胀果甘草化学成分的研究（Ⅲ）

继前文工作,本文报道从胀果甘草(Glycyrrhiza inflata Bat)根及根茎用95％乙醇渗滤后的提取部分中获得的另外五个化合物的结构鉴定。经理化性质及波谱分析,分别鉴定为胡萝卜甙(Daucosterol)、甘草查尔酮甲(Licochalcone A)、β-谷甾醇(β-Sitosterol),异芒柄花甙(Isoononin)和4＇,7一二羟基黄酮(4＇,7-Dihydroxy-flavone)。其中胡萝卜甙和异芒柄花甙为首次从该植物中获得。药理实验表明,甘草查尔酮甲对H_2O_2诱异的溶血有极好的抑制作用(97.3％),但甘草甙在三个体外氧化体系中都没有明显的活性。     

Perspectives on the nanocarriers with miRNAs for targeting melanoma stemness through epigenetic regulation

Several research reports delineated the significant role of miRNAs in cancer proliferation, and their modulatory role in cancer mitigation, and drug resistance. Melanoma cells have been acquiring stemness to several chemotherapeutic agents through drug efflux proteins, epigenetic modulation, and DNA repair. miRNAs could be applied as novel therapeutic modalities for treating several kinds of cancers to modulate these mechanisms involved in stemness. Nanocarriers to carry these tumor-targeting miRNAs to modulate stemness are a prominent strategy to overcome their low penetrability, minimal stability, and nonspecificity. We have searched several public databases such as PubMed, Medline, Google scholar, and NLM and obtained the information pertinent to the miRNA-based nanocarrier systems to target stemness through epigenetic modulation in melanomas. This review delineates that various miRNAs can modulate the stemness in melanomas by specific intricate epigenetic signaling, and other cell-based signaling mechanisms. Specific nanocarrier formulations with specific miRNAs are optimal methods to deliver these miRNAs in order to achieve significant entrapment efficiency, loading efficiency, and stability. Furthermore, the combinatorial regimen of FDA-approved chemotherapeutic molecules with tumor-targeting miRNAs and chemotherapy combined with nanocarriers can efficiently deliver the utmost therapeutic window by targeting tumor matrix, invasion, metastasis, and angiogenesis in melanomas. Substantial research should focus on the clinical application of this gene therapy in melanomas using these low immunogenic, highly degradable, and biocompatible combinatorial nanotherapeutic regimens.     

CARBON FIXATION IN CULTURED MARINE BENTHIC DIATOMS1

The enzyme activity of ribulose 1, 5-bisphosphate carboxylase-oxygenase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC) was measured in four species of marine benthic diatoms isolated from subtidal sediments of Graveline Bayou, Mississippi. Enzyme activities were measured in cultures of Amphora micrometra Giffen, A. tenerrima Aleem and Hustedt, Nitzschia fontifuga Cholnoky, and Nitzschia vermicularis Grunow that were grown at light levels supporting μ_max and at light-limiting irradiances. All four species exhibited similar RuBisCO: PEP ratios (range = 1–1.8) at μ_max the lowest ratio (0.4) was observed in A. micrometra. Reduced light levels increased PEPC relative to that measured at μ_max in two species. Two-dimensional paper chromatography was used to determine the first products of carbon fixation in A. micrometra After a 15 s incorporation period, the first product of photosynthetic carbon fixation was 3-phosphoglycerate even though this alga had a PEPC activity that was three times higher than that of RuBisCO. After 30 s, over 50% of the recovered radioactivity was still in this compound. Stable carbon isotope analyses of a mixture of the four pennate diatoms also suggest the predominant carbon fixation pathway in these benthic diatoms was similar to C3 plants.     

Pathways,pathway tubes,pathway docking,and propagators in electron transfer proteins

The simplest views of long-range electron transfer utilize flat one-dimensional barrier tunneling models, neglecting structural details of the protein medium. The pathway model of protein electron transfer reintroduces structure by distinguishing between covalent bonds, hydrogen bonds, and van der Waals contacts. These three kinds of interactions in a tunneling pathway each have distinctive decay factors associated with them. The distribution and arrangement of these bonded and nonbonded contacts in a folded protein varies tremendously between structures, adding a richness to the tunneling problem that is absent in simpler views. We review the pathway model and the predictions that it makes for protein electron transfer rates in small proteins, docked proteins, and the photosynthetic reactions center. We also review the formulation of the protein electron transfer problem as an effective two-level system. New multi-pathway approaches and improved electronic Hamiltonians are described briefly as well.     

Hypoxia Increases the Susceptibility to Oxidant Stress and the Permeability of the Blood-Brain Barrier Endothelial Cell Monolayer

Abstract: Using a cell culture model of the blood-brain barrier (BBB), we investigated the brain capillary endothelial cell (EC) response to hypoxia. The activities of antioxidant enzymes such as glutathione peroxidase, glutathione reductase, catalase, and superoxide dismutase and the GSH level of brain capillary ECs alone or in coculture with astrocytes, as well as those of pericytes, were compared with those obtained with freshly isolated microvessels. These results demonstrated that brain capillary ECs cocultured with astrocytes and used in the presence of a coculture-conditioned medium provided a relevant in vitro model for studying the effect of hypoxia-reoxygenation at the BBB level. The effect of hypoxia on antioxidant enzymes, GSH, and ATP levels was studied, as well as the modification of the permeability to small weight molecules. A decrease in all enzymes and the GSH level could explain an increase in the susceptibility of the brain capillary ECs to further oxidant injury. Second, profound rearrangements of F-actin filaments of the ECs and a decrease in the ATP level could be associated with an increase in the permeability of the monolayer. Furthermore, an apoptotic process was detected by in situ end labeling of DNA. These results indicate that hypoxia distorts the function of ECs and that these cells in culture provide a valuable tool for exploring mechanisms after hypoxia-reoxygenation.     

