Biomedical subjects

C Köster

Publications and source records attributed to C Köster.

5 recordsLinked to original sources

PubMed2005

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.

Animals↗

PubMed1995

[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.

Adult↗

PubMed1993

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.

Fourier Analysis↗

PubMed1992

Matrix-assisted laser desorption/ionization of high-mass molecules by Fourier-transform mass spectrometry.

Following the first demonstrations of high-mass analysis using time-of-flight matrix-assisted laser desorption/ionization (MALDI) techniques by Hillenkamp, Tanaka and their co-workers, there have been significant efforts in a number of laboratories to adapt the new methodology to Fourier-transform mass spectrometry (FTMS). The motivation for this research is obvious. Namely, it would be desirable to couple the unparalleled high mass resolution of FTMS with the extended mass range provided by MALDI, particularly for analysis of polymers and biomolecules. Unfortunately, prior to the present work, attempts to mate FTMS and MALDI have met with limited success. The highest mass matrix-assisted laser-desorption-FTMS result previously obtained appears to be the unpublished low resolution spectrum of bovine insulin recently reported by Russell and co-workers. We, Campana and co-workers, and Hettich and Buchanan have had some success with MALDI-FTMS of biomolecules with masses lower than 3000 Da, including melittin, a variety of lower mass peptides, and oligonucleotides with masses lower than 1800 Da. Furthermore, with the single exception of Campana's report of obtaining mass resolution of 5000 for the molecular ion of melittin, such spectra have not displayed high resolution. Here, we report successful development of MALDI-FTMS, demonstrated with spectra obtained from a variety of high-mass polymer and biomolecule samples, using 355 nm radiation from an excimer-pumped dye laser for desorption/ionization and sinapinic acid as matrix. Some of these spectra are of much higher mass resolution than is possible with current time-of flight mass spectrometers.

Animals↗

PubMed1986

[Ultrasound-guided fine needle puncture of the abdominal organs: indications, results, risks].

2072 patients underwent ultrasonically guided fine-needle biopsy. 1384 patients could be assessed with regard to the final diagnosis. 854 patients underwent fine-needle biopsy of the liver, 322 of the pancreas and 218 of retroperitoneal lesions. The effective sampling rate was 97% for liver biopsies, 86% for pancreas biopsies and 87% for the biopsy of the retroperitoneum. The sensitivity for the detection of malignancies was 90% in liver biopsies, 69% in pancreatic biopsies and 85% in biopsies of the retroperitoneum. The specificity of cytological findings was 100%. Complications occurred in 13 cases. There were two fatalities due to of bleeding, resulting in a complication rate of 0.6% and a lethality of 0.1% of all biopsied patients. The biopsy of the liver proved most dangerous with a complication rate of 1.4%. The bleeding risk of a haemangioma (2.5%) was nearly the same as the bleeding risk of a malignant liver tumour (1.5%).

Abdominal Neoplasms↗