Leaf water stable isotopes and water transport outside the xylem

How water moves through leaves, and where the phase change from liquid to vapour occurs within leaves, remain largely mysterious. Some time ago, we suggested that the stable isotope composition of leaf water may contain information on transport pathways beyond the xylem, through differences in the development of gradients in enrichment within the various pathways. Subsequent testing of this suggestion provided ambiguous results and even questioned the existence of gradients in enrichment within the mesophyll. In this review, we bring together recent theoretical developments in understanding leaf water transport pathways and stable isotope theory to map a path for future work into understanding pathways of water transport and leaf water stable isotope composition. We emphasize the need for a spatially, anatomically and isotopically explicit model of leaf water transport.

A single-substrate model to interpret intra-annual stable isotope signals in tree-ring cellulose

The carbon and oxygen stable isotope composition of wood cellulose (delta(13)C(cellulose) and delta(18)O(cellulose), respectively) reveal well-defined seasonal variations that contain valuable records of past climate, leaf gas exchange and carbon allocation dynamics within the trees. Here, we present a single-substrate model for wood growth to interpret seasonal isotopic signals collected in an even-aged maritime pine plantation growing in South-west France, where climate, soil and flux variables were also monitored. Observed seasonal patterns in delta(13)C(cellulose) and delta(18)O(cellulose) were different between years and individuals, and mostly captured by the model, suggesting that the single-substrate hypothesis is a good approximation for tree ring studies on Pinus pinaster, at least for the environmental conditions covered by this study. A sensitivity analysis revealed that the model was mostly affected by five isotopic discrimination factors and two leaf gas-exchange parameters. Modelled early wood signals were also very sensitive to the date when cell wall thickening begins (t(wt)). Our model could therefore be used to reconstruct t(wt) time series and improve our understanding of how climate influences this key parameter of xylogenesis.

Components of ecosystem evaporation in a temperate coniferous rainforest, with canopy transpiration scaled using sapwood density

Here we develop and test a method to scale sap velocity measurements from individual trees to canopy transpiration (E(c)) in a low-productivity, old-growth rainforest dominated by the conifer Dacrydium cupressinum. Further, E(c) as a component of the ecosystem water balance is quantified in relation to forest floor evaporation rates and measurements of ecosystem evaporation using eddy covariance (E(eco)) in conditions when the canopy was dry and partly wet. Thermal dissipation probes were used to measure sap velocity of individual trees, and scaled to transpiration at the canopy level by dividing trees into classes based on sapwood density and canopy position (sheltered or exposed). When compared with ecosystem eddy covariance measurements, E(c) accounted for 51% of E(eco) on dry days, and 22% of E(eco) on wet days. Low transpiration rates, and significant contributions to E(eco) from wet canopy evaporation and understorey transpiration (35%) and forest floor evaporation (25%), were attributable to the unique characteristics of the forest: in particular, high rainfall, low leaf area index, low stomatal conductance and low productivity associated with severe nutrient limitation.

Drug therapy and prevalence of erectile dysfunction in the Massachusetts Male Aging Study cohort

STUDY OBJECTIVE

To examine the association of commonly used drugs with erectile dysfunction (ED) at two time points.

DESIGN

Population-based, cross-sectional, survey analysis.

PARTICIPANTS

Randomly selected cohort of men in the Massachusetts Male Aging Study (MMAS) that included 1476 men for the baseline (1987-1989) and 922 for the follow-up (1995-1997) analyses.

INTERVENTION

Crude associations between specific drug categories were examined with chi2 statistics. Logistic regression analysis was used to separate the effect of drugs from the influence of heart disease, hypertension, untreated diabetes, or depressive symptoms.

