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At least 19 recordsLinked to original sources
PubMed1992

Does microwave irradiation have other than thermal effects on histological staining of the mammalian CNS? A light microscopical study of microwave stimulated staining under isothermal conditions in man and rat.

The question whether or not microwave irradiation exerts other than thermal effects on histological staining is still a matter of controversy. The present study was undertaken to reveal or reject such a so far hypothetical non-thermal irradiation effect. A device was developed, which enables exposure of histological sections or tissue pieces to microwave irradiation under isothermal conditions, i.e. with synchronous removal of the internal heat produced. Three classical neuroanatomical staining methods were tested on human and rat CNS. As control, identical procedures were performed without simultaneous microwave irradiation. The experiments were performed at three different temperature levels ranging from 5 to 50 degrees C. In none of the cases studied was a light microscopically appreciable difference observed between the microwave and non-microwave versions of a stain at the same temperature. The hypothesis of a separate non-thermal effect of microwave irradiation on histological staining is therefore rejected.

Animals↗
PubMed1975

The properties of bird feathers as converse piezoelectric transducers and as receptors of microwave radiation. II. Bird feathers as dielectric receptors of microwave radiation.

The characteristics of bird feathers as receptors of microwave fields were investigated in the 10- to 16-GHz region. Experiments were conducted coupling the specimen (feather) to a length of waveguide which served, together with other microwave components, as a primary detector. Microwave power radiation patterns were measured both in the presence and in the absence of the specimen. Results indicated a substantial increase in the microwave power collected in the forward direction and a decrease of the radiation pattern beam width when the feather was present. Fruthermore, some experiemental evidence indicated the possibility of inducing piezoelectric effects in the specimen by audiofrequency pulse-modulated microwave fields. These results are important in view of (i) the fundamental role that feathers play in the life of birds and (ii) the influence of environmental factors on bird behaviour.

Animals↗
PubMed1979

The role of water in microwave absorption by biological material with particular reference to microwave hazards.

The problem of the absorption of the energy of plane electromagnetic radiation by an aqueous solution of macromolecules is considered. A simplified model for the hydrated molecule is employed, consisting of a spherical shell of bound water surrounding a spherical core. The power deposition per unit volume of the shell is calculated in the frequency range 100 MHz-100 GHz for several bound water relaxation frequencies. In each case the corresponding values are also calculated for free water for comparison. The values obtained for the bound water are shown to be significantly higher than those for the free water up to frequencies of at least 1 GHz. The maximum difference between these two sets of values is of the order of a factor of five and occurs roughly at the bound water relaxation frequency. Because of the strong coupling between the bound water molecules and the macromolecules present in biological material this result could be a significant factor in the explanation of the biological effects of microwaves at a molecular level.

Macromolecular Substances↗
PubMedDate not supplied

Microwave interrogation of dielectric targets. Part II: by microwave time delay spectroscopy.

A method is described which overcomes the problems of multipath propagation and range ambiguity that is suffered by the single-frequency continuous-wave microwave-imaging system described in part I. This technique is essentially a variation of chrip radar techniques, which have been adapted to time delay and attenuation measurements through a target. The feasibility of discriminating between paths whose differential time delay is on the order of 100 ps is demonstrated. Further, the need for small physical aperture in the transmitting and receiving antennas is demonstrated.

Electric Conductivity↗
PubMed1992

Effects of whole body microwave exposure on the rat brain contents of biogenic amines.

The effects of whole body microwave exposure on the central nervous system (CNS) of the rat were investigated. Rats weighing from 250 to 320 g were exposed for 1 h to whole body microwave with a frequency of 2450 MHz at power densities of 5 and 10 mW.cm-2 at an ambient temperature of 21-23 degrees C. The rectal temperatures of the rats were measured just before and after microwave exposure and mono-amines and their metabolites in various discrete brain regions were determined after microwave exposure. Microwave exposure at power densities of 5 and 10 mW.cm-2 increased the mean rectal temperature by 2.3 degrees C and 3.4 degrees C, respectively. The noradrenaline content in the hypothalamus was significantly reduced after microwave exposure at a power density of 10 mW.cm-2. There were no differences in the dopamine (DA) content of any region of the brain between microwave exposed rats and control rats. The dihydroxyphenyl acetic acid (DOPAC) content, the main metabolite of DA, was significantly increased in the pons plus medulla oblongata only at a power density of 10 mW.cm-2. The DA turnover rates, the DOPAC:DA ratio, in the striatum and cerebral cortex were significantly increased only at a power density of 10 mW.cm-2. The serotonin (5-hydroxytryptamine, 5-HT) content in all regions of the brain of microwave exposed rats was not different from that of the control rats. The 5-hydroxyindoleacetic acid (5-HIAA) content in the cerebral cortex of microwave exposed rats was significantly increased at power densities of 5 and 10 mW.cm-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Microwave coagulation therapy on VX-2 carcinoma implanted in rabbit urinary bladders.

