Immunohistochemical identification of cells in the pars distalis of the pituitary of the lizard anolis carolinensis

Summary Immunocharacteristics of the pars distalis cells of the pituitary of the male lizard A. carolinensis are determined by employing the immunoperoxidase technique with antisera to mammalian pituitary hormones. On the basis of their immunoreactivity, 5 different cell types with characteristic anatomical distribution are recognized. ACTH cells are found in the rostral half of the pars distalis, and PRL cells in the rostral two thirds of the pars distalis. GH and TSH cells are located in the caudal half of the pars distalis. GTH cells are distributed throughout the gland. When consecutive sections are stained with antiserum to ovine FSH or its -subunit and to ovine LH, the same cells show immunoreactivity to all the three antisera. None of the GTH cells show positive immunoreactivity to ovine -LH antiserum. The results suggest the existence of one gonadotropic cell type in the pituitary of this lizard.Supported by U.S. Council for International Exchange of Scholars (to D.R.N.) and PHS Grant NS09914     

Demonstration of gonadotropic cells in the adenohypophysis (pars distalis and pars tuberalis) of the monkey Macacus irus. Immunofluorescence study using human anti-beta-FSH and ovine anti-beta-LH antibodies

Indirect immunofluorescence technique with anti-beta FSH and anti-beta oLH antisera has allowed us to detect "gonadotropic cells" in the pars distalis and in the pars tuberalis of the adenohypophysis of the monkey Macacus irus. In the pars distalis, 85-90 % of the "gonadotropic cells" react simultaneously with these two antisera ; 10-15 % of these cells react only either with anti-beta hFSH or anti-beta oLH antisera. The gonadotropic cells are dispersed in the whole pars distalis, amid the other cellular types ; indeed, in the female, there is a "gonadotropic zone" in the median zone of the lateral lobes of the gland. In the pars tuberalis, we have observed "gonadotropic cells" which react only with anti-beta oLH antiserum. These results are compared with observations of some authors.     

Immunohistochemical identification of cells in the pars distalis of the pituitary of the lizard Anolis carolinensis

Immunocharacteristics of the pars distalis cells of the pituitary of the male lizard A. carolinensis are determined by employing the immunoperoxidase technique with antisera to mammalian pituitary hormones. On the basis of their immunoreactivity, 5 different cell types with characteristic anatomical distribution are recognized. ACTH cells are found in the rostral half of the pars distalis, and PRL cells in the rostral two thirds of the pars distalis. GH and TSH cells are located in the caudal half of the pars distalis. GTH cells are distributed throughout the gland. When consecutive sections are stained with antiserum to ovine FSH or its beta-subunit and to ovine LH, the same cells show immunoreactivity to all the three antisera. None of the GTH cells show positive immunoreactivity to ovine beta-LH antiserum. The results suggest the existence of one gonadotropic cell type in the pituitary of this lizard.     

Changes in the pituitary of the migrating European eel during its journey from rivers to the sea

Summary The present studies demonstrate that, as migrating European silver eels enter the sea, important changes occur in the pars distalis of the pituitary. A decrease of Type A neurosecretory material in all nerve tracts penetrating the pars distalis was observed, as was an increased activity of Type B neurosecretion in the tracts of the proximal pars distalis.In the proximal pars distalis, gonadotropic cells show striking changes, and in the rostral pars distalis thyrotropic and prolactin cells. It is discussed whether these changes are related to migration to breeding grounds or to changes in the environment.Dedicated to Dr. Berta Scharrer on her 60th birthday.     

The goldfish pituitary

Summary In the goldfish, Carassius auratus, morphological and functional aspects of the pituitary gland were studied at the ultrastructural level and six cell types could be distinguished in the pars distalis. Acidophilic cells of the rostral pars distalis were identified as prolactin cells, the chromophobic cells of the rostral pars distalis as ACTH cells, the non-globular basophilic cells of the rostral and the proximal pars distalis as TSH cells, the globular basophils of the proximal pars distalis as gonadotropic cells and the acidophils of the proximal pars distalis as somatotrophs.Besides some of the well established criteria of morphological and functional identification of different cell types, two new approaches have been used in the present study. One was to express the electron density of secretory granules objectively by means of a photometric method. It was found that both types of acidophilic cells which produce the proteohormones prolactin and somatotropin respectively, had granules with the highest electron densities. The basophilic cells producing the glycoproteins gonadotropin and TSH respectively, possessed granules of intermediate electron density whereas the chromophobic cells storing the peptide hormone ACTH had granules of lowest densities. The second new approach was the administration of the synthetic mammalian releasing hormones LH-RP and TRF, which helped in identifying gonadotropic and thyrotropic cells respectively. In the goldfish there is evidence for the presence of only one type of gonadotropic cell.Supported by a grant of the Science Research Council of Great Britain to Professor Sir Francis Knowles, F.R.S. The electron microscope used was provided by the Medical Research Council of Great Britain. The integrating photometer IPM2 was kindly on loan from Messrs. Carl Zeiss, Oberkochen, Germany. For technical advice we are greatly indebted to Mr. P. K. Kaul, B. E., M.I. Struct. E., C. Eng.     

