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The role of thymectomy for the treatment of myasthenia gravis has evolved since the initial descriptions by Sauerbruch in 1913 and Blalock and colleagues in 1939. Currently, thymectomy is the treatment of choice for patients with stable myasthenia gravis or thymomas. There is considerable debate with regard to the approach and extent of thymectomy, especially for patients with myasthenia gravis without thymoma. Some authors have advocated minimally invasive approaches to total thymectomy, including transcervical, thoracoscopic, and modified sternotomy techniques. Unfortunately, these techniques may not fully remove all thymic tissue, which has been reported by Jaretzki and colleagues to be frequently distributed throughout the anterior (including superior) mediastinum. Consequently, Jaretzki has been a consistent proponent of “maximal thymectomy,” resecting all thymic tissue through a transsternal approach. We agree with Jaretzki’s approach to the surgical treatment of myasthenia gravis and thymoma, and since 1986, we have used a modified transsternal technique for the treatment of these patients. The purpose of this article is to describe this technical approach, which we term “anterior-superior cervicomediastinal exenteration,” for the treatment of myasthenia gravis or thymoma.

Endothelial cell ICAM-1 upregulation in response to TNF-α is mediated in part by reactive oxygen species (ROS) generated by the endothelial membrane-associated NADPH oxidase and occurs maximally after 4 h as the synthesis of new protein is required. However, thrombin-stimulated P-selectin upregulation is bimodal, the first peak occurring within minutes. We hypothesize that this early peak, which results from the release of preformed P-selectin from within Weibel-Palade bodies, is mediated in part by ROS generated from the endothelial membrane-associated xanthine oxidase. We found that this rapid expression of P-selectin on the surface of endothelial cells was accompanied by qualitatively parallel increases in ROS generation. Both P-selectin expression and ROS generation were inhibited, dose dependently, by the exogenous administration of disparate cell-permeable antioxidants and also by the inhibition of either of the known membrane-associated ROS-generating enzymes NADPH oxidase or xanthine oxidase. This rapid, posttranslational cell signaling response, mediated by ROS generated not only by the classical NADPH oxidase but also by xanthine oxidase, may well represent an important physiological trigger of the microvascular inflammatory response.

Xanthine oxidoreductase (XOR) is a ubiquitous metalloflavoprotein that appears in two interconvertible yet functionally distinct forms: xanthine dehydrogenase (XD), which is constitutively expressed in vivo; and xanthine oxidase (XO), which is generated by the posttranslational modification of XD, either through the reversible, incremental thiol oxidation of sulfhydryl residues on XD or the irreversible proteolytic cleavage of a segment of XD, which occurs at low oxygen tension and in the presence of several proinflammatory mediators. Functionally, both XD and XO catalyze the oxidation of purines to urate. However, whereas XD requires NAD+ as an electron acceptor for these redox reactions, thereby generating the stable product NADH, XO is unable to use NAD+ as an electron acceptor, requiring instead the reduction of molecular oxygen for this purine oxidation and generating the highly reactive superoxide free radical. Nearly 100 years of study has documented the physiologic role of XD in urate catabolism. However, the rapid, posttranslational conversion of XD to the oxidant-generating form XO provides a possible physiologic mechanism for rapid, posttranslational, oxidant-mediated signaling. XO-generated reactive oxygen species (ROS) have been implicated in various clinicopathologic entities, including ischemia/reperfusion injury and multisystem organ failure. More recently, the concept of physiologic signal transduction mediated by ROS has been proposed, and the possibility of XD to XO conversion, with subsequent ROS generation, serving as the trigger of the microvascular inflammatory response in vivo has been hypothesized. This review presents the evidence and basis for this hypothesis.

Chronic granulomatous disease (CGD) is an inherited disorder of the NADPH oxidase in which phagocytes are defective in generating superoxide and downstream microbicidal reactive oxidants, leading to recurrent life-threatening bacterial and fungal infections. Xanthine oxidase (XO) is another enzyme known to produce superoxide in many tissues. Using the p47phox−/−mouse model of CGD, we evaluated the residual antibacterial activity of XO. Clearance ofBurkholderia cepacia, a major pathogen in CGD, was reduced in p47phox−/−mice compared to that in wild-type mice and was further inhibited in p47phox−/−mice by pretreatment with the specific XO inhibitor allopurinol. HepaticB. cepaciaburden was similar in the two genotypes, but allopurinol significantly reduced net hepatic killing and killing efficiency only in p47phox−/−mice. Clearance and killing of intravenousEscherichia coliwas intact in p47phox−/−mice and was unaffected by pretreatment with allopurinol. In CGD, XO may contribute to host defense against a subset of reactive oxidant-sensitive pathogens.

Previous studies indicate that cardiogenic shock (tamponade) in swine produces selective mesenteric ischemia due to disproportionate mesenteric vasospasm mediated primarily by the renin-angiotensin axis. Here, we characterized the systemic and mesenteric hemodynamic responses to hypovolemic shock to better understand the neurohumoral mechanisms controlling this response. Varying degrees of hypovolemic shock were produced by graded levels of hemorrhage, from 12.5 to 50% of the calculated blood volume. Systemic and mesenteric pressures and blood flows were measured, and corresponding vascular resistances were calculated. The hemodynamic responses of the mesenteric vascular bed were compared with those of the systemic (nonmesenteric) vasculature. These experiments were then repeated after confirmed blockade either of the alpha-adrenergic nervous system (phenoxybenzamine), of vasopressin (Manning compound), or of the renin-angiotensin axis (enalapril). Graded levels of hemorrhage produced corresponding graded, reproducible, steady-state levels of systemic hypotension, hypoperfusion, and peripheral vasoconstriction, i.e., hemorrhagic shock. This was associated with disproportionate degrees of mesenteric ischemia due to disproportionate mesenteric vasoconstriction. The selective component of this mesenteric vasoconstrictive response was not attenuated by a-adrenergic blockade nor by vasopressin blockade but was blocked by ablation of the renin-angiotensin axis with enalapril. Like cardiogenic shock, hemorrhagic shock generates selective mesenteric ischemia by producing a disproportionate mesenteric vasospasm that is mediated primarily by the renin-angiotensin axis.

The goals of this study were to (1) determine the utility of quantification of ethane as a marker of ischemia-reperfusion during human cardiopulmonary bypass (CPB); and (2) determine, using an animal model for this surgical procedure, whether the mode of surgical approach produced increases the quantity of exhaled ethane. Human CPB was initiated following standard anesthetic and monitoring regimens. Samples of gas were collected at baseline and at multiple defined time points throughout the studies. Ethane was determined using cryogenic concentration and gas chromatography. Sternotomy increased exhaled ethane compared to baseline (p.007; 5.8 +/- 1.7 vs. 3.0 +/- 0.7 nmol/m2 x min); ethane returned to baseline levels prior to the initiation of CPB. Aortic unclamping produced ethane elevation (p.05; 2.3 +/- 0.8 vs. 1.5 +/- 0.4 nmol/m2 x min) with the levels being related to a lower cardiac index and a higher systemic vascular resistance post aortic unclamping. Termination of CPB significantly increased ethane levels compared to baseline (p.002; 4.8 +/- 1.7 vs. 3.0 +/- 0.7 nmol/m2 x min). Independent variables that correlated with increased ethane measurements included a higher arterial blood pH on bypass and the change in hemoglobin pre- and post-CPB. Electrocautery, but not scalpel, incision of the porcine abdominal wall increased ethane levels significantly (p.02). These results indicate that exhaled ethane may be a valuable marker of lipid peroxidation during and following CPB.

