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241.
1. Understanding the conditions that allow for the occurrence of an additional generation in populations that are usually univoltine is important under the present climate warming. In temperate areas, a second generation is enabled through the emergence of a time window that opens when first-generation individuals are ready to reproduce and closes when second-generation individuals cannot complete development before the onset of winter. 2. The conditions that limit the width of this window were studied in Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae), a ground-inhabiting heteropteran overwintering in facultative adult diapause, whose populations in Central Europe have typically been univoltine until the 1980s. 3. The frequency of females of the first generation that started to lay eggs decreased from 70% in June to zero in early August, but oviposition of these females continued until the end of August. Using thermal constants for egg–adult development and temperature data, this study found that the development of most second-generation individuals could only be completed before the start of winter if hastened through behavioural thermoregulation. 4. Consequences of temperature increase on the width of the thermal window were calculated. Increasing temperature causes the time window to open earlier and close later by accelerating maturation of first-generation females and improving conditions for maturing of the second-generation individuals in late summer and autumn. 5. Climate warming will create conditions that facilitate the occurrence of a second generation in a year in typically univoltine populations of this species. 相似文献
242.
Andreja Zelenik Pevec Zdenka ?lejkovec Johannes T. van Elteren Ingrid Falnoga 《Biometals》2012,25(1):103-113
The ability of As2O3 to induce apoptosis in various malignant cell lines has made it a potential treatment agent for several malignancies. In
this study the chemical stability of As2O3 (As(III)) in cell-free growth media with various compositions was studied (MEM with different amount of amino acids and DMEM).
Special attention was given to evaluate the influence of serum (FBS; fetal bovine serum) absence and vitamin C addition on
the oxidation of As(III) to As(V) in cell-free growth media. FBS is an important source of antioxidants and vitamin C (ascorbic
acid) is acting as a prooxidant in millimolar concentrations. Media were incubated with As(III) (0.6, 2 and 7 μmol l−1) up to 72 h. Experiments were performed at 37°C in light or/and in the dark, with or without added serum (10%) or vitamin
C (1.4, 0.14 mM). Metabolites were followed with high-performance liquid chromatography directly coupled to a hydride generation-atomic
fluorescence spectrometry system. After 72 h up to 30% of As(III) was transformed into As(V) in MEMs and up to 35% in DMEM
when exposed in dark. Light had no influence on transformations in MEMs, but changed the situation dramatically in DMEM where
almost all As(III) was oxidized to As(V) after 72 h when exposed to light. Except for some faster oxidation rate the absence
of FBS had little effect on the transformation rate in all media. The most visible impact on As(III) oxidation was observed
by addition of vitamin C. Addition of vitamin C (1.4 mM) transformed almost all As(III) to As(V) within 72 h. In lower concentrations
(0.14 mM) a pro-oxidative effect was still observed reaching approximately 60% oxidation of As(III) during 72 h. All oxidation
processes could be explained by pseudo first order reaction kinetics, yielding reaction rates increasing with initial As(III)
concentration and vitamin C concentration whereas the FBS content additionally increased the As(III) oxidation rate in the
DMEM (light). The temporal oxidation of As(III) to As(V) in various cell-free growth media necessitates routine checking of
the valence state of arsenic during cell culture experiments and the results of biological effects attributed to As(III) should
be interpreted with caution. Special attention is needed particularly in cases with vitamin C which was acting pro-oxidatively
in all conditions examined. 相似文献
243.
This work presents an analytical chemist’s view on the sometimes unconscious use of arsenic trioxide in (bio)medical research.
Arsenic trioxide is a frequently used chemical in cancer treatment research and its action to various malignant cells has
been extensively studied and published. Unfortunately some research articles show trivial errors with regards to background
knowledge of the chemical, handling the chemical, experimental design and interpretation of results like e.g. in a range of
articles comparing advantages of tetraarsenic oxide over arsenic trioxide (dimeric/monomeric) although the dissolution of
both yields the same active compound (HAsO2). To fully understand the implications of these errors we will highlight some of them with the intent to harmonize future
work in this field. 相似文献
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247.
Zdenka Balcarová Vladimír Kleinwächter Günter Löber Gerhard Luck Christoph Zimmer Renate Klarner Emil Smékal 《Biophysical chemistry》1979,9(2):121-131
Fluorescence and circular dichroism spectral measurements, thermal denaturation studies and binding competition experiments with netropsin and actinomycin D were carried out in systems containing phenosafranine bound to DNA's differing in base composition. The investigated properties exhibit a heterogeneity related to the content of A.T and G.C pairs in DNA and to the nature of phenosafranine binding modes. At low level of saturation of binding sites (r less than 0.1) phenosafranine does not show strong preference for any of the DNA base pairs in the overall binding. However, the strong monomer non-cooperative binding outside the helix (mode I1) occurs predominantly, even though not exclusively in G.C rich regions. The strong binding modes involving intercalated dye molecules (mode I2 and eventually mode II1) prevail in A.T rich regions. These binding modes become the principal types of strong phenosafranine interaction with DNA when the level of saturation of binding sites increases, i.e. at r greater than 0.1.20 相似文献
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249.
Zdenka Drastichova Jitka Skrabalova Jan Neckar Frantisek Kolar Jiri Novotny 《Journal of biomedical science》2011,18(1):89
Background
Morphine is used in clinical practice as a highly effective painkiller as well as the drug of choice for treatment of certain heart diseases. However, there is lack of information about its effect on protein expression in the heart. Therefore, here we aimed to identify the presumed alterations in rat myocardial protein levels after prolonged morphine treatment. 相似文献250.