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Biomedical subjects

A Faulkner

Publications and source records attributed to A Faulkner.

At least 91 records · Page 5Linked to original sources
PubMed1990

Residual frequency selectivity in the profoundly hearing-impaired listener.

The extent to which auditory frequency analysis is retained in profoundly hearing-impaired listeners has major implications for hearing aid design. We have measured simplified psychoacoustic tuning curves in nine such listeners, using sinusoidal probes at 125 and 250 Hz, and 80-Hz wide narrow-band noise maskers. Two listeners showed PTCs at 125 and 250 Hz whose shapes were independent of probe frequency and parallel to their absolute thresholds, indicating the complete absence of frequency selectivity. Seven listeners showed evidence of frequency selectivity at 125 or 250 Hz or at both frequencies; at 250 Hz, frequency selectivity was evident in the six listeners whose 250-Hz hearing level was 95 dB or less, but not in the listeners with 250 Hz hearing levels above 95 dB. Where conventional 'v'-shaped PTCs were observed, estimated 3-dB auditory filter bandwidths were two to three times larger than those typically found in normal listeners. Notched-noise masking results at 250 Hz from the least hearing-impaired listener gave an estimated 3-dB bandwidth in reasonable agreement with that from the same listener's PTC data. Listeners who retain some frequency selectivity are able to make some use of first formant information in vowel identification, and preliminary results from one patient showed the ability to distinguish a variety of noise spectra. Both of these abilities could be of potential importance as a basis for the recoding of speech spectral patterning through stimulation matched to the listener's residual frequency selectivity.

Auditory Threshold↗
PubMed1990

The effects of two different speech-coding strategies on voice fundamental frequency control in deafened adults.

Control of voice fundamental frequency (Fx) during reading of a standard passage was assessed for four profoundly deafened adults receiving auditory feedback in one of two conditions: (i) with an extended low-frequency response amplifying aid; (ii) with the SiVo aid, which provided only Fx information. A third condition, where the subjects were unaided, was also included. For each feedback condition, quantitative analyses of laryngograph recordings were used to provide measures of Fx mode, 90% Fx range and the regularity of vocal fold vibration. In baseline unaided recordings, three subjects (S1, S2 and S4) showed some aspects of Fx control outside the normal range, while the other (S3) had appropriate Fx control. In the three subjects with impaired control, simplified Fx feedback led to better control than feedback from amplified speech. In two of these subjects, these differences were statistically significant. S3, who showed unimpaired Fx control, did not show any changes in Fx control under the different feedback conditions. Although the patterns of data were different in the individual subjects, simplified Fx feedback led to either improved or unimpaired control of Fx relative to speech feedback or to not feedback. These findings have important implications for speech-processing strategies implemented in hearing aids and cochlear implants, where the effects of different speech-coding strategies on production have been largely ignored.

Adult↗
PubMed1990

The psychoacoustics of profound hearing impairment.

A group of profoundly hearing-impaired adults is being studied in order to determine their residual auditory capabilities. Most tests use acoustic contrasts that have relevance for the perception of speech, so that the results obtained may be used to guide the development of appropriate hearing aids. All the listeners are postlingually deafened, with losses greater than 95 dB HL at and above 500 Hz, and least loss at low frequencies. Trends in detection thresholds, discomfort levels, dynamic ranges, intensity discrimination (both static and dynamic), frequency selectivity, spectral shape discrimination, gap detection, tone/noise discrimination, frequency discrimination and phase sensitivity are reported and discussed. Generally speaking, temporal resolving power seems to be more resistant to degradation than mechanisms of frequency selectivity. Furthermore, at least some of the differences in performance between normal and profoundly-impaired listeners may be attributable to the loss of frequency selectivity. Implications are drawn for hearing aid fitting and design, and comparisons made to the electro-auditory abilities of users of single-channel cochlear implants.

Adult↗
PubMed1990

Psychoacoustic aspects of speech pattern coding for the deaf.

