The inability to preserve vascular organs beyond several hours contributes to the scarcity of organs for transplantation
. Standard hypothermic preservation at +4 °C (refs.
) limits liver ...preservation to less than 12 h. Our group previously showed that supercooled ice-free storage at -6 °C can extend viable preservation of rat livers
However, scaling supercooling preservation to human organs is intrinsically limited because of volume-dependent stochastic ice formation. Here, we describe an improved supercooling protocol that averts freezing of human livers by minimizing favorable sites of ice nucleation and homogeneous preconditioning with protective agents during machine perfusion. We show that human livers can be stored at -4 °C with supercooling followed by subnormothermic machine perfusion, effectively extending the ex vivo life of the organ by 27 h. We show that viability of livers before and after supercooling is unchanged, and that after supercooling livers can withstand the stress of simulated transplantation by ex vivo normothermic reperfusion with blood.
Abstract
Biodiversity of zooplankton is central to the functioning of ocean ecosystems, yet morphological taxonomic analysis requires teams of experts and detailed examination of many samples. ...Metabarcoding (DNA sequencing of short amplified regions of one or a few genes from environmental samples) is a powerful tool for analysis of the composition and diversity of natural communities. The 18S rRNA V9 hypervariable region was sequenced for 26 zooplankton samples collected from the Gulf of Maine, Georges Bank, and Mid-Atlantic Bight during ecosystem monitoring surveys by the U.S. Northeast Fisheries Science Center during 2002–2012. A total of 7 648 033 sequences and 22 072 operational taxonomic units (OTUs) were identified and classified into 28 taxonomic groups of plankton. Comparative analysis of molecular (V9 sequence numbers) and morphological (abundance counts) focused on seven taxonomic groups and revealed similar patterns of variation among years and regions. Sequence numbers and abundance counts showed positive correlation for all groups, with significant correlations (p < 0.05) for Calanoida, Gastropoda, and Chaetognatha. Shannon diversity index values calculated using sequence numbers and abundance counts showed highly significant correlation (r = 0.625; p < 0.001) across all regions during 2002–2012. This study demonstrates the potential of metabarcoding for time-series analysis of zooplankton biodiversity, ocean ecosystem assessment, and fisheries management.
Liver transplantation offers life-saving therapy for patients with decompensated liver disease or T2 hepatocellular carcinomas. In the United States, deceased donor livers are primarily allocated by ...Model for End-Stage Liver Disease (MELD) score within each of the country's more than 50 donation service areas (DSAs). Variation in DSA size, population, and organ availability have engendered concern that unequal access to deceased donor livers across DSAs contributes to geographic variability in outcome.
To determine the extent to which DSA variability in organ availability correlated with combined waitlist and posttransplant mortality, we analyzed retrospectively national waitlist and posttransplant data for a 7-year period after implementation of the current MELD-based allocation system.
Marked variation among DSAs was evident in death rate (3.3-fold), transplant rate (20-fold), and mean transplant MELD (>10 points). Death rate correlated with organ availability was assessed by transplant rate and transplant MELD. DSAs with low organ availability included the country's largest cities, had more new listings per capita, larger waitlists, more transplant centers per DSA, and a higher proportion of black and Asian patients. DSAs of organ shortage were also characterized by more frequent dual listing at another transplant center, more living donor liver transplants, and increased average length of the transplant admission.
Geographic differences in deceased donor organ availability contribute to variation in overall death rate of liver transplant patients, shape the clinical practice of transplant, and influence the resources consumed per transplant. Geographic variation in organ access results primarily from rates of listing rather than donation. Our findings highlight the need to restructure organ distribution areas to achieve equal access to deceased donor livers for transplantation in the United States.
