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S Z Haslam

Publications and source records attributed to S Z Haslam.

At least 37 records · Page 2Linked to original sources
PubMed1992

EGF receptor regulation in normal mouse mammary gland.

Estrogen (E), progesterone (P), and epidermal growth factor (EGF) are known to regulate growth and development of the normal mammary gland, and it is possible that EGF may interact with E and/or P. Estrogen (ER), progesterone (PR), and EGF receptors (EGF-R) have been detected in both mammary epithelial and stromal cells, and the relative roles of the various cells types in hormone-dependent growth regulation are not known. The present studies were undertaken to determine if E and/or P influence EGF action by exerting a regulatory effect on EGF-R levels and which cell types are affected. The comparative effects of ovariectomy and hormone treatments on EGF-R levels were examined in immature, pubertal 5-week-old and sexually mature 10-week-old female mice. EGF-R were characterized as a single class of high affinity sites and EGF-R concentration was 2-fold higher in glands of 5-week-old mice. Ovariectomy had no significant effect on EGF-R concentration in either age group, and treatment with E and/or P had no effect on EGF-R levels in either epithelial or stromal cells in 5-week-old mice. In contrast, E+P treatment caused a 2-fold increase in receptor concentration in 10-week-old mice in the mammary epithelium. Thus it appears that the developmental state of the gland may determine the nature and extent of the interaction of of EGF, E, and P.

Animals↗
PubMed1992

The ontogeny and cellular distribution of estrogen receptors in normal mouse mammary gland.

The appearance, epithelial and stromal cell distribution of estrogen receptors (ER) in normal mouse mammary gland were determined between 1 and 10 weeks of age using immunohistochemistry. The effect of ovariectomy and estrogen (E)-treatment on the distribution and concentration of ER-positive cells at various ages was also analyzed. These studies demonstrate that ER are present in both mammary epithelial and stromal cells before the mammary gland exhibits a proliferative response or increase in progesterone receptor concentration as a result of E-treatment. Furthermore, an analysis of E-treatment suggests that although ER are present at an early age, there may be additional factors that determine the nature and extent of E-responsiveness.

Animals↗
PubMed1992

Characterization of the mammary hyperplasia, dysplasia and neoplasia induced in athymic female adult mice by polyomavirus.

We have characterized mammary oncogenesis induced after polyomavirus infection of adult female nude mice regarding histopathogenesis, viral replication and viral and cellular oncogene expression. A unique transient generalized epithelial hyperplasia was observed (starting at 2 weeks post infection), preceding the development of dysplasias (onset 6 weeks post infection) and multiple neoplasias (onset 6 weeks post infection) in all glands. The ductal epithelium was the target for neoplastic transformation, and the occurrence of numerous ductal dysplasias coincided with the appearance of frank tumors. Stromal abnormalities were also seen. Tumor growth was not dependent upon ovarian hormones, and new tumors continued to develop in ovariectomized mice. Viral replication, high although variable, preceded but did not correlate with oncogenesis. Most but not all tumors contained high levels of unintegrated viral DNA. Tumors produced very low levels of live virus. Viral gene expression was markedly increased in the tumors compared with the infected but morphologically normal glands. The expression of c-myc was moderately increased (fourfold); changes in c-int-2 and c-Ha-ras expression were slight and inconsistent, while expression of c-neu and c-int-1 was unchanged.

Animals↗
PubMed1991

Mammary stroma modulates hormonal responsiveness of mammary epithelium in vivo in the mouse.

