Role of water-soluble polysaccharides in bacterial cellulose production

Acetobacter xylinum BPR2001 produces water-insoluble bacterial cellulose (BC) and a water-soluble polysaccharide called acetan in corn steep liquor-fructose medium. Acetobacter xylinum EP1, which is incapable of acetan production was derived by disrupting the aceA gene of BPR2001. The BC production by EP1 (2.88 g/L) was lower than that by BPR2001 (4.6 g/L) in baffled-flask culture. When purified acetan or agar was added to the medium from the start of cultivation, the BC production by EP1 was enhanced and the final BC yield of EP1 was almost the same as that of BPR2001. A similar improvement of BC production by EP1 by the addition of agar was also confirmed by cultivation in a 50-L airlift reactor. From these results, the role of acetan in BC production is associated with the increase in the viscosity of the culture medium which may hinder coagulation of BC and cells in the culture, thereby accelerating the growth of BPR2001 and BC production by BPR2001.     

Developmentally regulated extrachromosomal circular DNA formation in the mesozoan <Emphasis Type="Italic">Dicyema japonicum</Emphasis>

The dicyemid mesozoans are simple multicellular parasites with a long cylindrical axial cell surrounded by a single outer layer of 20 to 30 ciliated peripheral somatic cells. Their larval development proceeds within the axial cell. Here we demonstrate the appearance of extrachromosomal circular DNAs and their fate during early embryogenesis in Dicyema japonicum. These DNAs are highly heterogeneous in sequence, suggesting that they consist of unique--not repetitive--elements. Potential open reading frames were not evident in the elements, so these DNAs are unlikely to have a protein-encoding function. In situ hybridization revealed that the circular DNA elements were restricted to the early embryonic larvae and gradually faded out as larvae approached maturity. Furthermore Southern blot analysis and polymerase chain reaction analysis using a high molecular weight DNA as a template provided evidence that the extrachromosomal DNA circles are originally present in chromosomes. These observations suggest DNA elimination--or selective replication--of the elements from chromosomes during early embryogenesis in dicyemid mesozoans.     

Hepatocyte nuclear factor (HNF)-4alpha triggers formation of functional tight junctions and establishment of polarized epithelial morphology in F9 embryonal carcinoma cells

F9 murine embryonal carcinoma cells provide an attractive system for facilitating molecular mechanisms for epithelial morphogenesis, since they have the capability of differentiating into polarized epithelial cells bearing an apical junctional complexes. We previously showed that a specific retinoid X receptor-retinoic acid receptor heterodimer transduced retinoid signals for biogenesis of functional tight junctions in F9 cells (Exp. Cell Res. 263, (2001) 163). In the present study we generated F9 cells expressing doxycycline-inducible hepatocyte nuclear factor (HNF)-4alpha, a nuclear receptor. We herein show that induction of HNF-4alpha initiates differentiation of F9 cells to polarized epithelial cells, in which tight-junction proteins occludin, claudin-6, claudin-7, and ZO-1 are concentrated at the apical-most regions of lateral membranes. Expression of occludin, claudin-6, and claudin-7 was induced in the cells by doxycycline treatment in a dose- and time-dependent manner, in terms of the amount of HNF-4alpha. In contrast, expression levels of ZO-1, ZO-2, E-cadherin, and beta-catenin were not altered by HNF-4alpha. We also demonstrate, by analysis of diffusion of labeled sphingomyelin, that the fence function of tight junctions is achieved by induction of HNF-4alpha. These findings indicate that HNF-4alpha triggers de novo formation of functional tight junctions and establishment of epithelial cell polarity.     

Isoproterenol produces a rapid increase in sialidase activity in rat heart tissue and cardiomyocyte-derived H9c2 cells in culture

The effects of isoproterenol on sialidase activity in rat cardiomyocytes were examined. Administration of isoproterenol to rats (0.2 or 2 mg/kg body weight) produced an increase in sialidase activity in total membrane fraction of heart tissue within 120 min (121+/-13% of the control at 120 min after administration of 0.2 mg isoproterenol/kg, n=5, P<0.05). Sialidase activity in cardiomyocyte-derived H9c2 cells was also increased by treatment with isoproterenol (10 microM) for 60 min. The effect of isoproterenol on sialidase activity was amplified by the addition of 3-isobutyl-1-methylxanthine (IBMX). Sialidase activity in H9c2 cells was elevated by treatment with dibutyryl cAMP plus IBMX without isoproterenol. The content of N-acetylneuraminic acid in cells decreased by 22% after treatment with isoproterenol plus IBMX. These results suggest that sialidase activity in rat cardiomyocytes is regulated by beta-adrenergic stimulators via a cAMP-dependent process. The increased activity of sialidase may account for the reduction of sialic acid content of cells.     

