Ascorbic acid-induced modulation of rectal temperature fluctuations in pigs during the harmattan season

The experiment was carried out with the aim of investigating the effect of ascorbic acid (AA) on fluctuations in rectal temperature (RT) of pigs during the harmattan season. Sixteen pigs administered with AA at the dose of 250 mg/kg orally and individually served as experimental animals, and 13 others administered orally with sterile water were used as control animals. The RT was measured from all the pigs at 06:00, 13:00 and 18:00 h twice in a week for three consecutive weeks. The lowest overall mean RT value of 37.52±0.90 °C was obtained at 06:00 h in the experimental pigs, while the corresponding value in control pigs was 37.63±0.90 °C (P>0.05). The maximum RT values of 38.75±0.18 °C and 39.27±0.11 °C were recorded at 13:00 h in experimental and control pigs, respectively (P<0.05). The results indicate that AA modulates the body temperature by decreasing the maximum RT value in pigs exposed to harmattan stress, and may alleviate the risk of adverse effects of the stress on health and productivity of pigs during the cold-dry season.     

Thermoregulation during mild exercise at different circadian times

Eight healthy subjects exercised at 90 watts on a cycle ergometer on four occasions, at times close to the minimum, maximum rate of rise, maximum, and maximum rate of fall of their resting core temperature. The duration of exercise was determined by the time taken for the core (rectal) temperature to reach an equilibrium value. Forearm skin blood flow and temperature were measured regularly during the exercise, as were heart rate and ratings of perceived exertion. Sweat loss was calculated by weighing the subjects nude before and after the exercise. The rise of heart rate was not significantly different at the four times of exercise, though the rating of perceived exertion was greatest at 05:00 h. Resting core temperatures showed a significant circadian rhythm at rest (the timing of which confirmed that exercise was being performed at the required times), but the amplitude of this rhythm was decreased significantly by the exercise. The initial rate of rise of core temperature, and the total rise from the resting to the equilibrium value, were both inversely proportional to resting temperature. The time-course of the rise was accurately described by a negative-exponential model, but this model gave no evidence that the kinetics of the equilibration process depended upon the time of day. The thermoregulatory responses to the rise in core temperature—the amount of total sweat loss and rises in forearm skin blood flow and temperature—differed according to the time of exercise. In general, the responses were significantly greater at 17:00 h compared with 05:00 h, and at 23:00 h compared with 11:00 h. The results accord with predictions made on the basis of previous work by us in which core temperature rhythms have been separated into components due to the endogenous body clock and due to the direct effects of spontaneous activity. The results are discussed in terms of the ecological implications of the differing capabilities of humans to deal with heat loads produced by spontaneous activity or mild exercise at different phases of the circadian rhythm of resting core temperature.     

Remote sensing of physiological data: Impact of long term captivity on body temperature variation of the feral cat (Felis catus) in Australia,recorded via Thermochron iButtons

This study reports body temperature regulation (T_b) and circadian rhythms of undisturbed feral cats in their natural environment in Australia over a continuous period of three months. It furthermore compares these data with T_b data collected of feral cats, after a period of one year in captivity. In free-ranging, undisturbed feral cats, a distinct robust, regular circadian rhythm (strength of rhythm) (21–59.8%) with higher body temperature in the dark (active) phase (mean±STD: 39.2±0.27 °C) and significantly lower body temperature during the light (rest) phase (mean±STD: 38.1±0.47 °C, P<0.001) was found. The acrophase (time of the daily peak) of the three free-ranging cats investigated varied from 22:34 h (LG 2), 22:57 h (LG 1) to 23:17 h (LG 3). In the course of captivity, the cats’ circadian rhythms shifted from nocturnality to a diurnal tendency, with an acrophase ranging from 12:00 h (MtK 2), 12:23 h (MtK 1) to 16:25 h (MtK 3). This change in rhythmicity was accompanied by a significant decrease in robustness (1.7–5.2%) and mean body temperature levels (37.77±0.34 °C) as well as minima and maxima (36–39 °C versus 35.5–41.9 °C, free-ranging cats) of three captive cats, resulting in a significant shift towards a decrease in amplitude.     

