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PubMed2005

Prognostic factors for survival in patients with hepatocellular carcinoma after percutaneous microwave ablation.

PURPOSE: To determine the long-term survival and prognostic factors in patients with hepatocellular carcinoma treated with percutaneous microwave ablation. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. A database of cases of hepatocellular carcinoma in 288 patients (259 men, 29 women; mean age, 54.8 years +/- 11.4 [standard deviation]; age range, 25-82 years) with 477 histologically proved lesions who underwent percutaneous microwave coagulation therapy between May 1994 and October 2002 was retrospectively analyzed. Prognostic factors for survival were evaluated by means of univariate and multivariate analyses. RESULTS: The mean follow-up period after microwave ablation was 31.41 months +/- 20.43 (range, 5-106 months). The 1-, 2-, 3-, 4-, and 5-year cumulative survival rates among all 288 patients were 93%, 82%, 72%, 63%, and 51%, respectively. Ninety-three patients (32%) died. Local recurrence or new tumors occurred in 100 patients (35%). Age (P = .836), sex (P = .073), preablation serum alpha-fetoprotein level (P = .136), and preablation treatment (P = .256) were not related to prognosis, while tumor number (P = .004), tumor size (P < .001), Child-Pugh classification (P = .003), tumor differentiation (P = .026), and local recurrence or presence of new tumors (P = .004) significantly affected survival at univariate analysis. At multivariate analysis, only tumor size (P < .001), number of nodules (P = .005), and Child-Pugh classification (P = .01) each had a significant effect on survival. CONCLUSION: With use of microwave ablation, there is a high probability of long-term survival of patients with a single lesion of 4.0 cm or less in maximum diameter and Child-Pugh class A cirrhosis.

Adult↗
PubMed1979

Effects of hypophysectomy and dexamethasone on rat adrenal response to microwaves.

Circulating corticosterone levels were measured to compare the adrenocortical response to acute microwave exposure of normal, hypophysectomized, or sham-hypophysectomized rats. Plasma corticosterone levels in acutely hypophysectomized rats exposed to 60 mW/cm2 for 60 min were below control levels, indicating that the microwave-induced corticosterone response observed in normal, intact rats is dependent on ACTH secretion by the pituitary. In other groups of rats pretreated with dexamethasone before being exposed to microwaves for 60 min, the corticosterone response to a 50-mW/cm2 exposure was completely suppressed by doses equal to or greater than 3.2 micrograms dexamethasone/100 g body weight. However, the corticosterone response to a 70-mW/cm2 exposure was only partially suppressed by prior administration of 3.2 or 5.6 micrograms dexamethasone/100 g BW. The evidence obtained in these experiments, in conjunction with the results of other experiments previously reported, is consistent with the hypothesis that the stimulation of the adrenal axis in the microwave-exposed rat is a systemic, integrative process due to a general hyperthermia.

Adrenal Glands↗
PubMed1982

Use of microwave oven for determination of postmortem water volume of lungs.

To determine if a microwave oven could be used to obtain accurate values of postmortem lung and blood water contents, we compared measurements made with a microwave oven to those obtained by drying the tissue in a vacuum oven set at room temperature. Tissue samples were obtained from 9 dogs and 10 sheep used for a variety of experiments resulting in a wide biological range of water fractions (0.74-0.88). The ratio of the values obtained by these two methods was 1.00 +/- 0.06 for dog tissues and 1.00 +/- 0.02 for sheep tissues. The use of a microwave oven for drying lung tissue and blood provides a measurement of lung water content that is not significantly different from values obtained by vacuum drying, but the microwave method requires only 1 h vs. several days or weeks.

Animals↗
PubMed1998

A new microwave acid digestion bomb method for the determination of total fluorine.

A new microwave acid digestion method for total fluorine analysis was compared to the reliable reverse-extraction technique. The commercially available Parr bombs which are compatible with microwave heating were modified for this purpose. The Mann-Whitney statistical test did not show any significant differences (p > 0.05) in the determinations of total fluorine in various samples between the two above-mentioned methods. The microwave method also gave high fluorine recoveries (> 97%) when fluoride was added to different samples. The great advantage of the microwave acid digestion bomb method is that the digestion under pressure is so aggressive that only a few minutes is needed for complete digestion (also of covalently bonded fluorine), which reduces the time for fluorine analysis dramatically, while no loss of fluorine or contamination from extraneous sources could take place during the ashing procedure. The digestion solution was made up of 300 microliter of concentrated nitric acid plus 537 microliter of water. After digestion 675 microliter of approximately 8.5 M sodium hydroxide plus 643 microliter of citrate/TISAB buffer was added resulting in an alkaline solution (pH approximately 12) which was finally adjusted to a pH of approximately 5.3 for fluoride determination.

Acids↗
PubMed2002

Application of the microwave tissue coagulator: is it beneficial to partial nephrectomy?

BACKGROUND/AIM: The indications of partial nephrectomy have expanded after the introduction of new techniques for preventing excessive blood loss and avoiding deterioration of the renal function after clamping the renal pedicle. We present our clinical experience of partial nephrectomy for renal tumors using a microwave tissue coagulator. PATIENTS AND METHODS: Between April 1996 and January 2000, 34 patients underwent open partial nephrectomies in the Kobe City General Hospital. The microwave tissue coagulator was used for resection of the renal parenchyma, but in deeper lesions a sharp dissection was performed. Twenty-two patients (groups 1 and 2) underwent partial nephrectomy without vascular control (14 renal pedicles were not disturbed in group 1 patients, and 8 renal pedicles were dissected but not clamped in group 2 patients). Another 12 patients (group 3) underwent vascular control with ligation of the tumor-feeding segmental arteries before parenchymal resection. The patients of group 1 underwent wedge resections, while those of groups 2 and 3 underwent segmental or transverse partial nephrectomies. RESULTS: Complete tumor resection was done in all 34 patients. In group 1, the microwave tissue coagulator was very effective to control the blood loss (mean 330 ml). In larger resections, this method only was inadequate to control the blood loss (mean 489 ml in group 2), so that we needed vascular control. However, despite vascular control, mean blood losses of about 943 ml because of deeper venous bleeding occurred in group 3, and, moreover, postoperative renal infarctions occurred in 2 patients. Other complications were urinary fistula formation in 16 patients (47%) and renal pelvic stenoses in 2 patients (5.8%). All of the urinary fistulas were easily repaired by simple suturing intraoperatively. CONCLUSIONS: Especially in wedge resection, the microwave tissue coagulator achieved safe resection without vascular control which differs from other new techniques. However, in larger resections, a combination with other techniques may be necessary to decrease blood loss and the rate of complications.

Adult↗
PubMed1983

Effects of microwave exposure in utero on embryonal, fetal and postnatal development of mice.

Pregnant Swiss mice were repetitively exposed during various periods of gestation to 2,450 MHz continuous wave microwave radiation. Irradiations were conducted daily in an anechoic chamber at a power density of 10 (subthermal) or 40 mW/cm2 (thermal) for 2 h/day, 7 sessions/week. Thermal exposures to microwaves resulted in significant inhibition of the embryonal and fetal development in utero, accompanied by an increased incidence of intrafetal bleedings, resorptions and deaths of fetuses. Moreover, nonspecific resistance to viral and bacterial infections was markedly depressed in pups of dams irradiated for the whole period of gestation with thermal doses of microwaves. No such effects were found following exposure of pregnant mice to 10 mW/cm2 power density of radiation. The results suggest that the observed effects of microwave exposure in the course of pregnancy are thermal in nature.

Animals↗
PubMed1988

Microwave coagulation therapy for urinary bladder tumors.

A new device has been developed for microwave coagulation of urinary bladder tumors. Twenty-one patients with urinary bladder tumors were treated by irradiation with microwave energy of 2,450 MHz. Results were obtained as follows: (1) microwave coagulation was performed in 21 patients with transitional cell carcinoma of the urinary bladder. Excluding 4 patients who subsequently received radical cystectomy, 17 patients showed a complete response, although 2 patients subsequently developed recurrences in different parts of the bladder within the following several months. Histological examination of the excised specimen revealed complete eradication of the tumor in 2 patients. In the remaining 2 patients with high-stage tumor (T4), viable tumor cells were noted in the urethra or vaginal wall. (2) Although neither technical difficulties nor severe complications were encountered, transient urinary frequency and calcification of the bladder wall were noted. The results of this study indicate that microwave coagulation may be used in the treatment of both superficial and invasive tumors.

