Poly[copper(I)-mu-bromo-mu-2,3-dimethylpyrazine-N:N']

In the structure of the title compound, [CuBr(C(6)H(8)N(2))](n), each Cu(2+) cation is surrounded by two 2,3-dimethylpyrazine ligands and two Br(-) anions in a distorted tetrahedral arrangement. The Cu(2+) cations and Br(-) anions form (Cu(2)Br(2))(2) rhomboid dimers located around a centre of inversion. The 2,3-dimethylpyrazine ligands connect the Cu(2+) cations in the dimers into sheets parallel to (010).

Cell analysis system based on immunomagnetic cell selection and alignment followed by immunofluorescent analysis using compact disk technologies

BACKGROUND

Although the flow cytometer has become the standard in cell analysis, it has limitations. Recently, we introduced a new cell analysis method based on immunomagnetic selection and aligning of cells. No flow system is needed and cell analysis can be performed in whole blood.

METHODS

Whole blood is incubated with fluorescent labels and immunomagnetic nanoparticles. The blood is injected into a capillary that is in a strong magnetic field. The immunomagnetic-labeled cells move upward and align themselves along ferromagnetic lines present on the upper surface of the capillary. An optical focus and tracking system analogous to that used in a conventional compact disk player focuses a 635-nm laser-diode on the magnetically aligned cells. The emitted fluorescence signals are projected on two photomultipliers. Allophycocyanin (APC)-labeled CD4 (CD4-APC) and Cyanin5.5 (Cy5.5)-labeled CD8 (CD8-Cy5.5) antibodies and Oxazine750, all red excited, are used as fluorescent labels.

RESULTS

A differential white blood cell count performed in whole blood is obtained using the CD4-APC in combination with Oxazine750. The results are compared with the Technicon-H1 hematology analyzer. Correlation coefficients of 0.91 for neutrophilic granulocytes, 0.93 for lymphocytes, 0.93 for monocytes, and 0.96 for eosinophilic granulocytes were obtained. Immunofluorescence is demonstrated using CD4-APC and CD8-Cy5.5. The absolute counts obtained for CD4+ and CD8+ are compared with the Coulter Epics XL flow cytometer. Correlation coefficients of, respectively, 0.91 and 0.94 were obtained.

CONCLUSION

We conclude that our system is as capable as a standard flow cytometer or hematology analyzer for a reliable routine white blood cell analysis, including immunophenotyping, and can be used as an easy-to-handle disposable white blood cell test.

Biomolecular interactions measured by atomic force microscopy

Atomic force microscopy (AFM) is nowadays frequently applied to determine interaction forces between biological molecules. Starting with the detection of the first discrete unbinding forces between ligands and receptors by AFM only several years ago, measurements have become more and more quantitative. At the same time, theories have been developed to describe and understand the dynamics of the unbinding process and experimental techniques have been refined to verify this theory. In addition, the detection of molecular recognition forces has been exploited to map and image the location of binding sites. In this review we discuss the important contributions that have led to the development of this field. In addition, we emphasize the potential of chemically well-defined surface modification techniques to further improve reproducible measurements by AFM. This increased reproducibility will pave the way for a better understanding of molecular interactions in cell biology.

[Change in technical aids (AT)--a technology assessment from the viewpoint of rehabilitation-anthropology]

Practical experience in adjusting complex computer-assisted (CAS) communication aids has resulted in a search for prognostic criteria useful in evaluating the efficacy of technical aids. Such evaluation implies a holistic approach as is included in the ICIDH-2. These circumstances are demonstrated by examples ranging from mechanical to computer-assisted (CAS) aids. "Reciprocity" has turned out to be a valid semi-qualitative criterion in describing the dynamic equilibration of the rehabilitative issues involved. Only a dialogical situation with reciprocity will lead to sustainable participation. In case of technical aids, a conjunction of abilities and the qualitative level of activities in disabled people have to be taken into account to provide all dimensions of participation. In this holistic approach, social participation and balance will equally be respected. The differentiation of social systems with unequal consequences for people with disabilities in terms of environmental factors, or e-code of the ICIDH-2, have to be considered for prognostic evaluation with regard to efficacy and possible participation. A comprehensive psycho-socio-functional rating therefore has to include a comparative (socio-structural or morphological) analysis of the environment at hand. This approach will invariably show that technical aids alone are unable to ensure individual independence but, rather, may lead to isolation if there is no regional or local networking based on partnership and close interpersonal relations to be drawn on "technically".

