硒,谷胱甘肽过氧化物酶和不饱和脂肪酸在鼠亚细胞中的分布

采和梯度离心和放射性同位素等方法从鼠脑中分离得到髓磷脂、突触囊、轻突触体、重突触体、线粒体６个亚细胞组分,分别测定了各亚细胞中硒－７５、谷胱甘肽过氧化物酶和不饱和脂肪酸的含量,结果表明这上结成分在鼠脑亚细胞中的分布呈明显的相关性,同时首次在突触囊、线粒体和微粒体中检测到三咱不同的谷胱甘肽过氧化物酶的活性峰,其中之一可能是红细胞谷胱甘过氧化物酶（ＥＣ１．１１．１．９）。还就机体的自我保护机制和硒在脑     

亚硒酸钠对小麦幼苗中谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及谷胱甘肽含量的影响

用1.0 mg·L-1的亚硒酸钠根施小麦幼苗,测定亚硒酸钠对谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及还原性谷胱甘肽含量的结果表明,外源亚硒酸钠对麦苗地上部的谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性均有诱导作用,使麦苗体内的谷胱甘肽含量水平增加.     

不饱和脂肪酸在牛、大鼠脑亚细胞组分中分布的比较

采用密度梯度离心等方法,从牛和大鼠脑组织中分别分离得到髓磷脂（A）、突触囊（B）、轻突触体（C）、重突触体（D）、线粒体（E）和微粒体（F）六个亚细胞组分。通过气相色谱－质谱联用手段和内标法测定了不饱和脂肪酸在各个亚细胞组分中的含量,结果表明牛和大鼠脑不饱和脂肪酸的亚细胞分布存在明显的差异。这种差异可能与动物种属、动物生活习惯等因素有关。     

纳米硒对肉鸡肝细胞中细胞谷胱甘肽过氧化物酶活性的影响

以亚硒酸钠和蛋氨酸硒为对照,研究了纳米单质硒(纳米硒)对肉鸡肝细胞中细胞谷胱甘肽过氧化物酶(cGPx)活性的影响。每种硒源分别以0.01、0.05、0.10、0.30、0.50、1.0μmol/L6个硒添加浓度培养肉鸡肝细胞,测定培养后0、24、48、72、96h肉鸡肝细胞cGPx活性。结果显示:亚硒酸钠添加浓度(以硒计)在0.01￣0.10μmol/L、蛋氨酸硒和纳米硒添加浓度(以硒计)在0.01￣0.30μmol/L,cGPx活性随着硒添加浓度的增加而增加;亚硒酸钠添加浓度在0.10￣1.0μmol/L、蛋氨酸硒添加浓度在0.30￣1.0μmol/L,cGPx活性随着硒添加浓度的增加而下降,而纳米硒添加浓度在0.30￣1.0μmol/L,cGPx活性始终保持在高峰平台。结果表明,3种硒源的剂量-效应关系曲线中的最适剂量范围宽度依次为:纳米硒>蛋氨酸硒>亚硒酸钠。     

植物谷胱甘肽过氧化物酶研究进展

氧化胁迫可诱导植物多种防御酶的产生,其中包括超氧化物歧化酶(SOD,EC1.15.L1)、抗坏血酸过氧化物酶(APX,EC1.11.1.11)、过氧化氢酶(CAT,E.C.1.11.1.6)和谷胱甘肽过氧化物酶(GPXs,EC1.11.1.9).它们在清除活性氧过程中起着不同的作用.GPXs是动物体内清除氧自由基的主要酶类,但它在植物中的功能报道甚少.最近几年研究表明,植物体内也存在类似于哺乳动物的GPXs家族,并对其功能研究已初见端倪.本文综述了有关GPXs的结构以及植物GPXs功能的研究进展.     