The endothelial expression of adhesion molecules by proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) has been suggested to contribute to the initiation of atherosclerotic plaque formation. Since lactosylceramide (LacCer) accumulates in large quantities in human atherosclerotic plaque, we have explored its role in TNF-alpha-induced expression of intercellular adhesion molecule-1 (ICAM-1) in human umbilical vein endothelial cells and their consequent adhesion to polymorphonuclear leukocytes (PMNs). We found that TNF-alpha increased LacCer synthesis by way of stimulating the activity of UDP-galactose:glucosylceramide beta(1--4)-galactosyltransferase in a time-dependent fashion. The TNF-alpha-induced expression of ICAM-1 was abrogated by D-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP), an inhibitor of UDP-galactose:glucosylceramide beta(1--4)-galactosyltransferase. However, the addition of LacCer reversed the D-PDMP effect on TNF-alpha-induced ICAM-1 expression in human umbilical vein endothelial cells. Northern hybridization analysis of mRNA levels and enzyme-linked immunosorbent assays revealed that LacCer (5 microM) specifically stimulated ICAM-1 at both the transcriptional and translational levels. This was accompanied by the adhesion of PMNs, which was visualized by confocal microscopy. Further studies revealed that LacCer stimulated the endogenous generation of superoxide radicals (O-2) about 5-fold compared with the control by specifically activating plasma membrane-associated NADPH-dependent oxidase. This phenomenon was blocked by the antioxidant N-acetyl-L-cysteine, pyrrolidine dithiocarbamate, and the NADPH oxidase inhibitor, diphenylene iodonium. Overexpression of endogeneous CuZn-superoxide dismutase via an adenoviral vector carrying cDNA for CuZn-superoxide dismutase, also inhibited LacCer-induced ICAM-1 expression in endothelial cells. In sum, our findings suggest that LacCer may play the role of a lipid second messenger in TNF-alpha-induced pathogenesis by activating an oxidant-sensitive transcriptional pathway that leads to the adhesion of PMNs to endothelial cells.

Background: Reactive oxygen metabolites generated from endothelial xanthine oxidase (XO) trigger reperfusion injury in many organs. We evaluated the possibility that endothelial XO was localized on the endothelial cell surface, as well as within the cytoplasm. Methods: Primary cultures of bovine (BAECs) and porcine (PAECs) aortic endothelial cells were grown in media documented to be free of XO. Polyclonal and monoclonal antibodies were developed against XO. These antibodies were used to evaluate BAEC and PAEC for cell surface XO through immunofluorescence staining, hybridoma cell surface labeling, and endothelial cell surface binding. Results: These antibodies bound specifically to the surface of these cells when the membrane was shown to be intact and impermeable (and the cytoplasm inaccessible) to immunoglobulins. Moreover, hybridoma cells expressing monoclonal antibody to XO bound specifically to the endothelial cell surface. Finally, intact endothelial cells bound specifically to the anti-XO polyclonal antibodies immobilized to the surface of a Petri dish. The integrity of these endothelial cell plasma membranes was demonstrated by the subsequent growth and replication of these cells in culture. Conclusions: These findings indicate that XO is present on the outside surface of the endothelial cell plasma membrane. This would not only explain the known in vivo efficacy of intravascularly administered large molecular weight antioxidants (such as superoxide dismutase) but could have important implications for inflammatory signaling. (Surgery 1998;124:551-60.)

Proinflammatory cytokines upregulate endothelial adhesion molecule expression, thereby initiating the microvascular inflammatory response. We re-evaluated the reported role of reactive oxygen metabolites (ROMs) in signalling upregulation of intercellular adhesion molecule 1 (ICAM-1) on endothelial cells by tumour necrosis factor alpha (TNF-alpha) in vitro. TNF-alpha upregulation of endothelial-cell ICAM-1 expression was inhibited by the cell-permeable antioxidants, or by the adenovirus-mediated intracellular overexpression of Cu,Zn-superoxide dismutase, but not by the exogenous (extracellular) administration of the cell-impermeable antioxidants, superoxide dismutase and/or catalase. This ICAM-1 upregulation was also inhibited by inhibitors of NADH dehydrogenase, cytochrome bc1 complex and NADPH oxidase. However, a measurable increase in net cellular ROM generation in response to TNF-alpha was not seen using four disparate sensitive ROM assays. Moreover, the stimulation of exogenous or endogenous ROM generation did not upregulate ICAM-1, nor enhance ICAM-1 upregulation by TNF-alpha. These findings suggest that an ambient background flux of ROMs, generated intracellularly, but not their net incremental generation, is necessary for TNF-alpha to induce ICAM-1 expression in endothelium in vitro.

Abstract —Glycosphingolipids (GSLs) and their metabolites play important roles in a variety of biological processes. We have previously reported that lactosylceramide (LacCer), a ubiquitous GSL, stimulates NADPH oxidase–dependent superoxide generation by aortic smooth muscle cells and their consequent proliferation. We postulated that LacCer may upregulate adhesion molecules on human polymorphonuclear leukocytes (hPMNs), perhaps also via NADPH oxidase–dependent reactive oxygen metabolite (ROM) generation. Incubation of hPMNs with LacCer upregulated CD11b/CD18 (Mac-1) and CD11c/CD18, as determined by fluorescence-automated cell sorting. LacCer also stimulated these hPMNs to generate superoxide via NADPH oxidase, as determined by lucigenin-enhanced chemiluminescence. However, the upregulation of Mac-1 by LacCer did not itself appear to be mediated by ROMs, since neither an antioxidant nor an NADPH oxidase inhibitor substantially inhibited the Mac-1 upregulation. However, this Mac-1 upregulation was significantly inhibited by two disparate phospholipase A 2 (PLA 2 ) inhibitors. Moreover, LacCer induced arachidonic acid metabolism, which was inhibited by the PLA 2 inhibitors, but not by an NADPH oxidase inhibitor. To evaluate the effect of LacCer on hPMN adhesion to endothelium, hPMNs stimulated with LacCer were allowed to adhere to unstimulated human endothelial cell monolayers. LacCer stimulated hPMN adhesion to endothelial cells, which was blocked by anti-CD18 and by the PLA 2 inhibitors. We conclude that LacCer stimulates both Mac-1 upregulation and superoxide generation in hPMNs but that ROMs are not the upstream signal for Mac-1 upregulation. This mechanism may well be relevant to acute endothelial injury in inflammation and other pathological conditions.

Proinflammatory cytokines initiate the vascular inflammatory response via the upregulation of adhesion molecules on the luminal endothelial surface. We investigated directly the role of protein tyrosine phosphorylation in the upregulation of the endothelial adhesion molecules, intercellular adhesion molecule 1 (ICAM-1) and E-selectin, and the consequent adhesion of neutrophils, after tumor necrosis factor (TNF)-alpha-stimulation of human aortic endothelial cells in vitro. Time- and dose-dependent TNF-alpha-stimulated ICAM-1 and E-selectin upregulation and neutrophil adhesion each were suppressed by tyrosine kinase inhibitors, including genistein (200 microM), but not genistein, its isoflavone analog without tyrosine kinase inhibitory activity. Tyrphostin AG 126, a synthetic selective tyrosine kinase inhibitor, also suppressed ICAM-1 and E-selectin upregulation and neutrophil adhesion, each in a dose-dependent manner, whereas tyrphostin AG 1288 had no effect. Tyrosine phosphorylation of two proteins (85 and 145 kDa in the cytoskeleton fraction) found minutes after TNF-alpha-stimulation was also inhibited by genistein. These findings suggest that, in endothelial cells, TNF-alpha upregulates ICAM-1 and E-selectin expression and consequent neutrophil adhesion via protein tyrosine phosphorylation.

