Total Aortic Arch Replacement: Superior Ventriculo-Arterial Coupling with Decellularized Allografts Compared with Conventional Prostheses.

BACKGROUND: To date, no experimental or clinical study provides detailed analysis of vascular impedance changes after total aortic arch replacement. This study investigated ventriculoarterial coupling and vascular impedance after replacement of the aortic arch with conventional prostheses vs. decellularized allografts. METHODS: After preparing decellularized aortic arch allografts, their mechanical, histological and biochemical properties were evaluated and compared to native aortic arches and conventional prostheses in vitro. In open-chest dogs, total aortic arch replacement was performed with conventional prostheses and compared to decellularized allografts (n = 5/group). Aortic flow and pressure were recorded continuously, left ventricular pressure-volume relations were measured by using a pressure-conductance catheter. From the hemodynamic variables end-systolic elastance (Ees), arterial elastance (Ea) and ventriculoarterial coupling were calculated. Characteristic impedance (Z) was assessed by Fourier analysis. RESULTS: While Ees did not differ between the groups and over time (4.1+/-1.19 vs. 4.58+/-1.39 mmHg/mL and 3.21+/-0.97 vs. 3.96+/-1.16 mmHg/mL), Ea showed a higher increase in the prosthesis group (4.01+/-0.67 vs. 6.18+/-0.20 mmHg/mL, P<0.05) in comparison to decellularized allografts (5.03+/-0.35 vs. 5.99+/-1.09 mmHg/mL). This led to impaired ventriculoarterial coupling in the prosthesis group, while it remained unchanged in the allograft group (62.5+/-50.9 vs. 3.9+/-23.4%). Z showed a strong increasing tendency in the prosthesis group and it was markedly higher after replacement when compared to decellularized allografts (44.6+/-8.3dyn.sec.cm-5 vs. 32.4+/-2.0dyn.sec.cm-5, P<0.05). CONCLUSIONS: Total aortic arch replacement leads to contractility-afterload mismatch by means of increased impedance and invert ventriculoarterial coupling ratio after implantation of conventional prostheses. Implantation of decellularized allografts preserves vascular impedance thereby improving ventriculoarterial mechanoenergetics after aortic arch replacement

Applicability of non-exhaustive extraction procedures with Tenax and HPCD

Chemical extraction techniques like non-exhaustive extraction with Tenax or hydroxypropyl--cyclodextrin (HPCD) have been shown to measure the biodegradable fraction of aromatic contaminants like PAHs in soil. However, there is little research on the chemical prediction of aliphatic hydrocarbon degradation. The aim of this study was to investigate the potential for HPCD and Tenax extractions to predict PAH and petroleum hydrocarbon biodegradation in soil. 11 historically contaminated soils with PAH concentrations between 74 and 680 mg/kg and concentrations of petroleum hydrocarbons from 330 to 4704 mg/kg were analysed. Both non-exhaustive extraction procedures showed promising results for estimating the available contaminant fraction of both contaminant groups concerning the feasibility, reproducibility and correlation with soil biodegradation applying single point testing. Both methods have the potential to be used to assess the biodegradable hydrophobic organic polluta nt fraction in contaminated soils. In a direct comparison of the two extraction procedures, Tenax extraction is assessed to be more time-consuming than HPCD extraction. Furthermore, a sufficient soil/Tenax ratio has to be considered

