Functional small-diameter neovessels created using endothelial progenitor cells expanded ex vivo

Arterial conduits are increasingly preferred for surgical bypass because of inherent functional properties conferred by arterial endothelial cells, especially nitric oxide production in response to physiologic stimuli. Here we tested whether endothelial progenitor cells (EPCs) can replace arterial endothelial cells and promote patency in tissue-engineered small-diameter blood vessels (4 mm). We isolated EPCs from peripheral blood of sheep, expanded them ex vivo and then seeded them on decellularized porcine iliac vessels. EPC-seeded grafts remained patent for 130 days as a carotid interposition graft in sheep, whereas non-seeded grafts occluded within 15 days. The EPC-explanted grafts exhibited contractile activity and nitric-oxide-mediated vascular relaxation that were similar to native carotid arteries. These results indicate that EPCs can function similarly to arterial endothelial cells and thereby confer longer vascular-graft survival. Due to their unique properties, EPCs might have other general applications for tissue-engineered structures and in treating vascular diseases.     

Hereditäre Chondrocalcinosis Articularis

Zusammenfassung Die Chondrocalcinosis articularis ist eine genetisch determinierte Krankheit, die mit charakteristischen Verkalkungen der hyalinen und fibrösen Knorpel einhergeht. Es wird über eine Untersuchung von fünf Personen einer Familie aus zwei Generationen berichtet, von denen vier Personen erkrankt sind.

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A family is reported with inherited Chondrocalcinosis articularis. Of the 5 family members studied, 4 had this disease. Three of these cases belonged to the first generation, one to the second. The disease is clinically manifested by episodic inflammatory involvement, acute or subacute, of one or more joints. The pathognomonic criterion for the diagnosis is the radiographic evidence of calcified hyalin and fibrous cartilage particularly in the large joints. In the articular cartilage a dense narrow band, continuous or discontinuous, followed the contur of the epiphysis. In the fibrocartilage, as seen in menisci or symphysis pubis, the calcification is more diffuse and of granular nature. The pathophysiology is unknown but it should be noted, that most cases of articular chondrocalcinosis give no evidence of a disturbance of the calcium or phosphorus metabolism. The chondrocalcinosis is an hereditary disease, but up to date it is impossible to define the type of hereditary transmission exactly. An autosomal dominant gene is the most polable explanation to date.

     

Identification of the RNA polymerase II subunit hsRPB7 as a novel target of the von Hippel-Lindau protein

Inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene is linked to the hereditary VHL disease and sporadic clear cell renal cell carcinomas (CCRCC). VHL-associated tumors are highly vascularized, a characteristic associated with overproduction of vascular endothelial growth factor (VEGF). The VHL protein (pVHL) is a component of the ubiquitin ligase E3 complex, targeting substrate proteins for ubiquitylation and subsequent proteasomic degradation. Here, we report that the pVHL can directly bind to the human RNA polymerase II seventh subunit (hsRPB7) through its beta-domain, and naturally occurring beta-domain mutations can decrease the binding of pVHL to hsRPB7. Introducing wild-type pVHL into human kidney tumor cell lines carrying endogenous mutant non-functional pVHL facilitates ubiquitylation and proteasomal degradation of hsRPB7, and decreases its nuclear accumulation. pVHL can also suppress hsRPB7-induced VEGF promoter transactivation, mRNA expression and VEGF protein secretion. Together, our results suggest that hsRPB7 is a downstream target of the VHL ubiquitylating complex and pVHL may regulate angiogenesis by targeting hsRPB7 for degradation via the ubiquitylation pathway and preventing VEGF expression.     

Combining population genetics and demographical approaches in evolutionary studies of plant mating systems

The striking amount of variation in the mating systems of higher plants has stimulated fruitful research by both ecologists and population geneticists. Historically, these two schools of thought have developed independent theoretical treatments and empirical approaches to account for the evolution of such diversity. We highlight the approach adopted by each field. Population geneticists have developed an approach centred on gene properties of individuals and their role on the evolution of self-fertilisation (transmission rules and the deleterious role of mutations), while ecologists have mostly focused on demographic properties of self-fertilisation (seed production, colonisation ability of selfers). As a result, the two approaches sometimes use conflicting notions of fitness. The recent empirical advances on inbreeding depression, a topic typically motivated by population genetic questions, have emphasized the need to adopt a demographical perspective for fitness. In this paper, we suggest generalizing this approach in mating system evolution and we expect further improvements by integrating demographic and genetics perspectives.     

