Active microwave tomographic imaging of isolated, perfused animal organs

The relative transparency of biological materials to high-frequency electromagnetic waves has encouraged the development of new systems for imaging. This report describes experiments of microwave tomography conducted on a prototype. The object to be analyzed is submerged in water and is illuminated by a plane wave. The total electric field is analyzed by a microwave camera. The recorded data are then processed numerically in order to reconstruct the image that corresponds to the distribution of equivalent currents in a defined plane of a section. Experiments have been conducted on isolated kidneys with and without perfusion. The influence of the perfusing solution temperature has also been studied. These experiments show the potential of this system, especially through the correlation between microwave images and the biological structures. They also confirm previous results concerning spatial resolution and depth of exploration. Finally, the results demonstrate the influence of temperature and support the applicability of this imaging system in non-invasive thermometry, especially for clinical hyperthermia.     

Lyotropic liquid crystal as a real-time detector of microbial immune complexes

AIMS: To design a simple method for the detection of microbe-immune complexes exploiting the optical and elastic properties of a biocompatible liquid crystalline material. METHODS AND RESULTS: Aqueous solution of disodium cromoglycate (DSCG), a lyotropic chromonic liquid crystal (LCLC), was aligned in a glass cell so as to be optically dark in polarized light. Immune complexes of at least three to four organisms altered the DSCG alignment such that polarized light was subsequently transmitted to reveal the presence of pathogens as optically bright regions around the immune complexes. CONCLUSIONS: This work describes the first method to detect viable micro-organisms in real time using LCLC. SIGNIFICANCE AND IMPACT OF THE STUDY: This technique provides a powerful tool for the detection of microbes in minutes, exploiting the optical and elastic properties of LC.     

Preparation and characterization of Pluronic-colloidal silicon dioxide composite particles as liquid crystal precursor

The purpose of this study was to produce spray-dried Pluronic-colloidal silicon dioxide (Aerosil) composite particles as a liquid crystal precursor that would form a liquid crystalline phase upon hydration. A Pluronic-colloidal silicon dioxide dispersion in isopropyl alcohol was spray-dried to obtain composite particles using different concentrations of Aerosil. Polarizing microscopy, gelation, gel melting, and rheological studies were employed to characterize the composite particles. The composite particles obtained were irregular, with concave depression. Gelation was found to decrease with the addition of Aerosil, while gel melting was found to increase with the concentration of Aerosil. Rheological studies showed an increase in elasticity as well as viscosity with an increase in the concentration of Aerosil. Composite particles showed improved gelation and rheological properties. These composite particles and the process by which they were obtained may be useful for designing various drug delivery systems.     

A comparison of heavy liquid floatation and microwave digestion techniques for the extraction of fossil phytoliths from sediments

This paper reports the results of a comparative analysis of two techniques used for the extraction of fossil phytoliths from sediments. The first is a standard heavy liquid floatation extraction technique that has been successfully used and proven to provide reliable phytolith assemblage data. A second technique using a Perkin-Elmer Multiwave Microwave Sample Preparation System is introduced, and the results are compared to those of the conventional technique. Results for both techniques, as well as the advantages and disadvantages of their use are discussed. This study provides an introduction to an alternative technique for the extraction of fossil phytoliths and possibly starch grains from sediments. The microwave technique is fast, inexpensive, omits the need for heavy liquid floatation and most importantly results in the appropriation of interpretable and replicable fossil phytolith assemblage data.     

Nonthermal effect of microwave irradiation on nitrite uptake in Chlamydomonas reinhardtii

When cells of the unicellular green alga Chlamydomonas reinhardtii were subjected to microwave irradiation at 2.45 GHz, nitrite uptake kinetics still obeyed the Michaelis-Menten equation, the Km of the process remaining constant, whereas V _max increased, which indicates an enhanced nonthermal permeability in irradiated cells.     

Influence of microwave irradiation on enzymatic properties: applications in enzyme chemistry

Although microwave-assisted reactions are widely applied in various domains of organic chemistry, their use in the area of enzyme chemistry has been rather limited, due to the high temperatures associated with the microwave heating: Because current technology, allows a good control of reaction parameters, several examples of microwave-assisted enzyme chemistry have been reported, using stable and effective biocatalysts (modified enzymes). The purpose of this review is to highlight the applications and studies on the influence of microwave irradiation on enzymatic properties and their application in enzyme chemistry.     

