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PubMed2006

A comparison of immunohistochemical stain quality in conventional and rapid microwave processed tissues.

Same-day turnaround of pathology specimens is desirable in this era of managed care, and rapid microwave tissue processing produces histologic features of a quality equivalent to overnight processing. We studied whether microwave-assisted rapid tissue processing adversely affects the quality of immunohistochemical staining. We selected 30 specimens (20 neoplastic and 10 nonneoplastic) from our routine surgical pathology workload. Paired large tissue blocks were made from each specimen type, one for microwave-assisted rapid processing and one for conventional processing. Two microarrays of 60 punches each were made from the donor blocks. The microarray blocks were examined for intensity and extent of staining by 44 commonly used antibodies. Slides were reviewed independently by 2 pathologists blinded to the type of processing used. In 5,280 tissue punches examined, we found a high degree of concordance in quality, as measured by intensity and extent of immunohistochemical staining, between microwave and routinely processed tissues. Our study demonstrates that quality of immunohistochemical staining is similar between rapid microwave and conventional processing. The potential need for immunohistochemical analysis is not a contraindication for microwave-assisted rapid tissue processing.

Histocytological Preparation Techniques↗
PubMed2006

Evidence for a specific microwave radiation effect on the green fluorescent protein.

We have compared the effect of microwave irradiation and of conventional heating on the fluorescence of solution-based green fluorescent protein. A specialized near-field 8.5 GHz microwave applicator operating at 250 mW input microwave power was used. The solution temperature, the intensity, and the spectrum of the green fluorescent protein fluorescence 1), under microwave irradiation and 2), under conventional heating, were measured. In both cases the fluorescence intensity decreases and the spectrum becomes red-shifted. Although the microwave irradiation heats the solution, the microwave-induced changes in fluorescence cannot be explained by heating alone. Several possible scenarios are discussed.

Dose-Response Relationship, Radiation↗
PubMedDate not supplied

Microwave treatment of eight seconds protects cells of Isatis indigotica from enhanced UV-B radiation lesions.

To determine the role of microwaves in the stress resistance of plants to enhanced ultraviolet-B (UV-B) radiation, Isatis indigotica Fort. seeds were subjected to microwave radiation for 8 s (wavelength 125 mm, power density 1.26 mW mm(-2), 2450 MHz). Afterwards they were cultivated in plastic pots in an artificial-glass greenhouse maintained at 25 degrees C, 70% relative humidity, and 400 micromol mol(-1) CO2, under visible-light conditions of 1500 micromol m(-2) s(-1) for 8 h day(-1). When the seedlings were 10 days old, they were subjected to 10.08 kJ m(-2) UV-B (PAR: 220 micromol m(-2) s(-1)) radiation for 8 days. Changes in a number of physiological and biochemical characteristics and in the thermal decomposition enthalpy of biomass were measured and used as indicators of the protective capacity of microwave radiation in this experiment. Our results revealed that microwave pretreatment of seeds enhanced UV-B stress resistance in the seedlings by decreasing the concentration of malondialdehyde (MDA) and increasing the concentration of ascorbic acid (AsA) and UV-B-absorbing compounds, increasing the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), and increasing the energy accumulation of photosynthesis. All these results suggest that microwave radiation enhances plant metabolism and results in increased UV-B stress resistance. This is the first investigation reporting the use of microwave pretreatment to protect the cells of Isatis indigotica from UV-B-induced lesions.

Ascorbic Acid↗
PubMed2003

Microwave-assisted solid-phase synthesis (MASS): parallel and combinatorial chemical library synthesis.

The use of microwave technology in solid-phase organic synthesis has attracted much attention in recent years. The combination of solid support, either as a medium for chemical synthesis or as a carrier for organic reagents, with microwave heating offers several advantages over conventional techniques. Rapid and elevated heating of reaction mixtures can induce the completion of chemical transformations in minutes while several hours or days may be required for the same chemistry under conventional conditions. With decreased time of exposure to high temperatures and lessened thermal degradation, microwave accelerated chemistries often deliver products of higher purity when compared to conventional heating techniques. Several chemical syntheses on solid-phase employing microwave irradiation have been reported in the literature. The reagents, solvents, and equipment selected for microwave-mediated synthesis are important contributors to the success of the chemical transformation. Owing to the timesavings in performing chemical synthesis under microwave irradiation, the technique has become an emerging partner in solid-phase organic synthesis.

Combinatorial Chemistry Techniques↗
PubMed1989

[Dimensional accuracy of microwave-cured denture base resin].

