Predictive value of inducible endothelial cell adhesion molecule expression for acute rejection of human cardiac allografts

We conducted a prospective longitudinal study to determine the clinical significance of endothelial adhesion molecule expression in endomyocardial biopsies from human cardiac allografts. Ten to 18 (mean 13) consecutive allograft biopsies were obtained from 20 serial human transplant recipients over a one-year period. A total of 267 biopsies was examined. The expression of endothelial adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, as well as the presence of CD3+ T cell infiltrates was assessed by immunocytochemical staining of frozen sections. Separate specimens taken at the same time were analyzed histologically for ischemic injury or rejection. ICAM-1--and, to a lesser extent VCAM-1--was expressed at low levels in normal biopsies. E-selectin was only expressed in 15% of histologically normal biopsy specimens. Ischemic injury noted in the immediate posttransplant period was associated with increased expression of all three adhesion molecules. VCAM-1 expression increased both with the degree of CD3+ T cell infiltrates (P < 0.001) and with the degree of rejection (P < 0.05). ICAM-1 increased over constitutive levels in association with diffuse CD3+ infiltrates (P < 0.001) and with rejection (P < 0.05). E-selectin was increased on occasional vessels in association with CD3+ infiltrates (P < 0.001), but was not associated with active rejection. Increases in E-selectin were most likely to occur in biopsies just prior to rejection episodes (odds ratio 3.3), and were least likely to occur in biopsies following rejection (odds ratio 0.3). ICAM-1, but not VCAM-1, was also elevated in prerejection specimens. VCAM-1 and ICAM-1 declined in postrejection specimens. These data suggest a dynamic pattern in the expression of endothelial cell adhesion molecules during the course of cardiac allograft rejection. This study also suggests that endothelial E-selectin expression may be a useful clinical marker of impending rejection. Finally, inducible VCAM-1 expression may be a helpful adjunct in the diagnosis of ongoing acute rejection, and decreases in its expression may be indicative of successful antirejection therapy.

Estrogen improves endothelium-dependent, flow-mediated vasodilation in postmenopausal women

OBJECTIVE

To assess the effect of estrogen replacement therapy on endothelium-dependent vasodilation in postmenopausal women.

DESIGN

Double-blind, placebo-controlled, crossover trial.

SETTING

University medical center.

PATIENTS

13 postmenopausal women aged 44 to 69 years (average age, 55 +/- 7 years).

INTERVENTION

Patients were randomly assigned to receive placebo, oral estradiol at a dose of 1 mg/d, and oral estradiol at a dose of 2 mg/d. Each treatment phase lasted 9 weeks.

MEASUREMENTS

High-resolution ultrasonography was used to measure vascular reactivity in a peripheral conduit vessel, the brachial artery. Endothelium-dependent vasodilation was determined by measuring the change in brachial artery diameter during increases in flow induced by reactive hyperemia. Endothelium-independent vasodilation was measured after sublingual nitroglycerin was administered.

RESULTS

Flow-mediated, endothelium-dependent vasodilation of the brachial artery was greater when patients received estradiol (13.5% and 11.6% for 1-mg and 2-mg doses, respectively) than when patients received placebo (6.8%; P < 0.05 for each dose compared with placebo). In contrast, estrogen administration had no effect on endothelium-independent vasodilation as assessed by sublingual nitroglycerin.

CONCLUSION

Short-term estrogen replacement therapy improves flow-mediated endothelium-dependent vasodilation in postmenopausal women. This improvement may be mediated by a direct effect of estrogen on vascular function or may be induced through modification of lipoprotein metabolism.

Nitric oxide and nitrovasodilators: similarities, differences and potential interactions

Many similarities exist between the exogenous nitrates and endothelium-derived relaxing factor, which is nitric oxide or a thiol derivative. Both act by way of guanylate cyclase, which increases intracellular concentrations of cyclic guanosine monophosphate, resulting in smooth muscle cell relaxation and antiplatelet effects. Thiols may be important in the biotransformation of exogenous nitrates and other intracellular processes involving nitric oxide. As such, important interactions might be expected between nitrates and endothelium-dependent processes that involve nitric oxide. This review explores the mechanisms of action, biologic effects and potential interactions between nitrates and endothelium-derived relaxing factor.

