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The author describes mainly on basis of his own studies, antagonistic interrelationships between the thyroid gland activity and the action of extrahypophyseal gonadotropins (PMSG, hCG) on ovaries in experimental (rats) and domestic animals (sheep, pigs). Hypothyroidism intensifies the action of gonadotropins on ovaries, thus increasing their activity as evidenced by the increase of ovarian weight, number of vesicles and by development of multiple vesicular cysts (PCO syndrome in women, rats, cattle and pigs). In hiperthyroidism these situations are absent or their development is resticted. In hypothyroidic animals an increased sensitivity of ovaries to the action of gonadotropins may result from an increased production of receptors for LH/hCS in ovaries and the decrease of their production in hiperthyroidic animals. Thyreotropic action of gonadotropins stated by the author has been confirmed lately. This activity in women in the first trimester of pregnancy is caused by certain isoforms of chorionic gonadotropin (hCG). The presented study points to a significant role of the functioning of the thyroid gland in the development of vesicular cysts in ovaries of women, rats, cattle and pigs.
Vomiting syndrome comprises three main components that can also occur separately nausea, retching and vomiting. Currently there is no doubt that multiple changes in gastrointestinal motility occur during the vomiting process. Little is known about motor phenomena during nausea. Distention of the gastrointestinal lumen, antral tachygastria, tonic contractions of glottis and cervical esophagus as well the relaxation of cardia and proximal stomach are the most common alterations. During retching a giant retrograde contraction travels from the jejunum toward the gastric antrum and is associated with slow wave disturbances. Gastric content is expelled to the distended esophagus and then is returned back to the stomach. In the course of vomiting gastric content is expelled outside as a consequence of the relaxation and then contraction of the esophagus. Ejection of gastric content is mainly due to rapid and strong contractions of the abdominal muscle and the diaphragm. Some changes in colon and gallbladder motility may accompany vomiting.
Bile acids exhibit detergent properties. Their influence on various types of cells in the gastrointestinal wall, including smooth muscle cell, is substantial. They are present in the intestinal lumen and circulation as conjugated or deconjugated salts. In studies in vitro they cause smooth muscle relaxations. Their effects in vivo can be due to their direct action on the smooth muscles or they act indirectly: the action can be mediated by the nervous system and gut hormone release. When the gastrointestinal mucosa is exposed to bile or bile acids the frequency of gastric contractions increases and the activity front of the migrating motor complex (MMC) is initiated. Bile acids exert a stronger effect than the entire bile. The type and amount of bile acids can also be important. The intraarterial route of bile acid administration appears to be more efficient than intraluminal route. Bile diversion from the duodenum induces contrary effects, i.e. a relaxing effect in the stomach and irregular motor activity in the small bowel or prolonged phase 2 MMC have been observed. These effects are apparently due to the interaction of bile acids with muscarinic receptors and mediated by motilin and cholecystokinin, two gut hormones the release of which is strongly influenced by luminal bile acids.
Examinations of the mechanical aspects of the gastrointestinal function discussed here represent the biophysical fragment of its motor activity. Their purpose is to obtain further characteristics of gastrointestinal smooth muscle layer properties and contractions and an analysis of the relationships between contraction and effect of contraction. Much effort in these studies will still be required because of the complexity of motor events and the multiplicity of the factors affecting these events. Several theoretical and practical, in vivo and in vitro methods were utilized in these investigations and the results of classical methods of gastrointestinal motility examinations have been useful in the characterization of mechanical properties of the gastrointestinal smooth muscle. The application of computer models allows for simulations of motor activity in the given conditions, for evaluation of contractile effect and for prediction of the given motor effect in the considered physiological or pathological situation. These examinations are still not developed in veterinary medicine and their greater usefulness in the veterinary clinics is mostly dependent on the progress in the diagnosis of gastrointestinal motor disturbances.
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