Endocrine Journal
Online ISSN : 1348-4540
Print ISSN : 0918-8959
ISSN-L : 0918-8959
Volume 44 , Issue 2
Showing 1-17 articles out of 17 articles from the selected issue
  • KOJI CHIBA, HISAE KOBAYASHI, KATSUMI WAKABAYASHI
    1997 Volume 44 Issue 2 Pages 205-218
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    A new preparative procedure without using ion-exchanger is described for the efficient purification of canine LH (cLH), FSH (cFSH) and TSH (cTSH) from the pituitary gland. The hormones were extracted from the pituitary homogenate with an ammonium sulfate solution, and were separated by Concanavalin (Con) A affinity-, hydrophobic interaction-, then immobilized metal ion affinity chromatography. In the immobilized metal ion affinity chromatography, we used copper (Cu2+) as chelated metal ion with ammonium ion gradient and pH gradient in phosphate buffer to attain separation of the hormones. High purity of cLH, cFSH and cTSH was indicated as single bands in SDSPAGE, with apparent molecular masses of 34, 36 and 37kDa, respectively. The purified hormones showed two bands corresponding to α (20kDa) and β subunits (cLHβ:16kDa, cFSHβ: 22kDa, cTSHβ:16 kDa) under reducing condition in SDS-PAGE. The purified hormones were prepared in good recovery (LH: 53%, FSH: 34%, TSH: 36%) with high biological activity or binding activity to the receptor. Crosscontamination of the purified hormone was less than 0.5%. Examination of the hormone fraction with isoelectric focusing showed that major peaks of isoelectric isoforms were maintained throughout the purification steps of cLH and cFSH, while a few peaks were lost in Con A affinity chromatography in cTSH purification. It was concluded that the present method could prepare highly purified cLH, cFSH and cTSH which retained isoforms of the hormones and biological activity or binding affinity to the receptor.
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  • KAZUMASA UEMURA, GEN-ICHI WATANABE, KEN-ICHI ITOH, TATSUO TAMAGAWA, NO ...
    1997 Volume 44 Issue 2 Pages 219-225
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    To investigate whether or not pressor responses to repeated stimulation of central cholinoceptive neurons are desensitized, mean arterial blood pressure (MAP) and heart rate (HR) were measured following repeated injections of neostigmine, an acetylcholinesterase inhibitor, into the third cerebral ventricle in conscious, unrestrained intact or adrenalectomized (ADX) rats. Neostigmine (5× 10-9 or 5×10-8mol) in 1μl saline increased MAP dose-dependently and increased HR in intact rats. The peak values in MAP and HR after three repeated injections at 4 hour intervals did not wane. Neostigmine (5×10-8mol) also increased MAP in ADX rats, and the peak values after the first injection were higher in the ADX rats than in the intact rats. The pressor responses to the second and third injection, however, were less than to the first injection in the ADX rats. HR responses to the repeated injections in the ADX rats were identical to those in the intact rats. These findings suggest that the adrenal gland plays a role in antagonizing the development of desensitization in the neostigmine-induced pressor response.
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  • SATOSHI KAKIYA, AKITOSHI KAWAKUBO, KIYONORI TOYAMA, MASAHIRO YAMAMOTO
    1997 Volume 44 Issue 2 Pages 227-231
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    We report two cases of acromegaly due to pituitary adenoma without any other endocrinopathy in a family. The patients had high plasma GH and were improved by transsphenoidal adenomectomy. Acromegaly is usually a clinical syndrome of sporadic nonfamilial occurrence. The familial occurrence of acromegaly not associated with multiple endocrine neoplasia is very rare. Our patients are unlikely to be associated with the multiple endocrine neoplasia type 1 syndrome. Here we describe two patients with acromegaly, a father and his daughter, and review familial cases reported.
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  • KAZUMI NOTSU, YASUO ITO, AKIHIRO HASEGAWA, OSAMU IWANARI, KENJI KATAMU ...
