Perioperative assessment of regional ventilation during changing body positions and ventilation conditions by electrical impedance tomography.

BACKGROUND: Lung-protective ventilation is claimed to be beneficial not only in critically ill patients, but also in pulmonary healthy patients undergoing general anaesthesia. We report the use of electrical impedance tomography for assessing regional changes in ventilation, during both spontaneous breathing and mechanical ventilation, in patients undergoing robot-assisted radical prostatectomy. METHODS: We performed electrical impedance tomography measurements in 39 patients before induction of anaesthesia in the sitting (M1) and supine position (M2), after the start of mechanical ventilation (M3), during capnoperitoneum and Trendelenburg positioning (M4), and finally, in the supine position after release of capnoperitoneum (M5). To quantify regional changes in lung ventilation, we calculated the centre of ventilation and 'silent spaces' in the ventral and dorsal lung regions that did not show major impedance changes. RESULTS: Compared with the awake supine position [2.3% (2.3)], anaesthesia and mechanical ventilation induced a significant increase in silent spaces in the dorsal dependent lung [9.2% (6.3); P<0.05]. Capnoperitoneum and the Trendelenburg position led to a significant increase in such spaces [11.5% (8.9)]. Silent space in the ventral lung remained constant throughout anaesthesia. CONCLUSION: Electrical impedance tomography was able to identify and quantify on a breath-by-breath basis circumscribed areas, so-called silent spaces, within healthy lungs that received little or no ventilation during general anaesthesia, capnoperitoneum, and different body positions. As these silent spaces are suggestive of atelectasis on the one hand and overdistension on the other, they might become useful to guide individualized protective ventilation strategies to mitigate the side-effects of anaesthesia and surgery on the lungs.

Spectroscopic detection and quantification of heme and heme degradation products.

Heme and heme degradation products play critical roles in numerous biological phenomena which until now have only been partially understood. One reason for this is the very low concentrations at which free heme, its complexes and the partly unstable degradation products occur in living cells. Therefore, powerful and specific detection methods are needed. In this contribution, the potential of nondestructive Raman spectroscopy for the detection, quantification and discrimination of heme and heme degradation products is investigated. Resonance Raman spectroscopy using different excitation wavelengths (413, 476, 532, and 752 nm) is employed to estimate the limit of detection for hemin, myoglobin, biliverdin, and bilirubin. Concentrations in the low micromolar range (down to 3 µmol/L) could be reliably detected when utilizing the resonance enhancement effect. Furthermore, a systematic study on the surface-enhanced Raman spectroscopy (SERS) detection of hemin in the presence of other cellular components, such as the highly similar cytochrome c, DNA, and the important antioxidant glutathione, is presented. A microfluidic device was used to reproducibly create a segmented flow of aqueous droplets and oil compartments. Those aqueous droplets acted as model chambers where the analytes have to compete for the colloid. With the help of statistical analysis, it was possible to detect and differentiate the pure substances as well as the binary mixtures and gain insights into their interaction.

Poly(A) tail shortening correlates with mRNA repression in tropoelastin regulation.

BACKGROUND: It has been shown for various organisms that expression of tropoelastin (TE) is high during fetal and neonatal growth and that it is reduced in adulthood by an unknown mechanism. OBJECTIVE: To highlight the process of TE mRNA repression in vivo, total RNA from human skin biopsies was analyzed and TE mRNA expression was compared in fetal and adult donors. METHODS: TaqMan Real-Time PCR, Poly(A) tail length assay, immunoblot. RESULTS: In this study a more than 30-fold reduction of mature TE mRNA was detected whereas the decline on pre-mRNA level was not pronounced. This finding supports the hypothesis that the repression of mature TE mRNA is for the most part due to posttranscriptional mechanisms. Since deadenylation-dependent mRNA destabilization is the major decay pathway for most mRNAs, poly(A) tail length of mature TE mRNA was analyzed in fetal and adult human skin, lung and uterus, showing a profound reduction of poly(A) tail length in the adult samples. While TE mRNA is repressed in adult tissues in vivo, TGF-ß(1) has been shown to induce expression of TE mRNA in vitro on the posttranscriptional level. To analyze the underlying mechanism, TE mRNA poly(A) tail length was analyzed in human dermal fibroblasts after treatment with TGF-ß(1)in vitro. Besides the expected increase in TE expression, TGF-ß(1) treatment resulted in a significant stabilization of TE mRNA poly(A) tail length. CONCLUSION: Our findings correlate for the first time TE expression level with poly(A) tail length and suggest that maintenance of poly(A) tail and deadenylation of TE mRNA might be general mechanisms involved in the regulation of TE expression.