Attenuated expression of inducible nitric oxide synthase in lung microvascular endothelial cells is associated with an increase in ICAM-1 expression.

BACKGROUND/PURPOSE: The molecular and cellular events that regulate inflammatory lung injury, a major cause of morbidity in surgical patients, remain unclear. The authors hypothesize that nitric oxide (NO) plays an important role in regulating polymorphonuclear cell (PMN)-induced acute lung injury, and further, that attenuated expression of inducible nitric oxide synthase (iNOS) and therefore decreased production of NO by lung microvascular endothelial cells (LMVEC), accelerates inflammation and injury. METHODS: LMVEC and aortic EC (AEC) from rat and human were stimulated with lipopolysaccharide (LPS) and cytokines; changes in iNOS mRNA expression and iNOS activity were determined. The role of NO in mediating inflammatory responses was evaluated by determining PMN adherence to LMVEC and lung tissue slices in the presence and absence of NOS inhibitors and NO donors. Human LMVEC and AEC were assessed by FACS analysis for ICAM-1 expression, because this is thought to be a critical determinant of PMN adherence. RESULTS: When stimulated with endotoxin and cytokines, rat AEC monolayers express nearly 3-fold more iNOS mRNA than rat LMVEC. The low levels of LMVEC iNOS expression are associated with a 4-fold lower nitrite and nitrate production. Similar trends are seen in human endothelial cells. When iNOS activity was blocked, PMN adherence to tumor necrosis factor alpha (TNFalpha)/LPS-stimulated LMVEC was markedly increased. In contrast, adding a nitric oxide donor to endotoxin/cytokine-stimulated LMVEC monolayers reduced PMN adherence to near background levels. Similar responses were observed in vivo. Human lung microvascular endothelial cells show a substantially increased level of ICAM-1 upregulation when compared with similarly stimulated human aortic macrovascular endothelial cells. CONCLUSIONS: These data indicate that LMVEC express less iNOS and produce less NO than AEC. This lower expression and activity of iNOS in LMVEC may be linked to increased expression of ICAM-1. Because ICAM-1 has been shown to be essential for tight PMN adherence, these data suggest that relatively low iNOS expression in LMVEC may contribute to a propensity for the lung to be injured by activated PMNs.

Acute abdominal symptoms and signs in children and young adults with spina bifida: ten years' experience.

BACKGROUND/PURPOSE: Diagnosis and management of the acute abdomen in patients with spina bifida (SB) can be problematic. There are at least 4 clinical factors that can predispose to the development of acute abdominal symptoms and signs, and patients with a thoracic level lesion can have a partially insensate abdomen. The authors analyzed their accumulated experience to determine the annual incidence of acute abdominal signs and symptoms in children and young adults with spina bifida, the differential diagnosis, the operative management, and the outcome. The pertinent literature was reviewed. METHODS: Cases were ascertained during a 10-year period at 1 institution and reviewed retrospectively. RESULTS: Twenty-two episodes of acute abdominal symptoms and signs in 19 children and young adults with SB were ascertained over 10 years at 1 institution, for an annual incidence of 0.74%. More patients had a thoracic level lesion (n = 12; 60%) than in the clinic population as a whole (27%; P =.04), but the gender distribution was similar (58% girls), as was the prevalence of ventriculoperitoneal shunts (VPS; 95%). The median age was 13 years (range, 1 year to 26 years). Hospitalization was necessary for 19 (86%) of the 22 episodes. The duration of symptoms before diagnosis was a median of 3 days (range, 1 to 14 days). Most patients (82%) presented with abdominal pain. Fever was present in 27%, shock in 23%, and peritoneal signs in 23%. There were 14 different final diagnoses, 10 (71%) of which were associated with a predisposing factor. Of the 22 episodes, 18 (82%) could be attributed to an underlying factor: (1) neurogenic bladder (9; 41%); (2) neurogenic bowel (3; 14%); (3) VPS (4; 18%); (4) complications from previous surgery (2; 9%). Thirteen patients (59%) underwent a total of 20 surgical procedures of 12 different kinds. Despite awareness of the complexities involved, 3 patients (14%) died: 1 from complications resulting from bladder perforation; 1 from urosepsis and shock; and 1 from peritonitis caused by VPS infection. CONCLUSION: The differential diagnosis of the acute abdomen in patients with SB is broad, conditions requiring surgery are frequently diagnosed, and the mortality rate is substantial, despite aggressive management.

