^^^^^v.^^ si,r^ <^\^^]p\

ANNUAL REPORT OF PROGRAM ACTIVITIES Or.'^tf^ ^Ai t NATIONAL HEART, LUNG, AND BLOOD INSTITUTE ** Fiscal Year 1979

^ja

-=n

^

O

(B

i-h

H-

D

O

H-

(D

l-i

fD

0

O

I-h

n

0

ri

NATIOJAL INSTITUTES OF HEALTH . .

NATIONAL HEART, LUNG, MD BLOOD INSTITUTE Annual Report October 1, 1978 - September 30, 1979 Office of the Director

The mission of the National Heart, Lung, and Blood Institute is to: / conduct and support research on the heart, blood vessels, lungs, and on the diseases that affect them;

develop and evaluate new or improved methods of prevention,

detection, diagnostic evaluation, and treatment for these diseases;

—encourage widespread application of proven new techniques by the research and medical ccrnmunities;

provide support for the training of research workers, clinicians, and teachers in the cardiovascular, blood, and pulmonary fields; and

^provide information on research and clinical cdvances arising from Institute programs to health professionals and to the general public

Toward fulfillment of its mission, the Institute plans, directs, and coordinates activities that range across the whole biomedical research spectrum: basic research; applied research and development; clinical investigations; clinical trials; demonstration projects; and prevention, education, and control activities. Highlights of progress resulting from some of these activities are briefly summarized in the sections that follow.

Heart and Blood Vessel Diseases

Arteriosclerosis, a blood-vessel disease almost ubiquitous among ^erican adults, is often the underlying cause of a variety of disabling or lethal cardiovascular conditions, including angina pectoris, acute heart attacks, sudden cardiac deatli, and strokes. Basic research on arteriosclerosis has included studies on the rrv^chanisms whereby blood lipids such as cholesterol invade the innermost layers of the arterial wall and accumulate there to form the early lesions of the disease.

Animal studies suggest that a compound called dermatan sulfate may play a role in this process. A canponent of the ground substance that provides a matrix for the collagen ard elastin fibers of arterial connective tissue, dermatan sulfate has a high affinity for lipids and preferentially binds them. NHLBI grantees noted increased concentrations of dermatan sulfate in the arteries of animals when they were fed atherogenic diets. Ihey suspect that dermatan sulfate may act as a lipid trapping agent in the development of arteriosclerotic deposits.

Studies in non-hi.iman primates have shown that during early stages of arteriosclerosis, when the deposits were still mainly lipid, lesions could be made to regress by measures that sharply reduced blood lipid levels. But as

OD-1

arteriosclerotic lesions mature, scar tissue may be laid down in and around the deposits and they may become encrusted with calcium and other substances deposited from the blood. Subsequent animal studies have indicated that lesions induced gradually over prolonged periods as probably occurs in human arteriosclerosis— contain more scar tissue and are less responsive to lipid- lowering measures. It appears that the older and more fibrous the lesion gets, the more resistant it becomes. Less and less regression can be achieved and the rate of that regression beconres slower and slower.

Blood platelets have been implicated both in the development of arteriosclerosis and in clotting complications of the disease. Blood platelet^ adhering to the blood vessel wall, particularly at injury sites, may take | part in the buildup of arteriosclerotic deposits. Studying pigs with von Willebrand's disease, a bleeding disorder in v^ich platelet adhesiveness is reduced, NHLBI grantees found these animals highly resistant to the arteriosclerosis normally induced by high-cholesterol diets, developing less extensive, less severe lesions than did normal pigs. The findings raise the ''\ possibility that agents capable of reducing platelet stickiness though not to the extent of inducing a hemorrhagic tendency might be of value in the ^ primary prevention of arteriosclerosis.

The aggregation or "clumping" of blood platelets appears to be an early j step in the formation of blood clots. Clots forming in diseased arteries or ' migrating as emboli to plug vessels elsev^ere in the cardiovascular system | are often the immediate cause of heart attacks, strokes, and other life- threatening manifestations of arteriosclerosis. !

i

Platelet aggregation can be inhibited by various drugs, including aspirin, and a growing body of evidence indicates that such agents can confer significant protection against tliromboembolic episodes. '

1 Aspirin inhibits platelet aggregation by inactivating the platelet enzyme

cyclooxygenase , which participates in the production of thratibox£ine A2, a

powerful aggregating agent and blood vessel constrictor. However, the blood

vessel wall also contains a cyclooxygenase, and here it is involved in the

production of prostacyclin. A platelet deaggregator and blood vessel

dilator, prostacyclin is thought to protect arteries against arteriosclerosis

and intravascular clottirg . It thus speared that whatever protection against

thra±>oemhx)lism aspirin, conferred by inactivating platelet cyclooxygenase

might well be negated by its effects on the blood-vessel cyclooxygenaise .

Fortunately, subsequent research has established that platelet cyclooxygenase is much tsie more sensitive of the tvvo to inhibition by aspirin. Work in progress is concerned with establishing dosages of aspirin that can halt thromboxane A2 production by platelets without hindering prostacyclin production in the blood vessel wall.

