Hypomorphic mutation in an essential cell-cycle kinase causes growth retardation and impaired spermatogenesis

Cdc7 kinase is essential for initiation of DNA replication. Cdc7(-/-) mouse embryonic stem (ES) cells are non-viable but their growth can be rescued by an ectopically expressed transgene (Cdc7(-/-)tg). Here we report that, despite the normal growth capability of Cdc7(-/-)tg ES cells, the mice with the identical genetic background exhibit growth retardation. Concomi tantly, Cdc7(-/-)tg embryonic fibroblasts (MEFs) display delayed S phase entry and slow S phase progression. Furthermore, spermatogenesis of Cdc7(-/-)tg mice is disrupted prior to pachytene stage of meiotic prophase I. The impairment in spermatogenesis correlates with the extremely low level of Cdc7 protein in testes, and is rescued by introducing an additional allele of transgene, which results in increase of Cdc7 expression. The increased level of Cdc7 also recovers the growth of Cdc7(-/-)tg MEFs and mice, indicating that the developmental abnormalities of Cdc7(-/-)tg mice are due to insufficiency of Cdc7 protein. Our results indicate the requirement of a critical level of a cell-cycle regulator for mouse development and provide genetic evidence that Cdc7 plays essential roles in meiotic processes in mammals.     

Membrane sterol composition modulates the pore forming activity of syringomycin E in human red blood cells

The syndrome of hypoparathyroidism associated with growth retardation, developmental delay, and dysmorphism (HRD) is a newly described, autosomal recessive, congenital disorder with severe, often fatal consequences. Since the syndrome is very rare, with all parents of affected individuals being consanguineous, it is presumed to be caused by homozygous inheritance of a single recessive mutation from a common ancestor. To localize the HRD gene, we performed a genomewide screen using DNA pooling and homozygosity mapping for apparently unlinked kindreds. Analysis of a panel of 359 highly polymorphic markers revealed linkage to D1S235. The maximum LOD score obtained was 4.11 at a recombination fraction of 0. Analysis of three additional markers-GGAA6F06, D1S2678, and D1S179-in a 2-cM interval around D1S235 resulted in LOD scores >3. Analysis of additional chromosome 1 markers revealed evidence of genetic linkage disequilibrium and place the HRD locus within an approximately 1-cM interval defined by D1S1540 and D1S2678 on chromosome 1q42-43.     

Functional metal-porphyrazine derivatives and their polymers, 10. Secondary fuel cells based on oxygen reduction on platinum electrode modified by polymers and metal-phthalocyanines

Secondary fuel cells based on oxygen reduction of platinum electrode modified by polymers and metal-phthalocyanine (Mt = Fe(III), Co(II), Ni(II), and Cu(II)) were studied. The discharge curves for the platinum electrode modified by poly(2-vinylpyridine) (or polystyrene) and Co-phthalocyanine in 30% KOH aqueous solution, for a 30 min charge at 500 μA, followed by a 100 μA discharge showed a stable plateau at about ?0.24 V SCE (Saturated Calomel Electrode). The open circuit voltage (vs. Zn) of the cell was 1.2 V, and the discharge capacity was of 46 A · h/kg. For this battery there was no significant decay in its characteristics after more than 30 charge-discharge cycles. In Mt-phthalocyanines, the values decreased in the order of Co(II) > Fe(III) > > Cu(II) > Ni(II). From a cyclic voltammogram for the electrode modified by the polymer and Co-Pc, the cathodic reactions were discussed.     

Functional monomers and polymers, 64. Synthesis of poly-β-alanine from β-alanine, β-alanyl-β-alanine,and β-alanyl-β-alanyl-β-alanine 4-dodecanoyl-2-nitrophenyl esters

Active 4-dodecanoyl-2-nitrophenyl esters of β-alanine, β-alanyl-β-alanine, and β-alanyl-β-alanyl-β-alanine were prepared, and tried to polymerize in various solvents. Nonpolar solvents were found to be convenient for the polycondensation reaction. The yield of the polycondensation was high for the monopeptide ester, and less for the dipeptide and tripeptide esters. The effect of temperature on the polycondensation reaction was also studied.     

