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PubMedDate not supplied

Microwave stimulation of an immunological reaction (CEA/anti-CEA) and its use in immunohistochemistry.

The effects of microwave stimulation on different aspects of immunohistochemical reactions were studied using Elisa as a model system. This technique allows monitoring of (i) the rates and recoveries of different antigen-antibody reactions, (ii) the formation of avidin/biotin complexes, (iii) the prevention of non-specific activity and (iv) the washing procedures. The binding reactions seemed to follow second-order kinetics, and reaction rates were considerably enhanced by microwave stimulation. The steps were aimed at preventing non-specific reactivity and the washing procedures could all be shortened to seconds. Such rate increases are far too large to be explained solely by the modest increase in temperature. Furthermore, microwave irradiation caused a major reduction in the yield of antigen-antibody complexes. This inhibitory effect can be compensated for by increasing the concentration of antibody. No significant effects of the microwaves on the antigen-antibody complexes were found once the complexes had been formed. The obtained results were then applied to the demonstration of carcinoembryonic antigen in histological material. By employing this method a complete immunohistochemical staining of a hydrated tissue section could be performed within 15 min, excluding the final development of colours.

Antigen-Antibody Complex↗
PubMedDate not supplied

Microwave stabilization versus chemical fixation. A morphometric study in glycolmethacrylate- and paraffin-embedded tissue.

A morphological and morphometrical study was performed on testicular cells after microwave stabilization of the tissue while immersed in phosphate buffered saline (PBS), 0.9 NaCl or Tris-HCl. Fixation in Carnoy's fluid without irradiation was chosen as a control chemical fixation method. After microwave stabilization or chemical fixation, the testes were embedded in paraffin or in plastic (glycolmethacrylate). An excellent morphology, comparable to that after chemical fixation in Carnoy's fluid, was observed in the plastic sections of tissue irradiated in PBS or NaCl, even when the sections were subsequently treated with an aggressive reagent at high temperature, required for the Feulgen reaction. The nuclear area of the microwave-stabilized Sertoli cells was 37-46% smaller in haematoxylin-eosin stained, paraffin sections in comparison with that in the glycolmethacrylate sections. The microwave-stabilized, paraffin-embedded tissue was much more vulnerable to the hot HCl treatment of the Feulgen staining than the chemically fixed tissue, resulting in an additional 10-20% decrease in nuclear size. The latter finding is particularly important for quantitative microscopy, where the Feulgen staining method is often employed.

Animals↗
PubMedDate not supplied

Physics of microwave technology in histochemistry.

Microwave technology has become important in preparatory techniques for microscopy in many different ways. This paper discusses various aspects of the physics of microwaves. It gives some theoretical background to understand the practical procedures. Some peculiarities in the optics of microwaves are pointed out, and the practical implications in particular of choosing the size and shape of samples and containers are discussed. Diffusion rates and chemical-reaction rates increase exponentially with temperature, so that precise temperature control is essential in most histochemical procedures. Such control is complicated by localized heating of the system, and of temperature sensors themselves, which may occur as a result of microwave irradiation.

Histocytochemistry↗
PubMed1995

Comparative effects of gamma and microwave irradiation on the quality of black pepper.

Powdered black pepper from Egyptian markets, was irradiated with different recommended doses of gamma rays (5.0 and 10.0 kGy) and with microwaves for different periods (20, 40 and 75 s) to improve its hygienic quality. The most common bacterial isolates were of three genera Bacillus, Clostridium and Micrococcus (7.5 x 10(6)), whereas the predominant fungi (7.8 x 10(4)) were Aspergillus species, A. glaucus, A. flavus, A. niger and A. ochraceus. Doses of gamma irradiation used (5.0 and 10 kGy) were sufficient to decrease spore-forming bacteria (SFB) and to inhibit the fungal flora and coliforms which contaminated the black pepper powder. Microwave treatments for 40 s and 75 s were of the same effectiveness whereas treatment for 20 s was less so. GLC analysis proved the presence of 31 peaks, only 19 compounds were identified as monoterpene hydrocarbons (56.21%), the major one being beta-phellandrene and limonene. Sesquiterpenes were also present, mainly beta-caryollphyllene (3.69%) as well as oxygenated compounds such as terpenol, geraniol, Me-chavicol, eugenol and anisol. Gamma irradiation at 5 kGy and 10 kGy respectively decreased the numbers of identified compounds from 21 (86.58% concentration) in untreated pepper to 16 (59.22% concentration), 15 (54.06% concentration). In comparison, microwave treatments, particularly for 40 s and 75 s, increased the concentration of the same compounds. The results obtained indicate that microwave treatment, under these conditions, is a safe and suitable technique for decontamination of black pepper which does not result in a great loss of flavour compounds, as compared with recommended doses of gamma irradiation.

