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At least 271 records · Page 15Linked to original sources
PubMed2002

[Effect of low-intensity microwave of on mitomycin C-induced genotoxicity in vitro].

OBJECTIVE: To study that low-intensity microwave whether or not enhances the genotoxic effects of mitomycin C(MMC) on human lymphocytes. METHODS: Single strand DNA breaks and chromosomal aberrations were measured by comet assay and cytokinesis-blocked micronucleus(CBMN) test in vitro when human lymphocytes were exposed to 2,450-MHz microwave (5.0 mW/cm2) alone and in combination with mitomycin C. RESULTS: In the comet assay, the average comet lengths of microwave group[(29.1 +/- 8.1) micron in male and (25.9 +/- 7.5) micron in female] were not significantly different from those of control groups [(26.3 +/- 6.6) and (24.1 +/- 4.3) micron respectively] (P > 0.05). The average comet lengths of MMC group(0.0125, 0.0250, 0.0500, 0.1000 microgram/ml) were significantly longer than those of control groups (P < 0.01) and were increased with the dose of MMC. The average comet lengths of microwave combined with MMC (MW + MMC) also were increased with the doses of MMC and were significantly longer than those of control groups (P < 0.01). When MMC was > or = 0.0250 microgram/ml, microwave and MMC synergistically increased the single strand DNA breaks. In the micronucleus test, the average micronucleus rates of microwave groups were not higher than those of control groups (P > 0.05). The average micronucleus rates of MMC groups and MW + MMC groups were significantly higher than those of control groups (P < 0.01) when MMC was > or = 0.0500 microgram/ml. The average micronucleus rates of MW + MMC groups seemed higher than those of corresponding MMC groups, however the difference was not significant (P > 0.05). CONCLUSION: Low-intensity(2,450-MHz) microwave did not induce DNA and chromosome damages on human lymphocytes, but enhanced the effects of DNA breaks induced by MMC.

Chromosome Aberrations↗
PubMed2003

[Effect of low-intensity microwave radiation on proliferation of cultured epithelial cells of rabbit lens].

OBJECTIVE: To compare the effects of different doses of microwave on the proliferative activity and cell cycle of cultured epithelial cells of rabbit lens, and to investigate the limit tolerant of microwave exposure. METHODS: Cultured epithelial cells of rabbit lens were exposed to microwave radiation with frequency of 2,450 MHz and power density of 0.10, 0.25, 0.50, 1.00, 2.00 mW/cm(2) for 8 h in vitro. HE staining was used to observe the morphological changes of lens epithelial cells, the proliferative activity and cell cycle were measured by MTT assay and PI fluorescent staining. RESULTS: 8 h after radiation, 0.50, 1.00 and 2.00 mW/cm(2) microwave could decrease the proliferation of lens epithelial cells, make the cells disordered arrangement, shrinkage, detachment, and inhibit the synthesis of cell DNA. The percentage of G(0)/G(1) phase cells were 71.95% +/- 2.12%, 75.68% +/- 3.35% and 82.40% +/- 8.68% respectively, which were higher than that in control group (61.68% +/- 5.76%, P < 0.05 or P < 0.01). The percentage of S phase cells were 19.32% +/- 3.07%, 16.08% +/- 4.91% and 12.98% +/- 8.08% respectively, which were lower than that in control group (28.05% +/- 5.12%, P < 0.05 or P < 0.01). No obvious changes could be detected in 0.10, 0.25 mW/cm(2) microwave groups (P > 0.05). CONCLUSION: Microwave exceeding 0.50 mW/cm(2) may make injury to lens epithelial cells after 8 hour radiation, which may be related to the effect of microwave radiation on cell cycle.

Animals↗
PubMed2004

[Effect of microwave irradiation on neurocyte mitochondrial ultrastructure and mtTFA mRNA expression in rats cerebral cortex and hippocampus].

