[Blood coagulation factor XIII: activation, substrates and structure of a transglutaminase]. / Blutgerinnungsfaktor XIII: Aktivierung, Substrate und Struktur einer Transglutaminase.

For a long time blood coagulation factor XIII did not get the attention it deserves, and research in the field of transglutaminases was neglected. The interesting results obtained in recent years demonstrate the importance of this protein for the stabilization of a blood clot. The accurate regulation of activation and of localization of factor XIII is not fully understood. Yet the proposed mechanisms suggest a high degree of complexity. In this review, recent biochemical and structural results on factor XIII are discussed.

Adverse drug reaction monitoring--digitoxin overdosage in the elderly.

Drug-related illness is an everlasting universal problem and also an important cause of admissions to hospitals. Adverse reactions are still grossly underreported by medical professions. Little information is available regarding the frequency or type of ADRs managed in hospitals. Since January 1997, we have taken part in a study, supported by the German Federal Institute for Drugs and Medical Device to improve the spontaneous drug information reporting system in Germany. Three German regionalized Departments of Clinical Pharmacology--Jena, Dresden, Rostock--serve as Pharmacovigilance Centers in collaboration with the Pharmacoepidemiology Research Group of the University of Munich. Since January 1997, the regional group in Jena has been monitoring the University Clinic of Internal Medicine for admissions caused by adverse drug reactions. All emergency cases and patients on intensive care units were checked for adverse drug reactions. We present our results, including clinical and demographic data, concerning intoxications and especially those involving digitoxin in 210 patients with ADR. Forty patients with digitoxin toxicity had an average age of 81 years (81.1+/-6.3), a low body weight (59.7+/-12.7 kg) and 3 out of 4 were women. 75% of all patients with digitoxin side effects had elevated serum digitoxin levels with concentrations higher than 25 microg/ml. The relatively high frequency of digitoxin intoxications in our hospital may reflect the advanced age and low body weight of patients. Patients received digitoxin regardless of age, weight and, sometimes, clinical indication. Physicians should be aware of drugs having a high risk when used in elderly patients. The use of digitoxin assays and keeping serum levels within or near the therapeutic range will diminish the incidence of overdoses.

Systemic vascular effects of thrombin and thrombin receptor activating peptide in rats.

The proteolytic enzyme thrombin activates its receptor by cleavage of a peptide from the extracellular N-terminus. The newly generated N-terminus acts as a tethered ligand to activate the receptor. Receptor-mediated cellular effects of thrombin can be mimicked by synthetic peptides, which correspond to the amino acid sequence of the newly formed N-terminus. The aim of the present study was to investigate vascular effects of thrombin and the thrombin receptor activating peptide (TRAP: SFLLRN) in vitro and in vivo in rats. In precontracted rat aortic rings, both thrombin (0.3, 1, 3 U/ml) and TRAP (1, 3, 10, 20, 40 microM) induced endothelium-dependent relaxant responses. In anaesthetized rats, the mean arterial blood pressure (MAP) was measured continuously in the carotid artery by a pressure transducer. Thrombin and TRAP were administered as intravenous bolus injection via the femoral vein. Thrombin at doses of 3-100 U/kg, as well as TRAP at doses of 0.1-0.6 mg/kg i.v., caused a reversible decrease in MAP. Administration of TRAP at doses of 0.3 and 0.6 mg/kg led to a triphasic response in most of the animals treated (50% and 75%, respectively), i.e. a short drop of MAP was followed by an increase and finally a longer lasting decrease in MAP. Pretreatment with the nitric oxide (NO)-synthase inhibitor N(G)-nitro-L-arginine-methylester (L-NAME) suppressed the dose-dependent vasodilator effects of thrombin. Heparin and hirudin also inhibited the hypotensive response to thrombin. The TRAP-induced triphasic reaction on MAP was not affected by the serotonin antagonists ketanserin and tropisetron, as well as the aminopeptidase inhibitor amastatin. Pretreatment with L-NAME led to an inhibition of hypotension induced by TRAP at 0.1 mg/kg, as well as of the initial transient fall in blood pressure at doses of 0.3 and 0.6 mg/kg. The studies suggest that the thrombin- and TRAP-induced vasodilation in vitro and in vivo is in part due to the release of endothelial NO. In the blood pressure response to TRAP, additional effects seem to be involved.

On the routine use of soft X-rays in macromolecular crystallography.

A diffraction data set has been collected from a blood coagulation factor XIII-Ca(2+) complex crystal at the X-ray diffraction beamline of the ELETTRA synchrotron (Trieste, Italy) at a wavelength of 2.6 A. The data collection could be carried out using the beamline as is, without making any time-consuming changes to the apparatus. Various data-processing schemes have been employed and it has been observed that local or detector scaling procedures are essential for producing the 'best' anomalous differences.