谷胱甘肽过氧化物酶的硒代半胱氨酸插入元件

真核生物将硒代半胱氨酸插入蛋白质必需硒代半胱氨酸插入元件（ＳＥＣＩＳ）的参与,后者位于硒蛋白ｍＲＮＡ的３′非翻译区．采用ＲＮＡ折叠程序对１５个谷胱甘肽过氧化物酶基因进行计算机处理发现,其可能的ＳＥＣＩＳ中都具有３段保守碱基ＡＵＧＡ－Ａ（Ｇ）ＡＡ－ＧＡ．根据Ａ（Ｇ）ＡＡ位于顶环或者顶环上游５′臂的突环上,可将ＳＥＣＩＳ分为Ⅰ型和Ⅱ型结构     

具有谷胱甘肽过氧化物酶活性的含硒单链抗体酶制备

 利用RT PCR从分泌有谷胱甘肽结合部位的单克隆抗体杂交瘤细胞株 2F3中 ,扩增出单抗重链可变区和轻链可变区基因 .经DNA测序后 ,用Linker(Gly4 Ser1) 3 构建成单链抗体 (scFv)表达载体pTMF scFv ,将重组质粒pTMF scFv转化到大肠杆菌BL2 1(DE3) ,实现了单链抗体的高效表达 .表达的单链抗体占菌体总蛋白 2 5%～ 30 % .该重组蛋白以包涵体形式存在 ,分子量为 30kD .经过金属螯合亲和层析纯化、复性和凝胶过滤纯化 ,得到电泳均一的单链抗体 .再经化学诱变 ,得到含硒单链抗体酶 ,其谷胱甘肽过氧化物酶活性为 330 0U μmol.采用荧光滴定法测定了单链抗体对谷胱甘肽的结合常数     

谷胱甘肽/谷胱甘肽过氧化物酶系统在微生物细胞抗氧胁迫系统中的作用

谷胱甘肽(GSH)/谷胱甘肽过氧化物酶(GPx)系统在不同微生物细胞抵抗氧胁迫中的生理功能不尽相同。该系统在真核模式微生物酿酒酵母中是必需存在的,在维持胞内氧化还原平衡和抵抗氧胁迫中发挥主要作用。然而,在原核微生物中,该系统只是条件性的,即部分胞内存在谷胱甘肽还原酶和GPx的原核微生物,如流感嗜血杆菌和乳酸乳球菌,可通过从胞外吸收GSH,形成条件性的依赖于GSH的GPx系统,参与抵抗氧胁迫。     

谷胱甘肽/谷胱甘肽过氧化物酶系统在微生物细胞抗氧胁迫系统中的作用

谷胱甘肽(GSH)/谷胱甘肽过氧化物酶(GPx)系统在不同微生物细胞抵抗氧胁迫中的生理功能不尽相同。该系统在真核模式微生物酿酒酵母中是必需存在的,在维持胞内氧化还原平衡和抵抗氧胁迫中发挥主要作用。然而,在原核微生物中,该系统只是条件性的,即部分胞内存在谷胱甘肽还原酶和GPx的原核微生物,如流感嗜血杆菌和乳酸乳球菌,可通过从胞外吸收GSH,形成条件性的依赖于GSH的GPx系统,参与抵抗氧胁迫。     

Subcellular Distribution of UDP-Galactose:Ceramide Galactosyltransferase in Rat Brain Oligodendroglia

Oligodendrocytes isolated from 18-19-day-old rat brain were homogenized in 0.32 M sucrose. The homogenate was centrifuged at 100,000 g for 50 min in a gradient containing 0.8, 1.05, and 1.3 M sucrose. Three discrete bands were obtained at the interfaces 0.32-0.8 (F1), 0.8-1.05 (F2), and 1.05-1.3 M (F3). The distribution of UDP-galactose:ceramide galactosyltransferase (CgalT) activity in each fraction was measured using liposomes containing normal fatty acid-containing ceramides (NFA-CgalT activity) or 2-hydroxy fatty acid-containing ceramides (HFA-CgalT activity). Although detection of both CgalT activities was possible in all fractions, HFA-CgalT activity was enriched in F1 and F2 fractions, which also showed an enrichment of Golgi and endoplasmic reticulum markers, respectively. It is interesting that NFA-CgalT activity was significantly enriched in the F2 fraction. These results suggest that hydroxylated and nonhydroxylated galactocerebrosides may be synthesized at different intracellular locations.     

