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PubMed2004

Magic angle effects and angular magnetoresistance oscillations as dimensional crossovers.

Interference effects between velocity and density of states, which occur as electrons move along open orbits in the extended Brillouin zone in anisotropic conductors, result in a change of wave functions' dimensionality at magic angle (MA) directions of a magnetic field. In particular, these 1D-->2D dimensional crossovers result in the appearance of sharp minima in a resistivity component rho perpendicular (H,alpha), perpendicular to conducting layers. This explains the main qualitative features of MA and angular magnetoresistance oscillations' phenomena observed due to the existence of quasi-one-dimensional sheets of Fermi surface in (TMTSF)2X, (DMET-TSeF)2X, and kappa-(ET)2Cu(NCS)(2) conductors.

Journal Article↗
PubMed2006

Direct observation of vortex shells and magic numbers in mesoscopic superconducting disks.

We have studied vortex configurations in mesoscopic superconducting disks using the Bitter decoration technique. For a broad range of vorticities L the circular geometry is found to lead to the formation of concentric shells of vortices. From images obtained on disks of different sizes in a range of magnetic fields we traced the evolution of vortex states and identified stable and metastable configurations of interacting vortices. Furthermore, the analysis of shell filling with increasing L allowed us to identify magic numbers corresponding to the appearance of consecutive new shells.

Journal Article↗
PubMed1997

Study of lignification by noninvasive techniques in growing maize internodes. An investigation by Fourier transform infrared cross-polarization-magic angle spinning 13C-nuclear magnetic resonance spectroscopy and immunocytochemical transmission electron microscopy.

Noninvasive techniques were used for the study in situ of lignification in the maturing cell walls of the maize (Zea mays L.) stem. Within the longitudinal axis of a developing internode all of the stages of lignification can be found. The synthesis of the three types of lignins, p-hydroxyphenylpropane (H), guaiacyl (G), and syringyl (S), was investigated in situ by cross-polarization-magic angle spinning 13C-solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and immunocytochemical electron microscopy. The first lignin appearing in the parenchyma is of the G-type preceeding the incorporation of S nuclei in the later stages. However, in vascular bundles, typical absorption bands of S nuclei are visible in the Fourier transform infrared spectra at the earliest stage of lignification. Immunocytochemical determination of the three types of lignin in transmission electron microscopy was possible thanks to the use of antisera prepared against synthetic H, G, and the mixed GS dehydrogenative polymers (K. Ruel, O. Faix, J.P. Joseleau [1994] J Trace Microprobe Tech 12: 247-265). The specificity of the immunological probes demonstrated that there are differences in the relative temporal synthesis of the H, G, and GS lignins in the different tissues undergoing lignification. Considering the intermonomeric linkages predominating in the antigens used for the preparation of the immunological probes, the relative intensities of the labeling obtained provided, for the first time to our knowledge, information about the macromolecular nature of lignins (condensed versus noncondensed) in relation to their ultrastructural localization and development stage.

Animals↗
PubMed1999

A cross-polarization, magic-angle-spinning, 13C-nuclear-magnetic-resonance study of polysaccharides in sugar beet cell walls

Solid-state nuclear magnetic resonance relaxation experiments were used to study the rigidity and spatial proximity of polymers in sugar beet (Beta vulgaris) cell walls. Proton T1rho decay and cross-polarization patterns were consistent with the presence of rigid, crystalline cellulose microfibrils with a diameter of approximately 3 nm, mobile pectic galacturonans, and highly mobile arabinans. A direct-polarization, magic-angle-spinning spectrum recorded under conditions adapted to mobile polymers showed only the arabinans, which had a conformation similar to that of beet arabinans in solution. These cell walls contained very small amounts of hemicellulosic polymers such as xyloglucan, xylan, and mannan, and no arabinan or galacturonan fraction closely associated with cellulose microfibrils, as would be expected of hemicelluloses. Cellulose microfibrils in the beet cell walls were stable in the absence of any polysaccharide coating.

Journal Article↗
PubMed2005

CD56 staining in Merkel cell carcinoma and natural killer-cell lymphoma: magic bullet, diagnostic pitfall, or both?

