Endothelial barrier dysfunction caused by LPS correlates with phosphorylation of HSP27 in vivo.

Lung edema during sepsis is triggered by formation of gaps between endothelial cells followed by macrophage infiltration. Endothelial gap formation has been proposed to involve changes in the structure of the actin filament cytoskeleton. Heat shock protein 27 (HSP27) is believed to modulate actin filament dynamics or structure, in a manner dependent on its phosphorylation status. We hypothesized that HSP27 may play a role in endothelial gap formation, by affecting actin dependent events in endothelial cells. As there has been no report concerning HSP27 in lung edema in vivo, we examined induction and phosphorylation of HSP27 in lung following LPS injection, as a model of sepsis. In lung, HSP27 mainly localized in capillary endothelial cells of the alveolus, and in smooth muscle cells of pulmonary arteries. HSP27 became significantly more phosphorylated at 3 h after LPS treatment, while the distribution of HSP27 remained unchanged. Pre-treatment with anti-TNFalpha antibody, which has been shown to reduce lung injury, blocked increases in HSP27 phosphorylation at 3 h. HSP27 phosphorylation was also increased in cultured rat pulmonary arterial endothelial cells (RPAEC) by treatment with TNFalpha, LPS, or H2O2. This phosphorylation was blocked by pre-treatment with SB203580, an inhibitor of the upstream kinase, p38 MAP kinase. Increased endothelial permeability caused by H2O2 in vitro was also blocked by SB203580. The amount of actin associated with HSP27 was reduced after treatment with LPS, or H2O2. In summary, HSP27 phosphorylation temporally correlated with LPS induced pathological endothelial cell gap formation in vivo and in a cell culture model system. This is the first report of increased HSP27 phosphorylation associated with pathological lung injury in an animal model of sepsis.

Use of a cell-based interactive wound dressing to enhance healing of excisional wounds in nude mice.

The need to have viable, metabolically active cells to heal wounds is well recognized, because there is clear evidence that cellular dysfunction delays healing. This suggests that addition of metabolically active cells to a delayed healing tissue could enhance the healing of the tissue. Therefore, we examined the ability of an interactive wound dressing composed of human keratinocytes or fibroblasts grown on microporous bio-reactor beads and placed into a polyethylene bag to facilitate the delayed healing of wounds in nude mice. A 1 x 1 cm wound was made on the backs of nude mice, and the dressing with or without viable cells was placed on the wound for 8 to 24 days, with dressing changes every other day. Wound area and time to heal measurements were compared after various interventions including freeze-thawing. The data shows that the interactive wound dressing was more effective than the control dressings (p<0.05) and that keratinocytes were more effective than fibroblasts in wound healing (p<0.05). Freezing-thawing of the interactive wound dressings destroyed the activity of the dressing. Studies examining cells using a live/dead viability assay showed that both keratinocytes and fibroblasts were alive after 2 days on the mice. Surprisingly, human fibroblasts appeared to exhibit bridging behavior that is indicative of fibroblast proliferation. We conclude that a simple interactive wound dressing using either keratinocytes or fibroblasts can enhance the healing of wounds in nude mice.

TGF-beta3 in the treatment of pressure ulcers: a preliminary report.

