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PubMed1992

The dynamics of beta-endorphin release by the hypothalamic nuclei and pituitary gland in sheep under physiological and stress condition.

The secretion of beta-endorphin (beta-End) by the infundibular nuclei--median eminence (IN-ME) and paraventricular nuclei (PVN) of the hypothalamus and the anterior lobe (AL) of the pituitary gland was determined in 18 anestrous ewes by RIA assay of this opioid in perfusates collected from these formations. Perfusion with Ringer-Locke solution was carried out on the animals under resting and stress-full conditions, using a pushpull cannula method. Electrical footshocks were used as stress stimuli. Two series of perfusion experiments were performed. In the first, the perfusions were carried out over two hours and perfusates were collected before and during stress for 1 h. In the second series of experiments the dynamics of the release of the opioid by the IN-ME and the pituitary gland were followed by collecting five or six perfusates in 20 min fractions before and during stress, respectively. The first series of experiments showed that the concentrations of beta-End in perfusates from the pituitary gland were much higher than those from the hypothalamic nuclei and that the concentrations of this opioid during stressing rose significantly only in perfusates from the IN-ME nuclei. In the second series of experiments the release of beta-End from the IN-ME and pituitary gland was altered by stress. The shift was very characteristic in that the concentrations of the opioid during stimulation initially significantly rose and then gradually declined. The concentration of the opioid in the peripheral blood also rose at the beginning of stimulation and declined as stimulation continued.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Molecular heterogeneity of prolactin in lactating rats and their pups: biological and immunological activities in pituitary gland, serum and milk.

Prolactin (PRL)-like bioactivities (in Nb2 lymphoma assay), immunoreactivities (in RIA) and B/I ratios in rat milk, maternal and neonatal pituitary glands and sera were investigated. The PRL-like bioactivity in the water-soluble fraction of rat milk (infranatant prepared by ultracentrifugation) exceeded its immunoreactivity 3-7-fold. The elevated B/I ratio was in part due to the presence of a glycosalated PRL (G-rPRL)-like material, since 5-70% of the PRL-like bioactivity was recovered from the glycosylated fraction of rat milk infranatant prepared by concanavalin-A affinity chromatography. We were unable to detect PRL-like immunoreactivity in the glycosylated fraction of rat milk, and calculated that the maximal cross-reactivity of G-rPRL in the RIA is less than 3.8%. In day 12 milk, over 80% of the G-rPRL-like bioactivity eluted from a Sephadex G-100 column as a high apparent molecular weight (Mr) substance (approximately 50 kD), while the rest eluted as a monomeric G-rPRL (24-25 kD). The PRL-like bioactivity in the nonglycosylated fraction eluted in three peaks (Mr: 50, 24 and 16 kD), while two immunoreactive peaks occurred (Mr: 24 and 8 kD). The concentration of rPRL-like immunoreactivity in rat milk increased during the first days of lactation, remained high in midlactation, and declined by the end of lactation. The PRL-like bioactivity in the nonglycosylated fraction of rat milk displayed a similar timecourse. G-rPRL-like bioactivity in rat milk, however, changes inversely, i.e. decreased between days 2 and 18 postpartum then increased by day 22. The concentration of high Mr PRL-like bioactivity in rat milk was greatly reduced by day 22 from day 2 postpartum. No PRL-like bioactivity or immunoreactivity was recovered from the IgG fraction (prepared by protein A affinity chromatography) of rat milk. The B/I ratio in day 2 maternal pituitary glands was close to 1. In neonatal pituitaries and in maternal sera, however, the B/I ratio was slightly elevated (2-3). The B/I ratio in day 2 neonatal serum was between 6 and 22, while the B/I ratio of PRL secreted by day 2 neonatal pituitary glands in vitro was 1. The present results demonstrate that the concentrations of PRL in rat milk and neonatal serum have been grossly underestimated because levels were detected by RIA. The high B/I ratio reflects the presence of PRL variants. Milk appears to be the most likely source of PRL variants in the circulation of the neonate.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Biological demonstration of nerve growth factor in the rat pituitary gland.

