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  • 1
    Electronic Resource
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    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 11 (1990), S. 27-36 
    ISSN: 0197-8462
    Keywords: bioelectrical stimulation ; rabbit ; ligament ; fibroblasts ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Effects of extremely-low-frequency (ELF) electromagnetic fields on proliferation of rabbit-ligament fibroblasts were examined. Markedly different effects, ranging from inhibition to stimulation of proliferation, were obtained, depending on the signal parameters of amplitude, frequency, and DC magnetic field. These results demonstrate that simple, single-frequency signals can have dramatic effects on ligament cells, which may be useful for bioelectrical stimulation of growth and repair. Also, the range of frequencies examined in this study covered those commonly used in transmission of electrical energy (50 or 60 Hz), which indicates that further study of possible effects of exposure to fields generated by power transmission equipment is warranted.
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  • 2
    ISSN: 0197-8462
    Keywords: ELF-VLF currents ; enzyme inactivation ; thermal inactivation ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A new experimental approach has been developed to determine kinetic and thermodynamic parameters of the inactivation of an enzyme under labile conditions both with and without exposure to electrical currents as sources of perturbation. Studies were undertaken to investigate if low-frequency electric currents can accelerate the thermal inactivation of an enzyme through interactions with dipole moments in enzymatic molecules and through related mechanical stresses. The experiments were conducted with the enzyme acid posphatase. The enzyme was exposed to a 50-Hz current at different densities (10 to 60 mA/cm2 rms) or to a sinusoidal or square-wave current at an average density of 3 mA/cm2 and frequencies from, respectively, 50 Hz to 20 kHz and 500 pulses per second (pps) to 50,000 pps. Positive-control experiments were performed in the presence of a stabilizer or a deactivator. The results indicate that the technique is sensitive to conformational changes that otherwise may be impossible to detect. However, exposure to electric currents under the experimental conditions described herein showed no effects of the currents.
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  • 3
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    Bioelectromagnetics 11 (1990), S. 101-102 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 4
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    Bioelectromagnetics 11 (1990), S. 103-103 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
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  • 5
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    Bioelectromagnetics 11 (1990), S. 129-137 
    ISSN: 0197-8462
    Keywords: ELF ; electric field ; sperm ; mutagenicity ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Male C3H/He mice were sham-exposed or exposed continuously for 2 weeks to a vertical, 50-Hz, electric field at 20 kV/m rms. Densities of currents induced in the testes are estimated to be near 100 μA/m2. After the exposure, each male was mated with two different female mice each week during a period of 8 weeks. By this schedule, female mice were impregnated with sperm that had been exposed to the electric field at different stages of the spermatogenic cycle. No significant differences as a function of exposure condition were observed in pregnancy rates or in survival of embryos before or after implantation. The absence of effects was not due to insensitivity of assays; other mice that were exposed to X-rays (dose to testes = 1.5 Gy) presented reliable evidence of mutagenesis.
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  • 6
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    Bioelectromagnetics 11 (1990), S. 189-201 
    ISSN: 0197-8462
    Keywords: magnetically induced E-fields ; surface currents ; thermal noise ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A method is described for evaluating electric fields induced by ELF magnetic fields into electrically inhomogeneous, low-conductivity (〈5 S/m) structures. It is applied to cylinders and spheres, and numerical results are given for electrical properties that are representative of some tissues, or of cells embedded either in saline solution or a tissue matrix. Surface currents on spherical cell boundaries are estimated and compared with thermal noise due to ion motion.
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  • 7
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    Bioelectromagnetics 11 (1990) 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 8
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    Bioelectromagnetics 11 (1990), S. 207-212 
    ISSN: 0197-8462
    Keywords: spinal reflex ; morphine ; pain threshold ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Adult male Long-Evans rats were exposed to negatively charged air ions at high concentrations (7 × 105/cm3) for six days. Sham-exposed rats were treated identically except that the source of ions was not activated. At the end of the exposure, the latency of the tail-flick reflex was measured in each rat before and 30 and 60 min after an injection of morphine sulphate. The tail-flick reflex was initiated by thermal stimulation. Two heat settings were employed, the lower considered to impart a submaximal and the higher a maximal thermal stimulus. Three morphine doses were tested: 0.5, 1.0, and 1.5 mg/kg. Statistically significant differences between ion-exposed and sham-exposed rats were observed in tail-flick latencies 30 min after the administration of the two lower doses, but not after the highest dose of morphine sulphate. These differences were found at both intensities of thermal stimulation. Tail-flick latencies measured in each group prior to morphine injection were not affected by negative-ion exposure. The data indicate that exposure of rats to negative air ions tends to inhibit the action of morphine on the latency of the tail-flick reflex at morphine doses below 1.0 mg/kg.
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  • 9
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    Bioelectromagnetics 11 (1990), S. 235-249 
    ISSN: 0197-8462
    Keywords: magnetically induced E-fields ; ELF induced fields ; fields in biological structures ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Electric fields induced by low-frequency magnetic fields into inhomogeneous structures, which have electric conductivities and dielectric permittivities of typical biological substances, are evaluated. Closed-form approximate and numerical solutions are obtained for nonconcentric cylinders with different electric properties (such as bone embedded in muscle), which are surrounded by a good electrical insulator (such as air). It is shown that even a single inhomogeneity in an otherwise homogenous cylinder, which is exposed to a uniform, axially directed magnetic field, can lead to substantial deviations from the direction and distribution of the induced electric field that would exist in the homogenous cylinder. Thus the induced field is not everywhere circumferential, nor does its magnitude at all angular positions increase linearly with the radial distance. Radially and circumferentially directed field components depend on size, electrical properties, and eccentricity of the inhomogeneities. Equations as well as graphical presentations are given that describe the induced fields when the enclosed inhomogeneities consist either of eccentrically located single cylinders or pairs of coaxial cylinders with different electrical conductivities or dielectric permittivities.
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  • 10
    ISSN: 0197-8462
    Keywords: blood-brain barrier ; pinocytosis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Far-field exposures of male albino rats to 2.45-GHz microwaves (10-μsec pulses, 100 pps) at a low average power density (10 mW/cm2; SAR ∼2 W/kg) and short durations (30-120 min) resulted in increased uptakes of tracer through the blood-brain barrier (BBB). The uptake of systemically administered rhodamine-ferritin complex by capillary endothelial cells (CECs) of the cerebral cortex was dependent on power density and on duration of exposure. At 5 mW/cm2, for example, a 15-min exposure had no effect. Near-complete blockade of uptake resulted when rats were treated before exposure to microwaves with a single dose of colchicine, which inhibits microtubular function. A pinocytotic-like mechanism is presumed responsible for the microwave-induced increase in BBB permeability.
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  • 11
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    Bioelectromagnetics 11 (1990), S. 5-11 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
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  • 12
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    Bioelectromagnetics 11 (1990), S. 37-45 
    ISSN: 0197-8462
    Keywords: cyclic magnetic fields ; embryogenesis ; developmental delay ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Continuous exposure of sea urchin (Strongylocentrotus purpuratus) embryos at 18°C to a cyclic 60-Hz magnetic field at 0.1 mT rms beginning 4 min after insemination caused a significant developmental delay during the subsequent 23 hours. No delay in development was recorded for periods up to 18 hours after fertilization. At 18 h, most embryos were in the mesenchyme blastula stage. At 23 h, most control embryos were in mid-gastrula whereas most magnetic-field-exposed embryos were in the early gastrula stage. Thus an estimated 1-h delay occurred between these developmental stages. The results are discussed in terms of possible magnetic-field modification of transcription as well as interference with cell migration during gastrulation. The present study extends and supports the growing body of information about potential effects of exposures to extremely-low-frequency (ELF) magnetic fields on developing organisms.
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  • 13
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    Bioelectromagnetics 11 (1990), S. 91-99 
    ISSN: 0197-8462
    Keywords: E fields ; H fields ; cancer ; epidemiology ; occupational ; residential ; study designs ; exposure assessment ; guidelines ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The reported association between the risk of human cancer and exposure to 50- or 60-Hz electric and magnetic fields is difficult to evaluate from studies published to date. The association is now being reexamined in several large epidemiologic studies. In most of the studies, exposure will be assessed with newly designed, portable meters that allow direct and precise measurements of exposure to be performed easily for large numbers of individuals. The main features of the studies are summarized. At a meeting of principal investigators held in 1988 at the International Agency for Research on Cancer, broad guidelines were agreed for the design of this new generation of studies. These guidelines should improve the comparability of results and eventually provide a clearer assessment of human-cancer risk from exposure to extremely low-frequency electric and magnetic fields.
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  • 14
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    Bioelectromagnetics 11 (1990), S. 105-116 
    ISSN: 0197-8462
    Keywords: rats ; 60-Hz electromagnetic fields ; perinatal exposure ; conditioning ; altered operant behavior ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rats were sham exposed or exposed perinatally to a 60-Hz electromagnetic field, 22 days in utero and the first 8 days post partum. Each of the 30 once-daily exposures was 20 h in duration. The electric component of the field was vertical 30 kV/m rms, and the magnetic field component was 100 μTG rms. Later, as adults, male rats were trained to emit an operant response when reinforced with food on a multiple, random-interval schedule. Exposed rats (N = 21) gradually came to respond at significantly lower rates than did sham-exposed controls (N = 20). This finding was confirmed and extended in a second, independently performed experiment. After a sequence including operant conditioning followed by experimental extinction of responding and then by a suspension of conditioning and finally by more than a month of reconditioning, slower rates of responding were found to persist in the adult animals. The evidence of altered behavior several months after combined, fetal-neonatal exposure to an electromagnetic field presents an interesting contrast with other findings: Field-exposed rats did not differ from sham-exposed rats in terms of body mass, physical appearance, grossly observed activity level, or incidence of disease.
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  • 15
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    Bioelectromagnetics 11 (1990), S. 139-147 
    ISSN: 0197-8462
    Keywords: power lines ; cancer ; electric blankets ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Emission data are inadequate to characterize the contribution of a source to the total personal extremely-low-frequency (ELF) magnetic field exposure. In this paper, a simple model is proposed that takes into consideration the position of the subject with respect to the source and the duration of exposure. The magnetic field is spatially averaged over the whole body of the exposed subject and integrated over time. Exposure is regarded as significant if it approaches or exceeds 400 μT-h/year. By use of this method, the ELF magnetic fields generated by several household sources were compared with the levels of residential external sources, to assess their relative significance. Some common domestic electrical appliances are found to be responsible for an exposure comparable to that from power lines. When the model is used to assess exposure to electric blankets, apparently conflicting findings may be reconciled.
