ACE phenotyping in Gaucher disease

BACKGROUND

Gaucher disease is characterized by the activation of splenic and hepatic macrophages, accompanied by dramatically increased levels of angiotensin-converting enzyme (ACE). To evaluate the source of the elevated blood ACE, we performed complete ACE phenotyping using blood, spleen and liver samples from patients with Gaucher disease and controls.

METHODS

ACE phenotyping included 1) immunohistochemical staining for ACE; 2) measuring ACE activity with two substrates (HHL and ZPHL); 3) calculating the ratio of the rates of substrate hydrolysis (ZPHL/HHL ratio); 4) assessing the conformational fingerprint of ACE by evaluating the pattern of binding of monoclonal antibodies to 16 different ACE epitopes.

RESULTS

We show that in patients with Gaucher disease, the dramatically increased levels of ACE originate from activated splenic and/or hepatic macrophages (Gaucher cells), and that both its conformational fingerprint and kinetic characteristics (ZPHL/HHL ratio) differ from controls and from patients with sarcoid granulomas. Furthermore, normal spleen was found to produce high levels of endogenous ACE inhibitors and a novel, tightly-bound 10-30 kDa ACE effector which is deficient in Gaucher spleen.

CONCLUSIONS

The conformation of ACE is tissue-specific. In Gaucher disease, ACE produced by activated splenic macrophages differs from that in hepatic macrophages, as well as from macrophages and dendritic cells in sarcoid granulomas. The observed differences are likely due to altered ACE glycosylation or sialylation in these diseased organs. The conformational differences in ACE may serve as a specific biomarker for Gaucher disease.

Isoflurane promotes phagocytosis of apoptotic neutrophils through AMPK-mediated ADAM17/Mer signaling

A patient’s recovery from lung inflammatory injury or development of multi-system organ failure is determined by the host’s ability to resolve inflammation and repair tissue damage, both of which require the clearance of apoptotic neutrophils by macrophages (efferocytosis). Here, we investigated the effects of isoflurane on macrophage efferocytosis and resolution of lung inflammatory injury. Treatment of murine bone marrow-derived macrophages (BMDMs) or alveolar macrophages with isoflurane dramatically enhanced phagocytosis of apoptotic neutrophils. Isoflurane significantly increased the surface expression of the receptor tyrosine kinase Mer in macrophages, but markedly decreased the levels of a soluble form of Mer protein in the medium. Isoflurane treatment also caused a decrease in a disintegrin and metalloproteinase 17 (ADAM17) on the cell surface and a concomitant increase in its cytoplasmic fraction. These responses induced by isoflurane were completely reversed by a pharmacological inhibitor or genetic deletion of AMP-activated protein kinase (AMPK). In a mouse model of lipopolysaccharide-induced lung injury, isoflurane accelerated the recovery of lung inflammation and injury that was coupled with an increase in the number of alveolar macrophages containing apoptotic bodies. In alveolar macrophage-depleted mice, administration of isoflurane-pretreated BMDMs facilitated resolution of lung inflammation following lipopolysaccharide challenge. Thus, isoflurane promoted resolution of lipopolysaccharide-induced lung inflammatory injury via enhancement of macrophage efferocytosis. Increased macrophage efferocytosis following isoflurane treatment correlates with upregulation of Mer surface expression through AMPK-mediated blockade of ADAM17 trafficking to the cell membrane.

Identifying S100B as a Biomarker and a Therapeutic Target For Brain Injury and Multiple Diseases

The calcium binding protein S100B has attracted great attention as a biomarker for a variety of diseases. S100B is mainly expressed in glial cells and functions through intracellular and extracellular signaling pathways. The biological roles of S100B have been closely associated with its concentrations and its physiological states. The released S100B can bind to the receptor of advanced glycation end products and induce the initiation of multiple cell signaling transductions. The regulation of S100B bioactivities has been suggested through phosphoinositide 3 kinase/Akt, p53, mitogen-activated protein kinases, transcriptional factors including nuclear factor-kappaB, and cyclic adenosine monophosphate. The levels of S100B in the blood may function to predict the progress or the prognosis of many kinds of diseases, such as cerebrovascular diseases, neurodegenerative diseases, motor neuron diseases, traumatic brain injury, schizophrenia, depression, diabetes mellitus, myocardial infarction, cancer, and infectious diseases. Given that the activity of S100B has been implicated in the pathological process of these diseases, S100B should not be simply regarded as a biomarker, it may also function as therapeutic target for these diseases. Further elucidation of the roles of S100B may formulate innovative therapeutic strategies for multiple diseases.

ACE Phenotyping as a Guide Toward Personalized Therapy With ACE Inhibitors

Background:

Angiotensin-converting enzyme (ACE) inhibitors (ACEI) are widely used in the management of cardiovascular diseases but with significant interindividual variability in the patient’s response.

Objectives:

To investigate whether interindividual variability in the response to ACE inhibitors is explained by the “ACE phenotype”—for example, variability in plasma ACE concentration, activity, and conformation and/or the degree of ACE inhibition in each individual.

Methods:

The ACE phenotype was determined in plasma of 14 patients with hypertension treated chronically for 4 weeks with 40 mg enalapril (E) or 20 mg E + 16 mg candesartan (EC) and in 20 patients with hypertension treated acutely with a single dose (20 mg) of E with or without pretreatment with hydrochlorothiazide. The ACE phenotyping included (1) plasma ACE concentration; (2) ACE activity (with 2 substrates: Hip-His-Leu and Z-Phe-His-Leu and calculation of their ratio); (3) detection of ACE inhibitors in patient’s blood (indicator of patient compliance) and the degree of ACE inhibition (ie, adherence); and (4) ACE conformation.

Results:

Enalapril reduced systolic and diastolic blood pressure in most patients; however, 20% of patients were considered nonresponders. Chronic treatment results in 40% increase in serum ACE concentrations, with the exception of 1 patient. There was a trend toward better response to ACEI among patients who had a higher plasma ACE concentration.

Conclusion:

Due to the fact that “20% of patients do not respond to ACEI by blood pressure drop,” the initial blood ACE level could not be a predictor of blood pressure reduction in an individual patient. However, ACE phenotyping provides important information about conformational and kinetic changes in ACE of individual patients, and this could be a reason for resistance to ACE inhibitors in some nonresponders.

The Role of HMGB1 in Pial Arteriole Dilating Reactivity following Subarachnoid Hemorrhage in Rats

High-mobility group box 1 protein (HMGB1) has been implicated in inflammatory responses, and is also associated with cerebral vasospasm after subarachnoid hemorrhage (SAH). However, there are no direct evident links between HMGB1 and cerebral vasospasm. We therefore investigated the effects of HMGB1 on pial arteriole reactivity following SAH in rats. We initially found that SAH induced a significant decrease in pial arteriole dilating responses to sciatic nerve stimulation (SNS), hypercapnia (CO2), and the topical suffusion of acetylcholine (ACh), adenosine (ADO), and s-nitroso-N-acetylpenicillamine (SNAP) over a 7-day period after SAH. The percent change of arteriolar diameter was decreased to the lowest point at 48 h after SAH, in response to dilating stimuli (i.e., it decreased from 41.0 ± 19.0% in the sham group to 11.00 ± 0.70% after SNS) (n = 5, p < 0.01). HMGB1 infusion in the lateral ventricle in normal rats for 48 h did not change the pial arteriole dilating response. In addition, inhibitors of HMGB1-receptor for advanced glycation end-product or HMGB1-toll-like receptor 2/4 interaction, or the HMBG1 antagonist did not improve pial arteriole reactivity 48 h after SAH. These findings suggest that HMGB1 may not be a major player in cerebral vascular dilating dysfunction after SAH.

