Continuous negative abdominal pressure device to treat pseudotumor cerebri.

OBJECTIVE: To study the effects of an externally applied negative abdominal pressure device designed to lower the effects of intra-abdominal pressure (IAP) on headaches and pulsatile tinnitus in severely obese women with pseudotumor cerebri (PTC). DESIGN: Short-term clinical intervention trial in the Clinical Research Center. Days 1 and 3 were 'control' days; on days 2 and 4-6 patients were in the device from 8:00 am to noon and from 1:00 to 5:00 pm, and on nights 7-11 they were in the device from 10:00 pm to 8:00 am. The last four patients were treated in a device with a counter-traction mechanism. SUBJECTS: Seven centrally obese women with PTC. MEASUREMENTS: Headache and pulsatile tinnitus severity were graded by the patient using visual analog scale (1-10) and averaged for the time that the device was in use or not in use. IAP was estimated from urinary bladder pressure (UBP) before and during device use. The internal jugular vein (IJV) elliptical cross-sectional area was measured with B-mode ultrasonography; the timed average velocity was measured by Doppler. RESULTS: There was a decrease in both headache (6.8+/-0.8 to 4.2+/-0.8, P<0.05) and pulsatile tinnitus (4.2+/-0.5 to 1.8+/-0.5, P<0.02) within 5 min, and in headache (to 2.2+/-0.8, P<0.01) and tinnitus (to 1.7+/-0.5, P<0.01) within 1 h of device activation. UBP decreased (P<0.001) from 19.1+/-3 to 12.5+/-2.8 cmH2O. Headache remained improved throughout time that the device was used. During the second week, five of seven patients slept in the device without difficulty and four awoke without headache. There was a progressive decrease (P<0.01) in headache during the day after sleeping in the device at night as compared with days 1 and 3 when it was not used (6.5+/-0.5, day 1; 4.1+/-0.7, day 3; 3.1+/-0.8, day 8; 2.3+/-0.8, day 10). Headaches returned late in the afternoon in two patients; the device was reactivated and headache again improved. Five patients underwent IJV sonography; the IJV area decreased (129+/-53 to 100+/-44 mm2, P=0.06) without a change in IJV flow (1004+/-802 to 1000+/-589 ml/min) with the device. When activated, the device was pulled into the patient, creating discomfort that was alleviated with the counter-traction mechanism in the last four patients. One patient developed a 5 cm area of blisters that resolved when the device was worn over a hospital gown. CONCLUSIONS: Decreasing IAP relieved headaches and pulsatile tinnitus in PTC. When patients slept in the device, they awoke without headache or tinnitus, which remained markedly improved throughout most of the following day. This study supports the hypothesis that PTC in obese women is secondary to an increased IAP.

The persistence of electrostatically seeded endothelial cells lining a small diameter expanded polytetrafluoroethylene vascular graft.

PURPOSE: The purpose of this study was to evaluate the persistence of electrostatically seeded endothelial cells (ECs) lining an expanded polytetrafluorethylene (e-PTFE) graft after one week exposure to in vivo circulation in a canine femoral artery bypass model. This was accomplished by visualizing the PKH 26 (red fluorescent) label placed in the EC membranes prior to the seeding procedure. Furthermore, this study was performed to confirm that the source of the ECs lining the graft were those from the initial inoculum. METHODS: This evaluation consisted of harvesting autologous, canine jugular vein ECs, PKH 26 labeling of the ECs, electrostatic EC seeding the e-PTFE grafts (4mm GORE-TEX, Length=6cm), implanting the grafts (femoral artery model) for one week, and explanting the grafts for light, fluorescent and scanning electron microscopy evaluations of the luminal surface. RESULTS: The unseeded grafts (controls) had a mean fluorescence surface coverage of 6.82 +/- 7.19%, while the EC seeded grafts had a mean of 90.3 +/- 14.3% which is significantly (p <0.001) different from the controls. Overall, the seeding time including the EC harvesting and PKH 26 labeling protocol was approximately 75 min. CONCLUSIONS: The electrostatically seeded ECs persisted after implantation of the graft as demonstrated by the PKH 26 labeling data. The fluorescent data also demonstrated that the neointima formed (EC luminal surface coverage) one week after implantation was in fact derived from the ECs initially seeded as determined by the abundance of the labeled ECs.

