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PubMedDate not supplied

Mensuration of the pituitary gland from magnetic resonance images in 17 cats.

The objective of this retrospective study was to estimate using magnetic resonance imaging the size range of the pituitary gland in cats who had no evidence of pituitary disease. The pituitary gland was measured from transverse and sagittal magnetic resonance postgadolinium T1-weighted images in 17 cats. The cats were 0.83 to 15 years of age and weighed between 2.9 and 6.5 kg. Linear pituitary measurements were performed on a dedicated workstation using electronic calipers. Mean (+/- standard deviation) pituitary gland length was 0.54 cm (+/- 0.06 cm) and mean width was 0.50 cm (+/- 0.08 cm). Mean pituitary gland height measured on sagittal images was 0.34 cm (+/- 0.05) and measured on transverse images was 0.32 cm (+/- 0.04 cm). Mean pituitary volume was 0.05 cm3 (+/- 0.01 cm3). There was no significant correlation between cat weight (kg) and pituitary volume or age and pituitary volume. The pituitary gland appearance varied on pre- and postcontrast T1-weighted images. On the precontrast images, the majority of pituitary glands had a mixed signal intensity. On postcontrast images, uniform pituitary gland enhancement was seen commonly.

Animals↗
PubMed2002

Morphological changes on MR imaging of the normal pituitary gland related to age and sex: main emphasis on pubescent females.

The pituitary gland of 300 individuals (ages: 3-85 years; 101 males and 199 females) with no pituitary gland related symptoms were studied using a 1.5-T superconductive magnetic resonance imaging (MRI) unit. The focus of the study was on morphological changes at puberty in females. Among three parameters related to pituitary size, height changed the most remarkably in relation to age and sex, reaching a peak towards the first half of the third decade of a women's life. However, the convex shaped upper pituitary surface was most often recognized in the first half of the second decade. Moreover, in children and adolescents, this shape was predominantly shown by females. A coronal deviation of the stalk attachment to the pituitary gland, which might be indicative of pituitary tumour, was most frequently observed in individuals less than 20 years of age and those over 50. The pituitary size and shape varied, especially with respect to height, likely in response to changes in the hormonal environment. Hence, care must be taken when evaluating the size of the pituitary gland by MRI, especially in the diagnosis of pituitary tumour.

Adolescent↗
PubMed1986

Melatonin's differential inhibition of FSH and LH release from hamster pituitary glands.

Melatonin initially inhibited FSH secretion from superfused adult male hamster anterior pituitary glands obtained at 8:30 a.m. However, there was a gradual rebound during melatonin superfusion followed by an overshoot above baseline when melatonin was discontinued (morning response). Melatonin continuously inhibited FSH secretion during superfusion of hamster anterior pituitary glands obtained at 3:30 p.m., with a rebound evident only when melatonin was withdrawn (afternoon response). Melatonin continuously inhibited LH secretion from these superfused pituitaries, with a return to baseline levels only upon melatonin withdrawal. Prior pinealectomy or constant light could reverse the FSH morning response to an afternoon response, and late-morning melatonin injections could reverse the FSH afternoon response to a morning response. Neither prior pinealectomy, constant light nor melatonin injections affected melatonin inhibition of LH secretion from superfused pituitary glands. These results suggest that melatonin differentially inhibits FSH and LH secretion from isolated superfused hamster anterior pituitary glands.

Animals↗
PubMed1994

Pituitary gland changes in canine hypoadrenocorticism: a functional and immunocytochemical study.

Pituitary gland changes were evaluated immunocytochemically in three dogs with primary hypoadrenocorticism (HAC) and one dog with secondary HAC and related to the clinical, endocrinological and pathological findings. In primary HAC, the adrenocorticotrophic hormone (ACTH) immunoreactivity was increased in the pars distalis of the pituitary gland and all cortical layers of the adrenal gland were severely atrophied. This increase would be expected to reflect a high level of ACTH synthesis in the corticotrophs due to a lack of negative cortisol feed-back. In contrast, in the dog with secondary HAC the ACTH immunoreactivity was decreased in the pituitary gland, the basal plasma ACTH concentration was low and the zona fasciculata and reticularis were atrophied, but the zona glomerulosa was well preserved. These findings are consistent with a diminished synthesis of ACTH. Thus, pituitary gland changes differ in primary and secondary HAC and are consistent with the clinical, endocrinological and histopathological findings.

Adrenal Cortex Diseases↗
PubMed1986

Microtubules are mobilized in the lactating rat anterior pituitary gland during suckling.

