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Biomedical subjects

T J Stephens

Publications and source records attributed to T J Stephens.

6 recordsLinked to original sources
PubMed1979

Skin carcinogenicity of synthetic and natural petroleums.

In a series of three separate experiments mice were exposed to various concentrations of fossil liquids obtained from coal, oil shale or natural petroleum. All materials were capable of inducing squamous cell carcinoma, but potency differed substantially. Skin carcinogenicity was markedly greater for both coal or oil shale liquids than for natural petroleums. None of the syncrudes approached the skin carcinogenicity of a pure reference carcinogen, benzo(a)pyrene (BP). It is unlikely that determination of the concentration of an active compound in material applied to the test animal will allow meaningful comparison among the diverse agents of interest to the synthetic fuels industry. To better establish the relationship between actual tissue dose and surface concentration the authors are investigating various in vitro and biochemical measures of hydrocarbon-skin interaction to determine which, if any, could serve as a more definitive measure of surface dose. Results, using BP as a marker carcinogenic hydocarbon, suggest that carcinogenic crudes inhibit both BP metabolism in skin organ culture and the interaction of BP adducts with epidermal DNA, in vivo.

Animals↗
PubMed1977

Chimeric drift in allophenic mice.

The composition of the immune system of 33 allophenic mice of four different types [C57BL/6 in equilibrium DBA/1, C57BL/6 in equilibrium (CBA X CBA/H-T6), C57BL/6 in equilibrium (A X SJL), DBA/1 in equilibrium (CBA X CBA/H-T6)] was studied. It was found that the parental composition of the peripheral white blood cells changed significantly during a two-month interval in 11/33 or 33% of the mice studied. This phenomenon has been termed chimeric drift. The animals were sacrificed between 9 and 16 months of age, and the parental composition of the peripheral white blood cells, spleen white blood cells, and thymocytes was determined on the day of sacrifice. It was foound that the peripheral white blood cell and spleen white blood cell compositions showed a high degree of correlation. However 8/33 or 24% of the mice studied showed discordance of the spleen and thymocyte cell populations. Seven of the 8 mice which showed spleen-thymocyte discordance, had also shown evidence of chimeric drift earlier in their lives. We suggest that this is evidence that chimeric drift may have an immunological basis.

Animals↗
PubMed1977

Chimeric drift in allophenic mice: analysis of changes in red blood cell and white blood cell populations in C57Bl/6 in equilibrium (A X SJL)F1, C57Bl/6 in equilibrium (CBA X CBA/H-T6)F1, and C57Bl/6 in equilibrium DBA/1 mice.

Forty-seven allophenic mice of three different types (C57BL/6 in equilibrium (A X SJL), C57BL/6 in equilibrium (CBA X CBA/H-T6), and C57BL/6 in equilibrium DBA/1) were analyzed for changes in their peripheral white blood cell composition and hemoglobin composition with age. It was found that 10 of the 47 mice showed significant changes termed "chimeric drift" in one or the other or both of these parameters. These 10 mice were classified as unstable chimeras, as opposed to the 37 stable chimeras, which showed no apparent chimeric drift. There was an excellent correlation of peripheral white blood cell and hemoglobin compositions of the stable chimeras. However, the unstable chimeras showed little or no correlation of these two markers. Possible mechanisms of chimeric drift are discussed.

Aging↗