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PubMed2003

Bioeffects of microwave--a brief review.

Since the 18th century scientists have been intrigued by the interaction of electromagnetic fields (EMFs) and various life processes. Attention has been focussed on EMFs in different frequency ranges, of which microwave frequency range forms an important part. Microwaves are part of the electromagnetic spectrum and are considered to be that radiation ranging in frequency from 300 million cycles per second (300 MHz) to 300 billion cycles per second (300 GHz), which correspond to a wavelength range of 1 m down to 1 mm. This nonionising electromagnetic radiation is absorbed at molecular level and manifests as changes in vibrational energy of the molecules or heat (Microwaves irradiating the community, Hidden hazards, Bantan Books publisher, Australia, 1991). Identifying and evaluating the biological effects of microwaves have been complex and controversial. Because of the paucity of information on the mechanism of interaction between microwave and biological systems, there has been a persistent view in physical and engineering sciences, that microwave fields are incapable of inducing bioeffects other than by heating (Health Physics 61 (1991) 3). Of late, the nonthermal effects of microwaves on tissue responses are being documented (Physiol. Rev. 61 (1981) 435; Annals of New York Acad. Sci. 247 (1975) 232; J. Microwave Power 14 (1979) 351; Bioelectromagnetics 7 (1986a) 45; Bioelectromagnetics 7 (1986b) 315; Biologic Effects and Health Hazards of Microwave Radiation, Warsaw, Polish Medical Publication (1974) 289; Biologic Effects and Health hazards of the microwave Radiation, Warsaw, Polish Medical Publication (1974) 22; Multidisciplinory perspectives in event-related brain potential research, Washington DC, US Environmental Protection Agency, (1978) 444). The present article is an attempt to familiarise the reader with pertinent information regarding the effects, mainly athermal, of microwave irradiation on biologic systems, especially microorganisms.

Animals↗
PubMed1993

Microwave dissociation of antigen-antibody complexes: a new elution technique to permit phenotyping of antibody-coated red cells.

To evaluate the effectiveness of microwave irradiation in dissociating IgG from red cells (RBCs), the use of chloroquine diphosphate (CDP) was compared to that of microwaves. Fifteen paired samples of RBCs from 15 patients with positive direct antiglobulin tests (DATs) were treated with both CDP and microwave radiation. Total microwave exposure times ranged from 20 to 100 seconds. Posttreatment DATs were performed, and the reaction grades of the posttreatment DATs were compared. RBC phenotyping was also performed on repeatedly microwaved RBCs to demonstrate possible effects on RBC antigen expression. Microwaves successfully reduced the reaction grade of the DAT in 14 of 15 samples; CDP reduced the reaction grade in 12 of 15 samples. In samples with a DAT of 2+ or greater (n = 13), the microwave method yielded a greater reduction in DAT strength in six cases (results in the other 7 cases were identical with both methods) (p = 0.01). Five of eight cases with a DAT of 3+ showed a greater reduction in the DAT with microwave treatment than with CDP treatment; results in the remaining three cases were identical (p = 0.03). RBC antigenicity remained unchanged after exposure to microwave radiation (A, B, C, c, D, E, e, Fya, Fyb, Jka, Jkb, K, k, S, and s). Microwave treatment required less than 10 minutes per sample, while CDP treatment required 30 to 120 minutes per sample (mean, 88 min). The microwave technique of antigen-antibody dissociation from RBCs provides a rapid and accurate method of facilitating the phenotyping of RBCs coated with warm autoantibodies and is superior to other methods, which destroy RBC antigens.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigen-Antibody Complex↗
PubMedDate not supplied

Migration testing of plastics and microwave-active materials for high-temperature food-use applications.

