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  • Articles: DFG German National Licenses  (9)
  • twins  (5)
  • Cell & Developmental Biology  (4)
  • heritability  (4)
  • 1
    Electronic Resource
    Electronic Resource
    A source of variance in IQ unique to the lower-scoring monozygotic (MZ) cotwin (1986)
    Springer
    Behavior genetics 16 (1986), S. 509-516 
    Details
    ISSN: 1573-3297
    Keywords: twins ; heritability ; environment ; intelligence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Environmental factors more common in twins than singletons appear to be disadvantageous with respect to intelligence. If these factors contribute to within-pair differences in IQ, the effect should be found more in the cotwin lower in IQ (the low twin) than in the cotwin higher in IQ (the high twin). In this case, the variance of the low twins should exceed that of the high twins. This hypothesis was tested for five samples of monozygotic (MZ) twins and three samples of dizygotic (DZ) twins but was confirmed only for the MZ samples. These results suggest that there are disadvantageous environmental factors unique to MZ twins which contribute to within-pair variability. Such factors will cause heritability coefficients obtained using MZ twins to be underestimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066337
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Estimating true scores in kinship data (1987)
    Springer
    Behavior genetics 17 (1987), S. 487-491 
    Details
    ISSN: 1573-3297
    Keywords: true scores ; measurement error ; kinship data ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Estimated true scores are occasionally used to provide an estimate of scores which would be obtained if measurement error could be removed from fallible measures. When one knows only a test's relibility and an observed score for each subject, true scores are estimated by regressing observed scores toward the group mean. When relatives' observed scores are also available, estimates of true scores can be improved by using the additional information. Observed scores of subjects and relatives can be used as predictors of subjects' true scores in a multiple regression. The resulting formula is presented for the case in which only one relative's score per subject is known. Estimation of true scores for the general case ofN relatives per subject is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01073115
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Sexual orientation, sexual identity, and sex-dimorphic behaviors in male twins (1991)
    Springer
    Behavior genetics 21 (1991), S. 75-96 
    Details
    ISSN: 1573-3297
    Keywords: sexual orientation ; twins ; heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Sexual orientation, sexual identity, and sex-dimorphic behaviors were assessed concurrently and retrospectively, for childhood, in 95 pairs of male monozygotic (MZ) twins and 63 pairs of dizygotic (DZ) twins. There was a significantly higher rate of adult homosexuality among the MZ than among DZ twins. We employed a model-fitting approach using LISREL to test for genetic and environmental influences on variation for each trait singly and on the covariation among all six traits (three for childhood and three for adulthood). Univariate analyses confirmed the presence of familial factors for five of the six variables but were generally unable to distinguish shared environmental from genetic influences. Hierarchial tests of multivariate models supported the existence of an additive genetic factor contributing to the covariance among the variables. More restrictive multivariate models yielded a significant genetic influence on sexual orientation. Because of the different rates of orientation by zygosity and because of the restrictive nature of some of the multivariate models, our results are best considered tentative but do suggest that further biometrically oriented studies of sexual orientation and its correlates would be worthwhile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067668
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Increased heritability for lower IQ levels? (1991)
    Springer
    Behavior genetics 21 (1991), S. 397-404 
    Details
    ISSN: 1573-3297
    Keywords: twins ; heritability ; environment ; intelligence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Dettermanet al. (1990) presented evidence based on twins that the heritability of IQ may be higher in the lower part of the IQ range. We first offer an alternative test for differential heritability across the IQ range, based on the analysis of absolute intrapair differences of monozygotic versus dizygotic twins. We then review two previous studies, each containing more twins than the sample of Dettermanea al., which examined the distribution of intrapair absolute differences. In contrast to the study of Dettermanet al., both yielded results more compatible with higher heritability in the upper range of IQ. We discuss various interpretations of these findings and show how our proposed test might aid in distinguishing among them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01065975
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement Models for Sexual Orientation in a Community Twin Sample (2000)
    Springer
    Behavior genetics 30 (2000), S. 345-356 
    Details
    ISSN: 1573-3297
    Keywords: Homosexuality ; sexual orientation ; heritability ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Multivariate structural equation modeling techniques have been applied to examine the causes of individual differences in responses to several items concerning sexual orientation. To minimize potential ascertainment and response biases, the study sample involved a large (N = 4901) community-based cohort of Australian twins aged 18–52 who answered an anonymous questionnaire on sexual behavior and attitudes. The statistical power of the analysis was increased by the availability of multiple measures of sexual orientation (behaviors, attitudes and feelings), providing stronger evidence for the existence of additive genetic influences on this phenotype than in a previous analysis (Bailey et al., 2000). Estimates of the heritability of homosexuality in this sample ranged between 50 and 60% in females but were significantly lower (heritability of approximately 30%) in males.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026557719181