MEASUREMENTS AND MAIN RESULTS

In the MMAS, medical history, current drug use, and erectile function status were ascertained with in-home interviews. In unadjusted analyses, thiazide and nonthiazide diuretics, beta-blockers, calcium channel blockers, angiotensin-converting enzyme inhibitors, benzodiazepines, digitalis, nitrates, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, and histamine2 receptor antagonists were associated with prevalent ED. Adjustment for comorbidities and health behaviors attenuated these associations, with only nonthiazide diuretics and benzodiazepines remaining statistically significant.

CONCLUSION

Several common drugs may increase prevalence of ED; however, additional data from larger populations are needed to determine whether these associations are independent of underlying health conditions and to explore the effects of dosage and duration of use.

Pharmacotherapy of systolic heart failure: emphasis on mortality outcomes

Mortality outcomes in clinical trials have become the foundation for the evidence-based management of patients with systolic heart failure. This review was intended to give the clinician a better understanding of newer pharmacological strategies in this patient population.

Pharmacology and pharmacotherapy of cardiovascular drugs in patients with chronic renal disease

Cardiovascular disease is a common comorbidity and a major cause of mortality in patients with chronic renal disease. Drug regimens in patients with cardiovascular disease are frequently complex and can be significantly affected by alterations in renal function. In addition, several cardiovascular drugs directly affect renal function and the management of patients with renal disease. This article reviews the impact of renal disease on the pharmacokinetics of cardiovascular drugs and identifies clinically important interactions between these and other drugs commonly used in the management of chronic renal disease. Several classes of cardiovascular drugs are also discussed in relationship to their differential effects on the management and progression of renal disease.

Variation in the oxygen isotope ratio of phloem sap sucrose from castor bean. Evidence in support of the Péclet effect

Theory suggests that the level of enrichment of (18)O above source water in plant organic material (Delta) may provide an integrative indicator of control of water loss. However, there are still gaps in our understanding of the processes affecting Delta. One such gap is the observed discrepancy between modeled enrichment of water at the sites of evaporation within the leaf and measured enrichment of the leaf water as a whole (Delta(L)). Farquhar and Lloyd (1993) suggested that this may be caused by a Péclet effect. It is also unclear whether organic material formed in the leaf reflects enrichment of water at the sites of evaporation within the leaf or Delta(L). To investigate this question castor bean (Ricinus communis L.) leaves, still attached to the plant, were sealed into a controlled-environment gas exchange chamber and subjected to a step change in leaf-to-air vapor pressure difference. Sucrose was collected from a cut on the petiole of the leaf in the chamber under equilibrium conditions and every hour for 6 h after the change in leaf-to-air vapor pressure difference. Oxygen isotope composition of sucrose in the phloem sap (Delta(suc)) reflected modeled Delta(L). A model is presented describing Delta(suc) at isotopic steady state, and accounts for 96% of variation in measured Delta(suc). The data strongly support the Péclet effect theory.

Antiischemic therapy in patients with coronary heart disease living in long-term care. Systematic Assessment of Geriatric Drug Use by Epidemiology (SAGE) Group

We evaluated antiischemic therapy in elderly nursing home residents with a diagnosis of coronary heart disease (CHD) using a population-based data base with over 300,000 residents (1992-1995) of all Medicare/Medicaid-certified nursing homes of five states. We identified 72,263 patients age 65 years or older with a diagnosis of CHD. We examined data collected with the federally mandated Minimum Data Set, drug information, and Medicare hospital claims. Antiischemics were defined as beta-adrenergic blockers, long-term nitrates, and calcium channel blockers. We determined factors associated with use of the drugs by logistic regression. Antiischemic therapy was inversely related to age and cognitive and physical functioning, but positively associated with recent hospitalization and concomitant cardiovascular diseases. beta-Adrenergic blockers were least likely to be administered regardless of age, gender, or cognitive or physical function. We conclude that antiischemic therapy in nursing home residents may not be optimal.

