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Biomedical subjects

K Yabe

Publications and source records attributed to K Yabe.

At least 91 records · Page 5Linked to original sources
PubMed1984

Preparatory process for anticipatory postural adjustments: modulation of leg muscles reflex pathways during preparation for arm movements in standing man.

We have investigated, in 6 standing subjects, the time course of amplitude changes in the short latency (40-60 ms) and long latency (60-80 ms) reflex response components of gastrocnemius medialis (GM) and soleus (S) muscles during the preparatory period (time between a warning signal and a response signal) as a function of the precued direction (pull or push) of arm movement. Subjects maintained their standing posture by visual feedback during the 1.5 s preparatory period of a reaction time task. A warning signal gave advance information concerning the voluntary response to be performed which consisted of either a pull or push movement of the right arm. The excitability of the reflex pathways was evaluated by triggering a rapid rotation of the right ankle joint (dorsiflexion) applied randomly at 100, 300 or 500 ms before the response signal for arm movement. Statistical analysis of EMG amplitude (ANOVA) showed that preparatory effects were different for the two synergistic muscles with both short (spinal) and longer latency components of GM showing generalized facilitation and of S showing generalized inhibition. In addition, the longer latency, presumably supraspinal, component of the two muscles was differentially modulated according to directional advance information, showing relative facilitation for pull as compared to push trials. These reflex response modulations were emphasized in faster reaction time (RT) performers at the end of the preparatory period. It is concluded that postural preparatory processes are reflected at the spinal level in global effects and at the supraspinal level in directionally specific effects.

Adolescent↗
PubMed1984

Purification and properties of aminoendopeptidase from rat epidermis.

An aminoendopeptidase isolated from 2-day-old rat epidermis was purified to apparent homogeneity by the procedures of ammonium sulfate fractionation, DE-52 column chromatography, Sephadex G-200 gel filtration, and CM-52 and DEAE-Sepharose 6B column chromatography. Enzymatic activity was exhibited only in the presence of sulfhydryl compounds and further enhanced by addition of 5 mM EDTA. It was inhibited by p-chloromercuribenzoate, other sulfhydryl blocking reagents, and o-phenanthroline. The monomer form of the enzyme is Mr = 52,000 +/- 2,300 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, but a native form was considered to be Mr = 400,000 +/- 26,000 having an isoelectric point of pH 5.25. Among synthetic substrates the enzyme hydrolyzed amino acid 2-naphthylamide derivatives and L-leucine amine (L-LeuNH2) most effectively. N-alpha-benzoyl-DL-arginine-2-naphthylamide (BANA) was the only endopeptidase substrate for the enzyme and a competitive inhibitor for its aminopeptidase activity. Protein substrates have not yet been found. The pH optimum is 7.5 and in a range of pH 6.5-7.5 it is stable at 37 degrees C for 30 min but loses about 50% of its activity at 50 degrees C.

Animals↗
PubMed1981

Changes of portal vein pressure and intrahepatic blood vessels after surgery for biliary atresia.

The portal vein pressure was measured and biopsies of the liver were taken during the corrective operation in 31 patients with biliary atresia and during relaparotomy in 16 patients free from jaundice 4 mo to 9 yr after a successful corrective operation. Because the portal vein pressure was higher than 200 mmH2O in about 70% of patients during the corrective operation, portal hypertension appears to have already developed in most of the patients with biliary atresia at 2-4 mo of age. In the patients who had had frequent episodes of postoperative cholangitis, the portal vein pressure was elevated and the amount of interstitial tissue in the liver was markedly increased at reoperation compared with those at the corrective operation. These results showed that postoperative cholangitis aggravated portal hypertension and fibrosis of the liver. On the contrary, the portal vein pressure declined in patients in whom active bile drainage had persisted and cholangitis had not been complicated after operation. An early corrective operation and prevention of postoperative cholangitis are of the greatest important for prevention of development of the portal hypertension and cirrhosis of the liver in long-term survivors after surgery for biliary atresia.

Bile Ducts↗
PubMed1976

Premotion silent period in rapid voluntary movement.

The silent period in the agonist prior to rapid voluntary movement (premotion silent period) was observed in the lower limb muscles. The subject was asked to respond to the flashing light by performing a vertical jump as quickly as possible. The most consistent results were obtained in the extensors, particularly the quadriceps. The frequency of the silence of six subjects was 53% in the rectus femoris, 61% in the vastus medialis, and 72% in the vastus lateralis. A neural switching mechanism, directing excitation from preparation phase of jumping into rapid contraction phase, seemed to be attributable to the occurrence of the premotion silent period.

Action Potentials↗
PubMed1976

Inhibitory effect of unilateral contraction on the contralateral arm.

Electromyograms of the triceps and biceps brachii of both arms of 6 subjects were recorded in reaction trials to flashing stimulus. Rapid voluntary elbow extension was immediately preceded by a silent period of the unexercised contralateral agonist (contralateral agonist silent period). Since this silent period was not accompanied by a contralateral antagonist contraction, the contralateral agonist silent period was not attributable to reciprocal inhibition in the spinal levels.

Arm↗
PubMed1975

[Role of the silent period preceding the rapid voluntary movement (author's transl)].

It has been shown that there is the silent period preceding the rapid voluntary movement. The present paper is designed to find the mechanisms of this inhibitory phenomenon and to investigate their role in the voluntary movement. The following results were obtained: 1. It was found that the silent period before the movement was observed not only in reaction trials to visual stimulus but also in voluntary trials without stimulus. 2. The silent period were simultaneously recorded from the rectus femoris, the vastus lateralis and the vastus medialis by upward jumping movement. This finding suggested that this inhibitory phenomenon was a change in excitability of motoneurons innervating the quadriceps. 3. When a subject extended his elbow and knee at the same time, the silent period before the movement could be seen in both triceps brachii and vastus medialis. 4. These results suggest that the upper center sends some inhibitory discharge to the motoneurons before the movement. It is supposed that the silent period preceding the voluntary movement plays a major role in the mechanisms of motor control.

Action Potentials↗