共查询到20条相似文献,搜索用时 156 毫秒
1.
非热微波和方位对水迷宫大鼠空间认知的影响 总被引:5,自引:1,他引:4
描述了四组大鼠六个训练期从上释放点寻找圆形水迷宫(Morris)固定没水平台的动物行为实验,四组动物为,脉冲微波组(2450,MHZ,调制脉宽2μs,每秒500脉冲,空间平均功率密度为2mW/cm^2,平均整体特异吸收率SAR,1.2w/kg),连续微波组(2450MHZ,无调制。空间平均功率宴席和SAR同于脉冲微波组),Sham辐射组以及笼养对照组。以平均逃逸时间和速度为测量,考查它们的空间记忆 相似文献
2.
在腺病毒介导的HSV-tk/NAS系统脑肿瘤基因治疗研究过程中,建立了野生型腺病毒(RCA)的检测系统,主要包括腺病毒E1区的PCR以及野生型病毒的细胞病理效应观察这两种方法,PCR的灵敏度为1个293细胞所含有的E1片段数。对基因治疗脑肿瘤所采用的重组腺病毒AdTK及其感染的细胞进行RCA的检测,没有发现RCA。通过离体实验首次发现,重组腺病毒对脑肿瘤细胞的杀伤作用明显高于正常的脑胶质细胞;大鼠 相似文献
3.
大肠杆菌精氨酰—tRNA合成酶的Lys306为酶活力所必需 总被引:2,自引:2,他引:0
将大肠杆菌精氨酰tRNA合成酶(ArgRS)上Lys306用基因点突变的方法分别变为Ala和Arg的密码子,得到变种基因args306KA和args306KR。变种基因重组在pUC18上,转化到大肠杆菌TG1中,转化子中ArgRS及其变种ArgRS306KA和ArgRS306KR所表达的蛋白量生活为TG1表达ArgRS蛋白量的100倍。细胞粗抽提液中ArgRS的比活TG1,转化子pUC18-arg 相似文献
4.
蓖麻蚕核糖体RNA基因(rDNA)5′-非转录间隔区有长约1kb的核骨架结合区SAR(scafold-associat-edregion)[1]。本文对该SAR元件的酵母自主复制功能进一步研究,证明该SAR5′端688bp含有12个ACS(ARS的核心序列)同源序列,但无ARS活性,而其3′端仅3个ACS同源序列,但对酵母的转化率比全片段还高40~50倍。体外结合实验证明,蓖麻蚕rRNA基因的SAR能专一地同酵母核骨架结合,提示ARS的功能体现与核骨架结合紧密相关。rRNA基因SAR与ARS的功能在进化上可能是很保守的。在此基础上可进一步分析SAR中与DNA复制相关的正调及负调元件。 相似文献
5.
将大肠杆菌精氨酰tRNA合成酶(ArgRS)上Lys306用基因点突变的方法分别变为Ala和Arg的密码子;得到变种基因args306KA和args306KR。变种基因重组在pUC18上,转化到大肠杆菌TG1中,转化子中ArgRS及其变种ArgRS306KA和ArgRS306KR所表达的蛋白量至少为TG1表达ArgRS蛋白量的100倍。细胞粗抽提液中ArgRS的比活TG1、转化子pUC18-args、pUC18-args306KA和pUC18-args306KR分别为1.65、210、1.8和38单位/毫克。结果表明ArsRS的Lys306为Ala取代使活力完全丧失;若被Arg取代,则活力丧失80%以上。Lys306为ArgRS活力所必需。 相似文献
6.
