低温强光下籼粳稻紫黄质脱环氧化酶活性和类囊体膜脂不饱和度的变化

为了阐明籼稻(Oryza sativa L.spp.indica)、粳稻(O.sativa L.spp.japonica)对低温强光敏感件的差异,着重研究了低温强光下水稻类囊体膜脂不饱和度与叶黄素循环的变化。随着低温强光处理时间的延长,类囊体膜脂不饱和脂肪酸含量降低,饱和脂肪酸含量增加,因而膜脂不饱和指数(IUFA)下降。同时,叶黄素循环的关键酶——紫黄质脱环氧化酶(VDE)活性降低,叶黄素循环组分中紫黄质(V)含量增加,而单环氧玉米黄质(A)和玉米黄质(Z)的含量减少,表现为(A Z)／(A Z V)比值下降。Arrhenius分析证明,VDE对低温和膜脂不饱和度都敏感。相关分析表明,类囊体IUFA分别与VDE活性、(A Z)／(A Z V)和D1蛋白量呈显著的正相关。与粳稻9516相比,籼稻汕优63类囊体膜的IUFA较低,低温下类囊体膜脂流动性和稳定性较筹,VDE活性和(A Z)／(A Z V)比值较低。     

低温强光胁迫下籼粳稻的PSⅡ光化学效率和膜脂过氧化表现

研究了温光胁迫下籼(Oryza sativa L. spp. indica)粳稻(O. sativa L. spp. japonica)生育后期叶片荧光参数和膜脂过氧化的关系.结果表明,低温强光下水稻光合机构中PSⅡ的D1蛋白量下降,叶黄素循环组分中环氧玉米黄质(A)和玉米黄质(Z)的形成受抑,PSⅡ光化学效率(Fv/Fm)和非光化学猝灭(qN)明显下降.加之内源活性氧清除剂超氧物歧化酶(SOD)活性降低,超氧阴离子自由基(O(-)/(*)2)和膜脂过氧化产物丙二醛(MDA)积累增加,导致光氧化发生.上述过程在籼粳稻间有明显差异,低温强光结合抑制剂处理证明,籼稻较粳稻对低温强光敏感和光氧化严重.相关分析表明,D1蛋白量分别与Fv/Fm和(A+Z)/(A+Z+V)呈极显著的正相关关系,Fv/Fm与MDA呈极显著的负相关关系.据此认为,逆境下Fv/Fm 是预测光氧化的     

低温强光胁迫下籼粳稻的PSⅡ光化学效率和膜脂过氧化表现

研究了温光胁迫下籼 (OryzasativaL .spp .indica)粳稻 (O .sativaL .spp .japonica)生育后期叶片荧光参数和膜脂过氧化的关系。结果表明 ,低温强光下水稻光合机构中PSⅡ的D1蛋白量下降 ,叶黄素循环组分中环氧玉米黄质 (A)和玉米黄质 (Z)的形成受抑 ,PSⅡ光化学效率 (Fv/Fm)和非光化学猝灭 (qN)明显下降。加之内源活性氧清除剂超氧物歧化酶 (SOD)活性降低 ,超氧阴离子自由基 (O-·2 )和膜脂过氧化产物丙二醛 (MDA)积累增加 ,导致光氧化发生。上述过程在籼粳稻间有明显差异 ,低温强光结合抑制剂处理证明 ,籼稻较粳稻对低温强光敏感和光氧化严重。相关分析表明 ,D1蛋白量分别与Fv/Fm 和 (A Z) / (A Z V)呈极显著的正相关关系 ,Fv/Fm 与MDA呈极显著的负相关关系。据此认为 ,逆境下Fv/Fm是预测光氧化的关键指标 ,D1蛋白合成能力和叶黄素循环的保护作用是其生理基础     

天线蛋白和类囊体膜脂对光合系统紫黄质循环的调节作用研究进展

紫黄质循环是紫黄质(V)经过中间物单环氧玉米黄质(A)形成玉米黄质(Z)的可逆转换,是光合系统聚光复合体在低光下的聚光状态与高光下的能量耗散状态之间的转换开关.叶黄素中的玉米黄质可钝化(去激发)激发三线态叶绿素(3Chl*)和激发单线态氧(1O2*),紫黄质循环可直接或间接地通过非光化学淬灭(NPQ)耗散PSⅡ天线蛋白中的过量光能.天线蛋白被认为是依赖玉米黄质(Z)耗散过量光能的部位,天线蛋白通过结合紫黄质循环组分(V,A和Z)来调节紫黄质循环.类囊体膜脂的性质和结构影响紫黄质循环组分(V,A和Z)间的转换,V的脱环氧化速率依赖于V在类囊体膜脂上侧向扩散的速率,紫黄质脱环氧化作用第一步(由V到A的转换)的速度常数是第二步(由A到Z的转换)速度常数的4～6倍.现有的结果表明,天线蛋白和类囊体膜脂是紫黄质循环最基本的调节器.该文对近年来国内外关于紫黄质循环的基本反应及其功能、紫黄质循环酶结构性质和辅因子以及天线蛋白和类囊体膜脂对紫黄质循环的调节作用及其机理等方面的研究进展进行了综述.     

