Partial Destabilization of Amyloid-β Protofibril by Methionine Photo-Oxidation: A Molecular Dynamic Simulation Study

Selective photosensitized oxidation of amyloid protein aggregates is being investigated as a possible therapeutic strategy for treating Alzheimer's disease (AD). Photo-oxidation has been shown to degrade amyloid-β (Aβ) aggregates and ameliorate aggregate toxicity in vitro and reduce aggregate levels in the brains of AD animal models. To shed light on the mechanism by which photo-oxidation induces fibril destabilization, we carried out an all-atom molecular dynamics (MD) simulation to examine the effect of methionine (Met35) oxidation on the conformation and stability of a β-sheet-rich Aβ9-40 protofibril. Analyses of up to 1 μs simulations showed that the oxidation of the Met35 residues, which resulted in the addition of hydrophilic oxygens in the fibril core, reduced the overall conformational stability of the protofibril. Specifically, Met35 disrupted the hydrophobic interface that stabilizes the stacking of the two hexamers that comprise the protofibril. The oxidized protofibril is more solvent exposed and exhibits more backbone flexibility. However, the protofibril retained the underlying U-shaped architecture of each peptide upon oxidation, and although some loss of β-sheets occurred, a significant portion remained. Our simulation results are thus consistent with our experimental observation that photo-oxidation of Aβ40 fibril resulted in the dis-agglomeration and fragmentation of Aβ fibrils but did not cause complete disruption of the fibrillar morphology or β-sheet structures. The partial destabilization of Aβ aggregates supports the further development of photosensitized platforms for the targeting and clearing of Aβ aggregates as a therapeutic strategy for treating AD.

Controlled and Selective Photo-oxidation of Amyloid-β Fibrils by Oligomeric p-Phenylene Ethynylenes

Photodynamic therapy (PDT) has been explored as a therapeutic strategy to clear toxic amyloid aggregates involved in neurodegenerative disorders such as Alzheimer's disease. A major limitation of PDT is off-target oxidation, which can be lethal for the surrounding cells. We have shown that a novel class of oligo-p-phenylene ethynylenes (OPEs) exhibit selective binding and fluorescence turn-on in the presence of prefibrillar and fibrillar aggregates of disease-relevant proteins such as amyloid-β (Aβ) and α-synuclein. Concomitant with fluorescence turn-on, OPE also photosensitizes singlet oxygen under illumination through the generation of a triplet state, pointing to the potential application of OPEs as photosensitizers in PDT. Herein, we investigated the photosensitizing activity of an anionic OPE for the photo-oxidation of Aβ fibrils and compared its efficacy to the well-known but nonselective photosensitizer methylene blue (MB). Our results show that, while MB photo-oxidized both monomeric and fibrillar conformers of Aβ40, OPE oxidized only Aβ40 fibrils, targeting two histidine residues on the fibril surface and a methionine residue located in the fibril core. Oxidized fibrils were shorter and more dispersed but retained the characteristic β-sheet rich fibrillar structure and the ability to seed further fibril growth. Importantly, the oxidized fibrils displayed low toxicity. We have thus discovered a class of novel theranostics for the simultaneous detection and oxidization of amyloid aggregates. Importantly, the selectivity of OPE's photosensitizing activity overcomes the limitation of off-target oxidation of traditional photosensitizers and represents an advancement of PDT as a viable strategy to treat neurodegenerative disorders.

Computational Investigation of the Binding Dynamics of Oligo p-Phenylene Ethynylene Fluorescence Sensors and Aβ Oligomers

Amyloid protein aggregates are pathological hallmarks of neurodegenerative disorders such as Alzheimer's (AD) and Parkinson's (PD) diseases and are believed to be formed well before the onset of neurodegeneration and cognitive impairment. Monitoring the course of protein aggregation is thus vital to understanding and combating these diseases. We have recently demonstrated that a novel class of fluorescence sensors, oligomeric p-phenylene ethynylene (PE)-based electrolytes (OPEs) selectively bind to and detect prefibrillar and fibrillar aggregates of AD-related amyloid-β (Aβ) peptides over monomeric Aβ. In this study, we investigated the binding between two OPEs, anionic OPE₁^2- and cationic OPE₂⁴⁺, and to two different β-sheet rich Aβ oligomers using classical all-atom molecular dynamics simulations. Our simulations have revealed a number of OPE binding sites on Aβ oligomer surfaces, and these sites feature hydrophobic amino acids as well as oppositely charged amino acids. Binding energy calculations show energetically favorable interactions between both anionic and cationic OPEs with Aβ oligomers. Moreover, OPEs bind as complexes as well as single molecules. Compared to free OPEs, Aβ protofibril bound OPEs show backbone planarization with restricted rotations and reduced hydration of the ethyl ester end groups. These characteristics, along with OPE complexation, align with known mechanisms of binding induced OPE fluorescence turn-on and spectral shifts from a quenched, unbound state in aqueous solutions. This study thus sheds light on the molecular-level details of OPE-Aβ protofibril interactions and provides a structural basis for fluorescence turn-on sensing modes of OPEs.

Determination of Trace Elements in Water by Inductively Coupled Plasma–Mass Spectrometry: Collaborative Study

A joint U.S. Environmental Protection Agency (U.S. EPA)—AOAC interlaboratory method validation study was conducted on U.S. EPA method 200.8, Determination of Trace Elements in Waters and Wastes by Inductively Coupled Plasma–Mass Spectrometry. The purpose of the study was to determine and compare the mean recovery and precision of the inductively coupled plasma–mass spectrometry (ICP–MS) analyses for 20 trace elements in reagent water, drinking water, and groundwater. The formal study was based on Youden’s nonreplicate plan for collaborative tests of analytical methods. The test waters were spiked with the 20 trace elements at 6 concentration levels in the 0.8–200 μg/L range, prepared as 3 Youden pairs. Thirteen collaborators spiked 100 mL aliquots of the test waters, acidified them with 1 mL concentrated HNO3 and 0.5 mL concentrated HCl, reduced the volume to 20 mL by heating in an open beaker at 85°C, refluxed them for 30 min at 95°C, and diluted them to 50 mL. After centrifuging or settling the samples, a 20 mL portion of the supernatant was diluted to 50 mL and analyzed by ICP–MS. Related experiments evaluated the method performance in wastewater and wastewater digestate at a single concentration pair, and an alternative nitric acid digestion procedure. Mean recoveries for reagent water, drinking water, and groundwater were generally 95–105% with between-laboratory relative standard deviations about 4–8%. The method also worked well with wastewaters and digestate, with between-laboratory relative standard deviations averaging 8% and recoveries averaging 100%. Recoveries of silver, however, were low in all matrixes at concentrations over 100 μg/L. The nitric acid digestion procedure was comparable in accuracy and precision to the mixed-acid digestion in U.S. EPA method 200.8. The method was adopted first action by AOAC INTERNATIONAL.