Temperatures have been measured using a fluoro-optic probe at the food/container or food/packaging interfaces as appropriate, for a range of foods heated in either a microwave or a conventional oven. Reheating ready-prepared foods packaged in plastics pouches, trays or dishes in the microwave oven, according to the manufacturers' instructions, resulted in temperatures in the range 61-121 degrees C. Microwave-active materials (susceptors) in contact with ready-prepared foods frequently reached local spot temperatures above 200 degrees C. For foods cooked in a microwave oven according to published recipes, temperatures from 91 degrees C to 200 degrees C were recorded, whilst similar temperatures (92-194 degrees C) were attained in a conventional oven, but over longer periods of time. These measurements form the basis for examining compliance with specific and overall migration limits for plastics materials. The testing conditions proposed depend on the intended use of the plastic - for microwave oven use for aqueous foods, for all lidding materials, and for reheating of foods, testing would only be required with aqueous simulants for 1 h at 100 degrees C; for unspecified microwave oven use, testing with olive oil would be required for 30 min at 150 degrees C; and for unspecified use in a conventional oven testing with olive oil would be required for 2 h at 175 degrees C. For microwave-active materials, it is proposed that testing is carried out in the microwave oven using a novel semi-solid simulant comprising olive oil and water absorbed onto an inert support of diatomaceous earth. The testing in this instance is carried out with the simulant instead of food in a package and heating in the microwave oven at 600 W for 4 min for every 100 g of simulant employed. There is an option in every case to test for migration using real foods rather than simulants if it can be demonstrated that results using simulants are unrepresentative of those for foods. The proposed testing conditions were validated as being realistic by measurement of the specific migration of various components from different plastics into foods under actual conditions of use and comparing with migration into simulants. Migration of plasticizers from PVC and VC/VDC copolymer films was monitored for both microwave reheating and cooking of foods. Total oligomer concentrations were measured from poly(ethylene terephthalate) (PET) trays, and volatile aromatics from thermoset polyester trays, using both types of container in microwave and conventional ovens.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipates↗
PubMed2005

Non-thermal microwave effects on protein dynamics? An X-ray diffraction study on tetragonal lysozyme crystals.

X-ray diffraction (XRD) was used to investigate the structural and dynamical effects of microwave fields on tetragonal single crystals of hen egg-white lysozyme at a resolution of 2.0 A. Using a modified slab-line waveguide allows on-line XRD to be carried out while the protein crystal is exposed to well defined microwave fields. High microwave power levels mainly lead to increased, but largely recoverable, lattice defects owing to the evaporation of crystal water. At lower microwave power levels, the presence of the microwave field results in localized reproducible changes in the mean-square displacements (B factors). At particular sites, it is found that the B factors even decrease with increasing microwave power. Most of these effects can be explained by a comparison of the data obtained under microwave irradiation with data obtained at elevated temperature which simulate heating owing to microwave absorption by unbound crystal water. The data show no indication of large microwave-driven displacements of structural subunits in the protein that would be expected if microwaves were to be absorbed resonantly by protein vibrations. Rather, the observed changes in the atomic mean-square displacements suggest that if microwaves couple non-thermally to globular proteins at hydration levels at which they still function, their effect on protein dynamics and structure is very small.

Crystallography, X-Ray↗
PubMed1994

Microwave elution of red cell antibodies.

Using a commercial microwave oven (750 W, 2,450 MHz), we compared the use of microwave energy to the commonly used method of acid-glycine elution (Elu-Kit II, Gamma Biologicals, Houston, Tex., USA) to elute antibodies from direct antiglobulin test positive red blood cells (RBC). Using a 33% suspension of RBCs in cold saline (1-6 degrees C) in a polypropylene test tube, the microwave technique was comparable for eluting Rh (except anti-c and anti-e) and Kell and superior for eluting Duffy, Kidd antibodies while acid-glycine was superior in eluting S and s antibodies. Consistent results were obtained using the microwave technique when the RBC suspension reached temperature of 57-64 degrees C. Heat or the rate of temperature rise appears to play an important role in the microwave elution process although other not yet identified microwave properties may also be a factor. Microwaves are a quick (8 s) alternative to well-established methods of elution and have shown to give consistent results in our study. Commercially available microwave ovens vary substantially in power, making it necessary to perform an initial calibration of the microwave in order to determine a location within the microwave cavity where exposure to microwaves will consistently achieve temperatures of 57-64 degrees C in all cell suspensions.

Acids↗
PubMed1997

Effects of exposure to microwaves on cellular immunity and placental steroids in pregnant rats.