Obesity is associated with an increased incidence of infection, diabetes, and cardiovascular disease, which together account for most obesity-related morbidity and mortality. Decreased expression of leptin or of functional leptin receptors results in hyperphagia, decreased energy expenditure, and obesity. It is unclear, however, whether defective leptin-dependent signal transduction directly promotes any of the conditions that frequently complicate obesity. Abnormalities in tumor necrosis factor α expression have been noted in each of the above comorbid conditions, so leptin deficiency could promote these complications if leptin had immunoregulatory activity. Studies of rodents with genetic abnormalities in leptin or leptin receptors revealed obesity-related deficits in macrophage phagocytosis and the expression of proinflammatory cytokines both in vivo and in vitro. Exogenous leptin up-regulated both phagocytosis and the production of proinflammatory cytokines. These results identify an important and nov...

This study was designed to quantify the role of reactive oxygen metabolites (ROMs) in two distinct components of murine peritoneal macrophage activity, phagocytosis and killing, and to discriminate quantitatively the degree to which each component is dependent on NADPH oxidase and/or xanthine oxidase. A fluorochromatic vital staining technique was modified to simultaneously quantify phagocytosis and microbicidal activity of macrophages incubated with Candida parapsilosis targets. To determine the role of ROMs, macrophages were preincubated with free radical scavengers [superoxide dismutase (SOD) and/or catalase] or with selective inhibitors of xanthine oxidase (XO, e.g., allopurinol) or NADPH oxidase [diphenyleneiodonium (DPI)]. Phagocytosis was not affected by treatment of macrophages with SOD, catalase, allopurinol, or DPI. Candidacidal activity, however, was inhibited by SOD, allopurinol, or DPI. The inhibitory effects of DPI and allopurinol were additive. Histochemical and biochemical assays demonstrated substantial quantities of XO in murine peritoneal macrophages. The findings suggest that the generation of ROMs by XO- and NADPH oxidase-dependent pathways are each important for phagocytic killing by murine peritoneal macrophages.

We investigated the role of reactive oxygen metabolites (ROMs) as potential mediators of tumor necrosis factor-alpha (TNF-alpha)-stimulated neutrophil adhesion to rat mesenteric venules in vivo, using intravital microscopy and fixed whole mount preparations of mesentery. Intraperitoneal injection of TNF-alpha significantly increased leukocyte rolling, adhesion, and emigration in a dose- and time-dependent manner. Leukocyte adhesion and emigration, but not rolling, were significantly attenuated by prior intravenous administration of monoclonal anti-intercellular adhesion molecule-1 (ICAM-1). Rolling leukocyte flux was significantly attenuated by intravenous preadministration of superoxide dismutase (SOD), catalase, or both. Only catalase or SOD plus catalase significantly inhibited leukocyte adhesion. Catalase alone inhibited emigration. Moreover, postadhesive treatment with catalase but not SOD, 4 h after TNF-alpha administration reduced the flux of rolling (but not adherent) leukocytes that had previously increased in response to TNF-alpha. Intragastric allopurinol (50 mg/kg at 3 and 18 h before TNF-alpha administration) or 3 wk of a tungsten-enriched diet substantially inhibited xanthine oxidase activity but had no significant effects on the above parameters of neutrophil dynamics. In parallel experiments using fixed whole mount preparations of the mesoappendix stained specifically for neutrophil esterase, neutrophil adhesion 2 h after TNF-alpha administration was also inhibited by continuous intravenous administration of catalase but not by SOD, intragastric allopurinol, or tungsten diet. These findings suggest that ROMs, apparently not from xanthine oxidase, are important mediators of TNF-alpha-induced upregulation of neutrophil adhesion in rat mesenteric venules.

We investigated the role of reactive oxygen metabolites (ROMs) as potential mediators of delayed "spontaneous" leukocyte adhesion to rat mesenteric venules after the manipulation for in vivo microscopy. Rats were anesthetized via tail vein and prepared for intravital microscopic viewing of a segment of mesenteric venule. Leukocyte rolling, adhesion, and emigration were quantitated every 30 min for 3 h. Intravital observation immediately after routine gentle manipulation revealed a substantial leukocyte rolling and a small number of adherent and emigrated leukocytes. This rolling leukocyte flux then declined to a minimal level for 60 min. The number of adherent and emigrated leukocytes did not change during the initial 90 min. After 120 min, the flux of rolling leukocytes, and adherent and emigrated leukocyte number began to increase and reached significant levels at 180 min. To determine the possible role of ROMs in this "spontaneous" adhesion, rats were treated continuously with superoxide dismutase (SOD) plus catalase given intravenously over 3 h. Rolling leukocyte flux after 120 min was significantly attenuated by SOD plus catalase. SOD + catalase also significantly inhibited delayed leukocyte adhesion and emigration. Allopurinol substantially inhibited xanthine oxidase activity but had no significant effects on the above parameters of neutrophil dynamics. These findings suggest that ROMs, probably derived from a source other than xanthine oxidase, constitute important mediators of "spontaneous" leukocyte adhesion in rat mesenteric venules.

An in vivo assay to quantify simultaneously two important components of hepatic reticuloendothelial system (RES) function—clearance and phagocytic killing—was developed in the rat. Intravenously injected E. coli labeled with Na51Cr and 5-[123I]-iodo-2′-deoxyuridine were cleared rapidly from the blood primarily by the liver. While hepatic 51Cr levels remained stable for 24 h following inoculation and provided a reliable measurement of clearance, hepatic 125I decreased over time. Hepatic 125I, calculated by sampling whole liver homogenates, accurately reflects the number of viable bacteria recovered from quantitative cultures of the same homogenates, thus validating this assay as a measure of bacteria killing. Pre-treatment of rats with substances previously shown to affect RES function (gadolinium, zymosan, and sheep erythrocytes) were found to selectively modulate clearance and/or killing. The correlation between hepatic isotope levels and viable hepatic bacteria, the gold standard for assessing the capacity of the liver to remove organisms from the blood and kill them, was preserved under conditions of up- and down-regulation of RES function. The ability to quantitatively discriminate two distinct components of the hepatic RES should provide a useful tool for future investigations of altered RES function. J. Leukoc. Biol. 55: 248–252; 1994.

Background/Aims: Both hemorrhagic and cardiogenic shock are associated with hepatic shock gene expression at resuscitation. This study investigated the potential role of intravascular superoxide anion as a proximal trigger of heat shock protein gene expression. Methods: Preanesthetized pigs were subjected to 120 m of total warm hepatic ischemia. The survival model consisted of warm, total hepatic ischemia and reperfusion (with active portal-systemic bypass) followed by reperfusion and survival for 3 days. Serial hepatic biopsy samples were evaluated for the expression of heat shock protein 72 (HSP-72) messenger RNA (mRNA) by Northern and Western analysis and by in situ RNA hybridization. The possible role of intravascular O 2 − as a mediator of heat shock response was evaluated by its specific inhibition by the intravenous infusion of recombinant human superoxide dismutase (SOD). Results: Ischemia for 120 minutes followed by 60 minutes of reperfusion caused accumulation of HSP-72 mRNA. Transcripts were localized to hepatocytes. HSP-72 mRNA was detected neither following ischemia alone nor when SOD was infused for 15 minutes at reperfusion. Three days later, transcripts were not detectable, but HSP-72 protein accumulated irrespective of SOD administration. Conclusions: Warm hepatic ischemia induces the hepatocyte expression of HSP-72 at reperfusion by a mechanism that is dependent upon the superoxide anion, probably generated intravascularly. However, the transient dismutation of superoxide is insufficient to suppress subsequent accumulation of HSP-72.

