Upconverting phosphor reporters in immunochromatographic assays

Immunochromatographic assays have become popular diagnostic tools in a variety of settings because they are sensitive, fast, and easy to use. Here, we describe the use of a novel reporter, upconverting phosphors (UCP), in this assay format. UCP are submicron-sized, inorganic crystals that are excited with infrared light and that emit photons in the visible range depending on the ion composition of the crystal. Using human chorionic gonadotropin (hCG) as a model analyte to describe the properties of phosphors in immunochromatographic assays, a detection limit of 10 pg hCG in a 100-microl sample has been achieved on a regular basis, with occasional detection of 1 pg hCG. This represents at least a 10-fold improvement over conventional reporter systems such as colloidal gold or colored latex beads. Quantitation of analytes is possible over at least 3 orders of magnitude. Furthermore, an example is given of how UCP can be used for analyte multiplexing using a two-plexed wick for the detection of mouse IgG and ovalbumin. Thus, UCP lateral flow assays can be used for applications that are currently limited by assay sensitivity, and they can increase the probability of a diagnosis by verifying the presence of several analytes in the same sample.

[The biological effect of tetrahydrobiopterin and its potential role in sepsis]

It is well known that overproduction of nitric oxide (NO) is the final common pathway in septic shock. Tetrahydrobiopterin (BH4), a low molecular weight pterdine, is an essential cofactor required for the activity of NO synthase (NOS). Existing evidences show that lipopolysaccharide and proinflammatory cytokines can cause significant rises in bipoterin levels, which in turn augments the synthesis of NO. Also inhibition of biosynthesis of BH4 can decrease NO formation, implying that BH4 may be involved in the pathophysiological alterations of sepsis. However, the precise mechanisms of BH4 in regulating NO formation are not yet fully understood. In this review, we focus on the biological effects and regulation of BH4, as well as its potential role in sepsis. The therapeutic significance of biopterin synthesis inhibitors in septic symptoms is also discussed.

High sensitivity immunoassays using particulate fluorescent labels

The use of polystyrene fluorescent microspheres as sensitive labels in direct-detection (not enzymatically amplified) heterogeneous equilibrium "sandwich" immunoassays in 96-well plates is described. With mouse IgG as a model antigen, a fluorescent particulate label is more sensitive than a corresponding soluble reporter. The limit of detection of mouse IgG in the multiparametrically optimized assay was 0.2 ng/ml (7.6 x 10(8) antigens/ml) for the particulate reporter and 50 ng/ml (1.9 x 10(11) antigens/ml) for the soluble reporter. The sensitivities of assays using the particulate label were dependent on the surface densities of the capture and reporter antibodies and the concentration of reporter beads. Sensitivity was improved by adding the preformed reporter antibody/fluorescent microsphere complex to trapped antigen on the well surfaces instead of sequentially adding the reporter antibody and then the fluorescent microspheres. Maximal (equilibrium) binding of the particulate reporter to captured antigen occurred after 20 h with a concentration of 1.4 x 10(9) reporter beads/ml. Thus, particulate fluorescent labels provide high sensitivity in direct-detection immunoassays.

The inflammatory basis of trauma/shock-associated multiple organ failure

Multiple alterations in inflammatory and immunologic function have been demonstrated in clinical and experimental situations after trauma and hemorrhage, in particular the activation of various humoral (e.g. complement, coagulation) and cellular systems (neutrophils, endothelial cells, macrophages). As a consequence of this activation process there is synthesis, expression and release of numerous mediators (toxic oxygen species, proteolytic enzymes, adherence molecules, cytokines), which may produce a generalized inflammation and tissue damage in the body. Mediators are responsible for ongoing interactions of different cell types and for amplification effects through their networks and feedback cycles, finally leading to a sustained inflammation and multiple organ damage in the body. In the setting of trauma/shock, many activators including bacterial as well as non-bacterial factors may be present that will induce local and systemic inflammatory responses. Although the potential role of bacteria/endotoxin translocation and its clinical relevance remains controversial, many lines of evidence support the concept that the gut may be the reservoir for systemic sepsis and subsequent MOF in a number of pathophysiologic states.

