Biomedical subjects

A M Raafat

Publications and source records attributed to A M Raafat.

10 recordsLinked to original sources

PubMed2002

Postmenopausal hormone replacement therapy: effects on normal mammary gland in humans and in a mouse postmenopausal model.

Endogenous estrogen exposure has long been implicated in the causation of breast cancer through a mechanism of epithelial cell proliferation. Whether estrogen, progesterone, or both exhibit mitogenic activity and promote carcinogenesis in the human breast has been the subject of considerable debate. The purpose of this review article is to examine the evidence for the effects of hormone replacement therapy in its various forms on the biology of the postmenopausal breast both in humans and in an animal model, and to identify the gaps in knowledge that research will need to address to further understand this complex issue.

Animals↗

PubMed2001

Estrogen and estrogen plus progestin act directly on the mammary gland to increase proliferation in a postmenopausal mouse model.

Hormone replacement therapy (HRT) with ovarian hormones is an important therapeutic modality for postmenopausal women. However, a negative side effect of HRT is an increased risk of breast cancer. Surgical induction of menopause by ovariectomy (OVX) in mice is an experimental model that may provide insights into the effects of hormone replacement therapy on the human breast. We have developed a mouse model of early and late postmenopausal states to investigate the effects of HRT on the normal mammary gland. The purpose of this study was to determine if HRT-induced proliferation was due to the direct action of the hormones on the mammary gland, or mediated systemically by hormones or growth factors produced elsewhere in the body. Estrogen (E) or E plus the synthetic progestin, R5020, were implanted directly into the mammary glands of early (1 week post OVX) and late (5 week post OVX) postmenopausal mice instead of administration by injection. We report that responses of early and late postmenopausal mice to implanted hormones were the same as those observed previously with systemically administered hormones. Implanted E conferred an enhanced proliferative response in the late postmenopausal gland characterized morphologically by enlarged duct ends. E+R5020 implants induced similar degrees of cell proliferation in both postmenopausal states but the morphological responses differed. Ductal sidebranching was observed in early postmenopausal mice, whereas duct end enlargement was observed in late postmenopausal mice. The differences in morphological response to E+R5020 in 5 week post OVX were associated with an inability of E to induce progesterone receptors (PR) in the late postmenopausal gland. The responses of the late postmenopausal glands to E and E+P were very similar to that observed previously in immature pubertal glands in ovary-intact mice. In pubertal mice, PR cannot be induced by E unless the mammary gland is pre-treated with EGF-containing implants. Similarly, herein pre-treatment of the late postmenopausal mammary gland with EGF-containing implants restored PR induction by E. Thus, EGF may determine the sensitivity of the mammary gland to E and E+P in late postmenopause and at puberty.

Animals↗

PubMed2001

Proliferative effects of combination estrogen and progesterone replacement therapy on the normal postmenopausal mammary gland in a murine model.

OBJECTIVE: The aim of the study was to analyze the proliferative response of the normal mammary gland to combination hormone replacement therapy with estrogen and progesterone in a murine model of early versus late postmenopausal states. STUDY DESIGN: Ovariectomized mice were injected daily for up to 56 days with estrogen plus progesterone, starting at either 1 or 5 weeks after ovariectomy to simulate early and late menopausal periods, respectively. At various times after treatment, proliferation was analyzed by deoxyribonucleic acid histoautoradiography and whole-mount preparations. The induction of progesterone receptor by estrogen was also analyzed. To distinguish between estrogen- and progesterone-specific responses, we tested the effects of the antiprogesterone mifepristone (RU 486) and the antiestrogen ICI 182,780. RESULTS: The acute response to estrogen-progesterone therapy in the early postmenopausal period resulted in duct-end enlargement, ductal side branching, alveolar bud formation, and a 100-fold increase in epithelial cell proliferation. This was caused by the dominant effect of progesterone acting through the progesterone receptor. In the late postmenopausal period the acute response produced only duct-end enlargement; the 100-fold increase in epithelial cell proliferation resulted from the dominant effect of estrogen. After long-term treatment, both early and late postmenopausal glands exhibited similar morphologic features and a 9-fold higher steady-state proliferation rate than was found in control-treated groups. CONCLUSIONS: Starting combined estrogen and progesterone hormone replacement therapy in either early or late postmenopause produced a persistent, steady-state 9-fold increase in epithelial cell proliferation, which could be a contributing factor to increased breast cancer risk. The acute response in the late postmenopausal period mimics the hormonal response of the pubertal mammary gland, which in rodents is the stage most susceptible to carcinogen-induced mammary tumorigenesis. These observations raise questions about increased susceptibility of the late postmenopausal gland to carcinogenesis and a role for hormone replacement therapy in the promotion of tumorigenesis.

Animals↗

PubMed1999

A mouse model to study the effects of hormone replacement therapy on normal mammary gland during menopause: enhanced proliferative response to estrogen in late postmenopausal mice.