NHLBI scientists have also investigated inhibitors of platelet aggregation as a means of improving collateral bloodflow to blood-deprived areas of heart muscle. Their vAorking hypothesis was that ischemia might trigger sludgirej of platelets in oollateral channels and thus impede bloodflow through them.

0!>2

They found that aspirin, sulfinpyrazone, or naproxin (all so-called "antiplatelet drugs") did increase collateral bloodflow by 25-50% in dogs subjected to acute coronary occlusion and also reduced the threat of arrhythmias during the post-attack period. However, the increased collateral bloodflow resulting from these agents, though beneficial, was not sufficient to salvage significant amounts of heart muscle threatened by ischemia. None of the agents had any apparent effect on the amount of heart muscle destruction resulting fron the coronary occlusion.

Women enjoy relative protection against heart attacks during their reproductive years; and, though this protection diminishes after menopause, their heart-attack rate remains lower than that for men into the seventh decade. But for woren who experience heart attacks, both the immediate and lorvg-term prospects are poorer tlian those of male heart-attack patients, according to recent findings fron the Framingham Study. Among patients aged 30-79, mortality within the first 30 days after onset of first heart attacks was 47% for women versus 38% for iren. Among patients surviving their first year, subsequent mortality rates were 7.0% per year for women and 5.1% for men.

Epidemiological evidence indicates that blood levels of high-density lipoproteins (HDL) are inversely related to risk from coronary heart disease: the higher the levels of HDL, the lower the risk and vice versa. Factors associated with lower HDL levels have included obesity, cigarette smoking, and a high dietary intake of sugar, vAiereas moderate alcohol consumption appears to raise HDL levels.

People who exercise regularly tend to have higher HDL levels than do sedentary people. But physically active people also tend to be leaner and may differ in other respects from their sedentary counterparts, so that it has not been ascertained v^ether exercise per se affects plasma HDL.

According to NHLBI scientists, it does not. They examined the effects of a physical training program in young adults over a six-week period, during v^ich the subjects consumed a constant composition diet also calculated to hold their weight steady. With diet and weight thus controlled, neither total HDL nor HDL subfractions were altered by the training program.

Significant narro\<ang of the left main coronary artery (the chief source of blood to the left ventricle) has been considered a major indication for coronary artery bypass surgery, since available evidence indicates that the procedure prolongs life in such patients. NHLBI studies indicate that exercise stress testing provides a highly reliable screening test for identi- fying these patients, even if they are asymptomatic or have only mild symptoms.

In the NHLBI series, only 7% of patients found to have left main coronary artery disease by coronary angiography had failed to show indicative ECG changes during stress testing. The scientists believe that stress testing could reduce the need for diagnostic angiograms by 50% among mildly symptomatic patients vrf:iile still identifying 90% or more of patients with left main artery disease requiring angiograms as a possible prelude to coronary bypass surgery.

OD-3

The Institute supports numerous studies concerned with development of techniques for precisely locating and quantifying threatened, damaged, or destroyed areas of heart muscle after acute heart attacks. Such techniques could be highly useful to clinicians, both in diagnosis and also in evaluating the effectiveness of treatment, especially therapeutic measures aimed at limitir, or reducing permanent heart damage occurring during the early hours or first fe? days after the attack.

1

In animal studies, NHLBI grantees have experimented with 1-131 labeled fragments of antibodies to myosin, one of the two contractile proteins of heart muscle. The antibodies exhibited a high affinity for the myosin of necrotic heart tissue and selectively labeled infarcted areas, but their buildup was slow when the fragments were administered intravenously. However, v^en administered directly into the coronary arteries via catheter following induced heart attacks, the labeled fragments rapidly accumulated in infarcted areas and produced high quality scans within 30 minutes. Itie fragments did not promote arrhythmias or have any deleterious effects on functional heart muscle.

Although the technique is still experimental, the grantees feel that it might find clinical application in the following situations: 1) during coronary angiography in patients with unstable angina to define possible regions of infarction; 2) to define areas of permanent heart damage in conjunction with therapeutic measures to reduce infarct size; and 3) in conjunction with coronary! bypass surgery to define any heart muscle injury occur ing in the course of the operation.

The Institute is currently supporting several large-scale clinical trials evaluatir^ measures for the primary or secondary prevention of arteriosclerosis and its conplications. The goal of the primary prevention studies is to avert o^ delay the onset of crippling or potentially lethal manifestions among persons at high risk by timely inter^/entions against modifiable factors knovTn to increase vulnerability to premature arteriosclerosis. Tlie secondary prevention studies seek to reduce disability and improve long-term survival among people who have already experienced serious clinical manifestations of the disease.

The Coronary Primary Prevention Trial involves 4,000 men with Type II hyperlipoproteinemia (one of the major metabolic disorders characterized by { elevated blood cholesterol) but with no clinical evidence of coronary heart ' disease at entry into the study. It is evaluating a cholesterol-lowering diet or the same diet supplemented with cholestyramine (a cholesterol-lov^ring drug) in reducing expected rates of morbidity or mortality from coronary heart disease in this high-risk group.

