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At least 19 recordsLinked to original sources
PubMed1981

The direct effect of reserpine in vitro on prolactin release from rat anterior pituitary glands.

Anterior pituitary glands from normal untreated rats synthesize and release the hormone prolactin (Prl) during incubation under in vitro conditions. Addition of dopamine (DA) greatly inhibits the release of Prl and to a lesser extent reduces Prl synthesis. When pituitary glands are incubated in the presence of reserpine, there is a similar significant dose-related inhibition of Prl release. This effect persists even in the presence of a DA antagonist (haloperidol) and after the depletion of hypothalamic amines by in vivo treatment with reserpine. Reserpine in vitro also inhibits release of newly synthesized growth hormone from the pituitary glands of male rats; however, this is not observed when female rats are studied. We conclude that the direct effect of reserpine to inhibit Prl release is apparently independent of any interaction with catecholamine systems and is mediated by other, presently undefined mechanisms.

Animals↗
PubMed1975

Characterization of the mannosyl and fucosyl transferases in the ovine anterior pituitary glands.

Ovine anterior pituitary glands contain mannosyl- and fucosyl-transferases localized in the microsomes and able to incorporate mannose or fucose as such from GDP-mannose or GDP-fucose into endogenous glycoproteins. The requirements and conditions necessary for maximum activity were investigated. The value of the Km is very similar for the two enzyme systems, 3 X 10(-7) M in the case of mannosyl-transferases and 5 X 10(-7) M in the case of fucosyl-transferases.

Animals↗
PubMed1976

Glycoproteins in membranes of secretory granules of the anterior pituitary gland.

Rat anterior pituitary glands were examined by electron microscopy after staining with five different histochemical stains. Histochemical reactions were observed in the cell coat, cell membrane and the membrane surrounding the secretory granules in all anterior pituitary cells following staining with phosphotungstic acid (PTA), chromic acid and PTA, the periodic acid-thiosemicarbazide-silver protein method (PA-TSC-SP) of Thiéry, ruthenium red and concanavalin A. The staining was abolished when the sections were preincubated with pronase, neuraminidase or trypsin and subsequently exposed to PTA, chromic acid and PTA or PA-TSC-SP. The possible functional role of the glycoproteins present in the membrane surrounding the secretory granules is considered.

Animals↗
PubMed1986

Blood flow in diethylstilbestrol-induced anterior pituitary gland hyperplasia.

Anterior pituitary hyperplasia was developed in female Fisher 344 rats by subcutaneously implanted slow-release diethylstilbestrol (DES) capsules. Blood flow was measured in two separate areas of the adenohypophysis using hydrogen clearance method at 6, 9, 10, and 13 weeks after the implantation. Blood flow progressively decreased while the DES capsules were in place (normal values in ml/g/min, mean +/- SD: 0.93 +/- .12 laterally and 1.15 +/- .11 medially, decreasing to 0.25 +/- .07 and 0.24 +/- .07, respectively, by 13 weeks). Histology confirmed nodular hyperplasia, development of large vascular lakes, and hemorrhages within the adenohypophysis. Total adenohypophysial blood flow was calculated as a product of mean blood flow as measured per unit weight and the weight of the gland. This figure progressively increased from 12.7 +/- 2 to 22.2 +/- 8 microliter/min by 13 weeks. All these changes were significant at the P less than 0.001 level. These blood flow measurements suggest that the hyperplastic adenohypophysis outgrows its blood supply which is additionally compromised by "useless" pooling of blood in the vascular lakes. However, there is an overall increase in the amount of blood flowing through the hyperplastic gland which may be explained by newly formed supplying vessels.

Animals↗
PubMed1984

Stimulation of 17 beta-hydroxy steroid dehydrogenase in the rat anterior pituitary gland by progesterone.

Anterior pituitary gland and hypothalamic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity was measured in the immature castrated estradiol primed rat to determine if differences in enzyme activity could explain the progesterone induced reduction of bound estradiol nuclear receptors of the anterior pituitary gland but not the hypothalamus. Higher levels of 17 beta-HSD activity were found in the anterior pituitary gland as compared to the hypothalamus. The enzyme activity in the anterior pituitary gland was stimulated by progesterone administered either in combination with estradiol for 4 days or as a single injection following 4 days of estradiol priming. No progesterone effects were found on hypothalamic 17 beta-HSD. Under the experimental conditions used, progesterone administration did not alter uterine 17 beta-HSD. An increase in anterior pituitary gland and uterine 17 beta-HSD was also induced by estrogen administration.

17-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

Thymulin stimulates corticotrophin release and cyclic nucleotide formation in the rat anterior pituitary gland.

