Ce4+对东北红豆杉细胞有丝分裂的影响

以悬浮培养的东北红豆杉细胞为材料,研究了不同浓度的Ce4 在不同处理时间对细胞有丝分裂的影响。结果显示,Ce4 能诱发东北红豆杉细胞多种异常有丝分裂,在浓度为0.5mmol/L、处理时间为5h时,即开始出现异常有丝分裂现象,而且细胞有丝分裂指数(MI)比对照组明显降低(P<0.05),表明细胞有丝分裂受到抑制,Ce4 对细胞有丝分裂过程有显著影响。Ce4 具有一定遗传毒性。     

Ce4+对悬浮培养南方红豆杉细胞DNA含量和PAL活性的影响

本文动态观察了不同浓度 Ce4 作用下悬浮培养体系中南方红豆杉细胞核 DNA含量、细胞活力、苯丙氨酸转氨酶 (PAL )活性及紫杉醇含量的变化规律 ,并比较了不同浓度 Ce4 对这些指标影响的差异。结果表明 :在悬浮培养体系中加入适当浓度 Ce4 ,在其作用早期对南方红豆杉细胞的增殖能力、细胞活力及紫杉醇含量均有明显的促进作用 ;Ce4 对细胞的生物效应中浓度是一重要因素 ,同时细胞自身所处的生理状态也影响稀土离子作用的结果     

火炬松胚性细胞系的生长动力学

以来源于火炬松（Ｐｉｎｕｓ ｔａｅｄａ Ｌ．）成熟合子胚的白色粘性胚性愈伤组织为材料建立了胚性细胞悬浮系，测定了其培养物的鲜重、细胞体积的增长特性及培养液中的蔗糖浓度、ｐＨ值和电导率等在培养过程中的变化规律．结果表明，在培养周期内，培养液中的蔗糖浓度、ｐＨ值和电导率的逐步降低与培养物的鲜重和细胞体积的逐步增加保持一致性。在培养的第１８￣２１ｄ蔗糖浓度，ｐＨ值和电导率均接近或降到最低点，而鲜重及细胞     

铈减轻铅对水稻幼苗毒害的机理初探

通过保护性酶活性及叶绿素、MDA含量的检测,根系活力及电导率测定研究铈减轻水稻幼苗抗重金属铅毒害能力的机理.结果表明,用适宜浓度Ce(NH4)2(NO3)6浸种后培养的幼苗,经重金属铅胁迫后,能有效地降低相对电导率,维持较高的SOD活性,提高POD、CAT活性,减缓MDA的积累.同时,能促进水稻幼苗叶绿素含量及根系活力的提高.     

外源水杨酸对番茄耐盐性的影响

[目的]探讨外源水杨酸(SA)对番茄耐盐性的影响,为SA在番茄生产中的应用提供理论依据.[方法]在盐胁迫条件下,对番茄喷施不同浓度(1、2、5 mmol/L)的SA,测定其叶片叶绿素含量、可溶性糖含量、过氧化物酶(POD)活性、相对电导率及根系活力,研究外源SA处理对番茄幼苗耐盐性的影响.[结果]外源SA能不同程度地提高番茄叶片叶绿素含量、可溶性糖含量、POD活性和根系活力,而降低叶片相对电导率.其中浓度2 mmol/L SA对叶绿素含量、POD活性和相对电导率的影响最佳,而浓度5 mmol/L SA对可溶性糖和根系活力的影响较大.[结论]外源SA能够提高番茄幼苗的耐盐性,但适宜施用浓度和施用周期尚需进一步研究.     

球等鞭金藻OA-3011积累脂肪酸的条件研究

以球等鞭金藻OA-3011培养液的细胞密度和脂肪酸含量为评价指标,利用均匀设计确定了硝酸钠和磷酸二氢钾的用量;选择影响球等鞭金藻积累脂肪酸的4个因素进行3水平的正交试验,确定其积累脂肪酸的最优条件.结果表明,海水培养基中硝酸钠的适宜浓度为75 mg/L,磷酸二氢钾的适宜浓度为8 mg/L;球等鞭金藻OA-3011的最佳培养条件为:盐度30‰,pH值7.5,接种量90×104个/ml,培养温度25 ℃,此条件下培养液中脂肪酸含量可达48 mg/L.     

