Obesity, inflammation, and vascular disease: the role of the adipose tissue as an endocrine organ

Insulin resistance, both in nondiabetic and diabetic subjects, is frequently associated with obesity, particularly with an excess of central fat. With the growing prevalence of obesity, scientific interest in the biology of adipose tissue has been extended to the secretory products of adipocytes, since they are increasingly shown to influence several aspects in the pathogenesis of obesity-related diseases Until relatively recently, the role of fat itself in the development of obesity and its consequences was considered to be a passive one; adipocytes were considered to be little more than storage cells for fat. It is now clear that, in addition to storing calories as triglycerides, they also secrete a large variety of proteins, including cytokines, chemokines and hormone-like factors, such as leptin, adiponectin and resistin. This production of pro-atherogenic chemokines by adipose tissue is of particular interest since their local secretion, e.g. by perivascular adipose depots, may provide a novel mechanistic link between obesity and the associated vascular complications. Recent research has revealed many functions of adipocytokines extending far beyond metabolism, such as immunity, cancer and bone formation. This remarkable understanding is allowing us to more clearly define the role that adipocytes play in health and in obesity and how inflammatory mediators act as signaling molecules in this process. Moreover, on a molecular level, we are beginning to comprehend how such variables as hormonal control, exercise, food intake, and genetic variation interact and result in a given phenotype, and how pharmacological intervention may modulate adipose tissue biology.

Helicobacter pylori infection stimulates intestinalization of endocrine cells in glandular stomach of Mongolian gerbils

Intestinal metaplasia has been investigated extensively as a possible premalignant condition for stomach cancer but its pathogenesis is still not fully understood. In the present study, we examined the relationship between endocrine and mucous cell marker expression periodically after Helicobacter pylori infection in the Mongolian gerbil model. The numbers of chromogranin A (CgA)-positive, gastrin-positive and gastric inhibitory polypeptide (GIP)-positive cells in H. pylori-infected groups was increased significantly compared with the non-infected case. However, CgA-positive and gastrin-positive cells then decreased from 50 through 100 experimental weeks after H. pylori infection, whereas GIP-positive cells increased. Coexistence of gastrin-positive and GIP-positive cells was detected in the same gastric and intestinal mixed phenotypic glandular-type glands. In conclusion, the endocrine cell phenotype is in line with that of the mucous counterpart in the glands of H. pylori-infected Mongolian gerbil stomach, supporting the concept that development of intestinal metaplasia is due to the abnormal differentiation of a stem cell.

Treatment of alternated water-electrolyte balance and endocrine status after removal of craniopharyngioma in adults

BACKGROUND

Water-electrolyte disturbance and endocrine alterations are common complications of adult patients with craniopharygioma in the postoperative period and may affect their recovery and prognosis. Some of these complications even lead to death. Appropriate remedy based upon the status of water-electrolyte balance and the endocrine system is essential to good therapeutic results of adult patients with craniopharyngioma.

METHODS

The alterations in water-electrolyte balance (117 patients) and endocrine status (42) of adult patients with craniopharyngioma after surgery were analyzed retrospectively.

RESULTS

Most patients with craniopharyngioma experienced postoperative water-electrolyte disturbances and hypotonic dehydration. Moreover, the incidences of hypothyroidism and hypoadrenocorticism were relatively high.

CONCLUSION

It is critical to deal with dehydration and endocrine disorders for a sound outcome of craniopharyngioma surgery.

A repeated 28-day oral dose toxicity study of nonylphenol in rats, based on the 'Enhanced OECD Test Guideline 407' for screening of endocrine-disrupting chemicals