Oligomeric Conjugated Polyelectrolytes Display Site-Preferential Binding to an MS2 Viral Capsid

Opportunistic bacteria and viruses are a worldwide health threat prompting the need to develop new targeting modalities. A class of novel synthetic poly(phenylene ethynylene) (PPE)-based oligomeric conjugated polyelectrolytes (OPEs) have demonstrated potent wide-spectrum biocidal activity. A subset of cationic OPEs display high antiviral activity against the MS2 bacteriophage. The oligomers have been found to inactivate the bacteriophage and perturb the morphology of the MS2 viral capsid. However, details of the initial binding and interactions between the OPEs and the viruses are not well understood. In this study, we use a multiscale computational approach, including random sampling, molecular dynamics, and electronic structure calculations, to gain an understanding of the molecular-level interactions of a series of OPEs that vary in length, charge, and functional groups with the MS2 capsid. Our results show that OPEs strongly bind to the MS2 capsid protein assembly with binding energies of up to -30 kcal/mol. Free-energy analysis shows that the binding is dominated by strong van der Waals interactions between the hydrophobic OPE backbone and the capsid surface and strong electrostatic free energy contributions between the OPE charged moieties and charged residues on the capsid surface. This knowledge provides molecular-level insight into how to tailor the OPEs to optimize viral capsid disruption and increase OPE efficacy to target amphiphilic protein coats of icosahedral-based viruses.

Neutrophil-mediated mycobacteriocidal immunity in the lung during Mycobacterium bovis BCG infection in C57BL/6 mice

Although neutrophils have been identified as sources of inflammatory cytokines and chemokines, little is known about their immunologic function during mycobacterial infection in the lungs. In this study, we examined the growth of Mycobacterium bovis BCG in the lungs under experimental conditions that altered neutrophil recruitment to the lungs. Depletion and recruitment of neutrophils was associated with respective increases and decreases in M. bovis BCG growth. Thus, neutrophils may enhance mycobacteriocidal immunity in the lungs.

Intravenous immunoglobulin in neurological disease: a specialist review

Treatment of neurological disorders with intravenous immunoglobulin (IVIg) is an increasing feature of our practice for an expanding range of indications. For some there is evidence of benefit from randomised controlled trials, whereas for others evidence is anecdotal. The relative rarity of some of the disorders means that good randomised control trials will be difficult to deliver. Meanwhile, the treatment is costly and pressure to "do something" in often distressing disorders considerable. This review follows a 1 day meeting of the authors in November 2000 and examines current evidence for the use of IVIg in neurological conditions and comments on mechanisms of action, delivery, safety and tolerability, and health economic issues. Evidence of efficacy has been classified into levels for healthcare interventions (tables 1 and 2).

Comparison of milrinone versus nitroglycerin, alone and in combination, on grafted internal mammary artery flow after cardiopulmonary bypass: effects of alpha-adrenergic stimulation

OBJECTIVES

To compare changes in blood flow in a grafted internal mammary artery (IMA) after cardiopulmonary bypass (CPB) in response to the administration of milrinone or nitroglycerin and to establish the effects of alpha-adrenergic stimulation.

DESIGN

Randomized study.

SETTING

A university medical center hospital and a Veterans Affairs Medical Center hospital.

PARTICIPANTS

Thirty consenting adults scheduled for elective coronary artery bypass graft surgery.

INTERVENTIONS

Patients were randomized to receive a 2 microg/kg/min infusion of nitroglycerin (n = 10), a loading dose of 50 microg/kg of milrinone (n = 10), or both drugs combined (n = 10) shortly after CPB. Intravenous phenylephrine was administered to increase mean arterial pressure by 20%. IMA flow was measured with a calibrated laser Doppler flow probe. Hemodynamic and flow measurements were obtained before and after every intervention.

MEASUREMENTS AND MAIN RESULTS

Nitroglycerin and milrinone increased mean IMA flow, but the increase was greater with milrinone. Both drugs combined were superior to nitroglycerin alone but not to milrinone. The addition of phenylephrine to nitroglycerin increased IMA flow in 6 of 10 patients. IMA flow decreased in 4 of 10 patients, however. Phenylephrine significantly increased IMA blood flow in patients receiving milrinone or in those given both drugs combined.

CONCLUSION

After CPB, milrinone and nitroglycerin vasodilate the IMA; however, the combination of both drugs was not superior to milrinone alone. When using alpha-adrenergic stimulation, milrinone proved superior to nitroglycerin in preserving IMA flow.

Single-stage transmediastinal replacement of the ascending, arch, and descending thoracic aorta

BACKGROUND

Aneurysms of the ascending, arch, and descending thoracic aorta are typically managed with two operations. The first stage involves replacement of the ascending and arch aorta leaving a segment of graft in the proximal descending aorta with a mortality and stroke risk of 8%. The second stage involves replacement of the descending aorta with a mortality of 5% and a paraplegia risk of 5% to 10%. Some patients refuse surgical completion and others are at increased risk to undergo the second stage thoracotomy, leaving them with untreated descending thoracic aortic aneurysms vulnerable to rupture. A single-stage transmediastinal operation used in 14 patients is described.

METHODS

Under circulatory arrest, the descending thoracic aorta is opened. A wire is passed up to the arch and a graft is brought down and secured excluding the descending thoracic aneurysm. The arch vessels are attached as a single patch and the graft is brought forward, replacing the ascending aorta.

RESULTS

Fourteen patients have undergone single-stage replacement of the ascending, arch, and descending aorta with a 14% mortality rate and 14% incidence of paraplegia.

CONCLUSIONS

Patients with aneurysms of the ascending, arch, and descending thoracic aorta can be managed with a single operation with comparable mortality and morbidity of the two-stage approach.