NiFe2O4基金属陶瓷的电导率

制备了铝电解用NiFe2O4基金属陶瓷惰性阳极,研究了环境温度及材料成分对电导率的影响.实验结果表明NiFe2O4基金属陶瓷的电导率主要受温度、陶瓷基体电导率、金属成分及金属相在陶瓷相中分散度的影响;当温度从573 K升至1 233 K时,NiFe2O4陶瓷的电导率由0.099 S/cm提高到2.105 S/em;与NiFe2O4陶瓷相比,金属陶瓷的电导率有极大的提高,但二者随温度的变化趋势是一致的;1 233 K时,金属含量为5%Ni,5%Cu和4.25%Cu+0.75%Ni的NiFe2O4基金属陶瓷的电导率分别为20.576 S/cm,14.970 S/cm和18.797 S/cm,用作铝电解惰性阳极已能满足要求,但与当前铝电解碳素阳极材料相比还存在很大距离.     

NaCl胁迫对菠菜不同组织器官的影响

[目的]研究不同浓度NaCl处理对菠菜幼苗各组织器官的影响.[方法]分别用0、10、50 mmol/L NaCl溶液处理菠菜幼苗,测定各处理下菠菜幼苗根、茎、叶的鲜重、干重,抗氧化酶活性,可溶性蛋白和丙二醛(MDA)含量.[结果]菠菜根在低NaCl浓度(10 mmol/L)处理下已与对照组产生明显不同,表现为舍水量下降、MDA含量明显升高、保护酶活性和可溶性蛋白含量下降的现象;菠菜叶在低NaCl浓度(10 mmol/L)处理下则表现为含水量、保护酶活性和可溶性蛋白含量的轻微下降,只有在高NaCl浓度(50 mmol/L)处理下才产生与根类似的反应;而一定浓度范围的NaCl对茎的生理指标影响均不大.[结论]菠菜不同组织器官对Nacl浓度的敏感程度不同,根反应最灵敏,叶的敏感性其次,而茎则只在高浓度NaCl下显现出生理指标的轻微下降.     

NaCl-KCl-Na2WO4熔融体系的电导率研究

针对NaCl-KCl-Na_2WO_4熔融体系,采用交流电极法对熔盐体系的电导率进行研究。结果表明:在1 173～1 203 K之间,NaCl-KCl-Na_2WO_4熔盐体系的电导率随着Na_2WO_4含量先逐渐减小再逐渐增大,在10%Na_2WO_4时电导率最小。在1 218～1 233 K之间,NaCl-KCl-Na_2WO_4熔盐体系的电导率随着钨酸钠含量的增加而逐渐增大。NaCl-KCl-Na_2WO_4(0%～15%)熔盐体系的电导率与温度之间呈线性关系。NaCl-KCl-10%Na_2WO_4熔盐体系受到温度的影响最大。     

耐盐碱细菌筛选、鉴定及其降碱机理探究

为解决高盐碱性赤泥高pH对赤泥堆场生态恢复的限制,从赤泥堆场中筛选出一株可高效降低赤泥pH的耐盐碱细菌菌株ZH1。研究显示,ZH1通过产酸的方式降低培养液pH,其最佳产酸培养基配比为葡萄糖8g/L、酵母膏3g/L、磷酸二氢钾0.3g/L、氯化镁0.3g/L。振荡培养时ZH1产生草酸含量最多,其次是α-酮戊二酸和乙酸、酒石酸;静置培养时ZH1产生草酸含量最多,其次是乳酸和酒石酸,但酒石酸都只在弱酸或中性条件下产生。两种培养方式最终均将培养液的pH降至6.0左右,振荡培养时所需时间较短(约48h),比静置培养快72h左右。通过对pH和有机酸之间的相关性检验发现,振荡培养时pH的下降主要是由草酸和α-酮戊二酸引起的,而静置培养时是由草酸、乳酸和酒石酸共同引起的。     