A 28-day repeated oral dose toxicity study of nonylphenol (NP) was performed for an international validation of the 'Enhanced OECD Test Guideline 407' paying particular attention to the sensitivity of individual endocrine-related parameters. Sprague-Dawley rats, each group consisting of ten males and ten females, were administered NP once daily by gavage at doses of 0 (control), 10, 50, or 250 mg/kg body weight. At 250 mg/kg, three females died or became moribund during the experiment. At this dose, hepatic and renal toxicity was evident in both sexes with increase of relative liver and kidney weights as well as histopathological changes, such as centrilobular liver cell hypertrophy and a variety of renal tubular lesions, and alteration of serum biochemical parameters, some of them being evident from 50 mg/kg in females (glucose and inorganic phosphates). Hematologically, development of anemia was evident at 250 mg/kg in both sexes. Regarding endocrine-related effects, increase of thyroid weight in males was detected from 50 mg/kg. At 250 mg/kg, males exhibited reduction of relative weights of the ventral prostate and seminal vesicles, and females developed irregular estrous cyclicity and vaginal mucosal hyperplasia. Although changes in serum hormone levels were detected in both sexes, magnitude of the changes was small to be regarded as a low toxicological significance. In summary, repeated oral doses of NP to rats for 28 days resulted in hepato-renal toxicity from 50 mg/kg and anemia at 250 mg/kg. Effects on the endocrine system were observed from 50 mg/kg, and assessment of weights and histopathology of endocrine-related organs and estrous cyclicity may be valid in a battery for detecting endocrine effects of NP. The no-observed-adverse-effect level of NP was estimated to be 10 mg/kg per day.

Fat as an endocrine organ: relationship to the metabolic syndrome

Obesity and the metabolic syndrome have both reached pandemic proportions. Together they have the potential to impact on the incidence and severity of cardiovascular pathologies, with grave implications for worldwide health care systems. The metabolic syndrome is characterized by visceral obesity, insulin resistance, hypertension, chronic inflammation, and thrombotic disorders contributing to endothelial dysfunction and, subsequently, to accelerated atherosclerosis. Obesity is a key component in development of the metabolic syndrome and it is becoming increasingly clear that a central factor in this is the production by adipose cells of bioactive substances that directly influence insulin sensitivity and vascular injury. In this paper, we review advances in the understanding of biologically active molecules collectively referred to as "adipokines" and how dysregulated production of these factors in obese states mediates the pathogenesis of obesity associated metabolic syndrome.

Exfoliated endometrial cell clusters in cervical cytologic preparations are derived from endometrial stroma and glands

Exfoliated endometrial cells are a common finding on Papanicolaou smears obtained during the menstrual period. They have a characteristic morphologic appearance, but whether they are of endometrial glandular, stromal, or mixed origin is still debated. Cervical ThinPrep (Cytyc, Marlboro, MA) slides obtained during menses from women younger than 40 years were immunostained for a stromal (CD10) and an epithelial (keratin proteins) marker. Endometrial cell clusters were scored as purely stromal (composed entirely of CD10+ cells), purely glandular (entirely keratin+ cells), or mixed stromal and glandular. Of the 59 endometrial cell clusters scored, 22 (37%) were purely stromal, 17 (29%) purely glandular, and 20 (34%) mixed stromal and glandular. Exfoliated endometrial cell clusters often are composed exclusively of stromal cells. Mixed stromal-glandular groups and entirely glandular groups also are common. The distinction between stromal and glandular cells is not always possible by conventional Papanicolaou staining but can be established by immunocytochemical study.

Tumeurs endocrines : biologie et physiopathologie

Endocrine tumors are defined as neoplastic lesions resulting from the proliferation of cells engaged in an endocrine differentiation pathway, as shown by their expression of a set of specific markers, including true endocrine markers (such as chromogranine A) and neuro-endocrine markers, shared between neurons and endocrine cells (such as synaptophysin). The demonstration of the synthesis and secretion of one or several hormones is not necessary for the assessment of the endocrine nature of a tumor; only tumors associated with a clinical syndrome resulting from hormone overproduction can be said functioning endocrine tumors. Beyond their common features, endocrine tumors are characterized by a marked diversity, which results from the large functional, structural and embryological heterogeneity of normal endocrine cells. The natural history of endocrine tumors is also characterized by a marked heterogeneity in their evolution and rate of progression. While most endocrine tumors are locally and slowly evolving, some of them behave as truly malignant tumors, as shown by their capacity of metastatic dissemination and their fatal evolution. A better understanding of the cellular and molecular mechanisms involved in tumor progression and metastatic dissemination is necessary for the identification of new prognostic tools and novel therapeutic targets.