Inhibition of phosphodiesterase type III before aortic cross-clamping preserves intramyocardial cyclic adenosine monophosphate during cardiopulmonary bypass

Inotropes are often used to treat myocardial dysfunction shortly after cardiopulmonary bypass (CPB). beta-Adrenergic agonists improve contractility, in part by increasing cyclic adenosine monophosphate (cAMP) production, whereas phosphodiesterase type III inhibitors prevent its breakdown. CPB is associated with abnormalities at the beta-receptor level and diminished adenyl cyclase activity, both of which tend to decrease cAMP. These effects may be increased in the presence of preexisting myocardial dysfunction. We tested the hypothesis that inhibition of phosphodiesterase type III before global myocardial ischemia and pharmacologic arrest results in the preservation of intramyocardial cAMP concentration during CPB. Twenty adult patients undergoing coronary artery bypass grafting with CPB were studied. After CPB was instituted, a myocardial biopsy was obtained from the apex of the left ventricle. Patients were randomized to receive either placebo or milrinone (50 micro/kg) through the bypass pump 10 min before aortic cross-clamping. Another myocardial biopsy was performed adjacent to the left ventricular apex just before weaning from CPB. Myocardial cAMP concentration was determined by radioimmunoassay. Myocyte protein content was determined by the Bradford method by using a commercial kit. There were no significant demographic differences between the groups; however, patients in the Milrinone group had a lower left ventricular ejection fraction than placebo (41% +/- 13% vs 53% +/- 7%; P < 0.05). Patients who received milrinone had larger cAMP concentrations at the end of CPB compared with placebo (21 +/- 12.5 pmol/mg protein versus 12.8 +/- 2.2 pmol/mg protein; P < 0.05). The administration of milrinone before aortic cross-clamping is associated with increased intramyocardial cAMP concentration at the end of CPB.

IMPLICATIONS

The administration of a single dose of milrinone before aortic cross-clamping resulted in significantly larger intramyocardial cyclic adenosine monophosphate concentration in myocardial biopsy specimens compared with controls.

Latency-associated peptide of transforming growth factor beta enhances mycobacteriocidal immunity in the lung during Mycobacterium bovis BCG infection in C57BL/6 mice

Latency-associated peptide of transforming growth factor beta (TGF-beta) (LAP) was used to determine whether in vivo modulation of TGF-beta bioactivity enhanced pulmonary immunity to Mycobacterium bovis BCG infection in C57BL/6 mice. LAP decreased BCG growth in the lung and enhanced antigen-specific T-cell proliferation and gamma interferon mRNA expression. Thus, susceptibility of the lung to primary BCG infection may be partially mediated by the immunosuppressive effects of TGF-beta.

The relationship between visceral ischemia, proinflammatory cytokines, and organ injury in patients undergoing thoracoabdominal aortic aneurysm repair

OBJECTIVES

Plasma proinflammatory, anti-inflammatory cytokine, and soluble tumor necrosis factor (TNF) receptor concentrations were examined in hospitalized patients after abdominal and thoracoabdominal aortic aneurysm (TAAA) repair, with and without left atrial femoral bypass. Changes in plasma cytokine concentrations were related to the duration of visceral ischemia and the frequency rate of postoperative, single, or multiple system organ dysfunction (MSOD).

DESIGN

Prospective, observational study.

SETTING

Two academic referral centers in the United States and The Netherlands.

PATIENTS

We included 16 patients undergoing TAAA repair without left atrial femoral bypass, 12 patients undergoing TAAA repair with left atrial femoral bypass, and nine patients undergoing infrarenal aortic aneurysm repair.

MEASUREMENTS AND MAIN RESULTS

Timed, arterial blood sampling for proinflammatory and anti-inflammatory cytokine and soluble TNF receptor concentrations (p55 and p75), and prospective assessment of postoperative single and MSOD. Plasma appearance of TNF-alpha, interleukin (IL)-6, IL-8, and IL-10 peaked 1 to 4 hrs after TAAA repair, and concentrations were significantly elevated compared with infrarenal abdominal aortic aneurysm repair (p < .05). Left atrial femoral bypass significantly reduced the duration of visceral ischemia (p < .05) and the systemic TNF-alpha, p75, and IL-10 responses (p < .05). Plasma TNF-alpha concentrations >150 pg/mL were more common in patients with extended visceral ischemia times (>40 mins). Additionally, patients with early peak TNF-alpha concentrations >150 pg/mL and IL-6 levels >1,000 pg/mL developed MSOD more frequently than patients without these elevated plasma cytokine levels (both p < .05).

CONCLUSIONS

Thoracoabdominal aortic aneurysm repair results in the increased plasma appearance of TNF-alpha, IL-6, IL-8, IL-10, and shed TNF receptors. The frequency and magnitude of postoperative organ dysfunction after TAAA repair is associated with an increased concentration of the cytokines, TNF-alpha, and IL-6 and the increased plasma levels of these cytokines appear to require extended visceral ischemia times.

Interleukin-10 appearance following thoraco-abdominal and abdominal aortic aneurysm repair is associated with the duration of visceral ischaemia

OBJECTIVES

to evaluate the plasma IL-10 levels during elective operative repair of thoraco-abdominal and abdominal aortic aneurysm repair. To study whether IL-10 plasma levels are associated with the duration of cross-clamping (ischaemia) and clinical outcome.

MATERIALS

fifteen consecutive patients undergoing surgery for TAAA and 10 consecutive patients undergoing surgical repair of AAA were included.

METHODS

plasma concentrations of IL-10 were measured by ELISA technique. Clinical outcome of the TAAA patients was prospectively analysed.

RESULTS

during aortic clamping IL-10 was produced in both populations. The plasma IL-10 peak (934+/-172 pg/ml) of the TAAA group was seen at 4 h after declamping and remained detectable after 48 h. The plasma IL-10 peak (212+/-32 pg/ml) of the AAA group was seen 30 min after declamping and fell to undetectable levels by 24 h. These data show that the peak IL-10 plasma levels in TAAA repair are significantly (p<0.05) higher compared to the peak IL-10 plasma levels as seen during AAA repair. A positive correlation was seen between cross-clamping and peak plasma IL-10 and organ dysfunction.

CONCLUSIONS

IL-10 plasma concentrations appear higher, later and are longer detectable in patients undergoing TAAA. Correlations were seen with duration of cross-clamping and MSOD.

