Structure and mechanical properties of wet-spun fibers made from natural cellulose nanofibers

Cellulose nanofibers were prepared by TEMPO-mediated oxidation of wood pulp and tunicate cellulose. The cellulose nanofiber suspension in water was spun into an acetone coagulation bath. The spinning rate was varied from 0.1 to 100 m/min to align the nanofibers to the spun fibers. The fibers spun from the wood nanofibers had a hollow structure at spinning rates of >10 m/min, whereas the fibers spun from tunicate nanofibers were porous. Wide-angle X-ray diffraction analysis revealed that the wood and tunicate nanofibers were aligned to the fiber direction of the spun fibers at higher spinning rates. The wood spun fibers at 100 m/min had a Young's modulus of 23.6 GPa, tensile strength of 321 MPa, and elongation at break of 2.2%. The Young's modulus of the wood spun fibers increased with an increase in the spinning rate because of the nanofiber orientation effect.     

Viscoelastic evaluation of average length of cellulose nanofibers prepared by TEMPO-mediated oxidation

Dynamic viscoelasticity measurements were performed for aqueous dispersions of cellulose nanofibers prepared by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and subsequent mechanical disintegration in water. The frequency dependence of the storage and loss moduli of 0.02% (w/v) dispersions of TEMPO-oxidized cellulose nanofibers in water showed terminal relaxation behavior at relatively lower angular frequencies. This strongly suggests that each cellulose nanofiber in the dispersion behaves as a semiflexible rod-like macromolecular chain or colloidal particle. Furthermore, a clear boundary was observed between the terminal relaxation and rubbery plateau regions. The longest viscoelastic relaxation time, τ, was estimated from the angular frequency, corresponding to the boundary point, and the average length of the cellulose nanofibers, L, was estimated using the equation τ = πη(s)L(3)/[18k(B)T ln(L/d)]. The equation gave a value of L = 2.2 μm, which was in good agreement with TEM observations.     

SLC5A9/SGLT4, a new Na+-dependent glucose transporter, is an essential transporter for mannose, 1,5-anhydro-D-glucitol, and fructose

We isolated a cDNA clone of SLC5A9/SGLT4 from human small intestinal full-length cDNA libraries, and functionally characterized it in vitro. The messenger RNA encoding SGLT4 was mainly expressed in the small intestine and kidney, among the human tissues tested. COS-7 cells transiently expressing SGLT4 exhibited Na(+)-dependent alpha-methyl-D-glucopyranoside (AMG) transport activity with an apparent K(m) of 2.6 mM, suggesting that SGLT4 is a low affinity-type transporter. The rank order of naturally occurring sugar analogs for the inhibition of AMG transport was: D-mannose (Man) > D-glucose (Glc) > D-fructose (Fru) = 1,5-anhydro-D-glucitol (1,5AG) > D-galactose (Gal). Recognition of Man as a substrate was confirmed by direct uptake of Man into the cell. COS-7 cells expressing a putative murine SGLT4 ortholog showed similar Na(+)-dependent AMG transport activity and a similar deduced substrate specificity. These results suggest that SGLT4 would have unique physiological functions (i.e., absorption and/or reabsorption of Man, 1,5AG, and Fru, in addition to Glc).     

Higher plant RecA-like protein is homologous to RadA

A novel RecA-like protein, differing from Dmc1 and Rad51, was characterized in Oryza sativa L. cv. Nipponbare. Because the protein is homologous to bacterial RadA, the gene was designated OsRadA. The open reading frame was predicted to encode a 66kDa protein of 619 amino acid residues and was found in plants but not animals or yeast. OsRadA showed D-loop and single-stranded DNA-dependent ATPase activities. Gene expression was found to be high in meristematic tissues, and was localized in the nucleus. An RNAi mutant of Arabidopsis thaliana RadA (AtRadA) was sensitive to mutagenic agents such as UV and MMC, suggesting that RadA functions in DNA repair.     

