Biomedical subjects

T Poulsen

Publications and source records attributed to T Poulsen.

51 records · Page 3Linked to original sources

PubMed1983

Carcinogenic effect of sequential artificial sunlight and UV-A irradiation in hairless mice. Consequences for solarium 'therapy'.

The carcinogenic effect of artificial UV sunlight followed by UV-A irradiation in human solaria doses has been studied with the use of the hairless mouse as an animal model. Artificial sunlight exposure alone induced only a moderate skin tumor incidence (animals with at least one tumor) of 0.15 after one year, and UV-A irradiation alone induced no tumor formation. However, the combination of artificial sunlight exposure and subsequent UV-A irradiation significantly increased the tumor incidence to 0.72. We conclude that, in humans, tanning with UV-A for cosmetic purposes may not be an innocuous procedure.

Animals↗

PubMed1982

Sunscreens for delay of ultraviolet induction of skin tumors.

Sunscreens with different sun protection factors (SPFs) have been tested for their capability of delaying or preventing actinic damage and skin cancer development in groups of hairless, pigmented mice exposed to artificial ultraviolet (UV) light of increasing intensity. The dose delivered was less than or equal to 1 minimal erythema dose (MED) in the group of untreated mice, so that the mice to which sunscreens were applied never obtained a sunburn after UV exposure. The quality of UV light was similar to bright midday sun at a latitude of 56 degrees (city of Copenhagen). Tumorigenesis was demonstrated to be delayed corresponding to the SPF claimed by the manufacturer, but almost all of the UV-irradiated mice developed skin tumors. Histologic examination revealed actinic degeneration and tumors of squamous cell type with marked variation in differentiation. Metastases to lymph nodes and lungs were found in only 10%. Toxic reactions, such as eczematous-like skin reactions, dark coloring, and amyloidosis, were observed predominantly in the group treated with the sunscreen of highest SPF value. Long-term investigations seem to be necessary to unveil these problems--in particular, the specific SPF value, in sunscreens, that should be recommended to the public for prevention or delay of actinic damage and/or cancer development.

4-Aminobenzoic Acid↗

PubMed1981

Loudness of tone pulses in a free field.

Investigations of temporal loudness summation of tone pulses have been performed. The investigations comprised equal loudness determinations between pairs of tone pulses with a duration ratio of 1:2, and threshold determinations of the same tone pulses. Pulse duration ranged from 5 to 640 ms. The frequencies were 500, 1000, and 4000 Hz. All pulses were shaped by means of 1/3 octave filters. For 25 normal hearing observers the investigations were performed at the observer's threshold, and at 35 and 55 dB SPL. Fitting of the experimental data to a single exponential function yields a time constant (tau) of about 200 ms near and at the threshold, whereas tau is about 100 ms at levels well above threshold. Discrepancies exist, nevertheless, between this single-time-constant model and the experimental data obtained for the pulses of shortest duration. To account for this, a model is proposed comprising a combination of two exponential functions. This yields a short time constant of 5 to 10 ms combined with the longer constant mentioned above.

Acoustics↗

PubMed1973