Trial of short-course antimicrobial therapy for intraabdominal infection.

BACKGROUND: The successful treatment of intraabdominal infection requires a combination of anatomical source control and antibiotics. The appropriate duration of antimicrobial therapy remains unclear. METHODS: We randomly assigned 518 patients with complicated intraabdominal infection and adequate source control to receive antibiotics until 2 days after the resolution of fever, leukocytosis, and ileus, with a maximum of 10 days of therapy (control group), or to receive a fixed course of antibiotics (experimental group) for 4±1 calendar days. The primary outcome was a composite of surgical-site infection, recurrent intraabdominal infection, or death within 30 days after the index source-control procedure, according to treatment group. Secondary outcomes included the duration of therapy and rates of subsequent infections. RESULTS: Surgical-site infection, recurrent intraabdominal infection, or death occurred in 56 of 257 patients in the experimental group (21.8%), as compared with 58 of 260 patients in the control group (22.3%) (absolute difference, -0.5 percentage point; 95% confidence interval [CI], -7.0 to 8.0; P=0.92). The median duration of antibiotic therapy was 4.0 days (interquartile range, 4.0 to 5.0) in the experimental group, as compared with 8.0 days (interquartile range, 5.0 to 10.0) in the control group (absolute difference, -4.0 days; 95% CI, -4.7 to -3.3; P<0.001). No significant between-group differences were found in the individual rates of the components of the primary outcome or in other secondary outcomes. CONCLUSIONS: In patients with intraabdominal infections who had undergone an adequate source-control procedure, the outcomes after fixed-duration antibiotic therapy (approximately 4 days) were similar to those after a longer course of antibiotics (approximately 8 days) that extended until after the resolution of physiological abnormalities. (Funded by the National Institutes of Health; STOP-IT ClinicalTrials.gov number, NCT00657566.).

Physiologic variability at the verge of systemic inflammation: multiscale entropy of heart rate variability is affected by very low doses of endotoxin.

INTRODUCTION: Human injury or infection induces systemic inflammation with characteristic neuroendocrine responses. Fluctuations in autonomic function during inflammation are reflected by beat-to-beat variation in heart rate, termed heart rate variability (HRV). In the present study, we determine threshold doses of endotoxin needed to induce observable changes in markers of systemic inflammation, investigate whether metrics of HRV exhibit a differing threshold dose from other inflammatory markers, and investigate the size of data sets required for meaningful use of multiscale entropy (MSE) analysis of HRV. METHODS: Healthy human volunteers (n = 25) were randomized to receive placebo (normal saline) or endotoxin/lipopolysaccharide (LPS): 0.1, 0.25, 0.5, 1.0, or 2.0 ng/kg administered intravenously. Vital signs were recorded every 30 min for 6 h and then at 9, 12, and 24 h after LPS. Blood samples were drawn at specific time points for cytokine measurements. Heart rate variability analysis was performed using electrocardiogram epochs of 5 min. Multiscale entropy for HRV was calculated for all dose groups to scale factor 40. RESULTS: The lowest significant threshold dose was noted in core temperature at 0.25 ng/kg. Endogenous tumor necrosis factor α and interleukin 6 were significantly responsive at the next dosage level (0.5 ng/kg) along with elevations in circulating leukocytes and heart rate. Responses were exaggerated at higher doses (1 and 2 ng/kg). Time domain and frequency domain HRV metrics similarly suggested a threshold dose, differing from placebo at 1.0 and 2.0 ng/kg, below which no clear pattern in response was evident. By applying repeated-measures analysis of variance across scale factors, a significant decrease in MSE was seen at 1.0 and 2.0 ng/kg by 2 h after exposure to LPS. Although not statistically significant below 1.0 ng/kg, MSE unexpectedly decreased across all groups in an orderly dose-response pattern not seen in the other outcomes. CONCLUSIONS: By using repeated-measures analysis of variance across scale factors, MSE can detect autonomic change after LPS challenge in a group of 25 subjects using electrocardiogram epochs of only 5 min and entropy analysis to scale factor of only 40, potentially facilitating MSE's wider use as a research tool or bedside monitor. Traditional markers of inflammation generally exhibit threshold dose behavior. In contrast, MSE's apparent continuous dose-response pattern, although not statistically verifiable in this study, suggests a potential subclinical harbinger of infectious or other insult. The possible derangement of autonomic complexity prior to or independent of the cytokine surge cannot be ruled out. Future investigation should focus on confirmation of overt inflammation following observed decreases in MSE in a clinical setting.

