首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
This study aimed to investigate temperature effect on physiological and biochemical responses of the marine medaka Oryzias melastigma larvae. The fish were subjected to a stepwise temperature change at a rate of 1 °C/h increasing or decreasing from 25 °C (the control) to six target temperatures (12, 13, 15, 20, 28 and 32 °C) respectively, followed by a 7-day thermal acclimation at each target temperature. The fish were fed ad libitum during the experiment. The results showed that cumulative mortalities were significantly increased at low temperatures (12 and 13 °C) and at the highest temperature (32 °C). For the survivors, their growth profile closely followed the left-skewed ‘thermal performance curve’. Routine oxygen consumption rates of fish larvae were significantly elevated at 32 °C but suppressed at 13 and 15 °C (due to a high mortality, larvae from 12 °C were not examined). Levels of heat shock proteins and activities of malate dehydrogenase and lactate dehydrogenase were also measured in fish larvae exposed at 15, 25 and 32 °C. The activities of both enzymes were significantly increased at both 15 and 32 °C, where the fish larvae probably suffered from thermal discomfort and increased anaerobic components so as to compensate the mismatch of energy demand and supply at these thermal extremes. Coincidently, heat shock proteins were also up-regulated at both 15 and 32 °C, enabling cellular protection. Moreover, the critical thermal maxima and minima of fish larvae increased significantly with increasing acclimation temperature, implying that the fish could develop some degrees of thermal tolerance through temperature acclimation.  相似文献   

2.
The Frank–Starling law is a fundamental property of the vertebrate myocardium which allows, when the end-diastolic volume increases, that the consequent stretch of the myocardial fibers generates a more forceful contraction. It has been shown that in the eel (Anguilla anguilla) heart, nitric oxide (NO) exerts a direct myocardial relaxant effect, increasing the sensitivity of the Frank–Starling response (Garofalo et al., 2009). With the use of isolated working heart preparations, this study investigated the relationship between NO modulation of Frank–Starling response and temperature challenges in the eel. The results showed that while, in long-term acclimated fish (spring animals perfused at 20 °C and winter animals perfused at 10 °C) the inhibition of NO production by L-N5 (1-iminoethyl)ornithine (L-NIO) significantly reduced the Frank–Starling response, under thermal shock conditions (spring animals perfused at 10 or 15 °C and winter animals perfused at 15 or 20 °C) L-NIO treatment resulted without effect. Western blotting analysis revealed a decrease of peNOS and pAkt expressions in samples subjected to thermal shock. Moreover, an increase in Hsp90 protein levels was observed under heat thermal stress. Together, these data suggest that the NO synthase/NO-dependent modulation of the Frank–Starling mechanism in fish is sensitive to thermal stress.  相似文献   

3.
Lake whitefish (Coregonus clupeaformis) embryos were exposed to thermal stress (TS) at different developmental stages to determine when the heat shock response (HSR) can be initiated and if it is altered by exposure to repeated TS. First, embryos were subject to one of three different TS temperatures (6, 9, or 12 °C above control) at 4 points in development (21, 38, 60 and 70 days post-fertilisation (dpf)) for 2 h followed by a 2 h recovery to understand the ontogeny of the HSR. A second experiment explored the effects of repeated TS on the HSR in embryos from 15 to 75 dpf. Embryos were subjected to one of two TS regimes; +6 °C TS for 1 h every 6 days or +9 °C TS for 1 h every 6 days. Following a 2 h recovery, a subset of embryos was sampled. Our results show that embryos could initiate a HSR via upregulation of heat shock protein 70 (hsp70) mRNA at all developmental ages studied, but that this response varied with age and was only observed with a TS of +9 or +12 °C. In comparison, when embryos received multiple TS treatments, hsp70 was not induced in response to the 1 h TS and 2 h recovery, and a downregulation was observed at 39 dpf. Downregulation of hsp47 and hsp90α mRNA was also observed in early age embryos. Collectively, these data suggest that embryos are capable of initiating a HSR at early age and throughout embryogenesis, but that repeated TS can alter the HSR, and may result in either reduced responsiveness or a downregulation of inducible hsps. Our findings warrant further investigation into both the short- and long-term effects of repeated TS on lake whitefish development.  相似文献   

