Biomedical subjects

X Bu

Publications and source records attributed to X Bu.

At least 55 records · Page 3Linked to original sources

PubMed1996

Multilocus genetic determinants of LDL particle size in coronary artery disease families.

Recent interest in atherosclerosis has focused on the genetic determinants of low-density lipoprotein (LDL) particle size, because of (i) the association of small dense LDL particles with a three-fold increased risk for coronary artery disease (CAD) and (ii) the recent report of linkage of the trait to the LDL receptor (chromosome 19). By utilizing nonparametric quantitative sib-pair and relative-pair analysis methods in CAD families, we tested for linkage of a gene or genes controlling LDL particle sizes with the genetic loci for the major apolipoproteins and enzymes participating in lipoprotein metabolism. We confirmed evidence for linkage to the LDL receptor locus (P=.008). For six candidate gene loci, including apolipoprotein(apo)B, apoAII, apo(a), apoE-CI-CII, lipoprotein lipase, and high-density lipoprotein-binding protein, no evidence for linkage was observed by sib-pair linkage analyses (P values ranged from .24 to .81). However, in addition, we did find tentative evidence for linkage with the apoAI-CIII-AIV locus (chromosome 11) (P=.06) and significant evidence for linkage of the cholesteryl ester transfer protein locus (chromosome 16) (P=.01) and the manganese superoxide dismutase locus (chromosome 6) (P=.001), thus indicating multilocus determination of this atherogenic trait.

Adolescent↗

PubMed1995

Arthrogryposis multiplex congenita in an Arab kindred: update.

We have restudied the genetic and clinical characteristics of a large Arab kindred previously reported in 1970 by Lebenthal et al. [Pediatrics 46:891-899]. At total of 40 affected individuals was identified; all, except one, were products of 22 different consanguineous matings between the parents. The syndrome, which is present at birth, is expressed mainly by flexion contractures at the knees and elbows, with muscle hypotrophy/weakness around the involved joints. Five of the 6 individuals who were originally reported as having congenital and lethal heart defects were limited to one sibship. None of the new cases had heart defect or any associated malformation. Neurologic examination and electrophysiological studies demonstrated a neuropathic (non-myopathic) type of arthrogryposis. This is an autosomal recessive trait with wide variability in expression and possibly incomplete penetrance in the females. Because of the high consanguinity rate, it allows the use of homozygosity linkage studies to map the gene for this disorder.

Arthrogryposis↗

PubMed1995

Susceptibility mutations in the mitochondrial small ribosomal RNA gene in aminoglycoside induced deafness.

Aminoglycoside induced deafness has been linked recently to a predisposing homoplasmic mutation in the 3' end of the small ribosomal RNA (rRNA) gene of the human mitochondria (1555 A-->G) that makes the mitochondrial rRNA structurally more similar to its bacterial counterpart. This mitochondrial DNA mutation was consistently found in families in which the susceptibility to develop ototoxic deafness was inherited through the maternal lineage. However, the 1555 A-->G mutation was rarely found in sporadic patients in China, where a significant proportion of the population has been exposed to aminoglycosides. To further characterize the mutations predisposing to aminoglycoside ototoxicity, we analysed the 12S rRNA gene in 35 Chinese sporadic patients without the 1555 A-->G mutation. Using single stranded conformational polymorphism (SSCP) analysis, heteroduplex (HD) analysis, sequencing, and allele specific oligonucleotide hybridization, we found three out of 35 sporadic patients with unique sequence changes in the 12S rRNA gene. Two of the patients had homoplasmic mutations. One patient displayed localized heteroplasmy around nt 961, with an absence of the thymidine at this position and different populations of mitochondrial DNA with varying numbers of inserted cytosines. The description of these putative susceptibility mutations, in particular the heteroplasmic mutation around nt 961, provides further support for the important role of the mitochondrial 12S rRNA in genetic predisposition to aminoglycoside induced ototoxic deafness.

Aminoglycosides↗

PubMed1995

Fluoresein diacetate uptake to determine the viability of human fetal cerebral cortical cells.

We investigated the accuracy of fluorescein diacetate uptake as an indicator of the viability of human fetal cerebral cortical cells. Cortical cells from 16-26-week-old normal fetuses were studied. The cortices were dissociated mechanically with normal saline to make a suspension. Fluorescein diacetate uptake and trypan blue exclusion were compared as methods for examining cell viability. Our results show that fluorescein diacetate uptake is a simple and sensitive method for examining human fetal cortical cell viability.