Monoclonal antibody to endotoxin attenuates hemorrhage-induced lung injury and mortality in rats

OBJECTIVES

To determine the possible role of enteric bacteria-derived endotoxin in the pathogenesis of the lung injury and mortality in rats following hemorrhagic shock and resuscitation.

DESIGN

Prospective, randomized study.

SETTING

Animal laboratory of an institute for research traumatology.

SUBJECTS

Male Sprague-Dawley rats, weighing 450 to 480 g.

INTERVENTIONS

Anesthetized rats were subjected to a prolonged hemorrhagic shock (mean arterial pressure of 30 to 35 mm Hg for 180 mins) followed by resuscitation. A murine monoclonal antibody to lipopolysaccharide from Escherichia coli and Salmonella, WN1 222-5, was administered at a total dose of 5 mg/kg i.v., starting at the onset of shock (WN1 group). The control group was treated similarly to the WN1 group but received saline at the same volume as WN1 222-5.

MEASUREMENTS AND MAIN RESULTS

The 48-hr mortality rate was significantly reduced by WN1 222-5 treatment (28.6% in the treatment group vs. 78.6% in the control group; p = .0169). The characteristic lung injury in this model was significantly reduced in the WN1 group, as assessed by microscopic histopathologic examination increase in lung wet weight (7.60 +/- 0.47 g/kg in the control group vs. 5.14 +/- 0.31 g/kg in the WN1 group; p = .0002), and pulmonary neutrophilic infiltration (myeloperoxidase activity: 1835 +/- 567 mU/g wet weight in the control group vs. 891 +/- 212 mU/g wet weight in the WN1 group).

CONCLUSIONS

These data suggest that a) endotoxin derived from enteric bacteria might play an important role in the pathogenesis of lung injury; and b) antiendotoxin agents, such as WN1 222-5, appear to protect against endogenous bacterial endotoxin-related disorders in severe hemorrhagic shock in rats.

IL-6 release after intestinal ischemia/reperfusion in rats is under partial control of TNF

Although there is much evidence to substantiate the view that tumor necrosis factor (TNF) plays a pivotal role in the pathogenesis of multiple organ injury subsequent to intestinal ischemia/reperfusion (I/R), it is still unclear whether TNF is involved in triggering the release of other inflammatory mediators in this condition. The current study was designed to determine the potential effects of TNF blockade, by means of monoclonal antibody (TNF MoAb) treatment, on plasma interleukin 6 (IL-6) in rats after acute intestinal I/R injury. Anesthetized rats underwent 75-min occlusion of superior mesenteric artery followed by 6 hr of reperfusion. The animals were treated with TNF MoAb or control protein at a dose of 20 mg/kg i.v. 30 min before the onset of I/R. Similar IL-6 responses in both the portal and the systemic circulation were observed in animals subjected to intestinal I/R, who showed a progressive increase in plasma IL-6 concentration upon release of the clamp. In animals receiving TNF MoAb before I/R, the subsequent IL-6 release following reperfusion was significantly blunted compared to the levels in controls (P < 0.05). The present study demonstrates that the activation and/or release of IL-6 in the setting of acute gut I/R may, at least in part, be mediated via TNF-dependent mechanisms, providing further evidence that a complex interaction exists between TNF and IL-6.

Influence of selective decontamination of the digestive tract on cell-mediated immune function and bacteria/endotoxin translocation in thermally injured rats

OBJECTIVE

To determine the influence of pretreatment with selective decontamination of the digestive tract (SDD) on systemic immunosuppression, and the relationship between bacteria/endotoxin translocation and abnormalities of immune function in thermally injured rats.

