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11.
Andrea Streng Hans G. Wallraff 《Ethology : formerly Zeitschrift fur Tierpsychologie》1992,91(3):203-219
The role of familiar visual landmarks in pigeon homing is still unsettled. If they are involved, they must be thought to be utilized in parallel with olfactory signals. In order to recognize the effectiveness of either one of the input channels separately, vision and olfaction, it is therefore necessary to interfere with both of them. Pigeons were temporarily deprived of image vision by spectacles made of translucent white paper, producing a condition called V- as compared with the largely unimpaired condition V+. Access to olfactory signals was temporarily prohibited by charcoal filters before release and nasal anaesthesia upon release, resulting in condition O- versus unimpaired smelling of natural air in O+. Prior to the test releases, all the participating pigeons had been made familiar with the two or four test sites (and with other sites in the area) by training flights. According to decreasing levels of initial homeward orientation and homing performance, the four combinations of treatments are to be arranged in the following order: V+O+, V+O-, V-O+, V-O-. In the last type, no trace of initial homeward orientation remained, indicating that at least one of the two input channels need be functional to enable home-related orientation. Over well known terrain, either alone seems to be more or less sufficient. The results are indicative but not definitely conclusive. Effects of visual impairment on behavioural activities in general cannot clearly be separated from orientation-specific effects. Therefore, and because many pigeons refuse to fly in V- condition or fail to provide useful data, we stopped applying this method. 相似文献
12.
Dall'Olio Fabio; Mariani Erminia; Tarozzi Andrea; Meneghetti Alessandra; Chiricolo Mariella; Lau Joseph T. Y.; Facchini Andrea 《Glycobiology》1997,7(4):507-513
The extent of processing of N-linked oligosaccharides and thesialylation of the target cell membranes has been positivelycorrelated with resistance to lysis mediated by NK cells, buta conclusive evidence has never been reached. Colon cancer tissuesexpress an increased activity of ß-ga-lactoside 相似文献
13.
Andrea Robitzki Alexandra Mack Arnaud Chatonnet Paul G. Layer 《Journal of neurochemistry》1997,69(2):823-833
Abstract: The function of the enzyme butyrylcholinesterase (BChE) in the developing and mature brain is still unclear. We have inserted 577 bp of the 5' upstream region plus 106 bp of the exon 1 of the rabbit BChE gene in reverse orientation under control of an SV40 early promoter derivative in an expression vector. This vector was introduced by calcium phosphate-mediated transfection into embryonic chicken retina cells during the first days of reaggregation culture. Depending on the retinal origin, the transfected cell population forms histotypic retina-like spheres, so-called rosetted or stratified retinospheroids. We show that antisense 5'-BChE gene expression decreased the steady-state mRNA level of BChE and the translation of the BChE protein, inhibited proliferation, and accelerated histogenesis in both cellular systems. The pronounced effects of antisense 5'-BChE transfection of spheroids document a key role of BChE during the early reaggregation process of retinal cells, most likely by regulating their growth and differentiation. 相似文献
14.
A mutation assay in cultured mammalian cells based on the direct analysis of minisatellite DNA was developed. Band pattern variations reflect DNA alterations ranging from single base changes to complex rearrangements. By DNA fingerprinting a large number of autosomal loci throughout the human genome can be simultaneously checked, therefore minimizing the size of the samples of cell colonies to be scored in the absence of phenotypic selection. For the mutation assay chinese hamster cells (V79) were treated with Nitrosoguanidine and 14 independent colonies were isolated and expanded. DNA fingerprints were obtained after digestion of the DNA extracted from each clone with bothHinfI andHae III, and hybridisation with both 33.15 and 33.6 probes. Twelve colonies from untreated cells were also analysed. Several differences in the band pattern of treated colonies were observed when compared with untreated cells; digestion withHae III and hybridisation with 33.15 probe allowed the detection of the highest frequency of induced variants. The results suggest that minisatellite sequences are hypermutable sites that can be used to monitor the mutagenic potential of chemical agents directly at the DNA level, without phenotypic selection. Moreover, with the method herein decribed, it is possible to distinguish between true mutations and epimutations, such as those caused by changes in DNA methylation. 相似文献
15.
H. Sinzinger K. Silberbauer A.K. Horsch Andrea Gall 《Prostaglandins & other lipid mediators》1981,21(1):49-51
During successful treatment of peripheral vascular disease with synthetic prostacyclin no alteration in platelet function was reported (1).In 8 patients infused with synthetic prostacyclin continuously for 7 days intraarterially, the platelet function was monitored. Special attention was drawn to the platelet sensitivity in vitro for PGI2, which is discussed as an important factor maintaining the hemostatic balance.In all the patients with peripheral vascular disease between 24 and 48 hours after the beginning of the infusion a sudden decrease in platelet sensitivity accompanied by an increase in platelet count could be seen.These dramatic alterations representing probably a rebound phenomenon occurring during long-term PGI2-treatment might be an explanation for a non-beneficial effect of the treatment and in some cases a limiting factor for the continuation of the infusion itself. It is not clear, if this rebound phenomenon is due to a stimulation of an endogenous inhibitor, lowering the synthesis of a naturally occurring substance acting against this inhibitor or tachyphylaxia. 相似文献
16.
