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排序方式: 共有72条查询结果,搜索用时 24 毫秒
1.
REINHARD B
SE KARL T. FRIEDHOFF SYLVIA OLBRICH 《The Journal of eukaryotic microbiology》1987,34(1):110-113
Four fallow deer, Cervus dama, became infected with Trypanosoma (Megatrypanum) sp. by oral application of triturated guts from tabanids collected in an area with deer but without any cattle; four control calves remained negative. Upon challenge with triturated guts from tabanids from an area with pastured cattle, the four calves became infected with Trypanosoma (M.) theileri. The prepatent period in deer was five days or less. Haematopota spp. and Tabanus spp. were identified as vectors of the deer trypanosomes. It is concluded that the trypanosomes of C. dama belong to a Megatrypanum species that is not identical with T. theileri. 相似文献
2.
The apple rootstock,A106(Malus sieboldii),had 17 bivalents in pollen mother cells at meiotic metaphase 1,and 17 chromosomes in a haploid pollen cell.Karyotypes were prepared from root-tip cells with 2n=34 chromosomes,Seven out of 82 karyotypes(8.5%) showed one pari of satellites at the end of the short arm of chromosome 3.C-bands were shown on 6 pairs of chromosomes 2,4,6,8,14,and 16 near the telomeric regions of short arms.Probes for three ripening-related genes from Malus x domestica:endopolygalacturonase(EPG,0.6kb),ACC oxidase(1.2kb),and ACC synthase(2kb)were hybridized in situ to metaphase chromosomes of A106.Hybridization sites for the EPG gene were observed on the long arm of chromosome 14 in 15 out of 16 replicate spreads and proximal to the centromere of chromosomes 6 and 11.For the ACC oxidase gene,hylridization sites were observed in the telomeric region of the short arm of chromosomes 5 and 11 in 87% and 81% of 16 spreads respectively,proxiaml to the centromere of chromosome 1 in 81% of the spreads,and on the long arm of chromosome 13 in 50% of the spreads. Physical mapping of three fruit ripening genes in an apple rootstock A106.Twenty five spreads were studied for the ACC synthase gene and hybridization sites were observed in the telomeric region of the short arm of chromosome 12 in 96% of the spreads.chromosomes 9 and 10 in 76% of the spreads,and chromosome 17 in 56% of the spreads. 相似文献
3.
The cytokineplast: purified, stable, and functional motile machinery from human blood polymorphonuclear leukocytes 总被引:11,自引:4,他引:7
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We examined the formation of motile, chemotactically active, anucleate fragments from human blood polymorphonuclear leukocytes (PMN, granulocytes), induced by the brief application of heat. These granule-poor fragments are former protopods (leading fronts, lamellipodia) that become uncoupled from the main body of the cell and leave it, at first with a connecting filament that breaks and seals itself. The usual random orientation of such filaments can be controlled by preorientation of cells in a gradient of the chemotactic peptide, N-formylmethionylleucylphenylalanine (F-Met-Leu-Phe) (2x10(-9) M- 1x10(-8)). Cytochalsin B, 2.5-5 μg/ml, prevents fragment formation; colchicine, 10(-5) M, does not. In scanning electron micrographs, fragments are ruffled and the cell body rounded up and rather smooth. In transmission electron micrographs, fragments contain microfilaments but lack centrioles and microtubules. Like intact cells, both bound and free fragments can respond chemotactically to an erythrocyte destroyed by laser microirradiation (necrotaxis); the free, anucleate fragments may do so repeatedly, even after having been held overnight at ambient temperatures. We propse the name cytokineplast for the result of this self-purification of motile apparatus. The exodus of the motile machinery from the granulocyte requires anchoring of the bulk of the cell to glass and uncoupling, which may involve heat-induced dysfunction of the centrosome. In ultrastructural studies of the centrosomal region after heat, centriolar structure remains intact, but pericentriolar osmiophilic material appears condensed, and microtubules are sparse. These changes are found in all three blood cell types examined: PMN, eosinophil, and monocyte. Of these, the first two make fragments under our conditions; the more sluggish monocyte does not. Uncoupling is further linked to centrosomal dysfunction by the observation that colchicines-treated granulocytes (10(-5)M, to destroy the centrosome’s efferent arm) make fragments after less heat than controls. If motive force and orientation are specified mainly from the organelle-excluding leading front, then endoplasmic streaming in PMN is a catch-up phenomenon, and microtubules do not provide the vector of locomotion but rather stabilize and orient the “baggage” (nucleus, granuloplasm)—i.e., they prevent fishtailing. Moreover, constraints emanating from the centrosome may now be extended to include, maintenance of the motile machinery as an integral part of the cell. 相似文献
4.