Correlates of oral contraceptive use in two New England communities: 1981-1993

This study compared the sociodemographic and cardiovascular correlates of oral contraceptive users and nonusers between 1981 and 1993. We also sought to determine changes in the prevalence of oral contraceptive use among older premenopausal women. Using data from six biennial cross-sectional household surveys in a population-based sample of two New England communities, 5239 women between ages 18 and 45 years were identified. Women using oral contraceptives were 5 years younger and better educated than nonusers, and users more frequently reported a per capita income above the median for the survey population than nonusers. Users were more likely to report smoking and have a lower body mass index than nonusers. Little use of oral contraceptives was detected among women ages 40-45 years despite changes in FDA recommendations about their use and increasing evidence of their noncontraceptive benefits in healthy older nonsmoking women.

Cardiovascular risk profiles of oral contraceptive users and nonusers: a population-based study

BACKGROUND

The purpose of this population-based study was to evaluate whether women taking oral contraceptive products (OCPs) have more favorable cardiovascular disease (CVD) risk profiles than women not taking OCPs.

METHODS

Data including sociodemographic variables and CVD risk factors from 5,239 women of reproductive age were gathered in six cross-sectional household surveys. Differences in CVD risk factor profiles between OCP users and nonusers were compared using logistic regression. younger users and older users were compared with nonusers of the same age groups.

RESULTS

Women using OCPs (n = 807) were younger and had higher socioeconomic status than nonusers (n = 4,432). More users than nonusers were current smokers (43.1% vs 36.6%, P = 0.0011), had a total serum cholesterol level > or = 240 mg/dl (12.7% vs 6.0%, P = 0.0001), and tended to rate themselves to be at low risk for CVD (48.3% vs 45.5%, P = 0.17). Fewer OCP users than nonusers had an HDL cholesterol level < or = 35 mg/dl (4.0% vs 6.9%, P = 0.0039).

CONCLUSIONS

Although they tended to perceive themselves to be at low risk, women taking OCPs in this study had worse CVD risk profiles than women not reporting hormonal contraception and are candidates for cardiovascular risk reduction strategies.

Is a history of depressive symptoms associated with an increased risk of infertility in women?

Researchers have reported an association between self-reported antidepressant use and increased risk of ovulatory infertility but could not control for confounding by the drug indication. We evaluated the role of depressive symptoms in the development of infertility. We recontacted a population-based sample of Pawtucket Heart Health Program (PHHP) health survey respondents to perform this case-control study. Self-reported infertility was defined as an inability to conceive after 12 months of unprotected intercourse. Controls were women who reported at least one pregnancy. The index age for infertile women was the age at which they first experienced fertility problems, and for the fertile women it was the age of their first pregnancy. History of depressive symptoms was based on self-report before the index age. Women with a history of depressive symptoms were nearly twice as likely to report infertility relative to women without a history of depressive symptoms before the index age after controlling for potential confounders (90% confidence interval: 0.9-3.2). Our data suggest that depressive symptoms as well as the drugs used to treat these conditions may play an important role in the pathogenesis of infertility. The association between depressive symptoms and infertility should be explored further.

Prior and current health characteristics of postmenopausal estrogen replacement therapy users compared with nonusers

OBJECTIVE

Our purpose was to investigate whether selection of healthy women for postmenopausal estrogen therapy may confound observational studies of estrogen use and cardiovascular disease risk.

STUDY DESIGN

Data were obtained from baseline (1981 to 1984) and follow-up (1990 to 1992) health surveys of two cohorts randomly selected from communities in southeastern New England. At follow-up postmenopausal women > or = 40 years old were categorized as current users (n = 70) or nonusers (n = 772) of noncontraceptive estrogen. Users and nonusers were compared on both prior characteristics from the baseline surveys and current characteristics measured at follow-up by use of analysis of covariance.

RESULTS

Prior levels of total and high-density lipoprotein cholesterol, body mass index, and blood pressure were similar for estrogen users and nonusers. Estrogen users were less likely to have smoked and more likely to have had their cholesterol checked and to exercise regularly. These differences were more pronounced for current characteristics than for baseline characteristics.

