Ultrastructure of the fetal rat anterior pituitary gland as term and during prolonged gestation.

The ultrastructure of the fetal rat anterior pituitary gland is described at term (day 22) and during experimentally prolonged gestation (days 23, 24, 25). The latter was achieved by daily subcutaneous injections of five mg progesterone to gravid females from the twentieth through the twenty-fourth day. Using morphological criteria for classifying pituitary cells (Moriarty, '73), six different types were observed: thyrotrophs, gonadotrophs, corticotrophs, mammotrophs, somatotrophs and non-granulated cells. During prolonged gestation (days 24 and 25 only), cells designated as corticotrophs revealed changes suggesting increased activity, i.e.,proliferation and dilation of the endoplasmic reticulum, dilated Golgi membranes and a redction of secretory granules. In addition, meconium staining , which is indicative of fetal distress, was also observed on days 24 and 25. The ultrastructural changes noted suggest an increased in corticotroph activity due to fetal hypoglycemia and hypoxia which are known to occur as a result of placental insufficiency during prolonged gestation (Roux et al., '64; Vorherr, '75; Thliveris, '76.     

Ultrastructure of the metrial gland cell in the pregnant rat

The metrial gland cells of the pregnant rat were studied with the electron microscope from day 12 through day 15 of pregnancy. Prominent features of their fine structure included abundant granular endoplasmic reticulum, a large Golgi complex, and numerous dense granules. These granules were bounded by a single membrane and contained a dense material, smooth vesicles, and membranous whorls. It is suggested that the dense material is aggregated in the mature granules by the coalescence of smaller progranules that are derived from the Golgi apparatus. The nature and fate of these granules is discussed in relation to the possible secretion of relaxin by metrial cells.     

Ultrastructure and morphometry of ACTH-producing cell in the rat anterior pituitary gland stimulated by lysin-vasopressin and prostaglandin E1

Summary The aim of this study was to investigate the qualitative and quantitative changes of ACTH-cells in the rat after application of a specific and a non-specific stimulus. A CRF-analog (lysin-vasopressin) and a prostaglandin (prostaglandin E1) were used. 40 rats were injected lysin-vasopressin or prostaglandin E1, respectively, for 4 weeks. The pituitary glands were investigated by means of light microscopy, electron microscopy and morphometry. Activation of the ACTH-cells could be observed after use of both substances, the effect of lysin-vasopressin being more intense than that of prostaglandin E1. Enlargement of the nucleus, the cytoplasm and the organelles involved in hormone-production and -transport were found and verified by morphometry. Additionally an increase in number of the cells could be demonstrated. Prostaglandin influenced not only ACTH-cells, but also other cells of the anterior pituitary.Supported by Deutsche Forschungsgemeinschaft, SFB 34, Endokrinologie, Hamburg     

Ultrastructure of the anterior medial glands of the rat nasal septum

The anterior medial glands lying in the submucosa of the rat nasal septum were studied by light and electron microscopy. The glands consist of a single long duct, which is studded with numerous solitary acinar formations connected perpendicularly to the main duct by short intercalated ducts. Proximal acini (those furthest from the stoma of the main duct) consist of typical serous cells with many dense secretory granules and an extensive rough endoplasmic reticulum. The most distal acini consist of cells whose major feature is the enwrapment of each mitochondrion by a cisternal profile of rough endoplasmic reticulum. Myoepithelial cells are absent from proximal acini, but are abundant on distal acini. Intracellular nerve terminals are extremely common, particularly in distal acini. The main ducts resemble, to a degree, the striated ducts of salivary glands.     

Coated vesicles in the rat anterior pituitary gland.

Ultrastructural documentation of the formation of coated vesicles in prolactin cells of the rat anterior pituitary gland is presented. Coated vesicles were observed forming from the secretory granular membrane in the Golgi area and between the Golgi complex and the plasmalemma. They were also found budding off the membrane lining the exocytotic pocket. Following peroxidase reaction product could be seen forming from the membrane of the exocytotic pocket and adjacent to it. These vesicles were found in transit towards the Golgi area or within lysosomes. It is proposed that these coated vesicles are important for membrane conservation and that this is occurring in developing secretory granules near the Golgi complex, in more mature secretory granules and at the level of the plasmalemma during exocytosis.     