OBJECTIVE: To explore molecular controlling mechanism of mitochondrial injury induced by different density of microwave irradiation. METHODS: Rats were exposed to microwave irradiation for 1 hour at average power density of 3 mW/cm(2) or 30 mW/cm(2). After microwave irradiation, the changes of pathological ultrastructure of rat cerebral cortex and hippocampus were observed by electron microscope, and mitochondrial transcription factor A (mtTFA) mRNA expression level were determined by RT-PCR. RESULTS: After 3 mW/cm(2) microwave irradiation for 0, 3, 24 h, mitochondrial ultrastructure and mtTFA mRNA expression level didn't significantly change in rat cerebral cortex and hippocampus. After 30 mW/cm(2) microwave irradiation for 0, 3, 24 h, mitochondrial ultrastructure obviously changed, mtTFA mRNA expression in rat hippocampus significantly increased by 67.00%, 80.00%, 30.00% respectively, and in rat cerebral cortex by 133.00%, 86.00%, 233.00% respectively. There were significant differences between the corresponding groups of hippocampus and cerebral cortex (P < 0.01). CONCLUSION: No obvious change in mitochondria was found after 3 mW/cm(2) microwave irradiation, but it was found after 30 mW/cm(2) microwave irradiation. Mitochondria injury in cerebral cortex was more severe than that in hippocampus. mtTFA mRNA may have certain regulation in mitochondrial energy metabolism.

Animals↗
PubMed2004

[Low-intensity microwave blockes cell cycle and regulate cell cycle related gene expression in rabbit lens epithelial cells].

OBJECTIVE: To study the cell cycle arrest induced by different doses of microwave in cultured rabbit lens epithelial cells (RLECs) and its effects on the related gene expression of P21(WAF1), P27(Kip1) and c-myc. METHODS: Cultured rabbit lens epithelial cells were exposed to microwave radiation with frequency of 2450 MHz and power density of 0.10 mW/cm(2) (A group), 0.25 mW/cm(2) (B group), 0.50 mW/cm(2) (C group), 1.00 mW/cm(2) (D group) and 2.00 mW/cm(2) (E group) for 8 hours. The morphological change of RLECs was observed under microscope, effects of microwave radiation on RLECs cell cycle were measured by flow cytometry. Expression of P21(WAF1), P27(Kip1) and c-myc were evaluated by western blot after 2.00 mW/cm(2) microwave radiation for 4 hours, 6 hours and 8 hours respectively. All the results were compared with F group, which was as controls without microwave radiation. RESULTS: 8 hours after radiation, RLECs of C, D and E groups showed RLECs cell swelling, congregation and detachment, the percentage of cells in G(0)/G(1) phase obviously was increased (P < 0.01). No obvious change could be detected in 0.10 mW/cm(2) and 0.25 mW/cm(2) microwave groups. The gene expression of P27(Kip1) was increased and c-myc was decreased after 2.00 mW/cm(2) radiation, it did not affect the gene expression of P21(WAF1). CONCLUSION: Microwave exceeding 0.50 mW/cm(2) can block RLECs cell cycle at G(0)/G(1) phase, which may be related to regulation of P27(Kip1) and c-myc expression, but not P21(WAF1).

Animals↗
PubMed2005

Microwave-stimulated formaldehyde fixation of experimental renal biopsy tissues: computerised morphometric analysis of distortion artefacts.

Although microwave irradiation has been used in the histopathology laboratory for several years, there has been minimal published experimental data on its effects on the technical and staining quality of histological sections. Furthermore, it has not been clear whether the advantages gained in reduction of fixation and staining duration has been at the expense of increasing architectural distortion to the tissues. We report here our experience with computerised morphometric analysis to investigate glomerular artifacts caused by microwave-stimulated fixation of renal tissues. 39 rat and 33 human autopsy kidney samples were subjected to (1) fixation in neutral buffered formaldehyde (control), (2) microwave-stimulated fixation followed by neutral buffered formaldehyde, and (3) neutral buffered formaldehyde followed by microwave irradiation. In addition, the effect of post-fixation in 70% ethanol was also investigated. Microwave irradiation was delivered through a dedicated laboratory microwave oven at 80% power and at 55 degrees C for 3 minutes. The different fixation methods were compared with regards to shrinkage (distortion) to glomerular structures (glomeruli and Bowman's spaces) on H and E sections, as determined by morphometric image analysis using a temporary assembled-system consisting of a trinocular microscope, a digital video camera and personal computer. A FlashPoint VGA 3.3 film-grabber card was used to capture images for morphometric analysis by using a Scion Image program. Morphometric analysis of glomerular structures showed that microwaves caused more shrinkage to the area bounded by the Bowman's capsule than the glomerulus proper, but post-fixation with ethanol reduced this shrinkage. These findings have implications on the logistics of tissue preparation of renal biopsies in clinical practice.

