催化动力学测定痕量钴研究综述

综述了近年来催化动力学光度法测定痕量钴的进展情况。对催化显色动力学光度法、催化褪色动力学光度法、催化荧光光度法、阻抑动力学光度法、催化化学发光光度法等几个类别，从反应介质、灵敏度、线性范围等方面介绍了对不同反应体系的研究情况，并对催化动力学光度法测定痕量钴的发展趋势做出预测。     

浅谈路基施工高边坡开挖安全专项措施

介绍了路基施工高边坡开挖安全措施,包括健全安全管理组织机构、施工安全措施、高空作业安全措施、机械作业安全措施等。     

A genome-wide scan identifies mutations in the gene encoding phosphodiesterase 11A4 (PDE11A) in individuals with adrenocortical hyperplasia

Phosphodiesterases (PDEs) regulate cyclic nucleotide levels. Increased cyclic AMP (cAMP) signaling has been associated with PRKAR1A or GNAS mutations and leads to adrenocortical tumors and Cushing syndrome. We investigated the genetic source of Cushing syndrome in individuals with adrenocortical hyperplasia that was not caused by known defects. We performed genome-wide SNP genotyping, including the adrenocortical tumor DNA. The region with the highest probability to harbor a susceptibility gene by loss of heterozygosity (LOH) and other analyses was 2q31-2q35. We identified mutations disrupting the expression of the PDE11A isoform-4 gene (PDE11A) in three kindreds. Tumor tissues showed 2q31-2q35 LOH, decreased protein expression and high cyclic nucleotide levels and cAMP-responsive element binding protein (CREB) phosphorylation. PDE11A codes for a dual-specificity PDE that is expressed in adrenal cortex and is partially inhibited by tadalafil and other PDE inhibitors; its germline inactivation is associated with adrenocortical hyperplasia, suggesting another means by which dysregulation of cAMP signaling causes endocrine tumors.     

The chick ovomucoid gene contains at least six intervening sequences.

A 15-kilobase pair EcoRI chick DNA fragment, containing both the termination codon UGA and the 5'-portion of the structural ovomucoid gene, has been cloned in lambda phage Charon 4A by in vitro packaging. Restriction mapping and electron microscopic analyses of this cloned DNA have revealed that the structural ovomucoid gene sequences are separated by at least six intervening sequences.     

Cdc25b phosphatase is required for resumption of meiosis during oocyte maturation

In a wide variety of animal species, oocyte maturation is arrested temporarily at prophase of meiosis I (ref. 1). Resumption of meiosis requires activation of cyclin-dependent kinase-1 (CDK1, p34cdc2), one component of maturation-promoting factor (MPF). The dual specificity phosphatases Cdc25a, Cdc25b and Cdc25c are activators of cyclin-dependent kinases; consequently, they are postulated to regulate cell-cycle progression in meiosis and mitosis as well as the DNA-damage response. We generated Cdc25b-deficient (Cdc25b-/-) mice and found that they are viable. As compared with wildtype cells, fibroblasts from Cdc25b-/- mice grew vigorously in culture and arrested normally in response to DNA damage. Female Cdc25b-/- mice were sterile, and Cdc25b-/- oocytes remained arrested at prophase with low MPF activity. Microinjection of wildtype Cdc25b mRNA into Cdc25b-/- oocytes caused activation of MPF and resumption of meiosis. Thus, Cdc25b-/- female mice are sterile because of permanent meiotic arrest resulting from the inability to activate MPF. Cdc25b is therefore essential for meiotic resumption in female mice. Mice lacking Cdc25b provide the first genetic model for studying the mechanisms regulating prophase arrest in vertebrates.     

Diverse supernova sources of pre-solar material inferred from molybdenum isotopes in meteorites

Variations in the isotopic composition of some components in primitive meteorites demonstrate that the pre-solar material was not completely homogenized, nor was it processed at sufficiently high temperatures to erase the signatures of the diverse stellar sources. This is in accord with the observation that accretion disks of young stellar objects are at relatively low temperatures. Carbonaceous chondrites are considered to represent the 'average' Solar System composition; the rare pre-solar grains in the matrixes of carbonaceous chondrites have been used to identify some sources of the pre-solar material. Here we report that the molybdenum isotopic composition of bulk carbonaceous chondrites is distinctly different from the accepted average solar value. We show that the Mo data require the presence of material produced in at least two different r-processes, and that the contribution from the p-process material is decoupled from the r-process, all occurring in supernova explosions. This is consistent with the emerging picture of diverse sources inferred from short-lived isotopes in the early Solar System and elemental analyses of metal-poor stars.