The effect of thermopreference on circadian thermoregulation in sprague-dawley and fisher 344 rats

Interstrain differences in thermoregulation of rats are important in biomedical research because subtleties in thermoregulatory sensitivities may greatly affect data collected. Little is known regarding how individual rodent strains differentially utilize behavioral thermal preference to regulate core temperature (Tc). Sprague-Dawley (SD) and Fischer 344 (F344) rats are known to have differences in thermoregulation including heat tolerance and are useful models to study interstrain differences in thermoregulation. Adult male SD and F344 rats of similar body size were implanted with radiotelemetry thermoprobes (DSI) to measure Tc and MA and housed in either a longitudinal temperature gradient with an ambient temperature (Ta) range of ∼15–40 °C to measure selected Ta (STa) or control environment maintained at a Ta of 23 °C. When continuously monitored for 48 h, Tc and MA increased at night, while STa decreased, according to their normal circadian cycle in both strains. SD rats were more active than F344 rats throughout the circadian cycle (SD gradient: day=12.9±1.2 m/h, night=32.1±2.4 m/h; F344 gradient: day=4.1±0.6 m/h, night=16.8±1.8 m/h; p<0.05 interstrain and circadian effects). The STa of each strain was greater during the daytime (SD: 26.4±0.2 °C; F344: 27.8±0.3 °C) than at night (SD: 24.7±0.3 °C; F344: 25.7±0.3 °C) confirming past studies that thermopreference during the day and night is greater than standard room temperature (∼23 °C). Correlations between MA and Tc suggest that MA has a greater effect on Tc in the F344 but not the SD strain when housed in a temperature gradient. There were significant strain differences in Tc depending on whether rats were housed in a temperature gradient. That is, the control F344 rats had a lower Tc during the transition from dark to light compared to rats housed in a gradient. Tc of the SD strain was unaffected by housing in the gradient. Rats are typically housed at a standard room temperature of 23 °C. However, the results demonstrate that when given the opportunity to behaviorally thermoregulate in a temperature gradient, the F344 strain selects a warmer environment that affects the regulation of Tc. This may be important in the experimenters' choice of ambient temperatures to house and study rats and other rodents.     

Daily variation in body core temperature using radio-telemetry in aluminium industry shift-workers

The aim of this study was to investigate the diurnal variation in core temperature in aluminium shift-workers exposed to hot ambient conditions. Core temperature was continuously recorded via an ingestible radio-telemetry thermistor in 29 shift-workers. Data from the morning, afternoon and night shifts were aggregated for each participant to obtain 24-h recordings during work duties. Complete data were obtained from 10 participants. Results showed that body core temperatures recorded in the afternoon (from 12:00 h to 20:00 h) were significantly higher (P<0.05) than in the late evening, night and early morning (from 21:00 h to 08:00 h). In addition, core temperature displayed a circadian variation with a mesor of 37.45 (±0.19) °C, an amplitude of 0.23 (±0.12) °C and an acrophase at 16:36 h (±3:37 h). The peak values of core temperature recorded at each hour of the day on the work site followed the same pattern with an acrophase in the early afternoon. In summary, our data showed that shift-workers present higher core temperatures in the afternoon than in the morning or during the night. In addition, it was not the work duration but the hour-of-day that triggered the variation in core temperature. This result partly explains previous observations that workers under heat stress have a higher probability of heat illness during daytime shifts than during the night shift, and suggests that special care should be given to the afternoon shift and to the end of the morning shift.     

Effects of acute exercise on serum interleukin-17 concentrations in hot and neutral environments in trained males

The purpose of this study was to determine the effects of acute exercise on IL-17 concentrations in hot and neutral environments in trained males. Ten trained, non-heat acclimated males performed two 1 h run on treadmill at 60% VO2max in neutral (22±1 °C, 50±5RH) and hot (35±1 °C, 50±5) temperature conditions. Samples of the venous blood were taken (Pre, post, 2 h post) for determination of serum IL-17, cortisol concentrations and numbers of leukocytes and neutrophils. In addition, body temperature, RPE and PVC during exercise were measured. The collected data were analyzed using the Repeated-Measures analyses of variance and Bonferroni post hoc and Paird T tests (p<0.05). The concentration of cortisol and total number of leukocytes increased significantly after exercise, in both conditions (p<0.0001) and were significantly higher in hot than neutral (p=0.016, p=0.002). During the rest period (2 h post) the number of neutrophils increased significantly in hot environment (p=0.018). The concentrations of IL-17 increased significantly only after exercise in hot (p<0.0001) and were significantly higher during hot than neutral (p=0.002). The results suggest that exercise in hot environment cause increase in body temperature, perceived exertion and cardiac-vascular changes which are sufficient to elicit immune, hormonal and inflammatory responses. The present results confirm the additive effect of heat stress on the IL-17 response during exercise.     

