The influence of low power microwave on the properties of DPPC vesicles

The effect of microwave exposure on liposome at non-thermal level are studied. Dipalmitoyl phosphatidylcholine (DPPC) liposomes were exposed to 950 MHz at power densities of 2.5 mW/cm², which is equivalent to specific absorption rate (SAR) of 0.238 W/K. The interaction of microwave with liposomes was investigated by membrane solubilization measurements using a non-ionic detergent, octylglucoside (OG), as well as Fourier transform infrared (FTIR) spectroscopy and flow activation energy measurements. The amount of detergent needed to completely solubilize the liposomal membrane was increased after exposure of liposomes to microwave irradiation, indicating an increased membrane resistance to the detergent and hence a change in the natural membrane permeation properties. In the analysis of FTIR spectra the symmetric and antisymmetric CH₂ (at 2070 cm^?1) band and the CO (at 1640 cm^?1) stretching bands were investigated after liposomal exposure to microwave irradiation. It is clearly shown from the flow activation energy measurements, that low-power microwave induce changes in the liposomes deformability (decreases the liposome fluidity and increases the liposome rigidity). Finally it could be concluded that low-power microwave of 950 MHz induced structural and functional changes in liposomes as a membrane model system.     

Studies on blood-brain barrier permeability after microwave-radiation

Summary 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 of¹⁴C-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.The research reported in this paper was conducted by personnel of the Radiation Sciences Division, USAF School of Aerospace Medicine, Brooks AFB, Tex. 78235. The animals involved in the study were procured, maintained, and used in accordance with the Animal Welfare Act of 1970 and the Guide for the Care und Use of Laboratory Animals prepared by the Institute of Laboratory Animal Resources, National Research Council     

Nitric oxide acts as a signal molecule in microwave pretreatment induced cadmium tolerance in wheat seedlings

The microwave has been widely used in the field of biology with the development of microwave technology. Previous studies suggest that suitable doses of microwave irradiation improved plant metabolism and enzymatic activities under cadmium stress and enhanced cadmium tolerance in wheat seedlings. The objective of this study was to test whether nitric oxide is involved in microwave pretreatment induced cadmium tolerance in wheat seedlings due to its nature as a second messenger in stress responses. Plant were treated with 10 s microwave pretreatment, microwave pretreatment in combination with NO scavenger, 2-(4-carboxyphenyl)-4, 4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) and their effects on the lipid peroxidation, the activities of antioxidant enzymes, the concentration of antioxidant compounds and wheat seedlings growth and development were compared. The results showed that 10 s microwave pretreatment dramatically alleviated growth suppression induced by cadmium stress, reflected by decreased malondialdehyde, hydrogen peroxide and superoxide radical production. Furthermore, the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) and the concentration of antioxidant metabolites (ascorbate, reduced glutathione, carotenoids and nitric oxide) were increased in wheat seedlings pretreated with microwave under cadmium stress. Nevertheless, the promotive effect of microwave pretreatment induced cadmium tolerance in wheat seedlings was effectively reversed by the addition of 0.5 % (w/v) cPTIO (NO scavenger), suggesting that NO was involved in microwave pretreatment induced cadmium tolerance in wheat seedlings.     

The effect of microwave irradiation on vasopressin in plasma and hypothalamo-neurohypophyseal system

Radioimmunoreactive vasopressin was measured in plasma, neurohypophysis and hypothalamus of the rats after different procedures of killing: a) microwave irradiation; b) decapitation; c) decapitation following a stress induced by immobilization in a restrainer. Vasopressin content in the neurohypophysis and hypothalamus was much lower in microwave irradiated than in both decapitated and stressed decapitated rats. In addition, the data from microwave technique were inconsistent with a large scatter. Plasma vasopressin concentration was elevated in both the microwave irradiated and stressed decapitated rats, demonstrating that restraining of the animals induced an excessive stress. Microwave irradiation technique including the necessary manipulation of the animal proved to be less suitable than decapitation technique for the measurement of vasopressin. It is likely that vasopressin in the hypothalamus and neurohypophysis is relatively resistant against post-mortem proteolysis.     