Milrinone, not epinephrine, improves left ventricular compliance after cardiopulmonary bypass

OBJECTIVE

To compare the effects of milrinone versus epinephrine administered after cardiopulmonary bypass (CPB) on left ventricular compliance.

DESIGN

Prospective and randomized.

SETTING

University-affiliated hospital.

PARTICIPANTS

Twenty consenting adult patients.

INTERVENTIONS

Patients undergoing aortocoronary bypass surgery were randomized to receive 50 microg/kg of milrinone (group M; n = 10) or 0.03 microg/kg/min of epinephrine (group E; n = 10) shortly after separation from CPB. Left ventricular compliance was assessed by observing changes in left ventricular end-diastolic area (LVEDA) in the short-axis view with transesophageal echocardiography, while maintaining a constant left atrial pressure. Measurements were performed (1) before CPB, (2) after separation from CPB, and (3) after either milrinone or epinephrine.

MEASUREMENTS AND MAIN RESULTS

Baseline LVEDA decreased by 20% after CPB in the milrinone group (from 16.6 +/- 3.1 cm2 to 14.3 +/- 2.4 cm2; p < 0.05) and by 22% in the epinephrine group (from 19.4 +/- 4.1 cm2 to 17.2 +/- 3.8 cm2; p < 0.05). LVEDA increased by 15% after milrinone (from 14.3 +/- 2.4 cm2 to 15.6 +/- 2.8 cm2; p < 0.05) but remained unchanged after epinephrine (from 17.2 +/- 3.8 cm2 to 17.1 +/- 4.2 cm2; p = ns).

CONCLUSIONS

Left ventricular compliance was decreased after CPB. The administration of milrinone, but not epinephrine, was associated with a partial return to prebypass values. The exact mechanism of action remains to be determined.

Pulmonary immune responses during primary mycobacterium bovis- Calmette-Guerin bacillus infection in C57Bl/6 mice

Mechanisms of protective immunity to mycobacterial infection in the lung remain poorly defined. In this study, T-cell subset expansion and cytokine expression in bronchoalveolar spaces, lung parenchyma, and mediastinal lymph nodes of mice infected intratracheally with Mycobacterium bovis-Calmette-Guerin bacillus (BCG) were analyzed in parallel with histopathology and bacterial burden. M. bovis-BCG was cleared rapidly from bronchoalveolar spaces without evidence for persistence. In lung parenchyma bacteria grew during the first 4 wk followed by gradual clearance with less than 0.1% of the original inoculum persisting for more than 8 mo. Clearance of M. bovis-BCG from bronchoalveolar lavage was associated with recruitment of both neutrophils and lymphocytes. Lung CD4(+), CD8(+), and gammadelta T-cell receptor-positive T cells expanded maximally by Week 4, and declined by Week 8 to control values despite bacterial persistence. Both CD4(+) and CD8(+) lung T cells produced interferon (IFN)-gamma in response to M. bovis-BCG. Four distinct pathologic states of lung parenchymal infection were noted. Early focal sub-bronchial inflammation with transmigration of cells into airways was followed by diffuse peribronchitis, perivasculitis, and alveolitis with activated macrophages, lymphoblasts, and occasional giant cells. The latter stage corresponded to maximal M. bovis-BCG growth. Resolving infection consisted of small lymphocytes and foamy macrophages, which coincided with decreasing M. bovis-BCG colony-forming units, T-cell infiltration, and IFN-gamma expression. A final quiescent phase consisted of residual lymphoid aggregates and perivasculitis associated with persistent spontaneous IFN-gamma production. Bacterial dissemination to lymph node and spleen occurred by Week 4 and declined in parallel to lung. In contrast to lung, IFN-gamma secretion was detected only late despite early expansion of CD4(+) and CD8(+) T cells. By reverse transcriptase/polymerase chain reaction, IFN-gamma and interleukin (IL)-12 p40 messenger RNA (mRNA) in lung paralleled IFN-gamma protein production. Tumor necrosis factor-alpha, IL-4 and IL-10 mRNA expression was not increased during M. bovis-BCG lung infection. Thus, protective immunity to M. bovis-BCG in the lung evolved differently in air space, lung, and lymph node.

Effects of milrinone versus epinephrine on grafted internal mammary artery flow after cardiopulmonary bypass

OBJECTIVE

To compare changes on grafted internal mammary artery (IMA) flow after cardiopulmonary bypass in response to the administration of milrinone or epinephrine.

DESIGN

Prospective and randomized.

SETTING

University-affiliated hospital.

PARTICIPANTS

Twenty consenting, adult patients undergoing CABG.

INTERVENTIONS

Patients were randomized to receive either milrinone, 50 microg/kg, or epinephrine, 0.03 microg/kg/min, immediately after cardiopulmonary bypass. IMA flow was measured with a laser Doppler flow probe before and after the administration of either drug.

MEASUREMENTS AND MAIN RESULTS

Baseline grafted IMA flow was similar for both groups (milrinone, 38+/-14 mL/min; epinephrine, 33+/-10 mL/min). In patients who received milrinone, flow increased by 24% to 50+/-17 mL/min, p<0.05; whereas with epinephrine, it remained essentially unchanged (33+/-10 v. 31+/-11 mL/min).

CONCLUSIONS

This study confirms that the vasodilatory effect of milrinone on the IMA is also present after its anastomosis, whereas low-dose epinephrine exhibits neither beneficial nor adverse effects. It is suggested that in the absence of excessive vasodilation, milrinone should be considered as a first-line inotrope after coronary artery bypass graft surgery, to achieve an increase in contractility and IMA artery flow.

Effects of calcium chloride on grafted internal mammary artery flow after cardiopulmonary bypass

OBJECTIVE

To examine the effects of calcium chloride (CaCl2) administration on blood flow through the grafted left internal mammary artery (IMA) after cardiopulmonary bypass (CPB).

DESIGN

Single-arm prospective study.

SETTING

University-affiliated hospital operating room.

PARTICIPANTS

Twenty adult patients scheduled for coronary artery bypass graft surgery with IMA graft.

INTERVENTIONS

IMA flow was measured noninvasively with a laser Doppler flow probe placed around the IMA, and measurements were recorded for 10 seconds and averaged. After separation from CPB under stable hemodynamics, baseline IMA flow was measured. CaCl2, 15 mg/kg, was administered intravenously over 1 minute. Blood pressure, left atrial pressure, heart rate, and IMA flow were then measured at 1, 5, and 10 minutes. Coronary perfusion pressure and IMA vascular resistance were calculated.

