The evolution of prey-attraction strategies in spiders: the interplay between foraging and predator avoidance.

Lures and other adaptations for prey attraction are particularly interesting from an evolutionary viewpoint because they are characterized by correlational selection, involve multicomponent signals, and likely reflect a compromise between maximizing conspicuousness to prey while avoiding drawing attention of enemies and predators. Therefore, investigating the evolution of lure and prey-attraction adaptations can help us understand a larger set of traits governing interactions among organisms. We review the literature focusing on spiders (Araneae), which is the most diverse animal group using prey attraction and show that the evolution of prey-attraction strategies must be driven by a trade-off between foraging and predator avoidance. This is because increasing detectability by potential prey often also results in increased detectability by predators higher in the food chain. Thus increasing prey attraction must come at a cost of increased risk of predation. Given this trade-off, we should expect lures and other prey-attraction traits to remain suboptimal despite a potential to reach an optimal level of attractiveness. We argue that the presence of this trade-off and the multivariate nature of prey-attraction traits are two important mechanisms that might maintain the diversity of prey-attraction strategies within and between species. Overall, we aim to stimulate research on this topic and progress in our general understanding of the diversity of predator and prey interactions.

Feline progressive histiocytosis: a retrospective investigation of 26 cases and preliminary study of Ki67 as a prognostic marker.

Feline progressive histiocytosis (FPH) is an uncommon and infrequently reported cutaneous histiocytic proliferative disorder, whose clinical presentation is solitary or multiple cutaneous nodules and papules, with late-course internal metastasis. We describe herein the clinical, epidemiologic, histologic, and immunohistochemical features of this entity, and document the outcome of FPH based on a retrospective study of 26 cases. Female and male cats were affected equally. Lesions were evident either as solitary (16 of 26 cases) or multiple (10 of 26 cases) nonpruritic and alopecic nodules or plaques, preferentially located on the legs and extremities (73%). Follow-up was complete for 19 cats, and ranged from 41 to 1,449 d. Nine died of FPH with a median overall survival of 96 d (range: 41-238 d). The disease recurred in 14 cats after surgical excision of the nodules, and the median disease-free survival was 175 d (range: 21-1,449 d). Five of the 26 cats were alive at the end of the study, and 4 had no progression of the disease. Histologically, lesions were characterized by poorly circumscribed, unencapsulated histiocytic infiltration of dermis and subcutis. Epitheliotropism was observed in 11 (42%) cats. Atypical histiocytes diffusely and consistently expressed MHC II, CD18, and Iba1. Statistically significant higher E-cadherin expression was observed in epitheliotropic cases compared to non-epitheliotropic cases. A negative correlation between overall survival and proliferation index was evident, thus suggesting Ki67 as a promising prognostic marker.

Prognostic value of BRAF(V6°°) mutations in melanoma patients after resection of metastatic lymph nodes.

PURPOSE: BRAF (V600) mutations are frequent in melanomas, and BRAF(V600)-targeted therapy have dramatic, but often transitory, efficacy in stage IV patients. Prognosis of patients with American Joint Committee on Cancer (AJCC) stage III melanoma is heterogeneous. We aimed to determine the overall survival (OS) of stage III patients with a nodal deposit of ≥2 mm according to BRAF (V600) mutations and other previously reported prognostic criteria. METHODS: This retrospective study included 105 consecutive patients with stage III cutaneous melanomas. Most patients underwent a prospective follow-up. BRAF (V600) mutations were detected by sequencing and pyrosequencing of DNA in samples containing >60 % melanoma cells. RESULTS: BRAF mutations (p.V600E and p.V600K in 83 and 14 % of cases, respectively) were detected in 40 % of the patients. For patients with and without BRAF mutations, death occurred in 83.3 and 60.3 %, with a median OS of 1.4 and 2.8 years, respectively. Patient age, primary melanoma ulceration, number of invaded lymph nodes, AJCC staging at study entry, and BRAF status were linked to OS in the univariate analysis. The only characteristics associated with OS in the multivariate analysis were number of invaded lymph nodes (P = 0.005, hazard ratio 2.2, 95 % confidence interval 1.3-3.9) and BRAF status (P = 0.005, hazard ratio 1.9, 95 % confidence interval 1.2-3.1). CONCLUSIONS: BRAF (V600) status could be used to stage melanoma patients with nodal deposits. Our results may also help to plan adjuvant trials in these patients, for whom the low tumor load may induce longer efficacy of BRAF-targeted therapies.

