Permeable (sandy) sediments cover half of the continental margin and are major regulators of oceanic carbon cycling. The microbial communities within these highly dynamic sediments frequently shift ...between oxic and anoxic states, and hence are less stratified than those in cohesive (muddy) sediments. A major question is, therefore, how these communities maintain metabolism during oxic-anoxic transitions. Here, we show that molecular hydrogen (H
) accumulates in silicate sand sediments due to decoupling of bacterial fermentation and respiration processes following anoxia. In situ measurements show that H
is 250-fold supersaturated in the water column overlying these sediments and has an isotopic composition consistent with fermentative production. Genome-resolved shotgun metagenomic profiling suggests that the sands harbour diverse and specialized microbial communities with a high abundance of NiFe-hydrogenase genes. Hydrogenase profiles predict that H
is primarily produced by facultatively fermentative bacteria, including the dominant gammaproteobacterial family Woeseiaceae, and can be consumed by aerobic respiratory bacteria. Flow-through reactor and slurry experiments consistently demonstrate that H
is rapidly produced by fermentation following anoxia, immediately consumed by aerobic respiration following reaeration and consumed by sulfate reduction only during prolonged anoxia. Hydrogenotrophic sulfur, nitrate and nitrite reducers were also detected, although contrary to previous hypotheses there was limited capacity for microalgal fermentation. In combination, these experiments confirm that fermentation dominates anoxic carbon mineralization in these permeable sediments and, in contrast to the case in cohesive sediments, is largely uncoupled from anaerobic respiration. Frequent changes in oxygen availability in these sediments may have selected for metabolically flexible bacteria while excluding strict anaerobes.
How teeth are replaced during normal growth and development has long been an important question for comparative and developmental anatomy. Non‐standard model animals have become increasingly popular ...in this field due to the fact that the canonical model laboratory mammal, the mouse, develops only one generation of teeth (monophyodonty), whereas the majority of mammals possess two generations of teeth (diphyodonty). Here we used the straw‐coloured fruit bat (Eidolon helvum), an Old World megabat, which has two generations of teeth, in order to observe the development and replacement of tooth germs from initiation up to mineralization stages. Our morphological study uses 3D reconstruction of histological sections to uncover differing arrangements of the first and second‐generation tooth germs during the process of tooth replacement. We show that both tooth germ generations develop as part of the dental lamina, with the first generation detaching from the lamina, leaving the free edge to give rise to a second generation. This separation was particularly marked at the third premolar locus, where the primary and replacement teeth become positioned side by side, unconnected by a lamina. The position of the replacement tooth, with respect to the primary tooth, varied within the mouth, with replacements forming posterior to or directly lingual to the primary tooth. Development of replacement teeth was arrested at some tooth positions and this appeared to be linked to the timing of tooth initiation and the subsequent rate of development. This study adds an additional species to the growing body of non‐model species used in the study of tooth replacement, and offers a new insight into the development of the diphyodont condition.