Real-time light-driven dynamics of the fluorescence emission in single green fluorescent protein molecules

Real-time single-molecule fluorescence detection using confocal and near-field scanning optical microscopy has been applied to elucidate the nature of the "on-off" blinking observed in the Ser-65 --> Thr (S65T) mutant of the green fluorescent protein (GFP). Fluorescence time traces as a function of the excitation intensity, with a time resolution of 100 micros and observation times up to 65 s, reveal the existence of a nonemissive state responsible for the long dark intervals in the GFP. We find that excitation intensity has a dramatic effect on the blinking. Whereas the time during which the fluorescence is on becomes shorter as the intensity is increased, the off-times are independent of excitation intensity. Statistical analysis of the on- and off-times renders a characteristic off-time of 1.6 +/- 0.2 s and allows us to calculate a transition yield of approximately 0.5 x 10(-5) from the emissive to the nonemissive state. The saturation excitation intensity at which on- and off-times are equal is approximately 1.5 kW/cm(2). On the basis of the single-molecule data we calculate an absorption cross section of 6.5 x 10(-17) cm(2) for the S65T mutant. These results have important implications for the use of the GFP to follow dynamic processes in time at the single-molecular level.

Intracellular reactions in single human granulocytes upon phorbol myristate acetate activation using confocal Raman microspectroscopy

We have obtained new evidence for the occurrence of intracellular NADPH-oxidase activity in neutrophilic and eosinophilic granulocytes upon stimulation with phorbol myristate acetate (PMA). PMA activation leads to a partial translocation of cytochrome b(558) from the membranes of the specific granules to the plasma membrane. It was suggested that NADPH-oxidase activity only takes place in the plasma membrane, leading to an extracellular release of oxygen metabolites because cellular self-destruction can be avoided in this way. The effects of PMA activation were indirectly studied in recent experiments employing scavengers of extracellular superoxide anion and hydrogen peroxide, and support for intracellular NADPH-oxidase activity was obtained. In this paper we use Raman microspectroscopy as a direct method to study intracellular molecular reactions that result from cellular triggering by PMA. The molecular specificity of this microscopic method enables us to show that intracellular reduction of both myeloperoxidase (MPO) and cytochrome b(558) occurs in neutrophilic granulocytes. Control measurements with cytochrome b(558)-deficient neutrophilic granulocytes did not show a reduction of intracellular MPO. This is direct support for the occurrence of intracellular NADPH-oxidase activity in organelles that must be in close contact with the azurophilic granules that contain MPO. Furthermore, a comparison was made with chemical reactions occurring in eosinophilic granulocytes after activation with PMA. Moreover, in these cells an intracellular reduction of eosinophil peroxidase was observed.

Optical tracking and detection of immunomagnetically selected and aligned cells

We have developed a platform for cell analysis based on immunomagnetic selection and magnetic alignment of cells in combination with an epi-illumination tracking and detection system. Whole blood was labeled with ferromagnetic nanoparticles and fluorescent probes, and placed in a magnetic field in a chamber. Cells labeled with ferromagnetic nanoparticles moved upward and aligned along ferromagnetic lines deposited by lithographic techniques on an optically transparent surface of the chamber. An epi-illumination system using a 635 nm laser diode as a light source scanned the lines and measured signals obtained from the aligned cells. The cell counts per unit of blood volume obtained with the system correlated well with those obtained from the counts from a standard hematology analyzer and flow cytometer. The cell analysis platform is significantly less complex and more sensitive than current cell analysis equipment and provides additional functionality through its ability to subject the cells to repeated and varied analyses while they remain in a natural environment (i.e., whole blood).

Orientation of the chromophore dipoles in the TOTO-DNA system

BACKGROUND

Flow cytometry has been applied successfully to the sizing of medium to large-sized DNA molecules, thanks to the excellent staining properties of cyanine chromophores such as TOTO (homodimer of thiazole orange) (Petty et al.: Anal Chem 67:1755-1761, 1995). The hydrodynamic flow, used to focus the sample molecules in a small laser-illuminated volume, is also responsible for their alignment, thereby allowing the determination of the TOTO-dipole orientation with respect to the DNA axis (Agronskaia et al.: Appl Opt 38:714-719, 1999).

