Period Of Cold Exposure Research Articles

Acute cold exposure and cognitive function: evidence for sustained impairment

Several industries experience periods of cold exposure and rewarming throughout the workday but mental performance under these conditions is unknown. A better understanding of cognition during the rewarming phase after cold exposure may help reduce accidents and improve performance. Ten young men (wearing ∼0.1 clo) underwent three consecutive mornings trials where they were exposed to cold air (10°C) and then subsequently rewarmed (25°C air). A computerised test battery was administered during each stage of the protocol to determine working memory, choice reaction time, executive function and maze navigation. Rectal and skin temperature, oxygen consumption and thermal sensation were also measured throughout and showed a typical response. Relative to baseline performance, working memory, choice reaction time and executive function declined during exposure to 10°C, and these impairments persisted 60 min into the recovery period (i.e. once physiological parameters had returned to baseline). Further work is needed to develop countermeasures to this predicament. Practitioner Summary: This study showed that working memory, choice reaction time and executive function declined during exposure to 10°C air, and these impairments persisted 60 min into the rewarming period (i.e. once measurable physiological parameters had returned to normal). Individuals may be at risk for injury after removal from a cold environment.

Observations on the epidemiology of autumn nematodirosis in weaned lambs in a Scottish sheep flock

Nematodirosis was diagnosed in the south-east of Scotland during two consecutive autumns in lambs which were grazed on the same field. The problem was unpredicted based on the knowledge of...

低温暴露和恢复对棘胸蛙雌性亚成体生存力及能量物质消耗的影响

The giant spiny frog(Paa spinosa),a typical amphibian,can exhibit abnormal hibernation caused by disturbances in energy and substrate metabolism,and can suffer decreases in egg quality during the following breeding season,especially for individuals spawning for the first time.Hibernation which is formed in the long evolutionary process of poikilothermal animals can be considered as a survival strategy and self-protective method to avoid starvation,cold,diseases and other adverse environmental factors for amphibians.Overwintering difficulty of amphibians is a widespread consequence of global climate change and habitat modification that result from human activities,and the following breeding can be influenced by abnormal hibernation with regard to the sub-adult female giant spiny frogs,which is common under the circumstance of artificial domestication.The aim of our study was to investigate the changes in viability and substrate utilization under the condition of artificial cold exposure(4 ℃,90 d) and during recovery(22 ℃,7 d) in the sub-adult female spiny frogs(1—2 year old) which were chosen as the objectives in the study.The results indicated that the survival rate of sub-adult female giant spiny frogs appeared to be a decreasing trend during the period of cold exposure and the mortality rate turned to be zero in the stage of recovery;the relative fatness(K) and the ratio of body weight to body length(Kwl),which presented to be ascendant during cold exposure,both returned to the initial levels(P 0.05) in the recovery stage;ascendant trend was found in both stomach and spleen coefficient during cold exposure(P0.05),particularly the both appeared to be higher in the 90th day in relation to the initial levels(P0.05),and the liver coefficient decreased dramatically in the recovery stage(P0.05).During cold exposure period,no statistical differences were observed in the lipid content in liver and muscle compared with the initial content levels(P 0.05);the moisture content in liver(P0.05) and the non-lipid dry matter content in muscle both decreased during cold exposure;the moisture content in muscle and the non-lipid dry matter content in liver(P0.05) increased during cold exposure;hepatic glycogen content increased by the 60th and 90th day of cold exposure compared to the initial level(P 0.05),with the growth rates of 59.4% and 60.1% respectively,and returned to the initial level during recovery(P 0.05).We might draw a conclusion that the sub-adult female spiny frogs made use of the non-lipid dry matters in muscle rather than lipid,or the non-lipid dry matters in muscle were transported in the tissues in order to adapt to cold exposure,which was concluded from the facts that the body condition indexes(K and Kwl),liver coefficient,non-lipid dry matter content in liver and hepatic glycogen content emerged to be ascendant to some extent,however,non-lipid dry matter content in muscle proved to be remarkably decreasing(P 0.05)and no significant changes were detected in the lipid content in liver and muscle during cold exposure.

