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Biomedical subjects

D M Wilson

Publications and source records attributed to D M Wilson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Location of death in Canada. A comparison of 20th-century hospital and nonhospital locations of death and corresponding population trends.

This report compares 20th-century Canadian hospital and nonhospital location-of-death trends and corresponding population mortality trends. One of the chief findings is a hospitalization-of-death trend, with deaths in hospital peaking in 1994 at 80.5% of all deaths. The rise in hospitalization was more pronounced in the years prior to the development of a national health care program (1966). Another key finding is a gradual reduction since 1994 in hospital deaths, with this reduction occurring across all sociodemographic variables. This suggests nonhospital care options are needed to support what may be an ongoing shift away from hospitalized death and dying.

Aged↗
PubMed2001

Does the availability of hospital beds affect utilization patterns? The case of end-of-life care.

Hospital downsizing in Canada during the 1990s raised public concern over the availability of hospital care, in addition to heightening administrative interest in improving or maximizing hospital utilization. One ongoing concern about hospital utilization is that a disproportionately large share of hospital resources is used by terminally ill and dying people. A research study using 1992/1993-1996/1997 in-patient abstracts data for the province of Alberta, Canada, was undertaken to explore and describe hospital utilization by dying in-patients. This investigation found only 48.2% of all deaths in Alberta over the five years studied involved hospital in-patients. An 18.5% reduction in the number of in-patient deaths and an 83.3% reduction in length of final stay occurred when 50% of acute care beds were closed, which was followed by an increase when beds began reopening--in terms of both the number of in-patient deaths (4.8%) and the average length of stay (2.6%). The ratio of men to women, the average age of dying in-patients, and the intensity of hospital care changed relatively little over those five years. Most in-patients were admitted for nursing care; in 51.3% of all cases, no diagnostic or therapeutic procedures were performed prior to death. These findings indicate hospital bed availability influences admission to hospital and length of stay, but not treatment decisions affecting seriously ill and dying patients. In addition, reduced length of stay appears to have been a widespread response to hospital downsizing, with this change substantially preserving individual access to hospitals.

Adolescent↗
PubMed2001

Assessment and treatment of problem behavior maintained by escape from attention and access to tangible items.

The results obtained from two consecutive functional analyses conducted with a 6-year-old child with autism are described. In the initial functional analysis, the highest rates of problem behavior occurred in the play condition. In that condition, the delivery of attention appeared to occasion problem behaviors. A second functional analysis was conducted wherein an escape from attention condition and a tangible condition were added. In the second functional analysis, higher rates of responding were observed in the escape from attention and tangible conditions. The results suggested that problem behavior was maintained by negative reinforcement in the form of escape from attention and positive reinforcement in the form of gaining access to preferred tangible items. Problem behavior was treated using functional communication training combined with noncontingent reinforcement.

Autistic Disorder↗
PubMed2001

High throughput log D determination using liquid chromatography-mass spectrometry.

A method has been developed which allows direct measurement of partition coefficients (log D, log P) using liquid chromatography-mass spectrometry (LC-MS). The high throughput, microtiter plate based protocol uses small quantities of 10 mM analyte in DMSO solution (5 microL) and is therefore amenable to standard archive and screening formats. Single Ion Monitoring (SIM) mass spectrometry is used to achieve optimal sensitivity. Experimental log D values for 34 known drugs have been determined, with partition coefficients ranging from -2 to 5, giving data very similar to literature values. In these analyses, deviations from known values average less than 0.3 log units. The sample handling and data processing have been significantly automated, and the protocol has been applied to over 800 in-house lead molecules to date. In its format, sensitivity, throughput, and amenability to automation, it represents significant progress in the direct measurement of partitioning behavior [1].

Cell Line↗
PubMed2000

Functional characterization of Ape1 variants identified in the human population.