    1997 Volume 44 Issue 2 Pages 233-237
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    The clinical courses including thyroid conditions of three infants born to a mother with primary hypothyroidism due to Hashimoto's thyroiditis were studied. The mother was positive for both TSH-binding inhibitor immunoglobulins (TBII) and thyroid stimulating-blocking antibodies (TSBAb) in her serum. The first infant died because of septic shock due to fistula formation between the large intestine and the bladder. Serum thyroid hormone levels during the first pregnancy were extremely low because of incomplete replacement therapy with levothyroxine. The second infant had almost normal thyroid function, so that the replacement therapy was not necessary. The third infant had transient and overt primary hypothyroidism. The replacement therapy was carried out for six months after birth. TSBAb activities in this mother were high in the third pregnancy. In general, these activities gradually increases with the clinical course in TSBAb-positive Hashimoto's patients. From these findings, it was suspected that the thyroid conditions in the second and the third infants reflected the natural course of TSBAb activities in this mother.
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  • TSUTOMU KAZUMI, HIROYUKI ODAKA, TOSHIKI HOZUMI, YOSHIHIKO ISHIDA, NOBU ...
    1997 Volume 44 Issue 2 Pages 239-245
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    Effects of dietary carbohydrates on triglyceride production and hepatic lipogenic enzyme activities were examined in Wistar fatty rats, an animal model of noninsulin dependent diabetes mellitus, fed fructose or glucose and were compared with those of Wistar lean rats. Carbohydrates were supplied in 10% drinking solutions for 21 days. As compared with lean rats, Wistar fatty rats were characterized by hyperglycemia, hyperinsulinemia and hypertriglyceridemia, the last of which was associated with an increased hepatic activity of fatty acid synthetase and an increased rate of triglyceride secretion from the liver to the circulation. Feeding fructose to genetically obese diabetic rats produced a threefold increase in the hepatic activity of fatty acid synthetase, a twofold increase in NADPH-generating enzymes (malic enzyme and glucose-6-phosphate dehydrogenase) and a 56% increase in the rate of triglyceride secretion, with a resultant 86% increase in plasma triglyceride concentrations. Feeding glucose produced a similar increase in the activity of NADPH-generating enzymes and triglyceride production in the fatty liver but it differed in producing no change in plasma triglyceride concentrations or hepatic fatty acid synthetase activity. Neither dietary fructose nor glucose changed glycemia or insulinemia. These results show that in genetically obese, diabetic rats feeding fructose and glucose is associated with an increase in hepatic lipogenic enzyme activities and triglyceride production, and suggest that fructose stimulates triglyceride production but impairs triglyceride removal, whereas glucose stimulates both of them.
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  • SHOICHIRO IKUYAMA, KENJI OHE, RYOICHI TAKAYANAGI, LEONARD D. KOHN, HAJ ...
    1997 Volume 44 Issue 2 Pages 247-256
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    We previouly identified an approximately 200bp “minimal promoter” of the rat TSH receptor (TSHR) gene which is essential for the promoter activity. In the present study, we have cloned and characterized an upstream region of the TSHR promoter to disclose additional functional element(s). We screened a rat genomic library and obtained a DNA fragment which contained a 4.2kb 5'-flanking region. This fragment was 2.5kb longer than that we previously studied (1.7kb). To assess the promoter activity, chimeric plasmids containing the 4.2kb promoter and its 5'-deletions ligated to a chloramphenicol acetyltransferase gene were transfected into thyroid and non-thyroid cells. These plasmids expressed significant promoter activity in FRTL-5 and FRT thyroid cells, but not in BRL liver cells. The strongest promoter activity was expressed by the -199bp promoter, and the longer promoter expressed rather decreased activity. Co-expression of thyroid transcription factor-1(TTF-1) increased the activity of the promoter region from -3187 to -199bp, which encompassed one or two TTF-1 binding sites we previously identified, but not the -4206bp promoter. In addition, FRTL-5 stable transfectants each having a chimeric construct were cultured in the presence or absence of TSH. All transfectants expressed higher promoter activity in the absence of TSH than in the presence of TSH, in particular, the -3187bp plasmid expressed significantly higher activity by comparison to the -2617 and -4206bp constructs. This result indicates that the region between -3187 and -2617bp may contribute to TSH/ cAMP-induced suppression and also suggests that the region between -4206 and -3187bp involves the element(s) for constitutive suppression of the promoter activity. These results not only suggest that the 4.2kb upstream region of the TSHR gene possibly contains some elements for the regulation of the gene expression, but also emphasize the importance of the minimal promoter region which we previouly identified for the efficient expression of the gene.