Test–retest reliability of Purdue Pegboard performance in thermoneutral and cold ambient conditions

In the cold, Purdue Pegboard (PP) performance declines. The purpose of this study was to determine if this cold-induced impairment is consistent across days (i.e. test–retest reliability) in 5°C. In thermoneutral air (25°C), 14 men were familiarised to the dominant hand (PPa) and bimanual (PPb) PP tasks. They then experienced two 90-min cold exposures (Day 1, Day 2) while wearing ∼1 clo. Bare hands were maintained throughout. Performance on both tasks showed high reliability from day to day (intraclass correlations >0.700) in both thermoneutral and cold conditions. However for both tasks, room temperature performance did not predict performance in the cold (intraclass correlations <0.450). When screening applicants for manual labour in the cold, one must consider that room temperature dexterity does not correlate with dexterity in the cold. It is recommended that a 60-min period of cold exposure be employed to assess manual dexterity in these workers. Statement of Relevance: This study shows that PP performance in room temperature does not predict performance in the cold but performance in the cold is consistent from day to day. When screening applicants for manual labour in the cold, it is recommended that dexterity tests be conducted in the same ambient conditions.

Functional and Expressional Analyses of PmDAM Genes Associated with Endodormancy in Japanese Apricot

Bud endodormancy in woody plants plays an important role in their perennial growth cycles. We previously identified a MADS box gene, DORMANCY-ASSOCIATED MADS box6 (PmDAM6), expressed in the endodormant lateral buds of Japanese apricot (Prunus mume), as a candidate for the dormancy-controlling gene. In this study, we demonstrate the growth inhibitory functions of PmDAM6 by overexpressing it in transgenic poplar (Populus tremula × Populus tremuloides). Transgenic poplar plants constitutively expressing PmDAM6 showed growth cessation and terminal bud set under environmental conditions in which control transformants continued shoot tip growth, suggesting the growth inhibitory functions of PmDAM6. In the Japanese apricot genome, we identified six tandemly arrayed PmDAM genes (PmDAM1-PmDAM6) that conserve an amphiphilic repression motif, known to act as a repression domain, at the carboxyl-terminal end, suggesting that they all may act as transcriptional repressors. Seasonal expression analysis and cold treatment in autumn indicated that all PmDAMs were repressed during prolonged cold exposure and maintained at low levels until endodormancy release. Furthermore, PmDAM4 to PmDAM6 responses to a short period of cold exposure appeared to vary between low- and high-chill genotypes. In the high-chill genotype, a short period of cold exposure slightly increased PmDAM4 to PmDAM6 expression, while in the low-chill genotype, the same treatment repressed PmDAM4 to PmDAM6 expression. Furthermore, PmDAM4 to PmDAM6 expression was negatively correlated with endodormancy release. We here discuss the genotype-dependent seasonal expression patterns of PmDAMs in relation to their involvement in endodormancy and variation in chilling requirements.

Effects of cold-exposure and subsequent recovery on cellular proliferation with influence of 20-hydroxyecdysone in a lepidopteran cell line (IAL-PID2)

In developing insects, the peak level of 20-hydroxyecdysone (20E) initiates a decrease in cyclin expression, which subsequently triggers an arrest of cellular proliferation and the start of differentiation, finally culminating in the moult. We investigated the impact of cold-exposure (4 °C) and recovery (26 °C) on the cell cycle activity of the Plodia interpunctella Lepidoptera cell line IAL-PID2 and on the expression of B-type cyclin (PcycB), ecdysone receptor (B1-isoform; PiEcR-B1), and Hsc70 (PiHsc70) mRNA. Cold-exposure significantly reduced expression of these mRNAs, while their levels increased to above control values during subsequent recovery at the normal growth temperature. When cold-exposed cells were returned to 26 °C, cell cycle activity restarted, but apoptosis was strongly increased. The presence of 20E appeared to increase this apoptotic phenomenon. This result is consistent with the described protective role of 20E against a variety of stressors and with the capacity of 20E to induce cell death in different situations. Here, we illustrate for the first time a connection between 20E treatment and Hsc70 expression during cold-exposure and subsequent recovery in insect cells. Combined with the 20E-induced apoptotic response, our results suggest that regulation of Hsc70 expression by 20E could act in synergy with the control of apoptotic cell death in order to optimize the survival of specific cell populations after a period of cold-exposure.

