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Biomedical subjects

S Z Child

Publications and source records attributed to S Z Child.

At least 55 records · Page 3Linked to original sources
PubMed1988

Murine ovulatory response to ultrasound exposure and its gynecological relevance.

Ultrasonographic assessment of ovarian follicular maturity was reportedly associated with atypically early ovulation in women; related studies reported reduced litter sizes in rats. To confirm these findings, mice which were midway between ovulatory gonadotropin (LH or human chorionic gonadotropin) stimulation and ovulation, were sham- or ultrasound-treated periovarially for 5 min. Exposure was at a spatial average, temporal maximum intensity of 60 W/cm2. Carrier frequency in the pulse was 2.2 MHz, pulse length was 10 microseconds, and pulse repetition frequency was 200 Hz. Spatial average, temporal average intensity was 0.12 W/cm2. At autopsy, ultrasound- and sham-treated groups responded similarly in proportions ovulating and in mean ova ovulated. Combined experiments had a 97% chance of detecting a significant (greater than 1 h) advance in ovulation time, had it occurred. Thus, our adequately sensitive mammalian ovulatory tests revealed no association of ultrasound with decrease in ovum number or acceleration in ovulation time (as reported in humans).

Animals↗
PubMed1988

Testing for the teratogenicity of pulsed ultrasound in mice.

Our replicate of a study by Takabayashi et al. (1981) Effects of pulse-wave ultrasonic irradiation on mouse embryo. Cho-Onpa Igaku (Supersonic Medicine) 8, 286-288 failed to show any effects of exposure in utero of mice to spatial average, temporal maximum intensities of 60 W/cm2. Fetuses were exposed at 8 days post fertilization and assessed at 18 days for fetal weight, resorptions, premature deaths, and malformations. Carrier frequency in the pulse was 2 MHz. Pulse lengths of 10 microseconds and pulse repetition frequencies of 1000 and 200 Hz yielded spatial average, temporal average intensities of 0.6 and 0.1 W/cm2. Total exposure time was 5 min. Our results provide no basis to conclude that conditions relevant to human fetal monitoring will cause developmental, externally visible anomalies in mice exposed as 8-day fetuses.

Animals↗
PubMed1984

A test for the effects of low-temporal-average-intensity pulsed ultrasound on the rat fetus.

In 1978, Pizzarello and co-workers reported that exposure of rat fetuses to diagnostic levels of ultrasound caused marked reduction in fetal weight. Replicates of these experiments have been conducted and, in addition, exposures at 10 times the peak and average intensity were used. No effect on fetal weight, numbers of living fetuses or resorptions could be attributed to ultrasound at either exposure level.

Animals↗
PubMed1983

Dielectric characterization of forespores isolated from Bacillus megaterium ATCC 19213.

Isolated stage III forespores of Bacillus megaterium ATCC 19213 in aqueous suspensions were nearly as dehydrated as mature spores, as indicated by low dextran-impermeable volumes of ca. 3.0 ml per g (dry weight) of cells compared with values of ca. 2.6 for mature spores and 7.3 for vegetative cells. The forespores lacked dipicolinate, had only minimal levels of calcium, magnesium, manganese, potassium, and sodium, and were more heat sensitive than vegetative cells. The effective homogeneous conductivities and dielectric constants measured over a frequency range of 1 to 200 MHz indicated that the inherent conductivities of the forespores were unusually low, in keeping with their low mineral contents, but that the forespores could be invaded by environmental ions which could penetrate dielectrically effective membranes. Overall, our findings support the view that the dehydration of a forespore during stage III of sporogenesis may be the result of ion movements out of the forespore into the sporangium.

Bacillus megaterium↗
PubMed1982

Effects of ultrasound on Drosophila--IV. Pulsed exposures of eggs.

Drosophila larvae are damaged by exposures to low temporal average intensity pulsed ultrasound with peak intensities of 10-20W/cm2 (2 MHz). Eggs of the same organism are affected by exposures to 3W/cm2 c.w. ultrasound. This experiment shows that eggs become sensitive to high peak intensity (50-100 W/cm2) pulsed ultrasound only shortly before hatching. At this age the larvae have formed and have taken air into the respiratory system. This observation supports the postulate that the sites of action of the ultrasound are the small stabilized gas bodies within the organisms.

