共查询到20条相似文献，搜索用时 31 毫秒
1.
Asara JM Schweitzer MH Freimark LM Phillips M Cantley LC 《Science (New York, N.Y.)》2007,316(5822):280-285
Fossilized bones from extinct taxa harbor the potential for obtaining protein or DNA sequences that could reveal evolutionary links to extant species. We used mass spectrometry to obtain protein sequences from bones of a 160,000- to 600,000-year-old extinct mastodon (Mammut americanum) and a 68-million-year-old dinosaur (Tyrannosaurus rex). The presence of T. rex sequences indicates that their peptide bonds were remarkably stable. Mass spectrometry can thus be used to determine unique sequences from ancient organisms from peptide fragmentation patterns, a valuable tool to study the evolution and adaptation of ancient taxa from which genomic sequences are unlikely to be obtained. 相似文献
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Organ CL Schweitzer MH Zheng W Freimark LM Cantley LC Asara JM 《Science (New York, N.Y.)》2008,320(5875):499
We report a molecular phylogeny for a nonavian dinosaur, extending our knowledge of trait evolution within nonavian dinosaurs into the macromolecular level of biological organization. Fragments of collagen alpha1(I) and alpha2(I) proteins extracted from fossil bones of Tyrannosaurus rex and Mammut americanum (mastodon) were analyzed with a variety of phylogenetic methods. Despite missing sequence data, the mastodon groups with elephant and the T. rex groups with birds, consistent with predictions based on genetic and morphological data for mastodon and on morphological data for T. rex. Our findings suggest that molecular data from long-extinct organisms may have the potential for resolving relationships at critical areas in the vertebrate evolutionary tree that have, so far, been phylogenetically intractable. 相似文献
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Asara et al. (Reports, 13 April 2007, p. 280) reported sequencing of Tyrannosaurus rex proteins and used them to establish the evolutionary relationships between birds and dinosaurs. We argue that the reported T. rex peptides may represent statistical artifacts and call for complete data release to enable experimental and computational verification of their findings. 相似文献
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Bryan AL Casamiquela RM Cruxent JM Gruhn R Ochsenius C 《Science (New York, N.Y.)》1978,200(4347):1275-1277
Excavation at Taima-taima in 1976 recovered artifacts of the El Jobo complex in direct association with the butchered remains of a juvenile mastodon. Radiocarbon dates on associated wood twigs indicate a minimum age of 13,000 years before the present for the mastodon kill, a dating significantly older than that of the Clovis complex in North America. The El Jobo complex must have evolved independently in northern South America. 相似文献
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Schweitzer MH Suo Z Avci R Asara JM Allen MA Arce FT Horner JR 《Science (New York, N.Y.)》2007,316(5822):277-280
We performed multiple analyses of Tyrannosaurus rex (specimen MOR 1125) fibrous cortical and medullary tissues remaining after demineralization. The results indicate that collagen I, the main organic component of bone, has been preserved in low concentrations in these tissues. The findings were independently confirmed by mass spectrometry. We propose a possible chemical pathway that may contribute to this preservation. The presence of endogenous protein in dinosaur bone may validate hypotheses about evolutionary relationships, rates, and patterns of molecular change and degradation, as well as the chemical stability of molecules over time. 相似文献
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壳寡糖对秋海棠叶片离体培养的影响 总被引：4，自引：0，他引：4
[目的]明确壳寡糖(COS)用于秋海棠叶片离体培养的可行性。[方法]以MS为基本培养基,添加不同浓度的壳寡糖和1.5 mg/L2,4-D(对照),对秋海棠叶片进行离体培养。[结果]对照处理的秋海棠叶片离体培养的效果最好。壳寡糖在秋海棠叶片培养中可起到生长激素的作用,最适合诱导愈伤组织的浓度是1.5 mg/L,继代增殖和不定芽分化效果最好的浓度是1.52、.0 mg/L,诱导生根效果最好的浓度为1.5 mg/L,浓度为0.75%~1.00%壳寡糖溶液浇灌的幼苗成活率最高,达90%以上;同时对培养基及外植体起到了防污抗病的保护作用。[结论]秋海棠叶片离体培养时,培养基中的壳寡糖浓度以1.5 mg/L为宜。 相似文献
7.
