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Biomedical subjects

W E Nance

Publications and source records attributed to W E Nance.

At least 55 records · Page 3Linked to original sources
PubMed1992

Development of the Virginia Congenital Anomalies Reporting and Education System (VaCARES): two pilot projects.

In 1986 legislation established the Virginia Congenital Anomalies Reporting and Education System (VaCARES). The system has three goals: to collect data that can be used to evaluate possible causes of congenital anomalies, to improve diagnosis and treatment, and to let parents and physicians know what resources are available to aid children born with anomalies. All children (from birth to age 2) with congenital anomalies admitted to Virginia hospitals after January 1, 1987, are being reported to VaCARES; VaCARES then contacts their families and physicians. Before the system was implemented statewide, its procedures were thoroughly tested through two pilot projects in selected hospitals. During the pilots, it was concluded that birth certificates alone are inadequate for case ascertainment. According to hospital reports, the incidence of all congenital anomalies during Pilot II was 562 out of 10,034 births (5.6%); birth certificates showed an incidence of only 83 out of 10,034 births (0.8%). During Pilot I, 3,466 (73.8%) of the diagnoses reported were perinatal conditions; the list of reportable conditions was accordingly altered, reducing perinatal conditions reported in Pilot II to 5 diagnoses (0.4%). It was estimated that there will be about 5000 to 7000 reports submitted to VaCARES each year. It was also shown that parents should be sent general rather than specific information about their child's birth defect and that quality control and close contact with reporting hospitals are essential to maintain the integrity of the registry data.

Congenital Abnormalities↗
PubMed1992

Multivariate genetic analysis of blood pressure and body size. The Medical College of Virginia Twin Study.

BACKGROUND: In subjects of all ages, those who weigh the most often have the highest blood pressure. Thus, in epidemiological studies, weight is the most important correlate of blood pressure. Using the data from the Medical College of Virginia Twin Study, we asked these questions: 1) Do the same genetic paths that regulate body size also regulate systolic and diastolic blood pressure? 2) Are there distinct genetic pathways that regulate each of these variables? 3) Does environment play a major regulatory role? 4) Are the correlations among these variables mainly due to genetic or environmental effects? 5) Do genetic paths that regulate body size mediate the correlation between systolic blood pressure and diastolic blood pressure? METHODS AND RESULTS: We ascertained 253 Caucasian twin pairs living in the Commonwealth of Virginia. The average age was 11.2 +/- 0.2 years. We used multivariate path analyses to investigate the genetic relations among systolic blood pressure, diastolic blood pressure, and body size. We found that there was a highly significant genetic relation between systolic blood pressure and body size and between systolic and diastolic blood pressure. There are genetic paths that are shared within these two sets of variables, but in each case, the paths for each pair appear to be separate from one another. CONCLUSIONS: These analyses provide a method to partition correlation coefficients found in epidemiological studies into genetic and environmental components. The correlations found among these three variables are in large part due to these genetic relations. We found no genetic relation between diastolic blood pressure and body size.

Blood Pressure↗
PubMed1992

The epidemiology of pregnancy complications and outcome in a Norwegian twin population.

OBJECTIVE: To measure the contribution of genetic factors to selected pregnancy complications, including miscarriage, twinning, hypertension-toxemia, and nausea-vomiting. METHODS: Information on 22,241 pregnancies of 8675 female twins or spouses of male twins was obtained by questionnaire from members of the population-based Norwegian Twin Panel. Comparisons of observed tetrachoric correlations were used to assess the importance of genetic influences on the variables examined. RESULTS: Pregnancy history information was provided by both members of 830 monozygotic and 902 dizygotic female twin pairs and by the spouses of both members of 459 monozygotic and 464 dizygotic male twin pairs. The incidence of twin pregnancy in general, and of opposite-sexed twins in particular, found among dizygotic twin women was nearly twice that observed for any other group. Monozygotic female twin pairs were more concordant than dizygotic female twin pairs for the occurrence of miscarriage, nausea or vomiting during pregnancy, and hypertension or overt toxemia. A similar pattern of twin similarity was observed for the use of certain medications during pregnancy including vitamins, aspirin, and nausea medication. CONCLUSIONS: Maternal genetic factors make an important contribution to a predisposition for dizygotic twinning, contribute to the risk of miscarriage, and appear to determine, in part, whether a woman experiences nausea-vomiting or hypertension-toxemia during pregnancy. In addition, health-seeking behaviors of women during pregnancy, as reflected by the use of several classes of medication, appear to be influenced somewhat by genetic factors.

