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Biomedical subjects

L Beckman

Publications and source records attributed to L Beckman.

At least 19 recordsLinked to original sources
PubMed1992

Idiopathic hemochromatosis and chromosomal damage.

Spontaneous and radiation-induced chromosome damage in cultured lymphocytes was examined in a pilot study of 11 patients with idiopathic hemochromatosis and matched controls. Increased frequencies of chromosome breaks were found in the patients, both spontaneously and after exposure to ionizing radiation, but the differences between patients and controls were not statistically significant (p greater than 0.05) when individual data were analyzed. When pooled (group) data for patients and controls were compared, significant increases in spontaneous and radiation-induced chromosome breaks were found among the patients. The results suggest that iron overload may lead to chromosome damage in idiopathic hemochromatosis.

Cells, Cultured↗
PubMed1992

DNA polymorphism of alkaline phosphatase isozyme genes: linkage disequilibria between placental and germ-cell alkaline phosphatase alleles.

The use of human placental alkaline phosphatase (PLAP) cDNA as a probe allows the detection and identification of restriction DNA fragments derived from three homologous genes, i.e., intestinal alkaline phosphatase (AP), germ-cell AP (GCAP), and PLAP. In previous RFLP studies we have reported linkage disequilibria between an RsaI and two PstI (a and b) polymorphic restriction sites and electrophoretic types of PLAP. In this report we present evidence that, in spite of the strong correlation with PLAP types, PstI(b) is an RFLP of GCAP. The data indicate close linkage between the PLAP and GCAP loci.

Alkaline Phosphatase↗
PubMed1991

Is the genotoxic effect of arsenic mediated by oxygen free radicals?

Previous investigations have shown that trivalent arsenic is inducing chromosomal aberrations and sister chromatid exchanges (SCEs). In a search for the genotoxic mechanism we have studied the effects of the oxygen-radical-scavenging enzymes superoxide dismutase (SOD) and catalase (CAT) on arsenic-induced SCEs in cultured human lymphocytes. The results indicate that SOD and possibly also CAT have a protective effect against arsenic-induced DNA damage. Arsenic, which is emitted in environmental pollutions e.g. from smelters and coal-fired power plants, appears to be underestimated as environmental mutagen and potential synergist to ionizing radiation.

Arsenic↗
PubMed1991

A new PstI restriction fragment length polymorphism (RFLP) of placental alkaline phosphatase. RFLP haplotypes and correlation with electrophoretic types.

A new PstI restriction fragment length polymorphism (RFLP) of placental alkaline phosphatase (PLAP) was discovered in a study of a Finnish population sample and designated PstI(b)1 or Pst(b)2 depending on the presence or absence of the cleavage site. The frequency of the PstI(b)2 allele was 0.24. This allele showed a positive (p = 3 x 10(-6) association with the electrophoretic allele 2(F) and a negative association (2 x 10(-7) with the electrophoretic allele 1(S). The previously described PstI RFLP [PstI(a)] was also found to be associated with electrophoretic types; the PstI(a)1 allele (presence of site) was associated with the electrophoretic type 2 (p = 0.023). Haplotype frequencies and disequilibria were calculated between PstI(a), PstI(b) and RsaI RFLPs. A complete disequilibrium (p = 1 x 10(-6) was found between PstI(a) and RsaI, whereas there was no significant disequilibrium between PstI(b) and RsaI. There was no strict correlation between the distances between the RFLP loci and the degree of linkage disequilibrium. The allele controlling the electrophoretic variant PLAP 18 (D) was found in polymorphic frequency (0.024) in the Finnish population.

Alkaline Phosphatase↗
PubMed1991

Population studies in northern Sweden. XVII. Estimates of Finnish and Saamish influence.

The North-Swedish population is a mixture of Finnish, Saamish and Central-Swedish ethnic groups. We have studied the Finnish and Saamish admixture by means of genetic markers in 23 North-Swedish subpopulations. The Finnish influence was estimated using the transferrin genes B0-1, DCHI and C3 and the enzyme gene SOD1*2, and markers for Saamish influence were the blood group gene ABO*A2, the serum group gene GC*1F and the enzyme gene 6PGD*C. In the subpopulations the Finnish influence (admixture) varied between 0 and 84% and the Saamish influence between 0 and 34%. The Saamish influence was strongest in the western and northern parts of the area. In the northern part of the area, between 1/4 and 1/3 of the gene pool of the present-day population may be Saamish in origin. The Finnish influence was strongest in the northern and northeastern parts of the area. In the subpopulations along the Finnish border, between 60 and 80% of the gene pool may be Finnish in origin. Significant correlations were found between the Saamish marker genes and between the Finnish marker genes. Due to geographical overlapping of Finnish and Saamish influence, significant correlations were also found between Finnish and Saamish marker genes. The geographical pictures of Saamish and Finnish influence in northern Sweden showed a fair agreement with the expectations derived from historical knowledge. Although a substantial part of the genetic heterogeneity of the North-Swedish population is ethnic in origin, it is obvious that founder effect and genetic drift also have played an important role.

