Large Spin-Wave Bullet in a Ferrimagnetic Insulator Driven by the Spin Hall Effect.

Because of its transverse nature, spin Hall effects (SHE) provide the possibility to excite and detect spin currents and magnetization dynamics even in magnetic insulators. Magnetic insulators are outstanding materials for the investigation of nonlinear phenomena and for novel low power spintronics applications because of their extremely low Gilbert damping. Here, we report on the direct imaging of electrically driven spin-torque ferromagnetic resonance (ST-FMR) in the ferrimagnetic insulator Y_{3}Fe_{5}O_{12} based on the excitation and detection by SHEs. The driven spin dynamics in Y_{3}Fe_{5}O_{12} is directly imaged by spatially resolved microfocused Brillouin light scattering spectroscopy. Previously, ST-FMR experiments assumed a uniform precession across the sample, which is not valid in our measurements. A strong spin-wave localization in the center of the sample is observed indicating the formation of a nonlinear, self-localized spin-wave "bullet".

Even-odd-layer-dependent symmetry breaking in synthetic antiferromagnets.

In this work we examine synthetic antiferromagnetic structures consisting of two, three, and four antiferromagnetic coupled layers, i.e. bilayers, trilayers, and tetralayers. We vary the thickness of the ferromagnetic layers across all structures and, using a macrospin formalism, find that the nearest neighbor exchange interaction between layers is consistent across all structures for a given thickness of the ferromagnetic layer. Our model and experimental results demonstrate significant differences in how the static equilibrium states of even and odd-layered structures evolve as a function of the external field. Even layered structures continuously evolve from a collinear antiferromagnetic state to a spin canted non-collinear magnetic configuration that is mirror-symmetric about the external field. In contrast, odd-layered structures begin with a ferrimagnetic ground state; at a critical field, the ferrimagnetic ground state evolves into a non-collinear state with broken symmetry. Specifically, the magnetic moments found in the odd-layered samples possess stable static equilibrium states that are no longer mirror-symmetric about the external field after a critical field is reached.

Controlled magnetic reversal in Permalloy films patterned into artificial quasicrystals.

We have patterned novel Permalloy thin films with quasicrystalline Penrose P2 tilings and measured their dc magnetization and ferromagnetic resonance absorption. Reproducible anomalies in the hysteretic, low-field data signal a series of abrupt transitions between ordered magnetization textures, culminating in a smooth evolution into a saturated state. Micromagnetic simulations compare well to experimental dc hysteresis loops and ferromagnetic resonance spectra and indicate that systematic control of magnetic reversal and domain wall motion can be achieved via tiling design, offering a new paradigm of magnonic quasicrystals.

A new approach to the isolation and characterization of wheat flour allergens.

BACKGROUND: The incidence of food allergy to wheat is increasing. Its diagnosis depends on the purity of major allergens and their inclusion in tests. Isolation and characterization of wheat allergens are therefore of utmost importance. OBJECTIVE: To purify and identify wheat flour allergens most frequently recognized by patients' IgE antibodies and to study their allergenicity. METHODS: Water/salt-soluble extracts from wheat flour were prepared and separated using a combination of ultrafiltration, isoelectric focusing and liquid chromatography. Purified proteins were analysed by immunoblotting using pooled sera from patients with atopic dermatitis who possessed IgE specific to wheat. Wheat proteins found to bind IgE were subsequently identified by matrix-assisted laser desorption/ionisation-time of flight mass spectrometry. The frequency and intensity of IgE binding of isolated proteins were tested using individual sera from patients and controls. RESULTS: We developed a procedure that allows isolation of wheat allergens from natural sources. Twenty-seven potential wheat allergens have been successfully identified; of these, the following seven are newly reported in food allergy: endogenous α-amylase/subtilisin inhibitor, trypsin/α-amylase inhibitor (AAI) CMX1/CMX3, thaumatin-like protein (TLP), xylanase inhibitor protein-1, ß-glucosidase, class II chitinase and 26 kDa endochitinase. TLP and wheatwin were shown to activate patients' basophils to a similar extent as two well-known allergens, lipid transfer protein (Tri a 14) and AAI 0.19 (Tri a 28.0101). CONCLUSION AND CLINICAL RELEVANCE: Our new approach enables the isolation of water/salt-soluble wheat allergens in their native form in amounts sufficient both for biological testing (in vivo and in vitro) and for physicochemical characterization. Such studies will lead to a more detailed knowledge of allergenicity of wheat proteins and to improved accuracy of diagnostic tests.