Expression of WRKY transcription factor and stress protein genes in wheat plants during cold hardening and ABA treatment

Changes in expression of WRKY transcription factor and stress protein genes (Wcor15, Wrab17, Wrab19, and Wcs120) were studied on wheat (Triticum aestivum L., cv. Moskovskaya 39) seedlings exposed to cold hardening for 7 days at 4°C. The high level of WRKY gene expression was noticed already in 15 min after the beginning of cold treatment, but the expression level lowered during longer treatments. Exogenous ABA (0.1 mM) suppressed the WRKY gene expression. The level of Wcor15 gene expression increased gradually, reaching the peak on the second day, and then decreased. Gene expression of Wrab17 remained elevated throughout the period of cold exposure (7 days), and expression of Wrab19 was promoted within the first two days. Exogenous ABA induced expression of Wcor15, Wrab17, and Wrab19 genes both at cold-hardening (4°C) and normal (22°C) temperatures. A significant increase in Wcs120 gene expression during cold hardening was ABA-independent. It is concluded that the increase of wheat plant resistance at the initial stage of cold hardening is related to gene expression of WRKY transcription factor and of stress proteins (Wcor15, Wrab17, Wrab19, and Wcs120), while the resistance increase during prolonged adaptation is related to gene expression of Wcor15 and Wrab17.

Cold exposure increases adiponectin levels in men

Sympathetic nerve activation is recognized at the adipose tissue level during cold exposure. Adiponectin is a key protein produced by adipose tissue, but its acute modulation remains unknown in humans exposed to cold. The aim of this study were (1) to examine the acute effects of cold exposure on circulating adiponectin and (2) to determine whether the changes are modulated by ( a) an acute glucose ingestion as well as ( b) a short-term modulation in carbohydrate (CHO) availability. Using a random crossover design, 6 healthy men were exposed to cold for 120 minutes with ingestion of beverages containing low (Control, 0.04 g/min) or high (High, 0.8 g/min) amounts of glucose during the course of the experiment (study 1). In study 2, 6 healthy men were exposed twice to cold for 120 minutes after equicaloric low-CHO diet and exercise and high-CHO diet without exercise. Plasma adiponectin concentrations were quantified before and during cold exposure. In study 1, adiponectin levels did not change during High, whereas a 20% rise was observed during Control (condition × time interaction, P = .06). In study 2, adiponectin levels increased by approximately 70% during cold exposure after both low- and high-CHO diets (effect of time, P < .05). A 120-minute period of cold exposure is accompanied by a significant increase in adiponectin levels in young healthy men. The rise in adiponectin levels observed during shivering is inhibited with glucose ingestion but not after diets varying in CHO content.

SUPPRESSOR OF FRIGIDA4, Encoding a C2H2-Type Zinc Finger Protein, Represses Flowering by Transcriptional Activation ofArabidopsis FLOWERING LOCUS C

FLOWERING LOCUS C (FLC), a strong floral repressor, is one of the central regulators of flowering in Arabidopsis thaliana. The expression of FLC is increased by FRIGIDA (FRI) but decreased by vernalization, a long period of cold exposure that accelerates flowering. Although many aspects of FLC regulation have been reported, it is not known how FLC is transcriptionally activated by FRI at the molecular level. We isolated suppressor of FRIGIDA4 (suf4), a mutant that flowers early as a result of low FLC expression. SUF4 encodes a nuclear-localized protein with two C2H2-type zinc finger motifs and a Pro-rich domain. SUF4 protein interacts with FRI and FRIGIDA-LIKE1 (FRL1), two genes for which single mutations have the same phenotype as suf4. SUF4 also bound to the promoter of FLC in a chromatin immunoprecipitation assay, suggesting that SUF4 acts as a transcriptional activator of FLC after forming a complex with FRI and FRL1. In addition, suf4 suppresses luminidependens (ld), a late-flowering mutation that causes an increase of FLC, and SUF4 protein directly interacts with LD. Thus, we propose that LD binds to SUF4 to suppress its activity in the absence of FRI.

