Multidrug resistance increment in a human colon carcinoma cell line by colchicine

The most important mechanism in drug resistance is the multidrug resistance (MDR) phenomenon. It is possible to select MDR cells by in vitro exposure to cytotoxic agents. The resistance is due to the hyperexpression of the P-glycoprotein (P-Gp) that take drugs out from the cells. In this study, a colchicine resistant subline (HCA-2/1cch) was selected from a human colon adenocarcinoma after a short period of drug exposure, as an in vitro model of drug resistance selection. These cells showed cross-resistance to other drugs, which were not present in the medium during selection. The relative resistance was 3.32 for colchicine, 3.15 for vinblastine, 2.62 for vincristine and 5.22 for mitomycin C. P-glycoprotein levels were assayed by flow cytometry. It was found that a significant increase of 2.35 and 1.59 had occurred in the peak and mean channel of fluorescence, respectively, indicating an increment of P-glycoprotein expression in relation to the parental line. Moreover, verapamil (10 microg/ml) produced a partial reversion of multidrug resistance. The sensitisation rates were 7.41 for colchicine, 1.25 for vinblastine, 2.36 for vincristine and 1.17 for mitomycin C. The data obtained suggest that colchicine exposure period (10 weeks) and dose (0.5 microg/ml) assayed were sufficient to produce an increment in multidrug resistance. This resistance could be due to higher level of P-Gp expression.     

Effects of PEMF on a murine osteosarcoma cell line: drug-resistant (P-glycoprotein-positive) and non-resistant cells

After pulsed exposure of Dunn osteosarcoma cells (nonresistant cells) to Adriamycin (ADR) at increasing concentrations and single-cell cloning of surviving cells, ADR-resistant cells were obtained. These resistant cells expressed P-glycoprotein and had resistance more than 10 times that of their nonresistant parent cells. Compared to the nonresistant cells not exposed to pulsing electromagnetic fields (PEMF) in ADR-free medium, their growth rates at ADR concentrations of 0.01 and 0.02 micrograms/ml, which were below IC50, were 83.0% and 61.8%, respectively. On the other hand, in the nonresistant cells exposed to PEMF (repetition frequency, 10 Hz; rise time, 25 microsec, peak magnetic field intensity, 0.4-0.8 mT), the growth rate was 111.9% in ADR-free medium, 95.5% at an ADR concentration of 0.01 micrograms/ml, and 92.2% at an ADR concentration of 0.02 micrograms/ml. This promotion of growth by PEMF is considered to be a result of mobilization of cells in the non-proliferative period of the cell cycle due to exposure to PEMF. However, at ADR concentrations above the IC50, the growth rate tended to decrease in the cells not exposed to PEMF. This may be caused by an increase in cells sensitive to ADR resulting from mobilization of cells in the non-proliferative period to the cell cycle. The growth rate in the resistant cells exposed to PEMF was significantly lower than that in the non-exposed resistant cells at all ADR concentrations, including ADR-free culture (P相似文献   

Chondroprotective effects of pulsed electromagnetic fields on human cartilage explants

This study investigated the effects of pulsed electromagnetic fields (PEMFs) on proteoglycan (PG) metabolism of human articular cartilage explants from patients with osteoarthritis (OA). Human cartilage explants, recovered from lateral and medial femoral condyles, were classified according to the International Cartilage Repair Society (ICRS) and graded based on Outerbridge scores. Explants cultured in the absence and presence of IL-1β were treated with PEMF (1.5 mT, 75 Hz) or IGF-I alone or in combination for 1 and 7 days. PG synthesis and release were determined. Results showed that explants derived from lateral and medial condyles scored OA grades I and III, respectively. In OA grade I explants, after 7 days exposure, PEMF and IGF-I significantly increased (35) S-sulfate incorporation 49% and 53%, respectively, compared to control, and counteracted the inhibitory effect of IL 1β (0.01 ng/ml). The combined exposure to PEMF and IGF-I was additive in all conditions. Similar results were obtained in OA grade III cartilage explants. In conclusion, PEMF and IGF-I augment cartilage explant anabolic activities, increase PG synthesis, and counteract the catabolic activity of IL-1β in OA grades I and III. We hypothesize that both IGF-I and PEMF have chondroprotective effects on human articular cartilage, particularly in early stages of OA.     