The aneurysm detection and management study screening program: validation cohort and final results. Aneurysm Detection and Management Veterans Affairs Cooperative Study Investigators.

BACKGROUND: We previously reported the prevalence and associations of abdominal aortic aneurysm (AAA) in 73451 veterans aged 50 to 79 years who underwent ultrasound screening. OBJECTIVE: To understand the prevalence of and principal positive and negative risk factors for AAA, and to assess reproducibility of our previous findings. METHODS: In the new cohort of veterans undergoing screening, 52 745 subjects aged 50 to 79 without history of AAA underwent successful ultrasound screening for AAA, after completing a questionnaire on demographics and potential risk factors. RESULTS: We detected AAA of 4.0 cm or larger in 613 participants (1.2%; compared with 1.4% in the earlier cohort). The direction and magnitude of the important associations reported in the first cohort were confirmed. Respective odds ratios for the major associations with AAA for the second and for the combined cohorts were as follows: 1.81 and 1.71 for age (per 7 years), 0.12 and 0. 18 for female sex, 0.59 and 0.53 for black race, 1.94 and 1.94 for family history of AAA, 4.45 and 5.07 for smoking, 0.50 and 0.52 for diabetes, and 1.60 and 1.66 for atherosclerotic diseases. The excess prevalence associated with smoking accounted for 75% of all AAAs of 4.0 cm or larger in the total population of 126 196. Associations for AAA of 3.0 to 3.9 cm were similar but tended to be somewhat weaker. CONCLUSIONS: Our findings confirm our previous cohort findings. Age, smoking, family history of AAA, and atherosclerotic diseases remained the principal positive associations with AAA, and female sex, diabetes, and black race remained the principal negative associations.

Vasomotor tone and the role of nitric oxide.

Vasomotor tone is the end result of a complex set of interactions that control relaxation and contraction of blood vessels. The critical role of nitric oxide (NO) in modulating vasomotor tone has become increasingly apparent over the last 15 years. A phenomenal amount of resources have been invested in the study of this simple molecule, and the volume of scientific literature that has resulted is astounding. In this review, we discuss the pertinent physiology and biochemistry of NO as it relates to the control of vasomotor tone. Methods of measuring NO in basic science and clinical settings are outlined, and the derangements of endothelial NO production and release (endothelial dysfunction) in pathophysiologic and disease states are discussed. Finally, potential therapies aimed at preserving endothelial function and augmenting NO production also are reviewed.

Decreased expression of tissue inhibitor of metalloproteinase 1 in stunned myocardium.

Ultrastructural studies of stunned myocardium have shown disorganization and loss of extracellular collagen and increased collagenase activity early after ischemia and reperfusion. The interplay between matrix metalloproteinase 1 (MMP-1) and tissue inhibitor of metalloproteinase 1 (TIMP-1) regulates the turnover of cardiac extracellular matrix fibrillar collagens. However, the gene expression of MMP-1 and TIMP-1 in stunned myocardium is not known. Here, we determined whether altered expression of MMP-1 and TIMP-1 occurs in globally stunned hearts. An isolated nonworking rabbit heart preparation, perfused with a bovine erythrocyte suspension in modified Krebs solution, was used. Two groups were studied: the stunned group was subjected to 20 min of normothermic global ischemia followed by 120 min of normal reperfusion (n = 8), and the control group underwent 140 min of uninterrupted perfusion (n = 7). The developed pressures at the end of reperfusion for ischemic and control hearts were 67.0 +/- 2.73 and 83.1 +/- 1.52 mm Hg (P < 0. 006) respectively. Ribonuclease protection assays of total left ventricular RNA using riboprobes for MMP-1, TIMP-1, and 18S rRNA were performed. A significant decrease (twofold, P < 0.03) in TIMP-1 gene expression was found in the stunned hearts, while MMP-1 mRNA expression was unchanged. Thus, in early stunning, the decrease in TIMP-1 expression could tip the balance favoring enhanced metalloproteinase activity, promoting collagen turnover, and initiating extracellular matrix remodeling. This may contribute to delayed recovery from myocardial stunning.