DESIGN, MATERIALS, AND METHODS

Animals were subjected to a 40% full-thickness scald injury, and divided into SDD-treated and control groups. The treatment group received SDD (polymyxin E, tobramycin, and 5-flucytosine) by gavage twice daily for 3 days before the experiment and continued for 5 days after thermal injury. The control group was given the same amount of water. The parameters reflecting cell-mediated immunity, including splenocyte proliferation in response to mitogens, interleukin 2 (IL-2) production, and lymphocyte subpopulation, were measured before injury and 1 and 5 days after burn, respectively.

MEASUREMENTS AND MAIN RESULTS

Thermal injury resulted in marked reduction in splenocyte proliferative response to T-cell mitogens, IL-2 production, and T-helper/suppressor cells (CD4/CD8) ratio. Prophylactic treatment with SDD significantly decreased the incidences of bacterial translocation and endotoxemia, prevented suppressive mitogenic response and inadequate IL-2 production (p < 0.05-0.01) but did not affect the abnormal ratio of CD4 to CD8 T lymphocytes in blood (p > 0.05).

CONCLUSIONS

These results suggest that bacteria/endotoxin translocation from the gut appears to be involved in cell-mediated immune dysfunction as a consequence of thermal injury. Pretreatment with SDD might attenuate postburn immunosuppression by preventing translocation events.

Significance of TNF in hemorrhage-related hemodynamic alterations, organ injury, and mortality in rats

To evaluate the role of tumor necrosis factor-alpha (TNF-alpha) in hemodynamic alterations, multiple organ damage, and mortality caused by hemorrhagic shock, we employed a monoclonal antibody to TNF-alpha (TNF-alpha MAb) in anesthetized rats subjected to prolonged hemorrhagic shock (mean arterial pressure of 30-35 mmHg for 180 min) followed by resuscitation over 50 min. Treatment of rats with 20.0 mg/kg TNF-alpha MAb 15 min after the end of resuscitation significantly decreased the total peripheral resistance index (P = 0.031) and provided remarkable protection from multiple organ damage compared with controls. The 48-h survival rate was significantly higher in the treatment group (73.3%) than in the control group (26.7%; P = 0.029). The results suggest that TNF-alpha induced by hemorrhagic shock in rats is an important mediator of pathophysiological alterations associated with cardiovascular abnormalities, multiple organ injury, and even lethality. Postresuscitation treatment with TNF-alpha MAb, even after an initial TNF-alpha formation had occurred, significantly attenuated the cardiovascular consequences and improved the survival rate. Thus monoclonal antibodies to TNF-alpha might provide new prospects in the treatment of hemorrhage-related disorders.

Monoclonal antibody to tumor necrosis factor-alpha attenuates hemodynamic dysfunction secondary to intestinal ischemia/reperfusion in rats

OBJECTIVE

To evaluate the effects of monoclonal antibody to tumor necrosis factor (TNF)-alpha on the hemodynamic alterations and survival rate in rats subjected to intestinal ischemia/reperfusion.

DESIGN

Prospective, randomized study.

SETTING

Animal laboratory of an institute for research in traumatology.

SUBJECTS

Male Sprague-Dawley rats, weighing 430 to 460 g.

INTERVENTIONS

Anesthetized rats underwent 75 mins of superior mesenteric artery occlusion followed by 6 hrs of reperfusion. The animals were treated intravenously with either TNF-alpha monoclonal antibody (TN3, 20 mg/kg) or the control protein (albumin, 20 mg/kg) 30 mins before the onset of ischemia.

MEASUREMENTS AND MAIN RESULTS

Pretreatment with TNF-alpha monoclonal antibody significantly attenuated the decreases in blood pressure and cardiac index (p < .01) compared with controls, for < or = 6 hrs after reperfusion. Stroke volume remained stable in the TNF-alpha monoclonal antibody-treated group and was significantly higher than in the control group at 0.5, 5, and 6 hrs after reperfusion (p < .05 at 0.5 and 5 hrs and p < .01 at 6 hrs). No differences in vascular resistance index values were observed between the two groups at any point in time (p > .05). After intestinal ischemia/reperfusion injury, both the portal and systemic TNF concentrations in the control animals were completely neutralized by TNF-alpha monoclonal antibody treatment. The 72-hr survival rate was significantly (p < .01) better in the treatment group (90%, 9/10) than in the control group (20%, 2/10).

