Biomedical subjects

R Tracy

Publications and source records attributed to R Tracy.

At least 19 recordsLinked to original sources

PubMed2001

Use of risk stratification to identify patients with unstable angina likeliest to benefit from an invasive versus conservative management strategy.

OBJECTIVES: This study was designed to determine whether patient characteristics collected at presentation can identify which patients benefit from immediate coronary angiography and revascularization. BACKGROUND: Risk stratification may offer a method for identifying which patients with unstable angina or non-Q-wave myocardial infarction (NQMI) are likeliest to benefit from invasive management strategies. METHODS: The analysis was based on data from a randomized controlled trial that enrolled 1,473 patients presenting with unstable angina or NQMI who were randomly assigned to an early invasive or early conservative (medical) management strategy. We constructed a risk-stratification score for each patient based on adjusted odds ratios for clinical variables likely to predict adverse outcomes. We stratified all trial subjects by their risk scores and studied the rates of death or myocardial infarction (MI) of the early invasive management strategy in each stratum. RESULTS: The final multivariate model included older age, ST segment depression on presentation, history of complicated angina before presentation, and elevation in baseline creatine kinase-MB fraction. Although patients with a higher risk score had an increased rate of death or MI within 42 days and 365 days (p < 0.001) in both management strategies, early invasive management for patients in the high and very high risk categories was associated with a lower rate of death or MI within 42 days compared with conservative management. No such benefit was seen in patients in the larger group of patients in the very low, low or moderate risk categories (p = 0.03 for the interaction between risk category and management assignment). CONCLUSIONS: Risk stratification may be an effective method for identifying those patients with unstable angina or NQMI most likely to benefit from early invasive management. Selective use of early invasive management can have a substantial impact in reducing morbidity and mortality in higher risk patients, but may not be warranted in lower risk patients.

Aged↗

PubMed2001

Frailty in older adults: evidence for a phenotype.

BACKGROUND: Frailty is considered highly prevalent in old age and to confer high risk for falls, disability, hospitalization, and mortality. Frailty has been considered synonymous with disability, comorbidity, and other characteristics, but it is recognized that it may have a biologic basis and be a distinct clinical syndrome. A standardized definition has not yet been established. METHODS: To develop and operationalize a phenotype of frailty in older adults and assess concurrent and predictive validity, the study used data from the Cardiovascular Health Study. Participants were 5,317 men and women 65 years and older (4,735 from an original cohort recruited in 1989-90 and 582 from an African American cohort recruited in 1992-93). Both cohorts received almost identical baseline evaluations and 7 and 4 years of follow-up, respectively, with annual examinations and surveillance for outcomes including incident disease, hospitalization, falls, disability, and mortality. RESULTS: Frailty was defined as a clinical syndrome in which three or more of the following criteria were present: unintentional weight loss (10 lbs in past year), self-reported exhaustion, weakness (grip strength), slow walking speed, and low physical activity. The overall prevalence of frailty in this community-dwelling population was 6.9%; it increased with age and was greater in women than men. Four-year incidence was 7.2%. Frailty was associated with being African American, having lower education and income, poorer health, and having higher rates of comorbid chronic diseases and disability. There was overlap, but not concordance, in the cooccurrence of frailty, comorbidity, and disability. This frailty phenotype was independently predictive (over 3 years) of incident falls, worsening mobility or ADL disability, hospitalization, and death, with hazard ratios ranging from 1.82 to 4.46, unadjusted, and 1.29-2.24, adjusted for a number of health, disease, and social characteristics predictive of 5-year mortality. Intermediate frailty status, as indicated by the presence of one or two criteria, showed intermediate risk of these outcomes as well as increased risk of becoming frail over 3-4 years of follow-up (odds ratios for incident frailty = 4.51 unadjusted and 2.63 adjusted for covariates, compared to those with no frailty criteria at baseline). CONCLUSIONS: This study provides a potential standardized definition for frailty in community-dwelling older adults and offers concurrent and predictive validity for the definition. It also finds that there is an intermediate stage identifying those at high risk of frailty. Finally, it provides evidence that frailty is not synonymous with either comorbidity or disability, but comorbidity is an etiologic risk factor for, and disability is an outcome of, frailty. This provides a potential basis for clinical assessment for those who are frail or at risk, and for future research to develop interventions for frailty based on a standardized ascertainment of frailty.