Ovarian size and blood flow in women with polycystic ovary syndrome and their correlations with endocrine parameters

OBJECTIVE

To determine how common polycystic ovarian morphology may be in women given the clinical diagnosis of polycystic ovary syndrome (PCOS) based on chronic anovulation and hyperandrogenism and whether certain hormonal factors correlate with ovarian morphology and blood flow.

DESIGN

Prospective study.

SETTING

Two academic endocrinology centers in Italy.

PATIENT(S)

Three hundred twenty-six women with PCOS and 50 age-matched and weight-matched ovulatory women.

INTERVENTION(S)

Ultrasound assessment of ovarian morphology in patients and controls and ovarian blood flow and fasting hormone levels in a subset of 50 patients and matched controls.

MAIN OUTCOME MEASURE(S)

Ovarian morphological assessments, ovarian blood flow by pulsatility index (PI) and resistance index (RI), and measurements of gonadotropins, estrogen, sex hormone-binding globulin, androgens, inhibin B, glucose, and insulin.

RESULT(S)

Using strict ultrasound criteria, 195 woman (60%) had enlarged ovaries, 135 (35%) had normal ovarian size but characteristic morphology, and 16 (5%) had normal size and morphology. Ovarian blood flow was increased (reduced PI and RI) in PCOS. All hormonal parameters were elevated in PCOS. Ovarian size correlated only with insulin and a measure of insulin resistance. Ovarian blood flow correlated positively with insulin, T, free T, and E2 but not with luteinizing hormone. Inhibin B showed a negative correlation with ovarian blood flow.

CONCLUSION(S)

When a clinical diagnosis of PCOS was made, virtually all women were found to have characteristic ovarian morphology. Insulin correlated with increased ovarian size as well as with increased blood flow. Blood flow also correlated positively with sex steroids but negatively with inhibin B.

Coexistence of gastric- and intestinal-type endocrine cells in gastric and intestinal mixed intestinal metaplasia of the human stomach

Intestinal metaplasia (IM) in the human stomach has previously been classified into a gastric and intestinal mixed (GI-IM) and a solely intestinal phenotype (I-IM). The phenotypes of mucous and endocrine cells were evaluated in 3034 glandular ducts associated with chronic gastritis. In the pyloric region, the relative expression of gastric endocrine cell markers, such as gastrin and somatostatin, decreased gradually from glandular ducts with only gastric mucous cell phenotype (G type) to GI-IM toward I-IM, while that of the intestinal endocrine cell markers, glicentin, gastric inhibitory polypeptide (GIP), and glucagon-like peptide-1 (GLP-1) was inversely correlated. In the fundic region, gastrin-positive cells emerged in the pseudo-pyloric and GI-IM glands, whereas I-IM glands did not possess any gastrin-positive cells, suggesting the presence of a distinct pathway of intestinalization. Double staining revealed coexistence of gastrin- and GLP-1-positive cells in the same gland and occasionally in the same cell in GI-IM glands. These results suggest that the phenotypes of endocrine cells are in line with those for mucous counterparts and support the concept that all of the different types of mucous and endocrine cells in normal and IM glands might be derived from a single progenitor cell in each gland.

Small fish models for identifying and assessing the effects of endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs), particularly those that affect the hypothalamic-pituitary-gonadal (HPG) axis of vertebrates, have become a focus of regulatory screening and testing throughout the world. Small fish species, principally the fathead minnow (Pimephales promelas), Japanese medaka (Oryzias latipes), and zebrafish (Danio rerio), are used as model organisms for several of these testing programs. Fish are appropriate models for testing EDCs, not only from the perspective of existing ecological impacts, but also in terms of species extrapolation. Specifically, there is a significant degree of conservation of basic aspects of the HPG axis across vertebrates, which provides a technically robust basis for using results from fish tests to predict likely modes/mechanisms of action of potential EDCs in other vertebrates. Different experimental designs/endpoints for partial- and full-life cycle tests with fish that enable a consideration of a broad range of EDCs are described. Examples of results with specific chemicals in tests with the fathead minnow, medaka, and zebrafish are presented and discussed in terms of sensitivity and specificity for different classes of EDCs.

