Extremely low frequency magnetic fields suppress the reduction of germination rate of Arabidopsis thaliana seeds kept in saturated humidity.

The effects of an extremely low frequency magnetic field (ELFMF) on the germination of plant seeds were examined. The decrease in the germination activity of the seeds of Arabidopsis thaliana WS kept in saturated humidity and high temperature (37 degrees C) was suppressed by the exposure to a 400 mT ELFMF.     

Effect of high-density extremely low frequency magnetic field on sister chromatid exchanges in mouse m5S cells

The induction of sister chromatid exchanges (SCEs) was evaluated in the cultured mouse m5S cells after exposure to extremely low frequency magnetic field (ELFMF; 5, 50 and 400 mT). Exposure to 5 mT and 50 mT ELFMF led to a very small increase in the frequency of SCEs, but no significant difference was observed between exposed and unexposed control cells. The cells exposed to 400 mT ELFMF exhibited a significant elevation of the SCE frequencies. There was no significant difference between data from treatments with mitomycin-C (MMC) alone and from combined treatments of MMC plus ELFMF (400 mT) at any MMC concentrations from 4 to 40 nM. These results suggest that exposure to highest-density ELFMF of 400 mT may induce DNA damage, resulting in an elevation of the SCE frequencies. We suppose that there may be a threshold for the elevation of the SCE frequencies, that is at least over the magnetic density of 50 mT.     

Increase in X-ray-induced mutations by exposure to magnetic field (60 Hz, 5 mT) in NF-kappaB-inhibited cells

It is established that extremely low frequency magnetic fields (ELFMF) at the flux densities, i.e., 5 mT and less, are not mutagenic. However, exposure to ELFMF enhances mutations induced by X-rays. In this study, we examined the effects of long-term exposure to 5 mT ELFMF on mutation induction and X-ray-induced mutations in human malignant glioma cells (MO54) with different mutant IkappaB-alpha (a critical inhibitor of NF-kappaB) genes. Cells were exposed or sham-exposed to 5 mT ELFMF for up to 8 days with or without initial X-rays (4 Gy), and the mutant frequency of hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene was analyzed. An obvious increase in X-ray-induced mutations was observed after treatment with ELFMF in combination with X-irradiation in MO54 cells with tyrosine mutant IkappaB-alpha gene other than with serine mutant IkappaB-alpha gene or vector alone. Exposure to ELFMF alone increased mutations significantly in MO54 cells with tyrosine mutant IkappaB-alpha gene. In addition, X-ray-induced apoptoic cells were increased in MO54-V cells after exposure to ELFMF, while an anti-apoptotic effect of magnetic field was found in MO54-SY4 cells. Our data suggest that exposure to 5 mT ELFMF may induce mutations and enhance X-ray-induced mutations, resulting from the inactivation of NF-kappaB through the inhibition of tyrosine phosphorylation.     

Enhanced NOR-1 gene expression by exposure of Chinese hamster cells to high-density 50 Hz magnetic fields

Enhanced expression of neuron derived orphan receptor (NOR-1) gene was observed by exposure of Chinese hamster ovary K1 (CHO-K1) cells to an extremely low frequency magnetic field (ELFMF) of 50 Hz at 400 mT, but not at 5 mT. The enhanced expression, reaching the maximum at 6 h, was transient and reduced to the control level after exposure to 400 mT ELFMF for 24 h. The NOR-1 expression induced by treatment with forskolin and TPA was further enhanced by the simultaneous treatment with 400 mT ELFMF, in which the maximum response was at 3 h. The NOR-1 expression by these treatments was induced more earlier than that by 400 mT ELFMF alone. When cells were treated with an inhibitor of the protein kinase C (calphostin C or crocetin) and Ca²⁺ entry blockers (nifedipin and dantrolen) during the 400 mT ELFMF exposure, the enhanced NOR-1 expression was not observed. Exposure of CHO-K1 cells to the high-density 400 mT ELFMF may affect the signal transduction in the cells, resulting in the enhanced NOR-1 gene expression.     

