De weigeringsgronden bij uitlevering en overlevering: Een vergelijking en kritische evaluatie in het licht van het beginsel van wederzijdse erkenning

Borgers, M.J. [Promotor]Rozemond, N. [Copromotor

Mechanical properties of mammalian single smooth muscle cells9

With the studies presented in this thesis it was attempted to achieve a discrimination between properties of smooth mus~ cle and of other components by measuring the passive and active properties of single smooth muscle cells isolated from both types of tissues. At the onset of the study experiments were solely performed on cells isolated from pig urinary bladders. which are quite similar to those of the human urinary bladder. In a later phase the study was extended to human uterine tissue fragments obtained at planned Caesarean sections. In order to achieve the goal of the study many practical and technical problems had to be solved. Some of the technical aspects have been published in international journals as a technical note or are embodied in the publications describing the results obtained. :Many others, although of crucial import: mce for the success of these experiments. especially in the field of cell and muscle physiology. were considered to have more practical and too little scientific value to be described in separate publications or in this thesi

Electrical stimulation of smooth muscle strips from the urinary bladder of the pig

Strips of smooth muscle from pig urinary bladders were electrically stimulated to contract. Stimulation parameters and conditions were optimized so as to obtain a maximum number of isometric contractions with maximal force. It was found that the contractions could be described mathematically by a simple model. In the model there is a constant probability for cells to pass from the non-contractile to the contractile state during stimulation; this leads to a linearly decreasing phase plot (a plot of the rate of rise of a variable as a function of the variable) for the force. 'Activation' of the cells is described by a physical step function. Isometric contractions were thus characterized by a set of three parameters: U, the time derivative of the force, extrapolated to zero force, Fiso the value of the isometric force which is approached asymptotically after infinitely long periods of stimulation and t1, the activation time. The sensitivity of these three parameters to variation of the stimulus parameters was investigated. It was found that the parameter U was consistently correlated with the stimulus parameters, suggesting that this parameter can be used to describe the effectiveness of electrical stimulation of such strips