Several lines of evidence indicate that there may be important stromal influences on epithelial behavior in a number of adult organs. The present studies were undertaken to examine the contribution of mammary gland stroma to mammary epithelial cell hormonal responsiveness in vivo. To accomplish this, mouse mammary epithelium from a developmental state that is not responsive to estrogen (E)-regulation of progesterone receptors (3-week-old) was surgically recombined with mammary stroma from a developmental state that is E-responsive (10-week-old) and vice versa. The recombinants were then tested in vivo for the ability of E to regulate epithelial progesterone receptors. The results demonstrate that when immature nonresponsive epithelium is transplanted to mature stroma of E-responsive mice, the epithelium prematurely acquires E responsiveness. When the converse experiment was carried out, mature E-responsive epithelium retained its responsiveness when transplanted to stroma of immature nonresponsive mice. The contribution of the host systemic milieu to changes observed upon transplantation was also assessed. To do this, mature stroma was transplanted to nonresponsive mice before transplantation with nonresponsive epithelium. Under these conditions, the mature stroma was still able to promote responsiveness. Analysis of mammary gland morphology of the surgical recombinants revealed no significant differences in epithelial structures or organization that could account for the observed differences in hormone responsiveness. From these results we conclude that the local environment of mammary stroma has the capacity to influence mammary epithelial cell behavior and can modulate epithelial hormonal responsiveness in vivo. The mechanisms underlying stromal influences on epithelial behavior remain to be elucidated.

Aging↗
PubMed1990

Progesterone action in normal mouse mammary gland.

Previously it has been shown that progesterone, as well as estrogen, plays an important role in the growth of the mammary gland. Eighty percent of mammary progesterone receptors (PgR) are estrogen-inducible and are localized in the epithelium; the remaining 20% of PgR are estrogen-independent and appear to be localized in the mammary stroma. The purpose of the present study was to investigate how progestins promote mammary growth in relation to their interactions with epithelial and stromal components of the gland and to assess the role of estrogen in these interactions. Progestins [progesterone, [17 beta-methyl-3H]promogestone (R5020), and medroxy progesterone acetate] alone or in combination with estrogen were combined with Elvax 40P and implanted directly into mammary glands. The effect of hormones on cell proliferation was determined by observing changes in mammary gland morphology and by quantitating DNA synthesis in both epithelial and stromal cells by DNA histoautoradiography. The results demonstrate that in mammary epithelial cells the effects of progestins on mammary gland morphology and DNA synthesis are locally mediated such that proliferative changes in the hormone-implanted glands were greater than in contralateral control glands. Dose-response studies with estrogen and R5020 revealed that the extent of progestin activity was only partially dependent upon the R5020 dose with the major determining factor being the dose of estrogen. Analysis of the effect of estrogen on mammary PgR concentration indicates that the degree and pattern of the morphological response of ductal sidebranching and increases in DNA synthesis are largely due to the increase in estrogen-dependent PgR. The antiprogestin, 11 beta-(4-dimethylamino-phenyl)1-17 beta-hydroxy-17 alpha-(prop-1ynyl)-estra-4,9-diene-3-one (RU486), blocks the proliferation in the epithelium that is mediated through estrogen-dependent PgR. In contrast, in stromal cells progestin activity is not estrogen-dependent, and stimulation of DNA synthesis was not confined to the hormone-implanted glands. Furthermore, RU486 stimulates stromal cell DNA synthesis, and this response is augmented by estrogen. While progestin effects in epithelial cells appear to be mediated by estrogen-dependent PgR, the mechanism operative in stromal cells appears to be different and remains to be elucidated.

Animals↗
PubMed1989

The ontogeny of mouse mammary gland responsiveness to ovarian steroid hormones.

