Macropinocytosis,mTORC1 and cellular growth control

The growth and proliferation of metazoan cells are driven by cellular nutrient status and by extracellular growth factors. Growth factor receptors on cell surfaces initiate biochemical signals that increase anabolic metabolism and macropinocytosis, an actin-dependent endocytic process in which relatively large volumes of extracellular solutes and nutrients are internalized and delivered efficiently into lysosomes. Macropinocytosis is prominent in many kinds of cancer cells, and supports the growth of cells transformed by oncogenic K-Ras. Growth factor receptor signaling and the overall metabolic status of the cell are coordinated in the cytoplasm by the mechanistic target-of-rapamycin complex-1 (mTORC1), which positively regulates protein synthesis and negatively regulates molecular salvage pathways such as autophagy. mTORC1 is activated by two distinct Ras-related small GTPases, Rag and Rheb, which associate with lysosomal membranes inside the cell. Rag recruits mTORC1 to the lysosomal surface where Rheb directly binds to and activates mTORC1. Rag is activated by both lysosomal luminal and cytosolic amino acids; Rheb activation requires phosphoinositide 3-kinase, Akt, and the tuberous sclerosis complex-1/2. Signals for activation of Rag and Rheb converge at the lysosomal membrane, and several lines of evidence support the idea that growth factor-dependent endocytosis facilitates amino acid transfer into the lysosome leading to the activation of Rag. This review summarizes evidence that growth factor-stimulated macropinocytosis is essential for amino acid-dependent activation of mTORC1, and that increased solute accumulation by macropinocytosis in transformed cells supports unchecked cell growth.     

Diet composition of an invasive population of Lithobates catesbeianus (American Bullfrog) from Argentina

The American bullfrog Lithobates catesbeianus has been introduced around the world, with invasive populations reported from almost all South American countries. A population of this species was introduced in the Calingasta department of San Juan province, which is an arid environment in western Argentina. This work provides information on the dietary composition of an invasive population of L. catesbeianus, and compares the degree of dietary overlap between adults and juveniles. Stomach contents of 169 bullfrogs (82 adults and 87 juveniles) were analysed. Adults consumed 40 prey taxa and Hymenoptera (Insecta) was the most numerous prey item (41.8%), followed by Araneae (13.6%) and Aeglidae (13.4%). Juveniles consumed 29 prey taxa and Hymenoptera constituted the highest percentage in prey number (77.2%). The trophic overlap niche index at the same level shows a value of 0.64 overlap in dietary community between adults and juveniles of this bullfrog. Aeglidae was volumetrically the most important trophic item (25.4%), followed by Anura (25.02%). Our results showed that cannibalism in bullfrogs is more common than the consumption of native anurans, coinciding with that reported in other populations of introduced bullfrogs. The high similarity in the diets of both size classes and the association between the size of the predator and prey suggest that the impact caused by bullfrogs throughout their ontogeny is high and probably has an impact on their prey. Freshwater crabs are the main items in the diet of Lithobates catesbeianus in other introduced populations and are usually the most conspicuous at our study site. The crabs in freshwater ecosystems are part of the lowest trophic level in the food chain. The major threats to the southern region’s freshwater crabs include deforestation, farming and exotic species. Lithobates catesbeianus has a generalist diet and high overlap between adults and juveniles.     

Scientific patronage in the age of Darwin: The curious case of William Boyd Dawkins

This essay examines the curious relationship between Charles Darwin and the palaeontologist William Boyd Dawkins (1837–1929). Dawkins was a beneficiary of Darwin's patronage and styled himself as a Darwinian to Darwin and the public, yet viciously attacked Darwin and his theory in anonymous reviews. This has confused historians who have misunderstood the exact nature of Dawkins's attitude towards evolution and his relationship to Darwin. The present study explains both the reasons for Dawkins's contradictory statements and his relationship with Darwin. I introduce Batesian mimicry as a conceptual framework to make sense of Dawkins's actions, suggesting that Dawkins mimicked a Darwinian persona in order to secure advancement in the world of Victorian science. Dawkins's pro-Darwinian stance, therefore, was a façade, an act of mimicry. I argue that Dawkins exploited Darwin for his patronage – which took the form of advice, support from Darwin's well-placed friends, and monetary assistance – while safely expressing his dissent from Darwinian orthodoxy in the form of anonymous reviews. This is, therefore, a case study in how scientific authority and power could be gained and maintained in Victorian science by professing allegiance to Darwin and Darwinism.     

Biogenic amino acid methionine-based corrosion inhibitors of mild steel in acidic media

N,N-Diallyl methionine ethyl ester hydrochloride 5 underwent alternating copolymerization with SO_2 via the Butler cyclopolymerization protocol in dimethyl sulfoxide(DMSO) to give water-soluble cycloterpolymer 6 with a ～1:1 molar ratio of sulfide and sulfoxide groups as a result of oxygen transfer from DMSO. Half of the sulfide groups in 6, upon oxidation with H_2O_2, afforded polymer sulfoxide 7 and polymer sulfone 8. The solution properties of these polymers were determined via a viscometric technique. The thermal stability of these polymers was determined by thermogravimetric analysis. The inhibition efficiency obtained from gravimetric mass loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques agreed well with each other. The corrosion efficiencies increase with increasing concentration of the polymers. At a polymer concentration of 175 mM, the maximum inhibition efficiency of copolymer compounds 6–8 was determined to be 92%, 97%, and 95%, respectively. The synthesized polymer compounds acted as mixed-type inhibitors. Polymer compound 7 adsorbed onto the metal surface via chemisorption and physisorption and obeyed Langmuir, Temkin, and Freundlich adsorption isotherms. Analyses by X-ray photoelectron spectroscopy and scanning electron microscopy–energy-dispersive X-ray spectroscopy indicated that the adsorbed polymers formed a thin film on the metal surface and prevented further corrosive attack.     

Erratum to: Hesperomyces virescens (Fungi,Ascomycota, Laboulbeniales) attacking Harmonia axyridis (Coleoptera,Coccinellidae) in its native range

正Published online:14 March 2014óScience China Press and Springer-Verlag Berlin Heidelberg 2014Erratum to:Chin.Sci.Bull.(2014)59(5–6):528–532DOI 10.1007/s11434-013-0060-1In the original publication of this paper,the first name and the last name of the first author has been documented     

Is the valid species Synchaeta monopus Plate, 1889 (Rotifera: Monogononta) a product of preparation artefacts?

The morphology of soft-bodied rotifers, including those of Synchaeta spp, can be strongly affected by preparation artefacts including contraction and deformation. The long-standing, valid species Synchaeta monopus is known exclusively from ethanol- or formaldehyde-preserved material and no live specimens of it have ever been described. Although this alone is cause for concern, we could also reproduce unique characteristics diagnostic for this species (e.g. the swollen body and the rudimental foot) by subjecting specimens of Synchaeta pectinata to the preservation conditions under which it was first described. This proxy experiment and comparisons to other Synchaeta species indicate that literature occurrences of S. monopus likely represent preserved and deformed specimens of Synchaeta cecilia or other marine species of Synchaeta, thereby highlighting the importance of thorough morphological investigations of the habitus using live specimens and of features that are unaffected by preservation (e.g. the trophi). We therefore recommend that S. monopus be listed as a species inquirenda until topotypes are examined. Furthermore, in ecological studies including rotifers, where the examination of preserved material is often unavoidable, we stress that light-microscopical images of the habitus and trophi of the specimens minimally be included to facilitate independent verification of the species assignments.