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At least 1,045 records · Page 58Linked to original sources
PubMed1986

Relationship between release of LH and incorporation of tritiated thymidine in the anterior pituitary gland of the castrated male rat: effect of LHRH and its highly active analogue buserelin.

Castration of the adult male rat significantly (P less than 0.01) increased the concentration of LH in serum and the incorporation of (3H) thymidine into the pituitary DNA. The administration of a single dose of LHRH or its analogue buserelin stimulated the release of LH but it did not modify (3H) thymidine incorporation. When multiple doses of LHRH or buserelin were injected, there was a significant (P less than 0.01) inhibition of LH release and also the incorporation of (3H) thymidine into the DNA of the anterior pituitary gland was significantly (P less than 0.01) diminished. These observations are compatible with the idea of the close relationship between hormonal release and DNA synthesis in the anterior pituitary gland of the rat.

Animals↗
PubMed1992

Evidence for neuromedin-B synthesis in the rat anterior pituitary gland.

Neuromedin-B shows a widespread distribution throughout mammalian neural and peripheral tissues and may be involved in the modulation of a variety of physiological processes. The highest concentrations of neuromedin-B are found in the anterior pituitary gland, suggesting that it may be of physiological importance within this tissue. To examine this hypothesis, we have used Northern blotting to demonstrate that neuromedin-B is present in the anterior pituitary as a result of local synthesis and have examined the effects of endocrine manipulations on its mRNA and immunoreactive peptide content. In thyroidectomized male rats, neuromedin-B content was decreased (104.1 +/- 5.8 vs. control, 390.9 +/- 23.3 fmol/gland; P less than 0.01) as was its mRNA (7 +/- 1.3% vs. 100%; P less than 0.014), while treatment of intact animals with T4 produced no effect on either peptide content or mRNA. Adrenalectomized male rats showed a significant increase in both neuromedin-B content (313.8 +/- 11.8 vs. control, 233.7 +/- 16.9 fmol/gland; P less than 0.05) and mRNA (377 +/- 27% vs. 100%; P less than 0.014), while dexamethasone treatment increased peptide content (347.8 +/- 32 vs. control, 233.7 +/- 16.9 fmol/gland; P less than 0.01) without any effect on mRNA levels. In female rats, ovariectomy decreased neuromedin-B content (132.4 +/- 13.3 vs. control, 335.0 +/- 37.2 fmol/gland; P less than 0.01) and mRNA levels (6 +/- 2% vs. 100%; P less than 0.014) while estrogen treatment of both ovariectomized and intact rats produced large increases in neuromedin-B (887.8 +/- 114.4 and 1328 +/- 175 fmol/gland, respectively, vs. control, 335.0 +/- 37.2 fmol/gland; both P less than 0.01) and its mRNA (246 +/- 18% and 378 +/- 31%, respectively, vs. 100%; both P less than 0.014). In castrated male rats, no significant alteration in peptide content was observed, and treatment of both castrated and intact male rats with testosterone was similarly without effect. These results demonstrate that 1) neuromedin-B is locally synthesized within the rat anterior pituitary gland; and 2) the local production of neuromedin-B is influenced by endocrine status, which is consistent with an autocrine/paracrine role for this peptide in this tissue.

Animals↗
PubMed1984

Substances resembling C-terminal vasopressin fragments are present in the brain but not in the pituitary gland.

In order to investigate the endogenous occurrence of vasopressin fragments that have previously been found to be generated in vitro by brain peptidases and to have highly potent central activity, extracts of hypothalamus, hippocampus and the pituitary gland were fractionated by high pressure liquid chromatography and analyzed by radioimmunoassay systems with different specificities. Substances that were immunologically and chromatographically similar to synthetic C-terminal vasopressin fragments were detected in brain tissue in different amounts, but were virtually absent in the pituitary gland. It is suggested that these components may represent endogenous vasopressin metabolites. The preferential presence in brain supports a selectively central function of these peptides.

Arginine Vasopressin↗
PubMed1988

Neither the pituitary gland nor the sympathetic nervous system is responsible for eliciting the large drop in elevated rat pineal melatonin levels due to swimming.

