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Biomedical subjects

J Bittel

Publications and source records attributed to J Bittel.

52 records · Page 3Linked to original sources
PubMed1990

[Circadian analysis of sleep, rectal temperature and immunological and endocrinological variables in sleeping sickness: preliminary study].

A multidisciplinary study was conducted in 8 patients with neurological Human African Trypanosomiasis. The sleep-wake cycle followed an ultradian pattern which was more pronounced in patients with more severe symptoms. The EEG trace was consistently interrupted by numerous cyclic activation patterns with K complexes, rapid low amplitude elements and slow high voltage elements. Circadian rhythmicity was also disturbed in other physiological (rectal temperature), immunological (interleukins) or hormonal (cortisol, prolactin) variables, the disturbance being greater in severely hit patients.

Adolescent↗
PubMed1988

Seasonal changes in circadian rhythms of body temperatures in humans living in a dry tropical climate.

Seven volunteers (3 females and 4 males; 3 Caucasians and 4 Africans) participated in two 24 h sessions during the cool dry (CD) and the hot dry (HD) seasons of the sahelian tropical climate. Body temperatures were taken on portable cassette recorders for 24 h. Rectal (Tre) and mean skin (Tsk) temperatures decreased in the HD compared to the CD conditions, meeting one of the criteria for adaptation to heat. No ethnic differences in thermal responses were found. Males and females differed in their body temperature rhythms and in their reactions to heat. Body temperatures were higher in females than in males. Males reacted to heat with a decrease in Tre, without change in the Tre-Tsk gradient. Females showed a decrease in both Tre and Tsk, more marked for Tsk, with an increase in the Tre-Tsk gradient. It was concluded that males showed seasonal acclimatization to heat via a decrease in metabolism confirmed by a decrease in plasma levels of thyroid stimulating hormone (TSH) in the HD condition. Females showed a mixed metabolic and thermolytic type of acclimatization, with an absence of variation in plasma TSH levels. In conclusion, the steady rise in temperature between the CD and HD conditions was sufficient to trigger an acclimatization to heat similar in Caucasian and African subjects, although exposure to the external climate differed widely.

Acclimatization↗
PubMed1988

Body temperature and plasma prolactin and norepinephrine relationships during exercise in a warm environment: effect of dehydration.

The effects of euhydration (Eh) and light (Dh1) and moderate (Dh2) dehydrations on plasma prolactin (PRL) levels were studied in 5 young male volunteers at rest and during exercise to exhaustion (50% of VO2max) in a warm environment (Tdb = 35 degrees C, rh = 20-30%). Light and moderate dehydrations (loss of 1.1 and 1.8% body respectively) were obtained before exercise by controlled hyperthermia. Compared to Eh, time for exhaustion was reduced in Dh1 and Dh2 (p less than 0.01) and rectal temperature (Tre) rose faster in Dh2 (p less than 0.05). Both venous plasma PRL and norepinephrine (NE) increased during exercise at any hydration level (p less than 0.05). Plasma PRL reached higher values after 40 and 60 min in Dh2 and Dh1 (p less than 0.05). Plasma NE values were higher in Dh2 at rest and at the 40th min during exercise (p less than 0.05). Plasma PRL was linearly correlated to Tre and plasma NE (p less than 0.001) but unrelated to plasma volume variation and osmolality. Our results provide further evidence for the major effect of body temperature in exercise-induced PRL changes. Moreover, the plasma PRL-NE relationship suggests that these changes may result from central noradrenergic activation.

Adult↗
PubMed1983

[Confinement].

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Air Pollution↗
PubMed1979

Thermogenesis and thermolysis during sleeping and waking in the rat.

Thermogenesis (VO2), sensible heat loss and subcutaneous back temperature were recorded simultaneously during sleeping and waking in both intact and depilated rats at Ra ranging from 21--28 degrees C. VO2 increased during wakefulness (W), decreased and plateaued during slow wave sleep (SWS) and then decreased 10% with each paradoxical sleep (PS) phase. Sensible heat loss, which represented about 90% of the heat production, increased and plateaued during SWS, decreased in W and generally rose abruptly (+40%) during PS. After removal of the fur the mean levels of VO2 and sensible heat loss were increased by 20--50% and returned to normal values within two weeks, although their variations related to stages of sleep were unchanged. These results concerning thermogenesis and thermolysis are in agreement with the variations of body temperature (brain excluded) during sleeping and waking.

Animals↗
PubMed1979

Thermal strain resulting from protective clothing of an armored vehicle crew in warm conditions.