Successful surgical outcome in children with sickle hemoglobinopathies: the Duke University experience.

BACKGROUND/PURPOSE: Surgery in patients with sickle hemoglobinopathies can be problematic because of the potential for sickling events in the perioperative and postoperative period. The authors and others have previously reported successful surgical outcomes using an aggressive erythrocyte transfusion regimen, designed to alleviate anemia and to reduce the percentage of sickle hemoglobin to below 30%. Recently, a randomized trial compared this aggressive regimen with a more conservative transfusion regimen and found no differences in perioperative complications. The incidence of complications, however, was very high in each group (31% to 35%). METHODS: The authors therefore analyzed retrospectively their surgical experience in children with sickle hemoglobinopathies over the past 10 years to determine the efficacy of an aggressive transfusion regimen and skilled perioperative care in their patient population. RESULTS: A total of 130 surgical procedures were performed on 92 children including 54 cholecystectomies (42%), 23 splenectomies (18%), 12 ENT procedures (9%), 11 central line placements and removals (8%), 7 herniorrhaphies (5%), 7 appendectomies (5%), and 16 miscellaneous operations (13%). The mean age of the children was 10 years (range, 1 to 22 years), and the mean weight was 32.1 kg (range, 9.9 to 76.8 kg). The average hemoglobin (mean +/- 1 SD) at the time of surgery was 11.2+/-1.3 g/dL, and the average percent hemoglobin S was 21+/-11%. CONCLUSIONS: Relatively few transfusions were required to achieve these endpoints, and the complications resulting from transfusions were minimal. Similarly, the number of perioperative and postoperative events was very low.

Differential nitric oxide production by microvascular and macrovascular endothelial cells.

Phenotypic heterogeneity among endothelial cell populations may account for important organ-specific behaviors. Experimental evidence suggests that endothelium-derived nitric oxide mediates certain of these unique responses. The purpose of these investigations was to compare rat pulmonary microvascular endothelial cells with pulmonary artery and aortic macrovascular endothelial cells in their ability to generate nitric oxide (NO). Cultures of these microvascular and macrovascular endothelial cells were incubated with interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and Salmonella typhimurium lipopolysaccharide (LPS) alone or in combination, and nitrite production was measured. Single-agent exposure with IFN-gamma (up to 1,000 U/ml), TNF-alpha (up to 60,000 U/ml), or LPS (up to 500 ng/ml) had little effect on nitrite generation. Nitrite production by rat aortic macrovascular endothelial cells (RAEC) was significantly greater than that by the rat lung microvascular endothelial cells (RLMVEC) when stimulated with TNF-alpha + IFN-gamma, LPS + IFN-gamma, or TNF-alpha + LPS. The maximal response by all endothelial cell types (approximately 15-fold increase in RAEC and 8-fold increase in RLMVEC) was observed with LPS + IFN-gamma. The nitrite generation from rat pulmonary artery endothelial cells was intermediate between RAEC and RLMVEC responses when stimulated with IFN-gamma + LPS or TNF-alpha. Similar patterns of heterogeneous inducible nitric oxide synthase mRNA induction occurred when Northern analysis of specimens from the cultured endothelial cell types was done. These data suggest that phenotypic heterogeneity between these endothelial cell populations is substantial and, by inference, that site-specific NO. generation may occur.

Successful formation of a chimeric human thymus allograft following transplantation of cultured postnatal human thymus.