4.
Increasing incubation temperatures, caused by global climate change or thermal effluent from industrial processes, may influence embryonic development of fish. This study investigates the cumulative effects of increased incubation temperature and repeated heat shocks on developing Lake Whitefish (Coregonus clupeaformis) embryos. We studied the effects of three constant incubation temperatures (2 °C, 5 °C or 8 °C water) and weekly, 1-h heat shocks (+3 °C) on hatching time, survival and morphology of embryos, as these endpoints may be particularly susceptible to temperature changes. The constant temperatures represent the predicted magnitude of elevated water temperatures from climate change and industrial thermal plumes. Time to the pre-hatch stage decreased as constant incubation temperature increased (148 d at 2 °C, 92 d at 5 °C, 50 d at 8 °C), but weekly heat shocks did not affect time to hatch. Mean survival rates and embryo morphometrics were compared at specific developmental time-points (blastopore, eyed, fin flutter and pre-hatch) across all treatments. Constant incubation temperatures or +3 °C heat-shock exposures did not significantly alter cumulative survival percentage (~50% cumulative survival to pre-hatch stage). Constant warm incubation temperatures did result in differences in morphology in pre-hatch stage embryos. 8 °C and 5 °C embryos were significantly smaller and had larger yolks than 2 °C embryos, but heat-shocked embryos did not differ from their respective constant temperature treatment groups. Elevated incubation temperatures may adversely alter Lake Whitefish embryo size at hatch, but weekly 1-h heat shocks did not affect size or survival at hatch. These results suggest that intermittent bouts of warm water effluent (e.g., variable industrial emissions) are less likely to negatively affect Lake Whitefish embryonic development than warmer constant incubation temperatures that may occur due to climate change.  相似文献   

5.
Effect of rearing temperature on growth and thermal tolerance of Schizothorax (Racoma) kozlovi Nikolsky larvae and juveniles was investigated. The fish (start at 12 d post hatch) were reared for nearly 6 months at five constant temperatures of 10, 14, 18, 22 and 26 °C. Then juvenile fish being acclimated at three temperatures of 14, 18 and 22 °C were chosen to determine their critical thermal maximum (CTMax) and lethal thermal maximum (LTMax) by using the dynamic method. Growth rate of S. kozlovi larvae and juveniles was significantly influenced by temperature and fish size, exhibiting an increase with increased rearing temperature, but a decline with increased fish size. A significant ontogenetic variation in the optimal temperatures for maximum growth were estimated to be 24.7 °C and 20.6 °C for larvae and juveniles of S. kozlovi, respectively. The results also demonstrated that acclimation temperature had marked effects on their CTMax and LTMax, which ranged from 32.86 °C to 34.54 °C and from 33.79 °C to 34.80 °C, respectively. It is suggested that rearing temperature must never rise above 32 °C for its successful aquaculture. Significant temperature effects on the growth rate and thermal tolerance both exhibit a plasticity pattern. Determination of critical heat tolerance and optima temperature for maximum growth of S. kozlovi is of ecological significance in the conservation and aquaculture of this species.  相似文献   

6.
Many mammals have specialized nose-tips with glabrous and often wet skin, called rhinaria. The function of the rhinarium is unknown in most species. Rhinaria differ not only in shape and skin structure, but also in skin temperature. They are considerably colder in carnivorans than in herbivorous artio- and perissodactyls. Domestic dogs are carnivorans and their noses often feel cold, such that they can be used as an abundant and easily accessible model species. We performed a study on rhinarium temperature in dogs under various ambient temperatures as well as in different behavioral and physiological contexts, breeds, and age groups. The rhinaria of adult, alert, and comfortable dogs are colder than ambient temperature from 30 °C (approximately 5 °C colder) down to a break point at about 15 °C. At an ambient temperature of 0 °C, rhinarium temperature is approximately 8 °C and the decrease in skin surface temperature with decreasing ambient temperature has not yet leveled off. The dog rhinarium warms up under a number of circumstances. In contrast to the continuously warm rhinaria of herbivores, our results suggest strongly that the cold state is the operating state of the dog rhinarium.  相似文献   

