Structure of a β-galactan isolated from the nuclei of Physarum polycephalum

A sulfated and phosphorylated β-D-galactan ([α]_D + 8°) was isolated from the nuclei of the acellular slime mould Physarum polycephalum. The polysaccharide was isolated from cesium chloride gradients during the preparation of ribosomal DNA and purified. The purified galactan contained 89% galactose, 2.5% phosphate and 9.6% sulfate groups and had an average degree of polymerisation of 560. Periodate degradation and permethylation studies indicated the presence of mainly (1 → 4)-, but also of (1 → 3)-, and (1 → 6)-linked galactose units with one branch every 13 units. These results suggested that the intranuclear galactan, apart from its higher sulfate content, is similar to the extra-cellular polysaccharide produced by P. polycephalum.     

Teleosemantic modeling of cognitive representations

Naturalistic theories of representation seek to specify the conditions that must be met for an entity to represent another entity. Although these approaches have been relatively successful in certain areas, such as communication theory or genetics, many doubt that they can be employed to naturalize complex cognitive representations. In this essay I identify some of the difficulties for developing a teleosemantic theory of cognitive representations and provide a strategy for accommodating them: to look into models of signaling in evolutionary game theory. I show how these models can be used to formulate teleosemantics and expand it in new directions.     

Novel Escherichia coli RF1 mutants with decreased translation termination activity and increased sensitivity to the cytotoxic effect of the bacterial toxins Kid and RelE

Novel mutations in prfA , the gene for the polypeptide release factor RF1 of Escherichia coli , were isolated using a positive genetic screen based on the parD ( kis , kid ) toxin–antitoxin system. This original approach allowed the direct selection of mutants with altered translational termination efficiency at UAG codons. The isolated prfA mutants displayed a ∼10-fold decrease in UAG termination efficiency with no significant changes in RF1 stability in vivo . All three mutations, G121S, G301S and R303H, were situated close to the nonsense codon recognition site in RF1:ribosome complexes. The prfA mutants displayed increased sensitivity to the RelE toxin encoded by the relBE system of E. coli , thus providing in vivo support for the functional interaction between RF1 and RelE. The prfA mutants also showed increased sensitivity to the Kid toxin. Since this toxin can cleave RNA in a ribosome-independent manner, this result was not anticipated and provided first evidence for the involvement of RF1 in the pathway of Kid toxicity. The sensitivity of the prfA mutants to RelE and Kid was restored to normal levels upon overproduction of the wild-type RF1 protein. We discuss these results and their utility for the design of novel antibacterial strategies in the light of the recently reported structure of ribosome-bound RF1.     

Solution conformation of lasalocid and lasalocid-Na+ (X-537A)

The complete unraveling of the proton nuclear magnetic resonance spectra at high field strength of Lasalocid (1) and its sodium salt (2) in different solvents allowed the definition of their solution conformations. The free acid, a lozengeshaped molecule of 17 × 13 × 9 Å is prefolded in a way almost identical to that of its sodium derivative, where the ion lies in the centre, surrounded by all the oxygen atoms in the molecule except for the phenolic one. Although the upper side of the molecule is rather accessible to hydrophilic approach, some alkyl substituents are arranged out- and upwards, thus shielding the ion from possible contact with lipophilic surroundings. The spatial picture suggests that the ion is trapped upon arrival at one side (the flat upper side) and is released either at the same or at the opposite side.     

Prostaglandin production by human epidermal cells in vitro: A model for studying pharmacologic inhibition of prostaglandin synthesis

An inv itro model for studying the biosynthesis of prostaglandins by isolated human epidermal cells is described. Production of prostaglandin E₂-equivalent activity over an 18-hour incubation period was measured using a radioimmunoassay. Prostaglandin production was significantly inhibited by indomethacin and aspirin in a concentration-dependent manner.     

Inter-locality variation in reproductive success of the citril finch Serinus citrinella

Habitat quality is generally thought to affect breeding success. We tested this effect comparing differences in clutch size and reproductive success between citril finch Serinus citrinella sub-populations closely located (<5 km) but differing in habitat quality, within the Port del Comte mountain, in the Catalonian Pre-Pyrenees. We found that birds in the low quality area (Bofia) showed significantly lower hatching, breeding and nesting success than finches in the high quality area (Vansa). These differences in reproductive success fit well with recently found differences in citril finch body mass, fat score, diet, survival rate and speed of moult between these two localities.