ABSTRACT
Water molecules are known to play crucial roles both in the formation and biological function of materials. Herein, we show the presence of "intermediate water" on an inorganic solid material, hydroxyapatite. In vitro experiments revealed that Mg substitution of apatite significantly enriched the amount of intermediate water, possibly due to the proton transfer to a hydrogen-bonded network of water around HPO42- on divalent-cation-deficient apatite surfaces. The intermediate water formation related to a markedly suppressed protein adsorption on apatite. Analysis of bone apatites suggested that the intermediate water on minerals could play crucial roles in regulating crystal growth.
ABSTRACT
Graft copolymers composed of poly(2-methoxyethyl acrylate) are prepared employing controlled radical polymerization techniques. Linear backbones bearing atom transfer radical polymerization (ATRP) initiating sites are obtained by reversible addition-fragmentation chain transfer copolymerization of 2-methoxyethyl acrylate (MEA) and 2-(bromoisobutyryloxy)ethyl methacrylate (Br(i) BuEMA) as well as 2-hydroxyethyl methacrylate and Br(i) BuEMA in a controlled manner . MEA is then grafted from the linear macroinitiators by Cu (I)-mediated ATRP. Fairly high molecular weights (>120 000 Da) and low polydispersity indices (1.17-1.38) are attained. Thermal investigations of the graft copolymers indicate the presence of the freezing bound water, and imply that the materials may exhibit blood compatibility.
Subject(s)
Acrylates/chemistry , Polymers/chemistry , Water/chemistry , Acrylates/chemical synthesis , Biocompatible Materials/chemistry , Polymers/chemical synthesisABSTRACT
The cerebellum develops from the rhombic lip of the rostral hindbrain and is organized by fibroblast growth factor 8 (FGF8) expressed by the isthmus. Here we report characterization of Irx2, a member of the Iroquois (Iro) and Irx class of homeobox genes, that is expressed in the presumptive cerebellum. When Irx2 is misexpressed with Fgf8a in the chick midbrain, the midbrain develops into cerebellum in conjunction with repression of Otx2 and induction of Gbx2. During this event, signaling by the FGF8 and mitogen-activated protein (MAP) kinase cascade modulates the activity of Irx2 by phosphorylation. Our data identify a link between the isthmic organizer and Irx2, thereby shedding light on the roles of Iro and Irx genes, which are conserved in both vertebrates and invertebrates.
Subject(s)
Cerebellum/embryology , Cerebellum/metabolism , Fibroblast Growth Factors/biosynthesis , Homeodomain Proteins/biosynthesis , MAP Kinase Signaling System/physiology , Transcription Factors/biosynthesis , Animals , COS Cells , Chick Embryo , Chlorocebus aethiops , Fibroblast Growth Factor 8 , Fibroblast Growth Factors/genetics , Gene Expression Regulation, Developmental/physiology , Homeodomain Proteins/genetics , Mice , Transcription Factors/geneticsABSTRACT
Extensive misexpression studies were carried out to explore the roles played by Tbx5, the expression of which is excluded from the right ventricle (RV) during cardiogenesis. When Tbx5 was misexpressed ubiquitously, ventricular septum was not formed, resulting in a single ventricle. In such heart, left ventricle (LV)-specific ANF gene was induced. In search of the putative RV factor(s), we have found that chick Tbx20 is expressed in the RV, showing a complementary fashion to Tbx5. In the Tbx5-misexpressed heart, this gene was repressed. When misexpression was spatially partial, leaving small Tbx5-negative area in the right ventricle, ventricular septum was shifted rightwards, resulting in a small RV with an enlarged LV. Focal expression induced an ectopic boundary of Tbx5-positive and -negative regions in the right ventricle, at which an additional septum was formed. Similar results were obtained from the transient transgenic mice. In such hearts, expression patterns of dHAND and eHAND were changed with definitive cardiac abnormalities. Furthermore, we report that human ANF promoter is synergistically activated by Tbx5, Nkx2.5 and GATA4. This activation was abrogated by Tbx20, implicating the pivotal roles of interactions among these heart-specific factors. Taken together, our data indicate that Tbx5 specifies the identity of LV through tight interactions among several heart-specific factors, and highlight the essential roles of Tbx5 in cardiac development.
Subject(s)
Heart Septum/anatomy & histology , Heart Septum/embryology , Heart Ventricles/anatomy & histology , Heart Ventricles/embryology , T-Box Domain Proteins/metabolism , Animals , Atrial Natriuretic Factor/genetics , Atrial Natriuretic Factor/metabolism , Basic Helix-Loop-Helix Transcription Factors , Chick Embryo , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Electroporation , Gene Expression Regulation, Developmental , Heart Septum/physiology , Humans , In Situ Hybridization , Mice , Mice, Transgenic , Promoter Regions, Genetic , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , T-Box Domain Proteins/genetics , Transcription Factors/genetics , Transcription Factors/metabolism , Transgenes , Ventricular Function , Zebrafish ProteinsABSTRACT
A tight loop between members of the fibroblast growth factor and the Wnt families plays a key role in the initiation of vertebrate limb development. We show for the first time that Tbx5 and Tbx4 are directly involved in this process. When dominant-negative forms of these Tbx genes were misexpressed in the chick prospective limb fields, a limbless phenotype arose with repression of both Wnt and Fgf genes By contrast, when Tbx5 and Tbx4 were misexpressed in the flank, an additional wing-like and an additional leg-like limbs were induced, respectively. This additional limb formation was accompanied by the induction of both Wnt and Fgf genes These results highlight the pivotal roles of Tbx5 and Tbx4 during limb initiation, specification of forelimb/hindlimb and evolution of tetrapod limbs, placing Tbx genes at the center of a highly conserved genetic program.
