305 research outputs found
3D analysis of tooth surfaces to aid accurate brace placement
Master'sMASTER OF ENGINEERIN
Osteochondral lesions in distal tarsal joints of Icelandic horses reveal strong associations between hyaline and calcified cartilage abnormalities
Osteochondral lesions in the joints of the distal tarsal
region of young Icelandic horses provide a natural model
for the early stages of osteoarthritis (OA) in low-motion
joints. We describe and characterise mineralised and
non-mineralised osteochondral lesions in left distal tarsal
region joint specimens from twenty-two 30 ±1 month-old
Icelandic horses. Combinations of confocal scanning light
microscopy, backscattered electron scanning electron
microscopy (including, importantly, iodine staining) and
three-dimensional microcomputed tomography were used
on specimens obtained with guidance from clinical imaging.
Lesion-types were described and classified into groups
according to morphological features. Their locations in
the hyaline articular cartilage (HAC), articular calcified
cartilage (ACC), subchondral bone (SCB) and the joint
margin tissues were identified and their frequency in the
joints recorded. Associations and correlations between
lesion-types were investigated for centrodistal joints only.
In centrodistal joints the lesion-types HAC chondrocyte
loss, HAC fibrillation, HAC central chondrocyte clusters,
ACC arrest and ACC advance had significant associations
and strong correlations. These lesion-types had moderate
to high frequency in centrodistal joints but low frequencies
in tarsometatarsal and talocalcaneal-centroquartal joints.
Joint margin lesion-types had no significant associations
with other lesion-types in the centrodistal joints but high
frequency in both the centrodistal and tarsometatarsal
joints. The frequency of SCB lesion-types in all joints
was low. Hypermineralised infill phase lesion-types were
detected. Our results emphasise close associations between
HAC and ACC lesions in equine centrodistal joints and the
importance of ACC lesions in the development of OA in
low-motion compression-loaded equine joints
Diverse Modes of Axon Elaboration in the Developing Neocortex
The development of axonal arbors is a critical step in the establishment of precise neural circuits, but relatively little is known about the mechanisms of axonal elaboration in the neocortex. We used in vivo two-photon time-lapse microscopy to image axons in the neocortex of green fluorescent protein-transgenic mice over the first 3 wk of postnatal development. This period spans the elaboration of thalamocortical (TC) and Cajal-Retzius (CR) axons and cortical synaptogenesis. Layer 1 collaterals of TC and CR axons were imaged repeatedly over time scales ranging from minutes up to days, and their growth and pruning were analyzed. The structure and dynamics of TC and CR axons differed profoundly. Branches of TC axons terminated in small, bulbous growth cones, while CR axon branch tips had large growth cones with numerous long filopodia. TC axons grew rapidly in straight paths, with frequent interstitial branch additions, while CR axons grew more slowly along tortuous paths. For both types of axon, new branches appeared at interstitial sites along the axon shaft and did not involve growth cone splitting. Pruning occurred via retraction of small axon branches (tens of microns, at both CR and TC axons) or degeneration of large portions of the arbor (hundreds of microns, for TC axons only). The balance between growth and retraction favored overall growth, but only by a slight margin. Given the identical layer 1 territory upon which CR and TC axons grow, the differences in their structure and dynamics likely reflect distinct intrinsic growth programs for axons of long projection neurons versus local interneurons
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