BACKGROUND: Antibodies to CD56 label natural killer (NK) cell lymphomas and neuroendocrine tumors such as Merkel cell carcinoma (MCC). In MCC altered by crush artifact or obscured by lymphocytes, the histologic features coupled with CD56 positivity can lead to an erroneous impression of NK-cell lymphoma. METHODS: Eighteen cases of MCC were stained for CD56, CK20, MNF116, and pankeratin. The results were compared to histologic features and CD56 staining pattern of three NK-cell lymphomas. RESULTS: Three of 18 cases of MCC histologically resembled lymphoma, and CD56 positivity with CD3 and CD20 negativity initially raised the possibility of NK-cell lymphoma. Two additional cases were obscured by dense inflammation, again suggesting the diagnosis of lymphoma. Seventeen of 18 MCC labeled for CD56 and an equal number stained for CK20. All MCC tested were positive for CAM5.2 (14/14) and MNF116 (17/17). Antibodies to pankeratin labeled only one of 18 MCC. Staining for CD56 was stronger in MCC than NK-cell lymphomas. CONCLUSIONS: CD56 is a sensitive marker for MCC as well as for NK-cell lymphoma, but is not specific. Importantly, CD56 positivity in crushed or inflamed biopsies of MCC may lead to an erroneous impression of NK lymphoma. Awareness of this potential pitfall will prevent misdiagnosis. McNiff JM, Cowper SE, Lazova R, Subtil A, Glusac EJ. CD56 staining in Merkel cell carcinoma and natural killer-cell lymphoma: Magic bullet, diagnostic pitfall, or both?

Aged↗
PubMed1993

Detection of specific IgE in isocyanate and phthalic anhydride exposed workers: comparison of RAST RIA, Immuno CAP System FEIA, and Magic Lite SQ.

Sera from 94 workers occupationally exposed to isocyanate were tested by RAST RIA, Immuno CAP FEIA, and Magic Lite SQ (ML) against the allergens HDI, MDI, TDI, and phthalic anhydride. Twenty sera showed increased levels of diisocyanate-specific IgE antibodies, and five sera were phthalic anhydride positive. High total IgE titer was not correlated with positive specific IgE titer (r = 0.47), showing that nonspecific IgE binding was low. The results of ML and CAP correlated well (r = 0.91), but tended to be slightly higher than the results obtained with the RAST isotope test. CAP and RAST data also correlated significantly (r = 0.90), but the correlation between ML and RAST data was lower (r = 0.82). The results of the new in vitro tests, CAP and ML, showed good reproducibility (5% CV for CAP and 8% CV for ML). In summary, the CAP and ML methods were found to be appropriate for routine diagnosis of specific IgE antibodies against the allergens HDI, MDI, TDI, and phthalic anhydride.

Adult↗
PubMed1996

Location of cholesterol in model membranes by magic-angle-sample-spinning NMR.

High-resolution magic-angle-sample-spinning 13C-NMR was applied to determine the specific location of cholesterol in non-perturbed multilamellar model membranes formed by egg yolk phosphatidylcholine. 13C spin-lattice relaxation times of both the phospholipid and cholesterol molecules were measured in the absence and in the presence of Gd3+, a paramagnetic agent, in order to obtain information on molecular distances. The effect of Gd3+ on the spin-lattice relaxation times of the lipid resonances has an explicit distance dependence, allowing it to be used to evaluate relative distances on a molecular scale. It has been found that cholesterol is placed in such a position that it is not readily exposed to the solvent: the hydrophobic steroid ring is oriented parallel to the membrane phospholipids, the hydroxyl group is in close vicinity to the phospholipid ester carbonyl groups and the isooctyl side chain is deeply buried in the center of the membrane. These data are consistent with an organization such that mixtures of cholesterol and phospholipids present a packing similar to that found in interdigitated lipid bilayer systems.

Animals↗
PubMed1992

Magic angle spinning NMR studies on the metarhodopsin II intermediate of bovine rhodopsin: evidence for an unprotonated Schiff base.