Cell Survival↗

PubMed1995

Genetic variation in lipoprotein (a) levels in families enriched for coronary artery disease is determined almost entirely by the apolipoprotein (a) gene locus.

Lipoprotein (a) (Lp[a]) is a cholesterol-rich lipoprotein resembling LDL but also containing a large polypeptide designated apolipoprotein (a) (apo[a]). Its levels are highly variable among individuals and, in a number of studies, are strongly correlated with the risk of coronary artery disease (CAD). In an effort to determine which genes control Lp(a) levels, we have studied 25 multiplex families (comprising 298 members) enriched for CAD. The apo(a) gene was genotyped among the families, using a highly informative pulse-field gel electrophoresis procedure. In addition, polymorphisms of the gene for the other major protein of Lp(a), apolipoprotein B (apoB), were examined. Quantitative sib-pair linkage analysis indicates that apo(a) is the major gene controlling Lp(a) levels in this CAD population (P = .001; 99 sib pairs), whereas the apoB gene demonstrated no significant quantitative linkage effect. We estimate that the apo(a) locus accounts for < or = 98% of variance of Lp(a) serum levels. Approximately 43% of this variation is explained by size polymorphisms within the apo(a) gene. These results indicate that the apo(a) gene is the major determinant of Lp(a) serum levels not only in the general population but also in a high-risk CAD population.

Alleles↗

PubMed1994

Linkage analysis of the genetic determinants of high density lipoprotein concentrations and composition: evidence for involvement of the apolipoprotein A-II and cholesteryl ester transfer protein loci.

We have tested for evidence of linkage between the genetic loci determining concentrations and composition of plasma high density lipoproteins (HDL) with the genes for the major apolipoproteins and enzymes participating in lipoprotein metabolism. These genes include those encoding various apolipoproteins (apo), including apoA-I, apoA-II, apoA-IV, apoB, apoC-I, apoC-II, apoC-III, apoE, and apo(a), cholesteryl ester transfer protein (CETP), HDL-binding protein, lipoprotein lipase, and the low density lipoprotein (LDL) receptor. Polymorphisms of these genes, and nearby highly polymorphic simple sequence repeat markers, were examined by quantitative sib-pair linkage analysis in 30 coronary artery disease families consisting of a total of 366 individuals. Evidence for linkage was observed between a marker locus D16S313 linked to the CETP locus and a locus determining plasma HDL-cholesterol concentration (P = 0.002), and the genetic locus for apoA-II and a locus determining the levels of the major apolipoproteins of HDL, apoA-I and apoA-II (P = 0.009 and 0.02, respectively). HDL level was also influenced by the variation at the apo(a) locus on chromosome 6 (P = 0.02). Thus, these data indicate the simultaneous involvement of at least two different genetic loci in the determination of the levels of HDL and its associated lipoproteins.

Apolipoprotein A-II↗

PubMed1994

Inhibition of human immunodeficiency virus proliferation by macrocyclic polyamines and their metal complexes.

The macrocyclic polyamines, cyclen and cyclam, and their derivatives have been tested for inhibitory activity against the cytopathogenic effect (CPE) of human immunodeficiency virus type 1 strain HTLV-IIIB (HIV-1IIIB) on CD4+ human lymphoblastoma MT-4 cells. Cyclam and its derivatives were complexed with a variety of transition metal ions NiII, ZnII, CuII, FeIII and CoIII. The divalent metal complexes effected lower toxicity and greater anti-HIV-1 activity, while the trivalent metal complexes had no effect on HIV-1-dependent CPE. When dimerized, the anti-HIV activity of monomers was significantly enhanced. A potent inhibition of CPE by biscyclam was transiently observed 4 d after the virus infection, but was not seen at 6 d due to severe toxicity. The toxicity of biscyclam, referred to as delayed toxicity, could be overcome by a metal complexation. The strain specificities of biscyclams were further studied by testing their effects on syncytium formation between HIV-infected and uninfected human acute lymphoblastic leukemia MOLT-4 cells. The 50% inhibitory concentrations of biscyclams against HIV-2GH-1-dependent syncytium formation were less than one hundredth those for the other HIV strains (HIV-1IIIB, HIV-1RF and HIV-1SF-2).

