Pituitary gland of the garter snake (Thamnophis): Morphology and immunocytochemistry

The three-dimensional gross morphology of the pituitary gland of the garter snake (Thamnophis sirtalis) is presented. Hormone-producing cells of the pars distalis were localized immunocytochemically. Corticotropes and lactotropes occur in the anterior two-thirds of the gland; corticotropes are especially numerous in the area of the pars distalis nearest the median eminence, and lactotropes are most abundant medially. Somatotropes are restricted to the posterior one-third of the pars distalis. Gonadotropes and thyrotropes are scattered throughout the pars distalis and in favorable sections form a network of cells enclosing clusters of peptide-secreting cells.     

Organization of tyrosine hydroxylase-immunoreactive neurons in the di-and mesencephalon of the American bullfrog (Rana catesbeiana) during metamorphosis

Summary We examined the immunocytochemical distribution of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis, in the di-and mesencephalon of developing bullfrog tadpoles. Special attention was given to catecholaminergic innervation of the median eminence and pituitary. In premetamorphic tadpoles, tyrosine hydroxylase-immunoreactive neurons were visualized in the suprachiasmatic and infundibular hypothalamus, the ventral thalamus, and midbrain tegmentum by Taylor-Kollros stage V. The number of labeled neurons in all these areas increased as metamorphosis progressed. By mid-prometamorphosis, labeled neurons appeared in the preoptic recess organ as well as in the posterior thalamic nucleus. The majority of cells in the preoptic recess organ, as well as occasional neurons in the suprachiasmatic nucleus, exhibited labeled processes which projected through the ependymal lining of the preoptic recess to contact cerebrospinal fluid. The modified CSF-contacting neurons of the nucleus of the periventricular organ were devoid of specific staining. By late prometamorphosis, labeled fibers from the suprachiasmatic nucleus were observed projecting caudally to enter the hypothalamo-hypophysial-tract en route to innervating the median eminence and pituitary. Labeled fibers arising from the dorsal infundibular nucleus projected ventrolaterally to contribute to catecholaminergic innervation of the median eminence and pituitary. Immunoperoxidase staining of tyrosine hydroxylase-immunoreactive fibers and terminal arborizations in the median eminence were restricted to non-ependymal layers, while labeled fibers in the pituitary were observed in the pars intermedia and pars nervosa. Staining of tyrosine hydroxylase-immunoreactive fibers in the median eminence and pituitary was sparse or absent in premetamorphic tadpoles, but became increasingly more intense as metamorphosis progressed.     

Organization of atrial natriuretic factor-like immunoreactive system in the brain of the frog Rana esculenta during development

Immunocytochemical distribution of the atrial natriuretic factor (ANF) has been studied in the brain and pituitary of the anuran Rana esculenta during development and in juvenile animals. Using human ANF and rat α-ANF antisera, immunoreactive cell bodies and nerve fibers were revealed in stage II–III tadpoles and in successive larval stages. Soon after hatching, stages II–III, the ANF-like-immunoreactive elements were confined to the preoptic area-median eminence complex. During successive stages of development, new groups of ANF-immunoreactive cell bodies appeared. In larval stage VI, immunoreactive perikarya were found in the rostral part of the anteroventral area of the thalamus and numerous ANF-like-immunoreactive cells appeared in the pars distalis of the pituitary. In larval stages XIV and XVIII, the distribution of ANF immunoreactivity was virtually similar. The ANF-immunoreactive cells in the preoptic nucleus and in the pituitary pars distalis were comparatively more abundant than in stage VI. During the metamorphic climax (stages XXI–XXII), a new group of ANF-immunoreactive cell bodies appeared in the rostral part of the ventrolateral area of the thalamus. During this stage, ANF-immunoreactive fiber projections were found in the pars intermedia for the first time. However, the pars distalis cells were very weakly immunofluorescent. The pattern of ANF immunoreactivity in the brain of juvenile animals was very similar to that described for stages XXI and XXII, whereas the pars distalis cells showed no immunoreactivity. It is conceivable that, early during development, ANF-related peptides may be involved in the regulation of pituitary secretion by means of autocrine mechanisms or may act as a classic pituitary hormone. Received: 28 July 1997 / Accepted: 8 December 1997     

Immunocytochemical localization of growth hormone and growth hormone-releasing hormone immunoreactivity in the brain and pituitary of the little brown bat