Transplantation of cultured postnatal human thymus was performed in a patient with complete DiGeorge syndrome. Biopsy of the graft 3 mo after implantation revealed normal CD1+ thymocytes in thymic cortical epithelial regions and CD1- thymocytes in thymic medullary epithelial regions, respectively. HLA analysis of graft thymocyte and thymic microenvironment components demonstrated that developing thymocytes and thymic macrophages were recipient derived, while thymic epithelial components were of donor origin. The patient, who initially had no T cells and had profoundly defective T cell function, developed normal T cell responses to mitogens and Ags, tolerance to donor in a mixed lymphocyte reaction, and normal Ab titers after tetanus toxoid and pneumovax immunization. Thus, transplantation of cultured postnatal human thymic tissue in humans can form functional chimeric thymic tissue, and may provide a strategy to reconstitute the peripheral T cell pool in select congenital and acquired immune deficiency syndromes.

The effect of intestinal reperfusion on renal function and perfusion.

This study examines the effect of intestinal reperfusion injury (IIR) on renal blood flow and relates this temporally to changes in renal ATP levels and renal tubular function. Sprague-Dawley rats underwent 120 min of intestinal ischemia and 60 min of reperfusion (IIR). Renal blood flow was measured with radiolabeled microspheres and a Doppler flow probe. Renal dysfunction was quantitated by measuring inulin clearance and fractional excretion of sodium (FENa) in the isolated perfused organ. Renal tissue ATP levels were measured using a luciferase-luciferin assay. Sham-operated animals served as controls (SHAM). Renal blood flow was reduced by > 80% in the animals sustaining IIR when compared to baseline measurements (P < 0.05) or SHAM (P < 0.05). Temporally this reduction in renal blood flow was associated with a 25% reduction in tissue ATP levels (P < 0.05). The kidneys of animals sustaining IIR had a significantly greater FENa than did those of controls. These data support the notion that IIR is associated with a profound reduction in renal blood flow which is temporally related to reduced renal tissue ATP levels and renal tubular dysfunction.

Hepatic hypoperfusion after intestinal reperfusion.

BACKGROUND: Intestinal ischemia-reperfusion injury (IIR) induces hepatic and pulmonary dysfunction and thus has been used as a model of multiple organ failure syndrome. This study examines the hypothesis that hepatic blood flow is markedly reduced in this injury model. METHODS: Sprague-Dawley rats underwent 120 minutes of intestinal ischemia and 60 minutes of reperfusion (IIR). Hepatic blood flow was measured with radiolabeled microspheres and Doppler flow probes. Hepatic dysfunction was quantitated by measuring bile flow and serum alanine aminotransferase and hepatic tissue adenosine triphosphate levels. Sham-operated animals served as controls. RESULTS: Intestinal ischemia reduced portal flow by 66% when compared with sham-operated animals (p = 0.0001) but had no effect on hepatic arterial flow. In contrast, reperfusion reduced hepatic artery flow by 80% when compared with controls (p = 0.002) with most of this change occurring within 5 minutes of reperfusion. IIR induced a 63% reduction in bile flow (p < 0.05), a fivefold rise in serum alanine aminotransferase level (p < 0.0002), and a 33% reduction in hepatic adenosine triphosphate level (p < 0.05). CONCLUSIONS: These data suggest that IIR induces profound hepatic hypoperfusion, which is temporally related to acute hepatic dysfunction. This observation suggests that hepatic ischemia may contribute to IIR-induced liver injury.

Oxidized glutathione as a marker of ischemia reperfusion associated with single lung transplantation.

