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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 31 (1990), S. 492-497 
    ISSN: 1432-1920
    Keywords: Tuberous sclerosis ; Magnetic resonance imaging ; Computed tomography ; Gadolinium-DTPA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ten patients with clinical tuberous sclerosis were examined with CT and MR imaging, before and after IV contrast in order to determine the role of Gd-DTPA. Gd-DTPA enhancement occured in eleven subependymal nodules which did not enhance on CT after IV contrast. As illustrated by previous CT and pathologic observations and related to the histologic similarity of the subependymal nodules and giant-cell astrocytomas, these hyperintense nodules could represent active lesions with the potential to evolve. Four giant-cell astrocytomas were detected both with CT and Gd-DTPA-enhanced MRI; tumor conspicuity and size assessment were improved by postcontrast MRI in two cases. No cortical tuber or heterotopic cluster enhanced; T2-weighted sequences therefore remain necessary for their detection. If pre and post-Gd-DTPA T1-and T2-weighted imaging is negative, CT is clearly the most sensitive modality in the detection of the small calcified subependymal nodules.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 34 (1992), S. 179-183 
    ISSN: 1432-1920
    Keywords: Trigeminal neuromas ; Magnetic resonance imaging ; Computed tomography ; Neurofibromatosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We report four cases of trigeminal neuroma. One of the patients had von Recklinghausen's neurofibromatosis with plexiform neurofibromas of the branches of the trigeminal nerve. MRI provided more information than CT as regards the spread of tumour: extension to the mandibular and maxillary division of the trigeminal nerve was well demonstrated on sagittal and coronal sections. This examination yielded an accurate census of the intraocular plexiform neurofibromas and allowed a correct preoperative diagnosis to be obtained. With Gd-DOTA, better definition of the outline of the tumours and of cystic components was obtained. However, CT was better for demonstration of bone erosions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Behavior genetics 12 (1982), S. 467-472 
    ISSN: 1573-3297
    Keywords: bias ; heritability ; truncation ; twins ; educational achievement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Sampling twins from a truncated distribution and ignoring this truncation in the estimation procedure lowers correlation coefficients and can considerably bias estimates of the proportions of genetic and environmental variance. A greater proportion of DZ than MZ twins will be missed in sampling for any heritable trait. The implications for two published sets of educational achievement data are considered.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-3297
    Keywords: multivariate genetical analysis ; educational achievement ; twins ; covariance structure ; specific abilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Using the genetical analysis of covariance structure it is shown that the single factor model of Plomin and DeFries [(1979).Behav. Genet. 9:505–517] fails as a description of the structure of genetic covariation between the subtests of the National Merit Scholarship Qualifying Test. A genetic group factor which loads on Vocabulary, Social Studies, and English greatly improves the fit of the model. There is also a large portion of genetic variance specific to Mathematics and it is argued that the genetic variance for different abilities is far from homogeneous in its origin. The data suggest that a single dimension of mate selection or cultural inheritance accounts for a significant part of the phenotypic covariance between measures.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-3297
    Keywords: primary dysmenorrhea ; genetics ; anxiety ; depression ; neuroticism ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Over 1200 pairs of female monozygotic and dizygotic twins with regular menses reported on the amount of flow, severity of pain, and degree of limitation experienced during menstruation. Fifty-two percent of the women reported moderate or severe menstrual pain and these reports were fairly repeatable (0.62–0.80) over a 3-month interval. Heritabilities were 0.22 for flow, 0.38 for pain, and 0.36 for limitation. Covariations between menstrual symptoms and the symptoms and personality variables of state anxiety and depression and trait neuroticism were shown to be almost entirely genetic in origin. There was also gene action specifically affecting menstrual pain and also menstrual flow, but genetic variation in limitation was entirely due to genes also affecting flow, pain, and personality variables-neuroticism in particular.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-3297
    Keywords: repeated measures ; simplex model ; twins ; alcohol ; psychomotor sensitivity ; LISREL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract As part of a larger study, data on arithmetic computation and motor coordination were obtained from 206 twin pairs. The twins were measured once before and three times after ingesting a standard dose of alcohol. Previous analyses ignored the time-series structure of these data. Here we illustrate the application of simplex models for the genetic analysis of covariance structures in a repeated-measures design and compare the results with factor models for the two psychomotor measures. We then present a bivariate analysis incorporating simplex processes common and specific to the two measures. Our analyses confirm the notion that there is genetic variation affecting psychomotor performance which is “switched on” in the presence of alcohol. We compare the merits of analysis of mean products versus covariance matrices and confront some practical problems that may arise in situations where the number of subjects is relatively small and where the causal structure among the latent variables places a heavy demand on the data.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Behavior genetics 19 (1989), S. 97-111 