普通小麦4A染色体重排的原位杂交研究 总被引:2,自引:0,他引:2
以普通小麦第四部分同源染色体组的13个RFLP(限制性片段长度多态性)标记为探针,通过原位杂交进行了物理定位和4A染色体重排的物理特征研究。RFLP分析确定的标记所在的染色体臂和原位杂交结果相一致。位于4AL上的9个RFLP探针有6个的杂交点集中分布在距着丝点约60%~70%的区域内。本结果支持了4A染色体来自于双重易位的假说,第一次易位产生的4AL/5AL染色体又和7BS发生易位,现在的4A染色体结构为4AL/5AL/7BS,保留在4A的5AL、7BS染色体片段约分别为05μm、22μm。所用RFLP标记杂交点聚集的区段分布于染色体臂的近端部,可能和易位断点及染色体的交换重组有关。4AL上C-带距着丝点的相对距离和各标记杂交点集中区段距着丝点的相对距离接近。 相似文献
7.
局部肾素-血管紧张素系统对心血管功能的调节作用 总被引:3,自引:0,他引:3
传统的肾素-血管紧张素系统(RAS)的概念是一个循环内分泌系统,它在维持心血管功能稳态,尤其对动脉血压的调节有重要意义。近年大量资料证明,RAS也存在于许多局部组织,它通过旁分泌或自身分泌作用调节器官的生理功能。本文着重介绍RAS在血管、心脏、脑和肾脏内存在及对心血管功能的调节作用。 相似文献
8.
蓖麻蚕核糖体RNA基因(rDNA)5'-非转录间隔区有长约1kb的核骨架结合区SAR。本文对该SAR元件的酵母自主复制功能进一步研究,证明该SAR 5'端688bp含有12个ACS(ARS的核心序列)同源序列,但无ARS活性,而其3'端仅3个ACS同源序列,但对酵母的转化率比全片段还高40 ̄50倍。体外结合实验证明,蓖麻蚕rRNA基因的SAR能专一地同酵母核骨架结合,提示ARS的功能体现与核骨架结 相似文献
9.
中国点池蝇属一新纪录种ANEWRECORDSPECIESOFGENUSSPILOGONAFROMCHINA关键词双翅目蝇科点池蝇属新纪录种中国半球点池蝇Spilogonasemiglobosa(Ringdah1,1916)Eet.Tidskr.,37... 相似文献
10.
球形幽门螺杆菌分子生物学研究 总被引:5,自引:1,他引:4
为研究幽门螺杆菌(HP)球形变异本质,作者通过延期培养和采用亚抑菌浓度抗生素,使3株HP发生球形变异,对弯曲形和球形HP作了SDS-PAGE、免疫印迹及4个毒力基因片段PCR和PCR-SSCP分析。SDS-PAGE图谱显示球形HP分子量在74×104以上的蛋白含量减少,免疫印迹显示球形HP125×104蛋白条带反应减弱,而抗生素诱变的球形HP分子量为11×104和63×104的蛋白条带反应增强。PCR及PCR-SSCP结果表明球形HP的hpaA,VacA,CagA和UreA4个毒力基因片段未发生缺失,但在hpaA或VacA基因中存在点突变 相似文献
11.
Bol'shakov MA Kniazeva IR Lindt TA Evdokimov EV 《Radiatsionnaia biologiia, radioecologiia / Rossi?skaia akademiia nauk》2001,41(4):399-402
Effect of electromagnetic radiation 460 MHz with 2.5-40 Hz pulse modulation rate on Drosophila embryos of 15 h 10 m age was studied. It was demonstrated that a 5-min irradiation with 0.12 W/kg average SAR (3 W/kg pulsed SAR) alters the Drosophila percentage of interrupted development. The effect strength depended on the modulation rate with a pronounced decrease at 10 and 16 Hz. A hypothesis about the presence of thermal and non-thermal mechanisms of action of pulse-modulated microwave radiation diversely effecting the embryos has been put forward and grounded. 相似文献
12.
