Inoculation of seven pine species or hybrid seedlings with Korean isolates of pinewood nematode under greenhouse conditions

? Seedlings of seven pine species or hybrids, Pinus densiflora, Pinus thunbergii, Pinus virginiana, Pinus echinata, Pinus koraiensis, Pinus thunbergii × Pinus massoniana and Pinus × rigitaeda, were inoculated in a greenhouse with 100, 1 000 and 10 000 pathogenic nematodes, Bursaphelenchus xylophilus, to compare initial symptom development and to evaluate susceptibility to pinewood nematodes.

? Genetic types were significantly different in the starting day of needle discoloration (χ² = 43.48; P < 0.001) and the period from nematode inoculation to seedling death (χ² = 32.85; P > 0.001), but treatment groups were not statistically different in the days from inoculation to seedling death in any of the pine species.

? There was no relationship between seedling mortality and the number of nematodes recovered from infected seedlings. Only eight of the nematode-inoculated seedlings remained alive by day 83 after inoculation, including four seedlings each of P. echinata and P. × rigitaeda grown from bulked seed collections.

? Seedlings from the bulk lots were likely more genetically diverse than those from the single-source lots. A broader genetic representation of pine species or hybrids is suggested for screening for planting stocks resistant to B. xylophilus.

     

Biological activity of the new herbicide LGC-40863 {benzophenone O-[2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy]benzoyl]oxime}

Herbicidal characteristics of the experimental compound LGC-40863 (ISO proposed common name: pyribenzoxim) were investigated in greenhouse and field. In the greenhouse, LGC-40863 had strong post-emergent activity on various grass and broadleaf weeds including Echinochloa crus-galli L. Beauv., Alopecurus myosuroides Huds. and Polygonum hydropiper L., while it was safe in rice (Oryza sativa L.), wheat (Triticum aestivum L.) and zoysiagrass (Zoysia japonica Steud; (a turf species). Among important rice weeds, E. crus-galli was controlled over a wide window from the one-leaf to the six-leaf stages. In the field, LGC-40863 provided excellent control of E. crus-galli (>95%) at 30 to 40 g ha^-1 when applied alone, or at 15 to 30 g ha^-1 when applied in combination with pendimethalin, while it did not cause injury to rice at up to 60 g ha^-1. These results suggest that LGC-40863 has potential as a new selective post-emergent herbicide in rice. © 1997 SCI     

Reproductive success and fry production of the paiche or pirarucu,Arapaima gigas (Schinz), in the region of Iquitos,Perú

Arapaima gigas (paiche) is the largest scaled fish species living in the Amazon basin. Its biology is both fascinating and misunderstood. In a context of overfishing, hence reduced natural populations, aquaculture of a fish with such interesting characteristics (large size, high growth rate, no intramuscular spines) is an important issue. The development of farming production would also reduce the fishing pressure on natural populations and allow re‐stocking programmes in certain areas. To determine what factors may influence the reproductive success in captivity, data from breeding reports for 2007–2010 were collected among fish farmers in the region of Iquitos. In parallel, we carried out physicochemical measurements in different ponds where these paiches breed, and conducted personal interviews about the general fish management conditions. The results show that reproduction occurs throughout the year but with a higher intensity during the rainy season. It also highlights farms that have performed much better than others, but no single factor except feeding level has been clearly associated with reproductive success. The environmental control of reproduction in paiche, therefore, remains partly mysterious. To deepen this study, we recommend the systematic sexing of breeders, extending reproductive behavioural studies, and examining the limnological factors involved in fry mortality.     

