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Biomedical subjects

J C DeFries

Publications and source records attributed to J C DeFries.

At least 109 records · Page 6Linked to original sources
PubMed1976

Developmental patterns of seizure susceptibility in inbred strains of mice.

Samples of mice from each of 6 inbred strains were tested for audiogenic and electroconvulsive seizures at 5 ages (14, 21, 28, 35, and 42 days). A moderately large within-strain correlation (.67) was found, indicating that developmental patterns of susceptibility to audiogenic and electroconvulsive seizures are similar within each strain. The finding of an even larger between-strain correlation (.91) indicated that strains which are highly susceptible to audiogenic seizures are also likely to be highly susceptible to electroconvulsive seizures. In a 2nd experiment, whole brain norepinephrine and serotonin were assayed in each of 5 inbred strains at 21 and 42 days of age. Results were consistent with the hypothesis that levels of these amines are inversely related to seizure susceptibility. Mice from strains which were susceptible to seizures at 21 days of age had significantly lower levels of norepinephrine and serotonin in brain than did 42-day-old, seizure-resistant animals.

Acoustic Stimulation↗
PubMed1975

Open-field behavior in mice: A diallel analysis of selected lines.

The open-field behavior of 719 mice resulting from a diallel cross among the six lines of the DeFries selection experiment was assessed. Results of several analyses employing different models and procedures in open-field activity and defecation among these lines have predominantly additive effects. Estimates of heritability obtained from these analyses were considerably higher than previous estimates based on familial resemblance or the realized response to selection; thus estimation of heritability from diallel analyses is clearly unwarranted when selected lines are employed and the character of interest has been either directly or indirectly subjected to artificial selection.

Alleles↗
PubMed1974

Near identity of cognitive structure in two ethnic groups.

As part of a large-scale family study in Hawaii, Americans of either Japanese or European ancestry were administered a battery of 15 cognitive tests. Principal component analyses (varimax rotations) yielded the same four major cognitive factors for each of the two ethnic groups, and these factors are defined by strikingly similar factor loadings.

Asian People↗
PubMed1966

Open-field behavior in mice: evidence for a major gene effect mediated by the visual system.

In segregating F(2), F(3), and F(4) generations, albino mice had lower activity and higher defecation scores than pigmented animals when tested in a brightly lighted open field. These differences persisted when members of an F(5) generation were tested under white light, but largely disappeared under red light. Thus it was concluded that there is a major gene effect on the quantitative traits of open-field activity and defecation which is mediated by the visual system and that albino mice are more photophobic than pigmented mice under conditions of bright illumination.

Animals↗
PubMedDate not supplied

Are RAN- and phonological awareness-deficits additive in children with reading disabilities?

The double-deficit hypothesis (Wolf, M. and Bowers, P.G. (1999) The double-deficit hypothesis for the developmental dyslexias. Journal of Educational Psychology, 91, 415-438) proposes that deficits in phonological processing and rapid automatized naming (RAN) are separable sources of reading dysfunction. Further, the double-deficit hypothesis predicts that the presence of deficits in both phonological processing and RAN have an additive negative influence on reading performance above and beyond that of a single deficit. The purpose of this study was to examine the additive nature of phonological awareness (PA)- and RAN-deficits on written language skill in children with reading disabilities (RD). Concurrent relationships between PA, RAN, and written language skills were examined in 476 children with RD, ranging in age from 8 to 18 years of age. Hierarchical regression analysis revealed that PA and RAN skill have an additive effect on a majority of the reading and spelling measures. When participants were classified into three deficit subtypes based on the double-deficit model (i.e. phonological-, rate-, and double-deficit), comparisons across the subtypes confirmed that individuals with double-deficits performed below the single-deficit groups on both subtyping variables (RAN and PA) and all measures of written language. When the double- and single-deficit groups were matched on the subtyping variable (i.e. double- and rate-deficit groups matched on RAN and double- and phonological-deficit groups matched on PA) differences between the double- and rate-deficit groups remained in non-word reading, whereas differences between the double- and phonological-deficit groups remained in timed word recognition and reading comprehension. These results support an additive model in which RAN-deficits primarily affect tasks that require speeded/fluent response, and PA-deficits primarily affect tasks that emphasize phonological processing skill. Results are also presented that illustrate several statistical problems associated with the formation of deficit groups by dichotomizing the RAN and PA variables.

Awareness↗