7.
Thermal stress in hot semi-arid environment is a major limitation of sheep production in tropical and sub-tropical climatic condition. The animals tend to maintain homeostasis through physiological adjustments in a hot environment (maximum temperature reaches up to 47.5 °C). Therefore, the present study was carried out to assess the effect of thermal exposure on physiological adaptability and seminal attributes of rams under semi-arid environment. The experiment was conducted for eight weeks involving sixteen Malpura crossbred rams (GMM: Garole X Malpura X Malpura). The rams were divided equally into two groups, designated as G1 and G2, respectively. The rams in G1 (Control) group were kept in a sheep shed under naturally prevailing environment without artificial manipulation of ambient temperature (Temperature 30.48±0.38 °C; Relative Humidity 28.59±1.15%). The rams of G2 group were exposed to different temperature at different hours of the day (38 °C at 1000–1100 h; 40 °C at 1100–1200 h; 42 °C at 12:00–1300 h; 43 °C at 1300–1400 h; 44 °C at 1400–1500 h and 42 °C at 1500–1600 h) in a climatic chamber for thermal exposure. Physiological responses, blood biochemical profile, blood endocrine profile, sexual behavior and seminal attributes were measured for both the groups. Thermal exposure significantly (P<0.05) increased the water intake; respiration rate, rectal temperature and skin temperature at afternoon in rams. Exposure of rams to thermal stress (G2) significantly (P<0.05) increased cortisol level and decreased tri-ido-thyronine level. The latency period after the first ejaculation, decreased significantly (P<0.05) in G2. The percentage of rapid motile sperm, linearity and average path velocity of sperm were also altered significantly (P<0.05) in thermal exposed rams as compared to control. However, comparable feed intake, body weight, and major blood biochemical parameters, as well as acceptable semen quality attributes of all the rams indicated that the Fec B gene introgressed Malpura cross rams adapted to the thermal exposure under semi-arid tropical climate.  相似文献   

8.
Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a worldwide emerging pest of soft fruits, but its cold tolerance has not been thoroughly explored. We determined the cold tolerance strategy, low temperature thermal limits, and plasticity of cold tolerance in both male and female adult D. suzukii. We reared flies under common conditions (long days, 21 °C; control) and induced plasticity by rapid cold-hardening (RCH, 1 h at 0 °C followed by 1 h recovery), cold acclimation (CA, 5 days at 6 °C) or acclimation under fluctuating temperatures (FA). D. suzukii had supercooling points (SCPs) between −16 and −23 °C, and were chill-susceptible. 80% of control flies were killed after 1 h at −7.2 °C (males) or −7.5 °C (females); CA and FA improved survival of this temperature in both sexes, but RCH did not. 80% of control flies were killed after 70 h (male) or 92 h (female) at 0 °C, and FA shifted this to 112 h (males) and 165 h (females). FA flies entered chill coma (CTmin) at approximately −1.7 °C, which was ca. 0.5 °C colder than control flies; RCH and CA increased the CTmin compared to controls. Control and RCH flies exposed to 0 °C for 8 h took 30–40 min to recover movement, but this was reduced to <10 min in CA and FA. Flies placed outside in a field cage in London, Ontario, were all killed by a transient cold snap in December. We conclude that adult phenotypic plasticity is not sufficient to allow D. suzukii to overwinter in temperate habitats, and suggest that flies could overwinter in association with built structures, or that there may be additional cold tolerance imparted by developmental plasticity.  相似文献   

