Explaining Atomic Spectra within Classical Physics: 1897-1913

In this paper we analyse the approach to interpreting atomic spectra in the framework of classical physics from the discovery of the electron in 1897 to Bohr's atomic model of 1913. Taken as a whole, efforts in this direction are part of a remarkable intellectual endeavour in which the classical theoretical framework seems to have been exploited to its full potential. By demonstrating the limits and weaknesses of classical physics in solving the problem of spectral emissions, these attempts opened the way to a complete break from traditional thought and the introduction of the new quantum ideas.     

Shedding light on mitophagy in neurons: what is the evidence for PINK1/Parkin mitophagy in vivo?

Neurons are highly specialised cells with a large bioenergetic demand, and so require a healthy mitochondrial network to function effectively. This network is compromised in many neurological disorders, in which damaged mitochondria accumulate. Dysfunctional mitochondria can be removed via an organelle-specific autophagic pathway, a process known as mitophagy. The canonical mitophagy pathway is dependent on the actions of PINK1 (PTEN-induced putative kinase 1) and Parkin and has been well studied in immortalised cells and cultured neurons. However, evidence for a role of this mitophagy pathway in the brain is still limited, and studies suggest that there may be important differences in how neurons respond to mitochondrial damage in vitro and in vivo. Here, we first describe the evidence for a functional PINK1/Parkin mitophagy pathway in neurons, and review how this pathway is affected in disease models. We then critically evaluate the literature by comparing findings from in vitro models and more recent in vivo studies in flies and mice. The emerging picture implicates that alternative mitophagy pathways operate in neurons in vivo. New mouse models that employ fluorescent biosensors to monitor mitophagy in vivo will be instrumental to understand the relative role of the different clearance pathways in the brain under physiological and pathological conditions.     

microRNA-122 target sites in the hepatitis C virus RNA NS5B coding region and 3′ untranslated region: function in replication and influence of RNA secondary structure

We have analyzed the binding of the liver-specific microRNA-122 (miR-122) to three conserved target sites of hepatitis C virus (HCV) RNA, two in the non-structural protein 5B (NS5B) coding region and one in the 3′ untranslated region (3′UTR). miR-122 binding efficiency strongly depends on target site accessibility under conditions when the range of flanking sequences available for the formation of local RNA secondary structures changes. Our results indicate that the particular sequence feature that contributes most to the correlation between target site accessibility and binding strength varies between different target sites. This suggests that the dynamics of miRNA/Ago2 binding not only depends on the target site itself but also on flanking sequence context to a considerable extent, in particular in a small viral genome in which strong selection constraints act on coding sequence and overlapping cis-signals and model the accessibility of cis-signals. In full-length genomes, single and combination mutations in the miR-122 target sites reveal that site 5B.2 is positively involved in regulating overall genome replication efficiency, whereas mutation of site 5B.3 showed a weaker effect. Mutation of the 3′UTR site and double or triple mutants showed no significant overall effect on genome replication, whereas in a translation reporter RNA, the 3′UTR target site inhibits translation directed by the HCV 5′UTR. Thus, the miR-122 target sites in the 3′-region of the HCV genome are involved in a complex interplay in regulating different steps of the HCV replication cycle.     

Ecosystem energetic implications of parasite and free-living biomass in three estuaries

Parasites can have strong impacts but are thought to contribute little biomass to ecosystems. We quantified the biomass of free-living and parasitic species in three estuaries on the Pacific coast of California and Baja California. Here we show that parasites have substantial biomass in these ecosystems. We found that parasite biomass exceeded that of top predators. The biomass of trematodes was particularly high, being comparable to that of the abundant birds, fishes, burrowing shrimps and polychaetes. Trophically transmitted parasites and parasitic castrators subsumed more biomass than did other parasitic functional groups. The extended phenotype biomass controlled by parasitic castrators sometimes exceeded that of their uninfected hosts. The annual production of free-swimming trematode transmission stages was greater than the combined biomass of all quantified parasites and was also greater than bird biomass. This biomass and productivity of parasites implies a profound role for infectious processes in these estuaries.     

A conserved microRNA module exerts homeotic control over Petunia hybrida and Antirrhinum majus floral organ identity

It is commonly thought that deep phylogenetic conservation of plant microRNAs (miRNAs) and their targets indicates conserved regulatory functions. We show that the blind (bl) mutant of Petunia hybrida and the fistulata (fis) mutant of Antirrhinum majus, which have similar homeotic phenotypes, are recessive alleles of two homologous miRNA-encoding genes. The BL and FIS genes control the spatial restriction of homeotic class C genes to the inner floral whorls, but their ubiquitous early floral expression patterns are in contradiction with a potential role in patterning C gene expression. We provide genetic evidence for the unexpected function of the MIRFIS and MIRBL genes in the center of the flower and propose a dynamic mechanism underlying their regulatory role. Notably, Arabidopsis thaliana, a more distantly related species, also contains this miRNA module but does not seem to use it to confine early C gene expression to the center of the flower.     

Insect antifeedant properties of withanolides and related steroids from Solanaceae

Summary Physalis peruviana shrubs were not attacked by larvae ofSpodoptera littoralis. It was demonstrated that withanolide E, a steroid isolated fromP. peruviana, as well as several related steroids, have insect antifeedant properties.