New 20 m Progressive Shuttle Test Protocol and Equation for Predicting the Maximal Oxygen Uptake of Korean Adolescents Aged 13-18 Years.

Background: Although several equations for predicting VO2max in children and adolescents have been reported, the validity of application of these equations to the Korean population has not been verified. The purpose of study was to develop and validate regression models to estimate maximal oxygen uptake (VO2max) using a newly developed 20 m progressive shuttle test (20 m PST) protocol in Korean male (n = 80, 15.3 ± 1.86 years) and female (n = 81, 15.5 ± 1.73 years) adolescents aged 13-18 years. Methods: The modified 20 m PST was performed and the VO2max was assessed in a sample of 161 participants. The participants underwent a treadmill test (TT) in the laboratory and the modified 20 m PST in a gymnasium. For the validation study, the participants performed the TT with a stationary metabolic cart and the 20 m PST with a portable metabolic cart once. In addition, they performed the 20 m PST two more times to establish test-retest reliability. Results: The mean VO2max (49.6 ± 8.7 mL·kg-1·min-1) measured with the potable metabolic cart was significantly higher than that measured in the graded exercise test with the stationary metabolic cart (46.6 ± 8.9 mL·kg-1·min-1, p < 0.001) using the new 20 m PST protocol. The standard error of the estimate (SEE) between these two measurements was 1.35 mL·kg-1·min-1. However, the VO2max derived from the newly developed equation was 46.7 ± 7.3 mL·kg-1·min-1 (p > 0.05) and the SEE was 2.90 mL·kg-1·min-1. The test and retest trials of the 20 m PST yielded comparable results (laps, r = 0.96; last speed, r = 0.93). Conclusions: Our data suggest that the new 20 m PST protocol is valid and reliable and that the equation developed in this study provides a valid estimate of VO2max in Korean male and female adolescents aged 13-18 years.

In vitro chondrocyte culture in a heparin-based hydrogel for cartilage regeneration.

In the present study, we applied and optimized a heparin-based hydrogel system, formed by thiolated heparin and diacrylated poly (ethylene glycol), for three-dimensional chondrocyte culture. Encapsulation by the heparin-based hydrogel did not affect the chondrocyte viability (better than calcium-induced alginate gel), and the heparin-based hydrogel promoted chondrocyte proliferation, while maintaining chondrogenic nature. Phenotypic analyses, such as glycosaminoglycan accumulation and histological staining, also supported the proper role of the heparin-based hydrogel for cartilage regeneration; a continuous increase in glycosaminoglycan amount was observed during the culture period. At the transcriptional level, the gene expression of type II collagen and Sox-9 was maintained, whereas type I collagen expression was not observed. The chondrocyte expansion was affected by the gel strength, and there existed an optimum gel concentration for it. Based on the results, the heparin-based hydrogel is a promising material for chondrocyte culture, potentially applicable for cartilage regeneration.

Formation of a novel heparin-based hydrogel in the presence of heparin-binding biomolecules.

An injectable, heparin-based hydrogel system with the potential to be gelled with cells was developed. First, heparin was modified to have thiol groups by the modification of carboxylic groups of heparin with cysteamine using carbodiimide chemistry. Thiol functionalization of heparin carboxylic groups was controlled from 10% to 60% of the available COOH groups, and the retained bioactivity of the modified heparin, characterized by its binding affinity to antithrombin III, decreased with increasing functionalization. Then, the thiol-functionalized heparin was reacted with poly(ethylene glycol) diacrylate to form a hydrogel. The gelation kinetics and mechanical properties of the final gel state could be tuned by controlling cross-link density. Fibroblast cell encapsulation using this hydrogel revealed the nontoxicity of the present system. Cell proliferation inside the hydrogel was observed, and it was significantly enhanced (more than 5-fold) by the addition of fibrinogen into the hydrogel during gelation.

Allele frequencies and haplotypes of the STR loci of the PowerPlex Y-system in southern populations from Korea.

In this study, 12 Y-specific STR loci--DYS391, DYS389 I, DYS439, DYS389 II, DYS438, DYS437, DYS19, DYS392, DYS393, DYS390, DYS385a/b--were analyzed in 259 unrelated males from the southern populations in Korea using the PowerPlex Y PCR system.