PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Complement C8”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1995

Molecular mapping of SSRs for Pgm1 and C8b in the vicinity of the rat fatty locus.

Recessive mutations at the rat fatty locus (fa, facp), which produce obesity, insulin resistance, and diabetes, provide useful experimental models for similar phenotypes in humans. The molecular pathogenesis of the metabolic phenotype in animals segregating for fa is unknown and difficult to study once the confounding metabolic effects of obesity are present. Although various experimental methods distinguish preobese from lean rats (phenotypic markers and molecular markers genetically linked to fatty), technical difficulties limit their utility. We report the identification of two (GT)n simple sequence repeats (SSRs) near the rat phosphoglucomutase gene (Pgm1) gene and two SSRs, (GA)n and (GT)n, near the rat complement component 8 beta gene (C8b). These SSRs map to an approximately 4-cM interval flanking the fatty locus on rat chromosome 5. Use of these molecular markers in combination offers an improved method for early assessment of gene dosage for fa and hence for studying the fundamental molecular physiology underlying the derangements of metabolism and behavior resulting from mutations in this gene.

Alleles↗
PubMed1986

Genetic polymorphism of human complement component C81 in the Japanese population.

Genetic polymorphism of human C81 has been investigated using polyacrylamide gel isoelectric focusing (PAGIEF) in the presence of 3.1 M urea followed by electroblotting with enzyme immunoassay. In 448 individuals phenotypes of C81 were classified into three common and four rare patterns, and these were considered to be controlled by two common alleles, C81 A and C81 B, and three rare alleles which were tentatively designated C81 A1J and C81 A2J for acidic variants and C81 B1J for the basic variant. The alleles of C81 A2J and C81 B1J are new rare alleles, but C81 A1J might correspond to C81 A1 in the former studies. Family data were in accordance with the hereditary rules. The gene frequencies were estimated as C81 A is 0.6228, C81 B is 0.3672, C81 A1J is 0.0078, C81 A2J is 0.0011, and C81 B1J is 0.0011, respectively. The gene frequencies of the two common alleles agreed approximately with other ethnic groups. PAGIEF of neuraminidase-treated plasma samples followed by electroblotting with enzyme immunoassay is applicable to the study of heterogeneity of C81.

Alleles↗
PubMed1989

Paroxysmal nocturnal hemoglobinuria: the biochemical defects and the clinical syndrome.

Paroxysmal nocturnal hemoglobinuria is a disorder characterized by the lack of membrane proteins affixed to the membrane by an anchor dependent upon phosphatidyl inositol, suggesting that some acquired abnormality in the metabolism of this class of proteins is basic to the disease. Most of the clinical symptoms can be explained by the lack of these proteins. However, much work is needed to understand completely the relationship of the biochemical facts and the clinical syndrome.

5'-Nucleotidase↗
PubMed1996

Invasive Haemophilus influenzae type b infection in a child with familial deficiency of the beta subunit of the eighth component of complement.

A child who had had meningitis caused by Haemophilus influenzae type b, and then had meningococcal meningitis, was found to have familial deficiency of the beta subunit of the eighth component of complement. The child had not received the H. influenzae type b vaccine. If this deficiency is discovered, we recommend that family members be screened, regardless of their health status.

Complement C8↗
PubMed1991

Human brain prostaglandin D synthase has been evolutionarily differentiated from lipophilic-ligand carrier proteins.

cDNAs for glutathione-independent prostaglandin D synthase were isolated from cDNA libraries of human brain. The longest cDNA insert was 837 base pairs long and contained a coding region of 570 base pairs corresponding to 190 amino acid residues with a calculated Mr of 21,016. Between two cDNA inserts isolated from the two different libraries, nucleotide substitutions were observed at 16 positions, including conservative amino acid substitutions at 2 positions and nonconservative substitutions at 5 positions, indicating genetic heterogeneity of this enzyme in humans. The computer-assisted homology search revealed that the enzyme is a member of the lipocalin superfamily, comprising secretory hydrophobic molecule transporters, showing the greatest homology (28.8-29.4% identity; 51.3-53.1% similarity) to alpha 1-microglobulin among the members of this superfamily. In a phylogenetic tree of the superfamily, this enzyme, alpha 1-microglobulin, and the gamma chain of the complement component C8 form a cluster separate from the other 14 members. The two distinctive characteristics of glutathione-independent prostaglandin D synthase, as compared to the other members of this superfamily, are its enzymatic properties and its association with membranes that were probably acquired after evolutionary divergence of the two lipocalins. Based on the observed sequence homology, the tertiary structure of the enzyme was deduced to consist of an eight-stranded anti-parallel beta-barrel forming a hydrophobic pocket. Furthermore, the Cys-65 residue in the pocket, which is conserved only in the human and rat enzymes but not in other lipocalins, was considered to be a putative active site of the enzyme.

Amino Acid Sequence↗
PubMed1988

The genetic polymorphism of complement component C81 (alpha-gamma) in two Chinese populations.