Highly toxic metabolites of oxygen are generated normally by aerobic metabolism in most cells, and this generation is often greatly increased in pathologic conditions. When this oxidant flux exceeds the capability of the multiple endogenous antioxidant mechanisms, tissue injury ensues. The pharmacologic modification of this injury process, with agents that scavenge these reactive oxygen metabolites, block their generation, or enhance the endogenous antioxidant capability, has shown great promise in animal models of common clinical conditions, and has already been successfully applied in controlled clinical trials. This approach represents an interruption of tissue injury at its most basic level.

In conclusion, most of the recent advances in the management of small bowel obstruction consist of developments in the imaging modalities available to assist in the diagnosis itself, particularly with regard to the distinction between partial and complete obstruction. Unfortunately, little progress has been made to enable physicians to detect early, reversible strangulation, and therefore the surgical management of small-bowel obstruction has changed very little over the past 10 years. Because of the inability to detect reversible ischemia, there is a substantial risk of progression to irreversible ischemia (and an inherent rise in morbidity and mortality) when surgery is delayed for an extended period of time, especially in the setting of suspected complete obstruction. However, almost all patients do benefit from an initial 12 to 24 hours of resuscitation and decompression in cases of complete obstruction; resuscitation and decompression can usually be extended for a longer period of time in those patients with partial obstruction who exhibit no signs of progression (Fig 6). It is encouraging, however, that some advances have been made in understanding the pathophysiology and prevention of adhesion formation. Research efforts in the future should continue to focus on these issues as well as on the development of methods to better recognize early signs of strangulation.

Kupffer cells (KC) act as APC in the liver and play a major role in the clearance of gut-derived antigens and pathogens entering the liver with portal venous blood. Antigen presentation by KC has been implicated in regulation of the local and systemic immune responses. In this study, modulation of KC antigen presentation by antioxidants and the role of reactive oxygen species (ROS) as essential mediators of antigen presentation in KC were investigated. Co-culture of KC with ovalbumin (OVA) antigens resulted in upstream intracellular endogenous ROS generation and increased expression of MHC class II and costimulator molecules, and consequent OVA-specific CD4(+) T-cell proliferation in response to antigen presentation by KC. Scavenging of KC ROS by antioxidants, or blocking of KC ROS generation by specific inhibitors of NADPH oxidase and/or xanthine oxidase, or by specific inhibitors of the mitochondrial electron transport chain, significantly decreased OVA-specific T-cell proliferation in response to antigen presentation by KC. Increased expression of MHC class II and costimulatory molecules in KC pulsed with OVA antigens was blocked by inhibiting ROS generation enzymatically. Intracellular endogenous ROS generation during antigen processing may therefore provide essential secondary signalling for KC antigen presentation.

Fas-Fas ligand (FasL)-dependent pathways exert a suppressive effect on inflammatory responses in immune-privileged organs. FasL expression in hepatic Kupffer cells (KC) has been implicated in hepatic immunoregulation. In this study, modulation of FasL expression of KC by endogenous gut-derived bacterial LPS and the role of reactive oxygen species (ROS) as potential mediators of FasL expression in KC were investigated. LPS stimulation of KC resulted in upstream ROS generation and, subsequently, increased FasL expression and consequent Jurkat cell (Fas-positive) apoptosis. The NADPH oxidase and xanthine oxidase enzymatic pathways appear to be major sources of this upstream ROS generation. Increased FasL expression was blocked by antioxidants and by enzymatic blocking of ROS generation. Exogenous administration of H2O2stimulated KC FasL expression and subsequent Jurkat cell apoptosis. Intracellular endogenous ROS generation may therefore represent an important signal transduction pathway for FasL expression in KC.

The relationship between hepatic ischemia-reperfusion (I-R) and subsequent injury through neutrophil accumulation is well described. Although alterations in reticuloendothelial system (RES) function (specifically Kupffer cell function) after I-R have been delineated, the degree to which discrete components of RES function (phagocytosis and killing) are independently modulated under these conditions has not been quantified. A hepatic segmental I-R model was established in mice, in which blood supply to the left lateral lobe of the liver was occluded for 45 minutes, the liver was reperfused, and the laparotomy incision was closed. Experimental animals were pretreated with either vinblastin (1.5 mg/kg) to induce neutropenia or anti-P-selectin monoclonal antibody (mAb; 50 microg/mice) 4 days and 5 minutes before ischemia, respectively. We previously reported that after intravenous injection of chromium 51 ((51)Cr) and iodine 125 ((125)I) double-labeled Escherichia coli, hepatic (51)Cr levels could be used to reliably quantify hepatic phagocytic clearance (HPC) of bacteria from blood, whereas the subsequent release of (125)I from the liver accurately paralleled hepatic bacterial killing efficiency (HKE). Using this double-label bacteria clearance assay, HPC and HKE were depressed after I-R, in association with hepatic neutrophil accumulation. Segmental I-R resulted in decreased HPC and HKE activity in both ischemic and nonischemic hepatic lobes. Depressions in HPC and HKE were attenuated by either vinblastin-induced neutropenia or blocking neutrophil adhesion to the hepatic endothelium with anti-P-selectin mAb. These findings support the hypothesis that I-R induces hepatic RES dysfunction, at least in part, through P-selectin-mediated neutrophil accumulation.

Septic complications are common in patients with biliary obstruction. This is thought to be related, in part, to dysfunction of the hepatic reticuloendothelial system (RES). It has been reported that nearly 80% of circulating microorganisms are phagocytosed and killed within the liver and that clearance of circulating pathogens is significantly impaired in patients with jaundice. However, the effect of biliary obstruction specifically on phagocytic killing within the liver is less well described. Therefore this study was designed to quantify the effect of biliary obstruction, simultaneously and discriminately, on two important components of hepatic RES function (phagocytosis and phagocytic killing). Rats were divided into three experimental groups: control, sham, and jaundiced (common bile duct ligation). At 7, 10, 14, and 21 days after operation, E. coli labeled with both 125I and 51Cr were injected intravenously. Using the previously validated double-labeled in vivo E. coli technique, hepatic phagocytic clearance (HPC), hepatic killing efficiency (HKE), and net hepatic killing (NHK) were measured. Common bile duct ligation resulted in a significant decrease in the HPC of E. coli 10, 14, and 21 days postoperatively. Similarly, HKE was significantly decreased in jaundiced animals by postoperative day 10, but returned to baseline values by day 14. The net effect of these changes in HPC and HKE values were reflected in a significant reduction in NHK in jaundiced animals. Results of the present study suggest that obstructive jaundice impairs both phagocytosis and phagocytic killing within the liver. These findings may help to explain the susceptibility of patients with biliary tract obstruction to the morbidity and mortality of septic complications.

The mesenteric hemodynamic response to circulatory shock is substantial and asymmetrical; the vasoconstrictive response disproportionately affects the mesenteric organs. The cardiac output is sustained partially, at no cost in nutrient flow to the mesenteric organs, by vasoconstriction of the mesenteric veins, resulting in the "autotransfusion" of up to 30% of the circulating blood volume into the systemic circulation.Hemorrhagic or cardiogenic shock also results in decreased perfusion pressure, prompting selective vasoconstriction of the mesenteric arterioles to maintain perfusion pressure of the vital organs, here at the selective expense of the mesenteric organs. Septic shock may be associated with increased or decreased mesenteric blood flow but is characterized by increased oxygen consumption, exceeding the capability of mesenteric oxygen delivery.The response to any of these conditions can, variably and unpredictably, cause hemorrhagic gastric stress erosions, nonocclusive mesenteric ischemia of the small bowel, ischemic colitis, ischemic hepatitis, acalculous cholecystitis, and/or ischemic pancreatitis. Injury to the mesenteric organs can also initiate the systemic inflammatory response syndrome and, consequently, multiple organ failure.