硝酸铈对红豆杉细胞培养及紫杉醇合成的影响

本文采用电子显微镜及聚丙烯酰胺凝胶电泳等方法 ,研究了稀土对红豆杉细胞培养中生物量积累及紫杉醇合成与释放的影响 ,同时进一步探讨了稀土调控次生代谢的机制。结果表明 ,适量稀土可促进紫杉醇合成 ,并对细胞的酶系统及超微结构产生一定影响。     

An immunologic approach to induction of epidermal growth factor deficiency: induction and characterization of autoantibodies to epidermal growth factor in rats

The role of glutamate as a possible mediator of neurodegeneration is well described, and the homeostasis of extracellular glutamate is considered of major importance when addressing the pathogenesis of excitatory neurodegeneration. Applying the 'indicator diffusion' method to the microdialysis technique, we present a method that is suitable for the in vivo investigation of the capacity of cellular uptake of glutamate. Using 14C-mannitol as reference, we measured the cellular extraction and the cell membrane permeability of the test substance 3H-D-aspartate in the corpus striatum of the rat brain. The cellular extraction fraction of 3H-D-aspartate was 0.29, and the cell membrane permeability 2.24 x 10(-4) cm/s. In the presence of the glutamate-uptake blocker DL-threo-beta-hydroxyaspartate (THA) the extraction of 3H-D-aspartate was completely abolished, indicating that extraction of 3H-D-aspartate was due to cellular uptake by glutamate transporters. The cell membrane permeability towards 3H-D-aspartate was reduced by approximately 98% due to THA, indicating that the cell membranes per se are highly resistant to diffusion of 3H-D-aspartate. It is concluded that the present method can be used in studying the capacity of the glutamate transporters in vivo.     

The effect of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate on CO2 permeability of the red blood cell membrane

It has long been assumed that the red cell membrane is highly permeable to gases because the molecules of gases are small, uncharged, and soluble in lipids, such as those of a bilayer. The disappearance of 12C18O16O from a red cell suspension as the 18O exchanges between labeled CO2 + HCO3- and unlabeled HOH provides a measure of the carbonic anhydrase (CA) activity (acceleration, or A) inside the cell and of the membrane self-exchange permeability to HCO3- (Pm,HCO-3). To test this technique, we added sufficient 4, 4'-diisothiocyanato-stilbene-2,2'-disulfonate (DIDS) to inhibit all the HCO3-/Cl- transport protein (Band III or capnophorin) in a red cell suspension. We found that DIDS reduced Pm,HCO-3 as expected, but also appeared to reduce intracellular A, although separate experiments showed it has no effect on CA activity in homogenous solution. A decrease in Pm,CO2 would explain this finding. With a more advanced computational model, which solves for CA activity and membrane permeabilities to both CO2 and HCO3-, we found that DIDS inhibited both Pm,HCO-3 and Pm,CO2, whereas intracellular CA activity remained unchanged. The mechanism by which DIDS reduces CO2 permeability may not be through an action on the lipid bilayer itself, but rather on a membrane transport protein, implying that this is a normal route for at least part of red cell CO2 exchange.     

