Author Keywords: Hypothalamic slice; thermosensitive neuron; threshold temperature response; guinea-pig 相似文献
- 1. 1. The preferred temperature of Bulla gouldiana is 26.7–28.7°C.
- 2. 2. In constant scotophase, photophase, and light and dark photoperiod the organisms do not have a diel cycle of thermoregulation.
- 3. 3. It takes the animal 6–16 h to reach the preferred temperature.
- 4. 4. The lowest and highest temperatures visited were 11 and 33°C.
- 5. 5. Spawning of the species occurred in the thermal gradient between 27 and 28.5°C.
- 1. 1. The thermal death point of the water flea Daphnia magna (age < 24 h, cultured at 20°C) varied considerably depending on the method used. The median lethal dose (LD50), induced by an acute 24 h heat exposure was 34.8°C. It was 37.8°C following a thermal shock for 15 min, and it was 39.4°C when a continuous temperature increase (0.2°C/min) was used.
- 2. 2. Heat death temperature of daphnids was related to the acute heating rate.
- 3. 3. The logarithm of median lethal time (Lt50) of daphnids, kept at a constant high temperature, had a linear relationship to temperature (°C) within the range of 28.0–38.5°C.
- 4. 4. The mortality after heat exposure increased with recovery time at 20°C for up to 3 days.
- 5. 5. The animals which survived the heat exposure produced eggs and offspring. Furthermore, no time lag in development between the control and heat exposure group was observed.
- 6. 6. The comparison of the results made by different heat tests categorized to Methods 1 and 2 by Precht (1973), for use in the determination of lethal limits of ectotherms, has been discussed.
- 1. 1. Human T cell proliferation is suppressed at 27°C, and is both diminished and delayed at 32°C.
- 2. 2. Temperature shift-up and viability assays indicated that concanavalin A stimulation at 27°C induced cell death in contrast to a transient unresponsiveness (anergy) induced by monoclonal anti-CD3 antibody (CD3) and the superantigen, staphylococcal exterotoxin B.
- 3. 3. Phytohemagglutinin also induced cell death at 27°C; however, some cells remained viable and proliferation occurred when such cultures were subsequently moved to 37°C.
- 4. 4. Low temperature suppression of T cell activation was not overcome by a mixture of phorbol ester and calcium ionophore indicating a probable block post-protein kinase C activation. This was confirmed in temperature shift-down assays where incubation for 18–24 h at 37°C was required to bypass the block at 27°C.
- 5. 5. With the exception of CD3, stimulation at 27°C with the mitogens resulted in interleukin-2 secretion, indicating that the low temperature block(s) is a relatively late event in cell activation.
- 1. 1. The thermoregulatory responses to manipulations of photoperiod in wood mice (Apodemus sylvaticus), which were drawn from a population living at a high latitude (57°N) were studied.
- 2. 2. Mice captured in spring were acclimated to two different photoperiod regimes 16L:8D and 8L:16D at a constant ambient temperature of 24°C, for 3 weeks.
- 3. 3. Daily rhythms of body temperature, oxygen consumption and body temperature at various ambient temperatures, nonshivering thermogenesis (the response to a noradrenaline injection) and body mass were measured. Minimal overall thermal conductance was calculated for both groups.
- 4. 4. Acclimation to long photophase increased the thermoregulatory abilities at relatively high ambient temperatures while that of long-scotophase increased thermoregulatory abilities at low ambient temperatures.
- 5. 5. Changes in photoperiod may therefore be used as cues for seasonal acclimatization of thermoregulatory mechanisms in this population of wood mice.
- 1. 1. Results of a study on lethal and sublethal responses of different size groups of the tropical brown mussel, Perna indica, when exposed to different temperatures are presented.
- 2. 2. Exposure to a temperature of 38°C showed 100% mortality of 9 mm size group mussels in 120 min.
- 3. 3. Mortality was dependent on age (size) of the mussels, young ones being more susceptible than older ones.
- 4. 4. All size groups showed a progressive reduction in physiological activities such as filtration rate, foot activity and byssus thread production when temperature was increased from 30°C.
- 5. 5. This study suggests that heat treatment is an attractive alternative to chlorination for mussel fouling control in tropical power stations.
- 1. 1. Myosin and its subfragment-1 (Sl) from carp acclimated to 10°C showed higher actin-activated Mg2+-ATPase activity and lower thermostability than their counterparts from carp acclimated to 30°C. Accordingly, filament velocity for the 10°C-acclimated carp myosin was higher at any measuring temperatures from 3 to 23°C than that for the 30°C-acclimated carp myosin.
