Adverse effects of prenatal exposure to atrazine during a critical period of mammary gland growth.

Prenatal exposure to 100 mg/kg atrazine (ATR) delays mammary gland (MG) development in resulting female offspring of Long-Evans rats. To determine if the fetal MG was sensitive to ATR effects during specific periods of development, timed-pregnant dams (n = 8/group/block) were dosed for 3- or 7-gestation day (GD) intervals (GD 13-15, 15-17, 17-19, or 13-19) with 100 mg ATR/kg/day or vehicle (C), and their offspring were evaluated for changes. Mammary glands taken from pups prenatally exposed to ATR displayed significant delays in epithelial development as early as postnatal day (PND) 4 compared to C, with continued developmental delays at later time points that varied by time of exposure. However, the most persistent and severe delays were seen in the GD 17-19 and GD 13-19 ATR exposure groups, demonstrating statistically similar growth retardation. Because MG developmental deficits persisted into adulthood, we hypothesized that ATR-exposed animals may have had difficulties nursing their young. Females exposed prenatally to either ATR (as defined) or C (n = 4 litters/group) were bred, and the resulting F(2) offspring from GD 17-19 and GD 13-19 exposure groups were significantly smaller in body weight (BW) than C. In a separate study, it was determined that ATR (25-100 mg/kg), delivered from GD 15-19, did not decrease fetal body weights on GD 20, even though the higher doses significantly decreased weight gain of the dosed dams. These data suggest that the consequences of brief ATR exposure during a critical period of fetal MG development (GD 17-19), are both delayed MG development of the offspring and inadequate nutritional support of F2 offspring, resulting in adverse effects on pup weight gain.     

Modulation of mammary gland development in prepubertal male rats exposed to genistein and methoxychlor.

The estrogenic isoflavone genistein is a common dietary component that has been shown to affect reproductive development in experimental animals at high doses. The objective of the present study was to examine interactions of genistein and the hormonally active pesticide methoxychlor on mammary gland development in juvenile rats. Timed-pregnant Sprague-Dawley rats were fed a soy- and alfalfa-free diet containing different combinations of genistein (300 and 800 ppm) and methoxychlor (800 ppm). Rats were fed these diets starting on gestation day (GD)1 and continuing through pregnancy and lactation until postnatal day (PND) 22, when the pups were killed. Inguinal mammary glands from both female and male pups were processed as whole-mount preparations for morphometric analysis. The total glandular area and the numbers of branch points, lateral buds, and terminal end buds in the male rats were found to be significantly greater in the groups exposed to methoxychlor than those exposed to genistein only. These effects were not observed in the female rats. In the male rats, methoxychlor had the most prominent effect on elongating the glandular ducts, while genistein enhanced the ductile branching. The 2 compounds in combination promoted the development of alveolar-lobular structure, an effect not observed with either compound alone. Immunostaining for proliferating cell nuclear antigen revealed a high percentage of immunopositive cells in the mammary epithelia of the males exposed to methoxychlor and genistein (800 ppm) compared to the controls. While no significant changes in serum levels of mammotrophic hormones were detected, increased immunostaining for insulin-like growth factor-1 receptor, estrogen receptor alpha, and progesterone receptor in the genistein + methoxychlor group suggested that local factors involved in regulating mammary growth may have played a role in propagating the endocrine effects of these two compounds. These results indicated that the mammary glands of juvenile male rather than juvenile female rats may be more sensitive to certain endocrine-active compounds and that high levels of phytoestrogens have the potential to alter the toxicological behaviors of other hormone mimics.     

Impact of gestational low protein diet and postnatal bisphenol A exposure on chemically induced mammary carcinogenesis in female offspring rats