The neuroendocrine system plays a key role in the regulation of the secretion of the thymic peptide, thymulin, but it remains to be determined whether thymulin exerts reciprocal regulatory actions on the functional activity of the hypothalamo-pituitary axis. In the present study, we have used a well established in vitro preparation to examine the influence of thymulin on cyclic nucleotide formation and hormone secretion by the rat anterior pituitary gland. Thymulin-Zn2+ (0.5-50 pM) stimulated the release of immunoreactive corticotrophin (ir-ACTH), producing effects which were maximal at 10 pM (p < 0.01). At the two highest concentrations tested (10 and 50 pM), it also produced small but significant increases in immunoreactive luteinising hormone (ir-LH) release (p < 0.05), but the secretion of immunoreactive growth hormone (ir-GH) was unaffected by the peptide (p > 0.05) while that of immunoreactive prolactin (ir-PRL) was reduced (p < 0.01). The ACTH responses to thymulin were accompanied by increased cyclic nucleotide formation. Thus, thymulin (0.5-50 pM) raised the cyclic 3',5'-adenosine monophosphate (cyclic AMP) content of the pituitary tissue (p < 0.01). At high concentrations (10-50 pM), it also increased cyclic 3',5'-guanosine monophosphate (cyclic GMP; p < 0.01) accumulation, although lower concentrations of the peptide were ineffective in this regard. The increases in ir-ACTH release provoked by thymulin-Zn2+ (0.5-5.0 pM) were potentiated markedly by rolipram (1 microM; p < 0.01), a selective inhibitor of the cyclic-AMP-specific phosphodiesterase enzyme. By contrast, zaprinast (10 microM), a selective inhibitor of cyclic-GMP-specific phosphodiesterase, attenuated the corticotrophic responses to higher concentrations of the peptide (10 and 50 pM; p < 0.05). Neither rolipram (1 microM) nor zaprinast (10 microM) influenced the release of ir-LH, ir-PRL or ir-GH in the presence or absence of thymulin-Zn2+ (0.5-50 pM; p > 0.05). The results suggest that thymulin modulates the secretion of ACTH and possibly LH by the anterior pituitary gland and that its actions are associated with increased cyclic nucleotide formation; in addition, it appears to exert an inhibitory influence on ir-PRL release.

Adrenocorticotropic Hormone↗
PubMed1975

Comparison of two isozymes of carbonic anhydrase in the rat anterior pituitary gland and pituitary tumors.

Two isozymes of carbonic anhydrase (EC 4.2.1.1.) were compared in the anterior pituitary gland of non-tumor-bearing rats and in the hormone-secreting pituitary tumors. In contrast to the pituitary gland, which contained 60 to 70% of the total carbonic anhydrase in the particulate subcellular fraction, three hormone-secreting pituitary tumors were devoid of the particulate (Triton X-100-solubilized)enzyme activity. Another pituitary tumor, 7315a, contained particulate carbonic anhydrase, but the activity was only 45% of the activity of normal pituitary gland. During the development of the rat brain, the particulate (Triton X-100-solubilized) carbonic anhydrase activity was undetectable in prepartions up to 21 days of age (body weight, 47 g). After that age, the carbonic anhydrase activity in the particulate fraction increased rapidly and reached the adult level at 37 days (body weight, 120 g), while the activity in the soluble fraction increased gradually after birth and then reached a plateau at 30 days (body weight, 81 g). These data show that the isozyme pattern of carbonic anhydrase in pituitary tumor tissue resembles the pattern in fetal cells more than the pattern in adult tissue.

Animals↗
PubMed1996

Nasal pyriform aperture stenosis and absence of the anterior pituitary gland: report of two cases.

We describe two female infants with congenital nasal pyriform aperture stenosis and severe pituitary insufficiency. The anterior pituitary gland was undetectable with magnetic resonance imaging. Consanguinity of parents in both cases suggests autosomal recessive inheritance of this disorder. An early fetal developmental defect may explain this syndrome, which affects midline craniofacial structures. In patients with congenital pyriform aperture stenosis, magnetic resonance imaging of the brain and endocrine investigations should be performed for rapid diagnosis and treatment of the latter to avoid major neurologic complications.

Abnormalities, Multiple↗
PubMed1988

Ultrastructural evidence for oxytocin in the rat anterior pituitary gland.

OT is synthetized in the hypothalamus. These neurons project to the posterior lobe of the pituitary and the external zone of the median eminence. In order to localize OT in the male rat anterior pituitary we have used immunocytochemistry on ultra-thin sections in target cell(s) obtained by cryoultramicrotomy. OT-like immunoreactivity was observed in lactotropes only. No immunoreactivity was observed in gonadotropes, somatotropes, corticotropes or thyrotropes. In lactotropes, immunoreactivity was localized at the plasma membrane level, in the cytoplasmic matrix and around the secretory granules, but not in the other organelles, and in the nucleus. No reaction was observed by using either non-immune serum or anti-OT serum incubated with OT. No modification of OT-like immunoreactivity was observed by using anti-OT serum incubated with heterologous peptides. These results 1) provide immunocytological evidence for the presence of OT in the anterior pituitary gland; 2) indicate the presence of this peptide in one particular cell type, and 3) support the hypothesis that OT could have a direct participation in the regulation of the PRL release.

