Comparative biodistribution of PAMAM dendrimers and HPMA copolymers in ovarian-tumor-bearing mice

The biodistribution profile of a series of linear N-(2-hydroxylpropyl)methacrylamide (HPMA) copolymers was compared with that of branched poly(amido amine) dendrimers containing surface hydroxyl groups (PAMAM-OH) in orthotopic ovarian-tumor-bearing mice. Below an average molecular weight (MW) of 29 kDa, the HPMA copolymers were smaller than the PAMAM-OH dendrimers of comparable molecular weight. In addition to molecular weight, hydrodynamic size and polymer architecture affected the biodistribution of these constructs. Biodistribution studies were performed by dosing mice with (125)iodine-labeled polymers and collecting all major organ systems, carcass, and excreta at defined time points. Radiolabeled polymers were detected in organ systems by measuring gamma emission of the (125)iodine radiolabel. The hyperbranched PAMAM dendrimer, hydroxyl-terminated, generation 5 (G5.0-OH), was retained in the kidney over 1 week, whereas the linear HPMA copolymer of comparable molecular weight was excreted into the urine and did not show persistent renal accumulation. PAMAM dendrimer, hydroxyl-terminated, generation 6.0 (G6.0-OH), was taken up by the liver to a higher extent, whereas the HPMA copolymer of comparable molecular weight was observed to have a plasma exposure three times that of this dendrimer. Tumor accumulation and plasma exposure were correlated with the hydrodynamic sizes of the polymers. PAMAM dendrimer, hydroxyl-terminated, generation 7.0 (G7.0-OH), showed extended plasma circulation, enhanced tumor accumulation, and prolonged retention with the highest tumor/blood ratio for the polymers under study. Head-to-head comparative study of HPMA copolymers and PAMAM dendrimers can guide the rational design and development of carriers based on these systems for the delivery of bioactive and imaging agents.     

Computational fluid dynamics analysis of drag and convective heat transfer of individual body segments for different cyclist positions

This study aims at investigating drag and convective heat transfer for cyclists at a high spatial resolution. Such an increased spatial resolution, when combined with flow-field data, can increase insight in drag reduction mechanisms and in the thermo-physiological response of cyclists related to heat stress and hygrothermal performance of clothing. Computational fluid dynamics (steady Reynolds-averaged Navier-Stokes) is used to evaluate the drag and convective heat transfer of 19 body segments of a cyclist for three different cyclist positions. The influence of wind speed on the drag is analysed, indicating a pronounced Reynolds number dependency on the drag, where more streamlined positions show a dependency up to higher Reynolds numbers. The drag and convective heat transfer coefficient (CHTC) of the body segments and the entire cyclist are compared for all positions at racing speeds, showing high drag values for the head, legs and arms and high CHTCs for the legs, arms, hands and feet. The drag areas of individual body segments differ markedly for different cyclist positions whereas the convective heat losses of the body segments are found to be less sensitive to the position. CHTC-wind speed correlations are derived, in which the power-law exponent does not differ significantly for the individual body segments for all positions, where an average value of 0.84 is found. Similar CFD studies can be performed to assess drag and CHTCs at a higher spatial resolution for applications in other sport disciplines, bicycle equipment design or to assess convective moisture transfer.     

GAP promoter‐based fed‐batch production of highly bioactive core streptavidin by Pichia pastoris

Streptavidin is a homotetrameric protein binding the vitamin biotin and peptide analogues with an extremely high affinity, which leads to a large variety of applications. The biotin‐auxotrophic yeast Pichia pastoris has recently been identified as a suitable host for the expression of the streptavidin gene, allowing both high product concentrations and productivities. However, so far only methanol‐based expression systems have been applied, bringing about increased oxygen demand, strong heat evolution and high requirements for process safety, causing increased cost. Moreover, common methanol‐based processes lead to large proportions of biotin‐blocked binding sites of streptavidin due to biotin‐supplemented media. Targeting these problems, this paper provides strategies for the methanol‐free production of highly bioactive core streptavidin by P. pastoris under control of the constitutive GAP promoter. Complex were superior to synthetic production media regarding the proportion of biotin‐blocked streptavidin. The optimized, easily scalable fed‐batch process led to a tetrameric product concentration of up to 4.16 ± 0.11 µM of biotin‐free streptavidin and a productivity of 57.8 nM h^?1 based on constant glucose feeding and a successive shift of temperature and pH throughout the cultivation, surpassing the concentration in un‐optimized conditions by a factor of 3.4. Parameter estimation indicates that the optimized conditions caused a strongly increased accumulation of product at diminishing specific growth rates (μ ≈ D < 0.01 h^?1), supporting the strategy of feeding. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:855–864, 2016     

Antibiotic-induced SOS response promotes horizontal dissemination of pathogenicity island-encoded virulence factors in staphylococci

