A cytosolic inhibitor of human neutrophil elastase and cathepsin G

The neutrophil serine proteinases elastase and cathepsin G produce connective tissue injury, the extent of which depends on the balance between these enzymes and their inhibitors. The most important of these inhibitors is alpha 1-proteinase inhibitor, a member of a superfamily of homologous proteins known as serpins. Neutrophil cytosol inhibited the activities of human neutrophil elastase and cathepsin G in a dose-dependent fashion. To demonstrate formation of an enzyme-inhibitor complex, we combined 125I-elastase or 125I-cathepsin G with neutrophil cytosol or alpha 1-proteinase inhibitor and analyzed the products by polyacrylamide gel electrophoresis. Unbound elastase and cathepsin G each migrated to an apparent molecular weight of 25 kDa. In the presence of cytosol from neutrophils both radiolabeled enzymes migrated with a relative size of 68 kDa, whereas in the presence of alpha 1-proteinase inhibitor the relative size was 85 kDa. Enzyme-inhibitor complexes were stable in sodium dodecyl sulfate at 100 degrees C but were dissociated by hydrolysis in ammonium hydroxide (1.5 mol/L) at 37 degrees C. Formation of each complex was prevented by pretreatment of elastase or cathepsin G with diisopropylfluorophosphate, indicating that the inhibitor binds to the active site of the enzyme. Exposure of either alpha 1-proteinase inhibitor or neutrophil cytosol to the myeloperoxidase-H2O2-halide system prevented complex formation, suggesting the presence of an oxidizable amino acid at the binding site of the inhibitor. By electrophoretic analysis, the molecular weight of the cytosolic inhibitor was 43 kDa and neutrophils contained approximately 1 attomol of inhibitor per cell. The isoelectric points of the elastase and cathepsin G inhibitor were 5.5-5.9 and inhibitors of the two proteinases coeluted using size exclusion chromatography. These data demonstrate that human neutrophil cytosol contains a single serpinlike protein that inhibits elastase and cathepsin G. The inhibitor may be important in protecting the intracellular environment from proteolytic injury during degranulation.

Hematogenous dissemination of Mycobacterium tuberculosis in patients with AIDS

Proof of hematogenous dissemination of Mycobacterium tuberculosis was initially reported in the early 1900s and was noted to be most frequent in patients with miliary tuberculosis. More recently, M. tuberculosis bacteremia has been reported in human immunodeficiency virus (HIV)-infected patients. We describe 13 adult HIV-infected patients in whom hematogenous M. tuberculosis dissemination was evident. Although for most patients whose bone marrow aspirate cultures yielded M. tuberculosis a chest roentgenogram revealed a miliary pattern, roentgenograms for those with M. tuberculosis bacteremia usually revealed evidence of lobar or diffuse infiltrates. Most patients with M. tuberculosis bacteremia had other risk factors for M. tuberculosis, and many had a rapid death, suggesting acute fulminant infection. Our own experience suggests that there are various syndromes associated with hematogenous dissemination in patients infected with M. tuberculosis.

MR imaging of periosteal and cortical changes of bone

The changes seen in the periosteum and cortical bone are fundamental radiographic features of bone disease. The basic radiographic findings used for diagnosis of bone lesions (patterns of cortical destruction and of periosteal new bone formation) can be well identified with magnetic resonance (MR) imaging. The authors used comparative radiographic, computed tomographic, and MR images to illustrate patterns of periosteal reaction (simple, laminated, spiculated, Codman triangle), geographic and permeative cortical destruction, cortical erosion, cortical expansion and continuity, and intraosseous and extraosseous calcification. The only feature not well demonstrated by MR imaging is pattern or extent of soft-tissue calcification. Although MR images are not required for diagnosis of most peripheral bone lesions, when they are obtained, these fundamental diagnostic features should not be ignored.