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  • NATEETIP KRISHNAMRA, JARUGOOL SEEMOUNG, LIANGCHAI LIMLOMWONGSE
    1997 Volume 44 Issue 2 Pages 257-264
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    In an attempt to evaluate the acute effect of PRL on bone turnover, experiments were performed in sexually mature female Wistar rats which were given an intraperitoneal (ip) administration of 1.25mM CaCl2 solution containing 6μCi 45Ca. Dose response study showed a two fold higher rate of 45Ca uptake in 30min by control trabecular bones (sternum and vertebrae 5-6) compared with control compact bones (femur and tibia). Femur exhibited a dose dependent increase in 45Ca uptake in response to pharmacological doses of 0.01 and 0.02mg PRL/100g body weight but was less responsive to 0.04mg PRL/100g body weight. Tibia only responded with increased 45Ca uptake to 0.02 and 0.04mg PRL/100 g body weight while trabecular bones were unresponsive. By varying the intervals between administration of 45Ca (0min) and PRL (0, 30 or 60min) and bone harvesting (30, 60 or 90min), it was found that 0.01mg PRL/100g body weight had a biphasic action on 45Ca movement. It initially enhanced 45Ca influx into femur by 30min followed by an accelerated 45Ca efflux from femur back to the circulation. It could be concluded that PRL acutely stimulated calcium turnover in compact bone.
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  • ATSUSHI IMAI, NAKA HATTORI, MITSUKO HIROSAWA, KUNIO SHIOTA, TOMOYA OGA ...
    1997 Volume 44 Issue 2 Pages 265-274
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    Amniotic fluid contains various bioactive substances including the placental PRL family. In the present study, it was elucidated that rat amniotic fluid contained immunoreactive proteins which had different molecular sizes and pI values from the authentic placental lactogens (PLs) in the rat, recognized by antipeptide antibody to the N-terminal peptide of rat PL-I. Immunoreactive PLs residing in the amniotic fluid were characterized further by two-dimensional sodium dodecyl sulfate gel electrophoresis (2DE), immunoblotting and anion-exchange chromatography. Amniotic fluid collected from rats on day 12 of pregnancy contained two PL-like molecules, tentatively called A1 (MW 75kDa, pI 4.6) and A2 (MW 99-102kDa, pI 5.3-5.4). A1 and A2 are specific to the amniotic fluid, because no such molecules were found in the serum or placental extracts. Immunoblot analysis of amniotic fluid revealed that A1 levels increased, whereas those of A2 decreased to an undetectable level up to day 16 of pregnancy. When the A1 concentrations from days 12 to 20 were monitored intensively, they increased from day 12 to 14, were maintained until day 18, and then decreased dramatically by day 20. The expression pattern for A1 was therefore completely different from those of authentic placental PRL family members found in serum and placental tissue, indicating that the A1 is distinct from them. Partial purification by anion-exchange chromatography and 2DE revealed that A1 consisted of 5 isoforms.
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  • YUICHI NAKAGAWA, KAZUHIKO TOYA, HIROMUNE NATSUME, KAORU NASUDA, HIROMI ...
    1997 Volume 44 Issue 2 Pages 275-281
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    We followed up a girl with the neonatal form of Bartter's syndrome for sixteen years and determined the sensitivity to angiotensin II before and during the indomethacin treatment. A 4-monthold girl was admitted to our hospital, because of severe hypokalemia and growth retardation. Initially we treated her with spironolactone and potassium supplements. This treatment increased plasma potassium levels and her growth. At the age of one year she was diagnosed as having Bartter's syndrome. Since then she has been treated with indomethacin at an initial dose of 3mg/kg/day combined with spironolactone and potassium. After the start of the indomethacin treatment, her growth increased dramatically, and her final height was normal adult height. Her puberty developed normally and menarche occurred at the age of 12 years. Levels of serum sodium, chloride, plasma aldosterone and urinary prostaglandin E2 were also normalized. Levels of angiotensin I and II were improved but not within the normal range, but plasma potassium levels slightly decreased after plasma aldosterone levels were normalized and did not change during the treatment period. Plasma renin activity remained high until about the age of 8 years, after which it decreased to almost within the normal range. At 5 months after the start of indomethacin (3mg/kg/day), her vascular sensitivity to angiotensin II had been improved, and after 2 years and 5 months, her vascular sensitivity was further improved. At this time renin activity had decreased after angiotensin II infusion, but plasma aldosterone did not change. At the age of 16 years (dose of indomethacin: 0.5mg/kg/day), plasma aldosterone increased after angiotensin II infusion. These data suggest that indomethacin and spironolactone are effective treatments for the neonatal form of Bartter's syndrome, especially during childhood.
