Effects of infrared laser damage to the Euglena photoreceptor on the control of flagellar motility.
When the area of the stigma of Euglena was irradiated with an infrared laser beam at a dose too low to cause permanent loss of motility, a reduction in flagellar motility was observed only when the external medium contained less than 1 mM Mg2+. At these low Mg2+ concentrations, the laser caused a decrease in flagellar frequency and a tendency for the flagellar waveform to shift towards that taken during reversed swimming. This suggests that the effect of the laser irradiation was to deplete the cells of Mg2+. After the laser pulse the reversal response remained sensitive to the wavelength of the illuminating light. In white light (420-700 nm) 60% of the Euglena showed a reversed waveform; in orange light (530-700 nm) this increased to 90%. This shows that the photoreceptor was not destroyed by the laser irradiation. These experiments were performed on cells that had been impaled on a microelectrode. If direct electric current was passed into the laser-irradiated cells, the current necessary to cause flagellar arrest was 2 to 4 times less than that for cells not laser irradiated. It is concluded that an internal Mg2+ store is present in the Euglena, localized in the area of the paraflagellar swelling; and that the laser irradiation eliminates this Mg2+ store, but at the power used it does not destroy the ability of the stigma-paraflagella to control the flagellar activity.
D000255:Adenosine Triphosphate / Q000502:physiology; D002118:Calcium / Q000502:physiology; D005055:Euglena / Q000502:physiology*; D005407:Flagella / Q000502:physiology*; D007834:Lasers; D008274:Magnesium / Q000502:physiology; D010786:Photoreceptor Cells / Q000528:radiation effects
D000255:Adenosine Triphosphate; D008274:Magnesium; D002118:Calcium