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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 155 (1993), S. 171-178 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previously we showed that CHO cell growth is arrested in the G1 or G0 phase within 24 h after the biosynthesis of mevalonic acid is blocked. The growth-limiting factor under these conditions appeared to be dolichyl phosphate or one of its glycosylated derivatives with consequent decrease in the synthesis of N-linked glycoproteins (Doyle, J.W., and A.A. Kandutsch, 1988, J. Cell Physiol. 137:133-140; Kabakoff, B., J.W. Doyle, and A.A. Kandutsch, 1990, Arch. Biochem. Biophys. 276:382-389). We show herein that cell surface glycoproteins are depleted in the inhibited cultures and that growth arrest is delayed when supraphysiological concentrations of insulin, insulin-like growth factor-1 (IGF-1) and bFGF are added to the culture medium. Apparently an elevated level of a growth factor increases the length of time during which a threshold level of occupied receptor is maintained as the number of glycosylated receptor molecules declines. The results support the idea that cellular levels of dolichyl phosphate and its derivatives may limit cell division by controlling the numbers of functional receptors for growth factors and of other glycoproteins on the cell surface. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 23 (1989), S. 441-449 
    ISSN: 0148-7280
    Keywords: boar ; spermatozoa ; membrane fluidity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Head plasma membranes were isolated from the sperm-rich fraction of boar semen and from sperm-rich semen that had been subjected to three commercial preservation processes: Ex tended for fresh insemination (extended), prepared for freezing but not frozen (cooled), and stored frozen for 3-5 weeks (frozen-thawed). Fluorescence polarization was used to determine fluidity of the membranes of all samples for 160 min at 25°C and also for membranes from the sperm-rich and extended semen during cooling and reheating (25 to 5 to 40°C, 0.4°C/min). Head plasma membranes from extended semen were initially more fluid than from other sources (P 〈 0.05). Fluidity of head membranes from all sources decreased at 25°C, but the rate of decrease was significantly lower for membranes from cooled and lower again for membranes from frozen-thawed semen. Cooling to 5°C reduced the rate of fluidity change for plasma membranes from the spernvrich fraction, while heating over 30°C caused a signifi cantly greater decrease. The presence of Ca++ (10 mM) lowered the fluidity of the head plasma membranes from sperm-rich and extended semen over time at 25°C but did not affect the membranes from the cooled or frozen-thawed semen. The change in head plasma membrane fluidity at 25°C may reflect the dynamic nature of spermatozoa membranes prior to fertilization. Extenders, preservation processes and temperature changes have a strong influence on head plasma membrane fluidity and therefore the molecular organization of this membrane.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 7 (1986), S. 1-11 
    ISSN: 0197-8462
    Keywords: ion exposure chamber ; ion concentration ; current density ; electric field ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Ion exposure chambers that have been designed and tested for use in biological and behavioral research with small animals are described in this report. The chambers exhibit an acceptable degree of uniformity in ion concentration, current density, and electric field within the exposure area. Gaseous by-products of corona discharge (O3 and NO2) have been measured and found to be 〈 .01 ppm and 〈 .1 ppm, respectively. Filtered air is fed to the individual exposure chambers, and temperature and humidity are well controlled. Noise due to corona and the air delivery system has been measured.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 7 (1986), S. 329-339 
    ISSN: 0197-8462
    Keywords: air ions ; DC electric fields ; locomotor activity ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Air ions and direct current (DC) electric fields have been reported to exert subtle behavioral and biological effects on rodents and humans. These effects often appear inconsistent, yet there have been few attempts to resolve these inconsistencies by experimental replication. Rats exposed to negatively or positively charged air ions over a wide range of concentrations and exposure periods have been reported to show alterations in their level of locomotor activity. In this study, locomotor activity of Sprague-Dawley rats was quantified during exposure to either (1) unipolar air ions and DC fields of the same polarity or (2) DC fields alone. Both polarities were studied. Air ion concentrations were 5.0 × 103, DC fields were 3 kV/m, and exposures lasted 2, 18, or 66 h. In one experiment rats were exposed to DC fields of 12 kV/m. No exposure condition exerted any effect on locomotor activity or rearing behavior. In addition, no behavioral perturbations were observed after the onset of any of the exposure conditions, suggesting that the rats may have failed to detect the altered environment.
    Additional Material: 5 Ill.