Fatal Acute Pancreatitis in a Patient Chronically Treated with Candesartan

Objective:

To summarize a case of acute pancreatitis in a patient receiving the angiotensin II receptor blocker (ARB) candesartan.

Case Summary:

A previously healthy 75-year-old white man presented with acute pancreatitis complicated by anuric renal failure, respiratory failure, circulatory collapse, and died within 24 hours despite resuscitation efforts. He had been receiving candesartan 32 mg/day for more than one year with no apparent adverse effects.

Discussion:

In recent years, angiotensin-converting enzyme (ACE) inhibitors have been linked with sporadic cases of acute pancreatitis. Recent case reports suggest a similar association between pancreatitis and the related drug class of ARBs. Animal data indicate that the renin–angiotensin system plays an important role in pancreatic hemodynamics and exocrine function and is activated in the setting of acute pancreatitis. Because both ARBs and ACE inhibitors affect angiotensin II, we hypothesize that a common pathophysiologic mechanism might apply to both ARB- and ACE inhibitor–induced pancreatitis.

Conclusions:

Although acute pancreatitis appears to be a rare complication of both ARBs and ACE inhibitors, the catastrophic outcome in this case mandates that clinicians be aware of this adverse effect. Further research into the role of the renin–angiotensin system in the pathogenesis of acute pancreatitis appears warranted.

Clinically relevant concentrations of lidocaine and ropivacaine inhibit TNFα-induced invasion of lung adenocarcinoma cells in vitro by blocking the activation of Akt and focal adhesion kinase

BACKGROUND

Matrix-metalloproteinases (MMP) and cancer cell invasion are crucial for solid tumour metastasis. Important signalling events triggered by inflammatory cytokines, such as tumour necrosis factor α (TNFα), include Src-kinase-dependent activation of Akt and focal adhesion kinase (FAK) and phosphorylation of caveolin-1. Based on previous studies where we demonstrated amide-type local anaesthetics block TNFα-induced Src activation in malignant cells, we hypothesized that local anaesthetics might also inhibit the activation and/or phosphorylation of Akt, FAK and caveolin-1, thus attenuating MMP release and invasion of malignant cells.

METHODS

NCI-H838 lung adenocarcinoma cells were incubated with ropivacaine or lidocaine (1 nM-100 µM) in absence/presence of TNFα (20 ng ml(-1)) for 20 min or 4 h, respectively. Activation/phosphorylation of Akt, FAK and caveolin-1 were evaluated by Western blot, and MMP-9 secretion was determined by enzyme-linked immunosorbent assay. Tumour cell migration (electrical wound-healing assay) and invasion were also assessed.

RESULTS

Ropivacaine (1 nM-100 μM) and lidocaine (1-100 µM) significantly reduced TNFα-induced activation/phosphorylation of Akt, FAK and caveolin-1 in NCI-H838 cells. MMP-9 secretion triggered by TNFα was significantly attenuated by both lidocaine and ropivacaine (half-maximal inhibitory concentration [IC50]=3.29×10(-6) M for lidocaine; IC50=1.52×10(-10) M for ropivacaine). The TNFα-induced increase in invasion was completely blocked by both lidocaine (10 µM) and ropivacaine (1 µM).

CONCLUSIONS

At clinically relevant concentrations both ropivacaine and lidocaine blocked tumour cell invasion and MMP-9 secretion by attenuating Src-dependent inflammatory signalling events. Although determined entirely in vitro, these findings provide significant insight into the potential mechanism by which local anaesthetics might diminish metastasis.

Tissue Specificity of Human Angiotensin I-Converting Enzyme

Background

Angiotensin-converting enzyme (ACE), which metabolizes many peptides and plays a key role in blood pressure regulation and vascular remodeling, as well as in reproductive functions, is expressed as a type-1 membrane glycoprotein on the surface of endothelial and epithelial cells. ACE also presents as a soluble form in biological fluids, among which seminal fluid being the richest in ACE content - 50-fold more than that in blood.

Methods/Principal Findings

We performed conformational fingerprinting of lung and seminal fluid ACEs using a set of monoclonal antibodies (mAbs) to 17 epitopes of human ACE and determined the effects of potential ACE-binding partners on mAbs binding to these two different ACEs. Patterns of mAbs binding to ACEs from lung and from seminal fluid dramatically differed, which reflects difference in the local conformations of these ACEs, likely due to different patterns of ACE glycosylation in the lung endothelial cells and epithelial cells of epididymis/prostate (source of seminal fluid ACE), confirmed by mass-spectrometry of ACEs tryptic digests.

Conclusions

Dramatic differences in the local conformations of seminal fluid and lung ACEs, as well as the effects of ACE-binding partners on mAbs binding to these ACEs, suggest different regulation of ACE functions and shedding from epithelial cells in epididymis and prostate and endothelial cells of lung capillaries. The differences in local conformation of ACE could be the base for the generation of mAbs distingushing tissue-specific ACEs.

Printed dose-recording tag based on organic complementary circuits and ferroelectric nonvolatile memories

We have demonstrated a printed electronic tag that monitors time-integrated sensor signals and writes to nonvolatile memories for later readout. The tag is additively fabricated on flexible plastic foil and comprises a thermistor divider, complementary organic circuits, and two nonvolatile memory cells. With a supply voltage below 30 V, the threshold temperatures can be tuned between 0 °C and 80 °C. The time-temperature dose measurement is calibrated for minute-scale integration. The two memory bits are sequentially written in a thermometer code to provide an accumulated dose record.

Ropivacaine attenuates endotoxin plus hyperinflation-mediated acute lung injury via inhibition of early-onset Src-dependent signaling

Background

Acute lung injury (ALI) is associated with high mortality due to the lack of effective therapeutic strategies. Mechanical ventilation itself can cause ventilator-induced lung injury. Pulmonary vascular barrier function, regulated in part by Src kinase-dependent phosphorylation of caveolin-1 and intercellular adhesion molecule-1 (ICAM-1), plays a crucial role in the development of protein-/neutrophil-rich pulmonary edema, the hallmark of ALI. Amide-linked local anesthetics, such as ropivacaine, have anti-inflammatory properties in experimental ALI. We hypothesized ropivacaine may attenuate inflammation in a “double-hit” model of ALI triggered by bacterial endotoxin plus hyperinflation via inhibition of Src-dependent signaling.

Methods

C57BL/6 (WT) and ICAM-1^−/− mice were exposed to either nebulized normal saline (NS) or lipopolysaccharide (LPS, 10 mg) for 1 hour. An intravenous bolus of 0.33 mg/kg ropivacaine or vehicle was followed by mechanical ventilation with normal (7 ml/kg, NTV) or high tidal volume (28 ml/kg, HTV) for 2 hours. Measures of ALI (excess lung water (ELW), extravascular plasma equivalents, permeability index, myeloperoxidase activity) were assessed and lungs were homogenized for Western blot analysis of phosphorylated and total Src, ICAM-1 and caveolin-1. Additional experiments evaluated effects of ropivacaine on LPS-induced phosphorylation/expression of Src, ICAM-1 and caveolin-1 in human lung microvascular endothelial cells (HLMVEC).

Results

WT mice treated with LPS alone showed a 49% increase in ELW compared to control animals (p = 0.001), which was attenuated by ropivacaine (p = 0.001). HTV ventilation alone increased measures of ALI even more than LPS, an effect which was not altered by ropivacaine. LPS plus hyperinflation (“double-hit”) increased all ALI parameters (ELW, EVPE, permeability index, MPO activity) by 3–4 fold compared to control, which were again decreased by ropivacaine. Western blot analyses of lung homogenates as well as HLMVEC treated in culture with LPS alone showed a reduction in Src activation/expression, as well as ICAM-1 expression and caveolin-1 phosphorylation. In ICAM-1^−/− mice, neither addition of LPS to HTV ventilation alone nor ropivacaine had an effect on the development of ALI.

