Cancer chemotherapy induces cardiotoxicity by targeting cardiac stem cells

Overwhelming data indicate that cancer survivors are at higher risk of cardiovascular diseases because chemotherapy induces cardiotoxicity. Mechanistic explanation of this phenomenon is necessary to advise the clinical practice on the prevention of cardiotoxicity in cancer patients. Here we propose that chemotherapy induces cardiotoxicity by inadvertently interrupting the homeostasis of cardiac stem cells and depleting the resident cardiac stem cells pool. As a result, the heart loses the capability of regeneration and repair and demonstrates the cardiotoxicity symptoms. Our hypothesis is supported by several lines of emerging evidence: the high incidence of cardiotoxicity in paediatric cancer patients who still have more cardiac stem cells in the myocardium; the rescue of anthracycline cardiomyopathy by injection of cardiac stem cells; and the adverse cardiotoxicity induced by inhibitors of oncogenic kinases or pathways which target cardiac stem cells besides cancer cells. This may promote our growing appreciation that cardiac stem cells represent new targets of chemotherapy that contribute to cardiotoxicity and open up novel strategies for the preservation or expansion of the cardiac stem cells pool to overcome cardiotoxicity associated with chemotherapy.     

Integrating ancient patterns and current dynamics of insect–plant interactions: Taxonomic and geographic variation in herbivore specialization

Abstract The search for pattern in the ecology and evolutionary biology of insect–plant associations has fascinated biologists for centuries. High levels of tropical (low-latitude) plant and insect diversity relative to poleward latitudes and the disproportionate abundance of host-specialized insect herbivores have been noted. This review addresses several aspects of local insect specialization, host use abilities (and loss of these abilities with specialization), host-associated evolutionary divergence, and ecological (including “hybrid”) speciation, with special reference to the generation of biodiversity and the geographic and taxonomic identification of “species borders” for swallowtail butterflies (Papilionidae). From ancient phytochemically defined angiosperm affiliations that trace back millions of years to recent and very local specialized populations, the Papilionidae (swallowtail butterflies) have provided a model for enhanced understanding of localized ecological patterns and genetically based evolutionary processes. They have served as a useful group for evaluating the feeding specialization/physiological efficiency hypothesis. They have shown how the abiotic (thermal) environment interacts with host nutrirional suitability to generate “voltinism/suitability” gradients in specialization or preference latitudinally, and geographical mosaics locally. Several studies reviewed here suggest strongly that the oscillation hypothesis for speciation does have considerable merit, but at the same time, some species-level host specializations may lead to evolutionary dead-ends, especially with rapid environmental/habitat changes involving their host plants. Latitudinal gradients in species richness and degree of herbivore feeding specialization have been impacted by recent developments in ecological genetics and evolutionary ecology. Localized insect–plant associations that span the biospectrum from polyphenisms, polymorphisms, biotypes, demes, host races, to cryptic species, remain academically contentious, with simple definitions still debated. However, molecular analyses combined with ecological, ethological and physiological studies, have already begun to unveil some answers for many important ecological/evolutionary questions.     

Flexible feeding on cultivated underground storage organs by rainforest-dwelling chimpanzees at Bossou, West Africa

It has been proposed that exploitation of underground storage organs (USOs) played an important role in the evolution of the genus Homo, these items serving as ‘fallback foods’ during periods of low food availability. The use of USOs as food by wild chimpanzees is infrequent and seen mostly in populations inhabiting relatively arid environments, such as the savanna. Here, we specifically test the hypothesis that chimpanzees (Pan troglodytes verus) inhabiting tropical wet forest at Bossou (Republic of Guinea, West Africa) exploit USOs as a fallback food during periods of fruit scarcity. Chimpanzees were never observed feeding on wild USOs, that is, those that were never cultivated, and rarely on other underground plant parts. However, direct observations revealed regular consumption of the USOs of cultivated cassava (Manihot esculenta), a spatially abundant and continuously available plant, although the chimpanzees did not use tools when acquiring and feeding on cassava. In agreement with the fallback foods hypothesis, our results show that chimpanzees exploited cassava USOs more frequently when both wild and cultivated fruits were scarce, and consumption patterns of cassava paralleled those of wild fallback foods. These seasonal extractive USO foraging strategies by chimpanzees can strengthen attempts to construct a clearer picture of the importance of USO feeding in hominoid evolution.     

The size-grain hypothesis: a phylogenetic and field test

Abstract.  1. The size-grain hypothesis predicts that environmental rugosity results in positive allometric scaling of leg length on body length because of changes in locomotion costs.
2. The scaling of leg length and body length in ants was re-examined using phylogenetic independent contrast methods, and the allometric relationship found by Kaspari and Weiser ( Functional Ecology , 13 , 530–538, 1999) was supported.
3. The size-grain hypothesis was tested further by comparing the body sizes of ants from areas of contrasting habitat complexity in two different savanna habitats. No support for the size-grain hypothesis was found. Small body size classes were no more speciose in the rugose than in the more planar environment, and small ants were more abundant in the planar environment.     

