Internal Body Temperature Research Articles

Non-contact measurement of internal body temperature using subcutaneously implanted diamond microparticles.

We constructed a highly sensitive fluorescence wide-field imaging system with a microwave source, implanted fluorescent diamond microparticles ("microdiamonds") subcutaneously into the dorsal skin of a mouse after sacrifice, and demonstrated the feasibility of using optically detected magnetic resonance (ODMR) to measure internal body temperature in a mammal.

Wearing a face mask during controlled-intensity exercise is not a risk factor for exertional heatstroke: A pilot study.

AimThis study aimed to measure the influence of wearing face masks on individuals’ physical status in a hot and humid environment.MethodsEach participant experienced different physical situations: (i) not wearing a mask (control), (ii) wearing a surgical mask, (iii) wearing a sport mask. An ingestible capsule thermometer was used to measure internal core body temperature during different exercises (standing, walking, and running, each for 20 min) in an artificial weather room with the internal wet‐bulb globe temperature set at 28°C. The change in the participants’ physical status and urinary liver fatty acid‐binding protein (L‐FABP) were measured.ResultsSix healthy male volunteers were enrolled in the study. In each participant, significant changes were observed in the heart rate and internal core temperatures after increased exercise intensity; however, no significant differences were observed between these parameters and urinary L‐FABP among the three intervention groups.ConclusionMask wearing is not a risk factor for heatstroke during increased exercise intensity.

Assessment of temperature changes in carcasses in the early post-mortem period using the spectrum of a thermal imaging camera

Precise determination of the time of death of a human being or animal is extremely important for investigations by law enforcement agencies. The aim of the study was to use a thermal imaging camera for imaging of the cooling of dog carcasses in controlled conditions, as a practical application of thermal imaging in veterinary forensics for the purpose of establishing the time of death of an animal, as well as to compare the usefulness of this method with that of the currently used Henssge nomogram. A thermographic technique exploiting infrared radiation was used in the study. The research material was 10 dog carcasses (5 female and 5 male) aged 6 to 16 years, with body weight from 23 to 36 kg. Thermal imaging of a carcass in combination with other methods, such as measurement of internal body temperature and analysis of post-mortem changes, enables reliable determination of the time of death of an animal, which is often of fundamental importance in veterinary forensic practice.

Radical Response: Effects of Heat Stress-Induced Oxidative Stress on Lipid Metabolism in the Avian Liver.

Lipid metabolism in avian species places unique demands on the liver in comparison to most mammals. The avian liver synthesizes the vast majority of fatty acids that provide energy and support cell membrane synthesis throughout the bird. Egg production intensifies demands to the liver as hepatic lipids are needed to create the yolk. The enzymatic reactions that underlie de novo lipogenesis are energetically demanding and require a precise balance of vitamins and cofactors to proceed efficiently. External stressors such as overnutrition or nutrient deficiency can disrupt this balance and compromise the liver’s ability to support metabolic needs. Heat stress is an increasingly prevalent environmental factor that impairs lipid metabolism in the avian liver. The effects of heat stress-induced oxidative stress on hepatic lipid metabolism are of particular concern in modern commercial chickens due to the threat to global poultry production. Chickens are highly vulnerable to heat stress because of their limited capacity to dissipate heat, high metabolic activity, high internal body temperature, and narrow zone of thermal tolerance. Modern lines of both broiler (meat-type) and layer (egg-type) chickens are especially sensitive to heat stress because of the high rates of mitochondrial metabolism. While this oxidative metabolism supports growth and egg production, it also yields oxidative stress that can damage mitochondria, cellular membranes and proteins, making the birds more vulnerable to other stressors in the environment. Studies to date indicate that oxidative and heat stress interact to disrupt hepatic lipid metabolism and compromise performance and well-being in both broilers and layers. The purpose of this review is to summarize the impact of heat stress-induced oxidative stress on lipid metabolism in the avian liver. Recent advances that shed light on molecular mechanisms and potential nutritional/managerial strategies to counteract the negative effects of heat stress-induced oxidative stress to the avian liver are also integrated.