Animals↗
PubMed1980

60 Hz electric field parameters associated with the perturbation of a eukaryotic cell system.

Roots of Pisum sativum were exposed for seven days to 60 Hz electric fields ranging from 70--430 V/m in an aqueous medium whose conductivity was approximately 0.07 mho/m. (Corresponding current densities in the exposure medium associated with these field strengths ranged from 0.5--3.0 mA/cm2). Control and exposed roots were grown concomitantly in the same tank whose growth medium was continuously circulated. Temperature in the exposure medium was held at a constant 19 degrees C. All experiments were conducted "double blind." Root growth rates were determined daily. No perturbations in root growth were observed with electric fields of 150 V/m; there was a slight effect at 360 V/m, and a pronounced decrease in growth rate occurred at 430 V/m. Root conductivities are comparable to that of the growth medium. Under conditions in which growth inhibition occurs, it is estimated that induced 60 Hz cell membrane potentials would be of the order of 3--8 mV.

Electric Conductivity↗
PubMed1980

Test for 'miniature flies' following exposure of Drosophila melanogaster larvae to diagnostic levels of ultrasound.

An attempt has been made to replicate an experiment which reported the appearance of 'miniature flies' after exposure of Drosophila melanogster larvae to the field of a pulsed diagnostic ultrasound unit. No effects were observed with 1.5 mW temporal average acoustic power, the level of the original report. However, when temporal peak powers were increased by a factor of 10, approximately one fourth of the larvae failed to survive to the imago stage. No miniature flies were seen in the entire study.

Animals↗
PubMed1979

Dielectric properties of native and decoated spores of Bacillus megaterium.

A general model for use in interpreting dielectric data obtained with bacterial endospores is developed and applied to past results for Bacillus cereus spores and new results for Bacillus megaterium spores. The latter were also subjected to a decoating treatment to yield dormant cells with damaged outer membranes that could be germinated with lysozyme. For both spore types, core ions appeared to be completely immobilized, and decoating of B. megaterium spores did not affect this extreme state of electrostasis in the core. The cortex of B. megaterium appeared to contain a high level of mobile ions, in the cortex of B. cereus. The outer membrane-coat complex of B. megaterium acted dielectrically as an insulating layer around the cortex, so that native dormant spores showed a Maxwell-Wagner dispersion over the frequency range from about 1 to 20 MHz. The decoating treatment resulted in a shift in the dispersion to frequencies below the range of observation. Increases in cell conductivity in response to increases in environmental ionic strength indicated that the coats. of B. megaterium could be penetrated by environmental ions and that they had an inherent fixed charge concentration of about 10 to 20 milliequivalents per liter. In contrast, the dispersion for B. cereus spores was very sensitive to changes in environmental ion concentration, and it appeared that some 40% of the spore volume could be penetrated by environmental ions and that these ions traversed a dielectrically effective layer, either the exosporium or the outer membrane. It appears that dormancy is associated with extreme electrostasis of core ions but not necessarily of ions in enveloping structures and that the coat-outer membrane complex is dielectrically effective but not required for maintenance of extreme electrostasis in the core.

Bacillus cereus↗
PubMedDate not supplied

Transplant immunity in hamsters treated with ultrasound.

Hamsters with subcutaneous fibrosarcomas were treated by excision and by exposure to 5-MHz ultrasound for six minutes at an intensity of 3 W/sq cm. Rates for successful elimination of the tumors were between 80% and 90% and were not significantly different for the two methods of treatment. After 30 days, the animals were challenged with the same tumor cells. Animals successfully treated with ultrasound or excision required at least 10 times as many cells to produce a tumor as controls, indicating that eradication of the tumor by ultrasound induced a level of transplant immunity at least as good as that resulting from surgical excision.

Animals↗
PubMedDate not supplied

Ultrasonic gas-body activation in Drosophila.

The role of gas bodies in the interaction of Drosophila eggs and larvae with ultrasonic fields has been studied (1) by direct microscopic examination, (2) by observation of gas body activation during sonation with a special microscope, (3) by direct measurement of the volume fraction of gas in eggs and (4) through the absorption of ultrasound. All approaches provide support for the postulate that these organisms contain a rich distribution of gas bodies which play a dominant role in the acoustic properties of eggs and are the most probable site of action for ultrasonic biological effects on these organisms.

Absorption↗