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Biomedical subjects

M Dean

Publications and source records attributed to M Dean.

At least 253 records · Page 14Linked to original sources
PubMed1994

von Willebrand's disease: use of collagen binding assay provides potential improvement to laboratory monitoring of desmopressin (DDAVP) therapy.

This report describes studies investigating the use of a collagen binding assay to improve the laboratory monitoring of desmopressin (DDAVP) therapy in patients with von Willebrand's disease (vWD). We evaluated the response of seven patients with vWD (four type I, three type IIA) to DDAVP, administered using a standard protocol, by assessing levels of von Willebrand factor (vWF) and factor VIII, as well as performing skin bleeding times (SBT) prior to, and at sequential time points following, DDAVP administration. The study employed the following assays: von Willebrand factor antigen assay (vWF:Ag; determined by ELISA); a novel functionally based collagen binding assay (CBA; determined by ELISA); ristocetin cofactor assay (RCof; determined by platelet aggregometry); von Willebrand factor multimer analysis (using SDS-agarose gels); factor VIII coagulant (FVIIIC; determined by clotting assay); and factor VIII antigen (FVIIICAG; determined by ELISA). All patients showed an initial incremental increase in vWF/FVIII levels using all assays above, and some showed some correction in SBT. Although the absolute levels of vWF/FVIII antigen or activity varied between patients, the CBA was found to provide consistently the greatest proportional incremental increases (i.e., -fold) compared to baseline (pre-DDAVP) levels. Accordingly, we consistently observed an increase in the CBA to vWF:Ag ratio for all patients evaluated. This supplements previous findings that have suggested a unique ability of our CBA procedure to bind preferentially to higher molecular weight (i.e., more functionally active) forms of vWF. We therefore propose that the use of the above test combination (e.g., vWF:Ag plus CBA) may provide the basis for more accurate estimation of a patient's functional responsiveness to DDAVP therapy in future studies.

Biopolymers↗
PubMed1994

Screening for CF mutations in adult cystic fibrosis patients with a directed and optimized SSCP strategy.

Twenty adolescent and adult cystic fibrosis (CF) patients have been studied for the presence of mutations in the CFTR gene. Mutations other than deltaF508 have been detected by comparison to the single-stranded conformation polymorphism (SSCP) pattern of known mutations in eight exons, in which 80% of the more common mutations are present. Each mutation was confirmed by direct sequencing. For each of the analyzed exons, optimal SSCP conditions have been determined that allow all available known mutations in that exon to be distinguished from each other. This approach allowed mutations to be defined in 75% of the non deltaF508 alleles and 92% of all CF alleles in this cohort.

Adolescent↗
PubMed1994

Mapping and sequencing of two yeast genes belonging to the ATP-binding cassette superfamily.

ATP-binding cassette (ABC) transporters share significant sequence identity within their ATP-binding domains. Degenerate oligonucleotides based on highly conserved portions of the ATP-binding domain genes were used to clone portions of two members of the ABC gene superfamily from Saccharomyces cerevisiae DNA. These genes were designated MDL1 and MDL2 (for multidrug resistance-like). Each MDL gene is predicted to encode a single set of transmembrane domains and a single ATP-binding domain, thus the MDL gene products are 'half-molecule' ABC proteins. The two genes were mapped to precise regions on chromosomes XII and XVI and show a considerable similarity to the mammalian P-glycoprotein/multidrug resistance (MDR) and peptide transporter (TAP) genes. Preliminary analysis of null mutants constructed by gene replacement has indicated that the MDL genes are not essential for viability of yeast. The sequences have been deposited in the GenBank data library under Accession Numbers L16958 (Locus YSCBCSA) and L16959 (Locus YSCBCSB).

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Polymorphisms in the 3' untranslated region of the I kappa B/MAD-3 (NFKBI) gene located on chromosome 14.

The NF-kappa B transcription factor regulates the expression of a number of genes, including immune function and growth control loci, and several viruses. For example, the long terminal repeat of the human immunodeficiency virus contains NF-kappa B binding sites. NF-kappa B activity in the nucleus is regulated by a cellular inhibitory protein I kappa B. To analyze the potential role of these genes in genetic disease we have mapped the NF-kappa B (NFKB2) and I kappa B/MAD-3 (NFKBI) loci in a panel of somatic cell hybrids to chromosomes 4 and 14, respectively. Amplification of the 3' untranslated region of NFKBI allows the detection of three independent polymorphisms within 410 bp. In combination these polymorphisms were informative in 27 of 36 CEPH families and allowed the gene to be placed onto the linkage map of chromosome 14, between the D14S32 and D14S42 markers.

Base Sequence↗
PubMed1994

Heterogeneity in the severity of cystic fibrosis and the role of CFTR gene mutations.

Cystic fibrosis is a common, fatal disorder caused by abnormalities in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. CFTR encodes a chloride channel that regulates secretion in many exocrine tissues. The presentation of cystic fibrosis is highly variable as measured by the age of onset of disease, the presence of pancreatic insufficiency, or the progression of lung disease. Over 400 mutations in the CFTR gene have been described in cystic fibrosis patients and considerable effort has focused on the correlation between specific mutations and genotypes and clinical characteristics. Individual tissues display variation in their sensitivity to CFTR mutations. The vas deferens is functionally disrupted in nearly all males, whereas mild and severe pancreatic involvement is determined by the patient's genotype. The severity of pulmonary disease is poorly correlated with genotype, suggesting that there are other important genetic and/or environmental factors that contribute to lung infections and the subsequent disruption of lung function.

Cystic Fibrosis↗
PubMed1994

Cystic fibrosis-related diabetes is associated with HLA DQB1 alleles encoding Asp-57- molecules.

