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51.
ABSTRACT. Extracts of corpora cardiaca from two cockroaches, Nauphoeta cinerea Olivier and Leucophaea maderae F., from a cricket, Gryllus bimaculatus De Geer, from the Colorado potato beetle, Leptinotarsa decemlineata Say, and from the sphinx moth, Sphinx ligustri L. were assayed for adipokinetic and hypertrehalosaemic activity, in acceptor locusts ( Locusta migratoria L.) and cockroaches ( Periplaneta americana L.) respectively. Both bioassays give positive results with all corpus cardiacum material tested except that from the sphinx moth; in this insect haemolymph lipid concentrations (but not those of the total carbohydrate) are, however, increased after injection of an extract of corpora cardiaca from the same species. A similar result is obtained when specimens of G. bimaculatus are injected with an extract of corpora cardiaca from G. bimaculatus. Biological activities of corpus cardiacum extracts from all species investigated can be resolved on reversed-phase high-performance liquid chromatography. Gland extracts from the two cockroach species each show a single absorbance peak which has hypertrehalosaemic activity, but with a (common) retention time distinct from all previously described arthropod neuropeptides. The corpora cardiaca of G. bimaculatus contain also a novel adipokinetic factor with a retention time distinct from previously characterized arthropod hormones, as well as from the new cockroach factor described in this study. The two hypertrehalosaemic factors from the corpora cardiaca of the potato beetle coelute with the hypertrehalosaemic hormones I and II of the American cockroach. The active (adipokinetic) compound from glands of S. ligustri appears to coelute with locust adipokinetic hormone I. 相似文献
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Rapid, Blue-Light-Induced Transpiration Response Restricted to Plants with Grass-like Stomata 总被引:6,自引:0,他引:6
It is shown that the response of transpiration to light is different in species from Gramineae and Cyperaceae compared to species from other families. Blue light (380–500 nm) causes both a rapid response (rise time 2 min) and a slow response (rise time 5 to 10 min) in species from these two families but induces only a slow response in other families. Red light results only in a slow response in all plants investigated. It is hypothesized that the rapid response to blue light is due to the special anatomy and/or function of the so-called grass-like (graminaceous) stomata of plants belonging to Gramineae or Cyperaceae. 相似文献
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MARIANNE HORAK 《Australian Journal of Entomology》1994,33(3):235-244
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WILLIAM B. COSGROVE MARIANNE J. SKEEN STEPHEN L. HAJDUK 《The Journal of eukaryotic microbiology》1979,26(4):643-648
SYNOPSIS Hydroxyurea (HU) inhibits increase in cell number in cultures of Crithidia fasciculata. Complete inhibition is produced by 8 mM and higher concentrations. If HU is not removed, population growth resumes in 45–50 h: if HU is removed, partially synchronous growth occurs through 2 cycles. During HU inhibition, the rate of DNA synthesis is reduced to 1% of that in exponentially growing cultures; protein and RNA syntheses continue at slightly reduced rates. Mean cell size and protein and RNA contents per cell increase; rate of oxygen consumption per mg cell protein remains constant. The behavior of a culture upon addition of HU and upon its removal agrees with predictions based on the hypothesis that the only direct effect of HU is to block DNA synthesis. The synchrony produced by HU is judged satisfactory for investigations of kinetoplast and nuclear replication but not for biochemical characterization of other aspects of the cell cycle. 相似文献
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Trophic relationships in the soil microfood-web: predicting the responses to a changing global environment 总被引:5,自引:0,他引:5
In this article, we evaluate how global environmental change may affect microfood-webs and trophic interactions in the soil, and the implications of this at the ecosystem level. First we outline how bottom-up (resource control) and top-down (predation-control) forces regulate food-web components. Food-web components can respond either positively or negatively to shifts in NPP resulting from global change, thus creating difficulties in developing general principles about the response of soil biota to global change phenomena. We also demonstrate that top-down effects can be important in soil food-webs, creating negative feed-backs which may partially counter bottom-up effects. Secondly, we determine how soil food-webs and the processes they regulate respond to various global change phenomena. Enhanced atmospheric CO2 levels can have two main effects on plants which are relevant for the soil food-web, i.e. enhanced NPP (often positive) and diminished organic matter quality (with negative effects, at least in the short term). Climate change effects resulting from elevated CO2 levels may be mainly secondary through alteration of vegetation, as shown by examples. Intensification of land management is usually associated with greater disturbance, which alters soil food-web composition and key processes; this is particularly apparent in comparisons of conventionally tilled and nontilled agroecosystems. Global change involves shifts in plant species composition and diversity, possibly affecting soil food-webs; we interpret this in terms of theories relating biodiversity to ecosystem function. We conclude that a more detailed understanding of interactions between NPP, soil organic matter and components of the soil food-web, as well as their regulation of biogeochemical processes and ultimately ecosystem-level properties, is essential in better understanding long-term aspects of global change phenomena. 相似文献
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