OBJECTIVE: To determine the safety, tolerability, and efficacy of TGF-beta3 in the treatment of chronic, nonhealing pressure ulcers. DESIGN: A subset analysis of data from a randomized, blind, parallel, placebo-controlled trial involving 270 patients. SETTING: University of Michigan Wound Care Center. PATIENTS: A total of 14 patients (6 women and 8 men aged > or = 18 years) with pressure ulcers were randomly assigned to 1 of 3 groups to receive once daily topical application of recombinant TGF-beta3 or placebo gel for a period of no more than 16 weeks. Group 1 (n=4) received 1.0 microg/cm2 of TGF-beta3, Group 2 (n=5) received 2.5 microg/cm2 of TGF-beta3, and Group 3 (n=5) received placebo gel. All subjects received standardized wound care as well. Weekly evaluations were performed for efficacy, determined by relative wound surface areas and volumes, and were compared with initial baseline values and safety parameters. MAIN OUTCOME MEASURE: Reduction in pressure ulcer area and volume. MAIN RESULTS: Group 2 had a significantly increased rate of wound healing at the fourth visit (P<.05). No significant difference was observed in the healing rate among the groups at the termination of the study. Treatment with TGF-beta3 was well tolerated and there were no significant adverse reactions. CONCLUSION: The findings of this study indicate that the topical application of TGF-beta3 is safe and useful in the treatment of pressure ulcers and is most effective at the earliest stages of therapy.

Osteomyelitis related to pressure ulcers: the cost of neglect.

Twelve patients with documented chronic osteomyelitis of the pelvis resulting from truncal pressure ulcers were examined retrospectively to identify the cost of treatment for this significant health care problem. The retrospective review of each case spanned an 18-month period--6 months prior to the initial positive bone biopsy to 1 year following bone biopsy. The financial charges associated with treatment of osteomyelitis were identified using the University of Michigan Health System's databases for hospital charges, professional charges, and pharmacy charges. Prior treatment of these patients included surgical debridement of the pressure ulcer, pelvic bone biopsy, and culture-specific antibiotic therapy. The total charges for this group of 12 patients was $715,204, or an average charge of $59,600 per patient. Each patient was hospitalized, with hospitalization charges of $587,212, or an average of $48,934 per patient. Pharmacy charges for culture-specific antibiotics totaled $85,217 for the 12 patients. Six of 8 flap repairs achieved successful surgical closure of the pressure ulcer (75%) postantibiotic therapy. Surgery charges are not included in the totals.

Role of platelet-derived growth factor as an adjunct to surgery in the management of pressure ulcers.

Management options for pressure ulcers include local wound care, surgical repair, and, more recently, topical application of platelet-derived growth factor (PDGF). PDGF is a glycoprotein that is mitogenic for mesenchymal cells and has been studied extensively for applicability in promoting the healing of chronic human wounds. Using data obtained from a multicenter clinical trial for the treatment of full-thickness pressure ulcers, a subset analysis was performed to investigate the outcome of salvage surgery for pressure ulcers, after incomplete closure occurred with the topical use of either recombinant human PDGF-BB (rhPDGF-BB) or placebo gel. At the University of Michigan Wound Care Center, subset data from a randomized, double-blind, placebo-controlled, parallel group clinical trial were reviewed to compare the effects of three concentrations of rhPDGF-BB on full-thickness pressure ulcers of the trunk with those of the placebo. Twenty-eight patients were enrolled and 27 completed the trial. An intent-to-treat analysis was used to evaluate data. If the ulcer did not heal by the end of the 16-week trial period, the surgeon, still blinded to the treatment group, offered salvage surgical repair of the pressure ulcer. Eleven patients underwent salvage surgical repair using myocutaneous flaps, primary closure, or skin grafts. Of three patients who received placebo followed by surgery, none progressed to full healing within 1 year. Of 12 patients in the treatment group who received rhPDGF-BB and salvage surgery, 11 (92 percent) ultimately healed the ulcers within 1 year after the start of the clinical trial. These findings suggest that treatment with rhPDGF-BB before surgery enhances the ability to achieve a closed wound over surgery alone. It must yet be determined to what degree rhPDGF-BB contributed to the excellent results seen in the rhPDGF-BB/surgery group. It is possible that rhPDGF-BB "primes" the local wound milieu to make it more responsive to complete closure following surgical treatment.

Becaplermin gel in the treatment of pressure ulcers: a phase II randomized, double-blind, placebo-controlled study.