Conclusions

Ropivacaine may be a promising therapeutic agent for treating the cause of pulmonary edema by blocking inflammatory Src signaling, ICAM-1 expression, leukocyte infiltration, and vascular hyperpermeability.

Autophagy in pulmonary macrophages mediates lung inflammatory injury via NLRP3 inflammasome activation during mechanical ventilation

The inflammatory response is a primary mechanism in the pathogenesis of ventilator-induced lung injury. Autophagy is an essential, homeostatic process by which cells break down their own components. We explored the role of autophagy in the mechanisms of mechanical ventilation-induced lung inflammatory injury. Mice were subjected to low (7 ml/kg) or high (28 ml/kg) tidal volume ventilation for 2 h. Bone marrow-derived macrophages transfected with a scrambled or autophagy-related protein 5 small interfering RNA were administered to alveolar macrophage-depleted mice via a jugular venous cannula 30 min before the start of the ventilation protocol. In some experiments, mice were ventilated in the absence and presence of autophagy inhibitors 3-methyladenine (15 mg/kg ip) or trichostatin A (1 mg/kg ip). Mechanical ventilation with a high tidal volume caused rapid (within minutes) activation of autophagy in the lung. Conventional transmission electron microscopic examination of lung sections showed that mechanical ventilation-induced autophagy activation mainly occurred in lung macrophages. Autophagy activation in the lungs during mechanical ventilation was dramatically attenuated in alveolar macrophage-depleted mice. Selective silencing of autophagy-related protein 5 in lung macrophages abolished mechanical ventilation-induced nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome activation and lung inflammatory injury. Pharmacological inhibition of autophagy also significantly attenuated the inflammatory responses caused by lung hyperinflation. The activation of autophagy in macrophages mediates early lung inflammation during mechanical ventilation via NLRP3 inflammasome signaling. Inhibition of autophagy activation in lung macrophages may therefore provide a novel and promising strategy for the prevention and treatment of ventilator-induced lung injury.

A novel angiotensin I-converting enzyme mutation (S333W) impairs N-domain enzymatic cleavage of the anti-fibrotic peptide, AcSDKP

BACKGROUND

Angiotensin I-converting enzyme (ACE) has two functional N- and C-domain active centers that display differences in the metabolism of biologically-active peptides including the hemoregulatory tetrapeptide, Ac-SDKP, hydrolysed preferentially by the N domain active center. Elevated Ac-SDKP concentrations are associated with reduced tissue fibrosis.

RESULTS

We identified a patient of African descent exhibiting unusual blood ACE kinetics with reduced relative hydrolysis of two synthetic ACE substrates (ZPHL/HHL ratio) suggestive of the ACE N domain center inactivation. Inhibition of blood ACE activity by anti-catalytic mAbs and ACE inhibitors and conformational fingerprint of blood ACE suggested overall conformational changes in the ACE molecule and sequencing identified Ser333Trp substitution in the N domain of ACE. In silico analysis demonstrated S333W localized in the S1 pocket of the active site of the N domain with the bulky Trp adversely affecting binding of ACE substrates due to steric hindrance. Expression of mutant ACE (S333W) in CHO cells confirmed altered kinetic properties of mutant ACE and conformational changes in the N domain. Further, the S333W mutant displayed decreased ability (5-fold) to cleave the physiological substrate AcSDKP compared to wild-type ACE.

CONCLUSIONS AND SIGNIFICANCE

A novel Ser333Trp ACE mutation results in dramatic changes in ACE kinetic properties and lowered clearance of Ac-SDKP. Individuals with this mutation (likely with significantly increased levels of the hemoregulatory tetrapeptide in blood and tissues), may confer protection against fibrosis.

Intravenous application of a primary sevoflurane metabolite improves outcome in murine septic peritonitis: first results

Volatile anesthetics are known to have immunomodulatory effects in conditions of organ injury. A recent study in an experimental sepsis model has shown remarkably improved survival when mice were exposed to volatile anesthetics. In the present study, we show that hexafluoroisopropanol – a water-soluble primary sevoflurane metabolite – has beneficial effects on the overall survival in a murine model of cecal ligation and puncture. Seven-day survival as well as tissue damage markers including transaminases and high mobility group box protein-1 were assessed as measures of end organ damage. In animals undergoing cecal ligation and puncture procedure hexafluoroisopropanol conditioning - but not late postconditioning 24 hours after sepsis induction - significantly increased survival rate (17% vs. 77%, p = 0.037) and attenuated secretion of organ damage markers. This study shows survival benefits by administration of the metabolite of a volatile anesthetic. If successfully translated, hexafluoroisopropanol might offer interesting therapeutic opportunities in the future treatment of abdominal sepsis.

Activation of NLRP3 inflammasome in alveolar macrophages contributes to mechanical stretch-induced lung inflammation and injury

Mechanical ventilation of lungs is capable of activating the innate immune system and inducing sterile inflammatory response. The proinflammatory cytokine IL-1β is among the definitive markers for accurately identifying ventilator-induced lung inflammation. However, mechanisms of IL-1β release during mechanical ventilation are unknown. In this study, we show that cyclic stretch activates the nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasomes and induces the release of IL-1β in mouse alveolar macrophages via caspase-1- and TLR4-dependent mechanisms. We also observed that NADPH oxidase subunit gp91(phox) was dispensable for stretch-induced cytokine production, whereas mitochondrial generation of reactive oxygen species was required for stretch-induced NLRP3 inflammasome activation and IL-1β release. Further, mechanical ventilation activated the NLRP3 inflammasomes in mouse alveolar macrophages and increased the production of IL-1β in vivo. IL-1β neutralization significantly reduced mechanical ventilation-induced inflammatory lung injury. These findings suggest that the alveolar macrophage NLRP3 inflammasome may sense lung alveolar stretch to induce the release of IL-1β and hence may contribute to the mechanism of lung inflammatory injury during mechanical ventilation.

Role of caveolin-1 expression in the pathogenesis of pulmonary edema in ventilator-induced lung injury

Caveolin-1 is a key regulator of pulmonary endothelial barrier function. Here, we tested the hypothesis that caveolin-1 expression is required for ventilator-induced lung injury (VILI). Caveolin-1 gene-disrupted (Cav-1^-/-) and age-, sex-, and strain-matched wild-type (WT) control mice were ventilated using two protocols: volume-controlled with protective (8 mL/kg) versus injurious (21 mL/Kg) tidal volume for up to 6 hours; and pressure-controlled with protective (airway pressure = 12 cm H₂O) versus injurious (30 cm H₂O) ventilation to induce lung injury. Lung microvascular permeability (whole-lung ¹²⁵I-albumin accumulation, lung capillary filtration coefficient [K_{f, c}]) and inflammatory markers (bronchoalveolar lavage [BAL] cytokine levels and neutrophil counts) were measured. We also evaluated histologic sections from lungs, and the time course of Src kinase activation and caveolin-1 phosphorylation. VILI induced a 1.7-fold increase in lung ¹²⁵I-albumin accumulation, fourfold increase in K_{f, c}, significantly increased levels of cytokines CXCL1 and interleukin-6, and promoted BAL neutrophilia in WT mice. Lung injury by these criteria was significantly reduced in Cav-1^-/- mice but fully restored by i.v. injection of liposome/Cav-1 cDNA complexes that rescued expression of Cav-1 in lung microvessels. As thrombin is known to play a significant role in mediating stretch-induced vascular injury, we observed in cultured mouse lung microvascular endothelial cells (MLECs) thrombin-induced albumin hyperpermeability and phosphorylation of p44/42 MAP kinase in WT but not in Cav-1^-/- MLECs. Thus, caveolin-1 expression is required for mechanical stretch-induced lung inflammation and endothelial hyperpermeability in vitro and in vivo.