Rectal,telemetry pill and tympanic membrane thermometry during exercise heat stress

We compared the accuracy of an ingestible telemetry pill method of core temperature (T_c) measurement and an infrared tympanic membrane thermometer to values from a rectal thermistor during exercise-induced heat stress. Ten well-trained subjects completed four exercise trials consisting of 40 min constant-load exercise at 63% of maximum work rate followed by a 16.1 km time trial at 30 °C and 70% relative humidity. Temperature at rest was not different between the three methods of T_c measurement (T_re: 37.2±0.3 °C; T_p: 37.2±0.2 °C; T_ty: 37.1±0.3 °C; P=0.40$P=0.40$). Temperature rose continuously during the exercise period (ΔT_re: 2.2±0.5 °C; ΔT_p: 2.2±0.5 °C; ΔT_ty: 1.9±0.5 ±°C and there were no differences between T_re and T_p measurements at any time throughout exercise (P=0.32$P=0.32$). While there were no differences between T_re and T_ty after 10 min (P=0.11$P=0.11$) and 20 min (P=0.06$P=0.06$) of exercise, T_ty was lower than T_re after 30 min of exercise (P<0.01$P<0.01$) and remained significantly lower throughout the remainder of the exercise period. These results demonstrate that the telemetry pill system provides a valid measurement of trunk temperature during rest and exercise-induced thermal strain. T_ty was significantly lower than T_re when temperature exceeded 37.5 °C. However, whether these differences are due to selective brain cooling or imperfections in the tympanic membrane thermometer methodology remains to be determined.     

Rectal temperature,distal sweat rate,and forearm blood flow following mild exercise at two phases of the circadian cycle

Changes in rectal temperature during mild exercise in the middle of the rising (11:00 h) and falling (23:00 h) phases of the circadian rhythm of resting core temperature have been compared. Seven healthy males were studied at rest, while exercising on a cycle ergometer (60 min at 80 W), and during the first 30 min of recovery. Rectal temperature, forearm blood flow, and forearm sweat rate were measured at 1 min intervals throughout. During exercise, there were significant time‐of‐day differences in the profiles of all three variables, and in the thresholds for increases in forearm blood flow and sweating. Forearm blood flow and sweat rate were recruited more rapidly and to a greater extent with evening exercise, and rectal temperature rose less. Analysis of covariance, with rectal temperature as the covariate, indicated the associations between it and forearm blood flow or sweating were significantly different (p<0.05) between the two times of day. There were also significant (p<0.05) time‐of‐day effects for forearm blood flow and sweating that were independent of rectal temperature. During recovery, rectal temperature fell more quickly in the late evening than late morning. Forearm blood flow and sweating also showed time‐of‐day differences, but these did not co‐vary with rectal temperature. Control of rectal temperature during exercise and recovery appears to be more effective in the late evening than late morning, and differences in forearm blood flow and sweating, as well as factors independent of these two variables, contribute to this difference. The results support our “heat‐gain/heat‐loss modes” hypothesis.     

Diurnal pollen tube growth rate is slowed by high temperature in field-grown Gossypium hirsutum pistils