CONCLUSIONS

These results suggest that intestinal ischemia/reperfusion injury can lead to increased TNF release into both the portal and the systemic circulation, which may be an important factor contributing to the development of hemodynamic dysfunction. Pretreatment with TNF-alpha monoclonal antibody significantly attenuates the cardiovascular consequences and improves the survival rate after acute intestinal ischemia/reperfusion injury.

Comparison of the efficacy of pentoxifylline and albifyllin (HWA 138) on endotoxin-induced cytokine production, coagulation disturbances, and mortality

We have evaluated two different xanthine derivatives, pentoxifylline (POF) and albifyllin (HWA), in rat endotoxemia for their ability to reduce 1) cytokine formation, 2) coagulation disturbances, and 3) mortality. The animals were injected with lipopolysaccharide (LPS) (15 mg/kg i.p.) and received HWA or POF (25, 50, or 100 mg/kg) or saline 30 min before LPS administration. The plasma tumor necrosis factor levels were significantly reduced and in a similar manner by pretreatment with HWA or POF in vivo as well as in vitro. Neither the coagulation disturbance nor the characteristic leukopenia that follow an LPS challenge were significantly influenced by the xanthine derivatives. At a dose of 100 mg/kg, the 6 day mortality was significantly reduced by HWA to 36% but only attenuated by POF to 55% as compared to 80% in the control group. The similar effect of both agents on cytokine formation and coagulation disturbances indicate that, at least to a substantial degree, other mechanisms may account for the significant protection of rats against endotoxin-induced mortality by HWA only. HWA 138 may, therefore, be a new powerful agent against endotoxin-related disorders and mortality.

Animal models as the basis of pharmacologic intervention in trauma and sepsis patients

With limited resources and the current concerns about using animals for research purposes, the needs must be clear when setting up trauma and sepsis experiments for pharmacologic interventions. Such interventions are performed typically for four reasons: (1) to study the pathophysiologic role of certain mediators (which can be influenced by pharmacologic agents); (2) to study the therapeutic efficacy of treatment strategies; (3) to study the overall safety of new drugs under trauma/sepsis conditions, which are adjunct studies to standard toxicology; (4) to test new diagnostic procedures in a defined trauma or sepsis setting. Intervention in the inflammatory response may be performed at several levels: (1) at the primary induction site (e.g., by antilipopolysaccharide or by preventing complement activation); (2) at the intermediate mediator level (e.g., by antitumor necrosis factor); (3) at the final mediator level (e.g. , by block of polymorphonuclear neutrophil elastase, and (4) at the target (e.g., by membrane stabilization or enhanced antioxidant defense).

Significance of NO in hemorrhage-induced hemodynamic alterations, organ injury, and mortality in rats

In an attempt to evaluate the role of nitric oxide (NO) in pathophysiological alterations and multiple organ damage caused by hemorrhagic shock, we employed NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthase, in anesthetized rats subjected to a prolonged hypovolemic insult (30-35 mmHg for 180 min). Infusion of 2.0 mg/kg L-NMMA at the end of resuscitation diminished the fall in mean arterial pressure (MAP) and significantly increased the cardiac index and stroke volume, together with remarkable protection from multiple organ damage compared with the controls. The 48-h survival rate was significantly improved from 26.7% in the control group to 68.8% in the treatment group (P < 0.05). In contrast, the high dose of 20.0 mg/kg L-NMMA resulted in a strong blood pressure response, but a marked reduction in cardiac index and stroke volume concomitant with an increased total peripheral resistance index within the observation period, and tended to increase damage to various organs at 2 h after treatment. In addition, marked elevation in both endotoxin and tumor necrosis factor levels were observed in animals subjected to shock insult. The results suggest that NO induced by hemorrhagic shock in rats is an important mediator for pathophysiological alterations associated with cardiovascular abnormalities, multiple organ dysfunction, and even lethality. Regulation of NO generation and use of NO inhibitors might provide new aspects in the treatment of hemorrhage-related disorders, whereas the administration of L-NMMA would be either deleterious or salutary in a dose-dependent manner.

