Biomedical subjects
Publications and source records attributed to K Shimoji.
Interaction between the slow negative-positive waves of human evoked electrospinograms produced by descending and segmental volleys was tested under general anaesthesia. A partial occlusion was demonstrated in these slow waves.
Human cord dorsum potential (CDP) was recorded from the posterior epidural space at the levels of cervical and lumbar enlargements, using epidural catheters as the recording electrodes, in 15 normal volunteers and six patients suffering from amyotrophic lateral sclerosis. In normal subjects the CDP elicited by descending volleys consisted of spike potentials followed by sharp negative and slow positive waves which were very similar to the P1, N1, and P2 potentials, respectively, of the CDP evoked segmentally. By contrast, in all patients with amyotrophic lateral sclerosis both the sharp negative and slow positive waves were absent in the CDP elicited by descending volleys, while the pattern of each component of the segmentally evoked CDP remained unchanged. Thus, the sharp negative and slow positive waves of human CDP elicited by descending volleys might reflect the activity of interneurones and primary afferent depolarisation respectively, produced by impulses through the corticospinal tract.
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Somatosensory evoked response from the cervical skin surface over the spine (the cervical SER) was recorded, and compared with the cord dorsum potential (CDP) simultaneously recorded from the posterior epidural space at the same segment. The cervical SER evoked by segmental nerve stimulation consisted of an initially positive spike (P1), the peak latency being the same as that of the P1 of the CDP, followed by a smaller negative wave with two peaks. The latency of the second peak of the negative wave (N1) coincided with that of the N1 of the CDP. Subsequent to this negative wave, a slow positive wave (P2) with peak latency similar to that of the P2 of the CDP, could be noticed in some subjects. The cervical SER could not be evoked even by strong stimulation of the cauda equina. Thus, the cervical SER might reflect a segmental phenomenon rather than the conducted potential along the cord, and originate from the spinal root and cord in the same way as the segmentally evoked CDP.
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Low-frequency (1.6-2.2 Hz) and weak-intensity electrical stimulation in the spinal extradural space produced complete to partial pain relief in a majority of patients (22 of 25) who suffered from intractable pain. Also it produced analgesia or hypoalgesia over a wide area of the body surface in 19 of the 25.
To determine whether neuronal firing is affected by anesthetics, the behavior of neurons in the mesencephalic reticular formation in response to repetitive somatosensory stimulation at 2/sec was studied during wakefulness and during nitrous oxide, halothane, and thiopental anesthesia in the cat. With clinical doses of the three anesthetics there were simultaneous blockades of both initial facilitation (28 of 32) and subsequent habituation (31 of 32) of the evoked responses in a majority of the mesencephalic reticular formation neurons. This dishabituation phenomenon was most prominent with thiopental and least prominent with nitrous oxide. Thus, it is suggested that progressive inactivation of not only the facilitatory process but also the inhibitory process in the neuronal activities of the mesencephalic reticular formation is associated with the so-called "anesthetic state" produced by these three anesthetics.
A simple gas chromatographic method for the determination of lidocaine in tissues is described. Lidocaine is extracted from the tissue samples using liquid nitrogen. The recoveries of lidocaine from brain, liver, and muscle were 98.6, 99.8 and 89.1%, respectively. Results were reproducible to within 1.0% of lidocaine administered.
The evoked spinal electrogram (SEG) in man was recorded from the epidural space, applying the technique of continuous epidural block, and compared with cord dorsum potential (CDP) in wakeful rabbits. Wave-form characteristics of the evoked SEG'S activated by the segmental nerves were almost the same in both cervical and lumbar regions. Somatosensory evoked response from the scalp was clearly demonstrated by stimulation of both the tibial nerve and fifth toe skin, whereas the evoked SEG was produced only by stimulation of the former. This finding might indicate that large nerve fibers are more responsible for producing the evoked SEG. Central latencies to the peaks of the second components of the P2 wave were 29 to 33 and 42 to 48 msec, in cervical and lumbar enlargements, respectively. This probably indicates the presence of a long feedback loop producing the second components. The amplitude of the N1 wave showed a steeper decline along the spinal cord than that of the P2 deflection, indicating between origins of these two components. Polarity of both the N1 and P2 waves became reversed when the recording electrode was situated in the anterior epidural space. The wave-form characteristics of the evoked SEG in man were very similar to those of the CDP in wakeful rabbits.
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Intractable pain in a patient with adiposis dolorosa (Dercum's disease) was treated by IV administration of lidocaine (200 to 400 mg). Relief was maximum 20 minutes after the end of drug infusion and persisted for over 10 hours. Toxicity was minimal. Slow EEG waves which appeared during drug administration disappeared within 20 minutes.