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Biomedical subjects

K O'Rourke

Publications and source records attributed to K O'Rourke.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of mouse thrombospondin 2 sequence and expression during cell growth and development.

Thrombospondin (TSP) is an extracellular matrix glycoprotein whose expression has been associated with a variety of cellular processes including growth and embryogenesis. The recent discovery of the existence of a second mouse TSP gene necessitates careful examination of the discrete biochemical and functional properties associated with each molecule. In this report, the primary structures of human TSP, mouse TSP1 (mTSP1), mouse TSP2 (mTSP2), and chicken TSP are compared; and the expression of mTSP1 and mTSP2 during embryogenesis and growth factor-mediated cell proliferation is examined. The cloning and sequencing of the entire coding regions of mTSP1 and mTSP2 revealed considerable conservation of residues critical for TSP structure and function; these data suggest that TSP2 is capable of trimer formation and many of the same cell-surface and ligand interactions that mediate TSP function. Comparison of the various TSP sequences also allowed the assignment based on sequence homology of previously reported human TSP as TSP1 and chicken TSP as TSP2. mTSP2, like mTSP1, was shown to be a primary response gene when quiescent Swiss 3T3 cells were stimulated with serum, platelet-derived growth factor BB, basic fibroblast growth factor, or interleukin-1 beta. Interestingly, TSP1 and TSP2 exhibited markedly different tissue- and stage-specific patterns of mRNA expression during mouse embryogenesis, implying that the two TSP molecules possess discrete functional properties important for development. Additionally, the TSP genes (Thbs1 and Thbs2) were mapped to single loci on mouse chromosomes 2 and 17, respectively.

3T3 Cells↗
PubMed1992

Pain relief: the perspective of Catholic tradition.

Efforts to study patient care from the perspective of Catholic ethics date back four centuries. In the course of this history, a prominent issue has always been management of pain and the efforts to avoid pain. Thus, Catholic theologians were concerned about the effects of pain medication upon the psychic function and considered whether or not hastening death for suffering people was allowed and the ethical norms for using opioids to remove pain when death is imminent. Moreover, the issue of "overmedication" for difficult or elderly patients has been a concern. The President's Commission on Ethics in Medicine and Human Research has utilized many of the principles developed by Catholic theologians when considering the matter of pain relief for dying persons.

Attitude to Death↗
PubMed1992

Incorporating variations in the quality of individual randomized trials into meta-analysis.

Meta-analysis is a method of synthesizing evidence from multiple sources. It has been increasingly applied to combine results from randomized trials of therapeutic strategies. Unfortunately there is often variation in the quality of the trials that are included in meta-analyses, limiting the value of combining the results in an overview. This variation in quality can lead to both bias and reduction in precision of the estimate of the therapy's effectiveness. There are a number of methods for quantifying the quality of trials including the detailed Chalmers system and simple scales. The nature of the relationship between these quality scores and the true estimate of effectiveness is unknown at this time. We discuss four methods of incorporating quality into meta-analysis: threshold score as inclusion/exclusion criterion, use of quality score as a weight in statistical pooling, visual plot of effect size against quality score and sequential combination of trial results based on quality score. The last method permits an examination of the relation between quality and both bias and precision on the pooled estimates. We conclude that while it is possible to incorporate the effect of variation of quality of individual trials into overviews, this issue requires more study.

Bias↗
PubMed1992

Application of a stopping rule based on total treatment failures: the postoperative Crohn's disease trial.

The Postoperative Crohn's Disease Trial (PCDT), a placebo-controlled randomized trial of Rowasa I in the prevention of postoperative recurrence of Crohn's disease, is used as an example of how a stopping rule based on total endpoint occurrences can provide considerable advantage over standard fixed sample size methods. It can be used when the primary outcome is occurrence or time to occurrence and does not raise the troublesome issues regarding the unblinding of group differences that other sequential methods create. The main advantage of the total endpoint stopping rule is that it provides set power. Standard fixed sample size designs provide a given power only on average. The power actually achieved in a particular fixed sample size trial is largely determined by the overall observed rate of endpoint occurrences. This claim about the total endpoint stopping rule is well established in the statistical literature and, as well as outlining the mathematical details in an Appendix, we use computer simulation of the PCDT to demonstrate that use of the stopping rule will allow termination of the trial while maintaining power and type I error at a predetermined level.

