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Biomedical subjects

K H Kaidbey

Publications and source records attributed to K H Kaidbey.

At least 37 records · Page 2Linked to original sources
PubMed1982

Human models for identification of photosensitizing chemicals.

The human is an appropriate and sensitive animal for identifying photosensitizing drugs administered either topically or systemically. Topically effective phototoxic agents are quite easily revealed when they are applied to normal or scarified skin which is subsequently exposed to 2 X 10(5) J.m-2 of near UV light (UVA, 320-400 nm). Systemically effective phototoxic drugs can be identified by exposing intradermally injected sites to either solar-simulating or UVA radiation. Drugs that cause photocontact allergy can usually be recognized by irradiating pretreated sites six times over a 3-week period with a solar simulator and then challenging the sites with UVA. Existing models, the human model especially, should make it possible to recognize important photosensitizing drugs before they are marketed.

Administration, Topical↗
PubMed1982

The influence of infrared radiation on short-term ultraviolet-radiation-induced injuries.

Because heat has been reported to influence adversely short- and long-term ultraviolet (UV)-radiation-induced skin damage in animals, we investigated the short-term effects of infrared radiation on sunburn and on phototoxic reactions to topical methoxsalen and anthracene in human volunteers. Prior heating of the skin caused suppression of the phototoxic response to methoxsalen as evidenced by an increase in the threshold erythema dose. Heat administered either before or after exposure to UV radiation had no detectable influence on sunburn erythema or on phototoxic reactions provoked by anthracene.

Adult↗
PubMed1982

Phototoxicity to benoxaprofen.

Photosensitization to benoxaprofen has been studied in human volunteers. The wavelengths that mediate the reaction lie mainly just outside the sunburn range in the near ultraviolet, UVA region including, however the terminal portion of the UVB region. The photosensitivity reaction begins with sharp burning during exposure, sometimes accompanied by itching. This may be followed by erythema and a flare, which generally fade in about one hour or less. High doses of ultraviolet light can elicit whealing. Photosensitivity to benoxaprofen is typically an immediate-type, short-lived reaction, dominated by subjective sensations of burning-smarting and redness. With large UVA doses, a sunburn-type reaction may also be present at 24 hours. The photosensitivity is of the phototoxic type. It may appear within 48 hours of starting the drug and usually disappears with 48 hours after stopping. The population most at risk are type 1 and type 2 light-skinned persons who burn easily and tan poorly. Pigmented races are quite resistant, viz, blacks and orientals. Dark-skinned type 4 Caucasoids, such as Mexicans, Indians, etc., have high innate protection. Deep tanning and SPF 15 sunscreens provide adequate protection.

Adolescent↗
PubMed1981

An appraisal of the efficacy and substantivity of the new high-potency sunscreens.

Several recently introduced sunscreens were evaluated using test procedures proposed by the Food and Drug Administration. The newer sunscreens proved to be highly protective, possessing Sun Protection Factors (SPF) of 15 or greater. Improvement in efficacy was achieved by the incorporation of a combination of active ingredients at larger concentrations, and by superior vehicle design. A procedure is also described for the laboratory assessment of wash-off resistance, which provides data comparable to those obtained from swimming tests. Two of the tested sunscreens resisted wash-off after 40 minutes of swimming.

Adolescent↗
PubMed1981

Ultraviolet light sensitivity and prolonged UVR-erythema.

We have compared the erythema and tanning responses in skin type I (n = 15) and skin type IV (n = 17) Caucasoids following a single exposure to solar simulated radiation. The former sunburn easily and do not tan while the latter do not burn and tan readily. The dose of radiation was 5 times the Minimal Erythema Dose (MED). The test sites were the extensor aspect of the forearm (exposed site) and flexor aspect of the upper arm (nonexposed site). The responses were monitored at 24 and 48 hr and then twice weekly for 8 weeks. The group of skin type I individuals had a lower MED and a much more prolonged erythema on both the exposed and nonexposed sites than the group of type IV individuals. All differences were highly significant (p less than 0.005). After 4 weeks erythema remained present in all of the type I subjects but had disappeared in 16 of the 17 type IV subjects. Within the groups there was no difference between erythema duration on exposed vs. nonexposed sites, but there was a highly significant difference (p less than 0.005) between the lower MED on the upper arm and higher MED on the forearm. These results contrast with those of other reports in which prolonged erythema could not be correlated with fair complexion, sunburn sensitivity, ethnic background, or skin type but was instead found to be a distinct feature of persons who had developed nonmelanoma skin cancer. Since prolonged erythema is related to skin type it is therefore not solely a feature of patients with skin cancer.

