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Aleš Škorjanc Aleš Lipičnik Kazimir Drašlar 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2013,199(10):807-815
We recorded the spontaneous activity of T1 and T2 filiform sensilla from October to May in Pyrrhocoris apterus acclimatized to outdoor conditions. The aim of the study was to determine how prolonged exposure to cold affects two closely related mechanosensitive sensilla. We recorded the activity at seven temperatures from 5 to 35 °C. In both sensilla types the activity level was reduced during winter, which correlated to changes in acclimatization temperature (r = 0.7), the reduction was greater at high recording temperatures, and the effects of exposure to cold were reversed by transferring the animals indoors. However, T1 activity always increased monotonically, if the recording temperature was increased from 5 to 35 °C, whereas T2 activity in cold-acclimatized animals increased to temperatures between 20 and 30 °C and then started decreasing. As a result, the temperature sensitivity of the activity was reduced more profoundly in T2 sensilla (in T2 Q 10 was reduced from 3.5 in October to 1.4 in January, whereas in T1 it was reduced from 2.5 to 2.2). In conclusion, we have shown that prolonged exposure to cold does affect filiform sensilla; however, the effect is significantly different in the two sensilla types. 相似文献
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The effects of photosystem II (PSII) exogenous electron donors and acceptors on the kinetics of weak light photoinhibition of NH2OH/EDTA-extracted spinach PSII membranes were examined. Under aerobic conditions, Mn2+ (approximately 1 Mn/reaction center; Km approximately 400 nM) inhibited photoinactivation and approximately 1 Mn/reaction center plus 100 microM NH2NH2 gave almost complete protection. In the absence of electron donors, strict anaerobiosis greatly inhibited photoinactivation even in the presence of an electron acceptor. Under aerobic conditions, the addition of electron acceptors (FeCN, DCIP), oxyradical scavengers, or superoxide dismutase strongly suppressed rates of photodamages. Increase in the concentrations of superoxide above those produced by illuminated NH2OH/EDTA-photosystem II membranes increased the rates of damage in the light but gave no damage in the dark. Scavengers of hydroxyl radicals and singlet oxygen did not suppress the rates of aerobic photoinhibition. These findings, along with others, lead us to conclude that photodamage of the secondary donors of the PSII reaction center occurs by two mechanisms: (1) a rapid superoxide and tyrosine YZ+ dependent process and (2) a slower process in which P680+/Chl+ catalyze the damages. 相似文献
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Kazimir Gasljevic Kimbal A. Hall Stephanie Oakes David J. Chapman Eric F. Matthys 《Engineering in Life Science》2009,9(6):479-489
Large‐size plate bioreactors were used to compare the production of extracellular polysaccharide by the red microalga Porphyridium cruentum when grown in suspension and in a foam sheet. A well‐defined illuminated area and unidirectional light propagation allowed us to generate information that is better quantified when expressed in terms of illuminated area. This is essential for meaningful comparison of data, especially considering that for a well‐designed and managed bioreactor, the culture production rates are believed to be light limited. At the same level of illumination, the culture immobilized in foam showed double the production rate of extracellular polysaccharide compared with the culture in suspension. The saturation level of biomass density per unit of illuminated area was eight times higher for the immobilized culture compared with the culture in suspension. Despite the increased biomass density for the immobilized culture, an increase in the light level above the optimum found for the culture in suspension reduced the extracellular polysaccharide production, suggesting that the photoinhibition light level was surpassed. 相似文献
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Aleš Škorjanc Gregor Zupančič Kazimir Drašlar 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2009,195(7):651-661
The resting activity was studied in filiform sensilla of the firebug (Pyrrhocoris apterus). Three functional types (T1, T2 and T3) were detected on the abdomen. A resting discharge of nerve impulses is present in all—always in types T1 and T2 and occasionally in type T3. In T1 the mean rate is 57, in T2 3.3 and in T3 0.5 imp/s. Shortening the hair length had a negligible effect on the resting discharge, which indicates an intrinsic origin.
The resting activity is highly temperature dependent. In T1, the activation energy was 56.8, in T2 84 and in T3 61.4 kJ/mol (Q
10: 2.27, 5.6 and 5.5, respectively). Such values are typical for mechano-transduction, suggesting the involvement of the transduction
mechanism itself. The destruction of the hair base in T1 caused halving of the original discharge rate and shifted the discharge to a regular interval mode. The activation energy
decreased to 38 kJ/mol. The destruction of the hair bases in T2 and T3 completely abolished the discharge. It appears that at least two mechanisms are involved in the generation of the resting
activity in T1 units while only one can be assumed in case of T2 and T3. 相似文献
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The study presented in this article investigated the influence of different Cr(III) and Cr(VI) compounds in the cultivation medium on the uptake and localization of chromium in the cell structure of the yeast Candida intermedia. The morphology of the yeast cell surface was observed by the scanning electron microscopy. Results demonstrated that the growth inhibitory concentration of Cr(III) in the cultivation medium induced changes in the yeast cell shape and affected the budding pattern, while inhibitory concentration of Cr(VI) did not cause any visible effects on morphological properties of the yeast cells. The amount of total accumulated chromium in yeast cells and the distribution of chromium between the yeast cell walls and spheroplasts were determined by atomic absorption spectroscopy. No significant differences were found neither in total chromium accumulation nor in the distribution of chromium in yeast cell walls and spheroplasts between the two of Cr(VI) compounds. Conversely, substantial differences between Cr(III) compounds were demonstrated in the total uptake as well as the localization of chromium in yeast cells. 相似文献
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We have conducted a study of the potential use of drag-reducing biopolymers produced by marine microalgae for engineering
applications. Several marine microalgae species were tested for their production of drag-reducing polysaccharides in large
custom-designed plate bioreactors. Promising species (such as Porphyridium cruentum, Rhodella maculata, Schizochlamydella capsulata and Chlorella stigmatophora) were cultured for periods of time ranging from a few weeks to over 6 months. The basic drag-reducing ability of the polysaccharides
was established by comparing their drag reduction effectiveness at various concentrations in water. The algal polysaccharide
mass productivity was also measured per unit area of bioreactor’s illuminated surface. Finally, an all-inclusive criterion,
the volumetric production of drag-reducing water giving a set level of drag reduction was quantified, and led us to a ranking
of the tested species in order of productivity relevant to implementation. Some aspects of polysaccharide production by aged
cultures were investigated as well. We also quantified the drag-reducing effectiveness of intracellular polysaccharides, and
visualized the presence of exopolymer particles in the medium. 相似文献
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