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Biomedical subjects

N Kudo

Publications and source records attributed to N Kudo.

At least 145 records · Page 8Linked to original sources
PubMed1982

Origins of the scalp-recorded somatosensory far field potentials in man and cat.

Short latency somatosensory evoked potentials preceding the primary cortical potential were recorded from the scalp in man and cats. Four positive potentials (P1, P2, P3 and P4 in man, and CI, CII, CIII and CIV in cats) were observed with non-cephalic reference recording and 3 or 2 positive components (P1a, P2a and P3a in man, and CIa and CIIa in cats) were recorded with earlobe reference. (1) The latencies of these potentials and the effects of lesions on them in man and (2) the effects of (i) supracollicular and medullo-cervical transections and (ii) intrathecal anaesthesia of the cervical cord on these components in cats suggest that: (1) P1 and CI originate in the brachial plexus beneath the clavicle; (2) P2, P3 and CII, CIII are generated in the cervical cord; (3) P4 and CIV reflect activity mainly in the brain stem or the cerebellum or both; (4) P1a and CIa arise in the cervical cord; (5) P3a and CIIa reflect activity mainly in the brain stem or the cerebellum or both. As the impulse initiated in the median nerve travels through various regions where the resistance might change suddenly, these far field potentials might be recorded as if generated at fixed sites such as just beneath the clavicle and foramen magnum.

Animals↗
PubMed1978

Evidence for the maintenance of motoneurone properties by muscle activity.

1. Electrophysiological properties of soleus motoneurones in adult cats were examined with intracellular electrodes following alterations of activity of the soleus muscle induced by transection of the thoracic spinal cord or by conduction block of the muscle nerve with tetrodotoxin (TTX) cuffs. Attempts were also made to maintain muscle activity by daily stimulation of the maintain muscle activity by daily stimulation of the peripheral nerve. 2. Within 8 days after transection of the thoracic cord, soleus motoneurones showed a significant decrease in the duration of afterhyperpolarization following action potentials. This change in motoneurone properties induced by cord transection was prevented by daily stimulation of the sciatic nerve. 3. Soleus motoneurones showed a significant decrease in the duration of after-hyperpolarization within 8 days after conduction block of the soleus nerve with TTX. This change in montoneurone properties was prevented by daily stimulation of the nerve peripheral to the TTX cuff but not central to the cuff. 4. The soleus muscle showed a significant decrease in weight relative to body weight within 8 days after transection of the thoracic cord. This decrease in muscle weight following cord transection was prevented by daily stimulation of the sciatic nerve. 5. No fibrillation was detected in the soleus muscle 8 days after conduction block of the soleus nerve with TTX. The maximum twitch tension of the soleus muscle evoked by nerve stimulation showed no significant difference between the two sides treated and untreated with TTX. Fast axoplasmic transport measured with cholinesterase as a marker was not affected by TTX. Thus, there was no sign of functional although morphological abnormalities were found in some nerve fibres. 6. It is concluded that motoneurone properties in an adult depend partly upon some factors associated with activity of the innervated muscles and that such trophic signals are retrogradely carried by the motor axons.

Action Potentials↗
PubMed1978

Disparity of motoneurone and muscle differentiation following spinal transection in the kitten.

1. The spinal cord of kittens, 3--5 days of age, was transected at the lower thoracic level. Isometric contractions of the medial gastrocnemius and soleus muscles as well as intracellular potentials of their motoneurones were recorded after varying post-operative periods of up to 110 days. Similar observations were made 52--59 days after cord transection in adult cats. 2. In cord-transected kittens, contraction time of the gastrocnemius muscle showed normal development, whereas the soleus muscle failed to maintain slow contraction. In adult cats, cord transection increased the speed of contraction in the soleus muscle without significant changes in contraction times of the gastrocnemius muscle. 3. Soleus motoneurones showed a normal post-natal increase in the duration of afterhyperpolarization (a.h.p.) up to a certain stage (61--71 days in age) following cord transection. However, the subsequent increase in the duration of a.h.p. of soleus motoneurones observed in normal kittens was lacking in cord-transected kittens. It is suggested that soleus motoneurones show two stages of differentiation in terms of the duration of a.h.p. 4. In adult cats, cord transection caused a decrease in the duration of a.h.p. of soleus motoneurones approximately to the value observed at the end of the first stage of differentiation in kittens. 5. The duration of a.h.p. of gastrocnemius motoneurones remained virtually unchanged follwoing cord transection in both kittens and adult cats. 6. The positive correlation between the duration of a.h.p. of soleus motoneurones and contraction time of the innervated muscle fibres normally observed in kittens and adult cats was absent following cord transection. 7. It was assumed that alteration s in contraction time of the muscle following cord transection are due to virtual elimination of motoneurone discharge and that the duration of a.h.p. reflects the discharge pattern of motoneurones under normal conditions. Based on these assumptions, a possible process for normal post-natal differentiation of motoneurone and muscle is proposed.

Age Factors↗
PubMed1977

Reaction of intact spinal motoneurones to partial denervation of the muscle.

