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At least 469 records · Page 26Linked to original sources
PubMed1988

Human cell transformation in the study of sunlight-induced cancers in the skin of man.

Human cell transformation provides a powerful approach to understanding--at the cellular and molecular levels--induction of cancers in the skin of man. A principal approach to this problem is the direct transformation of human skin cells by exposure to ultraviolet and/or near-UV radiation. The frequency of human cells transformed to anchorage independence increases with radiation exposure; the relative transforming efficiencies of different wavelengths implies that direct absorption by nucleic acids is a primary initial event. Partial reversal of potential transforming lesions by photoreactivation suggests that pyrimidine dimers, as well as other lesions, are important in UV transformation of human cells. Human cells can also be transformed by transfection with cloned oncogenes, or with DNAs from tumors or tumor cell lines. Cells treated by the transfection procedure (but without DNA) or cells transfected with DNAs from normal mammalian cells or tissues show only background levels of transformation. Human cells can be transformed to anchorage-independent growth by DNAs ineffective in transformation of NIH 3T3 cells (including most human skin cancers), permitting the analysis of oncogenic molecular changes even in tumor DNAs difficult or impossible to analyze in rodent cell systems.

Cell Division↗
PubMed1994

Immune surveillance and sunlight-induced skin cancer.

Immune surveillance poses the existence of a recirculating pool of lymphocytes that migrate randomly through somatic tissues. Upon recognition of neoantigens on malignantly transformed cells, lymphocytes proceed to attack and destroy degenerate cells before a tumor emerges. Here, J. Wayne Streilein and colleagues review the effects of ultraviolet B irradiation on the induction of cutaneous immunity in the skin of mice and humans. Furthermore, they discuss the possibility of a genetic predisposition to skin cancer, mediated by a defect in the normal process by which contact hypersensitivity, and therefore immunogenicity, is elicited.

Animals↗
PubMed1989

Design for a bioreactor with sunlight supply and operations systems for use in the space environment.

An experiment was carried out to determine the characteristics of an operations system that can support fast cultivation of algae at high densities in the weightlessness of space. The experiment was conducted in glass bioreactor tanks, in which light was supplied by radiator rods connected to optical fiber cables. The illumination areas of the tanks were 2600 cm2, 6000 cm2, and 9200 cm2 per liter of solution. The characteristics of O2-CO2 gas exchange, concentration and separation of chlorella in the growth medium, dialysis of ionic salts in the growth medium, etc. were examined. Chloralla ellipsoidea was used in the experiment, yielding the following results: (1) By increasing the ratio of illumination area to volume, growth rates of up to approximately 0.6 g/L h could be obtained in a highly concentrated solution (one that contains 20 g/L or more of algae). (2) The most suitable proportions of carbon dioxide and oxygen gases for growing algae quickly at high concentrations were found to be 10% CO2 and 10% O2 (by volume). (3) There was a high optimum concentration for fast cultivation, and the data obtained resembled the theoretical curve postulated by P. Behrens et al. (4) It was possible to exchange carbon dioxide and oxygen using gas-permeable membrane modules. (5) It was possible to separate the chlorella from the growth medium and recycle the medium.

Bioreactors↗
PubMed2006

Monitoring the photochemical degradation of triclosan in wastewater by UV light and sunlight using solid-phase microextraction.

Photo solid-phase microextraction (photo-SPME) is applied for the first time to study the photochemical behavior of an emerging pollutant, triclosan, in real contaminated wastewater samples using a solar simulator. In this study, water samples are extracted by SPME and then, the fiber coating is irradiated for a selected time. This on-fiber procedure, so-called photo-SPME, followed by gas chromatography-mass spectrometry makes it possible to study photodegradation kinetics and the generation of byproducts. Several photoproducts were identified in the real samples including the 2,8-dichlorodibenzo-p-dioxin, dichlorophenols and a compound tentatively identified as other DCDD congener or a dichlorohydroxydibenzofuran. Accordingly, it was possible to postulate main photodegradation mechanisms. Photo-SPME demonstrated slower kinetics in wastewater than in spiked ultrapure water probably due to the presence of dissolved organic matter. This technique was extensively compared with conventional aqueous photodegradation showing high similarity. The influence of pH on the triclosan photolysis and on the triclosan-dioxin conversion was also investigated in wastewater. Photodegradation of triclosan and formation of 2,8-DCDD occurred independently of sample pH. This study represents an advance in the use of photo-SPME to understand the photochemical fate of environmental organic pollutants and demonstrates its clear advantages with real samples.

