Aromatase activity in ovarian follicles of the golden hamster

The aromatizing ability of recombined granulosa and thecal cells in culture, isolated from hamsters 72-78 h and 96-102 h after PMSG-stimulation, was assessed by the addition to the culture medium of androstenedione, testosterone, dehydroepiandrosterone (DHEA) or 5 alpha-dihydrotestosterone (DHT), and measuring the output of oestradiol 4 h later. The cells from all follicles taken after 96-102 h had a reduced oestradiol output compared to those isolated after 72-78 h (P less than 0.02). Recombined cells from the unluteinized follicles at 96-102 h (Group I) showed similar oestradiol output in the presence of androstenedione, testosterone and DHEA to the cells from follicles taken at 72-78 h. However, the recombined cells from the luteinized follicles (Group II) showed a reduced output of oestradiol in the presence of androstenedione, testosterone and DHEA when compared to the recombined cells from the previous period cultured with the corresponding C19 steroid. The results show that a reduced oestradiol output can be caused by (1) the reduced availability of aromatizable substrate and (2) a reduced potential aromatase activity.     

Spermatogenesis in the golden hamster: the role of c-kit.

c-kit is related to the family of transmembrane tyrosine kinase receptors. Mutations in genes for either c-kit or its ligand, Steel factor, result in infertility, but the role of c-kit/SCF system in spermatogenesis is not well understood. In this study Western blot analysis together with confocal microscopy were used to follow c-kit expression in hamsters during the first spermatogenic wave in mature animals and in old age. Three antibodies raised against different domains of c-kit were tested on Western Blot. Confocal microscopy was performed after incubation of fixed seminiferous tubules with tested antibodies followed by binding of FITC-labeled secondary antibody. Longitudinal sections of seminiferous tubule were observed by confocal microscopy to determine in which stages of spermatogenesis and in which cell types c-kit was found. C-kit bands of 80,140, and 150 kDa were observed on Western blot, indicating that c-kit is a name related to several proteins sharing some common domains. Only the band of 150 kDa correlated with positive staining of c-kit in tubules using confocal microscopy. We term this protein c-kit150T (150 kDa, testis). We demonstrated that c-kit150T appeared in differentiating hamster spermatogonia at stages VII-VIII of adult spermatogenesis and at day 13-14 during the first spermatogenic wave. It remained attached to the cell until late pachytene. This suggests that c-kit may play a role in preparing the germinal cells to enter meiosis. In order to evaluate the effect of aging on the number of germ cells, B2 spermatogonia/Sertoli cell ratio was calculated in the group of young animals (5-7 months) compared to this ratio in older ones (20-26 months). A significant decrease (P < 0.01) in the number of B2 spermatogonia in the group of old hamsters as compared to young ones was seen. The calculated value for the B2 spermatogonia/Sertoli cell ratio was 5.6 +/- 0.7 in young animals and 3.8 +/- 1.2 in the 20-26 months ones. In addition, decrease in the intensity of staining for c-kit was detected in the old hamsters. These may be the reasons for subfertility in old age and in other cases of testicular disorders.     

Ultrastructural morphology and relaxin immunolocalization in giant trophoblast cells of the golden hamster placenta

Relaxin immunoreactivity was previously demonstrated in three cell types within the hamster placenta; fetal primary and secondary giant trophoblast cells (GTCs) and maternal endometrial granulocytes. The objectives of the present research were to examine the ultrastructure of the GTCs and identify the intracellular relaxin storage site. Primary GTCs, first present on day 8 of gestation, were characterized by numerous polyribosomes and large heterogeneous cytoplasmic inclusions suggesting phagocytic activity. Primary and secondary GTCs from days 10, 14, and 15 of gestation contained numerous polyribosomes, mitochondria with tubular cristae, and extensive Golgi complex, and abundant rough endoplasmic reticulum, all characteristics of a cell actively involved in protein synthesis. Membrane-bound secretory granules were not present. Relaxin was immunolocalized within the Golgi complex of primary and secondary GTCs using the avidin-biotin-peroxidase method. Following differential centrifugation of hamster placental homogenates and radioimmunoassay (RIA) of subcellular fractions, the majority of relaxin immunoactivity was detected in the postmicrosomal fraction; however, the majority of relaxin immunoactivity from similarly treated pig corpora lutea was present in the mitochondrial/granule fraction. These data indicate that hamster placental relaxin is not stored in membrane-bound secretory granules but is contained within the extensive Golgi complex of the GTC.     