METHODS

We present model calculations of the fluorescence yield of TOTO-stained DNA measured in a flow-cytometric setup with high numerical aperture. The models consider different orientations of the chromophore dipoles.

RESULTS

Comparison of measurement and calculation suggests that the absorption dipoles of the TOTO molecule make a mean angle of 61 degrees with the helix axis of the DNA molecule. This mean angle can be the consequence of two binding modes.

CONCLUSIONS

Our results indicate that any model with a significant contribution of perpendicularly-oriented chromophores fails to reproduce the experimental results.

High speed atomic force microscopy of biomolecules by image tracking

An image-tracking procedure for atomic force microscopy is proposed and tested, which allows repeated imaging of the same area without suffering from lateral drift. The drift correction procedure is based on on-line cross-correlation of succeeding images. Using the image-tracking procedure allows zooming in on a small scan area over a long period and thus increases the frame rate inversely proportional to the scan area. Application of the procedure is demonstrated for diffusion of 5.4-kb DNA plasmids. With a scan area of 500 * 500 nm(2), a single plasmid can be imaged for more than 30 min at 4 s per frame, with a drift less than 10 nm. The high temporal resolution allows detailed analysis of the diffusion of DNA molecules. A diffusion coefficient of 30 nm(2)/s is found for most DNA molecules, though many molecules are temporally pinned to the mica surface, restricting diffusion.

DNA bending by photolyase in specific and non-specific complexes studied by atomic force microscopy

Specific and non-specific complexes of DNA and photolyase are visualised by atomic force microscopy. As a substrate for photolyase a 1150 bp DNA restriction fragment was UV-irradiated to produce damaged sites at random positions. Comparison with a 735 bp undamaged DNA fragment made it possible to separate populations of specific and non-specific photolyase complexes on the 1150 bp fragment, relieving the need for highly defined substrates. Thus it was possible to compare DNA bending for specific and non-specific interactions. Non-specific complexes show no significant bending but increased rigidity compared to naked DNA, whereas specific complexes show DNA bending of on average 36 degrees and higher flexibility. A model obtained by docking shows that photolyase can accommodate a 36 degrees bent DNA in the vicinity of the active site.

Optimization of adhesion mode atomic force microscopy resolves individual molecules in topography and adhesion

The force sensor of an atomic force microscope (AFM) is sensitive enough to measure single molecular binding strengths by means of a force-distance curve. In order to combine high-force sensitivity with the spatial resolution of an AFM in topography mode, adhesion mode has been developed. Since this mode generates a force-distance curve for every pixel of an image, the measurement speed in liquid is limited by the viscous drag of the cantilever. We have equipped our adhesion mode AFM with a cantilever that has a low viscous drag in order to reach pixel frequencies of 65 Hz. Optimized filtering techniques combined with an auto-zero circuitry that reduces the drift in the deflection signal, limited high- and low-frequency fluctuations in the height signal to 0.3 nm. This reduction of the height noise, in combination with a thermally stabilized AFM, allowed the visualization of individual molecules on mica with an image quality comparable to tapping mode. The lateral resolution in both the topography and the simultaneously recorded adhesion image are only limited by the size of the tip. Hardware and software position feedback systems allows individual molecules to be followed in time during more than 30 min with scan sizes down to 60 x 60 nm2.

Doppler Monte Carlo simulations of light scattering in tissue to support laser-Doppler perfusion measurements

Doppler Monte Carlo (DMC) simulations of the transport of light through turbid media, e.g., tissue, can be used to predict or to interpret measurements of the blood perfusion of tissue by laser-Doppler perfusion flowmetry. We describe the physical and mathematical background of Doppler Monte Carlo calculations, and present some comparisons with measurements, performed with experimental flow models, built to mimic skin tissue characteristics and for the calibration of perfusion instruments,which are important goals of the Biomed-I concerted action. The measurements deal with coherence effects.

