Molecular characterization and gene expression of Japanese eel (Anguilla japonica) gonadotropin receptors.

A luteinizing hormone receptor (lhr) cDNA with high identity to other fish lhrs was fully cloned from the ovary of the Japanese eel (Anguilla japonica). The genes for two gonadotropin receptors (Gthr), follicle-stimulating hormone receptor (fshr) and lhr, were differentially expressed during oogenesis, which was artificially induced by salmon pituitary extract, a gonadotropin-rich source. Transcript abundance of fshr was significantly elevated at the early vitellogenic stage and peaked at the late vitellogenic stage, while lhr gene expression rapidly induced at the late vitellogenic stage and thereafter remained at a high level. The abundance of fshr and lhr transcripts was highest in the ovary in female eels. In addition to the ovary, forebrain was a major site for the fshr transcript, although the level did not change with reproductive status. Furthermore, it was examined how eel Gthrs were activated by two mammalian chrionic gonadtropin (CG), equine CG (eCG) and human CG (hCG), that have been used for study of fish reproduction as substitutes for homologous Gths. Both CGs specifically activated eel Lhr, but not Fshr, although the degree of effectiveness was different; thus the concentration of hCG (0.1 ng/ml) required for significant activation of Lhr was much lower than that of eCG (100 ng/ml). These data on gene expression and ligand-activation of Gthrs suggest that Fsh and Lh act differentially in the regulation of reproductive function in Japanese eel.

Oligonucleotide bearing ethylenediamine-N,N,N'-Triacetates for gap-selective DNA hydrolysis by Ce4+/EDTA.

With the use of two oligonucleotides bearing ethylenediamine-N,N,N'-triacetate groups as additives, gap sites were formed at predetermined sites in substrate DNA. Upon treating these systems with a Ce(4+)/EDTA complex at pH 7.0 and 37 degrees C, the phosphodiester linkages at the gap site were selectively hydrolyzed. The DNA scission was greatly promoted by the introduction of ethylenediaminetriacetate groups, and the scission efficiency increased as the number of these groups increased. Even a one-base gap was successfully hydrolyzed when three ethylenediaminetriacetate groups were placed consecutively at both edges of the gap, although the scission was minimal in the absence of these groups. The site-selective scission could be also achieved at higher temperatures without any significant loss of site-selectivity.

Occurrence of Vibrio vulnificus in fish and shellfish available from markets in China.

Vibrio vulnificus is a naturally occurring estuarine bacterium often associated with disease such as septicemia in humans following consumption of raw and lightly cooked seafood. In China and neighboring countries, rapid economic growth has encouraged increased consumption of seafood, and dietary habits are changing, with more people eating raw fish. In this study, the prevalence of V. vulnificus was investigated in 48 samples from 11 species of live seafood available from markets in coastal cities of China. The bacterium was detected in four of four razor clam samples, in seven of seven giant tiger prawn samples, and in five of nine mantis shrimp samples. The bacterium was also found in water samples of the prawn aquaria at the markets. The maximum level of V. vulnificus was 3.4 log CFU/g in the razor clam samples and 4.9 log CFU/g in the prawn samples by a direct spreading method. Differential bacterial counts on the prawn body revealed that most of the bacteria were found on the shells (exoskeletons), with very few in the edible muscle. However, dense populations can be found in the intestines. Biochemical tests indicated that the isolates of V. vulnificus were biotype 1 strain, which is pathogenic to humans. These isolates were susceptible to ampicillin, penicillin, kanamycin, streptomycin, and erythromycin. These results suggest that V. vulnificus is a potential health hazard to humans in cities consuming and handling live shellfish, especially giant tiger prawns.

Site-selective DNA hydrolysis by the combination of Ce(IV) and oligonucleotide bearing EDTA groups.

By using appropriately modified oligonucleotides, a gap-structure is formed in substrate DNA, and 2-6 ethylenediamine-N,N,N'-triacetate residues are placed near this gap. When these composites are treated with homogenous Ce(IV)/EDTA complex, the phosphodiester linkages in the gap-site are selectively hydrolyzed at much greater rates than achieved previously by using unmodified oligonucelotides.