The Multiple Risk Factor Intervention Trial involves nearly 13,000 men at heightened risk of coronary heart disease (CHD) because of various combinations of elevated blood cholesterol, elevated blood pressure, and/or cigarette smoking.] Any one of these factors roughly doubles CTD risk, and the presence of all three ' may run it up by a factor of ten or more. We are hopeful that systematic modification of these factors over a 6-year period , will produce substantial reductions in that risk and will be reflected in lovvered CHD mortality rates.

The Aspirin Myocardial Infarction Study sought to determine whether daily L! doses of aspirin could rec3uce the threat of recurrent heart attacks and the nurrbe of heart attack deaths among 4,200 subjects who had previously experienced one or,

or>-4

more such attacks. A high proportion of heart attacks v/hether initial episodes or recurrences are precipitated by clotting phenomena in the coronary arteries, ana it was hoped that aspirin, an inhibitor of platelet aggregration, would protect against such complications. The clinical pnase of the study has been completed and the results are currently being readied for publication.

The Beta-Blocker Heart Attack Trial is evaluating another type of drug that may provide long-term protection to heart attack survivors. Propranolol, the drug being tested, has a number of potentially beneficial effects: it reduces heart rate and blood pressure, reduces the cardiac workload, is a blood vessel dilator, and protects against certain types of arrhythmias. Recruitment of participants for this trial is underway toward the goal of enrolling 4,200 patients by the middle of 1980.

Tne Multicenter Investigation for the Limitation of Infarct Size (MILIS) is investigating the effectiveness of propranolol or the enzyme hyaluronidase in salvaging threatened, but still viable heart muscle when infused early after the onset of acute heart attacks. It is hoped that either or both agents V7ill reduce mortality fron acute heart failure or cardiogenic shock ccmplications usually stemming fron massive heart muscle damage sustained during or after the attack and may also reduce residual disability after recovery. Entry of patients into the study began August 1978; 1500 will eventually participate.

The Coronary Artery Surgery Study is comparing medical management of advanced coronary heart disease with coronary bypass surgery / a procedure that has cone into widespread use during recent years for the treatment of intractable or unstable angina pectoris. Among still controversial questions that this study will attempt to answer: 1) Does the procedure improve the patient's life expectancy? 2) Does coronary artery bypass reduce the heart attack risk of patients with advanced coronary obstructions or the risk of recurrent attacks in patients \^/ho have previously experienced them? 3) What is the quality of life over an extend period for patients undergoing the procedure as conpare to those receiving only medical therapy?

A technique called percutaneous transluminal coronary angioplasty may provide an alternative to coronary bypass surgery in sarie patients with coronary heart disease. In patients with a well localized, non-calcified lesion narrowing a single coronary vessel, a balloon-tipped catheter may te passed through the site of obstruction under fluoroscopic guidance, then inflated briefly. The sausage shaped balloon, v^en properly positioned and inflated, compresses the malleable lesion against the blood vessel wall, thereby increasing the size of the blood channel.

Clinical experience with the technique is limited probably about 300 procedures worldwide thus far so that both its benefits ar^ attendant risks are difficult to quantify. Hov\?ever, it has appeared sufficiently pranising for NHLBI to establish a registry to facilitate further evaluation of its effectiveness and to define its limitations. Additional laboratory and clinical research with the technique is also being encouraged.

OD-5

.!

In coronary artery bypass surgery, obstructions in coronary vessels are usually bypassed by splicing segments of saphenous vein (obtained from the patient's legs at time of operation) into the coronary artery beyond the major site of obstuction, then splicing the other end of the graft into the aorta. Alternatively, the left and right internal mammary arteries (v^iich normally supply blood to the chest wall) may be mobilized as bypass vessels. Artificial blood vessel grafts had not been used because even slight blood incompatibilities of most graft materials, together with the small sizes required in coronary bypass surgery (usually less than 5 mm. in diameter), made graft closure by clots almost inevitable

However, NHLBI grantees report using artifical grafts of polytetrafluoethylene to bypass coronary artery obstructions in five patients for whom no other alternatives were feasible because of earlier vein stripping operations and/or obstuctions unreachable with internal mammary bypasses. To help insure continued patency, the ends of each graft were expanded into a "cobra head" shape before splicing, and meticulous technique was employed in suturing them into place. Followup studies 9 to 14 months after surgery showed 4 of the 5 grafts still functional. These preliminary results are premising, though followup for much longer periods will be necessary before polytetrafluoethylene grafts can be recanmended as an alternative to saphenous vein or mammary artery grafts in coronary bypass procedures.

Hypertension is another priority target of NHLBI programs because of its high prevalence in the U.S. population (an estimated 35 million Americans have it) and because of its importance as a risk factor for heart attacks, strokes, congestive heart failure, and kidney failure. \

Essential hypertension is usually considered a disease of adult life i because it most often beccoies manifest during the third decade or later.

