Phototherapeutic modalities pose no significantly increased risk of oxidative damage to DNA in dark skinned individuals.

BACKGROUND: 8-oxoguanine, a major product of DNA oxidation, is considered a key parameter in measuring the carcinogenic effects of ultraviolet radiation. OBJECTIVE: To assess and compare the carcinogenic potential of different photo (chemo) therapeutic modalities in photoresponsive skin diseases by measuring the levels of 8-oxoguanine in dark-skinned individuals before and after photo (chemo) therapy. METHODS: A prospective, randomized controlled pilot study was conducted in 63 patients of skin types III-V with photo-responsive dermatoses including vitiligo, psoriasis and mycosis fungoides. Patients were divided into three groups; Group 1 (received narrowband ultraviolet-B), Group 2 (received psoralen plus ultraviolet-A) and Group 3 (received broadband ultraviolet-A). Biopsies were taken before and after phototherapy to measure 8-oxoguanine levels using enzyme-linked immunosorbent assay. Biopsies were also taken from the sun-protected skin in 21 controls subjects who had no dermatological disease. RESULTS: Regardless of the disease, a significantly higher level of 8-oxoguanine was found after treatment when compared to the pre-treatment baseline levels; however, these levels were comparable to those in control subjects. A weakly significant positive correlation was found between cumulative dose and 8-oxoguanine levels following psoralen plus ultraviolet-A therapy. In controls, comparing the 8-oxoguanine levels between skin types III and IV showed significantly lower 8-oxoguanine in skin type IV. CONCLUSION: Therapeutic doses of ultraviolet radiation are relatively safe in dark skinned patients; however, minimizing the cumulative dose of phototherapeutic modalities (particularly psoralen plus ultraviolet-A) is recommended.

Significant differences between the G+C content of synonymous codons in orthologous genes and the genomic G+C content.

The relationship between the overall G+C content of the genome (GC) and the GC content at the third codon positions (GC3) of genes, which we refer to as a GC3-plot, was examined using 15 currently available complete genome sequences. A remarkably linear relationship was found between these two quantities, confirming previous observations of a strong positive correlation in the GC3-plot. In order to conduct a more detailed analysis of the GC3-plot, we examined the GC3 content by separating orthologous codons into three categories: synonymously different codons (namely identical amino acids, IA), different amino acids (DA), and identical codons (IC), for a pairwise comparison of two closely related species. When we took pairwise species comparisons between Mycoplasma genitalium (Mg) and Mycoplasma pneumoniae (Mp) and between Mycobacterium tuberculosis (Mt) and Mycobacterium leprae (Ml) as examples, we found that for Mp and Ml, the GC3 for IA deviated the most from the linear expectation in the GC3-plot, whereas for Mg and Mt the deviation was minimal. These findings suggest that the major changes of GC content took place in Mp and Ml, but not in Mg and Mt. This analysis also enables us to predict the future direction of the evolutionary changes of the genomic GC content.

Conspecificity of Hanseniaspora nodinigri and Hanseniaspora vineae: comparison by DNA reassociation.

Hanseniaspora nodinigri Lachance 1981, found in black knots (caused by Dibotryon morbosum) of Prunus virginiana, was described as a new species, some time after publication of the extensive study by Meyer et al. (1978) on the systematics of Hanseniaspora Zikes and its imperfect counterpart Kloeckera Janke. Lachance delimited the species from other members of the genus because of absence of growth on glucono-delta-lactone. He also stated that this species, although evidently similar in many ways to H. vineae van der Walt et Tscheuschner and H. osmophila (Niehaus) Phaff et al., has 'diverged from them, possibly in its adaptation to growth in association with black knots'.

DNA isolated from Mycobacterium leprae: genome size, base ratio, and homology with other related bacteria as determined by optical DNA-DNA reassociation.

DNA derived from Mycobacterium leprae (grown in armadillos) was isolated, purified, and analyzed spectrophotometrically. The genome size and the guanine-plus-cytosine content of M. leprae were 1.3 x 10(9) and 55.8%, respectively. Among selected strains of mycobacterial, nocardial, and corynebacterial species, Corynebacterium sp. 2628 LB, isolated from a human leprosy patient, showed the highest DNA homology with M. leprae. Of the DNAs derived from mycobacteria, those of M. tuberculosis and M. scrofulaceum showed a comparatively high reassociation with the DNMA of M. liprae.

Systematics of Hanseniaspora Zikes and Kloeckera Janke.

The physiological and morphological characteristics of eighty-two strains of Hanseniaspora and Kloeckera, represented twenty-nine described species, were examined. These results along with DNA base composition and DNA/DNA reassociation experiments revealed that the genus Hanseniaspora comprises six distinct species, viz. H. valbyensis, H. uvarum, H. guilliermondii, H. occidentalis, H. osmophila and H. vineae, with K. japonica, K. apiculata, K. apis, K. javanica, K. corticis and K. africana, respectively, as their imperfect states.

Clofazimine binding studies with deoxyribonucleic acid.

1. The antileprosy drug, clofazimine, formed stable complexes with DNA and transfer RNA. A quantitative study was made of the spectral red shifts that occurred when clofazimine interacted with DNA. The red shift appeared specific for clofazimine binding to nucleic acid polymers. 2. The degree of clofazimine interaction with DNA was related to the G+C content of the DNA strand. As compared to the human strand, clofazimine interacted with the mycobacterial strand to give a larger red shift which was consistent with the increased G+C content of mycobacterial DNA. 3. It was found that clofazimine interacted with the synthetic single-stranded polynucleotide, poly G, whereas little interaction occurred withpoly A, poly C, or poly U. It was concluded that the guanine base region was a predominant site of clofazimine binding to DNA. 4. No evidence was found to indicate that clofazimine underwent intercalative binding between the base pairs of DNA. 5. It was proposed that clofazimine underwent binding along the minor groove region of DNA at appropriate base sequences which contain guanine. The resultant effect would inhibit template function of the DNA strand.