Acute effects of combined burn and smoke inhalation injury on carboxyhemoglobin formation, tissue oxygenation, and cardiac performance

The objective of this study was to determine the relationship between carboxyhemoglobin (COHb) formation, global oxygen transport, and cardiac performance in the acute phase of combined burn and smoke inhalation injury. Following a third degree burn of 20% of the total body surface area, adult sheep were subjected to cotton smoke (4x12 breaths) according to an established protocol. Compared with baseline (BL), the burn injury led to an immediate and sustained COHb-independent depression in myocardial contractility. Despite a progressive increase in COHb formation, up to a maximum of 78+/-3% (P < 0.001 vs BL), smoke inhalation did not further impair these hemodynamic changes. This study demonstrated that in the early stage of combined burn and smoke inhalation injury, the depression in cardiac function is basically triggered by the burn injury, whereas COHb generation secondary to cotton smoke exposure primarily contributes to pulmonary shunting.     

A murine model of sepsis following smoke inhalation injury

Acute lung injury (ALI) by smoke inhalation with subsequent pneumonia and sepsis represents a major cause of morbidity and mortality in burn patients. The aim of the present study was to develop a murine model of ALI and sepsis to enhance the knowledge of mechanistic aspects and pathophysiological changes in patients with these injuries. In deeply anesthetized female C57BL/6 mice, injury was induced by four sets of cotton smoke using an inhalation chamber. Afterward, live Pseudomonas aeruginosa (3.2 × 10⁷ colony-forming units) was administered intranasally. The indicated dose of bacteria was determined based on the results of a dose-response study (n = 47). The following study groups were monitored for survival over 96 h: (1) sham injury group, (2) only smoke inhalation group, (3) only bacteria group, and (4) smoke inhalation plus bacteria group. Each group included 10 mice. The survival rates were 100%, 90%, 30%, and 10%, respectively. The double hit injury was associated with excessive releases of pro-inflammatory cytokines in the plasma, and enhanced neutrophil accumulation, increased lipid peroxidation, and excessive formation of reactive nitrogen species in the lung. In mice receiving only smoke inhalation injury, no systemic cytokine release and increased lung tissue lipid peroxidation were observed. However, smoke alone significantly increased neutrophil accumulation and formation of reactive nitrogen species in lung tissue. In conclusion, bacterial pneumonia is predominantly responsible for mortality and morbidity in this novel murine model of smoke inhalation and pulmonary sepsis. Reactive oxygen and nitrogen species mediate the severity of lung injury.     

Inducible nitric oxide synthase dimerization inhibitor prevents cardiovascular and renal morbidity in sheep with combined burn and smoke inhalation injury

Inducible nitric oxide synthase (iNOS) is implicated in the pathogenesis of acute respiratory distress syndrome (ARDS). ARDS treatment is frequently complicated by significant extrapulmonary comorbidity. This study was designed to clarify the role of iNOS in mediating extrapulmonary comorbidity in sheep after combined burn and smoke inhalation injuries using a potent and highly selective iNOS dimerization inhibitor, BBS-2. Twenty-two female sheep were operatively prepared. After 5 days of recovery, tracheostomy was performed under ketamine-halothane anesthesia. Sheep were given a 40% total body surface third-degree burns and insufflated with cotton smoke (48 breaths, <40 degrees C). Sheep were divided into four groups: noninjured and nontreated (sham group; n = 6), noninjured but treated with BBS-2 (sham/BBS-2 group; n = 4), injured but nontreated (control group, n = 6), and injured but treated with 100 microg.kg-1.h-1 BBS-2 (BBS-2 group; n = 6). Evaluation was in a laboratory intensive care unit setting for 48 h. The sham group had stable cardiopulmonary and systemic hemodynamics. Control animals showed multiple signs of morbidity. Decreased left ventricular stroke work index and stroke volume index with elevated left atrial pressure indicated myocardial depression. Systemic vascular leak was evidenced by robust hemoconcentration, decreased plasma oncotic pressure, and increased transvascular fluid flux into the lymphatic system. Finally, severely impaired renal function (urinary output) was associated with adverse net fluid balance. Treatment with BBS-2 prevented all these morbidities without adversely effecting cardiovascular hemodynamics such as cardiac index and mean arterial pressure. The results identify a major role for iNOS in mediating extrapulmonary comorbidity in a clinically relevant and severe trauma model and support the use of highly selective iNOS inhibitors as novel treatments in critical care medicine.     