Animals↗
PubMed1991

No evidence for effects of mild microwave irradiation on electrophysiological and morphological properties of cultured embryonic rat dorsal root ganglion cells.

Effects of mild microwave treatment (1 hr, 37 degrees C) on the in vitro development of rat mechanically dissociated dorsal root ganglion (DRG) neurons were investigated to establish whether microwave irradiation effects exist on nervous tissue other than heat induced tissue fixation. Phase contrast microscopy and immunocytochemical neurofilament stainings did not reveal significant differences between irradiated (2 hr after isolation) and control cultures, maintained up till 21 days. The electrophysiological properties of microwave exposed and non-exposed DRG neurons were compared using the whole-cell patch-clamp technique. Control neurons, in culture for 0-12 days, were excitable. In cultured cells (1-12 days), microwaved 2 hr after isolation, the action potentials were similar to or slightly different from those of the control cells. No acute microwave effects were found on neurons irradiated after 1 day of culture. These results suggest that mild microwave irradiation has neither significant acute nor strong long-term effects on DRG culture development and DRG neuron membrane properties, consistent with the notion that microwave effects essentially are temperature effects.

Action Potentials↗
PubMed1988

Microwaves and the cell membrane. IV. Protein shedding in the human erythrocyte: quantitative analysis by high-performance liquid chromatography.

The erythrocyte responds to microwave fields by shedding at least 11 low-molecular-weight proteins of less than or equal to 31,000 Da, with components of 28,000-31,000 Da released during the destabilization of divalent calcium-protein bridges [R.P. Liburdy and P.F. Vanek, Radiat. Res. 109, 382-395 (1987)]. Significantly, protein shedding was shown to be restricted to exposure temperatures coinciding with the cell membrane phase/structural transition temperature, Tc, of 17-25 degrees C. We report here a further characterization of protein shedding at Tc using high-performance liquid chromatography and membrane-associated blood group antigen testing. Proteins shed from human erythrocytes in microwave fields (2450 MHz, CW) compared to sham-heating displayed a twofold increase in total protein mass released concomitant with the appearance of unique protein species during reverse-phase, hydrophobic interaction, and anion-exchange HPLC. These HPLC analyses indicate that microwaves result in the shedding of proteins which are relatively nonpolar and hydrophobic and which carry a net positive electrostatic charge compared to those released during sham-heat treatment. Assessment of 23 blood group antigens that represent integral protein markers on the erythrocyte cell surface indicates that microwave fields do not result in the exhaustive loss of these proteins. The class of proteins that is shed in response to microwave fields most likely is the loosely bound "peripheral" or extrinsic proteins associated with the exterior of the cell surface. Such proteins play a major role in the transduction of signals to integral membrane proteins which span the bilayer. That this class of proteins is susceptible to release by microwave fields is discussed in relation to microwave absorption at the cell surface by membrane-associated bound water, field interaction with dipolar side groups, and the disruption of divalent cation bridges known to stabilize peripheral membrane proteins.

Blood Proteins↗
PubMed1978

Microwave fixation versus formalin fixation of surgical and autopsy tissue.

