Rise In Rectal Temperature Research Articles

102 Circadian patterns of behavior, respiration, rectal temperature, saliva melatonin, cytokine concentrations, and milk immune cells are altered by cooling heat-stressed lactating sows

Abstract Lactating sows are particularly vulnerable to heat stress (HS) due to the increased metabolism from milk production. A greater understanding of HS response could assist in mitigating its detrimental effects on animal production. Two core circadian clock genes were pinpointed in a recent genome study as potential mediators of HS response, indicating the possible alteration of circadian clocks by HS exposure. This study aimed to assess how cooling of lactating sows under natural heat stress conditions in the summer influenced circadian patterns of respiration rate (RR), rectal temperature (RT), behaviors, salivary concentration of cortisol and melatonin, milk cell populations and relative abundance of multiple cytokines in saliva. Lactating sows of mixed parities were divided into two treatment groups: treated with electronic cooling pad (C; n=9) and heat-stressed control (H; n=9). Experiments were conducted during two 48 h periods of increased environmental temperatures from summer heatwaves. During the initial 48 h period, rectal temperature (RT) was monitored every 60 min, rectal temperature (RT) every 30 min, and behaviors of eating, standing, sitting, laying, sleeping, drinking, and nursing every 5 min. Morning milk samples were collected following the completion of the first phase and utilized to categorize and count somatic cells. The second trial was approximately 1 wk later, and during this period saliva samples were collected every 4 h over the 48-h period. Results were analyzed for significant effect of treatments and interaction using periodic regression while circadian patterns were further detected by incorporating a Fourier series model utilizing sine-cosine variables that denote a fit and/or shift in circadian pattern. The analysis revealed that cooling decreased RT and RR while also modifying circadian patterns (P < 0.05). Cooling had no impact on the percentage of time spent in any activity over the 48-h period (P > 0.05). Nevertheless, the daily patterns of eating, standing, and sitting were different between the treatments (P < 0.05). A shift in eating time to later in the day in H sows relative to C sows related to a second rise in RT during the dark phase of the light-dark cycle (P < 0.05). Saliva melatonin concentrations were increased in C sows and circadian pattern altered relative to H (P < 0.05), but there was no effect on salivary cortisol concentrations (P > 0.05). Cooling reduced milk lymphocytes (P < 0.05) and influenced diurnal pattern of saliva cytokines including interleukins (IL) IL-1 alpha, IL-1 beta, IL-10, and IL-15 and transforming growth factor-beta 1. In conclusion, the cooling of heat-stressed sows altered the circadian patterns of physiology, behavior and melatonin, suggesting the need for additional research to investigate whether circadian disruption contributes to reduced production efficiency observed in HS animals.

Sexual Dimorphism in the Slope of Rectal Temperature Rise Before Heat Acclimation, but Not After Heat Acclimation

Purpose: Our study aimed to identify if sexual dimorphism exists surrounding the slope of rectal temperature rise during a steady state exercise in the heat before and after heat acclimation (HA). In this study, we hypothesized that women would have a greater tolerance to heat stress resulting from a lesser slope of rectal temperature rise when compared to men. Methods: Physically active men (M) (n=12, VO2max: 51.3 ± 6.1 mL·kg−1·min−1, Age: 21±2 yo) and women (W) (n=12, VO2max: 44.2±5.8±6.1 mL·kg−1·min−1, Age: 24±4 yo) completed a steady state treadmill based heat tolerance test (HTT) (3 mph 2% grade for 120 minutes (min) in 40°C, 40% relative humidity). Rectal temperature (Trec) was collected during the first 10-min (PreHAF) and the last 10-min (PreHAL) of the HTT before HA, as well as the first 10-min (PostHAF) and last 10-min (PostHAL) after HA. The slope of rectal temperature rise for the first 10min was calculated by taking the difference of Trec at 10min and 0min, with the slope for the last 10min calculated using Trec at 120min and 110min. Both Trec differences were divided by 10min to obtain the slope in °C/min. One tailed independent T-tests were used to determine sex differences and dependent T-tests to determine differences within sex, both with significance at p≤0.05. All data are presented as mean ± SD. Results: Before acclimation, W demonstrated a greater slope of Trec rise PreHAF when compared to M (M: 0.01 ± 0.02°C/min, W: 0.03 ± 0.01°C/min, p=0.006) with opposite findings PreHAL (M: 0.01 ± 0.01°C/min, W: 0.00 ± 0.00°C/min, p=0.046). Following HA, there were no differences between the slope of Trec rise in M vs. W at both PostHAF (M: 0.02 ± 0.01°C/min, W: 0.02 ± 0.01°C/min, p>0.05) and PostHAL (M: 0.00 ± 0.01°C/min, W: 0.00 ± 0.00°C/min, p>0.05). In M, the PreHAL slope of Trec rise was greater than PostHAL (PreHAL: 0.01 ± 0.01°C/min, PostHAL: 0.00 ± 0.01°C/min, p=0.019), with no differences found within the first 10min (PreHAF: 0.01 ± 0.01°C/min, PostHAF: 0.02 ± 0.01°C/min, p=0.060). No differences in the slope of Trec rise between HA statuses were found in W (PreHAF: 0.03 ± 0.01°C/min, PostHAF: 0.02 ± 0.01°C/min, p>0.05; PreHAL: 0.00 ± 0.01°C/min, PostHAL: 0.00 ± 0.01°C/min, p>0.05). Conclusion: Consistent with previous literature, men exhibit better adaptations displayed by greater reductions in rectal temperature after HA, while women demonstrated consistent responses in both the first and last 10-min. These findings contribute to our understanding of sex-specific physiological adaptations to heat acclimation and underscore the importance of considering sex-based differences in heat-related research and interventions. Funding: DoD BA200299. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Hot water immersion is associated with higher thermal comfort than dry passive heating for a similar rise in rectal temperature and plasma interleukin-6 concentration.

