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Biomedical subjects

L T Happel

Publications and source records attributed to L T Happel.

4 recordsLinked to original sources
PubMed1992

Enhancement of hippocampal excitatory synaptic transmission by platelet-activating factor.

The biologically active lipid platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine; PAF) is a mediator of inflammatory and immune responses, and it accumulates in the brain during convulsions or ischemia. We have examined whether PAF may play a second messenger role in the central nervous system by studying effects on synaptic transmission in cultured hippocampal neurons. Carbamyl-PAF, a nonhydrolyzable PAF analog with a similar pharmacologic profile, augmented glutamate-mediated, evoked excitatory synaptic transmission and increased the frequency of spontaneous miniature excitatory synaptic events without increasing their amplitude or altering their time course. This compound had no significant effect on gamma-aminobutyric acid-mediated inhibitory synaptic responses. Lyso-PAF, the biologically inactive metabolic intermediate, had no effect on synaptic transmission. Moreover, the enhancement of excitatory synaptic transmission by carbamyl-PAF was blocked by a PAF receptor antagonist. These results indicate a specific presynaptic effect of PAF in enhancing excitatory synaptic transmission in cultured rat hippocampal neurons.

Animals↗
PubMed1977

Cerebral cortical isolation in infantile neuroaxonal dystrophy.

Three patients with infantile neuroaxonal dystrophy (INAD, Seitelberger's disease) studied between ages 2 and 5 years, with the characteristic electroencephalographic pattern of high-voltage, fast (16-24 c/sec) rhythms and absence of reactivity on eye-opening or closure (Radermecker and Dumon-Radermecker 1972), also showed no changes in response to intermittent photic stimulation and absence of evoked potentials to flashes, clicks or median nerve stimuli. Although some theta rhythms and delta activity appeared during drowsiness and sleep, the fast rhythms persisted as the dominant feature. There were no central transients or K-complexes. When the patients cried, with hyperventilation, and also during breath-holding spells, slow rhythms appeared and the fast rhythm was reduced. These findings are interpreted as evidence of cerebral cortex isolation, the fast rhythm representing the spontaneous ("idling") activity of the cortex largely disconnected from subcortical or remote cortical influences by the slowly progressive, selective degeneration of axons, characteristic of the pathology of INAD, but the cortex remains responsive to chemical influences. These electrophysiological features become established furing the third year of age, prior EEGs being normal and later ones showing paroxysmal and other abnormal features in addition to the fast rhythm.

Acoustic Stimulation↗
PubMed1975

Spinal cord potentials evoked by peripheral nerve stimulation.

Lumbar, thoracic, and cervical spinal cord responses evoked by sciatic nerve stimulation were measured in 20 cats at the skin level and directly from the dorsal surface of the cord. Computer averaging techniques were used for both skin level recordings and cord surface recordings at all levels. Recordings made directly from the cord surface at lumbar levels were large and were characterized by a large, initial, negative transient, followed by a more complicated and variable waveform. As recording electrodes were moved rostrally, the initial large spike decreased in amplitude and the duration and latency of the response increased. At cervical levels were large and were characterized by a large, initial, negative transient, followed by a more complicated and variable waveform. As recording electrodes were moved rostrally, the initial large spike decreased in amplitude and the duration and latency of the response increased. At cervical levels the responses were polyphasic, of long duration and small amplitude. Deafferentation by posterior rhizotomy of all lumbar and sacral roots ipsilateral to sciatic nerve stimulation abolished the response at all levels. Thoracic cord section also abolished the response over the cervical cord. Skin level recordings were of shorter latency than direct recordings, especially at cervical levels. Response configurations were similar for both recording techniques at lumbar levels, but had different waveforms at both thoracic and cervical levels. Clinical implications of the techniques and possible explanations of the waveforms recorded are discussed.

Animals↗