Distribution of salps near the South Shetland Islands during austral summer, 1990–1991 with special reference to krill distribution

Distribution and biomass of salps and Antarctic krill (Euphausia superba) were investigated near the South Shetland Islands during austral summer 1990–1991. Salp biomass ranged between 0 and 556 mgC·m^–3 and was greatest at a station in the Bransfield Strait in late December 1990. Salp biomass was lower than that of E. superba. Two species of salps; Salpa thompsoni and Ihlea racovitzai were found, and the former was dominant numerically. Spatial distribution and generation composition of these two species was different. Spatial distributions of salps and E. superba did not overlap particularly so the January–February period. While E. superba was found mainly in the coastal area which showed high-chlorophyll a values, salps exhibited high biomass in the oceanic area with low chlorophyll a concentrations. Predation by salps on small krill and the competitive removal of food by them, are discussed as potential reasons for the relatively low abundance of E. superba at the stations where salps were present in great numbers.     

Comparative studies for amyloid beta degradation: “Neprilysin vs insulysin”, “monomeric vs aggregate”, and “whole Aβ40 vs its peptide fragments”

Amyloid beta (Aβ) proteins are produced from amyloid precursor protein cleaved by β- and γ-secretases, and are the main components of senile plaques pathologically found in Alzheimer's disease (AD) patient brains. Therefore, the relationship between AD and Aβs has been well studied for both therapeutic and diagnostic purposes. Several enzymes have been reported to degrade Aβs in vivo, with neprilysin (NEP) and insulysin (insulin-degrading enzyme, IDE) being the most prominent. In this article, we describe the mass spectrometric characterization of peptide fragments generated using NEP and IDE, and clarify the differences in digestion specificities between these two enzymes for non-aggregated Aβ₄₀, aggregated Aβ₄₀, and Aβ₄₀ peptide fragments, including Aβ₁₆. Our results allowed identification of all the peptide fragments from non-aggregated Aβ₄₀: NEP, 23 peptide fragments consisting of 2–11 amino-acid residues, 17 cleavage sites; IDE, 23 peptide fragments consisting of 6–33 amino-acid residues, 15 cleavage sites. Also, we confirmed that IDE can digest only whole Aβ₄₀, whereas NEP can digest both Aβ₄₀ and partial structures such as Aβ₁₆ and peptide fragments generated by the digestion of Aβ₄₀ by IDE. Furthermore, we confirmed that IDE and NEP are unable to digest aggregated Aβ₄₀.     

Temporal dynamics and resilience of fine litterfall in relation to typhoon disturbances over 14 years in an old-growth lucidophyllous forest in southwestern Japan

We examined fine litterfall fluctuations on a seasonal and annual scale for 14 years (1992–2005) in a 1.2-ha plot in an old-growth lucidophyllous (evergreen broad-leaved) forest within the Aya Research Site, southwestern Japan. The average total litterfall input was 6.32 Mg ha^–1, of which leaf litter accounted for 60% of the total. Two high-impact typhoons struck the study area in 1993 (T9313) and 2004 (T0416) during the observation period; however, the subsequent pattern of litterfall after disturbance was different between the two typhoons. T9313 disturbance caused a reduction of biomass (ca. 10% of basal area (BA)) and a sharp decrease in litterfall input following a massive input in 1993. On the other hand, T0416 caused a minor decline in litterfall input, accompanied by a relatively small reduction of BA (5.2% of the 2001 BA). In spite of large fluctuations, litterfall input increased year by year after the T9313 disturbance. In 2000, 7 years after T9313, leaf input showed no significant differences and recorded more than 90% of pre-T9313 levels. Re-leafing from typhoon survivors may play an important role in the recovery of litterfall input in this forest. This study demonstrated how one high-impact typhoon can alter the temporal fluctuations in fine litterfall in lucidophyllous forest ecosystems.     

Leaf contents differ depending on the position in a rice leaf sheath during sink-source transition.

Carbohydrate contents varied with position in a leaf sheath, and differed between the flag leaf sheath and the second leaf sheath below the flag leaf (-2 leaf sheath) in rice (Oryza sativa L.). In the -2 leaf sheath before heading, light microscopy revealed differences in the distribution of starch granules depending on position. Leaf sheaths were divided into several parts, and the contents of carbohydrates (starch, sucrose, and hexoses) were measured in each part. Before heading, the content of accumulated starch increased linearly from the top to the bottom in -2 leaf sheaths (r2=0.99, P<0.001), as did the contents of accumulated sucrose and hexoses in flag leaf sheaths (r2=0.94, P<0.01). In flag leaf sheaths, the relative content of sucrose synthase (SuS), which plays a central role in the degradation of sucrose into hexoses, increased from the top to the bottom, consistent with hexose contents. After heading, the accumulated carbohydrates were dramatically decreased. In -2 leaf sheaths, the activity of alpha-amylase (EC 3.2.1.1), the rate-limiting step in starch degradation, was consistent with the degree of starch degradation, but in flag leaf sheaths with little starch before heading. These results show that carbohydrate contents differ, depending on the position in a leaf sheath. In addition, there were big differences in leaf contents between flag leaf sheaths and -2 leaf sheaths.     

Food regulation of growth and maturation in a natural population of Aurelia aurita (L.)

