Melanic color-dependent anti-predator behavior strategies in barn owl nestlings

The arms race between predators and prey has led to morphological and behavioral adaptations. Different antipredator strategies can coexist within a population if each strategy is the result of a trade-off with competing demands. Antipredator behavior can be associated with morphological traits, like color patterns, either because in the context of sexual selection, coloration signals the ability to avoid predators or because coloration is a naturally selected trait useful in avoiding predators. Because in the barn owl (Tyto alba), heritable eumelanic plumage coloration is associated with the glucocorticoid-dependent response to stress, we tested whether antipredator behavior is also related to this trait. Compared with small-spotted nestlings, individuals displaying larger black spots hissed more intensely in the presence of humans, feigned death longer, had a lower breathing rate under stress, and were more docile when handled. Cross-fostering experiments showed that the covariation between the spot size and the duration of feigning death was inherited from the biological mother, whereas covariation between spot size and docility was inherited from the biological father. Our results confirm that melanin-based coloration is associated with suites of behavioral traits, which are under both genetic and environmental influence. Coloration can thus evolve as a direct or indirect response to predation, but it can also be a signal of antipredator strategies to potential mates.

Small RNA-dependent expression of secondary metabolism is controlled by Krebs cycle function in Pseudomonas fluorescens.

Pseudomonas fluorescens CHA0, an antagonist of phytopathogenic fungi in the rhizosphere of crop plants, elaborates and excretes several secondary metabolites with antibiotic properties. Their synthesis depends on three small RNAs (RsmX, RsmY, and RsmZ), whose expression is positively controlled by the GacS-GacA two-component system at high cell population densities. To find regulatory links between primary and secondary metabolism in P. fluorescens and in the related species Pseudomonas aeruginosa, we searched for null mutations that affected central carbon metabolism as well as the expression of rsmY-gfp and rsmZ-gfp reporter constructs but without slowing down the growth rate in rich media. Mutation in the pycAB genes (for pyruvate carboxylase) led to down-regulation of rsmXYZ and secondary metabolism, whereas mutation in fumA (for a fumarase isoenzyme) resulted in up-regulation of the three small RNAs and secondary metabolism in the absence of detectable nutrient limitation. These effects required the GacS sensor kinase but not the accessory sensors RetS and LadS. An analysis of intracellular metabolites in P. fluorescens revealed a strong positive correlation between small RNA expression and the pools of 2-oxoglutarate, succinate, and fumarate. We conclude that Krebs cycle intermediates (already known to control GacA-dependent virulence factors in P. aeruginosa) exert a critical trigger function in secondary metabolism via the expression of GacA-dependent small RNAs.

Jagged1-dependent Notch signaling is dispensable for hematopoietic stem cell self-renewal and differentiation.

Jagged1-mediated Notch signaling has been suggested to be critically involved in hematopoietic stem cell (HSC) self-renewal. Unexpectedly, we report here that inducible Cre-loxP-mediated inactivation of the Jagged1 gene in bone marrow progenitors and/or bone marrow (BM) stromal cells does not impair HSC self-renewal or differentiation in all blood lineages. Mice with simultaneous inactivation of Jagged1 and Notch1 in the BM compartment survived normally following a 5FU-based in vivo challenge. In addition, Notch1-deficient HSCs were able to reconstitute mice with inactivated Jagged1 in the BM stroma even under competitive conditions. In contrast to earlier reports, these data exclude an essential role for Jagged1-mediated Notch signaling during hematopoiesis.

Catch-up growth strategies differ between body structures: interactions between age and structure-specific growth in wild nestling Alpine swifts

1. Little is known on the occurrence and magnitude of faster than normal (catch-up) growth in response to periods of undernutrition in the wild, and the extent to which different body structures compensate and over what timescales is poorly understood. 2. We investigated catch-up growth in nestling Alpine Swifts, Apus melba, by comparing nestling growth trajectories in response to a naturally occurring 1-week period of inclement weather and undernutrition with growth of nestlings reared in a good year. 3. In response to undernutrition, nestlings exhibited a hierarchy of tissues preservation and compensation, with body mass being restored quickly after the end of the period of undernutrition, acceleration of skeletal growth occurring later in development, and compensation in wing length occurring mostly due to a prolongation of growth and delayed fledging. 4. The effect of undernutrition and subsequent catch-up growth was age-dependent, with older nestlings being more resilient to undernutrition, and in turn having less need to compensate later in the development. 5. This shows that young in a free-living bird population can compensate in body mass and body size for a naturally occurring period of undernutrition, and that the timing and extent of compensation varies with age and between body structures.

