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1.
It has been reported that mammotropes in a rodent pituitary gland are derived from somatotropes via somatomammotropes (SMTs), cells that produce both growth hormone (GH) and prolactin (Prl). However, no studies have been done on the transdifferentiation of somatotropes in the chicken pituitary gland. In this study, in order to determine the origin of mammotropes, we studied detail property of appearance of chicken somatotropes, mammotropes and pit-1 cells and then evaluated the existence of SMTs in the chicken embryonic pituitary gland. Immunohistochemical analysis revealed that GH-immunopositive (GH-ip) cells appeared on embryonic day (E) 14 and were mainly distributed in the caudal lobe, while Prl-immunopositive (Prl-ip) cells appeared in the cephalic lobe of the pituitary gland on E16. In situ hybridization (ISH) and RT-PCR analysis showed that expression of GH and Prl mRNA starts at E12 in the caudal lobe and at E14 in the cephalic lobe respectively. Pit-1 mRNA was first detected on E5 by RT-PCR, and pit-1 mRNA-expressing cells were found in the cephalic lobe on E8. Then with the ontogeny of the chicken, these cells spread into both lobes. Using a double staining method with ISH and immunohistochemistry, we could not detect the existence of SMTs in the chicken embryonic pituitary gland even in the marginal region of either lobe. These results suggest that chicken somatotropes and mammotropes independently appear in different lobes of pituitary gland and that transdifferentiation from somatotropes to mammotropes is not the central route for differentiation of mammotropes in the embryonic chicken pituitary gland.  相似文献   

2.
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.  相似文献   

3.
Research in mammals has demonstrated a variety of regulatory effects of vasopressin and oxytocin on endocrine functions of the anterior pituitary gland. Less evidence is available regarding the hypophysiotropic action of arginine vasotocin (AVT) comprising vasopressic and oxytocic activities in birds. Some hypophysiotropic effects of AVT may result from its interactions with brain circuits controlling pituitary functions, whereas others are caused by its direct affect on pituitary cells. Use of an antiserum to the vasotocin receptor VT2 (VT2R) has revealed numerous immunoreactive cells in the anterior pituitary gland of the chicken. The objective of the present study has been to identify endocrine phenotypes of chicken pituitary cells containing VT2R by means of immunohistochemical labeling. VT2R immunoreactivity has been found in all cells immunoreactive for adrenocorticotropin and alpha-melanotropin. Approximately 10% of labeled lactotropes are also immunoreactive for VT2R and lie around the anatomical boundary dividing the cephalic and caudal lobes. In both corticotropes/melanotropes and lactotropes, immunoreactive VT2R is present in a narrow layer outlining cell bodies. Immunoreactive VT2R is not found in gonadotropes, thyrotropes, or somatotropes. These results provide evidence for the important role of VT2Rs in mediating effects of AVT on endocrine secretion from corticotropes and, partially, from lactotropes.  相似文献   

4.
The effects of thyroidectomy, adrenalectomy, and castration on the pars distalis of male Japanese quail, and of injection of LH-RH on sexually inactive females, were investigated by light and electron microscopy. Correlation between light and electron microscopy was attained by use of alternate thin and thick sections. Six types of secretory cells were identified and the ultrastructural characteristics described. Putative endocrine functions have been designated on the basis of responses to experimental interventions and on other criteria. The putative STH cells are characterized by the presence of large dense secretory granules (250-300 nm) that are stained with orange-G by the trichrome method. They occur only in the caudal lobe and appear to be unchanged by castration, thyroidectomy, adrenalectomy and LH-RH injection. The putative prolactin cells are characterized by large (400-600 nm), spherical or polmorphic, dense secretory granules stainable with acid fuchsin and aniline blue; prominent Golgi apparatus and well developed endoplasmic reticulum with densely packed, regularly parallel lamellae. They are found mainly in the cephalic lobe. The prolactin cells develop some vacuolization after adrenalectomy and undergo some degeneration after castration. The ACTH cells, which are restricted to the cephalic lobe, are identified by the dense, spherical granules (250-300 nm) that are stained with acid fuchsin. After adrenalectomy, they lose their secretory granules and are transformed into large, chromophobic adrenalectomy cells. TSH cells are so designated by their response to thyroidectomy including loss of their fine secretory granules and transformation to large, vacuolated thyroidectomy cells. We have found TSH cells and thyroidectomy cells only in the cephalic lobe. Basophilic cells, considered to be gonadotropes, occur in both the cephalic and caudal lobes. The gonadotropes of the cephalic lobe appear to have slightly larger (120-200 nm) granules than the caudal lobe (120-150 nm). However, after castration, the gonadotropes in both lobes become hypertrophied and vacuolated and are transformed into mutually indistinguishable castration cells. Twenty minutes after injection with LH-RH, the gonadotropes of both lobes increase in size and number, degranulate, develop vacuoles in the cytoplasm, and appear very similar to castration cells.  相似文献   