Bit-Babik G Guy AW Chou CK Faraone A Kanda M Gessner A Wang J Fujiwara O 《Radiation research》2005,163(5):580-590
The level and distribution of radiofrequency energy absorbed in a child's head during the use of a mobile phone compared to those in an adult head has been a controversial issue in recent years. It has been suggested that existing methods that are used to determine specific absorption rate (SAR) and assess compliance with exposure standards using an adult head model may not adequately account for potentially higher levels of exposure in children due to their smaller head size. The present study incorporates FDTD computations of locally averaged SAR in two different anatomically correct adult and child head models using the IEEE standard (Std. C95.3-2002) SAR averaging algorithm. The child head models were obtained by linear scaling of the adult head model to replicate the conditions of previous studies reported in the literature and also by transforming the different adult head models based on data on the external shapes of children's heads. The tissue properties of the adult and corresponding child head models were kept the same. In addition, modeling and experimental measurements were made using three spheres filled with a tissue-equivalent mixture to approximate heads of increasing size. Results show that the peak local average SAR over 1 g and 10 g of tissue and the electromagnetic energy penetration depths are about the same in all of the head models under the same exposure conditions. When making interlaboratory comparisons, the model and the SAR averaging algorithm used must be standardized to minimize controversy. 相似文献
13.
The so-called carousel setup has been widely utilized for testing the hypotheses of adverse health effects on the central nervous system (CNS) due to mobile phone exposures in the frequency bands 800-900 MHz. The objectives of this article were to analyze the suitability of the setup for the upper mobile frequency range, i.e., 1.4-2 GHz, and to conduct a detailed experimental and numerical dosimetry for the setup at the IRIDIUM frequency band of 1.62 GHz. The setup consists of a plastic base on which ten rats, restrained in radially positioned tubes, are exposed to the electromagnetic field emanating from a sleeved dipole antenna at the center. Latest generation miniaturized dosimetric E field and temperature probes were used to measure the specific absorption rate (SAR) inside the brain of three rat cadavers of the Lewis strain and two rat cadavers of the Fisher 344 strain. A numerical analysis was conducted on the basis of three numerical rat phantoms with voxel sizes between 1.5 and 0.125 mm3 that are based on high resolution MRI scans of a 300 g male Wistar rat and a 370 g male Sprague-Dawley rat. The average of the assessed SAR values in the brain was 2.8 mW/g per W antenna input power for adult rats with masses between 220 and 350 g and 5.3 mW/g per W antenna input power for a juvenile rat with a mass of 95 g. The strong increase of the SAR in the brain with decreasing animal size was verified by simulations of the absorption in numerical phantoms scaled to sizes between 100 and 500 g with three different scaling methods. The study also demonstrated that current rat phantom models do not provide sufficient spatial resolution to perform absolute SAR assessment for the brain tissue. The variation of the SAR(brain)(av) due to changes in position was assessed to be in the range from +15% to -30%. A study on the dependence of the performance of the carousel setup on the frequency revealed that efficiency, defined as SAR(brain)(av) per W antenna input power, and the ratio between SAR(brain)(av) and SAR(body)(av) are optimal in the mobile communications frequency range, i.e., 0.8-3 GHz. 相似文献
14.
Electric fields (E-fields) induced within a phantom head from exposure to three different advanced mobile phone system (AMPS) hand-held telephones were measured using an implantable E-field probe. Measurements were taken in the eye nearest the phone and along a lateral scan through the brain from its centre to the side nearest the phone. During measurement, the phones were positioned alongside the phantom head as in typical use and were configured to transmit at maximum power (600 mW nominal). The specific absorption rate (SAR) was calculated from the in situ E-field measurements, which varied significantly between phone models and antenna configuration. The SARs induced in the eye ranged from 0.007 to 0.21 W/kg. Metal-framed spectacles enhanced SAR levels in the eye by 9–29%. In the brain, maximum levels were recorded at the measurement point closest to the phone and ranged from 0.12 to 0.83 W/kg. These SARs are below peak spatial limits recommended in the U.S. and Australian national standards [IEEE Standards Coordinating Committee 28 (1991): C95.1-1991 and Standards Australia (1990): AS2772.1-1990] and the IRPA guidelines for safe exposure to radio frequency (RF) electromagnetic fields [IRPA (1988): Health Phys 54:115–123]. Furthermore, a detailed thermal analysis of the eye indicated only a 0.022°C maximum steady-state temperature rise in the eye from a uniform SAR loading of 0.21 W/kg. A more approximate thermal analysis in the brain also indicated only a small maximum temperature rise of 0.034°C for a local SAR loading of 0.83 W/kg. © 1995 Wiley-Liss, Inc. 相似文献
15.