Cations, Divalent↗

PubMed1994

[Effects of lidocaine on contraction of isolated rabbit aortic rings].

The mechanism of relaxing effects of lidocaine (Lid) on the contraction of isolated rabbit thoracic aortic rings was studied. Verapamil (Ver) was used for comparison. Lid and Ver showed obvious relaxing effect on contraction evoked by high K+ depolarization. In the study of contractions induced by noradrenaline (NA), both Lid and Ver were shown to suppress the component elicited by calcium release from the intra-cellular store, but not that induced by calcium influx. Lid shifted the dose-response curves for KCl and NA to the right nonparallelly and depressed their maximal responses. The inhibition to KCl was more potent than that to NA. This suggests that Lid has selective blocking effects on PDC channel, but not the ROC channel. Lid shifted the dose-response curve for CaCl2 to the right nonparallelly and depressed its maximal response. The results indicate that the calcium antagonistic property of Lid may be one of the mechanisms of its vascular smooth muscle relaxing effect.

Animals↗

PubMed1993

Evidence for linkage of the apolipoprotein A-II locus to plasma apolipoprotein A-II and free fatty acid levels in mice and humans.

Although it has been hypothesized that the synteny between mouse and human genes provides an approach to the localization of genes that determine quantitative traits in humans, this has yet to be demonstrated. We tested this approach with two quantitative traits, plasma apolipoprotein A-II (apoAII) and free fatty acid (FFA) levels. ApoAII is the second most abundant protein of high density lipoprotein particles, but its function remains largely unknown. We now show that, in a backcross between strains Mus spretus and C57BL/6J, apoAII levels correlate with plasma FFA concentrations on both chow (P < 0.0001) and high-fat (P < 0.0003) diets and that apoAII levels are linked to the apoAII gene (P < 0.0002). To test whether variations of the apoAII gene influence plasma lipid metabolism in humans, we studied 306 individuals in 25 families enriched for coronary artery disease. The segregation of the apoAII gene was followed by using an informative simple sequence repeat in the second intron of the gene and two nearby genetic markers. Robust sib-pair linkage analysis was performed on members of these families using the SAGE linkage programs. The results suggest linkage between the human apoAII gene and a gene controlling plasma apoAII levels (P = 0.03). Plasma apoAII levels were also significantly correlated with plasma FFA levels (P = 0.007). Moreover, the apoAII gene exhibited linkage with a gene controlling FFA levels (P = 0.003). Evidence for nonrandom segregation was seen with markers as far as 6-12 centimorgans from the apoAII structural locus. These data provide evidence, in two species, that the apoAII gene is linked to a gene that controls plasma apoAII levels and that apoAII influences, by an unknown mechanism, plasma FFA levels. The results illustrate the utility of animal studies for analysis of complex traits.

Animals↗

PubMed1993

Wolfram syndrome: a mitochondrial-mediated disorder?

Mitochondrial DNA mutations cause several human diseases, (eg, Leber's hereditary optic neuropathy). Wolfram syndrome (characterised by diabetes insipidus, diabetes mellitus, optic atrophy, and deafness) also has, in some cases, a mitochondrial origin. The disease, often familial, has been well documented as an autosomal recessive disorder, and most of the clinical phenotypes are consistent with an ATP supply defect that is often seen in mitochondrial-mediated disorders. We propose a dual genome defect model for Wolfram syndrome in which nuclear genetic defects or mitochondrial genetic defects can independently lead to the disease. This model suggests that besides a mitochondrial gene defect alone, a nuclear gene defect, which interferes with the normal function of mitochondria (probably with a normal mitochondrial genome), can also be the underlying explanation for the pleiotropic features of Wolfram syndrome. This hypothesis explains how an autosomal recessive disorder can result in mitochondrial dysfunction, and has a general application in the identification of candidate genes for the various important phenotypes (eg, deafness and diabetes mellitus) seen in mitochondrial disorders.

DNA, Mitochondrial↗

PubMed1993

Regional mapping of the gene for familial Mediterranean fever on human chromosome 16p13.