光和水分胁迫对臭柏实生幼苗光化学效率及色素组成的影响

为探明毛乌素沙地3年生臭柏(Sabina vulgaris)实生苗在不同光照和水分条件下的光抑制响应机制,研究了各处理臭柏实生苗的最大光化学效率(F_v/F_m)及叶绿素(Chla+Chlb)和叶黄素(A+V+Z)含量,分析了其叶绿素循环和叶黄素循环的变化规律。结果表明,77%透光区通过减少Chlb含量,升高Chla/Chlb,避免光能过剩;同时,增加A+V+Z及热散逸色素(A+Z)含量、提高(A+V+Z)/(Chla+Chlb)和(A+V)/(A+V+Z)值,耗散过剩光能,避免光破坏。25%透光区的叶绿素和叶黄素循环机制随着水分条件的变化迅速发生改变。10%透光区通过增加Chlb含量,降低Chla/Chlb,捕捉更多的光能,几乎不存在光抑制。毛乌素臭柏实生幼苗能够适应不同的光照和水分条件,在恶劣的沙漠中完成天然更新,形成独特的群落景观,与叶绿素循环和叶黄素循环有着密切的关系。     

不同温光条件下籼粳稻叶片的光抑制和光氧化表现

不同温光条件（4d)下,以粳稻（Dryza sativaL.sp.japonica)“9516”和籼稻（O.sativaL.sp.indica)“汕优63”为材料,测定了与PSⅡ光能转化效率（Fv/Fm)和膜脂过氧化作用有关的生理指标。结果表明：适温、中等光强下两品种Fv/Fm和膜脂过氧化作用的产物（MDA）无变化,未见光抑制和光氧化表现;适温、强化下籼稻“汕优63”的Fv/Fm明显下降,MDA未见变化,有光抑制无光氧化表现;低温、强光下两品种有光抑制和光氧化表现。低温、强光下结合抑制剂实验证明,与粳稻相比,籼稻的D1蛋白量和SOD活性下降较多,叶黄素循环和非光化学猝灭（qN)受抑制程度较大,膜脂过氧化产物MDA含量较高,因而光抑制和光氧化现象较明显。实验提出：光能转化效率和膜脂过氧化表现是预测光氧化的关键指标。     

光照下叶黄素循环与非辐射能量耗散的关系

离体玉米叶片在光照下叶黄素循环与非辐射能量耗散发生明显变化.随着光强提高,玉米黄质(Z)含量显著上升,单环氧玉米黄质(A)含量在中低光强时增加但在较强光照下略有降低,紫黄质(V)含量则呈下降趋势,但叶黄素循环组分库V+A+Z上升幅度不大;相同条件下非辐射能量耗散增强,表现为非光化学猝灭荧光参数(NPQ)明显上升,同时F_v/F_m下降.分析表明,(Z+0.5A)/(V+A+Z)与NPQ呈明显正相关,而与F_v/F_m呈显著负相关,(V+0.5A)/(V+A+Z)则与之相反.由此推测,离体条件下玉米叶片中Z的环氧化和V的脱环氧化明显与非辐射能量耗散和PSⅡ光能转化过程相关.     

高温胁迫对转反义LeGPAT番茄PSⅡ光化学活性的影响

以冷敏感植物番茄(Lycopersicon esculentum Mill.)为材料,研究高温胁迫下转反义番茄甘油-3-磷酸酰基转移酶基因(LeGPAT)的番茄叶片膜脂含量、光合速率、荧光参数和叶黄素循环等的变化,以探讨LeGPAT表达与番茄植株耐热性的关系.结果表明:转反义基因株系磷脂酰甘油(PG)的饱和脂肪酸含量(16∶0+16∶1+18∶0)显著高于野生型;但不饱和脂肪酸含量(18∶1+18∶2+18∶3)却显著低于野生型.在45℃高温处理过程中,野生型和转反义基因的番茄植株净光合速率(Pn)、暗中最大光化学效率(Fv/Fm)和实际光化学效率ΦPSⅡ都显著降低,但野生型番茄降低幅度更大;同时野生型和转反义基因株系的非光化学猝灭(NPQ)及叶黄素循环脱环氧化状态(A+Z)/(V+A+Z)都增加,但反义株系比野生型增加更明显.研究发现,转基因番茄植株LeGPAT的表达被抑制,其饱和脂肪酸含量升高,而不饱和脂肪酸含量降低,高温胁迫下PSⅡ受到的伤害较轻光化学活性更高,植株抵抗高温的能力更强.     

