Search PubMed⌕ Search

Biomedical subjects

D M Gregory

Publications and source records attributed to D M Gregory.

At least 19 recordsLinked to original sources
PubMed2004

Need for coronary artery bypass grafting in Newfoundland and Labrador: the impact of increased demand.

BACKGROUND: In the past decade, growth of coronary revascularization in Canada has been substantial. It was hypothesized that as coronary angiography (CA) rates increased, referral for necessary coronary artery bypass grafting (CABG) would also increase, and include patients with multivessel disease and class I to III angina who required elective surgery. Furthermore, it was proposed that the number of CABG surgeries needed would increase at a similar rate to that of CA. METHODS: An incident cohort of patients who received CA in 1998/1999 was identified, and the group referred for CABG was followed. Clinical characteristics, appropriateness and necessity scores using specific criteria, and waiting times were evaluated and compared with a similar cohort from 1994/1995. Utilization data for coronary revascularization procedures from 1994 to 2002 were reviewed. RESULTS: Between 1994/1995 and 1998/1999, the number of CAs per year increased by 37%. The inappropriateness rate for CA was 4% in 1998/1999. The proportion of patients diagnosed with critical coronary artery disease increased from 68% in 1994/1995 to 74% in 1998/1999. The number referred for CABG increased by 48%, and the number for percutaneous transluminal coronary angioplasty (PTCA) increased by 137%. The increase in the number referred for CABG was attributable to the increase in the number of patients with less severe symptoms who required delayed elective CABG. The necessity rate for CABG in the referred group was 94% in 1994/1995 and 95% in 1998/1999. A further 91 patients were identified who needed CABG but did not receive it, 86% of whom had PTCA. From 1999 to 2002, the annual growth rate in those referred for CABG was higher than the growth rate for CA. CONCLUSIONS: With the growth in CA, the rate of discovery of high risk coronary anatomy actually increased. Growth in CABG volume was attributable to growth in the need for elective surgery in patients with class I to III angina. The rate of CABG increased disproportionately to the rate of CA, despite higher rates of PTCA with stenting. It is likely that the demand for CABG will continue to rise steadily, as expansion of angiography occurs, and may be higher than expected from the growth in CA.

Adult↗
PubMed2003

Pore structure and sorption properties of silica aerogels studied by magnetic resonance imaging and pulsed-field gradient spectroscopy.

Magnetic resonance imaging (MRI) has provided direct visualization of gaseous xenon and methane in the void spaces of aerogels, offering unique information and insights into the pore structure and molecular diffusivities of occluded sorbates. Nuclear magnetic resonance (NMR) pulsed-field gradient (PFG) techniques were used to characterize exchange and diffusive motion of sorbed xenon gas at equilibrium. PFG measurements showed evidence of anisotropic diffusion; nominal self-diffusivity coefficients of xenon on the order of D = 10(-7) m2/s were determined. Based on a mathematical relationship for the restricted diffusion of gases in confined environments, an expression for estimating the mean free path was derived, from which the average pore size could be obtained from the extrapolated value of the diffusion coefficient to low xenon pressures.

Adsorption↗
PubMed2000

Two-dimensional structure of beta-amyloid(10-35) fibrils.

Beta-amyloid (Abeta) peptides are the main protein component of the pathognomonic plaques found in the brains of patients with Alzheimer's disease. These heterogeneous peptides adopt a highly organized fibril structure both in vivo and in vitro. Here we use solid-state NMR on stable, homogeneous fibrils of Abeta(10-35). Specific interpeptide distance constraints are determined with dipolar recoupling NMR on fibrils prepared from a series of singly labeled peptides containing (13)C-carbonyl-enriched amino acids, and skipping no more that three residues in the sequence. From these studies, we demonstrate that the peptide adopts the structure of an extended parallel beta-sheet in-register at pH 7.4. Analysis of DRAWS data indicates interstrand distances of 5.3 +/- 0.3 A (mean +/- standard deviation) throughout the entire length of the peptide, which is compatible only with a parallel beta-strand in-register. Intrastrand NMR constraints, obtained from peptides containing labels at two adjacent amino acids, confirm the secondary structural findings obtained using DRAWS. Using peptides with (13)C incorporated at the carbonyl position of adjacent amino acids, structural transitions from alpha-helix to beta-sheet were observed at residues 19 and 20, but using similar techniques, no evidence for a turn could be found in the putative turn region comprising residues 25-29. Implications of this extended parallel organization for Abeta(10-35) for overall fibril formation, stability, and morphology based upon specific amino acid contacts are discussed.

