Ontogenesis of corticotropes and lactotropes in situ in the pituitary gland of the hamster

Summary The development of corticotropes and lactotropes was investigated in the golden Syrian hamster using an anti-porcine ACTH antiserum and a homologous antihamster PRL antiserum. Oval corticotropes were first visible in the ventral region of the pars distalis at 13 days of gestation. By the end of gestation, corticotropes were found throughout the pars distalis and in the pars intermedia. Corticotropes in the pars distalis of postnatal hamsters were either round or irregularly-shaped, often appearing in clusters. Throughout development, corticotropes often appeared to be surrounding other cells. Scarce, very small lactotropes were first observed in the pars distalis of hamsters on the first postnatal day. The number of these cells, which were either round or polyhedral, increased dramatically between 4 and 20 days of postnatal life. These observations indicate that the sequence of appearance of corticotropes and lactotropes in the hamster is similar to that in other species and that lactotropes are confined to the pars distalis of postnatal hamsters.     

Identification of lactotropes (PRL cells), somatotropes (GH cells), corticotropes (ACTH cells) and thyrotropes (TSH cells) in the pituitary gland of the musk shrew, Suncus murinus L. (Insectivora), by immunohistochemistry

By means of immunohistochemistry, lactotropes, somatotropes, corticotropes and thyrotropes in the pituitary of the male musk shrew, Suncus murinus L., were identified at the electron-microscopic level. Lactotropes were classified into three types: type I containing large (200-450 nm in diameter) round secretory granules, type II with medium-sized (150-250 nm in diameter) ones and type III with small (50-150 nm in diameter) ones. Somatotropes were also classified into type I somatotropes that contain large (450 nm in diameter) spherical secretory granules and type II somatotropes containing comparatively small (300 nm in diameter) round granules. Both type I and II somatotropes were small and sometimes contained rod-shaped granules. Corticotropes were round or oval cells with round secretory granules in various densities and sizes (150-500 nm in diameter) scattered all over the cytoplasm. Thyrotropes were angular or polyhedral cells containing electron-transparent round secretory granules (200-300 nm in diameter) and large irregularly shaped granules with a maximum diameter of about 1,500 nm. Each type of the cells may be distinguished by its respective ultrastructural characteristics alone without the aid of immunohistochemistry.     

Nongranulated cells in the mouse adenohypophysis

Summary Follicular cells in the mouse adenohypophysis were studied electron microscopically. These elements appear to be very similar to the marginal cells that delineate both sides of the hypophyseal cleft.The mouse differs from most other species in that the follicular cells in the pars distalis and the marginal cells look completely inactive in young, intact animals. This makes the mouse exceptionally favorable for correlating morphological changes in the cells of both types with changes in the physiological state of the animal. Different treatments applied in the present investigation all induced morphological reactions in the follicular and/or marginal cells; these reactions were generally similar. Thus, morphological changes in the follicular or marginal cells should be considered as general phenomena accompanying many changes in the physiological state of the animal, rather than as a specific result of the treatment applied.In three experiments, the follicular and marginal cells were involved in the digestion of waste material from other cells. It is suggested that the morphological changes in the other experiments should also be interpreted as signs of such an activity.In the pars tuberalis of the young, intact mouse the follicular cells may show characteristics that in the pars distalis are found only under experimental conditions. Therefore, the follicular cells in this part of the hypophysis are probably in an active state.     

Calcium homeostasis in a clonal pituitary cell line of mouse corticotropes.

Calcium homeostasis was studied following a depolarization-induced transient increase in [Ca2+]i in single cells of the clonal pituitary cell line of corticotropes, AtT-20 cells. The KCl-induced increase in [Ca2+]i was blocked in (i) extracellular calcium-deficient solutions, (ii) external cobalt (2.0 mM), (iii) cadmium (200 microM), and (iv) nifedipine (2.0 microM). The mean increase in [Ca2+]i in single cells in the presence of an uncoupler of mitochondrial function [carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone, FCCP, 1 microM] was 54 +/- 13 nM (n = 9). The increase in [Ca2+]i produced by FCCP was greater either during or following a KCl-induced [Ca2+]i load. However, FCCP did not significantly alter the clearance of calcium during a KCl-induced rise in [Ca2+]i. Fifty percent of the cells responded to caffeine (10 mM) with an increase in [Ca2+]i (191 +/- 24 nM; n = 21) above resting levels; this effect was blocked by ryanodine (10 microM). Thapsigargin (2 microM) and 2,5 di(-t-butyl)-1,4 hydroquinone (BuBHQ, 10 microM) produced increases in [Ca2+]i (47 +/- 11 nM, n = 6 and 22 +/- 4 nM, n = 8, respectively) that increased cell excitability. These results support a role for mitochondria and sarco-endoplasmic reticulum calcium stores in cytosolic [Ca2+]i regulation; however, none of these organelles are primarily responsible for the return of [Ca2+]i to resting levels following this KCl-induced [Ca2+]i load.     