Arithmetic problems at school: when there is an apparent contradiction between the situation model and the problem model.

BACKGROUND: Understanding and solving problems involves different levels of representation. On the one hand, there are logico-mathematical representations, or problem models (PMs), which contain information such as 'the size of the flock changed from 31 sheep to 42' while, on the other hand, there are more qualitative representations, or qualitative situation models (QSMs), comprising events expressed in everyday terms, such as 'a lot of lambs had been born'. AIMS: We set out to show that an apparent contradiction between a PM and a QSM can result in poorer performances, especially when the activation of formal representations is not fully automatic. SAMPLE: We tested 44 third years (mean age 8;6) and 46 fourth years (mean age 9; 8) from two primary schools in France. METHOD: Change problems and compare problems were drafted in two versions: one where the QSM and PM were consistent and one where they appeared to be contradictory but were not (referred to hereafter as the inconsistent version). For example, if the numerical data proved that the size of a flock of sheep had increased (PM), the consistent version would state that a lot of lambs had been born (QSM), whereas the inconsistent version would state that the wolf had devoured some of the sheep (QSM). Each pupil was given 7 consistent problems and 7 'inconsistent' ones to solve. RESULTS: For the change problems, errors were more frequent on the inconsistent versions, especially among the younger subjects. For the compare problems, there were more errors on the inconsistent versions regardless of the subjects' age. CONCLUSION: It is in situations where the problem schema is not automatically activated (younger subjects or compare problems) that the QSM plays its role of intermediate representation and causes performances to deteriorate if it does not correspond to the PM.

Comprehension of arithmetic word problems by fifth-grade pupils: representations and selection of information.

BACKGROUND: Understanding word problems leads to the construction of different levels of representation. Some levels specify the elements which are indispensable for solving the problem (problem model, PM) and others specify the agents, actions and events in everyday concepts (situation model, SM). AIMS: By studying how the information is selected, we try to specify the nature of the representations constructed during the reading of a word problem: understanding a problem leads to the construction of two complementary levels of representation (PM and SM) or to the construction of only one representation (PM)? SAMPLE: Ninety-one fifth-grade pupils (mean age 10 years 9 months) took part in this study and were divided into two groups according to their mathematical ability. METHOD: As well as the information considered as indispensable for solving the problems (solving information), different types of information (situational information) were introduced into standard word problems. In a first task, participants were asked to select the information in order to 'make the word problem as short as possible' (locate the elements used for developing PM). In a second task, they were asked to select the information in order to 'make the word problem easier to understand' (determine whether the participants developed a SM). RESULTS: The participants successfully differentiated between the solving information and the situational information. An interaction was also observed between the type of information and the task. The mathematical ability of the participants was seen to have an influence on the selection of situational information. CONCLUSION: Understanding leads to the construction of two complementary representation levels: the problem model and the situation model.

Rational determination of transfer free energies of small drugs across the water-oil interface.

The application of statistical simulations to the estimation of transfer free energies of pharmacologically relevant organic molecules is reported. Large-scale molecular dynamics simulations have been carried out on a series of four solutes, viz. antipyrine, caffeine, ganciclovir, and alpha-D-glucose, at the water-dodecane interface as a model of a biological water-membrane interfacial system. Agreement with experimentally determined partition coefficients is remarkable, demonstrating that free energy calculations, when executed with appropriate protocols, have reached the maturity to predict thermodynamic quantities of interest to the pharmaceutical world. The computational effort that warrants accurate, converged free energies remains, however, in large measure, incompatible with the high-throughput exploration of large sets of pharmacologically active drugs sought by industrial settings. Compared to the cost-effective, fast estimation of simple partition coefficients, the present free energy calculations, nevertheless, offer a far more detailed information about the underlying energetics of the system when the solute is translocated across the water-dodecane interface, which can be valuable in the context of de novo drug design.