Pressure ulcers are associated with significant rates of morbidity and mortality, particularly in the geriatric and spinal cord-injured populations. Newer pharmacologically active therapies include the use of topically applied recombinant human platelet-derived growth factor-BB (becaplermin), the active ingredient in REGRANEX) (becaplermin) Gel 0.01%, which has been approved in the United States for treatment of lower extremity diabetic neuropathic ulcers that extend into the subcutaneous tissue or beyond and have an adequate blood supply. In this study, the efficacy of becaplermin gel in the treatment of chronic full thickness pressure ulcers was compared with that of placebo gel. A total of 124 adults (>/= 18 years of age) with pressure ulcers were assigned randomly to receive topical treatment with becaplermin gel 100 microg/g (n = 31) or 300 microg/g (n = 32) once daily alternated with placebo gel every 12 hours, becaplermin gel 100 microg/g twice daily (n = 30), or placebo (sodium carboxymethylcellulose) gel (n = 31) twice daily until complete healing was achieved or for 16 weeks. All treatment groups received a standardized regimen of good wound care throughout the study period. Study endpoints were the incidence of complete healing, the incidence of >/= 90% healing, and the relative ulcer volume at endpoint (endpoint/baseline). Once-daily treatment of chronic pressure ulcers with becaplermin gel 100 microg/g or 300 microg/g significantly increased the incidences of complete and >/= 90% healing and significantly reduced the median relative ulcer volume at endpoint compared with that of placebo gel (p < 0.025 for all comparisons). Becaplermin gel 300 microg/g did not result in a significantly greater incidence of healing than that observed with 100 microg/g. Treatment with becaplermin gel was generally well tolerated and the incidence of adverse events was similar among treatment groups. In conclusion, once-daily application of becaplermin gel is efficacious in the treatment of chronic full thickness pressure ulcers.

Effects of glutathione depletion on oxidant-induced endothelial cell injury.

Ischemia-reperfusion produces edema in vivo by disrupting endothelial cell junctional integrity. A cultured rat pulmonary artery endothelial cell (RPAEC) model was used to analyze the effects of oxidants and ischemic plasma in vitro. RPAEC cultures were treated with ischemic human plasma from transverse rectus abdominis musculocutaneous (TRAM) flaps following mastectomy or with an equal quantity of nonischemic plasma taken peripherally. Endothelial cells treated with ischemic plasma rounded and formed gaps within 5 min, then ruffled and blebbed after 10 min. Cultures treated with human nonischemic plasma had no gross morphological changes. Additionally, cultures treated with human ischemic plasma demonstrated an increase in diffusion rate of 125I-albumin across monolayers while monolayers treated with human nonischemic plasma had no increase in diffusion rate. RPAEC monolayers were treated with malic acid diethyl ester (DEM) or L-buthionine-[S, R]-sulfoximine (BSO) to decrease cellular stores of glutathione before exposure to oxidant stress. Cultures depleted of cellular glutathione stores were significantly (P < 0.05) more susceptible to 50 microM H2O2 than controls, as determined by an increase in diffusion rate of 125I-albumin across monolayers. To determine if ischemic plasma effects were mediated by oxidants, cultures were depleted of glutathione by DEM or BSO pretreatment before exposure to plasma from the ischemic hind limbs of Sprague-Dawley rats. Glutathione-depleted RPAEC monolayers were significantly (P < 0.05) and substantially (2-3 X) more susceptible to the effects of ischemic plasma than were cultures with normal glutathione levels. Glutathione depletion had no effect on cultures treated with an equal amount of nonischemic plasma from sham-operated rats. These data strongly suggest that ischemic plasma in the absence of any cellular component are able to induce an oxidant injury in endothelial cells and thereby compromise junctional integrity.

TNF-alpha potentiates oxidant and reperfusion-induced endothelial cell injury.