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  • 16
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    Bioelectromagnetics 11 (1990), S. 297-312 
    ISSN: 0197-8462
    Keywords: ELF fields ; transient response ; chemical-reaction model ; rate constant ; RNA synthesis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The exposure of cells to relatively low-intensity, pulsed, low-frequency electromagnetic fields can result in a transient augmentation of mRNA synthesis. Under certain conditions of irradiation, the augmentation is a function of the strength of the electromagnetic field. A linear, multi-step, chemical-reaction model accounts for many of the principal features that are observed in both the time- and intensity-dependent variations of transcriptional effects. The crucial assumption in the model is that the direct effect of electromagnetic fields on exposed cells is an increase in the rate constant that characterizes one of the intermediate sequential reactions in the synthesis of mRNA.
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  • 17
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    Bioelectromagnetics 11 (1990), S. 349-358 
    ISSN: 0197-8462
    Keywords: VHF ; Crawford cell ; calcium ions ; intensity window ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Isolated frog hearts were exposed for 30-min periods in a Crawford cell to a 240-MHz electromagnetic field, either continuous-wave or sinusoidally modulated at 0.5 or 16 Hz. Radiolabeled with calcium (45Ca), the hearts were observed for movement of Ca2+ at calculated SARs of 0.15, 0.24, 0.30, 0.36, 1.50, or 3.00 mW/kg. Neither CW radiation nor radiation at 0.5 Hz, which is close to the beating frequency of the frog's heart, affected movement of calcium ions. When the VHF field was modulated at 16 Hz, a field-intensity-dependent change in the efflux of calcium ions was observed. Relative to control values, ionic effluxes increased by about 18% at 0.3 mW/kg (P 〈.01) and by 21% at 0.15 mW/kg (P 〈.05), but movement of ions did not change significantly at other rates of energy deposition. These data indicate that the intact myocardium of the frog, akin to brain tissue of neonatal chicken, exhibits movement of calcium ions in response to a weak VHF field that is modulated at 16 Hz.
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  • 18
    ISSN: 0197-8462
    Keywords: alkaline elution ; human lymphocytes ; DNA damage ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: DNA damage was induced in isolated human peripheral lymphocytes by exposure at 5 Gy to 60Co radiation. Cells were permitted to repair the DNA damage while exposed to 60-Hz fields or while sham-exposed. Exposed cells were subjected to magnetic (B) or electric (E) fields, alone or in combination, throughout their allotted repair time. Repair was stopped at specific times, and the cells were immediately lysed and then analyzed for the presence of DNA single-strand breaks (SSB) by the alkaline-elution technique. Fifty to 75 percent of the induced SSB were repaired 20 min after exposure, and most of the remaining damage was repaired after 180 min. Cells were exposed to a 60-Hz ac B field of 1 mT; an E field of 1 or 20 V/m; or combined E and B fields of 0.2 V/m and 0.05 mT, 6 V/m and 0.6 mT, or 20 V/m and 1 mT. None of the exposures was observed to affect significantly the repair of DNA SSB.
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  • 19
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    Bioelectromagnetics 11 (1990), S. 251-255 
    ISSN: 0197-8462
    Keywords: dosimetry ; exposure system ; induced current ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: An experimental arrangement is described that maximizes the dosimetric information that can be obtained during in vitro studies with ELF magnetic fields. The arrangement enables researchers to distinguish between a purely magnetic-field effect and one that also involves the electric fields and currents induced by the magnetic field.
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  • 20
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    Bioelectromagnetics 11 (1990), S. 257-259 
    ISSN: 0197-8462
    Keywords: chromodacryorrhea ; stress ; haderian gland ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: An increased incidence and severity of a brownish coloration of hair has been observed around the nose and on the ears of female rats that were chronically exposed to 60-Hz electric fields. Microscopic examination of the colored areas revealed a red-brown globular deposit on hair shafts in affected areas without signs of physical injury.
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  • 21
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    Bioelectromagnetics 11 (1990), S. 273-282 
    ISSN: 0197-8462
    Keywords: electric field ; ion current ; ion concentration ; average daily gain ; reproduction ; cow ; calf ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Two herds of beef cattle were maintained beneath a ±500 kV direct-current transmission line during a 30-month period, and were compared with two similar herds maintained away from the transmission line. Exposures of animals under the line were five to 30 times greater than those of control animals, depending on the parameter of interest, with average exposure magnitudes of 5.6 kV/m, 4.1 nA/m2, and 13 k ions/cm3, respectively, for electric field, ion current, and density of ions. Productivity and health status of cows and calves were similar between lines and control treatments. Mean body mass of cows increased with maturity, from 438 kg in 1985 to 496 kg in 1987. Calf gain averaged 0.93 kg per head per day. No unusual sources of mortality were observed. Based on this confinement study, beef cattle permitted to graze in the vicinity of a high-voltage, direct-current transmission lines are not expected to experience any decrease in frequency of conception, calving, growth rate, or survival.
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  • 22
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    Bioelectromagnetics 11 (1990), S. 359-362 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
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  • 23
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    Bioelectromagnetics 11 (1990), S. 337-347 
    ISSN: 0197-8462
    Keywords: electrical utility workers ; dosimetry ; health effects ; epidemiology ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Occupational, environmental, or domestic exposure of human beings to extremely low-frequency (50- or 60-Hz) electric and magnetic fields varies continuously over time. In epidemiological studies of possible health effects, exposures over long durations must be aggregated in terms of simple summary indices. However, there are many different, biologically plausible, ways of aggregating the data. While awake, each of 20 electric utility personnel and 16 office workers had provided minute-by-minute measures of incident electric (V/m) and magnetic (μ T) fields over a 7-day period via personal dosimeters. Once the measures were aggregated as means, medians, peaks, and other indices, intercorrelations between all index pairs were calculated; correlation matrices are presented for the utility and office workers both by group and when pooled. Product-moment coefficients (r) greater that .80 were found between the time-weighted arithmetic mean (TWA) and indices that explicitly emphasize short but highly intense exposures, such as peak values and time above thresholds. Medians and geometric means were less highly correlated with the TWA. Use of only a few indices, perhaps the TWA alone, may sacrifice but little statistical power in most epidemiological studies of utility workers exposed to ELF fields. However, correlations between electric-field strength and magnetic-field density were generally quite weak, as were correlations of either with high-frequency transients; these findings underscore the need to measure each of these variables in epidemiological studies. Indices of exposure incurred outside the workplace were less strongly correlated, which may indicate the need to use several indices in general-population studies.
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  • 24
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    Bioelectromagnetics 11 (1990) 
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    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 25
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    Bioelectromagnetics 11 (1990), S. 203-205 
    ISSN: 0197-8462
    Keywords: cyclotron resonance ; ion transport ; ion collision frequency ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The cyclotron-resonance model, which has been suggested as an explanation of a purported enhancement of transport of ions through the membranes of cells exposed to weak, lowfrequency-modulated RF fields, is shown to be inconsistent with basic physical principles. Under the conditions of the model, in which the ions are presumed to circulate under the constraint of the earth's magnetic field, the radii of gyration of the ions would approximate 50 m and, thus, are much larger than the cells. Moreover, from general considerations, the collision-damping time of such ions is expected to be less than 10-10 s, much smaller than the times of the order of 10-2 s, shown to be necessary if the conditions for low-frequency resonance are to be satisfied.
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  • 26
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    Bioelectromagnetics 11 (1990), S. 1-4 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 27
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    Bioelectromagnetics 11 (1990), S. 13-25 
    ISSN: 0197-8462
    Keywords: molluscan neurons ; resting potential ; input resistance ; stationary magnetic fields ; glia ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Identified cells of Helix lucorum L. received 20 min exposures to 23, 120, or 200 mT stationary magnetic field (MFs). Resting potentials and input resistances were measured. Controls were instituted for temperature changes and for mechanical and other sources of artifact. Resting potentials did not change with MF exposure. Input resistances decreased significantly in normally silent cells during MF exposure, but increased significantly in spontaneously active cells. The magnitudes of changes were monotonically related to strength of the MF. Changes in excitatory postsynaptic potentials were observed during MF exposure. Elimination of perineuronal glia by proteolytic enzymes eliminated the MF effects.
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  • 28
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    Bioelectromagnetics 11 (1990), S. 47-56 
    ISSN: 0197-8462
    Keywords: lymphocyte activation ; isothermal control ; shortwave ; microwave ; mitogenic stimulation ; biphasic dose dependence ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Whole human blood was exposed or sham-exposed in vitro for 2 h to 27 or 2,450 MHz radio-frequency electromagnetic (RF) radiation under isothermal conditions (i.e., 37 ± 0.2 °C). Immediately after exposure, mononuclear cells were separated from blood by Ficoll density-gradient centrifugation and cultured for 3 days at 37°C with or without mitogenic stimulation by phytohemagglutinin (PHA). Lymphocyte proliferation was assayed at the end of the culture period by 6 h of pulse labeling with 3H-thymidine 3H-TdR). Exposure to radiation at either frequency at specific absorption rates (SARs) below 50 W/kg resulted in a dose-dependent, statistically significant increase of 3H-TdR uptake in PHA-activated or unstimulated lymphocytes. Exposure at 50 W/kg or higher suppressed 3H-TdR uptake relative to that of sham-exposed cells. There were no detectable effects of RF radiation on lymphocyte morphology or viability. Notwithstanding the characteristic temperature dependence of lymphocyte activation in vitro, the isothermal exposure conditions of this study warrant the conclusion that the biphasic, dose-dependent effects of the radiation on lymphocyte proliferation were not dependent on heating.
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  • 29
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    Bioelectromagnetics 11 (1990), S. 71-89 
    ISSN: 0197-8462
    Keywords: 3-D modeling ; induced electric field ; induced current ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A user-friendly, numerical program has been developed to permit the calculation of induced currents in modeled bodies of human and infrahuman subjects. The program is based on a charge-simulation method (CSM), and it takes into account the three-dimensional (3-D) character of the extremely-low-frequency (ELF) electric field and of the models to be exposed. The principle of the method is to simulate a 3-D object, for example, an animal model, by a combination of several parts (blocks) having simple geometric forms such as a sphere, a cylinder, or a cone. This approach permits easy preparation of input data on the dimensions of the blocks and their positions in a 3-D arrangement. Other input data, such as the coordinates of the contour points and the imaginary values of charges inside objects, which are necessary in the calculations by CSM, are produced automatically by selecting an appropriate “level” for each block, according to its importance. To simulate parts having irregular shapes, special blocks may be added. In one series of experiments, induced currents were calculated for a baboon model in various postures: standing upright, positioned on four legs, and sitting on the floor. Calculated currents. the total induced current in particular, agreed very well with experimental values. Local currents in parts of the baboon models were more variable, ranging from 5% to 17% of measured values in the case of induced currents in the head. Some problems with this method, such as the effect of the dimensions of blocks or the choice of block levels, are discussed.