Characterization of surfactant liquid crystal phases suitable for molecular alignment and measurement of dipolar couplings

Media employed for imparting partial alignment onto solute molecules have recently attracted considerable attention, since they permit the measurement of NMR parameters for solute biomolecules commonly associated with solid state NMR. Here we characterize a medium which is based on a quasi-ternary surfactant system comprising cetylpyridinium bromide/hexanol/sodium bromide. We demonstrate that dilute solutions of this system can exist in liquid crystalline phases which orient in the magnetic field and allow the measurement of residual dipolar couplings under a variety of conditions. The present system is extremely versatile and robust, tolerating different buffer conditions, temperature ranges and concentrations.     

Synthesis of diazoluminomelanin (DALM) in HL-60 cells for possible use as a cellular-level microwave dosimeter

Chemical and bacterial synthesis of a thermochemiluminescent polymer known as diazoluminomelanin (DALM) has been previously reported. This paper focuses on the intracellular synthesis of aminomelanin (AM) in mammalian cell lines and subsequent DALM synthesis from this core molecule. B16 melanoma cells, HL-60 myeloid leukemia cells, and RAW 264.7 macrophages show AM and DALM production. Macroscopic image analysis of HL-60 cell lysates containing DALM using the Quantitative Luminescence Imaging System (QLIS) showed increased chemiluminescence (CL) with increased microwave power input and increased temperature. This work represents a first step toward the goal of microscopic radiofrequency dosimetry of individual DALM-loaded cells using image analysis. © 1994 Wiley-Liss, Inc.     

The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation

doi: 10.1111/j.1741‐2358.2011.00587.x The influence of double flask investing on tooth displacement in dentures processed by microwave irradiation Objective: This study evaluated the influence of the bimaxillary flask (BMF) and two different investing materials on first molar inclination in dentures processed by microwave irradiation. Background: The BMF may minimise tooth displacement, saving time and improving occlusion. Methods and materials: Forty pairs of dentures were randomised into four groups: stone wall in monomaxillary flask; silicone wall in BMF; stone wall in BMF; acrylic resin retentions and silicone in BMF. Dentures were processed by microwave irradiation. Two referential points were established on tooth surface. A microscope and a digital pachymeter were used to measure the distance between these points, and the angles α (right maxillary molar), β (left maxillary molar), α′ (right mandibular molar) and β′ (left mandibular molar) were calculated by the law of cosines. Data were submitted to Kruskal–Wallis (5% significance). Results: No difference was observed among the groups (p > 0.05). In the intra‐group analysis, α was significantly different for groups I, II and III; α′, for groups II and IV; β, for all groups; β′, for groups III and IV. Conclusion: First molar inclination was similar for monomaxillary and BMFs. The use of stone or silicone as investing materials presented the same effect on tooth inclination.     

Bacillus thuringiensis crystal toxin: Ultrastructural studies of its effect on silkworm midgut cells

Bacillus thuringiensis crystal toxin induced a cytoplasmic response in columnar cells within 1 min after ingestion although external symptoms were not exhibited by larvae until 15 min after ingestion. Microvilli became less consistently uniform in diameter; their organized internal microfilaments were disrupted and disappeared. The cisternae of rough endoplasmic reticulum were enlarged and denuded of ribosomes. By 5 min after ingestion, microvilli of some columnar cells disappeared entirely and gross ultrastructural changes were observed in other regions of the cells. Up to 5 min after ingestion there were few, if any, ultrastructural changes observed within goblet cells. Mitochondria in columnar cells were swollen but did not exhibit the condensed configuration reported by other workers. Both the buffer system used in the fixation medium and its osmolarity influenced the changes in the ultrastructure of midgut cells exposed to B. thuringiensis crystal toxin.     

Induction of stress proteins in anoxic and hyperthermicSpodoptera frugiperda cells

In this study, we compare stress protein induction in anoxic and hyperthermicSpodoptera frugiperda cells. Anoxia transiently induces a cluster of heat shock proteins at 71 and 72 kDa. This is a subset of a larger group of stress proteins induced by heat shock. Several heat shock proteins reported in this study were previously undetected inS. frugiperda. With these additional proteins, the stress response of hyperthermicS. frugiperda closely resembles that ofDrosophila melanogaster. Prior investigations of stress protein induction during oxygen deprivation focused on mammalian cells. In sharp contrast to these cells, anoxicS. frugiperda cells neither induce glucose-regulated proteins nor suppress the heat shock family of 71/72 kDa proteins. These findings provide insight into the virtually unexplored area of stress protein induction in anoxic insect cells. In addition, they help to explain the effects of oxygen deprivation on heterologous protein yield from virally infected insect cells and to develop an oxygenregulated promoter for stably transformed insect cells.Abbreviations DO dissolved oxygen concentration - GRP's glucose-regulated proteins - HSP's heat shock proteins - ORP's oxygen-regulated proteins - PAGE polyacrylamide gel electrophoresis - Sf9 Spodoptera frugiperda cells     

