Production of Hexanal and Ethane by Phaeodactylum triconutum and Its Correlation to Fatty Acid Oxidation and Bleaching of Photosynthetic Pigments

In a light-dependent reaction (3.5 kilolux) at pH 5, the evolution of hexanal, ethane, and ethylene has been established with cell suspensions of the diatom, Phaeodactylum tricornutum. During this process, chlorophyll and carotenoids are partially bleached. Addition of 25 millimolar α-linolenic acid or 12 millimolar docosahexaenoic acid yield total pigment destruction and enhancement of ethylene and ethane formation (by about 150 and 7,600%, respectively), whereas hexanal production decreases by 70%. Eicosapentaenoic acid, the major polyunsaturated fatty acid in diatoms, stimulates both ethane and hexanal formation (by about 1,400 and 130%, respectively), but reduces ethylene production (by about 60%). This competition suggests that the production of the volatile compounds is closely connected, although hexanal and ethylene obviously possess different unsaturated fatty acids as precursors. Both the kind of the fatty acids and their relative amounts seem to determine the pattern of the evolved hydrocarbons. The presence of 10 millimolar propylgallate inhibits the evolution of the volatile compounds by about 80%, indicating that radical formation might play a key role in this light-dependent cascade of reactions.     

In vivo synthesis of 6-azauridine 5'-triphosphate and incorporation of 6-azauridine into RNA of germinating wheat embryonic axes

The cytostatic effect of 6-azauridine on cell growth is generally regarded to be a consequence of the inhibition of de novo pyrimidine biosynthesis by the metabolite, 6-azauridine 5'-monophosphate. We show here that wheat embryonic axes further metabolize 6-azauridine to the 5'-triphosphate and incorporate the analogue into RNA, thus offering an alternative mechanism for growth inhibition. At a level of 6-azauridine required to maximally inhibit UTP biosynthesis, the ratio of 6-azaUTP to UTP is about 2:1 and substitution of 6-azauridine for uridine in new RNA is on the order of 1 in 18. The new metabolites of 6-azauridine are identified by high pressure and thin layer chromatography coupled with enzyme treatments.     

Genetics of morphological variation in geographically distant populations of the sea urchin,Arbacia punctulata (Lamarck)

Individuals of Arbacia punctulata (Lamarck) from Woods Hole, Massachusetts, and the northeastern Gulf of Mexico were reared from fertilized eggs through metamorphosis under comparable laboratory conditions. Interpopulation differences in spine length development were significant between pure-bred offsprings of these two widely separated geographic areas. Spine lengths of hybrid urchins were intermediate to pure-bred animals. Interpopulation differentiation of specific portions of the genome is proposed to account for the observed phenotypic variation in spine length.     

Terminal deoxyribonucleotidyl transferase activity in acute undifferentiated leukemia.

Guanosine, rather than its methylated derivative, was found to be the inverted nucleoside present in the 5′ terminal capping structure of insect oocyte messenger RNA. Since methylation of the terminal guanosine at the 7 position is necessary for the initiation of protein synthesis in eukaryotes, this evidence suggests that the translational inactivity of the mRNA prior to fertilization may be associated with the absence of methylation.     

Optimization of a series of quinazolinone-derived antagonists of CXCR3

The evaluation of the CXCR3 antagonist AMG 487 in clinic trials was complicated due to the formation of an active metabolite. In this Letter, we will discuss the further optimization of the quinazolinone series that led to the discovery of compounds devoid of the formation of the active metabolite that was seen with AMG 487. In addition, these compounds also feature increased potency and good pharmacokinetic properties. We will also discuss the efficacy of the lead compound 34 in a mouse model of cellular recruitment induced by bleomycin.     

HIV Evolution in Early Infection: Selection Pressures,Patterns of Insertion and Deletion,and the Impact of APOBEC

The pattern of viral diversification in newly infected individuals provides information about the host environment and immune responses typically experienced by the newly transmitted virus. For example, sites that tend to evolve rapidly across multiple early-infection patients could be involved in enabling escape from common early immune responses, could represent adaptation for rapid growth in a newly infected host, or could represent reversion from less fit forms of the virus that were selected for immune escape in previous hosts. Here we investigated the diversification of HIV-1 env coding sequences in 81 very early B subtype infections previously shown to have resulted from transmission or expansion of single viruses (n = 78) or two closely related viruses (n = 3). In these cases, the sequence of the infecting virus can be estimated accurately, enabling inference of both the direction of substitutions as well as distinction between insertion and deletion events. By integrating information across multiple acutely infected hosts, we find evidence of adaptive evolution of HIV-1 env and identify a subset of codon sites that diversified more rapidly than can be explained by a model of neutral evolution. Of 24 such rapidly diversifying sites, 14 were either i) clustered and embedded in CTL epitopes that were verified experimentally or predicted based on the individual''s HLA or ii) in a nucleotide context indicative of APOBEC-mediated G-to-A substitutions, despite having excluded heavily hypermutated sequences prior to the analysis. In several cases, a rapidly evolving site was embedded both in an APOBEC motif and in a CTL epitope, suggesting that APOBEC may facilitate early immune escape. Ten rapidly diversifying sites could not be explained by CTL escape or APOBEC hypermutation, including the most frequently mutated site, in the fusion peptide of gp41. We also examined the distribution, extent, and sequence context of insertions and deletions, and we provide evidence that the length variation seen in hypervariable loop regions of the envelope glycoprotein is a consequence of selection and not of mutational hotspots. Our results provide a detailed view of the process of diversification of HIV-1 following transmission, highlighting the role of CTL escape and hypermutation in shaping viral evolution during the establishment of new infections.     

Surface enlargement in the rumen of free-ranging muskoxen (<Emphasis Type="Italic">Ovibos moschatus</Emphasis>)

The intraruminal papillation pattern indicates the degree of rumen contents stratification and is related to the feeding niche of a ruminant. Muskoxen (Ovibos moschatus) display a variety of morphophysiological adaptations typical for grazers. We investigated the intraruminal papillation of 22 free-ranging muskoxen from five different months by comparing the surface enlargement factor both between seasons and between individual rumen regions. The seasonal pattern of rumen papillation indicated a distinct seasonality in food quality. The intraruminal papillation indicated a moderate degree of rumen contents stratification typical for intermediate feeders. The nutritional ecology of muskoxen is characterised by specific morphophysiological adaptations to a grass-dominated diet that nevertheless allow extensive seasonal use of browse forage.