Effects of artificial obstruction on the function of the upper urinary tract of Guinea pigs, rats and pigs.

Purpose: Four different experiments in animals were performed to evaluate the influence of pyelo-ureteral surgery on the function of the upper urinary tract.

Methods: Experiment I: In 17 female guinea pigs pyelo-ureteral anastomosis was performed microsurgically. Three months later, the ureteral peristalsis was investigated by measuring the intraureteral pressure and the in vitro activity of the renal pelvic and ureteric wall was analysed.

Temperature effects on isometric contractions of slow and fast twitch muscles of various rodents--dependence on fibre type composition: a comparative study.

The influence of temperature (range 15-37 degrees C) on the isometric contractions of the slow twitch soleus (SOL) and the fast twitch extensor digitorum longus (EDL) muscles of mice, rats and guinea pigs were investigated in vitro. Cooling of the bathing solution prolonged the time parameters of single twitches and tetanic contractions in a non-linear manner in both muscle types of all animals. In muscles containing predominately fast twitch fibres like the EDL of all animals cooling was followed by an increase of the single twitch tension (cold potentiation) with a maximum of 160-180% at about 20 degrees C.

Motoneuronal location and acetylcholine sensitivity of developing rat slow and fast twitch muscle fibres.

The postnatal changes of the extrajunctional acetylcholine (ACh) sensitivity of fast twitch (extensor digitorum longus muscle, EDL) and slow twitch (soleus muscle, SOL) of the rat were investigated in vitro. As a measure of the ACh-sensitivity serves the threshold dose of ACh necessary to evoke a contracture. Immediately after birth rat muscles show a high extrajunctional ACh-sensitivity, but the SOL exhibits a somewhat higher sensitivity (threshold dose 0.