9.
10.
The objective of this study was to investigate the effect of high and moderate summer ambient temperatures on testicular structures and endocrine profile of developing ram lambs. Twenty fall-born ram lambs were randomly divided into two groups: animals were kept outdoor (n = 10) under ambient temperature (31–50 °C) or maintained indoor (26–32 °C) from May to October 2007. Daily maximum ambient temperature was recorded for both environments. Monthly serum testosterone and cortisol concentrations were compared between two groups throughout the experiment. The animals were slaughtered at the end of the study and their testes subjected to histopathology exam. The results showed that maximum outdoor ambient temperature was significantly higher than indoor. There was no difference between two groups on serum testosterone concentration. There was no effect on serum cortisol levels except in August and October. Histolopathological examination revealed a severe testicular degeneration with significant germ line degeneration without any impact on somatic cells. In conclusion, direct exposure of developing lambs during non-breeding season impairs testicular germ cells without significant effect on testicular endocrine function.  相似文献   

11.
12.
Many frogs from temperate climates can tolerate low temperatures and increase their thermal tolerance through hardening and acclimation. Most tropical frogs, on the other hand, fail to acclimate to low temperatures. This lack of acclimation ability is potentially due to lack of selection pressure for acclimation because cold weather is less common in the tropics. We tested the generality of this pattern by characterizing the critical temperature minimum (CTMin), hardening, and acclimation responses of túngara frogs (Engystomops pustulosus). These frogs belong to a family with unknown thermal ecology. They are found in a tropical habitat with a highly constant temperature regime. The CTMin of the tadpoles was on average 12.5 °C. Pre-metamorphic tadpoles hardened by 1.18 °C, while metamorphic tadpoles hardened by 0.36 °C. When raised at 21 °C, tadpoles acclimated expanding their cold tolerance by 1.3 °C in relation to larvae raised at 28 °C. These results indicate that the túngara frog has a greatly reduced cold tolerance when compared to species from temperate climates, but it responds to cold temperatures with hardening and acclimation comparable to those of temperate-zone species. Cold tolerance increased with body length but cold hardening was more extensive in pre-metamorphic tadpoles than in metamorphic ones. This study shows that lack of acclimation ability is not general to the physiology of tropical anurans.  相似文献   

13.
Plant cold shock domain proteins (CSDP) participate in maintenance of plant stress tolerance and in regulating their development. In the present paper we show that two out of three extremophyte plant Eutrema salsugineum proteins EsCSDP1-3, namely EsCSDP1 and EsCSDP3, possess high DNA-melting activity. DNA-melting activity of proteins was evaluated using molecular beacon assay in two ways: by measuring Tm parameter (the temperature at which half of the DNA beacon molecules is fully melted) and the beacon fluorescence at 4 °C. As the ratio protein/beacon was increased, a decrease in Tm was observed. Besides DNA-melting activity of full proteins, activity was measured for three isolated cold shock domains EsCSD1-3, C-terminal domain of EsCSDP1 (EsZnF1), as well as a mixture of EsCSD1 and EsZnF1. The Tm reduction efficiency of proteins formed the following sequence: EsCSDP3≈EsCSDP1>(EsCSD1+EsZnF1)>EsZnF1>EsCSDP2. Only full proteins EsCSDP3 and EsCSDP1 demonstrated DNA-melting activity at 4 °C. The presented experimental data indicate that i: interaction of EsCSDP1-3 with beacon single-stranded region is obligatory for efficient melting; ii: cold shock domain and C-terminal domain with zinc finger motifs should be present in one protein molecule to have high melting activity.  相似文献   