Measurement of normal human airways response to beta-adrenoceptor stimulation using a forced oscillation technique

The purpose of the present study was to evaluate the responsiveness of normal human airways to beta-adrenoceptor stimulation using a forced oscillation technique. Seven normal volunteers (aged 25 +/- 2 year) were studied on three occasions, separated by weekly intervals, using a single-blind randomized design. On day 1, subjects were given cumulative doses of inhaled salbutamol (100, 200, 500, 1000 micrograms); and identical placebo was given on the other two visits. Respiratory oscillation impedance (Ros) was measured at baseline and 15 min after each dose increment. The coefficients of variation (CV) for short-term intra-individual variability on each placebo day were 7.5 and 9.5, and 9.6% for long-term variability (measured over all three visits). The 95% confidence values (2SD) for the change in Ros required to exclude natural variability were 0.39, 0.50 and 0.53 cmH2O l-1 s, respectively. There was a small fall in Ros in response to salbutamol although the mean maximum change (0.46 cmH2O l-1 s) was not significant (by ANOVA). Thus, the change in Ros (sensitivity) was no greater than the 95% confidence value for natural variability (reproducibility). Regression analysis also showed no evidence of a dose-response relationship for Ros.

Assembly of the neutrophil respiratory burst oxidase. Protein kinase C promotes cytoskeletal and membrane association of cytosolic oxidase components

Activated human polymorphonuclear neutrophils (PMNs) convert molecular oxygen into superoxide anion, a process known as the respiratory burst, through the activity of a latent multicomponent NADPH-dependent oxidase. Components of this respiratory burst oxidase include the membrane-bound cytochrome b558 and the cytosolic factors p47-phox and p67-phox. We initiated these studies based on three observations: 1) that stimulation of PMN oxidase activity is associated with translocation of the cytosolic oxidase components to the plasma membrane; 2) that p47-phox is phosphorylated during PMN activation and that there is a sequential relationship between phosphorylation of p47-phox in the cytosol and appearance of the phosphoprotein in the membran; and 3) that the predicted amino acid sequences of p47-phox and of p67-phox contain regions of homology to the SH3 or A domain of the src family of tyrosine kinases, a region found in a variety of proteins which interact with the cytoskeleton or the subplasmalemmal cytoskeleton. Thus the purpose of our studies was to examine the role of protein kinase C (PKC)-dependent phosphorylation in the stimulus-induced association of p47-phox and p67-phox with the plasma membrane and the cytoskeleton. Using the PKC activator phorbol myristate acetate (PMA) as the agonist, we found that activation of the respiratory burst oxidase was associated with translocation of cytosolic p47-phox and p67-phox to the plasma membrane as well as redistribution of p47-phox to the Triton-insoluble cytoskeleton. Furthermore, the PKC inhibitor staurosporine inhibited phosphorylation of p47-phox, interrupted the redistribution of cytosolic oxidase factors, and blocked PMA-induced generation of superoxide anion. Taken together these results indicate that PKC-dependent phosphorylation of p47-phox correlates with association of p47-phox with the cytoskeleton and with translocation of p47-phox and p67-phox to the plasma membrane, with the ensuing assembly of an active superoxide-generating NADPH-dependent oxidase.

Neutrophil nicotinamide adenine dinucleotide phosphate oxidase assembly. Translocation of p47-phox and p67-phox requires interaction between p47-phox and cytochrome b558

Two of the cytosolic NADPH oxidase components, p47-phox and p67-phox, translocate to the plasma membrane in normal neutrophils stimulated with phorbol myristate acetate (PMA). We have now studied the translocation process in neutrophils of patients with chronic granulomatous disease (CGD), an inherited syndrome in which the oxidase system fails to produce superoxide due to lesions affecting any one of its four known components: the gp91-phox and p22-phox subunits of cytochrome b558 (the membrane-bound terminal electron transporter of the oxidase), p47-phox, and p67-phox. In contrast to normal cells, neither p47-phox nor p67-phox translocated to the membrane in PMA-stimulated CGD neutrophils which lack cytochrome b558. In one patient with a rare X-linked form of CGD caused by a Pro----His substitution in gp91-phox, but whose neutrophils have normal levels of this mutant cytochrome b558, translocation was normal. In two patients with p47-phox deficiency, p67-phox failed to translocate, whereas p47-phox was detected in the particulate fraction of PMA-stimulated neutrophils from two patients deficient in p67-phox. Our data suggest that cytochrome b558 or a closely linked factor provides an essential membrane docking site for the cytosolic oxidase components and that it is p47-phox that mediates the assembly of these components on the membrane.

