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Biomedical subjects

D Wells

Publications and source records attributed to D Wells.

At least 73 records · Page 4Linked to original sources
PubMed1997

Hereditary multiple exostoses (EXT): mutational studies of familial EXT1 cases and EXT-associated malignancies.

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the formation of cartilage-capped prominences that develop from the growth centers of the long bones. EXT is genetically heterogeneous, with three loci, currently identified on chromosomes 8q24.1, 11p13, and 19q. The EXT1 gene, located on chromosome 8q24.1, has been cloned and is encoded by a 3.4-kb cDNA. Five mutations in the EXT1 gene have been identified--four germ-line mutations, including two unrelated families with the same mutation, and one somatic mutation in a patient with chondrosarcoma. Four of the mutations identified resulted in frameshifts and premature termination codons, while the fifth mutation resulted in a substitution of leucine for arginine. Loss of heterozygosity (LOH) analysis of chondrosarcomas and chondroblastomas revealed multiple LOH events at loci on chromosomes 3q, 8q, 10q, and 19q. One sporadic chondrosarcoma demonstrated LOH for EXT1 and EXT3, while a second underwent LOH for EXT2 and chromosome 10. A third chondrosarcoma underwent LOH for EXT1 and chromosome 3q. These results agree with previous findings that mutations at EXT1 and multiple genetic events that include LOH at other loci may be required for the development of chondrosarcoma.

Bone Neoplasms↗
PubMed1996

Human guanylate kinase (GUK1): cDNA sequence, expression and chromosomal localisation.

Guanylate kinase (GK) catalyses the conversion of GMP to GTP as part of the cGMP cycle. In mammalian phototransduction, this cycle is essential for the regeneration of cGMP following its hydrolysis by phosphodiesterase. Mutations in different parts of this signalling cascade lead to retinal degeneration in humans. Protein studies have localized a locus for GK to a region of human chromosome 1 that also contains an autosomal recessive form of retinitis pigmentosa (RP12) and Usher's type 11a (USH2A). We report the sequence of this human GK (GUK1) and a further refinement of its localization to 1q32-41, placing it in the same interval as USH2A.

Amino Acid Sequence↗
PubMed1996

Hereditary multiple exostoses: confirmation of linkage to chromosomes 8 and 11.

Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the formation of cartilage capped prominences that develop from the epiphyses of the long bones. EXT is heterogeneous with three different locations currently identified on chromosomes 8, 11, and 19. Recently, we identified and studied 12 large multigenerational EXT families. Linkage analyses demonstrates that 6 of these families map to 8q24 and 6 to 11p. None of the families map to the chromosome 19 locus. The results suggest that there are two major loci, on chromosomes 8 and 11, involved in the cause of EXT. The locus on chromosome 19 remains to be confirmed.

Chromosomes, Human, Pair 11↗
PubMed1995

Construction of 110 cosmid markers and a 4.5-Mb YAC contig on human chromosome 8p12-q11.

Microcell hybrids containing various regions of human chromosome 8 were formed by microcell-mediated transfer of neo-tagged chromosome 8 into the cells derived from severe combined immunodeficiency (SCID) mouse. Thus, 110 cosmid markers were isolated from SV40-transformed SCID fibroblast cell line (SCVA) containing a p12-q11.1 region of human chromosome 8 and were assigned to eight regions in 8p12-q11.1, using a microcell-hybrid panel. For positional cloning of a human gene that restores the DNA-repair defect in a mouse with SCID on 8p11.1-q11.1 (SCID region), we constructed a yeast artificial chromosome (YAC) contig of about 4.5 Mb. Overlapping YACs were further aligned by restriction mapping, using rare-cutting restriction endonucleases. The cosmids and YAC contig should facilitate isolation of the SCID gene and other genes, such as the Werner syndrome-responsible gene in or near this region.

Animals↗
PubMed1995

Correlation of loss of heterozygosity with cytogenetic analysis using G-banding and fluorescence in situ hybridization in aneuploid cultures from two human testicular germ-cell tumors.

A detailed karyotype analysis using fluorescence in situ hybridization (FISH), with 24 chromosome-specific paint probes has been carried out on newly established cell lines from two testicular tumors, an i(12p)-positive teratoma, and an i(12p)-negative combined seminoma/teratoma. This has been correlated with loss of heterozygosity (LOH) and allelic imbalance, using DNA RFLP analysis to clarify the genetic changes and to identify any common regions of deletion or rearrangement. With G-banding alone, a total of 11 breakpoints were recognized. After FISH, the position of seven required revision, and 21 new ones were identified. The chromosomes involved most frequently in both tumors were numbers 1, 12, and 18. Breakpoints in 11q and 16q were also seen in both, and seven or more copies of 12p per cell were found in all clones. LOH was found for 18q in both tumors, and overall was much more frequent in underrepresented regions (one or two copies). On the whole, there was good agreement between the cytogenetic and DNA RFLP data; loci showing allelic imbalance generally had an odd number of copies of the chromosome region in which they were known to be located. Combined data on the chromosome 1 translocations in both tumors suggested that rearrangements were more complicated than cytogenetics alone had predicted.

