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  • 1
    ISSN: 0888-7543
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Human genetics 〈Berlin〉 14 (1972), S. 142-150 
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Das durch Ultrazentrifugation und Gelfiltration and Sepharose 4 B isolierte Lp(a)-Lipoprotein des menschlichen Serums zerfällt spontan oder nach milder Behandlung mit Detergentien in mehrere Komponenten: 1. Ein Lipoprotein mit den Eigenschaften der LDL2; 2. einen lipidfreien Proteinkomplex, der immunologisch mit Anti-Lp(a)-Antiseren reagiert; 3. Albumin und 4. zwei weitere Proteinkomponenten, die auch in gealterten LDL2-Präparationen beobachtet wurden, die aber hier nicht weiter charakterisiert wurden. Der Lp(a)-positive Proteinanteil konnte von allen anderen Bestandteilen durch Chromatographie an Hydroxylapatit abgetrennt werden. Es wird geschlossen, daß das Lp(a)-Lipoprotein ein komplexes Protein darstellt, das aus LDL2-Lipoprotein, dem Lp(a)-Protein und möglicherweise Albumin zusammengesetzt ist.
    Notes: Summary Lp(a)-lipoprotein of human serum, when isolated by ultracentrifugation and gelfiltration on Sepharose 4 B, may disaggregate into several components either spontaneously or by mild treatment with detergents: 1. A lipoprotein with characteristics of LDL2; 2. a lipid-free protein complex, which reacts immunologically with anti-Lp(a)-sera; 3. albumin and 4. two other protein components, which were also observed in aged LDL2-preparations and have not been characterized further. The Lp(a)-positive protein moiety could be separated from all other components by chromatography on hydroxyl-apatite. It is concluded that the Lp(a)-lipoprotein represents a complex protein composed of LDL2-lipoprotein, the Lp(a)-protein moiety, and possibly albumin.
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Apolipoprotein(a) [apo(a)] exhibits a genetic size polymorphism explaining about 40% of the variability in lipoprotein(a) [Lp(a)] concentration in Tyroleans. Lp(a) concentrations and apo(a) phenotypes were determined in 7 ethnic groups (Tyrolean, Icelandic, Hungarian, Malay, Chinese, Indian, Black Sudanese) and the effects of the apo(a) size polymorphism on Lp(a) levels were estimated in each group. Average Lp(a) concentrations were highly significantly different among these populations, with the Chinese (7.0mg/dl) having the lowest and the Sudanese (46mg/dl) the highest levels. Apo(a) phenotype and derived apo(a) allele frequencies were also significantly different among the populations. Apo(a) isoform effects on Lp(a) levels were not significantly different among populations. Lp(a) levels were however roughly twice as high in the same phenotypes in the Indians, and several times as high in the Sudanese, compared with Caucasians. The size variation of apo(a) explains from 0.77 (Malays) to only 0.19 (Sudanese) of the total variability in Lp(a) levels. Together these data show (I) that there is considerable heterogeneity of the Lp(a) polymorphism among populations, (II) that differences in apo(a) allele frequencies alone do not explain the differences in Lp(a) levels among populations and (III) that in some populations, e.g. Sudanese Blacks, Lp(a) levels are mainly determined by factors that are different from the apo(a) size polymorphism.
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  • 4
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Lipoprotein(a) [Lp(a)] is a quantitative trait in human plasma. Lp(a) consists of a low-density lipoprotein and the plasminogen-related apolipoprotein(a) [apo(a)]. The apo(a) gene determines a size polymorphism of the protein, which is related to Lp(a) levels in plasma. In an attempt to gain a deeper insight into the genetic architecture of this risk factor for coronary heart disease, we have investigated the basis of the apo(a) size polymorphism by pulsed field gel electrophoresis of genomic DNA employing various restriction enzymes (SwaI, KpnI, KspI, SfiI, NotI) and an apo(a) kringle-IV-specific probe. All enzymes detected the same size polymorphism in the kringle IV repeat domain of apo(a). With KpnI, 26 different alleles were identified among 156 unrelated subjects; these alleles ranged in size from 32kb to 189kb and differed by increments of 5.6kb, corresponding to one kringle IV unit. There was a perfect match between the size of the apo(a) DNA phenotypes and the size of apo(a) isoforms in plasma. The apo(a) DNA polymorphism was further used to estimate the magnitude of the apo(a) gene effect on Lp(a) levels by a sib-pair comparison approach based on 253 sib-pairs from 64 families. Intra-class correlation of log-transformed Lp(a) levels was high in sib-pairs sharing both parental alleles (r = 0.91), significant in those with one common allele (r = 0.31), and absent in those with no parental allele in common (r = 0.12). The data show that the intra-individual variability in Lp(a) levels is almost entirely explained by variation at the apo(a) locus but that only a fraction (46%) is explained by the DNA size polymorphism. This suggests further heterogeneity relating to Lp(a) levels in the apo(a) gene.
