Host characteristics and infection level of an intestinal parasite Corynosoma strumosum (Acanthocephala) in the Kuril harbor seal of Erimo Cape,Hokkaido, Japan

The Kuril harbor seal around Hokkaido is presently recovering from a resource crisis while conflicts with local fisheries have become a concern. However, its feeding habits, which are fundamental information for taking proper preventive measures, are still poorly understood. We thus examined the infection status of a trophically-transmitted parasite, Corynosoma strumosum in the seals of Erimo Cape, to assess the host's feeding habits with a practical view of the parasite as a biological indicator. A total of 2802 worms were found from 20 male and 20 female by-caught animals in salmon set nets within local fisheries during August to November 2014. The parasite abundance was explained mainly by the host's developmental stage and intestinal length while weakly affected by gender and body size, through an estimation of generalized linear models combined with hierarchical partitioning. Considering the past records that demersal fishes are the probable main sources of infection, the infection level may owe to individual host differences regarding these sources and/or feeding grounds with relating the host characteristics. This supports that the resource management of Kuril harbor seals requires careful consideration of the individual differences in feeding behavior.     

Zinc Deficiency Affects the Levels of Endogenous Gibberellins in Zea mays L.

Zinc deficiency in Zea mays L. markedly reduced the level ofGA₁, but not GA₂₀, suggesting blockage of 3rß-hy-droxylation.The level of IAA was also decreased although not as markedly.Castasterone was affected less than IAA by zinc deficiency. (Received February 24, 1997; Accepted June 24, 1997)     

Zoospore-specific antigen as a useful marker for molecular analysis of net formation in Hydrodictyon reticulatum (Chlorococcales, Chlorophyceae)

In the green alga Hydrodictyon reticulatum zoospores are arranged in a regular fashion to form an intricate hexagonal network during the asexual reproductive cycle. A monoclonal antibody which was raised against a homogenate of zoospores recognized a single poly‐peptide in zoospores with a molecular mass of 31 kDa. The antigenic polypeptide, which was designated Amy1, was localized within the cytoplasm of zoospores. The accumulation of Amy1 occurred concomitantly with the transition from multinuclear vegetative cells to mononuclear zoospores, and the degradation of Amy1 occurred concomitantly with the further development of zoospores. Amy1 was constantly expressed during the period of mononuclear zoospores. Thus, we conclude that Amy1 is a zoospore‐specific polypeptide. Using the anti‐Amy1 monoclonal antibody, we could easily distinguish between mononuclear zoospores and multinuclear vegetative net‐cells. This provides an important tool for analysing the molecular mechanisms involved in the hexagonal net formation by zoospores.     

Chemical synthesis of polysaccharides. 7. Enzymatic hydrolysis of (1 → 6)-α-DL-glucopyranan (DL-dextran)

Hydrolysis of (1 → 6)-α-DL -glucopyranan (synthetic DL -dextran) by an endo-dextranase from a Penicillium species was examined in an acetate buffer solution (pH 5.3) at 37°C. Three samples of different tacticities (isotactic dyad content, 55, 63, and 72%) were employed with a clinical dextran for comparison. Colorimetric determination of the reducing end units of the saccharides produced during hydrolysis showed that the maximum degrees of hydrolysis based on the D-glucose units, (D.H.)_D, for the DL -dextrans were 21.4, 27.8, and 33.0% in the order of increasing isotacitic dyad content, whereas the (D.H.)_D value for the clinical dextran was 51.9%. A statistical treatment of the enzymatic hydrolysis is proposed to interpret the experimental results.     

Drebrin attenuates the interaction between actin and myosin-V

Drebrin-A is an actin-binding protein localized in the dendritic spines of mature neurons, and has been suggested to affect spine morphology [K. Hayashi, T. Shirao, Change in the shape of dendritic spines caused by overexpression of drebrin in cultured cortical neurons, J. Neurosci. 19 (1999) 3918-3925]. However, no biochemical analysis of drebrin-A has yet been reported. In this study, we purified drebrin-A using a bacterial expression system, and characterized it in vitro. Drebrin-A bound to actin filaments with a stoichiometry of one drebrin molecule to 5-6 actin molecules. Furthermore, drebrin-A decreased the Mg-ATPase activity of myosin V. In vitro motility assay revealed that the attachment of F-actin to glass surface coated with myosin-V was decreased by drebrin-A, but once F-actin attached to the surface, the sliding speed of F-actin was unaffected by the presence of drebrin A. These findings suggest that drebrin-A may affect spine dynamics, vesicle transport, and other myosin-V-driven motility in neurons through attenuating the interaction between actin and myosin-V.     

Inhibitory effect of the catalytic domain of myosin light chain kinase on actin-myosin interaction: insight into the mode of inhibition.

