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At least 37 records · Page 2Linked to original sources
PubMed1976

Genetic basis of hair medulla by twin study.

Data on the incidence of medulla of human head hair based on 9,600 strands examined from 48 pairs of zygosity--determined German twins were quantified as medullary ratio and subjected to variance analysis to give information about genetic significance of the character concerned. The results of F test and heritability estimate yielded significant values indicating the presence of a strong genetic component of variability in the incidence of medulla of human head hair. Sex influence upon the character is found to be absent.

Female↗
PubMed1975

Genetic effects in the cortical auditory evoked potential: a twin study.

An experiment was carried out on 40 pairs of adult male twins to investigate the extent of genetical determination in the cortical auditory evoked potential. Tonal stimuli of 1 sec duration, at an intensity of 95 dB and a frequency of 100 c/sec, were used. The inter-stimulus interval was 33 sec and the bipolar evoked potential was measured between the CZ and T3 scalp positions. The reliability of the seven latency and amplitude measures was also calculated and this was taken into account in the subsequent genetic analysis. The biometrical gentical approach, which gives maximal information particularly on small samples, was used to analyse the data. A strong genetic influence was found on all the amplitude scores. The environment made no significant contribution to these. For the latencies there was some evidence for a genetic effect; however, this was not very strong and can well be interpreted as being due to between family environmental effects.

Adolescent↗
PubMed1979

[Ankylosing spondylitis in monozygous twins. Study of HLA complex (author's transl)].

A study of HLA complex (HLA A, B, C, DRw, Bf, chiddo) in monozygous twins suffering from ankylosing spondylitis with different clinical courses. All the markers studied were identified. The results would tend to suggest that hereditary factors are not alone responsible in the course of ankylosing spondylitis. Furthermore, they are not the sole causative factor of the disease since the literature contains reports of discordant pairs of twins.

Adolescent↗
PubMed1976

A twin study of dental dimension. I. Discordance, asymmetry, and mirror imagery.

Bilateral tooth measurements in twins are partitioned into three orthogonal contrasts, each associated with one degree of freedom, to estimate three parameters: discordance, asymmetry, and mirror imagery. The probability levels of the within-pair variance ratios were used to test for significance of these estimates. The results provided strong evidences for the existence of significant genetic determinants of almost all of the individual tooth dimensions, but little or no evidence for a genetic basis of asymmetry. The analysis gave no indication that monozygotic twinning was associated with an increased degree of either fluctuating asymmetry or mirror imagery, when compared to dizygotic twins. The data on monozygotic twins further suggested that for most variables examined, the increment of environmental discordance resulting from the twinning phenomena was greater than the developmental noise that caused asymmetry within individual cotwins.

Female↗
PubMed1977

A twin study of temperament in young children.

Temperament was assessed in 182 young children (91 pairs of twins, average age of 3.6 years) with use of the Colorado Childhood Temperament Inventory (CCTI). The CCTI represents a merger of dimensions suggested by two approaches to the study of the development of temperament: the New York Longitudinal Study and Buss and Plomin's temperament theory. Of the six traits measured by the CCTI, genetic factors were implicated in the etiology of five (sociability, emotionality, activity, attention span-persistence, and soothability). One trait, reaction to food, showed no genetic influence and indicated strong between-family environmental effects. A negative correlation between emotionality and soothability may also have a genetic basis. These results suggest that the development of certain personality traits--those that we include as temperament--are substantially influenced by heredity.

Attention↗
PubMed1978

Lithium accumulation in erythrocytes of manic-depressive patients: an in vivo twin study.

Genetic factors play an important role in drug metabolism and drug response. In order to investigate genetic variables in lithium prophylaxis and lithium distribution across the erythrocyte in manic-depression, we have examined forty-two pairs of twins monozygotic (n = 25) and dizygotic (n = 17) with manic-depression. Concordant twins as a group show better lithium prophylaxis than do discordant twins. These results are consistent with previously published family studies of affective illness suggesting a positive relationship between genetic background and success of lithium prophylaxis. Lithium distribution across the red blood cell (RBC) was assessed by estimating lithium RBC/plasma ratios. The lithium ratio's intrapair differences in both groups of twins were minimal with a high heritability index suggesting that genetic factors play a role in lithium ion distribution. A high linear correlation was found between lithium ratio and plasma lithium and there was no difference in lithium ratios according to sex, affective state and response to lithium. The distribution of lithium ratios was homogenous in the lithium responders' population but this was not the case in the non-responders, suggesting biological heterogeneity of lithium distribution in lithium failures. The implications of these results are discussed as they relate to the genetic determinates of lithium prophylaxis in manic-depressive illness. These results indicate that lithium ratios are of limited value in lithium maintenance therapy. Our lithium kinetic data, however, are consistent with the concept of a lithium extrusion mechanism from red blood cells.

Adult↗
PubMed1978

A twin study on three enzymes (DBH, COMT, MAO) of catecholamine metabolism. Correlations with MMPI.

Ina a sample of 48 healthy adult male twin pairs (24 MZ, 24 DZ) the activities of DBH (serum), COMT (red blood cells), and MAO (platelets) were determined. The twins had undergone a detailed psychodiagnostic test procedure before. Interindividual variability of enzyme activities is almost exclusively genetically determined. No correlation between enzyme activities within one subject is found. Correlations between enzyme activities and MMPI test scores were calculated. As in a comparable investigation by Murphy et al. (1977), negative correlations between MAO activity and MMPI scores prevailed.

Adult↗
PubMed1976

A twin study of dental dimension. II. Independent genetic determinants.

To demonstrate the presence of independent genetic determinants of multiple correlated tooth dimensions from twin data, a multivariate analysis was performed on the covariance matrices of monozygotic and dizygotic within-pair differences for mesiodistal and buccolingual dimensions of 28 teeth of the secondary dentition. The results provided strong evidences that the correlation among tooth dimensions is primarily genetic in origin, probably attributable to the pleiotropic action of either independent genes or groups of genes. Among the genetic factors that were identified, one appeared to affect the maxillary teeth in general while a second influenced primarily the anterior mandibular teeth. There was a striking tendency for homologous measurements on the right and left sides to be associated with the same genetic factor. In contrast, genetic determination of the maxillary and mandibular dentition seemed to be independent of each other, and a wider range of genetic factors were found to influence the mandibular than the maxillary teeth, suggesting that a differential degree of evolutionary stability may have been achieved in the teeth of the two jaws.

Female↗