The effect of molecular packing on the occurrence of spin crossover phenomena in one-dimensional Fe(II)-bis-Schiff base complexes

Two new one-dimensional Fe(II)-bis-Schiff base complexes, [Fe(L1)(pyz)] · CH₂Cl₂ (1) and [Fe(L2)(pyz)] · 2CH₂Cl₂ (2) (H₂L1 = bis(O-vanillin)-O-phenylenediimine, H₂L2 = bis(O-vanillin)-2,3-naphthalenediimine, pyz = pyrazine) are reported with their crystal structures and magnetic property. Compound 1 shows a two-step SCO behavior while 2 shows HS at all the temperature range measured. Although the extension of aromatic moiety from benzene (L1) to naphthalene (L2) was introduced for the purpose of strengthening the cooperativity, it leads to the absence of SCO, due to the unanticipated π–π interaction, which leads to the longer Fe–N bond lengths and a weak ligand field around Fe(II) ion.     

Culture of endodermal stem/progenitor cells of the mouse tongue

The tongue represents a very accessible source of tissue-specific epithelial stem cells of endodermal origin. However, little is known about the properties of these cells and the mechanisms regulating their proliferation and differentiation. Foxa2, an endodermal marker, is expressed throughout the tongue epithelium during embryonic development but becomes confined to a minority of basal cells and some taste bud sensory cells in the adult tongue. Using a previously described line of transgenic mice in which enhanced green fluorescent protein (eGFP) is expressed under the control of a human keratin 5 promoter region (Krt5-eGFP), we have isolated a subpopulation of cells in the basal epithelial layer of the mouse tongue with a high efficiency of generating holoclones of undifferentiated cells in culture with a feeder layer. Krt5-GFP(hi) cells can both self renew and give rise to differentiated stratified keratinized epithelial cells when cultured on an air-liquid interface.     

Chemical modification of aryl-1,2,3,6-tetrahydropyridinopyrimidine derivative to discover corticotropin-releasing factor(1) receptor antagonists: aryl-1,2,3,6-tetrahydropyridino-purine, -3H-1,2,3-triazolo[4,5-d)pyrimidine, -purin-8-one, and -7H-pyrrolo[2,3-d]pyrimidine derivatives

Structure-affinity relationships (SARs) of non-peptide CRF(1) antagonists suggest that such antagonists can be constructed of three units: a hydrophobic unit (Up-Area), a proton accepting unit (Central-Area), and an aromatic unit (Down-Area). Recently, various non-peptide corticotropin-releasing factor(1) (CRF(1)) receptor antagonists obtained by modification of the Central-Area have been reported. In contrast, we modified the Up-Area and presented 4- or 5-aryl-1,2,3,6-tetrahydropyridinopyrimidine derivatives including potent CRF receptor ligands 1a-c, and proposed that the 4- or 5-aryl-1,2,3,6-tetrahydropyridino moiety might be useful as a substituent in the Up-Area. Our interest shifted to the chemical modification in which the pyrimidine ring of 1a-c was replaced by other heterocycles, purine ring of 2, 3H-1,2,3-triazolo[4,5-d]pyrimidine ring of 3, purin-8-one ring of 4 and 7H-pyrrolo[2,3-d]pyrimidine ring of 5. Among them, 5-aryl-1,2,3,6-tetrahydropyridinopurine compound 6j (CRA0186) had the highest affinity for CRF(1) receptors (IC(50)=20nM). We report here the synthesis and SARs of derivatives 6-9.     

Association of Veterinary Third-Generation Cephalosporin Use with the Risk of Emergence of Extended-Spectrum-Cephalosporin Resistance in Escherichia coli from Dairy Cattle in Japan

The use of extended-spectrum cephalosporins in food animals has been suggested to increase the risk of spread of Enterobacteriaceae carrying extended-spectrum β-lactamases to humans. However, evidence that selection of extended-spectrum cephalosporin–resistant bacteria owing to the actual veterinary use of these drugs according to criteria established in cattle has not been demonstrated. In this study, we investigated the natural occurrence of cephalosporin-resistant Escherichia coli in dairy cattle following clinical application of ceftiofur. E. coli isolates were obtained from rectal samples of treated and untreated cattle (n = 20/group) cultured on deoxycholate-hydrogen sulfide-lactose agar in the presence or absence of ceftiofur. Eleven cefazoline-resistant isolates were obtained from two of the ceftiofur-treated cattle; no cefazoline-resistant isolates were found in untreated cattle. The cefazoline-resistant isolates had mutations in the chromosomal ampC promoter region and remained susceptible to ceftiofur. Eighteen extended-spectrum cephalosporin–resistant isolates from two ceftiofur-treated cows were obtained on ceftiofur-supplemented agar; no extended-spectrum cephalosporin–resistant isolates were obtained from untreated cattle. These extended-spectrum cephalosporin–resistant isolates possessed plasmid-mediated β-lactamase genes, including bla _CTX-M-2 (9 isolates), bla _CTX-M-14 (8 isolates), or bla _CMY-2 (1 isolate); isolates possessing bla _CTX-M-2 and bla _CTX-M-14 were clonally related. These genes were located on self-transmissible plasmids. Our results suggest that appropriate veterinary use of ceftiofur did not trigger growth extended-spectrum cephalosporin–resistant E. coli in the bovine rectal flora; however, ceftiofur selection in vitro suggested that additional ceftiofur exposure enhanced selection for specific extended-spectrum cephalosporin–resistant β-lactamase-expressing E. coli clones     

Procedure for the efficient acquisition of progeny seeds from crossed potato plants grafted onto tomato

Potato, Solanum tuberosum L. is an important crop. However, it is difficult to breed potato cultivars by applying conventional crossing methods because potato has a tetraploid genome and is vegetatively propagated. Flower formation and tuber development occur simultaneously. Many potato cultivars hardly produce any fruits after crossing and fail to produce seeds. We report an improved procedure for obtaining progeny seeds by grafting potatoes onto tomatoes. The rate of fruit formation was more than 19% when the grafted potatoes were used for the crossing experiments, whereas crossing using the ungrafted plants showed a rate of 1.1%. This result suggests that our procedure results in the easy acquisition of null-segregant progenies by crossing mutant lines. It is also expected to improve conventional potato breeding.     

Structure and function of psychrophilic alanine racemase

We describe the structure and function of psychrophilic alanine racemases from Bacillus psychrosaccharolyticus and Pseudomonas fluorescens. These enzymes showed high catalytic activities even at 0°C and were extremely labile at temperatures over 35°C. The enzymes were also found to be less resistant to organic solvents than alanine racemases from thermophilic and mesophilic bacteria, both in vivo and in vitro. Both enzymes have a dimeric structure and contain 2 mol of pyridoxal 5′-phosphate (PLP) per mol as a coenzyme. The enzyme from B. psychrosaccharolyticus was found to have a markedly large K_m value (5.0 μM) for PLP in comparison with other reported alanine racemases, and was stable at temperatures up to 50°C in the presence of excess amounts of PLP. The dissociation of PLP from the P. fluorescens enzyme may trigger the unfolding of the secondary structure. The enzyme from B. psychrosaccharolyticus has a distinguishing hydrophilic region around residue no. 150 in its deduced amino acid sequence, whereas the corresponding regions of other Bacillus alanine racemases are hydrophobic. The position of this region in the three dimensional structure of this enzyme was predicted to be in a surface loop surrounding the active site. This hydrophilic region may interact with solvent, reduce the compactness of the active site, and destabilize the enzyme.