Pulmonary edema following reperfusion is a major clinical problem. Changes in endothelial cell shape induced by oxidant injury may account for immediate capillary leakage associated with reperfusion injury. In these experiments we examined the role of tumor necrosis factor-alpha (TNF-alpha) in acute endothelial cell injury following ischemia-reperfusion. Sprague-Dawley rats were treated with a neutralizing antisera directed against TNF-alpha prior to production of distal ischemia. These rats demonstrated a significant reduction (P < 0.05) in acute lung edema in response to 4 hr of ischemia and 30 min of reperfusion when compared to rats undergoing the same procedure without antisera treatment. An in vitro model was developed to determine if TNF-alpha had a direct effect on endothelial cell response to ischemia-reperfusion. The effects of TNF-alpha and oxidant stress on the integrity of cultured endothelial cell monolayers was measured. Rat pulmonary artery endothelial cell monolayers reacted in vitro to oxidant stress by an increase in permeability. The cells changed shape and an increase in diffusion of 125I-albumin across cell monolayers resulted when these cells were exposed to 50 microM hydrogen peroxide (H2O2) or plasma from the ischemic hind limb of a Sprague-Dawley rat (50 microliters/ml). Pretreatment of cultured cells with low levels of recombinant mouse TNF-alpha significantly affected both the cell shape change and the increase in permeability (P < 0.05). Increased permeability of cell monolayers in vitro was not due to cell lysis as determined by media lactate dehydrogenase levels. The effect appeared to be due to cellular rounding and contraction seen using video time lapse microscopy. These data suggest a direct effect of TNF-alpha on endothelial cells, whereby the cells are rendered more susceptible to oxidant injury accompanying reperfusion.

Oxidant stress: the role of the glutathione redox cycle in skin preconditioning.

The role of the glutathione redox cycle in cellular protection form skin necrosis during the ischemic stress response (preconditioning) is unknown. In this series of experiments, we tested the hypothesis that oxidant stress reduces available total glutathione during injury and contributes to skin necrosis in flaps. Dorsal skin flaps (10 x 4 cm) were raised as acute flaps and skin grafts were obtained from the flaps at 0, 1, 4, 6, 12, or 24 hr. Some flaps were preconditioned as bipedicle flaps for 24, 48, 72, or 96 hr and the distal attachment divided before skin grafts were obtained 24 hr later. Flap survival was measured at 7 days. Total glutathione (GSH) and oxidized GSH (GSSG) were extracted and their levels determined enzymatically. Tissue GSH reductase (GR) activity was assayed with a spectrofluorometer and expressed as mumoles of NADPH oxidized/hr/g. Biochemical data were compared between the proximal and distal ends of the flaps using a two-tailed Student t test while differences between groups were compared using ANOVA. Skin necrosis was 5.4 +/- 0.12 cm in the distal ends at 7 days in acute flaps, while there was no skin necrosis in flaps preconditioned for 7 days. In acute flaps, total GSH levels fell precipitously in the distal end at 24 hr (P < 0.05). However, after 72 hr of preconditioning, the GSH levels in the distal end of the flap remained elevated while GSSG levels were undetectable. At 24 hr of ischemia, GR activity was 79 +/- 4 in the distal ends of acute flaps, while after preconditioning and 24 hr of ischemia, the GR activity increased to 172 +/- 13 in the distal ends (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Is aggressive surgical management justified in the treatment of Merkel cell carcinoma?

Since its original description in 1972, we have seen and personally treated a group of 15 patients with Merkel cell carcinoma at the Vanderbilt Medical Center and the Nashville VA Hospital. We will review the demographics, management, and clinical course of this extremely lethal but initially benign appearing cutaneous malignancy. The majority of lesions occur on the head and neck, followed by the extremities and trunk. Location of the primary tumor has no effect on outcome. Despite a high mortality in our series (10 of 15), early recognition and aggressive surgical therapy may be the only way to prolong survival. No other adjuvant therapy has proved effective.

Venoatrial pathways after the Mustard operation for transposition of the great arteries: anatomic and functional MR imaging.