The SiVo aid, which provides a sinusoidal signal indicating voice fundamental frequency and voicing information, was compared as an aid to lipreading to a conventional hearing aid having extended low-frequency output. Speech perceptual measures of consonant confusions in lipreading and the identification of a simple intonation contrast were collected from a group of 8 profoundly deaf adults. Audiometric and psychoacoustic measures were also collected. In the intonation task, 6 of the 7 patients tested performed better with the SiVo aid and the seventh scored perfectly with both aids. Four patients (out of 8) preferred to use the SiVo aid rather than the conventional aid, and 2 of these showed a significant advantage with the SiVo aid in the aided lipreading of consonants. The remaining 4 patients preferred the conventional aid, although none of these patients showed a significant advantage with the conventional aid in the lipreading of consonants. The 4 patients who preferred the SiVo aid over the conventional aid had very profound hearing loss and minimal dynamic range at 500 Hz and above, and those receiving the greatest benefit showed no measurable frequency selectivity. In the 2 patients who preferred the SiVo aid, yet showed no significant advantage for the SiVo aid in consonant lipreading, consonant confusions were also measured for aided lipreading, using a prototype aid providing both voice fundamental frequency and voiceless excitation patterns. Both patients showed additional and significant benefit from inclusion of the voiceless pattern element.

Audiometry, Pure-Tone↗
PubMed1989

Changes in the concentration of metabolites in milk from cows fed on diets supplemented with soyabean oil or fatty acids.

Cows were fed on diets supplemented with soyabean oil or soyabean fatty acids which in some cases were protected from rumen hydrogenation. The fat-containing diets reduced the output of short- and medium-chain fatty acids in milk. Associated with this fall in short- and medium-chain fatty acids was a decrease in the concentration of 2-oxoglutarate and an increase in that of isocitrate and citrate. Protection of polyunsaturated fat from rumen hydrogenation had no significant effect. Milk yields were unaffected by diet, but the variation in milk yield among cows correlated positively with the concentration of glucose in milk.

Analysis of Variance↗
PubMed1988

The effects of concanavalin A on milk secretion and mammary metabolism in the goat.

The effects of concanavalin A on the rate of milk secretion and the concentration of metabolites in milk were studied following intramammary injection of the lectin via the teat canal into one mammary gland of lactating goats. Concanavalin A decreased milk secretion from the treated gland, reduced the concentrations of phosphoenolpyruvate, nucleoside diphosphate and 2-oxoglutarate in milk and increased the concentrations of glucose, galactose, glycerol, L-lactate, pyruvate, isocitrate and citrate. The changes in the concentrations of the metabolites in milk are discussed in relation to biochemical changes occurring in the mammary gland during the suppression of milk secretion. It is suggested that, when lactose synthesis and secretion is decreased, substantial metabolism of glucose via glycolysis occurs.

Animals↗
PubMed1988

Fatty acid metabolism of the perfused caudate lobe from livers of fed and fasted non-pregnant and fasted late pregnant ewes.

1. Fatty acid metabolism has been compared in perfused liver lobes from fed and fasted non-pregnant sheep and fasted pregnant sheep to provide further information on the control of ketogenesis in this species. 2. Ketogenesis from exogenous palmitate was greatest in lobes from fasted pregnant sheep and least in lobes from fed non-pregnant sheep, whereas rates of ketogenesis from exogenous octanoate (0.4 mM) were similar in lobes from sheep in all three states. 3. High rates of ketogenesis from endogenous fatty acids occurred in perfused lobes from fasted pregnant sheep, apparently owing to enhanced lipolysis. 4. Activities of glycerol-3-phosphate acyltransferase, carnitine palmitoyl transferase (CPT) and other enzymes involved in ketone production did not change with physiological state; sheep differ markedly from rats in this respect. 5. The results suggest that the primary point of control of ketogenesis within the liver of sheep is at the level of CPT; the lack of change in maximum CPT activity suggests that control by modulators of this enzyme activity is even more important in sheep than in rats.

Animals↗
PubMed1987

Effects of long-term thrice-daily milking on mammary enzyme activity, cell population and milk yield in the goat.

