Thermoregulatory Mechanisms Research Articles

Pre-warming before general anesthesia with isoflurane delays the onset of hypothermia in rats.

General anesthesia causes hypothermia by impairing normal thermoregulatory mechanisms. When using inhalational anesthetic agents, Redistribution of warm blood from the core to the periphery is the primary mechanism in the development of hypothermia and begins following induction of anesthesia. Raising skin temperature before anesthesia reduces the temperature gradient between core and periphery, decreasing the transfer of heat. This prospective, crossover study (n = 17 adult male and female SD rats) compared three treatment groups: PW1% (pre-warming to increase core temperature 1% over baseline), PW40 (pre-warming to increase core temperature to 40°C) and NW (no warming). The PW1% group was completed first to ensure tolerance of pre-warming. Treatment order was then randomized and alternated after a washout period. Once target temperature was achieved, anesthesia was induced and maintained with isoflurane in oxygen without further external temperature support. Pre-warming was effective at delaying the onset of hypothermia, with a significant difference between PW1% (12.4 minutes) and PW40 (19.3 minutes, p = 0.0044 (95%CI -12 to -2.2), PW40 and NW (7.1 minutes, p < 0.0001 (95%CI 8.1 to 16.0) and PW1% and NW (p = 0.003, 95%CI 1.8 to 8.7). The rate of heat loss in the pre-warmed groups exceed that of the NW group: PW1% versus NW (p = 0.005, 95%CI 0.004 to 0.027), PW40 versus NW (p < 0.0001, 95%CI 0.014 to 0.036) and PW1% versus PW40 (p = 0.07, 95%CI -0.021 to 0.00066). Pre-warming alone confers a protective effect against hypothermia during volatile anesthesia; however, longer duration procedures would require additional heating support.

RNA-seq profiling of skin in temperate and tropical cattle.

Skin is a major thermoregulatory organ in the body controlling homeothermy, a critical function for climate adaptation. We compared genes expressed between tropical- and temperate-adapted cattle to better understand genes involved in climate adaptation and hence thermoregulation. We profiled the skin of representative tropical and temperate cattle using RNA-seq. A total of 214,754,759 reads were generated and assembled into 72,993,478 reads and were mapped to unique regions in the bovine genome. Gene coverage of unique regions of the reference genome showed that of 24,616 genes, only 13,130 genes (53.34%) displayed more than one count per million reads for at least two libraries and were considered suitable for downstream analyses. Our results revealed that of 255 genes expressed differentially, 98 genes were upregulated in tropically-adapted White Fulani (WF; Bos indicus) and 157 genes were down regulated in WF compared to Angus, AG (Bos taurus). Fifteen pathways were identified from the differential gene sets through gene ontology and pathway analyses. These include the significantly enriched melanin metabolic process, proteinaceous extracellular matrix, inflammatory response, defense response, calcium ion binding and response to wounding. Quantitative PCR was used to validate six representative genes which are associated with skin thermoregulation and epithelia dysfunction (mean correlation 0.92; p < 0.001). Our results contribute to identifying genes and understanding molecular mechanisms of skin thermoregulation that may influence strategic genomic selection in cattle to withstand climate adaptation, microbial invasion and mechanical damage.

Intermittent binge-like ethanol exposure during adolescence attenuates the febrile response by reducing brown adipose tissue thermogenesis in rats

Ethanol (EtOH) consumption is a primary health risk worldwide, which generally starts during adolescence in a binge pattern (i.e., the episodic consumption of high amounts). Binge EtOH consumption can lead to modifications of the innate and adaptive immune responses, including fever. The present study evaluated the febrile response that was induced by lipopolysaccharide (LPS) and prostaglandins E2 (PGE2) and the mechanisms of thermoregulation in adolescent rats that were exposed to EtOH in a binge-like pattern. Male Wistar rats were treated with an intraperitoneal (i.p.) injection of EtOH or saline on postnatal days (PND) 25, 26, 29, 30, 33, 34, 37, and 38. On PND 51, they received a pyrogenic challenge with LPS (i.p.) or PGE2 (intracerebroventricular) to induce a febrile response. Interscapular brown adipose tissue (BAT) mass and uncoupling protein (UCP) activity in isolated mitochondria were evaluated on PND 51. The rats were then subjected to cold challenges to analyze adaptive thermogenesis. Intermittent EtOH exposure during adolescence impaired the LPS- and PGE2-induced febrile response 12 days after the end of EtOH exposure. Ethanol exposure decreased interscapular BAT mass, oxygen consumption, and UCP activity in isolated mitochondria, resulting in an impairment in thermogenesis at 5 °C. No morphological changes in BAT were observed. These findings indicate that binge-like EtOH exposure during adolescence impairs thermoregulation by reducing BAT mass and function. This reduction may last for a prolonged period of time after the cessation of EtOH exposure and may affect both cold defenses and the febrile response during the development of infectious diseases.