BACKGROUND: Previous data have shown that glutathione (GSH), an endogenous antioxidant, is converted to its oxidized form (GSSG) after oxidative ischemia-reperfusion events. As GSSG is toxic to cells and is extruded through an active mechanism dependent on intracellular GSSG levels, substance appears in plasma. STUDY DESIGN: Single lung transplantation was performed upon 18 puppies, 3 to 5 kg, with a two hour ischemic time for the donor lung before reimplantation. Recipient animal plasma was obtained after anesthesia induction, pulmonary artery ligation, recipient pneumonectomy, reestablishment of blood flow to the donor lung, completion of transplant, and one, two, and three hours postoperatively. Donor lung bronchoalveolar lavage fluid (BALF) was obtained at the time of harvest, after perfusion of the donor lung with EuroCollins, immediately pretransplant, and after completion of the vascular anastomoses. Oxidized and total GSH levels in plasma and BALF samples were determined by a spectrophotometric assay. RESULTS: After reimplantation of the ischemic donor lung, there was a statistically significant increase in both GSSG and GSH in plasma samples, and a statistically significant increase in GSSG in the BALF. CONCLUSIONS: Compartmental differences between arterial and venous plasma, as well as the increase in GSSG in the BALF, implicated the lung that was transplanted as the source of oxygen free radical generation and GSSG release. Plasma GSSG levels seem to provide a sensitive, noninvasive, repeatable measure of ongoing tissue response and oxygen free radical production.

Cytoprotection by diclofenac sodium after intestinal ischemia/reperfusion injury.

Intestinal injury resulting from ischemia/reperfusion (I/R) is of fundamental importance in clinical pediatric surgery. I/R injury results from inadequate oxygen delivery as well as a secondary inflammatory response involving neutrophils and oxidants. This study was designed to evaluate a novel use for diclofenac sodium (DS), a nonsteroidal antiinflammatory agent, and to compare it with traditional antioxidants in this setting. Rats were subjected to intestinal ischemia followed by reperfusion. When killed, samples were obtained for measurement of intestinal myeloperoxidase (MPO), a measure of neutrophil sequestration, as well as for adenosine triphosphate (ATP) content, a marker of tissue injury. Animals exposed to I/R injury had significant neutrophil sequestration in the intestine by 120 minutes of ischemia, and this persisted after 60 minutes of reperfusion. DS pretreatment did not prevent neutrophil sequestration in the intestine. Analysis of intestinal ATP content demonstrated a decrease in intestinal ATP after 120 minutes of ischemia, and this did not change with 60 minutes of reperfusion. Pretreatment with DS significantly attenuated this intestinal ATP depletion. Furthermore, with 120 minutes of ischemia and 60 minutes of reperfusion, ATP preservation with DS pretreatment exceeded that obtained using the following conventional antioxidants: a xanthine-oxidase inhibitor (lodoxamide), deferoxamine, dimethysulfoxide, and superoxide dismutase plus catalase. DS has a significant cytoprotective effect for intestine subjected to I/R injury, exceeding that of conventional antioxidants. DS does not attenuate injury by preventing neutrophil influx into injured intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

Endotoxemia and remote organ injury following intestinal reperfusion.

This study addresses the hypothesis that endotoxin (LPS) is an important proximal mediator of remote organ dysfunction following intestinal reperfusion. Sprague-Dawley rats underwent intestinal ischemia for 120 min followed by 60 min of reperfusion (IIR). Animals underwent pretreatment with polymyxin B (PMB, 200 micrograms, sc) or the induction of tolerance to LPS prior to assignment to the IIR or sham group. Controls received equal volumes of normal saline. Lung and intestinal injury was quantitated using an edema index. Bile flow was quantitated by measuring the volume of bile produced per 15 min. The intestinal edema index of IIR animals pretreated with PMB was nearly 50% less than that of saline-treated animals sustaining the same injury (P < 0.05). The induction of LPS tolerance reduced the edema index of IIR animals by 28% compared to the saline-treated IIR group (P < 0.05). Neither treatment reduced this parameter to that of sham-operated controls (P < 0.05). The lung edema index of animals pretreated with PMB was 50% of that of saline-treated IIR animals (P < 0.05). This remained significantly greater than that of sham-operated controls (P < 0.05). LPS tolerance did not affect the lung edema index of animals sustaining IIR. Bile flow rates following IIR were not significantly affected by PMB or LPS tolerance. These data do not support the hypothesis that LPS is an important proximal mediator of the remote organ injury associated with IIR. However, they do suggest that LPS may be one of many mediators responsible for this injury.