Laboratory animal science issues in the design and conduct of studies with endocrine-active compounds

The use of rodent models for research and testing on endocrine-active compounds necessitates an awareness of a number of laboratory animal science issues to standardize bioassay methods and facilitate reproducibility of results between laboratories. These issues are not unique to endocrine research but are particularly important in this field due to the complexities and interdependencies of the endocrine system, coupled with the inherently sensitive and variable nature of physiological endpoints. Standardization of animal models and the control of animal environments depend on the establishment of strong scientific partnerships between research investigators and laboratory animal scientists. Laboratory animal care and use programs are becoming increasingly complex and are constantly changing, fueled in part by technological advances, changes in regulations concerning animal care and use, and economic pressures. Since the early 1980s, many institutions have moved to centralization of animal facility operations concomitant with numerous changes in housing systems, barrier concepts, equipment, and engineering controls of the macro- and microenvironment. These and other changes can have an impact on animals and the conduct of endocrine experiments. Despite the potential impact of animal care and use procedures on research endpoints, many investigators are surprisingly naive to the animal facility conditions that can affect in vivo studies. Several key animal care and use issues that are important to consider in endocrine experiments with rodent models are described.

Factors considered in using birds for evaluating endocrine-disrupting chemicals

Documented effects on fish and wildlife populations, coupled with evidence from human poisonings, epidemiology, and experimental toxicology, led to the formation of the Endocrine Disruptor Screening Program within the US Environmental Protection Agency. The main objectives of the program are to validate and implement the screens and tests that have been proposed for evaluating possible endocrine-disrupting activity of chemicals. An avian two-generation test is one of the recommended higher tier tests currently undergoing prevalidation. The advantages and disadvantages of the two species of quail considered as candidates, the northern bobwhite (Colinus virginianus) and the Japanese quail (Coturnix japonica), are described as well as the basis for final selection of the Japanese quail. Among the numerous considerations necessary for ultimately optimizing a two-generation test method using birds, the following key factors are discussed: the number of birds used in the test, when to begin exposure of the P generation, selection and exposure of the F1 generation, and endpoints.

In vitro models in endocrine disruptor screening

The public and scientific concern that chemicals present in the human diet and the environment and their ability to disrupt the normal hormonal milieu in humans and wildlife have become a high-profile international issue. In 1998, the Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) convened by the Environmental Protection Agency (EPA) recommended a tiered testing approach for the evaluation of estrogen, androgen, and thyroid-related effects of some 87,000 commercial chemicals and environmental contaminants. The function of this committee concluded with its final report, and the further implementation of the recommended testing strategy has now been carried forward with the assistance of the Endocrine Disruptor Methods Validation Subcommittee. The function of this body is to provide advice to the EPA on scientific and technical issues related specifically to the conduct of studies required for the validation of assays proposed by the EDSTAC as part of the tiered screening program. The EDSTAC recommended and alternative screening batteries encompass four in vitro mammalian assays. The current methodologies and validation status of the proposed in vitro EDSTAC assays are discussed and consist of estrogen/androgen receptor binding, estrogen/androgen gene transactivation, and minced testis, and one alternate (placental aromatase) in vitro screening assay.

Selecting the appropriate rodent diet for endocrine disruptor research and testing studies

Selecting the optimum diet for endocrine disruptor (ED) research and testing studies in rodents is critical because the diet may determine the sensitivity to detect or properly evaluate an ED compound. Dietary estrogens can profoundly influence many molecular and cellular event actions on estrogen receptors and estrogen-sensitive genes. The source, concentration, relative potency, and significance of dietary estrogens in rodent diets are reviewed, including dietary factors that focus specifically on total metabolizable energy and phytoestrogen content, which potentially affect ED studies in rodents. Research efforts to determine dietary factors in commercially available rodent diets that affect uterotrophic assays and the time of vaginal opening in immature CD-1 mice are summarized. A checklist is provided of important factors to consider when selecting diets for ED research and testing studies in rodents. Specific metabolizable energy levels are recommended for particular bioassays. Discussions include the between-batch variation in content of the phytoestrogens daidzein and genistein, the effects of total metabolizable energy and phytoestrogens on the timing (i.e., acceleration) of vaginal opening, and increased uterine weight in immature CD-1 mice. It is concluded that rodent diets differ significantly in estrogenic activity primarily due to the large variations in phytoestrogen content; therefore animal diets used in all ED studies should ideally be free of endocrine-modulating compounds.

