Hemorrhagic complications of oral anticoagulant therapy.

Hemorrhage is the major complication of anticoagulant therapy. The criteria for classifying the severity of bleeding has varied between studies, which has resulted in variability in the rate of bleeding reported in the literature. The major determinants of oral anticoagulant-related bleeding are the intensity of the anticoagulant effect, baseline patient characteristics, and the length of therapy. Older patients have characteristics that may place them at higher risk for anticoagulant-related bleeding, but they also have characteristics that make them more likely to benefit. The risk for anticoagulant-related bleeding cannot be considered in isolation and the potential benefits need to be weighed carefully in each individual patient, irregardless of age.

A multicomponent intervention to prevent major bleeding complications in older patients receiving warfarin. A randomized, controlled trial.

BACKGROUND: Warfarin is effective in the treatment and prevention of many venous thromboembolic disorders, but it often leads to bleeding. OBJECTIVE: To develop a multicomponent program of management of warfarin therapy and to determine its effect on the frequency of warfarin-related major bleeding in older patients. DESIGN: Randomized, controlled trial. SETTING: University hospital in Cleveland, Ohio. PATIENTS: 325 patients 65 years of age or older who started warfarin therapy during hospitalization. INTERVENTIONS: Patients were stratified according to baseline risk for major bleeding and were randomly assigned to receive the intervention (n = 163) or usual care (n = 162) by their primary physicians for 6 months. The intervention consisted of patient education about warfarin, training to increase patient participation, self-monitoring of prothrombin time, and guideline-based management of warfarin dosing. MEASUREMENTS: Major bleeding, death, recurrent venous thromboembolism, and therapeutic control of anticoagulant therapy at 6 months. RESULTS: In an intention-to-treat analysis, major bleeding was more common at 6 months in the usual care group than in the intervention group (cumulative incidence, 12% vs. 5.6%; P = 0.0498, log-rank test). The most frequent site of major bleeding in both groups was the gastrointestinal tract. Death and recurrent venous thromboembolism occurred with similar frequency in both groups at 6 months. Throughout 6 months, the proportion of total treatment time during which the international normalized ratio was within the therapeutic range was higher in the intervention group than in the usual care group (56% vs. 32%; P < 0.001). After 6 months, major bleeding occurred with similar frequencies in the intervention and usual care groups. CONCLUSIONS: A multicomponent comprehensive program of warfarin management reduced the frequency of major bleeding in older patients. Although the generalizability and cost-effectiveness of this program remain to be demonstrated, these findings support the premise that efforts to reduce the likelihood of major bleeding will lead to safe and effective use of warfarin therapy in older patients.

Major bleeding after hospitalization for deep-venous thrombosis.

PURPOSE: Most studies of oral anticoagulant-related bleeding have analyzed the incidence of adverse outcomes among patients with a variety of different conditions and without any comparison with a control group. We determined the incidence, time course, and risk factors associated with major bleeding after hospital discharge among patients with deep-vein thrombosis, and estimated the excess risk of bleeding associated with oral anticoagulant therapy. METHODS: A total of 22,000 adults were hospitalized in California for 3 or more days with a diagnosis of deep-venous thrombosis between January 1, 1992, and September 30, 1994. We determined the risk factors associated with readmission for bleeding. We compared the incidence of readmission for bleeding with comparison cohorts of patients with pneumonia or cellulitis who were matched for age, gender, race, and length of hospital stay. RESULTS: Of 21,250 patients with deep-venous thrombosis who were discharged without bleeding, 1.4% were readmitted for bleeding within 91 days; the rate was 2.7 times greater in the first 30 days than in the next 61 days. Risk factors for bleeding included hospitalization with gastrointestinal bleeding during the previous 18 months (relative hazard [RH] = 2.6, 95% confidence interval [CI]: 1.6 to 4.1), hospitalization with an alcohol-related diagnosis during the previous 18 months (RH = 2.6, 95% CI: 1.4 to 4.8), chronic renal disease (RH = 2.4, 95% CI: 1.4 to 4.2), female gender (RH = 1.7, 95% CI: 1.3 to 2.2), presence of a malignancy (RH = 1.6, 95% CI: 1.2 to 2.2), nonwhite race (RH = 1.6, 95% CI: 1.2 to 2.1), and age over 65 years (RH = 1.3, 95% CI: 1.0 to 1.7). Significantly more women (n = 40) had intracranial bleeding than men (n = 18, P = 0.02). In the comparison cohorts, the incidence of readmission for bleeding within 3 months of discharge was 0.7%, and the relative risk (RR) of readmission was greater in those with deep-venous thrombosis than in those with cellulitis (RR = 2.0, 95% CI: 1.6 to 2.5) or pneumonia (RR = 2.0, 95% CI: 1.7 to 2.5). CONCLUSIONS: The incidence of rehospitalization for bleeding was greatest in the first 30 days after discharge, and was approximately twice that seen in patients hospitalized for cellulitis or pneumonia. Further studies are needed to determine why women and nonwhite patients are at increased risk for anticoagulant-related bleeding.

