After preliminary adaptation of rats to heat (for 3 h daily at 35°C for 1 month) the amplitude of contractions of the isolated papillary muscles from the left ventricle at 28°C at high frequency was higher than in control animals. This difference persisted at 36°C and disappeared at 25°C. It is postulated that adaptation to heat leaves a definite structural imprint in heart muscle cells.Laboratory of Pathophysiology of the Heart, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Institute of Physiology and Experimental Pathology of the Arid Zone, Academy of Sciences of the Turkmenian USSR, Ashkhabad. (Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 10, pp. 1168–1170, October, 1976. 相似文献
In three factorial experiments, auditory vs visual vs tactile feedback, analog feedback vs analog feedback which was anchored, and sex, were varied to assess the effects of these variables on performance in short-term biofeedback training of heart rate reduction, hand temperature increase, and forehead muscle tension reduction. A total of 108 subjects served in the study. Moderate but reliable changes were found during the course of the training session for all three physiological responses. The ability to reduce heart rate in a single training session did not appear to be a function of any of the variables manipulated in this study, but rather could be attributed to adaptation. In both muscle tension and temperature training, however, there were significant interactions between sex and sensory modality of the feedback stimulus and, in the case of muscle tension training, between information content of the feedback signal and sex. The overall pattern of results indicated that performance during biofeedback training is a complicated function of sex and the type of signal used to provide feedback, and that this function is not constant across physiological response systems. 相似文献
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
The prediction of the mean skin temperature used for the Required Sweat Rate index was criticised for not being valid in
conditions with high radiation and high humidity. Based on a large database provided by 9 institutes, 1999 data points obtained
using steady-state conditions, from 1399 experiments and involving 377 male subjects, were used for the development of a new
prediction model. The observed mean skin temperatures ranged from 30.7 °C to 38.6 °C. Experimental conditions included air
temperatures (Ta) between 20 and 55 °C, mean radiant temperatures (Tr) up to 145 °C, partial vapour pressures (Pa) from 0.2 to 5.3 kPa, air velocities (va) between 0.1 and 2 m/s, and metabolic rates (M) from 102 to 620 W. Rectal temperature (Tre) was included in the models to increase the accuracy of prediction. Separate models were derived for nude (clothing insulation,
Icl, ≤0.2 clo, where 1 clo=0.155 m2 · °C · W−1, which is equivalent to the thermal insulation of clothing necessary to maintain a resting subject in comfort in a normally
ventilated room, air movement=10 cm/s, at a temperature of 21 °C and a humidity of less than 50%) and clothed (0.6 ≤ Icl ≤ 1.0 clo) subjects using a multiple linear regression technique with re-sampling (non-parametric bootstrap). The following
expressions were obtained for nude and clothed subjects, respectively: Tsk=7.19 + 0.064Ta + 0.061Tr + 0.198Pa− 0.348va + 0.616Tre and Tsk=12.17 + 0.020Ta + 0.044Tr + 0.194Pa − 0.253va + 0.0029M + 0.513Tre. For the nude and clothed subjects, 83.3% and 81.8%, respectively, of the predicted skin temperatures were within the range
of ±1 °C of the observed skin temperatures. It is concluded that the proposed models for the prediction of the mean skin temperature
are valid for a wide range of warm and hot ambient conditions in steady-state conditions, including those of high radiation
and high humidity.
