Estimates of Denitrification and Nitrification in Coastal and Estuarine Sediments

Denitrification and nitrification in sediments of Tama Estuary and Odawa Bay, Japan, were investigated by the combined use of a continuous-flow sediment-water system and a ¹⁵N tracer technique. At Odawa Bay, the nitrification rate was comparable to the nitrate reduction rate, and 70% of the N₂ evolved originated from nitrogenous oxides (nitrate and nitrite) which were produced by the action of nitrifying bacteria in the sediments. At Tama Estuary, the nitrate reduction rate was 11 to 17 times higher than the nitrification rate, and nitrogenous oxides derived from ammonium accounted for only 6 to 9% of the N₂ evolution by denitrification.     

Serologic dissection of HLA-D specificities by the use of monoclonal antibodies

To study the gene products of the HLA complex, we produced two monoclonal antibodies, termed HU-18 and HU-23. They were active in complement-dependent cytotoxicity and detected B-cell alloantigens encoded by a locus (or loci) linked to HLA. When three types of HLA-DR4 homozygous B-cell lines with different HLA-D specificities were tested for reactivity with HU-18 and HU-23, they displayed distinct reaction patterns depending on the HLA-D specificities they possessed: EBV-Wa (HLA-DYT homozygous), negative for both HU-18 and HU-23; KT2 and KOB (HLA-DKT2 homozygous), positive only for HU-18; and ER (HLA-Dw4 homozygous), positive for both. These differential reaction patterns were further confirmed by testing against a panel of 17 HLA-DR4-positive peripheral blood lymphocytes with known HLA-D specificities. Thus, these monoclonal antibodies allow us to identify HLA-DYT, HLA-DKT2, and HLA-Dw4 solely by serologic methods. This is the first clearcut serologic identification of these three HLA-DR4-associated HLA-D specificities, which have been indistinguishable by conventional serology and identified only by cellular techniques. It is hoped that immunochemical investigations using HU-18 and HU-23 will advance our understanding of the HLA-D region on a molecular level.     

Distribution and serological specificity of sialidase produced by various groups of streptococci

The occurrence of a streptococcal sialidase (designated St-sialidase) in culture fluids of various streptococci was investigated. St-sialidase was found to occur in strains belonging to groups A, B, C, E, G, H, and L, and the unclassified strains, Streptococcus sanguis and Streptococcus uberis. St-sialidase of group A was confined predominantly to types 4 and 22. St-sialidases, extracted from the culture fluids of some selected strains, were antigenic, eliciting the formation of antibody which effectively neutralized the enzymatic activity of the enzyme. Antisera to the St-sialidases of groups A, B, C, E, G, and L, and Streptococcus sanguis were produced in rabbits. The St-sialidases of groups A, B, and E streptococci were serologically distinct and group-specific. The St-sialidases from groups C, G, and L were serologically homologous, but distinct from St-sialidases of the other groups. Antiserum to the enzyme of strain 10557 (S. sanguis) cross-reacted with the St-sialidase of strain 9927 (S. uberis).     

Xenobrama microlepis,a new genus and species of bramid fish,from subantarctic waters of the South Pacific

Xenobrama microlepis gen. et sp. nov. is described on the basis of 17 adult and subadult specimens collected by surface gill nets, bottom trawl and midwater trawl from the subantarctic waters of the South Pacific Ocean. This monotypic new genus is distinguished from other bramid genera by the following characters: inner lower edges of mandible touching each other (except near symphysis); gill rakers short, thick, and stout; subpectoral region very narrow; interpelvic space flat and wide; vertebrae 49–51; and scales in longitudinal series more than 83. The new taxon is widely distributed in the high seas of the South Pacific, 38–54°S, 79–176°W, but is rather rare compared toBrama spp. in catches of drift gill nets.     

Combined action of paraquat and superoxide on the peroxidation of detergent-dispersed linolenic acid.

We investigated the peroxidative effect of paraquat and active oxygens on detergent-dispersed linolenic acid in phosphate buffer (pH 7.5) from the malondialdehyde (MDA) level. Our complete system and further inclusion of catalase were effective in stimulating MDA formation. On the other hand, xanthine oxidase (XOD) or paraquat omission, superoxide dismutase (SOD) inclusion or anaerobic incubation inhibited the formation of MDA. Ferrous ion was weakly associated with phosphate of the buffer, forming a complex, and the release of ferrous ion from the complex intensified the MDA levels with the complete and catalase inclusion systems. The electron paramagnetic resonance (EPR) spectra using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) showed that superoxide, produced immediately after the addition of XOD, played a crucial role. We could obtain a DMPO-OOH signal at the starting stage whenever MDA stimulation was observed. The omission of paraquat, however, produced no increase in MDA level in spite of an appearance of DMPO-OOH signal, indicating that paraquat also plays an important role. On the other hand, Desferal, a ferric chelator, showed a concentration-dependent inhibition effect. There was an immediate strong intensity of DMPO-OOH and paraquat signals. We did not, however, observe MDA stimulation at 250 microM Desferal, which confirms that ferrous ion plays an essential role in the lipid peroxidation. These results indicate a combined action of paraquat (or its radical) and superoxide on the accessibility of ferrous ion, including its release from the complex with phosphate, which may be an endogenous chelator. The possibility of ternary complex participation is also discussed.     

Comparison of fish assemblages among an artificial reef, a natural reef and a sandy-mud bottom site on the shelf off Iwate, northern Japan

Synopsis Fish assemblages at an artificial reef site, a natural reef site and a sandy-mud bottom site, on the shelf (depth 130 m) off Iwate Prefecture, northern Japan, were surveyed by using a bottom trammel net from May 1987 to March 1993. A total of 12 173 fishes of 48 species were recorded. Physiculus maximowiczi was dominant and comprised 69% of the total numerical abundance. Total fish number was lowest in March at all the 3 sites when P. maximowiczi migrated to deeper and warmer waters. Assemblage equitability and species diversity also varied seasonally in accordance with the abundance fluctuation of P. maximowiczi. P. maximowiczi, Alcichthys alcicornis and Hexagrammos otakii were more abundant at the artificial reef and natural reef sites, while Dexistes rikuzenius and Hemitripterus villosus were more abundant at the sandy-mud bottom site; total fish abundance was largest at the artificial reef site mainly due to the large number of P. maximowiczi. Species richness was similar among sites, but equitability, and consequently species diversity, was lowest at the artificial reef site. The main effect of the artificial reef seemed the attraction of P. maximowiczi from nearby bottoms, especially from natural rocky reefs; its large abundance determined the structure of the artificial reef fish community.     

Phospholipase D production using immobilized cells of Streptoverticillium cinnamoneum

Summary Production of phospholipase D (PLD) by Streptoverticillium cinnamoneum immobilized within porous particles was investigated in repeated batch fermentation. The enzyme productivity in repeated batch fermentation was 2.2-fold that obtained in batch fermentation without immobilization, since many of the immobilized cells could be utilized as seed cells for each subsequent batch cycle.