The hepatic reticuloendothelial system (RES) is the primary mechanism for removing circulating bacteria from the systemic circulation. While Kupffer cells are important for this process, leukocytes appear to play a significant role as well. Hepatic leukocyte accumulation following ischemia/reperfusion or cytokine stimulation is well documented, but its contribution to phagocytic killing by the hepatic RES is not fully understood. We evaluated the role of leukocytes in general, and leukocyte-endothelial adhesion in particular, in hepatic RES function. This was done by inducing confirmed leukopenia with cyclophosphamide or by blocking leukocyte-endothelial adhesion molecules with specific blocking antibodies. Hepatic phagocytic clearance (HPC) and hepatic phagocytic killing (HKE) of systemically intravenously injected E. coli were assayed and quantitated by a validated dual isotope label technique. HPC among the various experimental groups and respective controls varied only slightly, with no statistically significant differences observed. Leukopenia or CD11b blockade each significantly decreased the HKE relative to the controls. Antibody blockade of certain other adhesion molecules had no significant effect on HKE (or HPC). The role of leukocytes in killing systemically circulating bacteria is an integral component of hepatic RES function. This capability of the leukocyte appears to be dependent, in part, on the adhesion molecule, Mac-1.

The intraarterial infusion of a vasodilator may be of benefit in the treatment of nonocclusive mesenteric ischemia, to overcome primary splanchnic vasoconstriction. 1–3 Such vasodilator therapy has also been advocated for the treatment of mesenteric vascular occlusion, 4,5 but these clinical reports are both anecdotal and uncontrolled with respect to vasodilator administration. We have previously characterized the physiology of mesenteric collateral blood flow, and its hemodynamic determinants, in a canine model of acute segmental mesenteric vascular occlusion. 6 Collateral flow from a nonischemic segment to an adjacent ischemic segment was found to be substantial and was redirected entirely by vasodilatation within the ischemic bed that produced a differential resistance that facilitated collateral nutrient blood flow from the nonischemic segment into the ischemic one. The only vasoactive determinant of this flow was the vasodilatation within the ischemic bed; all other hemodynamic factors, including those in the adjacent, nonischemic segment, played only a passive role. The collateral conduits themselves, primarily the marginal arteries, were not vasoactively responsive to ischemia nor a determinant of collateral flow. These findings indicated that collateral flow after acute segmental mesenteric occlusion was determined primarily by the relative vascular resistances of the ischemic and the adjacent, nonischemic vascular beds. In a subsequent study, the acute infusion of pharmacologic doses of a vasodilator, either isoproterenol or papaverine, had only a marginal effect on vascular resistance in the ischemic bed but substantially dilated the nonischemic bed, with a consequent increase in blood flow to the nonischemic segment. 7 This preferential dilation of the nonischemic bed decreased perfusion pressure to both beds, distal to the site of vascular occlusion, and thereby actually reduced collateral blood flow into the ischemic segment to a small but significant degree. These hemodynamic changes are characteristic of a vascular steal phenomenon. Findings from these previous studies suggested an apparently paradoxical hemodynamic effect of intraarterial vasodilator infusion on collateral blood flow during acute segmental mesenteric vascular occlusion. However, they do not preclude the possibility that prolonged vasodilator infusion might reverse a superimposed splanchnic vasospasm that has been postulated to appear several hours after the onset of occlusion. 2 Because the clinically meaningful end point of mesenteric vascular occlusion is consequent bowel viability, the present study was designed to evaluate directly the effect of prolonged intraarterial infusion of vasoactive (vasodilator and vasoconstrictor) agents on intestinal viability after acute segmental mesenteric vascular occlusion.

The mesenteric hemodynamic response to circulatory shock is characteristic and profound; this vasoconstrictive response disproportionately affects both the mesenteric organs and the organism as a whole. Vasoconstriction of post-capillary mesenteric venules and veins, mediated largely by the alpha-adrenergic receptors of the sympathetic nervous system, can effect an "autotransfusion" of up to 30% of the total circulating blood volume, supporting cardiac filling pressures ("preload"), and thereby sustaining cardiac output at virtually no cost in nutrient flow to the mesenteric organs. Under conditions of decreased cardiac output caused by cardiogenic or hypovolemic shock, selective vasoconstriction of the afferent mesenteric arterioles serves to sustain total systemic vascular resistance ("afterload"), thereby maintaining systemic arterial pressure and sustaining the perfusion of non-mesenteric organs at the expense of mesenteric organ perfusion (Cannon's "flight or fight" response). This markedly disproportionate response of the mesenteric resistance vessels is largely independent of the sympathetic nervous system and variably related to vasopressin, but mediated primarily by the renin-angiotensin axis. The extreme of this response can lead to gastric stress erosions, nonocclusive mesenteric ischemia, ischemic colitis, ischemic hepatitis, ischemic cholecystitis, and/or ischemic pancreatitis. Septic shock can produce decreased or increased mesenteric perfusion, but is characterized by an increased oxygen consumption that exceeds the capacity of mesenteric oxygen delivery, resulting in net ischemia and consequent tissue injury. Mesenteric organ injury from ischemia/reperfusion due to any form of shock can lead to a triggering of systemic inflammatory response syndrome, and ultimately to multiple organ dysfunction syndrome. The mesenteric vasculature is therefore a major target and a primary determinant of the systemic response to circulatory shock.

Post-ischemic hepatic injury is observed commonly following cardiogenic or hypovolemic shock. We evaluated the putative roles of the alpha-adrenergic sympathetic nervous system and the renin-angiotensin axis in the pathogenesis of hepatic injury following cardiogenic shock. Previous studies have characterized the hepatic hemodynamic response to shock, while the relationship of these hemodynamic changes to ischemic hepatic injury has not been defined. Sustained (4 h) periods of pericardial tamponade (after mild hemorrhage) followed by 2 h of resuscitation generated a reproducible model of cardiogenic shock and consequent post-ischemic hepatic injury in anesthetized pigs. In a separate group of pigs, the alpha-adrenergic component of the sympathetic nervous system was ablated with phenoxybenzamine or, in other groups, the renin-angiotensin axis was ablated by either prior nephrectomy or, separately, by confirmed angiotensin converting enzyme inhibition with teprotide. The hepatic injury response in each case was reevaluated. Compared to sham-shocked pigs, those subjected to tamponade alone manifested selective splanchnic vasospasm and consequent biochemical and histological evidence of classic post-ischemic liver injury (centrilobular necrosis involving about a third of each hepatic lobule). These manifestations of splanchnic vasospasm and the consequent ischemic injury were not ameliorated by confirmed alpha-adrenergic blockade, but significantly attenuated by either method of prior ablation of the renin-angiotensin axis. This model of sustained cardiogenic shock and resuscitation generates the manifestations of ischemic hepatic injury associated with selective splanchnic vasospasm, findings consistent with previous, short-term, hemodynamic studies. The major mediator of this response, and the consequent hepatic injury, is the selective hypersensitivity of the mesenteric vasculature to the renin-angiotensin axis.

