This study investigated energy expenditure and obstacle course negotiation between the C-leg 1 and various non-microprocessor control (NMC) prosthetic knees and compared a quality of life survey (SF-36v2 TM ) of use of the C-leg 1 to national norms. Thirteen subjects with unilateral limb loss (12 with trans-femoral and one with a knee disarticulation amputation) participated in the study. The mean age was 46 years, range 30 -75. Energy expenditure using both the NMC and C-leg 1 prostheses was measured at self-selected typical and fast walking paces on a motorized treadmill. Subjects were also asked to walk through a standardized walking obstacle course carrying a 4.5 kg (10 lb) basket and with hands free. Finally, the SF-36v2 TM was completed for subjects while using the C-leg 1 . Statistically significant differences were found in oxygen consumption between prostheses at both typical and fast paces with the C-leg 1 showing decreased values. Use of the C-leg 1 resulted in a statistically significant decrease in the number of steps and time to complete the obstacle course. Scores on a quality of life index for subjects using the C-leg 1 were above the mean for norms for limitation in the use of an arm or leg, equal to the mean for the general United States population for the physical component score and were above this mean for the mental component score. Based on oxygen consumption and obstacle course findings, the C-leg 1 when compared to the NMC prostheses may provide increased functional mobility and ease of performance in the home and community environment. Questionnaire results suggest a minimal quality of life impairment when using a C-leg 1 for this cohort of individuals with amputation.

Cortical collecting tubules (CCT) dissected from rabbits fed a diet designed to stimulate potassium transport secreted potassium in direct proportion to the flow rate in the range of 0.4-3 nl/min (r = 0.79). This relationship was also evident in tubules from rabbits maintained on standard laboratory chow (r = 0.80). The slope of the line relating the two parameters was almost six times greater in tubules from animals fed the special diet. When the range of flow rates was expanded, potassium secretion in nine CCTs appeared to peak at 5-6 nl/min and then failed to increase despite further elevation of flow to nearly 15 nl/min. We investigated the effects of the electrical and chemical gradients on flow-dependent potassium secretion. Because transepithelial voltage was unaffected by changes in axial flow, we conclude that the flow-dependent fraction of potassium secretion is not explained by the electrical gradient. To evaluate the role of luminal potassium concentration on flow-dependent potassium secretion, 11 CCTs were perfused with both 5 and 50 mM potassium solutions at two flow rates (approximately 1.5 and 4.0 nl/min). Increases in both potassium secretion (15.6 +/- 3.9 peq.mm-1.min-1) and sodium reabsorption (11.9 +/- 5.2 peq.mm-1.min-1) were evident in the tubules perfused with 5 mM potassium. Potassium secretion was not reduced by 50 mM luminal potassium at the low flow rate when the largest chemical gradients opposing net secretion were generated. When 50 mM potassium was present in the lumen, increasing flow did not stimulate potassium secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Patch clamp methods were used to characterize sodium channels on the apical membrane of Ambystoma distal nephron. The apical membranes were exposed by everting and perfusing initial collecting tubules in vitro. In cell-attached patches, we observed channels whose mean inward unitary current averaged 0.39 +/- 0.05 pA (9 patches). The conductance of these channels was 4.3 +/- 0.2 pS. The unitary current approached zero at a pipette voltage of -92 mV. When clamped at the membrane potential the channel expressed a relatively high open probability (0.46). These characteristics, together with observation that doses of 0.5 to 2 microM amiloride reversibly inhibited the channel activity, are consistent with the presence of the high amiloride affinity, high sodium selectivity channel reported for rat cortical collecting tubule and cultured epithelial cell lines. We used antisodium channel antibodies to identify biochemically the epithelial sodium channels in the distal nephron of Ambystoma. Polyclonal antisodium channel antibodies generated against purified bovine renal, high amiloride affinity epithelial sodium channel specifically recognized 110, 57, and 55 kDa polypeptides in Ambystoma and localized the channels to the apical membrane of the distal nephron. A polyclonal antibody generated against a synthetic peptide corresponding to the C-terminus of Apx, a protein associated with the high amiloride affinity epithelial sodium channel expressed in A6 cells, specifically recognized a 170 kDa polypeptide. These data corroborate that the apically restricted sodium channels in Ambystoma are similar to the high amiloride affinity, sodium selective channels expressed in both A6 cells and the mammalian kidney.

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The role of the anti-HIV agent zidovudine (ZDV = AZT) in the generation of mitochondrial myopathies and subsequent skeletal muscle contractile deficiencies was evaluated in male rats given ZDV in drinking water (1 mg/mL). After 6 weeks, there was no difference in treadmill run time between experimental (n = 6) and control (n = 6) rats. ZDV did not affect tension output by the gastrocnemius-plantaris-soleus muscle group when stimulated in situ at frequencies of 15, 30, 45, and 75 tetani/min, nor did the drug affect the cytochrome oxidase activity of fast glycolytic, fast oxidative glycolytic, or slow oxidative fiber types after 6 or 15 weeks of treatment. A group of female rats, similarly evaluated after 6 weeks of ZDV at 1 (n = 4) or 2 (n = 4) mg/mL, also did not display any discernable deficiencies. However, when the data from all 10 control rats were compared with those of the 19 ZDV rats, the cytochrome oxidase activity of fast oxidative glycolytic muscle of the ZDV rats was significantly higher (35.0 +/- 1.36 versus 40.7 +/- 1.14 mumol.min-1.g-1; p < 0.05). No ultrastructural abnormalities were observed in 15-week ZDV-treated cardiac muscle or in any of the three skeletal muscle fiber types. These results suggest that ZDV-related myopathies observed in AIDS patients may be due to interactions between the drug and complications associated with HIV infection.