Ethnicity↗
PubMed1991

GC serum groups and otosclerosis.

Five genetic serum protein marker systems (HP, TF, GC, BF and PI) were studied in patients with otosclerosis and in controls. The distributions of GC phenotypes and alleles showed significant differences between patients and controls with an excess of the IF-allele and the IF-variant among the patients.

Alleles↗
PubMed1990

Association of C3 and C4A complement types with familial amyloidotic polyneuropathy.

A mutant variant of the serum protein transthyretin (TTR-met30) appears to be a necessary but not sufficient condition for the development of familial amyloidotic polyneuropathy (FAP). We have studied a number of serum protein markers (alpha 1-antitrypsin, properdin factor B, C3, C4A, C4B, haptoglobin, transferrin and group-specific component) in FAP patients and healthy controls in an attempt to identify additional pathogenic factors which may influence the risk for developing FAP in male and female patients as well as the age of onset of the disease. Statistically significant associations were found in the complement systems C3 and C4A. The C3F variant was significantly increased in all FAP patients with a relative risk (RR) of 2.0, more pronounced in female patients (RR = 2.6) and patients with an early onset of the disease (RR = 4.5). In the FAP patients only the variants A3 and A4 were found in the C4A system. C4A3 was found in all patients, which was significantly higher than in the controls. The remaining serum protein systems showed no statistically significant associations with FAP. The results suggest that genetic variants of complement factors C3 and C4A may interact with the mutant TTR-met30 by modifying the expression and onset of FAP.

Age Factors↗
PubMed1990

Heterozygosity effects in studies of genetic markers and disease.

Examples were discussed where heterozygosity was associated with increased or decreased disease risks and where the apparent mechanism is direct functional involvement of gene products and not linkage disequilibrium. Special attention was paid to the impact of Hp (haptoglobin) heterozygosity on a number of different multifactorial disorders. When phenotype distributions in patients show large deviations from the Hardy-Weinberg equilibrium significant differences between patients and controls may be found concerning phenotype distributions but not with respect to the frequencies of alleles and phenotypic factors. The common method of studying ratios of phenotypic factors by pooling homo- and heterozygotes is in principle a conservative approach which tends to underestimate the strength of associations and to obscure heterozygosity effects. A significant deviation from the Hardy-Weinberg equilibrium in a marker system examined in a group of patients is in itself a sensitive indicator of phenotypic association with the disease in question.

Arthritis, Rheumatoid↗
PubMed1989

Impact of medical genetics on environmental medicine.

Medical genetics as a discipline has contributed basic knowledge of great applicability in environmental medicine, e.g. 1) the demonstration that environmental agents may cause chromosomal damage, 2) that chromosome aberrations are correlated with increased risks for cancer and spontaneous abortion, and 3) that the susceptibility to cyto- and genotoxic damage may be influenced by genetic factors. This paper discusses examples of applications of genetic knowledge in environmental medicine and areas for future research.

Chromosome Aberrations↗
PubMed1989

Correlation between RsaI restriction fragment length polymorphism and electrophoretic types of human placental alkaline phosphatase.

Restriction fragment length polymorphism (RFLP) of human alkaline phosphatases was studied in a population sample from northern Sweden using a placental alkaline phosphatase (PLAP) cDNA probe. After digestion of human genomic DNA with RsaI the Southern blots showed DNA fragments most probably derived from three genes: PLAP, germ cell alkaline phosphatase (PLAP-like) and intestinal alkaline phosphatase. In agreement with a previous study, a two-allele polymorphism was found in PLAP with bands at 1.6 kilobases (A1) and 1.8 kilobases (A2). The gene frequencies of A1 and A2 were 0.46 and 0.54, respectively. There was a significant correlation between the RsaI RFLPs and electrophoretic types of PLAP; RSAI A2 showed an association with the ALP2p allele of PLAP.

Alkaline Phosphatase↗
PubMed1989

Population studies in northern Sweden. XVI. GC subtypes.

