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.     

Performance and design evaluation of WDM stars

A performance tool for evaluating the design of a wavelength-division-multiplexing (WDM) passive star is provided. The design parameters that determine the system performance are the number of wavelengths in the system, the number of receivers per node, the wavelength allocation per receiver, the transmitter tunability range, and the node buffer size. An exact analysis becomes prohibitively complex for even moderately sized systems. Therefore, an efficient approximate analysis with drastically reduced computational complexity is presented, incorporating all of the above design parameters, in addition to the channel access protocol and the nonhomogeneous traffic patterns of high-bandwidth networks. The approach produces very accurate results and can help in selecting the most cost-effective system design for given performance requirements     

Large electroabsorption effect in GaInAs/InP multiple quantum well(MQW) optical modulator grown by OMVPE

To make short, high-speed electroabsorption modulators, it is necessary to use a material and device structure that displays a large change in absorption coefficient, Δα. The authors report a device with Δα=7800 cm^-1, which provides an on/off ratio of 44:1 at λ=1.6 μm with a drive voltage of 10 V     

A WDM receiver photonic integrated circuit with net on-chip gain

We demonstrate a photonic circuit with an optical preamplifier, a WDM filter and a fast photodetector integrated on the same chip. The passive integrated filter is formed by an aspheric waveguide lens and a planar Bragg grating. This arrangements yields narrow filter response (8 Å width at -3 dB is demonstrated) and high rejection ratio of 24 dB. The optical preamplifier consisting of strained multi-quantum well layers provides sufficient amplification to overcome the passive losses. Response curves demonstrate net on-chip gain with low ripple     

A wideband all-optical WDM network

We describe some of the results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks in developing architectures, technology components, and applications for the realization of scaleable, wideband, and transparent optical wavelength-division multiplexing (WDM) networks. Our architecture addresses all-optical transport over the wide, metropolitan, and local areas. It utilizes wavelength partitioning, routing, and active multiwavelength cross-connect switches to achieve a network that is scaleable in the number of users, data rates, and geographic span. The network supports two services which can be point-to-multipoint or multipoint-to-multipoint simplex or duplex connections. The A service is a transparent physically circuit-switched service and the B-service is a scheduled time-slotted circuit which is transparent within its time slots. We have developed a 20-channel local and metropolitan area WDM testbed deployed in the Boston area, now undergoing characterization and experimental applications     

Three-channel buried-crescent InGaAsP laser with 1.51 ?m wavelength on semi-insulating InP

Laser diodes with current threshold as low as 16 mA for lasers of 300 ?m length and channel width of 2?3 ?m were obtained with operational wavelength of 1.51 ?m. These lasers are fabricated with one liquid-phase-epitaxy growth step and a lateral zinc diffusion process. Current confinement is achieved by use of the semi-insulating substrate material.