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At least 955 records · Page 53Linked to original sources
PubMed2005

Intensity-dependent effects of microwave electromagnetic fields on acetylcholinesterase activity and protein conformation in frog skeletal muscles.

BACKGROUND: This study was conducted to investigate the effects of continuous microwaves (2.45 GHz) of different field intensity on acetylcholinesterase activity and protein conformation in muscle fractions from frog skeletal muscles. MATERIALS/METHODS: [corrected] Acetylcholinesterase activity in samples from muscle homogenate fractions exposed for 30 min to microwaves of low (10 mW/cm2) or high (20 mW/cm2) intensity at almost constant temperature (1.8 degrees - 2.0 degrees C) was measured by spectrophotometry for three consecutive days after irradiation and compared with the activity in a sham-exposed fraction. Infrared spectroscopy (between 1400 cm(-1)-1800 cm(-1) was performed on the lyophilised fractions using Bruker IFS 113 v. RESULTS: A significant decrease in enzyme activity on the day of exposure (by 8.4% and 13.6% at high and low field intensity, respectively) was observed. Forty-eight hours later the decrease in enzyme activity in samples exposed to both high- and low-intensity microwaves was less than that in sham-exposed samples. Infrared spectroscopy data showed the Amide I band to be negligibly affected and the absorption maximum in the Amide II band to be significantly shifted from 1540 cm-' (shamexposed) to 1559 cm(1) (exposed) after irradiation. CONCLUSIONS: Exposure to microwaves results in non-thermal, intensity-dependent, prolonged modification of acetylcholinesterase activity in frog skeletal muscles traced up to 48 hrs after exposure. Infrared spectroscopy data argue for induced conformational changes in the secondary structure of muscle proteins: increased content of beta-structures, random coils, and amorphous structures, which were more expressed at low field intensity.

Acetylcholinesterase↗
PubMed1997

[Microwave extraction technique].

A new microwave aided extraction (MAE) technique is introduced in this paper. It gives the extraction method as well as reagents, equipment and conditions used in the technique. In temperature controlled pressurized vessels, polar solvent (eg. acetone) and the combinations of polar and non-polar solvents can be heated to approximately 100 degrees C above their normal boiling points. It is told that the higher the extraction temperature the more the recovery is. The ratio of polar to non-polar solvents affects not only the microwave heating rate but also the extraction recovery. The highest recovery ratios are gotten at the solvent ratio of three parts of acetone to two parts of hexane. We can see from the pesticides chromatogram with MAE, that very little break-down of endrin or DDT are detected and they are well below the EPA specified tolerance limits. We can find from the comparison of MAE with sonication and Soxhlet extraction techniques that microwave extraction technique has not only higher average recoveries (%) but also good precision (RSD, %). The data and comparison results illustrate that the microwave extraction is a rapid method (about 15 minutes) with less solvent consumption (about 30-50 mL), good recovery, and easy to be controlled automatically in comparison with the Soxhlet extraction, sonication and other extraction methods.

Chemical Fractionation↗
PubMed1997

[Analysis of ECG on the staffs exposed to microwave in the radio calling signal station].

321 electrocardiographies (ECG) from the staffs exposed to microwave in a radio calling signal station were analysed. The subjects exposed to microwave were female computer operators, who worked over six months in the station. 107 female non-exposers were served as control. The intensities of microwave in work site were below the standard (20-50 mW/m2). The abnormal prevalence of ECG in the exposed group was 27.73%, which was significantly higher than that in the control group (11.21%, P<0.01). The prevalence of sinus arrhythmia in exposed group (19.63%) was significantly higher than that in the control group (5.60%, P<0.01). The P-R intervals were also lengthened in exposed group [(0.1554+/-0.021) ms] than that in control group [(0.1487+/-0.0227) ms, P<0.01]. No significant differences were found in the heart rate, QRS intervals, Q-T intervals, sinus bradycardia, sinus tachycardia and left axis deviation between exposed and control groups (P>0.05). It suggested that computer operators exposed to microwave of lower intensity in the radio calling signal station might lead to sinus arrhythmia, due to the disorder of vegetative nerve system.

