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排序方式: 共有374条查询结果,搜索用时 15 毫秒
1.
DB ADAMS JJ LYNCH† BH ANDERSON LR FELL‡ GN HINCH§ RK MUNRO¶ 《Australian veterinary journal》1990,67(12):443-445
Three-year-old, non-lactating and non-pregnant Merino ewes, raised on pasture under a program of strategic treatment with anthelmintic and found to be extremely resistant to "trickle" infection with Haemonchus contortus, were given single-dose infections with either H. contortus or Trichostrongylus colubriformis or both species together. The purpose was to ascertain the intensity of protective immunity against the 2 parasites in sheep with immunity acquired from a presumably slight exposure to infection. To provide a criterion, some infected ewes were immunosuppressed with corticosteroid, dexamethasone. Untreated ewes were extremely resistant to challenge infection with either 15,000 or 150,000 H. contortus or 15,000 T. colubriformis. Surprisingly, when mixed infection was given, egg counts for H. contortus were significantly elevated compared with infection by that species alone. Antibody to antigens from infective larval and adult H. contortus was measured in serum by enzyme-linked-immunosorbent assay (ELISA) during the course of infection. Serum titres against larval antigens were significantly depressed when infections with either H. contortus or T. colubriformis were permitted by immunosuppression with dexamethasone, whereas those against adult antigen were depressed when infection with T. colubriformis was permitted. 相似文献
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The taxonomy and phylogeny of Indian Citrus is revisited using PCR-RFLP of the trnD-trnT and rbcL-ORF 106 regions as well as sequence data analysis of the trnL-trnF intergenic spacer region of cpDNA. The study was based on 50 accessions of Citrus genotypes, collected from wild, semi-wild and domesticated stocks. Of the 13 restriction enzymes (RE) used for restriction digestion of the polymerase chain reaction (PCR) amplicons, four (Hinf I, Msp I, Alu I, Hae III) generated 47 restriction fragments, of which 24 (51%) were polymorphic. PCR-RFLP data showed a genetic distance ranging from 0 to 0.79 among 50 accessions of Citrus, and a cluster analysis, based on Neighbor-Joining (NJ) method, placed all the accessions in eight major clusters. Analysis of trnL-trnF sequences from 23 representative accessions of Citrus showed a pair-wise sequence divergence rate in the range of 0–0.064. NJ, minimum evolution (ME) and maximum parsimony (MP) analyses of trnL-trnF sequences produced phylogenetic trees, which placed all the 23 accessions in five clusters. PCR-RFLP analysis resulted in a well resolved phylogenetic tree with branches supported by moderate to high bootstrap values, while the trnL-trnF sequence-based trees showed only moderate to low bootstrap support for the internal tree branches, indicating uncertain origin of some Citrus genotypes. This study shows that the trnL-trnF spacer sequence data can detect genetic variation in Indian Citrus genotypes, but the utility of the data in inferring phylogeny at intra and inter-specific levels is limited probably by factors such as hybridization, bud mutations, apomixis and polyploidy. However, PCR-RFLP and trnL-trnF data supported the recognition of C. maxima, C. medica, and C. reticulata as the basal species of edible Citrus. 相似文献
4.
Leila Hayashi Nair S. Yokoya Srgio Ostini Ricardo T.L. Pereira Elisabete S. Braga Eurico C. Oliveira 《Aquaculture (Amsterdam, Netherlands)》2008,277(3-4):185-191
The potential of the red alga Kappaphycus alvarezii to remove nutrients was tested to treat effluents of Trachinotus carolinus fish cultivation, and the production of carrageenan in this condition was analyzed. Experiments were conducted in four tanks of 8000 L with approximately 1200 fishes of 30 g each integrated with three tanks of 100 L with 700 g of K. alvarezii, as initial biomass per tank. Seawater was re-circulated between tanks with seaweed and with fish. As a control, three tanks with seawater circulating in an open system were utilized. Seawater samples were collected daily for 10 days and concentrations of nitrate, nitrite, ammonium and phosphate were determined in the inflow and outflow water of the tanks. Significant differences between both collecting points were considered as nutrient removal by the seaweed. Growth rates and carrageenan yields were also analyzed in seaweed cultivated in seawater and in effluents. Growth rates of seaweed cultivated in tanks were lower than those obtained in open sea and in laboratory cultivation. Effluents had concentrations of nitrate and nitrite ca. 100 times higher than in the control. Maximum values of nutrient removal on effluents were: nitrate = 18.2%; nitrite = 50.8%; ammonium = 70.5% and phosphate = 26.8%. All plants survived throughout the experimental period, but some developed “ice–ice”, a disease associated with physiological stress. After the experimental period, some plants selected and cultivated in open sea presented higher growth rates in 40 days, indicating nutrient storage. No significant differences between carrageenan yields of K. alvarezii cultivated in seawater and in the effluents were observed. Our results show that K. alvarezii can be utilized as a biofilter for fish cultivation effluents, reducing the eutrophication process and can also be processed for carrageenan production, which provides an additional benefit to the fisheries. 相似文献
5.
