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  • 1
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 106-108 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 46 (1990), S. 1097-1106 
    ISSN: 1420-9071
    Keywords: Genetic code ; directional mutation pressure ; GC-content ; unassigned codon ; tRNA ; codon capture ; codon usage ; Mycoplasma ; mitochondria ; Micrococcus ; methanogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The prokaryotic genetic code has been influenced by directional mutation pressure (GC/AT pressure) that has been exerted on the entire genome. This pressure affects the synonymous codon choice, the amino acid composition of proteins and tRNA anticodons. Unassigned codons would have been produced in bacteria with extremely high GC or AT genomes by deleting certain codons and the corresponding tRNAs. A high AT pressure together with genomic economization led to a change in assignment of the UGA codon, from stop to tryptophan, inMycoplasma.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 79 (1990), S. 357-364 
    ISSN: 1432-1106
    Keywords: Movement preparation ; Ankle dorsiflexion ; Ankle plantar flexion ; H-reflex ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Changes in excitability of the spinal motoneuron pool during the foreperiod, which was fixed at 0.8 s, in simple and choice reaction time experiments using ankle dorsiflexion and plantar flexion were studied in fourteen healthy normal subjects by combining the visually guided tracking and H-reflex testing methods. Almost all cases showed a significant facilitation in the soleus H-reflex within the time interval between 100 and 300 ms after a warning signal (Phase I), irrespective of movement direction and task modality. The pretibial H-reflex was also facilitated. On the other hand, variable effects were noted in the later half of the foreperiod, particularly within the 200 ms prior to the response signal (Phase II). Using a simple reaction task with dorsiflexion, six cases showed no changes in the soleus H-reflex, while four others showed statistically significant inhibitory changes and the remaining four showed facilitation. The inhibition and facilitation were often accompanied with very weak and unintended EMG activities in the pretibial and Sol muscles respectively. A similar finding was obtained in the simple plantar flexion task and the choice reaction task with dorsiflexion or plantar flexion. We suggest that the facilitation at Phase I represents a perceptual orienting response to a warning signal and the effects seen in Phase II represent the difference in the waiting attitude of each subject anticipating initiation of the coming task, or the preparatory “set” which primed the spinal motor structure in a biased position.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 32 (1990), S. 237-240 
    ISSN: 1432-1920
    Keywords: Pachygyria ; Vascular anomaly ; Perfusion failure ; Magnetic resonance imaging ; Neuropathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of focal pachygyria with an unusual vascular anomaly is reported. Preoperative magnetic resonance imaging demonstrated few and broad gyri, and an abnormally thickened cortex of the right frontal lobe. In addition, T2-weighted imaging showed a high intensity lesion beneath the thickened cortex. In the pachygyric cortex, the peripheral portions of the arteries were tortuous and irregularly dilated, and prominent deep medullary veins were found draining into the subependymal veins. Histological examination revealed a decreased number of neurons with no tendency towards lamination, and degenerative changes with gliosis in the white matter. These findings suggest that the etiology of this anomaly may be gradual perfusion failure restricted to the territory of the anomalous vessels through the period of neuronal migration to the post-migratory, perinatal stage.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 32 (1990), S. 146-150 
    ISSN: 1432-1920
    Keywords: CT ; Glioblastoma ; Seeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Computed tomography (CT) findings in eleven patients with symptomatic cerebrospinal fluid (CSF) dissemination from cerebral glioblastoma were analyzed and, in seven cases subsequently autopsied, they were compared with histological observations. Each patient had multiple CT abnormalities including periventricular enhancement (5/11), subarachnoid enhancement (10/11) and progressive hydrocephalus (7/9) by cranial CT, and small filling defects with or without block (5/5) by CT myelography. The areas that showed periventricular or subarachnoid enhancement on CT were confirmed to have macroscopically detectable seeding at autopsy. On the other hand, microscopic deposits were more widely distributed than the enhancement suggested, and were hardly visualized on CT. In association with subarachnoid seeding, we found low-density lesions on CT which had resulted from ischemia or reinvasion of adjacent structures by disseminated glioblastoma and resulting parenchymal edema. By cranial CT, subarachnoid enhancement seems to be a very reliable sign of CSF seeding, whereas periventricular enhancement due to CSF metastases should be carefully distinguished from that due to periventricular tumor infiltration. CT myelography is capable of revealing minute metastatic spinal deposits and may be helpful for ruling out spinal seeding as well as its precise evaluation.
    Type of Medium: Electronic Resource
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