The role of Mn-dependent peroxidase in dye decolorization by static and agitated cultures of Irpex lacteus.

Dye decolorization capacity of two white-rot fungi, Irpex lacteus and Phanerochaete chrysosporium, was compared in N-limited liquid cultures. The agitated cultures showed lower ability to decolorize azo dyes Reactive Orange 16 and Naphthol Blue Black than static cultures. Similar effect was also observed with other structurally different synthetic dyes. The effect of surfactants on the decolorization process is discussed. A significant increase in the Reactive Orange 16 decolorization by the agitated I. lacteus cultures was observed after adding 0.1% Tween 80, following a higher Mn-dependent peroxidase production. The in vitro dye decolorization using the purified enzyme proved its decolorization ability.

Large-scale identification of membrane proteins based on analysis of trypsin-protected transmembrane segments.

Integral membrane proteins are generally under-represented in routine proteomic analyses, mostly because of their relatively low abundance, hydrophobicity and lack of trypsin-cleavage sites. To increase the coverage of membrane proteomes, various strategies have been developed, targeting mostly the extra-membrane segments of membrane proteins. We focused our attention to the rather overlooked hydrophobic transmembrane segments. Such peptides can be isolated after carbonate stripping and protease "shaving" of membranes isolated by simple centrifugation procedure. The treated membranes with embedded hydrophobic peptides can then be solubilized in organic solvents, re-digested with CNBr, delipidated and subjected to LC-MS/MS analysis. We modified the original "hppK" method, and applied it for the analysis of human lymphoma cells. We identified 1224 proteins of which two-thirds were IMPs with 1-16 transmembrane segments. This method allowed us to identify 13 "missing proteins" - proteins with no previous evidence on protein level. BIOLOGICAL SIGNIFICANCE: Integral membrane proteins execute numerous essential functions and represent substantial part of eukaryotic proteomes. Our knowledge of their function and expression is, however, limited. Novel approaches extending our knowledge of membrane proteome are therefore highly desired. As we demonstrate here, a non-conventional method which targets rather overlooked hydrophobic transmembrane segments of integral membrane proteins has wide potential to provide the missing information on the membrane proteome. We show that it can deliver identification and potentially also quantification of hundreds of integral membrane proteins including the so called "missing proteins".

Noninvasive prediction of ultimate infarct size at the time of acute coronary occlusion based on the extent and magnitude of collateral-derived myocardial blood flow.

BACKGROUND: We hypothesized that by detecting regions with adequate collateral-derived myocardial blood flow (MBF) within the risk area (RA), we could predict ultimate infarct size (IS) at the time of coronary occlusion. METHODS AND RESULTS: Group 1 dogs (n=15) underwent coronary occlusion without reperfusion, whereas group 2 dogs (n=6) underwent both occlusion and reperfusion. RA was measured with aortic root injections of microbubbles. Myocardial contrast echocardiography (MCE) was performed with high mechanical index intermittent harmonic imaging at pulsing intervals (PIs) of <1 to 30 cardiac cycles during an intravenous infusion of microbubbles (Sonozoid). MBF was measured with radiolabeled microspheres, and postmortem tissue staining was used to determine IS. Perfusion defect size (PDS) on MCE varied with the PI and was largest at a PI of 2.6+/-0.4 seconds, where it correlated well with RA (r=0.82). PDS was smallest at a PI of >/=10.6+/-1.5 seconds, where it correlated closely with IS (r>/=0.92). Areas that underwent necrosis could be identified early after coronary occlusion as having the lowest microvascular flow velocity (beta) and MCE-derived MBF (Axbeta). The results were similar with or without reperfusion. Because of variability in collateral-derived MBF, there was no correlation between RA and ultimate IS (P=0.37). The extent of regional dysfunction also correlated poorly with IS (r=0.31). CONCLUSIONS: MCE can be used immediately after coronary occlusion to define ultimate IS by measuring the magnitude and spatial extent of collateral-derived residual MBF within the RA. Thus, it could help individualize risk and management in acute myocardial infarction.

Detection of coronary artery stenosis with power Doppler imaging.

