Ultrastructure of endocrine cells in the stomach of two teleost fish Perca fluviatilis L. and Ameiurus nebulosus L.

Summary In the gastric mucosa of two teleost species, the perch (Perca fluviatilis) and the catfish (Ameiurus nebulosus) three endocrine cell types were found, located predominantly between the mucoid cells of the gastric mucosa. A fourth cell type is present in the gastric glands of catfish. Each cell type was defined by its characteristic secretory granules. Type-I cells were predominant in both fish. These cells contained round or oval granules with a pleomorphic core. The average diameter of granules was 400 nm for the perch and 270 nm for the catfish. Type-II cells of both species displayed small, highly osmiophilic granules about 100 nm in diameter. The secretory granules of type-III cells (260 nm in the perch and 190 nm in the catfish) were round or slightly oval in shape and were filled with a finely particulate electron-dense material. Type-IV cells of the catfish were found in the gastric glands only. Their cytoplasm was filled with homogeneous, moderately electron-dense granules averaging 340 nm in diameter. The physiological significance of these different morphological types of gastric endocrine cells requires further investigation.     

Immunocytochemical studies on prolactin cells in the adenohypophysis of the golden hamster

Mammotrophs or prolactin (PRL) cells were identified in the adenohypophysis of adult golden hamsters by immunocytochemical techniques with a polyclonal anti-PRL, that was proved to be specific to PRL by the dot immunoblotting test. Postembedding immunostaining was performed on Araldite thin sections by immunoperoxidase and immunogold methods. PRL cells were classified into three types according to the different size of the secretory granules. The Type A cells were usually small and angular or oval in shape, and had secretory granules ranging in diameter from 100-230 nm, and showed poorly developed organelles. The Type B and C cells were larger and round or ovoid in shape, contained larger granules, 230-280 nm and 280-570 nm, respectively, and displayed well developed organelles. Immunoreactive PRL cells in the male pituitaries were far less numerous than in the nonpregnant female glands, and were mostly of the Type A and B, whereas in the female the Type C and B cells predominated. In pregnant females, Type C cells became activated and increased in number, while the other two types decreased in proportion. In lactating females, Type A and B cells significantly increased in number at the expense of the Type C cells; meanwhile, the exocytosis of secretory granules was frequently found in all types of PRL cells. The present findings suggest that Type C and B PRL cells, especially the former, are potent in producing and releasing PRL and highly responsive to various physiological stimuli, while Type A cells are probably relatively inert in synthetic activity.     

Ultrastructural localization of thyrotropin (TSH)-like immunoreactivity in specific secretory cells of the hypophyseal pars tuberalis in the Djungarian hamster,Phodopus sungorus

Summary Specific secretory cells in the hypophyseal pars tuberalis of Djungarian hamsters maintained under different photoperiods were investigated immunocytochemically by means of the colloidal gold technique using antibodies against rat thyrotropin (TSH). Secretory cells of animals kept under long photoperiods (LD16:8) showed positive staining of secretory granules (diameters 90–130 nm), whereas other intracellular structures were free of immunoreactivity. In animals kept under short photoperiods (LD8:16) secretory cells displayed increased numbers of secretory granules, but these organelles were devoid of immunoreactivity. In contrast, immunoreactivity of thyrotropes in the pars distalis did not differ between the two groups of animals investigated. The present results confirm earlier light-microscopical studies that in the pars tuberalis specific secretory cells show TSH-like immunoreactivity; however, they differ in their reactivity pattern from classical thyrotropes in the pars distalis.     

Immunocytochemical study of the GH cells in the anterior pituitary gland of human fetus II. Anencephalic fetus

In order to elucidate the effects of hypothalamic regulation on the morphology of GH cells, light and electron microscopic immunocytochemical examinations were carried out comparing GH cells in the anterior pituitary gland of anencephalic fetus with those of normal fetuses. Three types of GH cells were identified in the anterior pituitary gland of anencephalic fetus as well as in the normal fetus. Type-I is a small, round cell containing a few small secretory granules. Type-III is a large, polygonal cell with numerous large secretory granules. Type-II is a polygonal cell with medium-sized secretory granules. The Type-II GH cell was predominant in both anencephalic and normal fetuses. The most striking difference between anencephalic and normal fetuses was the presence of atypical forms of the Type II cell. These were polygonal cells containing secretory granules, which were either immunopositive or immunonegative to anti-human GH (anti-hGH) serum. Furthermore, two other types of GH cells were identified. The somatomammotroph (SM cell) contained GH and PRL in different granules within the same cell. Also, a different type of the GH cell was noted containing two varieties of secretory granules; one was immunolabeled only with anti-hGH and the other was not immunolabeled to either anti-hGH or anti-human PRL (anti-hPRL). From these results, we suggest that an absence of hypothalamic regulation in the anencehpalic does not seriously modify GH cell morphology but induces an altered GH storage pattern in some of the cells.     