14.
To determine the interactions between temperature and cadmium on zebrafish (Danio rerio) development, fertilized eggs were exposed to combinations of three temperature levels (21 °C, 26 °C, and 33 °C) and six cadmium concentrations (0, 0.25, 0.5, 2.0, 5.0, and 10.0 mg/L). Endpoints used included LC50 value (48 h), developmental rate, mortality, heart rate, hatching success, liver histopathology, embryo abnormalities, and heat shock protein (hsp) induction. Results showed a significant acceleration in the developmental rate with increasing temperature and irrespective of the presence of cadmium. Data on LC50 and ELS-test revealed that simultaneous exposure to both cadmium ions and cold stress (21 °C) was highly detrimental to growing embryos, causing a pronounced mortality and a significant reduction in average heart rate and embryo hatchability. In contrast, no similar reactions to cadmium were observed in pre-hatched embryos exposed to both control (26 °C) and high temperature (33 °C), and this can be explained by the significantly higher expression of hsp (hsp70) in embryos at these temperatures. Upon hatching, however, the larvae showed increased sensitivity to cadmium. The severity of malformations in the post-hatched larvae was in the order: hot cadmium stress>cold cadmium stress>cadmium stress alone>no stress at all. Liver histopathology as well as depletion in glycogen reserves exhibited greater severity with increasing cadmium concentration, irrespective of temperature. The present study confirms that temperature effectively confounds cadmium toxicity and needs to be considered for the accurate prediction and assessment of cadmium-induced toxicity in fish.  相似文献   

15.
Ambient temperature can affect physical performance, and an ambient temperature range of −4 °C to 11 °C is optimal for endurance performance in male athletes. The few similar studies of female athletes appear to have found differences in response to cold between the genders. This study investigated whether ambient temperature affects female endurance performance. Nine athletes performed six tests while running on a treadmill in a climatic chamber at different ambient temperatures: 20, 10, 1, −4, −9 and −14 °C and a wind speed of 5 m s−1. The exercise protocol consisted of a 10-min warm-up, followed by four 5-min intervals at increasing intensities at 76%, 81%, 85%, and 89% of maximal oxygen consumption. This was followed by an incremental test to exhaustion. Although peak heart rate, body mass loss, and blood lactate concentration after the incremental test to exhaustion increased as the ambient temperature rose, no changes in time to exhaustion, running economy, running speed at lactate threshold or maximal oxygen consumption were found between the different ambient temperature conditions. Endurance performance during one hour of incremental exercise was not affected by ambient temperature in female endurance athletes.  相似文献   

16.
The effect of dietary l-carnitine supplementation on cold tolerance, growth and survival of the ornamental cichlid Pelvicachromis pulcher was tested under laboratory conditions. Fish were reared for a period of 82 days on a diet containing different levels of added l-carnitine: 0, 500 (3.1 mmol), 1000 (6.2 mmol) and 2000 (12.4 mmol) mg/kg. At the end of the growth period the fish were exposed to a cold shock. Fish which received dietary l-carnitine supplementation (at all tested levels) exhibited significantly better survival rates following exposure to a cold shock, and readapted quicker to normal temperatures compared to the control group which had no l-carnitine added to their diet. The addition of l-carnitine to the diet at a level of 1000 mg/kg seems to yield the best protection against exposure to cold shock.Growth differences among the treated fish were not significant, although the fish which received 500 mg/kg supplementation exhibited slightly better growth.  相似文献   

17.
We investigated the metabolic rate of the Tasmanian marsupial, the eastern barred bandicoot, Perameles gunnii, before and after acclimation to cold temperature (5 °C) for a 2-week period. Although body temperature did not change significantly, we observed a significant increase in the metabolic rate (MR) when measured at 5 °C before and after cold acclimation. Nor-epinephrine had a significant effect on the metabolic rate when measured in the thermoneutral zone and when measured at 5 °C after cold acclimation; however, there was no significant increase when measured at 5 °C before cold acclimation. Nor-epinephrine also resulted in a small but significant decrease in body temperature. Electromyography (EMG) measurements were obtained before and after cold acclimation during shivering. Shivering decreased after two weeks of cold exposure indicating that the bandicoot had acclimated to that temperature. Nor-epinephrine (NE) significantly reduced shivering before but not after cold acclimation. The metabolic rate and shivering decreased in the adult eastern barred bandicoot after acclimation at 5 °C and nor-epinephrine had similar effects to cold acclimation. Our findings of minor changes in thermal conductance suggest that insulation differences were unlikely explanations for our results. These experiments indicate that this marsupial is able to increase its heat production by non-shivering thermogenesis.  相似文献   

