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At least 1,045 records · Page 58Linked to original sources
PubMed1997

Rapid microwave-stimulated fixation of entire prostatectomy specimens. Biomed-II MPC Study Group.

Conventional fixation of large solid surgical specimens is a slow process. Consequently, autolytic damage to tissues may occur if the fixative does not reach the central part of the specimen in time. However, as there is also a time relationship between formalin fixation and antigen masking, fixation for too long can also be detrimental. In seeking the optimum balance for fixation, microwave irradiation might be of assistance. This study set out to evaluate methods for fixing entire prostate glands within a brief period of time, using microwave-stimulated formalin fixation. The results show that entire prostates can be optimally fixed if formalin is present throughout the tissue as the temperature is increased by microwave irradiation. This is achieved by injecting the fixative into the prostate at multiple sites immediately following prostatectomy. The technique described ensures standardization of a critical step during tissue processing, leading to uniform microscopic results with both routine and immunohistochemical stains. It is a simple, rapid method, suitable for routine diagnostic use. Using this modified approach, DNA of much larger sizes can be extracted from paraffin-embedded material, which could expand the possibilities for molecular analysis.

Cadherins↗
PubMed1996

Transurethral microwave thermotherapy for benign prostatic hyperplasia: relation between clinical response and prostate histology.

The effectiveness of transurethral microwave thermotherapy (TUMT) for BPH has been confirmed. To identify the characteristics of the ideal candidate, retrospective analysis and morphometric study of prostatic tissue were performed. Forty-two patients with symptomatic BPH were included in the study; these comprised 10 patients treated for more than 3 months with anti-androgen pre-TUMT (group A) and 32 fresh cases (group B). Subjective and objective responses were evaluated at 2 months post TUMT. In 12 fresh cases who underwent pre-TUMT biopsy of the prostate, the stromal-to-epithelial ratio was determined via quantitative image analysis on a computer-assisted morphometry system. No significant differences in baseline patient characteristics were found between the two groups: age, prostate volume, peak flow rate (PFR), or International Prostate Symptom Score (I-PSS). However, significant differences in treatment outcome were found between the two groups (group A vs. group B, respectively): total energy delivered to the prostate: 96 kJ vs. 125 kJ: I-PSS decrease from baseline: 5.9 vs. 11.6; PFR increase from baseline: 1.1 vs. 4.7 ml/sec. There was a positive correlation between the I-PSS change from baseline and the stromal-to-epithelial ratio of the prostatic tissue (r = 0.4857). The results suggest that microwave interacts poorly with the prostate due to the artificially created "lack" of glandular tissue. The morphometric study also supports the contention that the histological composition of the prostatic tissue plays an important role in terms of microwave thermal interactions and treatment outcome.

Aged↗
PubMed1994

Ultrasonically guided percutaneous microwave coagulation therapy for small hepatocellular carcinoma.

BACKGROUND: The authors have used percutaneous microwave coagulation therapy (PMCT) as a new percutaneous local treatment for single unresectable hepatocellular carcinoma (HCC) measuring 2 cm or less in greatest dimension (small HCC). PMCT was used to attempt a cure of the disease. In this study, the efficacy of this treatment was assessed. METHODS: PMCT was performed on 18 patients with single small HCC. A microwave electrode (custom-made, 30-cm long by 1.6-mm thick) was inserted percutaneously into the tumor area under ultrasonic guidance. Microwaves at 60 W for 120 seconds were used to irradiate the tumor and surrounding area. RESULTS: After PMCT was administered, various image findings were correlated with tissue necrosis. At the tumor and surrounding area, ultrasonography showed echogenic change, contrast enhancement disappeared on contrast enhanced computed tomography, and magnetic resonance imaging (T2-weighted image) showed decreased intensity in all cases after treatment. Complete necrosis of the tumor area in a specimen obtained from one patient who underwent hepatectomy after PMCT also was confirmed. The treatment reduced levels of the tumor marker, alpha-fetoprotein, which had been high in some patients. Although the follow-up period was short (11-33 months), 17 patients remain alive. Local recurrence in the treated area has not been detected, and no serious side effects or complications have been encountered. CONCLUSIONS: PMCT may be an effective and safe treatment for small HCCs.