Amino Acid Sequence↗
PubMed1999

Elder-caregiver care negotiations as dances of dependency.

Well-developed metaphors function as heuristic devices for the communication of scientific ideas. When applied to common, typical situations, metaphorical conceptualization enables a richer and deeper understanding. In this article, the routinized and taken-for-granted situation of elder-caregiver care negotiations is examined through the use of a dance metaphor, the dance of dependency. Metaphorical models of theory are intended to be elaborated and developed in ways that good poetic metaphors are not. Therefore, we systematically describe the general aspects of the dance (rules, facilitators, performances, aesthetics) and relate the specific elements of a dance to the dance of dependency. The picture that emerges is one of elder-caregiver care negotiations as performances, with elders as agents who actively and creatively engage caregivers in their dances of dependency. Participants in these dances sustain a complex organization of behavior to meet the situational demands and maintain themselves as fully integrated participants, based on standards set forth by the jointly negotiated working consensus of the dyad. The resulting description extends what is currently understood about everyday care negotiations, allowing an appreciation of the processes and dynamics by which care negotiations and elder-caregiver relational cultures in multiple contexts unfold, change, and are challenged.

Aged↗
PubMed1998

Propagating structure of Alzheimer's beta-amyloid(10-35) is parallel beta-sheet with residues in exact register.

The pathognomonic plaques of Alzheimer's disease are composed primarily of the 39- to 43-aa beta-amyloid (Abeta) peptide. Crosslinking of Abeta peptides by tissue transglutaminase (tTg) indicates that Gln15 of one peptide is proximate to Lys16 of another in aggregated Abeta. Here we report how the fibril structure is resolved by mapping interstrand distances in this core region of the Abeta peptide chain with solid-state NMR. Isotopic substitution provides the source points for measuring distances in aggregated Abeta. Peptides containing a single carbonyl 13C label at Gln15, Lys16, Leu17, or Val18 were synthesized and evaluated by NMR dipolar recoupling methods for the measurement of interpeptide distances to a resolution of 0.2 A. Analysis of these data establish that this central core of Abeta consists of a parallel beta-sheet structure in which identical residues on adjacent chains are aligned directly, i. e., in register. Our data, in conjunction with existing structural data, establish that the Abeta fibril is a hydrogen-bonded, parallel beta-sheet defining the long axis of the Abeta fibril propagation.

Alzheimer Disease↗
PubMed1998

Dipolar recoupling NMR of biomolecular self-assemblies: determining inter- and intrastrand distances in fibrilized Alzheimer's beta-amyloid peptide.

We demonstrate a new method for investigating the structure of self-associating biopolymers using dipolar recoupling NMR techniques. This approach was applied to the study of fibrillar beta-amyloid (Abeta) peptides (the primary component of the plaques of Alzheimer's disease) containing only a single isotopic spin label (13C), by employing the DRAWS (dipolar recoupling with a windowless sequence) technique to measure 13C-13C distances. The 'single-label' approach simplified analysis of DRAWS data, since only interstrand contacts are present, without the possibility of any intrastrand contacts. As previously reported [T.L.S. Benzinger, D.M. Gregory, T.S. Burkoth, H. Miller-Auer, D.G. Lynn, R.E. Botto, S.C. Meredith, Proc. Natl. Acad. Sci. 95 (1998) 13407.], contacts of approximately 5 A were observed at all residues studied, consistent with an extended parallel beta-sheet structure with each amino acid in exact register. Here, we propose that our strategy is completely generalizable, and provides a new approach for characterizing any iterative, self-associating biopolymer. Towards the end of generalizing and refining our approach, in this paper we evaluate several issues raised by our previous analyses. First, we consider the effects of double-quantum (DQ) transverse relaxation processes. Next, we discuss the effects of various multiple-spin geometries on modeling of DRAWS data. Several practical issues are also discussed: these include (1) the use of DQ filtering experiments, either to corroborate DRAWS data, or as a rapid screening assessment of the proper placement of isotopic spin labels; and (2) the comparison of solid samples prepared by either lyophilization or freezing. Finally, data obtained from the use of single labels is compared with that obtained in doubly 13C-labeled model compounds of known crystal structure. It is shown that such data are obtainable in far more complex peptide molecules. These data,taken together, refine the DRAWS method, and demonstrate its precision and utility in obtaining high resolution structural data in complex biomolecular aggregates such as Abeta.