Evaluation of solar photovoltaic systems to shade cows in a pasture-based dairy herd

The combined use of solar photovoltaics and agriculture may provide farmers with an alternative source of income and reduce heat stress in dairy cows. The objective of this study was to determine the effects on grazing cattle under shade from a solar photovoltaic system. The study was conducted at the University of Minnesota West Central Research and Outreach Center in Morris, Minnesota on a grazing dairy. Twenty-four crossbred cows were randomly assigned to 2 treatment groups (shade or no shade) from June to September in 2019. The replicated (n = 4) treatment groups of 6 cows each were provided shade from a 30-kW photovoltaic system. Two groups of cows had access to shade in paddocks, and 2 groups of cows had no shade in paddocks. All cows were located in the same pasture during summer. Behavior observations and milk production were evaluated for cows during 4 periods of summer. Boluses and an eartag sensor monitored internal body temperature, activity, and rumination on all cows, respectively. Independent variables were the fixed effects of breed, treatment group, coat color, period, and parity, and random effects were replicate group, date, and cow. No differences in fly prevalence, milk production, fat and protein production, or drinking bouts were observed between the treatment groups. Shade cows had more ear flicks (11.4 ear flicks/30 s) than no-shade cows (8.6 ear flicks/30 s) and had dirtier bellies and lower legs (2.2 and 3.2, respectively) than no-shade cows (1.9 and 2.9, respectively). During afternoon hours, shade cows had lower respiration rates (66.4 breaths/min) than no-shade cows (78.3 breaths/min). From 1200 to 1800 h and 1800 to 0000 h, shade cows had lower body temperature (39.0 and 39.2°C, respectively) than no-shade cows (39.3 and 39.4°C, respectively). Furthermore, between milking times (0800 and 1600 h), the shade cows had lower body temperature (38.9°C) than no-shade cows (39.1°C). Agrivoltaics incorporated into pasture dairy systems may reduce the intensity of heats stress in dairy cows and increase well-being of cows and the efficiency of land use.

Estrogen-sensitive medial preoptic area neurons coordinate torpor in mice

Homeotherms maintain a stable internal body temperature despite changing environments. During energy deficiency, some species can cease to defend their body temperature and enter a hypothermic and hypometabolic state known as torpor. Recent advances have revealed the medial preoptic area (MPA) as a key site for the regulation of torpor in mice. The MPA is estrogen-sensitive and estrogens also have potent effects on both temperature and metabolism. Here, we demonstrate that estrogen-sensitive neurons in the MPA can coordinate hypothermia and hypometabolism in mice. Selectively activating estrogen-sensitive MPA neurons was sufficient to drive a coordinated depression of metabolic rate and body temperature similar to torpor, as measured by body temperature, physical activity, indirect calorimetry, heart rate, and brain activity. Inducing torpor with a prolonged fast revealed larger and more variable calcium transients from estrogen-sensitive MPA neurons during bouts of hypothermia. Finally, whereas selective ablation of estrogen-sensitive MPA neurons demonstrated that these neurons are required for the full expression of fasting-induced torpor in both female and male mice, their effects on thermoregulation and torpor bout initiation exhibit differences across sex. Together, these findings suggest a role for estrogen-sensitive MPA neurons in directing the thermoregulatory and metabolic responses to energy deficiency.

