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排序方式: 共有459条查询结果,搜索用时 15 毫秒
1.
Olgierd Pucilowski W. Danysz D.H. Overstreet A.H. Rezvani B. Eichelman D.S. Janowsky 《Brain research bulletin》1991,26(4):621-625
The Flinders Sensitive Line (FSL) of rats has been selectively bred to have increased sensitivity to cholinergic agonists. However, these rats exhibit altered responsiveness to a number of noncholinergic agents, such as apomorphine, buspirone and ethanol. This study compared the FSL and control Flinders Resistant Line (FRL) rats in terms of their hyperthermic response to the phencyclidine (PCP) receptor agonist, MK-801 (0.2 mg/kg SC) and their MK-801 binding characteristics. We have found that FSL rats react with a delayed hyperthermia, having a significantly lower hyperthermia for the first 120 min of observation. Thereafter the response does not differ in FSL and FRL rats. Both groups had similar affinities and numbers of [3H]MK-801 binding sites in the hippocampus/cerebral cortex. Pretreatment with scopolamine (1 mg/kg SC) failed to affect MK-801-induced hyperthermia in either line of rats. These findings suggest that selective breeding of FSL rats attenuated the secondary mechanisms involved in the PCP receptor-mediated hyperthermic response. However, by itself cholinergic supersensitivity does not appear to be a major factor in the blunted responsiveness of FSL rats to MK-801. 相似文献
2.
G. Dewasmes B. Bothorel A. Hoeft V. Candas 《European journal of applied physiology》1993,66(6):542-546
Summary Thermoregulatory sweating [total body (m
sw,b), chest (m
sw,c) and thigh (m
sw,t) sweating], body temperatures [oesophageal (T
oes) and mean skin temperature (T
sk)] and heart rate were investigated in five sleep-deprived subjects (kept awake for 27 h) while exercising on a cycle (45 min at approximately 50% maximal oxygen consumption) in moderate heat (T
air andT
wall at 35° C. Them
sw,c andm
sw,t were measured under local thermal clamp (T
sk,1), set at 35.5° C. After sleep deprivation, neither the levels of body temperatures (T
oes,T
sk) nor the levels ofm
sw, b,m
sw, c orm
sw, t differed from control at rest or during exercise steady state. During the transient phase of exercise (whenT
sk andT
sk,1 were unvarying), them
sw, c andm
sw, t changes were positively correlated with those ofT
oes. The slopes of them
sw, c versusT
oes, orm
sw, t versusT
oes relationships remained unchanged between control and sleep-loss experiments. Thus the slopes of the local sweating versusT
oes, relationships (m
sw, c andm
sw, t sweating data pooled which reached 1.05 (SEM 0.14) mg·cm–2·min–1°C–1 and 1.14 (SEM 0.18) mg·cm–2·min–1·°C–1 before and after sleep deprivation) respectively did not differ. However, in our experiment, sleep deprivation significantly increased theT
oes threshold for the onset of bothm
sw, c andm
sw, t (+0.3° C,P<0.001). From our investigations it would seem that the delayed core temperature for sweating onset in sleep-deprived humans, while exercising moderately in the heat, is likely to have been due to alterations occurring at the central level. 相似文献
3.
Thermoregulatory heat-loss responses at high ambient temperatures were studied in intact cats and those with bilateral electrolytic lesions in the pontine tegmentum during wakefulness (W), slow-wave sleep (SWS), paradoxical sleep (PS) and PS without atonia induced by the lesions. Panting (respiratory rate 90/min) was present W, SWS, and in some cases, during PS. The percentage of the PS episodes with panting was directly related ambient temperature. In intact cats at 30 °C, panting occurred in 8% of the PS episodes; at 35 °C, in 52%, and at 40 °C, in 77%. The percentage of PS episodes with panting higher in the pontine-lesioned cats (90% at 35 °C), probably another indication of the altered thermoregulation of such animals. Thermoregulatory responses to heat load, and thermoregulation in general, have previously been shown to be suppressed in PS. Because hypothalamic thermosensitive neurons lack thermal responses during PS, the partial activation of heat-loss responses observed here may depend upon the function of extrahypothalamic brainstem areas. 相似文献
4.
Using radio-biotelemetry, the timecourse of recovery and sensitivity to ambient temperature (Ta) of the thermogenic response
of methylenedioxymethamphetamine (MDMA or “Ecstasy”) was examined. Ambient temperatures of 17 and 22°C produced very different
response profiles, with the lower temperature producing a hypothermic response to 10 and 15 mg/kg doses of MDMA, and the higher
temperature producing a profound hyperthermia to the same doses. Although the peak responses to the drug had subsided within
5 h of administration, residual effects, in the form of an elevation of body temperature during the “low” phase of the diurnal
cycle, were present for a further 48 h. Long-lasting disruption of the thermoregulatory system following a short series of
MDMA administrations (10 mg/kg once per day for 4 days) was shown by exposing the rats in the undrugged state to a thermoregulatory
challenge, consisting of 60-min exposure to a Ta of 30°C, at 1 week before, and at 4 weeks and 14 weeks after the drug administration.