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.     

Histology of the pituitary gland of the grey mullet, Mugil cephalus L.

The present communication deals with a histological study of the pituitary gland of the teleost fish Mugil cephalus , found in the estuarine waters of Cochin area. Six different cell types were identified in the pituitary gland on the basis of their grouping, distribution and staining properties. The prolactin and the TSH cells (thyroid stimulating hormone producing cells or thyrotrops) were identified in the rostral pars distalis and the ACTH cells (adrenocorticotropic hormone producing cells or corticotrops) in the interphase between the neurohypophysis and the rostral pars distalis. The STH cells (somatotropic hormone producing cells or somatotrops) and the gonadotropic cells were distinguished in the proximal pars distalis and the MSH cells (melanin stimulating hormone producing cells or melanotrops) in the pars intermedia.     

Light and electron microscopic investigations of six types of glandular cells of the bovine adenohypophysis

Summary Twelve bovine adenohypophyses were prepared for light and electron microscopy of the cell types of pars distalis. Correlation between the light and electron microscopy was effected by use of alternate thin and thick sections. Cytological changes in the experimental animals were used as criteria for the identification of six different types of secretory cells.Two types of acidophils, alpha and epsilon cells, are recognized in peripheral area of the pars distalis by light and electron microscopy. The alpha cells contain orangeophilic secretory granules of a maximum diameter of 400–450 m and correspond to ordinary acidophils (STH cells). The second type, epsilon cells, contains larger, fuchsinophilic granules of 600 to 900 m in diameter, increase in number and granulation after pregnancy and thyroidectomy, and are thought to be prolactin cells (LTH cells).Two types of amphophils, zeta and delta 1 cells, were found in the central area of the pars distalis. The zeta cells contain smaller numbers of amphophilic, cored granules (200 m maximum diameter) and based on the comparison with literature on other species of animals, are designated as ACTH cells. The delta 1 cells are round or oval and contain very dense, spherical granules (250–300 m) which are stained red or reddish purple with PAS, aldehyde thionin and PAS-methyl blue methods. They show extreme enlargement and bizarre cytoplasmic appearance after castration and are designated tentatively as LH gonadotrophs or LH cells.Two types of basophils, beta and delta 2 cells, were also identified by correlative light and electron microscopy. The beta cells are polygonal in outline, distributed exclusively in the zona tuberalis and contain large, less dense secretory granules (300–400 m) which are stained selectively with Gomori's aldehyde fuchsin. After thyroidectomy, they lose their secretory granules and are transformed into large, vacuolated thyroidectomy cells. They are therefore, identified as thyrotrophs or TSH cells. The delta 2 cells are round, oval or polygonal in shape and contain basophilic granules ranging from 220 to 300 m in diameter. They show extreme enlargement and vacuolization due to the dilation of endoplasmic reticulum, after castration, and are designated tentatively as FSH gonadotrophs or FSH cells.The investigation reported herein was supported by a Scientific Research Grant (No. 291049) from the Ministry of Education of Japan.     

Fine structure of the stellate cell in the pars distalis of the lizard, Anolis carolinensis

The stellate cell in the pars distalis of Anolis carolinensis has been studied with the electron microscope. This cell type is characterized by the lack of secretory granules, and it possesses elongate processes that insert between secretory cells. Few cytoplasmic filaments are present in these processes, and desmosomes linking them to adjacent stellate cells or to secretory cells are seen infrequently in control animals. Stellate cells are often encountered in the caudal half of the pars distalis, but they are less commonly found in the rostral half. In animals undergoing thyroidal depression, thyroidectomy cells arise in the caudal pars distalis. Concurrently, stellate cells of that region hypertrophy and exhibit increased numbers of desmosomes, complex intercellular junctions, and micropinocytotic vesicles. Injected horseradish peroxidase penetrates the intercellular spaces, enters the micropinocytotic vesicles, and is transported to the interior of the stellate cell. It is suggested that stellate cells in Anolis under certain conditions may transport materials between the bloodstream and secretory cells.     