PSVII-6 Effects of heat stress on proteolysis in dairy cattle skeletal muscle

Abstract Heat stress (HS) occurs when internal body temperatures are elevated above a thermoneutral zone in response to extreme environmental temperatures. In the U.S. dairy industry, HS results in economic loss due to decreased feed intake, milk quality, and milk yield. Previous work has demonstrated increased plasma urea nitrogen in heat stressed dairy cattle which is thought to originate from increased skeletal muscle proteolysis, however this has not been empirically established. The objective of this investigation was to determine the extent to which HS promotes proteolysis in skeletal muscle of dairy cattle. We hypothesized HS would increase activation of the calpain and proteasome systems in skeletal muscle. To test this hypothesis, following a 3-d acclimation period in individual box stalls, all lactating dairy cows were held under thermoneutral (TN) conditions for 4-d for collection of baseline measures and then exposed to TN or HS conditions for 7-d followed by a biopsy of semitendinosus (n=8/group). To induce HS, cattle were fitted with electric heating blankets, which they wore for the duration of the heating period. This approach increased rectal temperature 1.1°C (P< 0.05), respiratory rate by 33 bpm (P< 0.05), plasma urea nitrogen by 19% (P=0.08) and milk urea nitrogen by 26% (P< 0.05), and decreased dry matter intake by 32% (P< 0.05) and milk production by 26% (P< 0.05) confirming HS. Contrary to our expectations, we discovered that calpain I and II abundance and activation, and calpain activity were similar between groups. Likewise, protein expression of E3 ligases, MafBx and Murf1, were similar between groups as was total ubiquitinated proteins and proteasome activity. Collectively, and counter to our hypothesis, these results suggest skeletal muscle proteolysis is not increased following 7-d of HS. These data question the presumed dogma that increased blood urea nitrogen is due to elevated proteolysis in skeletal muscle.

PSX-37 Late-Breaking Abstracts: Effects of metformin on body temperature regulation and breast muscle growth in male broiler chickens

Abstract Chickens provide models for human physiology research, as their normal physiological status mimics mammalian obesity and human Type II diabetes. Metformin is a common medication used to treat Type II diabetes. Prior studies have demonstrated metformin’s ability to induce the “browning” phenomenon of white adipose tissue and promote non-shivering thermogenesis (NST). The objective of this study was to determine if dietary supplementation of metformin can promote NST to reduce body fat mass and increase metabolism in broiler chickens. Male broiler chicks (n = 72) were randomly assigned to 12 pens (6 chickens/pen). Pens were randomly assigned to control basal diet (CON), basal plus 0.5 g/kg metformin (MET05), or basal plus 1.0 g/kg metformin (MET1). Two chicks were harvested from each pen on d7, d14, and d21. Total breast weight (TBW) and liver weight (LW) were recorded. IButton temperature loggers were implanted in chickens on d19. ADFI was highest in MET05 at d7 and d21, lowest in MET1 at d7, and highest in MET1 at d14. ADFI was lowest in CON group at d14 and d21. MET1 showed a negative effect on G:F at d7 and d14. MET05 group had the highest BW, TBW, and LW at all intervals. CON group had the lowest TBW at d14, but significantly higher than MET1 at d21. MET1 group had the lowest TBW at d7 and d21, lowest LW at d7 and d14, while CON group had the lowest LW at d21. CON had the highest breast/BW ratio, while MET1 group had the lowest. MET05 and MET01 had higher liver:BW ratio than CON group at d21. Data distribution showed less variation for internal body temperature in the MET05 group compared with CON and MET1. These results suggest that low dosage metformin helps regulate body temperature and increase breast muscle growth in broilers in earlier life stage.

Thermosensation involving thermo-TRPs

The transient receptor potential (TRP) channels constitute a superfamily of large ion channels that are activated by a wide range of chemical, mechanical and thermal stimuli. TRP channels with temperature sensitivity are called thermo-TRPs. They are involved in diverse physiological functions through their detection of external environmental temperature and internal body temperature. Each thermo-TRP has its own characteristic temperature threshold for activation. As a group, they cover temperatures ranging from cold to nociceptive high temperatures. Recently, many studies have identified the functions of thermo-TRPs residing in deep organs where they are exposed to body temperature. Importantly, temperature thresholds of thermo-TRPs can be regulated by physiological factors enabling their function at relatively constant body temperature. Moreover, several thermo-TRPs are reportedly engaged in body temperature regulation. This review will summarize the current understanding of thermo-TRPs, including their roles in thermosensation and functional regulation of physiological responses at body temperature and the regulation of body temperature.

