Non-granulated Cells Research Articles

Structure of the pars distalis in pouch-young tammar wallabies (Macropus eugenii).

The pars distalis of pouch-young wallabies (Macropus eugenii) aged 1 to 50 days was studied by means of light-microscopic immunohistochemistry and electron microscopy. In the pars distalis of these pouch-young presumptive somatotrops, which constituted up to 70% of the gland, and nongranulated cells were the most numerous cell types. Small numbers (together representing less than 30% of the pars distalis) of immunoreactive mammotrops, thyrotrops, gonadotrops and corticotrops were also found. The presumptive mammotrops, gonadotrops and thyrotrops increased in number and apparent activity between 1 and 50 days postpartum. Presumptive corticotrop cells in 25 to 30 day-old animals were relatively most numerous, and apparently more active than at any other stage of pouch life; these cells decreased in apparent activity and relative number in older animals. The changes in number and activity of cell types in the pars distalis correlated well with major developmental events such as the onset of adrenal activity, the rapid growth phase in the first 100 days postpartum, and the generally low thyroid activity in pouch-young of less than 50 days of age.

Structure of the pars distalis in the adult tammar wallaby (Macropus eugenii).

An immunohistochemical, light- and electron-microscopial study was made of the pars distalis in adult tammar wallabies (Macropus eugenii). The pars distalis of this marsupial mammal was divided into three regions, based on the distribution of cell types within the gland. Somatotropic, mammotropic, luteotropic, folliculotropic, corticotropic and thyrotropic cells were identified on the basis of their immunohistochemistry, cytology and ultrastructure. Non-granulated (folliculo-stellate) cells, identified in electron micrographs, were found throughout the pars distalis. Somatotropic cells were predominant in the posterior pars distalis in all animals examined. In the single male specimen and in the non-lactating females examined, small numbers of apparently inactive mammotropic cells were scattered throughout the pars distalis; the same cell type was apparently active and present in considerable numbers in lactating females. Only one morphological type of gonadotropic cell was evident; these cells were scattered throughout the pars distalis, but in largest numbers in the median region. Small numbers of thyrotropic cells were found, most commonly in the anterior pars distalis. Corticotrops were also observed in moderate numbers, predominantly in the anterior regions of the pars distalis.

Phasic secretion by follicular cells of the bat adenohypophysis during the prearousal period of their annual life cycle.

The fine structure of the follicular (nongranulated) cells of the adenohypophysis of the bat was examined at different periods of the annual life cycle. Follicular cells were found in all regions of the pars distalis of both active and hibernating bats. Throughout the active phase of the life cycle and during most of the hibernating period, the structure of follicular cells is unchanged. Toward the end of hibernation, however, striking ultrastructural changes occur. The most obvious of these alterations is the appearance in follicles of dense rod-shaped bodies within the follicular luminal space. Just prior to arousal, the rodlike bodies become much wider and appear more as paracrystalline aggregates of dense material. Images indicate that the dense rod-shaped bodies are packaged in vesicles in the cytoplasm of the follicular cells. The fusion of the membrane of filled vesicles with the plasma membrane of the follicular cell results in the release of their dense rod-shaped bodies into the follicular lumen by exocytosis. These cyclic ultrastructural changes indicate that follicular cells have a phasic secretory activity.

Penetration of horseradish peroxidase into the extravascular channel system of in vitro European eel (Anguilla anguilla) pars distalis, with comments on the role of the nongranulated cells

Horseradish peroxidase (HPO) was used as an extracellular space marker to investigate the characteristics of the extravascular network in in vitro cultured hemipituitaries of Anguilla anguilla. HPO penetrated large extravascular channels in both the rostral and proximal pars distalis. In the rostral pars distalis the channels were associated with the base of the columnar prolactin cells and in the basal lamina between the corticotropes and anterior neurohypophysis in the dorsal region. In the proximal pars distalis the channels separated the cords of granulated cells. HPO also penetrated into fine extracellular spaces, which appeared to be continuous with the extravascular channels, in both rostral and proximal pars distalis. HPO penetrated only those extracellular spaces associated with the nongranulated (NG) cells, suggesting a related function between the movement of large molecules in the extravascular network and NG cell function. However, in in vitro situations which alter pars distalis cell activity (altered osmotic pressure of the incubation medium or incubation in the presence of metabolic inhibitors such as dinitrophenol or KCN) penetration of HPO did not appear to be affected, suggesting that the HPO penetration was passive, at least in the in vitro conditions used here.