Relation of restenosis after excimer laser angioplasty to fasting insulin levels

Several studies have shown that diabetes mellitus increases the risk of restenosis after coronary intervention, but the role of insulin in restenosis has not been defined. The relation between fasting insulin levels and restenosis was evaluated prospectively at 6-month angiographic follow-up in 70 patients undergoing excimer laser coronary angioplasty of 75 lesions. Restenosis (> 50% diameter narrowing on quantitative angiography) was observed at 37 of 75 treated sites (49%). Although patients with glucose intolerance and noninsulin-dependent diabetes mellitus showed a trend toward increased restenosis (restenosis rate 69%; odds ratio for restenosis 2.7 [95% confidence interval 0.76, 9.82]; p = 0.124), those with increased fasting insulin levels > 15 muU/ml had reduced restenosis (restenosis rate 24%; odds ratio 0.22 [0.07, 0.67]; p = 0.008). Other factors including fasting serum glucose, glycated hemoglobin and lipoprotein fraction were not predictive of restenosis. The relation between insulin levels and restenosis after excimer laser angioplasty may provide insights into the biology of vascular injury and repair after coronary intervention.

Sustained activation of vascular cells and leukocytes in the rabbit aorta after balloon injury

BACKGROUND

To improve understanding of the cellular basis of the arterial response to injury, we tested whether balloon withdrawal can induce certain inflammatory functions of vascular cells and leukocytes and whether such "activation" persists even after the acute phase of injury.

METHODS AND RESULTS

We examined the expression of several inducible cell surface molecules in the rabbit aorta at 2, 5, 10, and 30 days after balloon injury. Longitudinal sections encompassing parts of the uninjured, border, and injured zones were examined for expression of vascular adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), class II major histocompatibility (MHC) antigens, and markers for smooth muscle cells (SMCs), macrophages, endothelial cells, and T-lymphocytes. Endothelial cell healing involved true endothelial regeneration as well as migration, as shown by nuclear incorporation of bromodeoxyuridine. Luminal endothelial cells at the leading edge of repopulation at each time point expressed VCAM-1. As healing progressed, VCAM-1 expression decreased in the regenerated endothelial cells. The neointimal endothelium also expressed high levels of ICAM-1 that persisted longer than the elevation of VCAM-1. SMCs in the neointima also showed increased levels of ICAM-1. Some neointimal endothelial cells, SMCs, and macrophages also expressed high levels of class II MHC antigens during 30 days after injury.

CONCLUSIONS

Local inflammatory activation of endothelial cells, SMCs, and leukocytes occurs in a predictable sequence and persists up to 30 days after balloon injury to the rabbit aorta. Our findings suggest that ongoing local signals persisting after the original balloon injury may contribute to later phases of intimal thickening.

Accuracy of electronic digital calipers compared with quantitative angiography in measuring coronary arterial diameter

BACKGROUND

Quantitative angiography is the accepted method for measuring coronary luminal diameter. Electronic digital calipers have been used to assess arterial diameters in vasomotor function studies and after interventional procedures. However, careful validation of calipers against quantitative angiography has not been described.