Effect of air temperature and humidity in a stable on basic physiological parameters in horses

The aim of the study was to analyse selected air parameters in a stable (microclimate) and the basic physiological parameters of horses housed in the stable in different seasons of the year. The research material was 12 adult hot-blooded horses kept in a brick stable with stalls. Air parameters in the stable (temperature in the passageway, temperature in the stall at two points, relative humidity in the passageway, and relative humidity in the stall at two points) were determined four times in one year, in summer, autumn, winter and spring. Measurements were made with a Bluetooth BLE-LOGGER LB-518 battery-operated cordless thermo-hygrometer at 12 noon at five points in the stable located 300 cm apart. Physiological parameters of the horses, i.e. internal body temperature (Veterinär SC 12 veterinary thermometer), heart rate (Polar ELECTRO OY RS800CX with PolarProTrainer 5.0. software), and respiratory rate (with a manual stopwatch) were measured at 6 a.m. and 6 p.m. on each day of the study. The season of the year was found to have a significant influence on the microclimate of the stable. To ensure optimal air humidity, airing of the stable should be limited only in winter and periodically in autumn. It is also worth emphasizing that the stable microclimate has a marked effect on the basic physiological parameters of horses. High temperature and relative humidity in the stable can cause unfavourable changes in the form of an increase in evening body temperature in the summer and a decrease in the winter. The remaining parameters, i.e. heart rate and respiratory rate, can also unfavourably increase, mainly in the summer. Horses should have fewer problems maintaining normal physiological parameters in winter, even fewer in autumn, and the fewest in spring.

Methods to quantify heat stress in ruminants: Current status and future prospects.

The physiology of hyperthermia or heat stress in mammals is complex. It is a totally systemic condition that in varying degrees involves all organs, tissues and body fluid compartments. The nature and magnitude of the response is influenced by animal specific characteristics (e.g. age, diet, body condition, gender, reproductive stage), environment and animal management. Given the multifaceted nature of heat stress, and the varied ruminant production systems based in varied geoclimatic zones, it has been difficult to find appropriate measures of heat stress for production ruminants. This has become an urgent challenge as production systems intensify globally in a warming climate. Bioclimatic indices such as the Temperature-Humidity Index (THI) have evolved to incorporate some measure of animal physiology. However, these indices do not have strong relationships with core temperature trajectories and altered respiratory dynamics of animals with excessive heat load. In recent decades, the careful physiology studies of the 1950-80s, have given way to numerous studies trialling a plethora of new technologies and computational approached to measure heat stress. Infrared thermography of body surface temperatures, automated measures of respiration rate and radiotelemetry of internal body temperatures are the most intensively researched. The common goal has been to find the 'holy grail' decision-making threshold or timepoint as to the animal's wellbeing. Are we making any progress?

Evidence from Tarentola mauritanica (Gekkota: Phyllodactylidae) helps validate thermography as a tool to infer internal body temperatures of lizards.

Infrared (IR) thermal imaging has become an increasingly popular tool to measure body temperature of animals. The high-resolution data it provides with short lag and minimum disturbance makes it an appealing tool when studying reptile thermal ecology. However, due to the common phenomenon of regional heterothermy and surface-to-core temperature gradients, it is essential to select the appropriate body part to measure and provide calibrations to accurately infer internal body temperatures. This work follows from a previous study on lacertid lizards to assess the reliability of thermography-measured body temperatures, from several body locations, as a proxy for internal body temperature in lizards. This study focuses on the Moorish gecko, Tarentola mauritanica, due to its distant phylogenetic relationship and its different ecology and morphology from the previously tested species. A total of 60 adult geckos of both sexes and of a range of sizes were tested in thermal gradients and subjected to a sequence of randomly assorted treatments of heating and cooling. The temperatures of the animals were periodically measured with a thermal camera at six different body parts and, immediately after, the cloacal temperature was then measured with a thermocouple probe. Body parts' temperatures, obtained thermographically, were regressed against cloacal temperature using OLS regression and the pairwise correlations were tested using Spearman coefficients. Relationships among all body parts and between all body parts and the cloaca were strong in all cases (R2>0.87, Spearman Correlation>0.95). The observed pattern was very similar to those previously obtained from lacertid lizards. Ultimately, the eye proved to provide the best overall proxy for internal temperature, when accounting for both the slope and intercept of the regression. Hence, this study provides further support for the establishment of the eye as the standard location to infer internal body temperatures of lizards through thermography.