Arrhythmia, Sinus↗
PubMed2004

[Determination of trace zinc, manganese, cadmium and lead in aloe by microwave-digestion atomic absorption spectrometry].

A microwave digestion procedure was developed for the determination of trace Zn, Mn, Cd and Pb in aloe-leaf cuticle and aloe-leaf gelatin, using the obturated vessel microwave digestion system with a pressure controlling part, and the amounts of these trace metallic elements were determined by atomic absorption spectrometry after microwave digestion. The effects of the composition of digestion solution, the ratio of the sample to digestion solution, and the digestion time were studied. It is satisfactory to apply the microwave digestion procedure to the determination of Zn, Mn, Cd and Pb under the optimized condition with the recovery of 95.0% to 110.0% and RSD of 0.3% to 6.2%. The results show that this method is rapid and simple with low environmental contamination and complete digestion of the sample.

Aloe↗
PubMed2004

[Effects of 2450 MHz microwave on long-term potentiation of hippocampus and lipofuscin contents in rat brain].

OBJECTIVE: To study the mechanism of the effects of microwave on learning and memory. METHOD: Long-term potentiation (LTP) of hippocampus induced potential and lipofuscin content in rat brain were studied. After irradiated by a 2450 MHz microwave, rats hippocampus induced potential in vivo was recorded and lipofuscin content in the brain was measured by fluorospectrophotometry. RESULT: Continuous microwave with 10-25 mW/cm2 intensity could inhibit the amplitude of the population spike (PS) of weak and strong stimuli induced LTP with an intensity-effect relationship. At 25 mW/cm2, lipofuscin content was significantly higher than control and 10 mW/cm2 group (P<0.05). CONCLUSION: Continuous microwave with 10-25 mW/cm2 intensity impairs learning and memory by restraining hippocampus LTP and brain lipofuscin content.

Animals↗
PubMedDate not supplied

[Use of microwave ovens in the prevention of opisthorchiasis].

The studies were performed to evaluate the impact of microwave radiation on the larval stages of parasites and particularly on the survival of Opisthorchis metacercariae when fish was cooked in domestic microwave ovens. It was found to take less time to free fish and its products from Opisthorchis metacercariae in the microwave oven than that to cook the product completely. The performed experiments have shown that the use of microwave ovens to domestically prepare carps from unfavorable opisthorchiasis water reservoirs is an effective mean of freeing fishes from Opisthorchis metacercariae.

Animals↗
PubMed2005

Applications of microwave-assisted organic synthesis on the multigram scale.

This review presents a summary of reactions performed using microwave irradiation on a multigram scale. Results are described in the context of existing equipment, and equipment currently in development, for the processing of multigram to kilogram quantities of materials including single- and multimode microwave reactors and batch, batch-flow and continuous-flow systems. Although limited in number, reports found in the literature to date suggest that with appropriate controls, reproducible scale-up of microwave reactions is feasible and requires minimal re-optimization of laboratory-scale reaction conditions. This feature, along with the dramatic reductions in reaction time generally observed for microwave reactions suggests that application of this technology in process research could be beneficial.

Benzopyrans↗
PubMedDate not supplied

High-level microwave disinfection of dental gypsum casts.