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  • 5
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Apolipoprotein(a) [apo(a)] contains a variable number of identical (K-IV A/B) or nearly identical (K-IV 1, K-IV 30–37) kringle repeats that are homologous to K-IV from plasminogen. The sizes of 414 apo(a) alleles were determined by pulsed-field gel electrophoresis (PFGE) of KpnI-digested DNA. Furthermore, sequence variation in the apo(a) K-IV 30–37 domain was analysed. Reverse transcription/polymerase chain reaction (RT-PCR) cloning of human liver poly A+ RNA followed by sequencing revealed a single nucleotide exchange in the ultimate K-IV (K-IV 37) of apo(a) (codon 4168); this results in an ATG (Met) to ACG (Thr) substitution. A PCR-based restriction assay of genomic DNA demonstrated that this substitution represents a common polymorphism. In 231 unrelated Tyroleans, the frequencies for the K-IV 37 Thr and K-IV 37 Met alleles were 0.66 and 0.34, respectively. The phase between the K-IV 37 Met/Thr and the KpnI size polymorphism was determined for 224 alleles. A significant linkage disequilibrium was detected between the sequence and size polymorphisms of apo(a). K-IV 37 Met was significantly associated with KpnI allele no. 18 (D AB= 0.0267 + 0.0101; χ2 = 10.09, df = 1). The Met/Thr polymorphism was further used to test whether deletions or duplications of K-IV 37 occur frequently in the apo(a) gene. Some 40 apo(a) alleles, 22 of which were from subjects that appeared to be double heterozygotes for K-IV repeat number and the Met/Thr variation were separated by PFGE and analysed for the 4168 Met/Thr polymorphism. The Met and Thr sequences were always present on different size alleles and no evidence for a duplication or deletion of K-IV 37 was obtained. This suggests that the copy number of K-IV 37 is invariable, in contrast to the highly variable K-IV A/B domain of the gene. The 4168 Met/Thr polymorphism had no effect on Lp(a) concentration, neither did it influence the lysine-binding property of the Lp(a) particle.
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  • 6
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lipoproteins from two sibs with familial lecithin-cholesterol-acyltransferase(LCAT)-deficiency were further characterized. Comparatively lipoproteins from patients with secondary LCAT-deficiency were studied. Both groups of patients had particles of unusual size and shape in the α1-(HD-2)-lipoprotein subfraction. The abnormal HDL-2 particles were disk-like in appearance with a major axis of about 180 Å and a minor axis of about 40 Å and tended to aggregate into long coinlike stacks. The abnormal HDL-2 particles contained the normal protein constituents of HDL Apo A-I, Apo A-II and Apo C but in addition a major polypeptide with a M.W. of 39 000 not seen in significant amounts in normal high-density-lipoproteins. This polypeptide was found identical in size, isoelectric focusing and immunochemically with an arginine-rich normal polypeptide constituent of very-low-density-lipoproteins designated apoprotein E. Presence of this protein marker in the HDL allowed the specific immunological detection of the abnormal HDL-2 (LP-E) in plasma. Further minor biochemical abnormalities were observed in the lipoproteins of the patients with familial LCAT-deficiency. However, the main protein constituents of their HDL, the Apo A, Apo C and Apo E polypeptides, were found to be identical electrophoretically and by analytical isoelectric focusing with their normal counterparts. The data suggest that the basic genetic defect in the hereditary disease leads to a deficient activity of the LCAT-enzyme and that all abnormalities in the lipoprotein spectrum are secondary.
