A compact 7-cell Si-drift detector module for high-count rate X-ray spectroscopy.

A new Si-drift detector module for fast X-ray spectroscopy experiments was developed and realized. The Peltier-cooled module comprises a sensor with 7 × 7-mm2 active area, an integrated circuit for amplification, shaping and detection, storage, and derandomized readout of signal pulses in parallel, and amplifiers for line driving. The compactness and hexagonal shape of the module with a wrench size of 16mm allow very short distances to the specimen and multi-module arrangements. The power dissipation is 186mW. At a shaper peaking time of 190 ns and an integration time of 450 ns an electronic rms noise of ~11 electrons was achieved. When operated at 7 °C, FWHM line widths around 260 and 460 eV (Cu-Kα) were obtained at low rates and at sum-count rates of 1.7 MHz, respectively. The peak shift is below 1% for a broad range of count rates. At 1.7-MHz sum-count rate the throughput loss amounts to 30%.

Purification and molecular cloning of a novel essential component of the apolipoprotein B mRNA editing enzyme-complex.

Editing of apolipoprotein B (apoB) mRNA requires the catalytic component APOBEC-1 together with "auxiliary" proteins that have not been conclusively characterized so far. Here we report the purification of these additional components of the apoB mRNA editing enzyme-complex from rat liver and the cDNA cloning of the novel APOBEC-1-stimulating protein (ASP). Two proteins copurified into the final active fraction and were characterized by peptide sequencing and mass spectrometry: KSRP, a 75-kDa protein originally described as a splicing regulating factor, and ASP, a hitherto unknown 65-kDa protein. Separation of these two proteins resulted in a reduction of APOBEC-1-stimulating activity. ASP represents a novel type of RNA-binding protein and contains three single-stranded RNA-binding domains in the amino-terminal half and a putative double-stranded RNA-binding domain at the carboxyl terminus. Purified recombinant glutathione S-transferase (GST)-ASP, but not recombinant GST-KSRP, stimulated recombinant GST-APOBEC-1 to edit apoB RNA in vitro. These data demonstrate that ASP is the second essential component of the apoB mRNA editing enzyme-complex. In rat liver, ASP is apparently associated with KSRP, which may confer stability to the editing enzyme-complex with its substrate apoB RNA serving as an additional auxiliary component.

C-type natriuretic peptide exerts stimulatory effects on the corticotropin-releasing hormone-induced secretion of hormones in normal man.

C-type natriuretic peptide and atrial natriuretic peptide have been reported to bind to distinct receptors and to exert opposing effects on different systems. Although it is known that atrial natriuretic peptide inhibits the corticotropin-releasing hormone-stimulated hormone release in man, the corresponding action of C-type natriuretic peptide has so far not been characterized. We investigated the effects of 30-min infusions of 150 and 300 micrograms C-type natriuretic peptide on adrenocorticotropin, cortisol, and prolactin release stimulated by 100 micrograms corticotropin-releasing hormone and on cardiovascular parameters in 8 healthy male volunteers. Compared with placebo, 300 micrograms C-type natriuretic peptide significantly (P < 0.05) enhanced the stimulation of cortisol (area under curve (arbitrary units): 520 +/- 35 vs 651 +/- 55) and prolactin (area under curve: 29 +/- 3 vs 37 +/- 5). Adrenocorticotropin levels were increased, but the differences did not reach statistical significance (maximum increment: 27 +/- 4 vs 36 +/- 2 pg/ml). C-type natriuretic peptide at a dose of 150 micrograms had no clear effect on these hormones and C-type natriuretic peptide also produced no cardiovascular or subjective effects. Our data suggest stimulatory effects of C-type natriuretic peptide on corticotropin-releasing hormone-induced hormone release and offer further evidence for a complex role of different natriuretic peptides in endocrine regulation.