Psychogenic fever: how psychological stress affects body temperature in the clinical population

Huddling substates in mice facilitate dynamic changes in body temperature and are modulated by Shank3b and Trpm8 mutation

Social thermoregulation is a means of maintaining homeostatic body temperature. While adult mice are a model organism for studying both social behavior and energy regulation, the relationship between huddling and core body temperature (Tb) is poorly understood. Here, we develop a behavioral paradigm and computational tools to identify active-huddling and quiescent-huddling as distinct thermal substates. We find that huddling is an effective thermoregulatory strategy in female but not male groups. At 23°C (room temperature), but not 30°C (near thermoneutrality), huddling facilitates large reductions in Tb and Tb-variance. Notably, active-huddling is associated with bidirectional changes in Tb, depending on its proximity to bouts of quiescent-huddling. Further, group-housed animals lacking the synaptic scaffolding gene Shank3b have hyperthermic Tb and spend less time huddling. In contrast, individuals lacking the cold-sensing gene Trpm8 have hypothermic Tb - a deficit that is rescued by increased huddling time. These results reveal how huddling behavior facilitates acute adjustments of Tb in a state-dependent manner.

Neural cell-types and circuits linking thermoregulation and social behavior

Understanding how social and affective behavioral states are controlled by neural circuits is a fundamental challenge in neurobiology. Despite increasing understanding of central circuits governing prosocial and agonistic interactions, how bodily autonomic processes regulate these behaviors is less resolved. Thermoregulation is vital for maintaining homeostasis, but also associated with cognitive, physical, affective, and behavioral states. Here, we posit that adjusting body temperature may be integral to the appropriate expression of social behavior and argue that understanding neural links between behavior and thermoregulation is timely. First, changes in behavioral states-including social interaction-often accompany changes in body temperature. Second, recent work has uncovered neural populations controlling both thermoregulatory and social behavioral pathways. We identify additional neural populations that, in separate studies, control social behavior and thermoregulation, and highlight their relevance to human and animal studies. Third, dysregulation of body temperature is linked to human neuropsychiatric disorders. Although body temperature is a "hidden state" in many neurobiological studies, it likely plays an underappreciated role in regulating social and affective states.

Behavioural and physiological responses to stressors in sheep with temperament classified by genotype or phenotype

The single nucleotide polymorphism (SNP) rs107856856, located in the tryptophan hydroxylase-2 gene, is associated with the behavioural phenotype for sheep temperament measured at weaning. Here, we tested the association between that SNP and physiological and behavioural responses to stressors in adult sheep. Two groups of adult sheep, one with genotype A/A (calm genotype) and the other with G/G (nervous genotype) in rs107856856, were selected from 160 sheep and were exposed, twice, to an open-field arena and an isolation box test (IBT). During each repeat, the behaviour and physiological responses (cortisol, prolactin, dehydroepiandrosterone [DHEA], brain derived neurotrophic factor [BDNF], characteristics of the response of body temperature, and oxidative stress) were measured. The behavioural and physiological responses of the sheep were compared between genotypes and also between groups classified on their phenotype as assessed by their initial isolation box score ("low responders" and "high responders"). The SNP rs107856856 had some effects on the behavioural phenotype (IBT score) but no effects on the physiological response to stress (cortisol, prolactin, DHEA, BDNF, oxidative stress or changes in body temperature) in the adult sheep, probably because the sheep were exposed, and therefore had adapted, to human contact during their life.

Disabling symptoms associated with increased axillary temperature in patients with functional hyperthermia

BACKGROUND

I previously reported a case of functional hyperthermia (FH) in a patient with an axillary temperature just slightly above 37.0 °C who persistently requested treatment. Because the severity of her fatigue increased remarkably when her axillary temperature increased above 37.0 °C, she felt that the temperature of 37.0 °C was disabling. In the present study, I analyzed a larger number of patients with FH to investigate the incidence of disabling symptoms with increasing body temperature, the kinds of symptoms associated with increased body temperature, and the temperatures at which these symptoms became disabling.

MAIN BODY

Twenty patients with FH (7 men, 13 women; mean age ± standard deviation, 31.2 ± 10.9 years) who visited my department were asked whether they had any disabling symptoms associated with an increase in axillary temperature and, if so, at what temperature the symptoms became disabling. Sixteen of 20 patients (80.0%) responded that they had such symptoms, which included worsening of general fatigue (n = 12, 75.0%), feelings that their brain did not work properly (n = 5, 31.3%), inability to move (n = 4, 25.0%), hot flashes/feeling of heat (n = 3, 18.8%), headache (n = 2, 12.5%), dizziness (n = 2, 12.5%) and anorexia (n = 1, 6.3%). The axillary temperatures at which patients felt worsening fatigue ranged from 37.0 °C to 37.4 °C in 7 of the 12 patients (58.3%) who experienced worsening fatigue. The patients also reported that the disabling symptoms, with the exception of headache, were not alleviated by antipyretics.

CONCLUSIONS

Many patients with FH reported worsening fatigue as a disabling symptom associated with increased axillary temperature; more than half of those patients experienced worsening fatigue in the temperature range of 37.0 °C to 37.4 °C. These findings suggest that the reasons patients with FH consider 37 °C disabling and seek medical treatment are that physical symptoms such as fatigue worsen at 37 °C, although this temperature is assumed by many physicians to be within the normal range or just above the normal range of axillary temperature, and that most hyperthermia-associated symptoms are not alleviated by antipyretic drugs.

Characteristics of Functional Hyperthermia Detected in an Outpatient Clinic for Fever of Unknown Origin

Background: Functional hyperthermia (FH) is characterized by hyperthermia resulting from sympathetic hyperactivity rather than inflammation, and it is frequently overlooked by medical practitioners due to the absence of abnormalities in a medical examination. Although FH is an important differential diagnosis for fever of unknown origin (FUO), the literature on FUO cases in Japan lacks information on FH. In this study, we aimed to uncover the population of FH patients hidden in FUO cases. Methods: An outpatient clinic for FUO was established at Okayama University Hospital, and 132 patients were examined during the period from May 2019 to February 2022. Results: A diagnosis of FH was made in 31.1% of the FUO cases, and FH predominantly affected individuals in their third and fourth decades of life with a higher incidence in females (68.3%). The frequency of a history of psychiatric illness was higher in patients with FH than in patients with other febrile illnesses. Although the C-reactive protein (CRP) is generally negative in FH cases, some obese patients, with a body mass index ≥ 25 had slightly elevated levels of CRP but were diagnosed with FH. Conclusions: The results showed the importance of identifying FH when encountering patients with FUO without any organic etiology.