Adult↗
PubMed2000

The effect of gamma and microwave irradiation of wheat grain on development parameters of some stored grain pests.

Wheat grain was treated with different doses of gamma irradiation or different times of microwaves. Gamma rays (0.05-10 kGy) caused statistically significant differences in soluble protein contents and kernel hardness. Microwave treatment (15-180 s) resulted in some statistically significant changes in moisture and soluble protein contents. Mortality, intensity of feeding, fertility of adults, progeny number and development time of larvae of the granary weevil (Sitophilus granarius L.) on treated grain were observed. On the basis of progeny number and larval development time the coefficient of food value (CFV) was calculated. Some statistical differences were stated in studied parameters, however no one in all calculated coefficients of food values. The same treated grain was also used as a food for larvae of the confused flour beetle (Tribolium confusum Duv.) and Mediterranean flour moth (Ephestia kuehniella Zell.). Mortality of larvae and their development time were studied. Only gamma irradiated wheat grain at the dose 0.1 kGy used as a food for larvae of T. confusum Duv. caused statistically significant extension of development time by 7 days, when comparing to the control food. On the other hand, microwave treatment of wheat grain used as food significantly shorten the development time of larvae in both species.

Animals↗
PubMed2002

Comparison of the effects of microwave cooking and conventional cooking methods on the composition of fatty acids and fat quality indicators in herring.

The aim of this study was to examine the changes which occur under the influence of different heating methods in the compositions of fatty acids and selected fat quality indicators in fillets of herring. The results that are compared herein were obtained via conventional culinary techniques and using microwave radiation. Culinary processes like boiling, grilling and frying, whether done conventionally or with a microwave oven, did not lead to a reduction in the n-3 polyunsaturated fatty acids (PUFAs) fraction of the total fatty acids, indicating that these fatty acids have a high durability and a low susceptibility to thermal oxidative processes. The culinary processes used in this study also had an insignificant influence on the fat quality indicators--the peroxide and anisidine value. The fat quality indicators in herring, both after conventional and microwave heating, differ little, and indicate a low content of primary and secondary products of oxidation.

Animals↗
PubMed2004

Controlled microwave heating in modern organic synthesis.

Although fire is now rarely used in synthetic chemistry, it was not until Robert Bunsen invented the burner in 1855 that the energy from this heat source could be applied to a reaction vessel in a focused manner. The Bunsen burner was later superseded by the isomantle, oil bath, or hot plate as a source for applying heat to a chemical reaction. In the past few years, heating and driving chemical reactions by microwave energy has been an increasingly popular theme in the scientific community. This nonclassical heating technique is slowly moving from a laboratory curiosity to an established technique that is heavily used in both academia and industry. The efficiency of "microwave flash heating" in dramatically reducing reaction times (from days and hours to minutes and seconds) is just one of the many advantages. This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.

Chemistry, Organic↗
PubMed2004

Influence of anesthesia on ocular effects and temperature in rabbit eyes exposed to microwaves.

To investigate the effect of systemic anesthesia on ocular effects and temperature in rabbit eyes exposed to microwaves, one eye each of 43 male pigmented rabbits (Dutch, 1.8-2.2 kg) was exposed at 2.45 GHz for 60-20 min (300 mW/cm2; 108 W/kg), either under anesthesia (ketamine hydrochloride (5 mg/kg) + xylazine (0.23 mg/kg)) or without anesthesia. Changes in the anterior segment were evaluated by image analysis utilizing a Scheimpflug camera, specular microscopy, and a laser flare cell meter. Temperatures within the eye were measured during microwave exposure by a Fluoroptic thermometer. The exposed eyes showed miosis, conjunctival congestion, corneal edema, and an increase in the light scattering of the anterior shallow cortex in the pupillary area of the lens. The group under systemic anesthesia showed much stronger symptoms than those treated without anesthesia. All of the anterior ocular changes disappeared within a week. The highest temperature during exposure was in the vitreous, followed by the anterior chamber, and the retrobulbar cavity of the orbit. The ocular temperatures of the rabbits under systemic anesthesia were 2-9 degrees C higher than those without anesthesia. Body temperature showed an increase of 1 degrees C during the exposure. Acute high intensity microwave exposure temporarily induced anterior segments inflammation and lens changes. The more pronounced ocular effects in the anesthetized rabbits were associated with the significantly higher ocular temperatures in the anesthetized animals. The influence of systemic anesthesia on ocular changes should be considered.