Aspergillus↗
PubMed1977

In vitro and in vivo inhibition of virus multiplicaton by microwave hyperthemia.

The effect of microwave hyperthermia (41 degrees and 43 degrees C) on virus multiplication have been explored in vitro (HSV-1 infected primary rabbit kidney cultures) and in vivo (mice infected with HSV-1 or vaccinia). In vitro the cells were inoculated with HSV-1 and heated to 41 degrees or 43 degrees C either before or after infection. Virus yields were significantly decreased when the cells were exposed to hyperthemia within the first few hours after infection, while hyperthemia was without effect when applied before infection or with several hours delay after infection. In mice inoculated intranasally with HSV-1, mortality due to herpes encephalitis was significantly reduced upon daily exposure to microwave hyperthermia from the day of infection onward. In mice inoculated intravenously with vaccinia, a significant decrease in the number of specific tail lesions was observed if the animals were exposed to microwave hyperthermia within the first three days after infection, while irradiation prior to infection or delayed until several days after infection did not exhibit an appreciable effect. Our data suggest that microwave hyperthermia interferes directly with the virus multiplication cycle both in vitro and in vivo.

Animals↗
PubMed1987

The microwave Rio-Hortega technique: a 24 hour method.

Application of microwaves in histochemistry and cytochemistry generally speeds up the technique. Microwaves stimulate diffusion into the tissue and influence the proteins and membrane of the cell. Silver impregnation techniques for the brain, such as the fast Rio-Hortega or the slow Golgi-Cox technique, normally require a minimum time period of 7 days and 20 days respectively. Using microwaves, the Rio-Hortega technique can be completed within 24 h. In sections prepared from mature brains, good silver impregnation of cell bodies, of axons and their terminals, and of dendrites and their spines are obtained. An explanation is given as to why the method cannot be further reduced in time. To our knowledge, this is the first report of the application of microwave irradiation for colouring pieces of tissue.

Animals↗
PubMed1978

Regional levels of histamine in rat brain after microwave irradiation: evidence for artifacts in the enzymatic--isotopic assay.

Histamine levels in the brain, measured fluorimetrically, were similar for rats killed by decapitation and microwave irradiation. However, enzymatic--isotopic assay yields 5--20 times higher value for microwave irradiation versus decapitation. Thin layer chromatography of the methylated products in the enzymatic--isotopic assay indicated the formation of artifacts following microwave irradiation. The results strongly suggest that a combination of microwave irradiation and enzymatic--isotopic assay is not suitable for histamine analysis in the rat brain.

Animals↗
PubMed1994

Microwave thermography as a noninvasive assessment of disease activity in inflammatory arthritis.

Microwave thermography is the technique of measuring natural thermal radiation from body tissues of clinical interest. It is safe, requires no control of environmental conditions and exposes the patient to no ionising radiation. In this study, we found that microwave thermography of the knee joints showed weak correlation with some global parameters of disease activity. Bed rest alone for three days had no significant effect on microwave thermographic index (MTI). Intra-articular steroid injection, however, was associated with a marked fall in MTI both in the injected knee and the contra-lateral knee. We conclude that microwave thermography can measure inflammatory activity in the knee joints of patients with inflammatory arthritis and can respond to clinical change brought about by major treatment intervention.

Adrenal Cortex Hormones↗
PubMed1993

Tomographic measurement of temperature change in phantoms of the human body by chirp radar-type microwave computed tomography.

The chirp radar-type microwave computed tomograph (CT) measures the temperature change in a human body noninvasively. The paper examines its feasibility. A chirp pulse signal between 1 and 2 GHz is radiated from the transmitting antenna to the phantom. The transmitted waves are detected by the receiving antenna, which is placed on the opposite side of the object, and the beat signal between the incident wave and the transmitted wave is produced by the mixer. By spectral analysis of the beat signal, only those signals transmitted on the straight line between the transmitting antenna and the receiving antenna are discriminated from multipath signals. The microwave tomogram can therefore be reconstructed easily using the conventional algorithms for an X-ray CT image. The microwave CT can use the chirp signal to remove the influence of multipath signals caused by diffraction and reflection. The imaging of dielectric materials with complicated structures is thus possible. The experimental results using phantoms show that the spatial resolution of this microwave CT is about 10 mm and that a two-dimensional distribution of temperature change can be measured.

Body Temperature↗
PubMed1975

Brain free fatty levels in rats sacrificed by decapitation versus focused microwave irradiation.