Reperfusion injury following single-lung transplantation: the tissue glutathione response.

Parenchymal injury following reperfusion of the donor lung remains a significant problem in clinical lung transplantation. It has been postulated that free oxygen radicals act as local mediators of this event, and that tissue oxidized glutathione levels which reflect local free oxygen radical production, may be useful as an indicator of this regional ischemia-reperfusion injury. The glutathione redox cycle plays a physiologically important role in the endogenous antioxidant defense system. Intracellular glutathione depletion has been shown to render cells vulnerable to oxidant mediated injury. Adequate glutathione stores may be vital in protecting the cell from oxidant injury, especially the relatively exposed pulmonary epithelial cells. Single lung transplantation was carried out in 10 3- to 5-kg mongrel puppies, with a standard 2-hour ischemic time for the donor lung prior to reimplantation. Four hours following transplantation, lung tissue was harvested from both the transplanted and native lung of the recipient animal, and compared to normal lung tissue from the donor animal. Tissue was prepared for histological evaluation and glutathione assay. Tissue glutathione levels were determined via a spectrophotometric assay. For determination of oxidized glutathione (GSSG), samples were prepared with 2-vinylpyridine and N-ethylmaleimide (NEM) to derivatize all reduced glutathione and leave only GSSG for measurement by the fluorometric assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Inflammatory cloacogenic polyp in a child: part of the spectrum of solitary rectal ulcer syndrome.

A 15-year-old boy with Marshall-Smith syndrome presented with increased frequency and urgency of stooling, hematochezia, and rectal pain. A polypoid mass was found at the anorectal junction and excised. Microscopically, the lesion was covered by both squamous and columnar mucosa. It was villiform in configuration with focal ulceration and strands of smooth muscle in the lamina propria. These features are characteristic of an inflammatory cloacogenic polyp, a lesion not previously reported in the pediatric age group. Inflammatory cloacogenic polyp is related to solitary rectal ulcer syndrome and is most likely due to prolapse of the anorectal transition zone. Although rare in this age group, solitary rectal ulcer and its variants should be considered in the differential diagnosis of anorectal and rectal lesions in the pediatric patient.

Decreased oxidized glutathione with aerosolized cyclosporine delivery.

Cyclosporine immunosuppression remains vital for successful lung transplantation. Cyclosporine also functions as a membrane active biological response modifier and has been noted to have a variable effect on ischemia-reperfusion (I/R) injury in various tissues. Glutathione plays an important role in the endogenous antioxidant defense system; plasma oxidized glutathione (GSSG) levels are useful as a sensitive indicator of in vivo oxidant stress and I/R injury. Lung transplantation results in ischemia, followed by a period of reperfusion, potentially producing functional injury. This study was designed to evaluate the effect of cyclosporine on oxygen radical generation in a model of single-lung transplantation. Single-lung transplantation was performed in 12 mongrel puppies, with animals assigned to receive either intravenous or aerosolized cyclosporine. Arterial blood and bronchoalveolar lavage fluid (BALF) samples were obtained to determine GSSG levels via a spectrophotometric technique. Samples were obtained both prior to and following the revascularization of the transplanted lung. Whole blood and tissue cyclosporine levels were determined via an high-performance liquid chromatography technique 3 hr following the completion of the transplant. Aerosolized cyclosporine administration resulted in greatly decreased arterial plasma and BALF GSSG levels, whole blood cyclosporine levels, and equivalent tissue cyclosporine levels when compared to intravenous cyclosporine delivery. These findings support the hypothesis that the transplanted lung is a source of GSSG production and release into plasma. Additionally, these findings suggest that cyclosporine may have a direct antioxidant effect on pulmonary tissue, with this activity occurring at the epithelial surface, an area susceptible to oxidant injury.

