. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INTERACTION OF ELECTROMAGNETIC FIELDS 171 L929 Cells- 3mT rms,60 Hz • 2 2mV/m 8 102mV/m • 155mV/m. Time (hrs) Figure 1. Doubling time of L929 cells for 3 values of the electric field induced by a 30 gauss (rms), 60 Hz magnetic field at T = 37°C. The field was off for the first 38 h, on for 52 h, then off for 39 h. evidence to assert that the growth rate was influenced by the applied electric field. It might be noted that in general an increase in initial growth rate is to be expected be- cause of the "conditioning of th
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INTERACTION OF ELECTROMAGNETIC FIELDS 171 L929 Cells- 3mT rms,60 Hz • 2 2mV/m 8 102mV/m • 155mV/m. Time (hrs) Figure 1. Doubling time of L929 cells for 3 values of the electric field induced by a 30 gauss (rms), 60 Hz magnetic field at T = 37°C. The field was off for the first 38 h, on for 52 h, then off for 39 h. evidence to assert that the growth rate was influenced by the applied electric field. It might be noted that in general an increase in initial growth rate is to be expected be- cause of the "conditioning of the medium" effect (Par- kinson 1983). In such measurements it is critical that the temperature be maintained constant with field on and off since the doubling time is an exponential function of temperature. [See for example the measured dependence of the mitotic period for L929 cells in Parkinson (1983).] It has been reported that appropriately pulsed electro- magnetic fields (Bassett et al, 1981) promote os- teogenesis and wound healing. There is also a report that pulsed electromagnetic fields stimulate DNA synthesis in fetal rat calvarial osteoblasts grown in culture (Hanley et al., 1981). There is, to our knowledge, only one report in a refereed journal of a response by transformed cells (Colacicco and Pilla, 1983). We have measured the up- take of tritiated thymidine (3H-TdR) by cultures of finite cell lines and continuous cell lines in response to pulsed electromagnetic fields (PEMF) using both the Bassett waveform ("c"-signal) and a repetitive rectangular pulse train. The finite cell lines were quail somite fibroblasts and periosteal cells from fetal rat calvarium; the continu- ous cell lines were L-929, Balb/c 3T3, Chinese hamster ovary (CHO), and rat osteosarcoma [ROS 17]. The apparatus for generating the pulsed electrical field is the same as that described earlier (Parkinson and Hanks, 1986). In that work, 24 well tissue culture dishes were use
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