Characterization of a T-DNA insertion mutant for the protein import receptor atToc33 from chloroplasts

In Arabidopsis thaliana, the Toc34 receptor component of the chloroplast import machinery is encoded by two independent but highly homologous genes, atToc33 and atToc34. We have isolated a T-DNA insertion mutant of atToc33 which is characterized by a pale phenotype, due to reductions in the levels of photosynthetic pigments, and alterations in protein composition. The latter involve not only chloroplast proteins but also some cytosolic polypeptides, including 14-3-3 proteins which, among other functions, have been proposed to be cytosolic targeting factors for nucleus-encoded chloroplast proteins. Within the chloroplast, many, though not all, proteins of the photosynthetic apparatus, as well as proteins not directly involved in photosynthesis, are found in significantly reduced amounts in the mutant. However, the accumulation of other chloroplast proteins is unaffected. This suggests that the atToc33 receptor is responsible for the import of a specific subset of nucleus-encoded chloroplast proteins. Supporting evidence for this conclusion was obtained by antisense repression of the atToc34 gene in the atToc33 mutant, which results in an exacerbation of the phenotype.

Improvement of Surface Acoustic Wave Gas and Biosensor Response Characteristics Using a Capacitive Coupling Technique

As for many other electronic devices and circuits, electrical contact to surface acoustic wave sensors is usually made using bonding wires. This technique is known to result in reliable contact under most conditions, but it does so with several disadvantages. First, electrical contact is not reversible, impeding replacement of sensor devices. Second, bonding wires are quite delicate and should not be exposed to high gas or liquid flows. Third, the presence of bonding wires may limit the potential to miniaturize a sensor housing or flow cell. Therefore, a capacitive coupling technique was developed to replace bonding wires. This permitted redesign of flow cells and sensor arrays, resulting in flow cell volumes of 80 microL to 60 nL. As a consequence, response times were reduced to 1-2 s in gas sensing and a few minutes in liquid sensing, respectively. At the same time, sensor devices can be easily replaced, and the system is less susceptible to malfunction.

Effects of retinoic acid on proliferation, apoptosis, cytotoxicity, migration, and invasion of neuroblastoma cells

BACKGROUND

Because of the known property of less aggressiveness of differentiated cells compared to immatured cells all attempts are made to elucidate whether differentiation inducers possibly could be applied for neuroblastoma therapy. We are interested in examining the influence of retinoic acid (RA) on proliferation, apoptosis, cytotoxicity, migration, and invasion in dependence of the differentiation of neuroblastoma cells classified into N-type (SK-N-FI, SH-SY5Y), I-type (SK-PN-DW), and S-type (SK-N-LO, SK-N-MC) cells.

PROCEDURE

Neuroblastoma cells were exposed to 10(-5) M RA and 200 ng/ml camptothecin (CAM) (control substance for apoptosis). Proliferation, apoptosis, and cytotoxicity were quantified by photometric assays. The influence on migration and invasion of neuroblastoma cells was examined by a scratch-test and by the measurement of the invasion through matrigel coated chamber inserts.

RESULTS

In general, RA treatment induced proliferation inhibition predominantly in the cell lines SK-PN-DW (16%, P < 0.05) and SK-N-MC (8%, (P < 0.001), respectively. In the N-type cell lines SK-N-FI (P > 0.05) and SH-SY5Y (P < 0.001) no proliferation inhibition was determined conforming with no detection of apoptosis. CAM confirmed its capability to induce apoptosis in the cell lines SH-SY5Y (43.6%, P < 0.05), SK-PN-DW (54.8%, P > 0.05), and SK-N-MC (28.9%, P < 0.0 01) except for SK-N-FI with only 9.3% (P > 0.05), but after 24 hr of treatment. Minor signs of restricted migration were observed, while RA treatment reduced significantly the invasion rate through Matrigel of SK-N-FI to 13.3% (P < 0.01), SH-SY5Y to 19.2% (P < 0.05), SK-N-MC to 27.8% (P < 0.05), and SK-N-LO to 17.7% (P < 0.01).