Montané J 《Science (New York, N.Y.)》1968,161(3846):1137-1138
Bone and stone tools associated with extinct fauna (horse and mastodon) place man's occupation in central Chile at 11,380 +/- 320 years ago. 相似文献
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不同比例玉米和豆粕日粮对泌乳獭兔生产性能的影响 总被引：1，自引：0，他引：1
[目的]研究不同比例玉米和豆粕日粮对泌乳獭兔生产性能的影响,筛选最佳饲料配方。[方法]选用80只同期分娩,体重相近健康泌乳獭兔,随机分为5组,16只/组。Ⅰ、Ⅱ、Ⅲ、Ⅳ组为试验组,分别饲喂单玉米型日粮、单豆粕型日粮、双兼型日粮和双无型日粮。Ⅴ组为对照组,饲喂常规玉米豆粕型日粮。饲喂30 d后,检测其对母兔泌乳性能、仔兔生长速度、体重及饲料成本的影响。[结果]试验Ⅴ组泌乳獭兔的泌乳性能和仔兔生长速度均与对照组相近,差异不显著;Ⅲ组仔兔断奶成活率最高,差异不显著;其他试验组均明显低于对照组,差异显著（P〈0.05）;Ⅰ、Ⅱ和Ⅲ组母兔体重变化与对照组相比均差异不显著;Ⅳ组母兔失重明显高于对照组和其他试验组,差异极显著（P〈0.01）。试验组饲料成本均低于对照组。[结论]日粮中适当的玉米和豆粕比例,不仅可以降低饲养成本,而且可获得最佳的饲养效果。 相似文献
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Waters MR Stafford TW McDonald HG Gustafson C Rasmussen M Cappellini E Olsen JV Szklarczyk D Jensen LJ Gilbert MT Willerslev E 《Science (New York, N.Y.)》2011,334(6054):351-353
The tip of a projectile point made of mastodon bone is embedded in a rib of a single disarticulated mastodon at the Manis site in the state of Washington. Radiocarbon dating and DNA analysis show that the rib is associated with the other remains and dates to 13,800 years ago. Thus, osseous projectile points, common to the Beringian Upper Paleolithic and Clovis, were made and used during pre-Clovis times in North America. The Manis site, combined with evidence of mammoth hunting at sites in Wisconsin, provides evidence that people were hunting proboscideans at least two millennia before Clovis. 相似文献
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HTLV-II transactivation is regulated by the overlapping tax/rex nonstructural genes 总被引：16，自引：0，他引：16
J D Rosenblatt A J Cann D J Slamon I S Smalberg N P Shah J Fujii W Wachsman I S Chen 《Science (New York, N.Y.)》1988,240(4854):916-919
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蟆叶秋海棠离体培养的研究 总被引：2，自引：0，他引：2
以蟆叶秋海棠(Begonia rex)的幼嫩叶片为外植体,采用L25(55)正交设计,研究了不同生长调节剂和培养基对愈伤组织诱导的影响.结果表明,培养基的类型对愈伤组织诱导的影响极大,生长调节荆对愈伤组织诱导有一定的影响,愈伤组织在不添加任何生长调节剂的培养基上即可进行分化.蟆叶秋海棠最佳愈伤组织诱导培养基组合为1/2 MS+0.5～1.5 mg·L-1 KT+0.5 mg·L-16-BA+0.5～2.0 mg·L-1α-NAA+0.8%琼脂+3%蔗糖,愈伤组织诱导率可高达100%.生根培养基为1/2 MS+0.2 mg·L-1α-NAA+0.8%琼脂+3%蔗糖,生根率高达100%. 相似文献
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[目的]探讨影响獭兔离体肠道平滑肌收缩的因素。[方法]以獭兔十二指肠平滑肌为试验材料,以平滑肌收缩波的振幅和周期为评价指标,考察影响试验的各主要因素。[结果]在(36.5±0.5)℃台氏液中,獭兔离体肠管的存活时间和保质期最长,振幅最稳定,肾上腺素使离体肠管平滑肌收缩幅度减弱,乙酰胆碱、氢氧化钠及氯化钙均导致平滑肌收缩频率及幅度升高,收缩力增强。[结论]獭兔离体肠道平滑肌易受到温度、pH、其他化学因素及药物的影响。 相似文献