Modulation by Unsaturated Fatty Acids of Norepinephrine- and Adenosine-Induced Formation of Cyclic AMP in Brain Slices

Abstract: The effect of linoleic acid on the formation of cyclic AMP in the slices of guinea pig cerebral cortex was examined. Treatment of the slices with linoleic acid resulted in an increase of basal and of norepinephrine-stimulated formation of cyclic AMP. The stimulatory effect on the basal level of cyclic AMP was not specific for linoleic acid: the potency of the fatty acid was related to the magnitude of unsaturation. In contrast, the enhancement of norepinephrine-stimulated formation of cyclic AMP seemed relatively specific for linoleic acid and arachidonic acid. Linoleic acid markedly enhanced the stimulated formation of cyclic AMP by histamine and adenosine, as well that by norepinephrine, without affecting that by excitatory amino acids and veratridine. Theophylline, adenosine deaminase, and 2'-deoxyadenosine antagonized the effect of linoleic acid. Linoleic acid enhanced the maximum responses to norepinephrine and adenosine without altering the ED₅₀ values for these agonists. When linoleic acid-treated slices were washed with Krebs-Ringer containing defatted bovine serum albumin, both enhancement of the response to norepinephrine and the amount of [¹⁴C]linoleic acid incorporated in a free form significantly diminished.     

植物不饱和脂肪酸的生物合成及调控

不饱和脂肪酸是植物细胞中的一类重要代谢物质,是组成细胞膜的主要成分,对调节细胞的生理功能起着重要作用。不饱和脂肪酸也是人类必须的一类营养物质,对健康发挥着重要作用。因此,研究植物不饱和脂肪酸的合成和调控机制具有着重要的理论和现实意义。不饱和脂肪酸的合成主要发生在质体和内质网,由一系列编码基因控制,并受到外在环境胁迫及发育的调控。本研究综述了近年来不饱和脂肪酸合成和调控机制相关的一些研究进展,解析了不饱和脂肪酸合成的一些关键基因,以期为将来利用相关基因进行种质创新,从而实现改良食用油品质或提升植物的抗性育种提供思路和实践。     

Subcellular Localization of Rat Brain Insulin Binding Sites

Fractions and subcellular structures were prepared from rat brain homogenate and their purity was assessed using enzyme markers, gamma-aminobutyric acid binding, DNA content, and electron microscopy. Insulin binding was highest on the plasma membrane preparations and approximately 50% less so on brain homogenate crude mitochondrial (P2), myelinated axon, and synaptosome preparations. Very low levels of binding were found on mitochondria and nuclei. Differences in binding between fractions were due to numbers of binding sites, and not variable binding affinity. There was a close relationship between insulin binding and the activity of Na/K ATPase (E.C. 3.6.1.4) in all fractions (r = 0.98). Insulin binding to the P2 was compared with plasma membrane fractions in seven brain regions, and the results demonstrated the same close relationship between insulin binding and plasma membrane content in all regions except hypothalamus. Plasma membrane insulin binding was well represented by the binding on P2 membranes in all regions except hypothalamus and brainstem. It was concluded that insulin binding is distributed evenly over the surface of brain cells and is not increased on nerve endings.     

Unsaturated Fatty Acids Esterified in 2-Acyl-1-Lysophosphatidylcholine Bound to Albumin Are More Efficiently Taken up by the Young Rat Brain than the Unesterified Form

The aim of the present study was to investigate whether unsaturated 2-acyl-lysophosphatidylcholine bound to plasma albumin is a relevant delivery form of unsaturated fatty acids to the developing brain. Twenty-day-old rats were perfused for 30 s with labeled palmitic, oleic, linoleic, and arachidonic acids in either their unesterified form or esterified in 2-acyl-lysophosphatidylcholine labeled on the choline and fatty acid moieties. Both forms were bound to albumin. Incorporation in brain lipid classes was followed within 1 h. The brain uptake of the unesterified fatty acids reached a plateau at 5-15 min and was maximal for arachidonic acid (0.45% of the perfused dose). The brain uptake of palmitoyl-lysophosphatidylcholine was similar to that of palmitic acid, whereas that of other lysophosphatidylcholines increased with the degree of unsaturation (rate and maximal uptake) and was six- to 10-fold higher than that of the corresponding unesterified fatty acid. 2-Acyl-lysophosphatidylcholines were taken up without prior hydrolysis and reacylated into doubly labeled phosphatidylcholine, which was the most labeled lipid class, whereas lipid distribution of the unesterified fatty acid was more diversified. Partial hydrolysis of 2-acyl-lysophosphatidylcholine occurred in the brain tissue, and redistribution of the fatty acyl moiety into other phospholipid classes was also observed and was the highest for arachidonic acid. In this case, the percentage of esterification of this fatty acid in phosphatidylinositol (expressed as a percentage of the total lipid fraction) was relatively lower than that observed when the unesterified form was used.(ABSTRACT TRUNCATED AT 250 WORDS)     