    ISSN: 1573-3297
    Keywords: alcohol sensitivity ; drunk driving ; personality ; twins ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract In a laboratory study of psychomotor sensitivity to alcohol, twins were asked “Would you drive a car now?” at 1, 2, and 3 h after drinking a standard dose of ethanol (0.75 g/kg). Correlations among these binary items, the Eysenck personality scales, and age were investigated using PRELIS and LISREL. Willingness to drive and Extraversion correlate at all three times in both males and females. In males, willingness to drive also correlates with Psychoticism, and in females it correlates negatively with the Lie (or Social Desirability) scale. Most correlations between cotwins in willingness to drive were significant in both monozygotic (MZ) and dizygotic (DZ) male twins but correlations were lower in female twins. Factor and Markovian models were fitted. In males there seem to be both genetic and cultural influences on willingness to drive when drunk. About half the genetic variance seems to be the pleiotropic effects of genes influencing Extraversion. The correlationswith Psychoticism, on the other hand, seem to be largely environmental in origin. The small sample size and lack of proper significance tests mean that these results must be interpreted with caution.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Behavior genetics 15 (1985), S. 93-109 
    ISSN: 1573-3297
    Keywords: alcohol metabolism ; twins ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Blood alcohol measurements were obtained for 206 pairs of twins who had ingested a standard dose of alcohol (0.75 g/kg body weight) and repeat measurements were obtained for 40 of these pairs on a second occasion. The repeatability of the peak blood alcohol concentration (BAC) was 0.66, that of the rate of elimination was 0.39, and that of the time to peak BAC was 0.27. Only a small portion of the nonrepeatable variance could be explained by measurement error or drinking experience. It is concluded that short-term environmental factors exercise considerable influence on alcohol metabolism, particularly in the absorption phase. All of the repeatable variance in peak BAC and rate of elimination was due to genetic factors. Only a small proportion of any of the genetic variance could be explained by individual differences in weight, adiposity, or lung function. Likewise, these three factors were unable to account for the fact that females had higher BACs than males during both absorption and elimination.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-3297
    Keywords: alcohol susceptibility ; psychomotor performance ; twins ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract A battery of psychomotor tasks and physiological measures was administered to 206 pairs of twins before alcohol and then three times at hourly intervals after they ingested a standard dose of ethanol (0.75 g/kg body weight). Repeat measurements were obtained for 41 of these pairs on a second occasion. Performance on motor coordination, standing steadiness, pursuit rotor, arithmetic computation, and reaction-time tasks deteriorated after alcohol, but decrements on the five tasks were generally independent of each other. Measurements of blood pressure, pulse rate, and skin temperature were all elevated following alcohol intake, but these responses were also uncorrelated. The variance in many of these measures increased after alcohol. An analysis of covariance structure revealed that most of this additional variance exposed by alcohol was genetic in origin, particularly for standing steadiness, pursuit rotor, arithmetic computation, and pulse rate. Up to 50% of the variance in body sway after alcohol was estimated to be due to genetic factors expressed only under the influence of alcohol. Although significant correlations were found with blood alcohol concentration, previous drinking experience, and the personality trait Extraversion, little of the genetic variance exposed by alcohol could be explained by these predictors. It is concluded that the sources of the considerable genetic variation affecting performance under alcohol must be sought elsewhere.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Behavior genetics 19 (1989), S. 63-78 
    ISSN: 1573-3297
    Keywords: twins ; alcohol ; LISREL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Age is a potential source of variation that contributes to differences between, but not within, twin pairs. In most genetic analyses of twin data, linear and other functions of age are usually removed prior to model fitting. This correction is typically applied only within twin groups of the same sex and zygosity, and no heterogeneity test of age regressions is performed. Here we include age as a variable in the model-fitting procedure and allow for tests of heterogeneity of age regressions across sex and zygosity groups. The LISREL formulation of the approach is illustrated with data collected from Australian twins on subjective impressions of drunkenness following alcohol consumption. The results indicate significant negative covariation of impressions of drunkenness with age. The data support a simple model of additive genetic and unique environmental variation. No evidence was found for sex differences in genetic or environmental components of variation.
    Type of Medium: Electronic Resource
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