高CO_2低O_2处理对苹果乙烯生成的抑制作用

乙烯是植物体内含有的五大激素之一。它除了对植物的生长发育等多种生理代谢活动有重要影响外,还对果实具有催熟作用,素有成熟激素之称。为此,在果蔬贮藏保鲜中,有关乙烯的生物合成及其调节作用的研究占有十分重要的地位。近年来,Adams等确认,1-氨基环内烷-1-羰酸(ACC)是植物体内形成乙烯的直接前体,ACC向乙烯的转化是一个需氧过程。低氧抑制乙烯生成的     

水杨酸对采后苹果果实乙烯生成的抑制作用

室温下用0．1-20mmol·L－1的外源水杨酸浸泡苹果果实的果肉和果皮圆片6h后,其乙烯生成量显著被抑,抑制效果随外源水杨酸浓度的提高而增强。外源水杨酸对种子的乙烯生成也有不同程度的抑制作用。     

红花注射液对慢性低O2高CO2肺动脉高压的影响

目的：探讨红花注射液对大鼠在慢性低O2高CO2下肺动脉高压的抑制作用。方法：将SD大鼠分为对照组,慢性低O2高CO2组,慢性低O2高CO2＋红花注射液组。用电镜、放免等方法,观察各组大鼠肺动脉平均压、颈动脉平均压、肺细小动脉显微结构、血浆和肺匀浆TXB2及6-keto-PGF1a含量的变化。结果：①慢性低O2高CO2组mPAP比对照组显著增高,红花注射液组的mPAP比慢性低O2高CO2组显著降低,3组间mCAP比较差异无显著性。②慢性低O2高CO2组与对照组相比血浆和肺匀浆TXB2浓度、TXB2／6-keto-PGF1a比值显著增高,6-keto-PGF1a浓度显著下降;红花注射液组与慢性低P2高CO2相比血浆和肺匀浆TXB2浓度、TXB2／6-keto-PGF1a显著下降,6-keto-PGF1a显著升高。③光镜下慢性低O2高CO2组与对照组相比,肺细小动脉管壁面积／管总面积（WA／TA）和肺细小动脉中膜厚度（PAMT）均显著增高。红花注射液组WA／TA和PAMT显著降低。④电镜下慢性低O2高CO2组大鼠肺细小动脉内皮细胞吞饮小泡增多,血管壁增厚,中膜平滑肌细胞增生,纤维细胞增多,肺泡Ⅱ型上皮细胞微绒毛脱落;红花注射液组肺细小动脉中膜平滑肌细胞增生减轻,纤维细胞少,胶原纤维减少,肺泡Ⅱ型上皮细胞微绒毛丰富、结构清。结论：红花注射液有减轻慢性低O2高CO2性肺动脉高压和肺血管结构重建的作用,可能与抑制TXA2的合成,保护血管内皮细胞,使TXA2/PGI2比值降低有关.     

低O2高CO2对肺动脉环氧酶-2基因表达的影响

目的：研究慢性低氧高二氧化碳对大鼠肺动脉环氧酶-2（COX-2）基因表达的影响。方法：将SD大鼠分为正常对照组（A组）,4周低O2高CO2组（B组）。采用免疫组化、原位杂交、图像分析等方法,观察两组大鼠肺动脉平均压（mPAP）、颈动脉平均压（mCAP）、右心室／（左心室＋室间隔）重量比[RV／（LV＋S）]、肺细小动脉显微结构及肺细小动脉COX-2活性及基因表达变化。结果：①B组mPAP、Rv／（LV＋S）显著高于A组（P〈0,01）。两组间mCAP比较差异无显著性（P〉0．05）。②光镜下正常对照组大鼠肺细小动脉内弹力板自然弯曲,平滑肌层未见明显增厚,管壁均匀一致,而低O2高CO2组内弹力板扭曲,中膜平滑肌细胞增生,管腔明显狭窄。③免疫组化、原位杂交发现B组肺细小动脉COX-2及COX-2mRNA平均吸光度值明显高于A组（P〈0．01）且与mPAP呈负相关（P〈0．01）。结论：环氧酶-2基因表达变化可能在慢性低氧高二氧化碳肺动脉高压形成中起调控作用。     

