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11.
Douglas Maciel Reisla Oliveira Paulo Enrique Cardoso Peixoto 《Ethology : formerly Zeitschrift fur Tierpsychologie》2023,129(2):99-106
Sexually selected traits, such as male weapons, are highly variable in shape and size across species. However, little is known about the mechanisms that may govern this variation. Because males with greater investment in weapon size tend to win more fights, but also pay higher costs related to weapon development and maintenance, larger weapons should be expected only in species in which victory in male–male fights generate reproductive benefits that outweigh investment costs. Here, we hypothesized that the reproductive characteristics that increase the chances of winners to access females or to fertilize eggs will favor the evolution of larger weapons. To evaluate this hypothesis, we conducted a meta-analysis using arthropods as model organisms. To measure investment in weapon size, we gathered both Pearson correlation coefficient and the standardized (but non centralized) slope values for the relationship between weapon size and body size. We found that none of the reproductive characteristics we investigated was related to male weapon size. Thus, it seems that greater certainty of accessing a female or fertilizing female eggs with a victory does not modulate the investment in male weapon size. Perhaps the cost–benefit ratio between weapon size investment and reproductive success is not the main factor driving the variation in weapon size. 相似文献
12.
Cardoso RA Filho AA Melo MC Lyerly DM Wilkins TD Lima AA Ribeiro RA Souza GE 《Mediators of inflammation》1996,5(3):183-187
This study investigated the ability of Clostridium difficile toxin B, isolated from the VPI 10463 strain, to induce fever and neutrophilia in rats. Intravenous injection of toxin B (0.005-0.5 mug/kg) evoked a dose-dependent increase in body temperature. The febrile response to 0.5 mug/kg of the toxin started in 2.5 h, peaked at 5 h, and subsided fully within 24 h. Toxin B also induced a dosedependent neutrophilia. Pretreatment with indomethacin (2 mg/kg, i.p.) did not affect the neutrophilia induced by toxin B, but significantly reduced the febrile response measured 4 to 8 h after toxin B injection. Dexamethasone (0.5 mg/ kg) also markedly diminished the febrile response induced by toxin B. These results show that Clostridium difficile toxin B induced a febrile response susceptible to inhibition by dexamethasone and indomethacin. Furthermore, they suggest that prostaglandins are not involved in the neutrophilia caused by this toxin. 相似文献
13.
T. Macedo C. A. Fontes Ribeiro D. Cotrim P. Tavares M. T. Morgadinho M. Caramona M. T. Nunes Vicente L. Rodrigues M. G. Cardoso M. L. Keating 《Molecular neurobiology》1995,11(1-3):21-29
This work evaluated in a population of heroin and heroin plus cocaine human addicts:
- Norepinephrine (NE), epinephrine (Epi), and 3-methoxy-4-hydroxyphenylglycol (MHPG) (the principal metabolite of brain NE) plasma levels;
- Monoamine oxidase (MAO) activity; and
- 3H-imipramine specific binding to the amine carrier in platelets.
14.
15.
Amphiphilic detergent-soluble acetylcholinesterase (AChE) from Torpedo is converted to a hydrophilic form by digestion with phospholipase C from Trypanosoma brucei or from Bacillus cereus. This lipase digestion uncovers an immunological determinant which crossreacts with a complex carbohydrate structure present in the hydrophilic form of all variant surface glycoproteins (VSG) of T. brucei. This crossreacting determinant is also detected in human erythrocyte AChE after digestion with T. brucei lipase. From these results we conclude that the glycophospholipid anchors of protozoan VSG and of AChE of the two vertebrates share common structural features, suggesting that this novel type of membrane anchor has been conserved during evolution. 相似文献
16.
Diel variation of phytoplankton functional groups in a subtropical reservoir in southern Brazil during an autumnal stratification period 总被引:1,自引:0,他引:1
A knowledge of diel variation and the vertical distribution of phytoplankton communities may contribute to a better understanding
of the driving factors of key species. Applying functional-group classification provides important information on the causes
of species selection in the pelagic community. The diel variation of phytoplankton functional groups was analysed during an
autumnal stratification period with the aim of understanding their changes in the vertical position related to light, mixing
regime and grazing pressure. Phytoplankton and zooplankton communities were sampled every 4 h during a 24-h period in a vertical
profile in a subtropical meso-eutrophic reservoir. Strong stratification during a 24-h cycle and a mixed clear epilimnion
with partial atelomixis marked the autumn season in the Faxinal reservoir, southern Brazil. The highest phytoplankton densities
and biomass were found during the second part of the day, a general pattern reported in the literature, and may be explained
by zooplankton dynamics. During the 24-h cycle, phytoplankton functional groups lacking a self-regulating capacity and those
able to regulate their vertical position were vertically segregated in the lake. The diel behaviour of both groups was driven
by the mixing regime (including atelomixis), light and zooplankton grazing pressure. 相似文献
17.
