Combined pre- and postsynaptic action of IgG antibodies in Miller Fisher syndrome.

BACKGROUND: Miller Fisher syndrome (MFS), a variant of the Guillain-Barré syndrome, is associated with the presence of neuromuscular blocking antibodies, some of which may be directed at the ganglioside GQ1b. MATERIALS AND METHODS: The authors investigated the in vitro effects of serum and purified immunoglobulin (Ig) G in a total of 11 patients with typical MFS during active disease, and in three of those patients after recovery. From one patient's serum, we prepared an IgG fraction enriched in anti-GQ1b antibodies by affinity chromatography. For combined pre- and postsynaptic analysis, endplate currents were recorded by a perfused macro-patch clamp electrode. Postsynaptic nicotinic acetylcholine receptor channels were investigated by an outside-out patch clamp technique in cultured mouse myotubes. RESULTS: AllMFS-sera depressed evoked quantal release and reduced the amplitude of postsynaptic currents. Five of the 11 sera were additionally examined by outside-out patch clamp analysis and caused a concentration-dependent and reversible decrease in acetylcholine-induced currents. The time course of activation and desensitization of nicotinic acetylcholine receptor channels was not altered by MFS-IgG. Nine patients (82 %) were positive for anti-GQ1b antibodies in ELISA and dot-blot. The enriched anti-GQ1b antibody fraction had a similar effect as whole serum. After recovery from MFS, blocking activity was lost and sera originally positive for anti-GQ1b antibodies became negative. CONCLUSION: Circulating IgG antibodies induce both pre- and postsynaptic blockade and may play a pathogenic role in acute MFS.

Flame flow tagging velocimetry with 193-nm H2O photodissociation.

In a new nonintrusive, instantaneous flow tagging method called hydroxyl tagging velocimetry (HTV), a molecular grid of hydroxyl (OH) radicals is written into a flame and the displaced grid is imaged at a later time to give the flame's velocity profile. Single-photon photodissociation of vibrationally excited H(2)O, when a 193-nm ArF excimer laser is used, produces a tag line of superequilibrium OH and H photoproducts in a high-temperature flow field that itself may contain ambient OH. The tag line OH concentration is composed mostly of direct OH photoproducts, but OH is also indirectly produced through H photoproduct reactions with oxygen-bearing species. For lean and modestly rich flames the OH tag lifetime is of the order of 1 ms. For very rich H(2)-air flames (equivalence ratio of 4.4) the lifetime drops to 200 ns. After displacement the position of the OH tag line is revealed through fluorescence caused by OH (A-X) (3 <-- 0) excitation by using a 248-nm tunable KrF excimer laser. A HTV grid of multiple tag lines, providing multipoint velocity information, is experimentally demonstrated in a turbulent H(2)/N(2)-air diffusion flame.

Purified IgG from seropositive and seronegative patients with mysasthenia gravis reversibly blocks currents through nicotinic acetylcholine receptor channels.

The mechanism of block of nicotinic acetylcholine receptor (nAChR) channels by purified antibodies from patients with myasthenia gravis (MG) was investigated by using an ultrafast system for solution exchange at outside-out patches. IgG of MG patients and controls was purified by using protein A-Sepharose columns. Probes from 9 seropositive MG patients and 3 seronegative MG patients were tested. As a preparation, cultured mouse myotubes expressing the embryonic-type nAChR channels were used. Twenty-millisecond pulses of 1.0 mM ACh were applied repetitively to outside-out patches. Outside-out patches were preexposed with IgG in concentrations between 0.1 and 200 mg/L during application of ACh pulses. The peak current amplitude was reduced to values between 6% and 71% of control for the 9 seropositive and 3 seronegative MG patients. The block was concentration dependent and fully reversible after washout of antibodies. Incubation with IgG from different control patients did not reduce the peak current amplitude. In addition, our findings with purified IgG from seronegative MG patients support the idea of the immunopathogenesis of this disorder and may allow the development of a diagnostic test for seronegative MG patients.

Unseeded velocity measurement by ozone tagging velocimetry.

Ozone tagging velocimetry is developed for unseeded velocity measurement of air flows. An ozone line is photochemically created by an ArF excimer laser. After a fixed time delay the ozone line is imaged with a KrF excimer laser sheet (248 nm) that photodissociates the ozone and produces vibrationally excited O(2). The O(2) is excited by the same 248-nm light through the Schumann-Runge band, B (3)Sigma(u)(-)(upsilon' =0, 2) ? X (3)Sigma(g)(-)(upsilon'' = 6, 7). An intensified CCD camera records the O(2) fluorescence from the initial and the final line positions to permit the velocity profile along the line to be determined.

Single-pulse, simultaneous multipoint multispecies Raman measurements in turbulent nonpremixed jet flames.

An imaging technique based on Raman scattering induced by a KrF excimer laser has been developed for quantitative simultaneous multiple-point measurements of absolute multispecies concentrations (O(2), N(2), H(2), and H(2)O) and temperature in turbulent flames. These multiparameter measurements along the laser line have a temporal resolution of 17 ns, a spatial resolution of 0.7 mm for each point, and single-shot standard deviations of ~8%. The UV Raman imaging system has been applied in turbulent nonpremixed hydrogen-air flames, providing what are to our knowledge the first reported single-pulse, simultaneous multiple-point quantitative images of multiple species and temperature.

Raman scattering measurements in flames using a tunable KrF excimer laser.