Aminosalicylic Acids↗
PubMed1992

Knowing and practicing ethics.

The interrelationship between ethics and child and adolescent psychiatry is discussed, particularly as it relates to clinical practice. Three principles for ethical clinical practice are presented from a philosophical perspective and illustrated with two case vignettes. A formulation is reached that states that ethical theory parallels clinical theory.

Adolescent↗
PubMed1991

A second, expressed thrombospondin gene (Thbs2) exists in the mouse genome.

The diverse and occasionally conflicting properties described for the extracellular, cell surface-associated protein thrombospondin (TSP) have raised the possibility that functionally distinct forms of the protein exist in the same organism. We have isolated and characterized a partial cDNA clone for mouse TSP that is clearly homologous to, but distinct from, the coding sequence for mouse TSP deduced from a mouse genomic clone (Bornstein, P., Alfi, D., Devarayalu, L., Framson, P., and Li, P. (1990) J. Biol. Chem. 265, 16691-16698). This second TSP, which we term thrombospondin 2, is the product of a separate gene (Thbs2) and is expressed in a variety of mouse tissues in a pattern that differs from that for TSP1. Based on their translated amino acid sequences, it seems likely that TSP1 and TSP2 will be found to have both common and unique properties and that the functional consequences of TSP production will reflect the ratio of the levels of these two related proteins.

Amino Acid Sequence↗
PubMed1991

Assisted suicide: an evaluation.

Physician-assisted suicide is a form of euthanasia. As such, it is contrary to one's ethical responsibility to self, community, and God. Religious tradition, medical tradition, and modern psychology attest that physician-assisted suicide does not solve any human problem.

Catholicism↗
PubMed1991

Synthesis of wild type and mutant human hemoglobins in Saccharomyces cerevisiae.

We have expressed human alpha and beta-globin cDNA clones from separate, synthetic galactose-regulated hybrid promoters contained on a single plasmid in Saccharomyces cerevisiae. Co-expression of the alpha and beta-globin chains in S. cerevisiae results in the assembly of these proteins into soluble tetrameric hemoglobin that accumulates to 3-5 percent of the total cell protein. Endogenously produced heme is incorporated into the tetramer and the protein produced is functionally and structurally indistinguishable from human Ao hemoglobin. This expression system has been used to produce both wild type hemoglobin and a low O2-affinity hemoglobin mutant that has oxygen binding and dissociation characteristics similar to human whole blood. The yeast expression system we describe may be suitable for the production of a recombinant hemoglobin based blood substitute as well as for detailed structure-activity studies of human hemoglobin.

Amino Acid Sequence↗
PubMed1990

Containing Ontario's hospital costs under universal insurance in the 1980s: what was the record?

In recent years the Ontario government has been concerned that the proportion of public expenditures devoted to health care is at an all-time high. In addition, the media have devoted considerable attention to specific incidents that may represent inadequate funding of hospital services. To shed light on the debate on health care expenditures we analysed the trend in expenditures of Ontario's hospital sector in the 1980s in terms of the amount of inputs (e.g., labour) used to produce hospital services (e.g., a patient-day or admission) and after adjustment for general inflation. As in the 1970s the number of inputs grew relatively slowly during the 1980s. Inputs per patient-day grew at an annual rate of 0.46% and inputs per admission at an annual rate of 2.4%. Cost increases were largely accounted for by hospital wage increases; this could have been due to Ontario's rapidly expanding economy. These findings indicate that Ontario has continued to be successful in containing the number of inputs used in the hospital sector. However, after two decades of substantial success with publicly acceptable cost control, the government faces increased scrutiny as the media and the public focus attention on several areas of perceived inadequate funding in health care services.

Costs and Cost Analysis↗
PubMed1990

Tumor necrosis factor-alpha induction of novel gene products in human endothelial cells including a macrophage-specific chemotaxin.

