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At least 613 records · Page 34Linked to original sources
PubMed1985

GnRH pulse frequency determines LH pulse amplitude by altering the amount of releasable LH in the pituitary glands of ewes.

We have measured the size of the releasable pools of LH and FSH in the pituitary glands of ovariectomized ewes in which the pituitary was isolated surgically from the hypothalamus. The ewes were given GnRH pulses (250 ng) every hour (N = 3) or every 2 h (N = 3) for 1 week and then given a high dose GnRH infusion (0.5 micrograms/min) for 4 h. Blood samples were collected to characterize the LH and FSH responses to the GnRH pulses and infusion. The LH, but not FSH, responses to the individual GnRH pulses were pulsatile and the amplitudes of the LH pulses were greater in the sheep receiving pulses every 2 h. The sheep receiving hourly pulses showed lower LH responses to the high-dose infusions than did the sheep receiving pulses every 2 h. These data indicate a relationship between the amplitude of LH pulses and the size of the releasable pool of LH in the pituitary gland. As the frequency of GnRH pulses is decreased the amplitude of the LH responses is increased in direct proportion to the size of the releasable LH pool.

Animals↗
PubMed1984

Serotonin and acetylcholine affect the release of prolactin and growth hormone from pituitary glands of domestic fowl in vitro in the presence of hypothalamic tissue.

Anterior pituitary glands from broiler fowl were incubated alone or with hypothalamic tissue in medium containing either serotonin or serotoninergic drugs, acetylcholine or cholinergic drugs, and the release of prolactin (Prl) and growth hormone (GH) measured by homologous radioimmunoassays. The neurotransmitters and drugs affected the release of hormones from the pituitary gland only when hypothalamic tissue was also present. Serotonin and its agonist quipazine stimulated the release of Prl and inhibited release of GH in a concentration-related manner. The antagonist methysergide blocked the effects of serotonin and quipazine on Prl. Acetylcholine and its agonist pilocarpine also stimulated release of Prl and inhibited release of GH in a concentration-related manner. Atropine blocked these responses. The results show that serotonin and acetylcholine affect pituitary hormone secretion by acting on the hypothalamus. They may stimulate the secretion of a Prl releasing hormone and somatostatin.

Acetylcholine↗
PubMed1983

The presence of LH components having different ratios of bioactivity to immunoreactivity in the rat pituitary glands.

The isoelectric components of LH have been isolated from the male rat pituitary glands by preparative isoelectric focusing. The biological activities of these components were measured in vitro from testosterone production in rat Leydig cells at equal doses and expressed as the equivalent of NIH-LH-S1 immunoreactivity. There were significant differences in the bioactivities among the components. The bioactivities of the components decreased with decreasing pI; components E (pI = 9.6) and F (pI = 9.8) showed about 5- to 6-fold higher activities than component A' (pI = 7.9). When the rat pituitary extracts were measured for LH by radioimmunoassay, and then measured for the ratio of biological activity to immunoreactivity (B:I), the order was as follows; intact female rats greater than intact male rats greater than orchidectomized rats. This phenomenon could be explained by the differences in the relative amounts of the LH components which changed according to the physiological states. These observations indicate that the LH components with different pIs and B:I ratio are related to the different estimation of total LH in the rat pituitary glands by bioassay and radioimmunoassay.

Animals↗
PubMed2006

Growth hormone and insulin-like growth factor gene expression prior to the development of the pituitary gland in rainbow trout (Oncorhynchus mykiss) embryos reared at two temperatures.

