Biomedical subjects

G R Price

Publications and source records attributed to G R Price.

At least 19 recordsLinked to original sources

PubMed1999

Auditory hazard from airbag noise exposure.

Airbag deployment includes very intense acoustic stimulation, yet almost no tests of auditory hazard have been done with real ears. Therefore 32 anesthetized cats, positioned at the driver and passenger locations in a pickup truck, were exposed in pairs to one airbag deployment (electrically initiated). Hearing was tested at 1, 2, 4, 8, and 16 kHz by evoked-response audiometry just before exposure, immediately after and at 1 month and 6 months. Exposure conditions included doors open, compartment closed, and closed compartment sealed with tape: seven exposures to passenger bag only and nine to driver and passenger bags. Peak pressures ranged from 167 to 173 dB with unweighted energies as high as 4000 J/m2 (or 8 hr LEQA = 95.5 dB). The immediate threshold shift averaged 60 dB at 4.0 kHz that resolved to an average permanent shift of 37 dB. By extrapolation, these data from cats may indicate that susceptible human ears risk permanent hearing loss from airbag noise.

Air Bags↗

PubMed1995

The nature of selection. (Written circa 1971, published posthumously)

A model that unifies all types of selection (chemical, sociological, genetical, and every other kind of selection) may open the way to develop a general "Mathematical Theory of Selection" analogous to communication theory. [Note added by S. A. Frank: This previously unpublished manuscript was found among Dr. Price's papers when he died in 1975. In this paper Dr. Price did not provide a complete, general theory of selection. Rather, he argued why such a theory is needed and what some of its properties might be. The accompanying article provides commentary on this paper and describes Dr. Price's significant contributions to evolutionary genetics (S. A. Frank, 1995, J. theor. Biol. 175, 373-388).]

Animals↗

PubMed1991

Compartmental analysis of diprenorphine binding to opiate receptors in the rat in vivo and its comparison with equilibrium data in vitro.

The regional binding of the opiate receptor ligand diprenorphine has been examined in rat brain both in vivo and in vitro. The time course of total label in specific brain regions was followed up to 2 h after intravenous bolus injection of [3H]diprenorphine, with or without a pulse chase of unlabelled diprenorphine at 30 min. In addition, total label was measured 30 min after injection of labelled diprenorphine at nontracer concentrations over a range of specific activities. Total data sets for each region were fitted simultaneously to a compartmental model to give estimates of maximal binding capacity (Bmax), the second-order apparent association rate constant, and the first-order dissociation rate constant of the receptor-ligand complex. The model incorporated the use of a reference region with low specific binding (cerebellum). The binding of diprenorphine to rat brain homogenates was measured in vitro under equilibrium conditions at 37 degrees C, pH 7.4, in the presence and absence of naloxone, to give corresponding regional estimates of Bmax and the half-saturation constant Kd. The results showed a close correlation between in vitro and in vivo regional estimates of Bmax over a wide range. There were no significant interregional differences either in Kd in vitro or in the Kd derived from the in vivo analysis, although in vitro and in vivo estimates differed by an order of magnitude. This work was carried out as part of a validation study with a view to the application of the compartmental model to data obtained in vivo in humans using positron emission tomography, when successive studies over a range of specific activities are not feasible.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Insights into hazard from intense impulses from a mathematical model of the ear.

In order to provide insight into the mechanisms that operate in the ear when it is exposed to intense sounds, time and frequency domain mathematical models of the ear including significant nonlinearities in the middle ear were developed to trace energy flow from the free field to the inner ear and ultimately allow the calculation of basilar membrane displacement and a consequent hazard function. These models match the ear's behavior at low intensities and also reproduce many of the features of the data on hearing hazard from intense impulses. They provide critical insights into the loss mechanisms, suggest new strategies for protecting hearing as well as reducing hazard at the source and could also serve as a framework for a new, accurate, theoretically based method for rating hazard from intense sounds.

Animals↗

PubMed1991

A new approach to a damage risk criterion for weapons impulses.