Burn and smoke inhalation injury in sheep depletes vitamin E: kinetic studies using deuterated tocopherols

To test the hypothesis that burn and smoke injury will deplete tissue alpha-tocopherol and cause its faster plasma disappearance, deuterium-labeled vitamin E was administered to sheep exposed to both surface skin burn and smoke insufflation, which cause injuries similar to those of human victims of fire accidents. Two different protocols were used: (1) deuterated vitamin E was administered orally with food at time 0 (just before injury) or (2) the labeled vitamin E was administered orally with food the day before injury. The animals, which had been operatively prepared seven days before, were anesthetized and then received both 40% body surface area third-degree burn and 48 breaths of cotton smoke or sham injuries. All were resuscitated with Ringer's lactate solution (4 ml/kg/% BSA burn/24 h) and mechanically ventilated. Blood samples were collected at various times after vitamin E dosing. In both studies the depletion of plasma alpha-tocopherol was faster in the injured sheep. The sheep given deuterated vitamin E 24 h before injury had similar maximum alpha-tocopherol concentrations at similar times. The exponential rates of alpha-tocopherol disappearance were 1.5 times greater and half-lives were 12 h shorter (p < 0.05) in the injured sheep. In separate studies, various tissues were obtained from sheep that were sacrificed from 4 to 48 h after injury. The liver alpha-tocopherol concentrations in sheep killed at various times after injury seem to show a linear decrease at a rate of 0.1 nmol alpha-tocopherol/g liver per hour, suggesting that the liver is supplying alpha-tocopherol to maintain the plasma and lung alpha-tocopherol concentrations, but that this injury is so severe the liver is unable to maintain lung alpha-tocopherol concentrations. These findings suggest that alpha-tocopherol should be administered to burn patients to prevent vitamin E depletion and to protect against oxidative stress from burn injury.     

Beneficial pulmonary effects of a metalloporphyrinic peroxynitrite decomposition catalyst in burn and smoke inhalation injury

During acute lung injury, nitric oxide (NO) exerts cytotoxic effects by reacting with superoxide radicals, yielding the reactive nitrogen species peroxynitrite (ONOO(-)). ONOO(-) exerts cytotoxic effects, among others, by nitrating/nitrosating proteins and lipids, by activating the nuclear repair enzyme poly(ADP-ribose) polymerase and inducing VEGF. Here we tested the effect of the ONOO(-) decomposition catalyst INO-4885 on the development of lung injury in chronically instrumented sheep with combined burn and smoke inhalation injury. The animals were randomized to a sham-injured group (n = 7), an injured control group [48 breaths of cotton smoke, 3rd-degree burn of 40% total body surface area (n = 7)], or an injured group treated with INO-4885 (n = 6). All sheep were mechanically ventilated and fluid-resuscitated according to the Parkland formula. The injury-related increases in the abundance of 3-nitrotyrosine, a marker of protein nitration by ONOO(-), were prevented by INO-4885, providing evidence for the neutralization of ONOO(-) action by the compound. Burn and smoke injury induced a significant drop in arterial Po(2)-to-inspired O(2) fraction ratio and significant increases in pulmonary shunt fraction, lung lymph flow, lung wet-to-dry weight ratio, and ventilatory pressures; all these changes were significantly attenuated by INO-4885 treatment. In addition, the increases in IL-8, VEGF, and poly(ADP-ribose) in lung tissue were significantly attenuated by the ONOO(-) decomposition catalyst. In conclusion, the current study suggests that ONOO(-) plays a crucial role in the pathogenesis of pulmonary microvascular hyperpermeability and pulmonary dysfunction following burn and smoke inhalation injury in sheep. Administration of an ONOO(-) decomposition catalyst may represent a potential treatment option for this injury.     

A new look at the Precambrian and Cambrian event chronostratigraphic correlation of Mongolia

The Mongolian Precambrian and Cambrian event chronostratigraphic classification of sedimentary, sedimentary—volcanogenic, volcanogenic, and metamorphic rock sediments spread over the territory of Mongolia according to the new chronostratigraphic classification approved by the International Stratigraphic Commission is discussed. These ancient rock units are readily divided into two independent complexes. The lower complex (1000–3500 m) is represented by the Archean and Early Proterozoic crystalline basement and the upper complex is the latest Precambrian–Cambrian sediments (220–7500 m). A detailed study of abundant Neoproterozoic and Early Cambrian faunal (ichnofossils, hexactinellid sponges, archaeocyaths, trilobites, etc.) and floral (stromatolites, microphytolites, cyanobacterial mats, microfossils, etc.) fossils provides the first regional chronostratigraphic subdivision of different facies sediments. Every stage is characterized by distinctive geohistorical and biological events.     

New data on the stratigraphy of the crystalline complexes of Mongolia

At present, in Mongolia crystalline complexes are reliably established in almost all major structural elements. The largest field of these complexes is recognized in the Early Caledonian structures of the North-Mongolian Folded Belt, in the Tarbagatai and Baidarik blocks. The crystalline complexes of the South Altai Belt have previously been interpreted as fragments of the Precambrian basement. Recent geochronological and isotope geochemical data have shown that pre-Riphean and Early Hercynian formations can be recognized in the Precambrian of Mongolia. These complexes show evidence of similar metamorphic processes, but are different in structural position and geological history. The paper contains new stratigraphic schemes for metamorphic complexes of the Baidarik and Tarbagatai blocks and also the South Altai Metamorphic Belt (SAMB).     

Pulmonary changes in a mouse model of combined burn and smoke inhalation-induced injury.

