title: Effects of infrared laser damage to the Euglena photoreceptor on the control of flagellar motility.
abstract: 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.
mesh_terms: 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
chemical_list: D000255:Adenosine Triphosphate; D008274:Magnesium; D002118:Calcium