Biomedical subjects
Publications and source records attributed to J C Christian.
It is shown that the within twin-pair difference is the most important source of information in determination of twin zygosity using dermatoglyphic data. Inclusion of a measure of among-pair variability provides added discrimination beyond that found with the within-pair difference alone.
A computer system for simulation of quantitative twin data is being developed. The capability is being built in a simulate distributions with known means, standard deviations, skewness and kurtosis.
Coronary heart disease (CHD) risk factors were studied in 250 monozygotic (MZ) and 264 dizygotic (DZ) male veteran twin pairs, aged 42-56. All coronary heart disease risk factors studied showed significant correlations in both MZ and DZ twins. Substantial genetic variation was detected for height, blood pressure, glucose intolerance, uric acid, plasma triglyceride, and relative weight but little or no significant genetic variability in low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), total plasma cholesterol or hematocrit was demonstrable. These findings suggest that familial aggregation results from genetic influence on blood pressure, glucose intolerance, uric acid, triglyceride and, possibly, obesity, while largely shared environmental factors contribute to familial similarities in HDL, LDL, total cholesterol and hematocrit.
Erythrocyte count, hematocrit, mean corpuscular volume and reticulocyte counts were measured in 59 pairs of monozygotic (MZ) and 69 pairs of dizygotic (DZ) adult, Caucasian male twins. The means of MZ and DZ twins were not significantly different for any of the traits measured. Erythrocyte count and mean corpuscular volume had significant estimates of genetic variance (P less than 0.05).
A syndrome compatible with an X-linked trait is described, affecting four male cousins in three sibships. The body had skeletal anomalies, including short stature, ridging of the metopic suture, fusion of cervical vertebrae, thoracic hemivertebrae, scoliosis, sarcral hypoplasia and short middle phalanges. In addition, they had moderate developmental retardation, and abducens palsies. Three of the four had glucose intolerance, and one was born with an imperforate anus. Of five female obligate carriers studied, three had fusion of cervical vertebrae, three had some shortening of the middle phalanges and three had glucose intolerance. The syndrome in this family was compared to previously reported syndromes, and the conclusion was reached that it represents a previously unreported X-linked syndrome with minor manifestations in carrier females.
A method for partitioning genetic variance estimated from twin data into additive and dominance variances was presented using Falconer's variance component model. The effects of dominance and environmental variances on a number of heritability estimates were also reviewed. A heritability estimate, based on the analysis of variance and the genetic variance estimates presented by HASEMAN and ELSTON and CHRISTIAN et al. which utilizes all available information from twin data, was proposed and discussed. This estimate seems to be the least affected by fluctuations in the magnitudes of dominance and environmental variances.
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Previous studies demonstrated a protective effect of hypoxia on subsequent death breathing oxygen. Four groups of rats were exposed to air for 120 hours plus 99% O2 for 52 hours (A + O2); 120 hours of hypoxia plus 52 hours 99% O2 (H + O2); 172 hours of only air (A); and 120 hours of only hypoxia (H). Rats were sacrificed and lung lavage protein (gm/ 100 ml) was 0.57 +/-0.18 in A + O2 and 0.26 +/- 0.12 in H + O2. Hematocrits were increased at sacrifice. Rats with induced hematocrits of 61% did not have a protective effect breathing oxygen. Mean total phospholipid in lung lavage was: A + O2 O.94; H + O2 1.10; A 1.08; and H 1.76 (micronM/ml). Phosphatidyl choline (lecithin) was: A + O2 0.49; H + O2 0.61; A 0.59; and H 1.15 micronM/ml. Differences among the groups were significant for total phospholipids and phosphatidyl choline except between air (A) and hypoxia + O2 (H + O2). Palmitic acid was decreased in A + O2 compared to the other groups. Oxygen breathing results in decreased total phospholipids and phosphatidyl choline in lung lavage. Pretreatment with hypoxia and subsequent oxygen breathing results in amounts similar to rats breathing air only.
Transposition of 1q31-1q32 from the q to p arm in a parent followed by crossing over resulted in a child with a duplication of this region. Concomitant C- and GTG-banding and genotyping were used to position the single crossover and to localize Fy to 1q2.
Evidence for maternal effects on plasma cholesterol was found by comparing the variance between maternal and paternal half siblings obtained from 83 families of monozygotic twin pairs (424 children). Maternal effects accounted for about one-fifth of the total variance.
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Variation in the fatty acid composition of fasting plasma lipids and of cholesteryl esters was studied in 69 sets of adult male twins and 25 of their brothers. Genetic variances were estimated using the twin model. In general, monozygotic (MZ) twins were characterized by the smallest within-pair variance, and brothers of twins by the largest. Variation within dizygotic pairs fell imtermediate to that of MZ twins and brothers. The present study did not reveal consistent significant (P greater than 0.05) genetic variation in plasma fatty acids from total plasma lipids or cholesteryl esters.
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The National Heart and Lung Institute Twin Study has examined 514 white adult male twin sets aged 42-56 with respect to blood pressure. The data were analyzed by a method of Christian et al. which eliminates possible biases in estimated genetic variances that could result from different total variances in MZ and DZ twins. Results of the test for the presence of genetic variance indicate that both systolic and diastolic blood pressure are to a considerable extent genetically controlled with an estimated heritability of 0.8 for systolic and 0.6 for diastolic pressure. Although these findings are at variance with some previous reports, it is thought that much of the discrepancy results from application of different analytic techniques, not in the data themselves. The application of these findings to our understanding of hypertension epidemiology and community hypertension control programs are discussed.
Fasting plasma triglycerides and cholesterol, as well as cholesterol in very low density, low density and high density lipoproteins, were measured in 250 MZ and 264 DZ adult male twin pairs. A new method was used to choose an estimate of genetic variance. This includes an estimate of genetic variance for use when the total variances of MZ and DZ twins are unequal. DZ twins had greater total variance for cholesterol. When genetic variance was estimated by subtracting the within-MZ-sets mean square from the within-DZ-sets mean square, all of the lipids had significant estimates of genetic variance; however, when genetic variance was estimated by a method designed to correct bias due to unequal total variances of MZ and DZ twins, only triglycerides had significant genetic variance. The heritability of plasma triglycerides was calculated to be 0.68.
The Dermatogram, a dermatoglyphic nomogram based upon four pattern areas, was compared with three other indices for the diagnosis of Down's syndrome (D.S.). The measure of diagnostic accuracy used was the percentage of patients scoring outside reported overlap scores between normal and D.S. The Dermatogram correctly diagnosed 79% of 119 D.S. patients. Two other indices, using more pattern areas and requiring calculations, correctly diagnosed more patients (81 and 87%), but one had several incorrect diagnoses and the other was less efficient when scored on a small sample of normal, karyotyped, non-D.S. retardates. The Dermatogram is suggested for use as a rapid diagnostic screen. For patients in the Dermatogram overlap, added discrimination may be obtained from secondary scoring on other indices.
Total, free and esterified cholesterol were measured in the plasma, high density lipoproteins, low density lipoproteins, and total cholesterol in the very low density lipoproteins of 141 pairs of adult white male twins. Free cholesterol in plasma, high density lipoproteins and low density lipoproteins had significant genetic variance. Esterified cholesterol had greater total variance in dizygotic than monozygotic twins, interpreted as evidence for greater environmental influences on the two types of twins. After bias due to unequal environmental effects on the two types of twins was removed, there was no significant genetic variance for any esterified fraction of cholesterol.