Elevated serum neopterin level: its relation to endotoxaemia and sepsis in patients with major burns

The present study was conducted to determine the relationship between levels of neopterin and endotoxin in the circulation, and whether the neopterin level was related to the development of severe sepsis after extensive burns. This prospective study included 35 patients with burn size greater than 30% (30-98%), and 22 healthy volunteers who served as a comparison group. Neopterin levels increased in most patients on day 3 post-burn, but they were not significantly correlated with the extent of the burn surface (P > 0 center dot 05). A high serum neopterin level was found in patients with sepsis (n = 15), and a marked elevation persisted throughout the observation period. The difference between septic and non-septic patients (n = 20) became significant on 14 and 28 days post-burn. Although the presence of early endotoxaemia did not influence the alterations in serum neopterin, patients with endotoxaemia had much higher neopterin values than those who showed no endotoxaemia from the second week onward (P < 0 center dot 05-0 center dot 01). In addition, circulating endotoxin and neopterin levels were positively correlated in patients who developed endotoxaemia on day 14 (r = 0 center dot 368, P < 0 center dot 05) and day 21 (r = 0 center dot 439, P < 0 center dot 01) after major burns. These results suggest that thermal injury can lead to an elevation of serum neopterin independent of the burn surface area. The initial increase in the neopterin level may be a part of the acute-phase response to tissue injury itself, whereas the endotoxin release in the circulation may be responsible for the continuous induction of neopterin during the late stage. In addition, the presence of a constant high neopterin level is associated with a critical event in the development of severe burn sepsis.

Reduction of circulating prostaglandin E2 level by antiserum against core lipopolysaccharide in a rabbit model of multiple organ failure

OBJECTIVE

To determine the potential role of prostaglandin E2 (PGE2) in the development of multiple organ dysfunction or failure (MOF), the possible effects of antiserum directed against Re chemotype lipopolysaccharide (LPS, from Re mutant of Escherichia coli F515) on circulating PGE2 level and survival rate, and whether there is an elevation in the plasma LPS concentration that could account for the induction of arachidonic acid metabolite in a rabbit model of MOF caused by acute hypovolemic insult.

DESIGN, MATERIALS, AND METHODS

An animal model of MOF in rabbits, engendered by feeding live Escherichia coli O111:B4 before hemorrhagic shock (35-40 mm Hg for 60 min), was used in the present study. Re-LPS antiserum was given intravenously in the treatment group at the onset of hemorrhage and 4 hours after resuscitation. The animals that received equal volumes of normal rabbit serum and antiserum served as the control group.

MEASUREMENTS AND MAIN RESULTS

The circulating PGE2 level was not increased at the end of shock (p > 0.05), but it was found to be significantly elevated 24 hours after hemorrhage and resuscitation in both groups. However, Re-LPS antiserum administration markedly decreased peak PGE2 level (p < 0.05) and attenuated multiple organ damage caused by acute insult. Concomitantly, there were also lower LPS concentrations in the treatment group as compared with the control group (p < 0.05-0.01). The survival rate was significantly increased in antiserum-treated rabbits 96 hours postinjury (treatment vs. control: 58.0% vs. 11.1%, p < 0.01).

CONCLUSIONS

The results suggest that an excessive generation and release of PGE2 may be involved in the pathogenesis of immunosuppression and MOF following hemorrhage and resuscitation. Re-LPS antiserum has an inhibitory effect on overproduction of circulating PGE2 and the ability to improve survival with MOF. Gut-derived endotoxemia, bacterial translocation, or both, could account, at least in part, for the PGE2 formation and release in animals response to acute hypovolemic insult.

