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Biomedical subjects

A F Markham

Publications and source records attributed to A F Markham.

At least 163 records · Page 9Linked to original sources
PubMed1996

Increased elafin expression in cystic, dysplastic and neoplastic oral tissues.

Expression of human leukocyte elastase inhibitor, elafin, otherwise known as skin-derived antileukoproteinase inhibitor (SKALP), was investigated in normal and abnormal oral tissues using a specific anti-SKALP rabbit antiserum. Weak staining was observed in keratinizing epithelia of normal oral mucosa but not in non-keratinizing mucosa. Increased expression was also observed in the suprabasal layers of dysplastic oral epithelia and in well-differentiated squamous cell carcinoma, but not in basal cell carcinoma. A uniform strong expression was observed in all supra-basal layers of odontogenic keratocyst epithelia, except in regions where inflammatory infiltrate was adjacent to keratocyst epithelia. In contrast, elafin expression in a small number of dentigerous cysts and ameloblastomas was more patchy. The increased levels of elafin in keratocyst epithelia and dysplastic tissue may be a cellular homoeostatic response to generate a protective barrier preventing proteolytic degradation of underlying elastic tissue.

Ameloblastoma↗
PubMed1996

Novel primer specific false terminations during DNA sequencing reactions: danger of inaccuracy of mutation analysis in molecular diagnostics.

The determination of nucleotide sequence is fundamental to the identification and molecular analysis of genes. Direct sequencing of PCR products is now becoming a commonplace procedure for haplotype analysis, and for defining mutations and polymorphism within genes, particularly for diagnostic purposes. A previously unrecognised phenomenon, primer related variability, observed in sequence data generated using Taq cycle sequencing and T7 Sequenase sequencing, is reported. This suggests that caution is necessary when interpreting DNA sequence data. This is particularly important in situations where treatment may be dependent on the accuracy of the molecular diagnosis.

Journal Article↗
PubMed1995

Molecular genetic analysis of the human sorbitol dehydrogenase gene.

The polyol pathway comprises the enzymes aldose reductase and sorbitol dehydrogenase, which convert glucose to sorbitol and sorbitol to fructose, respectively, particularly in hyperglycemic states. The accumulation and toxicity of sorbitol in specific tissues has been implicated in the development of microvascular problems in some diabetic patients. Inappropriate sorbitol accumulation in some patients may be the result of polymorphic variation in the human sorbitol dehydrogenase gene, causing reduced expression levels or enzymatic activity. We now describe the structure and expression profile of the human sorbitol dehydrogenase gene and identify a range of polymorphic variants that may be useful for co-segregation studies in diabetic patients with and without severe clinical complications from their disease.

Adult↗
PubMed1995

A human ubiquitin conjugating enzyme, L-UBC, maps in the Alzheimer's disease locus on chromosome 14q24.3.

We have identified a novel ubiquitin conjugating enzyme gene, L-UBC, which maps to human Chromosome (Chr) 14q24.3. This is also the location of the major early onset familial Alzheimer's disease gene (FAD3). L-UBC encodes a protein that demonstrates homology to the yeast ubiquitin conjugating enzyme, UBC-4, and human UbcH5. Their functions are to ubiquitinate specific proteins targeted for degradation. The protein also exhibits very strong homology to a rabbit protein, E2-F1, which mediates p53 degradation driven by papilloma virus E6 protein in vitro. The accumulation of specific proteins that have undergone aberrant processing in neurofibrillary tangles and amyloid plaques is the classic pathological feature in brains of Alzheimer's disease patients. Abnormal ubiquitination has previously been suggested to play a role in the etiology of Alzheimer's disease. This gene therefore represents a plausible candidate gene for FAD3.

Alzheimer Disease↗
PubMed1995

Human glucokinase regulatory protein (GCKR): cDNA and genomic cloning, complete primary structure, and chromosomal localization.

Null mutations in the glucokinase (GCK) gene can cause autosomal dominant type 2 diabetes (maturity onset diabetes of the young, MODY); however, MODY is genetically heterogeneous. In both liver and pancreatic islet, glucokinase is subject to inhibition by a regulatory protein (GCKR). Given the role of GCK in MODY, GCKR is itself a candidate type 2 diabetes susceptibility gene. Here we describe the structure of full-length (2.2 kb) cDNA for human GCKR, from the hepatoblastoma cell line HepG2. The human GCKR translation product has 625 amino acids and a predicted molecular weight of 68,700. It has 88% amino acid identity to rat GCKR. Yeast artificial chromosomes (YAC clones) containing human GCKR were isolated, and the gene was mapped to Chromosome (Chr) 2p23 by fluorescent in situ hybridization and somatic cell hybrid analysis.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Yeast artificial chromosome cloning of the beta-catenin locus on human chromosome 3p21-22.