Chromatography, Ion Exchange↗
PubMed2007

Sunlight, skin cancer and vitamin D: What are the conclusions of recent findings that protection against solar ultraviolet (UV) radiation causes 25-hydroxyvitamin D deficiency in solid organ-transplant recipients, xeroderma pigmentosum, and other risk groups?

A connection between vitamin D deficiency and severe health problems including various types of cancer has been demonstrated. We have shown that patients that have to protect themselves against solar UV radiation for medical reasons, including patients with xeroderma pigmentosum (XP), basal cell nevus syndrome (BCNS), lupus erythematodes (LE) or transplant recipients, are at risk to develop vitamin D deficiency. We conclude that 25-hydroxyvitamin D serum levels as a measure of vitamin D status have to be analyzed in patients that have to protect themselves against solar UV radiation for medical reasons. Suboptimal vitamin D status has to be substituted (e.g. via oral treatment) to protect against serious vitamin D deficiency-related health problems without increasing the risk to develop solar UV-induced skin cancer. Our finding that protection against solar UV radiation causes vitamin D deficiency underlines the need for re-defining dermatological recommendations for solar UV protection in skin cancer prevention programs.

Health↗
PubMed2006

The challenge resulting from positive and negative effects of sunlight: how much solar UV exposure is appropriate to balance between risks of vitamin D deficiency and skin cancer?

There is no doubt that solar ultraviolet (UV) exposure is the most important environmental risk factor for the development of non-melanoma skin cancer. Therefore, sun protection is of particular importance to prevent these malignancies, especially in risk groups. However, 90% of all requisite vitamin D has to be formed in the skin through the action of the sun-a serious problem, for a connection between vitamin D deficiency and a broad variety of independent diseases including various types of cancer, bone diseases, autoimmune diseases, hypertension and cardiovascular disease has now been clearly indicated in a large number of epidemiologic and laboratory studies. An important link that improved our understanding of these new findings was the discovery that the biologically active vitamin D metabolite 1,25(OH)(2)D is not exclusively produced in the kidney, but in many other tissues such as prostate, colon, skin and osteoblasts. Extra-renally produced 1,25(OH)(2)D is now considered to be an autocrine or paracrine hormone, regulating various cellular functions including cell growth. We and others have shown that strict sun protection causes vitamin D deficiency in risk groups. In the light of new scientific findings that convincingly demonstrate an association of vitamin D deficiency with a variety of severe diseases including various cancers, the detection and treatment of vitamin D deficiency in sun-deprived risk groups is of high importance. It has to be emphasized that in groups that are at high risk of developing vitamin D deficiency (e.g., nursing home residents or patients under immunosuppressive therapy), vitamin D status has to be monitored. Vitamin D deficiency should be treated, e.g., by giving vitamin D orally. Dermatologists and other clinicians have to recognize that there is convincing evidence that the protective effect of less intense solar UV radiation outweighs its mutagenic effects. Although further work is necessary to define an adequate vitamin D status and adequate guidelines for solar UV exposure, it is at present mandatory that public health campaigns and recommendations of dermatologists on sun protection consider these facts. Well-balanced recommendations on sun protection have to ensure an adequate vitamin D status, thereby protecting people against adverse effects of strict sun protection without significantly increasing the risk of developing UV-induced skin cancer.

Animals↗