Body temperature changes in dogs exposed to varying effective temperatures

Adult male and female Beagle dogs (eight total) were exposed individually, in series, to each of 23 effective temperatures for a period of 2 hours or until rectal temperature increased 1.1 degrees C. Rectal temperature was measured to the nearest 0.1 degree C by thermistor probes in the pre-test condition (basal temperature) and at each 5-minute interval during the test conditions (effective temperatures between 21.1 degrees C and 34.7 degrees C). The frequency at which dogs displayed a 1.1 degree C rise in rectal temperature was related to the magnitude of the effective temperature. At an effective temperature of 32.6 degrees C or greater, 100% of the dogs displayed a 1.1 degree C rise in rectal temperature. Between an effective temperature of 29.3 degrees C and 31.4 degrees C, some animals displayed a 1.1 degree C rise while others did not. At an effective temperature of 28.4 degrees C or below no animals displayed a 1.1 degree C rise. The mean time necessary for a 1.1 degree C rise was negatively correlated (P less than 0.01) to the magnitude of the effective temperature. The minimum effective temperature necessary to increase rectal temperature by 1.1 degree C in male Beagles (29.6 +/- 1.0 degree C) was not significantly different from females (30.8 +/- 0.4 degrees C).     

Mutual stimulation of temperature and light effects on C(4) phosphoenolpyruvate carboxylase in leaf discs and leaves of Amaranthus hypochondriacus

This article reports marked modulation of the activity and regulatory properties of phosphoenolpyruvate carboxylase (PEPC) by temperature and light in leaf discs as well as leaves of Amaranthus hypochondriacus. The activity of PEPC increased by 1.7-fold at 45 degrees C over 25 degrees C. Warm temperature also stimulated the photoactivation of PEPC. The activation by light of PEPC was 1.9-fold at 25 degrees C and increased to 2.2-fold at 45 degrees C. The sensitivity of PEPC to its inhibitor malate was less and the activation by glucose-6-phosphate (G-6-P) or inorganic phosphate (Pi) was more at 45 degrees C than that at 25 degrees C. These effects of temperature were quite pronounced in light. Similar responses were observed when detached leaves were exposed to varying ambient temperature (dry heat). The activity of PEPC increased by 1.6-fold at 45 degrees C over 25 degrees C in the dark. The activation of PEPC by light was 2.1-fold at 25 degrees C and increased to 2.6-fold at 45 degrees C. Inhibition by malate was less and activation by G-6-P or Pi was more at 45 degrees C than that at 25 degrees C. Thus, there was a marked modulation of not only the activity but also the regulatory properties of the enzyme by temperature and light, independently as well as cooperatively with each other. Further experiments suggested that PEPC was able to memorize to a significant extent the changes induced by warm temperature and that these changes were complemented by subsequent illumination. These effects were not due to changes in PEPC protein levels. We conclude that temperature and light can modulate PEPC activity and regulatory properties not only individually but also in a significantly cooperative manner with each other. As significant increases in temperature are common during daytime in tropical or subtropical conditions, we suggest that the synergistic effects of temperature and light are quite relevant in optimizing the activity of PEPC in leaves of C(4) plants.     

Effect of culture temperature on erythropoietin production and glycosylation in a perfusion culture of recombinant CHO cells