Vinyl polymerization by metal complexes. XVIII. Kinetics of the polymerization of acrylonitrile initiated by imidazole-copper-(II) complexes

A study on the kinetics and mechanism of the polymerization of acrylonitrile initiated by imidazole and 2-substituted imidazole-copper-(II) complexes was made in dimethyl sulfoxide solution at 40–70°C. The rate of polymerization, Rp, could be expressed as follows: The overall activation energies of these polymerization processes are in a range from 14.2 to 69.1 KJ mole^-1. From the data of electronic spectra and electron paramagnetic resonance, it was confirmed that the polymerization in question could be initiated by free radicals which were formed by the reduction of copper-(II) complex to copper-(I) complex, and the latter formed a new complex with polyacrylonitrile resulted.     

Synthesis of High Density and Transparent Forsterite Ceramics Using Nano-Sized Precursors and Their Dielectric Properties

Forsterite (Mg₂SiO₄) ceramics were prepared using Mg(OH)₂ and SiO₂ as precursors, and the effect of powder characteristics of Mg(OH)₂ on calcination and sintering was investigated. The use of highly dispersed Mg(OH)₂ powder (HD powder) resulted in a lower calcination temperature. Forsterite powder of high homogeneity and small particle size prepared from the HD powder enabled synthesis of high-density forsterite ceramics by ordinary sintering without applying external pressure. Moreover, transparent forsterite ceramics were successfully synthesized through addition of excess Mg to the precursors to compensate for Mg evaporated during the sintering process. Subsequent dielectric measurements revealed that the transparent forsterite ceramics had a very low dielectric loss (tan δ<10⁻⁴).     

The yttrium effect on the corrosion resistance of CO2-laser processed MCrAlY coatings

To improve the corrosion resistance and to study the effect of yttrium in the behavior of coatings produced by thermal spraying MCrAlY (M=Ni, Co) powders, CO₂ laser processing was conducted. Three methods were used: (1) a combination of gas flame and plasma spraying in air followed by laser glazing in argon, (2) low-pressure plasma spraying (LPPS) and laser glazing in argon, and (3) LPPS and laser-gas (O₂) alloying. Laser glazing in argon of the MCrAlY coatings sprayed in air promoted formation of weakly adherent agglomerates of Al–Y oxides and an alumina-chromia solid solution. Glazing in argon atmosphere of LPPS CoNiCrAlY and NiCrAlY coatings caused the formation of nickel aluminides besides the formation of Y–Al compounds. Gas (O₂)-alloying of these coatings produces continuous and adherent (yttrium-containing) alumina and chromia layers. The effects of yttrium on the characteristics of the oxides formed in the coatings during laser glazing, laser-gas alloying, and high-temperature oxidation is discussed. This work also investigated the oxidation resistance of the laser-processed MCrAlY coatings in air and in the presence of 85 mol/o V₂O₅–Na₂SO₄ fused salt at 900°C.     

Fracture dynamics of sprayed and laser-glazed titania by an inverse processing of elastic waves

A new elastic wave (EW) or acoustic emission (AE) monitoring and signal processing system has been developed and used to elucidate the fracture behavior of sprayed and laser-glazed ceramic coatings. The system measures the minute surface displacements excited by the propagation of elastic waves. It enables elucidation of the fracture dynamics (fracture mode and kinetics) of stressed coatings. The surface displacement at the sensor position was computed by the convolution integral of an assumed source wave with the dynamic Green’s function until signals resembled the measured wave. This new signal processing method was used to determine the fracture strength and dynamics of microcracks in sprayed and laser-glazed titania subjected to four-point bending. It was found that mode II shear cracking along the interface between the coating and substrate occurred prior to mode I cleavage cracking. The fracture strength of laser-glazed titania was higher than that of as-sprayed titania in most cases; however, this depended on the coating structure. This article introduces the principle of source inversion processing of elastic waves, the monitoring system, laser glazing of sprayed titania, and experimental work on the fracture behavior of titania coatings.