Nude mice are not bald but instead show an ‘abortive’ reduced hair growth on different sites of the integument. An albino (NMRI-nu) and a pigmented (C57BL/6-nu) strain of nude mice were examined as to whether the regional distribution pattern of this anagen hair proliferation is subject to the same ontogenetic development as in hairy mice. Hairy mice of both strains served as a comparison. Hair distribution was documented macroscopically by drawing and photography in a total of 415 mice of both sexes up to 421 days of age. Because of the pigmentation of the growing anagen hair follicles, the growth areas in the pigmented nude mice were distinctly visible whereas in the albino mice they were roughly recognisable from the boundaries of hair covering. The regional distribution of the ‘abortive’ anagen hair pattern in both nude strains corresponded to the wave-like course of the adult hair generations of hairy mice. As in older hairy mice, the hair cycle duration in nude mice was prolonged from an age of 121–180 days, the hair growth areas appeared reduced and less symmetrically orientated. Differences of up to 33% in body mass between the lighter nude and +/nu mice made ontogenetic comparison impossible so that all information is based on direct pattern or age comparison. The significance of experiments on the skin and hair follicles of nude mice is further increased if litters are examined comparatively and the temporal and spatial dimension of the follicle proliferation is considered more carefully than has been the case until now.

SummaryThe mouse inbred strain HLG has only recently been submitted for international registration. It has been widely used in radiological studies. Since these mice tend to become obese, they may be of interest for studies concerning fat metabolism. Therefore, the present ageing study examines the sex-specific development of body weight, body composition, adipocyte size as well as the organ weight of liver, heart and thigh muscles of the inbred strain HLG (54 males/53 virgin females) between day 40 and 360 of life.The body weight development showed a distinct sexual dimorphism, quickly increasing in the case of males but comparatively protracted in females until maturity. Significantly higher values for body and fat-free dry weight as well as body water were found in males of all ages. Body fat and adipocyte diameter were only higher in the 80 and 120 day-old males. Thus, the increase in female body weight resulted largely through a rise in body fat as additionally evidenced by the sex-specific correlation of characteristics. A 2-fold analysis of variance showed sex differences in the relative weights of liver and muscle, but not of the heart. A sex-specific close correlation was observed between body and liver weights in males until day 180. Correlations between body fat and other characteristics were only rarely found. Differences in coefficients of variation largely depended on the characteristics. A higher variability was also found for some characteristics in the youngest groups (40 days). A sex-specific difference was only seen in the case of body fat content for 60 day-old mice (female>male).

In 5 different mouse strains, we observed alopecic lesions most commonly in male breeding animals kept with C57BL females. Alopecic areas were located most frequently on the head, but were also found over the shoulders, the back and the pelvic regions. Observations gained through time-lapse photography indicate the cause is a slight increase in self-grooming and a dramatic increase in allogrooming by their female partners. The increased frequency of lesions of males kept with C57BL females suggests that the increased grooming activity may be genetically determined.

The design and application of a simple capsule administration tube for miniature capsules are described. Experiments with rats have shown that the tube is capable of depositing capsules at the distal end of the oesophagus. Regardless of the location of the capsule in the oesophagus, provided normal peristaltic action occurs, the capsule will have reached the stomach and discharged its contents within 10 min. After a short training period of 3-4 days the insertion of the tube does not appear to cause the rats undue discomfort, nor does it cause tissue damage. The procedure, which can be performed rapidly by 1 technician, is ideally suited for dispensing solid materials to fully conscious animals.

Spontaneous behavioral categories such as attack. submission. boxing. allogrooming, mounting. and anogenital control were investigated in nine groups of three rats each. At the same time. the number of wins in the runway test and the amount of time spent occupying access-to-water space were registered in competitive tests. Antagonistic behavior jattack and induction of submission) permitted no significant relationships to be drawn as to the results of the competitive tests. The competitive parameters. too. showed no correlation among themselves. In agreement with other authors. we reject the existence of an encompassing unidimensional rank order in rats on the basis of these results. Attack wins and induction of submission showed a positive correlation to one another as well as to relative thymus and testes weights. A high antagonistic activity was also correlated with low relative adrenal weight. large number of nuclei in the adrenal cortex. and wide tubuli seminiferi in the testes. As indicated by factor analysis. a significant decrease in body weight. low heart. thymus. liver. spleen. kidney. and testes weights. and high adrenal weight with decreased number of nuclei in the adrenal cortex were typical for rats with low aggressive rank positions. The influence of endocrine organs and diminished physical vitality in these low-ranking animals was also observed following nonsocial stress.