Contribution of age and gender to outcome of blunt splenic injury in adults: multicenter study of the eastern association for the surgery of trauma.

BACKGROUND: The purpose of this study was to examine the contribution of age and gender to outcome after treatment of blunt splenic injury in adults. METHODS: Through the Multi-Institutional Trials Committee of the Eastern Association for the Surgery of Trauma (EAST), 1488 adult patients from 27 trauma centers who suffered blunt splenic injury in 1997 were examined retrospectively. RESULTS: Fifteen percent of patients were 55 years of age or older. A similar proportion of patients > or = 55 went directly to the operating room compared with patients < 55 (41% vs. 38%) but the mortality for patients > or = 55 was significantly greater than patients < 55 (43% vs. 23%). Patients > or = 55 failed nonoperative management (NOM) more frequently than patients < 55 (19% vs. 10%) and had increased mortality for both successful NOM (8% vs. 4%, p < 0.05) and failed NOM (29% vs. 12%, p = 0.054). There were no differences in immediate operative treatment, successful NOM, and failed NOM between men and women. However, women > or = 55 failed NOM more frequently than women < 55 (20% vs. 7%) and this was associated with increased mortality (36% vs. 5%) (both p < 0.05). CONCLUSION: Patients > or = 55 had a greater mortality for all forms of treatment of their blunt splenic injury and failed NOM more frequently than patients < 55. Women > or = 55 had significantly greater mortality and failure of NOM than women < 55.

Surgery induces human mononuclear cell arginase I expression.

BACKGROUND: Arginase is a metabolic enzyme for the amino acid arginine that participates in the immune response to trauma. We hypothesize that surgical trauma induces arginase expression and activity in the human immune system. METHODS: Peripheral mononuclear cell (MNC) arginase activity and expression and plasma nitric oxide metabolites and interleukin (IL)-10 were measured in patients undergoing elective general surgery. Twenty-two healthy volunteers served as a comparison population. RESULTS: MNC arginase activity increased within 6 hours of surgery (p < 0.05) and coincided with increased arginase I protein expression. Plasma nitric oxide metabolites decreased significantly postoperatively (p < 0.05). Patients lacking an elevation in IL-10 failed to demonstrate increased MNC arginase activity. CONCLUSION: Increased MNC arginase expression may contribute to postsurgical immune dysfunction by affecting arginine use and availability and nitric oxide metabolism in the immune system. Plasma IL-10 may play a role in regulating MNC arginase activity.

The routine use of sonography in penetrating torso injury is beneficial.

BACKGROUND: Torso sonography (focused assessment with sonography for trauma [FAST]) has been added to our protocols for the evaluation of penetrating torso injury. The purpose of this study was to evaluate our recent experience and determine whether the use of FAST is beneficial. METHODS: From January 1999 to January 2000, patients with penetrating torso injury and no clinical indication for surgery were evaluated by sonography with a selective use of other investigations. FAST consisted of sonographic views of the peritoneum and/or pericardium to determine the presence or absence of fluid. RESULTS: During the study period, there were 238 victims of penetrating injury assessed by our trauma service, and sonography was performed in 72 (30%) patients as per our protocols. There were 31 stab, 37 gunshot/shotgun and, and 4 puncture wounds. Thirty-eight patients had peritoneal views, 6 patients had pericardial views, and 28 patients had both pericardial and peritoneal views obtained. Thirteen of 66 patients had free fluid in the peritoneal cavity and 12 of the 13 patients had a therapeutic laparotomy. No peritoneal fluid was seen in 53 of 66 patients, of whom 6 had abdominal injuries, 5 requiring surgery for diaphragm or bowel injuries. The sensitivity of FAST alone for abdominal injury was 67%, specificity was 98%, positive predictive value was 92%, and negative predictive value was 89%. Pericardial fluid was seen in 3 of 34 patients; one had a heart wound and two had negative pericardial windows. All 31 patients without pericardial fluid recovered without surgery. CONCLUSION: The routine use of sonography in penetrating torso injury is beneficial. The detection of pericardial or peritoneal fluid is clinically useful. However, a negative FAST examination does not exclude abdominal injury, such as a diaphragm or hollow viscus wound, and further investigation or close follow-up is required.

[Treatment of caustic stenosis of the esophagus with self-expanding devices]. / Tratamiento de las estenosis cáusticas del esófago mediante dispositivos de autoexpansión.

