Immunostimulation effect of jellyfish collagen

Certain edible large jellyfishes belonging to the order Rhizostomeae are consumed in large quantities in China and Japan. The exumbrella part of the edible jellyfish Stomolophus nomurai was cut and soaked in dilute hydrochloric acid solution (pH 3.0) for 12 h, and heated at 121 degrees C for 20 min. The immunostimulation effects of the jellyfish extract were examined. The jellyfish extract enhanced IgM production of human hybridoma HB4C5 cells 34-fold. IgM and IgG production of human peripheral blood lymphocytes (PBL) were also accelerated, 2.8- and 1.4-fold respectively. Moreover, production of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha by human PBL was stimulated 100- and 17-fold respectively. Collagenase treatment inactivated the immunostimulation activity of the jellyfish extract. In addition, purified collagen from bovine Achilles' tendon accelerated IgM production of hybridoma cells. These facts mean that collagen has an immunostimulation effect, and that the active substance in jellyfish extract is collagen.     

Identification and characterization of Arabidopsis thaliana genes involved in xylem secondary cell walls

The xylem of higher plants offers support to aerial portions of the plant body and serves as conduit for the translocation of water and nutrients. Terminal differentiation of xylem cells typically involves deposition of thick secondary cell walls. This is a dynamic cellular process accompanied by enhanced rates of cellulose deposition and the induction of synthesis of specific secondary-wall matrix polysaccharides and lignin. The secondary cell wall is essential for the function of conductive and supportive xylem tissues. Recently, significant progress has been made in identifying the genes responsible for xylem secondary cell wall formation. However, our present knowledge is still insufficient to account for the molecular processes by which this complex system operates. To acquire further information about xylem secondary cell walls, we initially focused our research effort on a set of genes specifically implicated in secondary cell wall formation, as well as on loss-of-function mutants. Results from two microarray screens identified several key candidate genes responsible for secondary cell wall formation. Reverse genetic analyses led to the identification of a glycine-rich protein involved in maintaining the stable structure of protoxylem, which is essential for the transport of water and nutrients. A combination of expression analyses and reverse genetics allows us to systematically identify new genes required for the development of physical properties of the xylem secondary wall.     

Soil and stream water acidification in a forested catchment in central Japan

Rapid industrialization in East Asia is causing adverse effects due to atmospheric deposition in terrestrial and freshwater ecosystems. Decreasing stream pH and alkalinity and increasing NO₃ ^? concentrations were observed throughout the 1990s in the forested Lake Ijira catchment in central Japan. We investigated these changes using data on atmospheric deposition, soil chemistry, stream water chemistry, and forest growth. Average atmospheric depositions (wet + dry) of 0.83, 0.57, and 1.37 kmol ha^?1 year^?1 for hydrogen, sulfur, and nitrogen, respectively, were among the highest levels in Japan. Atmospheric deposition generally decreased before 1994 and increased thereafter. The catchment was acid-sensitive; stream alkalinity was low (134 μmol_c l^?1) and pH in surface mineral soils decreased from 4.5 in 1990 to 3.9 in 2003. Stream NO₃ ^? concentration nearly doubled (from 22 to 42 μmol_c l^?1) from the late 1980s to the early 2000s. Stream NO₃ ^? concentration was controlled primarily by water temperature before 1996/1997 and by stream discharge thereafter. Stream NO₃ ^? concentrations decreased during the growing season before 1996/1997, but this seasonality was lost thereafter. The catchment became nitrogen-saturated (changing from stage 1 to 2) in 1996/1997, possibly because of declining forest growth rates due to the 1994 summer drought, defoliation of Japanese red pine by pine wilt disease, maturation of Japanese cedar stands, and stimulation of nitrogen mineralization and nitrification due to alkalinization of soils (increased exchangeable Ca²⁺ and soil pH) after the summer drought. Stream pH and alkalinity began decreasing in 1996/1997. The enhanced growing-season NO₃ ^? discharge since 1996/1997 appeared to be the major cause of stream acidification. Increased atmospheric deposition since 1994 may have contributed to this change.     

