• Asian-Australasian Journal of Animal Sciences
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• v.1 no.1
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• pp.43-46
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• 1988

Based on our previous results that among 4 strains of mice SHN and GR/A showed the highest mammary growth potentials in females and males, respectively. Effects of crossbreeding on normal and neoplastic mammary growth were studied in $(SHN\;{\times}\;GR/A)F_1$ virgin female mice. $F_1$ mice were higher than the parental strains in the end-bud formation and the ductal growth of mammary glands at 60 days of age and at tumorous age, respectively. While there was little difference between $F_1$ and both parental strains in the onset age of the first mammary tumors, mammary tumorigenic potential was apparently higher in the former than in the latters. This would be the first report that demonstrated directly the contribution of mammary growth potential of males to that of female offspring.

• Asian-Australasian Journal of Animal Sciences
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• v.11 no.3
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• pp.300-306
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• 1998

An experiment was conducted to investigate correlations of litter size and average serum progesterone concentrations during pregnancy with mammary gland growth and development at parturition. Twenty ewes (5, 9, 4, and 2 ewes carrying 0, 1, 2, and 3 lambs, respectively) were used to measure weekly serum progesterone concentration during pregnancy. At parturition, the experimental ewes were slaughtered for determination of mammary gland growth and development at parturition (mammary dry fat-free tissue [DFFT], DNA, RNA, collagen, protein, and glycogen). Correlation of mammary DFFT with litter size and averages serum progesterone concentrations were 0.75 and 0.72, respectively. Litter size or maternal serum progesterone concentrations did not correlate with the mammary DNA concentration. However, litter size or maternal serum progesterone concentrations positively correlated (p < 0.01) with the mammary RNA and protein concentrations, but negatively correlated with the mammary collagen (p < 0.01) and. glycogen (p < 0.05) concentrations. Litter size or maternal serum progesterone positively correlated (p < 0.01) with the total mammary DNA, RNA, collagen, protein and glycogen contents. These results implied that the increased concentrations of progesterone with the increased litter size during pregnancy improved mammary gland growth and development at parturition.

• Korean Journal of Animal Reproduction
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• v.21 no.4
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• pp.325-333
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• 1997

Recent evidence indicates that growth factors modulate response of mammary epithelial cells to environmental stress. The objective of this study was to examine the cellular and biochemical responses of mammary tissue to environmental stress caused by artificial mastitis. For experimental a, pp.oach, toxins of most mastitis causing organisms(Staph. aureus or Strep. agalactiae) and heat stress(42$^{\circ}C$) were artificially exposed to mammary tissue. Effects of these environmental stresses on cell growth, cell death and heat shock protein synthesis were examined. Lactating mammary tissure were cultured under basal medium(DMEM) su, pp.emented with insulin(10$\mu\textrm{g}$/ml) and aldosterone(1$\mu\textrm{g}$/ml). All treatment groups in heat stress at 42$^{\circ}C$ incubation significantly decreased DNA synthesis rates in comparison with those at 39$^{\circ}C$(P<0.05), however, these decreased DNAa synthesis rates were recovered by addition of adenosine(10$\mu$M) and IGFI(10ng/ml). Similar results were obtained when tissue growth rates were measured by DNA content/tissue. Strep. agalactiae toxin did not significantly decreased DNA content/tissue in comparison with no treatment of bacterial toxin with or without heat stress, however, tended to decrease DNA contents/tissue without heat stress. In the fluorography analysis, heat stress(42$^{\circ}C$ incubation) slightly increased 35S-methoionine labelled 70kd protein synthesis. These results indicate that environmental stress caused by artificial mastitis slightly decreased mammary growth or mammary size, however, these results could be recovered by addition of adenosine and IGF-I.

• Development and Reproduction
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• v.4 no.2
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• pp.221-229
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• 2000

Lactogenesis in mammary gland is under the control of various lactogenic hormones including hypophysial growth hormone and prolactin. Recent studies reported that such pituitary lactogenic hormones are also expressed in mammary cells as well as in pituitary. For the purpose to analyze the role of these non-pituitary hormones in mammary cells, $\beta$ -lactoglobulin (BLG) gene promoter was selected as a model system. The growth hormone suppressed BLG promoter activity when it was applied alone on cultured mammary HCll cells. Along with lactogenic hormones such as insulin, prolactin and glucocorticoid, however, it significantly enhanced expression of BLG promoter activity in a dosage- dependent manner. Exogenous expression of the growth hormone gene in cultured mammary cells also strongly promoted cell proliferation and BLG promoter activity. Bovine growth hormone promoter, on the contrary, did not revealed any notable activity. Above results suggest that endogenous expression of the pituitary hormone genes in mammary cells is not a regulation leakage but a physiological control. Moreover, artificial overproduction of the growth hormone in mammary gland may help increase milk production.

