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Biomedical subjects

R Lee

Publications and source records attributed to R Lee.

At least 415 records · Page 23Linked to original sources
PubMed1969

Chemistry and end-group analysis on purified M protein of type 12 group A streptococcal cell walls.

M protein was extracted from the cell walls of streptococci by use of both acidic and alkaline buffers. These extracts were further purified by ammonium sulfate fractionation and column chromatography. Both diethylaminoethyl and carboxymethyl celluloses were employed to cover the pH range of 3.0 to 9.0. All of the M proteins isolated were immunologically related, but their physical and chemical properties varied dependent upon the pH range of isolation. Each isolate appeared to be homogeneous on the basis of immunodiffusion analysis, electrophoretic mobility, and ultracentrifugal analysis, but their amino acid analyses differed slightly. Two factors were shared by all isolates: (i) they all reacted with type-specific antisera and (ii) each seemed to have l-lysine as a single N-terminal amino acid.

Amino Acids↗
PubMedDate not supplied

Factors affecting the bioavailability of benzo[a]pyrene from oils in mouse skin: oil viscosity, grooming, activity and its prevention.

In the main study, tritium-labelled benzo[a]pyrene ([3H]BaP) was added to oils of a wide range of viscosity (from 13.5 to ca. 8000 cSt at 40 degrees C) and these were applied once to mouse skin under conditions where grooming was either allowed or prevented. The binding of [3H]BaP to epidermal protein and DNA was assessed. In addition, some studies were conducted to investigate the effect of prior oil exposure on binding levels and to compare binding levels following single and multiple application. It was found in the main study that the binding of [3H]BaP to both DNA and protein was increased as the viscosity of the oil vehicle decreased. Whereas only a twofold difference in DNA binding was found between the lowest and highest viscosity oil vehicle if grooming was allowed, a 14-fold difference was seen if grooming was prevented. This was due to much higher binding levels with low viscosity oils when grooming was prevented. Protein binding showed similar results, although the difference between the grooming and non-grooming situations was slightly less. Whether grooming was prevented or not, both DNA and protein binding of [3H]BaP were found to be inversely proportional to the logarithm of viscosity of the oil vehicle, but when grooming was prevented, the slope for DNA binding was 10 times steeper than when it was permitted. Exposure of the skin to either high or low viscosity oils prior to the application of [3H]BaP in the same oil inhibited the binding to DNA but not to protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

DNA adduct formation by mineral oils and their fractions as indicated by 32P-postlabelling: is adduct formation truly indicative of carcinogenic potential?

Oils of differing types, physical properties and carcinogenic activity were tested for ability to produce epidermal DNA adducts 24 h after application to the skin of mice, using the 32P-postlabelling method. Two studies were carried out, the first on three oils to identify the adduct-forming components, and the second on nine oils to investigate whether the nature of the oils affected their adduct-forming potential. In addition to the whole oils, fractions of the oils containing saturated hydrocarbons, 2-6-ring aromatic compounds and polar compounds were tested in both studies in proportion to their concentration in the original oil. In addition, a further examination of the aromatic fractions from two carcinogenic oils was carried out in the first study by testing 2-3-ring and 4-6-ring subfractions (the latter containing carcinogenic polycyclic aromatic compounds (PACs)). Results from the first study indicated that carcinogenic oils do produce adducts and that the adduct-forming components were mainly in the aromatic fraction. When, however, subfractions of the aromatic fraction were examined, it was found that slightly higher adduct levels were produced by the 2-3-ring aromatic fraction than with the 4-6-ring PAC fraction. This was contrary to expectation from published work on the skin carcinogenicity of oils and suggested that some non-carcinogenic PACs may produce adducts. The second study indicated that although most carcinogenic oils produced adducts, some non-carcinogenic oils can also do so.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