Differential metabolism of 1,1-dichloroethylene in livers of A/J, CD-1, and C57BL/6 mice.

1,1-Dichloroethylene (DCE) causes hepatocellular necrosis that preferentially affects centrilobular hepatocytes. The cytotoxic lesion has been attributed to DCE oxidation mediated mainly by CYP2E1, resulting in formation of reactive intermediates including the DCE epoxide. Here, we have tested the hypothesis that differing levels of hepatic CYP2E1 in A/J, CD-1, and C57BL/6 (B6) mice lead to differences in magnitudes of DCE metabolism and severities of hepatotoxicity. Our results showed that amounts of the CYP2E1 protein were higher in A/J mice than in B6 and CD-1 mice. Covalent binding of DCE to liver proteins was variable in the three strains of mice and was higher in A/J than in B6 mice; intermediate levels were found in CD-1 mice. Levels of a DCE epoxide-derived glutathione conjugate detected in liver cytosol correlated with those present in bile extracts and were significantly higher in A/J than in CD-1 and B6 mice. Immunohistochemical studies showed that formation of DCE epoxide-cysteine protein adducts was enhanced in the livers of A/J mice, compared with those produced in the livers of CD-1 and B6 mice. Similarly, centrilobular necrosis was more severe in the livers of A/J mice than in those in either CD-1 or B6 mice. Levels of glutathione were similar in the three strains of untreated mice and were diminished at comparable levels in all mice. These results indicated that high expression of hepatic CYP2E1 in A/J mice coincided with increased DCE metabolism and enhanced severity of hepatotoxicity, relative to those in CD-1 and B6 mice.

Pulmonary bioactivation of 1,1-dichloroethylene is associated with CYP2E1 levels in A/J, CD-1, and C57BL/6 mice.

1,1-Dichloroethylene (DCE) elicits lung cytotoxicity and selectively targets Clara cells of bronchioles. The toxic effects are ascribed to CYP2E1-mediated formation of reactive intermediates including the DCE epoxide. Here we tested the hypothesis that differential CYP2E1 levels in the lungs of A/J, CD-1, and C57BL/6 mice lead to differences in the extents of DCE bioactivation and lung damage. Our results showed that lung CYP2E1 levels differed significantly in the three murine strains, and followed the rank order A/J > CD-1 > C57BL/6. Covalent binding of [(14)C]DCE to lung proteins in A/J mice was significantly higher than in either CD-1 or C57BL/6 mice. HPLC analysis of lung cytosol from DCE-treated mice showed that 2-S-glutathionyl acetate, a glutathione (GSH) conjugate derived from the epoxide (conjugate [C]), was the major metabolite formed. Levels of [C] detected in cytosol from A/J and CD-1 mice were significantly higher than in C57BL/6 mice. Immunohistochemical staining for [C] was pronounced in the lungs of A/J mice, was lower in CD-1 mice, and was lowest in C57BL/6 mice. Levels of GSH were similar in the lungs of all untreated mice. However, significant reduction in GSH was found in DCE-treated mice, with decreases comparable in all three strains. Bronchiolar Clara cell damage was more severe in A/J and CD-1 mice than in C57BL/6 mice. These results showed differences in CYP2E1 levels in the lungs of A/J, CD-1, and C57BL/6 mice that correlated with the extent to which the DCE epoxide is formed as well as with the severity of lung cytotoxicity.

Measurement of radiofrequency electromagnetic fields in and around ambulances.

Electromagnetic interference (EMI) with medical devices can threaten patient safety. More information is needed regarding circumstances in health care environments in which electromagnetic (EM) field strengths are expected to be high, such as emergency/transport. In ambulances medical devices and communications equipment must function properly in close proximity. This study characterized EM fields in and around ambulances under realistic conditions. Two types of ambulances were surveyed: the advanced life support (ALS) unit and the basic life support (BLS) unit. The surveys were conducted on-site using the ambulance mobile radio as the primary source of EM energy. Broadband field-strength measurements were collected at various locations in and around the ambulance to map interior and exterior EM field distributions. Nine ambulances were surveyed. In addition to the transmitter power and frequency, the field strengths measured were shown to be dependent upon the shielding provided by the ambulance roof and proximity of the measurement probe to the antenna. Field-strength measurements frequently exceeded the 3 V/m standard immunity level for devices set by the IEC Standard 601-1-2. The results indicate that the ambulance environment presents a considerable challenge to medical devices specifically used for emergency medical care. In order to assure their proper operation, medical devices used for transport emergency care must be able to withstand exposure to EM field strengths comparable to those reported in this study.