Nowadays, consumer’s awareness regarding edible and functional coatings used in the food industry is increasing because of their novel approach on prolonging the shelf life of agri-food products that ...during storage, are subjected to a loss of quality attributes, which inevitably contributes to food waste. In order to combat this problem, functional coatings and edible films can be used because of their capability to extend the shelf life of food products by providing gas and water barrier properties and delaying microbial spoilage. The aim of this study is to review the literature and outline the most recent findings and developments regarding edible and functional coatings used in the food industry. Functional and edible coatings can be applied on different types of food products, like meat products, different kinds of cheeses and fruits and vegetables. mainly because they help maintain the organoleptic proprieties, such as aroma, taste and appearance and prologue their shelf life. The new concept of functional coatings and edible packaging has significantly influenced the marketing and safety aspects of food products and further studies and developments are needed to improve these technologies
A new generation of scaffolds capable of acting not only as support for cells but also as a source of biological cues to promote tissue regeneration is currently a hot topic of in bone Tissue ...Engineering (TE) research. The inclusion of growth factor (GF) controlled release functionalities in the scaffolds is a possible strategy to achieve such goal. Platelet Lysate (PL) is an autologous source of GFs, providing several bioactive agents known to act on bone regeneration. In this study, chitosan-chondroitin sulfate nanoparticles loaded with PL were included in a poly(d,l-lactic acid) foam produced by supercritical fluid foaming. The tridimensional (3D) structures were then seeded with human adipose-derived stem cells (hASCs) and cultured in vitro under osteogenic stimulus. The osteogenic differentiation of the seeded hASCs was observed earlier for the PL-loaded constructs, as shown by the earlier alkaline phosphatase peak and calcium detection and stronger Runx2 expression at day 7 of culture, in comparison with the control scaffolds. Osteocalcin gene expression was upregulated in presence of PL during all culture period, which indicates an enhanced osteogenic induction. These results suggest the synergistic effect of PL and hASCs in combinatory TE strategies and support the potential of PL to increase the multifunctionality of the 3D hybrid construct for bone TE applications.
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The goal of the present paper is to explore the properties of medium molecular-weight chitosan/polyvinyl alcohol blends mixed in volume ratios of 75:25, 50:50, and 25:75 obtained by solution casting. ...Cross-linked chitosan/poly(vinyl alcohol) nanostructures were obtained by treating these blends with 5% (v/v) glutaraldehyde. The prepared chitosan/polyvinyl alcohol films were characterized by attenuated total reflectance - Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering, and cytotoxicity, while the nanostructured materials were examined by scanning electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction. Also, the removal of lead(II) ions from aqueous solution by adsorbents nanostructures was studied in the batch adsorption mode. The effects of adsorbent dosages, initial metal concentration, and contact time on the adsorption capacity were investigated. The FT-IR spectra indicated the interactions of polyvinyl alcohol with chitosan. DSC and TGA analyses revealed the loss of water up to 100 °C. The zeta potential and mobility of the prepared nanostructures were enhanced with the increasing ratio of the cationic polymer. The results showed that the 100% chitosan adsorbent provided the highest removal of Pb(II) during the first 15 min (̴94%). The chitosan100/polyvinyl alcohol0 and chitosan75/polyvinyl alcohol25 nanostructures fitted well with the Langmuir isotherm model. The maximum adsorption capacities for Pb(II) ions reached maxima of 7.36 and 7.67 mg/g, respectively. The Freundlich isotherm model best described the Pb(II) adsorption on the 50% chitosan/50% polyvinyl alcohol and 25% chitosan/75% polyvinyl alcohol adsorbents. Furthermore, (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay results demonstrated that chitosan/polyvinyl alcohol films are biocompatible with more than 90% cell viability.
Research on the role of values in science and objectivity has typically approached trust through its epistemic aspects. Yet, recent work on public trust in science has emphasized the role of ...non-epistemic values in building and maintaining trust. This paper will use a concept of trust that adds concerns about justice to epistemic conditions to investigate this problem in relation to public health. I will argue that trust-conducive values, particularly justice, are relevant in deciding which value influences are legitimate in scientific decision-making. Drawing on public health ethics, I will provide a consequentialist justification for employing trust-conducive values. While several concepts of justice have been explored in the context of public health, I will further draw on public health ethics, focusing on a view that brings together both distributive and procedural aspects. For illustration, I will use the case of cardiovascular disease prevention, particularly how concerns about justice apply when choosing between population-based and individual-based approaches.