Microwave-assisted synthesis of galacto-oligosaccharides from lactose with immobilized beta-galactosidase from Kluyveromyces lactis

Galacto-oligosaccharides (GOS) were synthesized from lactose by immobilized and free -galactosidase from Kluyveromyces lactis (Lactozym 3000 L HP-G) using either focused microwave irradiation or conventional heating. Immobilization of the -galactosidase on to Duolite A-568 increased the synthesis of GOS. GOS selectivity (GOS synthesis/lactose hydrolysis ratio) increased when the water activity of the media was reduced, notably with a high initial lactose concentration but also by using co-solvents in the media. The advantage of microwave heating on GOS formation was also examined. Addition of solvent and carrying out the reaction under microwave irradiation resulted an increase in the production of GOS. The selectivity for GOS synthesis can be increased by 217-fold under microwave irradiation, using immobilized -glucosidase and with added co-solvents such as hexanol.     

Reduction of Phosphorylated Synapsin I (Ser-553) Leads to Spatial Memory Impairment by Attenuating GABA Release after Microwave Exposure in Wistar Rats

Background

Abnormal release of neurotransmitters after microwave exposure can cause learning and memory deficits. This study investigated the mechanism of this effect by exploring the potential role of phosphorylated synapsin I (p-Syn I).

Methods

Wistar rats, rat hippocampal synaptosomes, and differentiated (neuronal) PC12 cells were exposed to microwave radiation for 5 min at a mean power density of 30 mW/cm². Sham group rats, synaptosomes, and cells were otherwise identically treated and acted as controls for all of the following post-exposure analyses. Spatial learning and memory in rats was assessed using the Morris Water Maze (MWM) navigation task. The protein expression and presynaptic distribution of p-Syn I and neurotransmitter transporters were examined via western blotting and immunoelectron microscopy, respectively. Levels amino acid neurotransmitter release from rat hippocampal synaptosomes and PC12 cells were measured using high performance liquid chromatograph (HPLC) at 6 hours after exposure, with or without synapsin I silencing via shRNA transfection.

Results

In the rat experiments, there was a decrease in spatial memory performance after microwave exposure. The expression of p-Syn I (ser-553) was decreased at 3 days post-exposure and elevated at later time points. Vesicular GABA transporter (VGAT) was significantly elevated after exposure. The GABA release from synaptosomes was attenuated and p-Syn I (ser-553) and VGAT were both enriched in small clear synaptic vesicles, which abnormally assembled in the presynaptic terminal after exposure. In the PC12 cell experiments, the expression of p-Syn I (ser-553) and GABA release were both attenuated at 6 hours after exposure. Both microwave exposure and p-Syn I silencing reduced GABA release and maximal reduction was found for the combination of the two, indicating a synergetic effect.

Conclusion

p-Syn I (ser-553) was found to play a key role in the impaired GABA release and cognitive dysfunction that was induced by microwave exposure.     

''Trouble-shooting'' microwave accelerated procedures in histology and histochemistry: understanding and dealing with artefacts, errors and hazards

Summary Heating by microwave irradiation (microwaving) is a controllable way to accelerate most processes of diffusion and many chemical reactions occurring in histoprocessing and histochemistry. Consequently, microwaving can be particularly time-saving. However, apart from desirable accelerations, unwanted diffusions and reactions may also occur. These can generate artefacts such as extraction of tissue components, chemical alterations of cellular content, and decomposition of thermally labile staining reagents. Artefacts may arise at all stages of histoprocessing, from fixation, through embedding, to staining. Whereas all artefacts result from heating, some specifically involve microwave ovens; e.g. irregular heating due to inhomogeneities in the microwave field, and ageing of the magnetron.Microwaving can involve certain hazards. Most of them also arise in conventional ovens, but a few are unique to microwave ovens; for example, aqueous contents heating faster than glass containers, and sparking due to labels written in pencil. The trouble-shooting of microwave procedures requires an understanding of the nature of the heating process and of the procedure in question. In order to achieve this, the development and application of trouble-shooting charts for commonly used procedures is both recommended and illustrated.     