Sevoflurane reduces clinical disease in a mouse model of multiple sclerosis

Background

Inhalational anesthetics have been shown to influence T cell functions both in vitro and in vivo, in many cases inducing T cell death, suggesting that exposure to these drugs could modify the course of an autoimmune disease. We tested the hypothesis that in mice immunized to develop experimental autoimmune encephalomyelitis (EAE), a well established model of multiple sclerosis (MS), treatment with the commonly used inhalational anesthetic sevoflurane would attenuate disease symptoms.

Methods

C57Bl6 female mice were immunized with myelin oligodendrocyte glycoprotein (MOG) peptide residues 35 to 55 to induce a chronic demyelinating disease. At day 10 after immunization, the mice were subjected to 2 h of 2.5% sevoflurane in 100% oxygen, or 100% oxygen, alone. Following treatment, clinical scores were monitored up to 4 weeks, after which brain histology was performed to measure the effects on astrocyte activation and lymphocyte infiltration. Effects of sevoflurane on T cell activation were studied using splenic T cells isolated from MOG peptide-immunized mice, restimulated ex vivo with MOG peptide or with antibodies to CD3 and CD28, and in the presence of different concentrations of sevoflurane. T cell responses were assessed 1 day later by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for proliferation, lactate dehydrogenase (LDH) release for cell death, and inflammatory activation by production of interleukin (IL)-17 and interferon (IFN)γ.

Results

Clinical scores in the oxygen-treated group increased until day 28 at which time they showed moderate to severe disease (average clinical score of 2.9). In contrast, disease progression in the sevoflurane-treated group increased to 2.1 at day 25, after which it remained unchanged until the end of the study. Immunohistochemical analysis revealed reduced numbers of infiltrating leukocytes and CD4⁺ cells in the CNS of the sevoflurane-treated mice, as well as reduced glial cell activation. In splenic T cells, low doses of sevoflurane reduced IFNγ production, cell proliferation, and increased LDH release.

Conclusions

These results are the first to show attenuation of EAE disease by an inhaled anesthetic and are consistent with previous reports that inhaled anesthetics, including sevoflurane, can suppress T cell activation that, in the context of autoimmune diseases such as MS, could lead to reduced clinical progression.

Conformational changes of blood ACE in chronic uremia

Background

The pattern of binding of monoclonal antibodies (mAbs) to 16 epitopes on human angiotensin I-converting enzyme (ACE) comprise a conformational ACE fingerprint and is a sensitive marker of subtle protein conformational changes.

Hypothesis

Toxic substances in the blood of patients with uremia due to End Stage Renal Disease (ESRD) can induce local conformational changes in the ACE protein globule and alter the efficacy of ACE inhibitors.

Methodology/Principal Findings

The recognition of ACE by 16 mAbs to the epitopes on the N and C domains of ACE was estimated using an immune-capture enzymatic plate precipitation assay. The precipitation pattern of blood ACE by a set of mAbs was substantially influenced by the presence of ACE inhibitors with the most dramatic local conformational change noted in the N-domain region recognized by mAb 1G12. The “short” ACE inhibitor enalaprilat (tripeptide analog) and “long” inhibitor teprotide (nonapeptide) produced strikingly different mAb 1G12 binding with enalaprilat strongly increasing mAb 1G12 binding and teprotide decreasing binding. Reduction in S-S bonds via glutathione and dithiothreitol treatment increased 1G12 binding to blood ACE in a manner comparable to enalaprilat. Some patients with uremia due to ESRD exhibited significantly increased mAb 1G12 binding to blood ACE and increased ACE activity towards angiotensin I accompanied by reduced ACE inhibition by inhibitory mAbs and ACE inhibitors.

Conclusions/Significance

The estimation of relative mAb 1G12 binding to blood ACE detects a subpopulation of ESRD patients with conformationally changed ACE, which activity is less suppressible by ACE inhibitors. This parameter may potentially serve as a biomarker for those patients who may need higher concentrations of ACE inhibitors upon anti-hypertensive therapy.

Activation of calpains mediates early lung neutrophilic inflammation in ventilator-induced lung injury

Lung inflammatory responses in the absence of infection are considered to be one of primary mechanisms of ventilator-induced lung injury. Here, we determined the role of calpain in the pathogenesis of lung inflammation attributable to mechanical ventilation. Male C57BL/6J mice were subjected to high (28 ml/kg) tidal volume ventilation for 2 h in the absence and presence of calpain inhibitor I (10 mg/kg). To address the isoform-specific functions of calpain 1 and calpain 2 during mechanical ventilation, we utilized a liposome-based delivery system to introduce small interfering RNAs targeting each isoform in pulmonary vasculature in vivo. Mechanical ventilation with high tidal volume induced rapid (within minutes) and persistent calpain activation and lung inflammation as evidenced by neutrophil recruitment, production of TNF-α and IL-6, pulmonary vascular hyperpermeability, and lung edema formation. Pharmaceutical calpain inhibition significantly attenuated these inflammatory responses caused by lung hyperinflation. Depletion of calpain 1 or calpain 2 had a protective effect against ventilator-induced lung inflammatory responses. Inhibition of calpain activity by means of siRNA silencing or pharmacological inhibition also reduced endothelial nitric oxide (NO) synthase (NOS-3)-mediated NO production and subsequent ICAM-1 phosphorylation following high tidal volume ventilation. These results suggest that calpain activation mediates early lung inflammation during ventilator-induced lung injury via NOS-3/NO-dependent ICAM-1 phosphorylation and neutrophil recruitment. Inhibition of calpain activation may therefore provide a novel and promising strategy for the prevention and treatment of ventilator-induced lung injury.

Transesophageal Echocardiography–Guided Aortic Thrombectomy in a Patient With a Mobile Thoracic Aortic Thrombus

Thoracic aortic thrombi are a well-known cause of distal embolic phenomena. There is a paucity of case reports because of the rarity of this condition, and thus clear management guidelines are lacking. The authors present a case of a mobile thoracic aortic thrombus managed by a surgical approach. This report demonstrates how intraoperative transesophageal echocardiography (TEE) proved to be critical in guiding surgical management. The utility of TEE in the diagnosis and management of aortic thrombi is also discussed. In addition, currently reported management strategies for this complex condition are reviewed.

Prolonged Transesophageal Echocardiography Use in the ICU

Transesophageal echocardiography (TEE) has gained increasing popularity in the operating room and intensive care settings. The use of TEE can often times diagnose pathology that is missed by transthoracic echocardiography (TTE); in addition, it can be used as a guide to continuously monitor a patient’s hemodynamics, along with observing the direct cardiac effects of fluid and vasopressor therapy. We present a case of acute fulminant hepatic failure in the ICU, where TEE allowed a rapid diagnosis. We performed prolonged TEE monitoring (72 hours) of the patient to monitor the patient’s response to therapeutic interventions. We also discuss the diagnostic and therapeutic implications of prolonged TEE placement in the ICU. In addition, particular strategies to optimize the benefit and minimize the risk of this exciting, yet underutilized, technology are discussed.

