Philip E. Hamrick

Ion Transport in Guinea Pig Cochlea:I. Potassium and Sodium Transport

The scala vestibuli and/or tympani in anesthetized guinea pigs was perfused with artificial perilymph containing 42K and 22Na for periods ranging from 5 to 60 minutes. Sound-evoked responses were recorded during the perfusion. The activities of 42K and 22Na in perilymph and endolymph were determined with a germanium detector in conjunction with a multichannel analyser. The perfusion of scala vestibuli and/or tympani did not result in appreciable changes in electrical responses. The introduction of 42K and 22Na into the scala tympani resulted in the rapid appearance of these radioisotopes in perilymph of the scala vestibuli. The activities of 42K and 22Na in perilymph of the scala tympani remained low with perfusion of scala vestibuli. This is in agreement with our Findings that the clearance of these radioisotopes was faster in scala tympani than in scala vestibuli. Our results further indicate that the endolymph took up 42K and extruded 22Na against the concentration gradients. The transport of 42K and 2...

Effects of exposure to noise on ion movement in guinea pig cochlea

Healthy guinea pigs were exposed to broad band noise at levels between 95 and 115 dBA for 7 days. A significant decrease of the sound-induced cochlear responses, together with a substantial increase of the endocochlear potential, was observed in guinea pigs exposed to noise at 105 or 115 dBA. Microsamples of the endolymph obtained from these guinea pigs showed a significant increase of K+ and Cl- concentrations and a decrease of Na+ concentration, when compared with those from control animals. The K+, Na+ and Cl- concentrations in the perilymph were not markedly affected by noise exposure. When the perilymphatic space was perfused with artificial perilymph containing 43K, 22Na or 36 Cl, the uptake of radiotracers into the endolymph showed a single exponential function of the perfusion time. When compared with rate constants in normal animals, the value of rate constant for K+ was significantly decreased in animals exposed to noise. These results indicate that ionic permeability changes of the endolymph-perilymph barrier are a significant factor in the physiological mechanisms underlying noise-induced hearing loss.

Ion Transport in the Cochlea of Guinea Pig:II. Chloride Transport

The -Cl transport of endolymph--perilymph barrier in guinea pigs was studied by perfusing the perilymphatic space with artificial perilymph containing 36Cl and measuring the uptake of 36Cl in the endolymph. In normal animals no marked difference in -Cl concentration was found between the endodlymph and perilymph. The data showed that the uptake of 36Cl in the endodlymph could be represented by a simple exponential function of the perfusion time, the rate constant being 0.01 min-1. The concentration of 36Cl in the endolymph was greater with perfusion of the scala vestibuli than with perfusion of the scala tympani, indicating the Reissners membrane is more permeable to -Cl than the rest of the endolymph-perilymph barrier. Anoxia and local application of ouabain decreased the -Cl concentration and 36Cl uptake in the endolymph. Our results imply that the endocochlear potential is the principal driving force for unidirectional flux of -Cl from perilymph to endolymph.

Laser‐Induced Acoustic Transients in the Mammalian Eye

Acoustic transients resulting from the absorption of normal mode and Q‐switched laser pulses in the mammalian eye have been implicated in damage to retinal tissue. A theoretical analysis indicated that acoustic transients with durations of the same order as the laser pulse (e.g., 100 msec for a Q‐switched pulse) and amplitudes of greater than 100 atm could be produced in model systems that simulate the retina. Piezoelectric transducers and a schlieren optical system were used to verify experimentally the theoretical predictions. By the use of these devices, studies were made of the production of laser‐induced acoustic transients in the rabbit eye. An 18‐mJ Q‐switched ruby‐laser pulse produced acoustic transients with amplitudes of 1000 atm in the immediate vicinity of the site of absorption, a 750‐μ‐diam spot on the retina. Normal‐mode laser pulses of the same energy but with durations of 0.5 msec produced a train of pulses with amplitudes 500–1000 times less than the Q‐switched pulse. The biological sign...

Water permeability of the endolymph-perilymph barrier in the guinea pig cochlea

The diffusional water permeability of the endolymph-perilymph barrier was determined in guinea pigs by perfusing the perilymphatic space with tritiated water and measuring the uptake of tritiated water into the endolymph. Assuming that the volume flow across the endolymph-perilymph barrier is negligible for short periods of perfusion, the water permeability of the barrier is approximately 130 times greater than its permeability to K+ in normal guinea pigs.