Existing damage-risk criteria for weapons impulses suffer from their lack of a theoretical basis, thereby limiting their generalizability and utility. Furthermore, a number of studies now indicate that they may be inaccurate for impulses with energy in the low frequency region (Dancer & al., 1985; Patterson & al., 1985; Price & al., 1989). We have approached the problem by modeling the ear mathematically as a means of gaining insight into the loss processes. In the model, the external and middle ears are linear at lower intensities; however, the stapes displacement is limited to 20 microns, as would be expected on anatomical/physical grounds. Susceptibility, in the inner ear, is modeled as mechanical stress, a function of basilar membrane displacement and number of flex cycles. The model, which is executable on a PC-based computer, reproduces the data on the ear that can be measured at lower intensities. It also ranks the known hazard from impulses in the correct order, explains the finding of loss in mid-cochlea regardless of spectral location of the weapons impulse, and suggests that the greatest hazard comes from that portion of the acoustic wave in which pressures cross through ambient and at a rate consistent with energy in the mid-range. Because the model is theoretically based, it has the potential for use as the basis for a damage risk criterion for impulse noise as well as for a design criterion for weapons.

Adult↗

PubMed1991

Firing recoilless weapons from enclosures.

THE PROBLEM: Recoilless weapons commonly release a great deal of energy rearward in the immediate vicinity of the crew. If such weapons are fired from within structures, there is concern that in addition to the acoustic hazard to the ear or other organs, there might be hazard associated with flying debris or even structural collapse. STUDIES: Two studies were conducted to evaluate such hazards by remotely firing a total of 24 rounds from the 90 mm recoilless rifle, LAW, TOW, and DRAGON weapons systems from within enclosures (Price, 1978; Shank & Garinther, 1975). The structures, selected from available buildings, were made of various materials (reinforced concrete, masonry, sandbags, and wood) and ranged in volume from 14m3 to 161 m3 with venting areas from 2.9 m2 to 11 m2. Data included pressure histories, motion pictures of the structures and small objects placed in the room, and physiological data from 32 goats (tissue/organ system damage) and 8 cats (hearing loss measures). RESULTS AND CONCLUSIONS: At the firer's locations, peak pressures ranged from 178 to 189 dB and B-durations ranged from 28 to 376 msec. Although the firings commonly produced some structural damage, none of the firings caused structural collapse or induced tissue damage to nonauditory organs. Ear drum rupture did occur in 5 goats and the cat ears exposed with no hearing protection did show permanent hearing losses. Of the cat ears exposed with hearing protection (EAR plugs), only one showed a permanent loss.

Female↗

PubMed1989

Hazard from weapons impulses: histological and electrophysiological evidence.

Current methods of rating the hazard of weapons impulses for the ear have recently been challenged by electrophysiological data from experiments with animal ears which indicate that the hazard from low-frequency impulses is much lower than the hazard from higher frequency impulses (Dancer et al., 1981; Price, 1986b). To supplement these data, histological data are reported here for 51 cats that were exposed on one occasion to either rifle or howitzer impulses at peak pressures from 145 to 155 dB or 153 to 166 dB, respectively. Histological procedures (scanning electron and light microscopy) were carried out over 2 months after the exposure and after electrophysiological measures had been made. For both types of impulse the losses tended to be in the middle of the cochlea in focused lesions, even though the spectral peaks of the acoustic stimuli had been at about 80 Hz (howitzer) and 1000 Hz (rifle). Outer hair cells were more susceptible than the inner hair cells and interindividual differences in effects were large. Furthermore, the two impulse sources were equally hazardous when the peak pressure of the rifle impulse was lower than the peak pressure of the howitzer impulse by about 9 dB. In terms of A-weighted energy, the exposures were equally hazardous when the rifle exposure contained about 35 times less energy than the howitzer exposure. The histological data are thus consistent with the electrophysiological data, which indicate that present standards for impulse noise exposure may overrate the hazard of low-frequency impulses relative to impulses in the midrange.

Animals↗

PubMed1989

Hazard from an intense midrange impulse.

