[Treatment of children's and adolescent's knee injuries]. / Gyermek- és serdülókori térdsérülések ellátása.

INTRODUCTION: Authors made 162 knee arthroscopic operations due to hemarthrosis of the knee, acute knee blocking or acute developed instability on patients under 18 years after knee injury during a 12 years period. The retrospective analysis of patient reports shows, that in 61.7% of the cases they found chondral- or osteochondral fracture in the knee. MATERIAL AND METHODS: On three dimensional routine X-ray pictures they were performed after the injury, in 85% of the cases fractures were not seen. Fortunately the most part of the hyalin surface injuries was smaller than 0.5 cm or were situated on less weight-bearing area only hemarthrosis evacuation and removing of loose body were done. If the osteochondral fractures was bigger than 0.5 cm or was broken from the weight-bearing surface, they were fixed by KFI or Herbert-screws. When refixation of osteochondral fracture was not possible technically or in cases of chondral fractures, primary mosaic chondroplasty was used. The correct diagnosis and the early reconstruction of injured hyalin surface in childhood and teenagers is essential regarding to the function of the knee.

Endogenous hydrogen peroxide regulates the excitability of midbrain dopamine neurons via ATP-sensitive potassium channels.

ATP-sensitive K+ (K(ATP)) channels link metabolic state to cell excitability. Here, we examined regulation of K(ATP) channels in substantia nigra dopamine neurons by hydrogen peroxide (H2O2), which is produced in all cells during aerobic metabolism. Blockade of K(ATP) channels by glibenclamide (100 nM) or depletion of intracellular H2O2 by including catalase, a peroxidase enzyme, in the patch pipette increased the spontaneous firing rate of all dopamine neurons tested in guinea pig midbrain slices. Using fluorescence imaging with dichlorofluorescein to visualize intracellular H2O2, we found that moderate increases in H2O2 during partial inhibition of glutathione (GSH) peroxidase by mercaptosuccinate (0.1-0.3 mM) had no effect on dopamine neuron firing rate. However, with greater GSH inhibition (1 mM mercaptosuccinate) or application of exogenous H2O2, 50% of recorded cells showed K(ATP) channel-dependent hyperpolarization. Responsive cells also hyperpolarized with diazoxide, a selective opener for K(ATP) channels containing sulfonylurea receptor SUR1 subunits, but not with cromakalim, a selective opener for SUR2-based channels, indicating that SUR1-based K(ATP) channels conveyed enhanced sensitivity to elevated H2O2. In contrast, when endogenous H2O2 levels were increased after inhibition of catalase, the predominant peroxidase in the substantia nigra, with 3-amino-1,2,4-triazole (1 mM), all dopamine neurons responded with glibenclamide-reversible hyperpolarization. Fluorescence imaging of H2O2 indicated that catalase inhibition rapidly amplified intracellular H2O2, whereas inhibition of GSH peroxidase, a predominantly glial enzyme, caused a slower, smaller increase, especially in nonresponsive cells. Thus, endogenous H2O2 modulates neuronal activity via K(ATP) channel opening, thereby enhancing the reciprocal relationship between metabolism and excitability.