Aged↗

PubMed2001

Associations of subclinical cardiovascular disease with frailty.

BACKGROUND: Frail health in old age has been conceptualized as a loss of physiologic reserve associated with loss of lean mass, neuroendocrine dysregulation, and immune dysfunction. Little work has been done to define frailty and describe the underlying pathophysiology. METHODS: Frailty status was defined in participants of the Cardiovascular Health Study (CHS), a cohort of 5,201 community-dwelling older adults, based on the presence of three out of five clinical criteria. The five criteria included self-reported weight loss, low grip strength, low energy, slow gait speed, and low physical activity. We examined the spectrum of clinical and subclinical cardiovascular disease in those who were frail (3/5 criteria) or of intermediate frailty status (1 or 2/5 criteria), compared to those who were not frail (0/5). We hypothesized that the severity of frailty would be related to a higher prevalence of reported cardiovascular disease (CVD), as well as to a greater extent of CVD, measured by noninvasive testing. RESULTS: Of 4,735 eligible participants, 2,289 (48%) were not frail, 299 (6%) were frail, and 2.147 (45%) were of intermediate frailty status. Those who were frail were older (77.2 yrs) compared to those who were not frail (71.5 yrs) or intermediate (73.4 yrs) (p < .001). Frailty status was associated with clinical CVD and most strongly with congestive heart failure (odds ratio [OR] = 7.51 (95% confidence interval [CI] = 4.66-12.12). In those without a history of a CVD event (n = 1.259), frailty was associated with many noninvasive measures of CVD. Those with carotid stenosis >75% (adjusted OR = 3.41), ankle-arm index <0.8 (adjusted OR = 3.17) or 0.8-0.9 (adjusted OR = 2.01), major electrocardiography (ECG) abnormalities (adjusted OR = 1.58), greater left ventricular (LV) mass by echocardiography (adjusted OR = 1.16), and higher degree of infarct-like lesions in the brain (adjusted OR = 1.71), were more likely to be frail compared to those who were not frail. The overall associations of each of these noninvasive measures of CVD with frailty level were significant (all p < .05). CONCLUSIONS: Cardiovascular disease was associated with an increased likelihood of frail health. In those with no history of CVD, the extent of underlying cardiovascular disease measured by carotid ultrasound and ankle-arm index, LV hypertrophy by ECG and echocardiography, was related to frailty. Infarct-like lesions in the brain on magnet resonance imaging were related to frailty as well.

Black or African American↗

PubMed2001

Absence of aquaporin-4 water channels from kidneys of the desert rodent Dipodomys merriami merriami.

Recently, we found that aquaporin-4 (AQP4) is expressed in the S3 segment of renal proximal tubules of mice but not in rat proximal tubules. Because mice have relatively larger papillae than rats, it was proposed that the renal distribution of AQP4 in various species could be related to their maximum urinary concentrating ability. Therefore, kidneys and other tissues of Merriam's desert kangaroo rat, Dipodomys merriami merriami, which produce extremely concentrated urine (up to 5,000 mosmol/kgH(2)O), were examined for AQP4 expression and localization. Contrary to our expectation, AQP4 immunostaining was undetectable in any region of the kidney, and the absence of AQP4 protein was confirmed by Western blotting. By freeze fracture electron microscopy, orthogonal arrays of intramembraneous particles (OAPs) were not detectable in plasma membranes of principal cells and proximal tubules. However, AQP4 protein was readily detectable in gastric parietal and brain astroglial cells. Northern blotting failed to detect AQP4 mRNA in kangaroo rat kidneys, whereas both in situ hybridization and RT-PCR experiments did reveal AQP4 mRNA in collecting ducts and proximal tubules of the S3 segment. These results suggest that renal expression of AQP4 in the kangaroo rat kidney is regulated at the transcriptional or translational level, and the absence of AQP4 may be critical for the extreme urinary concentration that occurs in this species.

