Membrane permeability of fructose-1,6-diphosphate in lipid vesicles and endothelial cells

Fructose-1,6-diphosphate (FDP) is a glycolytic intermediate which has been used an intervention in various ischemic conditions for two decades. Yet whether FDP can enter the cell is under constant debate. In this study we examined membrane permeability of FDP in artificial membrane bilayers and in endothelial cells. To examine passive diffusion of FDP through the membrane bilayer, L-a-phosphatidylcholine from egg yolk (Egg PC) (10 mM) multi-lamellar vesicles were created containing different external concentrations of FDP (0, 0.5, 5 and 50 mM). The passive diffusion of FDP into the vesicles was followed spectrophotometrically. The results indicate that FDP diffuses through the membrane bilayer in a dose-dependent fashion. The movement of FDP through Egg PC membrane bilayers was confirmed by measuring the conversion of FDP to dihydroxyacetone-phosphate and the formation of hydrozone. FDP (0, 0.5, 5 or 50 mM) was encapsulated in Egg PC multilamellar vesicles and placed in a solution containing aldolase. In the 5 and 50 mM FDP groups there was a significant increase in dihydroxyacetone/hydrazone indicating that FDP crossed the membrane bilayer intact. We theorized that the passive diffusion of FDP might be due to disruption of the membrane bilayer. To examine this hypothesis, small unilamellar vesicles composed of Egg PC were created in the presence of 60 mM carboxyfluorescein, and the leakage of the sequestered dye was followed upon addition of various concentrations of FDP, fructose, fructose-6-phosphate, or fructose-1-phosphate (0, 5 or 50 mM). These results indicate that increasing concentrations of FDP increase the leakage rate of carboxyfluorescein. In contrast, no concentration of fructose, fructose-6-phosphate, or fructose-1-phosphate resulted in any significant increase in membrane permeability to carboxyfluorescein. To examine whether FDP could pass through cellular membranes, we examined the uptake of ¹⁴C-FDP by endothelial cells cultured under hypoxia or normoxia for 4 or 16 h. The uptake of FDP was dose-dependent in both the normoxia and hypoxia treated cells, and was accompanied by no significant loss in endothelial cell viability. Our results demonstrate that FDP can diffuse through membrane bilayers in a dose-dependent manner.     

维生素E对免疫功能的影响

适当剂量的维生素Ｅ（ＶＥ）,能增强抗体和补体的产生以及抗体对抗原的应答反应,促进淋巴细胞的增殖、分化和细胞因子的产生,提高免疫细胞的细胞毒作用和吞噬细胞的吞噬作用。ＶＥ缺乏或过量,能抑制机体的免疫机能,降低对疾病的抵抗能力。     

森林流域土壤饱和渗透系数与有效孔隙度模型的研究

以长白山自然保护区内未受扰动的两种典型原始森林土壤为对象,通过野外选取原状土样,在实验室内测定其饱和渗透系数和有效孔隙度,利用回归分析法分别建立了森林土壤内饱和渗透系数和有效孔隙度随深度变化的数学模型,即Ｋｓ（ｚ）＝Ｋ０－ｆ１ｌｎａ１ｚ和ω（ｚ）＝ω０－ｆ２ｌｎａ２ｚ．将所得出的对数模型与Ｂｅｖｅｎ所提出的指数模型进行比较表明,在森林流域内对数模型不仅适用范围比指数模型广,而且精度明显高于指数模型,它更接近于野外实际情况．     

Photosynthetic characteristics of coffee (Coffea arabusta) plantlets in vitro in response to different CO2 concentrations and light intensities

The photosynthetic characteristics of coffee ( Coffea arabusta) plantlets cultured in vitro in response to different CO₂ concentrations inside the culture vessel and photosynthetic photon flux (PPF) were investigated preliminarily. The estimation of net photosynthetic rate (P_n) of coffee plantlets involved three methods: (1) estimating time courses of actual P_n in situ based on measuring CO₂ concentrations inside and outside the vessel during a 45-day period, (2) estimating P_n in situ at different CO₂ concentrations and PPFs using the above measuring approach for 10-day and 30-day old in vitro plantlets, and (3) estimating P_n of a single leaf at different CO₂ concentrations and PPFs by using a portable photosynthesis measurement system for 45-day old in vitro coffee plantlets. The results showed that coffee plantlets in vitro had relatively high photosynthetic ability and that the P_n increased with the increase in CO₂ concentration inside the vessel. The CO₂ saturation point of in vitro coffee plantlets was high (4500–5000 μmol mol^-1); on the other hand, the PPF saturation point was not so high as compared to some other species, though it increased with increasing CO₂ concentration inside the vessel. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Level of Expression of Thioredoxin is Linked to Fundamental Properties and Applications of Wheat Seeds

Work with cereals （barley and wheat） and a legume （Medicago truncatula） has established thioredoxin h （Trx h） as a central regulatory protein of seeds. Trx h acts by reducing disulfide （S-S） groups of diverse seed proteins （storage proteins, enzymes, and enzyme inhibitors）, thereby facilitating germination. Early in vitro protein studies were complemented with experiments in which barley seeds with Trx h overexpressed in the endosperm showed accelerated germination and early or enhanced expression of associated enzymes （α-amylase and pullulanase）. The current study extends the transgenic work to wheat. Two approaches were followed to alter the expression of Trx h genes in the endosperm： （1） a hordein promoter and its protein body targeting sequence led to overexpression of Trx hS, and （2） an antisense construct of Trx h9 resulted in cytosolic underexpression of that gene （Arabidopsis designation）. Underexpression of Trx h9 led to effects opposite to those observed for overexpression Trx h5 in barley--retardation of germination and delayed or reduced expression of associated enzymes. Similar enzyme changes were observed in developing seeds. The wheat lines with underexpressed Trx showed delayed preharvest sprouting when grown in the greenhouse or field without a decrease in final yield. Wheat with overexpressed Trx h5 showed changes commensurate with earlier in vitro work： increased solubility of disulfide proteins and lower aUergenicity of the gliadin fraction. The results are further evidence that the level of Trx h in cereal endosperm determines fundamental properties as well as potential applications of the seed.     

Merosesquiterpenoids and Ten‐Membered Macrolides from a Soft Coral‐Derived Lophiostoma sp. Fungus

One new merosesquiterpenoid, craterellin D ( 1 ), along with one known analog, craterellin A ( 2 ), and five known ten‐membered macrolides, 3 – 7 , were isolated from a soft coral‐derived Lophiostoma sp. fungus. The absolute configuration of 1 was established based on biogenetic consideration with the co‐isolated analog 2 , whose configuration was determined by modified Mosher's method and single‐crystal X‐ray diffraction analysis using CuK_α radiation. The absolute configuration of 3 was determined by X‐ray diffraction analysis using CuK_α radiation. Compounds 2 and 3 showed antibacterial activities against Bacillus cereus with a MIC value of 3.12 μM .