Sex differences in body temperature and neural power spectra in response to repeated restraint stress

Repeated stress is associated with an increased risk of developing psychiatric illnesses such as post-traumatic stress disorder (PTSD), which is more common in women, yet the neurobiology behind this sex difference is unknown. Habituation to repeated stress is impaired in PTSD, and recent preclinical studies have shown that female rats do not habituate as fully as male rats to repeated stress, which leads to impairments in cognition and sleep. Further research should examine sex differences after repeated stress in other relevant measures, such as body temperature and neural activity. In this study, we analyzed core body temperature and EEG power spectra in adult male and female rats during restraint, as well as during sleep transitions following stress. We found that core body temperature of male rats habituated to repeated restraint more fully than female rats. Additionally, we found that females had a higher average beta band power than males on both days of restraint, indicating higher levels of arousal. Lastly, we observed that females had lower delta band power than males during sleep transitions on Day 1 of restraint, however, females demonstrated higher delta band power than males by Day 5 of restraint. This suggests that it may take females longer to initiate sleep recovery compared with males. These findings indicate that there are differences in the physiological and neural processes of males and females after repeated stress. Understanding the way that the stress response is regulated in both sexes can provide insight into individualized treatment for stress-related disorders.

'Functional hyperthermia': a historical overview

The management of low-grade fever in adults has not been codified. This gap is related not only to the numerous possible aetiologies but also to the difficulty of escaping the monocausal model of diseases. This article explores the complex issue of positive signs in 'psychogenic fever' through Reimann's 1930s series. The discussion emphasises Canguilhem's positions regarding vital signs and proposes (1) a semantic clarification of 'habitual hyperthermia' and (2) an amendment of the Belgian diagnostic criteria based on the concept of functional disorder. This paper also suggests following Peirce's pragmatism in the face of an uncommon clinical picture.

Catecholamine Variations in Pediatric Gastrointestinal Disorders and Their Neuropsychiatric Expression

The interplay between the central nervous system and the intestinal environment hinges on neural, hormonal, immune, and metabolic reactions. Over decades, significant effort has gone into exploring the link between the digestive system and the brain. The primary objective of this study is to assess catecholamine levels in children with neuropsychiatric disorders. We aim to examine how these levels impact the mental and physical wellbeing of these children, with a specific focus on psychoemotional symptoms and cognitive performance. Our research seeks to identify the significance of modifying neurotransmitter levels in pediatric medical interventions, ultimately striving to reduce mental health risks and enhance children's future development. A total of 135 individuals were chosen to partake, and they engaged in regular monthly consultations according to established study protocols. Clinical evaluations were conducted in a medical environment, encompassing the observation of constipation, diarrhea, and additional gastrointestinal anomalies not confined to constipation or diarrhea. This entailed the assessment of neurotransmitter imbalances, with a specific focus on dopamine, adrenaline, noradrenaline, and the noradrenaline/adrenaline ratio. Gastrointestinal disorders are indicative of imbalances in catecholamines, with lower gastrointestinal problems being correlated with such imbalances. In subjects with psychiatric disorders, a more pronounced dopamine and noradrenaline/adrenaline ratio was observed, while elevated adrenaline levels were associated with psychoanxiety disorders.

ILF3 prion-like domain regulates gene expression and fear memory under chronic stress

The prion-like domain (PrLD) is a class of intrinsically disordered regions. Although its propensity to form condensates has been studied in the context of neurodegenerative diseases, the physiological role of PrLD remains unclear. Here, we investigated the role of PrLD in the RNA-binding protein NFAR2, generated by a splicing variant of the Ilf3 gene. Removal of the PrLD in mice did not impair the function of NFAR2 required for survival, but did affect the responses to chronic water immersion and restraint stress (WIRS). The PrLD was required for WIRS-sensitive nuclear localization of NFAR2 and WIRS-induced changes in mRNA expression and translation in the amygdala, a fear-related brain region. Consistently, the PrLD conferred resistance to WIRS in fear-associated memory formation. Our study provides insights into the PrLD-dependent role of NFAR2 for chronic stress adaptation in the brain.

Short Communication: Use of Infrared Thermometers for Cutaneous Temperature Recording: Agreement with the Rectal Temperature in Felis catus

Simple Summary

The recording of body temperature by rectal temperature assessments is a stressful procedure for cats. For this purpose, alternative methods for using rectal digital thermometers to monitor body temperature were investigated. Skin temperature was recorded in 20 cats, in 5 different body regions, and compared with the rectal temperature. The obtained data indicated that the cutaneous temperature recorded by the infrared thermometers was not in agreement with the data recorded by the digital thermometer in the rectum.

Abstract

In veterinary medicine, the gold standard for assessing body temperature is rectal temperature assessment. Considering that this procedure is stressful for many species, in particular for cats, it could be clinically important to consider an alternative approach for the monitoring of core body temperature. The aim of this study was to test if cutaneous temperature measurements by means of different infrared thermometers are in agreement with the most commonly used method for body temperature measurement in cats. The cutaneous temperature was recorded in the jugular, shoulder, rib, flank, and inner thigh, using three different non-contact infrared thermometers (IR1, IR2, and IR3) in 20 cats. The cutaneous temperature was then compared to the rectal temperature, recorded by means of a digital thermometer. The obtained data indicated that the cutaneous temperature recorded by the infrared thermometers was not in agreement with the data recorded by the digital thermometer in the rectum. In cats, the use of non-contact infrared thermometers gave no reproducible or constant data to justify their application for the recording of body temperature instead of rectal temperature recording. In addition, the infrared temperature measurement devices generated results that were not in good agreement among themselves, providing a novel result of clinical importance.

Psychogenic fever and postural tachycardia syndrome among school-aged children and adolescents with fever of unknown origin

Background

Although fever is a common symptom in pediatric practice, its origin is often unknown in pediatric patients. Psychogenic fever is a stress-related, psychosomatic disease observed especially in young women. This study aimed to estimate the prevalence of psychogenic fever in pediatric patients with fever of unknown origin by surveying the medical records of school-aged children and adolescents.

Methods

The study subjects included 47 patients aged 6–15 years who visited the Department of Pediatrics in Kansai Medical University Medical Center between January 2006 and December 2020 with fever of unknown origin. Data on age, sex, final estimated diagnosis, and comorbid psychosocial issues were collected from the medical records.

Results

The study was composed of 47 patients, including 22 male and 25 female patients (male/female ratio, 1:1.36). The mean age was 10.1 (standard deviation, 2.4) years for boys and 11.6 (standard deviation, 2.7) years for girls (p = .047). The final estimated diagnoses were psychogenic fever, physical disorder, infection of unknown origin, and miscellaneous in 18, 12, 12, and 5 patients, respectively. The most common comorbidity in these pediatric patients with psychogenic fever was postural tachycardia syndrome.