3D single-particle tracking and optical trap measurements on adhesion proteins

A three-dimensional single-particle tracking system was combined with an optical trap to investigate the behavior of transmembrane adhesion proteins. We exploited this setup to investigate which part of the cell adhesion protein LFA-1 forms a connection to the cytoskeleton after binding to its ligand ICAM-1. LFA-1 is an integrin consisting of an alpha and a beta chain. Thus far, only the cytoplasmic tail of the beta chain is known to form a connection to the cytoskeleton. We investigated cells that express a mutant form of LFA-1 that lacks the complete beta cytoplasmic tail and therefore is not thought to bind to the cytoskeleton. Interestingly, single-particle tracking measurements using beads coated with the ligand ICAM-1 indicate that this mutant form of LFA-1 does not move freely within the cell membrane, suggesting that LFA-1 is still connected to the cytoskeleton network. This finding is strongly supported by the observation that LFA-1 exhibits a more diffusive motion when the cytoskeleton network is disrupted and confirmed by the optical trap measurements used to force the proteins to move through the membrane. Collectively, our findings suggest that the interaction of LFA-1 with the cytoskeleton cannot solely be attributed to the cytoplasmic part of the beta chain.

Single-molecule manipulation of double-stranded DNA using optical tweezers: interaction studies of DNA with RecA and YOYO-1

By using optical tweezers and a specially designed flow cell with an integrated glass micropipette, we constructed a setup similar to that of Smith et al. (Science 271:795-799, 1996) in which an individual double-stranded DNA (dsDNA) molecule can be captured between two polystyrene beads. The first bead is immobilized by the optical tweezers and the second by the micropipette. Movement of the micropipette allows manipulation and stretching of the DNA molecule, and the force exerted on it can be monitored simultaneously with the optical tweezers. We used this setup to study elongation of dsDNA by RecA protein and YOYO-1 dye molecules. We found that the stability of the different DNA-ligand complexes and their binding kinetics were quite different. The length of the DNA molecule was extended by 45% when RecA protein was added. Interestingly, the speed of elongation was dependent on the external force applied to the DNA molecule. In experiments in which YOYO-1 was added, a 10-20% extension of the DNA molecule length was observed. Moreover, these experiments showed that a change in the applied external force results in a time-dependent structural change of the DNA-YOYO-1 complex, with a time constant of approximately 35 s (1/e2). Because the setup provides an oriented DNA molecule, we determined the orientation of the transition dipole moment of YOYO-1 within DNA by using fluorescence polarization. The angle of the transition dipole moment with respect to the helical axis of the DNA molecule was 69 degrees +/- 3.

Visualising individual green fluorescent proteins with a near field optical microscope

The use of the green fluorescence protein (GFP) as an individual marker for applications in molecular biology requires detailed understanding of its photophysical and photodynamical properties. We investigated individual S65T mutants of GFP both on a glass surface and embedded in a water-pore gel. An aperture-type near field scanning optical microscope (NSOM) with two polarisation detection channels was applied to afford high spatial (approximately 70 nm) and temporal (0.5 ms) resolution. Shear-force and near field fluorescence imaging were performed simultaneously, allowing direct correlation between topographic and optical features. Polarisation data showed that the emission dipole moment of the proteins is fixed in space within both the barrel structure of the protein and the gel matrix used for spatial confinement of the proteins. The photophysical behaviour of the S65T-GFP mutants was monitored in time, with 500-micros real-time resolution and continuous imaging for periods of more than 2 h. Our results show the reversible on-off behaviour on a time scale that spans from 10(-4) to 10(3) s. Even a process generally identified as "bleaching" turns out to be reversible if a sufficient long observation time is allowed. As such, the photodynamics of individual GFPs appear to be much more complex than the properties deduced from ensemble-averaged measurements.

A physical approach to reduce nonspecific adhesion in molecular recognition atomic force microscopy

Atomic force microscopy is one of the few techniques that allow analysis of biological recognition processes at the single-molecule level. A major limitation of this approach is the nonspecific interaction between the force sensor and substrate. We have modeled the nonspecific interaction by looking at the interaction potential between a conical Si3N4 tip with a spherical end face and a mica surface in solution, using DLVO (Derjaguin, Landau, Verwey, Overbeek) theory and numerical calculations. Insertion of the tip-sample potential in a simulation of an approach-retract cycle of the cantilever gives the well-known force-distance curve. Simulating a force-distance curve at low salt concentration predicts a discrete hopping of the tip, caused by thermal fluctuations. This hopping behavior was observed experimentally and gave rise to a novel approach to making measurements in adhesion mode that essentially works in the repulsive regime. The distance between tip and sample will still be small enough to allow spacer-involved specific interactions, and the percentage of nonspecific interactions of the bare tip with the mica is minimized. We have validated this physical model by imaging intercellular adhesion molecule 1 (ICAM-1) antigen with a tip functionalized with anti-ICAM-1 antibody. The measurement demonstrated that a significant decrease in the number of nonspecific interactions was realized, and the topographical image quality and the specific bonding capability of the tip were not affected.

