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Biomedical subjects

N Chino

Publications and source records attributed to N Chino.

At least 19 recordsLinked to original sources
PubMed2000

Quantitative EMG and motor unit recruitment threshold using a concentric needle with quadrifilar electrode.

According to Henneman's size principle, small motor units are recruited before large ones. We used the electromyographic (EMG) signal decomposition technique to determine the quantitative relationships between five motor unit action potential (MUAP) parameters (amplitude, duration, area, thickness, and size index) and the recruitment threshold of the motor units recruited up to 50% of the maximum voluntary contraction in the first dorsal interosseous, biceps brachii, rectus femoris, and tibialis anterior muscles of 5 healthy young men. In each muscle, the amplitude, duration, area, and size index had significant, positive high correlations with the motor unit recruitment thresholds. We conclude that the size principle applies to recordings made with concentric needle EMG electrodes under special recording conditions, and therefore that more importance should be attached to the patient's contraction force during EMG examinations in order to evaluate MUAPs for electrodiagnostic purposes.

Adult↗
PubMed2000

Physiologic decrease of single thenar motor units in the F-response in stroke patients.

OBJECTIVE: To investigate the left-right difference and the reproducibility by the F-wave motor unit number estimation and to compare the motor unit number between the hemiplegic and unaffected side in stroke patients. SETTING: A referral center and institutional practice providing outpatient care. SUBJECTS: Seven healthy volunteers and 15 consecutive stroke patients. DESIGN: Diagnostic statistical test and correlational study. METHOD: Submaximal stimuli were used to evoke a sample of surface motor unit action potentials (S-MUAPs) in the F-waves that are entirely representative of the relative numbers of detected S-MUAPs of different sizes. The average S-MUAP amplitude was calculated from a selected population of F-wave responses for each abductor pollicis brevis (APB) muscle. The motor unit number was calculated by dividing the maximum M-potential negative peak amplitude by the average S-MUAP negative peak amplitude. RESULT: There was no statistical difference between motor unit numbers on either side and between test and retest in this motor unit number estimation method among normal subjects. The motor unit number on the hemiplegic side was significantly lower than on the unaffected side (p < .05, Mann-Whitney test) among stroke patients. CONCLUSION: The motor unit could decrease in the hemiplegic side after a moderate-to-severe hemiplegic stroke and this decrement might be due to the transsynaptic degeneration secondary to an upper motor neuron lesion.

Action Potentials↗
PubMed2000

Structural analysis of human beta-defensin-1 and its significance in urinary tract infection.

Human beta-defensin-1 (hBD-1) is a 36-amino-acid antimicrobial peptide that functions in the host innate defense. We developed a highly sensitive radioimmunoassay for hBD-1 and identified several hBD-1 peptides in human kidney, urine, and plasma by amino acid sequencing and mass spectrometry. Large quantities of hBD-1 peptides are produced in the kidney, are released into the tubular lumen as 47-amino-acid pro-hBD1, and then undergo proteolytic processing and generate multiple truncated forms. The respective urine and plasma concentrations of hBD-1 in patients with pyelonephritis are 48.1 +/- (SEM) 15.7 pmol/mg creatinine and 2.66 +/- 0.41 pmol/ml, 3.1-fold and 1.8-fold those of normal individuals. hBD-1 is thought to contribute to mucosal defense in the urinary tract. Our findings provide a better understanding of the biosynthesis of this peptide and its pathophysiological significance in infectious diseases.

Adult↗
PubMed1999

Relationship between hypoxemia and fibrillation potential firing rate in denervated muscle.

The effects of hypoxia and ischemia on the firing rate of fibrillation potentials in denervated rat muscle were examined. We recorded electromyograms from the denervated left extensor digitorum longus muscle. Hypoxia was induced by low-oxygen ventilation. Ischemia was established by ligating the abdominal aorta and inferior vena cava, with or without extracorporeal hindlimb perfusion. The fibrillation potential firing rate correlated with the PaO2 (P < 0.0001) and temperature (P = 0.0001). Fibrillation potentials disappeared after the initiation of ischemia and reappeared after restitution of blood flow; they disappeared during ischemia with extracorporeal perfusion. The attenuation curves for the firing rate of fibrillation potentials during ischemia were well-described by exponential curves, but there was no significant difference in the attenuation constants for circulatory arrest and perfusion with a physiologic salt solution. We conclude that the fibrillation potential firing rate is proportional to oxygen supply, presumably because of the rate of aerobic metabolism.