Conclusion

Psychogenic fever was a common cause of fever of unknown origin in pediatric patients, and postural tachycardia was prevalent among children with psychogenic fever. Enhanced sympathetic response to stress might play an important role in both psychogenic fever and postural tachycardia.

Meta-Analysis of Children's Acute Psychological Stress and Action Stress on Immune Function under Microscope Images

The immune system is a complex system, mainly including immune cells and immune organs. When the human body is invaded by foreign substances, the immune system will play a role in resisting the attack of harmful substances and pure necrotic cells, which is the defense structure of the body. The purpose of this study was to analyze children's acute psychological stress and action stress, and judge the adverse effects on immune function. Through the stress experiment of rats, three experimental groups were set up, which were placebo control group, placebo stress group, and drug stress group. The experiments include material-level test, sugar preference test, body weight test, and lymphocyte test. The experimental data show that stress reaction not only causes negative emotions, but also reduces weight gain by about 5%, and sugar preference decreases by about 40% compared with the normal group. There was no significant difference in the number of granulocytes and intermediate cells in the blood, but the number of lymphocytes increased from 2.49 × 109/L to 5.03 × 109/L. It shows that acute psychological stress has an inhibitory effect on the immune function of the body; not only suitable load exercise can improve the immune function of the body but also the mechanism may be that moderate load exercise makes the rat axis has better adaptability, and improves hormones, cytokines, and cytokines. The secretion of neurotransmitters can maintain the stability of the body's immune function.

Postoperative hyperthermia-induced multiple organ failure in a child with Down syndrome: a case report

Background

Psychological stress has been reported to cause hyperthermia. Persistent excessive hyperthermia can, in turn, cause hypercytokinemia and organ damage. We report a case of postoperative severe hyperthermia leading to a systemic inflammatory response and multiple organ failure in a child with Down syndrome.

Case presentation

A 10-month-old native Japanese boy with Down syndrome and Hirschsprung’s disease is described. Newborn screening showed congenital hypothyroidism and a ventricular septal defect, but these conditions were stable upon administration of levothyroxine and furosemide. His development was equivalent to that of a child with Down syndrome. He developed a noninfectious high fever twice after preoperative preparations at age 8 months and again at 9 months. He was readmitted to hospital at age 10 months to undergo the Soave procedure to correct Hirschsprung’s disease. However, he contracted a fever immediately after the surgical procedure. Hyperthermia (42 °C) was refractory to acetaminophen treatment and deteriorated to multiple organ failure due to hypercytokinemia, with increased serum levels of interleukin-6 (44.6 pg/mL) and interleukin-10 (1010 pg/mL). He died on postoperative day 2 with hypoxemia, respiratory/metabolic acidosis, increased serum levels of transaminases, reduced coagulation, and pancytopenia. Various infectious and noninfectious causes of hyperthermia could not be identified clearly by culture or blood tests.

Conclusions

We speculated that the proximate cause of the fever was psychological stress, because he suffered repeated episodes of hyperthermia after the invasive procedure. Hyperthermia, together with the immune-system disorders associated with Down syndrome, may have induced hypercytokinemia and multiple organ failure. This rare case of noninfectious postoperative hyperthermia leading to multiple organ failure may help to shed further light on the currently unclear pathogenic mechanism of hyperthermia and associated multiple organ failure during the perioperative period in children.

A Systematic Review of Thermosensation and Thermoregulation in Anxiety Disorders

Objectives: Sweating, hot flushes, and blushing are symptoms frequently reported by individuals with anxiety disorders. They represent important reinforcers of anxiogenic cognitions and behaviours. One system that may be involved in the manifestation of these symptoms is the thermosensory/thermoregulatory system. The aim of the present study was to investigate to what extent individuals with anxiety disorders are characterised by alterations in this system.

Methods: PubMed and PsycINFO were systematically searched. Studies were eligible if they (i) assessed individuals with anxiety disorders, (ii) thermosensation or thermoregulatory effectors/outcomes, and (iii) used a case-control design.

Results:N = 86 studies were identified. There was no evidence of altered thermosensation in individuals with anxiety disorders. Regarding thermoregulatory effectors, individuals with social anxiety disorder exhibited altered cutaneous vasodilation upon pharmacological challenge; individuals with specific phobia showed increased sweating upon confrontation with phobic stimuli; individuals with panic disorder showed increased daily sweating as well as increased sweating in response to non-phobic and phobic stimuli. Regarding thermoregulatory outcomes, there was evidence for altered skin temperature in all subtypes of anxiety.

Conclusion: Whereas there was no evidence of altered thermoregulation in specific phobia, a subgroup of individuals with social anxiety and panic disorder appears to exhibit altered vasodilation and sweating, respectively. Longitudinal research is warranted to investigate whether this represents a vulnerability to anxiety/panic.

Central sympathetic network for thermoregulatory responses to psychological stress

In mammals, many types of psychological stressors elicit a variety of sympathoexcitatory responses paralleling the classic fight-or-flight response to a threat to survival, including increased body temperature via brown adipose tissue thermogenesis and cutaneous vasoconstriction, and increased skeletal muscle blood flow via tachycardia and visceral vasoconstriction. Although these responses are usually supportive for stress coping, aberrant sympathetic responses to stress can lead to clinical issues in psychosomatic medicine. Sympathetic stress responses are mediated mostly by sympathetic premotor drives from the rostral medullary raphe region (rMR) and partly by those from the rostral ventrolateral medulla (RVLM). Hypothalamomedullary descending pathways from the dorsomedial hypothalamus (DMH) to the rMR and RVLM mediate important, stress-driven sympathoexcitatory transmission to the premotor neurons to drive the thermal and cardiovascular responses. The DMH also likely sends an excitatory input to the paraventricular hypothalamic nucleus to stimulate stress hormone release. Neurons in the DMH receive a stress-related excitation from the dorsal peduncular cortex and dorsal tenia tecta (DP/DTT) in the ventromedial prefrontal cortex. By connecting the corticolimbic emotion circuit to the central sympathetic and somatic motor systems, the DP/DTT → DMH pathway plays as the primary mediator of the psychosomatic signaling that drives a variety of sympathetic and behavioral stress responses. These brain regions together with other stress-related regions constitute a central neural network for physiological stress responses. This network model is relevant to understanding the central mechanisms by which stress and emotions affect autonomic regulations of homeostasis and to developing new therapeutic strategies for various stress-related disorders.

