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51.
Life table studies were performed in 1996 with Aedes aegypti (L.) during the low (cool/dry) and high (hot/rainy) dengue virus transmission seasons in Puerto Rico. Mated adult females from field-collected pupae were placed individually in cages and divided into 2 treatment groups: one was fed only human blood and the other human blood plus a 10% sucrose solution. Survival and number of eggs laid were recorded daily for each female. During both seasons, age specific survivorship was higher for the blood plus sugar group, groups fed only human blood had higher reproductive outputs (mx), and net replacement rates (Ro) for blood only groups were higher than for those fed blood plus sugar. Intrinsic rates of growth (r) were the same for both treatments during the low (cool/dry) transmission season, but higher for the blood-only treatment during the high (hot/rainy) transmission season. Our results indicate that feeding on only human blood provides an evolutionary advantage to Ae. aegypti females in Puerto Rico. These results are similar to those from an earlier study carried out with Ae. aegypti in Thailand; the advantage of feeding on human blood does not seem to be restricted to a particular geographic region. We also found that the benefits associated with human feeding persist through epidemiologically different times of the year. We conclude that feeding on human blood is reproductively beneficial for Ae. aegypti, which may increase their contact with human hosts, and therefore may influence their vectorial capacity for dengue viruses through frequent feeding on blood. 相似文献
52.
Spatial modulation of magnetization (SPAMM) is a well established imaging technique which superimposes a tagging pattern on conventional magnetic resonance (MR) images, allowing movement to be visualized. A modification to the SPAMM technique, called complementary spatial modulation of magnetization (CSPAMM), which improves the contrast of the tagging pattern is explained. The application of CSPAMM to the visualization of pulsatile cerebrospinal fluid flow (CSF) using an 8 frame cardiac-gated cine sequence is described. Various combinations of binomial pulses, up to the fifth order, were investigated to see which produces the optimum tagging pattern in the CSPAMM images. The flip angles of the imaging RF pulses were studied to see which would give equal maximum CSF signal intensity in all the cine images. The optimized cine CSPAMM technique was compared in vivo with SPAMM and CSF motion was found to be more easily visualized in the CSPAMM images. 相似文献
53.
FR Matuschka TW Schinkel B Klug A Spielman D Richter 《Canadian Metallurgical Quarterly》1998,64(8):3089-3091
To define conditions promoting inherited infection by Lyme disease spirochetes in Ixodes ticks, we variously infected ticks with Borrelia afzelii and examined their progenies by dark-field microscopy, immunofluorescence, PCR, and serial passage. No episode of inherited infection was evident, regardless of instar or gender infected or frequency of exposure. We suggest that these spirochetes rarely, if ever, are inherited by vector ticks. 相似文献
54.
Pretreatment of murine leukaemia L1210 cells with non-lethal concentrations of various antimetabolites increased the in vitro invasive capacity of these cells into monolayers of rat embryo fibroblasts. The increase in invasive capacity was partly correlated with the induced cell cycle arrest. The concomitant increase in cell surface fucosylation and inhibition of invasion with sulphate indicate a role for glycoproteins in this process. Our results suggest that treatment with antimetabolites may lead to a more aggressive phenotype by altering cell surface properties. 相似文献
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57.
We have shown that autoxidized polyphenolic nutraceuticals oxidize H2S to polysulfides and thiosulfate and this may convey their cytoprotective effects. Polyphenol reactivity is largely attributed to the B ring, which is usually a form of hydroxyquinone (HQ). Here, we examine the effects of HQs on sulfur metabolism using H2S- and polysulfide-specific fluorophores (AzMC and SSP4, respectively) and thiosulfate sensitive silver nanoparticles (AgNP). In buffer, 1,4-dihydroxybenzene (1,4-DB), 1,4-benzoquinone (1,4-BQ), pyrogallol (PG) and gallic acid (GA) oxidized H2S to polysulfides and thiosulfate, whereas 1,2-DB, 1,3-DB, 1,2-dihydroxy,3,4-benzoquinone and shikimic acid did not. In addition, 1,4-DB, 1,4-BQ, PG and GA also increased polysulfide production in HEK293 cells. In buffer, H2S oxidation by 1,4-DB was oxygen-dependent, partially inhibited by tempol and trolox, and absorbance spectra were consistent with redox cycling between HQ autoxidation and H2S-mediated reduction. Neither 1,2-DB, 1,3-DB, 1,4-DB nor 1,4-BQ reduced polysulfides to H2S in either 21% or 0% oxygen. Epinephrine and norepinephrine also oxidized H2S to polysulfides and thiosulfate; dopamine and tyrosine were ineffective. Polyphenones were also examined, but only 2,5-dihydroxy- and 2,3,4-trihydroxybenzophenones oxidized H2S. These results show that H2S is readily oxidized by specific hydroxyquinones and quinones, most likely through the formation of a semiquinone radical intermediate derived from either reaction of oxygen with the reduced quinones, or from direct reaction between H2S and quinones. We propose that polysulfide production by these reactions contributes to the health-promoting benefits of polyphenolic nutraceuticals. 相似文献
58.
