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Biomedical subjects

R H Wilson

Publications and source records attributed to R H Wilson.

At least 127 records · Page 7Linked to original sources
PubMed1979

Factors influencing the acoustic-immittance characteristics of the acoustic reflex.

Measurements of the aural acoustic-immittance (admittance and impedance) characteristics of the middle-ear transmission system in humans during the quiescent (static) and reflexive states were made (N = 36) utilizing a signal-averaging technique. Three pure tones (750, 1000, and 2000 Hz) and broadband noise stimuli elicited the acoustic reflex in 2-dB steps at sound-pressure levels from 84-116 dB (tones) and 66-116 dB (noise) during ascending- and descending-intensity level runs. The contralateral middle-ear activity was monitored with a 220-Hz probe by digitizing the conductance and susceptance outputs of an admittance meter. A computer corrected for the ear-canal volume utilizing measurements made at ear-canal pressures of 0 and --350 daPa and then converted the conductance and susceptance values into admittance and impedance units. The results were reported in absolute and relative immittance units, including components, as a function of both stimulus sound-pressure level and intensity level above the acoustic-reflex threshold. The static immittance of the middle ear changed nonlinearly over time to lower admittance or higher impedance values. The influence of this static-immittance shift on the reflex magnitude was discussed. The largest mean reflex magnitude and the slowest rate of growth were observed with broadband noise, although eight of the 36 subjects demonstrated the largest reflex magnitude in response to one or more of the tonal stimuli. Although static-immittance values and acoustic-reflex thresholds were poorly correlated, the reflex magnitudes were proportional to static immittance. The variability of the reflex measures was similar to the variability of the static-immittance values. Finally, bi-directional changes in resistance during the reflexive state were observed and discussed.

Acoustic Impedance Tests↗
PubMed1978

Threshold and growth of the acoustic reflex.

Measurements of the threshold and growth function of the acoustic reflex in man were made utilizing a signal-averaging technique. Pure tones (250, 500, 1000, 2000, and 4000 Hz) and broadband noise served as the contralateral stimuli delivered at intensity levels from the reflex threshold to 116 dB SPL. The acoustic conductance and susceptance components of admittance, at 220 and 660 Hz, were used to measure the reflex activity. The results are reported as changes in conductance, susceptance, and admittance in cgs mmho. The acoustic reflex thresholds were similar to those reported in other studies, with the 220-Hz probe yielding thresholds that averaged 3.5 dB higher than those obtained with the 660-Hz probe. Broadband noise and 1000-Hz stimuli produced the largest reflex magnitudes, while the smallest were observed with 250- and 4000-Hz signals. The dynamic ranges of the restricted growth functions were frequency dependent for pure tones and ranged from greater than 16 dB with 250 Hz to greater than 28 dB with 1000 Hz, while that for noise was greater than 50 dB. The first derivative of the best-fit third-degree polynomial was used to describe the slope characteristics of the growth functions, in which frequency and intensity effects were found. Relationships between the acoustic reflex and tympanometry were observed and are also discussed.

Acoustic Impedance Tests↗
PubMed1978

Adaptation of the acoustic reflex.

The characteristics of acoustic reflex adaptation were studied in human subjects. Contralateral stapedial reflex measurements were made by monitoring changes in acoustic conductance and susceptance with a 220-Hz probe. The reflex activators included four tonal stimuli (500, 1000, 2000, and 4000 Hz) and broadband noise presented for 180 s at 96, 104, and 112 dB SPL. The data are presented as change in acoustic admittance and in percent of maximum admittance change. The static admittance of the ear was found to drift systematically toward lower admittance values in the absence of contralateral stimulation. All stimulus conditions demonstrated some reflex adaptation. The half-life and time of onset of adaptation were found to vary directly with intensity and inversely with frequency. The effects of stimulus parameters on the rates of reflex adaptation are discussed. A previously described exponential model of reflex adaptation provided a reasonable first approximation to the data.

Acoustic Stimulation↗
PubMed1977

Evaluation of tetracycline or penicillin and ampicillin for treatment of acute pelvic inflammatory disease.

