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11.
The presence or absence of cyanogenic glycosides was determined for individuals from nine populations of Sambucus canadensis L. (elderberry) of east-central Illinois. In most of the populations tested, all or most of the individuals did not produce these compounds, in one, all were cyanogenic, whereas in another population this trait was highly variable. Addition of the enzyme emulsin to negative tests did not result in any further release of cyanide. The glycoside responsible is (S)-sambunigrin. 相似文献
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This article introduces a new method to represent bone surface geometry for simulations of joint contact. The method uses the inner product of two basis functions to provide a mathematical representation of the joint surfaces. This method guarantees a continuous transition in the direction of the surface normals, an important property for computation of joint contact. Our formulation handles experimental data that are not evenly distributed, a common characteristic of digitized data of musculoskeletal morphologies. The method makes it possible to represent highly curved surfaces, which are encountered in many anatomical structures. The accuracy of this method is demonstrated by modeling the human knee joint. The mean relative percentage error in the representation of the patellar track surface was 0.25% (range 0-1.56%) which corresponded to an absolute error of 0.17mm (range 0-0.16mm). 相似文献
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T Banaszak A LaJeunesse TC Trench RK 《Journal of experimental marine biology and ecology》2000,249(2):219-233
We tested the hypothesis that there is a relation between phylotypes (phylogenetic types, as determined by restriction fragment length polymorphism (RFLP) and partial sequence analysis of the small subunit ribosomal RNA gene (SSUrDNA)) and the synthesis of mycosporine-like amino acids (MAAs) by symbiotic dinoflagellates under the influence of ultraviolet radiation (UV-B/A) and photosynthetically active radiation (PAR). We exposed 27 isolates of symbiotic dinoflagellates simultaneously to UV-B/A and PAR, and subsequently determined the MAAs present in cell extracts and in the media. The algae used included 24 isolates of Symbiodinium spp. originating from jellyfishes, sea anemones, zoanthids, scleractinians, octocorals, and bivalves, and three others in the genera Gymnodinium, Gloeodinium and Amphidinium from a jellyfish, an hydrocoral and a flatworm, respectively. In this study, all of the phylotype A Symbiodinium spp. synthesized up to three identified MAAs. None of the 11 cultured phylotypes B and C Symbiodinium spp. synthesized MAAs. The three non-Symbiodinium symbionts also synthesized up to three MAAs. The results support a conclusion that phylotype A Symbiodinium spp. have a high predilection for the synthesis of MAAs, while phylotypes B and C do not. Synthesis of MAAs by symbiotic dinoflagellates in culture does not appear to relate directly to depths or to the UV exposure regimes from which the consortia were collected. 相似文献
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CC to TT mutation in the mitochondrial DNA of normal skin: relationship to ultraviolet light exposure 总被引:1,自引:0,他引:1
We have previously reported that ultraviolet (UV)-specific (CC to TT) mutations in p53 gene can be detected in normal skin. This, however, cannot be used as a cumulative marker of UV exposure, since cells with the p53 mutation acquire a clonal growth advantage. Moreover, a large skin biopsy is necessary for each assay. In order to circumvent these problems, we have measured mitochondrial (Mt) DNA mutations; there are more than 1000 copies of the Mt genome per cell, and Mt genes are not directly involved in cell growth. We have established a sensitive allele-specific polymerase chain reaction (AS-PCR) assay capable of detecting one CC to TT mutation in Mt DNA among 10(7) wild-type genes using a mismatch allele-specific primer. With this assay, we found no mutation-positive samples from internal non-exposed tissue (stomach, colon, and blood) (0/50). In contrast, 17 out of 111 skin samples were positive: the mutation frequency in positive samples was around 10(7)-10(-6) (10-100 copies of mutant in 10(8) wild-type Mt DNA). In normal skin tissue, the prevalence of positive samples was higher in those from exposed sites (13/51) than in those from less-exposed sites (1/26) (p<0.05). However, a quantitative correlation between sunlight exposure and the accumulation of mutations was not found. We conclude that the UV exposure-associated CC to TT mutation in Mt DNA can be detected in normal skin, but that further studies are required to develop this as a quantitative marker for UV exposure. 相似文献
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鱼鳞胶原蛋白提取及对成纤维细胞功能的影响 总被引:1,自引:0,他引:1
通过水提法提取鱼鳞胶原蛋白,分离大鼠皮肤成纤维细胞,观察鱼鳞胶原蛋白对成纤维细胞增殖,细胞内血小板衍生因子(platelet derived growth factor,PDGF)、转化生长因子β(transforming growth factorβ,TGFβ)mRNA表达、蛋白合成及cGMP含量的影响。结果发现:鱼鳞胶原蛋白可促进成纤维细胞增殖,并呈一定的剂量依赖关系,当质量浓度达到40mg/L时,增值率可达42.75%;鱼鳞胶原蛋白能通过促进cGMP合成,明显促进成纤维细胞PDGF、TGFβmRNA表达及蛋白合成,当质量浓度为40mg/L时,PDGF、TGFβmRNA表达量分别为对照组的1.514±0.047和1.595±0.032倍。水提法提取的鱼鳞胶原蛋白具有良好的相容性,可促进成纤维细胞增殖及活化,具有潜在的临床应用价值。 相似文献
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