METHODS AND RESULTS

We used digital calipers and quantitative angiography to measure 517 arterial diameters (88 nonstenotic segments) in 24 transplant patients undergoing vasomotor function studies with acetylcholine and nitroglycerin, 20 stenoses in 14 patients with coronary artery disease, and 15 stenoses in 15 patients before and after excimer laser-facilitated coronary angioplasty and at 6 months' follow-up. In nonstenotic arterial segments ranging in size from 0.6 to 3.5 mm, calipers overestimated diameters measured by quantitative angiography by 0.29 +/- 0.21 mm (mean +/- SD) (limits of agreement, -0.13 to 0.71 mm). However, when the vasomotor responses were expressed as percent diameter change, the two methods did not differ significantly (-1 +/- 10%; limits of agreement, -21% to 19%). In the 35 stenoses measured before intervention and 30 stenoses measured after intervention, calipers and quantitative angiography differed by 3 +/- 9% (limits of agreement, -15% to 21%) across a range of stenosis severity (11% to 80%). Repeat caliper measurements by the same observer of the percent diameter change in the transplant patients and the percent stenosis in the coronary artery disease patients led to standard deviations of the differences of 9.3% and 7.6%, respectively. Two different observers recorded percent diameter change and percent stenosis that differed with standard deviations of 9.6% and 7.8%, respectively.

CONCLUSIONS

Quantitative angiography and electronic digital calipers produce similar relative changes in arterial diameters and percent stenosis in a broad range of severities. Digital calipers thus are a rapid and convenient alternative to computerized quantitative angiography in certain research studies and clinical practice of assessing stenosis severity.

Electrostatic and nonpolar peptide-membrane interactions. Lipid binding and functional properties of somatostatin analogues of charge z = +1 to z = +3

The interaction of four structurally related somatostatin analogues (effective electric charge +0.4 < or = < or = +3) with lipid membranes was studied with titration calorimetry and was compared with the functional activity of the peptides. Surface activity measurements provided average cross-sections of 70 or 135 A2, indicating that the cyclic molecules orient at the air-water interface with their ring system either parallel (z = +3) or perpendicular (z = +1) to the surface or switching between the two orientations according to the surface density (z = +2). The nonspecific binding of the peptides to sonified lipid vesicles was enthalpy-driven with a delta H of -4 to -7.5 kcal/mol. A consistent quantitative analysis of the binding isotherms was achieved by combining electrostatic attractions, calculated via the Gouy-Chapman theory, with a nonspecific surface partition equilibrium for the nonpolar interactions. The electrostatic attraction of the cationic peptides varied strongly according to the peptide charge. Due to the flat ring structure of the cyclic peptides, their true physical charge was sensed at the membrane surface, and no "charge screening" was observed. Peptide binding to the negative charged membrane was accompanied by a proton-uptake of the N-terminal amino group of 0.23-0.38 H+/peptide. Deviations from the theoretical prediction of 0.39 H+/peptide can be explained by a preferential binding of the nonprotonated species. The nonpolar interactions, as described by the surface partition coefficients of the four peptides, fell into a narrow range of K congruent to 50-230 M-1 whereas the apparent overall binding constants were between 200 and 5000 M-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of endothelium in ischemic coronary syndromes

The recent discovery that the endothelium synthesizes several powerful vasodilators, including prostacyclin and endothelium-derived relaxing factor, has substantially changed our view of the importance of the vascular endothelium and the perspective from which we consider the mechanisms of vascular control. It is now known that the vascular endothelium plays a key role in circulatory homeostasis through its ability to sense the local vascular milieu and respond to it by the synthesis and release of a variety of biologically active substances. The endothelium influences not only vascular tone, but also vascular remodeling via the production of growth-promoting and growth-inhibiting substances; hemostasis and thrombosis through antiplatelet, anticoagulant, and fibrinolytic effects; and inflammation through the expression of chemotactic and adhesion molecules on the cell membrane. In diseases such as atherosclerosis, however, these functions of the endothelium are impaired and may even become counterproductive and disease-promoting. The "activated" or injured endothelial cells paradoxically become prothrombotic, growth-promoting, and leukocyte-adhesive. The endothelium also loses its vasodilating ability, rendering the underlying vascular smooth muscle susceptible to a preponderance of vasoconstrictive forces. It is now recognized that these disturbances in endothelial function are principal players in the ischemic manifestations of coronary artery disease. Endeavors to modify or reverse endothelial dysfunction may therefore be of significant therapeutic benefit in the treatment of myocardial ischemia. This review outlines several important insights into the biology of the arterial wall that are currently being applied to the study of coronary artery disease in humans.