Exposure to extremely low frequency magnetic fields affects insulin-secreting cells

To evaluate the effects of extremely low frequency magnetic field (ELFMF) on beta-cell survival and function, we cultured a hamster-derived insulin-secreting cell line (HIT-T15), which exhibits responsiveness to glucose in a semi-physiological range, under exposure to sham and ELFMF conditions, and assessed cell survival and function. We used our previously developed ELFMF exposure unit (a sinusoidal magnetic field at a frequency of 60 Hz, 5 mT) to culture cells under exposure to ELFMF conditions. We found that exposure to ELFMF for 5 days in the absence of glucose increased cell number, exposure for 2 days in the absence of glucose and for 5 days with 100 mg/dl glucose increased the insulin secretion to the culture medium, and exposure for 2 and 5 days with 40 and 100 mg/dl glucose increased intracellular insulin concentration in HIT-T15 cells. The increase in cell number under apoptotic culture conditions by exposure to ELFMF could lead to new therapeutic concepts in the treatment of diabetes. The ELFMF-induced increase in intracellular insulin concentration could be utilized to develop culture conditions to enhance intracellular insulin concentration in insulin-secreting cells that would be useful for cell transplantation to cure diabetes mellitus.     

Exposure to extremely low frequency magnetic fields suppresses x-ray-induced transformation in mouse C3H10T1/2 cells

We designed and manufactured equipment for exposure of cultured cells to extremely low frequency magnetic fields (ELFMF) at 5, 50, and 400 mT and examined the effect of ELFMF on cellular transformation in mouse C3H10T1/2 cells (clone 8). Transformed foci, Type II and Type III, were independently counted as transformants. The cells were exposed to ELFMF alone at 5, 50, and 400 mT for 24 h or X-irradiated with 3 Gy followed by the ELFMF exposure. No significant difference in the transformation was observed between sham-exposed control and the ELFMF exposure from 5 to 400 mT. The transformation frequency for X-rays plus ELFMF was decreasing compared with X-rays alone. When 12-O-tetra-decanoylphorbol-13-acetate (TPA) was contained in the medium throughout the experiment, the transformation frequency by X-rays alone was elevated more. In the combined treatment with X-rays followed by ELFMF, the transformation frequency was slightly decreased at 50 and 400 mT even in the medium containing TPA. The long-term exposure at 5 mT suppressed both spontaneous and X-ray-induced transformations significantly. It is well known that overexpressing protein kinase C (PKC) failed to yield identifiable transformation of foci induced by ionizing radiation. We demonstrated previously that exposure to high-density ELFMF induced expression of several genes through an increase in PKC activity. From these results, it is suggested that ELFMF might suppress X-ray-induced transformation through activation of PKC by ELFMF.     

An extremely low frequency magnetic field attenuates insulin secretion from the insulinoma cell line, RIN-m

In this study, we investigated the effects of exposure to an extremely low frequency magnetic field (ELFMF) on hormone secretion from an islet derived insulinoma cell line, RIN-m. We stimulated RIN-m cells to secrete insulin under exposure to an ELFMF, using our established system for the exposure of cultured cells to an ELFMF at 5 mT and 60 Hz, or under sham exposure conditions for 1 h and observed the effects. In the presence of a depolarizing concentration of potassium (45 mM KCl), exposure to ELFMF significantly attenuated insulin release from RIN-m cells, compared to sham exposed cells. Treatment with nifedipine reduced the difference in insulin secretion between cells exposed to an ELFMF and sham exposed cells. The expression of mRNA encoding synaptosomal associated protein of 25 kDa (SNAP-25) and synaptotagmin 1, which play a role in exocytosis in hormone secretion and influx of calcium ions, decreased with exposure to an ELFMF in the presence of 45 mM KCl. These results suggest that exposure to ELFMF attenuates insulin secretion from RIN-m cells by affecting calcium influx through calcium channels.     