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  • 5
    ISSN: 0197-8462
    Keywords: exposure chamber ; psychophysics ; detection ; environmental guidelines ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The objective of this study was to assess the ability of humans to detect the presence of DC electric fields and ion currents. An exposure chamber simulating conditions present in the vicinity of high-voltage DC (HVDC) lines was designed and built for this purpose. In these experiments, the facility was used to expose observers to DC electric fields up to 50 kV/m and ion current densities up to 120 nA/m2. Forty-eight volunteers (25 women and 23 men) between the ages of 18 and 57 years served as observers. Perception of DC fields was examined by using two psychophysical methods: an adaptive staircase procedure and a rating method derived from signal-detection theory. Subjects completed three different series of observations by using each of these methods: one was conducted without ion currents, and the other two involved various combinations of electric fields and ion currents. Overall, subjects were significantly more likely to detect DC fields as the intensity increased. Observers were able to detect the presence of DC fields alone, but only at high intensities; the average threshold was 45 kV/m. Except in the most sensitive individuals, ion current densities up to 60 nA/m2 did not significantly facilitate the detection of DC fields. However, higher ion current densities were associated with a substantial lowering of sensory thresholds in a large majority of observers. Data analysis also revealed large variations in perceptual thresholds among observers. Normative data indicating DC field and ion current intensities that can be detected by 50% of all observers are provided. In addition, for the most sensitive observers, several other detection proportions were derived from the distribution of individual detection capabilities. These data can form the basis for environmental guidelines relating to the design of HVDC lines. © 1996 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 0197-8462
    Keywords: microwave exposure ; behavior ; physiology ; pathology ; blood chemistry ; neurobehavioral toxicology ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Long-Evans male adult rats were intermittently exposed for 14 weeks to continuous wave (CW) 2450-MHz microwaves at an average power density of 2.5 mW/cm2. The mean specific absorption rate was 0.70 W/kg (± 0.02 SEM). The rats were exposed 7 h/day, 7 days/week in a radiation chamber with a monopole above ground, while housed in Plexiglas cages. Weekly measures of body mass and food intake did not indicate statistically significant effects of microwave irradiation. Assessments of threshold for electric-footshock detection revealed a significant difference between microwave and sham-exposed animals. Assessments of cholinesterase and sulfhydryl groups in blood and 17-ketosteriods in urine did not distinguish the two groups of rats. Behavioral measures made at the end of the 14-week exposure included an open-field test, shuttlebox avoidance performance, and schedule-controlled lever-pressing for food pellets. Statistically significant differences between microwave- and sham-exposed rats were observed for these measures. Examination of adrenal tissue, plasma electrolytes, and organ masses after 14 weeks of exposure revealed no difference between the two groups of rats.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 8 (1987), S. 173-181 
    ISSN: 0197-8462
    Keywords: DC electric fields ; 5-hydroxyindoleacetic acid ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Exposure to electrically charged gas molecules (air ions) has been reported to influence physiological and behavioral functions in animals and humans although there is controversy as to whether these findings are valid. A popular hypothesis concerning the reported effects of air ions is that alterations in serotonin (5HT) metabolism, particularly in the brain, are involved. We measured the concentration and turnover of 5HT in rats exposed to 5.0 × 105 ions/cm3 for up to 66 hours. Contrary to previous reports of other investigators, we were unable to demonstrate any effect of exposure to air ions or associated DC electric fields on the concentration or turnover of 5HT in rats under carefully controlled and characterized exposure conditions.
    Additional Material: 3 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 6 (1985), S. 199-206 
    ISSN: 0197-8462
    Keywords: microwave ; SAR ; hotspots ; dose distribution ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Experiments were conducted using twin-well calorimetry to determine the averaged whole-body specific absorption rate (SAR) for rat carcasses exposed to 360, 700, 915, and 2,450 MHz CW radiation in an anechoic chamber. All exposures were done with the long axis of the rat in an E-polarization. Additional experiments were conducted using a fiber optical temperature probe to determine local SAR in the brain, esophagus, colon, rectum, and tail during microwave exposure. The whole-body averaged SAR for the radiation frequencies examined follows a nonmonotonic function with 700 MHz as the resonant frequency. This result agrees with previous analytical estimates. Local SARs within the body and tail are nonuniform with significant frequency-specific hotspots in the colon, rectum, and tail.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 6 (1985), S. 415-425 
    ISSN: 0197-8462
    Keywords: air ions ; DC electric fields ; brain catecholamines ; dopamine ; norepinephrine ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Exposure to air ions has been reported to influence serotonin (5HT), although critical reviews of these studies and previous measurements in our laboratory of the concentration, release, and utilization of brain 5HT indicate that neither the data nor the interpretations of the data are particularly convincing. Measurements of other possibly relevant neuro-transmitter systems - norepinephrine (NE) and dopamine (DA) - were made in brain regions selected because of their importance in the modulation of brain functions relating to motivation, arousal, endocrine function, and motor activity, all responses that have been reported to be influenced by air ion exposure. Results indicate that exposure of male Holtzman rats to high concentrations (5.0 × 105/cm3) of positive or negative air ions or to DC electric fields (3.0 kV/m) for periods up to 66 h failed to affect the concentration of NE or DA significantly in any of the brain regions.
    Additional Material: 6 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 19 (1997), S. 985-992 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The two vegetative cell types of the acellular slime mould Physarum polycephalum - amoebae and plasmodia - differ greatly in cellular organisation and behaviour as a result of differences in gene expression. The development of uninucleate amoebae into multinucleate, syncytial plasmodia is under the control of the mating-type locus matA, which is a complex, multi-functional locus. A key period during plasmodium development is the extended cell cycle, which occurs in the developing uninucleate cell. During this long cell cycle, many of the changes in cellular organisation that accompany development into the multinucleate stage are initiated including, for example, alterations in microtubule organisation. Genes have been identified that show cell-type specific expression in either amoebae or plasmodia and many of these genes alter their pattern of expression during the extended cell cycle. With the introduction of a DNA transformation system for P. polycephalum, it is now possible to investigate the functions of genes in the vegetative cell types and their roles in the cellular reorganisations accompanying development.
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