PURPOSE: To test whether microwave oven irradiation can disinfect gypsum casts in compliance with current disinfection requirements, and to determine whether this procedure would be as effective as a validated method of chemical disinfection of impressions. MATERIALS AND METHODS: In 2 in vitro experiments, samples of 5 irreversible hydrocolloid impressions of a disinfected acrylic resin model were contaminated with suspensions of recommended test organisms Staphylococcus aureus and Pseudomonas aeruginosa, respectively. In 1 in vivo experiment, 10 impressions were made of 10 subjects. All impressions were poured and the resulting casts cut in 2 halves. One half of each cast was exposed to 5 minutes of irradiation in a microwave oven at 2,450 MHz and 900 W. The other halves were left untreated as controls. In a second in vivo experiment, 10 impressions were disinfected by immersion in a 0.07% solution of NaOCl at pH of about 10 for 3 minutes, and then poured. All casts were incubated aerobically in Bacto tryptic soy broth at 37 degrees C for 6 hours and assessed for bacterial growth by counting colony-forming units per milliliter (cfu/mL) of the culture. The results were analyzed using the Wilcoxon signed-rank test. RESULTS: Untreated gypsum casts showed cfu/mL counts with a median log value of 6, while microwave-irradiated ones had median cfu/mL counts of 0. Casts poured from chemically disinfected impressions demonstrated cfu/mL counts with a median log value of 4. CONCLUSION: Under the described conditions, microwave-irradiated gypsum casts satisfy current disinfection requirements, but gypsum casts poured from chemically disinfected impressions do not.

Alginates↗
PubMed2005

[Clinical efficacy of endoscopic epicardial microwave ablation for isolated atrial fibrillation].

OBJECTIVE: To assess the efficacy of endoscopic epicardial microwave ablation, a new completely endoscopic technique, for isolated atrial fibrillation (AF). METHODS: From July to October of 2004, 5 patients with isolated permanent AF underwent this procedure. We performed epicardial microwave ablation using FLEX10 probe under the guide of VasoView 5 endoscope. The probe was placed around left and right pulmonary vein orifices, the microwave application was set 65 W/90 s, and a continuous ablation line was obtained encircling the pulmonary veins. Echocardiography and electrocardiography were carried out in all patients before and after operation. RESULTS: Five patients received electrical conversion after ablation. Average ablation time was 35.0 min and average procedure time was 2.5 h without any procedure-related complications. At the 3-month, 6-month and 12-month follow-up, 4 patients (80%) were in sinus rhythm, associated with a reduced left atrial diameter and an improved cardiac function. CONCLUSION: Endoscopic epicardial microwave ablation for isolated atrial fibrillation appears to be safe and effective.

Adult↗
PubMed1991

ELISA incubation times can be reduced by 2.45-GHz microwaves.

The ELISA (Enzyme Linked Immuno Sorbent Assay) technique is widely applied in the field of immunology. The use of this technique implies several incubation periods, often requiring more than one hour each. Microwave irradiation is known to be very useful in accelerating different kinds of processes. This knowledge has led to the present study in which it is proved that 2.45-GHz microwaves are able to reduce ELISA incubation times. This time reduction of 50% or more concerns each of the four incubation steps of the specific indirect ELISA which is used to determine the amount of antibodies in NF90-hybridoma cell culture supernatants. These incubation steps involve the coating of the microtiter plate, the incubation with BSA against non-specific binding, and the incubations with the first and second antibody. Combinations of more microwave-influenced steps in one ELISA save a considerable amount of time. When in addition air is blown through the incubation fluid during microwaving, the extinction values are almost the same as those of conventionally performed ELISAs. Thus, a good match of power setting and irradiation time results in a total incubation time reduction from 5.5 hours to 2 hours in this particular ELISA. Carefully monitoring the temperature of the incubation fluids during irradiation with the use of a fiberoptic thermometer appeared to be of crucial importance in the development of an optimal procedure.

Enzyme-Linked Immunosorbent Assay↗
PubMed2006

[Long-term results of percutaneous sonographically-guided microwave ablation therapy of early-stage hepatocellular carcinoma].