BACKGROUND: Power Doppler is a new imaging method for detecting microbubbles during myocardial contrast echocardiography (MCE) based on the registration of variance resulting from ultrasound-induced nonlinear bubble behavior. We tested the hypothesis that power Doppler imaging can be used to quantify coronary stenoses. METHODS AND RESULTS: Three left anterior descending (LAD) coronary stenoses of varying severity were created in each of 9 open-chest dogs. MCE was performed by continuous intravenous infusion of a nitrogen-filled bilayer shell microbubble, PB127, during triggered power Doppler imaging at incremental pulsing intervals. MCE and radiolabeled microsphere measurements were made at baseline and during each stenosis, with and without adenosine stress. Videointensities in the LAD and left circumflex (LCx) beds were plotted against pulsing interval and fit to a previously described exponential function modeling microbubble destruction and replenishment, which was used to derive parameters of bubble velocity (beta) and peak plateau videointensity (A). Contrast defects matching the location of radiolabeled microsphere hypoperfusion were clearly seen, without need for image processing. The product of beta and A was linearly related to LAD/LCx flow (r=0.90, P<0.0001) and inversely related to stenosis gradient (r=-0.70, P<0.0001). Endocardial/epicardial flow ratios were visualized and quantifiable. CONCLUSIONS: As with B-mode harmonics, a model of microbubble destruction/replenishment can be applied to power Doppler data as a means to detect a broad range of stenoses. Image clarity and the lack of attenuation or requirement for background subtraction are additional advantages of this imaging approach. Power Doppler MCE imaging holds promise for the detection of coronary artery disease.

Determination of the complete covalent structure of the major glycoform of DQH sperm surface protein, a novel trypsin-resistant boar seminal plasma O-glycoprotein related to pB1 protein.

The complete covalent structure of a novel boar DQH sperm surface protein resistant to many classical procedures of enzymatic fragmentation was determined. The relative molecular mass of the major form of this protein determined by ESI-MS and MALDI-MS was 13,065.2+/-1.0 and 13,065.1, respectively. However, additional peaks differing by 162 Da (i.e., minus hexose), 365 Da (i.e., minus hexose and N-acetylhexosamine), 146 Da (i.e., plus deoxyhexose), and 291 Da (i.e., plus sialic acid) indicated the heterogeneity due to differences in glycosylation. The complete covalent structure of the protein was determined using automated Edman degradation, MALDI-MS, and post-source decay (PSD) MALDI-MS, and shown to consist of N-terminal O-glycosylated peptide followed by two fibronectin type II repeats. The carbohydrates are O-glycosidically linked to threonine 10, as confirmed by PSD MALDI-MS of the isolated N-terminal glycopeptide. Eight cysteine residues of the protein form four disulfide bridges, the positions of which were assigned from MALDI-MS and Edman degradation data. We conclude that mass spectral techniques provide an indispensable tool for the detailed analysis of the covalent structure of proteins, especially those that are refractory to standard approaches of protein chemistry.

A computer-aided approach for the quantitation of regional left ventricular function using two-dimensional echocardiography.

Quantitation of regional left ventricular function is becoming increasingly important in this era of interventional cardiology. In this article we describe a computer-assisted approach for the assessment of regional left ventricular function that integrates three features. First, it measures left ventricular wall thickening and endocardial motion and curvature during an entire systolic contraction sequence. Second, it allows us to easily define endocardial and epicardial borders without actually having to manually trace the entire border. Third, it displays complex data in a simple format for easy assimilation. We believe that this approach is practical and comprehensive and can be used to quantitate regional left ventricular function with two-dimensional echocardiography.

Ordering an echocardiogram for evaluation of left ventricular function: level of expertise necessary for efficient use.

This prospective study was performed to test the hypothesis that the yield of 2-dimensional echocardiography (2DE) would be higher when it is ordered by a cardiologist than by a noncardiologist. Patients referred for transthoracic 2DE for the evaluation of left ventricular systolic function for the 11-month period between July 10, 1995, and June 10, 1996, were included in the study. Demographic, historical, and clinical findings were recorded. Whether the patient was referred by a cardiologist versus a noncardiologist was used as the predictor variable in a binary logistic regression analysis. To address the possibility that the yield of 2DE may be higher for cardiologists because the prevalence of disease in patients referred to them may be higher (selection bias), the analysis was subjected to a propensity score adjustment. Of 2176 patients referred for 2DE during the study, 1033 were referred for the evaluation of left ventricular function. The test had a positive yield in 52% of patients for cardiologists versus 31% for noncardiologists (chi(2) = 45.5, P <.0001, odds ratio 2.4 [CI = 1. 9-3.1]). This difference remained highly significant even when propensity score risk adjustment was made (chi(2) = 54.2, P <.0001, odds ratio 2.0 [CI = 1.5-2.8]). We conclude that the yield of 2DE is higher for cardiologists compared with noncardiologists and that this result was not related to differences in patient populations examined by the two groups. Thus, more efficient use of 2DE may be achieved if patients are referred to cardiologists rather than directly sent for 2DE.

