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Volume 67 (1991)
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Volume 68, Issue 5
Displaying 1-6 of 6 articles from this issue
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Mitsuo SUZUKI1992 Volume 68 Issue 5 Pages 507-525
Published: May 20, 1992
Released on J-STAGE: September 24, 2012
JOURNAL FREE ACCESSThe densest distribution of somatostatin (SRIF) neuron perikarya is localized in the hypothalamic periventricular nucleus (Pe) close to the third ventricle, from which many fibers are projected to the median eminence. The release of SRIF in the neurohemal organ into the anterior pituitary modulates GH secretion from pituitary somatotrophs. When SRIF input from the hypothalamus to rat anterior pituitary is reduced by either neurosurgery or SRIF antiserum iv injection, the responsiveness of the pituitaries to human GH releasing factor (hGRF) in an in vitro perifusion system is markedly attenuated. Moreover, SRIF pretreatment facilitates the GH release response of dispersed anterior pituitary cells to hGRF. The long lasting SRIF effect to sensitize somatotrophs appears to take place beyond cAMP formation or as an unknown distal effect. These findings indicate that SRIF neurons in the Pe play a role in maintaining the pituitary responsiveness to GRF in addition to the original action to inhibit GH secretion. Neuronal networks between Pe SRIF neurons, and intra- and extrahypothalamic nuclei are identified by Pe stimulation test on GRF-GH secretion. In addition to the physiological role in maintaining pituitary responsiveness, Pe SRIF neurons have a wide influence on specific SRIF receptor binding in various brain regions as well as in the anterior pituitary. Shortly after lesioning the Pe neurons, there is a continuous increase in plasma GH level with a transient increase in specific binding of 125I-Tyr11I-SRIF-14 to the anterior pituitary. Furthermore, there is a similar but a little longer increase in binding of the radioligand to some brain areas such as the cerebral cortex, hippocampus, and amygdala nuclei. However, neuronal connections between the SRIF neurons and nuclei which are up-regulated by the lesioning have not been fully proven. When the labeled ligand is infused into the lateral ventricle, it is rapidly and widely distributed in many periventricular structures in the lateral and third ventricles. These findings suggest that SRIF produced in the Pe neurons is transported to other brain areas via cerebrospinal fluid in addition to neuronal connections for modulating the activity of neurons which have SRIF receptors. Thus, hypothalamic Pe SRIF neurons have dualistic roles for controlling anterior pituitary function and modulating CNS neuron activity.View full abstractDownload PDF (2254K) -
Toshio MATSUMOTO1992 Volume 68 Issue 5 Pages 526-537
Published: May 20, 1992
Released on J-STAGE: September 24, 2012
JOURNAL FREE ACCESSAfter the discovery of the effect of vitamin D on cell differentiation by Abe, Suda and their colleagues, it has become clear that many of the vitamin D actions are mediated by their effect on terminal differentiation of various cells. Similarly important are the findings that the vitamin D receptors are almost ubiquitously distributed in various tissues, and the active metabolite of vitamin D exerts its effects in almost all types of cells. Thus, the actions of vitamin D are not confined to their classical target tissues that regulate calcium metabolism, but also are extended to the regulation of the proliferation and differentiation of various cells such as immunoregulatory cells, epidermal cells and malignant tumor cells. These discoveries have created a new era in the field of vitamin D endocrinology, and led to the development of vitamin D analogues that exert their effects mostly in the nonclassical target tissues with little effects on calcium metabolism. Efforts are currently under way to apply these analogues to the treatment of various disturbances such as immunological disorders, skin lesions and malignant tumors. This review briefly summarizes the current understandings on the effect of vitamin D on cell differentiation and proliferation, and discusses the future prospects of the application of these effects on the treatment of various disorders.View full abstractDownload PDF (1230K) -
Masaru IZUO1992 Volume 68 Issue 5 Pages 538-549
Published: May 20, 1992
Released on J-STAGE: September 24, 2012
JOURNAL FREE ACCESSTherapeutic access in the treatment of breast cancer with the antiestrogen tamoxifen has been established by world-wide clinical trials since the drug was introduced by Cole et al, in 1971. In recent years, however, a new series of antiestrogens (the derivatives of tamoxifen) such as trioxifene, toremifene and droloxifene have been studied with regard to clinical efficacy as a first-line treatment for postmenopausal patients with breast cancer and occasionally even for patients who previously responded to tamoxifen and then relapsed. Luteinizing hormone releasing hormone (LHRH) agonists are now available for premenopausal patients that will produce a medical castration, when given continuously, by down-regulation of the pituitary LHRH receptors. Four compounds, leuprolide, buserelin, tryptorelin and goserelin have been available for clinical use, but goserelin (Zoladex) is now widely used by long - acting depot preparations, which are given subcutaneously once every 4 weeks. Another series of drugs which inhibit estrogen synthesis in postmenopausal patients and are termed “aromatase inhibitors” have been developed. The pure aromatase inhibitors newly developed include two types of both a steroidal compound (4-hydroxyandrostenedione) and a non-steroidal one which is a tetrahydroimidazopyrimidine derivative (CGS 16949A).
