Plasmid curing of Oenococcus oeni

Two strains of Oenococcus oeni, RS1 (which carries the plasmid pRS1) and RS2 (which carries the plasmids pRS2 and pRS3), were grown in the presence of different curing agents and at different temperatures. Sublethal temperature together with acriflavine generated all possible types of cured strains, i.e., lacking pRS1 (from strain RS1), and lacking pRS2, pRS3, or both (from strain RS2). Sublethal temperature together with acridine orange only generated cured strains lacking pRS3. These results suggest that acriflavine is a better curing agent than acridine orange for O. oeni, and that pRS3 is the most sensitive to these curing agents. We also observed spontaneous loss of pRS2 or both pRS2 and pRS3 by electroporation. The ability to cure O. oeni strains of plasmids provides a critical new tool for the genetic analysis and engineering of this commercially important bacterium.     

Plasmid curing effect of trovafloxacin

The effect of sub-inhibitory concentrations of trovafloxacin, a recently developed fluoroquinolone molecule, on the capability of Escherichia coli cells to maintain three different types of plasmids has been investigated by a number of approaches, including the quantification of the loss of plasmid-borne functions and of plasmid DNA by quantitative PCR. The results obtained demonstrate that at concentrations ranging from the MIC to 1/8 of the MIC, trovafloxacin induces a clear, albeit incomplete, 'episome-curing' effect which was observed with plasmids differing in copy number, size and nature of the replication origin of the episome. This effect was most likely not due to an alteration of DNA supercoiling.     

Protoplast-induced curing of bacteriocin plasmid in Lactococcus lactis subsp. lactis 484

Plasmid-specified traits like lactose metabolism and bacteriocin production could be eliminated from Lactococcus lactis subsp. lactis 484 culture during production and regeneration of protoplasts with lysozyme at the concentration of 300 μg/ml after 3 h treatment. Plasmid-free strains and cured derivatives harbouring only a single plasmid (2 MDa) were also obtained. Loss of high molecular weight (65 MDa) low copy number Lac plasmid occurred more frequently compared with low molecular weight (2 MDa) high copy number plasmid. Treatment of L. lactis subsp. lactis 484 cells with lysozyme at concentrations of 1000 μg/ml could produce a large number of Lac⁻ Bac⁻ variants at a very high frequency (94%). The curing data confirmed the linkage of Lac and Bac phenotypes to 65 and 2 MDa plasmids, respectively.     

Effect of inorganic phosphate on acridine inhibition and plasmid curing in Escherichia coli.

Some mutants and stock strains of Escherichia coli K12 were sensitive to acriflavine in the presence of inorganic phosphate but were resistant to acriflavine in its absence. They mutated spontaneously to resistance to acriflavine plus phosphate. The synergistic effect of phosphate on acriflavine sensitivity was increased at high pH values. Genetic analysis suggested that the mutations occurred in the gene acrA. Electron microscopic observation suggested that the presence of acriflavine plus phosphate affected the structure of the plasma membrane and the cytoplasm under it. This structural alteration was not caused by acriflavine alone. Acridine orange plus phosphate can more effectively eliminate the plasmid F8-gal+ than acridine orange alone.     

Antibacterial effect, plasmid curing activity and chemical structure of some tricyclic compounds.

Diethazine, amitriptyline and imipramine showed bacteriostatic and bactericidal effect on different bacteria. Chlorpromazine sulphoxide and fluorescein were ineffective even at 1000 microgram/ml. The antibacterial compounds deleted at 40-70% frequency the F'lac plasmid of Escherichia coli K12 LE-140.     

Phenological observations of grass curing in Germany

The degree of grass curing, i.e. the proportion of dehydrated dead grass per unit grassland area, is one of the most important parameters affecting grassland fire risk and fire behaviour. The objective of the present study was to develop a simple relationship between grass moisture and grass curing to use as an input into the next-generation fire-danger rating models of the Deutscher Wetterdienst. Seasonal changes in yellow and green portions of grass plots were estimated visually at weekly intervals. At the same time, the grass-moisture content was measured gravimetrically after destructive sampling. Regression analysis revealed an exponential relationship between decreasing leaf moisture and increasing yellowing level, in rough agreement with findings reported from Australia and North America.     

A kinetic model for plasmid curing

A simple mathematical model of drug-induced plasmid elimination (curing) considering density-dependent growth rates and plasmid transfers is presented. It describes nonlinear population dynamics of conjugative plasmids during in vitro curing experiments in batch culture. The model was tested on kinetics of acridine orange curing of F'lac plasmid. Effects of density dependence, plasmid elimination, selection for plasmidless segregants, conjugation, initial and maximal population density, and postsegregational killing on curing kinetics are simulated and discussed.     

蕲蛇酶治疗脑梗死疗效观察

脑梗死是由于脑供血障碍使脑组织缺血缺氧而引起的脑软化所致神经功能缺陷性疾病。为提高疗效，1995年12月-2004年12月，我们用蕲蛇酶治疗53例脑梗死患者。现报告如下。     

Medical cost of curing childhood acute lymphoblastic leukaemia

Between 1970 and 1979 acute lymphoblastic leukaemia was diagnosed in 378 children at this hospital. The outcome for the 181 survivors was examined six or more years after diagnosis to assess morbidity in an unselected group of long term survivors. One hundred and thirty seven of the survivors were in first remission and probably cured (group I). Forty four (group II) had had one or more relapses, some of whom, who had isolated extramedullary relapses, also have a good chance of cure.In group I 136 patients had prophylactic cranial or craniospinal irradiation, while patients in group II, in addition to having that treatment, received local testicular (17) or craniospinal radiation (seven) for testicular or central nervous system relapse. Eight had additional prophylactic cranial radiotherapy after bone marrow relapse, and six had total body irradiation before bone marrow transplantation. The incidence of clinically important growth and endocrine morbidity was 20% in group I and 68% in group II. The morbidity in patients in group I was mainly attributable to early pubertal maturation. In group II 30 patients had growth failure, of whom 19 had gonadal failure from testicular or total body irradiation, 14 had growth hormone deficiency after doses of cranial irradiation of over 2400 cGy, and 10 had spinal growth impairment after craniospinal irradiation. Two also had early pubertal maturation. Five out of six patients who received total body irradiation had multiple endocrine deficiency. Neuropsychological sequelae of treatment were seen in 40 (42%) of 96 schoolchildren in group I and in 12 (38%) of 32 schoolchildren in group II. Postinfective sequelae of treatment were found in patients in both groups.These results show that the survivors who were in their first remission had a 42% residual morbidity related to treatment compared with an 82% morbidity in the survivors of one or more relapses who had multiple treatments.     

茯苓多糖在治疗肿瘤方面的临床研究进展

茯苓在药物化学、药理学、临床应用等方面有很高的使用价值。本文主要论述了茯苓药用的主要化学成分,在抗肿瘤和增强免疫力方面的作用,并对茯苓的前景进行了展望,为茯苓的进一步开发提供依据。     

Plasmid profiles and curing of plasmids in Lactobacillus plantarum strains isolated from green olive fermentations.

Plasmid profiles of 35 Lactobacillus plantarum strains isolated from different green olive fermentors were obtained. A large number of plasmids in the CCC form (from 5 to 16) were present in all the tested strains as confirmed by a second dimension electrophoresis of DNA. These plasmids, all of which remain cryptic, ranged from 2.0 to 68 kb in size. Novobiocin, sodium dodecyl sulphate and ethidium bromide were used as plasmid-curing agents but only novobiocin induced loss of extrachromosomal DNA at a high frequency in these strains.