Visual documentation of ovine pituitary gland development with magnetic resonance imaging following zeranol treatment

The objective of the current study was to determine whether magnetic resonance imaging (MRI) could be successfully utilized to document the effect of an oestrogenic anabolic agent on pituitary gland growth. The experimental animals consisted of two 1/2 sibling Suffolk wethers (castrated rams), which received either no implant (control, n = 1) or a 24 mg zeranol implant at day 0 and day 42 (zeranol; n = 1). Animals were anaesthetized with propofol and supported with oxygen during the MRI procedure. A mobile MRI unit with a 0.5 tesla (T), superconducting magnet was used to obtain 3 mm thick, non-contrast enhanced, T1-weighted (TR 500-600, TE25) sagittal, transverse and dorsal images of the pituitary gland. Sagittal images were recorded only when the mesencephalic aqueduct and infundibulum were distinctly visible in the same image. Pituitary glands were imaged at 14-day intervals for 70 days to determine if and when the anabolic effects of zeranol on pituitary gland growth could be visualized using MRI techniques. Three separate measurements of the pituitary gland dimensions made with the on-screen cursor were averaged to calculate pituitary gland dimensions and volume. A computer-assisted image analysis system and laser film images were used to determine pituitary gland area. Increases in pituitary gland volume for control and zeranol-treated animals were evident within 14 days, and by the end of the 70-day study, the increase in pituitary volume for the zeranol-treated animal was three times greater than that of the control animal. Overall, our results indicate that MRI technology can be successfully used to document the development of the pituitary gland in vivo. Application of knowledge gained from this novel approach to study the growth, development and function of endocrine glands over time, and within the same animal, will enhance human and animal endocrine diagnostic procedures.     

Cytology of the pituitary gland of the Plains viscacha (Lagostomus maximu)

The anatomy of the pituitary gland of the Plains viscacha ( Lagostomus maximus ) is described. The pituitary gland in various physiological states has been investigated in order to localise the secretory sites of the trophic hormones. The various cell types of the pituitary gland were distinguished on the basis of their morphological characteristics, tinctorial properties and differential solubilities of the protein hormones in trichloroacetic acid solutions. Two cell types were found in the pars tuberalis, three cell types in the pars intermedia and six chromophi1 cell types in the pars anterior. Their possible functions are discussed.     

Coexisting acromegaly and primary empty sella syndrome

The normal functions of the pituitary gland may be suppressed when the gland is compressed onto the sella floor by arachnoid tissue extending through an impaired sella diaphragm. Interestingly, pituitary hormone hypo- and hypersecretion, including acromegaly, have been observed in patients with an 'empty sella'(1-4). This 'empty sella syndrome' has been classified into a primary form, in which no inciting factor (pituitary irradiation or surgery for a pituitary tumor) is present, and a secondary form, in which the empty sella occurs after pituitary procedures. In this report we describe a patient who presented with clinical and biochemical features of acromegaly and who had an empty sella on pituitary magnetic resonance imaging (MRI).     

WNT5A signaling affects pituitary gland shape

Wnt signaling is important in organogenesis, and aberrant signaling in mature cells is associated with tumorigenesis. Several members of the Wnt family of signaling molecules are expressed in the developing pituitary gland. Wnt5a is expressed in the neuroectoderm that induces pituitary gland development and has been proposed to influence pituitary cell specification. We discovered that mice deficient in Wnt5a display abnormal morphology in the dorsal part of the developing pituitary. The expression of downstream effectors of the canonical Wnt pathway is not altered, and expression of genes in other signaling pathways such as Shh, Fgf8, Fgf10 and Fgfr2b is intact. Prop1 and Hesx1 are also important for normal shape of the pituitary primordium, but their expression is unaltered in the Wnt5a mutants. Specification of the hormone-producing cell types of the mature anterior pituitary gland occurs appropriately. This study suggests that the primary role of Wnt5a in the developing pituitary gland is in establishment of the shape of the gland.     