A hypothalamomedullary network for physiological responses to environmental stresses

Various environmental stressors, such as extreme temperatures (hot and cold), pathogens, predators and insufficient food, can threaten life. Remarkable progress has recently been made in understanding the central circuit mechanisms of physiological responses to such stressors. A hypothalamomedullary neural pathway from the dorsomedial hypothalamus (DMH) to the rostral medullary raphe region (rMR) regulates sympathetic outflows to effector organs for homeostasis. Thermal and infection stress inputs to the preoptic area dynamically alter the DMH → rMR transmission to elicit thermoregulatory, febrile and cardiovascular responses. Psychological stress signalling from a ventromedial prefrontal cortical area to the DMH drives sympathetic and behavioural responses for stress coping, representing a psychosomatic connection from the corticolimbic emotion circuit to the autonomic and somatic motor systems. Under starvation stress, medullary reticular neurons activated by hunger signalling from the hypothalamus suppress thermogenic drive from the rMR for energy saving and prime mastication to promote food intake. This Perspective presents a combined neural network for environmental stress responses, providing insights into the central circuit mechanism for the integrative regulation of systemic organs.

A Broader Perspective: Functional Symptoms Beyond Neurology

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Functional (psychogenic) symptoms exist in all specialties.

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They are by definition not under voluntary control, unlike factitious disorders and malingering.

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The diagnostic approach to functional symptoms varies among specialties.

Effect of agarwood leaf extract on production performance of broilers experiencing heat stress

Background and Aim:

The open house cage is mainly influenced by the environmental heat from the sun and the heat released by the chicken. Heat stress can affect physiological conditions so that it has an impact on decreasing productivity. This study aims to determine the effect of agarwood leaf extract in feed on the physiological condition and production performance of broilers experiencing heat stress and to generate prediction equations for the optimal level of the extract in feed.

Materials and Methods:

A total of 200 22-day-old broilers (Cobb 500™) underwent four treatments with five replications each, namely, feed without agarwood leaf extract (control) (T0), and feed with 250 (T1), 300 (T2), and 350 mg of agarwood leaf extract/kg body weight (T3). The parameters observed include physiological condition (heart rate, respiratory frequency, and body temperature) as well as production performance (feed consumption, body weight gain [BWG], and feed conversion).

Results:

The administration of agarwood leaf extract significantly (p<0.05) decreased heart rate and respiratory frequency. However, there was no significant difference (p>0.05) in body temperature, glucose levels, hemoglobin and erythrocyte concentrations, as well as production performance which include weight gain, feed consumption, and feed conversion ratio. Meanwhile, broilers treated with agarwood leaf extract had a significantly lower heart rate and respiratory frequency (p<0.05) compared to the control. However, broilers given agarwood leaf extract showed better body weight, consumption, and ration conversion compared to the control.

Conclusion:

Agarwood leaf extract in feed reduces heart rate and respiratory frequency but has no significant effect on body temperature and hematological parameters (glucose levels, hemoglobin, and erythrocyte concentrations) as well as production performance (feed consumption, weight gain, and feed conversion). These results indicate that the administration of 350 mg/kg body weight agarwood leaf extract is most effective to reduce feed consumption and increase BWG.

Pathophysiology of Fever and Application of Infrared Thermography (IRT) in the Detection of Sick Domestic Animals: Recent Advances

Body-temperature elevations are multifactorial in origin and classified as hyperthermia as a rise in temperature due to alterations in the thermoregulation mechanism; the body loses the ability to control or regulate body temperature. In contrast, fever is a controlled state, since the body adjusts its stable temperature range to increase body temperature without losing the thermoregulation capacity. Fever refers to an acute phase response that confers a survival benefit on the body, raising core body temperature during infection or systemic inflammation processes to reduce the survival and proliferation of infectious pathogens by altering temperature, restriction of essential nutrients, and the activation of an immune reaction. However, once the infection resolves, the febrile response must be tightly regulated to avoid excessive tissue damage. During fever, neurological, endocrine, immunological, and metabolic changes occur that cause an increase in the stable temperature range, which allows the core body temperature to be considerably increased to stop the invasion of the offending agent and restrict the damage to the organism. There are different metabolic mechanisms of thermoregulation in the febrile response at the central and peripheral levels and cellular events. In response to cold or heat, the brain triggers thermoregulatory responses to coping with changes in body temperature, including autonomic effectors, such as thermogenesis, vasodilation, sweating, and behavioral mechanisms, that trigger flexible, goal-oriented actions, such as seeking heat or cold, nest building, and postural extension. Infrared thermography (IRT) has proven to be a reliable method for the early detection of pathologies affecting animal health and welfare that represent economic losses for farmers. However, the standardization of protocols for IRT use is still needed. Together with the complete understanding of the physiological and behavioral responses involved in the febrile process, it is possible to have timely solutions to serious problem situations. For this reason, the present review aims to analyze the new findings in pathophysiological mechanisms of the febrile process, the heat-loss mechanisms in an animal with fever, thermoregulation, the adverse effects of fever, and recent scientific findings related to different pathologies in farm animals through the use of IRT.

Psychogenic fever due to worry about COVID-19: A case report

Psychogenic fever is stress-related hyperthermia that is recognized as a psychosomatic condition. We treated a 46-year-old Japanese man who was worrying about the coronavirus infection (COVID-19) and had a fever with a maximum temperature of 38.1℃. The patient was tested twice for SRAS-CoV-2 using polymerase chain reaction (PCR), but both tests were negative. All tests were negative for organic diseases, including infections, allergy/collagen diseases, endocrine disorders, malignancies, and drugs-induced conditions. The more he doubted the COVID-19 in him, the more he complained of the already known various symptoms, such as smelling disorder. The patient believed firmly that he had COVID-19 because PCR can be false negative. Finally, the patient was treated with the anxiolytic, loflazepate, at 4 mg/day. This treatment was highly effective. The patient's serum IL-6 was 1.1 pg/ml (≤4.0). The patient was diagnosed with psychogenic fever due to irrational worry over coronavirus. Such typical cases should be treated with an anxiolytic.