This study evaluated the effect of gestational low protein diet (LPD) and/or postnatal bisphenol A (BPA) exposure on mammary gland development and carcinogenesis in female offspring. Pregnant Sprague‐Dawley rats were fed a normal protein diet (NPD, 17% protein) or LPD (6% protein). At weaning, female offspring were distributed in four groups (NPD, LPD, NPD + BPA, and LPD + BPA) and received vehicle or BPA in drinking water (0.1%), during postnatal day (PND) 21 to 51. On PND 51, some female offspring were euthanized or received a single dose of 7,12‐dimethylbenzoanthracene (DMBA, 30 mg/kg, i.g.) and were euthanized on PND 250. On PND 51, neither gestational LPD nor postnatal BPA exposure, individually or in combination, significantly altered the development of mammary gland tree, mean number of terminal structures or estrogen receptor beta (ER‐β), proliferating cell nuclear antigen (PCNA) or caspase‐3 protein expression in the mammary tissue. A significant reduction in mammary epithelial area (%) was observed in both LPD groups and a significant increase in ER‐α protein expression was detected only in LPD group. In LPD + BPA group was observed a significant increase in both fat pad area (%) and in mean number of mammary epithelial cells positive for progesterone receptor (PR). On PND 250, the groups that received BPA presented lower latency and higher tumor incidence and tumor multiplicity and LPD + BPA group more aggressive tumors. These findings suggest that postnatal BPA exposure associated with gestational LPD is able to induce morphological changes in the mammary gland and increase susceptibility to mammary carcinogenesis.     

Estrogenic effect of soy isoflavones on mammary gland morphogenesis and gene expression profile.

We examined the effect of 17beta-estradiol (E2) and soy isoflavones' exposure on morphogenesis and global gene expression in the murine mammary gland. Three exposure regimens were applied: isoflavones added to the diet throughout either the lactational period (via the dams) or the postweaning period and E2 administered orally during the lactational period. Whole mounts of mammary glands were evaluated both in juvenile and adult animals with respect to branching morphogenesis and terminal end bud (TEB) formation. At postnatal day (PND) 28, we observed a significant increase in branching morphogenesis in all treated groups with the most pronounced effect after E2 exposure. For the E2-treated animals there was also a significant increase in TEB formation. At PNDs 42-43 the postweaning isoflavone and the E2 groups showed a transient reduction in the number of TEBs. A similar response after isoflavone and E2 exposure was further substantiated by changes in gene expression, since the same groups of genes were up- and downregulated, particularly in the E2 and postweaning isoflavone regimen. All changes in gene expression correlated with changes in the cellular composition of the gland, i.e., more and larger TEBs and ducts. The results suggest an estrogenic response of physiological doses of isoflavones on mammary gland development at both the morphological and molecular level, which resembled that induced by puberty.     

A novel effect of dioxin: exposure during pregnancy severely impairs mammary gland differentiation.

Many ligands for the aryl hydrocarbon receptor (AhR) are considered endocrine disruptors and carcinogens, and assessment of adverse health effects in humans exposed to such chemicals has often focused on malignancies, including breast cancer. Mammary tissue contains the AhR, and inappropriate activation of the AhR during fetal development causes defects in mammary development that persist into adulthood. However, it is not known whether the extensive differentiation of mammary tissue that occurs during pregnancy is also sensitive to disruption by AhR activation. To examine this, we exposed pregnant C57Bl/6 mice to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on days 0, 7, and 14 of pregnancy. Examination of mammary glands on days 9, 12, and 17 of pregnancy and on the day of parturition showed severe defects in development, including stunted growth, decreased branching, and poor formation of lobular alveolar structures. This impaired differentiation was biologically significant, as expression of whey acidic protein in the gland was suppressed, and all pups born to TCDD-treated dams died within 24 h of birth. Analysis of circulating progesterone, prolactin, and estradiol suggest that hormone production was slightly impaired by inappropriate activation of the AhR. However, hormone levels were affected only very late in pregnancy. Given that the observed defects in gland development preceded these hormonal effects, altered hormone levels are an unlikely mechanistic explanation for impaired mammary development. This novel finding that AhR activation during pregnancy disrupts mammary gland differentiation raises questions about the susceptibility of mammary tissue to direct injury by endocrine disrupting agents and the potential for AhR-mediated signaling to adversely affect lactation and breast tissue development in human populations.     