Methamphetamine-induced toxicity in cultured adult rat cardiomyocytes

In an attempt to differentiate the direct effects of methamphetamine from the indirect sympathomimetic effects on the myocardium, primary culture of adult rat myocytes were established under serum-free conditions, and they were exposed to methamphetamine (1 x 10(-5) and 1 x 10(-3) M) for 1 to 24 h in the presence and absence of 1 x 10(-6) M propranolol. Cardiotoxicity was evaluated by light and ultramicroscopy, release of cytoplasmic enzymes (Lactate dehydrogenase: LDH and Creatine phosphokinase: CPK) and change in membrane permeability (Trypan blue stain). After 24 h methamphetamine treatment, light microscopy exhibited cellular granulation and swelling, myocyte hypercontraction, broken cellular membrane and cellular destruction. After the same time, electron microscopy revealed swelling and irregular mitochondria with disrupted cristaes, clump of sarcomeres with nearly complete loss of organized contractile elements, injury of intracellular membrane system and dissolution of myofibrils. These injurious features were more severe with the 1 x 10(-3) M methamphetamine. Propranolol (1 x 10(-6) M), a beta-adrenergic antagonist, failed to protect the myocytes against methamphetamine-induced cell injury. Release of LDH from methamphetamine (1 x 10(-5) and 1 x 10(-3) M)-treated myocytes increased significantly only after 24 h, while significant CPK release was observed in 1 x 10(-3) M methamphetamine-treated myocytes at 4 h. These findings suggest that methamphetamine exerts direct toxic effects on adult rat myocytes rather than indirect ones via receptors, although further experiments on more concentrations of propranolol are required.     

Ley specific antibody with potent anti-tumor activity is internalized and degraded in lysosomes

BR96 is a monoclonal antibody (MAb) that recognizes many human carcinomas and can kill antigen-positive tumor cells in vitro. Using both gold and radiolabeled MAb, the distribution and cellular processing of BR96 during cytolysis has been determined. After a brief (< 3 minutes) MAb treatment, cells in suspension are stained by the nuclear viability dye propidium iodide. Whole MAb and F(ab')2 fragments are equally cytotoxic; monovalent F(ab) fragments, however, have no effect on dye uptake unless cross-linked with goat anti-mouse IgG. The level of toxicity is dependent on both MAb dose and on cell surface receptor density. Cell contact may regulate receptor expression. BR96 receptors are more abundant on cells migrating into the open areas of a scratch wounded confluent culture than on the adjacent contact-inhibited cells. BR96 can also inhibit the anchorage-independent growth of tumor cells in soft agar showing that its effects on propidium iodide staining are not due to transient changes in membrane permeability. Immunogold electron microscopy reveals that, after a 1-minute treatment, BR96 induces significant infolding of the plasma membrane and that internalized MAb is localized to these structures. Immediately thereafter, large cell surface and intracellular vesicles form, mitochondria are swollen, and membrane integrity is lost. Therefore, BR96 seems to cause morphological changes characteristic of necrosis rather than apoptosis. When bound to adherent carcinoma cells, BR96 is distributed uniformly on the apical surface of cells labeled at 4 C and is enriched at points of cell substratum contact. Upon warming of the cells to 37 C, BR96 localizes in small perinuclear clusters and the cell margin is now devoid of label. Immunogold electron microscopy reveals that BR96 undergoes receptor mediated internalization and is localized within the same coated pits, endosomes, and lysosomes as the transferrin receptor. Quantitative studies using iodinated BR96 show that after 6 hours of chase, a maximum of 53% of the radiolabel is located within the intracellular pool. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates that 84% of this fraction is nondegraded. BR96 probably cycles between the medium and intracellular pools because the remainder of the radiolabel is in the medium as intact MAb. By 24 hours of chase, the intracellular fraction drops to 30%, while the remaining 70% is present in the culture medium, mostly as low molecular weight degradation products.     

Enhancement of structure stability and luminescence intensity of LiYF_4:Ln~(3+) nanocrystals

LiYF_4 nanocrystals with tetragonal structure were adopted as the host materials for the phosphors and scintillators owing to the low phonon energy and high optical transparency. LiYF_4:Ln~(3+)(Ce~(3+),Eu~(3+)) nanocrystals were fabricated by solvothermal method. Under UV excitation, they could emit visible light. In order to improve the luminescence intensity, the method of co-doping LiYF_4 nanocrystals with Sc was adopted. Sc~(3+) ions could reduce the lattice expansion caused by the doping of Ce~(3+) or Eu~(3+) whose ionic radius was larger than Y~(3+). Crystal structure of Li(Y,Sc)F_4:Ln~(3+) kept much more stable and the luminescence intensity could be significantly enhanced when the concentration of Sc was a moderate value. Thermoluminescence was employed to analyze the electron traps in Li(Y,Sc)F_4:Ce~(3+). Results suggested that the suppression of the generation of electron traps with the co-doping of Sc contributed to the enhancement of luminescence intensity of LiYF_4:Ce~(3+).     