Recently, microwave-cured denture base resin was developed, and the resin solved the problem of internal porosity which had been generated by curing the conventional denture base resins with microwave irradiation. In this study, the dimensional accuracy of microwave-cured denture base resin was compared with that of other denture base resins, such as pour-type resin, heat-cured resin and heat-shock resin. From the experiment, the following results were obtained. 1. Dimensional accuracy of microwave-cured denture base resin was better than that of heat-cured resin and heat-shock resin, and was similar to that of pour-type resin. 2. Dimensional accuracy of microwave-cured denture base resin by slow cooling method and rapid cooling method was almost the same. Those findings suggest that microwave-cured denture base resin is valuable in clinic.

Denture Bases↗
PubMed2005

Open-configuration MR-guided microwave thermocoagulation therapy for metastatic liver tumors from breast cancer.

BACKGROUND: Liver metastases from breast cancer are associated with a poor prognosis, however, local control with microwave thermocoagulation therapy has been used in certain subgroups of these patients in the past decade. In this study, open-configuration magnetic resonance (MR) -guided microwave thermocoagulation therapy was used for metastatic liver tumors from breast cancer, and the efficacy of this treatment was assessed. METHODS: Between June 2000 and April 2004, we used MR-guided microwave thermocoagulation therapy on 11 nodules in 8 patients with metastatic liver tumors from breast cancer. The procedure was carried out under general anesthesia. A 0.5 T open-configuration MR system and a microwave coagulator were used. Near-real-time MR images and real-time temperature images were collected and displayed on the monitor. The MR-compatible thoracoscope was used and combined with MR imaging guidance. Navigation software, a 3D Slicer, was installed and customized. RESULTS: The customized navigation software displayed near-real-time MR images. The percutaneous puncture into the tumors was successful in all cases. No mortality or major complications occurred as a result of the procedures. Five of the 8 patients are alive with new metastatic foci with a mean observation period of 25.9 months. CONCLUSIONS: We developed several devices to allow safe, easy, and accurate MR-guided microwave thermocoagulation therapy of liver tumors. Open-configuration MR-guided microwave thermocoagulation therapy appears to be a feasible method for tumor ablation of metastatic liver tumors from breast cancer.

Adult↗
PubMed1986

Behavioral observations and operant procedures using microwaves as a heat source for young chicks.

Four trials, using operant conditioning procedures, were conducted to study the response of chicks, housed at 16 C, to microwave or infrared heat. Microwave power density was 26 mW/cm2 in Trial 1, 13 mW/cm2 in Trial 2, and 10 mW/cm2 in Trials 3 and 4. Chicks voluntarily demanded between 28 and 63% as much heat (min heat/hr) from microwave source as from infrared source at all power densities. There was no correlation, however, between the ratio of heat demanded and the power density used. There were no significant differences in growth between infrared- or microwave-heated chicks. It is evident from these studies that 8-day-old broiler chicks are capable of associating the performance of a task with a thermal reward provided by the microwaves. They are also able to utilize these microwaves through operant conditioning without any visible detrimental effect to their health or behavior.

Animals↗
PubMed2003

Lethal effect of microwaves on spores of Bacillus spp.

Strains representing four types of common heat-resistant spores of Bacillus spp., B. cereus CCRC 14655, B. coagulans CCRC10606, B. licheniformis CCRC14693, and B. subtilis CCRC14199, were heated with microwaves at different power levels and under different conditions in salt solutions, starch solutions, and containers. The results of this study showed that B. licheniformis spores had the highest microwave tolerance at a power level of 100% for different incubation times. B. coagulans spores showed the lowest microwave tolerance in salt solutions with water activity values of 0.6, 0.7, 0.8, and 0.9, and B. licheniformis spores were the most resistant in the tested salt solutions at different incubation times. An analysis of the effect of the viscosity of the medium revealed that the bacteria had the lowest microwave resistance in a medium containing <0.8% starch in solution. The microwave resistance levels of the test microorganisms were the lower in glass containers than in polypropylene containers and aluminum foil-enclosed pouches. Of the four species of bacilli, B. licheniformis had the highest microwave tolerance (P < 0.05) under all conditions.

Bacillus↗
PubMed1999

A novel intraurethral prostatic bridge catheter for prevention of temporary prostatic obstruction following high energy transurethral microwave thermotherapy in patients with benign prostatic hyperplasia.

