Ryuichi Sakamoto

Microstructural evolution induced by low energy hydrogen ion irradiation in tungsten

Abstract The microstructural evolution in tungsten during hydrogen ion irradiation with energies ranging from 0.5 to 8 keV at several temperatures between room temperature and 1073 K has been observed for the purpose of evaluating performance of tungsten during exposure to plasma and elucidating the underlaying mechanisms. It is shown that defect accumulation in tungsten is very small because of a high threshold energy for defect production by hydrogen and slipping out of dislocation loops to surfaces. This would lead to low hydrogen retention. These properties, however, may be degraded when the specimen purity is lower.

Retention and desorption of implanted deuterium and high-Z plasma facing materials

Abstract Thermal desorption after D 2 + irradiation from high-Z materials (W and Mo) has been compared with radiation induced microstructural evolution to investigate the details of retention and desorption of the implanted deuterium and underlying microscopic mechanism of the processes. The experimental results indicate that residual impurities act as major trapping sites for implanted deuterium independently of the ion energy for relatively low dose. The trapped deuterium is desorbed in two steps between 470 K and 660 K for high purity Mo, and 400 K and 650 K for high purity W. In the case of Mo damaged heavily at room temperature (1 × 10 22 ions/m 2 ), small cavities trap deuterium and give a large desorption stage at around 640 K. Radiation induced dislocation loops also trap the implanted deuterium effectively.

GLI1, a crucial mediator of sonic hedgehog signaling in prostate cancer, functions as a negative modulator for androgen receptor.

Sonic hedgehog (SHH) signaling, acting in a combinatorial manner with androgen signaling, is essential for prostate patterning and development. Recently, elevated activation of SHH signaling has been shown to play important roles in proliferation, progression and metastasis of prostate cancer. In this report, we demonstrate for the first time, that GLI1, which has been shown to play a central role in SHH signaling in prostate cancer, can act as a co-repressor to substantially block androgen receptor (AR)-mediated transactivation, at least in part, by directly interacting with AR. Our observations suggest that the SHH-GLI pathway might be one of determinants governing the transition of prostate cancer from anandrogen-dependent to an androgen-independent state by compensating, or even superseding androgen signaling.

Importance of contralateral aldosterone suppression during adrenal vein sampling in the subtype evaluation of primary aldosteronism

Adrenal vein sampling (AVS) is the standard criterion for the subtype diagnosis in primary aldosteronism (PA). Although lateralized index (LI) ≥4 after cosyntropin stimulation is the commonly recommended cut‐off for unilateral aldosterone hypersecretion, many of the referral centres in the world use LI cut‐off of <4 without sufficient evidence for its diagnostic accuracy.

Radiation damage and deuterium trapping in deuterium ion injected beryllium

Abstract Thermal desorption of D from its ion injected Be at several temperatures was compared with microstructural evolution during irradiation and annealing to know the details of retention and desorption of the implanted D and to identify responsible traps. In the case of the irradiation at 300 K, black dot defects and very small bubbles are formed at low doses and at high doses, respectively. The bubbles grow by annealing above 573 K and act as major trapping sites for D at low doses less than 1 × 10 21 ions/m 2 . D trapped in the bubbles finally released at around 880 K. Long and thin bubbles are developed by the irradiation at 673 K. These are responsible for high retention under the irradiation at high temperatures.

In situ study of microstructural evolution in molybdenum during irradiation with low energy hydrogen ions

For the purpose of fundamental investigations of the response of materials exposed to a plasma, a duoplasma ion gun-transmission electron microscope (TEM) interface was constructed. This facility is capable of irradiating hydrogen ions with energies ranging from 0.1 to 10 keV onto TEM specimens, allowing in situ microstructural observations. The evolution of dislocations bubbles and other aggregates in Mo at 573 K and their dependence on ion energy were investigated. The microstructures are found to be sensitive to ion energy. They are composed of a dislocation network and bubbles in the case of high energy ions, and in contrast to this, of a low density of planar dark images, which are expected to be platelet hydrogen clusters, in the case of low energy ions. It is suggested that the hydrogen retention, as well as materials damage, should significantly be reduced when the energy of hydrogen ions is reduced to or below the threshold of displacement damage production.

