What function for human lithostathine?: structural investigations by three-dimensional structure modeling and high-resolution NMR spectroscopy

Human lithostathine is a 144-residue protein, expressed in variousorgans and pathologies. Several biological functions have beenproposed for this protein. Among others, inhibition of nucleationand growth of CaCO₃ crystals in the pancreas and bacterial aggregationhas retained attention, because lithostathine presents highsequence similarities with calcium-dependent (or C-type) lectins.To study its structure-function relationship and compare itwith that of C-type lectins, we have built a model for lithostathine.This model is derived from the only two C-type lectins of knownstructures: rat mannose binding protein and human E-selectin.An original strategy, inspired by that proposed by Havel andSnow, was designed for model building. We have undertaken NMRstudies on the natural protein. Although complete structuredetermination has not yet been achieved, the NMR studies didconfirm the main characteristics of the model. From analysisof the proposed model, we concluded that lithostathine is notexpected to present sugar- or calcium-binding properties. Therefore,the mechanisms of bacterial aggregation and inhibition of CaCO₃nucleation and growth have not yet been elucidated.     

Sexual and asexual development of Cryptosporidium parvum in five oocyst- or sporozoite-infected human enterocytic cell lines

The human enterocytic cell lines Caco-2, HT29, HCT8 and the Caco-2 clones TC7 and PF11 were studied for their ability to support Cryptosporidium parvum development. Following the addition in cultures of either oocysts or excysted sporozoites, immunofluorescent and transmission electron microscopy revealed the presence of all stages of the parasite life cycle by both procedures, and no difference in the ratio of infected cells was found among cell lines. More oocysts were seen in cell monolayers infected with oocysts than with sporozoites (p < 0.0001). The number of meronts observed was the same after either oocysts or sporozoites inoculation. Data suggest that the two methods yield a same cell infection rate.     

Adhesion properties of mutants of Staphylococcus aureus defective in fibronectin-binding proteins and studies on the expression of fnb genes

Staphylococcus aureus 8325-4 has the potential to express two distinct cell wall-associated fibronectin-binding proteins called FnBPA and FnBPB. In order to test if both proteins are expressed in S. aureus and if both are required for promoting bacterial adhesion to fibronectin-coated surfaces, insertion mutations were isolated in each gene. A DNA fragment encoding tetracycline resistance was inserted into fnbA and a fragment encoding erythromycin resistance was inserted into fnbB. A double fnbAfnbB mutant was also constructed. The fnbA and fnbB single mutants showed no significant reduction in their adhesion to polymethylmethacrylate coverslips that had been coated in vitro with fibronectin. However, the double mutant was completely defective in adhesion. Monospecific antibodies directed against the non-conserved N-terminal regions of both proteins confirmed the lack of expression of FnBPs in the mutant strains. Wild-type fnbA and fnbB genes cloned seperately on a multicopy plasmid were each able to restore fully the adhesion-defective phenotype of the 8325-4 fnbAfnbB mutant. This demonstrates that both fnb genes are expressed in S. aureus and that both contribute to the ability of strain 8325-4 to adhere to fibronectin-coated surfaces. The double mutant was also defective in adhesion to coverslips that had been removed from tissue cages implanted subcutaneously in guinea-pigs, which suggests that fibronectin is important in promoting attachment of S. aureus to biomaterial in vivo.     

Development of construction materials using sulfite-rich scrubber sludge and fly ash

Construction materials with characteristics suitable for a variety of applications have been developed using up to 95% of coal combustion by-products comprising of sulfite-rich scrubber sludge and fly ash. These materials can be produced as soil-like mixes that can be prepared at the power plant, transported to the deployment site and compacted using conventional road building equipment without a need for forms. These developed materials provide an early strength of 5.8-8.3 MPa after 7-14 d and are environmentally benign. For a cattle feeding pad application, which is the focus of this paper, the cost is estimated be about 25-30% of the cost of developing a conventional concrete feeding pad. Following mix development and establishment of quality assurance/quality control protocols, a commercial cattle feeding pad has been designed and demonstrated using the developed mix.     

Varistor versus Environment: Winning the Rematch

An unusual case of difficult application of surge protective devices was solved by field measurements with retrofit of protective devices suitable for the particular environment. Onsite measurements indicated that capacitor switching transients were causing excessive current surges in the varistors and fuses protecting the input to a thyristor motor drive. Knowledge of the environment gained by the measurements allowed understanding of the problem and specification of matching surge protective devices.     

