Effects of exposure to short-term heat stress on male reproductive fitness in a soil arthropod

Ambient temperature is a key environmental factor influencing a variety of aspects of the ecology and evolution of ectotherms. Reproductive traits have been suggested to be more sensitive to thermal stress than other life history traits. This study investigated the direct and indirect effects of heat shock on male reproductive success in the widespread springtail Orchesella cincta. Male springtails were exposed to four temperature treatments: heat hardening (35.2 °C for 1 h), heat shock (37.2 °C for 1 h), heat hardening + heat shock (35.2 °C for 1 h, followed 15 h later by 37.2 °C for 1 h), and control (20 °C). The heat shock gene Hsp70 showed high expression in all the heat treatments, indicating that the treatments indeed induced thermal stress. Significant mortality was only found in the treatment with heat shock, both with and without heat hardening. A direct effect of heat treatment was found on time to first reproduction, which was significantly longer after heat shock (with or without heat hardening) than in the control treatment. There was no difference among treatments in the number of spermatophores produced in the first reproductive instar. Heat treatment also had indirect effects on male reproductive success. Females chose significantly more spermatophores from control males than from males that received heat shock, heat hardening or both. A high percentage of spermatophores produced by heat shocked males caused reproductive failure in females, but no significant differences among treatments were found.Our results suggest that not all traits were equally affected by the heat stress. Heat hardening did not protect reproductive traits against the negative effects of heat shock. The indirect effects of heat shock on reproduction may be equally important as the direct effects.     

The effect of heat stress on intestinal integrity and Salmonella invasion in broiler birds

The intestinal mucosa works as a barrier to protect the internal environment of the animal from bacteria and bacterial toxins found in the gut lumen. Heat stress may harm this function. Therefore, we designed the current experiment to investigate the effect of heat stress on intestinal integrity, physiological and immunological responses and Salmonella invasion in broiler chickens. At 26 days of age, 72 birds were randomly distributed into 3 treatments, with 8 replicates per treatment and 3 birds per replicate. The three treatments were control treatment; kept at thermoneutral environmental conditions (20 ± 2 °C), chronic heat stress treatment (exposed to 30 ± 2 °C; 24 h/day) and acute heat stress treatment (exposed to 35 ±2 °C from 09:00 to 13:00 and kept at 20 ± 1 °C from 13:00 to 09:00). The heat stress exposure was conducted for 10 successive days. Compared with the control treatment, birds subject to chronic and acute heat stress had reduced (P < 0.05) body weight and body gain and increased (P < 0.05) feed conversion ratio. However, feed intake and mortality rate were only increased (P < 0.05) in the acute heat stress treatment. Rectal temperature and Δ rectal temperature (°C/h) increased (P < 0.05) sharply during the first 2 days of exposure followed by gradual decreases until a plateau was achieved. Heat-stressed birds had increased (P < 0.05) serum concentrations of corticosterone, endotoxin lipopolysaccharide and the systemic inflammatory cytokine: TNF-α and IL-2, as well as a higher (P < 0.05) prevalence of Salmonella spp. in meat and livers, as compared with control treatment. It can be concluded that heat stress impaired intestinal integrity which resulted in increased intestinal permeability to endotoxin, translocation of intestinal pathogens (Salmonella spp.) and serum inflammatory cytokines. Therefore, avoiding thermal dysfunction of intestinal barrier is a significant factor in maintaining welfare, immune status and meat safety of broiler birds.     

Tumor necrosis factor alpha gene variants do not display allelic imbalance in circulating myeloid cells

Carriage of the TNF −308 A allele (rs1800629 A) has been associated with increased serum TNF-α levels, the development of sepsis syndrome, and fatal outcome, in severely traumatized patients (Menges et al., 2008 [1]). Herein, we analysed the putative allelic imbalance of TNF-α release from myeloid cells. Circulating peripheral blood cells from healthy human blood donors (n = 104) and monocyte-derived macrophages (n = 158) were analysed for their ex vivo capacity of TNF-α expression. Our findings indicate that carriage of the TNF −308 A allele is not associated with high TNF-α expression in circulating human leucocytes and monocyte-derived macrophages. Other cellular sources, e.g. tissue-resident cells like mast cells and/or tissue specific macrophages might be the cellular source of high TNF-α serum levels shortly after trauma.     