Real time RT-PCR was used to measure the changes in the rates of synthesis of mRNA encoding for growth hormone-1 (GH1) and -2 (GH2) and insulin-like growth factor-1 (IGF-1) and -2 (IGF-2), and whole embryo GH content was measured in early stage rainbow trout (Oncorhynchus mykiss) embryos reared at two incubation temperatures (8.5 and 6.0 degrees C). Particular attention was paid to the phase of embryo development that preceded the appearance of the pituitary gland. GH was present in zygotes, and there were no significant changes in whole embryo GH content of the two temperature treatment groups from fertilization (t0) until the time at which GH was detectable in the pituitary gland by immunostaining. The expression of the two GH genes decreased during the first 24 h post-fertilization, and then increased significantly by 17 dpf in embryos reared at both temperatures. There was a subsequent steep increase in the number of copies of GH1 and GH2 mRNA associated with the formation of the pituitary gland evident at 23 and 34 dpf in the 8.5 and 6.0 degrees C groups, respectively. The number of copies of mRNA encoding for IGF-1 and IGF-2 did not change during the first 24 h post-fertilization; however, there was a significant increase in the numbers of transcripts for both genes evident by 13 dpf in embryos reared at the two incubation temperatures. The differences in the timing of the increases in GH and IGF mRNA may suggest that IGF gene expression is not GH-dependent at that stage. Moreover, the increased expression of the GH genes prior to the formation of the pituitary gland suggests that tissues other than the pituitary are expressing these genes in early embryos. The pattern of changes in GH content was similar to the pattern of GH gene expression in embryos reared at the two incubation temperatures when the age of embryos was plotted using degree-days. There were no apparent compensatory responses in GH1, GH2, IGF-1 or IGF-2 gene expression related to altered growth rates. The number of copies of IGF-2 mRNA was higher than that of IGF-1 mRNA during the early developmental period; this is consistent with the hypothesis that IGF-2 predominates during embryonic development. A differential expression of GH2 and GH1 was also observed with the overall copy numbers of GH2 mRNA being consistently higher than those of GH1.

Animals↗
PubMedDate not supplied

Age-dependent expression of 8-hydroxy-2'-deoxyguanosine in human pituitary gland.

A major oxidative product, 8-hydroxy-2'-deoxyguanosine (8-OHdG) is involved in ageing, carcinogenesis, and different diseases. The expression of 8-OHdG in the human pituitary gland was investigated immunohistochemically using specimens from individuals aged 19-88 years. 8-OHdG was localized at the nuclei of the anterior lobar parenchymal cells of the pituitary gland. The number of cells positive for 8-OHdG were counted, and the ratio of the positive cells to the total parenchymal cells was evaluated. The ratios increased in accordance with the ages of the individuals examined. Statistically, there was a significant correlation between the ages in years and the 8-OHdG positive ratios in the anterior lobar parenchymal cells (r = 0.757, p < 0.01). These findings indicate an age-dependent accumulation of 8-OHdG in the pituitary gland, which may also be related to the ageing of neuroendocrine systems as well.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1986

ACTH-related material in the pituitary gland of the chinook salmon (Oncorhynchus tschawytscha).

The distribution and nature of ACTH-related material in the pituitary gland of chinook salmon (Oncorhynchus tschawytscha) was studied. Pars distalis (PD) and neurointermediate lobe (NIL) extracts were analyzed by gel filtration on BioGel P6 and the resultant fractions assayed for ACTH immunoreactivity (ACTH-IR) using six different antibodies, all of which were specific for ACTH when applied to mammalian samples, and for alpha-MSH. In the PD a number of distinct peaks of ACTH-IR were observed, which were detected to different degrees by the different ACTH antibodies. Three of the ACTH antibodies produced essentially similar results. The other ACTH antibodies produced results quite distinct from these, and distinct from one another. Thus ACTH-IR is present in the salmon PD in a number of distinct forms, all of which appear to have molecular weights between about 2000 and 5000. No alpha-MSH was detected in the PD. All of the ACTH antibodies also detected material in the NIL. In general the different antibodies produced similar results. There were fewer peaks of ACTH-IR in the NIL than in the PD. The major one of these, which eluted between the void volume and 1-39 ACTH, was detected by all the antibodies. One of the antibodies also detected a peak of ACTH-IR which eluted close to where alpha-MSH eluted. All of the ACTH antibodies detected more material in the PD than in the NIL, the ratio being about 3:1 in every case. alpha-MSH-IR eluted as a minor peak at the void volume, and a major peak in the position of authentic 1-13 alpha-MSH.