Anterior pituitary cells exhibiting growth hormone (GH) immunoreactivity and forebrain neurons containing growth hormone-releasing hormone (GHRH) immunoreactivity were identified in little brown bats (Myotis lucifugus) using light microscopic immunocytochemistry. Pituitary somatotropes appeared as ovoid or polyhedral cells that were distributed throughout most of the pars distalis, with the exception of its most rostral region where this cell type was scarce. GH-immunoreactive cells occupied approximately one-third of the total volume of the pars distalis; this proportion did not differ significantly between males and females or in bats collected at different times of year. Neuronal perikarya containing immunoreactive GHRH were observed in the hypothalamic arcuate and suprachiasmatic nuclei, as well as in the cortical and subcortical telencephalon. Fibers were most evident in the median eminence, paraventricular and periventricular nuclei, and molecular layer of the cerebral cortex. Fine fibers were also accumulated in the bed nucleus of the stria terminalis and in the amygdala.     

Immunohistochemical localization of delta sleep-inducing peptide (DSIP) in the brain and pituitary of the cartilaginous fish Scyliorhinus canicula.

The distribution of delta sleep-inducing peptide (DSIP) in the brain and pituitary of the cartilaginous fish Scyliorhinus canicula was investigated using the indirect immunofluorescence technique. Delta sleep-inducing peptide-like immunoreactive cell bodies were mainly observed in the nucleus lateralis tuberis of the hypothalamus. Immunolabeled perikarya were also distributed in the nucleus lobi lateralis hypothalami and in the dorso-lateral wall of the recessus posterioris. Most of these cells, located in the subependymal layers of the infundibulum and lateral lobes, had the typical aspect of cerebrospinal fluid-contacting elements. The DSIP-like immunoreactive fibers were localized in the basal telencephalon, within the regions of the nucleus interstitialis commissurae anterioris and the nucleus entopeduncularis. A dense network of DSIP-positive fibers was seen throughout the midcaudal hypothalamus, the lateral lobes, and the posterior lobe. In the pituitary, numerous DSIP-like immunoreactive cells were detected in the median lobe of the pars distalis. In particular, a high concentration of cells was seen in the dorsal wall of the median lobe, an area which is known to contain melanin-concentrating hormone (MCH)-producing cells. Comparison of the distribution of DSIP- and MCH-like immunoreactive cells revealed that the two neuropeptides are stored in the same cells of the median lobe of the pituitary. These findings provide the first evidence for the presence of a DSIP-related peptide in fish. The distribution of the immunoreactive material supports the view that DSIP may act as a neuromodulator and/or a hypophysiotropic factor. Moreover, the presence of DSIP-like immunoreactive cells in the pars distalis suggests that this peptide may exert autocrine or paracrine effect in the pituitary.     

Anterior and posterior groups of portal vessels in the avian pituitary: incidence in forty nine species.

The hypophyseal portal vessels were studied in forty nine species of birds. The primary capillary plexus in the median eminence is single or divided into an anterior and a posterior plexus. Irrespective of whether the primary capillary plexus is single or divided, distinct, non-interconnected anterior and posterior groups of portal vessels are present in all the species investigated. The anterior group of portal vessels originates in the anterior region of the median eminence and breaks up into capillaries in the cephalic lobe of the pars distalis; the posterior group of portal vessels originates in the posterior region of the median eminence and breaks up into capillaries in the caudal lobe of the pars distalis. This type of regional distribution of portal vessels appears to be of general occurrence in the avian pituitary. The median eminence in the species investigated shows an AF-positive anterior region and an AF-negative posterior region. The pars distalis is differentiated into histologically distinct cephalic and caudal lobes. The arrangement of the portal vessels into anterior and posterior groups provides morphological basis for the view that the functions of the cephalic lobe may be controlled by the anterior median eminence, whereas those of the caudal lobe may be controlled by the posterior median eminence. However, experimental data available to date do not suggest a physiological significance to the widespread incidence of the regional distribution of portal vessels in the avian pituitary.     