An investigation was carried out to define the ontogeny of normal mouse mammary gland responsiveness to the proliferative effects of estrogen (E) and/or progesterone (P). Since hormone receptors for both estrogen (ER) and progesterone (PgR) are present in both epithelial and stromal cells, we have investigated how the effects of E and P are related to the presence of receptor activity in the epithelium and stroma. Intact or ovariectomized mice, between 3 days and 10 weeks of age, were used to study the effects of E and/or P on DNA synthesis, as determined by DNA histoautoradiography; the cellular distribution of ER and PgR was investigated by steroid autoradiography. The results indicate that the mammary gland sequentially acquires the ability to respond to the stimulatory effects of E and/or P. In the early postnatal period (3-14 days) neither hormone was effective. Both epithelial and stromal cells first became responsive to E at 3-4 weeks of age. Estrogen receptors were first detected in stromal cells at 5 days of age and in epithelial cells at 2 weeks of age. Thus, the acquisition of estrogen responsiveness did not appear to be tightly coupled to the presence of ER in either epithelial or stromal cells. In contrast, responsiveness to P was acquired significantly later, at 7 weeks of age, and was closely linked to the presence of E-inducible PgR in epithelial cells. P caused a highly synergistic effect on epithelial cell DNA synthesis when combined with E, providing further support for the concept that the major proliferative effect of P is mediated via E-inducible PgR. PgR were also present in stromal cells, but the proliferative effect of P in that cell type was not correlated with the presence of PgR.

Aging↗
PubMed1988

Acquisition of estrogen-dependent progesterone receptors by normal mouse mammary gland. Ontogeny of mammary progesterone receptors.

Progesterone is known to stimulate cell proliferation of normal and neoplastic rodent mammary tissues. Recently we have observed that while progesterone is highly effective in sexually mature mice, no significant effect of progesterone can be demonstrated in immature, pubertal mammary gland. In the case of the adult gland, the mitogenic effects of progesterone appear to be related to the presence of E-dependent progesterone receptors (PgR). By contrast, immature mammary glands lack E-dependent PgR. The purpose of the present studies was to study the ontogeny of E-dependent PgR and the factors that lead to the acquisition of responsiveness to progesterone. The results obtained demonstrate that E-dependent PgR are first detectable at 7 weeks of age. Analysis of changes occurring in the mammary gland around this time indicate that E-dependent PgR are not acquired until the pubertal mammary epithelial growth phase has occurred. Furthermore both the growth phase and acquisition of PgR are dependent upon the presence of the ovaries. Analysis of concentration and subcellular distribution of both PgR and estrogen receptors indicate that there are no differences between pubertal and adult mice that could account for the absence of this estrogenic response and lack of E-dependent PgR in immature mammary gland.

Animals↗
PubMed1988

Progesterone effects on deoxyribonucleic acid synthesis in normal mouse mammary glands.

Current in vivo and in vitro data indicate that progesterone (P) is required for epithelial proliferation in mammary glands of adult mice. P receptors (PgR) in adult mammary glands are under estrogenic regulation. By contrast in immature, pubertal 5-week-old mice, PgR are present only in low concentration and cannot be increased by estrogen (E). Having identified two different mammary gland developmental states with differing PgR compositions, the purpose of the present studies was to investigate the roles of E-dependent and -independent PgR in epithelial cell proliferation. DNA histoautoradiography was used to quantitate the effect of P on DNA synthesis; hormonal effects on mammary gland morphology were also assessed. The results demonstrate the P, rather than E, has a major role in stimulating epithelial DNA synthesis in the adult mammary gland. The morphological correlate of P's stimulatory effect on cell proliferation was increased ductal side-branching. We postulate that P is acting via E-dependent PgR and that one important way in which E promotes epithelial cell proliferation in adult tissue is by its ability to increase PgR concentration. In the immature mammary gland E rather than P is primarily responsible for stimulation of epithelial cell proliferation at this developmental stage. It appears likely that the absence of a predominant, P-mediated cell proliferative effect is related to the lack of E-dependent PgR.

Animals↗
PubMed1988

Local versus systemically mediated effects of estrogen on normal mammary epithelial cell deoxyribonucleic acid synthesis.

