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91.
Fractionation of a bacterial cell population by adsorption to erythrocytes and yeast cells 总被引:1,自引:0,他引:1
Bogdan Nowicki Mikael Rhen Vuokko Väisänen-Rhen Auli Pere Timo K. Korhonen 《FEMS microbiology letters》1985,26(1):35-40
Abstract Fluorochrome-labeled antibodies specific for either S or type-1 fimbriae of Escherichia coli were used to show that in broth culture the two fimbrial types of strain 3040 mostly occurred on different cells. 12% of the cells were nonfimbriated. A fractionation procedure that involved adsorption of bacterial cells onto erythrocytes and yeast cells was developed to isolate homogeneous subpopulations (S-fimbriated, type-1-fimbriated, and non-fimbriated) of. E. coli. The level of contamination in each isolated subpopulation was 4% at the highest. The method is useful in obtaining homogeneous bacterial populations for adherence studies and for purification of specific fimbrial antigens. 相似文献
92.
A TGF-β type I receptor-like molecule with a key functional role in Haemonchus contortus development
Li He Robin B. Gasser Pasi K. Korhonen Wenda Di Fangfang Li Hongrun Zhang Facai Li Yanqin Zhou Rui Fang Junlong Zhao Min Hu 《International journal for parasitology》2018,48(13):1023-1033
Here we investigated the gene of a transforming growth factor (TGF)-β type I receptor-like molecule in Haemonchus contortus, a highly pathogenic and economically important parasitic nematode of small ruminants. Designated Hc-tgfbr1, this gene is transcribed in all developmental stages of H. contortus, and the encoded protein has glycine-serine rich and kinase domains characteristic of a TGF-β family type I receptor. Expression of a GFP reporter driven by the putative Hc-tgfbr1 promoter localised to two intestinal rings, the anterior-most intestinal ring (int ring I) and the posterior-most intestinal ring (int ring IX) in Caenorhabditis elegans in vivo. Heterologous genetic complementation using a plasmid construct containing Hc-tgfbr1 genomic DNA failed to rescue the function of Ce-daf-1 (a known TGF-β type I receptor gene) in a daf-1-deficient mutant strain of C. elegans. In addition, a TGF-β type I receptor inhibitor, galunisertib, and double-stranded RNA interference (RNAi) were employed to assess the function of Hc-tgfbr1 in the transition from exsheathed L3 (xL3) to the L4 of H. contortus in vitro, revealing that both galunisertib and Hc-tgfbr1-specific double-stranded RNA could retard L4 development. Taken together, these results provide evidence that Hc-tgfbr1 is involved in developmental processes in H. contortus in the transition from the free-living to the parasitic stage. 相似文献
93.
94.
The sequences of the 5' long-terminal repeat (LTR) and adjacent leader
regions of 27 full-length copia elements isolated from natural populations
of Drosophila melanogaster, D. simulans, and D. mauritiana are presented.
Phylogenetic analyses indicate that although D. melanogaster copia elements
are distinct from those of D. simulans and D. mauritiana, the elements of
these latter two species are not distinguishable from one another. LTRs and
adjacent 5' leader regions of elements isolated from D. simulans and D.
mauritiana are structurally similar to one another and carry substantial
deletional variation mapping to regions previously identified as being of
potential importance for copia expression.
相似文献
95.
Dominance relationships were studied in captive Arctic blue fox (Alopex lagopus) groups comprising adults (four males, five females) and juveniles (four males, five females). The results showed that Arctic blue foxes easily formed a social organization with an observable hierarchy, in which adults typically dominated over juveniles. Within the same age group, males usually dominated over females. Dominance correlated most significantly with body weight in autumn, but later that correlation decreased. Urine marking activity was very low during autumn and early winter, but increased significantly prior to and during the breeding season when aggressive encounters were also most pronounced. In addition to several adults, the social status of some juveniles was high at breeding time. Altogether 7 out of 11 females (63.6%) whelped, but the survival rate of litters was low and kits of only two adult females survived (18.2%). It can be concluded that hierarchical development and reproduction in Arctic blue fox groups are markedly influenced by dominance relationships. 相似文献
96.
Comparisons of the molecular evolutionary process at rbcL and ndhF in the grass family (Poaceae) 总被引:2,自引:1,他引:1
We examine rate heterogeneity among evolutionary lineages of the grass
family at two plasmid loci, ndhF and rbcL, and we introduce a method to
determine whether patterns of rate heterogeneity are correlated between
loci. We show both that rates of synonymous evolution are heterogeneous
among grass lineages and that are heterogeneity is correlated between loci
at synonymous sites. At nonsynonymous sites, the pattern of rate
heterogeneity is not correlated between loci, primarily due to an aberrant
pattern of rate heterogeneity at nonsynonymous sites of rbcL. We compare
patterns of synonymous rate heterogeneity to predictors based on the
generation time effect and the speciation rate hypotheses. Although there
is some evidence for generation time effects, neither generation time
effects nor speciation rates appear to be sufficient to explain patterns of
rate heterogeneity in the grass plastid sequences.