Role of gut-derived endotoxaemia and bacterial translocation in rats after thermal injury: effects of selective decontamination of the digestive tract

This study was performed to investigate: (1) the role of gut-derived endotoxin/bacterial translocation in the pathogenesis of sepsis, and (2) the possible effects of selective decontamination of the digestive tract (SDD) on mortality in rats following 40 per cent full-thickness scald injury. In the SDD-treated group, Enterobacteriaceae and yeasts were eradicated from the caecal mucosa, while the mucosal flora consisting of mainly anaerobes was well preserved, within 3 days. The incidence of bacterial translocation to the mesenteric lymph nodes (MLN) and viscerae was significantly lowered on postburn days 1, 3 and 5 (P < 0.05-0.01). Meanwhile, pretreatment with SDD resulted in reductions of the faecal endotoxin levels in different segments of intestinal tract to less than 0.5 per cent (0.04-0.45 per cent) of the untreated control; there was also a significant attenuation of the elevation of endotoxin concentrations in both portal and systemic blood. Intestinal diamine oxidase (DAO) activity returned to baseline on day 5 in rats receiving SDD but not in controls. The 5-day survival rate in the SDD-treated group was elevated by 26.7 per cent as compared with controls (P < 0.05). These data suggested that endotoxin/bacterial translocation took place early and commonly, which in turn contributed to postburn sepsis and mortality. SDD was effective in preventing gut origin endotoxaemia and bacterial translocation, and improving the survival rate in rats following severe thermal injuries.

Inhibitory effects of low-dose polymyxin B on hemorrhage-induced endotoxin/bacterial translocation and cytokine formation in rats

The current experiments were performed to determine the effects of a subtherapeutic dose of polymyxin B sulfate on gut origin endotoxemia/bacterial translocation, and tumor necrosis factor (TNF) and interleukin-1 (IL-1) release following hemorrhagic shock (30 mm Hg, 90 min) in rats. The results showed that significant portal and systemic endotoxemia took place in the control group (portal, 0.269 to 0.845 endotoxin units (EU)/mL; systemic, 0.164 to 0.655 EU/mL), but not in the treatment group (except 0.5 hour in portal blood: 0.207 +/- 0.094 EU/mL). Concomitantly, the incidence of bacterial translocation to the mesenteric lymph nodes and viscera were reduced significantly at 0.5, 2, 6, and 24 hours postresuscitation in animals receiving polymyxin B (p < 0.05 to 0.01), whereas there were no differences with respect to number of translocating bacteria between the two groups (p > 0.05). Marked elevation of plasma TNF levels and IL-1 activities of peritoneal macrophages were also found in untreated controls at 0.5 to 2 hours (p < 0.05) and 6 to 24 hours (p < 0.05 to 0.01), respectively, but prevented by administration of low-dose polymyxin B. The 48-hour survival rate was improved from 41.7% in the control group to 75.0% in the treatment ones (p > 0.05). These data suggest that pretreatment with a subtherapeutic dose of polymyxin B is effective to inhibit hemorrhage-induced endotoxin/bacterial translocation from the gut and excessive TNF and IL-1 production.

The association of circulating endotoxaemia with the development of multiple organ failure in burned patients

In this study, we examined the relationship of plasma endotoxin levels to the development of multiple organ failure (MOF), and the outcome in patients with thermal injury. A prospective cohort study of 17 patients admitted with burns covering more than 70 per cent of body surface area was undertaken. Circulating endotoxin concentrations were measured by modified limulus amoebocyte lysate assay in serial samples of plasma. Seven out of 17 burned patients developed MOF according to multiple criteria. The plasma endotoxin concentrations of patients with MOF were 0.512-1.127 EU/ml, which were significantly higher than that of 10 patients without MOF (0.216-0.553 EU/ml), on 3, 14, 21 and 28 days postburn (p < 0.05-0.01). A significantly higher incidence of positive endotoxin tests (> or = 0.120 EU/ml) was found in patients who developed MOF as compared to those patients who did not develop MOF during the observation period (p < 0.05). As the mean endotoxin levels increased, the incidence of MOF and death rate also increased, and persistent endotoxemia carried a poor prognosis. The present investigation provides further evidence that endotoxemia in severely burned patients commonly occurs. Circulating endotoxin has also been found to be strongly associated with the development of MOF and mortality following major burn injury.