Liver tissue engineering has emerged as a promising approach in organ transplantation but has been hampered by the lack of a reliable and readily available cell source. Human induced pluripotent stem ...cells hiPSCs have been highlighted as a desirable source, due to their differentiation potential, ability to self‐renew, and the possibility of making patient‐specific cells. We developed a decellularization protocol that efficiently removes cellular material while retaining extracellular matrix components. Subsequently, hiPSCs were differentiated on decellularized human liver extracellular matrix (hDLM) scaffolds using an established hepatic differentiation protocol. We demonstrate that using hDLM leads to upregulation markers of hepatic functions when compared with standard differentiation conditions. In addition, expression of a number of hepatic transcription and nuclear factors were found to be within levels comparable with those of primary human adult hepatocytes. Analysis of progression of differentiation on hDLM demonstrated that hepatic developmental marker expression was consistent with hepatic development. The hDLM‐derived cells exhibited key hepatic characteristics that were comparable with those observed in primary neonatal human hepatocytes. We investigated the optimal timing of the introduction of hDLM into the differentiation protocol and found that the best results are obtained when cells are plated on hDLM since the earliest stages and accompanied by a progressive loss of sensitivity to substrate composition at later stages. The significance of this work is that it allows for the development of differentiation protocols that take into account signals from extracellular matrix, closely recapitulating of the in vivo micro‐environment and resulting in cells that are phenotypically closer to mature hepatocytes.
Background & Aims The peribiliary glands of large bile ducts have been identified as a niche of progenitor cells that contribute to regeneration of biliary epithelium after injury. We aimed to ...determine whether injury to the peribiliary glands of donor livers is a risk factor for development of non-anastomotic biliary strictures (NAS) after liver transplantation. Methods In 128 liver transplant procedures, biopsies were taken from the donor bile duct and injury was assessed using an established histological grading system. Histological severity of injury was subsequently compared in liver grafts that later developed biliary structures vs. uncomplicated liver grafts. Results Luminal biliary epithelial loss >50% was observed in 91.8% of the grafts before transplantation, yet NAS occurred in only 16.4%. Periluminal peribiliary glands were more severely injured than deep peribiliary glands located near the fibromuscular layer (>50% loss in 56.9% vs. 17.5%, respectively; p <0.001). Injury of deep peribiliary glands was more prevalent and more severe in livers that later developed NAS, compared to grafts without NAS (>50% loss in 50.0% vs. 9.8%, respectively; p = 0.004). In parallel, injury of the peribiliary vascular plexus was more severe in livers that developed NAS, compared to grafts without NAS (>50% vascular changes in 57.1% vs. 20.3%; p = 0.006). Conclusion Injury of peribiliary glands and vascular plexus before transplantation is strongly associated with the occurrence of biliary strictures after transplantation. This suggests that insufficient regeneration due to loss of peribiliary glands or impaired blood supply may explain the development of biliary strictures.
Prior observations suggest that foraminiferan protists use their reticulopodia (anastomosing pseudopodia) to alter sediment fabric by disrupting laminations of subtidal marine stromatolites, erasing ...the layered structures in an experimental setting. Because microbialites and foraminifera are found in non-marine settings, we hypothesized that foraminifera living in lakes could also disrupt layered microbialite fabric. With this aim and using a variety of multidisciplinary approaches, we conducted field surveys and an experiment on microbialites from Green Lake (GL; Fayetteville, New York State, United States), which has been studied as a Proterozoic ecosystem analog. The lake is meromictic and alkaline, receiving calcium sulfate-rich water in the monimolimnion; it supports a well-developed carbonate platform that provides access to living and relict microbialites. The living microbialites grow from early spring to autumn, forming a laminated mat at their surface (top ~5 mm), but a clotted or massive structure exists at depth (> ~ 1 cm). We observed a morphotype of "naked" foraminiferan-like protist in samples from GL microbialites and sediments; thus, considered the possibility of freshwater foraminiferan impact on microbialite fabric. Results of an experiment that seeded the cultured freshwater foraminifer
onto the GL microbialite surface indicates via micro-CT scanning and anisotropy analysis that the introduced foraminifer impacted uppermost microbialite layering (
= 3 cores); those cores with an added inhibitor lacked changes in anisotropy for two of those three cores. Thus, it remains plausible that the much smaller, relatively common, native free-form reticulate protist, which we identified as
, can disrupt microbialite fabrics on sub-millimeter scales. Our observations do not exclude contributions of other possible causal factors.