Animals↗

PubMed2001

Vascular stiffness in women with systemic lupus erythematosus.

Large-vessel manifestations of systemic lupus erythematosus (SLE), a multisystem disease characterized by disturbances in the immune system, include higher than expected rates of hypertension and cardiovascular disease. Reductions in the elasticity of central arteries may act as a marker of early changes that predispose to the development of major vascular disease. This study evaluated risk factors associated with aortic stiffness measured by pulse wave velocity (PWV) in women with SLE. We expected SLE-specific factors, especially variables indicative of inflammation and active disease, to be associated with increasing PWV. The study population included 220 women currently enrolled in the Pittsburgh Lupus REGISTRY: All risk factor data were collected on the day of the ultrasound examinations. PWV waveforms were collected from the right carotid and femoral arteries by Doppler probes. The mean age of the women was 45.5+/-10.8 years, the median SLE disease duration approximated 9 years, and the mean PWV was 6.1+/-1.7 m/s. Multiple regression models were stratified by menopausal status. Among postmenopausal women, PWV risk factors were primarily traditional factors and included age, systolic blood pressure, family history of vascular disease, carotid plaque, creatinine, obesity, glucose, white cell count, and cumulative SLE organ damage. Among premenopausal women, PWV risk factors consisted of a mix of SLE-related and traditional variables and included higher C3 levels, presence of ds-DNA antibodies, nonuse of hydroxychloroquine, lower leukocyte count, higher mean arterial pressure, and carotid plaque. SLE-specific variables appeared to be associated with increases in aortic PWV, indicating central artery stiffening. This was seen most clearly among premenopausal women. This finding may partially explain the higher rates of cardiovascular disease and hypertension observed in young women with SLE.

Adult↗

PubMed1999

Interleukin-6 exacerbates early atherosclerosis in mice.

Acute-phase proteins, which respond to systemic proinflammatory cytokines such as interleuken-6, are elevated in cardiovascular disease and are predictive markers of future ischemic events, even over decades. This suggests a role for proinflammatory cytokines and/or acute phase proteins in early lesion development. To explore this issue, we fed C57Bl/6 and nonobese diabetic male mice high-fat (20% total fat, 1.5% cholesterol) diets and ApoE-deficient male mice both high-fat and normal chow diets for 6 to 21 weeks, injecting them weekly with either 5000 U recombinant interleukin-6 (rIL-6) or saline buffer. Blood was collected when animals were euthanized and assayed for cytokines, acute-phase proteins, and cholesterol. Across all mice, IL-6 injection resulted in significant increases in proinflammatory cytokines (IL-6, 4.6-fold; IL-1beta, 1.6-fold; and tissue necrosis factor-alpha, 1.7-fold) and fibrinogen (1.2-fold) and with decreased concentrations of albumin (0.9-fold) in plasma. Total cholesterol levels were unchanged between rIL-6-treated and nontreated groups. Serial sections through the aortic sinus were stained with oil red O to detect fatty streaks, and area of the lesions was determined by image analysis. Although no fatty streaks were detected in the nonobese diabetic mice with or without rIL-6 treatment, rIL-6 treatment increased lesion size in C57Bl/6 and ApoE-deficient mice 1.9- to 5.1-fold over lesions in saline-treated animals. These results suggest that under the appropriate circumstances changes in circulating proinflammatory cytokines and acute-phase proteins may be more than just markers of atherosclerosis but actual participants in early lesion development.

Animals↗

PubMed1999

Low-density lipoprotein particle size is inversely related to plasminogen activator inhibitor-1 levels. The Insulin Resistance Atherosclerosis Study.

