Masafumi Muraji

Primary root growth rate of Zea mays seedlings grown in an alternating magnetic field of different frequencies

Abstract We have studied the effect of an alternating magnetic field on the growth rate of primary roots in Zea mays. Corn seedlings were grown in the dark, under constant conditions of temperature (25°C) and humidity (100%). They were also subjected to a 5 mT magnetic field, alternating at frequencies of either 5, 10, 20 or 40 Hz. The rate of primary root growth, in plants grown at each frequency, was measured and compared to a control group. Control plants were grown under similar conditions, in the absence of the magnetic field. The growth rate of primary roots in seedlings grown at each of the magnetic field frequencies used, was increased compared to the control group. The highest growth rate was seen in seedlings exposed to a magnetic field alternating at 10 Hz.

Resistance of yeast and bacterial spores to high voltage electric pulses

Abstract Spores of a yeast, Saccharomyces cerevisiae , and a bacterium, Bacillus subtilis , were exposed to high voltage electric pulses. The viabilities of spores and vegetative cells of the yeast were significantly decreased after the electric pulse treatment, and some of the spores and almost all of the cells were stained red with an agent, phloxine B. On the other hand, (endo) spores of the bacterium were highly resistant to the electric pulses and little decrease in viability was observed, although the viability of vegetative cells was sharply lowered. The results revealed marked structural and/or biochemical differences between eukaryotic and prokaryotic spores.

Effect of electrical energy on the electropermeabilization of yeast cells

Abstract A suspension of yeast cells (Saccharomyces cerevisiae) in NaCl solution was exposed to high voltage pulses under defined conditions. The results on perforation through the membrane and the cell wall structure (electropermeabilization) and the resealing process are presented. Capacitor discharges were applied to yeast cells in their logarithmic growth phase. A dye was added at a predetermined time after the electric pulse. Dyed and total (dyed plus undyed) yeast cells were counted microscopically and the rate was calculated. Dyed cells were assumed to have pores. For simplicity, the time constant of the electric circuit was adjusted so that it was almost the same for each capacitance by changing the conductivity of the yeast suspension. The capacitances used in the experiments were 1, 2, 4 and 8 μF yielding different initial field strengths. It was calculated that, under similar perforation and resealing conditions, almost the same energy was applied to the yeast suspension. Our conclusion is that the electrical energy is closely concerned with the electropermeabilization and resealing of the membrane and cell wall.

Effect of alternating magnetic field on the growth of the primary root of corn

Corn seeds each with a primary root were exposed to alternating magnetic fields. Locations of the root before and after exposure were accurately measured, and the growth during the exposure was calculated. These values were compared with those of the control group. Results indicate that the relatively low frequencies used in the experiments hastened the growth of the primary root while relatively high frequencies slowed root development. >

Examination of the relationship between parameters to determine electropermeability of Saccharomyces cerevisiae.

A rectangular electric pulse was applied to Saccharomyces cerevisiae suspensions in NaCl solutions. The relationship between field strength, pulse width and conductivity of extracellular media of key--factors to determine the yield of electropermeability--was examined at the time when the same permeability occurred. The results showed that the dependence of the yield of permeability upon the width of applied pulse was mutually related with the conductivity of extracellular media. Namely at one field strength, the value of pulse width is inversely proportional to that of conductivity of media and its relationship holds true for any field strength. Further, the relationship between parameters considered bears a close resemblance to that recognized between stress amplitude and the number of cycles to failure in the fatigue fracture of materials.

Re-examination of electropermeabilization on yeast cells: dependence on growth phase and ion concentration

Abstract By applying an electric pulse to yeast cell suspensions, we re-examined the dependence of electropermeabilization on the growth phase of the cells and the ion concentration. It was found that the growth phase and the ion concentration play a major role in determining the electropermeabilization yield.

The relationship between electropermeabilization and cell cycle and cell size of Saccharomyces cerevisiae

Yeast cells (Sacchromyces cerevisiae) in 0.9% NaCl solution containing phloxine B (dye) were treated by an application of a rectangular electric pulse. We input microscopic images of the yeast suspensions after the application into a computer, and measured whether each cell dyes or not, the phase in the cell cycle, and each cell size, using the software we had developed. After those measurements, we discussed the relationship between the yield of electropermeabilization (the ratio of dyed cells to the total cell number) and the phase in the cell cycle, and cell size. From the results, it was found that the yeast cells from S-phase to M-phase (S-M phase) in the cell cycle tend to be more permeated than G1-phase yeast cells, and in both phases the yield decreases with the increase in cell size.

The estimation of the yeast growth phase by nonlinear dielectric properties of the measured electric current

Abstract We measured the activity of yeast in each growth phase by using nonlinear dielectric properties. In this paper, we used a 2-electrode system, rather than the previous 4-electrode system, to measure the current waves for the analysis of the phase angle of response waves and the facilitation of the measurements. As a result, in the exciting frequency and field, 14 Hz and 0.75 V cm or 1.25 V cm −1 , the 2nd harmonic of the response wave for cell suspensions showed a significant difference between the induction phase and the others. However, for the supernatant of suspensions, there was no difference in the power spectrum of the even-numbered harmonics. With the phase angle, the same tendency was observed in the power spectrum. When another combination of field and frequency (0.25 or 1.75 V cm −1 and 7, 28, 35 or 42 Hz) was applied, there were no significant differences in either the power spectrum or the phase angle. These results were different from those measured by a 4-electrode system, although the range of frequency and field are almost the same. However, we found that the 2nd harmonics in the induction phase were different from those in the other phases. We can say that this 2-electrode system is applicable for the estimation of the growth of yeast cells.