Polarization effects in flow cytometric DNA sizing

We have investigated the influence of the polarization direction of excitation light on DNA sizing results obtained by a flow cytometric technique. We found strong fluorescence anisotropy of the fluorescent signal from lambda DNA stained with the bis-intercalating dye TOTO-1. Small fragments of DNA are less sensitive to polarization than larger pieces. This effect is more pronounced at faster flow speeds. These observations show a noticeable orientation of the DNA molecules introduced by the shear forces in the flow system. The data are consistent with an angle between the transition moment of fluorescence of TOTO-1, and the long axis of DNA is approximately 62 degrees .

Simultaneous height and adhesion imaging of antibody-antigen interactions by atomic force microscopy

Specific molecular recognition events, detected by atomic force microscopy (AFM), so far lack the detailed topographical information that is usually observed in AFM. We have modified our AFM such that, in combination with a recently developed method to measure antibody-antigen recognition on the single molecular level (Hinterdorfer, P., W. Baumgartner, H. J. Gruber, K. Schilcher, and H. Schindler, Proc. Natl. Acad. Sci. USA 93:3477-3481 (1996)), it allows imaging of a submonolayer of intercellular adhesion molecule-1 (ICAM-1) in adhesion mode. We demonstrate that for the first time the resolution of the topographical image in adhesion mode is only limited by tip convolution and thus comparable to tapping mode images. This is demonstrated by imaging of individual ICAM-1 antigens in both the tapping mode and the adhesion mode. The contrast in the adhesion image that was measured simultaneously with the topography is caused by recognition between individual antibody-antigen pairs. By comparing the high-resolution height image with the adhesion image, it is possible to show that specific molecular recognition is highly correlated with topography. The stability of the improved microscope enabled imaging with forces as low as 100 pN and ultrafast scan speed of 22 force curves per second. The analysis of force curves showed that reproducible unbinding events on subsequent scan lines could be measured.

[Indications for evaluation scales in quality assurance in rehabilitation--16]

Prognostic evaluations are necessary to predict efficiency and possible success in social medicine. For this reasons the "Integration Prognosis Index" (IPI) is giving criteria. The structure of the special indices are compiled under interdisciplinary aspects (by bio-socio-morphological interactionistic details). The IPI was proved by investigations on vocational integration (done by EAM and IMBA assessments). Because vocational integration is one aspect of participation classified by ICIDH-2 the importance of the IPI for quality assurance and for further social and therapeutic support could be demonstrated. Validity and Sensitivity was shown for structuring rehabilitative procedures. It is stressed that selectivity according to a priority principle is only acceptable in rehabilitation if all aspects of integration are realized in practice to improve the situations of handicapped people.

Confocal Raman microspectroscopy of the activation of single neutrophilic granulocytes

Confocal Raman micro-spectroscopy has been applied to investigate the activation process of single, living neutrophilic granulocytes. Both resting cells as well as activated cells were measured. The activation of cells was performed with phorbol-12-myristate-13-acetate activator and Escherichia Coli bacteria. Raman microspectroscopy combines a high spatial resolution inside a single, living cell with detailed material information. Using this approach it can be concluded that activation of the cells with phorbol-12-myristate-13-acetate causes a change in the redox state of cytochrome b558. This protein is a part of the NADPH-oxidase complex that neutrophilic granulocytes employ to generate O-2, superoxide anion. Additionally a change in the redox state of myeloperoxidase can be observed. Myeloperoxidase is known to react with O-2. Activation of the cells with bacteria gives rise to corresponding changes in the Raman spectra. From this single cell study it can be concluded that the enzymes cytochrome b558 and myeloperoxidase are present inside the cytoplasm of the living cell, while participating in the redox processes. Activation causes an intra-cellular release of oxygen metabolites. Activation with bacteria of neutrophilic granulocytes from a patient with chronic granulomatous disease, that contain no cytochrome b558, led to typical changes in the redox state of myeloperoxidase. This indicates that in the bacterium/neutrophilic granulocyte system oxygen metabolites are generated that are capable of reacting with MPO.

