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1.
A series of laboratory experiments was conducted on a colony of Bracon celer Szépligeti (Hymenoptera: Braconidae) reared on the olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae). Female B. celer preferentially probe and oviposit into olives containing late third-instar fly larvae. The parasitoid develops as a solitary, ectoparasitic idiobiont. Mean development time (oviposition to adult eclosion) at 22 °C was, for females, 36±1 (SE) days, and for males, 34±1 days. The mean longevity of adult female wasps when provided honey and water was significantly greater than when they were provided water alone, or nothing. The females produced an average of 9.7±7.2 progeny during their lifetimes, but production levels in the insectary colony suggested that this level of fecundity was artificially low and could be improved. The discrepancy may be a consequence of constraints on oviposition behavior imposed by the experimental design. The results are discussed with respect to insectary production methods and the potential use of B. celer as a biological control agent for olive fly in California.  相似文献   
2.
Induced defence responses are elicited when plants are exposed to biotic stresses such as attack by herbivores or pathogens. In nature, plants are often subjected to attack by more than one organism, and defence responses elicited by one organism can thereby be modified by the presence of another. Below-ground attack can influence responses to above-ground attack and vice versa, due to systemic induction of defence metabolism. In some interactions defence is enhanced through prior attack by another organism, whereas in others there are conflicting signals. Recent research has shown how plants integrate these signals to coordinate defence by regulation of key metabolic pathways, although there is still much to be learnt.  相似文献   
3.
A novel iron uptake system was observed in pseudorevertants of Escherichia,coli strains defective in ferrienterochelin transport. The new system is unique in that it is an active transport system that does not utilize any known siderophore. Acquisition of the new uptake system occurs concomitantly with the loss of two major outer membrane proteins (b and c) believed to function as structural components of transmembrane pores.  相似文献   
4.
A neoplastic mast cell tumor was grown in mice which had been raised since birth on a diet enriched with eicosapentaenoic acid. Intact harvest mastocytoma cells were stimulated with calcium ionophpore A23187 to produce lipoxygenase products from the polyunsaturated fatty acids liberated from the cellular membranes. Leukotriene B4, B5, C4 and C5 were isolated and characterized by HPLC retention time, ultraviolet absorption spectrometry and mass spectrometry. The arachidonic acid content of the mast cell tumor lipids was altered from 9.2 to 3.9 mole% while eicosapentaenoic acid increased from 0.5 to 4.5 mole % in response to the fish oil-supplement diet.The relative amount of arachidonic and eicosapentaenoic acids (3.9 and 4.5 mole % respectively) were associated with similar amounts of LTB4 and LTP5 synthesized by the cells. These results suggest that the epoxide leukotrine (LTA) derivative can be made efficiently from either arachidonic or eicosapentaenoic acids when both are present in cellular lipids. In contrast, the ratio of LTC4 to LTC5 (10 to 1) indicates that the reaction of LTA with glutathione may be critically dependent upon the structure of the unsaturated fatty acid with the ratio of LTC4/LTB4 (2.0) more than 10 times greater than that (0.16) for LTC5/LTP5.  相似文献   
5.
Candida humicola acts on benzenearsonic acid to produce dimethylphenylarsine, which was identified by mass spectroscopy following the chemofocusing of the volatile metabolite onto a mercuric chloride impregnated filter. The same technique established that trimethylarsine is the volatile metabolic product obtained from C. humicola treated with 4-NH2-2-OHC6H3AsO(OH)2 and (CH3)3AsO. Arsanilic acid, 4-NH2C6H4AsO(OH)2, is not metabolized to a volatile arsine.  相似文献   
6.
An emerging generalization from theoretical and empirical studies on conservation biology is that high levels of environmental stochasticity increase the likelihood of population extinction. However, coexistence theory has illustrated that there are circumstances under which environmental stochasticity can increase the chance of population persistence. These theoretical studies have shown that the sign of the effect of environmental stochasticity on population persistence is determined by interactions between life history and environmental stochasticity. These interactions mean that the stochastic and deterministic rates of population growth might differ fundamentally. Although difficult to demonstrate in real systems, observed life histories and variance in the vital rates of populations suggest that this phenomenon is likely to be common, and is therefore of much relevance to conservation biologists.  相似文献   
7.
    
Previous research has shown that administration of either testosterone or estradiol to male quail embryos will demasculinize behavior and morphology. Six experiments in which embryos were treated were conducted to test the hypothesis that this testosterone-induced demasculinization is due to conversion of testosterone to estrogen (aromatization). In Experiment 1, dihydrotestosterone propionate, a nonaromatizable androgen, failed to demasculinize copulatory behavior, but did demasculinize crowing, strutting, and proctodeal glands. In Experiment 2, injection of the aromatizable androgens testosterone propionate (TP), testosterone, or androstenedione demasculinized copulatory behavior, the nonaromatizable androgen androsterone failed to have such an effect, and all androgens demasculinized proctodeal glands. In Experiment 3, Silastic implants of testosterone demasculinized all male characteristics, whereas implants of androsterone demasculinized only proctodeal glands. In Experiment 4, the antiestrogen tamoxifen prevented TP from demasculinizing copulatory behavior, but had no such effect with respect to crowing and strutting. In Experiments 5 and 6, the aromatization inhibitor 1,4,6-androstatrien-3,17-dione (ATD) prevented TP but not estradiol benzoate from demasculinizing copulatory behavior. Thus (1) in quail, testosterone-induced demasculinization of copulatory behavior is due to androgen aromatization, whereas testosterone-induced demasculinization of crowing, strutting, and proctodeal glands is not; (2) the distinct components of normal male reproductive behavior exhibit different patterns of steroid specificity during the organizational period, as was previously shown for the activational period; (3) the steroid specificity of crowing, strutting, and proctodeal glands changes between the organizational and activational periods. During organization, there is little specificity, whereas during activation, these characteristics respond only to androgens, never to estrogens. This difference suggests that developmental changes have occurred in the underlying biochemical substrates.  相似文献   
8.
9.
Stream and lake water from the Mammoth Lakes region of California was sampled for Yersinia enterocolitica. From 10 of the 34 sites examined, organisms were isolated that were biochemically identified as Y. enterocolitica. Only one of the ten strains could be serologically confirmed. This strain was identified as Y. enterocolitica serotype 16. Although an outbreak of enteritis in the area prompted this study, no correlation with gastrointestinal disease could be established since the majority of the strains were untypeable.  相似文献   
10.
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