SIRT3, a Mitochondrial Sirtuin Deacetylase, Regulates Mitochondrial Function and Thermogenesis in Brown Adipocytes

SIRT3 is one of the seven mammalian sirtuin homologs of the yeast Sir2 gene, which mediates the effect of caloric restriction on life span extension in yeast and Caenorhabditis elegans. Because adipose tissue is essential in energy homeostasis and also plays a role in life span determination, we decided to investigate the function of sirtuin members in fat. We report here that murine SIRT3 is expressed in brown adipose tissue and is localized on the mitochondria inner membrane. Caloric restriction activates SIRT3 expression in both white and brown adipose. Additionally, cold exposure up-regulates SIRT3 expression in brown fat, whereas elevated climate temperature reduces the expression. Enforced expression of SIRT3 in the HIB1B brown adipocytes enhances the expression of the uncoupling protein PGC-1alpha, UCP1, and a series of mitochondria-related genes. Both ADP-ribosyltransferase and deacetylase activities of SIRT3 are required for this action. Furthermore, the SIRT3 deacetylase mutant exhibits a dominant negative effect by inhibiting UCP1 expression. This inhibitive effect can be abolished by the coexpression of PGC-1alpha, indicating a major role of PGC-1alpha in the SIRT3 action. In addition, SIRT3 stimulates CREB phosphorylation, which reportedly activates PGC-1alpha promoter directly. Functionally, sustained expression of SIRT3 decreases membrane potential and reactive oxygen species production while increasing cellular respiration. Finally, SIRT3, along with genes related to mitochondrial function, is down-regulated in the brown adipose tissue of several genetically obese mice. In summary, our results demonstrate that SIRT3 activates mitochondria functions and plays an important role in adaptive thermogenesis in brown adipose.

Relationship between alcohol dehydrogenase activity and low-temperature in two maize genotypes, Silverado F 1 and Adh1 –Adh2 – doubly null

We have examined the role of alcohol dehydrogenase (ADH, E.C.1.1.1.1) in chilling tolerance using maize ( Zea mays L.) Adh1 –Adh2 – doubly null mutant. Adh1 –Adh2 – doubly null seedlings were found to have lowered survival rates compared to non-doubly null maize seedlings (Silverado F 1) when held at 2 °C for varying periods. Exposure to ethanol did not increase the chilling tolerance in either Silverado F 1 or Adh1 –Adh2 – doubly null. ADH activity in Silverado F 1 remained steady when held at 2 °C for up to 3 d. ADH1 protein accumulation in chilled Silverado F 1 seedlings remained unchanged throughout the period of cold exposure. Chilling led to a significant inhibition of the P–H +-ATPase (E.C. 3.6.3.6) activity in Adh1 –Adh2 – doubly null, but minimal inhibition was seen in Silverado F 1. Though P–H +-ATPase activity in Adh1 –Adh2 – decreased, P–H +-ATPase protein levels remained constant during the chilling period. Levels of ATP slightly fluctuated in both types of seedlings during the duration of chilling. Lipid peroxidation levels in Adh1 –Adh2 – doubly null increased with chilling exposure, but not in the Silverado F 1. We suggest that ADH activity may play a role in chilling tolerance that is not related to maintenance of glycolysis and ATP production as has been observed during oxygen depravation.

THE QUANTITATIVE GENETICS OF SUSTAINED ENERGY BUDGET IN A WILD MOUSE

We explored how morphological and physiological traits associated with energy expenditure over long periods of cold exposure would be integrated in a potential response to natural selection in a wild mammal, Phyllotis danwini. In particular, we studied sustained energy expenditure (SusMR), the rate of expenditure fueled by concurrent energy intake, basal metabolic rate (BMR), and sustained metabolic scope (SusMS = SusMR/BMR), a measure of the reserve for sustained work. We included the masses of different central processing organs as an underlying factor that could have a mechanistic link with whole animal traits. Only the liver had heritability statistically different from zero (0.73). Physiological and morphological traits had high levels of specific environmental variance (average 70%) and postnatal common environmental variance (average 30%) which could explain the low heritabilities estimates. Our results, (1) are in accordance with previous studies in mammals that report low heritabilities for metabolic traits (SusMR, BMR, SusMS), (2) but not completely with previous ones that report high heritabilities for morphological traits (masses of central organs), and (3) provide important evidence of the relevance of postnatal common environmental variance to sustained energy expenditure.

