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J Nelles

Publications and source records attributed to J Nelles.

7 recordsLinked to original sources
PubMed1996

Development of auditory information integration abilities.

The ability of normal-hearing children (aged 4 through 7 years) and adults to integrate information was measured in an auditory sample discrimination task. On each trial a pair of tonal sequences was played whose component frequencies were randomly drawn from two equal-variance, Gaussian distributions with different means. The listeners task was to identify the sequence drawn from the distribution with the higher mean frequency. Performance was first evaluated as a function of the number of components in each sequence. Results showed that discrimination accuracy improved with increasing age until age 7, at which time performance was adult-like. The 7-year-olds and the adults discriminated the sequences with increasing accuracy as the sequence length was increased, but the 4-to 6-year-old listeners, as a group, did not. Data were fitted with a model with two free parameters, one representing resolution of the components and presumed to reflect peripheral processing, and another representing central noise added to the decision process after the component information is combined [R. Lutfi, J. Acoust. Soc. Am. 86, 934-944 (1989)]. On average, both parameters showed gradual changes as age increased, with adult-like values by 7 years of age. Individual data however suggest that the changes in central noise with age may be less gradual than the changes in peripheral resolution. In a second condition, increases in component duration produced improved performance for the 7-year-olds and the adults, while that of the younger listeners remained the same. Fitted parameters suggested improvements in component resolution for the older children, with no changes in central noise levels. In a third condition, reducing the overlap in the distributions improved performance for only a few of several younger children. This improvement was attributable to lower levels of central noise. Overall, these results suggest that with increasing age children are better able to discriminate between sounds that are variable and have overlapping acoustic characteristics. This age-related improvement may be attributed both to improvements in the ability to resolve the components and to reductions in central noise.

Adult↗
PubMed1995

Divergence of ethanol and acetaldehyde kinetics and of the disulfiram-alcohol reaction between subjects with and without alcoholic liver disease.

Despite standardization, marked interindividual variation in the severity of the disulfiram-alcohol reaction (DAR) has been observed. We studied the DAR in 51 consecutive alcoholics with (n = 16) and without (n = 35) significant alcoholic liver disease. Clinical signs of the DAR were much weaker in the patients with compared with those patients without liver disease. Because acetaldehyde is thought to be the main cause of the DAR, we studied ethanol and acetaldehyde kinetics in 13 patients (6 females, 7 males) with alcoholic liver disease (documented by biopsy, clinical and/or radiological findings, and by quantitative liver function) [galactose elimination capacity (GEC) 4.2 +/- SD 1.0 mg/min/kg; aminopyrine breath test (ABT) 0.14 +/- 0.10% dose x kg/mmol CO2] and 13 age- and sex-matched controls (alcoholics without significant liver disease, GEC 7.1 +/- 0.7; ABT 0.81 +/- 0.35). Clinical signs of acetaldehyde toxicity during the DAR (flush, nausea, tachycardia, and blood pressure drop) were absent in alcoholic liver disease, but clearly evident in controls. Blood ethanol kinetics were similar in both groups, Cmax and area under the concentration-time curve (AUC) being 6.27 +/- 1.82 and 368.9 +/- 72.9 mmol x min/liter in alcoholic liver disease, and 6.62 +/- 1.71 and 377.6 +/- 124.5 in controls, respectively. In contrast, there was a strong (p < 0.001) difference in Cmax and AUC of acetaldehyde, respective values being 33.46 +/- 21.52 and 1463.8 +/- 762.5 mumol x min/liter in alcoholic liver disease, and 110.87 +/- 56.00 and 4162.0 +/- 2424.6 in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1988

Ethanol decreases plasma sulphydryls in man: effect of disulfiram.

Based on animal experiments, interactions of ethanol and its metabolites with sulphydryls have been implicated in the toxicity of ethanol, but acute effects of ethanol on sulphydryls have not been documented in man. Plasma free glutathione and cysteine were therefore measured following the administration of 0.2 g kg-1 ethanol to normal healthy volunteers and chronic alcoholics on disulfiram, where the effects of high concentrations of acetaldehyde can be observed. In both groups, plasma glutathione decreased shortly following ethanol, and a sustained decreased in glutathione was seen in the subjects on disulfiram. In patients on disulfiram, but not the healthy controls, plasma cysteine decreased significantly. The decrease in plasma cysteine was correlated to the rise in acetaldehyde, suggesting that cysteine, but not glutathione, forms an adduct with acetaldehyde in man. We conclude that even moderate doses of ethanol may disturb the sulphydryl homeostasis and could interfere with biologically important processes that depend on sulphydryl groups.

Acetaldehyde↗