Effect of high-density extremely low frequency magnetic field on sister chromatid exchanges in mouse m5S cells

The induction of sister chromatid exchanges (SCEs) was evaluated in the cultured mouse m5S cells after exposure to extremely low frequency magnetic field (ELFMF; 5, 50 and 400 mT). Exposure to 5 mT and 50 mT ELFMF led to a very small increase in the frequency of SCEs, but no significant difference was observed between exposed and unexposed control cells. The cells exposed to 400 mT ELFMF exhibited a significant elevation of the SCE frequencies. There was no significant difference between data from treatments with mitomycin-C (MMC) alone and from combined treatments of MMC plus ELFMF (400 mT) at any MMC concentrations from 4 to 40 nM. These results suggest that exposure to highest-density ELFMF of 400 mT may induce DNA damage, resulting in an elevation of the SCE frequencies. We suppose that there may be a threshold for the elevation of the SCE frequencies, that is at least over the magnetic density of 50 mT.     

Suppression of heat-induced HSP-70 by simultaneous exposure to 50 mT magnetic field

Effect of extremely low frequency magnetic field (ELFMF) at 50 mT and 60 Hz on heat-induced expression of heat shock protein 70 (hsp-70) was examined in HL60RG cells. No increase in hsp-70 production was observed in the cells after exposure to 50 mT ELFMF alone. Simultaneous exposure to 50 mT ELFMF in combination with mild heat at 42 and 40 degrees C suppressed heat-induced hsp-70 expression. The suppression of hsp-70 occurred when cells were simultaneously exposed to both for longer periods of more than 5 h. However, the suppression of hsp-70 was not observed at a magnetic density of 5 and 0.5 mT. This result suggests that exposure to 50 mT ELFMF may act on a protection against the concomitant mild heat stress in HL60RG cells.     

A meta-analysis of the effects of frugivory (endozoochory) on seed germination: role of seed size and kind of dormancy

Heretofore, no study has determined how germination of ingested seeds is affected by the kind (class) of dormancy nor by seed dormancy x seed size interaction. Thus, we aimed to determine the effects of seed size, kind of dormancy and their interaction on germination of defecated seeds using a meta-analysis. We collected data for 366 plant species in 97 plant families from 76 publications. In general, gut passage significantly increased germination percentage of defecated seeds by 5% compared with that of control seeds. Germination percentages of non-dormant, physiologically dormant, and morphologically/morphophysiologically dormant seeds (all water-permeable) significantly decreased after gut passage by 40, 18, and 14%, respectively, compared with control seeds (non-gut-passed). Changes in germination percentage of seeds with physical dormancy (water-impermeable) were positive, and gut passage increased germination by 69% compared with control seeds. Germination of small seeds decreased 8% after gut passage, whereas germination of both medium and large seeds increased by 18%. However, changes in germination percentage differed between categories of seed size in each class of dormancy. In physically dormant seeds, germination of all seed sizes improved after gut passage, and the magnitude of increase was higher for large than for medium and small seeds. Thus, gut passage increased germination of medium-size water-permeable seeds (physiologically dormant and morphologically/morphophysiologically dormant) more than it did for large and small seeds. However, gut-passage decreased or did not change the germination percentage of non-dormant seeds. Seed size and kind of dormancy should be included in studies on the effect of gut passage on germination.     

