Decreased expression of ubiquinol-cytochrome c reductase subunits in patients exhibiting mitochondrial myopathy with progressive exercise intolerance.

The expression of mitochondrial proteins of two patients suffering from myopathy with progressive exercise intolerance and exhibiting a deficiency in the enzymatic activity of complex III (ubiquinol-cytochrome c reductase) has been analyzed by immunological titration. In both patients, the Fe-S protein, the cytochrome b and the 9.5 kDa protein were decreased while the expression of the other complex III subunits were close to normal values. This data indicates that, in some mitochondrial myopathies, proteins of the respiratory chain complexes can be accumulated in mitochondria without being integrated into a functional complex. This may be explained either by a lack of control of the coordination between the synthesis of subunits of mitochondrial and nuclear origin or by a difference in the degradation rate of the various subunits which are not properly assembled.

[Study of the criteria of evaluation of the exercise capacity of the chronic hemodialyzed subject]. / Etude des critères d'appréciation de l'aptitude a l'exercice du sujet hémodialysé chronique

Direct measurement methods (or the forecast related to indirect measurements) of the maximal oxygen uptake are reviewed. 15 patients suffering from renal failure, performed a total of 28 exercises. One can draw the conclusion that the maximum VO2 is inferior in these subjects to the values usually determined in normal healthy subjects of the same age. This decrease can be significantly correlated with the haematocrit. Comparison between direct measurement methods of the maximal oxygen uptake and indirect methods allowing its forecast from the heart rate, shows that only direct methods are to be used in these patients.

Relationship between oxygen uptake and mixed venous oxygen saturation in the immediate postoperative period.

BACKGROUND: During muscular exercise, a negative correlation has been demonstrated between the value of mixed venous oxygen saturation (SvO2) and the level of muscular work, expressed at each level as the ratio of oxygen uptake (VO2) to each subject's maximal oxygen uptake (VO2max). Because the immediate postoperative period is associated with an increase in whole body oxygen demand, and in this regard resembles the effects of muscular exercise, a similar correlation may exist during this period. METHODS: VO2max was determined in 11 patients 3-5 days before coronary artery bypass surgery. During the first 2 postoperative h, VO2 and SvO2 were monitored. VO2 was measured by indirect calorimetry and SvO2 by a fiberoptic pulmonary arterial catheter. RESULTS: The highest postoperative value of VO2 was most often associated with visible shivering and ranged among patients from 19% to 53% of preoperatively measured VO2max. There was a highly significant negative correlation between SvO2 and the ratio VO2/VO2max. This correlation was observed when data were examined collectively (136 simultaneous determinations of the two variables) and at the individual level (10-18 determinations for each patient). The slopes and the y intercepts of individual lines of correlation were within a narrow range. CONCLUSIONS: During the first 2 postoperative h after coronary artery bypass surgery, VO2 rarely exceeds 50% of preoperative VO2max. Assuming a stable state of myocardial function, SvO2 measurement may provide an indirect means of assessment of the "exercise test" imposed on patients recovering from general anesthesia.

An abnormal exercise test response revealing a respiratory chain complex III deficiency.

A 29-year-old man with a progressive exertional muscle intolerance since childhood was referred for incremental exercise test on a bicycle ergometer. The response pattern suggested a mitochondrial myopathy: that is, a greatly reduced maximum oxygen consumption with appropriate heart rate increase and an anaerobic threshold point reached early. The metabolic investigation in plasma revealed an abnormal oxidoreduction status (hyperlactataemia and high lactate/pyruvate ratio) at rest and after a carbohydrate rich meal. The histochemical examination of a muscle biopsy revealed red granular deposits under the sarcolemma for all type 1 fibers. Oxypolarographic and enzymological studies of the mitochondrial respiratory chain in both isolated mitochondria and muscle homogenate demonstrated a marked deficiency of ubiquinol cytochrome c reductase (complex III) activity.