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At least 973 records · Page 54Linked to original sources
PubMedDate not supplied

Comparison of microwave digestion with conventional wet ashing and dry ashing digestion for analysis of lead, cadmium, chromium, copper, and zinc in shellfish by flame atomic absorption spectroscopy.

A closed vessel microwave digestion procedure was developed for shellfish samples. This procedure was compared with wet and dry ash procedures for levels of lead, cadmium, chromium, copper, and zinc. Results obtained for microwave and conventional wet ash digestion were comparable. The dry ashing procedure produced results consistently lower than either of the other methods. Recoveries ranged from 80-92% for microwave and wet ashing procedures and 54-72% for the dry ashing procedure. Accuracy was also determined by analyzing lobster hepatopancreas marine reference material. Values for Pb, Cd, and Cr fell within the range specified for the reference material for all 3 digestion procedures; however, values were lower for Cu and Zn. Results of this study show that microwave digestion is comparable to wet ashing.

Animals↗
PubMedDate not supplied

Comparison of microwave-polymerized denture base resins.

Three denture base resins, two designed for microwave polymerization and one for host-water-bath-processing, were compared. Results indicated that all four tested thicknesses (3, 6, 11.6, and 17.7 mm) of the water-bath-polymerized samples and one of the microwave-polymerized resins were porosity-free. When the water-bath-polymerized material was microwave processed, porosity was found when resin thickness exceeded 3 mm. When one resin designed for microwave polymerization was irradiated using the high-wattage (513 W), shorter cycle (4 minutes 52 seconds), porosity also occurred when the thickness exceeded 3 mm. Porosity did not occur until there was 9 mm of thickness when the lower-wattage (75.9 W), longer cycle (15 minutes 26 seconds) was used. No significant differences in transverse strength or hardness were noted between the materials.

Denture Bases↗
PubMed1990

[Noncontact and noninvasive microwave biological measurements].

Without contact probes, the signals of small human body surface movements were obtained with microwave Doppler sensors using a two-phase interferometric method. The signals were then compared with mechanocardiographic records routinely obtained by contact transducers. Furthermore, this system was applied to patients wearing clothes. The study subjects consisted of 20 cardiac patients and 10 normal controls. 1. The microwave signals obtained in the cervical and precordial regions were similar to those of the mechanocardiographic recordings, such as the carotid pulse and jugular venous pulse tracings and the apexcardiogram. There was a significant correlation between left ventricular ejection time (LVET) obtained by microwave Doppler sensors and that by the carotid pulse tracing (r = 0.95). 2. The signals of the microwave Doppler sensor were obtained from the patients wearing clothes. The heart beat components were distinguished from respiratory motion and patients' movements using band-pass filters. These results suggest that this method is capable of evaluating cardiac function noninvasively and thus has a distinct advantage in the field of non-contact measurements.

Heart Function Tests↗
PubMed1990

[Clinical research on hyperthermia of cancer using microwave heating equipment of lens applicator type].

Ninety cases with 96 tumors were treated by the 430 MHz microwave heating systems, HTS-100, at Tokyo Metropolitan Komagome Hospital, Kyoto University and Aichi Cancer Center. The results of treatment were analyzed, and the following have been clarified. Three cases are demonstrated showing feature of HTS-100. 1) The results of 383 sessions of heating by HTS-100 were analyzed, and it has been clarified that even the larger tumors, more than 5 cm both in size and depth, can be heated satisfactorily to temperatures higher than 42 degrees C. This system is capable of heating remarkably wider areas compared with the conventional microwave heating systems. 2) Hyperthermia by HTS-100 and radiotherapy were combined for treatment. The success rate (total percentage of CR plus PRa) of 89 cases analyzed was as high as 66.3%. Furthermore, local heating was successful for 60.7% of tumors, larger than 5 cm and deeper than 4 cm. 3) Combination of microwave heating and RF wave heating is a new method which is helpful for expansion of indications. 4) The frequencies of side effects of HTS-100 heating were: pain, 15.6%; sensation of heat, 6.3%; burns, 3.6%. Most of side effects were transient and slight. The higher frequency of pain than the conventional microwave heating is attributable to expansion of heating area.

Adenocarcinoma↗
PubMed1985

Microwave enhancement of membrane conductance: calmodulin hypothesis.