SOME EFFECTS OF EXPOSURE OF THE JAPANESE QUAIL EMBRYO TO 2.45‐GHz MICROWAVE RADIATION

Exposure of quail eggs 4 hr per day during the first 5 incubation days at 2450 MHz and in an exposure field of 30 mW/cm-2 and at an absorbed power of 14 mW/g does not cause any great change in body weight, observed gross malformations, rbc, wbc, hematocrit, hemoglobin, or differential wbc percentages. If small differences exist in these parameters due to microwave exposure, they are obscured by the large variability between individual quail. This variability is believed to partially result from changing blood values in the developing young quail, and the 2-day spread in ages at the time of sacrifice could account for some of the variability. The overall hatch percentages for the exposed and control eggs were approximately equal. A slight significant decrease (11%) in hemoglobin was noted in the birds irradiated on Day 2. Additional verification, however, is needed, because the observed change is less than the normal range of values observed in young quail. These data do suggest, however, that exposure of developing Japanese quail embryo to microwave radiation of the frequency and power density level used in this study does not preclude normal systemic development, hematologic differentiation, or the general hardiness of the hatched quail.

Exposure of Japanese quail embryos to 2.45-GHz microwave radiation during development.

Japanese quail embryos were exposed during the first 12 days of development to 2.45 GHz microwave radiation at an incident power density of 5 mW/cm/sup 2/ and specific absorption rate of 4.03 mW/g. No gross deformities were observed in the exposed quail when examined and sacrificed at 24 to 36 hr after hatch. No significant changes in the total body weight or weights of the heart, liver, gizzard, adrenals, and pancreas were found in the treated birds. Hematological parameters were also measured in the study. The results showed a statistically significant increase in hemoglobin and statistically significant decrease in monocytes in birds treated with microwave radiation. No statistically significant changes in hematocrits, red blood cells, total white blood cells, lymphocytes, heterophils, basophils, or eosinophils were detected.

Exposure of the Japanese Quail Embryo to 2.45 GHz Microwave Radiation During the Second Day of Development

ABSTRACTThe Japanese quail, (Coturnix coturnix japonica), embryo was exposed to 2.45 GHz continuous wave microwave radiation through the intact shell. The eggs were exposed continuously for 24 hours beginning 24 hours after the start of incubation at an exposure intensity of 30 mW/cm2. The quail were examined after hatching for gross deformities, changes in organ weight and hematological changes. No highly significant effects due to microwave radiation were detected.

Humoral immunity of Japanese quail subjected to microwave radiation during embryogeny.

Fertile Japanese quail eggs were exposed to continuous wave microwave radiation at an intensity of 5 mW/cm2 (50 W/m2) and a frequency of 2450 MHz. The absorbed power density was determined to be 4.03 W/kg. The eggs were exposed throughout the first 12 days of the normal incubation period of 17.5 days. Non-exposed control eggs were incubated in a chamber identical to the exposure chamber. After hatching, exposed and control quail were reared in the conventional laboratory manner. Weekly body weight measurements were made to compare the growth patterns of exposed and control quail. The weights of the exposed male at the ages of 4 and 5 weeks were 12 and I % , respectively, less than the control males. These differences approached statistical significance ( P ~ 0 . 0 5 ) . At 5 weeks of age the quail were challenged with sheep red blood cells (SRBC) and the levels of the anti-SRBC antibodies were determined. The levels of specific anti-SRBC antibodies, determined 4 days after antigen challenges, were of the same magnitude for both the exposed and control quail. Following this assessment of humoral immunity, the quail were sacrificed and the bursa of Fabricius and spleen were removed and a comparison was made of exposed and control birds. The weights of the bursa of Fabricius and spleen were not altered significantly by the microwave exposure. Research Triangle Park, NC27709 PAUL THAXTON and CARMEN R. PARKHURST

Breakage of Tobacco Mosaic Virus by Acoustic Transients: A Hydrodynamical Model

Tobacco Mosaic Virus (TMV) particles have been exposed to single pulse acoustic transients of 10−7 sec duration produced by the rapid thermal expansion following the absorption of an intense pulse of light from a Q‐switched ruby laser in an optically dense media. A hydrodynamical model is proposed, which relates the observed breakage at the center of the TMV particles, as seen in electron micrographs of exposed particles, to the structure of the TMV particles and to the amplitude and form of the acoustic transient. A velocity gradient of 4 × 107 per sec, which produces a force at the center of the TMV particle of the order of the force necessary to break a carbon‐carbon bond, has been found to be sufficient to break the TMV particle.