ELF electromagnetic fields increase hydrogen peroxide (H2O2)-induced mutations in pTN89 plasmids

We have examined the mutational effects of hydrogen peroxide (H(2)O(2)) in the presence and absence of an extremely low-frequency magnetic field (ELFMF), using pTN89 plasmids. Mutations were detected in the supF gene carried by these plasmids in Escherichia coli. The plasmids were either treated with H(2)O(2) (1microM) alone at 37 degrees C for 4h, or were exposed to an ELFMF (60Hz, 5millitesla (mT)) simultaneously with H(2)O(2) treatment. The mutation frequency was 2.28 x 10(-4) for H(2)O(2) treatment alone, and 5.81 x 10(-4) for ELFMF exposure with H(2)O(2) treatment. We did not observe any mutations using treatment with ELFMF exposure alone. This indicates that the ELFMF may potentiate H(2)O(2)-induced mutation. Sequence analysis of the supF mutant plasmids revealed that base substitutions, G: C-->A :T transitions and G:C-->T:A transversions were dominant in both treatment groups, and there was no difference in the mutation spectrum or the hotspots between the groups. Therefore, ELFMFs may interact and potentiate the damage induced by H(2)O(2), resulting in an increase in the number of mutations.     

盐生植物角果碱蓬种子二型性对环境的适应策略

角果碱蓬(Suaeda corniculata)是藜科一年生盐生植物, 在我国分布于北方盐碱滩涂和盐碱荒漠地区。角果碱蓬具有棕色和黑色两种异型体种子(简称棕色和黑色种子)。对采自内蒙古鄂托克前旗盐渍化生境的角果碱蓬二型种子的形态、休眠和萌发特性开展对比研究, 测定了二型种子休眠和萌发行为对温度、光照和盐分(NaCl)的响应, 以揭示盐生植物异型种子对温带盐漠生境的适应对策。结果表明: (1)二型性种子在大小、种皮特性和结实比例方面有显著差异。与黑色种子相比, 棕色种子个体较大, 种皮透水性强。黑色种子与棕色种子的结实比例约为5.6 : 1。(2)新成熟的棕色种子的萌发对各温度梯度和光照条件不敏感, 萌发率较高(84%-100%); 而新成熟的黑色种子萌发率较低(8%-78%), 萌发对光照敏感。(3)黑色种子具有浅度生理休眠, 种皮划破、赤霉素处理和低温层积均可有效地提高种子的萌发率。(4)二型种子萌发对土壤盐分的胁迫具有不同的响应。与黑色种子相比, 棕色种子对盐分胁迫不敏感, 在较高的盐分浓度下仍有较高的萌发率, 低温层积处理能够降低黑色种子对盐胁迫的敏感性, 有效地提高种子的初始萌发率、萌发恢复率和最终萌发率。角果碱蓬二型种子不同的形态、休眠和萌发特性, 提高了该物种在高度异质性生境中的适合度, 对种群成功地适应温带盐漠环境具有重要的意义。     

Bimodal changes in germinability of pea seeds under the influence of low doses of gamma-radiation

Pea seeds (cv. 'Nemchinovskii-85', harvest of 2002, 80%-germination percentage) were exposed to gamma-radiation with doses ranging from 19 cGy to 100 Gy. One week after the irradiation with doses of 19 cGy and 3 Gy. the germination percentage decreased to 58 and 45%, respectively; at doses of 7 and 10 Gy it was 73 and 70% respectively. At greater doses (25, 50, and 100 Gy), germination percentage decreased in proportion. Anomalous changes in seed germination percentage (as a function of irradiation dose) were caused by the redistribution of irradiated seeds between fractions I and II. The measurements of room temperature phosphorescence in air-dry seeds and the phosphorescence of endogenous porphyrines of imbibing seeds showen that the germination decrease after the irradiation with low doses (19 cGy and 3 Gy) was caused by the increase in the number of weak seeds of fraction II, which had high rates of water uptake and suffered from hypoxia under seed coat. Some of these seeds suffocated from hypoxia, and other seeds produced seedlings with morphological defects (such seeds were considered incapable of germination). During storage of seeds irradiated at doses 19 cGy-10 Gy, the recovery of germination percentage (after its initial decrease) was caused by the decrease in seed number in fraction II. The subsequent germination decrease was caused by seed death. The higher was the irradiation dose, the faster were changes in germination percentage during storage of irradiated seeds. Bimodal changes in pea seed germination with the increase of y-irradiation dose has apparently the same origin as the changes in seed germination during accelerated ageing.     