The relationship between clinical assessments of nutritional status and adverse outcomes in older hospitalized medical patients.

BACKGROUND: Malnutrition is common in hospitalized older people and may predict adverse outcomes. Previous studies of the relationship between nutritional status and hospital outcomes are limited by inadequate accounting for other potential predictors of adverse outcomes, the failure to consider functional outcomes, and the omission of clinical assessments of nutritional status. OBJECTIVE: To measure the relationship between a clinical assessment of nutritional status on hospital admission and subsequent mortality, functional dependence, and nursing home use. DESIGN: Prospective cohort study SETTING: A tertiary care hospital PATIENTS: A total of 369 patients at least 70 years old (mean age 80.3, 62% women) admitted to a general medical service MEASUREMENTS: Nutritional status was measured with the Subjective Global Assessment, a validated measure of nutritional status based on historical and physical exam findings. Patients were classified as severely malnourished (generally at least a 10% weight loss over the previous 6 months and marked physical signs of malnutrition), moderately malnourished (generally a 5 to 10% weight loss and moderate physical signs), or well nourished. Vital status, independence in activities of daily living, and nursing home use were determined through patient or surrogate interview at admission and 90 days and 1 year after discharge. Indices of comorbidity and illness severity were determined from chart review. RESULTS: 219 patients (59.3%) were well nourished, 90 (24.4%) were moderately malnourished, and 60 (16.3%) were severely malnourished. Severely malnourished patients were more likely than moderately malnourished or well nourished patients to die by 90 days (31.7%, 23.3%, and 12.3%, respectively, P < .001) and 1 year (55.0%, 35.6%, and 27.9%, P < .001) after discharge. In logistic regression models controlling for acute illness severity, comorbidity, and functional status on admission, severely malnourished patients were more likely than well nourished patients to die within 1 year of discharge (OR = 2.83, 95% CI, 1.47-5.45), to be dependent in activities of daily living 3 months after discharge (OR = 2.81, 1.06-7.46), and to spend time in a nursing home during the year after discharge (OR = 3.22, 1.05-9.87). CONCLUSION: Malnutrition was common in hospitalized patients with medical illness and was associated with greater mortality, delayed functional recovery, and higher rates of nursing home use. These adverse outcomes were not explained by greater acute illness severity, comorbidity, or functional dependence in malnourished patients on hospital admission.

Epidemiology of adverse drug reactions in the elderly by drug class.

As the growth of the elderly population continues, the burden on the health care system and society will also increase. Since chronic diseases such as hypertension, coronary artery disease, arthritis, stroke, cancer and diabetes mellitus are more prevalent with age, the number of people with multiple chronic diseases will also increase. These patients are likely to be treated for some or all of their conditions with drug therapies. When used appropriately, drugs may be the single most important intervention in the care of an older patient, but when used inappropriately they no longer provide therapeutic benefit, and they may even endanger the health of an older patient by causing an adverse drug reaction (ADR). Factors believed to be responsible for increased adverse reactions in elderly patients are polypharmacy (including prescription and over-the-counter medications), increased drug-drug interaction, pharmacokinetic changes, pharmacodynamic changes, the pathology of aging and compliance. The exact role that age plays in ADRs is not clear. This is in part because few older patients are included in the large randomised trials, and so much of the information used to ascertain the age-associated risks of drugs comes from observational studies. Although the interactions of aging, concurrent comorbidities and polypharmacy are known, older patients do appear to be at increased risk. Improvements in the management of drug therapies of older patients can lead to improvements in their overall health, functioning and safety, as well as providing potential benefits to society by ameliorating some of the burden of their health care.

Prospective evaluation of an index for predicting the risk of major bleeding in outpatients treated with warfarin.