It has been found that 2450 MHz microwave radiation increases membrane conductance in molluscan neurons. Analysis of this effect points to the important role of Ca++ in the mechanism of neuron microwave response. However, regulation of many intracellular processes is not a direct Ca++ effect, but is mediated through calmodulin, a Ca++-binding multifunctional protein. Furthermore, there is some evidence showing that Ca++ regulation of a Ca pump, endoplasmic reticulum Ca++ buffering, and Ca++-activated K+ conductance are mediated via calmodulin. Based on that, calmodulin is hypothesized to be a microwave susceptible protein, and a qualitative model of microwave enhancement of membrane conductance is suggested.

Animals↗
PubMed1978

A review of microwave oven safety.

The microwave leakage from current microwave ovens, which are manufactured to meet government emission standards, is reviewed. Typical leakage values imply exposure values well below the most conservative exposure standards in the world. A review of recent developments discloses increasingly stringent government regulation along with advances in techniques for suppression of microwave leakage. The nature of the leakage field is described and studies relating emission to exposure are reviewed. Field survey data are reviewed and it is found that the overwhelming majority of certified ovens in the field show leakage well below permissible limits with an increasing degree of certainty as time goes on. The conclusion is that microwave ovens are not only just as safe as they were in 1973 but they are being accepted as safe under essentially equivalent emission regulations in various countries including those in Eastern Europe.

Canada↗
PubMed1989

[Clinical study of the surgical treatment of hepatocarcinoma with an implantable microwave device].

This article reports the surgical treatment to 51 patients with mid and advanced hepatocarcinoma by the self-made implantable microwave radiation apparatus from April, 1987 to April 1989. By way of histology, histochemistry, and electronic microscopy, we studied the killing effect on cancer cells, the range of the effect and the remarkable hemostatic mechanism of this implantable microwave device. Clinically, we developed six different methods of operate with the microwave. Without the need of blocking hepatic portal, this new approach simplifies the operation. The risk of iatrogenic cancerous diffusion and hemorrhage is also greatly reduced or prevented in hemihepatectomy. Initial results shows that the resection rate of the hepatocarcinoma went up from 20-42.5 percent to 74.5 percent. Microwave operation on 38 patients with advanced hepatocarcinoma reveals a survival rate of 75 percent over 6 months. The authors believe that this new operative method is effective in the treatment to advanced hepatic carcinoma, and prolongs the life of the patients.

Adolescent↗
PubMed1988

[Digital noninvasive microwave thermography in the diagnosis of breast disease].

Thermography is a noninvasive technic of examination. Liquid-Crystal Thermography and Infrared Thermography have provided great help in the general survey of breast diseases during the past twenty years but not without some limitations. Recently, by applying the microwave technic clinically, progress has been made to measure minute temperature changes in the deeper tissues. Differential diagnosis of breast disease is possible by statistical calculating the temperature difference of the two breasts. A prospective study was done in 96 women who had both X ray mammography and digital noninvasive microwave thermography. 70/96 were proved by pathology. In this group of patients, the accuracy rate was 70.00% for digital microwave thermography, 81.82% for X ray mammography and 95.50% for the two combined. The false positive rates and false negative rates, advantages, disadvantages and the for general survey of breast disease of the digital microwave thermography discussed.

Adenofibroma↗
PubMed1988

Microwave sterilization of Candida on underwear fabric. A preliminary report.

Candida-contaminated underwear might not be sterilized by ordinary laundering. The effectiveness of microwaving against Candida albicans on fabric was therefore determined. Swatches of Candida-impregnated cotton underpants fabric were subjected to domestic microwaving at the high setting for up to 30 minutes. If the fabric was microwaved dry, the Candida organisms survived. If the fabric was moistened, sterilization occurred within five minutes. Microwaving wet, freshly laundered cotton underpants should sterilize residual Candida and reduce the risk of reinfection.

Candida albicans↗
PubMed1987

[Fundamental study of differential hypothermia treatment of brain tumor using an interstitial microwave antenna].

An interstitial microwave antenna system was devised for differential hypothermia treatment. It was evaluated for its ability to induce localized brain hyperthermia in hypothermic monkey. Ten brain hyperthermia trials have been performed in 6 monkeys. Under general anesthesia, the animals were put into ice water bath to keep the total body temperature at 30 degrees C. Following parieto-occipital craniectomy, a microwave antenna of 1.5 mm in diameter was inserted into the brain at depth of 2 cm, and the brain tissue was heated by 2450 MHz microwave irradiation. Thermal distribution was measured by thermistor probes and local cerebral blood flow (1-CBF) before and after heating was simultaneously measured by hydrogen clearance method. After the experiment, the animals were sacrificed and histopathological changes of the heated brain tissue were studied. Under total body hypothermia of 30 degrees C, the maximum cross-sectional diameter of the heated brain to 37 degrees C or above was about 4 cm. The temperature profile on the vertical plane presented a bell-shaped distribution. The 1-CBF of the heated brain increased with the elevation of the brain temperature and the blood flow at 37 degrees C is nearly twice as much as that of 30 degrees C. After one hour DH treatment, necrotic tissue was noted along the antenna axis where the temperature was maintained more than 50 degrees C, and this change was not recognized at a distance of 1 cm from the antenna where the temperature was maintained at 42 degrees C. This study indicates that interstitial microwave hyperthermia system can be used effectively to heat the localized brain tissue.

