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431.
432.
IlariaDi Silvestre Ottavio Novelliand Giuseppe Bogliani 《African Journal of Ecology》2000,38(2):102-107
The food habits of the spotted hyaena were studied during the dry season in relation to food availability in the Niokolo Koba National Park, Senegal. Frequency of occurrence of the different foods was quantified by means of scat analysis; species occurrence in the diet was compared with availability in the study area. Large and medium-sized mammals, such as the buffalo, the hartebeest and the warthog, were eaten more often than expected. 相似文献
433.
Martins Rogerio P.; Antonini Yasmine; da Silveira Fernando A.; West Stuart A. 《Behavioral ecology》1999,10(4):401-408
We carried out a field study on the life history and sex allocationof the
ground-nesting solitary bee Diadasina distincta (Hymenoptera:
Anthophoridae).This species is multivoltine, undergoing five generations a
yearbetween February and September. The numerical sex ratio of thisspecies
was female biased overall (approximately 38% males)and showed a strong and
consistent seasonal pattern. The numericalsex ratio was extremely female
biased (approximately 20% males)from February until May, and then slightly
male biased (approximately60% males) from June until September. Females were
3.26 timesthe size of males, and so the overall investment ratio was female
biasedthroughout the year. The overall female bias and seasonal variationin
sex allocation is unlikely to be explained by models thatinvoke overlapping
generations or competition between brothersfor mates (local mate
competition). We suggest that a possibleexplanation for the female bias in
the early part of the seasonis local resource enhancement (LRE): nesting near
larger numbersof sisters reduces parasitism. LRE is likely to decrease in
importancein the later part of the season, when the biased numerical and
investmentratios may be explained by models in which male and female
offspringgain different fitness returns from resources invested. 相似文献
434.
435.
J Fruebis M Silvestre D Shelton C Napoli W Palinski 《Journal of lipid research》1999,40(11):1958-1966
We previously established that probucol decreases basal expression of VCAM-1 in the aorta of WHHL rabbits and inhibits the up-regulation of VCAM-1 expression that normally accompanies atherogenesis. To determine whether this effect is shared by other antioxidants in vivo, we now investigated whether a structurally unrelated antioxidant, vitamin E, also inhibits arterial VCAM-1 expression and whether the degree of VCAM-1 inhibition correlates with the reduction of atherosclerosis or the antioxidant protection of LDL. Atherogenesis and VCAM-1 mRNA and protein were determined in four groups of NZW rabbits (n = 6;-8) fed 0.5% cholesterol alone or supplemented with 0.1% vitamin E, a low dose (0.04;-0.075%) of probucol yielding the same degree of antioxidant protection of plasma LDL as vitamin E, or a high dose (0.5%) of probucol, and in normocholesterolemic rabbits. After 81 days, extensive atherosclerosis and a greater than 4-fold up-regulation of VCAM-1 mRNA was seen in rabbits on high cholesterol diet, mostly in the intima. Treatment with vitamin E, high-dose probucol, and low-dose probucol significantly decreased VCAM-1 mRNA by 49.0, 74.9, and 57. 5%, respectively, and reduced atherosclerosis in adjacent segments of the thoracic aorta to a similar degree as reported by previous studies. Immunocytochemistry confirmed that lesions of antioxidant-treated animals also contained less VCAM-1 protein. Neither the degree of VCAM-1 inhibition nor the extent of atherosclerosis correlated with the degree of antioxidant protection of plasma LDL.In summary, treatment with structurally unrelated antioxidants conveyed different degrees of antioxidant protection to plasma LDL but significantly reduced VCAM-1 expression in vivo and inhibited atherogenesis. This is consistent with the assumption that antiatherogenic effects of antioxidants may in part be mediated by interference with oxidation-dependent intracellular signaling. 相似文献
436.
Aim
Many aspects of vegetation response to increased drought remain uncertain but it is expected that phenotypic plasticity may be key to early adaptation of plants to environmental stress. In this work we observe the response of specific leaf area (SLA) of woody shrub vegetation to the summer drought typical of the Mediterranean climate. In addition, to observe the possible interaction between the impact of drought and the environmental characteristics of the ecosystems, communities from different edaphic and structural contexts distributed along the double stress gradient of the Mediterranean mountains (high temperature and low precipitation at low elevation; low temperature and high irradiation at high elevation) have been analysed.Location
Central Mountain range of the Iberian Peninsula.Methods
Along the entire altitudinal gradient, 33 shrub communities belonging to different habitat typologies (shrublands, rocky areas, hedgerows, understorey) were sampled before and after the passage of summer, both in 2017 and 2019. A total of 1724 individuals and 15,516 leaves were collected and measured to estimate the mean values and diversity of SLA of each community.Results
The community-weighted mean and functional divergence have inverse quadratic relationships with the environmental gradient. Shrub communities at both ends of the gradient have low mean SLA values and high functional divergence of this trait. Summer drought implies a generalised decrease in the mean SLA of the communities throughout the gradient, as well as an alteration in functional richness and uniformity. However, the effect of summer drought on the plant community is mediated by the microenvironmental characteristics of its habitat.Conclusions
Drought acclimatisation of shrub communities through phenotypic plasticity leads to rapid changes in their functional leaf structure. In the long term, our results point to an increase in plant conservative strategies, reduced ecosystem productivity, slower nutrient recycling and the reduction of communities of specific habitats as drought increases. 相似文献437.
438.
Simon Gras Anna Byzia Florence B. Gilbert Sheena McGowan Marcin Drag Anne Silvestre Alisson Niepceron Fabien Lecaille Gilles Lalmanach Fabien Brossier 《Eukaryotic cell》2014,13(7):884-895
Aminopeptidases N are metalloproteases of the M1 family that have been reported in numerous apicomplexan parasites, including Plasmodium, Toxoplasma, Cryptosporidium, and Eimeria. While investigating the potency of aminopeptidases as therapeutic targets against coccidiosis, one of the most important avian diseases caused by the genus Eimeria, we identified and characterized Eimeria tenella aminopeptidase N1 (EtAPN1). Its inhibition by bestatin and amastatin, as well as its reactivation by divalent ions, is typical of zinc-dependent metalloproteases. EtAPN1 shared a similar sequence, three-dimensional structure, and substrate specificity and similar kinetic parameters with A-M1 from Plasmodium falciparum (PfA-M1), a validated target in the treatment of malaria. EtAPN1 is synthesized as a 120-kDa precursor and cleaved into 96-, 68-, and 38-kDa forms during sporulation. Further, immunolocalization assays revealed that, similar to PfA-M1, EtAPN1 is present during the intracellular life cycle stages in both the parasite cytoplasm and the parasite nucleus. The present results support the hypothesis of a conserved role between the two aminopeptidases, and we suggest that EtAPN1 might be a valuable target for anticoccidiosis drugs. 相似文献