Fine structural and immunohistochemical studies of goat adenohypophysial cells

Summary The fine structure of each type of anterior pituitary cell in the male goat was studied through the application of a superimposition technique in which adjacent thick sections were used to identify individual cells beforehand by light-microscopic immunohistochemistry. A cone of the pars intermedia protrudes into the pars anterior, being surrounded by the narrow pituitary cleft; the immunohistochemical appearances of the cells forming the cone resemble those of the pars anterior. Several follicles appear in the pars anterior. Ultrastructurally GH cells resemble prolactin cells. The secretory granules of both types are spherical; the diameter of the former is about 340 nm, whereas that of the latter is about 440 nm. ACTH cells are polygonal in shape with secretory granules, about 180 nm in diameter, scattered throughout the cytoplasm. TSH cells, which are spherical in shape, contain the smallest secretory granules, 150 nm in diameter. The highly electron-dense LH cells contain numerous secretory granules about 210 nm in diameter. Their nuclei are irregular with incisures. Thus, the anterior pituitary cells of the goat are ultrastructurally characteristic and species-specific.     

Secretory organelles in ECL cells of the rat stomach: an immunohistochemical and electron-microscopic study

ECL cells are numerous in the rat stomach. They produce and store histamine and chromogranin-A (CGA)-derived peptides such as pancreastatin and respond to gastrin with secretion of these products. Numerous electron-lucent vesicles of varying size and a few small, dense-cored granules are found in the cytoplasm. Using confocal and electron microscopy, we examined these organelles and their metamorphosis as they underwent intracellular transport from the Golgi area to the cell periphery. ECL-cell histamine was found to occur in both cytosol and secretory vesicles. Histidine decarboxylase, the histamine-forming enzyme, was in the cytosol, while pancreastatin (and possibly other peptide products) was confined to the dense cores of granules and secretory vesicles. Dense-cored granules and small, clear microvesicles were more numerous in the Golgi area than in the docking zone, i.e. close to the plasma membrane. Secretory vesicles were numerous in both Golgi area and docking zone, where they were sometimes seen to be attached to the plasma membrane. Upon acute gastrin stimulation, histamine was mobilized and the compartment size (volume density) of secretory vesicles in the docking zone was decreased, while the compartment size of microvesicles was increased. Based on these findings, we propose the following life cycle of secretory organelles in ECL cells: small, electron-lucent microvesicles (pro-granules) bud off the trans Golgi network, carrying proteins and secretory peptide precursors (such as CGA and an anticipated prohormone). They are transformed into dense-cored granules (approximate profile diameter 100 nm) while still in the trans Golgi area. Pro-granules and granules accumulate histamine, which leads to their metamorphosis into dense-cored secretory vesicles. In the Golgi area the secretory vesicles have an approximate profile diameter of 150 nm. By the time they reach their destination in the docking zone, their profile diameter is between 200 and 500 nm. Exocytosis is coupled with endocytosis (membrane retrieval), and microvesicles in the docking zone are likely to represent membrane retrieval vesicles (endocytotic vesicles).     

Gene expression and intracellular localization of somatolactin in the pituitary of rainbow trout

The gene expression and intracellular localization of somatolactin (SL), a putative pituitary hormone structurally related to both growth hormone and prolactin, were investigated in the pituitary of rainbow trout, Oncorhynchus mykiss. Using an in situ hybridization technique, we demonstrated the gene expression of the SL molecule in cells bordering the neurohypophysial tissue in the pars intermedia. These cells were identified immunocytochemically as SL-cells on the adjacent section. Electron-microscopic immunocytochemistry by means of the protein A-gold technique, also revealed that the SL-immunoreactivity was located mostly on the secretory granules in SL-cells. Our findings clearly indicate that SL is biosynthesized and stored in the granules in these cells.     