For Gossypium hirsutum pollination, germination, and pollen tube growth must occur in a highly concerted fashion on the day of flowering for fertilization to occur. Because reproductive success could be influenced by the photosynthetic activity of major source leaves, we hypothesized that increased temperatures under field conditions would limit fertilization by inhibiting diurnal pollen tube growth through the style and decreasing subtending leaf photosynthesis. To address this hypothesis, G. hirsutum seeds were sown on different dates to obtain flowers exposed to contrasting ambient temperatures while at the same developmental stage (node 8 above the cotyledons). Collection and measurement were conducted at 06:00, 09:00, 12:00, 15:00, and 18:00 h on August 4 (34.6 °C maximum air temperature) and 14, 2009 (29.9 °C maximum air temperature). Microclimate measurements included photosynthetically active radiation, relative humidity, and air temperature. Pistil measurements included pistil surface temperature, pollen germination, pollen tube growth through the style, fertilization efficiency, fertilized ovule number, and total number of ovules per ovary. Subtending leaf measurements included leaf temperature, photosynthesis, and stomatal conductance. Under high temperatures the first measurable pollen tube growth through the style was observed earlier in the day (12:00 h) than under cooler conditions (15:00 h). Also, high temperature resulted in slower pollen tube growth through the style (2.05 mm h⁻¹) relative to cooler conditions (3.35 mm h⁻¹), but there were no differences in fertilization efficiency, number of fertilized ovules, or ovule number. There was no effect of sampling date on diurnal photosynthetic patterns, where the maximum photosynthetic rate was observed at 12:00 h on both dates. It is concluded that, of the measured physiological and reproductive processes, pollen tube growth rate showed the greatest sensitivity to high temperature under field conditions.     

Force variability depends on core and muscle temperature

The aim of this study was to investigate if voluntary activation and force variability during maximal voluntary contraction (MVC) depends more on muscle (local) or body (core) temperature. Ten volunteers performed a 2-min MVC of the knee extensors under the control (CON) conditions (ambient temperature (21 °C), relative humidity (30%), and air velocity (∼0.1 m/s)) as well as after heating (HT) and cooling (CL) of the lower body. During water manipulation procedure lower body was immersed up to the waist in a water bath at ∼44 °C for 45 min for HT experiment, and ∼15 °C for 30 min for CL experiment. Peak torque, torque variability, muscle voluntary activation and half-relaxation time were assessed during the exercise. HT increased muscle (2.8±0.2 °C) and rectal (1.9±0.1 °C) temperatures while CL lowered muscle (2.2±0.2 °C) temperature, but did not affect rectal temperature. During 2-min MVC, peak torque decreased (P<0.05; SP>90%) and to a lower level in HT compared to CON and CL experiments (52.6±2.3% versus 69.0±2.3% and 65.6±1.9% MVC, respectively, P<0.05; SP>90%). Torque variability increased significantly during exercise and was significantly larger in HT and lower in CL compared to CON experiment. Voluntary activation of exercising muscle was more depressed in HT (i.e. greater central fatigue) and the smallest effect was found in CL compared to CON. In conclusion increased core and muscle temperature impairs voluntary activation and increases force variability of the exercising muscles while a local muscle cooling decrease force variability but has a small effect on central fatigue.     

Rectal temperature, distal sweat rate, and forearm blood flow following mild exercise at two phases of the circadian cycle

Changes in rectal temperature during mild exercise in the middle of the rising (11:00 h) and falling (23:00 h) phases of the circadian rhythm of resting core temperature have been compared. Seven healthy males were studied at rest, while exercising on a cycle ergometer (60 min at 80 W), and during the first 30 min of recovery. Rectal temperature, forearm blood flow, and forearm sweat rate were measured at 1 min intervals throughout. During exercise, there were significant time-of-day differences in the profiles of all three variables, and in the thresholds for increases in forearm blood flow and sweating. Forearm blood flow and sweat rate were recruited more rapidly and to a greater extent with evening exercise, and rectal temperature rose less. Analysis of covariance, with rectal temperature as the covariate, indicated the associations between it and forearm blood flow or sweating were significantly different (p<0.05) between the two times of day. There were also significant (p<0.05) time-of-day effects for forearm blood flow and sweating that were independent of rectal temperature. During recovery, rectal temperature fell more quickly in the late evening than late morning. Forearm blood flow and sweating also showed time-of-day differences, but these did not co-vary with rectal temperature. Control of rectal temperature during exercise and recovery appears to be more effective in the late evening than late morning, and differences in forearm blood flow and sweating, as well as factors independent of these two variables, contribute to this difference. The results support our "heat-gain/heat-loss modes" hypothesis.     