Explants of anterior, intermediate and posterior pituitary lobes of rats at various ages evoked an intense nerve fibre outgrowth when co-cultured with neonatal sympathetic superior cervical ganglia in a collagen gel medium. Freezing and thawing of pituitary lobes, prior to culture, did not abolish their growth-promoting effect. Since the addition of antiserum to nerve growth factor in the culture medium inhibited totally the stimulative action of both fresh and frozen pituitary explants it is suggested that the stimulation is mediated by nerve growth factor or an immunologically related molecule. Based on the present results it is concluded that nerve growth factor is synthesized by both the anterior, intermediate and posterior lobes throughout the postnatal period, as well as in adult rats. The function of nerve growth factor in the pituitary gland is discussed.

Animals↗
PubMed1985

Differential regulation of tuberohypophysial dopaminergic neurons terminating in the intermediate lobe and in the neural lobe of the rat pituitary gland.

In order to characterize the properties of tuberohypophysial dopaminergic neurons which terminate in the intermediate (IL) and neural (NL) lobes of the pituitary gland a technique was developed which permitted the selective dissection of the rat pituitary into its three distinct lobes (NL, IL and anterior lobe, AL). The success of the dissection was evaluated histologically and biochemically by measuring the distribution of peptide hormones characteristic of the dissected regions. As would be predicted, prolactin was found almost exclusively in the AL, arginine-vasopressin in the NL and alpha-melanotropin in the IL. Over two-thirds of total immunoreactive beta-endorphin was located in the IL and less than 30% was found in the AL. The concentration of dopamine (DA) was greater in the IL than in the NL, but the rate of turnover of the amine was approximately the same suggesting that the basal activity of tuberohypophysial DA neurons is similar in both regions. On the other hand, the turnover of DA in the IL, but not NL, was increased following the administration of a DA antagonist (haloperidol) and decreased following a DA agonist (bromocriptine). Thus, the activity of DA neurons terminating in the IL is regulated, at least in part, by DA receptor-mediated mechanisms and in this regard these neurons resemble DA neurons terminating in the nucleus accumbens and striatum. Since DA turnover in NL was not altered by the administration of haloperidol or bromocriptine it is proposed that these neurons lack DA receptor-mediated regulatory mechanisms and thus resemble tuberoinfundibular DA neurons terminating in the median eminence.

Animals↗
PubMed2005

Sexually dimorphic gene expression in the hypothalamus, pituitary gland, and cortex.

We examined sex differences in the transcriptomes of hypothalamus, pituitary gland, and cortex of male and female mice using serial analysis of gene expression. In total 940,669 tags were sequenced. In hypothalamus, 3 transcripts are differentially expressed by gender, including growth hormone (neuromodulation) and 3beta-hydroxysteroid dehydrogenase-1 (steroidogenesis). In pituitary gland, 43 transcripts are differentially expressed, including RAS guanyl-releasing protein 2 (cell signaling), ornithine transporter (mitochondrial transport), H3 histone family 3B (chromatin structure), heterogeneous nuclear ribonucleoprotein U (chromatin remodeling), NADH dehydrogenase (mitochondrial oxidative phosphorylation), neuronatin (cell differentiation), and ribosomal protein S27a (protein metabolism). EST X (inactive)-specific transcript antisense is expressed at a higher level in the three female organs, whereas growth hormone and NADH dehydrogenase are expressed at higher levels in female cortex. Thus, the current study has characterized key sexual dimorphisms in the transcriptomes of the hypothalamus, pituitary, and cortex.

Animals↗
PubMedDate not supplied

Technical note: removal of the unfragmented pituitary gland (hypophysectomy) in the rat.

A technique to excise the pituitary gland (hypophysis) in rats is described. The basisphenoid bone is reached from the ventral neck and is perforated to expose the pituitary gland and its stalk. An aspirator allows the removal of the hypophysis and the stalk, including pars tuberalis, in one piece. The advantages of this new technique include: 1) immediate verification of the entirety of hypophysectomy; 2) broad operating field which exposes the pituitary stalk up to the hypothalamus; 3) the use of tracheal intubation and artificial respiration to improve postoperative recovery and to allow expanded operation field even during prolonged surgery. Pre- and postoperative care are described. The mean survival rate after this type of operation was 79% in rats weighing 50 to 130 g and 90% in rats larger than 130 g.

Animals↗
PubMed1993

[Dynamic MR imaging of the pituitary gland by the fast spin echo (RARE) sequence].