To compare the perceptual responses and interleukin-6 (IL-6) concentration following rectal temperature-matched dry heat exposure (DH) and hot water immersion (HWI). Twelve healthy young adults (BMI 23.5 ± 3.6kg/m2; age: 25.8 ± 5.7years) underwent 3 trials in randomised order: DH (air temperature 68.9°C), HWI (water temperature 37.5°C), and thermoneutral dry exposure (CON, air temperature 27.3°C). Blood samples to determine IL-6 plasma concentration were collected; basic affect and thermal comfort, rectal and skin temperature (Tskin) were assessed throughout the intervention. Rectal temperature (Trec) did not differ between DH (end temperature 38.0 ± 0.4°C) and HWI (37.9 ± 0.2°C, P = 0.16), but was higher compared with CON (37.0 ± 0.3°C; P ≤ 0.004). Plasma IL-6 concentration was similar after DH (pre to post: 0.8 ± 0.5 to 1.4 ± 1.5pg·ml-1) and HWI (0.5 ± 0.2 to 0.9 ± 0.6pg·ml-1; P = 0.46), but higher compared with CON (0.6 ± 0.5 to 0.6 ± 0.4pg·ml-1; P = 0.01). At the end of the intervention, basic affect and thermal comfort were most unfavourable during DH (Basic affect; DH: - 0.7 ± 2.9, HWI: 0.8 ± 1.9, CON 1.9 ± 1.9, P ≤ 0.004; Thermal comfort; 2.6 ± 0.8, HWI: 1.4 ± 0.9 and CON: 0.2 ± 0.4; P ≤ 0.004). Mean Tskin was highest for DH, followed by HWI, and lowest for CON (DH: 38.5 ± 1.3°C, HWI: 36.2 ± 0.5°C, CON: 31.6 ± 0.7°C, P < 0.001). The IL-6 response did not differ between DH and HWI when matched for the elevation in Trec. However, thermal comfort was lower during DH compared to HWI, which may be related to the higher Tskin during DH.

Role of maternal variables on the development of neonatal hypoglycaemia and influence of neonatal hypoglycaemia on performance of goat kids

The study evaluated the influence of maternal variables (age, body weight and body mass index; BMI) during mating on the development of hypoglycaemia and investigated whether hypoglycaemia at birth impairs thermoregulation, metabolism, body weight gain and immunoglobulin concentration in neonatal goat kids. Post-kidding, the kids born with hypoglycaemia (n = 19) and normoglycaemia (n = 19) were immediately identified and postnatal blood samples, body weight and cardinal physiological variables were determined. Results revealed no significant (P < 0.05) difference in pre-mating maternal variables between dams that kidded hypoglycaemic and normoglycaemic kids. Kids born with hypoglycaemia had lower (P <0.05) blood glucose concentration from birth, until Day 2, when values became comparable between the two groups. Afternoon respiratory and pulse rates were markedly (P < 0.05) unstable in kids born with hypoglycaemia and the early postnatal rise (P < 0.05) in morning rectal temperature in both groups was accompanied by a decrease (P < 0.05) on day 20 in kids born with hypoglycaemia. Blood cholesterol and triglyceride concentrations were lower (P < 0.05) in hypoglycaemic kids and the normoglycaemic kids showed marked increase (P < 0.05) in circulating immunoglobulin concentration 24 h after birth, while age had no (P > 0.05) effect in hypoglycaemic kids. A more pronounced decrease (P < 0.05) in weekly weight gain was observed in hypoglycaemic kids. It was concluded that neonatal goat kids born with hypoglycaemia may have compromised thermoregulation, metabolism and body weight gain, and the cause of hypoglycaemia in kids may not be related to pre-mating maternal variables.