David M. Cole Timothy L. White P. K. R. Nair 《Genetic Resources and Crop Evolution》2007,54(1):189-204
Knowledge of the effects of farmer practices on population genetic parameters of peach palm (Bactris gasipaes Kunth) is relevant to the improvement and conservation of the palm’s genetic resources. Microsatellite markers were used
to assess genetic diversity and population structure of peach palm in swidden-fallow agroforestry systems in northeastern
Peru. The study covered eight communities, comprising two study areas 160 km apart – one occupied by indigenous Amerindians
and the other by mixed race campesinos. Simultaneous analysis of an ex situ peach palm germplasm collection provided a means to compare population genetic parameters. Farmers who were surveyed on seed
selection practices for peach palm reported that an average of only four palms (4.3 for campesino and 1.5 for indigenous populations)
were used to provide seed for the establishment of the forest gardens sampled. As expected, inbreeding coefficients observed
within communities were relatively high (f = 0.105 − 0.210), however, observed heterozygosities within communities were also high (0.625–0.741). A metapopulation approach
was used to describe migration within and among regions, implying a hierarchical structure of gene flow which maintains relatively
high levels of genetic diversity. Seed migration was found to occur over longer distances (≤600 km) and at a higher frequency
(46% of palms sampled) in the indigenous study area, and a proportionally greater number of alleles was found (49 vs. 43 over
three loci) with twice as many private alleles occurring only in the indigenous populations. The farmers’ practice of preserving
remnant palms through successive swidden generations may have contributed to the maintenance of alleles by reducing the severity
of founder effects. Although the campesino study area exhibited a significant (20% of the variation; p < 0.01) isolation-by-distance relationship across 35 km distance, in general, both study populations had relatively limited
genetic structure (θ = 0.012–0.03), which is believed to have resulted from the exchange of seeds over long distances and
periods of time. 相似文献
6.
Vimal Nair Min Cheol Kim James A. Golen Arnold L. Rheingold Gabriel A. Castro Paul R. Jensen William Fenical 《Marine drugs》2020,18(11)
A new cytotoxic thiodepsipeptide, verrucosamide (1), was isolated along with the known, related cyclic peptide thiocoraline, from the extract of a marine-derived actinomycete, a Verrucosispora sp., our strain CNX-026. The new peptide, which is composed of two rare seven-membered 1,4-thiazepane rings, was elucidated by a combination of spectral methods and the absolute configuration was determined by a single X-ray diffraction study. Verrucosamide (1) showed moderate cytotoxicity and selectivity in the NCI 60 cell line bioassay. The most susceptible cell lines were MDA-MB-468 breast carcinoma with an LD50 of 1.26 µM, and COLO 205 colon adenocarcinoma with an LD50 of 1.4 µM. Also isolated along with verrucosamide were three small 3-hydroxy(alkoxy)-quinaldic acid derivatives that appear to be products of the same biosynthetic pathway. 相似文献
7.
A study was conducted in northwest Florida, USA, to investigate root development and morphology of cotton (Gossypium hirsutum L.) under pecan (Carya illinoensis K. Koch) trees in an alleycropping experiment. Root:shoot ratio, root biomass, total root length and root length density
were examined under three treatments: (1) barrier (separating belowground interspecific competition by trenching to a depth
of 120 cm and installing polyethylene barrier), (2) non-barrier (root systems were free to interact), and (3) monoculture
of cotton (without above and belowground interspecific competition with trees). Results indicated that plants in the barrier
and non-barrier treatments had lower root:shoot ratios compared to the monoculture treatment. Belowground competition for
resources between pecan and cotton in the non-barrier treatment resulted in 25 and 33% reduction of total root length (359 cm)
when compared to that of the barrier (477 cm) and monoculture (539 cm) treatments, respectively. The non-barrier plants also
exhibited the lowest root length density. Specific root length was highest for the monoculture (179 cm g−1) and lowest for the non-barrier treatment (146 cm g−1) with the barrier treatment being intermediate (165 cm g−1). Interspecific competition with pecan significantly altered root development and morphology of cotton plants. Research in
agroforestry should take into account the developmental differences in root systems of the associated crop species so that
better models incorporating nutrient and water uptake can be developed. 相似文献
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笔者在临床上曾遇到一疑似“碘酊”致牛死亡的病例,由于未曾见过碘酊致牛死亡的报道,查阅资料也终未得到答案.笔者将其整理如下,供同行探讨。 相似文献
10.