The nitric oxide precursor L-arginine reduces expression of hyaluronan synthase in experimental vein bypass grafts.

BACKGROUND: The success of vascular bypass procedures is limited by the development of intimal hyperplasia (IH). The nitric oxide (NO) precursor, L-arginine (L-ARG) significantly reduces IH in both arteries and experimental vein grafts; however, the precise mechanism has yet to be elucidated. Hyaluronan synthase-1 (HAS-1) is one of the two enzymes believed to be responsible for making hyaluronan, a key component extracellular matrix composition. PURPOSE: To determine how L-ARG supplementation affects the gene expression of HAS-1 in experimental vein grafts. METHODS: Thirty-four male New Zealand white rabbits were divided into three groups: control (no operation, regular chow and water, n = 4); L-ARG supplemented (n = 15); and no L-ARG (n = 15). The latter two groups underwent a right interposition carotid bypass using jugular vein. Vein grafts were harvested at 7, 14, and 21 days after surgery. Ribonuclease protection assays were performed using 32P-labeled riboprobes for HAS-1 and 18S rRNA as an internal control and expressed as a ratio (HAS-1/rRNA). RESULTS: There was a significant rise in HAS-1 expression in the vein grafts 7 (1.57 +/- 0.5), 14 (0.7 +/- 0.2), and 21 days (2.82 +/- 0.7) after grafting compared to control (0.14 +/- 0.08) (P < 0.05). L-ARG-supplemented animals had a significant decrease in HAS-1 expression at 21 days (0.65 +/- 0.1) compared to nonsupplemented vein grafts (2.82 +/- 0.7) (P < 0.02). CONCLUSIONS: These results demonstrate for the first time a significant rise in HAS expression in the early experimental vein grafts. Furthermore, L-ARG supplementation significantly diminishes the expression of HAS at 21 days. These results may represent a potential mechanism by which augmentation of the L-ARG/NO pathway inhibits IH in experimental vein grafts and may ultimately provide for improved therapeutic interventions in alleviating IH.

Hypercholesterolemia alters the gene expression of novel components of the extracellular matrix in experimental vein grafts.

The success rate of vascular bypass procedures is limited by the development of intimal hyperplasia (IH). Hypercholesterolemia has been shown to accelerate IH in both arteries and experimental vein grafts; however the mechanism remains uncertain. Hyaluronic acid synthase (HAS-1) is a transmembrane enzyme responsible for the formation of hyaluronan; an important constituent of extracellular matrix (ECM). The integrin receptor for hyaluronan is CD-44. Both CD-44 and HAS-1 have been studied in the development of ECM of wounds but have yet to be examined in the ECM of IH within vein grafts. The purpose of this study was to determine if the expression of CD-44 and HAS-1 is increased during the early stages of IH and how cholesterol supplementation affects these genes. Forty white male New Zealand rabbits were divided into two groups: cholesterol supplemented (1% cholesterol chow) and noncholesterol supplemented. Each set of 20 rabbits was then divided into four additional groups (n = 5); a nonoperative group (control) and three operative groups that underwent a right interposition carotid bypass using jugular vein. Grafts were harvested at 3, 7, and 21 days after surgery for molecular studies and histology. Ribonuclease protection assays were performed using 32P-labeled riboprobes for HAS-1, CD-44, and 18s rRNA. Densitometric analysis is expressed as a ratio (riboprobe/rRNA). Cholesterol levels differed significantly between cholesterol supplemented and nonsupplemented groups (1419 +/- 130 mg/dl and 48 +/- 12 mg/dl) (p < 0.01). There was a significant increase in the expression of HAS-1 and CD-44 in the vein grafts compared to normal jugular vein. Cholesterol supplementation caused a further increase in CD-44 gene expression versus nonsupplemented vein grafts. These data demonstrate a role for CD-44 and HAS-1 transcription in vein graft intimal hyperplasia, which is further altered by cholesterol supplementation. Lastly, these results could explain differences seen in the development of IH with hypercholesterolemia and ultimately provide for improved therapies in alleviating this process.

The limits of generalized cardiac screening tests for predicting cardiac complications after infrainguinal arterial reconstruction.