PURPOSE: To evaluate spin-echo (SE) and cine gradient-echo (GRE) magnetic resonance (MR) imaging with velocity mapping for detecting late complications of the Mustard operation. MATERIALS AND METHODS: Twenty-one patients were studied with MR imaging 1-22 years after undergoing the Mustard operation. Twenty were also studied with transthoracic echocardiography, 18 with angiocardiography, and five with transesophageal echocardiography. RESULTS: MR imaging showed no venoatrial obstruction in nine patients. This result was confirmed with angiocardiography in seven cases and postmortem examination in one case. In one case, MR imaging demonstrated a leak at the baffle suture line. Of 12 cases with venoatrial obstruction at MR imaging, nine were confirmed with angiocardiography or surgery. There were two false-positive MR studies and one case in which no conclusion was reached. CONCLUSION: With addition of cine GRE sequences and velocity mapping to SE sequences, MR imaging is a useful noninvasive method of investigating late complications of the Mustard operation.

Acute skin injury releases neutrophil chemoattractants.

BACKGROUND: Progressive or ongoing skin necrosis after traumatic injury is well known. Experimental evidence has associated these events with neutrophil activation and secondary oxidant injury. To determine the mechanism by which neutrophils migrate to a site of injury, cytokine release from injured skin was measured. METHODS: Twenty-five skin biopsy specimens of acute partial thickness skin injuries were compared with uninjured skin of the same patient. Conditioned medium from explanted skin was assayed for tumor necrosis factor (TNF), interleukin-6 (IL-6), and IL-8. RESULTS: Acute skin injury resulted in a significant release of IL-8 but not IL-6 or TNF. In eight patients gradient cytokine release was found; IL-8 levels for partial thickness burn were 26.4 ng/ml, for unburned skin adjacent to the burn were 2.1 ng/ml, and for distal normal skin were 0.2 ng/ml. CONCLUSIONS: IL-8 is released from acutely injured skin; IL-6 and TNF are not. This selective release suggests a mechanism whereby neutrophils are recruited into injured tissue. These neutrophils might then induce further injury, increasing the extent of posttraumatic tissue loss.

dT diaphorase: increased enzyme activity and mRNA expression in oxidant stress of skin.

DT diaphorase is a flavoprotein that enzymatically transfers two electrons from quinones as intermediate substrates and has been reported to increase its activity in the liver after exposure to toxicants. In this series of experiments, we tested the hypothesis that DT diaphorase also increases its activity after exposure to oxidants following gradient ischemia in skin. Using dorsal rat flaps, oxidant stress was induced immediately or during a 7-day period of preconditioning as a bipedicle flap before the distal attachment was divided. DT diaphorase activity (delta Abs/min/100 g) or expression of message was measured during the period of preconditioning to determine the relationship between skin survival, enzyme activity, and expression of message. There was 4.7 +/- 0.8 cm of skin necrosis in the distal end of acute flaps while the preconditioned flaps had no skin necrosis after the distal attachment was divided. In the acute flaps, the DT diaphorase activity was equal throughout the flap for the first 6 hr. After 24 hr of ischemia, the DT diaphorase activity was significantly higher in the proximal end of the flap (1.83 +/- 0.21 delta Abs/min/100 g) than that in the distal end (0.005 +/- 0.01 delta Abs/min/100 g), which was significant (P < 0.05). In the preconditioned flaps, enzyme activity did not increase but there was as 50-fold increase in DT diaphorase activity at the distal end 24 hr after they were divided (P < 0.05). Maximal enzyme induction of DT diaphorase activity occurred after 4 days of preconditioning and correlated with the maximal expression of mRNA. These studies provide the first evidence that DT diaphorase enzyme activity is inducible after oxidant stress. The data also suggests that DT activity remains elevated for at least 6 hr of ischemia and may be a potential source of anti-oxidant activity in ischemic skin.