OBJECTIVES: Microwaves produce various detrimental changes based on actions of heat or non-specific stress, although the effects of microwaves on pregnant organisms has not been uniform. This study was designed to clarify the effect of exposure to microwaves during pregnancy on endocrine and immune functions. METHODS: Natural killer cell activity and natural killer cell subsets in the spleen were measured, as well as some endocrine indicators in blood--corticosterone and adrenocorticotrophic hormone (ACTH) as indices of the hypothalamic-pituitary-adrenal axis--beta-endorphin, oestradiol, and progesterone in six female virgin rats and six pregnant rats (nine to 11 days gestation) exposed to microwaves at 10 mW/cm2 incident power density at 2450 MHz for 90 minutes. The same measurements were performed in control rats (six virgin and six pregnant rats). RESULTS: Skin temperature in virgin and pregnant rats increased immediately after exposure to microwaves. Although splenic activity of natural killer cells and any of the subset populations identified by the monoclonal antibodies CD16 and CD57 did not differ in virgin rats with or without exposure to microwaves, pregnant rats exposed to microwaves showed a significant reduction of splenic activity of natural killer cells and CD16+CD57-. Although corticosterone and ACTH increased, and oestradiol decreased in exposed virgin and pregnant rats, microwaves produced significant increases in beta-endorphin and progesterone only in pregnant rats. CONCLUSIONS: Microwaves at the power of 10 mW/cm2 produced activation of the hypothalamic-pituitary-adrenal axis and increased oestradiol in both virgin and pregnant rats, suggesting that microwaves greatly stress pregnant organisms. These findings in pregnant rats suggest that--with exposure to microwaves--pregnancy induces immunosuppression, which could result in successful maintainance of pregnancy. This enhancement of adaptability to heat stress with pregnancy may be mediated by activation of placental progesterone and placental or pituitary beta-endorphin.

Adrenocorticotropic Hormone↗
PubMed1985

The relationship of decreased serum thyrotropin and increased colonic temperature in rats exposed to microwaves.

Although decreased serum thyrotropin (TSH) concentration has been found to be part of the endocrine response pattern in rats exposed to microwaves and other stimuli, the response of individual endocrine organs was not activated simultaneously by a given irradiance. Therefore, analytical evaluation of the function of endocrine organs individually as well as collectively is required to characterize the extent of biological involvement in microwave exposure. We have studied the changes in TSH concentration in unanesthetized rats exposed to 2.45 GHz amplitude modulated (120 Hz) microwaves in the far field for 2 and 4 h, between 0 and 55 mW/cm2, and from 1 to 10 times to demonstrate any possible cumulation, acclimation, or sensitization process. Ether inhalation was administered to test the responsiveness of TSH in groups of rats that failed to respond to microwave exposure by lowering TSH concentration. In addition, groups of rats were sampled 24 h after microwave exposure to test the persistency of the microwave effect on serum TSH concentration. Results showed that TSH concentration decreased in rats after microwave exposure. Influence of microwave exposure on serum TSH concentration was independent of the number of exposures indicating absence of cumulation, acclimation, or sensitization. The microwave effect on serum TSH could be dependent on duration of exposure. Decreased TSH concentration was usually accompanied by increased colonic temperature. For 4-h exposure, the lowest irradiance was 20 mW/cm2 or a 0.3 degree C increase in colonic temperature independent of the number of exposures. For 2-h exposure, the lowest irradiance was 30 mW/cm2 or a 1.1 degree C increase in colonic temperature regardless of the number of exposures. All the rats exposed at 10 mW/cm2 for 2 h had a lower TSH concentration than those of sham-exposed rats. Occasionally, significant reduction in TSH concentration could not be found in rats exposed to 20 or 25 mW/cm2 for 2 h. None of the rats exposed at an irradiance lower than 10 mW/cm2 had any change in TSH concentration. Failure of change in TSH concentration in response to microwave exposure was not a reflection of a deficiency since these rats responded to ether inhalation by lowering their TSH concentration. The effect of microwave exposure on TSH concentration was not persistent after exposure. The relation between TSH concentration and colonic temperature was curvilinear (exponential). From these results, two mechanisms and their implications for man were discussed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

[Endocrine mechanism of placental circulatory disturbances induced by microwave in pregnant rats].