Fayos-Fernandez J Arranz-Faz C Martinez-Gonzalez AM Sanchez-Hernandez D 《Bioelectromagnetics》2006,27(5):337-353
A study of the interaction between mobile phone antennas and a human head in the presence of different types of metallic objects, attached and pierced to the compressed ear, is presented in this article. Computed and measured results have been performed by considering a quasi-half-wavelength dipole as the radiating source and measurements with the DASY4 dosimetric assessment system. Two different human head models have been implemented: a homogeneously shaped sphere and a three-level head model with four different kinds of tissue. Antenna input impedance, reflection coefficient, radiation patterns, SAR distribution, absorbed power, and peak SAR values have been computed and measured for diverse scenarios, electromagnetic simulators, and organs. Despite the measuring accuracy limitations of the study, both simulated and measured results suggest that special attention has to be paid to peak SAR averaged values when wearing metallic objects close to the radiation source, since some increment of peak SAR averaged values is expected. 相似文献
16.
本文分析了静适应和不同类型的噪声对615鼠和小白鼠脑内5-HT代谢的影响.静适应可引起大多数615鼠脑内5-HT代谢显著性下降15.1%和19.6%.连续脉冲噪声可使其脑内5-HT代谢显著性增高10.2%和22.5%.静适应和连续脉冲噪声对大多数小白鼠脑内5-HT的代谢无显著性影响.但是优势频率为125-250Hz的低频杂乱噪声和粉红噪声都可引起静适应小白鼠脑内5-HT代谢显著性增高,分别增高29.0-39.7%和28.0-32.7%. 相似文献
17.
Lerchl A 《Progress in biophysics and molecular biology》2011,107(3):404-407
Despite the fact that no plausible biological mechanism has yet been identified how electromagnetic fields below recommended exposure limits could negatively affect health of animals or humans, many experiments have been performed in various animal species, mainly mice and rats, to investigate the possible effects on growth and development. While older studies often suffered from sub-optimal exposure conditions, recent investigations, using sophisticated exposure devices and thus preventing thermal effects, have been performed without these limitations. In principle, two types of studies can be addressed: those which have investigated the carcinogenic or co-carcinogenic effects of exposure in developing animals, and those which have been done in developing animals without the focus on carcinogenic or co-carcinogenic effects. In both areas, the vast majority of publications did not show adverse effects. The largest study so far has been done in normal mice which have been chronically exposed to UMTS signals up to 1.3 W/kg SAR, thus 16 times higher than the whole-body exposure limit for humans. Even after four generations, no systematic or dose-dependent alterations in development or fertility could be found, supporting the view that negative effects on humans are very unlikely. Ongoing experiments in our laboratory investigate the effects of head-only exposure in rats (up to 10 W/kg local SAR) which are exposed from 14 days of age daily for 2 h. A battery of behavioral tests is performed in young, adult, and pre-senile animals. The results will help to clarify possible effects of exposure on brain development. 相似文献
18.
