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Biomedical subjects

L Iselius

Publications and source records attributed to L Iselius.

At least 73 records · Page 4Linked to original sources
PubMed1986

Segregation analysis of balanced pericentric inversions in pedigree data.

The results of the recent European collaborative prenatal study suggested a segregation distortion of balanced pericentric inversions from carrier fathers but not carrier mothers (Boué & Gallano 1984). In an attempt to confirm these unexpected results, we examined 216 pedigrees with balanced pericentric inversions collected from three centers and from the literature. We were unable to detect any significant deviation from the expected 1:1 segregation of balanced pericentric inversions to normal karyotypes among the offspring of either carrier parent. To clarify the discrepancy between the studies, we reanalyzed the data from the prenatal study using all karyotyped individuals and, assuming conventional ascertainment rules, found a normal segregation pattern. We conclude that balanced pericentric inversions segregate normally in both males and females and that some retrospectively selected pedigrees were included as prospective in the prenatal study and this misclassification caused the apparent segregation distortion from carrier fathers.

Chromosome Inversion↗
PubMed1986

Changes in the incidence of Down syndrome in Sweden during 1968-1982.

A continuous increase in the incidence of Down syndrome in Sweden was noted during 1979-1981. This increase mainly occurred among children of younger mothers and was more pronounced for the males than for the females. There was no evidence of a significant seasonal variation, increased frequency of prematurely born children, or decrease in the number of cases aborted after prenatal diagnosis. An analysis of the whole 15-year period indicates that the incidence of Down syndrome has increased slowly in both sexes, and that there might have been a superimposed cyclic variation limited to the males.

Adult↗
PubMed1985

A family study of genetic and environmental factors determining polymorphic hydroxylation of debrisoquin.

Debrisoquin hydroxylation capacity determined as the ratio of debrisoquin to 4-OH-debrisoquin (DMR) in urine after a single oral dose (10 mg) was studied in 52 nuclear families comprising 226 subjects. The relative importance of genetic and environmental factors for DMR was studied by path analysis. There was a significant negative correlation between DMR and coffee intake but no significant correlations between DMR and sex, age, alcohol intake, or smoking habits. Path analysis showed that genetic heritability was 0.79 while cultural heritability was only 0.06. Complex segregation analysis gave evidence for a major locus with incomplete dominance (d = 0.28) between a recessive and an additive gene. The frequency of the major gene was 0.31, allowing an estimate of the frequency of slow hydroxylators in the Swedish population of 9.4%. There was also evidence for a multifactorial component accounting for 14% of the total variation. It was not possible to distinguish between the different genotypes within the rapid hydroxylator phenotype. Our data agree with previous studies in British and German populations showing that two alleles at a major autosomal locus can explain most of the observed variation in DMR. The frequency of slow hydroxylators in Sweden is very similar to that reported in other European studies. The debrisoquin metabolic phenotype seems to be extensively controlled by a monogenic system and not significantly influenced by environmental factors or age.

Administration, Oral↗
PubMed1985

Genetic and environmental determinants for lipoprotein concentrations in blood.

Path and segregation analyses have been performed on cholesterol and triglyceride contents of serum as well as on very low, low and high density lipoproteins in 78 Swedish nuclear families. The effect of environmental variables like alcohol and smoking on the concentrations of the different lipoproteins has been studied. Genetic heritability was 0.16-0.68 for the cholesterol fractions and 0-0.56 for the triglyceride fractions. No major gene was evident for any of the variables studied.

Adolescent↗
PubMed1985

Genetic regulation of the kinetics of glucose-induced insulin release in man. Studies in families with diabetic and non-diabetic probands.

Insulin release and sensitivity were estimated from glucose and insulin curves obtained at a glucose infusion test performed on altogether 601 subjects belonging to 155 nuclear families. Ascertainment was through one of the parents, and 96 of the probands had diabetes with clinical onset after the age of 30 years, while 59 were healthy subjects. Three variables obtained by a computer model were analysed, i.e. the glucose regulation of insulin release by a direct stimulatory event (KI) and time-dependent modulatory events (KP) as well as insulin sensitivity (KG). Complex segregation analysis revealed that the variables are genetically regulated, but there was no evidence for a major locus. The children of the diabetics did not differ from those of the non-diabetics as far as insulin release is concerned.