Physical and social warmth: Warmer daily body temperature is associated with greater feelings of social connection.

Growing evidence suggests that physical warmth and social warmth-feeling socially connected to others-are linked. In particular, thermoregulatory systems that maintain a relatively warm internal body temperature may also support feelings of social connection. However, it is unknown whether and how feelings of physical and social warmth fluctuate together across time in daily life. To this end, the current study examined tympanic temperature, a measure of internal body temperature, and feelings of social connection assessed multiple times a day over 1 week. Consistent with hypotheses, moment-to-moment changes in tympanic temperature covaried with feelings of social connection across assessments. Thus, warmer body temperatures, in the nonfebrile range, were associated with greater feelings of social connection, and cooler body temperatures were associated with lower feelings of social connection. These findings provide further evidence for the link between physical and social warmth and contribute to an understanding of the dynamic fluctuation of affective experience across time. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Interaction of Exercise Intensity and Simulated Burn Injury Size on Thermoregulation.

This study aimed to test the hypothesis that the elevation in internal body temperature during exercise in a hot environment is influenced by the combination of exercise intensity and BSA burned. Ten healthy participants (8 males, 2 females; 32 ± 9 yr; 75.3 ± 11.7 kg) completed eight exercise trials on a cycle ergometer, each with different combinations of metabolic heat productions (low, 4 W·kg-1; moderate, 6 W·kg-1) and simulated BSA burn in a hot environmental chamber (39.9°C ± 0.3°C, 20.1% ± 1.5% RH). Burns were simulated by covering 0%, 20%, 40%, or 60% of participants' BSA with a highly absorbent, vapor-impermeable material. Gastrointestinal temperature (TGI) was recorded, with the primary analysis being the increase in TGI after 60 min of exercise. We identified an interaction effect for the increase in TGI (P < 0.01), suggesting TGI was influenced by both intensity and simulated burn BSA. Regardless of the percentage BSA burn simulated, the increase in TGI was similar across low-intensity trials (0.70°C ± 0.26°C, P > 0.11 for all). However, during moderate-intensity exercise, the increase in TGI was greater for the 60% (1.78°C ± 0.38°C, P < 0.01) and 40% BSA coverage trials (1.33°C ± 0.44°C, P = 0.04), relative to 0% (0.82°C ± 0.36°C). There were no differences in TGI responses between 0% and 20% trials. These data suggest that exercise intensity influences the relationship between burn injury size and thermoregulatory responses in a hot environment.

Mechanisms of thermal dysregulation in primary hyperhidrosis and hypohidrosis.

Mechanisms of thermal dysregulation in primary hyperhidrosis and hypohidrosis.

Non-Contact Evaluation of Pigs' Body Temperature Incorporating Environmental Factors.

Internal body temperature is the gold standard for the fever of pigs, however non-contact infrared imaging technology (IRT) can only measure the skin temperature of regions of interest (ROI). Therefore, using IRT to detect the internal body temperature should be based on a correlation model between the ROI temperature and the internal temperature. When heat exchange between the ROI and the surroundings makes the ROI temperature more correlated with the environment, merely depending on the ROI to predict the internal temperature is unreliable. To ensure a high prediction accuracy, this paper investigated the influence of air temperature and humidity on ROI temperature, then built a prediction model incorporating them. The animal test includes 18 swine. IRT was employed to collect the temperatures of the backside, eye, vulva, and ear root ROIs; meanwhile, the air temperature and humidity were recorded. Body temperature prediction models incorporating environmental factors and the ROI temperature were constructed based on Back Propagate Neural Net (BPNN), Random Forest (RF), and Support Vector Regression (SVR). All three models yielded better results regarding the maximum error, minimum error, and mean square error (MSE) when the environmental factors were considered. When environmental factors were incorporated, SVR produced the best outcome, with the maximum error at 0.478 °C, the minimum error at 0.124 °C, and the MSE at 0.159 °C. The result demonstrated the accuracy and applicability of SVR as a prediction model of pigs′ internal body temperature.