Tolerance requirements for dispersion free single-mode fiber design: Influence of geometrical parameters, dopant diffusion, and axial dip

The dispersion sensitivity to small changes in index-differences, radius, and wavelength is investigated in the case of dispersion free single-mode fibers. If a minimum bandwidth is required, tolerances on the various parameters can then be deduced: singly- and doubly-clad structures are compared. Constant reference is made to the HE11mode spot-size to relate dispersion properties and attenuation. A nonzero fundamental mode cutoff is shown to induce an enhanced sensitivity to a change in fiber geometrical characteristics. The effect of dopant diffusion and axial dip on dispersion is then considered and conclusions are drawn concerning the use of profiles measured on preforms to predict fiber propagation properties.     

Zero dispersion in attenuation optimized doubly clad fibers

In a weakly guiding single-mode fiber, there exists an optimum value for the HE11mode spot size, which minimizes splicing and microbending losses. Zero dispersion and this optimum spot size for the mode can simultaneously be achieved with any inner-cladding depth; increasing the inner-cladding depth, however, allows smaller dopant concentrations in the core and thus lower intrinsic losses, but this induces an enhanced sensitivity to curvatures and to parameter fluctuations. When the inner-cladding depth is sufficiently high, on the other hand, the fundamental mode has a nonzero cutoff and dispersion can be minimized over a wide spectral range. Atlambda = 1.55mum, we determine the optimum value for the inner-cladding depth from criteria of both sensitivity to bending and fabrication tolerances or by requiring a given mode dispersion behavior over a wide spectral range.     

Nonlinear Devices Acting as SNR Amplifiers for a Harmonic Signal in Noise

A harmonic signal corrupted by an additive white noise is processed by an arbitrary memoryless nonlinear device. The transformation of the signal-to-noise ratio (SNR) by the nonlinearity is explicitly computed and analyzed for Gaussian and non-Gaussian noise. Simple nonlinearities, easily implementable as electronic circuits, are shown capable of producing an amplification of the SNR. Such an amplification is not obtainable with linear filters, whatever their complexity or high order, but becomes easily accessible with simple nonlinear devices.     

Length optimization of single-mode rare-earth doped waveguidesusing saturated absorption

Absorption saturation was demonstrated to provide a high, uniform population inversion over a length of waveguide longer than the material absorption length. The small signal gain was measured experimentally in single-mode waveguides, made by silver ion exchange, on a commercially available neodymium doped glass. The ratio of the excited states was calculated as a function of waveguide length and was shown to be a convenient criteria to determine the optimum device length     

Experimental right ventricle to pulmonary artery discontinuity: outcome of polyurethane valved conduits

OBJECTIVE: The ideal substitute for the treatment of ventricle-pulmonary artery discontinuity remains a topic of controversy, because of calcifications and degeneration of biologic substitutes leading to subsequent reoperations. Because polyurethane valves used in ventricular assist devices show a satisfactory biocompatibility, the aim of this study was to evaluate a valved conduit composed of a Dacron graft incorporating a trileaflet 25 mm polyurethane valve. METHODS: The conduit was implanted between the right ventricle and the main pulmonary artery in adult sheep, with ligation of the proximal pulmonary artery. The animals received no medications. Serial hemodynamic data were collected at the time of implantation and at postoperative intervals of 6 and 12 months. RESULTS: The peak pressure gradient across the valve increased significantly between implantation (0.17 +/- 5.6 mm Hg) and 6 months after operation (7.3 +/- 3 mm Hg, p = 0.0007) and remained stable thereafter (6.7 +/- 3 mm Hg at 12 months), whereas the cardiac output remained unchanged (4.6 +/- 0.6 L/min at implantation, 4 +/- 0.6 L/min at 6 months, and 3.9 +/- 1.1 L/min at 12 months). At the completion of the study, valve samples were processed and vapor coated with carbon for microscopic examination. There was one instance of nonadherent thrombus formation inside a cusp but no structural failures. The other valves were free of calcium deposits and no significant amounts of phosphorus could be detected by scanning electron microscopy and energy dispersive spectrometry. CONCLUSIONS: These data demonstrate the good hemodynamic performance, low thrombogenicity, and acceptable durability of the polyurethane valves implanted in the right side of the heart in a chronic sheep model.