Action Potentials↗
PubMed1999

Osteoporosis in hemiplegic stroke patients as studied with dual-energy X-ray absorptiometry.

OBJECTIVES: To compare bone mineral densities (BMDs) of the affected and unaffected limbs in stroke patients at multiple sites; to study longitudinal changes during a 3-month rehabilitation program; and to relate BMDs to demographic, impairment, and disability variables. DESIGN: Descriptive study. SETTING: Tertiary rehabilitation center. PATIENTS: One hundred four consecutive hemiplegic inpatients, 69 men, age 56.5 +/- 13.2 yrs, 47 with left-sided brain lesion. Median days from onset to admission and median length of stay days were 83 and 105.5, respectively. MAIN OUTCOME MEASURES: BMDs of proximal humerus, distal radius, femoral neck, and calcaneus bilaterally, and third lumbar vertebra, measured with dual-energy x-ray absorptiometry (DXA), were compared between affected and unaffected sides at admission and discharge. RESULTS: Stroke Impairment Assessment Set (SIAS) motor scores, Functional Independence Measure (FIM) scores, grip strength, and awake/sleep heart rate counts (activity index) improved significantly at discharge. Affected/unaffected BMD ratios were 88.3% to 98.4% at admission and 79.6% to 98.8% at discharge, lowest for the humerus. Discharge/admission ratios were 89.1% to 97.8% for the affected and 97.4% to 100% for the unaffected side. All BMDs were intercorrelated (R = .438 to .873). They correlated significantly with age, body weight, grip strength, FIM scores, and activity index. Factors selected to explain BMD with multiple regression analysis differed according to the site and timing of the measurement. CONCLUSIONS: BMDs of the affected side were lower and most marked in the humerus. Longitudinally, not only the affected but the unaffected BMDs decreased. Age, sex, duration of stroke, anthropometric measurements, motor paralysis, muscle strength, and activity level contributed differently to bone loss according to the site and timing of the measurement.

Absorptiometry, Photon↗
PubMed1999

Bridging activity as a mode of stress testing for persons with hemiplegia.

OBJECTIVE: To establish a stress testing protocol for hemiplegic persons using graded bridging activity at the rates of 3 to 24 repetitions per minute. DESIGN: Paired comparisons of exercise parameters and admission and discharge data between hemiplegic and control groups. SETTING: Inpatient rehabilitation program of a tertiary rehabilitation center in Japan. PATIENTS: (1) Preliminary study: five hemiplegic patients. (2) Comparison with normal subjects: 39 hemiplegic patients and 10 age-matched controls. (3) Study of reproducibility: five hemiplegic patients and five controls. (4) Longitudinal changes: 30 hemiplegic patients. MAIN OUTCOME MEASURES: Oxygen consumption (VO2), heart rate (HR), and HR oxygen coefficient (regression coefficient between HR and VO2). RESULTS: The testing protocol was applicable to 88.6% of hemiplegic patients. The relationship between HR and VO2 was linear, and HR oxygen coefficient was significantly lower in hemiplegic patients than the controls. The intraclass correlation coefficients were greater than 0.7 for VO2, HR, and HR oxygen coefficient, indicating satisfactory reproducibility. HR decreased longitudinally for the same stress levels and the HR oxygen coefficient increased, indicating improved fitness level. CONCLUSIONS: The bridging activity protocol is a useful mode for stress-testing hemiplegic persons. The linearity between HR and VO2 with this protocol allows us to use the indices of fitness obtainable from this relationship.

Activities of Daily Living↗
PubMed1999

The size index as a motor unit identifier in electromyography examined by numerical calculation.

A computer simulation was performed to investigate the size index as a motor unit identifier in electromyography. The size index calculated from the amplitude and area of the simulated motor unit action potential (MUP) was plotted against the distance between the needle electrode and current source to show how the index changes as a function of the distance. The index of the MUP also was plotted against the number of muscle fibers belonging to a single motor unit, the size of the motor unit territory, and the diameter of the muscle fibers in order to establish the major determinants of the index. The index was relatively constant for the distance less than 2 mm between the needle electrode and closest edge of the current source. It changed logarithmically with the number of muscle fibers and with the diameter of the fibers.