Caustic stenosis is a serious problem in children due to its complicated resolution and implications in important areas like nutrition, as well as the child's tolerance to the measures taken to correct them. After dealing extensively with this problem over the last twenty five years, always from a conservative approach using traditional methods like dilatations, we believe we have found a technique that brings together all the necessary conditions to achieve a favorable and definitive solution. Our ideal goal to achieve a device that provides a well-tolerated permanent esophageal expansion during the scarring process, also permitting normal swallowing, seems to have been reached through the use of the new generation of silicone stents. The authors present their experience in the first seven cases of caustic stenosis treatment through the placement of silicone stents, describing a precise placement technique while establishing a standard protocol for the use of these devices.

L-Arginine regulates the expression of the T-cell receptor zeta chain (CD3zeta) in Jurkat cells.

L-Arginine is a versatile amino acid that plays a central role in the normal function of several organ systems including the immune system. Its availability is tightly controlled and varies significantly in different organs and tissues in the body. L-Arginine plays an important role in supporting T-cell proliferation. Its depletion in certain disease states results in a diminished T-cell response. The main purpose of this study was to determine the effect of the depletion of L-arginine on the expression of the T-cell receptor (TCR) proteins. When the helper T-cell line Jurkat was cultured in arginine-free medium, there was a preferential decrease in the expression of the TCR zeta chain (CD3zeta). The reduced expression of CD3zeta was observed within 24 h of culture in L-arginine-free medium and was completely reversed with the replenishment of L-arginine. Furthermore, the absence of L-arginine blocked the normal re-expression of the TCR that had been internalized after antigen stimulation. There also was a significant decrease in proliferation of Jurkat cells in the absence of L-arginine; however, L-arginine depletion did not prevent the up-regulation of the interleukin 2 receptor chains upon stimulation, nor did it significantly diminish the production of interleukin 2. The changes in the expression of CD3zeta chain were not induced by apoptosis. Thus, the availability of L-arginine in the microenvironment may play a significant role in regulating the expression of the TCR.

Alterations in arginine metabolic enzymes in trauma.

Arginine is the sole substrate for nitric oxide (NO) synthesis by NO synthases (NOS) and promotes the proliferation and maturation of human T-cells. Arginine is also metabolized by the enzyme arginase, producing urea and ornithine, the precursor for polyamine production. We sought to determine the molecular mechanisms regulating arginase and NOS in splenic immune cells after trauma. C3H/HeN mice underwent laparotomy as simulated moderate trauma or anesthesia alone (n = 24 per group). Six, 12, 24, or 48 h later, 6 animals from each group were sacrificed, and splenectomy was performed and plasma collected. Six separate animals had neither surgery nor anesthesia and were sacrificed to provide resting values (t = 0 h). Spleen arginase I and II and iNOS mRNA abundance, arginase I protein expression, and arginase activity were determined. Plasma NO metabolites (nitrite + nitrate) were also measured. Trauma increased spleen arginase I protein expression and activity (P = 0.01) within 12 and for at least 48 h after injury and coincided with up-regulated arginase I mRNA abundance at 24 h. Neither arginase II nor iNOS mRNA abundance in the spleen was significantly increased by trauma at 24 h. Plasma nitrite + nitrate was decreased in animals 48 h post-injury compared to anesthesia controls (P < 0.05). Trauma induces up-regulation of arginase I gene expression in splenic immune cells within 24 h of injury. Arginase II is not significantly up-regulated at that time point. Arginase I, rather than iNOS appears to be the dominant route for arginine metabolism in splenic immune cells 24 h after trauma.

Arginase I expression and activity in human mononuclear cells after injury.

