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151.
Tandem arrangement of tubulin genes in the protozoan parasite Leishmania enriettii. 总被引:22,自引:5,他引:17 下载免费PDF全文
The arrangement of developmentally regulated alpha- and beta-tubulin genes has been studied in the parasitic protozoan Leishmania enriettii by using Southern blot hybridization analysis. The alpha-tubulin genes occur in a tandem repeat whose monomeric unit may be represented by a 2-kilobase PstI fragment. Similarly, the beta-tubulin genes probably occur in a separate tandem repeat consisting of approximately 4-kilobase units unlinked to the alpha-tubulin repeats. 相似文献
152.
Philip W. Wirth E. Sue Watson Mahmoud ElSohly Carlton E. Turner James C. Murphy 《Life sciences》1980,26(23):1991-1995
It was not known if Cannabichromene (CBC), which is a major constituent of drug types of , has anti-inflammatory properties as do other cannabinoids. CBC was tested using the rat paw edema test and using the erythrocyte membrane stabilization assay. CBC was as effective as phenylbutazone (PBZ) at equivalent doses. Since CBC is less toxic than PBZ, larger doses may be given to produce a greater therapeutic effect. 相似文献
153.
Administration of 5-hydroxy[1-14C]-and [4-14C]levulinic acid to Helleborus foetidus led to the isolation of [1-14C]- and [4-14C]protoanemonin, respectively. There was also incorporation of radioactivity into the four glucosides ranunculin, isoranunculin, ranuncoside and ranunculoside. Acid hydrolysis of radioactive ranuncoside gave labelled 5-hydroxylevulinic acid (HKV). A study of the incorporation of various 14C-labelled tracers into protoanemonin suggested that HKV is formed in higher plants by a new reduction of 2-ketoglutarate (2-KG) without free 4,5-dioxovalerate (DOVA) as an intermediate. A scheme for the biosynthesis of the antibiotic protoanemonin and its glucosidic precursors is proposed. It is shown that 5-(β-d-glucopyranosyloxy)levulinic acid could be the genuine precursor of all the compounds studied. 相似文献
154.
155.
R Wirth V Volf 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1984,46(6):787-792
This interim report summarizes the results of observations during the first year after a single injection of 237Np nitrate (0.2 or 1.0 mg/kg body weight) into adult female rats and further preliminary data obtained with young animals. The retention of 237Np was followed by whole body counting and serial sacrifice of groups of animals. The retention data could be fitted to three-component exponential equations which show no major differences between the two 237Np dose levels. The half-times and extrapolated initial fractions calculated from the first two exponential terms indicate that one fraction, representing about 40 per cent of the injected 237Np was excreted within the first 5 days and an additional 15 per cent within the first 5 months, while the rest was excreted with a half-time of about 3.5 years. This final long term component is assumed to indicate the rate of loss of 237Np from the skeletal compartment. In young animals both whole-body and skeletal retention of 237Np during the first 5 months of observation was about 50 per cent higher than in the adults. Several soft tissue tumours, mostly mammary tumours, have appeared to approximately the same extent in both control and 237Np treated adult rats but no osteosarcomas were detected up to 15 months after injection of 237Np. 相似文献
156.
The carbohydrates of mouse hepatitis virus (MHV) A59: structures of the O-glycosidically linked oligosaccharides of glycoprotein E1 总被引:11,自引:0,他引:11 下载免费PDF全文
Two size classes of O-glycosidically linked oligosaccharides were liberated from glycoprotein E1 of mouse hepatitis virus (MHV) A59 by reductive beta-elimination and separated by h.p.l.c. The structures of the reduced oligosaccharides were determined by successive exoglycosidase digestions and by methylation analyses involving combined capillary gas chromatography-mass spectrometry and mass fragmentography after chemical ionization with ammonia. Oligosaccharide A (Neu5Ac alpha 2----3 Gal beta 1----3 GalNAc) comprised 35% of the total carbohydrate side chains, while the remaining 65% of the oligosaccharides of E1 had the branched structure B: Neu5Ac alpha 2----3 Gal beta 1----3 (Neu5Ac alpha 2----6) GalNAc. Both oligosaccharides were linked to the E1 polypeptide via N-acetylgalactosamine, and 20% of the sialic acids present in E1 glycopeptides were found to consist of N-acetyl-9-mono-O-acetylneuraminic acid. The reported structures of the O-linked glycans are discussed in the context of the amino acid sequence of E1, which exhibits a cluster of four hydroxyamino acids (Ser-Ser-Thr-Thr) as potential O-glycosylation sites at the amino terminus. Oligosaccharides with identical structures and an identical O-glycosylated tetrapeptide sequence are present in the blood group M-active glycophorin A of the human erythrocyte membrane. 相似文献
157.
A professional approach to conservation of biodiversity requires good knowledge, but we do not even know anywhere near how many species do occur on earth. We even know less on the conservation status of the living world. Factors threatening biodiversity are many and diverse. In addition to key problems such as human population growth, or ever increasing and unsustainable use of resources, effective biodiversity conservation is also hampered by massive lack of knowledge, a growing gap of trained taxonomists and ecologists, bureaucracy, politics and serious misinterpretation of important issues affecting biodiversity. In order to reduce the knowledge gap, the need to catalogue and conserve the diversity of live on earth must be seen as an important global challenge and must be funded with appropriate resources accordingly. 相似文献
158.
Isolation and Functional Characterization of Two Distinct Sexual-Stage-Specific Promoters of the Human Malaria Parasite Plasmodium falciparum 总被引:4,自引:0,他引:4 下载免费PDF全文
159.
Ronald J. Prokopy Catherine B. Wirth Tracy C. Leskey 《Entomologia Experimentalis et Applicata》1999,91(3):385-392
Adult plum curculios, Conotrachelus nenuphar (Herbst), were dislodged from branches of apple trees by tapping on 14 days between blossom petal fall and 3 weeks thereafter. They fell onto a small square of framed white cloth that was quickly but carefully moved to a position beneath or adjacent to the canopy of another apple tree.There, adults were observed for 50-min periods from 0800–1950 h for propensity to fly from or walk off the cloth or move to hide beneath foliage on the cloth. At each position, the mean time from observation initiation until flight, walking off or hiding did not differ significantly among these behaviors (averaging 21–30 min), but significantly more flew (31–40%) than crawled off (16–19%) or hid (18–20%). Substantial walking off but no flights occurred at air temperatures below 20 °C, whereas at temperatures of 20 °C or greater, propensity for flight was usually significantly greater than that for walking off.Flights were predominantly toward the tree canopy or inter-tree space, with only a small proportion (17% or less) toward the tree trunk or (in a parallel study) toward an unbaited black pyramid trap (mimicking a tree trunk). Walking was overwhelmingly toward the tree trunk or a black pyramid trap adjacent to the trunk. Our observations lead us to conclude that unbaited black pyramid traps next to trunks of host trees (the most attractive position) can be effective at air temperatures below 20 °C by attracting plum curculio adults that would have entered host trees by walking toward and up tree trunks.Such traps appear to be less effective at 20 °C or greater because under such conditions, adults tend to enter host trees by flight into the canopy. 相似文献
160.