A 3D scaffold has been developed that has the potential to fulfil the criteria for an ideal scaffold for bone tissue engineering. Sol–gel derived bioactive glasses of the 70S30C (70
mol% SiO
2, 30
...mol% CaO) composition have been foamed to produce 3D bioactive scaffolds with hierarchical interconnected pore morphologies similar to trabecular bone. The scaffolds consist of a hierarchical pore network with macropores in excess of 500
μm connected by pore windows with diameters in excess of 100
μm, which is thought to be the minimum pore diameter required for tissue ingrowth and vasularisation in the human body. The scaffolds also have textural porosity in the mesopore range (10–20
nm). The scaffolds were sintered at 600, 700, 800 and 1000
°C. As sintering temperature was increased to 800
°C the compressive strength increased from 0.34 to 2.26
MPa due to a thickening of the pore walls and a reduction in the textural porosity. The compressive strength is in the range of that of trabecular bone (2–12
MPa). Importantly, the modal interconnected pore diameter (98
μm) was still suitable for tissue engineering applications and bioactivity is maintained. Bioactive glass foam scaffolds sintered at 800
°C for 2
h fulfill the criteria for an ideal scaffold for tissue engineering applications.
Bioactive glass scaffolds have been produced, which meet many of the criteria for an ideal scaffold for bone tissue engineering applications, by foaming sol-gel derived bioactive glasses. The ...scaffolds have a hierarchical pore structure that is very similar to that of cancellous bone. The degradation products of bioactive glasses have been found to stimulate the genes in osteoblasts. This effect has been found to be dose dependent. The addition of silver ions to bioactive glasses has also been investigated to produce glasses with bactericidal properties. This paper discusses how changes in the hierarchical pore structure affect the dissolution of the glass and therefore its bioactivity and rate of ion delivery and demonstrates that silver containing bioactive glass foam scaffolds can be synthesised. It was found that the rate of release of Si and Ca ions was more rapid for pore structures with a larger modal pore diameter, although the effect of tailoring the textural porosity on the rate of ion release was more pronounced. Bioactive glass scaffolds, containing 2 mol% silver, released silver ions at a rate that was similar to that which has previously been found to be bactericidal but not high enough to be cytotoxic to bone cells.
Co-continuous composites consisting of a porous calcium phosphate matrix (hydroxyapatite, HA, or β-tricalcium phosphate, TCP) filled with poly(d,l-lactide) (PDLLA) were produced with two different ...methods: in situ polymerization of d,l-lactide monomer inside the matrix, or infiltration of the matrix with molten polymer. The influence of the calcium phosphate matrix as well as the manufacturing method on the degradation were investigated with accelerated in vitro studies at 42 °C in pH 7.4 phosphate-buffered saline (PBS), with some controls at 37 °C. The results show that samples produced with the infiltration method had higher initial molecular weights leading to a later onset of mass loss. Heterogenous polymer degradation was still present in the composites, as indicated by molecular weight distributions and glass transition temperature measurements. The calcium phosphate matrix delayed degradation, with evidence from X-ray microtomography suggesting that the polymer degrades more slowly in proximity to the matrix.
Hyphae, 2 to 8 days postinoculation (dpi), and haustoria, 5 dpi, were isolated from Uromyces appendiculatus infected bean leaves (Phaseolus vulgaris cv. Pinto 111) and a separate cDNA library ...prepared for each fungal preparation. Approximately 10,000 hyphae and 2,700 haustoria clones were sequenced from both the 5' and 3' ends. Assembly of all of the fungal sequences yielded 3,359 contigs and 927 singletons. The U. appendiculatus sequences were compared with sequence data for other rust fungi, Phakopsora pachyrhizi, Uromyces fabae, and Puccinia graminis. The U. appendiculatus haustoria library included a large number of genes with unknown cellular function; however, summation of sequences of known cellular function suggested that haustoria at 5 dpi had fewer transcripts linked to protein synthesis in favor of energy metabolism and nutrient uptake. In addition, open reading frames in the U. appendiculatus data set with an N-terminal signal peptide were identified and compared with other proteins putatively secreted from rust fungi. In this regard, a small family of putatively secreted RTP1-like proteins was identified in U. appendiculatus and P. graminis.
