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D Wells

Publications and source records attributed to D Wells.

At least 37 records · Page 2Linked to original sources
PubMed2000

NPS 1506, a moderate affinity uncompetitive NMDA receptor antagonist: preclinical summary and clinical experience.

NPS Pharmaceuticals, Inc. (NPS) has synthesized a series of open-channel blockers with varying potencies at the NMDA receptor. NPS 1506 (Fig. 1) is a moderate affinity antagonist that inhibits NMDA/glycine-induced increases in cytosolic calcium in cultured rat cerebellar granule cells (IC50 = 476nM) and displaces the binding of [3H]MK-801 to rat cortical membranes (IC50 = 664nM).

Adolescent↗
PubMed2000

Comparative genomic hybridization reveals extensive variation among different MCF-7 cell stocks.

Comparative genomic hybridization (CGH) allows the detection of DNA sequence copy number changes on a genome-wide scale in a single hybridization reaction. The ability of CGH to be applied to formalin-fixed, paraffin-embedded tumor samples has lead to its widespread application in the cytogenetic analysis of archival material. When setting up CGH in the laboratory, rigorous control experiments must be carried out to ensure that the losses and gains are scored correctly. Groups interested in breast cancer frequently use the MCF-7 cell line as a positive control in these experiments, comparing the results to previously described genetic alterations. Here we present the results of CGH carried out with three stocks of MCF-7 cells. The cells differ widely in their proliferative response to 17-beta estradiol and show extensive variation in copy number changes affecting specific chromosomal regions. We suggest that care must be taken, therefore, when choosing a cell line as a positive control for CGH experiments.

Breast Neoplasms↗
PubMed2000

Comparative genomic hybridization analysis of myoepithelial carcinoma of the breast.

Although there seems to be a common stem cell for the two epithelial cell types in the breast, the vast majority of breast cancers exhibit a luminal phenotype. Pure myoepithelial carcinomas are rare. We report our findings of genetic alterations in these tumors. We have analyzed 10 cases of pure myoepithelial cell carcinomas using laser capture microdissection and comparative genomic hybridization. The mean number of changes was 2.1 (range 0-4), compared with a mean of 8.6 (range 3.6-13.8) in unselected ductal carcinomas. Common alterations included loss at 16q (3/10 cases), 17p (3/10), 11q (2/10), and 16p (2/10), regions also commonly deleted in ductal carcinomas. The single case in which both pure myoepithelial carcinoma and invasive ductal carcinoma was present showed 2 alterations in the myoepithelial tumor (losses at 17p and 17q), whereas the invasive ductal component showed 15 alterations (5 gains and 9 losses), including loss at 17p. The sharing of 17p loss in myoepithelial and ductal carcinoma is consistent with a common stem cell model in the breast. The relatively few genetic alterations in otherwise aggressive neoplasms suggests that myoepithelial tumors may be a good model for the delineation of genes important in breast tumorigenesis.

Aged↗
PubMed2000

Psychiatric nurses' thoughts and feelings about restraint use: a decision dilemma.

Patients continue to be physically restrained in psychiatric in-patient units. Studies concerned with staff-related variables have suggested that the emotional reactions of professionals to violent or potentially violent patients may influence their use of restrictive measures. However, no research existed that described psychiatric nurses' thoughts and feelings while they were involved in restraint situations nor what effects their thoughts and feelings had on their decision to restrain. Therefore, an ethnographic qualitative study was conducted in order to describe systematically nurses' thoughts and feelings toward restraint use in the in-patient psychiatric setting. The conceptual approach guiding the study was Etzioni's (1992) theoretical work on the role of normative-affective factors in decision making. Following ethical approval of the study, ethnographic interviews were conducted with six nurses from an in-patient psychiatric unit who had participated in a situation involving the physical restraint of a patient. The analysis of the nurses' thoughts and feelings revealed that the restraint situation represented a decision dilemma for them. This overall finding was supported by four themes: (1) the framing of the situation: the potential for imminent harm; (2) the unsuccessful search for alternatives to physical restraints; (3) the conflicted nurse; and (4) the contextual conditions of restraint. The results indicated that restraint use is more complex than is currently conveyed in the literature in that normative-affective factors influenced nurses' restraint decisions. The findings advance our understanding of why restraints continue to be used in psychiatric units. Further research is necessary to examine the findings in other settings and with a larger and more diverse population in order to draw definitive conclusions about the continued use of physical restraints in the care of patients on psychiatric units in hospitals.

Adult↗
PubMed2000

Comprehensive chromosomal analysis of human preimplantation embryos using whole genome amplification and single cell comparative genomic hybridization.