17.
Maura Marinozzi Andrea Carotti Roccaldo Sardella Federica Buonerba Federica Ianni Benedetto Natalini Daniela Passeri Giovanni Rizzo Roberto Pellicciari 《Bioorganic & medicinal chemistry》2013,21(13):3780-3789
An asymmetric synthetic strategy was designed for the preparation of the four possible diastereoisomers of 3,6-dimethyl-1-(2-methylphenyl)-4-(4-phenoxyphenyl)-4,8-dihydro-1H-pyrazolo[3,4-e][1,4]thiazepin-7-one, a non-steroidal FXR agonist, we recently discovered following a virtual screening approach. The results obtained from an AlphaScreen assay clearly demonstrated that only the isomer endowed with 4R,6S absolute configuration is responsible for the biological activity. A deep investigation of the different putative binding modes adopted by these enantiomerically pure ligands using computational modeling studies confirmed the enantioselectivity of FXR towards this class of molecules. 相似文献
18.
Uric Acid Amplifies Aβ Amyloid Effects Involved in the Cognitive Dysfunction/Dementia: Evidences From an Experimental Model In Vitro 下载免费PDF全文
19.
Andrea E Bialocerkowski Mary Galea 《Journal of brachial plexus and peripheral nerve injury》2006,1(1):1-6
Background
Animal studies have demonstrated complex cortical reorganization following peripheral nerve lesion. Central projection fields of intact nerves supplying skin areas which border denervated skin, extended into the deafferentiated cortical representation area. As a consequence of nerve lesions and subsequent reorganization an increase of the somatosensory evoked potentials (SEPs) was observed in cats when intact neighbouring nerves were stimulated. An increase of SEP-components of patients with nerve lesions may indicate a similar process of posttraumatic plastic cortical reorganization.Methods
To test if a similar process of post-traumatic plastic cortical reorganization does occur in humans, the SEP of intact neighbouring hand nerves were recorded in 29 patients with hand nerve lesions. To hypothetically explain the observed changes of SEP-components, SEP recording following paired stimulation of the median nerve was performed in 12 healthy subjects.Results
Surprisingly 16 of the 29 patients (55.2%) showed a reduction or elimination of N35, P45 and N60. Patients with lesions of two nerves showed more SEP-changes than patients with a single nerve lesion (85.7%; 6/7 nerves; vs. 34.2%; 13/38 nerves; Fisher's exact test, p < 0.05). With paired stimulation a suppression of the amplitude of N20, P25 and P45 (p < 0.05; sign test), and a marked increment of N35 (p < 0.05; sign test) and N60 (not significant; sign test) of the second response could be observed.Conclusion
The results of the present investigation do not provide evidence of collateral innervation of peripherally denervated cortical neurons by neurons of adjacent cortical representation areas. They rather suggest that secondary components of the excitatory response to nerve stimulation are lost in cortical areas, which surround the denervated region. 相似文献20.
Reinvasion of pest animals after incomplete control is a major challenge for invasive species management, yet little is known about the behavioural and demographic categories of reinvaders or the mechanisms that drive population‐level responses to control. To understand the fine‐scale mechanisms of reinvasion, we examined changes in demography, movements and activity patterns of reinvading alien black rats Rattus rattus in the short (4 weeks) and longer term (3 months) following localised experimental pest removal. Using recovery and invasion theory, we tested three hypothesised mechanisms of reinvasion: the ‘in situ effect’, the ‘trickle effect’ and the ‘vacuum effect’. We created space for reinvasion by removing black rats from the core of replicate 1‐ha plots (short‐term experiment) and later by removing animals from the entire plot (longer‐term experiment). Reinvaders were characterised as dispersing juveniles, floaters or neighbours. Radio‐tracking quantified home range changes for adjacent resident animals (short‐term experiment only). In the short term, there was no net influx of rats after targeted removal. Radio‐tracked residents’ movements were highly variable and displayed no directional changes after nearby conspecifics were removed. However, in the longer term, removal led to slow population recovery through a mix of reinvading floaters, dispersing juveniles and shifting residents. These responses best support a hypothesis of reinvasion through a trickle effect, with rats being extremely mobile and having a high degree of population turnover, even in untreated sites. Our findings provide the first test of reinvasion theory at a small scale, demonstrating the importance of understanding the differing categories of reinvaders and mechanisms of reinvasion after population control. These mechanisms drive the rate of population recovery and, in turn, should help determine which strategy of pest control should be used, and the frequency with which they are implemented, in order to slow the recovery of pest populations. 相似文献