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Physiological Reports Sep 2023The cardiovascular system is primarily controlled by the autonomic nervous system, and any changes in sympathetic or parasympathetic activity also have an impact on... (Review)
Review
The cardiovascular system is primarily controlled by the autonomic nervous system, and any changes in sympathetic or parasympathetic activity also have an impact on myocardial activity. Heart rate variability (HRV) is a readily available metric used to assess heart rate control by the autonomic nervous system. HRV can provide information about neural (parasympathetic, sympathetic, reflex) and humoral (hormones, thermoregulation) control of myocardial activity. Because there are no relevant reference values for HRV parameters in rats in the scientific literature, all experimental results are only interpreted on the basis of changes from currently measured control or baseline HRV values, which are, however, significantly different in individual studies. Considering the significant variability of published HRV data, the present study focused primarily on comparing control or baseline HRV values under different conditions in in vivo experiments involving rats. The aim of the study was therefore to assess whether there are differences in the starting values before the experiment itself.
Topics: Male; Animals; Rats; Heart Rate; Autonomic Nervous System; Body Temperature Regulation; Myocardium; Reference Values
PubMed: 37735345
DOI: 10.14814/phy2.15827 -
Ecology and Evolution Jun 2023Discussion regarding the gaps of knowledge on Odonata is common in the literature. Such gaps are even greater when dealing with basic biological data for biodiverse...
Discussion regarding the gaps of knowledge on Odonata is common in the literature. Such gaps are even greater when dealing with basic biological data for biodiverse environments like the Amazon Rainforest. Therefore, studies that address, classify, and standardize functional traits allow the elaboration of a wide range of ecological and evolutionary hypotheses. Moreover, such endeavors aid conservation and management planning by providing a better understanding of which functional traits are filtered or favored under environmental changes. Here, our main goal was to produce a database with 68 functional traits of 218 Odonata species that occur in the Brazilian Amazon. We extracted data on behavior, habit/habitat (larvae and adults), thermoregulation, and geographic distribution from 419 literature sources classified into different research areas. Moreover, we measured 22 morphological traits of approximately 2500 adults and categorized species distributions based on approximately 40,000 geographic records for the Americas. As a result, we provided a functional matrix and identified different functional patterns for the Odonata suborders, as well as a strong relationship between the different trait categories. For this reason, we recommend the selection of key traits that represent a set of functional variables, reducing the sampling effort. In conclusion, we detect and discuss gaps in the literature and suggest research to be developed with the present Amazonian Odonata Trait Bank (AMO-TB).
PubMed: 37332521
DOI: 10.1002/ece3.10149 -
The Journal of Neuroscience : the... Jul 2023Sudden unexpected death in epilepsy (SUDEP) has been linked to respiratory dysfunction, but the mechanisms underlying this association remain unclear. Here we found that...
Sudden unexpected death in epilepsy (SUDEP) has been linked to respiratory dysfunction, but the mechanisms underlying this association remain unclear. Here we found that both focal and generalized convulsive seizures (GCSs) in epilepsy patients caused a prolonged decrease in the hypercapnic ventilatory response (HCVR; a measure of respiratory CO chemoreception). We then studied (Dravet syndrome; DS) and (D/+) mice of both sexes, two models of SUDEP, and found that convulsive seizures caused a postictal decrease in ventilation and severely depressed the HCVR in a subset of animals. Those mice with severe postictal depression of the HCVR also exhibited transient postictal hypothermia. A combination of blunted HCVR and abnormal thermoregulation is known to occur with dysfunction of the serotonin (5-hydroxytryptamine; 5-HT) system in mice. Depleting 5-HT with -chlorophenylalanine (PCPA) mimicked seizure-induced hypoventilation, partially occluded the postictal decrease in the HCVR, exacerbated hypothermia, and increased postictal mortality in DS mice. Conversely, pretreatment with the 5-HT agonist fenfluramine reduced postictal inhibition of the HCVR and hypothermia. These results are consistent with the previous observation that seizures cause transient impairment of serotonergic neuron function, which would be expected to inhibit the many aspects of respiratory control dependent on 5-HT, including baseline ventilation and the HCVR. These results provide a scientific rationale to investigate the interictal and/or postictal HCVR as noninvasive biomarkers for those at high risk of seizure-induced death, and to prevent SUDEP by enhancing postictal 5-HT tone. There is increasing evidence that seizure-induced respiratory dysfunction contributes to the pathophysiology of sudden unexpected death in epilepsy (SUDEP). However, the cellular basis of this dysfunction has not been defined. Here, we show that seizures impair CO chemoreception in some epilepsy patients. In two mouse models of SUDEP we found that generalized convulsive seizures impaired CO chemoreception, and induced hypothermia, two effects reported with serotonergic neuron dysfunction. The defects in chemoreception and thermoregulation were exacerbated by chemical depletion of serotonin and reduced with fenfluramine, suggesting that seizure-induced respiratory dysfunction may be due to impairment of serotonin neuron function. These findings suggest that impaired chemoreception because of transient inhibition of serotonergic neurons may contribute to the pathophysiology of SUDEP.