Effects of microwaves on fetus and female genital organs remain to be elucidated. To demonstrate the placental circulatory disturbances induced by microwaves and to clarify the endocrine pathogenesis, placental blood flow and five endocrine indicators, i.e., corticosterone (CS), estradiol (E2), progesterone (P), prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) were measured in rats exposed to whole-body microwaves with an intensity of 10 mW/cm2 at a frequency of 2,450 MHz. The placental blood flow at 45-90 min after exposure was significantly decreased in the rats exposed to the microwaves. Placental blood flow at 15 and 30 min was increased by pretreatment with intraperitoneal administration of angiotensin II (AII). In contrast, no significant change in placental blood flow was recognized in the AII pretreated rats exposed to the microwaves. An increase in CS and a decrease in E2 were induced by the microwave exposure independent of pretreatment with AII. P was increased by microwave exposure in the rats without pretreatment with AII. PGE2 was not changed by the microwave exposure in the case of either nonpretreatment or pretreatment with AII. PGF2 alpha was increased by the microwave exposure in the rats without pretreatment with AII. The present results indicate that excessive exposure to whole-body microwave disorders pregnancy in terms of placental circulatory dysfunction. The data suggest the involvement of endocrine mechanisms in the decrease in placental blood flow which is induced via a detrimental effect of microwaves on PGF2 alpha and on pituitary functions such as general emotional stress.

Angiotensin II↗
PubMed2004

Structural and antigenic preservation of plant samples by microwave-enhanced fixation, using dedicated hardware, minimizing heat-related effects.

We explored the use of microwave technology in fixation with the objective of achieving quicker fixation regimes, lower concentrations of toxic and volatile reagents, and enhanced antigen detection. We used a modified domestic microwave oven (900 W) and a low-power (5 W) microwave bench. The work was done on plant materials. The oven was supplemented with a cooling device, a stirring system, and a record of the sample temperature and the time of effective irradiation. The sample, immersed in a fixative solution of 1% paraformaldehyde (PFA) in PBS, was irradiated for only 10 minutes. The sample temperature did not exceed 37 degrees C. In these mild conditions, the quality of the (ultra)structural preservation of the samples, morphometrically assessed, was at the same level as obtained with the same fixative, using conventional methods. On the contrary, samples fixed in the same conditions without irradiation showed a poor structural preservation. The antigenic preservation of the irradiated samples was excellent, since the labeling levels of two nucleolar proteins, detected by immunogold, were three times higher than in conventionally fixed samples. In the so-called microwave bench, the pathway of microwaves is guided, so that low-power microwaves directly hit the sample and there is no dispersion of energy. Temperature of fixative did not increase after microwave irradiation. Fixation in the bench with either 4% PFA, or 1% PFA, for 20 minutes resulted in structural preservation of samples similar in quality as obtained with conventional fixation and in a similar or better level of antigen preservation. Therefore, controlling temperature and effective irradiation is crucial in order to obtain optimal structural and antigen preservation with microwave-enhanced fixation. The dramatic differences observed between microwave-irradiated samples and samples fixed in the same conditions without irradiation, strongly support the existence of specific effects of microwaves on fixation, independent from the mere heating of the samples.

Allium↗
PubMed2005

Preparation and characterization of microwave-treated carboxymethyl chitin and carboxymethyl chitosan films for potential use in wound care application.

CM-chitin and CM-chitosan films were successfully crosslinked by microwave treatment. Crosslinking of the microwave-treated CM-chitin films involved mainly the carboxylate and the secondary alcohol groups, while crosslinking of microwave-treated CM-chitosan films involved the carboxylate and the amino groups. In addition, the crystallinity of CM-chitin increased with increasing microwave treatment time, whereas an increase in the crystallinity of the microwave-treated CM-chitosan films was not observed. At a similar percentage of weight loss, the crosslinking of either CM-chitin or CM-chitosan films by microwave treatment required much less stringent condition when compared with the crosslinking by autoclave treatment. Based on both direct and indirect cytotoxicity assays, the cytotoxicity of the microwave-treated CM-chitin films was negative, while that of the microwave-treated CM-chitosan films was positive. Human fibroblasts adhered on the surface of microwave-treated CM-chitosan films much better than on the surface of microwave-treated CM-chitin films.

Animals↗
PubMed1994

Application of microwave fixation techniques in pathology to neuroscience studies: a review.