Behavioral effects of endocrine-disrupting substances: phytoestrogens

A major source of endocrine-disrupting substances, usually not considered in laboratory animal experiments, is the diet used in research investigations. Soy represents the main protein source in almost all natural-ingredient commercially available formulated diets. Soy-derived isoflavones are the most abundant and in many ways the most studied phytoestrogens, and phytoestrogens (isoflavones) are known endocrine disruptors. Research is reviewed that identifies the physiological and behavioral endocrine-disrupting effects of dietary phytoestrogens (isoflavones) in animal diets, including most of the isoflavones, which are in a glycoside form and biologically inactive, and those in the gastrointestinal tract, which are biologically active. The isoflavones genistein and daidzein have similar molecular weights and structural characteristics to that of 17-beta estradiol, which may enable them to exert estrogenic and antiestrogenic properties are described and characterized. Daidzein can be further metabolized to the potent and abundant molecule equol, which in rodents is produced in very large amounts and represents the major circulating metabolite among all biologically active isoflavones. Equol has the unique and important ability to specifically bind 5 alpha-dihydro-testosterone, and to act in turn to inhibit the action of this potent androgen. The specific influence of dietary soy phytoestrogens on consumptive, learning and memory, and anxiety-related behaviors is identified. Regulatory behaviors such as food and water intake, adipose deposition and leptin, and insulin levels affected by dietary isoflavones are also discussed.

[Cellular functional changes in the endocrine system of the rats upon exposure to coal rock dust and during exercise]

Exposure to coal rock dust in combination with exercise for 2 months was found to have a negative impact on cellular metabolism in the endocrine system. The early form of anthracosilicosis developed in this period. Cytomorphological study revealed cellular changes in the pituitary, thyroid, parathyroid, and pancreatic glands. The cells of the endocrine organs are functionally tense upon exposure to toxic and physical factors and they are most vulnerable in this period of an experiment.

Early-stage carcinoids of the gastrointestinal tract: an analysis of 1914 reported cases

BACKGROUND

Gastrointestinal (GI) carcinoids, considered to be endocrine neoplasms with relatively low levels of malignancy, have never been examined in large, statistically reliable series to determine their true aggressive behavior in the early stage of both minute (</= 5 mm) or small (5.1-10.0 mm) tumors at a depth of invasion restricted to the mucosa and submucosa (sm carcinoids).

METHODS

Of a total number of 1914 cases of GI sm carcinoids selected from the Niigata Registry, 1614 with the tumor size recorded on a millimeter scale were categorized in 5-mm size intervals and rates of metastases were calculated for those in each size category. Of statistical significance was confirmation that the rectum (n = 849), the stomach (n = 449), the duodenum (n = 349), and the jejunoileum (n = 149) were among the principal growth sites. The Kaplan-Meier method was used to calculate 5-year-survival rates (5YSRs) and a comparative study was undertaken.

RESULTS

GI sm carcinoids exhibited a metastasis rate of 16.4% (264 of 1614) as a whole and minute carcinoids (</= 5 mm) revealed an unexpectedly high metastasis rate of 6.0% (24 of 399) on average, which ranged from 3.7% (8 of 216) in the rectum to 17.2% (5 of 29) in the jejunoileum. Small carcinoids measuring 5.1-10 mm also showed a high metastasis rate of 13.3% (90 of 675) on average, ranging from 9.6% (12 of 125) in the stomach to 41.2% (14 of 34) in the jejunoileum. The combined average metastasis rate for both minute and small carcinoids combined (</= 10 mm) was as high as 10.6% (114 of 1074). The comparative study confirmed that, in both the stomach and the rectum, the metastasis rate of sm carcinoids was significantly higher than that for ordinary sm carcinomas in tumors > 10 mm. Although most patients (92.8%; 1777 of 1914) underwent an endoscopy and/or a wider resection of the lesions, nonresectable metastases were found in 22 patients (1.1%). Of these, 16 had undergone a laparotomy and 6 had not received surgery. Among 1001 patients with GI sm carcinoids, the 5YSRs after curative resection ranged from 98.3% in the rectum to 89.6% in the stomach (P < 0.05), representing an average of 96.7% for the entire series.