Age-Dependent Variations in Peroxide-Utilizing Enzymes from Rat Brain Mitochondria and Cytoplasm

Abstract: The location of peroxide-utilizing enzymes has been studied in rat brain. Glutathione peroxidase and glutathione reductase distributions indicate that both enzymes are located in the cytoplasm and in the matrix space of "synaptosomal" and "free" mitochondria. On the other hand, catalase distribution parallels that of NADH-cytochrome c reductase (rotenone-insensitive), and appears to be associated with the outer membrane of brain mitochondria. Whereas no gross age-dependent changes in various marker enzymes were found, a gradual but significant increase in glutathione peroxidase from the soluble fraction of free mitochondria was detected. The consequences of such increase are discussed with regard to the reducing potential of the cell.     

Subcellular and Perisynaptic Distribution of Rat Brain Aldehyde Dehydrogenase Activity

Abstract: The nuclear mitochondrial and synaptosomal fractions of rat brain were each found to contain some 25–30% of the total aldehyde dehydrogenase activity. The cytoplasmic fraction had a very low total aldehyde dehydrogenase activity. There were differences in the distribution of the activity when different aldehydes were used as substrates, suggesting the presence of isoenzymes in the various subcellular compartments. When rats were treated intra-cisternally with 6-hydroxydopamine there was no change in brain aldehyde dehydrogenase activity, although the noradrenaline content and the activities of tyrosine hydroxylase and dopamine-β-hydroxylase were markedly decreased. Treatment with 6-hydroxydopamine also had no significant effect on the aldehyde dehydrogenase activity in retinal homogenates. The results suggest that the aldehyde dehydrogenase activity in rat brain is predominantly outside the catecholaminergic nerve terminals.     

Free Fatty Acids in the Rat Brain in Moderate and Severe Hypoxia

Abstract: The effects of mild, moderate, and severe hypoxia on cerebral cortical concentrations of free fatty acids (FFAs) were investigated in artificially ventilated rats under nitrous oxide anaesthesia. No change occurred during either mild (arterial Po₂ 35–40 mm Hg) or moderate (Po₂ 25–30 mm Hg) hypoxia. The effects of severe hypoxia (Po₂ about 20 mm Hg) combined with hypotension (mean arterial blood pressure 80–85 mm Hg) varied with the EEG pattern and the tissue energy state. Thus, a major increase in total as well as in individual FFAs occurred first when EEG was severely depressed (almost isoelectric) and energy homeostasis disrupted. On a relative basis the greatest change occurred in free arachidonic acid. It is concluded that hypoxia is associated with an increase in the concentrations of FFAs in brain tissue, provided that tissue oxygen deficiency is severe enough to cause tissue energy failure. However, an increase in FFAs does not invariably accompany minor reductions in the adenylate energy charge (EC) of the tissue.     

Subcellular Distribution of Tyrosine Hydroxylase in Some Catecholaminergic Rat Brain Areas Determined by a Quantitative Immunoblot Assay

The subcellular distribution of the protein tyrosine hydroxylase (TH) after fractionation of rat brain tissue was studied by a sensitive technique of immunoblot quantification in the dopaminergic nigrostriatal and the dorsal noradrenergic pathways and in the ventrolateral medulla. This repartition indicates that in all catecholaminergic regions of the cell bodies studied, the contribution of the nerve endings to the total TH amount is very low (less than 7%), in contrast to that observed in the terminal fields. The correlative subcellular determination of the TH amount and activity in the same tissue could be a useful approach for studying experimentally induced mechanisms of catecholamine synthesis modulation in different brain catecholaminergic pathways.