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  • DAG MALM, STEFAN LINDSKOG, BO AHRÉN, JON FLORHOLMEN
    1997 Volume 44 Issue 2 Pages 283-288
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    The intracellular mechanism whereby the neuropeptide galanin inhibits insulin secretion is not established, since the peptide affects several signal pathways, including intracellular messengers such as calcium and cyclic AMP. In this study, we have assessed the effect of galanin on the inositol-specific phospholipase C (iPLC) activity in isolated rat pancreatic islets. The iPLC activity was measured as the generation of inositol 1, 4, 5-trisphosphate and its metabolite inositol 1, 3, 4-trisphosphate from the hydrolysis of polyphosphoinositides. Inositol phosphates were measured by anion-exchange fast protein liquid chromatography (FPLC) analysis of extracts from islets prelabelled with myo-3H-inositol. Galanin (1 to 100nM) significantly increased the glucose-induced (12mM) accumulation of inositol 1, 4, 5-trisphosphate after 2min, but this stimulation of iPLC activity was followed by a significant suppression after 15min. In the absence of extracellular calcium, both the stimulatory and inhibitory effects of galanin on the iPLC activity vanished. We therefore conclude that galanin initially stimulates iPLC in a calcium-dependent manner, followed by a secondary inhibitory effect. The secondary inhibition of iPLC activity might contribute to the insulinostatic action of the neuropeptide.
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  • TORU YAMAGUCHI, SABURO HATTORI, MASAMICHI NAKAI, KENICHI SEKITA, YOSHI ...
    1997 Volume 44 Issue 2 Pages 289-297
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    In this study, we investigated the relationship between the concentrations of intact parathyroid hormone (i-PTH) and midregion PTH (m-PTH) measured by an immunoradiometric assay and a radioimmunoassay, respectively, versus various demographic and biochemical parameters, bone mineral density (BMD) of the lumbar spine (LS) and radius, and the radiographic findings of osteosclerosis and aortic calcification in hemodialysis (HD) patients. m-PTH correlated positively and more significantly with serum calcium (Ca), serum phosphorus (P), Ca-P solubility products (Ca×P) and LS-BMD than i-PTH did (P=0.024 vs. 0.531, 0.001 vs. 0.061, 0.0001 vs. 0.125, and 0.017 vs. 0.284, respectively). A positive correlation between the percent changes in serum P over the 1-month measurement period and those in m-PTH rather than in i-PTH was also observed (P=0.021 vs. 0.869). These data indicate that m-PTH is distinct from i-PTH in its positive correlation with serum Ca, serum P, Ca ¥ P and LS-BMD in HD patients. Since m-PTH is known to consist mostly of the midregion and carboxyl-terminal fragments of PTH in HD patients, the present study suggests that these PTH fragments may be biologically significant in the patients in vivo.
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  • TOMOYASU KATO, JUI-TUNG CHEN, KATSUYOSIHI KATASE, YASUO HIRAI, KATSUHI ...
    1997 Volume 44 Issue 2 Pages 299-304
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    To evaluate the effects of 1α-hydroxyvitamin D3 (1α(OH)D3), a series of clinical trials, preventive and therapeutic, were performed in an open label manner in women immediately after oophorectomy. The series included a total of 121 oophorectomized subjects, whose lumbar bone mineral density (L2-4BMD) was followed by the use of dual energy X-ray absorptiometry. (1) Preventive trial: 61 women who had undergone premenopausal bilateral oophorectomy, were divided into 3 groups (Group C: control; Group L: 0.25μg 1α(OH)D3/day; Group H: 0.50-0.75μg 1α(OH)D3/day). The changes in BMD and chemical indices were followed up for one year. (2) Therapeutic trial: the trial included 60 premenopausally oophorectomized subjects having L2-4BMD lower than the normal control level minus 1SD which has been reported in age-matched normal Japanese women. These subjects were divided into 3 groups and treated in the same way as in the preventive trial. In the preventive trial, L2-4BMD decreased by 8.2%, 6.5% and 4.5% in groups C, L and H, respectively, at 12 months of treatment, whereas in the therapeutic trial, L2-4BMD decreased by 3.6%, 3.2% and 0.8% in the groups C, L and H, respectively, at 12 months of treatment. In conclusion, 1α(OH)D3 was found to be effective both to prevent the bone loss subsequent to bilateral oophorectomy and improve low bone mass after oophorectomy.