In order to evaluate the effectiveness of microwave coagulation therapy on urinary bladder carcinoma, we conducted a series of experiments using carcinoma VX-2 cells designed for the application on animal hosts. Three days after implantation of VX-2 cells into the bladder of the rabbits, microwave coagulation therapy was performed. The antitumor effect, i.e. the survival rate, the histological study and the immunological response of the microwave therapy was examined in comparison with the control group (no treatment), the partially cystectomized group and the sham-operated group (no tumor cell implantation). The results were obtained as follows. (1) The survival rate in the microwave group was greater than that in the control group. (2) The stimulation index value (SI), which represents humoral immunity, decreased postoperatively in all groups. In the microwave group, SI increased gradually beginning 21 days after the transient decrease. (3) Histological findings revealed severe degeneration, necrosis and complete eradication of the cancer cells of the bladder wall in the microwave group, however, perforation of the urinary bladder could not be detected. The results indicate that microwave coagulation therapy is an effective procedure for urinary bladder tumors. Furthermore, microwave therapy may also accelerate the inactivation of immunological suppressors in the carcinoma host, an additional benefit of the microwave procedure.

Animals↗
PubMed1977

Effect of microwave radiation on cells treated with membrane-injuring substances.

WISH cells grown in vitro were pretreated with subcytotoxic concentrations of digitonin, cortisol and purified bacterial toxins -- staphylococcal beta-haemolysin or Clostridium perfringens alpha-toxin and irradiated with 3 GHz electromagnetic wave (microwaves) at the field power densities 5 or 40 mW/cm2. At 40 mW/cm2 increase in temperature of the culture medium of about 2-3 degrees C was noted, while at 5 mW/cm2 no detectable increase in temperature was found. Control and pretreated WISH cells after irradiation in the microwave field were used for evaluation of their viability, incorporation of tritiated thymidine, glycine and uridine and level of intracellular cyclic AMP. Irradiation with microwaves resulted in lowering of thymidine and glycine incorporation along with changes in the intracellular amount of cAMP (decrease in cells exposed to 5 mW/cm2 and increase in those exposed to 40 mW/cm2). Under both conditions viability of the cultures was normal. Pretreatment of cells with digitonin or purified bacterial toxins followed by irradiation with microwaves resulted in enhancement of the cytotoxic effect with lowering of cell viability, especially after exposition to power density of 40 mW/cm2. Cortisol led to decrease in 3H-glycine and 3H-uridine incorporation into WISH cells, but did not influence the reaction of the cells to microwave radiation. In view of the results presented it may be concluded that substances injuring cell membranes sensitize cell cultures to electromagnetic radiation of the microwave range and may enhance the specific (non-thermal) effect of microwaves.

Cells, Cultured↗
PubMed1978

Microwave fixation versus formalin fixation of surgical and autopsy tissue.

Microwave irradiation of surgical and autopsy tissue penetrates, fixes, and hardens the tissue almost immediately (the fluid media used in the microwave consisted of saline, ten percent phosphate buffered formalin, and distilled water). Tissue sections from a representative sample of organs were tested. Comparable sections were simultaneously fixed in a phosphate buffered ten percent formalin bath in a vaccum oven as a control. Hematoxylin and eosin were used to stain the sections. Results equal to and superior to the control method were obtained. Saline microwave fixation was superior to formalin microwave fixation. Tissues placed in Zenker's solution and fixed in standard microwave oven (for approximately one minute) yielded results at least equal to conventional Zenker fixation (approximately two hours). No tissue hardening resulted from Zenker microwave fixation. A unique time versus temperature graph (microwave heating curve) reduces individual variation with this technique.

Autopsy↗
PubMed1979

Microwave cookery of beef patties: browning methods.

Four microwave cooking/browning methods were studied to determine their effects on energy consumption, cooking time, cooking losses, and sensory quality. Ground beef patties were cooked by the following methods: Microwave and browning element, microwave with browning grill, microwave and broiler, combination range oven, microwave only, and conventional range oven. Browning plus microwave cooking increased cooking time by 51 to 71 per cent and energy consumption by 53 to 87 per cent, depending on the method. The microwave-with-browning-grill method showed an over-all advantage over other browning methods. The combination range oven was the least efficient.

Animals↗
PubMed1979

The effect of environmental temperature and average dose rate of microwave radiation on the oxygen-consumption rate of mice.

The oxygen consumption rate of CF1 male mice was determined before, during, and after sham- and microwave-irradiation at environmental temperatures of 20 degrees C, 24 degrees C, 30 degrees C, and 35 degrees C, relative humidity of 55%, and air flow rate of 78 ml/min. Five forward power levels ranging from 0.09 to 3.3 W, which resulted in corresponding average dose rates ranging from 1.2 to 45.1 mW/g were used. The values of the oxygen consumption rate were converted to those of the specific metabolic rate (SMR). The result indicates that with high levels of microwave dosing (greater than 10 mW/g) the specific metabolic rate of mice decreased in some cases, in the environmental temperatures of 20 degrees C and 24 degrees C. However, the decreased SMR values were not lower than the SMR values of the sham-irradiated group in 30 degrees C. In the case of 35 degrees C, the high level dosing with microwave radiation caused increases in the SMR value over the sham value. A possible trend towards increased SMR value during and after irradiationwith low level (1.6 mW/g) microwave radiation in the environmental temperatures of 24 degrees C and 30 degrees C suggests further experiments with low level microwave radiation to determine possible effects of low level microwave radiation in stimulating increases in specific metabolic rate.

Animals↗