To investigate the effect of culture temperature on erythropoietin (EPO) production and glycosylation in recombinant Chinese hamster ovary (CHO) cells, we cultivated CHO cells using a perfusion bioreactor. Cells were cultivated at 37 degrees C until viable cell concentration reached 1 x 10(7) cells/mL, and then culture temperature was shifted to 25 degrees C, 28 degrees C, 30 degrees C, 32 degrees C, 37 degrees C (control), respectively. Lowering culture temperature suppressed cell growth but was beneficial to maintain high cell viability for a longer period. In a control culture at 37 degrees C, cell viability gradually decreased and fell below 80% on day 18 while it remained over 90% throughout the culture at low culture temperature. The cumulative EPO production and specific EPO productivity, q(EPO), increased at low culture temperature and were the highest at 32 degrees C and 30 degrees C, respectively. Interestingly, the cumulative EPO production at culture temperature below 32 degrees C was not as high as the cumulative EPO production at 32 degrees C although the q(EPO) at culture temperature below 32 degrees C was comparable or even higher than the q(EPO) at 32 degrees C. This implies that the beneficial effect of lowering culture temperature below 32 degrees C on q(EPO) is outweighed by its detrimental effect on the integral of viable cells. The glycosylation of EPO was evaluated by isoelectric focusing, normal phase HPLC and anion exchange chromatography analyses. The quality of EPO at 32 degrees C in regard to acidic isoforms, antennary structures and sialylated N-linked glycans was comparable to that at 37 degrees C. However, at culture temperatures below 32 degrees C, the proportions of acidic isoforms, tetra-antennary structures and tetra-sialylated N-linked glycans were further reduced, suggesting that lowering culture temperature below 32 degrees C negatively affect the quality of EPO. Thus, taken together, cell culture at 32 degrees C turned out to be the most satisfactory since it showed the highest cumulative EPO production, and moreover, EPO quality at 32 degrees C was not deteriorated as obtained at 37 degrees C.     

Behavioral thermoregulation in Hemigrapsus nudus,the amphibious purple shore crab

The thermoregulatory behavior of Hemigrapsus nudus, the amphibious purple shore crab, was examined in both aquatic and aerial environments. Crabs warmed and cooled more rapidly in water than in air. Acclimation in water of 16 degrees C (summer temperatures) raised the critical thermal maximum temperature (CTMax); acclimation in water of 10 degrees C (winter temperatures) lowered the critical thermal minimum temperature (CTMin). The changes occurred in both water and air. However, these survival regimes did not reflect the thermal preferences of the animals. In water, the thermal preference of crabs acclimated to 16 degrees C was 14.6 degrees C, and they avoided water warmer than 25.5 degrees C. These values were significantly lower than those of the crabs acclimated to 10 degrees C; these animals demonstrated temperature preferences for water that was 17 degrees C, and they avoided water that was warmer than 26.9 degrees C. This temperature preference was also exhibited in air, where 10 degrees C acclimated crabs exited from under rocks at a temperature that was 3.2 degrees C higher than that at which the 16 degrees C acclimated animals responded. This behavioral pattern was possibly due to a decreased thermal tolerance of 16 degrees C acclimated crabs, related with the molting process. H. nudus was better able to survive prolonged exposure to cold temperatures than to warm temperatures, and there was a trend towards lower exit temperatures with the lower acclimation (10 degrees C) temperature. Using a complex series of behaviors, the crabs were able to precisely control body temperature independent of the medium, by shuttling between air and water. The time spent in either air or water was influenced more strongly by the temperature than by the medium. In the field, this species may experience ranges in temperatures of up to 20 degrees C; however, it is able to utilize thermal microhabitats underneath rocks to maintain its body temperature within fairly narrow limits.     

Control of local heat gain by vasomotor response of the hand

Finger blood flow (BF) was measured by venous occlusion plethysmography using mercury-in-Silastic strain gauges during immersion of one hand in hot water (raised by steps of 2 degrees C every 10 min from 35 to 43 degrees C), the other being a control (kept immersed in water at 35 degrees C). The measurements were made in three different thermal states on separate days: 1) cool-25 degrees C, 40% rh, esophageal temperature (Tes) = 36.64 +/- 0.10 degrees C; 2) warm-35 degrees C, 40% rh, Tes = 36.71 +/- 0.11 degrees C; and 3) hot-35 degrees C, 80% rh with the legs immersed in water at 42 degrees C, Tes = 37.26 +/- 0.11 degrees C. When water temperature was raised at 42 degrees C, Tes = 37.26 +/- 0.11 When water temperature was raised to 39-41 degrees C in the warm state, finger BF in the hand heated locally (BFw) decreased. When water temperature was raised to 43 degrees C, however, BFw returned to the control value. In the hot state, Tes rose steadily, reaching 37.90 +/- 0.12 degrees C at the end of the 50-min sessions. BF in the control finger also increased gradually during the session. BFw showed a tendency to decrease when water temperature was raised to 39 degrees C, but the change was not greater than that observed in the warm state. In the cool state, no such reduction in BFw was observed when water temperature was raised to 39-41 degrees C. On the contrary, BFw increased at water temperatures of 41-43 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Temperature-dependent changes of chloride transport kinetics in human red cells