Familial Mediterranean fever (FMF) is an autosomal recessively inherited inflammatory disorder characterized by recurrent short episodes of fever, peritonitis, arthritis, and pleuritis. Recently, linkage was demonstrated between FMF and the VNTR probes 3'HVR and 5'HVR of the alpha-globin complex at 16p13.3 (theta = 0.06-0.10, Lodmax = 9.76-14.47) and the insertion/deletion polymorphism detected by the probe CMM65 of D16S84 (theta = 0.04, Lodmax = 9.17). We have now mapped the FMF gene between the two flanking markers D16S283/D16S291 (theta = 0.038) and D16S80 (theta = 0.159). The proximity of the microsatellite markers in D16S283 and D16S291 to the FMF gene allows preclinical diagnosis in most pedigrees with affected individuals.

Chromosomes, Human, Pair 16↗

PubMed1993

Novel phosphorylation sites of eukaryotic initiation factor-4F and evidence that phosphorylation stabilizes interactions of the p25 and p220 subunits.

Only serine phosphorylation of eukaryotic initiation factor-4E (eIF-4E) has been previously reported in intact cells. We found that treatment of HepG2 cells with okadaic acid resulted in as much as 20% of eukaryotic initiation factor (eIF)-4E phosphorylation occurring on threonine residues and that tryptic phosphopeptide maps showed several previously unrecognized phosphopeptides. Analysis of p220 from control and okadaic acid-treated cells demonstrated serine and threonine phosphorylation under both conditions. However, a unique pattern of phosphopeptides in okadaic acid-treated cells was observed. The most notable finding was that hyperphosphorylation of eIF-4E and p220 increased binding of p220 but not eIF-4E to the m7GTP cap structure. We suggest that phosphorylation of eIF-4E is more complicated than previously recognized and that hyperphosphorylation of eIF-4E and p220 recruits more p220 into the protein complex that associates with mRNA caps. A better understanding of these protein-protein and protein-mRNA interactions may aid the design of anti-sense directed chemistries that disrupt such interactions for a specific target mRNA (Baker, B.F., Miraglia, L., and Hagedorn, C. H. (1992) J. Biol. Chem. 267, 11495-11499).

Cells, Cultured↗

PubMed1993

A form of sensorineural deafness is determined by a mitochondrial and an autosomal locus: evidence from pedigree segregation analysis.

We have previously reported a large Israeli-Arab pedigree with sensorineural deafness possibly determined simultaneously by two loci--one mitochondrial, and one autosomal recessive. This was analyzed by extending classic segregation analysis methods to the many nuclear families derived from the maternal line pedigree. Here we expand this pedigree and extend our analysis by using the regressive models for segregation analysis on the entire pedigree. The corresponding REGD computer program was utilized and the marrying-in males' and paternal line members' affection statuses were assigned as unknown to accommodate the exclusive maternal transmission pattern. For the autosomal locus, a simple autosomal recessive (q = 0.52) model with a nearly complete penetrance (0.93) was found to be the best-fitting model. Equally importantly, we were also able to use the power of the regressive models to test the hypothesis of mitochondrial heteroplasmy as an alternative for the proposed autosomal locus. We found no evidence for the heteroplasmy hypothesis as an explanation for the incomplete maternal transmission of deafness in this pedigree. Thus, even if the mitochondrial mutation occurred in a heteroplasmic distribution in the family members, this could not explain the familial aggregation in this pedigree, and an autosomal recessive locus is still required. These results provide further support for the concept that the sensorineural deafness occurring in this large Israeli-Arab pedigree results from simultaneous involvement of two genes at two different loci, one mitochondrial and likely homoplasmic, and the other autosomal and recessive.

Computer Simulation↗

PubMed1993

Mitochondrial ribosomal RNA mutation associated with both antibiotic-induced and non-syndromic deafness.

Maternally transmitted non-syndromic deafness was described recently both in pedigrees with susceptibility to aminoglycoside ototoxicity and in a large Arab-Israeli pedigree. Because of the known action of aminoglycosides on bacterial ribosomes, we analysed the sequence of the mitochondrial rRNA genes of three unrelated patients with familial aminoglycoside-induced deafness. We also sequenced the complete mitochondrial genome of the Arab-Israeli pedigree. All four families shared a nucleotide 1555 A to G substitution in the 12S rRNA gene, a site implicated in aminoglycoside activity. Our study offers the first description of a mitochondrial rRNA mutation leading to disease, the first cases of non-syndromic deafness caused by a mitochondrial DNA mutation and the first molecular genetic study of antibiotic-induced ototoxicity.

