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791.
792.
Craig A. Walling Nick J. Royle Neil B. Metcalfe Jan Lindström 《Behavioral ecology and sociobiology》2007,61(7):1007-1014
It is well documented that poor early nutrition can have profound negative effects on adult life-history traits. However,
it has also been demonstrated that organisms can undergo compensatory resource allocation strategies (such as an accelerated
growth rate) if food availability improves, so as to mitigate the effects of the poor early conditions. Previous research
has indicated that elevated growth rates can incur costs in the longer term, such as an increased rate of senescence and shorter
lifespan. We tested whether a phase of compensatory growth after a period of reduced food availability earlier in life affected
the sexual attractiveness of adult male green swordtails Xiphophorus helleri, a species in which it has previously been documented that females prefer larger-bodied and longer-tailed males. The experiment
compared the attractiveness of size-matched brothers that had experienced contrasting growth trajectories as juveniles; the
experiments were initially conducted in the middle of a male’s sexually reproductive life and were then repeated towards the
very end of life. At both ages, males that had undergone compensatory growth were equally as attractive as their brothers
that had grown normally. These results suggest that the growth compensation benefits males through an increase in their attractiveness
over that which they would have had if they had remained on their original growth trajectory. The lack of change in relative
attractiveness with age indicates that the compensation does not cause greater deterioration in secondary sexual characters
at older ages than in continuously well-fed males. 相似文献
793.
Summary Gyrinid beetles are common in freshwater habitats. They have paired pygidial glands with a secretion that contains high molecular weight substances rendering them toxic for predatory fish. In this paper we report on a laboratory study on volatile components released by three different gyrinid species when irritated. The volatile pattern had a clear difference between the different species.Gyrinus substriatus andG. aeratus, both produced 3-methyl-1-butanal and 3-methyl-1-butanol when irritated, but in quite different amounts. The third tested species,G. minutus, did not produce any substances above the detection level. It is suggested that the volatile compounds may be part of the beetles' communication and/or defence system. 相似文献
794.
Primary hepatocytes of the rainbow trout (Oncorhynchus mykiss), flounder (Platychthis flesus), dab (Limanda limanda) and lemon sole (Microstomus kitt) were exposed to 3,3'4,4'5 pentachlorobiphenyl (PCB 126) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for two days. This resulted in a dose-dependent induction of cytochrome P4501A (CYP1A) activity, measured as ethoxyresorufin O-deethylase (EROD), or methoxyresorufin O-deethylase (MROD) activity. In all species, a linear relationship was observed between EROD and MROD activities, suggesting that the same CYP1A enzyme metabolizes the two alkoxy-resorufin substrates. Exposures of hepatocytes of flounder or dab to TCDD, resulted in a 59-fold and 8.2-fold induction of EROD activity, respectively. This did not concur with a change in the in vitro testosterone hydroxylation profiles of both species. These and other in vitro data indicate that TCDD exposure does not influence monooxygenase activities involved in testosterone hydroxylation. Furthermore, CYP1A is of minor importance for testosterone hydroxylation in these fish species. 相似文献
795.
Isabel W.C.E. Arends Jan G.P. Born W.Ren Ophorst Peter Mulder Robert Louw 《Chemosphere》1989,18(9-10):1965-1970
Pyrolysis (800–900°C, ca. 5 s) of benzene/HC1 mixtures leads to chlorobenzene (1) even in a reducing environment of H2 and/or CH4. With added oxygen, 1 is formed even at 550°C; such slow combustions also yield chlorinated phenols and dibenzofurans. 相似文献
796.
Erisman JW Hensen A de Vries W Kros H van de Wal T de Winter W Wien JE van Elswijk M Maat M Sanders K 《Ambio》2002,31(2):190-196
A nitrogen decision support system in the form of a game (NitroGenius) was developed for the Second International Nitrogen Conference. The aims were to: i) improve understanding among scientists and policy makers about the complexity of nitrogen pollution problems in an area of intensive agricultural, industrial, and transportation activity (The Netherlands); and ii) search for optimal policy solutions to prevent pollution effects at lowest economic and social costs. NitroGenius includes a model of nitrogen flows at relevant spatial and temporal scales including emissions of ammonia and nitrogen oxides and contamination of surface- and groundwaters. NitroGenius also includes an economic model describing relationships for important sectors and impacts of different nitrogen control measures on Gross Domestic Product (GDP), unemployment, energy use, and environmental costs. About 50 teams played NitroGenius during the Second International Nitrogen Conference. The results show that careful planning and selection of abatement options can solve Dutch nitrogen problems at reasonable cost. 相似文献
797.
