ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16979.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryConcern about the ozone‐depleting potential of man‐made chemicals has led the United Nations to control their usage. Under the present arrangements, fully halogenated chlorofluorocarbons, halons and carbon tetrachloride will be phased out by the year 2000, and methylchloroform by the year 2005. Even so, atmospheric chlorine is expected to rise to seven times its natural level, so further ozone losses and greater ultraviolet B (UVB) exposure can be expected over heavily populated areas of the globe. Calculating changes in skin cancer incidence is a two‐stage process which must take account of the increase in biologically effective UVB that results from an ozone loss of 1% (optical amplification factor, OAF) and the percentage increase in skin cancer incidence that results from a 1% increase in annual UV dose (biological amplification factor, BAF). Epidemiological data provide a BAF value of approximately 1·7 for basal cell carcinoma and 3·0 for squamous cell carcinoma. The absorption spectrum of ozone and the increased carcinogenic impact of UV radiation around 300 nm results in a value for OAF of approximately 1·6%; thus a 10% loss of ozone, if sufficiently sustained, would eventually increase the incidence of basal and squamous cell carcinomas by almost 30% and 50%, respectively. Dermatologists, therefore, need to look carefully at the environment in order to safeguard the health of future gen

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16980.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe use of non‐invasive and invasive techniques for the assessment of human photodamaged skin is reviewed. Physical changes during photodamage and its treatment are best scored using a visual analogue scale rather than a short, non‐equal interval scale. Epidermal thickness can be measured by histometric methods but dermal thickness can be measured non‐invasively using pulsed A‐scan and B‐scan ultrasound techniques. These approaches are not effective in detecting any changes due to photodamage. Mechanical properties of the dermis can be determined using either a static or a dynamic test mode. The authors have used extensometry to provide a measure of the laxity of skin. Replicas of the crow's foot areas have been taken before and after tretinoin treatment, and the replicas have been inspected by optical profilometry. Reductions of blood flow in photodamaged skin have been established using laser Doppler measurements, the effect being reversed by topical tretinoin. Invasive biochemical techniques have the disadvantage that they generally require large amounts of tissue. Cytochemical techniques, however, have shown increased glucose‐6‐phosphate dehydrogenase activity in the granular cell layer of patients with non‐melanoma skin cancer, premalignant epidermal lesions, sundamaged epidermis and artificially irradiated skin. This technique may provide an important model for the study of photodamage. It is concluded that there is no single method available to quantify the degenerative changes associated with photodamage and the effec

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16981.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryExtensive well‐controlled clinical studies performed over the past 5 years have demonstrated a consistent, dose‐dependent, statistically significant improvement in the appearance of photodamaged skin after 3–6 months of daily treatment with topical 0·001–0.1% tretinoin cream. Clinical changes included decreases in surface roughness, irregular pigmentation, fine and coarse wrinkling, and sallowness. Actinic keratoses have also been reported to decrease in size and number. Blinded analysis of biopsies from more than 500 subjects showed that there was compaction of the stratum corneum, an increase in the number of granular layers, thickening of the epidermis and a decrease in epidermal melanin. There were no detectable histological changes in any dermal parameters. The specific cellular mechanisms by which retinoic acid (RA) exerts its beneficial effect on photodamaged skin are currently the subject of intensive investigation. It is well established that RA enters the nucleus where it binds to an RA receptor (RAR), and that the RA‐RAR complex then binds to specific RA response elements in the DNA, modulating the expression of target genes. It is thus likely that RA improves at least some aspects of photoageing by modifying cellular differentiation programmes, as retinoids have been shown to do during embryogenesis. in malignantly transformed cells and in skin affected by certain

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16982.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe ability of topically applied retinoic acid to improve photoaged skin has stimulated research interest into its mechanism of action. Currently available assay systems are eitherin‐vitroor mouse models, neither of which are truly representative of thein‐vivosituation in man. Another drawback is that skin biopsies available from studies using retinoic acid to treat photoageing are of insufficient size to accomplish biochemical and molecular assays. In order to address these problems, a 4‐dayin‐vivoretinoid assay has been developed which serves as a good predictive model for the chronic effects of retinoic acid on skin and helps to characterize the mechanism of action of retino

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16983.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIt is now well established that ageing occurs at the level of individual cells in the skin and other organ systems. Changes in cell behaviour, protein production and gene expression in response to standardized stimuli are readily observed in cultured cells derived from youngvsold donors and from photoagedvssun‐protected body sites. Whether these changes are best viewed as a cause or a consequence of ageing cannot be determined at present. Nevertheless, available data now provide cellular and molecular correlates for the well‐known differences in clinical responsiveness between newborn, adult and photoaged skin. From this basis, it will hopefully be possible to develop a more comprehensive understanding of cutaneous ageing proces

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16984.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryTopical tretinoin is a well‐established treatment for acne, with a low incidence of reported adverse effects, most of which are local skin reactions. The retinoid has limited absorption through the skin, so that even with repeated applications plasma concentrations do not exceed normal endogenous levels. In mice, lifetime treatment with topical tretinoin improved skin texture and did not have any tumorigenic effects. Data from multicentre clinical trials have shown that 0·05% tretinoin emollient cream reduced fine wrinkling, surface roughness and mottled hyperpigmentation caused by photodamage. Improvement of these clinical signs was maintained after 12 months of daily tretinoin therapy, and regressed slowly after cessation of therapy. However, maintenance of the visible effects of topical tretinoin was reported after continued therapy with once or three times weekly applications of tretinoin emollient cream. Data from multicentre studies suggested that 0·1% tretinoin cream has a potential role in the treatment of solar keratoses. It is concluded that the application of tretinoin to photodamaged skin used in conjunction with sunscreens and judicious sun exposure is an effective regimen to treat the damaging cutaneous effects of chronic sun expos

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16985.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe distinction between intrinsic and extrinsic ageing can be made on both histological and clinical grounds. Clinical criteria associated with the diagnosis of extrinsic ageing are coarse wrinkles, actinic lentigines, elastotic conditions, purpura, telangiectasia and cutaneous neoplasms. These parameters are always superimposed on changes associated with intrinsic ageing: namely, fine wrinkles and benign growths. There is heightened interest in extrinsic ageing as a result of studies demonstrating the efficacy of topical tretinoin in improving this condition. As a consequence, systems for grading extrinsic ageing have been developed, including a photographic standard scale which removes some of the subjectivity inherent to current methodology.

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16986.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryTopical tretinoin improves mottling and hyperpigmented lesions of photodamaged skin. The basic mechanisms underlying these effects are not known. It is demonstrated that retinoids inhibit the growth and enhance the differentiation of melanoma cellsin vitro, and stimulate the constitutive melanogenesis in melanoma cellsin vitro.On the other hand, they inhibit hormonally or pharmacologically induced melanogenesis in these cells. Very few data are available concerning the effect of retinoic acid on normal human melanocytes, but there is some inhibition of growth as in melanoma cells. Retinoic acid appears to have little effect on the melanogenesis of normal human melanocytes grownin vitrousing serum‐free culture medium. Changes in the shape of these melanocytes suggest that retinoic acid acts on cytoskeleton proteins. Further studies, bothin vitroandin vivo, are needed to clarify the effects of retinoic acid on melanocyte

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16987.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0007-0963    

DOI:10.1111/j.1365-2133.1992.tb16988.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY