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  • 1
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Increasing evidence supports the idea that the finite proliferative life span of normal fibroblasts is a differentiation-like phenomenon. If this were correct, an ordered sequence of differential gene expression should be associated with the in vitro progression of cells from low passage to high passage (senescence). To define the pattern of expression of fibroblast differentiation-associated genes during this in vitro progression, we have determined the temporal pattern of expression of extracellular matrix (ECM) genes in Syrian hamster dermal fibroblasts as a function of passage level and percentage of proliferative life span in vitro. Steady-state mRNA levels were determined by Northern and dot blot analyses of total cellular RNA hybridized with cDNA probes specific for fibronectin, procollagen α1 III, and procollagen α1 I. Cells were analyzed at 24 hr postconfluence to minimize the presence of actively proliferating cells, and because maximal levels of fibronectin, α1 III, and α1 I mRNAs were observed 24 hr postconfluence. Unique, multiphasic patterns of expression of each of these ECM components were observed as the cells progressed from low passage to high passage. As the cells reached midhigh passage, fibronectin mRNA levels increased. This midpassage increase in fibronectin was followed by an increase in the level of α1 III mRNA as the cells reached the end of their in vitro proliferative life span, and then α1 I when the cells entered the postmitotic senescert phase, at which time the level of fibronectin mRNA also declined. A similar overlapping cascade pattern of up-regulation of these genes is seen during development and wound repair. This suggests that as cultured fibroblasts reach the end of their proliferative life span, they reinitiate a gene expression program used in tissue development and repair. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 8 (1987), S. 183-193 
    ISSN: 0197-8462
    Keywords: hypothermia ; RF rewarming ; rhesus monkey ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: To obtain more detailed information relative to the potential usefulness of using radio frequency (RF) energy in treating hypothermia, anesthetized rhesus monkeys were used in a rewarming study that compared a conventional method (heating pad) with an RF induction coil system. Rectal temperature (Tre) of each subject was monitored, and enzyme and isoenzyme levels were determined from blood samples collected before, during, and up to 48 h after hypothermia in order to assess the effects of each rewarming method. The previously observed postprocedure rise in serum enzymes (most visible at 24 h) was again seen, with no statistically significant difference in the time course of serum enzyme levels between the two treatments for comparable durations of hypothermia. To test the limits of the ability of the RF induction coil system, successively more severe hypothermia was induced in the subjects to the point of cardiovascular collapse (Tre 〈 20°C); RF energy was successful in resuscitating the profoundly hypothermic subjects without discernible harmful effects.
    Additional Material: 9 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 79-88 
    ISSN: 0197-8462
    Keywords: circular waveguide exposure system ; radiofrequency dosimetry ; rhesus monkey ; radiofrequency exposure ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A 275-MHz exposure system, consisting of a circular waveguide irradiator and a transparent plastic animal cage, has been developed to accommodate rhesus monkeys weighing up to 15 kg. The vertically oriented waveguide is composed primarily of stainless steel and is fitted with an inner cage fabricated from a tubular section of acrylic plastic. Circularly polarized electromagnetic energy at 275 MHz, either pulsed or continuous wave (CW), can be propagated from the removable top section of the waveguide. The cage is designed to function as the monkey's permanent home. It is fitted with a lever-actuated behavioral performance device on which the monkey responds according to a predetermined schedule to obtain a daily food ration. The system can be adapted to provide for the collection of metabolic and physiologic data as well. Dosimetric measurements were conducted with six rhesus monkeys weighing 3.0-7.2 kg and with a 4-kg model. The dosimetric results show that about one-third of the net incident energy is absorbed by a subject in this system at a normalized specific absorption rate (SAR) of 0.33 (W/kg)/(mW/cm2).
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 8 (1987), S. 377-384 
    ISSN: 0197-8462
    Keywords: EM dosimetry ; man model ; rhesus model ; microwave absorption ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Full-size models of a man and a rhesus monkey were exposed to radiofrequency (RF) radiation at 225 MHz. The model of man was also exposed to 2,000 MHz. Specific absorption rates (SARs) were measured in partial-body sections, such as the arms, legs, etc., using gradient-layer calorimeters. Also, front-surface thermographic images were obtained to qualitatively show the heating patterns. For all of the configurations used, the SAR in the limbs was much higher than in the torso. Agreement (whole-body SARs) with spheroidal models was better for both models at 225 MHz than at 2,000 MHz. These results indicate that in the frequency range two orders of magnitude above whole-body resonance, SAR in the limbs significantly contributes to the whole-body average SAR.