Mobile phones are widely used in the modern world. However, biological effects of electromagnetic radiation produced by mobile phones are largely unknown. In this report, we show biological effects of the mobile phone 835 MHz electromagnetic field (EMF) in the Drosophila model system. When flies were exposed to the specific absorption rate (SAR) 1.6 W/kg, which is the proposed exposure limit by the American National Standards Institute (ANSI), more than 90% of the flies were viable even after the 30 h exposure. However, in the SAR 4.0 W/kg strong EMF exposure, viability dropped from the 12 h exposure. These EMF exposures triggered stress response and increased the production of reactive oxygen species. The EMF exposures also activated extracellular signal regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling, but not p38 kinase signaling. Interestingly, SAR 1.6 W/kg activated mainly ERK signaling and expression of an anti-apoptotic gene, whereas SAR 4.0 W/kg strongly activated JNK signaling and expression of apoptotic genes. In addition, SAR 4.0 W/kg amplified the number of apoptotic cells in the fly brain. These findings demonstrate that the exposure limit on electromagnetic radiation proposed by ANSI triggered ERK-survival signaling but the strong electromagnetic radiation activated JNK-apoptotic signaling in Drosophila. 相似文献
19.
1439 MHz pulsed TDMA fields affect performance of rats in a T-maze task only when body temperature is elevated 总被引:7,自引:0,他引:7
Yamaguchi H Tsurita G Ueno S Watanabe S Wake K Taki M Nagawa H 《Bioelectromagnetics》2003,24(4):223-230
This study sought to clarify the effects of exposure to electromagnetic waves (EMW) used in cellular phones on learning and memory processes. Sprague-Dawley rats were exposed for either 1 h daily for 4 days or for 4 weeks to a pulsed 1439 MHz time division multiple access (TDMA) field in a carousel type exposure system. At the brain, average specific absorption rate (SAR) was 7.5 W/kg, and the whole body average SAR was 1.7 W/kg. Other subjects were exposed at the brain average SAR of 25 W/kg and the whole body average SAR of 5.7 W/kg for 45 min daily for 4 days. Learning and memory were evaluated by reversal learning in a food rewarded T-maze, in which rats learned the location of food (right or left) by using environmental cues. The animals exposed to EMW with the brain average SAR of 25 W/kg for 4 days showed statistically significant decreases in the transition in number of correct choices in the reversal task, compared to sham exposed or cage control animals. However, rats exposed to the brain average SAR of 7.5 W/kg for either 4 days or for 4 weeks showed no T-maze performance impairments. Intraperitoneal temperatures, as measured by a fiber optic thermometer, increased in the rats exposed to the brain average SAR of 25 W/kg but remained the same for the brain average SAR of 7.5 W/kg. The SAR of a standard cellular phone is restricted to a maximum of 2 W/kg averaged over 10 g tissue. These results suggest that the exposure to a TDMA field at levels about four times stronger than emitted by cellular phones does not affect the learning and memory processes when there are no thermal effects. 相似文献
20.
Radiofrequency radiation-induced calcium ion efflux enhancement from human and other neuroblastoma cells in culture 总被引:2,自引:0,他引:2
To test the generality of radiofrequency radiation-induced changes in 45Ca2+ efflux from avian and feline brain tissues, human neuroblastoma cells were exposed to electromagnetic radiation at 147 MHz, amplitude-modulated (AM) at 16 Hz, at specific absorption rates (SAR) of 0.1, 0.05, 0.01, 0.005, 0.001, and 0.0005 W/kg. Significant 45Ca2+ efflux was obtained at SAR values of 0.05 and 0.005 W/kg. Enhanced efflux at 0.05 W/kg peaked at the 13-16 Hz and at the 57.5-60 Hz modulation ranges. A Chinese hamster-mouse hybrid neuroblastoma was also shown to exhibit enhanced radiation-induced 45Ca2+ efflux at an SAR of 0.05 W/kg, using 147 MHz, AM at 16 Hz. These results confirm that amplitude-modulated radiofrequency radiation can induce responses in cells of nervous tissue origin from widely different animal species, including humans. The results are also consistent with the reports of similar findings in avian and feline brain tissues and indicate the general nature of the phenomenon. 相似文献