Spectral resolution of the split EPR signals induced by illumination at 5 K from the S1, S3, and S0 states in photosystem II

S-State-dependent split EPR signals that are induced by illumination at cryogenic temperatures (5 K) have been measured in spinach photosystem II without interference from the Y(D)* radical in the g approximately 2 region. This allows us to present the first decay-associated spectra for the split signals, which originate from the CaMn4 cluster in magnetic interaction with a nearby radical, presumably Y(Z)*. The three split EPR signals that were investigated, "Split S1", "Split S3", and Split S0", all exhibit spectral features at g approximately 2.0 together with surrounding characteristic peaks and troughs. From microwave relaxation studies we can reach conclusions about which parts of the complex spectra belong together. Our analysis strongly indicates that the wings and the middle part of the split spectrum are parts of the same signal, since their decay kinetics in the dark at 5 K and microwave relaxation behavior are indistinguishable. In addition, our decay-associated spectra indicate that the g approximately 2.0 part of the "Split S1" EPR spectrum contains a contribution from magnetically uncoupled Y(Z)* as judged from the g value and 22 G line width of the EPR signal. The g value, 2.0033-2.0040, suggests that the oxidation of Y(Z) at 5 K results in a partially protonated radical. Irrespective of the S state, a small amount of a carotenoid or chlorophyll radical was formed by the illumination. However, this had relaxation and decay characteristics that clearly distinguish this radical from the split signal spectra. In this paper, we present the "clean" spectra from the low-temperature illumination-induced split EPR signals from higher plants, which will provide the basis for further simulation studies.     

Calreticulin attenuated microwave radiation-induced human microvascular endothelial cell injury through promoting actin acetylation and polymerization

Recent work reveals that actin acetylation modification has been linked to different normal and disease processes and the effects associated with metabolic and environmental stressors. Herein, we highlight the effects of calreticulin on actin acetylation and cell injury induced by microwave radiation in human microvascular endothelial cell (HMEC). HMEC injury was induced by high-power microwave of different power density (10, 30, 60, 100 mW/cm², for 6 min) with or without exogenous recombinant calreticulin. The cell injury was assessed by lactate dehydrogenase (LDH) activity and Cell Counting Kit-8 in culture medium, migration ability, intercellular junction, and cytoskeleton staining in HMEC. Western blotting analysis was used to detected calreticulin expression in cytosol and nucleus and acetylation of globular actin (G-actin). We found that HMEC injury was induced by microwave radiation in a dose-dependent manner. Pretreatment HMEC with calreticulin suppressed microwave radiation-induced LDH leakage and increased cell viability and improved microwave radiation-induced decrease in migration, intercellular junction, and cytoskeleton. Meanwhile, pretreatment HMEC with exogenous calreticulin upregulated the histone acetyltransferase activity and the acetylation level of G-actin and increased the fibrous actin (F-actin)/G-actin ratio. We conclude that exogenous calreticulin protects HMEC against microwave radiation-induced injury through promoting actin acetylation and polymerization.     

Distribution and release of adenosine triphosphate in rat brain

The steady-state level of brain ATP was measured after the tissue had been treated with a focused microwave irradiation system. The brain ATP content (1.50 nmol/mg tissue) obtained by microwave fixation is similar to that observed by others using fast-freezing and microwave fixation techniques. The concentrations of ATP in different brain regions show a rather uniform distribution, ranging from 1.918±0.059 (brainstem) to 2.393±0.19 (caudate) nmol/mg tissue; however, insufficient microwave fixation time seems to produce a greater regional variation of ATP. Release of ATP was investigated by placing a cup on the sensory-motor cortex. The rate for basal release of ATP is 1.43±0.14 femtomole/min/mm². A 30-fold increase in ATP release was obtained by direct stimulation of the cortex with 5 mA pulses of 0.2 msec duration at a rate of 20/sec over a period of 10 min. These results, in conjunction with others describing the potent pharmacological action of the nucleotide, seem to suggest that ATP could be a mediator in a purinergic system in the CNS.     

