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排序方式: 共有559条查询结果,搜索用时 15 毫秒
1.
Matthew E. Downs Amanda Buch Carlos Sierra Maria Eleni Karakatsani Shangshang Chen Elisa E. Konofagou Vincent P. Ferrera 《PloS one》2015,10(5)
Focused Ultrasound (FUS) coupled with intravenous administration of microbubbles (MB) is a non-invasive technique that has been shown to reliably open (increase the permeability of) the blood-brain barrier (BBB) in multiple in vivo models including non-human primates (NHP). This procedure has shown promise for clinical and basic science applications, yet the safety and potential neurological effects of long term application in NHP requires further investigation under parameters shown to be efficacious in that species (500kHz, 200–400 kPa, 4–5μm MB, 2 minute sonication). In this study, we repeatedly opened the BBB in the caudate and putamen regions of the basal ganglia of 4 NHP using FUS with systemically-administered MB over 4–20 months. We assessed the safety of the FUS with MB procedure using MRI to detect edema or hemorrhaging in the brain. Contrast enhanced T1-weighted MRI sequences showed a 98% success rate for openings in the targeted regions. T2-weighted and SWI sequences indicated a lack edema in the majority of the cases. We investigated potential neurological effects of the FUS with MB procedure through quantitative cognitive testing of’ visual, cognitive, motivational, and motor function using a random dot motion task with reward magnitude bias presented on a touchpanel display. Reaction times during the task significantly increased on the day of the FUS with MB procedure. This increase returned to baseline within 4–5 days after the procedure. Visual motion discrimination thresholds were unaffected. Our results indicate FUS with MB can be a safe method for repeated opening of the BBB at the basal ganglia in NHP for up to 20 months without any long-term negative physiological or neurological effects with the parameters used. 相似文献
2.
The number of orientation, feeding and social calls emitted by pipistrelle batsPipistrellus pipistrellus Schreber, 1774 andP. pygmaeus Leach, 1825 was recorded throughout the night at eight different sites. Social calls were unaffected by weather variables,
whereas orientation calls and feeding buzzes were both significantly affected by cloud and temperature conditions. The number
of emissions of each call type was significantly different between sites, indicating that the bats used different sites for
different activities. Significant positive correlations between all three combinations of call types occurred only during
the middle of the night, corresponding with the nadir of flying insects. This suggests that bats were engaged in activities
other than feeding at this time, such as territory protection or mate attraction. 相似文献
3.
Nathan Downs Alfio Parisi Joanna Turner David Turnbull 《Photochemical & photobiological sciences》2008,7(6):700-710
A technique has been developed to represent erythemally effective ultraviolet radiation exposure within a school environment. The technique models the erythemally effective exposure onto a horizontal plane representation of a mapped school environment located in Hervey Bay (25 degrees S, 153 degrees E), Australia. The input parameters used to model the ultraviolet exposures received within the school playground included the measured sky view, ground albedo and standing surface albedo. Estimates of the erythemally effective ultraviolet exposure received within the school playground during morning tea and lunch time meal breaks during a winter and summer school day are presented. The influence of tree shade and building structure was found to vary significantly with solar zenith angle modelled over the winter and summer school meal break times with horizontal plane exposures predicted to vary from between 0 and 7 SED at different locations within the playground. The technique presented provides a method that can be followed to examine the effect of surrounding buildings and surface structures of real environments on the predicted horizontal plane ultraviolet exposure. 相似文献
4.
The cyclic adenosine monophosphate (cAMP) content of intact oocyte-cumulus cell complexes at various times after the induction of oocyte maturation in mice in vivo was correlated with the time of commitment by the oocytes to undergo germinal vesicle breakdown (GVB) and metabolic coupling between the oocyte and cumulus cells. Seventy-nine percent of the oocytes either underwent GVB or were committed to do so by 2 h after injection of human chorionic gonadotropin (hCG). This occurred without a decrease in the coupling between cumulus cells and the oocyte and with increasing cAMP levels in the oocyte-cumulus cell complex. Maintenance of threshold levels of cAMP within mammalian oocytes appears essential for the maintenance of meiotic arrest, but data presented here suggest that oocyte maturation in mice is induced by gonadotropins in nonatretic follicles in vivo by some mechanism other than one which decreases the cAMP content of the intact oocyte-cumulus cell complex. 相似文献
5.
