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At least 793 records · Page 44Linked to original sources
PubMed2006

17 beta-estradiol modifies nitric oxide-sensitive guanylyl cyclase expression and down-regulates its activity in rat anterior pituitary gland.

Previous studies showed that 17 beta-estradiol (17 beta-E2) regulates the nitric oxide (NO)/soluble guanylyl cyclase (sGC)/cGMP pathway in many tissues. Evidence from our laboratory indicates that 17 beta-E2 disrupts the inhibitory effect of NO on prolactin release, decreasing sGC activity and affecting the cGMP pathway in anterior pituitary gland of adult ovariectomized and estrogenized rats. To ascertain the mechanisms by which 17 beta-E2 affects sGC activity, we investigated the in vivo and in vitro effects of 17 beta-E2 on sGC protein and mRNA expression in anterior pituitary gland from immature female rats. In the present work, we showed that 17 beta-E2 acute treatment exerted opposite effects on the two sGC subunits, increasing alpha1 and decreasing beta1 subunit protein and mRNA expression. This action on sGC protein expression was maximal 6-9 h after 17 beta-E2 administration. 17beta-E2 also caused the same effect on mRNA expression at earlier times. Concomitantly, 17 beta-E2 dramatically decreased sGC activity 6 and 9 h after injection. These effects were specific of 17 beta-E2, because they were not observed with the administration of other steroids such as progesterone and 17 alpha-estradiol. This inhibitory action of 17beta-E2 on sGC also required the activation of estrogen receptor (ER), because treatment with the pure ER antagonist ICI 182,780 completely blocked 17 beta-E2 action. 17 beta-E2 acute treatment caused the same effects on pituitary cells in culture. These results suggest that 17 beta-E2 exerts an acute inhibitory effect on sGC in anterior pituitary gland by down-regulating sGC beta 1 subunit and sGC activity in a specific, ER-dependent manner.

Animals↗
PubMed2000

Characterization and distribution of gonadotrophs in the pars distalis and pars tuberalis of the equine pituitary gland during the estrous cycle and seasonal anestrus.

Little is known about the neuroendocrine control of fertility in the horse. In this species, unusual features characterize the normal estrous cycle such as a prolonged preovulatory LH surge during the follicular phase and a distinctive FSH surge during the midluteal phase. This study investigated the distribution and hormonal identity of gonadotrophs in the pars distalis (PD) and pars tuberalis (PT) of the equine pituitary gland as possible morphological bases for the referred unusual endocrine characteristics. In addition, the proportion of gonadotrophs in relation to other pituitary cell types during both the estrous cycle and anestrus were investigated. Pituitary glands were collected from sexually active (n = 5) and seasonally anestrous (n = 5) mares in November, and single or double immunofluorescent staining was carried out on 6-microm sections using monoclonal antibodies to the LHbeta or FSHbeta subunits and a polyclonal antibody to ovine LHbeta. Gonadotrophs were densely distributed around the pars intermedia in the PD and in the caudal ventral region of the PT. In addition to isolated cells, clusters of gonadotrophs were found surrounding the capillaries. No significant differences were detected in the number of gonadotrophs between sexually active and anestrous mares in either the PD or PT. In the PD, gonadotrophs represented 22.7 +/- 5. 8% and 19.1 +/- 2.1% of the total cell density in sexually active and anestrous animals, respectively (P: > 0.05). However, in the PT, gonadotrophs accounted for a higher proportion of the total cell population in sexually active (6 +/- 0.1%) than in anestrous (1.2 +/- 0.05%) mares (P: < 0.02). Double immunofluorescence revealed that the majority of gonadotrophs were bihormonal (i.e., positive for LH and FSH); however, in the sexually active mare, a larger proportion of gonadotrophs (22.5 +/- 3.6%) were monohormonal for either LH or FSH, when compared to anestrous animals (9.7 +/- 1.2%; P: < 0.02). Based on these findings we conclude that: 1) although the relative distribution of gonadotrophs is similar to those reported for other species, a significantly larger proportion of gonadotroph cells is present in the equine pituitary gland; 2) gonadotroph density does not appear to differ between sexually active and anestrous mares in the PD; 3) a larger proportion of gonadotrophs is apparent in the PT of sexually active animals; and 4) although a large incidence of bihormonal gonadotrophs is present in the horse, specific LH or FSH cells differentiate predominantly during the sexually active phase.

Anestrus↗
PubMed2000

[Pituitary gland MRI and Cushing disease: report of 14 operated patients].

PURPOSE: Evaluate the MR sensibility for detection and localisation of ACTH-secreting microadenomas of the pituitary gland. PATIENTS: and method. The MRI studies of the pituitary gland, performed before transsphenoidal surgical exploration, about 14 patients who present clinical and biological signs of Cushing disease, were reviewed retrospectively. We have always used unenhanced sagittal and coronal spin-echo T1 sequences, and coronal T1 after injection of gadolinium (1 Tesla). RESULTS: The global sensibility for detection of an adenoma was 100% (84 to 92% when the lesional localisation was considered). The injection of gadolinium increased the sensibility of 38 to 42% according the readers. 7 to 14% of the lesions were isointense after injection. The estimation of lesional size after injection was the nearer to the surgical results. The indirect sign most frequently seen (35.7 to 64.3%) was focal bulging of the sellar diaphragm. The only differences between the different radiologists, statistically significant, concerned the lesional size before injection and location of the lesion in the sagittal plane. CONCLUSION: This study confirmed the good sensibility of contrast-enhanced MRI in detection of ACTH-secreting microadenomas. The anatomo-radiological correlations are nevertheless incomplete.

Adult↗
PubMed1986

High resolution CT scanning of the pituitary gland in growth disorders.