Functional significance of intimal thickening as detected by intravascular ultrasound early and late after cardiac transplantation

BACKGROUND

Detection of transplant coronary disease remains difficult. Both intravascular ultrasound (IVUS) imaging and functional coronary vasomotion studies have been used to evaluate this process. However, the time course of intimal thickening as assessed by IVUS and the relation between structure and function have not been explored.

METHODS AND RESULTS

In 40 patients 1 to 8 years after transplantation, 108 coronary artery segments were analyzed by IVUS. Intimal index [% intimal area (lumen+intimal area)] and maximal thickness were used to quantify intimal thickening. Abnormal IVUS was present in 53 of 108 segments (49%) (mean intimal index of diseased segments, 23 +/- 2%; maximal thickness, 530 +/- 47 microns). For those patients with intimal thickening in all segments of the analyzed artery, more time had elapsed since transplantation (4.3 +/- 0.6 years) than for those whose arteries contained some normal (2.6 +/- 0.3 years) or all normal segments (2.2 +/- 0.6 years, P < .05). Both the proportion of segments with intimal thickening and the degree of thickening increased as a function of time after transplantation (P < .5). By multivariate analysis, the independent predictors of intimal thickening were increasing time after transplantation and pretransplantation hypercholesterolemia (P = .02). Within the cohort of 40 patients, endothelium-dependent vasomotor function was evaluated in 26 matched segments from 11 patients studied 1 year after transplantation and in 15 matched segments from 8 patients studied > or = 5 years after transplantation by serial infusions of acetylcholine (10(-8) to 10(-6) mol/L). Of the 26 segments assessed for structure/function correlation at 1 year after transplantation, 22 had no intimal thickening by IVUS. However, endothelial dysfunction was present in 13 of these normal segments (mean diameter constriction, 18.8 +/- 2.3%). Of the 15 segments studied > or = 5 years after transplantation, 11 had intimal thickening. Nine of these 11 segments had preserved endothelial function (mean diameter dilation, 8.6 +/- 2.9%). There was no relation between the degree of intimal thickening and the magnitude of the endothelium-dependent response to acetylcholine.

CONCLUSIONS

This study has shown that intimal thickening after transplantation begins as a heterogeneous process and increases in extent and magnitude over time. Also, endothelial dysfunction occurs early before the intimal thickening; yet in those patients surviving > or = 5 years, endothelial function may recover even in the presence of moderate intimal pathology. The variable relation between intimal pathology and endothelial function is probably a result of the episodic nature of immune injury.

Changing vasomotor responses of coronary arteries to nifedipine

Coronary vasomotion is influenced by a variety of factors, including atherosclerosis and diurnal variations in alpha-adrenergic tone. The effect of such factors on the coronary response to vasodilator drugs is unknown. To determine whether there is a diurnal variation to the response of coronary arteries to nifedipine, and whether this response is altered by atherosclerosis, we studied 11 patients with smooth coronary arteries, six in the morning and five in the afternoon, and 12 patients with irregular coronary arteries, six in the morning and six in the afternoon. Changes in coronary blood flow and the vasomotor response of an epicardial coronary artery were measured before and after a 2 mg intracoronary infusion of nifedipine. There were no appreciable differences in epicardial vessel dilator response or coronary blood flow in the morning and afternoon among patients with smooth coronary arteries. By contrast, patients with irregular coronary arteries had a significantly diminished dilator response in the afternoon, without an appreciable change in coronary blood flow. We postulate that normal coronary arteries maintain basal tone throughout the day. By contrast, atherosclerotic coronary arteries cannot do the same, increasing tone in the morning in response to catecholamines. When catecholamine levels drop in the afternoon, basal tone decreases in atherosclerotic vessels, and the dilator response to nifedipine is blunted. This observation may have an important impact on the expected benefits and timing of vasodilator therapy in patients with coronary artery disease.

