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81.
A.-C. Mailleux G. Sempo S. Depickère C. Detrain J. L. Deneubourg 《Insectes Sociaux》2011,58(2):219-225
Spatial distribution of ant workers within the nest is a key element of the colony social organization contributing to the
efficiency of task performance and division of labour. Spatial distribution must be efficiently organized when ants are highly
starved and have to get food rapidly. By studying ants’ behaviour within the nest during the beginning of food recruitment,
this study demonstrates how the spatial organization is affected by starvation and improves the efficiency and the speed of
recruitment as well as the allocation of food. (1) In starved nests, nestmates left the deep part of the nest and crowded
near the nest entrance. This modification of the spatial distribution is a local phenomenon concerning only the individuals
situated in the first chamber near the nest entrance. These starved individuals have a higher probability of leaving the nest
after a contact with recruiters than nestmates situated deeper in the nest. This strongly suggests that nestmates situated
near the nest entrance have a low response threshold to the signals emitted by recruiters. Their higher responsiveness speeds
up their exit to the foraging area and hence may increase the efficiency of highly starved colonies in exploiting new food
opportunities. (2) In starved nests, the trajectory covered by recruiters between contacts with nestmates was nearly twice
as small. For recruiters, this represented a gain of time in the allocation of food. As the recruitment process follows snowball
dynamics, this gain of time by starved recruiters might also speed up the exploitation of food. This study evidences how the
spatial distribution of individuals as a function of their motivational state might have a regulatory function in the recruitment
process, which should be generic for many social species. 相似文献
82.
Zhang J Liu Z Rasschaert J Blero D Deneubourg L Schurmans S Erneux C Pesesse X 《Cellular signalling》2007,19(10):2194-2200
Reactive oxygen species (ROS) are known to be involved in redox signalling pathways that may contribute to normal cell function as well as disease progression. The tumour suppressor PTEN and the inositol 5-phosphatase SHIP2 are critical enzymes in the control of PtdIns(3,4,5)P(3) level. It has been reported that oxidants, including those produced in cells such as macrophages, can activate downstream signalling via the inactivation of PTEN. The present study evaluates the potential impact of SHIP2 on phosphoinositides in cells exposed to sodium peroxide. We used a model of SHIP2 deficient mouse embryonic fibroblasts (MEFs) stimulated by H(2)O(2): at 15 min, PtdIns(3,4,5)P(3) was markedly increased in SHIP2 -/- cells as compared to +/+ cells. In contrast, no significant increase in PtdIns(3,4)P(2) could be detected at 15 or 120 min incubation of the cells with H(2)O(2) (0.6 mM). PKB activity was also upregulated in SHIP2 -/- cells as compared to +/+ cells in response to H(2)O(2). SHIP2 add back experiments in SHIP2 -/- cells confirm its critical role as a lipid phosphatase in the control of PtdIns(3,4,5)P(3) level in response to H(2)O(2). We conclude that SHIP2 lipid phosphatase activity plays an important role in the metabolism PtdIns(3,4,5)P(3) which is demonstrated in oxygen stressed cells. 相似文献
83.
Jorit JL Meesters Ann Bremander Stefan Bergman Ingemar F Petersson Aleksandra Turkiewicz Martin Englund 《Arthritis research & therapy》2014,16(5)
Introduction
Depression is frequent in ankylosing spondylitis (AS) patients. However, epidemiological data about the potential increase in risk are lacking. This study compares the rate of doctor-diagnosed depression in a well defined cohort of AS patients to the general population seeking care.Methods
The Skåne Healthcare Register comprises healthcare data of each resident in Region Skåne, Sweden (population 1.2 million), including ICD-10 diagnoses. Using physician coded consultation data from years 1999 to 2011, we calculated depression consultation rates for all AS patients. We obtained standardized depression-rate ratios by dividing the observed depression rate in AS patients by the expected rate based on the corresponding age- and sex-specific rates of depression in the general population seeking care. A ratio >1 equals a higher rate of depression among AS patients.Results
The AS cohort consisted of 1738 subjects (65% men) with a mean age of 54 years. The reference population consisted of 967,012 subjects. During the 13-year observation period 10% (n = 172) of the AS cohort had a doctor-diagnosed depression compared to 6% (n = 105) to be expected. The standardized estimate of depression-rate ratio was 1.81 (95% confidence interval 1.44 to 2.24) in women men and 1.49 (1.20 to 1.89) in men.Conclusions
The rate of doctor-diagnosed depression is increased about 80% in female and 50% in male AS patients. Future challenges are to timely identify and treat the AS patients who suffer from depression. 相似文献84.
Relationships we have with our friends, family, or colleagues influence our personal decisions, as well as decisions we make together with others. As in human beings, despotism and egalitarian societies seem to also exist in animals. While studies have shown that social networks constrain many phenomena from amoebae to primates, we still do not know how consensus emerges from the properties of social networks in many biological systems. We created artificial social networks that represent the continuum from centralized to decentralized organization and used an agent-based model to make predictions about the patterns of consensus and collective movements we observed according to the social network. These theoretical results showed that different social networks and especially contrasted ones--star network vs. equal network--led to totally different patterns. Our model showed that, by moving from a centralized network to a decentralized one, the central individual seemed to lose its leadership in the collective movement's decisions. We, therefore, showed a link between the type of social network and the resulting consensus. By comparing our theoretical data with data on five groups of primates, we confirmed that this relationship between social network and consensus also appears to exist in animal societies. 相似文献
85.