Amyloid beta-Peptides↗
PubMed1998

Patients' perceptions of their experiences with ESRD and hemodialysis treatment.

A grounded theory methodology was used to explore patients' experiences with end-stage renal disease (ESRD) and hemodialysis. The emerging theory suggests that a "new sense of self" is an emotional/psychological state that fluctuates with the evolving meanings of illness and treatment and perceived quality of supports. The findings indicate that when confronted with this new way of being in the world, the individual becomes cognizant of an uncertain future, continued dependence on life-sustaining technology and the expertise of health care providers, and the demands on and sacrifices incurred by significant others. All aspects of patients' experiences with ESRD and hemodialysis treatment must be considered if health care providers are to facilitate positive health outcomes.

Adult↗
PubMed1998

Patients' explanatory models for heart failure and COPD exacerbations.

Although there is extensive information on the disease aspect of heart failure (HF) and chronic obstructive pulmonary disease (COPD), the illness aspect of these diseases has received limited attention. This limitation in our knowledge is of concern because these diseases are increasing in incidence and prevalence and contributing to the premature morbidity and mortality of thousands of persons. This naturalistic inquiry study was undertaken to describe the explanatory models (EMs) of persons hospitalized for HF (n = 30) or COPD (n = 30) exacerbations. In semistructured interviews, participants offered descriptions of the etiology, cause, and effects of their disease exacerbations and identified interventions that they believed would have helped prevent their hospitalizations or helped them to live better at home. The findings provide a basis for understanding the EMs of persons with HF or COPD as an initial step in making health care more relevant.

Adult↗
PubMed1997

Protective care-receiving: the active role of care-recipients.

Historical and contemporary conceptualizations of caregiving have not addressed the active role of care recipients within caregiver-care-recipient relationships. Using an interpretive synthesis method, the authors developed the concept of protective care-receiving from three qualitative studies of different groups of care receivers (older adults with chronic illnesses, persons with AIDS, and persons in treatment for active cancer). This paper describes the focus of care recipients' protective care-receiving efforts, the goals they hoped to achieve, and the strategies they used to assist themselves in attaining their goals. Examples of their efforts and strategies are illustrated with quotations from the data. These findings extend what is known about care recipients' selfcare activities. Moreover, the findings reveal a new dimension in the role of care recipients--protective care given by care recipients to their professional care providers, family and friend caregivers, and other care recipients. The concept of protective care-receiving advances our understanding of caregiving relationships and presents researchers with the opportunity to investigate the complex encounter between caregiver and care recipient. Recognizing and facilitating care recipients' protective care-receiving is an ethical imperative for a 'caring' profession such as nursing.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Distance measurements in nucleic acids using windowless dipolar recoupling solid state NMR.

A windowless, homonuclear dipolar recoupling pulse sequence (DRAWS) is described and a theoretical basis for describing its recoupling performance is developed using numerical techniques. It is demonstrated that DRAWS recouples weak dipolar interactions over a broad range of experimental and molecular conditions. We discuss two spectroscopic control experiments, which help to take into account effects due to insufficient proton decoupling, relaxation, and static dipolar couplings to nearby 13C spins at natural abundance. Finally DRAWS is used in combination with selective 13C labeling to measure 13C-13C distances in five doubly labeled DNA dodecamers, [d(CGCGAAT*T*CGCG)]2, which contain the binding site for the restriction enzyme EcoRI. The longest distance reported is 4.8 A. In most cases the distances agree well with those derived from X-ray crystallographic data, although small changes in hydration level can result in relatively large changes in internuclear distances.

