Absence of papillomavirus in skin tumors induced in SENCAR mice by a two-stage carcinogenesis protocol.

SENCAR mice are unusually sensitive to induction of papillomas and squamous cell carcinomas by initiation with 7,12-dimethylbenzanthracene (DMBA) and promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA). Tumors induced by this protocol were tested for the presence of papillomavirus by immunohistochemistry, Southern blot, reverse Southern blot and dot blot hybridization techniques. Papillomavirus antigens were not detected in any of 235 tumors or 142 non-tumor-bearing skin samples analyzed. Southern blots and dot blots, using a mixed probe of cloned rodent papillomavirus DNA from the multimammate rat, Mastomys natalensis, and the European harvest mouse, Micromys minutus, did not reveal the presence of either episomal or integrated papillomavirus genomes in total cellular DNA extracts from the tumors or non-tumor-bearing skin. To circumvent the possibility that insufficient cross-homology existed to detect a papillomavirus genome with the mixed probe used, DNAs extracted from six papillomas were labeled and each used to probe reference blots that contained 25 cloned papillomavirus genomes excised from their vectors. No evidence for the presence of a papillomavirus genome was detected by this method. Therefore, it is unlikely that papillomaviruses play a role in the induction of tumors in SENCAR mice by two-stage carcinogenesis protocols.

Phototoxicity, photoallergy, and contact sensitization of nitro musk perfume raw materials.

The potential of 4 related nitro musk substances (musk tibetene, musk ketone, musk xylol, and musk moskene) to cause photoallergy, phototoxicity, and/or contact sensitivity was compared to that of musk ambrette, a known photoallergen. Musk ambrette caused a high incidence of photoallergy as indicated by the severity of the skin grades as compared to a control group. Musk tibetene and musk moskene were negative for phototoxicity, photoallergenicity and contact sensitivity under the test conditions. Musk xylol was shown to be a weak contact sensitizer. Musk ketone gave challenge responses suggestive of a weak phototoxin and a weak contact sensitizer. The latter was not affected by light exposure. These data suggest that except for musk ambrette, the nitro musks as a group do not have the potential to produce photoallergy. Some members of this type of perfume raw material could be classified as weak sensitizers (musk xylol, musk ketone) or weakly phototoxic (musk ketone). These latter biological qualities have not been expressed clinically.

A device for irradiating guinea-pig skin with ultraviolet light.

Animal methodology for investigating photosensitization is of interest because of the potential of some photodynamic chemicals to produce adverse skin reactions. A system has been developed that provides procedural flexibility and the ability to standardize individual guinea-pig exposures to ultraviolet light (UVA and UVB). It consists of a non-stressful restraining method that also protects the animals' eyes from the harmful effects of UV light while allowing reproducible exposure of the backs of the guinea-pigs. The procedure is described in detail and the qualitative and quantitative aspects of the system are presented. In addition, some quantitative aspects of the phototoxic variation in response to 8-methoxypsoralen are investigated.

Use of the occlusive patch to evaluate the photosensitive properties of chemicals in guinea-pigs.

Guinea-pig tests were conducted on a known photocontact allergen, tetrachlorosalicylanilide (TCSA), a known phototoxin, 8-methoxypsoralen, two reportedly weak photoallergens, musk ambrette and 6-methylcoumarin, and a negative control, octylphenoxy polyethoxyethanol (Triton X-15). The data show that under the test conditions used, photosensitivity responses can be produced, and combinations of these as well as the other biological responses can be readily defined. The results indicate that musk ambrette is photoallergenic, that 8-methoxypsoralen is phototoxic and that Triton X-15 is only a slight irritant. On the other hand, results with TCSA suggest that it is a strong contact allergen and photoallergen, while 6-methylcoumarin would be considered to be a weak contact allergen with weak phototoxic properties. Previous reports that barrier destruction or adjuvanticity is necessary to produce photoallergy to musk ambrette were not confirmed; by ensuring occlusion using standard methods, the photoallergic nature of the response to this material was clearly demonstrated. A device described elsewhere (Newmann & Parker, Fd Chem. Toxic. 1985, 23, 683) has made it possible to develop methods that can be used to differentiate clearly among the possible biological responses that can occur in guinea-pigs when photoreactive materials are applied to their skin and irradiated. The probable biological responses that need to be defined, under the above conditions, are primary irritation, delayed contact hypersensitivity, phototoxicity and/or photoallergenicity.

A proposed plan for the detection and identification of potential sensitizers.

For toxicologists who are actively involved in safety testing and risk assessment, the ideal animal model should accurately predict the biologic response of humans after any contact with potentially hazardous materials. Unfortunately this goal is seldom, if ever, approached. Therefore, the toxicologist must design and execute experiments that will define to a higher degree of accuracy the inherent toxicity of the chemical and the biological response of the model. If the biologic response can be defined and understood and if the relevant information is available for comparable human responses, then the extrapolation to the human situation, although not always precise, can be made with a measure of assurance. Finally, and perhaps most importantly, it is essential that follow-up on human exposures be in sufficient detail so that the variations in biologic response can be further defined. In this way the precision and accuracy of the safety assessment can be checked.

Delayed contact hypersensitivity in the vagina and skin of the guinea pig.

A new method was developed to permit the contact of haptens exclusively with the vaginal mucosal surfaces of the guinea pig. The method described has some unique characteristics that make it potentially useful, not only for studies of the immune response but also for other areas of toxicologic concern. Utilizing this approach it was demonstrated that delayed contact hypersensitivity was as readily produced in the vagina as it was in the skin. Grossly, the vaginas of sensitized animals appeared normal when challenged with a non-irritating concentration of hapten but, histologically, a perivascular lymphocytic cuffing, that is the hallmark of the delayed hypersensitivity response, was demonstrated.