Myosin heavy chain composition in the vastus lateralis muscle in relation to oxygen uptake and heart rate during cycling in humans

In this study we examined the relationship between fast myosin heavy chain (MyHC2) content in the vastus lateralis and the rate of oxygen uptake (VO2) and heart rate (HR) increase during an incremental exercise in 38, young, healthy men. Prior to the exercise test, muscle biopsies were taken in order to evaluate the MyHC composition. It was found that during cycling performed below the lactate threshold (LT), a positive relationship between MyHC2 and the intercept of the oxygen uptake and power output (VO2-PO) relationship existed (r=0.49, P=0.002), despite no correlation between MyHC2 and the slope value of the VO2-PO relationship (r= -0.18, P=0.29). During cycling performed above the LT, MyHC2 correlated positively with the magnitude of the nonlinearity in the VO2-PO relationship; i.e. with the accumulated VO2'excess' (r=0.44, P=0.006) and peak VO2'excess' (r=0.44, P=0.006), as well as with the slope of the HR-PO relationship (r=0.49, P=0.002). We have concluded that a greater MyHC2 content in the vastus lateralis is accompanied by a higher oxygen cost of cycling during exercise performed below the LT. This seems to be related to the higher energy cost of the non-cross-bridge activities in the muscles possessing a greater proportion of MyHC2 content. In the case of heavy-intensity exercise, a higher MyHC2 content in the vastus lateralis is accompanied by greater non-linearity in the VO2-PO relationship, as well as a steeper increase in HR in the function of an increase of PO. This relationship can be explained by greater disturbances in metabolic stability in type II muscle fibres during exercise, resulting in a decrease of muscle mechanical efficiency and greater increase of heart rate at a given power output. Therefore, MyHC composition has an impact on the oxygen cost of cycling both below and above the LT

The origin of lead artifacts from Novae: applications of Pb isotopes in identifying the provenance of Roman artifacts from N. Bulgaria

Abstract This study identifies the lead ores used to produce lead artifacts used by the Romans between the first and eighth centuries AD during the construction of the fort and then the town of Novae (N. Bulgaria). For this purpose, lead samples were taken from pipes, joints of columns and pedestals, and from a lead ingot. The samples were analyzed for lead isotopes and the results were compared to literature data for Roman mines from what is now Bulgaria, Greece, North Macedonia, Montenegro, Bosnia and Herzegovina, Italy, Germany, and Romania. Pb isotope results indicate that during the earlier stages of Novae's establishment, lead was most likely supplied from several different mines located in the Balkan area. Several samples also show Pb isotopes indicating mixing of lead from mines in the Balkan area. Then in the fourth—fifth century AD lead began to be supplied mainly from mines located in NW Bulgaria, with one sample possibly from deposits in German. This is evidenced by the matching of the results obtained for the ores to the data for deposits from these regions. Two possibly recycled samples were also identified. Deposits from other European regions did not match samples from Novae, indicating that majority of the lead was sourced from mines in the Balkan region