Microstructure Evolution of the Ti-46Al-8Nb-2.5V Alloy during Hot Compression and Subsequent Annealing at 900 °C.

TiAl alloys are high-temperature structural materials with excellent comprehensive properties, and their ideal service temperature range is about 700-950 °C. High-Nb containing the Ti-46Al-8Nb-2.5V alloy was subjected to hot compression and subsequent annealing at 900 °C. During hot compression, work-hardening and strain-softening occurred. The peak stresses during compression are positively correlated with the compressive strain rates and negatively correlated with the compression temperatures. The α2 phase exhibited a typical (0001)α2 basal plane texture after hot compression, while the ß0 and γ phases did not show a typical strong texture. Subsequent annealing at 900 °C of the hot-compressed samples resulted in significant phase transformations, specifically the α2 → γ and ß0 → γ phase transformations. After 30 min of annealing, the volume fraction of the α2 phase decreased from 39.0% to 4.6%. The microstructure characteristics and phase fraction after 60 min of annealing were similar to those after 30 min. According to the calculation of Miller indexes and texture evolution during annealing, the α2 → γ phase transformation did not follow the Blackburn orientation relationship. Multiple crystal-oriented α2 phases with nanoscale widths (20~100 nm) precipitate within the γ phase during the annealing process, which means the occurrence of γ → α2 phase transformation. Still, the γ → α2 phase transformation follows the Blackburn orientation relationship.

Molecular Characterization and Chemotactic Function of CXCL8 in Northeast Chinese Lamprey (Lethenteron morii).

Chemokine-induced chemotaxis of leukocytes is an important part of the innate immunity and has been shown to mediate inflammation in all groups of jawed vertebrates. For jawless vertebrates, hagfish leukocytes are known to show chemotaxis toward mammalian complement anaphylotoxin and Gram-negative bacteria lipopolysaccharide. However, whether chemokines mediate chemotaxis of leukocytes in jawless vertebrates has not been conclusively examined. Here, we show C-X-C motif chemokine ligand 8 (CXCL8, also named interleukin 8) of the Northeast Chinese lamprey (Lethenteron morii) (designated as LmCXCL8) induces chemotaxis in its leukocytes. We identified LmCXCL8 and found it possesses the characteristic N-terminal cysteine residues and GGR (Gly-Gly-Arg) motif. The Lmcxcl8 gene was found to be expressed in all examined tissues, and its expression was inducible in the lamprey challenged by an infectious bacterium, Pseudomonas aeruginosa. A recombinant LmCXCL8 protein elicited concentration-dependent chemotaxis in peripheral blood leukocytes isolated from the Northeast Chinese lamprey. Based on these results, we conclude that LmCXCL8 is a constitutive and inducible acute-phase cytokine that mediates immune defense and trace the chemotactic function of chemokine to basal vertebrates.

The mitogenomes of the pouched lamprey (Geotria australis) and least brook lamprey (Lampetra aepyptera) with phylogenetic considerations.

We report the mitogenomes of the pouched lamprey (Geotria australis) and least brook lamprey (Lampetra aepyptera) in the families Geotriidae and Petromyzontidae, respectively. Both of the mitogenomes contain the 37 typical vertebrate genes. Their gene order and contents are identical to those of previously described lamprey mitogenomes. The mitogenome of G. australis (17 080 bp) is the largest among the 10 reported lamprey mitogenomes, owed to two long noncoding regions. The mitogenome of L. aepyptera is 77 bp longer (16 236 bp) than that of the congeneric European river lamprey L. fluviatilis, a size difference mostly due to different copy numbers of tandem repeats in the noncoding regions. The phylogenetic analysis supports that the pouched lamprey (Geotriidae) diverged earlier from the common ancestor of lampreys than the Petromyzonids, and the placement of the least brook lamprey in the genus Lampetra.

Complete mitochondrial genomes of Korean lamprey (Lethenteron morii) and American brook lamprey (L. appendix).

The complete mitogenomes of two lampreys with complex taxonomic histories, the Korean lamprey (Lethenteron morii) and the American brook lamprey (L. appendix) were determined. Three-nt length difference between two genomes occurred on tRNA-Ser2 and control region 2. Except for 3 indel sites, there are 58 variable sites between two genomes which occurred on 11 of the 13 protein-coding genes (aside from COX3 and ND3) and 2 of rRNAs, tRNAs, control regions and intergenic regions. Among these sites, 15 sites are non-synonymous substitution sites occurred on 8 protein-coding genes including COX1-COX2, ND1-ND2, ND4-ND6 and ATPase6. Control region 1 contains 4 consecutive 39-nt repetitive strings and a 26-nt repetitive string in control region 2 is repeated 3.8 times in both lampreys. The observed level of similarity between nucleotide sequences (99.62%) implies the Korean lamprey and American brook lamprey are very close relatives and should be assigned into the same taxonomic genus.

Complete mitochondrial genomes of paired species northern brook lamprey (Ichthyomyzon fossor) and silver lamprey (I. unicuspis).

The complete mitogenomes of paired species northern brook lamprey (Ichthyomyzon fossor) and silver lamprey (I. unicuspis) is reported. The two mitogenomes show a 13 bp length difference on the tRNA-Gly and two control regions. The gene order and contents are conserved in the two lampreys and identical to the lamprey mitogenomes published. Except for three indel polymorphic sites, there are 27 SNP sites which are all synonymous substitution sites and occurred on 9 protein-coding genes, two rRNAs and one tRNA. The control region1 contains six consecutive 39-nt repetitive strings in both lampreys. A 7-nt repetitive string in the control region2 is repeated 3 and 5 times in northern brook lamprey and silver lamprey, respectively. The observed level of similarity between nucleotide sequences (99.74%) is consistent with the hypothesis that northern brook lamprey and silver lamprey represent two ecotypes of one species.