beta-Catenin has emerged as an important component of the adherens junctions between epithelial cells. As a result of studies of its interaction with the APC gene product, it has been implicated in the development of colorectal cancer. alpha-Catenin, beta-catenin, E-cadherin and APC appear to mediate contact inhibition in epithelia. As part of the study of the organization of the beta-catenin gene, we have isolated yeast artificial chromosomes (YACs) to characterize its intron/exon structure. YAC fluorescence in situ hybridization analysis and polymerase chain reaction analysis of somatic cell hybrid DNAs show that beta-catenin maps in the 3p21-22 region, the location of tumour-suppressor genes deleted in small-cell lung cancer (SCLC) and other disorders. beta-Catenin YACs will provide a source of microsatellite markers useful in loss of heterozygosity studies to assess the importance of beta-catenin deletions in SCLC.

Base Sequence↗
PubMed1995

Molecular basis of inherited factor XIII deficiency: identification of multiple mutations provides insights into protein function.

Factor XIII (FXIII) is a zymogen essential for normal haemostasis. In inherited FXIII deficiency the majority of cases show absence of the FXIIIa subunit. Molecular analysis of PCR-amplified FXIIIa subunit exonic regions, and of RT-PCR amplified cDNA from six patients with FXIIIa subunit deficiency, from five unrelated families, has revealed 10 sequence changes: three mutations resulting in abnormal splicing of pre-mRNA, one nonsense mutation, one deletion/insertion change, three point mutations producing Val34Leu, Asn60Lys and Arg408Gln changes, and two silent mutations. In three families the patients are homozygous for a specific deficiency causing mutation, and patients from the remaining two families are compound heterozygotes. Understanding the molecular pathology of the disorder provides insights into the structure-function relationships of the various domains within the FXIII protein. From a clinical point of view, it enables direct diagnosis at the DNA level and may aid the development of FXIII analogues to promote wound healing.

Base Sequence↗
PubMed1993

The production of PCR products with 5' single-stranded tails using primers that incorporate novel phosphoramidite intermediates.

We have prepared several novel phosphoramidites and have synthesised oligonucleotides incorporating them internally. The presence of these residues in an oligonucleotide template presents an impossible barrier to primed synthesis by Taq DNA polymerase. When extended as polymerase chain reaction products, these oligonucleotides no longer serve as templates for the polymerase beyond the insertion sites of the modified intermediates, thereby producing single-stranded tails on amplification products. These tails can then be used for solid phase capture and colorimetric detection of PCR products.

Alkaline Phosphatase↗
PubMed1992

A human aldehyde dehydrogenase (aldose reductase) pseudogene: nucleotide sequence analysis and assignment to chromosome 3.

Four cosmid clones containing putative pseudogenes for human aldehyde dehydrogenase (Aldose reductase) were isolated from libraries made to two individuals. These clones show different patterns on digestion with restriction endonucleases and probably represent distinct and separate loci. The DNA sequence of one of the putative pseudogenes (cosmid AR.F) was determined, and comparisons demonstrate 89.7% homology with the cDNA sequence of the functional aldose reductase gene. This pseudogene sequence contains no intronic sequences, whereas the functional aldose reductase has nine introns. In addition, the homology disappears in region 5' to the transcription start site for the cDNA, implying that regulatory elements such as the promoter are missing from this pseudogene. The pseudogene defined by cosmid AR.F has been mapped to chromosome 3 by polymerase chain reaction using amplimers specific for this pseudogene to amplify DNA from somatic cell hybrids.

Aldehyde Reductase↗
PubMed1992

Walking, cloning, and mapping with yeast artificial chromosomes: a contig encompassing D21S13 and D21S16.

Chromosome 21 has often been used as a model system for the development of genome mapping and cloning strategies in humans. In this report methods for systematic chromosome walking, cloning, and mapping are exemplified in the construction of a 1.5-Mb yeast artificial chromosome (YAC) contig encompassing and extending 400 kb beyond each of the genetic loci D21S13 and D21S16. Isolation of insert-terminal sequences from YACs in this contig provides a set of closely spaced physical markers. These have been used to generate a long-range genomic restriction map.

Base Sequence↗
PubMed1992

Application of PCR to human gene detection.

The advent of the polymerase chain reaction has stimulated the development of a number of rapid methods for characterizing human genes. In addition, the unprecedented level of sensitivity offered by some of these methods may prove to be of great value in the detection of minority cell populations. Over the past year, technical developments have been made in this area.

Genes↗