Adolescent↗
PubMed1981

Cumulative effects from repeated exposures to ultraviolet radiation.

Repeated exposures to subliminal doses of UVR, given at 24-hr intervals, resulted in a lowering of the erythema threshold dose. At erythemogenically equivalent doses, UV-A was the most effective and UV-C the least. A similar and more pronounced effect was observed following repeated exposures to subthreshold doses of UV-A and topically applied 8-methoxypsoralen. These findings provide quantitative evidence for the cumulative nature of acute UVR damage in human skin.

Adolescent↗
PubMed1981

Photocontact allergy to benzocaine.

A photodermatitis developed in two patients after the use of commercial sunscreens and a topical anesthetic lotion containing benzocaine. Photopatch testing indicated the presence of photocontact allergy to benzocaine. One patient had a positive photopatch test to a commercial glyceryl para-aminobenzoic acid (PABA) preparation that was heavily contaminated with benzocaine, but not to a benzocaine-free sample of glyceryl PABA. Benzocaine failed to produce phototoxic reactions in normal volunteers. Efforts to induce photocontact allergy in guinea pigs were unsuccessful.

4-Aminobenzoic Acid↗
PubMed1981

Photosensitization by coumarin derivatives.

Coumarin and several of its derivatives were investigated for their photosensitizing properties. With a few exceptions, the coumarins are potentially strong photocontact sensitizers but do not evoke phototoxic reactions. Substitution at the 6 or 7 positions of the benzopyrone ring confers photoallergenic capability, whereas hydrogenation abolishes activity. Photo-cross-reactions among closely related derivatives can develop. The action spectrum for contact photodermatitis extends from 360 nm down to at least 300 nm. Data are presented to show that the photocontact allergic response is related to the ultraviolet A dose and to the concentration of the offending chemical.

Adult↗
PubMed1980

Sunscreens prevent sunburn cell formation in human skin.

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.

Adolescent↗
PubMed1980

Photomaximization test for identifying photoallergic contact sensitizers.

The photomaximization procedure was designed to identify topical photocontact sensitizers following the format of the maximization test for contact sensitizers. The test agent is applied for 24 hours followed by exposure to three Minimal Erythema Doses (MED) of solar simulated radiation twice weekly for 3 weeks (six exposures) in a panel of 25 white Caucasoids. The subjects are challenged 2 weeks later with 4.0 J/cm2 of long-wave ultraviolet radiation (UV-A). Photocontact sensitization was induced to 3,3'4',5-tetrachlorosalicylanilide (TCSA); dibromosalicylanilide (DBS) but not to tribomosalicylanilide unless the latter was contaminated with DBS. Jadit and bithionol were weak photoallergens. The highest rate of sensitization was given by 6-methylcoumarin, a widely used synthetic fragrance. Hexachlorophene and trichlorocarbanilide were negative.

Adult↗
PubMed1979

Photoprotection by melanin--a comparison of black and Caucasian skin.