Developmental correlation between hypothalamic somatostatin and hypophysial growth hormone

Summary The objective of the present study was to determine, by means of immunocytochemistry, the age in fetal development at which GH is first detectable in the pituitary gland and somatostatin in the median eminence, and to correlate temporally the development of these two hormones throughout the remainder of pregnancy. Mice were studied at 15–19 days of gestation with the peroxidase-antiperoxidase (PAP) technique of Sternberger. Somatotropes in the pars distalis were initially detected at 16 days of gestation and by 17 days they were a prominent component of the parenchymal cell population of the hypophysis. These cells were ovoid and distributed uniformly throughout the pars distalis; many were located adjacent to sinusoidal capillaries. Their number and staining intensity increased by 19 days. Somatostatin was not consistently observed in the median eminence until 19 days of gestation. Reaction product indicative of the presence of somatostatin in presumptive nerve endings was located on the ventral surface of the median eminence and in the external lamina of the infundibulum in proximity to the superficial portal capillaries. Results of the present investigation support the concept that the potential for neuroendocrine control of GH secretion exists in the mouse by the end of fetal development. Several hypotheses concerning the temporal relationship between the appearance of somatostatin in the hypothalamus and of GH in the anterior pituitary gland are discussed.Supported by a Biomedical Research Support Grant (NIH RR 5417). Appreciation is extended to the National Pituitary Agency, NIAMDD for the following radioiodination-grade hormones: hGH, rPRL, rTSH, rFSH and hCG     

Immunohistochemistry of the hypothalamic neuropeptides and anterior pituitary cells in the Japanese quail

The pars distalis of the avian adenohypophysis consists of well-defined cephalic and caudal lobes which are distinct in their cellular constituents. Immunocytochemical investigations on the pituitary hormones of the pars distalis of the Japanese quail reveal five types of secretory cells, adenocorticotropin (ACTH) cells, prolactin (PRL) cells, thyroid-stimulating hormone (TSH) cells, growth hormone GH (STH) cells, and FSH/LH (gonadotropic) cells. The ACTH cells, TSH cells, and PRL cells are restricted to the cephalic lobe, and GH (STH) cells are confined to the caudal lobe, while FSH/LH cells are distributed throughout the cephalic and caudal lobes. The median eminence of birds has distinct anterior and posterior divisions, each with different neuronal components. The avian hypophysial portal vessels also consists of two groups, anterior and posterior. The peculiar arrangement and distribution of the avian hypophysial portal vessels are possibly related to the distribution of neuropeptides in the two divisions of the median eminence and to the cytological and functional differentiation of two lobes of the pars distalis. The localization of perikarya and fibers containing luteinizing hormone releasing hormone (LHRH), somatostatin, vasotocin, mesotocin, corticotropin-releasing factor (CRF), vasoactive intestinal polypeptide (VIP), glucagon, metenkephalin, and substance P in the hypothalamus and median eminence of the Japanese quail has been investigated by means of immunohistochemistry using antisera against the respective neuropeptides. LHRH-, somatostatin-, VIP-, met-enkephalin-, and substance P-immunoreactive fibers are localized in the external layer of the anterior and posterior divisions of the median eminence, while CRF- and vasotocin-reactive fibers are demonstrated only in the external layer of the anterior division of the median eminence. The metenkephalin fibers are thicker in the anterior median eminence but the substance P fibers are more abundant in the posterior division. Mesotocin fibers occur only in the internal layer of the median eminence and neural lobe.     

Structure of the neurohypophysis and the hypothalamo-hypophysial vascularization in the teleost Channa punctatus Bloch.

In C. punctatus the median eminence includes the subterminal region of the hypothalamus and the anterior neurohypophysis. It is formed of ependymal, fibrous and reticular layers as in the tetrapods. Primary capillary plexus extends from the subterminal region to the extremity of the anterior neurohypophysis. Only few portal vessels from the hypothalamus enter in the pars distalis. All the components of pituitary including the pars intermedia are irrigated by the secondary plexus formed from the portal vessels emerging out of the anterior neurohypophysis. The neurosecretory axons and the ependymal cells are in close morphological contact with the primary plexus. Several axons have perivascular endings at the median eminence. Some axons were found to be only silver or aldehyde fuchsin positive whereas some others take up both. The silver positive axons were abundant in the pars distalis and the AF positive ones were more concentrated in the pars intermedia with greater accumulation of neurosecretory material.     

