磁场与辐照联合的生物学效应

利用辐照的放射治疗(放疗)是临床治疗肿瘤的主要方法之一。近年来,随着磁共振成像引导放疗以及多方法联合治疗的逐渐推广,磁场与辐照联合对人体的影响逐渐引起了人们的关注。大量研究表明,磁场会对辐照效应产生一定的影响,但目前并没有统一的结论。本文系统比较并分析了多种参数的磁场与辐照联合所产生的生物学效应,发现其结果不一致性与研究对象、磁场参数(包括磁场强度、方向、处理时间等)和辐照剂量等都有关。虽然目前对相关机制的探索并不多,但已有证据表明,磁场可能通过影响细胞周期和凋亡相关信号转导通路、DNA损伤修复以及线粒体功能等影响辐照效应。这不仅有助于我们深入了解磁场与辐照联合的生物学效应,并且可能为未来磁场与放疗联用在肿瘤治疗中的参数优化设计提供依据。     

极低频磁场对人乳腺癌细胞蛋白质表达谱的影响

极低频磁场(ELF MF)被国际癌症研究中心列为可疑致癌物, 但其诱发肿瘤的具体机制并不清楚. 为此, 采用蛋白质组技术研究人乳腺癌细胞MCF7受ELF MF辐照后蛋白质表达谱的变化, 以探索确定该细胞的极低频磁场反应蛋白质. 在将MCF7细胞暴露于50 Hz, 0.4 mT正弦极低频磁场中24 h后, 直接抽提蛋白, 进行双向凝胶电泳. 凝胶经银染后, 使用PDQuest软件分析假辐照组与磁场辐照组间差异表达蛋白质斑点. 结果显示, 与假辐照组相比, 磁场辐照组中有6个蛋白质斑点的表达量发生显著改变(至少5倍的增加和减少), 同时, 在磁场辐照组中有19个蛋白点消失和19个新蛋白点出现. 通过搜索SWISS-PROT蛋白数据库, 对差异蛋白的类别和功能进行了初步推测. 在此基础上, 进一步选择3个差异表达蛋白斑点, 经胶内酶解后, 进行串联质谱分析, 分别鉴定为RNA结合蛋白调节亚基、 蛋白酶体β亚基7型前体和翻译调控肿瘤蛋白. 结果表明, 50 Hz, 0.4 mT极低频磁场辐照24 h改变了MCF7细胞内多种蛋白的表达水平, 影响环节涉及基因转录、蛋白翻译、蛋白代谢、功能蛋白相互作用等多个层面, 说明极低频磁场可能作为一种环境应激因素改变细胞的正常生理功能.     

弱极低频磁场对Actin骨架组装效率的频率窗口效应初探

前期研究发现,50 Hz弱磁场辐照能明显降低细胞的微丝含量和组装效率,对actin骨架形态也有明显影响.电磁生物学效应是否与辐照场频率相关,一直受到研究者的关注.单体球状肌动蛋白(G-actin)是带电结构,电磁场频率会影响其振荡频率并对微丝聚合效率产生影响.本文从细胞骨架形态和蛋白质两层次,采用免疫荧光技术考察0.4 m T,在35~140 Hz范围内5个频率的极低频磁场(ELF-MF)对FL细胞中纤维状肌动蛋白(F-actin)含量的影响,并采用荧光共振能量转移技术(FRET)验证效应最明显的频率对离体G-actin组装效率的干扰程度.结果显示,相比假辐照组,细胞中F-actin含量在50 Hz辐照组下降了(34.66±3.14)%,110 Hz次之,而另外3组(35、70和140 Hz)无显著性差异.同时利用FRET方法验证,在50 Hz磁场辐照下,离体环境中G-actin组装成F-actin的效率较假辐照组、35和70 Hz组显著降低.经初步分析,G-actin在弱ELF-MF中受到以洛伦兹力和感生电场力的合力为主的相关电磁力干扰,致使组装效率下降,且由于工频磁场周期与微丝组装周期的特殊相干性,在50 Hz频率附近可能存在一个外磁场干扰actin骨架组装的频率窗口.     