MDMA-treated rats showed a prolonged hyperthermic response to the challenge at both post-drug intervals compared with fenfluramine-treated
rats and saline-treated controls. Thus, the results indicate both that MDMA’s thermogenic effects are more sensitive to Ta
than previously demonstrated, and that the serotonergic neurotoxicity of the drug may produce long-lasting changes in thermoregulatory
mechanisms.
Received: 7 December 1997/Final version: 23 January 1998 相似文献
5.
Summary The effects of ambient and hypothalamic temperatures were studied on the hyperthermic responses to prostaglandins E1 and E2 (PGE1 and PGE2) injected intraventricularly in the unanesthetized rabbit. Hyperthermic responses to PGE1 observed at different thermal environments were approximately equal in magnitude and time course. However, the prevailing ambient temperature influenced the thermoregulatory mechanisms by which the hyperthermia was achieved. In a hot environment, PGE1-hyperthermia was brought about by suppression of heat loss mechanism with little change in heat production. During cold exposure body temperature was raised mainly by an increase in heat production without a significant change in heat loss. PGEs-hyperthermias were attenuated by warming and enhanced by cooling the anterior hypothalamus. These changes in the hyperthermic responses to PGE1 and PGE2 are in contrast to those obtained with intraventricular injection of noradrenaline at different ambient temperatures and during hypothalamic heating and cooling. It is therefore unlikely that noradrenaline is involved in the hyperthermic responses to PGEs. On the other hand, the results support the view that prostaglandins may be mediators of pyrogen-induced fever. 相似文献
6.
William D. McArdle Michael M. Toner John R. Magel Robert J. Spinal Kent B. Pandolf 《European journal of applied physiology》1992,65(3):265-270
Summary The influence of exercise intensity on thermoregulation was studied in 8 men and 8 women volunteers during three levels of arm-leg exercise (level I: 700 ml oxygen (O2) · min–1; level II: 1250 ml O2 · min–1; level III: 1700 ml O2 · min–1 for 1 h in water at 20 and 28°C (T
w). For the men inT
w 28°C the rectal temperature (T
re) fell 0.79°C (P<0.05) during immersion in both rest and level-I exercise. With level-II exercise a drop inT
re of 0.54° C (P < 0.05) was noted, while at level-III exerciseT
re did not change from the pre-immersion value. AtT
w of 20°C,T
re fell throughout immersion with no significant difference in finalT
re observed between rest and any exercise level. For the women at rest atT
w 28°C,T
re fell 0.80°C (P<0.05) below the pre-immersion value. With the two more intense levels of exercise,T
re did not decrease during immersion. InT
w 20°C, the women maintained higherT
re (P<0.05) during level-II and level-III exercise compared to rest and exercise at level I. TheT
re responses were related to changes in tissue insulation (I
t) between rest and exercise with the largest reductions inI
t noted between rest and level-I exercise acrossT
w and gender. For men and women of similar percentage body fat, decreases inT
re were greater for the women at rest and level-I exercise inT
w 20°C (P< 0.05). With more intense exercise, the women maintained a higherT
re than the men, especially in the colder water. These findings indicate that exercise is not always effective in offsetting the decrease inI
t and facilitated heat loss in cool or cold water compared to rest. The factors of exercise intensity,T
W, body fat, and gender influence the thermoregulatory responses. 相似文献
7.
Kacin A Golja P Eiken O Tipton MJ Gorjanc J Mekjavic IB 《European journal of applied physiology》2005,95(2-3):213-220
The effect of graded ischaemia in the legs on the regulation of body temperature during steady-state exercise was investigated in seven healthy males. It was hypothesised that graded ischaemia in the working muscles increases heat storage within the muscles, which in turn potentiates sweat secretion during exercise. Blood perfusion in the working muscles was reduced by applying a supra-atmospheric pressure (+6.6 kPa) around the legs, which reduced maximal working capacity by 29%. Each subject conducted three separate test trials comprising 30 min of steady-state cycling in a supine position. Exercise with unrestricted blood flow (Control trial) was compared to ischaemic exercise conducted at an identical relative work rate (Relative trial), as well as at an identical absolute work rate (Absolute trial); the latter corresponding to a 20% increase in relative workload. The average (SD) increases in both the rectal and oesophageal temperatures during steady-state cycling was 0.3 (0.2)°C and did not significantly differ between the three trials. The increase in muscle temperature was similar in the Control (2.7 (0.3)°C) and Absolute (2.4 (0.7)°C) trials, but was substantially lower (P<0.01) in the Relative trial (1.4 (0.8)°C). Ischaemia potentiated (P<0.01) sweating on the forehead in the Absolute trial (24.2 (7.3) g m–2 min–1) compared to the Control trial (13.4 (6.2) g m–2 min–1), concomitant with an attenuated (P<0.05) vasodilatation in the skin during exercise. It is concluded that graded ischaemia in working muscles potentiates the exercise sweating response and attenuates vasodilatation in the skin initiated by increased core temperature, effects which may be attributed to an augmented muscle metaboreflex. 相似文献
8.