Cyclic stretch induces alveolar epithelial barrier dysfunction via calpain-mediated degradation of p120-catenin

Lung hyperinflation is known to be an important contributing factor in the pathogenesis of ventilator-induced lung injury. Mechanical stretch causes epithelial barrier dysfunction and an increase in alveolar permeability, although the precise mechanisms have not been completely elucidated. p120-catenin is an adherens junction-associated protein that regulates cell-cell adhesion. In this study, we determined the role of p120-catenin in cyclic stretch-induced alveolar epithelial barrier dysfunction. Cultured alveolar epithelial cells (MLE-12) were subjected to uniform cyclic (0.5 Hz) biaxial stretch from 0 to 8 or 20% change in surface area for 0, 1, 2, or 4 h. At the end of the experiments, cells were lysed to determine p120-catenin expression by Western blot analysis. Immunofluorescence staining of p120-catenin and F-actin was performed to assess the integrity of monolayers and interepithelial gap formation. Compared with unstretched control cells, 20% stretch caused a significant loss in p120-catenin expression, which was coupled to interepithelial gap formation. p120-Catenin knockdown with small interfering RNA (siRNA) dose dependently increased stretch-induced gap formation, whereas overexpression of p120-catenin abolished stretch-induced gap formation. Furthermore, pharmacological calpain inhibition or depletion of calpain-1 with a specific siRNA prevented p120-catenin loss and subsequent stretch-induced gap formation. Our findings demonstrate that p120-catenin plays a critical protective role in cyclic stretch-induced alveolar barrier dysfunction, and, thus, maintenance of p120-catenin expression may be a novel therapeutic strategy for the prevention and treatment of ventilator-induced lung injury.

Conformational fingerprinting of the angiotensin I-converting enzyme (ACE). 1. Application in sarcoidosis

Fine epitope mapping of monoclonal antibodies (mAbs) to 16 epitopes on human angiotensin I-converting enzyme (ACE) revealed that the epitopes of all mAbs contained putative glycosylation sites. ACE glycosylation is both cell- and tissue-specific and, therefore, the local conformation of ACE produced by different cells could be also unique. The pattern of ACE binding by a set of mAbs to 16 epitopes of human ACE - "conformational fingerprint of ACE" - is the most sensitive marker of ACE conformation and could be cell- and tissue-specific. The recognition of ACEs by mAbs to ACE was estimated using an immune-capture enzymatic plate precipitation assay. Precipitation patterns of soluble recombinant ACE released from Chinese hamster ovary (CHO)-ACE cells was influenced by conditions that alter ACE glycosylation. This pattern was also strongly cell type specific. Patients with sarcoidosis exhibited conformational fingerprints of tissue ACE (lungs and lymph nodes), as well as blood ACE, which were distinct from controls. Conformational fingerprinting of ACE may detect ACE originated from the cells other than endothelial cells in the blood and when combined with elevated blood ACE levels in patients with sarcoidosis may potentially reflect extrapulmonary sarcoidosis involvement (bone marrow, spleen, liver). If proven true, this would serve as a biomarker of enormous potential clinical significance.

Reduced expression of angiotensin I-converting enzyme in caveolin-1 knockout mouse lungs

Reduced lung capillary expression of angiotensin I-converting enzyme (ACE), a key enzyme in cardiovascular pathophysiology, and of caveolin-1, an important regulator of endothelial cell signalling, has been demonstrated in various models of pulmonary arterial hypertension (PAH). We addressed the relationship between PAH and ACE expression in caveolin-1 knockout mice (Cav1(-/-)), which have moderate PAH. Tissue ACE activity was reduced by 50% in lungs from 3-month-old Cav1(-/-) mice compared to wild type (WT). A similar reduction in lung endothelial ACE expression was observed by measuring the lung uptake of (125)I-labeled monoclonal anti-ACE antibody and by quantitative immunohistochemistry. These alterations in ACE are limited to capillary segments of the pulmonary circulation. Functionally, the increase in pulmonary artery pressure (PAP) in response to ACE conversion of angiotensin I to angiotensin II in isolated, perfused mouse lungs was reduced significantly in Cav1(-/-) mice compared to WT. Thus, these complementary approaches demonstrate the dependence of lung microvascular endothelial cell ACE protein expression on caveolin-1 expression and underscore the vital role of caveolin-1-regulated pulmonary vascular homeostasis on endothelial ACE expression and activity. In summary, we have revealed a novel role of caveolin-1 in the regulation of ACE expression in pulmonary capillary endothelial cells. Further understanding of the mechanism by which reduced caveolin-1 expression leads altered pulmonary vascular development, PAH, and reduced ACE expression may have important clinical implications in patients with these severe lung diseases.

Angiotensin I-converting enzyme mutation (Trp1197Stop) causes a dramatic increase in blood ACE

Background

Angiotensin-converting enzyme (ACE) metabolizes many peptides and plays a key role in blood pressure regulation and vascular remodeling. Elevated ACE levels may be associated with an increased risk for different cardiovascular or respiratory diseases, including asthma. Previously, a molecular mechanism underlying a 5-fold familial increase of blood ACE was discovered: Pro1199Leu substitution enhanced the cleavage-secretion process. Carriers of this mutation were Caucasians from Europe (mostly Dutch) or had European roots.

Methodology/Principal Findings

We have found a family of African-American descent whose affected members' blood ACE level was increased 13-fold over normal. In affected family members, codon TGG coding for Trp1197 was substituted in one allele by TGA (stop codon). As a result, half of ACE expressed in these individuals had a length of 1196 amino acids and lacked a transmembrane anchor. This ACE mutant is not trafficked to the cell membrane and is directly secreted out of cells; this mechanism apparently accounts for the high serum ACE level seen in affected individuals. A haplotype of the mutant ACE allele was determined based on 12 polymorphisms, which may help to identify other carriers of this mutation. Some but not all carriers of this mutation demonstrated airflow obstruction, and some but not all have hypertension.

Conclusions/Significance

We have identified a novel Trp1197Stop mutation that results in dramatic elevation of serum ACE. Since blood ACE elevation is often taken as a marker of disease activity (sarcoidosis and Gaucher diseases), it is important for clinicians and medical scientists to be aware of alternative genetic causes of elevated blood ACE that are not apparently linked to disease.

Fine epitope mapping of monoclonal antibodies 9B9 and 3G8 to the N domain of angiotensin-converting enzyme (CD143) defines a region involved in regulating angiotensin-converting enzyme dimerization and shedding

A panel of monoclonal antibodies (mAbs) raised against both the N and C domains of angiotensin-I-converting enzyme (ACE, peptidyl dipeptidase, EC 3.4.15.2) have been extensively mapped and have facilitated the study of various aspects of ACE structure and biology. In this study, we characterize two mAbs, 9B9 and 3G8, that recognize the N domain of ACE and that influence shedding and dimerization. Fine epitope mapping was performed, which mapped the epitopes for these mAbs to the N terminal region of the N domain where they overlap to a large extent, despite having different effects on ACE processing. The mAb 3G8 epitope appears to be shielded by the C domain and to be carbohydrate dependent as binding increased significantly as a result of underglycosylation, whereas these factors did not influence mAb 9B9 recognition. Three mutations within the overlapping region of these two epitopes, Q18H, L19E, and Q22A, which decreased mAb 3G8 binding to the soluble N domain, were introduced into full-length somatic ACE (sACE) to determine their influence on ACE expression and processing. Increased ACE expression, cell surface expression, and basal shedding were observed with all three mutations. Furthermore, cross-linking and western blotting of Chinese hamster ovary (CHO) cell lysates detected two distinct ACE dimers, a native and cross-linked dimer. Increasing amounts of the cross-linked dimer were observed for the mutant sACEQ22A, further implicating the overlapping region of the mAb 9B9 and 3G8 epitopes in ACE processing.