In cat papillary muscle and nictitating membrane block of extraneuronal catechol-O-methyl transferase (COMT) by 3',4'-dihydroxy-alpha-methyl propiophenone (U-0521) or of extraneuronal uptake by hydrocortisone causes supersensitivity to catecholamines whenever the experimental conditions result in a high sensitivity of the organ to catecholamines. After block of monoamine oxidase the extraneuronal O-methylation of (-)-[3H]norepinephrine by the isolated nictiating membrane is due to two O-methylating systems (Km and Vmax: 7.5 muM and 0.73 nmoles - g-1 - min-1, and 131 muM and 8.5 nmoles - g-1 - min-1, respectively). Hydrocortisone (28 muM) blocked the activity of the high affinity system without affecting the low affinity system. Apparently, there exists an extraneuronal compartment of high affinity that has a hydrocortisone-sensitive uptake mechnism; this compartment influences the concentration of catecholamines below the Km of this compartment. Supersensitivity ensues when either uptake or enzyme is blocked. Since the sensitivity effects of U-0521 and hydrocortisone are not additive, the high affinity compartment must a) metabolize most of the catecholamine transported into the compartment, and b) have a limited storage capacity for catecholamines after block of COMT. 相似文献
5.
Hernandez-Trejo A B Estrada-Drouaillet JA López-Santillán C Rios-Velasco SE Varela-Fuentes R Rodríguez-Herrera E Osorio-Hernández 《Phyton》2019,88(1):47-54
The control of Spodoptera frugiperda is based
on synthetic insecticides, so some alternatives are the use of
entomopathogenic fungi (EF) and neem extract. The objective of
the study was to evaluate in vitro effectiveness of native EF and
neem extracts on S. frugiperda larvae. Six EF were identified by
DNA sequencing of ITS regions from three EF (Fusarium solani,
Metarrhizium robertsii, Nigrospora spherica and Penicillium
citrinum). They were evaluated in concentrations of 1 × 10⁸ spores/
mL. In addition, a second bioassay was carried out evaluating
only F. solani, M. robertsii and N. sphaerica and the addition
of vegetable oil. On the other hand, extraction of secondary
metabolites from neem seed (Azadirachta indica) was carried
out by performing, mass (g) and solvent volume (mL ethanol
and water) combinations, which were subjected to microwaves
and ultrasound. Subsequently, these extracts were evaluated
in concentrations of 3%, 4% and 5%. A survival analysis was
performed for each of the bioassays. With respect to the results
of the first bioassay, F. solani obtained a probability of survival of
0.476 on the seventh day, while in the second bioassay, M. robertsii
obtained 0.488 survival probability. This suggests that the expected
percentage of larvae that stay alive on the sixth day is 48.8%.
However, in the evaluation of the neem extract the combination
1:12/70% to 4% caused 84% mortality of larvae. The use of native
HE and neem extracts has potential for the control of S. frugiperda. 相似文献
6.
Graefe SE Jacobs T Gaworski I Klauenberg U Steeg C Fleischer B 《Microbes and infection / Institut Pasteur》2003,5(10):833-839
Protective immunity to the parasite Trypanosoma cruzi in mice depends on a pro-inflammatory T cell response involving the production of interferon-gamma (IFN-gamma). In conjunction with interleukin-12 (IL-12), IL-18 promotes the synthesis of IFN-gamma and a T helper type 1 immune response. We investigated the requirements of IL-12 and IL-18 in murine T. cruzi infection by use of C57BL/6 mice genetically deficient in either cytokine. IL-12p40(-/-) mice succumbed to infection at doses of 100 parasites, whereas IL-18(-/-) and wild-type mice resisted infectious doses up to 1000 parasites to the same extent. Levels of parasitemia were comparable between the latter groups, as were tissue parasite burdens according to quantitative real-time PCR. In contrast, IL-12p40(-/-) mice displayed vastly increased levels of parasites both in blood and in tissue. IFN-gamma concentrations in the serum of infected mice and in supernatants of splenocytes stimulated in vitro were decreased in IL-18(-/-) mice, whereas in IL-12p40(-/-) mice, IFN-gamma was undetectable in the serum and drastically reduced in cell supernatants. Levels of IL-12 production were generally comparable between wild-type and IL-18(-/-) mice, as were levels of IL-4, IL-2 and nitric oxide. Thus, the requirement for endogenous pro-inflammatory cytokines for a protective murine immune response against T. cruzi is satisfied by the expression of IL-12, while IL-18 is dispensable. 相似文献
7.