The introduction of microwave energy into the scientist's repertoire of fixation modalities offers for the first time in relatively large specimens the potential for 'instantaneous' preservation of cellular structure for light and electron microscopy with minimal alteration of cellular biochemistry and antigenicity. Because of the rapid evolution of this new technology, we provide a classification system of newly generated microwave methods as applied to specimen preservation for microscopic analysis. With emphasis on neuronal tissue, we review qualitative and quantitative microscopy data of specimens fixed by two microwave methods in common use: (1) microwave stabilization and (2) fast and ultrafast, primary microwave-chemical fixation. In addition, we provide a table of neuropeptides or proteins in neuronal tissues that are preserved by various microwave fixation methods for histochemistry, immunohistochemistry, and immuno-electron microscopy studies. Commercial microwave ovens have limitations which can result in irreproducible fixation results. Therefore, we present a calibration protocol that is used to identify the best locations for fixation within large cavity (i.e., household) microwave ovens. We also provide a standardization protocol to improve the reproducibility of microwave fixation in calibrated, large-cavity microwave ovens.

Animals↗
PubMed2005

Effect of microwave dielectric heating on intraparticle diffusion in reversed-phase liquid chromatography.

The influence of microwave (MW) irradiation on the mass transfer kinetics in reversed-phase liquid chromatography (RPLC) was studied by placing a column in a microwave oven and measuring the incremental change in the temperature of the column effluent stream at various microwave energies and mobile phase compositions. The microwave energy dissipated in the column was set between 15 and 200 W and the mobile phase composition used varied from 100 to 70, 50, and 10% methanol in water at 1.2 mL/min. At all the mobile phase compositions considered, the effluent temperature increased with increasing microwave energy. At 70% methanol, the mobile phase flow rate was set at 1.2, 2.0, and 2.8 mL/min. At 1.2 mL/min, the effluent temperatures at the lowest (15 W) and highest (200 W) microwave energy inputs were 25 +/- 1 degrees C and 41 +/- 1 degrees C for pure methanol, 25 +/- 1 degrees C and 48 +/- 1 degrees C for 70% methanol, 25 +/- 1 degrees C and 50 +/- 1 degrees C for 50% methanol, and, 25 +/- 1 degrees C and 52 +/- 1 degrees C for 10% methanol, respectively. With 70% methanol and microwave energy inputs of 15, 30, and 50 W, the effluent temperature did not change with increasing flow rate; a considerable change was observed at 100, 150, and 200 W between 1.2 and 2.0 mL/min and none between 2.0 and 2.8 mL/min. Chromatographic elution band profiles of propylbenzene were recorded under linear conditions, in 70% methanol solutions, for microwave energy inputs of 0, 15 and 30 W, at constant temperature. The intraparticle diffusion coefficient, De, under microwave irradiation was ca. 20% higher than without irradiation. These preliminary results suggest that microwave irradiation may have a considerable influence on intraparticle diffusion in RPLC.

Chromatography, Liquid↗
PubMed2005

Effect of microwave disinfection on the flexural strength of hard chairside reline resins.

OBJECTIVES: This study investigated the effect of microwave disinfection (650W/6 min) on the flexural strength of five hard chairside reline resins (Kooliner, Duraliner II, Tokuso Rebase Fast, Ufi Gel Hard, New Truliner) and one denture base resin (Lucitone 550). METHODS: Thirty-two specimens (3.3x10x64 mm) from each acrylic resin were produced and divided into four groups of eight specimens each. The flexural test was performed after polymerization (G1), after two cycles of microwave disinfection (G2), after 7 days storage in water at 37 degrees C (G3) and after seven cycles of microwave disinfection (G4). Specimens from group G4 were microwaved daily being stored in water at 37 degrees C between exposures. The specimens were placed in three-point bend fixture in a MTS machine and loaded until failure. The flexural values (MPa) were submitted to ANOVA and Tukey's test (p=0.05). RESULTS: Two cycles of microwave disinfection promoted a significant increase in flexural strength for materials Kooliner and Lucitone 550. After seven cycles of microwave disinfection, materials Kooliner and New Truliner showed a significant increase (p<0.05) in flexural values. The flexural strength of the material Tokuso Rebase was not significantly affected by microwave irradiation. Seven cycles of microwave disinfection resulted in a significant decrease in the flexural strength of material Duraliner II. Material Ufi Gel Hard was the only resin detrimentally affected by microwave disinfection after two and seven cycles. CONCLUSIONS: Microwave disinfection did not adversely affect the flexural strength of all tested materials with the exception of material Ufi Gel Hard.

Acrylic Resins↗
PubMed1997

Quality of life assessment in patients treated with lower energy thermotherapy (Prostasoft 2.0): results of a randomized transurethral microwave thermotherapy versus sham study.

