菠萝叶片中有机酸含量,转氨酶和脱氨酶活性的昼夜变化

研究了菠萝叶片中苹果酸,柠檬酸,草酰乙酰,α－酮戊二酸和草酸等有机酸和转氨酶、脱氢酶活性的昼夜变化。结果表明,除了草酸外,其他４种机酸的含量都呈白天降低晚上增高的趋势。     

白地霉的氧化代谢

1．自地霍完整静息幼胞氧化乙醇、乙酸、丙酮酸及草酰乙酸的速度很高,对其他三羧酸循环各酸如：琥珀酸、延胡索酸、a-酮戊二酸、苹果酸、柠檬酸、顺岛头酸及异柠檬酸也能氧化,但速度甚低。 2．在白地霉无细胞提取液中测出了三羧酸循环中以下各种酶活力：柠檬酸精合酶、异柠檬酸脱氢酶、顺岛头酸酶、a-酮戊二酸脱氢酶、琥珀酸脱氢酶、延胡索酸酶、苹果酸脱氢酶、苹果酸酶、草酰乙酸羧化酶等,并间接得知有乙酸激活酶及L-谷氨酸脱氢酶存在。 3．在白地霉无捆胞提取液中测出了乙醛酸循环的两个关键的酶皂口异柠檬酸酶及苹果酸合成酶。 4．由以上结果可知白地霉可利用三羧酸循环及乙醛酸循环作为末端呼吸途径。     

烤烟生育期间主要非挥发性有机酸含量及相关酶活性变化特征

以12个烤烟品种为材料,通过测定烤烟中部叶有机酸总量、苹果酸含量、柠檬酸含量、代谢相关酶活性的动态变化以及烤后烟碱含量和感官质量,探讨烤烟生长过程中叶片主要非挥发性有机酸含量及代谢相关酶活性变化规律。结果表明:(1)随着烟株的生长发育,烤烟中部叶有机酸总量呈先升高后降低趋势,于叶龄50~60d时达到最高值;烤烟品种间中部叶有机酸总量在各叶龄时期存在极显著差异,而在调制前后变化不大。(2)苹果酸含量呈"逐渐升高"趋势;柠檬酸含量呈缓慢"增-减"的趋势;苹果酸含量与苹果酸脱氢酶(NAD-MDH)活性之间极显著负相关;柠檬酸含量与柠檬酸合成酶(CS)活性之间极显著正相关,而与异柠檬酸脱氢酶(NAD-IDH)活性相关性不大。(3)当有机酸总量大于32%,同时烟碱含量介于1.5%~2.6%时,"酸碱比"较高的烟叶感官质量较好。研究认为,烤烟叶片苹果酸和柠檬酸的积累受其代谢相关酶活性变化的调控,"酸碱比"影响烤烟烟气的醇和度,可通过调控NAD-MDH和CS活性来调节苹果酸和柠檬酸的含量,协调"酸碱比",提高烟叶质量。     

过氧化物酶体膜对各种光呼吸代谢物的透性和Percoll对其完整性的影响

利用氧极谱法测定依赖乙醇酸和乙醛酸的氧吸收,利用分光光度计测定转氨酶活性的方法,检查了光呼吸碳代谢中各种中间产物对过氧化物酶体膜的透性,结果表明,O2,乙醇酸,乙醛酸,丝氨酸,天冬氨酸,草酰乙酸,α－酮戊二酸能透过过氧体膜,过氧体膜可能有谷氨酸和NADH进入的屏障,过氧体悬浮液Percoll存在,很快使过氧体膜破坏,Percoll也使羟基丙酮酸还原酶和苹果酸脱氢酶的活性很快降低。     

过氧化物酶体膜对各种光呼吸代谢物的透性和Percoll对其完整性的影响

利用氧极谱法测定依赖乙醇酸和乙醛酸的氧吸收,利用分光光度计测定转氨酶活性的方法,检查了光呼吸碳代谢中各种中间产物对过氧化物酶体膜的透性,结果表明,O2,乙醇酸,乙醛酸,丝氨酸,天冬氨酸,草酰乙酸,α－酮戊二酸能透过过氧体膜,过氧体膜可能有谷氨酸和NADH进入的屏障,过氧体悬浮液Percoll存在,很快使过氧体膜破坏,Percoll也使羟基丙酮酸还原酶和苹果酸脱氢酶的活性很快降低。     

光滑球拟酵母中α-酮戊二酸脱氢酶系生理作用解析

[目的]研究α-酮戊二酸脱氢酶系在光滑球拟酵母碳代谢流、能量代谢和氨基酸代谢中的生理作用.[方法]通过敲除光滑球拟酵母中编码α-酮戊二酸脱氢酶系中E1酶的基因kgd1,构建α-酮戊二酸脱氢酶活性缺失菌株T.glabrata kgd1::kan,并考察KGDH缺失引起TCA循环关键酶活性,碳代谢流量以及胞内氨基酸和能荷水平等方面的变化.[结果]光滑球拟酵母中α-酮戊二酸脱氢酶活性的缺失导致:(1)细胞启动乙醛酸途径,通过形成TCA-乙醛酸循环实现TCA循环的正常代谢;(2)胞内NADH/NAD+水平下降33.7%,ATP/ADP水平下降31.8%,而与NADH代谢相关的丙酮酸脱氢酶、异柠檬酸脱氢酶和苹果酸脱氢酶的活性分别提高58.1%、33.3%和32.5%;(3)胞内丙酮酸含量下降50.1%,而胞内琥珀酸、苹果酸和α-酮戊二酸含量则分别增加了172.7%、66.1%和41.1%;(4)丙酮酸族氨基酸含量下降29.3%,而胞内谷氨酸族氨基酸和天冬氨酸族氨基酸含量则提高了34.7%和26.8%.[结论]上述研究结果表明,α-酮戊二酸脱氢酶系在微生物细胞中心碳代谢、能量代谢和氨基酸代谢中发挥着重要作用.     