Adrenocorticotropic Hormone↗
PubMed1982

Ultrastructural evidence for endogenous vasoactive intestinal peptide-like immunoreactivity in the pituitary gland.

The immunocytological method was used to investigate whether vasoactive intestinal peptide (VIP) is present in the pituitary gland and to localize the peptide at the cellular and subcellular levels. Pituitaries of Wistar male and female rats (Iffa Credo) were fixed in glutaraldehyde 2.5% and postosmicated and frozen in liquid nitrogen. Ultrathin slices, obtained by cryo-ultramicrotomy were incubated with the antiserum. The antigen-antibody reaction was detected by peroxidase-antiperoxidase complexes revealed by 4-chloro-1-naphtol. The prolactin (PRL)-secreting cells were identified by using an anti-oPRL antiserum. The PRL immunoreactivity was localized in secretory granules of irregular shapes. An anti-VIP serum was used which neither cross-reacted with the several fragments of VIP molecule nor with peptides from gut or hypothalamus. The VIP immunoreactivity obtained with this antiserum, was observed in PRL cells only but never in so-matotropic, gonadotropic, corticotropic and thyrotropic cells. The immunoreactivity was localized in the cytoplasmic matrix between and around the secretory granules but not in the organelles, and in the nucleus distributed all over the euchromatin near to the heterochromatin regions. No reaction was observed by using either nonimmune serum or anti-VIP antiserum incubated with VIP. No modification of VIP immunoreactivity was observed by using anti-VIP antiserum incubated with somatostatin, gonado- or thyroliberin. These data (1) provide immunocytological evidence for presence of VIP in pituitary gland; (2) indicate the presence of this peptide in one particular pituitary cell type, and (3) support the hypothesis that VIP could have a direct effect on the control of PRL secretion.

Animals↗
PubMed1984

Magnetic resonance imaging of the pituitary gland.

Magnetic resonance imaging (MRI), a nonionizing, biologically safe imaging technique, is bringing the desired goal of directly imaging the pituitary gland very close to reality. The exquisite anatomic demonstration of the gland and hypophyseal stalk and the perisellar structures and the usefulness of tissue characterizations (T1 and T2 values) firmly establish the role of MRI in imaging of pituitary gland abnormalities, with the potential of becoming the procedure of choice.

Adenoma↗
PubMed1989

Concentrations of glycosylated prolactin in the pituitary gland and plasma of lean and obese barrows.

We measured glycosylated PRL (G-PRL) in the pituitary gland and plasma of lean and obese barrows (castrated male pigs) by immunoblotting. We found that G-PRL constituted 40% or more of total monomeric PRL in the pituitary gland of these animals. Furthermore, pituitary G-PRL concentrations in obese barrows averaged 58% higher than in those of lean controls. The non-glycosylated PRL concentrations were also higher in the pituitaries of obese barrows in comparison to lean controls, but the magnitude of the difference was smaller (42%). Plasma concentrations of the two forms, or total immunoreactive PRL measurable by radioimmunoassay, did not differ significantly between the two groups. The pituitary data suggest that the state of PRL secretion is altered in obese barrows, and that the alteration is more pronounced for G-PRL than for the non-glycosylated counterpart.

Animals↗
PubMed1993

Isolation of FSH from bovine pituitary glands.