How Can We Adapt Thermal Comfort for Disabled Patients? A Case Study of French Healthcare Buildings in Summer

This paper investigates adaptive thermal comfort during summer in medical residences that are located in the French city of Troyes and managed by the Association of Parents of Disabled Children (APEI). Thermal comfort in these buildings is evaluated using subjective measurements and objective physical parameters. The thermal sensations of respondents were determined by questionnaires, while thermal comfort was estimated using the predicted mean vote (PMV) model. Indoor environmental parameters (relative humidity, mean radiant temperature, air temperature, and air velocity) were measured using a thermal environment sensor during the summer period in July and August 2018. A good correlation was found between operative temperature, mean radiant temperature, and PMV. The neutral temperature was determined by linear regression analysis of the operative temperature and Fanger’s PMV model. The obtained neutral temperature is 23.7 °C. Based on the datasets and questionnaires, the adaptive coefficient α representing patients’ capacity to adapt to heat was found to be 1.261. A strong correlation was also observed between the sequential thermal index n(t) and the adaptive temperature. Finally, a new empirical model of adaptive temperature was developed using the data collected from a longitudinal survey in four residential buildings of APEI in summer, and the obtained adaptive temperature is 25.0 °C with upper and lower limits of 24.7 °C and 25.4 °C.

Temperature sensitivity after burn injury: A Burn Model System National Database Hot Topic

BACKGROUND

People living with burn injury often report temperature sensitivity. However, its epidemiology and associations with health-related quality of life (HRQOL) are unknown. We aimed to characterize temperature sensitivity and determine its impact on HRQOL to inform patient education after recovery from burn injury.

METHODS

We used the multicenter, longitudinal Burn Model System National Database to assess temperature sensitivity at 6, 12 and 24 months after burn injury. Chi-square and Kruskal-Wallis tests determined differences in patient and injury characteristics. Multivariable, multi-level generalized linear regression models determined the association of temperature sensitivity with Satisfaction with Life Scale (SWL) scores and Veterans RAND 12 (VR-12) physical (PCS) and mental health summary (MCS) component scores.

RESULTS

The cohort comprised 637 participants. Two thirds (66%) experienced temperature sensitivity. They had larger burns (12% TBSA, IQR 4-30 vs 5% TBSA, IQR 2-15; p<0.0001), required more grafting (5% TBSA, IQR 1-19 vs 2% TBSA, IQR 0-6; p<0.0001), and had higher intensity of pruritus at discharge (11% severe vs 5% severe; p=0.002). After adjusting for confounding variables, temperature sensitivity was strongly associated with lower SWL (OR -3.2, 95% CI -5.2, -1.1) and MCS (OR -4.0, 95% CI -6.9, -1.2) at 6-months. Temperature sensitivity decreased over time (43% at discharge, 4% at 24-months) and was not associated with poorer HRQOL at 12 and 24 months.

CONCLUSION

Temperature sensitivity is common after burn injury and associated with worse SWL and MCS during the first year after injury. However, temperature sensitivity seems to improve and be less intrusive over time.

The Concept of Advanced Multi-Sensor Monitoring of Human Stress

Many people live under stressful conditions which has an adverse effect on their health. Human stress, especially long-term one, can lead to a serious illness. Therefore, monitoring of human stress influence can be very useful. We can monitor stress in strictly controlled laboratory conditions, but it is time-consuming and does not capture reactions, on everyday stressors or in natural environment using wearable sensors, but with limited accuracy. Therefore, we began to analyze the current state of promising wearable stress-meters and the latest advances in the record of related physiological variables. Based on these results, we present the concept of an accurate, reliable and easier to use telemedicine device for long-term monitoring of people in a real life. In our concept, we ratify with two synchronized devices, one on the finger and the second on the chest. The results will be obtained from several physiological variables including electrodermal activity, heart rate and respiration, body temperature, blood pressure and others. All these variables will be measured using a coherent multi-sensors device. Our goal is to show possibilities and trends towards the production of new telemedicine equipment and thus, opening the door to a widespread application of human stress-meters.

Preoperative psychogenic fever: to operate or not to operate

Postponing elective surgery because of fever on the morning of the operation is frustrating for patients as well as doctors. It is also not cost effective and the unused operation capacity could have been used on other patients. On the other hand, surgery and general anaesthesia will put unwanted physiological strain on a patient fighting an on-going infection. Preoperative fever therefore poses a dilemma; to proceed with-, or to postpone the scheduled operation.

We report a case where a 58-year-old woman, scheduled for prophylactic bilateral mastectomy and primary implant-based reconstruction, was postponed because of a temperature of 37.9°C. The morning of her new operation date, she developed a fever of 39.2°C which fell to 38.2°C shortly after administration of 0.25 mg triazolam. She was diagnosed with psychogenic fever, and we went through with the operation, even though the patient was febrile. The operation was successful, and she had no post-operative complications.

A Review of Biophysiological and Biochemical Indicators of Stress for Connected and Preventive Healthcare

Stress is a known contributor to several life-threatening medical conditions and a risk factor for triggering acute cardiovascular events, as well as a root cause of several social problems. The burden of stress is increasing globally and, with that, is the interest in developing effective stress-monitoring solutions for preventive and connected health, particularly with the help of wearable sensing technologies. The recent development of miniaturized and flexible biosensors has enabled the development of connected wearable solutions to monitor stress and intervene in time to prevent the progression of stress-induced medical conditions. This paper presents a review of the literature on different physiological and chemical indicators of stress, which are commonly used for quantitative assessment of stress, and the associated sensing technologies.

Infrared Thermography Reveals Sex-Specific Responses to Stress in Mice

Psychogenic hyperthermia is a stress-related condition reported mostly in women. Neuroendocrine responses to stress in females differ from those in males, and these differences cannot be explained solely based on hypothalamic-pituitary-adrenal (HPA) axis activity. Here, we used infrared (IR) thermographic imaging to record changes in cutaneous temperature following two types of stressful experiences in female and male mice. Mice were exposed to either single-session restraint stress or vertical exploration (rearing) deprivation and were monitored for exploratory activity and IR surface thermal changes. Females displayed higher rearing activity than males during the dark phase of the light cycle. Both sexes showed similar plasma corticosterone (CORT) responses after a challenge with restraint and rearing deprivation. However, only females responded to rearing deprivation with increased cutaneous temperature in the head and back, and a reduced thermal response in the tail. Circulating CORT levels were not correlated with the thermal variations. These findings, for the first time, provide evidence for sex-specific cutaneous thermal responses to short-term stress in mice following transient vertical-activity deprivation that may mimic clinical psychogenic hyperthermia.

A central master driver of psychosocial stress responses in the rat

The mechanism by which psychological stress elicits various physiological responses is unknown. We discovered a central master neural pathway in rats that drives autonomic and behavioral stress responses by connecting the corticolimbic stress circuits to the hypothalamus. Psychosocial stress signals from emotion-related forebrain regions activated a VGLUT1-positive glutamatergic pathway from the dorsal peduncular cortex and dorsal tenia tecta (DP/DTT), an unexplored prefrontal cortical area, to the dorsomedial hypothalamus (DMH), a hypothalamic autonomic center. Genetic ablation and optogenetics revealed that the DP/DTT→DMH pathway drives thermogenic, hyperthermic, and cardiovascular sympathetic responses to psychosocial stress without contributing to basal homeostasis. This pathway also mediates avoidance behavior from psychosocial stressors. Given the variety of stress responses driven by the DP/DTT→DMH pathway, the DP/DTT can be a potential target for treating psychosomatic disorders.