Alleles↗
PubMed1995

Rapid detection of rare variants and common polymorphisms in the APC gene by PCR-SSCP for presymptomatic diagnosis and showing allele loss.

During the course of screening the 5' half of exon 15 of the APC gene for germline and somatic mutations in two groups of patients, those with the inherited cancer prone syndrome adenomatous polyposis coli (APC) or with sporadic colorectal cancer, we have identified a number of intragenic changes that are not associated with the disease phenotype. Four of these changes are rare variants, each confined to one or two families and not detected in 50 additional unrelated people. Two common polymorphisms, at codon 1493 (exon 15I) and codon 1678 (exon 15J), were extensively investigated and found to be in almost complete linkage disequilibrium not only with each other but with a previously described polymorphism at codon 1960 (exon 15N). The rapid and sensitive single strand conformation assay used provides an efficient method for presymptomatic diagnosis using intragenic variants and was additionally used to show allele loss at the APC locus in sporadic colorectal carcinomas.

Adenomatous Polyposis Coli↗
PubMed1995

Localisation of the gene encoding diacylglycerol kinase 3 (DAGK3) to human chromosome 3q27-28 and mouse chromosome 16.

The gene encoding a 90 kDa diacylglycerol kinase protein, DAGK3, that is predominately expressed in the retina, was localised by fluorescence in situ hybridisation to human chromosome 3q27-28. This was subsequently confirmed by mapping of its mouse homologue to chromosome 16, a region syntenic to this part of human chromosome 3. No retinopathies have so far been assigned to this region.

Animals↗
PubMed1994

Analysis of a 70 kb segment of DNA containing the human zeta and alpha-globin genes linked to their regulatory element (HS-40) in transgenic mice.

We have ligated two cosmids through an oligonucleotide linker to produce a single fragment spanning 70 kb of the human alpha-globin cluster, in which the alpha-like globin genes (zeta 2, alpha 2 and alpha 1), their regulatory element (HS-40) and erythroid-specific DNase I hypersensitive sites accurately retain their normal genomic organization. The zeta (embryonic) and alpha (embryonic, fetal and adult) globin genes were expressed in all 17 transgenic embryos. Similarly, all fetal and adult mice from seven transgenic lines that contained one or more copies of the fragment, produced up to 66% of the level of endogenous mouse alpha-globin mRNA. However, as for smaller constructs containing these elements, human alpha-globin expression was not copy number dependent and decreased by 1.5-9.0 fold during development. These findings suggest that either it is not possible to obtain full regulation of human alpha-globin expression in transgenic mice or, more likely, that additional alpha-globin regulatory elements lie beyond the 70 kb segment of DNA analysed.

Animals↗
PubMed1994

A panel of radiation hybrids for human chromosome 8.

We have developed a panel of radiation hybrids containing fragments of chromosome 8 as the only human material. The human chromosome content of each cell line was determined relative to an ordered map of sequence tagged sites (STSs) specific to chromosome 8. Between one and four fragments of chromosome 8 were identified in each cell line, with an average of 25% of the STSs retained in each line. Subclones of one radiation hybrid were examined to determine whether all cells within a line are homogeneous with respect to chromosome 8 sequence content. There was considerable variability between subclones, with retention rates for individual STSs ranging from 5 to 100% in different clones. Furthermore, a gradient of retention of sequences along the length of one large chromosome fragment was found, suggesting that sequence loss involved deletions from one end of the fragment at early stages in the establishment of the cell line. We have also made use of the radiation hybrids to develop novel sequence tagged sites for the pericentromeric region of chromosome 8.

Adenine Phosphoribosyltransferase↗
PubMed1994

Loss of chromosome arm 8p loci in prostate cancer: mapping by quantitative allelic imbalance.

A previous study of 18 primary or metastatic prostate cancers showed loss of genetic markers on chromosome 8; 10, or 16 in more than 50% of cases [Bergerheim USR et al. (1991) Genes Chromosom Cancer 3:215-220]. The small size and infiltrative nature of primary prostatic tumors have hindered efforts to assess allelic losses by traditional restriction fragment length polymorphism (RFLP)/Southern blotting methods. To improve the sensitivity and specificity of this analysis in early prostate cancer, we have amplified polymorphic microsatellite repeats by polymerase chain reaction (PCR), and have quantitated allelic imbalances with phosphor imaging technology. In this study, 63 primary prostate tumors and matched benign tissues obtained by radical prostatectomy were examined at 28 genetic loci on chromosome 8, all but five of which were located on the short arm. Twenty-nine (46%) of the 63 cases showed loss of at least one locus. Multiple adjacent loci, usually including the LPL and MSR genes in 8p22, were lost in 28 cases. In 10 of these, losses were observed at all informative loci on the p arm. In another 15 tumors, losses were restricted to subregions of the p arm by loci retained either distally toward the p terminus or proximally at the 8p12-8p21 border, or both. In three tumors, two discrete regions of loss were observed within 8p, separated by several retained loci. Allelic loss of 8p loci was associated with higher tumor grade. These data are complementary to previous reports of allelic deletions in colorectal, hepatocellular, and non-small cell lung cancers and suggest the existence of one or more pleotropic tumor suppressor genes on 8p.

