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。     

稳恒磁场抑制肿瘤增殖的实验研究与理论探讨

作为模型处理最简单的稳恒磁场,其与肿瘤作用的研究是最具理论和实际意义的。分别介绍了稳恒磁场作用于微循环系统、免疫系统对肿瘤的间接抑制和杀伤作用,磁场影响自由基代谢和细胞膜及细胞内结构对肿瘤的抑制作用;回顾了磁场干扰细胞周期、诱导细胞凋亡对肿瘤的影响,并介绍了稳恒磁场联合抗癌药物在治癌中的应用现状;最后结合实验的进展情况,分析探讨了稳恒磁场抑制肿瘤细胞增殖的物理机理,对肿瘤磁疗的发展前景进行了展望。     

基于磁性纳米材料的肿瘤靶向治疗研究进展

磁性纳米材料具有独特的磁学性质，可响应外磁场，产生力、热等效应。如在静磁场下将药物磁靶向递送至肿瘤部位；低频交变磁场下可将纳米药物主动渗透至病灶部位，实现瘤内均一分布；中频交变磁场作用下磁滞损耗产生热和增强的活性氧，用于肿瘤治疗。磁性纳米材料同时具有尺寸依赖的磁学性质以及表面多功能化等特点，可将磁靶向、分子靶向以及磁热疗联合。此外，磁性纳米材料具有磁共振成像性能以及纳米酶催化特性，使其在肿瘤诊疗一体化治疗方面获得了广泛应用。近年来，纳米给药系统不断被优化，基于磁性纳米材料的肿瘤靶向治疗也得到了长足的发展。鉴于此，本文围绕提高靶向肿瘤治疗效果，从磁靶向药物治疗、被动靶向磁热疗和主动分子靶向磁热疗、纳米酶特性以及诊疗一体化应用等几方面出发，综述了基于磁性纳米材料的肿瘤靶向治疗研究进展。     

稳恒磁场抑制肿瘤增殖的实验研究与理论探讨

作为模型处理最简单的稳恒磁场,其与肿瘤作用的研究是最具理论和实际意义的.分别介绍了稳恒磁场作用于微循环系统、免疫系统对肿瘤的间接抑制和杀伤作用,磁场影响自由基代谢和细胞膜及细胞内结构对肿瘤的抑制作用;回顾了磁场干扰细胞周期、诱导细胞凋亡对肿瘤的影响,并介绍了稳恒磁场联合抗癌药物在治癌中的应用现状;最后结合实验的进展情况,分析探讨了稳恒磁场抑制肿瘤细胞增殖的物理机理,对肿瘤磁疗的发展前景进行了展望.     

磁场治病机理的几点体会

现代某些疾病如肩痛和腰背痛等症状,用磁场治疗能发挥一定的疗效。利用磁场镇痛效应,既无副作用,又无吃药打针之苦,简便又易于掌握,这些治疗均为病人有口皆碑,也为临床医生所称赞。曾在全国第一次磁疗保健用品展览会上,北京301医院常汉英介绍了该院从1974年开始8年经过5000多例临床应用证明,磁疗对于多种常见病确有良好的作用。笔者亦在临床治疗各类慢性病5000多例。磁场究竟怎样能够治疗疾病呢?结合中外学者以及笔者的一些实际工作给予简略的综述,以求同道来探讨。日本中川恭一医学博士关于磁力与健康的机理研究进行了30多年。并调查了磁力…     

超工频交变衰减磁场镇痛消炎效果的实验与临床研究

超工频交变衰减磁场（UWFAWM产生的效应为退磁效应,这种新型磁场曾名为退磁效应、调磁效应等。以往多用于钢铁、石油、煤炭等工业,UWFAWM是否能用于人体在国内外除我院外尚未见报道犤１犦。UWFAWM与医用的静磁场、脉冲磁场、脉动磁场和交变磁场不同。我们从１９８９年开始进行了UWFAWM的镇痛消炎效果的实验研究与临床观察。材料与方法制造UWFAWM的方法：在实验研究及临床应用中使用退磁器。技术参数：交变磁场的频率是７００Hz,最高磁场强度的衰减变化频率是５０Hz,磁场强度在０～０．１T之间迅速变化。治疗线圈直径２２c…     