The incidence of insulin-dependent diabetes in individuals with cystic fibrosis is nearly 100 times greater than in the general population. In the latter group, strong associations with specific HLA DQA1 and DQB1 alleles have been observed. To determine if a similar distribution of alleles occurs in cystic fibrosis patients with diabetes, a cohort of these individuals was typed for DQA1 and DQB1 alleles. HLA DQB1*0201 (Asp57-) was more frequent in diabetics compared to controls (40.4 vs 28%), while the frequency of alleles encoding Asp57+ molecules was lower in diabetics relative to both the cystic fibrosis-only controls (P = 0.025) and the general population (P = 0.008). The presence of at least one protective DQA1-DQB1 heterodimer (i.e., Arg52- and Asp57+, respectively) in cis or trans was significantly lower in the diabetics than in either of the control groups. Thus, the HLA alleles known to be associated with insulin-dependent diabetes mellitus in the general population are also found in diabetics with cystic fibrosis.

Adolescent↗
PubMed1994

Sensitivity of single-strand conformation polymorphism and heteroduplex method for mutation detection in the cystic fibrosis gene.

The gene responsible for cystic fibrosis (CF) contains 27 coding exons and more than 300 independent mutations have been identified. An efficient and optimized strategy is required to identify additional mutations and/or to screen patient samples for the presence of known mutations. We have tested several different conditions for performing single-stranded conformation polymorphism (SSCP) analysis in order to determine the efficiency of the method and to identify the optimum conditions for mutation detection. Each exon and corresponding exon boundaries were amplified. A panel of 134 known CF mutations were used to test the efficiency of detection of mutations. The SSCP conditions were varied by altering the percentage and cross-linking of the acrylamide, employing MDE (an acrylamide substitute), and by adding sucrose and glycerol. The presence of heteroduplexes could be detected on most gels and in some cases contributed to the ability to distinguish certain mutations. Each analysis condition detected 75-98% of the mutations, and all of the mutations could be detected by at least one condition. Therefore, an optimized SSCP analysis can be used to efficiently screen for mutations in a large gene.

Base Sequence↗
PubMed1994

Localization of the gene for the nevoid basal cell carcinoma syndrome.

The nevoid basal cell carcinoma syndrome (NBCC) is an autosomal dominant multisystem disorder characterized by multiple basal cell carcinomas, jaw cysts, pits of the palms and/or soles, ectopic calcification, and skeletal malformations. The NBCC gene has recently been mapped to chromosome 9q22.3-9q31. In order to further define the region containing the NBCC gene, we have analyzed 137 individuals from eight families for linkage, using 11 markers from the region. Eight markers showed statistically significant evidence for linkage to NBCC. Three markers (D9S180, ALDOB, and D9S173) showed no definite recombination with the disease locus. All families showed some evidence for linkage to markers in this region. On the basis of the inspection of individual recombinants and previously published information about map location, we suggest the following order for the markers: D9S119-D9S12-D9S197-D9S196-(NBCC,D9S180 -D9S173,ALDOB)-D9S109- D9S127-(D9S53,D9S29). We are currently developing YAC contigs for the most closely linked markers, to further refine the location of the NBCC gene.

Alleles↗
PubMed1994

Polymorphic admixture typing in human ethnic populations.

A panel of 257 RFLP loci was selected on the basis of high heterozygosity in Caucasian DNA surveys and equivalent spacing throughout the human genome. Probes from each locus were used in a Southern blot survey of allele frequency distribution for four human ethnic groups: Caucasian, African American, Asian (Chinese), and American Indian (Cheyenne). Nearly all RFLP loci were polymorphic in each group, albeit with a broad range of differing allele frequencies (delta). The distribution of frequency differences (delta values) was used for three purposes: (1) to provide estimates for genetic distance (differentiation) among these ethnic groups, (2) to revisit with a large data set the proportion of human genetic variation attributable to differentiation within ethnic groups, and (3) to identify loci with high delta values between recently admixed populations of use in mapping by admixture linkage disequilibrium (MALD). Although most markers display significant allele frequency differences between ethnic groups, the overall genetic distances between ethnic groups were small (.066-.098), and < 10% of the measured overall molecular genetic diversity in these human samples can be attributed to "racial" differentiation. The median delta values for pairwise comparisons between groups fell between .15 and .20, permitting identification of highly informative RFLP loci for MALD disease association studies.

Alleles↗
PubMed1993

Cloning and organization of the abc and mdl genes of Escherichia coli: relationship to eukaryotic multidrug resistance.

Using degenerate oligodeoxyribonucleotides from conserved regions of the gene family encoding ATP-binding domain of the active transporter, two new Escherichia coli genes were identified. The first of the genes, named mdl (multidrug resistance-like), is located at min 10.2 of the E. coli chromosome and encodes two ATP-binding motifs and two hydrophobic (transmembrane) domains. The ATP-binding domains of mdl show 35-38% amino acid (aa) identity with members of the eukaryotic P-glycoprotein/multidrug resistance family. To date, 25 members of the ATP-transporter/permease gene family have been characterized in E. coli. Comparison of the ATP-binding domains from this family indicates that mdl is part of a distinct subfamily of sequences that includes hlyB, msbA, and cvaB. Gene-disruption studies revealed that mdl is not essential for cell growth. The second open reading frame, named abc (ATP-binding cassette), is located at min 4.9 of the chromosome, encodes a single ATP-binding domain, and is most homologous to ftsE, a cell division control gene of E. coli. The abc gene product also shows aa sequence homology to several E. coli permeases.

ATP Binding Cassette Transporter, Subfamily B, Mem↗