Unusual distribution of floating seaweeds in the East China Sea in the early spring of 2012

Floating seaweeds play important ecological roles in offshore waters. Recently, large amounts of rafting seaweed have been observed in the East China Sea. In early spring, juveniles of commercially important fish such as yellowtail accompany these seaweed rafts. Because the spatial distributions of seaweed rafts in the spring are poorly understood, research cruises were undertaken to investigate them in 2010, 2011, and 2012. Floating seaweed samples collected from the East China Sea during the three surveys contained only Sargassum horneri. In 2010 and 2011, seaweed rafts were distributed only in the continental shelf and the Kuroshio Front because they had become trapped in the convergence zone of the Kuroshio Front. However, in 2012, seaweed was also distributed in the Kuroshio Current and its outer waters, and massive strandings of seaweed rafts were observed on the northern coast of Taiwan and on Tarama Island in the Ryukyu Archipelago. Environmental data (wind, currents, and sea surface height) were compared among the surveys of 2010, 2011, and 2012. Two factors are speculated to have caused the unusual distribution in 2012. First, a continuous strong north wind produced an Ekman drift current that transported seaweed southwestward to the continental shelf and eventually stranded seaweed rafts on the coast of Taiwan. Second, an anticyclonic eddy covering northeast Taiwan and the Kuroshio Current west of Taiwan generated a geostrophic current that crossed the Kuroshio Current and transported the rafts to the Kuroshio Current and its outer waters. Such unusual seaweed distributions may influence the distribution of fauna accompanying the rafts.     

Dielectric analysis of mitochondria isolated from rat liver II. Intact mitochondria as simulated by a double-shell model

The dielectric dispersion of isolated intact mitochondria in suspension has been measured between 10 kHz and 500 MHz. In isotonic KCI media at 4°C, the mitochondria maintained their characteristic ‘double membrane’ structure as examined by electron microscopy, and the observed dispersion curves were successfully simulated in terms of a superposition of two sub-dispersions having different characteristic frequencies and different permittivity magnitudes. Taking these observations into account we analyzed the dispersion data on the basis of a ‘double-shell’ model in which two concentric shells are meant to represent the mitochondrial outer and inner membranes. The analyses by a computerized curve-fitting method revealed that: (i) electric capacities for the outer and the inner membrane are 1.7 and 0.5 μF/cm², respectively, (ii) relative permittivity for the inner compartment (or the equivalent homogeneous matrical space) = 50–60, (iii) outer compartment-to-external conductivity ratio = 0.4–0.6, and (iv) inner compartment-to-external conductivity ratio = 0.14. The implications of these parameter values are discussed with due attention paid to the limitations inherent in our ‘double-shell’ model approach.     

Immune Response to Toxoplasma gondii

Peripheral blood leukocytes (PBL) from patients with toxoplasmosis were shown to be highly responsive to in vitro stimulation with Toxoplasma gondii extract as measured by incorporation of [³H]methylated thymidine. Analysis of Toxoplasma-specific proliferative cells in PBL by using monoclonal antibodies specific for human T cell subsets revealed that the Toxoplasma-specific proliferation response of PBL from the patients was mediated by Leu 1, Leu 3a positive cells, that is, helper/inducer T cells. Tests for the Toxoplasma-specific proliferation response may provide a readily available method for the diagnosis of congenital toxoplasmosis, especially during the newborn period.     

Selection of DNA aptamers using atomic force microscopy

Atomic force microscopy (AFM) can detect the adhesion or affinity force between a sample surface and cantilever, dynamically. This feature is useful as a method for the selection of aptamers that bind to their targets with very high affinity. Therefore, we propose the Systematic Evolution of Ligands by an EXponential enrichment (SELEX) method using AFM to obtain aptamers that have a strong affinity for target molecules. In this study, thrombin was chosen as the target molecule, and an ‘AFM-SELEX’ cycle was performed. As a result, selected cycles were completed with only three rounds, and many of the obtained aptamers had a higher affinity to thrombin than the conventional thrombin aptamer. Moreover, one type of obtained aptamer had a high affinity to thrombin as well as the anti-thrombin antibody. AFM-SELEX is, therefore, considered to be an available method for the selection of DNA aptamers that have a high affinity for their target molecules.     