PURPOSE: We evaluate the efficacy and safety of a novel intraurethral prostatic bridge catheter in preventing temporary prostatic obstruction following targeted high energy transurethral microwave thermotherapy in patients with benign prostatic hyperplasia. MATERIALS AND METHODS: A total of 54 patients with benign prostatic hyperplasia underwent high energy transurethral microwave therapy under topical urethral anesthesia followed by placement of a prostatic bridge catheter, which remained indwelling as long as 1 month (prostatic bridge catheter group). Patient evaluation included determination of peak urinary flow rate, International Prostate Symptom Score (I-PSS) and quality of life score at baseline, immediately following transurethral microwave therapy and prostatic bridge catheter placement, and periodically thereafter for 1 month. Results were retrospectively compared with those of 51 patients who underwent transurethral microwave therapy followed by standard temporary urinary catheterization, typically for 24 hours (standard catheterization group). RESULTS: Immediately following transurethral microwave therapy and prostatic bridge catheter placement significant improvements (p <0.0005) were observed in mean peak flow rate, I-PSS and quality of life score of 59.3, 33.5 and 23.6%, respectively, compared with baseline values. Further improvements were noted up to 1 month, at which time mean peak flow rate, I-PSS and quality of life score had improved 79.0, 54.9 and 56.5%, respectively, versus baseline (p <0.0005). In a retrospective comparison at baseline and 14 days between the prostatic bridge catheter group and standard catheterization group mean baseline peak flow rate, I-PSS and quality of life score were similar. However, at the 14-day followup evaluation in the prostatic bridge catheter group mean peak flow rate was 101.8% higher, and I-PSS and quality of life score were 47.9 and 51.1% lower, respectively, than the corresponding values in the standard catheterization group (p <0.0005). The prostatic bridge catheter was well tolerated and remained indwelling throughout the entire 1-month followup in 48 of 54 patients (88.9%). Early prostatic bridge catheter removal was required in 3 patients (5.6%) due to urinary retention and in 3 (5.6%) due to catheter migration. CONCLUSIONS: Prostatic bridge catheter placement provides an effective and well tolerated option for preventing prostatic obstruction in the acute period after transurethral microwave therapy. This approach avoids the inconvenience and infection risk of standard indwelling catheters or intermittent self-catheterization. Prostatic bridge catheter insertion and removal are rapid, facile, nontraumatic procedures. Prostatic bridge catheter may potentially be used in an array of minimally invasive procedures involving thermal treatment of the prostate gland.

Diathermy↗
PubMed1976

Quality factors in beef, pork, and lamb cooked by microwaves.

Three cooking treatments were applied to the longissimus muscle of beef and of pork and to deboned leg of lamb. Cooking treatments included: Intermittent energy application (3-min. cycle) with a microwave range operated at 220V and intermittent energy application (6-min. cycle) with a microwave range operated at 115V. Control roasts were cooked in a conventional gas oven (163+/-3 degrees C.). Cooking was adjusted so that roasts achieved an internal temperature of 70 degrees C. when cut for analyses. Cooking losses were significantly greater for microwave than for conventionally cooked beef. However, microwave cooking resulted in beef, pork, and lamb roasts with flavor of interior portions similar to those prepared conventionally. Flavor differences in samples from the edge of the slices of lamb and of pork and tenderness of lamb appeared to be related to cooking method. For these attributes, meat cooked conventionally was superior. In contrast, patterns in significant differences in tenderness and juiciness of beef and of pork were not consistent and were not related solely to method of cookery. Neither creatine nor creatinine was a good index of flavor of meat cooked by these methods. Aside from the time-saving aspect of microwave heating, there was no major advantage of one method of cooking over another. Thus, either high- or low- powered microwave equipment, operated at 2450 MHz, can be used satisfactorily for cooking tender cuts of beef, pork, and lamb.

Animals↗
PubMed2000

Acute exposure to pulsed 2450-MHz microwaves affects water-maze performance of rats.

Rats were trained in six sessions to locate a submerged platform in a circular water maze. They were exposed to pulsed 2450-MHz microwaves (pulse width 2 micros, 500 128;pulses/s, average power density 2 mW/cm(2), average whole body specific absorption rate 1.2 W/kg) for 1 h in a circular waveguide system immediately before each training session. One hour after the last training session, they were tested in a probe trial during which the platform was removed and the time spent in the quadrant of the maze in which the platform had been located during the 1-min trial was scored. Three groups of animals, microwave-exposed, sham-exposed, and cage control, were studied. Microwave-exposed rats were slower than sham-exposed and cage control rats in learning to locate the platform. However, there was no significant difference in swim speed among the three groups of animals, indicating that the difference in learning was not due to a change in motor functions or motivation. During the probe trial, microwave-exposed animals spent significantly less time in the quadrant that had contained the platform, and their swim patterns were different from those of the sham-exposed and cage control animals. The latter observation indicates that microwave-exposed rats used a different strategy in learning the location of the platform. These results show that acute exposure to pulsed microwaves caused a deficit in spatial "reference" memory in the rat.