OBJECTIVE: To determine the effect of trauma on arginase, an arginine-metabolizing enzyme, in cells of the immune system in humans. SUMMARY BACKGROUND DATA: Arginase, classically considered an enzyme exclusive to the liver, is now known to exist in cells of the immune system. Arginase expression is induced in these cells by cytokines interleukin (IL) 4, IL-10, and transforming growth factor beta, corresponding to a T-helper 2 cytokine profile. In contrast, nitric oxide synthase expression is induced by IL-1, tumor necrosis factor, and gamma interferon, a T-helper 1 cytokine profile. Trauma is associated with a decrease in the production of nitric oxide metabolites and a state of immunosuppression characterized by an increase in the production of IL-4, IL-10, and transforming growth factor beta. This study tests the hypothesis that trauma increases arginase activity and expression in cells of the immune system. METHODS: Seventeen severely traumatized patients were prospectively followed up in the intensive care unit for 7 days. Twenty volunteers served as controls. Peripheral mononuclear cells were isolated and assayed for arginase activity and expression, and plasma was collected for evaluation of levels of arginine, citrulline, ornithine, nitrogen oxides, and IL-10. RESULTS: Markedly increased mononuclear cell arginase activity was observed early after trauma and persisted throughout the intensive care unit stay. Increased arginase activity corresponded with increased arginase I expression. Increased arginase activity coincided with decreased plasma arginine concentration. Plasma arginine and citrulline levels were decreased throughout the study period. Ornithine levels decreased early after injury but recovered by postinjury day 3. Increased arginase activity correlated with the severity of trauma, early alterations in lactate level, and increased levels of circulating IL-10. Increased arginase activity was associated with an increase in length of stay. Plasma nitric oxide metabolites were decreased during this same period. CONCLUSIONS: Markedly altered arginase expression and activity in cells of the human immune system after trauma have not been reported previously. Increased mononuclear cell arginase may partially explain the benefit of arginine supplementation for trauma patients. Arginase, rather than nitric oxide synthase, appears to be the dominant route for arginine metabolism in immune cells after trauma.

Effects of L-arginine on the proliferation of T lymphocyte subpopulations.

BACKGROUND: Dietary supplementation of L-arginine as a mechanism to enhance cellular immune response (T lymphocytes), has slowly gained approval, and appears especially important during critical illness. Despite its clinical use, little is known as to the direct effects of L-arginine on the different T lymphocyte subpopulations. METHODS: Lymphocytes were harvested from spleens of C57 B1/6 mice, and proliferation was induced with anti-CD3 in the presence of different concentrations of L-arginine ranging from 0 to 1000 micromol/L. Flow cytometry was used to evaluate the effect of L-arginine on T lymphocyte subpopulations. Interleukin-2 production was measured by ELISA and gene expression by RT-PCR. RESULTS: L-Arginine at or greater than 100 micromol/L significantly enhanced anti-CD3 stimulated T lymphocyte proliferation (p = .01). L-Arginine was essential for adequate T lymphocyte (CD3+) cellular maturation (p = .01). Proliferation of Helper T cells (CD4+) was not dependent on L-arginine. In contrast, Cytotoxic T cells (CD8+) showed a dose dependent proliferation in response to L-arginine (p = .01). Of the CD8+ cells, an increase in the CD45RA negative CD8 positive (memory) T cell subpopulation was observed with the addition of L-arginine. In addition, the number of cell surface CD8 receptors (CD8R) and CD3 receptors (CD3R) increased in the presence of L-arginine (p = .01, p = .04). Interleukin-2 receptor (IL-2R) expression was not up-regulated by L-arginine. L-Arginine modestly increased IL-2 production and had pronounced effects on its disappearance from the culture media (p < .0001). Interleukin-2 mRNA expression was not dependent on L-arginine. CONCLUSIONS: The requirements for L-arginine for the proliferation of CD3 stimulated T lymphocytes vary widely, and have to be taken into account when studying the mechanism of how L-arginine enhances cellular proliferation. L-Arginine may increase cellular proliferation by increasing specific receptor expression and the utilization of interleukin-2.

Blunt splenic injury in adults: Multi-institutional Study of the Eastern Association for the Surgery of Trauma.