Pathogenesis of pulmonary fibrosis in interstitial lung disease. Alveolar macrophage PDGF(B) gene activation and up-regulation by interferon gamma

Alveolar macrophages are believed to be central in orchestrating the fibrotic response in interstitial lung disease (ILD). To test the hypothesis that macrophages from patients with ILD were dedicated to growth factor production and that this was independent of other indices of macrophage activation, we measured the mRNA of the B chain of PDGF and TGF-beta, as well as HLA-DR-alpha in alveolar macrophages from patients with ILD and from normal control subjects. When alveolar macrophages were examined immediately after lavage, cells from patients with ILD had increased PDGF(B) but similar TGF-beta and HLA-DR-alpha mRNA when compared with control subjects. Discoordinate regulation of these genes was observed when alveolar macrophage PDGF(B) mRNA increased while TGF-beta and HLA-DR-alpha mRNA decreased after culture for 24 h. This response was not disease-related as these changes were similar in cells from patients with ILD and from control subjects. Because a lymphocytic alveolitis is present in many cases of ILD, we asked whether interferon gamma (IFN-gamma) modulated the activation of these genes. In both the patients and the control subjects, PDGF(B) and HLA-DR-alpha, but not TGF-beta, mRNA were increased after incubation with IFN-gamma. These results indicate that PDGF(B) mRNA may be increased in alveolar macrophages in ILD and that PDGF(B), TGF-beta, and HLA-DR-alpha are independently regulated genes in alveolar macrophages, but that IFN-gamma increases both PDGF(B) and HLA-DR-alpha mRNA. We speculate that IFN-gamma induced PDGF(B) gene activation may be an important mechanism by which lymphocytes promote pulmonary fibrosis.

Immunochemical and electrophoretic analyses of phosphorylated native and recombinant neutrophil oxidase component p47-phox

Human polymorphonuclear neutrophils (PMNs) possess a potent oxygen-dependent microbicidal system that depends on the activity of a stimulus-activated multicomponent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Patients with chronic granulomatous disease (CGD) lack activity of this oxidase and consequently suffer severe and frequent infections. Components of the oxidase include both membrane-bound factors (most notably, cytochrome b559, which is absent in the X-linked form of CGD) and at least two cytosolic factors, one or the other of which is absent in autosomal CGD. Patients with CGD, particularly the autosomal type, have defective phosphorylation of proteins in the 44 to 48 Kd range. A polyclonal antiserum (B-1) that recognizes cytosolic oxidase components of 47 and 67 Kd was used to identify phosphoproteins in a cell-free oxidase system. Two-dimensional gel electrophoresis showed the identity of the 47-Kd cytosolic protein (p47-phox) recognized by B-1 and the cationic 47-Kd protein that is phosphorylated in normal but not p47-phox-deficient CGD cytosol during activation of the NADPH-dependent oxidase. All full-length and C-terminal recombinant p47-phox proteins augmented the superoxide-generating capacity of the cell-free system and were phosphorylated when added to cytosol from normal subjects or from a patient with p47-deficient autosomal CGD. These studies provide compelling evidence that the 47-Kd cationic protein that is a substrate for phosphorylation during the activation of PMNs is, in fact, p47-phox, a cytosolic protein previously shown to be critical for normal activity of the NADPH-dependent oxidase of PMNs.

Total body irradiation as an alternative to systemic chemotherapy in small-cell anaplastic lung cancer

The effectiveness of total body irradiation (TBI) plus local radiotherapy in the treatment of small-cell lung cancer was studied in 13 patients, using 4,000 cGy in 15 fractions over three weeks to the local site and 150 cGy in ten fractions over two weeks to the whole body. The mean survival for 12 patients was 31 weeks, with a median survival of 32 weeks. One patient received six courses of combination chemotherapy for recurrent disease four months after TBI without marrow depression and survived 72 weeks, the longest survivor in this series. Brain metastases occurred in only one patient, the most common site of metastases being the liver. All patients tolerated TBI well without nausea, vomiting or hair loss. When bone marrow suppression occurred it was asymptomatic, requiring no treatment and resolving within eight weeks.