Growth and maturity development of the moon jellyfish. Aureliaaurita, were recorded in Vgsbpollen, a small and semi-enclosedbay on the Norwegian west coast, and compared to those of medusaetransferred to excess food and starving conditions, respectively.Mesozooplankton were extremely scarce in Vgsbpollen. The abundanceand biomass of the medusae in the poll were higher than thosetypicallyfound in open waters, reaching a maximum of 22 ind.m^–3 and 710 mg C m^–3 in June. The average diameterof medusae in the p increased to 8 cm until the last part ofJune, with an instantaneous growth rate between 1.5 and 20%day^–1, thereafter retarding somewhat, giving a negativegrowth rate of up to 2.6% day^–1. Starving medusae showeda negative growth rate ofup to 13.4% day^–1, and all thernedusae were dead after 49 days. Well-fed medusae showed avery stable growth over a 56 day period, diverging from thepollpopulation from early June, and with a growth rate between3.8 and 9.8% day^–1. Medusae from the pollpopulation begancarrying planulae on their oral arms when at least 5 cm in diameter,whereas not even the largest medusa of 15.6 cm diameter amongthose in the well-fed group produced any planulae. For the firsttime, it is thus explicitly shown that thesize and maturityof A.aurita are externally controlled through food availability.Scarcity of food reduces the growth rate, but also changes theenergy allocation towards reproduction, which thus occurs ata smaller size than for well-fed rnedusae. Its plasticity makesit possible for this species to exploit environments with lowadvection of food and develop high abundance in such environments,without losing fecundity.     

Development time of planula larvae on the oral arms of the scyphomedusa Aurelia aurita

The development time from zygote to late stage of planula larvaeon the oral arms of Aurelia aurita was found to be 270 and 170h at 12 and 22°C, respectively. The mean ratio of the diameterof the long axis to the short axis in newly released planulaewas 2.27.     

Seasonal courtship role change and reproductive behavior of the combtooth blenny Meiacanthus kamoharai

Ichthyological Research - Reproductive behavior of the blenniid fish Meiacanthus kamoharai was investigated in Tachibanaura Bay, Kochi Prefecture, Japan in 2016–2018. The species is sexually...     

Discovery of S1P agonists with a dihydronaphthalene scaffold

Structure-activity relationship of sphingosine-1-phosphate receptor agonists was examined. Cinnamyl derivative 1 was modified to improve S1P₁ agonistic activity as well as selectivity over S1P₃ agonistic activity. Dihydronaphthalene derivative 10d was identified as a potent S1P₁ receptor agonist with high selectivity against S1P₃ and enhanced efficacy in lowering peripheral lymphocyte counts in mice.     

Ontogenetic changes in the predator–prey interactions between threadsail filefish and moon jellyfish

The global climate change may lead to more extreme climate events such as severe flooding creating excessive pulse-loading of nutrients, including nitrogen (N), to freshwaters. We conducted a 3-month mesocosm study to investigate the responses of phytoplankton, zooplankton and Vallisneria spinulosa to different N loading patterns using weekly and monthly additions of in total 14 g N m^?2 month^?1 during the first 2 months. The monthly additions led to higher phytoplankton chlorophyll a and total phytoplankton biomass than at ambient conditions as well as lower leaf biomass and a smaller ramet number of V. spinulosa. Moreover, the biomass of cyanobacteria was higher during summer (August) in the monthly treatments than those with weekly or no additions. However, the biomass of plankton and macrophytes did not differ among the N treatments at the end of the experiment, 1 month after the termination of N addition. We conclude that by stimulating the growth of phytoplankton (cyanobacteria) and reducing the growth of submerged macrophytes, short-term extreme N loading may have significant effects on shallow nutrient-rich lakes and that the lakes may show fast recovery if they are not close to the threshold of a regime shift from a clear to a turbid state.     

Unusual heme binding in the bacterial iron response regulator protein: spectral characterization of heme binding to the heme regulatory motif

We characterized heme binding in the bacterial iron response regulator (Irr) protein, which is a simple heme-regulated protein having a single "heme-regulatory motif", HRM, and plays a key role in the iron homeostasis of a nitrogen-fixing bacterium. The heme titration to wild-type and mutant Irr clearly showed that Irr has two heme binding sites: one of the heme binding sites is in the HRM, where (29)Cys is the axial ligand, and the other one, the secondary heme binding site, is located outside of the HRM. The Raman line for the Fe-S stretching mode observed at 333 cm(-1) unambiguously confirmed heme binding to Cys. The lower frequency of the Fe-S stretching mode corresponds to the weaker Fe-S bond, and the broad Raman line of the Fe-S bond suggests multiple configurations of heme binding. These structural characteristics are definitely different from those of typical hemoproteins. The unusual heme binding in Irr was also evident in the EPR spectra. The characteristic g-values of the 5-coordinate Cys-ligated heme and 6-coordinate His/His-ligated heme were observed, while the multiple configurations of heme binding were also confirmed. Such multiple heme configurations are not encountered for typical hemoproteins where the heme functions as the active center. Therefore, we conclude that heme binding to HRM in the heme-regulated protein, Irr, is quite different from that in conventional hemoproteins but characteristic of heme-regulated proteins using heme as the signaling molecule.