Relationship between angioarchitecture of the testicular artery and spermiogram parameters in Egyptian buffalo bulls (bubalus bubalis).

The current study aimed to investigate the effect of testicular artery angioarchitecture on the spermiogram parameters in Egyptian Buffalo bulls. Eight adult buffalo bulls aged between 2 and 8years were used for semen evaluation. For anatomical studies, the masculine gonads were collected after slaughtering 30 adult bulls and prepared for injection by different masses (Urographine® , Latex and Epoxy) through the testicular artery. The mass activity of the ejaculate was assessed immediately after collection. The sperm motility in fresh bull ejaculate was more than 80%. The overall mean percentage of sperm abnormalities was <18%. The recorded sperm abnormalities were mostly secondary one including distal protoplasmic droplet, fragmented tail, detached head, detached galea capitis and bent tail. The highest percentage of sperm viability was recorded just after sperm collection (alive>85%). The results revealed that testicular artery can be divided into three parts (abdominal, funicular and marginal parts) along its course. The coils of the funicular part forming a cone-like structure with its base fixed to the head of the testis. Two epididymal branches to the head and tail of epididymis emanate from the funicular part which continues as pars marginalis on the lateral surface of testis before its division into the lateral and medial testicular arteries on approaching the tail extremity of the testis. The increase in the length of the testicular artery with increase in the size of the testes played a great role in the degree of complexity of the architectural vascular patterns. The degree of complexity is affected by the number of coils formed by the vessel. The increase in the convolutions of the vessel will reduce the speed of blood flow to the gonads. Thus in turn will enabling the thermoregulatory mechanism to work more efficiently and will affect the semen value.

Diving in the Arctic: Cold Water Immersion's Effects on Heart Rate Variability in Navy Divers.

IntroductionDiving close to the Arctic circle means diving in cold water regardless of the time of year. The human body reacts to cold through autonomous nervous system (ANS)-mediated thermoregulatory mechanisms. Diving also induces ANS responses as a result of the diving reflex.Materials and MethodsIn order to study ANS responses during diving in Arctic water temperatures, we retrospectively analyzed repeated 5-min heart rate variability (HRV) measures and the mean body temperature from dives at regular intervals using naval diving equipment measurement tests in 0°C water. Three divers performed seven dives without physical activity (81–91 min), and two divers performed four dives with physical activity after 10 min of diving (0–10 min HRV recordings were included in the study).ResultsOur study showed a significant increase in parasympathetic activity (PNS) at the beginning of the dives, after which PNS activity decreased significantly (measure 5–10 min). Subsequent measurements (15–20 min and onward) showed a significant increase in PNS activity over time.ConclusionOur results suggest that the first PNS responses of the human diving reflex decrease quickly. Adverse effects of PNS activity should be considered on long and cold dives. To avoid concurrent sympathetic (SNS) and PNS activity at the beginning of dives, which in turn may increase the risk of arrhythmia in cold water, we suggest a short adaptation phase before physical activity. Moreover, we suggest it is prudent to give special attention to cardiovascular risk factors during pre-dive examinations for cold water divers.

An experimental study on effects of radiofrequency electromagnetic fields on sleep in healthy elderly males and females: Gender matters!