Flowering in Response to Cold

Flowering in Arabidopsis is coordinated through numerous genes that are responsive to factors such as day length and exposure to cold, ensuring that the plant will flower under the most appropriate conditions. Plants adapted to northern latitudes, for instance, flower earlier following prolonged exposure to cold during germination, a process called vernalization. FLC (FLOWERING LOCUS C), which acts a flowering repressor, plays a key role in vernalization; FLC expression decreases during vernalization so that flowering can take place. However, null flc mutants still show a vernalization response, suggesting that multiple genes regulate this complex process. Ratcliffe et al. used mutational analysis to analyze the effects of four genes closely related to FLC, MAF2 (MADS AFFECTING FLOWERING) through MAF5. The authors investigated the effects of MAF2 loss-of-function and gain-of-function mutants on flowering in unvernalized plants or plants exposed to cold for different durations. The maf2-null mutant flowered earlier after brief periods of cold that did not affect flowering in wild-type plants, whereas MAF2 overexpression prevented vernalization. In contrast to FLC, which declined throughout the period of cold exposure, MAF2 levels only declined following prolonged cold exposure. Thus, MAF2 appears to prevent premature flowering following brief cold spells. Overexpression of MAF3, MAF4, and MAF5 could all delay flowering. MAF5 mRNA increased during vernalization, leading the authors to postulate that MAF5 might act as a floral activator by competing with more potent floral repressors such as FLC. Thus, the closely related FLC, MAF2, and MAF5 genes all play distinct roles in the vernalization process.O. J. Radcliffe, R. W. Kumimoto, B. J. Wong, J. L. Riechmann, Analysis of the Arabidopsis MADS AFFECTING FLOWERING gene family: MAF2 prevents vernalization by short periods of cold. Plant Cell 15, 1159-1169 (2003). [Abstract] [Full Text]

Flowering in Response to Cold

Flowering in Arabidopsis is coordinated through numerous genes that are responsive to factors such as day length and exposure to cold, ensuring that the plant will flower under the most appropriate conditions. Plants adapted to northern latitudes, for instance, flower earlier following prolonged exposure to cold during germination, a process called vernalization. FLC (FLOWERING LOCUS C), which acts a flowering repressor, plays a key role in vernalization; FLC expression decreases during vernalization so that flowering can take place. However, null flc mutants still show a vernalization response, suggesting that multiple genes regulate this complex process. Ratcliffe et al. used mutational analysis to analyze the effects of four genes closely related to FLC , MAF2 ( MADS AFFECTING FLOWERING ) through MAF5 . The authors investigated the effects of MAF2 loss-of-function and gain-of-function mutants on flowering in unvernalized plants or plants exposed to cold for different durations. The maf2 -null mutant flowered earlier after brief periods of cold that did not affect flowering in wild-type plants, whereas MAF2 overexpression prevented vernalization. In contrast to FLC , which declined throughout the period of cold exposure, MAF2 levels only declined following prolonged cold exposure. Thus, MAF2 appears to prevent premature flowering following brief cold spells. Overexpression of MAF3 , MAF4 , and MAF5 could all delay flowering. MAF5 mRNA increased during vernalization, leading the authors to postulate that MAF5 might act as a floral activator by competing with more potent floral repressors such as FLC . Thus, the closely related FLC , MAF2 , and MAF5 genes all play distinct roles in the vernalization process. O. J. Radcliffe, R. W. Kumimoto, B. J. Wong, J. L. Riechmann, Analysis of the Arabidopsis MADS AFFECTING FLOWERING gene family: MAF2 prevents vernalization by short periods of cold. Plant Cell 15 , 1159-1169 (2003). [Abstract] [Full Text]

Effects of Prenatal Ethanol Exposure on Hypothalamic‐Pituitary‐Adrenal Responses to Chronic Cold Stress in Rats

