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The δ-chain of catfish IgD was initially characterized as a unique chimeric molecule containing a rearranged VDJ spliced to Cμ1, seven C domain-encoding exons (δ1–δ7), and a transmembrane tail. The presence of cDNA forms showing splicing of δ7 to an exon encoding a secretory tail was interpreted to indicate that membrane (δm) and secreted (δs) forms were likely expressed from a single gene by alternative RNA processing. Subsequent cloning and sequence analyses have unexpectedly revealed the presence of three δ C region genes, each linked to a μ gene or pseudogene. The first (IGHD1) is located 1.6 kb 3′ of the functional Cμ (IGHM1). The second (IGHD3) is positioned immediately downstream of a pseudo Cμ (IGHM3P), ∼725 kb 5′ of IGHM1. These two δ genes are highly similar in sequence and each contains a tandem duplication of δ2-δ3-δ4. However, IGHD1 has a terminal exon encoding the transmembrane region, whereas IGHD3 has a single terminal exon encoding a secreted tail. The occurrence of IGHD3 immediately downstream of a μ pseudogene indicates that the putative δs product may not be expressed as a chimeric μδ molecule. Western blots and protein sequencing data indicate that an IGHD3-encoded protein is expressed in catfish serum. Thus, catfish δm transcripts appear to originate from IGHD1, whereas δs transcripts originate from IGHD3 rather than, as previously inferred, from a single expressed δ gene. The third δ (IGHD2) is associated with a pseudo Cμ (IGHM2P); its presence is inferred by Southern blot analyses.

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Most of the previously studied teleost MHC class I molecules can be classified into two broad lineages: "U" and "Z/ZE." However, database reports on genes in cyprinid and salmonid fishes show that there is a third major lineage, which lacks detailed analysis so far. We designated this lineage "L" because of an intriguing linkage characteristic. Namely, one zebrafish L locus is closely linked with MHC class II loci, despite the extensively documented nonlinkage of teleost class I with class II. The L lineage consists of highly variable, nonclassical MHC class I genes, and has no apparent orthologues outside teleost fishes. Characteristics that distinguish the L lineage from most other MHC class I are (1) absence of two otherwise highly conserved tryptophan residues W51 and W60 in the alpha1 domain, (2) a low GC content of the alpha1 and alpha2 exons, and (3) an HINLTL motif including a possible glycosylation site in the alpha3 domain. In rainbow trout (Oncorhynchus mykiss) we analyzed several intact L genes in detail, including their genomic organization and transcription pattern. The gene Onmy-LAA is quite different from the genes Onmy-LBA, Onmy-LCA, Onmy-LDA, and Onmy-LEA, while the latter four are similar and categorized as "Onmy-LBA-like." Whereas the Onmy-LAA gene is organized like a canonical MHC class I gene, the Onmy-LBA-like genes are processed and lack all introns except intron 1. Onmy-LAA is predominantly expressed in the intestine, while the Onmy-LBA-like transcripts display a rather homogeneous tissue distribution. To our knowledge, this is the first description of an MHC class I lineage with multiple copies of processed genes, which are intact and transcribed. The present study significantly improves the knowledge of MHC class I variation in teleosts.

Abstract. Streptococcus spp. were recovered from diseased tilapia in Thailand during 2009-2010 (n = 33), and were also continually collected from environmental samples (sediment and water) from tilapia farms for 9 months in 2011 (n = 25). The relative percent recovery of streptococci from environmental samples was 13-67%. All streptococcal isolates were identified as S. agalactiae (group B streptococci [GBS]) by a species-specific polymerase chain reaction. In molecular characterization assays, 4 genotypic categories comprised of 1) molecular serotypes, 2) the infB allele, 3) virulence gene profiling patterns (cylE, hylB, scpB, lmb, cspA, dltA, fbsA, fbsB, bibA, gap, and pili backbone-encoded genes), and 4) randomly amplified polymorphic DNA (RAPD) fingerprinting patterns, were used to describe the genotypic diversity of the GBS isolates. There was only 1 isolate identified as molecular serotype III, while the others were serotype Ia. Most GBS serotype Ia isolates had an identical infB allele and virulence gene profiling patterns, but a large diversity was established by RAPD analysis with diversity tending to be geographically dependent. Experimental infection of Nile tilapia (Oreochromis niloticus) revealed that the GBS serotype III isolate was nonpathogenic in the fish, while all 5 serotype Ia isolates (3 fish and 2 environmental isolates) were pathogenic, with a median lethal dose of 6.25-7.56 log 10 colony-forming units. In conclusion, GBS isolates from tilapia farms in Thailand showed a large genetic diversity, which was associated with the geographical origins of the bacteria.

Octacalcium phosphate (Ca8H2(PO4)6 * 5H2O; OCP) has been advocated to be a precursor of biological apatite crystals in bone and tooth. Recent studies, using physical techniques, showed that OCP is present as a transient phase during biological apatite formation in human dentin, porcine enamel and murine bone. However, there is still a controversy regarding the chemical nature of the first mineral formed in the biominerals. A number of studies have demonstrated that synthetic OCP shows bone regenerative and biodegradable characteristics, rather than other calcium phosphate bone substitute materials, such as hydroxyapatite (Ca10(PO4)6(OH)2; HA) ceramic. It seems likely that synthetic OCP may be an alternative to autogenous bone graft. It is known that OCP contains alternative layers of water molecules and an apatite structure, and that the transition of OCP to HA is likely to be spontaneous and irreversible. The conversion process induces modification of local environment adjacent to OCP surface, including the changes in adsorption of serum proteins and concentration of calcium and inorganic phosphate ions. This article reviews the possible application to bone regeneration by synthetic OCP and the mechanism to enhance bone regeneration in relation to biological mineralization in bone and tooth.

In the course of our search for new melanin synthesis inhibitors from plants, 40 new flavonoids and 11 known flavonoids were isolated from the roots of Lespedeza floribunda Bunge. The structures of the new compounds were determined by MS and NMR analyses, and the absolute configurations by CD spectra. Many of the compounds inhibited melanin synthesis in normal human epidermal melanocytes (NHEM), and compounds 3, 7, 8, 11, 16, 24, 27, 29, 33, 43, 45, and 51 were particularly inhibitory. Their activities were stronger than that of hydroquinone, which is known as a major skin-lightening drug.

SummaryBacterial arti®cial chromosome (BAC) libraries are important tools for genomic research. We have constructed seven genomic BAC libraries from three ®sh species, rainbow trout (Oncorhynchus mykiss), carp (Cyprinus carpio) and tilapia (Oreochromis niloticus). The two rainbow trout BAC libraries have average insert sizes of 58 and 110 kb. The average size of inserts in the carp BAC library is 160 kb. The average insert sizes of the four tilapia BAC libraries are 65, 105, 145 and 194 kb, respectively. These libraries represent good coverage of each genome (2±64´coverage). The libraries can be screened by conventional colony hybridization and provide a starting point for the construction of high-density ®ltres or polymerase chain reaction (PCR) screening approaches. These BAC libraries will facilitate the positional cloning of quantitative trait loci (QTLs) for a variety of economically important traits in these species.