Selective enzymic esterification of free fatty acids with n-butanol under microwave irradiation and under classical heating

Selective enzymic esterification of free fatty acids, obtained from blackcurrant oil by chemical saponification, with n-butanol using four immobilized lipases under microwave irradiation and under classical heating was studied. A positive effect of microwave irradiation on chemical yields of the products of the enzymic reactions and specificity of lipases were observed in comparison with a controlled heating in an incubator equipped with shaking (classical heating) applied during the identical enzyme-mediated processes. The maximum quantity of -linolenic acid (30%) was obtained with Lipozyme used as biocatalyst of the reaction under microwave irradiation. The maximum quantity of butyl -linolenate (20%) was obtained by a Pseudomonas cepacia lipase catalyzed esterification under classical heating.     

Effect of chronic microwave radiation on T cell-mediated immunity in the rabbit

Experiments were conducted to elucidate the effects of chronic low power-level microwave radiation on the immunological systems of rabbits. Fourteen male Belgian white rabbits were exposed to microwave radiation at 5 mW/cm², 2.1 GHz, 3 h daily, 6 days/week for 3 months in two batches of 7 each in specially designed miniature anechoicchambers. Seven rabbits were subjected to sham exposure for identical duration. The microwave energy was provided through S band standard gain horns connected to a 4K3SJ2 Klystron power amplifier. The first batch of animals were assessed for T lymphocyte-mediated cellular immune response mechanisms and the second batch of animals for B lymphocyte-mediated humoral immune response mechanisms. The peripheral blood samples collected monthly during microwave/sham exposure and during follow-up (5/14 days after termination of exposures, in the second batch animals only) were analysed for T lymphocyte numbers and their mitogen responsiveness to ConA and PHA. Significant suppression of T lymphocyte numbers was noted in the microwave group at 2 months (P<0.01, % 21.5%) and during follow-up (P<0.01, % 30.2%). The first batch animals were initially sensitised with BCG and challenged with tuberculin (0.03 ml) at the termination of microwave irradiation/sham exposure and the increase in foot pad thickness ( mm), which is a measure of T cell-mediated immunity (delayed type hypersensitivity response, DTH) was noted in both the groups. The microwave group revealed a better response than the control group (%+12.4 vs.+7.54). The animals were sacrified and the tissue T lymphocyte counts (spleen and lymph node) were analysed. No significant variation was observed in the tissue T lymphocyte counts of microwave-irradiated rabbits. From these results it is speculated that the T lymphocytes are sequestered to various lymphoid organs under the influence of microwaves. A sub-population of T cells known as T helper cells (mediating DTH response) are probably not affected by microwave radiation. It is clear from our experiments that although chronic microwave radiation at 5 mW/cm² leads to suppression of peripheral T lymphocyte numbers, there is no concomitant functional impairment of these cells as evidenced by functional assays.     

Significance of microthermal effects derived from low level UHF-microwave irradiation of the head: indirect caloric vestibular stimulation

Reports of behavioral and clinical changes following weak microwave irradiation, though not fully documented, are of sufficient moment to require examination of each possible biological consequence of low level exposure, particularly with respect to the central nervous system. In this report the hypothesis that significant cytological microthermal effects are induced by low intensity microwave fields (10 mW/cm² incident power density) is examined. An estimate of the upper bound on the thermal effects thus produced is made, showing the thermal variations to be no larger than those endogenous to neural tissue. A similar analysis of microthermal effects within the vestibulo-cochlear apparatus, however, suggests the more limited hypothesis that this structure is responsive to weak, absorbed microwave energy. An estimate of the temperature gradients, hence, local fluid density changes within the labyrinth supports the existence of detectable intralabyrinthine convective forces at incident power densities as low as 15–20 mW/cm². This suggests (i) that microwave induced vestibular effects may provide a cue to alert personnel to significant acute microwave exposure, (ii) that reports of behavioral and/or clinical reactivity to low level microwave exposure may derive from such a benign but potentially useful interaction and (iii) that geometric peculiarities of the vestibulo-cochlear apparatus may result in markedly enhanced microwave-labyrinthine coupling at particular radiation wavelengths.     