The Fast Spin Echo (RARE: Rapid Acquisition with Relaxation enhancement) sequence for the dynamic MRI of the pituitary gland was performed in 18 patients suspected of the intracranial lesions. The SNR of the plain image of 5 pituitary glands was measured on the FSE 400 and 200/17/8/2 (TR/effective TE/echo train length/excitation) and the spin echo 100/11/2 (TR/TE/excitation) sequence. The FSE (TR = 400) provided the highest SNR than others, The FSE sequence was able to acquire increased spatial resolution and reduced acquisition time, and was the significant sequence for the dynamic MRI of the pituitary gland.

Adolescent↗
PubMed1987

Immunoelectron microscopic study of corticotropin-releasing factor in the human hypothalamus and pituitary gland.

Ultrastructural localization of immunoreactive corticotropin-releasing factor (CRF) was visualized for the first time in the human hypothalamus and pituitary gland with specific antibodies against human/rat CRF. In the hypothalamus most of the positive immunoreactivity to CRF was present in granules with a wide range of diameters, 50-250 nm, in the perikarya of parvocellular neurons in the paraventricular nucleus. Among these, neurosecretory type granules, 100-150 nm in diameter, were dominant, and small vesicles, 50-80 nm in diameter, were sparse. Some of surfaces of rough endoplasmic reticulum and polyribosomes were also positive in some of these cells. CRF-positive reactions were also observed in the nerve fibers of the pituitary stalk and the posterior pituitary gland revealing two types of granules: small vesicles, 50-80 nm in diameter, and neurosecretory granules, 100-150 nm in diameter. These results support the theory that the human CRF, which is identical to rat CRF, is synthesized in parvocellular neurons of paraventricular nucleus, transported in nerve fibers, and controls ACTH secretion in the human anterior lobe of pituitary gland via the portal system.

Corticotropin-Releasing Hormone↗
PubMed1977

Metabolism of testosterone in the anterior pituitary gland and the central nervous system of the European starling (Sturnus vulgaris).

The metabolism of testosterone was studied in vitro in anterior pituitary, hypothalamic and hyperstriatal tissues taken from male European starlings in the autumn. In all the tissues studied, testosterone was converted into 5alpha-androstan-17beta-ol-3-one (5alpha-DHT), 5beta-androstan-17beta-ol-3-one (5beta-DHT), 5beta-androstane-3alpha,17beta-diol (5beta-THT), 5beta-androstane-3,-17-dione and androst-4-ene-3,17-dione. The 5alpha-DHT was produced in significantly greater amounts by the pituitary gland than by the hypothalamus and hyperstriatum. The amount of 5alpha-DHT produced, however, was very low in comparison with the amounts of 5beta-reduced metabolites. The amount of 5beta-reductase was also higher in the pituitary gland than in the two nervous tissues. The ratios between the production of 5beta-DHT, 5beta-THT and 5beta-androstane-3,17-dione were, however, different in the three tissues: 5beta-DHT was produced in the greatest quantities by the hyperstriatum, while the production of 5beta-THT, 5beta-androstane-3,17-dione and androst-4-ene-3,17-dione was greatest in pituitary tissue. The role of 5alpha- and 5beta-reduced metabolites in the pituitary gland and in the brain of birds is unknown, but some possibilities arising from the present results are discussed.

Androstane-3,17-diol↗
PubMed1997

Effects of ovariectomy and hypothalamic-pituitary disconnection on amounts of steroidogenic factor-1 mRNA in the ovine anterior pituitary gland.

Steroidogenic factor-1 (SF-1) is a transcription factor involved in regulation of steroidogenic enzymes. Recent evidence indicates that SF-1 is also important in the anterior pituitary gland, where it may influence gene expression in gonadotropes. We isolated a cDNA encoding ovine SF-1 and demonstrated that the SF-1 gene is expressed in the anterior pituitary gland of sheep. SF-1 transcripts and luteinizing hormone (LH) were colocalized in gonadotropes by in situ hybridization and immunohistochemistry, respectively. To test the hypothesis that GnRH stimulates pituitary expression of ovine SF-1 mRNA, ewes were ovariectomized to increase endogenous secretion of GnRH. Compared to ovary-intact ewes, ovariectomy resulted in three- and fourfold increases in steady-state amounts of mRNA encoding SF-1 and LH beta subunit, respectively. In ovariectomized ewes in which delivery of GnRH to the anterior pituitary gland was prevented by hypothalamic-pituitary disconnection (HPD), steady-state amounts of mRNA encoding SF-1 and LH beta-subunit were decreased. These results provide evidence that pituitary SF-1 gene expression in sheep is regulated by GnRH. Coordinate regulation of mRNAs encoding SF-1 and LH beta-subunit raises the possibility that SF-1 may be an important transcriptional regulator of LH beta-subunit gene expression in ovine gonadotropes.