Alpha2-adrenergic receptor agonists prevent emotional hyperthermia

Emotionally significant stimuli, including potential threats from the external environment, trigger an increase in body temperature, a response known as emotional hyperthermia. Sympathetically-mediated brown adipose tissue (BAT) thermogenesis contributes substantially to this hyperthermic response. The systemic administration of α₂-adrenergic agonists is known to inhibit both febrile and shivering responses. In the present study, we investigated whether systemic administration of clonidine, a α₂-adrenoceptor agonist, attenuates the emotional hyperthermia evoked in conscious unrestrained rats suddenly confronted with a second (intruder) rat, itself confined to a small cage. Pre-implanted thermistors were used to measure BAT and body temperature in conscious, freely moving, male Sprague-Dawley rats. The rats were pre-treated with intraperitoneally administered vehicle (Ringer solution) or clonidine (1, 10 and 100 µg/kg). Clonidine, in a dose-dependent manner, reduced the intruder-elicited increases in BAT (log-dose linear regression F(1,16) = 9.52, R² = 0.37, P < 0.01) and body temperature (F(1,16) = 6.48, R² = 0.29, P < 0.05). We also investigated, in anesthetized rats, whether systemic clonidine administration inhibits BAT sympathetic nerve discharge evoked via activation of neurons in the lateral habenula (LHb) - a nucleus involved in the regulation of emotional hyperthermia. In anesthetized rats, clonidine abolished the BAT sympathetic nerve discharges elicited via bicuculline-mediated disinhibition of the LHb. These results suggest that activation of central α₂-adrenergic receptors attenuates the process of emotional hyperthermia by reduction of BAT thermogenesis.

Recent Progress and Perspectives of Thermally Drawn Multimaterial Fiber Electronics

Fibers are the building blocks of a broad spectrum of products from textiles to composites, and waveguides to wound dressings. While ubiquitous, the capabilities of fibers have not rapidly increased compared to semiconductor chip technology, for example. Recognizing that fibers lack the composition, geometry, and feature sizes for more functions, exploration of the boundaries of fiber functionality began some years ago. The approach focuses on a particular form of fiber production, thermal-drawing from a preform. This process has been used for producing single material fibers, but by combining metals, insulators, and semiconductors all within a single strand of fiber, an entire world of functionality in fibers has emerged. Fibers with optical, electrical, acoustic, or optoelectronic functionalities can be produced at scale from relatively easy-to-assemble macroscopic preforms. Two significant opportunities now present themselves. First, can one expect that fiber functions escalate in a predictable manner, creating the context for a "Moore's Law" analog in fibers? Second, as fabrics occupy an enormous surface around the body, could fabrics offer a valuable service to augment the human body? Toward answering these questions, the materials, performance, and limitations of thermally drawn fibers in different electronic applications are detailed and their potential in new fields is envisioned.

Activating dopamine D2 receptors reduces brown adipose tissue thermogenesis induced by psychological stress and by activation of the lateral habenula

Emotional hyperthermia is the increase in body temperature that occurs as a response to an animal detecting a salient, survival-relevant stimulus. Brown adipose tissue (BAT) thermogenesis, controlled via its sympathetic innervation, contributes to this temperature increase. Here, we have used an intruder rat experimental model to determine whether quinpirole-mediated activation of dopamine D₂ receptors attenuates emotional hyperthermia in conscious rats. In anesthetized rats, we determined whether systemic quinpirole reduces BAT nerve discharge induced by activation of the medullary raphé and the lateral habenula (LHb). We measured BAT and body temperature with chronically implanted thermistors in conscious, freely moving, individually housed, male rats (resident rats). Either vehicle or quinpirole was administered, intraperitoneally, to the resident rat 30 min before introduction of a caged intruder rat. Quinpirole, in a dose-dependent manner, reduced intruder-elicited increases in BAT and body temperature. Pre-treatment with the D₂ antagonist spiperone, but not the selective D₁ antagonist SCH-23390, prevented this quinpirole-elicited decrease. In anesthetized rats, quinpirole abolished BAT sympathetic nerve discharge elicited by bicuculline-mediated activation of the LHb, but not the medullary raphé. Thus, activation of dopamine D₂ receptors reduces the BAT thermogenesis that contributes to emotional hyperthermia. We provide evidence that these dopamine D₂ receptors are located in the thermogenic pathway between the LHb and the lower brainstem pre-sympathetic control centre in the medullary raphé.

Diagnostic approach for patients with unidentified fever according to the classical criteria of fever of unknown origin in the field of autoimmune disorders

Fever of unknown origin (FUO) is caused by various diseases, making differential diagnosis difficult. This study aimed to determine the clinical features of patients with FUO for use in daily medical practice. Medical records of patients who first visited our department for FUO between January 2008 and December 2017 were reviewed. We classified the diagnostic categories as infection, non-infectious inflammation, neoplasm, others, and unidentified through definitive diagnosis and compared the clinical characteristics of patients who fulfilled the criteria of classical FUO and those who did not. The most prevalent diseases in patients who fulfilled the criteria were adult-onset Still's disease, Behçet's disease (BD), and polymyalgia rheumatica, which do not have any specific image inspection or specific serological markers. BD and familial Mediterranean fever were most prevalent in patients who did not fulfill the criteria. All neoplasms fulfilled the criteria of classical FUO. The most useful diagnostic procedure was determined according to the criteria of each disease. The key factor that did not fulfill the criteria was periodic fever continuing for less than 3 weeks. When examining patients with FUO, we should strictly diagnose in accordance with the criteria of each disease and consider diseases that cause periodic fever.

Comprehensive Analysis of Temperature in Hospitalized Patients

BACKGROUND

Human body temperature is believed to be linked to clinical diagnoses. However, most of the available data stems from healthy individuals, with no large-scale studies addressing body temperature in the inpatient setting, which is the focus of our study.

MATERIALS AND METHODS

This is a retrospective analysis of a total of 695,107 temperature readings from 16,245 patients hospitalized over a 1-year period at a tertiary medical center, ages 0-105 years, 50% female, with rectal, monotherm, axillary, oral, temporal and tympanic measurement sites. The average temperature (T_ave) per patient and per measurement site was used in all calculations. Descriptive statistics, Student's t-test, and Pearson's correlation were used, where appropriate, with statistical significance set at P < 0.05.