BACKGROUND: Nonoperative management of blunt injury to the spleen in adults has been applied with increasing frequency. However, the criteria for nonoperative management are controversial. The purpose of this multi-institutional study was to determine which factors predict successful observation of blunt splenic injury in adults. METHODS: A total of 1,488 adults (>15 years of age) with blunt splenic injury from 27 trauma centers in 1997 were studied through the Multi-institutional Trials Committee of the Eastern Association for the Surgery of Trauma. Statistical analysis was performed with analysis of variance and extended chi2 test. Data are expressed as mean +/- SD; a value of p < 0.05 was considered significant. RESULTS: A total of 38.5 % of patients went directly to the operating room (group I); 61.5% of patients were admitted with planned nonoperative management. Of the patients admitted with planned observation, 10.8% failed and required laparotomy; 82.1% of patients with an Injury Severity Score (ISS) < 15 and 46.6% of patients with ISS > 15 were successfully observed. Frequency of immediate operation correlated with American Association for the Surgery of Trauma (AAST) grades of splenic injury: I (23.9%), II (22.4%), III (38.1%), IV (73.7%), and V (94.9%) (p < 0.05). Of patients initially managed nonoperatively, the failure rate increased significantly by AAST grade of splenic injury: I (4.8%), II (9.5%), III (19.6%), IV (33.3%), and V (75.0%) (p < 0.05). A total of 60.9% of the patients failed nonoperative management within 24 hours of admission; 8% failed 9 days or later after injury. Laparotomy was ultimately performed in 19.9% of patients with small hemoperitoneum, 49.4% of patients with moderate hemoperitoneum, and 72.6% of patients with large hemoperitoneum. CONCLUSION: In this multicenter study, 38.5% of adults with blunt splenic injury went directly to laparotomy. Ultimately, 54.8% of patients were successfully managed nonoperatively; the failure rate of planned observation was 10.8%, with 60.9% of failures occurring in the first 24 hours. Successful nonoperative management was associated with higher blood pressure and hematocrit, and less severe injury based on ISS, Glasgow Coma Scale, grade of splenic injury, and quantity of hemoperitoneum.

A single-center 8-year experience with percutaneous dilational tracheostomy.

OBJECTIVE: To determine surgical, postoperative, and postdischarge complications associated with percutaneous dilational tracheostomy (PDT) in an 8-year experience at the University of Kentucky. SUMMARY BACKGROUND DATA: There are known risks associated with the transport of critically ill patients to the operating room for elective tracheostomy, and less-than-optimal conditions may interfere with open bedside tracheostomy. PDT has been introduced as an alternative to open tracheostomy. Despite information supporting its safety and utility, the technique has been criticized because advocates had not provided sufficient information regarding complications. METHODS: A prospective database was initiated on all patients who underwent PDT between September 1990 and May 1998. The database provided indication, procedure time, duration of intubation before PDT, and intraoperative and postoperative complications. Retrospective review of medical records and phone interviews provided long-term follow-up information. RESULTS: In the 8-year period, 827 PDTs were performed in 824 patients. Two patients were excluded because PDT could not be completed for technical reasons. There were 519 male and 305 female patients. Mean age was 56 years. Prolonged mechanical ventilatory support was the most common indication. Mean procedure time was 15 minutes, and the average duration of intubation before PDT was 10 days. The intraoperative complication rate was 6%, with premature extubation the most common complication. The procedure-related death rate was 0.6%. Postoperative complications were found in 5%, with bleeding the most common. With a mean follow-up of greater than 1 year, the tracheal stenosis rate was 1.6%. CONCLUSIONS: On the basis of this large, single-center study, the authors conclude that when performed by experienced surgeons, PDT is a safe and effective alternative to open surgical tracheostomy for intubated patients who require elective tracheostomy.

Beta adrenoceptor regulation of macrophage arginase activity.

BACKGROUND: Arginase, which metabolizes L-arginine within the urea cycle, is essential for production of polyamines and affects production of nitric oxide by depletion of L-arginine, the common substrate for both arginase and nitric oxide synthase. Having shown that trauma increases splenic macrophage arginase activity, we seek to define the mechanisms for this. RAW macrophage arginase activity and expression are increased by 8-bromo-cAMP in vitro. We hypothesize that since catecholamines increase cAMP, trauma-induced splenic arginase activity may be mediated by post-injury catecholamine release. METHODS: RAW 264.7 macrophage arginase activity was measured in vitro in response to 4 catecholamines with or without propranolol or lipopolysaccharide (LPS). C57BL/6 mice underwent laparotomy as a model of moderate trauma after propranolol treatment, with and without intraperitoneal Escherichia coli LPS administration as a simulated pro-inflammatory stimulus. RESULTS: Macrophage arginase activity increased in vitro in response to catecholamines or LPS (P < .05). Propranolol pretreatment blocked macrophage arginase activity induced by epinephrine (10 mumol/L) in vitro (P < .05). Trauma or LPS alone increased splenic arginase activity in vivo (P < .05). Propranolol did not alter LPS-induced splenic arginase activity but did significantly reduce trauma-induced splenic arginase activity (P < .05). CONCLUSIONS: Catecholamines alone increase macrophage arginase activity through beta-adrenoceptor activation. Increased splenic arginase activity induced by moderate trauma is decreased by beta-adrenoceptor blockade, suggesting that trauma-induced arginase activity is partly mediated by endogenous catecholamines.

