Claudia Lange — Page 2

PubMed2002

Left ventricular response to dynamic exercise in young cyclists.

PURPOSE: The purpose of this study was to compare cardiac physiological and dimensional responses to exercise in highly trained young male cyclists (mean age 13.7 +/- 1.0 yr) with those of nontrained boys. METHODS: Ventricular systolic and diastolic dimensions were measured by two-dimensional echocardiography, and stroke volume was estimated by Doppler echocardiography during a progressive maximal upright cycle test. RESULTS: At rest, the cyclists demonstrated larger left ventricular dimensions relative to body size than the nonathletes. Maximal stroke index and cardiac index were significantly greater in the cyclists. The pattern of stroke volume response to exercise was similar in the two groups, with an early rise and then plateau to exhaustion. Left ventricular diastolic dimension increased slightly at onset of exercise and then gradually declined as workload increased in both groups. CONCLUSION: Factors responsible for the greater maximal stroke volume in young endurance athletes involve those variables that contribute to resting left ventricular diastolic filling (preload).

Adolescent↗

PubMedDate not supplied

Fetal and adult liver stem cells for liver regeneration and tissue engineering.

For the development of innovative cell-based liver directed therapies, e.g. liver tissue engineering, the use of stem cells might be very attractive to overcome the limitation of donor liver tissue. Liver specific differentiation of embryonic, fetal or adult stem cells is currently under investigation. Different types of fetal liver (stem) cells during development were identified, and their advantageous growth potential and bipotential differentiation capacity were shown. However, ethical and legal issues have to be addressed before using fetal cells. Use of adult stem cells is clinically established, e.g. transplantation of hematopoietic stem cells. Other bone marrow derived liver stem cells might be mesenchymal stem cells (MSC). However, the transdifferentiation potential is still in question due to the observation of cellular fusion in several in vivo experiments. In vitro experiments revealed a crucial role of the environment (e.g. growth factors and extracellular matrix) for specific differentiation of stem cells. Co-cultured liver cells also seemed to be important for hepatic gene expression of MSC. For successful liver cell transplantation, a novel approach of tissue engineering by orthotopic transplantation of gel-immobilized cells could be promising, providing optimal environment for the injected cells. Moreover, an orthotopic tissue engineering approach using bipotential stem cells could lead to a repopulation of the recipients liver with healthy liver and biliary cells, thus providing both hepatic functions and biliary excretion. Future studies have to investigate, which stem cell and environmental conditions would be most suitable for the use of stem cells for liver regeneration or tissue engineering approaches.

Animals↗