5.
Although it is known that glucocorticoids induce differentiation of growth hormone (GH)-producing cells in rodents and birds, the effect of mineralocorticoids on GH mRNA expression and the origin of corticosteroids affecting somatotrope differentiation have not been elucidated. In this study, we therefore carried out experiments to determine the effect of mineralocorticoids on GH mRNA expression in the chicken anterior pituitary gland in vitro and to determine whether corticosteroids are synthesized in the chicken embryonic pituitary gland. In a pituitary culture experiment with E11 embryos, both corticosterone and aldosterone stimulated GH mRNA expression and increased the number of GH cells in both lobes of the pituitary gland in a dose-dependent manner. These effects of the corticosteroids were significantly reversed by pretreatment with mifepristone, a glucocorticoid receptor (GR) antagonist, or spironolactone, a mineralocorticoid receptor (MR) antagonist. Interestingly, an in vitro serum-free culture experiment with an E11 pituitary gland showed that the GH mRNA level spontaneously increased during cultivation for 2 days without any extra stimulation, and this increase in GH mRNA level was completely suppressed by metyrapone, a corticosterone-producing enzyme P450C11 inhibitor. Moreover, progesterone, the corticosterone precursor, also stimulated GH mRNA expression in the cultured chicken pituitary gland, and this effect was blocked by pretreatment with metyrapone. We also detected mRNA expression of enzymes of cytochrome P450 cholesterol side chain cleavage (P450scc) and 3β-hydroxysteroid dehydrogenase1 (3β-HSD1) in the developmental chicken pituitary gland from E14 and E18, respectively. These results suggest that mineralocorticoids as well as glucocorticoids can stimulate GH mRNA expression and that corticosteroids generated in the embryonic pituitary gland by intrinsic steroidogenic enzymes stimulate somatotrope differentiation.  相似文献   

6.
Incubation behavior or broodiness in turkey hens is characterized by ovarian regression, hyperprolactinemia, and persistent nesting. Nest-deprivation of incubating turkey hens results in disruption of broodiness accompanied by a precipitous decline in plasma prolactin (PRL) concentrations. The objective of the present study is to examine cellular changes in the pituitary gland associated with nest-deprivation for 0, 1, 2, 3, 4, or 7 days. Bromodeoxyuridine (BrdU) was administered prior to kill to study proliferative activity. Pituitary tissue sections were immunostained using turkey growth hormone (GH) antibody, and/or chicken PRL peptide antibody, and BrdU antibody. Plasma PRL concentrations declined significantly following nest-deprivation for 1 or more days. The midsagittal pituitary area immunoreactive (ir) to GH was significantly increased while that of PRL was significantly decreased following nest-deprivation for 2 or more days. Terminal deoxy-UTP nick end labeling and PRL-immunostaining revealed an abundance of apoptotic nuclei in both cephalic and caudal lobes of the anterior pituitary gland, suggestive of programmed cellular death of lactotrophs in the pituitary gland of hens nest-deprived for 2 or more days. Mammosomatotrophs were abundant in hens nest-deprived on Day 0 but were absent in hens nest-deprived for 1 or more days. Proliferating (BrdU-ir) cells were significantly abundant in the pituitary cephalic and caudal lobes following nest-deprivation for 1 or more days but were absent on Day 0 or in laying hens. Dual-labeling studies indicated that most of the BrdU-ir nuclei in the caudal lobe were not colocalized in somatotrophs in hens nest-deprived for 1-4 days but did colocalize with GH following 7 days of nest-deprivation. In conclusion, nest-deprivation of incubating turkey hens results in 1) a precipitous decline in plasma PRL concentration, 2) programmed cell death of lactotrophs, 3) disappearance of mammosomatotrophs, 4) increased proliferative activity of pituitary cells, and 5) recruitment of somatotrophs arising primarily from mitosis of nonsomatotrophic cells.  相似文献   