Methyl CpG-binding proteins induce large-scale chromatin reorganization during terminal differentiation
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Brero A Easwaran HP Nowak D Grunewald I Cremer T Leonhardt H Cardoso MC 《The Journal of cell biology》2005,169(5):733-743
Pericentric heterochromatin plays an important role in epigenetic gene regulation. We show that pericentric heterochromatin aggregates during myogenic differentiation. This clustering leads to the formation of large chromocenters and correlates with increased levels of the methyl CpG-binding protein MeCP2 and pericentric DNA methylation. Ectopic expression of fluorescently tagged MeCP2 mimicked this effect, causing a dose-dependent clustering of chromocenters in the absence of differentiation. MeCP2-induced rearrangement of heterochromatin occurred throughout interphase, did not depend on the H3K9 histone methylation pathway, and required the methyl CpG-binding domain (MBD) only. Similar to MeCP2, another methyl CpG-binding protein, MBD2, also increased during myogenic differentiation and could induce clustering of pericentric regions, arguing for functional redundancy. This MeCP2- and MBD2-mediated chromatin reorganization may thus represent a molecular link between nuclear genome topology and the epigenetic maintenance of cellular differentiation. 相似文献
18.
In this paper, we further investigate the new paradigm for the rupture of thin cap fibroatheroma (TCFA) proposed in Vengrenyuk et al. (2006 PNAS 103:14678) using a multilevel micro-CT based 3D numerical modeling. The new paradigm proposes that the rupture of TCFA is due to stress-induced interfacial debonding of cellular--level, 10-20 microm microcalcifications in the fibrous cap proper. Such microcalcifications, which lie below the visibility of current in vivo imaging techniques, were detected for the first time using confocal microscopy and high resolution microcomputed tomography (micro-CT) imaging in Vengrenyuk et al. (2006) In the present study, we use high resolution (7 microm) micro-CT imaging to construct accurate geometries of both these microcalcifications and larger mm size macrocalcifications at the cap shoulders to evaluate their biomechanical stability. The analysis shows that cellular-level calcifications by themselves are not dangerous unless they lie in a region of high background stress. This high level of background stress only occurs in caps whose thickness is < approximately 80 microm. Whereas a spherical microcalcification will increase peak circumferential stress (PCS) by a factor of two, in agreement with previous local analytical solutions, this can be increased several fold by elongated microcalcifications. The most dangerous situation is when a microinclusion appears in close proximity to a region where the PCS is already high. This stress will be substantially increased if the inclusion is elongated. In contrast, macrocalcifications at the cap shoulders are shown to actually increase plaque stability. 相似文献
19.
Recent discovery of 5-hydroxymethylcytosine (5hmC) in genomic DNA raises the question how this sixth base is recognized by cellular proteins. In contrast to the methyl-CpG binding domain (MBD) of MeCP2, we found that the SRA domain of Uhrf1, an essential factor in DNA maintenance methylation, binds 5hmC and 5-methylcytosine containing substrates with similar affinity. Based on the co-crystal structure, we performed molecular dynamics simulations of the SRA:DNA complex with the flipped cytosine base carrying either of these epigenetic modifications. Our data indicate that the SRA binding pocket can accommodate 5hmC and stabilizes the flipped base by hydrogen bond formation with the hydroxyl group. 相似文献
20.
The loss of biotic integrity in ecosystems due to human pressure has been receiving much attention from the scientific community.
The primary aim of this study is to understand how the increasing human pressure on natural forests in the Azorean archipelago
(North Atlantic) is affecting their epigean arthropod communities and which biological parameters it affects most. An expert
team did fieldwork covering most of the natural forests (mainly inside nature reserves) of the archipelago using standardized
pitfall trapping. To build a multimetric index we tested a number of taxonomic and ecological parameters that can potentially
be influenced by disturbance. Sixteen of these were found to be significantly influenced by disturbance in forests. We retained
seven metrics due to both, desirable scalability properties and relatively low correlation between them. These included the
percentages of endemic and predator species richness and also predator abundance, which are inversely related to disturbance;
and the percentages of native and saprophagous species richness and introduced and herbivore abundance, which are positively
related to disturbance. All seven metrics were combined in an Index of Biotic Integrity (IBI) value. We then proceeded to
understand which potential disturbance factors are influencing the biotic integrity of communities and how such influence
is felt. Five disturbance factors were found to influence the IBI, although in different ways: the size and fragmentation
of reserves, the distance of sites to the reserve borders, the invasion by alien plants and the density of human paths at
the sites. Given that only percentages of taxonomical or ecological characteristics were chosen as metrics, we tested and
found the scalability of the IBI to be possible, allowing the comparison of sites with different collecting effort or even
the comparison of reserves with different areas and numbers of collecting sites in each. Finally, we propose a novel graphical
representation for multimetric indices like the IBI, one which allows retaining much of the information that is usually lost
in multimetric indices. 相似文献