18.
The present study aimed to investigate in Hoplosternum littorale (Hancock, 1828) the effects of different water temperatures (10 °C, 25 °C-control group- and 33 °C) on physiologic and metabolic traits following acute (1 day) and chronic (21 days) exposures. We analyzed several biomarker responses in order to achieve a comprehensive survey of fish physiology and metabolism under the effect of this natural stressor. We measured morphological indices, biochemical and hematological parameters as well as oxidative stress markers. To evaluate energy consumption, muscle and hepatic total lipid, protein and glycogen concentrations were also quantified. Extreme temperatures exposures clearly resulted in metabolic adjustments, being liver energy reserves and plasma metabolites the most sensitive parameters detecting those changes. We observed reduced hepatosomatic index after acute and chronic exposure to 33 °C while glycogen levels decreased at both temperatures and time of exposure tested. Additionally, acute and chronic exposures to 10 °C increased liver lipid content and plasma triglycerides. Total protein concentration was higher in liver and lower in plasma after chronic exposures to 10 °C and 33 °C. Acute exposition at both temperatures caused significant changes in antioxidant enzymes tested in the different tissues without oxidative damage to lipids. Antioxidant defenses in fish failed to protect them when they were exposed for 21 days to 10 °C, promoting higher lipid peroxidation in liver, kidney and gills. According to multivariate analysis, oxidative stress and metabolic biomarkers clearly differentiated fish exposed chronically to 10 °C. Taken together, these results demonstrated that cold exposure was more stressful for H. littorale than heat stress. However, this species could cope with variations in temperature, allowing physiological processes and biochemical reactions to proceed efficiently at different temperatures and times of exposure. Our study showed the ability of H. littorale to resist a wide range of environmental temperatures and contributes for the understanding of how this species is adapted to environments with highly variable physicochemical conditions.  相似文献   

19.
Studies on how flatfish cardiovascular function responds to environmental challenges are limited, and have largely relied upon indirect methodologies (i.e. Fick principle). Thus, we measured dorsal aortic blood pressure (PDA) and cardiac function in 8 and 15 °C-acclimated flounder exposed to graded hypoxia, and in 8 °C-acclimated fish exposed to an acute temperature increase to their critical thermal maximum (CTM). The extent of bradycardia in 8 °C-acclimated fish (decrease in heart rate of 41%) was consistent with that observed for other teleosts, as was this species' CTM (25.8 ± 0.5 °C) and its cardiac response to increasing temperature. However, this study provides further examples of how cardiovascular function is controlled differently in the flounder as compared with other fishes. First, the onset of bradycardia in 8 °C-acclimated fish occurred earlier than expected for this inactive and hypoxia-tolerant species (60% water air saturation). Second, resting cardiac output was similar in flounder acclimated to 8 and 15 °C (~ 15 mL min? 1 kg? 1), and hypoxic bradycardia was surprisingly absent at 15 °C. Finally, systemic vascular resistance decreased when flounder were exposed to elevated temperature, and this resulted in a 26% fall in PDA. These are novel findings, however, the extent to which the flounder's behaviour influenced some of the results is unclear.  相似文献   

20.
Antarctica is subjected to extremely variable conditions, but the importance of the temperature increase in cold adapted bacteria is still unknown. To study the molecular adaptation to warming of Antarctic bacteria, cultures of Shewanella frigidimarina were incubated at temperatures ranging from 0 °C to 30 °C, emulating the most extreme conditions that this strain could tolerate. A proteomic approach was developed to identify the soluble proteins obtained from cells growing at 4 °C, 20 °C and 28 °C. The most drastic effect when bacteria were grown at 28 °C was the accumulation of heat shock proteins as well as other proteins related to stress, redox homeostasis or protein synthesis and degradation, and the decrease of enzymes and components of the cell envelope. Furthermore, two main responses in the adaptation to warm temperature were detected: the presence of diverse isoforms in some differentially expressed proteins, and the composition of chaperone interaction networks at the limits of growth temperature. The abundance changes of proteins suggest that warming induces a stress situation in S. frigidimarina forcing cells to reorganize their molecular networks as an adaptive response to these environmental conditions.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号