Prior heat exposure diminishes upper-body endurance work capacity and maximal arm and leg strength in young men.

Workers often experience heat exposure before manual labour. This study investigated whether prior heat exposure diminished upper-body endurance work capacity and maximal isokinetic arm and leg strength in young men. Ten male participants completed two trials in a climatic chamber maintained at 25°C with 50% relative humidity. The two trials required them to complete a 30-min pre-exercise water-immersion at either 40°C (HOT) to provoke an approximately 1°C rise in rectal temperature (Tre) or 36°C (CON) to maintain a normal Tre. Pre- and post-immersion and following arm-cranking, isokinetic maximal voluntary contraction (MVC) torque was assessed for the elbow flexors and knee extensors. During arm-cranking, time to exhaustion was measured using arm crank ergometry at 60% peak oxygen uptake. Electromyography was recorded from the elbow flexors and knee extensors to calculate the integrated electromyography. Tre at post-immersion was higher in HOT (Mean ± SD, 38.1 ± 0.3°C) than CON (37.1 ± 0.3°C; P < 0.01). Time to exhaustion was less in HOT (41 ± 13min) than CON (52 ± 12min; P < 0.01). Isokinetic MVC torque in the elbow flexors and knee extensors was lower in HOT than CON (both P < 0.05). The integrated electromyography of the elbow flexors and knee extensors were lower in HOT than CON (both P < 0.05). This study indicates that a 1°C rise in Tre by prior heat exposure reduces time to exhaustion during arm-cranking and isokinetic MVC torque of the elbow flexors and knee extensors. Workers should be careful about reductions in upper-body endurance work capacity and maximal arm and leg strength when exposed to heat before manual labour.

Effect of Serial in Vivo Passages on The Adaptation of H1N1 Avian Influenza Virus To Pigs.

IntroductionThe lack of proofreading activity of the viral polymerase and the segmented nature of the influenza A virus (IAV) genome are responsible for the genetic diversity of IAVs and for their ability to adapt to a new host. We tried to adapt avian IAV (avIAV) to the pig by serial passages in vivo and assessed the occurrence of point mutations and their influence on viral fitness in the pig’s body.Material and MethodsA total of 25 in vivo avIAV passages of the A/duck/Bavaria/77 strain were performed by inoculation of 50 piglets, and after predetermined numbers of passages 20 uninoculated piglets were exposed to the virus through contact with inoculated animals. Clinical signs of swine influenza were assessed daily. Nasal swabs and lung tissue were used to detect IAV RNA by real-time RT-PCR and isolates from selected passages were sequenced.ResultsApart from a rise in rectal temperature and a sporadic cough, no typical clinical signs were observed in infected pigs. The original strain required 20 passages to improve its replication ability noticeably. A total of 29 amino-acid substitutions were identified. Eighteen of them were detected in the first sequenced isolate, of which 16 were also in all other analysed strains. Additional mutations were detected with more passages. One substitution, threonine (T) 135 to serine (S) in neuraminidase (NA), was only detected in an IAV isolate from a contact-exposed piglet.ConclusionPassaging 25 times allowed us to obtain a partially swine-adapted IAV. The improvement in isolate replication ability was most likely related to S654 to glycine (G) substitution in the basic protein (PB) 1 as well as to aspartic acid (D) 701 to asparagine (N) and arginine (R) 477 to G in PB2, glutamic acid (E) 204 to D and G239E in haemagglutinin and T135S in NA.

Pre-Weaning Exposure to Maternal High-Fat Diet Is a Critical Developmental Window for Programming the Metabolic System of Offspring in Mice.

BackgroundMaternal high-fat diet (HFD) during pregnancy and lactation exerts long-term effects on the health of offspring. However, the critical developmental window for metabolic programming of maternal exposure to HFD on pathogenesis of obesity in offspring needs further clarification.Materials & MethodsFemale ICR mice were fed low-fat diet (LFD) or HFD for 8 weeks until delivery. During lactation, half of LFD dams received HFD while the other half of LFD dams and HFD dams maintained the previous diet. Male offspring were weaned at postnatal day 21 (P21) and fed LFD or HFD for 7 weeks. Metabolic parameters, biochemical, and histological indicators of thermogenesis, rectal temperature, and sympathetic nerve tone were detected at P21 and 10 weeks old.ResultsAt P21, LH (maternal LFD before delivery but HFD during lactation) and HH (maternal HFD before delivery and during lactation) offspring gained more body weight and showed higher serum glucose and triglyceride levels as compared with LL (maternal LFD before delivery and during lactation), and the metabolic characters were maintained until 10 weeks age when fed with LFD after weaning. However, LH offspring exhibited a greater degree of metabolic abnormalities compared to HH offspring, with increased body weight, as well as lower norepinephrine (NE)-stimulated rectal temperature rise when fed with HFD after weaning. The lower UCP1 levels and HSL phosphorylation in LH offspring further suggested that brown adipose tissue (BAT) thermogenic function was impaired.ConclusionExposure to maternal HFD feeding during pre-weaning period alone showed similar detrimental effects on programming metabolic system of offspring as those of both prenatal and early postnatal HFD feeding. Early postnatal stage is a critical time window for metabolic programming and has profound and long-lasting effects on BAT development and function through sympathetic nerve-mediated thermogenesis.