菠萝叶片绿色组织与贮水组织中代谢物水平的昼夜变化

研究了景天酸代谢（CAM）植物菠萝叶片绿色组织与贮水组织（WSP）的苹果酸、柠檬酸、异柠檬酸、淀粉、果糖、葡萄糖、蔗糖、葡糖－1－磷酸（G－1－P）、葡糖－6－磷酸（G－6－P）、果糖6－磷酸（F－6－P）、草酰乙酸（OAA）及磷酸烯醇式丙酮酸（PEP）水平的昼夜变化。夜间苹果酸的积累仅发生在绿色组织中,表明只有绿色组织才能进行CAM。可溶性已糖（葡萄糖和果糖）是绿色组织中夜间苹果酸累积的主要碳源。绿色组织G－1－P、G－6－P和F－6－P水平在夜间的初期上升,后期下降,昼间的头3h仍下降,3h后变化不明显。绿色组织中OAA和PEP水平也发生昼夜变化。在贮水组织中没有测到淀粉、蔗糖、OAA和PEP。除葡萄糖和果糖外,WSP中其它代谢物的含量都远低于绿色组织,而且WSP中所有代谢物都无明显的昼夜变化。     

向日葵叶片的有机酸

有机酸是植物代谢的重要产物之一.其作用有五点:①作为代谢的中间产物(如丙酮酸、α-酮戊二酸),可进一步转化为其他化合物;②构成植物体内的缓冲体系(如柠檬酸),使酸碱度变化不大,创造一个比较稳定的内环境,从而使各种生理生化过程有序地进行;③中和植物体内过多的阳离子,例如草酸可与钙离子结合,生成草酸钙结晶;④参与调节气孔的开闭运动,如苹果酸;⑤通过四碳二羧酸途径固定CO_2,使C_4植物的光合速率大大提高. 本文主要介绍向日葵在开花期、乳熟期、完熟期时叶片中有机酸含量的动态变化.     

硅和稻瘟病菌接种对水稻植株有机酸含量的影响

以抗病性不同的一对水稻近等基因系——感病CO39和抗病C101LAC(Pi-1)为实验材料,在水培条件下研究了施硅和稻瘟病接菌对水稻根系和叶片抗性物质有机酸含量的影响,揭示硅提高水稻对稻瘟病抗性的机理。结果表明:接菌条件下硅处理显著降低了2个基因型材料的叶片反丁烯二酸、柠檬酸的含量,而增加了叶片中草酸、顺丁烯二酸的含量;加硅显著降低接菌后第3天的CO39叶片酒石酸含量,但增加了C101LAC(Pi-1)接菌后第7天的叶片酒石酸含量;硅处理还显著增加了根系中苹果酸和草酸的含量;各种有机酸在水稻植株体内的分布也不尽相同,如柠檬酸主要分布在叶片中,苹果酸主要分布在根系中,顺丁烯二酸、反丁烯二酸、酒石酸和草酸在叶片和根系中都有分布。研究表明,硅可能通过影响植株体内的有机酸代谢而增强稻瘟病的抗性。     

外源水杨酸对铝胁迫下菊芋根系分泌物的影响

为探究铝胁迫对菊芋根系分泌物的影响以及外源水杨酸(SA)的缓解作用,该文以耐铝型南京菊芋和铝敏感型资阳菊芋为试验材料,采用土培法,设置铝浓度500μmol·L^-1,分析了不同浓度(10、100、1 000μmol·L^-1)SA对铝胁迫下菊芋根系分泌物中有机酸、氨基酸以及根尖相关代谢酶活的影响。结果表明：(1)单铝胁迫会导致菊芋根系分泌物中柠檬酸、草酸、苹果酸浓度升高,且南京菊芋升高幅度大于资阳菊芋;柠檬酸合酶和苹果酸脱氢酶在单铝胁迫下活性增强;脯氨酸含量显著提升,总氨基酸浓度均显著减少。(2)外源SA加入后,南京菊芋根系分泌的柠檬酸、草酸、苹果酸浓度均得到不同程度提高,但经高浓度(1 000μmol·L^-1)SA处理后资阳菊芋根系分泌草酸显著降低,且在各浓度SA处理下苹果酸浓度均无明显变化;柠檬酸合酶活性出现不同程度的增强,但对南京菊芋根尖中苹果酸脱氢酶活性影响不大,且高浓度(1 000μmol·L^-1)SA处理后显著降低了资阳菊芋根尖中苹果酸脱氢酶活性;脯氨酸含量显著下降,从总氨基酸浓度变化来看,...     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.