The morbidity and mortality of burn victims increase when burn injury is combined with smoke inhalation. The goal of the present study was to develop a murine model of burn and smoke inhalation injury to more precisely reveal the mechanistic aspects of these pathological changes. The burn injury mouse group received a 40% total body surface area third-degree burn alone, the smoke inhalation injury mouse group received two 30-s exposures of cotton smoke alone, and the combined burn and smoke inhalation injury mouse group received both the burn and the smoke inhalation injury. Animal survival was monitored for 120 h. Survival rates in the burn injury group, the smoke inhalation injury group, and the combined injury group were 70%, 60%, and 30%, respectively. Mice that received combined burn and smoke injury developed greater lung damage as evidenced by histological changes (septal thickening and interstitial edema) and higher lung water content. These mice also displayed more severely impaired pulmonary gas exchange [arterial PO2 (PaO2)/inspired O2 fraction (FiO2)<200]. Lung myeloperoxidase activity was significantly higher in burn and smoke-injured animals compared with the other three experimental groups. Plasma NO2-/NO3-, lung inducible nitric oxide synthase (iNOS) activity, and iNOS mRNA increased with injury; however, the burn and smoke injury group exhibited a higher response. Severity of burn and smoke inhalation injury was associated with more pronounced production of nitric oxide and accumulation of activated leukocytes in lung tissue. The murine model of burn and smoke inhalation injury allows us to better understand pathophysiological mechanisms underlying cardiopulmonary morbidity secondary to burn and smoke inhalation injury.     

Comparison of Gene Expression by Sheep and Human Blood Stimulated with the TLR4 Agonists Lipopolysaccharide and Monophosphoryl Lipid A

Background

Animal models that mimic human biology are important for successful translation of basic science discoveries into the clinical practice. Recent studies in rodents have demonstrated the efficacy of TLR4 agonists as immunomodulators in models of infection. However, rodent models have been criticized for not mimicking important characteristics of the human immune response to microbial products. The goal of this study was to compare genomic responses of human and sheep blood to the TLR4 agonists lipopolysaccharide (LPS) and monophosphoryl lipid A (MPLA).

Methods

Venous blood, withdrawn from six healthy human adult volunteers (~ 28 years old) and six healthy adult female sheep (~3 years old), was mixed with 30 μL of PBS, LPS (1μg/mL) or MPLA (10μg/mL) and incubated at room temperature for 90 minutes on a rolling rocker. After incubation, 2.5 mL of blood was transferred to Paxgene Blood RNA tubes. Gene expression analysis was performed using an Agilent Bioanalyzer with the RNA6000 Nano Lab Chip. Agilent gene expression microarrays were scanned with a G2565 Microarray Scanner. Differentially expressed genes were identified.

Results

11,431 human and 4,992 sheep probes were detected above background. Among them 1,029 human and 175 sheep genes were differentially expressed at a stringency of 1.5-fold change (p<0.05). Of the 175 sheep genes, 54 had a known human orthologue. Among those genes, 22 had > 1.5-fold changes in human samples. Genes of major inflammatory mediators, such as IL-1, IL-6 and IL-8, TNF alpha, NF-kappaB, ETS2, PTGS2, PTX3, CXCL16, KYNU, and CLEC4E were similarly (>2-fold) upregulated by LPS and MPLA in both species.

Conclusion

The genomic responses of peripheral blood to LPS and MPLA in sheep are quite similar to those observed in humans, supporting the use of the ovine model for translational studies that mimic human inflammatory diseases and the study of TLR-based immunomodulators.     

Inhibition of neuronal nitric oxide synthase by 7-nitroindazole attenuates acute lung injury in an ovine model

Nitric oxide (NO) has been shown to play a major role in acute lung injury (ALI) after smoke inhalation. In the present study, we developed an ovine sepsis model, created by exposing sheep to smoke inhalation followed by instillation of bacteria into the airway, that mimics human sepsis and pneumonia. We hypothesized that the inhibition of neuronal NO synthase (nNOS) might be beneficial in treating ALI associated with this model. Female sheep (n = 26) were surgically prepared for the study and given a tracheostomy. This was followed by insufflation of 48 breaths of cotton smoke (40 degrees C) into the airway of each animal and subsequent instillation of live Pseudomonas aeruginosa [5 x 10(11) colony forming units (CFU)] into each sheep's lung. All sheep were mechanically ventilated using 100% O2. Continuous infusion of 7-nitroindazole (7-NI), an nNOS inhibitor, NG-monomethyl-l-arginine (l-NMMA), a nonspecific NOS inhibitor, or aminoguanidine (AG), an inducible NOS inhibitor, was started 1 h after insult. The administration of 7-NI improved pulmonary gas exchange (PaO2/FiO2; where PaO2 is arterial PO2 and FiO2 is fractional inspired oxygen concentration) and pulmonary shunt fraction and attenuated the increase in lung wet-to-dry weight ratio seen in the nontreated sheep. Histologically, 7-NI prevented airway obstruction. The increase in airway blood flow after injury in the nontreated group was significantly inhibited by 7-NI. The increase in plasma concentration of nitrate and nitrite (NOx) was inhibited by 7-NI as well. Posttreatment with l-NMMA improved the pulmonary gas exchange, but AG did not. The results of the present study show that nNOS may be involved in the pathogenesis of ALI after smoke inhalation injury followed by bacterial instillation in the airway.