Inhibin-like and gonadotropin-like immunoreactivity in pituitary cells of male monkeys (Macaca fascicularis,Macaca mulatta)

Summary Inhibin-like immunoreactivity was detected by immunocytochemistry in the pituitaries of untreated male crab-eating macaques (cynomolgus monkey) and rhesus monkeys, in rhesus monkeys actively immunized against FSH, and in one orchidectomized crab-cating macaque. Localizations were performed by the immunogold-silver staining with 5-nm colloidal gold-conjugated second or third antibodies and by the alkaline phosphatase-anti-alkaline-phosphatase technique. Two different inhibin-specific antisera, raised against the -subunit or the entire inhibin molecule, provided identical staining patterns. Positive label was confined to the pars distalis of the pituitary and occurred exclusively in the cytoplasm of morphologically different cell types throughout the pars distalis in all pituitaries. Staining was most prominent in clusters of chromophobic cells. The presence of inhibin-like activity in the pituitary of an orchidectomized monkey with undetectable serum inhibin levels suggests that inhibin is produced within the pituitary gland. Co-localization studies for the -subunits of the gonadotropic hormones revealed that on average 82% of the gonadotropes were bihormonal. Using the same protocol, co-localization of inhibin-like activity with gonadotropin-like immunoreactivity revealed only a small degree of common distribution (<15%). Inhibinpositive cells were frequently in close proximity to gonadotropic cells and, thus, paracrine effects of inhibin on gonadotropin-synthesizing cells are conceivable.     

An immunocytochemical study of the pituitary gland of the white seabream (Diplodus sargus)

The adenohypophysis of the white seabream (Diplodus sargus) was studied using histochemical and immunocytochemical techniques. The adenohypophysis was composed of rostral pars distalis, proximal pars distalis and pars intermedia. Prolactin (anti-chum salmon prolactin positive) and adrenocorticotropic (anti-human ACTH positive) cells were found in the rostral pars distalis. Prolactin cells were organized into follicles, while ACTH cells were arranged in cords around neurohypophyseal tissue branches that penetrated the rostral pars distalis. In the proximal pars distalis, somatotropic (anti-chum salmon and anti-gilthead seabream growth hormone positive), gonadotropic (anti-chum salmon -gonadotrophin II and anti-carp -gonadotrophin II positive, but anti-chum salmon -gonadotrophin I negative) and thyrotropic (anti-human -thyrotropin positive) cells were observed. Growth hormone cells were restricted to the dorsal and ventral part of the proximal pars distalis. They were clustered or surrounded the neurohypophyseal branches. Only one type of gonadotrophin cell was identified and they were clustered or isolated in the proximal pars distalis. Scattered groups of thyrotropin cells were located throughout the proximal pars distalis. In the pars intermedia somatolactin (anti-chum salmon and anti-gilthead seabream somatolactin positive) and melanotropic (anti--melanotropic hormone positive) cells were localized. In addition, gonadotrophin cells surrounded the pars intermedia or distributed evenly between somatolactin and melanotropic hormone cells. Somatolactin cells were periodic acid-Schiff negative and surrounded the neurohypophyseal branches intermingled with melanotropic cells. These cells were also immunoreactive to anti-human ACTH antiserum.     

Ultrastructure of the pituitary gland (pars distalis) in sockeye salmon (Oncorhynchus nerka) during gonad maturation

Summary The fine structure of the various hormone-producing cell types (with the exclusion of the prolactin cells) in the pituitary gland (pars distalis) of migratory sockeye salmon is described. All fish were in an advanced stage of sexual maturation. In the proximal pars distalis five cell types were distinguished: growth hormone cells, ACTH cells, gonadotrops, vesicular cells, and chromophobe cells. Gonadotrops were also found throughout the rostral pars distalis. A conspicuous feature of the gonadotrops was the presence of two kinds of secretory inclusions: small electron-dense granules (200–375 m) and large, relatively electron-translucent globules (400–2 000 m). The large vesicular cells, so called because of their conspicuous vesicular endoplasmic reticulum, were numerous and often appeared to contain some small granules. It is argued that they may represent a second type of gonadotropic cell, which, in earlier stages of gonad development, contains many granules but becomes largely degranulated near the time of reproduction when the other gonadotrops (globular gonadotrops) abound. The chromophobes, which were smaller and far less abundant than the vesicular cells, also appeared to contain small granules (120–280 m). They are probably thyrotrops.The assistance of Mr. S. Killick, of the International Pacific Salmon Fisheries Commission, who helped in the collection of salmon, is gratefully acknowledged.     

