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Biomedical subjects

D Wells

Publications and source records attributed to D Wells.

At least 37 records · Page 2Linked to original sources
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

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↗
PubMed1993

Germline rearrangement of MCC and APC detected by pulsed field gel electrophoresis and fluorescent in situ hybridization.

Pulsed field gel electrophoresis was carried out on lymphocyte DNA obtained from ten patients with the inherited premalignant condition adenomatous polyposis coli and a similar number of control samples to search for large scale molecular rearrangements in the vicinity of the APC locus. DNA from one patient showed a rearranged pattern which was interpreted as evidence for an inversion of approximately 150 kb, changing the transcriptional orientation of the neighbouring MCC gene and bringing it closer to APC. Such an interpretation was supported by fluorescent in situ hybridization data.

Adenomatous Polyposis Coli↗
PubMed1993

Adolescent affective aggression: an intervention model.

Affective aggression among adolescents is defined and described based upon primary research. A model of affective aggression is provided as a means of delineating the functional and observable components. Based upon these components, various interventions are provided as means of altering the aggression in adolescents.

Adolescent↗
PubMed1992

Closely linked H2B genes in the marine copepod, Tigriopus californicus indicate a recent gene duplication or gene conversion event.

Two nonallelic histone gene clusters were characterized in the marine copepod, Tigriopus californicus. The DNA sequence of one of the clusters reveals six genes in the contiguous arrangement of H2B, H1, H3, H4, H2B and H2A. The order of genes within the second cluster is H3, H4, H2B and H2A. There is no evidence for the presence of an H1 gene in this cluster. Comparison of the three copepod H2B genes reveals a high degree of similarity between the 5' upstream regions and between the amino terminal halves of the two H2B genes found within the same cluster. From these data we infer that gene duplication and/or gene conversion events occurred within this cluster in the recent past.

Alleles↗
PubMed1991

Method for separation and determination of lactone and hydroxy acid forms of a new HMG CoA reductase inhibitor (RG 12561) in plasma.

The new drug RG 12561 (I) is a lactone that is undergoing clinical evaluation for its cholesterol lowering effect based on potent HMG CoA reductase inhibitory activity displayed by its open hydroxy acid form. To determine the dispositional characteristics of the drug, a method was developed for determination of the two forms in plasma. A 0.25-ml aliquot of plasma was deproteinized with 0.5 ml of methanol, and the lactone was extracted with hexane-ethyl acetate (75:25, v/v). The methanolic plasma was then acidified followed by extraction of the hydroxy acid with hexane-ethyl acetate. The extracts were dried, reconstituted and analyzed by isocratic, reversed-phase high-performance liquid chromatography using ultraviolet absorbance at 254 nm. The separations were performed utilizing a C18 column with mobile phase consisting of acetonitrile, 2-propanol and 0.1 M acetate buffer (pH 5), the proportions of which differed depending on the form of drug analyzed. The method was found to be selective and a quantitation limit of 50 ng/ml was established. Validation studies demonstrated that the method was sufficiently accurate and precise for determining disposition of the drug in the dog.

Animals↗
PubMed1991

An H3-H4 histone gene pair in the marine copepod Tigriopus californicus, contains an intergenic dyad symmetry element.

Histone genes are one of the most widely studied multigene families in eucaryotes. Over 200 histone genes have been sequenced, primarily in vertebrates, echinoderms, fungi and plants. We present here the structure and genomic orientation of an H3-H4 histone gene pair from the marine copepod, Tigriopus californicus. These histone gene sequences are the first to be determined for the class Crustacea and among the first to be determined for protostomes. The H4 and H3 genes in Tigriopus are shown to be adjacent, to have opposite polarity, and to contain a 26 bp region of dyad symmetry centrally located within the spacer region between the two genes. A similarly located dyad element has been found in yeast which contributes to the coordinated cell cycle control of the adjacent histone genes. The Tigriopus H3-H4 histone gene pair is clustered with one H2A and two H2B histone genes on a 15 kb genomic Bam H1 fragment. The H4 gene sequence predicts an H4 protein with an unusual serine to threonine substitution at the amino terminal residue. The H3 gene sequence predicts an H3 protein which is identical to the vertebrate H3.2 histone.

Amino Acid Sequence↗
PubMed1991

Characterization of an unusual human histone H3.3 pseudogene.

The analysis of a genomic loci containing human histone H3.3 processed pseudogenes, has revealed two regions that are unusually rich in other retroposons. At one of the loci the H3.3 pseudogene is itself interrupted by 2 Alu repetitive sequences. The characterization of these two recently transposed Alus provides confirmation of the "multiple origin" hypothesis of these repetitive elements. The unusual occurrence of 3 different types of retroposons in a small region suggests that there may be particular chromosomal regions that are hot spots for retroposon insertion.

Base Sequence↗