While it has been shown that estrogen promotes mammary gland growth in vivo, it has not been demonstrated if estrogen acts locally in the mammary gland to produce a mitogenic effect in the epithelial cells or if the mitogenic effect is mediated systemically. The purpose of this study was to distinguish between local vs. systemically mediated modes of estrogen action in normal mammary glands of both immature 5-week-old and sexually mature 10-week-old mice. Elvax 40P, noninflammatory, easily manipulated implant material, was combined with 17 beta-estradiol and placed either directly into the mammary gland to elicit a localized effect or implanted sc to produce a systemic effect. The effect of estrogen on epithelial cell proliferation was assessed by its effect on mammary gland morphology from whole mount examinations and on DNA synthesis by DNA histoautoradiography. The effects of implant location and estrogen dose on mammary and uterine progesterone receptor (PgR) concentrations were also analyzed. The results indicate that estrogen can act locally to stimulate increased epithelial DNA synthesis and an increase in end-bud size in the immature mammary gland. By contrast, no localized effect of estrogen could be demonstrated in the mature mammary gland; it appears that increased epithelial DNA synthesis and ductal side-branching are systematically mediated effects of estrogen. On the other hand, in the case of PgR regulation, estrogen can act locally to increase receptor concentration in the adult gland. In contrast, in the immature mammary gland only low levels of PgR were detectable, and they could not be increased by any method of estrogen treatment. Thus, these results demonstrate that estrogen can act either locally or systemically to produce mitogenic effects on mammary epithelium. However, the age and/or developmental stage of the target tissue are important factors that determine the hormonal responsiveness of normal tissue and which mode (local vs. systemic) of estrogen action will be operative.

Aging↗
PubMed1988

Cell to cell interactions and normal mammary gland function.

The nonepithelial components of the mammary gland are reviewed and their potential for regulatory cell-cell interactions with the epithelial cells are discussed. Studies undertaken to examine the regulatory potential of mammary stromal fibroblasts using an in vitro cell culture system are presented. The influence was examined of epithelial-fibroblast interactions on estrogenic regulation of progesterone receptor concentration in epithelial cells and on epithelial and fibroblast DNA synthesis. Mammary fibroblasts affect estrogen responsiveness in epithelial cells by two different mechanisms. In the case of progesterone receptor regulation, fibroblasts promote estrogen-dependent increases in the receptor via a substratum effect possibly by the production of collagen type I. By contrast, the fibroblast effect promoting estrogen-dependent cell proliferation requires fibroblasts to be metabolically active and in close contact with the epithelium. Additionally, under coculture conditions, estrogen-dependent stimulation of fibroblast DNA synthesis is also observed, indicating a bidirectional, interactive phenomenon between the two types of cells. It is possible that the modulations in epithelial responsiveness to estrogen that are associated with the presence of mammary fibroblasts in vitro reflect regulatory mechanisms that operate in vivo.

Animals↗
PubMed1986

Mammary fibroblast influence on normal mouse mammary epithelial cell responses to estrogen in vitro.

Estrogen-dependent stimulation of progesterone receptor (PgR) concentration or cell proliferation of normal mammary epithelial cells in vitro has been shown to be associated with the presence of mammary fibroblasts. To investigate further the nature of fibroblast influence on epithelial cells, Percoll-purified epithelial cells from collagenase-dissociated mammary glands of mid-pregnant BALB/c mice were co-cultured with mammary fibroblasts that were either untreated, irradiated, or glutaraldehyde-killed or with fibroblast-conditioned medium. Epithelial cells were then assayed for either estrogen-dependent stimulation of PgR by measuring specific [3H]R5020 binding or for estrogen-dependent stimulation of DNA synthesis by [3H]thymidine autoradiography. The results demonstrate that stimulation of PgR does not require the presence of live fibroblasts; either glutaraldehyde-killed fibroblasts or conditioned medium was effective. Pretreatment of culture dishes with type I collagen was equally effective, indicating that fibroblasts may promote the PgR response via a substratum effect. In distinct contrast, estrogen-dependent stimulation of DNA synthesis occurred only when live fibroblasts were present in high numbers and/or in direct contact with epithelial cells. Furthermore, under these latter conditions, epithelial cells also promoted estrogen-dependent stimulation of fibroblast DNA synthesis. Differences in both epithelial and fibroblast cell morphologies were also observed under co-culture conditions, which suggested that cell-cell communication or another interactive phenomenon takes place and is bidirectional. Thus there appear to be at least two different mechanisms by which fibroblasts can influence two specific responses of epithelial cells to estrogen. The present results demonstrate that the specific nature of epithelial-stromal interactions can determine and modulate epithelial cell responses to estrogen and may reflect in vivo regulatory processes affecting normal and neoplastic mammary cells.