Since the pineal gland is an end organ of the sympathetic nervous system, stress might increase the synthesis of its hormone, melatonin. The stress of a 10 min swim, which elicits a marked rise in circulating catecholamines, causes a dramatic depression of high pineal melatonin levels at night within 15 min after swimming onset. N-acetyltransferase (NAT) activity is unaffected by the treatment at 15 or 30 min after swimming onset. Within 90 min after initiation of a 15 min swim, high nighttime pineal melatonin levels are restored while NAT values remain elevated. The swimming-induced reduction in high pineal melatonin levels is not influenced by either hypophysectomy, superior cervical ganglionectomy, prazosin (alpha 1-adrenergic receptor blocker) pretreatment, yohimbine (alpha 2-adrenergic receptor blocker) pretreatment, or reserpine (amine depletor) pretreatment. These results indicate that neither hormones secreted from the pituitary gland nor catecholamines secreted from the sympathetic nerves are involved in eliciting the dramatic reduction in elevated pineal melatonin levels in the rat.

Animals↗
PubMed1994

MR imaging diagnosis of central precocious puberty: importance of changes in the shape and size of the pituitary gland.

OBJECTIVE: Central precocious puberty occurs as a result of premature pituitary stimulation and increased secretion of gonadotropins. The aims of this study were to analyze MR imaging findings in the pituitary glands of children with central precocious puberty compared with matched control subjects, to define MR imaging-derived variables useful in the diagnosis of central precocious puberty, and to correlate MR imaging-derived variables with the hormonal profile and other imaging and clinical findings. MATERIALS AND METHODS: Twenty-six children with central precocious puberty (two boys and 24 girls) were divided into two subgroups according to MR imaging findings: idiopathic (21 patients) and nonidiopathic (five patients: three hypothalamic hamartomas, one pineal tumor, one empty sella syndrome). The control group consisted of 17 normal age- and sex-matched children (two boys, 15 girls). Analyzed parameters included pituitary height, length, width, midsagittal cross-sectional area, calculated volume, and shape. The shape was assessed by a pituitary grading system and two other shape indexes (length-to-height and length-to-width ratios). Pituitary grade was defined by the concavity of the upper pituitary surface (grade 1 = marked concavity, grade 2 = mild concavity, grade 3 = flat, grade 4 = mild convexity, grade 5 = marked convexity). RESULTS: Pituitary grade showed a highly significant difference among groups (p < .001). Area, height, and length-to-height ratio were significantly different (p < .05), whereas length, width, length-to-width ratio, and volume were not. There was no significant difference in any of the variables compared between idiopathic and nonidiopathic groups. When selected variables (pituitary grade, area, height, length) in the central precocious puberty group were stratified by bone age and findings on pelvic sonograms, patients with advanced bone age had a significantly higher pituitary grade (p < .01) and had a tendency toward a greater pituitary length. Pituitary size and shape correlated with the hormonal profile. CONCLUSION: Change in pituitary grade is the most helpful variable for the diagnosis of central precocious puberty in a prepubertal child. A high pituitary grade (4 or above) is highly predictive of central precocious puberty, with the highest specificity and positive predictive value, but with low sensitivity. The use of combinations of high pituitary grade with two other positive findings (height and area greater than 1 SD from the respective means in the control group) improves the sensitivity, specificity, and predictive value of MR imaging in the diagnosis of central precocious puberty.

Analysis of Variance↗
PubMed1996

Contrast-enhanced MRI of intrasellar arachnoid cysts: relationship between the pituitary gland and cyst.

We recently encountered two large intrasellar arachnoid cysts extending to the suprasellar region. The intensity of the cyst contents was identical to that of the cerebrospinal fluid on both T1- and T2- weighted MRI. On contrast-enhanced MRI, the pituitary gland was compressed posteroinferiorly and flattened in the sella turcica. In this report of rare intrasellar arachnoid cysts the discussion is focused on dislocation of the pituitary gland.

Arachnoid Cysts↗
PubMed1985

Effects of putative neurotransmitters on release of prolactin from pituitary glands of the domestic fowl co-incubated with hypothalamic tissue.

