Migration of intravascular trophoblast cells in uterine arteries of the golden hamster: A scanning electron microscopic study

Intravascular trophoblast (IVT) cells, derived from the trophoblast of the developing hamster embryo, are known to migrate in retrograde fashion into the uterine arteries. There they migrate to a certain point, destroy and replace the endothelial lining, and modify the smooth muscle of the arteries. The dilated vessels that result presumably enhance the flow of blood to the placental exchange area. The morphology of IVT cells in the hamster placenta was investigated by scanning and transmission electron microscopy. Although occasional single migrating cells were observed, the IVT generally appear as sheets of large, contiguous, sometimes overlapping cells that spread over the endothelial surfaces of the uterine central terminal arteries and vascular knot arteries. This process seems to be aided by the appearance of filopodia, which make contact either with other intravascular trophoblast cells or the endothelium. After consolidation, the IVT cells act as a functional part of the vessel lining and are readily distinguished from the surrounding endothelium by their numerous microvilli. The final distribution of the IVT cells is patchy rather than uniform. © 1994 Wiley-Liss, Inc.     

An electron microscopic study of the closure of the optic fissure in the golden hamster.

During early development of the mammalian eye, invagination and differential growth result in the formation of a cleft, the optic fissure, through which the hyaloid artery reaches the interior of the optic cup. Closure of this fissure was studied by electron microscopy in hamster embryos from days 10 through 12 of gestation. Closure occurred only when and where the basal lamina, which invests the entire wall of the optic cup, had disappeared. No morphological evidence was found that indicated a mechanism for the breakdown of the basal lamina lining the fissure, the fusion of surface cells of opposing sides and restoration of the basal lamina along inner and outer margins of the wall after closure. While in previous light microscopic investigations of the developing human eye eversion of the inner layer into the fissure has been reported, an inversion of the outer layer was found in this study. During inversion cells of the outer layer temporarily changed their orientation. While most of these cells remained within the layer when it returned to its normal position, some cells became separated and degenerated. Inversion of the outer layer, breakdown of the basal lamina and degeneration of superfluous cells appear to be necessary events for a normal closure to occur.     

Histochemistry and electron microscopy of the embryonal development of the golden hamster kidney: study of the interstitial cells]

The structure and the origin of the interstitial cells in the kidney of the golden Hamster during its embryonic development was studied. For this purpose kidneys from 11, 13, 15 and 17 day-old embryos were used. The histochemical observations as well as the electron microscopy demonstrated that the interstitial cells have a metanephric origin and are embryonically similar to the cellular elements that differentiate the primordial renal vesicles and later organise the epithelial portion of the nephrons. These cells seem to take part in the formation of the basal membranes during tubular genesis.     

Synaptic ribbons during postnatal development of the pineal gland in the golden hamster (Mesocricetus auratus)

Summary Synaptic ribbons, functionally enigmatic structures of mammalian pinealocytes, were studied during the postnatal development of the pineal gland in the golden hamster (Mesocricetus auratus). On day 4 post partum, synaptic ribbons appear in cells that have already started to differentiate into pinealocytes. Between days 4 and 9, an increase in the number of synaptic ribbons occurs, concomitant with the continuing differentiation of the pineal tissue. Between days 9 and 16, when differentiation of this tissue is almost completed, the number of synaptic ribbons decreases and approaches that characteristic of the adult pineal gland. During development, the synaptic ribbons increase in length, and dense core vesicles are frequently found in the vicinity of these structures. It is assumed that a functional relationship exists between dense core vesicles and the synaptic ribbons, which are considered to be engaged in a certain form of secretory activity of the mammalian pineal gland.Supported by the Deutsche Forschungsgemeinschaft     

Compensatory hypertrophy of golden hamster ovaries during early postnatal ontogenesis]

The right-side ovariectomy in the golden hamster females during the prepubertate period resulted in the compensatory hypertrophy of the rest paired organ. The morphological rearrangement of the hypertrophied ovary represented the shift in the quantitative distribution of follicles by the maturation stages towards the predominance of mature forms. The accelerated growth and differentiation along the path of normal postnatal ontogenesis led to the earlier ovulations in the hypertrophied ovary.     

Differentiation of mast cells during postnatal development of neonatally estrogen-treated rats

Summary The accumulation of mast cells in the testicular interstitium of neonatally estrogen-treated rats was studied from 15 to 90 days of age. The maturation of these cells was assessed by ultrastructural analysis and their histochemical properties were examined with the sequential alcian blue-safranin staining method. The first identifiable mast cells appeared in the testis at 17–20 days of age, as immature cells with proliferative capacity. The density of mast cells increased up to 45 days of age, showing a slight decrease from 45 to 90 days of age. Before 45 days of age, most mast cells showed alcian blue-stained granules, whereas at 45 days of age, most cells presented a mixture of alcian blue and safranin-stained granules. From this age onward, most cells were stained with safranin. These maturational changes were well-correlated with their ultrastructural features. Mast cells presented few and heterogeneous immature granules up to 45 days of age, and many uniform electron-dense granules at 90 days of age. These results indicate that the testicular interstitium of neonatally estrogen-treated rats provides an adventageous environment for the recruitment, proliferation and maturation of connective tissue mast cells.     