This review describes the pharmacological and clinical aspects of these new agents.View full abstractDownload PDF (1131K) -
Yoshimochi ISHIZUKI, Yoshifumi HIROOKA, Yoshiharu MURATA1992 Volume 68 Issue 5 Pages 550-556
Published: May 20, 1992
Released on J-STAGE: September 24, 2012
JOURNAL FREE ACCESSIn order to assess the Japanese dietary iodine intake, we examined the urinary iodine excretion of those on an ordinary Japanese diet chosen at random and observed whether the thyroid function might affect the amounts of urinary iodine excretion.
The subjects consisted of cases of untreated hypothyroidism and chronic thyroiditis (CT) and euthyroid controls who were healthy people or had non-thyroidal disorders such as diabetes mellitus or hypertension. Eight cases of hypothyroidism were composed of 3 cases of secondary hypothyroidism with empty sella syndrome and 5 cases of primary hypothyroidism and 32 patients with CT have been maintained in euthyroid states with T4 medication. We selected 32 cases of sex and age-matched healthy people as controls.
The mean levels of excreted urinary iodine were 465.6μg/day in the healthy controls and 471.8μg/ day in patients with Cr, respectively. Urinary iodine excretion was significantly correlated to serum inorganic iodide in both controls and CT patients, of which correlation coefficients were +0.35 and +0.5, respectively. Urinary iodine and serum inorganic iodide ratios (U/S) in hypothyroidism were significantly (p<0.05) depressed compared with those in CT.
The present study indicated that recent Japanese dietary iodine intake was estimated to be approximately 470μg/day and that the urinary iodine excretion would be influenced not only by iodine intake but also by thyroid function.View full abstractDownload PDF (565K) -
Shinichi SATOH, Taro Tamada1992 Volume 68 Issue 5 Pages 557-567
Published: May 20, 1992
Released on J-STAGE: September 24, 2012
JOURNAL FREE ACCESSHuman amniotic fluid contains a very high concentration of PRL. And it is widely accepted that decidual cells are the origin of amniotic fluid PRL, and decidual cell PRL is transported into amniotic fluid across the fetal membranes. However, the decidual cells are, in their lower aspect, in contact with chorion cells. Because of this complex structural relationship, decidual cells are often called decidua-chorion cells, besides, chorion PRL reproduction remains to be elucidated. Consequently, we further examined tissue of chorion laeve which had been obtained at spontaneous term vaginal delivery.
The results of our examinations are as follows;
1] Chorion PRL was determined with precipitation method of radioimmunoassay, and it was concluded that chorion tissue contains no small amounts of human PRL; 391±24ng/g in tissue, whereas decidual PRL was 225±91ng/g in tissue.
2] Using immunohistochemical procedures and PAP complex methods, immunized anti - ovine PRL serum revealed PRL reactivity around the numerous granules or globules in term chorion cells.
These data suggest that the chorion cells are the site of reproducible PRL localization and synthesis and, comparable to decidual cells, are the possible source of human PRL in term fetal membrane.View full abstractDownload PDF (2885K) -
-The Importance of Ca2+ InfluxNoriyuki SATO, Monte A GREER, Yhonosuke SHIMOMURA, Hiroyuki SHIMIZU, Y ...1992 Volume 68 Issue 5 Pages 568-575
Published: May 20, 1992
Released on J-STAGE: September 24, 2012
JOURNAL FREE ACCESSIt is still unknown how extracellular hyperosmolarity suppresses exocytosis. To evaluate the possibility that extracellular hyperosmolarity affects one of the most important second messenger system, Ca2+ signal, we evaluated the effect of hyperosmolarity on the thyrotropin releasing hormone (TRH) -induced changes in both intracellular Ca2+concentration ([Ca2+]i) and prolactin (PRL) secretion in GH4C1 cells. TRH caused two phases of [Ca2+]i: an initial high-amplitude phase (first phase), which was not inhibited by Ca2+ free medium, and a sustained low - amplitude phase (second phase), which was abolished by Ca2+ free medium. Medium hyperosmolarity (isotonic=300mOsm, hypertonic=338, 375, 450, and 600mOsm) suppressed both TRH-induced phases of [Ca2+]i in a dose dependent manner, however, the suppressive effect was clearly stronger in the second phase of [Ca2+]i than in the first phase of [Ca2+]i. Low doses of medium hyperosmolarity (338 and 375mOsm) suppressed PRL secretion, which was dependent on Ca2+ influx. However, high doses of medium hyperosmolarity (450 and 600mOsm) also blocked PRL secretion, which was dependent on Ca2+ mobilized from cytosolic Ca2+ pools. These data indicate that in GH4C1 cells medium hyperosmolarity may inhibit PRL secretion by both blocking Ca2+ influx and a mechanism unrelated to Ca2+.View full abstractDownload PDF (771K)
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