Free radical production, catalase and superoxide dismutase activities and membrane integrity during senescence of petals of cut carnations (Dianthus caryophyllus)

There is a sudden increase in free radical levels, measured from the electron spin resonance (ESR) signal, in cut carnation ( Dianthus caryophyllus L. cv. Ember) petal powders between the end of blooming and the onset of withering. There is also an increase in the microsomal generation of superoxide radicals (measured from the ESR-Tiron signal). These increases correspond to a decrease of polar lipids content, a slight increase in peroxides and to the onset of a sudden efflux of electrolytes. A correlation is established between free radical production and the loss of membrane integrity. Catalase (EC 1.11.1.6) activity increases progressively until complete withering and an hypothesis concerning the action of this enzyme is proposed. The changes in superoxide dismutase (EC 1.15.1.1) activity appear to be independent of the amplitude of the ESR-Tiron signal.     

残缺类囊体膜与嵴膜小囊的融合膜结构观察

观察了菠菜叶绿体类囊体膜与残缺膜的表面结构及鼠肝线粒体嵴膜小囊在制备过程中的生成过程,证明了嵴膜小囊可有两种,F_1在膜外侧或膜内侧,它们都可与残缺膜组成镶嵌膜,进行光下磷酸化功能。而F_1在膜外侧的嵴膜小囊与残缺膜的嵌合膜活力更高。     

缺硼与低温对黄瓜幼苗—些生理反应的影响

营养液培养试验表明,缺硼明显降低黄瓜幼苗植株的生长量,植株叶片细胞质膜K 的渗漏增加,细胞结构受损。此外,叶片中蔗糖和还原糖都明显积累。缺硼的上述反应在低温胁迫（7－8℃,FX25－28℃为对照）时表现更为明显。试验结果表明硼对于细胞膜的完整性具有重要的作用;充分供硼可以减轻低温对细胞膜的伤害。     

Water state and diffusion through lipid bilayers: Effect of hydration degree

The dependences of adsorbed water state (obtained from the variations in ¹H NMR spectra with the angle between the bilayer normal and magnetic field direction) and water diffusion along the bilayer normal (measured using pulsed field gradient ¹H NMR) on hydration degree have been studied in macroscopically oriented bilayers of dioleoylphosphatidylcholine. The angle dependences of the shape of NMR spectrum are qualitatively different only for water concentrations higher and lower than that achieved by hydration from saturated vapors (χ_eq, about 23%). At concentrations lower than χ_eq, all water in the sample either makes the hydration shells of the lipid polar heads or is in fast exchange with the shell water, so the spin-echo signal from water is detected only within a narrow range of angles close to the magic angle, 54.7°. At concentration exceeding χ_eq, the spin-echo signal from water is retained at all orientations, suggesting that a portion of water between bilayers (quasi-free water) slowly exchanges with water bound to the polar heads. There is an inverse dependence of the coefficient of water self-diffusion through the bilayer system on the hydration degree, which is described in the Tanner model with account of water self-diffusion in the hydrophobic part of the bilayer. Bilayer permeability, distribution coefficient of molecules between aqueous and lipid phases, and water self-diffusion coefficient in the hydrophobic region of the bilayer are estimated.     

Recent advances in the understanding of polyamine functions during plant development

Suggested roles for polyamine function, and the evidence for these functions, is reviewed. These include membrane stabilization, free radical scavenging, effects on DNA, RNA and protein synthesis, effects on the activities of RNase, protease and other enzymes, the interaction with ethylene biosynthesis, and effects on second messengers. It is concluded that in addition to interacting with plant hormones, polyamines are able to modulate plant development through a fundamental mechanism(s) common to all living organisms.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - ADC arginine decarboxylase - Chl chlorophyll - DAP diaminopropane - DFMA DL--difluoromethylarginine - DFMO DL--difluoromethylornithine - PAs polyamines - Put putrescine - SAM S-adenosylmethionine - Spd spermidine - Spm spermine     

Cholesterol trafficking and raft-like membrane domain composition mediate scavenger receptor class B type 1-dependent lipid sensing in intestinal epithelial cells

Scavenger receptor Class B type 1 (SR-B1) is a lipid transporter and sensor. In intestinal epithelial cells, SR-B1-dependent lipid sensing is associated with SR-B1 recruitment in raft-like/ detergent-resistant membrane domains and interaction of its C-terminal transmembrane domain with plasma membrane cholesterol. To clarify the initiating events occurring during lipid sensing by SR-B1, we analyzed cholesterol trafficking and raft-like domain composition in intestinal epithelial cells expressing wild-type SR-B1 or the mutated form SR-B1-Q445A, defective in membrane cholesterol binding and signal initiation. These features of SR-B1 were found to influence both apical cholesterol efflux and intracellular cholesterol trafficking from plasma membrane to lipid droplets, and the lipid composition of raft-like domains. Lipidomic analysis revealed likely participation of d18:0/16:0 sphingomyelin and 16:0/0:0 lysophosphatidylethanolamine in lipid sensing by SR-B1. Proteomic analysis identified proteins, whose abundance changed in raft-like domains during lipid sensing, and these included molecules linked to lipid raft dynamics and signal transduction. These findings provide new insights into the role of SR-B1 in cellular cholesterol homeostasis and suggest molecular links between SR-B1-dependent lipid sensing and cell cholesterol and lipid droplet dynamics.     

蜂毒肽在磷脂膜上取向的高效液相色谱和质谱研究

利用脂质体模型系统研究了跨膜电位对蜂毒肽在磷脂磷上取向的影响,采用高效液相色谱与质谱技术相结合方法,分析了蜂毒肽与磷脂膜作用后的胰蛋白酶酶解产物,结果发现,当蜂毒肽分子与没有跨膜电位的脂质体结合后,它的所有酶切位点都能够酶有效切断,当蜂毒肽与带负向膜电全的脂质体结合后,其Ｎ端的一个酶切位点被封闭,从而说明跨膜电位造成了蜂毒肽在膜上的重瓣取向。     

妊娠妇女阴道微生态和B族链球菌与胎膜早破及母婴结局的相关性

探讨妊娠妇女阴道微生态状况和B族链球菌（GBS）感染与妊娠晚期胎膜早破及母婴结局的相关性。

回顾性收集2021年1月至2022年12月我院114例临床确诊足月胎膜早破妊娠妇女为研究对象（胎膜早破组）,随机选取同期分娩的129例健康妊娠妇女为对照组。收集两组对象临床资料,比较两组对象阴道微生态变化、GBS感染及不良母婴结局发生情况。

两组妊娠妇女阴道假丝酵母菌菌体及孢子检出情况比较差异均无统计学意义（均P＞0.05）。胎膜早破组患者阴道pH≥4.5、细菌性阴道病、需氧菌性阴道炎的发生率及微生态失衡率高于对照组（均P＜0.05）。胎膜早破组妊娠妇女绒毛膜羊膜炎、产褥感染、胎儿窘迫及新生儿肺炎等不良母婴结局发生率高于对照组（均P＜0.05）。单因素分析结果显示,阴道pH≥4.5、有GBS感染、阴道微生态失调与不良母婴结局有关（均P＜0.05）。

妊娠晚期阴道微生态失衡、GBS感染与妊娠晚期胎膜早破的发生相关,同时会增加不良母婴结局的发生率。加强相关危险因素的干预可降低妊娠晚期女性胎膜早破发生率,改善不良母婴结局。