APOε4 is associated with enhanced in vivo innate immune responses in human subjects.

BACKGROUND: The genetic determinants of the human innate immune response are poorly understood. Apolipoprotein (Apo) E, a lipid-trafficking protein that affects inflammation, has well-described wild-type (ε3) and disease-associated (ε2 and ε4) alleles, but its connection to human innate immunity is undefined. OBJECTIVE: We sought to define the relationship of APOε4 to the human innate immune response. METHODS: We evaluated APOε4 in several functional models of the human innate immune response, including intravenous LPS challenge in human subjects, and assessed APOε4 association to organ injury in patients with severe sepsis, a disease driven by dysregulated innate immunity. RESULTS: Whole blood from healthy APOε3/APOε4 volunteers induced higher cytokine levels on ex vivo stimulation with Toll-like receptor (TLR) 2, TLR4, or TLR5 ligands than blood from APOε3/APOε3 patients, whereas TLR7/8 responses were similar. This was associated with increased lipid rafts in APOε3/APOε4 monocytes. By contrast, APOε3/APOε3 and APOε3/APOε4 serum neutralized LPS equivalently and supported similar LPS responses in Apoe-deficient macrophages, arguing against a differential role for secretory APOE4 protein. After intravenous LPS, APOε3/APOε4 patients had higher hyperthermia and plasma TNF-α levels and earlier plasma IL-6 than APOε3/APOε3 patients. APOE4-targeted replacement mice displayed enhanced hypothermia, plasma cytokines, and hepatic injury and altered splenic lymphocyte apoptosis after systemic LPS compared with APOE3 counterparts. In a cohort of 828 patients with severe sepsis, APOε4 was associated with increased coagulation system failure among European American patients. CONCLUSIONS: APOε4 is a determinant of the human innate immune response to multiple TLR ligands and associates with altered patterns of organ injury in human sepsis.

Cellular metabolic regulators: novel indicators of low-grade inflammation in humans.

OBJECTIVE: The Toll-like receptor 4 (TLR4) ligand endotoxin triggers robust systemic inflammatory responses in humans at doses equal to or greater than 1 ng/kg. In this study, we tested the hypothesis that evidence of TLR4-induced responses would be detectable in leukocytes challenged with endotoxin doses that are below the threshold needed to trigger a characteristic systemic inflammatory phenotype in humans. METHODS: Subjects were challenged with endotoxin at 1, 0.5, or 0.1 ng/kg (n = 5 per dose). Systemic responses were monitored for 24 hours. Blood samples, collected at designated intervals, were used to determine plasma cytokines levels, total and differential leukocyte counts, expression of leukocyte cell surface receptors, and changes in the leukocyte transcriptome. Western blotting was used to determine changes in leukocyte protein expression. RESULTS: We found that in vivo endotoxin at doses below 1.0 ng/kg triggers weak and variable responses in humans. In marked contrast, we show that endotoxin at a concentration as low as 0.1 ng/kg triggers a transient decline in cellular ATP levels in leukocytes. This is associated with the appearance of a unique protein expression signature in leukocytes. The protein expression signature includes 3 prominent features: (i) AMP-activated protein kinase subunit α (AMPKα) degradation, (ii) increased hypoxia inducible factor-1 (HIF-1) α expression, and (iii) autophagy, collectively indicative of a regulated metabolic response. An indistinguishable response phenotype was observed in human leukocytes treated with endotoxin in vitro. CONCLUSIONS: These data demonstrate for the first time in humans that a TLR4 ligand concentration that is below the threshold needed to trigger clinically evident systemic inflammatory manifestations initiates a transient decline in ATP levels, AMPKα degradation, HIF-1α expression, and autophagy in leukocytes. This establishes that low-grade TLR4 activation exerts control over leukocyte metabolism in the absence of systemic inflammatory indicators.