CONCLUSIONS

Unexpectedly high aggressiveness in metastasis rates in both rectal and gastric sm carcinoids > 10 mm exhibiting values significantly higher than those of sm carcinomas were found in 1914 patients suffering from GI sm carcinoids. However, in sm carcinoids at either the minute or small tumor stage (tumors </= 10 mm), the metastasis rates were comparable to those of sm carcinomas. It should be emphasized that the 5YSRs for patients with GI sm carcinoids may be comparable to those with sm carcinomas in certain cases. These points should be taken into consideration when treating patients with GI carcinoids, particularly in the early stage, and even with the depth of invasion confined to the submucosa.

Metastatic mammary carcinomas with endocrine features: Potential diagnostic pitfalls

Mammary carcinomas with endocrine differentiation (MCED) are an uncommon subtype of breast carcinomas that are morphologically indistinguishable from low-grade endocrine neoplasms arising in other organs. Aspirates of MCED yield relatively monotonous cells with eccentrically placed nuclei containing characteristic "salt and pepper" chromatin. In the breast, these features represent MCED. In extramammary sites, the differential is more extensive, and diagnosing MCED metastases to the lung, a common location for primary and metastatic endocrine tumors, can be a challenging task, with significant clinical implications. Although primary MCED have been described extensively in the cytology literature, secondary pulmonary MCED have not been reported to the best of our knowledge. We report three cases of MCED metastatic to the lung and present the cytological and immunohistochemical features.

Comparative toxicological pathology in mammals and fish: some examples with endocrine disrupters

Toxicologic pathology is a classical discipline in the toxicology arena, and despite various emerging techniques, still is a major cornerstone in the process of hazard identification and risk characterization. Most knowledge derives from laboratory animal studies and, to a lesser extent, human data. Currently interest is growing in applying toxicological pathology for lower animals, in particular fish as being the most developed aquatic genus. This is triggered by the interest in so-called endocrine disrupting chemicals (endocrine disrupters, EDCs), xenobiotics that interfere with the endocrine system and thus may affect reproduction and/or development, and for which pathology is an essential technique in general in vivo studies. As the aquatic ecosystem is a major recipient of pollutants, fish constitute an important potential target and can be used as a research and bio-monitoring tool. For this goal knowledge of the pathological responses of fish to EDCs is essential and therefore we have studied the responses of laboratory fish to a set of reference endocrine modulating chemicals. In this paper, such effects are compared with known response patterns in mammals, thereby accounting for the specific aspects of anatomy and physiology in fish.

Coordinated regression of adrenocortical endocrine and endothelial compartments under adrenocorticotropin deprivation

The adrenal cortex is a complex tissue comprising different cell types, including endocrine, stromal, nerve, perivascular, and endothelial cells. The pituitary hormone ACTH controls the coordinated development of the vasculature and the endocrine tissue mass. This suggests that paracrine secretions between steroidogenic cells and capillary endothelial cells participate in the control of adrenocortical homeostasis. In this paper, we present data demonstrating that ACTH deprivation-induced adrenal atrophy results from alterations of both endocrine and endothelial compartments. These data support the concept that, in addition to its protective effect on endocrine cells, ACTH controls adult adrenal cortex trophicity through an additional paracrine mechanism implying maintenance of the vasculature by VEGF.