相似文献
97.
The stocking of newly hatched pike Esox lucius labelled with radioactive strontium (85 Sr) and later electrofishing of the same area was found to be a workable tool in assessing the success of pike stockings. 85 Sr‐labelled individuals constituted 96% of the 0+year pike catch from late summer electrofishing in the stocked littoral areas of the heavily regulated Lokka Reservoir. The density of 0+year pike reached 2·1 individuals 100 m−2 in the stocked areas in comparison to 0·3 individuals 100 m−2 in the reference areas. In the three other stocked lakes the proportion of labelled pike in the catch ranged from 0 to 42% in late summer. The results suggest that pike stockings are profitable in filling empty or nearly empty 0+year pike habitats of regulated lakes or other waterbodies, where the natural reproduction of pike has declined due to human activities. 相似文献
98.
Anita Laitinen Sofia Oja Lotta Kilpinen Tanja Kaartinen Johanna Möller Saara Laitinen Matti Korhonen Johanna Nystedt 《Cytotechnology》2016,68(4):891-906
Efficient xenofree expansion methods to replace fetal bovine serum (FBS)-based culture methods are strongly encouraged by the regulators and are needed to facilitate the adoption of mesenchymal stromal cell (MSC)-based therapies. In the current study we established a clinically-compliant and reproducible animal serum-free culture protocol for bone marrow-(BM-) MSCs based on an optimized platelet-derived supplement. Our study compared two different platelet-derived supplements, platelet lysate PL1 versus PL2, produced by two different methods and lysed with different amounts of freeze–thaw cycles. Our study also explored the effect of a low oxygen concentration on BM-MSCs. FBS-supplemented BM-MSC culture served as control. Growth kinetics, differentiation and immunomodulatory potential, morphology, karyotype and immunophenotype was analysed. Growth kinetics in long-term culture was also studied. Based on the initial results, we chose to further process develop the PL1-supplemented culture protocol at 20 % oxygen. The results from 11 individual BM-MSC batches expanded in the chosen condition were consistent, yielding 6.60 × 109 ± 4.74 × 109 cells from only 20 ml of bone marrow. The cells suppressed T-cell proliferation, displayed normal karyotype and typical MSC differentiation potential and phenotype. The BM-MSCs were, however, consistently HLA-DR positive when cultured in platelet lysate (7.5–66.1 %). We additionally show that culture media antibiotics and sterile filtration of the platelet lysate can be successfully omitted. We present a robust and reproducible clinically-compliant culture method for BM-MSCs based on platelet lysate, which enables high quantities of HLA-DR positive MSCs at a low passage number (p2) and suitable for clinical use. 相似文献
99.
Associative Nitrogen Fixation by Klebsiella spp.: Adhesion Sites and Inoculation Effects on Grass Roots 总被引:1,自引:0,他引:1 下载免费PDF全文
Adhesion sites on grass roots for Klebsiella strains carrying type 3 or type 1 fimbriae or both were determined. Adhesion of the strains to the roots of Poa pratensis and Festuca rubra was highly localized; the bacteria adhered strongly to root hairs and with a markedly lower efficiency to the surface of the zone of elongation and to the root cap mucilage. No adhesion to the epidermal cells between root hairs was observed. The adhesion sites were identical for the type 3- and 1-fimbriated bacteria and for P. pratensis, F. rubra, and Trifolium pratense. Inoculation of P. pratensis seedlings with Klebsiella pneumoniae strain As resulted in morphological changes in plant roots. The roots of infected plants were heavily covered with root hairs, which often were deformed and branched. 相似文献
100.
Timo K. Korhonen Ritva Virkola Vuokko Väisänen-Rhen Harry Holthöfer 《FEMS microbiology letters》1986,35(2-3):313-318
Abstract Binding characteristics of the purified Escherichia coli O75X adhesin in frozen sections of human kidney were determined, using antibodies raised against the purified antigen and rhodamine-conjugated second antibodies. To identify the adhesin-binding nephron domains, the same tissue sections were double stained with fluorescein isothiocynate-conjugated nephron site-specific lectins. The results revealed that, at the tubular pole, the O75X adhesin bound selectively to the basement membrane of proximal and distal tubules and, with a slightly lower efficiency, of collecting ducts. In the glomerulus, the O75X adhesin bound only to the parietal epithelial cells (Bowman's capsule). The purified O75X adhesin bound also to exfoliated epithelial cells in human urine. Our results suggest that the O75X adhesin may contribute to the uropathogenicity of E. coli by binding the bacteria to tissue structures in the human urinary tract. 相似文献