Cell types of the endocrine pancreas in the shark Scyliorhinus stellaris as revealed by correlative light and electron microscopy

Summary In the pancreas of Scyliorhinus stellaris large islets are usually found around small ducts, the inner surface of which is covered by elongated epithelial cells; thus the endocrine cells are never exposed directly to the lumen of the duct. Sometimes, single islet cells or small groups of endocrine elements are also incorporated into acini. Using correlative light and electron microscopy, eight islet cell types were identified:Only B-cells (type I) display a positive reaction with pseudoisocyanin and aldehyde-fuchsin staining. This cell type contains numerous small secretory granules (Ø280 nm). Type II- and III-cells possess large granules stainable with orange G and azocarmine and show strong luminescence with dark-field microscopy. Type II-cells have spherical (Ø700 nm), type III-cells spherical to elongated granules (Ø450 × 750 nm). Type II-cells are possibly analogous to A-cells, while type III-cells resemble mammalian enterochromaffin cells. Type IV- cells contain granules (Ø540 nm) of high electron density showing a positive reaction to the Hellman-Hellerström silver impregnation and a negative reaction to Grimelius' silver impregnation; they are most probably analogous to D-cells of other species. Type VI-cells exhibit smaller granules (Ø250 × 500 nm), oval to elongated in shape. Type VI-cells contain small spherical granules (Ø310 nm). Type VII-cells possess two kinds of large granules interspersed in the cytoplasm; one type is spherical and electron dense (Ø650 nm), the other spherical and less electron dense (Ø900 nm). Type VIII-cells have small granules curved in shape and show moderate electron density (Ø100 nm). Grimelius-positive secretory granules were not only found in cell types II and III, but also in types V, VI, and VII. B-cells (type I) and the cell types II to IV were the most frequent cells; types V to VII occurred occasionally, whereas type VIII-cells were very rare.This work was supported by a fellowship from the Ministry of Education of Japan and the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg (La 229/8)     

Localization and development of chromogranin A and luteinizing hormone immunoreactivities in the secretory-specific cells of the hypophyseal pars tuberalis of the chicken

 The pars tuberalis mainly consists of the secretory cells specific to this portion of the pituitary. We examined the localization and development of luteinizing hormone (LH) and chromogranin A in the chicken pars tuberalis by immunohistochemistry. The vast majority of the chicken pars tuberalis was occupied by cells immunoreactive for both LH and chromogranin A. Furthermore, immunoblot analysis of chicken pars tuberalis extracts with LH antiserum demonstrated that two bands, the large α-subunit and small β-subunit of the LH molecule, were expressed in this tissue as well as in the pars distalis. A band for chromogranin A was also detected in pars tuberalis extracts with chromogranin A antiserum. In contrast to the cells of mammalian species that contain only a few small secretory granules, the specific cells of the chicken pars tuberalis were characterized by the presence of many secretory granules ranging from 90 to 400 nm in diameter. Postembedding immunogold labeling showed that gold particles representing immunoreactivity for LH were densely located on all secretory granules of the secretory-specific cells. Many secretory granules, especially the large ones, of the cells were also loaded with immunogold particles for chromogranin A. Double immunogold labeling confirmed that LH and chromogranin A were colocalized on the same secretory granules. During embryonic development, the primordium of the pars tuberalis was first detected at 8 days of incubation as a small group of cells containing LH- and chromogranin-immunoreactive cells. In the pars distalis, the onset of LH and chromogranin expression occurred earlier, at 6 days of incubation. At 10 days of incubation, the pars tuberalis primordium became large cell masses consisting of LH- and chromogranin-immunoreactive cells, which were located close to the median eminence. Subsequently, the primordium extended along the median eminence progressively with age. At 14 days of incubation, it reached to the rostral end and surrounded the median eminence as slender cell cords. These results indicate that specific cells of the chicken pars tuberalis synthesize a glycoprotein hormone related to the LH molecule, which is stored in the secretory granules together with chromogranin A. The pars tuberalis may be involved in the regulation of gonadal function in a different way from that of the pars distalis. Accepted: 26 August 1997     

Light and electron microscopic study on the endocrine cells of the pancreas in a marine teleost,Fugu rubripes rubripes

