Thyroxine depression of compensatory hypertrophy of the thyroid gland in rats of different ages]

It was shown on hemithyroidectomized male rats (2--2.5, 8--10 and 14--16--month-old) that with the advance of age there occurred an increase in the inhibitory effect of the same (as per 100 g of body weight) dose of the exogenous thyroxine on the thyroid compensatory hypertrophy. It is supposed that the threshold of hypothalamo-pituitary-thyroid system to homeostatic inhibition decreased with ageing.     

Rosette-forming T cells in human peripheral blood at different ages

Rosette-forming T cells (RFC) were studied in 51 human volunteers, ranging in age from 16 to 69 yr. Subjects were divided in six groups, according to age (Table 1). The percentage of RFC was constant in Groups 2, 3, and 4 (20–49 yr) and slightly but significantly higher in Group 1. On the contrary, it dropped significantly in Groups 5 and 6. This drop in per cent of RFC is coincident with a drop of thymic function; it should be taken in account whenever RFC are studied as a clinical test.     

Mixing at young ages reduces fighting in unacquainted domestic pigs

Under normal farming practices, piglets from different litters are often mixed around the time of weaning, and a high incidence of fighting and minor injuries often occur. The aim of this experiment was to determine the effect of age on the incidence of fighting in piglets mixed before weaning, at different ages between 5 and 26 days. We found no significant relationship between age and the likelihood that a pair of piglets would fight during the first 75 min after mixing. However, the duration of the first fight observed increased from 101+/-38 s at 5 days to 621+/-278 s at 26 days, mainly because of higher levels of unretaliated harassment and resting during the bouts. Younger pigs also showed 80% fewer injuries from the fighting. The results suggest some potential welfare advantage to allowing litters to mix at younger ages.     

EB virus antibody at different ages

In relation to the study of infectious mononucleosis a survey of the prevalence of antibody to EB virus was made on the sera of persons of varying age from several different areas in England by the indirect immunofluorescence technique. About half those tested were found to have acquired antibody by the age of 4 years and there was a further significant increase in the proportion of those positive between the ages of 15 and 24 years. The finding of seroconversion in two patients who developed infectious mononucleosis provides further support for an association between EB virus and this condition.     

Health status of cloned cattle at different ages

The procedure of somatic cloning is associated with important losses during pregnancy and in the perinatal period, reducing the overall efficacy to less than 5% in most cases. A mean of 30% of the cloned calves die before reaching 6 months of age with a wide range of pathologies, including, for the most common, respiratory failure, abnormal kidney development, liver steatosis. Heart and liver weight in relation to body weight are also increased. Surviving animals, although mostly clinically normal, differ from controls obtained by artificial insemination (AI) within the first 1-2 months, to become undistinguishable from them thereafter. Hemoglobin concentrations, for instance, are lower, and leptin concentrations are elevated. In response to the lack of prospective studies addressing the health of adult clones, a long-term, 3-4-year study is currently being conducted to assess the health of mature bovine clones at INRA. Preliminary results over 1 year of study do not show any statistical difference between groups for hematological parameters.     

The temporal patterns of food intake and allelomimetic feeding by pigs of different ages

The feeding behaviour of 4 castrated boars was studied over 24 hours using a photoelectric cell and continuous recorder at 4 body-weight stages, viz. 20, 40, 60 and 80 kg. Two of the pigs were on continuous light, and 2 were on 8.5 h light and 15.5 h of darkness. The 2 pigs in each treatment were in adjacent stalls but well separated from the other pair and other pigs. There were no differences in total food consumption between the animals in the 2 treatments. Eating speed also did not differ between treatments; neither did it differ between body-weight stages when adjusted for body weight. The percentage of the total time devoted to feeding differed between body-weight stages but not between treatments. However, over the first 8-h period of the day, the pigs on the short day-length spent more time feeding, but body weight did not affect this measure. Meal intervals were determined by a logarithm survivorship curve analysis, and it was found that pigs on the long day-length had significantly more meals than the others. Body weight also affected the number of meals, with the youngest taking most. Furthermore, both pairs showed a significant degree of synchronized feeding.     

fMRI mapping of cortical centers following visual stimulation in postnatal pigs of different ages

Classical studies have demonstrated that the visual centers in primates consist of cortical areas V1, V2 and V4 and their branches. However, nothing is known about how these visual areas change in postnatal development. In the present studies, therefore, pigs aged 2, 4, and 6 months old, were stimulated visually with a colored checker board and the active sites in the cortex, cerebellum and brainstem recorded using functional magnetic resonance imaging (fMRI). In pigs aged 2 months old, visual stimulation induced an increase in activation of sites in the V2 and V4 cortical areas, as well as in the areas of the inferior aspect of the parietal and middle aspect of the temporal cortices, but not in the medial and caudal occipital cortex (V1 area). At 4 months old, the V1 area was also activated, and by 6 months old, an inferior sector in the prefrontal cortex was also activated. As the pigs aged, functional active sites were further demonstrated in the cerebellum and the brainstem, which probably had to do with action memory, and the control of the ocular muscles, respectively. It is concluded that the visual pathway of the pig mainly involves cortical areas that mature at 6 months of age.