Pituitary glands and hypothalami from broiler fowl heads were incubated alone or together with histamine, gamma-aminobutyric acid (GABA) or acetylcholine (ACh) as well as with catecholamines or neurotransmitter antagonists. Histamine and ACh stimulated, whereas GABA inhibited, the hypothalamus-induced release of prolactin, responses blocked by their specific antagonists. The dopamine antagonist pimozide, but not adrenergic (both alpha and beta), serotoninergic or cholinergic antagonists, prevented the actions of histamine and GABA. None of the antagonists except the cholinergic blocker, atropine, affected ACh-induced release of prolactin. Neither histamine nor ACh prevented inhibition of prolactin release by dopamine or stimulation of prolactin release by noradrenaline. GABA did not affect the response to noradrenaline. Furthermore, histamine, GABA and ACh had no effects on thyrotrophin releasing hormone-stimulated release of prolactin directly at the pituitary level. These results suggest that histamine and GABA affect prolactin release from chicken pituitaries in vivo by modifying the activity of the dopaminergic system. Acetylcholine may stimulate the secretion of prolactin releasing factor from the hypothalamus.

Acetylcholine↗
PubMed1982

Biosynthesis of two structurally different pro-opiomelanocortins in the pars intermedia of the amphibian pituitary gland.

This study reports the biosynthesis of two forms of pro-opiomelanocortin in the pars intermedia of the pituitary gland of the African clawed toad Xenopus laevis. The two forms could be resolved by dodecyl sulphate gel electrophoresis on a 9-16% acrylamide gradient and their molecular weights were 38200 and 37300. Incubation of neurointermediate lobes with [3H]glucosamine followed by tryptic digestion of the newly synthesized glycoproteins, revealed that both prohormones have only one glycosylated site, namely within the region corresponding to gamma 3-melanotropin. Biosynthesis of proteins in lobes treated with tunicamycin to prevent glycosylation again resulted in the production of two pro-opiomelanocortins (Mr 35000 and 34200), indicating that the two forms differ in their primary structure. This notion was corroborated by the results of tryptic mapping of the newly synthesized prohormones. The maps showed that the primary structures of the two forms of pro-opiomelanocortin differ in at least two parts of the molecules, one part concerning the endorphin region.

Animals↗
PubMed1997

Synaptophysin immunoreactivity in the aging rat pituitary gland.

The density of synaptophysin (SN)-immunoreactivity (IR) was examined in pituitary glands of aging male Sprague-Dawley rats. SN-IR was observed as dense dots among endocrine cells of the intermediate lobe, while the neural lobe contained numerous, highly dense immunopositive regions. Some anterior lobe secretory cells contained SN-IR within the cytoplasm, suggestive of the presence of the protein in secretory granules, but no dot-like staining was observed between endocrine cells of that region. A quantitative analysis of the dot-like SN-immunostaining within the intermediate lobe found that tissue from groups of rats aged 13 months, or 15-17 months, contained significantly fewer SN-immunopositive areas than did tissues from 8-month-old animals. Diminished SN immunostaining is suggestive of reduced numbers of synapses in the intermediate lobe, which may lead to alterations in regulation of pituitary hormone secretion from endocrine cells in the older animals.

Aging↗
PubMed1988

Isolation and characterization of growth hormone from blue fox pituitary glands.

Growth hormone has been purified to homogeneity from blue fox pituitary glands. It has 191 amino acids with two disulfide bridges and a single tryptophan residue. The somatotropin activity is only 8% when compared with the bovine hormone in the receptor-binding assay. From radioimmunoassay data using baboon antisera to porcine or bovine growth hormone, the fox hormone has 14-17% immunoreactivity of bovine or porcine hormone.

Amino Acid Sequence↗
PubMedDate not supplied

Pituitary gland. Variable signal intensities on MRI. A pictorial essay.

The anterior pituitary gland may exhibit high signal on T1-weighted (T1w) images and/or low signal on T2-weighted (T2w) images in several normal and pathological states. High T1w signal may be seen in normal fetuses, neonates, and in pregnant and postpartum women. It may also occur in Rathke's cleft cyst, craniopharyngioma, subacute hemorrhage, manganese deposition, melanoma, dermoid, and lipoma. Low T2w signal may be seen in hemorrhage, calcification, cystic lesion, hemochromatosis, melanoma, and vascular lesions. These are described and illustrated.

Adult↗
PubMed1984

Identification of the progesterone target cells in the female baboon pituitary gland.

