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1.
Biophysics - Invagination of epithelial sheets is an important type of morphogenetic deformation. Primary invagination during gastrulation in the sea urchin provides one of the simplest and... 相似文献
2.
Significant portion (up to 20%) of dominant mutations (rifd mutations) was observed among spontaneous mutations of rifampicin resistance picked up in cells of haploid Escherichia coli strain. These mutations are similar to rifd mutations obtained earlier when selecting them in rif-s/rif-s merodiploids. On the basis of analysis of nucleotide substitutions taking place in formation of spontaneous and induced mutations, it is established that rifd mutations are caused by single nucleotide substitution. The majority of rifd mutations are localized in a small region of the central part of RNA polymerase beta-subunit gene covering less than 200 base pairs. A rifd mutant has been described which occurred as a result of micro-deletion in one of the "hot" spots of the central region of beta-subunit gene. 相似文献
3.
34Fusarium graminearum Schw isolates produced 4-deoxynivalenol to form significant amounts of 4, 7 — dideoxynivalenol and lesser amounts of 4 — deoxynivalenol monoacetates on grain substratesin vitro. This is the first report on the capability a large group of naturally occurring isolates to produce 4,7-dideoxynivalenol. The average levels of 4,7-dideoxynivalenol on rice, corn, barley, and wheat as a substrate were respectively 26.8, 14.0, 12.8, and 10.5% of the level of 4-deoxynivalenol. 4, 7 — dideoxynivalenol was present in all examined naturally contaminated wheat kernel samples at levels of 1.7 to 7.9% of the level of 4-deoxynivalenol. These findings suggest that more attention should be given to the occurrence of 4,7-dideoxynivalenol in cereals. 相似文献
4.
Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex 总被引:1,自引:0,他引:1
The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S
nuclear ribosomal DNA sequence and the intervening 5.8S region were
sequenced from three individuals in each of eight taxa of the Mimulus
guttatus species complex. Three discrete variants, or "types," of ITS
sequences were found, among which 30%-40% of sites differed, compared with
1%-2% within types. Dot plots indicate that these types were not related by
conspicuous rearrangements or inversions. More than one ITS type was often
found in the same taxon, and two of three ITS types span species
boundaries, indicating their presence prior to speciation. These ITS
sequences showed essentially no positional homology with the nearest
sequenced relative, tomato. In contrast, the 5.8S region was relatively
unvaried, with 8 of 162 sites varied in the sample among all eight taxa.
The phylogeny inferred by the most common ITS sequence type, rooted by the
two other ITS types, agreed with isozymes in showing the distinctness of M.
nudatus, M. laciniatus, and M. tilingii from the other five taxa.
相似文献
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In experiments with Wistar rats it was found that the increase in the length of the "hexenal dream" during the first week after the effect of a mixture of radiation and heat is much more pronounced than that observed after exposure to radiation alone and independent of the severity of a radiation component (gamma radiation, 4, 6 and 7.5 Gy). The peculiarities revealed in the hypnotic effect of hexenal develop against the background of the postirradiation aggravation of hypoalbuminemia and decrease in the liver ATP. 相似文献
7.
E A Dyskin T M Mefodovskaia M L Moiseeva L P Tikhonova 《Arkhiv anatomii, gistologii i émbriologii》1976,71(11):105-108
The method of detection of lactate dehydrogenase with some modification was used to study the microcirculatory bed in total preparations of serous membranes and plane sections of organs of any square surface. The employment of non-fixed material, the short time (from 15 to 60 min) necessary to obtain preparations of any size and simultaneous determination of the localization and the degree of the activity of the enzyme--are, to the authors opinion, undoubtful advantages of the given method, which can be an addition to the well-known impregnation method of determination of the microcirculatory bed. 相似文献
8.
大中型食肉动物肇事事件导致人类与野生动物关系恶化,给生物多样性保护工作带来巨大的挑战。若尔盖湿地是我国三大湿地之一,湿地、草原分布广泛,生物多样性丰富,畜牧业发达,但近年来狼(Canis lupus)捕杀牲畜的肇事事件时有发生。为了解若尔盖野生狼肇事件的空间分布以及牧民对人-狼冲突管理的看法,本研究于2022年对若尔盖县13个乡镇83个行政村进行走访调查。结果表明:(1)多数受访者(66.0%)认为在过去5年内,若尔盖县野生狼数量有所增加;(2)狼肇事事件具有明显的空间分异性,最严重的是包座乡。包座乡临近山区,该区域牧场面积广阔、牧民饲养牲畜数量多等原因导致该镇发生狼肇事事件较多;(3)对于狼肇事,绝大多数牧民(85.0%)更希望采取经济补偿或者驱赶措施,只有少数牧民(9.4%)希望采取捕杀的措施;(4)影响牧民对狼肇事管理措施的偏好因子中,受教育程度、年龄、民族以及被杀牲畜数量有显著影响。建议加强狼种群监测管理,采取措施减少狼捕杀牲畜,优化补偿机制,缓解当地牧民与狼之间的矛盾。本研究为当前若尔盖县野生动物保护和管理决策提供了依据,对其他地区大型食肉动物与当地居民冲突管理具有借鉴意义。 相似文献
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10.
从茎花葱臭木种子中分离得到5个化合物,经理化与波谱分析鉴定为β-谷甾醇(1)、没食子酸乙酯(2)、胡萝卜苷(3)、1-O-β-D-吡喃葡萄糖基-(2S,3S,4R,8Z)-2-N-(2 ′-羟基二十四烷酰氨基)十八二氧鞘氨-8-烯(4)和2,3,2″,3″-四氢穗花杉双黄酮(5).这5个化合物均首次从该植物中分离得到.其中化合物5进行细胞毒活性测试,没有显示抑制活性. 相似文献