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  • 30
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    Bioelectromagnetics 11 (1990) 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 31
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    Bioelectromagnetics 11 (1990), S. 117-128 
    ISSN: 0197-8462
    Keywords: magnetic resonance ; electromagnetic dosimetry ; computer model ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The three-dimensional impedance method was used to estimate specific absorption rate (SAR) in a human-torso model during exposure to the time-varying and static magnetic fields used in magnetic resonance imaging (MRI). Analytical data for discrete tissues as well as the entire torso are presented. Generalized equations were derived that enable calculation of whole-torso SAR over a broad range of conditions. In addition, the impedance method can generate data about internal distributions of SAR, which are needed to predict critical organs that might undergo excessive elevations of temperature. Fair to good agreement was found between impedance-method SAR and those predicted by simple phenomenological models.
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  • 32
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    Bioelectromagnetics 11 (1990), S. 149-157 
    ISSN: 0197-8462
    Keywords: L5178Y cells ; mammalian cells ; mutation ; thymidine kinase assay ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The potential ability of radiofrequency electromagnetic radiation (RFR) in the microwave range to induce mutagenesis, chromosomal aberrations, and sister chromatid exchanges in mammalian cells is being explored in our laboratories. In addition, we have also been examining the ability of simultaneous exposure to RFR and chemical mutagens to alter the genotoxic damage induced by chemical mutagens acting alone. We have performed experiments to determine whether there is an interaction between 2.45-GHz, pulsed-wave, RFR and proflavin, a DNA-intercalating drug. The endpoint studied was forward mutation at the thymidine kinase locus in L5178Y mouse leukemic cells. Any effect on the size distribution of the resulting colonies of mutated cells was also examined. The exposures were performed at net forward powers of 500 or 600 W, resulting in a specific absorption rate (SAR) of ∼40 W/kg. The culture-medium temperature reached a 3°C maximal increase during the 4-h exposure; appropriate 37°C and convection-heating temperature controls (TC) were performed. In no case was there any indication of a statistically significant increase in the induced mutant frequency due to the simultaneous exposure to RFR and proflavin, as compared with the proflavin exposures alone. There was also no indication of any change in the colony-size distribution of the resulting mutant colonies, neither, and there was no evidence in these experiments of any mutagenic action by the RFR exposure alone.
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  • 33
    ISSN: 0197-8462
    Keywords: magnetic resonance ; ionic resonance ; calcium efflux ; behavior ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The frequency dependence of the electric and magnetic (EM)-field-induced release of calcium ions from an in vitro brain tissue preparation has been shown to be a function of the density of the local DC magnetic field (BdC). In this study, we demonstrate that the relative orientation of the Bdc and the magnetic component (Bac) of a 315-Hz EM signal (15 Vrms/m and 61 nTrms) are crucial for the induced release to be observed. The induced release occurs only when the Bdc and the Bac are perpendicular, and not when they are parallel. This finding is consistent with a magnetic resonance-like transduction mechanism for the conversion of EM energy into a physicochemical change, and contrasts with the requirement for parallel Bdc and Bac components in the diatom-mobility experiments of Smith et al. A review of the exposure conditions in the rat behavioral experiments conducted by Thomas et al. identifies unhydrated calcium and zinc ions as alternatives to lithium ions as candidates for interaction under parallel magnetic-field orientations but fails to reject perpendicular orientations as an alternative basis for the phenomenon. Investigators that attempt to confirm the rat behavioral experiments should be aware of the conflicting exposure conditions that can be assumed to be operative, and they should design their experiments to test all conditions accordingly.
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  • 34
    ISSN: 0197-8462
    Keywords: abnormalities ; chick embryos ; pulsed magnetic fields ; development ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Six independent experiments of common design were performed in laboratories in Canada, Spain, Sweden, and the United States of America. Fertilized eggs of domestic chickens were incubated as controls or in a pulsed magnetic field (PMF); embryos were then examined for developmental anomalies. Identical equipment in each laboratory consisted of two incubators, each containing a Helmholtz coil and electronic devices to develop, control, and monitor the pulsed field and to monitor temperature, relative humidity, and vibrations. A unipolar, pulsed, magnetic field (500-μs pulse duration, 100 pulses per s, 1-μT peak density, and 2-μs rise and fall time) was applied to experimental eggs during 48 h of incubation. In each laboratory, ten eggs were simultaneously sham exposed in a control incubator (pulse generator not activated) while the PMF was applied to ten eggs in the other incubator. The procedure was repeated ten times in each laboratory, and incubators were alternately used as a control device or as an active source of the PMF. After a 48-h exposure, the eggs were evaluated for fertility. All embryos were then assayed in the blind for development, morphology, and stage of maturity. In five of six laboratories, more exposed embryos exhibited structural anomalies than did controls, although putatively significant differences were observed in only two laboratories (two-tailed Ps of .03 and 〈.001), and the significance of the difference in a third laboratory was only marginal (two-tailed P = .08). When the data from all six laboratories are pooled, the difference in incidence of abnormalities in PMF-exposed embryos (∼25 percent) and that of controls ( ∼ 19 percent) although small, is highly significant, as is the interaction between incidence of abnormalities and laboratory site (both Ps 〈 .001). The factor or factors responsible for the marked variability of inter-laboratory differences are unknown.
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  • 35
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    Bioelectromagnetics 11 (1990), S. 213-228 
    ISSN: 0197-8462
    Keywords: modeling ; finite difference ; ELF ; dosimetry ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The current-density distribution produced inside irregularly shaped, homogeneous human and rat models by low-frequency electric fields is obtained by a two-stage finite-difference procedure. In the first stage the model is assumed to be equipotential. Laplace's equation is solved by iteration in the external region to obtain the capacitive-current densities at the model's surface elements. These values then provide the boundary conditions for the second-stage relaxation solution, which yields the internal current-density distribution. Calculations were performed with the Excel spread-sheet program on a Macintosh-II microcomputer. A spread sheet is a two-dimensional array of cells. Each cell of the sheet can represent a square element of space. Equations relating the values of the cells can represent the relationships between the potentials in the corresponding spatial elements. Extension to three dimensions is readily made. Good agreement was obtained with current densities measured on human models with both, one, or no legs grounded and on rat models in four different grounding configurations. The results also compared well with predictions of more sophisticated numerical analyses. Spread sheets can provide an inexpensive and relatively simple means to perform good, approximate dosimetric calculations on irregularly shaped objects.
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  • 36
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    Bioelectromagnetics 11 (1990) 
    ISSN: 0197-8462
    Keywords: Life and Medical Sciences ; Occupational Health and Environmental Toxicology
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  • 37
    ISSN: 0197-8462
    Keywords: c-myc ; histone H2B ; dot-blot hybridization ; transcription ; human cells ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Human HL-60 cells were exposed for 20 min to an electromagnetic field at frequencies ranging from 15 to 150 Hz and at densities from 0.2 to 2.3 mT (2 to 23 gauss). Following each exposure, quantitative levels of c-myc and histone H2B transcripts were determined by dot-blot hybridization analyses and compared with unexposed control samples. The most pronounced increase in each transcript occurred after exposure at 45 Hz, with levels more than four times that found in unexposed controls.
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  • 38
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    Bioelectromagnetics 11 (1990), S. 283-296 
    ISSN: 0197-8462
    Keywords: grounding currents ; ELF ; exposure assessment ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A model is presented that permits the calculation of densities of 60-Hz magnetic fields throughout a residence from only a few measurements. We assume that residential magnetic fields are produced by sources external to the house and by the residential grounding circuit. The field from external sources is measured with a single probe. The field produced by the grounding circuit is calculated from the current flowing in the circuit and its geometry. The two fields are combined to give a prediction of the total field at any point in the house. A data-acquisition system was built to record the magnitude and phase of the grounding current and the field from external sources. The model's predictions were compared with measurements of the total magnetic field at a single location in 23 houses; a correlation coefficient of .87 was obtained, indicating that the model has good predictive capability. A more detailed study that was carried out in one house permitted comparisons of measurements with the model's predictions at locations throughout the house. Again, quite reasonable agreement was found. We also investigated the temporal variability of field readings in this house. Daily magnetic field averages were found to be considerably more stable than hourly averages. Finally, we demonstrate the use of the model in creating a profile of the magnetic fields in a home.
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  • 39
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    Bioelectromagnetics 11 (1990), S. 313-335 
    ISSN: 0197-8462
    Keywords: risk communication ; public understanding ; mental models ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: People do not start with a blank slate when they hear risk-communication messages. All such messages are processed through existing knowledge structures and understanding. Hence, to design effective and reliable risk-communication materials one must understand the state of people's knowledge - correct and incorrect - about an issue. We developed a simple “mental model” of what people minimally need to know to make informed decisions about field-related issues. Then we performed studies to explore how and to what extent respondents of various groups understood physical properties of 60-Hz electric and magnetic fields. Actual knowledge of respondents was then compared with the predicates of the model. Electrical engineering juniors and semi-technical employees of utilities displayed a good command of most of the concepts in the simple model, but little awareness of the limits to their knowledge. Lay respondents correctly knew only a few of the simplest elements of the model, but they displayed a much greater awareness of the limits to their knowledge. Both lay and semi-technical respondents were found to share several misconceptions. On average, they correctly rank-ordered some common field-exposure conditions by field strength, but they could not differentiate between electric and magnetic fields and could not differentiate among field strengths associated with different appliances. Most respondents dramatically underestimated the range of actual field strengths. Many respondents understood that field strength decreases with distance from a source, but they underestimated the rate of decrease. In contrast to X-rays and microwaves, which respondents appeared to think about in rather similar terms, 60-Hz fields were not thought of as being highly similar to any other agent, although the closest parallels were found with ultrasound. Changes in mood, thought, and behavior, and the existence of an “electrical aura,” were all seen as plausible results of exposure to a 60-Hz field. Although lay respondents displayed a variety of incomplete and confusing ideas, most of these ideas probably do not pose significant obstacles to the learning of a correct, simple, mental model.