Pulsed electromagnetic field stimulation of bone marrow cells derived from ovariectomized rats affects osteoclast formation and local factor production

This study examined the effects of a specific pulsed electromagnetic field (PEMF) stimulation on osteoclast formation in bone marrow cells from ovariectomized rats and to determine if the signal modulates the production of cytokines associated with osteoclast formation. Adult female Wistar rats were subjected to bilateral or sham ovariectomy, and primary bone marrow cells were harvested at 4 days (Subgroup I) and 7 days (Subgroup II) after surgery. Primary bone marrow cells were subsequently placed in chamber slides and set inside solenoids powered by a pulse generator (300 micros, 7.5 Hz) for 1 h per day for 9 days (OVX + PEMF group). Others (INT, SHAM, and OVX groups) were cultured under identical conditions, but no signal was applied. Recruitment and authentication of osteoclast-like cells were evaluated by determining multinuclear, tartrate-resistant acid phosphatase (TRAP) positive cells on day 10 of culture and by pit formation assay, respectively. The PEMF signal caused significant reductions in osteoclast formation in both Subgroups I (-55%) and II (-43%). Tumor necrosis factor-alpha (TNF-alpha), interleukin 1beta (IL-1beta), and interleukin 6 (IL-6) in OVX + PEMF group of Subgroup I were significantly reduced at 5, 7, and 9 days as compared to OVX group. The results found in this study suggest that osteoclastogenesis can be inhibited by PEMF stimulation, putatively due to a concomitant decrease in local factor production. Bioelectromagnetics 25:134-141, 2004.     

Spontaneous expulsion of micronuclei by enucleation in the micronucleus assay

The effect of enucleation on the frequency of micronuclei induced by mitomycin C (MMC) and vincristine (VCR) was examined in mouse L-929 cells enucleated with cytochalasin B (Cyt-B). Approximately 30% of the L-929 cells became enucleated cells during the 8-h incubation in medium containing 8 micrograms/ml of Cyt-B. Using this enucleation technique, we estimated the reduction rate of 2 mutagen-induced micronuclei by enucleation. Treatment with MMC caused a dose-dependent induction of micronuclei in L-929 cells, with the reduction rate being 38.6% at the lowest dosage (0.0125 microgram/ml), which induced mostly mono-micronuclei in L-929 cells, and 6.8% at the highest dosage (0.1 microgram/ml), which induced many multi-micronuclei. Furthermore, VCR also induced micronuclei in a dose-dependent way in L-929 cells, and the same tendency for micronucleus reduction as with MMC was observed. The reduction rate of micronucleated cells by enucleation was estimated to be about 31-39% when the micronucleated cells contain mono-micronuclei. Therefore, the rate of reduction is affected by the number of micronuclei per cell, and the reduction depends on the increase in the number of micronuclei per cell.     

Therapeutic Effects of 15 Hz Pulsed Electromagnetic Field on Diabetic Peripheral Neuropathy in Streptozotocin-Treated Rats

Although numerous clinical studies have reported that pulsed electromagnetic fields (PEMF) have a neuroprotective role in patients with diabetic peripheral neuropathy (DPN), the application of PEMF for clinic is still controversial. The present study was designed to investigate whether PEMF has therapeutic potential in relieving peripheral neuropathic symptoms in streptozotocin (STZ)-induced diabetic rats. Adult male Sprague–Dawley rats were randomly divided into three weight-matched groups (eight in each group): the non-diabetic control group (Control), diabetes mellitus with 15 Hz PEMF exposure group (DM+PEMF) which were subjected to daily 8-h PEMF exposure for 7 weeks and diabetes mellitus with sham PEMF exposure group (DM). Signs and symptoms of DPN in STZ-treated rats were investigated by using behavioral assays. Meanwhile, ultrastructural examination and immunohistochemical study for vascular endothelial growth factor (VEGF) of sciatic nerve were also performed. During a 7-week experimental observation, we found that PEMF stimulation did not alter hyperglycemia and weight loss in STZ-treated rats with DPN. However, PEMF stimulation attenuated the development of the abnormalities observed in STZ-treated rats with DPN, which were demonstrated by increased hind paw withdrawal threshold to mechanical and thermal stimuli, slighter demyelination and axon enlargement and less VEGF immunostaining of sciatic nerve compared to those of the DM group. The current study demonstrates that treatment with PEMF might prevent the development of abnormalities observed in animal models for DPN. It is suggested that PEMF might have direct corrective effects on injured nerves and would be a potentially promising non-invasive therapeutic tool for the treatment of DPN.     