Efferent projections from the retrochiasmatic area to the median eminence and to the pars nervosa of the hypophysis with special reference to the A15 dopaminergic cell group in the sheep

Anterograde tracers, viz. Phaseolus vulgaris leucoagglutinin and fluorescein dextran, were used in conjunction with tyrosine hydroxylase immunohisto-chemistry to study the projections of the A15 dopaminergic cell group towards the median eminence and pituitary in sheep. After injection of the tracers in the retrochiasmatic area, which contains the cell group A15, fibres containing anterograde tracer were observed in the internal zone of the median eminence and in the pars nervosa of the pituitary. Numerous tyrosine hydroxylase immunoreactive fibers were present in the external zone of the median eminence and in the pars intermedia and the pars nervosa of the pituitary, with characteristic patterns of organisation in each area. Most tyrosine hydroxylase-immunoreactive fibres containing fluorescein dextran were located in the pars nervosa, whereas only a few were observed in the internal zone of the median eminence. It was concluded that at least part of the dopaminergic innervation of the pars nervosa originated from the A15 group. These results provide morphological evidence for (1) the role of dopaminergic neurons of the A15 cell group in the seasonal control of prolactin secretion via the release of dopamine in the pars nervosa, and (2) putative physiological interactions between dopamine and the secretion of neurohypophysial hormones in sheep.     

Experimental identification of a hypothalamic gonadotropic centre

Summary In a large group of adult female and male specimens of Rana temporaria all nervous pathways to the median eminence and hypophysis were extirpated without disturbing the normal blood supply of the median eminence and hypophysis. The total interruption of the nervous pathways persisted in all animals. In all animals gametogenesis and seasonal development of the gonads and of the secondary sexual characteristics were absent. In another large group of animals, the pars ventralis of the tuber cinereum of the hypothalamus was isolated from the brain. The pars ventralis retained its normal connections with the median eminence and hypophysis. The normal blood supply of the whole isolated region (pars ventralis tuberis + median eminence + hypophysis) was preserved. Four months after operation, in the majority of the animals, the isolation was still complete. In all animals, normal gametogenesis and seasonal development of the gonads and of the secondary sexual characteristics had occurred.In accordance with previous experiments, the present experiments showed that the pars ventralis tuberis contains an important gonadotropic centre. The activity of the gonadotropic centre of the pars ventralis tuberis is, at least, mainly exerted by its influence on the gonadotropic function of the pars distalis of the hypophysis. This is shown morphologically by a gradient of nuclear volume and by the mean nuclear volume of the P.A.S. positive cells of the pars distalis. The influence of the gonadotropic centre on the pars distalis is exerted by A.F.-negative nerve fibres to the median eminence. It is highly probable that all these nerve fibres end on the primary capillary network of the hypophysial portal system. The experiments strongly suggested that the axon endings of the gonadotropic centre would influence the gonadotropic activity of the pars distalis of the hypophysis by releasing of gonadotropic releasing factors into the blood capillaries of the median eminence.The gonadotropic centre of the pars ventralis tuberis is necessary for the normal gametogenesis and for the seasonal development of the gonads and of the secondary sexual characteristics. So far as concerned the gametogenesis and the seasonal development of the gonads, the function of the gonadotropic centre is largely autonomous.Exclusion of the function of a part of the pars ventralis tuberis produces quantitative, but no qualitative changes in gametogenesis.     

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     

The distribution of monoamine oxidase and acetylcholinesterase in the brain of Xenopus laevis tadpoles

Summary The distribution of monoamine oxidase (MAO) in the brain of Xenopus laevis tadpoles (stage 52–56) was studied histochemically with a modified Glenner's tryptamine-tetrazolium method. A moderate activity was observed in fibre regions of the striatum and septum (including the medial and lateral forebrain bundles), in the neuropil of the nucleus amygdalae, in the commissura anterior and commissura hippocampi, in the fibre regions of the diencephalon (including the optic chiasma), in the fibre regions of the tectum opticum and the tegmentum of the mesencephalon and in the white substance of the ventral half of the medulla oblongata. A greater MAO activity was found in the neuropil of the entire nucleus praeopticus. In the partes anterior and magnocellularis of this nucleus, MAO positive fibres are present in close contact with the perikarya, indicating a monoaminergic innervation of these neurons. The perikarya themselves did not show MAO activity. In the neurons of the nucleus praeopticus epichiasmaticus, the paraventricular organ (PVO) and nucleus infundibularis dorsalis (NID), only a slight MAO activity has been demonstrated in the perikarya, whereas a strong MAO positivity was found in the intraventricular protrusions and the neuropil. These data indicate the aminergic character of the neurons of these nuclei. From the postoptic fibre region a MAO positive tract was observed towards the developing median eminence and pars intermedia of the hypophysis. The pars nervosa and some cells of the pars distalis also contained MAO. Along the border of the aquaeduct of Silvius and the fourth ventricle, MAO positive liquor-containing neurons are also present.The distribution of acetylcholinesterase (AChE) was investigated in the hypothalamohypophysial region. AChE activity was found in the neuropil of the nucleus praeopticus magnocellularis, in the fibres of the optic chiasma and in the postoptic fibre region. The neurons of the PVO and NID were AChE negative. An AChE positive tract could be traced from the postoptic fibre region to the developing median eminence and pars nervosa. The pars distalis did not show AChE activity. However, in tadpoles reaching the metamorphic climax, ChE activity appeared in certain cells of the pars distalis; this might be related to degenerative phenomena in the acidophilic cells. The absence of AChE activity in the pars intermedia indicates a regulation of MSH release by peptidergic nerves to be unlikely.The stimulating interest and helpful advice of Prof. Dr. P. G. W. J. van Oordt is gratefully acknowledged. Thanks are also due to Mr. H. van Kooten and his co-workers for making the photographs.     