慢性低O2高CO2大鼠肺肥大细胞对肺小动脉的作用

目的：探讨慢性低Ｏ２高ＣＯ２大鼠肺肥大细胞（ＭＣ）对肺小动脉的作用。方法：条用慢性低Ｏ２高ＣＯ２肺动脉高压模型,观察大鼠肺ＭＣ和肺小动脉形态改变及测定肺动脉压。结果：观察到大鼠肺动脉压力高和肺ＭＣ脱颗粒及空泡变。结论：肺ＭＣ可能也是肺动脉高压形成的因素之一。     

阿斯匹林对大鼠在低O2高CO2下肺动脉高压的作用

目的：研究阿斯匹林(ASA)对慢性低O2高CO2性肺动脉高压的抑制作用。方法：将SD大鼠分为正常对照组,慢性低O2高CO2组,慢性低O2高CO2 阿斯匹林组。用光镜、放射免疫等方法,观察各组大鼠肺动脉平均压(mPAP)、颈动脉平均压(mCAP)、肺细小动脉显微结构、血浆和肺匀浆TXB2及6-keto-PGF1α含量的变化。结果：①低O2高CO2组mPAP比正常组显著增高,ASA组的mPAP比低O2高CO2组显著降低,3组间mCAP比较差异无显著性。②光镜下低O2高CO2组与正常组相比,肺细小动脉管壁面积／管总面积(WA／TA)和肺细小动脉中膜厚度(PAMT)均显著增高。ASA组WA／TA和PAMT显著降低。③低O2高CO2组血浆和肺匀浆TXB2、6-keto-PGF1α浓度以及TXB2／6-keto-PGF1α比正常组显著增高,而ASA组与低O2高CO2组相比显著降低。结论：ASA有抑制慢性低O2高CO2性肺动脉高压和肺血管重构的作用。     

游泳对慢性低O2高CO2大鼠肺肥大细胞及肺动脉形态的影响

自Ｅｈｒｌｉｃｈ第一次描述肥大细胞 (ＭａｓｔＣｅｌｌ,ＭＣ)以来 ,ＭＣ的组织分布、形态结构、生理特征已有许多研究。肺中含ＭＣ较多 ,主要分布在小血管周围 ,ＭＣ颗粒含组胺、5 羟色胺、肝素、血小板激活因子、激肽缓激肽等活性物质 ,参与重要生理过程。在高原缺Ｏ2 时及低Ｏ2 高ＣＯ2 时 ,肺ＭＣ脱颗粒 ,影响肺动脉形态结构 ,在慢性阻塞性肺部疾病 (ＣＯＰＤ)时往往存在缺Ｏ2 高ＣＯ2 ,运动锻炼是康复疗法之一 ,但其机理尚未完全清楚。本实验采用本研究室先期建立的慢性低Ｏ2 高ＣＯ2 大鼠模型及大鼠游泳锻炼 ,观察肺ＭＣ的形态改变…     

知母宁对慢性低O2高CO2大鼠肺动脉高压的影响及其机制研究

目的：研究知母宁对慢性低氧高二氧化碳性肺动脉高压的抑制作用及其作用机制。方法：将SD大鼠分为正常对照组,4周低O2高CO2组,4周低O2高CO2^ 知母宁组（知母宁组）。用透射电镜、图像分析、免疫组化、组织原位杂交技术等方法,观察各组大鼠肺动脉平均压（mPAP)、颈动脉平均压（mCAP)、肺细小动脉显微和超微结构、血CO浓度、血红素氧合酶－1（HO－1）及其基因表达的变化。结果：①低O2高CO2组mPAP比正常组显著增高,知母宁组mPAP比低O2高CO2组显著降低;3组间mCAP比较差异无显著性。②全血CO浓度低O2高CO2组比正常组显著增高,知母宁组比低O2高CO2组增高。③光镜下低O2高CO2组与正常组相比,肺细小动脉管壁面积／管总面积、肺细小动脉中膜平滑肌细胞核密度、肺细小动脉中膜厚度均显著升高,知母宁组与低O2高CO2组相比以上指标显著降低。④电镜下知母宁组肺细小动脉中膜平滑肌细胞增生、面积增大、染色质增多、外膜胶原纤维增生均较低O2高CO2组明显减轻。⑤免疫组化、原位杂交发现低O2高CO2组大鼠肺细小动脉HO－1及mRNA与正常组比较均明显增加,知母宁组大鼠肺细小动脉HO－1及mRNA表达均较低O2高CO2组为高。结论：知母宁有抑制慢性低氧高二氧化碳性肺动脉高压和肺血管结构重建的作用,上调HO－1及其基因表达、使CO合成增多可能为其重要作用机制。     

