100 research outputs found
More maximal arcs in Desarguesian projective planes and their geometric structure
In a previous paper R. Mathon gave a new construction method for maximal arcs in finite Desarguesian projective planes via closed sets of conics, as well as giving many new examples of maximal arcs. In the current paper, new classes of maximal arcs are constructed, and it is shown that every maximal arc so constructed gives rise to an infinite class of maximal arcs. Apart from when they are of Denniston type or dual hyperovals, closed sets of conics are shown to give maximal arcs that are not isomorphic to the known constructions. An easy characterisation of when a closed set of conics is of Denniston type is given. Results on the geometric structure of the maximal arcs and their duals are proved, as well as on elements of their collineation stabilisers
In vitro and in vivo biological performance of modified gellan gum-based hydrogels for nucleus pulposus tissue engineering
Ionic- (iGG-MA) and photo-crosslinked (phGG-MA) methacrylated
gellan gum hydrogels have been proposed as biomaterials for supporting
nucleus pulposus (NP) regeneration and/or repair. In this study, the
mechanical stability and biocompatibility of these hydrogels have been
evaluated in vitro. Human intervertebral disc cells obtained from herniated
patients were cultured within both hydrogels, for 1–21 days.
Dynamic mechanical analysis and biological characterization (Live/ Dead assay, ATP and DNA quantification, PCR and immunocytochemistry)
were performed after specific times of culturing. The in vitro study
showed that both cell loading and culturing time do not affect the
mechanical properties of hydrogels. In addition, the iGG-MA and
phGG-MA hydrogels showed to be effective on supporting cells encapsulation
and viability up to 21 days of culturing. In vivo biocompatibility
screening was also performed, by subcutaneous implantation of
both hydrogels in Lewis rats for the period of 10 and 18 days. Haematoxylin
& eosin staining revealed that the hydrogels do not elicit necrosis,
calcification or acute inflammatory reaction. The present study
demonstrates that the iGG-MA and phGG-MA hydrogels support cells
encapsulation and viability, and are well-tolerated, stable and non-cytotoxic
in vitro and in vivo, thus possessing promising features for finding
application as viable NP substitutes
Mechanical performance and biocompatibility study of methacrylated Gellan gum hydrogels with potential for nucleus pulposus regeneration
Methacrylated gellan gum hydrogels, obtained either by ionic- (iGGMA)
and photo-crosslinking (phGG-MA), have been investigated as
potential biomaterials for supporting nucleus pulposus (NP) regeneration
and/or repair [1,2]. In previous work, some advantages were
attributed to GG-MA hydrogels, such as: (i) the possibility to control
endothelial cells infiltration and blood vessel ingrowth’s, (ii) tunable
and improved mechanical properties, and (iii) in situ gelation, within
seconds to few minutes. In this study, the mechanical and biological
performance of these hydrogels was firstly evaluated in vitro. Human
intervertebral disc (hIVD) cells obtained from herniated patients were
cultured within both hydrogels, for 1 up to 21 days. Dynamic mechanical
analysis and biological characterization (calcein-AM staining, ATP
and DNA quantification and PCR) were performed after specific times
of culturing. A biocompatibility study was also performed in vivo, by
subcutaneous implantation of acellular iGG-MA and phGG-MA hydrogels
in Lewis rats for the period of 10 and 18 days. Tissue response to
the hydrogels implantation was determined by histological analysis
(haematoxylin-eosin staining). The in vitro study showed that both cell
loading and culturing time do not have an effect on the mechanical
properties of the hydrogels. Regarding their biological performance,
the iGG-MA and phGG-MA hydrogels showed to be effective on supporting
hIVD cells encapsulation and viability up to 21 days of culturing.
Human IVD cells were homogeneously distributed within the
hydrogels and maintained its round-shape morphology during culturing
time. The in vivo biocompatibility study showed that iGG-MA and
phGG-MA hydrogels do not elicit any deleterious effect, as denoted by
the absence of necrosis and calcification, or acute inflammatory reaction.
A thin fibrous capsule was observed around the implanted hydrogels.
The results presented in this study indicate that the iGG-MA and
phGG-MA hydrogels are stable in vitro and in vivo, support hIVD cells
encapsulation and viability, and were found to be well-tolerated and
non-cytotoxic in vivo, thus being potential candidates for NP regeneration
In vitro concurrent endothelial and osteogenic commitment of adipose-derived stem cells and their genomical analyses through CGH array: novel strategies to increase the succesfull engraftement of a tissue engineered bone grafts
In the field of tissue engineering, adult stem cells are increasingly recognized as an important tool for in vitro reconstructed tissue-engineered grafts. In the world of cell therapies, mesenchymal stem cells from bone marrow or adipose tissue are undoubtedly the most promising progenitors for tissue engineering applications. In this setting, adipose-derived stem cells (ASC) are generally similar to those derived from bone marrow and are most conveniently extracted from tissue removed in elective cosmetic liposuction procedures; they also show a great potential for endothelization. The aim of the present work was to investigate how the co-commitment into a vascular and bone phenotype of ASC could be a usefull tools for improving the in vitro and in vivo reconstruction of a vascularized bone graft. Human ASC obtained from abdominoplasty procedures were loaded in a hydroxyapatite clinical-grade scaffold, co-differentiated and tested for proliferation, cell distribution, and osteogenic and vasculogenic gene expression. The chromosomal stability of the cultures was investigated using the CGH array for 3D cultures. ASC adhesion, distribution, proliferation and gene expression not only demonstrated a full osteogenic and vasculogenic commitment in vitro and in vivo, but also showed that endothelization strongly improves their osteogenic commitment. In the end, genetic analyses confirmed that no genomical alteration in long-term in vitro culture of ASC in 3D scaffolds occurs
Dietary soy and meat proteins induce distinct physiological and gene expression changes in rats
This study reports on a comprehensive comparison of the effects of soy and meat proteins given at the recommended level on physiological markers of metabolic syndrome and the hepatic transcriptome. Male rats were fed semi-synthetic diets for 1 wk that differed only regarding protein source, with casein serving as reference. Body weight gain and adipose tissue mass were significantly reduced by soy but not meat proteins. The insulin resistance index was improved by soy, and to a lesser extent by meat proteins. Liver triacylglycerol contents were reduced by both protein sources, which coincided with increased plasma triacylglycerol concentrations. Both soy and meat proteins changed plasma amino acid patterns. The expression of 1571 and 1369 genes were altered by soy and meat proteins respectively. Functional classification revealed that lipid, energy and amino acid metabolic pathways, as well as insulin signaling pathways were regulated differently by soy and meat proteins. Several transcriptional regulators, including NFE2L2, ATF4, Srebf1 and Rictor were identified as potential key upstream regulators. These results suggest that soy and meat proteins induce distinct physiological and gene expression responses in rats and provide novel evidence and suggestions for the health effects of different protein sources in human diets
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