Trauma increases extrahepatic arginase activity.

BACKGROUND: Although expressed primarily in the liver, arginase activity also is present in extrahepatic tissues and specifically in macrophages, where it may play diverse physiologic roles in wound healing, cellular proliferation, and the regulation of nitric oxide production. Arginase activity in immune cells is upregulated by certain cytokines such as IL-4, IL-10, and TGF-beta and by catecholamines. Since the release of these substances is increased after trauma, we hypothesized that arginase activity would also be increased in immune cells after trauma. The current work tests this hypothesis. METHODS: A model of surgical trauma was created in C3H/HeN mice by performing an exploratory laparotomy. Tissue arginase activity and arginase I protein expression were determined. As a control, arginase activity and expression were also stimulated with the use of endotoxin. In addition, we evaluated the expression of inducible nitric oxide synthase and the accumulation of nitric oxide metabolites in plasma. RESULTS: Surgical trauma was associated with a significant increase in arginase activity in splenic and renal tissues (P < .05). Splenic macrophages from trauma animals exhibited arginase activity levels approximately 10 times those of controls (P < .05). Endotoxin alone increased arginase activity in the spleen, but this increase was less than that of trauma alone (P < .05). Arginase activity remained elevated after trauma for up to 4 days and normalized by day 7. Arginase I expression was upregulated by trauma in both splenic and renal tissue and by endotoxin in the spleen only. Despite upregulation of inducible nitric oxide synthase in trauma animals, circulating nitric oxide metabolites were decreased 2 days after trauma compared with controls (P < .05). Endotoxin-induced nitric oxide metabolites were also reduced in trauma animals compared with endotoxin treatment alone (P < .05), but this normalized by day 4. CONCLUSIONS: Extrahepatic arginase expression and activity is increased after trauma and may provide the necessary precursors for cellular proliferation and repair or may play a regulatory role in the production of nitric oxide.

Conservative treatment of caustic esophageal injuries in children: 20 years of experience.

The authors present their experience in the medical treatment of 1, 296 caustic esophageal injuries in children over the last 20 years in two study groups, one comprising the period up to 1989 and the other 1990 to 1996, comparing the different treatments used in each group. The treatment was based fundamentally on dilatations with anterograde mercury bougies, Savary bougies, or retrograde thread-guided bougies with gastrostomy. Pneumatic balloons or stenting procedures have also been employed in the last 3 years. Early fiberendoscopy was used systematically in the second group, which provides a more accurate evaluation of the esophageal lesions. Antibiotic coverage was done systematically during the first 10 days in all serious cases, while steroids were employed routinely only in the last 3 years. The results were similar in both groups, with a dilatation average of 32 in the first and 30 in the second group and an initial dilatation interval of 3 to 4 weeks in both. Using updated exploration and dilatation techniques, we drastically reduced the number of gastrostomies needed for retrograde thread-guided dilatations from 51 in the first group to 5 in the second, consequently improving the patients' life quality. There was no mortality and only five esophageal perforations, which did not require surgical treatment.

Nitric oxide production is inhibited in trauma patients.

Elevated levels of nitrates/nitrites, the stable endproducts of nitric oxide (NO), were recently observed in septic patients. In this setting, NO maintains blood flow by vasodilation and inhibition of platelet aggregation. Trauma patients were found to have low plasma levels of nitrates/nitrites, even when they developed sepsis. The current study substantiated that trauma patients have suppressed production of NO; reductions in plasma nitrate/nitrite levels correlated with low urinary excretion of these endproducts. Nitric oxide production was upregulated in trauma patients with clinical infection compared with trauma patients without infection, but was still significantly suppressed compared with nitric oxide production in normal controls. The inability of trauma patients to produce NO may be an important component of the susceptibility of these patients to infection.

Nitric oxide synthesis serves to reduce hepatic damage during acute murine endotoxemia.