Two types of mammosomatotropes in mouse adenohypophysis

Summary Two types of mammosomatotropes (MS), the small-granule and vesicle-granule MS, were detected in mouse adenohypophysis by electron microscopy and immunohistochemistry. Both cell-types were immunoreactive to prolactin (PRL) and growth hormone (GH) antisera. The small-granule MS contained small, round, solid secretory granules about 100 nm in diameter, and were smaller than the classical GH and PRL cell-types. The vesicle-granule MS contained secretory granules like cored vesicles, and were larger than classical GH and PRL cells. Small-granule MS were immunoreactive to both PRL and GH antisera in the same region of the cell cytoplasm; the vesicle-granule MS, however, were immunoreactive to only PRL antiserum in most cytoplasmic areas, and a positive response to both PRL and GH antisera was confined to only certain small areas.     

On the cilium cell relationship in the adenohypophysis of the mouse

Summary The 8+1 cilia previously reported in the adenohypophysis have been reinvestigated with special emphasis on their relation to the parent cell. In contrast to the fibril pattern which is remarkably constant, this relation shows great variation, supporting the hypothesis that the cilia are rudimentary.This study was supported in part by Grant NB 02215 of The National Institute of Neurological Diseases and Blindness, U. S. Public Health Service. This aid is gratefully acknowledged. The author wishes to thank Dr. Th. Blackstad for valuable advices and Mrs. J. L. Vaaland for skillful technical assistance.     

Localization by immunohistochemistry of renal ornithine decarboxylase in the mouse with and without testosterone treatment

The immunohistochemical distribution of renal ornithine decarboxylase was studied in male mice both with and without testosterone treatment. Testosterone (1 mg per mouse) induced a marked increase in ornithine decarboxylase activity of the mouse kidney, whereas no significant immunohistochemical difference was observed either in immunoreactivity or its localization. In intact male as well as androgen-treated mice dense ornithine decarboxylase-immunoreactive cells were observed mainly in the cortex, especially many ornithine decarboxylase-immunoreactive cells were observed in the inner portion, while a much weaker immunoreactivity was observed in the medulla. The largest number of ornithine decarboxylase-immunoreactive cells seemed to be localized in the pars recta of the proximal tubule. The immunoreactivity was not detected in all the tubular cells but scattered among them. The renal corpuscles were not immunoreactive. In each ornithine decarboxylase-immunoreactive cell, the cytoplasm showed much denser immunoreactivity than the nucleus.     

Application of immunohistochemistry to the isolated mucosa of the mouse gastrointestinal tract, with special reference to somatostatin cells

In the present study, in order to easily grasp whole images of somatostatin (D) cells, the isolated mucosa of the mouse gastrointestinal tract was immunohistochemically treated. The present study revealed that: (1) in the stomach, small-intestinal villi and colon, about 20% of the D cells extrude basal cytoplasmic processes, showing terminal expansions in many cases; on the other hand, in the crypts of the small intestine, few D cells possess basal processes, and (2) in the stomach, there is no determined tendency in the direction of the basal processes of the D cells; on the other hand, in the small-intestinal villi and colon, most D cell basal processes run toward the villus base and colon crypt bottoms. The direction of the basal processes of the D cells in the gastrointestinal tract seems to be mostly in favor of the migration pattern of epithelial cells described previously. It is likely that, if the targets of the D cells are near the D cells, the basal process is not necessary for local secretion of somatostatin. During migration, however, D cells might extrude basal processes to keep relationships with their targets.     

Ultrastructural identification of corticotropes of the fetal rat

Corticotropes of rat fetuses aged 16, 18 and 21 days were localized by the indirect antibody-enzyme method on semithin sections of the pituitary. The development of the ultrastructure of these cells was observed on consecutive ultrathin sections. In comparison with previous data our present results show that identification of a fetal cell type cannot be based entirely on morphological criteria. The structural peculiarities of corticotropes obtained from studies in vivo are compared with those observed in cells maintained in vitro.     

Peptides with NH2-terminal tryptophan in the adenohypophysis

Summary In the mammalian pituitary formaldehyde-ozone treatment induces strong fluorescence in the cells of the pars intermedia and moderate to strong fluorescence in numerous cells of the pars distalis. Maximum excitation is at 370–375 nm and maximum emission at 495–505 nm. The properties of the cellular fluorescence are indistinguishable from those of tryptamine or peptides with NH₂-terminal tryptophan. From chemical analysis such peptides seem to occur abundantly in the mammalian pituitary. The concentration of these peptides agrees very well with the number and fluorescence intensity of the cells in all species studied. Furthermore, the tryptophyl peptides in the various parts of the pig pituitary have a distribution quite parallel to that of the fluorescent cells. As we have failed to detect tryptamine in the pituitary, we conclude that the formaldehyde-ozone-induced fluorescence in the adenohypophysis reflects the presence of tryptophyl peptides.This study was supported by grants from the Swedish Medical Research Council (04X-1007; 04X-3764), the Ford Foundation, Harald and Greta Jeanssons stiftelse and Riksföreningen mot Cancer (660-K73-01X).For brevity occasionally referred to as tryptophyl peptides.     