Sinoatrial and atrioventricular block caused by intracoronary infusion of adenosine early after heart transplantation

Intracoronary adenosine was infused in 22 patients early (less than 2 months) after heart transplantation to study coronary flow reserve in the left anterior descending artery. Potentially serious bradycardia requiring discontinuation of the infusion occurred in three patients. This complication had not been noted when adenosine was given to 84 patients with at least 1 year after transplantation. Newly transplanted hearts may therefore have increased susceptibility to the bradycardic action of adenosine, which should be used with caution in this population.

Hypertension and left ventricular hypertrophy are associated with impaired endothelium-mediated relaxation in human coronary resistance vessels

BACKGROUND

Patients with hypertension and myocardial hypertrophy may have signs and symptoms of myocardial ischemia in the absence of obstructive coronary disease. Prior investigations have demonstrated impaired coronary flow reserve and have led to speculation that microvascular dysfunction might contribute to ischemia in these patients. Experimental studies have shown that the endothelium, an important regulator of microvascular tone, can be damaged by hypertension and is dysfunctional in cardiomyopathy. We hypothesized that endothelium-dependent vasodilation is impaired in the coronary microvasculature of patients with hypertension and ventricular hypertrophy.

METHODS AND RESULTS

We studied coronary microvascular responses in 10 patients with left ventricular hypertrophy secondary to essential hypertension (HTN) (mean arterial pressure at catheterization, 151/94 mm Hg; mean posterior wall thickness, 1.4 +/- 0.1 cm) and nine normal control subjects with no history of hypertension (mean arterial pressure at catheterization, 128/75 mm Hg; mean posterior wall thickness, 1.0 +/- 0.02 cm) using the intracoronary Doppler catheter and quantitative angiography to assess changes in coronary blood flow (CBF). All patients had normal left ventricular systolic function. To assess microvascular endothelial function, we infused the endothelium-dependent vasodilator acetylcholine (10(-8)-10(-6) M) and the endothelium-independent vasodilator adenosine (10(-6)-10(-4) M) into the left anterior descending coronary artery. In response to acetylcholine, CBF increased only 32 +/- 25% in HTN patients, whereas CBF increased 192 +/- 39% in normal control subjects (p = 0.003). CBF increased 465 +/- 93% in HTN patients and 439 +/- 41% in normal control subjects in response to adenosine (p = NS). The proportion of coronary flow reserve attributable to endothelium-dependent dilation (obtained from peak acetylcholine/peak adenosine flow response) was 48 +/- 9% in normal control subjects but only 7 +/- 8% in HTN patients (p = 0.008).

CONCLUSIONS

Endothelium-dependent vasodilation is markedly impaired in the coronary microvessels of patients with hypertension and ventricular hypertrophy. Loss of this vasodilator mechanism may contribute to disordered coronary flow regulation and the ischemic manifestations of hypertensive heart disease.

New insights into the management of myocardial ischemia

Episodes of ST depression are closely related to transient decreases in regional myocardial perfusion during physical or mental stress. At the onset of these events, there is transient constriction of atherosclerotic stenoses, with an increase in myocardial demand as reflected by increases in heart rate and blood pressure. Recent research has shown that normal epicardial coronary arteries respond to these provocations and to increasing blood flow with progressive vasodilation. In contrast, atherosclerotic vessels lose this ability to dilate and may show paradoxical constriction. This abnormal constriction parallels the response of the arteries to acetylcholine, which can be used to assess the ability of the coronary endothelium to regulate vasodilation. The loss of endothelium-dependent vasodilation appears to be an important functional manifestation of coronary atherosclerosis and a potential triggering mechanism for transient ischemia. Dysfunctional endothelium may also result in a procoagulant surface, with cell adherence and local thrombus formation. Restoration of normal endothelial function is likely to emerge as an important therapeutic objective in the management of myocardial ischemia and coronary atherosclerosis.

Loss of the coronary microvascular response to acetylcholine in cardiac transplant patients

BACKGROUND

The coronary arteries of transplanted hearts frequently develop accelerated diffuse arteriosclerosis. The effects of this disease on resistance vessel function are unknown.