CONCLUSIONS

Selection of healthy women for treatment may not fully explain the apparent protective effect of estrogen replacement on cardiovascular risk. However, more healthy profiles among estrogen users may inflate the apparent benefit of treatment in observational studies.

Is the use of psychotropic drugs associated with increased risk of ischemic heart disease?

Earlier reports of associations between panic disorder, depression, and ischemic heart disease have not evaluated the role of the drugs used to treat these conditions. As part of a larger study on reducing cardiovascular disease in an entire community, we estimated the association between psychotropic drugs and ischemic heart disease in a large community-based population using a cohort study design. We defined exposure as current use of psychotropic medications at the time of the health interview. We determined ischemic heart disease by International Classification of Diseases, 9th revision, Clinical Modification, codes and by an epidemiologic algorithm using clinical diagnostic criteria. An elevated risk for clinically significant ischemic cardiac events was moderately associated with benzodiazepine use [relative risk (RR) = 2.0; 90% confidence interval (CI) = 1.1-3.9] and strongly associated with antidepressant use (RR = 5.7; 90% CI = 2.6-12.8), although the latter estimate was based on only six antidepressant users who had an ischemic event.

Predictors of future antihypertensive use in patients with mildly elevated blood pressure

We prospectively identified predictors of future antihypertensive use in untreated persons age 18-65 years who had elevated diastolic blood pressures of 90-104 mm Hg or systolic blood pressures of at least 140 mm Hg. Data were derived from two independent cohorts completing household surveys conducted in 1981-1984 and 8 years later, as part of the Pawtucket Heart Health Program. Demographics, self-reported health behaviors and beliefs, and physiologic measurements were obtained. Drug use was determined through structured interviews. Analysis of covariance and logistic regression were performed. In the 492 subjects, independent baseline predictors of future antihypertensive use (p < 0.05) included female gender, older age, diastolic blood pressure elevation, self-perceived high blood pressure, and self-reported salt limitation. Antihypertensive use for previously untreated mild hypertension is diverse. Older women with diastolic elevations who are health conscious are most likely to be treated.

Is antidepressant use changing? Prevalence and clinical correlates in two New England communities

We attempted to determine whether the prevalence of antidepressant use had increased in population-based samples between 1981 and 1993, and compared the characteristics of antidepressant users and nonusers. Data were derived from six biennial, random sample, cross-sectional household surveys conducted between 1981 and 1993 in two southeastern New England communities. For each survey, point prevalence estimates were determined for the major antidepressant categories. Antidepressant users were most likely to be women, slightly older, and less likely to be employed than nonusers (p < 0.0001). Comorbid conditions and concurrent drug therapy were present more frequently among users. The overall prevalence of antidepressant use per 1000 population increased from 7.8 (95% confidence interval 4.3, 11.3) in 1981-1982 to 31.4 (95% CI 23.9, 38.9) in 1992-1993, especially among women and respondents between ages 40 and 59 years.

Comparison of dobutamine and exercise using technetium-99m sestamibi imaging for the evaluation of coronary artery disease