Green hemoprotein of erythrocytes: methemoglobin superoxide transferase

Influences of base (pH 10), heat (50 degrees C), microwave radiation (2450 MHz, 103 +/- 4 W/kg), and hydrogen peroxide (5.6 mM) generated by glucose oxidase on oxidation of human oxyhemoglobin to methemoglobin were examined. Conversion of oxyhemoglobin to methemoglobin was followed by the difference in absorbancy of 540 or 542 nm and 576 nm wavelength light versus time. Fresh basic hemolysates auto-oxidized on heating with a zero order rate constant, implying that hemoglobin or another protein saturated with oxyhemoglobin catalyzed the oxidation. Simultaneous microwave irradiation inhibited thermally induced auto-oxidation on the average by 28.6%. However, there was great variability among samples and a decrease in auto-oxidation with aging of individual samples. The auto-oxidation rate was independent of initial oxyhemoglobin concentration. Oxidation of partially purified oxyhemoglobin by hydrogen peroxide was not influenced by microwave irradiation. Adding green hemoprotein isolated from human erythrocytes to the oxyhemoglobin/glucose oxidase reaction mixture yielded absorption spectra (500-600 nm) that were a combination of oxyhemoglobin, deoxyhemoglobin, and methemoglobin spectra. Green hemoprotein was labile in hemolysates but stable in a partially purified ferric form. These results imply that thermally unstable reduced green hemoprotein can reverse oxidation of oxyhemoglobin by hydrogen peroxide and could mediate the thermally induced and microwave inhibited auto-oxidation of oxyhemoglobin.     

Altered restriction patterns of microwave irradiated lambdaphage DNA.

Samples of lambdaphage DNA exposed to short pulses of microwave irradiation were subjected to restriction fragmentation by Eco RI and Bam HI. Eco RI digests of microwaved DNA samples yielded three additional fragments ranging in base pair lengths between 24,226 and 7,421 besides the six expected fragments. While Bam HI digests of the microwaved samples did not yield any additional fragments, mobilities of the Bam HI fragments from the microwaved DNA samples were slower and the bands were broader in comparison to those from native samples. We attribute these altered restriction patterns to the conformational anomolies in DNA resulting from single strand breaks and localized strand separations induced by microwave irradiation.     

微波对阿维拉霉素产生菌诱变效应的研究

阿维拉霉素产生菌SV微波诱变效应的研究发现：菌株SV对微波敏感（微波处理60s,SV菌株存活率低于10％）,菌落形态变化大。微波诱变处理最佳作用方式为培养皿不加盖、快速冰上冷却,最佳处理时间为50s（其正突变率25．3％）。通过微波诱变处理、阿维拉霉素推理筛选,最终获得一株稳定性良好,阿维拉霉素产量达到21．5mg／L,较出发菌株提高119．4％的突变株SV-15。     

Acute effects of pulsed microwaves and 3-nitropropionic acid on neuronal ultrastructure in the rat caudate-putamen