Summary The pancreatic endocrine tissue of Fugu rubripes rubripes consists of numerous round principal islets (Brockmann bodies) of various sizes scattered around the gall-bladder. The endocrine cells are divided into A-, B-, D-, and F_f-cells. Each cell type was identified by comparing thick and thin sections in both light and electron microscopy. Aldehyde-fuchsin positive B-cells contain numerous round secretory granules (average diameter 300 nm) each of which has a round compact core of moderate density; a narrow space exists between this core and the limiting membrane. Grimelius' silver positive A cells contain round secretory granules (average diameter 360 nm) with a hexagonal or tetragonal crystalline core (average diameter 170 nm) of high density; the silver grains preferentially appear in the space between the limiting membrane and the core. The crystalline core of each -granule often contains an appendix-like structure of variable shape. D cells blackened by the silver impregnation method of Hellman and Hellerström (1960) have round secretory granules (average diameter 320 nm) filled with a flocculent material of low density. The fourth cell type (F_f-cell) has a clear cytoplasm after differential staining for light microscopy. By electron microscopy, this cell has elongated fusiform secretory granules (520 nm average length × 230 nm average width) filled with numerous filaments arranged in parallel with the longitudinal axis. Figures suggesting granule formation in the sacs of the Golgi apparatus were obtained in all of islet cell types. Equivalents of emiocytotic release of secretory granules were encountered in the A and F_f cells.     

Localization of a 16,000-dalton fragment of the common precursor of adrenocorticotropin and beta-lipotropin in the rat and human pituitary gland

To clearly identify cells and organelles containing the common precursor (31,000 dalton) for both adrenocorticotropin (ACTH) and beta-lipotropin (beta-LPH), an immunohistochemical localization of a fragment (16,000 dalton) of the precursor that is not common to beta-LPH and ACTH was conducted in rat and human pituitary glands. With the help of specific antibodies that do not cross-react with beta-LPH and ACTH, the 16,000-dalton fragment was localized in the cells that also produce ACTH and beta-LPH in both the pars distalis and pars intermedia of the rat pituitary. At the electron microscope level, the secretory granules that contain ACTH were also stained for 16,000-dalton fragment. In the human pituitary, the 16,000-dalton fragment was also observed in all the secretory granules of lipocorticotrophs. These results suggest that, after enzymatic cleavage, fragment(s) of the common precursor and/or the whole common precursor remain packaged within the secretory granules with peptides of known activity.     

A whole range of fine structural criteria for immunohistochemically identified LH cells in rats

Summary Pituitaries from normal, young and adult male rats were fixed either in sublimate-formalin or in glutaraldehyde-osmium. In adjacent Paraplast sections, almost all the gonadotrophs were immunostained with both LH and FSH antisera. The rat LH and FSH antisera used were shown to be highly specific by the absorption test and by double antibody radioimmunoassay. Thin and thick adjacent Epon sections were prepared for EM and immunohistochemical examination. Cells stained with the rat LH antiserum were identified by LM, and then observed in detail by EM. On the basis of these observations we suggest that the LH cells are arranged in a sequence of basophils, i.e., Types II/III, III, III/IV and IV: Type II/III basophils are elongate with a cytoplasmic process and less vesiculated. They have morphological features of Type II (classical thyrotrophs) and also of Type III basophils. Type III basophils are oval in shape and moderately vesiculated. Both Types II/III and III basophils can be divided into two classes of cell characterized mainly by the existence of only small secretory granules (150–220 nm in diameter) (Type A) or by the coexistence of small and large (350–500 nm) (Type B). Type III/IV basophils are cells intermediate between types III and IV basophils, and moderately vesiculated with an abundance of secretory granules (150–300 nm in diameter). Type IV basophils are large, spherical or oval cells whose RER cisternae are conspicuously dilated; they contain less numerous secretory granules (150–300 nm in diameter). It is concluded that LH cells are not a single cell type, but include a wide range of subtypes.     

