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Biomedical subjects

S M Boyd

Publications and source records attributed to S M Boyd.

16 recordsLinked to original sources
PubMed2001

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.

Animals↗
PubMed2001

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.

Animals↗
PubMed1995

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.

Binding Sites↗
PubMed1995

Characterising the geometric diversity of functional groups in chemical databases.

We have developed a program, HookSpace, which provides a simplistic approach to assessing the diversity of molecular databases. The spatial relationship between pairs of intramolecular functional groups can be analysed in a variety of ways to provide both qualitative and quantitative measures of diversity. Results are described and contrasted for two commercially available databases and a combinatorial library of benzodiazepam derivatives. HookSpace highlights the main differences in molecular content of these data sets.

Crystallography, X-Ray↗
PubMed1994

Immunobiology of the serine protease allergens from house dust mites.

Extracts of Dermatophagoides pteronyssinus and D. farinae were shown to contain a variety of 30 kDa serine proteases, including trypsin, chymotrypsin, and an elastase-like enzyme. The mite trypsin, unlike chymotrypsin and the elastase enzyme, was heterogeneous with regard to charge. The enzymes were shown to be present at higher concentration in fecally enriched extracts than in whole mite extracts. The proteases were shown to induce vascular permeability and to detach cells in tissue culture. Further study showed that the mite elastase induced non-IgE mediated rat mast cell degranulation. Such properties may contribute to immunogenicity.

Allergens↗
PubMed1994

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.

Abdomen↗
PubMed1993

Dimerization specificity of the leucine zipper-containing bZIP motif on DNA binding: prediction and rational design.

We propose an interhelical salt bridge rule to explain the dimerization specificity between the two amphipathic alpha-helices in the leucine zipper structure. Using the bZIP class of DNA-binding proteins as a model system, we predicted and designed novel dimerization partners. We predicted that ATF4, a member of the ATF/CREB family of transcription factors, would preferentially form heterodimers with IGEBP1, a member of the C/EBP superfamily. These predictions were verified using a gel mobility-shift assay. To further test the value of this interhelical salt bridge rule, we modified the bZIP protein C/EBP attempting to design molecules that would form preferentially heterodimers with C/EBP or molecules that would not interact with C/EBP. These designed molecules behaved as predicted. Therefore, we conclude that this interhelical salt bridge rule is useful in understanding the dimerization specificity of bZIP proteins. In addition, we suggest that this rule could be used to design novel "dominant-negative" molecules to specifically inhibit the function of target leucine zipper proteins in vivo.

Activating Transcription Factor 4↗
PubMed1991

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.

Adenocarcinoma, Mucinous↗
PubMed1984

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.

Animals↗
PubMedDate not supplied

Measurement of radiated electromagnetic field levels before and after a changeover to energy-efficient lighting.

An energy-efficient lighting retrofit at the Food and Drug Administration (FDA) Winchester Engineering and Analytical Center (WEAC) presented the opportunity to measure the electromagnetic (EM) environments in several rooms before and after changing the fluorescent lighting systems and to compare the changes in EM fields with the proposed standard EM immunity levels. Three rooms, representing the types of work areas in the laboratory, were selected and measured before and after the lighting changeover. Electric and magnetic field measurements were taken in the extremely low frequency (ELF), very low frequency (VLF), and radio frequency (RF) ranges of the EM spectrum. In 2 rooms, ELF electric fields were reduced and VLF and RF electric fields were increased as a result of the changeover to high-frequency fixtures. A third room received low-frequency, energy-efficient fixtures during this changeover, and this change resulted in only a slight increase of the ELF electric fields. The ELF magnetic fields were greatly reduced in 2 but only slightly reduced in the third room. No significant change was seen in VLF or RF magnetic fields for any of these rooms. Some field-strength measurements exceeded the proposed immunity levels recommended in the draft International Electrotechnical Commission standard IEC 60601-1-2 (rev. 2). The data show that increasing the separation distance from the fluorescent light fixtures greatly reduces the field-strength levels, limiting the potential for EM interference.

Electromagnetic Fields↗
PubMedDate not supplied

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.

Ambulances↗