Cloning, tissue and ontogenetic expression of the taurine transporter in the flatfish Senegalese sole (Solea senegalensis)

Flatfish species seem to require dietary taurine for normal growth and development. Although dietary taurine supplementation has been recommended for flatfish, little is known about the mechanisms of taurine absorption in the digestive tract of flatfish throughout ontogeny. This study described the cloning and ontogenetic expression of the taurine transporter (TauT) in the flatfish Senegalese sole (Solea senegalensis). Results showed a high similarity between TauT in Senegalese sole and other vertebrates, but a change in TauT amino acid sequences indicates that taurine transport may differ between mammals and fish, reptiles or birds. Moreover, results showed that Senegalese sole metamorphosis is an important developmental trigger to promote taurine transport in larvae, especially in muscle tissues, which may be important for larval growth. Results also indicated that the capacity to uptake dietary taurine in the digestive tract is already established in larvae at the onset of metamorphosis. In Senegalese sole juveniles, TauT expression was highest in brain, heart and eye. These are organs where taurine is usually found in high concentrations and is believed to play important biological roles. In the digestive tract of juveniles, TauT was more expressed in stomach and hindgut, indicating that dietary taurine is quickly absorbed when digestion begins and taurine endogenously used for bile salt conjugation may be recycled at the posterior end of the digestive tract. Therefore, these results suggest an enterohepatic recycling pathway for taurine in Senegalese sole, a process that may be important for maintenance of the taurine body levels in flatfish species

Functional oligosaccharides: application and manufacture.

Oligosaccharides are attracting increasing interest as prebiotic functional food ingredients. They can be extracted or obtained by enzymatic hydrolysis from a variety of biomass sources or synthesized from simple oligosaccharides by enzymatic transfer reactions. The major prebiotic oligosaccharides on the market are inulin, fructo-oligosaccharides, and galacto-oligosaccharides. They have been evaluated using a range of in vitro and in vivo methods, although there is a need for more large-scale human trials using modern microbiological methods. Prebiotics are being studied for their effects on gut health and well being and specific clinical conditions, including colon cancer, inflammatory bowel disease (IBD), acute infections, and mineral absorption. Developing understanding of the functional ecology of the human gut is influencing current thinking on what a prebiotic might achieve and is providing new targets for prebiotic intervention

Quantitative trait loci for grain fructan concentration in wheat (Triticum aestivum L.)

Fructans (fructo-oligosaccharides) are prebiotics that are thought to selectively promote the growth of colonic bifidobacteria, thereby improving human gut health. Fructans are present in the grain of wheat, a staple food crop. In the research reported here, we aimed to detect and map loci affecting grain fructan concentration in wheat using a doubled-haploid population derived from a cross between a high-fructan breeding line, Berkut, and a low-fructan cultivar, Krichauff. Fructan concentration was measured in grain samples grown at two locations in Australia and one in Kazakhstan. Fructan concentration varied widely within the population, ranging from 0.6 to 2.6% of grain dry weight, and was quite repeatable, with broad-sense heritability estimated as 0.71. With a linkage map of 528 molecular markers, quantitative trait loci (QTLs) were detected on chromosomes 2B, 3B, 5A, 6D and 7A. Of these, the QTLs on chromosomes 6D and 7A had the largest effects, explaining 17 and 27% of the total phenotypic variance, respectively, both with the favourable (high-fructan concentration) alleles contributed from Berkut. These chromosome regions had similar effects in another mapping population, Sokoll/Krichauff, with the favourable alleles contributed from Sokoll. It is concluded that grain fructan concentration of wheat can be improved by breeding and that molecular markers could be used to select effectively for favourable alleles in two regions of the wheat genome.Bao-Lam Huynh, Hugh Wallwork, James C. R. Stangoulis, Robin D. Graham, Kerrie L. Willsmore, Steven Olson, Diane E. Mathe

Electrochemical measurements bearing on the oxidation state of the Skaergaard Layered Intrusion

The oxygen fugacities (fO 2 's) of magnetically-concentrated fractions (MCF) of three rock samples from the Skaergaard Layered Intrusion were measured between 800–1150° C using oxygen-specific, solid zirconia electrolytes at atmospheric pressure. Two of the bulk rock samples (an oxide cumulate and an oxide-bearing gabbro) are from the Middle Zone (MZ) and the other (an olivine plagioclase orthocumulate) is from the Lower Zone (LZ). All MCF define fO 2 versus T arrays that lie 1.5–0.5 log units above the fayalite-magnetite-quartz (FMQ) buffer. Experiments with different cell-imposed initial redox states (one from a reduced direction and one from an oxidized direction) were run on each sample in an attempt to achieve experimental reversibility. This was accomplished by imposing a known redox memory on the galvanic cell prior to loading each sample. Reversibility for each sample agreed to better than 0.2 of a log unit. Irreversible autoreduction of 0.2 of a log unit was observed on the two MZ samples at temperatures exceeding 1065° C. Scanning electron microscope and electron microprobe study of pre- and post-run products shows that reaction and textural re-equilibration occurred among the oxide phase assemblages under the experimental conditions employed. Careful characterization of pre- and post-run assemblages is clearly necessary before adequate interpretation of the experimental results can be made in these types of electrochemical studies. Different approaches to investigations of the fO 2 of the Skaergaard Intrusion, be it thermodynamic calculations or experimental methods, should yield concordant results or at least understandable discrepancies. Calculated fO 2 's using thermobarometry applied to the ilmenite-magnetite pairs in the post-experimental assemblages agree with the experimentally determined fO 2 's to within one log unit at a given temperature. These results are also consistent with previously calculated fO 2 values (Buddington and Lindsley 1964; Morse et al. 1980), but are considerably more oxidized than a previous electrolyte-based fO 2 study of a different sample suite from the Skaergaard (Sato and Valenza 1980) that include values close to the iron-wustite (IW) buffer from both MZ and LZ oxide separates. Differences between this electrochemical study and that of Sato and Valenza (1980) may be due to variations in the level of indigenous (or curatorially-introduced) carbon in the samples studied. Despite a number of experimental difficulties, electrochemical cells can provide an accurate and precise method of determining the oxygen fugacity of naturally occurring, complex oxide assemblages. Tight experimental reversals and reproducible values obtained in heating and cooling cycles are an indication of the precision and accuracy of the data recoverable with electrochemical cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47287/1/410_2004_Article_BF00373730.pd

Silicon in magnetite: High resolution microanalysis of magnetite-ilmenite intergrowths

Magnetite-ilmenite “oxidation-exsolution” intergrowths from an original titanomagnetite microphenocryst from an ash flow tuff unit have been studied using conventional transmission electron microscopy and analytical electron microscopy. Silicon has been found to be in solid solution in all of the magnetite studied and in some of the coexisting ilmenite. The average value in magnetite is 1.2 wt.% Si, equivalent to solid solution of 9 mole % Fe 2 SiO 4 . Silicon is also present in very small silicate inclusions and as unusual Si-rich domains of uncertain origin in magnetite. The inclusions and domains may be irregularly distributed through the magnetite in sizes well below those resolvable with the electron microprobe. Microprobe analyses for Si in magnetite generally reflect these heterogeneities in addition to a component presumably in solid solution. The petrologic implications of the data can be assessed only when relevant thermochemical data become available and the distribution of Si in magnetite is better understood.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47334/1/410_2004_Article_BF00378006.pd