Hormone replacement therapy (HRT) with estrogen alleviates menopausal symptoms and is effective in reducing osteoporosis and cardiovascular disease when taken in early postmenopause. Older, late postmenopausal women who never previously received HRT are also believed to benefit from estrogen treatment. On the other hand, increased lifetime exposure of the mammary gland to estrogen may increase the risk of breast cancer. The development of suitable experimental animal model systems can advance our understanding of the effects of estrogen and the timing of HRT on the postmenopausal breast. Toward this end, early and late postmenopausal states were induced in mice by short vs. long term ovariectomy (1 vs. 5 weeks), and the effects of 17beta-estradiol (E) on mammary gland morphology, cell proliferation, and progesterone receptor (PR) levels were investigated. We report that in late postmenopausal mice, E caused a pronounced enlargement of duct ends and 6.5- and 4-fold greater mitogenic responses in the duct end epithelium and adjacent stromal cells, respectively, compared with the response in early postmenopausal mice. Furthermore, after long term, daily treatment with E, steady state levels of proliferation remained 2-fold higher than those of similarly treated, early postmenopausal mice. E failed to increase mammary PR levels in late postmenopausal, but not in early postmenopausal mice. Stimulation of duct ends by E and lack of PR inducibility are characteristics of the immature pubertal mammary gland and indicate that the late postmenopausal mammary gland resembled the immature state. In contrast, minimal E-induced proliferation and increased PR inducibility, characteristics of the adult, sexually mature mammary gland, were retained in early postmenopausal mice. The lack of difference in the numbers of estrogen receptor-positive epithelial or stromal cells or in estrogen receptor cellular concentration after short vs. long term ovariectomy indicates that the observed greater efficacy of E is mediated at a step beyond receptor-ligand binding. This mouse model of experimentally induced early vs. late postmenopausal states should prove useful in better understanding alterations in hormone responsiveness and their implications for timing of HRT on the human breast.

Age Factors↗

PubMed1999

Hormone replacement therapy with estrogen or estrogen plus medroxyprogesterone acetate is associated with increased epithelial proliferation in the normal postmenopausal breast.

The relative effects of postmenopausal hormone replacement therapy (HRT) with estrogen alone vs. estrogen+progestin on breast cell proliferation and on breast cancer risk are controversial. A cross-sectional observational study was carried out to examine the proliferative effects of HRT with estrogen or estrogen plus the progestin, medroxyprogesterone acetate, in breast tissue of postmenopausal women. Benign breast biopsies from 86 postmenopausal women were analyzed with antiproliferating cell nuclear antigen (anti-PCNA) and Ki67 antibodies to measure relative levels of cell proliferation. Epithelial density and estrogen and progesterone receptor status were also determined. The women were categorized either as users of: 1) estrogen (E) alone; 2) estrogen+medroxyprogesterone acetate (E+P); or 3) no HRT. Compared with no HRT, the breast epithelium of women who had received either E+P or E alone had significantly higher PCNA proliferation indices, and treatment with E+P had a significantly higher index (PCNA and Ki67) than treatment with E alone. Breast epithelial density was significantly greater in postmenopausal women treated with E and E+P, compared with no HRT. Thus, the present study shows that postmenopausal HRT with E+P was associated with greater breast epithelial cell proliferation and breast epithelial cell density than E alone or no HRT. Furthermore, with E+P, breast proliferation was localized to the terminal duct-lobular unit of the breast, which is the site of development of most breast cancers. Further studies are needed to assess the possible association between the mitogenic activity of progestins and breast cancer risk.

Adult↗

PubMed1998

Mammary gland growth and development from the postnatal period to postmenopause: ovarian steroid receptor ontogeny and regulation in the mouse.

Ovarian steroid hormones play a critical role in regulating mammary gland growth and development. The mammary gland sequentially acquires and cyclically exhibits proliferative responses to estrogen and/or progesterone from birth to postmenopause. The focus of this review is to present our current understanding of estrogen and progesterone receptor distribution in epithelial and stromal cells and their functions in relation to mammary gland development. Insights gained from the study of the normal mammary gland are relevant to our understanding of the conditions which may predispose women to the development of breast cancer as well as to alterations in hormonal regulation that occur in breast cancer.

Animals↗

PubMed1997

Effect of thyroid hormone (T3)-responsive changes in surfactant apoproteins on surfactant function during sepsis.