Fungicidal synergism of fluconazole and cyclosporine in Candida albicans is not dependent on multidrug efflux transporters encoded by the CDR1, CDR2, CaMDR1, and FLU1 genes.

The combination of fluconazole (FLC) and cyclosporine (CY) is fungicidal in FLC-susceptible C. albicans (O. Marchetti, P. Moreillon, M. P. Glauser, J. Bille, and D. Sanglard, Antimicrob. Agents Chemother. 44:2373-2381, 2000). The mechanism of this synergism is unknown. CY has several cellular targets including multidrug efflux transporters. The hypothesis that CY might inhibit FLC efflux was investigated by comparing the effect of FLC-CY in FLC-susceptible parent CAF2-1 (FLC MIC, 0.25 mg/liter) and in FLC-hypersusceptible mutant DSY1024 (FLC MIC, 0.03 mg/liter), in which the CDR1, CDR2, CaMDR1, and FLU1 transporter genes have been selectively deleted. We postulated that a loss of the fungicidal effect of FLC-CY in DSY1024 would confirm the roles of these efflux pumps. Time-kill curve studies showed a more potent fungistatic effect of FLC (P = 0.05 at 48 h with an inoculum of 10(3) CFU/ml) and a more rapid fungicidal effect of FLC-CY (P = 0.05 at 24 h with an inoculum of 10(3) CFU/ml) in the FLC-hypersusceptible mutant compared to those in the parent. Rats with experimental endocarditis were treated for 2 or 5 days with high-dose FLC, high-dose CY, or both drugs combined. FLC monotherapy for 5 days was more effective against the hypersusceptible mutant than against the parent. However, the addition of CY to FLC still conferred a therapeutic advantage in animals infected with mutant DSY1024, as indicated by better survival (P = 0.04 versus the results obtained with FLC) and sterilization of valves and kidneys after a very short (2-day) treatment (P = 0.009 and 0.002, respectively, versus the results obtained with FLC). Both in vitro and in vivo experiments consistently showed that the deletion of the four membrane transporters in DSY1024 did not result in loss of the fungicidal effect of FLC-CY. Yet, the accelerated killing in the mutant suggested a "dual-hit" mechanism involving FLC hypersusceptibility due to the efflux pump elimination and fungicidal activity conferred by CY. Thus, inhibition of multidrug efflux transporters encoded by CDR1, CDR2, CaMDR1, and FLU1 genes is not responsible for the fungicidal synergism of FLC-CY. Other cellular targets must be considered.

Calpain 3, the "gatekeeper" of proper sarcomere assembly, turnover and maintenance.

Calpain 3 is a member of the calpain family of calcium-dependent intracellular proteases. Thirteen years ago it was discovered that mutations in calpain 3 (CAPN3) result in an autosomal recessive and progressive form of limb girdle muscular dystrophy called limb girdle muscular dystrophy type 2A. While calpain 3 mRNA is expressed at high levels in muscle and appears to have some role in developmental processes, muscles of patients and mice lacking calpain 3 still form apparently normal muscle during prenatal development; thus, a functional calpain 3 protease is not mandatory for muscle to form in vivo but it is a pre-requisite for muscle to remain healthy. Despite intensive research in this field, the physiological substrates of the calpain 3 protein (hereafter referred to as CAPN3) and its alternatively spliced isoforms remain elusive. The existence of these multiple isoforms complicates the search for the physiological functions of CAPN3 and its pathophysiological role. In this review, we summarize the genetic and biochemical evidence that point to loss of function of the full-length isoform of CAPN3, also known as p94, as the pathogenic isoform. We also argue that its natural substrates must reside in its proximity within the sarcomere where it is stored in an inactive state anchored to titin. We further propose that CAPN3 has many attributes that make it ideally suited as a sensor of sarcomeric integrity and function, involved in its repair and maintenance. Loss of these CAPN3-mediated activities can explain the "progressive" development of muscular dystrophy.