Anesthetics↗
PubMed2005

915 MHz microwaves and 50 Hz magnetic field affect chromatin conformation and 53BP1 foci in human lymphocytes from hypersensitive and healthy persons.

We used exposure to microwaves from a global system for mobile communication (GSM) mobile phone (915 MHz, specific absorption rate (SAR) 37 mW/kg) and power frequency magnetic field (50 Hz, 15 muT peak value) to investigate the response of lymphocytes from healthy subjects and from persons reporting hypersensitivity to electromagnetic field (EMF). The hypersensitive and healthy donors were matched by gender and age and the data were analyzed blind to treatment condition. The changes in chromatin conformation were measured with the method of anomalous viscosity time dependencies (AVTD). 53BP1 protein, which has been shown to colocalize in foci with DNA double strand breaks (DSBs), was analyzed by immunostaining in situ. Exposure at room temperature to either 915 MHz or 50 Hz resulted in significant condensation of chromatin, shown as AVTD changes, which was similar to the effect of heat shock at 41 degrees C. No significant differences in responses between normal and hypersensitive subjects were detected. Neither 915 MHz nor 50 Hz exposure induced 53BP1 foci. On the contrary, a distinct decrease in background level of 53BP1 signaling was observed upon these exposures as well as after heat shock treatments. This decrease correlated with the AVTD data and may indicate decrease in accessibility of 53BP1 to antibodies because of stress-induced chromatin condensation. Apoptosis was determined by morphological changes and by apoptotic fragmentation of DNA as analyzed by pulsed-field gel electrophoresis (PFGE). No apoptosis was induced by exposure to 50 Hz and 915 MHz microwaves. In conclusion, 50 Hz magnetic field and 915 MHz microwaves under specified conditions of exposure induced comparable responses in lymphocytes from healthy and hypersensitive donors that were similar but not identical to stress response induced by heat shock.

Adult↗
PubMed1980

Tests of mutagenesis and reproduction in male rats exposed to 2,450-MHz (CW) microwaves.

Tests of mutagenesis and reproduction were conducted in male rats which were irradiated by 2,450-MHz, continuous-wave (CW) microwaves, 4 hr/day from day 6 of gestation to 90 days of age at 5 mW/cm2; or 5 hr/day for five days beginning on the 90th day of age at 10 mW/cm2; or 4 hr/day, 5 days/wk for four weeks, beginning on the 90th day of age. During selected weekly periods after treatment, the rats were bred to pairs of untreated, normal female rats that were examined in late pregnancy by means of dominant lethal assay. The reproductive efficiency of these males, as reflected in their breeding, was also examined for changes relating to their microwave experience. No significant evidence of germ-cell mutagenesis was detected when data of microwave-exposed males were compared with those of sham-exposed males, even though there were significant increases in rectal and intra-testicular temperatures at a power density of 28 mW/cm2. Temporary sterility, as indexed by fewer pregnancies, was seen at the highest power density.

Animals↗
PubMed1980

Modification of the repeated acquisition of response sequences in rats by low-level microwave exposure.

The acute effects of microwave exposure on a repeated acquisition baseline were investigated in three rats. Each session the animals acquired a different four-member response sequence. Each of the first three correct responses advanced the sequence to the next member, and the fourth correct response produced food reinforcement. Incorrect responses produced a three-second timeout. Baseline and control sessions were characterized by a decrease in errors within each session. The animals were acutely exposed to a 2.8 GHz pulsed-microwave field prior to test sessions, with average power densities ranging from 0.25 to to 10 mW/cm2. In comparison to control sessions, 1/2 hour of exposure to microwave radiation at power densities of 5 and 10 mW/cm2 increased errors and altered the pattern of within-session acquisition. Exposure to the 10 mW/cm2 power density decreased the rate of sequence completion in all animals. The results of exposures at 0.25, 0.5, and 1 mW/cm2 power densities were generally within the control range. The results are interpreted as indicating a disruption in the discriminative stimulus control of the repeated acquisition behavior.