慢性低O2高CO2对大鼠脑组织的损伤作用及川芎嗪对其影响的研究

目的：探讨慢性低O2高CO2条件下脑烯醇化酶（NSE）、蛋白S100、超微结构等改变及川芎嗪对其影响。方法：将SD大鼠分为正常对照组（A组）,低O2高CO2组（B组）,低O2高CO2＋川芎嗪组（C组）,采用免疫组织化学、透射电镜方法,观察平均肺动脉压（mPAP）、颈动脉压（mCAP)、血清NO浓度、脑NSE、S100变化及脑超微结构等改变。结果：①B组mPAP明显高于A组,C组低于B组,三组间mCAP无明显差异。②B组血清NO浓度低于A组（P＜0．01）,C组血清NO浓度高于B组（P＜0．01）。③B组比A组NSE、S100吸光度值降低,C组比B组NSE、S100吸光度值增高。④B组神经元、神经胶质细胞水肿,C组神经细胞损害明显减轻。结论：慢性低O2高CO2脑NSE、S100降低,川芎嗪对脑损害有保护作用。     

内源性硫化氢体系与低O2高CO2性肺动脉高压的相关性研究

目的：研究低O2高CO2性肺动脉高压（HHPH）时大鼠肺组织内硫化氢（H2S）体系变化的改变及相关性,并探讨其机制。方法：20只SD大鼠随机分为正常对照组（C组）和低O2高CO2组（HH组）（n=10）。监测其血流动力学变化,光镜观察肺细小动脉管壁面积／管总面积比值（WA／TA）,测右心室／左心室＋室间隔（RV／LV＋SP）比值。原位缺口末端标记法（TUNEL法）观测肺细小动脉凋亡情况,并计算凋亡指数（AI）,免疫组化检测肺细小动脉Bcl-2、Bax蛋白表达。敏感硫电极法测定血浆H2S含量及肺组织匀浆胱硫醚-γ-裂解酶（CSE）活性变化。RT-PCR法测定肺组织中CSE基因表达。结果：HH组肺平均动脉压（mPAP）、WA／TA、RV／LV＋SP明显高于C组（P〈0．05或P〈0．01）。与C组相比,HH组AI显著下降（P〈0．01）,Bcl-2表达加强,Bax减弱,Bax／Bcl-2比值上升（均P〈0．01）。血浆H2S含量、肺组织匀浆CSE活性、肺组织CSE基因表达水平HH组明显低于C组（P〈0．01）。血浆H2S、肺组织CSE活性、肺组织CSE mRNA相对含量与mPAP,Bcl-2／Bax比值均呈显著负相关,与AI呈显著正相关。结论：H2S／CSE体系与低O2高CO2性肺动脉高压关系密切,HHPH时H2S／CSE体系的明显受抑,可使Bcl-2／Bax比值升高,肺动脉平滑肌细胞凋亡减少,促进肺血管重建和肺动脉高压的形成。     

Ethylene Sensitivity and Response Sensor Expression in Petioles of Rumex Species at Low O2 and High CO2 Concentrations

Rumex palustris, a flooding-tolerant plant, elongates its petioles in response to complete submergence. This response can be partly mimicked by enhanced ethylene levels and low O2 concentrations. High levels of CO2 do not markedly affect petiole elongation in R. palustris. Experiments with ethylene synthesis and action inhibitors demonstrate that treatment with low O2 concentrations enhances petiole extension by shifting sensitivity to ethylene without changing the rate of ethylene production. The expression level of the R. palustris gene coding for the putative ethylene receptor (RP-ERS1) is up-regulated by 3% O2 and increases after 20 min of exposure to a low concentration of O2, thus preceding the first significant increase in elongation observable after 40 to 50 min. In the flooding-sensitive species Rumex acetosa, submergence results in a different response pattern: petiole growth of the submerged plants is the same as for control plants. Exposure of R. acetosa to enhanced ethylene levels strongly inhibits petiole growth. This inhibitory effect of ethylene on R. acetosa can be reduced by both low levels of O2 and/or high concentrations of CO2.     