激光辐照血液疗法和激光磁化血液疗法

简要回顾光辐照血液疗法的发展和类型以及激光磁化血液疗法的兴起。概述光、激光和磁场对血液的生物效应,初步探讨激光磁化血液疗法可能的作用机制。最后进行了多种光辐照血液疗法的初步对比。     

激光和磁场对滇紫草愈伤组织色素含量的影响

用He-Ne激光和一定强度的磁场处理滇紫草愈伤组织,发现2~3h激光辐照可提高色素含量;而1.0T磁场能促进细胞生长和色素形成。硅胶薄层层析比较两种物理因子对紫草色素成分无显著影响。     

60Co-γ辐照在秀珍菇中的应用研究

采用不同剂量的^60 Co-γ射线辐照秀珍菇进行贮藏保鲜试验,结果表明：常温下210辐照,并采用聚乙烯塑料袋分装,可以延长鲜菇的保鲜期约10天。通过对维生素C和氨基酸含量的测定试验表明：辐处理前后无明显变化。辐照灭菌与常规高温灭菌相比,秀珍菇鲜菇产量高于对照。菌丝在经辐照灭菌的培养料上生长快,污染率下降,而且出菇快。     

弱磁场对骨骼肌肌质网钙调控作用的研究

目的：探讨弱磁场对提取的骨骼肌肌质网系（SR）Ca（2＋）转运、钙泵（Ca（2＋）-Mg（2＋）-ATPase）及钙释放通道（RyR）活性的影响,从分子水平和细胞信号系统的角度来解释生物电磁效应。方法：利用动态光谱法检测0.4 mT弱磁场辐照过的SR Ca（2＋）转运、Ca（2＋）-ATPase活性,还原型辅酶（NADH）的氧化初速率和超氧（O_2-）产率,以及用同位素标记方法检测[3H]-Ryanodine与RyR的平衡结合度。结果：弱磁场辐照引起SR的Ca（2＋）摄取功能和Ca（2＋）-ATPase的活性明显下降,Ca（2＋）释放和[3H]-Ryanodine平衡结合度上升,同时上调了NADH的氧化初速率和O_2-的产率。结论：提示0.4 mT弱磁场辐照30 min对SR Ca（2＋）-ATPase活性有明显抑制,对RyR有一定的激活效果。     

激光和磁场对滇紫草愈伤组织色素含量的影响

用Ｈｅ－Ｎｅ激光和一定强度的磁场处理滇紫草愈伤组织,发现２～３ｈ激光辐照可提高色素含量;而１．０Ｔ磁场能促进细胞生长和色素形成,硅胶薄层层析比较两种物理因子对紫草色素成分无显著影响。     

羊粪-菇渣蚓粪与化肥配施对油麦菜产量及品质的影响

开展蚓粪与化肥配施对蔬菜产量与品质影响的研究,对于合理施肥促进蔬菜清洁生产具有指导意义。本研究采取盆栽试验,调查了以羊粪和菇渣为原料生产的蚓粪与化肥配施对油麦菜产量、硝酸盐含量、氨基酸含量与组成等的影响。结果表明,与单施化肥相比,适量蚓粪配施化肥可在一定程度上提高油麦菜产量,使油麦菜含水量降低1.02%～2.46%,硝酸盐含量降低20.78%～30.30%,显著提高了油麦菜氨基酸总量、必需氨基酸、鲜味氨基酸、甜味氨基酸和药效氨基酸含量。综合来看,等氮量条件下,蚓粪氮占比30%～50%时效果最佳。因此,以适量蚓粪配施化肥提高油麦菜产量,改善油麦菜品质是可行的。     

含硫氨基酸对猪生长性能及肠道功能的影响机制

含硫氨基酸包括甲硫氨酸(又名蛋氨酸)、胱氨酸和半胱氨酸,其中蛋氨酸是动物的含硫必需氨基酸,是猪必不可少的营养元素。研究表明,科学地添加含硫氨基酸对猪的摄食、生长、免疫等方面有着重要的作用。肠道是消化、吸收营养物质最主要的场所,含硫氨基酸的主要代谢产物谷胱甘肽可促进肠道屏障功能的恢复,牛磺酸能参与抗氧化反应、渗透调节等生理过程。因此,添加适量的含硫氨基酸有助于提高猪的生长性能,维持猪的肠道健康。     