Apurinic/apyrimidinic (AP) sites are common mutagenic and cytotoxic DNA lesions. Ape1 is the major human repair enzyme for abasic sites and incises the phosphodiester backbone 5' to the lesion to initiate a cascade of events aimed at removing the AP moiety and maintaining genetic integrity. Through resequencing of genomic DNA from 128 unrelated individuals, and searching published reports and sequence databases, seven amino acid substitution variants were identified in the repair domain of human Ape1. Functional characterization revealed that three of the variants, L104R, E126D and R237A, exhibited approximately 40-60% reductions in specific incision activity. A fourth variant, D283G, is similar to the previously characterized mutant D283A found to exhibit approximately 10% repair capacity. The most common substitution (D148E; observed at an allele frequency of 0.38) had no impact on endonuclease and DNA binding activities, nor did a G306A substitution. A G241R variant showed slightly enhanced endonuclease activity relative to wild-type. In total, four of seven substitutions in the repair domain of Ape1 imparted reduced function. These reduced function variants may represent low penetrance human polymorphisms that associate with increased disease susceptibility.

Amino Acid Substitution↗
PubMed2000

The human homolog of Escherichia coli Orn degrades small single-stranded RNA and DNA oligomers.

We report here the identification of human homologues to the essential Escherichia coli Orn protein and the related yeast mitochondrial DNA-escape pathway regulatory factor Ynt20. The human proteins appear to arise from alternatively spliced transcripts, and are thus identical, except the human Ynt20 equivalent contains an NH(2)-terminal extension that possesses a predicted mitochondrial protease cleavage signal. In vitro analysis revealed that the smaller human protein exhibits a 3' to 5' exonuclease activity for small (primarily </=5 nucleotides in length) single-stranded RNA and DNA oligomers. We have named this human protein Sfn for small fragment nuclease to reflect its broad substrate range, and have termed the longer protein hSfnalpha. Sfn prefers Mn(2+) as a metal cofactor and displays a temperature-resistant (to 50 degrees C) nuclease activity. Kinetic analysis indicates that Sfn exhibits a similar affinity for small RNAs and DNAs (K(m) of approximately 1.5 micrometer), but degrades small RNAs approximately 4-fold more efficiently than DNA. Mutation of a conserved aspartate (Asp(136)) to alanine abolishes both nuclease activities of Sfn. Northern blot analysis revealed that a 1-kilobase transcript corresponding to SFN and/or SFNalpha (these mRNAs differ by only two nucleotides) is expressed at varying levels in all fetal and adult human tissues examined. Expressed tag sequence clone analysis found that the two splice variants, SFN to SFNalpha, are present at a ratio of roughly 4 to 1, respectively. The results presented within suggest a role for human Sfn in cellular nucleotide recycling.

14-3-3 Proteins↗
PubMed2000

Pharmacological evaluation of aerosolized cannabinoids in mice.

The reemergence on the debate of the use of marijuana for medicinal purposes has been the impetus for developing an acceptable delivery form of aerosolized cannabinoids. The goals of the present study were to: (1) develop and characterize the physical properties of an aerosolized form of Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the major psychoactive constituent present in marijuana; and (2) assess the pharmacological effects of cannabinoid inhalation in mice. A Small Particle Aerosol Generator (SPAG) nebulizer, used to generate the aerosol, had an output of approximately 0.154 mg/l of aerosolized Delta(9)-THC with a 2.0 microm mass median aerodynamic diameter and a 2.2 geometric standard deviation (GSD). Virtually all the particles were less than 5.0 microm in diameter suggesting that they were sufficiently small to penetrate deeply into the lungs. Inhalation exposure to aerosolized Delta(9)-THC in mice elicited antinociceptive effects that were dependent on concentration and exposure time with an estimated Delta(9)-THC dose of 1.8 mg/kg. On the other hand, inhalation exposure to Delta(9)-THC failed to produce two other indices indicative of cannabinoid activity, hypothermia and decreases in spontaneous locomotor activity. The antinociceptive effects occurred within 5 min of exposure and lasted approximately 40 min in duration. The cannabinoid receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide HCl (SR 141716A), but not naloxone, blocked these antinociceptive effects (AD(50)=0.09 mg/kg) indicating a cannabinoid receptor mechanism of action. Similarly, inhalation exposure to a water soluble cannabinoid analog, 3-(5'-cyano-1', 1'dimethylheptyl)-1-(4-N-morpholinobutyrloxy)-Delta(8)-te trahydrocann abinol (O-1057), produced antinociception that was blocked by SR 141716A. These results demonstrate that the development of an aerosolized form of cannabinoids for human medicinal use is feasible.

