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Sunscreens with different sun protection factors were examined for their ability to prevent sunburn cell formation in human skin exposed to ultraviolet radiation from a xenon solar simulator. There was either complete or partial protection against the cytotoxic effects of ultraviolet radiation. Protection was related to the sun protection factor of the sunscreen and to the dose of radiation administered.

Cytophotometric measurements of single-cell DNA content were used to study human epidermal cell proliferation in vivo. It was found that Feulgen-DNA profiles can be used to assess proliferative activity in involved, uninvolved, and nonpsoriatic skin. Profiles of involved psoriatic skin were bimodal as is characteristic of actively proliferating populations. This was due to the presence of cells with twice (2C--presynthetic) or four times (4C--post-synthetic) the amount of DNA of the gametes, separated by the intermediate values of cells undergoing scheduled DNA synthesis. Profiles of uninvolved psoriatic as well as nonpsoriatic epidermis were unimodal with the majority of cells containing a 2C amount of DNA incating relatively low levels of proliferative activity. The observed variations in proliferative activity of these samples are discussed in terms of two alternative models. Since radioisotopes are not required, this technique presents a useful approach to studying human epidermal proliferation in vivo.

Scanning DNA-cytophotometry was performed on touch imprints of 26 lymph nodes (LN) obtained from 25 patients with cutaneous T-cell lymphoma (CTCL), stained by the Feulgen technique, and interpreted without knowledge of histopathologic diagnosis. Four patterns of DNA distribution were identified, but only histograms that demonstrated cells containing nuclei with more than 4C DNA content (hypertetraploidy) reliably distinguished LN involved with CTCL from LN with reactive changes; for example, dermatopathic lymphadenitis. An abnormal DNA histogram with evidence of hypertetraploidy was demonstrated in 9 of 12 LN showing histopathologic evidence of involvement compared with no abnormal histograms in 14 LN without histopathologic involvement. One LN that was diffusely involved with CTCL had a DNA distribution characteristic of a relatively high level of cell proliferation, but without definite hypertetraploidy. Cytogenetic studies on the blood of this patient, who had Sézary syndrome, demonstrated a clone of lymphocytes with a pseudodiploid karyotype without a related polyploid subline. The remaining two histopathologically involved LN had normal DNA histograms; these LN were only focally involved with CTCL. These observations indicate that DNA-cytophotometry correlates well with the histopathologic findings in LN diffusely involved with CTCL, but may be normal in LN with focal involvement or in those that contain cytogenetically abnormal cells with a near-diploid DNA content.

Exfoliative cytological procedures, based on the sticky slide and detergent scrub techniques, were used in the nonintrusive collection of horny cells from the skin surface of volunteers 20 to 30 yr of age and 65+ yr of age. These samples were analyzed with a variety of instruments, including a Magiscan image analyzer, a Vickers M-85 microspectrophotometer, and a Coulter electronic cell counter. The results indicate that age-associated changes in horny cells may be useful in monitoring objectively aging of skin and in assessing the impact of various environmental insults on aging.