Studies using dobutamine thallium-201 myocardial perfusion imaging have suggested a high sensitivity and specificity for the detection of coronary artery disease. However, few data are available comparing dobutamine with exercise stress for the detection and localization of perfusion defects. This study compared the effects of dobutamine and exercise stress using technetium-99m sestamibi single-photon emission computed tomographic imaging in the same patients in a prospective crossover trial. Twenty-four patients with a high likelihood of coronary artery disease underwent tomographic myocardial imaging at rest, after symptom-limited treadmill exercise, and after intravenous dobutamine (maximum 30 micrograms/kg/min). Tomograms of the left ventricle were divided into 20 segments and were interpreted without knowledge of patient identity or stress protocol. Dobutamine was well tolerated by all patients. Segment-by-segment concordance between exercise and dobutamine images was highly significant (kappa = 0.56, p < 0.0001). Global first-order agreement (normal vs abnormal) between exercise and dobutamine studies was 96% (kappa = 0.65, p = 0.02); global second-order agreement (normal vs fixed vs ischemic defect) was 88% (kappa = 0.45, p = 0.02). Regional first- and second-order agreement were 96 and 93%, respectively (p < 0.001 for both). Twenty patients underwent coronary angiography. Comparisons between exercise and angiography and between dobutamine and angiography were similar for both global agreement (95 vs 100%, p = NS) and regional agreement (77 vs 72%, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Pretreatment with theophylline does not affect adenosine-induced thallium-201 myocardial imaging

This study was designed to evaluate the effects of intravenous theophylline given before intravenous adenosine for thallium-201 imaging. Sixteen patients with known reversible thallium-201 defects were randomized to a double-blind crossover study of a 45-minute infusion of placebo or theophylline (given as the ethylenediamine salt, aminophylline, mean concentration 16.1 mg/L) before adenosine thallium-201 imaging. Adenosine was infused for 6 minutes at a rate of 140 micrograms/kg/min. Thallium-201 (2.5 to 3.0 mCi) was administered after 3 minutes of infusion. Blood pressure, heart rate, symptoms, and the electrocardiogram were monitored continuously. Planar thallium-201 imaging was obtained in three standard views and was interpreted using blinded segmental analysis and computerized quantitation. Systolic and diastolic blood pressure at baseline and during adenosine administration were similar following treatment with theophylline and placebo. The increase in heart rate observed during adenosine infusion was significantly reduced by theophylline pretreatment. Adenosine-induced symptoms (both cardiac and noncardiac) as well as ischemic electrocardiographic changes were significantly reduced after theophylline infusion (p < 0.05). In one patient, Mobitz type II heart block seen during adenosine infusion following placebo was absent with theophylline pretreatment. The size of adenosine-induced thallium-201 defects was unchanged by theophylline infusion using either segmental analysis (8 +/- 4 vs 9 +/- 5) or a computerized score (47 +/- 27 vs 45 +/- 21). Despite reduction in both symptoms and ischemic electrocardiographic changes, theophylline does not alter thallium-201 imaging following intravenous adenosine infusion.

Effects of intravenous theophylline on exercise-induced myocardial ischemia: II. A concentration-dependent phenomenon

OBJECTIVES

The effects of varying concentrations of theophylline on exercise-induced myocardial ischemia were evaluated in patients with stable coronary artery disease.

BACKGROUND

Theophylline is a competitive antagonist of adenosine and may have potential as an anti-ischemic medication. It is not known whether these effects on myocardial ischemia are concentration dependent.

METHODS

In a double-blind, randomized, crossover manner, 11 patients received, at 1-week intervals, placebo and each of three theophylline doses by intravenous infusion for 45 min. Graded exercise testing was performed before randomization and immediately after each infusion. Concurrent anti-ischemic medications were withheld for 24 h before each exercise test. Serum theophylline concentrations achieved were 3.9 +/- 1.0 mg/liter (low), 8.2 +/- 1.8 mg/liter (medium) and 13.2 +/- 2.3 mg/liter (high).

RESULTS

Compared with placebo, none of the three theophylline infusions produced a significant alteration in rest heart rate, blood pressure, mean frequency or severity of ventricular ectopic activity or noncardiac symptoms. The time to onset of ischemia was progressively increased, with medium and high concentrations achieving statistical significance. Similar patterns were observed for oxygen uptake and the heart rate-systolic blood pressure product at the onset of ischemia. Total exercise duration was significantly prolonged with the medium and high concentrations.

CONCLUSIONS

It is concluded that administration of varying doses of theophylline before exercise produces a clinically significant and concentration-dependent improvement in the indicators of myocardial ischemia in patients with chronic stable coronary artery disease.