Mikael Gillner Birgitta Fernstrm Jan-ke Gustafsson Jan Bergman Christian Cambillau 《Chemosphere》1986,15(9-12):1673-1680
We have investigated the capacity of various indoles to inhibit specific binding of [1,6-3H]2,3,7,8-tetrachlorodibenzo-
-dioxin ([3H]TCDD) in rat liver cytosol, as analyzed by electrofocusing in polyacrylamide gels. Of these indoles, indolo[3,2-
]carbazole was the most active. The IC50 value for TCDD receptor binding of indolo[3,2-
]carbazole as well as for 2,3,7,8-tetrachlorodibenzofuran was 3.6 nM. We have also studied the influence on binding exerted by introduction of some substituents on indolo[3,2-
]carbazole. Substitution with methyl groups at the 5 and 11 positions resulted in an increased affinity (IC50 1.2 nM) for the TCDD receptor as compared to the parent compound. Computer-supported molecular structure studies indicated that if the van der Waals radii of atoms are included, a rectangle of 6.8 × 13.7 Å may account for the binding of high-affinity ligands to the TCDD receptor. 相似文献
798.
Jan M. Everaarts 《Environmental monitoring and assessment》1986,7(3):273-283
Haemoglobin in Arenicola has a high oxygen affinity, with a half saturation oxygen pressure of about 180 Pa at pH 7.4 and 15°C. The oxygen affinity decreases with increasing copper concentration in the blood to about 300 Pa at pH 7.4, 15°C. at a copper concentration of 35 g ml-1. Copper exerts only a slight influence on the subunit cooperativity in oxygen binding. The oxygen affinity, subunit cooperativity and the Bohr effect are pH dependent. Copper affects the functioning of the blood by inhibiting oxygen binding to the haemoglobin in the respiratory area and oxygen delivery in the tissues. 相似文献
799.
Glasius M Christensen JH Platz J Vorkamp K 《Journal of environmental monitoring : JEM》2005,7(2):127-131
Mussels and marine fish (shorthorn sculpin and Greenland cod) were sampled at three locations with varying human activity. Fish livers and mussels were analysed for polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and chlorinated pesticides including chlordane and toxaphene. Levels of chlorinated contaminants in shorthorn sculpins from the background location, [capital Sigma]PCB (217-224 ng g(-1) lw), [capital Sigma]DDT (180 ng g(-1) lw) and hexachlorobenzene (32-44 ng g(-1) lw), were in the same range as previously observed in eastern Greenland but exceeded the levels previously observed in southern and western Greenland. Multivariate analysis showed that pollutant concentrations were mainly explained by trophic levels of the species (cod > sculpins > mussels). A pooled sample of shorthorn sculpins from the harbour of Qaqortoq had significantly higher PCB and PBDE concentrations with a different congener pattern compared to the background site, while other contaminants were comparable. This points towards local pollution sources, possibly accumulated emissions from burning of waste. 相似文献
800.
Valentina Krysanova Frank Wechsung Alfred Becker Werner Poschenrieder Jan Gräfe 《Environmental Modeling and Assessment》1999,4(4):259-271
Hydrological processes and crop growth were simulated for the state of Brandenburg (Germany) using the hydrological/vegetation/water quality model SWIM, which can be applied for mesoscale river basins or regions. Hydrological validation was carried out for three mesoscale river basins in the area. The crop growth module was validated regionally for winter wheat, winter barley and maize. After that the analysis of climate change impacts on hydrology and crop growth was performed, using a transient 1.5 K scenario of climate change for Brandenburg and restricting the crop spectrum to the three above mentioned crops. According to the scenario, precipitation is expected to increase. The impact study was done comparing simulation results for two scenario periods 2022–2030 and 2042–2050 with those for a reference period 1981–1992. The atmospheric CO2 concentrations for the reference period and two scenario periods were set to 346, 406 and 436 ppm, respectively. Two different methods – an empirical one and a semi-mechanistic one – were used for adjustment of net photosynthesis to altered CO2. With warming, the model simulates an increase of evapotranspiration (+9.5%, +15.4%) and runoff (+7.0%, +17.2%). The crop yield was only slightly altered under the climate change only scenario (no CO2 fertilization effect) for barley and maize, and it was reduced for wheat (–6.2%, –10.3%). The impact of higher atmospheric CO2 compensated for climate-related wheat yield losses, and resulted in an increased yield both for barley and maize compared to the reference scenario. The simulated combined effect of climate change and elevated CO2 on crop yield was about 7% higher for the C3 crops when the CO2 and temperature interaction was ignored. The assumption that stomatal control of transpiration is taking place at the regional scale led to further increase in crop yield, which was larger for maize than for wheat and barley. The regional water balance was practically not affected by the partial stimulation of net photosynthesis due to higher CO2, while the introduction of stomatal control of regional transpiration reduced evapotranspiration and enlarged notably runoff and ground water recharge. 相似文献