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Bruna Tadolini Diana Fiorentini Laura Landi Luciana Cabrini 《Free radical research》1989,5(4):245-252
To find experimental conditions to selectively study the propagation phase of lipoperoxidation we studied the lipoperoxidation, catalyzed by FeCl2, of liposomes in a buffering condition where Fe2+ autoxidation and oxygen active species generation does not occur. Liposomes from egg yolk phosphatidylcholine. prepared by vortex mixing, do not oxidize Fe2+: on the contrary they oxidize Fe2+ when prepared by ultrasonic irradiation. Dimyristoyl phosphatidylcholine liposomes prepared by ultrasonic irradiation do not oxidize Fe2+. During sonication polyunsaturated fatty acid residues autoxidize and lipid hydroperoxides (LOOH) are generated. Only when LOOH are present in the liposimes Fe2+ oxidizes and its rate of oxidation depends on the amount of LOOH in the assay. The reaction results in the generation of both LOOH and thiobarbituric acid reactive material (TBAR): it is inhibited by butylated hydroxytoluene and has a acidic pH optimum; it is not inhibited by catalase and OH' scavengers. The reaction studied. thus, appears to be the chain branching and propagation phase of lipoperoxidation. When we studied the dependence of Fe2+ oxidation, LOOH and TBAR generation on FeCl2 concentration, we observed that at high FeCl2 concentrations the termination phase of lipoperoxidation was prevalent. Thus. by selecting the appropriate FeCl2 concentration the proposed experimental system allows study of either the propagation or the termination phase of lipoperoxidation. 相似文献
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Tiziana Bellini Diana Degani Maurizio Matteuzzi Franco Dallocchio 《Bioscience reports》1990,10(1):73-78
Pre-treatment of human lymphocytes with 17-estradiol diminishes the increase in concentration of cytosolic free calcium after stimulation with phytohaemagglutinin. The effect is dependent on 17-estradiol concentration and on the preincubation time. The effect is not due to an interaction between 17-estradiol and phytohaemagglutinin, but appears to be a consequence of the binding of the hormone to the cell surface. The effect is specific for 17-estradiol, since the isomer and other steroid hormones (progesterone, testosterone, diethylstilbestrol and 5-androstan), have no effect. Since the effect of the 17-estradiol can be suppressed by treatment of lymphocytes with ouabain, it appears that the effect of estradiol on the rise of cytosolic calcium induced by phytohaemagglutinin is mediated by the (Na, K)-ATPase. 相似文献
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Diana Pilson 《Evolution; international journal of organic evolution》1996,50(4):1492-1500
Although most plants experience herbivory by several insect species, there has been little empirical work directed toward understanding plant responses to these simultaneous selection pressures. In an experiment in which herbivory by flea beetles (Phyllotreta cruciferae) and diamondback moths (Plutella xylostella) was manipulated in a factorial design, I found that selection for resistance to these herbivores is not independent in Brassica rapa. Specifically, the effect of flea beetle damage on B. rapa fitness depends on the amount of diamondback moth damage a plant experiences: damage by these herbivores has a nonadditive effect on plant fitness. When diamondbacks are abundant, plants that sustain high levels of damage by flea beetles are favored by natural selection, but when diamondbacks are rare, a low level of damage by flea beetles is favored. However, resistance to the later-feeding diamondback moth is not affected by the presence or absence of damage by early-feeding flea beetles. Thus, there are no plant-mediated ecological interactions between these herbivores that affect the outcome of selection for resistance. Because these herbivores do not independently affect plant fitness, neither is likely to develop a pairwise coevolutionary relationship with its host. Instead, coevolution is diffuse. 相似文献
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Chromosomal polymorphism was assessed in the southern short-tailed shrew (Blarina carolinensis) using standard metaphase chromosome and G-banding techniques. Twenty-one animals (11 males, 10 females) from the Meeman Biological Station in Shelby Co., Tennessee, were examined for diploid number. Results showed diploid numbers of 35, 36, 37, 38, 39, 40 and 41 and fundamental numbers of 41, 42, 43, 44 and 45. No diploid numbers or fundamental numbers were unique to a specific collecting locality. The first G-banded karyotypes are reported for the species. These results indicate that Robertsonian polymorphisms, inversions, and possibly other events are responsible for chromosomal variation in B. carolinensis. 相似文献
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Ma Rosario de la Torre Angela Casado Ma Encarnación López-Fernández Diana Carrascosa Ma Concepción Casado Domenico Venarucci Vincenzo Venarucci 《Neurochemical research》1996,21(8):885-888
In order to investigate the role of two free radical detoxificant enzymes in patients with aging brain disorders, superoxide
dismutase (SOD) and catalase (CAT) activities have been measured in blood from male and female human patients of different
ages with several types of aging brain disorders. When compared with activities in the normal population, we have detected:
1) SOD and CAT activities are decreased in patients with Parkinson disease. 2) SOD activity seems to be normal and CAT activity
is decreased in patients with dementia. 3) In the patients with stroke, SOD activity is normal, while CAT activity is decreased.
SOD activity was measured in red blood cells using the Minami and Yoshikawa method. CAT activity was measured in hemolysates
by the method of Aebi. We can conclude that SOD and CAT activities in patients with Parkinson disease are decreased. 相似文献
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The behaviour of the endoparasitic tracheal mite, Acarapis woodi (Rennie) on honey bees (Apis mellifera L.) is a challenge to observe because of its small size. Through a microscope, we videotaped this mite's movement on young bees, dead bees and bees exposed to vegetable oil. Previous studies have shown that solid vegetable oil decreases mite infestations in a bee colony. We hypothesized that the oil alters mite behaviour to the detriment of the parasite, thus helping to safeguard the host. Habitat-seeking behaviour, identified as necessary for mites to locate a new host environment, was disrupted on both dead and oil-treated bees. Questing behaviour, which is associated with transfer between hosts, increased significantly on the dead and oily bees. The behaviours of mites were significantly different between all three treatments (x
2=494.96, p<0.001 on dead bees and x
2=851.11, p<0.001 on oily bees). Both questing and seeking behaviours were significantly different on each of the thoracic treatments (F
2,66=7.88, p<0.001 and F
2,66=21.28, p<0.001) and mite questing behaviour was not altered between males and females on live or oily bees (F
1,22=0.25, p<0.62), but habitat seeking was (F
1,22=7.42, p<0.012). The male questing and habitat-seeking behaviours were observed. We conclude that oil-treated bees gained protection from habitat-seeking mites because the normal behaviour of the mites seeking an oviposition site is interrupted. 相似文献
30.
Abstract. The Argentine Chaco is a mosaic of grassland and open forest habitats maintained by natural disturbance activities such as fire. Since the introduction of domestic livestock and other human activities, the balance of this mosaic has been significantly altered, both in plant species and structural composition. This study focuses on the impact of such changes on the diversity of ground-dwelling arthropods within semi-arid Chaco forest. Quantitative measures of habitat structure and arthropod diversity were taken in forest areas previously subjected to grazing, logging and ploughing. Results indicated that arthropod diversity was smaller on sites with reduced structural complexity, with marked changes in arthropod family composition. The habitat components relating to plant architectural and vertical diversity were particularly influential on arthropod diversity. The guild size ratio of predatory to non-predatory arthropods also differed significantly between habitats suggesting a change in the resource base available to some groups. The latter suggests a shift in the functional organisation of the forest ecosystem which could have important repercussions for the diversity of other trophic levels. 相似文献