Postischemic hepatic injury can be seen after hypovolemic shock, major surgery, liver transplantation, trauma, and other forms of severe physiologic stress. 1–5 This condition, variously termed ischemic hepatitis, postshock hepatic insufficiency, or shock liver, is thought to be a consequence of hepatic ischemia followed by reperfusion. 2,6–8 Although the clinical consequences of hepatic insufficiency are frequently transient and self-limited, 3 more severe degrees of insult can lead to terminal hepatic failure or can contribute to the evolution of multiple organ dysfunction syndrome. 9 For example, we have found that hepatic reticuloendothelial function, normally accounting for approximately 80% of the clearance and killing of bacteria from the systemic circulation, 10 is profoundly influenced by hepatic ischemia/reperfusion in a complex and biphasic manner. 11 Much of the injury sustained by many organs, including the liver, as a consequence of ischemia is triggered by the generation of reactive oxygen metabolites by activated xanthine oxidase at reperfusion. 12 This paradigm of reperfusion injury, described first in the feline small intestine, 13,14 entails the initial activation of xanthine oxidase by ischemia, the generation of superoxide at the reintroduction of oxygen at reperfusion, and a characteristic free radical cascade as the unpaired electron is passed from molecule to molecule within the endothelial cell. The resultant upregulation of endothelial adhesion molecules, particularly within the venules, and the consequent trapping and activation of circulating leukocytes, results in microvascular injury and ultimately in parenchymal organ dysfunction. 15,16 More recent studies have indicated that platelet activating factor (PAF) may well play an important early role in this inflammatory sequence. 17 Although several studies have evaluated these individual components of this system with respect to the liver, 18,19 we are aware of no studies that have evaluated this entire paradigm sequentially and in vivo. This deficiency has been exacerbated by the need for most hemorrhagic shock/resuscitation (S/R) models to use heparin to maintain the patency of intravascular catheters and to prevent thrombosis in the shed blood, thereby allowing it to be reinfused at reperfusion. 20,21 There are severe limitations of heparinized models of hemorrhagic shock, however, particularly because microvascular patency is one of the limiting factors in tissue recovery after ischemia, and the use of heparin alone has been found to improve recovery substantially. 21,22 Moreover, heparin has been reported to release xanthine oxidase from the surface of endothelial cells into the circulation 23 and therefore could profoundly affect the results of any experiments evaluating the role of xanthine oxidase in this mechanism. We therefore modified a standardized hemorrhagic S/R model in rats, 20,24 based on the isobaric principle of Wiggers, 25 to be functional and reproducible without the use of heparin. Using this model, we evaluated the relative, potentially sequential roles of PAF, xanthine oxidase, the generation of reactive oxygen species, hepatic oxidant stress, and hepatic neutrophil accumulation in the evolution of postischemic hepatic injury after whole-body S/R.

The immunomodulatory function of endothelial cells (EC) includes the initiation of leukocyte margination, diapedesis, and activation through the upregulation of various cell surface-associated molecules. However, the effect that EC have on the phagocytic function of neighboring monocytes and macrophages is less well described. To address this issue, microvascular EC were cocultured with murine peritoneal macrophages, first in direct contact, then in a noncontact coculture system, and macrophage phagocytosis and phagocytic killing were assessed. The presence of increasing concentrations of EC resulted in a dose-dependent increase in macrophage phagocytic killing. This stimulatory effect was inhibited in a dose-dependent manner by the pretreatment of macrophage/EC cocultures with WEB-2086 or CV-6209, specific platelet-activating factor (PAF)-receptor antagonists, but not by anti-tumor necrosis factor-α, anti-interleukin (IL)-1α, or anti-IL-1β. Furthermore, the effect was reproduced in the absence of EC by the exogenous administration of nanomolar concentrations of PAF. Microvascular EC potentiate macrophage phagocytic killing via the release of a soluble signal; PAF appears to be an important component of that signal.

Thymomas are the most common primary anterior mediastinal tumor and account for 15% to 20% of all mediastinal masses. 1 Thymomas are derived from thymic epithelial cells and are distinguished from thymic lymphomas, germ cell tumors, and carcinoid tumors. 2 Few tumors are associated with as many paraneoplastic syndromes, including myasthenia gravis (MG), pure red cell aplasia, acquired hypogammaglobulinemia, and connective tissue disorders. 1,3 Myasthenia gravis is by far the most common, reported in 25% to 35% of patients with thymoma. 3–8 Several studies have indicated the importance of initial tumor invasion and the extent of surgical resection as predictors of recurrence and survival after resection of a thymoma. 5–15 The most widely employed system for clinical staging at initial presentation is that proposed by Masaoka (Table 1). Stage I tumors are completely encapsulated, both grossly and microscopically. This staging system then advances sequentially, with increasing degrees of invasion and spread, to stage IVb (distant [hematogenous] metastatic disease). 7 Table 1. CLINICAL STAGING AND PATHOLOGIC CLASSIFICATION OF THYMOMAS Rosai and Levine have proposed the simple division of thymomas into benign and malignant, based on the presence or absence of invasion and/or cellular atypia at initial presentation. 16 Malignant thymomas are additionally divided into type I and type II. Type I malignant thymomas are epithelial tumors that show invasion without evidence of cytologic atypia; type II thymomas (thymic carcinomas) display cytologic atypia, with or without evidence of capsular invasion. Although most authors believe that tumor stage at initial presentation and the extent of surgical resection reliably predict thymoma prognosis, the findings have been equivocal when other predictors of prognosis are examined. Several histologic classifications of thymoma have been proposed (see Table 1), including the traditional (American, or Lattes and Bernatz [L/B]) system proposed by Bernatz and modified by Lattes 2 and Salyer and Eggleston, 17 in which thymomas are divided into predominantly epithelial, predominantly lymphocytic, or mixed lymphoepithelial types. Marino and Muller-Hermelink histologically graded thymomas based on their differentiation toward normal thymic cortical or medullary epithelium. 18–20 Although predominantly epithelial 5,6,8,9,12 and cortical 10,14,15,18,21–27 thymomas have been described as more invasive tumors, the importance of histologic classification as an independent predictor of overall prognosis remains unclear. Because of the relative rarity of thymomas, most series (all retrospective) contain inadequate numbers of patients to quantitate the independent predictive values of putative clinical and histologic indicators of prognosis. To this end, we evaluated the Johns Hopkins experience with 136 thymomas over the past 40 years. This number of patients allowed us to apply contemporary statistical analysis to estimate the independent predictive values of prominent clinical and histologic features of this disease.

Objective To assess the etiology, treatment, and utility of anal ultrasound in men with fecal incontinence and to review the outcomes of conservative (nonoperative) treatment. Background Data The etiology of fecal incontinence in women is almost exclusively from obstetric or iatrogenic surgical injuries resulting in damage to the anal sphincters and/or pudendal nerves. Corresponding data on men with fecal incontinence are sparse. Methods Between January 1995 and January 1998, 37 men with fecal incontinence were evaluated in the John Radcliffe Hospital anorectal ultrasound unit. Their clinical histories, anal ultrasound results, anorectal physiology studies, and responses to conservative therapy were reviewed. Results Median age was 57 years. Major incontinence was present in 27% of the patients. Anal ultrasound localized anal sphincter damage in nine patients, and the characteristics of these nine patients with sphincter damage were then compared with the remaining 28 without sphincter damage. Prior anal surgery was more common in patients with sphincter damage. Hemorrhoids were more common in patients without sphincter damage. Anorectal physiology studies revealed significantly lower mean maximum resting and squeeze pressures in patients with sphincter damage, confirming poor sphincter function. With 92% follow-up, patients without sphincter damage were more likely to improve with nonoperative therapy. Conclusions Anal ultrasound is extremely useful in the evaluation of fecal incontinence in men. Unlike women, the majority of men do not have a sphincter defect by anal ultrasound, and conservative management is usually successful in these patients. In contrast, in men with anal sphincter damage, almost all of these defects resulted from previous anal surgery. Conservative management rarely is successful in these cases, and surgical repair of the anal sphincter may be indicated. Therefore, because the presence or absence of sphincter damage on anal ultrasound usually predicts the response to nonoperative treatment, anal ultrasound should be used to guide the initial management of men with fecal incontinence.