Cytokines such as tumor necrosis factor alpha (TNF) profoundly affect endothelial cell function, promoting for example interaction with leukocytes and inducing a procoagulant phenotype. Changes of this nature are likely to be central to the proinflammatory effects of TNF. In order to elucidate molecular mechanisms by which TNF alters endothelial cell function we utilized differential plaque hybridization to identify TNF-responsive genes. Forty TNF-inducible cDNAs were identified which on cross-hybridization were found to arise from six unique genes. DNA sequencing of these cDNAs revealed two encoded known cytokine-induced genes, endothelial leukocyte adhesion molecule 1 and neutrophil chemotactic factor. One of the cDNAs encodes a recently described monocyte-specific chemotactic factor not previously associated with endothelium. The production of a monocyte chemotaxin by cytokine-activated endothelium has important implications for understanding the role of the vessel wall in disease states such as atherosclerosis and may also in part explain the indirect angiogenic activity of TNF. The three other cDNAs are completely novel as judged by data bank searches of partial DNA sequences and remain unidentified. On exposure of endothelial cells to TNF there is a rapid and substantial increase in levels of mRNA encoding the six genes, which are further superinduced by cycloheximide. Thus these represent primary response genes as their induction does not depend on protein synthesis. Interleukin-1 beta and lipopolysaccharide are also potent inducers. Nuclear run-on studies revealed that in most cases induction by TNF is mediated largely at the transcriptional level.

Biological Factors↗
PubMed1990

Ethical, legal, and psychodynamic considerations in intervention of a possible cult member.

A 17-year-old boy is brought involuntarily by his parents for admission to an adolescent unit after running away from home to join a cult. The adolescent is admitted to the hospital for a multidisciplinary assessment. Follow-up 6 months after discharge shows the family to have continued in family therapy with the patient remaining at home with no additional contact with the cult. The case raises important ethical and dynamic issues about whom the child psychiatrist serves--the parents, the adolescent, or society. Discussion by an ethicist, lawyer, and child and adolescent psychoanalyst follows the case presentation.

Adolescent↗
PubMed1989

Parenteral nutrition with branched-chain amino acids in hepatic encephalopathy. A meta-analysis.

Meta-analytic methods were applied to review clinical trials published in English that have assessed the efficacy of parenteral nutrition for cirrhotic patients with acute hepatic encephalopathy. Modified amino acid solutions containing increased amounts of branched-chain amino acids were used as part of the treatment regimen in all studies. Pooled analysis of five randomized controlled studies showed a highly significant improvement in mental recovery (p less than 0.001) from high-grade encephalopathy over follow-up times varying from 5 to 14 days. The significance level of the treatment effect did not change when the analysis was repeated using alternative methods of counting and attributing events in these trials. Sharp differences in direction of treatment effect precluded pooling case fatality data. Two studies reported an increased risk of death in the treatment group. Two others showed a clear benefit from administration of parenteral nutrition: the aggregate relative risk reduction was 0.59 (95% confidence interval: 0.23-0.80, p = 0.002). Addition of unpublished data from a third positive study increased the relative risk reduction to 0.82 (p less than 0.0001), and the most conservative interpretation of the published data still yielded a significant reduction in mortality (p = 0.023). However, given the uncertainty about effects on mortality and short follow-up times in all studies, a confirmatory randomized controlled trial with longer follow-up periods is warranted.

Adolescent↗
PubMed1989

Meta-analysis in medical research: strong encouragement for higher quality in individual research efforts.

In this article, we counter some criticism regarding the desirability of performing meta-analysis in clinical research. These criticisms, we argue, are based mainly on current difficulties in deriving firm conclusions based on meta-analysis, resulting from poor methodology and reporting of primary studies. This is not a fault of meta-analysis. In fact, with a better understanding of meta-analysis in the context of the full scientific research process, meta-analysis is seen as a key element for improving individual research efforts and their reporting in the literature. This in turn will further enhance the role of meta-analysis in helping clinicians and policy makers answer clinical questions.

Humans↗
PubMed1989

Expression and analysis of COOH-terminal deletions of the human thrombospondin molecule.

