Thermoregulation during exercise in relation to sex and age

The thermoregulatory responses to 1 h exercise of 14 male (age range 18--65 year) and 7 female (age range 18--46 year) athletes and 4 (3 male and 1 female) non-athletic subjects have been investigated in a moderate environment (Tdb = 21 degrees C, Twb = 15 degrees C and rh less than 50%) and analysed in relation to age, sex, and maximum aerobic power output (VO2max). The maximal sweat loss (Msw max) under the given conditions was closely related (r = + 0.90) to VO2max and for a given relative work load (%VO2max), rectal (Tre) and mean skin (Tsk) temperatures was the same in all subjects. Sweat loss (Msw) was linearly related to total heat production (H) and to peripheral tissue heat conductance (K) and if expressed in relative terms (%Mswmax) was linearly related to Tre. For a given Tre relative sweat rate was identical in the groups studied. From these results it would seem that during exercise Tre rises to meet the requirements of heat dissipation by establishing a thermal gradient from core to skin and stimulating sweating in proportion to maximal capacity of the system. Thus provided the thermal responses to work were standardised using the appropriate physiological variables, there was no evidence to be found for differences in thermoregulatory function which could be ascribed to sex or age.     

Sister-chromatid exchange in childhood in relation to age and sex

Small children have been found to have a lower SCE/cell than adults and in recent reports females have had higher SCEs/cell than males. We here describe the relationship between SCE/cell and age and sex in 46 girls and 39 boys with an age range of 1.4-19.2 years and 2.6-18.7 years, respectively. For the calculation a transformation y = (sum SCE)1/2 + (sum SCE + 1)1/2 was used. The best fit to our material was represented by the equation y = b0 + b1 X log age. A common slope (b1) could be used for the boys and girls. This slope was significantly different from zero (P less than 0.0005). The levels of the regression lines for the two sexes were different (P = 0.0006). The girls had a 0.55-0.7 higher SCE/cell than the boys, depending on age. The following equations were found: Girls: y = 22.49 + 6.53 X log age. Boys: y = 21.11 + 6.53 X log age. By this model 43% of the variation in y could be explained. As a consequence of the result it is absolutely essential, when planning studies of children, to use age-matched groups to decrease the variability of the test system.     

Usual meal times in relation to age, sex, work activity and morningness-eveningness

Meal-timing is considered an important socio-environmental synchronizer of circadian rhythms and influences human metabolism; the temporal distribution of food intake has also an influence on human performance. In these last years, in industrialized countries, remarkable changes, both in quality and quantity and in timing, have been determined in eating behavior brought about by changes in social and working organization. In this study the authors have verified the usual mealtimes during working and free-days in a population of 670 city-dwellers, 404 men and 266 women, aged between 17 and 60, including students, housewives, clerks, artisans, tradesmen and industrial workers. The results can be summarized as follows: a. the times of the two main meals show a high stability, both in working and in free-days, at about 1230 for lunch and 1915 for dinner, with a higher variability for the dinner-time; b. there are no relevant differences between men and women; c. there is a progressive advance of the breakfast-time (together with sleeping and waking times) with oncoming age; d. industrial workers advance the breakfast-time, on work days, compared to housewives, clerks, artisans and tradesmen, while the latter delay dinner-time as compared to the others; e. shiftwork breaks up the usual timetables interfering with at least one of the main meals, according to the different shifts (morning, afternoon, night); f. morning types anticipate meal and sleeping times in comparison to evening types, both while working and, above all, on free-days.     

Morphology of the Hooded crow Corvus corone cornix in relation to age, sex and latitude

The morphological variation of the Hooded crow at Trondheim, Norway, was studied, based on a sample of 734 birds collected during a six year period. Mouth colour, plumage colour, skull thickness and feather length were found to be characters which could readily be used to separate juveniles from adults. Females aged 15–19 months had a thinner skull roof than older female birds. Low coefficients of variation were found for the lengths of the third primary and of the tail feathers. A discriminant analysis showed that of the various body dimensions studied bill height and bill length distinguished the sexes most precisely. A high degree of sexual dimorphism was also found to exist in body weight and in the thickness of the skull roof.
Those body structures which develop at about the same stage during the juvenile growth period were associated with the same principal component, viz. the lengths of bony structures, parts that develop early on in life, were intercorrelated (wing bones, tarsus, bill basis and the width of foramen magnum). The lengths of the primaries and of tail feathers were also intercorrelated, structures which develop late.
The mean body weight of the Hooded crow population studied in Norway was intermediate between that of the Hooded crow in Germany and of the Carrion and Hooded crows in England and Scotland. No such differences were found in wing length. Norwegian Hooded crows have shorter tails than German ones, but their bills are much larger, in particular for the females. Therefore, the degree of sexual dimorphism in bill size seems to be reduced at high latitudes.