MORPHOLOGICAL AND MORPHOMETRIC STUDIES ON THE FINE STRUCTURE OF DUCT SYSTEMS OF THE SUBMANDIBULAR GLANDS IN NORMAL AND CASTRATED RATS AS REVEALED BY ELECTRON MICROSCOPY

The sexual dimorphism and the effects of castration on the duct system of the rat submandibular glands were studied with the transmission electron microscope. Not only the simple observation of fine structure, but also morphometric measurement of various inclusions and elements of the constituent cells of the duct system were performed.1. The duct system of the rat submandibular gland consists of the intercalated duct, striated duct, granular duct and excretory duct. The intercalated duct contains three cell types ; dark cell, granulated cell and basal cell. The striated duct is composed of only one cell type that is called striated duct cell, though its cytoplasm varies in electron density from cell to cell. The constituent cells of the granular duct are classified into five types in this paper as follows : basal cell, dark narrow cell, light narrow cell, light granular cell, and dark granular cell. The excretory duct consists of three types of cells ; light columnar cell, dark columnar cell and basal cell.2. The granulated cells of the intercalated duct contain secretory granules in both sexes, but the number of granules predominates in female over male glands. The castration of male rats causes the decrease of granule number in this cell type.3. The development of striated duct is better in female than in male. Almost all cells of the striated duct of female rats contain secretory granules, but in male non-granulated cells predominate over the granulated cells. Instead of granules, there are very small vesicles in the apical part of the non-granulated cells of the male striated duct. The effect of castration is slight in this part of the duct, but the appearance of cells after castration is a little similar to the case in female.4. The two courses of differentiation of epithelial cells of the granular duct were assumed : a) basal cell → dark narrow cell → dark granular cell → light granular cell, b) striated duct cell →light narrow cell → light granular cell.5. The granular duct shows most conspicuously the sexual dimorphism among various parts of the rat submandibular gland. The male granular duct always predominates over the female duct. Castration may inhibit the differentiation of cells in the granular duct, resulting in the decrease in volume of light granules as well as the number of light granular cells, that is thought to be the most differentiated type of the cells. The number of dark granular cells was increased, probably as the result of inhibition of differentiation from the dark granular cells into light granular cells.6. The sexual difference as well as the effect of castration was vague in fine structure of cells in the final part of the duct system, that is the excretory duct.

Prenatal cytodifferentiation in the pars distalis of the dwarf mutant mouse.

The pars distalis of the pituitary gland was studied by means of electron microscopy in 14- to 18-day dwarf embryos (dw/dw) obtained from matings of dwarf homozygotes in which reproductivity was induced by hormone supplementation and pituitary transplants to the renal capsule. At 14 days of gestation the dwarf pars distalis shows fewer granulated cells than in the normal. Although somatotroph-like and mammotroph-like cells are identifiable in the normal pars distalis as early as 15 days, comparable cells are not present in the dwarf. By 17 and 18 days, the dwarf exhibits an ambiguous cell-type with a combination of somatotroph and mammotroph characteristics. At 18 days the dwarf also continues to show numerous nongranulated cells with large aggregates of glycogen, whereas in the normal pars distalis comparable glycogen-containing cells are relatively scarce.

The origin of pituitary cysts in the rostral pars distalis of the nine-spined stickleback, Pungitius pungitius L.

