Hemopoietic cell expression of the chemokine decoy receptor D6 is dynamic and regulated by GATA1

D6 scavenges inflammatory chemokines and is essential for the regulation of inflammatory and immune responses. Mechanisms explaining the cellular basis for D6 function have been based on D6 expression by lymphatic endothelial cells. In this study, we demonstrate that functional D6 is also expressed by murine and human hemopoietic cells and that this expression can be regulated by pro- and anti-inflammatory agents. D6 expression was highest in B cells and dendritic cells (DCs). In myeloid cells, LPS down-regulated expression, while TGF-beta up-regulated expression. Activation of T cells with anti-CD3 and soluble CD28 up-regulated mRNA expression 20-fold, while maturation of human macrophage and megakaryocyte precursors also up-regulated D6 expression. Competition assays demonstrated that chemokine uptake was D6 dependent in human leukocytes, whereas mouse D6-null cells failed to uptake and clear inflammatory chemokines. Furthermore, we present evidence indicating that D6 expression is GATA1 dependent, thus explaining D6 expression in myeloid progenitor cells, mast cells, megakaryocytes, and DCs. We propose a model for D6 function in which leukocytes, within inflamed sites, activate D6 expression and thus trigger resolution of inflammatory responses. Our data on D6 expression by circulating DCs and B cells also suggest alternative roles for D6, perhaps in the coordination of innate and adaptive immune responses. These data therefore alter our models of in vivo D6 function and suggest possible discrete, and novel, roles for D6 on lymphatic endothelial cells and leukocytes.     

Should females prefer to mate with low-quality males?

We analyse a model of mate choice when males differ in reproductive quality and provide care for their offspring. Females choose males on the basis of the success they will obtain from breeding with them and a male chooses his care time on the basis of his quality so as to maximise his long-term rate of reproductive success. We use this model to establish whether high-quality males should devote a longer period of care to their broods than low-quality males and whether females obtain greater reproductive success from mating with higher quality males. We give sufficient conditions for optimal care times to decrease with increasing male quality. When care times decrease, this does not necessarily mean that high-quality males are less valuable to the female because quality may more than compensate for the lack of care. We give a necessary and sufficient condition for high-quality males to be less valuable mates, and hence for females to prefer low-quality males. Females can prefer low-quality males if offspring produced and cared for by high-quality males do well even if care is short, and do not significantly benefit from additional care, while offspring produced and cared for by low-quality males do well only if they receive a long period of care.     

The behavioural ecology of personality: consistent individual differences from an adaptive perspective

Individual humans, and members of diverse other species, show consistent differences in aggressiveness, shyness, sociability and activity. Such intraspecific differences in behaviour have been widely assumed to be non‐adaptive variation surrounding (possibly) adaptive population‐average behaviour. Nevertheless, in keeping with recent calls to apply Darwinian reasoning to ever‐finer scales of biological variation, we sketch the fundamentals of an adaptive theory of consistent individual differences in behaviour. Our thesis is based on the notion that such ‘personality differences’ can be selected for if fitness payoffs are dependent on both the frequencies with which competing strategies are played and an individual's behavioural history. To this end, we review existing models that illustrate this and propose a game theoretic approach to analyzing personality differences that is both dynamic and state‐dependent. Our motivation is to provide insights into the evolution and maintenance of an apparently common animal trait: personality, which has far reaching ecological and evolutionary implications.     

The effect of thermoregulatory substitution on optimal energy reserves of small birds in winter

Previous models have predicted the body mass of small birds in winter on the basis of a trade-off between starvation and predation. Many of these models have assumed that energy expenditure while active increases with body mass. The implications of the fact that the metabolic cost of activity can substitute for internal heat production and help keep the bird warm have not been investigated. In this paper we show that if thermoregulatory substitution occurs then there is a critical level of energy reserves above which an active bird is thermoneutral. This critical level increases as temperature decreases. Below this level, substitution of energy results in higher optimal levels of reserves than would be predicted in the absence of substitution. Our model thus predicts that at low temperatures body mass will be higher when thermoregulatory substitution occurs.     