The Effect Of Burn Location On Internal Body Temperature Responses During Exercise In The Heat

According to the US Army’s Standard of Medical Fitness (AR 40-501), extensive burn injuries will disqualify individuals from US Army service, depending in part on the anatomic location of the injury. Specifically, these guidelines state that “extensive burns on the torso will most significantly impair heat dissipation.” and that burn injuries could be a disqualifying criteria for continued service. However, the effects of the location of the burn injury on thermoregulation during exercise is currently unknown. PURPOSE: This study tested the hypothesis that a torso burn injury is not any more detrimental to whole-body heat dissipation relative to a similar sized non-torso burn injury. METHODS: Nine healthy subjects (29±6 years; 72.44±11.29 kg; 1.86±0.17 m2) walked on a treadmill (~3.3mph) in the heat (40 °C and 20% relative humidity) for 60 minutes at a fixed rate of metabolic heat generation (5.7±0.5 W/kg). Identical ~25% body surface area (BSA) burn injuries to the torso or non-torso extremities (randomized) were simulated by applying a highly absorbent vapor-impermeable material over those regions. The elevation in internal body temperature assessed via an ingestible telemetry pill, was the primary variable of interest. Additional analyses were performed to assess differences in heart rate and thermal sensation. RESULTS: The statistical model (2 way repeated measures ANOVA) identified a main effect of time (p<0.001; 0.94±0.33 °C for torso and 0.91±0.34°C for extremity at end of exercise) on the increase in internal body temperature, with no effect of simulated burn location (p=0.76) or interaction (p=0.10). Heart rate and thermal sensation showed similar responses, with a significant main effect of time (p<0.001) with no effect of burn location (p=0.09) or interaction (p=0.13). CONCLUSION: Contrary to the Army’s guidelines, these results suggest that torso burns do not limit heat dissipation and exacerbate thermal strain compared to non-torso burn injuries. Therefore, the Army should not consider torso burns as being more detrimental when determining whether a soldier meets the Standard of Medical Fitness. Funding: Department of Defense - US Army W81XWH-15-1-0647

Interaction Between Exercise Intensity And Burn Size Affects Body Temperature During Exercise In The Heat

US Army Standards of Medical Fitness exclude personnel who have sustained burn injuries covering 40% or more of their body surface area (BSA). However, this requirement is not specific to different exercise intensities that an individual is expected to perform and therefore does not take metabolic heat generation into account. PURPOSE: To test the hypothesis that the magnitude of the elevation in internal body temperature during exercise in a warm environment is influenced by the combination of exercise intensity and percentage BSA burned. METHODS: Nine healthy participants (8 males, 1 female; 33±9 y; 176±7 cm, 75.2±12.0 kg) completed eight exercise trials on a cycle ergometer, each with differing combinations of exercise intensities (Low: 4 W/kg and Moderate: 6 W/kg) and simulated BSA burn percentages in a warm environmental chamber (39.8±0.3°C, 20.5±1.5 %rh). Burns were simulated by covering 0%, 20%, 40% or 60% of participants’ BSA with a highly absorbent, vapor-impermeable material. Gastrointestinal temperature (TGI) was recorded throughout exercise, with the primary analysis (mixed-model with contrasts and Bonferroni corrections comparing simulated burn trials to 0%, with p<0.017 for significance) being the magnitude of the elevation in TGI after 60 min of exercise. RESULTS: The statistical model identified an interaction effect (p=0.005), suggesting that the magnitude of the elevation in TGI was influenced by both exercise intensity and simulated BSA. Regardless of the percentage BSA burn simulated, the increase in TGI was similar across low intensity trials (mean increase: 0.69±0.27°C, p>0.05), However, during moderate intensity exercise the magnitude of the increase in TGI was greater for the 60% (1.76±0.39°C; p<0.001) and 40% (1.23±0.51°C; p=0.0014) BSA coverage trials, relative to the 0% (0.80±0.42°C) BSA coverage trial. There were no differences between 0% and 20% (1.06±0.42°C; p=0.049) BSA coverage trials. CONCLUSIONS: These data suggest that exercise intensity influences the relationship between burn injury size and thermoregulatory responses during exercise in a warm environment. Clinical guidance and US Army Standards for burn survivors should, therefore, consider the intensity of the exercise bout alongside BSA burned when determining limitations to physical activity.