Temporal expression analyses of pancreatic and gastric digestive enzymes during early development of the olive flounder (Paralichthys olivaceus)

The olive flounder (Paralichthys olivaceus) is one of the most important aquaculture species in Korea. Previous studies focused on the morphological changes and only analysed digestive enzyme expression patterns of certain digestive systems. A comprehensive analysis of the pancreatic and gastric digestive enzymes of the olive flounder in its early developmental stages has not been performed. In this study, we determined the mRNA expression levels of pancreas and stomach digestive enzymes by extracting total RNA from the whole body of olive flounders from hatching to post‐metamorphosis and conducting real‐time PCR analysis with gene‐specific primers for each isoform. The pancreatic digestive enzymes were initially and strongly expressed from the first feeding period to pre‐metamorphosis. The expression of trypsinogen 3 was detected from the early stage of development to metamorphosis, whereas trypsinogen 2 was significantly increased only in the post‐metamorphosis period. The mRNA expression of pepsinogen was only detected at metamorphosis and corresponded to stomach differentiation. The lipid digestive‐related enzymes had already reached a certain level at the beginning of hatching, then increased during the early developmental stage and gradually decreased before metamorphosis. These results suggest that food ingestion is exclusively digested by pancreatic digestive enzymes and trypsinogen 3 during the early developmental stage until pre‐metamorphosis, and it then fully switches to digestion by pepsinogen and trypsinogen 2 in mid‐metamorphosis. In conclusion, understanding the expression profiles of digestive enzymes in the pancreas and stomach during the early developmental stages is an important consideration when developing formulated larval diets for aquacultured olive flounder.     

Influence of Ovulation Status,Seasonality and Embryo Transfer Method on Development of Cloned Porcine Embryos

To improve pig cloning efficiency, the present study evaluated the effect of ovulation status, seasonality and embryo transfer (ET) method on in vivo development of cloned porcine embryos. Cloned embryos were transferred to surrogate mothers on the same day of somatic cell nuclear transfer. In pre‐ovulation stage (PO), pregnancy rate (PR) and delivery rate (DR) were 36.3% and 9.4%, respectively. In post‐ovulation stage, 22.7% PR and 2.1% DR were recorded (both PR and DR are significantly higher in PO). When ET was performed during winter (December–February), spring (March–May), summer (June–August) and autumn (September–November), the PRs were 13.4%, 37.3%, 24.6% and 51.0%, while DRs were 0%, 12.7%, 4.3% and 7.8%, respectively. The highest PRs were recorded in autumn groups. However, DRs were significantly lower in autumn (7.8%) group compared with spring (12.7%) group. The PR was the lowest and no piglets were born in winter group, which might be because of the effect of low temperature during ET. To overcome the low PR in winter group, 0.25 ml straws were used for ET to minimize exposure time of embryos to ambient temperature. The straw ET group showed significantly higher PR in the winter group (23. 9%) compared with the conventional catheter‐loading group (7.7%). We suggest that using PO recipient and ET in spring is the best condition for pig cloning. In addition, alternative method to reduce cold shock during ET in winter is necessary.     

spa typing and enterotoxin gene profile of Staphylococcus aureus isolated from bovine raw milk in Korea

Staphylococcus aureus is a major etiological pathogen of bovine mastitis, which triggers significant economic losses in dairy herds worldwide. In this study, S. aureus strains isolated from the milk of cows suffering from mastitis in Korea were investigated by spa typing and staphylococcal enterotoxin (SE) gene profiling. Forty-four S. aureus strains were isolated from 26 farms in five provinces. All isolates grouped into five clusters and two singletons based on 14 spa types. Cluster 1 and 2 isolates comprised 38.6% and 36.4% of total isolates, respectively, which were distributed in more than four provinces. SE and SE-like toxin genes were detected in 34 (77.3%) isolates and the most frequently detected SE gene profile was seg, sei, selm, seln, and selo genes (16 isolates, 36.3%), which was comparable to one of the genomic islands, Type I νSaβ. This is a first report of spa types and the prevalence of the recently described SE and SE-like toxin genes among S. aureus isolates from bovine raw milk in Korea. Two predominant spa groups were distributed widely and recently described SE and SE-like toxin genes were detected frequently.     

