Adaptive changes of rat liver cells induced by repeated intraperitoneal injections of d-galactosamine. III-Light- and electron-microscopic investigations of hepatocellular cytoplasmic changes.

In rats hepatocellular cytoplasmic changes after daily repeated D-galactosamine (GalN) intoxication--i.e. subacute GalN intoxication--were studied by light and electron microscopy. The number of GalN injections--and thus the days of survival--was between one and 30. The rats were killed six hours after the last GalN injection. Less degenerative changes were found after repeated GalN injections. An increased formation of atypical dense bodies (ADB), a temporary pronounced lipid accumulation and changes of the rough and smooth endoplasmic reticulum were prominent features of subacute GalN intoxication. The implications with respect to a modified GalN action in subacute GalN intoxication are discussed with special reference to biochemical data obtained in the same experimental model (Schuchhardt et al., 1977).     

Gut microbiota composition is associated with environmental landscape in honey bees

There is growing recognition that the gut microbial community regulates a wide variety of important functions in its animal hosts, including host health. However, the complex interactions between gut microbes and environment are still unclear. Honey bees are ecologically and economically important pollinators that host a core gut microbial community that is thought to be constant across populations. Here, we examined whether the composition of the gut microbial community of honey bees is affected by the environmental landscape the bees are exposed to. We placed honey bee colonies reared under identical conditions in two main landscape types for 6 weeks: either oilseed rape farmland or agricultural farmland distant to fields of flowering oilseed rape. The gut bacterial communities of adult bees from the colonies were then characterized and compared based on amplicon sequencing of the 16S rRNA gene. While previous studies have delineated a characteristic core set of bacteria inhabiting the honey bee gut, our results suggest that the broad environment that bees are exposed to has some influence on the relative abundance of some members of that microbial community. This includes known dominant taxa thought to have functions in nutrition and health. Our results provide evidence for an influence of landscape exposure on honey bee microbial community and highlight the potential effect of exposure to different environmental parameters, such as forage type and neonicotinoid pesticides, on key honey bee gut bacteria. This work emphasizes the complexity of the relationship between the host, its gut bacteria, and the environment and identifies target microbial taxa for functional analyses.     

The ectomycorrhizal basidiomycete Hebeloma circinans harbors a linear plasmid encoding a DNA- and RNA polymerase

Bulk DNA isolated from the ectomycorrhizal basidiomycete Hebeloma circinans was treated with proteinase K and submitted to agarose gel electrophoresis. In addition to high molecular weight genomic DNA, three minor bands were detected. The band with the highest electrophoretic mobility (2.2 kbp) corresponds to double-stranded RNA. The two other bands, termed pHC1 and pHC2, were shown to be dsDNA molecules of 10.3 and 9.1 kbp, respectively. Treatment of the pHC elements with 3'- and 5'-specific exonucleases revealed a linear structure and proved that the 5' ends are protected from digestion; for pHC2, linearity was confirmed by restriction mapping. A 3.2 kbp HindIII fragment of pHC2 was cloned and sequenced; it contains two open reading frames encoding putative viral B type DNA and RNA polymerases. Thus, the fungus harbors a typical linear plasmid, up to now, rarely described for basidiomycetes and hitherto unknown for mycorrhizal species.     

Structural polymorphism of Alzheimer A�� and other amyloid fibrils

Deposits of amyloid fibrils characterize a diverse group of human diseases that includes Alzheimer disease, Creutzfeldt-Jakob disease and type II diabetes. Amyloid fibrils formed from different polypeptides contain a common cross-β spine. Nevertheless, amyloid fibrils formed from the same polypeptide can occur in a range of structurally different morphologies. The heterogeneity of amyloid fibrils reflects different types of polymorphism: (1) variations in the protofilament number, (2) variations in the protofilament arrangement and (3) different polypeptide conformations. Amyloid fibril polymorphism implies that fibril formation can lead, for the same polypeptide sequence, to many different patterns of inter- or intra-residue interactions. This property differs significantly from native, monomeric protein folding reactions that produce, for one protein sequence, only one ordered conformation and only one set of inter-residue interactions.Key words: Alzheimer disease, aggregation, neurodegeneration, prion, protein folding