Hazard assessment of a silver nanoparticle in soil applied via sewage sludge

Background: Silver nanoparticles (AgNPs) are widely used in many fields of application and consumer products due to their antibacterial properties. The aim of this study was to prepare a hazard assessment for one specific AgNP in soil, incorporated via sewage sludge (the sewage sludge pathway). The effects of pristine AgNPs on microorganisms, plants and earthworms were first determined in screening tests. Long-term tests over 140 days were then conducted with AgNPs added to soil via sewage sludge. AgNPs were incorporated into the sludge through a simulated sewage treatment plant (STP) over 10 days to allow transformation to occur and also by manual spiking over 2 h. The results of the most sensitive organism from the long-term tests, the soil microorganisms, are presented. Results: The STP simulations confirmed that at environmentally relevant concentrations >90% of AgNPs remain bound to sewage sludge. Effects of AgNPs bound to sewage sludge and added to soil were similar to that of pristine NM-300K after degradation of the sludge. The predicted no-effect concentration for NM-300K in soil of 0.05 mg/kg dry soil determined a maximum threshold of 30 mg/kg dry sludge per application, considering the maximum addition of sewage sludge in Germany (5 tons per hectare every 3 years). Conclusion: At environmentally relevant concentrations, AgNP absorption to sludge and aging in soil (even after transformation) cause toxic effects on soil microorganisms of the terrestrial ecosystem

Soil-plant transfer of organic chemicals and derivation of trigger values

The Federal Soil Protection Act [Anonymus, 1998] was technically realized by the Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV) of July 12th, 1999. Precautionary values and trigger values as laid down in the Law(1) are an important instrument to realise its requirements. Trigger values are related to various soil uses and objectives of protection, which are "human health", "quality of food and feed", and "leachate to ground-water". Any procedure to derive trigger values for the objective "quality of food and feed" has to consider the soil-plant transfer of chemicals for soils under agricultural use and household gardens. Thus, the production function of soil is taken into account. The exact procedure to obtain trigger values for "quality of food and feed" is explained. By this means, trigger values for "quality of food and feed" already were derived for some metal compounds, namely arsenic, lead, mercury and thallium. Beside metal compounds several organic substances are also of priority; for example, a trigger value for benzo(a)pyrene and an action value for PCBs has to be defined. The pathway soil-plant is a sensible exposure route due to potential accumulation in the food chain. A summary on the methodology and results of trigger value derivation for some selected organic chemicals previously used as pesticides and of different data sizes with respect to the soil-plant transfer process is given

Polychlorierte Dibenzo-p-dioxine, -furane (PCDD/F) und Analoga in datierten aquatischen Sedimenten und terrestrischen Boeden

In aquatischen Sedimenten akkumulieren die unbeabsichtigt formierten PCDD/F final. Anhand datierter Sedimentkerne sind PCDD in 8.120 Jahre alten Sedimenten in Japan und in 350 bis 400 Jahre alten Sedimenten in der Ostsee detektiert worden. Sedimente eignen sich unter Beruecksichtigung von Transformationsprozessen als Quellenindikatoren, in ihnen sind PCDD/F 30 km vom Emittenten nachgewiesen worden, im Benthos in bis zu 50 km Distanz, ein beachtliches Bioakkumulationspotential indizierend. Neben fehlenden Kontaminationsdaten sind unbedingt die sedimentinternen Verteilungs- und Diageneseprozesse, die Prozesse an der Sediment/Wasser-Grenzflaeche, die aeroben und anaeroben Degradationsreaktionen und die Bioverfuegbarkeit aus Sedimenten zu analysieren. Die Quellen und die Transportpfade sind weitergehend zu erforschen. Eine Kontaminationsbewertung hinsichtlich der PCDD/F inklusive Analoga von Sedimenten und aquatischen Oekosystemen ist zu erarbeiten. (orig.)Aquatic sediments are the final sinks of unintentional formed PCDD/F's. In dated sediment cores in Japan PCDD's have been detected in 8.120 years old sediments and in the Baltic PCDD/F's in 350 - 400 years old sediments. Sediments are means of source identification of transformation processes are taken in consideration, in view of hydrological conditions PCDD/F's have been analysed 30 km from the source into sediments and over a distance of 50 km in benthos, a remarkable bioaccumulation potential indicating. Elaborated data of the PCDD/F sediment contamination are missing, the processes in the sediment, the diagenetic processes and at the sediment/water-interface are urgently to be studied, also the aerobic and anaerobic biodegradation and bioavailability of PCDD/F's in sediments. More research is needed for elucidating additional sources and transport paths. Quality criteria for sediments and aquatic ecosystems remain to be elaborated. (orig.)SIGLEAvailable from TIB Hannover: RN 8422(1995,42) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman