14 research outputs found
Functionalisation of PLLA nanofiber scaffolds using a possible cooperative effect between collagen type I and BMP-2: impact on growth and osteogenic differentiation of human mesenchymal stem cells
Mesenchymal stem cell differentiation of osteoblasts is triggered by a series of signaling processes including integrin and bone morphogenetic protein (BMP), which therefore act in a cooperative manner. The aim of this study was to analyze whether these processes can be remodeled in an artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffold. Matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen type I were seeded with human mesenchymal stem cells (hMSC) and cultivated over a period of 22Ā days, either under growth or osteoinductive conditions. During the course of culture, gene expression of alkaline phosphatase (ALP), osteocalcin (OC) and collagen I (COL-I) as well as Smad5 and focal adhesion kinase (FAK), two signal transduction molecules involved in BMP-2 or integrin signaling were analyzed. Furthermore, calcium and collagen I deposition, as well as cell densities and proliferation, were determined using fluorescence microscopy. The incorporation of BMP-2 into PLLA-collagen type I nanofibers resulted in a decrease in diameter as well as pore sizes of the scaffold. Mesenchymal stem cells showed better adherence and a reduced proliferation on BMP-containing scaffolds. This was accompanied by an increase in gene expression of ALP, OC and COL-I. Furthermore the presence of BMP-2 resulted in an upregulation of FAK, while collagen had an impact on the gene expression of Smad5. Therefore these different strategies can be combined in order to enhance the osteoblast differentiation of hMSC on PLLA based nanofiber scaffold. By doing this, different signal transduction pathways seem to be up regulated
How useful could Arabic documentary sources be for reconstructing past climate?
Trees, corals, ice cores and documentary
evidence provide high-resolution proxies
that allow past climate to be reconstructed
(Jones et al., 2009). Documentary evidence
includes all forms of written historical information
about past climate or weather, but
its use for climate reconstruction is restricted
to locations for which there is a rich documentary
legacy. Several climate analyses
and reconstructions have been undertaken
using documentary evidence from Europe
(BrƔzdil et al., 2005; 2010), North and South
America (Dupigny-Giroux and Mock, 2009;
Prieto and GarcĆa-Herrera, 2009; Neukom
et al., 2010), Asia (Ge et al., 2005; 2010; Aono
and Kazui, 2008; Hirano and Mikami, 2008)
and oceanic areas (GarcĆa-Herrera et al.,
2005). The Islamic World is a region for
which such sources could also be used to
reconstruct past climate, as indeed they
have been widely used for astronomy and
geophysics. Astronomers have used the
observations made by Arab astronomers for
centuries, with some remarkable examples.
Historical eclipse observations, recorded by
various ancient and mediaeval cultures
including Arabs, have enabled changes in
the Earthās rate of rotation to be monitored
with fair precision as far back as around
700 AD (Stephenson, 2003). Rada and
Stephenson (1992) catalogued meteor
showers using mediaeval Arab chronicles
and Ahn (2003) investigated the spatial distribution
of meteor streams crossing the orbit of the Earth from the tenth to the fourteenth
centuries using chronicles from
Korea, Japan, China, Arabia and Europe.
Documentary sources from Iberia have been
used to identify and date such astronomical
phenomena as eclipses and comets (Vernet,
1982), naked-eye sunspots (Vaquero and
Gallego, 2002) and aurora sightings
(Vaquero and Gallego, 2001). The work of
Basurah (2006) provides descriptions for 18
aurora displays on various dates at low latitudes
in the Mediterranean area taken from
Islamic chronicles (ninth to sixteenth centuries).
In seismology, Arabic chronicles
were extensively used to prepare the
Seismic Catalogue of the Iberian Peninsula
(MartĆnez and Mezcua, 2002) and to study
seismic activity in Syria and Palestine
(Ambraseseys, 2005).
However, the use of these sources to
recover climate information is, to the best
of our knowledge, still very limited (Bulliet,
2009; Jones et al., 2009). Here we describe
a preliminary inquiry based on Arabic documentary
sources from Iraq. We would stress
the antiquity of the documents used, with
dates in the period 816ā1009 AD. The
sources consulted are Arabic chronicles that
narrate the social, political and religious history
of different regions in a form very characteristic
of Arab culture.Peer reviewe