Azimuthal single-spin asymmetries of leptoproduced pions and charged kaons were measured on a transversely polarized hydrogen target. Evidence for a naive-T-odd, transverse-momentum-dependent parton ...distribution function is deduced from nonvanishing Sivers effects for pi(+), pi(0), and K(+/-), as well as in the difference of the pi(+) and pi(-) cross sections.
This study investigates the in vitro degradation properties of composites consisting of a porous tricalcium phosphate (TCP) foam filled with degradable poly(dl-lactic acid) (PDLLA) via either in situ ...polymerization or infiltration. The motivation was to develop a material for bone repair that would be initially mechanically strong and would develop porosity during degradation of one of the components. A thorough analysis of the physical in vitro degradation properties has been conducted and reported by the same authors elsewhere. Synchrotron micro-computer tomography analysis (conducted at ID19, ESRF, Grenoble, France) allowed detailed insights to be gained into the process of the composites' degradation, which was discovered to be strongly influenced by the manufacturing method. The polymer phase of in situ-polymerized TCP–PDLLA degraded as a bulk sample, with faster degradation in the centre of the sample as a whole. In contrast, the polymer phase of infiltrated TCP–PDLLA degraded as individual polymer spheres with faster degradation in the centre of each sphere.
Experiments were conducted to determine the total residues remaining in ocular tissues of cattle and turkeys after oral administration of 14Cractopamine HCl. Twelve cattle were intraruminally dosed ...with 0.9 mg x kg(-1) x d(-1) of 14Cractopamine HCl for 7 d. Four cattle each were slaughtered with withdrawal periods of 48,96, and 144 h. Radioactive residues were not detectable in whole-eye homogenates from the cattle. Eight male and eight female turkeys per treatment received either 7.5, 22.5, or 30 ppm dietary 14Cractopamine HCl (0.33, 1.02, and 1.36 mg x kg(-1) x d(-1); treatment groups 1, 2, and 3, respectively) for 7 d, and the birds were slaughtered with a 0-d withdrawal period. Eyes were dissected into retina/choroid/schlera (RCS), cornea/iris (CI), and aqueous humor (AH) fractions. Residues in RCS, CI, and AH of treatment 1 turkeys were not detectable. Residues in AH were < 0.02 ppm in treatment groups 2 and 3. Mean residues in RCS ranged from 0.15 to 0.26 ppm, and mean CI residues ranged from <0.09 to 0.17 ppm for treatment groups 2 and 3, respectively. The propensities of ractopamine and synthetic ractopamine metabolites to bind to melanin were studied in vitro using radiolabeled ligands with centrifugal filtration to separate melanin from unbound ligand. In vitro studies showed that 14Cractopamine HCl binds to melanin rapidly and was displaced from melanin by other beta-agonists. Glucuronidation of ractopamine, which produced the major biotransformation product of ractopamine in all species studied to date, prevented binding to melanin. These studies demonstrate that the propensity for the in vivo binding of ractopamine HCl to pigmented ocular tissues is less than that reported for clenbuterol.
Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The ...asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.
A
bstract
Beam-helicity and beam-charge asymmetries in the hard exclusive leptoproduction of real photons from an unpolarised hydrogen target by a 27.6 GeV lepton beam are extracted from the H
ermes
...data set of 2006-2007 using a missing-mass event selection technique. The asymmetry amplitudes extracted from this data set are more precise than those extracted from the earlier data set of 1996-2005 previously analysed in the same manner by H
ermes
. The results from the two data sets are compatible with each other. Results from these combined data sets are extracted and constitute the most precise asymmetry amplitude measurements made in the H
ermes
kinematic region using a missing-mass event selection technique.
Double-spin asymmetries in exclusive electroproduction of real photons from a transversely polarized hydrogen target are measured with respect to the product of target polarization with beam helicity ...and beam charge, and with respect to the product of target polarization with beam helicity alone. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe–Heitler process. They are related to the real part of the same combination of Compton form factors as that determining the previously published transverse target single-spin asymmetries through the imaginary part. The results for the double-spin asymmetries are found to be compatible with zero within the uncertainties of the measurement, and are not incompatible with the predictions of the only available GPD-based calculation.
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