Ultrastructure of lipid-containing cells of the anterior pituitary gland of the domestic chicken,Gallus domesticus

A combination of light and electron microscopy techniques was applied to characterize a luteinizing hormone (LH)-gonadotroph-like cell in the anterior pituitary gland of the adult domestic chicken. This cell type (mean ± sem, 91 ± 8 μm²) was larger than typical LH-gonadotrophs (71 ± 5 μm², P < 0.01) and seen in pituitary glands from adult males but not those from adult females of the same age. The ultrastructural features of these cells were similar to typical LH-gnoadotrophs in the same section, except for the presence of large (1,126 ± 77 nm diameter), round, or polymorphic electron-dense inclusions (14 ± 3 per cell) in the cisternae of the endoplasmic reticulum. When resin sections of anterior pituitary gland were stained with the vapours from the fixative osmium tetroxide and a solution of potassium ferricyanide, inclusions were found that appeared to be lipid in nature and were circumscribed by the cisternal membranes of the endoplasmic reticulum. These lipid inclusions were associated occasionally with acid phosphatase and lysosome-like bodies. The cellular pigment, lipofuscin, considered to be a marker of aging, was absent from the anterior pituitary glands from these adult chickens. These observations suggest that the appearance of lipid in LH-gonadotrophs is unlikely to be age-related and an alternative explanation is discussed in relation to a sex difference in the LH response of adult chickens to gonadotrophin-releasing hormone (GnRH). © 1993 Wiley-Liss, Inc.     

Ultrastructure of the cat sublingual gland

The sublingual gland of the cat consists primarily of branched secretory tubules that open into an abbreviated duct system. The simple epithelium that composes the secretory tubules consists of an admixture of mucous and serous cells, with the former predominating. Some secretory tubules are capped by a serous demilune. Regardless of position, almost all serous cells have prominent basal folds and border on at least one intercellular canaliculus as well as on the tubule lumen. Serous cells possess an extensive array of irregular, distended cisternae of rough-surfaced endoplasmic reticulum that frequently contain dense intracisternal granules. Serous granules are relatively few in number and rarely show evidence of substructure. Mucous cells, which lack basal folds, contain an apical mass of secretory material in the form of partially fused droplets. The duct system is somewhat less ordered than in most major salivary glands; secretory tubules empty into structures resembling intercalated ducts or may be in direct continuity with ducts intermediate in morphology between intercalated and excretory ducts. The absence of striated ducts noted in this study may be correlated with the high sodium content of cat sublingual saliva. The main excretory duct of the sublingual gland closely resembles that of the cat submandibular gland in terms of morphology, but exhibits little of the transport functions reported in the latter duct.     

Ultrastructure of the fetal rat adrenal gland at full-term and during prolonged gestation

The ultrastructure of the fetal rat adrenal gland is described at full-term (day 22) and during artificially prolonged gestation (days 23, 24, 25). The latter was achieved by daily subcutaneous injections of seven mg progesterone to gravid females from the twentieth through the twenty-fourth day. Cortical and medullary cells contained well developed organelles at all stages. Nonetheless, zonation of the gland was not yet distinct. Whereas the zona glomerulosa and zona fasciculata were fairly well delineated, the zona reticularis and medulla were as yet poorly defined. The latter regions were intermingled, and thus collectively referred to as the “zona reticulo-medullaris.” During prolonged gestation (days 24 and 25 only), many cells of the zona fasciculata and zona reticulo-medullaris contained dilated smooth endoplasmic reticulum and numerous enlarged mitochondria. Enlarged mitochondria were observed also in medullary cells concurrent with a paucity of catecholamine storage granules. Moreover, meconium staining, which is indicative of fetal stress, was also observed on days 24 and 25. The ultrastructural changes observed were interpreted to be an expression of response by the fetal adrenal gland to fetal stress produced by as yet undetermined factors arising during prolonged gestation.     

