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Biomedical subjects

S Sueoka

Publications and source records attributed to S Sueoka.

17 recordsLinked to original sources
PubMed2006

Microscale multiple scattering of coherent surface acoustic wave packets probed with gigahertz time-reversal acoustics.

The multiple scattering of coherent surface acoustic wave packets in a microstructure is studied using an ultrafast optical technique. By recording a set of acoustic transfer functions, we show that it is possible to implement time-reversal acoustics and refocus the wave packets up to the GHz range, two orders of magnitude higher than usual. Many applications in time-reversal acoustics are thus transposable to correspondingly smaller structures, opening the way to efficient nondestructive characterization and manipulation of multiple scattering on the microscale.

Journal Article↗
PubMed1982

Specific binding sites for epidermal growth factor and its effect on human chorionic gonadotrophin secretion by cultured tumour cell lines: comparison between trophoblastic and non-trophoblastic cells.

Using human trophoblastic (SCH) and nontrophoblastic (HeLa S3) tumour cell lines, specific binding sites for epidermal growth factor (EGF), a potent stimulator of growth in many tissues, and its effect on secretion of human chorionic gonadotrophin (hCG) and/or its subunits were compared between these two tumour cells. Both SCH and HeLa S3 cells possessed two populations of specific binding sites for 125I-labelled EGF: the high affinity (Kd approximately 10(-10) M) and the low affinity (Kd approximately 7 x 10(-10) M) system. Tetradecanoyl phorbol acetate (TPA), a tumour promotor, showed a potent competitor of labelled tracer binding to its receptor sites in both cell lines. EGF stimulated both hCG-alpha and hCG and/or hCG-beta secretion in a dose-responsive manner from SCH cells, whereas it had no effect on hCG-alpha secretion from HeLa S3 cells. In contrast, dibutyryl cyclic AMP plus theophylline, a phosphodiesterase inhibitor, enhanced hCG-alpha secretion from both cells, while TPA had no effect in either cells. These data suggest that EGF may play a physiological role in hCG secretion from trophoblastic tissues and that the mechanism by which hCG and/or its subunits are secreted may differ between trophoblastic and non-trophoblastic tumour cells.

Bucladesine↗
PubMed1981

Presence of ectopic beta-adrenergic receptors on human adrenocortical cortisol-producing adenomas.

A direct binding study of radioligand [3H]dihydroalprenolol (DHA), a potent beta-adrenergic antagonist, was performed on the particulate fractions of four adrenocortical adenomas (three cortisol-producing adenomas and one aldosterone-producing adenoma) and normal adrenal tissues. The effect of epinephrine on cortisol production was also evaluated in vitro from the cultured tumor cells from one cortisol-producing adenoma. Saturable binding of [3H]DHA to the tumor membranes was observed in two of three cortisol-producing adenomas, but not in the aldosterone-producing adenoma or in normal adrenal tissues. Scatchard analysis of equilibrium binding of [3H]DHA revealed a single class of binding sites on the tumor membranes; the apparent dissociation constant (Kd) was 1 nM in each, and the numbers of binding sites were 108 and 45 fmol/mg protein, respectively. Competition by adrenergic agents with [3H]DHA for binding sites on the membranes from one cortisol-producing adenoma revealed that (+/-)propranolol, a beta-adrenergic antagonist, was about 350-fold more potent than phentolamine, an alpha-adrenergic antagonist, suggesting the beta-adrenergic nature of receptor sites. In addition, stereospecificity was demonstrated by about 1000-fold greater affinity of (-)alprenolol than to (+)alprenolol, both of which are stereoisomers of the beta-adrenergic antagonist. Furthermore, production of cortisol from the cultured tumor cells prepared from the same adenoma was significantly stimulated by epinephrine in addition to ACTH. These data indicate that ectopic beta-adrenergic receptor sites are present in some human adrenocortical tumors which may be functionally related to the activation of adenylate cyclase by catecholamines other than ACTH in those tumors, as previously demonstrated. The mechanism by which such altered cellular membrane characteristics occur in association with neoplastic alteration of the endocrine tissues remains unanswered.

Adenoma↗
PubMed1980

Concomitant production of beta-endorphin in ectopic ACTH/beta-LPH-producing tumors.