Light-microscope studies of the cytology of the adenohypophysis of the white-crowned sparrow,Zonotrichia leucophrys gambelii

Summary Adenohypophyses from more than two hundred white-crowned sparrows of both sexes and different ages, and from different periods of their annual reproductive cycle, have been used for this investigation. In addition to examination of these normal birds, we have also studied the adenohypophyses of 23 castrates and 24 controls held in different photoperiodic conditions.Cytologically the pars distalis of the adenohypophysis of the white-crowned sparrow is typically avian with distinct cephalic and caudal lobes, each with characteristic cell-types.Four basic cell-types, the acidophils, basophils, amphophils, and chromophobes, have been identified in the pars distalis by means of Matsuo tetrachrome and Matsuo modified PAS-methyl blue staining methods.Three types of acidophils, orange, red, and small, are confined to the caudal lobe of the pars distalis. Their possible functions are discussed.Light basophils (PAS-light red cells) and deep basophils (PAS-deep red cells) are equally distributed in both lobes. It is suggested that basophils may be involved in gonadotropic function since their appearance correlates well with the annual gonadal cycle and photoperiodic stimulation of gonadal growth and with the results of castration.The amphophils or PAS-purple cells (aldehyde-fuchsin positive) are found only in the cephalic lobe. Their probable function is discussed.Two types of chromophobes, specific and ordinary chromophobes, have been observed. The specific chromophobes are found only in the cephalic lobe and are similar to the Kernhaufen described by Romeis (1940). The ordinary chromophobes are similar to those of the pars distalis of other avian species and of mammals.The castration cells are found in both lobes of the photosensitive castrates under natural photoperiodic conditions as well as in those subjected artificially to photostimulation (20-hour daily photoperiods). Similar cells have also been observed in the pars tuberalis of the castrated photostimulated birds.The relations of the rostral and caudal groups of the portal vessels to the cell-types found in the cephalic and caudal lobes are discussed.Dedicated to Professor Dr. Y. Kato, Department of Anatomy of the Domestic Animals, Kyushu University, Fukuoka, Japan, and to President Dr. H. Mimura, Shinshu University, Matsumoto, Japan, in honor of their retirement.The investigation reported herein was supported by a research grant (5RO 1-HEO7240 NEUA) from the National Institutes of Health to Professor Vitums, by funds for biological and medical research made available by State of Washington Initiative Measure No. 171 to Professor Vitums; by a Research Career Development Award (5K3 AM-18, 370) from the National Institutes of Arthritis and Metabolic Diseases to Professor King; and by a research grant (5RO 1 NB 06 187) from the National Institutes of Health to Professor Farner. The senior author is greatful to Professor Dr. Hideo Murai and Doctor Yasukuni Watanabe, Department of Animal Science, Shinshu University,Ina,Japan, for their cooperation and support in this investigation. We wish to thank Mrs. Sumiko Sumida for technical assistance, and Miss Kathleen Reinhardt for the preparation of the drawings.     

Effects of Methallibure (ICI 33,828) on the pars distalis of pituitary,testis and thumb pad of the green frog,Rana esculenta L.

Summary The influence of ICI compound 33,828 (1--methylallylthiocarbamoyl-2-methylthiocarbamoylhydrazine = Methallibure) on the pars distalis of pituitary, testes and thumb pads was investigated in the intact adult male green frog, Rana esculenta. Methallibure affected the gonadotropic basophils (particularly the B2 cells) of the pars distalis, which showed varying degrees of degranulation and underwent a notable decrease in their percentage. Within the testis this compound caused the arrest of spermatogenesis. The most uniform effect of Methallibure was observed in the thumb pads, which invariably showed regression of the epidermis and glandular epithelium. No histological changes occurred in the thyroid and adrenal glands and the B1 and A1 cells of the pars distalis remained unchanged cytologically. It is concluded, in concordance with the available data, that Methallibure is a non-steroidal antigonadotropic compound. The important question about its mode of action has been brought into discussion.Work supported by the National Research Council of Italy, and the Population Council (Grant No. M70.082 C) of New York.     

