In Shik Kim

Hypoxic resistance to articular chondrocyte apoptosis – a possible mechanism of maintaining homeostasis of normal articular cartilage

Hypoxia and hypoxia‐related genes are important factors in articular chondrocytes during cartilage homeostasis and osteoarthritis. We have investigated the various apoptotic factors that show significance in synovial fluid obtained from normal and experimental osteoarthritic animal models and have evaluated the effect of hypoxia on articular chondrocyte apoptosis induced by these apoptotic factors. Mature beagle dogs underwent surgical transections of ligaments and medial meniscectomies to explore the underlying mechanisms of osteoarthritis. Cartilage and synovial fluid obtained from normal animals and those with osteoarthritis were evaluated via proteasome inhibition, tumour necrosis factor‐related apoptosis‐inducing ligand (TRAIL) protein expression, mitochondrial transmembrane potential and levels of reactive oxygen species. Canine chondrocytes were exposed to the proteasome inhibitor N‐acetyl‐Leu‐Leu‐Norleu‐al and treated with recombinant TRAIL protein under normoxic and hypoxic conditions, measuring chondrocyte cell viability, proteasome activity and levels of apoptotic factors. TRAIL protein expression and ubiquitinated proteins were increased significantly, but the proteasome activity in the synovial fluid of osteoarthritic joints relative to that in normal joints was not. Primary cultured articular chondrocytes cotreated with the proteasome inhibitor and TRAIL progressed to severe apoptosis under normoxic conditions, but the sensitization caused by the combined treatment was suppressed by exposure to hypoxia. Caspase‐8 activation, c‐Jun N‐terminal kinase phosphorylation, the mitochondrial transmembrane potential and the generation of reactive oxygen species involved in cell death regulation were significantly inhibited under hypoxic conditions. These findings suggest that proteasome inhibition and TRAIL may be possible mechanisms in cartilage degradation and joint‐related diseases. Furthermore, the maintenance of hypoxic conditions or therapy with hypoxia‐related genes in the joint may be successful for the treatment of joint‐related diseases, including osteoarthritis.

Morphometric Studies on the Testis of Korean Ring-necked Pheasant (Phasianus colchicus karpowi) during the Breeding and Non-breeding Seasons

The purpose of this study was to obtain detailed quantitative information on all cell types in the testis interstitium of Korean ring-necked pheasants and to combine these data with changes in the steroidogenic function of the testis during the breeding and non-breeding seasons. For animals collected during the breeding season, their testis weights, sperm production, serum testosterone levels and leuteinizing hormone (LH)-stimulated testosterone secretion were significantly (p < 0.01) increased compared to the non-breeding season. Testes of the pheasants during the non-breeding season displayed a 98% reduction in testis volume that was associated with a decrease in the absolute volume of seminiferous tubules (98% reduction), tubular lumen (100%), interstitium (90%), blood vessels (84%), lymphatic spaces (97%), Leydig cells (79%), mesenchymal cells (51%) and myoid cells (61%) compared to the breeding season. The numbers of Leydig cells, mesenchymal cells and myoid cells per testis in the breeding season were much higher than in the non-breeding season. Although the mean volume of a Leydig cell was 74% lower in the non-breeding season, the mean volumes of myoid and mesenchymal cells remained unchanged. These results demonstrate that there are striking differences in the testicular structure of the Korean ring-necked pheasant during the breeding and non-breeding seasons. Every structural parameter of the Leydig cell was positively correlated with both testosterone serum levels and LH-stimulated testosterone secretion. The correlation of changes in hormonal status with the morphometric alterations of Leydig cells suggests that the Korean-ring necked pheasant may be used as a model to study structure-function relationships in the avian testis.

Branching Patterns of the Subclavian Arteries in German Shepherd Dogs

With 2 figures and 3 tables