In two separate experiments, lactating goats were milked unilaterally thrice daily instead of twice daily for periods of 13 and 37 wk, starting at 2 to 5 wk after parturition. The other gland was milked twice daily throughout. In both experiments thrice-daily milking increased milk yield significantly. In the first experiment, after 37 wk the amounts of RNA and DNA, rate of cell proliferation and activities of several enzymes per cell were greater in the thrice-milked gland (P less than .05). In the second experiment, after 9 or 10 d of thrice-daily milking the activities of several key mammary enzymes per cell measured in biopsy samples had increased in the thrice-milked but not the twice-milked gland. After 13 wk of thrice-daily milking, the DNA content of the glands and the activity per cell of the key enzymes was the same in both glands, showing that the synthetic capacity of the gland was being used more effectively in the treated gland. These results indicate that several mechanisms contributed to the increased milk yield induced by thrice-daily milking.

Animals↗
PubMed1987

Enzymes of glucose and fatty acid metabolism of liver, kidney, skeletal muscle, adipose tissue and mammary gland of lactating and non-lactating sheep.

The effect of peak lactation on the activities of a number of enzymes of glucose and lipid metabolism of perirenal and subcutaneous adipose tissue, skeletal muscle, liver, kidney cortex and mammary parenchyma of sheep are described. Enzymes studied included hexokinase (glucose utilization), pyruvate carboxylase (gluconeogenesis), pyruvate dehydrogenase (glucose oxidation and production of acetyl CoA for fatty acid synthesis), acetyl CoA carboxylase (fatty acid synthesis) and glycerol-3-phosphate acyltransferase (fatty acid esterification). Major changes that were found include a decrease in activities of enzymes of fatty acid synthesis and esterification in adipose tissues, decreased activity of pyruvate dehydrogenase in muscle and adipose tissues and increased pyruvate carboxylase; there was no change in activities of enzyme of fatty acid esterification in liver. Activities of hexokinase, acetyl CoA carboxylase and glycerol-3-phosphate acyltransferase have been estimated per tissue; this shows the quantitative importance of limiting glucose utilization by muscle and of suppression of fatty acid synthesis in adipose tissue for efficient partitioning of nutrients for milk production.

Adipose Tissue↗
PubMed1987

Kinetics of chylomicron remnant clearance in normal and in hyperlipoproteinemic subjects.

The kinetics of chylomicron metabolism have been studied by measuring retinyl palmitate in chylomicrons and their remnants for 10-12 hr following oral administration of vitamin A and Lipomul in three groups of adult male subjects: A) normal plasma triglyceride levels (n = 7); B) endogenous hypertriglyceridemia (n = 12); C) apolipoprotein E (apoE) phenotype E2/2, with Type 3 hyperlipoproteinemia (n = 4) or normal plasma lipids (n = 1). A multicompartmental model was developed using SAAM 27 to characterize the appearance, intravascular metabolism, and clearance from the plasma of retinyl palmitate-labeled dietary lipoproteins. The half-times for retinyl palmitate clearance from the chylomicron remnant fraction (T1/2 REMNANT) were 14.1 +/- 9.7 min in Group A; they were prolonged in Group B (50.7 +/- 20.8 min) and were extremely prolonged for Type 3 subjects in Group C (611.9 +/- 419.9 min). One subject with the apoE 2/2 phenotype and normal plasma triglycerides had a T1/2 REMNANT of 66.8 min. T1/2 REMNANT was highly correlated with fasting plasma triglycerides in Group A and B (r = 0.77, slope = 0.15), and in Group C (r = 0.97, slope = 0.85). These results support the interpretation that delayed chylomicron remnant clearance in subjects with endogenous hypertriglyceridemia may be largely secondary to overproduction of VLDL particles, whose remnants compete with chylomicron remnants for removal by the liver via apoE receptor-mediated endocytosis. The subjects with apoE 2/2 have an additional defect in the removal of chylomicron remnants presumably due to the structural abnormality in their apoE.

Adult↗