Correlates of postmenopausal estrogen use and trends through the 1980s in two southeastern New England communities

Correlates and prevalence of current postmenopausal estrogen use were examined in two southeastern New England communities for the period 1981 through 1990. Data were obtained from five biennial cross-sectional household health surveys, with current use of postmenopausal estrogen determined by inspection of medication bottles. Analysis included 3,279 women aged 40-64 years, of whom 2,215 (67.6%) were postmenopausal. The prevalence of estrogen use among all postmenopausal women increased from 5.3% (95% confidence interval (CI) 3.2-7.4) in 1981-1982 to 10.9% (95% CI 7.5-14.4) in 1989-1990. Among women with surgical menopause, prevalence increased from 11.4% (95% CI 6.6-16.2) to 20.3% (95% CI 13.6-27.0), while use among women with natural menopause increased from 1.5% (95% CI 0.04-2.9) to 3.5% (95% CI 0.74-6.2). Logistic regression was used to compute age-adjusted prevalence of estrogen use according to demographic characteristics and cardiovascular risk factors. Postmenopausal estrogen use was positively associated with income, and a positive trend with education was suggested. Estrogen use was positively associated with high density lipoprotein cholesterol and was inversely associated with body mass index. Nonsmokers, women who exercised at least once per week, and women who reported having their cholesterol checked in the past year were more likely to use estrogen. These findings suggest that estrogen users have a more healthy profile than do nonusers. In addition, the prevalence of postmenopausal estrogen use appears to be substantially lower in women with natural versus surgical menopause throughout the period studied.

The drug data base of the Pawtucket Heart Health Program: development and description

Pharmacoepidemiology has become an important tool for identifying patterns of drug use and adverse drug reactions in the general population. Drug data bases derived from population-based samples have been particularly useful in addressing questions such as adherence to national guidelines for the treatment of chronic diseases. As part of the Pawtucket Heart Health Program, a continuing community-based research and demonstration project, detailed information regarding the use of drugs among the general population of two southeastern New England cities was collected using cross-sectional and longitudinal methodologies.

Changing trends in antihypertensive therapy in two New England communities during the 1980s

The prevalence rates and correlates of antihypertensive drug use among individuals with hypertension were determined using data derived from five biennial population-based surveys conducted between 1981 and 1990 in two New England communities. Point prevalence estimates were determined for nine categories of antihypertensive agents at five time points, and were analyzed by age and sex using multiple logistic regression. In the first cross-sectional survey, the prevalence of use per 1000 individuals with hypertension was 235.4 for diuretics, 57.1 for beta-blockers, 65.5 for combination products, 29.2 for central alpha-agonists, 2.8 for peripheral alpha-antagonists, and 8.4 each for adrenergic blockers and direct vasodilators. The prevalence rates for calcium channel blockers and angiotensin-converting enzyme inhibitors increased sharply between the third and fourth survey cycles. Significant age- and sex-related differences in antihypertensive use were detected.

Effects of intravenous theophylline on exercise-induced myocardial ischemia. I. Impact on the ischemic threshold

OBJECTIVES

Theophylline has been shown to delay the onset of myocardial ischemia and to prolong exercise duration. The present study was done to evaluate the mechanisms and actions of intravenous theophylline on the onset of ischemia and exercise duration.

BACKGROUND

The ischemic threshold may be altered by the differential coronary vasodilation induced by endogenous adenosine. Theophylline is a competitive receptor antagonist of adenosine and may have a potential as an anti-ischemic medication.

METHODS

A double-blind, placebo-controlled crossover trial using an infusion of intravenous theophylline (8.0 +/- 2.0 mg/liter) or placebo before exercise in 12 patients was done. Oxygen uptake, heart rate, blood pressure and heart rate-blood pressure product were determined at the onset of > or = 0.1-mV ST segment depression and angina pectoris, as well as at peak exercise. The extent of myocardial ischemia was evaluated by electrocardiographic criteria and quantitation of thallium-201 images at peak exercise.