Animals↗
PubMed2001

[Increased T1 signal of the residual normal anterior pituitary gland following medical treatment of pituitary prolactinoma].

PURPOSE: To illustrate that residual normal pituitary gland may show hyperintense signal on T1-weighted image after medical treatment of pituitary prolactinoma. MATERIAL: and methods. Three patients treated with bromocriptine for a prolactinoma and showing hyperintense signal of the residual normal pituitary tissue on T1-weighted images were studied. In all patients, measurements of the anterior pituitary gland signal (APGS) and the temporal lobe white matter signal (TLWMS) were obtained by a "region of interest" (ROI) on coronal T1-weighted images. The APGS/TLWMS ratios were calculated and compared to those of a control group of 30 normal subjects. RESULTS: In the three patients, the measurements obtained by ROI confirmed the visual impression of high signal of the residual normal pituitary tissue. Ratios were ranging from 1.15 to 1.21, while they were ranging, in the control group from 0.92 to 1.09. CONCLUSION: In patients with prolactin-secreting adenoma seen after medical treatment, high signal of the residual normal pituitary tissue can be observed, probably due to cellular hyperactivity as it can be noticed during some physiological states. This pattern has to be differentiated from other pituitary abnormalities demonstrating T1 hyperintensity such as hemorrhagic changes of a prolactinoma.

Adult↗
PubMed2004

Intercellular communication within the rat anterior pituitary gland: X. Immunohistocytochemistry of S-100 and connexin 43 of folliculo-stellate cells in the rat anterior pituitary gland.

Since Rinehart and Farquhar reported the presence of agranulated cells in the anterior pituitary gland in 1953, the functions of the folliculo-stellate cell remain to be clarified. Intercellular junctions have been described in the monkey, rat, and teleost anterior pituitary glands, indicating the existence of cell-to-cell communication within the organ. We pointed to their possible role in the rapid dissemination of information through a complex interconnecting system of follicles involving gap junctions. The gap junctional/folliculo-stellate cellular network was essential in the maturation and regulation of the pituitary gland system such as the hypothalamic-pituitary-gonadal axis. It has been was shown that a network participated in the conduction of electrophysiological information over a long distance using the ion Ca(++), which propagates to other folliculo-stellate cells by signaling through gap junctions. Sixty-day-old male rats were used in this study for light microscopic immunohistochemistry of S-100 protein, type I collagen, and connexin 43, and for electron microscopy to observe the morphological relationships between the cellular networks of folliculo-stellate cells and granulated pituitary cells. Clusters of anti-S-100 protein-positive cells were clearly observed in a region of the hypophysis tentatively named the transition zone. Anti-S-100 protein-positive cells and their cytoplasmic processes were also present in the anterior lobe and assembled together to form follicular lumina. Type I collagen was clearly shown outlining the incomplete lobular or ductule-like structure making cell cords in the anterior pituitary gland. Numerous microvilli were present within the follicular lumen while around the lumina, junctional specializations including gap junctions were positive for the connexin 43 protein. A nonuniform distribution of the connexin 43-positive sites were observed. Small or dot-shaped positive sites were noted where two clusters of cells were connected; the cells were identified as S-100 cells. Double immunohistochemical staining of the connexin 43 and growth hormone (GH) or connexin 43 and luteinizing hormone (LH) was also performed, demonstrating no direct relationship between the connexin 43 and either the GH or LH cells. These findings indicate that there are two kinds of messages necessary for the hormone release in the pituitary gland. One is via the portal vein system, the other is through the gap junction-mediated networks of folliculo-stellate cells. The granulated cells directly associate with cell membrane of folliculo-stellate cells are able to discharge secretory granules through communication via gap junctions, while those granulated cells that are more distant from the folliculo-stellate cells are only able to discharge hormones via the pituitary hormone-releasing hormone from the portal vein system.

Animals↗
PubMed1982

Multiple species of follicle-stimulating hormone exist within the anterior pituitary gland of male golden hamsters.