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Vascular networks from explants of human synovialis in vitroSupported in part by grant AM-02520 from the National Institute of Arthritis and Metabolic Diseases, NIH Bethesda, Maryland, and by private funds from Southwestern Clinic & Research Institute, Inc. (1963)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 147 (1963), S. 525-531 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Explants of human synovialis obtained surgically were cultivated under dialysis membrane in the multipurpose Rose chamber and in Eagle's medium enriched with 20% pooled human cord sera. Within 24 hours monocytes and lymphocytic cells emerged from the majority of explants while spindle and stellate cells appeared later on the second and third days of culture. A monolayer of cells developed in which active mitosis was observed. Between 12 to 15 days, fingerlike projections of cells adjacent to the explants branched out between the cover glass and the monolayer of mesenchymelike growth and by the twenty-fifth day had developed into anastomosing networks eventually ranging in length from 1.2 to 3.2 mm. Ciné and still phase photomicrographs decumented findings. Vascular networks developed in vitro in 85% of the total 80 Rose chambers examined over an average period of 58 days. Minute vessels, patent for only short distances, were lined with endothelial cells characterized by slender elongated nuclei and with two or three small nucleoli. In contrast, flanking fibroblasts were considerably larger with clear oval nuclei containing conspicuous nucleoli. Differential stains demonstrated reticular fibers and distinct bundles of collagen lying along the vessels, particularly in the area adjacent to the fragment. In the study of rheumatoid arthritis, where vascular lesions are known to occur, it is possible that such preparations may provide favorable test objects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091470407
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of cold shock and phospholipase A2 on intact boar spermatozoa and sperm head plasma membranes (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 143-149 
    Details
    ISSN: 1040-452X
    Keywords: Fertility ; Ca2+ uptake ; Head plasma membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Head plasma membranes (HPM) isolated from cryopreserved boar spermatozoa show an excessive fluidization (Buhr et al., Gamete Res 23:441-449, 1989), which might be involved in the loss of fertility. The current study assessed the ability of cold shock (5°C) and phospholipase A2 (PA2) to duplicate these effects on membrane structure and to affect 45Ca2+ uptake and gross morphological characteristics of whole, fresh boar sperm. The HPM from cold-shocked sperm showed a significantly greater rate of fluidization over time than did HPM from control sperm. Addition of PA2 (bee or snake venom, 0.1 or 10.0 ng/ml) to HPM from control sperm caused fluidization similar to cold shocking, but to a lesser degree (P 〈 0.05). Cold-shocked intact sperm exhibited severe acrosomal disruption, loss of motility, and increased 45Ca2+ uptake relative to control sperm. Addition of PA2 (bee or snake venom, 0.1, 1.0., 10.0, and 1,000 ng/ml) to control sperm had not effect on gross morphology or motility while maintaining or increasing sperm extrusion of 45Ca2+. Therefore, although PA2 can, to some extent, duplicate the effects of cold shock on HPM molecular organization, its lipid hydrolytic action is insufficient to cause all the gross disruptions of severe thermal shock. Both PA2 and cold shock disrupted HPM structure, but only cold shock increased 45Ca2+ uptake, suggesting that cold shock may be increasing 45Ca2+ uptake in areas other than the head. Cold shock disrupts sperm on three levels; membrane molecular organization, intracellular Ca2+ regulation, and gross morphology/motility.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080260208
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of ethanol dehydration and critical point drying on fish tissue culture cell membrane elemental composition by scanning electron microscopy/X-ray microanalysis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 259-260 
    Details
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070280310
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of semen preservation on boar spermatozoa head membranes (1989)
    New York, NY : Wiley-Blackwell
    Gamete Research 23 (1989), S. 441-449 
    Details
    ISSN: 0148-7280
    Keywords: boar ; spermatozoa ; membrane fluidity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Head plasma membranes were isolated from the sperm-rich fraction of boar semen and from sperm-rich semen that had been subjected to three commercial preservation processes: Ex tended for fresh insemination (extended), prepared for freezing but not frozen (cooled), and stored frozen for 3-5 weeks (frozen-thawed). Fluorescence polarization was used to determine fluidity of the membranes of all samples for 160 min at 25°C and also for membranes from the sperm-rich and extended semen during cooling and reheating (25 to 5 to 40°C, 0.4°C/min). Head plasma membranes from extended semen were initially more fluid than from other sources (P 〈 0.05). Fluidity of head membranes from all sources decreased at 25°C, but the rate of decrease was significantly lower for membranes from cooled and lower again for membranes from frozen-thawed semen. Cooling to 5°C reduced the rate of fluidity change for plasma membranes from the spernvrich fraction, while heating over 30°C caused a signifi cantly greater decrease. The presence of Ca++ (10 mM) lowered the fluidity of the head plasma membranes from sperm-rich and extended semen over time at 25°C but did not affect the membranes from the cooled or frozen-thawed semen. The change in head plasma membrane fluidity at 25°C may reflect the dynamic nature of spermatozoa membranes prior to fertilization. Extenders, preservation processes and temperature changes have a strong influence on head plasma membrane fluidity and therefore the molecular organization of this membrane.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120230409
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