RESULTS

T_ave from all measurement sites was 98.13 ± 0.48(SD)F(36.74 ± 0.27°C). T_ave varied by the site of measurement, in decreasing order highest-to-lowest being rectal, monotherm, axillary, oral, temporal, and tympanic, all of which were higher than the available reported averages for healthy subjects. T_ave decreased as patients' age increased. There was only slight and likely clinically insignificant difference between the sexes. There were differences in T_ave between the intensive care units (ICUs), listed from highest-to-lowest: Neuro ICU, Pediatric ICU, Surgical ICU, Cardiac ICU and Medical ICU. However, there was no difference between all ICU and non-ICU patients.

CONCLUSIONS

Our inpatient data demonstrate that previously identified body temperature trends among healthy subjects are preserved, to an extent, in the inpatient setting. To our knowledge, ours is the first study that evaluates the temperatures of all hospitalized patients at a large tertiary medical center.

Activation of Anxiogenic Circuits Instigates Resistance to Diet-Induced Obesity via Increased Energy Expenditure

Anxiety disorders are associated with body weight changes in humans. However, the mechanisms underlying anxiety-induced weight changes remain poorly understood. Using Emx1^Cre/+ mice, we deleted the gene for brain-derived neurotrophic factor (BDNF) in the cortex, hippocampus, and some amygdalar subregions. The resulting mutant mice displayed impaired GABAergic transmission and elevated anxiety. They were leaner when fed either a chow diet or a high-fat diet, owing to higher sympathetic activity, basal metabolic rate, brown adipocyte thermogenesis, and beige adipocyte formation, compared to control mice. BDNF re-expression in the amygdala rescued the anxiety and metabolic phenotypes in mutant mice. Conversely, anxiety induced by amygdala-specific Bdnf deletion or administration of an inverse GABA_A receptor agonist increased energy expenditure. These results reveal that increased activities in anxiogenic circuits can reduce body weight by promoting adaptive thermogenesis and basal metabolism via the sympathetic nervous system and suggest that amygdalar GABAergic neurons are a link between anxiety and metabolic dysfunction.

Psychogenic stress in hospitalized veterinary patients: Causation, implications, and therapies

OBJECTIVE

To review the sources, adverse effects, diagnosis, treatment, and prevention of psychogenic stress in hospitalized human and veterinary patients.

DATA SOURCES

Data were collected by searching PubMed for veterinary and human literature from the past 10 years.

HUMAN DATA SYNTHESIS

Psychogenic stress has been linked to immune suppression; gastrointestinal, cardiovascular, and cutaneous diseases; delayed wound healing; alterations in pain perception; and neurologic impairment. Sources of psychogenic stress include environmental alterations such as excessive noise and light, social and physical factors, sleep disruption, drugs, and underlying disease. Nonpharmacologic options for stress reduction include environmental and treatment modifications, music therapy, and early mobilization. Pharmacologic options include sedation with benzodiazepines and dexmedetomidine. Trazodone and melatonin have been examined for use in sleep promotion but are not currently recommended as standard treatments in ICU.

VETERINARY DATA SYNTHESIS

Activation of the stress response in veterinary patients is largely the same as in people, as are the affected body systems. Possible sources of stress can include social, physical, and environmental factors. No gold standard currently exists for the identification and quantification of stress. A combination of physical examination findings and the results of serum biochemistry, CBC, and biomarker testing can be used to support the diagnosis. Stress scales can be implemented to identify stressed patients and assess severity. Nonpharmacologic treatment options include low-stress handling, pheromones, environmental modifications, and sleep promotion. Pharmacologic options include trazodone, benzodiazepines, dexmedetomidine, and melatonin.

CONCLUSION

The prevalence and clinical significance of psychogenic stress in hospitalized veterinary patients is unknown. Future studies are needed to specifically examine the causative factors of psychogenic stress and the effects of various therapies on stress reduction. The recognition and reduction of psychogenic stress in veterinary patients can lead to improvements in patient care and welfare.

Vital signs changes during different dental procedures: A prospective longitudinal cross-over clinical trial

OBJECTIVES

The purpose of this study was to evaluate the magnitude of vital signs changes during 3 different dental treatments.

STUDY DESIGN

A prospective longitudinal multiarm cross-over clinical trial was conducted. Three dental procedures were performed on each participant: supragingival scaling, dental restoration under local anesthesia (LA), and exodontia under LA. The following parameters were recorded for in each dental procedure: body temperature (BT), respiratory rate (RR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), and peripheral oxygen saturation (SpO₂). Three repeated measurements of each parameter were recorded at 3 phases of each procedure.

RESULTS

A total of 150 dental interventions were performed on 50 patients. Scaling caused a statistically significant rise in BT, RR, and SpO₂, and a reduction in HR. Restorative treatment caused a statistically significant rise in SpO₂ during LA. Exodontia caused a statistically significant rise in BT, RR, SBP (during the procedure), and SpO₂ (during LA).

CONCLUSIONS

Scaling and restorative treatment did not significantly impact heart rate. The respiratory rate may temporarily rise during LA injection and some dental procedures, especially exodontia. Increase in systolic blood pressure and heart rate during exodontia was tolerated by healthy patients.

A Glutamatergic Hypothalamomedullary Circuit Mediates Thermogenesis, but Not Heat Conservation, during Stress-Induced Hyperthermia

Stress elicits a variety of autonomic responses, including hyperthermia (stress fever) in humans and animals. In this present study, we investigated the circuit basis for thermogenesis and heat conservation during this response. We first demonstrated the glutamatergic identity of the dorsal hypothalamic area (DHA^Vglut2) neurons that innervate the raphe pallidus nucleus (RPa) to regulate core temperature (Tc) and mediate stress-induced hyperthermia. Then, using chemogenetic and optogenetic methods to manipulate this hypothalamomedullary circuit, we found that activation of DHA^Vglut2 neurons potently drove an increase in Tc, but surprisingly, stress-induced hyperthermia was only reduced by about one-third when they were inhibited. Further investigation showed that DHA^Vglut2 neurons activate brown adipose tissue (BAT) but do not cause vasoconstriction, instead allowing reflex tail artery vasodilation as a response to BAT-induced hyperthermia. Retrograde rabies virus tracing revealed projections from DHA^Vglut2 neurons to RPa^Vglut3, but not to RPa^GABA neurons, and identified a set of inputs to DHA^Vglut2 → RPa neurons that are likely to mediate BAT activation. The dissociation of the DHA^Vglut2 thermogenic pathway from the thermoregulatory vasoconstriction (heat-conserving) pathway may explain stress flushing (skin vasodilation but a feeling of being too hot) during stressful times.