PURPOSE: To evaluate the accuracy and clinical utility of the Outpatient Bleeding Risk Index for estimating the probability of major bleeding in outpatients treated with warfarin. The index was previously derived in a retrospective cohort of 556 patients from a different hospital (derivation cohort). SUBJECTS AND METHODS: We enrolled 264 outpatients starting warfarin (validation cohort) to validate the index prospectively. All patients were identified upon hospital discharge, and physician estimates of the probability of major bleeding were obtained before discharge in the validation cohort. RESULTS: Major bleeding occurred in 87 of 820 outpatients (6.5%/yr). The index included four independent risk factors for major bleeding: age 65 years or greater; history of gastrointestinal bleeding; history of stroke; and one or more of four specific comorbid conditions. In the validation cohort, the index predicted major bleeding: the cumulative incidence at 48 months was 3% in 80 low-risk patients, 12% in 166 intermediate-risk patients, and 53% in 18 high-risk patients (c index, 0.78). The index performed better than physicians, who estimated the probability of major bleeding no better than expected by chance. Of the 18 episodes of major bleeding that occurred in high-risk patients, 17 were potentially preventable. CONCLUSIONS: The Outpatient Bleeding Risk Index prospectively classified patients according to risk of major bleeding and performed better than physicians. Major bleeding may be preventable in many high-risk patients by avoidance of over-anticoagulation and nonsteroidal anti-inflammatory agents.

Failure to prescribe warfarin to patients with nonrheumatic atrial fibrillation.

OBJECTIVE: To determine how often warfarin was prescribed to patients with nonrheumatic atrial fibrillation in our community in 1992 when randomized trials had demonstrated that warfarin could prevent stroke with little increase in the rate of hemorrhage, and to determine whether warfarin was prescribed less frequently to older patients-the patients at highest risk of stroke but of most concern to physicians in terms of the safety of warfarin. DESIGN: Cross-sectional study. Appropriateness of warfarin was classified for each patient based on the independent judgments of three physicians applying relevant evidence and guidelines. SETTING: Two teaching hospitals and five community-based practices. PATIENTS: Consecutive patients with nonrheumatic atrial fibrillation (n = 189). MEASUREMENTS AND MAIN RESULTS: Warfarin was prescribed to 44 (23%) of the 189 patients. Warfarin was judged appropriate in 98 patients (52%), of whom 36 (37%) were prescribed warfarin. Warfarin was prescribed to 11 (14%) of 76 patients aged 75 years or older with hypertension, diabetes mellitus, or past stroke, the group at highest risk of stroke. In a multivariable logistic regression model controlling for appropriateness of warfarin and other patient characteristics, patients aged 75 years or older were less likely than younger patients to be treated with warfarin (odds ratio 0.25; 95% confidence interval 0.10, 0.65). CONCLUSIONS: Warfarin was prescribed infrequently to these patients with nonrheumatic atrial fibrillation, especially the older patients and even the patients for whom warfarin was judged appropriate. These findings indicate a substantial opportunity to prevent stroke.

Why isn't warfarin prescribed to patients with nonrheumatic atrial fibrillation?

OBJECTIVE: To determine the opinions of selected physicians in our community about use of warfarin for patients with nonrheumatic atrial fibrillation, and to determine the relation of the physicians' opinions to their practices. DESIGN: Survey of physicians, using eight hypothetical clinical vignettes to characterize physicians' opinions about use of warfarin in patients with nonrheumatic atrial fibrillation, according to patient age, risk of bleeding, and risk of stroke. SETTING: Two teaching hospitals and five community-based practices. PARTICIPANTS: Eighty physicians who cared for 189 consecutive patients with nonrheumatic atrial fibrillation. MEASUREMENTS AND MAIN RESULTS: The survey response rate was 73%. Nearly all responding physicians (90%) recommended warfarin for at least one vignette. However, physicians recommended warfarin less often for vignettes depicting 85-year-old patients than for matched vignettes depicting 65-year-old patients (odds ratio [OR] 0.03; 95% confidence interval [CI] 0.01, 0.08), and less often for cases with specified risk factors for bleeding than for matched cases without the risk factors (OR 0.01; 95% CI 0.004, 0.03); warfarin was recommended more often for cases with a recent stroke than for matched cases without this history (OR 8.2; 95% CI 3.6, 18). In practice, warfarin was prescribed more often (p < or = .05) by physicians reporting good personal experience and by those who had favorable opinions about its use. However, even physicians with good experience and favorable opinions did not prescribe warfarin to half of their patents for whom warfarin was independently judged appropriate. CONCLUSIONS: Physicians' opinions frequently opposed warfarin for older patients with nonrheumatic atrial fibrillation, and for those with bleeding risk factors. Physicians' opinions, as well as other barriers to warfarin therapy, most likely contribute to its infrequent prescription.