METHODS AND RESULTS

To investigate the integrity of endothelium-dependent small-vessel vasodilation in transplanted hearts, coronary blood flow (CBF) responses to the endothelium-dependent dilator acetylcholine (10(-8) to 10(-6) M) and the essentially endothelium-independent dilator adenosine (10(-6) to 10(-4) M) were assessed in 40 studies of 29 transplant patients 1-3 years after transplantation and in seven nontransplanted controls. CBF was measured at constant arterial pressure with a Doppler catheter in the left anterior descending coronary artery. Controls, year 1 transplant patients, and year 2 transplant patients had similar increases in CBF in response to acetylcholine (232 +/- 40%, 200 +/- 41%, and 201 +/- 54%, respectively; p = NS), whereas year 3 transplant patients had increased CBF of only 100 +/- 39% (p less than 0.05 versus controls). An index of the proportion of CBF reserve attributable to endothelium-dependent dilation was obtained by normalizing each patient's peak acetylcholine flow response by the peak adenosine flow response. In patients receiving both acetylcholine and adenosine, endothelium-dependent flow responses declined over time [57 +/- 9% in controls, 56 +/- 10% for year 1, 47 +/- 12% for year 2, and 29 +/- 9% for year 3 (p less than 0.05 versus controls)]. An increased mean cyclosporine level (range, 99-261 ng/ml) (r = 0.67, p = 0.004) and increased transplant recipient age (range, 20-63 years) (r = 0.51, p = 0.004) predicted a preserved endothelium-dependent microvascular response.

CONCLUSIONS

Thus, microvascular endothelium-dependent dilation deteriorates over time in the transplanted heart, which may reflect underlying graft arteriosclerosis and contribute to ischemic damage of the myocardium.

Epicardial coronary artery responses to acetylcholine are impaired in hypertensive patients

Hypertension is a risk factor for coronary atherosclerosis possibly via an adverse effect on the vascular endothelium. Endothelium-mediated relaxation is impaired in animal models of hypertension. However, the effects of hypertension on human coronary artery endothelial cell function are unknown. To test whether endothelium-mediated relaxation is impaired in the coronary arteries of patients with hypertension, we studied 14 patients with essential hypertension requiring therapy and 15 nonhypertensive control patients undergoing cardiac catheterization. All had angiographically normal, smooth-appearing coronary arteries. Patients were matched for age and other coronary atherosclerosis risk factors. To assess endothelial cell function, the endothelium-dependent vasodilator acetylcholine (ACh, 0.01, 0.1, and 1.0 microM) and the endothelium-independent vasodilator nitroglycerin (40 micrograms) were selectively infused into the left anterior descending or circumflex coronary artery. Diameter change (expressed as percent) was assessed using quantitative angiography. There was a marked vasoconstrictor response to serial doses of ACh in hypertensive patients (-7%, -21%, and -27%) compared with control patients (-4%, -5%, and -7%) (p less than 0.02). The vasodilator response to nitroglycerin was preserved in hypertensive patients (+29%) and control patients (+25%) (p = NS), suggesting that endothelial cell dysfunction accounted for the differences in response to ACh. Thus, patients with hypertension have an accentuated coronary vasoconstrictor response to ACh, suggesting that endothelium-mediated regulation of coronary vascular tone is impaired by essential hypertension. This may reflect more generalized coronary endothelial changes contributing to the pathogenesis of atherosclerosis as well as hypertension.

Patients with evidence of coronary endothelial dysfunction as assessed by acetylcholine infusion demonstrate marked increase in sensitivity to constrictor effects of catecholamines

BACKGROUND

Studies in patients undergoing cardiac catheterization have demonstrated that normal coronary arteries dilate and atherosclerotic arteries constrict in response to exercise and the cold pressor test, but the mechanisms are unknown. These vasomotor responses are mirrored by the vasomotor response to the endothelium-dependent agent acetylcholine. Exercise and the cold pressor test are associated with adrenergic stimulation and increased circulating catecholamines. The present study tested the hypothesis that coronary arteries with intact endothelial function are relatively resistant to the constrictor effects of catecholamines, whereas arteries with loss of endothelial function have increased sensitivity to catecholamine-induced constriction.