Immunohistochemical characterization of chicken pituitary cells containing the vasotocin VT2 receptor

Research in mammals has demonstrated a variety of regulatory effects of vasopressin and oxytocin on endocrine functions of the anterior pituitary gland. Less evidence is available regarding the hypophysiotropic action of arginine vasotocin (AVT) comprising vasopressic and oxytocic activities in birds. Some hypophysiotropic effects of AVT may result from its interactions with brain circuits controlling pituitary functions, whereas others are caused by its direct affect on pituitary cells. Use of an antiserum to the vasotocin receptor VT2 (VT2R) has revealed numerous immunoreactive cells in the anterior pituitary gland of the chicken. The objective of the present study has been to identify endocrine phenotypes of chicken pituitary cells containing VT2R by means of immunohistochemical labeling. VT2R immunoreactivity has been found in all cells immunoreactive for adrenocorticotropin and alpha-melanotropin. Approximately 10% of labeled lactotropes are also immunoreactive for VT2R and lie around the anatomical boundary dividing the cephalic and caudal lobes. In both corticotropes/melanotropes and lactotropes, immunoreactive VT2R is present in a narrow layer outlining cell bodies. Immunoreactive VT2R is not found in gonadotropes, thyrotropes, or somatotropes. These results provide evidence for the important role of VT2Rs in mediating effects of AVT on endocrine secretion from corticotropes and, partially, from lactotropes.     

The hypothalamo-hypophysial vascular relationship in Indian fresh-water goby, Glossogobius giuris (Ham.).920u.

The hypothalamo-hypophysial vascular relationship and intra-hypophysial vasculatisation have been described in order to understand the regulatory mechanism of hypothalamic control over the functions of the pituitary gland. In Glossogobius giuris, the disposition of the blood vessels in the head region is on typical teleostean pattern with certain modifications. The nucleus preopticus is supplied through the nucleus preopticus artery, a small blood vessel arising from the anterior branch of the posterior cerebral artery, whereas the pituitary gland receives blood through a pair of hypophysial arteries. The blood from the pituitary is drained off by the pituitary veins whch pour their blood into the supra-orbital sinus. The anterior cerebral vein after taking the blood from anterior part of the brain including the hypothalamus and the nucleus preopticus joins with the supra-orbital sinus. The hypothalamo-hypophysial portal system is absent in this fish. The saccus vasculosus receives blood from the posterior cerebral artery through a small blood vessel and is collected by a prominent saccus vasculosus vein which pours blood into the supra-orbital sinus before it joins the infra-orbital sinus to form the heat vein. There seems to be no physological connection between the saccus vasculosus and pituitary gland. The highly vascularised neurohypophysis interdigitate with the pars intermedia and extends upto the proximal pars distalis. The blood vessels are restricted to the neurohypophysial extensions only. However, in the rostral pars distalis the blood vessels are present but the neurohypophysis does not extend to this part. The blood capillaries enter the rostral pars distalis from the capillary network on the surface of pituitary gland along with the connected tissue covering of the pituitary. The neurohypophysis shows a greater vascularisation in comparison to that of the other glandular part of the pituitary gland. In the present study of Glossogobius giuris, though an extensive ramification of neurohypophysis occurs with the pars intermedia and the proximal pars distalis, the neurosecretory axons do not innervate the endocrine cells of the pituitary gland and the blood vessels are found restricted to the neurohypophysial extensions except that of the rostral pars distalis. The neuro-vascular way of hypothalamic control over the functions of the pituitary gland seems to be justified as the neurosecretory fibres have been found associated with the blood vessels.     

Genetic interaction between the homeobox transcription factors HESX1 and SIX3 is required for normal pituitary development

Hesx1 has been shown to be essential for normal pituitary development. The homeobox gene Six3 is expressed in the developing pituitary gland during mouse development but its function in this tissue has been precluded by the fact that in the Six3-deficient embryos the pituitary gland is not induced. To gain insights into the function of Six3 during pituitary development we have generated Six3^+/−;Hesx1^Cre/+ double heterozygous mice. Strikingly, these mice show marked dwarfism, which is first detectable around weaning, and die by the 5th-6th week of age. Thyroid and gonad development is also impaired in these animals. Analysis of Six3^+/−;Hesx1^Cre/+ compound embryos indicates that hypopituitarism is the likely cause of these defects since pituitary development is severely impaired in these mutants. Similar to the Hesx1-deficient embryos, Rathke's pouch is initially expanded in Six3^+/−;Hesx1^Cre/+ compound embryos due to an increase in cell proliferation. Subsequently, the anterior pituitary gland appears bifurcated, dysmorphic and occasionally ectopically misplaced in the nasopharyngeal cavity, but cell differentiation is unaffected. Our research has revealed a role for Six3 in normal pituitary development, which has likely been conserved during evolution as SIX3 is also expressed in the pituitary gland of the human embryo.     