Chloride self-exchange in human red cells was studied between 0 degrees C and 38 degrees C. At higher temperatures the flow-tube method was used. Although the general features of chloride transport at 0 degrees C and 38 degrees C are similar, the following differences were found: (a) the maximum pH of chloride self-exchange flux was lowered 0.6 pH unit from 7.8 to 7.2 when temperature was increased from 0 degrees C to 38 degrees C; (b)the apparent half-saturation constant increased from 28 mM at 0 degrees C to 65 mM at 38 degrees C; (c) chloride transport at body temperature is slower than predicted by other investigators by extrapolation from low-temperature results. Chloride transport increased only 200 times when temperature was raised from 0 degrees C to 38 degrees C, because the apparent activation energy decreased from 30 kcal mol(-1) to 20 kcal mol(-1) above a temperature of 15 degrees C; (d) a study of temperature dependence of the slower bromide self-exchange showed that a similar change of activation energy occurred around 25 degrees C. Both in the case of Cl(-) (15 degrees C) and in the case of Br(-) (25 degrees C), critical temperature was reached when the anion self-exchange had a turnover number of about 4x10(9) ions cell (-1)s(-1); (e) inhibition of chloride transport by DIDS (4,4’- diisothiocyano-stilbene-2,2’-disulfonate)revealed that the deflection persisted at 15 degrees C at partial inhibition (66 percent) presumably because DIDS inactivated 66 percent of the transport sites. It is suggested that a less temperature- dependent step of anion exchange becomes rate limiting at the temperature where a critical turnover number is reached.     

松毛虫狭颊寄蝇实验种群生态学研究

松毛虫狭颊寄蝇(Carcelia matsukarehae)是松毛虫重要的寄生天敌之一。在控制松毛虫自然种群增长中起重要的作用。本文在15℃、18℃、22℃、25℃、29℃、32℃6个恒温。相对湿度为70％～85％,光照为12：12(L：D)的条件下研究了松毛虫狭颊寄蝇的生态学特性。结果表明,松毛虫狭颊寄蝇的世代发育起点温度是5．23℃。积温为523．73日·度。成虫寿命在没有补充营养的条件下为1．3～8．06d,喂以30％蜜糖水。寿命可以从9．63d延长到36．42d。成虫产卵的最适温度为236℃,每雌最大产量为86粒．种群增长最适温度22～25℃．以近似方法计算22℃和25℃下实验种群繁殖特征生命表参数。在22℃,R0、T0、rc和A值分别为24．89、37．33、0．086和1．089。在25℃时分别为20．01、32．38、0．09和1．10．22℃时种群最大LxMx出现在成虫羽化后第33～38天。25℃时的LxMx最大值出现在成虫羽化后第29～34天。     

Temperature acclimation of photosynthesis and related changes in photosystem II electron transport in winter wheat

Winter wheat (Triticum aestivum L. cv Norin No. 61) was grown at 25 degrees C until the third leaves reached about 10 cm in length and then at 15 degrees C, 25 degrees C, or 35 degrees C until full development of the third leaves (about 1 week at 25 degrees C, but 2-3 weeks at 15 degrees C or 35 degrees C). In the leaves developed at 15 degrees C, 25 degrees C, and 35 degrees C, the optimum temperature for CO(2)-saturated photosynthesis was 15 degrees C to 20 degrees C, 25 degrees C to 30 degrees C, and 35 degrees C, respectively. The photosystem II (PS II) electron transport, determined either polarographically with isolated thylakoids or by measuring the modulated chlorophyll a fluorescence in leaves, also showed the maximum rate near the temperature at which the leaves had developed. Maximum rates of CO(2)-saturated photosynthesis and PS II electron transport determined at respective optimum temperatures were the highest in the leaves developed at 25 degrees C and lowest in the leaves developed at 35 degrees C. So were the levels of chlorophyll, photosystem I and PS II, whereas the level of Rubisco decreased with increasing temperature at which the leaves had developed. Kinetic analyses of chlorophyll a fluorescence changes and P700 reduction showed that the temperature dependence of electron transport at the plastoquinone and water-oxidation sites was modulated by the temperature at which the leaves had developed. These results indicate that the major factor that contributes to thermal acclimation of photosynthesis in winter wheat is the plastic response of PS II electron transport to environmental temperature.     