RESULTS

When compared with placebo, theophylline significantly delayed time to the onset of exercise-induced ischemia. Ischemia occurred at a higher heart rate-blood pressure product and oxygen uptake. Exercise duration was prolonged but was not associated with greater ischemia, as determined by oxygen uptake, ST segment depression, angina pectoris and size of thallium-201 defect.

CONCLUSIONS

It is concluded that theophylline favorably alters myocardial ischemia not only by delaying its onset but also by enabling it to occur at a higher threshold without causing deleterious effects during exercise. The mechanism for the increased ischemic threshold may be through the inhibition of adenosine and the coronary steal phenomenon.

Prevalence and descriptors of aspirin use as an antiplatelet agent in two New England communities

OBJECTIVE

To determine the overall prevalence of aspirin use as an antiplatelet agent in a population-based sample of respondents between the ages of 18 and 64 years, and to describe their sociodemographic characteristics.

DESIGN

Data were derived from five biennial cross-sectional household surveys conducted between 1981 and 1990 in two southeastern New England communities by the Pawtucket Heart Health Program. Individuals reporting aspirin use as an antiplatelet agent were identified using data from a structured medication interview.

RESULTS

The prevalence of aspirin use per 1000 population was 2.5 (95 percent confidence interval [CI] 0.5, 4.4), 5.0 (95 percent CI 2.4, 7.6), 7.8 (95 percent CI 4.6, 11.0), 7.5 (95 percent CI 4.3, 10.6), and 11.8 (95 percent CI 7.1, 16.5) in the first through the fifth survey periods, respectively (p = 0.0002). The prevalence of aspirin use per 1000 men increased from 4.9 (95 percent CI 0.6, 9.1), 8.7 (95 percent CI 3.3, 14.1), 12.3 (95 percent CI 6.1, 18.5), 8.5 (95 percent CI 3.5, 13.5) to 23.2 (95 percent CI 13.4, 32.9) for the first through the fifth survey periods, respectively. The corresponding prevalence rates of aspirin use per 1000 women were 0.7 (95 percent CI 0, 2.1), 2.43 (95 percent CI 0.05, 4.80), 4.6 (95 percent CI 1.4, 7.8), 6.6 (95 percent CI 2.7, 10.6), and 2.7 (95 percent CI 0, 5.7). Both a gender trend (p = 0.0002) and a survey trend (p = 0.0001) were detected. A gender-survey interaction was not found.

CONCLUSIONS

In this population, aspirin use was reported primarily by middle-aged men who had coexisting cardiovascular disease as indicated by concurrent medications. Aspirin use as antiplatelet therapy increased in the population-based samples of two New England communities over the past nine years, with slightly more than one percent of the respondents reporting its use in the fifth cross-sectional survey conducted in 1989-1990. This finding may reflect the publication of important clinical trials near the time the survey was performed and subsequent dissemination of the findings both in the professional and lay press.

Influence of exercise intensity on the presence, distribution, and size of thallium-201 defects

The effects of two levels of exercise intensity on the size and location of thallium-201 defects were compared in 22 patients with known ischemic coronary artery disease. A symptom-limited incremental exercise test was performed followed (greater than 48 hours) by submaximal steady-state exercise at 70% of the peak heart rate achieved during the incremental test. Planar thallium-201 myocardial scans obtained after each protocol were analyzed by means of both visual qualitative and computerized quantitative methods. After incremental exercise all patients exhibited reversible thallium-201 defects, and submaximal exercise still resulted in reversible defects in 20 (91%) patients. However, the size of the ischemic area and the degree of ischemia were significantly reduced by both qualitative and quantitative criteria after submaximal exercise. Therefore interpretation of thallium-201 scans with regard to severity of disease and prognosis should take into account exercise intensity.