Segregated responses of mammary gland development and vaginal opening to prepubertal genistein exposure in Bscl2−/− female mice with lipodystrophy

Berardinelli-Seip congenital lipodystrophy 2-deficient (Bscl2^−/−) mice recapitulate human BSCL2 disease with lipodystrophy. Bscl2-encoded seipin is detected in adipocytes and epithelium of mammary gland. Postnatal mammary gland growth spurt and vaginal opening signify pubertal onset in female mice. Bscl2^−/− females have longer and dilated mammary gland ducts at 5-week old and delayed vaginal opening. Prepubertal exposure to 500 ppm genistein diet increases mammary gland area and accelerates vaginal opening in both control and Bscl2^−/− females. However, genistein treatment increases ductal length in control but not Bscl2^−/− females. Neither prepubertal genistein treatment nor Bscl2-deficiency affects phospho-estrogen receptor α or progesterone receptor expression patterns in 5-week old mammary gland. Interestingly, Bscl2-deficiency specifically reduces estrogen receptor β expression in mammary gland ductal epithelium. In summary, Bscl2^−/− females have accelerated postnatal mammary ductal development but delayed vaginal opening; they display segregated responses in mammary gland development and vaginal opening to prepubertal genistein treatment.     

Persistent abnormalities in the rat mammary gland following gestational and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure during gestation has revealed reproductive anomalies in rat offspring, including inconclusive reports of stunted mammary development in females (Brown et al., 1998, Carcinogenesis 19, 1623-1629; Lewis et al., 2001, TOXICOL: Sci. 62, 46-53). The current studies were designed to examine mammary-gland development in female offspring exposed in utero and lactationally to TCDD, and to determine a critical exposure period and cellular source of these effects. Long-Evans rats were exposed to 1 microg TCDD/kg body weight (bw) or vehicle on gestation day (GD) 15. TCDD-exposed females sacrificed on postnatal days (PND) 4, 25, 33, 37, 45, and 68 weighed significantly less than control litter mates, and peripubertal animals exhibited delayed vaginal opening and persistent vaginal threads, yet did not display altered estrous cyclicity. Mammary glands taken from TCDD-exposed animals on PND 4 demonstrated reduced primary branches, decreased epithelial elongation, and significantly fewer alveolar buds and lateral branches. This phenomenon persisted through PND 68 when, unlike fully developed glands of controls, TCDD-exposed rats retained undifferentiated terminal structures. Glands of offspring exposed to TCDD or oil on gestation days 15 and 20 or lactation days 1, 3, 5, and 10 were examined on PND 4 or 25 to discern that GD 15 was a critical period for consistent inhibition of epithelial development. Experiments using mammary epithelial transplantation between control and TCDD-exposed females suggested that the stroma plays a major role in the retarded development of the mammary gland following TCDD exposure. Our data suggest that exposure to TCDD prior to migration of the mammary bud into the fat pad permanently alters mammary epithelial development in female rat offspring.     

数字化乳腺摄影在福田区适龄女性乳腺癌筛查中的价值研究

目的 探讨数字化乳腺摄影在福田区适龄女性乳腺癌筛查中的价值.方法 对福田区2451名适龄女性采用数字化乳腺摄影进行乳腺癌筛查,采用数字化钼靶拍片机,对所有筛查者常规摄取双乳轴位、侧斜位片,由两名放射科主治医师进行读片诊断.结果 所有筛查对象中,乳腺呈脂肪型443例（18.1％）、少腺体型821例（33.5％）、多腺体型984例（40.1％）、致密型203例（8.3％）;乳腺摄影结果：0级249例（10.16％）、Ⅰ级2042例（83.31％）、Ⅱ级78例（3.18％）、Ⅲ级71例（2.90％）、Ⅳ级9例（0.37％）、V级2例（0.08％）;共筛查出6例乳腺癌患者,脂肪型乳腺1例,少腺体型乳腺2例,多腺体型乳腺2例,致密型乳腺1例.结论 数字化乳腺摄影的图像清晰,密度分辨率及空间分辨率高,对乳腺癌的敏感性强,可作为福田区适龄女性乳腺癌筛查首选的影像学方法.     