7.
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.  相似文献   

8.
9.
We previously reported that annexin 5 is found specifically in gonadotropes and that the expression is dramatically enhanced after ovariectomy. In the present study, the expression of annexin 5 was examined in the primary culture of rat anterior pituitary cells using semiquantitative RT-PCR to determine if it is under the direct control of gonadotropin-releasing hormone (GnRH). Continuous administration of GnRH analog for 1 h enhanced the expression of both FSH beta subunit and annexin 5 mRNA. The expression of annexin 5 mRNA was also augmented by phorbol 12-myristate 13-acetate but not by forskolin. Administration of recombinant rat annexin 5 to the culture increased LH beta mRNA expression. These data clearly demonstrate that the expression of annexin 5 mRNA is directly controlled by GnRH and suggest that annexin 5 is involved in mediating GnRH action in the pituitary gland.  相似文献   

10.
As is the case in other tetrapod species, the chicken gonadotropins LH and FSH consist of a common alpha subunit and a hormone-specific beta subunit. Gonadotrophs containing LH were shown earlier to be distributed throughout both the caudal and cephalic lobes of the chicken anterior pituitary, but the cellular distribution of FSH in avian species is still uncertain. The purpose of this study was to determine the cellular distribution of FSH-containing chicken gonadotrophs by use of FSH-specific monoclonal antibodies (mAbs). Three new mAbs toward chicken FSH were proven hormone specific by immunodetection of purified hormones on dot blots and by dual-label immunohistochemistry (IHC) on sagittal sections of chicken pituitaries. A rabbit antibody was used to detect chicken LH. Results showed that LH-containing gonadotrophs were densely distributed throughout the anterior pituitary, whereas gonadotrophs containing FSH were much less numerous; in addition, while also present in both lobes, FSH-positive cells were largely absent from the outer margin of the gland. Dual-label IHC revealed that LH and FSH reside almost exclusively in separate gonadotrophs. The identity of FSH-containing cells was further confirmed through use of an antibody to the chicken alpha subunit, which showed that FSH immunoreactivity was always colocalized with the alpha subunit. Our results suggest the possibility that production and secretion of LH and FSH may be regulated differently in chickens than in most other species studied to date.  相似文献   

11.
Tissue‐specific expression of cre recombinase is a well‐established genetic tool to analyze gene function, and it is limited only by the efficiency and specificity of available cre mouse strains. Here, we report the generation of a transgenic line containing a cre cassette with codon usage optimized for mammalian cells (iCre) under the control of a mouse glycoprotein hormone α‐subunit (αGSU) regulatory sequences in a bacterial artificial chromosome genomic clone. Initial analysis of this transgenic line, Tg(αGSU‐iCre), with cre reporter strains reveals onset of cre activity in the differentiating cells of the developing anterior pituitary gland at embryonic day 12.5, with a pattern characteristic of endogenous αGSU. In adult mice, αGSU‐iCre was active in the anterior lobe of the pituitary gland and in the cells that produce αGSU (gonadotropes and thyrotropes) with high penetrance. Little or no activity was observed in other tissues, including skeletal and cardiac muscle, brain, kidney, lungs, testis, ovary, and liver. This αGSU‐iCre line is suitable for efficient, specific, and developmentally regulated deletion of floxed alleles in anterior pituitary gonadotropes and thyrotropes. genesis 51:785–792. © 2013 Wiley Periodicals, Inc.  相似文献   

