Biomedical subjects

J Ohashi

Publications and source records attributed to J Ohashi.

At least 19 recordsLinked to original sources

PubMed1995

Difference in changes of surface EMG during low-level static contraction between monopolar and bipolar lead.

The changes in surface electromyogram(EMG) during sustained contractions were compared between monopolar and bipolar lead. Ten subjects performed static elbow flexion at contraction levels of 10 and 40% of maximum voluntary contraction(MVC). Seven subjects performed static knee extension at contraction levels of 3, 8, and 15%MVC. Surface EMGs were recorded from the biceps brachii, vastus lateralis, rectus femoris and vastus medialis in monopolar and bipolar lead. Mean amplitude of EMG(AEMG) and frequency spectra of EMG were calculated. AEMG was larger in monopolar EMG than in bipolar EMG except 3 cases. AEMG changed more abruptly in bipolar EMG than in monopolar EMG. Relative power in low frequencies increased(slowing) during contractions in all cases of monopolar EMG. But bipolar EMG sometimes did not show slowing. Decrease of relative power in low frequencies(quickening) was sometimes seen during contractions. This quickening was not marked in monopolar EMG because of its large slowing. This study shows that obscure EMG slowing during a low-level fatiguing contraction is related to the lead methods. Led amplitude was compared between the lead methods using a simple model. The sphere that EMG reflects(pickup sphere) is larger in monopolar EMG than in bipolar EMG. This difference in the pickup sphere is thought not to be the main reason for the difference in the slowing.

Adult↗

PubMed1994

The relation between contact lens oxygen transmissibility and binding of Pseudomonas aeruginosa to the cornea after overnight wear.

PURPOSE: To assess adverse effects of contact lens-induced hypoxia on the rabbit cornea in vivo and determine the relation between binding of Pseudomonas aeruginosa and oxygen transmissibility for rigid and hydrogel lenses. METHODS: Six rigid lenses with Dk/Ltotal values between 0 and 97 x 10(-9) (cm/second) (ml O2/ml mmHg) and four hydrogel lenses (Dk/Ltotal 9, 20, 39, 51) were tested. All lenses had 14.0-mm diameters and a thickness (parallel) of 0.12 or 0.15 mm. Tear lactate dehydrogenase activity and tandem scanning confocal microscopy determinations were performed after the lens was worn for 24 hours. Binding of P. aeruginosa then was separately determined by the colony-forming unit method. Scanning electron microscopy was used to confirm in vivo tandem scanning confocal microscopy findings. RESULTS: Lens oxygen transmissibility determines binding of P. aeruginosa to the cornea after the lens is worn for 24 hours; epithelial damage produced by lenses of lower Dk/Ltotal appears to be the dominant biologic factor for P. aeruginosa binding and not lens rigidity. CONCLUSIONS: These results suggest that the risk of P. aeruginosa keratitis developing with overnight wear will be enhanced significantly for contact lenses with Dk/Ltotal values less than 50 x 10(-9) (cm/second) (ml O2/ml mmHg) (human equivalent oxygen percentage < or = 15%), and this risk will increase with further decreases in oxygen transmissibility. Because no hydrogel lenses approved by the Food and Drug Administration are available with oxygen transmission at this level, patients should be made aware of the increased risk of infectious keratitis associated with the overnight wear of current extended wear hydrogel lenses. Results of this study also demonstrate that quantitative clinical tandem scanning confocal microscopy imaging and tear lactate dehydrogenase activity measurements can provide prospective, noninvasive methods for assessing the ongoing interaction between contact lens and cornea in vivo.

Animals↗

PubMed1994

The effects of daily wear of rigid gas permeable contact lenses treated with contact lens care solutions containing preservatives on the rabbit cornea.

We evaluated the effects on the rabbit cornea of daily wear of rigid gas permeable (RGP) contact lenses treated with preserved care solutions by measuring concomitant tear lactate dehydrogenase (LDH) activity followed by in vivo tandem scanning confocal microscopy (TSCM). In vivo morphologic changes were confirmed by in vitro scanning electron microscopy (SEM). Two standard commercial RGP lens wetting and soaking solutions from the same manufacturer were tested: solution A with 0.004% benzalkonium chloride (BAK) and solution B with 0.003% chlorhexidine digluconate (CHX) and 0.002% thimerosal. Two experimental PBS-based wetting and soaking solutions were also tested: solution C with 0.005% BAK and 2% hydroxypropylmethylcellulose (HPMC) and solution D with 0.005% BAK without HPMC. Instillation of solution A without contact lens wear caused significant (P < 0.01) increases in desquamation of the superficial corneal epithelium and tear LDH activity compared with control eyes. After 3 weeks of RGP contact lens daily wear (8 hours/day), modified Draize scores of ocular surface lesions on the eyes wearing RGP lenses treated with solution A increased according to the duration of lens wear. Solution B did not produce significant change. With daily wear for 4 days (8 hours/day), RGP lenses treated with solution C and solution D produced increased corneal epithelium desquamation and an increase of LDH activity in tears. These effects were greater with HPMC (solution C) than without HPMC (solution D).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effects of contraction level on the changes of surface electromyogram during fatiguing static contractions.