METHODS AND RESULTS

The vasomotor function of the coronary endothelium was assessed by serial acetylcholine infusions (final concentration, 10(-8) to 10(-6) M) in 30 segments in 15 patients with minimal or no evidence of coronary atherosclerosis. The acetylcholine responses were related to the vasomotor response to intracoronary phenylephrine infusion (final concentration, 10(-9) to 10(-6) M) in the same segments. In the group of 18 segments that constricted to acetylcholine, there was a constrictor response to phenylephrine at an approximately 100-fold lower concentration than the group of 12 segments that did not constrict to acetylcholine.

CONCLUSIONS

These results suggest that the endothelial dysfunction that characterizes early and late atherosclerosis is associated with a marked increase in sensitivity to the constrictor effects of catecholamines. This finding may explain the constrictor responses of atherosclerotic coronary arteries to exercise and the cold pressor test. In stenotic coronary arteries this mechanism may play a role in the production of myocardial ischemia.

Circadian rhythms and coronary events: implications for therapy

Obstructive coronary disease has many clinical expressions and some are used as useful indicators of risk. Apart from symptoms, transient ischaemia occurs during daily life, is mostly silent and represents one measure of risk. Ambulatory monitoring of the electrocardiogram shows that ischaemia occurs with increased frequency during the morning hours while waking and rising. This coincides with other damaging vascular events, increased sympathetic activity and changes in coronary blood supply and myocardial oxygen demand that may favour a lower threshold to ischaemia. Calcium blockers, beta-blockers and aspirin can favourably affect this process and long-acting drugs appear to be a more rational approach given the variability of ischaemia over time.

Cancer control and the older person. Psychosocial issues

Three major areas related to psychosocial issues pertinent to the provision of cancer control services to older people have been delineated. These are values and medical decision making, psychosocial barriers to screening and access to care and services, and quality of life, including rehabilitation. These areas are explored, salient issues are defined, and specific questions and areas for consideration in future research are identified at the macro and micro levels.

The effect of atherosclerosis on the vasomotor response of coronary arteries to mental stress

BACKGROUND

Mental stress can cause angina in patients with coronary artery disease, but its effects on coronary vasomotion and blood flow are poorly understood. Because atherosclerosis affects the reactivity of coronary arteries to various stimuli, such as exercise, we postulated that atherosclerosis might also influence the vasomotor response of coronary arteries to mental stress.

METHODS

We studied 26 patients who performed mental arithmetic under stressful conditions during cardiac catheterization. (An additional four patients who did not perform the mental arithmetic served as controls.) Coronary segments were classified on the basis of angiographic findings as smooth, irregular, or stenosed. In 15 of the patients without focal stenoses in the left anterior descending artery, acetylcholine (10(-8) to 10(-6) mol per liter) was infused into the artery to test endothelium-dependent vasodilation. Changes in coronary blood flow were measured with an intracoronary Doppler catheter in these 15 patients.

RESULTS

The response of the coronary arteries to mental stress varied from 38 percent constriction to 29 percent dilation, whereas the change in coronary blood flow varied from a decrease of 48 percent to an increase of 42 percent. The direction and magnitude of the change in the coronary diameter were not predicted by the changes in the heart rate, blood pressure, or plasma norepinephrine level. Segments with stenoses (n = 7) were constricted by a mean (+/- SE) of 24 +/- 4 percent, and irregular segments (n = 20) by 9 +/- 3 percent, whereas smooth segments (n = 25) did not change significantly (dilation, 3 +/- 3 percent; P less than 0.0002). Coronary blood flow increased by 10 +/- 10 percent in smooth vessels, whereas the flow in irregular vessels decreased by 27 +/- 5 percent. The degree of constriction or dilation during mental stress correlated with the response to the infusions of acetylcholine (P less than 0.0003, r = 0.58).