Microwave irradiation of surgical and autopsy tissue penetrates, fixes, and hardens the tissue almost immediately (the fluid media used in the microwave consisted of saline, ten percent phosphate buffered formalin, and distilled water). Tissue sections from a representative sample of organs were tested. Comparable sections were simultaneously fixed in a phosphate buffered ten percent formalin bath in a vaccum oven as a control. Hematoxylin and eosin were used to stain the sections. Results equal to and superior to the control method were obtained. Saline microwave fixation was superior to formalin microwave fixation. Tissues placed in Zenker's solution and fixed in standard microwave oven (for approximately one minute) yielded results at least equal to conventional Zenker fixation (approximately two hours). No tissue hardening resulted from Zenker microwave fixation. A unique time versus temperature graph (microwave heating curve) reduces individual variation with this technique.

Autopsy↗
PubMed1979

Microwave cookery of beef patties: browning methods.

Four microwave cooking/browning methods were studied to determine their effects on energy consumption, cooking time, cooking losses, and sensory quality. Ground beef patties were cooked by the following methods: Microwave and browning element, microwave with browning grill, microwave and broiler, combination range oven, microwave only, and conventional range oven. Browning plus microwave cooking increased cooking time by 51 to 71 per cent and energy consumption by 53 to 87 per cent, depending on the method. The microwave-with-browning-grill method showed an over-all advantage over other browning methods. The combination range oven was the least efficient.

Animals↗
PubMed1984

Microwave and thermal interactions with oxidative hemolysis.

The influence of microwave radiation (2450 MHz, 3,333 pulses per second, duty factor of 0.02, and average specific absorption rate of 0.4 W/kg) on spontaneous hemolysis of human erythrocytes was examined. Cells were exposed to microwave radiation for 20 minutes at 37 degrees, 42 degrees, or 48 degrees C. Some of these cells were sensitized to oxidative damage by treatment with 1-chloro-2,4-dinitrobenzene (CDNB) and/or by coating with wheat germ agglutinin-horseradish peroxidase (WGA-HRP) conjugate. Microwave radiation significantly decreased spontaneous hemolysis of untreated cells at 42 degrees C but had no effect at 37 degrees or 48 degrees C. Microwave exposure significantly enhanced a CDNB membrane stabilizing effect at 42 degrees C but had no effect at 37 or 48 degrees C. At 42 degrees C, microwave exposure increased hemolysis of WGA-HRP coated cells. Cells treated with both WGA-HRP and CDNB showed no change in fragility at 42 degrees C and increased fragility at 48 degrees C without a microwave effect. The microwave effects observed appear to involve perturbation of the thermal threshold for oxidative hyperthermic hemolysis.

Dinitrochlorobenzene↗
PubMed1983

Immunization with infective larvae of Strongyloides ratti (Nematoda) exposed to microwave radiation.

Microwaves have not been tested previously for possible application in producing immunogenic preparations of parasites. This study examines the immunizing capacity of microwave-irradiated, infective larvae of Strongyloides ratti in rats. Rats were inoculated subcutaneously with untreated, microwaved, or microwaved and homogenized larvae, or distilled water, and challenged with untreated larvae. Data were collected on egg production and worm number/rat during primary infections and on egg production, worm number/rat, worm size, and eggs in utero/worm following challenge. Our results demonstrated that microwaved, infective larvae (intact or homogenized) of S. ratti were immunogenic for rats, even though they were incapable of reaching the intestine and maturing to adult worms. The immunity elicited by exposure to microwaved larvae was characterized on challenge by a significant reduction in the number of eggs produced/worm, by the formation of perioral plugs, and by reductions in worm numbers and size. These results suggest that microwave radiation may provide a valuable new tool for parasitic vaccine production. In addition, we have demonstrated the occurrence of a feature of the immune response of rats to S. ratti that may have been overlooked previously; i.e., a gut-level response that was elicited by larvae, but manifested against adult worms in the intestine.

Animals↗
PubMed1983

Results of our 15-year study into the biological effects of microwave exposure.

