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Bonobos have a reputation as a female-dominated and egalitarian species. We examined the 2 aspects of dominance in 6 captive bonobo groups. Females do not consistently evoke submission from all males in all contexts. Though females occupy the highest-ranking positions in the dominance hierarchy, there are in each group males that obtain rather high ranks and are able to dominate ≥1 female. Thus female dominance is not complete and hierarchies can be better described as nonexclusive female dominance. We studied egalitarianism by measuring linearity and steepness of dominance hierarchies. The hierarchies of all groups are highly linear. Hierarchies among males are steeper than among females. On average, male bonobos are more despotic than females, but females too can have despotic relations, both with other females and with males. Hence one can call bonobos in captivity semidespotic rather than egalitarian.  相似文献   
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In this paper, we present a model for the development of connections between muscle afferents and motoneurones in the human spinal cord. The model consists of a limb with six muscles, one motoneurone pool, one pooled (Ia-like) afferent for each muscle and a central programme generator. The weights of the connections between the afferents and the motoneurone pools are adapted during centrally induced movements of the limb. The connections between the afferents and the motoneurone pools adapt in a hebbian way, using only local information present at the synapses. This neural network is tested in two examples of a limb with two degrees of freedom and six muscles. Despite the simplifications, the model predicts the pattern of autogenic and heterogenic monosynaptic reflexes quite realistically.  相似文献   
4.
In order to investigate variations in the microenvironment of oocytes within a cohort of maturing follicles the follicular volumes as well as the intrafollicular concentrations of oestradiol (E2) and progesterone (P) were measured in the golden hamster. At 10 h before ovulation the follicular volumes varied from 0.009 to 0.037 mm3 (mean +/- SD: 0.0187 +/- 0.0071 mm3; n = 36). Large follicles (greater than 0.025 mm3; n = 8) contained statistically significantly lower E2 and P levels (30.1 +/- 10.4 and 517 +/- 113 mumol/l, respectively) than the medium sized group (less than 0.025 and greater than 0.015 mm3; n =20): 46.9 +/- 16.0 (P less than 0.02) and 919 +/- 264 (P less than 0.0001) mumol/l, respectively. Small follicles (less than 0.015 mm3) showed the highest steroid levels: 97.0 +/- 33.3 and 1590 +/- 517 mumol/l for E2 and P (P less than 0.001 versus the medium sized group values). Correlation coefficients for the steroid concentrations and the follicular volumes appeared to be -0.674 for E2 and -0.612 for P (P less than 0.001). At the time studied a positive correlation between E2 and P concentrations in the follicles was found: r = 0.655 (P less than 0.001). The mean ratios of intrafollicular over serum steroid concentrations appeared to be approx 36 x 10(3) in the case of E2 and about 17 x 10(3) in the case of P. These results clearly show that there is an inverse relationship between follicular volume and intrafollicular steroid concentrations. The presence of a fine regulatory mechanism for a collective maturation of follicles is hypothesized.  相似文献   
5.
 Subjects made fast goal-directed arm movements towards moving targets. In some cases, the perceived direction of target motion was manipulated by moving the background. By comparing the trajectories towards moving targets with those towards static targets, we determined the position towards which subjects were aiming at movement onset. We showed that this position was an extrapolation in the target’s perceived direction from its position at that moment using its perceived direction of motion. If subjects were to continue to extrapolate in the perceived direction of target motion from the position at which they perceive the target at each instant, the error would decrease during the movements. By analysing the differences between subjects’ arm movements towards targets moving in different (apparent) directions with a linear second-order model, we show that the reduction in the error that this predicts is not enough to explain how subjects compensate for their initial misjudgements. Received: 10 February 1995/Accepted in revised form: 30 May 1995  相似文献   
6.
Chitin is a homopolymer of β-(1,4)-linked N-acetyl-D-glucosamine (GlcNAc) and a major structural component of fungal cell walls. In plants, chitin acts as a microbe-associated molecular pattern (MAMP) that is recognized by lysin motif (LysM)-containing plant cell surface-localized pattern recognition receptors (PRRs) that activate a plethora of downstream immune responses. To deregulate chitin-induced plant immunity and successfully establish infection, many fungal pathogens secrete LysM domain-containing effector proteins during host colonization. The LysM effector Ecp6 from the tomato (Solanum lycopersicum) leaf mold fungus Cladosporium fulvum can outcompete plant PRRs for chitin binding because two of its three LysM domains cooperate to form a composite groove with ultra-high (pM) chitin-binding affinity. However, most functionally characterized LysM effectors contain only two LysMs, including Magnaporthe oryzae MoSlp1, Verticillium dahliae Vd2LysM, and Colletotrichum higginsianum ChElp1 and ChElp2. Here, we performed modeling, structural, and functional analyses to investigate whether such dual-domain LysM effectors can also form ultra-high chitin-binding affinity grooves through intramolecular LysM dimerization. However, our study suggests that intramolecular LysM dimerization does not occur. Rather, our data support the occurrence of intermolecular LysM dimerization for these effectors, associated with a substantially lower chitin binding affinity than monitored for Ecp6. Interestingly, the intermolecular LysM dimerization allows for the formation of polymeric complexes in the presence of chitin. Possibly, such polymers may precipitate at infection sites to eliminate chitin oligomers, and thus suppress the activation of chitin-induced plant immunity.

Fungal LysM effectors composed of two LysM domains bind chitin via intermolecular LysM dimerization, leading to polymers that may precipitate to eliminate chitin from infection sites to prevent the activation of host immune receptors.  相似文献   
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Urban expansion threatens global biodiversity through the destruction of natural and semi-natural habitats and increased levels of disturbance. Whilst woodlands in urban areas may reduce the impact of urbanisation on biodiversity, they are often subject to under or over-management and consist of small, fragmented patches which may be isolated. Effective management strategies for urban woodland require an understanding of the ecology and habitat requirements of all relevant taxa. Yet, little is known of how invertebrate, and in particular moth, assemblages utilise urban woodland despite being commonly found within the urban landscape. Here we show that the abundance, species richness, and species diversity of moth assemblages found within urban woodlands are determined by woodland vegetation character, patch configuration and the surrounding landscape. In general, mature broadleaved woodlands supported the highest abundance and diversity of moths. Large compact woodlands with proportionally less edge exposed to the surrounding matrix were associated with higher moth abundance than small complex woodlands. Woodland vegetation characteristics were more important than the surrounding landscape, suggesting that management at a local scale to ensure provision of good quality habitat may be relatively more important for moth populations than improving habitat connectivity across the urban matrix. Our results show that the planting of broadleaved woodlands, retaining mature trees and minimising woodland fragmentation will be beneficial for moth assemblages.  相似文献   
9.
Prediction of effective genome size in metagenomic samples   总被引:3,自引:0,他引:3       下载免费PDF全文
We introduce a novel computational approach to predict effective genome size (EGS; a measure that includes multiple plasmid copies, inserted sequences, and associated phages and viruses) from short sequencing reads of environmental genomics (or metagenomics) projects. We observe considerable EGS differences between environments and link this with ecologic complexity as well as species composition (for instance, the presence of eukaryotes). For example, we estimate EGS in a complex, organism-dense farm soil sample at about 6.3 megabases (Mb) whereas that of the bacteria therein is only 4.7 Mb; for bacteria in a nutrient-poor, organism-sparse ocean surface water sample, EGS is as low as 1.6 Mb. The method also permits evaluation of completion status and assembly bias in single-genome sequencing projects.  相似文献   
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