Effect of temperature shifts on gliding motility, adhesion, and fatty acid composition of Cytophaga sp. strain U67.

Gliding motility and flipping of 25 degrees C-adapted Cytophaga sp. strain U67 were inhibited when the bacteria were shifted to a less than or equal to 12 degrees C environment; motility was not blocked by a shift to 13 degrees C. Bacteria adapted to 4 degrees C were motile over the entire 4 to 25 degrees C temperature range tested. U67 adhesion to the substratum appeared to be unaffected by temperature shifts. Bacteria adapted to 4 degrees C had higher proportions of unsaturated and branched-chain fatty acids than did those grown at 25 degrees C. When 25 degrees C-adapted bacteria were subjected to a gradual temperature decline, the time of reappearance of gliding competence at 4 to 5 degrees C was correlated with these changes in fatty acid composition.     

Temperature dependence of ADP/ATP translocation in mitochondria

The temperature dependence of the adenine nucleotide exchange in mitochondria has been determined by employing a rapid mixing, quenching and sampling apparatus and the inhibitor quench-back exchange method. Thus the exchange is resolved down to 0.1 s. Rates are evaluated from accumulating the time-dependent progress at about 10 points. The exchange rate in liver mitochondria was determined from -10 degrees C to + 10 degrees C in the presence of 20% glycol, from 0 degrees C to 25 degrees C, and from 20 degrees C to 40 degrees C under partial inhibition by carboxyatractylate. The total range between -10 degrees C to + 40 degrees C has only one temperature break at 13 degrees C. From the Arrhenius plot between -10 degrees C to + 13 degrees C, EA approximately equal to 140 kJ and above 13 degrees C, EA approximately equal to 56 kJ is evaluated, corresponding to a Q10 of 8 and 2 respectively. In beef heart mitochondria the exchange rate was measured between 0 degrees C and 20 degrees C, and between 15 degrees C and 30 degrees C under partial inhibition with carboxyatractylate. There is a temperature break around 14 degrees C with EA approximately equal to 143 kJ between 0 degrees C and 14 degrees C and EA approximately equal to 60 kJ from 15 degrees C to 30 degrees C. The extrapolated translocation rates at 37 degrees C are 500 and 1800 mumol min-1 (g protein)-1 for rat liver and for beef heart mitochondria respectively. The temperature break is suggested to reflect a conformation change since there is no reversed break at low temperature, the temperature break changes in sonic particles and no lipid phase transition at 14 degrees C in mitochondria has been reported.     

工厂化黄瓜穴盘育苗昼温适应性

在人工气候室内以黄瓜穴盘苗为材料,测定不同昼温处理下(昼温分别为30℃、27℃、24℃、21℃、18℃、15℃,夜温均为15℃)黄瓜幼苗下胚轴长、下胚轴粗、第一叶片和第二叶片的长和宽、地上部和地下部干物质积累量、叶片含水率及叶片的叶绿素荧光特性,并用主成分分析法和聚类分析法对不同昼温处理下的黄瓜穴盘苗质量进行分析.结果表明:不同昼温处理下黄瓜穴盘苗各生长指标存在显著性差异,幼苗质量的昼温反应表现为24℃＞21℃＞27℃＞30℃＞18℃＞15℃;通过主成分分析和系统聚类可以把各温度处理分为:最适温度处理(24℃/15℃)、适宜温度处理(21℃/15℃)和不适宜温度处理3类;不适宜温度处理又可分为高温抑制类(27C/15℃,30℃/15℃)和低温抑制类(15℃/15℃,18℃/15℃)2类.     