Genomic responses in mouse models poorly mimic human inflammatory diseases.

A cornerstone of modern biomedical research is the use of mouse models to explore basic pathophysiological mechanisms, evaluate new therapeutic approaches, and make go or no-go decisions to carry new drug candidates forward into clinical trials. Systematic studies evaluating how well murine models mimic human inflammatory diseases are nonexistent. Here, we show that, although acute inflammatory stresses from different etiologies result in highly similar genomic responses in humans, the responses in corresponding mouse models correlate poorly with the human conditions and also, one another. Among genes changed significantly in humans, the murine orthologs are close to random in matching their human counterparts (e.g., R(2) between 0.0 and 0.1). In addition to improvements in the current animal model systems, our study supports higher priority for translational medical research to focus on the more complex human conditions rather than relying on mouse models to study human inflammatory diseases.

An agent-based model of cellular dynamics and circadian variability in human endotoxemia.

As cellular variability and circadian rhythmicity play critical roles in immune and inflammatory responses, we present in this study an agent-based model of human endotoxemia to examine the interplay between circadian controls, cellular variability and stochastic dynamics of inflammatory cytokines. The model is qualitatively validated by its ability to reproduce circadian dynamics of inflammatory mediators and critical inflammatory responses after endotoxin administration in vivo. Novel computational concepts are proposed to characterize the cellular variability and synchronization of inflammatory cytokines in a population of heterogeneous leukocytes. Our results suggest that there is a decrease in cell-to-cell variability of inflammatory cytokines while their synchronization is increased after endotoxin challenge. Model parameters that are responsible for IκB production stimulated by NFκB activation and for the production of anti-inflammatory cytokines have large impacts on system behaviors. Additionally, examining time-dependent systemic responses revealed that the system is least vulnerable to endotoxin in the early morning and most vulnerable around midnight. Although much remains to be explored, proposed computational concepts and the model we have pioneered will provide important insights for future investigations and extensions, especially for single-cell studies to discover how cellular variability contributes to clinical implications.

Impact of infectious complications after elective surgery on hospital readmission and late deaths in the U.S. Medicare population.

BACKGROUND AND PURPOSE: Whereas the negative impact of infectious complications (IC) during the index hospitalization after elective surgery is well established, the long-term ramifications of hospital-acquired post-operative infections are not well studied. This analysis evaluated the impact of a hospital-acquired IC after open abdominal vascular surgery on the readmission rate and the mortality rates 30 and 90 days after initial discharge. METHODS: Data from all hospitals in the United States that performed elective open abdominal vascular operations in the Medicare population from 2005 to 2007 were extracted from the national Medicare Provider Analysis and Review database. The cohort consisted of all patients undergoing open abdominal vascular operations, including aortic, iliac, and visceral procedures. The ICs evaluated were pneumonia, urinary tract infection (UTI), postoperative sepsis (sepsis), surgical site infection (SSI), and Clostridium difficile infection (CDI). Patients were categorized as either developing an IC during their initial hospitalization (Index+INF) or not developing an IC (No INF). The rates of 30-day readmission, 30-day IC, and 30- and 90-day mortality after the initial discharge were evaluated longitudinally and compared in patients with and without an IC. RESULTS: A total of 29,549 open abdominal vascular procedures were identified, and 4,016 patients (13.6%) developed an IC during their index hospitalization: Pneumonia (5.1% of the total), UTI (2.7%), sepsis (1.6%), SSI (1.4%), and CDI (0.6%). Additionally, 1.13% of patients developed pneumonia, UTI, SSI, or CDI complicated by sepsis. The hospital mortality rate during the initial hospitalization was 13.7% (Index+INF) versus 4.0% (No INF) (p<0.0002). Infectious processes (pneumonia, UTI, SSI, and CDI) complicated by sepsis had an in-hospital mortality rate significantly higher than patients having an IC alone (50.9% vs. 13.7%; p<0.002). The mortality rate 30 and 90 days after the initial discharge was significantly higher for Index+INF than for No INF (4.4% vs. 1.2% and 8.6% vs. 2.6%, respectively; p<0.0002). The highest 30-day mortality rates after discharge were found after CDI+sepsis (30%), pneumonia+sepsis (12.6%), and postoperative sepsis alone (8.6%). The same rank was found for the 90-day mortality rate: 30%, 22.5%, and 13.8%. Overall, readmission was more likely for Index+INF than for No INF (33.7% vs. 21.5%; p<0.0002). Rates of 30-day readmission after an index IC ranged from 32% to 50%. CONCLUSION: For Medicare beneficiaries undergoing elective open abdominal vascular procedures, the development of any IC significantly increased not only the in-hospital mortality rate but also the mortality rates 30 and 90 days after discharge from the hospital. Index ICs also were associated with a higher 30-day readmission rate. Hospital-acquired infections have a profound late effect on outcomes after discharge. Future programs targeting high-risk patients may improve long-term survival and minimize readmissions.

