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- Charifi, N., et al.
(author)
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Enhancement of microvessel tortuosity in the vastus lateralis muscle of old men in response to endurance training
- 2004
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In: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 554:Pt 2, s. 559-569
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Journal article (peer-reviewed)abstract
- Muscle microvascularization is usually quantified in transverse sections, in absolute terms (capillaries around fibres, CAF, or capillary-to-fibre ratio, C/F) or as CAF related to fibre area (CAF/area, CAFA). The capillary-to-fibre perimeter exchange ratio (CFPE) has been introduced in order to assess the role of the capillary-to-fibre interface in resistance to O(2) diffusion. The ratio between the length of capillaries in contact with fibres and fibre perimeter (LC/PF) has also been used as an index for capillary tortuosity. The possibility of change in capillary tortuosity with endurance training was not considered in previous studies. Consequently, this study investigated the effect of 14 weeks of endurance training on muscle microvascularization, including microvessel tortuosity, in 11 elderly men (8th decade). Microvessels were analysed using the CD31 antibody. Together with the significant increase in peak oxygen exchange and citrate synthase activity, there was a significant increase in C/F. While CFPE and CAFA remained unchanged, an important finding was the clear increase in LC/PF (56%; P < 0.001) for a same sarcomere length. We also found a strong correlation between oxidative enzyme activity and LC/PF both before and after training. These results indicate that endurance training induces significant remodelling in the microvessel network in elderly men and that an increase in the degree of microvessel tortuosity would be an important mechanism of adaptation to endurance training.
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- Gonçalves, Maria M., et al.
(author)
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Cationic and anionic environments in mono-urethanesil hybrids doped with magnesium triflate
- 2004
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In: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 166:1-2, s. 103-114
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Journal article (peer-reviewed)abstract
- Sol–gel derived poly(oxyethylene), POE/siloxane hybrids (mono-urethanesils) with a wide range of magnesium triflate (Mg(CF3SO3)2) concentrations were analyzed by infrared and Raman spectroscopies with the goal of examining the cation/polymer, cation/cross-link, hydrogen bonding and cation/anion interactions. In the host matrix of these xerogels short CH3-terminated POE segments are covalently bonded to the siliceous backbone through urethane linkages. Samples with ∞>n≥6 (where n is the molar ratio of (OCH2CH2) moieties per Mg2+ ion) were synthesized.The spectral data obtained provided conclusive evidence that the ether oxygen atoms of the polymer chains of the host structure complex the alkaline-earth ions in materials with n≤60. "Free" triflate ions and weakly coordinated anions were detected over the whole range of salt concentration examined. The coordinated triflate species are formed in two different bonding environments. Contact ion pairs appear in materials with n≤60.This work confirms previous studies that suggested that the nature of the cations added to the mono-urethanesil-type framework plays a key-role in the properties of these composites.
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