Pituitary cysts in the nine-spined stickleback, Pungitius pungitius L., developed next to blood vessels passing through the prolactin zone of the rostral pars distalis to the connective tissue capsule at its periphery. Cysts were most frequent when pituitaries were large compared with body lengths. However, the incidence of cysts could not be closely related to body length alone. As the rostral pars distalis is more highly vascularised in fish with large pituitaries, and as there was no evidence of accumulating secretion around these blood vessels, it is suggested that cysts develop when vascular demands (or supplies) become excessive. Associated with the greater vascularity of the rostral pars distalis in large pituitaries was a remarkable development of non-granulated cells. Indeed cysts may originate as enlarged intercellular spaces between such cells, as the latter often surround blood vessels. The non-granulated cells are also important in enlarging cyst cavities (by phagocytosing prolactin-cell debris) and perhaps for maintaining their structural integrity. It is suggested that the macrophages within cyst cavities are derived from the non-granulated cells.

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.

Ultrastructural studies on prolactin and growth hormone cells in Anguilla pituitaries in long term cultures.

Eel hemi-pituitaries were cultured in vitro on high or low sodium media, previously shown to affect differentially prolactin and growth hormone release. After 6 days culture, there were marked differences in the ultrastructure or both prolactin and growth hormone cells from the two groups. Morphometric data on the prolactin cells from SW-adapted eels showed a greater abundance of RER and paucity of secretory granules in cells from the low sodium medium. The size of the Golgi apparatus and the number of exocytosed secretory granules did not differ markedly between experimental groups, in contrast to previous findings on short-term cultures. Differences in the profile diameters of secretory granules are recorded between the experimental groups and the pattern differs markedly from that previously recorded for short-term cultures. The growth hormone cells from low sodium media were characterised by abundant, vesiculated RER, a prominent Golgi apparatus (in SW-adapted animals) and relatively few secretory granules. The activity of these growth hormone cells is in marked contrast to previous findings relating to short-term cultures. The shape and size of the non-granulated (stellate) cells of the RPD was again affected by the osmotic pressure of the medium.

Ultrastructure of the Non-granulated Hypophysial Cells in the TeleostPseudocrenilabrus philander (Hemihaplochromis philander), with Particular Reference to Cytological Changes in Culture

In the intact gland, non-granulated cells are most numerous in the rostral pars distalis; they are characterized by a lack of typical secretory granules, a ribosome-rich cytoplasm and long cytoplasmic processes. The latter extend between the granulated cells and often form a layer beneath the capsule and at the zone of contact between adenohypophysis and neurohypophysis. Study of cultured hypophysial tissue provides unequivocal evidence for the phagocytosis of cytoplasm of granulated cells by non-granulated cells. In short-term cultures (1.5 h), non-granulated cells envelop small portions of granulated cell cytoplasm and their processes extend into intercellular spaces and contact tissue fragments located there. In longer term cultures (6—120 h), large areas of cytoplasm belonging to presumptive prolactin and somatotropic cells are engulfed by non-granulated cells; these phagosomes undergo progressive breakdown to form residual bodies. It is suggested that an accumulation of cellular debris and/or stale secretory material may be important factors promoting phagocytic activity in cultured non-granulated cells.

Influence of salinity on ultrastructure of the secretory cells of the adenohypophyseal pars distalis in yearling coho salmon (Oncorhynchus kisutch).

Six different types of secretory cells were identified by light and electron microscopy in the adenohypophyseal pars distalis of yearling coho salmon acclimated to fresh or salt water. Prolactin cells are markedly more active in the freshwater than the seawater fish; these cells exhibit definite functional activity 3 days after transfer from salt to fresh water, indicating an osmoregulatory role of prolactin in the freshwater environment. Plasma sodium showed a significant decline 6 h after transfer from sea water to fresh water and, even after 1 week, remained lower than in the fully acclimated freshwater fish. Corticotropic (ACTH) cells did not appear cytologically different in freshwater and seawater fish. GH cells, the most prominent cells in the proximal pars distalis, appear more numerous and more granulated in the seawater fish, suggesting an osmoregulatory involvement in young coho salmon. Putative thyrotropic (TSH) and putative gonadotropic cells (GTH) can be distinguished by differences in granulation; only one type of GTH cell is evident with ultrastructural features that differ from those of sexually mature salmon. Stellate, non-granulated cells occur in all regions of the adenohypophysis but more frequently in the prolactin follicles; they are much more prominent in the seawater than freshwater fish.