Gut-derived endotoxemia and multiple system organ failure following gunshot wounds combined with hemorrhagic shock: an experimental study in the dog

The purpose of this study was to explore the causative effects of high-velocity bullet injury (5.56 mm, 930 m/sec) combined with hemorrhagic shock on gut-derived endotoxemia and multiple system organ dysfunction or failure. The concentration of endotoxin in both portal and systemic blood was markedly increased after gunshot wounds together with hemorrhagic shock (p < 0.05-0.01). The portal/systemic lipopolysaccharide ratio persistently decreased in the combined wound (CW) group at 24 to 72 hours after injury, and it was much lower in the CW group than that in the single gunshot wound (SW) group. Also, a significant increase of fecal endotoxin content was found in the CW group as compared to the SW group (118.30 +/- 75.36 vs. 8.89 +/- 3.32 micrograms/g, p < 0.01), which was paralleled with the population of gram-negative bacilli in the intestinal tract. The incidence of multiple system organ failure, multiorgan dysfunction (including single organ failure) in the CW group were 30.8% (4 of 13) and 38.5% (5 of 13), respectively. These results suggested that severe trauma could lead to gut origin endotoxemia and bacterial translocation, which might play an important role in the pathogenesis of sepsis and multiple system organ failure following gunshot wounds.

The potential etiologic role of tumor necrosis factor in mediating multiple organ dysfunction in rats following intestinal ischemia-reperfusion injury

Endogenous inflammatory cytokines may function as mediators in the development of remote organ damage in response to local ischemic insult. This study was designed to (a) explore the potential role of tumor necrosis factor (TNF) formation in the pathogenesis of systemic tissue injury, (b) determine the relationship between induction of TNF and gut-derived endotoxemia and/or bacterial translocation, and (c) evaluate the protective effect of anti-TNF monoclonal antibody (MoAb) for vital organs following intestinal ischemia-reperfusion in rats. Animals were subjected to superior mesenteric artery occlusion (SMAO) for 45 min. Systemic plasma TNF levels increased rapidly after the onset of reperfusion, reaching a peak value 2 h later (P < 0.01). TNF elevation was found to be associated with gut origin endotoxemia, where the maximal TNF levels occurred approximately 2 h after the initial appearance of endotoxin in portal vein. Prophylactic treatment with anti-TNF MoAb markedly blunted the elevation in plasma TNF levels and afforded protection from the development of hypotension, vital organs dysfunction, and metabolic acidosis. Significant improvement in 48-h survival rate was observed by administration of anti-TNF MoAb prior to inducing ischemia (P = 0.007). These findings suggest that intestinal ischemia-reperfusion could result in TNF production, which may play a key role in mediating subsequent septic response and systemic tissue injury. It seems likely that passage of endotoxin and bacteria from the gut can be responsible for the TNF formation

Pathogenesis of hemorrhage-induced bacteria/endotoxin translocation in rats. Effects of recombinant bactericidal/permeability-increasing protein

OBJECTIVES

This study was conducted to determine the role of gut-derived bacteria/endotoxin in the pathogenesis of the multiple-organ damage and mortality, the possible beneficial effect of recombinant bactericidal/permeability-increasing protein (rBPl21), and whether neutralizing endotoxemia by rBPl21 treatment influences tumor necrosis factor (TNF) formation in rats after hemorrhagic shock and resuscitation.

SUMMARY BACKGROUND DATA

Hypovolemic shock might be associated with bacterial or endotoxin translocation as well as systemic sepsis. Similar to bactericidal/permeability-increasing (BPl) protein, rBPl21 has been found to bind endotoxin and inhibit TNF production.