CONCLUSIONS

It is demonstrated that RA treatment can interfere with cell growth and in invasion by inducing neuronal differentiation in N-type and apoptosis in S-type neuroblastoma cell lines.

Hydroxypyridinium collagen crosslinks in serum, urine, synovial fluid and synovial tissue in patients with rheumatoid arthritis compared with osteoarthritis

OBJECTIVE

To investigate the relationship between inflammation markers and content of pyridinium crosslinks in hydrolysates of synovial tissue and to specify the significance of urinary excreted pyridinoline, released primarily from collagen I and II of bone and cartilage, and deoxypyridinoline released especially from collagen I of bone and dentin, dependent on disease activity in rheumatoid arthritis (RA).

METHODS

Synovial tissue and fluid from knee endoprosthesis surgery, as well as simultaneously obtained serum and urine, were collected from 12 patients with inactive RA or RA with low disease activity [iRA: C-reactive protein (CRP) <28 mg/l], 10 with active RA (aRA: CRP > or =28 mg/l) and 21 with OA. After preparation of the synovial tissue, including hydrolysis, completely released synovial pyridinoline and deoxypyridinoline crosslinks as well as those from synovial fluid, serum and urine were investigated using a gradient ion-paired reversed-phase HPLC method. Crosslink levels in synovial tissue are expressed as mol/mol collagen, assuming 300 residues of hydroxyproline per collagen molecule, also measured by HPLC.

RESULTS

In the synovial tissue of aRA patients we found significantly elevated total pyridinoline concentrations and pyridinoline/deoxypyridinoline (Pyr/Dpyr) quotients compared with the iRA and OA controls, indicating an elevated crosslinking density of mature synovial tissue collagen with increased activity of RA. Pyridinoline levels and the Pyr/Dpyr ratio were correlated with those of urine and with acute-phase reactants in RA patients. Compared with serum crosslink levels, which were unrelated to disease activity, the urinary concentration of pyridinoline was increased by a factor of 2 and showed a simultaneous increase with increasing synovitis.

CONCLUSION

Both crosslinking density and degradation of mature collagen from synovial tissue depend on the disease activity in RA. Urinary excretion of associated crosslinks, expressed as the Pyr/Dpyr ratio, correlates with those in synovial tissue and may be confirmed as a marker of synovial tissue collagen degradation. We suggest that increased crosslinking of mature collagen in the synovial tissue of RA is related to an inflammation-dependent regulation of collagen synthesis in activated synovial fibroblasts, in which lysyl oxidase represents the final enzymatic step for crosslinking.

Hollow polymer shells from biological templates: fabrication and potential applications

Three-dimensional ultrathin polymer shells have been produced by a combination of step-by-step adsorption of polyelectrolytes on glutaraldehyde-treated human erythrocytes and subsequent solubilization of the cytoplasmatic constituents by means of a deproteinizing agent. The obtained hollow films preserve both the size and shape of the templating cells. This opens a pathway for the fabrication of polymeric capsules within a wide range of size and shape by using various biological templates. They may have exciting potential applications, such as templates for nanocomposites, as containers for a large class of materials, or as cages for chemical reactions. The thickness of the films can be adjusted over a large range: from a few nm up to several tens of nm. The polymer shells are permeable to small molecules and ions but not to macromolecules. An increase in the ionic strength of the solution up to 100 mmol make the capsules permeable for proteins. Permeability and conductivity studies have provided evidence that the adsorption of lipids on polyelectrolyte layers is a means of producing capsules with controlled permeability properties. 6-Carboxyfluorescein and Rhodamin 6G were precipitated within the capsules.

BCRP gene expression is associated with a poor response to remission induction therapy in childhood acute myeloid leukemia

