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641.
642.
In young male chicks a single injection of testosterone oenanthate leads to a long-lasting facilitation of behaviour patterns related to adult attack, courtship and copulation. The same responses, in particular facilitated pecking, may be evoked, with a similar time course of facilitation and subsequent waning, by a human hand or a white featureless sphere. The dose-response curve to the androgen is also similar for these two objects. A very simple stimulus thus appears to be capable of evoking at least one major component of aggressive behaviour, as well as other responses normally directed to conspecifics. Pecking of the sphere increases within 4–7 h of a second injection of the androgen, given after facilitation due to the first has disappeared, whereas the first requires 48–72 h to become effective. This rapid effect is not dependent on the age of the animal, nor on prior experience of pecking the sphere—indeed this causes marked habituation of all response to the sphere, whether or not response is facilitated by testosterone during the initial experience. It appears to result from central ‘priming’, perhaps by a process similar to the reversal of refractoriness to central androgen implants by prior systemic priming with testosterone, which has been previously reported for adult castrates. 相似文献
643.
Brain cholecystokinin (CCK) peptides have been proposed to be involved in the control of feed intake. We have examined the importance of the cerebral ventricular system in CCK-mediated satiety in sheep. Continuous injection of 0.64 pmol/min CCK-8 into the lateral ventricles (LV) decreased feeding, whereas injection of neither 0.64 nor 2.55 pmol/min CCK-8 into the cisterna magna (CM) significantly affected feeding. Thus, it is likely that the rostral, but not caudal, ventricular compartments and/or adjacent brain areas are involved in CCK-8 mediated satiety. The rate of injection of carrier solution (synthetic cerebrospinal fluid [sCSF]) was found to affect feed intake during a continuous 75 min injection: feed intakes were greater during injection of sCSF at 0.10 ml/min than during either 0.03 ml/min sCSF or no injection (sham). Injection of 0.64 pmol/min CCK-8 in either 0.03 or 0.10 ml/min decreased feeding. The increased feeding during 0.10 ml/min sCSF injection may have been due to dilution of endogenous CCK released into CSF during the meal. To determine the percent recovery from CSF of exogenous CCK-8, CSF samples from CM were collected during 3 hr continuous LV injections of CCK-8 and inulin (for measurement of bulk absorption). Only 20 to 40 percent of administered CCK-8 was recovered in CM CSF. The loss of CCK-8 was probably not due to degradation in the CSF by proteolytic enzymes, since CCK-8 concentrations did not decrease during in vitro incubation at 37°C for up to 24 hr. We propose that CCK-8 is released during feeding into the ventricular system, and subsequently taken up from CSF by specialized ependymal cells for transport to sites of action. 相似文献
644.
645.
Doris M. Kupfer C.Adonis Reece Sandra W. Clifton Bruce A. Roe Rolf A. Prade 《Fungal genetics and biology : FG & B》1997,21(3):364-372
Fungi comprise a large monophyletic group of uni- and multicellular eukaryotic organisms in which many species are of economic or medical importance. Fungal genomes are variable in size (13–42 Mb), and multicellular species support true spatial and temporal cell-type-specific regulation of gene expression. In a 38.8-kbAspergillus nidulanscontiguous genomic DNA region, a transposable element and 12 potential genes were identified, 7 similar to genes in other organisms. This observation is consistent with the prediction that multicellular ascomycetous fungi harbor 8000–9000 genes in a 36-Mb average genome. Thus, the genomic DNA sequence of filamentous fungi will provide substantial amounts of genetic and functional information that is not available in yeast, for the human and other metazoan minimal gene complement. 相似文献