An improved method is described for the isolation of FSH from bovine pituitary glands. The purification procedure consisted of an initial ammonium sulphate precipitation step followed by triazine-dye chromatography, immobilized metal affinity chromatography, high-performance anion-exchange chromatography and gel filtration. Three highly purified bovine FSH preparations (designated bFSH-A, -B and -C) were obtained, giving yields of approximately 5.7 mg FSH/kg bovine pituitary glands (wet weight), with specific radioreceptor activities for bFSH-A, -B and -C of 61, 25 and 29 units (NIH-FSH-S1)/mg protein respectively. The corresponding biological activities were 217 (bFSH-A), 62 (bFSH-B) and 86 (bFSH-C) units/mg, as measured by an FSH in-vitro bioassay. LH levels were found to be < 1% (w/w) as determined by an LH in-vitro bioassay. SDS-PAGE of these bFSH preparations under reducing conditions in 16% polyacrylamide gels showed two major silver-staining bands of apparent molecular masses 19.5 kDa and 15.8 kDa. Their amino acid compositions were in close agreement with the expected composition, based on the bFSH cDNA sequence and results reported by other investigators. N-terminal sequencing of the bFSH-A preparation yielded two major sequences consistent with alpha- and beta-subunits, and a third minor (< 20%) sequence consistent with the alpha-subunit clipped at amino acid residue 6. It was concluded that the bFSH purification procedure reported here is a rapid method which produces bFSH in high yield and high purity, with radioreceptor and in-vitro specific activities comparable with those previously reported by other investigators.

Animals↗
PubMed1984

Interaction of (+)- and (-)-3-PPP with the dopamine receptor in the anterior pituitary gland.

The interaction of the enantiomers of the novel dopamine agonist, 3-PPP (3-hydroxyphenyl)-N-n-piperidine) with the dopamine receptor in the anterior pituitary gland was examined. Both (+)- and (-)-3-PPP were effective in suppressing the elevation in serum prolactin (PRL) concentrations in rats treated with alpha-methyl-paratyrosine, an inhibitor of dopamine synthesis. The (+)-enantiomer was slightly more potent than the (-)-enantiomer in this regard. In addition, the secretion of PRL from anterior pituitary tissue under in vitro conditions was significantly inhibited by both isomers of 3-PPP, with (+)-3-PPP being approximately 10 times more potent than (-)-3-PPP. Both (+)- and (-)-3-PPP displaced 3H-(-)-N-n-propylnorapomorphine (3H-NPA) and 3H-spiperone from bovine anterior pituitary membranes. The Hill coefficients of (+)- and (-)-3-PPP for the displacement of 3H-spiperone were 0.6 and 0.7, respectively. These results are consistent with the view that the (+)- and (-)-enantiomer exhibit dopamine agonist effects at dopamine receptor sites in the anterior pituitary gland. However, (+)-3-PPP demonstrated marked differences in affinity for 3H-NPA- and 3H-spiperone labeled-sites, whereas (-)-)3-PPP showed the same order of affinity for these two sites. In view of these results and the fact that (-)-3-PPP has also been characterized as a dopamine antagonist at postsynaptic receptor sites in the striatum, (-)-3-PPP might be best described as a partial agonist at pituitary dopamine receptors. Moreover, these data are suggestive of a similarity, at least on a pharmacological basis, between dopamine autoreceptors and dopamine receptors in the anterior pituitary gland.

Animals↗
PubMed2001

Localization of metallothionein I-II immunoreactivity in bovine pituitary gland.

Metallothioneins belong to a family of shock proteins characterized by an unusual high content of cystein, absence of aromatic amino acids and high metal content (Zinc and Copper). Metallothioneins are ubiquitously present in a large variety of prokaryotic and eukaryotic species as well as in all mammalian organs and tissues examined thus far. To the best of our knowledge this is the first report describing the presence of metallothioneins in the pituitary gland. Metallothioneins were identified immunohistochemically and chromatographically both in the neuro and adenohypophysis of the bovine pituitary gland. Metallothioneins are highly expressed in the neurohypophyseal glial cells, and in a subpopulation of folliculo-stellate cells located in the pars intermedia of the adenohypophysis. While the specific role of these proteins in the pituitary gland remains to be established, we hypothesize that, besides their protective action against free radicals, hypophyseal metallothioneins might be involved in the regulation of metal ion homeostasis with putative implication in release of hypothalamic peptide hormones in the neurohypophysis and synthesis/release of alpha-MSH by POMC-cells located in the pars intermedia of the adenohypophysis.