Continuous enteral and parenteral feeding each reduces heart rate variability but differentially influences monocyte gene expression in humans.

Enteral (EN) or parenteral (PN) nutrition is used to support critically ill patients until oral feeding resumes. Enteral nutrition is assumed preferable to PN, but the differential influence on immune function is not well defined. Autonomic nervous activity is known to influence innate immune responses, and we hypothesized that EN and PN could influence both autonomic signaling and gene activation in peripheral blood monocytes (PBMs). Ten subjects (aged 18-36 years) received continuous EN or PN for 72 h. Peripheral blood monocytes were isolated from whole blood before and after continuous feeding and were analyzed for gene expression using a microarray platform. Gene expression after feeding was compared from baseline and between groups. To measure autonomic outflow, subjects also underwent heart rate variability (HRV) monitoring during feeding. Time and frequency domain HRV data were compared between groups and five orally fed subjects for changes from baseline and changes over time. During continuous EN and PN, subjects exhibited declines in both time and frequency domain HRV parameters compared with baseline and with PO subjects, indicating a loss of vagal/parasympathetic tone. However, PN feeding had a much greater influence on PBM gene expression compared with baseline than EN, including genes important to innate immunity. Continuous EN and PN are both associated with decreasing vagal tone over time, yet contribute differently to PBM gene expression, in humans. These preliminary findings support assumptions that PN imposes a systemic inflammatory risk but also imply that continuous feeding, independent of route, may impart additional risk through different mechanisms.

Entrainment of peripheral clock genes by cortisol.

Circadian rhythmicity in mammals is primarily driven by the suprachiasmatic nucleus (SCN), often called the central pacemaker, which converts the photic information of light and dark cycles into neuronal and hormonal signals in the periphery of the body. Cells of peripheral tissues respond to these centrally mediated cues by adjusting their molecular function to optimize organism performance. Numerous systemic cues orchestrate peripheral rhythmicity, such as feeding, body temperature, the autonomic nervous system, and hormones. We propose a semimechanistic model for the entrainment of peripheral clock genes by cortisol as a representative entrainer of peripheral cells. This model demonstrates the importance of entrainer's characteristics in terms of the synchronization and entrainment of peripheral clock genes, and predicts the loss of intercellular synchrony when cortisol moves out of its homeostatic amplitude and frequency range, as has been observed clinically in chronic stress and cancer. The model also predicts a dynamic regime of entrainment, when cortisol has a slightly decreased amplitude rhythm, where individual clock genes remain relatively synchronized among themselves but are phase shifted in relation to the entrainer. The model illustrates how the loss of communication between the SCN and peripheral tissues could result in desynchronization of peripheral clocks.

Transcriptional implications of ultradian glucocorticoid secretion in homeostasis and in the acute stress response.