Stability-dependent behavioural and electro-cortical reorganizations during intentional switching between bimanual tapping modes

This study investigated behavioural and electro-cortical reorganizations accompanying intentional switching between two distinct bimanual coordination tapping modes (In-phase and Anti-phase) that differ in stability when produced at the same movement rate. We expected that switching to a less stable tapping mode (In-to-Anti switching) would lead to larger behavioural perturbations and require supplementary neural resources than switching to a more stable tapping mode (Anti-to-In switching). Behavioural results confirmed that the In-to-Anti switching lasted longer than the Anti-to-In switching. A general increase in attention-related neural activity was found at the moment of switching for both conditions. Additionally, two condition-dependent EEG reorganizations were observed. First, a specific increase in cortico-cortical coherence appeared exclusively during the In-to-Anti switching. This result may reflect a strengthening in inter-regional communication in order to engage in the subsequent, less stable, tapping mode. Second, a decrease in motor-related neural activity (increased beta spectral power) was found for the Anti-to-In switching only. The latter effect may reflect the interruption of the previous, less stable, tapping mode. Given that previous results on spontaneous Anti-to-In switching revealing an inverse pattern of EEG reorganization (decreased beta spectral power), present findings give new insight on the stability-dependent neural correlates of intentional motor switching. © 2010 Elsevier Ireland Ltd. All rights reserved

Mating order-dependent female mate choice in the polygynandrous common lizard Lacerta vivipara.

Recent studies indicate that directional female mate choice and order-dependent female mate choice importantly contribute to non-random mating patterns. In species where females prefer larger sized males, disentangling different hypotheses leading to non-random mating patterns is especially difficult, given that male size usually correlates with behaviours that may lead to non-random mating (e.g. size-dependent emergence from hibernation, male fighting ability). Here we investigate female mate choice and order-dependent female mate choice in the polygynandrous common lizard (Lacerta vivipara). By sequentially presenting males in random order to females, we exclude non-random mating patterns potentially arising due to intra-sexual selection (e.g. male-male competition), trait-dependent encounter probabilities, trait-dependent conspicuousness, or trait-dependent emergence from hibernation. To test for order-dependent female mate choice we investigate whether the previous mating history affects female choice. We show that body size and body condition of the male with which a female mated for the first time were bigger and better, respectively, than the average body size and body condition of the rejected males. There was a negative correlation between body sizes of first and second copulating males. This indicates that female mate choice is dependent on the previous mating history and it shows that the female's choice criteria are non-static, i.e. non-directional. Our study therefore suggests that context-dependent female mate choice may not only arise due to genotype-environment interactions, but also due to other female mating strategies, i.e. order-dependent mate choice. Thus context-dependent female mate choice might be more frequent than previously thought.

An angiotensin II- and NF-kappaB-dependent mechanism increases connexin 43 in murine arteries targeted by renin-dependent hypertension.

AIMS: Connexins (Cxs) play a role in the contractility of the aorta wall. We investigated how connexins of the endothelial cells (ECs; Cx37, Cx40) and smooth muscle cells (SMCs; Cx43, Cx45) of the aorta change during renin-dependent and -independent hypertension. METHODS AND RESULTS: We subjected both wild-type (WT) mice and mice lacking Cx40 (Cx40(-/-)), to either a two-kidney, one-clip procedure or to N-nitro-l-arginine-methyl-ester treatment, which induce renin-dependent and -independent hypertension, respectively. All hypertensive mice featured a thickened aortic wall, increased levels of Cx37 and Cx45 in SMC, and of Cx40 in EC (except in Cx40(-/-) mice). Cx43 was up-regulated, with no effect on its S368 phosphorylation, only in the SMCs of renin-dependent models of hypertension. Blockade of the renin-angiotensin system of Cx40(-/-) mice normalized blood pressure and prevented both aortic thickening and Cx alterations. Ex vivo exposure of WT aortas, carotids, and mesenteric arteries to physiologically relevant levels of angiotensin II (AngII) increased the levels of Cx43, but not of other Cx. In the aortic SMC line of A7r5 cells, AngII activated kinase-dependent pathways and induced binding of the nuclear factor-kappa B (NF-kappaB) to the Cx43 gene promoter, increasing Cx43 expression. CONCLUSION: In both large and small arteries, hypertension differently regulates Cx expression in SMC and EC layers. Cx43 is selectively increased in renin-dependent hypertension via an AngII activation of the extracellular signal-regulated kinase and NF-kappaB pathways.

Calpain 3, the "gatekeeper" of proper sarcomere assembly, turnover and maintenance.