Electromagnetic effects on forearm disuse osteopenia: a randomized, double-blind, sham-controlled study

A randomized, double‐blind, sham‐controlled, feasibility and dosing study was undertaken to determine if a common pulsing electromagnetic field (PEMF) treatment could moderate the substantial osteopenia that occurs after forearm disuse. Ninety‐nine subjects were randomized into four groups after a distal radius fracture, or carpal surgery requiring immobilization in a cast. Active or identical sham PEMF transducers were worn on the distal forearm for 1, 2, or 4 h/day for 8 weeks starting after cast removal (“baseline”) when bone density continues to decline. Bone mineral density (BMD) and bone geometry were measured in the distal forearm by dual energy X‐ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) at entry (“baseline”) and 8, 16, and 24 weeks later. Significant average BMD losses after baseline were observed in the affected forearm at all time points (5–7% distally and 3–4% for the radius/ulna shaft). However, after adjusting for age, gender, and baseline BMD there was no evidence of a positive effect of active versus sham PEMF treatment on bone loss by DXA or pQCT for subjects completing all visits (n = 82, ～20 per group) and for an intent‐to‐treat analysis (n = 99). Regardless of PEMF exposure, serum bone‐specific alkaline phosphatase (BSAP) was normal at baseline and 8 weeks, while serum c‐terminal collagen teleopeptide (CTX‐1) was markedly elevated at baseline and less so at 8 weeks. Although there was substantial variability in disuse osteopenia, these results suggested that the particular PEMF waveform and durations applied did not affect the continuing substantial disuse bone loss in these subjects. Bioelectromagnetics 32:273–282, 2011. © 2010 Wiley‐Liss, Inc.     

Optimum Parameters of Specific 7.5 Hz Single Pulsed Electromagnetic Field Stimulation on Osteoblast Growth

This study examines the response of different time constant 7.5 Hz pulsed electromagnetic field (PEMF) stimulation on rat osteoblasts and tries to determine the shortest exposure time to the selected time constant PEMF that is necessary to increase cell viability in vitro. We use an in vitro rat osteoblast model to investigate, for different periods of time (1, 2, or 3 days), rat osteoblasts to 7.5 Hz PEMF of different time constants (694, 432, and 268 µsec) or exposure time (20 min, 1, 3, 9, and 24 hr) and have evaluated the field's effects on the cell viability by colorimetric tetrazolium (MTT) assay and PGE₂ concentrations by enzyme‐linked immunosorbent assay (ELISA). It was shown that time constant was not the dominant parameter affecting osteoblast growth, and a short time exposure of PEMF 20 min/day could increase cell viability and PGE₂ secretion significantly.     

Effects of extremely low-frequency-pulsed electromagnetic field on different-derived osteoblast-like cells

The aim of this study is to investigate the effects of extremely low-frequency pulsed electromagnetic field (PEMF) on osteoblast-like cells. PEMF with a magnetic flux density of 1.55 mT at 48 Hz was employed to stimulate the MC3T3-E1 cell and the primary osteoblast cell derived from 2-day-old Sprague Dawley (SD) rat calvaria for different time. MTS method was applied to analyze cell proliferation and flow cytometry to detect cell cycle. The intracellular alkaline phosphatase (ALP) activity was measured by colorimetry. Our results demonstrated that PEMF of 1.55 mT at 48 Hz did not affect cell number of MC3T3-E1 cell, whereas the cell percentage of S and G(2)M phase decreased significantly. Although the cell number of the primary osteoblast cell did not alter by MTS assay after being exposed to PEMF for 24 h continuously, the cell percentage of S and G(2)M phase increased significantly. When culture time extended to 48 h, the cell number increased greatly and the cell percentage of S and G(2)M phase decreased significantly despite of the exposure type. After the primary osteoblast cell was exposed to PEMF for 24 h continuously, the ALP activity decreased significantly, whereas it increased significantly when being exposed to PEMF for 48 h continuously. From the results we concluded that PEMF of 1.55 mT at 48 Hz did not affect proliferation and differentiation of MC3T3-E1 cell, but it promoted proliferation, inhibited differentiation at proliferation stage, and promoted differentiation at differentiation stage of primary osteoblast cells.     

