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Biomedical subjects

J C Christian

Publications and source records attributed to J C Christian.

At least 91 records · Page 5Linked to original sources
PubMed1980

Diethylstilbestrol-exposed monozygotic twins discordant for cervicovaginal clear cell adenocarcinoma.

Monozygotic, 17-year-old, female twins exposed to diethylstilbestrol (DES) in utero and discordant for cervicovaginal clear cell adenocarcinoma are reported. Benign teratologic changes were present in both. The twin with cancer was treated by extensive operation and postoperative irradiation. No tumor has appeared in either twin in the 4 years subsequent to therapy. Discordance for cervicovaginal clear cell adenocarcinoma in this situation suggests that factors other than embryonic exposure to DES, extrauterine in location and nongenetic in character, were operative in tumorigenesis. The twins were compared in regard to lifetime radiation exposure and evidence of previous viral disease. The only substantial difference was an elevated titer of antibody in the twin with cancer to the capsid antigen of the Epstein-Barr virus, a herpesvirus with oncogenic capability.

Adenocarcinoma↗
PubMed1980

Data from kinships of monozygotic twins indicate maternal effects on verbal intelligence.

Familial resemblance in intellectual skills is well documented, but its interpretation is a source of continuing controversy. The critical problem is that a family's shared genes are confounded with its shared experiences, and controls possible in animal research (selective mating, cross-fostering, and uniform or randomised environments) do not directly apply to human subjects. Conventional twin and family methods reveal substantial genetic variance in intelligence quotient (IQ) test scores, but the same methods also document significant environmental influences. Research designs which can identify the nature of these environmental factors may effect progress in the 'IQ debate' (ref. 1). The families of monozygotic (MZ) twins provide a new research design which permits a unique assessment of maternal influences in quantitative traits. We describe here initial applications of the design to verbal IQ, with results suggesting that maternal effects significantly contribute to familial similarity in verbal intelligence.

Adolescent↗
PubMed1980

A family with three recessive traits and homozygosity for a long 9qh+ chromosome segment.

We report a family in which a mentally retarded, proportionately dwarfed girl had a child from a presumably incestuous mating that had the Ellis van-Creveld syndrome, presumed autosomal recessive hydrocephalus (Dandy-Walker type), and homozygosity for an extremely long 9qh+ chromosomal marker. The mentally retarded mother had normal birth weight, unusual facial appearance, and virtual absence of secondary sexual hair; she developed severe hypoglycemia during pregnancy. Her parents were first cousins, and she may have a previously unreported autosomal recessive syndrome.

Chromosomes, Human, 6-12 and X↗
PubMed1980

Familial variation of head size and adjustment for parental head circumference.

Occipitofrontal head circumference was measured on 122 twin pairs, their spouses, and their children. These data indicate that approximately 50% of normal head size variation is familial. Because of the relationship between the head size of normal children and their parents, adjustment of a child's head size value by the average parental value permits better definition of the range of normalcy. A method is presented that will allow physicians to make this adjustment, providing a more refined assessment of head size when there is a suspected abnormality.

Adolescent↗
PubMed1980

Estimates of genetic variance for anterior fontanelle development in the NCPP twin population.

There are several dynamic influences on anterior fontanelle development in infants; among them, brain growth, dural attachments, suture development, and osteogenesis, It thus seems reasonable to hypothesize that variation in anterior fontanelle development between infants, related and unrelated, might have a significant genetic component. Anterior fontanelle size was quantitated by the method of Popich and Smith for 94 monozygotic (MZ) and 187 dizygotic (DZ) four-month-old twin pairs. The general model for estimating genetic variance from quantitative twin data was applied to MZ and DZ twins and then separately by chorion type. Since there were significant mean differences between blacks and whites, races were analyzed separately. The within-pair mean square estimates of genetic variance (GWT) were highly significant for both blacks (less than 0.02) and whites (P less than 0.002). Comparisons of means, total variances, and among-pair mean squares within races revealed no heterogeneity. There were also no significant chorion effects. Since the anterior fontanelle closes at around 1--1 1/2 years of age, it was evaluated at age one in 95 MZ and 194 DZ twin pairs as a qualitative trait - ie, open vs closed, concordance vs discordance. There were no significant differences in proband concordance rates between MZ and DZ twin pairs for either blacks (P greater than 0.5) or whites (P greater than 0.10). Again, there were no significant chorion effects. These data suggest that anterior fontanelle developmental variation has a significant genetic variance component at four months of age but not at one year. This finding may be related to the rapid brain growth witnessed between birth and eight to nine months of age.

Anthropometry↗
PubMed1980

Determinants of plasma cholesterol in children--a family study.

