Enhanced production of cytidine 5'-monophosphate using biocatalysis of di-enzymes immobilized on amino-functionalized sepharose

Cytidine 5'-monophosphate(5'-CMP)is an essential nucleotide for additives.In this study,enhanced production of 5'-CMP was realized by the transformation of cytidine using co-immobilized di-enzymes,uridine-cytidine kinase(UCK)and acetate kinase(AcK).The immobilization yield of the enzyme had a clear correlation with the surface charges as zeta potential(ξ).Among them,ε-polylysinefunctionalized sepharose(SA-EPL,ξ=9.31 m V)showed high immobilization yield(78.8%),which was4.9-fold than that of nitrilotriacetic acid functionalized sepharose(SA-NTA,ξ=-12.6 m V).The residual activity of affinity co-immobilized enzyme(EPL-Ni/EPL@Ac K-UCK)was higher than 70.6%after recycled 10 times.Thus,this study provides an effective approach for the production of 5'-CMP with the advantages of low adenosine 5'-triphosphate(ATP)consumption,reduced side reactions,and improved reusability by co-immobilized UCK and Ac K on the functionalized Sepharose.

双核Pt(Ⅳ)配合物与Guanosine-5′-Monophosphate和Glutathione反应的核磁共振光谱研究(英文)

合成了一个新型的双核Pt(Ⅳ)配合物｛[cis-Pt(NH3)2Cl(OH)2]2(4,4′-methylenedianiline)｝(NO3)2(化合物1)及相应的15N标记化合物｛[cis-Pt(15NH3)2Cl(OH)2]2(4,4′-methylenedianiline)｝(NO3)2(化合物15N-1)。利用1HNMR和ESMS进行了结构表征,化合物15N-1的2D[1H,15N]HSQCNMR发现,该化合物在水溶液中存在同分异构体。2D[1H,15N]HSQCNMR技术跟踪了化合物15N-1与Guanosine-5′-Monophosphate(5′-GMP)和Glutathione(GSH)的反应。结果显示,5′-GMP能在0.5h内将化合物1还原,而GSH在6h以后才能够部分的将化合物1还原。化合物1所表现出来的反应性能将有利于提高其治疗效果和降低毒副作用。

A unique insertion of low complexity amino acid sequence underlies protein-protein interaction in human malaria parasite orotate phosphoribosyltransferase and orotidine 5'-monophosphate decarboxylase

Objective:To investigate the multienzyine complex formation of human malaria parasite Plasmodium falciparum[P.falciparum)orotate phosphoribosyltransferase(OPRT)and orotidine5'-monophosphate decarboxylase(OMPDC),the fifth and sixth enzyme of the de novo pyrimidine biosynthetic palhway.Previously,we have clearly established that the two enzymes in the malaria parasite exist physically as a heterotetrameric(OPRT)_2(OMPDG)_2 complex containing two subunits each of OPRT and OMPDC.and that the complex have catalytic kinetic advantages over the monofunetional enzyme.Methods:Both enzymes were cloned and expressed as recombinant proteins.The protein-protein interaction in the enzyme complex was identified using bifunctionul chemical cross-linker,liquid chromatography-mass spectrometric analysis and homology modeling,Results:The unique insertions of low complexity region at the a 2 and a 5 helices of the parasite OMPDC,characterized by single amino acid repeat sequence which was not found in homologous proteins from other organisms,was located on the OPRT-OMPDC interface.The structural models for the protein-prolein interaction of the helerotetrameric(OPRT)_2(OMPDC)_2multienzyme complex were proposed.Conclusions:Based on the proteomic data and structural modeling,it is surmised that the human malaria parasite low complexity region is responsible for the OPRT-OMPDC interaction.The structural complex of the parasite enzymes,thus,represents an efficient functional kinetic advantage,which in line with co-localization principles of evolutional origin,and allosteric control in protein-protein-interactions.

