Relevance of the direct pathway of sensitization in corneal transplantation is dictated by the graft bed microenvironment

Corneal grafts were until recently considered entirely devoid of resident APCs, giving rise to the tenet that alloantigen recognition is mediated exclusively by the indirect (host APC-dependent) pathway. The recent discovery of a resident myeloid corneal dendritic cell population that is normally MHC class II(-) but can readily up-regulate class II expression during inflammation led us to hypothesize that under certain conditions the direct pathway of allosensitization becomes operative. To test this, corneal allotransplants were performed in either inflamed (high-risk (HR)) or uninflamed (low-risk (LR)) host beds in mice, and the frequencies of host T cells activated via the direct pathway were determined. We found that directly primed CD4(+) T cells were detected in the HR but not LR setting, and these cells displayed a clear Th1 phenotype by 2 wk after grafting. Moreover, the use of MHC class II knockout donor tissue led to significantly enhanced survival of HR but not LR allografts. Finally, we show that donor corneal APC demonstrate high expression of CD40, CD80, and CD86 costimulatory molecules when derived from HR but not LR grafts. These data are the first to report that a functional donor APC-dependent direct response is elicited in corneal transplant hosts when the graft bed is inflamed and underscore the relevance of the graft microenvironment in dictating the pathway of allosensitization.     

Social structure and consanguinity in a French mountain Population (1550-1849)

Sociocultural factors play a crucial role in the variation of consanguinity in a population. The choice of specific matrimonial strategies can favor the closure or opening of the group to the outside, whereas differential fertility affects the gene flow from one generation to another. In the present study we analyzed the role of socioprofessional groups in the maintenance of endogamy and consanguinity in a French Alpine valley: Vallouise in the Brian?on area. In mountain environments, where the reproductive space is limited and quickly saturated, the autochthonous families adopt diversified matrimonial strategies. These marriage practices tend to prevent fragmentation of agricultural property. We analyzed the matrimonial behavior in the two main social groups of this population (décideurs and farmers) from 1550 to 1849. To better understand the behavior of the two social groups, we considered the two components of consanguinity, close and distant. Our study showed that the two groups had similar behavior regarding consanguinity. The way to prevent fragmentation of the patrimony was to choose a consanguineous spouse. This type of strategy inevitably leads to a high percentage of endogamy, which in this region of the Alps exceeded 90% through many centuries.     

A spatial statistical model for landscape genetics

Landscape genetics is a new discipline that aims to provide information on how landscape and environmental features influence population genetic structure. The first key step of landscape genetics is the spatial detection and location of genetic discontinuities between populations. However, efficient methods for achieving this task are lacking. In this article, we first clarify what is conceptually involved in the spatial modeling of genetic data. Then we describe a Bayesian model implemented in a Markov chain Monte Carlo scheme that allows inference of the location of such genetic discontinuities from individual geo-referenced multilocus genotypes, without a priori knowledge on populational units and limits. In this method, the global set of sampled individuals is modeled as a spatial mixture of panmictic populations, and the spatial organization of populations is modeled through the colored Voronoi tessellation. In addition to spatially locating genetic discontinuities, the method quantifies the amount of spatial dependence in the data set, estimates the number of populations in the studied area, assigns individuals to their population of origin, and detects individual migrants between populations, while taking into account uncertainty on the location of sampled individuals. The performance of the method is evaluated through the analysis of simulated data sets. Results show good performances for standard data sets (e.g., 100 individuals genotyped at 10 loci with 10 alleles per locus), with high but also low levels of population differentiation (e.g., F_ST < 0.05). The method is then applied to a set of 88 individuals of wolverines (Gulo gulo) sampled in the northwestern United States and genotyped at 10 microsatellites.     

Sugar composition and FT-IR analysis of exopolysaccharides produced by microbial isolates from paper mill slime deposits

Thirty exopolysaccharides (EPS) produced by bacteria isolated from biofilms or slimelayers from different paper and board mills in Finland, France and Spain were subjected to size exclusion chromatography and sugar compositional analysis. High performance size exclusion chromatography (HPSEC) analysis revealed that some samples were composed of several molecular weight populations. These samples were fractionated by size exclusion chromatography and pooled accordingly. Principal components analysis (PCA) of the sugar compositions of the different pools indicated the presence of glucans and mannans caused by insufficient removal of the carbon or nitrogen source (yeast extract) from the bacteria growth medium leading to an overestimation of the glucose and mannose level in the sample, respectively. From the point of view of slime problems the EPS populations are the most important for multivariate analysis. Four groups of EPSs have been recognized by PCA analysis: a group of EPSs produced by Enterobacter and related genera similar to the regularly reported colanic acid; a group of Methylobacterium EPSs having high galactose and pyruvate levels and two groups that showed less dense clusters produced by Bacillus and related genera, showing high mannose and/or glucose levels and Klebsiella EPSs that showed galactose with rhamnose as major characteristic sugar moieties. Fourier transform infrared spectroscopy (FT-IR) of the same samples followed by discriminant partial least squares regression (DPLS) and linear discriminant analysis (LDA) showed that, when used with a well-defined training set, FT-IR could be used clustering instead of time-consuming sugar composition analysis. The Enterobacter and Methylobacetrium EPS groups could be recognized clearly. However the fact that this could hardly be done for the other two groups in the dataset indicates the importance of a larger and well-defined training or calibration set. The potential to use FT-IR, as a tool for pattern recognition and clustering with respect to EPS structures produced by micro organisms isolated from a paper mill environment is discussed.     