Ho\^ver, growing evidence suggests that forerunners of the disease may be 1

identifiable much earlier. '

Studies among children ard adolescents indicate that blood pressures higher than the norm for children of the same age group tend to persist at these higher levels as the child grows older, possibly moving into the hypertensive range during adult life.

Urinary kallekrein levels may also be an early indicator of hypertension risk. Kallekreins are enzymes that participate in the production of kinins, many of which are potent blood vessel dilators. The kallekrein- kinin system is suspected of playing an important, though still unspecified role in blood pressure regulation. In adults, urinary levels of kallekreins appear to be inversely related to blood pressure levels: the lower the urinary kallekrein levels, the higher the mean blood pressure and vice versa. The saire inverse relationship appears to hold among children and adolescents. And, as with blood pressure levels, low urinary kallekrein levels during childhood tend to persist as the child grows older, possibly indicating a heightened risk of developing hypertension during adult life.

OD-6

Also assigned an important role in blood pressure regulation and in sane forms of hypertension is the renin-angiotensin system. Renin, an enzyme produced by the kidney, acts on a plasma protein to generate angiotensin I. Angiotensin I is relatively inactive, but as it traverses the lungs (and possibly other tissues) it is exposed to a converting enzyme in cells lining the pulmonary blood vessels, generating angiotensin II. A powerful blood vessel constrictor, angiotensin II is the chief culprit in renal hypertension, a major factor in the malignant phase of essential hypertension, and is suspected of involvement in earlier stages of the disease as well as later complications, such as congestive heart failure.

Recently, drugs have been developed that impede angiotensin II production by inhibiting the converting enzyme that generates it fron angiotensin I. One of the most promising of these drugs, Captopril, had performed well in the treatment of both renal and essential hypertension in limited clinical trials reported earlier by NHLBI grantees. Now other grantees report that Captopril may also prove valuable in the treatn^nt of chronic congestive heart failure that responds poorly to other therapeutic measures.

With the development of congestive heart failure, diminished heart output elicits widespread blood-vessel constriction, v^ich forces the heart to pump against a higher resistance. Another factor in this higher resistance is thought to be increased stiffness of the blood-vessel walls, possibly due to their increased sodium content. The renin-angiotensin system may well be involved in both phenanena, since angiotensin II is not only a blood-vessel constrictor but also a potent stimulus for the production and release of aldosterone, a salt-retaining honione from the adrenal cortex.

In any case, impedence of angiotensin II production by Captopril brought about substantial reductions in systemic and pulmonary vascular resistance, decreases in arterial pressure, improved heart performance, and clinical improvement in the patients receiving the drug.

The renin-angiotensin-aldosterone system affects and is affected by dietary salt. A low sodium intake results in increased plasma renin activity, generatirvg irore angiotensin II and thereby stimulating increased production and release of aldosterone. Aldosterone, in turn, prcsrotes sodium conservation by tlie kidneys. Recent research suggests that these effects of dietary salt may be mediated through larger, biologically inert molecules (sometimes called "big renins") that serve as precursors for the smaller, biologiccilly active renins secreted by the kidneys. With sodium depletion, the concentrations of the larger molecules decrease as concentrations of the smaller renins and plasma renin activity increase.

A high salt intake is thought to contribute to the development of essential hypertension in scsre people, and here again the renin-angiotensin- aldostercne system appears to be involved. High salt intakes normally reduce plasma renin activity and thereby curb angiotensin and aldosterone production. Without tlie aldosterone stimulus, the kidneys excrete sodium

01>7

in excess of bodily needs. But the response of this system is apparently blunted in seme people, said to be "salt sensitive." In such people, persistently high salt intakes are thought to increase their vulnerability j to essential hypertension. I

Race may be a factor in salt sensitivity. Studies conparing the responses of normotensive white or black subjects to an administered salt load indicated that, as a group, the whites excreted the excess salt more readily. Plasma renin activity was less effectively suppressed by salt loading in the black subjects and excess sodium was retained longer. The findings raise the possibility that the greater salt sensitivity of blacks could v^ll be a factor in their higher prevalence of hypertension, nearly twice that of whites in the U.S.

Thiazide diuretics promote salt excretion by the kidneys and also exert a direct blood-pressure-lowering effect. Tniazides alone can often control mild hypertension, and these agents also potentiate the effects of other blood pressure drugs. As a result, they are a component of most antihypertensive regimens.

But thiazides also tend to raise serum uric acid levels, and this is a potential source of problems for the 25% of hypertensive patients who also have hyperuricemia, ^proximately 12% of such patients may develop gout on regimens that include thiazides. Adding a uricosuric agent, such as probenecoid or allopurinol, to the regimen may eliminate this risk, but also makes the regimen a bit more complicated to follow.