Extremely low frequency pulsed electromagnetic field designed for antinociception does not affect microvascular responsiveness to the vasodilator acetylcholine

A 225 µT, extremely low frequency, pulsed electromagnetic field (PEMF) that was designed for the induction of antinociception, was tested for its effectiveness to influence blood flow within the skeletal microvasculature of a male Sprague–Dawley rat model (n = 103). Acetylcholine (0.1, 1.0, or 10 mM) was used to perturb normal blood flow and to delineate differential effects of the PEMF, based on degree of vessel dilation. After both 30 and 60 min of PEMF exposure, we report no effects on peak perfusion response to acetylcholine (with only 0.2% of the group difference attributed to exposure). Spectral analysis of blood flow data was generated to obtain information related to myogenic activity (0.15–0.40 Hz), respiratory rate (0.4–2.0 Hz), and heart rate (2.0–7.0 Hz), including the peak frequency within each of the three frequency regions identified above, peak power, full width at half maximum (FWHM), and mean within band. No significant effects due to exposure were observed on myogenic activity of examined blood vessels, or on heart rate parameters. Anesthesia‐induced respiratory depression was, however, significantly reduced following PEMF exposure compared to shams (although exposure only accounted for 9.4% of the group difference). This set of data suggest that there are no significant acute physiological effects of 225 µT PEMF after 30 and 60 min of exposure on peak blood flow, heart rate, and myogenic activity, but perhaps a small attenuation effect on anesthetic‐induced respiratory depression. Bioelectromagnetics 31:64–76, 2010. © 2009 Wiley‐Liss, Inc.     

Correlation between pulsed electromagnetic fields exposure time and cell proliferation increase in human osteosarcoma cell lines and human normal osteoblast cells in vitro

We have exposed cultured bone cells to a pulsed electromagnetic field (PEMF) for different times to find the minimal exposure time necessary to stimulate an increase of DNA synthesis. We used two different human osteosarcoma cell lines, TE-85 and MG-63, and human normal osteoblast cell (NHOC) obtained from surgical bone specimens. The cells were placed in multiwell plates and set in a tissue culture incubator between a pair of Helmoltz coils powered by a pulse generator (1.3-ms pulse, repeated at 75 Hz) for different periods of time. [3H]Thymidine incorporation was used to evaluate cell proliferation. The two osteosarcoma cell lines increase their thymidine incorporation when exposed to a PEMF for at least 30 min, both in a medium containing 10% fetal calf serum and in a serum-free medium. NHOC are known to increase their cell proliferation when exposed to PEMF but only if cultured in the presence of 10% fetal calf serum. In this experimental condition, three of the four cell lineages studied required at least 9 h of PEMF exposure to increase their DNA synthesis, whereas one cell lineage increased its cell proliferation after 6 h of PEMF exposure. Our observations confirm the hypothesis that the proliferative responses of NHOC and human osteosarcoma cell lines to PEMF exposure are quite different. Moreover, NHOC required minimal exposure times to PEMF to increase their cell proliferation, similar to that needed to stimulate bone formation in vivo.     

Effects of pulsing electromagnetic fields on the prenatal and postnatal development in mice and rats: in vivo and in vitro studies

Electromagnetic fields (EMF) might have various biological effects on the developing embryo. We studied the effects of pulsing electromagnetic fields (PEMF) on the in vitro development of preimplantation mouse embryos and of early somite rat embryos as well as on the in vivo development of rat embryos. We used PEMF at frequencies of 1, 20, 50, 70, and 100 Hz with a tension of 0.6 V/m. The embryos were exposed to PEMF throughout the experimental period. PEMF at frequencies of 20 and 50 Hz were embryotoxic, inhibiting over 50% of blastocysts from hatching and further development, all within 72 h of culture. PEMF at frequencies of 50 and 70 Hz induced 22% and 30% incidence of malformations in 10.5 day old rat embryos after 48 h in culture. The main malformations were absence of telencephalic, optic, and otic vesicles and of forelimb buds. In addition, retarded growth and development manifested by fewer somites, reduction in crown-rump length, and retarded closure of the neural tube were found in many embryos. No significant pathological changes were found by TEM in PEMF-exposed embryos. Disappearance of microvilli and collapse of apical parts of endodermal cells were observed by SEM in many yolk sacs of embryos exposed to 50 and 70 Hz PEMF. A slightly reduced litter average, a reduction or increase of weight, and a delay in eye opening was observed among offspring of pregnant rats exposed throughout pregnancy to PEMF at frequencies of 20, 50, and 100 Hz. No malformations were observed among these offspring. The mechanism of PEMF-induced embryotoxicity and teratogeneity is unknown, as is the mechanism of the "protective effects" of the mother on the rat embryos exposed to PEMF in vivo.     

