Search PubMed⌕ Search

Biomedical subjects

M L Olsson

Publications and source records attributed to M L Olsson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Heterogeneity of the blood group Ax allele: genetic recombination of common alleles can result in the Ax phenotype.

The Ax phenotype is an important subgroup of the ABO blood group system. Its inheritance does not always follow Mendelian rules and recent studies suggested that different alleles can result in this phenotype. This suggestion has been explored by cloning and sequencing exons 6 and 7 of the ABO gene and the intervening intron from members of six unrelated families expressing the Ax phenotype. Two families showed the previously described T646A 'Ax' mutation as the only deviation from the consensus A1 allele. In two other families the Ax phenotype was inherited as two different recombinational gene products. Combination of exon 6 derived from A or B/O2 alleles with exon 7 from the O1v allele created two novel alleles that have four O1v-characteristic nucleotide substitutions in exon 7, including T646A. Sequencing and analysis of polymorphisms in intron 6 defined the crossing-over zones of these hybrid alleles. Southern blot confirmed the hybrid formation by detecting ABO-related polymorphisms approximately 1.35 kb downstream from the ABO reading frame. The remaining two families expressed the Ax phenotype via an allele having A2-specific mutations. Thus, a heterogeneous molecular background leads to the serologically defined Ax phenotype and may well explain the different modes of inheritance observed.

ABO Blood-Group System↗
PubMed1998

A clinically applicable method for determining the three major alleles at the Duffy (FY) blood group locus using polymerase chain reaction with allele-specific primers.

BACKGROUND: The clinically significant antigens of the Duffy (Fy [FY]) blood group system are expressed on the red cell form of the FY glycoprotein, a promiscuous chemokine receptor and also a receptor for malarial parasites. After the cloning of cDNA coding for FY glycoprotein, the molecular basis of the three major alleles (Fya/Fyb/Fy) has been established. Because of the mistyping of the silent Fy allele as Fyb, the error rate of current genotyping methods is high in black populations. STUDY DESIGN AND METHODS: Two hundred blood donors (European whites and African Blacks) and some amniotic DNA samples were investigated by a new allele-specific primer polymerase chain reaction technique. Sense primers corresponding to normal and GATA-1-mutated FY gene promoter region sequences were combined with antisense primers discriminating the Fya/Fyb polymorphism. RESULTS: Complete correlation between FY phenotypes and genotypes was obtained in all samples studied, although, in two whites and one black, serology showed weak Fyb expression while polymerase chain reaction indicated a Fyb allele. Gene frequencies were calculated. CONCLUSION: This simple and rapid polymerase chain reaction method was shown to detect the three common alleles at the FY locus in two representative ethnic populations. Its future use as an independent technique in red cell FY investigations and for fetal genotyping in hemolytic disease of the newborn is predicted.

Alleles↗
PubMed1998

Heterogeneity of the O alleles at the blood group ABO locus in Amerindians.

BACKGROUND AND OBJECTIVES: Amerindians are blood group O, but the distribution of the various O alleles is unknown. Their ABO genotypes were compared with samples from other Brazilian ethnic groups. MATERIALS AND METHODS: Genomic DNA was examined by PCR-RFLP analysis, PCR-SSP and direct sequencing. RESULTS: An unusual allele distribution was found, with 91% of the O alleles being O1variant. Almost half of these alleles had an additional novel mutation (G542A), which was also detected in a few other Brazilian and European samples. The O alleles correlated completely with ABO-related haplotypes previously determined by Southern blot. CONCLUSION: The three Amerindian tribes represent a homogeneous (ABO blood group) population, except for the G542A mutation. The presence of this mutation in all other populations examined suggests that it originated before the migration of man into America.

ABO Blood-Group System↗
PubMed1998

Different genotypes causing indiscernible patterns of A expression on A(el) red blood cells as visualized by scanning immunogold electron microscopy.