Effect of thermal and chemical denaturants on Thermoanaerobacter ethanolicus secondary-alcohol dehydrogenase stability and activity

Thermoanaerobacter ethanolicus 39E secondary-alcohol dehydrogenase (2 degrees ADH) was optimally active near 90 degrees C displaying thermostability half-lives of 1.2 days, 1.7 h, 19 min, 9.0 min, and 1.3 min at 80 degrees C, 90 degrees C, 92 degrees C, 95 degrees C, and 99 degrees C, respectively. Enzyme activity loss upon heating (90-100 degrees C) was accompanied by precipitation, but the soluble enzyme remaining after partial inactivation retained complete activity. Enzyme thermoinactivation was modeled by a pseudo-first order rate equation suggesting that the rate determining step was unimolecular with respect to protein and thermoinactivation preceded aggregation. The apparent 2 degrees ADH melting temperature (T(m)) occurred at approximately 115 degrees C, 20 degrees C higher than the temperature for maximal activity, suggesting that it is completely folded in its active temperature range. Thermodynamic calculations indicated that the active folded structure of the 2 degrees ADH is stabilized by a relatively small Gibbs energy (triangle upG(stab.)(double dagger) = 110 kJ mol(-1)). 2 degrees ADH catalytic activities at 37 degrees C to 75 degrees C, were 2-fold enhanced by guanidine hydrochloride (GuHCl) concentrations between 120 mM and 190 mM. These results demonstrate the extreme resistance of this thermophilic 2 degrees ADH to thermal or chemical denaturation; and suggest increased temperature or GuHCl levels seem to enhance protein fixability and activity.     

Influence of temperature on blood coagulation in vitro (author's transl)]

The influence of different temperatures between 13 degrees C and 45 degrees C on coagulation factors in vitro was studied by measuring clotting time with the recalcification time, partial thromboplastin time (PTT), and thromboplastin time test. In all three tests the shortest clotting times were measured at a temperature of 40 degrees C. The relation between temperature and clotting time was similar in fresh plasma and in plasma which had been stored at a temperature of --20 degrees C before examination. However, in all tests stored plasma showed shorter coagulation times. Prolongation of coagulation time at 45 degrees C is caused by irreversible reduction of coagulation activity in the plasma. At the same time thromboplastin- and PTT-reagent are imparied in their coagulation acitvity by a temperature of 45 decrees C. In comparison to plasma obtained from healthy persons plasma from patients with hemophilia A or B or with v. Willebrand's disease reacted more sensitive to changes in temperature in the PTT test. The coagulation defect was definitely more pronounced at 27 degrees and 17 degrees C than at 37 degrees C. It was not possible to differentiate these three coagulopathies with the PTT test at 27 degrees and 17 degrees C.     

Temperature-induced alanine oxidation in a psychrotrophic Pseudomonas.

A psychrotrophic pseudomonad isolated from iced fish oxidized alanine at temperatures close to 0 degrees C and grew over the range 0 degrees C-35 degrees C. The rate of oxidation of alanine, measured manometrically, by cells grown at 2 degrees C was lower than that of cells grown at 22 degrees C. However, the consumption of oxygen after heat treatment at 35 degrees for 35 min was reduced considerably by 2 degrees C grown cells. Alanine oxidase activity was tested in an extract from cells grown at 2 degrees C and 22 degrees C with alanine as the sole carbon, nitrogen, and energy source. Cells grown at 2 degrees C produced an alanine oxidase with a temperature optimum of 35 degrees C and pH optimum of 8, which lost about 80% activity by heat treatment at 40 degrees C for 30 min. There was no change in activity after dialysis at pH 7, 8, or 9. Extracts from cells grown at 22 degrees C contained an alanine oxidase system with an optimum temperature of 45 degrees C, a pH optimum above 8, and only about 30% reduction of activity after heat treatment. This enzyme activity was concentrated in the 0.5 M elution fraction from a Sephadex column, and dialysis reduced the activity at pH 7 and 8. Mesophilic enzyme synthesis apparently started around a growth temperature of 10 degrees C. The crude alanine oxidase systems of Pseudomonas aeruginosa derived from cells grown at 13 degrees C and 37 degrees C had a common optimum temperature of 45 degrees C. These data suggest that one mechanism of psychrophilic growth by psychrotrophic bacteria may be the induction of enzymes with low optimum temperatures in response to low temperature conditions.     