86.
Ant colonies that undergo long starvation periods have to tune their exploratory and foraging responses to face their food
needs. Although the number of foragers is known to increase with food deprivation in the ant Lasius niger, such enhanced food exploitation is not related to a more intense recruitment by successful scouts. We thus suggest that
the colony’s response to a food shortage could result from changes at the level of the ant recruits, in particular from changes
in their spatial organization inside the nest. Since aggregation plays a key role in the social organization of ants, we assume
that the colony’s response to starvation could be due to changes in the aggregative behaviour of L. niger nestmates.We thus compared the aggregation dynamics of inner-nest workers and foragers having undergone either a short or
a long-lasting starvation period. Whatever the ethological group (foragers or inner-nest workers), there was no significant
influence of starvation on the aggregation dynamics nor on any feature of the observed clusters. This result shows that an
increased foraging response to food shortage cannot be explained by changes in the tendency of nestmates to aggregate within
the nest. Finally, we discuss other behavioural mechanisms, in particular changes in behavioural thresholds that could underlie
the adaptive changes seen in colony foraging after long starvation periods.
Received 25 June 2007; revised 21 January 2008; accepted 24 January 2008. 相似文献
87.
In social biology, it is often considered that an organized society cannot exist without exclusion behaviour towards newcomers
from another nest. Unlike most vertebrate and invertebrate social species, social spiders such as Anelosimus eximius accept unrelated migrants without agonistic behaviour. Does it imply that spiders cannot recognize non-nestmates from nestmates
or is there any evidence of recognition without aggression ? In order to answer this question, we studied behavioural differences
between groups coming from single and mixed-nests in the overall context of swarming.
Our study shows that the presence of non-nestmate conspecifics reduces the cohesion of the swarm groups during the settlement
process and increases the spatial dispersion of spiders, the asymmetry in the spatial distribution being less pronounced.
Individuals belonging to different nests are not as mutually attractive. This paper shows that, during the induced migration,
two processes counteract each other: the amplification process resulting from the addition of silk drives individuals to form
groups with non-nestmates and the recognition process reduces the cohesion of groups composed of non-nestmates. The collective
decision-making during migration results from the balance between these two trends.
Received 30 October 2007; revised 3 April and 19 May 2008; accepted 22 May 2008. 相似文献
88.
Background
The leukocyte common antigen related receptor (LAR) protein has been shown to modulate the signal transduction of a number of different growth factors, including insulin and insulin-like growth factor 1. Splice variants exhibit differing roles and are expressed according to tissue type and developmental stage. 相似文献89.
Esther Heikens Masja Leendertse Lucas M Wijnands Miranda van Luit-Asbroek Marc JM Bonten Tom van der Poll Rob JL Willems 《BMC microbiology》2009,9(1):19-7
Background
Enterococcus faecium has globally emerged as a cause of hospital-acquired infections with high colonization rates in hospitalized patients. The enterococcal surface protein Esp, identified as a potential virulence factor, is specifically linked to nosocomial clonal lineages that are genetically distinct from indigenous E. faecium strains. To investigate whether Esp facilitates bacterial adherence and intestinal colonization of E. faecium, we used human colorectal adenocarcinoma cells (Caco-2 cells) and an experimental colonization model in mice. 相似文献90.
The activity budget hypothesis has been proposed to explain the social segregation commonly observed in ungulate populations. This hypothesis suggests that differences in body size – i.e. between dimorphic males and females – may account for differences in activity budget. In particular, if females spend more time grazing and less time resting than males, activity synchrony would be reduced. Increased costs of maintaining synchrony despite differences in activity budget would facilitate group fragmentation and instability of mixed-sex groups. In this paper two prerequisites of the activity budget hypothesis were tested: (1) that males should spend less time feeding and more time resting than females in single-sex groups and (2) that lower activity synchrony should be observed in mixed-sex compared to single-sex groups. The activity budget and synchrony in mixed and single-sex groups of merino sheep (Ovis aries) of different sizes (2, 4, 6, 8 individuals) were measured in three contiguous 491-m2 arenas located in a natural pasture. Three same-size groups, one of each category, were observed simultaneously. We found no sexual differences in the time spent inactive and active (i.e. grazing, standing, moving, interacting). Males spent significantly more time grazing and less time standing than females. These differences disappeared when yearling males were omitted from the group. Males and females had similar bite and step rates. Sheep of both sexes spent less time resting and more time grazing and moving and had lower bite rates when in mixed-sex groups than when in single-sex groups. The synchrony among visually isolated groups was near zero, indicating that they changed activities independently. On the contrary, within-group synchrony was high; however it was higher in single-sex groups, in particular for males, than in mixed-sex groups. Our results suggest that differences in activity budget and synchrony alone are insufficient to explain social segregation. 相似文献