MEASUREMENTS AND MAIN RESULTS

After CaCl2 administration, IMA blood flow significantly decreased from baseline at 1, 5, and 10 minutes (from 28+/-9 mL/min to 19+/-8 mL/min, 22+/-6 mL/min, and 25+/-4 mL/min), with gradual return toward baseline over time. Blood pressure, coronary perfusion pressure, and IMA vascular resistance significantly increased at 1 and 5 minutes after CaCl2. Left atrial pressure and heart rate remained unchanged. No systolic regional wall motion abnormalities were detected on transesophageal echocardiography.

CONCLUSIONS

CaCl2, administered as a bolus dose after separation from CPB, transiently but significantly reduces IMA flow and can potentially trigger vasospasm, increasing the risk for myocardial ischemia or infarction in susceptible patients. Further studies are needed to determine whether this effect also occurs with nitrosodilators or phosphodiesterase inhibitors.

Coordinate regulation of lipogenesis, the assembly and secretion of apolipoprotein B-containing lipoproteins by sterol response element binding protein 1

Stable plasmid-driven expression of the liver-specific gene product cholesterol 7alpha-hydroxylase (7alpha-hydroxylase) was used to alter the cellular content of transcriptionally active sterol response element binding protein 1 (SREBP1). As a result of stable expression of 7alpha-hydroxylase, individual single cell clones expressed varying amounts of mature SREBP1 protein. These single cell clones provided an opportunity to identify SREBP1-regulated genes that may influence the assembly and secretion of apoB-containing lipoproteins. Our results show that in McArdle rat hepatoma cells, which normally do not express 7alpha-hydroxylase, plasmid-driven expression of 7alpha-hydroxylase results in the following: 1) a linear relationship between (i) the cellular content of mature SREBP1 and 7alpha-hydroxylase protein, (ii) the relative expression of 7alpha-hydroxylase mRNA and the mRNA's encoding the enzymes regulating fatty acid, i.e. acetyl-CoA carboxylase and sterol synthesis, i.e. HMG-CoA reductase, (iii) the relative expression of 7alpha-hydroxylase mRNA and microsomal triglyceride transfer protein mRNA, a gene product that is essential for the assembly and secretion of apoB-containing lipoproteins; 2) increased synthesis of all lipoprotein lipids (cholesterol, cholesterol esters, triglycerides, and phospholipids); and 3) increased secretion of apoB100 without any change in apoB mRNA. Cells expressing 7alpha-hydroxylase contained significantly less cholesterol (both free and esterified). The increased cellular content of mature SREBP1 and increased secretion of apoB100 were concomitantly reversed by 25-hydroxycholesterol, suggesting that the content of mature SREBP1, known to be decreased by 25-hydroxycholesterol, mediates the changes in the lipoprotein assembly and secretion pathway that are caused by 7alpha-hydroxylase. These data suggest that several steps in the assembly and secretion of apoB-containing lipoproteins by McArdle hepatoma cells may be coordinately linked through the cellular content of mature SREBP1.

Exogenously administered interleukin-10 decreases pulmonary neutrophil infiltration in a tumor necrosis factor-dependent murine model of acute visceral ischemia

INTRODUCTION

Visceral ischemia and reperfusion associated with thoracoabdominal aortic aneurysm (TAAA) repair results in lung injury, which appears to be mediated in part by proinflammatory cytokines. The purpose of this study was to determine the effect of exogenous administration of the antiinflammatory cytokine, recombinant human IL-10 (rhIL-10), on proinflammatory cytokine production (IL-6 and TNF alpha) and pulmonary neutrophil infiltration after acute visceral ischemia-reperfusion.

METHODS

Two hours before 25 minutes of supraceliac aortic occlusion, 80 C57BL/6 mice (20 to 22 g) received an intraperitoneal injection of rhIL-10 (0.2 microgram [n = 20], 2 micrograms [n = 20], 5 micrograms [n = 25], or 20 micrograms [n = 15]), and 16 mice received murine anti-IL-10 IgM 200 micrograms. Twenty-five additional mice underwent visceral ischemia-reperfusion without treatment (controls), and 16 mice underwent laparotomy without aortic occlusion (sham).

RESULTS

Pretreatment with exogenous rhIL-10 resulted in significant reductions in lung neutrophil infiltration with 0.2 microgram, 2 micrograms, and 5 micrograms per mouse of rhIL-10 compared with lung neutrophil levels in control mice that underwent acute visceral ischemia-reperfusion alone (p < 0.05). In addition, serum TNF alpha was detected in 50% of control mice and in 75% of mice that received murine anti-IL-10, but in none of the mice that received rhIL-10 (2 micrograms per mouse) or the mice that underwent sham operative procedures (p < 0.05 by chi 2 analysis).

CONCLUSION

Exogenous IL-10 limits pulmonary neutrophil recruitment and the appearance of TNF alpha in this model of visceral ischemia-reperfusion injury. Thus the use of exogenous IL-10 may offer a novel therapeutic approach to decrease the complications that are associated with TAAA repair.

The effect of temperature management during cardiopulmonary bypass on neurologic and neuropsychologic outcomes in patients undergoing coronary revascularization

Several studies suggest that normothermic ("warm") bypass techniques may improve myocardial outcomes for patients undergoing cardiac operations. Normothermic temperatures during cardiopulmonary bypass may, however, decrease the brain's tolerance to the ischemic insults that accompany all cardiac procedures. To assess the effect of bypass temperature management strategy on central nervous system outcomes in patients undergoing coronary revascularization, 138 patients were randomly assigned to two treatment groups: (1) hypothermia (n = 70), patients cooled to a temperature less than 28 degrees C during cardiopulmonary bypass, or (2) normothermia (n = 68), patients actively warmed to a temperature of at least 35 degrees C. Patients underwent detailed neurologic examination before the operation, on postoperative days 1 to 3 and 7 to 10, and at approximately 1 month after operation. In addition, a battery of five neuropsychologic tests was administered before operation, on postoperative days 7 to 10, and at the 4- to 6-week follow-up visit. Patients in the normothermic treatment group were older (65 +/- 10 vs 61 +/- 11 years in the hypothermic group), had statistically less likelihood of preexisting cerebrovascular disease, and had higher bypass blood glucose values (276 +/- 100 mg/% vs. 152 +/- 66 mg/% in the hypothermic group). All other patient characteristics and intraoperative variables were similar in the two treatment groups. Seven of 68 patients in the normothermic group were found to have a central neurologic deficit, compared with none of the patients cooled to 28 degrees C (p = 0.006). Performance on at least one neuropsychologic test deteriorated in the immediate postoperative period in more than one half of all patients in both treatment groups but returned to preoperative levels approximately 1 month after the operation in most (85%). This pattern was not related to bypass temperature management strategy. We conclude that active warming during cardiopulmonary bypass to maintain systemic temperatures > or = 35 degrees C increases the risk of perioperative neurologic deficit in patients undergoing elective coronary revascularization.