Animals prenatally exposed to ethanol typically exhibit hypothalamic-pituitary-adrenal (HPA) hyperresponsiveness to stressors. In contrast to previous studies that have investigated effects of prenatal ethanol exposure on HPA responses to acute or intermittent stressors, our study investigated HPA responses to a chronic continuous stressor, cold stress (4 degrees C for 0, 1, or 3 days). We tested the hypothesis that prenatal ethanol exposure would result in increased plasma corticosterone (CORT) and adrenocorticotropin (ACTH) responses and increased peptide [corticotropin-releasing factor and vasopressin] mRNA levels in the paraventricular nucleus (PVN) of the hypothalamus compared to that in control animals. In addition, CORT and ACTH responses were measured after exposure to an acute stressor (i.p. isotonic saline injection), superimposed during chronic cold exposure, to examine possible sensitization of the HPA response to the acute stress. Thus, blood samples were collected at the end of each of the three periods of cold exposure, either before (0 min) or 15 min after acute stress. The subjects were adult male and female Sprague-Dawley rat offspring from prenatal ethanol (E), pair-fed (PF), and ad libitum-fed control (C) treatment groups. Exposure to cold stress resulted in significant body weight loss in E males at 1 day and in both males and females of all prenatal treatment groups by 3 days of cold stress. Males in all prenatal groups also exhibited significant increases in adrenal weight:body weight ratios. Cold stress alone (0 min condition) increased CORT levels in E males and overall ACTH levels in E males and females compared to controls. ACTH levels were also higher overall in E compared to control males after acute stress (15 min condition). Sensitization of the CORT response to acute stress was observed in males but not females across all prenatal treatment groups. Corticotropin-releasing factor and vasopressin mRNA levels in the PVN were not significantly affected by prenatal treatment or chronic cold stress in either males or females. In contrast, both males and females displayed increases in PVN thyrotropin-releasing hormone (TRH) mRNA levels after cold stress. These data support and extend previous work demonstrating differential effects of prenatal ethanol exposure on HPA responsiveness of male and female offspring, and suggest that E males may be more vulnerable to the effects of chronic cold stress than E females.

Cold acclimation-induced increase of systolic blood pressure in rats is associated with volume expansion

To investigate the mechanisms of cold-induced hypertension, the systolic blood pressure (SBP) and average daily water consumption were measured weekly in 6-month-old male Wistar rats; they were subsequently acclimated to thermoneutrality (26°C for 7 weeks), to cold temperature (6°C for 9 weeks), and then again reacclimated to 26°C for 5 weeks. Circulating plasma volume and whole blood viscosity were measured in subgroups of rats at the end of acclimation to 26°C after 2 days, after 1, 6, and 8 weeks of cold, and after 2 and 5 weeks of rewarming. The control values obtained at the end of thermoneutral period were: SBP = 130.8 ±18.6 mm Hg, plasma volume = 41.9 ± 4.64 mL/kg, whole body viscosity at shear rate of 22.5 per sec = 6.7 ± 0.48 cps, and daily water consumption = 42.25 ± 16.81 mL. After 48 h of cold exposure there was almost a 50% increase in plasma volume that persisted to a lesser degree throughout the whole period of cold exposure ( P < .05). After 2 weeks of cold exposure the daily water consumption increased and SBP began to increase. After 6 weeks of cold exposure the SBP was 30 mm Hg above that of the control level ( P < .001) and was accompanied by a 25% increase in whole blood viscosity ( P < .05). At the end of 8 weeks of cold exposure the plasma volume was 56.8 ± 9.51 mL/kg and the whole blood viscosity was 8.0 ± 1.79 cps at the 22.5 per sec shear rate. During the 5 weeks of rewarming the elevation of SBP and increased whole blood viscosity persisted, whereas the increased daily water consumption and expanded plasma volume returned to normal. Therefore, the acclimation to cold is accompanied by the development of a volume-associated hypertension, which is sustained after rewarming without volume expansion.

In Vivo Hippocampal Acetylcholine Release During Exposure to Acute Stress

Hippocampal extracellular acetylcholine (ACh) and choline levels were evaluated using in vivo microdialysis in male Fischer 344 rats before, during, and following an 80-min exposure to two different stress conditions. Measurements were taken in rats restrained and immersed in a water bath containing either 37°C (normothermic-restraint) or 20°C (cold-restraint) water. Results were compared to normothermic-freely-moving rats. Cold-restrained rats displayed decreased ACh levels during cold exposure relative to both normothermic-restrained and normothermic-freely-moving rats. By the end of the cold exposure period and following removal from cold, ACh levels had returned to near-baseline values. Normothermic-restrained rats had levels similar to those of normothermic-freely-moving rats, except for a marked increase in ACh following removal from restraint. Cold-restrained rats displayed a gradual elevation in choline levels during cold stress, followed by a gradual decline after stress termination, whereas both normothermic-restrained and normothermic-freely-moving rats displayed gradual decreases during the microdialysis session. These findings demonstrate that central cholinergic neurotransmission can be altered by the application of, and removal from, acute stressors. In addition, the results suggest a possible relationship between the magnitudes of both the stressor and its cholinergic consequences.