Two cytosolic components of the neutrophil NADPH oxidase, P47-phox and P67-phox, are not flavoproteins

Two cytosolic proteins, p47-phox and p67-phox, have been shown to be essential components of the NADPH-dependent oxidase of human neutrophils, although the specific role of each of these proteins in the multicomponent electron transport complex is undetermined. The superoxide-generating activity of this oxidase can be reproduced in a cell-free system, combining cytosol and membranes from unstimulated neutrophils in the presence of fatty acid and NADPH. In the present studies, cytosol was treated with myristic acid, arachidonic acid, or sodium dodecyl sulfate in the absence of membranes and the resultant precipitate collected by centrifugation and analyzed. Both p47-phox and p67-phox precipitated in the presence of fatty acid. However, neither FAD nor FMN was localized in the precipitates, even though substantial amounts of p47-phox and p67-phox precipitated. These results suggest that neither p47-phox nor p67-phox is a flavoprotein and that neither, therefore, is the oxidase component which accepts electrons from NADPH.

Adherence-dependent increase in human monocyte PDGF(B) mRNA is associated with increases in c-fos, c-jun, and EGR2 mRNA

Adherence is an important initial step in the transition of a circulating monocyte to a tissue macrophage. This differentiation is accompanied by an augmented capacity to generate growth factors. We hypothesized that adherence itself might be an important trigger for a sequence of gene activation culminating in cells with increased mRNA encoding profibrotic growth factors such as platelet-derived growth factor B subunit (PDGF[B]) and transforming growth factor-beta (TGF-beta). After in vitro adherence, human monocytes had a biphasic increase in PDGF(B) mRNA with peaks at 6 h and 13 d. No increase in TGF-beta mRNA was observed. The 6-h increase in PDGF(B) mRNA was adherence dependent, and in addition, was abrogated when the cytoskeletal integrity was compromised by cytochalasin D. The 6-h increase in PDGF(B) mRNA was unaltered by adherence in the presence of the monocyte stimulus lipopolysaccharide. Adherence to either fibronectin or collagen-coated plastic had little consistent effect on PDGF(B) mRNA accumulation. The increased PDGF(B) mRNA observed in adherent monocytes was accompanied by increases in mRNAs of the early growth response genes c-fos (maximal at 20 min), c-jun, and EGR2 (maximal at 6-24 h). The increase in c-jun and EGR2, but not c-fos, mRNA was also abrogated by cytochalasin D. These observations suggest that adherence results in increases of c-fos, c-jun, EGR2, and PDGF(B) mRNA. In addition, the increases in c-jun, EGR2, and PDGF(B) may depend on cytoskeletal rearrangement. Modulation of these events at the time of adherence offers a mechanism by which differential priming of the cells may be accomplished.

Transforming growth factor-beta modulates plasminogen activator activity and plasminogen activator inhibitor type-1 expression in human keratinocytes in vitro

Transforming growth factor beta (TGF-beta) is a multifunctional mediator with effects on cellular growth, differentiation, and extracellular matrix (ECM) metabolism. Because TGF-beta stimulates fibronectin expression in cultured human keratinocytes, we wished to determine whether it might also affect ECM degradation through the plasminogen activator (PA)-plasminogen activator inhibitor (PAI) system. Immunofluorescence of human keratinocytes using a monospecific antiserum to type 1 PAI (PAI-1) showed enhanced cellular and ECM staining when they were cultured in the presence of TGF-beta. The antiserum also identified an Mr 50,000 protein in conditioned media that was markedly enhanced by TGF-beta. A corresponding stimulation of PAI-1 mRNA was demonstrated by quantitative RNA blot analysis. Total plasminogen activating activity of conditioned medium was markedly decreased by TGF-beta. Zymography showed this to be at least partially due to decreased secreted urokinase activity. TGF-beta may play an important role in stabilizing the provisional matrix synthesized by keratinocytes in healing wounds.

Fibronectin fragments containing the RGDS cell-binding domain mediate monocyte migration into the rabbit lung. A potential mechanism for C5 fragment-induced monocyte lung accumulation