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.     

Opposing effects of heat stress on male versus female reproductive success in Bicyclus anynana butterflies

In ectothermic organisms, reproductive success and survival are vitally affected by temperature. Here, we analyzed the effects of a short-time exposure to heat stress (1 h at 40 °C versus controls) on reproductive success and longevity in Bicyclus anynana butterflies. After having applied heat stress or a control treatment, individuals were mated in all four possible sexes by treatment combinations. Heat exposure of females caused a subsequent reduction in longevity, fecundity, egg size and concomitantly reproductive investment. Heat exposure of males also reduced longevity, but had in general little effect on the reproduction of female mates. However, females having mated with heat-stressed males showed surprisingly an increased rather than decreased early fecundity, which may indicate an increased investment in current reproduction in stressful environments. Heat stress had no significant effect on egg hatching success, time to copulation and copulation duration. Our results suggest that a short period of heat stress may substantially reduce longevity and reproductive output, with striking differences among sexes. We found no evidence for males being more strongly affected by heat stress than females.     

Heat tolerance and physiological plasticity in the Antarctic collembolan, Cryptopygus antarcticus, and mite, Alaskozetes antarcticus

Polar amplification of global warming has led to an average 2 °C rise in air temperatures in parts of the polar regions in the last 50 years. Poikilothermic ectotherms that are found in these regions, such as Collembola and mites, may therefore be put under pressure by changing environmental conditions. However, it has also been suggested that the thermal sensitivity of invertebrates declines with higher latitudes and, therefore, that polar ectotherms may not be at risk. In the current study, the heat tolerance and physiological plasticity to heat stress of two well-studied Antarctic invertebrates, the collembolan, Cryptopygus antarcticus, and the mite, Alaskozetes antarcticus, were investigated. Both species showed considerable heat tolerance, with each having an Upper Lethal Temperature (ULT) above 35 °C (1 h exposure). These species were also able to survive for over 43 d at 10 °C and for periods of 5–20 min at 40 °C. Across all experimental procedures, A. antarcticus possessed a somewhat greater level of heat tolerance than C. antarcticus. Water loss during short duration exposures did not differ between the two species at 30, 35 and 40 °C, suggesting that the greater tolerance of A. antarcticus over this timescale was not due to higher desiccation resistance. Physiological plasticity was investigated by testing for Rapid Heat Hardening (RHH) and long-term acclimation. RHH was observed to a small degree in both species at a warming rate of 0.5 °C min⁻¹, and also 0.2 °C min⁻¹ in A. antarcticus alone. Longer-term acclimation (1 week at 10 °C) did not enhance the heat tolerance of either species. Even with this limited physiological plasticity, the results of this study indicate that C. antarcticus and A. antarcticus have capacity in their heat tolerance to cope with current and future environmental extremes of high temperature.     

Gender-specific cold responses induce a similar body-cooling rate but different neuroendocrine and immune responses

This study investigated whether there are any gender differences in body-heating strategies during cold stress and whether the immune and neuroendocrine responses to physiological stress differ between men and women. Thirty-two participants (18 men and 14 women) were exposed to acute cold stress by immersion to the manubrium level in 14 °C water. The cold stress continued until rectal temperature (T_RE) reached 35.5 °C or for a maximum of 170 min. The responses to cold stress of various indicators of body temperature, insulation, metabolism, shivering, stress, and endocrine and immune function were compared between men and women. During cold stress, T_RE and muscle and mean skin temperatures decreased in all subjects (P < 0.001). These variables and the T_RE cooling rate did not differ between men and women. The insulative response was greater in women (P < 0.05), whereas metabolic heat production and shivering were greater (P < 0.05) in men. Indicators of cold strain did not differ between men and women, but men exhibited larger changes in the indicators of neuroendocrine (epinephrine level) and in immune (tumor necrosis factor-α level) responses (both P < 0.05). The results of the present study indicated that men exhibited a greater metabolic response and shivering thermogenesis during acute cold stress, whereas women exhibited a greater insulative response. Despite the similar experience of cold strain in men and women, the neuroendocrine and immune responses were larger in men. Contrary to our expectations, the cooling rate was similar in men and women.     