Ultrastructural studies on prolactin and growth hormone cells in Anguilla pituitaries in vitro

Eel hemi-pituitaries were cultured in vitro on high or low sodium media which are known to affect differentially prolactin and growth hormone release. Ultrastructural examination of the prolactin cells after 24 h culture showed the Golgi bodies were markedly more abundant and widely distributed in hemi-pituitaries from the low sodium medium. Secretory granule release profiles and dense bodies were also more frequent, but the percentage of the cytoplasmic volume occupied by secretory granules was lower than on the high sodium medium. RER was only slightly modified. Significant differences were noted in the shape and processes of the non-granulated (stellate) cells of the RPD, but there were only slight differences in the the ultrastructure of the somatotropes.

Fine structure of the rostral pars distalis follicle cells in homotransplanted pituitaries of rainbow trout, Salmo gairdneri.

Pituitary glands from 'donor' rainbow trout were transplanted into the anterior eye compartment of 'recipient' fish to examine the nature of hypothalamic control of the follicle cells in salmonid fishes and to explore the possibility of using the eye as a site of pituitary implantation that permits successful recovery of the grafted gland. After 7 weeks the transplanted prolactin cells appeared less active than in in situ glands and some of the follicle cells appeared to be undergoing degenerative processes. This inhibition of prolactin cell activity was thought to be due to the higher osmotic pressure of the ocular fluid.The follicular formation of the prolactin and non-granulated cells was retained in transplanted glands, although the follicle lumina were smaller than in in situ glands and commonly contained cellular debris. This may suggest that the lumina are sites of cellular degradation and possibly stores of precursor substances.

Electron microscopic studies on the pars tuberalis of the rat hypophysis.

The pars tuberalis of the rat hypophysis was studied with the electron microscope. The pars tuberalis consists of several layers of relatively small epithelial cells lying along the ventral surface of the median eminence. The epithelial cells may be classified into two types. One is the non-granulated cell constituting the major part of the pars tuberalis. These cells show a morphological structure similar to the chromophobes of the pars distalis. Most of them contain relatively large nuclei, a few mitochondria, rough and smooth endoplasmic reticula, and Golgi apparatus. In some places, desmosomes and junctional complexes are observed between the adjacent non-granulated cells. Sometimes, a colloid-like substance fills the intercellular space, into which a great number of microvilli and cilia may project. The other celltype is granulated cells which are large in size and contain a large number of mitochondria, well-developed rough and smooth endoplasmic reticula and Golgi apparatus. The most prominent characteristic of this cell type is the presence of many dark granules, about 150mμ in diameter. These cells resemble the basophils of the pars distalis. The presence of these granulated cells suggests a possible secretory function of the pars tuberalis. In order to clarify the function of the granulated cells, animals were also investigated under several experimental conditions such as adrenalectomy, thyroidectomy and gonadectomy. However, there was no marked morphological change in the fine structure of the pars tuberalis following these experimental conditions.

‘Endogenous Factor’ in Sporogenesis in Bacteria

EXTENSIVE investigations on the morphological changes during sporogenesis have afforded valuable information about this phenomenon1. The initiation of eporulation can be better understood if the metabolic events during the transition from a vegetative cell to its sporulating phase are known. Several attempts have been made to investigate the physiology of growth distinct from sporulation. Foster et al.2 found that when vegetative cells of B. mycoids were removed from the complex growth media before the point of maximal growth and transferred to distilled water, they formed spores. This was termed ‘endotrophic sporulation’. But experiments with B. cereus strain T (phage-resistant organisms) showed that ‘endotrophic sporulation’ can be observed only when granulated cells were suspended in a medium containing sufficient calcium ions3. (The shortening and granulation of cells are usually noticed only long after the cessation of growth.) Non-granulated vegetative cells lysed on transfer into a non-growth supporting medium. In this communication, we report observations which lend evidence to the presence of an ‘endogenous factor’ involved in the initiation of the morphogenesis in the vegetative cell leading to the formation of a granulated cell (Fig. 1) possessing the ability to sporulate in a medium which does not support growth.