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  • Electronic Resource  (3)
  • 2000-2004
  • 1985-1989  (3)
  • 1950-1954
  • Cerebral blood flow  (2)
  • Anxiety  (1)
Material
  • Electronic Resource  (3)
Years
  • 2000-2004
  • 1985-1989  (3)
  • 1950-1954
Year
  • 1
    ISSN: 1432-1920
    Keywords: Cerebral blood flow ; Computed tomography ; Partition coefficients ; Xenon contrast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Methods are described for non-invasive, computer-assisted serial scanning throghout the human brain during eight minutes of inhalation of 27%–30% Xenon gas in order to measure local cerebral blood flow (LCBF). Optimized Xenonenhanced computed tomography (XeCT) was achieved by 5-second scanning at one-minute intervals utilizing a state-of-the-art CT scanner and rapid delivery of Xenon gas via a face mask. Values for local brain-blood partition coefficients (Lλ) measured in vivo were utilized to calculate LCBF values. Previous methods assumed Lλ values to be normal, introducing the risk of systematic errors, because Lλ values differ throughout normal brain and may be altered by disease. Color-coded maps of Lλ and LCBF values were formatted directly onto CT images for exact correlation of function with anatomic and pathologic observations (spatial resolution: 26.5 cubic mm). Results were compared among eight normal volunteers, aged between 50 and 88 years. Mean cortical gray matter blood flow was 46.3±7.7, for subcortical gray matter was 50.3±13.2 and for white matter was 18.8±3.2. Modern CT scanners provide stability, improved signal to noise ratio and minimal radiation scatter. Combining these advantages with rapid Xenon saturation of the blood provides correlations of Lλ and LCBF with images of normal and abnormal brain in a safe, useful and non-invasive manner.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1920
    Keywords: Cerebral blood flow ; Partition coefficient ; Computed tomography ; Stable xenon ; Aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Results of measurements of LCBF and Lλ values utilizing optimal CT-CBF methods under resting conditions are reported among thirty-two neurologically normal volunteers aged between 20 and 88 years. Measurements were made during inhalation of 26–30% stable xenon gas for 8 min and serial scanning utilizing a state-of the-art CT scanner with both eyes closed and ears unplugged. LCBF values for cortical gray matter were lowest in occipital cortex and highest in frontal cortex. Gray matter flow values were also high in subcortical structures with highest values measured in the thalamus. For white matter, highest flow values were measured in the internal capsule. Changes in LCBF and Lλ values were analyzed with respect to advancing age. Significant age-related declines in LCBF values were observed in occipital cortex and frontal white matter. Significant age-related increases in Lλ values were measured in frontal and temporal cortex, caudate nucleus and thalamus. Possible explanations are offered for these age-related increases in Lλ values for gray matter, such as accumulation of lipofuscin in neurons and relative compacting of gray matter with advancing age. The latter increases the numbers of nerve cells sampled per volume of gray matter measured.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Benzodiazepines ; Triazolopyridazines ; Corticosterone ; Anxiety ; Stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fifteen minute exposure to a novel environment plus 120 dB sound stimulation produced a three-fold increase in serum corticosterone concentrations in rats. A low dose of intraperitoneally (IP) administered chlordiazepoxide (CDP) (5 mg/kg) attenuated this response, whereas a higher dose (20 mg/kg) elevated corticosterone concentrations in rats not subjected to sound stress. Parallel results were obtained after intracerebroventricular (ICV) drug administration, with a low dose of CDP (5 μg) reducing the sound stress response and higher doses (25 and 50 μg) increasing corticosterone concentrations in unstressed animals. Thus, despite the presence of benzodiazepine (BDZ) receptors at every level of the hypothalamic-pituitary-adrenocortical axis, it appears that BDZs alter the activity of this system via an interaction with BDZ receptors in brain. CL 218,872 (2.5–20 mg/kg), a novel non-BDZ anxiolytic compound, did not attenuate the corticosterone elevation produced by sound stimulation, and also failed to alter baseline corticosterone concentrations in unstressed animals. The fact that CL 218,872 is a selective agonist for brain Type I BDZ receptors suggests that BDZs are not influencing corticosterone secretion through an interaction with this BDZ receptor subtype. Furthermore, these results indicate that stress (as measured by pituitary-adrenocortical activation) can be dissociated from anxiety (as measured by conflict paradigms), thus challenging the validity of the corticosteroid stress test as a screening procedure for anxiolytic activity.
    Type of Medium: Electronic Resource
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