[Determination of the energy density of rapid periodic laser light patterns of homogeneous superficial coverage for medical applications]

Plants grow better if seeds see green

We report on the response of dry plant seeds to their irradiation with intense green light applied at biostimulatory doses. Red and near-infrared light delivered by lasers or arrays of light emitting diodes applied at such doses have been shown previously by us to have effects on mammalian cells. Effects include cell proliferation and elevation of cell vitality, and have practical applications in various biomedical fields. Growth processes induced by photoreceptor stimulation (phytochromes and cryptochromes) in plant seeds with green light were described so far only for imbibed seeds. In this paper, we show that irradiation of dry cress, radish and carrot seeds with intense green light (laser or arrays of light emitting diodes), applied at biostimulatory doses, resulted in a significant increase in biomass--14, 26, and 71 days after seeding, respectively. In the case of radish and carrot, the irradiation led to important changes in the root-to-foliage surface ratio. Seeds with a potential to grant growth acceleration could be of special interest in agricultural applications, and could even compensate for shorter growth seasons caused by climate change.

Light-induced replication of nanobacteria: a preliminary report

OBJECTIVE

The purpose of the present study was to investigate the effect of light on nanobacteria.

BACKGROUND DATA

Since their first description in literature, it is not clear whether the nanoparticles called "nanobacteria" are alive or not. The 80-1,000-nm-sized spherical particles are protected by a crystalline carbonate apatite shell and are culturable in cell culture media. Present in mammalians, including humans, nanobacteria seem to cause diseases related to biomineralization processes. Mesoscopic structures found on Martian meteorites and terrestrial rocks indicated that nanobacteria-like biological objects forming apatite, a material fairly transparent to visible light, could have been present on the primitive Earth during an era with the sun as the principal terrestrial energy source.

MATERIALS AND METHODS

To evaluate possible biomedical effects of therapeutically relevant irradiation sources on nanobacteria, we irradiated nanobacteria cultures with polarized light and laser-light at low, nonthermal energy density levels.

RESULTS

Our observations indicated that nanobacteria are alive. Polarized white light was found to clearly accelerate their replication in vitro, resulting in significant dose-dependent increases in the turbidity of the cultures, compared to nonirradiated controls. Laser irradiation did not affect their replication.

CONCLUSION

The possibility that primordial and present nanobacteria could have been not only exposed to, but actively harvested, solar irradiation for their own development suggests itself. Considering that there exists no published material on the action of light on nanobacteria, the reported effects are expected to have an impact on modeling biomineralization processes, associated photoreceptor mechanisms, and astrobiological and evolutionary theories-on Earth and in space.

Biostimulatory windows in low-intensity laser activation: lasers, scanners, and NASA's light-emitting diode array system

OBJECTIVE

The purpose of this study was to assess and to formulate physically an irreducible set of irradiation parameters that could be relevant in the achieving reproducible light-induced effects in biological systems, both in vitro and in vivo.

BACKGROUND DATA

Light-tissue interaction studies focusing on the evaluation of irradiation thresholds are basic for the extensively growing applications for medical lasers and related light-emitting systems. These thresholds are of central interest in the rejuvenation of collagens, photorefractive keratectomy, and wound healing.

METHODS

There is ample evidence that the action of light in biological systems depends at least on two threshold parameters: the energy density and the intensity. Depending on the particular light delivery system coupled to an irradiation source, the mean energy density and the local intensity have to be determined separately using adequate experimental methods.

RESULTS

From the observations of different research groups and our own observations, we conclude that the threshold parameters energy density and intensity are biologically independent from each other.

CONCLUSIONS

This independence is of practical importance, at least for the medical application of photobiological effects achieved at low-energy density levels, accounting for the success and the failure in most of the cold laser uses since Mester's pioneering work.