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The initiating potential of a range of 4 MeV X-rays was studied using the mouse skin two-stage model of carcinogenesis. A single dose of radiation was followed by promotion with 12-O-tetradecanoyl phorbol-13-acetate (TPA). The effect of TPA on tumor incidence when applied as a single dose 24 hours prior to irradiation was examined. Studies were also designed to investigate the effect of promotion duration on tumor incidence. Animals were promoted with TPA for 10 or 60 weeks. Evidence presented here indicates that ionizing radiation can act as an initiator in this model system. All animals that were promoted with TPA for the same duration had a similar incidence of papillomas (pap) regardless of radiation or TPA pretreatment. However, squamous cell carcinomas (scc) arose only in animals that were initiated with ionizing radiation followed by TPA promotion. Increasing the promotion duration enhanced the incidence of scc at the lower initiation dose. TPA pretreatment at the higher irradiation dose resulted in an overall decrease in tumor incidence. At the lower dose of radiation, TPA pretreatment resulted in an increase in the incidence of scc. The incidence of basal cell carcinomas (bcc) was dose dependent and appeared to be independent of TPA promotion. Although ionizing radiation acts as a weak initiator in mouse skin, the conversion of pap to scc was higher than that reported for chemical initiators. To test this further animals were initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) followed by biweekly promotion with TPA. After 20 weeks of promotion, the animals were treated with either acetone, TPA or 8 fractions of 1 MeV electrons. Data indicate that the dose and fractionation protocol used in this study enhanced the progression of pre-existing pap. To examine the role of oncogene activation in radiation induced mouse skin tumors, DNA from various tumors (pap, bcc, scc) were examined for the presence of dominant transforming activity by the NIH3T3 and Rat-2 focus assays. Dominant transforming activity was observed in all tumor types but not in normal or treated epidermis or corresponding liver. The transformed phenotype was further confirmed by growth in soft agar and tumorigenicity in Nude mice. Southern blot hybridization to ras (Ha, Ki, N), raf, neu, erbB and β-lym indicate that these genes are not responsible for the observed transforming activity. These data suggest that the oncogenic sequences activated in these tumors are unique. The work presented here also provides evidence for novel c-myc transcripts and corresponding genomic rearrangements in a few of the tumors studied.

Three different types of radiometry have been examined to find the best type for solar spectral irradiance measurements requiring long-term (22 years) and ultra-high precision (0.1% uncertainty) in the near-UV, visible, and near infrared. It has been determined that the best radiometry uses the self-calibration technique developed at NBS using laser lines. Normalization techniques were applied to silicon reflectivity and quantum efficiency models for use with thermal sources and grating spectrometers. The results compared with similar laser-source calibration showed disagreement less than 0.1%. Germanium and GaAsP detectors were also investigated in the infrared and deep blue wavelengths. The germanium detector showed significant recombination loss of photogenerated carriers due to the ion implantation fabrication process. GaAsP detectors have very small dark currents ( < 1 nA), but also demonstrate significant recombination losses inside the photodiode. The possible loss mechanism of the Ge and GaAsP detectors are suggested for future study.