Shamsuddin AK Kuwahara T Oue A Nomura C Koga S Inoue Y Kondo N 《European journal of applied physiology》2005,94(4):442-447
The effect of skin temperature on the ion reabsorption capacity of sweat glands during exercise in humans is unknown. In this study, eight healthy subjects performed a 60-min cycling exercise at a constant intensity (60% VO2max) under moderate (25°C) and cool (15°C) ambient temperatures at a constant relative humidity of 40%. The sweating rate (SR), index of sweat ion concentration (ISIC) by using sweat conductivity, esophageal temperature (Tes), mean skin temperature, and heart rate (HR) were measured continuously under both ambient temperatures. The SR and ISIC were significantly lower at the cool ambient temperature versus the moderate temperature. There were no significant differences in the changes in HR and esophageal temperature between these ambient temperature conditions, while the mean skin temperature was significantly lower at the cool ambient temperature by almost 3°C (P<0.05). The slopes of the relationships between Tes and the SR and ISIC were significantly lower and the thresholds of these relationships were significantly higher at the cool ambient temperature (P<0.05). The ion reabsorption capacity of the sweat glands was significantly lower (P<0.05) in a cool environment (0.21±0.04 vs. 0.52±0.06 mg/cm2/min at 15 and 25°C, respectively) as evaluated using the relationships for SR and ISIC. The results suggest that the ion reabsorption capacity of the sweat glands is influenced by skin temperature during exercise in humans. 相似文献
9.
Mathematical Modeling of the Human Body During Water Replacement and Dehydration: Body Water Changes
A model of the human body that integrates the variables involved in temperature regulation and blood gas transport within the cardiovascular and respiratory systems is presented here. It expands upon previous work to describe the competition between skin and muscles when both require increased blood flows during exercise and/or heat stress. First, a detailed study of the control relations used to predict skin blood flow was undertaken. Four other control relations employed in the model were also examined and modified as indicated by empirical results found in literature. Internal responses to exercise and/or heat stress can affect both thermoregulation and the cardiorespiratory system. Dehydration was studied in addition to complete water replacement during similar environmental and exercise situations. Control relations for skin blood flow and evaporative heat loss were modified and a water balance was added to study how the loss of water through sweat can be limiting. Runoff from sweating as a function of relative humidity was introduced along with evaporation, and these results were compared to data to validate the model. © 2000 Biomedical Engineering Society.
PAC00: 8719Pp, 8719Uv, 8719Ff, 8710+e 相似文献
10.
Alla Zontak Samuel Sideman Oleg Verbitsky Rafael Beyar 《Annals of biomedical engineering》1998,26(6):988-993
Exercise has a noted effect on skin blood flow and temperature. We aimed to characterize the normal skin temperature response to exercise by thermographic imaging. A study was conducted on ten healthy and active subjects (age=25.8 ± 0.7 years) who were exposed to graded exercise for determination of maximal oxygen consumption (VO2 max), and subsequently to constant loads corresponding to 50%, 70%, and 90% of VO2 max. The skin temperature response during 20 min of constant load exercise is characterized by an initial descending limb, an ascending limb and a quasi-steady-state period. For 50% VO2 the temperature decrease rate was --0.0075±0.001°C/s during a time interval of 390 ±47 s and the temperature increase rate was 0.0055 ± 0.0031 °C/s during a time interval of 484 ±99 s. The level of load did not influence the temperature decrease and increase rates. In contrast, during graded load exercise, a continuous temperature decrease of --0.0049 ± 0.0032 °C/s was observed throughout the test. In summary, the thermographic skin response to exercise is characterized by a specific pattern which reflects the dynamic balance between hemodynamic and thermoregulatory processes. © 1998 Biomedical Engineering Society.
PAC98: 8722Pg, 8759Wc, 8745Dr, 0180+b, 8745Hw 相似文献