12.
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.  相似文献   

13.
V M Barabanov 《Ontogenez》1990,21(6):585-592
We have studied differentiation of prolactin cells in explants of cephalic and caudal parts of Rathke's pouch of 4.5 day and 5.5 day old chick embryos after their incubation in vitro lasting for 7-8 days. Indirect immunofluorescence using an antiserum against bovine prolactin was used to detect prolactin cells in the cultures. Differentiation of prolactin cells was detected regularly in explants of the cephalic lobe of the adenohypophysis anlage in 5.5 day old embryos; under certain growth conditions prolactin cells were found in explants of the same lobe in 4.5 day old embryos. Prolactin cells were either absent or found in small numbers in cultures of the caudal part of adenohypophysis of 5.5 day old embryos. Our results provide evidence for the appearance of the committed precursors of prolactin cells in the Rathke's pouch at late stages of its formation and for their regional localization in the cephalic part of the anlage. This localization is in correspondence with the distribution of differentiated cells of this type in definitive adenohypophysis.  相似文献   

14.
Cells displaying combined expression of different pituitary hormone genes (further referred to as 'multi-hormone mRNA cells') were identified in normal rat and mouse pituitary by single cell RT-PCR. These cells do not seem to produce or store all the respective hormones the mRNAs encode for. The cells are already developed at day 16 of embryonic life (E16) in the mouse. Different peptides, such as gamma3-melanocyte-stimulating hormone (gamma3-MSH) and gonadotropin-releasing hormone (GnRH), affect different subsets of these cells. In culture, estrogen and GnRH increase the number of 'multi-hormone mRNA cells' that contain prolactin (PRL) mRNA or mRNA of the alpha-subunit of the glycoprotein hormones (alpha-GSU) but not the number of 'multi-hormone mRNA cells' not containing PRL or alpha-GSU mRNA. 'Multi-hormone mRNA cells' may function as 'reserve cells' in which a particular hormone mRNA may be translated under a particular physiological condition demanding a rapid increase of that hormone.  相似文献   

15.
Patterns of gonadotropin storage in individual gonadotropes change with alterations in the physiological state. After castration in the male rat, there is a 2.5-fold increase in the percentage of gonadotropes and an increase in the proportion of gonadotropes storing both LH and FSH. In addition, there are 6- to 8-fold increases in the pituitary concentrations of LH beta subunit mRNAs. In order to determine whether these changes are due to increases in the number of gonadotropes containing subunit mRNA, or the amount of mRNA per cell or both, an in situ hybridization technique using a photobiotinylated rat LH beta cRNA probe (bio-LH beta-cRNA) was applied to detect LH beta mRNA in fixed whole rat pituitary cells from intact or castrated rats. After hybridization, the bio-LH beta-cRNA was localized with either avidin-biotin peroxidase complex or the fluorescent streptavidin phycoprobe methods. The cells containing LH beta mRNA were then counted and the amount of mRNA per cell was measured by video microdensitometry. Ten percent of the anterior pituitary cells from intact animals contained LH beta mRNA. After castration (2-4 weeks) this percentage rose to 19-24.5%. Image and microdensitometric analyses showed that castration produced a 1.9-fold increase in the amount of LH beta mRNA per cell, and a 2.2-fold increase in the area of cells containing LH beta mRNA. Hence, castration resulted in an increase in the level of LH beta mRNA per cell as well as the number of LH beta mRNA-containing cells. When in situ hybridization was followed by immunocytochemistry in cells from intact rats, 83% of gonadotropes that stained for LH beta and 80% of gonadotropes that stained for FSH beta contained LH beta mRNA whereas after castration 99% of LH-storing and 93% of FSH-storing cells contained LH beta mRNA. This new in situ hybridization protocol is rapid and allows quantification of mRNA within individual gonadotropes. In addition, since the hybridization protocol does not apparently alter the gonadotropin antigens, the hormone content of the same gonadotrope may be defined by immunocytochemistry.  相似文献   