Utilizing laboratory and field studies to determine physiological responses of cattle to multiple environmental stressors

Heat stress studies are often conducted using controlled laboratory exposures or field exposures. Each approach has limitations and provides a partial understanding of complex interactions between simultaneous environmental stressors. The question is how similar the responses are in each situation. Several physiological measures of thermal status were used to compare heat stress responses of cattle in controlled chamber stress tests and fluctuating field conditions. Angus steers (N=23; 318±8 kg BW) were first placed on either endophyte-infected or -uninfected tall fescue pastures for the field exposure, followed by a controlled heat challenge, which exacerbates the condition known as fescue toxicosis. During the controlled heat challenge, steers were assigned to diets of either 0 or 40 μg ergovaline/kg/d to maintain the treatment states. Respiration rate (RR) was measured via flank counting and telemetric temperature transmitters in the rumen of each animal monitored core temperature (T_rum). Linear regression fit models for RR, T_rum, and air temperature (T_a) were utilized to compare relationships between field and chamber exposure. Correlation coefficients for RR were similar during both chamber (R=0.69) and field exposures (R=0.72). Respiration rate showed greater responsiveness to change in T_a under field conditions having twice the slope (4.40 versus 1.75 bpm/°C) and a lower Y-intercept (−42.14 versus +30.97 bpm) compared to the chamber run. Ruminal temperature was consistent between exposures showing a similar slope (0.04 versus 0.03 °C T_rum/°C T_a) and Y-intercept (38.40 versus 39.30 °C) for its relationship with T_a. Despite respiration rate being the more sensitive indicator of heat stress, ruminal temperature proved to be the most consistent between environments.     

Protective effects of antimicrobial peptide S-thanatin against endotoxic shock in mice introduced by LPS

Sepsis continues to be a major unresolved medical challenge of the present. Severe sepsis and septic shock are the leading causes of multiple organ failure and mortality in noncoronary intensive care units (ICUs). The primary reason of septic shock is the activation of host effecter cells by endotoxin and lipopolysaccharide (LPS) associated with cell membranes of gram-negative bacteria. For these reasons, the key point of treatment is removing LPS. S-thanatin (Ts), an analog of thanatin, was synthesized by substituting the 15th amino acid of threonine with serine, which showed a broad antimicrobial activity against gram-negative and gram-positive bacteria. We have reported its LPS-binding and -neutralizing activity in vitro. The aim of this study is to examine the LPS-neutralizing activities and the protective effects of S-thanatin in vivo. Every mice was injected intraperitoneally with LPS (from Escherichia coli O111:B4) 150 μg before injected intraperitoneally or vena caudalis with 3 mg/kg, 6 mg/kg and 12 mg/kg, and measured endotoxin and tumor necrosis factor alpha (TNF-α) concentrations in plasma, as well as lethality. The results showed that S-thanatin can significantly reduce endotoxin and TNF-α level in plasma, at the same time resulting in the highest survival rates.     

Testicular gene expression in male mice divergent for fertility after heat stress

Fertility losses in male mice occur approximately 18-28 d after heat stress. The objective of this study was to identify gene expression differences in males highly versus lowly fertile after heat stress. Mature male mice were exposed to heat stress (35 ± 1 °C; n = 50) or thermoneutral (21 ± 1 °C; n = 10) conditions for 24 h (Day 0) and hemicastrated (Day 1) to collect tissue for gene expression analyses. Males were subjected to a mating test from Days 18 to 26 when variation in fertility was anticipated. A fertility index was used to rank heat-stressed males and identify those males resistant and susceptible to heat stress, respectively. Microarray analyses were conducted on testis tissues from control (n = 5), heat stress resistant (n = 5), and heat stress susceptible (n = 5) males, and 225 genes were observed to be differentially expressed (P < 0.05), including genes involved in chaperone (Canx, Hspcb1, and Tcp1) and catalytic (Fkpb6, Psma7, and Idh1) activity. Expression patterns of these genes were confirmed using real-time RT-PCR. Male progeny from selected sires were similarly divergent in fertility after heat stress. Testicular expression levels of Canx, Hspcb, and Tcp1 genes were determined in these progeny. Hspcb expression was moderately heritable (0.31 ± 0.25); however, expression patterns of Canx and Tcp1 were not heritable.     