Changes in Ethylene Production and 1-Aminocyclopropane-l-carboxylic acid Levels in Climacteric Apple Fruits Ralls under Low O2 and High CO2

Ethylene production was severely inhibited in climacteric applefruits treated with either low O2(O2 :1–3%, CO2: 0%)or high CO2(O2:15–21%, CO2:10–20%) for 4, 10, and 15 days, respectively. In treatment with low O2 for 10 or 15days, 1-aminocyclopropane-1-carboxylic acid (ACC) was accumulated in large quantity,but in the fruit treated with high CO2, the content of ACC was slightly lower than thatin control fruit. When the fruit was turned to air after 4-days treatment with low O2, ethylene production and ACC content were able to recover to control level. But in the fruits withlow O2 for 10 or 15 days ethylene production was 100 times lower, and ACC contentwas much higher than those in control even 30-35 days after they were turned to air. It appears that inhibitory effect of the low O2 treatment for longer than 10 days on theconversion of ACC to ethylene was irreversible. In the case of high CO2 treatment fordifferent periods ethylene production obviously decreased at first, then followed by arapid increase. When the fruits were turned to air ethylene production in the treat-ment for 4 days was able to recover to control level, but it remained much lower in tre-atment for 10 or 15 days than that in control throughout the period of recovery. However, ACC contents in both treatments were slightly lower than those in control during a few days after the removal of treatment, but increased slightly after 2-3 weeks.Furthemore, the ability of flesh discs to convert exogenous ACC to ethylene was redu-ced remarkably by the treatment of fruits with either low O2 or high CO2 for longerthan 10 days.     

Maximum Quantum Yields of O2 Evolution in C4 Plants under High CO2

The quantum yields of photosynthetic O₂ evolution were measuredin 15 species of C₄ plants belonging to three different decarboxylationtypes (NADP-ME type, NAD-ME type and PEP-CK type) and 5 speciesof C₃ plants and evaluated relative to the maximum theoreticalvalue of 0.125 mol oxygen quanta^-1. At 25°C and 1% CO₂,the quantum yield in C₄ plants averaged 0.079 (differences betweensubgroups not significant) which was significantly lower thanthe quantum yield in C₃ plants (average of 0.105 for 5 species).This lower quantum yield in C₄ plants is thought to reflectthe requirement of energy in the C₄ cycle. For the C₄ NADP-MEtype plant Z. mays and NAD-ME type plant P. miliaceum, quantumyields were also measured over a range of CO₂ levels between1 and 20%. In both species maximum quantum yields were obtainedunder 10% CO₂ (0.105 O₂ quanta_-1 in Z. mays and 0.097 O₂ quanta_-1in P. miliaceum) indicating that at this CO₂ concentration thequantum yields are similar to those obtained in C₃ plants underCO₂ saturation. The high quantum yield values in C₄ plants undervery high CO₂ may be accomplished by direct diffusion of atmosphericCO₂ to bundle sheath cells, its fixation in the C₃ pathway,and feedback inhibition of the C₄ cycle by inorganic carbon. (Received June 6, 1995; Accepted August 15, 1995)     

The Effect of High CO2 and Low O2 Concentrations in Simulated Landfill Gas on the Growth and Nodule Activity of Leucaena leucocephala