Long-term supplementation of culture medium with essential fatty acids alters alpha-linolenic acid uptake in Caco-2 clone TC7

We investigated the influence of four different culture media: 20% fetal bovine serum (FBS), 5% FBS, 5% FBS supplemented with 10 mg x L(-1) linoleic acid (18:2(n-6)) or alpha-linolenic acid (18:3(n-3)) on alpha-linolenic acid apical uptake in clone TC7 of human intestinal Caco-2 cell line. Neither cellular viability nor cell monolayer integrity and permeability were altered by the four culture conditions. Our results show that the different culture media led to changes in alpha-linolenic acid maximal rate of uptake (Vmax) but did not alter the apparent transport constant (Km). Reducing FBS concentration from 20% to 5% increased significantly the rate of alpha-linolenic acid uptake, which was further increased by supplementation of the medium with 18:2(n-6) or 18:3(n-3). Supplementation with essential fatty acids led to a marked enrichment of brush-border membrane phospholipids in polyunsaturated fatty acids of the corresponding series and decreased significantly the levels of monounsaturated fatty acids. Saturated fatty acids, unsaturation index, and cholesterol/fatty acid ratios were unchanged. No clear relation could be established between the changes in membrane lipid composition and the alterations of alpha-linolenic acid uptake. These results indicate a weak influence of membrane lipid composition in the modulation of the uptake. Therefore, the increase of uptake following long-term supplementation of TC7 cells with essential fatty acids could be attributed to an increase of the expression of membrane protein(s) involved in the apical uptake of long-chain fatty acids. This remains to be established.     

Tunable luminescence,energy transfer and excellent thermal stability of SrMg_2(PO_4)_2:Ce~(3+),Tb~(3+) phosphors for LEDs

A series of novel SrMg_2(PO_4)_2:Ce~(3+),Tb~(3+)(SMP:Ce~(3+),Tb~(3+)) phosphors with tunable emission spectra were produced via high temperature solid phase method.XRD,fluorescence spectrum and fluorescence lifetime for SMP:Ce~(3+),Tb~(3+)were studied in detail.Under the excitation at 308 nm,SMP:Ce~(3+),Tb~(3+) samples can emit high efficiency tunable blue-green light by controlling the proportion of dopant concentration.Through the spectral overlap and the regular change of fluorescence lifetime,it is proved that there is a significant energy transfer between Ce~(3+) and Tb~(3+) in SMP matrix and the energy transfer mechanism is determined to be an electric dipole-dipole interaction with energy transmission efficiency of 55%.In additional,Commission International de L'Eclairage(CIE) color coordinates and thermal stability were studied.All above findings suggest that SMP:Ce~(3+),Tb~(3+)can be regarded as the potential bluish green phosphor for LED applications.     

Molecular size-dependent leakage of intracellular molecules from frog skeletal muscle fibers permeabilized with beta-escin

The permeability of beta-escin-treated cell membrane was characterized in terms of the permeant molecular size, by monitoring the leak of cytoplasmic molecules in frog skeletal muscle fibers. With a low concentration of beta-escin (5 microM), most of the cellular ATP was lost within 30-40 min (as revealed by rigor force generation), whereas a fluorescence-labeled dextran injected into the cytoplasm (approximately 10 kDa) and cytoplasmic proteins (14-80 kDa) slowly leaked out of the cell. A high concentration of beta-escin (50-100 microM) accelerated the leak of large molecules. Therefore, low concentrations of beta-escin may be used as a means of permeabilizing the cell membrane to relatively small molecules, while retaining a major fraction of the cellular macromolecules.