Analysis of PFOA in dosed CD-1 mice. Part 2: Disposition of PFOA in tissues and fluids from pregnant and lactating mice and their pups

Previous studies in mice with multiple gestational exposures to perfluorooctanoic acid (PFOA) demonstrate numerous dose dependent growth and developmental effects which appeared to worsen if offspring exposed in utero nursed from PFOA-exposed dams. To evaluate the disposition of PFOA in the pregnant and lactating dam and her offspring, time-pregnant CD-1 mice received a single 0, 0.1, 1, or 5 mg PFOA/kg BW dose (n = 25/dose group) by gavage on gestation day 17. Maternal and pup fluids and tissues were collected over time. Pups exhibited significantly higher serum PFOA concentrations than their respective dams, and their body burden increased after birth until at least postnatal day 8, regardless of dose. The distribution of milk:serum PFOA varied by dose and time, but was typically in excess of 0.20. These data suggest that milk is a substantial PFOA exposure route in mice and should be considered in risk assessment modeling designs for this compound.     

The mammary gland is a sensitive pubertal target in CD-1 and C57Bl/6 mice following perinatal perfluorooctanoic acid (PFOA) exposure

Perfluorooctanoic acid (PFOA) is a developmental toxicant in mice, with varied strain outcomes depending on dose and period of exposure. The impact of PFOA on female mouse pubertal development at low doses (≤1 mg/kg) has yet to be determined. Therefore, female offspring from CD-1 and C57Bl/6 dams exposed to PFOA, creating serum concentrations similar to humans, were examined for pubertal onset, including mammary gland development. Pups demonstrated a shorter PFOA elimination half-life than that reported for adult mice. Prenatal exposure to PFOA caused significant mammary developmental delays in female offspring in both strains. Delays started during puberty and persisted into young adulthood; severity was dose-dependent. Also an evaluation of female serum hormone levels and pubertal timing onset revealed no effects of PFOA compared to controls in either strain. These data suggest that the mammary gland is more sensitive to early low level PFOA exposures compared to other pubertal endpoints, regardless of strain.     

Distribution of lead in lactating mice and suckling offspring with special emphasis on the mammary gland

 The distribution of lead in lactating mice and suckling offspring was studied with whole body autoradiography at 4 and 24 h after a single intravenous injection of ²⁰³Pb (50 nmol Pb/kg) to the dams. In the lactating mice on day 14 of lactation, the highest uptake of radioactivity at 4 h after administration was recorded in renal cortex, skeleton and liver. A high uptake was also evident in the mammary gland. At 24 h after administration, the radioactivity had decreased in most organs except in the skeleton. In the suckling pups, exposed to lead only via dams’ milk for 24 h, the highest level of radioactivity was present in the intestinal mucosa and a much lower level of radioactivity was present in the skeleton. The mammary glands from mice given three daily intravenous injections of 240 μmol Pb/kg were examined with X-ray microanalysis. At 4 h after the last injection, lead was found associated with casein micelles both inside the alveolar cell and in the milk lumen, indicating that lead is excreted into the milk, bound to casein, via the Golgi secretory system. Received 8 May 1995 / Accepted 16 July 1995     

喉罩通气在乳腺手术中的运用

目的:探讨采用喉罩通气的方法在乳腺良性肿瘤手术中的应用.方法:选择乳腺良性肿瘤手术患者20例,麻醉诱导后置入喉罩,术中异丙酚,瑞芬,阿曲库胺维持麻醉,分别在麻醉前、手术前及手术后40 min监测分钟通气量、呼气末二氧化碳分压、动脉血气及麻醉并发症.结果:手术前分钟通气量,呼气末二氧化碳分压,pH及PaCO2较麻醉前明显降低(P＜0.05),并超过正常范围,但与手术后40 min相比差异无显著性(P＞0.05).20例患者在术中均未出现反流误吸及呛咳.术后随访3例(7%)诉有咽喉疼痛.结论:喉罩是集合面罩与气管内导管优点的通气设备,可以在乳腺手术中得到推广使用.     

Effects of maternal xenoestrogen exposure on development of the reproductive tract and mammary gland in female CD-1 mouse offspring