High levels of plasminogen activator inhibitor-1 (PAI-1) and preponderance of small dense low-density lipoproteins (LDL) have both been associated with atherosclerotic disease and with the insulin resistance syndrome (IRS). In vitro studies have shown a stimulatory effect of various lipoproteins on PAI-1 release from different cells, including endothelial cells and adipocytes. The authors sought to investigate the relation of PAI-1 to LDL particle size in a large tri-ethnic population (n=1549) across different states of glucose tolerance. LDL size was determined by gradient gel electrophoresis, and PAI-1 was measured by a 2-site immunoassay, sensitive to free PAI-1. PAI-1 was inversely related to LDL size in the overall population (r=-0.21, P<0.0001), independent of gender and ethnicity. However, the authors found a significant interaction with glucose tolerance status (P=0.035). In univariate analysis, the association between PAI-1 and LDL size was most pronounced in subjects with normal glucose tolerance (NGT, r=-0.22, P<0.0001) and weaker in impaired glucose tolerance (IGT, r=-0.12, P=0.03) and type-2 diabetes (r=-0.10, P=0.02). After adjustment for demographic variables and metabolic variables known to influence PAI-1 levels (triglyceride and insulin sensitivity), a significant inverse relation of LDL size to PAI-1 levels was only present in NGT (P=0. 023). In subjects with IGT or overt diabetes, who usually have elevated PAI-1 levels, additional factors other than LDL size seem to contribute more importantly to PAI-1 levels. The demonstrated inverse relation of LDL size and PAI-1 levels provides one possible explanation for the atherogeneity of small dense LDL particles.

Adipose Tissue↗

PubMed1999

Insulin sensitivity in subjects with type 2 diabetes. Relationship to cardiovascular risk factors: the Insulin Resistance Atherosclerosis Study.

OBJECTIVE: Among nondiabetic subjects, insulin resistance has been associated with increased cardiovascular risk factors, including dyslipidemia, hypertension, impaired fibrinolysis, and coagulation. Less is known about the relationship between insulin resistance and cardiovascular risk factors in subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: To examine this issue, we determined insulin sensitivity (SI) in 479 type 2 diabetic subjects by minimal model analyses of frequently sampled intravenous glucose tolerance tests in the Insulin Resistance Atherosclerosis Study (IRAS), a large multicenter study of insulin sensitivity and cardiovascular disease in African-Americans, Hispanics, and non-Hispanic whites. We defined insulin-sensitive subjects as having SI > or = 1.61 x 10(-4) min-1.microU-1.ml-1 (above median in nondiabetic subjects of all ethnic groups in the IRAS). Using this definition, only 37 type 2 diabetic subjects were insulin sensitive, and the remaining 442 were insulin resistant. RESULTS: After adjustment for age, sex, ethnicity, and clinic, insulin resistance was significantly correlated with total triglycerides, VLDL cholesterol, VLDL triglyceride, fibrinogen, PAI-1, and fasting glucose, and was inversely correlated with HDL cholesterol level and LDL size. Carotid intimal-medial thickness was greater in insulin-resistant than in insulin-sensitive subjects, but this difference was not statistically significant. After further adjustment for waist circumference (marker of visceral adiposity), insulin-resistant subjects continued to have higher plasminogen activator inhibitor 1 and VLDL triglyceride levels, lower HDL cholesterol levels, and smaller LDL particle size than did insulin-sensitive subjects. After further adjustment for fasting glucose levels, these results were very similar. CONCLUSIONS: We conclude that insulin-resistant type 2 diabetic subjects have more atherogenic cardiovascular risk factor profiles than insulin-sensitive type 2 diabetic subjects and that this is only partially related to increased obesity and an adverse body fat distribution.

Black or African American↗

PubMed1998

Relationship between ApoE, MRI findings, and cognitive function in the Cardiovascular Health Study.