16.
Transforming growth factor-alpha (TGF-alpha), a member of the epidermal growth factor (EGF) family, is produced within the mouse anterior pituitaries. However, the cell types of TGF-alpha-expressing cells and the physiological roles of TGF-alpha within mouse pituitary glands remain unclear. The aim of the present study was to localize TGF-alpha mRNA-expressing cells, and to clarify the involvement of TGF-alpha in estrogen-induced DNA replication in mouse anterior pituitary cells. Northern blot analysis demonstrated TGF-alpha mRNA expression in adult male and female mouse anterior pituitaries. In situ hybridization analysis of the pituitaries in these mice showed that TGF-alpha mRNA-expressing cells in the anterior pituitary are round, oval, and medium-sized. TGF-alpha mRNA was colocalized in most of the growth hormone (GH) mRNA-expressing cells, while only some of the prolactin (PRL) mRNA-expressing cells. DNA replication in the anterior pituitary cells was detected by monitoring the cellular uptake of a thymidine analogue, bromodeoxyuridine (BrdU) in a primary serum-free culture system. Estradiol-17beta (E2) and TGF-alpha treatment increased the number of BrdU-labelled mammotrophs, indicating that E2 and TGF-alpha treatment stimulates the DNA replication in mammotrophs. Immunoneutralization of TGF-alpha with anti-TGF-alpha-antibodies nullified the E2-induced increase in DNA replication. RT-PCR analysis of TGF-alpha mRNA expression in ovariectomized female mice revealed that E2 increases TGF-alpha mRNA levels. These results indicate that the TGF-alpha produced primarily in the somatotrophs mediates the stimulatory effects of estrogen on the DNA replication of pituitary cells in a paracrine or autocrine manner.  相似文献   

17.
Sperm protein 22 (SP22) was recently identified in the anterior pituitary gland (AP) of male Golden Syrian hamsters using ion trap mass spectrometry. SP22 has been implicated in apoptosis, androgen receptor function, fertility, and ontogeny of early-onset Parkinson's disease. However, the role of SP22 in the pituitary has not been investigated. We cloned the cDNA for full-length SP22 from AP and posterior lobe (posterior pituitary and intermediate lobe) of the pituitary gland in adult male rats and Golden Syrian hamsters, confirming the presence of SP22 mRNA in the AP and posterior lobe. Because gonadal steroids are important regulators of AP function, and SP22 is associated with androgen receptor function, we used Western blots to compare SP22 in the AP of intact and orchidectomized male rats given placebo or a low or high dose of testosterone. SP22 did not differ with treatment, indicating that AP SP22 concentration was not regulated by testosterone. To localize SP22 to specific cells of the AP, mirror-image paraffin sections were labeled against SP22 and either luteinizing hormone (LH)beta, thyroid-stimulating hormone (TSH)beta, prolactin, adrenocorticotropic hormone (ACTH), or growth hormone (GH) using peroxidase-conjugated secondary antibody. Additional sections were colabeled with SP22 and one of the AP hormones using fluorescent secondary antibodies. SP22 colocalized in somatotropes and thyrotropes in rat and hamster. We identified SP22 in a small percentage of corticotropes, gonadotropes, and lactotropes. This is the first report that SP22 mRNA is present specifically in the AP, and SP22 is localized primarily in somatotropes and thyrotropes. SP22 may help regulate AP function and be particularly important for the control of GH and TSH secretion.  相似文献   

