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MR imaging of Creutzfeldt-Jakob disease 总被引:13,自引:0,他引:13
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Cholangiocarcinoma: delayed CT contrast enhancement patterns 总被引:17,自引:0,他引:17
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To investigate the use of UvrB-binding to detect DNA damage, mobility shift
gel electrophoresis was used to detect binding of UvrB protein to a 136 bp
DNA fragment that was randomly adducted with aflatoxin B1 8,9- epoxide and
end-labelled with 32P. After polyacrylamide gel electrophoresis, the
shifted band that contained DNA bound by UvrB was quantified as a
percentage of total radioactive substrate DNA. This method was applied to
analyse plasmid DNA that was adducted with various DNA modifying agents in
vitro. These adducts competed for UvrB- binding to the labelled substrate.
By competing for UvrB-binding with 10 ng of plasmid DNA that was adducted
with known levels of aflatoxin B1, 2-amino-3-methylimidazo[4,5-f]quinoline,
or benzo[a]pyrene diol epoxide, UvrB competition could be quantified for
DNA adducted with between one adduct in 10(2) and one adduct in 10(5)
normal nucleotides. However, plasmid DNA exposed to N-methyl-N-nitrosourea
or methylene blue + visible light, did not compete for UvrB-binding, even
though the presence of UvrABC sensitive sites were confirmed on this DNA by
a UvrABC incision assay. Mono-adducted 96-bp DNA substrates, which
contained an internal 32P-label and either a single apurinic site,
aflatoxin B1-guanine adduct, O6-methylguanine, 8-oxo-deoxyguanosine or
non-adducted guanine, were also used as substrates for UvrA- and UvrB-
binding to examine the stability of UvrB-DNA complexes with specific
adducts. Under similar conditions used for the competition assay,
significant UvrB-binding was seen only for the aflatoxin adducted
substrate. These results suggest that stability of UvrB-binding varies
greatly between bulky and non-bulky adducts. It was also found that rat
liver DNA from untreated rats inhibited UvrB-binding to the substrate DNA
in the competition assay, to a degree that was equivalent to competition
with plasmid adducted at one adduct in 10(3) normal nucleotides.
相似文献
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New hepatitis B virus mutant form in a blood donor that is undetectable in several hepatitis B surface antigen screening assays 总被引:10,自引:0,他引:10
JM Jongerius ; M Wester ; HT Cuypers ; WR van Oostendorp; PN Lelie ; CL van der Poel; EF van Leeuwen 《Transfusion》1998,38(1):56-59
BACKGROUND: Envelope mutant forms of hepatitis B virus (HBV), impairing HBV antibody recognition, have been reported with mutations in single or multiple sites of the hepatitis B surface antigen (HBsAg) group- specific "a" determinant. Blood donors infected with such an HBsAg mutant form of HBV may escape detection by HBsAg screening assays and therefore may affect the safety of the blood supply. CASE REPORT: A repeat blood donor became HBsAg-reactive in an enzyme immunoassay. Confirmatory testing yielded negative results for HBsAg in a radioimmunoassay and in four enzyme immunoassays used in blood donor screening. The specificity of the HBsAg reactivity in the first enzyme immunoassay was confirmed by HBsAg neutralization with antibody to HBsAg. Additional HBV confirmatory test results were positive for antibody to hepatitis B core antigen and antibody to hepatitis B e antigen; negative for antibody to HBsAg and for hepatitis B e antigen; and positive for HBV DNA. DNA sequence analysis of the "a" determinant region of HBsAg revealed amino acid substitutions from Q (Gln) to R (Arg) at codon 129 and from M (Met) to T (Thr) at codon 133. CONCLUSION: This case illustrates the presence of HBsAg mutant forms of HBV in a West European blood donor population that were undetected by several HBsAg screening assays. Adaptation of HBsAg screening is indicated to overcome deficiencies in sensitivity in detecting HBsAg mutant forms of HBV. Screening for antibody to hepatitis B core antigen or HBV DNA may also detect blood donors infected with HBsAg mutant forms of HBV 相似文献