Induction of Cytosolic Progestin Binding Sites by Catecholestrogens in Rat Pituitary Gland and Uterus: Different Potencies of 2- and 4-Hydroxyestradiol

The ability of catecholestrogens to induce cytosolic progestin binding sites in the hypothalamus, pituitary gland, and uterus of ovariectomised-adrenalectomised rats was demonstrated by the increase in high-affinity [3H]promegestone binding sites (KD 1.39, 0.50, and 0.54 nM, respectively) following a single subcutaneous injection (26.4 micrograms/animal) of the 3.4-dibenzoate ester of 4-hydroxyestradiol. The affinity and the time course of induction of these binding sites were very similar to those after a single injection of an equivalent dose (20 micrograms/animal) of estradiol 3-benzoate, exhibiting maximal receptor levels after 44 h. Widely differing efficacies in the induction of progestin binding sites were observed between the dibenzoate esters of 2- and 4-hydroxyestradiol. 2-Hydroxyestradiol 2,3-dibenzoate was ineffective in the pituitary gland up to a dose of 132 micrograms/animal, whereas 4-hydroxyestradiol dibenzoate was equipotent to estradiol benzoate, showing a maximal induction of progestin binding sites at single doses in the range of 13.2-26.4 micrograms/animal (equivalent to 10-20 micrograms of estradiol benzoate). As compared to the pituitary gland, the uterus was much more sensitive to the systemic administration of estrogen benzoates. At single doses in the range of 1.32-6.6 micrograms/animal (equivalent to 1-5 micrograms of estradiol benzoate), 4-hydroxyestradiol dibenzoate induced maximal levels of progestin receptors, and even 2-hydroxyestradiol dibenzoate, when given at a high dose (132.4 micrograms/animal, equivalent to 100 micrograms of estradiol benzoate), produced a slight increase in progestin binding sites.     

Expression of retinaldehyde dehydrogenase 1 in the anterior pituitary glands of adult rats

Retinoic acid (RA) plays a critical role in cell growth and tissue development and is also a regulatory factor of pituitary function. However, whether RA is generated in the pituitary gland and plays a role as a paracrine and/or autocrine factor is generally unknown. RA is synthesized from retinoids through oxidation processes. Dehydrogenases that catalyze the oxidation of retinal to RA are members of the retinaldehyde dehydrogenase (RALDH) family. Recently, we demonstrated that RALDH2 and RALDH3, but not RALDH1, were expressed in the developing anterior pituitary gland of rats, but the expression of RALDHs in the adult pituitary gland was not determined. Therefore, we have now examined the expression of RALDH1, RALDH2, and RALDH3 mRNAs in the pituitary gland of adult rats. Analysis by quantitative real-time polymerase chain reaction of adult pituitary glands has revealed a high level of RALDH1 mRNA but not of RALDH2 mRNA or RALDH3 mRNA. We have also detected mRNA expression for RALDH1 in the anterior pituitary gland by in situ hybridization with digoxigenin-labeled cRNA probes. Double-staining for RALDH1 mRNA and pituitary hormones or S-100 protein, a marker of folliculo-stellate cells (FS-cells), has revealed RALDH1 mRNA expression in a portion of prolactin-producing cells, marginal layer cells, and FS-cells. Our results suggest that RA is generated in the adult anterior pituitary gland, and that it may act locally on pituitary cells. This work was supported by a Grant-in-Aid for Young Scientists (B) from the Japanese Ministry of Education, Culture, Sports, Science, and Technology (18790149) and by the Foundation of Growth Science.     