Visceral ischemia and organ dysfunction after thoracoabdominal aortic aneurysm repair. A clinical and cost analysis

OBJECTIVE

Repair of thoracoabdominal aortic aneurysms (TAAAs) is associated with significant postoperative morbidity and mortality. Reperfusion of acutely ischemic abdominal viscera in animals leads to release of multiple factors that cause local and distant organ damage, and similar phenomena occurring in humans after TAAA repair could contribute to the high morbidity/mortality and cost associated with this procedure.

METHODS

Twenty-nine patients undergoing elective TAAA repair were studied prospectively. Preoperative organ dysfunction and intraoperative risk factors (cross-clamp time, blood loss, operative time) were assessed and compared with postoperative organ dysfunction (defined as: pulmonary, positive pressure ventilation for > 7 days; renal, increase in serum creatinine > 2.0 mg/dL over baseline; hepatic, lactate dehydrogenase > 500 international units and total bilirubin > 3.0 mg/dL or serum transaminase level > 200 international units; hematopoietic, platelet count > 50 K or leukocyte count > 4.5 K, mortality, and costs.

RESULTS

No relationship between preoperative organ dysfunction, blood loss, or operative time and postoperative organ dysfunction or mortality was seen; however, cross-clamp times > 40 minutes were associated with a significantly greater incidence of pulmonary (59%), renal (47%), hepatic (35%), and hematopoietic (47%) dysfunction. In addition, multiple-organ dysfunction (> 2 organ systems) was more common after > 40 minutes of visceral ischemia and led to significantly greater overall hospital ($88,465 + $76,155 vs. $41,782 + $31,244) and intensive care unit ($26,726 + $28,256 vs. $11,234 + $12,146) costs (p < 0.01, Mann-Whitney U test). Mortality associated with leukopenia was 67% compared with 4% without leukopenia (p < 0.01).

CONCLUSION

Increasing durations of acute visceral ischemia led to significant multiple organ dysfunction after TAAA repair. Methods of limiting visceral ischemia or the systemic effects of visceral ischemia may decrease both the morbidity and mortality and the overall hospital cost associated with this procedure.

Increased soluble interleukin-1 type II receptor concentrations in postoperative patients and in patients with sepsis syndrome

Plasma interleukin-1 (IL-1) activity is modulated in part through the simultaneous appearance of several inhibitors of IL-1 action, including interleukin-1 receptor antagonist (IL-1ra) and the soluble IL-1 type II receptor (IL-1RII). However, little is known concerning the plasma appearance of these inhibitors in patients following operative trauma or those with sepsis syndrome. In the present report, plasma IL-1beta, IL-1ra, and soluble IL-1RI and IL-1RII concentrations were evaluated in 118 patients with sepsis syndrome or after elective operative trauma. Plasma concentrations of IL-1ra increased significantly following elective operative repair of thoraco-abdominal and abdominal aortic aneurysms, and after bowel resection for inflammatory bowel disease, but did not increase after laparoscopic cholecystectomy. Plasma IL-1ra levels were also elevated in patients with sepsis syndrome. In contrast, soluble IL-1RII levels were only increased in patients after operative repair of thoraco-abdominal aortic aneurysms and in sepsis syndrome, whereas concentrations were unaffected by the other more modest surgical procedures. Plasma IL-1RI concentrations decreased in all postoperative patients in the first 24 hours after surgery. We conclude that both plasma IL-1ra and soluble IL-1RII concentrations often increase in sepsis and following some operative trauma. Less severe operative trauma increases the plasma concentration of only IL-1ra, whereas both IL-1ra and soluble IL-1RII are increased in patients with sepsis syndrome or following thoraco-abdominal aneurysm repair.

Should the freehand allograft be abandoned as a reliable alternative for aortic valve replacement?

Cryopreserved aortic allografts were used for aortic valve replacement in 80 patients between 1986 and 1994 (infracoronary in 46 and complete root replacement in 34). Hospital mortality was 6.3% (5/80) with all deaths occurring in the infracoronary group. Three of five deaths were in patients with endocarditis and valve ring abscess. Left ventricular-aortic mean pressure gradients across the allograft valves were significantly lower for root replacement patients (mean, 9.0 +/- 6.9 mm Hg versus 18.1 +/- 8.7 mm Hg for infracoronary patients) (p = 0.0001). No patient having root allograft replacement had early echocardiographic aortic insufficiency greater than grade 1 versus 28% of those having infracoronary implantations. Late aortic insufficiency of grade 2 or greater was seen in 46% of patients having infracoronary implantation versus 17% of patients having root implantation. Nine patients had explantation of an aortic allograft (eight infracoronary and one root). Reasons for explantation were as follows: endocarditis (three infracoronary, one root), technical (three infracoronary), undiagnosed idiopathic hypertrophic subaortic stenosis (1 patient), and prolapsing infracoronary leaflet (1 patient). Actuarial freedom from grade 3 and 4 aortic insufficiency or explantation was 77% at 7 years for infracoronary implantations. We conclude that the infracoronary aortic allograft has an unacceptable frequency of late insufficiency and its use in this position should be abandoned. The substantial incidence of late endocarditis in the infracoronary (free-hand) aortic allograft was surprising.(ABSTRACT TRUNCATED AT 250 WORDS)

Prospective, randomized trial of retrograde warm blood cardioplegia: myocardial benefit and neurologic threat