三角鲂和长春鳊肌肉营养成分分析与品质评价

用常规方法测定、分析了三角鲂(Megalobrama tarminalis)和长春鳊(Parabramis pekinensis肌肉中营养成分组成与含量.结果显示,三角鲂肌肉蛋白质、脂肪含量分别为18.19％和3.06％,长春鳊肌肉蛋白质、脂肪含量分别为19.38％和2.89％.三角鲂和长春鳊肌肉中均检测出18种氨基酸,其中包括了8种人体必需氨基酸.三角鲂肌肉中氨基酸总量为76.27％,其中,8种人体必需氨基酸含量为32.17％,占氨基酸总量的42.18％;长春鳊肌肉中氨基酸总量为77.60％,其中,8种人体必需氨基酸含量为31.70％,占氨基酸总量的40.85％.必需氨基酸的构成比例基本符合FAO/WHO的标准.三角鲂肌肉中限制性氨基酸主要为甲硫氨酸加胱氨酸,必需氨基酸指数为63.55,4种呈味氨基酸为氨基酸总量的32.81％;长春鳊肌肉中限制性氨基酸主要为色氨酸,必需氨基酸指数为66.81,4种呈味氨基酸为氨基酸总量的33.80％.脂肪酸中二十碳五烯酸(EPA)与二十二碳六烯酸(DHA)含量均较高,三角鲂为7.96％,长春鳊为3.11％.矿物元素比值合理.以上分析表明,三角鲂和长春鳊均为营养价值、经济价值都较高的优质鱼类,相比而言,三角鲂肌肉脂肪、脂肪酸含量和质量更优,而长春鳊肌肉在蛋白质、氨基酸组成与含量方面更优.     

Investigation of the temporal and spatial dynamics of muscular action potentials through optically pumped magnetometers

AimThis study aims to simultaneously record the magnetic and electric components of the propagating muscular action potential.MethodA single-subject study of the monosynaptic stretch reflex of the musculus rectus femoris was performed; the magnetic field generated by the muscular activity was recorded in all three spatial directions by five optically pumped magnetometers. In addition, the electric field was recorded by four invasive fine-wire needle electrodes. The magnetic and electric fields were compared by modelling the muscular anatomy of the rectus femoris muscle and by simulating the corresponding magnetic field vectors.ResultsThe magnetomyography (MMG) signal can reliably be recorded following the stimulation of the monosynaptic stretch reflex. The MMG signal shows several phases of activity inside the muscle, the first of which is the propagating muscular action potential. As predicted by the finite wire model, the magnetic field vectors of the propagating muscular action potential are generated by the current flowing along the muscle fiber. Based on the magnetic field vectors, it was possible to reconstruct the pinnation angle of the muscle fibers. The later magnetic field components are linked to the activation of the contractile apparatus.InterpretationMMG allows to analyze the muscle physiology from the propagating muscular action potential to the initiation of the contractile apparatus. At the same time, this methods reveals information about muscle fiber direction and extend. With the development of high-resolution magnetic cameras, that are based on OPM technology, it will be possible to image the function and structure of the biomagnetic field of any skeletal muscle with high precision. This method could be used both, in clinical medicine and also in sports science.     

The primary structure of chicken muscle acylphosphatase isozyme Ch1

The amino acid sequence of chicken muscle acylphosphatase isozyme Ch1 was determined. The protein consists of 102 amino acid residues, does not contain histidine, and the NH2-terminus is acetylated: Ac-Ser-Ala-Leu-Thr-Lys-Ala-Ser-Gly-Ser- Leu-Lys-Ser-Val-Asp-Tyr-Glu-Val-Phe-Gly-Arg-Val-Gln-Gly-Val-Cys-Phe-Arg- Met- Tyr-Thr-Glu-Glu-Glu-Ala-Arg-Lys-Leu-Gly-Val-Val-Gly-Trp-Val-Lys-Asn- Thr- Ser-Gln-Gly-Thr-Val-Thr-Gly-Gln-Val-Gln-Gly-Pro-Glu-Asp-Lys-Val-Asn-Ala- Met- Lys-Ser-Trp-Leu-Ser-Lys-Val-Gly-Ser-Pro-Ser-Ser-Arg-Ile-Asp-Arg-Thr-Lys- Phe-Ser- Asn-Glu-Lys-Glu-Ile-Ser-Lys-Leu-Asp-Phe-Ser-Gly-Phe-Ser-Thr-Arg-Tyr-OH. This sequence differs in 44% of the total positions from the other isozyme (Ch2) of chicken muscle acylphosphatase (Ohba et al., the accompanying paper). The sequence of Ch1 has three substitutions from that of turkey muscle acylphosphatase; these are Ser from Ala at position 9, Ser from Arg at 47, and Lys from Asn at 83. The sequence has about 80% homology with those mammalian muscle acylphosphatases.     

