Anne‐Lise ‐L Børresen

Lp(a) phenotypes, other lipoprotein parameters, and a family history of coronary heart disease in middle aged males

In a study of 95 presumably healthy, 4CM2‐year‐old males from Northern Sweden, the Lp(a) phenotype distribution differed between those who had, and those who did not have one or more close relatives (parent or sib) with coronary heart disease. In the former group, 60% of the males were Lp(a+), as opposed to 28 % in the latter group. Thus, in the homogeneous population sample studied, analysis of the normal, inherited Lp(a) variation permitted the identification of distinct subpopulations, with respect to familial occurrence of coronary heart disease. None of a series of other parameters distinguished such sub‐populations.

Apparent influence of marker genotypes on variation in serum cholesterol in monozygotic twins

Ninety‐seven monozygotic (MZ) twin pairs were grouped by marker system genotypes, and mean intrapair differences in serum total cholesterol level were compared between groups. Significant differences were found when the MNSs and the Kidd blood group systems were considered. The results appear to suggest a restrictive effect of certain normal marker genes on environmentally caused variation in serum cholesterol level.

High density lipoprotein (HDL) polymorphisms in rabbit. I. A comparative study of rabbit and human serum high density lipoprotein.

Different classes of rabbit serum lipoprotein were prepared by ultracentrifugal flotation at densities 1·006, 1·063 and 1·21 g/ml. Agarose gel electrophoresis on rabbit whole serum and the serum fractions with different densities showed that this technique separates the different lipoprotein classes reasonably well.

Metachromatic leukodystrophy: Prenatal detection of arylsulphatase A deficiency

Amniocentesis and culturing of amniotic fluid cells were performed in the sixteenth week of two subsequent pregnancies in a woman who had previously given birth to two children with metachromatic leucodystrophy. On both occasions, amniotic fluid cells deficient in arylsulphatase A were found and the diagnosis was confirmed in the aborted fetuses.

Metachromatic leukodystrophy: Direct determination of arylsulphatase A activity in amniotic fluid

Very low arylsulphatase A (ARA) activity was found directly in amniotic fluid from two pregnancies where cultured amniotic fluid cells as well as cultured fibroblasts from the aborted fetuses were deficient in ARA. These observations differed significantly from parallel determinations of ARA activity in amniotic fluid, cultured amniotic fluid cells and cultured fibroblasts from the aborted fetuses in normal pregnancies

Deficiency of fumarylacetoacetase without hereditary tyrosinemia

A variant of the enzyme fumarylacetoacetase (FAH) (E.C.3.7.1.2) in healthy individuals, determined by the enzyme activity, is reported. Analysis of family members of probands with low FAH activity suggests that the enzyme variant causing low activity could be the product of a pseudodeficiency gene. Assumed homozygotes for this gene have only slightly higher enzyme activity than patients with the metabolic disorder hereditary tyrosinemia I (hepatorenal type). No clinical abnormalities have been found in association with the postulated gene.

PURIFICATION AND PARTIAL CHARACTERIZATION OF THE apoA‐I OF RABBIT HIGH DENSITY LIPOPROTEIN

Purfication of apoA‐I from rabbit high density lipoproteins (HDL) gave one single band in sodium dodecylsulphate‐polyacrylamide disc electrophoresis and reacted only with antiserum to apoA‐I. The molecular weight was about 25000. The amino acid composition of rabbit apoA‐I gave a difference index of 7.4 compared to human apoA‐I and of 6.5 compared to dog apoA‐I. Of the three carboxy terminal amino acid residues the rabbit protein has one in common with the dog.

Low density lipoprotein receptor activity in cultured fibroblasts from subjects with or without ischemic heart disease (in the absence of familial hypercholesterolemia)

Fibroblast strains from six subjects with ischemic heart disease (IHDs) were compared to strains from 43 subjects without a history of IHD (non‐IHDs), with respect to association (plasma membrane binding plus intracellular accumulation) and degradation of radio‐iodinated LDL (125I‐LDL). The subjects (25 females and 24 males) were selected on the criteria that they were twins (one from each pair), 58–61 years old, and living within 200 km of Oslo. None of them suffered from autosomal, dominant hypercholesterolemia, which is associated with reduced cell surface LDL receptor activity and increased susceptibility to IHD.

A twin study of aryl hydrocarbon hydroxylase (AHH) inducibility in cultured lymphocytes

Aryl hydrocarbon hydroxylase (AHH) inducibility was studied in cultured lymphocytes from 28 monozygotic (MZ) and 19 dizygotic (DZ) twin pairs. The results indicate that the induced level of AHH activity as well as inducibility (expressed as the ratio between levels in induced and non‐induced cells) are inherited. The best (h2) estimate of heritability is 0.7. There was no suggestion that non‐induced AHH activity level is an inherited trait. Inducibility of AHH was not normally distributed and the distribution observed in this limited series might even be trimodal. The results of the study appear to confirm previous reports that AHH inducibility is an inherited trait, and do not exclude the possibility that the major part of the variation is controlled by one locus.

HIGH DENSITY LIPOPROTEIN (HDL) POLYMORPHISMS IN RABBIT II. A STUDY OF THE INHERITED HI 1 AND R 67 ANTIGENS IN RELATION TO HDL POLYPEPTIDES

Rabbit high density lipoprotein (HDL) has been isolated by ultracentrifugation, delipidated by ether and ethanol, and treated with urea prior to separation of the different polypeptides by gel nitration. The two different genetic polymorphisms known in rabbit HDL were found to reside in two different polypeptides. This conclusion was reached in experiments where a quantitative radial immunodiffusion technique was employed. The results of polyacrylamide gel electrophoresis in SDS indicate that the H1 1 antigen resides in a polypeptide chain with a molecular weight of 40,000, whereas the R 67 antigen resides in a chain with a molecular weight of 17,000.