We have performed 217 GEC 8800 CT scans of the hypothalamus and pituitary glands of 202 children with disorders of growth and development. Pituitary morphological abnormalities were common. Intrapituitary low density lesions were found in 17% of the whole series and in 58% of children with tall stature. Seventy-seven children with idiopathic growth hormone deficiency could be divided on the basis of pituitary morphology seen on CT scan into pituitary aplasia (n = 11) and pituitary hypoplasia (n = 53). Patients with pituitary aplasia had an absent adenohypophysis which probably dated from early intrauterine life and therefore could not be related to birth trauma. We have found a high incidence of evolving endocrinopathy in children with pituitary insufficiency: thus, if a short child is investigated the initial endocrine findings need to be repeated as the pattern of pituitary insufficiency changes with time. An evolving endocrinopathy starting in later childhood is suggestive of the presence of a cerebral tumour. Children with subnormal growth velocities and a normal growth hormone response to pharmacological tests have a wide spectrum of pituitary morphological abnormalities which may be associated with growth hormone neurosecretory dysfunction.

Adolescent↗
PubMed1977

Pituitary gland of a hillstream sisorid catfish, Pseudecheneis sulcatus (McClelland).

Pituitary gland of a hillstream sisorid catfish, Pseudecheneis sulcatus has been studied light microscopically. The pituitary is suspended from the hypothalamus by a slender infundibular stalk which enters the gland antero-dorsally, giving rise to the dorso-elptobasic condition. The pituitary is demarcated into pars nervosa, rostral pars distalis, proximal pars distalis and pars intermedia regions. Pars nervosa is formed of neurosecretory fibres which ramify extensively in the pars intermedia. The rostral pars distalis has predominantly acidophils which are arranged in rosettes. Proximal pars distalis has cyanophils, acidophils and few chromophobes while only acidophils and cyanophils are present in the pars intermedia. Sparse cyanophils and chromophobes are also present in the rostral pars distalis. The acidophils of proximal pars distalis are of two types which differ in tinctorial and morphological characteristics, from the acidophils of rostral pars distalis. The cyanophils are positively stained with AF, AT, PAS and aniline blue.

Animals↗
PubMed1995

Ultrastructural modifications and changes in the expression of hormonal genes produced by indomethacin in the anterior pituitary gland of the rat.

Indomethacin decreases the level of prolactin (50%) and growth hormone (70%) mRNA in the anterior pituitary gland of the rat. Actin mRNA increases (59%). Ultrastructurally there is a decrease in the number of secretory granules. Indomethacin also prevents the increase in prolactin secretory granules produced by the administration of estradiol. The results indicate that indomethacin inhibits hormonal synthesis in the APG at a transcriptional level. This effect appears selective because mRNA level for actin synthesis in the pituitary gland was higher than in nontreated rats.

Actins↗
PubMed1975

The effect of the chronic administration of D-amphetamine upon circadian changes in amino acids in the pineal and pituitary glands of the rat.

The formation of dansyl derivatives of amino acids, 5-hydroxyindoleacetic acid and histamine, and their separation on polyamide plates provided a reliable and sensitive method for studying circadian changes in single pineal and pituitary glands of the rat. There appears to be no correlation between the circadian changes in concentrations of these substances in the pineal and pituitary glands. Chronically administered D-amphetamine altered the circadian rhythms of five amino acids in the pituitary, including the putative transmitters taurine, glycine, and glutamate; in the pineal gland only the rhythmical changes of lysine and 5-hydroxyindoleacetic acid were affected.

Amino Acids↗
PubMed2004

Regulation of mouse spermatogonial stem cell self-renewing division by the pituitary gland.

Spermatogenesis originates in spermatogonial stem cells, which have the unique mode of replication. It is considered that a single stem cell can produce two stem cells (self-renewing division), one stem and one differentiating (asymmetric division), or two differentiating cells (differentiating division). However, little is known regarding how each type of division is regulated. In this investigation, we focused on the analysis of self- renewing division and examined the effect of the pituitary gland using two models of stem cell self-renewing division. In the first experiment using newborn mice, the administration of GnRH- analogue, which represses the release of gonadotropin, reduced the number of stem cells during postnatal testicular development, suggesting that the pituitary gland enhances stem cell self- renewing division. In the second experiment, however, the number of stem cells increased dramatically in hypophysectomized adult recipients after spermatogonial transplantation. Thus, the pituitary gland affects the self-renewing division of stem cells, but these contradictory results suggest that its role may be different depending on the stage of the testicular development.

Animals↗
PubMed1975

Characteristics of action of prostaglandins on cyclic AMP accumulation in rat anterior pituitary gland.

Prostaglandins (PGs) were found to lead to a marked stimulation of cyclic AMP accumulation in rat anterior pituitary gland in vitro in the following decreasing order of potency: PG E-1 E-2 GREATER THAN A-1 A-I GREATER THAN F-1ALPHA F-2ALPHA. The effect of PGs is potentiated by theophylline. The stimulatory effect of PGs on cyclic AMP accumulation is already detected 2min after the addition of 1-x 10-7 to 1-x 10-6 M PG E-2 and its maximal effect is reached after approximated 30 min of incubation, with a progressive decrease toward basal cyclic AMP levels at later time intervals. Increased intracellular cyclic AMP concentrations are accompanied by an increased release of the nucleotide into incubation medium. Complete removal of Ca-e+ from the incubation medium by addition of EGTA was found to increase the stimulatory effect of PG E-2 ON CYCLIC AMP accumulation. The action of PGs on hormonal release and cyclic AMP accumulation support the hypothesis of a role of PGs in the mechanism of anterior pituitary hormone (particularly growth hormone) release.

Animals↗