Drying of Tribenuron,a Thermosensitive Biochemical

The extension of microwave use in the biochemical industry was explored by drying tribenuron, a thermosensitive biochemical, in a microwave oven and in a thermal vacuum oven. Tribenuron wet cakes, containing a mixture of solvents, methanol and water, were heated at 40 °C in both ovens. Nitrogen purge was used to prevent the decomposition of tribenuron from prolonged heating. Microwave heating dried tribenuron in twenty minutes while the vacuum oven heating required eighteen hours to dry the wet cakes. In addition, the tribenuron quality was maintained under microwave drying, but deteriorated in the thermal vacuum oven. Therefore, microwave technology is more effective in drying tribenuron than conventional vacuum ovens. The results of this study are important for the use of microwave drying on a large scale in biochemical companies.     

Microwave histoprocessing of bone marrow trephine biopsies

Summary In recent years, the microwave oven has been increasingly used in the pathology laboratory for processing of tissue for diagnostic purposes with a remarkable reduction in processing time and also reports of excellent morphology and immunohistochemistry. We evaluated some of these processes on post mortem bone marrow trephine biopsies and describe a novel way of processing these biopsies in the microwave oven.     

微波—吸附法提取朱砂玉兰鲜花香气成分

朱砂玉兰(Magnolia soulangeana)鲜花经微波处理,用XAD-4吸附提取头香物质。该方法不仅可以较快速地得到挥发性成分,而且提取的精油能保持原鲜花的香气香味。本文还讨论了用微波处理与不处理朱砂玉兰鲜花样品以及用水蒸汽蒸馏3种方法得到的精油在收率及化学成分上的差异及变化。     

Microwave applications in classical staining methods in formalin-fixed human brain tissue: a comparison between heating with microwave and conventional ovens.

The quality of microwave adaptations of three classical neuroanatomical staining methods (the Nissl, Klüver-Barrera and H?ggqvist stains) was tested on frozen serial sections from human brain specimens which has been stored for up to 10 years in 10% formalin. The conclusion was that the use of microwave irradiation reduces processing time and/or concentrations of the chemicals used, whereas the light microscopical quality of the stains considered is equal or improved as compared to their original counterparts. Next, a comparison was made between microwave adapted stains and classical procedures, which, except for the use of a conventional oven as heat source together with pre-heated solutions, were entirely identical. It appeared, that at light microscopical level no difference can be appreciated between the effect of internally (using microwave irradiation) and externally (using a conventional oven) supplied heat on the staining result.     

Mechanism of microwave sterilization in the dry state.

With an automated computerized temperature control and a specialized temperature measurement system, dry spores of Bacillus subtilis subsp. niger were treated with heat simultaneously in a convection dry-heat oven and a microwave oven. The temperature of the microwave oven was monitored such that the temperature profiles of the spore samples in both heat sources were nearly identical. Under these experimental conditions, we unequivocally demonstrated that the mechanism of sporicidal action of the microwaves was caused solely by thermal effects. Nonthermal effects were not significant in a dry microwave sterilization process. Both heating systems showed that a dwelling time of more than 45 min was required to sterilize 10(5) inoculated spores in dry glass vials at 137 degrees C. The D values of both heating systems were 88, 14, and 7 min at 117, 130, and 137 degrees C, respectively. The Z value was estimated to be 18 degrees C.     

Mechanism of microwave sterilization in the dry state

With an automated computerized temperature control and a specialized temperature measurement system, dry spores of Bacillus subtilis subsp. niger were treated with heat simultaneously in a convection dry-heat oven and a microwave oven. The temperature of the microwave oven was monitored such that the temperature profiles of the spore samples in both heat sources were nearly identical. Under these experimental conditions, we unequivocally demonstrated that the mechanism of sporicidal action of the microwaves was caused solely by thermal effects. Nonthermal effects were not significant in a dry microwave sterilization process. Both heating systems showed that a dwelling time of more than 45 min was required to sterilize 10(5) inoculated spores in dry glass vials at 137 degrees C. The D values of both heating systems were 88, 14, and 7 min at 117, 130, and 137 degrees C, respectively. The Z value was estimated to be 18 degrees C.     

