Oxygen uptake efficiency slope: a reliable surrogate parameter for exercise capacity in healthy and cardiac children?

OBJECTIVES

Cardiopulmonary exercise test (CPET) provides accurate evaluation of physical capacity and disease severity in children with congenital heart disease (CHD). However, full participation to obtain optimal measure of VO_2max may be difficult. As an alternative, the oxygen uptake efficiency slope (OUES) is a reproducible and reliable parameter measured during CPET, which does not require a maximal exercise to be interpretable. This study aimed to evaluate the OUES of a large cohort of children with CHD, in comparison with healthy controls. We also intended to identify, in this specific population, the clinical and CPET variables associated with the OUES.

METHODS

This cross-sectional study was carried out between November 2010 and September 2015 in two tertiary care paediatric and congenital cardiology centres.

RESULTS

709 children were included (407 CHD and 302 healthy controls). The association of clinical characteristics with weight-normalised OUES (OUES_kg) was studied using a multivariable analysis. The mean OUES_kg was significantly lower in CHD than in healthy controls (38.6±8.5 and 43.9±8.5; p<0.001, respectively), especially in the most severe CHD. The OUES_kg correlated with VO_2max (r=0.85, p<0.001), with cut-off values for normal exercise capacity of 38.4 in boys and 31.0 in girls. The decrease of OUES_kg was associated with increased age, increased Body Mass Index, number of cardiac catheter or surgical procedures, female gender and decreased forced vital capacity (Z-score).

CONCLUSION

The OUES is significantly impaired in children with CHD and strongly correlates with VO_2max. The OUES has the same clinical determinants as VO_2max and therefore may be of interest in submaximal exercise.

TRIAL REGISTRATION NUMBER

NCT01202916.

Site-selective mapping of metastable states using electron-beam induced luminescence microscopy

Metastable states created by electron or hole capture in crystal defects are widely used in dosimetry and photonic applications. Feldspar, the most abundant mineral in the Earth’s crust (> 50%), generates metastable states with lifetimes of millions of years upon exposure to ionizing radiation. Although feldspar is widely used in dosimetry and geochronometry, the creation of metastable states and charge transfer across them is poorly understood. Understanding such phenomena requires next-generation methods based on high-resolution, site-selective probing of the metastable states. Recent studies using site-selective techniques such as photoluminescence (PL), and radioluminescence (RL) at 7 K have revealed that feldspar exhibits two near-infrared (NIR) emission bands peaking at 880 nm and 955 nm, which are believed to arise from the principal electron-trapping states. Here, we map for the first time the electron-trapping states in potassium-rich feldspar using spectrally-resolved cathodoluminescence microscopy at a spatial resolution of ~ 6 to 22 µm. Each pixel probed by a scanning electron microscope provides us a cathodoluminescence spectrum (SEM-CL) in the range 600–1000 nm, and elemental data from energy-dispersive x-ray (EDX) spectroscopy. We conclude that the two NIR emissions are spatially variable and, therefore, originate from different sites. This conclusion contradicts the existing model that the two emissions arise from two different excited states of a principal trap. Moreover, we are able to link the individual NIR emission peaks with the geochemical variations (K, Na and Fe concentration), and propose a model that explains the quenching of the NIR emission by Fe⁴⁺. Our study contributes to an improved understanding of charge storage in feldspathic minerals, with implications for developing sub-single grain (micrometer scale) measurement techniques in radiation dosimetry.

A comparison of quartz OSL and isothermal TL measurements on Chinese loess

The reliability of equivalent doses (De) from Chinese loess, measured using isothermal thermoluminescence (ITL) is tested. Dose calculations use the single-aliquot regenerative-dose (SAR) procedure. Despite good reproducibility of laboratory-induced signals and negligible response at zero dose, a significant overestimation of De is observed, compared with OSL measurements. Measurement of a known laboratory dose administered after optical bleaching, but before any heating, demonstrates that the first heating during measurement of the natural signal causes a significant sensitivity change, undetected by SAR. Using the single-aliquot regeneration and added (SARA) dose procedure, which allows for initial sensitivity change, good agreement with OSL is obtained after allowance is made for initial incomplete bleaching. It is concluded that SAR-ITL, in its present form, is not a suitable method for dating Chinese loess; it is very important to undertake a dose recovery test before any TL procedure is used to date sediments.