Intercellular communication within the rat anterior pituitary gland: X. Immunohistocytochemistry of S-100 and connexin 43 of folliculo-stellate cells in the rat anterior pituitary gland

Since Rinehart and Farquhar reported the presence of agranulated cells in the anterior pituitary gland in 1953, the functions of the folliculo-stellate cell remain to be clarified. Intercellular junctions have been described in the monkey, rat, and teleost anterior pituitary glands, indicating the existence of cell-to-cell communication within the organ. We pointed to their possible role in the rapid dissemination of information through a complex interconnecting system of follicles involving gap junctions. The gap junctional/folliculo-stellate cellular network was essential in the maturation and regulation of the pituitary gland system such as the hypothalamic-pituitary-gonadal axis. It has been was shown that a network participated in the conduction of electrophysiological information over a long distance using the ion Ca(++), which propagates to other folliculo-stellate cells by signaling through gap junctions. Sixty-day-old male rats were used in this study for light microscopic immunohistochemistry of S-100 protein, type I collagen, and connexin 43, and for electron microscopy to observe the morphological relationships between the cellular networks of folliculo-stellate cells and granulated pituitary cells. Clusters of anti-S-100 protein-positive cells were clearly observed in a region of the hypophysis tentatively named the transition zone. Anti-S-100 protein-positive cells and their cytoplasmic processes were also present in the anterior lobe and assembled together to form follicular lumina. Type I collagen was clearly shown outlining the incomplete lobular or ductule-like structure making cell cords in the anterior pituitary gland. Numerous microvilli were present within the follicular lumen while around the lumina, junctional specializations including gap junctions were positive for the connexin 43 protein. A nonuniform distribution of the connexin 43-positive sites were observed. Small or dot-shaped positive sites were noted where two clusters of cells were connected; the cells were identified as S-100 cells. Double immunohistochemical staining of the connexin 43 and growth hormone (GH) or connexin 43 and luteinizing hormone (LH) was also performed, demonstrating no direct relationship between the connexin 43 and either the GH or LH cells. These findings indicate that there are two kinds of messages necessary for the hormone release in the pituitary gland. One is via the portal vein system, the other is through the gap junction-mediated networks of folliculo-stellate cells. The granulated cells directly associate with cell membrane of folliculo-stellate cells are able to discharge secretory granules through communication via gap junctions, while those granulated cells that are more distant from the folliculo-stellate cells are only able to discharge hormones via the pituitary hormone-releasing hormone from the portal vein system.     

Ultrastructure of baboon parotid gland

The parotid gland of the olive baboon, Papio anubis, was examined by electron microscopy. The acini are all serous in nature, and consist of pyramidal cells with abundant secretory granules of varying size. These granules consist of a dense matrix in which a denser spherule or lenticular body is present. Granules linked by a short isthmus are observed in the apical cytoplasm, and granules in the process of discharging their contents to the acinar lumen may be connected to the luminal plasma membrane by a neck-like protrusion. Intercalated duct cells contain granules reminiscent of those found in the rat submandibular acinar cells. The striated ducts consist of tall cells interloked in a complex fashion near their bases, with numerous vertically-oriented mitochondria lodged in their basal crenulations. Small vesicles whose contents vary in density are present in the apical cytoplasm as are large deposits of lipofuscin. The striated duct cells display a proclivity for ballooning into the duct lumen. Excretory ducts consist of simple to pseudostratified columnar epithelium, and lack basal striations or apical blebs.     

Ultrastructural localization of exogenous silver in the anterior pituitary gland of the rat

Silver accumulations in the anterior pituitary of argyric rats were demonstrated using a histochemical method that visualizes minute traces of the metal. Silver was localized intra- and extracellularly throughout the anterior pituitary. Intracellular deposits were found within the lysosomes of somatotrophs and gonadotrophs. Extracellularly, the grains were located in basal laminae of portal veins and sinusoidal capillaries and in the membrane separating the anterior pituitary and part intermedia. The amount of deposited silver was dependent upon the dose of silver administered. Increasing the dose of silver lactate from 10 to 30 mg resulted in increased deposition, whereas a further increase to 60 mg did not alter the amount of silver deposited.     

