Effect Of Elevated Ambient Temperature Research Articles

MULTIFACTORIAL REGRESSION MODEL FOR PREDICTING THE LEVEL OF HEAT SENSITIVITY IN HEALTHY YOUNG PEOPLE IN THE CONTEXT OF GLOBAL WARMING.

The aim: To create a mathematical model for predicting the level of heat sensitivity in healthy young people based on multivariate regression analysis. Materials and methods: 150 healthy young people aged 17-20 years answered the questionnaire "Levels of heat sensitivity", underwent a heat test and mathematical analysis of the heart rate, after which the results were used to build a regression model of heat sensitivity. Results: The model of mathematical prediction of heat sensitivity (CHSL1/CHSL2), which we proposed for the first time, takes into account the most significant factors that influence the determination of higher and lower sensitivity to heat (Q1-Q6, %LF2, %HF1, %HF2, HR1, HR2), so its use will allow timely identi¬fication of individuals who are particularly susceptible to the effects of elevated ambient temperature and prevent the development of potential negative consequences of this exposure. Conclusions: Based on the results obtained, it is possible to use this prognostic model in the future to develop a diagnostic system for determining the level of heat sensitivity.

Effect of Elevated Ambient Temperature on Maternal, Foetal, and Neonatal Outcomes: A Scoping Review.

This scoping review provides an overview of the published literature, identifies research gaps, and summarises the current evidence of the association between elevated ambient temperature exposure during pregnancy and adverse maternal, foetal, and neonatal outcomes. Following the PRISMA extension for scoping reviews reporting guidelines, a systematic search was conducted on CINAHL, PubMed, and Embase and included original articles published in the English language from 2015 to 2020 with no geographical limitations. A total of seventy-five studies were included, conducted across twenty-four countries, with a majority in the USA (n = 23) and China (n = 13). Study designs, temperature metrics, and exposure windows varied considerably across studies. Of the eighteen heat-associated adverse maternal, foetal, and neonatal outcomes identified, pre-term birth was the most common outcome (n = 30), followed by low birth weight (n = 11), stillbirth (n = 9), and gestational diabetes mellitus (n = 8). Overall, papers reported an increased risk with elevated temperature exposures. Less attention has been paid to relationships between heat and the diverse range of other adverse outcomes such as congenital anomalies and neonatal mortality. Further research on these less-reported outcomes is needed to improve understanding and the effect size of these relationships with elevated temperatures, which we know will be exacerbated by climate change.

Differential effects of elevated nest temperature and parasitism on the gut microbiota of wild avian hosts

BackgroundChanges in wild animal gut microbiotas may influence host health and fitness. While many studies have shown correlations between gut microbiota structure and external factors, few studies demonstrate causal links between environmental variables and microbiota shifts. Here, we use a fully factorial experiment to test the effects of elevated ambient temperature and natural nest parasitism by nest flies (Protocalliphora sialia) on the gut microbiotas of two species of wild birds, the eastern bluebird (Sialia sialis) and the tree swallow (Tachycineta bicolor).ResultsWe find that bacterial communities from the nestlings of each host species show idiosyncratic responses to both heat and parasitism, with gut microbiotas of eastern bluebirds more disrupted by heat and parasitism than those of tree swallows. Thus, we find that eastern bluebirds are unable to maintain stable associations with their gut bacteria in the face of both elevated temperature and parasitism. In contrast, tree swallow gut microbiotas are not significantly impacted by either heat or nest parasitism.ConclusionsOur results suggest that excess heat (e.g., as a result of climate change) may destabilize natural host-parasite-microbiota systems, with the potential to affect host fitness and survival in the Anthropocene.