Magic angle spinning (MAS)13C-NMR spectra of the metarhodopsin II intermediate have been obtained using bovine rhodopsin regenerated with retinal 13C-labeled at the C-13 and C-15 positions to investigate the protonation state of the retinal Schiff base linkage. The 13C-labeled rhodopsin was reconstituted into 1,2-dipalmitoleoylphosphatidylcholine bilayers to increase the amount of meta II trapped at low temperature. Both the 13C-15 (159.2 ppm) and 13C-13 (144.0 ppm) isotropic chemical shifts are characteristic of an unprotonated Schiff base, while the 13C-15 shift is significantly different from that of retinal (191 ppm) or a tetrahedral carbinolamine group (70-90 ppm) previously proposed as an intermediate in the hydrolysis of the Schiff base at the meta II stage. This rules out the possibility that meta II non-covalently binds retinal or is a carbinolamine intermediate and provides convincing evidence that Schiff base deprotonation occurs in the meta I-meta II transition, an event that is likely to be important in triggering the activation of transducin.

Animals↗
PubMed1997

Cross-Polarized Magic-Angle Spinning (sup13)C Nuclear Magnetic Resonance Spectroscopic Characterization of Soil Organic Matter Relative to Culturable Bacterial Species Composition and Sustained Biological Control of Pythium Root Rot.

We report the use of a model system that examines the dynamics of biological energy availability in organic matter in a sphagnum peat potting mix critical to sustenance of microorganism-mediated biological control of pythium root rot, a soilborne plant disease caused by Pythium ultimum. The concentration of readily degradable carbohydrate in the peat, mostly present as cellulose, was characterized by cross-polarized magic-angle spinning (sup13)C nuclear magnetic resonance spectroscopy. A decrease in the carbohydrate concentration in the mix was observed during the initial 10 weeks after potting as the rate of hydrolysis of fluorescein diacetate declined below a critical threshold level required for biological control of pythium root rot. Throughout this period, total microbial biomass and activity, based on rates of [(sup14)C]acetate incorporation into phospholipids, did not change but shifts in culturable bacterial species composition occurred. Species capable of inducing biocontrol were succeeded by pleomorphic gram-positive genera and putative oligotrophs not or less effective in control. We conclude that sustained efficacy of naturally occurring biocontrol agents was limited by energy availability to this microflora within the organic matter contained in the potting mix. We propose that this critical role of organic matter may be a key factor explaining the variability in efficacy typically encountered in the control of pythium root rot with biocontrol agents.

Journal Article↗
PubMed1993

Evaluation of Clearview and Magic Lite tests, polymerase chain reaction, and cell culture for detection of Chlamydia trachomatis in urogenital specimens.

The Clearview Chlamydia test (CV; Unipath Ltd., Bedford, United Kingdom), the Magic Lite Chlamydia test (ML; CIBA Corning, Medfield, Mass.), a polymerase chain reaction (PCR), and cell culture (CC) were evaluated for detection of Chlamydia trachomatis in urogenital specimens. Specimens were collected from 283 men and 724 women visiting the outpatient clinic for Sexually Transmitted Diseases at the University Hospital Rotterdam, Rotterdam, The Netherlands. ML, PCR, and CC were all performed on the same sample to prevent swab-to-swab variability. CV was performed on a separate sample. Analysis of discordant results was performed by application of the following confirmatory assays: first, PCR on the CC, second, ML was repeated, and third, PCR was repeated by using a different DNA extraction protocol. If more than one test was positive, the sample was considered true positive. If only one test was positive, which was confirmed by the confirmatory assay, the sample was also considered true positive. By using these interpretations, the following results were obtained. The sensitivity and specificity of CV for samples from men were 60.4 and 86.3%, respectively. For samples from women, these values were 62.3 and 99.7%, respectively. The low specificity for samples from men was caused by unidentified substances in the swab that was used. The use of CV on samples from men is not recommended by the manufacturer. For samples from women, the specificity of CV was high, but the low sensitivity of CV limits its use for diagnostic purposes. The sensitivities of ML were low for samples from both men and women (68.8% and 50.9% respectively), while specificities were excellent for samples from both groups (100 and 99.9%, respectively). The low sensitivity of ML limits its diagnostic value. The PCR technique was highly specific for samples from both men (99.6%) and women (99.9%). The sensitivity of PCR, however, was unexpectedly low for samples from both groups (men, 87.5%; women, 79.2%), most likely because of the sample treatment method used. The sensitivity and specificity values of CC for samples from men were 95.8 and 100%, respectively. For samples from women, these values were 100 and 99.9%, respectively. In the present study, CC was the most reliable technique for the detection of C. trachomatis.