It has been hypothesized that the ear would become increasingly susceptible to impulses (gunfire) as the spectral peak of the impulse approached the frequency region where the ear was tuned best (about 4 kHz for the cat ear) [G. R. Price, J. Acoust. Soc. Am. Suppl. 1 62, S95 (1977)]. This prediction was counter to the predictions of the world's damage-risk criteria for impulse noise. It has been supported by experiments using exposures to 100-Hz and 800- to 1000-Hz impulses; but no test had been run at the point of predicted maximum susceptibility. In the present experiment, three groups of cats were exposed to 50 impulses produced by a primer explosion (spectral peak at 4 kHz) at peak levels of 135, 140, or 145 dB. Auditory thresholds were electrophysiologically measured from the vertex to 2-, 4-, 8-, and 16-kHz tone pips and losses were determined 30 min after exposure and more than 2 months post-exposure. Losses were greatest at 4 kHz, began to develop at 134-dB peak pressure, and the immediate losses grew at a rate of about 7 dB for every dB increase in peak pressure. About half of the loss measured immediately became permanent. The energy required to begin producing a permanent threshold shift was only about 0.07 J/m2, far lower than that required with continuous noises at lower sound pressures. The data were interpreted as supporting the original hypothesis of greater susceptibility in the midrange.

Acoustic Stimulation↗

PubMed1989

Toward a measure of auditory handicap in the Army.

The effect of a soldier's ability to hear on the capacity to perform a mission was calculated for a variety of militarily relevant tasks through the use of mathematical models. Changes in hearing can result from organic loss, hearing protectors, the masking effect of noises, etc. The effects were calculated for the detection of sounds of enemy personnel (speech, movement noises) or their equipment (rifle bolt, tank, generator). We also calculated the effects on the ability to control/communicate with troops verbally. The normal ear is highly effective in detecting noises of personnel or their equipment or in understanding speech, even in noise. By contrast, even modest hearing losses and/or the wearing of hearing protectors can have profound effects on military performance, for example, reducing the area that can be monitored acoustically by more than 30-fold or cutting warning times for other sounds by a factor of more than 100. Hearing protectors may have the conflicting effects of protecting hearing while producing unacceptable performance because of their attenuation.

Disability Evaluation↗

PubMed1986

Hazard from intense low-frequency acoustic impulses.

It was predicted that because the ear is spectrally tuned, it should be most affected by intense impulses with spectral peaks near the frequency where it is tuned best (3.0 kHz for the human ear) and progressively less affected by impulses at lower frequencies [G.R. Price, Scand. Audiol. Suppl. 16, 111-121 (1982)]. This prediction is counter to all the DRCs for impulse noise; therefore an adequate test is essential. In order to augment the data on hearing loss to low-spectral-frequency impulses, three groups of cats (eight, nine, and ten animals) were exposed on one occasion to 50 impulses from a 105-mm howitzer at peak SPLs of 153, 159, and 166 dB. Threshold shifts were measured electrophysiologically on the day of exposure (CTS) and following a 2-month recovery period (PTS). Maximum PTSs appeared at 4 kHz (even though the spectral peak of the impulse had been at about 100 Hz), and CTSs recovered into PTSs about half as large. Furthermore, for group data, even small CTSs tended to have a permanent component. These data raise the question as to whether or not any threshold shift persisting an hour or two after exposure to high levels should be considered tolerable. When compared with data from rifle fire exposures, the data confirmed the earlier prediction that as the spectral frequency drops, hazard declines at the rate of a little more than 3 dB/oct, contrary to the rating by existing DRCs.

Acoustics↗

PubMed1983

Relative hazard of weapons impulses.

Arguments in favor of a theoretically based damage-risk criterion (DRC) for intense noise [G.R. Price, J. Acoust. Soc. Am. 69, 171-177 (1981); 66, 456-465 (1979); J. Acoust. Soc. Am. Suppl. 1 62, S95 (1977)] are further developed here to make a crucial prediction. Based on measured spectral differences, it was predicted that rifle impulses would cause permanent threshold shifts at approximately 9 dB lower peak pressures than cannon impulses. In contrast, DRCs in use in the world predict that the cannon would be more hazardous than the rifle by 7 to 10 dB. Electrophysiological measures of sensitivity were used in 38 cats (76 ears) which were exposed to 60 impulses, approximately 3 s apart, at various peak pressures, from either a rifle or a 105-mm Howitzer. Hearing changes were followed until recovery was complete (2 months). Permanent threshold shifts began at about 140 dB for rifle impulses and 150-155 dB for cannon impulses, confirming the prediction and supporting the contention that there is a spectrally dependent critical level for the ear at high intensities. Implications for present DRCs and future risk assessment schemes are discussed.