High temperature impairs cognitive performance during a moderate intensity activity

High temperatures are one of the main causes of work safety accidents associated with cognitive impairment. However, the effects of elevated ambient temperature on cognitive performance during moderate-intensity activities are unclear. In this study, subjects (N = 32) were exposed to four different air temperatures, i.e., 26, 30, 33, and 37 °C, and a relative humidity of 70% in a climate chamber. During the experiment, the subjects were required to complete neurobehavioral cognitive tests while walking on a treadmill with an estimated metabolic rate of 165 W/m2. During the 90-min experiment, the tympanic temperature, weight loss, heart rate, and percentage of adjacent inter-beat cardiac intervals differing by > 50 ms (pNN50) were measured. Subjective responses were collected using questionnaires.The accuracy of subjects’ responses to the semantic interference and visual perception tests were significantly decreased at 37 °C after 45 min of exercise. Additionally, over the exposure period at 37 °C, the accuracy of various cognitive tests also decreased, while the speed increased. The changes in the cognitive test results at 37 °C were associated with the elevation of the tympanic temperature, heart rate, dehydration rate, and decline of the pNN50. Similarly, the elevated thermal discomfort and intensity of neurobehavioral symptoms were related to these changes.In conclusion, exposure to a temperature of 37 °C for 45 min has a negative impact on the accuracy of personnel with moderate-activity intensity. Therefore, 45 min is recommended as a safe time for continuous work with moderate intensity at 37 °C.

Effect of Elevated Ambient Temperature on Simulator-Derived Oscillometric Blood Pressure Measurement.

BACKGROUNDOscillometric blood pressure (BP) devices are typically labeled for use up to 40 °C. Many geographic regions have ambient temperatures exceeding 40 °C. We assessed the effect of increased ambient temperature (40–55 °C) on simulator-derived oscillometric BP measurement.METHODSThree Omron BP769CAN devices, 3 A&D Medical UA-651BLE devices, and accompanying cuffs were used. A custom heat chamber heated each device to the specified temperature. A noninvasive BP simulator was used to take 3 measurements with each device at differing temperatures (22, 40, 45, 50, and 55 °C) and BP thresholds: 80/50, 100/60, 120/80, 140/90, 160/110, and 180/130 mm Hg. Using each device as its own control (22 °C), we determined the relative differences in mean BP for each device at each temperature and BP setting, assessed graphical trends with increasing temperature, and examined variability.RESULTSGraphical trends of mean simulator-subtracted BP differences from room temperature showed no discernable pattern, with differences clustered around zero. Overall mean difference in BP (combined elevated temperatures minus room temperature) was −0.8 ± 2.1 (systolic ± SD)/1.2 ± 3.5 (diastolic ± SD) mm Hg for the A&D device and 0.2 ± 0.4 (systolic ± SD)/−0.1 ± 0.1 (diastolic ± SD) mm Hg for the Omron. All individual elevated temperature differences (elevated temperature minus room temperature) except A&D diastolic BP at 50 °C were within 5 mm Hg.CONCLUSIONSIn this simulator-based study assessing within-device differences, higher ambient temperatures resulted in oscillometric BP measurements that were comparable to those performed at room temperature.

Effects of elevated ambient temperature and local testicular heating on the expressions of heat shock protein 70 and androgen receptor in boar testes

Heat stress damaged spermatogenesis and semen quality, however, the exact molecular mechanism is not clear. The objective of this study was to determine the effects of elevated ambient temperature and local testicular heating on the expressions of heat shock protein 70 and androgen receptor in boar testes. A growing body of evidence demonstrated that germ cell apoptosis can be aggravated by heat stress and androgen deprivation, and at normal temperature, withdrawal of androgen led to germ cell apoptosis. There were no reports that heat stress damaged spermatogenesis has relationship with androgen. In this study, adult boars (Landrace, n = 9) were used and randomly divided into: control group (CON), 20–27 °C; environmental hyperthermia group (EH), 37–40 °C, 3 h/d 42 d; and local testicular heating group (LTH), 42 °C 1 h. After heat treatments, all boars were castrated and the testes were harvested. qRT-PCR and Western Blot results showed that the mRNA and protein levels of heat shock protein 70 and androgen receptor were significantly increased after heat treatments. Immunohistochemistry results showed that heat stress caused a redistribution of heat shock protein 70 from the cytoplasm to the nucleus, and androgen receptor was mainly expressed in Sertoli cells. These results indicated that heat stress promoted the inhibition of heat shock protein 70 on the androgen receptor, suggesting that the possible mechanism of heat stress damaged spermatogenesis and semen quality was that heat stress reduced the sensitivity of testicular cells to androgen by up-regulating heat shock proteins.