Computer Simulation↗
PubMed1999

Relationship between shoulder muscle strength and functional independence measure (FIM) score among C6 tetraplegics.

The degree of disability varies widely among C6 tetraplegic patients in comparison with that at other neurological levels. Shoulder muscle strength is thought to be one factor that affects functional outcome. The aim of this study was to examine the relationship between shoulder muscle strength and the Functional Independence Measure (FIM) motor score among 14 complete C6 tetraplegic patients. The FIM motor score and American Spinal Injury Association (ASIA) motor score of these patients were assessed upon discharge. We evaluated muscle strength of bilateral scapular abduction and upward rotation, shoulder vertical adduction and shoulder extension by manual muscle testing (MMT). The total shoulder strength score was calculated from the summation of those six MMT scores. The relationships among ASIA motor score, total shoulder strength score and FIM motor score were analyzed. The total shoulder strength score was significantly correlated with the FIM motor score and the score of the transfer item in the FIM. In the transfer item of the FIM, the total shoulder strength score showed a statistically significant difference between the Independent and Dependent Group. Shoulder muscle strength appears to be an important factor in the functional abilities of those with C6 complete tetraplegia. Functional variation depends on the strength of shoulder muscles, especially among C6 tetraplegics.

Activities of Daily Living↗
PubMed1999

The chimeric peptide [Lys(-2)-Arg(-1)]-sarafotoxin-S6b, composed of the endothelin pro-sequence and sarafotoxin, retains the salt-bridge staple between Arg(-1) and Asp8 previously observed in [Lys(-2)-Arg(-1)]-endothelin. Implications of this salt-bridge in the contractile activity and the oxidative folding reaction.

The chimeric peptide [Lys(-2)-Arg(-1)]-sarafotoxin-S6b (KR-SRTb) designed from the Lys-2-Arg-1 dipeptide of the endothelin pro-sequence and the sarafotoxin-S6b sequence was synthesized. Its contractile activity was found to be decreased markedly when compared with that of the parent SRTb. In contrast, the extension by the Lys-Arg dipeptide was found to increase the formation of the native disulfide isomer (82/18 versus 96/4) when the reaction was carried out in the presence of redox reagents. The solution structure of KR-SRTb was determined by NMR as a function of pH. In the carboxylic acid state, the structure consists of the cystine-stabilized alpha-helical motif, with the alpha-helical part spanning residues 9-15, and of an unstructured C-terminal tail. In the carboxylate state, the structure is characterized by a salt-bridge between Arg(-1) and Asp8, which we identified previously in the [Lys(-2)-Arg(-1)]-endothelin-1 peptide (KR-ET-1). The fact that this salt-bridge is commonly observed in KR-SRTb and KR-ET-1, despite the 33% sequence difference between the corresponding parental peptides, highlights the remarkable adaptability of the Lys-Arg extension for the formation of a special salt-bridge. As a consequence, this salt-bridge, which does not depend on either the 4-7 sequence of the loop or the C-terminal sequence, appears to be particularly well suited to improve the stability of the cystine-stabilized alpha-helical motif. Therefore, because of its high yield in the native disulfide arrangement and its high permissiveness for sequence mutation in the 4-7 loop, such a stabilized cystine-stabilized alpha-helical motif could be a valuable scaffold for the presentation of a library of constrained short peptides.

Amino Acid Sequence↗
PubMed1999

The influence of non-paretic leg movement on muscle action in the paretic leg of hemiplegic patients.

The aim of this investigation was to study the effect of non-involved-side exercise on the involved (paretic) leg-muscle of patients with stroke. Each of the ten adults studied attempted to perform, while seated, a predetermined sequence of the following actions : (1) a voluntary knee extension on the involved side; (2) a maximal, isometric knee-flexion on the non-involved side; (3) a maximal, isometric knee-flexion on the non-involved side with counter-resistance (in front of the ankle joint) on the involved side. The root-mean-square voltage was measured across the rectus femoris, the medial hamstring, the tibialis anterior, and the medial gastrocnemius muscles (on the involved side) with surface electrodes. The root-mean-square voltages of the involved-side rectus femoris and the tibialis anterior muscles were found to increase substantially during non-involved-side knee flexion relative to that detected for voluntary knee extension on the involved side. The voltage of the rectus femoris muscle increased substantially also when counter-resistance was present. There was no similar substantial increase of muscular activity, in the medial hamstring and medial gastrocnemius, induced by contralateral isometric knee-flexion. This study suggests that, among patients with severe hemiplegia, isometric knee flexion in the non-involved side may be useful for facilitating the paretic rectus femoris and tibialis anterior muscular activities.