Topics: Male; Female; Mice; Animals; Sudden Unexpected Death in Epilepsy; Serotonin; Carbon Dioxide; Hypothermia; Seizures; Respiration; Epilepsy; Respiration Disorders; Death, Sudden; Fenfluramine; Serotonergic Neurons; Body Temperature Regulation; NAV1.6 Voltage-Gated Sodium Channel
PubMed: 37160367
DOI: 10.1523/JNEUROSCI.0450-23.2023 -
Maturitas Dec 2023The huge impact of climate change on humankind is multidimensional, and includes direct and indirect challenges to the physical, psychological and socio-cultural... (Review)
Review
The huge impact of climate change on humankind is multidimensional, and includes direct and indirect challenges to the physical, psychological and socio-cultural wellbeing. Women may be more vulnerable to climate-sensitive diseases, but little attention has been paid to specific needs and challenges associated with the menopause transition. The increase in average and extreme temperatures may modulate the manifestation of vasomotor symptoms; in particular, environmental temperature and seasonality may affect hot flushes and night sweats. However, more research is needed to define the impact of climate-related factors among the determinants influencing the individual experience of menopause. In addition, increased exposure to environmental pollution and toxins may also have a role in the modulation of ovarian aging mechanisms, possibly influencing timing of menopause. Finally, both air pollution and menopause transition are associated with unfavorable modifications of cardio-metabolic, bone and cognitive health, and account should be taken of these in the evaluation of the individual woman's health vulnerabilities. Overall, the evidence reported in this narrative review supports the need for specific strategies aimed at reducing the burden of climate and environmental change on menopausal women. Healthcare providers should promote behavioral measures that reduce anthropogenic climate change and at the same time have a beneficial role on several domains of physical and psychological wellbeing. From this perspective, menopause represents a golden moment to implement virtuous behaviors that will benefit at the same time women's longevity and the planet.
Topics: Female; Humans; Menopause; Hot Flashes; Women's Health; Sweating
PubMed: 37634295
DOI: 10.1016/j.maturitas.2023.107825 -
International Journal of Biometeorology Jun 2023Healthy adult horses can balance accumulation and dissipation of body heat to maintain their body temperature between 37.5 and 38.5 °C, when they are in their... (Review)
Review
Healthy adult horses can balance accumulation and dissipation of body heat to maintain their body temperature between 37.5 and 38.5 °C, when they are in their thermoneutral zone (5 to 25 °C). However, under some circumstances, such as following strenuous exercise under hot, or hot and humid conditions, the accumulation of body heat exceeds dissipation and horses can suffer from heat stress. Prolonged or severe heat stress can lead to anhidrosis, heat stroke, or brain damage in the horse. To ameliorate the negative effects of high heat load in the body, early detection of heat stress and immediate human intervention is required to reduce the horse's elevated body temperature in a timely manner. Body temperature measurement and deviations from the normal range are used to detect heat stress. Rectal temperature is the most commonly used method to monitor body temperature in horses, but other body temperature monitoring technologies, percutaneous thermal sensing microchips or infrared thermometry, are currently being studied for routine monitoring of the body temperature of horses as a more practical alternative. When heat stress is detected, horses can be cooled down by cool water application, air movement over the horse (e.g., fans), or a combination of these. The early detection of heat stress and the use of the most effective cooling methods is important to improve the welfare of heat stressed horses.
Topics: Humans; Horses; Animals; Humidity; Respiration; Hot Temperature; Body Temperature; Fever; Body Temperature Regulation
PubMed: 37060454
DOI: 10.1007/s00484-023-02467-7 -
European Journal of Sport Science Oct 2023We determined the effects of topically applied (i) isolated menthol cream, (ii) menthol and capsaicin co-application or (iii) placebo cream on exercise tolerance,... (Randomized Controlled Trial)
Randomized Controlled Trial
Topical application of isolated menthol and combined menthol-capsaicin creams: Exercise tolerance, thermal perception, pain, attentional focus and thermoregulation in the heat.
