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81.
ANDREAS BAUMANN WERNER FESER PETER CRAMER RASOUL S. KERDAR HARTMUT BLODE JURGEN KORBER 《Biomarkers》2013,18(3):188-202
In the present study, a new in vitro model combining the short-term incubation of precision-cut human liver slices with DNA-adduct analysis by the 32P-postlabelling technique is proposed for investigation of the genotoxic potential of xenobiotics. For method validation, the metabolic turnover of testosterone (TES) and the DNA-adduct inducing potential of 2-aminofluorene (2-AF) were used. Precision-cut human liver slices were prepared from a total of 12 human liver samples which were freshly obtained as parts of resectates from liver surgery. The slices were incubated as submersion cultures with TES and 2-AF for up to 6 h in 12-well tissue culture plates at concentrations of 10-50 and 0.06-28 μM, respectively. Slices recovered from the slicing procedure in the 4 °C cold Krebs-Henseleit buffer as indicated by intracellular potassium concentrations which increased for 2 h and then remained stable until the end of the incubation. TES was extensively metabolized by human liver slices with a similar metabolite pattern as observed in vivo. Almost 90% of the metabolites were conjugates. Major phase-I metabolites were androstendione, 6β-OH-androstendione, 6β-OH-TES, and 15β-OHTES. After incubation with 2-AF, substance related DNA-adducts were detected which increased dose-dependently from 12 to 1146 adducts per 109 nucleotides. The adduct pattern consisted of one major adduct spot, A, representing 80-90% of the total adduct level and up to four minor adduct spots, B-E. In summary, the present data demonstrate that precision-cut liver slices are a valuable alternative in vitro system for DNA-adduct determination to screen chemicals for potential genotoxicity in humans. 相似文献
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83.
ABSTRACT “Pure tones” are a distinctive acoustic feature of many birdsongs. Recent research on songbird vocal physiology suggests that such tonal sounds result from a coordinated interaction between the syrinx and a vocal filter, as demonstrated by the emergence of harmonic overtones when a bird sings in helium. To investigate the communicative significance of vocal tract filtration in the production of birdsong, we used field playback experiments to compare the responses of male swamp sparrows Melospiza georgiana to normal songs and those same songs recorded in helium. We also measured responses to pure tone songs that had been shifted upward in frequency to match the average spectra of those songs with added harmonics. Male sparrows were significantly more responsive to the playback of normal songs than to either helium songs with added harmonics or frequency- shifted pure tone songs. Songs with harmonics retained a high degree of salience, however. We conclude that explanations for the occurrence of tonal sounds in birdsongs must consider perceptual attributes of songs as communicative signals, as well as problems of song production and transmission. 相似文献
84.
PETER L. TYACK 《Bioacoustics.》2013,22(1-2):21-46
ABSTRACT Bottlenose dolphins Tursiops truncatus produce individually distinctive signature whistles. Dolphins recognize the signature whistles of animals with which they share a social bond. Signature whistles develop within the first few months of life and are stable for a lifetime. Vocal learning appears to play a role in the development of signature whistles in bottlenose dolphins. The signature whistles of most female dolphins and about half of male dolphins differ from those of their mothers. Some dolphin calves born in captivity develop a signature whistle that matches either man-made whistles or those of an unrelated dolphin. Dolphins retain the ability as adults to imitate the whistles of animals with which they share strong individual-specific social relationships, bonds which may change throughout their lifetime. The exceptional imitative abilities of dolphin infants and the retention of this ability in adults may be related to the maintenance of changing individual specific social relationships. Individual recognition by the voice may differ in marine vs terrestrial mammals. Diving marine mammals may not be able to rely upon involuntary voice cues for individual recognition, but rather may require vocal learning to maintain a stable signature as their vocal tract changes shape with increasing pressure during a dive. 相似文献
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87.
Floral symmetry and nectar guides: ontogenetic constraints from floral development, colour pattern rules and functional significance 总被引:1,自引:0,他引:1
AMOTS DAFNI PETER G. KEVAN 《Botanical journal of the Linnean Society. Linnean Society of London》1996,120(4):371-377
The accord between symmetries of flower shape (external contours) and nectar guides (internal contours) was examined using the bulbous flora of South Africa, and in the general floras of Britain, Alpine Colorado, Canadian Arctic and Israel. It was found that radially symmetrical flowers have radially symmetrical nectar guides whereas bilaterally symmetrical flowers have bilaterally symmetrical nectar guides. It is suggested that the complementarity between the external and the internal contours of the flower increases the probability that, and efficiency with which, a bee moves into the flower's centre and towards the sporophylls and access to floral rewards, regardless of the flower's form and the bee's previous experience. Patterns of coloration of tepals against background and nectar guides against tepals also accord with behavioural and sensory characteristics of pollinators. It is suggested that the complementarity of contours is probably constrained by floral development, but patterns of coloration of tepals against background and nectar guides against tepals is constrained by pollinators' sensory physiology. 相似文献
88.
