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At least 1,099 records · Page 61Linked to original sources
PubMed1988

Application of invasive microwave hyperthermia for the treatment of gliomas.

Twenty five cases of gliomas of the brain were operated upon by debulking the tumour masses. Following this, microwave hyperthermia was given by heating a measured volume of Ringer's solution instilled into the tumour cavity. This was followed by a 'dry treatment' without Ringer's solution. The follow up of these cases revealed that 11 cases have died and 14 cases are alive post-operatively. For those that are alive, the follow up period ranges from 21 to 41 months with the mean survival period of 31.1 months; in this group, 12 cases have a Kanofsky scale of 80-100, i.e. they are fully independent. The other two cases have a score of 50 or under and they need institutional care. In this study, we believe that the first order effect of microwave hyperthermia is predominantly thermal and in the published literature, and in this investigation, there is no clear evidence that microwave radiation produces any other beneficial and quantifiable effect on the tissue.

Brain Neoplasms↗
PubMed1980

Effect of microwave irradiation on brain tissue structure and catecholamine distribution.

Recently we reported regional levels of norepinephrine and dopamine in rat brain following microwave irradiation. In our report, we also compared these levels with those of norepinephrine and dopamine following decapitation. Catecholamine levels following exposure to microwave irradiation significantly increased in several areas. However, whether these increases resulted from compound transfer associated with tissue disruption due to high intensity microwave irradiation was not determined. Sections of corpus striatum and locus coeruleus were examined with a light microscope and the interface of the striatum and the cortex showed no trace of tissue breakdown. Transformed cells, vacuolation, and indications of pyknotic degeneration in the nucleus were found in locus coeruleus after irradiation, but the shapes of these cells were well-defined. Electron microscopic photographs of synapses in the same area showed membrane damage after exposure for 5 s at 1.3 kW, but synaptic vesicles were clearly defined. It was concluded that the increased catecholamine levels were not the result of tissue disruption following rapid heating of the brain by irradiation.

Animals↗
PubMed1979

Dopamine diffusion after microwave fixation at 986 MHz.

It has been previously demonstrated by us that microwave irradiation at 2450 MHz causes diffusion of dopamine from rat brain regions of high dopamine concentration to contiguous regions low in dopamine. Because we have found that the heating pattern at 986 MHz is opposite to that seen at 2450 MHz, we attempted in the present study to eliminate DA diffusion by heating at 986 MHz. However, dopamine levels were elevated in frontal and parietal cortex, remainder of cortex, and amygdala after sacrifice by microwave irradiation at 986 MHz. Norepinephrine levels were unaffected by sacrifice method. Microwave-induced diffusion of certain substances must be considered in the interpretation of regional neurochemical data.

Animals↗
PubMedDate not supplied

Histoprocessing with the microwave oven: an update.

This paper evaluates and extends the novel method of preparing tissue blocks for paraffin sections within 30 to 60 min, that was proposed in early 1985 in a paper by Boon et al. (1986). More than 2 years' additional experience and testing various microwave ovens has led to new protocols reported in this paper. Results are given of testing (i) an especially designed microwave oven for histoprocessing, (ii) microwavable reagents, (iii) processing larger numbers of specimens simultaneously, (iv) handling different types and sizes of tissue. It is concluded that effective temperature control offers substantial advantages. In addition, the possibilities of performing routine diagnostic pathology omitting formalin altogether are sketched.

Female↗
PubMedDate not supplied

Microwave-aided technique to detect bromodeoxyuridine in S-phase cells using immunogold-silver staining and plastic-embedded sections.