Synthesis and localization of the Salmonella SPI-1 type III secretion needle complex proteins PrgI and PrgJ

An essential component of type III secretion systems (TTSS) is a supramolecular structure termed the needle complex. In Salmonella enterica, at least four proteins make up this structure: InvG, PrgH, PrgK, and PrgI. Another protein, PrgJ, is thought to play a role in the assembly of this structure, but its function is poorly understood. We have analyzed the expression and localization of PrgJ and the needle protein PrgI in different S. enterica serovar Typhimurium mutant strains. We found that the levels of PrgI and PrgJ were significantly reduced in a TTSS-deficient invA mutant strain and that the decreased levels were due to protein instability. In addition, we found that PrgJ, although associated with the needle complex in wild-type S. enterica serovar Typhimurium, was absent from needle complexes obtained from an invJ mutant strain, which exhibits very long needle substructures. We suggest that PrgJ is involved in capping the needle substructure of the needle complex.     

Molecular cloning of a novel transmembrane protein MOLT expressed by mature oligodendrocytes

A novel oligodendrocyte (OL)-specific cDNA was isolated from brain capillary endothelial cells and characterized. The cDNA encodes a protein of 1099 amino acids that contains a signal peptide and a transmembrane domain. The protein was expressed in mature OLs in vivo and in vitro cell cultures and was thus designated as mature OL transmembrane protein (MOLT). RT-PCR analysis showed that MOLT mRNA was expressed in brain, lung, pancreas, and testis. A polyclonal antibody raised against a part of the mouse MOLT reacted specifically with multipolar OLs possessing radially oriented processes that penetrated into the gray matter. More cells were detected in the white matter, and these had longitudinally oriented processes. In a rat OL lineage culture system, oligodendrocyte precursor cells did not initially produce MOLT mRNA and protein, but when they begun to differentiate into mature OLs, they started expressing MOLT. Consequently, MOLT may function as OLs become mature and may serve as a cell-surface marker for OL differentiation.     

Effects of ionic valency of interacting metal elements in ion uptake by carrot (Daucas carota cv. U.S. harumakigosun)

Interaction of elements in the course of element uptake by carrot (Daucas carota cv. U.S. harumakigosun) exerted by the addition of elements, such as Rb, Zn, and Al, was investigated. For the purpose of precise evaluation of uptake behavior, the simultaneous determination of absorption of Na, Be, Sr, Mn, Co, Zn, Ce, Pm, and Gd was conducted by the multitracer technique. For root uptakes, Al exhibited its influence on the uptake of essential elements and on the uptake of toxic or unbeneficial ones, presumably as a result of the large electric valency that caused cell membrane disintegrity. On the other hand, Zn as a divalent cation only affected the uptake of essential and beneficial elements. Rubidium, which is a monovalent cation, did not exhibit any effect on the uptake of other ions. Concerning shoot uptakes, inhibition by Zn and Al, but not by Rb, was observed for the uptake of Sr, Mn, Co, and Zn. From the present investigation, it is suggested that there exists an interaction between added ions and the elements taken into plants and that the degree of interaction increases in the increasing order of ionic valency: M+ (Rb), M2+ (Zn), and M3+ (Al).     

Effect of addition of water-soluble polysaccharides on bacterial cellulose production in a 50-L airlift reactor

Bacterial cellulose (BC) production was carried out in a batch cultivation of Acetobacter xylinum in a 50-L internal loop airlift reactor by addition of water-soluble polysaccharides into the medium. When 0.1% (w/w) agar was added, BC production reached 8.7 g/L compared with 6.3 g/L in the control, and duration of the cultivation period to reach the maximum concentration of BC was almost half of that without addition of polysaccharides. During cultivation, BC was formed into pellets whose size was smaller when the productivity of BC was higher, indicating that increase in the relative viscosity by addition of polysaccharides hindered formation of large clumps of BC and increase in the volumetric oxygen transfer coefficient at high flow rate led to increase in BC productivity.     

Development of lateral line organs in leptocephali of the freshwater eel Anguilla japonica (Teleostei,Anguilliformes)

A study of the ontogeny of the lateral line system in leptocephali of the Japanese eel Anguilla japonica reveals the existence of three morphologically different types of lateral line organs. Type I is a novel sensory organ with hair cells bearing a single kinocilium, lacking stereocilia, distributed mainly on the head of larvae, and morphologically different from typical superficial neuromasts of the lateral line system. Its developmental sequence suggests that it may be a presumptive canal neuromast. Type II is an ordinary superficial neuromast, common in other teleost larvae, which includes presumptive canal neuromasts that first appear on the trunk and accessory superficial neuromasts that later appear on the head and trunk. Type III is a very unusual neuromast located just behind the orbit, close to the otic vesicle, with radially oriented hair cells, suggesting that these serve as multiple axes of sensitivity for mechanical stimuli. The behavior of larval eels suggests that the radially oriented neuromasts may act as the sole mechanosensory organ until the ordinary superficial neuromasts develop. The finding that larval eels possess a well-developed mechanosensory system suggests the possibility that they are also capable of perceiving weak environmental mechanical stimuli, like other teleost larvae.