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  • NAOKI SAKANE, TOSHIHIDE YOSHIDA, AKIRA SHIMATSU, TUNEKAZU UMEKAWA, MOT ...
    1997 Volume 44 Issue 2 Pages 305-310
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    An acromegalic patient with nontoxic autonomous goiter was sequentially treated with octreotide and bromocriptine. Before therapy, serum GH, PRL and insulin-like growth factor-I (IGF-I) levels were increased. Free T3 and free T4 were within the normal range with suppressed TSH levels, whereas 123Iodine-uptake of thyroid was 5.6% after 24h. During treatment with octreotide and bromocriptine, serum GH, PRL, and IGF-I became normal and free T3 and free T4 were slightly but significantly decreased, but TSH levels remained very low. After thyroidectomy, thyroglobulin, free T3 and free T4 were further decreased, and the TSH levels were recovered to normal. These findings suggested that octreotide and bromocriptine inhibit the release of thyroid hormones from the autonomous thyroid gland directly or indirectly through the decline in IGF-I.
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  • KYUZI KAMOI, MIYUKI ISHIBASHI, TOHRU YAMAJI
    1997 Volume 44 Issue 2 Pages 311-317
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    Vasopressin (AVP) secretion is principally under osmotic regulation, which is altered by nonosmotic stimuli. It is known that the manner of osmotic regulation of AVP secretion in hypoosmolar state of man consists of four types. The types have (A) random changes in plasma AVP without relation of plasma osmolality; (B) plasma AVP secretion correlated closely to plasma osmolality with a low osmotic threshold for AVP release; (C) nonsuppressible AVP secretion with normal osmotic release of AVP; (D) no abnormalities in AVP secretion. In this study, we found an entirely different type of AVP secretion from the above types in six patients with hyponatremia resulting from various causes during infusion of 5% hypertonic saline. To clarify the mechanism underlying the AVP secretion, we analyzed the interaction between osmotic and nonosmotic stimuli of AVP secretion in these patients. Despite hyponatremia, plasma AVP levels in all patients were not suppressed, which was attributed at least in part to the presence of nonosmotic stimuli for AVP release. These stimuli include nausea, hypotension, blood volume contraction, glucocorticoid deficiency or their combinations. Hypertonic saline infusion increased both serum sodium concentrations and plasma osmolality, although to subnormal levels, and concomitantly, alleviated some of the nonosmotic stimuli for AVP release formerly present in these patients. However, plasma AVP concentrations decreased rapidly during the infusion and reached the nadir in all patients. This phenomenon may be due to alleviation of nonosmotic stimuli for AVP release. Thus, the findings indicate that the potentiating effect of nonosmotic stimuli for AVP secretion may odify the osmotic regulation of AVP secretion in hypoosmolar state, resulting in the type of AVP secretion in this study.
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  • NORIKO KIMURA, WAKAKO MIURA, TAKAO NOSHIRO, KAZUTOSHI MIZUNASHI, KUNIH ...