The frequencies of group-specific component (GC) subtypes were studied in a population of 4,053 conscripts and blood donors from the counties of Västerbotten and Norrbotten in northern Sweden. The individuals were distributed according to place of birth into 23 subpopulations. A significant heterogeneity between the 23 regions was observed for the GC*1F, GC*1S and GC*2 genes, and clines were found for all genes. The frequency of the GC*1F gene was increasing in the northern direction, and the frequencies of the GS*1S and GC*2 genes were increasing in the southern direction. The geographical pattern of the GC*1F gene frequency could be explained in terms of Lappish influence.

Ethnicity↗
PubMed1988

Gc subtypes in Finns, Swedes and Swedish Lapps.

The group-specific component (Gc) subtypes were determined by isoelectric focusing and immunoblotting. The gene frequencies in the Swedish Lapps were Gc1F = 0.412, Gc1S = 0.367 and Gc2 = 0.221, which was significantly different from the frequencies found in Finns and in the populations of northern and central Sweden (p less than 0.001). The gene frequencies in the Swedish Lapps, although similar to those in Asiatic populations, are probably not reflecting an Asiatic influence, since the accumulated genetic information on the Swedish Lapps suggests that founder effect and genetic drift are to a large extent responsible for the peculiar gene pool of the original Lapp population.

Finland↗
PubMed1988

Serum protein markers in systemic lupus erythematosus.

Serum protein markers (alpha 1-AT, Bf, C3, C4A, C4B, Hp and Tf) were studied in a series of 36 patients with systemic lupus erythematosus (SLE) and compared to normal blood donors. In agreement with the results of previous investigations a significant increase of complement C4 deficiency was found among the SLE patients. The relative risks for AQ0 and BQ0 homozygosity were 7.2 and 4.1, respectively. Simultaneous occurrence of AQ0 and BQ0 was found in three patients with a calculated relative risk of about 65. A significant increase of the haptoglobin type 2-2 (p less than 0.05) was found among SLE patients. The remaining serum protein systems showed no statistically significant associations with SLE.

Blood Proteins↗
PubMed1988

Transferrin C2 and radiation-induced chromosomal damage.

Radiation-induced chromosomal damage (after exposure to 1 Gy) in lymphocytes was studied in relation to transferrin C subtype (C1 vs. C2). In 72-hour lymphocyte cultures a significantly increased frequency of cells with radiation induced aberrations was observed in individuals with the transferrin type C2. Thus the results lend some support to the hypothesis that transferrin C2 may act as an enhancer of chromosomal damage.

Chromosomes↗
PubMed1988

Population studies in northern Sweden. XIII. The 6-phosphogluconate dehydrogenase polymorphism.

Frequencies of the 6-phosphogluconate dehydrogenase (6-PGD) genes were studied in a series of 314 Finns from northern Finland and in a material of 4,348 conscripts and blood donors from the counties of Norrbotten and Västerbotten in northern Sweden. The Swedish individuals were distributed into 23 subpopulations according to place of birth. The frequency of the PGDC gene was comparatively high in Finns (5.3%) and showed significant variations between subpopulations (from 5.3 to 0.0%). The frequency of the PGDC gene showed a cline, with a decreasing gene frequency in the north-south direction. This geographical pattern could be explained in terms of Lappish and Finnish influence.

Gene Frequency↗
PubMed1988

Possible influence of major gene heterozygosity on variation of quantitative traits.

The possible explanations for heterosis and heterozygous advantage have included the hypothesis that the metabolic versatility of heterozygotes for functional alleles of structural genes would enhance resistance to environmental insult, i.e. would result in enhanced developmental homeostasis. Evidence on this hypothesis is conflicting. The paper presents additional evidence, based on four human polymorphisms and 9 quantitative traits in a sample of mother-offspring data from Sweden. These data do not support the hypothesis of interest. Reasons for the conflicting results are discussed.

Acid Phosphatase↗
PubMed1988

Population studies in northern Sweden. XIV. Variation of the A1A2B0 blood group gene frequencies.

Frequencies of the A1A2B0 blood group genes were studied in a material of 5,632 conscripts and blood donors from the counties of Norrbotten and Västerbotten in northern Sweden. The individuals were distributed according to place of birth into 23 subpopulations. In northern Sweden different clines were found for the A1, A2 and 0 genes. The frequencies of the A1 and A2 genes were increasing in the northeastern respectively northern direction, and the frequency of the 0 gene was increasing in the southwestern direction. These geographical patterns could be explained in terms of Finnish and Lappish influence.

ABO Blood-Group System↗