MethyLight droplet digital PCR for detection and absolute quantification of infrequently methylated alleles

Aberrant DNA methylation is a common epigenetic alteration found in colorectal adenomas and cancers and plays a role in cancer initiation and progression. Aberrantly methylated DNA loci can also be found infrequently present in normal colon tissue, where they seem to have potential to be used as colorectal cancer (CRC) risk biomarkers. However, detection and precise quantification of the infrequent methylation events seen in normal colon is likely beyond the capability of commonly used PCR technologies. To determine the potential for methylated DNA loci as CRC risk biomarkers, we developed MethyLight droplet digital PCR (ddPCR) assays and compared their performance to the widely used conventional MethyLight PCR. Our analyses demonstrated the capacity of MethyLight ddPCR to detect a single methylated NTRK3 allele from among more than 3125 unmethylated alleles, 25-fold more sensitive than conventional MethyLight PCR. The MethyLight ddPCR assay detected as little as 19 and 38 haploid genome equivalents of methylated EVL and methylated NTRK3, respectively, which far exceeded conventional MethyLight PCR (379 haploid genome equivalents for both genes). When assessing methylated EVL levels in CRC tissue samples, MethyLight ddPCR reduced coefficients of variation (CV) to 6–65% of CVs seen with conventional MethyLight PCR. Importantly, we showed the ability of MethyLight ddPCR to detect infrequently methylated EVL alleles in normal colon mucosa samples that could not be detected by conventional MethyLight PCR. This study suggests that the sensitivity and precision of methylation detection by MethyLight ddPCR enhances the potential of methylated alleles for use as CRC risk biomarkers.     

In Vitro Measurement and Modeling of Platelet Adhesion on VWF-Coated Surfaces in Channel Flow

The process of platelet adhesion is initiated by glycoprotein (GP)Ib and GPIIbIIIa receptors on the platelet surface binding with von Willebrand factor on the vascular walls. This initial adhesion and detachment of a single platelet is a complex process that involves multiple bonds forming and breaking and is strongly influenced by the surrounding blood-flow environment. In addition to bond-level kinetics, external factors such as shear rate, hematocrit, and GPIb and GPIIbIIIa receptor densities have also been identified as influencing the platelet-level rate constants in separate studies, but this still leaves a gap in understanding between these two length scales. In this study, we investigate the fundamental relationship of the dynamics of platelet adhesion, including these interrelating factors, using a coherent strategy. We build a, to our knowledge, novel and computationally efficient multiscale model accounting for multibond kinetics and hydrodynamic effects due to the flow of a cellular suspension. The model predictions of platelet-level kinetics are verified by our microfluidic experiments, which systematically investigate the role of each external factor on platelet adhesion in an in vitro setting. We derive quantitative formulas describing how the rates of platelet adhesion, translocation, and detachment are defined by the molecular-level kinetic constants, the local platelet concentration near the reactive surface determined by red-blood-cell migration, the platelet effective reactive area due to its tumbling motion, and the platelet surface receptor density. Furthermore, if any of these aspects involved have abnormalities, e.g., in a disease condition, our findings also have clinical relevance in predicting the resulting change in the adhesion dynamics, which is essential to hemostasis and thrombosis.     

Relationships in a simple harmonic mean two-sex fertility model

A continuous time two-sex stable population model that does not recognize age is examined under the “harmonic mean” consistency condition of equation (2). Solutions for the stable population intrinsic growth rate r and the sex composition 5 are presented in equations (5) and (6). The process of stabilization is examined, and it is shown that, given two basic constraints, any initial population sex composition will eventually converge to the stable population value. An algebraic solution for the discrete case where the sex ratio at birth is unity is presented and used to describe the trajectory to stability of several hypothetical populations. A closed form algebraic expression for the trajectory to stability is presented for the continuous model in the special case of no mortality.