Experimental neurology
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Experimental neurology · Jun 1985
Posture-correlated responses to vestibular polarization in vermal versus intermediate posterior cerebellar cortex.
Cerebellar lesion experiments have led to the concept that the medial longitudinal zone controls postural tone while the intermediate zone controls discrete movement. This study is a test of the hypothesis that, of the two zones, the medial zone is more closely linked to the resting discharge of vestibular afferent fibers, a prime source of neural tonus underlying the tonus of posture. ⋯ In the medial and the intermediate cerebellar cortices of the posterior lobe, the proportion of step-like responses was similar, in contradiction to the hypothesis. This suggests that the cerebellar computations for controlling both postural tonus and discrete movements require information about vestibular tonus in terms of simple spike activity.
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Experimental neurology · Nov 1984
Retrograde and transganglionic degeneration of sensory neurons after a peripheral nerve lesion at birth.
The sciatic nerve of newborn rats (less than or equal to 16 h old) was crushed with a watchmaker forceps. During the first 4 weeks after the injury, examination of ipsilateral L4 through L6 dorsal root ganglia, their dorsal nerve roots, and the dorsal funiculus revealed the presence of degenerating myelin and axons. Chromatolysis was not observed. ⋯ A total loss of about 60% of sensory neurons was found in the L4 through L6 spinal ganglia. About 58 and 64% of the myelinated axons were lost in L4 and L5 dorsal roots, respectively. The remaining perikarya and dorsal root axons were hypoplastic.
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Experimental neurology · Jul 1984
Synaptic density in chronic animals with experimental neurofibrillary changes.
Synaptic density was quantitated in the cerebral cortex and subiculum of rabbits with experimental neurofibrillary changes. Animals were subjected to subcutaneous injection of aluminum tartrate for 90 days, and synapses stained with ethanolic phosphotungstic acid were analyzed in animals killed 100, 200, or 300 days postinjection with aluminum tartrate. ⋯ In contrast, animals killed 100 days postinjection revealed the same synaptic density as their control. The data suggest that the synaptic depopulation associated with experimental neurofibrillary changes is a gradual process, and such changes are demonstrable only long after the initial appearance of neurofibrillary changes.
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Experimental neurology · Apr 1984
Paroxysmal discharges during paradoxical sleep anticipating the occurrence of focal motor seizures in cats.
Sleep recordings were made some days before the occurrence of focal motor seizures in cats injected with alumina cream in the motor cortex. The wakefulness EEG was completely normal. ⋯ They were only electrographic and never produced arousal of the animals. The precipitating role of phasic paradoxical sleep on focal motor seizures is proposed.
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Experimental neurology · Oct 1983
Spinal fluid formation and glucose influx in normal and experimental hydrocephalic rats.
Cerebrospinal fluid (CSF) turnover and glucose influx were measured in normal and kaolin-induced hydrocephalic rats. The CSF formation rate of normal rats was 2.8 microliter/min and after intracisternal kaolin it was reduced to 1.8 microliter/min. The CSF-serum glucose concentration ratio of normal rats was 0.57 and was reduced to 0.47 in hydrocephalic rats. ⋯ The fraction of serum glucose transported from blood to CSF in normal and hydrocephalic rats decreased as serum glucose increased above 200 mg/dl. At all serum glucose concentrations studied, the influx of glucose in normal rats was always 2.6 times greater than that in hydrocephalic rats. These results suggest that because the glucose transport mechanism of both groups of rats is only quantitatively different, the number of sites available for glucose transport from blood to CSF is reduced in hydrocephalic rats.