Administration, Inhalation↗
PubMed2000

New insights into the structure of abasic DNA from molecular dynamics simulations.

Abasic (AP) sites constitute a common form of DNA damage, arising from the spontaneous or enzymatic breakage of the N-glycosyl bond and the loss of a nucleotide base. To examine the effects of such damage on DNA structure, especially in the vicinity of the abasic sugar, four 1.5 ns molecular dynamics simulations of double-helical DNA dodecamers with and without a single abasic (tetrahydrofuran, X) lesion in a 5'-d(CXT) context have been performed and analyzed. The results indicate that the abasic site does not maintain a hole or gap in the DNA, but instead perturbs the canonical structure and induces additional flexibility close to the abasic site. In the apurinic simulations (i.e., when a pyrimidine is opposite the AP site), the abasic sugar flipped in and out of the minor groove, and the gap was water filled, except during the occurrence of a novel non-Watson-Crick C-T base pair across the abasic site. The apyrimidinic gap was not penetrated by water until the abasic sugar flipped out and remained extrahelical. Both AP helices showed kinks of 20-30 degrees at the abasic site. The Watson-Crick hydrogen bonds are more transient throughout the DNA double helices containing an abasic site. The abasic sugar displayed an unusually broad range of sugar puckers centered around the northern pucker. The increased motion of the bases and backbone near the abasic site appear to correlate with sequence-dependent helical stability. The data indicate that abasic DNA contorts more easily and in specific ways relative to unmodified DNA, an aspect likely to be important in abasic site recognition and hydrolysis.

Apurinic Acid↗
PubMed2000

Identification of factors interacting with hMSH2 in the fetal liver utilizing the yeast two-hybrid system. In vivo interaction through the C-terminal domains of hEXO1 and hMSH2 and comparative expression analysis.

Mutations in DNA mismatch repair (MMR) genes have been shown to segregate with Hereditary Nonpolyposis Colorectal Cancer (HNPCC). However, because many HNPCC families fail to display mutations in known MMR genes, we argued that changes in other components of the MMR pathway may be responsible. The increasing number of proteins reported to interact in the MMR pathway suggests that larger complexes are formed, the composition of which may differ among cell types and tissues. In an attempt to identify tissue-specific MMR-associated factors, we employed the yeast two-hybrid system, using the human hMSH2 as bait and a human fetal liver library as prey. We demonstrate that hMSH2 interacts with a human 5'-3' exonuclease 1 (hEXO1/HEX1) and that this interaction is mediated through their C-terminal domains. The hMSH6 protein does not interact with hEXO1 in the two-hybrid system. Dot-blot analysis of multiple tissue RNA revealed that hMSH2 and hEXO1 are coexpressed at high levels in fetal liver as well as in adult testis and thymus. Northern blot analysis also revealed that hEXO1/HEX1 is highly expressed in several liver cancer cell lines as well as in colon and pancreas adenocarcinomas, but not in the corresponding non-neoplastic tissue.

14-3-3 Proteins↗
PubMed2000

Mapping the protein-DNA interface and the metal-binding site of the major human apurinic/apyrimidinic endonuclease.