Animals↗
PubMed1998

[Effect of microwave on the dentin of root canal wall].

OBJECTIVE: To investigate the effect of microwave on dentin of root canal wall. METHODS: Ten pairs of clinically sound single rooted premolars(totally 30 root canals: 10 teeth had only one calal and 10 had two canals) were collected. The root canals were treated with microwave of different irradiation energy except one canal of the two canal teeth, they were served as controls. The teeth were dissected longitudinally into two parts and prepared for SEM examination. RESULTS: The microwave of 35 mA irradiated for 3 seconds would not damage the dentin and was safe for clinical usage. But, microwave over 75 mA or with a prolonged irradiation time could damage the dentin of the root canal wall to different extents. The damaged dentin presented incomplete fractures. At the same time, such damage also involved another canal in the same tooth which was not treated with microwave. CONCLUSION: It is necessary to choose a suitable level of energy and control the irradiation time when a root canal is sterilized by microwave.

Adolescent↗
PubMed2001

Low power density microwave radiation induced early changes in rabbit lens epithelial cells.

OBJECTIVE: To determine whether low power density microwave radiation can induce irreversible changes in rabbit lens epithelial cells (LECs) and the mechanisms of the changes. METHODS: One eye of each rabbit was exposed to 5 mW/cm2 or 10 mW/cm2 power density microwaves for 3 hours, while the contralateral eye served as a control. Annexin V-propidium iodide (PI) two-color flow cytometry (FCM) was used to detect the early changes in rabbit lens epithelial cells after radiation. RESULTS: Lots of rabbit LECs were in the initial phase of apoptosis in the 5 mW/cm2 microwave radiation group. A large number of cells became secondary necrotic cells, and severe damage could be found in the group exposed to 10 mW/cm2 microwave radiation. CONCLUSION: Low power densities of microwave radiation (5 mW/cm2 and 10 mW/cm2) can induce irreversible damage to rabbit LECs. This may be the non-thermal effect of microwave radiation.

Animals↗
PubMed1992

Structure of rat kidneys following microwave accelerated fixation.

In contrast to fixation of tissue in externally heated fixative, microwave-irradiation can generate uniform internal heat, which is of utmost importance for successful fixation of biological tissue. To evaluate the effectiveness of microwave-accelerated chemical fixation, we compared the structure of rat kidney fixed by a conventional method and a microwave-accelerated method, by scanning and transmission electron microscopy. Following perfusion, rat kidney pieces 1-2 mm in size were irradiated in Karnovsky's fixative in a domestic Amana microwave oven, till the temperature of the fixative reached 45-50 degrees C. For conventional fixation, tissue pieces were fixed overnight at room temperature in the same fixative. Both types of samples were processed further for electron microscopy using identical protocols. The microwave fixed samples showed excellent preservation of structure comparable to the samples fixed by the conventional method. Glomeruli and the renal tubules showed normal morphology with no cellular swelling. The cytoplasm and nuclear matrix of the epithelial cells was uniformly dense. Other fixation sensitive organelles like mitochondria and Golgi apparatus showed superior preservation with continuous membranes. These results demonstrate that microwave accelerated chemical fixation results in excellent preservation of tissue structure, reduces processing time significantly and is therefore a practical alternative to conventional protocols.

Animals↗
PubMed1992

Effects of microwave radiation on anti-infective factors in human milk.

In intensive care nurseries it has become common practice to use microwave thawing of frozen human milk for more rapid accessibility. Twenty-two freshly frozen human milk samples were tested for lysozyme activity, total IgA, and specific secretory IgA to Escherichia coli serotypes 01, 04, and 06. The samples were heated by microwave for 30 seconds at a low- or high-power setting and then reanalyzed. One-mL aliquots of 10 additional human milk samples were microwaved at low (20 degrees C to 25 degrees C), medium (60 degrees C to 70 degrees C), and high (greater than or equal to 98 degrees C) setting before the addition to each of 1 mL of diluted E coli suspension. E coli growth was determined after 3 1/2 hours of incubation at 37 degrees C. Microwaving at high temperatures (72 degrees C to 98 degrees C) caused a marked decrease in activity of all the tested antiinfective factors. E coli growth at greater than or equal to 98 degrees C was 18 times that of control human milk. Microwaving at low temperatures (20 degrees C to 53 degrees C) had no significant effect on total IgA, specific IgA to E coli serotypes 01 and 04, but did significantly decrease lysozyme and specific IgA to E coli serotype 06. Even at 20 degrees C to 25 degrees C, E coli growth was five times that of control human milk. Microwaving appears to be contraindicated at high temperatures, and questions regarding its safety exist even at low temperatures.