Aged↗
PubMed2003

Microwave-mediated analysis for sugar, fatty acid, and sphingoid compositions of glycosphingolipids.

For chemical characterization of glycosphingolipids, it is necessary to determine the chemical compositions of three constituents, i.e., sugars, fatty acids, and sphingoids. A new rapid analytical method is described using a one-pot reaction in a household microwave oven, producing sugars, fatty acids, and especially sphingoids free of by-products, from a single aliquot of a biological sample. Glycosphingolipids were hydrolyzed by microwave exposure with 0.1 M NaOH/CH(3)OH for 2 min followed by 1 M HCl/CH(3)OH for 45 s. The alkaline methanolysis step produced intermediate lysoglycosphingolipids virtually free of by-products such as the O-methyl ethers usually seen. The fatty acid methyl esters were extracted with n-hexane, and other reaction products were dried, taken up in aqueous alkaline methanol, and shaken with chloroform. Sphingoids partitioned into the organic phase under these conditions, whereas the sugar portion that partitioned into the aqueous phase was re-N-acetylated and remethanolyzed for 30 s by microwave exposure. Analysis of the profiles of glycosphingolipid constituents obtained using the microwave oven method showed that they were quantitatively and qualitatively comparable to those obtained by time-consuming conventional methods, which require reaction for several hours. Analysis of the three constituents, including analysis by gas chromatography, may be obtained within 1 day using the method described here.

Acetylation↗
PubMed2006

The effect of microwave thermal denaturation on release properties of bovine serum albumin and gluten matrices.

The purpose of this study was to compare the effects of denaturation by microwave irradiation on release properties of 2 physically different proteins. Matrices were prepared from water-soluble bovine serum albumin loaded with metoclopramide and sorbed with adequate amount of moisture were thermally denatured in a microwave oven. The release profile of the rather insoluble denatured albumin matrices followed the classical Fickian diffusion profile. The release rate was dependent on the degree of denaturation, which was highly dependent on the level of moisture originally absorbed by the albuminoidal matrices and the period of exposure to microwave energy. Conversely, attempts to reduce the rate of drug release through microwave irradiation of metoclopramide-loaded matrices prepared from water-insoluble gluten were futile. The denaturation process was shown to be limited to the relatively water-soluble protein core fraction, while aggregation between neighboring gluten proteins in the matrix was not achieved even in the presence of considerable amounts of sorbed water.

Diffusion↗
PubMed1980

The tissue content of cyclic AMP in rats after microwave irradiation in vivo.

When anesthetized rats were exposed to microwave (power output 1.3 kw, frequency 2,450 MHz), the cyclic AMP phosphodiesterase activity showed a rapid decline in the skeletal muscle, heart, trachea and lung; no activity essentially could be detected after a 30 sec irradiation. Cyclic AMP levels in these tissues also decreased rapidly to constant values within 30 sec. Concentrations of cyclic AMP in the heart, skeletal muscle, trachea and lung measured by the tissue fixation with liquid nitrogen were approximately 3, 3, 4 and 4 times higher than those after microwave irradiation, respectively. The intravenous injection of procaterol (1 mu mol/kg), a beta 2-adrenoceptor agonist, caused a 6-fold increase in the trachea cyclic AMP level when measured after microwave fixation but only a 2-fold increase when measured after liquid nitrogen fixation. It is concluded that rapid tissue fixation by microwave irradiation may provide a useful means for obtaining reliable values of the tissue cyclic AMP content.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

External control of drug release. IV. Controlled release of 5-fluorouracil from a hydrophilic polymer matrix by microwave irradiation.

A polymeric system capable of delivering 5-fluorouracil (5-FU) at increased rates on demand by external microwave irradiation was developed. Sustained-release systems were made by incorporating 5-FU into an ethylene-vinyl alcohol copolymer. When exposed to release medium, the delivery systems released the drug slowly and continuously. Upon exposure to microwave irradiation, the drug was released at a much higher rate. Release rates returned to base line levels when the microwave irradiation was discontinued. This study demonstrated that release rates of 5-FU from a polymer matrix can be increased at desired times by external microwave irradiation.