Apurinic/apyrimidinic (AP) endonuclease Ape1 is a key enzyme in the mammalian base excision repair pathway that corrects AP sites in the genome. Ape1 cleaves the phosphodiester bond immediately 5' to AP sites through a hydrolytic reaction involving a divalent metal co-factor. Here, site-directed mutagenesis, chemical footprinting techniques, and molecular dynamics simulations were employed to gain insights into how Ape1 interacts with its metal cation and AP DNA. It was found that Ape1 binds predominantly to the minor groove of AP DNA, and that residues R156 and Y128 contribute to protein-DNA complex stability. Furthermore, the Ape1-AP DNA footprint does not change along its reaction pathway upon active-site coordination of Mg(2+) or in the presence of DNA polymerase beta (polbeta), an interactive protein partner in AP site repair. The DNA region immediately 5' to the abasic residue was determined to be in close proximity to the Ape1 metal-binding site. Experimental evidence is provided that amino acid residues E96, D70, and D308 of Ape1 are involved in metal coordination. Molecular dynamics simulations, starting from the active site of the Ape1 crystal structure, suggest that D70 and E96 bind directly to the metal, while D308 coordinates the cation through the first hydration shell. These studies define the Ape1-AP DNA interface, determine the effect of polbeta on the Ape1-DNA interaction, and reveal new insights into the Ape1 active site and overall protein dynamics.

Amino Acid Substitution↗
PubMed2000

Macrophage colony-stimulating factor can modulate immune responses and attract dendritic cells in vivo.

Studies have indicated that professional APCs in the periphery, such as dendritic cells and macrophages, play an important role in initiating DNA vaccine-specific immune responses. To engineer the immune response induced by DNA vaccines in vivo we investigated the modulatory effects of codelivering growth factor genes for the hematopoietic APCs along with DNA vaccines. Specifically, we examined the effects on the antigen-specific immune responses following the codelivery of the gene expression cassettes for M-CSF, G-CSF, and GM-CSF along with HIV-1 DNA immunogen constructs. We observed that coimmunization with GM-CSF increased the antibody response and resulted in a significant enhancement of lymphoproliferative response. Furthermore, among all coinjection combinations, we found that M-CSF coinjections resulted in a high level of CTL enhancement. This enhancement of CTL responses observed from the coinjection with M-CSF was CD8+ T cell dependent and was associated with the presence of CD11c+ cells at the site of injection and with the antigen-specific induction of the beta-chemokine MIP-1beta, suggesting a role for this chemokine in CTL induction. These results suggest that hematopoietic growth factors should be further studied as potential adjuvants for in vivo modulators of immune responses.

Animals↗
PubMed2000

Randomized trial of a "stage-of-change" oriented smoking cessation intervention in infertile and pregnant women.

OBJECTIVE: To assess a "stage-of-change" oriented smoking cessation intervention for infertile and pregnant women, compared with standard of care. DESIGN: Randomized controlled trial. SETTING: Three university teaching hospitals in Hamilton, Ontario, Canada. PATIENT(S): Infertile women at their first visit to a tertiary referral infertility clinic (n = 94) and new patients seeking pre-natal care (n = 110) who had smoked >/= 3 cigarettes in the past six months. INTERVENTION(S): A three to five minute scripted intervention and booklet specific to the woman's "stage-of-change" in the smoking continuum, versus standard of care. Exhaled carbon-monoxide (CO) monitoring was used to validate exposure in both groups. MAIN OUTCOME MEASURE(S): Delta "stage-of-change" and rate of maintained cessation at 12 months post follow-up. RESULT(S): Intervention and control were similarly effective for infertile women: the rate of maintained cessation rose significantly from 4% to 24% over twelve months, with a mean delta "stage-of-change" 0.28. In prenatal women, neither approach was effective. Maintained cessation did not significantly change from 0 to 12 months (19% to 18%). Mean delta "stage-of-change" declined by -0.62. CONCLUSION(S): For infertile women, basic information describing the impact of smoking on fertility, along with exhaled CO monitoring and a more intensive intervention were both highly effective. In pregnant women neither approach was beneficial, with some evidence of post-partum relapse.

Adult↗
PubMed2000

Targeted antigen delivery to antigen-presenting cells including dendritic cells by engineered Fas-mediated apoptosis.