Animals↗
PubMed1992

Importance of thiol groups in ligand binding to D2 dopamine receptors from brain and anterior pituitary gland.

The effects of the thiol group reagent 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) on D2 dopamine receptors have been examined in three brain regions (caudate nucleus, putamen and olfactory tubercle), and in the anterior and neurointermediate lobes of the pituitary gland. Whereas the receptors in brain were insensitive to DTNB, a dose-dependent inhibition of [3H]spiperone binding to D2 receptors in both lobes of the pituitary gland was observed. The effects in the pituitary could be reversed by subsequent treatment with dithiothreitol and could be prevented by prior occupancy of the receptor binding site with a ligand. The effect of DTNB was to decrease the number of ligand-binding sites without altering the affinity of those remaining. The results show that modification of a thiol group of the D2 dopamine receptor in the two lobes of the pituitary gland tested here significantly affects ligand binding. There is therefore a difference between the D2 dopamine receptor populations in brain and pituitary in their sensitivity to modification by DTNB, and this may imply the existence of different receptor isoforms in the two issues.

Animals↗
PubMed1995

Evidence that melatonin acts in the pituitary gland through a dopamine-independent mechanism to mediate effects of daylength on the secretion of prolactin in the ram.

A previous study provided evidence that melatonin acts in the pituitary gland to mediate the effects of daylength on the secretion of prolactin in sheep. This was based on the observation that hypothalamo-pituitary disconnected (HPD) Soay rams showed normal patterns in the changes in the peripheral blood concentrations of prolactin in response to alterations in photoperiod (10-fold higher concentrations under long than short days), and in response to exogenous melatonin (rapid decline following the administration of a constant-release implant of melatonin). The purpose of this study was to establish whether dopamine (DA) might be involved in mediating the effects of melatonin on the secretion of prolactin. Groups of HPD (n = 7) and control Soay rams (n = 8) were treated with vehicle (control, 2.0 ml 0.1 M tartaric acid/saline sc), bromocriptine (DA agonist, 0.06 mg/kg sc) or sulpiride (DA antagonist, 0.6 mg/kg sc), and the acute prolactin responses were measured over the next 4 h. Treatments were carried out under short days (8L: 16D, low prolactin), long days (16L: 8D), high prolactin), and under long days in the presence of a constant-release implant of melatonin (low prolactin). The prolactin response to TRH (1.25 micrograms/kg iv) was also measured. Bromocriptine caused a decrease in the plasma concentrations of prolactin in both HPD and control rams under short and long days. Sulpiride had no effect in the HPD rams on any occasion, but caused a very marked increase in the plasma concentrations of prolactin in the control rams under short days, long days, and under long days + melatonin. TRH caused an acute increase in the plasma concentrations of prolactin in the HPD rams under both long and short days although the responses were notably reduced compared with the controls especially under long days + melatonin. Overall, the inhibitory response to the DA agonist in HPD rams indicates the presence of DA D2 receptors linked to functional lactotrophs in the isolated pituitary gland. However, the total lack of a response to the DA antagonist indicates the absence of endogenous DA mechanisms regulating the secretion of prolactin in the HPD rams. The conclusion is that melatonin acts directly on the pituitary gland to mediate effects of photoperiod through a DA-independent mechanism.

Animals↗
PubMed1985

Mechanisms of release of prolactin from fowl anterior pituitary glands incubated in vitro: effects of calcium and cyclic adenosine monophosphate.

