Pregnancy dating in the rat: placental morphology and maternal blood parameters

The rat is commonly used as a model in studies on embryology and reproduction toxicology. Surprisingly, the current literature does not provide a comprehensive reference data set on placental development in rat. Therefore, we have evaluated morphological changes of the placenta and maternal blood parameters during pregnancy of the Sprague-Dawley rat. The morphologic data presented in this study may be useful as reference material. This study revealed that placental development in the rat is a well-defined process, characterized by key synchronized morphological events at specific points in time, convenient for laboratory practice and provides the toxicologist with a sensitive tool to distinguish between normal and abnormal placental development and to detect fetal and placental mismatches. During rat pregnancy, significant changes were observed in maternal blood parameters strongly reminiscent of those observed in pregnant women. These changes included: (a) decreased blood cell volume as a result of hemodilution, (b) increased white blood cell counts reflecting the response of the mother to the fetal allograft, (c) increased blood clotting values, (d) decreased plasma glucose and increased lipid content maximizing fetal glucose availability and maternal energy conservation, and (e) decreased electrolyte values reflecting plasma volume expansion. It was concluded that the combined data set on placental morphology and maternal blood parameters in pregnant rats provides powerful tools for recognition of abnormal pregnancies.

The Macaque Placenta—A Mini-Review

As part of an overview of the female reproductive organs in the macaque monkey, the present paper presents normal placental development. Although normally not examined in routine toxicologic pathology, the interest in the macaque as a model for reprotoxicity studies is increasing significantly. Based on different classifications, the macaque placenta belongs to the chorioallantoic, (bi)discoid, villous, deciduate, and hemochorial placental type. Within the first fourteen days after fertilization, a large number of events subsequently occur (apposition, adhesion, penetration and traversal of trophoblasts, blood vessel penetration, and development of villi). After this period, the basic placental structure has been laid down in the endometrium, and the initial communication between mother and fetus has been established. Further expansive growth of the placenta and development of anchoring villi are believed to be accomplished by continuous proliferation and migration of the trophoblasts from the trophoblastic shell. Despite the same function of human and macaque placentas, the morphologic structure and developmental timelines are different. Possible toxicological and physiological implications of these differences toward the value of macaques within reprotoxicity studies is discussed at the end of this paper. Besides a transporting role between mother and fetus, the placenta is also an endocrine organ that synthesizes a variety of hormones and cytokines. They influence ovarian and uterine physiology at the start of pregnancy and fetal and mammary physiology during gestation and around labor, respectively.

Competing Interests: This article was sponsored by Covance Inc. and Schering-Plough. Eveline P. C. T. de Rijk and Eric Van Esch are employed by Schering-Plough. No other competing interests were declared.

Selected Background Findings and Interpretation of Common Lesions in the Female Reproductive System in Macaques

The authors describe a selection of normal findings and common naturally occurring lesions in the reproductive system of female macaques, including changes in the ovaries, uterus, cervix, vagina, and mammary glands. Normal features of immature ovaries, uteri, and mammary glands are described. Common non-neoplastic lesions in the ovaries include cortical mineralization, polyovular follicles, cysts, ovarian surface epithelial hyperplasia, and ectopic ovarian tissue. Ovarian neoplasms include granulosa cell tumors, teratomas, and ovarian surface epithelial tumors. Common non-neoplastic uterine findings include loss of features of normal cyclicity, abnormal bleeding, adenomyosis, endometriosis, epithelial plaques, and pregnancy-associated vascular remodeling. Hyperplastic and neoplastic lesions of the uterus include endometrial polyps, leiomyomas, and rarely endometrial hyperplasia and endometrial adenocarcinoma. Vaginitis is common. Cervical lesions include endocervical squamous metaplasia, polyps, and papillomavirus-associated lesions. Lesions in the mammary gland are most often proliferative and range from ductal hyperplasia to invasive carcinoma. Challenges to interpretation include the normal or pathologic absence of menstrual cyclicity and the potential misinterpretation of sporadic lesions, such as epithelial plaques or papillomavirus-associated lesions. Interpretation of normal and pathologic findings is best accomplished with knowledge of the life stage, reproductive history, and hormonal status of the animal.

Summary Comparison of Female Reproductive System in Human and the Cynomolgus Monkey (Macaca fascicularis)

Competing Interests: This article was sponsored by Covance Inc. and Schering-Plough. Gerhard F. Weinbauer and Eberhard Buse are employed by Covance Inc. Eveline P. C. T. de Rijk and Eric Van Esch are employed by Schering-Plough. No other competing interests were declared.

A fast histochemical staining method to identify hyaline droplets in the rat kidney

Hyaline droplet formation in the proximal tubular cells of the kidney commonly occurs under different pathological conditions in experimental animals. In rats, intracytoplasmic hyaline droplet formation is predominantly associated with accumulation of the male rat-specific alpha(2u)-globulin, whereas under other (pathological) conditions (eg, histiocytic sarcoma and chronic progressive nephropathy [CPN]) other proteins are involved. Staining methods to visualize hyaline droplets either need plastic embedded material or time-consuming (immuno)histochemical methods. A fast Chromotrope-Aniline-Blue-staining on formalin-fixed paraffin-embedded kidneys taking only 30 minutes is described. Using this method, hyaline droplets consisting of different types of proteins are easily recognized by their bright-red color.