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.     

Seasonal variations of gonadotropins in the pars distalis male viscacha pituitary. Effect of chronic melatonin treatment

The gonadotropes, LH and FSH cells, were immunohistochemically identified in the pituitary pars distalis of the adult male viscacha (Lagostomus maximus maximus) using specific antibodies against hLHbeta and hFSHbeta with the streptavidin-biotin-peroxidase complex. The distribution, size and percentage immunopositive area of these cells were analyzed by image analysis in viscachas captured during the annual reproductive cycle and after the chronic administration of melatonin. The LHbeta and FSHbeta cells showed seasonal changes in the distribution, size and percentage immunopositive area. The LHbeta cells were found widely distributed throughout the pars distalis during the reproductive period, and they were found in the ventro-medial region in the pars distalis during the gonadal regression and gonadal recovery periods. The LHbeta cells reached the largest size and immunopositive area during the reproductive period and the smallest size and immunopositive area during the gonadal regression period. The FSHbeta cells were found in the ventro-medial region during reproductive and gonadal regression periods. The FSHbeta cells were found widely distributed throughout the pars distalis during the gonadal recovery period when they showed the maximum percentage immunopositive area. A decrease in the size of LHbeta and FSHbeta cells was observed after the chronic administration of melatonin. Moreover, it produces a decrease in the immunopositive area occupied by the LHbeta cells but not in the immunopositive area occupied by the FSHbeta cells. Our results show great activity of LHbeta and FSHbeta cells in different moments of the annual reproductive cycle demonstrating that these cells do not secrete in parallel. Moreover, melatonin acts differentially on the activity of the gonadotrope cells.     

Localization of galanin-like immunoreactive structures in the brain of the Senegalese sole, Solea senegalensis

The distribution of galanin-like immunoreactive structures was studied in the brain of the Senegalese sole, Solea senegalensis, using immunohistochemical methods. Periventricular immunoreactive cell bodies were observed in the rostral pole of the preoptic recess, within the pars parvocellularis of the nucleus preopticus parvocellularis. Another galanin-immunoreactive cell population was observed more caudal in the ventromedial hypothalamus, along the medial evaginations of the lateral recess. These cells appear within the cytoarchitectonic limits of the nucleus recessus lateralis pars ventralis. We found an extensive presence of galanin-immunoreactive fibres throughout the entire brain, although the most massive network of fibres was observed in the caudal olfactory bulbs, ventral telencephalon, preoptic area and around diencephalic ventricular recesses. Also, the hypophysis, ventricular mesencephalic area, median reticular formation and viscerosensory rhombencephalon displayed important plexuses of galanin-immunoreactive axons.The widespread distribution of these immunoreactive structures in the brain and pituitary of the Senegalese sole suggests an important role for galanin in neuroendocrine regulation of brain and adenohypophyseal functions.     

Distribution of B/K protein in rat brain

B/K protein is a recently isolated member of the double C2-like-domain protein family, which is highly abundant in rat brain. We generated high-titer rabbit polyclonal antibodies with specificity to the 55-kDa rat B/K protein, and examined the expression pattern of B/K protein in rat brain using an immunohistochemical staining method. Immunoreactivity to B/K protein was widely found in distinct regions of rat brain: strongly in the hypothalamus, most of the circumventricular organs, the locus coeruleus, the A5 neurons of the pons, and the anterior pituitary; moderately in the anterior olfactory nucleus, the raphe nucleus, the subfornical organ, and the median eminence; and faintly in the olfactory bulb, the telencephalon, the substantia nigra pars compacta, and the ventral tegmental area. In contrast, immunoreactivity to B/K protein was not observed in the thalamus, the cerebellum, the posterior pituitary, or the spinal cord. In most of the B/K-expressing neurons, immunoreactivity was expressed mainly in soma but not in nerve fibers. B/K was also expressed in nonneuronal cells such as the tanycytes and the subcommissural organ. In the vasopressin-secreting supraoptic and paraventricular nuclei of the hypothalamus, the site where B/K cDNA was originally isolated from, all of the neurons showing vasopressin immunoreactivity also expressed B/K protein, suggesting an overlap of their expression patterns.     