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Location and chemical synthesis of a pre-S gene coded immunodominant epitope of hepatitis B virus 总被引：27，自引：0，他引：27
Immunodominant, disulfide-bond independent epitopes recognized by human antibodies to hepatitis B virus (HBV) are located within the 55-residue amino terminal portion (coded for by the pre-S region of HBV DNA) of minor HBV envelope components larger than the major protein constituents encoded by the S gene. A peptide having the sequence of the first 26 amino acids from the amino terminal methionine was synthesized and elicited antibodies (at dilutions of greater than or equal to 1 to 10(5) ) to the HBV envelope. These antibodies can be utilized for diagnostic tests. The immunogenicity of the peptide was substantially increased by covalent attachment to liposomes. The disulfide bond-independent determinants on sequences coded for by the pre-S gene may be more easily mimicked by peptide analogs than "conformational" determinants on the S-gene product. 相似文献
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为了给獭兔的饲养管理、品种选育、肉质研究和临床诊疗提供依据,选择美系獭兔20只(雌雄各半),比利时兔10只(雌雄各半),对其血液生理生化指标进行了测定.结果表明:美系獭兔血液指标中的血小板数目、红细胞平均血红蛋白浓度、谷草转氨酶、谷氨酰转肽酶、钾离子和钙离子的含量分别为292.4×109·L-1、379.0 g·L-1... 相似文献
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6个家兔群体KAP6.1基因的遗传多样性分析 总被引：1，自引：1，他引：0
设计了2对特异性引物,经过序列拼接,获得了家兔KAP6.1基因的全长CDS序列,并采用PCR-SSCP方法对6个家兔群体KAP6.1基因的全长CDS序列进行分析.结果显示,KAP6.1-1座位发现了2个等位基因,3种基因型,且A755G突变处于该基因的增强子区域,而KAP6.1-2座位未发现突变位点;6个家兔群体均处于哈代-温伯格平衡,表现为中度或低度多态;福建黑兔与九嶷山兔、有色獭兔与白色獭兔、皖系长毛兔与苏系长毛兔的不同基因型分布差异不显著(P0.05),而其他家兔群体彼此间的不同基因型分布存在显著(P0.05)或极显著差异(P0.01). 相似文献
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蟆叶秋海棠“光灿”组织培养技术研究 总被引：2，自引：0，他引：2
以蟆叶秋海棠"光灿"的叶片、叶柄作为外植体材料进行组织培养,通过控制培养基组分、光照条件、培养时间等对其最佳组培条件进行探讨。结果表明,生长较为成熟的叶片为最佳外植体,最佳不定芽诱导培养基为MS+6-BA 1.5 mg/L+NAA 0.5 mg/L,最佳增殖培养基为MS+6-BA 1.0 mg/L+NAA 0.5 mg/L,最佳生根培养基为1/2 MS+NAA 0.2 mg/L。初代培养的光照强度以1200 lx为最佳,继代与生根培养的光照强度以1500 lx为最佳。诱导初期适当的暗培养有助于促进后期芽点的分化。 相似文献
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中草药饲料添加剂对獭兔肉品质的影响 总被引：4，自引：0，他引：4
[目的]为中草药饲料添加剂在獭兔养殖业中的推广应用提供理论依据。[方法]将108只40日龄断奶獭兔分成3组（每组36只）,A组饲喂基础日粮;B组饲喂基础日粮＋0.3%中草药饲料添加剂;C组饲喂基础日粮＋0.4%中草药饲料添加剂。饲养至150日龄时,测定肌肉品质指标。[结果]各组间pH值、失水率、贮存损失率、粗蛋白含量差异显著（P〈0.05）;嫩度、熟肉率、水分含量、粗脂肪含量差异不显著（P〉0.05）。氨基酸总量,必需和半必需氨基酸总量,主要鲜味氨基酸总量C组最高,为23.84%、11.47%、8.32%;B组次之,为20.94%、10.64%、6.81%;A组（对照组）最低,为19.06%、9.61%、6.46%,[结论]该中草药饲料添加剂能改善獭兔肉品质,最佳添加量为0.4%。 相似文献