Postnatal development of depth-dependent collagen density in ovine articular cartilage

<p>Abstract</p> <p>Background</p> <p>Articular cartilage (AC) is the layer of tissue that covers the articulating ends of the bones in diarthrodial joints. Adult AC is characterised by a depth-dependent composition and structure of the extracellular matrix that results in depth-dependent mechanical properties, important for the functions of adult AC. Collagen is the most abundant solid component and it affects the mechanical behaviour of AC. The current objective is to quantify the postnatal development of depth-dependent collagen density in sheep (<it>Ovis aries</it>) AC between birth and maturity. We use Fourier transform infra-red micro-spectroscopy to investigate collagen density in 48 sheep divided over ten sample points between birth (stillborn) and maturity (72 weeks). In each animal, we investigate six anatomical sites (caudal, distal and rostral locations at the medial and lateral side of the joint) in the distal metacarpus of a fore leg and a hind leg.</p> <p>Results</p> <p>Collagen density increases from birth to maturity up to our last sample point (72 weeks). Collagen density increases at the articular surface from 0.23 g/ml ± 0.06 g/ml (mean ± s.d., <it>n </it>= 48) at 0 weeks to 0.51 g/ml ± 0.10 g/ml (<it>n </it>= 46) at 72 weeks. Maximum collagen density in the deeper cartilage increases from 0.39 g/ml ± 0.08 g/ml (<it>n </it>= 48) at 0 weeks to 0.91 g/ml ± 0.13 g/ml (<it>n </it>= 46) at 72 weeks. Most collagen density profiles at 0 weeks (85%) show a valley, indicating a minimum, in collagen density near the articular surface. At 72 weeks, only 17% of the collagen density profiles show a valley in collagen density near the articular surface. The fraction of profiles with this valley stabilises at 36 weeks.</p> <p>Conclusions</p> <p>Collagen density in articular cartilage increases in postnatal life with depth-dependent variation, and does not stabilize up to 72 weeks, the last sample point in our study. We find strong evidence for a valley in collagen densities near the articular surface that is present in the youngest animals, but that has disappeared in the oldest animals. We discuss that the retardance valley (as seen with polarised light microscopy) in perinatal animals reflects a decrease in collagen density, as well as a decrease in collagen fibril anisotropy.</p

Citizen science networks in natural history and the collective validation of biodiversity data

Biodiversity data are in increasing demand to inform policy and management. A substantialportion of these data is generated in citizen science networks. To ensure the quality of biodiversity data,standards and criteria for validation have been put in place. We used interviews and document analysis from the United Kingdom and The Netherlands to examine how data validation serves as a point of connection between the diverse people and practices in natural history citizen science networks. We found that rather than a unidirectional imposition of standards, validation was performed collectively. Specifically, it was enactedin ongoing circulations of biodiversity records between recorders and validators as they jointly negotiated the biodiversity that was observed and the validity of the records. These collective validation practices contributed to the citizen science character or natural history networks and tied these networks together. However, when biodiversity records were included in biodiversity-information initiatives on different policy levels and scales, the circulation of records diminished. These initiatives took on a more extractive mode of data use. Validation ceased to be collective with important consequences for the natural history networks involved and citizen science more generally

Opinie:Reductie van stikstof is niet genoeg, er moet meer natuur bij

De stikstofcrisis is een ecologische crisis, waarin behalve de reductie van stikstof ook pesticiden en verdroging moeten worden aangepakt en er vooral extra ruimte nodig is voor natuur

Doelwijziging Natura 2000: weer op zoek naar geitenpaadjes

In een nieuwe conceptrapportage over doelwijziging voor Natura2000-gebieden wordt door de overheid wederom gezocht naar mogelijkheden om de ambities voor natuurbehoud te minimaliseren, precies wat er in de afgelopen decennia is misgegaan. Dertig jaar nadat de Habitatrichtlijn is aangenomen, heeft Nederland de bescherming van natuurgebieden nog steeds niet op orde

Het belang van kritische depositiewaarden in het stikstofbeleid

Nederland heeft een enorme opgave om natuur te herstellen. Een forse vermindering van de stikstofdepositie is daarvoor noodzakelijk. In het stikstofbeleid speelt het begrip 'kritische depositiewaarde' een belangrijke rol. In dit artikel leggen we kort uit wat het begrip inhoudt en waarom het zo belangrijk is geworden

Colorful Protein-Based Fluorescent Probes for Collagen Imaging

<div><p>Real-time visualization of collagen is important in studies on tissue formation and remodeling in the research fields of developmental biology and tissue engineering. Our group has previously reported on a fluorescent probe for the specific imaging of collagen in live tissue <i>in situ</i>, consisting of the native collagen binding protein CNA35 labeled with fluorescent dye Oregon Green 488 (CNA35-OG488). The CNA35-OG488 probe has become widely used for collagen imaging. To allow for the use of CNA35-based probes in a broader range of applications, we here present a toolbox of six genetically-encoded collagen probes which are fusions of CNA35 to fluorescent proteins that span the visible spectrum: mTurquoise2, EGFP, mAmetrine, LSSmOrange, tdTomato and mCherry. While CNA35-OG488 requires a chemical conjugation step for labeling with the fluorescent dye, these protein-based probes can be easily produced in high yields by expression in <i>E. coli</i> and purified in one step using Ni²⁺-affinity chromatography. The probes all bind specifically to collagen, both <i>in vitro</i> and in porcine pericardial tissue. Some first applications of the probes are shown in multicolor imaging of engineered tissue and two-photon imaging of collagen in human skin. The fully-genetic encoding of the new probes makes them easily accessible to all scientists interested in collagen formation and remodeling.</p></div

Solid-phase collagen binding of FP-CNA35 and CNA35-FP probes.

<p>Normalized fluorescence emission of FP-CNA35 and CNA35-FP probes bound to surface-immobilized rat tail collagen type I or BSA. mTurquoise2-CNA35 and CNA35-mTurquoise2 (A), EGFP-CNA35 and CNA35-EGFP (B), mAmetrine-CNA35 and CNA35-mAmetrine (C), LSSmOrange-CNA35 and CNA35-LSSmOrange (D), tdTomato-CNA35 and CNA35-tdTomato (E), mCherry-CNA35 and CNA35-mCherry (F), CNA35-OG488 (G) were loaded on collagen (closed circle for N-terminal fusion, closed triangle for C-terminal fusion) or BSA (open circle for N-terminal fusion, open triangle for C-terminal fusion) that were immobilized in wells of a 96-well plate. Emission of the fluorescent proteins was measured at the indicated wavelengths when excited at the excitation maxima (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114983#pone-0114983-t001" target="_blank">Table 1</a>). Assays were performed in HEPES (pH 7.2), 150 mM NaCl. Binding of the FP-CNA35 and CNA35-FP probes to collagen was measured in triplicate. The binding experiments of all probes with BSA were performed in duplicate. Binding of CNA35-OG488 to collagen was also measured in duplicate. Error bars indicate ±1 SD.</p