From March 1991 through July 1992, 1,001 patients having elective coronary artery bypass grafting were randomized to receive either continuous warm (> or = 35 degrees C) blood cardioplegia with systemic normothermia (> or = 35 degrees C) or intermittent cold (< or = 8 degrees C) oxygenated crystalloid cardioplegia and moderate systemic hypothermia (< or = 28 degrees C). Preoperative variables including age, sex, prior coronary bypass grafting, hypertension, prior myocardial infarction, diabetes, angina class, and preoperative heart failure class were similar in both groups, as were the intraoperative variables of number of coronary grafts, mammary artery use, and cardiopulmonary bypass time. Aortic cross-clamp time was significantly longer in the warm group (46 +/- 23 minutes versus 40 +/- 21 minutes). Most postoperative variables including mortality (warm, 1.0%, and cold, 1.6%), Q wave infarction (warm, 1.4%, and cold, 0.8%), and need of an intraaortic balloon pump (warm, 1.4%, and cold, 2.0%) were similar between groups. Total neurologic events (warm, 4.5%, and cold, 1.4%; p < 0.005) and perioperative strokes (warm, 3.1%, and cold, 1.0%; p < or = 0.02) were significantly higher in the warm group. Neurologic events included perioperative stroke (warm, 15 patients, and cold, 5 patients; p < 0.02), perioperative encephalopathy (warm, 2 patients, and cold, 1 patient), and delayed (> or = 3 in-hospital days) stroke (warm, 5 patients, and cold, 1 patient). All patients experiencing a stroke had a persistent neurologic deficit at the time of discharge. Encephalopathy resolved completely in all instances.(ABSTRACT TRUNCATED AT 250 WORDS)

Megaaorta and aortoiliac obstruction: alternate method of cannulation

The case of a 69-year-old man with aneurysms of the ascending aorta, transverse aortic arch, and thoracoabdominal aorta combined with coronary artery disease, aortic insufficiency, and severe aortoiliac occlusive disease is presented. Femoral arterial cannulation was contraindicated owing to the aortoiliac disease. Successful surgical treatment is described using an alternate method of cannulation and perfusion.

Diagnosis of aortic transection by transesophageal echocardiography

Transesophageal echocardiography (TEE) offers spectacularly detailed images of thoracic aortic anatomy and blood flow; however, its utility for diagnosis of aortic trauma is unknown. Our case underscores the ability of TEE to diagnose aortic transection. The speed, mobility, and accuracy of TEE makes it an attractive means of diagnosing aortic trauma in the critically ill.

Lung glutamine flux following open heart surgery

Despite the attenuated skeletal muscle proteolysis that occurs following hypothermic anesthesia and open heart surgery, blood amino acid levels are maintained, suggesting enhanced amino acid release by another organ. To investigate the role of the lung in this response, we determined the release of glutamine (Gln) and alanine by the lung, since these two amino acids transport two-thirds of circulating amino acid nitrogen. Three groups of patients were studied: (a) preoperative non-stressed controls; (b) postoperative general surgical patients; and (c) postoperative cardiac surgical patients studied on Postoperative Day 1 following open heart surgery requiring cardiopulmonary bypass and hypothermic anesthesia. In preoperative controls the lung was an organ of glutamine and alanine balance. These exchange rates were unaffected by the stress of an abdominal surgical procedure despite a mild increase in pulmonary blood flow. However, lung Gln release in the cardiac surgical patients was significantly increased (-0.6 +/- 1.2 mumole/kg/min in controls vs -6.5 +/- 1.3 mumole/kg/min in postoperative hearts, P less than 0.05) and was due exclusively to an increase in the pulmonary artery-systemic arterial concentration difference. Alanine release by the lungs was also increased in the postoperative cardiac surgical patients. The mechanism by which this augmented pulmonary glutamine release occurs following open heart surgery is unclear, but the lungs appear to play a central role in maintaining amino acid homeostasis. This metabolic role of the lungs following hypothermic anesthesia and cardiopulmonary bypass has not been previously described.

Perivalvular pseudoaneurysm complicating bacterial endocarditis: MR detection in five cases

Bacterial endocarditis usually affects the valve leaflets, but erosion into the valve anulus and adjacent myocardium may form a myocardial abscess. Perivalvular abscesses can drain into the ventricles or aorta, forming a life-threatening pseudoaneurysm. We reviewed our experience with cardiac MR imaging of this disorder. Fourteen patients with complicated bacterial endocarditis underwent ECG-gated spin-echo cardiac MR imaging in addition to conventional duplex two-dimensional echocardiography (2-D echo). Angiography was performed in seven patients, six of whom underwent surgery for valve replacement. MR imaging detected the pseudoaneurysms in all five of the surgically proved cases, while 2-D echo detected only three. Clinical follow-up suggested there were no false-negative examinations, but no autopsy data were available for confirmation. Postoperative MR imaging studies were conducted in three patients, revealing two recurrent pseudoaneurysms and one thrombosed aneurysm. Cardiac MR imaging provides useful pre- and postoperative information in patients with perivalvular pseudoaneurysms due to endocarditis.

Accelerated lung amino acid release in hyperdynamic septic surgical patients

Amino acid flux across the lungs was studied in humans to gain further insight into the altered nitrogen metabolism that characterizes catabolic disease states. Lung flux of glutamine, glutamate, and alanine was determined in three groups of surgical patients with indwelling pulmonary artery catheters: (1) preoperative controls (n = 14), (2) postoperative elective general surgical patients (n = 10, and (3) hyperdynamic septic surgical patients (n = 17). In controls the lung was an organ of amino acid balance. These exchange rates did not change in general surgical patients. In the septic group, glutamine release by the lung increased markedly from a control value of 0.80 +/- 0.99 mumol/kg per minute to 6.80 +/- 1.32 mumol/kg per minute. This accelerated release rate was secondary to both an increase in total pulmonary blood flow and an increase in the pulmonary artery-systemic arterial concentration difference. The lung also became an organ of significant alanine release in septic patients. The lung plays an active metabolic role in the processing of amino acids and may be a key regulator in interorgan nitrogen flux after major injury and infection.