Prenatal development of the microphthalmic eye in the golden hamster

Prenatal development of the eye in a microphthalmic hamster strain (“anophthalmic white”) is compared with established normal developmental periods. The mutant eye primordium is first distinguished at an average of ten gestational days (Period 6) by an incompletely invaginated optic cup, uniformly pseudostratified outer neuroepithelial layer and widely separated margins of the optic fissure. The outer layer of the mutant cup subsequently becomes abnormally thickened, especially posteriorly and midventrally, and, except in a few eyes with localized imperfect fusion, the optic fissure is unfused at twelve days (Period 9), by which time fusion is normally complete. At 13 to 15 days (Periods 10–11) the fissure is unfused or irregularly fused in regions of variable location and extent. The occurrence of fissure fusion with concomitant loss of continuity between inner and outer epithelial layers is generally restricted to expanded anterior regions in 14–16 day (Periods 11–12) eyes. The presence of presumptive neural retina in the outer layer of the cup characterizes the mutant eye; and to varying degrees, in day 13–16 eyes, the presumptive neural retina (1) provides persistent continuity between the two cup layers, (2) forms both fused and unfused margins of the optic fissure, and (3) extends into an outer position of the optic cup. As early as 13 days (Period 10), nerve fibers are present in the outer layer of the cup, and by the last prenatal and first postnatal days (Period 12), ectopic nerve fiber bundles are widely distributed.     

Early stage biliary and intrahepatic migration of Opisthorchis viverrini in the golden hamster

In Thailand, infection with the liver fluke Opisthorchis viverrini is a serious health problem, with over 8.6 million human infections each year. Early stage biliary intrahepatic migration and infection of O. viverrini in the Syrian golden hamster were used to study the growth and development of this fluke. Fifty metacercariae of O. viverrini were introduced into each hamster by gastric intubation. Worms were found to migrate rapidly from the stomach to the gall bladder and hepatic duct, where they remained in relatively constant numbers until the end of week 8. Sexual development of worms was rapid, with full development of the uterus and testes by one and one half weeks and the appearance of eggs in the uterus by the beginning of the third week of infection. Worm growth as indicated by body length had ceased by week 8. Hamsters demonstrated development of a full reproductive cycle with in three to four weeks, and this generation continued until 8 weeks.     

Hemeoxygenase expression in human placenta and placental bed implies a role in regulation of trophoblast invasion and placental function.

The purpose of this study was to examine the expression of hemeoxygenases HO-1 and HO-2, which are responsible for the production of carbon monoxide (CO), in the human placenta and placental bed and to determine the role of inhibitors of HO on placental perfusion pressure. We hypothesized that HO is expressed within the placenta and that invading cytotrophoblast cells (CTB) express HO isoforms. The expression of HO-1 and HO-2 was studied on placenta and placental bed biopsies, obtained using a transcervical sampling technique, from normal human pregnancies between 8 and 19 wk gestation and at term. In the placenta, HO-2 immunostaining was prominent in syncytiotrophoblast in the first trimester and reduced toward term (P<0.0005). HO-2 endothelial immunostaining was weak in the first trimester, but increased by term (P<0.0005). Within the placental bed, HO-2 was expressed by CTB in cell columns, the cytotrophoblast shell, and cell islands. Both intravascular CTB and interstitial CTB expressed HO-2. HO-1 immunostaining was low in the placenta but intense on the CTB within the placental bed. A striking feature was the absence of HO-1 from the proximal layers of cell columns, with strong expression on the more distal CTB layers of the cell columns. In placental perfusion studies, a significant dose-dependent increase in perfusion pressure was observed in the presence of zinc protoporphyrin, an inhibitor of HO. These results suggest a role for CO in placental function, trophoblast invasion, and spiral artery transformation. Hemeoxygenase expression in human placenta and placental bed implies a role in regulation of trophoblast invasion and placental function.     

Dietary protein level and skeletal development in the golden Syrian hamster

The hamster was used as a model for investigating the effect of low, moderate, and high protein intake (12, 18, and 36% casein) on bone mineral content. Animals fed the low level of protein between 3 and 8 months of age had a reduction in the weight of all skeletal components measured, with the exception of the diaphyseal portion of the long bones. Diaphyseal weight and calcium remained significantly lower when expressed as a percentage of body weight. However, urinary calcium excretion was not lower than that of animals consuming an adequate protein intake. Ingesting a high protein diet resulted in a significant increase in urinary calcium excretion, and a reduced amount of both mineral and organic material in the diaphyses. We conclude that long-term consumption of a high protein ration led to the development of a mild osteoporotic condition in the hamster which was limited to the diaphyseal portions of the long bones.     