The results obtained during 15 years of clinical and experimental examinations of biological microwave exposure effects are briefly surveyed. Some important results are reported. Based on their experience, the authors present their attitudes concerning harmful microwave effects on living matter. They consider that microwave effects, either direct or indirect, are the results of hyperthermia. Exposure of the living body to irradiation intensities not causing thermal effects do not induce important pathological alterations in the irradiated organisms. Also, it has been pointed out that the term "injury" is more suitable than the term "microwave sickness" when harmful effects of microwaves to the living organism are concerned. According to the authors, the term "microwave sickness" is not acceptable as a synonym for professional diseases of persons working with sources of microwave energy, since it refers to the complex of insufficiently defined symptoms of uncertain etiology.

Animals↗
PubMed1995

High-peak-power microwave pulses: effects on heart rate and blood pressure in unanesthetized rats.

INTRODUCTION: Exposure sources capable of generating high-peak-power microwave pulses, with relatively short pulse widths, have recently been developed. Studies of the effect of these sources on the cardiovascular systems of animals have not been reported previously. METHODS: We exposed 14 unanesthetized male Sprague-Dawley rats to 10 high-peak-power microwave pulses generated by a transformer-energized megawatt pulsed output (TEMPO) microwave source, at frequencies ranging from 1.2-1.8 GHz. Peak power densities were as high as 51.6 kW/cm2. At 14 d prior to irradiation, the animals were implanted with chronic aortic cannulae. With appropriate shielding of the transducer, blood pressure recordings were obtained during microwave pulsing. RESULTS: In a preliminary series of exposures at 1.7-1.8 GHz (peak power density 3.3-6.5 kW/cm2), an immediate but transient increase in mean arterial blood pressure (significant) and decrease in heart rate (non-significant) were observed. A loud noise was associated with each pulse produced by the TEMPO; this factor was subsequently attenuated. In a second series of exposures at 1.2-1.4 GHz (peak power density 14.6-51.6 kW/cm2), there were no significant changes in mean arterial blood pressure or heart rate during microwave exposure. CONCLUSIONS: The earlier significant increase in blood pressure that occurred during microwave exposure appeared to be related to the sharp noise produced by the TEMPO source. After appropriate sound attenuation, there were no significant effects of exposure to the microwave pulses.

Animals↗
PubMed1996

[US-guided microwave in the treatment of liver cancer: experimental study and preliminary clinical application].

OBJECTIVE: To completely coagulate deep tumor and protect normal tissue by using microwave electrode is vivo and in vitro animal experimental study, under US-guided percutaneous microwave coagulation. METHOD: The Ultrasound Microwave Therapy-I (UMT-I) equipment was utilized at 2450 MHz in frequency. RESULTS: Microwave coagulation could produce a stable necrosis area of 2cm in diameter with irradiation at 60-80W for 60-180 seconds, and the corresponding temperature at its surrounding area was 61.95 +/- 5.81 degrees C. Microwave induced coagulation of tumor correlated well with the sonographic changes. The shape of coagulated area was elliptic when 27 mm or 9 mm of the inner conductor of electrode was exposed, and the temperature of the shaft of the electrode raised smaller and slowly based on our animal experimental study, 15 nodules of 12 patients with liver cancer were microwave-coagulated under US-guide. The temperature of tumor surrounding area raised to 54-69.5 degrees C during operation. After treatment, all lesions had smaller size, hypoechogenicity and disappearance of blood flow. AFP titer dropped in 7 patients and normalized in 4. CONCLUSION: US-guided microwave for the treatment of liver cancer is effective in coagulating deep tumor and protecting normal tissue.

Animals↗
PubMedDate not supplied

Release of fumigant residues from grain by microwave irradiation.

Multiresidue analysis of fumigants is important because of their widespread use on staple foodstuffs, such as grain. Fumigants are usually extracted from grain either by solvent extraction or by purge-and-trap techniques. In this paper, fumigant residues in wheat were "extracted" by a microwave procedure. Wheat, in gas-tight Erlenmeyer flasks, was placed in a domestic microwave oven, and fumigants were released into the headspace by microwave irradiation. Power settings for maximum release of fumigants were determined for CH3Br, PH3, CS2, and COS. Recoveries of fortified samples were > 90%. Completeness of extraction was assessed from the amount of fumigant retained by the microwave-irradiated wheat. This amount, determined from both solvent extraction and from further microwave irradiation, was always small (< 5% of the amount obtained from the initial procedure). Limits of quantitation were < 1 ng/g for CH3Br, PH3, and CS2. These low limits were essentially due to the absence of interference from solvents. The microwave method is rapid and solvent-free. However, care is required in selecting the appropriate power setting. The safety implications of heating sealed flasks in microwave ovens should be noted.