No effect of pulsed electromagnetic fields on PC12 and HL-60 cells

The effect of pulsed electromagnetic fields (PEMF) similar to those used in transcranial magnetic stimulation (TMS) on two tumour cell lines, the human promyelocytic leukaemia cell line (HL-60) and the rat pheochromocytoma cell line (PC12), was investigated. The two cell lines were exposed to non-homogeneous pulsed electromagnetic fields (about 0.25–4.5 T peak magnetic field strength; 1–8 exponential pulses, 0.25 Hz) at different positions on the coil (2×25 mm). After exposure with various intensities, various numbers of pulses and at different coil positions, cell viability and the intracellular cyclic AMP content were determined in the two cell lines. Additionally, in HL-60 cells the intracellular Hsp72 content and in PC12 cells the release of the neurotransmitters dopamine, noradrenaline and acetylcholine were measured after PEMF treatment. The results of these analyses do not hint at alterations in the cell viability or in the content of cAMP, Hsp72, dopamine, noradrenaline, and acetylcholine in the two tumour cell lines after PEMF exposure under various conditions.     

High-level resistance to Bacillus thuringiensis toxin crylac and cadherin genotype in pink bollworm

Resistance to transgenic cotton, Gossypium hirsutum L., producing Bacillus thuringiensis (Bt) toxin Cry1Ac is linked with three recessive alleles of a cadherin gene in laboratory-selected strains of pink bollworm, Pectinophora gossypiella (Saunders), a major cotton pest. Here, we analyzed a strain (MOV97-R) with a high frequency of cadherin resistance alleles, a high frequency of resistance to 10 microg of Cry1Ac per milliliter of diet, and an intermediate frequency of resistance to 1000 microg of Cry1Ac per ml of diet. We selected two strains for increased resistance by exposing larvae from MOV97-R to diet with 1000 microg of Cry1Ac per ml of diet. In both selected strains, two to three rounds of selection increased survival at 1000 microg of CrylAc per ml of diet to at least 76%, indicating genetic variation in survival at this high concentration and yielding >4300-fold resistance relative to a susceptible strain. Variation in cadherin genotype did not explain variation in survival at 1000 microg of Cry1Ac per ml of diet, implying that one or more other loci affected survival at this concentration. This conclusion was confirmed with results showing that when exposure to Cry1Ac stopped, survival at 1000 microg of Cry1Ac per ml of diet dropped substantially, but survival at 10 microg Cry1Ac per ml of diet remained close to 100% and all survivors had two cadherin resistance alleles. Although survival at 1000 microg of Cry1Ac per ml of diet is not required for resistance to Bt cotton, understanding how genes other than cadherin confer increased survival at this high concentration may reveal novel mechanisms of resistance.     

Protection against focal cerebral ischemia following exposure to a pulsed electromagnetic field

There is evidence that electromagnetic stimulation may accelerate the healing of tissue damage following ischemia. We undertook this study to investigate the effects of low frequency pulsed electromagnetic field (PEMF) exposure on cerebral injury in a rabbit model of transient focal ischemia (2 h occlusion followed by 4 h of reperfusion). PEMF exposure (280 V, 75 Hz, IGEA Stimulator) was initiated 10 min after the onset of ischemia and continued throughout reperfusion (six exposed, six controls). Magnetic resonance imaging (MRI) and histology were used to measure the degree of ischemic injury. Exposure to pulsed electromagnetic field attenuated cortical ischemic edema on MRI at the most anterior coronal level by 65% (P < 0.001). On histologic examination, PEMF exposure reduced ischemic neuronal damage in this same cortical area by 69% (P < 0.01) and by 43% (P < 0.05) in the striatum. Preliminary data suggest that exposure to a PEMF of short duration may have implications for the treatment of acute stroke. © 1994 Wiley-Liss, Inc.     