Anterior pituitary glands were collected from immature and mature (intact and castrated) male hamsters. The various species of FSH present within these glands were separated by Concanavalin A (Con A) chromatography and polyacrylamide gel isoelectric focusing (PAG-IEF) and measured by a specific FSH radioimmunoassay (RIA) as well as a radioreceptor assay (RIA). Two distinct forms of FSH (Con A unbound and bound) were separated by Con A chromatography and detected by both RIA and RRA. These two populations of FSH were present within anterior pituitary glands of all three animal models tested. Castration before collection of anterior pituitary glands reduced the ratio of Con A unbound: bound immunoreactive FSH. When measured by RRA this reduction was no observed. When homogenates of anterior pituitary glands obtained from mature animals were separated by PAG-IEF, six distinct species of FSH were observed by RIA with isoelectric points (pI) of 6.0, 5.7, 5.3, 5.0, 4.7 and 4.2-3.8. Homogenates of anterior pituitary glands obtained from immature male hamsters did not contain one of these species of FSH (pI values 4.7). The relative contribution of some of the species of FSH to the total amount of detectable FSH differed depending upon the endocrine status of the animal. The species with pI value of 4.2-3.8 did not show any receptor-binding activity in any of the three models studied. The overall ratio of the activity of FSH measured by RRA compared with RIA was highest in anterior pituitary glands from intact mature and immature hamsters and lowest in anterior pituitary glands obtained from castrated animals. The RRA:RIA ratio for each species of FSH in all models tested declined as the isoelectric point of that species decreased. Thus, these results demonstrated the presence of multiple species of FSH within the anterior pituitary of immature and mature male hamsters. The relative proportions and receptor-binding activities of these species differed according to the isoelectric point and the pattern of hormone secretion at the time of collection of pituitary glands. Gonadal and other endocrine factors may influence not only the relative amount of each species of FSH but also the receptor-binding capacity of the FSH species synthesized by the anterior pituitary gland.

Animals↗
PubMed2001

Long-term transgene expression within the anterior pituitary gland in situ: impact on circulating hormone levels, cellular and antibody-mediated immune responses.

Adenoviral vectors have been identified as useful tools for gene transfer to the pituitary gland with the aim of providing therapeutic treatments for pituitary diseases. Although successful adenovirus-mediated gene transfer to the pituitary has been shown, the duration of transgene expression, local immune responses and consequences on circulating pituitary hormone levels have not been investigated. These are critical not only for the successful implementation of these gene transfer techniques both for physiological and/or therapeutic applications but also for assessing the safety of these approaches. We have therefore assessed duration and levels of transgene expression 3 days, 14 days, 1, 2, and 3 months after delivery of adenoviruses expressing herpes simplex virus type 1 thymidine kinase (HSV1-TK), under the control of the major immediate early human cytomegalovirus (RAd-hCMV/TK) or human PRL (RAd-hPrl/TK) promoters, to the anterior pituitary (AP) gland in situ. The presence of vector genome and cellular immune infiltrates within the AP gland were also studied along with the levels of circulating anti-adenovirus neutralizing antibodies and AP hormones in sera. Ubiquitous or cell-type specific expression of HSV1-TK within the AP gland was seen from RAd-hCMV/TK and RAd-hPrl/TK respectively at all time points, although a reduction in expression was seen over time. PCR amplification of HSV1-TK specific sequences showed the persistence of adenoviral genomes for up to 3 months. Analysis of the AP showed the presence of a virus-induced inflammation that peaked around day 14 and was resolved between 2-3 months. ED1-positive macrophages, CD8-positive T-cells and CD161-positive NK cells were identified up to 1 month after virus administration. A virus-induced humoral immune response was also present as anti-adenovirus neutralizing antibodies were detected from 14 days after virus administration. Levels of circulating pituitary hormones were unaffected by virus administration with the exception of the stress hormone ACTH which was increased at 3 days but normalized by 14 days. In conclusion, our data indicates that adenovirus-mediated delivery to the AP gland in situ may be a useful tool for the treatment of pituitary diseases as no major cytotoxicity or disruption of AP hormonal functions are seen. Despite of this, further developments to this approach still need to be made to combat the reduced transgene expression seen over time and the induction of virus-induced immune responses.

Adenoviridae↗
PubMed1986

Ectopic pituitary adenomas with normal anterior pituitary glands.

Two patients with ectopic pituitary adenomas and biopsy-proven normal anterior pituitaries are described. Both tumors were located in the sphenoid sinus. One tumor produced prolactin, and the other one was a plurihormonal adenoma that produced predominantly adrenocorticotropin and to a lesser extent thyroid stimulating hormone and alpha subunit. The patient with the plurihormonal tumor, who had Cushing's disease, was cured by surgery while the patient with the prolactinoma was treated by surgery and medical therapy. A review of these two cases and an additional nine cases from the literature of ectopic pituitary adenomas in patients with normal intrasellar anterior pituitaries indicate that these uncommon tumors are capable of secretory function and may be the only cause of excessive pituitary hormone production.

Adenoma↗