Long-term outcomes of deep-vein thrombosis.

OBJECTIVE: To assess the long-term outcomes of patients with acute deep-vein thrombosis. METHODS: We followed up 124 patients with deep-vein thrombosis 6 to 8 years after the index thrombosis to determine the frequency of death, recurrent venous thromboembolism, postphlebitic symptoms, and their relationship to three domains of health-related quality of life. RESULTS: Fifty-two (42%) of the 124 patients died. The cumulative incidence of death was 17% at 1 year and 39% at 5 years. Death was especially common among patients older than 75 years and those with cancer or stroke (5-year cumulative incidence, 66%, compared with 12% among other patients; P < .0001). Most deaths were attributable to cancer or cardiovascular disease. Venous thromboembolism recurred in 18 patients (15%); the cumulative incidence was 6% at 1 year and 13% at 5 years. Recurrence was more common, however, among patients younger than 65 years with a history of recurrent venous thromboembolism (5-year cumulative incidence, 34%, compared with 10% among other patients; P < .01). In interviews with 52 patients 6 to 8 years after the index deep-vein thrombosis, 42% reported pain, swelling, or discoloration in the leg affected by the index thrombosis. Perceptions of health, physical functioning, and role limitations attributed to physical health were worse (P < .01 for each domain) in symptomatic patients than in asymptomatic patients. CONCLUSIONS: Six to 8 years after deep-vein thrombosis, many patients had died of preexisting cancer or cardiovascular disease. Recurrent venous thromboembolism was uncommon. Symptoms in the leg affected by the index thrombosis were common, however, and were associated with worse health-related quality of life.

Anticoagulants in older patients. A safety perspective.

Although anticoagulants are beneficial in the prevention and management of many thromboembolic disorders, they can cause serious bleeding. However, the risk of anticoagulant-related bleeding is not clearly defined for older patients, who are likely to benefit the most from anticoagulant therapy. Older patients may be at increased risk for anticoagulant-related bleeding because of their increased incidence of adverse drug reactions, increased prevalence of comorbidity and polypharmacy and increased vascular and endothelial fragility. Furthermore, the anticoagulant effect of warfarin is increased in older patients. Therefore, it is important to determine whether or not heparin-related and warfarin-related bleeding are more common in older patients. Most studies that have examined age as a risk factor for heparin-related bleeding have found bleeding to be more frequent in older patients: patients 60 years and older were approximately 3 times as likely to develop bleeding during heparin therapy than were younger patients. Studies that have examined age as a risk factor for warfarin-related bleeding have found conflicting results. Seven studies, enrolling a total of 14,388 patients, found that older patients were approximately twice as likely to bleed during warfarin therapy. In contrast, 7 studies, enrolling a total of 2940 patients, found no increase in the frequency of warfarin-related bleeding in older patients. These findings provide a basis for weighing the risks of anticoagulant therapy and for making decisions about the use of anticoagulants in older patients. These findings also indicate the potential value of methods to decrease the frequency of anticoagulant-related bleeding in older patients. Such methods include maintaining the anticoagulant effect within the therapeutic range and recognising other modifiable factors, such as medication use, that may promote bleeding.

Anticoagulant-related bleeding: clinical epidemiology, prediction, and prevention.