Immunocytochemistry of gonadotropic cells and identification of cell types in ultrathin cryosections of the pituitary of the rainbow trout,Salmo gairdneri

Summary The most frequently occurring cell types in the pars distalis of the pituitary gland of the rainbow trout, (i) the lactotropic, (ii) the gonadotropic, and (iii) the somatotropic cells, were identified in cryosections. Their morphological characteristics were compared with those of Epon-embedded material. Cell location, cell form, position of the nucleus, arrangement of rough endoplasmic reticulum and sizes of secretory granules proved to be useful parameters for identification. The size distribution of secretory granules of corresponding cells in cryosections and Epon sections proved to be similar. Additionally, both the immunoferritin and the unlabeled antibody enzyme method were applied for the immunocytochemical labeling of gonadotropic hormone-producing cells in cryosections. Anti-salmon-GTH as well as anti-carp-GTH serum showed the presence of GTH in both the smaller and the larger granules of the classical GTH cells, but also produced a reaction in TSH cells. Labelling of TSH cells was absent when using anti--carp-GTH. Specificity of the reaction depended upon the degree of dilution of the anti-GTH serum. Results with dilutions of 14,000 and 18,000 in the unlabeled antibody enzyme method, and of 18,000 up to 132,000 in the immunoferritin technique were optimal. Acid phosphatase activity in the smaller granules was demonstrated by enzyme cytochemistry in Epon sections. The relationship of the presence of hormone in these granules is discussed. The high sensitivity of the immunocytochemical labeling procedure is discussed with respect to cryo-ultramicrotomy.     

Diurnal rhythm of hypophyseal cells in mice. IV. Pars Distalis∗

Abstract

Using various staining techniques and methods, the following cells were differentiated from pars distalis of the pituitary gland in the mouse: corticotropic, somatotropic, lactotropic, thyrotropic and gonadotropic cells.

Diurnal activity of the differentiated cells in pars distalis of the pituitary gland was determined by the method of karyometry.

The karyometric analysis showed the existence of a distinct diurnal rhythm in nuclear volume in all five types of the differentiated cells in both sexes.     

Cellular composition of the human pituitary pars tuberalis as revealed by immunocytochemistry

Summary An attempt was made to determine if any of the specialized secretory cell types common to the pars distalis also occur in the pars tuberalis of the human hypophysis. Available for study were 18 specimens of the inferior pars tuberalis, which partially surrounds the infundibular stem, and 3 specimens of the superior pars tuberalis that is attached to the median eminence. Antisera to human somatotropin, mammotropin, chorionic gonadotropin, follicle-stimulating hormone, FSH , luteinizing hormone, LH , thyrotropin, TSH , as well as to ^1–24-corticotropin, porcine ^17–39-corticotropin, and ovine LH were used with the Sternberger peroxidase-antiperoxidase immunocytochemical procedure to identify the probable cells of origin for these hormones.The evidence indicated that gonadotropic cells constitute the major portion of the parenchymal cell population in the pars tuberalis. They occurred throughout all of the pars tuberalis and were usually arranged in clusters. Somatotropic, mammotropic, corticotropic, and thyrotropic cells were rare and not found in all specimens. When present, they often formed a common group suggesting that their occurrence in the pars tuberalis resulted from displacement of primordial tissue of the pars distalis during embryogenesis.Supported in part by research grants HD-03159 and HD-08333 from the National Institute for Child Health and Human DevelopmentWe thank Dr. L.A. Sternberger for providing the PAP complex and others for antisera (Table 2) and hormones (Footnote 2) as listed     

Ultrastructure of the male rat hypophysis chronically grafted under the kidney capsule