Currently undergoing clinical trials is a new diuretic agent, ticrynafen, v/nich reduces serum uric acid. In trials comparing it with a tliiazide, NHLBI grantees found that both agents produced very similar effects on the patients' blood pressure; but whereas their uric acid levels rose with thiazide therapy, they fell with ticrynafen therapy. The results suggest that ticrynafen may find a most useful niche in the management of hypertension accompanied by hyperuricemia.

The Hypertension Efetection and Followup Program involved 11,000 patients followed for five years to assess the impact of controlling moderately elevated blood pressure in reducing irorbidity and nortality from hypertension-associated cardiovascular disorders. The clinical phase of the program was completed this year and the results are being analyzed and prepared for publication. They will compare the morbidity and mortality experience in an intensively treated stepped-care group with that of patients referred, to their usual sources of medical care.

Coordinated by NHLBI, the National High Blood Pressure Education Program, since its inception in 1972, has carried out a wide range of activities concerned with alerting health professionals and the general public to the wide prevalence of hypertension, the dangers that uncontrolled hypertension poses to the victim's health and life, and the benefits of early detection and adequate treatment. The program enjoys the support and cooperation of numerous federal agencies, 150 or more national organizations, and virtually all state health departjnents . Its success

0I>8

has been reflected in sharp decreases in the numbers of hypertensives ' unaware of their disease, by dramatic increases in patient visits for hypertension and in prescriptions written for blood-pressure drugs, and by substantial increases in the numbers of hypertensive patients whose blood pressure is under adequate control.

In 1977 the Institute provided funds to initiate large-scale demonstration projects in hypertension education, screening, ard control throughout the states of California, Connecticut, Maryland, and South Carolina. Similar projects have since been funded in Georgia, Maine, and Michigan. The goals of these projects are to provide expansion and effective coordination of ongoing education, screening, and treatment activities so as to avoid needless duplication or- fragmentation of effort vrf:iile insuring the availability of effective methods of hypertension detection and control, not only to canmunities throughout the state but to rural areas as well. It is also hoped that the experience of these states may provide encouragement and possible nodels for other states desiring to undertaJce similar programs.

Ihe Institute is also funding demonstration projects concerned with hypertension detection and control in the work setting at four Ford plants in Southeastern Michigan, five Westinghouse plants around the U.S., and among Maryland state employees in Baltimore. Pilot evaluation studies of hypertension control in canmunities with a high prevalence of the disease have been initiated in Detroit; Berkeley, California; and also in rural areas of North Cairolina, Georgia, and Kentucky.

NHLBI scientists have found that a frequent cause of sudden death arrang athletes or other young, vigorous, seemingly healthy people is hypertrophic cardiomyopathy (HCM) . Evidence of HCM v/as found at autopsy in nearly half of 29 athletes aged 14-30 years wbD died suddenly and unexpectedly and also in the majority of 25 other patients in v-Jhom sudden death was the first overt manifestation of disease. The usual features of HCM are marked thickening of the ventricular septum and the presence of nun>erous disorganized cardiac muscle cells, not only in the septum but also in the free wall of the left ventricle. This diffuse cellular disorganization is thought to predispose to the arrhythmias that are usually the cause of sudden death in HCM patients.

The electrocardiogram is usually abnormal in HQ-l and the tliickening of the ventricular septum is readily detectable by echocardiography. But neither test is likely to be used routinely in examining v/ould-be athletes or team members, nor would the need for such tests be obvious in a young, seemingly robust athlete v;ho just happens to have HCM.

The drug of choice for treating HCM is propranolol. In the obstructive form of the disease, surgery may provide relief of symptoms if propranolol is ineffective. But until recently there had teen no satisfactory therapeutic alternative for the patient with non-obstructive HCM who did not respond well to propranolol.

NHLBI scientists report that the calcium antagonist verapamil may provide that much-needed alternative, both in obstuctive and nonobstructive

OD-9

HCM. Comparing verapamil and propranolol in subjects with obstructive HCM, the scientists found both about equally effective in relieving outflow obstruction and improvirg exercise tolerance, /gainst the other major threat of HCM cardiac arrhythmias verapamil was highly effective against atrial arrhythmias but less consistently so against ventricular arrhy tJimias .

The scientists also noted that about one-third of HCM patients either could not tolerate verapmil or else did not respond to it, so that further clinical studies are needed to determine the place of this drug in the treatment of HCM.

For replacement of damaged heart valves, the Hancock, porcine biopros- thesis a specially treated pig heart valve mounted on a prosthetic frame for ease of insertion caribines good performance characteristics with exceptionally low risk of engendering clots or emboli, thus obviating the need for anticoagulants postoperatively. The unanswered questions | about this valve, as with bicprosthetic valves in general, had concerned | its durability. r-

NHLBI studies anong 69 recipients of Hancock valves— all are followed fot; more than 4.5 years—have disclosed late valve failures in 6 patients. The failures occurred 56-100 months after iiisertion and usually resulted i fran cadcif iciaton or disruption of the valve leaflets. Microscopic I exsimination of the leaflets revealed degeneration of tlieir collagen j fibrils, calcification, and infiltration by lipid and fibrinoid substances.

