Biomedical subjects

N Chino

Publications and source records attributed to N Chino.

114 records · Page 7Linked to original sources

PubMedDate not supplied

Synaptic connections from large muscle afferents to motoneurones in human lower limbs.

OBJECTIVES: Our study was undertaken to investigate reciprocal inhibition in humans both from ankle flexors to extensors and from ankle extensors to flexors. METHODS: Changes in the firing probability of single motor units in response to electrical stimulation of muscle nerves (the peristimulus time histogram technique) were used to derive the reciprocal projections of muscle spindle Ia afferents to the motoneurones of ankle muscles. Discharges of units in ankle flexors (the tibialis anterior muscle [TA]) and extensors (soleus [SOL] and medial gastrocnemius [MG] muscles) were investigated respectively after stimulation of the posterior tibial (PTN) and common peroneal (CPN) nerves (predominantly on the deep branch). In eight normal subjects aged 24 to 40 years, one motor unit per each muscle was studied. RESULTS: CPN stimulation produced reciprocal Ia inhibition in the SOL of 5 of 7 of them and in the MG of 3 of 5, whereas PTN stimulation produced reciprocal Ia inhibition in the TA of only 2 of 6 subjects. CONCLUSIONS: These findings suggest that at low level contraction reciprocal Ia inhibition from ankle flexors to extensors may be stronger than that from ankle extensors to flexors.

Adult↗

PubMedDate not supplied

Solution synthesis of Na+,K(+)-ATPase inhibitor-1 (SPAI-1).

SPAI-1, a 49-amino acid peptide including eight Cys residues with Na+,K(+)-ATPase inhibitory activity, was synthesized by the solution procedure. Protecting groups, including the formyl group on the Trp residue, were cleaved simultaneously by HF treatment in the presence of a sufficient amount of thiol compound. After removal of the Acm group on the Cys residue, the resulting octa SH peptide was subjected to an oxidative folding reaction in the presence or absence of redox reagents and/or denaturant. Addition of redox reagents accelerated the reaction but was not crucial to the formation of the correct disulfide bonds in the molecule. The product was purified to homogeneity and found to have the same physicochemical properties and inhibitory potency as those reported for the natural product. Four intramolecularly linked disulfide bridges were assigned as connecting Cys8 to Cys37, Cys15 to Cys41, Cys24 to Cys36, and Cys30 to Cys45 based on results from a combination of enzymatic and synthetic approaches.

Amino Acid Sequence↗

PubMedDate not supplied

Changes of reflex size in upper limbs using wrist splint in hemiplegic patients.

We evaluated the effect of prolonged wrist extension on H reflex in the flexor carpi radialis (FCR) muscle and tendon jerk (T) reflex in the biceps brachii (BB) muscle of 17 chronic hemiplegic patients. H reflex of the FCR and T reflex of the BB were assessed every 5 minutes within 20 minutes during prolonged wrist extension and post-20 minutes after the extension. As a result, H reflex in the FCR was reduced by passive wrist stretch in 82% of the spastic limbs. The effect was larger in the higher spastic group. In 45% of the spastic limbs, T reflex in the BB also was reduced by passive wrist stretch. The inhibitory effects had a tendency to strengthen in accordance with the grade of muscle tone. We considered from these results, prolonged wrist extension generated inhibitory projections via probably group II afferents of the FCR in the homonym and in the transjoint in spastic limbs.

Afferent Pathways↗

PubMedDate not supplied

Relation between macro-EMG and muscle Uber conduction velocity.

We investigated the relationship between macro-EMG and muscle Uber conduction velocity in the right biceps brachii in 5 normal subjects using a single-Uber macroelectrode and surface array electrodes. The macro-EMG signal and the surface electrode signals were triggered and averaged by the single-Uber action potential. The amplitude and area of the macro-EMG was correlated with the muscle Uber conduction velocity, suggesting that the macro-EMG can serve as a parameter of the size principle in both the clinical and research settings.

Adult↗

PubMedDate not supplied

Effects of visual and auditory stimuli on median nerve somatosensory evoked potentials in man.

To demonstrate electrophysiological evidence of neural connections of somatosensory with visual and auditory pathways, interactions of median nerve somatosensory evoked potentials (SEPs) with visual evoked potentials (VEPs) and auditory evoked potentials (AEPs) were analyzed in 12 healthy subjects. In Experiment I (SEP vs. VEP), three patterns of stimulation, namely, electric stimulation of left median nerve, binocular LED flash, and simultaneous electric and flash stimulation, were applied with random interstimulus intervals of 2-4 sec until more than 100 responses had been obtained and averaged for each pattern of stimulation. Simultaneous electric and visual responses were subtracted from arithmetical sums of SEPs and VEPs to show interactions between somatosensory and visual responses. In Experiment II (SEP vs. AEP), binaural short-duration tone bursis instead of LED flashes were used in the same manner as in Experiment I, and interactions between somatosensory and auditory responses were analyzed. Results indicated that the effects of both visual and auditory interaction on SEPs were significant around 120-130 msec of latency. In other words, cross-modal sensory interaction occurred in the late phase of sensory processing.

Acoustic Stimulation↗

PubMedDate not supplied

Solution synthesis of mu-conotoxin GIIIB: optimization of the oxidative folding reaction.

mu-Conotoxin GIIIB, a skeletal muscle sodium channel specific blocker, was synthesized by the solution procedure. The whole molecule, which is composed of 22 amino acid residues including six cysteinyl and three trans-4-hydroxy-L-prolyl residues, was constructed from three segments. After removal of all protecting groups, the hexa-SH peptide was subjected to an oxidative folding reaction at a peptide concentration of 1 x 10(-5) M. Three major products 1, 2 and 3 were formed in a ratio of 1:4:3. Determination of the disulfide structures in each product revealed them to be disulfide isomers, with similar connectivities in the latter two. Study of the biological activities of the three products in mice indicated that only product 1, which is a minor component, has the same potency as the natural product. Analysis of the folding process at a peptide concentration of 1 x 10(-5) M showed that the disulfide bond between Cys10 and Cys15 was initially formed, thus leading to the predominant generation of products 2 and 3. The optimal conditions for the formation of product 1 (mu-conotoxin GIIIB) were obtained by increasing the peptide concentration in the oxidation reaction mixture or by using redox reagents, both of which functioned as promoters for the thiol-disulfide exchange reaction of the mismatched disulfide bond between Cys10 and Cys15.

Amino Acid Sequence↗