Hydrogen-rich saline reduces lung injury induced by intestinal ischemia/reperfusion in rats

Objective. Hydrogen has been reported to selectively reduce the hydroxyl radical, the most cytotoxic of reactive oxygen species. In this study we investigated the effects of hydrogen-rich saline on the prevention of lung injury induced by intestinal ischemia/reperfusion (I/R) in rats. Methods. Male Sprague-Dawley rats (n = 30, 200-220 g) were divided randomly into three experimental groups: sham operated, intestinal I/R plus saline treatment (5 ml/kg, i.v.), and intestinal I/R plus hydrogen-rich saline treatment (5 ml/kg, i.v.) groups. Intestinal I/R was produced by 90 min of intestinal ischemia followed by a 4 h of reperfusion. Results. Hydrogen-rich saline treatment decreased the neutrophil infiltration, the lipid membrane peroxidation, NF-κB activation and the pro-inflammatory cytokine interleukin IL-1β and TNF-α in the lung tissues compared with those in saline-treated rat. Conclusion. Hydrogen-rich saline attenuates lung injury induced by intestinal I/R.     

Heat shock induces oxidative stress in rotan Perccottus glenii tissues

The effects of temperature transition from 19 to 32 °C on oxidative stress indices and activities of the main antioxidant enzymes were investigated in the rotan, Perccottus glenii. Levels of lipid peroxides (LOOH), thiobarbituric acid-reactive substances (TBARS), low- (L-SH) and high-molecular mass (H-SH) thiols and activities of superoxide dismutase (SOD) and catalase were measured in rotan brain, liver and muscle over 1–12 h of high-temperature exposure followed by 3 or 24 h lower (19 °C) temperature recovery. Heat shock exposure during 1 h transiently increased 1.5–3.2-fold LOOH levels in rotan tissues with subsequent suppression of their content; however, 12 h exposure again increased LOOH levels in the brain. TBARS content were elevated by 2–3-fold during the entire heat shock exposure in the brain and liver. Levels of both products of lipid peroxidation were generally near control values during return to 19 °C. L-SH content was lowered during heat shock exposure in the brain, transiently increased after 6 h in the liver and almost disappeared after longer treatment in the muscle. Liver H-SH content slightly decreased under heat shock exposure, but was elevated after 6 h in the brain and muscle. In the latter case, L-SH level was below control values during recovery. SOD activities increased 2-fold in the liver after 6–12 h heat shock. Liver catalase activities decreased at the same conditions. Generally, a quick response to suppression of lipid peroxidation and possible involvement of its products in the up-regulation of antioxidant enzymes seem to be key adaptations to high temperature.     

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.     

Early release of macrophage migration inhibitory factor after liver ischemia and reperfusion injury in rats

Macrophage migration inhibitory factor (MIF) is an important mediator of ischemia/reperfusion (I/R) injury in heart, brain and intestine. We previously demonstrated that MIF was released during warm/cold ischemia in vitro. However, the role of MIF in liver I/R injury remains unclear. We aimed to test the hypothesis that MIF acts as an early proinflammatory cytokine and could mediate the inflammatory injury in liver I/R. Rats (n = 6 per group) were subjected to 90 min warm ischemia followed by 0.5 h, 6 h and 24 h reperfusion, respectively to liver transplantation (LTx) after 6 h of cold ischemia followed by 24 h of reperfusion. The expression of MIF, its receptor (cluster of differentiation 74 (CD74)) and the downstream inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)) were analyzed. Peritoneal macrophages were cultured for 6 h alone or in the presence of effluent from cold-preserved livers or effluent depleted of MIF. Warm I/R increased hepatic MIF-mRNA and protein expression. MIF-protein was released into peripheral circulation in vivo with a maximum at 0.5 h after reperfusion. Induction of MIF-expression was associated with the expression of proinflammatory cytokines and its receptor in both models. MIF released by isolated cold preserved livers, induced TNF-α and IL-1β production by cultured peritoneal macrophages. Intrahepatic upregulation of MIF, release into systemic circulation and the associated upregulation of the proinflammatory mediators suggest a role of MIF in mediating the inflammatory response to I/R injury. Blocking experiments will help to elucidate its role as potential molecular target for preventing hepatic I/R injury.     