A non-invasive device to continuously determine heat strain in humans

Heat stroke remains a very dangerous, potentially lethal illness in humans. The Physiological Strain Index (PSI), originally based on heart rate and rectal temperature recordings in humans, describes heat strain in quantitative terms. The objective of our study was to establish whether the rectal temperature recordings serving to determine the PSI could be replaced by a non-invasive skin temperature sensor combined with a heat flux sensor (Double Sensor) attached to the inside of a helmet. We assumed (i) that the difference between the recordings by the device under test and the rectal temperature should be less than ±1.0 °C for ±2 S.D. at 10, 25, and 40 °C ambient temperature, and (ii) that the temperature predictions based on the Double Sensor temperature should differ by less than 1 PSI score from the calculations based on recordings of the rectal temperature. Twenty male subjects participated in the study. Rectal, nasopharyngeal, and skin temperatures, heat flux, and cardiovascular data were collected continuously during different experimental setups at ambient temperatures of 10, 25, and 40 °C. Depending on the protocols, the exercise intensities varied from 25% to 55% of the individual VO_2max. A comparison of the recordings obtained from the device under test with those of the rectal temperature revealed that (i) the recordings of the Double Sensor differed by −0.16 to 0.1 °C from the mean rectal temperature, (ii) the concordance correlation coefficients (CCC) during all work and rest periods rose with rising ambient temperatures (all work periods: 10 °C: 0.49; 25 °C: 0.69; 40 °C: 0.75; all rest periods: 10 °C: 0.39; 25 °C: 0.81; 40 °C: 0.74), and that (iii) the Double Sensor in the helmet showed that during all rest periods and in all ambient conditions, the temperature dropped much more quickly than what was recorded when taking the rectal temperature (p<0.01). When we compared the PSI values based on the rectal temperature recordings to those determined by the Double Sensor, it was found that (i) the PSI based on the Double Sensor recordings differed by −0.27 to 0.17 from the mean PSI established by rectal temperature recordings. Furthermore, the CCC for the PSI rose during all work periods (10 °C: 0.81, 25 °C: 0.93, 40 °C: 0.87) and rest periods (10 °C: 0.68; 25 °C: 0.93; 40 °C: 0.79). In conclusion, under warm/hot environmental conditions the device under test provided a reliable method of assessing the PSI in operational environments to improve physiological situational awareness and safety in action. However, there are some limitations that reduce the device's performance in cold environments; these need to be investigated further.     

Relationship between change in core temperature and change in cortisol and TNFα during exercise

The combined thermal load created by exercise and a hot environment is associated with an exaggerated core temperature response. The elevated core temperature is believed to increase the total stress of the exercise. Increased stress during exercise has been associated with increased levels of cortisol. The association of cortisol with increased inflammatory responses following exercise in the heat is equivocal. Thus, the purpose of the current investigation was to explore the relationship between increases in rectal temperature (T_re) and TNFα and cortisol. To induce T_re changes, 8 male subjects (mean±SD, age=23.6±2 yr, VO₂max=52.8±3.7 mL/kg/min, BMI=24.2±1.9) participated in two 40 min trials of cycle ergometry at 65% of VO₂peak immersed to chest level in cool (25 °C) and warm (38.5 °C) water. T_re was monitored throughout each trial, with blood samples taken immediately pre and post of each trial. Neither cortisol nor TNFα changed significantly during exercise in the cool water; however, in the warm trial, both cortisol and TNFα significantly increased (p<0.004). Concordance correlations (R_c) between Δ cortisol and Δ TNFα indicated a strong but non-significant correlation (R_c=0.833, p=0.135). In conclusion, changes in core temperature may be impacting the relationship between exercise induced changes in cortisol and TNFα. Therefore, acute moderate-intensity exercise (40 min or less) in warm water impacts the stress and inflammatory response. Understanding this is important because exercise load may need to be adjusted in warm and hot environments to avoid the negative effects of elevated stress and inflammation response.     