BackgroundResults from human experimental studies investigating possible effects of radiofrequency electromagnetic fields (RF-EMF) on sleep are heterogeneous. So far, there is no study on possible sex-differences in RF-EMF effects. ObjectivesThe present study aimed at analyzing differences in RF-EMF effects on the macrostructure of sleep between healthy elderly males and females. MethodsWith a double-blind, randomized, sham-controlled cross-over design effects of two RF-EMF exposures (GSM900 and TETRA) on sleep were investigated in samples of 30 elderly healthy male and 30 healthy elderly female volunteers. Participants underwent each of the three exposure conditions on three occassions following an individually randomized order resulting in a total of nine study nights per participant. Exposure was delivered for 30 min prior to sleep and for the whole night (7.5 h) by a head worn antenna specifically designed for the projects. The peak spatial absorption rate averaged over time in head tissues (psSAR10g) was 6 W/kg for TETRA and 2 W/kg for GSM900. Thirty variables characterising the macrostructure of sleep and arousals as well as four subjective sleep variables were considered for statistical analyses. ResultsMultivariate analyses revealed that exposure to GSM900 and/or TETRA resulted in a significant reduction in arousals, a shorter latency to sleep stage N3, and a shorter self-reported time awake after sleep in both males and females. Exposure effects depending on sex (significant interactions) were observed. Latency to sleep stage R was shorter in females and tended to be longer in males under both exposures. Latency to stage N3 was shorter in females under TETRA exposure and almost not affected in males. The time awake within the sleep period under TETRA exposure was shorter in females and only slightly longer in males. Under GSM exposure, the self-rated total sleep time tended to be longer in females and to be shorter in males. Finally, the number of awakenings was lower only in females and tended to be higher in males under GSM exposure. DiscussionWith regard to RF-EMF effects on human sleep it seems that gender matters since GSM900 and TETRA led to significantly more exposure effects in females. Regardless of gender, none of the observed changes is indicative of a sleep disturbing effect of RF-EMF exposure. Observed effects might be mediated by skin related thermoregulatory mechanisms.

Two-dimensional finite element model to study the effect of periodic physical exercise on temperature distribution in peripheral regions of human limbs

The human body regulates the body core temperature at a uniform temperature to maintain the structure and function of various physical and physiological processes. The physical exertion causes thermal stress which can disturb these mechanisms of thermoregulation under various environmental conditions and can lead to impairment of physiological functions. In view of the above, a finite element model has been developed to study thermal stress in peripheral regions of human limbs during periodic exercise and rest. It is assumed that the subject is doing exercise periodically by taking rest at regular intervals. The human limb is assumed to be of cylindrical shape. The peripheral region of a limb is divided into three natural components, namely epidermis, dermis and subdermal parts. Appropriate boundary conditions have been framed based on physical conditions of the problem. Finite element has been employed along radial and angular directions, and the finite difference is employed for time variable to obtain the solution. The numerical results have been used to obtain temperature profiles and study the effect of light-, moderate- and vigorous-intensity activities on thermal distribution in human limbs under moderate and hot climatic conditions. The results obtained by the present model are in agreement with the physiological facts and can be employed to predict the amount of acclimatization and rest required to cope up with such thermal stresses. Such models can be developed further to obtain thermal information in human organs involving physical exercise. This thermal information can be useful for developing strategies for the time period of different intensities of physical exercise and rest required for optimum performance of sportsman, labourers, workers and military person. Also the thermal information obtained from such models can be useful for developing protocols for heat stress required for therapeutic purposes during infection and physical exercise prescriptions for healthy lifestyles.

Skin Application of 4% Menthol Enhances Running Performance in Hot and Humid Climate.

Aerobic performance is negatively impacted by tropical climate due to impairment of thermoregulatory mechanisms. We tested the hypothesis that a torso application of a 4% menthol solution would have the same effect on a best performance 10-km run as an external use of cold water. Thirteen trained male athletes completed four outdoor 10-km runs (T=29.0±1.3°C, relative humidity 59.0±13.6%) wearing a tee-shirt soaked every 2-km either in a cold (~6°C) or warm/ambient (~28°C) solution, consisting in water or in a 4% menthol solution, (CTL, MENT-Amb, CLD and MENT-CLD). Run performances were improved from 4.8 to 6.1% in CLD (51.4±5.5 min), MENT-Amb (52.2±5.9 min) and MENT-CLD (51.4±5.1 min) conditions (vs. CTL, 55.4±8.4 min, P<0.05), without differences between these three conditions, whereas heart rate (177±13bpm), body temperature (38.7±0.6°C) and drink ingestion (356±170 g) were not modified. Thermal sensation after running was lower in MENT-CLD (vs. CTL, P<0.01) and thermal acceptability was higher in CLD and MENT-Amb (vs. CTL, P<0.05), but thermal comfort, feeling scale and rate of perceived exertion remained unchanged. The use of menthol on skin enhances aerobic performance in a tropical climate, and no differences in performance were observed between menthol and traditional percooling strategies. However, combining both menthol and traditional percooling brought no further improvements.

