Laser (and LED [light-emitting diode]) phototherapy will continue to live outside of the mainstream of science and medicine until authors, reviewers, and editors learn the fundamentals of photobiology. The purpose of this letter is to explain some of these fundamentals. The science of photobiology 1 is composed of a number of subspecialties. Bioluminescence deals with emitted light from organisms, for example, the study of fireflies. In addition to the basic fields of photochemistry, photophysics, and spectroscopy, the other fields of photobiology deal with the absorption of light by plants and animals. Under photomedicine are the studies of both the detrimental effects of light (e.g., ultraviolet [UV] radiation causing cancer) and the beneficial effects of light (e.g., treating jaundice in premature infants). There is also photoimmunology (UV radiation affecting the immune system) and photosensitization (e.g., certain drugs increasing skin sensitivity to solar radiation). In photosynthesis, the energy of the light absorbed by plants is converted into chemical energy, which is used to support growth. Under environmental photobiology are the studies of photosensitization and UV radiation effects. These are not just problems affecting humans; they also affect our environment. Under photosensory biology are chronobiology (biological clocks), photomorphogenesis (light signals regulating changes in structure and form in plants), photomovement (e.g., sunflowers moving to face the sun), photoreception (perception of light by receptors other than true eyes), and vision. Photobiology covers a wide range of topics that are important to humans and the environment. Specific scientific and/or medical training is needed to study each of these areas of photobiology, and they all require expert training in scientific methodology. However, it is also necessary for anyone working in these areas to learn the basics of photobiology. Unfortunately, all too frequently the people in the laser (and LED) phototherapy field are untrained in the basics of photobiology. This leads to bad science and bad clinical trials, which lead to conflicting results concerning a given endpoint, diminishes the stature of the field, and delays the admission of laser (and LED) phototherapy into the mainstream of science and medicine.
Isogenic Escherichia coli strains carrying single DNA-repair mutations were compared for their capacity for (i) the repair of X-ray-induced DNA double-strand breaks (DSB) as measured using neutral sucrose gradients; (ii) medium-dependent resistance, i.e., a recA-dependent X-ray survival phenomenon that correlates closely with the capacity for repairing DSB; and (iii) the growth medium-dependent, recA-dependent repair of X-ray-induced DNA single-strand breaks (SSB) as measured using alkaline sucrose gradients (about 80% of these SSB are actually parts of DSB). These three capacities were measured to quantitate more accurately the involvement of the various genes in the repair of DSB over a wide dose range. The mutations tested were grouped into five classes according to their effect on the repair of X-ray-induced DSB: (I) the recA, recB, recC, and lexA mutants were completely deficient; (II) the radB and recN mutants were about 90% deficient; (III) the recF and recJ mutants were about 70% deficient; (IV) the radA and uvrD mutants were about 30% deficient; and (V) the umuC mutant resembled the wild-type strains in its capacity for the repair of DSB.
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