RESUMEN
In general, human hair is claimed to turn yellower after sun exposure. This is particularly affirmed for white hair. However, quantitative data relating yellowness to hair type and to the radiation wavelength are missing. This work shows results of the effect of full or UVB-filtered radiation of a mercury vapor or a xenon-arc lamp on the yellowness of virgin white, dark-brown, blond and red hair. All hair types showed a substantial change in yellowness after irradiation, which is dependent on the hair type and radiation wavelength. Surprisingly, white hair turns less yellow after both full and UVB-filtered radiation exposure. This effect is more pronounced when UVB is filtered from the radiation system. The only radiation that shows a photo-yellowing effect on white hair is infrared. As the yellowness of white hair is commonly related to tryptophan degradation, fluorescence experiments with hair solutions were performed to identify the natural degradation of tryptophan which occurs in hair after light irradiation. Pigmented hairs were also studied, as well as hair treated with a bleaching solution. Although we observe a decrease in tryptophan content of hair after lamp radiation, a direct correlation with hair yellowness was not achieved. Results are discussed in terms of hair type, composition and melanin content.
Asunto(s)
Filtración/métodos , Color del Cabello/efectos de la radiación , Cabello/efectos de la radiación , Mercurio , Rayos Ultravioleta , Xenón , Relación Dosis-Respuesta en la Radiación , Cabello/química , Cabello/metabolismo , Color del Cabello/fisiología , Humanos , Melaninas/análisis , Melaninas/química , Melaninas/metabolismo , Pigmentos Biológicos/análisis , Pigmentos Biológicos/metabolismo , Factores de Tiempo , Triptófano/química , Triptófano/metabolismoRESUMEN
This paper reviews the current knowledge about human hair photodamage and the photodegradation mechanisms proposed in the literature. It is shown that there are still a number of questions without answer regarding this issue. For example, a better understanding of the hair structural changes caused by different radiation wavelengths is still lacking. We also find controversies about the effects of sun exposure on different hair types. Explanations to these questions are frequently sustained on the amount and type of melanin of each hair, but factors such as the absence of knowledge of melanin structure and of established methodologies to use in human hair studies make it difficult to reach a general agreement on these issues.
Asunto(s)
Cabello/efectos de la radiación , Rayos Ultravioleta/efectos adversos , Cabello/química , Humanos , Melaninas/química , FotoquímicaRESUMEN
An effective diet that attends patient's needs is being study by researchers connected with enteral nutrition and dietetics. The aim of study is to develop formulations for enteral products based on digestic bovine, chicken and fish meat by bromelin