• Asian-Australasian Journal of Animal Sciences
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• v.1 no.3
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• pp.139-142
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• 1988

Effects of anthranilic acid on normal mammary gland growth were examined in SHN/Mei female virgin mice. Anthranilic acid was given to the experimental groups as drinking water at the concentrations of 0.01, 0.02 or 0.04% for 21 days beginning 2-3 months of age. The control group received tap water only. RNA content and RNA/DNA ratio in mammary glands were significantly higher in mice given 0.04% anthranilic acid than in the control, while not mammary DNA content. The results indicate that chronic ingestion of anthranilic acid can induce an enhancement of proliferation and differentiation of mammary cells.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.9
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• pp.1338-1350
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• 2012

This review focuses on the nutritional effects from birth until age at first calving on growth, mammary developmental changes, and first-lactation milk yield in heifer calves. The advancement in the genetic potential and the nutritional requirements of the animals has hastened the growth rate. Genetic selection for high milk yield has suggested higher growth capacity and hence increasing nutritional inputs are required. Rapid rearing by feeding high energy or high concentrate diets not only reduces the age of sexual maturity but also lowers the time period of attaining the age of first calving. However, high energy diets may cause undesirable fat deposition thereby affecting future milk yield potential. Discrepancies exist whether overfed or overweight heifers at puberty can influence the mammary development and future milk yield potential and performance. The data on post-pubertal nutritional management suggested that body weight at calving and post-pubertal growth rate is important in first lactation milk yield. There is a continuous research need for strategic feeding that accelerates growth of dairy heifers without reduction in subsequent production. Nutritional management from birth, across puberty and during pregnancy is critical for mammary growth and for producing a successful cow. This review will mostly highlight studies carried out on dairy breeds and possible available opportunities to manipulate nutritional status from birth until age at first calving.

• Asian-Australasian Journal of Animal Sciences
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• v.10 no.2
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• pp.233-239
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• 1997

A mammary epithelial cell line (MAC-T) established as a model for lactation was utilized to identify and characterize effects of various hormones upon insulin-like growth factor binding protein secretion. Ligand and immunoblot analyses of conditioned media indicated that insulin-like growth factor binding protein-2 was secreted by MAC-T cells. Insulin-like growth factor-I stimulated insulin-like growth factor binding protein-2 secretion in a dose-dependent manner, but prolactin and bovine somatotropin did not alter insulin-like growth factor binding protein-2 secretion. Insulin increased and cortisol decreased insulin-like growth factor binding protein-2 secretion. Effects of insulin-like growth factor-I on insulin-like growth factor binding protein-2 secretion support previous studies using primary cultures of bovine mammary cells and bovine fibroblasts. Effects of cortisol and insulin on insulin-like growth factor binding protein-2 secretion may be explained by changes in protein synthesis. In addition, supraphysiological doses of insulin can cross-react with the insulin-like growth factor-I receptor and stimulate insulin-like growth factor binding protein-2 secretion. MAC-T cells provide a model system to study mechanisms that regulate local insulin-like growth factor-I bioactivity.

• Korean Journal of Animal Reproduction
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• v.20 no.2
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• pp.135-141
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• 1996

Growth, mammary development, serum concentrations of growth hormone, prolactin and estradiol which affect the growth and mammary development, were investigated in Korean Native heifers and Holstein heifers from 5 months old to 15 months old. From 5 months old to 15 months old, body weights in Korean Native heifers averaged 37%, lower than those in Holstein heifers of the same age (P<.01). Teat volumes in Korean Native heifers are average 67% smaller than those in Holstein heifers. Analysis of serum protein by secondary electrophoresis showed differences in protein pattern between the breeds and between the individuals. From 5 months old to 15 months old, serum concentration of growth hormone in Korean Native heifers was averge 47% lower than that in Holstein (P<.01), yet prolactin concentrations in serum were about the same between the two breeds. However serum concentration of estradiol in Korean Native heifers was average 20% higher than that in Holstein of same age (P<.01). This result showed evidently that the decrease of the growth hormone concentration in serum, while growing up, causes to retard the growth and mammary development in Korean Native heifers compared to Holstein heifers.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.8
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• pp.1198-1203
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• 2002

To understand molecular mechanisms involved in bovine mammary gland growth, expression of stat5a gene was examined in bovine mammary tissues. We found that stat5a gene was highly induced at pregnant 7 and 8 months compared to virgin mammary tissues. To examine function of bovine stat5a in mammary epithelial cell proliferation, stat5a expression vector was transfected into mammary epithelial HC11 cells. Cell proliferation rate in stat5a gene-transfected cells was 26%, 95% and 85% higher at 24 h, 48 h and 72 h after seeding, respectively, compared to control vector-transfected cells. Results demonstrate that bovine stat5a enhances proliferation of mammary epithelial cells.

• Development and Reproduction
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• v.20 no.3
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• pp.179-185
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• 2016

The insulin-like growth factor (IGF) pathway is a key signal transduction pathway involved in cell proliferation, migration, and apoptosis. In dairy cows, IGF family proteins and binding receptors, including their intracellular binding partners, regulate mammary gland development. IGFs and IGF receptor interactions in mammary glands influence the early stages of mammogenesis, i.e., mammary ductal genesis until puberty. The IGF pathway includes three major components, IGFs (such as IGF-I, IGF-II, and insulin), their specific receptors, and their high-affinity binding partners (IGF binding proteins [IGFBPs]; i.e., IGFBP1-6), including specific proteases for each IGFBP. Additionally, IGFs and IGFBP interactions are critical for the bioactivities of various intracellular mechanisms, including cell proliferation, migration, and apoptosis. Notably, the interactions between IGFs and IGFBPs in the IGF pathway have been difficult to characterize during specific stages of bovine mammary gland development. In this review, we aim to describe the role of the interaction between IGFs and IGFBPs in overall mammary gland development in dairy cows.