Epitope mapping of mAbs to denatured human testicular ACE (CD143)

Angiotensin I-converting enzyme (ACE; CD143) has two homologous enzymatically active domains (N and C) and plays a crucial role in blood pressure regulation and vascular remodeling. A wide spectrum of monoclonal antibodies (mAbs) to different epitopes on the N and C domains of human ACE have been used to study different aspects of ACE biology. In this study, we characterized a set of nine mAbs, developed against the C domain of human ACE, which recognize the denatured forms of ACE and thus are suitable for the detection and quantification of somatic ACE (sACE) and testicular ACE (tACE) using Western blotting and immunohistochemistry on paraffin-embedded human tissues. The epitopes for these mAbs were defined using species cross-reactivity, phage display library screening, Western blotting and ACE mutagenesis. Most of the mAbs recognized common/overlapping region(s) on both somatic and testicular forms of human ACE, whereas mAb 4E10 was relatively specific for the testicular isoform and mAb 5B9 mainly recognized the glycan attached to Asn 731. This set of mAbs is useful for identifying even subtle changes in human ACE conformation because of denaturation. These mAbs are also sensitive tools for the detection of human sACE and tACE in biological fluids and tissues using proteomic approaches. Their high reactivity in paraffin-embedded tissues provides opportunities to study changes in the pattern of ACE expression and glycosylation (particularly with mAb 5B9) in different tissues and cells.

Mapping of conformational mAb epitopes to the C domain of human angiotensin I-converting enzyme

Angiotensin I-converting enzyme (ACE, CD143) has two homologous domains, each having a functional active site. Fine epitope mapping of 8 mAbs to the C-terminal domain of human ACE was carried out using plate precipitation assays, mAbs' cross-reactivity with ACE from different species, site-directed mutagenesis, and antigen- and cell-based ELISAs. Almost all epitopes contained potential glycosylation sites. Therefore, these mAbs could be used to distinguish different glycoforms of ACE expressed in different tissues or cell lines. mAbs 1B8 and 3F10 were especially sensitive to the composition of the N-glycan attached to Asn 731; mAbs 2H9 and 3F11 detected the glycosylation status of the glycan attached to Asn 685 and perhaps Asn1162; and mAb 1E10 and 4E3 recognized the glycan on Asn 666. The epitope of mAb 1E10 is located at the N-terminal end of the C domain, close to the unique 36 amino acid residues of testicular ACE (tACE). Moreover, it binds preferentially to tACE on the surface of human spermatozoa and thus may find application as an immunocontraceptive drug. mAb 4E3 was the best mAb for quantification of ACE-expressing somatic cells by flow cytometry. In contrast to the other mAbs, binding of mAb 2B11 was not markedly influenced by ACE glycosylation or by the cell culture conditions or cell types, making this mAb a suitable reference antibody. Epitope mapping of these C-domain mAbs, particularly those that compete with N-domain mAbs, enabled us to propose a model of the two-domain somatic ACE that might explain the interdomain cooperativity. Our findings demonstrated that mAbs directed to conformational epitopes on the C-terminal domain of human ACE are very useful for the detection of testicular and somatic ACE, quantification using flow cytometry and ELISA assays, and for the study of different aspects of ACE biology.

Intercellular adhesion molecule-1-dependent neutrophil adhesion to endothelial cells induces caveolae-mediated pulmonary vascular hyperpermeability

We investigated the role of caveolae in the mechanism of increased pulmonary vascular permeability and edema formation induced by the activation of polymorphonuclear neutrophils (PMNs). We observed that the increase in lung vascular permeability induced by the activation of PMNs required caveolin-1, the caveolae scaffold protein. The permeability increase induced by PMN activation was blocked in caveolin-1 knockout mice and by suppressing caveolin-1 expression in rats. The response was also dependent on Src phosphorylation of caveolin-1 known to activate caveolae-mediated endocytosis in endothelial cells. To address the role of PMN interaction with endothelial cells, we used an intercellular adhesion molecule (ICAM)-1 blocking monoclonal antibody. Preventing the ICAM-1-mediated PMN binding to endothelial cells abrogated Src phosphorylation of caveolin-1, as well as the increase in endothelial permeability. Direct ICAM-1 activation by crosslinking recapitulated these responses, suggesting that ICAM-1 activates caveolin-1 signaling responsible for caveolae-mediated endothelial hyperpermeability. Our results provide support for the novel concept that a large component of pulmonary vascular hyperpermeability induced by activation of PMNs adherent to the vessel wall is dependent on signaling via caveolin-1 and increased caveolae-mediated transcytosis. Thus, it is important to consider the role of the transendothelial vesicular permeability pathway that contributes to edema formation in developing therapeutic interventions against PMN-mediated inflammatory diseases such as acute lung injury.

Isoflurane, but Not Sevoflurane, Increases Transendothelial Albumin Permeability in the Isolated Rat Lung

Background

Caveolae mediated transendothelial transport of albumin has recently been shown to be the primary mechanism regulating microvascular endothelial albumin permeability. The authors investigated the effects of isoflurane and sevoflurane on pulmonary endothelial albumin permeability and assessed the potential role of the caveolae scaffold protein, caveolin-1, in these effects.

Methods

Isolated rat lungs and cultured rat lung microvessel endothelial cells (RLMVECs) were exposed to 1.0 or 2.0 minimum alveolar concentration (MAC) isoflurane or sevoflurane for 30 min. I-albumin permeability-surface area product and capillary filtration coefficient were determined in the isolated lungs. In RLMVECs, uptake and transendothelial transport of I-albumin were measured in the absence and presence of pretreatment with 2 mm methyl-beta-cyclodextrin, a caveolae-disrupting agent. Uptake of fluorescent-labeled albumin, as well as phosphorylation of Src kinase and caveolin-1, was also determined. In Y14F-caveolin-1 mutant (nonphosphorylatable) expressing RLMVECs, uptake of I-albumin and phosphorylation of caveolin-1 were evaluated.

Results

In the isolated lungs, 2.0 MAC isoflurane increased I-albumin permeability-surface area product by 48% without affecting capillary filtration coefficient. In RLMVECs, isoflurane more than doubled the uptake of I-albumin and caused a 54% increase in the transendothelial transport of I-albumin. These effects were blocked by pretreatment with methyl-beta-cyclodextrin. The isoflurane-induced increase in uptake of I-albumin in wild-type RLMVECs was abolished in the Y14F-caveolin-1 mutant expressing cells. Isoflurane also caused a twofold increase in Src and caveolin-1 phosphorylation. Neither 1.0 MAC isoflurane nor 1.0 or 2.0 MAC sevoflurane affected any index of albumin transport or phosphorylation of caveolin-1.

Conclusion

Isoflurane, but not sevoflurane, increased lung transendothelial albumin permeability through enhancement of caveolae-mediated albumin uptake and transport in the isolated lung. This effect may involve an enhanced phosphorylation of caveolin-1.

Postural Headache in the Presence of Cerebral Venous Sinus Thrombosis

Cerebral venous sinus thrombosis (CVST) can present with a headache similar to that after a dural puncture. We report on a patient who developed postural headache after epidural anesthesia for delivery. The headache became more intense during the following 6 days, and the patient had a tonic clonic seizure. A magnetic resonance angiogram demonstrated CSVT, and anticoagulation therapy was started, with resolution of the symptoms over 2 wk. Any postdural-puncture headache that loses its positional character, becomes persistent, or does not improve with a properly performed blood patch should raise the suspicion of CVST.

