热胁迫诱导玉米幼苗γ-氨基丁酸积累的生理作用

采用高温与外源γ-氨基丁酸( GABA)处理玉米幼苗,研究GABA对玉米幼苗抗热性的作用,结果表明,高温胁迫能够诱导玉米幼苗中GABA的表达,GABA对玉米抵抗高温环境起着一定作用;同时施加外源GABA,能够提高玉米幼苗中SOD、POD活性及MDA、GABA含量.     

Mutation of the GABA receptor associated with fipronil resistance in the whitebacked planthopper, Sogatella furcifera

We found the A2′N mutation (index number for M2 membrane spanning region) in the GABA receptor subunit of fipronil-resistant Sogatella furcifera, by analyzing DNA sequences amplified from fipronil-resistant and -susceptible S. furcifera. In order to confirm the role of A2′N mutation in the fipronil resistance, we expressed the wild-type and A2′N mutant Drosophila GABA receptors in Drosophila Mel-2 cells stably. Amino acid sequences of three membrane spanning regions (M1-M3), which are important for binding of fipronil, are conserved between Drosophila and S. furcifera. So the results of A2′N mutant Drosophila GABA receptor suggest the role of A2′N mutation in fipronil-resistant S. furcifera. The membrane potential assay showed that the A2′N mutant Drosophila GABA receptor was not inhibited by fipronil at all, while the IC₅₀ value of fipronil for wild-type Drosophila GABA receptor was 172 nM. These results suggest that A2′N mutation confers the resistance of fipronil in S. furcifera.     

The role of GABA and glutamate receptors in susceptibility and resistance to chloride channel blocker insecticides

Despite a point mutation in the pore-forming segment of the Rdl GABA receptor subunit that is widespread and persistent in insect populations and confers high levels of resistance to dieldrin and other polychlorocycloalkane (PCCA) insecticides, the phenylpyrazole insecticide fipronil, which binds at same site, has proven to be effective in controlling many insects, including dieldrin-resistant populations. Fipronil and its major sulfone metabolite are unique among chloride channel blocking insecticides in that they also potently block GluCls. We present here a patch clamp study of the action of fipronil sulfone on native GABA receptors and GluCl receptors from susceptible and dieldrin-resistant German cockroaches, to provide a better understanding of the effect of the Rdl mutation on the function and insecticide sensitivity of these two targets, and its role in resistance. Dieldrin blocked GABA currents with an IC₅₀ of 3 nM in wild-type cockroaches, and 383 nM in resistant insects, yielding a resistance ratio of 128. Fipronil sulfone blocked GABA currents with an IC₅₀ of 0.8 nM in susceptible insects and 12.1 nM, or 15-fold higher, in resistant insects. While both GluClD (desensitizing) and GluClN (non-desensitizing) receptors were found in German cockroach neurons, GluClN receptors were rare and could not be included in this study. GluClD receptors from resistant insects had reduced sensitivity to glutamate and a lower rate of desensitization than those from susceptible insects, but their sensitivity to block by fipronil sulfone was not significantly changed, with an IC₅₀ of 38.5 ± 2.4 nM (n = 8) in the susceptible strain and 40.3 ± 1.0 nM (n = 7) in the resistant strain. Fipronil sulfone also slowed the decay time course of GluClD currents. These results suggest that GluClD receptors contain the Rdl subunit, but their sensitivity to fipronil sulfone is not altered in resistant insects.     

Effects of monoterpenoid insecticides on [H]-TBOB binding in house fly GABA receptor and Cl uptake in American cockroach ventral nerve cord

Monoterpenoids and their derivatives from plant essential oils showed good insecticidal activities in previous studies, but the mechanisms of their action as natural insecticides are not known yet. In the present work, we evaluated the pharmacological action of five monoterpenoids (α-terpineol, carvacrol, linalool, pulegone, and thymol) on native insect GABA receptors from house flies and American cockroaches using radiotracer methods. In the [³H]-TBOB binding assay, carvacrol, pulegone, and thymol all enhanced the [³H]-TBOB binding to membrane preparation of house fly heads with EC₅₀ values of 48 μM, 432 μM, and 6 mM, respectively. Moreover, these three monoterpenoids at concentrations of 500 μM and 1 mM also significantly increased the ³⁶Cl⁻ uptake induced by GABA in membrane microsacs prepared from American cockroach ventral nerve cords. These results revealed that carvacrol, pulegone, and thymol are all positive allosteric modulators at insect GABA receptors. The other two monoterpenoids that were tested, α-terpineol and linalool, showed little or no effect in both the [³H]-TBOB binding and ³⁶Cl⁻ uptake assays.     