Validation of measurement of regional myocardial perfusion in humans by ultrafast x-ray computed tomography.

The objective was to validate the measurement of myocardial perfusion in humans by ultrafast computed tomography (CT), by comparing measurements with those from single photon emission computed tomography (SPECT). Measurement of myocardial perfusion with high spatial resolution (including the differentiation of subendocardial and subepicardial perfusion) may be possible by ultrafast CT in humans. Although there are encouraging data from experiments with dogs, the technique has not been validated in humans. In 11 patients, ultrafast CT measurement of regional perfusion in a single short-axis slice was compared with that obtained by SPECT, and in 14, reproducibility of ultrafast CT was evaluated. The ultrafast CT scanner was set to acquire 20 images, gated to end-diastole. The images were divided into 32 equal segments, and the time course and extent of opacification of the left ventricular cavity and myocardium were analyzed to calculate absolute perfusion. The thallium tomograms were also divided into 32 segments for comparison. The pattern of relative perfusion by segment was represented as a curve. In 18 of 22 paired scans, the mean difference of the position of the minimum and maximum points of the curves was less than 4, indicating close agreement between the two techniques. When scoring segmental perfusion as normal or abnormal, there was agreement between the methods in 129 of 176 segments ([symbol: see text] 0.41). Reproducibility (mean difference +/- 1 SD) of basal scans was 0.005 +/- 0.2 mL/min/mL, and during adenosine vasodilation was 0.05 +/- 0.32 mL/min/mL. Absolute perfusion (mean +/- 1 SD) at rest was 0.52 +/- 0.21 mL/min/mL. During adenosine infusion, perfusion increased to a mean of 0.84 +/- 0.42 mL/min/mL. Ultrafast CT and intravenous contrast can be used to assess relative myocardial perfusion in humans, at rest and during adenosine vasodilatation, although it may underestimate absolute perfusion, particularly at high flow.

Wound complications and treatment of the infected implantable cardioverter defibrillator generator.

Since 1980, the automatic implantable cardioverter defibrillator (ICD) has evolved as effective therapy for prevention of sudden cardiac death following documented sustained ventricular tachycardia or fibrillation. During a 5-year period, 412 ICD devices were implanted at the University of Michigan Hospitals with a wound complication rate of 4.1%. In this group, there were 13 infections, 3 erosions of the generator pocket, and 1 wound hematoma. Of the 16 patients with infection or erosion, 12 patients were treated with a rectus abdominis muscle flap closure and 4 with ICD generator removal. In 83% (n = 12) of the muscle flap patients, the wound healed uneventfully. Preoperative chest CT scanning was found to be helpful in identifying probable infection of the epicardial leads. In these cases, all hardware had to be removed to achieve resolution of the infection. We concluded that rectus abdominis muscle flaps were helpful in salvaging infected or exposed ICD generators in the absence of infected epicardial leads.

Identification of xanthine oxidase activity following reperfusion in human tissue.

In this series of experiments, we surveyed xanthine oxidase activity after microvascular transfer in the venous effluent after reperfusion of human rectus abdominis muscle (n = 8) and jejunum (n = 4). Enzyme activity was correlated with duration of ischemia and biochemical markers of cellular injury. Xanthine oxidase (XO) activity was measured spectrofluorometrically using a pterin assay, whereas cellular injury was measured with commercial creatinine phosphokinase activity assay and lipid peroxidation products using a spectrophotometer. The data demonstrated that XO activity was statistically significantly increased in muscle flaps kept at room temperature during ischemia compared with muscle flaps that were cooled (p < 0.05). Creatinine phosphokinase activity was also increased after 15 minutes of reperfusion in muscle flaps that were not cooled (p < 0.05). Two of the jejunal free flaps had ischemia times of > 1 hour and had elevated XO activity after reperfusion despite cooling (p < 0.05). Two other jejunal flaps had ischemia times of < 1 hour, but in one case, the XO activity was increased before harvest. The other case had no increase in XO activity.