Fowl anterior pituitary glands were bisected and each half was pretreated in either Medium 199 or medium containing EGTA to deplete endogenous calcium (Ca2+) stores, after which they were incubated in Medium 199, or Ca2+-free medium, containing prolactin release-stimulating agents and verapamil, a Ca2+ channel blocker. High K+ concentrations, hypothalamic extract, synthetic thyrotrophin-releasing hormone (TRH) and dibutyryl cyclic AMP (dbcAMP) all stimulated release of prolactin from control (non EGTA-treated) hemianterior pituitary glands. The effects of TRH and dbcAMP were not additive, but the response to submaximal concentrations of TRH was augmented by theophylline, a phosphodiesterase inhibitor. Reduction of Ca2+ availability with EGTA or verapamil reduced basal release of prolactin, prevented the prolactin-stimulating effects of high K+ concentrations and TRH, and markedly attenuated responses to hypothalamic extract and dbcAMP, EGTA being more effective than verapamil. Increasing the Ca2+ concentration of the medium did not augment basal or stimulated release of prolactin. These results suggest that both Ca2+ and cyclic AMP may act as intracellular mediators in the release of prolactin. Both basal and stimulated release of prolactin depend upon the presence of Ca2+. Although influx from the medium may be the major source of Ca2+, endogenous stores of Ca2+, perhaps mobilized by dbcAMP, may be able to maintain some release of prolactin. The prolactin-stimulating effects of TRH may be mediated by cyclic AMP.

Animals↗
PubMed1999

Immature teratoma originating from the pituitary gland: case report.

OBJECTIVE AND IMPORTANCE: Recently, it has been suggested that the primary site of suprasellar germinomas is the neurohypophysis, but nongerminomatous germ cell tumors originating from the pituitary gland have been rarely reported. CLINICAL PRESENTATION: A 27-year-old man presented with panhypopituitarism, bitemporal hemianopsia, and mild right oculomotor nerve paralysis. Diabetes insipidus was not observed. The tumor was shown by magnetic resonance imaging to extend and invade bilateral cavernous sinuses, sellar and clival dura mater, and the sphenoid sinus mucosa. INTERVENTION: Transsphenoidal removal yielded a diagnosis of immature teratoma. Serum alpha-fetoprotein was prominently elevated. Magnetic resonance imaging and surgical findings of the superiorly displaced residual pituitary gland strongly suggest the pituitary origin of this rare tumor. CONCLUSION: In contrast to the neurohypophyseal germinomas, nongerminomatous malignant germ cell tumors originating from the pituitary gland tend not to be associated with diabetes insipidus and thus mimic adenomas. Evaluation of the tumor markers is necessary in young patients with cavernous sinus syndrome and invasive pituitary tumors with heterogeneous intensity revealed by magnetic resonance imaging.

Adult↗
PubMed1986

gamma-Endorphin and schizophrenia: amino acid composition of gamma-endorphin and nucleotide sequence of gamma-endorphin cDNA from pituitary glands of schizophrenic patients.

The possibility has been mentioned that a change in the structure is responsible for the deviant behavioral activity of gamma-endorphin in extracts of postmortem brain and pituitary gland samples of schizophrenic patients. This paper describes the investigation of this possibility by means of: amino acid composition analysis of alpha- and gamma-endorphin isolated from a pituitary gland of a schizophrenic patient; and nucleotide sequence analysis of the gamma-endorphin coding region of pro-opiomelanocortin (POMC) mRNA from two other pituitary glands, using the primer extension method. Both methods require no more than a single pituitary to obtain reliable results. alpha- and gamma-endorphin were isolated from an acid extract by gel filtration and two subsequent HPLC steps. In addition, the gamma-endorphin region of beta-endorphin was analyzed by enzymatic cleavage of beta-endorphin and isolation of the resulting fragment. Single-stranded gamma-endorphin cDNA was synthesized by reverse transcriptase using total cellular pituitary RNA and a 5' 32P-labeled oligodeoxyribonucleotide primer (20-mer) hybridizing close to the gamma-endorphin coding region of POMC mRNA. Single-stranded cDNA was digested with restriction enzyme HaeIII which generated a 148 nucleotides long radioactive cDNA fragment containing the gamma-endorphin cDNA sequence. The sequence of the 148 nucleotides fragment was determined. Neither the amino acid composition analysis nor the amino acid sequence derived from the cDNA nucleotide sequence revealed differences between schizophrenics and controls. Thus, no evidence was found for changes in the amino acid sequence of pituitary gamma-endorphin in these analyses, which include 3 cases of schizophrenia.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