100 research outputs found
A standalone bioreactor system to deliver compressive load under perfusion flow to hBMSC-seeded 3D chitosan-graphene templates
The availability of engineered biological tissues holds great potential for both clinical applications and basic research in a life science laboratory. A prototype standalone perfusion/compression bioreactor system was proposed to address the osteogenic commitment of stem cells seeded onboard of 3D chitosan-graphene (CHT/G) templates. Testing involved the coordinated administration of a 1 mL/min medium flow rate together with dynamic compression (1% strain at 1 Hz; applied twice daily for 30 min) for one week. When compared to traditional static culture conditions, the application of perfusion and compression stimuli to human bone marrow stem cells using the 3D CHT/G template scaffold induced a sizable effect. After using the dynamic culture protocol, there was evidence of a larger number of viable cells within the inner core of the scaffold and of enhanced extracellular matrix mineralization. These observations show that our novel device would be suitable for addressing and investigating the osteogenic phenotype commitment of stem cells, for both potential clinical applications and basic research
Human Bone-Marrow-Derived Stem-Cell-Seeded 3D Chitosan–Gelatin–Genipin Scaffolds Show Enhanced Extracellular Matrix Mineralization When Cultured under a Perfusion Flow in Osteogenic Medium
Tissue-engineered bone tissue grafts are a promising alternative to the more conventional use of natural donor bone grafts. However, choosing an appropriate biomaterial/scaffold to sustain cell survival, proliferation, and differentiation in a 3D environment remains one of the most critical issues in this domain. Recently, chitosan/gelatin/genipin (CGG) hybrid scaffolds have been proven as a more suitable environment to induce osteogenic commitment in undifferentiated cells when doped with graphene oxide (GO). Some concern is, however, raised towards the use of graphene and graphene-related material in medical applications. The purpose of this work was thus to check if the osteogenic potential of CGG scaffolds without added GO could be increased by improving the medium diffusion in a 3D culture of differentiating cells. To this aim, the level of extracellular matrix (ECM) mineralization was evaluated in human bone-marrow-derived stem cell (hBMSC)-seeded 3D CGG scaffolds upon culture under a perfusion flow in a dedicated custom-made bioreactor system. One week after initiating dynamic culture, histological/histochemical evaluations of CGG scaffolds were carried out to analyze the early osteogenic commitment of the culture. The analyses show the enhanced ECM mineralization of the 3D perfused culture compared to the static counterpart. The results of this investigation reveal a new perspective on more efficient clinical applications of CGG scaffolds without added GO
Distribution and abundance of long-finned pilot whales in the North Atlantic, estimated from NASS-87 and NASS-89 data
During the summers of 1987 and 1989, large scale transect surveys were conducted
throughout the North Atlantic by several national agencies in Denmark (off Greenland),
Faroe Islands, Iceland, Norway and Spain (North Atlantic Sightings Surveys, NASS-87 and
NASS-89). This paper analyses the pilot whale (Globicephala melas) survey data collected by
three Icelandic and one Faroese survey vessel in 1987, and four Icelandic, one Faroese and
one Spanish vessel in 1989. Norwegian survey vessels operated north and east of this area in
both years, but only five groups (three primary sightings) were observed in 1989 and none in
1987. Furthermore, no sightings were made in the area north and northeast of Iceland, thus
indicating that the joint surveys covered the northernmost areas of pilot whale distribution
east of 42°W. The area further to the west was not covered in either survey. The coastal
European waters between 42-52°N were covered by the Spanish vessel in 1989. Sightings
made in 1989 by the Icelandic vessels tended to be at the southernmost boundaries of the
survey area.
The present data were examined with respect to several potential stratification factors,
namely geographic block, Beaufort (i.e. wind speed), vessel and school size, but sample size
precluded stratification by all these factors simultaneously. The encounter rate was generally
lower in the 1987 survey than in 1989, but the difference was not statistically significant. The
total estimate for the 1989 survey, covering a wider area and further to the south than in 1987,
was 778,000 (CV=0.295). This is regarded as the best available estimate of the total stock of
long-finned pilot whales in the northeastern North Atlantic Ocean, although small numbers
occur outside the NASS survey areas. The paper discusses potential biases in the abundance
estimates, and the problems of estimating pilot whale abundance from sightings data
Distribution of mtDNA haplotypes in North-Atlantic humpback whales:The influence of behavior on population structure
Samples from 136 humpback whales Megaptera novaeangliae, representing 5 feeding aggregations in the North Atlantic and 1 in the Antarctic, were analyzed with respect to the sequence variation in the mitochondrial (mt) control region. A total of 288 base pairs was sequenced by direct sequencing of asymmetrically amplified DNA. Thirty-one different haplotypes were identified. The nucleotide diversity for the total sample was estimated to be 2.6 %, which is high relative to other North Atlantic cetaceans. The degree of genetic differentiation in various subsets of the samples was estimated and tested for statistical significance by Monte Carlo simulations. Significant degrees of heterogeneity were found between the Antarctic and all North Atlantic areas, as well as between Iceland and the western North Atlantic samples. A genealogical tree was estimated for the 31 haplotypes and rooted with the homologous sequence from a fin whale Balaenoptera physalus. The branching pattern in the genealogical tree suggests that the North Atlantic Ocean has been populated by 2 independent influxes of humpback whales. The combined results from the homogeneity tests and the genealogical tree indicate that behaviour (in this case maternally directed site fidelity to a foraging area) can influence the population structure of marine cetaceans on an evolutionary time scale
Distribution of mtDNA haplotypes in North-Atlantic humpback whales:The influence of behavior on population structure
Samples from 136 humpback whales Megaptera novaeangliae, representing 5 feeding aggregations in the North Atlantic and 1 in the Antarctic, were analyzed with respect to the sequence variation in the mitochondrial (mt) control region. A total of 288 base pairs was sequenced by direct sequencing of asymmetrically amplified DNA. Thirty-one different haplotypes were identified. The nucleotide diversity for the total sample was estimated to be 2.6 %, which is high relative to other North Atlantic cetaceans. The degree of genetic differentiation in various subsets of the samples was estimated and tested for statistical significance by Monte Carlo simulations. Significant degrees of heterogeneity were found between the Antarctic and all North Atlantic areas, as well as between Iceland and the western North Atlantic samples. A genealogical tree was estimated for the 31 haplotypes and rooted with the homologous sequence from a fin whale Balaenoptera physalus. The branching pattern in the genealogical tree suggests that the North Atlantic Ocean has been populated by 2 independent influxes of humpback whales. The combined results from the homogeneity tests and the genealogical tree indicate that behaviour (in this case maternally directed site fidelity to a foraging area) can influence the population structure of marine cetaceans on an evolutionary time scale
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