Intestinal ischemia-reperfusion injury causes pulmonary endothelial cell ATP depletion.

Intestinal ischemia-reperfusion is a common clinical event associated with both clinical and experimental distant organ injury. In particular, the pulmonary microvasculature appears to be susceptible to injury resulting from systemic inflammatory mediator activation. This study was designed to evaluate the hypothesis that noncellular humoral factors associated with intestinal ischemia-reperfusion result in pulmonary endothelial cell adenosine triphosphate (ATP) depletion. Male Sprague-Dawley rats had intestinal ischemia induced by microvascular clip occlusion of the superior mesenteric artery (SMA) for 120 minutes. Reperfusion resulted from superior mesenteric artery clip removal. After reperfusion for 0, 15, or 30 minutes, plasma samples were obtained from the portal vein. Monolayers of cultured rat pulmonary artery endothelial cells then were incubated with the plasma samples. Adenosine triphosphate levels were determined using a luciferin-luciferase assay. A 51Cr-release assay using labeled endothelial cells was performed under identical conditions to assess cytotoxicity. Potential mechanisms of ATP depletion were evaluated by analysis of cellular energy charge and assessment of microfilament architecture. Endothelial cell ATP levels decreased from 2.23 +/- 0.16 x 10(-11) moles/microgram DNA in sham preparations to 1.23 +/- 0.09 x 10(-11) moles/microgram DNA (p < 0.001) after 4 hours in plasma from animals undergoing 120 minutes of intestinal ischemia. For plasma obtained after 15 minutes of reperfusion, the decrease in cellular ATP concentration persisted (1.23 +/- 0.27 x 10(-11) moles/microgram DNA, p < 0.001 vs. sham). After 30 minutes' reperfusion, cellular ATP levels increased only slightly after the 4-hour incubation (1.39 +/- 0.26 x 10(-11) moles/microgram DNA, p < 0.005 vs. sham). No significant cytotoxic injury occurred in any group when compared with controls. Cellular energy charge was unchanged, and microfilament architecture was preserved. These data confirm the hypothesis that humoral factors, independent of the neutrophil, result in endothelial cell ATP depletion without metabolic inhibition or cell death. Depletion of energy stores by noncellular humoral factors may represent an early event that predisposes the cell to more severe injury by other mediators of the endogenous inflammatory response.

Mycotic thromboaneurysmal disease of the abdominal aorta in preterm infants: its natural history and its management.

Five infants with mycotic complications of umbilical artery catheterization were evaluated with abdominal ultrasound and followed serially to document their natural history. Methicillin-resistant Staphylococcus aureus was always the infecting organism. There were one female and four male infants and they weighed between 900 and 1,200 g at birth. While two of the catheters were positioned in the abdominal aorta, three were located above the diaphragm. The predominate signs and symptoms included: thrombocytopenia, unexplained anemia, renal failure, hypertension, and embolic phenomena to the toes. Real-time ultrasound always proved sufficient for diagnosis. Serial studies detected the initial aortic thrombosis in three patients and accurately documented its progression to aneurysmal disease over 10 days in one patient and 17 days in another. Three of the infants were diagnosed with aneurysms at their initial examination. Of the five patients, three were treated nonoperatively and died of complications of their aortic disease. One patient was discovered at operation to have necrotic ischemic intestine. Aortic repair was postponed and he died of septic complications. The remaining patient underwent a PTFE interposition graft and survived for 6 months, dying of pulmonary failure with autopsy confirmed graft patency.

Pulmonary endothelial cell ATP depletion following intestinal ischemia.