The effects of time of seed production on the germination response of Spergularia marina

Germination studies were carried out with seeds of Spergularia marina L. Griseb produced over an interval of six months (June-November). The response of the seeds to light and dark, various constant and alternating temperature regimes, and salinity were determined. In addition, the effects of soil moisture status at the time of seed production on the subsequent germination response of seeds were also determined. Light was an absolute requirement for germination. While a constant temperature regime did not generally favour germination of seed of any month, alternating temperature greatly enhanced germination with an optimum at 5/15°C in all seeds. When imbibed in solutions of different salinities, seeds collected in July and October behaved like true halophyte seeds whereas those collected in June. August, September and November behaved like glycophyte seeds.
High concentration of gibberellic acid (3 000 μ M ) stimulated dark germination in the June and November seed lots, but in light, low GA3 concentration (300 μ M ) stimulated germination most. The addition of kinetin (30 μ M ) plus gibberellic acid enhanced germination in the dark in contrast to GA3 alone; kinetin alone stimulated a very low percentage germination.
The moisture status of the soil at the time seeds were produced did not affect the germination response of an early seed crop (July) but affected that of the later seeds (August).
Judging from the different germination responses, it appears that the seeds belong to at least two physiological groups, one which appears to need either a dark-wet or cold-wet pretreatmem for high germination to occur; and the other group which does not need pretreatmem. The ecological significance of these varied responses is discussed in relation to the survival of the species in its habitat.     

Decrease in glucose-stimulated insulin secretion following exposure to magnetic fields

We evaluated the effects of extremely low frequency magnetic field (ELFMF) on glucose-stimulated insulin secretion from HIT-T15 cells and investigated the mechanisms of these effects. We demonstrated that exposure to ELFMF at 5mT decreased glucose-stimulated insulin secretion by preventing the increases in cellular adenosine 5'-triphosphate/adenosine 5'-diphosphate, membrane depolarization, and cytosolic free calcium ion concentration. The glucose-induced upregulation of insulin mRNA expression was also attenuated by exposure to ELFMF, although cell viability was not affected. These findings demonstrate the potential of exposure to ELFMF for clinical use as a novel inhibitory method of insulin secretion.     

Cytokinin profile during early phase of germination of gram seeds after application of benzylaminopurine

Qualitative and quantitative differences in cytokinin levels of gram seeds were observed during germination of control and 6-benzylaminopurine (BAP; 4.44 x 10^t-5 M) treated seeds. Zeatin riboside (ZR), zeatin (Z), dihydrozeatin (DHZ), isopentenyladenosine (iPA) and isopentenyladenine (iP) were determined using high pressure liquid chromatography. In the control seeds the ZR content increased markedly only after 24 h of germination. In BAP treated seeds, the increase in ZR content was stronger than in control seeds and it persisted during further germination. Z content increased during germination in both control and treated seeds. After 48 h of germination iP appeared in control and especially in treated seeds. Acknowledgements: The senior author is thankful to University Grants Commision, New Delhi for award of Research Associateship.     

新疆干旱区植物藜的种子异型性及其萌发机理

新疆干旱区分布的植物藜(Chenopodium album)的种子有黑色和褐色两种类型。对藜的异型性种子从形态结构、不同环境因素及激素或化学物质对萌发的影响以及同工酶谱等方面进行了研究,并对其萌发及适应异质环境的机理进行了讨论。结果表明:(1)藜的异型性种子在形态结构、萌发休眠特性等方面都存在明显差异:黑色种子种皮厚且硬,休眠,萌发慢,萌发率低;褐色种子种皮薄而软,不休眠,萌发快且萌发率高;(2)黑色种子的休眠可通过切除胚根外缘种皮得以完全解除;(3)赤霉素、乙烯利对黑色种子的萌发无明显促进作用;KNO3可较显著促进黑色种子的萌发;协同使用乙烯利和KNO3时,可显著提高黑种子萌发率,完全打破休眠;(4)黑色种子和褐色种子的酯酶、过氧化物酶及过氧化氢酶同工酶谱带存在差异;(5)黑色种子的萌发需要光照,而褐色种子则对光不敏感;低温贮藏对二者的萌发均无显著影响,尽管黑色种子的萌发率有波动。研究结果初步显示黑色种子的休眠是内源(胚)和外源(种皮)因素共同所致。藜的种子异型性及其萌发机理的形成是其对新疆干旱区异质化环境的高度适应。     