A technique is described to detect bromodeoxyuridine (BrdU) incorporated by cells in S-phase, with a monoclonal antibody, using removable plastic embedding and immunogold-silver staining (IGSS). The incubation times were reduced and the immunological reactions enhanced by microwave irradiation. The embedding in methyl methacrylate enabled us to make thinner sections and it improved the quality of the preparations. The methyl methacrylate did not hinder the reaction of BrdU with the antibody because it could be removed prior to the IGSS procedure. The IGSS procedure appeared to be very sensitive, requiring lower concentrations of the antibodies than other methods. The use of microwave irradiation shortened the time needed to stain a section from 7 to less than 4 h. Furthermore, using microwave irradiation, the concentration of the antibodies needed could be reduced even further compared with the normal IGSS procedure. In sections of the mouse testis and small intestine only nuclei of cells known to be able to proliferate appeared BrdU positive. The non-specific background staining was found to be negligible. In testes of mice that received both 3H-thymidine and BrdU more than 95% of the radioactively labelled cells also showed BrdU label and vice versa. This indicates that both methods are equally sensitive for detecting cells in S-phase.

Animals↗
PubMedDate not supplied

Differentiating the effects of microwave and heat on tissue proteins and their crosslinking by formaldehyde.

Alkaline phosphatase activity in mouse liver blocks, cooled by an ice-bath, decreased by 50% in 5 min of microwave irradiation (280 W). This loss of protein tertiary structure has been mirrored by ultrastructural changes in the same tissue. Microwave irradiation did not produce cleavage or polymerization of lysozyme or haemoglobin. Protein formaldehyde reaction mixtures produced protein polymers between 0 degree and 40 degrees C which could be separated by SDS-polyacrylamide gel electrophoresis. Microwave irradiation of lysozyme or haemoglobin plus formaldehyde on ice-bath up to 30 min produced a similar electrophoretic pattern. When lysozyme or haemoglobin plus formaldehyde was heated to 60 degrees C for 30 min, the protein polymers migrated faster on electrophoresis, suggesting a smaller hydrodynamic volume than expected due to intramolecular crosslink formation, not opened up under the conditions of electrophoresis.

Alkaline Phosphatase↗
PubMedDate not supplied

Microwave irradiation in label-detection for diagnostic DNA-in situ hybridization.

A DNA-in situ hybridization protocol was adapted for application to sections of routinely processed paraffin embedded material. This protocol was developed previously for detecting DNA-virus infected cells in whole cell preparations and employs biotinylated DNA as probe. Three different biotin detection methods were optimized and applied. The first uses streptavidin and a biotinylated complex of alkaline phosphatase, the second consists of an immunogold-silver staining, and the third of a peroxidase technique using a silver amplification. The alkaline phosphatase method was the most rapid, and as sensitive as the immunogold-silver staining. The peroxidase method was the most sensitive. Microwave irradiation was applied to the different incubation steps of these three detection methods. Short incubations with microwave irradiation gave results comparable to those obtained with conventional incubations, when streptavidin, antibiotin, complexed alkaline phosphatase, or gold labelled goat antirabbit were used. It was thus shown that microwave irradiation creates the possibility of a very rapid label-detection for nonradioactive DNA-in situ hybridization.

Alkaline Phosphatase↗
PubMedDate not supplied

A comparison of microwaves and heat alone in the preparation of tissue for electron microscopy.

Microwaves have been used to stabilize tissues from the gastrointestinal tract for scanning electron microscopy. The temperature reached is important. Above 55-60 degrees C, epithelial cell sheets begin to lift revealing the underlying basement membrane. These cells may be recovered from the supernatant by micropore filtration or the celloidin sock technique. At higher temperatures, produced either by microwave irradiation or in a water bath, more enterocytes are released. The epithelial cells are larger with increasing temperatures, less with microwaves than with heat alone or in the presence of formaldehyde. At 70 degrees C and above, some proteins are lost and there is false localization of RNA. Some immunoperoxidase reactions are still positive after exposure of the tissue to 60 degrees C. Tissues fixed in boiling formaldehyde retain a surprisingly good morphology.

Animals↗
PubMedDate not supplied

Microwave-assisted staining procedures in routine histopathology.