BACKGROUND AND METHODS: Nitric oxide synthesis occurs both in vitro and in vivo in response to inflammatory stimuli and can have profound effects on the local cellular environment. Hepatocytes, Kupffer cells, and endothelial cells produce nitric oxide in vitro, but the in vivo role of this reactive mediator in the liver is unknown. We assessed the role of nitric oxide synthesis during endotoxemia in mice by inhibiting its synthesis with NG-monomethyl-L-arginine after lipopolysaccharide injection and by determining the effects of this inhibition on hepatic damage. RESULTS: Injection of lipopolysaccharide in mice increased plasma nitrite and nitrate concentrations, the stable end products of nitric oxide metabolism, and caused mild hepatic damage as measured by increased circulating hepatocellular enzyme levels. NG-monomethyl-L-arginine decreased plasma nitrite and nitrate values, but increased the lipopolysaccharide-induced hepatic injury. NG-monomethyl-L-arginine caused no hepatic damage when given without lipopolysaccharide. The extent of hepatic damage with NG-monomethyl-L-arginine was proportional to the dose of lipopolysaccharide used and could be reduced with concurrent administration of L-arginine but not D-arginine. CONCLUSIONS: Nitric oxide synthesis provides a protective function against lipopolysaccharide-induced liver injury that increases in importance as the degree of endotoxemia increases. The production of nitric oxide is, therefore, an important part of the liver's response to a systemic inflammatory stimulus.

Increased circulating nitrogen oxides after human tumor immunotherapy: correlation with toxic hemodynamic changes.

BACKGROUND: Toxicity to interleukin-2 (IL-2) tumor immunotherapy is manifested principally by the vascular leak syndrome, hypotension, and a hyperdynamic response with low systemic vascular resistance. Nitric oxide (.N = O), a recently discovered biological mediator of vascular smooth muscle relaxation, is produced in increased amounts by numerous cell types exposed to a number of inflammatory cytokines. PURPOSE: Our purpose was to determine if there is an increased production of .N = O in patients receiving IL-2 tumor immunotherapy, and, if so, whether increases in .N = O production correlate with hemodynamic instability. METHODS: Twelve patients undergoing immunotherapy trials with IL-2 and anti-CD3 monoclonal antibody-activated lymphocytes (T-AK cells) were studied. Plasma levels of nitrate (NO3-), the stable end metabolic product of .N = O synthesis, were measured before and at the end of IL-2 treatment cycles. RESULTS: We observed a ninefold increase in plasma levels of NO3- in patients after 7 days of treatment (P less than .0001). A significant decrease in both systolic and diastolic blood pressures was observed in all patients (P less than .001). CONCLUSIONS: We propose that mediated induction of .N = O synthase enzyme leads to progressive increases in .N = O production which, in turn, produces clinically significant hypotension. IMPLICATIONS: Since .N = O synthesis can be competitively inhibited by L-arginine analogues, a possible pharmacologic modulation of .N = O production could potentially contribute to better management of toxic side effects seen in IL-2 cancer therapies.

Evaluation of endothelium-derived nitric oxide mediated vasodilation utilizing ex vivo perfusion of an intact vessel.

The traditional evaluation of the endothelium-derived nitric oxide (EDNO) pathway involves isolated aortic rings with attached strain gauges. This model is nonphysiologic and does not permit studies lasting longer than several hours. Our objective was to overcome the limitations of these "traditional" methods utilizing a physiologic, whole vessel model as a reproducible assay of EDNO. Canine carotid arteries (n = 4) were removed (maintaining in vivo arterial geometry), mounted in a specially designed, continuous-flow circuit, and perfused at 100 ml/min, 80 mm Hg with Medium-199/10% canine serum. Physiologic pH, pCO2, pO2, and temperature were precisely regulated. A non-contacting, helium-neon laser micrometer was interfaced with the current system to provide continuous measurement of vessel external diameter and to quantitate changes in vessel wall geometry in response to epinephrine (EPI; 2 x 10(-5) to 2 x 10(-3) mg/ml) and acetylcholine (ACh; 0.1 to 100 microM) challenge. Further characterization of the perfusion system included the use of a competitive inhibitor to EDNO production, NG-monomethyl-L-arginine (L-NMMA), and the effect of this compound on ACh-induced vasodilation. The reversibility of this blockade was verified via the sequential addition of L-arginine (L-ARG; 0 to 3 mM). Data are expressed as the ratio of steady-state vessel cross-sectional area (CSA) following administration of vasoactive substance to the CSA prior to vasoactive challenge. Our results indicate that EPI and ACh produced significant dose-dependent vasoconstrictive and vasodilatory responses, respectively (P less than 0.001, ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)

Association between synthesis and release of cGMP and nitric oxide biosynthesis by hepatocytes.

