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  • 1
    ISSN: 1059-910X
    Keywords: Rat ; Albumin ; Fibrinogen ; Immunohistochemistry ; Electromagnetic fields ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Biological effects of electromagnetic fields (EMF) on the blood-brain barrier (BBB) can be studied in sensitive and specific models. In a previous investigation of the permeability of the blood-brain barrier after exposure to the various EMF-components of proton magnetic resonance imaging (MRI), we found that the exposure to MRI induced leakage of Evans Blue labeled proteins normally not passing the BBB of rats [Salford et al. (1992), in: Resonance Phenomena in Biology, Oxford University Press, pp. 87-91].In the present investigation we exposed male and female Fischer 344 rats in a transverse electromagnetic transmission line chamber to microwaves of 915 MHz as continuous wave (CW) and pulse-modulated with repetition rates of 8, 16, 50, and 200 s-1. The specific energy absorption rate (SAR) varied between 0.016 and 5 W/kg.The rats were not anesthetized during the 2-hour exposure. All animals were sacrificed by perfusion-fixation of the brains under chloral hydrate anesthesia about 1 hour after the exposure. The brains were perfused with saline for 3-4 minutes, and thereafter fixed in 4% formaldehyde for 5-6 minutes. Central coronal sections of the brains were dehydrated and embedded in paraffin and sectioned at 5 μm. Albumin and fibrinogen were demonstrated immunohistochemically.The results show albumin leakage in 5 of 62 of the controls and in 56 of 184 of the animals exposed to 915 MHz microwaves. Continuous wave resulted in 14 positive findings of 35, which differ significantly from the controls (P = 0.002). With pulsed 915 MHz microwaves with repetition rates of 200, 50, 16, and 8 s-1, 42 of 149 were positive, which is highly significant at the P = 0.001 level. This reveals that both CW and pulsed 915 MHz microwaves have the potential to open up the BBB for albumin passage. However, there is no significant difference between continuous and pulsed 915 MHz microwaves in this respect.The frequency of occurrence of extravasates (26%) was found to be independent of SAR for SAR 〈 2.5 W/kg, but rose significantly for the higher SAR values (to 43%).The question of whether the opening of the blood-brain barrier constitutes a health hazard demands further investigation. © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-6903
    Keywords: Diabetes ; protein ; microvessel ; blood-brain-barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To determine the effect of diabetes mellitus on cerebral microvessel protein composition, post translational modification of proteins with glucose and malondialdehyde (MDA) was determined and the abundant protein species found in cerebral microvessels isolated from control and streptozotocin-induced diabetic rats were studied. Two dimensional gel electrophoresis and computer assisted densitometry revealed that only one out of 25 quantitated proteins was significantly altered in diabetic rats after 5 weeks of uncontrolled hyperglycemia. The level of glycosylation of cerebral microvessel protein mixture was significantly increased in diabetic rats compared to control rats (168.8±25 vs 109.5±4.8 nmol/mg) (p〈0.05). Western blot analysis of cerebral microvessel proteins from diabetic rats using a specific antibody against MDA-modified proteins revealed three protein spots with molecular weights of approximately 60,000 Kd. These were shown not to be contaminants from cerebral tissue or plasma proteins modified with MDA. It is concluded that short duration of streptozotocin-induced diabetes mellitus in rats is associated with some qualitative changes in protein composition of cerebral microvessels. These changes may contribute to the diabetes-related alterations in the blood-brain barrier.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    AI & society 6 (1992), S. 62-77 
    ISSN: 1435-5655
    Keywords: Human-computer interface ; Information transfer ; Communication ; Linguistics ; Speech acts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract When people speak about “communication barriers”, what they usually think about are such things as the limitations set by human nature itself, or the constraints that are inherent in the tools we use for communicating. As an example of the first, consider the limited range of the naked human voice; for the second, we may think of the limitations imposed by such primitive communicative devices as the bonfire, the heliograph, or an old-fashioned megaphone. Our contribution draws attention to the fact that, despite enormous advances on the technological side of human communication (such as demonstrated by the existence and use of computers as communication devices), there still are some barriers to be removed as far as the human side is concerned. We call these barriers the “stumble-blocks of the mind”. Their existence is demonstrated by the study of two case stories, which show that understanding the communicative implications of computerizing information is more important than increased emphasis on ever fancier and more expensive hardware products. The next question has to do with the reasons for these “stumbling blocks” to occur. Current communicative and linguistic theoretical findings are used in an effort to explain and solve the communicative dilemmas that are encountered in the organization of our communication, among others in the area of human-computer interface. In particular, the notion of “privacy” in speech acting is suggested as an overlooked aspect, and the notion of “information transfer” is replaced by that of “creating mental activity”. Finally, some conclusions are drawn, and a number of practical applications are offered.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    AI & society 6 (1992), S. 180-185 
    ISSN: 1435-5655
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Conclusion The conclusion to be drawn from the preceding observations and theorizing should be that we must be very much aware of what has been called “technological functionalism” (Pieper, 1986:11). While functionalism as such is not bad, the moment it succumbs to mere structural technicality, the functions stop functioning: forced “adaptivity” takes the place of “adaptable” interaction. That this problem is not due to a primordial blame, to be attached to the computer, becomes clear when one compares the computerized environment to other surroundings, such as, for example, the psychiatric treatment. In the psychiatric interview, as Davis (1986, 1988) has shown, the interest of the therapist is often limited to establishing a “contract” for treatment: for the therapist to function properly, there must be a therapy-defined (or therapy-definable) problem for him/her to attack, using the skills and experiences of the profession of which he/she is a representative and for which he/she has been properly trained. This function, however, may not coincide with the patient's needs: it may well be the case that the problem which originally caused the patient to approach the therapist for treatment, in the end turns out not to be the problem that both agree on as the objective of the therapeutic treatment. “Re-formulating” the patients' problem in terms suitable to the available resources and techniques is thus typically a case of adapting the human to the system: again, we're faced with technological functionalism in the shape of what has been called “forced adaptivity” (see Mey, 1986). We need to think seriously about the way we handle our computerized structures and their functions, and in particular about the design of supportive systems such as large databases, computer conferencing, or even simple electronic mail services. While adaptivity always is a case of manipulation, by which humans are tooled to the needs and strictures of the computer, adaptability, by contrast, allows such manipulation only inasmuch as those needs and strictures reflect, and are imposed by, the users' needs. The blind, mechanical force that makes us adapt ourselves to the machine should be replaced by the enlightened, humanizing force of the adaptable computer.
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