The Importance of Ambient Temperature to Growth and the Induction of Flowering.

Plant development is exquisitely sensitive to the environment. Light quantity, quality, and duration (photoperiod) have profound effects on vegetative morphology and flowering time. Recent studies have demonstrated that ambient temperature is a similarly potent stimulus influencing morphology and flowering. In Arabidopsis, ambient temperatures that are high, but not so high as to induce a heat stress response, confer morphological changes that resemble the shade avoidance syndrome. Similarly, these high but not stressful temperatures can accelerate flowering under short day conditions as effectively as exposure to long days. Photoperiodic flowering entails a series of external coincidences, in which environmental cycles of light and dark must coincide with an internal cycle in gene expression established by the endogenous circadian clock. It is evident that a similar model of external coincidence applies to the effects of elevated ambient temperature on both vegetative morphology and the vegetative to reproductive transition. Further study is imperative, because global warming is predicted to have major effects on the performance and distribution of wild species and strong adverse effects on crop yields. It is critical to understand temperature perception and response at a mechanistic level and to integrate this knowledge with our understanding of other environmental responses, including biotic and abiotic stresses, in order to improve crop production sufficiently to sustainably feed an expanding world population.

Effect of elevated ambient temperature at parturition on duration of gestation, ruminal temperature, and endocrine function of fall-calving beef cows.

Fall-calving Angus cows were used to evaluate the effect of ambient temperature on duration of gestation. In Exp. 1, cows were AI and calved in August (n = 14) or October (n = 10). Cows grazed native prairie pasture in Oklahoma and had a BCS of 6.0 ± 0.5 (1 = emaciated, and 9 = obese) at parturition. Commencing 2 wk before the expected calving date, blood samples were taken from the coccygeal vein every 2 to 3 d until calving. Cows that calved in August tended to have shorter gestations (P = 0.07) compared with cows that calved in October. Maximum daily ambient temperature during the last 14 d of gestation was greater for August-calving cows (P < 0.001) compared with October cows. Concentrations of cortisol in plasma during the last 4 d of gestation were greater in cows that calved in August (P < 0.04) compared with cows that calved in October. In Exp. 2, cows were AI and calved in either mid-August (n = 7), late-August (n = 6), September (n = 6), or October (n = 8) to evaluate the effects of elevated ambient temperature on duration of gestation, ruminal temperature at parturition, and plasma cortisol, progesterone, and estradiol. Temperature boluses (SmartStock, LLC, Pawnee, OK) programmed to transmit temperature every hour were place in the rumen at 255 d of gestation. Cows grazed native prairie pasture in Oklahoma and had a BCS of 6.5 ± 0.4 at calving. Maximum ambient temperatures during d 263 to 273 of gestation were influenced by month of calving × day (P < 0.001). Duration of gestation was shorter for mid-August cows (P < 0.05) compared with October cows, but did not differ compared with late-August (P = 0.29) and September (P = 0.50) cows. Ruminal temperature during the 4 d before calving was not influenced by month of calving (P = 0.76). Ruminal temperature was decreased during the 24 h before parturition for cows in all months (P < 0.01) compared with 2 to 4 d before parturition. Concentrations of cortisol in plasma during d 271 to 276 of gestation were less (P < 0.05) for late-August compared with cows that calved during the other months. Concentrations of progesterone were greater during 7 d before parturition in October compared with cows that calved in September. Estradiol in plasma of cows during late gestation was not affected by month of calving (P = 0.76). Exposure of beef cows to elevated ambient temperature resulted in shorter gestations. Ruminal temperature in cows decreased ≥ 0.3°C the day before parturition.