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  • 40
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    Journal of Electron Microscopy Technique 14 (1990), S. 63-69 
    ISSN: 0741-0581
    Keywords: Filtration barrier ; Renal sections ; Resinless ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Following the removal of polyethylene glycol (PEG) from thin sections, and viewing through the endothelial fenestrae and/or the interpedicel spaces, the rat renal glomerular basement membrane in situ was revealed to consist of meshworks and to be electron-transparent when examined at right angles to the plane of the membrane. By subsequent platinum replication of the embedment-free sections, the lamina densa of the basement membrane appeared as a veil composed of rather closely packed particles. The architecture of the slit diaphragm and the surface morphology of the endothelial cell membrane were also clearly revealed. The present results indicate that the PEG method, with or without replication, can provide valuable information on basement membrane morphology.
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  • 41
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    Journal of Electron Microscopy Technique 14 (1990), S. 140-151 
    ISSN: 0741-0581
    Keywords: Hepatocyte ; Endocytosis ; Receptor ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 42
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    Journal of Electron Microscopy Technique 14 (1990), S. 92-105 
    ISSN: 0741-0581
    Keywords: Hepatocyte organelles ; Bile canaliculi ; Postnatal hepatocyte differentiation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper reviews the fine structure and function of hepatocytes during fetal and postnatal development. Bile canaliculi develop to a mature appearance during perinatal and early postnatal periods, while bile secretory function is immature at birth and develops during the postnatal period. The rough endoplasmic reticulum is prominent and remains unchanged in amount during development, and the Golgi complex is large from early stages of fetal life. The smooth endoplasmic reticulum (SER) appears shortly before birth and increases in quantity to the adult level after birth. In mouse hepatocytes, Sv (area per unit cytoplasmic volume) of SER increases in perivenular cells between 1 and 10 days of age, although it remains low in periportal cells. Similarly, Sv of total ER increases in both periportal and perivenular cells between 1 and 5 days of age and then becomes greater in perivenular than periportal cells. This suggests that the postnatal increase in the drug-metabolizing capacity occurs predominantly in perivenular hepatocytes. SER proliferates after phenobarbital (PB) administration in both perivenular and periportal cells in 3-, 5-, and 10-day-old mice, and predominantly in perivenular cells in 20-day-old and adult mice. Thus the conspicuous proliferation of SER in perivenular hepatocytes after PB administration, characteristic of adult liver, becomes manifest during postnatal development. In mouse hepatocytes, Vv (volume per unit cytoplasmic volume) of mitochondrial matrix and peroxisomes and Sv of mitochondrial inner membrane and cristae increase in both periportal and perivenular cells between birth and 10 days of age. Then, Vv of mitochondrial matrix remains unchanged in periportal cells but decreases in perivenular cells. In general, the process of postnatal hepatocyte differentiation appears to include several phases of development; cell organelles develop during the early postnatal period, subsequently the cells undergo both functional and structural heterogeneity, and the late postnatal period after weaning is the time for a marked increase in cell size.
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  • 43
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    Journal of Electron Microscopy Technique 14 (1990), S. 106-125 
    ISSN: 0741-0581
    Keywords: Aging ; Ultrastructure ; Liver volume ; Lysosomes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Aging is accompanied by a myriad of changes in cell structure, function, and composition. The fact that much of the information concerning age-related alterations in cellular morphology is qualitative precludes meaningful correlations with biochemical changes in order to enhance data interpretation. The mammalian liver has been subjected to both qualitative and quantitative evaluations of hepatocyte structure as a function of aging, i.e., development, maturation, and senescence. Although these data are characterized by considerable variability and, in some instances, blatant contradictions, there exists sufficient agreement in several parameters to permit a consensus in the inbred rat model. Certainly the volume of individual hepatocytes increases with age, and many of the organelle compartments reflect this change. While old rats exhibit a high incidence of polyploidy, there is no definitive evidence to demonstrate a concomitant increase in the binuclear hepatocyte index. Several specific hepatocellular organelles undergo changes in their relative volume or surface area that appear to correlate with functional alterations. The volume density of the lysosomal compartment enlarges significantly during senescence and is accompanied by increased activities of several constituent hydrolases. The hepatic concentration of smooth-surfaced endoplasmic reticulum declines markedly with aging, as does the yield of liver microsomes and the activities of several microsomal enzymes, e.g., mono-oxygenases and glucose-6-phosphatase. However, the responses of the majority of hepatocyte organelles to aging is varied and inconsistent based on the limited data currently available.
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  • 44
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    Journal of Electron Microscopy Technique 14 (1990), S. 179-207 
    ISSN: 0741-0581
    Keywords: Ultrastructure ; Liver disease ; Hepatitis ; Alcoholic injury ; Storage diseases ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Hepatocytes respond to injury by a few basic pathological reactions that are reflected in cell death, different types of degeneration, regeneration, or tumorous transformation. At the ultrastructural level, alterations of cell organelles can be observed in different combinations as a result of the injury, depending on the etiological agent(s) or pathological conditions developed. Nuclear bodies, dilation and fragmentation of rough endoplasmic reticulum (rer), swelling of mitochondria, and an increased number of lysosomes occur during acute viral hepatitis. The core and surface components of the hepatitis B virus can be localized in the liver cells in chronic hepatitis and in carriers. Close contact of hepatocytic and lymphocytic cell membranes were observed in chronic active hepatitis. Hepatocytes surrounded by an increased amount of collagen fibers are characteristic of cirrhosis. Loosely arranged, fine fibrils or condensed forms of Mallory bodies are pathognomic for alcoholic injury. A wide spectrum of alterations are noted after drug treatment: the proliferation of smooth endoplasmic reticulum (ser) as an adaptive phenomenon, focal or complete necrosis of the cell, inflammation, and the like. The fine structural analysis of hepatocytic inclusions in storage diseases has a differential diagnostic value. The storage of copper and other elements can be measured by x-ray microanalysis. The study of the hepatocytic differentiation in liver tumors is highly important in establishing the diagnosis and in proving the hepatocytic origin of the tumor.
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  • 45
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    Journal of Electron Microscopy Technique 14 (1990), S. 237-246 
    ISSN: 0741-0581
    Keywords: Liver ; Sinusoid ; Phagocytosis ; Endocytosis ; Host defense ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Kupffer cells are macrophages that are attached to the luminal surface or inserted in the endothelial lining of hepatic sinusoids. In this site, Kupffer cells play a key role in host defense by removing foreign, toxic and infective substances from the portal blood and by releasing beneficial mediators. Under some conditions, toxic and vasoactive substances also are released from Kupffer cells which are thought to play a role in a variety of liver diseases. Many of these activities may be modulated by the levels of gut derived endotoxin normally present in the portal blood.The ultrastructural aspects of Kupffer cell structure function in situ are best studied using perfused-fixed livers. In fixed livers, transmission and scanning electron microscopy reveal Kupffer cells during health to be irregular in shape with their exposed surfaces presenting numerous microvilli, filopodia, and lamellopodia. Long filopodia penetrate endothelial fenestrae to secure Kupffer cells to the sinusoid lining. Specific membrane invaginations known as worm-like bodies or vermiform processes are seen in the cytoplasm of Kupffer cells as are numerous endocytotic vesicles and lysosomes which vary in density, shape and size. Sometimes, annulate lamellae connected to the rough endoplasmic reticulum also are found. The principal endocytic mechanisms of Kupffer cells are phagocytosis of particulates and cells, and bristle-coated micropinocytosis for fluid-phase endocytosis of smaller substances. Many of these events are mediated by specific receptors. In some species, Kupffer cells can be distinguished from other sinusoidal lining cells and monocytes by specific cytoplasmic staining or monoclonal antibodies. Kupffer cells have been shown to be of monocytic origin as well as having the capacity for self-replication.
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  • 46
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    Journal of Electron Microscopy Technique 14 (1990), S. 247-256 
    ISSN: 0741-0581
    Keywords: Sinusoidal cells ; Fat-storing cells ; Ito-cells ; Natural killer cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The present paper reviews the literature on the ultrastructure and function of sinusoidal fat-storing cells and pit cells in the mammalian liver.Ultrastructurally, fat-storing cells are characterized by the presence of cytoplasmic fat droplets, well developed rough endoplasmic reticulum; a Golgi complex; multivesicular bodies; one or two centrioles; and few, rather small, lysosomes. These lysosomes are sometimes associated with fat droplets. Fat-storing cells may bear a cilium and project characteristic cytoplasmic processes into the space of Disse. These processes contain microtubules and filaments. Fat-storing cells are the main storage site of retinol esters in the mammalian body. Moreover, these cells have the potential of synthesizing several connective tissue components including the collagens type I, III, and IV; fibronectin; laminin; heparan sulfate; chondroitin sulfate; and dermatan sulfate.Pit cells are polarized cells, with most organelles localized at one site of the nucleus near the cytocentre. They are characterized electron microscopically by the presence of dense cytoplasmic granules with a specific ultrastructure, by rod-cored vesicles, and by multivesicular bodies. It has recently been shown that pit cells have natural killer activity to certain tumor cells and have many features in common with large granular lymphocytes. They therefore may act in the liver as a first line of defense against neoplasia, metastasis, and viral infections.
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  • 47
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    Journal of Electron Microscopy Technique 14 (1990), S. 257-282 
    ISSN: 0741-0581
    Keywords: Sinusoids ; Endothelial cells ; Kupffer cells ; Perisinusoidal cells ; Pit cells ; Space of Disse ; Extracellular matrix ; Disease ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Liver sinusoids are special capillaries that are limited by fenestrated endothelial cells, without a genuine basement membrane, surrounded by perisinusoidal cells storing vitamin A, and harbouring Kupffer cells and pit cells, resident macrophages, and large granular lymphocytes, respectively. Each nonparenchymal cell and parenchymal cell of the liver interacts with all others and with the extracellular matrix. Therefore, the functional ability of each cell is constantly being modified by the metabolic activity of the others.Human liver biopsies (132), needle or surgical, perfusion-fixed with glutaraldehyde and processed for transmission electron microscopy (TEM), and occasionally for scanning electron microscopy (SEM), were examined. The study included liver diseases (such as alcoholic liver diseases, benign and malignant liver tumors, cholestasis of various origins, fulminant hepatitis, acute rejection after orthotopic liver transplantation, Budd-Chiari syndrome), as well as general or extrahepatic diseases (such as diabetes, hemochromatosis, hypervitaminosis A, various hematological disorders), and normal controls.Ultrastructural abnormalities are described and illustrated under two different headings: (1) elementary lesions of sinusoidal cells (endothelial, Kupffer, perisinusoidal and pit cells), nonsinusoidal cells (in the space of Disse and/or in the lumen), the extracellular matrix; and (2) the major pathological entities including perisinusoidal fibrosis, capillarization of sinusoids, sinusoidal dilatation, and peliosis. In the discussion, an overview of the major abnormalities reported in the literature is presented, and some specific questions regarding (1) perisinusoidal fibrosis in liver with normal histology, (2) the overload of perisinusoidal cells with lipids in non-hypervitaminosis A intoxication and (3) the etiological relationship of sinusoidal dilatation, peliosis, perisinusoidal fibrosis, or sinusoidal tumors with drugs and toxic compounds are discussed. In the event that lesions are not specific to any diagnosis, the knowledge of the ultrastructure of sinusoids is extremely useful from the perspective of the liver as an ecosystem.