The use and practicability of microwave-assisted staining procedures in routine histopathology over more than three years has been evaluated. A domestic microwave oven was used to speed up the following staining procedures: Haematoxylin-Eosin (for frozen sections), Romanowsky-Giemsa, Periodic acid-Schiff (PAS), Ziehl-Neelson, Papanicolaou, Feulgen and Grocott--stain on buffered formalin fixed sections or cytologic smears. These staining procedures can be made highly reproducible providing; (1) Staining vessels are placed in the same position inside the oven; (2) Accurate timing in seconds is observed. Microwave-assisted staining procedures are equal to or even superior to those of the standard methods. Staining times can be reduced to 2%-10% of the conventional staining procedures. The basic staining protocols are presented.

Azure Stains↗
PubMedDate not supplied

Decalcification of teeth in a microwave oven.

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 degrees C for repeated periods of 1-2 h. Control specimens were placed in a conventional oven at 39 degrees 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.

Animals↗
PubMed1990

An improved technique for hyaluronan histochemistry using microwave irradiation.

A hyaluronan binding protein (HABP), extracted from cartilage, was biotin-labelled and used for histochemical localization of hyaluronan (HA) in tissue sections. Various tissues were fixed for a mixture of formaldehyde and glutaraldehyde during microwave irradiation. The microwave oven when set at 700 W and 45 degrees C yielded an intense and specific staining of HA. Under these conditions the relative proportion of the two aldehydes did not influence the staining intensity. Aldehyde fixation during microwave irradiation for HA histochemistry, (1) save time, (2) eliminates the use of cetylpyridinium chloride (CPC), and (3) improves the reproducibility.

Adrenal Glands↗
PubMed1989

Effects of 2.8-GHz microwaves on restrained and ketamine-anesthetized rats.

To compare the effects of ketamine anesthesia and mild restraint on microwave-induced thermal and cardiovascular changes, sixteen Fischer 344 rats were irradiated in two states: 1) unanesthetized, restrained, and 2) ketamine-anesthetized (150 mg/kg, I.M.). Individual animals were exposed in H orientation to far-field continuous-wave 2.8-GHz microwaves. Irradiation was conducted at a power density of 60 mW/cm2 (whole-body average specific absorption rate of 14.4 W/kg) to cyclicly increase colonic temperature from 38.5 to 39.5 degrees C. Colonic and subcutaneous temperatures, aortic blood pressure, and heart rate were continuously monitored. The time required for colonic temperature to increase 1 degree C was significantly longer in the anesthetized state; however, the time to return to baseline was similar under both conditions. Heart rate and blood pressure significantly increased during irradiation in the unanesthetized state, but remained virtually unchanged in the anesthetized state. The subcutaneous temperature increase during exposure was significantly greater in the anesthetized state. The differences in responses of anesthetized and mildly restrained animals should be considered when conducting experiments on thermoregulatory responses to microwave irradiation.

Animals↗
PubMed1978

Studies on blood-brain barrier permeability after microwave-radiation.

Since the reported alterations of permeability of the blood-brain barrier by microwave radiation have implications for safety considerations in man, studies were conducted to replicate some of the initial investigations. No transfer of parenterally-administered fluorescein across the blood-brain barrier of rats after 30 min of 1.2-GHz radiation at power densities from 2--75 mW/cm2 was noted. Increased fluorescein uptake was seen only when the rats were made hyperthermic in a warm-air environment. Similarly, no increase of brain uptake of 14C-mannitol using the Oldendorf dual isotope technique was seen as a result of exposure to pulsed 1.3-GHz radiation at peak power densities up to 20 mW/cm2, or in the continuous wave mode from 0.1--50 mW/cm2. An attempt to alter the permeability of the blood-brain barrier for serotonin with microwave radiation was unsuccessful. From these studies it would appear that the brain must be made hyperthermic for changes in permeability of the barrier induced by microwave radiation to occur.

Animals↗
PubMed1982

Interaction of microwave radiation with turkey sperm.

