Enzymatic formation of UDP-N-acetylgalactosamine in epiphysial-plate cartilage.

The activity of UDP-N-acetylglucosamine 4'-epimerase (EC 5.1.3.7) from newborn pig epiphysial-plate cartilage was investigated. The formation of radioactive UDP-N-acetylgalactosamine from UDP-N-acetyl[U-14C]-glucosamine was demonstrated by radioautography, after hydrolysis of UDP-derivatives and separation of the hexosamines by paper chromatography. The pH optimum and the Km values for UDP-N-acetylglucosamine and NAD were determined. At equilibrium, the ratio UDP-N-acetylglucosamine/UDP-N-acetylgalactosamine reaches a value of about 2.3. The effect of UDP-xylose and UDP-glucuronic acid on the enzyme activity was investigated. NADH inhibits UDP-N-acetylglucosamine 4'-epimerase activity. The inhibitory effect of NADH seems to be strikingly correlated with the value of NAD/NADH ratio and pH

Biochemical changes in the articular cartilage of the patella and femoral condyles in the lateral hyperpatellar syndrome.

The biochemical changes in the articular cartilage of the femoral condyles and the patella were studied during the earliest stage of patello-femoral arthrosis, with particular reference to chondromalacia of the patella in the "lateral hypertension syndrome", with the object of comparing them with the results obtained by Boni et al. (1977) in the initial phases of experimental arthrosis induced in rabbits by means of vitamin A. The biochemical determinations were done on samples of cartilage removed at operation from the medial and lateral femoral condyles and the medial and lateral patellar articular facets in ten patients. The biopsy samples were fixed in 80% alcohol and dried in the oven at 50 degrees C for twenty-four hours. The hexosamine and hydroxyproline content was then determined. This investigation demonstrated significant biochemical changes in this syndrome in the four areas examined. The data obtained indicate that only the mucopolysaccharide component of the joint cartilage is involved at this stage. The most interesting finding was marked diminution in the galactosamine/glucosamine ratio, which was markedly diminished - the opposite of what occurs in established arthrosis. These data appear to be identical with those found in the early phases of vitamin A induced arthrosis in experimental rabbits. The diminution of hexosamine content and the diminished galactosamine/glucosamine ratio were more marked in the femoral condyles, which appeared to have few lesions macroscopically. These changes were also present in both articular facets of patella, but were less marked, probably because the degeneration was more advanced in those areas, thus more closely resembling frank arthrosis

Heparin protection against Fe2+-and Cu2+-mediated oxidation of liposomes.

Heparin (HE) exhibited a protective effect on liposome peroxidation induced by Fe2+ and Cu2+, decreasing the formation of both conjugated dienes and thiobarbituric acid reactive substances (TBARS) in a dose-dependent manner. The antioxidant activity was more relevant in the oxidizing system employing Fe2+ and H2O2 and generating the highly reactive OH radical. The analysis of liposome size distribution by quasielastic laser light scattering showed that: (1) the native structure of the particles was completely lost after exposure to Fenton reagent; (2) the presence of HE in the reaction mixture completely prevented the peroxidative damage on liposomes. Thus, HE acts as an antioxidant factor on membrane lipid bilayer. This suggests that HE, released from mast-cell granules during inflammatory processes, might locally protect the cell membrane from the oxidative injuries

Modificazioni dei proteoglicani nel tessuto di granulazione a diversi stadi di sviluppo

Si presentano i risultati degli studi sui proteoglicani nel tessuto di granulazione a diversi stadi di sviluppo: la sua evoluzione si accompagna ad un calo del contenuto totale di glicosaminoglicani (in particolare di acido jaluronico) e ad un aumento delle interazioni esistenti tra i proteoglicani e le altre componenti della matrice extracellular