The expression of proprotein convertase PACE4 is highly regulated by Hash-2 in placenta: possible role of placenta-specific basic helix-loop-helix transcription factor, human achaete-scute homologue-2

PACE4 is a member of the mammalian subtilisin-like proprotein convertase (SPC) family, which contribute to the activation of transforming growth factor (TGF) beta family proteins. We previously reported that PACE4 is highly expressed in syncytiotrophoblasts of human placenta [Tsuji et al. (2003) BIOCHIM: Biophys. Acta 1645, 95-104]. In this study, the regulatory mechanism for PACE4 expression in placenta was analyzed using a human placental choriocarcinoma cell line, BeWo cells. Promoter analysis indicated that an E-box cluster (E4-E9) in the 5'-flanking region of the PACE4 gene acts as a negative regulatory element. The binding of human achaete-scute homologue 2 (Hash-2) to the E-box cluster was shown by gel mobility-shift assay. The overexpression of Hash-2 caused a marked decrease in PACE4 gene expression. When BeWo cells were grown under low oxygen (2%) conditions, the expression of Hash-2 decreased, while that of PACE4 increased. In both cases, other SPCs, such as furin, PC5/6, and PC7/8, were not affected. Further, PACE4 expression was found to be developmentally regulated in rat placenta. By in situ hybridization, Mash-2 (mammalian achaete-scute homologue 2) mRNA was found to be expressed in the spongiotrophoblast layer where PACE4 was not expressed. In contrast, the PACE4 mRNA was expressed mainly in the labyrinthine layer where Mash-2 was not detected. These results suggest that PACE4 expression is down-regulated by Hash-2/Mash-2 in both human and rat placenta and that many bioactive proteins might be regulated by PACE4 activity.     

Two Types of Alpha Satellite DNA in Distinct Chromosomal Locations in Azara's Owl Monkey

Alpha satellite DNA is a repetitive sequence known to be a major DNA component of centromeres in primates (order Primates). New World monkeys form one major taxon (parvorder Platyrrhini) of primates, and their alpha satellite DNA is known to comprise repeat units of around 340 bp. In one species (Azara''s owl monkey Aotus azarae) of this taxon, we identified two types of alpha satellite DNA consisting of 185- and 344-bp repeat units that we designated as OwlAlp1 and OwlAlp2, respectively. OwlAlp2 exhibits similarity throughout its entire sequence to the alpha satellite DNA of other New World monkeys. The chromosomal locations of the two types of sequence are markedly distinct: OwlAlp1 was observed at the centromeric constrictions, whereas OwlAlp2 was found in the pericentric regions. From these results, we inferred that OwlAlp1 was derived from OwlAlp2 and rapidly replaced OwlAlp2 as the principal alpha satellite DNA on a short time scale at the speciation level. A less likely alternative explanation is also discussed.     

Estimation of the ecosystem carbon budget in South Korea between 1999 and 2008

A carbon flux model, the vegetation integrated simulator for trace gases, was employed to estimate the carbon budgets of vegetation ecosystems in South Korea. The geographic information system was used to prepare the input variables for the model, such as climate, soil, and land-cover data, from reliable national inventories. Model simulation results indicated that the annual average gross primary production, net primary production, and soil respiration (SR) for 10 years were 91.89, 40.16, and 62.91 Tg C year^?1, respectively. The model also estimated a net ecosystem production with a value of 3.51 Tg C year^?1 between 1999 and 2008. Such results indicate that the vegetation ecosystems of South Korea offset 3.3 % of anthropogenic emissions as a net carbon sink. Latitudinal and topographical gradients over the total simulation area were found for all estimates. In addition, the estimates varied between seasons and years, especially in estimates for biomass growth and carbon uptake, because of variations in the weather conditions. Finally, model validation was conducted using measured soil efflux and flux measurement data from the Gwangneung experimental forest (GEF). The estimated SR accounted for 81.6 % of the observed SR at the GEF site (P < 0.005). Further, the model accounted well for the observed phase and amplitude of changes in the summer and autumn seasons.     

Display of active beta-glucosidase on the surface of Schizosaccharomyces pombe cells using novel anchor proteins

Here, we demonstrate display of beta-glucosidase (BGL) on the surface of Schizosaccharomyces pombe cells using novel anchor proteins. A total of four candidate anchor proteins (SPBC21D10.06c, SPBC947.04, SPBC19C7.05, and SPBC359.04c) were selected from among almost all of S. pombe membrane proteins. The C-terminus of each anchor protein was genetically fused to the N-terminus of BGL, and the fusion protein was expressed using S. pombe as a host. The highest cell surface-associated BGL activity (107 U/10⁵ cells was achieved with SPBC359.04c serving as the anchor, followed by SPBC947.04 (44 U/10⁵ cells) and SPBC21D10.06c (38 U/10⁵ cells). S. pombe displaying BGL with SPBC359.04c as an anchor showed the highest growth on 2 % cellobiose (10.7?×?10⁷ cells/mL after 41 h of cultivation from an initial density of 0.1?×?10⁷ cells/mL). Additionally, culturing BGL-displaying S. pombe in medium containing cellobiose as the sole carbon source did not affect protein expression, and ethanol fermentation from cellobiose was successfully demonstrated using BGL-displaying S. pombe. This is the first report describing a cell surface display system for the functionalization of S. pombe.