A novel mutation 3090 G>A of the mitochondrial 16S ribosomal RNA associated with myopathy.

We describe a young woman who presented with a progressive myopathy since the age of 9. Spectrophotometric analysis of the respiratory chain in muscle tissue revealed combined and profound complex I, III, II+III, and IV deficiency ranging from 60% to 95% associated with morphological and histochemical abnormalities of the muscle. An exhaustive screening of mitochondrial transfer and ribosomal RNAs showed a novel G>A substitution at nucleotide position 3090 which was detected only in urine sediment and muscle of the patient and was not found in her mother's blood cells and urine sample. We suggest that this novel de novo mutation in the 16S ribosomal RNA, a nucleotide which is highly conserved in different species, would impair mitochondrial protein synthesis and would cause a severe myopathy.

Clinical evaluation of a screen pneumotachograph as an in-line filter.

The American Thoracic Society/European Respiratory Society Task Force underlined that the use of in-line filters during respiratory function tests "is an area of controversy". The aim of the present study was to measure the contamination occurring during forced expiration downstream from a screen pneumotachograph (SP) with and without an in-line filter (Pall PF30S). A total of 40 healthy subjects performed eight consecutive maximal expiratory manoeuvres into four sterile apparatuses (A1: no filter, no SP; A2: filter-only; A3: SP-only; A4: filter and SP) in random order. A blood agar plate was fixed downstream from the apparatus. Colony-forming units (CFUs) were counted after 24 h incubation at 37 degrees C. Of the 40 plates obtained with each apparatus, 13 were sterile with A1 (range 0-679 CFUs), 25 with A2 (0-49 CFUs), 30 with A3 (0-35 CFUs) and 39 with A4 (one CFU in the only positive plate). A1 versus A2 and also A3 versus A4 gave different values for the CFU number, but A2 and A3 showed similar contamination levels. The authors conclude that: 1) the in-line filter does not perform better than a screen pneumotachograph; 2) it does not eliminate the need to decontaminate the pneumotachograph; and 3) equipment placed downstream from an in-line filter and a screen pneumotachograph is almost protected from contamination.

Single-breath transfer factor in young healthy adults: 21% or 17.5% inspired oxygen?

For the measurement of the single-breath transfer factor of the lung for carbon monoxide (TL,CO,sb), the American Thoracic Society (ATS) recommends using a test gas with a 21% inspired fraction of oxygen (FI,O2) whereas the European Respiratory Society (ERS) expressly recommends 17-18% FI,O2. The ERS committee argues that with a higher concentration (e.g. 21%) the alveolar fraction of oxygen (and accordingly TL,CO,sb) "varies with the volume of the test gas which is inspired", that is, presumably, in proportion to the volume of the test gas that is diluted in the alveolar volume. The current study measured TL,CO,sb and the transfer coefficient (KCO,sb) in duplicate in 67 healthy adults (age 17-23 yrs) using, in random order, an inspired gas containing either 17.5% or 21% oxygen. A correction was applied for carboxyhaemoglobin, in line with ATS recommendations. As expected, TL,CO,sb was higher with 17.5% FI,O2 test gas compared with 21% FI,O2 test gas (11.98 +/- 2.68 versus 11.38 +/- 2.56 mmol x min(-1) x kPa(-1), respectively) as well as KCO,sb (1.98 +/- 0.24 versus 1.90 +/- 0.23 mmol x min(-1) x kPa(-1), respectively). The ratio of TL,CO,sb measurements was strictly independent of the residual volume/total lung capacity ratio measured with plethysmography. Hence, the rationale used by the European Respiratory Society, which utilises a 17-18% inspired fraction of oxygen test gas for single-breath transfer of the lung for carbon monoxide measurements, would appear to be unwarranted in young healthy adults.