Microstructural evolution in molybdenum during hydrogen ion implantation with energies comparable to the boundary plasma

In situ observation of microstructural evolution in molybdenum during hydrogen ion irradiation with energies comparable to the boundary plasma of fusion devices (< 1 keV) were carried out in comparison with those with higher energies. Dislocation loops were formed by irradiation with 8 keV or 4 keV H+ ions, while platelet hydrogen clusters, which were unstable during subsequent annealing, were formed by irradiation with 0.5 keV H+ ions. The microstructure with 2 keV H+ ions was composed of the mixture of these two types of defect clusters. The strong dependence of microstructure on the ion energy suggested that the effects of higher energy ion irradiations in the case of simulation irradiation experiments should be different from those of lower energy ion irradiations expected in the plasma-facing component of fusion devices.

Adrenal Venous Sampling in Patients With Positive Screening but Negative Confirmatory Testing for Primary Aldosteronism

Adrenal venous sampling is considered to be the most reliable diagnostic procedure to lateralize aldosterone excess in primary aldosteronism (PA). However, normative criteria have not been established partially because of a lack of data in non-PA hypertensive patients. The aim of the study was to investigate aldosterone concentration and its gradient in the adrenal vein of non-PA hypertensive patients. We retrospectively studied the results of cosyntropin-stimulated adrenal venous sampling in 40 hypertensive patients who showed positive screening testing but negative results in 2 confirmatory tests/captopril challenge test and saline infusion test. Plasma aldosterone concentration, aldosterone/cortisol ratio, its higher/lower ratio (lateralization index) in the adrenal vein with cosyntropin stimulation were measured. Median plasma aldosterone concentration in the adrenal vein was 25 819 pg/mL (range, 5154–69 920) in the higher side and 12 953 (range, 1866–36 190) pg/mL in the lower side (P<0.001). There was a significant gradient in aldosterone/cortisol ratio between the higher and the lower sides (27.2 [5.4–66.0] versus 17.3 [4.0–59.0] pg/mL per &mgr;g/dL; P<0.001) with lateralization index ranging from 1.01 to 3.87. The aldosterone lateralization gradient was between 1 to 2 in 32 patients and 2 to 4 in 8 patients. None of the patients showed lateralization index ≥4. The present study demonstrated that plasma aldosterone concentration in the adrenal veins showed significant variation and lateralization gradient even in non-PA hypertensive patients. Adrenal venous sampling aldosterone lateralization gradients between 2 and 4 should be interpreted with caution in patients with PA because these gradients can be found even in patients with negative confirmatory testing for PA.

Optimum position of left adrenal vein sampling for subtype diagnosis in primary aldosteronism

Although adrenal vein sampling (AVS) is the standard method for subtype diagnosis in primary aldosteronism (PA), protocol details including the sampling position in the adrenal vein are not standardized.

Activin stimulates CYP19A gene expression in human ovarian granulosa cell-like KGN cells via the Smad2 signaling pathway.

Activin, a transforming growth factor β family member, has a wide range of physiological roles during embryonic development and organogenesis. In the ovary, activin, secreted from ovarian granulosa cells, not only acts on the pituitary gland to regulate the gonadotropin secretion from the pituitary gland in an endocrine manner but also acts on granulosa cells in a paracrine/autocrine manner to regulate folliculogenesis. Previously, we showed that activin signals through activin type IB receptor (ActRIB) and up-regulates follicle-stimulating hormone receptor expression and P450 aromatase activity in human ovarian granulose cell-like KGN cells. In the current study, we demonstrate the direct involvement of Smad2 as a downstream signal mediator of ActRIB in the transcriptional regulation of the P450 aromatase gene (CYP19A) in KGN cells. Upon activin stimulation, Smad2 activation and an increase in P450 aromatase messenger RNA (mRNA) were observed in KGN cells. Interestingly, Smad2 phosphorylation correlated well with the increase in P450 aromatase mRNA. Reciprocally, knockdown of Smad2 mRNA in KGN cells led to a decrease in the P450 aromatase mRNA expression, suggesting that Smad2 regulates CYP19A gene expression. Further analysis of CYP19A promoter activity revealed that the 5 upstream region between -2069 and -1271bp is required for the activation by Smad2. Finally, we provide compelling evidence that Smad2 shows follicular stage-specific expression, which is high in granulosa cells of preantral or early antral follicles in mice. Our results suggest that activin signaling through the ActRIB-Smad2 pathway plays a pivotal role in CYP19A expression and thus in follicular development.