Should human chondrocytes fly? The impact of electromagnetic irradiation on chondrocyte viability and implications for their use in tissue engineering

A significant logistic factor as to the successful clinical application of the autologous tissue engineering concept is efficient transportation: the donor cells need to be delivered to tissue processing facilities which in most cases requires air transportation. This study was designed to evaluate how human chondrocytes react to X-ray exposure. Primary cell cultures were established, cultured, incubated and exposed to different doses and time periods of radiation. Subsequently, quantitative cell proliferation assays were done and qualitative evaluation of cellular protein production were performed. Our results show that after irradiation of chondrocytes with different doses, no significant differences in terms of cellular viability occurred compared with the control group. These results were obtained when chondrocytes were exposed to luggage transillumination doses as well as exposure to clinically used radiation doses. Any damage affecting cell growth or quality was not observed in our study. However, information about damage of cellular DNA remains incomplet

First Principles Calculations of Fe on GaAs (100)

We have calculated from first principles the electronic structure of 0.5 monolayer upto 5 monolayer thick Fe layers on top of a GaAs (100) surface. We find the Fe magnetic moment to be determined by the Fe-As distance. As segregates to the top of the Fe film, whereas Ga most likely is found within the Fe film. Moreover, we find an asymmetric in-plane contraction of our unit-cell along with an expansion perpendicular to the surface. We predict the number of Fe 3d-holes to increase with increasing Fe thickness on $p$-doped GaAs.Comment: 9 pages, 14 figures, submitted to PR

LEED Holography applied to a complex superstructure: a direct view of the adatom cluster on SiC(111)-(3x3)

For the example of the SiC(111)-(3x3) reconstruction we show that a holographic interpretation of discrete Low Energy Electron Diffraction (LEED) spot intensities arising from ordered, large unit cell superstructures can give direct access to the local geometry of a cluster around an elevated atom, provided there is only one such prominent atom per surface unit cell. By comparing the holographic images obtained from experimental and calculated data we illuminate validity, current limits and possible shortcomings of the method. In particular, we show that periodic vacancies such as cornerholes may inhibit the correct detection of the atomic positions. By contrast, the extra diffraction intensity due to slight substrate reconstructions, as for example buckling, seems to have negligible influence on the images. Due to the spatial information depth of the method the stacking of the cluster can be imaged down to the fourth layer. Finally, it is demonstrated how this structural knowledge of the adcluster geometry can be used to guide the dynamical intensity analysis subsequent to the holographic reconstruction and necessary to retrieve the full unit cell structure.Comment: 11 pages RevTex, 6 figures, Phys. Rev. B in pres

SMF-1, SMF-2 and SMF-3 DMT1 Orthologues Regulate and Are Regulated Differentially by Manganese Levels in C. elegans

Manganese (Mn) is an essential metal that can exert toxic effects at high concentrations, eventually leading to Parkinsonism. A major transporter of Mn in mammals is the divalent-metal transporter (DMT1). We characterize here DMT1-like proteins in the nematode C. elegans, which regulate and are regulated by Mn and iron (Fe) content. We identified three new DMT1-like genes in C. elegans: smf-1, smf-2 and smf-3. All three can functionally substitute for loss of their yeast orthologues in S. cerevisiae. In the worm, deletion of smf-1 or smf-3 led to an increased Mn tolerance, while loss of smf-2 led to increased Mn sensitivity. smf mRNA levels measured by QRT-PCR were up-regulated upon low Mn and down-regulated upon high Mn exposures. Translational GFP-fusions revealed that SMF-1 and SMF-3 strongly localize to partially overlapping apical regions of the gut epithelium, suggesting a differential role for SMF-1 and SMF-3 in Mn nutritional intake. Conversely, SMF-2 was detected in the marginal pharyngeal epithelium, possibly involved in metal-sensing. Analysis of metal content upon Mn exposure in smf mutants revealed that SMF-3 is required for normal Mn uptake, while smf-1 was dispensable. Higher smf-2 mRNA levels correlated with higher Fe content, supporting a role for SMF-2 in Fe uptake. In smf-1 and smf-3 but not in smf-2 mutants, increased Mn exposure led to decreased Fe levels, suggesting that both metals compete for transport by SMF-2. Finally, SMF-3 was post-translationally and reversibly down-regulated following Mn-exposure. In sum, we unraveled a complex interplay of transcriptional and post-translational regulations of 3 DMT1-like transporters in two adjacent tissues, which regulate metal-content in C. elegans

Genome sequencing and analysis of the versatile cell factory Aspergillus niger CBS 513.88

The filamentous fungus Aspergillus niger is widely exploited by the fermentation industry for the production of enzymes and organic acids, particularly citric acid. We sequenced the 33.9-megabase genome of A. niger CBS 513.88, the ancestor of currently used enzyme production strains. A high level of synteny was observed with other aspergilli sequenced. Strong function predictions were made for 6,506 of the 14,165 open reading frames identified. A detailed description of the components of the protein secretion pathway was made and striking differences in the hydrolytic enzyme spectra of aspergilli were observed. A reconstructed metabolic network comprising 1,069 unique reactions illustrates the versatile metabolism of A. niger. Noteworthy is the large number of major facilitator superfamily transporters and fungal zinc binuclear cluster transcription factors, and the presence of putative gene clusters for fumonisin and ochratoxin A synthesis