Ultrastructure of the medium sized "spiny" neuron in rat dorsal-lateral caudate-putamen was assessed after administration of 3-nitropropionic acid (3-NP) and exposure to pulsed microwaves. Sprague-Dawley male rats were given two daily intraperitoneal doses of 0 or 10 mg/kg 3-NP and 1.5 h after each dose were exposed to microwave radiation at a whole body averaged specific absorption rate (SAR) of 0 (sham exposure), 0.6, or 6 W/kg for 30 min. Microwave exposure consisted of 1.25 GHz radiation delivered as 5.9 micros pulses with repetition frequency 10 Hz. Tissue samples taken 2-3 h after the second sham or microwave exposure showed no injury with light microscope methods. Blinded qualitative assessment of ultrastructure of randomly selected neurons from the same samples did reveal differences. Subsequent detailed, quantitative measurements showed that, when followed by sham exposure, administration of 3-NP significantly increased endoplasmic reticulum (ER) intracisternal width, ER area density, and nuclear envelope thickness. Microwave exposure at 6 W/kg alone also significantly increased these measures. Exposure of 3-NP treated animals at 6 W/kg significantly increased effects of 3-NP on ultrastructure. Although exposure at 0.6 W/kg alone did not affect ultrastructure measures, exposure of 3-NP treated animals at 0.6 W/kg reduced the effects of 3-NP. We concluded that 3-NP changed neuronal ultrastructure and that the microwave exposures used here changed neuronal ultrastructure in ways that depended on microwave SAR and neuron metabolic status. The apparent cancellation of 3-NP induced changes by exposure to pulsed microwaves at 0.6 W/kg indicated the possibility that such exposure can protect against the effects of mitochondrial toxins on the nervous system.     

Weak microwave can alleviate water deficit induced by osmotic stress in wheat seedlings

The aim of the investigation is to determine the effect of microwave pretreatment of wheat seeds on the resistance of seedlings to osmotic stress. Changes in biophysical, physiological and biochemical characters were measured. The results showed: (1) The magnetic field intensity and seeds temperature increased progressively with microwave pretreatments of 5, 10, 15, 20 s and 25 s compared with controls. Although each microwave pretreatment resulted in an increase in alpha-amylase activity and photon emission intensity, the increase of alpha-amylase activity and photon emission intensity was maximal at a microwave pretreatment of 10 s. (2) Osmotic stress induced by PEG treatment enhanced the concentration of malondialdehyde, while decreasing the activities of nitricoxide synthase, catalase, peroxidase, superoxide dismutase and the concentration of nitric oxide, ascorbic acid, glutathione in the seedlings compared with controls. However, compared to osmotic stress alone, in the seedlings treated with microwave irradiation plus osmotic stress the concentration of malondialdehyde decreased, while the activities of nitricoxide synthase, catalase, peroxidase, superoxide dismutase and the concentration of nitric oxide, ascorbic acid and glutathione increased. These results suggest that a suitable dose of microwave radiation can enhance the capability to eliminate free radicals induced by osmotic stress in wheat seedlings resulting in an increase in resistance to osmotic stress.     

Microwave radiation can alter protein conformation without bulk heating

Exposure to microwave radiation enhances the aggregation of bovine serum albumin in vitro in a time- and temperature-dependent manner. Microwave radiation also promotes amyloid fibril formation by bovine insulin at 60 degrees C. These alterations in protein conformation are not accompanied by measurable temperature changes, consistent with estimates from field modelling of the specific absorbed radiation (15-20 mW kg(-1)). Limited denaturation of cellular proteins could explain our previous observation that modest heat-shock responses are induced by microwave exposure in Caenorhabditis elegans. We also show that heat-shock responses both to heat and microwaves are suppressed after RNA interference ablating heat-shock factor function.     

Absence of Non-Thermal Microwave Effects on the Function of Giant Nerve Fibers

Functioning of the giant axon of the isolated earthworm ventral nerve cord was examined during exposure to 6.45 GHz microwaves. We used continuous wave and pulsed irradiation, either synchronized with stimuli or asynchronous, lasting for 10–50 min at specific absorption rate from 30 to 230 W/kg. Action potential (AP) conduction velocity and the capability of nerve fiber to answer long-lasting high-frequency stimulation served as indices of microwave effect. Under some experimental conditions the nerve appeared to have extreme sensitivity to subtle temperature changes, induced by irradiation, but no non-thermal microwave effects were detected.