Physics of mind: Experimental confirmations of theoretical predictions

What is common among Newtonian mechanics, statistical physics, thermodynamics, quantum physics, the theory of relativity, astrophysics and the theory of superstrings? All these areas of physics have in common a methodology, which is discussed in the first few lines of the review. Is a physics of the mind possible? Is it possible to describe how a mind adapts in real time to changes in the physical world through a theory based on a few basic laws? From perception and elementary cognition to emotions and abstract ideas allowing high-level cognition and executive functioning, at nearly all levels of study, the mind shows variability and uncertainties. Is it possible to turn psychology and neuroscience into so-called "hard" sciences? This review discusses several established first principles for the description of mind and their mathematical formulations. A mathematical model of mind is derived from these principles. This model includes mechanisms of instincts, emotions, behavior, cognition, concepts, language, intuitions, and imagination. We clarify fundamental notions such as the opposition between the conscious and the unconscious, the knowledge instinct and aesthetic emotions, as well as humans' universal abilities for symbols and meaning. In particular, the review discusses in length evolutionary and cognitive functions of aesthetic emotions and musical emotions. Several theoretical predictions are derived from the model, some of which have been experimentally confirmed. These empirical results are summarized and we introduce new theoretical developments. Several unsolved theoretical problems are proposed, as well as new experimental challenges for future research.

Etizolam attenuates the reduction in cutaneous temperature induced in mice by exposure to synthetic predator odor

Anxiety- and stress-related disorders can be debilitating psychiatric conditions in humans. To prevent or ameliorate these conditions, reliable animal models are needed to evaluate the effects of anxiolytic drugs. Previously, we found that a mixture of three pyrazine analogues (P-mix) that were present at high levels in wolf urine induced fear-related responses in mice, rats and deer. A change in cutaneous temperature was shown to be induced by acute stress simultaneously with changes in heart rate, arterial pressure and freezing behavior, raising the possibility that cutaneous temperature could be used as an index of stress. In the present study, using infrared thermography, we showed that exposure of mice to P-mix induced a decrease in cutaneous temperature. We then examined the dose-dependent effects of an anxiolytic drug, etizolam (0-20 mg/kg), on the temperature decrease. Pre-administration of etizolam (5 mg/kg or higher) inhibited the P-mix-induced decrease in cutaneous temperature. Exposure to P-mix induced Fos-immunoreactivity, a marker of neuronal excitation, at the mouse amygdala and hypothalamus, and etizolam (5 mg/kg) attenuated that immunoreactivity. The present results suggested that the measurement of cutaneous P-mix-induced temperature changes in mice could be used as an animal model for evaluating the effects of anxiolytic drugs.

The histaminergic system is involved in psychological stress-induced hyperthermia in rats

The histaminergic system modulates numerous physiological functions such as wakefulness, circadian rhythm, feeding, and thermoregulation. However, it is not yet known if this system is also involved in psychological stress-induced hyperthermia (PSH) and, if so, which histamine (H) receptor subtype mediates the effect. Therefore, we investigated the effects of pretreatments with intraperitoneal injections of mepyramine (an H1 receptor inverse agonist), cimetidine (an H2 receptor antagonist), and ciproxifan (an H3 receptor inverse agonist) on cage-exchange stress-induced hyperthermia (a model of PSH) by monitoring core body temperature (T_c) during both light (10:00 am-12:00 pm) and dark (10:00 pm-12:00 am) phases in conscious, freely moving rats. We also investigated the effects of these drugs on stress-induced changes in locomotor activity (L_a) to rule out the possibility that effects on T_c are achieved secondary to altered L_a Cage-exchange stress increased T_c within 20 min followed by a gradual decrease back to baseline T_c during both phases. In the light phase, mepyramine and cimetidine markedly attenuated PSH, whereas ciproxifan did not affect it. In contrast, in the dark phase, mepyramine dropped T_c by 1°C without affecting cage-exchange stress-induced hyperthermia, whereas cimetidine and ciproxifan did not affect both postinjection T_c and PSH Cage-exchange stress induced an increase in L_a, especially in the light phase, but none of these drugs altered cage-exchange stress-induced L_a in either circadian rhythm phase. These results suggest that the histaminergic system is involved in the physiological mechanisms underlying PSH, particularly through H1 and H2 receptors, without influencing locomotor activity.

Stress-induced hyperthermia and hypothermia

Stress affects core body temperature (T_c). Many kinds of stress induce transient, monophasic hyperthermia, which diminishes gradually if the stressor is terminated. Stronger stressors produce a longer-lasting effect. Repeated/chronic stress induces anticipatory hyperthermia, reduces diurnal changes in T_c, or slightly increases T_c throughout the day. Animals that are exposed to chronic stress or a cold environment exhibit an enhanced hyperthermic response to a novel stress. These changes persist for several days after cessation of stress exposure. In contrast, long-lasting inescapable stress sometimes induces hypothermia. In healthy humans, psychologic stress induces slight increases in T_c, which are within the normal range of T_c or just above it. Some individuals, however, develop extremely high T_c (up to 41°C) when they are exposed to emotional events or show persistent low-grade high T_c (37-38°C) during or after chronic stress situations. In addition to the nature of the stressor itself, such stress-induced thermal responses are modulated by sex, age, ambient temperature, cage mates, past stressful experiences and cold exposure, and coping. Stress-induced hyperthermia is driven by mechanisms distinct from infectious fever, which requires inflammatory mediators. However, both stress and infection activate the dorsomedial hypothalamus-rostral medullary raphe region-sympathetic nerve axis to increase T_c.

Increased core body temperature in astronauts during long-duration space missions

Humans’ core body temperature (CBT) is strictly controlled within a narrow range. Various studies dealt with the impact of physical activity, clothing, and environmental factors on CBT regulation under terrestrial conditions. However, the effects of weightlessness on human thermoregulation are not well understood. Specifically, studies, investigating the effects of long-duration spaceflight on CBT at rest and during exercise are clearly lacking. We here show that during exercise CBT rises higher and faster in space than on Earth. Moreover, we observed for the first time a sustained increased astronauts’ CBT also under resting conditions. This increase of about 1 °C developed gradually over 2.5 months and was associated with augmented concentrations of interleukin-1 receptor antagonist, a key anti-inflammatory protein. Since even minor increases in CBT can impair physical and cognitive performance, both findings have a considerable impact on astronauts’ health and well-being during future long-term spaceflights. Moreover, our findings also pinpoint crucial physiological challenges for spacefaring civilizations, and raise questions about the assumption of a thermoregulatory set point in humans, and our evolutionary ability to adapt to climate changes on Earth.