Animals↗
PubMed1984

Size, shape, and appearance of the normal female pituitary gland.

One hundred seven women 18-65 years old were studied who were referred for suspected central nervous system disease not related to the pituitary gland or hypothalamus. High-resolution, direct, coronal, contrast-enhanced computed tomography (CT) was used to examine the size, shape, and density of the normal pituitary gland. There were three major conclusions: (1) the height of the normal gland can be as much as 9 mm; (2) the superior margin of the gland may bulge in normal patients; and (3) both large size and convex contour appear to be associated with younger age. It was also found that serum prolactin levels do not appear to correlate with the CT appearances. Both low- and high-density areas were seen within the gland, and may be due to either tumors, cysts, infarcts, or metastases. Noise artifacts inherent in high-detail, thin-section, soft-tissue scanning may be a limiting factor in defining reproducible patterns in different parts of the normal pituitary gland.

Adolescent↗
PubMed1986

Immunohistochemical evidence of progestin target cells in the pituitary gland of ovariectomized rat.

Progestin (P) target cells were identified in the pituitary gland of gonadectomized female rats which had been primed with estrogen (E). P staining was localized using the immunohistochemical avidin-biotin-peroxidase (ABP) complex method. Dark brown precipitates were primarily found over the cytoplasm of cells in the pars distalis, but not in the pars intermedia nor in the pars nervosa. The majority of P-sensitive cells in the pars distalis were identical with luteotrophs, a few being lactotrophs. These observations suggest a role of P in the regulation of production and secretion of gonadotrophins in the pituitary glands of female rats.

Animals↗
PubMed1985

Spontaneous action potentials recorded from the isolated, whole, encapsulated bovine pituitary gland: changes induced by certain physiological agents.

Extracellular spontaneous action potentials (SAP) were recorded from each lobe of the whole, isolated, encapsulated bovine pituitary gland bathed in Ringer's solution and maintained at 37 degrees C. All recordings were made with the gland in a shielded cage. Subdermal electrodes inserted into the various lobes of the gland were attached to a polygraph outside of the cage. Agents: dopamine (DA), norepinephrine (NE), gamma-aminobutyric acid (GABA) and serotonin (5HT) known to induce changes in the frequency and amplitude of the SAP in dissociated pituitary cells were used in this study. Although there are some questions about recording from dissociated pituitary cells in culture, in general, using these agents, there were no major differences in the SAP recorded from either dissociated cells in culture or cells in the whole intact bovine pituitary gland. Since pituitary cells and cells in nervous tissue share a common parentage, a comparative study of the SAP recorded from these cells show that the potentials recorded from cells in nervous tissue, e.g. ganglia, are inconsistent whereas those from pituitary cells show a consistent pattern of activity.

Action Potentials↗
PubMed1987

Physiologically-induced changes in proopiomelanocortin mRNA levels in the pituitary gland of the amphibian Xenopus laevis.

In the pars intermedia of the pituitary gland of the amphibian Xenopus laevis the level of mRNA encoding proopiomelanocortin (POMC), the precursor protein for alpha-melanophore-stimulating hormone (alpha-MSH), is shown to be dependent on physiological parameters. POMC mRNA levels in the pars intermedia of black-background-adapted Xenopus are much higher than those of white-adapted animals. These physiological changes in POMC mRNA levels are tissue-specific because they were not found in the pars distalis of the pituitary gland. Background transfer experiments revealed that modulation of POMC gene activity is much slower than changes in the secretion of alpha-MSH.

Adaptation, Physiological↗
PubMed1984

Constitution and behavior of follicular structures in the human anterior pituitary gland.