GABA对小麦幼苗耐盐性的影响

以小麦为试验材料,研究了NaCl胁迫下外源GABA浓度对小麦发芽率、芽长、根长、鲜干重、相对电导率及其酶活性的影响.结果表明:与对照相比,GABA浸种促进了小麦幼苗芽的生长,对根的生长影响较小;在GABA浓度为0.5 mmol.L-1条件下,小麦幼苗的发芽率及其鲜干重有明显的提高;相对电导率的测定结果显示,不同浓度GABA对膜都有不同程度的保护作用,在GABA浓度为0.5 mmol.L-1时效果最显著;对SOD、POD和CAT这几种酶活性的测定结果显示,随着GABA浓度的增加其活性都有不同程度的增加;由此推断,外源GABA可以减轻盐胁迫对小麦幼苗造成的伤害,具有一定的生理保护作用.     

GABA免疫阳性神经元在三黄鸡小脑内的分布

为探明三黄鸡小脑皮质各层的细胞构筑和GABA免疫反应神经元在其小脑内的分布情况,采用尼氏染色和免疫组织化学SABC技术,对10羽三黄鸡的小脑进行了研究。研究发现:三黄鸡小脑皮质各层的细胞构筑与北京鸭、乌鸡、鸽子和非洲鸵鸟的大体相似;GABA免疫阳性细胞位于小脑皮质的蒲肯野细胞层中,阳性较明显;小脑中央核也有大量阳性神经元,多数呈梭形或不规则多边形,多数神经元胞质呈强阳性染色。以上结果表明:GABA阳性神经元在三黄鸡小脑皮质各层均有分布,GABA可能在介导小脑复杂功能中发挥重要作用。     

通气处理对发芽糙米生理活性及主要物质含量影响

在浸泡条件下,探讨通气处理对发芽糙米生理活性及γ-氨基丁酸(GABA)等主要物质含量的影响。结果表明: 0．5-2．0 L·min-1的通气处理有利于发芽糙米生长和呼吸代谢,加速淀粉和可溶性蛋白质降解,促进还原糖和游离氨基酸生成。当通气量为1．0 L·min-1时,发芽糙米中GABA累积量最高。     

桑叶中γ-氨基丁酸含量的测定

γ-氨基丁酸(γ-aminobutyricacid,简称GABA)是动物中枢神经系统中的一种主要的抑制性神经递质,也是广泛地存在于植物体内的一种与逆境胁迫有关的非蛋白氨基酸.实验探索出了适合桑叶的测定方法为比色法,利用AlCl3有效去除桑叶中的水溶性色素后,采用分光光度法准确地测定桑叶中GA-BA的含量.同时,对目前生产上主要栽种的23个桑树品种的GABA的含量进行了测定,其结果显示含量较高的桑树品种为火桑,其新鲜桑叶中GABA的含量为1.224 mg/g,为GABA的进一步研究和桑叶中功能性成分的开发利用奠定了试验理论基础.     

利用大豆发芽开发富含γ-氨基丁酸的玉米味豆乳

以富含γ-氨基丁酸(GABA)的大豆芽和玉米浓浆为原料研制玉米味发芽豆乳。研究了大豆发芽过程中,适宜用来制作豆乳的最佳芽长,并采用正交试验设计优化豆乳配方和稳定剂添加量。结果表明:芽长为3~4 cm,发芽时间37~43 h,GABA含量是对照组的6~8倍,制作的豆乳无豆腥味、青芽味。白砂糖、玉米浓浆和Na Cl添加量分别为30,50和0.75 g·L~(-1)时,豆乳口感清甜,玉米味、豆乳味协调。采用0.75 g·L~(-1)复合磷酸盐2号,2 g·L~(-1)复合增稠剂(黄原胶∶海藻酸钠=2∶3),0.8 g·L~(-1)复合乳化剂(蔗糖脂肪酸酯+分子蒸馏单甘酯,HLB值=11)复配的稳定剂得到的豆乳稳定性最好。