Protective effect of ferulic acid on gamma-radiation-induced micronuclei, dicentric aberration and lipid peroxidation in human lymphocytes

In this study we examined radioprotective effect of ferulic acid (FA) on gamma radiation-induced dicentric aberration and lipid peroxidation with reference to alterations in cellular antioxidant status in cultured lymphocytes. To establish most effective protective support we used three different concentrations of FA (1, 5 and 10 microg/ml) and three different doses of gamma-radiation (1, 2 and 4 Gy). Treatment of lymphocytes with FA alone (at 10 microg/ml) gave no significant change in micronuclei (MN), dicentric aberration (DC), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) or glutathione peroxidase (GPx) activities when compared with normal lymphocytes; irradiation at 1, 2 and 4 Gy increased the MN and DC frequencies in a dose-dependent manner. Treatment with FA for 30 min before radiation exposure resulted in a significant decline of MN and DC yields as FA concentration increased. Compared to 1 Gy exposure alone, the extent to which FA (1 microg/ml) reduced the MN and DC yields was 75% and 50%, respectively. With 4 Gy irradiation, FA (10 microg/ml) decreased 45% MN and 25% DC frequencies. FA-pretreated lymphocytes (1, 5 and 10 microg/ml) showed progressively decreased TBARS levels after irradiation. Irradiation (1, 2 and 4 Gy) significantly decreased GSH levels, SOD, CAT and GPx activities in a dose-dependent manner. Pretreatment with 10 microg/ml of FA significantly (p<0.05) prevented the decreases in the radiation-induced GSH, SOD, CAT and GPx activities. These findings suggest potential use and benefit of FA as a radioprotector.     

Pulsed Electromagnetic Field Versus Whole Body Vibration on Cartilage and Subchondral Trabecular Bone in Mice With Knee Osteoarthritis

Pulsed electromagnetic field (PEMF) and whole body vibration (WBV) interventions are expected to be important strategies for management of osteoarthritis (OA). The aim of the study was to investigate the comparative effectiveness of PEMF versus WBV on cartilage and subchondral trabecular bone in mice with knee OA (KOA) induced by surgical destabilization of the medial meniscus (DMM). Forty 12-week-old male C57/BL mice were randomly divided into four groups (n = 10): Control, OA, PEMF, and WBV. OA was induced (OA, PEMF, and WBV groups) by surgical DMM of right knee joint. Mice in PEMF group received 1 h/day PEMF exposure with 75 Hz, 1.6 mT for 4 weeks, and the WBV group was exposed to WBV for 20 min/day with 5 Hz, 4 mm, 0.3 g peak acceleration for 4 weeks. Micro-computed tomography (micro-CT), histology, and immunohistochemistry analyses were performed to evaluate the changes in cartilage and microstructure of trabecular bone. The bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and trabecular number (Tb.N) increased, and bone surface/bone volume (BS/BV) decreased by micro-CT analysis in PEMF and WBV groups. The Osteoarthritis Research Society International (OARSI) scores in PEMF and WBV groups were significantly lower than in the OA group. Immunohistochemical results showed that PEMF and WBV promoted expressions of Aggrecan, and inhibited expressions of IL-1β, ADAMTS4, and MMP13. Superior results are seen in PEMF group compared with WBV group. Both PEMF and WBV were effective, could delay cartilage degeneration and preserve subchondral trabecular bone microarchitecture, and PEMF was found to be superior to WBV. Bioelectromagnetics. 2020;41:298–307 © 2020 Bioelectromagnetics Society     

DNA damage in rat lymphocytes treated in vitro with iron cations and exposed to 7 mT magnetic fields (static or 50 Hz)