Animals↗
PubMed1987

Rapid microwave fixation of rat mast cells. I. Localization of granule chymase with an ultrastructural postembedding immunogold technique.

We defined the ultrastructural localization of chymase in rat peritoneal mast cells using standard aldehyde fixation and a newly described microwave fixation method (Login GR, Dvorak AM: Microwave energy fixation for electron microscopy. Am J Pathol 120: 230, 1985; Login GR, Stavinoha WB, Dvorak AM: Ultrafast microwave energy fixation for electron microscopy. J Histochem Cytochem 34:381, 1986) and postembedding immunogold labeling. Thin sections were exposed first to goat IgG anti-rat chymase and second to gold-conjugated rabbit Ig directed against goat IgG. By transmission electron microscopy, gold particles were localized to the matrix of cytoplasmic granules. Control sections treated with nonimmune sera did not exhibit labeling of mast cells. Thin sections treated simultaneously with purified rat mast cell chymase and anti-chymase antibody in competition studies, showed a marked reduction in granule staining. These findings demonstrate that a microwave fixation method can be used to rapidly fix cell suspensions for postembedding immunocytochemical studies.

Animals↗
PubMed1987

Evaluation of microwave-thawed canine plasma for transfusion.

Units of fresh-frozen canine plasma were thawed rapidly in a microwave oven, using a mean of 15.4 thawing periods of 10 seconds each. The activated partial thromboplastin times, the one-stage prothrombin times, concentrations of fibrinogen, factor-VIII coagulant activity, and von Willebrand factor antigen of microwave-thawed units were not significantly different from those measured in small aliquots of the same units thawed in a warm water bath (n = 5). Five dogs were given a unit of their own microwave-thawed plasma. During the 24 hours after infusion, no significant changes were measured in temperature, heart rate, or respiration rate. In addition, significant changes in PCV, total protein concentrations, estimates of platelet numbers, total RBC counts, total WBC counts, and differential WBC counts were not measured in blood specimens obtained before infusion and 24 hours after the infusion of microwave-thawed plasma.

Animals↗
PubMed1987

Microwave effects on plasmid DNA.

The exposure of purified plasmid DNA to microwave radiation at nonthermal levels in the frequency range from 2.00 to 8.75 GHz produces single- and double-strand breaks that are detected by agarose gel electrophoresis. Microwave-induced damage to DNA depends on the presence of small amounts of copper. This effect is dependent upon both the microwave power and the duration of the exposure. Cuprous, but not cupric, ions were able to mimic the effects produced by microwaves on DNA.

Copper↗
PubMed1986

Microwave facilitation of methylatropine antagonism of central cholinomimetic drug effects.

Pilocarpine-induced hypothermia and oxotremorine-induced tremors in mice are central cholinomimetic drug effects that are readily blocked by the muscarinic antagonist atropine. However, the quaternary ammonium derivative of atropine, methylatropine, is unable to block these cholinomimetic drug effects by virture of its inability to penetrate the blood-brain barrier (BBB) and blood-cerebral spinal fluid barrier (B-CSFB). Dose-response curves for pilocarpine and oxotremorine effects are not appreciably affected either by pretreatment with methylatropine (1.0 mg/kg) or by exposure to moderate-level microwave irradiation (2.45 GHz, 23.7 W/kg, CW, 10-min exposure). However, in mice receiving both the methylatropine pretreatment and microwave irradiation, the dose-response curves for both pilocarpine and oxotremorine effects were significantly shifted to the right, signifying a central anticholinergic action by methylatropine. These data indicate that a single acute exposure to a thermogenic level of microwave irradiation facilitates methylatropine antagonism of centrally mediated cholinomimetic drug effects. One possible explanation for this observation is that microwave radiation may enhance passage of quaternary ammonium compounds like methylatropine across the BBB and B-CSFB.

Animals↗
PubMed1985

Current and future foodservice applications of microwave cooking/reheating.