We examined the relative efficacies of different cardiac screening strategies for infrainguinal arterial bypass. The outcomes of 205 elective leg bypass procedures over a 10-year period, including myocardial infarction (MI), total cardiac complications, and mortality were tallied. Clinical risk factors popularized by Goldman and Eagle, and the results of dipyridamole thallium myocardial imaging (DThal) were recorded. The overall mortality rate was 3.4%, with a 3.4% incidence of MI and a 5.4% total cardiac complication rate. Both abnormal DThal (p = 0.011) and Goldman class II-IV (p = 0.030) were significant predictors of MI and cardiac death, but both suffered from poor specificity and positive predictive value. Because logistic regression analysis identified a correlation between angina, CHF, and an abnormal DThal, a customized screening strategy was developed to include the presence of angina, CHF and an abnormal DThal. Eighty-eight percent of patients suffering MI or death met these criteria, while only 11% of the complication-free group did. This screening strategy provided a superior sensitivity of 88%, specificity of 89%, positive predictive value of 25%, and 99% negative predictive value. A customized screening strategy (angina, CHF, abnormal DThal), developed from a 10-year experience with a single patient group, provided better predictive accuracy than any generalized screening formula.

Inducible nitric oxide synthase expression in human vein grafts.

BACKGROUND: The patency of vascular reconstructive procedures is limited by the development of intimal hyperplasia (IH). Nitric oxide (NO) seems to be beneficial in abrogating this process. Currently, there is little information concerning inducible nitric oxide synthase (iNOS), the enzyme responsible for NO synthesis, and human vein grafts. The purpose of this study was to examine iNOS gene expression in human aortocoronary vein grafts (ACVG) and infrainguinal vein bypass grafts (IVG). METHODS: Nonthrombosed sections from ACVG (n = 5), IVG (n = 5), and control saphenous vein (SV; n = 4) were harvested and processed for RNA isolation. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed on samples using 32P radioactively end labeled primers. Glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) was the internal control, and results were expressed as iNOS pmol/GAPDH pmol. RESULTS: There was a significant increase in the iNOS gene expression in the ACVG (0.049 +/- 0.01) when compared with IVG (0.019 +/- 0.001) or normal SV (0.011 +/- 0.002; P < or = 0.05). There was no significant difference between normal vein and the infrainguinal grafts. Sequencing of a fragment of the amplified 428 bp gene product confirmed 84% homology with the available gene bank human sequence. CONCLUSIONS: This study proves that iNOS is expressed in human vein bypass grafts. Additionally, there is a significant elevation of iNOS message in human ACVGs compared with IVG or normal SV. This difference may be the result of the unique vascular beds supplied by these grafts. Ultimately, manipulation of iNOS expression may lead to therapies to alleviate IH in these grafts.

The temporal expression of transforming growth factor-beta 1 in early aortocoronary vein grafts.

The success of coronary reconstructive procedures is limited by the high incidence of restenosis secondary to intimal hyperplasia (IH). Transforming growth factor-beta 1 (TGF-beta 1) is a growth factor which has been shown to be important in the early development of IH in arteries and peripheral vein grafts. To date, there is little information concerning the early remodeling in aortocoronary vein grafts (ACVG). The purpose of this study was to characterize the expression of TGF-beta 1 expression in early aortocoronary vein grafts. Eighteen mongrel dogs underwent aortocoronary vein bypass grafting. Vein grafts were excised at 2 hr, 4 hr, and 7 days after implantation, snap frozen, and processed for ribonuclease protection assays (RPA) using 32P-labeled riboprobes for TGF-beta 1 and 18 S rRNA. TGF-beta 1 expression was quantified by densitometric analysis of autoradiographs which were expressed as a ratio TGF-beta 1/rRNA. Representative vessel rings were also collected for histology. There was a significant rise in TGF-beta 1 expression in the 2-hr vein grafts (0.42 +/- 0.04 compared to control saphenous vein (0.21 +/- 0.05, P < 0.02). In addition, there was significant downregulation of TGF-beta 1 at 4 hr (0.28 +/- 0.05) and at 7 days (0.18 +/- 0.01) when compared to 2 hr (P < 0.05). Histological specimens showed minimal intimal hyperplasia at 7 days. These results show for the first time an acute rise in TGF-beta 1 expression in ACVG. This upregulation quickly subsides by 4 hr and gene expression approaches control values by 7 days. By understanding this temporal relationship of expression one could better target potential therapeutic modalities to attenuate IH.