Increased Carboxyhemoglobin in a Patient with a Large Retroperitoneal Hematoma

In humans, the sole endogenous source of carbon monoxide is heme degradation. We report the development of prolonged carboxyhemoglobinemia in a critically ill mechanically ventilated patient who required massive transfusion because of retroperitoneal hemorrhage secondary to pheochromocytoma. After the transfusion of 27 U of packed red blood cells, the maximum carboxyhemoglobin level was 6.4%. Although ventilation was controlled with a fraction of inspired oxygen of 0.35-0.5 and external drainage of blood occurred, the concentration of carboxyhemoglobin remained at 1.7%-5.6% for days. Red blood cells for transfusion may be contaminated with carbon monoxide and may have carboxyhemoglobin levels of up to 12%; this may also have contributed to carboxyhemoglobinemia in our patient. If significantly increased concentrations of carboxyhemoglobin develop, therapy to decrease the concentration of carboxyhemoglobin (such as fraction of inspired oxygen of 1.0 and/or minute ventilation or hyperbaric oxygen) or removal of the source should be considered.

Treatment of life-threatening hyperkalemia using hemoconcentration in parallel to venovenous bypass during orthotopic liver transplantation

IMPLICATIONS

The elimination of potassium in patients with end-stage kidney failure is limited. An increase in potassium concentrations can lead to lethal arrhythmias. In the described case, a large potassium concentration was treated during a liver transplantation using a new technical approach.

Severe status asthmaticus: management with permissive hypercapnia and inhalation anesthesia

OBJECTIVE

To describe the difficulties that can be encountered during mechanical ventilation of severe status asthmaticus and to discuss the safety of permissive hypercapnia as a ventilatory strategy and the role and limitations of inhalation anesthesia in the treatment of refractory cases.

DESIGN

Case series and review of literature.

SETTING

Intensive care unit of a tertiary care hospital.

PATIENTS

Two patients with severe status asthmaticus.

INTERVENTIONS

Administration of inhalational anesthetics.

MEASUREMENTS AND MAIN RESULTS

Both patients had respiratory failure secondary to status asthmaticus requiring mechanical ventilation and permissive hypercapnia. They also received inhalational anesthetics because of refractory bronchoconstriction. Levels of PaCO(2) in each case were among the highest and most prolonged elevations (>150 mm Hg for several hours) reported to date. In one case, life-threatening difficulties with ventilation were encountered related to the use of an anesthesia ventilator. Although they had complications related to the severity of their illnesses, both were treated to recovery.

CONCLUSIONS

Mechanical ventilation in severe status asthmaticus can be challenging. Permissive hypercapnia is a relatively safe strategy in the ventilatory management of asthma. High levels of hypercapnia and associated severe acidosis are well tolerated in the absence of contraindications (i.e., preexisting intracranial hypertension). Inhalation anesthesia may be useful in the treatment of refractory cases of asthma but should be used carefully because it may be hazardous owing to poor flow capabilities of most anesthesia ventilators.

Molecular characteristics of the inhibition of human neutrophil elastase by nonsteroidal antiinflammatory drugs

Nonsteroidal antiinflammatory drugs(NSAIDs) are known as clinically effective agents for treatment of inflammatory diseases. Inhibition of cyclooxygenase has been thought to be a major facet of the pharmacological mechanism of NSAIDs. However, it is difficult to ascribe the antiinflammatory effects of NSAIDs solely to the inhibition of prostaglandin synthesis. Human neutrophil elastase (HNElastase; HNE, EC 3.4.21.37) has been known as a causative factor in inflammatory diseases. To investigate the specific relationship between HNElastase inhibition and specificity of molecular structure of several NSAIDs, HNElastase was purified by Ultrogel AcA54 gel filtration, CM-Sephadex ion exchange, and HPLC (with TSK 250 column) chromatography. HNElastase was inhibited by aspirin and salicylate in a competitive manner and by naproxen, ketoprofen, phenylbutazone, and oxyphenbutazone in a partial competative manner, but not by ibuprofen and tolmetin. HNElastase-phenylbutazone-complex showed strong Raman shifts at 200, 440, 1124, 1194, 1384, 1506, and 1768 cm(-1). The Raman bands 1194, 1384, and 1768 cm(-1) may represent evidences of the conformational change at -N=N-phi radical, pyrazol ring, and -C=O radical of the elastase-drug complex, respectively. Phenylbutazone might be bound to HNElastase by ionic and hydrophobic interaction, and masked the active site. Inhibition of HNElastase could be another mechanism of action of NSAIDs besides cyclooxygenase inhibition in the treatment of inflammatory diseases. Different inhibition characteristics of HNE-lastase by NSAIDs such as aspirin, phenylbutazone-like drugs and ineffective drugs could be important points for drawing the criteria for appropriate drugs in clinical application.

Propofol-induced pancreatitis: recurrence of pancreatitis after rechallenge

We report a case of pancreatitis, which occurred while the patient was on a propofol drip and then recurred after resolution following an inadvertent rechallenge with propofol. The initial episode was associated with hypertriglyceridemia, whereas the latter was not. The association between propofol and pancreatitis is definite and may occur independently of significant hypertriglyceridemia.

Gamma Knife treatment of 100 consecutive meningiomas

Clinical and imaging results of Gamma Knife treatment of 100 consecutive patients with intracranial meningiomas are reported. Only 1 patient refused follow-up imaging and her symptoms remain improved after 1 year. Mean values for the patient and treatment parameters were age 61 years, duration of symptoms 3.6 years, time since diagnosis 3 years, average tumor diameter 2.4 cm, surface radiation dose 15 Gy and number of isocenters 5. Clinical outcomes revealed that 6 were improved, 75 were unchanged and 17 had deteriorated. Of the latter, 8 were operated, 4 were treated medically and 5 died. Imaging follow-up showed no growth in 87 patients. The size of tumors treated ranged from 0.66 to 6.8 cm average diameter. In the 77 patients with tumors with an average diameter of 3 cm or less, only 2 (3%) showed further growth, and none died of tumor-related causes.

Search for life on Mars: evaluation of techniques

An important question for exobiology is, did life evolve on Mars? To answer this question, experiments must be conducted on the martian surface. Given current mission constraints on mass, power, and volume, these experiments can only be performed using proposed analytical techniques such as: electron microscopy, X-ray fluorescence, X-ray diffraction, alpha-proton backscatter, gamma-ray spectrometry, differential thermal analysis, differential scanning calorimetry, pyrolysis gas chromatography, mass spectrometry, and specific element detectors. Using prepared test samples consisting of 1% organic matter (bovine serum albumin) in palagonite and a mixture of palagonite, clays, iron oxides, and evaporites, it was determined that a combination of X-ray diffraction and differential thermal analysis coupled with gas chromatography provides the best insight into the chemistry, mineralogy, and geological history of the samples.

Death and other complications of emergency airway management in critically ill adults. A prospective investigation of 297 tracheal intubations

BACKGROUND

Hospitalized patients outside of the operating room frequently require emergency airway management. This study investigates complications of emergency airway management in critically ill adults, including: (1) the incidence of difficult and failed intubation; (2) the frequency of esophageal intubation; (3) the incidence of pneumothorax and pulmonary aspiration; (4) the hemodynamic consequences of emergent intubation, including death, during and immediately following intubation; and (5) the relationship, if any, between the occurrence of complications and supervision of the intubation by an attending physician.

METHODS

Data were collected on consecutive tracheal intubations carried out by the intensive care unit team over a 10-month period. Non-anesthesia residents were supervised by anesthesia residents, critical care attending physicians, or anesthesia attending physicians.