The objective of this study was to examine the effects of maternal exposure to xenoestrogen, at levels comparable to or greater than human exposure, on development of the reproductive tract and mammary glands in female CD-1 mouse offspring. Effects of genistein (GEN), resveratrol (RES), zearalenone (ZEA), bisphenol A (BPA) and diethylstilbestrol (DES) were examined. Beginning on gestational day 15, pregnant CD-1 mice were administered four daily subcutaneous injections with 0.5 or 10 mg/kg/day of GEN, RES, ZEA or BPA, 0.5 or 10 μg/kg/day of DES dissolved in dimethylsulfoxide (DMSO), or DMSO vehicle (n = 6). Vaginal opening was monitored, 6 animals per group were autopsied at 4, 8, 12 and 16 weeks of age and estrous cyclicity was monitored from 9 to 11 weeks of age. Maternal exposure to xenoestrogen accelerated puberty onset (vaginal opening) and increased the length of the estrous cycle; mice treated with GEN, RES, BPA or DES spent more time in diestrus, and ZEA-treated mice spent more time in estrus. Lack of corpora lutea and vaginal cornification were observed at 4 weeks of age in the high-dose GEN (33%) and RES (17%) groups, and in the high- and low-dose BPA groups (33 and 50%, respectively) and DES groups (83 and 100%, respectively). Lack of corpora lutea and vaginal cornification was observed in the high-dose ZEA group at 4, 8, 12 and 16 weeks of age (83, 100, 83 and 33%, respectively). Mammary gland differentiation was accelerated in ZEA- and BPA-treated mice with corpora lutea at 4 weeks of age. ZEA-treated mice without corpora lutea showed mammary growth arrest at 8, 12 and 16 weeks of age; their mammary glands consisted only of a dilatated duct filled with secreted fluid. Mammary gland growth was similar with xenoestrogens other than ZEA or BPA to that of the controls at all time points. High-dose GEN and RES and high- and low-dose BPA and DES exerted transient effects on the reproductive tract and mammary glands, whereas ZEA exerted prolonged effects.     

Differential effects of peripubertal exposure to perfluorooctanoic acid on mammary gland development in C57Bl/6 and Balb/c mouse strains

Perfluorooctanoic acid (PFOA), a common and persistent industrial byproduct detected in human sera, has raised health concerns. PFOA is detrimental to lactational function and postnatal mammary gland development in CD-1 mice after gestational exposure. We have examined the peripubertal period (21 through 50 days of age) as an important window of mammary gland susceptibility to environmental exposures that may affect breast cancer risk later in life. The effects of PFOA (0.1–10 mg/kg BW) were examined in Balb/c and C57BL/6 mice. PFOA treatment caused hepatocellular hypertrophy and delayed vaginal opening in both mouse strains. While Balb/c mice exhibited only inhibition of mammary gland and uterine development (5, 10 mg/kg), C57BL/6 mice exhibited stimulatory effects in both organs at low dose (5 mg/kg) and inhibition at higher dose (10 mg/kg). This underscores the need for caution when drawing conclusions about the effects of PFOA and possibly other environmental pollutants on the basis of studies in a single mouse strain.     

Estrogens in the wrong place at the wrong time: Fetal BPA exposure and mammary cancer

Iatrogenic gestational exposure to diethylstilbestrol (DES) induced alterations of the genital tract and predisposed individuals to develop clear cell carcinoma of the vagina as well as breast cancer later in life. Gestational exposure of rodents to a related compound, the xenoestrogen bisphenol-A (BPA) increases the propensity to develop mammary cancer during adulthood, long after cessation of exposure. Exposure to BPA during gestation induces morphological alterations in both the stroma and the epithelium of the fetal mammary gland at 18 days of age. We postulate that the primary target of BPA is the fetal stroma, the only mammary tissue expressing estrogen receptors during fetal life. BPA would then alter the reciprocal stroma-epithelial interactions that mediate mammogenesis. In addition to this direct effect on the mammary gland, BPA is postulated to affect the hypothalamus and thus in turn affect the regulation of mammotropic hormones at puberty and beyond.     

Effects of perfluorooctanoic acid on mouse mammary gland development and differentiation resulting from cross-foster and restricted gestational exposures

The adverse consequences of developmental exposures to perfluorooctanoic acid (PFOA) are established in mice, and include impaired development of the mammary gland (MG). However, the relationships between timing or route of exposure, and consequences in the MG have not been characterized. To address the effects of these variables on the onset and persistence of MG effects in female offspring, timed pregnant CD-1 dams received PFOA by oral gavage over various gestational durations. Cross-fostering studies identified the 5 mg/kg dose, under either lactational- or intrauterine-only exposures, to delay MG development as early as postnatal day (PND) 1, persisting beyond PND 63. Intrauterine exposure during the final days of pregnancy caused adverse MG developmental effects similar to that of extended gestational exposures. These studies confirm a window of MG sensitivity in late fetal and early neonatal life, and demonstrate developmental PFOA exposure results in early and persistent MG effects, suggesting permanent consequences.     