Fumigation↗
PubMed2006

Microwave synthesis of nanoporous materials.

Studies in the last decade suggest that microwave energy may have a unique ability to influence chemical processes. These include chemical and materials syntheses as well as separations. Specifically, recent studies have documented a significantly reduced time for fabricating zeolites, mixed oxide and mesoporous molecular sieves by employing microwave energy. In many cases, microwave syntheses have proven to synthesize new nanoporous structures. By reducing the times by over an order of magnitude, continuous production would be possible to replace batch synthesis. This lowering of the cost would make more nanoporous materials readily available for many chemical, environmental, and biological applications. Further, microwave syntheses have often proven to create more uniform (defect-free) products than from conventional hydrothermal synthesis. However, the mechanism and engineering for the enhanced rates of syntheses are unknown. We review the many studies that have demonstrated the enhanced syntheses of nanoporous oxides and analyze the proposals to explain differences in microwave reactions. Finally, the microwave reactor engineering is discussed, as it explains the discrepancies between many microwave studies.

Journal Article↗
PubMed2002

Development of microwave-assisted drying methods for sample preparation for dried spot micro-X-ray fluorescence analysis.

Although dried spot micro X-ray fluorescence (MXRF) is an effective analytical technique for trace elemental analysis, the sample preparation procedures currently used suffer from a number of drawbacks. These drawbacks include relatively long preparation times, lack of control of the sample preparation environment, and possibility of loss of volatile analytes during the drying process. Microwave-assisted drying offers several advantages for dried spot preparation, including control of the environment and minimized volatility because of the differences between microwave heating and conventional heating. A microwave-assisted drying technique has been evaluated for use in preparing dried spots for trace analysis. Two apparatus designs for microwave drying were constructed and tested using multielement standard solutions, a standard reference material, and a "real-world" semiconductor cleaning solution. Following microwave-assisted drying of these aqueous samples, the residues were redissolved and analyzed by ICPMS. Effective recovery was obtained using the microwave drying methods, demonstrating that the microwave drying apparatus and methods described here may be more efficient alternatives for dried spot sample preparation.

Journal Article↗
PubMedDate not supplied

Automated library generation using sequential microwave-assisted chemistry. Application toward the Biginelli multicomponent condensation.

The concept of automated sequential microwave-assisted library synthesis is introduced. For this purpose a dedicated single-mode microwave reactor with a robotics interface including a liquid handler and gripper was employed. The liquid handler allows dispensing of reagents into the Teflon sealed reaction vials, while the gripper moves each sealed vial in and out of the microwave cavity after irradiation. This technology was employed for the Biginelli three-component cyclocondensation reaction. A diverse set of 17 CH-acidic-carbonyl compounds (1A-Q), 25 aldehydes (2a-y), and 8 urea/thioureas (3alpha-varphi) was used in the preparation of a dihydropyrimidine (DHPM) library. Out of the full set of 3400 possible DHPM derivatives, a representative subset of 48 analogues was prepared using automated addition of building blocks and subsequent sequential microwave irradiation of each process vial. For most building block combinations 10 min of microwave flash heating at 120 degrees C using AcOH/EtOH (3:1) and 10 mol % Yb(OTf)(3) as solvent/catalyst system proved to be successful, leading to an average isolated yield of 52% of DHPMs with >90% purity. For some building block combinations the general conditions were modified, for example, by changing the solvent, catalyst, reaction temperature, or irradiation time. This flexibility is a distinct advantage of sequential over parallel microwave-assisted processes where all reactions are exposed to the same irradiation conditions. When the unattended automation capabilities of the microwave synthesizer are used, a library of this size can be synthesized within 12 h.

Journal Article↗