Herbert B. Hechtman

The roentgenographic finding hepatic--portal venous gas (HPVG) has been reported extensively in the pediatric and radiology literature. The surgical implications and clinical significance have yet to be fully defined. This study reviews the 60 reported cases in the literature and adds four new cases. HPVG appears as a branching radiolucency extending to within 2 cm of the liver capsule. HPVG is associated with necrotic bowel (72%), ulcerative colitis (8%), intra abdominal abscess (6%), small bowel obstruction (3%), and gastric ulcer (3%). Mucosal damage, bowel distention and sepsis predispose to HPVG. The current mortality rate of 75% represents an improvement from previous experience. Analysis of survivors indicates that the finding of HPVG requires urgent surgical exploration except when it is observed in patients with stable ulcerative colitis.

To examine the hypothesis that surface P-selectin-positive (degranulated) platelets are rapidly cleared from the circulation, we developed novel methods for tracking of platelets and measurement of platelet function in vivo. Washed platelets prepared from nonhuman primates (baboons) were labeled with PKH2 (a lipophilic fluorescent dye), thrombin-activated, washed, and reinfused into the same baboons. Three-color whole blood flow cytometry was used to simultaneously (i) identify platelets with a mAb directed against glycoprotein (GP)IIb-IIIa (integrin alpha 11b beta 3), (ii) distinguish infused platelets by their PKH2 fluorescence, and (iii) analyze platelet function with mAbs. Two hours after infusion of autologous thrombin-activated platelets (P-selectin-positive, PKH2-labeled), 95 +/- 1% (mean +/- SEM, n = 5) of the circulating PKH2-labeled platelets had become P-selectin-negative. Compared with platelets not activated with thrombin preinfusion, the recovery of these circulating PKH2-labeled, P-selectin-negative platelets was similar 24 h after infusion and only slightly less 48 h after infusion. The loss of platelet surface P-selectin was fully accounted for by a 67.1 +/- 16.7 ng/ml increase in the plasma concentration of soluble P-selectin. The circulating PKH2-labeled, P-selectin-negative platelets were still able to function in vivo, as determined by their (i) participation in platelet aggregates emerging from a bleeding time wound, (ii) binding to Dacron in an arteriovenous shunt, (iii) binding of mAb PAC1 (directed against the fibrinogen binding site on GPIIb-IIIa), and (iv) generation of procoagulant platelet-derived microparticles. In summary, (i) circulating degranulated platelets rapidly lose surface P-selectin to the plasma pool, but continue to circulate and function; and (ii) we have developed novel three-color whole blood flow cytometric methods for tracking of platelets and measurement of platelet function in vivo.

OBJECTIVES: We sought to examine whether patients with stable coronary artery disease (CAD) have increased platelet reactivity and an enhanced propensity to form monocyte-platelet aggregates. BACKGROUND: Platelet-dependent thrombosis and leukocyte infiltration into the vessel wall are characteristic cellular events seen in atherosclerosis. METHODS: Anticoagulated peripheral venous blood from 19 patients with stable CAD and 19 normal control subjects was incubated with or without various platelet agonists and analyzed by whole blood flow cytometry. RESULTS: Circulating degranulated platelets were increased in patients with CAD compared with control subjects (mean [+/- SEM] percent P-selectin-positive platelets: 2.1 +/- 0.2 vs. 1.5 +/- 0.2, p < 0.01) and were more reactive to stimulation with 1 micromol/liter of adenosine diphosphate (ADP) (28.7 +/- 3.9 vs. 16.1 +/- 2.2, p < 0.01), 1 micromol/liter of ADP/epinephrine (51.4 +/- 4.6 vs. 37.5 +/- 3.8, p < 0.05) or 5 micromol/liter of thrombin receptor agonist peptide (TRAP) (65.7 +/- 6.8 vs. 20.2 +/- 5.1, p < 0.01). Patients with stable CAD also had increased circulating monocyte-platelet aggregates compared with control subjects (percent platelet-positive monocytes: 15.3 +/- 3.0 vs. 6.3 +/- 0.9, p < 0.01). Furthermore, patients with stable CAD formed more monocyte-platelet aggregates than did control subjects when their whole blood was stimulated with 1 micromol/liter of ADP (50.4 +/- 4.5 vs. 28.1 +/- 5.3, p < 0.01), 1 micromol/liter of ADP/epinephrine (60.7 +/- 4.3 vs. 48.0 +/- 4.8, p < 0.05) or 5 micromol/liter of TRAP (67.6 +/- 5.7 vs. 34.3 +/- 7.0, p < 0.01). CONCLUSIONS: Patients with stable CAD have circulating activated platelets, circulating monocyte-platelet aggregates, increased platelet reactivity and an increased propensity to form monocyte-platelet aggregates.

Ischaemia is a common clinical event leading to local and remote injury. Evidence indicates that tissue damage is largely caused by activated neutrophils which accumulate when the tissue is reperfused. If the area of ischaemic tissue is large, neutrophils also sequester in the lungs, inducing non-cardiogenic pulmonary oedema. Ischaemia reperfusion injury is initiated by production of reactive oxygen species which initially appear responsible for the generation of chemotactic activity for neutrophils. Later, once adherent to endothelium, neutrophils mediate damage by secretion of additional reactive oxygen species as well as proteolytic enzymes, in particular elastase. Therapeutic options for limiting ischaemia reperfusion injury include inhibition of oxygen radical formation, pharmacological prevention of neutrophil activation and chemotaxis, and also the use of monoclonal antibodies which prevent neutrophil-endothelial adhesion, a prerequisite for injury.

Reperfusion of ischemic tissue induces an acute inflammatory response that can result in necrosis and irreversible cell injury to both local vascular endothelium and parenchyma. To examine the pathogenesis of ischemia/reperfusion injury, we have used mice deficient in complement components C3, C4, or serum immunoglobulin in a hindlimb model of ischemia. We found that mice homozygous deficient in C3 or C4 were equally protected against reperfusion injury based on a significant reduction in leakage of radiolabeled albumin out of the vasculature. This demonstrates that classical pathway complement is an important factor in the initiation of inflammation following reperfusion. Furthermore, mice deficient in serum immunoglobulin were equally protected and this protection could be reversed by reconstitution with serum from normal mice. Thus, this report describes a novel mechanism for reperfusion injury that involves antibody deposition and activation of complement leading to inflammation permeability.