Enhanced Na+/H+ exchange in Cushing's syndrome reflects functional hypermineralocorticoidism

BACKGROUND: Patients with Cushing's syndrome exhibit a bimodal distribution of maximal rates of the erythrocyte amiloride-sensitive Na+/H+ exchange (NHE). Enhanced erythrocyte NHE has recently been found in patients with primary aldosteronism. OBJECTIVE: To test the hypothesis that occult hypermineralocorticoidism in a subset of patients with Cushing's syndrome is responsible for the greater than normal NHE. METHODS: NHE was measured as maximal initial rate (Vmax) of amiloride-inhibited efflux of H+ into an alkaline Na+-containing medium, for 47 patients with hypercortisolism (20 with pituitary adenomas, 18 with adrenal adenomas, and nine with ectopic production of adrenocorticotropin). Clinical appearance, blood pressure levels, plasma aldosterone and deoxycorticosterone levels, serum electrolytes, and urine (tetrahydrocortisol plus 5-alpha-tetrahydrocortisol) : tetrahydrocortisone ratios were assessed for all patients. Twenty patients (10 with greater than normal NHE and 10 with low-to-normal NHE) were randomly selected from 47 patients with hypercortisolism, and treated with 200 mg/day spironolactone for 7 days. NHE in these patients was assessed before starting the treatment and 2 days after its cessation. RESULTS: Greater than normal NHE (Vmax) was associated with peripheral edema, high diastolic blood pressure, hypokalemia, and high urine (tetrahydrocortisol plus 5-alpha-tetrahydrocortisol) : tetrahydrocortisone ratios. The enhanced NHE was rapidly normalized by treatment with spironolactone. CONCLUSION: Erythrocyte NHE in patients with hypercortisolism and functional hypermineralocorticoidism is greater than normal due to incomplete peripheral conversion of cortisol (which binds to mineralocorticoid receptors) into metabolically inactive cortisone.     

新型坐标测量机结构设计及数学模型

文章阐述了新型平行双关节坐标测量机的优点,介绍了其机械结构设计和电机控制系统,建立了数学模型,为进一步进行误差补偿提供了理论基础。     

基于LEON3的中央控制器设计及EDAC功能实现

针对目前空间机器人中央控制器运行速度较低、实时控制性弱等缺点,设计了基于LEON3处理器核的中央控制器,用做空间机器人控制的初步研究。同时,为了解决太空环境中电子控制系统中存储器易出现单粒子翻转效应(SEU)的问题,设计了一种基于Hsiao码的EDAC电路,以实现"纠一检二"(SEC-DED)的基本功能。使用VHDL语言描述该EDAC功能,使其兼容LEON3的AM-BA2.0总线,通过仿真试验验证了电路的可靠性。     

Separation from related compounds and assay of calcipotriol by high-performance liquid chromatography

In this paper, two methods are presented. One involves the separation of calcipotriol, a new synthetic analogue, from two related compounds, specifically cholecalciferol (Vitamin D3) and calcitriol (1,25-dihydroxyvitamin D3). The other involves the isolation and assay of calcipotriol from a topical ointment. The study was performed with reversed-phase high-performance liquid chromatography using an RP18 column and ultraviolet detection. Applying the method of Snyder, a mobile phase mixture containing methanol-acetonitrile-water (67:23:10, v/v) was found which achieved a total separation within 18 min. A mobile phase of methanol-water (80:20, v/v) attained a slower elution of calcipotriol. For isolation and assay of calcipotriol from an ointment (Daivonex), dissolution in chloroform gave the highest recovery (> 98%). The isolation and assay process can be performed within 2 h.     

Superluminescence in an AlGaAsSb/InGaAsSb/AlGaAsSb double heterostructure

Intense electroluminescence is observed for the first time in a AlGaAsSb/In_0.9Ga_0.1As_0.89Sb_0.21/AlGaAsSb double heterostructure in the 3–4 μm wavelength range at T=77 K. The structure was grown on a GaSb substrate by liquid-phase epitaxy. The photon energy at the maximum of the narrow emission band with a half-width of 9–10 eV is hv=387 meV which is 60 meV greater than the band gap of the narrow-gap InGaAsSb solid solution (E _g =326 meV). This behavior is attributed to the population inversion characteristics of the active region when an external bias is applied Pis’ma Zh. Tekh. Fiz. 23, 68–74 (May 12, 1997)