PETER G. LANGDON ZOE RUIZ SHIRLEY WYNNE CARL D. SAYER THOMAS A. DAVIDSON 《Freshwater Biology》2010,55(3):531-545
1. To correctly interpret chironomid faunas for palaeoenvironmental reconstruction, it is essential that we improve our understanding of the relative influence of ecosystem variables, biotic as well as physicochemical, on chironomid larvae. To address this, we analysed the surface sediments from 39 shallow lakes (29 Norfolk, U.K., 10 Denmark) for chironomid head capsules, and 70 chironomid taxa (including Chaoborus) were identified. 2. The shallow lakes were selected over large environmental gradients of aquatic macrophytes, total phosphorus (TP) and fish communities. Redundancy analysis (RDA) identified two significant variables that explained chironomid distribution: macrophyte species richness (P < 0.001) and TP (P < 0.005). Generalised linear models (GLM) identified specific taxa that had significant relationships with both these variables. Macrophyte percentage volume infested (PVI) and species richness were significant in classifying the lake types based on chironomid communities under twinspan analysis, although other factors, notably nutrient concentrations and fish communities, were also important, illustrating the complexities of classifying shallow lake ecosystems. Lakes with plant species richness >10 all had relatively diverse (Hill’s N2) chironomid assemblages, and lakes with Hill’s N2 >10 all had TP <250 μg L−1 and total fish densities <2 fish per m2. 3. Plant density (PVI), and perhaps more importantly species richness, were primary controls on the distribution of chironomid communities within these lakes. This clearly has implications for palaeoenvironmental reconstructions using zoobenthos remains (i.e. chironomids) and suggests that they could be used to track changes in benthic/pelagic production and could be used as indicators of changing macrophyte habitat. 4. Measuring key biological gradients, in addition to physicochemical gradients, allowed the major controls on chironomid distribution to be assessed more directly, in terms of plant substrate, food availability, competition and predation pressure, rather than implying indirect mechanisms through relationships with nutrients. Many of these variables, notably macrophyte abundance and species richness, are not routinely measured in such studies, despite their importance in determining zoobenthos in temperate shallow lakes. 5. When physical, chemical and ecological gradients are considered, as is often the case with palaeo‐reconstructions rather than training sets chosen to maximise one gradient, complex relationships exist, and attempting to reconstruct a single trophic variable quantitatively may not be appropriate or reliable. 相似文献
89.
Mottishaw PETRA D.; Thornton SHEILA J.; Hochachka PETER W. 《Integrative and comparative biology》1999,39(2):434-450
During the last half century or more, studies of diving physiologyand biochemistry made great progress in mechanistically explainingthe basic diving response of aquatic mammals and birds. Keycomponents of the diving response (apnea, bradycardia, peripheralvasoconstriction, redistribution of cardiac output) were foundin essentially all species analyzed and were generally takento be biological adaptations. By the mid 1970s, this approachto unravelling the diving response had run 'out of steam' andwas in conceptual stasis. The breakthrough which gave renewalto the field at this time was the development of microprocessorbased monitoring of diving animals in their natural environments,which led to a flurry of studies mostly confirming the basicoutlines of the diving response based upon laboratory studiesand firmly placing it into proper biological context, underliningits plasticity and species specificities. Now towards the endof the millenium, despite ever more detailed field monitoringof physiology, behaviour and ecology, mechanistic studies areagain approaching a point of diminishing returns. To avoid anotherconceptual stasis, what seems required are new initiatives whichwe anticipate may arise from two differing approaches. The firstis purely experimental, relying on magnetic resonance imaging(MRI) and spectroscopy (MRS) to expand the framework of theoriginal "diving response" concept. The secondevolutionarystudy of the diving responseis synthetic, linked to bothfield and laboratory studies. To date the evolution of the divingresponse has only been analyzed in pinnipeds and from thesestudies two kinds of patterns have emerged. (1) Some physiologicaland biochemical characters, required and used in diving animals,are highly conserved not only in pinnipeds but in all vertebrates;these traits are necessarily similar in all pinnipeds and includediving apnea, bradycardia, tissue specific hypoperfusion, andhypometabolism of hypoperfused tissues. (2) Another group offunctionally linked characters are more malleable and include(i) spleen mass, (ii) blood volume, and (iii) hemoglobin (Hb)pool size. Increases in any of these traits improve diving capacity.Assuming that conserved physiological function means conservedsequences in specific genes and their products (and that evolvingfunction requires changes in such sequences), it is possibleto rationalize both above trait categories in pinniped phytogeny.However, it is more difficult for molecular evolution theoryto explain how complex regulatory systems like those involvedin bradycardia and peripheral vasoconstriction remain the samethrough phylogenetic time than it is to explain physiologicalchange driven by positive natural selection. 相似文献
90.
The Physiological Mechanisms of Acclimatization in Tropical Reef Corals 总被引:12,自引:1,他引:11
SYNOPSIS. The ability of scleractinian corals to survive changesthat are predicted in the global environment over the next centurywill lie in their physiological mechanisms of acclimatization.Corals display rapid modifications in behavior, morphology andphysiology enabling them to photoacclimate to changing lightconditions, a scenario that demonstrates considerable biologicalflexibility. Here we argue that the acclimatization mechanismsin corals are fundamentally similar to those exhibited by otherinvertebrate taxa. We discuss protein metabolism as a mechanismunderlying acclimatization responses in reef corals, and explorethe relationship between protein turnover, metabolic rate, growthrate, and acclimatization capacity. Our preliminary analysessuggest that corals with low growth rates (µCa/mgN/h)and high metabolic rates (µO2/cm2/hr), such as the massivespecies, acclimatize more effectively than those with high growthrates and low metabolic rates, a feature that is characteristicof branching species. We conclude that studies of protein turnover,combined with temporally relevant investigations into the dynamicaspects of coral dinoflagellate symbioses will provide considerableinsight into why corals exhibit such a high level of variationin response to the same environmental challenge. Furthermore,a more detailed understanding of acclimatization mechanismsis essential if we are to predict how a coral assemblage willrespond to present and future environmental challenges. 相似文献