高温强光下水杨酸对黄瓜叶片叶绿素荧光和叶黄素循环的影响

在高温强光条件下,研究了外源水杨酸对黄瓜叶片叶绿素荧光参数和叶黄素循环的影响.结果表明,在高温强光胁迫前2 d用50～400 μmol·L^-1水杨酸处理叶片,抑制了高温强光下原初光能转换效率(F_v/F_m)、光合电子传递量子效率(ΦPSⅡ)、最大荧光(F_m)和光化学猝灭系数(qP)的下降,分别比对照提高了16.1%～30.2%、11.9%～33.0%、7.2%～41.0%和27.2%～160.8%,促进了非光化学猝灭系数(NPQ)的升高,比对照提高了13.1%～62.9%,而对初始荧光(F_o)影响不大.水杨酸处理可减小高温强光下叶黄素循环库的下降幅度,使(A+Z)/(V+A+Z)升高,分别比对照高29.5%和24.6%.这些结果说明,水杨酸可通过提高非辐射能量耗散,对高温强光引起的黄瓜叶片光合机构的破坏具有保护作用.     

依赖于叶黄素循环的热耗散对茶树叶片防御强光破坏的相关试验研究

经叶黄素循环抑制剂——二硫苏糖醇(DIT)处理的茶树叶片,以850μmol．m^-2．s^-1的PFD照射120min后,福鼎大白茶的叶黄素循环组分中的环氧玉米黄素(A)和玉米黄素(Z)含量之和降低了76．5％,结果导致非光化学猝灭(NPQ)、光系统Ⅱ(PSⅡ)的光化学效率(Fv／Fm)、光化学猝灭系数(qP)、PSⅡ实际光化学量子效率(ψPSⅡR)和光合电子传递速率(ETR)明显下降,而F0显著上升,暗恢复后Fv／Fm恢复程度小于未经DIT处理的叶片。自然光强下,NPQ与与叶黄素循环的脱环氧化程度(A Z)/(V A Z)比值呈明显的正线性关系(R=0．9488^***)。这些结果充分证明依赖与叶黄素循环的热耗散是茶树叶片光合器官防御强光破坏的主要途径。     

Race and Racism in America and in Anthropology

Race in North America: Origin and Evolution of a Worldview . Audrey Smedley
Anthropology and Race . Eugenia Shanklin     

Degradation and conversion of somatostatin in normal and diabetic rats in vivo and in vitro

Plasma somatostatin-like immunoreactivity in the portal and jugular veins of streptozotocin diabetic rats was compared with that in normal control rats. In the diabetic group, somatostatin levels in the portal (p less than 0.05) and jugular (p less than 0.01) veins were both elevated compared with those in the control group. Moreover, the degree of elevation was greater in the jugular vein than in the portal vein. To further investigate the role of the liver in the clearance of somatostatin-28 in vivo, 2 micrograms of somatostatin-28 was administered as a bolus into the external jugular vein of intact and functionally hepatectomized rats. The mean half-time of somatostatin-28 was significantly longer in intact diabetic rats than in controls (p less than 0.05). The functional hepatectomy did not cause a significant difference in the half-time in diabetic rats but made it longer in control rats. These results suggest that the longer half-time of somatostatin-28 in diabetic rats in vivo is due to its slower hepatic clearance. The hepatic clearance of somatostatin-28 and somatostatin-14 was further studied in vitro using a recirculating liver perfusion method. The hepatic clearance of 1.2 nM of either somatostatin-28 or somatostatin-14 was significantly lower in diabetic rats than in controls (p less than 0.01). This indicates that elevated plasma somatostatin levels in diabetic rats are caused at least in part by decreased hepatic clearance of somatostatin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Variation in infectivity and aggressiveness in space and time in wild host-pathogen systems: causes and consequences