Female↗
PubMed1992

Aphidicolin-inducible common fragile-site expression: results from a population survey of twins.

Common chromosomal fragile sites appear to be ubiquitous in humans and other mammals, and, although the molecular basis and function of these sites remain an enigma, it has been speculated that they may be a cytogenetic expression of gene activity. A population survey of 28 twin pairs was conducted to assess the heritability of common fragile-site expression. Our data yielded a heritability estimate of .88 for total site expression, suggesting that these sites may result from some common process that is under relatively stringent genetic control. An analysis of the expression of individual autosomal sites revealed that expression on both homologues in the same cell occurred more frequently than expected.

Adolescent↗
PubMed1991

Bivariate genetic analysis of left ventricular mass and weight in pubertal twins (the Medical College of Virginia twin study).

Left ventricular (LV) hypertrophy in adults is a recognized risk factor for the subsequent development of cardiovascular morbidity. To make informed preventive health decisions it is important to understand the interaction of genes and environment on LV mass. In both children and adults, weight is a strong correlate of LV mass. We hypothesized that genetic influences common to both of these variables could in part explain the strong relation between weight and LV mass in children. In a population of 341 twins (11 years old), these questions were asked: (1) How much of the total variance of LV mass is under genetic control? (2) After accounting for weight and weight adjusted for sexual maturity, how much of the remaining variance is genetic? (3) Of the total genetic variance, what proportion is specific for LV mass and what proportion is common to both weight and LV mass? (4) How much of the correlation between these 2 variables is explained by genes common to both LV mass and weight? Univariate genetic analyses documented that genes operating at different magnitudes in boys (63%) and girls (71%) explain a significant proportion of the variance of LV mass. After removing the effect of weight and sexual maturity by regression methods, genes remain an important influence. Bivariate genetic analyses confirmed that genes common to LV mass and weight significantly influence the covariation of these variables and that greater than 90% of the correlation of LV mass and weight is due to common genes.

Body Mass Index↗
PubMed1991

Statistical approaches for the detection of heterozygotes for biotinidase deficiency.

We applied and evaluated 3 statistical approaches for the detection of heterozygotes for biotinidase deficiency in a randomly selected population of French adults. The first method, which used a cutoff value to dichotomize the population, lacked sensitivity. The second approach calculated the probability of heterozygosity for a given enzyme activity through the application of Bayes theorem to the normal density functions of the enzyme distributions of the obligate heterozygote and the test populations. A priori values of the means and standard deviations (SDs) of the genotypic distributions were used. This method was sufficiently sensitive for both population screening and genetic counseling, but requires prior knowledge of the frequency of the deficient gene (q). The third approach was similar to the second, however, maximum likelihood estimates of the means and SDs of the genotypic distributions were calculated and used to determine the probability of heterozygosity for a given enzyme activity. This method was as sensitive as the second method and is appropriate for screening populations for which there is little prior information about the gene frequency and the genotypic distributions. This method can also be used to estimate the gene frequency of the disorder within a given ethnic or racial population. Using this method, we estimated the frequency of heterozygotes (2pq) in the French population to be 0.012, which was similar to that estimated from the results of neonatal screening for biotinidase deficiency. These methods can be used to detect heterozygotes and to estimate the gene frequency of other inherited enzyme deficiencies.

Amidohydrolases↗
PubMed1991

The occurrence of epilepsy and febrile seizures in Virginian and Norwegian twins.

