Contractile fatigue, muscle morphometry, and blood lactate in chronic obstructive pulmonary disease

We hypothesized that patients with chronic obstructive pulmonary disease developing contractile fatigue of the quadriceps during cycle exercise may have characteristic metabolic and muscle features that could increase their susceptibility to fatigue, thus differentiating them from those who do not develop fatigue. We examined, in 32 patients, the fiber-type proportion, enzymatic activities, and capillary density in the vastus lateralis and the arterial blood lactate level during constant work-rate cycling exercise. Contractile fatigue was defined as a postexercise fall in quadriceps twitch force greater than 15% of resting values. Twenty-two patients developed contractile fatigue after exercise. No significant differences were found between fatiguers and non-fatiguers for the endurance time, fiber-type proportion, and oxidative enzyme activities. The lactate dehydrogenase activity was significantly higher (p < 0.05) and muscle capillarization significantly reduced in fatiguers (p < 0.05). Compared with non-fatiguers, the arterial lactate level during exercise was significantly higher in fatiguers (p < 0.001). A significant relationship was found between the fall in quadriceps twitch force and lactate dehydrogenase activity, capillary/fiber ratio, and blood lactate level. We conclude that changes in muscle enzymatic profile and capillarization with a greater reliance on glycolytic metabolism during exercise are associated with contractile fatigue in patients with chronic obstructive pulmonary disease.     

Bilateral anterior optic neuritis in adult measles infection without encephalomyelitis

PURPOSE: To describe anterior optic neuritis in adult measles infection.DESIGN: Interventional case report. METHODS: A 31-year-old woman presented with bilateral visual loss 6 days after the onset of maculopapular rash. Complete ophthalmic and neurologic examinations, radiologic studies, and lumbar puncture were performed. RESULTS: Visual acuities were counting fingers in both eyes, with bilateral optic disk hyperemia and swelling noted. Neurologic examination was unremarkable, and computed tomography and magnetic resonance imaging of the brain were normal. The cerebrospinal fluid (CSF) was devoid of white cells, although measles immunoglobulin M (IgM) antibodies were detected in both CSF and serum. Intravenous corticosteroids were administered, and clinical findings resolved within 1 month. A fall in serum IgM and a rise in serum IgG titers were observed. CONCLUSIONS: Although rare, optic neuritis in the absence of encephalomyelitis may occur in measles. Whether treatment is effective is unknown.