- 2. 2. Three types of cDNA clones encoding myosin heavy chains were isolated from thermally acclimated carp. The 10 and 30°C types were predominating in carp acclimated to 10 and 30°C, respectively, whereas the intermediate type was found as a minor component in the 10°C-acclimated carp with an intermediate feature in both DNA nucleotide and deduced amino acid sequences between those of the 10 and 30°C types.
- 3. 3. The three types of myosin rod all showed a typical coiled-coil structure of -helices. DSC scans demonstrated that myosin rod prepared from carp acclimated to 10°C had a lower thermostability than that from carp acclimated to 30°C, showing that low thermostability in cold-acclimated carp myosin prevails over the entire molecule.
- 4. 4. cDNA clones encoding myosin alkali light chains were isolated from thermally acclimated carp. Northern blot analysis showed that the ratios of LC3/LC1 mRNAs were significantly higher (3.92) in the 30°C- than 10°C-acclimated (3.10) carp.
- 1. 1. Effects of 1-day deprivation from water, food or both on responses of mice pial microvessels to local cerebral hyperthermia were compared to fed mice and with access to water.
- 2. 2. A set of protocol for all groups was followed, which involved microsurgery and utilized intravital videomicroscopy. Core body temperature was kept at 37°C and hyperthermic exposure was applied locally by heating the artificial cerebrospinal fluid irrigating the brain surface, at 45°C for 25 min.
- 3. 3. Monitored responses included intravascular thrombo-embolic events and changes in microvascular diameter. Dehydration and food deprivation shortened the time for appearance of passing emboli and lowered the thermal threshold at which thrombo-embolic processes occur.
- 4. 4. Arteriolar constriction was observed in all groups, coupled with full occlusion.
- 5. 5. Data of this study revealed that dehydration and food deprivation exacerbate pial microcirculatory responses to local hyperthermia.
- (1)Final temperature preferendum of juvenile (0.9–1.9 g) and adult (5.2–12.5 g) angelfish Pterophyllum scalare were determined with acute and gravitation methods. The final preferenda were similar, independent of the method and development stage (29.0–31.1°C).
- (2)The critical thermal maxima (CTMax) for juveniles were 36.9°C, 37.6°C, 40.6°C, 40.8°C and for adults 38.4°C, 38.6°C, 41.0°C, 42.1°C. Adult angelfish CTMax was slightly higher than in juveniles (1°C; P<0.05); the endpoint of CTMax was the onset of spasms.
- (3)The acclimation response ratio for both stages had an interval of 0.33–0.44; these values are in agreement with results for subtropical and tropical fishes.
- (4)Therefore it is recommended that angelfish cultivation should be consistent with temperatures that do not change abruptly throughout the year and temperature maximum does not exceed 30°C.
- 1. 1. Neural activity was recorded in hippocampal slices from deep hibernating Yakut ground squirrels and in hippocampal and septal slices from non-hibernating animals.
- 2. 2. Slices were placed immediately after preparation in hypothermic conditions (3–4°C). Their activity was tested under standard conditions at 31°C in the incubation chamber. Some of the prepared slices were tested after maintenance in hypothermia for 2 or 24 h.
- 3. 3. In the hippocampal slices of hibernating ground squirrels, neural activity was present, irrespective of the period in hypothermia.
- 4. 4. Slices from guinea-pigs and hamsters did not possess neural activity after either 2 or 24 h of hypothermic treatment.
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- 1. 1. Various devices have been used to estimate the equilibrium body temperature of ectotherms occupying natural environments. We tested the accuracy of such devices under a range of conditions.
- 2. 2. We measured body temperatures of lizards (Sceloporus magister) exposed to short-wave radiation under varying convective conditions and compared these to temperatures of hollow metal casts duplicating the animal's shape and reflectivity, as well as to the temperatures of cylinders similar to those used by other workers.
- 3. 3. Casts equilibrated within 2–3°C of live animals, yielding errors of 14–37% of the radiation-produced elevation of body temperature.
- 4. 4. Various cylinders differed from animal body temperature more than lizard casts did, producing errors equally 33–53% of the radiation-produced elevation.
- 5. 5. It is imperative that workers using operative-temperature thermometers experimentally confirm the adequacy of the devices they use for the range of conditions encountered within a specific analysis.