Endogenous glucocorticoids are secreted by the hypothalamic-pituitary-adrenal (HPA) axis in response to a wide range of stressors. Glucocorticoids exert significant downstream effects, including the regulation of many inflammatory genes. The HPA axis functions such that glucocorticoids are released in a pulsatile manner, producing ultradian rhythms in plasma glucocorticoid levels. It is becoming increasingly evident that this ultradian pulsatility is important in maintaining proper homeostatic regulation and responsiveness to stress. This is particularly interesting from a clinical perspective given that pathological dysfunctions of the HPA axis produce altered ultradian patterns. Modeling this system facilitates the understanding of how glucocorticoid pulsatility arises, how it can be lost, and the transcriptional implications of ultradian rhythms. To approach these questions, we developed a mathematical model that integrates the cyclic production of glucocorticoids by the HPA axis and their downstream effects by integrating existing models of the HPA axis and glucocorticoid pharmacodynamics. This combined model allowed us to evaluate the implications of pulsatility in homeostasis as well as in response to acute stress. The presence of ultradian rhythms allows the system to maintain a lower response to homeostatic levels of glucocorticoids, but diminished feedback within the HPA axis leads to a loss of glucocorticoid rhythmicity. Furthermore, the loss of HPA pulsatility in homeostasis correlates with a decrease in the peak output in response to an acute stressor. These results are important in understanding how cyclic glucocorticoid secretion helps maintain the responsiveness of the HPA axis.

A genomic storm in critically injured humans.

Human survival from injury requires an appropriate inflammatory and immune response. We describe the circulating leukocyte transcriptome after severe trauma and burn injury, as well as in healthy subjects receiving low-dose bacterial endotoxin, and show that these severe stresses produce a global reprioritization affecting >80% of the cellular functions and pathways, a truly unexpected "genomic storm." In severe blunt trauma, the early leukocyte genomic response is consistent with simultaneously increased expression of genes involved in the systemic inflammatory, innate immune, and compensatory antiinflammatory responses, as well as in the suppression of genes involved in adaptive immunity. Furthermore, complications like nosocomial infections and organ failure are not associated with any genomic evidence of a second hit and differ only in the magnitude and duration of this genomic reprioritization. The similarities in gene expression patterns between different injuries reveal an apparently fundamental human response to severe inflammatory stress, with genomic signatures that are surprisingly far more common than different. Based on these transcriptional data, we propose a new paradigm for the human immunological response to severe injury.

Pulsatile glucocorticoid secretion: origins and downstream effects.

Glucocorticoids are steroid hormones which, among other functions, exert an antiinflammatory effect. Endogenous glucocorticoids are normally secreted by the adrenal gland in discrete bursts. It is becoming increasingly evident that this pulsatile secretion pattern, leading to ultradian rhythms of plasma glucocorticoid levels, may have important downstream regulatory effects on glucocorticoid-responsive genes. Mathematical modeling of this system can compliment recent experimental data and quantitatively evaluate hypothesized mechanistic underpinnings of differential pulsatile signal transduction. In this paper, we describe an integrated model of pulsatile secretion of glucocorticoids by the hypothalamic-pituitary-adrenal (HPA) axis and the pharmacodynamic effect of glucocorticoids. This model is used to investigate the difference in transcriptional responses to pulsatile and constant glucocorticoid exposure. Nonlinearity in ligand-receptor kinetics leads to the differential expression of glucocorticoid-responsive genes in response to different patterns of glucocorticoid secretion, even when the total amount of glucocorticoid exposure is held constant. Understanding the implications of ultradian rhythms in glucocorticoids is important in studying the dysregulation of HPA axis function leading to altered glucocorticoid secretion patterns in disease.

Computational identification of transcriptional regulators in human endotoxemia.

One of the great challenges in the post-genomic era is to decipher the underlying principles governing the dynamics of biological responses. As modulating gene expression levels is among the key regulatory responses of an organism to changes in its environment, identifying biologically relevant transcriptional regulators and their putative regulatory interactions with target genes is an essential step towards studying the complex dynamics of transcriptional regulation. We present an analysis that integrates various computational and biological aspects to explore the transcriptional regulation of systemic inflammatory responses through a human endotoxemia model. Given a high-dimensional transcriptional profiling dataset from human blood leukocytes, an elementary set of temporal dynamic responses which capture the essence of a pro-inflammatory phase, a counter-regulatory response and a dysregulation in leukocyte bioenergetics has been extracted. Upon identification of these expression patterns, fourteen inflammation-specific gene batteries that represent groups of hypothetically 'coregulated' genes are proposed. Subsequently, statistically significant cis-regulatory modules (CRMs) are identified and decomposed into a list of critical transcription factors (34) that are validated largely on primary literature. Finally, our analysis further allows for the construction of a dynamic representation of the temporal transcriptional regulatory program across the host, deciphering possible combinatorial interactions among factors under which they might be active. Although much remains to be explored, this study has computationally identified key transcription factors and proposed a putative time-dependent transcriptional regulatory program associated with critical transcriptional inflammatory responses. These results provide a solid foundation for future investigations to elucidate the underlying transcriptional regulatory mechanisms under the host inflammatory response. Also, the assumption that coexpressed genes that are functionally relevant are more likely to share some common transcriptional regulatory mechanism seems to be promising, making the proposed framework become essential in unravelling context-specific transcriptional regulatory interactions underlying diverse mammalian biological processes.

