The use of dyes in modern biomedicine.

The discovery of the aniline dyes in the 19th century and contemporary investigation of their use as biological stains by scientists such as Koch and Ehrlich led to the idea of selectivity and formed the basis of modern chemotherapy; several of these dyes remain in pharmacopoeias. While the development of therapeutics has tended to avoid colored compounds due to unwanted coloration, the modern application of photosensitizing dyes, both in the fields of cancer therapy and anti-infection, depends on this phenomenon. In addition, the fluorescence of some anticancer photosensitizers allows their use as tumor localizing agents, which is particularly useful in precancerous conditions. It is also fitting that dyes employed in Ehrlich's original studies, such as the phenothiazinium dye, methylene blue, are now in clinical use for disinfecting donated blood products.     

Heritability and components of phenotypic expression in skin reflectance of Mestizos from the Peruvian Lowlands

Skin reflectance was measured on the inner upper arm and forehead of a sample of 209 Mestizos ranging in age from 2 to 64 years living in the town of Lamas in the Eastern Peruvian Lowlands. The sample consisted of 43 father-son, 42 father-daughter, 62 mother-son, and 70 mother-daughter pairs. The sample also consisted of 57 brother-brother, 60 sister-sister and 139 brother-sister pairs. The reflectance measurements were made with a Photovolt Reflection Meter, model 670. Stepwise polynomial regression techniques were used to derive standardized residual values. Then using these residual values parent-offspring, sibling intraclass correlations and components of the phenotypic expression of skin reflectance were calculated. The study indicates that 1) the parent-offspring and sibling correlation coefficients conformed with the theoretical correlations expected assuming polygenic inheritance; 2) the husband-wife correlations indicate a high degree of assortative mating for skin color, but despite this effect the parent-offspring and sibling correlation coefficients are lower than the values expected under the influence of autosomal genes; 3) estimates of heritability and components of phenotypic expression indicate that about 55% of the total variability in skin reflectance could be attributed to the influence of additive genetic factors; and 4) there is no evidence of X-linkage in the inheritance of skin color.     

Analysis of protein binding to the Sma/Cla DNA repeat in pathogenic Neisseriae.

Antigenic variation of the pilus is an essential component of Neisseria gonorrhoeae pathogenesis. Unidirectional recombination of silent pilin DNA into an expressed pilin gene allows for substantial sequence variation of this highly immunogenic surface structure. While the RecA protein is required for pilin gene recombination, the factors which maintain the silent reservoir of pilin sequences and/or allow unidirectional recombination from silent to expression loci remain undefined. We have previously shown that a conserved sequence at the 3'end of all pilin loci (the Sma/Cla repeat) is required to be present at the expression locus for efficient recombination from the silent loci. In this study, the binding of gonococcal proteins to this DNA sequence was investigated. Gel mobility shift assays and competition experiments using deletion derivatives of the repeat, show that multiple activities bind to different regions of the Sma/Cla repeat and define the boundaries of the binding sequences. Moreover, only the pathogenic Neisseria harbor proteins which specifically bind to this repeat, suggesting a correlation between the expression of these DNA binding proteins and the potential to cause disease.