Although the liver is the most common site of metastatic disease from a variety of tumor types, isolated hepatic metastases most commonly occur from colorectal cancer and, less frequently, from neuroendocrine tumors, gastrointestinal sarcoma, ocular melanoma, and others. Complete evaluation of the extent of metastatic disease, both intrahepatically and extrahepatically, is important before considering treatment options. Based on a preponderance of uncontrolled studies for hepatic metastatic colorectal carcinoma, surgical resection offers the only potential for cure of selected patients with completely resected disease, with 5-year survival rates of 25% to 46%. Systemic and hepatic arterial infusion chemotherapy may be useful treatment options in patients with unresectable disease and possibly as an adjuvant treatment after liver resection. Other techniques of local tumor ablation, including cryotherapy and radiofrequency ablation, although promising, remain unproved. Management of hepatic metastases from neuroendocrine tumors and other noncolorectal primary tumors should be individualized based on the patient's clinical course, extent of disease, and symptoms.

OBJECTIVE: To evaluate the short- and long-term consequences of palliative reresection of specific symptomatic lesions in patients with widely disseminated (incurable) medullary thyroid cancer (MTC). SUMMARY BACKGROUND DATA: Although reoperative neck microdissections can normalize calcitonin levels in patients with metastatic MTC confined to regional lymph nodes, there is no curative therapy for widely metastatic disease. However, these patients frequently have prolonged survival, but often with debilitating symptoms. METHODS: Between October 1981 and January 1997, 16 patients (mean age, 46 +/- 3 years; 10/16 female) underwent 21 palliative reoperations for unresectable MTC at the Johns Hopkins Hospital. All patients had significant symptom(s) or impending compromise of vital structures by a discrete lesion and had unequivocal preoperative evidence of a total disease burden that was unresectable. RESULTS: The mean interval from initial thyroidectomy to palliative surgery was 5.8 +/- 1.5 years. All patients had significant tumor burdens as evidenced by preoperative calcitonin values ranging from 900 to 222,500 pg/mL (nL < or = 17 pg/mL). The palliative operations consisted of reoperative neck dissection/mass excision (11), mediastinal mass resection (4), esophagectomy (1), liver trisegmentectomy (1), sigmoidectomy (1), bilateral simple mastectomies (1), pituitary resection (1), and subcutaneous mass excisions (1). All but two of the operative specimens contained MTC. There was no perioperative mortality. The long-term morbidity rate was limited to one recurrent laryngeal nerve injury. All patients had initial relief of the index symptom(s) after the palliative surgery, followed by a median actuarial symptom-free survival rate of 8.2 years. CONCLUSIONS: Patients with widely metastatic MTC often live for years, but many develop symptoms secondary to tumor persistence or progression. Judicious palliative, reoperative resection of discrete, symptomatic lesions can provide significant long-term relief of symptoms with minimal operative mortality and morbidity. In selected patients with metastatic MTC lesions causing significant symptoms or physical compromise, palliative reoperative resection should be considered despite the presence of widespread incurable metastatic disease.

Phagocytosis and killing of circulating organisms by Kupffer cells (KCs) are discrete, important components of host defense. However, the killing mechanism(s) are not fully understood, and the potential role of adjacent nonparenchymal cells such as hepatic endothelial cells has not been defined. Rat KCs ∓ an hepatic endothelial cell enriched cellular fraction (HECEF) were incubated with Candida parapsilosis and assayed for phagocytosis and phagocytic killing by validated fluorochromatic vital staining. The role of reactive oxygen metabolites in KC phagocytic functions was examined by inhibition with superoxide dismutase and/or catalase. Diphenyleneiodonium and allopurinol were used to examine the potential roles of NADPH oxidase and xanthine oxidase, respectively, in generating these toxic oxidants. Coculture with HECEF increased KC phagocytic activity (from 75% to 88%) and candidacidal activity (from 20% to 31%). Superoxide dismutase, catalase, diphenyleneiodonium, or allopurinol caused inhibition of candidacidal activity, but did not affect phagocytosis, and did not block the potentiation of phagocytosis or of killing caused by coculture with HECEF. Reactive oxygen intermediates generated by both NADPH oxidase and xanthine oxidase-dependent pathways are important in KC killing of Candida parapsilosis. In vitro, KC phagocytosis and killing are potentiated (via a non-oxidant-mediated mechanism) by coculture with a preparation of hepatic non-parenchymal cells composed primarily of endothelial cells.

OBJECTIVE: The authors evaluated the response to extended cervicomediastinal thymectomy as a component of the integrated management of patients with myasthenia gravis in a large series of patients from a single institution. The authors evaluated the response to therapy with respect to a graded, multivariate, ordinal scale chosen to reflect the full range of the disease's manifestations. SUMMARY BACKGROUND DATA: A number of series, of varying sizes, describe the response of patients with myasthenia gravis to thymectomy primarily with respect to the bivariate endpoint of the presence or absence of "remission." These studies fail to describe the full spectrum of postoperative disease severity and have been unable to quantify definitively the influence of putative prognostic variables, nor to assess definitively the statistical significance of apparent improvements over time. METHODS: The authors evaluated 202 consecutive patients who underwent trans-sternal thymectomy for symptomatic myasthenia gravis from 1969 through 1996 at the Johns Hopkins Hospital. The response to surgery, combined with postoperative medical therapy, was evaluated by a standardized scale reflecting the full spectrum of the disease. These data were analyzed by a novel mean multivariate regression analysis, which allowed the quantification of the statistical significance of apparent responses over time and the evaluation of the independent influence of each of nine putative prognostic indicators. RESULTS: There was no perioperative mortality and a 33% perioperative morbidity. There was a marked clinical response at 6 months to 1 year after surgery that was sustained for at least 10 years thereafter. The median increment of improvement was two (of five) classes. Eighty-six percent and 83% of the patients had improved by at least one class at 5 and 10 years, respectively. These changes were statistically significant (p < 0.001). Whereas the use of extended cervicomediastinal thymectomy was associated with a greater than twofold chance of improvement, compared to conventional trans-sternal thymectomy, neither the pathologic diagnosis (presence of thymoma) nor the age at surgery proved to be negative predictors of postoperative response. CONCLUSIONS: Extended cervicomediastinal thymectomy is the procedure of choice as a component of the integrated management of myasthenia gravis, with significant improvement seen in the group as a whole, as well as in subgroups of patients with thymoma and those older than 40 years of age.

