利用米曲霉自身溶壁酶制备原生质体的研究

真菌原生质体融合作为生物工程的一种新技术,日益受到了人们广泛的重视,而制备原生质体则是原生质体融合的前提。各种真菌细胞壁的结构与化学组成不尽相同,因此制备不同种真菌的原生质体所要求的溶壁酶也有差异。曲霉制备原生质体一般可采用蜗牛酶,但米曲霉     

用三种不同方法生产的BT(库斯塔克变种)制剂及其对家蚕的毒力

一前言在微生物杀虫剂中,苏芸金杆菌是最成功的商品制剂。活孢子和足量的σ-內毒素是该产品主要的毒素成分。众所周知,产品的毒力是根据菌株(不同菌株及同一菌株的不同株系)、培养基和生长条件的不同而异(Dulmage and Rhodes,1971)。但是,使用相同菌株在体外和体内条件下的培养物所进行的毒性比较尚未见报道。最近,我们用苏芸金杆菌(简称     

超声图像定量诊断研究——附123例分析

自1993年以来,我们用自制的DFY—Ⅰ型多功能超声定量诊断仪,测定组织结构超声图像的分贝(dB)、灰阶(GS)值。本文检测分析123例正常心脏,肝脏、肾脏、胎盘及胎儿骨骼测值,在超声定量诊断上迈出了步子。     

THE LASER TOMOGRAPHICAL METHOD USINGMINIMUM OF PROJECTION FOR BIOLOGICAL OBJECT STRUCTURE STUDY

ＴＨＥＬＡＳＥＲＴＯＭＯＧＲＡＰＨＩＣＡＬＭＥＴＨＯＤＵＳＩＮＧＭＩＮＩＭＵＭＯＦＰＲＯＪＥＣＴＩＯＮＦＯＲＢＩＯＬＯＧＩＣＡＬＯＢＪＥＣＴＳＴＲＵＣＴＵＲＥＳＴＵＤＹＹｕｒｉＮ．Ｋｕｌｃｈｉｎ;ＯｌｅｇＢ．Ｖｉｔｒｉｋ;ＯｌｅｇＶ．Ｋｉｒｉｃｈｅｉ...     

Chemiluminescence of enterococci isolates from freshwater

All Enterococcus spp., isolated from environmental water samples (n=81), emitted a high chemiluminescence signal in the presence of luminol (10(-2) M). Kinetic studies of chemiluminescence show a close correlation between chemiluminescence and growth curves during the exponential phase, with a maximum chemiluminescence reached just before bacterial growth entered in the stationary phase. On the other hand, genera closely related to Enterococcus such as Streptococcus or Lactococcus produced a very weak chemiluminescent signal. Chemiluminescence of enterococci could therefore offer a rapid test, in aiding the identification of the genus Enterococcus and in the survey of the microbiological quality of water supplies.     

The role of monocyte/macrophages as vehicles of dissemination of Simkania negevensis: an in vitro simulation model

Exposure to Simkania negevensis (Sn), an intracellular microorganism that has been associated with respiratory tract infections in infants and adults, is prevalent. Sn can multiply within free-living amoebae and has been detected in domestic water supplies, which may constitute a source of infection with the organism. Its path of transport from its portal of entry to the body to its target organs is unknown. In this study, the possibility that monocytes/macrophages may serve as vehicles of transmission was examined. In vitro cocultivation of Sn-infected Acanthamoeba polyphaga with the monocyte/macrophage cell line U937 resulted in the death of the amoebae and infection of the U937 cells. Sn entered and multiplied in U937 cells within short periods of time, and the microorganism could be transferred from U937 cells to cell cultures of various origins. Uninfected monocyte/macrophages could become infected when in contact with either actively or persistently Sn-infected cell cultures. Persistently infected cultures in contact with uninfected U937 cells became actively infected. The results of this study provide a basis for determination of the molecular mechanisms of monocyte/macrophage-cell interactions in transfer of infection and may contribute to a better understanding of the pathogenesis of Sn infections in vivo.     