Monitoring of the Middle East Respiratory Syndrome Coronavirus Activity in a Secluded Herd of Camels Kept Under Field Conditions.

Background: Camel-to-human transmission of the Middle East Respiratory Syndrome coronavirus (MERS-CoV) was confirmed as a cause of primary infection in humans. There is a dearth of information regarding the behavior of the virus in camels and the mode of spread among them under natural conditions. The aim of this study was to monitor exposure of camels to the MERS-CoV under field conditions. Methods: From January 1 to November 30, 2015, a secluded herd of 20 pregnant female camels and their neonate calves was established. Nasal and rectal swabs were collected from calves daily for 90 days after birth, then weekly until the end of the study. Nasal and rectal samples were collected from the dams at outset and then weekly until the end of the study. The samples were tested with rtRT-PCR to detect the MERS-CoV RNA. Results: All purchased pregnant camels were MERS-CoV RNA negative at outset. Nineteen dams and 15 calves completed the study. Seven (46.7%) of the 15 calves developed a rise in rectal temperature (39-40°C), shivering, rhinitis, anorexia, and general weakness at a mean ± standard deviation of 18.9 ± 4.9 days of age and their MERS-CoV RNA test was positive on the first day of illness. Three of the seven infected calves died 14 ± 9.1 days postonset of illness at age 17, 14, and 46 days, respectively. The remaining four infected calves fully recovered and they were MERS-CoV RNA positive for 17.5 ± 8.8 days. Four (21.1%) of the 19 dams had positive tests; three dams had no clinical signs, whereas the fourth dam exhibited signs not compatible with MERS-CoV infection and died three days after the positive test, 33 days after parturition. All MERS-CoV infections occurred within 22 days. Conclusions: This study has expanded our understanding of the MERS-CoV epidemiology among camels, which is an important step forward to device effective preventive measures.

Antipyretic Activity of Hydroalcoholic Extract of Leaves of Colocasia esculenta

In this paper the antipyretic effect of the Hydroalcoholic extract of leaves of Colocasia esculenta against Brewer yeast induced pyrexia model in Wistar rats of either sex was investigated. Colocasia esculenta (Apiaceae) is a tropical perennial plant. It contain flavonoids, alkaloids, apigenin, anthocyanin, carbohydrates, fiber, minerals, protein, fat, calcium and iron, Fever induced in the animal (rats) by the injection 15%w/v of brewer’s yeast suspension (10mg/kg according to body weight of rats) subcutaneously in the back below the nape of the neck. . After 18 hr. of Brewer’s yeast injection and rise in rectal temperature was recorded. The temperature of animal was recorded at 0, 1, 2, 3 and 4hr after drug administration. Paracetamol (100 mg/kg p. o.) was used as standard drug. The group received Hydroalcoholic extract 200mg/kg and 400mg/kg showed significant decrease in rectal temperature respectively as compared with the group received standard drug. All the values are expressed as mean ± standard deviation and analysed for ANOVA. Differences between controls, standard ant test groups were considered significant at P &lt; 0.001 levels. . The Hydroalcoholic extract of Colocasia esculenta leaves (200mg/kg and 400mg/kg) possesses dose dependent, significant antipyretic activity against Brewer yeast induced pyrexia.&#x0D; Keywords: Antipyretic activity, ethanolic extract, Colocasia esculenta, Dunnet’s t –test, ANOVA.

Antipyretic activity of mrityunjaya rasa prepared by various compounds of mercury in experimental animals

Introduction: Mrityunjaya Rasa(MR) is a herbomineral Ayurvedic anti-pyretic formulation containing Shuddha Hingula (Purified Cinnabar), Shuddha Gandhaka (Purified Sulphur), Shuddha Tankana (Purified Borax), Shuddha Vatsanabh (Purified Aconite) Pippali (Piper lonum) and Maricha (Piper nigrum). Objective: The present pharmacological study was undertaken to study the comparative antipyretic activity of different samples of Mrityunjaya Rasa with slight variations in ingredients; Mrityunjaya Rasa 'A' (Hingula based), Mrityunjaya Rasa 'B' (Kajjali based), Mrityunjaya Rasa 'C' (Rasasindura based), Mrityunjaya Rasa 'D' (without metallic content). Material and Method: Pyrexia was induced by subcutaneous injection of 20% wt/v of Brewer's yeast in distilled water (10ml/kg) in 36 animals divided into 6 groups, each group containing 6 animals. Basal rectal temperature was measured before the injection of yeast, and the rise in rectal temperature was recorded after 18 hrs of yeast injection. Group 'A' treated as normal control while group 'B' as standard control (treated with Paracetamol) Group C, D, E, F were drug tested groups. Results: The data generated during all stages of study showed that all samples of Mrityunjaya Rasa (22.5 mg/kg per day) exert highly significant (P

