The knee is the most common site for translational cartilage research in sheep, though topographic features of articular cartilage across surfaces are unspecified. We aimed to characterize the mechanical, morphological, and biochemical properties of articular cartilage across ovine knee surfaces and document variations between and within surface locations. Regions of interest (ROIs) were delineated across surfaces of 10 healthy ovine knees. Articular cartilage at each ROI was measured for creep indentation, thickness, and glycosaminoglycan (GAG) and collagen content. Variables were compared between surface locations (trochlea, and lateral [LFC] and medial [MFC] femoral condyles) and between ROIs within each surface location. Correlations between variables were also assessed. Articular surface location had a significant effect on creep (P < .

Objective. Shoulder pain is commonly attributed to rotator cuff injury or osteoarthritis. Ovine translational models are used to investigate novel treatments aimed at remedying these conditions to prevent articular cartilage degeneration and subsequent joint degradation. However, topographical properties of articular cartilage in the ovine shoulder are undefined. This study investigates the biomechanical, morphological, and biochemical attributes of healthy ovine humeral head articular cartilage and characterizes topographical variations between surface locations. Design. Ten humeral heads were collected from healthy skeletally mature sheep and each was segregated into 4 quadrants using 16 regions of interest (ROIs) across the articular surface. Articular cartilage of each ROI was analyzed for creep indentation, thickness, and sulfated glycosaminoglycan (sGAG) and collagen quantity. Comparisons of each variable were made between quadrants and between ROIs within each quadrant. Results. Percent creep, thickness, and sGAG content, but not collagen content, were significantly different between humeral head quadrants. Subregion analysis of the ROIs within each surface quadrant revealed differences in all measured variables within at least one quadrant. Percent creep was correlated with sGAG (r = −0.32, P = 0.0001). Collagen content was correlated with percent creep (r = 0.32, P = 0.0009), sGAG (r = −0.19, P = 0.049), and thickness (r = −0.19, P = 0.04). Conclusions. Topographical variations exist in mechanical, morphologic, and biochemical properties across the articular surface of the ovine humeral head. Recognizing this variability in ovine humeral head cartilage will provide researchers and clinicians with accurate information that could impact study outcomes.

A myxoid cyst on the dorsum of the left index finger is presented. A connection of this pseudocyst to the underlying joint was shown by means of magnetic resonance imaging. Surgically the connecting tract to the distal interphalangeal joint was easily demonstrated and histologically a ductal structure was focally seen by means of serial sections. These structures also suggest such a connection. These findings confirm the view that this pseudocyst can be interpreted as a ganglion. Therapeutically complete excision with careful tying off of the channel to the joint appears to be the best method to avoid recurrence. The injection of sclerosing agents, a conservative treatment modality proposed by some authors, may be problematic in the light of the pathogenesis discussed here; however damage to the finger joint has not been so far observed.

Extracellular matrix materials known as perineuronal nets (PNNs) have been shown to have remarkable consequences for the maturation of neural circuits and stabilization of behavior. It has been proposed that, due to the possibly long-lived biochemical nature of their components, PNNs may be an important substrate by which longterm memories are stored in the central nervous system. However, little empirical evidence exists that shows that PNNs are themselves stable once established. Thus, the question of their temporal dynamics remains unresolved. We leverage the dramatic morphological and behavioral transformations that occur during amphibian metamorphosis to show that PNNs can be highly dynamic in nature. We used established lectin histochemistry to show that PNNs undergo drastic reconstruction during the metamorphic transition. Pre-metamorphic tadpoles have abundant lectinlabeled pericellular material, which we interpret to be PNNs, surrounding neurons throughout the central nervous system. During the metamorphic transition, these structures degrade, and begin to reform in the months following metamorphosis. We show that PNN sizes and staining intensity further change over metamorphosis, suggesting compositional rearrangement. We found PNNs in brain regions with putative homology to regions in mammals with known PNN function, and in other shared

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