NHLBI experience thus far suggests that the probable useful life of Hancock valves is 5-8 years, after wiiich a high failure rate is likely. Henceforth, these scientists will continue to use the Hancock valve in patients sixty or older, but v;ill select seme other suitable artificial valve for use in younger patients.

Lung Diseases

Oxygen therapy is often essential in the clinical management of respiratory distress syndrores, advanced emphysema, and other lung disorders. But prolonged exposure to high concentrations of oxygen is toxic to the lung and can lead to fibrosis or other degenerative changes. The culprit in oxygen toxicity appears to be free radicals of oxygen. Such free radicals are highly reactive and may conbine avidly with intracellular sulostances, including enzymes and other macromolecules , sometimes with disruptive effects on their functions.

Basic research in animals has disclosed that antioxidant enzymes including superoxide dismutase helps protect the lung against oxygen toxicity by converting free radicals into non- toxic products. The protection afforded by this antioxidant system is greatest in the lungs of immature animals, in whom exposure to toxic levels of oxygen elicits an increase in superoxide dismutase activity. As the animal matures, however, the responsiveness of the s^'stem diminishes, as does its .

OD-10

protection agairist oxygen toxicity.

But it appsars that the antioxidant system can be activated in mature animals by ei-idotoxin. A single dose of endotoxin protected animals against lung damage following exposure to oxygen

at levels that produced severe pulmonary fibrosis or even death in untreated animals. These findings raise the possibility that other activators of this antioxidant system that are less toxic than endotoxin may be found, with possible application to the prevention of toxicity that might otherwise result from prolonged or intensive oxygen therapy.

A sonar-like technique that shows pronise in pulmonary-disease screening especially in young children -employs a transducer tliat generates oscillating sounjdv/aves at the subject's mouth. Ihe sound waves are beamed down the trachea and, as they traverse the lang airways, their reflections are picked up and analyzed. The teclinique can provide valuable information on airv/ay geometry and reliably detects airvay obstruction, a cardinal feature of a number of pulmonary disorders. Tine technique causes no disconfort to the subject, so tliat frequent or repeated measurements are possible.

Research evidence continues to accumulate in support of the protease- antiprotease theory of emphysema. The theory holds that the lung damage of emphsema may stem, at least in part, from local imbaJLances in lung tissues between enzymes capable of degrading the collagen or elastin of lung connective tissue and the antiproteases that normally neutralize them The sources of these proteases are white blood cells, especially neutrophils and alveolar macrophages, \\tiich release them in the course of their battles with bacteria and other foreign invaders of the lung. Ironically, these byproducts of lung defense mechanisms can themselves attack lung connective tissue unless inactivated.

A small segiTK^nt of the population (about 0.02%) is rendered particu- larly vulnerable to emphysema by a marfced hereditary deficiency of alpha- 1-anti trypsin, one of the most important of the antiproteases. These people, homozygous for the enzyme deficiency, have alpha- 1-anti trypsin levels only about one-ninth normal. (Although heterozygotes also have lower than normal enzynie levels, they are apparently still adequate to prevent any significant increase in emphysema risk.)

In hoirozygotes , alpha-1-anti trypsin synthesis by the liver continues, though possibly at a reduced rate. But, possibly because of structural alterations in tlie protein molecule, it cannot be secreted normally by the cells in which it is made. Recent NHLBI studies indicate that an androgen-like drug, danazol, somehow helps alleviate this block on alpha- 1-antitrypsin release. In tomozygous patients, it raised blood levels of the enzyme by 40%. However, further detailed study will be needed to ascertain whetlier such drug-induced increases in serum enzyme levels will appreciably decrease tlie emphysema risk in honiozygotes or mitigate the course of the disease in those already afflicted.

OD-11

The scientists have also drawn up a protocol for a clinical study to determine whether alpha-1-antitrypsin replacement is feasi±)le in hoirozygotes It calls for intravenous infusions, once a v/eek, of partially purified alpha-1-anti trypsin in amounts equivalent to that present in two liters of normal plasma. The goal is to find out whether protective levels of | the enzyme can be maintained in this fashion. |

Other NHLBI studies suggest some possible reasons v;hy cigarette smokers j are at increased risk from emphysema. Tney showed that alveolar macrophages obtained by lavage from the lungs of siiokers produced a chemotactic substance that attracts neutrophils. Macrophages from the lungs of non- smokers could also be induced to release this substance when these cells were exposed in culture to cigarette smoke.

The findings may help explain v^y, in smokers, neutrophils (a prime source of proteases) constitute a higher proportion of the leukocyte population in their lower respiratory tract (2-3% versus less then 1% in nonsmokers). Moreover, the same chemotactic factor that attracts increased numbers of neutrophils to the lung also "activates" these cells for

subsequent release of various substances, inc]uding proteases against both collagen and elastin of lung connective tissue.

The studies further disclosed that the lungs of sirokers may have less protection against these proteases: their antiproteases against elastin- digesting enzymes v/ere only about half as effective as those from non- smokers .

