Kidney graft outcome and quality (after transplantation) from uncontrolled deceased donors after cardiac arrest

The use of uncontrolled deceased donors after cardiac arrest (uDDCA) has been developed in France to compensate for organ shortage. The quality of these kidneys remains unclear. We analyzed kidney graft function and histology from 27 uDDCA and compared them with kidneys from 30 extended criteria donors (ECD) and from 24 simultaneous pancreas kidney (SPK) donors as a control group of optimal deceased donors. Kidneys from ECD and SPK donors were preserved by static cold storage while kidneys from uDDCA were preserved by pulsatile perfusion. The uDDCA graft function at 3 years posttransplantation (estimated with MDRD and measured with inulin clearance) did not differ from that of the ECD group (eGFR 44.1 vs. 37.4 mL/min/1.73 m(2) , p = 0.13; mGFR 44.6 vs. 36.1 mL/min/1.73 m(2) , p = 0.07 in the uDDCA and ECD groups, respectively). The histological assessment of 3-month and 1-year protocol biopsies did not show differences for interstitial lesions between the uDDCA and ECD grafts (IF score at M3 was 30 vs. 28% and at M12 36 vs. 33%, p = NS). In conclusion, the results at 3 years with carefully selected and machine-perfused uDDCA kidneys have been comparable to ECD kidneys and encourage continuation of this program and development of similar programs.

Interstitial fibrosis evolution on early sequential screening renal allograft biopsies using quantitative image analysis

Screening renal biopsies (RB) may assess early changes of interstitial fibrosis (IF) after transplantation. The aim of this study was to quantify IF by automatic color image analysis on sequential RB. We analyzed RB performed at day (D) 0, month (M) 3 and M12 from 140 renal transplant recipients with a program of color segmentation imaging. The mean IF score was 19 ± 9% at D0, 27 ± 11% at M3 and 32 ± 11% at M12 with a 8% progression during the first 3 months and 5% between M3 and M12. IF at M3 was correlated with estimated glomerular rate (eGFR) at M3, 12 and 24 (p < 0.02) and IF at M12 with eGFR at M12 and 48 (p < 0.05). Furthermore, IF evolution between D0 and M3 (ΔIFM3-D0) was correlated with eGFR at M24, 36 and 48 (p < 0.03). IF at M12 was significantly associated with male donor gender and tacrolimus dose (p = 0.03). ΔIFM3-D0 was significantly associated with male donor gender, acute rejection episodes (p = 0.04) and diabetes mellitus (p = 0.02). Thus, significant IF is already present before transplantation. IF evolution is more important during the first 3 months and has some predictive ability for change in GFR. Intervention to decrease IF should be applied early, i.e. before 3 months, after transplantation.

Coupled parametric active contours

We propose an extension of parametric active contours designed to track nonoccluding objects transiently touching each other, a task where both parametric and single level set-based methods usually fail. Our technique minimizes a cost functional that depends on all contours simultaneously and includes a penalty for contour overlaps. This scheme allows us to take advantage of known constraints on object topology, namely, that objects cannot merge. The coupled contours preserve the identity of previously isolated objects during and after a contact event, thus allowing segmentation and tracking to proceed as desired.

The membrane-microfilament linker ezrin is involved in the formation of the immunological synapse and in T cell activation

Dynamic interactions between membrane and cytoskeleton components are crucial for T cell antigen recognition and subsequent cellular activation. We report here that the membrane-microfilament linker ezrin plays an important role in these processes. First, ezrin relocalizes to the contact area between T cells and stimulatory antigen-presenting cells (APCs), accumulating in F-actin-rich membrane protrusions at the periphery of the immunological synapse. Second, T cell receptor (TCR)-mediated intracellular signals are sufficient to induce ezrin relocalization, indicating that this protein is an effector of TCR signaling. Third, overexpression of the membrane binding domain of ezrin perturbs T cell receptor clustering in the T cell-APC contact area and inhibits the activation of nuclear factor for activated T cells (NF-AT).

Dual function of rhoD in vesicular movement and cell motility

The trafficking of intracellular membranes requires the coordination of membrane-cytoskeletal interactions. Rab proteins are key players in the regulation of vesicular transport, while Rho family members control actin-dependent cell functions. We have previously identified a rho protein, rhoD, which is localized to the plasma membrane and early endosomes. When overexpressed, rhoD alters the actin cytoskeleton and plays an important role in endosome organization. We found that a rhoD mutant exerts its effect on early endosome dynamics through an inhibition in organelle motility. In these studies, the effect of rhoD on endosome dynamics was evaluated in the presence of a constitutively active, GTPase-deficient mutant of rab5, rab5Q79L. As rab5Q79L itself stimulates endosome motility, rhoD might counteract this stimulation, without itself exerting any effect in the absence of rab5 activation. We have now addressed this issue by investigating the effect of rhoD in the absence of co-expressed rab5. We find that rhoDG26V alone alters vesicular dynamics. Vesicular movement, in particular the endocytic/recycling circuit, is altered during processes such as cell motility. Due to the participation of vesicular motility and cytoskeletal rearrangements in cell movement and the involvement of rhoD in both, we have addressed the role of rhoD in this process and have found that rhoDG26V inhibits endothelial cell motility.

Nuclear pore complexes in the organization of silent telomeric chromatin

The functional regulation of chromatin is closely related to its spatial organization within the nucleus. In yeast, perinuclear chromatin domains constitute areas of transcriptional repression. These 'silent' domains are defined by the presence of perinuclear telomere clusters. The only protein found to be involved in the peripheral localization of telomeres is Yku70/Yku80. This conserved heterodimer can bind telomeres and functions in both repair of DNA double-strand breaks and telomere maintenance. These findings, however, do not address the underlying structural basis of perinuclear silent domains. Here we show that nuclear-pore-complex extensions formed by the conserved TPR homologues Mlp1 and Mlp2 are responsible for the structural and functional organization of perinuclear chromatin. Loss of MLP2 results in a severe deficiency in the repair of double-strand breaks. Furthermore, double deletion of MLP1 and MLP2 disrupts the clustering of perinuclear telomeres and releases telomeric gene repression. These effects are probably mediated through the interaction with Yku70. Mlp2 physically tethers Yku70 to the nuclear periphery, thus forming a link between chromatin and the nuclear envelope. We show, moreover, that this structural link is docked to nuclear-pore complexes through a cleavable nucleoporin, Nup145. We propose that, through these interactions, nuclear-pore complexes organize a nuclear subdomain that is intimately involved in the regulation of chromatin metabolism.