Ca2+ signaling and exocytosis in pituitary corticotropes

The secretion of adrenocorticotrophin (ACTH) from corticotropes is a key component in the endocrine response to stress. The resting potential of corticotropes is set by the basal activities of TWIK-related K(+) (TREK)-1 channel. Corticotrophin-releasing hormone (CRH), the major ACTH secretagogue, closes the background TREK-1 channels via the cAMP-dependent pathway, resulting in depolarization and a sustained rise in cytosolic [Ca(2+)] ([Ca(2+)](i)). By contrast, arginine vasopressin and norepinephrine evoke Ca(2+) release from the inositol trisphosphate (IP(3))-sensitive store, resulting in the activation of small conductance Ca(2+)-activated K(+) channels and hyperpolarization. Following [Ca(2+)](i) rise, cytosolic Ca(2+) is taken into the mitochondria via the uniporter. Mitochondrial inhibition slows the decay of the Ca(2+) signal and enhances the depolarization-triggered exocytotic response. Both voltage-gated Ca(2+) channel activation and intracellular Ca(2+) release generate spatial Ca(2+) gradients near the exocytic sites such that the local [Ca(2+)] is ~3-fold higher than the average [Ca(2+)](i). The stimulation of mitochondrial metabolism during the agonist-induced Ca(2+) signal and the robust endocytosis following stimulated exocytosis enable corticotropes to maintain sustained secretion during the diurnal ACTH surge. Arachidonic acid (AA) which is generated during CRH stimulation activates TREK-1 channels and causes hyperpolarization. Thus, corticotropes may regulate ACTH release via an autocrine feedback mechanism.     

Whole ovary immunohistochemistry for monitoring cell proliferation and ovulatory wound repair in the mouse

Background  

Ovarian surface epithelial cells are thought to be a precursor cell type for ovarian carcinoma. It has been proposed that an increased rate of ovarian surface epithelial cell proliferation during ovulatory wound repair contributes to the accumulation of genetic changes and cell transformation. The proliferation of ovarian surface epithelial cells during ovulatory wound repair has been studied primarily using immunohistochemical staining of paraffin-embedded ovary sections. However, such analyses require complex reconstruction from serially-cut ovary sections for the visualization and quantification of the cells on the ovarian surface. In order to directly visualize the proliferation and organization of the ovarian surface epithelial cells, we developed a technique for immunohistochemical staining of whole mouse ovaries. Using this method, we analyzed cell proliferation and morphologic changes in mouse ovarian surface epithelial cells during follicle growth and ovulatory wound repair.     

Structure of the adenohypophysis in juvenile harp seal,Pagophilus groenlandicus

Summary A study was made of the morphology of the adenohypophysis in immature harp seals and the fine structure of cellular components of the pars tuberalis, pars intermedia and pars distalis was described.The pars intermedia composed 8–15% of the hypophysis and contained colloid filled vesicles similar to those found in the other mammalian species.The pars distalis cells were grouped into more or less well defined regions, thus facilitating the correlation of cellular identification from both light and electron micrographs. Five chromophilic cell types were tentatively identified, one acidophil (putative somatotroph), four basophils (3 putative gonadotrophs and one cell type with the characteristics of both corticotrophs and thyrotrophs) and non-granulated stellate cells. The absence of a positive prolactin cell identification was thought to be due to the immaturity of the seals used in the study.The mercury exposure experiment was supported by a contract grant from the Halifax Laboratory of Fisheries and Marine Service. Drs. Uthe and Freeman of that laboratory also carried out the methyl mercury analyses. We recognize the support in maintaining the seals provided by Mrs. C. Rae, Mrs. H. Pedersen, Mr. S. Tessaro and Dr. J. M. Terhune. We also wish to thank Mrs. L. Lin for her technical assistance. Further financial support was provided through operating and development grants. The paper is number 134 in the physiology of migration series     

The adenohypophysis of the flounder,Pleuronectes flesus,and the minnow,Phoxinus phoxinus

Summary The pituitary gland of the flounder, Pleuronectes flesus, showed several unusual cytological features. Between the RPD and the PPD was a zone of cells that stained purple with Alcian blue—PAS—orange G. Many of these cells were apparently degenerating. In the PPD the strands and coils of presumptive STH cells showed a tremendous variation in both size and staining properties. In the PI there were two cell types, the PAS-positive one bordering the neurohypophysis. Around the periphery of the PI was a zone of chromophobic cells, and throughout the PI were numerous intracellular and extracellular acidophil spheres.No well defined ACTH cells were found in the RPD of the minnow (Phoxinus phoxinus). The Alcian blue—PAS—orange G technique distinguishes between blue TSH cells and purple GTH cells in the RPD and PPD. GTH cells from animals collected in the winter were vacuolated. The PI contained two cell types whose staining reactions and ultrastructure were extremely variable. Intra- and extra-cellular acidophil spheres were present.I should like to thank Dr. T. Kerr of the Zoology Department, Leeds University, for his help and encouragement, and Mr. J. Dingley of the Department of Zoology, Aberystwyth, for collecting the flounders.