DALDINIA CONCENTRICA ATTACKING THE WOOD OF FRAXINUS EXCELSIOR 总被引:1,自引:0,他引:1
8.
J. Graefe P. Bogaerts J. Castillo M. Cherlet J. Wérenne P. Marenbach R. Hanus 《Bioprocess and biosystems engineering》1999,21(5):423-429
Modeling of bioprocesses for engineering applications is a very difficult and time consuming task, due to their complex nonlinear dynamic behavior. In the last years several propositions for hybrid models, and especially serial approaches, were published and discussed, in order to combine analytical prior knowledge with the learning capabilities of Artificial Neural Networks (ANN). These approaches often require synchronous and equidistant sampled training data. However, in practice concentrations are mostly off-line measured, rare, and asynchronous. In this paper a new training method especially suited for very few asynchronously sampled data is presented and applied for modeling animal cell cultures. The achieved model is able to predict the concentrations of the reaction components inside a stirred tank bioreactor. 相似文献
9.
Kerstin A. Graefe Zhe Tang H. Thomas Karnes 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,745(2)
The combination of immunoassays with separation techniques such as chromatography can result in enhanced selectivity and sensitivity. This paper describes an on-line chromatography with immunochemical post-column fluorescence energy transfer detection for digoxin and its metabolites. R-phycoerythrin (PE) was used as the donor and an indodicarbocyanine dye (Cy5) as the acceptor label. These labels allow the detection in the far-red spectral region, which is more selective for biological samples. Hence, digoxin was labeled with PE using the activated digoxigenin-NHS-ester and monoclonal anti-digoxin antibody was labeled with Cy5. Digoxin and its metabolites was injected into the HPLC system followed by post-column injection of R-phycoerythrin labeled digoxin and by Cy5 labeled anti-digoxin antibody. Incubation time was provided using an open tubular reactor coil at room temperature. The detection was performed by measurement of the sensitized emission of Cy5 at 670 nm due to fluorescence energy transfer from PE labeled with digoxin. The system was optimized with regard to the concentrations of the used post-column reagents as well as incubation time and temperature. The dynamic range of digoxin spiked in 0.01 M phosphate buffer (pH 7.4) was 0.05 to 10 ng/ml with a correlation coefficient of 0.989. The limit of detection was 33 pg/ml. The precision of two controls, 0.4 and 4 ng/ml, was found to be 2.2 and 8.7% RSD, respectively, accuracy was 10.7 and 20.3% (n=6 in each case). 相似文献
10.
Phenylalanine uptake in Chlorella fusca was measured, using the membrane filter technique. The cells were synchronized, and harvested at specific points of the life cycle. Experiments with autospores showed that the uptake followed saturation kinetics, with a Km= 5 μM. Vmax, was 0.1 nmol/min × 107 cells. The optimum temperature for the uptake was 40°C, and the activation energy was 1700 J/mol. The uptake showed a high specificity towards l -phenylalanine; presence of the unlabelled stereoisomer did not inhibit the uptake. Uptake of l -phenylalanine was inhibited in the presence of other analogues or other amino acids, but only if they were present in concentrations considerably higher than that of L-phenylalanine. Variations in the ratio of Na4+ to K+ in the external solution during uptake experiments did not have any influence upon the uptake rate of l -phenylalanine. The cells were able to take up the amino acid against a concentration gradient. At pool maximum the ratio between internal and external amino acid concentration was 1000/1. 2,4-Dinitro-phenol inhibited the uptake completely. Exchange between internal and external l -phenylalanine could not be demonstrated. The Km value did not change during the life cycle of the cells. The uptake rate reached a maximum at the end of the light period, and fell to a minimum just before sporulation started. It is concluded that Chlorella fusca cells have a highly specific, active uptake system for l -phenylalanine. The system is constitutive, independent on the K or Na concentration, and the mechanism of uptake does not change during the life cycle of the cells. 相似文献