Animals↗
PubMed1981

Flight, orientation, and homing abilities of honeybees following exposure to 2.45-GHz CW microwaves.

Foraging-experienced honeybees retained normal flight, orientation, and memory functions after 30 minutes' exposure to 2.45-GHz CW microwaves at power densities from 3 to 50 mW/cm2. These experiments were conducted at power densities approximating and exceeding those that would be present above receiving antennas of the proposed solar power satellite (SPS) energy transmission system and for a duration exceeding that which honeybees living outside a rectenna might be expected to spend within the rectenna on individual foraging trips. There was no evidence that airborne invertebrates would be significantly affected during transient passage through microwaves associated with SPS ground-based microwave receiving stations.

Animals↗
PubMed1981

In vitro microwave effects on human neutrophil precursor cells (CFU-C).

Human marrow cells were irradiated with 2450-MHz CW microwaves in a fluid-filled waveguide irradiation system. Cell exposure was conducted by placing a marrow cell suspension in 20-microliter glass microcapillary tubes were positioned in the exposure chamber, and irradiated at power densities from 31 to 1,000 mW/cm2 (with corresponding specific absorption rates of 62 to 2,000 mW/g) for 15 minutes. The temperature of the sample was maintained at a fixed point. Sham-irradiated (SI) and microwave-irradiated (MWI) cells were cultured in a methylcellulose culture system for neutrophil colony proliferation. There was no reduction in neutrophil colony number on days 6-7 or 12-14 in cells exposed at 31 or 62 mW/cm2, but as the power density was increased to 1,000 mW/cm2, there was a reduction in colony number of MWI cells compared with SI cells. The microwave interaction with the human neutrophil colony-forming cells was apparently not related to temperature rise, or to the state of cells cycle, and was irreversible.

Bone Marrow↗
PubMed1982

Photic cuing of escape by rats from an intense microwave field.

A total of 16 female hooded rats was first observed for baseline behaviors and then they received 25 2-min trials of training, five trials per day, under one of four stimulus conditions (all ns = 4): exposure to a highly intense 918-MHz field (dose rate, 60 mW/g); exposure to photic stimulation (approximately 350 1x); exposure to the field in synchrony with photic stimulation; or exposure to faradic shock (approximately 800 micro A rms). During conditioning trials, which were separated by 2-min intertrial intervals, entry by a rat into a safe area of a multimode cavity resulted in immediate and complete cessation of stimulation; exit, in resumption. Acquisition of the escape response was rapid and highly efficient for shocked animals and was less rapid and efficient but was reliably demonstrated by irradiated animals that were also signaled by light. In the absence of microwave irradiation, cessation of light did not reliably motivate escape behavior. Although there was weak evidence of escape learning by rats subjected only to microwave irradiation, their performance failed to differ reliably from those of rats in the light-only condition. These data confirm and extend those of Carroll et al, which indicate that potentially lethal, deeply penetrating, nonpulsed microwaves in a multipath field lack the sensory quality to motivate efficient aversive behavior by the rat.

Animals↗
PubMed1982

Lack of effect of 2.45-GHz microwave radiation on the development of preimplantation embryos of mice.

The development of preimplantation embryos after exposure to microwave radiation was studied. Female CD-1 mice were induced to superovulate, mated, and exposed to 2.45-GHz microwave or sham radiation for 3 h at power densities of 9 mW/cm2 and 19 mW/cm2 on either day 2 or 3 of pregnancy (plug day was considered day 1). Another group of mice was exposed to heat stress by placing the dams in an environmental room at an ambient temperature of 38 degrees C and relative humidity at 62% for 3 h on day 2 of pregnancy. All groups were euthanized on day 4 of pregnancy and embryos were recovered by flushing excised uterine horns. Embryos were examined for abnormalities and classified by the developmental stages. They were then treated with hypotonic solution and dissociated for counting blastomeres. Heat stress caused stunted development of embryos, but no remarkable effect of microwave radiation could be found on the development of preimplantation embryos.