    1997 Volume 44 Issue 2 Pages 319-327
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    Plasma levels of chromogranin A (CgA) were measured by ELISA in 22 patients with pheochromocytoma (18 non-metastatic, 3 metastatic, and 1 mixed neuroendocrine-neural tumor), 9 patients with primary hyperparathyroidism, and 9 patients with pituitary adenoma. The plasma levels of CgA were compared with norepinephrine, epinephrine, parathyroid hormone and pituitary hormones, i.e., growth hormone and prolactin. In pheochromocytoma, CgA in preoperative plasma of the patients without metastasis was 228±38U/L (mean±SEM) and significantly higher than healthy controls (30±11U/L, n=40). Plasma CgA was decreased after removal of the tumors (28±6.0U/L), except in three patients with metastatic pheochoromocytoma and a mixed neuroendocrine neural tumor. The concentration of CgA in the patients with non-metastatic pheochromocytoma was significantly correlated with that of plasma norepinephrine (P<0.005, r=0.68) and urinary norepinephrine (P<0.05, r=0.65), but not with that of epinephrine. There was an exceptional case in which CgA was extremely high, but the CA level was normal. This tumor was a highly malignant pheochromocytoma with extensive metastases composed of small tumor cells which were occasionally positive for tyrosine hydroxylase immunohistochemically. These cells were considered to be poorly differentiated tumor cells and synthesized a very small amount of norepinephrine. Plasma levels of the patients with primary hyperparathyroidism and the patients with pituitary adenoma were 44±4U/L and 48±8U/L, respectively. Only one patient with a growth hormone-producing pituitary adenoma had a high level of CgA. Plasma CgA is a useful tumor marker for pheochromocytoma, even for malignant pheochromocytoma without elevated CA level, but not for hyperparathyroidism, or pituitary adenoma.
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  • HIROMI SAKAGUCHI, HIROYUKI KOSHIYAMA, TOSHIAKI SANO, DAISUKE INOUE, NO ...
    1997 Volume 44 Issue 2 Pages 329-333
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    It has been indicated that some subsets of clinically nonfunctioning pituitary adenoma exhibit immunohistochemical and ultrastructural features of somatotroph or corticotroph cells, which are described as silent somatotroph and corticotroph adenomas, respectively. We here describe a 70-year-old woman with nonfunctioning pituitary adenoma presenting with visual disturbance. None of the pituitary hormones show abnormal finding. Magnetic resonance imaging study revealed a pituitary tumor which developed inferiorly into the sphenoidal sinus. Tumor resection was performed by a transsphenoidal approach, and resulted in a partial resection of the tumor. The specimen indicated chromophobic adenoma. Immunohistochemical examination revealed a characteristic distribution pattern of cytokeratin staining for ACTH cell adenoma, although immunostaining for ACTH was only weakly positive. After the operation, only ACTH secretion was impaired, requiring replacement therapy with glucocorticoid. Bromocriptine was administered in order to prevent the recurrence of the tumor. It remains to be elucidated whether the present case could be classified as silent corticotroph adenoma, which was origially indicated to have aggressive characteristics, i.e. progressive visual defect, high incidence of infarction and frequent recurrence.
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  • TOSHIKAZU KIGOSHI, HIROSHI OKAMOTO, TAKASHI ISHII, TOMOHIKO ITO, FUMIT ...
    1997 Volume 44 Issue 2 Pages 335-339
    Published: 1997
    Released: November 25, 2006
    JOURNALS FREE ACCESS
    We previously reported the potentiation of basal aldosterone production by the addition of the calcium chelator ethyleneglycol-bis-(β-aminoethyl ether)-N, N, N', N'-tetraacetic acid (EGTA) to an extracellular solution of bovine adrenal glomerulosa cells in vitro. To assess whether the addition of the calcium chelators ethylenediamine-N, N, N', N'-tetraacetic acid (EDTA) and EGTA can potentiate basal and stimulated aldosterone production, we compared the effect of EDTA with that of EGTA on basal and the agonist (potassium; 8mM, angiotensin II; 10nM, ACTH; 10nM)-stimulated aldosterone production by the cells in vitro. These two chelators lowered the extracellular ionized calcium ([Ca2+]o) concentration in a similar manner. The levels of basal and the agonist-stimulated aldosterone production in the presence of EDTA (1mM) and EGTA (1mM) were significantly (P<0.01 or less) increased when compared with those in the absence of EDTA and EGTA, respectively. These results show that the addition of EDTA and EGTA to an extracellular solution potentiates basal and the agoniststimulated aldosterone production in vitro. Although an increase in basal aldosterone production in the presence of EDTA (1mM) and EGTA (1mM) was completely inhibited by the voltage-dependent calcium channel antagonist nifedipine (1μM) or the calmodulin antagonist pimozide (1μM), the potentiation of the agonist-stimulated aldosterone production does not seem to be induced by Ca2+/ calmodulin-dependent nor cAMP-dependent systems. These findings suggest that calcium chelators such as EDTA and EGTA may possess activating effect on basal and stimulated aldosterone production in bovine adrenal glomerulosa cells.
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