Photon-counting device compatible with conventional flow cytometric data acquisition electronics

We present an electronic scheme that enables us to use a photon-counting device (photomultiplier or avalanche photodetector) for measuring extremely weak signals in a flow cytometer. It can be used as a sole detector, or in combination with other (conventional) detectors using the data acquisition hardware of a conventional flow cytometer. The essential principle is that photon-counting pulses are converted to an analogue signal that is continuously proportional to the number of detected photons during the last integration time. The integration time should be approximately equal to the time an object is illuminated in the flow chamber. In this way, the photon burst due to real events is measured correctly and discriminated from the background pulses (fluorescence and Raman). The use of this scheme for the measurement of single DNA molecules is illustrated.

Resonance Raman microspectroscopy of myeloperoxidase and cytochrome b558 in human neutrophilic granulocytes

With (resonance) Raman microscospectroscopy, it is possible to investigate the chemical constitution of a very small volume (0.5 fl) in a living cell. We have measured resonance Raman spectra in the cytoplasm of living normal, myeloperoxidase (MPO)-deficient, and cytochrome b558-deficient neutrophils and in isolated specific and azurophilic granule fractions, using an excitation wavelength of 413.1 nm. Similar experiments were performed after reduction of the redox centers by the addition of sodium dithionite. The specific and azurophilic granules in both redox states appeared to have clearly distinguishable Raman spectra when exciting at a wavelength of 413.1 nm. The azurophilic granules and the cytochrome b558-deficient neutrophils showed Raman spectra similar to that of the isolated MPO. The spectra of the specific granules and the MPO-deficient neutrophils corresponded very well to published cytochrome b558 spectra. The resonance Raman spectrum of the cytoplasmic region of normal neutrophilic granulocytes could be fitted with a combination of the spectra of the specific and azurophilic granules, which shows that the Raman signal of neutrophilic granulocytes mainly originates from MPO and cytochrome b558, at an excitation wavelength of 413.1 nm.

New technique for high resolution DNA sizing in epi-illumination

We present a high-resolution DNA-sizing technique based on the principles of flow cytometry, using a high numerical aperture objective and epi-illumination. The new technique, designed for small fluorescing samples/particles (sub-micron diameter) suspended in a weakly fluorescent medium, makes use of an additional focus for high-precision particle localisation. This way, only those particles are considered that flow exactly through a well-defined volume. Results are presented for fluorescent beads, as well as for YOYO-stained plasmids containing 5,500 basepairs. The latter were measured with 6.2% resolution, setting a new limit to flow-based sizing of DNA.

Direct visualization of dynamic protein-DNA interactions with a dedicated atomic force microscope

Photolyase DNA interactions and the annealing of restriction fragment ends are directly visualized with the atomic force microscope (AFM). To be able to interact with proteins, DNA must be loosely bound to the surface. When MgCl2 is used to immobilize DNA to mica, DNA is attached to the surface at distinct sites. The pieces of DNA in between are free to move over the surface and are available for protein interaction. After implementation of a number of instrumental improvements, the molecules can be visualized routinely, under physiological conditions and with molecular resolution. Images are acquired reproducibly without visible damage for at least 30 min, at a scan rate of 2 x 2 microm2/min and a root mean square noise of less than 0.2 nm. Nonspecific photolyase DNA complexes were visualized, showing association, dissociation, and movement of photolyase over the DNA. The latter result suggests a sliding mechanism by which photolyase can scan DNA for damaged sites. The experiments illustrate the potential that AFM presents for modern molecular biology.

Feasibility of picosecond laser-Doppler flowmetry provides basis for time-resolved Doppler tomography of biological tissues

A detectable signal is obtained from a laser Doppler flowmeter operating in the heterodyne mode with nano- and pico-second pulse laser sources. The ultrashort pulse probing may be useful for depth-dependent time-resolved laser Doppler velocity measurements of blood perfusion in biological tissues. © 1998 Society of Photo-Optical Instrumentation Engineers.

The waveguide Mach-Zender interferometer as atrazine sensor

Immunoanalytical techniques used in combination with a highly sensitive Mach-Zender waveguide sensor give a device that is capable of fast on-line monitoring of immunoreactions. The on-line monitoring is especially attractive when the sensor can be used as an environmental probe. It is demonstrated that low concentrations of atrazine can be measured with a sensitivity around the EC limit of 100 ng/L. These measurements are performed with an inhibition technique. In combination with "a dynamic slope method" one complete measurement is done within 10 min. Sensor measurements show the same sensitivity and errors as parallel ELISAs.