The functional significance of panting as a mechanism of thermoregulation and its relationship to the critical thermal maxima in lizards.

Because most desert-dwelling lizards rely primarily on behavioral thermoregulation for the maintenance of active body temperature, the effectiveness of panting as a thermoregulatory mechanism for evaporative cooling has not been widely explored. We measured changes in body temperature (Tb) with increasing air temperature (Ta) for 17 species of lizards that range across New Mexico and Arizona and quantified the temperatures associated with the onset of panting, and the capacity of individuals to depress Tb below Ta while panting, and estimated the critical thermal maxima (CTmax) for each individual. We examined these variables as a function of phylogeny, body mass and local acclimatization temperature. We found that many species can depress Tb 2-3°C below Ta while panting, and the capacity to do so appears to be a function of each species' ecology and thermal environment, rather than phylogeny. Panting thresholds and CTmax values are phylogenetically conserved within groups. Understanding the functional significance of panting and its potential importance as a thermoregulatory mechanism will improve our understanding of the potential for species' persistence in an increasingly warmer world.

Temperature Measurements in Neonates: Assessing the Agreement of Two Methods

Background: Neonatal temperature response during illness is unpredictable. Whereas accurate temperature measurement is an important diagnostic step in Neonatal practice. Abnormalties in temperature pattern may be a pointer to a sinister condition especially in neonates, whose thermoregulatory mechanism is immature. There are several methods of temperature measurements and the search for a suitable thermometry method in neonates continues. This study compared the forehead non touch infra-red thermometer (NTIT) with the axilllary mercury-in-glass (MIGT) method of temperature measurement in neonates. Method: Four hundred babies aged 1 to 28 days were recruited from the immunization clinic of the University of Ilorin Teaching Hospital between August 2016 and May 2017. Temperatures were taken using both NTIT and MIGT in the standard way and recorded. Result: The mean age and SD was 5.10 ± 4.28 days. Pearson correlation showed a positive correlation between the Axillary Mercury-in-Glass and Forehead Non-Touch Infra-red thermometry readings (r = 0.426, p 0.001). Bland-Altman method revealed a good agreement between both methods of thermometry as 95.5% of the readings were within the limits of agreement. Conclusion: Axillary Mercury-in-Glass thermometer and Forehead Non touch Infra-red thermometers have a good agreement and can be used interchangeably in neonates.

A Structured Cleaving Mesh for Bioheat Transfer Application.

Goal: The thermoregulation mechanism is a complex system that executes vital processes in the human body. Various models have been proposed to simulate the thermoregulatory response of an adult human to environmental stimuli. However, these models generally rely on stylized phantoms that lack the anatomical details of voxel phantoms used in radiation dosimetry and shielding research. The goal of this work is to introduce voxel phantoms to thermoregulation research by modeling the physical energy exchange between tissue and its surroundings, discuss a specific challenge associated with voxel phantoms, propose a method to address this challenge, and demonstrate its application. Method: One of the major challenges in using voxel phantoms is the stair-step effect on the surface of the voxelized domain. This effect causes over-estimation of surface area, accurate knowledge of which is critical for modeling heat exchanging systems. A methodology to generate a voxel domain from medical imaging data and reduce error in the surface area caused by the stair-step effect is presented. The methodology, based on a structured mesh and finite-volume method, is demonstrated with tumors generated from magnetic resonance imaging (MRI) scans of mice. Results: The methodology discussed in the paper shows a decrease in surface area over-estimation from 50% to 15% for a sphere and 47% to 17% for tumor models generated directly from MRI scans. Conclusion: This work provides a direct method to generate a smoother domain from medical imaging data and reducing surface area error in a voxelized domain. The technique presented is independent of domain material, including tissue type, and can be extended to any homogeneous or inhomogeneous domain. The increase in surface area accuracy obtained by smoothing the voxel domain results in more accurate temperature estimates in heat transfer simulation.