OBJECTIVE: To evaluate the long-term results of percutaneous microwave coagulation therapy in the treatment of early hepatocellular carcinoma. METHODS: From May 1994 to June 2004, a total of 216 patients with 275 nodules of hepatocellular carcinoma whose diameter <or= 5 cm had undergone percutaneous microwave coagulation therapy (193 men, 23 women; mean age, 54.68 years). Institute review board approval and informed consent were obtained. Complete tumor necrosis rates, long-term survival rates, recurrence rates and the complications of the patients were analyzed. RESULTS: The mean follow-up period after microwave ablation was 40 months +/- 24 (range, 6 - 127 months). One hundred fifty-nine remained alive and consulted our hospital periodically as outpatients. Fifty-seven patients died. Complete tumor necrosis was seen in 95.64% (263/275) patients. One, 2, 3, 4 and 5-year cumulative survival rates were 94.87%, 88.81%, 80.44%, 74.97% and 68.63%, respectively. One, 2, 3, 4 and 5-year cumulative recurrence rates were 20.01%, 32.04%, 39.57%, 44.97% and 52.90%, respectively. Three patients have severe complications, including needle track implantation in one patient, biliary fistula in two patients. One patient died of pulmonary infection one week after the treatment. CONCLUSION: Sonographically-guided microwave coagulation therapy could make complete tumor necrosis in most cases of early hepatocellular carcinoma with low incidence of complications and this method has satisfactory long-term curative effect.

Adult↗
PubMedDate not supplied

Effectiveness of microwave irradiation on the disinfection of complete dentures.

PURPOSE: The purpose of this study was to evaluate the effectiveness of microwave irradiation on the disinfection of simulated complete dentures. MATERIALS AND METHODS: Eighty dentures were fabricated in a standardized procedure and subjected to ethylene oxide sterilization. The dentures were individually inoculated (10(7) cfu/mL) with tryptic soy broth (TSB) media containing one of the tested microorganisms (Candida albicans, Streptoccus aureus, Bacillus subtilis, and Pseudomonas aeruginosa). After 48 hours of incubation at 37 degrees C, 40 dentures were individually immersed in 200 mL of water and submitted to microwave irradiation at 650 W for 6 minutes. Forty nonirradiated dentures were used as positive controls. Replicate aliquots (25 microL) of suspensions were plated at dilutions of 10(-3) to 10(-6) on plates of selective media appropriate for each organism. All plates were incubated at 37 degrees C for 48 hours. TSB beakers with the microwaved dentures were incubated at 37 degrees C for 7 more days. After incubation, the number of colony-forming units was counted and the data were statistically analyzed by Kruskal-Wallis test (alpha = .05). RESULTS: No evidence of growth was observed at 48 hours for S. aureus, B. subtilis, and C. albicans. Dentures contaminated with P. aeruginosa showed small growth on 2 plates. After 7 days incubation at 37 degrees C, no growth was visible in the TSB beakers of S. aureus and C. albicans. Turbidity was observed in 3 broth beakers, 2 from P. aeruginosa and 1 from B. subtilis. CONCLUSION: Microwave irradiation for 6 minutes at 650 W produced sterilization of complete dentures contaminated with S. aureus and C. albicans and disinfection of those contaminated with P. aeruginosa and B. subtilis.

Acrylic Resins↗
PubMed2006

[Study of microwave-assisted extraction on total flavones content in Hibiscus manihot L. flower].

OBJECTIVE: To study the extraction process of the total flavones content in Hibiscus manihot L. flower. METHODS: it was investigated that effect of ethanol concentration, extracting time, power of microwave oven and Solid/Liquid ratio (g/mL) on total flavones content using the orthogonal design. RESULTS: The optimum microwave-assisted extraction conditions included: ethanol concentration of 70%, extraction time of 30s, the power of microwave oven of 360w, solid/liquid ratio of 1 : 50 (g/ml) and granularity < or = 80 pore. CONCLUSION: There are broad possibilities for the extraction of the total flavones content from Hibiscus manihot L flower using Microwave-assisted technigue.

Drugs, Chinese Herbal↗
PubMed2006

[Study on the membrane protein conformational changes and mechanisms of myocardial cell irradiated by pulse microwave].

