PubMed Health⌕ Search

Biomedical subjects

R Tracy

Publications and source records attributed to R Tracy.

At least 37 records · Page 2Linked to original sources
PubMed1995

Subclinical disease as an independent risk factor for cardiovascular disease.

BACKGROUND: The primary aim of the present study was to determine the relation between measures of subclinical cardiovascular disease and the incidence of clinical cardiovascular disease among 5201 adults 65 years of age or older who were participating in the Cardiovascular Health Study. METHODS AND RESULTS: A new method of classifying subclinical disease at baseline examination in the Cardiovascular Health Study included measures of ankle-brachial blood pressure, carotid artery stenosis and wall thickness, ECG and echocardiographic abnormalities, and positive response to the Rose Angina and Claudication Questionnaire. Participants were followed for an average of 2.39 years (maximum, 3 years). For participants without evidence of clinical cardiovascular disease at baseline, the presence of subclinical disease compared with no subclinical disease was associated with a significant increased risk of incident total coronary heart disease including CHD deaths and nonfatal MI and angina pectoris for both men and women. For individuals with subclinical disease, the increased risk of total coronary heart disease was 2.0 for men and 2.5 for women, and the increased risk of total mortality was 2.9 for men and 1.7 for women. The increased risk changed little after adjustment for other risk factors, including lipoprotein levels, blood pressure, smoking, and diabetes. CONCLUSIONS: The measurement of subclinical disease provides an approach for identifying high-risk older individuals who may be candidates for more active intervention to prevent clinical disease.

Aged↗
PubMed1995

Clotting for the Clinician: An Overview of Thrombosis and Antithrombotic Therapy.

The use of antithrombotic therapy has taken on central importance in the field of cardiovascular disease. Currently, anticoagulants and antiplatelet drugs are central to the treatment and the primary and secondary prevention of coronary artery disease. New insights into the "revised" coagulation cascade have highlighted new targets for intervention. In addition, the interactions between the coagulation system and platelets demonstrate ways that anticoagulants may affect platelet function and how antiplatelet agents may have anticoagulant effects. This overview will describe the present understanding of primary and secondary hemostasis, and current and future therapeutic approaches to modify these systems for therapeutic effects in cardiovascular medicine.

Journal Article↗
PubMed1994

DBA/2 and C57BL/6 mice differ in contextual fear but not auditory fear conditioning.

It has been proposed that DBA/2 and C57BL/6 mice perform differently on some learning and memory tasks because of functional differences in the hippocampal formation. To evaluate this hypothesis, DBA/2 and C57BL/6 mice were tested on 2 forms of conditioned fear: contextual fear conditioning, which depends on the integrity of the hippocampal formation, and auditory cue conditioning, which does not. Both mouse strains displayed equivalent conditioning when the auditory cue was paired with shock, but DBA/2 mice showed significantly less conditioning to the context in which shock was experienced. These results are consistent with the hypothesis that the pattern of spared and impaired performance, which DBA/2 mice display on a variety of learning and memory tasks, is related to impaired hippocampal formation function.

Animals↗
PubMed1994

Contracting for emergency room coverage by rural hospitals.

Obtaining adequate physician availability remains a challenge to many rural communities. To ensure 24-hour emergency room physician coverage, many rural hospitals contracted for emergency room services from out-of-area and/or local physician. Survey findings for 99 rural and rural referral Iowa hospitals addressing the nature, extent, and cost of contracting physician coverage of the emergency room are presented. While nearly two-thirds of the hospitals reported contracting for at least some emergency room coverage, the extent and costs of contracts vary widely. Advantages and disadvantages of contracting for emergency room services are discussed.

Contract Services↗
PubMed1991

Heparin pharmacokinetics and in vitro anticoagulant activity in patients receiving nonionic radiographic contrast media.

