Histological and Morphometrical Studies on the Rat Nipple during the Reproductive Cycle.

Toyoshima, Yuka; Ohsako, Seiichiroh; Matsumoto, Mitsuharu; Hidaka, Sachinobu; Nishinakagawa, Hayao

doi:10.1538/expanim.47.29

Cited by 12 publications

(11 citation statements)

References 13 publications

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“…In our previous study, we confirmed that the rat nipple begins to increase considerably in size during the second half of pregnancy [16]. In the present study, we observed similar morphological and histological changes in the mouse nipple.…”

Section: Discussionsupporting

confidence: 91%

“…In reproductive biology, the nipple is usually considered to be a part of the mammary apparatus [7,10,11,18]. Previously, we described histometric changes in the rat nipple as it develops into the structure used for nursing during the reproductive cycle [16]. A marked increase in size of the nipple was observed during the second half (days 15 and 20) of pregnancy and the size was the maximal during lactation.…”

Section: Animalsmentioning

confidence: 99%

“…length, width of the middle portion [16], and the areas of epidermis, dermis and epithelium of the lactiferous sinus were measured with an image analyzer (Nikon COSMOZONE Is, Tokyo). All cells observed in each part of the nipple were counted.…”

Section: Animalsmentioning

confidence: 99%

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Histological Changes in Mouse Nipple Tissue during the Reproductive Cycle.

Toyoshima

Ohsako

Nagano

et al. 1998

The Journal of Veterinary Medical Science

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ABSTRACT. To obtain detailed information about the histological changes occurring in the mouse nipple during the reproductive cycle, we examined and quantified the S-phase of cell by immunohistochemical staining with bromodeoxyuridine (BrdU), and analysed histologically the subepithelial fibrous elements. The nipple markedly increased in size dramatically on days 15-18 of pregnancy. The densities of cells in the epidermis and dermis were very high during the early stages of pregnancy but low during lactation. In the epithelium of the lactiferous sinus, the densities of cells did not differ significantly among stages. The BrdU antibody labeling revealed a number of BrdUpositive cells in the basal layer of the epidermis and epithelium of the lactiferous sinus. The ratios of BrdU-positive cells to total cells in the epidermis and the epithelium of the lactiferous sinus were highest on day 15 and day 10 of pregnancy, respectively. After lactation, however, the ratios were similar to those in the virgin stage. No significant differences were detected in the dermis among all stages. The number of collagen and elastic fibers increased during lactation. These results indicate that cells in the epidermis and lactiferous sinus proliferated actively from day 10 to day 15 of pregnancy. The observation that cellular proliferation in the epithelial system of the nipple was stimulated at the early stage of pregnancy, while the dermis has two growth phases, with cellular proliferation during pregnancy and an increase in extracellular matrix during lacation, suggests that these two phenomena might be regulated by different factors. MATERIALS AND METHODS Animals:The Jcl-ICR strain mice used in this study were bred and maintained as a closed colony in our laboratory. They were all housed in an environmentally controlled airconditioned room (temperature: 23 ± 3°C, humidity: 60 ± 10%, light-dark cycle: 12-12 hr) and given a commercial diet (MF, Oriental Yeast Co., Tokyo) and tap water ad libitum. A total of 33 female mice (80-day-old) were mated with males of the same age, and the day when a vaginal plug was found was determined as day 0 of pregnancy. They were divided into 11 groups; i. e. virgin, days 5, 10, 15 and 18 of pregnancy, days 5, 10, 15 and 20 of lactation, days 5 and 10 of post-weaning. Each group consisted of 3 mice. At the lactating stage, each dam was housed with her 10 pups and separated from the young for 30 min before sampling.Administration of BrdU: BrdU (50 mg/kg b.w., Sigma, MO) was injected intraperitoneally into female mice at each reproductive stage. One hour after the injection, the nipples were excised under sodium pentobarbital anesthesia and fixed with Bouin's solution for 2 hr at room temperature. Mice have 3 pairs of thoracic and 2 pairs of abdominoinguinal nipples, and the first left abdomino-inguinal nipple was examined. The specimens were routinely embedded in paraffin and longitudinal sections 3 µm thick were cut.Immunohistochemical staining: To detect the S-phase cells, BrdU administration and an...

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Section: Discussionsupporting

confidence: 91%

Section: Animalsmentioning

confidence: 99%

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Histological Changes in Mouse Nipple Tissue during the Reproductive Cycle.

Toyoshima

Ohsako

Nagano

et al. 1998

The Journal of Veterinary Medical Science

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“…Serial sections were longitudinally or transversally cut at 6 µm and stained with haematoxylineosin (HE). An Olympus BH2 microscope was used to obtain photographs of the prepared tissues samples [19].…”

Section: Histological Analysismentioning

confidence: 99%

Inhibition of DMBA Induced Rat Mammary Duct Damage by Novel Synthetic Organoselenium Compounds

et al. 2006

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“…During pregnancy and lactation, they further increase in diameter, and the epidermis becomes more pigmented (Neifert et al, 1990; Rohn, 1989). During pregnancy and lactation, the nipple of both rats and mice lengthens and increases in diameter ~3-fold (Toyoshima et al, 1998a; Toyoshima et al, 1998b); however, in these species the presence of an areola has not been noted.…”

Section: Introductionmentioning

confidence: 99%

Expansion of specialized epidermis induced by hormonal state and mechanical strain

Easwaran

Offutt

et al. 2015

Mechanisms of Development

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In mammals, some sites of specialized skin such as the palms, soles, and lips grow proportionally with the animal. However, other types of specialized skin such as the nipple and anal/genital region are dramatically altered with changes of reproductive status. The specific cell types that mediate the growth of these sites have not been identified. In the mouse, we observed a dramatic expansion of the specialized epidermis of the nipple, coupled to changes in connective tissue and hair shaft density, which we designate as areola formation. During this process thymidine analog uptake was elevated in the epidermis and hair follicles. Although there were no changes in connective tissue cell proliferation, we did observe an altered expression of extracellular matrix genes. In addition, the fibroblasts of the virgin nipple areola and region showed increased transcript and protein levels for estrogen, progesterone, relaxin, and oxytocin relative to those of ventral skin. To determine the role of pregnancy, lactation hormonal milieu, and localized mechanical strain on areola formation, we created models that separated these stimuli and evaluated changes in gross structure, proliferation and protein expression. While modest increases of epidermal proliferation and remodeling of connective tissue occurred as a result of individual stimuli, areola formation required exposure to pregnancy hormones, as well as mechanical strain.

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Histological and Morphometrical Studies on the Rat Nipple during the Reproductive Cycle.

Cited by 12 publications

References 13 publications

Histological Changes in Mouse Nipple Tissue during the Reproductive Cycle.

Histological Changes in Mouse Nipple Tissue during the Reproductive Cycle.

Inhibition of DMBA Induced Rat Mammary Duct Damage by Novel Synthetic Organoselenium Compounds

Expansion of specialized epidermis induced by hormonal state and mechanical strain

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