Thrombospondin (TSP) is a homotrimeric extracellular glycoprotein with a subunit molecular mass of 140 kD. The subunits have a modular or domain-like structure and are held together by interchain disulphide bonds. A number of domains have been identified including those for the binding of collagen, fibrinogen, and heparin. Due to the trimeric form of the TSP molecule, the various domains are trivalent in nature and this contributes to the ability of TSP to mediate cell-substrate interactions. Indeed, TSP has recently been shown not only to promote cell adhesion but also to be intimately involved in cell growth and migration. The adhesive function of TSP is attributable to the "solid-phase" or matrix-bound form of the molecule. There is some evidence that the heparin-binding domain mediates incorporation of soluble TSP into the insoluble matrix form. The heparin-binding domain of TSP is a compact globular amino-terminal moiety that contains two clusters of basic amino acids and a single intrachain disulphide bond. To delineate the role of the heparin-binding domain in matrix assembly and to define further the precise region of interchain disulphide bonding that results in trimer formation, we have expressed deleted forms of the cDNA encoding TSP in SV-40-transformed. African green monkey kidney cells. The proteins synthesized from the various deleted TSP cDNAs were examined for (a) secretion into the culture medium and incorporation into the extracellular matrix; (b) binding to heparin-Sepharose; (c) immunoprecipitability by a conformation-specific monoclonal antibody; and (d) ability to form trimers. This analysis allowed us to draw the following conclusions. (a) A 218 amino acid NH2-terminal protein that preserves the intrachain disulphide bridge of the heparin-binding domain is capable of binding to heparin-Sepharose and incorporating into the extracellular matrix. (b) A shorter 164 amino acid NH2-terminal peptide that does not contain the intrachain disulphide bridge of the heparin-binding domain is neither able to bind to heparin-Sepharose nor able to incorporate into the extracellular matrix. (c) The region of interchain disulphide bridging necessary for trimer assembly resides within a cluster of seven cysteine residues immediately adjacent to the heparin-binding domain.

Animals↗
PubMed1988

Thrombospondin binding by human squamous carcinoma and melanoma cells: relationship to biological activity.

Human squamous carcinoma cells attach and spread on thrombospondin (TSP)-coated culture dishes but exhibit significant variability among individual cell lines in their degree of responsiveness. Using a highly responsive squamous carcinoma line and a cell line which is much less responsive (as well as a human melanoma cell line which does not respond at all in the adhesion assay), we have examined binding of exogenous radiolabeled TSP. The cells which were the most responsive to TSP in the adhesion assay bound the greatest amount of radiolabeled ligand. Binding was time- and dose-dependent, saturable, inhibitable with excess unlabeled TSP, reversible, and specific. The less-responsive squamous carcinoma cells bound only 25-30% of the amount of TSP bound by the highly responsive cells while the nonresponsive melanoma cells bound less than 10% of the amount bound by the highly responsive squamous carcinoma cells. Our previous studies (J. Varani et al. (1986) Exp. Cell Res. 167, 376) have shown that the highly responsive squamous carcinoma cells also synthesized the greatest amount of TSP as indicated by biosynthetic labeling studies. The less-responsive squamous carcinoma cells were intermediate in synthetic activity and no synthetic activity was seen with the melanoma cells. These findings suggest that the amount of ligand bound may determine the degree of biological responsiveness and that endogenously synthesized TSP may be the source of that ligand.

Antibodies, Monoclonal↗
PubMed1988

Antiviral, anti-glycoprotein and neutralizing antibodies in foals with equine infectious anaemia virus.

Equine infectious anaemia virus is related by genome sequence homology to human immunodeficiency virus, caprine arthritis-encephalitis virus and visna virus. Failure of the host to mount a strong neutralizing response detectable in vitro or to eliminate persistent infection in vivo characterizes lentivirus infections in the natural host. In this study the specificities and neutralizing activity of antibodies induced during experimental infection with equine infectious anaemia virus were investigated using antiviral ELISA, radioimmunoprecipitation and neutralization assays. ELISA antibody titres of 10(5) to 10(6) were demonstrated in samples collected 30 and 60 days after infection. Immunoprecipitation titrations demonstrated that antibody titres to the glycoproteins gp90 and gp45 were 10 to 100 times higher than titres to the internal structural protein, p24. Low levels of neutralizing antibody appeared at 23 to 46 days post-infection. The presence of low levels of neutralizing activity in the presence of high levels of anti-glycoprotein activity suggests that the major immunogenic sites on the viral surface are not sensitive to neutralization.

Animals↗