Chemistry, Pharmaceutical↗
PubMed2004

Laparoscopic partial nephrectomy using a microwave tissue coagulator for treating small peripheral renal tumors.

BACKGROUND: Laparoscopic partial nephrectomy has been recently applied as a minimally invasive procedure. Several non-ischemic operation devices in partial nephrectomy have been developed. However, the problem related to maintenance of renal homeostasis remains. We investigated the efficacy and safety of a microwave tissue coagulator in laparoscopic partial nephrectomy. METHODS: Between April 2001 and February 2003, eleven patients with small renal tumors underwent laparoscopic partial nephrectomy using a microwave tissue coagulator. Seven patients underwent hand-assisted laparoscopic procedure and 4 pure laparoscopic procedure. RESULTS: The mean tumor size on preoperative CT scan was 2.5 cm (range: 2.0 to 4.0 cm), the mean operative time was 307 minutes (range: 160 to 580 minutes), and the mean estimated blood loss was 154.4 ml (range: 50 to 1,140 ml). The microwave tissue coagulator well controlled the renal bleeding and maintained renal function. All patients safely underwent partial nephrectomy without inducing renal ischemia. A complication of urine leakage was recognized in only one patient with hypoproteinemia caused by nephrotic syndrome. CONCLUSIONS: Laparoscopic partial nephrectomy using a microwave tissue coagulator was a useful method for achieving homeostasis, and was less invasive for treating small renal tumors.

Aged↗
PubMed1989

Results of a United States and Soviet Union joint project on nervous system effects of microwave radiation.

During the course of a formal program of cooperation between the United States and the Soviet Union concerning the biological effects of physical factors in the environment, it was concluded that duplicate projects should be initiated with the general goal of determining the most sensitive and valid test procedures for evaluating the effects of microwave radiation on the central nervous system. This report details an initial step in this direction. Male rats of the Fischer 344 strain were exposed or sham exposed to 10 mW/cm2 continuous wave microwave radiation at 2.45 GHz for a period of 7 hr. Animals were subjected to behavioral, biochemical, or electrophysiological measurements during and/or immediately after exposure. Behavioral tests used were passive avoidance and activity in an open field. Biochemical measurements were ATPase (Na+, K+; Mg2+, Ca2+) and K+ alkaline phosphatase activities. Electrophysiological measurements consisted of EEG frequency analysis. Neither group observed a significant effect of microwave irradiation on open field activity. Both groups observed changes in variability of the data obtained using the passive avoidance procedure, but not in the same parameters. The U.S. group, but not the USSR group, found significantly less Na+,K+-ATPase activity in the microwave-exposed animals compared to the sham exposed animals. Both groups found incidences of statistically significant effects in the power spectral analysis of EEG frequency, but not at the same frequency. The failure of both groups to substantiate the results of the other reinforces our contention that such duplicate projects are important and necessary.

Adenosine Triphosphatases↗
PubMed2005

Increased efficiency of fluorescence in situ hybridization (FISH) using the microwave.

A new method is described for performing fluorescence in situ hybridization (FISH). FISH signals are enhanced by microwave pulses applied during the DNA-DNA hybridization process. It is the first description of FISH with a single/low-copy probe done more efficiently by application of microwave; the latter leads to quick results or enhancement of weak signals. Microwave FISH has been compared systematically with normal FISH, and we could demonstrate the efficiency of microwave irradiation especially in the first 100 min of hybridization.

Chromosome Aberrations↗
PubMed2003

Indicators of erythrocyte damage after microwave warming of packed red blood cells.

