Showing papers by "Children's Hospital Oakland Research Institute published in 1992"

Linkage of atherogenic lipoprotein phenotype to the low density lipoprotein receptor locus on the short arm of chromosome 19.

Abstract: The atherogenic lipoprotein phenotype (ALP) is a common heritable trait characterized by a predominance of small, dense low density lipoprotein (LDL) particles (subclass pattern B), increased levels of triglyceride-rich lipoproteins, reductions in high density lipoprotein, and a 3-fold increased risk of myocardial infarction. Significant two-point linkage was found between ALP and the LDL receptor locus on the short arm of chromosome 19 in 51 relatives of nine probands with ALP pattern B. The maximum logarithm of odds (LOD) score of 4.07 was observed at a recombination fraction of 0.04, assuming 100% penetrance of ALP pattern B, and 4.27 at a recombination fraction of zero, assuming 90% penetrance of pattern B. Haplotyping data and multipoint linkage analysis suggest that the gene [named ATHS for atherosclerosis susceptibility (lipoprotein-associated)] responsible for ALP is located distal to D19S76 near or at the LDL receptor locus. This result suggests the possibility that genetic variation at the LDL receptor locus or a closely linked locus on chromosome 19 may be responsible for metabolic alterations in ALP pattern B that account for a substantial proportion of the familial predisposition to coronary artery disease in the general population.

Fetal alcohol syndrome and fatty acid ethyl esters.

Abstract: Fetal alcohol syndrome is the leading known cause of mental retardation. The syndrome, defined as growth retardation, midface hypoplasia, and neurologic dysfunction, represents only part of the spectrum of fetal alcohol effects. The biochemical mechanism of teratogenesis is unknown. In adults, metabolites of ethanol, FAEE, are known to accumulate in major organs. The formation of FAEE is catalyzed by a family of enzymes, FAEE synthases. Our hypothesis is that accumulation of FAEE in the embryo results in fetal alcohol syndrome. We have developed assays for FAEE and FAEE synthase activity using mg of tissue. Using these assays, we have shown the following: Human placenta, mouse placenta, heart, and liver are active in catalyzing the formation of FAEE. One h after maternal ethanol administration on gestational d 14, mouse placenta and fetuses accumulated significant quantities of FAEE. The fatty acid incorporated into FAEE was tissue dependent. Tissues from pregnant animals given ethanol on gestational d 7 showed persistence of FAEE on gestational d 14. We conclude that: 1) human and mouse placentas have significant FAEE synthase activity, 2) mouse heart, liver, placenta, and fetal tissues accumulate significant amounts of FAEE after maternal ethanol exposure, 3) there is tissue specificity for the fatty acid incorporated into FAEE, and 4) FAEE may persist for 7 d in placentas. These results provide a basis for further research into the role of FAEE in the development of fetal alcohol syndrome.

Intron-exon organization of the gene for the multifunctional animal fatty acid synthase.

Abstract: The complete intron-exon organization of the gene encoding a multifunctional mammalian fatty acid synthase has been elucidated, and specific exons have been assigned to coding sequences for the component domains of the protein. The rat gene is interrupted by 42 introns and the sequences bordering the splice-site junctions universally follow the GT/AG rule. However, of the 41 introns that interrupt the coding region of the gene, 23 split the reading frame in phase I, 14 split the reading frame in phase 0, and only 4 split the reading frame in phase II. Remarkably, 46% of the introns interrupt codons for glycine. With only one exception, boundaries between the constituent enzymes of the multifunctional polypeptide coincide with the location of introns in the gene. The significance of the predominance of phase I introns, the almost uniformly short length of the 42 introns and the overall small size of the gene, is discussed in relation to the evolution of multifunctional proteins.

α‐ and β‐haemoglobin chain induced changes in normal erythrocyte deformability: comparison to β thalassaemia intermedia and Hb H disease

Abstract: The alpha- and beta-thalassaemias are characterized by decreased erythrocyte deformability. To determine what effects excess alpha- and beta-haemoglobin (globin) chains have on cellular and membrane deformability, purified haem-containing alpha- and beta-chains were entrapped within normal erythrocytes. Entrapment of purified alpha-chains in normal erythrocytes resulted in a significant decrease in cellular and membrane deformability similar to that observed in beta-thalassaemia intermedia. The decreased deformability was correlated with alpha-chain membrane deposition, an alteration in membrane proteins and a decrease in membrane reactive thiol groups. These changes in membrane and cellular deformability were time dependent and closely correlated with membrane alpha-chain deposition. The membrane changes and the loss of membrane deformability appeared to account for the loss of cellular deformability in the alpha-chain loaded cells. While both beta-chain loaded and Hb H erythrocytes demonstrated a significant loss of cellular deformability, this loss was less pronounced than in the alpha-chain loaded and beta-thalassaemic cells and may arise from either the increased intracellular viscosity of the beta-chain loaded cells or to the smaller amount of membrane bound globin. In summary, these studies demonstrate that alteration of cellular and membrane deformability occurs very rapidly and as a direct consequence of the autoxidation and membrane binding of the unpaired globin chains.