The photoprotective role of melanin was evaluated by comparing the transmission of ultraviolet (UV) radiation through skin samples of blacks and Caucasians, using both biologic and spectroscopic techniques. UVA transmission was measured using fluoranthene, which causes a phototoxic response to UVA wavelength. UVB was measured by monitoring erythema produced by either a 150-watt xenon arc or FS-20 sunlamps. It was found that on the average, five times as much ultraviolet light (UVB and UVA) reaches the upper dermis of Caucasians as reaches that of blacks. Differences in transmission between the stratum corneum of blacks and of Caucasians were far less striking. The main site of UV filtration in Caucasians is the stratum corneum, whereas in blacks it is the malpighian layers. Melanin acts as a neutral density filter, reducing all wavelengths of light equally. The superior photoprotection of black epidermis is due not only to increased melanin content but also to other factors related to packaging and distribution of melanosomes. Not only are these data consistent with epidemiologic evidence, but they also may indicate why blacks are less disposed to phototoxic drug responses as well as less susceptible to acute and chronic actinic damage.

Adult↗
PubMed1979

The influence of longwave ultraviolet radiation on sunburn cell production by UVB.

The potentiation of sunburn by longwave ultraviolet radiation (photoaugmentation) has been examined with regard to the influence of these waves on sunburn cell production in human skin. It was found that UVA did not enhance sunburn cell production. Photoaugmentation is limited to the erythemal component of the sunburn reaction.

Adolescent↗
PubMed1979

The acute effects of long-wave ultraviolet radiation on human skin.

The erythematogenic and melanogenic properties of polychromatic long-wave ultraviolet light (UV-A) has been re-examined. Redness appeared immediately after exposure and persisted for 24 hr with doses of about 50 Joules/cm2. With threshold erythemal doses, about 13 J/cm2, the redness faded after a few minutes. The response was not biphasic. Pigmentation also appeared immediately after exposure and faded rapidly with threshold doses of 4 J/cm2. With larger doses (18 J/cm2) immediate pigmentation gave way without fading to delayed pigmentation (true melanogenesis). Thus, the acute effects of UV-A, unlike other wavelengths within the UV-spectrum, are immediate and appear without latency. The responses are also most intense immediately after exposure.

Adult↗
PubMed1978

Identification of topical photosensitizing agents in humans.

A method is described for the detection of topical photosensitizers in humans. Test agents were applied to the untanned midback under an occlusive dressing for 6 hr and then exposed to broad-spectrum radiation containing UV-A and visible wavelengths from a Xenon arc source. Well-known topical photosensitizers were readily identified. It was found that with certain poorly-penetrating substances, such as water-soluble dyes, applications to scarified skin were necessary to reveal phototoxic activity. In addition, these dyes were activated by wavelengths in the visible region of the spectrum.

Administration, Topical↗
PubMed1978

Identification of systemic phototoxic drugs by human intradermal assay.

An improved method is presented for the detection of systemically administered photosensitizing drugs in humans. Test agents were injected intradermally in physiologic saline and then exposed to broad spectrum radiation from a Xenon solar simulator. Several clinically recognized photosensitizers were identified by this technique. The activating spectrum depended on the test drug. Sulfonamides and vinblastin were activated by sunburning erythemic radiation (UV-B), while tetracyclines, nalidixic acid and phenothiazines by near UV (UV-A), and chlorothiazide by both. It is suggested that intradermal phototesting offers a means of verifying the phototoxic potential of agents suspected clinically of provoking a photosensitivity eruption.

Adult↗
PubMed1978

Photocontact allergy to 6-methylcoumarin.

A proprietary sunscreen-induced photosensitivity reactions in a small number of users. Laboratory study revealed that the reactions were of the photoallergic type and were due to the presence of a synthetic fragrance, 6-methylcoumarin. By photomaximization testing 6-methylcoumarin was found to be a potent photocontact allergen.

Adult↗
PubMed1978

Sunburn protection by longwave ultraviolet radiation-induced pigmentation.

The role of melanin pigment in sunburn protection was investigated. Deep tans were induced over the backs of volunteers with repeated exposure to longwave ultraviolet radiation (UV-A). Melanogenesis was stimulated without an appreciable thickening of the stratum corneum. Two to three times the minimal erythema dose was required to produce redness in UV-A-tanned skin. Transmission studies through isolated corneum sheets revealed that specimens from tanned skin were about twice as efficient in filtering sunburn rays as stratum corneum from untanned skin. Tanning with UV-A does not provide a substantial resistance against sunburn.

Adult↗