BACKGROUND: Localized overheating of packed red blood cells (PRBCs) after microwave warming with consequent damage to erythrocytes has been reported. We therefore compared possible cellular markers of erythrocyte damage, as measured by flow cytometry, with laboratory indicators of hemolysis to evaluate the effects of microwave warming on PRBCs. METHODS: PRBC samples were warmed to room temperature or to 37, 42, 47, 52, or 57 degrees C in a water bath. Flow cytometry was performed after fluorescein labeling using antibodies to spectrin, Ca(2+)-ATPase, and Na(+)-K(+)-ATPase. The forward-to-sideward scatter (FSC/SSC) ratio and antibody binding were evaluated. Plasma free hemoglobin (FHb) and alpha-hydroxybutyrate dehydrogenase (HBDH) were measured immediately after heating and after 48 h. In addition, all measurements were made before and after the heating of PRBCs to 35 degrees C by a microwave blood warmer. RESULTS: Analysis of 15000 erythrocytes showed a decrease in the FSC/SSC ratio and antibody binding above 47 degrees C [at 37 degrees C, median (SD) of 94.2 (7.4) with 0.07 (0.05)% fluorescein-positive; at 52 degrees C, median (SD) of 177.0 (19.0) with 18.5 (6.4)% positively gated; P <0.001]. FHb [room temperature, 0.3 (0.2) g/L] was increased 2-fold at 37 and 42 degrees C, 4-fold at 47 degrees C, and 25-fold at 52 degrees C. HBDH increased in parallel. Hemolysis markers showed an additional twofold increase 48 h after heating to 42 and 47 degrees C. Microwave heating to 35 degrees C did not produce significant changes of any marker. CONCLUSIONS: All markers of cellular damage were altered after heating to >47 degrees C, and a substantial part of hemolysis was delayed. The methodology can be used for future testing of other blood warming devices.

Biomarkers↗
PubMedDate not supplied

Resonance effect of microwaves on the genome conformational state of E. coli cells.

The effect of low intensity microwaves on the conformational state of the genome of X-irradiated E. coli cells was studied by the method of viscosity anomalous time dependencies. It has been established that within the ranges of 51.62-51.84 GHz and 41.25-41.50 GHz the frequency dependence of the observed effect has a resonance nature with a resonance half-width of the order of 100 MHz. The power dependence of the microwave effect within the range of 0.1-200 microW/cm2 has shown that a power density of 1 microW/cm2 is sufficient to suppress radiation-induced repair of the genome conformational state. The effect of microwave suppression of repair is well reproduced and does not depend on the sequence of cell exposure to X-rays and microwave radiation in the millimeter band. The results obtained indicate the role of the cell genome in the resonant interaction of cells with low intensity millimeter waves.

DNA, Bacterial↗
PubMedDate not supplied

A simple method to obtain essential oils from Salvia triloba L. and Laurus nobilis L. by using microwave-assisted hydrodistillation.

A microwave-assisted hydrodistillation protocol was modified to extract essential oils from leaves of Salvia triloba L. and Laurus nobilis L. The essential oils of these plants are generally obtained by hydrodistillation or steam distillation. The volatile compounds obtained by microwave-assisted hydrodistillation and hydrodistillation methods were analyzed by GC and GC/MS. Both distillation methods and analytical results were compared. 1,8-Cineole (46.8-54.2%) was the main component in the leaf oils of both samples. Although the distillation was accomplished in a shorter time, oil yields and 1,8-cineole contents were slightly higher in the microwave-assisted hydrodistillation compared to usual hydrodistillation. Microwave-assisted hydrodistillation appears to be an effective method for the production of essential oils.

Laurus↗
PubMed1991

[The use of microwave ovens to thaw frozen rat serum].

This study was performed to examine the optimum conditions for thawing frozen rat serum in a microwave oven (Toshiba, Type ER-1345 JF). The thawing temperature must be kept at 37 degrees C or less to maintain the blood biochemical values within the normal ranges because the values of alkaline phosphatase, cholinesterase, glucose and albumin were markedly altered at 40 degrees C or above. For thawing frozen serum, the best conditions were as follows: a sample volume of 0.5 ml was convenient to control the thawing temperature; locating the samples 10-12 cm out from the center of the turning table in the oven resulted in a thawing temperature of 10-20 degrees C; a microwave irradiation time of 1 min 45 sec thawed samples frozen at -20 degrees C. Using the sample plate that we made, 80 samples could be thawed at the same time under almost the same conditions. The blood biochemical values obtained from sera thawed in the microwave oven showed good correlation with those from sera in a water bath (37 degrees C) and had excellent reproducibility. These results suggest that thawing frozen rat serum by microwave irradiation is rapid and easy and without adverse effects on the blood biochemical values.

Animals↗