Glucose control of sucrose synthase in the maize scutellum

The in vivo amounts of UDPG, UTP, UDP and UMP, metabolites known to influence the activity of sucrose phosphate synthase (SPS) and sucrose synthase (SS), were measured throughout 5 hr incubations of scutellum slices in fructose or water, i.e. under conditions of sucrose synthesis or breakdown. Cytosolic concentrations were estimated assuming that these metabolites were confined to the cytosol. Within the estimated in vivo concentration ranges, UDPG, UTP and UDP had little effect on the in vitro SS activity, but glucose (100 mM) inhibited SS in the synthesis direction by 63–70% and in the breakdown direction by 86–93%. Glucose inhibition of SS was considerably less when saturating levels of substrates were used. Sucrose did not inhibit SS. It is concluded that during germination the glucose produced from starch breakdown in the maize endosperm enters the scutellum and inhibits SS, preventing a futile cycle and limiting SS participation in sucrose synthesis.     

Exoantigens of Trypanosoma cruzi. I. Conditions for Their Detection and Immunogenic Properties in Experimental Infections1

ABSTRACT Exoantigens of Trypanosoma cruzi were produced in experimentally infected BALB/c mice. The exoantigens were detected by the counterimmunoelectrophoresis method (CIE), with antisera raised in rabbits by immunization with total homogenates of culture forms of ***T. cruzi in plasma from ***field animals obtained by centrifugation and filtration. Control experiments indicated that exoantigens are not somatic components of T. cruzi leaked during the preparative procedure. Exoantigens were detected in male and female mice, 11-90 days old, between 6 and 60 days of infection, and in all mice with patent parasitemia. After 13 days of infection, mice developed antibodies to exoantigens; by CIE up to three populations of antibodies were revealed in different groups of animals. In mice between 13 and 60 days of infection, the coexistence of exoantigens and homologous antibodies was also observed. The exoantigens are not strain specific since a cross reactivity between antigens from three strains of T. cruzi (Tulahuén, Higueras, and Alejandro) was seen. Finally, the presence of antibodies to exoantigens in humans with chronic Chagas’ disease was demonstrated.     

Complete sequence of a new HLA-B35 allele found in a tribe of Mapuche Indians in the south of Argentina

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number U17107. The nameB*3509 was officially assigned by the WHO Nomenclature Committee in December 1994     

A NEW PHYLOGENY FOR CHROMOPHYTE ALGAE USING 16S-LIKE RRNA SEQUENCES FROM MALLOMONAS PAPILLOSA (SYNUROPHYCEAE) AND TRIBONEMA AEQUALE (XANTHOPHYCEAE)1

The 16S-like ribosomal RNA genes from Mallomonas papillosa Harris et Bradley (Synurophyceae) and Tribonema aequale Pascher (Xanthophyceae) were sequenced and compared to those of other eukaryotes. Mallomonas is closely related to Ochromonas (Chrysophyceae) and supports the general hypothesis of a close phylogenetic relationship between the Synurophyceae and Chrysophyceae. Tribonema is specifically related to Costaria costata (C. A. Agardh) Saunders (Phaeophyceae) demonstrating an unexpected phylogenetic relationship between the Xanthophyceae and Phaeophyceae. Distance and parsimony analysis place these four chromophyte genera in a complex evolutionary assemblage that includes the Bacillariophyceae and Oomycetes but excludes the Dinophyceae. The close relationship between the chromophyte algae and the Öomycete fungi supports the hypothesis that protists with tripartite hairs form a natural assemblage.     

Life cycle environmental impacts of non-cellulosic fermentable carbohydrates for the production of biofuels and chemicals

The International Journal of Life Cycle Assessment - Fermentable carbohydrates (FC) are raw materials from agriculture common in the production of bio-based products like biofuels and renewable...     

Foraging shifts and visual preadaptation in ecologically diverse bats

Changes in behaviour may initiate shifts to new adaptive zones, with physical adaptations for novel environments evolving later. While new mutations are commonly considered engines of adaptive change, sensory evolution enabling access to new resources might also arise from standing genetic diversity, and even gene loss. We examine the relative contribution of molecular adaptations, measured by positive and relaxed selection, acting on eye‐expressed genes associated with shifts to new adaptive zones in ecologically diverse bats from the superfamily Noctilionoidea. Collectively, noctilionoids display remarkable ecological breadth, from highly divergent echolocation to flight strategies linked to specialized insectivory, the parallel evolution of diverse plant‐based diets (e.g., nectar, pollen and fruit) from ancestral insectivory, and—unusually for echolocating bats—often have large, well‐developed eyes. We report contrasting levels of positive selection in genes associated with the development, maintenance and scope of visual function, tracing back to the origins of noctilionoids and Phyllostomidae (the bat family with most dietary diversity), instead of during shifts to novel diets. Generalized plant visiting was not associated with exceptional molecular adaptation, and exploration of these novel niches took place in an ancestral phyllostomid genetic background. In contrast, evidence for positive selection in vision genes was found at subsequent shifts to either nectarivory or frugivory. Thus, neotropical noctilionoids that use visual cues for identifying food and roosts, as well as for orientation, were effectively preadapted, with subsequent molecular adaptations in nectar‐feeding lineages and the subfamily Stenodermatinae of fig‐eating bats fine‐tuning pre‐existing visual adaptations for specialized purposes.     

Oxidative stress alters neuronal RNA- and protein-synthesis: Implications for neural viability

Recent studies have demonstrated that impaired protein synthesis occurs in several neurodegenerative conditions associated with oxidative stress. Studies have also demonstrated that administration of oxidative stressors is sufficient to impair different and discrete regulatory aspects of protein synthesis in neural cells, with the majority of these studies focused on the effects of oxidative stressors towards initiation factors. Currently, little is known with regards to oxidative stress effects on the rates of RNA- and protein-synthesis, or the relationship between oxidant-induced impairments in RNA-/protein-synthesis to subsequent neuron death. In the present study, we demonstrate that administration of an oxidative stressor (hydrogen peroxide) induces a significant and time-dependent decrease in both RNA- and protein-synthesis in primary neurons and neural SH-SY5Y cells. Increases in RNA oxidation and disruption of ribosome complexes were selectively observed following the longer durations of oxidant exposure. Significant correlations between the loss of RNA- and protein-synthesis and the amount of oxidant-induced neuron death were also observed. Interestingly, the addition of a protein synthesis inhibitor (cycloheximide) did not significantly alter the amount of neuron death induced by the oxidative stressor. These data demonstrate that oxidant exposure promotes a time-dependent decrease in both RNA- and protein-synthesis in neurons, and demonstrate a role for elevations in RNA oxidation and ribosome dysfunction as potential mediators of impaired protein synthesis. These data also suggest that there is a complex relationship between the ability of oxidative stressors to modulate RNA- and protein-synthesis, and the ability of oxidative stressors to ultimately induce neuron death.     

Riparian and adjacent forests differ both in the humid mountainous ecoregion and the semiarid lowland

Plant Ecology - Few studies have quantified changes in riparian and adjacent forest across landscape units. In this study, the composition and structure of riparian and adjacent forest were...