Method for the quantitation of myocardial perfusion during myocardial contrast two-dimensional echocardiography.

This article describes the hardware and software components of two systems designed for quantitative analysis of data obtained during myocardial contrast two-dimensional echocardiography. One system is meant for off-line analysis of data, whereas the other is designed for on-line analysis, especially in the operating room. The algorithms used for data transfer, selection of appropriate frames, data alignment, derivation of time-intensity plots, and curve-fitting and parameter generation are described in some detail. It is hoped that this information will be of use to others who work in the field of myocardial perfusion imaging.

Integrated backscatter and digital acquisition during myocardial contrast echocardiography: is there an advantage over conventional echocardiography for intracoronary injections?

This study was designed to answer the question of whether, despite their theoretic superiority, integrated backscatter imaging (IBS) and digital data acquisition (DA) offer any advantage over conventional echocardiography (CE) during quantitative myocardial contrast echocardiography. In vitro experiments were performed (1) to determine the microbubble concentration versus videointensity relationships for CE and IBS and (2) to define the relationship between flow through and microbubble transit rates for CE and IBS. These data were stored on videotape. In vivo experiments were performed whereby microbubbles were injected into the left anterior descending artery at different flow rates in 14 dogs and IBS and CE data were stored both in digital format and on videotape. Although the level of compression did not affect the microbubble concentration versus videointensity plots during IBS compared with CE, in practical terms the mean transit rate, peak intensity, and area under the curve were not affected by the level of compression for both forms of imaging as long as the postprocessing used for CE imaging was linear and the microbubble dose was small. In addition, although DA resulted in higher peak intensity and area under the curve compared with storage on videotape because of its broader dynamic range, the correlation between these measurements was excellent with both forms of image storage. We conclude that, although differences exist between CE and IBS and between Da and analog acquisition, these differences do not significantly affect the derivation of parameters from time-intensity plots during myocardial contrast echocardiography when contrast material is injected into a coronary artery.

Potential advantage of flash echocardiography for digital subtraction of B-mode images acquired during myocardial contrast echocardiography.

Optimal assessment of myocardial perfusion with contrast echocardiography by using B-mode imaging often requires image alignment and background subtraction, which are time consuming and need extensive expertise. Flash echocardiography is a new technique in which primary images are gated to the electrocardiogram and secondary images are obtained by transmitting ultrasound pulses in rapid succession after each primary image. Myocardial opacification is seen in the primary image and not in the secondary images because of ultrasound-induced bubble destruction. Because the interval between the primary and first few secondary images is very short, cardiac motion between these images should be minimal. Therefore we hypothesized that 1 or more secondary images could be subtracted from the primary image without the need for image alignment. The ability of ultrasound to destroy microbubbles was assessed by varying the sampling rate, line density, and mechanical index in 6 open-chest dogs. The degree of translation between images was quantified in the x and y directions with the use of computer cross-correlation. At sampling rates of 158 Hz or less and a mechanical index of more than 0.6, videointensity rapidly declined to baseline levels by 25 ms. Significant translation between images was noted only at intervals of more than 112 ms. It is concluded that flash echocardiography can be used for digital subtraction of baseline from contrast-enhanced B-mode images without image alignment. Background subtraction is therefore feasible on-line, potentially eliminating the need for off-line image processing in the future.

Evidence supportive of impaired myocardial blood flow reserve at high altitude in subjects developing high-altitude pulmonary edema.

