RESUMO
(1) Background: Cardiorespiratory fitness (CRF) is known to be a prognostic factor regarding long-term morbidity and mortality. This study aimed to develop a standardized Stair Climbing Test (SCT) with a reliable correlation to spiroergometry and the 6MWT which can be used in healthy children as well as patients with congenital heart disease (CHD) and a restricted exercise capacity. (2) Methods: A total of 28 healthy participants aged 10-18 years were included. We tested the individuals' CRF by cardiopulmonary exercise testing (CPET) on a treadmill, the 6MWT, and a newly developed Stair Climbing Test (SCT). For the SCT, we defined a standardized SCT protocol with a total height of 13.14 m to achieve maximal exercise effects while recording time and vital parameters. To compare the SCT, the 6 Min Walking Test, and CPET, we introduced an SCT-Index that included patient data (weight, height) and time. To assess the SCT's feasibility for clinical practice, we also tested our protocol with five adolescents with complex congenital heart disease (i.e., Fontan circulation). (3) Results: A strong correlation was observed between SCT-Index and O2 pulse (r = 0.921; p < 0.001). In addition, when comparing the time achieved during SCT (tSCT) with VO2max (mL/min/kg) and VO2max (mL/min), strong correlations were found (r = -0.672; p < 0.001 and r = -0.764; p < 0.001). Finally, we determined a very strong correlation between SCT-Index and VO2max (mL/min) (r = 0.927; p = <0.001). When comparing the 6MWD to tSCT, there was a moderate correlation (r = -0.544; p = 0.003). It appears to be feasible in patients with Fontan circulation. (4) Conclusions: We were able to demonstrate that there is a significant correlation between our standardized SCT and treadmill CPET. Therefore, we can say that the SCT can be used as an easy supplement to CPET and in certain contexts, it can also be used as a screening tool when CPET is not available. The advantages would be that the SCT is a simple, quick, cost-effective, and reliable standardized (sub)maximal exercise test to evaluate CRF in healthy children on a routine basis. We can even assume that it can be used in patients with congenital heart disease.
RESUMO
The high mobility group (HMG) proteins of the HMGB family are chromatin-associated proteins that act as architectural factors in nucleoprotein structures, which regulate DNA-dependent processes including transcription and recombination. In addition to the previously identified HMGB1-HMGB6 proteins, the Arabidopsis genome encodes at least two other candidate family members (encoded by the loci At2g34450 and At5g23405) having the typical overall structure of a central domain displaying sequence similarity to HMG-box DNA binding domains, which is flanked by basic N-terminal and acidic C-terminal regions. Subcellular localisation experiments demonstrate that the At2g34450 protein is a nuclear protein, whereas the At5g23405 protein is found mainly in the cytoplasm. In line with this finding, At5g23405 displays specific interaction with the nuclear export receptor AtXPO1a. According to CD measurements, the HMG-box domains of both proteins have an alpha-helical structure. The HMG-box domain of At2g34450 interacts with linear DNA and binds structure-specifically to DNA minicircles, whereas the HMG-box domain of At5g23405 does not interact with DNA at all. In ligation experiments with short DNA fragments, the At2g34450 HMG-box domain can facilitate the formation of linear oligomers, but it does not promote the formation of DNA minicircles. Therefore, the At2g34450 protein shares several features with HMGB proteins, whereas the At5g23405 protein has different characteristics. Despite the presence of a region with similarity to the nucleosome-binding domain typical of HMGN proteins, At2g34450 does not bind nucleosome particles. In summary, our data demonstrate (i) that plant HMGB-type proteins are functionally variable and (ii) that it is difficult to predict HMG-box function solely based on sequence similarity.