Transformation of microstructure and phase of disodium guanosine 5′-monophosphate: Thermodynamic perspectives

Microstructure and phase transformation of disodium guanosine 5′-monophosphate(5′-GMPNa_2) are extremely important for controlling the process and understanding the mechanism of crystallization. In this work, the thermodynamic properties of polymorphous 5′-GMPNa_2 especially the solubility were studied, the solubility results show that 5′-GMPNa_2 is more soluble in ethanol–water(E–W) than in isopropanol–water(I–W). The amorphous form of 5′-GMPNa_2 is more soluble than the crystalline form at the same mole fraction and temperature. Meanwhile, the crystalline forms and morphologies of the residual solids were characterized by PXRD and SEM. The results indicate that solid forms of 5′-GMPNa_2 transformed spontaneously from amorphous to crystalline when the ethanol proportion is ≥20%. In addition, increasing the pH facilitates the dissolution of 5′-GMPNa_2 and helps to maintain the crystalline form. The associated Gibbs free energy values were calculated to verify the trend of transformation from amorphous to crystalline 5′-GMPNa_2. These results should help to guide the industrial crystallization process and to obtain the crystalline form of 5′-GMPNa_2.

Efficacy of Cytidine-5'-diphosp-bocholine Combined with Compound Anisodine in the Treatment of Early Optic Nerve Contusion

Purpose:To investigate the efficacy of anisodine combined with cytidine-5'-diphosp-bocholine (citicoline) in the treatment of early optic nerve contusion.Methods:A total of 33 subjects eligible for inclusion were selected from 105 patients clinically diagnosed with optic nerve contusion.These patients were subsequently divided into the control group (n =16) and the intervention group (n =17).In the control group,the participants received therapy consisting of glucocorticoids,mannitol,vasodilators and vitamin B.The patients in the intervention group additionally received anisodine in combination with citicoline.The visual acuity was graded on a scale from 0 to 8.Results:Prior to treatment,.the 25th,50th and 75th percentiles of visual acuity grade were 3,4 and 6.75 for the controls,and 3,4 and 6.5 for the patients in the intervention group (P=0.97).After treatment,the 25th,50th and 75th percentiles of visual acuity grade were 4,6 and 7.75 in the control group,and 7,7 and 8 in the intervention group (P=0.046).A significant difference was observed in both control (P=0.005) and intervention groups(P=0.001) when comparing presenting visual acuity before and after treatment.Conclusion:The combination of anisodine and citicoline with standard steroid and mannitol therapy appears to be effective in the treatment of early optic nerve contusion.

甲基化抑制剂5-氮杂胞苷对HL-60细胞增殖及凋亡的影响

目的:观察5-氮杂胞苷对髓系白血病细胞系HL-60的增殖抑制作用,探讨其对细胞周期、细胞凋亡的影响。方法:常规方法培养HL-60细胞,加入不同浓度的5-氮杂胞苷,以MTT法测定对HL-60的抑制作用,计算细胞生长抑制率;流式细胞术检测小剂量5-氮杂胞苷处理HL-60细胞后48h的细胞凋亡率及细胞周期分布特点。结果:不同浓度5-氮杂胞苷均可以不同程度的抑制细胞生长,且表现为时间、浓度依赖性。在小剂量浓度5-氮杂胞苷处理HL-60细胞48h后,随着5-氮杂胞苷浓度的增加,凋亡细胞百分比逐渐增多(P<0.05);G1期细胞逐渐增多,S期细胞减少,G2/M期细胞相对增多,细胞阻滞在G1期。结论:5-氮杂胞苷对髓系白细胞细胞系HL-60的生长抑制表现为浓度和时间依赖性,一定剂量的5-氮杂胞苷诱导细胞凋亡,使细胞阻滞在G1期。

胃癌细胞三磷酸腺苷酶、5′—核苷酸酶和胞嘧啶单核苷酸酶活性定位的电镜细胞化学研究

应用电镜酶细胞化学方法对12例胃癌细胞三磷酸腺苷酶(Mg^(2+)—ATPase,Ca^(2+)—ATPase),5~1—核苷酸酶(5NPase)及胞嘧啶单核苷酸酶(CMPase)进行了超微结构水平的定位观察。结果表明:胃管状腺癌细胞腔缘微绒毛丰富,Mg^(2+)—ATPase、Ca^(2+)—ATPase及5NPase定位于微绒毛表面,反应明显,提示其功能代谢具有极性分布特点。粘液腺癌细胞出、入胞现象活跃,Mg^(2+)—ATPase、Ca^(2+)—ATPase及CMPase反应明显,认为与其粘液的大量分泌,营养物质的摄取与加工以及逃避免疫细胞的杀伤机制有关。低分化腺癌上述酶大都无反应或反应微弱。作者认为胃癌细胞的酶活性及其分布与其分化程度及功能状况有关。