Values are presented for whole brain free fatty acid levels of rats sacrificed by decapitation vs focused microwave irradiation. Free fatty acids were quantitated by specific colorimetric analysis. Within ca. 1 min of sacrifice by either decapitation or microwave, rat whole brain free fatty acid concentrations ranged from ca. 80-100 mug/g fresh tissue. If the brain remained in the head for a total of 5 min after decapitation, free fatty acid levels increased by over 100%. The free fatty acids at this time were enriched with arachidonic acid. The increase in free fatty acid levels following decapitation was completely absent in rats sacrificed by the microwave irradiation. This microwave technique could be a valuable tool in determining free fatty acid and other heat stable compounds in brain tissue.

Animals↗
PubMed1991

Endoscopic microwave coagulation therapy for villous adenoma of the duodenum--a case report.

The effects of endoscopic microwave coagulation therapy on duodenal adenoma in a 58-year-old man are reported. The patient had a 35-mm sessile tubulo-villous adenoma in the duodenal bulb. Endoscopic polypectomy followed by microwave coagulation therapy for duodenal adenoma was performed to avoid a major surgical procedure which would disturb the physiological functions of the gastrointestinal tract. After partial polypectomy which included the core of the adenoma, the entire remaining adenoma was destroyed after three microwave therapy sessions. During a follow-up period of 14 months, neither endoscopic nor histologic evidence of recurrence has been noted. Endoscopic microwave coagulation therapy is considered to be useful in the treatment of large sessile duodenal villous adenoma, provided that repeated endoscopic follow-up surveillance is also performed.

Adenoma↗
PubMed2003

Microwave-assisted steam distillation with simultaneous liquid/liquid extraction of pentachlorophenol from organic wastes and soils.

An efficient method for extracting pentachlorophenol (PCP) from organic solid matrices and soils using direct excitation of the fresh samples by microwave energy is presented. Steam-volatile PCP partitioned into the organic solvent n-hexane within the closed extraction vessel, resulting in recovery rates of 85-92% from aged samples. Condensed water provided a boundary layer between extract and sample thus preventing any contact of PCP with and re-partitioning into the sample. Duration of the microwave-assisted process was 35 min. Crude extracts were derivatized by heptafluorobutyric anhydride (HFBA) to improve selectivity and sensitivity resulting in detection limits of 1-2 micro g kg(-1). GC-MS/MS analyses proved that suitable extracts with only minor impurities were obtained. Common sample treatment steps like drying, thorough grinding, frequent transferring, and tedious clean-up, and concentration procedures which all can cause certain losses of analyte were minimized. The efficiency of the method was verified by comparison with an established ultrasonic extraction procedure. This microwave-assisted pressurized steam distillation with simultaneous partition into an organic phase thus provides a streamlined and efficient strategy which requires no additional investment in standard equipment for microwave-assisted extractions (MAE). Degradation of analytes at longer extraction times must be taken into account.

Chemical Fractionation↗
PubMed2000

Optimization of microwave-assisted extraction of hydrocarbons in marine sediments: comparison with the Soxhlet extraction method.

Microwave energy was applied to extract polycyclic aromatic hydrocarbons (PAHs) and linear aliphatic hydrocarbons (LAHs) from marine sediments. The influence of experimental conditions, such as different extracting solvents and mixtures, microwave power, irradiation time and number of samples extracted per run has been tested using real marine sediment samples; volume of the solvent, sample quantity and matrix effects were also evaluated. The yield of extracted compounds obtained by microwave irradiation was compared with that obtained using the traditional Soxhlet extraction. The best results were achieved with a mixture of acetone and hexane (1:1), and recoveries ranged from 92 to 106%. The extraction time is dependent on the irradiation power and the number of samples extracted per run, so when the irradiation power was set to 500 W, the extraction times varied from 6 min for 1 sample to 18 min for 8 samples. Analytical determinations were carried out by high-performance liquid chromatography (HPLC) with an ultraviolet-visible photodiode-array detector for PAHs and gas chromatography (GC) using a FID detector for LAHs. To test the accuracy of the microwave-assisted extraction (MAE) technique, optimized methodology was applied to the analysis of standard reference material (SRM 1941), obtaining acceptable results.

Chromatography, Gas↗
PubMed2000

Microwave assisted extraction of polycyclic aromatic hydrocarbons from atmospheric particulate samples.

For several years, microwave assisted extraction (MAE) was applied to extract organic compounds such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, etc., from soils, sediments and standard reference materials. Very few authors applied this methodology for the extraction of PAHs from atmospheric particulate matter. In the present study, MAE of polycyclic aromatic hydrocarbons with hexane/acetone (1:1) from real atmospheric particulate samples was investigated and the effect of microwave energy and irradiation time studied. The yields of extracted compounds obtained by microwave irradiation were compared with those obtained using traditional Soxhlet extraction. MAE was evaluated using spiked real atmospheric particulate samples and two standard reference materials. Analytical determinations of PAHs were carried out by high performance liquid chromatography (HPLC) with ultraviolet and fluorescence detection. The best recoveries were achieved with a microwave energy of 400 W and an irradiation time of 20 min.