Changes of the surface electromyogram (EMG) during a fatiguing static contraction were studied at contraction levels of 5, 10, 15, 20, 30, 40, and 50% of the maximum voluntary contraction (MVC). Seven subjects performed the static contractions of the elbow flexion and 6 subjects performed those of the planter flexion. Bipolar surface EMG was led from biceps brachii (BB) in the elbow flexion and from soleus in the planter flexion. Power spectra, mean amplitudes of EMG (AEMG) and durations of averaged waves classified by amplitude (AWCA) were calculated from EMG. The AWCA was calculated by averaging EMG waves separately for the 5 amplitude ranges of the trigger points. Relative power increased below 50 Hz in BB and 120 Hz in soleus during the contractions with time. Relative power in low frequencies (RPWL) increased with time even at the low contraction levels during one third part of the contraction from the start. But the RPWL decreased with time in some cases below and equal to 20% MVC. The increase in the RPWL was larger at 20-50% MVC than at 5-15% MVC contraction. The duration of AWCA increased with time at 30-50% MVC and decreased at 5-20% MVC. The duration, however, correlated positively with RPWL in part even at 5-20% MVC. The changes in the AWCA duration were attributed to the changes in conduction velocity (CV) of muscle action potential, since the relation between the changes in the duration by fatigue and the contraction levels was the same with the reported relation between changes in CV and the contraction levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Changes in relations between surface electromyogram and fatigue level by repeating fatiguing static contractions.

Changes in relations between surface electromyogram (EMG) and fatigue level estimated by fatigue sensation were studied during repeated fatiguing static contractions. Six male subjects performed elbow flexion of 13-15%MVC. Contractions were repeated 5 times (C1, C2, C3, C4, C5) with 5 min intervals of rests. The contractions continued until the onset of fatigue sensation such as obvious pain or considerable tiredness. Bipolar surface EMGs were recorded from 6 synergists of elbow flexors. Mean amplitude (AEMG) and relative power spectrum (RPW) of EMG were calculated. Partial correlation coefficients between time, AEMG, and RPW during each contraction were calculated. AEMG increased with time. EMG spectrum shifted towards lower frequencies with time. The correlations between AEMG and RPW were negative below 60Hz. AEMG and RPW were compared between C1 and C2-C5 being related with fatigue sensations. The changes in AEMG and EMG spectrum with the repeated contractions were similar to those with the development of fatigue. The increases in AEMG with the repeats were seen in most synergists in 4 subjects. Though EMG roughly reflected the fatigue during work, the changes of EMG were thought to include active adaptation to work.

Adult↗

PubMed1993

Effects of the direction and distance of horizontal arm movements on local muscular strain--a fundamental study on the teller workplace in bank.

This study was conducted to examine the relative differences in the muscular strain of the hand-arm-shoulder system in the repetitive arm movements which would directly depend on the layout of devices at teller counter. The subjects were five young male adults. The manual handling task was standardized and the repetition frequency was in self-pace. The arm movements were characterized by the different direction measured from the frontal plane of the subject between 0 degrees to 150 degrees combined with the distance measured from the acromion to the fixed points of 300, 500 and 700mm. The movements to all of the fourteen points tested were evaluated on both sides of the arms and shoulders by the integration of the EMG signals (IEMG) as to m. deltoid pars media and clavicularis, m. trapezius pars descendens, m. pectoralis major pars clavicularis and m. extensor carpi radialis brevis. It was found that IEMG of the deltoid muscles were sensitive to the direction and distance of the arm movements while the trapezius muscle showed the relative lower dependence on the direction. There were significant combined effects of the direction and distance in all muscles; i.e. effect of reach distance was greater with decreasing the arm angle, which was obvious at distance longer than 500mm in the arm abduction. When IEMG was divided by the task time in self-pace which increased in the arm abduction, the peak value was observed at the angle of 30 degrees. It was suggested that if the repetitive movement was required at the same frequency as at the angle of 30 degrees the position near the arm abduction (the angle of 0 degrees) would become the most expensive working direction.

Adult↗

PubMed1993

Effects of rigid gas permeable contact lens extended wear on rabbit cornea assessed by LDH activity, MDH activity, and albumin levels in tear fluid.