Age Factors↗
PubMed1985

Segregation and linkage analyses of 72 leprosy pedigrees.

Data on 72 families with multiple cases of leprosy were analyzed for a susceptibility gene linked to the HLA loci. We conducted segregation analysis with the program POINTER and identity of HLA types by descent analysis to determine the most likely mode of inheritance. We then conducted linkage analysis with the program LINKAS, first assuming linkage equilibrium and then allowing for linkage disequilibrium and etiological heterogeneity. Segregation results suggest a recessive mode of inheritance, especially for the tuberculoid forms of leprosy. The linkage results, limited to tuberculoid forms and assuming a recessive model, suggest a hypothesis of loose linkage with no unlinked locus. When an additive model is assumed, the best fit is obtained with a hypothesis of complete linkage (theta = 0.0) with heterogeneity. We currently favor the additive model as the more plausible one.

Disease Susceptibility↗
PubMed1985

Genetics and clinical significance of thyroxine binding globulin deficiency, an analysis of seven families.

Seven families, ascertained through probands with undetectable levels of thyroxine binding globulin (TBG) were studied from clinical and genetic points of view. The blood levels of TBG, thyroxine binding prealbumin (TBPA), thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) were determined in altogether 128 family members. The concentration of free thyroxine (FT4) was calculated from the concentrations of T4, TBG and TBPA. Only men (n = 15) were found to have total TBG deficiency. Their TSH levels were within normal range and they did not show any clinical symptoms of thyroid dysfunction. The mothers and daughters of the affected men had significantly lower TBG levels than control women. Segregation analysis performed on 46 nuclear families showed significant evidence for an X-linked additive mode of transmission and an additional multifactorial component with heritability 0.47.

Adolescent↗
PubMed1985

Resolution of genetic and cultural inheritance in twin families by path analysis: application to HDL-cholesterol.

A path model and associated statistical method for the analysis of data on twin families are introduced and applied to high density lipoprotein cholesterol (HDL-c) observations in the Swedish Twin Family Study. The proposed path model incorporates both genetic and environmental sources of familial resemblance, maternal environmental effects, intergenerational differences in heritabilities, marital resemblance due to either primary or secondary phenotypic homogamy, and twin residual environmental correlations. Application of the model to HDL-c levels resulted in parameter estimates consistent with those reported in earlier reviews and in the analysis of nuclear family and twin data. Genetic heritability was estimated as h2 = .363 +/- .243, cultural heritability as c2 = .187 +/- .082, and the proportion of phenotypic variance due to residual environmental effects as r2 = .450 +/- .207. Although the parameter estimates were comparable, the statistical tests of hypotheses were, relative to other designs, of low statistical power. It appears that environmental indices are necessary for powerful tests of hypotheses.

Analysis of Variance↗
PubMed1984

European collaborative study on prenatal diagnosis: mosaicism, pseudomosaicism and single abnormal cells in amniotic fluid cell cultures.

A report is given of the results of a European collaborative study on mosaicism, pseudomosaicism and single abnormal cells in amniotic fluid cell cultures. The mean frequency of cases with mosaicism was 0.10 per cent, with pseudomosaicism 0.64 per cent and with single abnormal cells 2.83 per cent in a series of 44 170 amniotic fluid samples. There was no significant difference between the colony (in situ) and the flask method with regard to the frequency of mosaicism. Pseudomosaicism and single abnormal cells were more frequent in cases studied with the flask method probably due to other factors than the method of cultivation of the cells. The frequency of maternal cell contamination was 0.17 per cent and the frequency of wrong sex assignment was 0.11 per cent. A more correct estimation is obtained if these frequencies are doubled. There was a considerable variation between laboratories with regard to the frequencies given above. One reason for this variation is that there are no sharp limits between mosaicism, pseudomosaicism and single abnormal cells. Thus the material contained cases diagnosed as having pseudomosaicism which turned out to be mosaics at birth and to have an abnormal phenotype. These cases were very rare but pose a definite problem in prenatal cytogenetic diagnosis.