Microwave oven and boiling waterbath extraction of hepatotoxins from cyanobacterial cells

Low-cost, straightforward methods for the extraction of microcystins and nodularins from cyanobacterial cells were developed using a microwave oven and boiling waterbath. The use of organic solvents, such as methanol, which can interfere with sensitive analytical procedures, e.g. immunoassays, can thus be avoided. Analysis by protein phosphatase inhibition assay and high performance liquid chromatography indicated that purified microcystin-LR was unaffected by the microwave oven and boiling waterbath treatments. Four microcystins of differing hydrophobicities were successfully extracted from Microcystis PCC 7813 by both treatments at yields equivalent to those obtained by longer protocols using methanol. Assessment of the microwave oven and boiling waterbath extraction methods with laboratory strains and environmental samples of cyanobacteria showed good correlation with results from lyophilisation and methanol extraction, when extracts were analysed by high performance liquid chromatography with diode array detection (R(2)>/=0.92). The microwave and boiling waterbath extraction methods also sterilised the environmental bloom samples, as evidenced by the abolition of heterotrophic bacterial growth.     

The use of microwave oven for the rapid hydrolysis of bile acid methyl esters.

An efficient and convenient procedure for the hydrolysis of bile acid methyl esters is described. This is achieved by the addition of aqueous lithium hydroxide in methanol/dioxane/tetrahydrofuran (or dimethylformamide) in the microwave oven. Under these conditions the formates as well as the acetate derivatives prepared under microwave irradiation conditions were also hydrolyzed, and the desired bile acids were isolated in 86-94% yield. All these reactions were completed in the microwave oven within 45-60 s.     

Evaluation of microwave radiation method for sample preparation of pine needles and wood for carbohydrate analysis

The aim of the current study was to test the suitability of microwave heating for stopping carbohydrate transformations in plant material. Needles and branches of Pinus sylvestris were treated in microwave oven (2.45 GHz, 800W) and compared to the samples treated in boiling ethanol (96 %). In extracts obtained from the microwaved material the ratio of sucrose to hexoses (glucose and fructose) decreased, while ethanol treatment resulted in stable extracts. The carbohydrate composition in dry samples estimated after a month of storage was persistent. The boiling of needles in ethanol in microwave oven gave the same results as boiling on a heating plate. In the woody material, differently from the needles, the total concentration of measured carbohydrates depended significantly on the preparation method. In the case of needles, the treatment of plant material in ethanol was better suited for the determination of carbohydrate levels than the microwave treatment.     

Microwave-stimulated glutaraldehyde and osmium tetroxide fixation of plant tissue: ultrastructural preservation in seconds.

Microwave-enhanced fixation of animal tissues for electron microscopy has gained in interest in recent years. Attempts to use microwave irradiation for the preparation of plant tissues are rare. In this study; I report on microwave conditions which allow a high quality preservation of plant cell structure. Tissues used were: internodes of Chara vulgaris, leaves of Hordeum vulgare, root tips of Lepidium sativum. Microwave irradiation was done with a commercial microwave oven (Sharp R-5975). Fixatives used were: 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer, pH 7.2 and 1% osmium tetroxide in veronal/acetate buffer, pH 7.2. Conventional fixations with glutaraldehyde/osmium were compared with microwave fixations. Examinations of thin sections showed that microwave fixation (glutaraldehyde or sequential aldehyde/osmium) is an attractive and rapid alternative method for processing plant tissues for electron microscopy. The optimal conditions found were: microwave oven at power level 50 W, 6.5 ml of fixative solution, irradiation times between 32-34 s, final temperature between 40 degrees C and 47 degrees C.     