Control of actin reorganization by Slingshot, a family of phosphatases that dephosphorylate ADF/cofilin

The ADF (actin-depolymerizing factor)/cofilin family is a stimulus-responsive mediator of actin dynamics. In contrast to the mechanisms of inactivation of ADF/cofilin by kinases such as LIM-kinase 1 (LIMK1), much less is known about its reactivation through dephosphorylation. Here we report Slingshot (SSH), a family of phosphatases that have the property of F actin binding. In Drosophila, loss of ssh function dramatically increased levels of both F actin and phospho-cofilin (P cofilin) and disorganized epidermal cell morphogenesis. In mammalian cells, human SSH homologs (hSSHs) suppressed LIMK1-induced actin reorganization. Furthermore, SSH and the hSSHs dephosphorylated P cofilin in cultured cells and in cell-free assays. Our results strongly suggest that the SSH family plays a pivotal role in actin dynamics by reactivating ADF/cofilin in vivo.     

Effect of hypergravity stimulus on XTH gene expression in Arabidopsis thaliana.

There are several reports indicating that hypergravity and microgravity influence the mechanical properties of cell walls in shoots, resulting in changes in the growth rate. The mechanical properties of cell walls in dicots are mainly determined by the physicochemical properties of xyloglucan, a matrix polysaccharide. An increase in the molecular mass of xyloglucan correlated with a decrease in cell wall extensibility. Hypergravity is known to increase the molecular mass of xyloglucan. The cell wall enzyme, xyloglucan endotransglucosylase/hydrolase (XTH) is involved in xyloglucan metabolism. Using Arabidopsis, it was examined whether or not the expression of XTH genes in the floral stem and rosette leaf is influenced by hypergravity. RT-PCR analysis revealed that the expression of XTH genes changes in response to hypergravity of 300 g.     

Affixin interacts with alpha-actinin and mediates integrin signaling for reorganization of F-actin induced by initial cell-substrate interaction

The linking of integrin to cytoskeleton is a critical event for an effective cell migration. Previously, we have reported that a novel integrin-linked kinase (ILK)-binding protein, affixin, is closely involved in the linkage between integrin and cytoskeleton in combination with ILK. In the present work, we demonstrated that the second calponin homology domain of affixin directly interacts with alpha-actinin in an ILK kinase activity-dependent manner, suggesting that integrin-ILK signaling evoked by substrate adhesion induces affixin-alpha-actinin interaction. The overexpression of a peptide corresponding to the alpha-actinin-binding site of affixin as well as the knockdown of endogenous affixin by small interference RNA resulted in the blockade of cell spreading. Time-lapse observation revealed that in both experiments cells were round with small peripheral blebs and failed to develop lamellipodia, suggesting that the ILK-affixin complex serves as an integrin-anchoring site for alpha-actinin and thereby mediates integrin signaling to alpha-actinin, which has been shown to play a critical role in actin polymerization at focal adhesions.     

Permanence of discrete-time Kolmogorov systems for two species and saturated fixed points

This paper considers the dynamics of a discrete-time Kolmogorov system for two-species populations. In particular, permanence of the system is considered. Permanence is one of the concepts to describe the species coexistence. By using the method of an average Liapunov function, we have found a simple sufficient condition for permanence of the system. That is, nonexistence of saturated boundary fixed points is enough for permanence of the system under some appropriate convexity or concavity properties for the population growth rate functions. Numerical investigations show that for the system with population growth rate functions without such properties, the nonexistence of saturated boundary fixed points is not sufficient for permanence, actually a boundary periodic orbit or a chaotic orbit can be attractive despite the existence of a stable coexistence fixed point. This result implies, in particular, that existence of a stable coexistence fixed point is not sufficient for permanence.     

Comprehensive approach to genes involved in cell wall modifications in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

The plant cell wall is of supermolecular architecture, and is composed of various types of heterogeneous polymers. A few thousand enzymes and structural proteins are directly involved in the construction processes, and in the functional aspects of the dynamic architecture in Arabidopsis thaliana. Most of these proteins are encoded by multigene families, and most members within each family share significant similarities in structural features, but often exhibit differing expression profiles and physiological functions. Thus, for the molecular dissection of cell wall dynamics, it is necessary to distinguish individual members within a family of proteins. As a first step towards characterizing the processes involved in cell wall dynamics, we have manufactured a gene-specific 70-mer oligo microarray that consists of 765 genes classified into 30 putative families of proteins that are implicated in the cell wall dynamics of Arabidopsis. By using this array system, we identified several sets of genes that exhibit organ preferential expression profiles. We also identified gene sets that are expressed differentially at certain specific growth stages of the Arabidopsis inflorescence stem. Our results indicate that there is a division of roles among family members within each of the putative cell wall-related gene families.