Multifocal ductal cell hyperplasia in the submandibular salivary glands of Wistar rats chronically treated with a novel steroidal compound

A high incidence of multifocal ductal hyperplasia was observed in the submandibular salivary gland of rats treated for 26 weeks with a high dose of a novel synthetic steroid with combined estrogenic and progestagenic properties. Hyperplastic foci consisted of microcystic duct-like structures lined by a single or multilayered epithelium, sometimes showing a tendency towards a cribiform growth pattern. The hyperplastic ducts wereembedded in a collagen-rich stroma and surrounded by numerous myoepithelial cells. Immunohistochemical methods used for the detection of estrogen- and progesterone receptors revealed that progesterone receptors were abundantly present in the nucleus of epithelial cells within the lesions, exclusively. Estrogen receptors could not be detected in both the normal tissue and hyperplasic foci. The morphological, ultrastructural, and immunohistochemical characteristics strongly suggest that these hyperplastic lesions originated from the intercalated ducts. The rodent-specific granular duct cell was not involved in the pathogenesis as was clearly demonstrated by the lack of immunoreactive epidermal growth factor within the lesions. Lesions were not observed in studies with progestagens and estrogens alone or with other combined estrogen/progestagen compounds, suggesting that the specific ratio of estrogenic and progestagenic activity of the present steroid had played an important role in the development of ductal hyperplasia in this study. Lesions of the intercalated ducts, as described in this study, have not been reported before in the literature.

Postsynthetic modification of human enolase isoenzymes

The original form of beta beta enolase (EC 4.2.1.11) in tissue is modified to two more electrophoretically distinct forms when incubated with human serum. The three postsynthetic forms are designated beta beta 3, beta beta 2, and beta beta 1, in order of increasing anodal mobility and increasing modification. Serum and carboxypeptidases A and B all produce identical modifications of beta beta enolase but exhibit very different pH-activity profiles. A purified human serum protein previously named "modifying protein," which is responsible for the modification of creatine kinase-M and alpha-enolase subunits, modifies beta beta enolase and also has a pH-activity profile identical to that for serum. Thus we conclude that the modifying protein is not identical to either carboxypeptidase A or B; it may, however, be an as-yet-undescribed carboxypeptidase. With increased modification, both alpha alpha and beta beta enolase decrease in apparent activation energy; gamma gamma enolase shows no evidence of modification, and its apparent activation energy remains stable. Measurement of activation energy is an easy tool for screening for postsynthetic modifications in an enzyme.

Drug-Induced Protoporphyria in Beagle Dogs

As part of regulatory safety testing program, a 13-week oral toxicity study with a new antipsychotic drug candidate was performed in beagle dogs. During this study, dark red/brown feces were recorded in treated dogs and increases in liver parameters (alanine aminotransferase, alkaline phosphatase, bilirubin) were measured biochemically. At the end of the study, livers of high-dose (50 mg/kg) animals were (mottled) dark brown, sometimes with pale foci. Histopathological examination of these livers showed dark globular pigment deposits in the hepatocellular cytoplasm and within the bile canaliculi. Varying numbers of inflammatory cell infiltrates were additionally present in association with the deposits. These pigment deposits showed birefringency with characteristic “Maltese Cross”-like structures under polarized light. Electronmicroscopy revealed the typical, so-called “sunburst” pattern with radiating double-lined crystalline structures. These morphologic characteristics strongly indicated at the presence of porphyrins, which was definitely confirmed biochemically. Published reports of drug-induced hepatic porphyria in dogs are rare. The possible underlying mechanism in the dog and man is discussed.

Postsynthetic modification of human enolase isoenzymes

The original form of beta beta enolase (EC 4.2.1.11) in tissue is modified to two more electrophoretically distinct forms when incubated with human serum. The three postsynthetic forms are designated beta beta 3, beta beta 2, and beta beta 1, in order of increasing anodal mobility and increasing modification. Serum and carboxypeptidases A and B all produce identical modifications of beta beta enolase but exhibit very different pH-activity profiles. A purified human serum protein previously named "modifying protein," which is responsible for the modification of creatine kinase-M and alpha-enolase subunits, modifies beta beta enolase and also has a pH-activity profile identical to that for serum. Thus we conclude that the modifying protein is not identical to either carboxypeptidase A or B; it may, however, be an as-yet-undescribed carboxypeptidase. With increased modification, both alpha alpha and beta beta enolase decrease in apparent activation energy; gamma gamma enolase shows no evidence of modification, and its apparent activation energy remains stable. Measurement of activation energy is an easy tool for screening for postsynthetic modifications in an enzyme.