Using a narrow-band tunable KrF excimer laser as a spontaneous vibrational Raman scattering source, we demonstrate that single-pulse concentration and temperature measurements, with only minimal fluorescence interference, are possible for all major species (O(2), N(2), H(2)O, and H(2)) at all stoichiometries (fuel-lean to fuel-rich) of H(2)-air flames. Photon-statistics-limited precisions in these instantaneous and spatially resolved single-pulse measurements are typically 5%, which are based on the relative standard deviations of single-pulse probability distributions. Optimal tuning of the narrow-band KrF excimer laser (248.623 nm) for the minimization of OH A(2)Sigma-X(2)II and O(2)B(3)Sigma(u)(-)-X(3)Sigma(g)(-) fluorescence interference is determined from fluorescence excitation spectra. In addition to the single-pulse N(2) Stokes/anti-Stokes ratio temperature measurement technique, a time-averaged temperature measurement technique ispresented that matches the N(2) Stokes Raman spectrum to theoretical spectra by using a single intermediate sta frequency to account for near-resonance enhancement. Raman flame spectra in CH(4)-air flames are presented that have good signal-to-noise characteristics and show promise for single-pulse UV Raman measurements in hydrocarbon flames.

Single pulse vibrational Raman scattering by a broadband KrF excimer laser in a hydrogen-air flame.

Spontaneous vibrational Raman scattering (VRS) is produced by a broadband excimer laser at 248 nm (KrF) in a H(2)-air flame and VRS spectra are recorded for lean, stoichiometric, and rich flames. Except at very lean flame conditions, laser-induced fluorescence (LIF) processes interfere with VRS Stokes lines from H(2), H(2)O, and O(2). No interference is found for the N(2) Stokes and N(2) anti-Stokes lines. In a stoichiometric H(2)/air flame, single-pulse measurements of N(2) concentration and temperature (by the VRS Stokes to anti-Stokes ratio) have relative standard deviation of 7.7 and 10%, respectively. These single pulse measurement errors compare well with photon statistics calculations using measured Raman cross sections.

Low level smoke emission measurements from a flame by photothermal deflection spectroscopy.

Smoke emission measurement by conventional filtering techniques is inaccurate for low levels of smoke (below ~2 mg/M(3)). Here photothermal deflection spectroscopy (PDS) is used to measure low levels of smoke emitted from a diffusion flame. In the PDS smoke instrument, an argon-ion laser heats the smoke sample and the deflection of a He-Ne laser probe beam is detected by a position sensor. The beam deflection is directly related to the smoke density. Using PDS, smoke emissions from an acetylene flame are detected at levels as low as 50 microg/m(3) (5 x 10(-6) cm(-1) light absorption).

Acoustically modulated optical transmission for low level gaseous species measurement.

A new optical technique has been developed for low level optical extinction measurements in gaseous media. It is a variation on direct light transmission where the sample gas density in a cell is modulated acoustically by a loudspeaker. The amplitude variation of the light transmission is proportional to the gas density and is insensitive to window contamination and detector instabilities. Preliminary analysis and experiments indicate tat the instrument promises to measure light absorption to < 1%/m. The technique has been demonstrated through the use of an absorbing gas, namely, 200 ppm of NO(2) in N(2) which produces 2.5% absorption over the observed path length of 10 cm.

Visualization of turbulent flame fronts with planar laser-induced fluorescence.

This report concerns the quantitative time-resolved visualization of reaction zones in laminar, transitional, and turbulent nonpremixed flames. Two-dimensional OH molecular concentrations were measured with planar laser-induced fluorescence excited by a sheet of light (formed from a single tunable ultraviolet laser pulse) and detected with a two-dimensional, image-intensified photodiode array camera. From the resulting data details of instantaneous flame front structures (including positions, shapes, and widths) were obtained.

Single-pulse, laser-saturated fluorescence measurements of OH in turbulent nonpremixed flames.

A single-pulse, laser-saturated fluorescence technique has been developed for absolute OH concentration measurements with a temporal resolution of 2 nsec, a spatial resolution of <0.1 mm(3), and an estimated accuracy of +/-30%. It has been applied in laminar, transitional, and turbulent hydrogen-air diffusion flames, providing the first reported quantitative measurements of average values, rms fluctuations, and probability density functions of OH radical concentration in nonpremixed flames.

[Studies on the mutagenic effect of extracts derived from airborne particulates within one year in differently burdened areas using the Ames test (author's transl)]. / Untersuchungen zur mutagenen Wirkung von Schwebstoffextrakten unterschiedlich belasteter Gebiete im Ames-Test während eines Jahres.

Suspended matter was collected at three sampling sites with different air pollution levels (DU = Duisburg, mining, iron and steel industry; D = Düsseldorf, residential city; K = Krahm, rural district) in 1978. The seasonal variations of the mutagenicity of extracts from samples collected monthly were assayed by the Ames-test. Th results are presented as the number of revertants related to air volume, weight of the suspended matter, weight of the dried extract and to the amount of benzo(a)pyrene in the extract. The mutagenicity varies according to the benzo(a)pyrene concentration in the atmosphere: the highest values are found during the winter, the lowest during the summer. When the mutagenicity is based on the benzo(a)pyrene content, it remains nearly constant throughout the year (sampling site DU) or rises in the summer (sampling sites D and K). These results indicate that at least in heavily polluted areas the larger part of the mutagens may originate from the same sources as benzo(a)pyrene (e.g. incomplete combustion). The direct (assayed without activating system) mutagenicity of the extracts is somewhat higher in winter than in summer. However, these differences are low or missing, when the mutagenicity is expressed as number of revertants per weight of suspended matter or dried extract. The mutagenicity reaches a maximum in summer, provided, the number of revertants is related to the benzo(a)pyrene concentration. These results indicate that the direct acting mutagens present in the air originate from other sources than that of benzo(a)pyrene (e.g. automobile exhaust). The mean values of the mutagenicity related to the number of revertants per dry-weight and weight of suspended matter do not differ among the three sampling sites. It can be assumed that the composition of the particulate matter may be similar with respect to mutagens regardless the level of pollution.