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  • 1
    Electronic Resource
    Electronic Resource
    Scanning electron microscopy of cardiac endothelium of the dogSupported by a grant from the United States Public Health Service, NS 09363 from the Institute of Neurological Diseases and Stroke. (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 142 (1975), S. 137-157 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Tissue obtained from young dogs was fixed in buffered aldehydes by vascular perfusion or direct immersion. Selected hearts were maintained in modified mammalian Ringer's solution for three to five minutes prior to fixation. The chambers of the heart and related valves were exposed by dissection and prepared by routine techniques for observation by scanning electron microscopy (SEM). Subsequent to SEM studies, selected specimens were embedded in Epon 812 and sectioned for transmission electron microscopy (TEM).The cardiac endothelium, when fixed immediately in buffered aldehydes, presents an essentially invariable surface throughout the interior of the heart. The predominant nuclear bulges and attenuated peripheral plasmalemma are consistently smooth, with occasional marginal ruffles, scattered microvilli and small blebs. Apart from the higher population of nuclear bulges on valvular surfaces, local variations in SEM of endocardium occur in response to the various stages of systole and diastole encountered. These physiological changes do not produce microappendages.Immersion for three to five minutes in (Chenoweth's) Ringer's solution, prior to fixation, produces a substantial population of microappendages. The cellular surface acquires a swirled appearance erupting in microvilli, blebs and ruffles. These exhibit considerable pleomorphism.There is great lability of the endocardial surface in response to a classic “holding solution” widely used in preparatory techniques. In preparing soft tissues for SEM caution must be used if physiological “holding solutions” are used prior to fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001420202
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  • 2
    Electronic Resource
    Electronic Resource
    Acute effects of 50 Hz magnetic field exposure on human visual task and cardiovascular performance (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 131-137 
    Details
    ISSN: 0197-8462
    Keywords: statistical power ; duration discrimination ; blood pressure ; heart rate ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: One hundred subjects, males and females with ages ranging between 18 and 48 years, were studied under both field-exposed and sham-exposed conditions. A 50 Hz, 100 μT magnetic field (MF) was used. To examine the effect of field exposure on performance, a two-alternative, forced-choice, duration-discrimination task with three levels of difficulty was used. The subject's task was to decide which of two sequentially presented light flashes had the longer duration. The standard duration was 50 ms, and the alternative durations were 65, 100, or 125 ms. Both reaction time and percentage of correct responses were recorded for each subject. MF and sham exposure were for 9 min each. Blood pressure and heart rate were also measured before and following MF exposure and sham-exposure trials. The study was performed double blind, with the exposure order counterbalanced. Compared to sham exposure, MF exposure significantly decreased reaction time on the hardest level of the performance task. MF exposure did not reliably affect percentage correct or cardiovascular performance. It was demonstrated that a relatively high level of statistical power was the basis for the observed MF effect, and the need to pay closer attention to power levels in future research is discussed. © 1996 Wiley-Liss, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of the Structure of a Natural Alternating d(TA)n Sequence in Yeast Chromatin (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 13 (1997), S. 313-326 
    Details
    ISSN: 0749-503X
    Keywords: TA tract ; Saccharomyces cerevisiae ; chromatin ; cruciform ; destabilized site ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We address here the question of the in vivo structure of a natural alternating d(TA)n sequence found at the 3′ region of the Saccharomyces cerevisiae FBP1 gene. This sequence consists of 13 TA pairs interrupted by a TT dinucleotide in the middle of the tract. Previous experiments with cruciform-specific nucleases S1 and Endonuclease VII demonstrated the presence in vitro of a cruciform in this region. We also showed this region to be part of a nuclease hypersensitive site flanked by nucleosomes in yeast chromatin. Here we demonstrate, by means of S1 in vivo footprinting, that in yeast plasmids also adopts in vivo a non B-DNA structure which is not a cruciform. A theoretical analysis of this region shows that it contains a site susceptible to superhelical stress duplex destabilization. The locations and conditions under which alternative structures form in the wild-type sequence and in deletion mutants agree with these theoretical predictions, suggesting that some kind of denaturation is the alternative structure adopted by the sequence in vivo. This suggests that negative superhelical stress sufficient for local denaturation exists in nucleosomal DNA. We also demonstrate by micrococcal nuclease digestions that the deletion of the alternating d(TA)n sequence modifies the chromatin hypersensitive site but does not affect nucleosome positioning. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Do ELF magnetic fields affect human reaction time? (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 16 (1995), S. 317-323 
    Details
    ISSN: 0197-8462
    Keywords: human performance ; statistical power ; parametric resonance theory ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Two double-blind studies were run in an attempt to confirm the finding that a 0.2 Hz magnetic field affects simple reaction time (RT) in humans, whereas a 0.1 Hz field does not. In the first experiment, 12 volunteer subjects were exposed to a continuous 0.2 Hz, 0.1 Hz, or sham field in a fully counter-balanced, within-subjects design. Subjects were run singly for one condition each day over 3 consecutive days with a field strength of 1.1 mT and a daily exposure duration of 5 min. Neither magnetic field had any effect on RT at any time during the exposure. One condition of a second study, using a new group of 24 volunteer subjects, also failed to find any field effects at 0.2 Hz. Additionally, the second study failed to show any effects when the frequency, flux density, and field orientation were set according to parametric resonance theory. It is suggested that, although ELF magnetic field effects on human behaviour may be elusive, future research can improve detection rates by paying greater attention to reducing error variance and increasing statistical power. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250160508
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  • 5
    Electronic Resource
    Electronic Resource
    Human performance and physiology: A statistical power analysis of ELF electromagnetic field research (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 274-278 
    Details
    ISSN: 0197-8462
    Keywords: power survey ; sample size ; effect size ; alpha level ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Research examining the effects of electromagnetic fields (EMFs) on human performance and physiology has produced inconsistent results; this might be attributable to low statistical power. Statistical power refers to the probability of obtaining a statistically significant result, given the fact that a real effect exists. The results of a survey of published investigations of the effects of EMFs on human performance and physiology show that statistical power levels are very low, ranging from a mean of.08 for small effect sizes to .46 for large effect sizes. Implications of these findings for the interpretation of results are discussed along with suggestions for increasing statistical power. © 1996 Wiley-Liss, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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