Analysis of small numbers of chromosomes using interphase fluorescent in-situ hybridization (FISH) probes has revealed that 50% of human preimplantation embryos contain abnormal cells. Detection of high levels of mosaicism with so few probes has led some researchers to extrapolate that a full analysis of all 23 pairs of chromosomes would reveal that all human embryos contain a proportion of abnormal cells. However, existing cytogenetic protocols cannot achieve such an analysis due to technical limitations. We have developed a novel technique based on whole genome amplification and comparative genomic hybridization (CGH), which for the first time allows the copy number of every chromosome to be assessed in almost every cell of a cleavage-stage embryo. We have successfully analysed 64 cells (blastomeres) derived from 12 embryos and have detected unusual forms of aneuploidy, high levels of chromosomal mosaicism, non-mosaic aneuploidy and chromosome breakage. This is the first report of a comprehensive assessment of chromosome copy number in human embryos and indicates that, despite high levels of mosaicism, some embryos do have normal chromosome numbers in every cell. Such embryos may have a superior developmental potential, and their low frequency may explain correspondingly low success rates of natural and assisted conception in humans.

Blastomeres↗
PubMed2000

Detection and characterisation of the genes encoding glyoxalase I and II from Neisseria meningitidis.

Glyoxalase enzymes I and II are involved in a detoxification process consisting of conversion of reactive dicarbonyl compounds (e.g., methylglyoxal) to less reactive hydroxy acids. The structural gene for meningococcal glyoxalase I (gloA) was identified by screening an expression library with a rabbit antiserum. The meningococcal gloA gene consisted of 138 deduced amino acids, with a calculated mol. wt of 15.7 kDa. The DNA and deduced protein sequence of gloA was compared to known sequences of glyoxalase I enzymes and showed high homology with gloA of several eukaryotic and prokaryotic species. Insertion of a gloA-containing plasmid in Escherichia coli increased the host organism's tolerance to methylglyoxal from <2 mM to >4 mM, thus demonstrating its functional identity. A databank search also revealed the presence of a putative gloB gene, encoding glyoxalase II (GlxII), in the recently released genomic sequences of Neisseria meningitidis and N. gonorrhoeae.

Amino Acid Sequence↗
PubMed1999

Control of fertilization-independent endosperm development by the MEDEA polycomb gene in Arabidopsis.

Higher plant reproduction is unique because two cells are fertilized in the haploid female gametophyte. Egg and sperm nuclei fuse to form the embryo. A second sperm nucleus fuses with the central cell nucleus that replicates to generate the endosperm, a tissue that supports embryo development. To understand mechanisms that initiate reproduction, we isolated a mutation in Arabidopsis, f644, that allows for replication of the central cell and subsequent endosperm development without fertilization. When mutant f644 egg and central cells are fertilized by wild-type sperm, embryo development is inhibited, and endosperm is overproduced. By using a map-based strategy, we cloned and sequenced the F644 gene and showed that it encodes a SET-domain polycomb protein. Subsequently, we found that F644 is identical to MEDEA (MEA), a gene whose maternal-derived allele is required for embryogenesis [Grossniklaus, U., Vielle-Calzada, J.-P., Hoeppner, M. A. & Gagliano, W. B. (1998) Science 280, 446-450]. Together, these results reveal functions for plant polycomb proteins in the suppression of central cell proliferation and endosperm development. We discuss models to explain how polycomb proteins function to suppress endosperm and promote embryo development.

Arabidopsis↗
PubMed1999

Detailed chromosomal and molecular genetic analysis of single cells by whole genome amplification and comparative genomic hybridisation.

Molecular genetic analysis of isolated single cells and other minute DNA samples is limited because there is insufficient DNA to perform more than one independent PCR amplification. One solution to this problem is to first amplify the entire genome, thus providing enough DNA for numerous subsequent PCRs. In this study we have investigated four different methods of whole genome amplification performed on single cells, and have identified a protocol that generates sufficient quantities of DNA for comparative genomic hybridisation (CGH) as well as more than 90 independent amplification reactions. Thus, numerous specific loci and the copy number of every chromosome can be assessed in a single cell. We report here the first reliable application of CGH to single cells from human preimplantation embryos (blastomeres) and to single fibroblasts, buccal cells and amniocytes.

Humans↗
PubMed1999

Recent advances and future developments in PGD.

PGD has now been practised for a decade. The basic techniques currently used involve embryo biopsy, polymerase chain reaction (PCR) and fluorescent in situ hybridization (FISH). Recent advances in molecular diagnostic techniques have included the use of fluorescent PCR, multiplex PCR and whole genome amplification. For cytogenetic analysis, many centres are now using five or more chromosome probes to examine for chromosome abnormalities, sexing and aneuploidy. Future improvements in molecular diagnosis include the use of quantitative PCR, DNA fingerprinting and microarray technology. Developments in methods to analyse chromosomes from a single cell have included interphase chromosome conversion, which has already been clinically applied, and the use of comparative genomic hybridization, which is still being developed. These methods will hopefully enable more accurate and a greater number of diseases to be diagnosed at the single cell level.