左旋多巴及胞二磷胆碱对单眼形觉剥夺大鼠视皮质α-氨基-3-羟基-5-甲基-4-异噁唑丙酸-GluR2表达的影响、

背景研究表明α-氨基-3-羟基-5-甲基±异嗯唑丙酸（AMPA）．GluR2与弱视的发生发展有关，左旋多巴及胞二磷胆碱对改善弱视患者的视功能有一定的疗效，但其作用机制尚不完全明了。目的检测敏感期单眼形觉剥夺（MD）大鼠分别应用左旋多巴及胞二磷胆碱后视皮质中AMPA—GluR2的表达情况，探讨左旋多巴及胞二磷胆碱改善视功能的作用机制。方法2周龄健康SD大鼠60只行单侧眼睑缝合31d制作MD动物模型，造模成功后与年龄匹配的正常大鼠15只在自然光条件下一起饲养。将大鼠用随机数字表法随机分为正常对照组、MD组、左旋多巴组、胞二磷胆碱组和生理盐水组，每组15只大鼠。造模后第32天左旋多巴组大鼠给予溶于1ml生理盐水中的左旋多巴40mg／kg灌胃，每日1次；胞二磷胆碱组大鼠给予胞二磷胆碱80mg／kg肌内注射，每日1次；生理盐水组给予1ml生理盐水灌胃，均连续给药28d。分别采用免疫组织化学法、Westernblot法、实时荧光定量PCR法检测各组大鼠视皮质中AMPA—GluR2的表达情况。结果MD组大鼠视皮质中AMPA—GluR2蛋白及mRNA表达均低于正常对照组，差异有统计学意义（0．32±O．02VS．0．64±0．05，t=13．287，P〈0．05；0．30±0．01VS．0．8±t-O．03，t=38．184，P〈0．05）；左旋多巴组视皮质中AMPA—GluR2蛋白及mRNA表达均高于生理盐水组（0．59±0．04VS．0．33±0．03，t=11．628，P〈0．05；0．71±0．06VS．0．33±0．02，t=13．435，P〈0．05）；胞二磷胆碱组大鼠视皮质中AMPA—GluR2蛋白及mRNA表达均高于生理盐水组，差异有统计学意义（0．52±0．04VS．0．33±0．03，t=8．497，P〈0．05；0．48±0．04VS．0．33±0．02，t=7．500，P〈0．05）。结论AMPA-GluR2与视觉发育的可塑性有关，左旋多巴、胞二磷胆碱能够在一定程度上逆转MD引起的AMPA．GluR2表达下降。这一机制可能与其能够改善视功能的作用有关，其作用部位可能在视皮质。

抗恶性肿瘤新药N^4-戊氧碳酰-5’-脱氧-5-氟胞嘧啶的合成

以去氧氟尿苷、盐酸羟胺、氯甲酸正戊酯等为原料合成N4-戊氧碳酰-5’-脱氧-5-氟胞嘧啶,反应经加成、氢化、缩合、酰胺化等步骤得目标产物。产物经元素分析、IR、1H-NMR、13C-NMR、EI-MS确证。五步合成目标产物N4-戊氧碳酰-5’-脱氧-5-氟胞嘧啶总产率20.05%(以去氧氟尿苷计)。

操作条件对5′-单磷酸胞苷晶体粒度分布的影响

为了研究操作条件对5。单磷酸胞苷（5′-CMP）晶体粒度分布的影响，分别采用不同形式的搅拌桨、搅拌速率以及反应液流加速率，并且运用激光粒度仪和扫描电镜对晶体粒度分布及形貌进行分析观测。结果显示：采用不同形式的搅拌桨形成的剪切力、颗粒聚集以及二次成核现象的差异导致了晶体粒度分布峰值数量不同；分别选取50、100和150r／min的搅拌速率以及1、3和6mL／h的流加速率时，晶体平均粒径在铆式搅拌桨作用下，在120．3—212．1μm范围内递减，而在45°斜角四折叶式搅拌桨作用下递减范围为3．17～150．2μm，且粒度分布更为均匀，为工业生产中的优化控制提供了一定的理论依据。

