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  • 1
    ISSN: 1432-2307
    Keywords: Key words Activin A ; Inhibin A ; Endocrine tumors ; Digestive system ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Activin A and inhibin A, first isolated from the ovary, are dimeric proteins able to modulate pituitary FSH secretion. Inhibin A is a heterodimer composed of one α-subunit and one βA-subunit (α-βA), while activin A is a homodimer of the βA-subunit (βA-βA). Their identification in several tissues has suggested that they have numerous physiological functions, acting as either paracrine or autocrine factors. The aim of this study was to evaluate the expression of activin A and inhibin A in normal endocrine cells and in 70 endocrine tumours from different sites in the gastro-entero-pancreatic system, using specific monoclonal antibodies directed against the α- and βA-subunits of inhibin/activin. Immunoreactivity for the βA-subunit, but not for the α-subunit, was observed in normal G, EC, and GIP cells of the antrum and duodenum, and in pancreatic A cells. βA-subunit expression was observed in G cell and A cell tumours, and in a few insulinomas and ileal EC cell carcinoids. The α-subunit was found in rare cells in 7 of the 70 tumours and was colocalized with the βA-subunit in only 1 tumor. Specific types of endocrine cells from the gut and pancreas appear to produce only activin A, a possible paracrine or autocrine modulator. Activin A is mainly produced by tumours derived from endocrine cells that normally express it.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2307
    Keywords: Acidic fibroblast growth factor ; Gastrointestinal endocrine tumours ; Carcinoid tumours ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Acidic fibroblast growth factor (aFGF) is a member of the structurally related heparin-binding growth factor family. The best studied members of this family are aFGF and basic FGF (bFGF), which are potent mitogens and differentiation factors for mesodermderived cells, including fibroblasts. This study was designed to verify the immunohistochemical expression of aFGF in normal human endocrine cells of the gut and in related endocrine tumours. We examined normal gastrointestinal mucosa from seven different subjects and 41 gut endocrine tumours from different sites, including stomach, duodenum, and small and large intestine, using an aFGF polyclonal antibody with no cross-reactivity for bFGF. We localized aFGF in a fraction of serotonin-producing enterochromaffin (EC) cells of the normal gut, while it was absent in gastrin (G), CCK, secretin (S), somatostatin (D) and glicentin (L) cells. aFGF immunoreactivity was also expressed in serotonin producing EC cell tumours, but not in other functional types of gut endocrine neoplasms investigated, including gastric ECL cell, duodenal somatostatin and gastrin cell, and rectal L cell tumours. A positive correlation was found between expression of aFGF and the amount of tumour fibrous stroma, suggesting that aFGF may be involved in proliferation and activity of stromal fibroblasts.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2307
    Keywords: Keywords Gonadotropin-releasing hormone receptor ; Pituitary gland ; Immunohistochemistry ; Colocalization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Gonadotropin-releasing hormone (GnRH), which is a well-known regulator of gonadotroph function, has recently been considered to be a paracrine factor involved in the control of somatotroph, lactotroph, and corticotroph cells. GnRH action is initiated by binding to a specific cell surface receptor, the gonadotropin-releasing hormone receptor (GnRHR), which is expressed by follicle-stimulating hormone/luteinizing hormone (FSH/LH) cells. Using in situ hybridization techniques, GnRHR messenger ribonucleic acid (mRNA) has recently been detected in normal human anterior pituitary gland and in various pituitary adenomas, including FSH/LH-cell, growth hormone (GH)-cell, adrenocorticotropic hormone (ACTH)-cell, and null-cell adenomas. However, immunohistochemical studies indicating the specific cell distribution of GnRHR in normal pituitary cells have never been reported. The aim of the present investigation was to evaluate the immunohistochemical expression of GnRHR in different types of normal pituitary cells and related tumors. Using double-label immunohistochemical techniques on formalin-fixed and paraffin-embedded tissues and specific antibodies directed against pituitary hormones and GnRHR, we found GnRHR immunoreactivity not only in FSH/LH cells, but also in GH- and thyroid-stimulating hormone (TSH) cells. GnRHR was detected in FSH/LH-cell, GH-cell, mixed GH- and prolactin (PRL)-cell, and α-subunit (α-SU)/null-cell adenomas. The findings of this study suggest that the interaction between GnRH and GnRHR may play a role in paracrine/autocrine regulation of different types of normal pituitary cells and pituitary adenomas.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-7403
    Keywords: inhibin ; activin ; pituitary ; immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The localization of inhibin/activin (I/A) subunits was investigated in human normal adenohypophysial cells and in 87 pituitary adenomas of different types, using immunohistochemistry. Monoclonal antibodies directed against α, βA and βB subunits of I/A were employed. In normal pituitary, α subunit of inhibin was detected only in FSH-positive gonadotrophs, while βA subunit of I/A was expressed in FSH-positive gonadotrophs, GH-cells and in a few PRL-cells. βB subunit was found in FSH-positive gonadotrophs, TSH-cells and a few LH-positive gonadotrophs. The three subunits of I/A were detected in the majority of nonfunctioning tumors, while functioning adenomas showed a significantly lower expression. This study shows that α, βA and βB subunits of I/A are expressed by specific adenohypophysial cell types and that they are characteristically present in nonfunctioning adenomas. These results suggest that inhibins and activins may play a role in the local regulation of pituitary hormonal secretion both in normal adenohypophysial cells and in pituitary adenomas.
    Type of Medium: Electronic Resource
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