BACKGROUND AND OBJECTIVES: The published sequence of the weak. A subgroup Ael gene from Swedish individuals showed a G insertion in exon VII, causing a frameshift at codon 268 (the A1 gene has 353 codons). We wished to sequence exons VI and VII of two Norwegian Ael individuals and compare the expression of A substance on RBC from different Ael individuals. MATERIALS AND METHODS: Exon VI and VII were amplified by PCR, cloned in M13 and sequenced. A structure expression on Ael RBC was studied by the immunogold technique. RESULTS: In contrast to the Swedish Ael individuals, the two Norwegians had consensus A1 sequences in exon VI and VII. However, the patterns of A expression were indiscernible from the Swedish cases as visualized by immunogold labeling in SEM. In both cases, a few (1-2%) RBC were very strongly labeled, some were weakly labeled and the majority (95%) were unlabeled. CONCLUSION: Although some Ael individuals have an inserted nucleotide in exon VII of the ABO gene, others have consensus A1 sequence in exon VI and VII. However, we could not find any differences in phenotype by immunogold labeling in SEM.

ABO Blood-Group System↗
PubMed1997

Molecular analysis of the O alleles at the blood group ABO locus in populations of different ethnic origin reveals novel crossing-over events and point mutations.

The blood group ABO genotypes of 138 group O individuals with three different ethnic origins in Brazil were determined, including Whites, Blacks and Amerindians. Several previously undescribed O alleles were found, predominantly in the Black group, in which about a third of the samples did not conform to previously known O allele structures. It has been well documented for the first time that some new alleles can arise from crossing-over events between known alleles in the ABO system. This was made possible by both restriction endonuclease analysis and direct sequencing of exons 3-7 in the ABO gene. The anticipated relatively high frequency of some of these new alleles in certain populations, necessitates great care when interpreting results from existing genotype screening methods.

ABO Blood-Group System↗
PubMed1996

Evidence for a new type of O allele at the ABO locus, due to a combination of the A2 nucleotide deletion and the Ael nucleotide insertion.

Using a recently introduced multiplex polymerase chain reaction and restriction fragment length polymorphism ABO genotype screening method we have found an anomalous ABO genotype (A2O1variant) not correlating with the serological phenotype (blood group O). The blood group was confirmed by absorption/elution and detection of blood group substances in saliva. Sequencing of exons 6 and 7 in the ABO genes of the propositus indicated an A2 gene (C467T and C1060-) apparently inactivated by the same single nucleotide insertion recently reported in individuals with the ABO subgroup Ael. Investigation of relatives confirmed the inheritance of this new inactive hybrid allele.

ABO Blood-Group System↗
PubMed1996

Polymorphisms at the ABO locus in subgroup A individuals.

BACKGROUND: The common ABO allele sequences are known, but little or no genetic information is available on the rare but important A subgroups. STUDY DESIGN AND METHODS: Blood group ABO polymorphism was analyzed in genomic DNA from 45 rare subgroup A individuals by sequence-specific primer polymerase chain reaction and amplified fragment length polymorphism investigating exons VI and VII in the ABO genes. These methods are used to detect specific mutations only, and not all changes that might be present can be detected. ABO genotypes discriminating six alleles (A1, A2, B, O1, O1var, and O2) were determined. RESULTS: The C-->T substitution at nucleotide position 467 (C467T) is not restricted to A2 and cis-AB individuals, but was found also in some A subgroups. Detection of the functionally more relevant C1060-single-point deletion in A2 was accomplished by a novel sequence-specific primer polymerase chain reaction approach. A 100-percent correlation between the C467T and the C1060-mutations was found. Fifteen of 17 samples showing the T646A mutation (described earlier in one case of Ax) showed a positive correlation with the C771T mutation in a frequently occurring O1var allele. The two exceptions were defined serologically as Ax. CONCLUSION: Indications have been found of an evolutionary relationship between A1 alleles and Ael and A3 subgroups as well as between A2 alleles and Aend and Aweak subgroups. Genetic heterogeneity within the Ax and Aint subgroups was also seen.

ABO Blood-Group System↗
PubMed1996

Frequent occurrence of a variant O1 gene at the blood group ABO locus.