The genetic polymorphism of the complement component C81 (alpha-gamma) in two Chinese populations (Beijing and Guangzhou) were investigated, using isoelectric focusing followed by an immunoblotting technique. Three common and two rare phenotypes were observed. The homozygote phenotype C81 A1 ascribed to a rare allele C81*A1 was newly detected. The frequencies calculated for the two common alleles were as follows: C81*A = 0.5674, C81*B = 0.4255 for the Beijing population; C81*A = 0.5117, C81*B = 0.4785 for the Guangzhou population. The gene frequencies of the two common alleles of C81 in both Chinese populations were similar to those for the other ethnic groups thus far reported, and there is no statistically significant difference between the Beijing and the Guangzhou populations.

Alleles↗
PubMed1987

First cysteine-rich repeat in ligand-binding domain of low density lipoprotein receptor binds Ca2+ and monoclonal antibodies, but not lipoproteins.

The ligand binding domain of the low density lipoprotein receptor consists of seven cysteine-rich repeats of approximately 40 amino acids each. These repeats, which are located at the NH2 terminus of the protein, are homologous to sequences in complement components C8 and C9. To determine the role of the first repeat (amino acids 2-42), we prepared two plasmids containing expressible low density lipoprotein receptor cDNAs. The first plasmid, p delta R1, lacks only the nucleotides encoding the first repeat. It produced a receptor that bound and internalized lipoproteins and recycled to the cell surface with the same efficiency as the normal receptor. This deleted receptor failed to bind two monoclonal antibodies, IgG-C7 and IgG-15C8, which were shown previously to react with the ligand-binding domain. The second plasmid, pR1, encodes a markedly truncated protein whose extracellular domain consists of the first repeat joined to the transmembrane and cytoplasmic domains. This protein bound the two monoclonal antibodies with the same affinity as the normal receptor, but failed to bind lipoproteins. Binding of IgG-15C8 to the normal receptor and the pR1-encoded protein was Ca2+-dependent, indicating that the first repeat binds Ca2+. We conclude that repeats 2-6 in the ligand-binding domain are sufficient for binding lipoproteins and that the first repeat is highly immunogenic, but is not required for lipoprotein binding.

Antibodies, Monoclonal↗
PubMed1994

Human liver-derived HEP G2 cells produce functional properdin.

Properdin stabilizes the alternative complement pathway C3 convertase and is synthesized by monocytes and myelomonocytic cell lines. Hepatic production of properdin has never been documented, although most other complement components are synthesized by liver. Human liver-derived Hep G2 cells were examined for the ability to produce properdin by using the polymerase chain reaction (PCR). Amplified properdin message was detected by using Southern transfer and hybridization to a murine properdin cDNA probe. Sequencing of the PCR product revealed that the Hep G2 message was nearly identical to the cDNA sequence from U937 cells. Subsequently Hep G2 cultures were stimulated with interleukin (IL-6), 25 micrograms/ml, and culture supernatants were assayed for the presence of properdin by using dot blots. Properdin concentration increased over time, and we found no obvious difference between properdin production by IL-6-stimulated and unstimulated Hep G2 cells. Finally, alternative pathway decay assays confirmed the presence of functionally active properdin in the culture supernatant. Thus, functional properdin is a product of Hep G2 cells, suggesting that biosynthesis of properdin may occur in hepatocytes. Properdin synthesis was not augmented by IL-6, a finding that is consistent with previous observations that properdin is not an acute phase reactant.

Base Sequence↗
PubMed1996

Regulation of complement activity by immunoglobulin. I. Effect of immunoglobulin isotype on C4 uptake on antibody-sensitized sheep erythrocytes and solid phase immune complexes.

Intravenous Ig, composed principally of IgG, prevents complement attack by inhibiting C3 and C4 uptake onto target cells and tissues. Using two different models, Ab-sensitized SRBC and BSA-anti BSA solid phase immune complexes, we have examined the complement inhibitory capacity of three Ig classes (IgG, IgM, IgA) focussing on inhibition of C4 uptake. It was found that on both a weight and molar basis, monomeric serum IgA and IgM were far more active than IgG (weight efficiency ratios were 1.0, 20.8, and 236.3, and molar efficiency ratios 1.0, 24.0, and 1382.9 for polyclonal IgG, IgA1, and IgM, respectively). Monoclonal IgM were less active than polyclonal IgM (50% inhibition was achieved in SRBC model by 0.022, 0.30, 1.6, and 1.6 mg/ml of polyclonal IgM and monoclonal IgM from patients Lew, Will, and Pri). Secretory IgA was less active than serum IgA1 and similar in inhibitory activity to IgG (weight and molar efficiency ratios 1.5 and 0.6 compared with IgG). All tested preparations were less active in the solid phase immune complex model than in the sensitized cell model. A mixture of Igs of different isotypes was somewhat more active than any isotype alone. These results suggest that polyclonal serum IgA and IgM can also be considered for active therapy in diseases accompanied by the activation of classical complement pathway.

Animals↗