The effect of acetylsalicylic acid and cold stress on the susceptibility of broilers to the ascites syndrome

Acetylsalicylic acid (ASA) inhibits the in vitro formation of many cyclooxygenases, some of which in mammals regulate pulmonary vasoconstriction. Pulmonary vasoconstriction occurs in some species subsequent to hypoxaemia, through the mediation of cyclooxygenases. If this effect also is manifested in broilers, ASA might have a therapeutic potential in ameliorating the pulmonary hypertension syndrome (clinically manifested as the ascites syndrome) induced by, amongst other factors, exposure to low ambient temperatures. Male broilers were fed pellets containing 500 parts/10(6) of ASA from 3 weeks of age. After 1 week, ASA-treated and control (no ASA) groups were moved to a cold environment for 4 weeks. The development of the ascites syndrome was monitored by recording haematocrit and mortality with ascites. The plasma levels of two cyclooxygenases, the prostaglandins PGE2 and PGF2alpha, were measured in birds in the cold-exposed groups. No differences in haematocrit values, overall mortality or plasma prostaglandins levels were noted between the ASA-treated and control groups during the period of cold exposure. There was an increased mortality in the ASA-treated groups during weeks 3 to 4 of cold exposure, indicating possible inhibition of a cyclooxygenase vasodilator, which could exacerbate a possible existing pulmonary vasoconstriction. The protocol of this field trial does not indicate that ASA might be of therapeutic use in preventing the ascites syndrome in broilers.

Effect of cold exposure on profiles of metabolic and endocrine responses and on responses to feeding and arginine injection in sheep1

The effect of cold exposure (0 degrees C) on profiles of total heat production (HP), energy metabolism, and blood metabolite and hormone concentrations were measured in nine shorn Suffolk rams. Blood metabolite and hormone responses to feeding and to i.v. arginine injection (.625 mmol/kg BW) and postprandial changes in HP were also measured. Heat production was greater (P < .05) during cold exposure than in the thermoneutral environment due to enhanced (P < .05) nonprotein oxidation. Protein oxidation and nitrogen balance remained unchanged during cold exposure. Plasma glucagon concentrations increased (P < .05) during the initial period of cold exposure. Heat production increased (P < .01) after the initiation of feeding in both environments. Heat production returned gradually to prefeeding values in the thermoneutral environment, but it remained close to the higher levels during cold exposure. Plasma insulin and glucagon concentrations increased (P < .05), and plasma growth hormone concentrations decreased (P < .10) after the initiation of feeding in both environments. Plasma glucagon responses to feeding (P < .05) and plasma insulin responses to arginine injection (P < .01) were reduced by cold exposure. We suggest that 1) enhanced HP in sheep exposed to cold is maintained by enhanced nonprotein oxidation and 2) endocrine responses to stimulants are influenced by cold exposure, even though profiles after cold exposure change little.

Effect of environmental conditions on progeny production by the oriental cockroach Blatta orientalis

AbstractOothecal production by both mated and unmated female oriental cockroaches Blatta orientalis L. (Dictyoptera: Blattidae) was measured at temperatures between 10° and 28 °C. Production was inhibited at 15 °C and below, and only partially recovered when cooled insects were returned to 28 °C. Mean incubation times for oothecae varied from 41.4 to 43.9 days at 28 °C, 60.5 to 60.8 days at 24 °C and 86.8 to 91.7 days at 20 °C depending on RH. No nymphs emerged from oothecae kept continously at 15 °C, 75% RH over a 6 month period, although hatch at both 10° and 15 °C was observed in a few cases when oothecae containing eggs close to hatching (28–35 days from deposition, maintained at 28 °C) were transferred to these lower temperatures. The mean number of nymphs emerging from oothecae (non‐hatching oothecae included) increased with temperature over the range 20–28 °C and with RH over the range 43–95% RH. At 28 °C there was a decline in oothecal viability in the range 95–100% RH attributable to fungal attack, and few nymphs emerged from oothecae kept at 0% RH. The viability of oothecae subjected to periods of cold exposure and then returned to 28 °C decreased with decreasing exposure temperature (10° to −5 °C), increasing exposure period (2 h to 30 days) and stage of embryogenesis when exposed (oothecae incubated for 0 to 7 days at 28 °C prior to cold exposure less cold‐tolerant than oothecae incubated for 28 to 35 days).