The follicular structures present in the human pituitary gland were studied, at the light-microscopic level, using histochemical and immunocytochemical techniques. The antisera applied in the peroxidase-antiperoxidase procedure were anti-hFSH beta, anti-hLH beta, anti-hPRL, anti-hGH, anti-hTSH beta, anti-hLPH beta, anti-pACTH, and anti-hACTH. In the 10 normal pituitaries examined, follicles were always found in the three areas of the adenohypophysis. The wall of the pars distalis follicles showed the seven immunoreactive cell types studied, while follicle-stimulating hormone (FSH) and luteinizing hormone (LH) cells were the only ones present in the wall of the pars tuberalis follicles. Most of the cell types studied were also present in the wall of the intermediate area follicles, but these follicles had characteristics not found in the other two areas. They were very large, with frequent interconnections forming a three-dimensional network of anastomotic cavities, and the colloid had different histochemical affinity. None of the hormones studied could be detected by immunocytochemistry within the follicular colloid. Three of the ten pituitary adenomas examined showed numerous follicular structures. Some of the follicles in the adenomatous pituitaries were similar to those found in the normal adenohypophysis, but there were also follicles filled with only traces of colloid and numerous blood cells in the cavity, and follicles filled with neoformed connective tissue. In one of these cases, FSH/LH immunoreactive adenoma cells were seen in the wall of the follicles. The results obtained suggest that the finding of pituitary adenomas with follicular structures is not uncommon and that the follicles originate from the tumor cells. In addition, the follicles seem to have several functional stages, explaining the finding of different types of follicular formation.

Adenoma↗
PubMedDate not supplied

Common disorders of the pituitary gland: hyposecretion versus hypersecretion.

An understanding of pituitary disorders requires much more than a knowledge of the definitions associated with them. To grasp fully their complexity, one must recognize not only the powerful role the pituitary gland plays in the endocrine system, but also its effects on homeostasis throughout the entire human body, its association with the hypothalamus, and ultimately its associated end organs. Because of the many hormones stored or produced by the pituitary, associated disorders often are confusing and challenging. However, by simplifying the classification of these disorders into the categories of hyposecretion and hypersecretion, the understanding of pituitary disorders is made simple, and the associated interventions become apparent.

Adrenocorticotropic Hormone↗
PubMed1988

Effect of salt loading on proopiomelanocortin (POMC) messenger ribonucleic acid levels, POMC biosynthesis, and secretion of POMC products in the mouse pituitary gland.

The effect of salt loading on POMC-derived peptide secretion, POMC mRNA levels, and POMC biosynthesis in the mouse pituitary gland was investigated. Plasma alpha MSH levels decreased to 56.9% of the control value after 2 days of salt loading. Concomitantly, POMC mRNA levels and POMC biosynthesis in the intermediate lobe decreased to 47.7% and 66.4% of the control value, respectively. After 4 days of salt loading, plasma alpha MSH levels, POMC mRNA, and POMC biosynthesis returned to control levels. ACTH secretion increased to 142.2% of the control value after 2 days of salt loading, but decreased to 73.4% of the control levels after 4 days. After 9 days, ACTH secretion was still low; however, by 12 days, plasma ACTH levels in salt-loaded mice were not significantly different from control levels. POMC mRNA levels in the anterior lobe increased to 205.0% of the control value after 2 days of salt loading, continued to be high after 4 days, but returned to control levels by 9 days. However, POMC biosynthesis was not altered under these conditions during the entire period of salt loading. Thus, POMC mRNA levels and biosynthesis were modulated differently in the intermediate and anterior lobes of the mouse pituitary gland during salt loading.

Adrenocorticotropic Hormone↗
PubMed1995

Effect of hypoglycemic stress on the pars intermedia of the mouse pituitary gland: an ultrastructural analysis.

The present study was made to clarify the relationship between functions of the pars intermedia of the mouse pituitary gland and hypoglycemic stress. Morphometrical analysis of the ultrastructures of the pars intermedia cells showed (1) a rise in the percentage volume of rough endoplasmic reticulum (r-ER) indicative of an increase in protein synthesis, (2) an increase in the number of Golgi granules per unit Golgi area showing an induction of granule-forming activity and (3) a decrease in the numerical density of secretory granules reflecting a release of the secretory granules. These findings suggest that hypoglycemic stress induced by daily treatment with insulin or restriction of food intake was able to elicit heightened secretory activity of the pars intermedia cells of the mouse pituitary gland. However, acute hypoglycemic stress induced by food deprivation did not cytologically affect the pars intermedia. These observations suggest that repeated hypoglycemic stress, rather than acute hypoglycemic stress, may be a natural physiological stimulus of the pars intermedia of the mouse pituitary gland.

Animals↗