THE IMPORTANCE OF CAFFEINE AS A FLAVOR COMPONENT IN BEVERAGES

Caffeine contributes to the flavor profiles of beverage and food products, and other bitter compounds, such as quinine, cannot replicate caffeine's bitterness. Research also has indicated caffeine's ability to enhance desirable tastes, such as sweetness and saltiness, in beverages by modifying neurological pathways. Caffeine may reduce potential " off-flavors" by solubilizing some compounds, while having little effect on other compounds considered important in beverage flavor profiles. Exposure to caffeine may enhance cognition and potentially heighten the capacity for smell and taste. Thus, use of caffeine in beverages may positively affect flavor profiles and the experience of beverage consumption.     

THE DEGENERATION AND REAPPEARANCE OF MITOCHONDRIA IN THE EGG CELLS OF A PLANT

Details are given of the elimination of mitochondria which occurs during the first 1 to 2 hours of the life of the egg of the fern Pteridium aquilinum (L.) Kuhn. During this phase the only mitochondria present are swollen and appear degenerate, but subsequently the cytoplasm of the egg becomes filled with large mitochondria containing numerous villi. Accompanying the appearance of these mitochondria, many, if not all of which have a peculiar umbo-like form, is the production by the nucleus of conspicuous and complex evaginations. The umbo-mitochondria are believed to be new, and a mechanism is suggested by which they may be generated from the complex evaginations of the nucleus.     

db-cAMP对转化细胞钙调素基因表达与细胞骨架的影响

转化的C_3H_(10)T_(1/2)细胞表现增殖速度加快、表面微绒毛增加,细胞变圆,叠层生长,ConA受体呈帽状分布,微管、微丝、纤粘蛋白分布明显减少。与增殖有关的癌基因c-fos表达增强,同时发现与细胞增殖、转化和细胞骨架调节有关的钙调素(CaM)基因表达加强。用1mmo/Ldb-cAMP处理转化细胞,观察到CaM基因和原癌基因c-fos的表达分别在处理后1小时和2小时急剧下降。处理后4—5天,转化细胞表型趋正常化,大部分细胞恢复单层生长。细胞表面微绒毛和泡状物减少,ConA受体帽状分布消失,恢复分散分布在细胞膜上的特点。细胞生长明显被抑制,用优先在G_1期表达的4F_1 cDNA为探针进行分子杂交,证实了经db-cAMP处理后的细胞被阻抑在G_1期。经db-cAMP处理6天的转化细胞中微管、微丝、纤粘蛋白基本恢复正常分布。实验表明CaM的表达增强与转化细胞表型变化和细胞骨架组装减弱密切相关,db-cAMP作用后CaM表达下降是抑制转化细胞增殖并使细胞表型和细胞骨架分布趋于正常的关键事件之一。     

黄蝉花生殖细胞有丝分裂期间微管的动态

用微管免疫荧光方法观察了黄蝉花生殖细胞在花粉管中进行有丝分裂时的微管动态。微管在不同分裂期的分布情形很不一样。当生殖细胞由花粉进入花粉管后,细胞便立刻开始分裂进入早前期,在这阶段微管以一个紧密微管网笼子形式存在生殖细胞内。之后,细胞进入中前期,在此阶段细胞核扩大,染色体变粗,而存在细胞内的微管网逐渐变为疏松散漫状,跟着细胞进入晚前期,而微管笼子则由网状变为纵向排列状。分裂进入早中期微管变细并呈波浪状,微管由笼子结构过渡到纺锤体结构。进入中期,纺锤体全部形成,在纺锤体内可以清楚地看到两种不同类型的微管束,一种附着在染色体上,而另一种则从一极延伸至另一极。跟着细胞进入早后期,在这一阶段姊妹染色体分开并分别移向两极,在赤道板位置微管明显减少。之后,细胞进入晚后期,姊妹染色体集中在两极,极端有新微管出现。在两个染色体团之间又汇集了许多类似成膜体微管的微管。细胞进入分裂末期,存在赤道板位置的微管又再次减少,而在中央部位则新形成一“成膜体联接区”,把两个新形成的精子连接着。     

植物细胞中间纤维角蛋白性质的分析

角蛋白是植物细胞中间纤维的主要成分。应用选择性抽提和生物化学技术,分离纯化了豌豆根尖细胞58-、52 kD、白菜子叶52kD和胡萝卜悬浮细胞64kD角蛋白,测定了它们的氨基酸组成,结果表明上述角蛋白与动物细胞中间纤维角蛋白的氨基酸组成有较大的相似性。比较了动、植物细胞角蛋白的肽谱,结果显示它们之间存在较大的差异,但是植物细胞间角蛋白的肽谱比较一致,这提示它们属于同一蛋白家族,为植物中间纤维及其角蛋白的存在提供了新的论据。     