The present study was undertaken to verify a hypothesis that exposure of the cells to static or 50 Hz magnetic fields (MF) and simultaneous treatment with a known oxidant, ferrous chloride, may affect the oxidative deterioration of DNA molecules.The comet assay was chosen for the assessment of DNA damage. The experiments were performed on isolated rat lymphocytes incubated for 3h in Helmholtz coils at 7 mT static or 50 Hz MF. During MF exposure, part of the cell samples were incubated with 0.01 microM H(2)O(2) and another one with 10 microg/ml FeCl(2,) the rest serving as controls.Lymphocyte exposure to MF at 7 mT did not increase the number of cells with DNA damage in the comet assay. Incubation of lymphocytes with 10 microg/ml FeCl(2) did not produce a detectable damage of DNA either. However, when the FeCl(2)-incubated lymphocytes were simultaneously exposed to 7 mT MF, the number of damaged cells was significantly increased and reached about 20% for static MF and 15% for power frequency MF. In the control samples about 97% of the cells did not have any DNA damage.It is not possible at present to offer a reasonable explanation for the findings of this investigation - the high increase in the number of lymphocytes showing symptoms of DNA damage in the comet assay, following simultaneous exposure to the combination of two non-cytotoxic factors -10 microg/ml FeCl(2) and 7 mT MF. In view of the obtained results we can only hypothesise that under the influence of simultaneous exposure to FeCl(2) and static or 50 Hz MF, the number of reactive oxygen species generated by iron cations may increase substantially. Further studies will be necessary to confirm this hypothesis and define the biological significance of the observed effect.     

消化道癌原代培养体外药敏试验的研究

目的 研究肠癌、胃癌、肝癌细胞在8种不同抗癌药物作用下的细胞抑制率,以筛选出敏感的化疗药物.方法 采用四甲基偶氮唑蓝着色法（MTT）,对97例消化道癌（43例肠癌、33例胃癌、21例肝癌）新鲜瘤组织进行原代细胞培养,同时进行顺铂（DDP）、丝裂霉素（MMC）、卡铂（CBP）、5-氟尿嘧啶（5-FU）、表阿霉素（EADM）、长春新碱（VCR）、羟基喜树碱（OPT）和环磷酰胺（CTX）8种常用化疗药物敏感检测,并对其结果作比较.结果 在肠癌中高度敏感率大于50%药物依次为MMC、5-FU、DDP、CBP.总敏感率大于50%的药物依次为DDP、MMC、5-FU、CBP.在胃癌中高度敏感率大于50%的药物依次为DDP、CBP.总敏感率大于50%的药物依次为DDP、CBP、MMC、5-FU、CTX、VCR.其中胃癌对CTX、VCR的敏感率明显高于肠癌细胞（P＜0.05）.肝癌细胞中高度敏感率＞50%的药物为零,而总敏感率＞50%的药物依次排序为MMC、EADM、CBP.结论 消化道肿瘤细胞对化疗药物的选择虽有一定共性,但同种肿瘤的不同个体对同种化疗药物的敏感性差异却存有显著性.体外检测消化道肿瘤对化疗药物的敏感性可为临床化疗提供指导.     

Evaluation of inflammatory biomarkers associated with oxidative stress and histological assessment of magnetic therapy on experimental myopathy in rats

The effect of pulsed electromagnetic field (PEMF) therapy, also called magnetic therapy, upon inflammatory biomarkers associated with oxidative stress plasma fibrinogen, nitric oxide (NO), L-citrulline, carbonyl groups, and superoxide dismutase (SOD) was evaluated through histological assessment, in rats with experimental myopathy.

The groups studied were: (A) control (intact rats that received PEMF sham exposures); (B) rats with myopathy and sacrificed 24 h later; (C) rats with myopathy; (D) rats with myopathy and treated with PEMF; and (E) intact rats treated with PEMF. Groups A, C, D, and E were sacrificed 8 days later. Myopathy was induced by injecting 50 μl of 1% carrageenan λ (type IV) once sub-plantar. Treatment was carried out with PEMF emitting equipment with two flat solenoid disks for 8 consecutive days in groups D and E, at 20 mT and 50 Hz for 30 min/day/rat. The biomarkers were determined by spectrophotometry. The muscles (5/8) were stained with Hematoxylin-Eosin and examined by optic microscopy. Quantitative variables were statistically analyzed by the Fisher test, and categorical applying Pearson's Chi Squared test at p < 0.05 for all cases.

In Groups B and C, the biomarkers were significantly increased compared to A, D, and E groups: fibrinogen (p < 0.001); NO, L-citrulline and carbonyl groups (p < 0.05); SOD (p < 0.01) as well as the percentage of area with inflammatory infiltration (p < 0.001).

PEMF caused decreased levels of fibrinogen, L-citrulline, NO, SOD, and carbonyl groups and significant muscle recovery in rats with experimental myopathies.