OBJECTIVE: To review (1) the clinical epidemiology of bleeding during anticoagulant therapy with heparin or warfarin, (2) data useful in estimating the risk for bleeding in individual patients, and (3) the efficacy of methods for its prevention. METHODS: Relevant literature was identified by a computerized search of the Medline database and by review of the bibliographies of original and review articles. Studies were classified according to their design. Estimates of the risk for bleeding during anticoagulant therapy, compared with the risk without therapy, were obtained from randomized trials. Estimates of the frequency of bleeding during the course of anticoagulant therapy and information about risk factors for bleeding were obtained primarily from longitudinal studies of inception cohorts of patients followed from the start of therapy. MAIN RESULTS: The average daily frequencies of fatal, major, and major or minor bleeding during heparin therapy were 0.05%, 0.8%, and 2.0%, respectively; these frequencies are approximately twice those expected without heparin therapy. The average annual frequencies of fatal, major, and major or minor bleeding during warfarin therapy were 0.6%, 3.0%, and 9.6%, respectively; these frequencies are approximately five times those expected without warfarin therapy. The risk for anticoagulant-related bleeding is highest at the start of therapy: during warfarin therapy, the risk for major bleeding during the first month of therapy is approximately 10 times the risk after the first year of therapy. An individual patient's risk for major anticoagulant-related bleeding can be estimated on the basis of specific risk factors such as the intensity of the anticoagulant effect achieved and the presence of serious comorbid diseases, especially cerebrovascular, kidney, heart, and liver disease; older age and concurrent medicines may also be independent risk factors. Major bleeding most often affects the gastrointestinal tract, soft tissues, and urinary tract. Diagnostic evaluation of gastrointestinal bleeding and gross hematuria leads to identification of previously unknown lesions in approximately one-third of cases, even when the prothrombin time is elevated. Intracranial bleeding is rare, but it is frequently fatal. The frequency of bleeding during warfarin therapy is reduced by less intense therapy achieving a prothrombin time with an International Normalized Ratio of 2.0 to 3.0, which is efficacious for most indications. CONCLUSION: Anticoagulant-related bleeding is common and often serious. The risk for bleeding can be estimated in an individual patient, giving the primary physician a quantitative basis for weighing the risks and benefits of therapy and for optimizing patient management. The frequency of anticoagulant-related bleeding is reduced by less intense warfarin therapy. Future studies should evaluate new approaches to management that may further reduce complications while maintaining efficacy.

Pancreatic carcinoma. An unusual presentation--inferior vena cava thrombosis.

The case reported here demonstrates the importance of considering the possibility of occult malignancy in young patients presenting with extensive or migratory thromboses in atypical locations that appear resistant to standard therapy. Suspicion for malignancy-related thrombosis is heightened by the absence of known precipitating causes and by a negative family history of thrombosis. The search for the responsible underlying neoplasm can be frustrating, but diagnosis and successful treatment of the tumor remain the keys to controlling the abnormal thrombotic state.

Heparan sulphate proteoglycan as mediator of some adhesive responses and cytoskeletal reorganization of cells on fibronectin matrices: independent versus cooperative functions.

Fibronectin is a multifunctional glycoprotein which promotes the adhesion of a variety of cell types to extracellular matrices, including artificial tissue culture substrata. Biochemical analyses of substratum adhesion sites indicated important functions for cell-surface heparan sulphate proteoglycan (HS-PG) in directly mediating adhesive responses by the binding of heparan sulphate sequences to fibronectin. In addition, fibronectin has a binding domain for a cell surface 'receptor' (possibly a 140K glycoprotein) important in these responses. To differentiate the relative importance of these two binding activities, a proteolytically generated cell-binding fragment of fibronectin has been isolated which binds to the 140K 'receptor' but not to HS or to collagen. Platelet factor 4 (PF4), a tetravalent HS-binding protein, provides a model of the tetravalent HS-binding activity of fibronectin, as supported by affinity chromatography studies (these studies also reveal the complexity of HS-PG metabolism in adhesion sites). Responses are measured on substrata coated with the cell-binding fragment of fibronectin, intact fibronectin, or PF4, singly or in combination. Fibroblast-like BALB/c 3T3 cells form both close and tight-focal adhesive contacts with associated microfilament stress fibres on intact fibronectin. Whereas HS-PG binding appears to mediate the formation of close contacts and linear microfilament bundles, a cooperative relationship exists between the HS- and the cell-binding activities of the intact fibronectin molecule in the formation of focal contacts and stress fibres. Human dermal fibroblasts generate different adhesive responses on HS-binding or cell-binding substrata, which are dependent on whether cells have been grown in medium with ascorbate to maximize production of their own collagenous matrix. As with 3T3 cells, focal contact and stress fibre formations of dermal cells require both binding activities in the intact fibronectin molecule. A third system consists of neuroblastoma tumour cells which adhere and extend neurites on fibronectin. Cell-body adherence, but not neurite extension, occurs on HS-binding matrices whereas neurite extension requires only fibronectin's cell-binding activity; the responses of primary peripheral neurons were exactly the opposite and CNS neurons did not respond at all. These studies indicate the diversity of molecular mechanisms by which various cells interact with the multifunctional fibronectin molecule in order to perform specialized functions, as well as the independent or cooperative functions of heparan sulphate proteoglycan on the cell surface in mediating these responses.

Glycosaminoglycan distribution in substratum adhesion sites of aging human skin fibroblasts, including papillary and reticular subpopulations.

