运动员使用咖啡因对运动能力的影响

目的:评估咖啡因在运动员训练和不同运动项目中应用研究新进展和合理的应用方法.方法:检索体育科学杂志主要的数据库中国知网,Springer,Ovid,LWW,science-direct,研究分析咖啡因在运动员训练中应用的原理研究进展和运动员应用效果、应用方法及对运动能力的影响.结果:咖啡因具有降低运动中中枢疲劳和/或提...     

测定咖啡因的几种方法比较

用紫外吸收光谱、导数光谱及高效液相色谱法测定两种速溶咖啡制品中的咖啡因含量,并对光谱法测定结果与ＨＰＬＣ法测定结果进行统计分析比较。结果表明：用二阶导数光谱法测定速溶咖啡制品中咖啡因,操作简便,结果准确可靠,可替代ＨＰＬＣ法分析此类样品。     

The first cleavage of the mouse zygote predicts the blastocyst axis

One of the unanswered questions in mammalian development is how the embryonic-abembryonic axis of the blastocyst is first established. It is possible that the first cleavage division contributes to this process, because in most mouse embryos the progeny of one two-cell blastomere primarily populate the embryonic part of the blastocyst and the progeny of its sister populate the abembryonic part. However, it is not known whether the embryonic-abembryonic axis is set up by the first cleavage itself, by polarity in the oocyte that then sets the first cleavage plane with respect to the animal pole, or indeed whether it can be divorced entirely from the first cleavage and established in relation to the animal pole. Here we test the importance of the orientation of the first cleavage by imposing an elongated shape on the zygote so that the division no longer passes close to the animal pole, marked by the second polar body. Non-invasive lineage tracing shows that even when the first cleavage occurs along the short axis imposed by this experimental treatment, the progeny of the resulting two-cell blastomeres tend to populate the respective embryonic and abembryonic parts of the blastocyst. Thus, the first cleavage contributes to breaking the symmetry of the embryo, generating blastomeres with different developmental characteristics.     

咖啡因在水和乙醇中介稳区的测定

测定了0—50℃范围内咖啡因晶体在水和乙醇溶剂中的溶解度和超溶解度曲线，同时拟合出咖啡因的溶解度和超溶解度方程，确定了晶体生长的介稳区范围。结果表明，咖啡因在水和无水乙醇中的介稳区较宽，将结晶操作控制在介稳区之内，添加晶种可以避免自发成核，这有助于咖啡因结晶生产。     

茶叶中提取咖啡因实验教学的探索

论述提取咖啡因实验中电压的调节、试剂的用量等方面的内容。本着安全、经济、高效、环保的原则，在实验的各个环节中进行了认真探索和改进。具有节省试剂，加热装置简便等优点，提高了学生实验的素养，在实验教学中取得了理想的效果。     

改进茶叶中提取咖啡因的有效方法

针对提取咖啡因常用的5种方法:"茶叶中加入生石灰在索氏提取器中用95%乙醇提取-升华法"、"茶叶中加入生石灰95%乙醇回流浸取-升华法"、"将茶叶在热水溶解浸取-氯仿萃取法"、"碳酸钠水溶液热浸取二氯甲烷萃取法"、"直接升华法",作者对提取咖啡因方法进行了实际比较,发现在茶叶末中混合一定量的碱碳酸钠,会改善咖啡因的收率,增强提取效果.     

IGF-Ⅱ and IGFBP-1 reversely regulate blastocyst implantation in mouse

Insulin-like growth factor (IGF)-Ⅱ and IGF binding protein (IGFBP)-1, members of IGF family, are important in the cyclic development of endometrium and the blastocyst implantation. In the present study, the indirect immunofluorescence showed that IGF-Ⅱ and IGFBP-1 were specifically expressed at the maternal-fetal interface. In a co-culture system, IGF-Ⅱ significantly enhanced the attachment and outgrowth of the blastocyst on monolayer of uterine epithelial cells, while IGFBP-1 did not affect the blastocyst attachment, but markedly inhibited the blastocyst outgrowth. The results of zymography showed that IGF-Ⅱ enhanced the activities of MMP-2 and MMP-9, while IGFBP-1 did not affect the activities of MMP-2 and MMP-9. In conclusion, the equilibrium between the invasion of trophoblast and the inhibition of deciduas may be regulated by the interaction between the IGF-Ⅱ-expressing invading cytotrophoblast and maternal deciduas-derived IGFBP-1.     

茶叶中提取咖啡因实验条件的研究

茶叶中提取咖啡因是有机化学教学中关于天然有机化合物提取与分离的重要实验,由于现使用的《有机化学》教材中实验条件不确切,升华产物色泽不好、晶体的量很少.经过多次实验条件研究,使茶叶中提取咖啡因实验教学效果良好.     

浅谈提高咖啡因产品纯度与产量的教学体会

＂从茶叶中提取咖啡因＂是医学院校有机化学中的一个经典实验。针对此实验常出现咖啡因产品的纯度和产量均低的现象,为了提高产品的纯度与产量,笔者对影响该实验结果的四个实验步骤进行操作要点的解析,粗浅的谈了一些教学体会,仅供实验者参考借鉴。     

茶叶中儿茶素,咖啡因和叶绿素的提取和分析鉴定

茶叶中儿茶素、咖啡因和叶绿素的提取和分析鉴定吴明光，王金茂（化学系）茶叶中的儿茶素咖啡因和叶绿素无论作为保健食品或医药、化妆品中的添加剂都具有不可忽视的应用前景。因而引起国内外有关专家的关注，已有不少研究结果发表，但多侧重于儿茶素类或多酚类化合物等的...     

几种天然材料对茶多酚和咖啡因的吸附与分离特性

用HPLC法测定表没食子儿茶素没食子酸酯(EpigaUocatechin-3-gallate,EGGG)和咖啡因含量,分光光度法测定总茶多酚含量,研究了几种天然材料对茶提取物中茶多酚和咖啡因的吸附与分离特性.谷壳和丝瓜络对茶多酚的吸附率分别为65%和62%,稍低于最佳吸附大孔树脂DM130(73%)和最佳分离树脂聚酰胺树脂(81%)的吸附率;对咖啡因的吸附率分别为24%和18%,介于DM130(68%)和聚酰胺(15%)之间.红砖粉、矿石粉末和河沙对茶多酚和咖啡因的吸附率都很低,分别为38%,29%,3%和24%,15%,15%.用1 BV水、20%乙醇、40%乙醇和3 BV 80%乙醇梯度洗脱,测定了它们对EGCG和咖啡因的柱层析分离效果.DM130不能将两者分离开,94%～96%的EGCG和咖啡因同时存在于40%和80%的乙醇相中.聚酰胺树脂能够很好地分离这两种成分,90%咖啡因在水和20%E,醇洗脱相中,而90%EGCG在80%乙醇相中.谷壳和丝瓜络对EGCG和咖啡因的分离效果介于DM130和聚酰胺之间.谷壳为吸附剂时,92%咖啡因在水,20%和40%乙醇相中,84%的EGCG在80%乙醇相中.丝瓜络吸附剂时,87%咖啡因在水,20%和40%乙醇相中,76%的EGCG在80%乙醇相中.调整和控制好洗脱条件和洗脱剂用量,可较好地分离EGCG和咖啡因.结果表明,谷壳和丝瓜络可用作EGCG和咖啡因的吸附分离材料,具有对环境和健康安全、廉价易得等特点.