Heat coma and its relationship to ocean dynamics in the oceanic sea skaters of Halobates (Heteroptera: Gerridae) inhabiting Indian and Pacific Oceans

This study was performed to clarify how weather and current dynamics affect the resistance to temperature change in the oceanic sea skaters, Halobates. Heat coma temperature (HCT) was measured for the adults and 5th instar larvae of four Halobates species collected from a fixed sampling location (12°00′N, 135°00′E ) in western tropical Pacific Ocean and from 13 locations in the eastern area of the India Ocean ranging from 08°00′N-06°00′S and 86°00-76°00′E. Both the gap temperature for heat coma (GTHC, mean±SD: 7.83±1.86 °C, n=32) and the heat coma temperature (HCP, 35.03±1.80 °C, n=32) of individuals collected from the Pacific Ocean, during the first half (10 days) of the sampling period at the fixed sampling point, were significantly higher than those during the second half (GTHC: 5.10±2.05 °C, n=63; HCP: 34.03±2.02 °C, n=63). The reduction in heat tolerance shown in the second half of the 20 day period may have been caused by a decrease in air temperature due to rainfall that occurred around the sampling point accompanied with the arrival of Typhoon No. 6.In the study of individuals collected from the Indian Ocean, significantly higher average GTHCs of >8 °C were recorded for the adult H. micans collected at 02°00′S and 06°00′S (89°00′E) than those at 0°00-8°00′N in the eastern Indian Ocean. Dynamic mixture of water from northern and southern currents occurs at 02°00-6°00′S of the Indian Ocean and might relate to such high heat tolerance.Temperature dynamics in the ocean habitat might directly affect the temperature resistance of the oceanic sea skaters.     

The Effect of Activity on the Waking Temperature Rhythm in Humans

Nine healthy female subjects were studied when exposed to the natural light-dark cycle, but living for 17 “days” on a 27h day (9h sleep, 18h wake). Since the circadian endogenous oscillator cannot entrain to this imposed period, forced desynchronization between the sleep/activity cycle and the endogenous circadian temperature rhythm took place. This enabled the effects of activity on core temperature to be assessed at different endogenous circadian phases and at different stages of the sleep/activity cycle. Rectal temperature was measured at 6-minute intervals, and the activity of the nondominant wrist was summed at 1-minute intervals. Each waking span was divided into overlapping 3h sections, and each section was submitted to linear regression analysis between the rectal temperatures and the total activity in the previous 30 minutes. From this analysis were obtained the gradient (of the change in rectal temperature produced by a unit change in activity) and the intercept (the rectal temperature predicted when activity was zero). The gradients were subjected to a two-factor analysis of variance (ANOVA) (circadian phase/ time awake). There was no significant effect of time awake, but circadian phase was highly significant statistically. Post hoc tests (Newman-Keuls) indicated that gradients around the temperature peak were significantly less than those around its trough. The intercepts formed a sinusoid that, for the group, showed a mesor (±SE) of 36.97 (±0.12) and amplitude (95% confidence interval) of 0.22°C (0.12°C, 0.32°C). We conclude that this is a further method for removing masking effects from circadian temperature rhythm data in order to assess its endogenous component, a method that can be used when subjects are able to live normally. We suggest also that the decreased effect of activity on temperature when the endogenous circadian rhythm and activity are at their peak will reduce the possibility of hyperthermia.     

Effects of heat acclimatisation on work tolerance and thermoregulation in trained tropical natives

This study aimed to investigate the effects of heat acclimatisation on thermoregulatory responses and work tolerance in trained individuals residing in the tropics. Eighteen male trained soldiers, who are native to a warm and humid climate, performed a total of four heat stress tests donning the Skeletal Battle Order (SBO, 20.5 kg) and Full Battle Order (FBO, 24.7 kg) before (PRE) and after (POST) a 10-day heat acclimatisation programme. The trials were conducted in an environmental chamber (dry bulb temperature: 32 °C, relative humidity: 70%, solar radiation: 400 W/m²). Excluding the data sets of which participants fully completed the heat stress tests (210 min) before and after heat acclimatisation, work tolerance was improved from 173±30 to 201±18 min (∼21%, p<0.05, n=9) following heat acclimatisation. Following heat acclimatisation, chest skin temperature during exercise was lowered in SBO (PRE=36.7±0.3 vs. POST=36.5±0.3 °C, p<0.01) and FBO (PRE=36.8±0.4 vs. POST=36.6±0.3 °C, p<0.01). Ratings of perceived exertion were decreased with SBO and FBO (PRE=11±2; POST=10±2; p<0.05) after heat acclimatisation. Heat acclimatisation had no effects on baseline body core temperature, heart rate and sweat rate across trials (p>0.05). A heat acclimatisation programme improves work tolerance with minimal effects on thermoregulation in trained tropical natives.     