Entrapment of Purified α-Hemoglobin Chains in Normal Erythrocytes as a Model for Human β Thalassemia

Abstract: The β thalassemias result from a number of underlying genetic defects that interfere with the synthesis of the β hemoglobin chain and the subsequent production of the normal α2β2 hemoglobin tetramer.1 As a consequence of this decreased β chain synthesis, unpaired α-hemoglobin chains (α-chains) are found within the erythrocyte. The presence of these α-chains are associated with a number of cellular defects including: membrane bound globin; membrane thiol oxidation; altered cytoskeletal proteins; decreased cellular and membrane deformability; and increased susceptibility to both endogenous and exogenous oxidants.1

Vaccine-induced human antibody responses to the haemophilus influenzae b polysaccharide in severe combined immunodeficient mice engrafted with human leukocytes

Abstract: We examined the ability of severe combined immunodeficient (SCID) mice-human peripheral blood leukocyte (PBL) chimeras to respond to immunization with Haemophilus influenzae b polysaccharide (Hib PS) vaccines. Two to 3 wk after PBL engraftment, human-PBL-SCID mice, prepared with PBL from one of five adult donors, were immunized with free or protein-conjugated Hib PS. Antibody to Hib PS was quantitated in preimmunization and postimmunization sera. Before immunization, anti-Hib PS antibody was detectable (greater than 10 ng/mL) in three of 40 mice. Of the 37 human-PBL-SCID mice not having detectable serum antibody before immunization, 31 produced greater than or equal to 20 ng/mL (greater than or equal to 2-fold increase) anti-Hib PS antibody 2 to 3 wk after immunization. Both free and protein-conjugated forms of Hib PS were immunogenic. Geometric mean anti-Hib PS antibody levels ranged from 50 to 139 ng/mL. Vaccine-induced anti-Hib PS antibodies frequently expressed HibId-1, a cross-reactive idiotype that predominates the in vivo human antibody response to Hib PS. However, among mice engrafted with PBL from a single donor, the HibId-1 distribution was highly skewed, suggesting that clonally distinct B cells were being stimulated in individual mice. These findings indicate that human PBL transplanted into SCID mice are functionally responsive to Hib PS antigenic challenge. This system may serve as a useful model for studying the regulation and cellular requirements for human polysaccharide immunity.

Osteogenesis imperfecta and Ebstein's anomaly: a case report with autopsy findings.

Abstract: Osteogenesis imperfecta is an inherited disorder of collagen synthesis. It has a wide range of phenotypic expressions, but cardiovascular anomalies tend to be rare. When they do occur, they usually consist of aortic or mitral valve disease. We report an autopsy case of a 36-week gestation infant with coexisting osteogenesis imperfecta and Ebstein's anomaly. The simultaneous occurrence of two relatively rare entities may reflect a generalized expression of an underlying collagen synthesis defect.

Oxidative Damage and Repair of Human Erythrocyte Lipids

Abstract: Biological membranes are composed of a complex and highly organized mixture of proteins and lipids. The complicated architecture of a membrane appears necessary for its optimal function, with each individual component an important and integral part in preserving structure and/or function of the membrane and of the cell as a whole. Most cells possess a very elaborate and ingenious apparatus to synthesize membrane components and to transport them to their site of destination. Routes of synthesis and transport of proteins and lipids are discussed by other contributors. We will focus on mechanisms that maintain the phospholipid molecular species composition and organization under conditions of oxidative stress in a relatively simple cell membrane, that of the red blood cell (RBC) or erythrocyte.

A new mutation responsible for severe G6PD deficiency in two ethnic Chinese with different clinical presentations: determination by a direct PCR sequencing technique.

Abstract: To test the hypothesis that clinical manifestation in G6PD deficiency correlates with a molecular lesion, we investigated the G6PD gene of two Chinese Americans both of whom had G6PD deficiency, but who manifested different clinical presentations. In this study, we have developed a direct PCR sequencing protocol to examine the human G6PD gene. By using optimized PCR conditions with internal primers, we were able to amplify a 4.2 kb DNA fragment (covering exon 3 through 13 of the G6PD gene) of consistently high quality. From this we were then able to generate high quality single-stranded DNA templates by asymmetric PCR for subsequent sequencing. We also overcame the crossband problem by using internal primers, high temperature reaction with Taq I DNA polymerase, and/or sequencing with gene 32 protein. We could consistently amplify exons 1 and 2 despite their high G/C content by substituting 75% of dGTP with deoxy-7-deaza-guanosine triphosphate. By using this novel approach, we have identified a new mutation at cDNA position 1376 from G to T, which causes substitution of Leu for Arg at amino acid position 459. This mutation has not been reported in other ethnic groups. It is the only genetic defect in the coding regions of the G6PD gene of these two G6PD deficient individuals. We speculate that in addition to a defect in the G6PD gene, other factors also play a role in the clinical manifestation of G6PD deficiency.