稳恒磁场联合抗肿瘤药物协同杀伤肝癌细胞Hepa1-6

化学疗法为肿瘤临床治疗的常规方法,存在毒副作用大、抗药性强等缺陷。为了提高药物的利用效率,减少药物引起的毒副作用,将8.8 m T稳恒磁场分别与顺铂、阿霉素联用,经MTT检测发现磁场与药物联用可对肝癌细胞Hepa1-6生长具有协同抑制的效应,经HE染色发现联合处理组细胞发生明显的形态学改变。流式细胞仪检测显示磁场能增加顺铂对G2/M期细胞的滞留,而磁场与阿霉素共同作用可将细胞阻止于G1期和G2/M期。经彗星电泳检测表明磁场能够增强药物对DNA的损伤,且原子力显微镜观察发现联合处理组细胞膜表面出现较大且较深的孔洞,表面结构破坏严重。实验结果表明,抗肿瘤药物与磁场联用技术可有效抑制肿瘤细胞的生长,减少药物的使用浓度,为将抗肿瘤药物与磁场应用于临床治疗恶性肿瘤提供了一个全新的思路与策略。     

调制磁性纳米颗粒提高磁热性能的研究

磁性纳米颗粒具有独特的磁学性质,即在外加交变磁场下因产生磁滞释放热量,使其在生物医学领域,特别是肿瘤磁热疗,获得了广泛应用.到目前为止,磁性纳米颗粒介导的磁热疗成为一种治疗癌症的有效手段,已进入临床三期实验.因此,针对磁性纳米颗粒本身,优化设计尺寸、形貌、组分和表面修饰来提高其磁热性能,进而减小临床应用中的颗粒浓度来最小化毒副作用的研究,对肿瘤治疗及生物医药研究具有十分重要的意义.本综述详述如何优化调制磁性纳米颗粒以提高其磁热性能,为高效、低毒的磁性纳米颗粒的设计提供了指导性的研究方向.     

抑癌基因DLC-1的研究进展

DLC-1(肝癌缺失基因1)是近年来被发现的一种重要的抑癌基因,目前研究发现其在多种肿瘤的发生、发展过程中产生了重要的作用。随着基因技术及分子生物技术的飞速发展,关于DLC-1基因以及与之相关的上、下游靶基因,DLC-1基因的甲基化修饰及其相互作用的信号传导通路的研究将更深入、更彻底、更清楚。通过构建肿瘤动物实验模型,我们可以对人类各种肿瘤进行去甲基化药物治疗,分析实验结果,综合评估治疗指征,为临床上对肿瘤的治疗提供理论基础及实践指导。相信在不久的将来,针对DLC-1基因在肿瘤分子生物学研究有望成为多种肿瘤诊断、治疗的突破。     

针对端粒酶的肿瘤治疗研究前景可能不容乐观

由于端粒酶在肿瘤发生和发展中可能起到的巨大作用及其在各类肿瘤组织中的高阳性率,使得近十几年来以端粒酶为靶标的肿瘤治疗研究方案层出不穷。但近来,在这类实验动物的肿瘤治疗中出现的一些问题给这类似乎颇有希望的治疗策略蒙上了阴影。     

Effect of magnetic fields on tumor growth and viability

Breast cancer is the most common nonskin cancer and is the second leading cause of cancer-related deaths in women. Most methods of intervention involve combinations of surgery, chemotherapy, and ionizing radiation. Both chemotherapy and ionizing radiation can be effective against many types of cancer, but they also harm normal tissues. The use of nonionizing, magnetic fields has shown early promise in a number of in vitro and animal studies. Our study tested the effect of varying durations of magnetic exposure on tumor growth and viability in mice injected with breast cancer cells. Cancer cells were labeled through stable expression of firefly luciferase for monitoring of tumor growth and progression by using an in vivo imaging system. We hypothesized that magnetic field exposure would influence tumor growth and progression. Our results showed that exposure of the mice to magnetic fields for 360 min daily for as long as 4 wk suppressed tumor growth. Our study is unique in that it uses an in vivo imaging system to monitor the growth and progression of tumors in real time in individual mice. Our findings support further exploration of the potential of magnetic fields in cancer therapeutics, either as adjunct or primary therapy.     

Hypothesis: The risk of childhood leukemia is related to combinations of power-frequency and static magnetic fields