Immunocytochemical and immuno-electron-microscopical study of growth hormone cells in male and female rats of various ages

Summary Growth hormone (GH) secretory cells were identified by immunogold cytochemistry, and were classified on the basis of the size of secretory granules. Type I cells contained large secretory granules (250\2-350 nm in diameter). Type II cells contained the large secretory granules and small secretory granules (100\2-150 nm in diameter). Type III cells contained the small secretory granules. The percentages of each GH cell type changed with aging in male and female rats of the Wistar/Tw strain. Type I cells predominated throughout development; the proportion of type I cell was highest at 6 months of age, and decreased thereafter. The proportion of type II and type III cells decreased from 1 month to 6 months of age, but then increased at 12 and 18 months of age. The pituitary content of GH was highest at 6 months of age, and decreased thereafter. Estrogen and androgen, which are known to affect GH secretion, caused changes in the proportion of each GH cell type. The results suggest that when GH secretion is more active the proportion of type I GH cell increased, and when GH secretion is less active the proportion of type II and type III cells increased. The type III GH cell may therefore be an immature type of GH cell, and the type I cell the mature type of GH cell. Type II cells may be intermediate between type I and III cells.     

Lysosomes in the cessation of vitellogenin secretion by the mosquito fat body; selective degradation of Golgi complexes and secretory granules

A massive and selective degradation of Golgi complexes, secretory granules, and RER is the mechanism responsible for the rapid termination of Vg secretion by trophocytes of the mosquito fat body. These cells are involved in an intensive synthesis of a glycoprotein, vitellogenin (Vg), which is accumulated by developing oocytes as yolk protein. Previously, assays for lysosomal enzymes have demonstrated that the cessation of Vg synthesis is characterized by a sharp increase in lysosomal activity; and fluorescent microscopy has shown that, during this intense lysosomal activity, Vg concentrates in lysosomes. In this report, electron microscopy combined with cytochemistry for lysosomal enzymes and localization of Vg with colloidal gold immunocytochemistry has shown that this lysosomal activity is directed towards selective degradation of Vg and organelles associated with its synthesis and secretion. Three organelles undergo lysosomal breakdown: the Golgi complex, Vg-containing secretory granules, and RER. The degradation of Golgi complexes occurs in two steps similar to that for RER: first, the organelle is sequestered by double isolation membranes, and the resulting pre-lysosome then fuses with a primary or secondary lysosome. In contrast, mature Vg-containing secretory granules fuse with lysosomes directly. This combination of crino- and autophagy is a specific, highly intense, and precisely timed event.     

Ultrastructural localization of prolactin,growth hormone and luteinizing hormone by immunocytochemical techniques in the bovine pituitary

Summary The technique of ultrastructural immunocytochemistry involving the unlabeled antibody and the soluble peroxidase-antiperoxidase complex was used to identify and describe the prolactin (P) cells, somatotropic (STH) cells and luteinizing hormone (LH) cells in the bovine anterior pituitary gland. This method was used to localize the three hormones at the electron microscopic level. Staining of varying intensity was found on the secretory granules and on the small granules and vesicles within the Golgi complex. No stain was found in nuclei, on mitochondria or in the endoplasmic reticulum.     

Electron microscopic demonstration of calcitonin in human medullary carcinoma of thyroid by the immuno gold staining method

In a human medullary carcinoma of thyroid gland containing calcitonin in light microscopic demonstration by the avidin biotin complex (ABC) method characteristic secretory granules were found electron microscopically in the cytoplasm of the tumour cells. They consisted in so-called type I granules (270 +/- 25 nm) and type II granules (135 +/- 17 nm). By the immuno gold staining (IGS) method the content of many secretory granules measuring 85-270 nm (152 +/- 18 nm) in diameter could be identified as calcitonin. These granules seemed to be predominantly of type II because of their nearly corresponding size and feature. The type I granules were less frequent in number and they showed no or little immunoreactivity. The results indicate that the IGS-method is practicable to demonstrate the ultrastructural localization of calcitonin and to identify clearly the nature of intracytoplasmic granules in electron microscopy.     

Classifications of somatotropes, lactotropes and corticotropes in the mouse adenohypophysis with immunohistochemistry

Somatotropes, lactotropes and corticotropes of adult male mice were identified with immunohistochemistry in the adenohypophysis fixed by OsO4 alone. Somatotropes were classified into type I somatotropes that contain large (350 nm in diameter) round secretory granules and type II somatotropes that contain small (100-200 nm in diameter) round secretory granules. Most somatotropes were type I somatotropes. Lactotropes were also classified into type I lactotropes that contain irregularly shaped secretory granules and type II lactotropes containing small (100-200 nm in diameter) round secretory granules. Corticotropes are irregular stellate or slender cells with little cytoplasm. They contain round solid secretory granules in various densities along the cell periphery. Most of these are low-density granules (200-300 nm in diameter) and a few are high-density granules (200-250 nm in diameter). These data were compared with the classical data of mouse adenohypophysial cells that were fixed in OsO4 alone and identified only by conventional electron microscopy.     