Intraspecific variation of spectral sensitivity in threespine stickleback (Gasterosteus aculeatus) from different photic regimes

To examine the influence of the spectral characteristics of underwater light on spectral sensitivity of the ON and OFF visual pathways, compound action potential recordings were made from retinal ganglion cells of threespine stickleback from different photic regimes. In fish from a red-shifted photic regime (P₅₀ 680 nm for downwelling light at 1m), peak sensitivity of both the ON and OFF pathways was limited to long wavelength light (_max 600–620). In contrast, the ON pathway of fish from a comparatively blue-shifted (P₅₀ 566 nm) photic regime exhibited sensitivity to medium (_max 540–560) and long (_max 600 nm) wavelengths, while the OFF pathway exhibited peak sensitivity to only medium (_max 540 nm) wavelength light. In a third population, where the the ambient light is moderately red-shifted (P₅₀ 629 nm), the ON pathway once again exhibited only a long wavelength sensitivity peak at 620 nm, while the OFF pathway exhibited sensitivity to both medium (_max 560 nm) and long (_max 600–620 nm) wavelength light. These findings suggest that the photic environment plays an integral role in shaping spectral sensitivity of the ON and OFF pathways.     

Oxidative stress during exercise: Implication of antioxidant nutrients

Research evidence has accumulated in the past decade that strenuous aerobic exercise is associated with oxidative stress and tissue damage in the body. There is indication that generation of oxygen free radicals and other reactive oxygen species may be the underlying mechanism for exercise-induced oxidative damage, but a causal relationship remains to be established. Enzymatic and nonenzymatic antioxidants play a vital role in protecting tissues from excessive oxidative damage during exercise. Depletion of each of the antioxidant systems increases the vulnerability of various tissues and cellular components to reactive oxygen species. Because acute strenuous exercise and chronic exercise training increase the consumption of various antioxidants, it is conceivable that dietary supplementation of specific antioxidants would be beneficial.     

Glycine cleavage and generation of one-carbon units in Euglena gracilis

Euglena gracilis Klebs (strain Z) was maintained in division synchronized autotrophic culture, receiving either air (low CO₂) or 5% CO₂ in     

刺激家兔中脑导水管周围灰质抑制束旁核伤害性放电的脊髓上机制

本工作比较了家兔脊髓背侧1/2进行横切前后刺激中脑中央灰质对束旁核伤害性放电的抑制率的改变。实验表明中央灰质既可通过公认的脊髓下行纤维抑制脊髓水平的痛传递,减弱束旁核单位的痛敏放电,也可通过某种脊髓上机制实现对束旁核的抑制。我们对这两种机制的相对重要性作了分析。用直11个束旁核痛敏单位所作的计算表明,在脊髓切割前,刺激中央灰质可使束旁核痛敏放电抑制67.5%,脊髓背侧1/2横切后,同样的中脑刺激只能使痛敏放电抑制42.9%。如以切割前的抑制率作为直100%,则切割可使抑制减弱36.5%,这一部分抑制应当是由被切断的脊髓下行纤维实现的,其余63.5%则可能主要通过脊髓上机制来实现。考虑到脊髓背半部横切不可能全部切断下行纤维,故实际上脊髓上机制的重要性不会有上述数值表示的那么大。     

羧基化多壁碳纳米管、混合盐及其复合胁迫对水稻幼苗生理特性的影响

将水稻（Oryza sativa L.）幼苗悬浮培养于含有羧基化多壁碳纳米管MWCNTs-COOH（0、2.5、5.0、10.0 mg/L）、50 mmol/L混合盐（1NaCl：9Na₂SO₄：9NaHCO₃：1Na₂CO₃）,以及MWCNTs-COOH+混合盐的复合溶液中,10 d后检测叶片生理生化指标变化,研究MWCNTs-COOH复合盐碱胁迫对水稻幼苗的毒性及生态风险。结果显示,与对照组相比,MWCNTs-COOH单一组诱导下水稻叶片O₂^·-和H₂O₂的产生不明显,而混合盐组和混合盐+MWCNTs-COOH复合组均诱导了O₂^·-和H₂O₂产物的大量累积。MWCNTs-COOH与混合盐复合后,加剧了O₂^·-和H₂O₂的累积,并有明显的浓度效应。活性氧（ROS）作为信号分子在一定程度上诱导了各处理组部分抗氧化酶（SOD、CAT、POD、APX）活性的升高;与混合盐组相比,低浓度混合盐+MWCNTs-COOH复合组中叶绿素a和胡萝卜素含量呈一定程度的升高;MWCNTs-COOH与混合盐复合后,抑制了叶片中可溶性糖（SS）和脯氨酸（Pro）的合成,致使相对电导率（REC）和丙二醛（MDA）含量显著升高。上述抗氧化酶活性及叶绿素a和胡萝卜素含量的升高对缓解水稻叶片氧化损伤、维持正常的光合电子传递及对过剩光能的热耗散是有益的,是水稻幼苗重要的防御机制。本研究表明MWCNTs-COOH单一处理在一定程度上诱导了水稻叶片的氧化胁迫和应激响应,与混合盐复合后加剧了叶片的氧化胁迫和应激损伤。