Animals↗
PubMed1985

Estrogen responsiveness of normal mouse mammary cells in primary cell culture: association of mammary fibroblasts with estrogenic regulation of progesterone receptors.

Estrogens enhance proliferation of normal mouse mammary cells in vivo. However, when cultured alone, normal mouse mammary epithelial cells fail to exhibit a proliferative response to estrogen in vitro; the basis for this lack of in vitro responsiveness to estrogen is not known. The purpose of the present study is to determine if cultured normal mouse mammary cells possess estrogen receptors (ER) and/or progesterone receptors (PgR) and if the ER mechanism is functional, as measured by the ability of estrogens to regulate PgR. Recent findings that mammary fibroblasts can influence the behavior of mammary epithelial cells in vitro led us to investigate their effect on epithelial cell responsiveness to estrogen. In these studies, collagenase-dissociated mammary glands of midpregnant BALB/c mice were the source of mixed cultures (containing both epithelial cells and fibroblasts) and epithelial or fibroblast cultures. The purity of epithelial or fibroblast cultures was quantified immunocytochemically using antivimentin antibody as a fibroblast marker. Steroid hormone binding was quantified in intact cultured cells using [3H]R5020 and 17 beta-[3H]estradiol as the ligands. Specific high affinity binding sites for estrogen (Kd = 3.1 +/- 0.8 X 10(-10] and progestins (Kd = 3.3 +/- 1.2 X 10(-9) M) were detected in mixed cultures. To assess the possible role of mammary fibroblasts, we investigated cultures containing only fibroblasts which were derived by differential centrifugation. When 17 beta-estradiol was added to the culture medium, a significant (P less than 0.01) increase in PgR concentration was observed in mixed cultures. While mixed cultures maintain responsiveness to estrogen in vitro, as measured herein, the epithelial cultures, derived by differential centrifugation and Percoll gradient sedimentation, did not. However, estrogenic regulation of PgR appears to be specific to epithelial cells in mixed cultures, since fibroblast cultures neither contained PgR nor displayed estrogen-inducible PgR. The lack of responsiveness of epithelial cultures is not due to a loss or decrease in the ER concentration. Thus, the presence of mammary fibroblasts appears to be associated with epithelial cell responsiveness to estrogen in vitro.

Animals↗
PubMed1984

Estrogen receptor activation in normal mammary gland.

Cytoplasmic estrogen receptor (CER) activation and nuclear estrogen receptor (NER) forms have been examined in normal virgin and lactating mammary gland by 1) measuring [3H]estradiol-receptor dissociation kinetics, and by 2) sucrose density gradient analysis of sedimentation behavior on high salt gradients. The data show two forms of CER in both virgin and lactating mammary gland: 1) a fast dissociating-nonactivated form which sediments at 4 S, and 2) a slow dissociating-activated form which sediments at 5 S. The 5 S slow dissociating estrogen receptor (ER) is the predominant form found in the nucleus. CER are activated by exposure to elevated temperature, high salt concentration, dilution, or ammonium sulfate fractionation. This is demonstrated by an increase in the proportion of the slow dissociating, 5 S ER form. Sodium molybdate inhibits activation and prevents heat- or ammonium sulfate-induced increase in the amount of the slow-dissociating CER as well as the 4 S to 5 S increase in sedimentation coefficient. We also found that cytoplasmic and nuclear 5 S ER forms were susceptible to 1) cold-induced dissociation, and to 2) degradation by nuclear protease activity. Thus, whereas mammary gland CER activation and NER forms described herein are very similar to those reported for other estrogen target tissues, the experimental conditions required to demonstrate the activated-nuclear form of ER differ substantially from those reported for uterine tissue. These findings may be important for assessing differences in ER forms in certain disease states such as mammary neoplasia. Previously we have shown that lactating mammary gland, in contrast to virgin mammary gland, is not responsive to estrogen. Having compared CER and NER forms and receptor activation in virgin vs. lactating mammary gland, we find no differences between ER in these two tissue states that can explain the absence of responsiveness to estrogen during lactation.