Influence of in vitro microwave radiation on the fertilizing capacity of turkey sperm

Turkey sperm were exposed to 2.45-GHz microwave radiation in a temperature-controlled wave-guide apparatus. Temperature was maintained at either 25 or 40.5 degrees C. The sperm were exposed for 30 min at a specific absorption rate (SAR) of 10 or 50 mW/g. Following irradiation, the sperm were used to inseminate virgin turkey hens artificially. During the 9 weeks following the single insemination, the following were assessed: mean number of eggs, percentage of fertile eggs, rate of decrease in egg fertility, percentage of hatched eggs, and percentage of early and late deaths. These data demonstrate that, for the conditions used in these experiments, microwave radiation has no effect on the fertilizing capacity of turkey sperm.     

Formation of liquid crystal structures in the tissue fluid in wound healing during periodic irradiation with helium-neon laser

Rabbit tissue fluid at different stages of wound healing was studied. Interaction between the formation of liquid crystalline fractions and the course of healing was revealed both under natural conditions and under periodic laser irradiation of the wound.     

Scheduled perturbation in DNA during in vitro differentiation of mouse embryo-derived cells

Studies of sister chromatid exchanges (SCE) and recombination rate of certain mini-satellite DNAs have demonstrated that their levels are considerably higher during the preimplantation stage than in latest developmental stages of embryos. It appeared likely that single-strand DNA breaks (SSB) may be relevant to both events during early development. With this in mind, we estimated SSB during in vitro retinoic acid (RA)-induced and spontaneous differentiation of mouse teratocarcinoma (EC) and embryonic stem (ES) cells. Using the method of nucleoid sedimentation and single-cell DNA electrophoresis, we have observed a dramatic increase in the SSB during the first 2–4 mitoses after beginning of differentiation of EC cells, followed by a gradual return to the basal level characteristic of undifferentiated cells. The increase in the SSB was manifested as the appearance of mass nucleoids with slow sedimentation rates, as well as the low-weight mass fragments in DNA patterns of most cells. We concluded that not less then half of genomic DNA has been nicked at the early steps of differentiation. The decrease in SSB level was observed in spite of continuing differentiation, as judged by embryonic antigens and morphological criteria. Also, the increase in the SCE level coincided with that of SSB, possibly being its consequence. The scheduled “surge” of SSB may be the earliest event in commencing differentiation at steps without a phenotypic manifestation. Mol. Reprod. Dev. 47:1–10, 1997. © 1997 Wiley-Liss, Inc.     

The effect of 2450 MHz microwave radiation on histamine secretion by rat peritoneal mast cells

Isolated rat peritoneal mast cells actively secrete histamine in response to reaginic or chemical stimulation. Mast cells were irradiated in a waveguide microwave exposure chamber at 2450 MHz with power absorptions of 8.2 and 41.0 mW/g for periods up to 3 h. These levels of microwave absorption caused no change in the morphological characteristics or viability of the cells. Irradiated mast cells were stimulated with compound 48/80, a potent, noncytotoxic histamine releasing agent. The dose response curves showed that neither prior nor simultaneous irradiation of mast cells at 37°C affected 48/80-induced secretion. However, microwave power absorptions of 41.0 mW/g inhibited secretion at 44.0°C. Precise measurements of the effect of heat on secretion indicated that this level of inhibition could have been produced by a radiation induced increase in cell temperature between 0.4 and 0.9°C above ambient levels. Alternatively, the heat stress produced at 44°C may have sensitized the cells to the electromagnetic effects of the microwave radiation. Rat peritoneal mast cells can therefore be useful as a model for the study of functioning secretory cells during microwave irradiation and can also be used to monitor the synergistic effects of cell heating during in vitro exposure.     