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  • 48
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    Journal of Electron Microscopy Technique 15 (1990), S. 81-96 
    ISSN: 0741-0581
    Keywords: Antibody ; GABA ; Glycine ; Acetylcholine ; Auditory system ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Over the last several years our knowledge of neurotransmitter receptors has increased dramatically as receptor types and subtypes have been identified through the development of selective antagonists, neuropharmacological studies, and radioactive ligand binding studies. At the same time major advances were made in the immunocytochemical localization of neurotransmitters and their related enzymes. However, only recently has immunocytochemistry been used to localize neurotransmitter receptors, and these studies have been limited. Four receptors have been localized in the CNS with immunocytochemistry: the nicotinic acetylcholine receptor, the beta-adrenergic receptor, the GABA/benzodiazepine receptor, and the glycine receptor. Of these the glycine receptor has been the most thoroughly characterized. Glycine receptor immunoreactivity is highly concentrated at postsynaptic sites, and the distribution of immunoreactivity appears to correlate closely with glycinergic neurons. However, immunocytochemical studies done on other receptors suggest such a distribution may not always be the case. Some receptors may not be concentrated at postsynaptic sites, and receptor distribution may not always closely fit the distribution of the respective neurotransmitter. Work is rapidly progressing on the purification of other receptors and on the production of selective antibodies which will allow immunocytochemical studies which address these and other questions.
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  • 49
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    Journal of Electron Microscopy Technique 15 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 50
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    Journal of Electron Microscopy Technique 15 (1990), S. 104-114 
    ISSN: 0741-0581
    Keywords: Nerve fiber ; Afferent and efferent nerves ; Cochlea ; Fetal inner ear ; Human ear ; SEM ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The cochleas of four human fetuses ranging 22-25 weeks gestation were studied by scanning electron microscopy (SEM) for the purpose of obtaining a better understanding of the nerve fiber arrangement in the human ear. After critical point drying, the specimens were dissected and the floor of the tunnel of Corti and the outer wall of Nuel's space were exposed for observation. Upper cochlear turns, especially the apical turn, seemed to be still immature.Observed nerve fibers were classified into three types:1Spiral fibers: Fibers traveling basalward and following the shape of the cochlea were found in both the tunnel of Corti and Nuel's space and believed to be the afferent nerves responsible for innervating the outer hair cells2Radial fibers: radiating outward from the osseous spiral lamina - one such radial fiber transversing high in the tunnel space (supposedly the efferent nerve servicing the outer hair cells), and another sort of radial fiber (found crossing the tunnel floor), the nature of which was uncertain.3Irregular fibers: Consisting of thin, randomly running fibers within the cochlea. The destination of these fibers was not determined, but possibly they represent transitory nerve branchings of afferent or more probably efferent nerves, which would later regress during maturation.
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  • 51
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    Journal of Electron Microscopy Technique 15 (1990), S. 155-164 
    ISSN: 0741-0581
    Keywords: Spiral ganglion ; Freeze-fracture ; Intermediate filaments ; Morphology ; Cytoskeleton ; Membrane ; Labyrinth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Freeze-fracture analysis of adult spiral ganglion cells of CBA/CBA mice revealed two types of membrane specializations. Most cells (type I) had a smooth surface and were surrounded by Schwann cells. Type II spiral ganglion cells showed numerous membrane specializations with well-delineated indentations similar to those previously found on hair cells adjacent to afferent and efferent nerve endings. Immunomorphological analysis (using well-defined monoclonal antibodies directed against different subclasses of intermediate filament proteins) revealed a unique co-expression of neurofilaments, vimentin and cytokeratins in spiral ganglion cells of 8-to 22-week human fetuses.
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  • 52
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    Journal of Electron Microscopy Technique 15 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 53
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    Journal of Electron Microscopy Technique 15 (1990), S. 245-260 
    ISSN: 0741-0581
    Keywords: Stereocilia ; Postmortem cochlea ; Scanning electron microscopy ; Human ; Guinea pig ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The morphology of hair bundles has been studied by high resolution scanning electron microscopy using a variety of fixatives, including glutaraldehyde, glutaraldehyde-picrate, glutaraldehyde-tannic acid, glutaraldehyde followed by post-fixation in osmium tetroxide, and the osmium thiocarbohydrazide technique. Critical evaluation of several metal coatings, gold, gold-palladium, and platinum has been carried out.Both the surface texture of stereocilia and their cross-links are sensitive to fixation and metal coating. We are of the opinion that glutaraldehyde gives the best general quality of fixation and preservation for all types of cross-links. We have described three major sets of cross-links: first, lateral links connecting stereocilia within the same row; second, lateral links connecting stereocilia of adjacent rows; and third, upward-pointing links, one per stereocilium, connecting the tip of each shorter stereocilium to the lateral surface of the adjacent taller stereocilium. Current physiological and anatomical evidence suggests that the lateral links couple the individual stereocilia within the hair bundle so that they function as a single mechanical unit. The upward-pointing tip links are ideally placed to respond to mechanical deformation of the hair bundle, being stretched when the stereocilia are deflected in the excitatory direction towards the tallest row and relaxed when deflected in the opposite, inhibitory direction.Postmortem morphological changes are detected within 15 minutes of cardiac arrest and become progressively more pronounced in time. These results enabled us to distinguish specific druginduced changes which could not be attributed simply to cell death. Effects of cisplatin and kanamycin upon hair bundles are described. The work reported here is based on studies using the guinea pig cochlea. Some of the postmortem changes described have also been confirmed in human cochleas.It is stressed that many of the postmortem and drug-induced effects can only reliably be studied by high resolution scanning electron microscopy coupled with appropriate prearation procedures.
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  • 54
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    Journal of Electron Microscopy Technique 16 (1990) 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 55
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    Journal of Electron Microscopy Technique 16 (1990), S. 15-24 
    ISSN: 0741-0581
    Keywords: Intestine ; Mucosal barrier ; Tight junction ; Freeze-fracture ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Rat colonic mucosae fixed in situ in Ussing chambers provided a model of the extrusion of absorptive enterocytes and less commonly of goblet and enteroendocrine cells. The cells were lost at extrusion zones midway between crypt mouths. Even in mucosae in which the number of extruding cells was large, epithelial continuity was maintained as evaluated morphologically and electrophysiologically. Beneath points of remaining contact between desquamating cells and the epithelial sheet, microfilaments of the terminal web formed band-like structures linking adjacent junctional complexes. Freeze-fracture replicas disclosed extensive macular regions of tight junction strands in the plasma membranes of desquamating cells. Tight junctions between newly neighboring cells were often irregular and often occurred beneath the terminal web region. Dithio-threitol enhanced cell loss and increased basal epithelial conductance, but histological continuity was maintained and the mucosae continued to respond typically to bradykinin. These observations suggest that during the loss of senescent enterocytes, tight junctions are maintained; old junctional elements are lost, and tight junctions are formed between remaining adjacent cells. This model offers a means to study the synthesis and turnover of tight junctions and the maintenance of the colonic epithelial barrier.
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  • 56
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    Journal of Electron Microscopy Technique 16 (1990), S. 81-82 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 57
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    Journal of Electron Microscopy Technique 16 (1990), S. 69-80 
    ISSN: 0741-0581
    Keywords: Secretory granules ; Bipartite ; Golgi apparatus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Paneth cells in the following species were observed under an electron microscope: human, rhesus monkey, hare, guinea pig, rat, nude rat, mouse, golden hamster, and insect feeder bat. Secretory granules containing homogeneous electron-dense materials were observed in the Paneth cells of humans, monkeys, hares, guinea pigs, and bats; mouse Paneth-cell granules were bipartite (central core and peripheral halo), and the Paneth cells in rats and golden hamsters had secretory granules showing various electron densities. In humans, monkeys, and bats, immature granules near the Golgi apparatus sometimes showed bipartite substructure. The number and size of secretory granules were also diverse among various animal species. Some lysosome-like bodies were commonly observed in peri- or supranuclear regions, though the size and shape of the bodies differed from cell to cell. In apical cytoplasm, small clear vesicles (100-200 nm diameter) were more-or-less observed in all species examined, and it was especially note that rat Paneth cells contained many clear vesicles. Small dense-cored vesicles (150-200 nm diameter) were rare. It is unlikely that the various ultrastructural features of Paneth cells correlate with the phylogenetical classification.
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  • 58
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    Journal of Electron Microscopy Technique 15 (1990), S. 397-399 
    ISSN: 0741-0581
    Keywords: YAG scintillator ; TEM ; Image detection ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A new image detection system has been developed to display transmission electron microscope (TEM) images on a CRT without a video camera system. Deflection coils placed in both the upper space of an objective lens and in the lower space of the first intermediate lens scan a small electron probe simultaneously. The electrical signal acquired through an improved scintillator and a photomultiplier is synchronized with the scanning signal and displayed in a similar fashion to a conventional scanning TEM (STEM) instrument. A preliminary system using a 100 kV conventional TEM (CTEM) equipped with a hairpin-type electron gun, produced an image with a spatial resolution of 1 nm.