Intracellular localization of serotonin in mast cells of the colon in normal and colitis rats

Intracellular localization of serotonin (5-HT) in the mast cells of two phenotypes in normal rat colon and dextran sodium sulphate-induced colitis was studied by immunoelectron microscopy with a quantitative analysis of the distribution of immunogold labelling. Mucosal mast cells in normal rats contained round shape secretory granules with varying electron density. Immunogold labelling for 5-HT was concentrated over the secretory granules. In mucosal mast cells from colitis rats, vacuolated granules without 5-HT labelling were frequently observed and immunogold labelling over the secretory granules was significantly increased compared to controls. On the other hand, connective tissue mast cells in normal rats contained oval shape secretory granules with homogeneous electron density. Their immunogold labelling was diffusely scattered over the secretory granules as well as over the cytoplasm. In connective tissue mast cells from colitis rats, secretory granules with high electron density were increased and the immunogold labelling over the secretory granules was much higher than that in controls. The present results suggest that intracellular localization of 5-HT is different in two phenotypes of mast cells and they may release 5-HT in a different manner. Mucosal mast cells may release 5-HT by a degranulation or exocytosis, while connective tissue mast cells may release 5-HT by a diacrine manner of secretion.     

Quick-freeze,deep-etch visualization of exocytosis in anterior pituitary secretory cells: localization and possible roles of actin and annexin II

The exocytotic process in the anterior pituitary secretory cells was studied using quick-freeze deep-etch electron microscopy, fluorescein-isothiocyanate-phalloidin staining, heavy meromyosin decoration, and immuno-electron microscopy. The subcortical actin filaments are distributed unevenly in the peripheral cytoplasm. Few secretory granules are seen beneath the plasma membrane in the region where the peripheral cytoplasm is occupied by numerous subcortical actin filaments. On the contrary, in the region free of the subcortical actin filaments, many secretory granules lie in contact with the plasma membrane. Thus, the subcortical actin filaments may control the approach of the secretory granules to the plasma membrane in these cells. The granule and plasma membranes that lie in close proximity are linked by intervening strands. Unfused portions of both membranes remain linked by these strands during membrane fusion and opening. These strands may be involved in membrane contact, fusion and opening during exocytosis. Annexin II (calpactin I) has been demonstrated immunocytochemically to be localized at the contact sites between the granule and plasma membranes, and is therefore a possible component of the intervening strands. Membrane fusion starts within focal regions of both membranes less than 50 nm in diameter. The plasma membrane shows inward depressions toward the underlying granules immediately before fusion. The disappearance of intramembranous particles from the exocytotic site of the membrane has not been observed.     

Immunohistochemical and ultrastructural study of anterior pituitary cells in the female Afghan pika,Ochotona rufescens rufescens

An immunohistochemical study of the anterior pituitary gland of the female Afghan pika was carried out to distinguish the ultrastructural features of GH, PRL, ACTH, TSH and LH cells. The histochemically identified GH cells resembled ultrastructurally oval or round GH cells of the rat laden with large, dense secretory granules. PRL cells were divided into three subtypes based on differences in the diameter of their spherical secretory granules. They lacked polymorphic or irregularly shaped secretory granules. ACTH cells resembled ultrastructurally, in some respects, Siperstein's "corticotrophs" of the rat with peripheral arrangement of secretory granules. However, they were not always stellate, but elongate or angular in shape. The dense secretory granules were concentrated in the peripheral area of cytoplasm. TSH cells were non-stellate, but usually oval in shape, containing the smallest spherical secretory granules (100-200 nm in diameter). Almost all LH cells reacted also with FSH antiserum. They were irregular in shape, sometimes in contact with or surrounded the GH cells. They contained an abundance of medium-sized secretory granules (140-260 nm in diameter) which were larger than those in the LH cells of the female rat throughout the estrous cycle. Large secretory granules in the LH cells of the female pika seemed to be related to the endocrine state of persistent estrus.