Cholesterol, phospholipid, and protein changes in focal opacities in the human eye lens

PURPOSE

Focal opacities are signs of early cataractogenesis in the human lens. They progress slowly over a lifetime and may be precursors of mature cataracts. The authors analyzed changes in proteins, phospholipids, and cholesterol in these opacities using in situ techniques: Raman microspectroscopy, filipin cytochemistry for cholesterol, and transmission electron microscopy (TEM).

METHODS

Human lenses with verified focal opacities were fixed in 1% paraformaldehyde. Slabs with opacities were analyzed using confocal Raman spectroscopy, then filipin Raman analysis of cholesterol, and finally TEM.

RESULTS

Compared with normal fibers, opacities consistently showed elevated levels of cholesterol and aliphatic chains, increased phospholipid acyl chain disorder, and changes in phospholipid lateral packing. Disulfide bridges of specific geometry (trans-gauche-trans) were found. Although protein content was unchanged, compared with normal fibers, aromatic amino acid content was significantly lower. The hydrophobicity of tyrosine residues showed a significant decrease, and a change in the tryptophan indole ring angle was found. The changes were abrupt and sharply delineated focal opacities. TEM confirmed this sharp boundary and showed that the opacities were densely packed with vesicles of varying size and electron density embedded in a homogenous matrix.

CONCLUSIONS

The Raman and TEM analyses of opacities showed that early cataractogenic events led to disruption of fiber membranes, formation of vesicles from the membrane constituents, and protein changes. The aberrant morphology of the membranes enveloping the focal opacities may have segregated the affected fibers from the surrounding normal tissue, thus explaining the stationary or slowly progressing character of these opacities.

[Water exchange in human crystalline lens studied by combined dispersion confocal microspectroscopy]

We have employed the technique of the confocal Raman microspectroscopy to monitor water exchange in human eye lens in vitro. Heavy water (D2O) was used as a marker of the exchange. Raman spectra in the high frequency range (2200-3500 cm-1) were successively recorded at several locations inside the lens in order to register dynamics of the replacement of H2O by D2O. The intensities of the Raman peaks at 2450 cm-1 (OD stretch) and 3390 cm-1 (OH stretch) were used as indicators of H2O/D2O exchange, whereas the Raman peak at 2935 cm-1 (CH stretch of protein) served as an internal standard. The ratios of the Raman intensities I2450/I2935 and I3390/I2935 determined the relative concentrations of D2O and H2O, respectively. For the quantitative description of the exchange, we proposed a diffusion model assuming a constant diffusion coefficient over the volume of the lens. We report the results of experiments performed on four fresh and one fixed lenses. The diffusion coefficient of D2O in the human eye lens was estimated using the least-squares fit of the experimental data.

Chromatin structure in bands and interbands of polytene chromosomes imaged by atomic force microscopy

Polytene chromosomes from Drosophila melanogaster, observed from squash preparations, and chromosomes from Chironomus thummi thummi, investigated under physiological conditions, are imaged using an Atomic Force Microscope. Various chromatin fiber structures can be observed with high detail in fixed chromosomes and correspond to structures which are also observed in chromosomes of diploid cells. Unfixed chromosomes can be imaged in buffer and show less fiber-like details because of the inherent soft nature of the chromatin material.

Experimental and model investigations of bleaching and saturation of fluorescence in flow cytometry

We investigated the fluorescence emission from three fluorophores commonly used for labeling cells in flow cytometry. We have demonstrated that the fluorescence emission from cells labeled with fluorescein-isothiocyanate (FITC), phycoerythrin (PE), and allophycocyanin (APC) is considerably saturated and bleached in standard flow cytometric conditions. Therefore, for optimization of fluorescence detection in a flow cytometer, it is important to know the emission kinetics in detail. We made a mathematical model of the optical processes involved: absorption, fluorescence emission, nonradiative decay, photodestruction, and triplet state occupation. The validity of the model was experimentally tested with a set of averaged fluorescence pulses, measured in a large range of intensities and illumination times. The fluorescence of APC could be completely described by the model and produced the following rate constants: photodestruction rate kb1 = 6 x 10(3) s(-1), triplet state population rate k12 = 2 x 10(5) s(-1), and depopulation rate k20 = 5 x 10(4) s(-1). The fluorescence kinetics of FITC- and PE-labeled cells could not be fitted with only three parameters over the entire range, indicating that other optical processes are involved. We used the model to determine the sensitivity of our flow cytometer and to calculate the optimum conditions for the detection of APC. The results show that in principle a single APC molecule on a cell can be detected in the presence of background, i.e., autofluorescence and Raman scattering by water.