Variation in host resistance and in the ability of pathogens to infect and grow (i.e. pathogenicity) is important as it provides the raw material for antagonistic (co)evolution and therefore underlies risks of disease spread, disease evolution and host shifts. Moreover, the distribution of this variation in space and time may inform us about the mode of coevolutionary selection (arms race vs. fluctuating selection dynamics) and the relative roles of G × G interactions, gene flow, selection and genetic drift in shaping coevolutionary processes. Although variation in host resistance has recently been reviewed, little is known about overall patterns in the frequency and scale of variation in pathogenicity, particularly in natural systems. Using 48 studies from 30 distinct host–pathogen systems, this review demonstrates that variation in pathogenicity is ubiquitous across multiple spatial and temporal scales. Quantitative analysis of a subset of extensively studied plant–pathogen systems shows that the magnitude of within‐population variation in pathogenicity is large relative to among‐population variation and that the distribution of pathogenicity partly mirrors the distribution of host resistance. At least part of the variation in pathogenicity found at a given spatial scale is adaptive, as evidenced by studies that have examined local adaptation at scales ranging from single hosts through metapopulations to entire continents and – to a lesser extent – by comparisons of pathogenicity with neutral genetic variation. Together, these results support coevolutionary selection through fluctuating selection dynamics. We end by outlining several promising directions for future research.     

Electroejaculation in chimpanzees and gorillas and artificial insemination in chimpanzees

Electroejaculation was performed in 3 chimpanzees, 1 pygmy chimpanzee, and 2 gorillas with an instrument that delivers a modified sine wave current with a frequency of 24 Hz. The current stimuli were applied by a rectal probe with longitudinal electrodes. The electrical parameters varied from 6 to 12 V and from 30 to 40 mA for response of erection and lay between 8 and 18 V and between 40 and 145 mA during semen emission. Eleven chimpanzee semen samples showed the following data (x ± SD): total volume 1.9 ± 1.3 ml, volume of the liquid fraction 0.3 ± 0.2 ml, spermatozoa per ejaculate 743 ± 376 × 10⁶, sperm motility 52.7 ± 9.6%, morphologically abnormal spermatozoa 12.2 ± 7.5%. From an adult gorilla, three semen samples were collected, in each case without spermatozoa. The electrostimulation of a 6-year-old gorilla led to an erection, but not to semen emission. Three female chimpanzees were inseminated with fresh or frozen semen, each of them within three different estrous cycles. None of these inseminations led to a pregnancy.     

Aminoacylation in Sulfolobus acidocaldarius and in methanogenic and halophilic archaebacteria

Abstract Phenylalanyl-tRNA synthetase (PRS) from the sulphur-metabolizing thermoacidophilic archaebacterium Sulfolobus acidocaldarius has been purified 150-fold using different chromatographic steps. The enzyme has a M _r of 270 000 and exhibits considerable thermostability in a temperature range up to 90°C with optimal activity at 70°C. Conservation of antigenic determinants could not be detected by antibodies against various PRS of all primary kingdoms. As a further means to detect traits of phylogenetic relationship, the cross-species reactivity between PRS and tRNAs of organisms from the three branches of archaebacteria and from all primary kingdoms reveals the group character of all 3 branches of the archaebacterial domain, the sulphur-metabolizing, methanogenic and halophilic archaebacteria.     

Advances in purine and pyrimidine metabolism in health and diseases

ABSTRACT

In June, 2015, the Purine and Pyrimidine Society organized the 16th biennial symposium on Purine and Pyrimidine metabolism at the Faculty House of Columbia University, New York City. This exciting meeting focused on these important molecules, new developments in inborn errors of metabolism; therapeutic analogs. In addition, the biochemistry of mammalian and non-mammalian systems were discussed. Due to significant advances in molecular medicine, the boundaries between clinical and basic sciences have merged into exciting translational research, of which a small portion was highlighted in the presymposium.     

Trajectories and Constraints in Brain Evolution in Primates and Cetaceans

A negative allometric relationship between body mass (BM) and brain size (BS) can be observed for many vertebrate groups. In the past decades, researchers have proposed several hypotheses to explain this finding, but none is definitive and some are possibly not mutually exclusive. Certain species diverge markedly (positively or negatively) from the mean of the ratio BM/BS expected for a particular taxonomic group. It is possible to define encephalization quotient (EQ) as the ratio between the actual BS and the expected brain size. Several cetacean species show higher EQs compared to all primates, except modern humans. The process that led to big brains in primates and cetaceans produced different trajectories, as shown by the organizational differences observed in every encephalic district (e.g., the cortex). However, these two groups both convergently developed complex cognitive abilities. The comparative study on the trajectories through which the encephalization process has independently evolved in primates and cetaceans allows a critical appraisal of the causes, the time and the mode of quantitative and qualitative development of the brain in our species and in the hominid evolutionary lineage.