Aged↗
PubMed1998

Identification of human beta-defensin-2 in respiratory tract and plasma and its increase in bacterial pneumonia.

Human beta-defensin-2 (hBD-2), a novel antimicrobial peptide, was originally isolated from human skin. We found that synthetic hBD-2 has high bactericidal activity against Escherichia coli under conditions nearly the same as in human bronchial airway surface liquid. We prepared an antiserum against hBD-2 and established a highly sensitive radioimmunoassay (RIA). Reverse-phase high-performance liquid chromatography coupled with the RIA showed that hBD-2 in patients with human lung, bronchoalveolar lavage flid, and plasma. The plasma concentration of hBD-2 in patients with bacterial pneumonia was 32.1 +/- 3.7 fmol/ml (mean +/- SE), 3.9-fold that of normal individuals. By reverse transcription-polymerase chain reaction, the hBD-2 gene transcript was detected in the respiratory epithelial surface of human lung. Human beta-defensin-2 seems to function in airway mucosal defense. Our findings provide a clue to elucidate its pathophysiological significance in respiratory infection.

Adult↗
PubMed1998

Relationship between nerve and muscle fiber conduction velocities of the same motor unit in man.

To test the hypothesis that the nerve fiber conduction velocity of a motor unit is correlated with the muscle fiber conduction velocity of the unit, the collision technique was used to discriminate the motor unit action potentials elicited by stimulation of a group of nerve fibers with known conduction velocity. Muscle fiber conduction velocity was determined from the propagating action potentials of the unit recorded by a surface electrode array. A weak but significantly positive correlation was found between nerve and muscle fiber conduction velocities in the thenar muscle of human subjects. The results indicate that the size principle that governs the relation between nerve and muscle fiber size is a fairly weak principle with occasional exceptions.

Action Potentials↗
PubMed1998

Formation of native disulfide bonds in endothelin-1. Structural evidence for the involvement of a highly specific salt bridge between the prosequence and the endothelin-1 sequence.

The [Lys-Arg]-endothelin-1 analogue (KR-ET-1) yields almost selectively the native disulfide pattern (96%), in contrast to endothelin-1 (ET-1) that gives at least 25% of the non-native disulfide pattern. We have previously shown that the carboxylate-state structure of KR-ET-1 is more constrained and stabilized by a salt bridge between Arg(-1) and the Asp8 or Glu10 side chain [Aumelas et al. (1995) Biochemistry 34, 4546-4561]. To identify this salt bridge and its potential involvement in the disulfide bond formation, [E10Q], [D18N], and [D8N] carboxamide analogues were studied, which led to the unambiguous identification of the Arg(-1)-Asp8 salt bridge. Furthermore, while [E10Q] and [D18N] analogues gave a high yield of the native isomer (>/=90%), the [D8N] analogue afforded a ratio of the two isomers close to that observed for ET-1 (68%) [Kubo et al. (1997) Lett. Pept. Sci. 4, 185-192]. Assuming that the formation of disulfide bonds occurs in a thermodynamically controlled step, we have hypothesized that the Arg(-1)-Asp8 salt bridge and concomitant interactions could be responsible for the increase in yield of the native isomer of KR-ET-1. In the present work, we describe the structural studies of the carboxamide analogues and of the minor non-native KR-ET-1 isomer. On the basis of 1H NMR and CD spectra as a function of pH, [E10Q] and [D18N] analogues display a conformational change similar to that of the parent peptide, whereas the structure of the [D8N] analogue is unchanged. For the non-native isomer, we measured a lower helical content than for the native isomer and observed a marked difference in the orientation of the KRCSC backbone. In addition, no salt bridge was experimentally observed. Altogether, these results allow us to hypothesize that the salt bridge between two highly conserved residues, one belonging to the prosequence [Arg(-1)] and the other to the mature sequence [Asp8], is involved in the formation of the native disulfide isomer of ET-1. The involvement of the prosequence in the formation of the native disulfide isomer strongly suggests that, in the maturation pathway of ET-1, cleavage of the Arg52-Cys53 amide bond occurs after native disulfide bond formation.