Other NI-ILBI research has centered on the synthesis and metabolism of collagen in lung tissues, on the mechanisms that regulate and mDdulate these processes, and on disturbances resulting fran various disease states that may lead to the destruction of functional lung canponents or else to widespread fibrosis throughout the lung,

A major site of collagen synthesis in lung is the fibroblast. NHLBI studies indicate tliat cyclic-AMP a "second messenger" si.±)stance that often mediates the effects of neural, huiroral, or other stimuli in susceptible tissues is also critically involved in collagen production by these cells. In general, agents that increased cyclic-AMP levels in fibroblasts resulted in decreased collagen production. All such agents that inhibited collagen synthesis were stimulants of beta adrenergic receptors. Conversely, agents that blocked beta adrenergic receptors increased collagen production.

The scientists suspect that intracellular substances acting on beta- adrenergic receptors in the fibroblast, possibly through the intermediary substance cyclic~MP, may regulate its collagen production. Under normal circumstances, they reason, collagen production is kept partially suppressed by endogenous stimulation of these receptors, tvlien increased collagen production is needed (as, for example, in tissue repair) endogenous stimulation of tliese receptors is diminished or v;ithdrawn, the bralces on collagen synthesis are released, and \Tore collagen is produced.

OD-12

This hypothesis suggests a possible mechemism for the fibrosis that has sonetimes occurred in various tissues of patients under treatment with propranolol. This drug is a potent beta adrenergic blocker and hence a potential stimulant of collagen production. The hypothesis could also lead to fresh insights or new approaches to the prevention or treatment of fibrotic lung disorders. Collectively, these conprise 15-30% of all noninfectious diseases of the lung, excluding tumors.

Each year in the U.S., some 50,000 nevTbom infants develop neonatal respiratory distress syndrane (RDS). Premature infants are especially susceptible because their lungs may not have matured sufficiently to produce adequate quantities of pulmonary surfactant.

The results of animal and clinical studies have indicated that certain steroids accelerate maturation of feted lungs. Currently, NHLBI is supporting a clinical trial to assess the effectiveness of steroids, administered antenatally to mothers, in preventing RDS among their infants at risk. Tne infants will subsequently be followed for 18 rronths to ascertain v^hetlier the steroids result in ajiy untoward short term or long term effects.

Blood Diseases and Resources

It is now possible to identify female carriers of hemophilia with accuracies up to 90% by ccmlDining the results of coagulation tests for norsTi.aJ. factor VIII with immunological tests which also react with the ab- normal variant tiiat does not participate in clotting. If the kno^m carrier becomes pregnant, it is also possible to identify the sex of the unborn fetus by amniocentesis. And now, NHLBI grantees report, if the fetus is male (and thus has a 50--50 chance of being hemophiliac) it can be determined during the second trimester whether the fetus is normal or has inherited the disease.

The test entails using a fetoscope to obtain a fetal blood sample from the placenta, then assaying its content of normal factor VIII. The procedure requires skilled fetoscopy and meticulous laboratory technique, since the blood sample is usually considerably diluted with amniotic fluid. However, using their technique in 14 carriers, the grantees correctly identified 7 of 7 hemophiliac fetuses (confirmed at autopsy after induced abortions); and of 7 other fetuses identified as normal, all five that had been bom at the time of the grantees' report had proved to be so.

The same technique can be onployed to identify fetuses who inherit von Willebrand's disease. Ihis disorder, like hemophilia, is characterized by a factor VIII deficiency, but it also involves a platelet defect that may contribute to the associated bleeding tendency. Von Willebrand's disease also differs from henraphilia in that the flawed gene is a dominant one and may be transmitted by either parent to offspring of either sex.

OD-13

I

Von Willebrand's disease appears to be the most conrnDn of the hereditary:

clotting factor deficiencies. Fortunately, in irost affected persons factor j

VIII levels are sufficiently high to prevent spontaneous hemorrhage, 1

though excessive bleeding may follow trauma, surgery, childbirth, and \

the like. But because the expression of the genetic flaw is highly '

variable, seme von Willebrand's patients exhibit very low factor VIII I levels and pronounced hemorrhagic tendencies.

The new technique can thus be immensely helpful to prospective parents vvtio are carriers of these diseases and v^o may find themselves faced with some wrenching decisions.

At the opposite pole from the heitorrhagic disorders are clotting conplications that are often directly responsible for the disabling or lethal manifestations of heart and blood vessel disorders. Recent NKLBI- supported research has been seeking rapid, reliable techniques for the detection and evaluation of intravascular clotting by measuring blood levels of various substances participating in coagulation or generated as byproducts of the process.

One such byproduct is f ibrinopeptide A, \"rf-iich is liberated during the formation of fibrin clots. The appearance in blood of significant quantities of this peptide is strongly indicative of intravascular clotting, even in the absence of overt clinical signs or symptoms . It is hoped that continued development and refinement of such techniques v/ill permit recog-nition in high-risk patients of "clinically silent" thrombo- embolic episodes or potentially serious clotting problems in the malcing so that appropriate therapeutic measures can be initiated pranptly to head them off or else to halt their progress.