BACKGROUND AND PURPOSE: We determined the relationship between apolipoprotein (Apo)E, MRI, and low cognitive scores. METHODS: The relationship between age, education, ApoE genotype, MRI examination of the brain, subclinical and clinical cardiovascular disease, and low (<80) score on the Modified Mini-Mental State Examination (3MSE, as modified by Teng and Chui) was evaluated for 3469 black and white participants in the Cardiovascular Health Study (CHS) in years 5 and 6 of the study. The participants were followed for up to 3 years. RESULTS: The prevalence of scores <80 in years 5 and 6 of the CHS was 8.2% for participants without and 20.4% for those with prior history of stroke. Age, race, and education were important determinants of low 3MSE scores. The prevalence of ApoE-4 (odds ratio [OR], 1.6 [1.1 to 2.1]) was directly related to scores <80, as was high ventricular volume (OR, 1.6 [1.2 to 2.3]), high white matter grade (OR, 1.4 [1.1 to 1.9]), and infarctlike lesions (OR, 1.6 [1.2 to 2.1]) on the MRI in the multivariate analysis. A five-point or greater decline in scores over up to 3 years was more often observed for participants with low 3MSE scores at year 5, at older ages, with lower education, and experiencing incident stroke (OR, 3.6 [1.2 to 10.6]), ApoE-4 genotype (OR, 1.8 [1.4 to 2.3]), and with MRI findings of high ventricular volume (OR, 2.0 [1.5 to 2.7]), and infarctlike lesions (OR, 1.2 [0.9 to 1.5]). CONCLUSIONS: These results demonstrate that vascular changes on MRI, measures of brain atrophy, ApoE-4, and age, education, and race are associated with low cognitive scores among older individuals. The MRI of the brain provides valuable information related to cognitive tests and decline over time. The potential exists for using MRI measurements to identify high-risk individuals for dementia and to test potential interventions to reduce the risk of dementia.

Aged↗

PubMed1998

Proinsulin and insulin concentrations in relation to carotid wall thickness: Insulin Resistance Atherosclerosis Study.

BACKGROUND AND PURPOSE: Insulin resistance and hyperinsulinemia have been associated with atherosclerosis. Recent attention has focused on the possible role of proinsulin because most radioimmunoassays for insulin cross-react with proinsulin. Therefore, it is not known which of the two, insulin per se or proinsulin, is more strongly related to atherosclerosis. METHODS: We examined the relation between fasting proinsulin, fasting split proinsulin, fasting and 2-hour insulin (after oral glucose load), and intima-media wall thickness (IMT) in the common carotid artery (CCA) and internal carotid artery (ICA) in 985 nondiabetic subjects from the Insulin Resistance Atherosclerosis Study, a multiethnic study of insulin resistance and atherosclerosis. RESULTS: In the overall population, a weak but significant relation between proinsulin and CCA IMT was observed (r=0.07, P=0.029). However, the relation between proinsulin and IMT was stronger in Hispanics and non-Hispanic whites than in African Americans. In non-Hispanic whites and Hispanics, significant correlations between CCA and proinsulin (r=0.087) and between ICA and proinsulin (r=0.101), split proinsulin (r = 0.092), and fasting insulin (r = 0.087) were observed. The significant correlations became more attenuated (and nonsignificant) after adjustment for cardiovascular risk factors, especially plasminogen activator inhibitor-1 (PAI-1). CONCLUSIONS: The association between proinsulin and IMT, while weak, appears to be stronger than the association between insulin and IMT. Adjustment for PAI-1 markedly attenuated the association between proinsulin and IMT, suggesting a possible mediating role for PAI-1 in this association. It is possible that proinsulin may represent a marker of atherosclerosis rather than a causal factor for atherosclerosis. Studies of the insulin resistance syndrome and atherosclerosis that use insulin as a surrogate for insulin resistance should consider the use of specific insulin assays as well as determination of proinsulin concentrations.

Arteriosclerosis↗

PubMed1997

Left ventricular mass in the elderly. The Cardiovascular Health Study.

