A Comprehensive Comparison of Bovine and Porcine Decellularized Pericardia: New Insights for Surgical Applications

Xenogeneic pericardium-based substitutes are employed for several surgical indications after chemical shielding, limiting their biocompatibility and therapeutic durability. Adverse responses to these replacements might be prevented by tissue decellularization, ideally removing cells and preserving the original extracellular matrix (ECM). The aim of this study was to compare the mostly applied pericardia in clinics, i.e., bovine and porcine tissues, after their decellularization, and obtain new insights for their possible surgical use. Bovine and porcine pericardia were submitted to TRICOL decellularization, based on osmotic shock, detergents and nuclease treatment. TRICOL procedure resulted in being effective in cell removal and preservation of ECM architecture of both species’ scaffolds. Collagen and elastin were retained but glycosaminoglycans were reduced, significantly for bovine scaffolds. Tissue hydration was varied by decellularization, with a rise for bovine pericardia and a decrease for porcine ones. TRICOL significantly increased porcine pericardial thickness, while a non-significant reduction was observed for the bovine counterpart. The protein secondary structure and thermal denaturation profile of both species’ scaffolds were unaltered. Both pericardial tissues showed augmented biomechanical compliance after decellularization. The ECM bioactivity of bovine and porcine pericardia was unaffected by decellularization, sustaining viability and proliferation of human mesenchymal stem cells and endothelial cells. In conclusion, decellularized bovine and porcine pericardia demonstrate possessing the characteristics that are suitable for the creation of novel scaffolds for reconstruction or replacement: differences in water content, thickness and glycosaminoglycans might influence some of their biomechanical properties and, hence, their indication for surgical use.

Exact Solution to the Extended Zwanzig Model for Quasi-Sigmoidal Chemically Induced Denaturation Profiles: Specific Heat and Configurational Entropy

Temperature and chemically induced denaturation comprise two of the most characteristic mechanisms to achieve the passage from the native state N to any of the unstructured states Dj in the denatured ensemble in proteins and peptides. In this work we present a full analytical solution for the configurational partition function 𝒵qs of a homopolymer chain poly-X in the extended Zwanzig model (EZM) for a quasisigmoidal denaturation profile. This solution is built up from an EZM exact solution in the case where the fraction α of native contacts follows exact linear dependence on denaturant’s concentration ζ; thus an analytical solution for 𝒵L in the case of an exact linear denaturation profile is also provided. A recently established connection between the number ν of potential nonnative conformations per residue and temperature-independent helical propensity ω complements the model in order to identify specific proteinogenic poly-X chains, where X represents any of the twenty naturally occurring aminoacid residues. From 𝒵qs, equilibrium thermodynamic potentials like entropy 𝒮 and average internal energy 〈E〉 and thermodynamic susceptibilities like specific heat C𝓋 are calculated for poly-valine (poly-V) and poly-alanine (poly-A) chains. The influence of the rate at which native contacts denature as function of ζ on thermodynamic stability is also discussed.

Characterization of matrix metalloprotease activities induced in the sea urchin extraembryonic matrix, the hyaline layer

Hyaline layers, freshly prepared from one-hour-old embryos, were devoid of gelatin-cleavage activity. However, upon storage at 4°C, gelatin-cleavage activities appeared; three species of apparent mol mass 94[Formula: see text]117-, 90-, and 45-kDa were seen. All three species required zinc for activity. Using gel-exclusion chromatography we separated the 94[Formula: see text]117-, and 90-kDa species from the 45-kDa activity. The two higher mol mass species were inhibited by ethylenebis (oxyethylenenitrilo) tetraacetic acid and the lost activity was restored by calcium. Reconstitution of activity occurred with an apparent dissociation constant (calcium) of 5 µM. The presence of millimolar concentrations of magnesium had a minimal inhibitory effect on activity. The thermal denaturation profile of the higher mol mass gelatin-cleavage activity was significantly different in the presence and absence of calcium. Stabilization of these activities against thermal denaturation at 60°C occurred with an apparent dissociation constant (calcium) of 0.6 mM. Magnesium had no significant effect on the thermal denaturation profile. Collectively, these results suggest at least two different modes of interaction between calcium and the higher mol mass gelatinases. These conclusions are discussed in the context of the high calcium and magnesium concentrations present in the sea water environment of the sea urchin embryo.Key words: sea urchin, embryo, matrix metalloprotease, calcium.

Analysis of plant genomes. IV. Isolation and characterization of satellite DNA components from two dicotyledons cucumber (Cucumis sativus) and radish (Raphanus sativus)

Satellite DNA fractions from cucumber and radish, two plants having low DNA contents and relatively small chromosomes, were isolated and characterized. Reassociation studies of satellite and total nuclear DNA showed that the satellite fractions in these two plants contain most of the rapidly reassociating DNA. Cucumber satellite I was found to contain one major component (70% of the total satellite) having a density of 1.706 g/cm3 and a Tm of 90.5 °C and a minor component with a density of 1.712 g/cm3 and a Tm of 93.5 °C. The complexity of the major component was estimated to be 3.8 × 105 daltons while that of the minor one was 12.9 × 107 daltons. Although cucumber satellite II banded as a single peak at adensity of 1.700 g/cm3 in neutral CsCl gradients, it was observed to have a rather broad denaturation profile with a Tm of 86.5 °C. Its Cot curve was also broader than that of satellite I and one of its components (40% of the total) had a complexity of 5.8 × 105 daltons. Two satellite fractions were also observed in the case of radish DNA but only satellite I was isolated in a pure form and characterized. This radish satellite formed a sharp, symmetrical peak at a density of 1.698 g/cm3 in neutral CsCl gradients and underwent denaturation in a narrow temperature range of 6 to 7 °C. An analysis of the optical reassociation kinetics showed that this satellite contained a major and a minor component. The major component, which comprised 80% of the satellite, had a complexity of 12.9 × 105 daltons. Hybridization experiments revealed that the ribosomal DNA was present in satellite II.