ACTION OF ND: YAG LASER ON GROWTH OF

A. Jadah, N.; M. Aziz, G.; G. Anwer, A.

	ACTION OF ND: YAG LASER ON GROWTH OF
IRAQ JOURNAL OF AGRICULTURE
Article 1, Volume 2, Issue 16, 2011, Pages 0-0
Authors
N. A. Jadah; G. M. Aziz; A. G. Anwer
Abstract
Irradiation with Q-switch Nd: YAG laser caused growth stimulation to the cells of Saccharomyces cerevisiae. The laser parameters that were used in cells irradiation include two wavelengths (1064 and 532nm) at a fixed energy density (11.3 mJ/cm2) with different number of pulses (15, 30 and 60). After irradiated cells were incubated in liquid nutritive broth for 24h, biomass, total cell number and viability were determined. It was found that irradiation with 532nm at 30 pulses produced noticeable increasing in values of biomass and viability of the irradiated cells compared to their values in the case of irradiation with 1064nm wavelength that, it also stimulated the increasing in the value of total cell number in to a maximum value. Introduction The concept of “biostimulation” occurring at low energy density of laser radiation is already generally accepted, despite some controversy concerning especially the mechanisms by which the biological response appears (22). The study of interaction between electromagnetic waves and the living systems involves many physical and biological aspects. On the one hand, it was demonstrated that there is a “threshold stimulus”, in the sense that the monochromatic signal carrier becomes stimulus only if its energy exceeds a threshold value (22). On the other hand, all observed biological effects of this signal action originate from changes in cellular membrane potentials, resulting from changes in membrane permeability and microviscosity. These changes are caused by the action of the excitation that provokes charge separations, which generate concentration and potential gradients (10). The irradiation effect, growth stimulation, was evaluated by counting the total cell number, biomass and viability (11). These were the basic measurements performed to characterize the quantitative laws of light action on the growth of microorganisms (dependences on wavelength, energy density and number of pulses) upon metabolism of eukaryotic microorganisms. The stimulatory effects of low-fluence laser irradiation at the cellular and molecular levels have been shown by many studies. Laser light affects the mitochondrial respiratory chain by changing the electric potential of cell membranes and, consequently,their selective permeability for sodium, potassium and calcium ions, or by increasing the activity of certain enzymes such as Cytochrome oxidase and adenosine triphosphatase (11). It also increases DNA synthesis (14), collagen and pro-collagen production (1,3), and may increase the cell proliferation (23). In contrast to these stimulatory effects, some investigators have found damaging or even destructive action of soft laser radiation. Ocana-Quero et al. for instance, described a degenerative effect of He-Ne laser irradiation on bovine oocytes (17). The aim of this study was to assess the effect of the fluence (energy

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