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The extrinsically denervated and vascularly perfused stomach of the hyperthyroid rat exhibits an increased basal gastrin release and an exaggerated response to stimulation with the b-agonist isoproterenol. The b-blocker propranolol does not inhibit the increased basal release of gastrin, but completely blocks the effect of isoproterenol. Vagal stimulation is not different between hyperthyroid and euthyroid rats. We conclude, that there are two mechanisms which are responsible for the increased release of gastrin in hyperthyroidism: firstly a direct effect of thyroid hormones on gastrin cells, and secondly an increase in sensitivity of gastrin cells towards b-adrenergic stimulation. 相似文献
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R A Pederson J R Dryburgh J C Brown 《Canadian journal of physiology and pharmacology》1975,53(6):1200-1205
Studies were carried out in conscious dogs in which the effect of intravenous somatostatin on immunoreactive gastric inhibitory polypeptide (IR-GIP) release was investigated. In addition, the inhibitory action of somatostatin on the insulin response to pure porcine GIP was assessed. Intravenous administration of somatostatin resulted in a delayed IR-GIP and immunoreactive insulin (IRI) response to oral glucose. Somatostatin also delayed the IR-GIP response to the ingestion of fat. In both types of experiments, initial depression of IRI levels was followed by a sharp rise in IRI release. Intravenous infusion of somatostatin produced 80% inhibition of the IRI response to pure porcine GIP. It was concluded that somatostatin inhibits the physiological release of IR-GIP and the insulinotropic action of exogenous porcine GIP. 相似文献
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Asia O. Armstrong Amelia J. Armstrong Michael B. Bennett Anthony J. Richardson Kathy A. Townsend Jason D. Everett Graeme C. Hays Hugh Pederson Christine L. Dudgeon 《Ecology and evolution》2021,11(10):5606
- Mutualism is a form of symbiosis whereby both parties benefit from the relationship. An example is cleaning symbiosis, which has been observed in terrestrial and marine environments. The most recognized form of marine cleaning symbiosis is that of cleaner fishes and their clients.
- Cleaner species set up cleaning stations on the reef, and other species seek out their services. However, it is not well understood how the presence of cleaning stations influence movements of large highly mobile species. We examined the role of cleaning stations as a driver of movement and habitat use in a mobile client species.
- Here, we used a combination of passive acoustic telemetry and in‐water surveys to investigate cleaning station attendance by the reef manta ray Mobula alfredi. We employed a novel approach in the form of a fine‐scale acoustic receiver array set up around a known cleaning area and tagged 42 rays. Within the array, we mapped structural features, surveyed the distribution of cleaner wrasse, and observed the habitat use of the rays.
- We found manta ray space use was significantly associated with blue‐streak cleaner wrasse Labroides dimidiatus distribution and hard coral substrate. Cleaning interactions dominated their habitat use at this site, taking precedence over other life history traits such as feeding and courtship.
- This study has demonstrated that cleaning symbiosis is a driver for highly mobile, and otherwise pelagic, species to visit inshore reef environments. We suggest that targeted and long‐term use of specific cleaning stations reflects manta rays having a long‐term memory and cognitive map of some shallow reef environments where quality cleaning is provided. We hypothesize that animals prefer cleaning sites in proximity to productive foraging regions.
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Environmental stress, heterozygote advantage and genotype-environment interaction in Arabidopsis 总被引:3,自引:0,他引:3
D G Pederson 《Heredity》1968,23(1):127-138
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