18.
The primordium of the mammalian adenohypophysis derived from Rathke's pouch (RP) is known to be formed by oral ectoderm invagination. However, in the early phase of pituitary development, the detailed process by which the oral ectoderm develops into the adenohypophysis remains largely unknown. Using high-resolution non-radiolabeled in situ hybridization and the BrdU and TUNEL methods, we have examined the detailed expression pattern of factors involved in the formation of RP of chicken and the changes in the mitotic and apoptotic cell regions in RP. In the chicken embryo, Sonic hedgehog (Shh) mRNA was initially expressed in the stomodeal plate but not in the oral ectoderm. After prospective diencephalon had detached from the oral ectoderm, another Shh-expressing region appeared in the most rostral part of the recess. LIM homeobox gene 3 (Lhx3) mRNA first appeared in the anterior area of Rathke's recess, and expression then spread to the caudal region. alphaGSU mRNA-expressing cells were observed at both ends of the Lhx3-expressing region, and thereafter the expression area moved to the posterior region. Furthermore, a close overlap was found between the proliferating region and Lhx3 mRNA-expressing area, and TUNEL-positive cells appeared in Seessel's pouch derived from the foregut. Thus, the primordium of the pituitary gland corresponding to the Lhx3-expressing region is surrounded by the Shh-expressing region, which appears in two steps, and the mass growth and invagination of RP of chicken result from the coordination of the dorsal extension of the anterior region and the ventral extension of the posterior region of RP.  相似文献   

19.
A recent report provides new evidence for the presence of glucokinase (GK) in the anterior pituitary. In the present study, immunohistochemistry was used to identify the cells containing GK in the pituitary of rats and monkeys. In rats, GK was detected as a generalized cytoplasmic staining in a discrete population of cells in the anterior pituitary. In colocalization experiments, the majority of cells expressing follicle-stimulating hormone (FSH) or luteinizing hormone (LH) also contained GK. In addition to the gonadotropes, GK was observed in a subpopulation of corticotropes and thyrotropes. GK was not detected in cells expressing growth hormone or prolactin. In monkeys, GK was also observed in a discrete population of cells. Intracellular distribution differed from the rat in that GK in most cells was concentrated in a perinuclear location that appeared to be associated with the Golgi apparatus. However, similar to rats, colocalization experiments showed that the majority of cells expressing FSH or LH also contained GK. In addition to the gonadotropes, GK was observed in a subpopulation of corticotropes and thyrotropes. In the monkey, only a few cells had generalized cytoplasmic staining for GK. These experiments provide further evidence for the presence of GK in the anterior pituitary. Although some corticotropes and thyrotropes contained GK, the predominant cell type expressing GK was gonadotropes. In view of the generally accepted role of GK as a glucose sensor in a variety of cells including the insulin-producing pancreatic beta-cells as the prototypical example, it is hypothesized that hormone synthesis and/or release in pituitary cells containing GK may be directly influenced by blood glucose.  相似文献   

20.
Neural cell adhesion molecules (NCAMs) can undergo post-translational modifications, such as the addition of polysialic acid chains, thus generating PSANCAMs, which are expressed mainly during development. Since polysialylation considerably modifies NCAM adhesivity, expression of NCAMs and PSANCAMs has been investigated in the developing hypophysis by immunohistochemistry. At embryonic day 13 (E13), an antibody against NCAM outlined all cellular profiles in the entire Rathke's pouch; this labelling persisted until adulthood. NCAM expression increased in all lobes during development and concerned all pituitary cell types. In contrast, at E13, PSA-NCAMs were only detected in the neural lobe, solely constituted of pituicytes at this stage, and the tuberal lobe, the only lobe expressing hormonal mRNA at the same stage. PSA-NCAMs expression increased in the neural lobe at E17 with the arrival of the neurosecretory fibres and persisted into adulthood. In the anterior lobe, PSA-NCAMs appeared at E15 where their distribution was similar to that of the differentiating corticotrophic cells; at subsequent stages, their expression extended to the whole anterior lobe. Only two cell types, corticotrophic and somatotrophic cells, remained labelled in the adult gland. In the intermediate lobe, melanotrophic cells never expressed PSA-NCAMs but these were expressed on folliculo-stellate cells at birth, preceding the onset of innervation. These results suggest that NCAMs and PSA-NCAMs play a role in pituitary histogenesis, cell differentiation and neurointermediate lobe innervation.  相似文献   

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