The identification of target cells for progesterone was conducted on pituitary glands obtained from long-term ovariectomized and adrenalectomized female baboons that had been injected with 3H-ORG 2058 (16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione; Amersham Corp). Binding sites were localized using autoradiography alone or in conjunction with immunocytochemistry. The synthetic progestin was primarily found over nuclei of cells in the pars distalis and pars intermedia, although a small population of pituicytes also bound the 3H-ORG 2058. The majority of steroid-sensitive cells in the pars distalis were gonadotrophs. These observations suggest a role for progesterone in the regulation of not only the gonadotropins but also those hormones secreted by the cells of the pars intermedia.

Animals↗
PubMed1980

Isolation and amino acid sequence of gamma-lipotropin from human pituitary glands.

gamma-Lipotropin has been purified to homogeneity from human pituitary glands. It consists of 56 amino acids with one residue each of Trp, Thr, Val, Tyr, and Phe. The amino acid sequence has been determined as follows: H-Glu-Leu-Thr-Gly-Gln-Arg-Leu-Arg-Gln-Gly-Asp-Gly-Pro-Asn-Ala-Gly-Ala-Asp-Asp-G ly-Pro-Gly-Ala-Gln-Ala-Asp-Leu-Glu-His-Ser-Leu-Leu-Val-Ala-Ala-Glu-Lys-Lys-Asp- Glu-Gly-Pro-Tyr-Arg-Met-Glu-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-Lys-Asp-OH. Comparison with the structure of the ovine and porcine hormones reveals that the 23-amino-acid sequence at the COOH terminus is highly conserved in evolution.

Amino Acid Sequence↗
PubMed1996

[Morphological studies of the adrenal zona glomerulosa cells and the thyroid and pituitary glands in streptozocin-induced experimental diabetic rats].

Changes in pathological morphology in the adrenal glomerulosa, the thyroid and pituitary glands in streptozotocin-induced experimental diabetic rats were studied by histologic, ultrastructural examination and morphometry. Experimental diabetes provoked atrophy and retrograde degeneration of organelles in the adrenal zona glomerulosa cells and the thyroid follicular epithelium. In the pituitary of diabetic rats, organelles in thyrotrophs were the same as the controls in morphometry, but TSH release was impaired. These studies indicate that pathological changes in the zone glomerulsa cells and the thyroid of diabetic rats appear to be responsible for the impaired function of these two glands. Moreover, reduced TSH release in the pituitary glands is also associated with impaired function of the thyroid gland.

Animals↗
PubMed1983

The influence of estrogen administration on the subcellular receptors distribution and its biological effect in the rat anterior pituitary gland.

We studied the effects of estrogen administration in the anterior pituitary gland (APG) of male rats. The subcellular distribution of estradiol receptors, and some biological responses, such as prolactin secretion and progestine receptors were examined. In the presence of circulating estrogens, the binding of [3H]-estradiol decreased in the cytosol and increased in nuclei. The total binding augmented significantly (P less than 0.05). These changes were dose and time dependent. So, in long chronic treatment, the changes in subcellular receptor distribution were greater, in accordance with higher serum estrogen level. Serum prolactin concentration and progestin receptor in the APG increased continuously as a function of time of the estrogen treatment. They were related to the presence of nuclear estradiol receptors, which remained elevated throughout the entire experimental period.

Animals↗
PubMed1985

Specific binding sites for insulin in the rat pituitary gland.

Studies were carried out in order to characterize specific insulin binding sites in the rat pituitary gland. Binding of labeled insulin by pituitary microsomes reached equilibrium after 4 h at 4 degrees C and remained stable over 16 h; at 25 degrees C the plateau was reached in 20 min. Equilibrium binding data analysis of competitive displacement of bound 125I-iodo insulin by unlabeled insulin yielded a non-linear Scatchard plot. At 25 degrees C the Kd for the high affinity component was 2.8 +/- 0.1 X 10(-9) M and the receptor concentration was 260 +/- 80 fmol/mg of microsomal protein. A Kd value of 4.6 +/- 0.4 X 10(-8) M and a binding capacity of 800 +/- 200 fmol/mg microsomal protein were obtained for the low affinity sites. Insulin binding to microsomes was enhanced 2.7 times by increasing the ionic strength of the incubation medium with 2 M NaCl, and was abolished when the microsome preparation was preincubated with trypsin prior to binding measurements. Other hormones, such as bovine thyrotropin, ovine follitropin, human somatotropin and ovine prolactin did not interact with the insulin receptor. Proinsulin displaced the labeled hormone in direct proportion to its insulin-like biological activity.

Animals↗