索拉非尼联合5-氮杂-2'-脱氧胞苷对肝癌SMMC-7721细胞DNMT3B基因表达的影响

目的:探讨索拉非尼联合5-氮杂-2'-脱氧胞苷(5-Aza-CdR)对人肝癌细胞SMMC-7721的作用及其调控DNMT3B基因表达可能的分子机制。方法:单独及联合给药后以MTT法测定SMMC-7721的增殖,Transwell检测其侵袭,流式细胞仪检测细胞凋亡,Western blot法观察DNMT3B、p-Akt-Ser473及ERK蛋白的表达。结果:索拉非尼、5-Aza-CdR对肝癌SMMC-7721细胞半数抑制浓度(IC50)分别为11、6μmol/L,联合用药选取(6+4)μmol/L作为后续用药浓度。与对照组比较单药及联合用药均能抑制细胞侵袭、促进细胞凋亡、减少p-Akt-Ser473和DNMT3B蛋白的表达(P<0.05~P<0.01)。结论:索拉非尼和5-AzaCdR联合用药能有效降低索拉非尼用药浓度,降低肝癌SMMC-7721细胞DNMT3B蛋白表达水平。

5-取代胞苷的合成与性质研究

本研究以3-丁炔-1-醇和苄溴为原料,合成3-炔-丁基苯甲醚,通过Sonogashira反应与5-碘胞苷合成得到(4-苄氧基)丁炔基-5-胞苷,其结构经核磁共振(1 H NMR和13 C NMR)以及质谱(MS)确证。最后通过研究极性、pH值以及粘度对其光谱性质的影响,考察其是否具有成为极性、pH值以及粘度荧光探针的潜在价值。结果表明,在不同溶剂中(4-苄氧基)丁炔基-5-胞苷均有很强发射性。随着极性增加,荧光强度出现减小趋势;荧光强度随着粘度的变化而呈上升趋势;并且插入寡聚核酸中能够保持荧光性,不对周围环境产生影响。说明其该化合物在一定程度上有成为荧光探针的价值。

(2'R)-N-苯甲酰基-2'-脱氧-2'-氟-2'-甲基胞苷3',5'-二苯甲酸酯的合成工艺改进

本文对(2’R)-N-苯甲酰基-2’-脱氧-2’-氟-2’-甲基胞苷3’,5’-二苯甲酸酯的合成路线进行了改进,以(2R)-2-脱氧-2-氟-2-甲基-D-赤式戊糖酸gamma-内酯3,5-二苯甲酸酯为起始原料,经过红铝还原,氯化,胞嘧啶活化,偶合,脱保护等反应步骤合成索非布韦重要中间体(2’R)-N-苯甲酰基-2’-脱氧-2’-氟-2’-甲基胞苷3’,5’-二苯甲酸酯,同时,为了适应大生产的环保要求,增加工艺三废中的胞嘧啶和氢氧化锡的回收改进。

Dan-gua Fang (丹瓜方) Improves Glycolipid Metabolic Disorders by Promoting Hepatic Adenosine 5'-monophosphate Activated Protein Kinase Expression in Diabetic Goto-kakizaki Rats

Objective：To investigate the effect of Dan-gua Fang（丹瓜方） on adenosine 5’-monophosphate（AMP） activated protein kinase（AMPK） α expression in liver and subsequent improvement of glucose and lipid metabolism.Methods：Forty 13-week-old diabetic Goto-Kakizaki（GK） rats were randomly divided into model,Dan-gua Fang,metformin and simvastatin groups（n=10 for each）,and fed high-fat diet ad libitum.Ten Wistar rats were used as normal group and fed normal diet.After 24 weeks,liver expression of AMPK α mRNA was assessed by real-time PCR.AMPK α and phospho-AMPK α protein expression in liver was evaluated by Western blot.Liver histomorphology was carried out after hematoxylin-eosin staining,and blood glucose（BG）,glycosylated hemoglobin A1c（HbA1c）,food intake and body weight recorded.Results：Similar AMPK α mRNA levels were found in the Dan-gua Fang group and normal group,slightly higher than the values obtained for the remaining groups（P〈0.05）.AMPK α protein expression in the Dan-gua Fang group animals was similar to other diabetic rats,whereas phospho-AMPK α（Thr-172） protein levels were markedly higher than in the metformin group and simvastatin group（P〈0.05）,respectively.However,phosphor-AMPKa/AMPK α ratios were similar in all groups.Dan-gua Fang reduced fasting blood glucose with similar strength to metformin,and was superior in reducing cholesterol,triglycerides,high-density lipoprotein cholesterol as well as improving low-density lipoprotein cholesterol in comparison with simvastatin and metformin.Dan-gua Fang decreases plasma alanine aminotransferase（ALT） significantly.Conclusion：Dan-gua Fang,while treating phlegm-stasis,could decrease BG and lipid in type 2 diabetic GK rats fed with high-fat diet,and effectively protect liver histomorphology and function.This may be partly explained by increased AMPK expression in liver.Therefore,Dan-gua Fang might be an ideal drug for comprehensive Intervention for glucose and lipid metabolism disorders in type 2 diabetes mellitus.

