RESUMEN
Acoustic transients can be thermally generated in water by pulsed microwave energy. The peak pressure level of these transients, measured within the audible frequency band as a function of the microwave pulse parameters, is adequate to explain the "clicks" heard by people exposed to microwave radiation.
Asunto(s)
Estimulación Acústica , Percepción Auditiva , Microondas , Fenómenos Electromagnéticos , Humanos , Modelos Teóricos , Oscilometría , AguaRESUMEN
Perpendicular and parallel elongation of the giant amoeba, Chaos chaos (Chaos carolinensis), have been observed in alternating electric fields over a wide frequency range (from about 1 hertz to about 10 megahertz). The characteristics change as a function of frequency. Simple dielectric forces may be important in the production of these effects.
Asunto(s)
Amoeba/fisiología , Electricidad , Amoeba/ultraestructura , Animales , Movimiento Celular , Seudópodos/fisiologíaRESUMEN
Water proton nuclear magnetic resonance relaxation measurements have been obtained for aqueous suspensions of red cell membranes. These data support a model in which water molecules are exchanging rapidly between a bound phase with restricted motions and a free phase with dynamic properties similar to liquid water. From this model and these data, estimates are obtained for the relaxation time for bound phase water. Possible relaxation mechanisms for bound phase water are discussed and some support is found for an intermolecular interaction modulated by translational motions characterized by a diffusion constant of 10(-9) cm2/s.
Asunto(s)
Membrana Celular/metabolismo , Eritrocitos/metabolismo , Agua/metabolismo , Membrana Celular/análisis , Eritrocitos/análisis , Humanos , Cinética , Espectroscopía de Resonancia Magnética , Matemática , Modelos Biológicos , Temperatura , TermodinámicaRESUMEN
Rabbits were irradiated with 2450-MHz continuous microwave energy. Effects of the radiation on the ocular lens were assessed by slit-lamp biomicroscopic examination of the eye. Two lenses were selected for electron microscopy, one that was severely damaged and one that appeared unaffected by the radiation. There were prominent ultrastructural changes in both lenses.
Asunto(s)
Catarata/etiología , Microondas/efectos adversos , Animales , Catarata/patología , Cristalino/lesiones , Cristalino/ultraestructura , Masculino , Microscopía Electrónica , Microscopía Electrónica de Rastreo , ConejosRESUMEN
Whole body exposure of rabbits to microwave radiation causes a decrease in ascorbic acid in the lens. In our study, rabbit lenses maintained in culture medium (37 degrees C) were exposed to either pulsed or continuous wave S-band radiation for 10-15 min at power densities between 0 and 200 mW/cm-2. Total ascorbic acid was measured in selected lenses 1-3 days after irradiation. The temperature of the culture medium was measured during irradiation. Matched control lenses were exposed to similar time-temperature environments, but without microwave irradiation. Ascorbic acid decreased significantly in lenses exposed to microwave radiation. No differences were found, however, between irradiated and control lenses subjected to identical time-temperature conditions. At a given average power density, the time-temperature variation was independent of modulation. A decrease in ascorbic acid is apparently a direct thermal effect of microwave radiation in rabbit lens culture.
Asunto(s)
Ácido Ascórbico/metabolismo , Cristalino/metabolismo , Microondas , Animales , Calor , Técnicas In Vitro , ConejosAsunto(s)
Conducta Animal , Microondas/efectos adversos , Animales , Condicionamiento Operante , Masculino , Ratas , Esquema de RefuerzoRESUMEN
Fatty acid spin-probe analyses at various depths in the membrane bilayer of intact erythrocytes indicate that compressional effects of pressure and fluidizing effects of lipid-soluble anesthetics are detectable only in hydrated regions of the membrane bilayer. Since current theories of anesthetic action cannot explain these observations, a proposal to do so is outlined.
Asunto(s)
Anestésicos/farmacología , Membrana Eritrocítica , Eritrocitos , Presión Hidrostática , Lípidos de la Membrana , Presión , Cloroformo/farmacología , Espectroscopía de Resonancia por Spin del Electrón , Membrana Eritrocítica/efectos de los fármacos , Eritrocitos/efectos de los fármacos , Halotano/farmacología , Helio/farmacología , Humanos , Fluidez de la Membrana , Nitrógeno/farmacología , Octanoles/farmacología , Fosfolípidos , Marcadores de SpinRESUMEN
Proton nuclear magnetic resonance (NMR) relaxation measurements are reported for frog muscle as a function of temperature and Larmor frequency. Each T(1rho), T(2), and T(1) measurement covered a time domain sufficient to identify the average relaxation time for most intracellular water. Using regression analysis the data were fit with a model where intracellular water molecules are exchanging between a large compartment in which mobility is similar to ordinary water and a small compartment in which motion is restricted. The regression results suggest that: the restricted compartment exhibits a distribution of motions skewed toward that of free water; the residence time of water molecules in the restricted compartment is approximately 1 ms; and, the activation entropy for some water molecules in the restricted compartment is negative.