THE ECOLOGY AND GENETICS OF FITNESS IN CHLAMYDOMONAS III. GENOTYPE-BY-ENVIRONMENT INTERACTION WITHIN STRAINS

The fitness of genotypes created by crossing strains of Chlamydomonas reinhardtii was measured in axenic pure culture in a set of chemically defined environments. There was substantial and highly significant genotype-by-environment interaction, with genetic correlations between environments averaging only about +0.1 for both r and K. Higher-order interactions with combinations of environmental factors appeared to be no less important than simple interactions with single factors. The importance of genotype-by-environment interaction increased with the number of environmental factors manipulated. The linear reaction norms of genotypic score on environmental mean score varied substantially among genotypes and often intersected. There was also some evidence that nonallelic genetic interactions were present, and varied among environments. The genetic correlation of r with K also varied among environments, being significantly negative in some but not in others. These results are similar in all important respects to those previously obtained with different species, and suggest that genotype-by-environment interaction is important at all genetic scales. It is argued that they provide empirical support for a general theory of diversity, the “Tangled Bank,” based on the different response of genotypes to the range of conditions found in heterogeneous natural environments.     

The Amazon River as a dispersal barrier to passerine birds: effects of river width, habitat and taxonomy

Aim To evaluate the relative effectiveness of the lower and upper sections, respectively, of the Amazon River as a barrier to bird distribution, and to evaluate ecological and taxonomic factors affecting the efficacy of the river barrier. Location Amazon River of South America between its confluence with the Napo River in the west and its delta in the east. Methods Using published distribution maps for 448 species of passerine birds occurring along the Amazon River, we evaluated whether each was distributed along one bank only (river presumed to be a barrier) or both banks (no barrier) to test the predictions that the river was more effective as a dispersal barrier: (1) along the lower, wider portion of the river than the upper, narrower portion; (2) for species inhabiting forests than open country; (3) for species inhabiting forest understorey than forest canopy; (4) for species restricted to terra firme (never inundated upland forest) than those not restricted to terra firme and (5) for certain taxonomic groups. Results Our analyses demonstrated that the Amazon River was most effective as a dispersal barrier along its lower portion and for species restricted to forests and terra firme. However, the river was not significantly more of a barrier for species inhabiting forest understorey than forest canopy. The river was most significant as a barrier to dispersal for the antbirds (Thamnophilidae) and was less significant as a barrier to species belonging to several large families including woodcreepers (Dendrocolaptidae), ovenbirds (Furnariidae), flycatchers (Tyrannidae), cotingids (Cotingidae), tanagers (Thraupidae), seed‐eating finches (Emberizidae) and blackbirds (Icteridae). Main conclusions The robust widths of Amazonian rivers are widely considered to represent impediments to dispersal and gene flow for many taxa of birds and other animals, and may have represented agents of vicariance in the diversification of species. Our study reaffirms the effectiveness of the lower Amazon River as a current barrier to bird dispersal for forest birds and provides new insights into the effects of habitat and taxonomy on the efficacy of the river barrier. Although supportive of several predictions of the river hypothesis of biological diversification, our study is limited in addressing the historical impact of river barriers as agents of vicariance in the process of diversification.     

Leafhopper-induced plant resistance enhances predation risk in a phytophagous beetle

Many herbivores elicit biochemical, physiological, or morphological changes in their host plants that render them more resistant to co-occurring herbivores. Yet, despite the large number of studies that investigate how induced resistance affects herbivore preference and performance, very few have simultaneously explored the cascading effects of induction on higher trophic levels and consequences for prey suppression. In our study system, early-season herbivory by leafhoppers elevated plant resistance to subsequent attack by chrysomelid beetles sharing the same host plant. Notably, beetles feeding on leafhopper-damaged plants incurred developmental penalties (e.g., prolonged time in early larval instars) that rendered them more susceptible to predation by natural enemies. As a result, the combined bottom-up effect of leafhopper-induced resistance and the top-down effect of enhanced predation resulted in the synergistic suppression of beetle populations. These results emphasize that higher trophic level dynamics should be considered in conjunction with induced resistance to better understand how plants mediate interspecific interactions in phytophagous insect communities.     

Beautiful parents have more daughters: a further implication of the generalized Trivers-Willard hypothesis (gTWH)

The generalized Trivers-Willard hypothesis (gTWH) [Kanazawa, S., 2005. Big and tall parents have more sons: further generalizations of the Trivers-Willard hypothesis. J. Theor. Biol. 235, 583-590) proposes that parents who possess any heritable trait which increases the male reproductive success at a greater rate than female reproductive success in a given environment will have a higher-than-expected offspring sex ratio, and parents who possess any heritable trait which increases the female reproductive success at a greater rate than male reproductive success in a given environment will have a lower-than-expected offspring sex ratio. One heritable trait which increases the reproductive success of daughters much more than that of sons is physical attractiveness. I therefore predict that physically attractive parents have a lower-than-expected offspring sex ratio (more daughters). Further, if beautiful parents have more daughters and physical attractiveness is heritable, then, over evolutionary history, women should gradually become more attractive than men. The analysis of the National Longitudinal Study of Adolescent Health (Add Health) confirm both of these hypotheses. Very attractive individuals are 26% less likely to have a son, and women are significantly more physically attractive than men in the representative American sample.