血管紧张素Ⅱ对成人脂肪间充质干细胞向心肌细胞分化的影响

目的:观察血管紧张素Ⅱ(AngⅡ)对成人脂肪间充质干细胞(ADMSCs)向心肌细胞方向分化的诱导作用,并与5-氮杂胞苷(5-aza)作比较.方法:自成人脂肪组织中分离培养ADMSCs,分别用AngⅡ(Ⅰ组)和5-aza(Ⅱ组)诱导ADM-SCs,同时设立对照组(Ⅲ组),光镜下观察细胞的生长情况及形态学变化,电镜下观察细胞的超微结构,免疫细胞化学方法检测心肌特异性肌钙蛋白-Ⅰ(cTn-Ⅰ),MTT法检测细胞活性,流式细胞术分析细胞周期及凋亡.结果:Ⅰ,Ⅱ组ADM-SCs诱导后呈现类似心肌细胞的形态学特征,第28日Ⅰ,Ⅱ组均表达cTn-Ⅰ,两组间诱导转化率无差别,其中Ⅰ组ADM-SCs增殖迅速,较少凋亡细胞.结论:AngⅡ在促进ADMSCs增殖的同时诱导其向心肌细胞分化,优于传统的化学诱导剂5-aza.

刺槐同源四倍体种子促萌措施研究

为了最大限度地保存刺槐同源四倍体有性繁殖过程中产生的变异材料资源,对其高度变异和难以萌发的种子进行了促萌试验。结果表明：①种子经温汤浸种可以明显地提高萌发率,90℃温水浸泡24 h,种子平均萌发率为5%、最高5.5%;②用PEG-6000处理刺槐同源四倍体种子时,平均萌发率1.11%、最高3.33%,表现为抑制作用;③5-氮杂胞苷浸种时,药液浓度对萌发率有显著的影响,用250μmol/L的5-氮杂胞苷水溶液处理种子24-48 h为较好处理方案,平均萌发率为5.6%;④种子培养促萌时,用10%H2O2浸泡24 h后转入赤霉素水溶液（3 mg/L）浸泡6h,之后再转入萘乙酸水溶液（15 mg/L）浸泡6 h,接种到MS或1/2MS培养基上促萌效果较好,平均萌发率为5.5%、最高6.0%;⑤将表型正常的种子胚接种到没有附加物的MS培养基上,有部分种子胚萌动后子叶变绿且张开。

利用重组嗜热栖热菌尿苷-胞苷激酶生产尿苷酸

尿苷-胞苷激酶(Uridine/cytidine kinase,UCK)作为生物体核苷酸代谢补偿途径中的重要催化剂,可以催化尿苷和胞苷磷酸化成为尿苷酸(5'-uridine monophosphate,5'-UMP)和胞苷酸(5'-cytidine monophosphate,5'-CMP)。利用大肠杆菌Escherichia coli BL21(DE3)分别成功克隆表达了来源于嗜热栖热菌(Thermus thermophilus HB8)以及枯草芽孢杆菌(Bacillus subtilis 168)的尿苷-胞苷激酶。对比分析了不同重组尿苷-胞苷激酶的催化特性发现,来源于嗜热栖热菌的尿苷-胞苷激酶能以鸟苷三磷酸(Guanosine 5'-triphosphate,GTP)或者腺苷三磷酸(Adenosine 5'-triphosphate,ATP)作为磷酸供体催化尿苷生成尿苷酸,而来源于枯草芽孢杆菌的尿苷-胞苷激酶只有以GTP作为磷酸供体时的催化效果较好。在优化的反应条件下,使用来源于嗜热栖热菌的尿苷-胞苷激酶,6 h可催化10 mmol/L的尿苷和10 mmol/L的ATP生成8.74 mmol/L尿苷酸。研究结果表明,以ATP作为磷酸供体的尿苷-胞苷激酶可作为一种新型的催化剂用于尿苷酸的研制与生产。