Feasibility of angle independent Doppler color imaging for in vivo application: preliminary study on carotid arteries.

An experimental system has been used to acquire Doppler color images using a linear transducer from an ultrasound scanner to reconstruct angle independent Doppler color (AIDC) images in normal carotid arteries in 21 volunteers. Images were first taken from relatively straight segments in the common carotid artery, and comparisons were made in a small area at the center stream. At peak systole, the correlation coefficient of the velocity amplitudes between AIDC imaging (AIDCI) and duplex scanning was 0.94; the correlation coefficient between the flow angles measured from AIDCI and the angles of the vessel wall was 0.99. Periodic variations of the flow angle over the cardiac cycle were always observed by AIDCI, whereas the changes in the geometric angle of the vessel itself were insignificant. This observation suggests that the AIDCI technique is sensitive to alterations of flow direction. On the other hand, the deviation of the flow angle from a fixed correction angle in duplex scanning may cause a certain degree of error in velocity determination. AIDC images were also obtained at the carotid bifurcation. The results show that the AIDCI technique is able to depict major flow features, such as velocity skewing, flow separation, flow reversal and vortical flow, in a complex flow field.

Early results of infrageniculate arterial reconstruction using cryopreserved homograft saphenous conduit (CADVEIN) and combination low-dose systemic immunosuppression.

BACKGROUND: The search continues for the ideal conduit for infrageniculate arterial reconstructions when the autogenous vein is unsuitable or unavailable. Based on experimental observations in our laboratory demonstrating improvement in canine cryopreserved allograft vein patency using systemic immunosuppression (Imsup), and the remarkable clinical success achieved in older (greater than 60 years of age) solid organ transplant recipients using combination low-dose Imsup, we studied the effects of Imsup on patency of cryopreserved homograft saphenous vein (CADVEIN) used for infrageniculate arterial reconstructions. STUDY DESIGN: Under the Institutional Review Board protocol, 21 infrageniculate CADVEIN grafts were placed in 19 patients between July 1993 and August 1994 for limb salvage when autogenous veins were unavailable. An immunopharmacologic protocol consisting of low-dose cyclosporine A, azathioprine, prednisone, warfarin, aspirin, and vasodilators given orally was instituted. For various reasons, 15 patients in group 1 received Imsup; five patients never received Imsup, and one patient in group 2 received Imsup briefly. Follow-up examinations were completed using the time range of six to 18 months (mean, eight plus or minus one month). RESULTS: One patient died (5.3 percent) 30 days after emergency combined venous graft and bilateral CADVEIN bypass. The actuarial 12-month primary patency in group 1 was 59.4 percent compared with 16.7 percent in group 2 (p < 0.015, log-rank test). Cellular rejection was typically seen in explanted CADVEIN. Systemic morbidity related to Imsup was minimal. The CADVEIN morbidity rate was significant: three graft aneurysms and four early graft ruptures. Major amputations were necessary in eight of 12 patients with graft closure. CONCLUSIONS: The data suggest that Imsup significantly improves CADVEIN patency with limited systemic morbidity; however, complications related to the conduit itself occurred with greater frequency and cause greater morbidity than when the autogenous veins were used. Much has yet to be learned regarding the preservation characteristics of CADVEIN and the immunologic interactions in patients receiving CADVEIN grafts, before further clinical use of this conduit can be recommended.

Heparinoids with low anticoagulant potency attenuate postischemic endothelial cell dysfunction.