1. The properties of soleus motoneurones of the cat were examined with intracellular electrodes about 3 weeks after partial denervation of the soleus muscle. Soleus motoneurones whose axons had been left intact were distinguished from those whose axons had been sectioned by the presence or absence of muscle contraction in response to intracellular stimulation of each motoneurone. 2. The average twitch tension of motor units evoked by intracellular stimulation of intact soleus motoneurones after partial denervation of the muscle was not significantly different from that observed in control, unoperated cats. Therefore, it was assumed that the majority of intact motoneurones had not been subject to injuries in their axons upon partial denervation. 3. Soleus motoneurones whose axons had been sectioned showed a significant increase in overshoot of action potentials and a significant decrease in resting membrane potential, in axonal conduction velocity and in the duration of after-hyperpolarization. 4. Soleus motoneurones whose axons had been left intact also showed a significantly shorter after-hyperpolarization than that seen in control, unoperated cats. Other electrophysiological properties of the intact soleus motoneurones were indistinguishable from those observed in unoperated animals. 5. The decrease of the duration of after-hyperpolarization in intact soleus motoneurones was greater in highly denervated preparations than in moderately denervated preparations. 6. The decrease of the duration of after-hyperpolarization in intact soleus motoneurones was associated with a decrease in contraction times of the innervated muscle fibres, the former preceding the latter by one to two weeks. 7. It is concluded that motoneurone properties can be modified without injury to their axons and that alterations in the properties of intact motoneurones depend upon the degree of partial denervation of the muscle. The possible signal for alterations of motoneurone properties is discussed. 8. It is also concluded that the contractile properties of muscle fibres can be modified without cross-union of the nerves. It is suggested that the contractile properties of muscle fibres may be linked to the duration of after-hyperpolarization or to some mechanism related to this factor in the innervating motoneurones.

Action Potentials↗
PubMed1977

Membrane properties and conduction velocity in sensory neurones following central or peripheral axotomy.

1. The properties of dorsal root ganglion cells in the lumbosacral segments were examined with intracellular electrodes about 3 weeks after section of the central (dorsal roots) or peripheral processes in the cat.2. Chronic section of the peripheral nerve in the hind limb resulted in a reduction in conduction velocity of both the central and peripheral processes of sensory neurones.3. Sensory neurones arising from the triceps surae and plantaris muscles were subject to ;disuse' conditions for about 3 weeks by section of the ventral roots combined with severance of the Achilles tendon. Under such conditions, the central and peripheral conduction velocities of these sensory neurones tended to decrease, but the decrease was significantly less than that following peripheral nerve section.4. Chronic section of the dorsal roots produced no significant changes in conduction velocity of the central processes of muscle sensory neurones but caused a significant increase in the peripheral conduction velocity.5. The only electrophysiological property of dorsal root ganglion cells which altered following axotomy was the time-dependent membrane rectification in response to hyperpolarizing current pulses. The rectification characteristics were modified by chronic section of the peripheral nerve but not by chronic section of the dorsal root.6. It is concluded that injuries in nerve fibres per se do not necessarily result in a decrease of their conduction velocity and that a decrease in their conduction velocity is associated with changes in the properties of the cell bodies.7. It is suggested that a decrease in conduction velocity following nerve section may require the participation of changes in the neurone cell body.

Animals↗
PubMed1976

[A photo-optical observation of gallbladder motility in dogs (author's transl)].

A photo-optical observation on gallbladder motility was made with the 16 mm cine-cholangiography. The subjects studied were thirty two mongrel dogs. The gallbladder was exposed by a short upper midline abdominal incision under pentothal anesthesia. Gallbladder bile was aspirated and contrast medium was given into the bladder, through a transhepatic route. The cine-cholangiography was done by an image intensifier at a speed of one frame every 2 to 4 seconds. The cinefilms taken were observed repeatedly by the screen projection at various speeds. The drawings were made by tracing the outline of the image of the gallbladder on each frame and were overlapped. Moreover, a contraction curve was made by the cholecystometry using of film motion analyzer in every case. At the same time bile flow into the duodenum was recorded to study a relationship between the gallbladder contraction and motility of the terminal common bile duct. The results obtained are as follows: 1. In a resting state any contraction of the gallbladder was not seen during 30 minutes, and a peristalsis-like movements of the neck portion was observed. However, there was not a relationship between the contraction curve of the gallbladder and the bile flow into the duodenum. 2. Immediately after giving Caerulein, the contrast medium injected into the gallbladder was rapidly discharged into the common bile duct by a peristalsis-like movement of the neck. The size of the gallbladder was markedly decreased into three fifths of the initial state three minutes after administration. At the same time contrast medium was continuously discharged into the duodenum. 3. After giving pilocarpine a marked contraction with forceful movement of the neck and body was observed, and the size of the gallbladder was decreased into three quarters ot the initial state. Bile discharge into the duodenum was markedly increased with an active open- and closing movement of the terminal common bile duct.

Animals↗