    Additional Material: 51 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 10 (1989), S. 209-213 
    ISSN: 0197-8462
    Keywords: thermometry ; nonperturbing probe ; dosimetry ; temperature ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: We present a simple readout device that fills the void produced by the gradual disappearance of the Vitek model 101 Electrothermia Monitor. The new device uses commercially available probes that are similar to Bowman's (IEEE Trans Microwave Theory Tech MTT-24:43-45, 1976) original design. As described, the device covers the range of 7 ° to 45 °C with an accuracy and resolution of better than 0.1 °C throughout. The digital readout (3½ digits) is proportional to the thermistor resistance in the tip of the probe; it is converted to temperature through a formula or printed table. Outdoor dosimetric comparisons between the new and Vitek devices were conducted. Results showed no significant difference in the calculated specific absorption rates (SARs); moreover, variance was lower in the data collected from the new device.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 45-54 
    ISSN: 0197-8462
    Keywords: pulsed microwaves ; thermoelastic waves ; simulated tissue ; hydrophone ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Microwave-induced mechanical stress waves were studied in simulated muscle tissue. Pulsed microwave energy at 5.655 GHz induced pressure waves that were recorded with a hydrophone transducer. Each pulse produced a peak power density greater than 1.5 kW/cm2. Microwave absorption measurements within the model showed energy deposition to be mostly confined to a region within 2 cm of the irradiated surface. The average specific absorption rate (SAR) at the surface of the sample was about 100 W/kg. The microwave-induced stress wave propagated at a velocity of 1,600 m/sec with peak pressures of approximately 300 pascals and was detectable after having traveled a total distance of 0.61 m on a path that included two reflections at model-container interfaces.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 149-160 
    ISSN: 0197-8462
    Keywords: microwaves ; microwave dosimetry ; rhesus monkey dosimetry ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Dosimetric measurements were made in a muscle-equivalent model of an adult rhesus monkey subjected to far-field irradiation at 1.29 GHz. Profiles of microwave-induced heating in the model were obtained at eight locations, and a gradient-layer whole-body calorimeter was used to measure total absorbed energy. Average specific absorption rate (SAR) was calculated both from the calorimeter experiments and from the local temperature measurements. Thermographic imaging techniques were used to qualitatively show the microwave-induced surface heating patterns. For this model the calculated average SAR was 0.155 (W/kg)/(mW/cm2) which, at 1.29 GHs, makes the absorption cross section 84% of the geometric shadow cross section. The SAR is about three times that predicted for a prolate spheroidal model of similar mass. A disproportionally high absorption occured in the legs of the model positioned parallel to the E-polarization because of what is believed to be partial-body resonance.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 3 (1982), S. 385-389 
    ISSN: 0197-8462
    Keywords: electromagnetic dosimetry ; rhesus model dosimetry ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Dosimetric measurements in a 9.5-kg tissue-equivalent rhesus model were conducted at 225 MHz using a nonperturbing temperature probe and a gradient-layer calorimeter. Temperature probe measurements showed deep penetration of electromagnetic energy, and calorimeter experiments showed an average SAR (0.285 W/kg per mW/cm2) that was nearly three times greater than that observed for the same model at 1.29 GHz.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 4 (1983), S. 397-400 
    ISSN: 0197-8462
    Keywords: acoustical imaging ; microwave-induced acoustics ; pulsed microwaves ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Pulsed 5.66-GHz microwave energy irradiated a model of a human hand that was positioned above a submerged planar array of 400 hydrophones. Hydrophone response data were analyzed by a computer that graphically reproduced the image.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 10 (1989), S. 161-171 
    ISSN: 0197-8462
    Keywords: EM dosimetry ; Man model ; calorimeter ; temperature probe ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Localized and averaged specific absorption rates (SARs) were obtained in a full-size muscle-equivalent human model exposed to near-field 29.9 MHz irradiation at an outdoor facility. The model was positioned erect on a metallic groundplane 1.22 m (4 ft) from the base of a 10.8-m (35 ft) whip antenna with an input power of 1.0 kW. For whole-body SAR, a mean value of 0.83 W/kg was determined using two gradient-layer calorimeters in a twin-well configuration. The localized SARs at 12 body locations were measured using nonperturbing temperature probes and were highest in the ankle region. We conclude that averaged SAR measurements in a full-size phantom are feasible using a twin-calorimeter approach; measurements in the field are practical when human-size (183 × 61 × 46 cm) calorimeters are used.
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