The distribution of neuropeptide Y and dynorphin immunoreactivity in the brain and pituitary gland of the platyfish,Xiphophorus maculatus,from birth to sexual maturity

Summary Immunoreactive neuropeptide Y and dynorphin have been localized in the brain and pituitary gland of the platyfish, Xiphophorus maculatus, at different ages and stages of development from birth to sexual maturity. Immunoreactive neuropeptide Y was found in perikarya and tracts of the nucleus olfactoretinalis, telencephalon, ventral tegmentum and in the neurohypophysis and in the three regions of the adenohypophysis. Immunoreactive dynorphin was found in nerve tracts in the olfactory bulb and in cells of the pars intermedia and the rostral pars distalis of the pituitary gland.     

Vascularization of the pituitary of the Australian lungfish and Neoceratodus forsteri

The vascularization of the brain and the pituitary region of the Australian lungfish, Neoceratodus forsteri is described from serial section reconstruction. The distal lobe has no direct arterial blood supply and receives blood solely from a pituitary portal system basically similar to that of other sarcopterygians. The primary capillary plexus of the median eminence receives its arterial blood from the infundibular arteries, which on their way distribute some small branches to the prechiasmatic region. The primary plexus also receives capillaries from the adjacent pial hypothalamic plexus. The primary capillary plexus of the median eminence comprises a rostral 'uncovered' and caudal 'covered' part which are not sharply delineated. Distinct portal vessels connect the 'uncovered' rostral part of the primary plexus with the secondary capillary plexus supplying the rostral subdivision of the pars distalis. The 'covered' caudal part of the primary plexus merges into the proximal subdivision of the pars distalis, apparently without formation of distinct portal vessels. The primary plexus has some connections with the plexus intermedius via a hypophysial stem capillary plexus. The plexus intermedius has a substantial arterial supply and gives off capillaries to the parenchyma of the pars intermedia. The adenohypophysis is drained into an unpaired hypophysial vein. The significance of the vascular pathways is discussed from comparative, functional, and evolutionary viewpoints.     

Expression of the common α-subunit mRNA of glycoprotein hormones during the chick pituitary organogenesis, with special reference to the pars tuberalis

The expression of a common alpha-subunit mRNA of glycoprotein hormones was examined in the pituitary of chick embryos at various stages of development by in situ hybridization with a digoxigenin-labeled quail alpha-subunit cRNA probe. As a comparison with the expression of alpha-subunit mRNA, the onset of luteinizing hormone (LH) immunoreactivity was examined by immunohistochemical staining with a chicken LH antiserum. Both alpha-subunit mRNA and LH immunoreactivity began to appear in the basal-posterior region of the Rathke's pouch at embryonic day (E) 3.5. At E4.5 when the cephalic and caudal lobes of the pars distalis could be distinguished in the Rathke's pouch, intense signal for alpha-subunit mRNA was restricted to the cephalic lobe, consisting of a high columnar epithelium. At E6, gonadotrophs that were ovoid in shape, expressed intense signal for alpha-subunit mRNA, and revealed intense immunoreactivity for LH, were first detected in the cephalic lobe. At this stage, alpha-subunit mRNA expression became weak in the undifferentiated columnar cells of the cephalic lobe. At E8, the pars tuberalis primordium located close to the median eminence was formed at the lateral-apical end of the cephalic lobe. The primordium expressed intense signal for alpha-subunit mRNA. Gonadotrophs showing immunoreactivity for LH were densely distributed throughout the cephalic and caudal lobes in 8-day-old embryos. The pars tuberalis primordium expressing alpha-subunit mRNA progressively extended along the median eminence with embryonal age and reached the rostoral end by E14. Thus, both primordia of the pars distalis and pars tuberalis expressed intense signal for the common alpha-subunit mRNA. This subunit may play a role in the cytodifferentiation of the adenohypophysis.