Summary Male rats were divided in two experimental groups. In group I two partes distales of the hypophysis were grafted under the kidney capsule and in group II two complete hypophyses were transplanted. Animals were killed 5 to 22 months after the operation. The grafted tissue was excised and processed for light and electron microscopy.The transplanted pars distalis tissue showed a well developed vascularisation in contrast to the pars intermedia which appeared poorly vascularised. Six different cell types were observed in grafted pars distalis. They correspond to the different types of cells found in the rat pars distalis in situ. The predominant cell type in the graft displayed all the morphological characteristics of stimulated prolactotrophs. Pars intermedia cells appeared hypertrophied resembling the MSH cells under stimulation. Two types of syncytial formations were frequently seen. One of them appeared to originate from prolactotrophs and the other from MSH cells. Bodian impregnated fibres and structures resembling either growth cones of axons or typical nerve endings were observed in the pars intermedia of long-term grafted hypophyses. Pituicytes remained as isolated clusters of cells. Canaliculi lined by two or more pituicytes were observed. Saccular formations resembling the hypophyseal cleft appeared in all grafts studied. The present findings suggest that in the male rat the chronically grafted pituitary gland is capable of synthesising most or all the hormones which are known to be produced by the gland in situ. Furthermore, prolactin and MSH seem to be the predominant secretion of the transplanted pituitary.Supported by the National Research Council of Argentina. Grant 7315/74Members of the Research Career of Conicet, Argentina     

Immunocytochemical studies on the pituitary pars distalis of the Japanese long-fingered bat,Miniopterus schreibersii fuliginosus

Summary Immunocytochemical studies were performed to describe the characteristics of cell types and their distribution in the pars distalis of Japanese long-fingered bat, Miniopterus schreibersii fuliginosus, collected at various stages of the reproductive cycle. Six distinct cell types have been identified in the pars distalis by the unlabeled immunoperoxidase technique and by the ABC method. Growth hormone (GH) and prolactin (PRL) cells were immunostained with antisera against chicken GH and ovine PRL. The GH-immunoreactive cells were round or oval orangeophilic cells distributed throughout the pars distalis with prominent aggregation in the posterolateral region. The PRL cells were pleomorphic carminophilic cells that occurred in small groups within the central and dorsocaudal regions of the pars distalis. They were sparsely distributed in the central region of the pars distalis in the hibernating bats, but increased significantly in the pregnant and lactating bats. The adrenocorticotropic (ACTH) cells were large round or polygonal amphophilic cells in the rostroventral and ventrolateral regions of the pars distalis. The thyrotropic (TSH) cells were small rounded or polygonal and distributed mainly in the ventrolateral region of the pars distalis. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) cells were identified immunocytochemically with antisera against the specific beta subunits of ovine LH and rat FSH. There were two populations of LH and FSH cells, one aggregated in the zona tuberalis and the other scattered singly throughout the rest of the pars distalis. The aggregated cells were immunoreactive with both antisera directed to LH and FSH, while scattered cells were reactive solely with antiserum to either LH or FSH and exhibited seasonal variations. In females, the proportional volume of the pars distalis occupied by LH cells was significantly reduced during pregnancy and lactation. No evidence of involution was observed in pars distalis cells except for PRL cells in males or females during hibernation.     

Embryology and cytodifferentiation of the pituitary gland in the lizard Anolis carolinensis

Anolis embryos have limb buds at the time eggs are laid and require about 39 days to complete development at 28°C. Rathke's pouch is present at five days, and the subdivisions of the adenohypophysis are differentiated by ten days after oviposition. The cells of the rostral half of the pars distalis (PD) are derived from the anterior face of Rathke's pouch; cells of the caudal half from the posterior face. Lateral lobe cells differentiate on the lateral margins of the developing caudal PD, and knob-like outgrowths of this tissue attach to the walls of the diencephalon to form the pars tuberalis (PT). Subsequently, the cells of the PT lose their connection with the PD and become a pair of flattened oblong plaques. They reach maximal size in midincubation, and are gradually invaded by nervous elements and incorporated into the walls of the hypothalamus. Electron micrographs demonstrate that the embryonic PT is secretory. Ultrastructurally the pars intermedia (PI) and PD are composed of parenchymous secretory cells in a framework of stellate cells. Stellate cells surround the lumen of Rathke's pouch and are connected laterally by complex junctions that exclude the secretory cells from the luminal surface. They extend in sheet-like processes among the secretory cells to the outer margin of the gland where they form a partial sheath within the basal lamina around the secretory tissue. As development proceeds, the lumen becomes subdivided and the resulting reduced lumina are recognizable as the forerunners of the follicles of the adult adenohypophysis. The cells of the PI are differentiated into secretory or stellate cells halfway through incubation. At this time only half of the cells of the PD can be so classified. Four of the five granulated cell types described in the adult are recognizable by mid-incubation; the fifth cell type (prolactin cell) becomes distinguishable within ten days thereafter, and at hatching appears to be actively synthesizing secretory products.