Glycosaminoglycan (GAG) distribution has been analyzed in the adhesion sites, left substratum-bound after EGTA-mediated detachment, of various human skin fibroblast populations grown in vitro in the presence (asc+) or absence (asc-) of ascorbate. Examination of these skin fibroblasts during the EGTA treatment by scanning electron microscopy reveals that (a) asc+ cells detach much more rapidly than asc- cells, but (b) asc- or asc+ cells leave the same two types of structures in longterm culture-generated substratum-attached material (L-SAM)--long linear retraction fibers and "footpad-like" structures. Most of the [3H]glucosamine-radiolabeled polysaccharides in L-SAM were shown to be GAGs. Fibroblasts from a full-thickness skin sample from a very young patient (AG4449) have similar distributions of the GAGs in both the EGTA-suspended cell and L-SAM fractions; however, asc+ cell and L-SAM fractions contain relatively more heparan sulfate than the asc- fractions. In contrast, full-thickness skin fibroblasts from an elderly patient (AG2261) generate GAG distributions in their L-SAMs (with greatly elevated levels of hyaluronate and chondroitin sulfate) that are very different from those of the cell fractions and from those of AG4449; furthermore, these distributions in AG2261 fractions do not change when shifted from asc- to asc+ medium. These studies led to analyses of the two major fibroblast subsets--papillary (PAP) or reticular (RET)--that can be isolated from the dermis of a newborn infant (patient 5). The GAG distributions in the RET fractions were different from those in PAP fractions; of special note was the greater length of heparan sulfate chains from all RET fractions examined when compared to PAP fractions. There was a remarkable similarity in the GAG distributions of asc+ RET fractions when compared to the full-thickness AG2261 cell fractions. In summary, these studies demonstrate that asc- or asc+ "young" cells generate different GAG distributions in their substratum adhesion sites, whereas "old" cells from a full-thickness skin sample do not alter their distribution when shifted from asc- to asc+ (this distribution is different from that of "young" cells). Furthermore, analyses of GAGs in papillary and reticular cell fractions reveal significant differences between the two, with considerable similarity of asc+ reticular fractions to the full-thickness AG2261 fibroblasts, which is consistent with the enrichment of reticular fibroblasts in the skin of aging individuals.

Complementary adhesive responses of human skin fibroblasts to the cell-binding domain of fibronectin and the heparan sulfate-binding protein, platelet factor-4.

Plasma fibronectin (pFN) contains binding domains for an unidentified receptor on the surface of fibroblasts and for heparan sulfate chains of proteoglycans on these same cells. A series of experiments were designed to assess the relative importance of these activities in mediating substratum adhesion of human skin fibroblasts (strain 4449) grown in the absence of ascorbate (asc-) or in its presence (asc+) to minimize or maximize collagen production-maturation, respectively. The cell-binding fragment (CBF) of pFN was purified from chymotryptic digests free of any heparan sulfate-binding activity. The responses of cells to CBF were then compared with those mediated by the heparan sulfate-binding protein, platelet factor-4 (PF4). At early time points when cells had spread effectively on pFN, both asc- or asc+ cells extended spiky projections on PF4 and long projections on CBF with actively ruffling membranes at their tips. By 4 h, asc+ cells had spread much more effectively on CBF than asc+ cells on PF4 or asc- cells on either binding activity. Mixtures (w/w) of CBF:PF4 between 1:1 and 9:1 generated a more physiologically normal response than to either of the binding proteins alone, particularly for asc+ cells. Examination of cytoskeletal reorganization by fluorescence analysis with an antibody to 7S tubulin (for microtubules) and NBD-phallacidin (for F-actin) revealed condensations of microfilaments at the ruffling edges of asc- cells on CBF or on PF4 and for asc+ cells on PF4; in contrast, asc+ cells on CBF generated long bundles of microfilaments in their spreading lamellae within 4 h. Microtubule networks reorganized very well on CBF but only partially on PF4 with either cell type. Microfilament reorganization was comparable to that on intact pFN with CBF:PF4 mixtures of 1:1 and 9:1 for asc+ cells, whereas asc- cells generated condensations of microfilaments but little bundling. These studies reveal that the adhesive responses to mixtures of these two binding activities are significantly greater than to the individual activities and that the responses of asc+ cells approach the properties of cells on intact pFN, whereas asc- cells remain incapable of forming stress fiber-like bundles of microfilaments under all conditions.