Physiological Responses To Heat Stress In Groundskeepers

PURPOSE: The extent to which groundskeepers experience heat strain, dehydration, and accompanying declines in kidney function during work in hot-humid conditions is unknown. METHODS: Hydration, cardiovascular, and internal body temperature measures were assessed in 20 groundskeepers (18 men; mean±SD age=38±8 y, body mass index=32±8 kg/m2) during work on 2 summer days. Before (PRE) and after (POST) the work shift, resting blood pressure (BP) and heart rate (HR) were measured and urine and blood samples were collected. At POST, fluid intake was recalled for the previous 24 h. Gastrointestinal temperature (TGI) was recorded every 5 min via ingestible telemetric sensor. RESULTS: Average highest daily wet bulb globe temperature=39.1±3.5 °C. In 45% of subjects, PRE BP>130/80 mm Hg on Day 1 (D1) and Day 2 (D2). Highest HR and TGI achieved across both days were 143±15 bpm and 37.7±0.3 °C, respectively. On D1 and D2, urine specific gravity (USG; 1.021±01) and urine color (UCOL; 6±1) did not change PRE to POST (all P>0.28), but subjects began the workday “underhydrated” (concentrated urine but normal serum osmolality (Sosm)]—62% had USG≥1.020 and 95% had UCOL≥4 despite Sosm=292±5. Fluid intake=2.3±1.6 L during work and consisted of 70% water and 25% sugar sweetened beverages. No subject lost ≥2% of body mass on D1 or D2. For 6 subjects, estimated glomerular filtration rate at PRE was ≤60 mL/min/1.73m2 averaged across D1 and D2. Although serum creatinine did not change statistically from PRE to POST across days (all P>0.18), 5 subjects had increases ≥0.3 mg/dL, signifying an acute kidney injury (AKI). CONCLUSIONS: While hyperthermia was not prevalent, subjects began and ended the workday underhydrated. Hypertension, obesity, and low water intake may have contributed to the overall low kidney function and AKIs observed. Using urine color as a self-assessment tool could be a beneficial intervention improve hydration status and kidney function.Funded by NIOSH

Bioresorbable, Wireless, Passive Sensors as Temporary Implants for Monitoring Regional Body Temperature

Measurements of regional internal body temperatures can yield important information in the diagnosis of immune response-related anomalies, for precisely managing the effects of hyperthermia and hypothermia therapies and monitoring other transient body processes such as those associated with wound healing. Current approaches rely on permanent implants that require extraction surgeries after the measurements are no longer needed. Emerging classes of bioresorbable sensors eliminate the requirements for extraction, but their use of percutaneous wires for data acquisition leads to risks for infection at the suture site. As an alternative, a battery-free, wireless implantable device is reported here, which is constructed entirely with bioresorbable materials for monitoring regional internal body temperatures over clinically relevant timeframes. Ultimately, these devices disappear completely in the body through natural processes. In vivo demonstrations indicate stable operation as subcutaneous and intracranial implants in rat models for up to 4 days. Potential applications include monitoring of healing cascades associated with surgical wounds, recovery processes following internal injuries, and the progression of thermal therapies for various conditions.