Notizen: Fast Pulsed Laser Induced Electron Generation for Electron Impact Mass Spectrometry

A new ultra fast electron impact (El) ion source is pre­sented that produces a very short, high intensity electron beam, allowing medium resolution mass spectra to be re­corded without pulsing the ion accelerating voltages in a time-of-flight mass spectrometer (TOF-MS). The ion source requires minimum modification of any TOF-MS equipped with an electrostatic ion reflector and UV-laser. El-spectra are presented for comparison with literature spectra.

Perp is required for tissue-specific cell survival during zebrafish development

The tumor suppressor p53 has two alternative effects, causing either cell cycle arrest or apoptosis. These different effects are supposed to be mediated by the transcriptional activation of different target genes. perp, encoding a transmembrane protein of the Pmp22 family, is a transcriptional p53 target exclusively upregulated in apoptotic cells. However, its role during normal development had remained largely unclear. Here, we report the isolation and characterization of a zebrafish perp homolog. Upon overexpression in early zebrafish embryos, perp induces apoptosis. In addition, it contributes to p53-dependent and UV-induced cell death. However, during normal zebrafish development, perp displays a p53-independent and spatially restricted expression in specific cell types and tissues. Antisense-mediated loss of Perp function leads to increased apoptosis in perp-expressing cells of the developing skin and notochord. We conclude that, in contrast to its proapoptotic function in stressed cells, Perp plays an antiapoptotic role during normal zebrafish development to regulate tissue-specific cell survival.

[Coronary reserve after orthotopic heart transplantation: quantification with N-13 ammonia and positron emission tomography]

Coronary transplant vasculopathy is known to be associated with an early impairment of endothelium-dependent vasodilatation. In this study the largely endothelium-independent dilator response to dipyridamole was evaluated in 22 patients 36 +/- 17 months after transplantation in relation to their angiographic findings. The dipyridamole coronary reserve was measured by N-13 ammonia and positron emission tomography (PET). Transplant vasculopathy was suspected or evident in 13 of 22 patients by coronary angiography. Coronary reserve was lower in transplant recipients than in normal controls (2.3 +/- 0.9 vs. 4.7 +/- 1.4). Those with a normal angiogram had a near normal minimal coronary resistance (0.3 +/- 0.04 mmHg.min.100 g/ml) and a normalized coronary reserve after correction for the increased resting blood flow (4.8 +/- 0.7). However, in patients with angiographic vasculopathy, coronary reserve was markedly reduced (1.8 +/- 0.7, corrected 2.7 +/- 1.0) and minimal coronary resistance was elevated (0.6 +/- 0.3, p < 0.001). Moreover, regional coronary reserve was homogeneously reduced throughout the myocardium without a clear segmental relationship to angiographic stenoses. After testing of other factors known to influence coronary resistance, our data are compatible with diffuse obstructions of the microvascular bed that are associated with an angiographically visible vasculopathy. The evaluation of coronary reserve by dipyridamole and PET provides a useful extension of angiography in these patients.

Investigation of a "screened" electrostatic ion trap for analysis of high mass molecules by fourier transform mass spectrometry

With the recent adaptation of matrix-assisted laser desorption/ionization (MALDI) of large biomolecules and polymers to Fourier transform mass spectrometric analysis, it is of interest to explore the possible advantages of using a "screened" electrostatic ion trapping technique. It is demonstrated that the observed rate of change of ion cyclotron resonance frequency with trapping potential is in excellent agreement with theory, being independent of mass and charge, in the mass range from 1185 to just under 17,000 Da. When a screened cubic trap is used in a ca. 7-T magnetic field, the electrical potential within the trap is effectively reduced, and ion cyclotron resonance frequency shifts as a function of trapping potential are decreased by a factor of 25. There is no evidence of significant improvement in mass resolution with this trap design, except when higher trapping potentials are compared. In a 9.7-V screened trap measurement, a bovine insulin spectrum with an average resolution of 10,000 is obtained. Comparable mass resolution under conventional trapping conditions could not be obtained for trapping potentials greater than 1.2 V. It is evident from this study that use of the screened trap technique could offer advantages for MALDI-Fourier transform mass spectrometry.