Accepted: 7 February 2000 相似文献
Increased nasal air flow during exercise was examined as a possible heat loss avenue contributing to selective brain cooling in hyperthermic humans. On 2 separate days, eight subjects [mean (SE) age, 26.4 (1.2) years] exercised on a cycle ergometer in a warm room [28 (0.2)°C; 28 (5)% relative humidity] to induce a moderate level of hyperthermia. In one session the nostrils were physically dilatated [average dilatation 1.55 (0.17) times] and in the other they were not (control). Both sessions started with a 5-min resting period; then subjects pedaled at 60 W for 5 min, 100 W for 15 min, and 150 W for 20 min. During dilatation both tympanic temperature (Tty) and forehead skin blood flow, estimated by laser doppler velocimetry, were significantly lower than during the control exercise of 150 W. Rates of increase of (Tty) during the 100-W exercise were the same in both conditions; however, during the 150-W exercise with dilatated nostrils (Tty) increased at a rate significantly lower than during control [1.1 (0.3)°C·h–1 vs 1.5 (0.4)°C·h–1]. The change in the rate of increase of Tty between conditions was significantly correlated to the degree of nostril dilatation (r = –0.77, P = 0.02), suggesting that the lower (Tty) observed was due to nostril dilatation. Facial skin temperature was not significantly different between sessions. The results suggest that the nasal cavity may act as a heat exchanger in selective brain cooling of exercising humans. 相似文献
The purposes of the present study were to examine the response of the skin blood flux (SBF) in the paralyzed lower limbs of persons with spinal cord injury (PSCI) and to clarify the relationship between the SBF and core temperature during prolonged arm exercise. Eight male PSCI with lesions from T6 to L5 and six male control subjects (CS) participated in this study. The subjects rested for 60 min and then performed arm-cranking exercise at 20 W for 30 min at 25 °C. The tympanic membrane temperature (Tty) and SBF in the anterior thigh (SBFT) and in the posterior calf (SBFC) were continuously measured throughout the experiment. The SBFC did not change in either PSCI or CS during the experiment. The SBFT in four PSCI with high lesions (T6 to T12), remained unchanged during exercise. The SBFT in the other four PSCI with low lesions (T12 to L5, SBFT+) began to elevate markedly when the T t, exceeded a threshold temperature of 36.69 °C. The pattern of increase of SBFT in SBFT+ was similar to that in CS, although onset of the increase in SBFT was delayed and the peak of SBFT during exercise was significantly lower in comparison with the CS. We consider that these differences between the SBFT+ and CS were largely attributable to the lowerTty in the former group, which took a prolonged time to reach the threshold of 36.69 °C. 相似文献
The thermo‐adjustable hydrophilic/hydrophobic properties of AB, ABA and BAB block copolymers in which A is poly(methyl vinyl ether) (PMVE) and B is poly(isobutyl vinyl ether) (PIBVE) have been investigated. The block copolymers were prepared by “living” cationic polymerization using sequential addition of monomers. The polymerizations were carried out with the system acetal/trimethylsilyl iodide as initiator and ZnI2 as activator. The initiating system based on diethoxyethane leads to AB block copolymers whereas the initiating system based on tetramethoxypropane leads to ABA or BAB triblock copolymers. Well‐defined block copolymers of different composition with controlled molecular weights up to approx. 10 000 have been prepared. When IBVE is added to living PMVE, PIBVE‐blocks form only in the presence of an additional amount of ZnI2, which is attributed to the fact that part of the ZnI2 is inactive because of complex formation with PMVE. At room temperature, the combination of hydrophilic (PMVE) and hydrophobic (PIBVE) segments provides the copolymers with surfactant properties. Above the lower critical solution temperature (LCST) of PMVE, situated around 36 °C, the PMVE‐blocks become hydrophobic and the amphiphilic nature of the block copolymers is lost. The corresponding changes in hydrophilic/hydrophobic balance have been evaluated by investigation of the emulsifying properties of the block copolymers for water/decane mixtures as a function of the temperature. Below the LCST, the block copolymers have emulsifying properties similar to or better than those of the commercial PEO‐PPO block copolymers (Pluronic®). Either oil‐in‐water or water‐in‐oil emulsions can be obtained, depending on the polymer architecture and the water/decane volume ratio. The emulsifying properties are strongly reduced or completely lost above 40 °C. Emulsions obtained with a PMVE36‐b‐PIBVE54 block copolymer for a water/decane (v/v) ratio of 85/15 remained stable for more than six months.
50/50 and a 85/15 water/decane w/o emulsion (15 g/l) with the PMVE36‐b‐PIBVE54 block copolymer at 20 °C. 相似文献