BACKGROUND: Long surfactant phospholipids are altered during sepsis; the role of surfactant apoproteins is unknown. This study investigates the effect of cecal ligation and puncture (CLP) on surfactant functional effectiveness and apoprotein transcriptional activity with or without T3 replacement. METHODS: Male Sprague Dawley rats underwent sham laparotomy or CLP with or without T3 replacement. Lung compliance, surfactant adsorption, and surface tension were measured with a surfactometer. Surfactant apoproteins A, B, and C (SP-A, SP-B, SP-C) mRNA was quantified by Northern blot analysis. RESULTS: Lung compliance was significantly decreased by sepsis; initial surface tension and adsorption values in CLP animals reflected apoprotein dysfunction. Sepsis decreased SP-A mRNA levels and increased SP-B mRNA; SP-C mRNA were unchanged. T3 treatment improved compliance, adsorption, and ST isotherms in septic animals. CONCLUSION: T3 attenuated sepsis-induced surfactant dysfunction and SP-A and SP-B transcriptional changes during sepsis. This suggests an interaction between the thyroid, surfactant apoproteins, and lung surfactant functional effectiveness and requires further study.

Animals↗

PubMed1997

Calcium blockade reduces renal apoptosis during ischemia reperfusion.

Apoptosis is well described in invertebrates and recently documented in mammals. The prevalence and pathophysiology of mammalian apoptosis is unknown and may have clinical ramifications. The aim of this study is to investigate the apoptotic response during kidney ischemia-reperfusion (I/R) injury. Kidney I/R was initiated in anesthetized rats by occlusion of the renal pedicle for 45 min with or without pretreatment with .2 mg/kg verapamil: control animals received sham exposure. Flow was re-established after ischemia and the animals were allowed to recover for 24 h. Bilateral kidneys were harvested for DNA electrophoresis, Western analysis for p53, Northern analysis for c-myc expression, and light and electron microscopic analysis. Kidney I/R caused characteristic DNA laddering in the clamped kidney, and less extensive laddering was seen in the contralateral kidney. Light and electron microscopic analysis confirmed apoptotic morphology in the reperfused tissues. Verapamil pretreatment completely abolished DNA laddering and attenuated the microscopic evidence of apoptosis. p53 levels were increased by I/R in the ischemic kidney and moderately increased in the contralateral organ. c-myc mRNA levels were increased by the I/R insult. Kidney I/R injury may induce global apoptosis, which seems to be associated with an alteration in calcium homeostasis. The increase in p53 and c-myc mRNA levels seen with I/R may facilitate apoptosis. Calcium modulation seems to reduce apoptosis during I/R and may have therapeutic implications.

Animals↗

PubMed1997

Effect of triiodothyronine augmentation on rat lung surfactant phospholipids during sepsis.

Surfactant functional effectiveness is dependent on phospholipid compositional integrity; sepsis decreases this through an undefined mechanism. Sepsis-induced hypothyroidism is commensurate and may be related. This study examines the effect of 3,3',5-triiodo-L-thyronine (T3) supplementation on surfactant composition and function during sepsis. Male Sprague-Dawley rats underwent sham laparotomy (Sham) or cecal ligation and puncture (CLP) with or without T3 supplementation [CLP/T3 (3 ng/h)]. After 6, 12, or 24 h, surfactant was obtained by lavage. Function was assessed by a pulsating bubble surfactometer and in vivo compliance studies. Sepsis produced a decrease in surfactant phosphatidylglycerol and phosphatidic acid, with an increase in lesser surface-active lipids phosphatidylserine and phosphatidylinositol. Phosphatidylcholine content was not significantly changed. Sepsis caused an alteration in the fatty acid composition and an increase in saturation in most phospholipids. Hormonal replacement attenuated these changes. Lung compliance and surfactant adsorption were reduced by sepsis and maintained by T3 treatment. Thyroid hormone may have an active role in lung functional preservation through maintenance of surfactant homeostasis during sepsis.

Animals↗

PubMed1996

Gallbladder and biliary tract candidiasis.

BACKGROUND: The clinical significance of Candida spp isolated from the gallbladder on the biliary tract is relatively unknown. METHODS: To provide this information, patients with Candida spp isolated from gallbladder and other biliary tract sources during a 10-year period were identified through the records of our clinical microbiology laboratory. Medical records were analyzed for biliary disease causes, culture data, treatment, and outcome. RESULTS: Twenty-seven patients were identified. Five of seven patients with cholecystitis were critically ill intensive care unit (ICU) patients in whom the mortality rate was 100%. Gallstone pancreatitis was found in four patients and was fatal in one patient with a pancreatic abscess and ongoing retroperitoneal sepsis. An external biliary shunt/endoprosthesis was placed in 16 patients to relieve biliary obstruction. Cholangitis was present in 14 patients, and most bile cultures contained Candida as part of a mixed flora. Only 3 of 27 patients had candidemia, and 22 of 27 patients were colonized with Candida at other sites. CONCLUSIONS: (1) The ICU patient with Candida cholecystitis has a grave prognosis. (2) Patients with Candida isolated from biliary stents placed for obstruction and cholangitis should be treated with both antifungal and broad spectrum antimicrobial agents. (3) Candidemia is not frequently seen in this setting.

Adult↗