International investment is protected by international law by setting the standards of legal treatment that host state governments have committed themselves to in their investment treaties. ...Therefore, these standards of protection must be respected even in times of crisis, regardless of the reason that generated it, the policy of attracting and maintaining an investment climate favorable to international investment being an attribute of each state. If he does not find adequate protection or if he cannot negotiate contracts adapted to these conditions, nothing can prevent an investor from changing the direction of his business, in order to protect the investment made. On the other side of the barricade, the states raise the shields of force majeure and necessity. Of course, it is preferable for the barricade to turninto a round table of cooperation. The issue of violating one or more standards by states is one of the most debated at the moment, as international arbitration practice has decisions that oblige states to significant compensation. In my study I used as a research method the interdependent introspection, analysis and synthesis through analogies developed in a comparative method.
Magnetic nanoparticles (MNPs) are attractive tools to overcome limitations of current regenerative medicine strategies, demonstrating potential to integrate therapeutic and diagnostic functionalities ...in highly controlled systems. In traditional tissue engineering (TE) approaches, the MNPs association with stem cells in a three-dimensional (3D) template offers the possibility to achieve a mechano-magnetic responsive system, enabling remote control actuation. Herein, we propose to study the role of MNPs integrated in κ-carrageenan (κC) hydrogels in the cellular response of human adipose-derived stem cells (hASCs) aiming at cartilage TE applications. The results indicated that the concentration of MNPs in the κC hydrogels influences cellular behavior, tuning a positive effect on cell viability, cell content and metabolic activity of hASCs, with the most promising outcomes found in 5% MNP-κC matrices. Although hASCs laden in MNPs-free- and MNPs-κC hydrogels showed similar metabolic and proliferation levels, MNPs κC hydrogels under magnetic actuation evidenced an instructive effect on hASCs, at a gene expression level, towards chondrogenic phenotype even in basic medium cultures. Therefore, the MNPs-based systems developed in this study may contribute to advanced strategies towards cartilage-like engineered substitutes.
The chitosan effect on the soil burial degradation of polylactic acid plasticized with tributyl o-acetyl citrate (ATBC) was studied by weight loss measurements, changes in average molecular weight ...and its distribution, mechanical, thermal and surface properties correlated with structural and morphological modifications. Besides the loss of transparency at the end of environmental degradation test, all composites became brittle. During degradation, Young modulus increases while elongation at break significantly decreased, mainly for the biocomposites with high content of chitosan which also showed a significant decrease of average molecular weight, increase of glass transition temperature and crystallinity degree values and decrease of cold crystallization and melting temperature when soil burial period is longer. The high content of chitosan led to increased hydrophilicity of biocomposite surfaces which favors interaction with moisture and attack of microorganisms. Chitosan as hydrophilic compound promotes the soil burial degradation of PLA. However, longer period of soil burial are necessary for totally degradation of the sheets of plasticized PLA/CS biocomposites.
During the formation of repetitive ectodermally derived organs such as mammary glands, lateral line and teeth, the tissue primordium iteratively initiates new structures. In the case of successional ...molar development, new teeth appear sequentially in the posterior region of the jaw from Sox2(+) cells in association with the posterior aspect of a pre-existing tooth. The sequence of molar development is well known, however, the epithelial topography involved in the formation of a new tooth is unclear. Here, we have examined the morphology of the molar dental epithelium and its development at different stages in the mouse in vivo and in molar explants. Using regional lineage tracing we show that within the posterior tail of the first molar the primordium for the second and third molar are organized in a row, with the tail remaining in connection with the surface, where a furrow is observed. The morphology and Sox2 expression of the tail retains characteristics reminiscent of the earlier stages of tooth development, such that position along the A-P axes of the tail correlates with different temporal stages. Sox9, a stem/progenitor cell marker in other organs, is expressed mainly in the suprabasal epithelium complementary with Sox2 expression. This Sox2 and Sox9 expressing molar tail contains actively proliferating cells with mitosis following an apico-basal direction. Snail2, a transcription factor implicated in cell migration, is expressed at high levels in the tip of the molar tail while E-cadherin and laminin are decreased. In conclusion, our studies propose a model in which the epithelium of the molar tail can grow by posterior movement of epithelial cells followed by infolding and stratification involving a population of Sox2(+)/Sox9(+) cells.
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