Monovalent cation conductance in Xenopus laevis oocytes expressing hCAT-3

hCAT-3 (human cationic amino acid transporter type three) was investigated with both the two-electrode voltage clamp method and tracer experiments. Oocytes expressing hCAT-3 displayed less negative membrane potentials and larger voltage-dependent currents than native or water-injected oocytes did. Ion substitution experiments in hCAT-3-expressing oocytes revealed a large conductance for Na+ and K+. In the presence of L-Arg, voltage-dependent inward and outward currents were observed. At symmetrical (inside/outside) concentrations of L-Arg, the conductance of the transporter increased monoexponentially with the L-Arg concentrations; the calculated Vmax and KM values amounted to 8.3 microS and 0.36 mM, respectively. The time constants of influx and efflux of [3H]L-Arg, at symmetrically inside/outside L-Arg concentrations (1 mM), amounted to 79 and 77 min, respectively. The flux data and electrophysiological experiments suggest that the transport of L-Arg through hCAT-3 is symmetric, when the steady state of L-Arg flux has been reached. It is concluded that hCAT-3 is a passive transport system that conducts monovalent cations including L-Arg. The particular role of hCAT-3 in the diverse tissues remains to be elucidated.     

Inter-segmental coordination: motor pattern in humans stepping over an obstacle with mechanical ankle joint friction

This study examined the influence of a mechanical perturbation of the ankle joint on obstacle avoidance pattern. A decoupled control between the distal joint and the combined (hip-knee) proximal joints was observed according to the task requirement. In this context, a greater mechanical friction at the ankle should be compensated at this joint (local compensation) or alternatively, by regulating more combined proximal joints (knee and/or hip). The leading limb inter-segmental coordination was evaluated in both no constraint and constraint conditions in calculating ranges of motion (ROM), moments of force and powers (from heel-off to obstacle) at the ankle, knee and hip joints. Electromyographic activities were also analyzed. With the constraint, the dorsiflexor moment and the tibialis anterior activity remained unchanged while both ROM and power bursts (absorbed and generated) decreased. The hip and knee ROM remain invariant. At heel-off the absorption by hip extensors decreased and the forthcoming generation by knee flexors increased in the constraint condition. To quantify the inter-joint coordination, principal component analysis was used and indicated a high level of inter-joint coupling (synergy) that decreased with the constraint (i.e. less inter-joint coupling). At the ankle joint, the results suggest that the central command was the same in both conditions thus, not be adapted. At both the hip and knee joints, a combined joints modulation occurred to overcome additional friction.     

Elbow flexibility and ligand-induced domain rearrangements in antibody Fab NC6.8: large effects of a small hapten

Four 700-ps molecular dynamics simulations were carried out to analyze the structural dynamics of the antigen-binding antibody fragment NC6.8, which is known to exhibit large structural changes upon complexation. The first simulation was started from the x-ray structure of the uncomplexed Fab and produced trajectory averages that closely match the crystallographic results. It allowed assessment of the flexibility of the Fab, revealing an elbow motion of the variable domains with respect to the constant domains. The second simulation was started from the uncomplexed x-ray structure after insertion of the ligand into the binding site. This perturbation resulted in a significantly altered trajectory, with quaternary structural changes corresponding in many aspects to the experimental differences between complexed and uncomplexed state. The observed trend toward a smaller elbow angle and a higher flexion of the H-chain could also be seen in the third simulation, which was started from the x-ray structure of the complex. The changes were revealed to be a clear consequence of the complexation with the ligand because in the fourth simulation (started from the experimental complex structure after removal of the hapten) the Fab remained close to its initial structure. Analyses of the quaternary structure and the binding site of Fab NC6.8 are presented for all four simulations, and possible interpretations are discussed.     

Isolation and Characterization of Microsatellite Loci for Striped Bass (Morone saxatilis)

Genetic variation has been difficult to detect in striped bass (Morone saxatilis). Therefore, we identified and characterized 13 microsatellite loci to provide additional genetic markers for striped bass. Microsatellites were identified by screening a striped bass genomic library or by using primers developed for European sea bass (Dicentrarchus labrax) microsatellite loci. We found that 6 of the 13 microsatellite loci were polymorphic in DNA samples obtained from wild populations of striped bass. The number of alleles per locus varied from 3 to 12, and the observed heterozygosities ranged from 0.55 to 0.78. These results indicate that microsatellite loci provide more alleles and higher heterozygosities than other genetic markers developed for striped bass. Received November 9, 1999; accepted February 11, 2000.     

Aluminium speciation in the Vienne river on its upstream catchment (Limousin region, France)

The aim of this study was to investigate the speciation of aluminium in the river Vienne on its upstream catchment (Limousin region, France) over a period of seven years (May 1998-September 2004) in order to assess harmful effects on aquatic life. Two sampling points were selected: the first at 4 km from the spring (Peyrelevade), and the second one at 89 km from the spring (Royères). The aluminium speciation was computed with Mineql+ 4.5 speciation software. Organic matter and phosphorous play a major role in aluminium speciation. If we consider the free aluminium ion (Al3+) as being the only toxic form of aluminium, the concentrations of toxic forms recorded at Peyrelevade and Royères were always below the toxic values for fish. However, if the sum of the concentrations of Al3+, Al(OH)2+, Al(OH)2+ and Al(OH)4- is taken into consideration, the concentration of aluminium recorded may have adverse effects on aquatic life in the upstream catchment of the river Vienne. Al(OH)4- is the major contributor to the concentration in toxic aluminium recorded. In general, Al(OH)4- forms appears in water during the summer with water alkalinisation due to an increase in photosynthetic activities.