Twin studies provide an efficient method for examining the importance of genetic and environmental factors in the etiology of disorders such as epilepsy. Population-based twin registries are especially valuable for studies of this type since effects of reporting and self-selection biases on the resulting data are minimized. Among 14,352 twin pairs contained in the Virginia and Norwegian twin panels for whom questionnaire information was available, there was a history of epilepsy in one or both members of 286 pairs; febrile seizures were reported in 257 pairs. Analyses of questionnaire data revealed no significant differences in concordance rates between Virginian and Norwegian twins for either epilepsy or febrile seizures. Probandwise concordance rates for epilepsy were 0.19 in monozygotic twins and 0.07 in dizygotic twins. Analogous rates for febrile seizures were 0.33 (monozygotic) and 0.11 (dizygotic). These results provide further evidence that genetic factors do have a role in the expression of epilepsy and febrile seizures.

Diseases in Twins↗
PubMed1990

Evidence for a major gene in familial anencephaly.

A 21-year-old white woman sought counseling after the birth of two consecutive anencephalic male fetuses with complete rachischisis and discordant renal dysplasia. The presence of parental consanguinity prompted reconsideration of recessive inheritance. The segregation ratio from 23 additional consanguineous cases was compared with that observed in 294 presumably nonconsanguineous families previously reported. Using classical segregation analysis, the segregation ratios in the non-sporadic cases were consistent with a major autosomal recessive locus in both populations.

Abortion, Spontaneous↗
PubMed1990

Genetic analysis of anthropometric measures in 11-year-old twins: the Medical College of Virginia Twin Study.

We have conducted a cross-sectional analysis of the genetic and environmental contributions to the variance of anthropometric measurements in children during early adolescence. Univariate path analysis was used to estimate the relative contributions of genes, individual environment, and family environment to measures of childhood obesity in 259 11-y-old Caucasian twin pairs. Triceps, subcapular, and suprailiac skinfold thicknesses, as well as waist circumferences, ht, and wt were measured in a standardized protocol. In this sample, a parsimonious model that included only additive genetic effects and environmental factors unique to the individual provided an adequate explanation for the variation in ht, wt, quetelet index, and subscapular and triceps skinfolds. In this largely preadolescent population, different magnitudes of genetic effects were seen in males and females for waist circumference, biiliac diameter, and suprailiac skinfold.

Anthropometry↗
PubMed1989

Univariate genetic analysis of blood pressure in children (the Medical College of Virginia Twin Study).

The relative contributions of genetic, individual environmental and shared environmental effects on resting blood pressure (BP) and heart rate (HR) were studied in prepubescent twins. The study population consisted of 251 caucasian 11-year-old twin pairs. Correlations were higher for all variables in monozygotic twins compared to dizygotic twins; this is consistent with a significant genetic effect. Path analysis revealed that the model of additive genetic and individual environmental effects fit systolic BP, diastolic BP and HR. In boys and girls, sex-specific genetic effects controlled systolic BP. The magnitudes of the sex-specific genetic effects on systolic BP were similar in both boys and girls and accounted for 66% of the variance. In boys, for diastolic BP, genetic effects accounted for 64% of the variance while in girls they accounted for 51%. These results provide no evidence for different genetic effects on HR in boys or girls. No shared environmental effects were detected. The large sample size and design, using different-sex dizygotic twins of the same age, establish that genes play an important role in the influence of resting BP and HR and that there are sex-specific genetic contributions in early pubertal children.

Blood Pressure↗
PubMed1989

Femoral duplication: a case report.

Femoral duplication is a rare anomaly that has been described as an isolated entity and in association with other congenital defects. Since the description by Erlich in 1885, 24 additional cases have been reported. The present report concerns a 34-week black female infant with apparent bilateral femoral duplication associated with a meningocele and abdominal, genitourinary, vertebral, and lower-limb anomalies. The cause is unknown. Femoral duplication is a developmental field defect, hence causally heterogeneous.

Abnormalities, Multiple↗
PubMed1989

Partitioned twin analysis: a power study.