Amniotic Fluid↗
PubMed1984

The mode of inheritance of psoriasis: evidence for a major gene as well as a multifactorial component and its implication for genetic counselling.

Complex segregation analysis of Lomholt's family data on psoriasis on the Faroe Islands gave evidence for an additive major gene with gene frequency of 0.07 and penetrance 0.12 and 0.44 in the heterozygote and in the homozygote, respectively. In addition, there was a multifactorial component with heritability 0.87. The implications of these findings for genetic counseling are discussed and analytical risk figures are presented for chosen pedigrees.

Age Factors↗
PubMed1984

A twin study of sister chromatid exchanges in human lymphocytes following carcinogen exposure and DNA repair incubation.

Sister chromatid exchanges (SCEs) were analyzed in peripheral lymphocytes obtained from nine healthy monozygotic (MZ) and nine healthy dizygotic (DZ) pairs of male twins. In addition, increases in SCE rates following in vitro treatment of whole blood with 100 microM N-acetoxy-2-acethylaminofluorene (NA-AAF), and after an 18-h DNA repair incubation period, were analyzed in the same twins. There was no significant intrapair difference in the variance of SCE frequencies among MZ and DZ twins at the baseline level, after NA-AAF treatment, or after a DNA repair incubation period. It was concluded that genetic factors probably do not contribute significantly to the individual variation that has been observed in baseline or NA-AAF-induced SCE rates. Thus, any observed alterations in SCE frequencies are probably caused by environmental influences.

2-Acetylaminofluorene↗
PubMed1983

The 11q;22q translocation: a collaborative study of 20 new cases and analysis of 110 families.

Following a previous collaborative study (Fraccaro et al. 1980), 20 new cases of 11q;22q translocation are described. Twelve families were ascertained through an unbalanced carrier of the translocation and eight cases were ascertained as balanced carriers. A segregation analysis was performed on the 110 families so far published. It was concluded that the 11q;22q translocation is a relatively frequent event, and that all the cases thus far reported might have the same breakpoints at 11q23.3 and 22q11.2. The translocation seems to be independent of environmental factors and it seems to have a low rate of mutation as indicated by the scarcity of de novo cases. The new data confirmed that only one type of unbalanced karyotype (47,XX or XY+der(22)t(11;22)(q23.3;q11.2)) is found among the offspring of the translocation carriers. The minimal overall recurrence risk for an unbalanced translocation was estimated to 2%. There was no difference between the recurrence risks for male and female balanced carriers, while the trend was confirmed of an excess of female balanced carriers among the phenotypically normal offspring of the t(11;22) female carriers.

Abnormalities, Multiple↗
PubMed1983

Family study of genetic and environmental factors determining the protein binding of propranolol.

The unbound fraction of propranolol was found to vary from 1.9 to 13.2% in 434 plasma samples from members of 132 families. As expected, there was a linear correlation between the ratio of bound/unbound propranolol and the orosomucoid concentration (r = 0.67, P less than 0.001). Albumin concentration did not influence propranolol binding. The unbound fraction was negatively correlated with obesity and alcohol intake, but was not significantly influenced by age and sex. By applying path analysis, 21% of the variability in propranolol binding could be ascribed to genetic factors and 5% to common environmental factors.

Adult↗
PubMed1983

Genetic and environmental determinants of cholesterol and HDL-cholesterol concentrations in blood.

Serum cholesterol and HDL-cholesterol have been studied in 274 Swedish nuclear families. The families were ascertained through the Swedish twin registry and consisted of married mono- and dizygous twins, their spouses and with at least one adult child. Total cholesterol was determined using an enzymatic colorimetric method and HDL-cholesterol by the heparin-manganese chloride precipitation method. The genetic analysis was performed using a path analytic model to resolve genetic and cultural heritability, marital correlations and maternal effects. Genetic heritability was 0.50 and 0.37 for total cholesterol and HDL-cholesterol, respectively. Cultural heritability was small, 0.04, for cholesterol but substantial 0.22, for HDL-cholesterol. A maternal effect was evident for cultural inheritance for HDL-cholesterol but not for cholesterol.

Adult↗