A practical approach to routine immunostaining of paraffin sections in the microwave oven

Summary The Streptavidin-Biotin Complex (SABC) Immunostaining method can be carried out by performing the rinsing and blocking steps and in addition the incubations with the primary and the secondary antibody sera in the microwave oven. Irradiation of the Streptavidin-Biotin Complex reduces stain activity due to destruction of horseradish peroxidase (HRP) (Boon & Kok, 1988). Therefore, we decided not to perform this step in the microwave oven. The microwave incubations can be performed using antisera dilutions of 1:1000 (instead of 1:50) in tissue fixed with Kryofix, allowing staining in staining racks. This keeps hands-on time low and simplifies the microwave steps. It is very difficult to obtain reproducible results in the microwave oven using droplet incubations due to problems with hot spots and antenna effects. These problems are avoided when cuvettes are used and air is blown through the solutions during microwave incubations. With effective temperature control the method is highly reproducible, and takes at least 100 min less than the conventional SABC method. It is, in particular, attractive when large series of slides must be routinely immunostained and when reproducible results are desired.     

Decalcification of teeth in a microwave oven

Summary The effects of microwave radiation in reducing decalcification time were evaluated by measuring rates of calcium removal from samples of rat and cat teeth in 0.1 mol l^–1 EDTA. In some cases, 3% glutaraldehyde was added to the decalcifying solution. Test specimens were placed in a microwave oven at 39±2°C for repeated periods of 1–2h. Control specimens were placed in a coventional oven at 39°C for the same times or held at room temperature. The calcium removed during each treatment was measured using an atomic absorption spectrophotometer. There was no consistent difference between the results obtained with microwave radiation as compared with heating in a conventional oven, although in both cases decalcification was slightly faster than at room temperature. These results are attributed to thermal effects. No evidence for non-thermal effects of micro-radiation was found.     

Procedure for Evaluating the Effects of 2,450- Megahertz Microwaves upon Streptococcus faecalis and Saccharomyces cerevisiae

Modifications of a commercial 2,450-megahertz microwave oven were made so that 6 ml of microbial suspension could be exposed to the microwave field for various periods of time. The microorganisms were contained in the central tube of a modified Liebig condenser positioned in the approximate geometric center of the oven cavity. Kerosene at -25 C was circulated through the jacket of the condenser during microwave exposure permitting microwaves to reach the microbial suspension. Flow rates of the kerosene were varied to permit the temperature of the suspension to range from 25 to 55 C during microwave exposure. Conductive heating experiments using similar temperatures were also conducted. A thermocouple-relay system was employed to measure the suspension temperature immediately after the magnetron shutoff. Continuous application of microwaves to suspensions of 10(8) to 10(9)Streptococcus faecalis or Saccharomyces cerevisiae per ml appeared to produce no lethal effects other than those produced by heat. Respiration rates of microwave-exposed Scerevisiae were directly related to decreases in viable count produced by increased microwave exposure times.     

Destruction of Bacillus licheniformis spores by microwave irradiation

Aims:  To investigate the sporicidal mechanisms of microwave irradiation on Bacillus licheniformis spores.
Methods and Results:  We measured spore viability and the release of DNA and proteins, and performed transmission electron microscopy (TEM). A microwave oven (0·5 kW) was modified to output power at 2·0 kW, which allowed a shorter sterilization cycle. A 2·0 kW microwave treatment at the boiling temperature for 1 min did not kill all spores, but killed most spores. The spore inactivation rate was faster than that of boiling and 0·5 kW microwave oven. In contrast to boiling and 0·5 kW microwave treatments, the 2·0 kW microwave resulted in significant leakage of proteins and DNA from spores due to injury to the spore structure. TEM revealed that 2·0 kW microwave irradiation affected spore cortex hydrolysis and swelling, and ruptured the spore coat and inner membrane.
Conclusions:  These results suggest that 2·0 kW microwave irradiation ruptures the spore coat and inner membrane, and is significantly different from boiling.
Significance and Impact of the Study:  This study provides information on the sporicidal mechanisms of microwave irradiation on B. licheniformis spores.     