Animals↗
PubMed1982

Low frequency amplitude modulated microwave fields change calcium efflux rates from synaptosomes.

Calcium (45Ca2+) efflux from preloaded synaptosomes was studied with a continuous perfusion technique and the rate constants of a two-phase efflux process calculated. When 16-Hz sinusoidally amplitude modulated 450-MHz microwave field (maximal incident intensity 0.5 mW/cm2, modulation depth 75%) was applied during the second phase, the rate constant increased by 38%. Unmodulated or 60-Hz modulated signals were not effective. This microwave field-induced change can be distinguished from CaCl2-stimulated 45Ca2+ efflux which is most probably derived intracellularly. These data suggest that the microwave-field induced change in calcium efflux probably did not involve intracellular calcium. Also, this change in the dynamic property of synaptosomes did not require gross anatomically intact tissue as a substrate for field-tissue interaction.

Animals↗
PubMed1982

Fluorescence depolarization studies of the phase transition in multilamellar phospholipid vesicles exposed to 1.0-GHz microwave radiation.

The phase transition in multilamellar dimyristoylphosphatidylcholine (DMPC) vesicles was studied during exposure to continuous wave 1.0-GHz microwave radiation. Fluorescence depolarization measurements using a lipid-seeking molecular probe, diphenylhexatriene (DPH), were performed as a function of temperature. Semilog plots of microviscosity versus temperature illustrate the phase transition which shows a 5 degree C shift when the vesicles are treated with chloroform as a positive control. No shift of the phase transition was found during exposure to microwave radiation at specific absorption rates between 1 and 30 W/kg. Samples were exposed in a rectangular transmission line (TEM cell), and specific absorption rates were calculated from electrical measurements of incident, reflected, and transmitted power. Samples were exposed to increasing intensities of radiation, while the temperature was maintained at either 23.5 or 25.5 degree C; these temperatures represented the two ends of the phase transition region for these vesicles. No statistically significant difference was found between exposed and control samples. These results are in contrast to those of others using laser Raman spectroscopy to measure the phase transition in similar multilamellar vesicles exposed to microwave radiation.

Dimyristoylphosphatidylcholine↗
PubMed1982

Measurement of blood-brain barrier permeation in rats during exposure to 2450-MHz microwaves.

Adult rats anesthesized with pentobarbital and injected intravenously with a mixture of [14C] sucrose and [3H] insulin were exposed for 30 min to an environment at an ambient temperature of 22, 30, or 40 degrees C, or were exposed at 22 degrees C to 2450-MHz CW microwave radiation at power densities of 0, 10, 20, or 30 mW/cm2. Following exposure, the brain was perfused and sectioned into eight regions, and the radioactivity in each region was counted. The data were analyzed by two methods. First, the data for each of the eight regions and for each of the two radioactive tracers were analyzed by regression analysis for a total of 16 analyses and Bonferroni's Inequality was applied to prevent false positive results from numerous analyses. By this conservative test, no statistically significant increase in permeation was found for either tracer in any brain region of rats exposed to microwaves. Second, a profile analysis was used for a general change in tracer uptake across all brain regions. Using this statistical method, a significant increase in permeation was found for sucrose but not for inulin. A correction factor was then derived from the warm-air experiments to correct for the increase in permeation of the brain associated with change in body temperature. This correction factor was applied to the data for the irradiated animals. After correcting the data for thermal effects of the microwave radiation, no significant increase in permeation was found.

Analysis of Variance↗
PubMed1983

An optical method for investigating the microwave absorption characteristics of DNA and other biomolecules in solution.

Direct determination of the microwave absorption characteristics of biological molecules in solution by an optical heterodyne technique is described. A visibly transparent sample is irradiated in a spatially nonuniform manner with pulsed microwaves, and the spatial variation in temperature increase measured by detecting the phase chirp impressed on a single-frequency He-Ne laser beam passing through the heated region. Results for several liquids and solutions such as water, methanol, various saline solutions, and solutions of DNA and DNA sodium salt in water are described. Where direct comparison is possible the results agree very well with published values. A significant increase in the absorption of DNA solutions compared with pure water has been observed that is consistent with microwave absorption by the longitudinal mode of the double helix.

DNA↗