Differential responses of normal human coronary artery endothelial cells against multiple cytokines comparatively assessed by gene expression profiles

Endothelial cells play an important role in terms of biological functions by responding to a variety of stimuli in the blood. However, little is known about the molecular mechanism involved in rendering the variety in the cellular response. To investigate the variety of the cellular responses against exogenous stimuli at the gene expression level, we attempted to describe the cellular responses with comprehensive gene expression profiles, dissect them into multiple response patterns, and characterize the response patterns according to the information accumulated so far on the genes included in the patterns. We comparatively analyzed in parallel the gene expression profiles obtained with DNA microarrays from normal human coronary artery endothelial cells (HCAECs) stimulated with multiple cytokines, interleukin-1β, tumor necrosis factor-, interferon-β, interferon-γ, and oncostatin M, which are profoundly involved in various functional responses of endothelial cells. These analyses revealed that the cellular responses of HCAECs against these cytokines included at least 15 response patterns specific to a single cytokine or common to multiple cytokines. Moreover, we statistically extracted genes contained within the individual response patterns and characterized the response patterns with the genes referring to the previously accumulated findings including the biological process defined by the Gene Ontology Consortium (GO). Out of the 15 response patterns in which at least one gene was successfully extracted through the statistical approach, 11 response patterns were differentially characterized by representing the number of genes contained in individual criteria of the biological process in the GO only. The approach to dissect cellular responses into response patterns and to characterize the pattern at the gene expression level may contribute to the gaining of insight for untangling the diversity of cellular functions.     

Live imaging of lymphatic development in the zebrafish

The lymphatic system has become the subject of great interest in recent years because of its important role in normal and pathological processes. Progress in understanding the origins and early development of this system, however, has been hampered by difficulties in observing lymphatic cells in vivo and in performing defined genetic and experimental manipulation of the lymphatic system in currently available model organisms. Here, we show that the optically clear developing zebrafish provides a useful model for imaging and studying lymphatic development, with a lymphatic system that shares many of the morphological, molecular and functional characteristics of the lymphatic vessels found in other vertebrates. Using two-photon time-lapse imaging of transgenic zebrafish, we trace the migration and lineage of individual cells incorporating into the lymphatic endothelium. Our results show lymphatic endothelial cells of the thoracic duct arise from primitive veins through a novel and unexpected pathway.     

Homogeneous suspensions of individualized microfibrils from TEMPO-catalyzed oxidation of native cellulose

Never-dried native celluloses (bleached sulfite wood pulp, cotton, tunicin, and bacterial cellulose) were disintegrated into individual microfibrils after oxidation mediated by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical followed by a homogenizing mechanical treatment. When oxidized with 3.6 mmol of NaClO per gram of cellulose, almost the totality of sulfite wood pulp and cotton were readily disintegrated into long individual microfibrils by a treatment with a Waring Blendor, yielding transparent and highly viscous suspensions. When observed by transmission electron microscopy, the wood pulp and cotton microfibrils exhibited a regular width of 3-5 nm. Tunicin and bacterial cellulose could be disintegrated by sonication. A bulk degree of oxidation of about 0.2 per one anhydroglucose unit of cellulose was necessary for a smooth disintegration of sulfite wood pulp, whereas only small amounts of independent microfibrils were obtained at lower oxidation levels. This limiting degree of oxidation decreased in the following order: sulfite wood pulp > cotton > bacterial cellulose, tunicin.     

Genetic organization of the hrp gene cluster in Acidovorax avenae strain N1141 and a novel effector protein that elicits immune responses in rice (Oryza sativa L.)

The immune system of plants consists of two main arms, pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI). The multiple effectors that trigger ETI are translocated into plant cells by the type III secretion system (T3SS) of pathogenic bacteria. The rice-avirulent N1141 strain of Acidovorax avenae causes ETI in rice, including hypersensitive response (HR) cell death. Sequence analysis indicated that the N1141 genome contains the hrp gene cluster (35.3 kb), including genes encoding the T3SS apparatus. The T3SS-defective N1141 mutant (NΔT3SS) did not cause HR cell death, suggesting that ETI is caused by translocation of effector proteins into rice cells via T3SS. Computational sequence analysis predicted that Lrp, HrpW, and HrpY are secreted by T3SS. The hrpY deletion mutant (NΔhrpY) did not cause ETI, suggesting that HrpY is an important effector of ETI in the interaction between A. avenae N1141 and rice.     

Discovery of cyclic amine-substituted benzoic acids as PPARα agonists

A series of novel cyclic amine-substituted benzoic acid derivatives were synthesized and evaluated for their PPARα agonist activity. Strucure-activity relationship studies led to the identification of (S)-3-[3-[2-(4-chlorophenyl)-4-methylthyazole-5-carboxamido]piperidin-1-yl]benzoic acid (S)-4f (KRP-105) as a potent and high subtype-selective human PPARα agonist. (S)-4f showed excellent PK profile and oral administration of (S)-4f to high-fat diet dogs effectively lowered triglycerides.