When roots of Leucaena leucocephala seedlings (White Popinac,a tropical legume tree belongs to the Family Mimosaceae) werefumigated with simulated landfill gas (CO₂ above 10% and O₂from 10% to atmospheric level), the stem elongation rate andstomatal conductance were inhibited at the absence of any apparentleaf water deficit. When compared with a treatment where rootsystem was flooded, the effect of gas fumigation on the shootphysiology was relatively mild and appeared later. On the otherhand, nodule activity (measured as rate of acetylene reductionactivity, ARA) was much more severely inhibited by gas fumigation.Although nodule dry weight and carbohydrate storage in noduleswere reduced, the inhibition was not likely a result of theshortage of carbohydrate reserve in the nodules. This was becausethe ARA of untreated fresh nodules was also inhibited immediatelyfollowing exposure to the simulated landfill gas. In furtherexperiments where CO₂ and O₂ were manipulated separately, althougha reduction of O₂ concentration to half of the atmospheric levelmight account for up to 30% loss of ARA with considerable variation,the high CO₂ alone showed a much more severe inhibition. ThisCO₂-induced inhibition was not reversible one hour after thehigh CO₂ gas was removed. There was some recovery of activity5 day after plants were fumigated, suggesting that the legumeplant can maintain some nitrogen-fixation activity under theinfluence of landfill gas. (Received April 10, 1995; Accepted August 22, 1995)     

Effect of a Brief CO(2) Exposure on Ethylene Production

Ethylene production and respiration by Granny Smith apples were inhibited by treatment with 20% CO₂ for 2 hours. A similar effect was observed in tissue slices when treated at either 0 or 25°C.

The inhibition continued even after an extended aeration period. There is also an inhibition of ethylene emission in tissue slices incubated with exogenous 1-aminocyclopropane-1-carboxylic acid (ACC).

In general, CO₂ treatment increased the ACC content of the tissue. These observations are consistent with the idea the action of CO₂ is directed toward the enzyme system responsible for the conversion of ACC into ethylene.

     

Selective Electroreduction of CO2 toward Ethylene on Nano Dendritic Copper Catalysts at High Current Density

In situ deposited copper nanodendrites are herein proven to be a highly selective electrocatalyst which is capable of reducing CO₂ to ethylene by reaching a Faradaic efficiency of 57% at a current density of 170 mA cm^?2. It is found that the desired structures are formed in situ under acidic pH conditions at high electrode potentials more negative than ?2 V versus Ag/AgCl. Detailed investigations on the preparation, characterization, and advancement of electrode materials and of the electrolyte have been performed. Catalyst degradation effects are intensively followed by scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HR‐TEM) characterization methods and found to be a major root course for selectivity losses.     

Effects of Methyl Jasmonate on Anthocyanin Accumulation, Ethylene Production, and CO2 Evolution in Uncooled and Cooled Tulip Bulbs

Effects of methyl jasmonate (JA-Me) on anthocyanin accumulation, ethylene production, and CO₂ evolution in uncooled and cooled tulips (Tulipa gesneriana L. cvs. Apeldoorn and Gudoshnik) were studied. JA-Me stimulated anthocyanin accumulation in stems and leaves from uncooled and cooled bulbs of both cultivars. The highest level of anthocyanin accumulation was observed in leaves from cooled bulbs treated with 200 μL/liter JA-Me. In sprouting bulbs treated with 100 μL/liter and higher concentrations of JA-Me, the ethylene production began to increase at 3 days after treatment, being extremely greater in uncooled bulbs than in cooled ones. JA-Me also stimulated CO₂ evolution in both cultivars, depending on its concentrations. CO₂ evolution in sprouting bulbs was not affected by cooling treatment. These results suggest that anthocyanin accumulation by JA-Me in tulip leaves is not related to ethylene production stimulated by JA-Me. Received October 10, 1997; accepted November 17, 1997     

Effects of CO(2) and O(2) on the Photosynthetic O(2) Evolution of Spirodela polyrrhiza Turions

Net photosynthetic rates of Spirodela polyrrhiza turions, at low O₂ levels, were 6.2 and 38.8 micromoles O₂ per gram fresh weight per hour at 1 millimolar HCO₃⁻ and CO₂ saturation, respectively, and much lower in a regular low-pH growth solution. Air equilibration O₂ concentrations decreased rates considerably, except at CO₂ saturation. The surfacing rate of turions in various inorganic carbon surroundings correlated positively with their photosynthetic rates, but were the same at high and low O₂ levels. The relevance of these findings in relation to environmental conditions conductive to germination of autotrophically growing turions is discussed.