Circadian aspects of body temperature regulation in exercise

Internal and external factors contribute to resting core temperature and affect thermoregulation. Also, a robust circadian rhythm exists, implying that the body is in “heat-gain” or “heat-loss” modes at different times during the 24 h. Moreover, many variables associated with exercise, and the body's capacity for exercise, show circadian variation. All these factors contribute to circadian changes in thermoregulation during exercise. Attention is focused on responses at the onset of exercise, “critical temperature”, and recovery after exercise. Practical implications of circadian changes in thermoregulation during exercise include ergogenic aids and inter-individual differences, including those due to gender, age and acclimatisation.     

The relative contribution of environmental and genetic factors to phenotypic variation in familial Mediterranean fever (FMF)

Introduction

Familial Mediterranean fever (FMF) is an autosomal recessive disease, caused by mutations in the FMF gene MEFV (MEditerranean FeVer). It has a large phenotypic diversity even in patients with similar genotypes. Despite evidence that environmental factors (EFs) and genetic factors, including MEFV mutations (such as M694V, E148Q) and background modifier genes (MGs), affect the clinical manifestations of FMF, the relative contribution of each remains unknown.

Methods

To investigate the relative contribution of environmental and genetic factors to the phenotype of FMF, we compared the intra-pair clinical concordance of 10 mono and 7 dizygotic twins with FMF. The part played by EFs was determined by the phenotypic discordance of the monozygous twins, and the MGs effect was determined by deducing the environmental effect, computed for MZ twins, from the phenotypic discordance of the dizygous twins.

Results

The mean ± SD of intra-pair concordance was higher in the MZ than in DZ twin group (88.1 ± 13.2 vs. 70.7 ± 14.1 respectively, P value < 0.05). Based on the concordance in clinical manifestations in MZ and DZ twins, the environmental effect on the phenotype of FMF is estimated as 11.9% ± 6.6% and the MGs effect as 17.4% ± 15.5% in average.

Conclusions

In FMF the phenotype is affected by MEFV mutations, MGs and EFs in an estimated ratio of about 6:1.5:1 respectively.     

Comparison of daily rhythm of rectal and auricular temperatures in horses kept under a natural photoperiod and constant darkness

The aim of this study was to assess the accuracy of auricular temperature (AT) recording in the determination of body temperature as well as rectal temperature (RT). For this purpose we compared RT and AT in five clinically healthy horses. Data collections were performed every 3 h over 2 different 24 h photoperiods, 13/11 light/dark cycle and constant darkness. Repeated measures multifactor analysis of variance (MANOVA) was applied to determine a statistical significant effect of time of day, side of temperature collection and photoperiods on AT and RT. Our finding showed a significant effect of time of day on the temperature values recorded and an influence of side of temperature collection. RT values were higher of about 4 °C than the AT values, and the pattern of the two temperatures was not comparable. A daily rhythmicity of rectal temperature was observed. Auricular temperature no showed daily rhythmicity in both periods of monitoring. On the basis of these findings AT does not reflect body temperature as well as RT in horse.     

Circadian variation of the phagocytic activity of polymorphonuclear leukocytes and of various other parameters in 13 healthy male adults.

Twenty-four different laboratory parameters including the phagocytic activity (phagocytic index) of polymorphonuclear leukocytes (PMNs) and various hematologic variables were investigated in 13 young healthy men during Spring 1988 in Munich, Germany. Venous blood of these volunteers was obtained under standardized conditions at 4-h intervals over a 24-h span. All parameters were analyzed by the single cosinor method and by a Kruskal-Wallis analysis of variance (ANOVA). Statistically significant circadian rhythms were found for the number of circulating lymphocytes and leukocytes (WBCs), potassium, systolic blood pressure, phagocytic index, Quick test, heart rate, and rectal body temperature (p less than 0.05; single cosinor). For all of these parameters except WBCs, rectal body temperature, and Quick test, a temporal variation was confirmed by the ANOVA (p less than 0.05; phagocytic index: p = 0.05). The circadian acrophases of WBC, number of circulating lymphocytes, and phagocytic index were all found at about 01:00 h. This temporal coincidence of the acrophases of the phagocytic index and the number of circulating lymphocytes may reflect the modulation of phagocytosis by T lymphocytes that release cytokines known to stimulate the phagocytic activity of PMNs.