PURPOSE: We evaluated the impact of lower energy transurethral microwave thermotherapy on quality of life and quality of sexual function in patients with benign prostatic hyperplasia (BPH). MATERIALS AND METHODS: A total of 50 patients with BPH were randomized to receive either lower energy transurethral microwave thermotherapy treatment (Prostasoft 2.0) or placebo treatment and followed for 26 weeks after treatment. All patients completed a Madsen symptom score and quality of life questionnaire to assess acceptability, daily activities, psychological well-being, social activities and improvement in quality of life. A sexual function questionnaire was used to assess changes in sexual function after microwave thermotherapy. RESULTS: A significant difference in voiding parameters and symptom score was found between the transurethral microwave thermotherapy and sham groups. Maximum uroflow changed from 9.6 ml. per second at baseline to 13.9 ml. per second and from 9.9 ml. per second at baseline to 9.6 ml. per second at 26 weeks for transurethral microwave thermotherapy and sham groups, respectively. Madsen score improved from 13.2 to 5.3 for the transurethral microwave thermotherapy group and from 11.9 to 9.1 for the sham group. For quality of life measures, a statistically significant difference in favor of the transurethral microwave thermotherapy group was found only for the acceptability item. At baseline and after 26 weeks no statistically significant difference was observed between the 2 groups for Quality of Life measures documenting sexual function. However, almost 20% of patients treated by either transurethral microwave thermotherapy or sham claimed at 26 weeks after treatment that treatment had influenced sexual function. CONCLUSIONS: Although significant changes in objective and subjective parameters were found in patients after lower energy microwave thermotherapy, the change in quality of life was minimal. In addition to the minimal invasiveness of transurethral microwave thermotherapy, preservation of sexual function is appealing.

Aged↗
PubMed1998

Microwave procedures for electron microscopy and resin-embedded sections.

Microwaves now have well-established applications in routine light microscopy. They are employed in tissue fixation and to accelerate a wide spectrum of staining procedures. Besides producing superior preservation of cellular antigens through microwave fixation, this form of irradiation has been employed for antigen retrieval, a procedure that has been a major factor in the optimization of immunolabelling in paraffin sections and cytological preparations. A commercial tissue processor has recently been developed which employs microwaves in a markedly accelerated, one-step processing of tissue blocks, completing the procedure within a fraction of conventional times. Microwaves have also been successfully applied in a variety of molecular techniques such as in situ hybridization and polymerase chain reaction. The adoption of microwaves in electron microscopic procedures has been slower, largely because the requirement for speed in processing is not as great, except in diagnostic samples. However, as this review will show, there are equally as many innovative applications of microwaves in electron microscopy. Microwaves have been employed for rapid processing of fine needle aspiration biopsy samples, in keeping with the requirement for speed in this method of diagnosis. Ultrafast fixation of tissue samples has resulted in the better demonstration of cellular enzymes and proteins. It has been clearly shown that microwave-stimulated on grid staining in uranyl acetate and lead citrate produces more consistent results and without background precipitation. Microwaves can be used to hasten resin polymerization and exposure to microwaves results in antigen retrieval in both resin-embedded thick sections and for immuno-electron microscopy. Immunolabelling shows enhanced sensitivity and the technique is anticipated to contribute greatly to the optimization of immuno-electron microscopy. The potential for greatly accelerated preparation of samples for electron microscopy exists but is yet to be fully realized.

Image Enhancement↗
PubMed2005

Quantitative neuropeptidomics of microwave-irradiated mouse brain and pituitary.

