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Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Physics, Chemistry and Medicine | Award Amount: | Year: 2000

Keyword(s): PIGEONS / STREPTOPELIA / BIRDS / SONGS / SOUND PRODUCTION / VIBRATION / MECHANICS / PHYSICAL MODELS / MUSCLES / ZOOLOGY


Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 2000

Fish larvae are among the smallest free-living vertebrates. On average they measure less than 10 mm total length. The larvae hatch without having (functional) gills and depend on diffusion over their body surface during the first period of their life. As fish larvae grow rapidly , the surface to volume ratio rapidly decreases. Larvae must therefore have developed a new functional respiratory apparatus before the moment when body surface becomes insufficient to fill the respiratory needs. | The aim of the study is to estimate the moment when gill respiration takes over the major part of the oxygen supply and to investigate how the respiratory needs are met during development until this moment. [Results:] | Observations of swimming behavior of larval carp (5-7 mm TL) show that the frequency of spontaneous swimming bouts correlates with the oxygen saturation of the water. At lower partial oxygen pressure this frequency increases. It appears that the oxygen is depleted in their boundary layer and fish larvae have to refresh it regularly. Swimming kinematics are therefore also studied. | Measurements of oxygen concentration levels in the boundary layer at different spots on the larval body indicate that local diffusion characteristics are mainly the result of local needs. In general, the typical larval median finfold appears adapted for larval swimming, not for larval respiration.


Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 2000

The discrimination between direct genomic control and the influence of environmental factors on gene expression and differentiation of cells is an important issue in biology and medicine. Environmental factors influencing cells may be of chemical (i.e. induction) or physical nature. In our group, this problem is tackled in a study of the formation, during development, of the serially arranged myomeres and myosepts in fish. Previously, we developed a biochemical model ( Van Leeuwen, 1999) that predicts several aspects of the complex shape of fish myomers from mechanical principles and functional demands. Recently, the self-organization of the internal architecture of the myoseptum was included in this model. The location and orientation of intra-muscular bones and main ligaments in the myoseptum were successfully predicted by assuming that the production or deletion of extra-ceullular substances by the cells depends on the experienced mechanical load. Strikingly, the model predicts that a complex adaptive and functional system can be built by defining simple rules for the response of the cellular elements. In vivo and in vitro studies on mammalian tissues shows that a number of mesodermal cell types may change gene expression patterns after mechanical stimulation. As a result, the cells (trans)differentiate to a particular type. (e.g. fibroblast, osteoblast or muscle cell), change shape, reorientate, and produce particular extra-cellular substances such as bone and collagen. We hypothesise that from the moment that mechanical strain is produced within cells of somitic origin these cells and their neighbours are influenced by these forces and may change gene expression patterns, leading to specific differentiation processes. Bones for example will be formed at those locations where pressure forces are produced. In combination with gene expression studies, the above model is a unique tool to tackle basic morphogenetic questions of complexes of muscle, collagenous tissue and bone.


Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 1982

How do behaviour and growth optimalize the chance to catch a prey in growing fish larvae. How is an optimal relation reached between energy expenditure and energy gain during feeding.


Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 1984

sense organs, mucus, muscle-bone, kinematics head parts, feeding habits

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