Thermoregulation in humid climate-adapted and Savannah breeds of goats exposed to West African cold (harmattan) season

Abstract The West African Dwarf (WAD) goats have hereditary dwarfism and are adapted to the humid climate. The study compared the cold tolerance of WAD and Savannah (Red Sokoto and Sahel) goats during the peak of the West African cold season in the Northern Guinea Savannah of Nigeria. A total of 18 adult non-pregnant, dry does comprising equal number of each breed (six per breed) were used for the study. Thermoregulatory variables were recorded four times in the morning (07:00 h) and afternoon (13:00 h) hours at two-day intervals. Results revealed that irrespective of the hour of day, the WAD had significantly (p &lt; 0.05) higher respiratory rate when compared with Red Sokoto and Sahel goats. The diurnal afternoon rise in respiratory rate and the magnitude of afternoon rise in rectal temperature was higher (p &lt; 0.0001) in WAD than Sahel and Red Sokoto goats. The body surface temperature in the morning hours was significantly lower in WAD compared with Sahel breed, while in the afternoon hours, the inter-digital space temperature was significantly lower in WAD compared with Savannah breeds. However, there were no significant (p &gt; 0.05) differences in heart rate, rectal, head and leg temperatures between the breeds in both morning and afternoon hours. Discriminant analysis revealed that the morning hours induced greater homogeneity in the thermoregulatory responses between the breeds adapted to the humid and Savannah climates as compared with the afternoon hours. It was concluded that although WAD goats employed more intense peripheral vasoconstriction to survive cold exposure and demonstrated greater diurnal amplitude in thermoregulatory variables, they maintained comparable core body temperature as the indigenous Savannah breeds. Thus, suggesting that despite the hereditary dwarfism, the WAD goats could conserve body heat during the West African cold season in the Northern Guinea Savannah zone of Nigeria.

Effects of Pre-Cooling on Thermophysiological Responses in Elite Eventing Horses.

Simple SummaryHorses have a high metabolic capacity for exercise, producing a great deal of heat, and have a small surface area for heat loss. Under limited circumstances, the regulation of heat loss (i.e., across the respiratory tract and by the evaporation of sweat) means heat build-up in the body is reduced. Thermoregulation can be assisted by cooling the horses down to safely perform exercise in thermally challenging environments. The present study showed that pre-cooling (i.e., cooling between the warm-up and exercise performance) slightly reduced the rise in rectal, shoulder and rump skin temperatures of ten international eventing horses during moderately intense canter training in moderate environmental conditions. During the canter training, heart rate, sweat rate and sweat composition were unaffected by pre-cooling. The pre-cooling strategy chosen here was cold-water rinsing for a short period of time (~8 min). Considering the limited time and space at equestrian events, such a pre-cooling strategy could easily be implemented. Reducing heat strain by pre-cooling may potentially improve equine welfare during events.In this study, we examined the effects of pre-cooling on thermophysiological responses in horses exercising in moderate environmental conditions (average wet bulb globe temperature: 18.5 ± 3.8 °C). Ten international eventing horses performed moderate intensity canter training on two separate days, and were either pre-cooled with cold-water rinsing (5–9 °C for 8 ± 3 min; cooling) or were not pre-cooled (control). We determined velocity (V), heart rate (HR), rectal temperature (Tre,), shoulder and rump skin temperature (Tshoulder and Trump), plasma lactate concentration (LA), gross sweat loss (GSL), and local sweat rate (LSR), as well as sweat sodium, chloride and potassium concentrations. The effect of pre-cooling on Tre was dependent on time; after 20 min of exercise the effect was the largest (estimate: 0.990, 95% likelihood confidence intervals (95% CI): 0.987, 0.993) compared to the control condition, resulting in a lower median Tre of 0.3 °C. Skin temperature was also affected by pre-cooling compared to the control condition (Tshoulder: −3.30 °C, 95% CI: −3.739, −2.867; Trump: −2.31 °C, 95% CI: −2.661, −1.967). V, HR, LA, GSL, LSR and sweat composition were not affected by pre-cooling. In conclusion, pre-cooling by cold-water rinsing could increase the margin for heat storage, allowing a longer exercise time before a critical Tre is reached and, therefore, could potentially improve equine welfare during competition.