The catalytic domain of myosin light chain kinase (MLCK) not only exerts kinase activity to phosphorylate the 20 kDa light chain but also inhibits the actin-myosin interaction. The site of action of this novel role of the domain has been suggested to be myosin [Okagaki et al. (1999) J. Biochem. 125, 619-626]. In this study, we have analyzed the amino acid sequences of MLCK and myosin that are involved in the inhibition. The ATP-binding peptide of Gly526-Lys548 of chicken gizzard MLCK exerted the inhibitory effect on the movement of actin filaments on a myosin-coated glass surface. However, the peptide that neighbors the sequence failed to inhibit the movement. The inhibition of the ATP-binding peptide was confirmed by measuring ATPase activities of the myosin. The inhibition by parent MLCK of the movement was relieved by the 20 kDa light chain, but not by the 17 kDa myosin light chain. The peptide of the 20 kDa light chain sequence of Ser1-Glu29 also relieved the inhibition. Thus, the interaction of the ATP-binding sequence with the 20 kDa light chain sequence should cause the inhibition of the actin-myosin interaction. Concerning the regulation of the inhibition, calmodulin relieved the inhibitory effect of MLCK on the movement of actin filaments. The calmodulin-binding peptide (Ala796 Ser815) prevented the relief, suggesting the involvement of this sequence. Thus, the mode of regulation by Ca2+ and calmodulin of the novel role of the catalytic domain is similar, but not identical, to the mode of regulation of the kinase activity of the domain.     

Sphingosine kinase expression increases intracellular sphingosine-1-phosphate and promotes cell growth and survival.

Sphingosine-1-phosphate (SPP) is a bioactive lipid that has recently been identified as the ligand for the EDG family of G protein-coupled cell surface receptors. However, the mitogenic and survival effects of exogenous SPP may not correlate with binding to cell-surface receptors (Van Brocklyn, J.R., M.J. Lee, R. Menzeleev, A. Olivera, L. Edsall, O. Cuvillier, D.M. Thomas, P.J.P. Coopman, S. Thangada, T. Hla, and S. Spiegel. 1998. J. Cell Biol. 142:229-240). The recent cloning of sphingosine kinase, a unique lipid kinase responsible for the formation of SPP, has provided a new tool to investigate the role of intracellular SPP. Expression of sphingosine kinase markedly increased SPP levels in NIH 3T3 fibroblasts and HEK293 cells, but no detectable secretion of SPP into the medium was observed. The increased sphingosine kinase activity in NIH 3T3 fibroblasts was sufficient to promote growth in low- serum media, expedite the G(1)/S transition, and increase DNA synthesis and the proportion of cells in the S phase of the cell cycle with a concomitant increase in cell numbers. Transient or stable overexpression of sphingosine kinase in NIH 3T3 fibroblasts or HEK293 cells protected against apoptosis induced by serum deprivation or ceramide elevation. N,N-Dimethylsphingosine, a competitive inhibitor of sphingosine kinase, blocked the effects of sphingosine kinase overexpression on cell proliferation and suppression of apoptosis. In contrast, pertussis toxin did not abrogate these biological responses. In Jurkat T cells, overexpression of sphingosine kinase also suppressed serum deprivation- and ceramide-induced apoptosis and, to a lesser extent, Fas-induced apoptosis, which correlated with inhibition of DEVDase activity, as well as inhibition of the executionary caspase-3. Taken together with ample evidence showing that growth and survival factors activate sphingosine kinase, our results indicate that SPP functions as a second messenger important for growth and survival of cells. Hence, SPP belongs to a novel class of lipid mediators that can function inside and outside cells.     

Deciphering the genomic architecture of the stickleback brain with a novel multilocus gene‐mapping approach

Quantitative traits important to organismal function and fitness, such as brain size, are presumably controlled by many small‐effect loci. Deciphering the genetic architecture of such traits with traditional quantitative trait locus (QTL) mapping methods is challenging. Here, we investigated the genetic architecture of brain size (and the size of five different brain parts) in nine‐spined sticklebacks (Pungitius pungitius) with the aid of novel multilocus QTL‐mapping approaches based on a de‐biased LASSO method. Apart from having more statistical power to detect QTL and reduced rate of false positives than conventional QTL‐mapping approaches, the developed methods can handle large marker panels and provide estimates of genomic heritability. Single‐locus analyses of an F₂ interpopulation cross with 239 individuals and 15 198, fully informative single nucleotide polymorphisms (SNPs) uncovered 79 QTL associated with variation in stickleback brain size traits. Many of these loci were in strong linkage disequilibrium (LD) with each other, and consequently, a multilocus mapping of individual SNPs, accounting for LD structure in the data, recovered only four significant QTL. However, a multilocus mapping of SNPs grouped by linkage group (LG) identified 14 LGs (1–6 depending on the trait) that influence variation in brain traits. For instance, 17.6% of the variation in relative brain size was explainable by cumulative effects of SNPs distributed over six LGs, whereas 42% of the variation was accounted for by all 21 LGs. Hence, the results suggest that variation in stickleback brain traits is influenced by many small‐effect loci. Apart from suggesting moderately heritable (h² ≈ 0.15–0.42) multifactorial genetic architecture of brain traits, the results highlight the challenges in identifying the loci contributing to variation in quantitative traits. Nevertheless, the results demonstrate that the novel QTL‐mapping approach developed here has distinctive advantages over the traditional QTL‐mapping methods in analyses of dense marker panels.