Microtubules in the lactating rat anterior pituitary gland were depolymerized into their constituent tubulin dimers by exposure of the pituitary to 4 C. The tubulin then was quantified with the [3H]colchicine binding assay, which was adapted for use with individual rat pituitary glands. The binding of [3H]colchicine to the tubulin fraction contained in high speed supernatants of lactating rat pituitary glands proved to be specific and saturable, and was pH, temperature, and time dependent. The amount of [3H]colchicine bound was linear over the range of protein concentrations tested (2-22 micrograms). To determine whether suckling affected the levels of microtubules in the anterior pituitary, tubulin levels were measured in groups of lactating rats after they were suckled (six pups per litter) for 0, 5, 10, 15, and 30 min following 4-5 h of nonsuckling. The tubulin concentration in the anterior pituitary progressively increased from 4 to 22 mumol during the 30 min of suckling; the increase was statistically significant (P less than 0.05) by the 10th min. Plasma PRL levels analyzed from trunk blood rose from 5 to 75 ng/ml during the 30-min suckling period. These results indicate that a mobilization of microtubules occurs in the anterior pituitary at the same time that PRL is being transformed and released into the circulation.

Animals↗
PubMedDate not supplied

Normal pituitary gland: 1. Macroscopic anatomy-CT correlation.

To improve the radiologic recognition of pituitary microadenomas that have subtle or no mass effect, the appearance of the normal pituitary gland on computed tomographic (CT) images was studied. Thirteen autopsy specimens of the pituitary gland and sella turcica were examined by coronal CT and histologically sectioned in similar coronal planes. The CT and histologic findings were correlated, then compared with the coronal CT images of 30 normal pituitary glands in vivo, most of which were contrast-enhanced. The normal pituitary gland had a nonhomogeneous CT appearance with a variety of frequently predictable patterns. This heterogeneity was in part the result of gross anatomic structural interrelations between the anterior lobe, para intermedia, and posterior lobe.

Adenoma↗
PubMed2000

Sex steroid influence on cannabinoid CB(1) receptor mRNA and endocannabinoid levels in the anterior pituitary gland.

Recent studies have demonstrated the occurrence of endocannabinoid synthesis and of gene expression and immunoreactivity for the cannabinoid CB(1) receptor in the anterior pituitary gland. Since the activity of this gland is under the influence of circulating sex steroids, the present study was designed to elucidate whether expression of the CB(1) receptor gene in the anterior pituitary gland is also under the influence of these steroids. To this aim, we first examined the possible changes in the levels of CB(1) receptor-mRNA transcripts in the anterior pituitary gland of intact male rats and normal cycling female rats at the different stages of the ovarian cycle. We observed that males had higher levels of CB(1) receptor-mRNA transcripts than females. In addition, these transcripts fluctuated in females during the different phases of the ovarian cycle, with the highest values observed on the second day of diestrus and the lowest on estrus. In these animals, we also measured the content of endocannabinoids in the anterior pituitary gland and the hypothalamus. We observed that females had higher contents of anandamide than males in both cases. The content of anandamide in females also fluctuated during the ovarian cycle in both the anterior pituitary gland and the hypothalamus. The highest values in the anterior pituitary gland were found in the estrus and the lowest on the first day of diestrus and proestrus, whereas the inverse tendency was found in the hypothalamus. No changes were observed in the other major endocannabinoid, 2-arachidonoyl-glycerol, between males and females and during the ovarian cycle. To further explore the potential influence of circulating sex steroids on CB(1) receptor gene expression in the anterior pituitary gland, as a second objective, we examined the possible changes in the amount of transcripts for this receptor in gonadectomized and sex steroid-replaced gonadectomized rats of both sexes. We observed that orchidectomy (ORCHX) in males reduced CB(1) receptor-mRNA levels, whereas replacement with dihydrotestosterone also maintained low levels of this messenger. In females, estradiol-replaced ovariectomized (OVX) rats exhibited significantly lower CB(1) receptor-mRNA levels than OVX animals that had not been replaced with this estrogen. In this experiment, we also examined if the previously reported response of the CB(1) receptor gene in the anterior pituitary lobe to chronic administration of Delta(9)-tetrahydrocannabinol (Delta(9)-THC) is under sex steroid influence. We observed that chronic Delta(9)-THC treatment decreased CB(1) receptor-mRNA levels in intact and ORCHX males, but not in dihydrotestosterone-replaced ORCHX males. In females, Delta(9)-THC treatment produced no effect in both OVX- and estradiol-replaced OVX rats. In summary, these data collectively support that expression of the CB(1) receptor gene in the anterior pituitary gland is regulated by sex steroids in both males and females. Furthermore, gonadal steroids appear to affect the response of this gene to chronic cannabinoid administration. We have also observed that anandamide contents in the anterior pituitary gland and the hypothalamus might be controlled by circulating sex steroids. The functional implications of these data are discussed.

Animals↗
PubMed1992

The pituitary gland in patients with breast carcinoma: a histologic and immunocytochemical study of 125 cases.