Hepatocytes are known to synthesize nitric oxide (NO) from L-arginine via an inducible NO synthase. Studies were performed to determine the relationship between hepatocyte NO production and the stimulation of hepatocyte soluble guanylate cyclase. A combination of lipopolysaccharide (LPS), interferon-gamma, tumor necrosis factor, and interleukin-1 stimulates the biosynthesis of large quantities of nitrite and nitrate (NO2- + NO3-). Hepatocyte NO2- + NO3- production was associated with only small increases in intracellular guanosine 3',5'-cyclic monophosphate (cGMP) levels but much greater increases in extracellular cGMP release over an 18-h time period. This cGMP synthesis was dependent on the L-arginine concentration and was inhibited in a reversible manner by NG-monomethyl-L-arginine. The cytokines or LPS added alone induced small increases in nitrogen oxide production and concomitant minor elevations in cGMP release. Atrial natriuretic peptide also stimulated the release of cGMP by hepatocytes which appeared to be independent of the cytokine+LPS-induced cGMP release. The addition of probenecid reduced the cGMP release by 66%, while cell damage was excluded as a cause for the extracellular release. Addition of 3-isobutyl-1-methylxanthine, but not M&B 22948, increased hepatocyte intra- and extracellular cGMP levels after cytokine+LPS stimulation. Induction of nitrogen oxide synthesis by hepatocytes in vivo by injecting rats with killed Corynebacterium parvum resulted in increased cGMP levels in freshly isolated hepatocytes and increased cGMP release by the hepatocytes when placed in culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that nitric oxide production by in vivo allosensitized cells inhibits the development of allospecific CTL.

The oxidative metabolism of L-arginine to its bioactive product, nitric oxide (.N = O) has been shown to inhibit rat splenocyte mixed lymphocyte reactions. To determine if alloantigen-induced .N = O production might be operative in vivo, cells that had infiltrated a rat sponge matrix allograft were tested for de novo .N = O production as well as .N = O production upon restimulation with the sensitizing alloantigen. When graft-infiltrating cells were placed in culture, a peak in de novo .N = O production was observed by day 6 graft-infiltrating cells, the time when donor-specific CTL activity by the graft-infiltrating cells was first observed. Upon restimulation with alloantigen, allograft-infiltrating cells produced greatly increased levels of .N = O, and this production was associated with inhibition of lymphocyte cytolytic function. The addition of NG-monomethyl-L-arginine (NMA), the competitive inhibitor of oxidative L-arginine metabolism, inhibited .N = O production and promoted allospecific CTL development. Both observed effects of NMA were reversed by addition of excess L-arginine. Cytokine(s) able to induce proliferation of the IL-2-dependent T cell line CTLL-2 could be detected in alloantigen-stimulated cultures in both the presence and absence of NMA. However, proliferation of the graft-infiltrating cells in response to these cytokines was observed only in the presence of NMA. The immunosuppressive macrolide FK506 was a potent inhibitor of .N = O production in these cultures, presumably acting by inhibiting the production of those cytokines that induce the oxidative L-arginine pathway.

Nitrogen oxide levels in patients after trauma and during sepsis.

The mediators responsible for maintenance of the hyperdynamic state and the low systemic vascular resistance (SVR) observed in sepsis have not been elucidated. Nitric oxide (.N = O) is a mediator with numerous functions, including regulation of vascular tone and a role in macrophage-mediated cytostasis and microbiostasis. Thirty-nine critically ill trauma and septic patients were studied to determine the relationship between .N = O production and the hyperdynamic state. high plasma levels of NO2-/NO3- (the stable end products of .N = O) were observed in septic patients (p less than 0.02). Low SVR and high endotoxin levels were associated with high NO2-/NO3- values (p = 0.029, p = 0.002). Changes in .N = O levels may mediate the vasodilation seen in sepsis. Low NO2-/NO3- levels were observed in trauma patients (p less than 0.001) and remained low even in the presence of sepsis (p = 0.001).