Effect of atorvastatin on expression of IL-10 and TNF-α mRNA in myocardial ischemia-reperfusion injury in rats

Myocardial ischemia and reperfusion (MI/R) is associated with an intense inflammatory reaction, which may lead to myocyte injury. Because statins protect the myocardium against ischemia-reperfusion injury via a mechanism unrelated to cholesterol lowering, we hypothesized that the protective effect of statins was related to the expression of TNF-alpha (TNF-α) and interleukin-10 (IL-10) mRNA. Seventy-two rats were randomly divided into three groups as follows: sham, I/R and I/R + atorvastatin. Atorvastatin (20 mg kg⁻¹ day⁻¹) treatment was administered daily via oral gavage to rats for 2, 7 or 14 days. Ischemia was induced via a 30-min coronary occlusion. Reperfusion was allowed until 2, 7 or 14 days while atorvastatin treatment continued. We measured infarct size, hemodynamics and the plasma levels and the mRNA expression of TNF-α and IL-10 in the three groups. We demonstrated that the up-regulation of expression of both TNF-α mRNA and IL-10 mRNA was associated the increased plasma levels of TNF-α and IL-10 in the ischemic and reperfused myocardium compared with that in the sham group (P < 0.01). Atorvastatin treatment prevented ischemia-reperfusion-induced up-regulation of both TNF-α and IL-10 mRNA, and improved left ventricular function (P < 0.01). Our findings suggested that atorvastatin may attenuate MI/R and better recovery of left ventricle function following ischemia and reperfusion and IL-10 was not directly likely involved in this protective mechanism.     

The effect of hyperthermia on cell viability,oxidative damage,and heat shock protein expression in hepatic cells of grass carp (Ctenopharyngodon idellus)

The purpose of the study was to investigate the effects of mild hyperthermia on cell viability, release of lactate dehydrogenase (LDH), superoxide dismutase (SOD) activity, malondialdehyde (MDA) formation, total antioxidant capacity (T-AOC), and the relative mRNA levels of heat shock protein (HSP60, 70, and 90) in hepatic cells of grass carp (Ctenopharyngodon idellus) before and after temperature stress. Cultured cells were exposed to thermal stress (32 °C) for 0.5, 1, 2, 4, and 8 h. The results showed that hyperthermia stress significantly reduced cell viability (P<0.01) and increased LDH release at 0.5 and 1 h (P<0.05). Additionally, hyperthermia stress led to oxidative stress as evidenced by significantly decreased T-AOC after treating cells for 0.5 and 8 h (P<0.05). SOD activity also significantly decreased after 1 h of stress (P<0.05), but MDA formation increased after 8 h of stress (P<0.05). This may be partly responsible for the lower cell viability and higher LDH release we observed. The differences between SOD activity, MDA formation, and T-AOC between the 2 h treatment group and the control were smaller than that of other groups. This indicated that cellular antioxidant enzyme systems play an important role in the defense against oxidative stress. Further tests showed that the expression of HSP60 at 1, 2, and 4 h (P<0.05), HSP70 at 0.5 and 1 h (P<0.01), and HSP90 at all time points after stress were higher (P<0.01) than pre-stress levels. This suggested that HSPs possess the ability to modulate cellular anti-stress responses and play key roles in protecting organisms from heat stress. In conclusion, hyperthermia inhibits cell proliferation, induces cell oxidative stress, and enhances HSP expression in hepatic cells of grass carp.