Effect of Elevated Ambient Temperature on Thermal Breakdown Behavior in BCD ESD Protection Devices Subjected to Long Electrical Overstress Pulses

We investigate the effect of elevated ambient temperature on thermal breakdown (TB) modes in linear-geometry electrostatic discharge (ESD) protection n-p-n transistors of smart power technology subjected to 0.5-1- μs-long ESD pulses. The current transport in these devices has a form of traveling current filaments (CFs) where TB at room temperature occurs at one of the device ends. An increase in ambient temperature gives rise additionally to another failure mode, inside the device. For the failure mode at the device end, the increase of ambient temperature in the range up to 100°C causes shortening of the averaged time to TB 〈 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TB</sub> 〉 by a duration that the CF needs for one round trip over the device width. At ambient temperatures up to 180°C, the TB may occur even at initial triggering CF position inside the device, before the CF starts to move. The ambient temperature at which the transition between CF modes with different 〈 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TB</sub> 〉 occurs is investigated as a function of stress current. Furthermore, inspecting the failure current of devices with different widths shows that there is an equivalence between the effect of increased ambient temperature and the effect of the preheating at the device end by a previous CF passage. The experiments are supported by 3-D thermal simulation of temperature in moving and standing CFs.

Effects of elevated ambient temperature on embryo implantation in rats

Implantation is a crucial step in mammalian reproduction as it is a gateway to further embryonic development and successful pregnancy. Changes in the environmental factors, such as temperature have adverse effects on reproduction. However, the impact of elevated temperature on the implantation process is not well defined. The objective of this study was to investigate the possible effect of elevated ambient temperature on implantation time and rate. The results revealed that exposure to elevated ambient temperature leads to a delayed implantation and reduced number of implantation sites in Sprague Dawley rats. Moreover, the exposure to elevated temperature resulted in change in the progesterone and estradiol patterns during the implantation time. These findings indicate that elevated temperature disturbs the implantation process.

Effects of Elevated Ambient Temperature on Reproductive Outcomes and Offspring Growth Depend on Exposure Time

Reproductive performance has been shown to be greatly affected by changes in environmental factors, such as temperature. However, it is also crucial to identify the particular stage of pregnancy that is most adversely affected by elevated ambient temperature. The aims of this study were to determine the effect on reproductive outcomes of exposure to elevated ambient temperature during different stages of pregnancy and to determine the effect of prenatal heat stress on offspring growth. Sixty pregnant rats were used in this study. The rats were divided equally into four groups as group 1 (control), group 2 (exposed to elevated temperature following implantation), group 3 (exposed to elevated temperature during pre- and periimplantation), and group 4 (exposed to elevated temperature during pre- and periimplantation and following implantation). Groups 3 and 4 had prolonged gestation periods, reduced litter sizes, and male-biased sex ratios. Moreover, the growth patterns of group 3 and 4 pups were adversely affected by prenatal exposure to elevated temperature. The differences between group 1 and group 3 and between group 1 and group 4 were highly significant. However, no significant differences were observed between groups 1 and 2 in the gestation length, sex ratios, and growth patterns. Thus, it can be concluded that exposure to elevated ambient temperature during pre- and periimplantation has stronger adverse effects on reproductive outcomes and offspring growth than postimplantation exposure.

Development of rabbit embryos during a 96-h period of in vitro culture after superovulatory treatment under conditions of elevated ambient temperature.

The effects of elevated ambient temperature on the response to exogenous gonadotropins were evaluated in female New Zealand White rabbits exposed to 33+/-1 degrees C (mean +/- SE) and 10-30% relative humidity (8 h/day) during a 5-day period. Does were treated with pFSH (0.3 mg/0.3 ml Standard Armour) twice daily during three consecutive days with a minimum interval of 8 h between injections. Six hours after the last FSH injection all does were removed from the experimental chamber, given hCG (25 IU/kg) and paired overnight. Nineteen hours after pairing, embryos were flushed from the reproductive tracts, evaluated, and subjected to in vitro culture during a 96-h period. The ovulatory responses to exogenous gonadotropins and fertilization rates did not differ significantly under conditions of elevated ambient temperature, whereas fewer blastocysts and increased number of degenerate embryos were observed after culture. We conclude that although hyperthermia was induced during exposure to elevated ambient temperature, it did not alter the ovulatory responses to gonadotropin treatment and plasma concentrations of FSH and LH compared with does in a thermoneutral environment. Exposure of donor rabbits to elevated ambient temperature before mating, however, increased embryonic degeneration.