Anti-stress activity of Propionibacterium freudenreichii: identification of a reactivative protein

Propionibacterium freudenreichii subsp. shermanii is known to prevent mutations caused by various agents such as N-methyl-N'-nitro-N-nitrosoguanidine, 9-aminoacridine, 4-nitro-quinoline-1-oxide and by UV radiation in both prokaryotic and eukaryotic cells. It was also shown to prevent or repair damage caused by H(2)O(2) or UV radiation in Salmonella typhimurium and Escherichia coli, a characteristic previously designated as reactivative effect. In order to characterise this effect at the molecular level, we have purified the active component from a P. freudenreichii cell-free extract using a combination of ammonium sulfate precipitation, anion-exchange and size-exclusion chromatography. The isolated 35 kDa protein was then identified using both N-terminal and internal peptide sequencing as a cysteine synthase. The latter was localised in the P. freudenreichii proteomic map. It is constitutively expressed but also clearly induced during adaptation to detergent and heat, but not acid, stresses. The biological meaning of cysteine synthase in the context of adaptation to oxidative and non-oxidative stresses is discussed.     

alpha2,6-Sialylation promotes binding of placental protein 14 via its Ca2+-dependent lectin activity: insights into differential effects on CD45RO and CD45RA T cells

Placental protein 14 (PP14; glycodelin) is a pregnancy-associated immunoregulatory protein that is known to inhibit T cells via T-cell receptor desensitization. The recent demonstration of PP14 as lectin has provided insight into how it may mediate its CD45 glycoprotein-dependent T-cell inhibition. In this study, we have investigated PP14's lectin-binding properties in detail. Significantly, PP14 reacts with N-acetyllactosamine (LacNAc) as was also found for members of the galectin family, such as the potent immunoregulatory protein, galectin-1. However, in contrast to galectin-1, PP14's binding is significantly enhanced by alpha2,6-sialylation and also by the presence of cations. This was demonstrated by preferential binding to fetuin as compared with its desialylated variant asialofetuin (ASF) and by using free alpha2,6- versus alpha2,3-sialylated forms of LacNAc in competitive inhibition and direct solid-phase binding assays. Interestingly, from immunological point of view, PP14 also binds differentially to CD45 isoforms known to differ in their degree of sialylation. PP14 preferentially inhibits CD45RA+, as compared with CD45RO+ T cells, and preferentially co-capped this variant CD45 on the T-cell surface. Finally, we demonstrate that PP14 promotes CD45 dimerization and clustering, a phenomenon that may regulate CD45 activity.     

Variation in the life history pattern of Tetranychus urticae (Acari: Tetranychidae) after selection for dispersal

The spider mite Tetranychus urticae shows variation in its dispersal capacity (i.e., the leaf quality at which a female decides to disperse). We were able to artificially select mites that had either a high or a low dispersal capacity, indicating that this trait was genetically controlled. We then compared correlated responses to this selection. Mites with a genetically high dispersal capacity (‘HD’ strains) had a higher diapause incidence and a lower performance compared to mites with a low dispersal capacity (‘LD’ strains). A possible effect of random genetic drift during the selection was negligible. Our results suggest that differential dispersal capacity is associated with contrasting life history patterns as a result of natural selection. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modification of a virulence-associated phenotype after growth of Listeria monocytogenes on food

AIM: To assess the effect of different foods, which have been implicated or not in cases of listeriosis, on the in vitro virulence-associated phenotype level of different Listeria monocytogenes strains. METHODS AND RESULTS: The virulence-associated phenotype level of L. monocytogenes was studied with the in vitro cell test based on a plaque-forming assay with a human adenocarcinoma cell line (HT-29) monolayer. Three strains of L. monocytogenes were grown in preparations (homogenate, 1-mum filtrate or 0.2-mum filtrate) of different food extracts ['rillettes' (potted minced pork), milk, raw salmon and cold-smoked salmon] or in a control medium, brain heart infusion (BHI). The bacterial suspensions grown in food extracts or in BHI at 37 degrees C were diluted with their growth medium (food extract or BHI) or with minimum essential medium before seeding on confluent HT-29 cell monolayers. Filtration of food extracts had no significant effect on the plaque numbers formed by the bacteria. A significant decrease in the plaque numbers was noted for the three strains when they grew in the rillettes extracts, compared with the other food extracts and BHI. The levels of in vitro virulence-associated phenotype of the strains after growth in the rillettes extract were similar to or lower than that of the hypovirulent internal reference strain L. monocytogenes 442. After growth in milk and cold-smoked salmon, the impact on virulence-associated phenotype depended on the strain. In contrast, plaque-forming assay indicated increased virulence-associated phenotype when the strains were switched from a nutrient-rich medium (food extract or BHI) to a minimum essential medium. CONCLUSIONS: In vitro virulence-associated phenotype level of the studied strains grown in BHI or cold-smoked salmon was the same as the control virulent strain EGD. In contrast, the nutrients present in rillettes may therefore substantially reduce the number of plaques but not the growth of L. monocytogenes. The utilization of minimum essential medium as diluent attenuates changes the effect of the food extract on virulence-associated phenotype in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: In the experimental design of this study, we showed that the nature of the food could affect the in vitro virulence-associated phenotype level of L. monocytogenes.