Left ventricular (LV) mass, as estimated from M-mode echocardiography (echo), has previously been shown to be an independent predictor of incident cardiovascular disease morbidity and mortality. We evaluated the relationship at baseline of echo LV mass to relevant cardiovascular disease risk factors and other potential covariates in the Cardiovascular Health Study, multicenter study sponsored by the National Heart, Lung, and Blood Institute of 5201 men and women aged 65 years or older (mean, 73). Two-dimensionally directed M-mode echo LV mass measurements could be obtained in 1357 men and 2053 women (66% of this elderly cohort). Stepwise linear regression analyses of the relationship of echo LV mass to demographic and risk factor, physical activity, electrocardiographic, and prevalent disease variables resulted in a model that explained 37% of the variance for the entire cohort. In order of decreasing importance, factors positively associated with echo LV mass were body weight, male sex, systolic pressure, presence of congestive heart failure, present smoking, major and minor electrocardiographic abnormalities, treatment for hypertension, valvular heart disease, aortic regurgitation by color Doppler, and mitral regurgitation by color Doppler (in men) whereas diastolic pressure, bioresistance (a measure of adiposity), and high-density lipoprotein cholesterol were inversely related to echo LV mass. Although height and weight were both related to LV mass, height added nothing once weight was entered in multiple linear regression analyses. Furthermore, in the multiple regression models, diastolic pressure was inversely and systolic BP positively related to LV mass, with similar magnitudes for their coefficients. In consonance with these findings, pulse pressure was positively related to LV mass in bivariate analyses. Multiple linear regression analyses explained less of the variance for ventricular septal thickness (R2 = .13) and LV posterior wall thickness (R2 = .14) than for LV mass (R2 = .37) and LV diastolic dimension (R2 = .27). Intriguing findings in the elderly Cardiovascular Health Study cohort included the presence of pulse pressure as a positive correlate, and high-density lipoprotein cholesterol as an inverse correlate, of LV mass. Longitudinal studies in the Cardiovascular Health Study cohort will help to clarify the importance of demographic, risk factor, and other variables, and changes in these variables, in predicting changes in echo LV mass and its components as well as the prognostic significance of LV mass in the elderly.

Aged↗

PubMed1997

Trends and implications of visiting medical consultant outpatient clinics in rural hospital communities.

The emergence of visiting consultant clinics (VCC) represents an unstudied but potentially important mechanism for importing specialty physician services into rural areas. An analysis of five years of one state's VCC experience reveals a substantial increase in both availability and geographic accessibility. This study documents the market's response to the oversupply and hypercompetition among urban-based physician specialists. Patterns of VCC growth have varied markedly for different specialties.

Economic Competition↗

PubMed1996

Guidelines of the National Heart, Lung, and Blood Institute Working Group on Blood Drawing, Processing, and Storage for Genetic Studies.

The guidelines presented here are intended for epidemiologic investigators who wish to store blood samples for genetic studies, either by extracting DNA directly from white blood cells or from immortalized cell lines. Recommended procedures for blood drawing and for processing samples are described. Protocols for freezing and storage of both white blood cells and extracted DNA are provided. Although the extraction of DNA and immortalization of cell lines should be conducted in collaboration with an experienced laboratory, a summary of the available methods with appropriate references is given, and a method for the extraction of DNA from clotted blood is referenced. In addition, criteria for selecting study subjects for whom immortalized cell lines are preferable to merely extracting DNA are presented. Finally, the use of alternative sources of genetic material, including cheek swabs and dried blood spots, is described briefly.

Blood Preservation↗

PubMed1996

Relationship of hepatic and peripheral insulin resistance with plasminogen activator inhibitor-1 in Pima Indians.