Amino Acid Sequence↗
PubMed1998

The intermediate form of glycine-extended adrenomedullin is the major circulating molecular form in human plasma.

Adrenomedullin (AM), a potent vasodilator peptide, is processed from its AM precursor as glycine-extended AM (AM-gly), an intermediate form of AM. Subsequently, mature AM is converted from AM-gly by enzymatic amidation. Using two kinds of radioimmunoassay which recognize the entire AM molecule (E-AM-RIA) and C-terminal amide structure (C-AM-RIA), human plasma AM immunoreactivity was chromatographically characterized. In analyses of gel filtration and reverse phase high-performance liquid chromatography, most of the AM immunoreactivity measured by E-AM-RIA was eluted at a position identical to where mature AM and AM-gly emerged and was not recognized by C-AM-RIA. These data show that immunoreactive AM measured by E-AM-RIA is not amidated. When amidated by peptidylglycine alpha-amidating enzyme, the immunoreactive AM was converted to a form that can be detected by C-AM-RIA. These results indicate that most of the total AM immunoreactivity measured by E-AM-RIA represents immunoreactivity of AM-gly and that the concentration of immunoreactive mature AM in plasma is much lower than that of AM-gly. In practice, plasma concentration of AM-gly and mature AM in healthy volunteers was 2.7 +/- 0.18 fmol/ml and 0.48 +/- 0.05 fmol/ml, respectively. Furthermore, plasma concentration of AM-gly and total AM was significantly elevated in patients with hypertension compared to normotensive control. The present data indicate that most of circulating plasma AM immunoreactivity is occupied by AM-gly, an intermediate form of AM, which may reflect the process of production of AM in tissues.

Adrenomedullin↗
PubMed1998

Topological isomers of human uroguanylin: interconversion between biologically active and inactive isomers.

The solution structures of the two compounds of human uroguanylin (I and II), which were generated during disulfide bond forming reaction, were found to be topological isomers by 1H-nuclear magnetic resonance spectroscopy. These isomers are interconvertible in aqueous media at rates which vary with the pH and temperature of the solution. Because compound I is active in the cGMP producing assay, but compound II is not, this interconversion may be useful for evaluating the activity of human uroguanylin both in vivo and in vitro.

Amino Acid Sequence↗
PubMed1998

Effects of dantrolene sodium on fibrillation potentials in denervated rat muscles.

To examine whether a decrease in cytosolic Ca2+ affects fibrillation potentials, we studied effects of dantolene on these potentials in denervated rat muscle. Administered intraperitoneally, dantrolene sodium (12-22 mg/kg) abolished fibrillation potentials and subthreshold oscillating potentials over 2.5-6 h without affecting excitability of the muscle to electrical stimulation. Fibrillation potentials reappeared 36-96 h after administration of dantrolene. We suggest that cytosolic Ca2+ has a specific role in generating fibrillations.

Animals↗
PubMed1998

Tissue distribution, cellular source, and structural analysis of rat immunoreactive uroguanylin.

Uroguanylin, a member of the guanylin peptide family, acts on guanylyl cyclase C (GC-C) to regulate intestinal and renal fluid and electrolyte transport through the second messenger, cGMP. Using an antiserum raised against synthetic rat uroguanylin, we established an RIA and identified three endogenous molecular forms in the intestine and kidney: a 15-amino acid uroguanylin, an 18-amino acid uroguanylin that is a monobasic processing product, and a 9.4-kDa prouroguanylin. Prouroguanylin is the major molecular form in these two tissues, whereas only 15-amino-acid uroguanylin is present in the urine. Rat uroguanylin is most abundant in the proximal small intestine, its content decreasing toward the colon. Uroguanylin is present immunohistochemically in the endocrine cells in the intestine and stomach, B cells in the pancreatic islets, and tubular epithelial cells in the kidney. Uroguanylin has a widespread tissue distribution and is located in cells that function in an endocrine, paracrine, and/or luminocrine (luminal secretion) fashion. Uroguanylin may have physiological functions other than the regulation of fluid and electrolyte transport in the intestine and kidney.

Amino Acid Sequence↗