Acoustics↗

PubMed1982

Rating the hazard from intense sounds: putting theory into practice.

Basilar membrane mechanics appear to be largely responsible for noise induced temporary threshold shift (TTS). Upon noise exposure, the single fiber loses sensitivity and sharpness. The amplitude and configuration (sharpness) of the basilar membrane vibration pattern is reduced. The "best frequency" changes about half an octave. The result is threshold shift and reduced frequency discrimination. The maximal TTS is generally seen one octave above the peak frequency of the stimulus. There appears to be a critical intensity level for noise exposure. Below the critical level little or no hearing damage will develop regardless of exposure time. Beyond the critical level, extensive damage will be caused even after short exposure time. The critical level appears to be a rather absolute measure: in animals, the state of the inner hair cells may change from "no loss" to "extensive loss" upon a stimulus increase of only 3dB. Addition of acoustical energy at a frequency different from that of the original stimulus, may reduce the threshold shift induced by the original stimulus alone. Sound in one ear may also influence the susceptibility of the other. Compared with its isoenergetic impulse noise, a continuous noise generally must be given a 3dB increase (its energy must be doubled) if both stimuli shall produce similar threshold shifts. Factors like frequency distribution, level, duration number, repetition rate and time distribution/presentation pattern of exposure apparently have to be considered in future damage risk criteria. Meanwhile isoenergy, or possibly "A-weighted" isoenergy, is our best indicator for noise hazard.

Animals↗

PubMed1979

Loss of auditory sensitivity following exposure to spectrally narrow impulses.

Damage-risk criteria (DRC) for impulse noise do not presently take the spectrum of an impulse into direct account; yet it is clear that the ear is spectrally tuned. In order to establish the sensitivity of various sections of the cochlear duct to trauma from impulses, ears were exposed to 100 spectrally narrow impulses (1.0, 5.0, or 10.0 kHz) delivered in 10 min. Changes in auditory sensitivity were measured by an electrocochleographic technique in 43 cat ears and a threshold of loss established for each type of impulse. Expressed in SPL at the ear drum, the loss threshold rose at 3.2 dB/octave between 1.0 and 10.0 kHz. Expressed in stapes displacements, the loss threshold fell at 5.4 dB/octave in the same region. This curve was used to establish a tentative shape for a DRC for the human ear for impulse noise. The patterns of loss, rates of loss, lack of recovery, and loss thresholds are discussed with respect to their probable physiological basis with conclusion that mechanical displacement rather than metabolic exhaustion is the most reasonable causative factor.

Animals↗

PubMed1978

Action potentials in the cat at low sound intensities: thresholds, latencies, and rates of change.

The interpretation of whole-nerve action potentials is a topic of increasing importance in both clinical and research settings. This effort has been hampered by a lack of data on the action potential that are theoretically interpretable and systematically measured over a wide range of frequencies and at low sound intensities. Therefore, the present study was designed to measure the thresholds, latencies, and rates of change in the whole-nerve action potential in response to constant-spectral-width tone pips at eight frequencies between 0.5 and 20 kHz in the cat ear. These quantities were calculated by a linear regression technique from round-window potentials in 28 normal ears. They were found to be consistently within approximately 18 dB of previously published behavioral measures, a difference attributable to temporal integration. The interanimal variability had a standard deviation of about 5 dB and the intra-animal variability was extremely low. The growth of amplitude across frequencies, the rate of change of latency with intensity changes, and the latency at threshold all demonstrated orderly relationships which are presented. The data were all consistent with contention that the potentials were being produced by a single population of cells located at a place consistent with the frequency of the eliciting tone. The methods used provide exceedingly stable measures and should be applicable in both clinical and research settings.

Acoustic Stimulation↗

PubMed1976