CONCLUSIONS

Atherosclerosis disturbs the normal vasomotor response (no change or dilation) of large coronary arteries to mental stress; in patients with atherosclerosis paradoxical constriction occurs during mental stress, particularly at points of stenosis. This vasomotor response correlates with the extent of atherosclerosis in the artery and with the endothelium-dependent response to an infusion of acetylcholine. These data suggest that in atherosclerosis unopposed constriction caused by a local failure of endothelium-dependent dilation causes the coronary arteries to respond abnormally to mental stress.

Nonclassical hydrophobic effect in membrane binding equilibria

The enthalpy of transfer of four different amphiphilic molecules from the aqueous phase to the lipid membrane was determined by titration calorimetry. The four molecules investigated were the potential-sensitive dye 2-(p-toluidinyl)naphthalene-6-sulfonate (TNS), the membrane conductivity inducing anion tetraphenylborate (TPB), the Ca2+ channel blocker amlodipine [Bäuerle, H. D., & Seelig, J. (1991) Biochemistry 30, 7203-7211], and the positively charged local anesthetic dibucaine. All four amphiphiles penetrate into the hydrophobic part of the membrane, and their binding constants, after correcting for electrostatic effects, range between 600 M-1 for dibucaine and 60,000 M-1 for tetraphenylborate. The corresponding changes in free energy were about -6 to -9 kcal/mol. Binding of the amphiphiles to membrane vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine was accompanied by exothermic heats of reaction for all four molecules. For TNS, TPB, and amlodipine, the enthalpies of transfer were almost identical and corresponded to delta H approximately -9 kcal/mol, essentially accounting for the total free energy change. Thus, the binding of these charged amphiphiles to the hydrophobic membrane was driven by enthalpy. This is in contrast to the classical hydrophobic effect, where the transfer is considered to be entropy driven. For dibucaine, the enthalpy of transfer was smaller with delta H approximately -2 kcal/mol but was still about one-third of the total free energy change. All enthalpies of transfer exhibited a distinct temperature dependence with molar heat capacities delta Cp of -30 to -100 cal mol-1K-1 for the transfer from water to the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Effective aortic regurgitant orifice area: description of a method based on the conservation of mass

The natural history of aortic regurgitation is incompletely understood in part because of the lack of a simple method to estimate the defect size. A method of determining the effective regurgitant orifice area that combines Doppler catheter and Doppler echocardiographic techniques and is based on the principle of conservation of mass (the continuity equation) is described. To validate the application of the Doppler catheter system for measuring regurgitant supravalvular diastolic flow, an in vitro model of retrograde aortic flow was used. These studies indicated that measurements of supravalvular retrograde velocity with the Doppler catheter accurately reflect retrograde diastolic velocity when the aorta is less than 4.8 cm in diameter. Twenty-three patients undergoing cardiac catheterization were studied; 20 of these patients had aortic regurgitation. Retrograde supravalvular diastolic velocity was determined from a Doppler catheter positioned above the aortic valve. The effective regurgitant orifice area was calculated with use of the Doppler catheter-derived regurgitant volume and mean transvalvular diastolic velocity as determined by either catheterization or continuous wave Doppler echocardiography. The catheterization-derived regurgitant orifice area increased with the angiographic grade of as follows: 1+ (0.04 to 0.10 cm2), 2+ (0.15 to 0.49 cm2), 3+ (0.29 to 1.11 cm2) and 4+ (1.24 to 1.33 cm2). By combining Doppler catheter, echocardiographic and cardiac catheterization techniques, the effective aortic regurgitant orifice area may be estimated; this hydrodynamic area correlates with grading by supravalvular aortography. Calculation of this area provides a quantitative alternative to aortography for estimating the severity of aortic regurgitation but should be used with caution in patients with a markedly dilated aorta.