The structural origins of the unusual specificities observed in the isolation of chymopapain M and actinidin by covalent chromatography and the lack of inhibition of chymopapain M by cystatin.

1. The selectivity observed when the potentially general technique for the isolation of fully active forms of cysteine proteinases, covalent chromatography by thiol-disulphide interchange, is applied to chymopapain M and to actinidin was investigated by a combination of experimentation and computer modelling. Neither of these enzymes is able to react with the original Sepharose-GSH-2-dipyridyl disulphide gel, but fully active forms of both enzymes are obtained by using Sepharose-2-hydroxypropyl-2'-dipyridyl disulphide gel, which is both electrically neutral and sterically less demanding than the GSH gel. Electrostatic potential calculations, minimization and molecular-dynamics simulations provide explanations for the unusual, but different, specificities exhibited by actinidin and chymopapain M in the interactions of their active centres with ligands. 2. The unique behaviour of chymopapain M in exerting an almost absolute specificity for substrates with glycine at the P1 position and in resisting inhibition by cystatin was examined by the computer-modelling techniques. A new, modelled, structure of the complete chicken egg-white cystatin molecule based on the crystal structure of a short form of cystatin was deduced as a necessary prerequisite. The results suggest that electrostatic repulsion prevents reaction of actinidin with the GSH gel, whereas a steric 'cap' resulting from a unique arginine-65-glutamic acid-23 interaction in chymopapain M prevents reaction of the gel with this enzyme and accounts for the lack of its inhibition by cystatin and its specificity in catalysis. 3. Use of chymopapain M as a structural variant of papain demonstrates the validity of the predictions of Lowe and Yuthavong [Biochem. J. (1971) 124, 107-115] relating to the structural requirements and binding characteristics of the S1 subsite of papain.

Case report: benign urachal neoplasm.

Benign urachal neoplasms have been rarely reported. We describe a case of a large benign mesenchymal neoplasm (21 x 19 x 14 cm) arising from the urachus, with imaging by computed tomography and ultrasound.

Histologic characteristics and outcome of familial non-polyposis colorectal carcinoma.

Familial cases of non-polyposis colorectal cancer have recently attracted much interest. Little is known about the characteristic histology or natural history of disease in such cases. Our aim was to determine, through a population-based study, whether mucin-secreting tumours were associated with a positive family history and whether 'familiality' was an independent prognostic variable. All patients under 55 years of age with histologically verified colorectal cancer in Northern Ireland during 1976-78 were studied. The family history was validated in 95% of all non-polyposis cases (n = 205), and the proband's histologic specimen reviewed in over 99%. Mucin-secreting tumours were significantly associated with a positive family history, but familiality was not found predictive of survival in a multivariate analysis controlling for age, sex, stage, site, symptom duration, differentiation, and histologic type.

The mode of cell death associated with cavitation in teratocarcinoma-derived embryoid bodies.

Cell death occurring in embryoid bodies derived from the embryonal carcinoma cell line, PSA4, which undergo cavitation, and in those from the related cell line S2, which do not undergo cavitation, was classified as apoptosis or necrosis by ultrastructural criteria. Both modes of cell death were seen in PSA4 embryoid bodies while apoptosis alone was seen in S2 embryoid bodies. No significant difference was found between PSA4 and S2 embryoid bodies either in apoptotic incidence score or in the spatial distribution of apoptotic events. We therefore conclude that although apoptosis and tissue modelling coexist in PSA4 embryoid bodies, necrosis rather than apoptosis is causally related to formation of the cavity.