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  • 59
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    Journal of Electron Microscopy Technique 15 (1990), S. 383-396 
    ISSN: 0741-0581
    Keywords: Embryo processing ; CNS cytology ; CNS fine structure ; CNS development ; Fixation artifacts ; Embryo dissection ; Telencephalon development ; Lipids in embryos ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: To study cellular shapes, growth patterns, and fine structure during early stages of CNS development in rat embryos, preparative procedures were evaluated and modified to meet two criteria: (1) Coronal semithin sections should reveal undeformed telencephalic hemispheres that were symmetrically expanded on both sides of midline structures and were surrounded by contiguous mesenchyme. (2) In electron micrographs, cells should have intact, undistorted surface membranes, evenly distributed nucleoplasm and well preserved cytoplasmic organelles. To meet these criteria, 378 fetuses with a gestational age of 11-20 days (E11-E20) were used to test and modify procedures for anesthesia, embryo removal and handling, dissection, fixation, dehydration, and embedding of the embryonic CNS. Most specimens were in an early stage of development (E11-E13), which, in case of the neopallial wall, is the preneural period. The tests produced methods that met the above criteria and identified the most common artifacts and their causes. Deformities of the cerebral hemispheres and separations between the brain and its coverings were usually caused by trauma during embryo removal and during handling before fixation. Changes in cellular volumes, especially swelling during fixation and dehydration, were the most important causes of histological artifacts. The procedures and methods that consistently produced the best light and electron microscopic preservation of the E11-E13 rat CNS are described. Fixation was best when the brains were treated with glutaraldehyde and s-collidine buffer, followed by osmium tetroxide in s-collidine buffer. A surprisingly beneficial effect of sodium chloride in the dehydrating alcohol was noted.
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  • 60
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    Journal of Electron Microscopy Technique 15 (1990), S. 416-420 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 61
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    Journal of Electron Microscopy Technique 16 (1990), S. 1-1 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 62
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    Journal of Electron Microscopy Technique 16 (1990), S. 25-36 
    ISSN: 0741-0581
    Keywords: Lectins ; Collodial gold ; LR White ; Lowicryl ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The plasmalemmal glycoconjugates of the HT29-18N2 (N2) cell line were characterized on cells grown as (1) undifferentiated multilayers in glucose-containing culture media and (2) monolayers of columnar cells acquiring the goblet cell phenotype in glucose-free media. Lectins were unable to bind sheets of detached N2 cells in the absence of fixation. Following fixation with aldehydes, a dramatic unmasking of lectin binding sites was seen. When fixed monolayers were stained prior to embedding, biotinylated lectins, visualized by the avidin-biotin-complexed peroxidase technique, were more efficient than collodial gold-coupled lectins. Lectin binding sites could also be detected by using collodial gold-coupled lectins to stain monolayers embedded in LR White, Lowicryl K4M, and Lowicryl HM20. The binding of 5 lectins (wheat germ, Dolichos bifluros, peanut, soybean, and Ulex europeus) was found to be independent of the stage of differentiation; “pre-differentiated” columnar cells which had prominent microvilli and no or few mucous secretory granules had identical staining patterns as well-differentiated goblet cells with large numbers of secretory granules. Ricinus communis I was the only lectin whose binding was influenced by the stage of differentiation; it intensely labeled undifferentiated multilayers of N2 cells but only weakly labeled basolateral membranes of differentiated monolayers. Canavalia ensiformas (ConA) caused a moderate and even labeling of both apical and basolateral membranes of fixed monolayers stained prior to embedding, but post-embedding labeling revealed heavy labeling along the lateral margins of all columnar cells and weak to moderate binding along the apical and basal cell surface.
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  • 63
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    Journal of Electron Microscopy Technique 16 (1990), S. 45-55 
    ISSN: 0741-0581
    Keywords: Villi ; Enterocytes ; Microvilli ; Stereology ; Length ; Diameter ; Number ; Surface area ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Different regions of small bowel were examined in five groups of rats in three separate experiments. The effects on mucosal morphology of position along the bowel, induced hypoproliferation (due to fasting), and induced hyperproliferation (due to streptozotocin diabetes) were investigated.Intestines fixed by in situ perfusion with buffered glutaraldehyde were sampled by strictly randomised procedures. Pieces of tissue from segments of roughly equal length were processed for electron microscopy and embedded in resin. Complete transverse sections were cut for light microscopy and estimates of villous surface areas were obtained by stereological methods devised for the purpose. Ultrathin sections from random sectors of the same tissue blocks were sampled systematically to obtain micrographs of the villous surface. These were analysed for quantitative information about microvilli (length, diameter, surface area, and number). Structural quantities from individual segments were pooled to provide values for the entire small bowel.Significant regional differences in villous and microvillous dimensions were found in all groups. The numbers of microvilli per bowel were remarkably constant in all control groups. Other variables were estimated reproducibly in rats of the same sex, strain, and average body weight.Effective absorptive surfaces did not show a linear gradient but tended to peak in middle segments. Neither fasting nor induced diabetes altered the mean length, diameter, or packing density of microvilli. However, surfaces due to villi and microvilli altered commensurately during fasting and induced diabetes. Therefore cell number seems to be the key quantity for determining villous and microvillous surface areas.The findings are discussed in the context of kinetic, biochemical, and physiological changes found in different adaptive states.
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  • 64
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    Journal of Electron Microscopy Technique 16 (1990), S. 83-84 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 65
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    Journal of Electron Microscopy Technique 16 (1990), S. 93-114 
    ISSN: 0741-0581
    Keywords: Ultrastructure ; Biochemistry ; Maturation ; Comparative ; Oocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This review of the anatomical, histological, biochemical, and molecular biological literature on echinoderm oogenesis includes the entire developmental history of oocytes; from their inception to the time they become ova. This is done from a comparative perspective, with reference to members of the five extant echinoderm classes; crinoids, holothurians, asteroids, ophiuroids, and echinoids. I describe the anatomy and fine structure of the echinoderm ovary, with emphasis on both the cellular relationships of the germ line cells to the somatic cells of the inner epithelium, and on the neuromuscular systems. I review the literature on the growth of oogonia into fully formed oocytes, including the process of vitellogenesis, presenting an ultrastructural analysis of the organelles and extracellular structures found in fully formed echinoderm oocytes. Echinoderm oocyte maturation is reviewed and a description of the ultrastructural, biochemical and molecular biological changes thought to occur during this process is presented. Finally, I discuss oocyte ovulation, the severing of cellular connections between the oocyte and its surrounding somatic epithelial cells.
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  • 66
    ISSN: 0741-0581
    Keywords: Stopped-flow ; Rapid-freezing ; Freeze-fracture ; Electron microscopy ; Rapid reactions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have developed an instrument capable of freezing transient intermediates in rapid biochemical reactions for subsequent freeze-fracturing, replication, and viewing by transmission electron microscopy. The machine combines a rapid mixing unit similar to one widely used in chemical kinetics (Johnson, 1986) with a propane jet freezing unit previously used to prepare static samples for freeze-fracturing (Gilkey and Staehelin, 1986). The key element in the system is a unique thin-walled flow cell of copper that allows for injection and aging of the sample, followed by rapid freezing. During freeze-fracturing, a tangential cut is made along the wall of the flow cell to expose the sample for etching and replication. The dead time required for mixing and injection of the reactants into the flow cell is less than 5 ms. Electronic controls allow one to specify, on a millisecond time scale, any time above 5 ms between initiation of the reaction and quenching by rapid freezing.
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  • 67
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    Journal of Electron Microscopy Technique 16 (1990), S. 202-234 
    ISSN: 0741-0581
    Keywords: Xenopus ; Meiosis ; Ultrastructure ; Intracellular signals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Amphibian oocytes, arrested in prophase I, are stimulated to progress to metaphase II by progesterone. This process is referred to as meiotic maturation and transforms the oocyte, which cannot support the early events of embryogenesis, into the egg, which can. Meiotic maturation entails global reorganization of cell ultrastructure: In the cell cortex, the plasma membrane flattens and the cortical granules undergo redistribution. In the cell periphery, the annulate lamellae disassemble and the mitochondria become dispersed. In the cell interior, the germinal vesicle becomes disassembled and the meiotic spindles form. Marked changes in the cytoskeleton and mRNA distribution also occur throughout the cell. All of these events are temporally correlated with intracellular signalling events: Fluctuations in cAMP levels, changes in pH, phosphorylation and dephosphorylation, and ion flux changes. Evidence suggests that specific intracellular signals are responsible for specific reorganizations of ultrastructure and mRNA distribution.
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  • 68
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    Journal of Electron Microscopy Technique 16 (1990), S. 240-248 
    ISSN: 0741-0581
    Keywords: Energy dispersive x-ray spectrometer ; Thin film ; K-factor ; High voltage transmission electron microscope ; Quantitative standardless analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Qualitative and quantitative x-ray energy dispersive spectroscopy is now used successfully to analyze many features and processes in inorganic samples. When applied to inorganic samples, however, the results are often less satisfactory due to problems of preparation of organic samples, difficulty of measuring x-rays from organic samples, damage of the sample by the electron beam, and other practical problems.In the present study we used a high voltage transmission electron microscope equipped with an energy dispersive x-ray spectrometer to examine accurate quantitative standardless analysis of thin sections of an organic sample, human dentin.Based on our experiments we found the important parameters for quantitative analysis were sample thickness and appropriate choice of model sample. Further, we show that the method of Cliff and Lorimer can be used with biological samples at 200 kV, and we show that quantitative analysis of human dentin can be carried out at 200 kV. Finally, we show that areas of human dentin can be differentiated by their morphological characteristics and x-ray analyses obtained in the transmission electron microscope.
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  • 69
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    Journal of Electron Microscopy Technique 16 (1990), S. 281-297 
    ISSN: 0741-0581
    Keywords: Mammalian spermatozoon ; Surface membrane ; Spermatogenesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The mammalian spermatozoon is a highly polarized cell whose surface membrane can be divided into five functionally, structurally, and biochemically distinct domains. These domains are formed during spermatogenesis, continue to be modified during passage through the epididymis, and are further refined in the female reproductive tract. The integrity of these domains appears to be necessary for the sperm to perform its function - fusion with the egg and subsequent fertilization. The domains can be identified morphologically by their surface contours and texture, the content, distribution, and organization of intramembranous particles after freeze-fracture, and by the density of surface and cytoplasmic electron-dense coatings in thin sections. By using a variety of labels that stain carbohydrates (lectins), lipids (filipin and polymyxin B), and monoclonal antibodies to specific membrane constituents, the biochemical composition of these contiguous membrane regions has also been partly elucidated. We review here what is known about the structure, composition, and behavior of each membrane domain in the mature sperm and include some information regarding domain formation during spermatogenesis. The sperm is an excellent model system to study the creation and maintenance of cell polarity, granule exocytosis, and fertilization. Hopefully this review will provide impetus for future studies aimed more directly at addressing the relationship of its morphology to its functions.