Distribution of a novel protein AgK114 expression in the normal tissues of adult mice: dual expression of AgK114 and growth hormone in anterior pituitary cells

The novel antigen K114 (AgK114) has been previously identified in normal hamster skin, and its expression has been up-regulated accompanying tissue damages of the skin, although there is no information on its biological functions. To determine the physiological role of AgK114, we prepared anti-mouse AgK114 monoclonal antibody and studied its tissue distribution in healthy adult mice by immunocytochemistry. A widespread and unique expression of AgK114 peptide was found in the selected organs of various systems (hair follicle cells and sebaceous gland of skin, ciliated epithelial cells of trachea and bronchial tube, striated portion of submandibular gland, distal convoluted tubule cells of kidney, ciliated epithelial cells of oviduct, medulla of adrenal gland and anterior lobe of pituitary gland). Interestingly, dual expression of AgK114 peptide and growth hormone in somatotrophs was found in anterior lobe of pituitary gland by double immunocytochemistry. AgK114 peptide was expressed widely in many regionally well-defined cellular systems in various peripheral tissues, suggesting that AgK114 peptide may have some roles of physiological functions in these organs. The data from our current study have provided a rationale for further studies of functional roles of AgK114 peptide in a variety of organs or tissues under physiological conditions.     

D－半乳糖致衰老小鼠与幼龄小鼠的垂体差异蛋白质分析

脑垂体是控制动物生长发育衰老死亡非常重要的一个器官.随着机体的衰老,垂体功能退化是必然趋势.D 半乳糖致衰老模型已被广泛用于研究衰老机制和筛选药物靶标,然而其分子机制尚未清楚.本研究采用差异蛋白质组学方法,以寻找D 半乳糖致衰老小鼠和幼龄小鼠垂体的差异蛋白质,为弄清其功能障碍的分子机制提供新的研究方法和线索.基于双相电泳和质谱结合的方法,本研究发现了46个大于2倍的差异蛋白质,其中32个得到可靠的鉴定（P <005）. 对差异蛋白质功能分析发现, 这些显著差异蛋白质主要分布于糖代谢通路,可能与线粒体功能紊乱有关.我们的研究数据为更好地理解D 半乳糖致衰老小鼠垂体功能障碍的内在机制提供了线索.     

Corticotrophin-related peptides in the intermediate lobe of the rodent pituitary gland: characterization by high performance liquid chromatography and radioimmunoassay

High performance liquid chromatography (HPLC) and radioimmunoassay have been used to characterize corticotrophin-related peptides in extracts of the intermediate lobe of the rat and mouse pituitary gland. Multiple peaks have been observed, which resemble corticotrophin-like intermediate lobe peptide (CLIP) in that they cross-react with antisera raised against the COOH-terminal region of corticotrophin (ACTH) but not against NH2-terminal directed antisera. These CLIP-like peptides were released from the incubated neurointermediate lobe and their secretion was inhibited in the presence of dopamine. Heterogeneity of peptide species was also observed with antisera raised against alpha-MSH. Multiple peaks of CLIP and alpha-MSH-like material were identified in pituitary extracts from the mouse and levels were elevated in the genetically obese (ob/ob) animal. The nature and possible functions of multiple forms of intermediate lobe peptides are discussed.     

A pituitary-salivary mixed gland induced by tissue recombination of embryonic pituitary epithelium and embryonic submandibular gland mesenchyme in mice

Renal subcapsular syngrafts of Day 9 to 11 mouse embryonic pituitary epithelium with Day 14 mouse embryonic submandibular gland mesenchyme produced mixed organs that include residual cleft structure surrounded by anterior pituitary cells some which are stained by anti-ACTH antiserum and submandibular gland-like structure with differentiated acinar cells which are stained by anti-alpha-amylase antiserum. However, when Day 8.5 or 12 embryonic pituitary epithelium was recombined with submandibular gland mesenchyme and syngrafted, development of submandibular gland-like or anterior pituitary tissues resulted, respectively. Thus, during organogenesis of the mouse anterior pituitary, there exists a developmental stage (Day 8.5-11 in utero), when prospective pituitary epithelium can respond to heterotypic submandibular gland mesenchyme with the development of a submandibular gland-like tissue.