Physical Stress Induced Reduction of Proliferating Cells and Differentiated Neuroblasts Is Ameliorated by Fermented Laminaria japonica Extract Treatment

Laminaria japonica is widely cultivated in East Asia, including South Korea. Fucoidan, a main component of L. japonica, protects neurons from neurological disorders such as ischemia and traumatic brain injury. In the present study, we examined the effects of extract from fermented L. japonica on the reduction of proliferating cells and neuroblasts in mice that were physically (with electric food shock) or psychologically (with visual, auditory and olfactory sensation) stressed with the help of a communication box. Vehicle (distilled water) or fermented L. japonica extract (50 mg/kg) were orally administered to the mice once a day for 21 days. On the 19th day of the treatment, physical and psychological stress was induced by foot shock using a communication box and thereafter for three days. Plasma corticosterone levels were significantly increased after exposure to physical stress and decreased Ki67 positive proliferating cells and doublecortin immunoreactive neuroblasts. In addition, western blot analysis demonstrated that physical stress as well as psychological stress decreased the expression levels of brain-derived neurotrophic factor (BDNF) and the number of phosphorylated cAMP response element binding protein (pCREB) positive nuclei in the dentate gyrus. Fermentation of L. japonica extract significantly increased the contents of reduced sugar and phenolic compounds. Supplementation with fermented L. japonica extract significantly ameliorated the increases of plasma corticosterone revels and decline in the proliferating cells, neuroblasts, and expression of BDNF and pCREB in the physically stressed mice. These results indicate that fermented L. japonica extract has positive effects in ameliorating the physical stress induced reduction in neurogenesis by modulating BDNF and pCREB expression in the dentate gyrus.     

Changes in cyclooxygenase-2 immunoreactivity in the hippocampus in a model of streptozotocin-induced type 1 diabetic rats

In this study, we investigated diabetic stage dependent cyclooxygenase-2 (COX-2) immunoreactivity in the dentate gyrus in streptozotocin (STZ)-induced type 1 diabetic rats. The animals were sacrificed at 2, 3 and 4 weeks after STZ treatment. Blood glucose levels were increased after STZ treatment. COX-2 immunoreactivity in dentate gyrus was significantly increased in these regions 3 weeks after STZ treatment and restored to its basal level to 4 weeks after STZ treatment. In contrast, COX-2 immunoreactivity was not changed in CA3 region in all groups. These results suggest that STZ-induced type 1 diabetes transiently, but not permanently, decreased synaptic transmission and plasticity 3 weeks after STZ treatment in the dentate gyrus.     

Soil metabolism of a new herbicide, [14C]Pyribenzoxim, under flooded conditions

To elucidate the fate of a new pyrimidinyloxybenzoic herbicide, pyribenzoxim, a soil metabolism study was carried out with [14C]pyribenzoxim applied to a sandy loam soil under flooded conditions. The material balance of applied radioactivity ranged from 96.4 to 104.4% and from 96.1 to 101.9% for nonsterile and sterile soils, respectively. The half-life of [14C]pyribenzoxim was calculated to be approximately 1.3 and 9.4 days for nonsterile and sterile soils, respectively. The metabolites identified during the study were 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid (M1) and 2-hydroxy-6-(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid (M2), resulting from the cleavage of the ester bond and subsequent hydrolysis. The nonextractable radioactivity levels increased to 37.8% for nonsterile conditions at 50 days after treatment and to 38.2% for sterile conditions at 60 days after treatment. Fractionation of the nonextractable soil residues indicated that bound radioactivity was associated mainly with humin fraction. No significant volatile products or [14C]carbon dioxide was observed during the study. On the basis of these results, pyribenzoxim is considered to undergo rapid degradation in soil by microbial and chemical reactions, mainly hydrolysis, which limits its transfer to and accumulation in lower soil layers and groundwater. Therefore, the possibility of environmental contamination from the use of pyribenzoxim is expected to be very low.