Uremic myopathy limits aerobic capacity in hemodialysis patients.

Eleven end-stage renal disease patients trained by stationary cycling during their hemodialysis treatments. After a 6-week control period, 12 weeks of training began and was increased to 30 to 60 minutes at > or = 70% of peak heart rate. Baseline, pretraining and, posttraining exercise tests were performed. Workload (WL), oxygen uptake (VO2peak), cardiac output (Q), heart rate (HR), and arterial oxygen content (CaO2) were measured. Stroke volume (SV), arteriovenous oxygen difference ((a-v)O2), and mixed-venous oxygen content (CvO2) were calculated. Rectus femoris biopsies were obtained pretraining and posttraining. At peak exercise, WL increased from 60 +/- 4 to 70 +/- 6 W (P < 0.05), VO2peak showed an upward trend from 14.8 +/- 0.9 to 16.8 +/- 1.3 mL/kg/min (P < 0.1), and Q, HR, SV, CaO2, CvO2, and (a-v)O2 were unchanged. Ten of the 11 patients increased WL, but only six increased VO2peak (five of 11 patients decreased VO2peak). The difference between groups (P < 0.02) was attributable to (a-v)O2, which increased in those who increased VO2peak (P < 0.02). There was an upward trend for succinate dehydrogenase activity (P < 0.06), and phosphofructokinase activity increased (P < 0.05). However, the rectus femoris capillary to fiber ratio, type I and II fiber areas, and fiber area variability were unchanged, and neither histomorphologic nor enzymatic activity changes were related to change in VO2peak. We conclude that not all dialysis patients increase VO2peak after training, but most can improve exercise capacity. Patients who improved VO2peak widened their (a-v)O2 difference, increasing oxygen extraction and showing that oxygen delivery is not always the limiting factor. Thus, the limitation of VO2peak in dialysis patients is a complex interaction of central and peripheral factors. Muscle therapies, such as exercise training, are needed in addition to increased oxygen delivery in rehabilitation of dialysis patients.

Capillaries measured in canine diaphragm by two methods.

We have measured capillary distribution in costal and crural canine diaphragm using two methods: histochemical processing and perfusion fixation. Each of 18 dogs was deeply anesthetized, the abdomen opened, and the left inferior phrenic artery cannulated. The animal was heparinized and overdosed with pentobarbital. The right hemidiaphragm was frozen, either postexcision (Protocol 1) or intact with no preload (Protocol 2), for histochemical processing. The left hemidiaphragm was fixed by perfusion in situ using 2% glutaraldehyde, either with preload (Protocol 1) or without (Protocol 2). Costal and crural regions of each hemidiaphragm were sampled for analysis. Frozen samples were sectioned and processed for acid-stable (pH 4.0) ATPase activity; perfusion-fixed samples were postfixed, stained, embedded in Epon, and sectioned. Measurements were made using a digital imaging system. We found that muscle fibers had smaller cross-sectional areas in costal than in crural diaphragm; capillary-to-fiber ratio (C:F) did not differ by region and regional differences in capillary density could be attributed to differences in fiber size. Results depended critically on methodology. In perfusion-fixed muscle, fiber area was less, C:F was greater, and capillary density was greater than in histochemically-processed tissue. We conclude that capillary distribution is similar in costal vs. crural diaphragm and that perfusion fixation identifies capillaries more effectively than histochemistry.

Type II collagen-induced arthritis. A morphologic and biochemical study of articular cartilage.

Articular cartilage was obtained from type II collagen-induced arthritic rat joints. Transmission electron microscopy showed a gradual degeneration of chondrocytes, disorganization of the collagenous extracellular matrix, and formation of microscars. Biochemical analyses indicated that type II collagen was the only collagen present and that it was normal in regard to hydroxylation of lysine and glycosylation of hydroxylysine. Analyses of the proteoglycan in the extracellular matrix revealed a 50% loss of chondroitin sulfate and keratan sulfate.

The hand in mixed connective tissue disease.

The mixed connective tissue disease syndrome has been described in the medical literature. The clinical and serological characteristics of the syndrome are defined in this paper. The hands of these patients differ from the hands of patients with systemic lupus, rheumatoid arthritis, or systemic sclerosis. In 10 patients there were no erosive changes on radiological examination and all 10 patients had Raynaud's phenomenon. The most striking finding was tightness in the flexors. Mild cases of flexor tightness improved with systemic steroids. One patient with severe flexor tightness required surgical release of adhesions from a chronic inflammatory process of fascia, muscle, and tenosynovium. Biochemical studies showed an abnormal collagen pattern that may be distinct for mixed connective tissue disease.

The effect of devascularization on the regeneration of lacerated peripheral nerves: an experimental study.

The functional, biochemical, and histological changes in a severed median nerve, 9 months after epineurial repair, were studied in 14 monkeys. In seven the mesoneurium had been stripped 5 cm proximal and 5 cm distal to the site of repair, and in seven the nerve had been stripped only over a 0.5 cm area, just enough to allow repair. In the first group the mean muscular strength in the abductor pollicis brevis was 197 gm, as compared to 257 gm in the second group. The amount of collagen in the perineurium was 57 microgram/mg, as compared to 43 microgram/mg, and the incidence of the h-l-h-nl cross-link was 16% to 21%, as compared to 9% to 11%. If the regeneration of the lacerated nerve was compromised by the deposition of collagen resulting from mobilization of the distal segment, as suggested by the decrease in the strength of the abductor pollicis brevis muscle, then any mobilization of a nerve necessary to obtain a sutured junction with minimum tension should be limited to the proximal segment.