Bacteriological Techniques↗
PubMed1995

Specific drugs for a complex disease: can there be a magic bullet against rheumatoid arthritis?

The complexity of RA challenges our search for a better understanding of the interconnected networks. Early treatment will certainly avoid some of the problems presented by the complexity of the disease, and combined treatments seem advantageous for advanced disease. The complexity of overt RA will probably not allow a single agent to exert superior efficacy. Unless a treatable infectious cause is identified, a magic bullet, though theoretically possible, might not exist in reality, in particular if the disease is advanced.

Antibodies, Monoclonal↗
PubMed2006

Laboratory markers in IBD: useful, magic, or unnecessary toys?

Laboratory markers have been investigated in inflammatory bowel disease (IBD) for diagnostic and differential diagnostic purposes, for assessment of disease activity and risk of complications, for prediction of relapse, and for monitoring the effect of therapy. The introduction of biological therapies in IBD has renewed interest in inflammatory markers (especially C reactive protein (CRP)), given their potential to select responders to these treatments. Of all the laboratory markers, CRP is the most studied and has been shown to have the best overall performance. CRP is an objective marker of inflammation and correlates well with disease activity in Crohn's disease (CD). Increased CRP levels are associated with better response rates and normal CRP levels predict high placebo response rates in clinical trials with biologicals. However, despite the advantages of CRP over other markers, it is still far from ideal. Furthermore, CRP correlates less well with disease activity in patients with ulcerative colitis (UC) as compared with CD. Other laboratory markers, including erythrocyte sedimentation rate (ESR), leucocyte and platelet count, albumin, and 1 acid glycoprotein (orosomucoid), have been studied either less extensively in IBD or have proven to be less useful than CRP. Faecal markers seem promising and may be more specific in detecting gut inflammation in patients with established IBD. Promising results have been reported with the use of faecal calprotectin in CD as well as in UC. Recent data however suggest that the performance of the faecal calprotectin test is superior for UC than for CD. Taken together, laboratory markers are useful and should be part of the global management of our IBD patients. They are however not magic and until more data become available, the use of CRP and other laboratory markers should be seen as an additive tool to clinical observation and physical examination rather than a replacement.

Acute-Phase Reaction↗
PubMed2000

Quantification of cholesteryl esters in human and rabbit atherosclerotic plaques by magic-angle spinning (13)C-NMR.

Accumulation of cholesteryl esters (CEs) is a key event in the formation of atherosclerotic plaques. More recent work suggests a role for CEs in plaque rupture leading to thrombosis, which can result in an acute event such as myocardial infarction or stroke. In this study, we present nuclear magnetic resonance (NMR) protocols for quantification of CEs in plaques in situ. Total CEs quantified by (13)C magic-angle spinning (MAS) NMR in excised plaques from human carotid arteries and rabbit aortic arteries were in good agreement with the amounts determined by subsequent standard chemical assays. The latter analysis is disadvantageous because it requires that plaque lipids be extracted from the tissue, resulting in the loss of all phase information of CEs as well as other major plaque components. With our MAS-NMR protocol, the plaque components are preserved in their native phases. Combining MAS and off-MAS NMR, we were able to quantitatively distinguish isotropic (liquid) CEs from anisotropic (liquid-crystalline) CEs in plaque tissues. In a recent study, we applied a different (13)C MAS-NMR protocol to quantify crystalline cholesterol monohydrate in plaques. Together, these 2 studies describe a new, noninvasive MAS-NMR strategy for the identification and quantification of the major lipid components in plaques in situ. This approach will be useful for investigation of the relationship between plaque rupture and specific lipids in their biologically relevant phases.