Angiogenesis and tumor proliferation/metastasis of human colorectal cancer cell line SW620 transfected with endocrine glands-derived-vascular endothelial growth factor, as a new angiogenic factor

Endocrine glands-derived-vascular endothelial growth factor (EG-VEGF) was recently cloned as a new angiogenic factor that selectively acts on the endothelium of endocrine gland cells. We evaluated the involvement of EG-VEGF in colorectal cancer. The expression of EG-VEGF was confirmed in all of the colorectal cancer cell lines. (On the other hand, the expression of EG-VEGF mRNA was not detected in colorectal normal mucosae.) Stable EG-VEGF infectors of colorectal cancer cell line SW620 were produced, EG-VEGF transfectants were implanted into cecum and s.c., and cell proliferation was evaluated. Angiogenesis was evaluated by dorsal air sac method. Liver metastasis was evaluated after the implantation of EG-VEGF transfectants into the mouse spleen. Tumor proliferation (cecum, s.c.) was significantly higher in the EG-VEGF transfectants than in the control cells. The small vessels were significantly increased in EG-VEGF transfectants as compared with those in control cells. Also, liver metastatic ratio was higher in the EG-VEGF transfectants than in the control cells. In this study, EG-VEGF, a new angiogenic factor, may lead to angiogenesis, promoting cell proliferation and liver metastasis in colorectal cancers. When the EG-VEGF gene-overexpressing colorectal cancer cell line that had been treated with phosphorothioate antisense EG-VEGF oligonucleotides was injected s.c. into mice, angiogenesis and tumor growth were inhibited. Although the novel angiogenesis factor EG-VEGF was not expressed in the normal colorectal mucosa, it was expressed in colorectal cancer cells, which indicates that it is a cancer-specific and possibly tissue-specific angiogenesis factor in the large intestine, and which suggests that it can be targeted by a novel antiangiogenesis therapy.

Selecting Appropriate Animal Models and Experimental Designs for Endocrine Disruptor Research and Testing Studies

Evidence that chemicals in the environment may cause developmental and reproductive abnormalities in fish and wildlife by disrupting normal endocrine functions has increased concern about potential adverse human health effects from such chemicals. US laws have now been enacted that require the US Environmental Protection Agency (EPA) to develop and validate a screening program to identify chemicals in food and water with potential endocrine-disrupting activity. EPA subsequently proposed an Endocrine Disruptor Screening Program that uses in vitro and in vivo test systems to identify chemicals that may adversely affect humans and ecologically important animal species. However, the endocrine system can be readily modulated by many experimental factors, including diet and the genetic background of the selected animal strain or stock. It is therefore desirable to minimize or avoid factors that cause or contribute to experimental variation in endocrine disruptor research and testing studies. Standard laboratory animal diets contain high and variable levels of phytoestrogens, which can modulate physiologic and behavioral responses similar to both endogenous estrogen as well as exogenous estrogenic chemicals. Other studies have determined that some commonly used outbred mice and rats are less responsive to estrogenic substances than certain inbred mouse and rat strains for various estrogen-sensitive endpoints. It is therefore critical to select appropriate biological models and diets for endocrine disruptor studies that provide optimal sensitivity and specificity to accomplish the research or testing objectives. An introduction is provided to 11 other papers in this issue that review these and other important laboratory animal experimental design considerations in greater detail, and that review laboratory animal and in vitro models currently being used or evaluated for endocrine disruptor research and testing. Selection of appropriate animal models and experimental design parameters for endocrine disruptor research and testing will minimize confounding experimental variables, increase the likelihood of replicable experimental results, and contribute to more reliable and relevant test systems.

Estrogen Receptor Knockout Mice as a Model for Endocrine Research

The biological effects of estrogen in mammalian target tissues are important for multiple organ systems including the male and female reproductive tract and the neuroendocrine, skeletal, and cardiovascular systems. Numerous physiological effects of estradiol are modulated by the estrogen receptor (ER), a Class I member of the nuclear receptor superfamily. However, more recent studies have also implicated nongenomic effects of estrogen, which may involve a membrane-binding site. The two forms of the ER are the classical estrogen receptor-alpha (ERalpha) and the more recently discovered estrogen receptor-beta (ERbeta). Gene-targeting techniques were used to generate mice lacking either functional ERalpha (alphaERKO), ERbeta (betaERKO), or both ERs (alphabetaERKO) to provide a model for evaluating estrogen receptor action. These knockout models provide a unique tool to study the effects of estrogen in the context of the whole animal and to discern the role of each ER in various tissues. The reproductive phenotypes as well as some of the nonreproductive phenotypes of the different ERKO models are summarized.