Calpain 3 is a member of the calpain family of calcium-dependent intracellular proteases. Thirteen years ago it was discovered that mutations in calpain 3 (CAPN3) result in an autosomal recessive and progressive form of limb girdle muscular dystrophy called limb girdle muscular dystrophy type 2A. While calpain 3 mRNA is expressed at high levels in muscle and appears to have some role in developmental processes, muscles of patients and mice lacking calpain 3 still form apparently normal muscle during prenatal development; thus, a functional calpain 3 protease is not mandatory for muscle to form in vivo but it is a pre-requisite for muscle to remain healthy. Despite intensive research in this field, the physiological substrates of the calpain 3 protein (hereafter referred to as CAPN3) and its alternatively spliced isoforms remain elusive. The existence of these multiple isoforms complicates the search for the physiological functions of CAPN3 and its pathophysiological role. In this review, we summarize the genetic and biochemical evidence that point to loss of function of the full-length isoform of CAPN3, also known as p94, as the pathogenic isoform. We also argue that its natural substrates must reside in its proximity within the sarcomere where it is stored in an inactive state anchored to titin. We further propose that CAPN3 has many attributes that make it ideally suited as a sensor of sarcomeric integrity and function, involved in its repair and maintenance. Loss of these CAPN3-mediated activities can explain the "progressive" development of muscular dystrophy.

Precision and scaling in morphogen gradient read-out.

Morphogen gradients infer cell fate as a function of cellular position. Experiments in Drosophila embryos have shown that the Bicoid (Bcd) gradient is precise and exhibits some degree of scaling. We present experimental results on the precision of Bcd target genes for embryos with a single, double or quadruple dose of bicoid demonstrating that precision is highest at mid-embryo and position dependent, rather than gene dependent. This confirms that the major contribution to precision is achieved already at the Bcd gradient formation. Modeling this dynamic process, we investigate precision for inter-embryo fluctuations in different parameters affecting gradient formation. Within our modeling framework, the observed precision can only be achieved by a transient Bcd profile. Studying different extensions of our modeling framework reveals that scaling is generally position dependent and decreases toward the posterior pole. Our measurements confirm this trend, indicating almost perfect scaling except for anterior most expression domains, which overcompensate fluctuations in embryo length.

Encapsulated, genetically engineered cells, secreting glucagon-like peptide-1 for the treatment of non-insulin-dependent diabetes mellitus.

Non-insulin-dependent, or type II, diabetes mellitus is characterized by a progressive impairment of glucose-induced insulin secretion by pancreatic beta cells and by a relative decreased sensitivity of target tissues to the action of this hormone. About one third of type II diabetic patients are treated with oral hypoglycemic agents to stimulate insulin secretion. These drugs however risk inducing hypoglycemia and, over time, lose their efficacy. An alternative treatment is the use of glucagon-like peptide-1 (GLP-1), a gut peptidic hormone with a strong insulinotropic activity. Its activity depends of the presence of normal blood glucose concentrations and therefore does not risk inducing hypoglycemia. GLP-1 can correct hyperglycemia in diabetic patients, even in those no longer responding to hypoglycemic agents. Because it is a peptide, GLP-1 must be administered by injection; this may prevent its wide therapeutic use. Here we propose to use cell lines genetically engineered to secrete a mutant form of GLP-1 which has a longer half-life in vivo but which is as potent as the wild-type peptide. The genetically engineered cells are then encapsulated in semi-permeable hollow fibers for implantation in diabetic hosts for constant, long-term, in situ delivery of the peptide. This approach may be a novel therapy for type II diabetes.

Activity-dependent phosphorylation of SNAP-25 in hippocampal organotypic cultures.

Synaptosomal-associated protein of 25 kDa (SNAP-25) is thought to play a key role in vesicle exocytosis and in the control of transmitter release. However, the precise mechanisms of action as well as the regulation of SNAP-25 remain unclear. Here we show by immunoprecipitation that activation of protein kinase C (PKC) by phorbol esters results in an increase in SNAP-25 phosphorylation. In addition, immunochemical analysis of two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels shows that SNAP-25 focuses as three or four distinct spots in the expected range of molecular weight and isoelectric point. Changing the phosphorylation level of the protein by incubating the slices in the presence of either a PKC agonist (phorbol 12,13-dibutyrate) or antagonist (chelerythrine) modified the distribution of SNAP-25 among these spots. Phorbol 12,13-dibutyrate increased the intensity of the spots with higher molecular weight and lower isoelectric point, whereas chelerythrine produced the opposite effect. This effect was specific for regulators of PKC, as agonists of other kinases did not produce similar changes. Induction of long-term potentiation, a property involved in learning mechanisms, and production of seizures with a GABA(A) receptor antagonist also increased the intensity of the spots with higher molecular weight and lower isoelectric point. This effect was prevented by the PKC inhibitor chelerythrine. We conclude that SNAP-25 can be phosphorylated in situ by PKC in an activity-dependent manner.