We present a hypothesis that the risk of childhood leukemia is related to exposure to specific combinations of static and extremely-low-frequency (ELF) magnetic fields. Laboratory data from calcium efflux and diatom mobility experiments were used with the gyromagnetic equation to predict combinations of 60 Hz and static magnetic fields hypothesized to enhance leukemia risk. The laboratory data predicted 19 bands of the static field magnitude with a bandwidth of 9.1 μT that, together with 60 Hz magnetic fields, are expected to have biological activity. We then assessed the association between this exposure metric and childhood leukemia using data from a case-control study in Los Angeles County. ELF and static magnetic fields were measured in the bedrooms of 124 cases determined from a tumor registry and 99 controls drawn from friends and random digit dialing. Among these subjects, 26 cases and 20 controls were exposed to static magnetic fields lying in the predicted bands of biological activity centered at 38.0 μT and 50.6 μT. Although no association was found for childhood leukemia in relation to measured ELF or static magnetic fields alone, an increasing trend of leukemia risk with measured ELF fields was found for subjects within these static field bands (P for trend = 0.041). The odds ratio (OR) was 3.3 [95% confidence interval (CI) = 0.4–30.5] for subjects exposed to static fields within the derived bands and to ELF magnetic field above 0.30 μT (compared to subjects exposed to static fields outside the bands and ELF magnetic fields below 0.07 μT). When the 60 Hz magnetic fields were assessed according to the Wertheimer-Leeper code for wiring configurations, leukemia risks were again greater with the hypothesized exposure conditions (OR = 9.2 for very high current configurations within the static field bands: 95% CI = 1.3–64.6). Although the risk estimates are based on limited magnetic field measurements for a small number of subjects, these findings suggest that the risk of childhood leukemia may be related to the combined effects of the static and ELF magnetic fields. Further tests of the hypothesis are proposed. © 1995 Wiley-Liss, Inc.     

Cancer promotion in a mouse-skin model by a 60-Hz magnetic field: II. Tumor development and immune response.

This paper describes preliminary findings on the influence of 60-Hz (2-mT) magnetic fields on tumor promotion and co-promotion in the skins of mice. The effect of magnetic fields on natural killer (NK) cell activity in spleen and blood was also examined. Groups of 32 juvenile female mice were exposed to the magnetic field as described in part I. The dorsal skin of all animals was treated with a subthreshold dose of the carcinogen 7,12-dimethyl-benz(a)anthracene (DMBA). One week after the treatment, two groups were sham exposed (group A) or field exposed at 2 mT (group B) 6 h/day for 21 weeks, to test whether the field would act as a tumor promoter. No tumors developed in these two groups of mice. To test whether the magnetic field would modify tumor development by directly affecting tumor growth or by suppressing immune surveillance, two additional groups of mice were treated weekly with the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA) and then either sham exposed (group C) or field exposed (group D). The time to appearance of tumors was shorter (but not statistically so) in the group exposed to magnetic fields and TPA. Some differences in NK cell activity and spleen size were observed between the sham- and field-exposed groups.     

A review of bioeffects of static magnetic field on rodent models

This review is aimed to summarize the experimental researches in the influences of static magnetic field on laboratory rodent models, reported by laboratory scientists, experimental technicians, clinical surgeons, animal veterinarians, and other researchers. Past studies suggested that static magnetic field-singly applied or used combined with other physical or chemical substances-significantly relieved some pains and ameliorated certain diseases in different organ systems, e.g. hypertension, osteoporosis, neuralgia, diabetes and leukemia etc. But on the other hand, some harmful events have also been observed in a number of investigations, from cellular level to fetal development. So exposure to static magnetic field might have dual effects on experimental rodent in various environments, viz. there are potentially therapeutic benefits, as well as adverse effects from it. The positive effect may relate to moderate intensities, while negative influence seems to be in connection with acute strong static magnetic fields. In addition, different orientations of static magnetic field exert different degrees of impact. Thus, the bioeffects of static magnetic field exposure on mice/rats depend on magnetic field intensities, durations and directions, though the exactly relationship between them is still vague. Further researches need to perform with appropriate methodologies, ingenious designs repeatedly and systemically, not only in animal models, but also in human volunteers and patients.     

Effect of low-intensity magnetic fields on the development of satellite muscle cells of a newborn rat in the primary culture

The influence of Earth magnetic field shielded down to 0.3 microT and static magnetic field (60-160 microT) on the proliferation and differentiation of satellite muscle cells in the primary culture has been investigated. A stimulatory effect of static magnetic fields on the rate of the formation of massive multinucleated myotubes and an increase in the intracellular calcium concentration ([Ca2+]i) have been detected for magnetic fields of the microtesla range. On the other hand, it was shown that the reduction of earth magnetic fields to 0.3 microT leads to the inhibition of proliferation and differentiation of skeletal muscle cells in the primary culture. Since the formation of contractile myotubes during in vitro experiments is similar to the regeneration of skeletal muscle fibers under muscle damage in vivo, it may be concluded that weak magnetic fields have a strong effect on intracellular processes by influencing all phases of muscle fiber formation. It is necessary to take this fact into consideration when forecasting probable complications of skeletal muscle regeneration during long-term exposure of man to low-intensity magnetic fields and also for the potential use of low static magnetic fields as a tool to recover the affected myogenesis.     