Evaluation of a Pasteurella multocida Respiratory Disease Induction Model for Goats (Capra aegagrus hircus).

Infectious respiratory diseases are a serious health concern worldwide. However, few models describe the experimental induction of lung infection, or the effect of experimental infection on clinical pathologic parameters in goats. Goats offer benefits compared to cattle because of size and tractability and compared to sheep with regard to specific features of their anatomy. In previous experimental models of infection in goats, coadministration of an immunosuppressive dose of a corticosteroid is common; however, protocols that use corticosteroid often note mortality as an adverse effect. We therefore investigated an infection protocol that did not use immunosuppression but instead relied on 2 intratracheal inoculations of Pasteurella multocida in healthy meat goats to induce clinical and hematologic changes associated with respiratory infection. Healthy Boer or Boer-Kiko cross goats (n = 6; age, 10 mo) were inoculated with Pasteurella multocida and were monitored over a 312-h period for clinical and hematologic parameters of infection. After induction of pneumonia, the goats had a significant 1.2 °C rise in rectal temperature and auscultatable rales for up to 96 h. Lymphocyte counts, serum amyloid A values, and respiratory scores were significantly different before and after induction of disease and were consistent with respiratory infection. No mortality was associated with this experimental infection, and minimal gross pathologic changes were noted at study termination. The clinical and pathologic findings of this study suggest a potentially reproducible method of establishing clinical respiratory infection in goats. The repeated intratracheal inoculation method of inducing caprine respiratory disease can be used to produce experimental respiratory disease in goats when the use of corticosteroid is not desirable. With the feasibility of this method established, additional research evaluating the optimal dose and frequency of P. multocida administration is needed.

Impact of 3-day high and low dietary sodium intake on sodium status in response to exertional-heat stress: a double-blind randomized control trial.

To determine the impact of altering dietary sodium intake for 3days preceding exercise on sweat sodium concentration [Na+], and cardiovascular and thermoregulatory variables. Fifteen male endurance athletes (runners n = 8, cyclists n = 7) consumed a low (LNa, 15mgkg-1day-1) or high (HNa, 100mgkg-1day-1) sodium diet, or their usual free-living diet [UDiet, 46 (37-56) mgkg-1day-1] for 3days in a double-blind, randomized cross-over design, collecting excreted urine (UNa) and refraining from exercise. On day 4, they completed 2h running at 55% [Formula: see text]O2max or cycling at 55% maximum aerobic power in Tamb 35°C. Pre- and post-exercise blood samples were collected, and sweat from five sites using absorbent patches along the exercise protocol. UNa on days 2-3 pre-exercise [mean (95% CI) LNa 16 (12-19) mgkg-1day-1, UDiet 46 (37-56) mgkg-1day-1, HNa 79 (72-85) mgkg-1day-1; p < 0.001] and pre-exercise aldosterone [LNa 240 (193-286) mgkg-1day-1, UDiet 170 (116-224) mg kg-1day-1, HNa 141 (111-171) mg kg-1day-1; p = 0.001] reflected sodium intake as expected. Pre-exercise total body water was greater following HNa compared to LNa (p < 0.05), but not UDiet. Estimated whole-body sweat [Na+] following UDiet was 10-11% higher than LNa and 10-12% lower than HNa (p < 0.001), and correlated with pre-exercise aldosterone (1st h r = - 0.568, 2nd h r = - 0.675; p < 0.01). Rectal temperature rose more quickly in LNa vs HNa (40-70min; p < 0.05), but was similar at the conclusion of exercise, and no significant differences in heart rate or perceived exertion were observed. Three day altered sodium intake influenced urinary sodium excretion and sweat [Na+], and the rise in rectal temperature, but had no effect on perceived exertion during moderate-intensity exercise in hot ambient conditions.

Brief in-play cooling breaks reduce thermal strain during football in hot conditions

ObjectivesThe study examined if three feasible strategies involving additional in-play cooling periods attenuate the core (rectal) temperature rise during simulated football matches. DesignFour counterbalanced experimental trials in an environmental chamber set to 35 °C ambient temperature, 55% relative humidity, and 30 °C WBGT. MethodsTwelve healthy well-trained football players completed a regular simulated match (REG), regular simulated match with additional 3-min cooling periods at the 30-min mark of each half inclusive of chilled water consumption (COOLwater), regular simulated match with additional 3-min cooling periods at the 30-min mark of each half inclusive of chilled water consumption and the application of an ice towel around the neck (COOLtowel), regular simulated match with an extended (+5 min; total of 20-min) half-time break (HTextended). ResultsThe difference in rectal temperature change was significantly lower in the COOLwater (−0.25 °C), COOLtowel (−0.28 °C), and HTextended (−0.21 °C) trials in comparison to the REG (all p < 0.05). Exercising heart rate and session rating of perceived exertion was lower in the COOLwater (−13 bpm; −1.4 au), COOLtowel (−10 bpm; −1.3 au), and HTextended (−8 bpm; −0.9 au) trials in comparison to the REG trial (all p < 0.05). The cooling interventions did not significantly change skin temperature or thermal sensation in comparison to the REG (all p > 0.05). ConclusionsAll three cooling interventions attenuated core body thermal strain during simulated matches. The laboratory-based study supports the use of brief in-play cooling periods as a means to attenuate the rise in core temperature during matches in hot and humid conditions.