Carbon Isotopes↗
PubMed1996

ACTION: application and extension of the GENESIS community analysis model.

GENESIS (General Ethnographic and Nursing Evaluation Studies In the State) is a tested and proven community analysis strategy that integrates ethnographic and epidemiologic data to arrive at a comprehensive, holistic description of the health of a community and its residents. Communities analyzed in most project GENESIS studies have been rural or semirural. ACTION (Assessing Communities Together in the Identification Of Needs) is an extension of the GENESIS community analysis model that was developed to meet the unique needs of community-level research and analysis in an urban, multicultural setting. Significant differences in the context in which the ACTION projects took place necessitated extensions in specific components of the GENESIS model. Application of the GENESIS model by the ACTION team is described. Based on the experiences with ACTION, recommendations are offered for future urban, multicultural community analysis projects.

Canada↗
PubMed1993

Issues for consideration when choosing a qualitative data management system.

A primary issue in conducting qualitative research is the time required for data analysis. Qualitative research can be costly, since data analysis is generally labour intensive and our time factors into money. There is, unfortunately, no magic formula for hastening the conceptual tasks associated with qualitative analysis, yet effective qualitative data management systems (QDMS) expedite the mechanical tasks, those tasks associated with storing and retrieving qualitative data. Rapid and smooth data management increases the time one can allot to data analysis. Although computer QDMS are increasingly recommended for their time-saving potential in relation to data management, some significant issues associated with the adoption of a computer versus a manual QDMS have not yet been fully explored. The purpose of this paper is to present major issues researchers should consider in choosing a computer or a manual QDMS. These issues include availability and accessibility, comfort, appropriateness, efficiency, thoroughness and contextualization.

Costs and Cost Analysis↗
PubMed1990

Elderly male spouses as caregivers--toward an understanding of their experience.

Male caregivers have difficulty assuming personal and household responsibilities; they seem to cope by focusing on the caregiving tasks and projects, establishing daily routines, and carving out their own territory in the home. To facilitate effective interventions, nurses should ascertain the elderly male spouse's meaning of caregiving. This would enable practitioners to foster the caregiver's strengths and provide support in those areas where burden or difficulties are experienced. Husbands as caregivers were more likely than wives to seek the help of formal providers and receive more informal support. Male caregivers tend to not participate in support groups. Before making a referal, nurses should ensure the group is geared to the special needs of the man.

Aged↗
PubMed1986

Plasma free amino acid values in normal children and adolescents.

We measured plasma free amino acids in 52 children (mean age 8 years) and 80 adolescents (mean age 16 years); conditions of diet and time of day were similar in the two groups. The protocols allowed us to compare their interindividual variation with values previously reported by us for adults. In children, the values for all but seven amino acids were normally distributed; in adolescents there were only six exceptions. Effects of age were apparent: values for only two amino acids were higher in children than adolescents. Values were significantly lower for ten amino acids in children v adolescents and for 11 amino acids in younger children (1 to 6 years) v older children (7 to 12 years). An effect of sex was apparent for five amino acids in adolescents; such differences were not apparent in children. All differences were quasicontinuous and occurred within the global distributions that define values for plasma amino acids in normal children and adolescents. Two artifacts (choice of anticoagulant and delay in deproteinization) affected values for taurine and cystine, respectively.

Adolescent↗
PubMed1985

Normal plasma free amino acid values in adults: the influence of some common physiological variables.

We measured plasma free amino acids in ten healthy adults (five males, five females, ages 26 to 54 years), at four times of day, under two dietary protocols. The design allowed us to measure the effects of some common physiological variables on the metrical distributions (mean, SD, skewness, kurtosis) of 80 values (in most cases), for each of 20 amino acids. Analysis of variance indicates that individuals in a "public" population possess "private" phenotypes for 18 plasma amino acids under typical external experiences; the exceptions were aspartate and taurine. The collective infradiem variation rarely exceeded 50% of the nadir value for any amino acid. We conclude that genotype is an important determinant of plasma amino acid phenotype in normal persons, and that there is striking homeostasis of plasma amino acid values in human adults adapted to normal daily activity.

Adult↗