We determined the effects of topically applied (i) isolated menthol cream, (ii) menthol and capsaicin co-application or (iii) placebo cream on exercise tolerance, thermal perception, pain, attentional focus and thermoregulation during exercise in the heat. Ten participants cycled at 70% maximal power output until exhaustion in 35°C and 20% relative humidity after application of (i) 5% isolated menthol, (ii) 5% menthol and 0.025% capsaicin co-application or (iii) placebo cream. Thermo-physiological responses were measured during exercise, with attentional focus and pain determined post-exercise on a 0-to-10 scale. Across the three conditions, time to exhaustion was 13.4 ± 4.8 min, mean ± SD infrared tympanic and skin temperature was 37.2 ± 0.6°C and 35.1 ± 1.2°C, respectively, and heart rate was 152 ± 47 bpm, with no changes between conditions (> 0.05). Perceived exertion was lower in the isolated menthol all other conditions (< 0.05, = 0.44). Thermal sensation was higher in menthol-capsaicin co-application isolated menthol (< 0.05, 1.1), while sweat rate was higher for capsaicin and menthol co-application compared to menthol (< 0.05, = 0.85). The median and interquartile range scores for pain were lower (< 0.05) in the menthol condition (8, 7-8) compared to both menthol and capsaicin (10, 9-10) and placebo (9, 9-10), which was coupled with a greater distraction (< 0.05) in the menthol condition (9, 7-10) compared to placebo (6, 5-7). Despite no performance effects for any topical cream application condition, these data reiterate the advantageous perceptual and analgesic role of menthol application and demonstrate no advantage of co-application with capsaicin.Topical application of isolated menthol cream to cold-sensitive areas of the body during exhaustive exercise in the heat, elicited reduced perception of pain and enhanced sensation of cooling.While this reduction in generally unpleasant feelings (i.e. pain and heat) were coupled with lower RPE scores in the menthol condition and could be considered beneficial, there was no apparent ergogenic effect in an exercise tolerance test.Co-application of capsaicin and menthol appeared to inhibit the positive sensory effects elicited by menthol.Isolated menthol can induce changes in cognitive processes related to pain and exertion, while also reducing thermal sensation; however, the decision to use menthol creams must be balanced with the limited performance or thermoregulatory effects reported herein during exercise in hot environments.
Topics: Humans; Body Temperature Regulation; Capsaicin; Exercise Tolerance; Hot Temperature; Menthol; Pain; Pain Perception; Thermosensing; Cross-Over Studies; Male; Female; Adult
PubMed: 37161852
DOI: 10.1080/17461391.2023.2211966 -
Brain Structure & Function Dec 2023The shape of the cranium is one of the most notable physical changes induced in domestic dogs through selective breeding and is measured using the cephalic index (CI)....
The shape of the cranium is one of the most notable physical changes induced in domestic dogs through selective breeding and is measured using the cephalic index (CI). High CI (a ratio of skull width to skull length > 60) is characterized by a short muzzle and flat face and is referred to as brachycephaly. Brachycephalic dogs display some potentially harmful changes in neuroanatomy, and there are implications for differences in behavior, as well. The path from anatomy to cognition, however, has not been charted in its entirety. Here, we report that sleep-physiological markers of white-matter loss (high delta power, low frontal spindle frequency, i.e., spindle waves/s), along with a spectral profile for REM (low beta, high delta) associated with low intelligence in humans, are each linked to higher CI values in the dog. Additionally, brachycephalic subjects spent more time sleeping, suggesting that the sleep apnea these breeds usually suffer from increases daytime sleepiness. Within sleep, more time was spent in the REM sleep stage than in non-REM, while REM duration was correlated positively with the number of REM episodes across dogs. It is currently not clear if the patterns of sleep and sleep-stage duration are mainly caused by sleep-impairing troubles in breathing and thermoregulation, present a juvenile-like sleeping profile, or are caused by neuro-psychological conditions secondary to the effects of brachycephaly, e.g., frequent REM episodes are known to appear in human patients with depression. While future studies should more directly address the interplay of anatomy, physiology, and behavior within a single experiment, this represents the first description of how the dynamics of the canine brain covary with CI, as measured in resting companion dogs using a non-invasive sleep EEG methodology. The observations suggest that the neuroanatomical changes accompanying brachycephaly alter neural systems in a way that can be captured in the sleep EEG, thus supporting the utility of the latter in the study of canine brain health and function.