Plasminogen activator inhibitor-1 (PAI-1) is related to insulin resistance and several components of the insulin resistance syndrome, and PAI-1 levels are elevated in subjects with non-insulin-dependent diabetes mellitus. Many Pima Indians are obese, insulin-resistant, and hyperinsulinemic, and they have high rates of diabetes but a low risk of ischemic heart disease. In contrast to whites and Asians, PAI-1 activity is similar between nondiabetic and diabetic Pima Indians. We therefore examined the association of PAI-1 with hepatic and peripheral insulin action measured using the hyperinsulinemic-euglycemic clamp. To investigate if insulin per se has any effect on PAI-1 in vivo, we also assessed the effects of endogenous (during a 75-g oral glucose load) and exogenous (during hyperinsulinemic clamp) insulin on PAI-1 antigen. Twenty-one (14 men and seven women; mean age, 26.3 +/- 4.8 years) Pima Indians underwent a 75-g oral glucose tolerance test (OGTT) and a sequential hyperinsulinemic-euglycemic clamp. Peripheral insulin action was measured as absolute glucose uptake (M value) and normalized to estimated metabolic body size (EMBS). Hepatic insulin action was measured as percent suppression of basal hepatic glucose output during hyperinsulinemia. PAI-1 antigen was determined using a two-site enzyme-linked immunosorbent assay that detects only free PAI-1. PAI-1 antigen concentrations were significantly related to body mass index ([BMI] rs = .54, P = .012), waist (rs=.52, P=.016) and thigh (rs=.63, P=.002) circumference, and fasting plasma insulin concentration (rs=.59, P=.004). PAI-1 antigen concentrations were not significantly associated with peripheral glucose uptake (M value) during either low-dose (rs= -.01, P=NS) or high-dose (rs= -.11, P=NS) insulin infusion. PAI-1 antigen was negatively correlated with basal hepatic glucose output (rs= -.57, P=.013) and percent suppression of hepatic glucose output during hyperinsulinemia (rs= -.69, P=.005). However, this relationship was largely due to the confounding effects of BMI, waist and thigh girth, fasting insulin, and 2-hour postload glucose concentrations, and was not significant when controlled for these variables (partial rs= -.30, P=NS). There was no significant relationship of PAI-1 antigen concentration with glucose storage or glucose oxidation. Despite a threefold increase in plasma insulin concentrations during the OGTT, there were no significant changes in PAI-1 antigen concentrations (median, 57, 61, 55, and 44 ng/mL at 0, 60, 120, and 180 minutes, respectively; P=NS by ANOVA). During the hyperinsulinemic clamp, mean plasma insulin concentrations at the end of low-dose (240 pmol/m2/min) and high-dose (2,400 pmol/m2/min) infusions were 1,005 and 14,230 pmol/L, respectively. However, PAI-1 antigen concentrations at the end of low-dose and high-dose insulin infusions were similar to those at baseline (median, 63, 43, and 58 ng/mL, respectively; P=NS by ANOVA). PAI-1 antigen in Pima Indians is related to several components of the insulin resistance syndrome. However, direct measurement of insulin resistance indicates that hepatic but not peripheral insulin resistance is related to PAI-1 antigen. Neither endogenous nor exogenous hyperinsulinemia for short periods had any significant effect on PAI-1 antigen concentrations. Short-term hyperinsulinemia is unlikely to be an important regulator of PAI-1 in Pima Indians. The relationship of PAI-1 antigen to hepatic insulin resistance is largely dependent on the relationship of PAI-1 to indices of obesity and fasting insulin concentrations.

Adult↗

PubMed1996

Amelioration of the inhibition of fibrinolysis in elderly, obese subjects by moderate energy intake restriction.

A possible cause of accelerated atherothrombosis in the syndrome of insulin resistance appears to be an elevated blood concentration of plasminogen activator inhibitor type-1 (PAI-1). Insulin resistance occurs with aging, attributable partly to increased adiposity. Scarce information exists regarding the effects of weight loss in elderly, obese individuals on PAI-1 concentrations. Consequently, weight loss (9 +/- 1 kg) was induced by energy intake restriction in 19 elderly, obese individuals, and its effect on fibrinolytic system peptides was measured. Initially elevated PAI-1 concentrations decreased by 50%, with a simultaneous decrease in the concentration of tissue-type plasminogen activator (t-PA)/PAI-1 complexes but no significant change in t-PA suggested a decrease in inhibition of the fibrinolytic system. The concentration of plasmin/antiplasmin complexes (PAP complex) increased by approximately 20%, indicating augmented fibrinolytic system activity. The decline in PAI-1 correlated with that of the decrease in body weight (r = 0.5, P < 0.05) and fat mass losses (r = 0.46, P < 0.05). The increase in PAP complexes correlated with weight and fat mass losses (r = 0.4 and r = 0.46, respectively; P < 0.05 for both). No correlation was seen between fibrinolytic system variables and baseline concentrations of substrates or insulin, but the change in PAI-1 correlated with the change in plasma triacylglycerols (r = 0.58, P < 0.05). Results indicate that energy restriction sufficient to induce moderate weight loss leads to diminution of elevated plasma PAI-1 and relief of inhibition of the fibrinolytic system in elderly, obese subjects. To the extent that these changes are associated with a decrease in the progression of vasculopathy, weight loss in elderly, obese individuals may be a useful means to reduce cardiovascular morbidity and mortality.