玫瑰花总黄酮对乳腺增生大鼠上皮-间质转换的影响

目的： 探讨玫瑰花总黄酮对实验性乳腺增生大鼠上皮-间质转换（EMT）的影响。方法： 通过注射雌激素和孕激素诱导大鼠乳腺增生,观察玫瑰花总黄酮（200和100 mg·kg^-1·d^-1）给药干预对乳腺组织形态学变化、乳腺fibronectin、α-SMA、E-cadherin、collagen-I和TGF-β1表达情况,以及微小RNA（miR）-21和miR-29a/b水平的影响。结果： 玫瑰花总黄酮给药能显著改善模型动物乳腺增生的趋势,抑制乳腺组织collagen-I沉积和TGF-β1表达,缓解EMT上皮标记物E-cadherin的缺失以及间质标记物fibronectin和α-SMA等的过度表达,降低miR-21并一定程度恢复miR-29a/b的水平。结论： 玫瑰花总黄酮对乳腺EMT发生的程度具有潜在的抑制作用。     

模式识别在乳腺病变鉴别诊断中的应用

本文以细胞核六项参数为指标,用模式识别对正常活动期乳腺及其良恶性病变(纤维腺瘤、单纯性增生、不典型增生和乳腺癌,进行判别分析。结果证明,细胞核形态参数的模式识利为鉴别诊断乳腺疾病提供了简单而准确的手段。     

Altered mammary gland development in male rats exposed to genistein and methoxychlor.

Genistein (GE) is a prevalent phytoestrogen whose presence in human and animal foods may affect biological actions of synthetic endocrine active compounds. We have previously reported that in utero and lactational exposure to high doses of GE or the endocrine active pesticide methoxychlor (MXC) caused mammary epithelial proliferation in 21-day-old male rats. Combined exposure to GE and MXC resulted in significant feminization of the male mammary glands. The goals of the current study were to evaluate mammary responses to GE and MXC at the adult stage and investigate relevant mechanisms. Following in utero, lactational exposure (through maternal diet), and direct dietary exposure, the inguinal mammary gland of male rats (90 days of age) was found to exhibit significant morphological alterations in the groups treated with GE and/or MXC compared to the control. GE exposure (at 300 and 800 ppm concentrations) caused lobular enlargement and epithelial proliferation, whereas MXC exposure (800 ppm) led to ductal elongation and lobular enlargement. Combining the two treatments caused prominent proliferation of both ducts and alveoli; secretory material was seen in readily recognizable alveolar lumens, which are absent in untreated male mammary. We also surveyed gene expression in the mammary tissue using a cDNA microarray and evaluated relevant protein factors. The results indicated that the treatment effects are likely due to interactions between steroid hormone receptor-mediated signals and growth factor-driven cellular pathways. The distinctive responses associated with the GE+MXC combination were likely linked to enhanced actions of insulin-like growth factor 1 and related downstream pathways.     

Mixtures of environmentally relevant endocrine disrupting chemicals affect mammary gland development in female and male rats

Estrogenic chemicals are able to alter mammary gland development in female rodents, but little is known on the effects of anti-androgens and mixtures of endocrine disrupting chemicals (EDCs) with dissimilar modes of action.Pregnant rat dams were exposed during gestation and lactation to mixtures of environmentally relevant EDCs with estrogenic, anti-androgenic or dissimilar modes of action (TotalMix) of 100-, 200- or 450-fold high end human intake estimates. Mammary glands of prepubertal and adult female and male offspring were examined.Oestrogens increased mammary outgrowth in prepubertal females and the mRNA level of matrix metalloproteinase-3, which may be a potential biomarker for increased outgrowth. Mixtures of EDCs gave rise to ductal hyperplasia in adult males. Adult female mammary glands of the TotalMix group showed morphological changes possibly reflecting increased prolactin levels. In conclusion both estrogenic and anti-androgenic chemicals given during foetal life and lactation affected mammary glands in the offspring.