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  • 70
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    Journal of Electron Microscopy Technique 16 (1990), S. 356-357 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 71
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    Journal of Electron Microscopy Technique 16 (1990), S. 351-355 
    ISSN: 0741-0581
    Keywords: Drying ; Electron microscopy ; Frozen hydrated specimen ; Specimen preparation ; Vitrified specimen ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Evaporation of water cannot be fully avoided when an unsupported thin vitrified film of an aqueous suspension is prepared for cryo-electron microscopy. This results in increasing concentration of solute which could affect the observed material. We have quantitatively studied this effect by measuring the contrast of polystyrene spheres in a metrizamide solution. The drying effect is generally negligible when specimens are prepared on a hydrophilic perforated support but it is frequently important when hydrophobic films are used instead. A flow of humid air, double blotting with minimal exposure of the thin liquid film to the atmosphere, or an automatic plunger optimizing the blotting conditions are simple methods for reducing drying effects. With this third device acting on a hydrophilic supporting film, the increase of solute concentration is limited to less than 20%.
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  • 72
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    Journal of Electron Microscopy Technique 14 (1990), S. 39-45 
    ISSN: 0741-0581
    Keywords: Exocrine pancreas ; Cryofixation ; Cryomicrotomy ; Freeze-drying ; Freeze-substitution ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper describes and compares the morphology of a relatively complex tissue, the exocrine pancreas, prepared by state-of-the-art anhydrous cryoprocedures. Cryopreparative procedures are being used increasingly for a wide range of applications, for example, electron-probe x-ray microanalysis and immunocytochemical localization of antigenic molecules, because they preserve the composition of the specimen better than procedures involving aqueous media. Some doubts have remained concerning the morphology of cryosections and the precise identification of subcellular structures.We show that thin and sufficiently large cryosections of fresh biological tissues can be produced using commercially available hardware. The freeze-dried cryosections display high intrinsic contrast, are stable under the beam, and allow identification of intracellular fine structure.
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  • 73
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    Journal of Electron Microscopy Technique 14 (1990), S. 32-38 
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Cell counts ; Nuclear shape ; Section compression ; Lung ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Counts of cells and nuclei from sections provide information central to studying structural changes in cells, tissues, and organs. This study considers some of the practical problems associated with counting cells with the newer random and serial sectioning methods of stereology and tests the hypothesis that similar cell counts can be obtained with both random and serial sectioning methods.Using irregularly shaped nuclei from alveolar cells of the goat lung, we compared cell counts derived from random (electron microscopic) and serial sectioning (light microscopic) methods. The results showed that both sectioning methods gave similar cell counts (107/cm3 of parenchyma) for type 1 epithelial cells (5.0 vs. 5.0; P=1.0), type 2 epithelial cells (8.6 vs. 9.8; P=0.42) and interstitial cells (34.6 vs. 33.4; P=0.64), provided that corrections were introduced for sectionrelated biases and that the nuclei of the random sectioning method were corrected for shape. We found counting biases of 5%-7% for nuclear shape and 16% for section compression. These observations support the hypothesis that similar cell counts can be obtained with random and serial sectioning, even when nuclei have irregular shapes.
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  • 74
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    Journal of Electron Microscopy Technique 14 (1990), S. 46-51 
    ISSN: 0741-0581
    Keywords: Lattice parameter determination ; Crystallographic orientations ; Image analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Oxygen-contaminated, melt-spun, binary Ti-Si alloys have been examined by using transmission electron microscopy. The microstructure of alloys in the range of 4 to 10% Si (by weight) are cellular and consist primarily of α-Ti and the silicide Ti5Si3. Contained only within the Ti5Si3regions are small, approximately spherical particles which are ≤ 10 nm in diameter. Due to their small size, the crystal structure of these particles could not be determined by using conventional diffraction techniques such as Selected Area or Convergent Beam Diffraction. By conducting a number of tilting experiments and observing the moire fringe patterns produced when various matrixTi5Si3 planes were used to image the sample, the crystal structure of the particles and the orientation relationship which exists between them and the matrix were deduced. The unknown particles, termed the Z phase, were found to be hexagonal with slightly different lattice parameters from the matrix Ti5Si3. Their relationship with the matrix was such that they appeared to be totally coherent. This may indicate that Z is an oxide based on the intermetallic Ti5Si3.
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  • 75
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    Journal of Electron Microscopy Technique 14 (1990), S. 70-78 
    ISSN: 0741-0581
    Keywords: Enamel crystals ; High resolution SEM ; Field emission ; Chromium coating ; Gold/palladium decoration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Until recently high resolution TEM was the only imaging mode capable of probing the atomic lattice structure of crystals composing tooth enamel. Studies designed to determine the polyhedral shape of normal enamel crystals and initiation of carious lesions in enamel crystals were hampered and limited by interpretation of two-dimensional TEM images from thin section and freeze fracture replica specimens lacking depth of field. The newly developed SE-I signal mode for SEM (SE-I/SE-II ratio) can produce images of enamel crystals approaching beam diameter dimensions (0.7-2.0 nm), rivaling the resolution of the TEM technique and generating topographic contrasts for three dimensional imaging at very high magnification (≍1,000,000 X). Ultrathin chromium (Cr) films generate enriched high resolution SE-I contrasts of enamel crystal surfaces and when imaged using an immersion lens field emission SEM operated at high voltage (20-30 KeV) produce unsurpassed topographic contrasts. Since the grain size of Cr is below the resolution of any SEM and is ultrathin (≍1 nm), then SE-I images can provide a more accurate representation of enamel crystal structure than TEM methodologies.Our SE-I SEM observations of normal human enamel crystals reveal fractured spicules which contain angled flat surfaces delineated by a prominent 2 nm wide SE-I edge brightness contrast. Although microscopic observations often show crystals which are hexagonal in cross-section, in both SEM and TEM many other growth habits, including rectangular or irregular crystals (30-40 nm in width) which contain “notches,” are also observed. More detailed morphological studies are therefore required to determine the most likely habit planes and their relevance to the function of the enamel crystals. The granular appearing fine structural contrast imposed onto 〈100〉 lattice planes of sectioned enamel in TEM micrographs is also resolved with topographic contrasts in SE-I micrographs. These granules probably represent one or both of the enamel protein classes.
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  • 76
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    Journal of Electron Microscopy Technique 14 (1990), S. 83-84 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A miniature vise built into a copper stub is described that holds bulk, pre-frozen, hydrated biological specimens during examination under the electron beam of the scanning electron microscope.
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    Journal of Electron Microscopy Technique 14 (1990), S. 86-86 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 78
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    Journal of Electron Microscopy Technique 14 (1990), S. 87-87 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 14 (1990), S. 90-91 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 80
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    Journal of Electron Microscopy Technique 14 (1990), S. 89-89 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 81
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    Journal of Electron Microscopy Technique 14 (1990), S. 126-139 
    ISSN: 0741-0581
    Keywords: Carbohydrate ; Metabolism ; Liver ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 82
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    Journal of Electron Microscopy Technique 14 (1990), S. 152-174 
    ISSN: 0741-0581
    Keywords: Liver weight ; Cytochrome P-450 ; Smooth endoplasmic reticulum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 83
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    Journal of Electron Microscopy Technique 14 (1990), S. 283-284 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 84
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    Journal of Electron Microscopy Technique 14 (1990), S. 289-297 
    ISSN: 0741-0581
    Keywords: Lowicryl K4M and HM20 ; Macrophage ; Ultrastructure preservation ; Immunogold labeling ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Lowicryl K4M-embedded Gram-positive and Gram-negative bacteria have a tendency to separate between the cell surface and the resin. This often leads to distortion of bacteria and more especially of mycobacteria. We describe attempts made to overcome this technical problem. Different assays were made on Bacillus subtilis, Escherichia coli, and Mycobacterium avium: (1) Modification of the bacterial surface by coating of bacteria with proteinic compounds; (2) treatment of bacteria with metallic salts known to modify cell wall polysaccharides; and (3) comparison between Lowicryl K4M and HM20.Conditions have been found in which the separation of all bacterial species from the resin is abolished. The most important factor appeared to be the treatment of bacteria before dehydration, with 0.5% uranyl acetate for 30 min. The second most important factor, especially for M. avium and to a lower extent for Gram-negative bacteria, was the use of Lowicryl HM20. Pre-embedding in gelatin instead of agar improved sectioning of M. avium, but had no effects on the other bacterial species. These conditions applied to macrophages infected with Shigella dysenteriae or M. avium also gave excellent results.In addition to sectioning improvement of bacteria, uranyl acetate improved the ultrastructure of bacteria and macrophages. All organelles were more clearly delineated and, hence, more easily identified. Finally, it was shown that UA treatment did not affect immunogold labeling of a variety of antigens.
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  • 85
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    Journal of Electron Microscopy Technique 14 (1990), S. 313-323 
    ISSN: 0741-0581
    Keywords: Fab labelling ; Immunoelectron microscopy ; Immunolabelling ; Fab-gold conjugates ; Antibody-gold conjugates ; Antibody-labelling ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Fab-colloidal gold labelling in conjunction with negative staining and high-resolution electron microscopy was used for targeting single protein units in regular arrays. These were bacteriophage T4 polyheads with Fab-Au2.5, and a specific antibody binding site on the haemagglutinin polypeptide of influenza virus with Fab-Au3, Fab-Au2.5, and Fab-Au1-2. For the latter, IgG-Au3 was also used. Experimental details are summarized to provide generally applicable methods for the preparation of small gold colloids Fab-Au and of labelling.The putative mechanism of protein-gold complex formation and adsorption to preferred sites on Fab and IgG, most probably to sulphur-rich regions, is discussed. The influence of pH during complex formation was found to be of minor importance in the samples investigated. Reported experimental details and our own experiences suggest that the importance of a protein's pI relative to its optimum gold complexing pH critically depends on the nature of the protein in question rather than being of general importance for protein-gold complex stability.
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  • 86
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    Journal of Electron Microscopy Technique 14 (1990), S. 329-334 
    ISSN: 0741-0581
    Keywords: Stimulator ; Polycrystalline ; Grain growth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The microstructure and growth of ZnTe films deposited onto glass and freshly cleaved NaCl substrates are carefully studied by a TEM. Effect of different stimulator on the grain growth is also described.
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  • 87
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    Journal of Electron Microscopy Technique 14 (1990), S. 342-347 
    ISSN: 0741-0581
    Keywords: Quick-freeze deep-etch rotary replication ; Cell monolayers ; Tissue culture ; Specimen preparation ; Freeze-etch artifacts ; Temperature control ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have made several technical improvements for quick-freeze, deep-etch replication of monolayers of cells grown on, or attached to, glass coverslips. Cells studied include muscle cells of rat and Xenopus cultured on glass coverslips, and erythrocytes attached to coverslips coated with poly-L-lysine. We describe methods for identifying particular areas of cultures, e.g., clusters of acetylcholine receptors on muscle cells, by light microscopy and then relocating these areas after replication. For good preservation of structure by quick-freezing, it is necessary to ensure that the surface to be frozen is covered by a minimum depth of water (〈 10 μm). Insufficient or excess water left on the sample during freezing causes recognizable artifacts in its replica. We describe two ways to control the water table-one by improving visual control of water removal, the other by blowing excess water off the sample surface with a jet of nitrogen applied during its descent to the freezing block. Finally, we describe a new specimen holder that allows us to etch and replicate six samples at once with good thermal contact between the stage and samples.