Low Strength Magnetic Fields Serve as a Cue for Foraging Honey Bees but Prior Experience is More Indicative of Choice

Species of migrating insects use magnetic fields as a navigational tool that is independent of current weather conditions and non-migrating species have been shown to discriminate anomalies in magnetic field from the earth's baseline. Honey bee discrimination of magnetic field has been studied in the context of associative learning, physiology, and whole hive responses. This article uses a combination of free-flight and laboratory studies to determine how small fluctuations from Earth's magnetic field affect honey bee (Apis mellifera L.) decision-making. Honey bees were tested in three experiments: (i) recruitment to an aqueous sucrose feeder, (ii) an artificial free-flight flower patch with floral color-dependent magnetic field strength, and (iii) a Y-maze with alternating colors on a stronger magnetic field. In free-flying feeder experiments, magnetic field served as a temporary cue, but when offered an equal caloric alternative with lesser magnetic field, the latter was preferred. Flower patch experiments showed initial color biases that were abandoned as a response to magnetic field induction. In laboratory experiments, bees showed a color-dependent behavioral response to the magnetic field. The results of this study indicate that bees may use small fluctuations in magnetic fields as a cue but that it is likely low-value as compared with other stimuli. Bioelectromagnetics. 2020;41:458–470. © 2020 Bioelectromagnetics Society.     

Circularly polarized,sinusoidal, 50 Hz magnetic field exposure does not influence plasma testosterone levels of rats

We exposed rats to circularly polarized 50 Hz magnetic fields to determine if plasma testosterone concentration was affected. Previous experiments indicate that magnetic fields suppress the nighttime rise in melatonin, suggesting that other neuroendocrine changes might occur as well. Male Wistar-King rats were exposed almost continuously for 6 weeks to magnetic flux densities of 1,5, or 50 μT. Blood samples were obtained by decapitation at 12:00 h and 24:00 h. Plasma testosterone concentration showed a significant day-night difference, with a higher level at 12:00 h when studied in July and December, but the day-night difference disappeared when concentrations were studied in April. In three experiments, magnetic field exposure had no statistically significant effect on plasma testosterone levels compared with the sham-exposed groups. These findings indicate that 6 weeks of nearly continuous exposure to circularly polarized, 50 Hz magnetic fields did not change plasma testosterone concentration in rats. © 1994 Wiley-Liss, Inc.     

Dependence of effects of weak combined low-frequency variable and constant magnetic fields on the intensity of asexual reproduction of planarians Dugesia tigrina on the magnitude of the variable field

It was shown that the stimulating effect of weak combined magnetic fields (constant component 42 microT, frequency of the variable component 3.7 Hz) on the division of planarians depends on the amplitude of the variable component of the field. The effect is particularly pronounced at 40 (the main maximum), 120, 160, and 640 nT. Narrow ranges of effective amplitudes alternate in some cases with equally narrow ranges in which the system does not respond to he treatment. In the range of super weak amplitudes of the variable field (0.1 and 1 nT), the stimulating effect is poorly pronounced. The data obtained indicate the presence of narrow amplitude windows in the response of the biological systems to weak and super weak magnetic fields. In a special series of experiments, it was shown that the effect of fields on planarians is partially mediated via aqueous medium preliminarily treated with weak magnetic fields. It is noteworthy that in experiments with water treated with weak magnetic fields, there were no pronounced maxima and minima in the magnitude of the effect in the range of amplitude of the variable magnetic field from 40 to 320 nT.     

Magnetic field direction differentially impacts the growth of different cell types

Magnetic resonance imaging (MRI) machines have horizontal or upright static magnetic field (SMF) of 0.1–3 T (Tesla) at sites of patients and operators, but the biological effects of these SMFs still remain elusive. We examined 12 different cell lines, including 5 human solid tumor cell lines, 2 human leukemia cell lines and 4 human non-cancer cell lines, as well as the Chinese hamster ovary cell line. Permanent magnets were used to provide 0.2–1 T SMFs with different magnetic field directions. We found that an upward magnetic field of 0.2–1 T could effectively reduce the cell numbers of all human solid tumor cell lines we tested, but a downward magnetic field mostly had no statistically significant effect. However, the leukemia cells in suspension, which do not have shape-induced anisotropy, were inhibited by both upward and downward magnetic fields. In contrast, the cell numbers of most non-cancer cells were not affected by magnetic fields of all directions. Moreover, the upward magnetic field inhibited GIST-T1 tumor growth in nude mice by 19.3% (p < 0.05) while the downward magnetic field did not produce significant effect. In conclusion, although still lack of mechanistical insights, our results show that different magnetic field directions produce divergent effects on cancer cell numbers as well as tumor growth in mice. This not only verified the safety of SMF exposure related to current MRI machines but also revealed the possible antitumor potential of magnetic field with an upward direction.