Reduced amino acid availability inhibits muscle protein synthesis and decreases activity of initiation factor eIF2B

We have examined the effect of a hemodialysis-induced 40% reduction in plasma amino acid concentrations on rates of muscle protein synthesis and breakdown in normal swine. Muscle protein kinetics were measured by tracer methodology using [(2)H(5)]phenylalanine and [1-(13)C]leucine and analysis of femoral arterial and venous samples and tissue biopsies. Net amino acid release by muscle was accelerated during dialysis. Phenylalanine utilization for muscle protein synthesis was reduced from the basal value of 45 +/- 8 to 25 +/- 6 nmol x min(-1) x 100 ml leg(-1) between 30 and 60 min after start of dialysis and was stimulated when amino acids were replaced while dialysis continued. Muscle protein breakdown was unchanged. The signal for changes in synthesis appeared to be changes in plasma amino acid concentrations, as intramuscular concentrations remained constant throughout. The changes in muscle protein synthesis were accompanied by a reduction or stimulation, respectively, in the guanine nucleotide exchange activity of eukaryotic initiation factor (eIF)2B following hypoaminoacidemia vs. amino acid replacement. We conclude that a reduction in plasma amino acid concentrations below the normal basal value signals an inhibition of muscle protein synthesis and that corresponding changes in eIF2B activity suggest a possible role in mediating the response.     

Alanine and glutamine synthesis and release from skeletal muscle. I. Glycolysis and amino acid release.

The synthesis and release of alanine and glutamine were investigated with an intact rat epitrochlaris muscle preparation. This preparation will maintain on incubation for up to 6 hours, tissue levels of phosphocreatine, ATP, ADP, lactate, and pyruvate closely approximating those values observed in gastrocnemius muscles freeze-clamped in vivo. The epitrochlaris preparation releases amino acids in the same relative proportions and amounts as a perfused rat hindquarter preparation and human skeletal muscle. Since amino acids were released during incubation without observable changes in tissue amino acids levels, rates of alanine and glutamine release closely approximate net amino acid synthesis. Large increases in either glucose uptake or glycolysis in muscle were not accompanied by changes in either alanine or glutamine synthesis. Insulin increased muscle glucose uptake 4-fold, but was without effect on alanine and glutamine release. Inhibition of glycolysis by iodacetate did not decrease the rate of alanine synthesis. The rates of alanine and glutamine synthesis and release from muscle decreased significantly during prolonged incubation despite a constant rate of glucose uptake and pyruvate production. Alanine synthesis and release were decreased by aminooxyacetic acid, an inhibitor of alanine aminotransferase. This inhibition was accompanied by a compensatory increase in the release of other amino acids, such as aspartate, an amino acid which was not otherwise released in appreciable quantities by muscle. The release of alanine, pyruvate, glutamate, and glutamine were observed to be interrelated events, reflecting a probable near-equilibrium state of alanine aminotransferase in skeletal muscle. It is concluded that glucose metabolism and amino acid release are functionally independent processes in skeletal muscle. Alanine release reflects the de novo synthesis of the amino acid and does not arise from the selective proteolysis of an alanine-rich storage protein. It appears that the rate of alanine and glutamine synthesis in skeletal muscle is dependent upon the transformation and metabolism of amino acid precursors.     

Effect of insulin on human skeletal muscle protein synthesis is modulated by insulin-induced changes in muscle blood flow and amino acid availability

