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  • 1
    Electronic Resource
    Electronic Resource
    In Vivo Development of Brain Phosphocreatine in Normal and Creatine-Treated Rabbit Pups (1999)
    Oxford UK : Blackwell Science Ltd.
    Journal of neurochemistry 73 (1999), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract : To study the effects of creatine (Cr) on brain energy metabolism and on hypoxia-induced seizures, 5-to 30-day-old rabbit pups were given subcutaneous Cr (3 g/kg) for 3 days before exposure to 4% O2 for 8 min. In saline-treated controls, hypoxic seizures were most frequent at 15 days (80% of pups) and 20 days (60%) of age. Seizures were prevented at 15 days and reduced 60% at 20 days in Cr-treated pups. In surface coil-localized brain 31P nuclear magnetic resonance spectra, with signal from both cerebral gray (GM) and white (WM) matter, the phosphocreatine (PCr)/nucleoside triphosphate (NTP) ratio doubled between 5 and 30 days of age in controls. In all Cr-injected pups, brain PCr/NTP increased to values seen in 30-day-old controls. When spectra were acquired in predominantly GM and WM slices in vivo, the PCr/NTP ratio was very low in GM at 5 days but reached adult levels by 15 days in controls. In WM, the ratio increased steadily from 5 to 30 days of age. In Cr-injected pups, PCr/NTP increased to mature levels in WM and in GM at all ages. In conclusion, hypoxic seizures occur midway in the time course of brain PCr/NTP increase in rabbit pups as previously described in rat pups. In both altricial pups, systemic Cr increases brain PCr/NTP ratio and prevents hypoxic seizures. These results suggest that mature levels of PCr and/or Cr in brain limit EEG activation either directly or indirectly by preventing hypoxic metabolic changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1999.0732477.x
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  • 2
    Electronic Resource
    Electronic Resource
    Gadolinium-enhanced MR imaging demonstrates abduction-caused hip ischemia and its reversal in piglets (1995)
    Springer
    Pediatric radiology 25 (1995), S. 578-587 
    Details
    ISSN: 1432-1998
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose To determine whether gadoliniumenhanced MR imaging can detect early reversible ischemia of the capital femoral epiphysis and physis induced by hip hyperabduction in piglets. Materials and methods Thirteen 1-to 3-week-old piglets were placed in maximal abduction of both hips and studied with dynamic gadolinium-enhanced MR imaging 1–6 h later to assess ischemia of the 26 femoral heads. They were then allowed to ambulate freely for 1 or 7 days, and reimaged in neutral position to assess reperfusion. Enhancement was evaluated on MR images and compared with histologic findings. Results Ischemia after hyperabduction developed in all 26 cartilaginous epiphyses and in 85% of the physes. The most frequent abnormality was a sharply marginated nonenhancing area in the anterior part of the femoral head. A smaller area of ischemia developed in the posterior part of the femoral head, adjacent to the acetabular rim. The secondary center of ossification was ischemic in 56% of the hips after 1 h of abduction and in all hips after 4 or 6 h (p=0.02). The overall severity of ischemia was greater with increasing abduction time (p〈0.001) and increasing degree of abduction (p〈0.01). There was partial reperfusion in 83% of the hips after 1 day of ambulation and complete reperfusion in all 26 hips (100%) after 1 week. Conclusion Enhanced MRI detects early ischemia of the epiphyseal and physeal cartilage and the epiphyseal marrow. In piglets, ischemia due to hyperabduction is reversible if corrected within 6 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02011824
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic Resonance Imaging Measurements of Bone Density and Cross-Sectional Geometry (2000)
    Springer
    Calcified tissue international 66 (2000), S. 74-78 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Magnetic resonance imaging — Bone density — Bone cross-sectional geometry.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Magnetic resonance imaging (MRI) is commonly used in the assessment of the musculoskeletal system and associated pathology. The ability of MRI to measure the signals from water and lipid protons enables quantitative measurements of bone porosity. The goal of this investigation was to demonstrate that the density and cross-sectional geometry of whole bones can be noninvasively measured using MRI. Ten trabecular specimens cored from whale vertebrae were used to compare apparent bone density measured directly, and using a quantitative MRI algorithm. Bone density and several cross-sectional geometric properties were also measured using MRI in the distal tibia of 14 volunteers. The MRI measurements were compared with measurements made using quantitative-computed tomography (QCT). A proton density sequence was used for all MRI studies. A porosity phantom was included in the MRI examinations and used to convert the MRI signal intensity to bone volume fraction. Bone density and cross-sectional bone geometry were calculated from the bone volume fractions by assuming constant tissue properties. The apparent density of trabecular bone cores measured directly and using quantitative MRI were linearly related (r2= 0.959; P 〈 0.01). A strong linear relation also existed between MRI and QCT measurements of ash density (r2= 0.923; P 〈 0.01) and cross-sectional geometric properties (r2= 0.976–0.992; P 〈 0.01). MRI data can be used to measure bone density and cross-sectional geometry of whole bones if a proton density sequence is used to homogenize differences in marrow composition and a porosity phatom is used for slice-specific volume fraction calibration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002230050015
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  • 4
    Electronic Resource
    Electronic Resource
    14N nuclear quadrupole resonance in substituted isatin compounds (1985)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 23 (1985), S. 801-803 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 14N nuclear quadrupole resonances have been found for eight substituted isatin compounds. Variations in the electric field gradient (EFG) and asymmetry parameter, η, have been attributed to inductive rearrangement of the electron distribution at the nitrogen site. A correlation between the inductive Taft parameter, σ*, of the substituent and the charge density difference between the hybridized nitrogen bonding orbitals, σNH—σNc, has been established. Implications of the results with respect to the available biological data on substituted isatins are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260231003
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