The purpose of the study is to define a method of evaluation of physiological strain resulting from protective garments worn in warm conditions by the armored vehicle crew. A technique is developed evaluating evaporative transfer through clothing by continuous weighing of the active man (accuracy +/- 3/g). An index is defined (Iw) as the ratio of steady-state evaporating rate in clothed conditions to steady-state evaporation of nude subject in the same conditions of work and heat stress. The Iw index is significantly related to physiological strain determined by increased body heat content and reduced tolerance time. The results are compared to other previous findings concerning evaporative transfer through clothing and physiological strain indexes. The technique shows that evaporation through heavy clothing is not negligible. It is suggested that usual static measurements using physical models underestimate the evaporative heat transfer through clothing layers.

Body Temperature↗
PubMed1977

Variations in evaporation and body temperatures during sleep in man.

The thermal balance in man was investigated during nocturnal sleep in neutral and warm environments (from 32 to 39.5 degrees C, 45%rh). Changes of body temperatures and skin evaporation were continuously monitored throughout the whole night. In neutral conditions (32 and 34 degrees C) body temperature and skin evaporation decreased during the night, following the circadian rhythm deltaT sk = -0.34 degrees C; deltaT re = -0.52 degrees C;deltaE = -12 W-m-2. In warm conditions, body temperatures and evaporation remained steady. Marked fluctuations of body temperatures and evaporation occurred synchronously with the rapid eye movement (REM) periods. Each REM period induced phasic increase of Tsk reaching +2 degrees C in some cases, with a cessation of evaporation. Tre showed upward and downward rhythmical waves synchronously with REM sleep occurrence. The nocturnal variations of thermal balance were characterized by two rhythms: a basal circadian rhythm and superimposed on it a rhythm conditioned by occurrence of REM sleep every 80-90 min. The phasic changes of body temperatures and evaporation only appeared with REM's. The results suggest that the nervous integrative function conditioning the patterns of sleep, conditions also the phasic cyclic changes of thermoregulatory function.

Adult↗
PubMed1977

Comparison of indirect calorimetry and direct heat flow discs results in measuring R+C heat loss in burned patients.

This study was carried out on 17 burned patients. Metabolic heat production, rectal and skin temperatures, and heat exchanges by R+C were measured. It was found that R+C heat loss takes into account 60 to 80% of the increased metabolic heat production. Two methods were used to measure R+C heat loss: calculation by indirect calorimetry and direct measurements by using heat flow discs. The direct relationship which exists between the results of these two methods showed the reliability of the use of heat flow discs for measuring R+C heat loss. This fast-responding techniques may allow the elaboration of a thermal setting system which could modulate ambient air temperature, thus limiting exagerated heat loss due to the skin lesions.

Body Temperature Regulation↗
PubMed1975

Comparison of thermal exchanges in men and women under neutral and hot conditions.

1. The thermoregulatory responses in unacclimatized men and women were analysed and compared by means of standard heat exposure tests which allowed evaporative losses, body temperatures, heat storage and the complete thermal balance to be continuously recorded in all subjects. 2. The most pronounced differences were observed in delay before onset of sweating. Sweating always occurred faster with lower body temperatures in men than in women. The period immediately following ovulation was characterized by an increase in onset delay and a decrease in the sensitivity in sweating response compared with the pre-ovulation period. 3. The evaporative rate in the steady state did not change significantly in the post-ovulation period and was found to be higher in men who consequently had lower mean skin temperatures. Skin conductances, different under thermo-neutral conditions, were the same in men and women under hot conditions. 4. Women showed a more definite increase of body temperatures and heat storage than men due to delayed sweating and decreased sweating sensitivity. The body heat content in the steady state increased more markedly in women than in men. Furthermore, the highest heat storage values were found during the post-ovulation period. A high degree of correlation was found between body heat content and absolute onset delay. 5. The sweating kinetics and the transient phase just before the steady state of the thermal balance appeared to be decisive factors in the differentiation of the thermoregulatory behaviour in women before and after ovulation. Heat storage achieved during the transient phase and not made up by adequate evaporation seemed to be the cause of the large increase of body temperatures and heat content shown by women in hot environments.

Adult↗
PubMed1975

Changes of thermal balance induced by passive heating in resting man.

Heat acclimatization has been induced in 12 resting healthy men by 90-min exposure to 45C dry bulb and 24% relative humidity for 9 successive days. The most significant results ovserved were 1) increased sensitivity of sweating with marked quickening of sweat measured, 2) decreased rate of body heat storage associated with a lower rectal temperature at end of exposure, as follows: 14.07 plus or minus 1.58 Wtimeshtimeskg-1 before and 9.39 plus or minus 1.69 afterward for body heat storage; 37.55 plus or minus 0.15C before and 36.99 plus or minus 0.24C afterward for rectal temperature. In contrast, no significant changes were observed in the final sweat rates, mean skin temperatures, or the heat conductance between the body interior and skin surface. The quickness of the heat dissipation process caused by both increased sensitivity of sweating and lower internal body temperature is the major factor in achieving a thermal balance and a decreased body heat content after acclimatization.

Acclimatization↗