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31.
Sporicidal properties of some halogens 总被引:4,自引:0,他引:4
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Jean-Louis Connat Ellen Marie Dotson Peter Allan Diehl 《Archives of insect biochemistry and physiology》1989,10(3):I-XV
Fifth (last) instar nymphs of th e tick Ornithodoros moubata convert ingested 20-hydroxyecdysone (20E) to apolar conjugates AP2, which are then converted to th e more polar conjugates API. Only small quantities of free hormone were transferred to th e hemolymph and the carcass within t h e first 2 days after the blood meal. The proportion of radiolabel in these two compartments was highest at the time of the endogenous ecdysteroid peak; however, no traces of free [3H]20E were detected. The conversion probably occurs principally in the intestinal cells. Eleven days after ingestion, 84% of the radiolabel is located in the digestive tract, mainly in the form of API conjugates. API obtained in second instar nymphs fed with [3H]ecdysone ([3H]E) remain stable throughout the following nymphal instars. The ecdysteroid moiety of APT remained unchanged. The hydrolysis, although not complete, always yielded a peak comigrating with the reference E but never 20E or any other clearly distinct peaks that may have corresponded to metabolites of 20E. Less label per individual was present in adults, but its nature remained the same, viz., API mainly located in the digestive tract. In females, 2.5% of the label was transferred to the progeny during the first ovipositional cycle. Apolar products (mainly AP2) that accumulated in eggs of females injected with [3H]E or [3H]20E during vitellogenesis remained unchanged during the whole embryonic development. During the molting cycle of larvae, there was only a slight conversion of AP2 to API, but esterase hydrolysis of these products released the same percentages of E and 20E as in the freshly laid eggs. We conclude that in this tick species apolar conjugates of ecdysteroids are inactivation metabolites that are not reutilized during the development of the animal. These metabolites are mainly retained in the tick, probably because of its peculiar blocked midgut. Several studies have shown that in other arthropod species (ticks, spiders, and insects), these apolar metabolites are excreted in the feces. 相似文献
35.
Characterization of the genome of Pseudomonas aeruginosa bacteriophage phi PLS27 with particular reference to the ends of the DNA. 总被引:1,自引:0,他引:1 下载免费PDF全文
The DNA of Pseudomonas aeruginosa rough-specific bacteriophage phi PLS27 was studied. The genome size as determined by summing the sizes of restriction fragments was 42.7 kilobase pairs. Of particular interest was the fact that the DNA was insensitive to certain common restriction endonucleases including EcoRI, BamHI, and HindIII. The ends of the phage DNA were cloned and sequenced, revealing direct repeats of 318 nucleotides. The left end of the genome when cloned into the promoter selection vector pKK232-8 exhibited promoter activity in Escherichia coli. Two promoters bearing greater than 70% sequence homology to the plasmid pNM74 TOL operon and PAK pilin promoters were identified. 相似文献
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Tissue-specific expression of two members of the cell wall hydroxyproline-rich glycoprotein (HRGP) family, extensin and potato tuber lectin, was examined by immunolocalization at the light microscope level in various organs (leaves, stems, roots, fruit, tuber) of carrot ( Daucus carota cv. Thumbelina), tomato ( Lycopersicon esclentum cv. Pixie Hybrid II), and potato ( Solanum tuberosum cv. Kennebec). Extensin was prominently expressed in vascular tissue, particularly xylem and also phloem, although virtually all cells displayed some degree of staining which varied as a function of the tissue, organ, and plant under study. Antibodies against potato tuber lectin (PTL) displayed a localization pattern similar to that observed for extensin; notably PTL did not stain cambium but did stain epithelial cells lining secretory cavities. These distribution patterns are consistent with a role for extensin, and possibly PTL, in providing mechanical support in tissues subjected to compression or torsional stress imparted by vascular growth, or by similar stress brought about by transport of vascular fluids. 相似文献
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Alejandro Lynch Allan J. Baker 《Evolution; international journal of organic evolution》1994,48(2):351-359
We investigated cultural evolution in populations of common chaffinches (Fringilla coelebs) in the Atlantic islands (Azores, Madeira, and Canaries) and neighboring continental regions (Morocco and Iberia) by employing a population-memetic approach. To quantify differentiation, we used the concept of a song meme, defined as a single syllable or a series of linked syllables capable of being transmitted. The levels of cultural differentiation are higher among the Canaries populations than among the Azorean ones, even though the islands are on average closer to each other geographically. This is likely the result of reduced levels of migration, lower population sizes, and bottlenecks (possibly during the colonization of these populations) in the Canaries; all these factors produce a smaller effective population size and therefore accentuate the effects of differentiation by random drift. Significant levels of among-population differentiation in the Azores, in spite of substantial levels of migration, attest to the differentiating effects of high mutation rates of memes, which allow the accumulation of new mutants in different populations before migration can disperse them throughout the entire region. 相似文献
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The anisotropic self-diffusion coefficient of 7Li+ (I = 3/2) counterions has been studied in hydrated, macroscopically oriented Li-(B)DNA fibers at relatively high water contents, corresponding to approximate DNA-DNA helix axis distances of 22–35 Å, using the pulsed field gradient hmr spin-echo method. Self-diffusion coefficients parallel (D∥) and perpendicular (D?) to the DNA helix axis increase with increasing salt content and with increasing DNA-DNA helix axis distance. The observed anisotropy D∥/D? decreases from 1.6 to 1.2 with the DNA-DNA separation increasing from 22 to 35 Å in the salt-free sample. This result can be understood by the obstruction effect caused by the DNA molecules themselves. The values of the Li+ self-diffusion coefficients in the most water-rich system with no added salt (corresponding to an approximate distance of 35 Å between the DNA helix axes) were D∥ ~ 1.15 × 10?10 m2 s?1 and D? ~ 0.98 × 10?10 m2 s?1, compared to 9.14 × 10?10 m2 s?1 for the diffusion of Li+ in an aqueous solution of LiCl (~ 2.1M). The possible occurrence of restriction effects in the DNA fibers have also been studied by determining the self-diffusion coefficient at different effective diffusion times. The self-diffusion coefficient of Li+ in the sample with the largest DNA-DNA helix axis distance seems to be independent of the effective diffusion time, which indicates that the lithium ions are not trapped within impermeable barriers. The possibility of diffusion through permeable barriers has also been investigated, and is discussed. © 1994 John Wiley & Sons, Inc. 相似文献
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Garry Lindsay Allan Jim Camakaris George J. F. Legge 《Biological trace element research》1994,40(2):103-126
A scanning proton microprobe has been used for the elemental microanalysis of individual fibroblast cells. Both normal fibroblasts and fibroblasts cultured from patients with Menkes' disease, an X-linked genetic disorder known to be associated with defective copper metabolism, were examined by the probe. The cells were cultured on a thin ultra-clean nylon foil and retained on that surface for analysis. The focused high-energy proton beam was used to irradiate selected individual cells and elemental information was derived from X-ray and backscattered proton data. The sensitivity of the scanning proton microprobe to trace concentrations of heavy elements has allowed this elemental information to be used to identify individual cells as being either normal or a Menkes' mutant. The cell identification was based on the application of discriminate analysis to a data set formed from the ratios of copper to each of the macroelements present in the cell. This method of cell identification offers the promise of rapid diagnosis of Menkes' disease. 相似文献