Micro-Fourier transform infrared spectroscopy (FTIR) technique was applied to study the membrane protein conformational and functional changes of myocardial cell irradiated by pulse microwave. The results show that pulse microwave could influence the membrane protein structure markedly. The stretching vibration of lipid--CH2--, lecithoid C=O, amide I and II region was decreased or displaced. The secondary structures of membrane protein were also changed by irradiation. The percentage of alpha-helix and beta-pleated sheet structure decreased remarkably, and the disordering of secondary membrane proteins increased. All the above changes are correlated with the irradiation dosage. The results indicated that the integrality of myocardial cell membrane was injured by pulse microwave, and the membrane fluidity and stability decreased. Multi-biochemically active structures were damaged. Then all the changes could make a biochemical foundation of pathologic effects, which included membrane function decline, cell morphological change, configuration injuring and apoptosis etc. This paper is from a new view of protein conformation to explore the molecular pathologic mechanism of the damage caused by pulse microwave irradiation.

Animals↗
PubMed1991

[Microwaves in morphologic examinations: technologic progress or whim?].

Microwave-ovens shorten the time and eliminate or reduce the formaldehyde concentration in the process of tissue-fixation for light- and electron microscopy. These devices can be also applied in dehydration, and in impregnation of tissues with paraffin as well as in staining of paraffin or cryostat cut-slices. The use of microwaves improves results of immunohistochemical and ultracytochemical stainings. The best results are given by precise laboratory microwave-devices, but domestic microwave-ovens can be also used in this procedure.

Histocytochemistry↗
PubMed1991

Microwave ovens: mapping the electrical field distribution.

Uniformity of electric field intensity of microwaves within the microwave oven cavity is necessary to ensure even load-heating, and is particularly important in pathology procedures where small volume irradiation is carried out. A simple and rapid method for mapping electric field distribution, using reversible thermographic paint, is described. Spatial heating patterns for various positions, and the effects of introducing dummy loads to modify heating distributions, have been obtained for a dedicated microwave processor, and comparison made with a domestic microwave oven.

Electricity↗
PubMed1991

Determination of Cd, Cr, Cu, Pb and Zn in human semen by graphite furnace atomic absorption spectrometry after microwave sample dissolution.

Human semen samples were analyzed by graphite furnace atomic absorption spectrometry, using L'vov platforms and the method of standard additions, to determine their Cd, Cr, Cu, Pb and Zn content. The samples were analyzed directly and after conventional and microwave wet acid dissolution. Matrix modification, using magnesium and palladium nitrates and ammonium biphosphate solutions, was evaluated for the analysis of the microwave-digested samples. The best results were obtained for Cr, Cu and Zn using Pd(NO3)2, and a mixture of Mg(NO3)2 and Pd(NO3)2 solutions. The direct analysis of water-diluted semen produced inaccurate results with unacceptably high standard deviations. The results obtained for the microwave-dissolved samples showed relative standard deviation values within the range 0.63-8.4%. The analysis of spiked semen solutions showed recoveries of the added analytes ranging from 96 to 104%. The accuracy of the measurements was checked against the NIST 1,577a, bovine liver, standard reference material. Sample dissolution time was drastically reduced from 3-4 hours, using the conventional method, to approximately 8 minutes using the microwave-assisted wet acid digestion procedure.

Cadmium↗
PubMed1991

Microwave processing of permanent soft denture liners.

This article describes a technique of processing a resilient soft denture liner using microwave irradiation. The technique employs a specially designed flask that can be heated in a microwave oven. The flask can be either fabricated using commonly available dental laboratory materials or purchased commercially. The microwave polymerization of the resilient soft denture liner reduces the potential warpage of the denture base that can occur during the conventional process of boiling in water for 2 hours. Additionally, microwave irradiation reduces processing time to less than 1 hour, allowing the dentist the opportunity to reline a patient's denture in a single visit. The technique is simple and requires no extensive or elaborate dental laboratory equipment.

Denture Liners↗