Air Pollutants↗
PubMed2000

Combined protocol for the analysis of polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBx) from sediments using focussed microwave assisted (FMW) extraction at atmospheric pressure.

A microwave-assisted protocol has been developed using focussed microwaves at atmospheric pressure for the extraction of PAHs and PCBs from sediments. It combines extraction and purification assisted by microwaves. This protocol has been applied to the quantification of 12 individual PAHs, 8 individual PCBs and 8 PCB coeluted mixtures from two Standard Reference Materials and one natural sediment. The results for both classes of compounds (PAHs and PCBs) are good in terms of recoveries, which are always greater than 70% and in most cases around 100%. The reproducibility is also good with coefficients of variation below 10% in most cases. This protocol has the great advantage of saving time, the time dedicated to the preparation / extraction assisted by microwaves being reduced to less than half an hour.

Atmospheric Pressure↗
PubMed1996

Qualitative enzyme histochemistry and microanalysis reveals changes in ultrastructural distribution of calcium and calcium-activated ATPases after microwave irradiation of the medial habenula.

The localization of calcium and calcium-activated ATPases was investigated electron microscopically in the medial habenula of mice after whole body irradiation with modulated microwaves. In non-irradiated animals calcium-containing precipitates were seen in different subcellular compartments and were often localized on the luminal side of membranes of synaptic vesicles in nerve terminals. At 1 h after 16-Hz modulated microwave irradiation, the number of synaptic vesicles containing calcium precipitates decreased, and reaction products appeared at new locations: in the synaptic clefts and on non-synaptic surfaces of the neuronal plasma membrane. This modified calcium distribution remained unchanged for 24 h following irradiation. Calcium-activated "ecto"-localized ATPase was detected as a punctuated-linear distribution of the reaction product outlining whole areas of glial and neuronal plasma membrane in the habenula of control animals. This pattern did not change on microwave irradiation. However, a quercetin-sensitive "endo"-localized Ca(2+)-ATPase activity appeared in some nerve terminals 24 h after irradiation. Thus, microwave irradiation can influence neuronal calcium homeostasis by inducing Ca2+ redistribution across the plasma membrane and by modifying Ca(2+)-ATPase activity. However, no direct correlation between these effects could be demonstrated by the present study.

Animals↗
PubMed2003

Usefulness of flexible colonoscopic microwave coagulation therapy for a colorectal anastomotic stricture.

PURPOSE: Several methods of treatment for benign anastomotic strictures after anterior resection have been described. We describe a simple, safe, effective, and inexpensive method for treating benign colorectal anastomotic stricture by means of microwave coagulation under flexible colonoscopic visualization. METHODS: Eighteen patients with rectal or rectosigmoidal cancer underwent low anterior resection or anterior resection without colonic pouch and colorectal anastomosis by a double-stapling technique with PCEEA. Two of 18 patients (11.1 percent) developed an anastomotic stenosis. A microwave electrode was passed through the biopsy channel of the flexible colonoscope. Under flexible colonoscopic visualization, microwave irradiation was performed at four points (3, 6, 9, and 12 o'clock) in the stricture site because of granulation scar to obtain an adequately coagulated area. No bougies were performed thereafter. RESULTS: The anastomotic strictures could be dilated adequately, the patients could defecate satisfactorily, and their abdominal distentions and bowel symptoms were resolved. No complications occurred. No occurrence of restricture has been observed. CONCLUSION: Flexible endoscopic, microwave coagulation therapy is a useful, simple, effective, and safe method for the treatment of benign colorectal anastomotic strictures.

Anastomosis, Surgical↗
PubMed2006

Microwave-triggered metal-enhanced chemiluminescence (MT-MEC): application to ultra-fast and ultra-sensitive clinical assays.

In this rapid communication we describe a new approach to protein detection with chemiluminescence. By combining common practices in protein detection with chemiluminescence, microwave technology, and metal-enhanced chemiluminescence, we show that we can use low power microwaves to substantially increase enzymatic chemiluminescent reaction rates on metal substrates. As a result, we have found that we can in essence trigger chemiluminescence with low power microwave (Mw) pulses and ultimately, perform on-demand protein detection assays. Using microwave triggered metal-enhanced chemiluminescence (MT-MEC), we not only improve the sensitivity of immunoassays with enhanced signal-to-noise ratios, but we also show that we can accurately quantify protein concentrations by integrating the photon flux for discrete time intervals.

Avidin↗