Turkey sperm were exposed to 2.45 GHz microwave radiation in a temperature controlled waveguide apparatus. Temperature was maintained at 40.0 +/- 0.5 degrees C. The sperm were exposed for 30 min to a specific absorption rate (SAR) of 1, 10, or 50 mW/g. Before and following microwave exposure the following parameters were examined: percentage viability, percentage abnormal sperm, and release of the enzymes lactate hydrogenase (LDH) and glutamic oxalic transaminase (GOT). These parameters were not altered significantly by microwave exposure under the conditions tested.

Animals↗
PubMed1990

[Chemical and microbiological studies of microwave-treated milk].

Pasteurized milk was treated with microwaves for 2.5 minutes (2450 MHz, 650 W). Important chemical components (vitamin A, beta-carotin, vitamins B1, B2, C, E; activity of peroxidase, xanthinoxidase; content of fat and peroxides, percentage of solids, content of raw protein, content of all microorganisms and storage stability were examined. Ascorbic acid (reduction of 36%) and alpha-tocopherol (reduction of 17%) were influenced by microwave treatment, whereas other chemical parameters, odor and flavor remained unchanged. The content of microorganisms was reduced from about 10(4) to 10(2) per milliliter. Untreated milk had a content of 10(7) microorganisms per milliliter after 10 days storage at 8 degrees C and a taste of acidity, whereas in milk treated with microwaves only 10(4) microorganisms per ml were identified and no organoleptic changes could be observed after 14 days storage at 8 degrees C.

Animals↗
PubMed1978

Studies on the interaction of microwave radiation with cholinesterase.

The significance of the enzyme cholinesterase in studies on the biological effects of microwaves is discussed. Experiments were performed on the direct effect of microwave radiation on the enzyme activity in aqueous solution, and in rabbit blood. Microwave radiation was found to have an effect only when the temperature increase was great enough to denature the enzyme.

Animals↗
PubMed1996

The use of microwave irradiation as a pretreatment to in situ hybridization for the detection of measles virus and chicken anaemia virus in formalin-fixed paraffin-embedded tissue.

Microwave irradiation was investigated as a pretreatment to in situ hybridization on formalin-fixed, paraffin-embedded tissue. Two probe/tissue systems were used: a single-stranded RNA probe for the detection of measles virus nucleocapsid genome in subacute sclerosing panencephalitis brain tissue, and a double stranded DNA probe for chicken anaemia virus in thymus of chicken infected with the virus. Microwaving, when used as sole pretreatment, was not as effective as the more traditional enzyme pretreatments for in situ hybridization. However, when used in combination with existing pretreatments, a significant increase was found in hybridization signal in both brain and thymus tissue. This was emphasized when combination enzyme/microwave pretreatments were used prior to detection of measles virus by in situ hybridization in a series of five archival subacute sclerosing panencephalitis cases. The use of microwave irradiation would be recommended as a means of supplementing in situ hybridization methods, especially when using long-term formalin fixed paraffin-embedded tissue.

Animals↗
PubMed2004

Monitoring water content of rat lung tissue in vivo using microwave reflectometry.

Measurement of lung water is an important diagnostic means of assessing pulmonary oedema. Water content affects the dielectric spectrum at microwave frequencies, but quantification is still a problem. A new lung tissue model is presented that allows the calculation of water content from dielectric permittivity. The dielectric permittivity of lung tissue was measured by microwave reflectometry using a non-invasive surface probe. During perfusion of rat lungs (n = 22) with blood, injury was induced by interruption of the blood supply for a duration between 0 (control) and 2 h. Water content was assessed from dielectric permittivity using a new mixture formula and was also determined by drying and weighing. The mixture formula allows for the dielectric polarisation of water, dry matter and air in the tissue. A linear correlation was found between total water content determined from dielectric permittivity and that from drying and weighing (y= 1.001x, R2 = 0.8). Lung injury showed an increase in total water content from 80.9 +/- 1.2% (control) to 84.1 +/- 0.9% (p < 0.01). The analysis of dielectric permittivity data at microwave frequencies with the new tissue model is sensitive enough to detect water accumulation produced by lung injury and it can be used to monitor total water content without tissue destruction.

Animals↗