- 1. 1. Lipid peroxidation, superoxide dismutase (SOD) activity, ascorbic acid (AsA) and individual phospholipid contents in liver of fresh water cat fish Heteropneustes fossilis were measured after exposure to different temperatures (25, 27, 32, 37°C) at various times (1–4 h).
- 2. 2. Lipid peroxidation and superoxide dismutase activity were significantly increased with increases in temperature at various times.
- 3. 3. Ascorbic acid content was depleted when temperature was increased.
- 4. 4. After temperature exposure, phosphatidyl inositol was increased while phosphatidyl choline, phosphatidyl serine and phosphatidyl ethanolamine were depleted. Phosphatidic acid level did not change.
- 5. 5. The findings indicated an increased oxidative stress in liver following increases in temperature at various times. Concurrent with the increase in lipid peroxidation, superoxide dismutase activity and ascorbic acid from the liver of fish varied. It is suggested that depletion of major individual phospholipids following temperature exposure could be due to superoxide created oxidative stress in the liver.
- 1. 1. Lymphocytes from sows maintained in a constant hot environment (32°C) showed reduced proliferative responses to mitogens PHA (P < 0.02) and PWM (P < 0.01) in comparison to sown maintained in a constant cool environment (21°C). In the piglets the hot constant temperature slightly reduced (P < 0.05) proliferative responses of lymphocytes to PHA.
- 2. 2. No significant effects of a cycling hot environment (27–32°C) were found for any proliferative responses of lymphocytes from sows and litters.
- 3. 3. In the constant hot environment, serum cortisol concentrations were significantly reduced in the sows (P < 0.0001) while no differences in serum cortisol concentrations were found in the litters.
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1. 1.|Neuronal activity in slices of the preoptic and anterior hypothalamic area of guinea-pigs during slow low-amplitude temperature changes analogous to temperature changes in the brain of endothermic animals, was extracellularly recorded.
2. 2.|42% of neurons showed threshold temperature responses. The threshold of response averaged 37.4°C for warm-sensitive neurons during warming and 37.0°C for cold-sensitive neurons during cooling.
3. 3.|The thresholds differed, on average, by 0.1°C in the same neuron at repeated temperature changes.
4. 4.|With temperatures 0.8°C above threshold on average (0.2°C in some units) neuronal activity reached a new high level that did not change either during a further exceeding of the threshold or prolonged maintenance of suprathreshold temperature.
5. 5.|The characteristics of the threshold temperature response of a hypothalamic neuron meet the criteria of thermoinduced structural rearrangements of cell membranes, caused by phase transitions of lipids, changes in protein conformation and cytoskeletal activity.
- 1. 1. The thermal characteristics of Petrodromus tetradactylus, Elephantulus intufi and E. brachyrhynchus were investigated and compared with other elephant-shrews that occur in the southern African subregion.
- 2. 2. E. intufi and E. brachyrhynchus appear to have lower than expected basal metabolic rates (1.1185 ± 0.1623 and 0.9649 ± 0.1638 ml O2 g−1 h−1, respectively) and high, narrow thermoneutral zones, similar to other elephant-shrews investigated previously. In contrast P. tetradactylus has a basal metabolic rate (0.871 ± 0.027 ml O2 g−1 h−1) close to expected for body mass, and a broad, low thermoneutral zone.
- 3. 3. The thermal biology of macroscelids is discussed in terms of their distribution, microhabitat and body size.
1. 1.|The effect of thyroidectomy at 12 days of age on weight gain, and on heat production and thermoregulatory ability of 4- to 5-week-old chickens at temperatures within and below the thermo-neutral zone was investigated.
2. 2.|Despit the absence of thyroid tissue, as demonstrated with radioiodine, a small amount of thyroxine was found in the plasma of some thyroidectomized (TX) birds.
3. 3.|Thyroidectomy depressed weight gain; pair-fed controls grew significantly faster than TX birds.
4. 4.|Resting heat production of TX birds at thermoneutrality (30°C) was depressed by 18% (P < 0.001) and body temperature by 0.4°C (P < 0.001).
5. 5.|At 12°C heat production of TX birds was similar to that of controls but the body temperature of TX birds was 0.7°C lower (P < 0.001).
6. 6.|Thyroidectomized birds were unable to regulate body temperature at 5°C even if thyroxine was provided on the day before and at the time of cold-exposure. This inability to thermoregulate was probably due to inadequate insulation and poor nutritional status.
Author Keywords: Gallus domesticus; thyroidectomy; thyroxine; heat production; thermoregulation; body temperature 相似文献