The Effects of a 3-day Increase of Ambient Temperature on Body Temperature and REM Sleep in an Animal Model of Depression

This study examined the effects of elevated ambient temperature (Ta) on body temperature (Tb) and rapid eye movement (REM) sleep in depressed and control rats. Previous studies have shown that elevations of Ta to the rat's thermoneutral zone of 29 degrees C produced an increase of REM sleep in control rats. In this study, 15 male Sprague-Dawley rats, seven saline control rats (SAL) and eight rats that were classified as depressed according to the chlorimipramine model of depression (CLI rats), were implanted for continuous Tb and polysomnographic recording and were exposed to two Ta's, 22 degrees C and 29 degrees C. CLI and SAL rats had significantly more REM sleep and a lower body temperature at 29 degrees C than at 22 degrees C. At 22 degrees C, CLI rats had significantly more REM sleep during the light period and a higher Tb in the light and dark periods than SAL control rats. At 29 degrees C, there were no significant differences in REM sleep or in Tb between CLI and SAL rats. Because human endogenous depression is associated with abnormal REM sleep and an elevated nocturnal Tb, these results give further support for the validity of the CLI model of depression and provide insight into the relationships among Tb, Ta, REM sleep and depression.

Factors affecting the response of working boars to changing environmental temperature

It is well established that high environmental temperature can have adverse effects on sperm concentration and the normality of sperm in the boar. Induced abnormalities include reduced motility, abnormal heads, proximal droplets, coiled and bent tails and abnormal acrosomes (Malmgren and Larsson, 1989). While all stages of spermatogenesis can be adversely affected, the primary spermatocytes are most vulnerable to these influences. Since spermatogenesis occurs over 45 days, any adverse effects of elevated ambient temperature can affect sperm quality for around 6 weeks. The maximum period of infertility appears around weeks 3 and 4 after heat stress. Reduced levels of testosterone and sometimes of LH following heat stress are implicated in these adverse effects. There is evidence that boars subjected to high constant temperature (30°C), which have become acclimatised to such, are affected less in terms of sperm output and quality (Cameron and Blackshaw, 1980) than when boars are subject to sudden major increases in temperature from fairly low levels (15 to 30 C) e.g. during the summer months (Antonyuk et al, 1983). There also appears to be large differences between boars in their ability to adapt to exposure to high environmental temperature by minimising temperature rise and avoiding adverse effects on semen quality (Cameron and Blackshaw, 1980). These workers found that boars prone to heat stress show an acute rise in body temperature in response to elevated environmental temperature and this sudden rise has a more adverse effect on semen quality than the length of exposure to the elevated temperature. There appears to be little information available on the reasons for such important between boar differences. This study was carried out to determine rectal temperature responses of boars to varying summer temperature in an intensive pig enterprise in Scotland and to attempt to determine some of the factors associated with ‘high’ and ‘low’ responding boars.

Effect of elevated ambient temperatures on puberty in gilts.

Effects of elevated ambient temperature on puberty and related physiological responses were studied in 40 gilts. Group 1 (n = 20) gilts were born in September and Group 2 (n = 20) gilts were born in March. Gilts were placed in environmentally controlled chambers at 140 d of age. After a 10-d acclimation period at 20 degrees C, 35% relative humidity (RH), and 12 h light (L)/12 h dark (D), gilts within each group were randomly assigned to one of two treatments: control (C; 15.6 degrees C, 35% RH, 12 h L/12 h D) or heat stress (HS; 33.3 degrees C, 35% RH, 12 h L/12 h D). Daily detection of estrus with a boar began at 180 d of age and continued for 50 d. All gilts not reaching puberty by 230 d of age received 1,000 IU pregnant mare serum gonadotropin (PMSG) and 7 d later were examined by laparotomy. Rectal temperatures (REC) and respiration rates (RESP) were taken twice daily. Food intake (FI) and water usage (WC) were recorded daily. Blood samples were collected weekly and BW recorded at 150, 190, and 230 d of age. No differences (P greater than .05) were observed due to season of birth. Heat-stressed gilts had greater (P less than .001) REC and RESP and consumed more (P less than .01) water than C gilts. Food intake and ADG were not different between treatments (P greater than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ambient temperature on free radical generation, antioxidant defenses and life span in the adult housefly, Musca domestica

