A group of 14 uremic patients on intermittent hemodialysis was admitted to a cross-over double-blind trial in order to evaluate serum and muscle carnitine levels before and after 60 days of L-carnitine oral (2 g/day) treatment. The morphology of muscle fragments was studied by light and electron microscopy. Symptoms (asthenia, cramps) occurring during hemodialysis were also recorded. After L-carnitine treatment the blood and muscle levels of the metabolite increased simultaneously to reduced asthenia and cramps. Morphological examination of the muscle of 13 of 14 patients did not reveal any pre- or posttreatment pathological alterations. The presence of nemaline rods was morphologically diagnosed in only one case and was no longer observed at the second biopsy at 2 months of L-carnitine treatment.

SUMMARY:Matrix metalloproteinases (MMPs) have been implicated in the formation of microvessels during angiogenesis, but their role in vascular regression is poorly understood. The rat aorta model of angiogenesis was used to study the function of MMPs at different stages of the angiogenic process. Gelatin zymography and Western analysis demonstrated production of MMP-2 and MMP-9 by aortic outgrowths in serum-free collagen gel culture. MMP-2 was found in both culture medium and collagen gel, whereas MMP-9 was predominantly associated with the gel. MMP expression increased gradually during the angiogenic growth phase and stayed high when vessels regressed and collagen lysed around the aortic rings. The MMP inhibitors, batimastat and marimastat, blocked formation of microvessels when added to the culture medium at the beginning of the experiment. They, however, stabilized the microvessels and prevented vascular regression after the angiogenic growth phase. This effect was observed also under conditions of angiogenic stimulation by basic fibroblast growth factor. MMP inhibitormediated stabilization of microvessels was associated with inhibition of collagen lysis and accumulation of collagen fibrils in the subendothelial space. This study demonstrates that MMPs promote microvessel formation during the early stages of angiogenesis, but also contribute to the reabsorption of the neovasculature in the later stages of this process. The time-dependent divergent effects of MMPs on microvessel growth and survival may influence the in vivo activity of MMP inhibitors used to treat angiogenesis-dependent disorders. (Lab Invest 2000, 80:545-555).

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The present study investigates 14 patients on intermittent haemodialysis. Pre-dialysis blood and muscle samples were taken for determining plasma free- and acetylcarnitine levels. The tissue fragments were used for light and electron microscopy studies. Our results support the findings of other investigators that patients on haemodialysis generally display decreased free- and acetylcarnitine levels both in plasma and skeletal muscle when compared with control values. Muscle carnitine deficiency was apparently more severe in the longer-term haemodialysis patients. Moreover, a significant correlation (p < 0.05) between plasma and muscle free-carnitine values was found. Morphologically no pathological alterations were observed in the muscle fibres in 13 of the patients. Light and electron microscopic studies of the muscle fibre of the 14th patient showed a typical nemaline myopathy with rod bodies in the cytoplasm. The muscle free-carnitine concentration in this patient was among the lowest of the group.

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