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  • 7
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The frequencies of genetic apo E isoforms E2, E3 and E4 were determined in 523 patients with myocardial infarction and compared to those in a control group (1031 blood donors). A significant difference in the frequency of apo E4 was noted between patients and controls (0.05〉 P〉0.025). No differences in the frequencies of isoforms E3 and E2 were observed. In particular, there was no significant difference between the two groups in the frequency of apo E2 homozygosity. a condition that is associated with type III hyperlipoproteinemia. However, all E2 homozygote survivors of myocardial infarction had hyperlipoproteinemia type III (cholesterol 269±29 mg/dl; triglyceride 419±150 mg/dl; age 54±14 years; N=5). On the contrary, E2 homozygote controls (all apo E-2/2 blood donors and their apo E-2/2 relatives who were from the same age range as the patients) had primary dysbetalipoproteinemia but normal or subnormal plasma cholesterol concentrations (cholesterol 184±28 mg/dl; triglyceride 151±52 mg/dl; age 56±13 years; N=11). This indicates that E2 homozygotes with hyperlipoproteinemia type III who occur rarely in the population but comprise about 1% of myocardial infarction patients have a markedly increase risk for coronary atherosclerosis, whereas the risk for E2 homozygotes with normal or subnormal plasma cholesterol (=primary dysbetalipoproteinemia) may be considerably lower than for the general population. The data illustrate the complex relationship between apo E genes, lipid levels, and risk for atherosclerosis.
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  • 8
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Apolipoprotein E phenotypes were determined in 361 patients with hyperlipidemia and in controls. The E2 isoform was significantly more frequent in the group of hyperlipidemics (P〈0.0005). This was not due to a higher frequency of E-2/2 homozygotes with type III hyperlipoproteinemia, but rather to a significantly higher frequency of E2 heterozygotes (P〈0.0005). Subgrouping of hyperlipidemics into patients with a) hypertriglyceridemia, b) hypercholesterolemia and c) mixed hyperlipidemia revealed i) that isoform E2 was significantly more frequent in patients with hypertriglyceridemia (0.001〉P〉0.005), ii) that isoform E4 was significantly more frequent in patients with hypercholesterolemia (0.01〉P〉0.005) and iii) that isoforms E2 (P〉0.005) and E4 (0.05〉P〉0.025) were both more frequent in patients with mixed hyperlipidemia. Roughly 20% of patients with mixed hyperlipidemia had one of the rare phenotypes E-4/4,-4/2 or-2/2. We conclude that alleles ε2 and ε4 both contribute to the susceptibility for, and/or phenotypic expression of hyperlipidemia. Whereas the gene ε2 seems to exert its influence on plasma lipoproteins by an abnormal gene product (E2) that has reduced binding activity to lipoprotein receptors, the mechanism underlying the association of the ε4 gene with hyperlipidemia is presently unclear.
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  • 9
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Unter Anwendung verfeinerter Trennverfahren wurde das β-Lp(a+)-Lipoprotein des menschlichen Serums in immunologisch und elektrophoretisch reiner Form dargestellt. Es wurde hinsichtlich seiner Lipidzusammensetzung analysiert und mit ebenfalls immunologisch und elektrophoretisch rein erhaltenen β-Lp(a-)- und α1-Lipoproteinen verglichen.
    Notes: Summary Through application of refined separation techniques the β-Lp(a+)-lipoprotein of human serum was characterized in an immunologically and electrophoretically pure form. It was analyzed with regard to its lipid-composition and compared to likewise electrophoretically and immunologically pure β-Lp(a-)- and α1-lipoproteins.
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  • 10
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Die Untersuchung der Serumlipoproteinfraktion HDL2 (1,063〈ϱ 〈1,125 g/ml) von 35 Personen mit Hilfe der Polyacrylamid-Gelelektrophorese zeigte, daß auch bei Anwendung dieser empfindlichen Technik eine eindeutige Einteilung in Lp(a+)- und Lp(a-)-Typen nicht möglich ist. Von den 20 Seren, die durch Agar-Gel-Doppeldiffusion als Lp(a-) bestimmt wurden, zeigten 19 in ihrer HDL2-Fraktion in der für das Lp(a)-Lipoprotein typischen Position eine Bande. Dieser Befund bestätigt die Annahme, daß der Faktor Lp(a) als ein quantitatives genetisches Merkmal angesehen werden muß. Die β-Lipoproteine des HDL2-Bereiches erwiesen sich als disk-elektrophoretisch heterogen.
    Notes: Summary Gelelectrophoretic studies of the serum lipoprotein fraction HDL2 (1.063〈ϱ 〈1.125 g/ml)_of 35 individuals showed, that using this technique no clear classification into Lp(a+) and Lp(a-)-types could be made. 19 out of 20 sera typed Lp(a-) by double diffusion contained in their HDL2-fraction a lipoprotein with the electrophoretic mobility characteristic of the Lp(a)-lipoprotein. This observation confirmes previous suggestions, that Lp(a) indeed is a quantitative genetic trait. The β-lipoproteins of the HDL2-fraction are heterogeneous in gelelectrophoresis.
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