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Previous studies have proposed varying causes for idiopathic sudden sensorineural hearing loss (SSNHL), including vascular occlusion, ruptured inner ear membrane, acoustic tumours and circulatory disturbances in the inner ear. The objective of this study was to characterise the autonomic regulation in 19 SSNHL patients in comparison to 19 healthy age-gender matched normal-hearing control subjects (CON) in order to improve the diagnostics of vascular caused hearing loss in SSNHL patients. A high-resolution short-term electrocardiogram (ECG) and the continuous noninvasive blood pressure signal were simultaneously recorded under resting conditions (30min). Linear and nonlinear indices of heart rate- and blood pressure variability (HRV, BPV) were calculated to characterise autonomic regulation. The results showed that HRV analysis did not produce significantly different results between SSNHL and CON, whereas linear and nonlinear BPV indices showed significant differences between both groups (p<0.01). This study was the first to show an altered cardiovascular regulation in SSNHL patients when compared to CON subjects, based on continuous blood pressure analysis. This was characterised by reduced variability, complexity and dynamics of blood pressure time series in SSNHL. These findings may contribute to an improved classification of the controversially discussed causes of SSNHL and, in addition, may lead to improved diagnostic strategies for a subgroup of SSNHL patients whose hearing loss is caused by cardiovascular factors., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Based on the iso-peptidase activity of human plasma FXIII, a novel fluorometric assay that determines FXIII concentrations in human plasma below 0.05 IU/ml is introduced. We considered a peptide sequence derived from alpha(2)-antiplasmin (n =12) to yield high sensitivity. Peptide Abz-NE(Cad-Dnp)EQVSPLTLLK exhibits a K(m) value of 19.8+/-2.8 microM and is used in a concentration of 50 microM. The assay design is suitable for measurements in cuvettes (1 ml volume) as well as for the microtiter plate (MTP) format (0.2 ml volume). It provides linear dose-response curves over a wide range of FXIII concentrations (0.05-8.8 IU/ml). The assay was validated with respect to precision, detection and quantitation limits, accuracy/specificity, linearity, and range. A comparison of the fluorometric assay with the photometric assay for FXIII determinations in plasma pools as well as single donor plasma revealed suitability of the fluorometric assay for FXIII determination in plasma of healthy individuals. FXIII concentrations in plasma samples of patients with severe FXIII deficiency are discussed in the context of FXIII antigen levels. These assays correlate well in the critical range below 0.1 IU/ml, whereas the photometric assay may overestimate residual FXIII activity in severe FXIII-deficient patients.

Metalloproteases such as dispase and thermolysin play a crucial role in the life cycle of bacteria. Commonly, they prefer hydrophobic amino acids at P1' of substrate proteins, thereby cleaving the peptide bond at the alpha amino group. Activity of such proteases has been measured by the use of tailor-made oligopeptides provided with fluorescence resonance energy transfer dyes. We can now show that the short dipeptide Dabcyl-Ser-Phe-EDANS is an appropriate substrate of dispase and thermolysin. It was cleaved by both enzymes at the single peptide bond accompanied by a steep increase in fluorescence. Substantial quenching effects of the formed products were observed only when more than 80microM substrate was hydrolyzed. High affinity of the proteases for the dipeptide resulted in low K(m) values of 91+/-9 and 104+/-18microM, which are comparable to those measured for longer peptides. Dabcyl-Ser-Phe-EDANS was also used to determine the pH and optimal temperature of dispase, which were found at pH 7.0 and 50 degrees C. Buffer substances such as acetate, citrate, and tris(hydroxymethyl)aminomethane had no significant effect on enzyme activity. Measurements up to 100 degrees C revealed that hydrolysis of the quenched fluorescent dipeptide took place only in the presence of active dispase.