23 research outputs found
Biochemical markers of type II collagen breakdown and synthesis are positioned at specific sites in human osteoarthritic knee cartilage
SummaryObjectiveTo investigate whether type II collagen turnover markers used for osteoarthritis (OA) activity evaluation in body fluids can be detected at the level of specific histological features of OA cartilage tissue, as well as how they relate with each other at this level.MethodsAdjacent sections were obtained from full-depth cartilage biopsies from 32 OA knees. Immunohistochemistry was performed for Helix-II and CTX-II, which are type II collagen fragments originating from the triple helix and the telopeptide region, respectively, and believed to reflect distinct breakdown events, as well as for type IIA N propeptide (PIIANP), a biochemical marker reflecting synthesis of type IIA collagen.ResultsHelix-II and CTX-II were detected in areas where collagen damage was reported previously, most frequently around chondrocytes, but also frequently in regions not previously investigated such as the margin area and close to subchondral bone, including vascularization sites and bone–cartilage interface. The latter is CTX-II's prevailing position and shows rarely Helix-II. PIIANP co-localized with Helix-II and CTX-II on a limited number of features, mainly in deep zone cartilage. Overall, our analysis highlights clear patterns of association of the markers with specific histological features, and shows that they spread to these features in an ordered way.ConclusionHelix-II and CTX-II show to some degree differential selectivity for specific features in cartilage tissue. CTX-II detection close to bone may be relevant to the possible role of subchondral bone in OA. The restricted co-localization of breakdown markers and PIIANP suggests that collagen fragments can result only partially from newly synthesized collagen. Our study strengthens the interest for the question whether combining several markers reflecting different regional cartilage contributions or metabolic processes should allow a broader detection of OA activity
Conductance anomalies and the extended Anderson model for nearly perfect quantum wires
Anomalies near the conductance threshold of nearly perfect semiconductor
quantum wires are explained in terms of singlet and triplet resonances of
conduction electrons with a single weakly-bound electron in the wire. This is
shown to be a universal effect for a wide range of situations in which the
effective single-electron confinement is weak. The robustness of this generic
behavior is investigated numerically for a wide range of shapes and sizes of
cylindrical wires with a bulge. The dependence on gate voltage, source-drain
voltage and magnetic field is discussed within the framework of an extended
Hubbard model. This model is mapped onto an extended Anderson model, which in
the limit of low temperatures is expected to lead to Kondo resonance physics
and pronounced many-body effects
Phonon driven transport in amorphous semiconductors: Transition probabilities
Inspired by Holstein's work on small polaron hopping, the evolution equations
of localized states and extended states in presence of atomic vibrations are
derived for an amorphous semiconductor. The transition probabilities are
obtained for four types of transitions: from one localized state to another
localized state, from a localized state to an extended state, from an extended
state to a localized state, and from one extended state to another extended
state. At a temperature not too low, any process involving localized state is
activated. The computed mobility of the transitions between localized states
agrees with the observed `hopping mobility'. We suggest that the observed
`drift mobility' originates from the transitions from localized states to
extended states. Analysis of the transition probability from an extended state
to a localized state suggests that there exists a short-lifetime belt of
extended states inside conduction band or valence band. It agrees with the fact
that photoluminescence lifetime decreases with frequency in a-Si/SiO
quantum well while photoluminescence lifetime is not sensitive to frequency in
c-Si/SiO structure.Comment: 41 pages, 3 figures, submitted to Phys. Rev.