Nonionic radiographic contrast media are used frequently in diagnostic and interventional angiography. However, there is concern that they may possess thrombogenic properties, and some studies have suggested that patients receiving nonionic contrast media are difficult to systemically anticoagulate with intravenous heparin. To investigate the potential effects of nonionic contrast media on systemic anticoagulation during diagnostic cardiac catheterization, pharmacokinetics and in vitro anticoagulant activity following a 3,000 U intravenous heparin bolus were assessed in 12 patients assigned randomly to either an ionic or a nonionic contrast agent. Independent of contrast agent, all patients exhibited biphasic (nonlinear) heparin pharmacokinetics characterized by an initial rapid disappearance phase, followed by a second slower phase. Each patient achieved a therapeutic plasma heparin concentration (greater than or equal to 0.2 U/ml) within 10 min of receiving the bolus, and maintained this level throughout the procedure. Heparin anticoagulant activity, as estimated by a standard activated partial thromboplastin time (APTT) was not affected differently by nonionic as compared with ionic contrast media (p greater than 0.05). Each patient rapidly achieved a level of systemic anticoagulation commonly considered therapeutic (APTT greater than or equal to 1.5 times the control), and maintained this level throughout the procedure. In both groups, APTT correlated directly with plasma heparin concentration (r = 0.95; p less than 0.0001), and inversely with the total amount of contrast media used during the procedure (r = -0.25; p = 0.01). Plasma heparin concentration did not correlate with total contrast media (r = -0.16; p greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗
PubMed1990

Effect of chewing rawhide and cereal biscuit on removal of dental calculus in dogs.

The effect of chewing rawhide and cereal biscuit on removal of dental calculus was studied in 67 dogs. Two methods were used to measure supragingival calculus and calculus removal as a function of time and acceptability. Trial 1 used a quantitative method based on actual measurement of the area of calculus on a tooth, and trial 2 used a quantitative method based on an arbitrary grading system to establish a supragingival calculus index. Analysis was performed, using 2-factor (trial 1) and a 3-factor (trial 2) analysis of variance. Results indicated that dogs removed calculus from their teeth by chewing rawhide; some teeth were cleaned better than others. The optimal amount or frequency of rawhide treatment was not necessarily determined. It was determined that regular consumption of up to 3 rawhide strips/d for 3 weeks was safe. Processed biscuits were sometimes effective in removing calculus from dog's teeth; however, biscuits were not as effective as the rawhide in removing supragingival calculus.

Animals↗
PubMed1990

Unstable angina or non-Q wave infarction despite long-term aspirin: response to thrombolytic therapy with implications on mechanisms.

The pathophysiology and optimal therapy of patients who develop unstable angina in spite of long-term aspirin intake ("aspirin failure") have not been well defined. As part of a prospective study of thrombolytic therapy, 19 consecutive patients were identified who were admitted with unstable angina despite long-term aspirin therapy, and they were compared with 12 patients with unstable angina without previous aspirin use. Both groups received urokinase (3.0 million units over 30 minutes intravenously), maximal antianginal therapy, and intravenous heparin. Fibrinolytic system effects were characterized with serial measurements of fibrinogen, d-dimer, and fibrinogen degradation products (FDPs) at baseline and over the 24 hours following therapy. In comparison with those without previous aspirin use, the aspirin failure patients demonstrated greater d-dimer production after treatment at all points, the values becoming highly significant at 24 hours (1337 +/- 671 versus 709 +/- 620 ng/dl, p less than 0.02), as well as significantly greater FDPs at all points in the first 24 hours after treatment. Post-treatment arteriography (at 24 to 72 hours) indicated more extensive coronary artery disease in the aspirin failure patients (2.56 +/- 8.3 versus 1.63 +/- 1.06 vessels with greater than 50% stenosis, p less than 0.01) and more severe stenoses of the culprit artery (92.7 +/- 22.9% versus 77.3 +/- 36.9% diameter reduction, p = 0.09). By 7 days, both groups had equally low rates of new ischemic events or infarction (3 of 12 for no aspirin versus 4 of 19 for aspirin failure patients). Despite more extensive underlying coronary disease, unstable angina after long-term aspirin therapy appears to respond equally well to thrombolytic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Specific expression of proteins and phosphoproteins in 3T3 T mesenchymal stem cells at distinct growth arrest and differentiation states.