The scaling of diving time budgets: insights from an optimality approach

Simple scaling arguments suggest that, among air-breathing divers, dive duration should scale approximately with mass to the one-third power. Recent phylogenetic analyses appear to confirm this. The same analyses showed that duration of time spent at the surface between dives has scaling very similar to that of dive duration, with the result that the ratio of dive duration to surface pause duration is approximately mass invariant. This finding runs counter to other arguments found in the diving literature that suggest that surface pause duration should scale more positively with mass, leading to a negative scaling of the dive-pause ratio. We use a published model of optimal time allocation in the dive cycle to show that optimal decisions can predict approximate mass invariance in the dive-pause ratio, especially if metabolism scales approximately with mass to the two-thirds power (as indicated by some recent analyses) and oxygen uptake is assumed to have evolved to supply the body tissues at the required rate. However, emergent scaling rules are sensitive to input parameters, especially to the relationship between the scaling of metabolism and oxygen uptake rate at the surface. Our results illustrate the utility of an optimality approach for developing predictions and identifying key areas for empirical research on the allometry of diving behavior.     

Sperm allocation strategies and female resistance: a unifying perspective

The classical viewpoint in sperm competition theory, which holds that males evolve sperm allocation strategies in response to a given degree of sperm competition, has recently been challenged by an alternative viewpoint, which holds that the degree of sperm competition is itself a consequence of these same strategies. Here, we present a game theory model that unites these alternative views as the endpoints of a continuum. Based on the recognition that female control over mating may limit the extent to which male strategies affect the degree of sperm competition, we investigate sperm allocation strategies in a setting where females can resist excessive matings more or less successfully. We discuss how conflicting predictions made by previous theory relate to implicit assumptions about female resistance behavior. Moreover, we show that female resistance, while being highly relevant to the predicted relationship between ejaculate size and the degree of sperm competition, has little effect on the predicted positive correlation between relative testis size and the degree of sperm competition. This result strengthens one of the central predictions of sperm competition theory and is in accordance with empirical findings from a wide range of taxa.     

Desulfonation and Degradation of the Disulfodiphenylethercarboxylates from Linear Alkyldiphenyletherdisulfonate Surfactants

Earlier work showed that the biodegradation of a commercial linear monoalkyldiphenyletherdisulfonate surfactant as a carbon source for microbial growth leads to the quantitative formation of corresponding disulfodiphenylether carboxylates (DSDPECs), which were not degraded. α-Proteobacterium strain DS-1 (DSM 13023) catalyzes these reactions. These DSDPECs have now been characterized by high-pressure liquid chromatography coupled via an electrospray interface to a mass spectrometer. DSDPECs were a complex mixture of compounds which indicated catabolism via ω-oxygenation and β-oxidation. DSDPECs were subject to quantitative desulfonation in bacterial cultures in which they served as sole sulfur sources for bacterial growth. On average, one sulfonate group per DSDPEC species was removed, and the organism responsible for this desulfonation was isolated and identified as Rhodococcus opacus ISO-5. The products were largely monosulfodiphenylether carboxylate-phenols (MSDPEC-phenols). MSDPEC-phenols were subject to extensive dissimilation by bacteria from activated sludge.     

State-dependent ideal free distributions

Summary The standard ideal free distribution (IFD) states how animals should distribute themselves at a stable competitive equilibrium. The equilibrium is stable because no animal can increase its fitness by changing its location. In applying the IFD to choice between patches of food, fitness has been identified with the net rate of energetic gain. In this paper we assess fitness in terms of survival during a non-reproductive period, where the animal may die as a result of starvation or predation. We find the IFD when there is a large population that can distribute itself between two patches of food. The IFD in this case is state-dependent, so that an animal's choice of patch depends on its energy reserves. Animals switch between patches as their reserves change and so the resulting IFD is a dynamic equilibrium. We look at two cases. In one there is no predation and the patches differ in their variability. In the other, patches differ in their predation risk. In contrast to previous IFDs, it is not necessarily true that anything is equalized over the two patches.