Mitotic inhibition and aneuploidy induction by naturally occurring and synthetic estrogens in Chinese hamster cells in vitro 总被引:2,自引:0,他引:2
We used a predominantly diploid Chinese hamster cell line to test a number of naturally occurring and synthetic estrogens for their ability to arrest cells at metaphase, their potential for allowing anaphase recovery, and their capability of inducing aneuploid progeny. The chemicals employed included diethylstilbestrol, dienestrol, hexestrol, beta-estradiol, ethynylestradiol and estriol. We also tested progesterone, estrone and testosterone in this regard. Only estrogens and their synthetic analogs caused mitotic arrest and aneuploidy, while progesterone, estrone and testosterone did not cause mitotic disturbances. Among the estrogens, DES was the most effective arrestant on a comparative molar basis, whereas dienestrol was most potent over a wide range of concentrations. Estriol was the least potent as an arrestant but was an effective inducer of aneuploidy. The addition of a metabolic activator (S9) did not alter the ability of DES to arrest mitosis. Following the removal of the drugs, cells were able to quickly reorganize a spindle apparatus and enter anaphase. Diethylstilbestrol, dienestrol, hexestrol, beta-estradiol, ethynylestradiol and estriol caused significant increase in aneuploidy within a narrow range of high concentrations in recovering cell populations. Aneuploidy was induced in a non-random manner. Immunofluorescence studies with anti-tubulin antibody indicate that estrogens may have a mechanism of mitotic arrest similar to that of colchicine and colcemid, viz inhibiting the polymerization of tubulin to form microtubules. These data suggest that the interaction between estrogens and microtubules may mediate the induction of aneuploidy in somatic cells. Aneuploidy induction by DES and similar compounds may be related to their carcinogenic potential. 相似文献
6.
Differential Dialysis Culture for Separation and Concentration of a Macromolecular Product 总被引:4,自引:0,他引:4
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A differential dialysis flask, constructed with three chambers and two membranes of different porosity, was used to effect the separation and concentration of enterotoxin B produced extracellularly by a culture of Staphylococcus aureus. Variables were examined that affected the diffusion of glucose, as measured by half-equilibration time and permeability coefficient; the relative chamber volume, type of membrane, membrane masking, and mixing all exerted a substantial influence on diffusion rates. A number of membrane filters were tested for usefulness; one type, made with vinylidene fluoride, had desirable physical and diffusional properties, but neither it nor others consistently withheld the bacteria for more than a marginally useful period of about 50 hr. In ordinary two-chambered dialysis culture, the amount of enterotoxin reached 10 times that in control culture; in differential, three-chambered dialysis culture the comparable factor of increase was about 7, with about two-thirds of this amount being separated from cells in the product chamber of the flask. 相似文献
7.
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9.
Purification and characterization of the major surface array protein from the avirulent Bacillus anthracis Delta Sterne-1. 总被引:1,自引:0,他引:1
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Many prokaryotic organisms possess surface layer (S-layer) proteins that are components of the outermost cell envelope. With immunogold labeling, it was demonstrated that the protein extractable antigen 1 (EA1) was localized on the outer surface and specifically to cell wall fragments from Bacillus anthracis which retained the S layer. When grown in rich medium under aerobic conditions, the avirulent strain Delta Sterne-1 released large amounts of EA1 into the medium. This EA1 had no higher-order structure initially but formed two-dimensional crystals under defined conditions. The released EA1 was purified in aqueous buffers with a three-step procedure and found to have a mass of 95 kDa when subjected to denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). N-terminal sequence data revealed exact identity to the first eight residues of the S-layer protein from B. thuringiensis 4045. Gel permeation chromatography of the purified EA1 under nondenaturing conditions revealed a single peak corresponding to a mass of approximately 400 kDa, suggesting that a tetramer or dimer of dimers was the primary species in solution. SDS-PAGE of EA1 purified in the absence of protease inhibitors revealed specific proteolytic processing to an 80-kDa form, which immunoreacted with polyclonal anti-EA1 antibodies. This proteolytic cleavage of EA1 to 80 kDa was duplicated with purified EA1 and the protease trypsin or pronase. 相似文献
10.
Phytochrome Regulation of Flowering in the Long-Day Plant, Hyoscyamus niger 总被引:2,自引:0,他引:2
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A daylength extension with incandescent light is more effective in promoting flowering of long-day plants like Hyoscyamus niger than fluorescent light. A low phytochrome photoequilibrium (Pfr/Ptot), attained by a far-red irradiation at the close of long days under fluorescent light, also promotes flowering. Moreover, if flower initiation processes are initiated by several long days, a low phytochrome photoequilibrium at the end of short, postinduction photoperiods also enhances flowering. The initiation phase of flowering requires Pfr to be present whereas the development phase proceeds more rapidly in the absence of Pfr. Spectral dependence studies, therefore, could be misinterpreted if the initiation and development stages are combined into a single audit of flowering. 相似文献