A dual negative regulation model of Toll-like receptor 4 signaling for endotoxin preconditioning in human endotoxemia.

We discuss a model illustrating how the outcome of repeated endotoxin administration experiments can emerge as a natural consequence of the tightly regulated signaling pathways and also highlight the importance of a dual negative feedback regulation including PI3K/Akt and IRAK-M (IRAK3). We identify the relative time scales of the onset and the magnitude of the stimulus as key determinants of outcome in repeated administration experiments. The results of our simulations involve potentiated response, tolerance, and protective tolerance. Moreover, the knockout of negative regulators shows that IRAK-M is a necessary and sufficient factor for generation of endotoxin tolerance (ET). The effects of the knockout of IRAK-M gene or administration of PI3K inhibitor do yield predictions that have been verified experimentally. Finally, the pretreatment with PI3K inhibitor reveals the interaction between these two negative regulations.

Modeling autonomic regulation of cardiac function and heart rate variability in human endotoxemia.

Heart rate variability (HRV), the quantification of beat-to-beat variability, has been studied as a potential prognostic marker in inflammatory diseases such as sepsis. HRV normally reflects significant levels of variability in homeostasis, which can be lost under stress. Much effort has been placed in interpreting HRV from the perspective of quantitatively understanding how stressors alter HRV dynamics, but the molecular and cellular mechanisms that give rise to both homeostatic HRV and changes in HRV have received less focus. Here, we develop a mathematical model of human endotoxemia that incorporates the oscillatory signals giving rise to HRV and their signal transduction to the heart. Connections between processes at the cellular, molecular, and neural levels are quantitatively linked to HRV. Rhythmic signals representing autonomic oscillations and circadian rhythms converge to modulate the pattern of heartbeats, and the effects of these oscillators are diminished in the acute endotoxemia response. Based on the semimechanistic model developed herein, homeostatic and acute stress responses of HRV are studied in terms of these oscillatory signals. Understanding the loss of HRV in endotoxemia serves as a step toward understanding changes in HRV observed clinically through translational applications of systems biology based on the relationship between biological processes and clinical outcomes.

Cdc42 controls vascular network assembly through protein kinase Cι during embryonic vasculogenesis.

OBJECTIVE: The goal of this study was to determine the role of Cdc42 in embryonic vasculogenesis and the underlying mechanisms. METHODS AND RESULTS: By using genetically modified mouse embryonic stem (ES) cells, we demonstrate that ablation of the Rho GTPase Cdc42 blocks vascular network assembly during embryoid body (EB) vasculogenesis without affecting endothelial lineage differentiation. Reexpression of Cdc42 in mutant EBs rescues the mutant phenotype, establishing an essential role for Cdc42 in vasculogenesis. Chimeric analysis revealed that the vascular phenotype is caused by inactivation of Cdc42 in endothelial cells rather than surrounding cells. Endothelial cells isolated from Cdc42-null EBs are defective in directional migration and network assembly. In addition, activation of atypical protein kinase Cι (PKCι) is abolished in Cdc42-null endothelial cells, and PKCι ablation phenocopies the vascular abnormalities of the Cdc42-null EBs. Moreover, the inhibitory phosphorylation of glycogen synthase kinase-3ß (GSK-3ß) at Ser9 depends on Cdc42 and PKCι, and expression of kinase-dead GSK-3ß in Cdc42-null EBs promotes the formation of linear endothelial segments without branches. These results suggest that PKCι and GSK-3ß are downstream effectors of Cdc42 during vascular morphogenesis. CONCLUSIONS: Cdc42 controls vascular network assembly but not endothelial lineage differentiation by activating PKCι during embryonic vasculogenesis.