Interactive effects of soil temperature and moisture on Concord grape root respiration

Root respiration has important implications for understanding plant growth as well as terrestrial carbon flux with a changing climate. Although soil temperature and soil moisture often interact, rarely have these interactions on root respiration been studied. This report is on the individual and combined effects of soil moisture and temperature on respiratory responses of single branch roots of 1-year-old Concord grape (Vitis labruscana Bailey) vines grown in a greenhouse. Under moist soil conditions, root respiration increased exponentially to short-term (1 h) increases in temperature between 10 degrees C and 33 degrees C. Negligible increases in root respiration occurred between 33 degrees C and 38 degrees C. By contrast to a slowly decreasing Q10 from short-term temperature increases, when roots were exposed to constant temperatures for 3 d, the respiratory Q10 between 10 degrees C and 30 degrees C diminished steeply with an increase in temperature. Above 30 degrees C, respiration declined with an increase in temperature. Membrane leakage was 89-98% higher and nitrogen concentration was about 18% lower for roots exposed to 35 degrees C for 3 d than for those exposed to 25 degrees C and 15 degrees C. There was a strong interaction of respiration with a combination of elevated temperature and soil drying. At low soil temperatures (10 degrees C), respiration was little influenced by soil drying, while at moderate to high temperatures (20 degrees C and 30 degrees C), respiration exhibited rapid declines with decreases in soil moisture. Roots exposed to drying soil also exhibited increased membrane leakage and reduced N. These findings of acclimation of root respiration are important to modelling respiration under different moisture and temperature regimes.     

Loss of secretory response of rat basophilic leukemia (2H3) cells at 40 degrees C is associated with reversible suppression of inositol phospholipid breakdown and calcium signals

Antigen-induced stimulatory signals as well as histamine secretion from the RBL-2H3 cells were found to be highly temperature dependent. There was no hydrolysis of inositol phospholipids, increase in cytosol calcium concentration (calcium signal), or secretion upon antigen stimulation at temperatures below 20 degrees C. At higher temperatures (i.e., 20 to 37 degrees C), all responses increased in extent with increase in temperature. Temperatures of 38 degrees C or higher, however, resulted in a marked decline in all responses, until no responses were observed at 40 to 42 degrees C. As indicated by the decay in calcium signal, the duration of response was also temperature dependent. The response was of long duration at 30 to 32 degrees C, but it became progressively more transient as the temperature was increased from 32 to 40 degrees C. The effects of low or high temperature were fully reversible. For example, in the presence of antigen, stimulatory signals immediately appeared once the temperature was decreased from 40 to 37 degrees C. Although the diminished responses could be explained, in part, by a reduction in rates of IgE receptor aggregation and phospholipase C activity, the reductions were insufficient to account for complete loss of activity at 40 degrees C. We conclude that generation of intracellular signals in 2H3 cells is blocked by quite small elevations in temperature above 37 degrees C, possibly as consequence of changes in membrane fluidity.     

海洋桡足类的热耐受性

为了探明热排放对近海生态的影响,选用我国东海近海主要桡足类,采用热升温实验方法对其半致死温度进行研究.结果表明,不同生物在相同适温条件下和同种生物在不同适温条件下的热耐受能力均存在差异.自然适应水温为13.5 ℃,中华哲水蚤(Calanus sinicus)和细巧华哲水蚤(Sinocalanus tenellus)的24 h半致死温度值分别为26.9 ℃和25.4 ℃;自然适应水温为14.2 ℃,中华异水蚤(Acartiella sinensis)和近缘大眼剑水蚤(Corycaeus affinis)的24 h半致死温度值分别为26.7 ℃和30.5 ℃;自然适应水温为28.0 ℃,背针胸刺水蚤(Centropages dorsispinatus)、强额拟哲水蚤(Paracalanus crassirostris)、刺尾纺锤水蚤(Acartia spinicauda)和尖额真猛水蚤(Euterpina acutifrons)的24 h半致死温度值分别为34.0 ℃、34.3 ℃、35.7 ℃和36.0 ℃.细巧华哲水蚤在自然适应水温分别为13.5 ℃和23.5 ℃下的24 h半致死温度值为25.4 ℃和33.0 ℃.     