An exaggerated increase in pulmonary arterial pressure is the hallmark of high-altitude pulmonary edema (HAPE) and is associated with endothelial dysfunction of the pulmonary vasculature. Whether the myocardial circulation is affected as well is not known. The aim of this study was, therefore, to investigate whether myocardial blood flow reserve (MBFr) is altered in mountaineers developing HAPE. Healthy mountaineers taking part in a trial of prophylactic treatment of HAPE were examined at low (490 m) and high altitude (4,559 m). MBFr was derived from low mechanical index contrast echocardiography, performed at rest and during submaximal exercise. Among 24 subjects evaluated for MBFr, 9 were HAPE-susceptible individuals on prophylactic treatment with dexamethasone or tadalafil, 6 were HAPE-susceptible individuals on placebo, and 9 persons without HAPE susceptibility served as controls. At low altitude, MBFr did not differ between groups. At high altitude, MBFr increased significantly in HAPE-susceptible individuals on treatment (from 2.2 +/- 0.8 at low to 2.9 +/- 1.0 at high altitude, P = 0.04) and in control persons (from 1.9 +/- 0.8 to 2.8 +/- 1.0, P = 0.02), but not in HAPE-susceptible individuals on placebo (2.5 +/- 0.3 and 2.0 +/- 1.3 at low and high altitude, respectively, P > 0.1). The response to high altitude was significantly different between the two groups (P = 0.01). There was a significant inverse relation between the increase in the pressure gradient across the tricuspid valve and the change in myocardial blood flow reserve. HAPE-susceptible individuals not taking prophylactic treatment exhibit a reduced MBFr compared with either treated HAPE-susceptible individuals or healthy controls at high altitude.

Quantification of images obtained during myocardial contrast echocardiography.

This article describes currently used quantitative methods for analysis of data obtained during myocardial contrast echocardiography. The specific issues addressed are: obtaining time-intensity curves from the myocardium in order to derive transit rates of microbubbles through the myocardium; defining spatial distribution of flow within a myocardial segment; and color-coding algorithms used to define the extent and magnitude of hypoperfusion within a cross-section of the heart. These methods are being adopted by several companies dealing with acquisition and analysis of echocardiographic data and should become available soon for clinical use.

Efficient utilization of echocardiography for the assessment of left ventricular systolic function.

BACKGROUND: We hypothesized that patients could be selected for echocardiographic evaluation of left ventricular (LV) systolic function on the basis of historic, clinical, radiographic, and electrocardiographic criteria. METHODS AND RESULTS: We prospectively evaluated 300 consecutive inpatients referred for the echocardiographic assessment of LV function, of whom 124 (41%) had LV systolic dysfunction (LVSD) (LV ejection fraction <0.45). Among the historic variables, male sex was the only predictor of LVSD, whereas of the abnormal physical and radiographic findings, cardiomegaly on chest radiography was the only predictor. Among the electrocardiographic findings, the presence of left bundle branch block was positively correlated with the presence of LVSD, whereas a normal electrocardiogram was negatively correlated with this finding. Only 2 patients with LVSD had a normal electrocardiogram. The addition of significant predictors on physical examination and chest radiography doubled the predictive value of the historic variables for determining LVSD. The addition of electrocardiographic findings further doubled the predictive value of the model. Almost 45% of the predictive power of the final multivariate model (chi-square of 48 of the total chi-square of 108) was based on the absence of normal electrocardiogram in patients with LVSD. When chest radiographic findings were excluded from the model, the overall predictive power of the model did not change, with the normal electrocardiogram gaining greater prominence: Full 56% of the predictive power of the model (chi-square of 60 of the total chi-square of 108) resided in the ability of a normal electrocardiogram to discriminate between patients with and those without LVSD. CONCLUSIONS: Historic, chest radiographic, and electrocardiographic variables can be used to predict low likelihood of LVSD on echocardiography. In particular, when the electrocardiogram is normal, it is extremely unlikely to have LVSD. It can be argued that such patients should not be referred for echocardiography.

NKR-P1A protein, an activating receptor of rat natural killer cells, binds to the chitobiose core of uncompletely glycosylated N-linked glycans, and to linear chitooligomers.

NKR-P1 represent a family of activating receptors in rodent natural killer cells related to C-type animal lectins. We identify here the elements involved in the reactivity of the major receptor of rat, NKR-P1A, with N-linked oligosaccharides of glycoproteins. Plate inhibition assays with isolated, structurally defined N-glycans as inhibitors of binding of NKR-P1A to GlcNAc16-BSA revealed that the removal of both the external sialic acids and the penultimate galactose residues resulted in attaining of significant inhibitory activities. Surprisingly, additional plate inhibition and glycoprotein overlay experiments brought evidence that the core chitobiose, depending on its substitution, can per se support the interaction with NKR-P1A. In a series of linear chitooligomers (n = 2-7), the inhibitory activities reached a maximum for the chitotetraose. The ability of NKR-P1 to recognize both the periphery and the core region of complex type oligosaccharides may define its dual specificity towards carbohydrate components of eukaryotic (e.g., tumor) cell surfaces, but also reflect an evolutionarily conserved reactivity with microbial saccharides important in immune recognition and signaling functions.