In vitro effects of polyhalogenated hydrocarbons on liver mitochondria respiration and microsomal cytochrome P-450

The present study evidenced the critical levels of six major polyhalogenated hydrocarbons (PHH's), namely chloroform, carbon tetrachloride, 1,1,1-trichloroethane, 1,2-dibromoethane,perchloroethylene, hexachlorobutadiene, over which significant inhibitory effects of the mitochondrial respiratory chain take place in vitro. At these critical levels, even in PB-induced animals only a very little fraction of cytochrome P-450 is saturated by the compounds and therefore the microsomal metabolism plays no effective role either in decreasing the levels of the test chemicals under the threshold of clear direct adverse effects in mitochondria, nor to the formation of toxic metabolites. Our data show also that phenobarbital not only enhances both the direct and metabolism-mediated interaction of most tested PHH with microsomal cytochrome P-450, but also increases the affinity of hexachlorobutadiene, chloroform and carbon tetrachloride for the mitochondrial sites resulting in respiration inhibition

A review of toxicological studies of stevioside

SIGLEITItal

Experimental results in damping evaluation of a high-speed railway bridge

Structural damping in high-speed railway bridges is a key parameter that affects significantly the performance of the structure in terms of fatigue life and comfort of the passengers and hence has a significant impact on the design procedures. For these reasons its accurate assessment is a paramount task to be performed and hence the results of an experimental campaign carried out on a prestressed concrete (four box-girder) beam bridge of the new Italian high-speed network are presented in this work. A total amount of fifteen accelerometers were used to ensure redundancy of measurements. Both a time domain technique and a Frequency-Domain Decomposition (FDD) technique are used to analyse the vibration signals and extract the modal frequencies, shapes and damping ratio of the first mode of the structure. The results are compared with the design provisions, and with other expectation provided by the technical literature. The paper from one hand provides a contribution in the framework of the damping evaluation of high-speed railway bridges, and from the other hand would furnish a first assessment of those damping sources that are not usually accounted for in the modelling process