Breast cancer resistance protein (BCRP), also known as mitoxantrone resistance protein (MRX) or placenta ABC protein (ABC-P), is the second member of the ABCG subfamily of ABC transport proteins (gene symbol ABCG2). Transfection and enforced expression of BCRP in drug-sensitive cells confers resistance to mitoxantrone, doxorubicin, daunorubicin and topotecan. In this study the expression of BCRP gene was measured using TaqMan real-time PCR in 59 children with newly diagnosed AML. Nine patients were also analyzed in relapse. The median of BCRP gene expression was more than 10 times higher in patients who did not achieve remission after the first phase of chemotherapy (n = 24) as compared to patients who did achieve remission at this stage (n = 21; P = 0.012). In first relapse the expression of the BCRP gene was higher than at diagnosis (P = 0.038). Although high levels of BCRP gene expression were more frequent in subtypes of AML with a favorable prognosis, we found that within both risk groups (high and low risk), patients who expressed high levels of BCRP had a worse prognosis (P = 0.023). Our results strongly suggest that the expression of the BCRP gene reduces the response to chemotherapy in AML and that BCRP expression is higher at the time of relapse.

Polyelectrolyte complexes and layer-by-layer capsules from chitosan/chitosan sulfate

Polyelectrolyte complex formation of chitosans of varying average molecular weight and degree of acetylation with chitosan sulfate or poly(styrene sulfonate) was studied by static light scattering in dilute solution at various ionic strengths. Unlike the molecular weight, the degree of acetylation was found to have a significant effect on the resultant structural densities of the complexes. The same system was applied to the preparation of micrometer-sized hollow shells by means of a layer-by-layer technique (in total eight layers). Their behavior toward fluorescent probes such as fluorescein and rhodamin 6G or fluorescein isothiocyanate labeled dextrans at various ionic strengths and pH (observed by confocal laser light scanning microscopy) could be understood through a discussion of electrostatic forces between the highly charged shells and the probes to be dominant. At an ionic strength of 0.1 M and above, charge effects are largely suppressed (screening effect) and a size-dependent "cutoff" for the permeation of the macromolecular fluorophore was observed.

Spontaneous generation of stable pnictinyl radicals from "jack-in-the-box" dipnictines: a solid-state, gas-phase, and theoretical investigation of the origins of steric stabilization

The molecular structures of the stable phosphinyl and arsinyl radicals, .PnR(2) [Pn = P (2); As (4); R = CH(SiMe(3))(2)], have been determined by gas-phase electron diffraction (GED) in conjunction with ab initio molecular orbital calculations. The X-ray crystal structures of the corresponding dipnictines, the "dimers", R(2)PnPnR(2) [Pn = P (1), As (3)], and the chloro derivatives R(2)PnCl [Pn = P (5), As (6)] have also been determined. Collectively, these structural investigations demonstrate that large distortions of the ligands attached to Pn occur when the pnictinyl radicals unite to form the corresponding dipnictine dimers. Principally, it is the shape and flexibility of the CH(SiMe(3))(2) ligands that permit the formation of the P-P and As-As bonds in 1and 3, respectively. However, theoretical studies indicate that in the process of pnictinyl radical dimerization to form 1 and 3, both molecules accumulate substantial amounts of potential energy and are thus primed to spring apart upon release from the solid state by melting, dissolution, or evaporation. The insights gleaned from these unusual systems have permitted a deeper understanding of the functioning of sterically demanding substituents.

Biological cells as templates for hollow microcapsules

Microcapsules in the micrometer size range with walls of nanometer thickness are of both scientific and technological interest, since they can be employed as micro- and nano-containers. Liposomes represent one example, yet their general use is hampered due to limited stability and a low permeability for polar molecules. Microcapsules formed from polyelectrolytes offer some improvement, since they are permeable to small polar molecules and resistant to chemical and physical influences. Both types of closed films are, however, limited by their spherical shape which precludes producing capsules with anisotropic properties. Biological cells possess a wide variety of shapes and sizes, and, thus, using them as templates would allow the production of capsules with a wide range of morphologies. In the present study, human red blood cells (RBC) as well as Escherichia coli bacteria were used; these cells were fixed by glutardialdehyde prior to layer-by-layer (LbL) adsorption of polyelectrolytes. The growth of the layers was verified by electrophoresis and flow cytometry, with morphology investigated by atomic force and electron microscopy; the dissolution process of the biological template was followed by confocal laser scanning microscopy. The resulting microcapsules are exact copies of the biological template, exhibit elastic properties, and have permeabilities which can be controlled by experimental parameters; this method for microcapsule fabrication, thus, offers an important new approach for this area of biotechnology.