Effects of starvation on the mammary tissues and vascular distribution of the mammary gland in mice
Nishinakagawa, H.; Suzuki, S.; Otsuka, J.
Bulletin of the Faculty of Agriculture, Kagoshima University 30: 79-86
The effects of starvation on the mammary gland, especially on mammary parenchyma, adipose tissue and vascular distributions, were investigated in virgin and lactating mice. In experiment [Ex] I, 90 day old female mice (102) weighing 30-32 g were sacrificed after the following periods of starvation: 1, 2, 3, 4 and 5 days. Ten intact mature female mice (ad lib fed) were sacrificed at the age of 90 days to serve as controls. In Ex II, 74 lactating mice weighing 43-50 g, separated from sucklings 12 days after parturition were given feed (Oriental's chow pellets) ad lib for 2 days prior to starvation. Thereafter, the animals were sacrificed after the following periods of starvation: 1, 2, 3, 4, 5 and 6 days, together with 30 intact mice (ad lib fed), serving as controls. All aniamls were provided with H2O ad lib. In Ex I, after 5 days of starvation the mean-value of body weight showed a distinguished decrease (about 9 g), and significant differences were observed between the body weights of the starved and the intact animals. The weights of the mammary glands and ovaries in mice starved for 5 days were .apprx. 1/3 and 1/2 times as weighty, respectively, as that of the intact female mice. In the mammary glands from mice starved for 1 day, the structures and vascularities were similar to those of 90 day old intact mice. After 2 days of starvation, the mammary gland showed a tendency to regress in a part of adipose tissues composed of large unilocular fat cells containing lipid droplets, and blood capillaries supplying these tissues were somewhat shrunken. By the 3rd day on conspicuous degeneration of the mammary parenchyma was noted, but the unilocular fat cells were diminished in amount and in size. The blood supply to the adipose tissues was more regressed than that of mice starved for 2 days. After 4 days of starvation, the mammary adipose tissues were composed of numerous gland-like cells because of lipid depletion, and the vascularities were markedly shrunken. In the mammary gland from mice starved for 5 days, the mammary areas were reduced in size, owing to the greater involution of fat cells and also to the partial regression of mammary buds and ducts. The vascularities of the mammary glands were low in density and markedly shrunken, in contrast to those seen in mice starved for 4 days. In the Ex II, the mean value of the body weight in lactating mice starved for 6 days decreased markedly (.apprx. 13 g), and the differences between the intact and the starved mice were statistically highly significant. At the same time, the weights of the mammary glands and ovaries were .apprx. 1/3 and 1/2 times as heavy, respectively, as that of intact mice. The structures of the mammary glands from mice starved for 1 day showed no differences in contrast to those of intact animals. After 2 days of starvation the alveoli showed a tendency to collapse, and the appearance of small unilocular fat cells was observed around the collapsed alveoli, but in fewer cases than those of intact animals. After 3 days of starvation, the alveoli showed an obvious collapse-irregularity, and although adipose tissue consisting of small unilocular and multilocular fat cells was observed to be more than that of mice starved for 2 days, the amount of adipose tissue was smaller than that in the intact mice. After 4 days of starvation, most alveoli had greatly collapsed and their lumina were no longer visible. Interstitial fat cells had completely disappeared. The vascular vessels distributed to the mammary glands were low in density and shrunken. After 5 and 6 days of starvation, the alveoli showed a great regression and reduction in the degenerating epithelial masses. The connective tissues were noted to have become richer around the ducts and lobules. With these regressive changes, the vascularities of mammary gland were generally regressed and the capillary plexuses of the ducts were partially disappeared. Starvation performed in the mature virgin stage may lead to the regression of adipose tissues and vascularity, and starvation performed in the l.