Immunophenotype of porcine oviduct epithelial cells during the oestrous cycle: a double-labelling immunohistochemical study

The luminal epithelium of the porcine oviduct is composed of ciliated cells and secretory cells, but it is assumed for several species that under the control of steroid hormones secretory cells are able to be transformed into ciliated cells. In order to better understand such physiological changes during the different stages of the oestrous cycle, we evaluated epithelial cell proliferation together with oestrogen receptor (ER) expression of porcine ampullary oviducts. To identify the immunophenotype of proliferating cells, double immunohistochemistry was performed using anti-chromogranin A antibody (anti-CgA) as the second primary antibody. Anti-CgA, recently shown to be an immunocytochemical marker of ciliated cells of the cow, also labelled specifically the luminal surface of ciliated cells of the pig. Double labelling of sections with the monoclonal antibody MIB-1 against the proliferation-associated nuclear epitope Ki-67 and anti-CgA clearly demonstrates that MIB-1 was selectively localised in the nuclei of secretory cells. Proliferative activity was not observed in CgA-positive ciliated cells in all examined stages of the oestrous cycle. The percentage of Ki-67-positive epithelial cells was higher at pro-oestrus, compared with the other stages of the oestrous cycle. Furthermore, ER immunoreactivity was exclusively detected in the nuclei of the epithelial cells, which were negative for CgA. We conclude, therefore, that oestrogen may induce the initial proliferation of secretory cells and promote the differentiation into ciliated cells.     

An electron microscopic study of the development of rat testis in the first 10 postnatal days

Summary The ultrastructure of testis of immature rats from birth to ten postnatal days was studied in order to describe the development of germ cells into definitive spermatogonia. The primordial germ cells showed no structural changes from birth to 4 days after birth. At the 5th postnatal day the gonocytes were transformed into darker cells and began to migrate towards the basement membrane. As they reached the periphery of the seminiferous cords they resumed mitoses and gave rise to smaller gonocytes, which were progressively transformed in definitive spermatogonia. A lighter kind of supporting cell was also detected.We wish to thank Mrs. L. Giaccardo, A. Pozzolini and E. Taccini for skilled technical assistance.From the Department of Medical Pathology, Pisa University, Pisa, Italia.     

Three-dimensional scanning electron microscopic study of the normal hamster olfactory epithelium

Brain Cell Biology - The olfactory epithelium of the adult hamster (Mesocricetus auratus) was studied using the scanning electron microscope. A method that produced fractures in the epithelium...     

Chick hepatic lectins: An electron microscopic study on isolated hepatocytes during development

We studied the carbohydrate recognition systems of hepatocytes isolated from 16-day-old embryos, 19-day-old embryos and chicks within 24 h of hatching. We localized and quantified at the ultrastructural level the binding sites for glycoproteins exposing terminal N-acetylglucosamine (GlcNAc), mannose and N-acetylgalactosamine (GalNAc) residues by means of protein-gold complexes. Binding sites specific for GlcNAc and mannose residues are present on hepatocytes from embryos and chicks. On the contrary GalNAc specific binding sites are exclusively observed on cells from 16-day-old embryos. The number and distribution of gold particles on hepatocyte cell surfaces depend on the binding sites and the age considered. We describe a modulation in the number of GlcNAc, and mannose specific receptors present on the cell surface between the embryonal stage and neonatal life.     

Evolution of the endoplasmic reticulum during spermiogenesis of the rooster: an electron microscopic study

The endoplasmic reticulum (ER) of rooster's spermatids was analyzed during spermiogenesis, which was subdivided into eight distinct steps on the basis of changes observed with the electron microscope in the nucleus, acrosome-perforatorium system, manchette, and flagellum. In steps 1 and 2, spermatids' ER cisternae presented the following specializations: A loose network of tubular cisternae was distributed throughout the cytoplasm. Six to eight tight networks of anastomosed tubular cisternae parallel to each other were closely stacked to form a discoid body (1.5-2.5 microns in diameter and 0.5-0.8-micron thick) in which spheroidal vesicles (0.4 micron in diameter) were inserted. Close to and connected with this body, called the alveolar body, there was a stack of annulate lamellae. Large, flattened ER cisternae were seen singly or in piles of two or three running parallel to the nuclear surface. A collection of tubular ER cisternae faced plaques of thickened plasma membranes. These elements of the ER system appear continuous with each other. During steps 3-5 of spermiogenesis, no modification of the alveolar body-annulate lamellae complex was noted; the large flattened ER cisternae disappeared, however, and the broad network of tubular cisternae developed markedly. During steps 6 and 7, the latter network of tubular cisternae fragmented into vesicles that swelled to give a vacuolated appearance to the cytoplasm. The alveolar body-annulate lamellae complex remained visible until late step 7, when it disintegrated just before spermiation. Thus the system of ER cisternae underwent marked structural modifications during spermiogenesis.