RESULTS

Two hundred ninety-seven consecutive intubations were carried out in 238 adult patients. Translaryngeal tracheal intubation was accomplished in all patients. Intubation was difficult in 8% of cases (requiring more than two attempts at laryngoscopy by a physician skilled in airway management). Esophageal intubation occurred in 25 (8%) of the attempts but all were recognized before any adverse sequelae resulted. New infiltrates suggestive of pulmonary aspiration were present on chest radiography after 4% of intubations. Seven patients (3%) died during or within 30 min of the procedure. Five of the seven patients had systemic hypotension (systolic blood pressure < or = 90 mmHg), and four of the five were receiving vasopressors to support systolic blood pressure. Patients with systolic hypotension were more likely to die after intubation than were normotensive patients (P < 0.001). There was no relationship between supervision by an attending physician and the occurrence of complications.

CONCLUSIONS

In critically ill patients, emergency tracheal intubation is associated with a significant frequency of major complications. In this study, complications were not increased when intubations were accomplished without the supervision of an attending physician as long as the intubation was carried out or supervised by an individual skilled in airway management. Mortality associated with emergent tracheal intubation is highest in patients who are hemodynamically unstable and receiving vasopressor therapy before intubation.

Synthesis and evaluation of nuclear targeting peptide-antisense oligodeoxynucleotide conjugates

An endogenous nuclear enzyme, RNase H, is an important component in determining the efficacy of antisense oligodeoxynucleotides (ODNs). In an effort to improve the potency of antisense ODNs, conjugates with three different nuclear targeting signal peptides were prepared. These short peptide sequences have been shown to facilitate transport of macromolecules into the nucleus of cells. Efficient chemistry for the synthesis of ODN-peptide conjugates is described. Reaction of 5'-aminohexyl-modified ODNs with iodoacetic anhydride gave pure iodoacetamide ODNs (IA-ODNs) in good yield. These electrophilic intermediates were reacted with thiol-containing peptides to give ODN-peptides in excellent yield and purity. The ODN-peptides were further characterized by proteolysis with trypsin. Thermal denaturation studies with ssDNA targets showed little effect of the 5'-peptide modifications on the hybridization properties of the ODN. The effect of the nuclear signal peptides on antisense potency was evaluated in the freshwater ciliate Paramecium. A 3'-hexanol-modified 24-mer antisense ODN, complementary to the mRNA for calmodulin, alters regulation of membrane ion channels and swimming behavior of these cells. A 2'-O-methyl analog of this ODN was inactive, thus providing evidence that this activity in Paramecium is mediated by RNase H. Antisense ODN-nuclear signal peptide conjugates were transfected into the cells by electroporation. Surprisingly, these conjugates showed no antisense effects in comparison to a 5'-unmodified control ODN. Random peptides or amino acids conjugated to the 5'-terminus did not decrease antisense activity.

Women are at greater risk than men for malpositioning of the endotracheal tube after emergent intubation

OBJECTIVES

To investigate the occurrence of endotracheal tube malpositioning after emergent intubation in critically ill adults and to determine the need for a routine postintubation chest radiography to assess endotracheal tube position.

DESIGN

Prospective study.

SETTING

All adult critical care and acute care units of a 560-bed university teaching hospital.

PATIENTS

Study of 297 consecutive intubations (185 intubations in males and 112 intubations in females) in 238 adult patients.

METHODS

Emergent endotracheal intubations were performed by resident physicians with supervision from an intensive care unit (ICU) or anesthesia attending physician or an anesthesia resident. After intubation, proper positioning of the endotracheal tube was verified by the intubating physician using clinical criteria, including auscultation of bilateral breath sounds, symmetric chest expansion, and palpation of the endotracheal tube cuff in the suprasternal notch. The endotracheal tube position relative to the lower anterior incisors or alveolar ridge was recorded using the centimeter markings printed on the endotracheal tube. A chest radiograph was obtained after intubation to verify endotracheal tube position. Appropriate endotracheal tube position on chest radiograph was defined as between > 2 and < or = 6 cm above the carina.

MEASUREMENTS AND MAIN RESULTS

Of the 297 intubations, 26 were excluded from analysis because a chest radiograph was not obtained or the patient was not of normal stature. For the remaining 271 intubations, 42 (15.5%) endotracheal tubes were inappropriately placed, according to the radiographic assessment. The percentage of malpositioned endotracheal tubes was significantly higher in women than in men (61.9% vs. 38.1%, respectively; chi-square: p < .001). Thirty-three (78.6%) of 42 malpositioned endotracheal tubes were placed < 2 cm from the carina, with the highest occurrence (24/33) of proximal malposition occurring in women. Positioning of endotracheal tubes using the centimeter markings printed on the tube referenced to the lower incisors did not accurately identify malposition as documented by chest radiograph.

CONCLUSIONS

Emergent endotracheal intubations result in a significant occurrence of malpositioned endotracheal tubes that are undetected by clinical evaluation. Malpositioning is not detected by routine clinical assessment, but only by chest radiograph. Women are at greater risk than men for endotracheal tube malpositioning after emergent intubation; in women, the endotracheal tube is more likely to be positioned too close to the carina. A chest radiograph for confirmation of endotracheal tube position after emergent intubation should remain the standard of practice.

The use of mineral crystals as bio-markers in the search for life on Mars

Photographs that depict presumed fluvial features on the martian surface have led geologists to hypothesize that water flowed across the early martian terrain. From this, it has been further hypothesized that the surface and atmospheric conditions on early Mars were similar to those on early Earth. Because the oldest fossil evidence of life on Earth dates back to this early period, at least 3.5 billion years ago, the possibility exists that the early Martian environment could have also been conducive to the origin of life. To investigate this possibility, universal signatures or bio-markers indicative of past (or present) biological activity must be identified for use in the search for life on Mars. Several potentially applicable biomarkers have been identified and include: organics (e.g., specific classes of lipids and hopanes), suites of specific inorganic and organic compounds, as well as the isotopic ratios of C, N, and S. Unfortunately, all of these bio-markers may be of biologic or abiotic origin; these origins are often difficult to distinguish. Thus, the discovery of any one of these compounds alone is not a bio-marker. Because minerals produced under biologic control have distinctive crystallographies, morphologies, and isotopic ratios that distinguishable from abiotically produced minerals with the same chemical composition, and are stable through geologic time, we propose the use of minerals resulting from biologically controlled mineralization processes as bio-markers.

Management of the difficult airway

For clinicians involved in airway management, a plan of action for dealing with the difficult airway or a failed intubation should be developed well in advance of encountering a patient in whom intubation is not routine. When difficulty is anticipated, the equipment necessary for performing a difficult intubation should be immediately available. It also is prudent to have a surgeon skilled in performing a tracheotomy and a criothyroidotomy stand by. The intubation should be attempted in the awake state, preferably using the fiberoptic bronchoscope. The more challenging situation is when the difficult airway is confronted unexpectedly. After the first failed attempt at laryngoscopy, head position should be checked and the patient ventilated with oxygen by mask. A smaller styletted tube and possibly a different laryngoscope blade should be selected for a second attempt at intubation. The fiberoptic bronchoscope and other equipment for difficult intubation should be obtained. A second attempt should then be made. If this is unsuccessful, the patient should be reoxygenated, and assistance including a skilled anesthesiologist and surgeon should be summoned. On a third attempt, traction to the tongue can be applied by an assistant, a tube changer could be used to enter the larynx, or one of the other special techniques previously described can be used. If this third attempt fails, it may be helpful to have a physician more experienced in airway management attempt intubation after oxygen has been administered to the patient. If all attempts are unsuccessful, then invasive techniques to secure the airway will have to be performed.