To evaluate guidelines for outpatient treatment of acute pelvic inflammatory disease recommended by the Center for Disease Control we studied 197 afflicted women. The women were treated either with tetracycline or with procaine penicillin and ampicillin, and 92% were subsequently seen at least once to assess efficacy of clinical and microbiologic treatment. Neisseria gonorrhoeae was isolated from the lower genital tract in 68% of these women, and although they had a quicker symptomatic response than those with nongonococcal infection (P less than 0.01), the two regimens were equally effective in producing clinical cure. However, subsequent identification of a pelvic abscess was 10 times more common in women from whom N. gonorrhoeae was not isolated. Therapy for pelvic inflammatory disease must be empirical since it is impossible to distinguish clinically between gonococcal and nongonococcal infection, and our data indicate that both regimens recommended by the Center for Disease Control are effective.

Acute Disease↗
PubMed1975

Functional and structural changes in isolated rabbit liver mitochondria induced by fluorodichloromethane.

Fluorodichloromethane caused changes in substrate respiration rates and also in adenosine diphosphate (ADP)-stimulated rates of oxidation of both succinate and glutamate. Active swelling of mitochondria also occurred, but only in the presence of magnesium ion. ADP/O ratios were not significantly affected by the fluorocarbon. State IV respiration was stimulated, and the respiratory control ratio was linearly reduced with increased levels of fluorocarbon when succinate was used as substrate. Glutamate-stimulated respiration was greatly affected by the presence of the halocarbon but contrasted to the succinate responses. Low levels of fluorocarbon stimulated the state IV rate with glutamate whereas higher concentrations inhibited respiration. States III and IV respiration were completely inhibited by levels of 4.7 mg/ml of fluorodichloromethane when the nicotinamide adenine dinucleatide (NADH)-linked substrate was used. The NADH-linked substrate was more sensitive to the fluorocarbon treatment than the flavoprotein-linked substrate. The respiratory control ratio reached 1.0 at one-half the concentration required to elicit the same response with the flavoprotein-linked substrate, which suggested that NADH-dehydrogenase was inhibited. Active swelling of mitochondria occurred in the presence of magnesium and fluorocarbon, greatly exceeding controls, suggesting a loss of structural integrity and osmoregulation capacity. Increased rates of reduction of exogenously added cytochrome c also suggested changes in membrane integrity at higher fluorocarbon site of action of this compound is probably not the NADH-dehydrogenase system but the membrane system per se. Structural changes in the membrane system could account for the reported respiratory inhibition.

Adenosine Diphosphate↗
PubMed1973

Ultrastructural transformations in bean inner mitochondrial membranes.

The ultrastructure of inner membrane-matrix mitochondria isolated from bean (Phaseolus vulgaris) shoots was examined in different metabolic states. Gross ultrastructural transformations analogous to the condensed-to-orthodox configurational changes reported in mammalian mitochondria are observed on transistion from nonrespiring to respiring metabolism. With the induction of oxidative phosphorylation, the particles remain in the orthodox configurational state. The reverse orthodox-to-condensed configurational changes observed in mammalian preparations does not occur. Optically monitored absorbancy studies with bean particles show a substrate-supported P(i)-induced swelling under the same conditions that induce the condensed-to-orthodox ultrastructural transformation. The swelling is associated with the net uptake of K(+) and P(i) as well as a small P(i)-induced respiratory stimulation. When phosphorylation is initiated with these swollen particles, the optically monitored volume remains unchanged. Thus a positive correlation exists between the ultrastructural configuration and the osmotic volume changes, which supports the conclusion that configurational changes reflect internal osmotic adjustments.

Journal Article↗
PubMed1973

Respiration-independent Binding of SR to Bean Mitochondria.

Binding of Sr(2+) to bean mitochondria (Phaseolus vulgaris) shows a dissociation constant of 25 x 10(-6) and results in 40 to 50 nmoles of Sr(2+) bound per mg protein. The binding is partially inhibited by valinomycin plus K(+), 2, 4-dinitrophenol, as well as ruthenium red at a level of the 120 nmoles per mg protein. These compounds also partially inhibit active uptake of Sr(2+). Calcium and Mg(2+) also partially inhibit binding in the same magnitude as previously reported for inhibition of transport. Phosphate which is required for divalent cation transport is without effect on the binding of Sr(2+). The possible role of the observed binding sites in divalent cation transport is discussed.

Journal Article↗