On refraction in Monte-Carlo simulations of light transport through biological tissues

To obtain reliable results from Monte-Carlo simulations of light scattering experiments, a statistically accurate procedure for positioning the photons after refraction between two different scattering media is necessary. Two statistically equivalent algorithms for calculating the position of the photons immediately after crossing an interface are described and justified.

Intracellular carotenoid levels measured by Raman microspectroscopy: comparison of lymphocytes from lung cancer patients and healthy individuals

Most studies concerning a possible protective role of carotenoids against cancer focus on serum carotenoid levels. We have used Raman microspectroscopy to study the intracellular amounts of carotenoids in lymphocytes of lung cancer patients and of healthy individuals. Our results indicate a significant decrease of carotenoids in lung carcinoma patients compared with healthy individuals, particularly in adenocarcinoma patients. Carotenoid supplementation raised the serum concentration in 2 lung cancer patients up to normal levels, whereas intracellular content remained significantly lower. This indicates that carotenoid uptake by lymphocytes is not only dependent on serum carotenoid concentration. Our findings indicate that Raman microspectroscopy, a recently developed technique to measure intracellular levels of drugs, is also well suited to obtain quantitative data on carotenoid amounts inside cells.

[Assessment methods for vocational integration of disabled persons--from ERTOMIS methods to the IMBA information system]

The background for the development of actual assessments for evaluation of vocational integration of disabled people (i.e., EAM, IMBA) in Germany is described. Resulting perspectives for future procedural approaches are presented. So far, the EAM, Ertomis Assessment Method, approach has gained limited acceptance only. In light of WHO and European impulses, as well as the economic constraints at hand, it remains to be seen whether the IMBA information system will turn out a practical and problem-focussed tool. A critical review is done to provide constructive suggestions for further applications of IMBA.

Probabilistic model of multiple light scattering based on rigorous computation of the first and the second moments of photon coordinates

We consider a concise method based on recurrent relations that permit rigorous computing of the first and the second moments of the components of the vector locating a randomly walking photon in an infinite homogeneous light-scattering medium. On assumption that the components obey a three-dimensional Gaussian distribution a probability density for the photon locations at the Nth scattering event can readily be written down and the light-intensity distribution in the medium may be calculated. The results from theoretical analyses are compared with the solution of a light-diffusion equation and with results of Monte Carlo simulations and show a better fit with simulated data than the diffusion approximation.

Stimulated Raman gain scattering in planar dielectric waveguides

We have measured the vibrational Raman spectrum of a 1.2-microm-thick polystyrene film by using this film as an optical waveguide in a waveguide-stimulated Raman gain experiment. A gain factor of 1.3% was measured for the strong benzene mode at 1002 cm(-1). This value is in reasonable agreement with theoretical predictions.

Toothpick perforation of the intestine diagnosed by a small bowel series

We report the case of a 50-yr-old man who unknowingly swallowed a double-pointed toothpick that ultimately perforated the distal small bowel over a period of several weeks. Appendicitis and ileitis were sequentially considered as diagnosis. A foreign body was diagnosed on a second small bowel series and removed. It has been noted that, because toothpicks are not radiopaque, radiographic studies are not useful in the diagnostic workup. In the case reported, the toothpick was seen on the contrast radiograph of the small bowel and the correct diagnosis ultimately made.

Fluorescence in situ hybridization on human metaphase chromosomes detected by near-field scanning optical microscopy

Fluorescence in situ hybridization on human metaphase chromosomes is detected by near-field scanning optical microscopy. This combination of cytochemical and scanning probe techniques enables the localization and identification of several fluorescently labelled genomic DNA fragments on a single chromosome with an unprecedented resolution. Three nucleic acid probes are used: pUC1.77, p1-79 and the plasmid probe alpha-spectrin. The hybridization signals are very well resolved in the near-field fluorescence images, while the exact location of the probes can be correlated accurately with the chromosome topography as afforded by the shear force image.