Many inflammatory processes are characterized by an early phase of neutrophil migration and a later phase of monocyte migration into the inflammatory site. Mechanisms that govern the transition between phases are the subject of these investigations. Acute lung inflammation induced by C5 fragments in the rabbit leads to an initial neutrophil influx and plasma leakage into the alveolar space, followed by monocyte influx that we have previously shown to be dependent on prior emigration of neutrophils. Neutrophil enzymes are known to cleave intact fibronectin into fragments that are monocyte chemotaxins in vitro. Accordingly, generation of appropriate fibronectin fragments in situ by proteolytic enzymes from infiltrating neutrophils might represent a potential mechanism for attraction of monocytes into the lung. The studies reported herein demonstrate that a 120-kD fragment of fibronectin containing the RGDS fibroblast cell-binding domain induced monocyte migration into the rabbit lung in vivo. Intact fibronectin was inactive. A significant proportion of the monocyte migration was neutrophil independent. Intact fibronectin was present in bronchoalveolar lavage fluid from C5 fragment-treated animals rendered neutropenic, but absent in lavage from normal C5 fragment-treated animals. Fibronectin fragments were present in bronchoalveolar lavage fluid from both C5 fragment-treated and control rabbits. In addition, the amount of fibronectin was significantly increased in lavage of C5 fragment-treated normal but not neutropenic animals. Monoclonal antibodies directed against an epitope of fibronectin containing the RGDS cell-binding domain significantly inhibited the C5 fragment-induced monocyte migration, but not neutrophil migration. These studies suggest that chemotactic fibronectin fragments may in part be responsible for the recruitment of monocytes into areas of acute lung inflammation.

Spectrum of Cryptococcus neoformans infection in 68 patients infected with human immunodeficiency virus

Sixty-eight patients infected with human immunodeficiency virus (HIV) and Cryptococcus neoformans who presented to three major medical centers in New Orleans, Louisiana, were studied retrospectively. In patients with meningitis the most common presenting symptoms were fever and headache. Those without central nervous system involvement generally had an isolated pulmonary infection due to C. neoformans and presented with cough and dyspnea. CSF parameters were abnormal in 41% of patients, and the India ink preparation was positive in 88% of patients with cultures of CSF positive for C. neoformans. The overall median survival time for the 47 patients who died was 5 months, with a range of 0-22 months. Of the 27 patients who received maintenance therapy with amphotericin B, two (7%) relapsed. The only factors found to be associated with a poor prognosis were abnormal computed tomography of the head and altered mental status on presentation. C. neoformans infections in HIV-infected patients remain difficult to treat and have a poor prognosis.

Comparison of the efficacy and systemic effects of 4 mg and 8 mg formulations of salbutamol controlled release in patients with asthma

The purpose of the present study was to compare the efficacy and systemic effects of 4 mg and 8 mg doses of salbutamol controlled release (SCR) after single dosing and at steady state in patients with asthma. Fifteen asthmatic patients (Age 36 y, FEV1 85% predicted) were given SCR 4 mg and 8 mg twice daily for 7 days in a randomised double-blind cross-over design, with at least 7 days washout between treatments. There were no differences between the bronchodilator effects of 4 mg and 8 mg doses. There was no evidence of tolerance to the bronchodilator effects after chronic dosing. Morning and evening PEFR measurements also showed improvements during treatment with SCR 4 mg and SCR 8 mg, although there were no differences between the two formulations. Both doses of SCR caused significant objective tremor responses which were maintained after chronic dosing. The 8 mg dose produced a larger tremor response after single dosing, but not at steady-state. Subjective tremor occurred in 7 patients with SCR 8 mg, and in 2 patients with SCR 4 mg. There were no cardiac arrhythmias on Holter ECG monitoring. These results suggest that the 8 mg dose of SCR was no more effective than the 4 mg formulation, and was associated with more systemic adverse effects.

Comparison of the effects of prolonged treatment with low and high doses of inhaled terbutaline on beta-adrenoceptor responsiveness in patients with chronic obstructive pulmonary disease

Eleven patients with chronic obstructive pulmonary disease (age, 61 +/- 2 yr; FEV1, 1.36 +/- 0.24 L, 46 +/- 7% predicted) were given 4 wk of treatment with either a conventional low dose of inhaled terbutaline (LDT), 500 micrograms four times a day, or a high dose of inhaled terbutaline (HDT), 2,000 micrograms four times a day, delivered by a spacer. A randomized double-blind crossover design was used with 2-wk run-in and washout periods, when ipratropium bromide was substituted for inhaled beta-agonists. Dose response curves (DRC) to cumulative doubling doses of inhaled terbutaline (125 to 4,000 micrograms) were constructed after each treatment period, and baseline spirometry, finger tremor (Tr), plasma potassium (K), plasma cAMP, and ECG (HR and T wave) were measured at each dose step of the DRC. Daily PEFR measurements (A.M. and P.M.) and Holter ECG were performed during run-in and treatment periods. Baseline values for FEV1 were not significantly different during run-in, treatment, or washout periods. There were dose-related increases in FEV1 (p less than 0.0001) with no significant differences between DRC after treatment with HDT compared with those with LDT: delta FEV1 max, 0.46 +/- 0.14 L, 15.5 +/- 3.7% predicted (HDT); 0.50 +/- 0.11 L, 16.0 +/- 3.1% predicted (LDT). There were also no differences between DRC for delta FVC: 1.08 +/- 0.22 L, 31.1 +/- 5.4% predicted (HDT); 0.99 +/- 0.14 L, 28.5 +/- 3.8% predicted (LDT). There were no significant changes in K or HR in response to cumulative doses of terbutaline after either treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of microfilaments in maintenance of proximal tubule structural and functional integrity