Antibodies, Bacterial↗
PubMed2005

[Treatment efficacy of preservation of uvulopalatopharyngoplasty by using microwave].

OBJECTIVE: To study the effect of uvulopalatopharyngoplasty (UPPP) by using microwave on obstructive sleep apnea-hypopnea syndrome (OSAHS) with Velo-pharyngeal obstruction. METHOD: Sixty-one cases who were diagnosed as OSAHS with Velo-pharyngeal obstruction were performed UPPP by using microwave, among which 9 cases received microwave palatopharyngoplasty only. Thirty-six cases underwent bilateral palatine tonsillectomy and another 16 cases underwent bilateral palatine tonsillectomy and tongue base microwave ablation apart from microwave pharyngoplasty. RESULT: Two weeks after operation, the preserved uvula began to contract. Three months after operation, the uvula contracted to be normal length and the anatomical shape. The pharyngeal cavity was preserved. No case appeared velopalatal insufficiency. Twenty-one patients felt foreign body in pharyngeal portion, which disappeared after 2-5 months. According to the evaluation standards set in Hangzhou Conference, follow-up was carried out after 6 months. It was found that 13 cases (21.31%) were cured, 32 (52.46%) appeared significant effect, 12 (19.67%) appeared effect and 4 (6.56%) appeared no effect with a total effect rate of 93.44%. CONCLUSION: Uvulopalatopharyngoplasty by using microwave needs less time less hemorrhage and good effects.

Adolescent↗
PubMed1990

[Study of the microwave fixation using the immunohistochemical method].

We evaluated microwave fixation of formalin immersed and microwave irradiated kidney and liver tissues by keratin immunostain using the paraffin embedded section. In the microwave irradiated tissues, the formalin fixed areas and the alcohol fixed areas were clearly detected because; 1) Alcohol fixed tissues are easily digested by pepsinization but formalin fixed tissues are not, and 2) Formalin fixed tissues revealed intense keratin staining after pepsinization, whereas intense keratin staining were noted in alcohol fixed tissues without preliminary pepsinization. The microwave irradiation fixed completely the tissues in about 20 sec. A thin, formalin-fixed layer was observed in the periphery of the tissues. A thin, alcohol-fixed layer was observed beneath the peripheral formalin fixed layer in some specimens. This area was thought to have been fixed during the dehydration of the paraffin blocks. However with microwave fixation, most of the central areas differed from those of the formalin or alcohol fixed areas. They showed sharp contrast on hematoxylin-eosin staining, conspicuous cellular membrane and only slight cellular shrinkage and swelling. Unlike the formalin and alcohol fixed tissues, the intensity of keratin staining was independent of preliminary pepsinization and keratin staining was observed. Therefore, the central areas were thought to be fixed by the microwave irradiation. This fixation method seems to be useful for immunostaining.

Alcohols↗
PubMed1990

Does rapid microwave fixation improve immunohistochemistry?

Microwave fixation in dilute aldehyde solution has been reported to be superior to fixation in formaldehyde for the preservation of antigens. We studied antigen preservation among tissues which were soaked in formaldehyde, dilute aldehyde, alcohol, and saline solution with or without microwave irradiation. Microwave fixation was found to be superior to conventional formaldehyde fixation with regard to antigen preservation. However, there was no detectable difference in immunostaining between any of the irradiated and nonirradiated alcohol-, aldehyde-, or even saline-treated tissues. Microwave-irradiated tissues, regardless of the fixative employed, displayed a tendency for tissue disintegration upon protease treatment, as is commonly seen in alcohol-fixed tissues. Our results suggest that the apparent improvement in antigen preservation when microwave fixation in dilute aldehyde solution is used is largely attributable to the fixation in alcohol during the graded alcohol dehydration steps in the tissue processor, rather than to any demonstrable effect of the microwave radiation per se.

Fixatives↗