眶脊巨蜂属一新种记述(膜翅目:姬蜂总科, 巨蜂科)

巨蜂科 Megalyridae 是姬蜂总科 Ichneumonoidea 的一个小科,主要分布于大洋洲及南非。寄生于树木的穿孔性昆虫幼虫,我国尚未见报道。眶脊巨蜂属 EttchellsiaCameron(1909)过去仅知2种,分别产于加里曼丹岛和菲律宾。该属的主要特征是:沿复眼上颊眶有一明显的脊(汉名即据此而拟),前缘脉和亚前缘分开;中胸盾片有一明显     

Molecular cloning, nucleotide sequence, and marker exchange mutagenesis of the exo-poly-alpha-D-galacturonosidase-encoding pehX gene of Erwinia chrysanthemi EC16.

The pehX gene encoding extracellular exo-poly-alpha-D-galacturonosidase (exoPG; EC 3.2.1.82) was isolated from a genomic library of the pectate lyase-deficient Erwinia chrysanthemi mutant UM1005 (a Nalr Kanr delta pelABCE derivative of EC16) by immunoscreening 2,800 Escherichia coli HB101 transformants with an antibody against exoPG protein. The cloned pehX gene was expressed highly from its own promoter in E. coli, and most of the enzyme was localized in the periplasm. The nucleotide sequence of pehX revealed the presence of an amino-terminal signal peptide and an open reading frame encoding a preprotein of 64,608 daltons. The cloned pehX gene was insertionally inactivated with TnphoA and used to mutate the chromosomal pehX gene of E. chrysanthemi AC4150 (Nalr) and CUCPB5006 (Nalr Kans delta pelABCE) by marker exchange mutagenesis. Analysis of the resulting mutants, CUCPB5008 (Pel+ Peh-) and CUCPB5009 (Pel- Peh-), indicated that exoPG can contribute significantly to bacterial utilization of polygalacturonate and the induction of pectate lyase in the presence of extracellular pectic polymers. CUCPB5009 retained a slight ability to pit polygalacturonate semisolid agar and macerated chrysanthemum pith tissues when large numbers of bacteria were inoculated.     

Genes of the Escherichia coli pur regulon are negatively controlled by a repressor-operator interaction.

Fusions of lacZ were constructed to genes in each of the loci involved in de novo synthesis of IMP. The expression of each pur-lacZ fusion was determined in isogenic purR and purR+ strains. These measurements indicated 5- to 17-fold coregulation of genes purF, purHD, purC, purMN, purL, and purEK and thus confirm the existence of a pur regulon. Gene purB, which encodes an enzyme involved in synthesis of IMP and in the AMP branch of the pathway, was not regulated by purR. Each locus of the pur regulon contains a 16-base-pair conserved operator sequence that overlaps with the promoter. The purR product, purine repressor, was shown to bind specifically to each operator. Thus, binding of repressor to each operator of pur regulon genes negatively coregulates expression.     

Establishment and characterization of 12S adenoviral E1A immortalized rat submandibular gland epithelial cells

Rat submandibular gland (RSMG) cells have been immortalized with a retrovirus vector which encodes the adenovirus 12S E1A gene product. The immortalized cells were epithelial-like in nature and displayed a beta-adrenergic coupled rise in intracellular cAMP upon exposure to norepinephrine. Western- and lectin-blotting experiments of cell lysates demonstrated the presence of blood group A-reactive oligosaccharides. Such oligosaccharides are characteristic of RSMG mucin-glycoproteins. These cells appear to be suitable for use in analysis of cell-specific factors which regulate RSMG glycosylation.