Arsenite (As(III)) contamination in drinking water has become a worldwide problem in recent years, which leads to development of various As(III) remediation approaches. In this study, two ...biomass-based nanostructured materials, microscale dialdehyde cellulose–cysteine (MDAC–cys) and nanoscale dialdehyde cellulose–cysteine (NDAC–cys) fibers, have been prepared from wood pulp. Their As(III) removal efficiencies and mechanism were determined by combined adsorption, atomic fluorescence spectrometry, microscopy (scanning electron microscopy, transmission electron microscopy, and atomic force microscopy), and spectroscopy (Fourier transform infrared, 13C CPMAS NMR) methods. The adsorption results of these materials could be well described by the Freundlich isotherm model, where the maximum adsorption capacities estimated by the Langmuir isotherm model were 344.82 mg/g for MDAC–cys and 357.14 mg/g for NDAC–cys, respectively. Both MDAC–cys and NDAC–cys materials were further characterized by X-ray diffraction and thermogravimetric analysis, where the results indicated that the thiol groups (the S content in MDAC–cys was 12.70 and NDAC–cys was 17.15%) on cysteine were primarily responsible for the adsorption process. The nanostructured MDAC–cys system appeared to be more suitable for practical applications because of its high cost-effectiveness.
There is a significant organ shortage in the field of liver transplantation, partly due to a high discard rate of steatotic livers from donors. These organs are known to function poorly if ...transplanted but make up a significant portion of the available pool of donated livers. This study demonstrates the ability to improve the function of steatotic rat livers using a combination of ex situ machine perfusion and a "defatting" drug cocktail. After 6 hours of perfusion, defatted livers demonstrated lower perfusate lactate levels and improved bile quality as demonstrated by higher bile bicarbonate and lower bile lactate. Furthermore, defatting was associated with decreased gene expression of pro-inflammatory cytokines and increased expression of enzymes involved in mitochondrial fatty acid oxidation. Rehabilitation of marginal or discarded steatotic livers using machine perfusion and tailored drug therapy can significantly increase the supply of donor livers for transplantation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The calanoid copepod Calanus finmarchicus is one of the most abundant and ecologically important species of the zooplankton assemblage of the North Atlantic Ocean and occupies a pivotal position in ...the pelagic food web. This study used metabarcoding analysis (high throughput DNA sequencing of target gene regions) to examine the diversity of the copepod gut content, including both eukaryotic and prokaryotic components of the diet and microbiome. Zooplankton samples were collected during the 2013 EuroBASIN cruise of the R/V G.O. Sars, which crossed the North Atlantic to survey in the Norwegian, Icelandic, Irminger, and Labrador Seas. Zooplankton samples were examined microscopically for C. finmarchicus; species identification was confirmed by genetic markers based on insertion-deletion sequence variation. DNA was extracted from the dissected gut contents of adult female copepods and sequenced for eukaryotic 18S V4 and prokaryotic 16S V3–V4 rRNA hypervariable regions. Prokaryotes identified in the gut contents of all copepods analyzed included Cyanobacteria, Proteobacteria, Bacteroidetes, Planctomycetes, Actinobacteria, and Acidobacteria. The eukaryotic gut content assemblage was diverse, dominated by Ocrophyta (diatoms), Dinophyta (dinoflagellates), Ciliophora (ciliates), as well as Cnidaria and Ctenophora. The diverse assemblage revealed by metabarcoding analysis of copepod gut contents likely represents prey, microbiome, parasites, symbionts, and pathogens. Significant differences in prokaryotic and eukaryotic diversity of the gut contents of copepods collected from four regional seas of the North Atlantic Ocean reflect and contribute to basin-scale differences in the pelagic food web of these ecosystems. This study provides evidence that diversity and variation of the copepod gut contents may both reflect and impact the functioning of pelagic food webs and regional variation in ocean ecosystems.
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