大鼠睾丸间质细胞的自体吞噬活动

本文结合超微结构和细胞化学观察,研究大鼠睾丸间质细胞(Leydig细胞)中溶酶体的结??构与功能。观察结果表明,大鼠睾丸间质细胞中高尔基体非常发达,在高尔基体的成熟面存在着CMP酶阳性反应的GERL系统,说明这种细胞有不断产生溶酶体的能力。细胞化学结果也证实在睾丸间质细胞有较多的初级和次级溶酶体。睾丸间质细胞不仅有较多的溶酶体,而且还有相当数量的自噬小体,存在着活跃的自体吞噬活动。自噬小体的界膜来源于特化的光面内质网或高尔基体膜囊,包围的内容物主要是光面内质网和少量线粒体。当自噬小体与溶酶体融合后即成为自体吞噬泡,由于酶的消化作用,自体吞噬泡内的细胞器有一系列形态变化。根据CMP酶细胞化学反应,可以区分自噬小体和自体吞噬泡,后者是一种次级溶酶体,呈CMP酶阳性反应。睾丸间质细胞是分泌雄性激素的内分泌细胞,其光面内质网和线粒体在类固醇激素分泌中起重要作用,自体吞噬活动的结果是去除部分内质网和线粒体,可能在细胞水平上起着对雄性激素分泌的调节作用。     

THE NORMAL TRANSPLACENTAL PASSAGE OF MATERNAL RED CELLS IN MICE

⁵¹Cr labelled red cells injected into pregnant mice were subsequently detected in peripheral blood of their progeny when examined in autoradiography. The fact that these labelled cells were seen in the offspring from five different strains of mice suggests that this transplacental passage is probably a 'normal' phenomenon.     

不同应激损伤所致血管内皮细胞中vWF的变化

目的：通过检测血管内皮细胞（ＶＥＣ）中ｖＷＦ的变化,评价ＶＥＣ的损伤。方法：利用免疫组化技术对体外培养的猪肺动脉内皮细胞（ＰＡＥＣ）和大鼠主动脉内皮细胞（ＡＥＣ）中ｖＷＦ进行免疫荧光标记,通过流式细胞仪对ｖＷＦ的细胞阳性率和荧光强度进行定性、定量分析,观察低氧和低温所引起的ｖＷＦ变化。结果：正常猪ＰＡＥＣ和大鼠ＡＥＣ的ｖＷＦ阳性率在８０％左右,阳性程序较高。但缺氧或冷冻损伤可使ＰＡＥＣ和ＡＥＣ的ｖ     

A POSSIBLE MECHANISM FOR THE MORPHOGENESIS OF LAMELLAR SYSTEMS IN PLANT CELLS

A mechanism for the formation of lamellar systems in the plant cell has been proposed as a result of electron microscope observations of young and mature cells of Nitella cristata and the plastids of Zea mays in normal plants, developing plants, and certain mutant types. The results are compatible with the concept that lamellar structures arise by the fusion or coalescence of small vesicular elements, giving rise initially to closed double membrane Structures (cisternae). In the chloroplasts of Zea, the cisternae subsequently undergo structural transformations to give rise to a compound layer structure already described for the individual chloroplast lamellae. During normal development, the minute vesicles in the young chloroplast are aggregated into one or more dense granular bodies (prolamellar bodies) which often appear crystalline. Lamellae grow out from these bodies. In fully etiolated leaves lamellae are absent and the prolamellar bodies become quite large, presumably because of inhibition of the fusion step which appears to require chlorophyll. Lamellae develop rapidly on exposure of the plant to light, and subsequent development closely parallels that seen under normal conditions. The plastids of white and very pale green mutants of Zea similarly lack lamellae and contain only vesicular elements. A specialized peripheral zone immediately below the double limiting membrane in Zea chloroplasts appears to be responsible for the production of vesicles. These may be immediately converted to lamellae under normal conditions, but accumulate to form a prolamellar body if lamellar formation is prevented, as in the case of etiolation and chlorophyll-deficient mutation, or when the rate of lamellar formation is slower than that of the production of precursor material (as appears to be the case in the early stages of normal development).     

小麦胚乳细胞中肌动蛋白纤丝分布格局的荧光显微观察

以异硫氰四甲基罗丹明－鬼笔环肽为探针,结合电视显微镜术对呈现原生质胞间运动的小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）胚乳细胞胞质中肌动蛋白纤丝（ＡＦｓ）的存在与分布格局进行了观察与分析。结果表明,ＡＦｓ以多种形式在胚乳细胞内呈区域性分布：胞核为ＡＦｓ网络所包围,ＡＦｓ成束由核周向四处辐射直抵周质层,大量纤细ＡＦｓ在胞质皮层内呈无序的密集分布以及腹沟区细胞内ＡＦｓ梭状体的大量汇集。联系胞质组分在胞间运动中的动态与胞质纤索对ＣＢ处理的反应,讨论了ＡＦｓ的不同存在状态与胞质纤索的伸缩穿越和细胞基质的集流迁移这两种胞间运动方式的关系     

THE NATURE OF PLASMODESMATA IN NORMAL (LIVING) PLANT TISSUE

Techniques have been devised for the demonstration and study of plasmodesmata in an unaltered state in plant tissues. Text figures and data are presented for plasmodesmata in the cambium and certain other tissues of Pinus strobus, parenchyma tissues of Lycopersicum esculentum, and ray and wood parenchyma tissue of Sequoia sempervirens. In all cases, the plasmodesmata were of similar morphology, with a diameter of approximately 0.2μ. Comparative studies are presented showing the effects of various swelling agents which were used in past studies, and of dehydration which is a normal concomitant of most histological procedures. The present paper provides an important base line for the comparison of the appearance of plasmodesmata in living tissue to the findings of recent studies with the electron microscope.     

A COMPARISON OF PERMEABILITY IN PLANT AND ANIMAL CELLS

Quantitative studies show a striking agreement between frog skin and plant tissues in respect to certain important aspects of permeability, antagonism, injury, recovery, and death.