Multiple organ failure (MOF) is known to follow systemic inflammatory mediator activation associated with intestinal ischemia-reperfusion injury. In particular, the pulmonary microvasculature appears to be susceptible to MOF-related injury. This study was designed to evaluate the hypothesis that non-cellular plasma factors associated with intestinal ischemia without reperfusion also mediate pulmonary endothelial cell injury. Male Sprague-Dawley rats had intestinal ischemia induced by microvascular clip occlusion of the superior mesenteric artery for 30, 60, 90, or 120 min. Following each period of ischemia, plasma samples were obtained from the protal vein. Time-matched sham-operated animals served as controls. Monolayers of cultured rat pulmonary artery endothelial cells were then incubated with the plasma samples and ATP levels determined using a luciferin-luciferase assay. A 51Cr-release assay using labeled endothelial cells was performed under identical conditions to assess cytotoxicity. Endothelial cell ATP levels were 1.99 +/- 0.23 x 10(-11) mole/micrograms DNA in sham preparations. After a 4-hr incubation in plasma from the 90 and 120 min ischemia groups, cellular ATP levels fell significantly to 1.07 +/- 0.23 x 10(-11) mole/micrograms DNA, respectively (P less than 0.005). No significant cytotoxic injury resulted from incubation with plasma from the 120 min group (1.0 +/- 0.4% versus 0.8 +/- 0.4% in sham group, P = NS). All animals survived 24 hr in the sham, 30, and 60 min groups. However, survival was 40 and 0% in the 90 and 120 min groups, respectively (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocellular oxidant stress following intestinal ischemia-reperfusion injury.

Reperfusion of ischemic intestine results in acute liver dysfunction characterized by hepatocellular enzyme release into plasma, reduction in bile flow rate, and neutrophil sequestration within the liver. The pathophysiology underlying this acute hepatic injury is unknown. This study was undertaken to determine whether oxidants are associated with the hepatic injury and to determine the relative value of several indirect methods of assessing oxidant exposure in vivo. Rats were subjected to a standardized intestinal ischemia-reperfusion injury. Hepatic tissue was assayed for lipid peroxidation products and oxidized and reduced glutathione. There was no change in hepatic tissue total glutathione following intestinal ischemia-reperfusion injury. Oxidized glutathione (GSSG) increased significantly following 30 and 60 min of reperfusion. There was no increase in any of the products of lipid peroxidation associated with this injury. An increase in GSSG within hepatic tissue during intestinal reperfusion suggests exposure of hepatocytes to an oxidant stress. The lack of a significant increase in products of lipid peroxidation suggests that the oxidant stress is of insufficient magnitude to result in irreversible injury to hepatocyte cell membranes. These data also suggest that the measurement of tissue GSSG may be a more sensitive indicator of oxidant stress than measurement of products of lipid peroxidation.

Anti-tumor necrosis factor antibody augments edema formation in caerulein-induced acute pancreatitis.

The pathogenesis of acute pancreatitis is incompletely defined, but the outcome is determined in part by an acute inflammatory process. Pancreatitis-associated inflammation appears to play a role in the local retroperitoneal injury as well as in the associated dysfunction of remote organs such as the lung. Tumor necrosis factor (TNF) appears to be a proximal mediator of the inflammatory response. In this study, anti-TNF antibody was administered to rats with caerulein-induced pancreatitis to determine if the observed increases in pancreatic and pulmonary microvascular permeability were related to plasma TNF activity. In contrast to the expected findings, blockade of TNF activity was found to increase the amount of edema formation in both the pulmonary and pancreatic microvascular beds. The mechanism is not known; however, blockade of TNF-induced down regulation of phagocytic cell activity, ablation of TNF-dependent feedback inhibition of other cytokines, failure of induction of endogenous antioxidant systems, or inactivation of the TNF control of microvascular tone are all possible explanations. This is potentially an important observation as clinical strategies are now being developed to modify the inflammatory response in ways presumed advantageous to an injured host.