Although mobile genetic elements have a crucial role in spreading pathogenicity-determining genes among bacterial populations, environmental and genetic factors involved in the horizontal transfer of these genes are largely unknown. Here we show that SaPIbov1, a Staphylococcus aureus pathogenicity island that belongs to the growing family of these elements that are found in many strains, is induced to excise and replicate after SOS induction of at least three different temperate phages, 80alpha, phi11 and phi147, and is then packaged into phage-like particles and transferred at high frequency. SOS induction by commonly used fluoroquinolone antibiotics, such as ciprofloxacin, also results in replication and high-frequency transfer of this element, as well as of SaPI1, the prototypical island of S. aureus, suggesting that such antibiotics may have the unintended consequence of promoting the spread of bacterial virulence factors. Although the strains containing these prophages do not normally contain SaPIs, we have found that RF122-1, the original SaPIbov1-containing clinical isolate, contains a putative second pathogenicity island that is replicated after SOS induction, by antibiotic treatment, of the prophage(s) present in the strain. Although SaPIbov1 is not induced to replicate after SOS induction in this strain, it is transferred by the antibiotic-activated phages. We conclude that SOS induction by therapeutic agents can promote the spread of staphylococcal virulence genes.     

Comparison of the hydrological characteristics of three small experimental holm oak forested catchments in NE Spain in relation to larger areas

Precipitation and streamflow have been measured in three small (0.04–0.52 km²) experimental catchments covered by dense holm oak (Quercus ilex L.) forests. Two of them are in the Prades mountains and one in the Montseny mountains (NE Spain). Here we test the hydrological representativeness of these catchments against the streamflow record at two nearby larger (34–60 km²) catchments, one from each massif. Comparisons of (i) annual streamflow, (ii) seasonal distribution of streamflow, and (iii) flow duration curves were made. At Prades, for the period of common record, mean annual precipitation was about 580 mm, and mean annual streamflow 44–81 mm at the two experimental catchments and 102 mm at the larger one. Most streamflow occurred during winter and spring in the three catchments. At Montseny, rainfall was higher, and mean annual streamflow was 495 mm in the experimental catchment, and 760 mm in the larger catchment, though these data were obtained in different periods in each catchment. Streamflow was roughly equal in autumn, winter and spring. At both sites flow duration curves were fairly similar in the small experimental catchments and the larger catchments. The higher streamflow at Montseny is reflected in its flow duration curves being well above those at Prades. The experimental catchments at Prades are thus fairly representative of the larger nearby catchment for the investigated hydrological characteristics. At Montseny, hydrological differences between the experimental catchment and the larger catchment are probably due to the higher mean altitude of the latter and to the non-overlapping periods of their streamflow records.     

Effect of 2,4-dichlorophenol on DPPC/water liposomes studied by X-ray and freeze-fracture electron microscopy

The effect of 2,4-dichlorophenol (DCP) was studied on the fully hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)--water liposomes. The structure and the thermotropic phase behaviour of the liposomes was examined in the presence of DCP (DCP/DPPC molar ratio, varied from 2x10(-2) up to 1) using small- and wide-angle X-ray scattering (SAXS, WAXS) and freeze-fracture electron microscopy. The structural behaviour of the DPPC/DCP/water system was strongly dependent on the concentration of the DCP. In the pretransition range the DCP molecules (at 2x10(-2) DCP/DPPC molar ratio) induced the interdigitated phase beside the parent (gel and rippled gel) phases, locally which can be form at higher DCP concentration. When the DCP/DPPC molar ratio was increased the pretransition disappeared and the main transition was shifted to lower temperatures. In the molar ratio range from 2x10(-1) up to 5x10(-1), a coexistence of different phases was observed in the wide temperature range from 20 up to 40 degrees C. With a further increase of the DCP/DPPC molar ratio (6x10(-1) to 1) only the interdigitated gel phase occurred below 25 degrees C. A schematic phase diagram of DPPC/DCP/water system was constructed to summarise the results.     

Spontanvegetation Nordgriechischer Bergdörfer

The synanthropic vegetation in seven villages of Northern Greece (N Pindhos and Olympus massif)—situated either in theQuercion confertae or in theFagetalia zone—is analyzed on the basis of about 100 phytosociological relevés. The most important vascular plant species of ruderal sites have also been mapped floristically. Nineteen plant communities are discernible, some of which are mentioned for the first time here. Nevertheless, the author refrains from hastily describing new associations, unless a more detailed phytosociological data basis on ruderal vegetation in the Southern Balkans is available. A table refers to differences and similarities between the recognized plant communities in Greek villages and those which correspond to them in Central Europe. Non-industrial methods of agriculture and animal husbandry are among the most important conditions for the remarkable rich vegetation in Greek mountain villages.