Blood group ABO polymorphism was analysed in genomic DNA isolated from 150 blood donors by restriction endonuclease digestion of three polymerase chain reaction-amplified exons in the ABO genes and by sequencing of randomly selected samples. An anomalous O1 allele first described in a cancer cell line is now shown to account for approximately 40% of the O alleles described to date. This is 10 times more frequent than the only other known variant O allele (O2). This variant O1 allele has at least seven point mutations when compared to the consensus gene, in addition to the deletion characterising the normal O1 allele.

ABO Blood-Group System↗
PubMed1995

An Ael allele-specific nucleotide insertion at the blood group ABO locus and its detection using a sequence-specific polymerase chain reaction.

Genomic DNA from each of four Acl individuals (genotypes AO1, AO1var, AO2) and one AclB individual was used as a template for amplifying exons 6 and 7 of the ABO genes, which were subsequently sequenced. In all the Ael alleles a single nucleotide insertion, compared to the A consensus sequence, was observed that would alter the amino acid sequence of the glycosyltransferase immediately after its postulated nucleotide sugar binding site and furthermore extend the translated protein by 37 amino acids (16 more than the A2 enzyme). A sequence-specific primer PCR assay was developed to detect the nucleotide insertion. It was possible to differentiate all 20 serologically defined Acl/AclB individuals available from 145 blood donors with normal ABO phenotypes and genotypes and 26 individuals with various A subgroups other than A1, A2 and Acl. This mutation explains the Acl phenotype and forms the basis of a method for detecting the Ael allele.

ABO Blood-Group System↗
PubMed1995

A rapid and simple ABO genotype screening method using a novel B/O2 versus A/O2 discriminating nucleotide substitution at the ABO locus.

An ABO genotype screening method discriminating the common alleles A1, A2, B, O1 and O2 at the ABO locus was made possible by the discovery of a novel nucleotide substitution (G1096A) present only in B and O2 alleles. A rapid and reliable single-tube approach using multiplex PCR with four primers amplifying exons 6 and 7 of the ABO genes followed by simultaneous addition of two restriction enzymes was developed and validated in a population of 150 Swedish blood donors. This technique is the most cost-efficient and informative ABO genotyping method reported to date.

ABO Blood-Group System↗
PubMed1991

Islet cell antibody reactivity with human fetal pancreatic islets.

To evaluate the possibility of autoimmune processes against pancreatic islets in fetal life, we tested islet cell antibody (ICA) reactivity with 14 fetal pancreata obtained after abortion at the 15th up to the 19th week of gestation. Pancreatic islets positive for a monoclonal proinsulin antibody but non-reactive with ICA negative control serum were found in 9/14 pancreata and all (9/9) of them showed a positive reaction with the ICA standard. It is concluded that ICA reactivity may be detected in fetal human pancreata. Further studies on fetal islet cell antibody reactivity in the development of insulin dependent diabetes mellitus (IDDM) are warranted.

Autoantibodies↗
PubMed1991

Characterization of monoclonal anti-alpha 1-microglobulin antibodies: binding strength, binding sites, and inhibition of lymphocyte stimulation.

Eleven monoclonal antibodies (MoAb) directed against the immunoregulatory plasma glycoprotein alpha 1-microglobulin were characterized. The MoAb were produced in mice immunized with a mixture of alpha 1-microglobulin homologues from man, guinea pig, rat and rabbit. Using radioimmunoassay, western blotting, affinity chromatography, and Scatchard analysis, the affinities and binding sites of the MoAb were analysed. All antibodies were more or less cross-reactive, but most showed a major specificity for one or two of the alpha 1-microglobulin homologues. None of the antibodies was directed against the carbohydrate moiety of alpha 1-microglobulin. Six of the MoAb had high affinity for the antigen and four of these were directed towards the same part of the molecule though differing in their species specificity. Five showed lower affinity for the antigen and were mainly directed towards epitopes on other parts of the molecule. Only some of the antibodies could block the proliferation of lymphocytes induced by human alpha 1-microglobulin. The blocking efficiency of the different antibodies was similar when tested on the stimulation of human or mouse lymphocytes, suggesting that the same part of the alpha 1-microglobulin molecule is responsible in both species. The magnitude of blocking by the different MoAb was not related to their affinities, emphasizing the importance of where on the alpha 1-microglobulin molecule, rather than how strongly, they bind. The binding of the strongest blocking antibody was shown to be directed to a C-terminal peptide of rat alpha 1-microglobulin, indicating that this part of alpha 1-microglobulin is important for the mitogenic effects. Thus the panel of anti-alpha 1-microglobulin MoAb should be a valuable tool for structural and functional studies of alpha 1-microglobulin.