Animals↗
PubMed2000

Quantification in situ of crystalline cholesterol and calcium phosphate hydroxyapatite in human atherosclerotic plaques by solid-state magic angle spinning NMR.

Because of renewed interest in the progression, stabilization, and regression of atherosclerotic plaques, it has become important to develop methods for characterizing structural features of plaques in situ and noninvasively. We present a nondestructive method for ex vivo quantification of 2 solid-phase components of plaques: crystalline cholesterol and calcium phosphate salts. Magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of human carotid endarterectomy plaques revealed (13)C resonances of crystalline cholesterol monohydrate and a (31)P resonance of calcium phosphate hydroxyapatite (CPH). The spectra were obtained under conditions in which there was little or no interference from other chemical components and were suitable for quantification in situ of the crystalline cholesterol and CPH. Carotid atherosclerotic plaques showed a wide variation in their crystalline cholesterol content. The calculated molar ratio of liquid-crystalline cholesterol to phospholipid ranged from 1.1 to 1.7, demonstrating different capabilities of the phospholipids to reduce crystallization of cholesterol. The spectral properties of the phosphate groups in CPH in carotid plaques were identical to those of CPH in bone. (31)P MAS NMR is a simple, rapid method for quantification of calcium phosphate salts in tissue without extraction and time-consuming chemical analysis. Crystalline phases in intact atherosclerotic plaques (ex vivo) can be quantified accurately by solid-state (13)C and (31)P MAS NMR spectroscopy.

Animals↗
PubMed2005

Stem cell-ness: a "magic marker" for cancer.

Transcriptional profiling of patient tumors is a much-heralded advancement in cancer therapy, as it provides the opportunity to identify patients who would benefit from more or less aggressive therapy and thus allows the development of individualized treatment. However, translation of this promise into patient benefit has proven challenging. In this issue of the JCI, Glinsky and colleagues used human and murine models to identify a potential stem cell mRNA signature, based on the hypothesis that tumors with stem cell-like characteristics are likely to have a poor prognosis. Remarkably, an 11-gene "expression signature" associated with "stem cell-ness" separated patients with different cancers into good- and poor-prognosis groups. Such a "magic marker" would, if validated, have a major impact on patient care. However, there remain challenges incumbent with creating and validating such signatures.

Animals↗
PubMed2003

Chaotic sepsis and the magic bullet.

All physiological systems have complex interactions--both intrinsic and with external systems. Sepsis is an archetypal example of a self-regulating complex system, with multiple cascading non-linear interactions and feedbacks, acting in series and in parallel, to form a "scale-free" network. The process of sepsis may be modelled in terms of complexity theory as an iterative progression from a stable, homeostatic pathway or attractor to an unstable attractor of immunological dissonance and death. Given the convolutions of the septic attractor, complexity theory neatly explains why so many "magic bullet" therapies for sepsis have failed when given alone, since reductionist approaches which test individual treatments one at a time are highly unlikely to be effective in isolation. A new methodology of synchronously testing multiple therapies needs to be developed.

Anti-Infective Agents↗
PubMed2002

Drag king magic: performing/becoming the other.

This chapter seeks to theorize drag king practice through the lenses of alterity, liminality, and performance theory, while attempting to complicate and reinvigorate discussions of identity raised by drag. I examine the ways in which drag king performance plumbs the concept of "the Other," and forces confrontation with a complex field of desire. Contemporary "queergirl" existence negotiates a range of desirable and desiring Others, from the polarities (i.e., butch-femme) unique to queer structures of desire, to the desire of those on the cultural margins for the power of those at the center, and vice versa. I employ anthropological theories of performance, mimesis, and liminality to establish a framework through which drag kings may be viewed as crucibles of this desire and agents of this power exchange. By performing maleness, drag kings expand and redraw the definitional boundaries of the male, interfere with the cultural power of mainstream maleness, and simultaneously transfer some of this power to themselves as queer women. At the same time, drag king existence forces a renegotiation of queergirl desire to encompass a range of masculinities. By performing/becoming the Other, drag kings engage in a practice of magic which transforms both margin and center.

Black or African American↗