Alleles↗
PubMed1994

Localisation of the human blue cone pigment gene to chromosome band 7q31.3-32.

Blue cone pigment (BCP) is one of three types of cone photoreceptors responsible for normal colour vision. In this study, the BCP gene has been localised to chromosome 7q31.3-32 by fluorescent in situ hybridisation of cosmid clones containing the gene. This is consistent with previous mapping of the BCP gene to chromosome 7q31-35.

Cells, Cultured↗
PubMed1994

Clinical experience with preimplantation diagnosis of sex by dual fluorescent in situ hybridization.

PURPOSE: Our purpose was to assess the clinical application of dual fluorescent in situ hybridization (FISH) for the diagnosis of sex in the human preimplantation embryo. RESULTS: Over a 2-year period, 18 couples at risk of transmitting X-linked recessive disorders underwent preimplantation diagnosis of embryo sex by dual FISH with X and Y chromosome-specific DNA probes. A total of 27 in vitro fertilization (IVF) treatment cycles led to nine pregnancies; 7 reached the stage of clinical recognition, of which 2 spontaneously aborted. There were five live births, three singleton and two twin: none in disagreement with the diagnosed sex. The diagnosis was corroborated in 51 of the 74 nontransferred embryos. The efficiency of the procedure improved throughout the four treatment cycles. This was reflected in the increased proportion of double embryo transfers (from 50% in series 1 and 2 to 100% in series 3 and 4), with a consequent improvement in pregnancy rate (from 28 to 71% per embryo transfer). The excess of male embryos (male:female, 60:40 overall) and the high proportion of biopsied embryos with abnormal numbers of X and Y chromosome signals (14.5%) effectively reduced the number of normal female embryos available for transfer. CONCLUSION: Dual FISH is an efficient technique for determination of the sex of human preimplantation embryos and the additional ability to detect abnormal chromosome copy numbers, which is not possible via the polymerase chain reaction, (PCR), makes FISH the preferred technique.

Adult↗
PubMed1994

A tiered healthcare system for persons in police custody--the use of a forensic nursing service.

In February 1992 the healthcare programme for persons held in police custody within the Melbourne metropolitan area was restructured. This was undertaken as a joint exercise between Police, the Health Department and the Office of Corrections as a response to the need to develop an efficient and cost effective healthcare delivery system. A tiered medical response was instituted, utilising a forensic nurse for the primary medical contact with forensic physicians providing medical consultation and support as necessary. Criteria were developed regarding the delineation of duties appropriate for the forensic nurse and for the forensic physician. The nurses were provided with transport, communication and basic medical supplies enabling a flexible response to requests for medical attention and for the nurse to perform triage, a basic medical assessment and administer appropriate treatment. Over the 15-month period since inception over 3000 consultations have been performed by the forensic nurses. The service has been commended by police, doctors working in the prison system, forensic physicians and community groups. A comprehensive review has demonstrated the efficiency and reliability of such a service. Costs in providing the service have not increased. We conclude that a forensic nursing service is of considerable benefit in complementing a range of services provided by forensic medical officers in a metropolitan setting.

Journal Article↗
PubMed1994

Regionally clustered APC mutations are associated with a severe phenotype and occur at a high frequency in new mutation cases of adenomatous polyposis coli.

Germline mutation in APC at 5q21-22 results in the dominantly inherited syndrome adenomatous polyposis coli (APC). Somatic mutation in this gene is an early event in colorectal tumourigenesis. Both types of mutation are concentrated in the 5' half of exon 15. We have used single strand conformational polymorphism (SSCP) and heteroduplex analysis to screen for variants in this region of the gene in a total of 45 affected but unrelated individuals. Eighteen patients had no family history of the disease; of these 11 were classified as having a severe phenotype, based on an early age at presentation or cancer development. This compared with 6 of 27 familial cases. A 5 bp deletion at codon 1309 reported to occur in 10-15% of unselected APC patients worldwide, was found in 5 of the 18 new mutation cases and 4 of the 27 familial cases: all nine were classed as severe. A further 3 new mutations and 1 familial mutation were located downstream from codon 1309, these individuals similarly being classed as phenotypically severe. In contrast all of the APC mutations detected in affected individuals with an average phenotype were located prior to codon 1309. The frequent association of a severe phenotype with fresh mutation may explain the apparent conflict of a high mutation rate (20-30%) in a condition, which on average, is lethal at a post-reproductive age.

Adenomatous Polyposis Coli↗