Direct gamma-spectrometric measurement of the 226Ra 186.2keV line for detecting 238U/226Ra disequilibrium in determining the environmental dose rate for the luminescence dating of sediments

In the age determination of sediments according to the luminescence method, it is important to know whether there was secular equilibrium in the Th and U decay series during accumulation of the environmental radiation dose in geological times. This can be investigated via gamma-ray spectrometry, whereby--in the (238)U series--(214)Pb and (214)Bi are considered as the indicators for (226)Ra-mobility, and (210)Pb as the indicator for (226)Rn-emanation. In the present work, the direct measurement of (226)Ra--which can give extra information on the interpretation of the radioactive equilibrium--is investigated as to its precision and accuracy. Since there is a serious spectral interference on its 186.2keV gamma-line (by (235)U at 185.7keV), various correction procedures were outlined and their performance was checked via the analysis of (certified) reference materials, leading to the recommendation of a "method of choice".

Acute percutaneous scaphoid fixation using a non-cannulated Herbert screw

Conservative treatment of fractures of the scaphoid often leads to an important physical and economic morbidity, especially in the young and active population. Acute percutaneous scaphoid fixation is a fast technique with minimal soft tissue damage, which allows immediate mobilisation without prolonged casting. We describe our operation technique in which we always use a non-cannulated Herbert screw. We place the screw freehand and always pass through the trapezium, a technique which is in our hands the best way to place the screw in the right position. It is not technically demanding, but has a considerable learning curve and requires a three-dimensional knowledge of the scaphoid. We reviewed the results of 44 patients treated in our centre between 1996 and 2001. Comparing with literature of percutaneous scaphoid fixation, we found similar results. Although in literature this technique is only indicated for minimally and non-displaced fractures of the waist (Herbert A2 and B2), we describe some good results with proximal pole fractures. Nevertheless we found that all cases of delayed and non-union occurred with this type of fracture.

Agrobacterium tumefaciens-mediated transformation of Artemisia annua L. and regeneration of transgenic plants

A transformation system was developed for Artemisia annua L. plants. Leaf explants from in vitro grown plants developed callus and shoots on medium with 0.05 mg/L naphthaleneacetic acid and 0.5 mg/L N(6)-benzyladenine after transformation with the C58C1 Rif(R) (pGV2260) (pTJK136) Agrobacterium tumefaciens strain. A concentration of 20 mg/L kanamycin was added in order to select transformed tissue. Kanamycin resistant shoots were rooted on naphthaleneacetic acid 0.1 mg/L. Polymerase chain reactions and DNA sequencing of the amplification products revealed that 75% of the regenerants contained the foreign genes. 94% of the transgenic plants showed a β-glucuronidase-positive response.

A 50 kDa protein present in conditioned medium of COLO-16 cells stimulates cell spreading and motility, and activates tyrosine phosphorylation of Neu/HER-2, in human SK-BR-3 mammary cancer cells

A factor present in conditioned medium of COLO-16 human cancer cells causes fast spreading, fast plasma membrane ruffling, cell shape change, net translocation, stimulation of chemotaxis and growth arrest in human SK-BR-3 mammary cancer cells. Based on the spreading effect, the factor was purified to homogeneity and migrated as a 50 kDa protein in SDS-polyacrylamide gel electrophoresis. Addition of the purified 50 kDa factor to the target cells in culture results in tyrosine phosphorylation of the p185erbB2 receptor concomitant with a fast redistribution and clustering of the receptor. The 50 kDa factor is also specifically retained by affinity chromatography on the immobilized extracellular domain of p185erbB2. Antibodies directed against this domain also inhibit the induction of motility. These data suggest that the 50 kDa factor is a putative ligand of p185erbB2 in SK-BR-3 cells. Biochemical and immunological evidence further indicate that this factor differs from p185erbB2 ligands described so far. Its activity could play a role in the pathogenesis of breast cancer.