Role and regulation of cAMP in seed germination of Phacelia tanacetifolia

Although adenosine 3',5'-cyclic monophosphate (cAMP) is known as a key second messenger in many living organisms, regulating a wide range of cellular responses, its biological function in higher plants is not well understood. In this study, the role and the regulation mechanism of cAMP in seed germination of Phacelia tanacetifolia Benth. were examined. The cAMP level of the seeds incubated under optimal conditions for germination showed a transient elevation before germination. When the seeds were exposed to light or supraoptimal temperature during incubation, elevation of cAMP levels as well as germination of the seeds were inhibited. Addition of membrane-permeable cAMP to the medium restored the germination rates of these seeds, suggesting that cAMP functions during germination. Treatment of the seeds with gibberellin (GA) was also effective to restore the elevation of cAMP levels and germination of the seeds. Uniconazole, a potent inhibitor of GA biosynthesis, blocked elevation of cAMP level under optimal conditions for germination. These results suggest that cAMP plays a role in the regulation of germination and that the cAMP level is regulated by GA in P. tanacetifolia seeds.     

Removal of the pericarp and testa of seeds of japonica and indica rice (Oryza sativa) at various oxygen concentrations has opposite effects on germination

The germination of intact, dehusked, and peeled seeds (caryopses) of the japonica rice cultivar Sasanishiki, harvested 30, 40, 47 and 60 days after anthesis, and of the indica rice cultivar Assam IV, harvested 14 and 28 days after anthesis, was examined. Dehusking strongly inhibited germination of Sasanishiki seeds, with the exception that seeds harvested 30 days after anthesis gave minimal germination percentages even when left intact. Peeling (removal of the pericarp and testa) restored or enhanced germination, and 60–100% of seeds germinated after 10 days. By contrast, the rank order of germination of Assam IV seeds was intact, dehusked, and peeled seeds, with peeled seeds yielding germination percentages of 100%. In Sasanishiki, inhibition of germination of peeled seeds was observed at reduced oxygen concentrations (1–4% oxygen). This inhibition might explain the inhibitory effects of dehusking on germination of seeds from the japonica cultivar. It is possible that the testa and pericarp, which cover the embryos of dehusked seeds, acted as a barrier to the diffusion of oxygen to the embryo.     

Extremely low frequency magnetic field and the hatching rate of Fasciola hepatica eggs, the fecundity and survival of liver fluke-infected snail, Lymnaea truncatula

Eggs of Fasciola hepatica were exposed for 10 days to extremely low frequency magnetic field (ELFMF) at the frequency of 50 Hz and density of 2 mT (rms). The results show an accelerated hatching of F. hepatica eggs in relation to control (non-exposed) group. The host snails, Lymnaea truncatula, were divided into three groups; those of groups I and II were infected with the miracidia of F. hepatica hatched from control egg culture, whereas those of group III were infected with miracidia hatched from eggs affected by ELFMF. Thereafter, snails of groups II and III were exposed to ELFMF for 53 days, whereas those of group I were not exposed. At day 14 post infection, a significant decrease was observed in the number of cocoons laid by snails of group III, compared with control. Also, significant mortality in group III snails was observed 42 days post infection. The increased mortality and a lower number of cocoons laid by group III snails have probably resulted from enhanced stimulation of metacercarial parthenogenetic reproduction in consequence of infecting the molluscs with miracidia reared under ELFMF.