Altered brain structure with preserved cortical motor activity after exertional hypohydration: a MRI study.

Hypohydration exceeding 2% body mass can impair endurance capacity. It is postulated that the brain could be perturbed by hypohydration, leading to impaired motor performance. We investigated the neural effects of hypohydration with magnetic resonance imaging (MRI). Ten men were dehydrated to approximately -3% body mass by running on a treadmill at 65% maximal oxygen consumption (V̇o2max) before drinking to replace either 100% [euhydration (EU)] or 0% [hypohydration (HH)] of fluid losses. MRI was performed before start of trial (baseline) and after rehydration phase (post) to evaluate brain structure, cerebral perfusion, and functional activity. Endurance capacity assessed with a time-to-exhaustion run at 75% V̇o2max was reduced with hypohydration (EU: 45.2 ± 9.3 min, HH: 38.4 ± 10.7 min; P = 0.033). Mean heart rates were comparable between trials (EU: 162 ± 5 beats/min, HH: 162 ± 4 beats/min; P = 0.605), but the rate of rise in rectal temperature was higher in HH trials (EU: 0.06 ± 0.01°C/min, HH: 0.07 ± 0.02°C/min; P < 0.01). In HH trials, a reduction in total brain volume (EU: +0.7 ± 0.6%, HH: -0.7 ± 0.9%) with expansion of ventricles (EU: -2.7 ± 1.6%, HH: +3.7 ± 3.3%) was observed, and vice versa in EU trials. Global and regional cerebral perfusion remained unchanged between conditions. Functional activation in the primary motor cortex in left hemisphere during a plantar-flexion task was similar between conditions (EU: +0.10 ± 1.30%, HH: -0.11 ± 0.31%; P = 0.637). Our findings demonstrate that with exertional hypohydration, brain volumes were altered but the motor-related functional activity was unperturbed. NEW & NOTEWORTHY Dehydration occurs rapidly during prolonged or intensive physical activity, leading to hypohydration if fluid replenishment is insufficient to replace sweat losses. Altered hydration status poses an osmotic challenge for the brain, leading to transient fluctuations in brain tissue and ventricle volumes. Therefore, the amount of fluid ingestion during exercise plays a critical role in preserving the integrity of brain architecture. These structural changes, however, did not translate directly to motor functional deficits in a simple motor task.

Upper body sweat mapping provides evidence of relative sweat redistribution towards the periphery following hot-dry heat acclimation

ABSTRACTPurpose: Produce a detailed upper-body sweat map and evaluate changes in gross and regional sweating rates (RSR) and distribution following heat acclimation (HA). Methods: Six males (25 ± 4 yrs) completed six consecutive HA days (45°C, 20% rh) requiring 90 minutes intermittent exercise to maintain a 1.4°C rectal temperature (Tre) rise. Pre- and post-HA upper-body RSR were measured at 55% (Intensity-1; I1) and 75% VO2 max (Intensity-2; I2) using a modified absorbent technique. Results: From day one to six of HA, work rate increased (n.s.), heart rate, Tre, and skin temperature were similar, and gross sweat loss (GSL) increased (P < 0.001). During pre and post-HA experiments, relative workloads were similar (Pre-I1 54 ± 3, Post-I1 57 ± 5%VO2max; Pre-I2 73 ± 4, Post-I2 76 ± 7%VO2max). Post-HA GSL was significantly higher (Pre 449 ± 90 g.m−2 h−1, Post 546 g.m−2 h−1; P < 0.01). Highest RSR were observed on the central back both pre and post-HA at I1 (pre 854 ± 269 post 1178 ± 402g.m−2 h−1) and I2 (pre 1221 ± 351 post 1772 ± 396 g.m−2 h−1). Absolute RSR increased significantly in 12 (I1) to 14 (I2) of the 17 regions. Ratio data indicated significant post-HA relative RSR redistribution, with decreased relative contributions to whole-body sweating on the back, chest staying the same and arms increasing. Conclusions: Hot-dry HA significantly increased GSL in aerobically trained males at I2. Absolute RSR significantly increased in I1 and I2, with a preferential relative redistribution towards the periphery of the upper-body.

Coumarin alleviates ovalbumin-induced food anaphylaxis in a mouse model by affecting mast cell function.