Alpha-Globulins↗
PubMed1991

Gingival fluid and tissues around successful titanium and ceramic implants. A comparative clinical, laboratory, and morphologic study.

The gingival tissue reactions around 19 titanium implants (Brånemark System) and 6 ceramic implants (Frialit) were studied by using established variables for monitoring periodontal status. Natural teeth in the same or the opposite jaw served as controls. Both clinical and laboratory examinations showed healthy gingival status. No differences in soft-tissue reactions between the two types of implant or between the implants and the natural teeth were registered.

Adult↗
PubMed1990

Alpha 1-microglobulin is mitogenic to human peripheral blood lymphocytes. Regulation by both enhancing and suppressive serum factors.

Human alpha 1-microglobulin (alpha 1-m), a 26 kilodalton serum glycoprotein, was found to exert mitogenic effects on human peripheral blood lymphocytes (PBL) in serum-free medium. Purified T cells, but not B cells, responded with proliferation to alpha 1-m, but only in the presence of monocytes. The mitogenic activity could be partially neutralized by a mouse monoclonal antibody against alpha 1-m. The mitogenicity was species-specific, since alpha 1-m homologues from rats, guinea pigs and rabbits had no effect on human PBL. In a previous study, no effect of alpha 1-m was seen on PBL in the presence of 20% serum, and, therefore, we studied the influence of different concentrations of serum on the alpha 1-m-induced mitogenicity. Thus, human serum enhanced the mitogenic effects of alpha 1-m on human PBL at 1% concentration (v/v) and suppressed the effects at 10%. The suppressing effect of serum at 10%, but not the enhancing effect at 1%, seemed to be conserved among several species. To test the effect of serum proteins of different molecular sizes, human autologous serum was separated by gel chromatography on Sephadex G-200 into four fractions. Fractions 1 and 2 (roughly containing proteins larger than 100 kilodaltons) suppressed the mitogenic effects of alpha 1-m, while fractions 3 and 4 enhanced the stimulation by alpha 1-m, at 0.5% and concentrations above. It is concluded that the mitogenic effect of alpha 1-m on lymphocytes is regulated by several serum factors, both enhancing and suppressive, that does not have any proliferative effect of their own. It can be speculated that the balance between enhancing and suppressing co-factors in the blood determines the degree of the stimulation of lymphocytes by alpha 1-m. This is compatible with an immunomodulatory role for alpha 1-m, in spite of its relatively constant plasma levels in health and disease.

Alpha-Globulins↗
PubMed1990

Late age at first full-term pregnancy as a risk factor for women with malignant lymphoma.

Women with malignant lymphoma, non-Hodgkin's lymphoma and Hodgkin's disease were of a significantly later age at first full-term pregnancy (AFFP) than controls without malignant disorders. The odds ratio (OR) of having the first pregnancy at 30 years of fertility was 6.4 for women with malignant lymphoma. This ratio was higher than the ratio of 3.9 in a group of breast cancer patients. A low parity in the lymphoma group enhanced the risk associated with a late AFFP.

Adolescent↗
PubMed1988

Characterization of human salivary beta-N-acetyl-D-glucosaminidase (NAGase).

NAGase activity was studied in mixed whole, parotid, and submandibular saliva. The maximum activity of NAGase was found to be at pH 5.0. NAGase activity varied considerably among the subjects. The data indicated that a large portion of NAGase activity originates from oral microorganisms. NAGase activity was greatly reduced after heating for 45 min at 50 degrees C. The residual activity after storage at -20 degrees C was higher than the original activity. The enzyme activity was markedly diminished after the addition of Sn++ and Ag+ ions, while no activity was detected after the addition of Hg+ ion.

Acetylglucosaminidase↗