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AIM: To examine stands of bracken fern (Pteridium esculentum) from throughout New Zealand for the presence and concentration of ptaquiloside (Pta), and to compare the presence and/or concentrations of Pta in areas where bovine enzootic haematuria (BEH) and/or acute haemorrhagic syndrome (AHS) has been known to occur with those where BEH/AHS has not been recorded. METHODS: Stands of bracken fern were sampled from 275 sites throughout New Zealand. Sixty-two stands were from a regional survey predominantly from the Waikato and Coromandel regions, 27 were from a farm in the King Country where BEH/AHS had been investigated previously, and 186 were from a national survey of the North and South Islands. Sampling sites were from a mixture of grazed paddocks, roadsides, and forest and bush areas. Samples comprised whole young fronds, the tops of unfurling young fronds, or, for the Regional Survey, mature green fronds from the previous season. Pta was extracted from the samples, and measured using high-performance liquid chromatography. Information on the occurrence of BEH/AHS at specific locations was obtained from published information and records from animal health laboratories in New Zealand. RESULTS: The 275 samples contained widely varying concentrations of Pta. In the Farm Survey, concentrations ranged from 280–13,300 (mean 3,800) µg/g (on a dry-weight basis) in the 63% of samples that contained Pta. A high proportion of samples from the Regional and National Surveys covering large areas of the country contained no detectable levels of Pta. The majority (61%) of samples from these two surveys which contained Pta were from areas where BEH/AHS was reported to occur. Combining data from all surveys, in areas with reported BEH/AHS, 42% of samples collected contained Pta, compared with 6% where BEH/AHS was not known to occur. CONCLUSIONS: Concentrations of Pta in bracken in New Zealand vary greatly, and in a high proportion of stands Pta is not found. A higher incidence of Pta, and some very high concentrations, are found in areas where BEH/AHS was known to occur. 相似文献
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Crustal temperatures within collisional orogens are anomalously high compared with temperatures at comparable depths in stable continents, which is evidence of thermal processes that are fundamental to orogenesis. These temperatures can be explained by the redistribution of crust enriched in heat-producing elements through the accretion of crust from the down-going plate to the upper plate and surface erosion. With the use of geologically reasonable rates, the model results predict high temperatures (over 600°C) and inverted upper-plate geotherms (about 100°C over 20 kilometers) at shallow depths (20 to 40 kilometers) by 25 to 35 million years after collision. This study emphasizes the interdependence of deformational, surficial, and thermal processes. 相似文献
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Role of Gene Interactions in Hybrid Speciation: Evidence from Ancient and Experimental Hybrids 总被引:6,自引:0,他引:6
LH Rieseberg B Sinervo CR Linder MC Ungerer DM Arias 《Science (New York, N.Y.)》1996,272(5262):741-745
The origin of a new diploid species by means of hybridization requires the successful merger of differentiated parental species' genomes. To study this process, the genomic composition of three experimentally synthesized hybrid lineages was compared with that of an ancient hybrid species. The genomic composition of the synthesized and ancient hybrids was concordant (rs = 0.68, P < 0.0001), indicating that selection to a large extent governs hybrid species formation. Further, nonrandom rates of introgression and significant associations among unlinked markers in each of the three synthesized hybrid lineages imply that interactions between coadapted parental species' genes constrain the genomic composition of hybrid species. 相似文献
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Artificial propagation of Monopterus albus (Zuiew) was conducted during their spawning season in the present study. Different doses of luteinizing-hormone-releasing-hormone analogue (LHRH-A) were tested for inducing the ovulation of brood females. No significant difference was found in the degree-hours and fertilization rates between three different doses (0.1, 0.2 and 0.3 μg LHRH-A g-1 fish). A fertilization solution of 0.3% NaCl produced significantly higher fertilization rates than the other three solutions (0.5% NaCl, 0.65% NaCl and water). Fertilization times ranging from 5 to 2 0 min gave no significant difference in the fertilization rates. The embryonic and larval development of M. albus was observed and illustrated. The hatching time of eggs of M. albus was about 140 h in the 28-3 0oC water temperature range. Using Tubifex spp. for the first food for the larval nursery gave higher growth rate than two other foods, zooplankton and artificial food. 相似文献