Effect of warm environment on the skin blood flow response to food intake

Background and objective Warm exposure places high demands on thermoregulation mechanisms, which depend on the effectiveness of the microvascular function. The associations between the microcirculation and metabolism in warm environments have received little attention. The purpose of this study was to explore skin blood flow (SkBF) in response to food intake in a warm environment compared to control. Methods Thirty-two healthy, acclimated-to-warm-environment and physically active participants were recruited (20 females and 12 males). They participated in two sessions (warm environment: 31 °C and control: 20 °C, presented in randomized order). SkBF was measured before and after standardized food intake through the acquisition of perfusion signals by laser Doppler flowmetry (Periflux System 5000), following a local heating protocol. Results SkBF was affected by the environmental temperature, showing an increase in the warm environment compared to control (all p < .001). SkBF was significantly affected by food intake (all p < .007), being reduced after meals. In the men’s group, SkBF was reduced in both environmental temperatures after meals. In women, meals affected SkBF at 20 °C but not in the warm environment. Conclusion These results may indicate a competition between thermo- and glyco-regulation in a warm environment to the detriment of glucose homeostasis in women.

Термоэлектрические и термоэлектрокинетические явления в коллоидных системах, модельных биологическим жидкостям живых организмов

The paper presents the results of experimental measurements of thermoelectromotive force, thermoelectrokinetic EMF and conductivity coefficient in aqueous solutions, model in their properties and composition of human blood: medical ringer solution, serum albumin, ringer solution containing serum albumin. The influence of organic colloidal particles present in aqueous solutions of inorganic electrolytes on the value of their coefficient of thermoelectromotive force is analyzed. As follows from the results of the experiments, the coefficient of thermoelectromotive force of the studied liquids, based on the ringer solution, has a sharp dependence on temperature and acquires a large value in the temperature range in which the living human body functions. The obtained result indicates that the studied phenomena can play an important role in triggering the mechanisms of thermoregulation of living organisms.

Heat-related illness—Clinical profile and predictors of outcome from a healthcare center in South India

Background:Heat-related illness is a common medical emergency. There is failure of thermoregulatory mechanisms of the body resulting in multiple organ dysfunction syndrome which if not identified and treated urgently can result in high mortality rate and permanent neurological damage. This study provides description of clinical profile patients presenting with heat-related illness and identifies clinical and laboratory variables resulting in poor outcome.Methods:This retrospective study was done identifying adult patients admitted with a diagnosis of heat-related illness from April to August 2019 in tertiary care center. Their clinical profile, laboratory investigations and outcome were extracted from medical records and variables associated with poor outcome were analyzed for statistical significance.Results:Mean age of the patients in the study was 61 years with mean heat index of the localities being 39.6-degree C. 66% of patients had multiple organ dysfunction with central nervous system dysfunction (77%) followed by respiratory distress syndrome (61%) as the most common organ derangement. Evaporative cooling measures were incorporated in management of all patients, followed by cold saline infusion in 60%. Higher J-ERATO score at admission was found to be a predictor for underlying multiple organ dysfunction syndrome (P value < 0.029). The mortality rate associated with heat-related illness in this study was 11.1%.Conclusions:Multiple organ dysfunction is seen in majority of the patients and calculation of simple admission J-ERATO score helps in predicting the same. Declining mortality rate observed in our study as compared to the earlier studies could be attributed to increased awareness, prompt diagnosis and initiation of rapid cooling measures.

Reducing Sharp Fluctuations in Body Temperature and Optimizing Production Index of Broilers Using Dietary Electrolytes