The impact of renal fusion and ectopia on aortic surgery

This article is concerned with observations in 17 patients with renal fusion and ectopic abnormalities: horseshoe kidney in 13 patients, crossed ectopia with fusion in two, pancake kidney in one, and pelvic kidney in one. Three patients had occlusive disease, one may have had renal artery occlusion, and 13 had aneurysms--three thoracoabdominal and 10 infrarenal. Rupture of aneurysm had occurred in one patient at each level and six patients had had one or more previous attempts at aneurysmal removal. Diagnosis and evaluation were made with the aid of intravenous pyelography, retrograde pyelography, CT scanning, and at operation (three patients). Three patients had two normally located right and left renal arteries. Twelve patients had one to three additional aberrant arteries arising from the aorta and iliac arteries. One patient's renal blood supply arose from multiple aberrant arteries. Ureters crossed the midline in two patients. Treatment of occlusive disease consisted of endarterectomy in one patient and percutaneous transluminal angioplasty in two. Aneurysms were treated by graft replacement with retroperitoneal exposure in seven patients and transabdominal exposure in six. One patient was treated medically. Renal isthmus division was employed in only two patients and involved accessory arteries were reattached to the grafts in all cases. Death from myocardial infarction occurred in two patients (12%). Eleven patients subjected to operation were alive 6 months to 14 years later.

Management of combined pancreatoduodenal injuries

From 1969 to 1985, 129 patients with combined pancreatoduodenal injuries were treated at one urban trauma center. A total of 104 patients (80.6%) had penetrating wounds, and multiple visceral and vascular injuries were usually associated with the pancreatoduodenal injury. Primary repair or resection of one or both organs coupled with pyloric exclusion and gastrojejunostomy (68 patients) and drainage was used in 79 patients (61.2%) in the entire study and in 59% (36 of 61) of all patients treated since 1976. Simple primary repair of one or both organs and drainage was performed in 31 patients (24%), whereas the remaining 19 patients (14.8%) had pancreatoduodenectomies (13 patients) or no repair before exsanguination (six patients). Major pancreatoduodenal complications occurring in the 108 patients surviving more than 48 hours included pancreatic fistulas (25.9%), intra-abdominal abscess formation (16.6%), and duodenal fistulas (6.5%). The overall mortality rate for the study was 29.5% (38 of 129). The acute mortality rate with these injuries will remain high secondary to injuries to associated organs and vascular structures. The morbidity and late mortality rates related to the moderate to severe pancreatoduodenal injury itself can be decreased by the addition of pyloric exclusion and gastrojejunostomy to the primary repairs.

Prosthetic grafts in vascular trauma: a controversy

Refinements in vascular surgery have made repair of arterial injuries common throughout the world. There seems to be little doubt among trauma surgeons that primary repair of arterial injuries is the method of choice, as long as there is little devitalized arterial tissue and the procedure can be accomplished without tension on the suture lines or stenosis at the repair. When a lateral repair or primary anastomosis is not feasible, the type of conduit to be used is still the subject of controversy. Most clinical reports within the past 30 years state that autogenous vein is the grafting material of choice in traumatic wounds. However, the most recent investigations of the data do not favor autogenous vein grafts and, in fact, may lean toward prosthetic materials as the most satisfactory conduits for repairing traumatized arteries.

Blunt cardiac rupture

Blunt injury to the heart ranges from contusion to disruption. This report comprises 14 patients seen during a 6-year period with cardiac rupture secondary to blunt trauma. Eight patients were injured in automobile accidents, two patients were injured in auto-pedestrian accidents, two were kicked in the chest by ungulates, and two sustained falls. Cardiac tamponade was suspected in ten patients. Five patients presented with prehospital cardiac arrest or arrested shortly after arrival. All underwent emergency department thoracotomy without survival. Two patients expired in the operating room during attempted cardiac repair; both had significant extracardiac injury. Seven patients survived, three had right atrial injuries, three had right ventricular injuries, and one had a left atrial injury. Cardiopulmonary bypass was not required for repair of the surviving patients. There were no significant complications from the cardiac repair. The history of significant force dispersed over a relatively small area of the precordium as in a kicking injury from an animal or steering wheel impact should alert the physician to possible cardiac rupture. Cardiac rupture should be considered in patients who present with signs of cardiac tamponade or persistent thoracic bleeding after blunt trauma.

Severe duodenal injuries. Treatment with pyloric exclusion and gastrojejunostomy

During a 12-year period, 313 patients with duodenal injuries were treated. Primary repair, pyloric exclusion, and gastrojejunostomy were used in 128 patients (41%) with severe duodenal and pancreaticoduodenal injuries, to reduce "duodenal" morbidity and mortality. The duodenal fistula rate was 2.2% overall, and 5.5% in the patients undergoing exclusion. Only two deaths were due to fistulas. Forty-two patients underwent upper gastrointestinal tract examinations after operation. In patients examined 21 days or more after operation, 94% had a patent pylorus. Marginal ulceration was infrequent (four patients), as were complications associated with the procedure (3%). Pyloric exclusion with gastrojejunostomy is a quick and simple procedure that allows return of pyloric patency and is associated with a low incidence of duodenal fistulas. When fistulas do develop, they are usually easily controlled and are associated with a low mortality. We believe pyloric exclusion with gastrojejunostomy to be the procedure of choice in patients with severe duodenal and pancreaticoduodenal trauma.

Aetiology and prevention of wound infection in appendicetomy

A study at the Reading District Hospitals on 451 consecutive patients undergoing appendicectomy through grid-iron incisions sought to determine factors influencing wound infection and the effects of a prophylactic wound-spraying procedure. Wound infection increased with the severity of appendicular inflammation and was well correlated with the degree and nature of bacterial contamination at the time of wound closure.

The infection rate was reduced by about one-half when either an aerosol dry-powder formulation of povidone iodine (Disadine D. P.) or an aerosol antibiotic powder spray containing neomycin, bacitracin and polymixin (Dispray) was sprayed on the wound before and after closure. The reduction of infection achieved by spraying with pouidine iodine was statistically significant (P &lt; 0.025). The results of the polyantibiotic spraying did not quite reach significance (P &lt; 0.06).

The povidone iodine dry powder was better overall since it reduced infection in all degrees of appendicular inflammation, in all age groups and in enlarged, drained, contaminated and non-contaminated wounds without the attendant disadvantages of antibiotics.

A non-starch-fermenting variant of Corynebacterium ulcerans

Recently a non-starch-fermenting strain of C. ulcerans was isolated and a strain which did not hydrolyse urea when first isolated has also been discovered. For full identification of C. ulcerans both intradermal and subcutaneous tests in guinea-pigs are required, and it is recommended that these tests should be carried out with all organisms which culturally and morphologically resemble diphtheria bacilli.