Temperature preference and respiration of acaridid mites

The thermal preferences in a grain mass and respiration at various temperatures in mites (Acari: Acarididae) of medical and economical importance [Acarus siro (L. 1758), Dermatophagoides farinae Hughes 1961, Lepidoglyphus destructor (Schrank 1871), and Tyrophagus putrescentiae (Schrank 1781)] were studied under laboratory conditions. Based on the distribution of mites in wheat, Triticum aestivum L., grain along a thermal gradient from 10 to 40 degrees C, L. destructor, D. farinae, and A. siro were classified as eurythermic and T. putrescentiae as stenothermic. The lowest preferred temperature was found for D. farinae (28 degrees C), followed by A. siro (28.5 degrees C), L. destructor (29.5 degrees C), and T. putrescentiae (31.5 degrees C). The relationship between the respiration rate and the temperature was similar for all four mite species. The highest respiration was found in the range from 31 to 33 degrees C. This is approximately 2 degrees C higher than the preferred temperature of these species. The lower temperature threshold of respiration ranged from 1 to 5 degrees C and the upper threshold ranged from 45 to 48 degrees C. Acclimatization of A. siro to temperature regimes of 5, 15, and 35 degrees C resulted in thermal preferences between 9 and 12 degrees C, 9 and 20 degrees C, and 28 and 35 degrees C, respectively. The respiration rate of acclimatized specimens increased with the temperature, reaching a maximum at 29.0 degrees C for mites acclimatized at 5 and 15 degrees C and a maximum at 33.7 degrees C for those acclimatized at 30 degrees C.     

Temperature-dependent switching between "wild-type" and "mutant" forms of p53-Val135

The p53 gene is a suppressor of abnormal cell growth but is also subject to oncogenic activation by mutation. The mutant allele p53-Val135, has recently been discovered to be temperature-sensitive and functions as an oncogene at 37 degrees C and as a tumor suppressor at 32.5 degrees C. In order to investigate the molecular mechanism underlying the temperature sensitivity of p53-Val135 rabbit reticulocyte lysate was used to translate the p53 mRNAs in vitro at 37 degrees C and at 30 degrees C. The immunoreactivity and T antigen binding of wild-type protein p53-Ala135 were unaffected by temperature and were similar to wild-type p53 expressed in vivo. In contrast, the mutant p53-Val135 protein was markedly affected by temperature. At 37 degrees C p53-Val135 showed reduced T antigen binding and did not react with monoclonal antibodies PAb246 and PAb1620. At 30 degrees C, p53-Val135 behaved as the wild-type p53. Temperature also exerted a post-translational effect on p53-Val135 with complete conversion from wild-type to mutant phenotype within two minutes of temperature shift from 30 degrees C to 37 degrees C. There was incomplete conversion from mutant to wild-type phenotype when the temperature was shifted down from 37 degrees C to 30 degrees C. We propose that the temperature dependent forms of p53-Val135 represent conformational variants of the p53 protein with opposing functions in cell growth control.     

Impact of intraischemic temperature on oxidative stress during hepatic reperfusion

This study was designed to investigate the influence of intraischemic liver temperature on oxidative stress during postischemic normothermic reperfusion. In C57BL/6 mice, partial hepatic ischemia was induced for 90 min and intraischemic organ temperature adjusted to 4 degrees C, 15 degrees C, 26 degrees C, 32 degrees C, and 37 degrees C. As detected by electron spin-resonance spectroscopy, plasma/blood concentrations of hydroxyl and ascorbyl radicals were significantly increased in all groups after ischemia/reperfusion independent of the intraischemic temperature. In tissue, however, postischemic lipid peroxidation was attenuated after organ cooling down to 32 degrees C-26 degrees C and not detectable after ischemia at 15 degrees C-4 degrees C. mRNA expression of superoxide dismutase-1 and heme oxygenase-1, measured during reperfusion, was significantly elevated in the group at 37 degrees C as compared to the hypothermic groups at 4 degrees C-32 degrees C. The reduction of radical generation was associated with a prevention of adenosine monophosphate hydrolysis during ischemia in the hypothermic groups. In conclusion, ischemia-reperfusion-induced oxidative stress in the liver tissue is non-linearly-dependent on intraischemic temperature, whereas the plasma/blood concentration of radicals is not affected by organ cooling. Oxidative stress is reduced through mild hypothermia at 32 degrees C-26 degrees C and inhibited completely at 15 degrees C. Reduction of initial intracellular radical generation and prevention of secondary oxidant-induced tissue injury are possible mechanisms of this protection.