Topics: Dogs; Humans; Animals; Sleep; Sleep, REM; Electroencephalography; Brain; Craniosynostoses
PubMed: 37742302
DOI: 10.1007/s00429-023-02706-y -
Scientific Reports Jun 2023Core body temperature (CBT) shows a diurnal rhythm, and the nocturnal decrease in CBT is blunted in older people. The physiological mechanisms responsible for the...
Core body temperature (CBT) shows a diurnal rhythm, and the nocturnal decrease in CBT is blunted in older people. The physiological mechanisms responsible for the blunted nocturnal decrease in CBT in older people remain to be revealed. The aim of this study was to compare heat production and heat dissipation in young and old subjects during sleep, as assessed by indirect calorimetry and the distal-proximal temperature gradient (DPG) of skin temperature. A complete dataset of 9 young (23.3 ± 1.1 years) and 8 old (72.1 ± 2.5 years) females was analyzed. CBT and energy metabolism were monitored during sleep using an ingestible temperature sensor in a metabolic chamber maintained at 25 °C. Skin temperature was measured at proximal and distal parts of the body. CBT, distal skin temperature, and DPG in older subjects were higher than in young subjects. Protein oxidation was similar between the two groups, but fat oxidation was lower and carbohydrate oxidation was higher in old subjects compared to young subjects. On the other hand, energy expenditure was similar between the two age groups. Thus, the elevated CBT in older subjects was not attributed to deteriorated heat dissipation or enhanced heat production, suggesting an alternative explanation such as deteriorated evaporative heat loss in old subjects.
Topics: Humans; Female; Aged; Body Temperature Regulation; Sleep; Body Temperature; Skin Temperature; Energy Metabolism
PubMed: 37369712
DOI: 10.1038/s41598-023-37407-3 -
Frontiers in Endocrinology 2023We review the evidence regarding the nongenomic (or non-canonical) actions of thyroid hormones (thyronines) and their derivatives (including thyronamines and... (Review)
Review
We review the evidence regarding the nongenomic (or non-canonical) actions of thyroid hormones (thyronines) and their derivatives (including thyronamines and thyroacetic acids) in the adult brain. The paper seeks to evaluate these compounds for consideration as candidate neurotransmitters. Neurotransmitters are defined by their (a) presence in the neural tissue, (b) release from neural tissue or cell, (c) binding to high-affinity and saturable recognition sites, (d) triggering of a specific effector mechanism and (e) inactivation mechanism. Thyronines and thyronamines are concentrated in brain tissue and show distinctive patterns of distribution within the brain. Nerve terminals accumulate a large amount of thyroid hormones in mature brain, suggesting a synaptic function. However, surprisingly little is known about the potential release of thyroid hormones at synapses. There are specific binding sites for thyroid hormones in nerve-terminal fractions (synaptosomes). A notable cell-membrane binding site for thyroid hormones is integrin αvβ3. Furthermore, thyronines bind specifically to other defined neurotransmitter receptors, including GABAergic, catecholaminergic, glutamatergic, serotonergic and cholinergic systems. Here, the thyronines tend to bind to sites other than the primary sites and have allosteric effects. Thyronamines also bind to specific membrane receptors, including the trace amine associated receptors (TAARs), especially TAAR1. The thyronines and thyronamines activate specific effector mechanisms that are short in latency and often occur in subcellular fractions lacking nuclei, suggesting nongenomic actions. Some of the effector mechanisms for thyronines include effects on protein phosphorylation, Na/K ATPase, and behavioral measures such as sleep regulation and measures of memory retention. Thyronamines promptly regulate body temperature. Lastly, there are numerous inactivation mechanisms for the hormones, including decarboxylation, deiodination, oxidative deamination, glucuronidation, sulfation and acetylation. Therefore, at the current state of the research field, thyroid hormones and their derivatives satisfy most, but not all, of the criteria for definition as neurotransmitters.
Topics: Adult; Humans; Brain; Thyroid Hormones; Thyronines; Memory; Recognition, Psychology
PubMed: 37701902
DOI: 10.3389/fendo.2023.1210540