Animals↗
PubMed1981

Relative distribution of estrogen and progesterone receptors among the epithelial, adipose, and connective tissue components of the normal mammary gland.

The present studies were undertaken to determine the relative distribution of estrogen and progesterone receptors (PgR) in the epithelial, adipose, and connective tissues of normal mouse mammary gland and to determine in which tissue(s) the modulations in PgR concentration and mammary gland sensitivity to estrogenic stimulation of PgR occur. Mammary epithelium was separated from adipose and connective tissues surgically in vivo according to the cleared fat pad technique. Binding studies using [3H]R5020 or [3H]estradiol were carried out on cytoplasmic extracts of intact mammary gland or cleared fat pads which were devoid of epithelium and contained only mammary adipose and connective tissues. We found that mammary adipose and connective tissues contain separate, high affinity, steroid-specific, macromolecular binding sites for estrogen and progesterone, and the majority of PgR are present only in the glandular epithelium. Furthermore, the modulation in PgR concentration relative to mammary gland development as well as the estrogenic regulation of PgR concentration appear to be restricted to the epithelial component of mammary gland. Since the major mammary gland developmental changes that occur during pregnancy and lactation also occur in the epithelium, it is proposed that the receptor modulations may serve a regulatory function in mammary gland.

Adipose Tissue↗
PubMed1980

The effect of age on the histopathogenesis of 7,12-dimethylbenz(a)-anthracene-induced mammary tumors in the Lewis rat.

The influence of age at time of DMBA administration on (1) the histopathogenesis and site of mammary tumor origin and (2) the precancerous nature of DMBA-induced mammary dysplasias was examined in Lewis rats between 25 and 200 days of age. Rats were killed at various times after carcinogen treatment and the numbers of tumors and dysplasias were recorded from microscopic examination of mammary gland wholemounts. We found that, in all age-groups tested, mammary tumors always appeared to originate within mammary end-buds and terminal ductules and that terminal ductule hyperplasia appeared to be an early stage in tumor formation. Age-related differences in susceptibility to tumor development were paralleled by similar differences in susceptibility to the development of terminal ductule hyperplasias. In contrast, although age-related differences in susceptibility to the development of hyperplastic alveolar nodules were also noted, they did not correspond to those observed for tumor development. Thus, hyperplastic alveolar nodules did not appear to be a site of tumor origin in situ or directly related to tumor development.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Progesterone receptors in normal mammary gland: receptor modulations in relation to differentiation.

The biological basis for the observed modulation in cytoplasmic progesterone receptors (PgR) of normal mammary gland occurring during mammary development was investigated. Specifically, the relative roles of hormones vs. differentiation on (a) the decrease in PgR concentration during pregnancy and lactation and (b) the loss of mammary responsiveness to estrogen during lactation were examined. PgR were measured using the synthetic progestin, R5020, as the ligand. The hormones estrogen and progesterone were tested in vivo for their effect of PgR concentration. Mammary gland differentiation was assessed morphologically and by measuring enzymatically active alpha-lactalbumin. These studies show that there is a stepwise decrease in PgR that occurs in two stages. The first decrease is completed by day 12 of pregnancy and the second decrease occurs only after parturition. There appears to be a hormonal basis for the first decrease and it appears to be caused by the negative effect of progesterone on estrogen-mediated increase in PgR. In direct contrast, the absence of PgR during lactation and the mammary tissue insensitivity to estrogenic stimulation of PgR were not related to the hormonal milieu of lactation but were directly related to the secretory state of the mammary gland and lactation per se.

Animals↗