Paired cisternae of endoplasmic reticulum in developing ovarian oocytes of the golden hamster

Paired cisternae of rough endoplasmic reticulum linked together by two parallel structures exhibiting periodic striations have been observed in the cytoplasm of small pre-antrum oocytes in the golden hamster. They are present only in oocytes from animals older than 3 weeks of age. Two or more such pairs may be associated with one another, and similar structures have been observed in contact with the nuclear envelope. The peak incidence of the paired membranes coincides with a sharp increase in rough endoplasmic reticulum as the oocyte commences rapid growth. A suggested role for the paired membranes in production of new endoplasmic reticulum is discussed.     

Immunohistochemical co-localization of placental lactogen II and relaxin in the golden hamster (Mesocricetus auratus)

Two hormones with lactogenic activity are produced by the hamster placenta during the second half of pregnancy. One of these hormones, hamster placental lactogen II (haPL-II), has been well characterized; however, its cellular source is not known. In the present study, haPL-II was localized in placental tissues using a specific antibody and the avidin-biotin-peroxidase immunohistochemical technique. Because relaxin has been localized in the hamster placenta, it was of interest to determine if haPL-II and relaxin are localized in the same cells. haPL-II immunoactivity was observed in primary and secondary giant trophoblast cells of the placenta on Days 12, 14, and 15 of pregnancy. On Day 15 positive staining was also observed in large cells located within mesometrial arteries and in eosinophilic bodies associated with degenerating sheathed arteries of the decidua basalis. haPL-II-positive staining was not observed in placentae from Days 8 or 10 of pregnancy. On Day 14, haPL-II was colocalized with relaxin in 75% of the giant trophoblast cells observed. Therefore, it is probable that these hormones are synthesized and secreted by the same cell.     

Basic protein and ribonucleic acid in the cytoplasm of the ovarian oocyte in the golden hamster

Summary Cytochemical and autoradiographic studies indicate that granular-fibrillar cytoplasmic bodies and intermitochondrial substance in the hamster ovarian oocyte contain both basic protein and ribonucleic acid. The studies suggest that the granular-fibrillar bodies and intermitochondrial substance, although morphologically similar, are not functionally identical. It is proposed that the granular-fibrillar bodies represent stored inactive maternal messenger RNA synthesized during the lampbrush chromosome stage of oogenesis for use in the developing embryo. The function of the intermitochondrial substance is still obscure. The suggestion is put forward that it may represent the synthetic machinery for the manufacture of those mitochondrial proteins for which the mitochondrial DNA is insufficient to code.The author wishes to thank Mrs. E. M. Lloyd-Davies for her expert technical assistance in preparing the material for autoradiography.     

The development of the Chondrocranium in the golden hamster, Mesocricetus auratus (Waterhouse).

3 -stages of development of the chondrocranium of the golden hamster have been described. The chondrocrania of the gerbil, mouse and white rat have been compared with the chondrocranium of the golden hamster and the main differences noted. In several respects, the chondrocranium of the golden hamster is primitive.     

A role for Notch signaling in trophoblast endovascular invasion and in the pathogenesis of pre-eclampsia

Placental trophoblasts (TBs) invade and remodel uterine vessels with an arterial bias. This process, which involves vascular mimicry, re-routes maternal blood to the placenta, but fails in pre-eclampsia. We investigated Notch family members in both contexts, as they play important roles in arterial differentiation/function. Immunoanalyses of tissue sections showed step-wise modulation of Notch receptors/ligands during human TB invasion. Inhibition of Notch signaling reduced invasion of cultured human TBs and expression of the arterial marker EFNB2. In mouse placentas, Notch activity was highest in endovascular TBs. Conditional deletion of Notch2, the only receptor upregulated during mouse TB invasion, reduced arterial invasion, the size of maternal blood canals by 30-40% and placental perfusion by 23%. By E11.5, there was litter-wide lethality in proportion to the number of mutant offspring. In pre-eclampsia, expression of the Notch ligand JAG1 was absent in perivascular and endovascular TBs. We conclude that Notch signaling is crucial for TB vascular invasion.