Gary E. Kaufman

Growth retardation in Chinese hamster V-79 cells exposed to 1 MHz ultrasound

Abstract Asynchronous Chinese hamster V-79 cells were exposed in suspension to continuous wave 1 MHz ultrasound for 1 min at an axial intensity of 2.5 W/cm 2 , then allowed to grow in monolayer culture. There was little if any growth, as determined by changes in the number of attached cells, for 24 hr after sonication, then a return to normal growth approximately 36 hr after sonication. The lack of growth during the first 24 hr appears to be due to an approximate balance between proliferation of viable cells and loss of non-viable cells into the medium.

Lysis and viability of cultured mammalian cells exposed to 1 MHz ultrasound

Abstract HeLa and CHO cells were exposed for 1 to 15 min to 1 MHz ultrasound at intensities up to 30 W/cm 2 . The threshold for cell lysis was approximately 1 W/cm 2 with the maximum effect at 10 W/cm 2 . Among the intact cells there was a decreased viability as determined both by trypan blue exclusion and by colony-forming ability; the intensity vs. response curve was similar to that fur cell lysis. Preliminary evidence also suggests that a decrease in proliferation rate and an increased incidence of giant cells occur for the remaining intact and viable cells.

Chromosome aberration yields from multiple fixation regimens.

Methods for obtaining quantitative information on chromosome aberration yields are examined. Single fixation regimens give valid results only for cell populations with a uniform sensitivity. Multiple fixation regimens are needed to sample adequately non-uniform populations. The resulting yield-time curves from such multiple fixation regimens do not directly reflect the profile of sensitivity throughout the cell cycle, and neither the peak aberration yield nor the integrated area under the yield-time curve is a valid measure of effect. Nevertheless, multiple fixation regimens can be used to determine the overall mean aberration frequency for an entire and identifiable population of cells. First the entire population is sampled in a series of non-overlapping fractions. For an “ideal” population this is done by fixing one sample and immediately treating the next with colchicine. The overall aberration yield is then a weighted average of the aberration frequencies in the samples. The w eighted a verage aberration y ield, W.A.Y. = ∑ i = 1 n f i A i , where n is the number of consecutive samples, Ai is the aberration frequency in the ith sample, and fi is the fraction of cells in the population which enter metaphase in the ith sampling interval. The metaphase fraction, fi, is normally determined indirectly as the product of two factors, the metaphase index in the ith sample, and a correction factor for changes in population size due to cell division. The determination of the W.A.Y. is described in detail for synchronous cell populations, and for S phase cells and G2 phase cells from asynchronous populations.

The Effect of 2 MHz Ultrasound Irradiation on Pisum sativum Roots

The effect of 2 MHz ultrasound at intensity levels from 2.5 to

Lack of effect of extremely low frequency electric and magnetic fields on roots of Vicia faba

22\ {\rm W}/{\rm cm}^{2}

Variable S-phase duration in Vicia faba root meristem cells

on the growth rate and mitotic index of Pisum sativum roots was studied. The ultrasound produced an immediate reduction in the growth rate on the first postexposure day, followed by a gradual recovery to the control value. Ultrasound reduced the root meristem mitotic index. Intensity- and time-dependent relations were found for the growth rate and mitotic index reductions.

Effects of short-duration exposures to 2MHz ultrasound on growth and mitotic index of Pisum sativum roots

Abstract Roots of Vicia faba were exposed for up to six days to 75 Hz magnetic fields up to 17 gauss and to 75 Hz electric fields of 10V/m. These fields are approximately 85 times and 100 times, respectively, the fields which would result from a buried extra low frequency antenna of the design proposed for the Navys Project Sanguine. No differences in growth or mitotic index were observed between control and exposed roots. Also, no chromosomal anomalies were observed.

Colony size and giant cell formation from mammalian cells exposed to 1 MHz ultrasound.

Abstract Autoradiography, using single and double labeling, was utilized to determine the range of S-phase durations in Vicia faba root meristem cells. Minimum and maximum S-phase durations were estimated to be 4.5 and 21.5 hr respectively, approximately a five-fold range. This range is similar to the range in G2 durations previously reported and suggests that variable rates of progression are characteristic of the entire cell cycle rather than of G1 and G2 only.

Agglomerated nuclei in ultrasonicated Vicia faba roots: A partial elucidation of their derivation

Abstract Roots of Pisum sativum were exposed to 2 MHz ultrasound for durations from 0.006 to 60 sec. Growth was noticably reduced by exposure durations of 0.03 sec and longer (at a spatial peak intensity of 20 w/cm 2 ) and mitotic index was noticably depressed by exposure durations of 0.06 sec and longer (at 30 W/cm 2 ). Additional increments of ultrasound exposure were progressively less effective in further reducing growth and mitotic index. Thus, a major part of the damage from a one-minute ultrasound exposure appears to be produced within the first few seconds after the beam is turned on.

Chromosomal anomalies cannot account for growth rate reduction in ultrasonicated Vicia faba root meristems

Chinese hamster ovary (CHO) cells were exposed to continuous wave 1 MHz,