To determine the selective effect of microfilament disruption on both cellular structure and function, microfilament-specific doses of cytochalasin D (10 microM) were used in an isolated perfused kidney system. Structurally, cytochalasin D resulted in extensive disruption of the apical surface with blebbing, vacuolization, and patchy loss and fusion of microvilli. Functionally, cytochalasin D resulted in an initial decrease in glomerular filtration rate (300.8 +/- 29.9 vs. 541.6 +/- 51 microliters.min-1.g-1, P less than 0.05) with subsequent stabilization throughout the duration of the perfusion. In contrast, the tubular reabsorption of sodium decreased significantly in a linear fashion from 97.1 +/- 0.7 to 64.3 +/- 7.0% over the duration of the perfusion. Similarly, the tubular reabsorption of lithium decreased linearly from 74.8 +/- 2.6%, before the addition of cytochalasin, to 33.6 +/- 6.8% by the end of the perfusion. Correlation of the decrements in percent tubular reabsorption of sodium and lithium for individual kidneys was 0.87 (P less than 0.01), suggesting the effect of microfilament disruption on tubular reabsorption of sodium was localized primarily to the proximal tubule. Because ischemic injury is characterized by time-dependent structural alterations in the apical membrane of proximal tubule cells, we set out to determine whether microfilament disruption occurs during ischemic acute renal failure. Utilizing indirect immunofluorescence with an anti-actin antibody, control kidneys demonstrated intact circumferential apical immunofluorescence representing brush-border and terminal web actin staining. Fifteen minutes of ischemia resulted in multiple large gaps in the terminal web, and 50 min of ischemia caused diffuse redistribution of actin immunofluorescence throughout the cytoplasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibronectin matrix deposition and fibronectin receptor expression in healing and normal skin

During cutaneous tissue organization, numerous critical interactions occur between cells and the extracellular matrix (ECM). Cell-matrix interactions depend on the presence of ECM receptors. Many ECM receptors, known as integrins, are heterodimeric glycoproteins consisting of one alpha and one beta chain. Integrins containing beta 1 or beta 3 chains are ECM receptors, whereas those containing beta 2 chains are leukocyte cell-cell receptors. We have used porcine cutaneous wounds as a paradigm for tissue organization and probed healing wounds and adjacent normal skin with polyclonal antibodies to fibronectin and fibronectin (alpha 5 beta 1) receptor. During re-epithelialization, the epidermis transits over a provisional matrix containing fibronectin. Migrating epidermal cells expressed fibronectin receptors in a bright linear peripheral pattern. At 10 days, when reepithelialization was complete and the basement membrane was re-established, the fibronectin matrix was markedly reduced and fibronectin-receptor expression was limited to the basolateral aspect of basal cells, as observed in normal epidermis. Beneath the migrating epidermis in 5-d wounds, granulation tissue had filled 80% of the wound space. Day-5 wound fibroblasts did not express fibronectin nor other beta 1 integrin receptors, were randomly oriented, and contained no actin bundles. Fibronectin fibrils were assembled on the surfaces of day-5 wound fibroblasts but formed few linkages between cells. Day-7 wound fibroblasts expressed fibronectin receptors, contained peripheral cytoplasmic actin bundles consistent with a contractile fibroblast phenotype, and were coaligned across the wound in parallel array with interconnecting fibronectin fibrils. The wounds contracted between 7 and 10 days. Thus the migrating epidermis consistently expressed fibronectin receptors. Fibronectin receptors were expressed by fibroblasts just prior to wound contraction.