Effect of dipyridamole therapy on myocardial ischemia in patients with stable angina pectoris receiving concurrent anti-ischemic therapy

The effects of oral dipyridamole on exercise performance and anginal symptoms were evaluated in 15 men with stable angina pectoris. In a double-blind, randomized, crossover design, patients received 75 mg of dipyridamole or placebo every 8 hours for 2 weeks in addition to their previously prescribed cardiac medications. Graded exercise tolerance testing was performed twice before randomization, at the end of each treatment period, and after single-blind placebo washout. When compared with baseline tests, the time to onset of 0.1 mV ST-segment depression was similar between dipyridamole and placebo treatments (316 +/- 89 vs 345 +/- 102 seconds, respectively, p = not significant). No significant differences existed between treatments in the peak systolic blood pressure-heart rate product or in the duration of exercise. Angina pectoris occurred during all 3 baseline exercise tests in 7 of the 15 subjects; the time to onset of angina was unchanged by either treatment. Analysis of symptom diaries conducted in 13 patients revealed no significant alteration in reported anginal symptoms during dipyridamole treatment compared with placebo treatment (0.6 +/- 0.9 vs 0.3 +/- 0.4 episodes per week). Ambulatory electrocardiographic monitoring in 12 patients revealed few episodes of ischemia during daily activities with no alteration in frequency of episodes during treatment periods. Plasma concentrations of dipyridamole did not correspond with the outcomes of exercise testing. It is concluded that chronic oral dipyridamole therapy given in its usual clinical dose does not adversely affect exercise performance, daily anginal episodes or ambulatory ischemia in patients receiving concurrent anti-ischemic medication.

Comparison of chest pain, electrocardiographic changes and thallium-201 scintigraphy during varying exercise intensities in men with stable angina pectoris

This study was performed to evaluate the presence of angina pectoris, electrocardiographic changes and reversible thallium-201 defects resulting from 2 different levels of exercise in 19 patients with known coronary artery disease and evidence of exercise-induced ischemia. The exercise protocols consisted of a symptom-limited incremental exercise test (Bruce protocol) followed within 3 to 14 days by a submaximal, steady-state exercise test performed at 70% of the maximal heart rate achieved during the Bruce protocol. The presence and time of onset of angina and electrocardiographic changes (greater than or equal to 0.1 mV ST-segment depression) as well as oxygen uptake, exercise duration and pressure-rate product were recorded. Thallium-201 (2.5 to 3.0 mCi) was injected during the last minute of exercise during both protocols, and the images were analyzed using both computer-assisted quantitation and visual interpretations. Incremental exercise resulted in anginal symptoms in 84% of patients, and electrocardiographic changes and reversible thallium-201 defects in all patients. In contrast, submaximal exercise produced anginal symptoms in only 26% (p less than 0.01) and electrocardiographic changes in only 47% (p less than 0.05), but resulted in thallium-201 defects in 89% of patients (p = not significant). The locations of the thallium-201 defects, when present, were not different between the 2 exercise protocols. These findings confirm the sequence of the ischemic cascade using 2 levels of exercise and demonstrate that the cascade theory is applicable during varying ischemic intensities in the same patient.

Altered theophylline metabolism in patients with psoriasis

We observed two patients on theophylline therapy with concomitant severe psoriasis and a two- to threefold greater theophylline clearance than that reported in healthy, nonsmoking adults. There were no factors known to induce theophylline clearance. In both cases, the induction of theophylline metabolism was relatively selective for the 1-methyluric acid pathway. The altered metabolism in these patients appeared to correlate with the clinical severity of the disease. The data suggest the possibility that an observed lack of efficacy for theophylline in psoriasis may be related to pharmacokinetic effects. The concept that altered drug metabolism may occur in the presence of skin disease has important implications for pharmacotherapeutics in dermatology.