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  • 88
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    Journal of Electron Microscopy Technique 14 (1990), S. 348-356 
    ISSN: 0741-0581
    Keywords: Cryofixation ; Cryoprotectant ; Dimethylformamide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Conditions for cryofixation and freeze-substitution crucial to the ultrastructural preservation of embryonic quail retina were improved. As freeze-substitution makes gentle dehydration and chemical fixation of tissue possible, the suitability of different cryoprotectants were tested in the preceding cryofixation. Additionally, different conditions for chemical prefixation were studied. In cryofixation, all of the “classic” cryoprotectants caused more or less severe tissue destruction. Only dimethylformamide (DMF) and-with certain reservations-dimethylsulfoxide (DMSO) yielded improved structure preservation. Perfusion fixation with a mixture of formaldehyde/glutaraldehyde (FA/GA) was superior to GA alone. In comparison to conventional fixation and dehydration methods, freeze-substitution yielded better ultrastructural preservation of the embryos with fewer artifacts.
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  • 89
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    Journal of Electron Microscopy Technique 15 (1990) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 90
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    Journal of Electron Microscopy Technique 15 (1990), S. 1-1 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 91
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    Journal of Electron Microscopy Technique 15 (1990), S. 20-33 
    ISSN: 0741-0581
    Keywords: Catecholamines ; Ultrastructure ; Synaptic terminals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The monoamines dopamine, noradrenaline, adrenaline, and serotonin as well as the diamine histamine have a widespread distribution in the central nervous system within synaptic terminals and nonsynaptic varicosities. In certain regions of the central nervous system the monoamines are contained in varicosities that have no synaptic specialization associated with them, suggesting a possible neuromodulatory role for some of the monoamines. The majority of monoamine labelled structures are synaptic terminals which are characterized by the presence of small, clear vesicles (40-60 nm) and large, granular vesicles (70-120 nm) within the terminal. A third population of vesicles - small, granular vesicles - which are visible only after histochemical staining, are probably the equivalent of the small, clear vesicles present after either autoradiographic or immunohistochemical labelling. Most monoamine containing terminals contact dendrites and dendritic spines and, less frequently, neuronal somata and other axons. Both asymmetrical and symmetrical membrane specializations are associated with monoaminergic terminals; however, asymmetrical contacts are the most frequent type found. These ultrastructural results indicate that monoamine containing terminals and varicosities in general share many common morphological features, but still have diverse functions.
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  • 92
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    Journal of Electron Microscopy Technique 15 (1990), S. 49-66 
    ISSN: 0741-0581
    Keywords: Amino acid neurotransmitters ; Spinal cord ; Spinal trigeminal nucleus ; Cochlear nuclei ; Cerebellum ; Hippocampus ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The ultrastructural localization of putative excitatory (glutamate, aspartate) and inhibitory (taurine, glycine) amino acid neurotransmitters is described in several selected rat brain regions. In general, axon terminal profiles immunoreactive for excitatory amino acids formed asymmetric synapses with non-immunoreactive small diameter dendritic profiles or dendritic spines. In the cerebellum, both mossy fiber terminals and parallel fiber terminals were immunoreactive for glutamate and aspartate. In the hippocampus, mossy fiber terminals within the stratum lucidum of the CA3 region were immunoreactive for glutamate. Localization of glutamate and aspartate to cerebellar parallel and mossy fibers, as well as the identification of glutamate in hippocampal mossy fibers, is consistent with the excitatory nature of these fibers as described in previous physiological studies. Glutamate-like immunoreactive terminals were also identified in subnucleus caudalis of the spinal trigeminal nucleus and in the dorsal horn of the spinal cord.Immunoreactive axon terminals for two putative inhibitory neurotransmitters, glycine and taurine, displayed a greater number of morphological variations in synaptic structure. In the cerebellum, taurine-like immunoreactivity was present in both basket cell axon terminals which formed symmetric synapses with Purkinje cell neurons, and in a few mossy fiber terminals which formed asymmetric synapses with dendritic spines. In the area dentata of the hippocampus, taurine-like immunoreactive profiles formed asymmetric synapses with dendritic elements. Glycine-like immunoreactive terminals formed symmetric synapses with cell perikarya in both the ventral horn of the spinal cord and in the cochlear nuclei, and on axon terminals in the spinal trigeminal and cochlear nuclei. In contrast, some glycine-like immunoreactive terminals formed asymmetric synapses with distal dendritic profiles in the spinal cord and spinal trigeminal nucleus. The localization of taurine to cerebellar basket cell axons and glycine to axon terminals that synapse on ventral horn motor neuron perikarya is consistent with the hypothesis that these amino acids are functioning as inhibitory neurotransmitters at these synapses. Taurine localization to cerebellar mossy fibers and to fibers in the molecular layer of the dentate gyrus may be more consistent with a proposed neuromodulator role of taurine.
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  • 93
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    Journal of Electron Microscopy Technique 15 (1990), S. 301-315 
    ISSN: 0741-0581
    Keywords: Inner/Outer spiral sulcus ; Lateral intercellular spaces ; Mitochondria ; Endoplas-mic reticulum ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The intercalated body is a newly discovered organelle in the inner and outer spiral sulcus cells of the mouse organ of Corti. The organelle was found in the cochleas of 14-day and older intact mice and in organs in culture of corresponding ages. The organelle consists of a stack of interconnected cisternae of endoplasmic reticulum and of membrane bound rodlets that are intercalated between, and run parallel to, the cisternae. The cisternal membranes are predominantly smooth, but some may display ribosomes. Most rodlets are from 1 to 2 μm long, about 0.1 μm wide, and contain electron dense material. Mitochondria are commonly associated with or incorporated into the organelle. Some electron micrographs suggest that the rodlets may originate from modified mitochondria. It is our impression that the formation of the organelle begins with the apposition of cisternae and mitochondria. Cisternal-associated mitochondria appear to constrict, elongate, and lose their inner membranes. In both the intact animal and in culture, the cells of the inner and outer spiral sulci display microvilli, apical junctional complexes, lateral intercellular spaces containing interdigitating cell processes, and appear to be involved in fluid formation. Moreover, in culture, the cells of inner and outer spiral sulci as well as some cells proliferating in the outgrowth zone participate in fluid formation, producing large fluid pockets. All these cells commonly contain intercalated bodies. It is possible that in the intact animal, as in culture, intercalated bodies may play a role in fluid regulation in the immediate vicinity of the hair cells.
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    Journal of Electron Microscopy Technique 15 (1990), S. 377-382 
    ISSN: 0741-0581
    Keywords: Vickers indentations ; Magnesium oxide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Single crystal MgO specimens having low load Vickers indentations were thinned in an ion milling machine employing a single ion gun, and their characteristics were investigated with optical microscopy and high voltage electron microscopy (HVEM). It was found that the state of cleanliness of the specimen chamber of the ion milling machine had a very marked influence on the quality of the thinned specimens. If the specimen chamber was not well cleaned before ion milling a fresh specimen, the latter tended to show amorphisation due to the deposition on the specimen of the debris left in the chamber from the previously ion-milled specimens. Such observations were made from MgO specimens ion milled in several different types of commercial ion milling machine employing a single gun. It is proposed that to obtain good-quality ion milled TEM specimens, it is important to clean the specimen chamber thoroughly prior to milling.
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    Journal of Electron Microscopy Technique 15 (1990), S. 414-415 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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    Journal of Electron Microscopy Technique 15 (1990), S. 316-317 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Natural Sciences in General
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    Journal of Electron Microscopy Technique 15 (1990), S. 318-319 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Electron Microscopy Technique 15 (1990), S. 321-321 
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 99
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    Journal of Electron Microscopy Technique 15 (1990), S. 322-331 
    ISSN: 0741-0581
    Keywords: Axon transport ; WGA-HRP ; Axonal degeneration ; Autoradiography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: In order to analyze connections between neurons in the vetebrate central nervous system, methods have been developed to label a given population of axons of known origin so that they can be differentiated from other, non-labeled structures. Three such methods are reviewed here: experimentally induced orthograde (Wallerian) degeneration, axon transport of radioactive proteins demonstrated by autoradiography, and axon transport of macromolecules that can be reacted histochemically to yield a visible reaction product. Each of the methods has particular strengths and weaknesses. Degeneration methods may differentiate between different functional classes of axons which have different fiber diameters. However, degeneration distorts the morphology of axon terminals, making them more difficult to interpret, and degenerating terminals may be removed rapidly by phagocytosis. Autoradiography of radioactive terminals preserves normal fine structure, but the necessary exposure times extend the method by weeks or months, and care must be exercised to distinguish labeled axons from other structures exhibiting background or transneuronal radioactivity. Histochemical methods, such as those used to demonstrate horseradish peroxidase conjugated to wheat germ lectin (WGA-HRP), are sensitive and rapid, but the injection site must be carefully characterized, and the presence of transneuronal label may make interpretation of the results difficult.Experimental methods of axonal labeling have been invaluable in studying neuronal networks. Each of the methods described here may be of particular value, given the nature of the system to be analyzed.
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    Journal of Electron Microscopy Technique 15 (1990), S. 332-351 
    ISSN: 0741-0581
    Keywords: Identified neurones ; Synaptic contacts ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: For more than a century the Golgi method has been providing structural information about the organization of neuronal networks. Recent developments allow the extension of the method to the electron microscopic analysis of the afferent and efferent synaptic connections of identified, Golgi-impregnated neurones. The introduction of degeneration, autoradiographic, enzyme histochemical, and immunocytochemical methods for the characterization of Golgi-impregnated neurones and their pre-and postsynaptic partners makes it possible to establish the origin and also the chemical composition of pre-and postsynaptic elements. Furthermore, for a direct correlation of structure and function the synaptic interconnections between physiologically characterized, intracellularly HRP-filled neurones and Golgi-impregnated cells can be studied. It is thought that most of the neuronal communication takes place at the synaptic junction. In the enterprise of unravelling the circuits underlying the synaptic interactions, the Golgi technique continues to be a powerful tool of analysis.
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