A degree centigrade fall or rise in body temperature of broiler chickens is sufficient to reduce performance, alter sound physiological state and divert nutritional metabolism in quest for ensuring thermal balance. Thermoregulatory mechanisms of newly hatched chicks are poorly developed, and fluctuations in brooding temperature coupled with severe environmental temperatures in the tropics could threaten the survivability, production and economic integrity of fast-growing strains of broilers. However, information on the effect of sharp fluctuations in body temperature on nutrient intake and European production index (EPI) of broilers fed dietary electrolytes is scanty and thus investigated. Using a total of 300, one-day-old unsexed broiler chicks (Arbor Acre) that were randomly allotted to six dietary treatments (T1-210, T2-240, T3270, T4-300, T5-330 and T6-360 mEq/kg electrolyte balance), data on performance characteristics and their correlations with body temperature and EPI at prestarter, starter and finisher phases were determined using standard procedures. Data were analysed using descriptive statistics and ANOVA at α = 0.05. At prestarter phase, feed intake (FI) had a strong and positive relationship with protein intake (r = 1.00; p < 0.01), EPI (r = 0.96; p < 0.01) and potassium (K) intake (r = 0.66; p < 0.01), but was negatively correlated with temperature change (r = ?0.39; p < 0.05). However, FI was not significantly correlated with body weight (BW), body weight gain (BWG), sodium (Na) and water intake. At starter phase, EPI was positively correlated to K intake (r = 0.38; p < 0.05), but not Na and chloride (Cl) intake. European production index of starter chicks could be enhanced by increasing the level of K intake through dietary supplementation up to 1.02%. Weight gain was adversely affected by sharp changes in temperature at finisher phase. Increase in water intake may not be a remedial tool in lowering sharp fluctuations in body temperature. However, sharp fluctuation in body temperature of broilers was reduced with DEB of 330, 270 and 240 mEq/kg at prestarter, starter and finisher phases, respectively.

Multy-system complications of accidental hypothermia: A case report

Introduction. Accidental hypothermia is an unintentional fall in core temperature to less than 35?C and it occurs when the body?s heat loss exceeds its heat production. The elderly population is particularly susceptible due to reduced adaptability to low temperatures and various comorbidities, which may be predisposing factors. Case Report. A 65-year-old Caucasian female was admitted to the hospital due to hypothermia (&lt; 34?C), severe hypoglycemia (0.7 mmol/L), metabolic acidosis (6.970), elevated urea (42.4 mmol/L) and creatinine (686 ?mol/L). The initial examination revealed shivering, dysarthria and general exhaustion. Hyperamylasemia (241 U/L) and hyperlipasemia (1920 U/L) were found on the second day after admission. Contrast enhanced computed tomography showed a focal asymmetric enlargement of the pancreatic head and body. Furthermore, a splenic infarction was also noticed. The complexity of human thermoregulatory mechanisms indicates the importance of precipitating factors in the development of hypothermia. Our patient presented with several precipitating factors such as age, sex, urinary tract infection, diabetes, and metformin-induced severe hypoglycemia. Conclusion. Based on the presented case and the relevant literature, it can be concluded that the clinical picture of hypothermia may be extremely complex. Knowledge of all the mechanisms involved in multi-organ failure due to hypothermia is of utmost importance, in order to conduct adequate and timely targeted diagnosis and apply appropriate treatment.

Preparation and thermal properties of NaOAc·3H2O-CO(NH2)2 non-eutectic binary mixture PCM for radiant floor heating system

To make full use of phase change material (PCM) in heat exchanger for radiant floor heating system, the NaOAc·3H2O-CO(NH2)2 non-eutectic binary mixture PCM, using NaOAc·3H2O as phase change principal component, CO(NH2)2 as temperature regulator and Na2HPO4·12H2O as nucleator as well as sucrose (C12H22O11) as auxiliary nucleator, was developed. The possible thermoregulation mechanism of CO(NH2)2 on NaOAc·3H2O was preliminarily discussed. Meanwhile, the supercooling degrees of the non-eutectic PCMs with different Na2HPO4·12H2O and C12H22O11 contents were also investigated. The results showed that the NaOAc·3H2O-CO(NH2)2 non-eutectic binary mixture PCM containing 8% CO(NH2)2, 1.5% Na2HPO4·12H2O and 2% C12H22O11 possessed a proper phase change temperature (48.45 °C), high latent heat (245.4 J/g), the low supercooling degree (2.60 °C), the enhanced crystallization behavior and an excellent thermal reliability. The hydrogen-bond interactions of -NH2 in CO(NH2)2 on three crystal H2O molecules and CH3COO− in NaOAc·3H2O weakened the intermolecular forces of NaOAc·3H2O and the coordination of NaOAc on H2O, thus resulting in a decrease in the phase change temperature of the non-eutectic mixture.

Effects of hair coat characteristics on radiant surface temperature in horses.