Coumarin is an important organic heterocyclic compound with a wide range of sources in nature. It plays an important role in the drug discovery process due to its existence in diverse biologically active compounds and its broad bioactivity. In this study, the anti-allergic activity of coumarin was evaluated using an ovalbumin (OVA)-induced mouse food allergy model and an immunoglobulin (Ig)E mediated mouse bone marrow-derived mast cell (BMMC) model. Coumarin could alleviate the OVA-induced allergic symptoms, decrease the diarrhea rates, and promote the rectal temperature rise in allergic mice. Moreover, coumarin had the ability to reduce the levels of histamine and mouse mast cell proteinases, inhibit OVA-specific IgE, and significantly decrease the population of mast cells in the spleen and mesenteric lymph nodes. Coumarin could also significantly suppress mast cell-dependent passive cutaneous anaphylaxis. Additionally, the number of mature BMMCs was decreased as coumarin caused the suppression of c-KIT receptors. Furthermore, coumarin up-regulated the apoptosis of OVA-activated BMMCs in a concentration-dependent manner. In conclusion, coumarin displayed effective anti-food allergy activity via the regulation of mast cell function and numbers. Coumarin and its derivatives provide a new direction for the development of anti-food allergic drug components.

Moisture vapour permeable gloves extend thermal endurance and safe work time more than other similarly permeable chemical-biological ancillary protective items

Working in Chemical Biological (CB) protective equipment causes thermoregulatory strain by restricting evaporative cooling. We quantified which impermeable ancillary items [gloves(G), body armour liner(BAL), respirator(R) and overboots(OB)] imposed the greatest and the least thermoregulatory strain through restricting evaporative cooling. The study was a five-condition repeated-measures design with male volunteers (n = 13) who stepped intermittently with recovery periods in a desert-like environment (40.5 °C, 20% rh). Conditions varied in the ensemble worn, with a matched weight secured to the area when an item was not worn: CON(CB suit plus all items), NR(no R), NBAL(no BAL [170g liner]), NG(no G) and NOB(no OB). The greatest reduction in thermoregulatory strain compared with CON occurred in NG when the rise of rectal temperature was attenuated by 0.37 °C.hr−1 (p < .001), extending tolerance time by 21.3% (p < .05) and improving perceived thermal comfort. The least improvement occurred for NOB. It is recommended that the G permeability be examined further.Practitioner summary: Thermoregulatory strain was quantified when wearing impermeable protective equipment. The thermal burden of intermittent exercise in desert-like environments was best alleviated by removing gloves compared to removing a respirator, overboots or body armour liner. Reducing the evaporative resistance of materials used for such kit, particularly gloves, should be investigated.

Thermoeffector Responses at a Fixed Rate of Heat Production in Heart Failure Patients.

Heart failure (HF) patients seem to exhibit altered thermoregulatory responses during exercise in the heat. However, the extent to which these responses are altered due to physiological impairments independently of biophysical factors associated with differences in metabolic heat production (Hprod), evaporative heat balance requirements (Ereq), and/or body size is presently unclear. Therefore, we examined thermoregulatory responses in 10 HF patients and 10 age-matched controls (CON) similar in body size during exercise at a fixed rate of Hprod and therefore Ereq in a 30°C environment. Rectal temperature, local sweat rate, and cutaneous vascular conductance were measured throughout 60 min of cycle ergometry. Whole-body sweat rate was estimated from pre-post nude body weight corrected for fluid intake. Despite exercising at the same rate of Hprod (HF, 338 ± 43 W; CON, 323 ± 31 W; P = 0.25), the rise in rectal temperature was greater (P < 0.01) in HF (0.81°C ± 0.16°C) than in CON (0.49°C ± 0.27°C). In keeping with a similar Ereq (HF, 285 ± 40 W; CON, 274 ± 28 W; P = 0.35), no differences in whole-body sweat rate (HF, 0.45 ± 0.11 L·h; CON, 0.41 ± 0.07 L·h; P = 0.38) or local sweat rate (HF, 0.96 ± 0.17 mg·cm·min; CON, 0.79 ± 0.15 mg·cm·min; P = 0.50) were observed between groups. However, the rise in cutaneous vascular conductance was lower in HF than in CON (HF, 0.83 ± 0.42 au·mm Hg; CON, 2.10 ± 0.79 au·mm Hg; P < 0.01). In addition, the cumulative body heat storage estimated from partitional calorimetry was similar between groups (HF, 154 ± 106 kJ; CON, 196 ± 174 kJ; P = 0.44). Collectively, these findings demonstrate that HF patients exhibit a blunted skin blood flow response, but no differences in sweating. Given that HF patients had similar body heat storage to that of CON at the same Hprod, their greater rise in core temperature can be attributed to a less uniform internal distribution of heat between the body core and periphery.