Immunity to tumors as well as to viral and bacterial pathogens is often mediated by cytotoxic T lymphocytes (CTLs). Thus, the ability to induce a strong cell-mediated immune response is an important requirement of novel immunotherapies. Antigen-presenting cells (APCs), including dendritic cells (DCs), are specialized in initiating T-cell immunity. Harnessing this innate ability of these cells to acquire and present antigens, we sought to improve antigen presentation by targeting antigens directly to DCs in vivo through apoptosis. We engineered Fas-mediated apoptotic death of antigen-bearing cells in vivo by co-expressing the immunogen and Fas in the same cell. We then observed that the death of antigen-bearing cells results in increased antigen acquisition by APCs including DCs. This in vivo strategy led to enhanced antigen-specific CTLs, and the elaboration of T helper-1 (Th1) type cytokines and chemokines. This adjuvant approach has important implications for viral and nonviral delivery strategies for vaccines or gene therapies.

Animals↗
PubMed2000

End-of-life care preferences of Canadian senior citizens with caregiving experience.

A grounded theory study of senior citizens' preferences for end-of-life care was conducted in 1998 in Canada. Seniors who had experienced the deaths of others and who had considered their own death and dying were the target population. The sample was 49 seniors who met the study criteria. Participants provided end-of-life care in a variety of settings for 1-8 family members or friends. Two concepts identified were expected dependency while dying and appropriate end-of-life care. Almost all participants preferred to be cared for at home, yet family caregivers who could provide appropriate end-of-life care when dependent were needed for this to occur. The appropriateness of end-of-life care was contingent upon the place where end-of-life care occurred, as well as the type of care provided. Life prolongation was not desired, 53% even endorsed euthanasia as a way of bringing about the inevitable end to life.

Aged↗
PubMed2000

Genomic structure and characterization of the Drosophila S3 ribosomal/DNA repair gene and mutant alleles.

The Drosophila S3 protein is known to be associated with ribosomes, where it is thought to play a role in the initiation of protein translation. The S3 protein also contains a DNA repair activity, efficiently processing 8-oxoguanine residues in DNA via an N-glycosylase/apurinic-apyrimidinic (AP) lyase activity. The gene that encodes S3 has previously been localized to one of the Minute loci on chromosome 3 in Drosophila. This study focused on the genomic organization of S3 at M(3)95A, initial promoter characterization, and analysis of three mutant alleles at this locus. The S3 gene was found to be a single-copy gene 2 to 3 kb in length and containing a single intron. The upstream 1.6-kb region was analyzed for promoter activity, identifying a presumptive regulatory domain containing potential enhancer and suppressor elements. This finding is of interest, as the S3 gene is constitutively expressed throughout development and mRNA is most likely maternally inherited. Lastly, three Minute alleles from the same locus were sequenced and two alleles found to contain a 22-bp deletion in exon 2, resulting in a truncated S3 protein, although wildtype levels of S3 mRNA and protein were detected in the viable heterozygous Minute alleles, possibly reflecting dosage compensation.

Alleles↗
PubMed2000

Growth hormone and hypophosphatemic rickets.

This review summarizes seven trials of growth hormone (GH) treatment for X-linked hypophosphatemic rickets (XLHR). These trials range in size from 5 to 30 patients; but despite the limited number of patients enrolled, they represent the largest studies to date of growth hormone in this disorder. Conventional treatment in XLHR, oral phosphate and calcitriol, is often unable to normalize serum phosphate concentration fully and many patients fail to reach normal adult height. The studies reviewed report increased growth velocity when exogenous GH is added to conventional therapy, although the independent effect of GH is difficult to evaluate. Younger patients appear to respond better to GH than do older patients. Disproportionate growth of the trunk may be a problem. Some patients with XLHR have received GH for more than 6 years, yet little is known about the impact of GH on adult height. Reported increases in phosphate concentrations following GH in XLHR are of uncertain clinical benefit. While GH appears to be safe in XLHR, long-term benefits remain unclear.

Body Height↗