Chromosome Aberrations↗
PubMed1999

Drug-mediated sexual assault.

Psychoactive substances may be given to a potential victim to alter their behaviour or conscious state. This problem is not new; alcohol has been used alone or in combination with other substances to the same effect. Doctors involved in the examination of complainants of sexual assault need to be aware of the effects of the drugs that may be used and ensure that a detailed history, examination and the appropriate specimens are taken. This report describes a series of incidents involving drug-mediated sexual assault and outlines the dilemmas that accompany such incidents.

Journal Article↗
PubMed1999

Enhanced expression of recombinant dystrophin following intramuscular injection of Epstein-Barr virus (EBV)-based mini-chromosome vectors in mdx mice.

Gene transfer by direct intramuscular injection of naked plasmid DNA has been shown to be a safe, simple but relatively inefficient method for gene delivery in vivo. Eukaryotic plasmid expression vectors incorporating the Epstein-Barr virus (EBV) origin of replication (oriP) and EBNA1 gene have been shown to act as autonomous episomally replicating gene transfer vectors which additionally provide nuclear matrix retention functions. Prolonged expression of a LacZ reporter gene and recombinant human dystrophin was shown using EBV-based plasmid vectors transfected into C2C12 mouse myoblast and myotube cultures. Intramuscular injection of EBV-based dystrophin expression plasmids into nude/mdx mice resulted in significant enhancement in the number of muscle fibres expressing recombinant dystrophin compared with a conventional vector. This effect was observed for over 10 weeks after a single administration. These results indicate the potential advantage of EBV-based expression vectors for focal plasmid-mediated gene augmentation therapy in Duchenne muscular dystrophy (DMD) and a range of other gene therapeutic applications.

Animals↗
PubMed1999

The biologic significance of rare peripheral blasts after hematopoietic cell transplantation is predicted by multidimensional flow cytometry.

A vexing problem after hematopoietic cell transplantation (HCT) for leukemia is assessing the biologic significance of low numbers of cells "suspicious" for relapse seen in morphologic review of peripheral blood smears (PBSs). In 27 patients, in apparent hematologic remission after HCT for leukemia, we studied the nature of such cells in PBSs to the endpoint of leukemic relapse by using multidimensional flow cytometry (MDF) on blood or bone marrow aspirates. Based on abnormal cytometric maturational patterns, +/- cell sorting of blasts with fluorescence in situ hybridization with informative markers, we differentiated benign recovering myeloid and lymphoid precursors from leukemic cells. In 17 patients, blasts were characterized by MDF as normal early hematopoietic precursors, lymphoblasts, or NK cells. Of these patients, 16 remained in remission for at least 42 days. In 10 patients, blasts were characterized by MDF as a malignant immunophenotype; 9 relapsed within 10 days and 1 relapsed 280 days after a graft-vs-leukemia effect. MDF status was strongly associated with a 90 x probability of relapse even after adjusting for other potential variables. Morphologic triggered MDF characterization of peripheral blasts is a powerful and rapid tool for distinguishing immature regenerative forms from early leukemic relapse.

Adolescent↗
PubMed1999

NPS 1506, a novel NMDA receptor antagonist and neuroprotectant. Review of preclinical and clinical studies.

NPS 1506 is a moderate affinity, uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. NPS 1506 is neuroprotective in rodent models of ischemic stroke, hemorrhagic stroke, and head trauma, with a 2-hr window of opportunity. Neuroprotectant doses of NPS 1506 ranged from approximately 0.1-1.0 mg/kg, with peak plasma concentrations ranging from 8-80 ng/mL. Even at doses producing behavioral toxicity, NPS 1506 did not elicit MK-801-like behaviors, did not generalize to phencyclidine (PCP), and did not elicit neuronal vacuolization. In a Phase I study, intravenous (i.v.) doses of NPS 1506 from 5-100 mg were well tolerated and provided plasma concentrations in excess of those required for neuroprotection in rodents. Adverse events at the 100-mg dose included mild dizziness and lightheadedness, and mild to moderate ataxia. Neither PCP-like psychotomimetic effects nor cardiovascular effects were noted. The long plasma half-life of NPS 1506 (approximately 60 hr) suggests that a single i.v. dose will provide prolonged neuroprotection in humans.

Adolescent↗
PubMed1999

School counselors' accuracy in identifying adolescents at risk for dropping out.

School counselors were asked to identify, using qualitative judgments alone, adolescents who they believed were at moderate risk for dropping out. These students were then administered a dropout prediction scale. Results indicated that the school counselors accurately identified potential dropouts. The paper concludes with a discussion of the ties between dropout identification and consultation with teachers.

Adolescent↗