Browse

You are looking at 1 - 10 of 77,425 items for

Authors: M. Michalis, K.J. Finn, R. Podstawski, S. Gabnai, Á. Koller, A. Cziráki, M. Szántó, Z. Alföldi and F. Ihász

Abstract

Within recent years the popularity of sportive activities amongst older people, particularly competitive activities within certain age groups has increased. The purpose of this study was to assess the differences in the cardiorespiratory output at anaerobic threshold and at maximal power, output during an incremental exercise, among senior and young athletes. Ten elderly male subjects [mean (SD) age: 68.45 ± 9.32 years] and eight young male subjects [mean (SD) age: 25.87 ± 5.87 years] performed an incremental exercise test on a treadmill ergometer. No significant differences in body size were evident; however, the differences between the groups for peak power (451.62 ± 49 vs. 172.4 ± 32.2 W), aerobic capacity (57.97 ± 7.5 vs. 40.36 ± 8.6 mL kg−1 min−1), maximal heart rate (190.87 ± 9.2 vs. 158.5 ± 9.1 beats min−1), peak blood lactate (11 ± 1.7 vs. 7.3 ± 1.4 mmol L−1), and % VO2max at ventilatory thresholds (93.18 ± 4.3 vs. 79.29 ± 9.9%) were significantly lower in the senior athletes. The power output at anaerobic threshold was also higher (392 ± 48 vs. 151 ± 23 W) in the young athletes, explaining the significant difference in terms of performance between these groups. We have observed an evident deterioration in some of the cardiovascular parameters; however, the submaximal exercise economy seems to be preserved with aging. Exercise economy (i.e. metabolic cost of sustained submaximal exercise) was not different considerably with age in endurance-trained adults.

Open access
Authors: M. Nakamura, N. Satoh, H. Tsukada, T. Mizuno, W. Fujii, A. Suzuki, S. Horita, M. Nangaku and M. Suzuki

Abstract

Purpose

Acid-base transport in renal proximal tubules (PTs) is mainly sodium-dependent and conducted in coordination by the apical Na+/H+ exchanger (NHE3), vacuolar H+-adenosine triphosphatase (V-ATPase), and the basolateral Na+/HCO3 - cotransporter. V-ATPase on PTs is well-known to play an important role in proton excretion. Recently we reported a stimulatory effect of insulin on these transporters. However, it is unclear whether insulin is involved in acid-base balance in PTs. Thus, we assessed the role of insulin in acid-base balance in PTs.

Methods

V-ATPase activity was evaluated using freshly isolated PTs obtained from mice, and specific inhibitors were then used to assess the signaling pathways involved in the observed effects.

Results

V-ATPase activity in PTs was markedly enhanced by insulin, and its activation was completely inhibited by bafilomycin (a V-ATPase-specific inhibitor), Akt inhibitor VIII, and PP242 (an mTORC1/2 inhibitor), but not by rapamycin (an mTORC1 inhibitor). V-ATPase activity was stimulated by 1 nm insulin by approximately 20% above baseline, which was completely suppressed by Akt1/2 inhibitor VIII. PP242 completely suppressed the insulin-mediated V-ATPase stimulation in mouse PTs, whereas rapamycin failed to influence the effect of insulin. Insulin-induced Akt phosphorylation in the mouse renal cortex was completely suppressed by Akt1/2 inhibitor VIII and PP242, but not by rapamycin.

Conclusion

Our results indicate that stimulation of V-ATPase activity by insulin in PTs is mediated via the Akt2/mTORC2 pathway. These results reveal the mechanism underlying the complex signaling in PT acid-base balance, providing treatment targets for renal disease.

Restricted access

Beköszöntő

111 éves az Üllői úti Semmelweis Egyetem I. sz. Sebészeti Klinikájának épülete

Author: Attila Szijártó
Restricted access
Restricted access
Authors: János Horányi, Rezső Szlávik, Krisztina Fekete and Attila Szijártó
Open access
Authors: László Harsányi, Tibor Tihanyi, Tamás Marjai, Márton Benke, Ákos Szücs and Attila Szijártó
Open access
Restricted access