Aminoglycosides↗

PubMed1992

Marked parental consanguinity as a cause for increased major malformations in an Israeli Arab community.

It is common among Israeli Arabs who live in the villages to prefer consanguineous marriages, particularly among first cousins. In addition, such villages are populated by a few (less than 20) original families, and inter-family/inter-village marriages are infrequent. The purpose of this study was to examine the consequences of such "consanguinity" in Taibe, a large Arab village, 30 km from Tel Aviv. Six hundred ten families were prospectively ascertained through infants who were routinely seen in the local "Well Baby Clinics." A significant increase in the incidence of major malformations was noted in relation to the closeness of the parental relationship. For the index cases group the prevalence of individuals with major malformations were 5.8% in the product of inter-village marriages, 8.3% in the intra-village non-related matings, 15.1% in the distant consanguineous group, and up to 15.8% in the progeny of first-cousin marriages (P less than 0.001). In the siblings of these index cases, the frequency of major malformations was 4.3%, 4.5%, 10.5%, and 10.3%, respectively. Analysis of the major malformations by each body system showed the same trend. The study demonstrates a marked high rate of consanguineous marriages, whose effect leads to a marked increase in major malformations and thus a prominent public health problem in such villages. This requires a unique genetic counseling approach.

Congenital Abnormalities↗

PubMed1992

Phosphoprotein phosphatase 2A dephosphorylates eIF-4E and does not alter binding to the mRNA cap.

The phosphorylation and dephosphorylation of the 25 kDa mRNA cap binding protein eukaryotic initiation factor-4E (eIF-4E) is regulated during different physiologic and pathophysiologic states that include cell growth and the late phase of adenovirus infection. We have found that okadaic acid is much more effective in increasing the phosphorylated fraction of eIF-4E than phorbol 12-myristate 13-acetate in Hep G2 cells. Phosphoprotein phosphatase 2A dephosphorylated eIF-4E isolated from both phorbol 12-myristate 13-acetate- or okadaic acid-treated cells, whereas alkaline and acid phosphatase were relatively ineffective. The ability of purified [35S]eIF-4E isolated from okadaic acid-treated cells to bind mRNA caps was compared to phosphoprotein phosphatase 2A-treated [35S]eIF-4E and found to be no different. This suggests that alternative explanations for the previously observed effects of eIF-4E phosphorylation on protein synthesis must be considered. In addition, our results indicate that the in vivo phosphorylation of eIF-4E is not catalyzed solely by protein kinase C.

Ethers, Cyclic↗

PubMed1992

Two-locus mitochondrial and nuclear gene models for mitochondrial disorders.

Stimulated by a large pedigree with a cochlear form of deafness, for which we considered a two-locus mitochondrial and nuclear gene model, we have extended the classic methods of segregation analysis to these classes of two-locus disorders. Based on the unique maternal transmission pattern of the mitochondria, we demonstrate that utilization of the maternal line pedigree allows us to simplify the various two-locus mitochondrial models to "one nuclear locus" models. Classifying the nuclear families into different independent groups by the mother's phenotypes allows us to estimate the nuclear gene frequency in one group and to use this estimate as the expected value to test the fitness of the model on the other group. In addition, if we restrict the analysis to specific subsets of the mating type(s), we can also test the model on specific groups of nuclear families without estimating the gene frequency. Goodness-of-fit tests can be performed on pooled sibship data as well as individual sibship data. These methods of analysis should assume increasing importance as more disorders with features of mitochondrial inheritance are identified.

Cell Nucleus↗

PubMed1992

Leber hereditary optic neuropathy: estimation of number of embryonic precursor cells and disease threshold in heterozygous affected females at the X-linked locus.

LHON has been suggested to involve both mitochondrial and X-chromosome-linked loci. By extending two-locus mitochondrial and nuclear gene analytic methods, we recently proposed that a proportion of affected females are likely heterozygous at the X-linked locus and affected due to unfortunate X-chromosome inactivation. Assuming that the optic tissue is the primary site of action of the mutant gene(s), we further propose here that there should be no fewer than six embryonic precursor cells for the involved optic tissue at the stage in early development when X-chromosome inactivation occurs. We also estimate that the disease threshold (i.e. proportion of cells with abnormal X-chromosome active in the responsible tissue at the time of X-chromosome inactivation) for a heterozygous female is in the range of 0.60 to 0.83.

DNA, Mitochondrial↗