BACKGROUND & AIMS: Previous studies have shown that the renin- angiotensin axis plays a pivotal role in vasoconstriction of the gastric, intestinal, and hepatic circulations during cardiogenic shock. The aim of this study was to evaluate the fundamental hemodynamic mechanism of pancreatic ischemia during cardiogenic shock induced by pericardial tamponade. METHODS: Cardiogenic shock was induced by pericardial tamponade. Cardiac output (and total peripheral vascular resistance) was determined by thermodilution. Pancreatic blood flow (and vascular resistance) was determined with radiolabeled microspheres. RESULTS: Graded increases in pericardial pressure produced corresponding decreases in cardiac output to 42% +/- 1% and arterial pressure to 67% +/- 3% of baseline and increases in total peripheral vascular resistance to 146% +/- 5% of baseline. Pancreatic blood flow decreased disproportionately to 30% +/- 3% of baseline, because of a disproportionate increase in pancreatic vascular resistance to 220% +/- 19% of baseline. Previously confirmed blockade of the renin-angiotensin axis ablated this response, whereas confirmed blockade of the alpha-adrenergic system or vasopressin system had no significant effect. Without shock, central intravenous infusions of angiotensin II closely mimicked this selective vasoconstriction. CONCLUSIONS: Angiotensin-mediated selective pancreatic vasoconstriction results in significant pancreatic ischemia during cardiogenic shock. (Gastroenterology 1997 Sep;113(3):938-45)

Most studies of neutrophil-endothelial interactions in vivo necessarily require the use of general anesthetic agents which are well known to be immunosuppressive. By using whole-mount preparations of the rat mesoappendix, we were able to study tumor necrosis factor alpha (TNF-alpha) induced neutrophil adhesion to the mesenteric venular endothelium in vivo without necessarily using general anesthesia. TNF-alpha significantly increased venular-neutrophil accumulation in a dose-dependent manner, accumulation was markedly increased at 1, 2, and 4 h, but returned to baseline after 24 h. After these preliminary dose-response and time-course studies, we evaluated the influence of standard clinically effective doses of several commonly used anesthetic agents (thiopental, pentobarbital, ketamine, alpha-chloralose, methoxyflurane, and halothane) on the extent of neutrophil-venular accumulation induced 2 h after intraperitoneal injection of 0.4 mg/kg TNF-alpha, compared to unanesthetized rats. All general anesthetics tested, with the exception of methoxyflurane, significantly suppressed this response. In most cases this suppression was striking (from 60 to 85%) such that a statistically significant proinflammatory response was obscured. Although methoxyflurane also tended to suppress this response to TNF-alpha, it was the only agent that allowed the response to be clearly seen. Because anesthesia markedly suppresses cytokine-induced neutrophil-venular adhesion, this model should provide an important complementary technique to the classical in vivo microcirculatory approaches which do necessarily require general anesthesia.

We evaluated the effects of hemorrhagic shock/resuscitation (S/R) on hepatic reticuloendothelial system function, using an in vivo assay that discriminantly quantitates its two essential components, phagocytic clearance and phagocytic killing of double-labeled Escherichia coli injected intravenously. Rats were subjected to hemorrhagic shock at mean arterial pressure at 50 +/- 5 torr for 2 h, resuscitated, and survived. Hepatic phagocytic clearance was significantly decreased immediately following and 6 h after S/R, compared with sham-shocked rats, but recovered to normal levels after 24 h. Although hepatic killing efficiency was increased initially, and transiently depressed 6 h later, it was strikingly upregulated after 24 h. As a consequence, net hepatic killing was transiently suppressed at 0 and 6 h, but upregulated after 24 h. Pre-treatment with proinflammatory agonists, including endotoxin, IFN-gamma, or IFN-gamma + TNF-alpha enhanced both hepatic killing efficiency and net hepatic killing. These observations suggest that although hepatic killing function is initially impaired after the onset of S/R, it is strikingly upregulated 24 h later, simulating both the initial immunosuppression, and the later hyperinflammatory response to systemic S/R that could lead to multiple organ dysfunction syndrome.

This study was designed to quantitatively discriminate the specific xanthine oxidase (XO) inhibitory from the relatively nonspecific antioxidant activities of allopurinol, both in vitro and in vivo in the rat. XO activity, determined by the spectrophotometric assay for urate generation over time, was completely inhibited in vitro by allopurinol at concentrationsor = 200 microM. Allopurinol's antioxidant activity was determined in vitro using a linolenic acid peroxidation (LAP) assay. Although the known antioxidant butylated hydroxytoluene effectively inhibited LAP (80% inhibition of malondialdehyde generation at 10(1) microM), allopurinol (10(1)-10(3) microM) did not inhibit this LAP (p.01). Rat serum obtained after oral administration of allopurinol (100 mg/kg x 2 doses) did not suppress LAP in vitro more than did control rat serum. Following oral administration of allopurinol (2-50 mg/kg x 2 doses), dose-dependent inhibition of XO activity was observed in the homogenates of the liver (to 5% of control level; p.001) and the intestine (to 12% of control level; p.001). We conclude that while 2-50 mg/kg of oral allopurinol effectively suppresses XO activity in the rat liver and intestine, antioxidant activity is not seen even in doses up to 100 mg/kg. The selective enzymatic inhibitory effect of allopurinol at these doses therefore should provide a useful tool to allow the discrimination of the effects of xanthine oxidase in particular from the effects of reactive oxygen metabolites in general.

Objective: To evaluate the potential role of reactive oxygen metabolites as signals for endothelial cell apoptosis. Design: A series of antioxidants were evaluated for their ability to block apoptosis in cultured porcine aortic endothelial cells in vitro. Results: Scavenging of the hydroxyl radical with the membrane-permeable scavenger dimethyl sulfoxide or blocking its generation via the Fenton reaction by the chelation of iron with o-phenanthroline blocked apoptosis, whereas the cell membrane—impermeable scavengers superoxide dismutase and catalase did not block apoptosis. Inhibition of xanthine oxidase with enzyme-inhibitory levels of allopurinol also failed to block apoptosis, whereas high levels of allopurinol, which also scavenge the hydroxyl radical in vitro, conferred protection. In each case (dimethyl sulfoxide, o -phenanthroline, and high-dose allopurinol), hydroxyl radical ablation was only effective when administered before the priming step (lipopolysaccharide) and was ineffective when administered later, prior to the activation step (heat shock). Conclusions: These findings suggest a novel role for the hydroxyl radical as a nonlethal intracellular signal in endothelial cell apoptosis. Moreover, the results support a role for programmed cell death in the pathogenesis of multiple organ dysfunction syndrome and suggest novel strategies for prophylaxis and therapy of the most common cause of death in surgical intensive care units. (Arch Surg. 1994;129:134-141)

Multiple organ dysfunction syndrome (MODS), previously known as multiple organ failure, has emerged as the leading cause of mortality in surgical critical care. It is a syndrome of sequential and progressive organ dysfunction, associated with a sustained, massive inflammatory response that is often preceded by insults such as sepsis, hemorrhagic shock, inflammatory states such as pancreatitis, and tissue injury. Classically, organ involvement occurs in a predictable sequence, initially involving the lung, then the liver, then the gut, and other organs. With four organ system involvement, mortality approaches 100%. Once the process is initiated, MODS often progresses despite eradication of the inciting cause.

The homeostatic response of complex eukaryotes to the challenge of environmental stress includes the induction of several programs of gene expression; among them are those for the acute phase genes and those for the heat shock genes. In some systems, the heat shock response, which is often elicited by more severe stimuli, preempts the acute phase response, which is seen in response to less severe challenges, as well as constitutive gene expression. Nevertheless, each response appears to provide a natural selective advantage for survival of the organism in a toxic environment. However, when cultured porcine endothelial cells were exposed first to a nonlethal level of bacterial endotoxin lipopolysaccharide (LPS), an inducer of the acute phase response, and then, simultaneously to standard stimuli, which normally elicit a salutary heat shock response, the cells died manifesting a pattern of DNA fragmentation (nucleolysis) characteristic of programmed cell death (apoptosis). The treatment of LPS-exposed cells with cycloheximide to block protein synthesis reproduced the lethal apoptosis that had been elicited by the induction of heat shock gene expression. Therefore, the preemption of other programs of stress gene expression by the prioritized expression of heat shock genes is associated with apoptosis.