Talin1 regulates integrin turnover to promote embryonic epithelial morphogenesis.

Talin is a cytoskeletal protein that binds to integrin ß cytoplasmic tails and regulates integrin activation. Talin1 ablation in mice disrupts gastrulation and causes embryonic lethality. However, the role of talin in mammalian epithelial morphogenesis is poorly understood. Here we demonstrate that embryoid bodies (EBs) differentiated from talin1-null embryonic stem cells are defective in integrin adhesion complex assembly, epiblast elongation, and lineage differentiation. These defects are accompanied by a significant reduction in integrin ß1 protein levels due to accelerated degradation through an MG-132-sensitive proteasomal pathway. Overexpression of integrin ß1 or MG-132 treatment in mutant EBs largely rescues the phenotype. In addition, epiblast cells isolated from talin1-null EBs exhibit impaired cell spreading and focal adhesion formation. Transfection of the mutant cells with green fluorescent protein (GFP)-tagged wild-type but not mutant talin1 that is defective in integrin binding normalizes integrin ß1 protein levels and restores focal adhesion formation. Significantly, cell adhesion and spreading are also improved by overexpression of integrin ß1. All together, these results suggest that talin1 binding to integrin promotes epiblast adhesion and morphogenesis in part by preventing integrin ß1 degradation.

The impact of hospital volume on the development of infectious complications after elective abdominal aortic surgery in the Medicare population.

OBJECTIVE: A relationship exists between higher hospital volume and lower mortality, yet the impact of hospital volume on infectious complications after elective abdominal aortic aneurysm (AAA) repair is unknown. METHODS: The Medicare database (2005-2007) was utilized. Top 10% for volume were categorized as high-volume (HV) and compared to low-volume (LV) centers for infectious complications and utilization. RESULTS: A total of 42 155 endovascular aneurysm repair (EVAR) and 17 210 open AAA were identified. Mortality in HV was significantly lower than in LV after EVAR and open AAA. After EVAR, HV had lower than LV rates of overall infection (3.10% vs 3.51%; P = .021), PNA (0.94% vs 1.27%, P = .002), and sepsis (0.31% vs 0.45%; P = .03). Length of stay (LOS) and total hospital charges were significantly lower at HV compared to LV after both EVAR and open AAA. CONCLUSION: For Medicare beneficiaries, undergoing elective AAA repair at hospitals performing higher volume significantly reduced postoperative infectious complications and hospital resource utilization. Further analysis identifying systematic reasons for disparities may offer cost savings and improve outcomes.

Lipopolysaccharide and sepsis-associated myocardial dysfunction.

PURPOSE OF REVIEW: Myocardial dysfunction in sepsis demonstrates acute reduction in left-ventricular function that is potentially reversible yet also associated with increased mortality. The purpose of this review is to discuss the most recent advances in the current knowledge regarding the pathophysiological mechanisms of septic cardiomyopathy. RECENT FINDINGS: There are numerous candidate pathophysiologic mechanisms for the induction of myocardial dysfunction in sepsis. Sarcolemmal and myofibrillar damage to septic rat cardiomyocytes has been observed, and is likely related to oxidative stress. In a septic chimeric murine model, wild-type mice had decreased cardiac function and increased myocardial TNF-α and IL-6 levels whereas TLR-4 knockout mice had attenuated responses to lipopolysaccharide challenge; thus contributing to the increasing evidence for TLR-4's role in the myocardial inflammatory response to lipopolysaccharide. A similar finding regarding endothelial cell NF-κß signaling inhibition was found using knockout mice. SUMMARY: Septic cardiomyopathy is a significant morbid component of severe sepsis and septic shock. Further research into reducing cardiomyocyte damage via oxidative stress, reducing pro-inflammatory responses induced by TLR-4/NF-κß signaling, decreasing mitochondrial dysfunction, and improving cellular respiration thereby decreasing apoptosis are examples of areas that may be future therapeutic targets.