Horse owners may lack knowledge about natural thermoregulation mechanisms in horses. Horses are managed intensively; usually stabled at night and turned out during the day. Some are clipped and many wear a blanket, practices which reduce the horse's ability to regulate heat dissipation. The aim of this study was to investigate the relationship between hair coat characteristics, body condition and infrared surface temperatures from different body parts of horses. Under standard conditions, the body surface temperature of 21 adult horses were investigated using infrared thermography. From several readings on the same body part, a mean temperature was calculated for each body part per horse. Detailed information on horse breed, age, management and body condition was collected. Hair coat samples were also taken for analyses. A mixed statistical model was applied. Warmblood horse types (WB) had lower hair coat sample weights and shorter hair length than coldblood horse types (CB). The highest radiant surface temperatures were found at the chest 22.5±0.9°C and shoulders 20.4±1.1°C and WB horses had significantly higher surface temperatures than CB horses on the rump (P<0.05). Horses with a higher hair coat sample weight had a lower surface temperature (P<0.001) and hind hooves with iron shoes had a significant lower surface temperature than unshod hind hooves (P=0.03). In conclusion, individual assessment of radiant surface temperature using infrared thermography might be a promising tool to gather data on heat loss from the horses' body. Such data may be important for management advice, as the results showed individual differences in hair coat characteristics and body condition in horses of similar breeds.

Activation of Kappa Opioid Receptor Regulates the Hypothermic Response to Calorie Restriction and Limits Body Weight Loss.

Mammals maintain a nearly constant core body temperature (Tb) by balancing heat production and heat dissipation. This comes at a high metabolic cost that is sustainable if adequate calorie intake is maintained. When nutrients are scarce or experimentally reduced such as during calorie restriction (CR), endotherms can reduce energy expenditure by lowering Tb [1-6]. This adaptive response conserves energy, limiting the loss of body weight due to low calorie intake [7-10]. Here we show that this response is regulated by the kappa opioid receptor (KOR). CR is associated with increased hypothalamic levels of the endogenous opioid Leu-enkephalin, which is derived from the KOR agonist precursor dynorphin [11]. Pharmacological inhibition of KOR, but not of the delta or the mu opioid receptor subtypes, fully blocked CR-induced hypothermia and increased weight loss during CR independent of calorie intake. Similar results were seen with DIO mice subjected to CR. In contrast, inhibiting KOR did not change Tb in animals fed ad libitum (AL). Chemogenetic inhibition of KOR neurons in the hypothalamic preoptic area reduced the CR-induced hypothermia, whereas chemogenetic activation of prodynorphin-expressing neurons in the arcuate or the parabrachial nucleus lowered Tb. These data indicate that KOR signaling is a pivotal regulator of energy homeostasis and can affect body weight during dieting by modulating Tb and energy expenditure.

Evaluation of Rectal and Skin Temperature Variations of Anesthetised Dogs Undergoing Magnetic Resonance Imaging Diagnosis

General anesthesia produces different degrees of central nervous depression and changes in the peripheral circulation, therefore affecting the patient’s thermoregulatory mechanism. Moreover, the lack of proper, specially designed equipment for magnetic resonance imaging (MRI) environment monitoring can represent a challenge for the anesthetist. We examined the temperature variations correlated with different anesthetic protocols in dogs that underwent general anesthesia in order to evaluate changes in rectal and distal extremities temperature, before and after anesthesia. This study was conducted at the Faculty of Veterinary Medicine in Bucharest, on 21 dogs that were divided in 3 groups depending on the anesthetic protocol used. First group (B) received butorphanol (0.2 mg/kg, intravenously IV), second group (BK) had butorphanol (0.2 mg/kg) and a low dose of ketamine (2 mg/kg) IV, and group 3 (BM) was premedicated with butorphanol (0.2 mg/kg) and midazolam (0.2 mg/kg) IV. All patients were induced with propofol i.v. (3.24±0.68), intubated and maintained with isoflurane and oxygen. We determined rectal temperature before and right after the end of anesthesia with a digital thermometer and distal extremities temperature with the use of a thermal imaging camera attached to a smartphone. There was no significant difference between the rectal temperature before and after anesthesia within the 3 groups. Patients in group BK had a significant change in skin temperature at the end of anesthesia in all limbs (from 310C to 29.8 0C, p=0.008 and from 31 0C to 29.70C, p=0.009), respectively). Temperature variations were presented before and at the end of anesthesia, for all the groups especially at skin level. This study revealed that mobile thermal imaging represents a non-invasive technique that is helpful in assessing real time temperature changes in patients undergoing general anesthesia.