Twin and family studies have revealed genetic and maternal influences on plasma cholesterol. This study was designed to identify familial and environmental variables related to cholesterol levels in children. Volunteer families (n = 74) were obtained from a previous study of cord blood cholesterol. When the children were 2.5 years old, blood samples, dietary histories, heights, weights, and skinfold thicknesses were obtained. Dietary variables were significantly correlated with plasma cholesterol levels in children but not in their parents. Stepwise multiple regression was used to identify sets of variables predictive of plasma cholesterol fractions of these children. For plasma total cholesterol, the set included previous history of breast feeding (versus formula), child's current dietary poly-unsaturated/saturated fatty acid ratio, maternal alcohol and fat consumption, paternal cholesteryl esters, and maternal hematocrit (r = 0.53). Free cholesterol had a similar predictive variable set (r = 0.52). More variation in esterified cholesterol of children was predicted (r = 0.69) by history of breast feeding, child's current protein and caloric intake, maternal total and esterified cholesterol, and proteinuria during pregnancy. Cord blood cholesterol was not predictive of any later cholesterol measurement. These correlations of children's plasma cholesterol with multiple factors emphasize the importance of focusing on very early childhood for study of both the normal developmental pattern of human cholesterol and intervention to prevent adult hypercholesterolemia.

Adult↗
PubMed1980

Genetic influences on plasma and urinary norepinephrine after volume expansion and contraction in normal men.

Heritable influences on venous plasma norepinephrine (PNe) and urinary norepinephrine (UNe) values were examined in normotensive monozygotic and dizygotic twins during volume expansion and contraction. The presence of genetic variance was tested by calculating the within-pair estimate of genetic variance. Significant genetic variance was found to influence PNe during recumbency before and after a 4-h iv infusion of 2 liters saline. Similarly, heritable influences on UNe excretion were observed in a 10-h urine collection after the sodium load. Heritable influences on PNe or UNe were not observed after postural stimulation or volume contraction. The data suggest that sympathetic nervous system activity is influenced by heritable factors which may contribute to the development of hypertension in some individuals.

Female↗
PubMed1979

Association of twin zygosity with the mean and variance of tooth size.

To search for an association of twin zygosity with tooth size, 56 dental variables measured from 65 pairs of twins (43 MZ, 22 DZ) were studied. Results of the t' test for equality of the means showed no association of zygosity with any of the variables in males or in females. Results of the F' test for homogeneity of total variances between zygosities showed evidence for unequal total variances in 15 variables in males and 13 in females. Sex influence was further noted on the association of zygosity with the variance of tooth size. Where total variances were unequal, genetic variance estimates differed when only the within-pair mean squares were used and when combined estimates designed to be unbiased by differences in environmental variances were used.

Female↗
PubMed1979

Glomerular filtration rate and electrolyte handling in response to sodium loading and depletion. A twin study.

Possible genetic influences on glomerular filtration rate and electrolyte excretion were investigated in 55 (37 monozygotic, 18 dizygotic) young adult white twin pairs. Subjects were studied during a five-day hospitalization involving sodium loading and sodium depletion. No evidence of genetic variability was found in the control levels of serum or urine sodium and potassium. Following a saline infusion it was possible to detect genetic influence in electrolyte handling. Creatinine clearance, used as a measure of glomerular filtration rate, did not appear to be genetically mediated. The results indicate that genetic factors are important in sodium handling in normal individuals and that this is independent of glomerular filtration rate.

Adolescent↗
PubMed1979

Quantitative twin analysis of radial and ulnar ridge counts and ridge count diversity.

Analysis of variance was performed on the radial and ulnar finger ridge counts and ridge count diversity index in 360 twin sets from which estimates of genetic variance were obtained. Findings for radial and ulnar counts paralleled those previously obtained for finger pattern type and ridge count (larger of radial and ulnar count). In contrast, ridge count diversity showed no indication of unequal total variances, as previously found for the total ridge count. One must be cautious not to exclude genetic influences on traits, such as the thumb variables in this study, where there are unequal total variances between monozygotic and dizygotic twins and the more conservative estimate of genetic variance is not significant.

Analysis of Variance↗
PubMed1979

Testing twin means and estimating genetic variance: basic methodology for the analysis of quantitative twin data.

Twin methodology for the analysis of continuously distributed traits is presented as a guideline for initial steps in the analysis of twin data. Tests for heterogeneity of twin means and variances are reviewed along with estimates of genetic variance. Analysis of twin data appears on the surface to be a rather simple task, but investigators may well be confused by the wealth of choices available for hypothesis testing. This paper is designed to help the less experienced investigator, with perhaps a modest amount of data, begin analysis with maximum attention to testing all testable assumptions of the twin model, and using recent examples of applications of the methods.

Female↗
PubMed1979

Effects of type of placentation on birthweight and its variability in monozygotic and dizygotic twins.

Birthweight was measured on 188 monochorionic monozygotic, 54 dichorionic monozygotic, 102 like-sexed dizygotic, and 94 unlike-sexed dizygotic liveborn twin pairs. Overall, males were found to be significantly heavier than females. These differences were not significant, however, when birthweights were compared within zygosity/chorion-type categories. Males were also characterized by a slightly greater overall total variance. Comparisons of intrapair variation of monochorionic and dichorionic monozygotic twins revealed significant differences between monochorionic pairs and dichorionic separate pairs and no significant differences between monochorionic pairs and dichorionic fused pairs. The results of this study suggest that placental proximity may have as important an influence on variation in birthweight as does the presence or absence of vascular anastomoses.

Birth Weight↗