W. R. Vogler A. C. Olson S. Okamoto M. Shoji R. L. Raynor J. F. Kuo W. E. Berdel H. Eibl J. Hajdu H. Nomura 《Lipids》1991,26(12):1418-1423
Alkyl lysophospholipids have been shown to be cytooxic to a number of neoplastic tissues. One, ET-18-OCH3, has been used to selectively purge leukemic cells from mixtures with normal marrow progenitor cells,in vitro andin vivo. We have measured the 50% inhibitory (IC50) effect of a series of ether, lipids (EL) on leukemic cells (HL60, K562, Daudi, KG-1, KG-1a) and normal marrow progenitor
cells. Cells were incubated with varying concentrations of EL for 4 hr and assayed for viability, [3H]thymidine incorporation and clonogenicity in semi-solid media. The effect on protein kinase C (PKC) activity was assayed
for each compound. Compounds tested included three glycerophosphocholine analogs-ET-18-OCH3, ET-16-NHCOCH3, and BM 41.440. In addition, a lipoidal amine, CP 46665, an ethyleneglycolphospholipid, AEPL, and four single chain alkylphosphocholine
analogs, HePC2, HePC3, HePC4 and HePC6 were also tested. During the period of incubation, the cells remained viable (>70%) as judged by trypan blue dye exclusion.
The glycerophosphocholines were the most active and showed the highest therapeutic index. The lipoidal amine was active, but
toxic to normal marrow progenitor cells. The ethyleneglycolphospholipid was active against HL60, but not against the other
cell lines. The single chain alkylphosphocholine analogs were less active. All of the compounds inhibited PKC activity; however,
the glycerophosphocholines were the most inhibitory.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May 1989. 相似文献
59.
Michael D. Dahlberg Richard L. Rohrer Daniel J. Fauth Richard Sprecher Gregory J. Olson 《Fuel》1993,72(12):1645-1649
A bacterium identified as Arthrobacter sp. was grown on dibenzothiophene (DBT) sulfone as a sole source of sulfur, producing sulfite and sulfate. Sulfur in DBT sulfone (1.0 mM) was nearly quantitatively converted to sulfate by the organism. The organism could also use DBT sulfone as a sole source of carbon and energy. There was evidence for transient accumulation of benzoic acid in the culture medium after growth of the cells slowed. The DBT sulfoxide analogue 9-fluorenone was converted by resting cells to a product identified as 1,10-dihydroxy-1,10-dihydrofluoren-9-one, suggesting that DBT sulfone may be metabolized via an angular hydroxylation resulting in carbon- sulfur bond cleavage. This strain of Arthrobacter showed no ability to desulfurize oxidized Illinois No. 6 coal. 相似文献
60.
Jialing Liu Yadav V. Sehgal H. Olson J.M. Haifeng Liu Elia N. 《Automatic Control, IEEE Transactions on》2008,53(8):1817-1825
In this paper, we study the phase transition behavior emerging from the interactions among multiple agents in the presence of noise. We propose a simple discrete-time model in which a group of non-mobile agents form either a fixed connected graph or a random graph process, and each agent, taking bipolar value either +1 or -1, updates its value according to its previous value and the noisy measurements of the values of the agents connected to it. We present proofs for the occurrence of the following phase transition behavior: At a noise level higher than some threshold, the system generates symmetric behavior (vapor or melt of magnetization) or disagreement; whereas at a noise level lower than the threshold, the system exhibits spontaneous symmetry breaking (solid or magnetization) or consensus. The threshold is found analytically. The phase transition occurs for any dimension. Finally, we demonstrate the phase transition behavior and all analytic results using simulations. This result may be found useful in the study of the collective behavior of complex systems under communication constraints. 相似文献