Ultrastructure of the pineal gland of the fox

The ultrastructure of the pineal gland of the fox was examined and compared with that of other mammals. The pineal gland of the fox is composed of two different populations of pinealocytes (I and II). The pinealocytes I were distributed homogeneously throughout the parenchyma, while pinealocytes II were located generally near blood vessels. A Golgi apparatus, granular endo-plasmic reticulum, mitochondria, lysosomes, centrioles, and cilia were present in both cell populations. A characteristic feature of pinealocytes I was the presence of dense-core vesicles, presumably of Golgi origin; whereas glycogen deposits and pigment granules were common features of pinealocytes II. In addition to the pinealocytes, the parenchyma contained fibrous astrocytes. The capillaries of the pineal gland of the fox consisted of a nonfenestrated endothelium. Numerous nerve fibers, presumably adrenergic, were observed throughout the parenchyma.     

Ultrastructure of the submandibular gland in the rabbit

The secretory endpieces of the rabbit submandibular gland are unusual in that they consist of seromucous acini (not demilunes) that empty into serous tubules that in turn drain into intercalated ducts. Seromucous granules consist of a moderately dense spherule in a fibrillogranular matrix. Serous granules contain a feltwork of filaments, which are liberated as a tangled skein during exocytosis. Peculiar granulated cells that have secretory granules of complex morphology are present at each end of the serous tubules. Intercalated ducts are, cytologically speaking, relatively simple, but the duct cells may contain a few oblong secretory granules. Striated ducts are typical in structure, although postfixation with ferrocyanide-reduced osmium reveals significant amounts of glycogen in the basal processes. Modified mitochondria are present in striated duct cells, but their frequency varies from rabbit to rabbit. Such mitochondria contain either an array of parallel, rigid cristae linked by intermembranous bridges, or a bundle of helical filaments within an expanded crista. Interspersed with the striated duct cells, especially near the duct origin, are some highly vacuolated cells with sparse mitochondria. Excretory ducts consisting of stratified columnar (sometimes pseudostratified) epithelium often show bleb formation of the luminal surface of the tall cells.     

Ultrastructure of human fetal mammary gland

Early cytodifferentiation of human fetal mammary gland was studied at the time of the beginning of the sexual differentiation during the sixth to eleventh developmental weeks. The gland appeared as a solid epithelial ingrowth into the underlying mesenchyme on both sides of the thoracic wall at the age of 5 weeks in both sexes. These ingrowths contained primitive glycogen-rich cells with large nuclei. The surrounding mesenchymal cells gathered around the basal lamina. These cells differentiated into fibroblasts, and collagen fibers were seen in the mesenchyme near the mammary buds. No lumina appeared within the buds during this study. Differences between the male and female mammary epithelium or mesenchyme were not observed, although androgen synthesis and secretion in the fetal testis had already begun. The close connections and concomitant differentiation of the mammary bud epithelium and mesenchyme during the early embryogenesis in this study suggest that epithelio-mesenchymal interaction plays an important role in the differentiation of human mammary gland.     

Distinctive localization of N- and E-cadherins in rat anterior pituitary gland

In the rat anterior pituitary gland, folliculo-stellate cells aggregate preferably to form pseudofollicles, and each type of hormone-producing cell shows adhesive affinity with particular types of heterologous hormone-producing cells. Distribution of cadherin types in the rat anterior pituitary was examined immunohistochemically to clarify the unique cell arrangements caused by homologous and heterologous affinities among cells. N- and E-cadherins were detected continuously along cell membranes, while P-cadherin was not. N- and E-cadherins showed distinct isolation in localization, with N-cadherins localized in hormone-producing cells of distal and intermediate lobes in various amounts, and E-cadherins limited to folliculo-stellate cells and marginal layer cells facing the residual lumen of Rathke's pouch. A similar distribution of cadherins was observed in cell clusters of primary cultured anterior pituitary cells. These findings suggest that differential expression of cell adhesion molecules may be partially responsible for localization of hormone-producing cells and folliculo-stellate cells.