Microwave ovens are widely used in foodservice establishments; currently, they are used primarily for reheating. In comparison with conventional methods, approximately 75% less energy is required for microwave cooking or heating. In the future, it is possible that minimal microwave energy will be used to extend shelf life of foods. It is expected that "combination" convention or convection/microwave systems and conveyor microwave systems that can be electronically programmed will be widely used in the future. New food product designs and types of disposable packaging are available.

Food Service, Hospital↗
PubMed1984

[Combined therapy with microwave hyperthermia and adriamycin in MM2-bearing mice].

C3H/He mice were inoculated i.p. with synergic MM2 tumor cells(2 X 10(6) cells/mouse), and subsequently treated either by systemic hyperthermia induced by microwave irradiation (2450 MHz)alone, administration of ADM alone, or a combination of both. The mice were exposed to hyperthermia for 5 minutes everyday at an output of 10, 20 or 30 watts. ADM was administered i.p. for 3 days at dose levels of 0.025 mg/kg, 0.05 mg/kg or 0.075 mg/kg body weight. The mean survival time and the mean relative body weight were recorded. From these data, tumor-suppressing effects of the treatments were analysed by one-way or two-way variance analysis. Mice treated with 30-watt microwave irradiation survived significantly longer than control mice without treatment (P less than 0.05), as did mice treated with ADM alone (P less than 0.01). The mean relative body weight was similar among the microwave, ADM and control groups. When the mice were given microwave treatment combined with ADM, significant difference was observed in the mean survival time by one-way variance analysis (P less than 0.01), but no significant difference was observed by two-way variance analysis. The best condition of mice and the optimal dose of ADM still remain to be determined to facilitate more efficient tumor-suppression using this combination therapy.

Animals↗
PubMed1980

Heat activation of Bacillus spores by the use of microwave irradiation.

A study was conducted in which microwave irradiation and conventional waterbath treatment were compared as to their efficiency for heat-activating Bacillus spores. Spore suspensions were prepared from B. brevis, B. cereus, B. licheniformis, a lysogenic strain of B. megaterium (NRRL-B-3695), two strains of B. stearothermophilus, and B.Subtilis. Suspensions were either irradiated for 30 sec in a microwave oven, or conventionally heat-treated in the waterbath for 60 min at 60 degrees C, the serially diluted and plated onto nutrient agar. Colonies of each species from each treatment were isolated, and cultures were inoculated into several biochemical media. Spore suspensions heat-activated by microwave irradiation resulted in plate counts that were from 3% to 24% greater than from suspension heat-activated by conventional mean (60 degrees C for 60 min). There were no observed alterations in biochemical activities in any of the representative colonies from either of the two treatments. No induction of bacteriophage from lysogenic B. megaterium NRRL-B-3695 was observed in colonies from either of the two treatments. Microwave irradiation appears to be more efficient, less time-consuming, and at least as effective as heat activation by conventional waterbath treatment for Bacillus spores.

Bacillus↗
PubMed1983

Stability of cimetidine hydrochloride in admixtures after microwave thawing.

The stability of cimetidine hydrochloride in admixtures subjected to freezing and subsequent microwave thawing was studied. Admixtures containing cimetidine 300 mg were prepared using 18 50-ml bags of 5% dextrose injection and 18 100-ml bags of 0.9% sodium chloride injection. A sample for analysis of pH and drug concentration was withdrawn from each bag, and all admixtures were frozen for 28 days. Nine admixtures of each solution were thawed at room temperature and the other nine in a microwave oven until a final solution temperature of 24 +/- 2 degrees C was reached. An additional five cimetidine admixtures in 0.9% sodium chloride injection were prepared and irradiated in the microwave oven until boiling occurred for five seconds. Samples of all admixture solutions were withdrawn within 30 minutes of thawing and again at 24 +/- 2 hours after thawing to determine pH and cimetidine concentration. Concentrations were measured by high-performance liquid chromatography. Admixtures pH after thawing did not vary substantially from baseline values. A significant difference in cimetidine concentration for each solution was observed between samples drawn at 0 and 24 hours after thawing; drug concentrations in 5% dextrose increased by 5.9% while those in 0.9% sodium chloride decreased by 1.5%. Thawing method had no significant effect on drug concentration in either admixture solution. In the solutions and drug concentrations tested, microwave thawing did not affect cimetidine stability. Increases in cimetidine concentrations in 5% dextrose solution may have been attributable to greater insensible water losses produced by heating of the small 50-ml bags.

Chromatography, High Pressure Liquid↗