It is generally accepted that ectopic ACTH-producing tumors produce not only ACTH but beta-MSH or beta-LPH as well. Using a sensitive radioimmunoassay for beta h-endorphin, we have demonstrated the presence of beta-endorphin immunoreactivity with size heterogeneity according to Sephadex gel chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis in 6 ectopic ACTH/beta-LPH-producing tumors, providing further evidence for the role of a common precursor to ACTH and beta-LPH/beta-endorphin in the peptide biosynthesis in these tumors, in a manner similar to the biosynthetic events in the pituitary gland of several species.

ACTH Syndrome, Ectopic↗
PubMed1980

High molecular weight forms of immunoreactive ACTH in a human pituitary and ectopic ACTH-producing tumors.

High molecular weight forms of immunoreactive ACTH (IR-ACTH) were studied in a human pituitary gland and 4 ectopic ACTH-producing tumors in man. Both the pituitary and tumor extracts contained "big" IR-ACTH, which eluted near the void volume, and a small amount of "intermediate" IR-ACTH components, which eluted between the void volume and 125I-alpha h1-39 ACTH, in addition to "little" ACTH which coeluted with 125I-alpha h1-39ACTH by Sephadex G-100 gel filtration. A significant amount of the "big" IR-ACTH applied bound to the concanavalin A-agarose column and was eluted with 0.2 M alpha-methyl-D-mannopyranoside, indicating the glycoprotein content of "big" IR-ACTH fractions. When the "big" and "intermediate" fractions were further analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, they were resolved into 4 molecular forms of IR-ACTH with apparent molecular weight of 37,000, 24,000 , 18,000 and 4,500, respectively. These results indicate that 3 high molecular forms of IR-ACTH are present in the human pituitary and the ectopic ACTH-producing tumors.

ACTH Syndrome, Ectopic↗
PubMed1980

Multiple hormone receptors in the adenylate cyclase of human adrenocortical tumors.

Adenylate cyclase responses to pituitary hormones including adrenocorticotropic hormone (ACTH), biogenetic amines, prostaglandin E1 (PGE1), angiotensin II, and glucagon were evaluated in adrenocortical tumors and hyperplastic adrenal tissues, obtained from patients with Cushing's syndrome at surgery, and in normal adrenals. The adenylate cyclase of two normal adrenals was activated only by ACTH and PGE1 among the hormones tested, while that of two hyperplastic adrenal tissues due to excessive pituitary ACTH secretion was stimulated only by ACTH. Of five ACTH-responsive adrenocortical adenomas, in contrast, three were stimulated by norepinephrine, two by epinephrine, one by thyroid-stimulating hormone, and one by luteinizing hormone in addition to ACTH, indicating the presence of multiple receptors for hormones other than ACTH and PGE1 in these four tumors. The cyclase of an ACTH-unresponsive adrenocortical carcinoma ws activated only by PGE1 and not by other hormones including ACTH, whereas that of an ACTH-responsive adrenocortical nodular hyperplasia was stimulated by ACTH and glucagon but not by other hormones including PGE1. These results indicate the presence of multiple receptors for hormones other than ACTH and PGE1, the normal adrenocortical stimulants, in human adrenocortical tumors, particularly in adrenal adenomas, but not in normal and hyperplastic (of whichever an etiology) adrenocortical tissues, suggesting a functional alteration of the cellular membrane receptors in human adrenocortical tumors.

Adenoma↗
PubMed1979

[Metopirone test].

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Adrenocorticotropic Hormone↗
PubMed1978

Effects of steroid hormones on the level of corticotropin messenger RNA activity in cultured mouse-pituitary-tumor cells.

Studies have been made with the mouse pituitary tumor cell line AtT-20 in culture to determine whether or not the suppression of pituitary corticotropin messenger RNA activity observed upon the administration of glucocorticoids to adrenalectomized rats is due to a direct action of these steroid hormones on the pituitary. The levels of corticotropin messenger RNA activity in AtT-20 cells treated with various steroid hormones were measured with the use of the cell-free protein-synthesizing system derived from wheat germ. The addition of dexamethasone to culture medium reduced the level of corticotropin messenger RNA activity to 30-40% of that in untreated cells. Corticosterone and cortisol exhibited a suppressive effect to a lesser extent. In contrast, nonglucocorticoids such as testosterone and 17beta-estradiol were essentially ineffective. These results indicate that at least part of the glucocorticoid action is exerted directly on the pituitary to suppress corticotropin messenger RNA activity.

Adrenocorticotropic Hormone↗