In neuropeptidomics, the degradation of a small fraction of abundant proteins overwhelms the low signals from neuropeptides, and many neuropeptides cannot be detected by mass spectrometry without extensive purification. Protein degradation was prevented when mice were sacrificed with focused microwave irradiation, permitting the detection of hypothalamic neuropeptides by mass spectrometry. Here we report an alternative and very simple method utilizing an ordinary microwave oven to inhibit enzymatic degradation. We used this technique to identify brain and pituitary neuropeptides. Quantitative analysis using mass spectrometry in combination with stable isotopic labeling was performed to determine the effect of microwave irradiation on relative levels of neuropeptides and protein degradation fragments. Microwave irradiation greatly reduced the levels of degradation fragments of proteins. In contrast, neuropeptide levels were increased about 2-3 times in hypothalamus by the microwave irradiation but not increased in pituitary. In a second experiment, three brain regions (hypothalamus, hippocampus, and striatum) from microwave-irradiated mice were analyzed. Altogether 41 neuropeptides or fragments of secretory pathway proteins were identified after microwave treatment; some of these are novel. These peptides were derived from 15 proteins: proopiomelanocortin, proSAAS, proenkephalin, preprotachykinins A and B, provasopressin, prooxytocin, melanin-concentrating hormone, proneurotensin, chromogranins A and B, secretogranin II, prohormone convertases 1 and 2, and peptidyl amidating monooxygenase. Although some protein degradation fragments were still found after microwave irradiation, these appear to result from protein breakdown during the extraction and not to an enzymatic reaction during the postmortem period. Two of the protein fragments corresponded to novel protein forms: VAP-33 with a 7-residue N-terminal extension and beta tubulin with a glutathione on the Cys near the N terminus. In conclusion, microwave irradiation with an ordinary microwave oven effectively inhibits enzymatic postmortem protein degradation, increases the recovery of neuropeptides, and makes it possible to conduct neuropeptidomic studies with mouse brain tissues.

Animals↗
PubMed2004

Effect of microwave radiation on Bacillus subtilis spores.

AIMS: To compare the killing efficacy and the effects exerted by microwaves and conventional heating on structural and molecular components of Bacillus subtilis spores. METHODS AND RESULTS: A microwave waveguide applicator was developed to generate a uniform and measurable distribution of the microwave electric-field amplitude. The applicator enabled the killing efficacy exerted by microwaves on B. subtilis spores to be evaluated in comparison with conventional heating at the same temperature value. The two treatments produced a similar kinetics of spore survival, while remarkably different effects on spore structures were seen. The cortex layer of the spores subjected to conductive heating was 10 times wider than that of the untreated spores; in contrast, the cortex of irradiated spores did not change. In addition, the heated spores were found to release appreciable amounts of dipicolinic acid (DPA) upon treatment, while extracellular DPA was completely undetectable in supernatants of the irradiated spores. These observations suggest that microwave radiation may promote the formation of stable complexes between DPA and other spore components (i.e. calcium ions); thus, making any release of DPA from irradiated spores undetectable. Indeed, while a decrease in measurable DPA concentrations was not produced by microwave radiation on pure DPA solutions, a significant lowering in DPA concentration was detected when this molecule was exposed to microwaves in the presence of either calcium ions or spore suspensions. CONCLUSIONS: Microwaves are as effective as conductive heating in killing B. subtilis spores, but the microwave E-field induces changes in the structural and/or molecular components of spores that differ from those attributable only to heat. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides information on the effect of microwaves on B. subtilis spore components.

Bacillus subtilis↗
PubMed1994

Microwave processing for immunohistochemical demonstration of proliferating cell nuclear antigen (PCNA) in formalin-fixed and paraffin-embedded tissue.

The effect of microwave irradiation on the immunoreactivity of proliferating cell nuclear antigen (PCNA) in five primary breast carcinomas, a tonsil with hyperplasia, and a seminoma of the testis was evaluated in formalin-fixed and paraffin-embedded sections using the monoclonal antibody PC-10. The tissues were fixed in 4% buffered formaldehyde for 6, 24, 28, 72 h, and 1 week. Before incubation with the primary antibody, sections were microwaved for x2 5 min in distilled water, in citrate buffer, or they were processed routinely without microwave irradiation. In sections microwaved in distilled water the immunoreactivity was found to be independent of the length of fixation. PCNA immunoreactivity in sections microwaved twice in citrate buffer was not satisfactory. The PCNA immunoreactivity in sections which were routinely processed without microwave irradiation was markedly decreased after 48 h of fixation, and was nearly absent in sections fixed for up to 1 week. In sections processed without microwave irradiation the optimal dilution of the primary antibody was 1:10, whereas in sections microwaved twice in distilled water the optimal dilution was 1:600. The morphology of the tissue was well preserved after microwave processing. We therefore recommend microwave processing in distilled water for x2 5 min for demonstration of PCNA in formalin-fixed and paraffin-embedded sections using the monoclonal antibody PC-10, since this technique yields optimal staining reactions independent of the length of fixation.

Breast Neoplasms↗