Life spans of poikilotherms like the housefly are shortened by elevation of ambient temperature. The objective of this study was to examine the possible involvement of active oxygen species in temperature induced life-shortening of the adult male housefly. Effects of varied ambient temperature, 20°C and 28°C, on life span, cyanide-resistant respiration, H 2O 2 concentration, superoxide dismutase (SOD) and catalase activities and glutathione (GSH) concentration were examined. Average life span of flies raised at 28°C was about 52% lower than those raised at 20°C. Rate of cyanide-resistant respiration, an indicator of oxygen free radical generation, was higher in flies raised at 28°C, whereas steady-state concentration of H 2O 2 was decreased at this temperature. Catalase activity and GSH concentration were lower at 28°C while SOD activity was unaffected by the ambient temperature. Results of this study suggest that life-shortening effects of elevated ambient temperature may due, in part, to increased oxidative stress.

The Effect of High Ambient Temperature and Hypercapnia on Postprandial Intestinal Hyperemia in Domestic Cockerels

Hubbard cockerels (2.8 to 3.6 kg) with chronically implanted electromagnetic blood flow probes placed on the celiac artery were used to determine the effect of elevated ambient temperature on postprandial intestinal hyperemia. Celiac mean blood flow (MBF) increased (P<.05) from approximately 25 to 50 ml/min in response to feeding. When a thermoneutral temperature of 25 C was maintained, celiac MBF remained above 40 ml/min up to 210 min but fell below 25 ml/min by 300 min postprandial. In response to an acute heat exposure of 37 C, postprandial celiac MBF was reduced by approximately 50% in comparison to thermoneutral control values. Changes in celiac MBF during heat exposure were significantly (P<.05) correlated (.60) with blood CO2 partial pressure (PCO2).To determine if flood PCO2 affected postprandial celiac MBF, cockerels were subjected to successive elevated ambient temperature and ambient CO2 treatments. Although cockerels exposed to 2.8% CO2 exhibited an increase in blood PCO2 regardless of temperature treatment, postprandial celiac MBF changes in these ambient CO2 experiments were only moderately correlated (P<.05) with blood PCO2 (.34) but inversely correlated (—.83) with celiac vascular resistance (P<.001), This study indicates that acute heat exposure reduces postprandial intestinal hyperemia and that this hemodynamic alteration was coincident with, but not necessarily dependent upon, changes in blood PCO2.

The effect of elevated ambient temperature on spermatogenesis in the boar.

Boars were heated for 6 h/day in a climate chamber (mean maximum temperatures, 33.4 +/- 3.1--37.7 +/- 2.0 degrees C, and relative humidities 40--80%) for 4, 5 and 7 days respectively (4 boars/group). Significant increases in the proportion of morphologically abnormal spermatozoa were seen in all groups for the end of Week 2 and up to Week 5 after treatment. Boars exposed for 7 days were, in general, more severely affected. Ejaculate volumes, gel volumes, sperm concentration and daily sperm outputs were not affected significantly in any of the groups, although changes were seen in individual animals. In some boars heat stress early in the treatment period produced an acute rise in body temperature which appeared to have a greater effect on semen quality than did the duration of exposure.

Hyperthermia-induced embryonic aneuploidy in mice

Chromosomal aneuploidy, as an effect of elevated ambient temperature during early gestation, was studied in 650 eight-day embryos from 60 females of two different mouse stocks. Exposure of treatment females to 34 C and 50% relative humidity during days 5 and 6 of gestation caused an increase in embryo chromosomal hyperploidy. No embryo sex interaction with the percent hyperploidy was found.

Effect of elevated ambient temperature on testis and blood levels and in vitro biosynthesis of testosterone in the ram.

Effect of elevated ambient temperature on testis and blood levels and in vitro biosynthesis of testosterone in the ram.