Glycosphingolipid biosynthesis during myogenesis of rat L6 cells in vitro

Summary Glycosphingolipid biosynthesis was examined using [³H]-galactose as a precursor as rat L6 myoblasts fused to form multinucleated myotubes. Incorporation of label into neutral glycolipids decreased steadily as the population of myotubes increased, so that final biosynthesis was one-half that observed with myoblasts (p < 0.02). Conversely, ganglioside biosynthesis doubled during myoblast confluency (p < 0.02) and then decreased as myotubes formed. Qualitatively, L6 cells synthesized large amounts of ganglioside GM3 during all myogenic phases. The major neutral glycosphingolipid products were lactosylceramide and paragloboside (nLcOse₄Cer). Few changes in TLC autoradiographic patterns were noted during differentiation, with the exception of a slight decrease in ganglioside GM1. The results indicate that the biosynthesis of glycosphingolipids is tightly regulated during myogenesis in vitro and suggest a role for membrane gangliosides in muscle cell differentiation.Abbreviations GM1 II³NeuAc-GgOse₄Cer - GM3 II³NeuAc-GgOse²Cer - MG4 IV³NeuAc-nLcOse₄Cer - MG6 VI³NeuAc V⁴Gal-IV³GlcNAc-nLcOse⁴Cer - TLC Thin-Layer Chromatography - DMEM Dulbecco's Modified Eagles' Medium     

In vitro study of microwave effects on calcium efflux in rat brain tissue

In this study we investigated the prospect of microwave-induced alteration of ⁴⁵Ca²⁺ efflux from rat neural tissue at low pulse repetition frequencies and low power densities under in vitro conditions. Rat cerebral tissue, preloaded with ⁴⁵Ca²⁺, was exposed to pulsed-microwave radiation (1-GHz carrier frequency) according to one of several PRF-power density exposure schemes: 16 Hz at 0.5, 1.0, 2.0, or 15 mW/cm², or 32 Hz at 1.0 or 2.0 mW/cm² average power density. Measurements of radioactivity in the efflux medium and in the tissue sample were used to calculate an efflux value for each sample. The results indicate that the radiation conditions used did not alter calcium efflux in rat brain tissue.     

Surface morphology of rat peritoneal mast cells during in vitro regeneration after histamine secretion

Summary Cell-surface morphology of regenerating mast cells was followed over a period of 48 h after histamine release. Control cells (not stimulated to secrete) were characterized by anastomosing folds of membrane of equal depth and width. During exocytosis these folds disappeared and were replaced by deep cup-shaped flaps of membrane evident in cells incubated for 10 min. During the first hours of regeneration these flaps fused mutually or with the plasma membrane. This activity suggests membrane retrieval, maybe specifically recycling the granule-type patches of membrane. Membrane-fusion activity was observed to some degree also after extended incubation. After 48 h of incubation the regeneration process was still not completed, as indicated by the fact that holes leading to intracellular cavities could still be found.     

Organ-specific change inDolichos biflorus lectin binding by myocardial endothelial cells during in vitro cultivation

Summary Endothelial cells of the NMRI mouse strain express a cell surface glycoprotein recognized by the lectinDolichos biflorus agglutinin (DBA). This study documents a marked organ-specific increase in DBA-specific lectin binding of myocardium-derived endothelial cells (MEC) of the NMRI/GSF mouse during in vitro cultivation. An up to 20-fold increase in DBA binding sites is observed in long-term culture, an increase not found in other NMRI-derived endothelial cell lines (e.g., brain, aorta). The increase appears restricted to DBA in that binding with other lectins (PNA, WGA) was unaltered. NMRI MEC cultures maintain typical endothelial cell attributes such as cobblestone morphology on confluence, expression of endothelial cell-specific surface markers, and production of angiotensin-converting enzyme. Cultures routinely become aneuploid within 4 passages, several passages before upregulation of the DBA binding site(s). Myocardial endothelial cells sorted to obtain DBA^hi and DBA^lo cell populations generally maintained their sorted phenotype for 3 to 4 passages. Limiting dilution cloning resulted in clones varying in DBA expression. Clones for DBA^hi expression maintained their DBA affinity for at least 10 passages (>30 doublings), whereas DBA^lo clones gave rise to varying numbers of DBA^hi cells within 2 to 4 passages. We hypothesize that the change in DBA affinity accompanies in vitro aging, that the change is independent of alterations in karyotype, and that the increase in DBA affinity may reflect a change in one or more other endothelial cell properties. Additional studies will be necessary to determine whether the in vitro changes are correlated with specific functional alterations and whether they accurately reflect progressive changes of MEC in vivo.