Individual differences in the human genome may now be measured with molecular genetic techniques. Therefore, dizygotic (DZ) twins may be classified as sharing two, one, or zero "genes" identical by descent for any measured polymorphism. As a result, we may partition genetic variation into two sources: (i) genotypes at and closely linked to particular marker loci identified with restriction fragment length polymorphisms (RFLPs) and (ii) other genetic variation. The power of the classical twin study to reject false models lacking either a marker effect or a residual genetic effect is explored. Additivity of genetic effects at or near the locus and of the residual genetic variation as well as random environmental variation are assumed. Results indicate that statistical rejection of models could be achieved with sample sizes which are within the range of several current twin registers. A design including monozygotic (MZ) twins is compared with one consisting of only DZ twins. MZ twins add considerable power for the detection of residual genetic variation but provide no information to resolve genetic marker effects.

Computer Simulation↗
PubMed1989

An automated procedure for measuring biotinidase activity in serum.

In this automated procedure for quantifying biotinidase activity in human serum, a manual colorimetric method that measures conversion of the enzyme's artificial substrate N-biotinyl p-aminobenzoate was modified for use with a Technicon AutoAnalyzer II. The intra-run replicate precision (CV) was 2.1% and the day-to-day CV was 4.6% for quality-control sera. Results were linearly related to biotinidase activity in serum over the complete range of clinically relevant values, 0.2 to 11.0 U/L. Moreover, results of the automated assay were not significantly different from those of the manual assay. Because the automated procedure is faster and more precise, we recommend it for population-based studies and some screening studies.

Amidohydrolases↗
PubMed1988

Familial aggregation of congenital dislocation of the hip in a Norwegian population.

Previous studies of congenital dislocation of the hip have not used adequate control groups in estimating the level of genetic influence on that trait. Furthermore, it could not be demonstrated that alleged maternal effects were not an artifact of reporting bias. To that end, information was obtained on the presence of the anomaly in the families of adult twins and their spouses participating in the Norwegian Twin Registry. The prevalence odds ratio for having that disorder in first degree relatives was 10.0. Stratifying by class of relatives, the prevalence odds ratio was 8.1 for fathers, 35.8 for mothers, 12.7 for siblings, and 3.3 for offspring. The increased prevalence odds ratio for mothers over that of fathers suggests a maternal effect. Since both males and females reported on the anomaly for each parental type, it is unlikely that the difference in prevalence odds ratios is due to general reporting bias.

Diseases in Twins↗
PubMed1988

Seroepidemiology of cytomegalovirus and herpes simplex virus in twins and their families.

To determine the importance of intrafamilial transmission of cytomegalovirus and herpes simplex virus (types 1 and 2), the authors investigated the presence of immunoglobulin G antibody to one or both of these viruses in the sera collected between 1976 and 1985 from 1,115 members of 301 kinships from Virginia consisting either of juvenile twins and their parents or of adult twins, their spouses, and offspring. The sample included 486 children and 629 adults, aged 1-68 years. Among the 125 couples in whom the wives were seropositive, 78 (62%) of the husbands were found to be seropositive. Among 77 couples in whom the wives were seronegative, only 32 (42%) of the husbands were seropositive (p less than 0.01). Of 105 couples in whom the wives were seropositive for herpes simplex virus, 81 (77%) husbands were seropositive compared with 20 (47%) of 43 husbands with herpes simplex virus-seronegative wives (p less than 0.001). In families with cytomegalovirus-seropositive mothers, 54 (25%) of 213 children were seropositive for cytomegalovirus compared with 13 (8%) of 168 children in families with seronegative mothers (p less than 0.001). Childhood cytomegalovirus infections showed no association with infection in the father. In contrast, among families in which both parents were seropositive for herpes simplex virus, 48 (31%) of 156 children were seropositive compared with only two (4%) of 48 children without herpes simplex virus-seropositive parents (p less than 0.001). Among all siblings, there were strong associations for both herpes simplex virus and cytomegalovirus infections. These data are consistent with the venereal transmission of cytomegalovirus in married couples, provide evidence for the intrafamilial spread of herpes simplex virus, and confirm the importance of the maternal-child transmission of cytomegalovirus.

Adolescent↗