Rapid identification of Streptococcus pneumoniae by PCR amplification of ribosomal DNA spacer region

Abstract Streptococcus pneumoniae is one of the important human pathogens in clinical microbiology. A polymerase chain reaction assay was designed to detect and identify S. pneumoniae through amplification of the ribosomal DNA spacer regions between the pneumococcal 16S-23S ribosomal RNA genes. Thirty-two Streptococcus and non- Streptococcus strains were tested to verify the specificity of the assay, and only S. pneumoniae strains gave a positive reaction. This method is a powerful technique for the rapid identification of S. pneumoniae .     

A Molecular Dynamics Study of the Stereoselective Interaction between an Enantiomeric Amino-Acid Ester and an l-Histidine-Containing Catalyst in the Bilayer Membrane

Molecular dynamics simulations were performed to investigate the stereoselective interaction between an enantiomeric amino acid substrate (N-acylated-l-phenylalanine-p-nitrophenyl ester) and an l-histidine-containing dipeptide catalyst (N-(N-benzyloxycarbonyl-l-leucyl)-l-histidine) in the bilayer of cationic surfactants (N,N-bisdodecyl-N,N-dimethylammonium chloride). We found that a catalyst–substrate complex, which had an interamide hydrogen bond, was formed spontaneously in vacuum at 500 K. This complex was found to be stable both in vacuum and in the bilayer membrane for 100 ps at 300 K. The distances between the hydrophobic side chains in the complex were consistent with experimental results. The interamide hydrogen bond was retained in the hydrophobic core of the membrane. These results suggest that the catalyst–substrate complex found in this work is relevant to the stereoselective hydrolysis of the l-enantiomer of the substrate.     

Are minichromosomes valid model systems for DNA replication control? Lessons learned from Escherichia coli

Initiation of chromosome replication is a key event in the life cycle of any organism. Little is known, however, about the regulatory mechanisms of this vital process. Conventionally, the initiation mechanism of chromosome replication in microorganisms has been studied using plasmids in which an origin of chromosome replication has been cloned, rather than using the chromosome itself. The reason for this is that even bacterial chromosomes are so large that biochemical and genetic manipulations become difficult and cumbersome. Recently, the combination of flow cytometry and genetic methods, in which modifications of the replication origin are systematically introduced onto the chromosome, has made possible detailed studies of the molecular events involved in the control of replication initiation in Escherichia coli . The results indicate that requirements for initiation at the chromosomal origin, oriC , are drastically different from those for initiation at cloned oriC .     

Cytological distribution of chorionic gonadotropin subunit and placental lactogen messenger RNA in neoplasms derived from human placenta

Normal trophoblast of the human placenta elaborates at least two major protein hormones, chorionic gonadotropin (hCG), and placental lactogen (hPL). There are several gestational trophoblastic diseases of the placenta called hydatidiform mole, invasive mole, and choriocarcinoma. Molar and choriocarcinoma tissues characteristically synthesize large amounts of hCG and small quantities of hPL. To examine the role of trophoblast differentiation in the expression of the hCG and hPL genes, we studied the cytological distribution of their messenger RNA (mRNA) in tissue sections of human hydatidiform mole and choriocarcinoma by in situ hybridization. Histologically, these tissues are in different stages of cellular differentiation. In normal placenta, hCG alpha and - beta mRNA can be localized to some cytotrophoblasts and primarily to the syncytium, whereas hPL mRNA appears only in the syncytial layer. In hydatidiform mole, which still retains placental villous morphology, the hPL gene and hCG alpha and -beta genes are expressed but are poorly localized because of the admixture of cyto- and syncytiotrophoblasts. By contrast, choriocarcinoma, which is devoid of placental villous pattern but in which the cyto- and syncytiotrophoblast-like components are distinguishable, expresses hCG alpha and -beta in the syncytial- like areas but little, if any, hPL. These results suggest that a certain level of trophoblast differentiation, such as villous formation, is associated with hPL expression, while the hCG alpha gene and the hCG beta gene can be expressed in more disorganized tissues that contain cytotrophoblastic elements.     

Vibronic attraction energy for superconductivity in the model of Si-containing organic polymers

Superconducting vibronic interaction has been examined for a model of Si-substituted polyacetylene. Large attractive vibronic interaction for the formation of superconducting electron pair has been found for the electron scattering process in between the and in-plane orbitals in silene unit. Doping of holes in these orbitals would be done by extracting electrons from the out-of-plane orbitals as well as from the in-plane orbitals. If stacking of the model polymers is performed in a parallel manner, the interplane electron pairing has also been found to be favorable on account of small Coulombic repulsion.     

Atypical virulence in a type III Toxoplasma gondii strain isolated in Japan

The virulence of a type III Toxoplasma gondii strain isolated in Japan and designated here as TgCatJpGi1/TaJ was examined in mice and micro minipigs in this study. Despite its type III genotype, oral or intraperitoneal inoculation of cysts from it resulted in severe virulence in C57BL/6J and BALB/c mice. In contrast, mice inoculated with a high dose of TgCatJpGi1/TaJ tachyzoites showed no obvious clinical signs of infection, and all of them survived for >21?days post-inoculation. Furthermore, no clinical signs of infection were seen when micro minipigs were inoculated with 900 cysts. Interestingly, our allelic type screening of the virulence-related rop5, rop16, rop17, and rop18 genes, as based on restriction fragment length polymorphism analysis (RFLP), revealed that the RFLP patterns for TgCatJpGi1/TaJ were identical to those from nonvirulent type III parasites. These results suggest that TgCatJpGi1/TaJ possesses an unknown virulence factor or factors.