胞二磷胆碱治疗中、重度弱视的临床观察

目的 :观察胞二磷胆碱治疗中、重度弱视后视力等指标的变化 ,评估其疗效和可行性。方法 :将 81例弱视患者 ,随机分成药物组 ,肌肉注射胞二磷胆碱 ;联合组 ,药物联合遮盖治疗 ;遮盖组 ,遮盖治疗加精细作业。严密观察各种可能的副作用。对视力等结果进行统计学分析处理。结果 :药物组视力提高出现最早 ,但 4月后呈下降趋势。联合组对各种弱视有效 ,视力能持续性提高。药物组和联合组视网膜光阈值有改善。治疗后三组视觉诱发电位P10 0 波潜伏期均无改善。一例患者注射胞二磷胆碱后诱发癫痫。结论 :胞二磷胆碱能提高弱视眼的视力 ,改善视网膜光阈值。胞二磷胆碱与遮盖治疗联合应用疗效较好。胞二磷胆碱可诱发癫痫发作。

DNA甲基化转移酶抑制剂和组蛋白脱乙酰化酶抑制剂的体外抗肿瘤作用

目的:通过在体外分别对DNA甲基化转移酶(DNA methyltransferase,DNMT)抑制剂5-氮杂胞苷(5-azacytidine,5-aza-C)和组蛋白脱乙酰化酶(histone seacetylase,HDAC)抑制剂苯丁酸钠(sodium phenylbu-tyrate,SPB)单独及联合用药于人大肠癌细胞LoVo和人肝癌细胞Hep3B的抗肿瘤作用的观察,探讨DNMT抑制剂和HDAC抑制剂联合用药的可能性。方法:使用MTT法测定5-aza-C和SPB单独用药或联合用药的抗癌活性,用抑制浓度的分数之和(a sum of fractional inhibitory concentration,SFIC)值及等效剂量分析方法(Isobologram)评价5-aza-C和SPB联合用药的作用性质。结果:5-aza-C和SPB联用时,LoVo细胞及Hep3B细胞得到的SFIC值均小于1.0,等效剂量分析图的形状呈现凹型,都表明了5-aza-C和SPB联用时两者之间具有明显的增效作用。结论:DNMT抑制剂5aza-C和HDAC抑制剂SPB联合应用于抗肿瘤临床是很有前景的。

己酮可可碱对嘧啶拮抗物细胞毒性的影响

目的:观察己酮可可碱(pentoxifylline,PTX)在体外对嘧啶拮抗物(E)-(2')-脱氧-氟亚甲基胞苷犤(E)-2'-deoxy-2'-(fluoromethylene)cytidine,FMdC犦和5-氟尿嘧啶(5-fluorouracil,5-FU)细胞毒性的影响。方法:用MTT法检测PTX和FMdC或5-FU对人结肠癌细胞系WiDr的细胞毒性。用流式细胞仪检测FMdC和PTX的细胞周期效应。结果:0.25-2.0mmol/LPTX增加FMdC和5-FU的细胞毒性。2mmol/LPTX能使FMdC的半数抑制浓度(IC50)从80nmol/L降到24nmol/L;对5-FU的IC50从10μmol/L降到1.1μmol/L。Isoborogram分析表明,PTX和FMdC或5-FU的细胞毒性作用为相乘作用。在WiDr细胞,20-40nmol/LFMdC引起S期阻滞,并与浓度相关。20nmol/LFMdC时,S期阻滞仅在48h能观察到;30nmol/L和40nmol/LFMdC时,12h开始出现S期阻滞,24h达高峰,48h仍可见明显阻滞。0.5-2.0mmol/LPTX和30nmol/LFMdC共同处理细胞24h,PTX能去除FMdC引起的S期阻滞。0.5mmol/L和1.0mmol/LPTX将S期比例从64.6%分别减少到54.4%和39.3%。结论:PTX能增强体外FMdC和5-FU的细胞毒性,通过PTX去除S期阻滞,为提高嘧啶拮抗物的细胞毒性提供了一种有效途径。