Measurement accuracy of cardiac output in humans: indicator-dilution technique versus geometric analysis by ultrafast computed tomography.

OBJECTIVES: The aim of this study was to evaluate measurement accuracy of cardiac output in humans by comparing the indicator-dilution technique with geometric analysis by ultrafast computed tomography. BACKGROUND: Ultrafast computed tomography can be used to measure cardiac output by two methods. First, by scanning to obtain end-systolic and end-diastolic short-axis images of the ventricular cavities at sequential tomographic levels, the stroke volume and therefore the cardiac output can be calculated. Second, indicator-dilution theory (the Stewart-Hamilton equation) can be applied to measurements of the concentration of radiographic contrast in the blood pool after a bolus injection. The latter method has not been validated in humans. METHODS: The accuracy of the geometric method itself was first established by comparing left and right ventricular stroke volumes in 29 patients without valvular regurgitation or an intracardiac shunt, whose left and right ventricular stroke volumes should have been identical (group A). In a subset of 17 patients, the geometric method was compared with the indicator-dilution method (group B). RESULTS: Geometric analysis showed that the mean difference between left and right ventricular stroke volume was 1.8 +/- 7.3 ml, with a percentage SD of the differences of 9.3% (r = 0.9). Comparison wih indicator dilution-calculated cardiac output showed a mean difference of 0.079 +/- 1.22 liters/min, with a percent SD of the differences of 23.7% (r = 0.6). There was no improvement in this comparison with individual calibration of the scanner for each patient. CONCLUSIONS: The disparity found between data obtained with the geometric and indicator-dilution methods may be a result of the hemodynamic effects of contrast medium or it may suggest the possibility that some assumptions of indicator-dilution theory are not valid.

Angioedema associated with lisinopril.

Angioedema has been reported to occur in association with all angiotensin-converting enzyme inhibitors used in the United States. We reviewed nine cases of angioedema associated with lisinopril use seen in the emergency department at our hospital among 1,970 patients that had been prescribed lisinopril from March 1989 to May 1990. Cases were considered as probably (six cases) or possibly (three cases) drug related, depending on the temporal relationship of the initiation of therapy and the onset of angioedema. All of the cases had edema of the lips, buccal mucosa, and or face. None presented with laryngeal edema or stridor. The angioedema resolved within 1 to 2 days with diphenhydramine treatment and discontinuation of lisinopril. Our data suggest that the incidence of angioedema associated with lisinopril is greater than that associated with captopril or enalapril.

An improved method of in vivo wound disruption and measurement.

Biomechanical studies of wound strength are important because of new investigations in growth factors, cytokines, and fetal wounds. We compared two traditional methods of wound disruption measurement with a novel computerized model designed for in vivo experiments. An Instron tensiometer (INSTS) and an air insufflated positive pressure device (AIPPD) were compared with a vacuum-controlled wound chamber device (VCWCD). The VCWCD produced vacuum at the wound site and wound disruption was monitored with two video camera/recorders. Rats were marked with a template guide for a 2.5 cm, full-thickness, abdominal incisional wound. Rats were divided into three groups and studied at 2, 7, or 14 days after wounding. The recorded images were computer digitalized to generate wound strength curves from a three-dimensional model. A comparison of the wound disruption curves demonstrated that the VCWCD was comparable to the INST or AIPPD in normal wound healing (P greater than .40). The VCWCD provided data with less standard error at 2 days after wounding (P less than 05). In separate series of experiments, VCWCD was tested in the early phases of healing and was found to be sensitive to change at intervals of 48 hr after wounding (P less than .005). The INST or AIPPD methods could not perform this task because of an unacceptable level of random error after tissue manipulation. The VCWCD system was considered superior for evaluating early wound healing because it was an in vivo method which required minimal wound manipulation.