PURPOSE: Although standard heparin has been demonstrated to reduce endothelial cell dysfunction in acute ischemia-reperfusion injury, its mechanism of action remains unknown. We hypothesized that heparin's salutary endothelial effects are independent of its conventional anticoagulant activity and are not caused by nonspecific polyanion effects. METHODS: Isolated rat hindlimbs were perfused at constant pressure with an albumin-enriched crystalloid buffer. After 60 minutes of normothermic ischemia, endothelial function was assessed by measurement of endothelial-dependent vasodilation by log increment infusion of acetylcholine. Endothelial-independent vasodilation was measured by exposure to nitroprusside. Some groups were pretreated with heparinoids possessing minimal or intermediate anticoagulant activity. RESULTS: Treatment with heparinoids with low anticoagulant activity significantly increased endothelial-dependent vasodilation when compared with the nontreated ischemic group and were statistically indistinguishable from the nonischemic control. Treatment with dextran sulfate, a randomly sulfated polymer with size and charge characteristics similar to heparin, did not change postischemic vasodilation. Endothelial-independent vasodilation was largely unaffected by ischemia-reperfusion or drug treatment. CONCLUSIONS: A heparinoid with negligible antithrombin-binding activity (Astenose) attenuated postischemic endothelial dysfunction, suggesting that its mechanism of action was independent of anticoagulant activity. Failure of dextran sulfate to be protective implied that the effect was not caused by nonspecific polyanion action.

Decreased splanchnic perfusion measured by duplex ultrasound in humans undergoing small volume hemorrhage.

OBJECTIVES: To quantitate duplex Doppler measurements of splanchnic perfusion to determine if these measurements are reproducible in euvolemic humans and if such measurements are sensitive to mild degrees of systemic hypovolemia. DESIGN: Prospective, nonrandomized, controlled trial. SETTING: Clinical research center. PARTICIPANTS: Seven fasting, healthy male and female volunteers, ranging in age from 25 to 37 yrs and weighing 60 to 90 kg. INTERVENTIONS: Pulse, blood pressure, hematocrit, and duplex Doppler measurements of the peak systolic velocity and time averaged velocity of the subdiaphragmatic aorta, celiac artery, and superior mesenteric artery were obtained at four time points. Time points I and II were on separate days before hemorrhage and consisted of routine blood donation of 450 mL. Time point III was immediately after blood donation. Time point IV was 24 hrs after donation. Estimated blood flow was calculated from time averaged velocity (estimated blood flow = 60[vessel cross-sectional area][time averaged velocity]). MEASUREMENTS AND MAIN RESULTS: Vital signs and hematocrit remained without significant change at all time points. Peak systolic velocity, time averaged velocity, and estimated blood flow were also unchanged between measurements at time points I and II. However, after a mean reduction of 9.1% of total blood volume, duplex ultrasound detected significant decreases of 14.5% in celiac artery and superior mesenteric artery peak systolic velocity, as well as 15.1%, 17.3%, and 20.2% decreases in aorta, celiac artery and superior mesenteric artery time averaged velocity and estimated blood flow, respectively (all values p < .05 vs. baseline, Duncan's multiple range test). All measured variables returned to baseline 24 hrs after hemorrhage. CONCLUSIONS: Noninvasive duplex Doppler measurements of splanchnic peak systolic velocity, time averaged velocity, and estimated blood flow are reproducible and sensitive to small changes in intravascular volume. These data suggest a potential clinical role for duplex imaging in the treatment of critically ill patients to guide therapy to optimize splanchnic perfusion.

Catheter-directed thrombolysis following vena cava filtration for severe deep venous thrombosis.

Massive deep venous thrombosis with marked venous outflow obstruction can result in limb loss or end-organ injury. Systemically administered drugs may not reach thrombi in therapeutic concentrations and surgical and thrombolytic strategies carry a small but real risk of pulmonary embolus--similar to the risks with anticoagulation alone. We therefore developed a strategy in which catheter-directed thrombolysis was used to deliver high concentrations of a plasminogen activator directly to the thrombus combined with placement of a downstream Greenfield filter to protect patients from pulmonary embolus. From 1984 to 1993 six patients were treated with this regimen. All had severe symptoms of less than 4 days' duration. On radiologic evaluation four patients had large iliofemoral and/or inferior vena cava thrombosis, one had subclavian/innominate vein thrombosis, and one had transplant renal vein/iliofemoral/inferior vena cava thrombosis. A Greenfield filter was first placed downstream prior to imbedding an infusion catheter in the greatest mass of thrombus for subsequent infusion of urokinase (n = 4) or streptokinase (n = 2). In four patients the catheter traversed the Greenfield filter. All patients were given bolus lytic therapy followed by maintenance infusions ranging in duration from 24 hours to 12 days. Five patients remained on heparin simultaneously. Clot lysis was achieved in all patients with hemodynamic, symptomatic, and arteriographic improvement. There were no deaths, pulmonary emboli, or complications of filter placement. One patient had minor bleeding at the puncture site and another had catheter-related infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of experimental vein graft intimal hyperplasia and preservation of nitric oxide-mediated relaxation by the nitric oxide precursor L-arginine.