Rapid hydrolysis of proteins and peptides by means of microwave technology and its application to amino acid analysis

A rapid heating method of hydrolysis by the use of microwave oven has been applied to amino acid analysis of proteins and peptides. This convenient method has been compared with the conventional 6 N HCl hydrolysis at 110 degrees for 24 h. The advantages of this new method are its expedition and the accurate and comparable results as compared to the tedious conventional technique. The method provides a rapid processing of multiple samples within minutes instead of days and inexpensive access to the important data of amino acid compositions of proteins by the commonly used microwave oven. The necessary change in the design of hydrolysis vials and the safety precautions accompanying this novel use of microwave acid-digestion method are also described.     

Rapid Bielschowsky silver impregnation method using microwave heating.

The Bielschowsky silver impregnation method has been used extensively to demonstrate neuronal processes including dendrites, axons and neurofibrils. In this study, we examined the differences in the time required for and the staining quality of the Bielschowsky method for neuronal processes when microwave heating was used instead of processing at room temperature. For this purpose, a control group of sections stained according to the conventional method at room temperature was compared to an experimental group stained in a microwave oven at 180 W for 2, 4 and 1 min in 2% silver nitrate, ammoniacal silver nitrate and gold chloride, respectively. Light microscopic examination demonstrated that the normal structure was preserved in both groups and that there was no difference in the staining quality between the control and the microwave groups. In addition, staining time for this procedure was reduced to 8 min by using the microwave oven. Our study revealed that microwave irradiation can be used safely for Bielschowsky silver impregnation of neuronal tissues.     

Rapid polymerisation with microwave irradiation for transmission electron microscopy

Successful results of microwave polymerisation of different epoxy formulations have been reported in the literature. The present study was intended to shorten the time needed for polymerisation of epoxy resin by the use of a microwave technique. A standard double fixation and tissue processing was applied to samples of rat kidney tissue. Tissue samples from the control group were polymerised in a conventional oven at 60 degrees C for 48 h, while tissue from the experimental group was irradiated in a microwave oven, initially at 900 W for 10 min and then at 360 W for another 100 min. During this irradiation, the sealed BEEM capsules were submerged in a water bath, so that the temperature rise was uniform and constant. This resulted in a homogeneous and rapid polymerisation. The cutting properties of the blocks in both groups were similar and no noticeable difference in the quality of the sections was evident when evaluated with TEM. The results showed that the use of a microwave oven reduced the time needed for the polymerisation of Epon blocks without any loss in quality.     

Rapid Bielschowsky silver impregnation method using microwave heating

The Bielschowsky silver impregnation method has been used extensively to demonstrate neuronal processes including dendrites, axons and neurofibrils. In this study, we examined the differences in the time required for and the staining quality of the Bielschowsky method for neuronal processes when microwave heating was used instead of processing at room temperature. For this purpose, a control group of sections stained according to the conventional method at room temperature was compared to an experimental group stained in a microwave oven at 180 W for 2, 4 and 1 min in 2% silver nitrate, ammoniacal silver nitrate and gold chloride, respectively. Light microscopic examination demonstrated that the normal structure was preserved in both groups and that there was no difference in the staining quality between the control and the microwave groups. In addition, staining time for this procedure was reduced to 8 min by using the microwave oven. Our study revealed that microwave irradiation can be used safely for Bielschowsky silver impregnation of neuronal tissues.     

Rapid Bielschowsky silver impregnation method using microwave heating

The Bielschowsky silver impregnation method has been used extensively to demonstrate neuronal processes including dendrites, axons and neurofibrils. In this study, we examined the differences in the time required for and the staining quality of the Bielschowsky method for neuronal processes when microwave heating was used instead of processing at room temperature. For this purpose, a control group of sections stained according to the conventional method at room temperature was compared to an experimental group stained in a microwave oven at 180 W for 2, 4 and 1 min in 2% silver nitrate, ammoniacal silver nitrate and gold chloride, respectively. Light microscopic examination demonstrated that the normal structure was preserved in both groups and that there was no difference in the staining quality between the control and the microwave groups. In addition, staining time for this procedure was reduced to 8 min by using the microwave oven. Our study revealed that microwave irradiation can be used safely for Bielschowsky silver impregnation of neuronal tissues.