Sexual differences in mammary morphology start to appear at the peripubertal stage, when allometric growth of the mammary gland manifests as a part of the overall pubertal developmental process Hovey et al. Mammary glands in immature male rats are similar to those seen in female immature rats, characterized by tubular epithelium and bud formation. The lumen structures in prepubertal males disappear during maturation as the production of gonadal steroid rises. The structures of mammary glands in mature male rats are distinctively different from both mature female glands and immature male glands.
Mature female rat mammary glands are characterized by scattered tubular ducts and distinct alveolar lumens that are lined by cuboidal epithelial cells; in contrast, the mature male mammary gland lacks such alveolar structures. Mammary glands in mature male rats are characterized by restricted glandular area and lobules of cellular clusters devoid of lumen.
Restricted glandular regions results in smaller size of the mammary gland compared to mature females. Within glandular structures, the male mammary gland contains contiguous epithelial cells in irregularly shaped lobular groups of epithelial cells Astwood et al.
Our previous You et al. These responses are distinct for GE, MXC, and their combination, suggesting additional pharmacological effects other than the estrogenicity of those compounds underlying these effects.
GE and MXC, when combined, produced a response pattern that differs from the effects caused by either compound alone. Such results argue for recognition that phytoestrogen has the potential to modulate biological responses to other endocrine-active compounds.
Thus, dietary GE should be considered as an important experimental parameter in pharmacological and toxicological studies. Because the treatment period spanned several life stages from early gestation to adult , much of the gene alterations observed in this study likely reflects cumulative and perhaps steady-state responses rather than immediate or transient changes. In the current model of male mammary response, ER activation by the test compounds is probably the major factor in the manifestation of steroid hormone-like effects of both GE and MXC.
On the other hand, neither alterations in the serum levels of steroids and other mammotrophic hormones nor changes in the levels of receptor protein in the mammary tissue were found to be associated with the observed responses.
Many of the gene expression changes detected by the microarray assay may represent nonspecific stress responses. Nonetheless, several observed changes in the gene and protein expression have shed important light on potential mechanisms.
IGF-1 plays a fundamental role in mammary gland development, as IGF-1 signaling is required at all stages of mammary gland development Laban et al. In the absence of IGF-1 e. IGF-1R is mostly found in the ductal epithelium, with higher levels of expression often found in mammary tumors compared to normal tissue Laban et al.
Thus, the estrogenic actions of GE and MXC may account for the enhanced mammary gland when both compounds were applied together. Taken together, the male mammary phenotype following combined exposure to GE and MXC is a result of interactions between growth factor-mediated signals and steroid hormone-mediated signals. It appears that the mammary gland of male rat is a rather sensitive organ to external endocrine stimuli. The sensitivity suggests a potential utility of this organ system in detecting the effects and investigating the relative mechanisms of environmental EACs.
Whether male human beings may be susceptible to such effects reminds unknown. This study was supported by funds from American Chemistry Council to L. The cDNA arrays used in this study were obtained by the U. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Anderson J. Health potential of soy isoflavones for menopausal women. Public Health Nutr. Astwood, E. Development of the mammary gland of the rat.
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Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract. Identification of melanin concentrating hormone MCH as the natural ligand for the orphan somatostatin-like receptor 1 SLC FEBS Lett. Melanin-concentrating hormone is the cognate ligand for the orphan G-protein-coupled receptor SLC The receptor for the orexigenic peptide melanin-concentrating hormone is a G-protein-coupled receptor.
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Mol Pharmacol. PubMed Abstract Google Scholar. Identification and characterization of a second melanin-concentrating hormone receptor, MCH-2R. Identification and pharmacological characterization of a novel human melanin-concentrating hormone receptor, mch-r2. Melanin-concentrating hormone receptor subtypes 1 and 2: species-specific gene expression. The melanin-concentrating hormone MCH system: a tale of two peptides.
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Prolactin PRL and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice. Endocr Rev. Mammary gland involution is delayed by activated Akt in transgenic mice. Mol Endocrinol. Nagasawa H, Yanai R. Mammary gland prolactin receptor and pituitary prolactin secretion in lactating mice with different lactational performance.
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Front Neuroendocrinol. The use, distribution or reproduction in other forums is permitted, provided the original author s and the copyright owner s are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Bittencourt, jcbitten icb. Battagello 1,2 , Aline R. Even when a female produces more than two dozen pups and has "only" a dozen mammary glands to feed them, naked mole-rat society has a way of keeping peace in the underground nests, according to the cover-story article in the August Journal of Mammalogy by Paul W.
Sherman, Stanton Braude and Jennifer U. That is, they produce about one-half as many young in each litter as they have mammae. In general, females have enough mammae for each young in the largest litters to have his or her own.
It even works for humans, where our average litter size is one, but twins sometimes occur. Nobody told naked mole-rats about the biologists' long-standing rule, however. Breeding female mole-rats have an average of 12 mammae See "An Odd Number of Mole-rat Facts," below and as many as 28 pups at a time. Yet, there are no tantrums in the African burrows where naked mole-rats come from or in the popular zoo exhibits where most in the United States now live.
The newest opened this month in Syracuse's Burnet Park Zoo. Pups in a naked mole-rat's litter may outnumber available mammary glands, but pups learn to share and the nursing mother's needs are tended to by helpers in the substerranean colonies.
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