNS) were compared in 125 subjects of newly detected diabetes mellitus (NDDM) and normal glucose tolerance (NGT) subjects who were diagnosed on the basis of oral glucose tolerance test (OGTT). Assessment of stress in them was done through stress scales - presumptive stressful life events scale (PSLES), perceived stress scale (PSS) and sense of coherence (SOC) and correlated with these and other stress response markers. Significantly higher 10 pm salivary cortisol and post dexamethasone salivary cortisol were found in NDDM subjects as compared to NGT. 10 pm salivary cortisol correlated significantly with fasting plasma glucose (FPG), 2 h plasma glucose (2h PG) and glycated hemoglobin (HbA1c) while post dex salivary cortisol correlated with 2h PG, HbA1c and salivary α-amylase with 2h PG. Stepwise logistic regression analysis showed that body mass index (OR: 1.840), SOC (OR: 0.688) and 10 pm salivary cortisol (OR: 1.427) were the strongest predictors of NDDM. The results of the present study indicate that NDDM subjects display significantly higher chronic stress and stress responses when compared to subjects with NGT. Chronic stress and endocrine stress responses are significantly associated with glucose intolerance, insulin resistance and diabetes mellitus.

Premenstrual syndrome is associated with blunted cortisol reactivity to the TSST.

This study assessed the effects of premenstrual syndrome (PMS) and menstrual phases on the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic nervous system axis and psychological responses to the Trier Social Stress Test (TSST). Thirty-six PMS women (mean age 21.69 ± 2.16 years) and 36 control women (mean age 22.03 ± 2.48 years) participated in the TSST task, either in the follicular phase or in the late luteal phase (each group N = 18). Saliva samples, heart rate and subjective stress levels were collected for seven time points throughout the test (10, 20, 30, 40, 55, 70 and 100 min). The results indicated that in comparison with control women, PMS women displayed blunted cortisol stress responses to the TSST irrespective of the menstrual phases, as indexed by the cortisol levels across time, area under the curve with respect to ground (AUCg) and peak change scores of cortisol. The results also demonstrated that the measurements indexed by cortisol levels across time, AUCg and peak change scores of heart rate were smaller in women tested during the late luteal phase than during the follicular phase. Correlation results indicated that AUCg was negatively correlated with PMS scores. These results suggest that measures of cortisol, rather than heart rate or subjective responses to stress, may be most closely associated with PMS. Furthermore, hypo-reactivity of the HPA axis may be pathologically relevant to PMS because it predicts heightened PMS severity.