METHODS

A rat model of prolonged hemorrhagic shock (30 to 35 mm Hg for 180 min) followed by adequate resuscitation was employed. Recombinant bactericidal/permeability-increasing protein was administered at 5 mg/kg intravenously. The control group was treated similarly to the BPl group, but received thaumatin as a protein-control preparation in the same dose as rBPl21.

RESULTS

Immediately after resuscitation (230 min), plasma endotoxin levels in the control group (61.0 +/- 16.3 pg/mL) were almost neutralized by rBPl21 treatment (13.8 +/- 4.8 pg/mL, p < 0.05). Plasma TNF levels were not significantly influenced by rBPl21 treatment. The 48-hour survival rate was 68.8% in the treatment group versus 37.5% in the control group (p = 0.08). Microscopic histopathologic examination revealed relatively minor damage to various organs in the treatment group.

CONCLUSIONS

These data suggest that hemorrhagic shock may lead to bacterial/endotoxin translocation with concomitant TNF formation, endogenous endotoxemia may play an important role in the pathogenesis of multiple-organ failure after shock and trauma, TNF formation at an early stage might be related mainly to mechanisms other than Kupffer's cells activation via lipopolysaccharide, and rBPl21 might be a useful therapeutic agent against endogenous bacteria/endotoxin related disorders in severe hemorrhagic shock.

Exposure of workers to a mixture of toluene and xylenes. II. Effects

The health effects of exposure to a mixture of toluene and xylene isomers was studied on the fourth or fifth days of a working week in factories in China. The study population comprised 233 subjects (122 men and 111 women), who were exposed to the time weighted geometric mean (maximum) concentrations of toluene (3 (203) ppm) and xylenes (4 (103) ppm). For comparison, 241 non-exposed controls (116 men and 125 women) were recruited from the same regions. The prevalence of some subjective symptoms significantly increased in the exposed population, and the symptom profiles were similar to those found after exposure to toluene or xylenes alone. Haematology and serum biochemistry did not show notable changes. It seems reasonable to conclude that the effects of the toxicities of toluene and xylenes in combination are additive.

[Protective effect of monoclonal antibody of tumor necrosis factor-alpha for vital organs in a model suffering from intestinal ischemia and reperfusion injury]

Monoclonal antibody to tumor necrosis factor-alpha (TNFa-MAb), z8, was used to explore protective effect on multiple organ dysfunction caused by intestinal ischemia and reperfusion in rats. Systemic plasma TNF level rose rapidly after release of the clamp, on superior mesenteric artery, and reached peak level 2 hours later. Endotoxemia and bacteremia were associated with systemic TNF level, and portal endotoxin concentration increased significantly before elevation of TNF activity. Pretreatment with anti-TNFa antibody markedly attenuated the increase of TNF level and provided protection from the development of hypotension, vital organ dysfunction, and metabolic acidosis. As a result the survival rate in treatment group increased by 35.7%. Our results demonstrated that TNF might play an important role in mediating the pathophysiologic changes in the pathogenesis of multiple organ damage in this intestinal ischemia-reperfusion injury model, and monoclonal antibody to TNF offered significant protection against multiple organ dysfunction or failure after severe trauma.

[Endotoxemia in severely burned patients]

Plasma endotoxin was determined by modified synthetic chromogenic limulus amebocyte lysate assay in 35 severely burned patients (30% to 98% TBSA). The results showed that the level of circulating endotoxin markedly increased during the early stage after injury, with a peak value at the 3rd postburn days. The relationship between burn size and the endotoxin value was significant (P < 0.01); The incidence of endotoxemia in the 35 patients was 36.8% to 74.7%. The plasma endotoxin concentrations of 7 burned patients with multiple system organ failure (MSOF) raced from 0.512 to 1.127 EU/ml, significantly higher than those of 10 patients without MSOF (0.216-0.553 EU/ml) at 3, 14, 21 and 28 postburn days. Endotoxemia in severely burned patients commonly occurred and was closely related to the development of sepsis and MSOF after burn injury. Dynamic observation of the changes in circulating endotoxin concentration was valuable as a marker for predicting sepsis and MSOF in critically ill patients with burns.