Aged↗

PubMed1996

Adjusting measures of physician availability to reflect importation of physician services into rural areas.

Recent changes in the organization and delivery of physician services in rural areas suggest the need to update how physician availability is viewed and measured. The objective of this study was to empirically examine the effect of rural hospitals contracting with outside physicians for part or all of their emergency room coverage, and the use of urban specialists to staff outpatient clinics, on measures used to assess physician availability. Based on data from one rural state, the findings demonstrate the importance of adjusting for the importation of physician services into rural areas.

Contract Services↗

PubMed1996

Thickening of the carotid wall. A marker for atherosclerosis in the elderly? Cardiovascular Health Study Collaborative Research Group.

BACKGROUND AND PURPOSE: We investigated the relationships between prevalent coronary heart disease (CHD), clinically manifest atherosclerotic disease (ASD), and major established risk factors for atherosclerosis and intima-media thickness (IMT) in the common carotid arteries (CCA) and internal carotid arteries (ICA) separately and in combination in older adults. We wished to determine whether a noninvasive measurement can serve as an indicator of clinically manifest atherosclerotic disease and to determine which of the two variables, CCA IMT or ICA IMT, is a better correlate. METHODS: IMT of the CCA and ICA was measured with duplex ultrasound in 5117 of 5201 individuals enrolled in the Cardiovascular Health Study, a study of the risk factors and the natural history of cardiovascular disease in adults aged 65 years or more. Histories of CHD, peripheral arterial disease, and cerebrovascular disease were obtained during baseline examination. Risk factors included cholesterol levels, cigarette smoking, elevated blood pressure, diabetes, age, and sex. Relationships between risk factors and IMT were studied by multiple regression analysis and canonical variate analysis. Prediction of prevalent CHD and ASD by IMT measurements in CCAs and ICAs were made by logistic regression, adjusting for age and sex. RESULTS: IMT measurements of the CCAs and ICAs were greater in persons with CHD and ASD than those without, even after controlling for sex (P < .001). IMT measurements in the ICA were greater than those in the CCA. Risk factors for ASD accounted for 17% and 18% of the variability in IMT in the CCA and ICA, respectively. These same risk factors accounted for 25% of the variability of a composite measurement consisting of the sum of the ICA IMT and CCA IMT. The ability to predict CHD and ASD was greater for ICA IMT (odds ratio [confidence interval]: 1.36 [1.31 to 1.41] and 1.35 [1.25 to 1.44], respectively) than for CCA IMT (1.09 [1.05 to 1.13] and 1.17 [1.09 to 1.25]). CONCLUSIONS: Whereas CCA IMT is associated with major risk factors for atherosclerosis and existing CHD and ASD in older adults, this association is not as strong as that for ICA IMT. The combination of these measures relates more strongly to existing CHD and ASD and cerebrovascular disease risk factors than either taken alone.

Adult↗

PubMed1996

Considerations in establishing visiting consultant clinics in rural hospital communities.

Establishing specialty clinics staffed by visiting medical consultants is one way that rural hospitals can increase local access to specialty care. This example of private sector-driven regionalization of health care services typically involves an agreement among urban specialists, rural hospitals, and local primary care physicians. The urban-based physicians provide limited on-site specialty services in the rural community for patients who are referred by local physicians or self-refer to the specialty clinics. The trend toward formalization of regional relationships across large geographic areas prompts both opportunity and need for careful consideration of visiting specialty clinic arrangements in rural hospital communities. This article delineates advantages and disadvantages associated with the development of Visiting Consulting Clinics (VCC) along with some ¿ground rules¿ to consider when establishing this type of service.

Appointments and Schedules↗