NHLBI research on sickle cell disease is pursuing a number of promising lines of inquiry- toward the goal of developing improved raecins of prevention or treatrrent.

One of these is concerned \7ith the sv/itchover in hemoglobin synthesis that occurs late in fetal life. Tlie hemoglobin molecule is assertt)led froB tv^?o pairs of protein chains. IXiring fetal life, two a].pha chains are paired with tvrc> gamma chains to form fetal hemogiobin. However, shortly before birth a changeover occurs: production of ga-nma chains virtu- ally ceases, production of beta chains begins, and thereafter alpha chains are paired with beta chains to produce adult hemoglobin. Unfortunately, in sickle cell disease, the beta chains are flawed; and the resulting molecules of sickle hemoglobin tend to aggr-egate into a rigid gel under various conditions, distorting the red cell into the characteristic sickled shape.

If fetal henoglobin synthesis could be stimulated and maintained in sickle cell patients, many of the problems of the disease would disappear along with the troublesome beta chains. Even achieving a mix of fetal and sickle hemcxjlobins by a particil replacement of the latter could help a lot.

OD-14

NHLBI scientists are studying honoglobin s^vitching in the sheep, v^ich undergoes a changeover fron fetal to adult hemoglobin synthesis that appears analogous to that occurring in man. In sheep, however, certain aspects of the changeover process can be manipulated reproducibly (though not, so far, a switch back from adult to fetal hemoglobin synthesis).

In addition, reccmbinant ENA, molecular cloning, and cell transforma- tion techniques are being employed in attempts to isolate alpha, beta, and gamma globin genes for study under defined conditions. By doing so, scientists hope to learn how the garma globin gene is "turned off" and the beta globin gene "turned on" and vice versa.

Another line of inquiry is concerned with developing means of increasing the affinity of sickle hemoglobin for the oxygen that it carries. Under normal circumstances, hemoglobin readily takes on oxygen in transit through the lungs and subsequently surrenders it just as readily to the tissues that need it. However, deoxygenated sickle heitKDglobin is particu- larly prone to aggregation. So, the scientists reason, if a small proportion of the hemoglobin could be induced to hold on to its oxygen a trifle more tenaciously sickle cell crises might be averted or their severity substantially reduced.

Measures to increase the oxygen affinity of sickle hemoglobin might reduce somewhat the efficiency of the red cell in delivering its oxygen to tissues; but the tradeoff V70uld be that unsickled cells could reach the tissues easily, whereas sickled cells often have trouble negotiating

the smallest blood vessels and frequently create "log jams" that impede blood flow or may cut it off canpletely.

Other investigations are employing x-ray diffraction and other techniques of physical chemistry to examine the molecular structure of sickle hemoglobin and to locate the molecular sites participating in the aggregation of these molecules into a rigid gel, as occurs in sickling.

By learning more about these "active" sites and the manner of their bonding to other sickle hemoglobin molecules, it may become possible to prevent sickling by introducing other small itolecules that selectively tie up these sites.

In Gooley's anemia (beta thalassemia), as with sickle cell anemia, the problem is in the adult hemoglobin beta chain, which is not made in sufficient quantities. An excess of a].pha chains builds up and precipitates in the red cell, blighting it and so reducing its lifespan. Hence the results are anemia that, at present, can be corrected only by repeated blood transfusions.

As fetal hemoglobin contains no beta chain, the research cited earlier seeking means of reinstating and maintaining fetal hemoglobin synthesis in sickle cell disease, if successful, could eliminate or mitigate many of the clinical problems of Cooley's anemia as well.

0I>-15

Iron overloading remains a serious problem of Ccoley's and other transfusion-dependent anemias. The iron-chelating agent desferrioxamine, continuously infused under the skin by a small clockwork pump for 6-12 hours a day, has been sho\-m capable of preventing excessive iron buildup in younger patients and of halting or even reversing iron deposition in older ones. Some patients, who had been sliding steadily into congestive heart failure because of iron deposition in heart muscle, improved dramatically with, desferrioxamine therapy. Meanwhile, other iron chelating agents are under study, including one called rhodotorulic acid that may prove to be even more effective than desferrioxamine.

NHLBI tlirough its Division of Blood Diseases and Resources carries the responsibility for research into bionedical as well as logistical and managerial aspects of the national blood resource. In both areas considerable progress has been m.ade during the past year.

DBDR has sponsored the development of artificial blood substitutes, an important research area that promises to bear fruit in the near future. It was shovTn some time ago that synthetic chemicals knov/n as f luorocarbons , v?hen injected, into the blood stream, can carry oxygen to the tissues in a manner somev^tiat anologous to the hemoglobin contained in the red corpuscles » IsIHLBI-supported investigators showed that conpletely exsanguinated animals, when perfused v/ith a fluorocarbon preparation knov«i as fluorodecaline, could survive for