BACKGROUND: Previous studies in animals and human beings have shown that vein bypass grafts exhibit diminished endothelium-dependent relaxation and the development of intimal hyperplasia. This study examines the effect of L-arginine on experimental vein graft endothelial cell function and the development of intimal hyperplasia. METHODS: Common carotid vein bypass grafts were performed in 24 New Zealand White rabbits: 12 were controls and 12 received L-arginine (2.25%) orally 7 days before operation and thereafter until harvest 28 days after operation. Intimal and medial dimensions were determined by planimetry on pressure-fixed vessels. Relaxation to acetylcholine, serotonin, calcium ionophore (A23187), and sodium nitroprusside was performed on precontracted vessel rings. RESULTS: Arginine-treated vein grafts showed a 47% reduction in mean intimal thickness (p < 0.001) compared with controls. By scanning and transmission electron microscopy, all vein grafts showed a confluent endothelium. In contrast to control grafts, which do not relax to acetylcholine and serotonin, arginine-treated vein grafts relaxed in response to both agonists. There was a significant increase (p < 0.05) in the maximal relaxation to calcium ionophore (A23187) in arginine-treated vein grafts compared with control grafts. Non-endothelium-dependent responses to sodium nitroprusside were equivalent in all vein grafts. CONCLUSIONS: This study shows that oral L-arginine supplementation significantly reduces intimal hyperplasia and preserves nitric oxide-mediated relaxation in experimental vein grafts, suggesting a role for nitric oxide in the regulation of the cellular events that lead to intimal hyperplasia.

Postischemic extremities exhibit immediate release of tumor necrosis factor.

PURPOSE: Although reperfusion of acutely ischemic extremities can cause cardiopulmonary collapse and death, the humoral agent(s) released from limbs promoting this distant organ injury are not well characterized. We hypothesized that tumor necrosis factor-alpha (TNF-alpha), a cytokine that causes cardiopulmonary dysfunction in septic shock, may be released from postischemic extremities. METHODS: Isolated rat hindlimbs were perfused at constant pressure with a nonrecirculating crystalloid-based buffer. After 60 or 120 minutes of normothermic ischemia, TNF activity was measured in sequential samples of venous effluent by L929 bioassay. Associated limb injury was assessed by the extent of no-reflow after reperfusion, changes in endothelial permeability to iodine 125-labeled albumin and skeletal muscle injury by uptake of technetium 99 pyrophosphate. RESULTS: After 120 minutes of normothermic ischemia (n = 10), a 15-fold increase in TNF-alpha activity in venous effluent occurred, with peak activity at 1.5 minutes of reperfusion (30.6 +/- 8.7 U/ml) falling to near control levels by 5 minutes. This group had a 3.3-fold increase in vascular permeability, a 2.2-fold increase in the muscle injury index and a 71.2% decline in reperfusion flow (all p < 0.05 vs control). Pretreatment of extremities with an anti-TNF-alpha antibody in a second group of limbs undergoing 120 minutes of ischemia (n = 10) decreased TNF activity to levels not significantly different from the nonischemic control group (n = 12). The extent of no-reflow in limbs treated with antibodies was significantly attenuated (flow 44.9% of control vs 29.8% [untreated], p < 0.05). Antibody treatment affected neither muscle injury nor vascular permeability. CONCLUSIONS: Postischemic extremities exhibited a transient, early burst of TNF release on reperfusion, which likely represented washout of TNF produced during ischemia. Suppression of TNF activity with an antibody to TNF-alpha resulted in a salutary increase in postischemic flow rates, suggesting that TNF may play a role in the no-reflow phenomenon.