Pituitary glands obtained at autopsy of 125 women with disseminated breast carcinoma were studied to determine whether pituitary prolactin cell abnormalities (hyperplasia or adenoma) might be involved in the pathogenesis of breast carcinoma. In addition, we studied 85 pituitary glands obtained from unselected, consecutive autopsies in women without breast carcinoma but who died of other diseases (control group). The frequency of lactotroph hyperplasia was slightly higher in patients with breast carcinoma than in the control group, but the difference was not statistically significant, nor were differences in the frequency and size of pituitary adenomas, prolactin-producing or otherwise. No correlation was found between the presence of lactotroph hyperplasia or prolactin-producing adenomas (or both) and such factors as the patient's age, bilaterality of the carcinoma, previous treatment with tamoxifen citrate or oophorectomy, stage of disease, or survival. The frequency of breast carcinoma metastatic to the pituitary gland was higher in the study group than in the control group; however, the difference was not statistically significant. No preferential site of metastatic involvement in the pituitary gland was noted. Relative proportions of other lesions such as infarcts, cysts, lymphocytic infiltrates, and basophilic invasion were similar in the study and control groups. This study indicates that accumulation of prolactin cells, whether hyperplastic or adenomatous, cannot be considered a major risk factor for the genesis or progression of breast carcinoma.

Adenoma↗
PubMed1999

The structure and function of folliculo-stellate cells in the anterior pituitary gland.

The folliculo-stellate cells (FS cells) in the anterior pituitary gland are characterized by their star-like appearance and their ability to form follicles. Although FS cells do not produce any pituitary hormones, their special tendency to surrounding endocrine cells with their long cytoplasmic processes suggests that they regulate endocrine cells by intercellular communication. In spite of many morphological and cytophysiological studies recently performed, a precise understanding of the major functions of FS cells in the pituitary gland remains obscure. We review here the morphological characteristics of FS cells and their suspected functions in the anterior pituitary gland. It is well established that the FS cell produces many kinds of growth factors, i.e., fibroblast growth factor, vascular endothelial cell growth factor and interleukin 6. The biological significances of these growth factors in the anterior pituitary gland are also discussed in this paper. The origin and differentiation of FS cells, especially the possibility that the FS cell is a kind of stem cell which has the potential to differentiate into endocrine cells, is also presented.

Animals↗
PubMed1985

Age-related changes in prolactin and growth hormone release from pituitary glands in vitro.

The basal release of prolactin from cockerel anterior pituitary glands in vitro declined between 1 and 7 weeks of age, to a level less than that released by pituitary glands from 18 week old (adult) cockerels and hens. Basal growth hormone (GH) release increased between 1 and 7 weeks of age but had declined in adults to a level similar to that released from 4 weeks old cockerels. The responsiveness of the pituitary gland to hypothalamic stimulation, using hypothalami from 8 week old broiler fowl, was also age-related. Prolactin release was considerably higher from pituitaries of 1 week old cockerels compared to the other age groups. Stimulation of GH release by the hypothalamus was higher from pituitaries of both 1 and 7 week old cockerels compared to the other groups of birds. The increase in release of prolactin following incubation with thyrotrophin releasing hormone (TRH) declined between 1 and 7 weeks, but increased slightly in adult birds, whereas the increase in release of GH following TRH was higher from pituitaries of both 1 and 7 week old cockerels. Hypothalamic prolactin (Prl) releasing activity, measured as the ability of the hypothalamus to stimulate hormone release from 8 week old broiler fowl anterior pituitary glands, declined with the age of the donor cockerels. The hypothalami from adult hens secreted significantly more Prl releasing activity than did adult cockerel hypothalami. The secretion of GH releasing activity decreased markedly with the age of the donor bird. These results suggest that maturational patterns of hormone secretion in fowl are partly due to changes in autonomous hormone release, to changing patterns of hypothalamic activity and to differences in pituitary responsiveness to provocative stimuli.

Age Factors↗
PubMed1984

Estradiol feedback effects on the alpha-subunit mRNA in the sheep pituitary gland: correlation with serum and pituitary luteinizing hormone concentrations.

The effects of estradiol feedback on pituitary luteinizing hormone (LH) content, serum LH concentration, and in vitro-translated alpha subunit was examined in the ewe. Three animal models were used representing positive, negative, and no estradiol feedback. Two experiments were carried out: (i) anestrous ewes were treated acutely with five Silastic estradiol implants to induce a LH surge (positive feedback) and (ii) ovariectomized ewes were treated chronically with an estradiol implant (negative feedback) or were not treated (no feedback). Pituitary RNA was prepared and translated in a cell-free system; the alpha subunit was identified by immunoprecipitation and NaDodSO4/PAGE. cpm/microgram of RNA and immunoprecipitated growth hormone and prolactin were used to evaluate possible differences in RNA translational efficiencies among the treatment groups. In experiment 1, significantly higher amounts of the alpha subunit were observed in animals exhibiting an estradiol-induced LH surge than in normal anestrous ewes (P less than 0.001). Examination of values from individual animals suggested a correlation between the stage of the LH surge, pituitary LH, and translated alpha subunit. In experiment 2, the amount of alpha subunit observed in animals exposed to chronic estradiol negative feedback was significantly less (P less than 0.005) than that in the untreated ovariectomized animals (no feedback) and no different from that in intact anestrous ewes. These results suggest that both the negative and the positive feedback effects of estradiol include regulation of the amount of alpha-subunit mRNA.

Animals↗