Insulin promotes muscle anabolism, but it is still unclear whether it stimulates muscle protein synthesis in humans. We hypothesized that insulin can increase muscle protein synthesis only if it increases muscle amino acid availability. We measured muscle protein and amino acid metabolism using stable-isotope methodologies in 19 young healthy subjects at baseline and during insulin infusion in one leg at low (LD, 0.05), intermediate (ID, 0.15), or high (HD, 0.30 mUxmin(-1)x100 ml(-1)) doses. Insulin was infused locally to induce muscle hyperinsulinemia within the physiological range while minimizing the systemic effects. Protein and amino acid kinetics across the leg were assessed using stable isotopes and muscle biopsies. The LD did not affect phenylalanine delivery to the muscle (-9 +/- 18% change over baseline), muscle protein synthesis (16 +/- 26%), breakdown, or net balance. The ID increased (P < 0.05) phenylalanine delivery (+63 +/- 38%), muscle protein synthesis (+157 +/- 54%), and net protein balance, with no change in breakdown. The HD did not change phenylalanine delivery (+12 +/- 11%) or muscle protein synthesis (+9 +/- 19%), and reduced muscle protein breakdown (-17 +/- 15%), thus improving net muscle protein balance but to a lesser degree than the ID. Changes in muscle protein synthesis were strongly associated with changes in muscle blood flow and phenylalanine delivery and availability. In conclusion, physiological hyperinsulinemia promotes muscle protein synthesis as long as it concomitantly increases muscle blood flow, amino acid delivery and availability.     

Amino acid repletion does not decrease muscle protein catabolism during hemodialysis

Intradialytic protein catabolism is attributed to loss of amino acids in the dialysate. We investigated the effect of amino acid infusion during hemodialysis (HD) on muscle protein turnover and amino acid transport kinetics by using stable isotopes of phenylalanine, leucine, and lysine in eight patients with end-stage renal disease (ESRD). Subjects were studied at baseline (pre-HD), 2 h of HD without amino acid infusion (HD-O), and 2 h of HD with amino acid infusion (HD+AA). Amino acid depletion during HD-O augmented the outward transport of amino acids from muscle into the vein. Increased delivery of amino acids to the leg during HD+AA facilitated the transport of amino acids from the artery into the intracellular compartment. Increase in muscle protein breakdown was more than the increase in synthesis during HD-O (46.7 vs. 22.3%, P < 0.001). Net balance (nmol.min(-1).100 ml (-1)) was more negative during HD-O compared with pre-HD (-33.7 +/- 1.5 vs. -6.0 +/- 2.3, P < 0.001). Despite an abundant supply of amino acids, the net balance (-16.9 +/- 1.8) did not switch from net release to net uptake. HD+AA induced a proportional increase in muscle protein synthesis and catabolism. Branched chain amino acid catabolism increased significantly from baseline during HD-O and did not decrease during HD+AA. Protein synthesis efficiency, the fraction of amino acid in the intracellular pool that is utilized for muscle protein synthesis decreased from 42.1% pre-HD to 33.7 and 32.6% during HD-O and HD+AA, respectively (P < 0.01). Thus amino acid repletion during HD increased muscle protein synthesis but did not decrease muscle protein breakdown.     

Tissue amino acid pool changes during the perinatal period of the rat

Total free amino acid content in foetal liver, kidney, skin and striated muscle increases sharply during pregnancy. After delivery, there is no significant change in tissue total amino acid pools. The essential free amino acid pool in striated muscle decreases after delivery. This decrease suggests a relationship with the increased protein content in striated muscle.     

Nonessential amino acids are not necessary to stimulate net muscle protein synthesis in healthy volunteers

The present study was performed to test the hypothesis that orally administered essential amino acids, in combination with carbohydrate, will stimulate net muscle protein synthesis in resting human muscle in vivo. Four volunteers ingested 500 mL of a solution containing 13.4 g of essential amino acids and 35 g sucrose (EAA). Blood samples were taken from femoral arterial and venous catheters over a 2-hour period following the ingestion of EAA to measure arteriovenous concentrations of amino acids across the muscle. Two muscle biopsies were taken during the study, one before administration of the drink and one approximately 2 hours after consumption of EAA. Serum insulin increased from normal physiologic levels at baseline (9.2 +/- 0.8 microU/mL) and peaked (48 +/- 7.1 microU/mL) 30 minutes after EAA ingestion. Arterial essential amino acid concentrations increased approximately 100 to 400% above basal levels between 10 and 30 minutes following drink ingestion. Net nitrogen (N) balance changed from negative (-495 +/- 128 nmol/mL) prior to consumption of EAA to a peak positive value (416 +/- 140 nmol/mL) within 10 minutes of ingestion of the drink. EAA resulted in an estimated positive net N uptake of 307.3 mg N above basal levels over the 2-hour period. Muscle amino acid concentrations were similar prior to and 2 hours following ingestion of EAA. We conclude that ingestion of a solution composed of carbohydrates to stimulate insulin release and a small amount of essential amino acids to increase amino acid availability for protein synthesis is an effective stimulator of muscle protein anabolism.