Murine mesenchymal stem cells can be induced to arrest their growth at a series of growth and differentiation states in the G1 phase of the cell cycle. These include the predifferentiation arrest state (GD) at which the integrated control of proliferation and differentiation is mediated, the growth factor/serum deficiency arrest state (GS), and the nutrient deficiency arrest state (GN). Cells at states of reversible nonterminal differentiation (GD') and irreversible terminal differentiation (TD) can also be isolated. In this paper we have employed 1- and 2-dimensional (D) gel electrophoresis to evaluate changes in specific proteins that occur during the various growth and differentiation states of 3T3 T mesenchymal stem cells. The protein composition of membrane, microsome and cytosol preparations of cells arrested at GD, GS and GN states was determined by 2-D gel electrophoresis. More than 50 distinct polypeptides could be identified for each arrest state in gels analysed by a silver staining procedure or by autoradiography following [35S]-methionine labelling. A second series of studies established that a more limited number of differences could be identified if phosphoproteins were analysed by 1-D gel electrophoresis in cells at the GS, GD, GD' and TD states. These results established that one distinct 37 kD phosphoprotein is present in all growth arrested cells and that two distinct differentiation-associated phosphoproteins with molecular weights of 29 kD and 72 kD are present in cells at the GD' and TD states. Thus, the composition of proteins and phosphoproteins in mesenchymal stem cells serves to characterize different states of growth arrest and differentiation.2+he identification of differential

Animals↗
PubMed1988

Coxsackievirus B-3-induced myocarditis. Virus and actinomycin D treatment of myocytes induces novel antigens recognized by cytolytic T lymphocytes.

BALB/c mice inoculated with 6 x 10(4) plaque-forming units of a myocarditic variant of Coxsackievirus, group B, type 3 (CVB3M) developed three distinct CTL populations recognizing putative virion (virus specific CTL, VCTL), normally expressed heart (autoreactive CTL, ACTL), and aberrant metabolic (MCTL) Ag. Induction of the MCTL-specific Ag on cardiocytes correlated with the ability of the myocarditic viruses and actinomycin D to interfere with cellular metabolism as measured by 3H-uridine and 3H-leucine incorporation. ACTL specifically lysed uninfected cardiocyte targets, but ACTL Ag expression was lost soon after infection of monocytes only to reappear 6 h later. MCTL and VCTL could be separated by adsorption to myocytes treated with either actinomycin D- or UV-inactivated CVB3M. MCTL cross-reactively lysed myocytes infected with another virus suppressing 3H-uridine incorporation (encephalomyocarditis virus) but failed to react to targets infected with viruses not inhibiting cell metabolism. VCTL specifically lysed only cells infected with the homologous virus. ACTL belonged to the CD8 (Lyt-2+) T cell subset, whereas both VCTL and MCTL were CD4 (L3T4+) T cells.

Animals↗
PubMed1985

Changes in the prevalence distribution of hypertension: Connecticut adults 1978-79 to 1982.

In the Spring and Summer of 1982 the Second Connecticut Blood Pressure Survey (CBPS-II) was completed. This survey is independent of, but essentially identical in design and implementation to the First Connecticut Blood Pressure Survey reported on by Freeman et al. [1]. This paper compares the results of the two surveys using the same analytic techniques as reported previously [2]. In addition, a model for analyzing the components of hypertension control is utilized in the analysis. Finally, the implications of the survey comparison are discussed in the context of the Connecticut High Blood Pressure Program (CHBP) [3].

Adolescent↗
PubMed1977

Influence of dietary trans-fatty acids on swine lipoprotein composition and structure.

Four groups of 20 weanling swine each were fed either (a) basal diet, (b) basal plus hydrogenated fat (13% trans), (c) basal plus hydrogenated fat (13% trans) and 0.4% cholesterol, or (d) basal plus beef tallow (all cis). After six months of feeding, the animals were killed and the blood and aortas were removed. Very low density, low density, and high density lipoproteins were then isolated from the plasma by ultracentrifugal flotation. Although the fatty acid composition of the basal diet was different from the diets supplemented with either hydrogenated fat containing trans-fatty acid or beef tallow containing all cis, the lipid and fatty acid compositions of each of the isolated lipoprotein classes for the four groups of animals were remarkably similar. Elaidate was clearly incorporated into the lipoproteins of animals fed hydrogenated fat, but the level of incorporation was generally less than 5%. In a direct comparison of the structure of the lipoproteins from the different groups, we did not find any significant differences in their physical properties as determined by pyrene fluorescence and electron paramagnetic resonance methods. Grossly visible fatty streaks and fibrous plaques were not found in any of the swine aorta. However, light and electron microscopy indicated the presence of atherosclerotic lesions in the distal abdominal aorta and bifurcation. These studies demonstrate that a diet containing a substantial amount of trans-fatty acid leads to a small but definite incorporation into the swine lipoproteins. However, such changes had relatively little effect on lipoprotein structure or the presence of atherosclerotic lesions in these 6-month-old swine.

Animals↗