We used noninvasive biochemical techniques to study the effects on rabbit corneas of 7-day extended wear of rigid gas permeable (RGP) contact lenses of varying oxygen transmissibilities. Corneal effects were assessed through measurement of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities and albumin levels in tears. The RGP contact lenses used had Dk/Ltotal values ranging from 33 to 64 x 10(-9) (cm/sec) (mL O2/mL mmHg) and were of uniform 0.15 mm center thickness. Extended wear of high Dk (Dk/Ltotal = 34) and super high Dk (Dk/Ltotal = 56) lenses caused an increase in tear LDH activity from 1,190 U/L (before lens wear) to over 18,000 U/L during 7 days of continuous wear. These contact lenses also caused gradual increases in tear MDH activity from 431 U/L (before lens wear) to over 750 U/L after 7 days of continuous wear. Extended wear of the ultra high Dk lens (Dk/Ltotal = 64), however, caused no significant increase in LDH or MDH activity in tears. Tear albumin levels in all contact lens wearing eyes increased after 1 day of lens wear, then gradually recovered to normal values after 2 days of continuous wear. The changes in albumin levels did not correlate with Dk/Ltotal values of lenses worn.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Ocular↗

PubMed1993

Morphological and biochemical evaluation for rigid gas permeable contact lens extended wear on rabbit corneal epithelium.

We studied the effects of 24-hour wear of rigid gas permeable (RGP) contact lenses of varying oxygen transmissibilities on the rabbit cornea by measuring concomitant lactate dehydrogenase (LDH) activity in tears and by in vivo tandem scanning confocal microscopy (TSCM). We used a PMMA lens and rigid gas permeable (RGP) lenses that had Dk/L values ranging from 7 to 64 x 10(-9) (cm/sec) (mL O2/mL mmHg) and a uniform 0.15 mm thickness. After 6- and 24-hour contact lens wear, rabbit tear LDH activity increased according to the decrease in the Dk of RGP lenses. Tear LDH activity after 24 hours of lens wear was higher than after 6 hours. The observed increase in tear LDH activity was correlated with in vivo corneal epithelial morphology by tandem scanning confocal microscopy. The observed severity of desquamation and swelling of corneal epithelial cells was dependent upon the Dk/Ltotal of contact lenses worn, which directly related to the contact lens induced corneal hypoxia. Based on the results of this study, we conclude that: 1) a nap or accidental overnight wear of contact lenses with less than 20 x 10(-9) Dk/Ltotal could cause severe corneal epithelial damage; 2) the ultra high Dk lens appeared to alter the ocular surface least; and 3) TSCM accompanied with tear LDH assay is an objective, non-invasive in vivo method to assess the effect of contact lens wear on the ocular surface over time at the cellular level.

Animals↗

PubMed1992

Effect of contact-lens-induced hypoxia on lactate dehydrogenase activity and isozyme in rabbit cornea.

Lactate dehydrogenase (LDH) levels and subunit isozyme patterns in cornea were monitored in 36 albino rabbits wearing thick, rigid, gas-permeable contact lenses for periods of 24 h, 2 and 7 days, and 1 and 3 months. The oxygen transmissibility of the contact lens was 15.3 x 10(-9) (cm/s) (ml O2/ml mm Hg). The activity of LDH in corneal tissue decreased according to the duration of lens wear. The LDH isozyme patterns shifted with lens wear from LDH1,2,3 (heart type, aerobic) to LDH4,5 (skeletal muscle type, anaerobic). The cornea swelled 8.8% with overnight contact lens wear, with increased swelling (11-12%) after further continuous lens wear. After contact lens removal, however, the LDH activity and the isozyme pattern returned to normal, and the corneal thickness quickly returned to normal. Based on these observations, it is suggested that LDH in rabbit corneas was physiologically affected by lens-induced hypoxia, but these changes were reversible. These results might further suggest that tear LDH levels in the human contact lens wearer could provide an ongoing assessment of the tolerance of the lens by the ocular surface.

Animals↗

PubMed1992

Effects of increasing Dk with rigid contact lens extended wear on rabbit corneal epithelium using confocal microscopy.

The effects of 24-h wear of various Dk-rigid gas-permeable (RGP) contact lenses on the rabbit corneal epithelium were studied by in vivo tandem scanning confocal microscopy (TSCM), and confirmed by scanning electron microscopy (SEM). Lenses used were polymethylmethacrylate (PMMA) (Dk/L = 0), RGP experimental A lens (siloxanylmethacrylate-fluoromethacrylate-methylmethacrylate , 33), experimental B (siloxanylmethacrylate-fluoromethacrylate, 56), and experimental C (siloxanylstyrene-fluoromethacrylate copolymer, 64 x 10(-9)) (cm/s) (ml O2/ml mm Hg) with 0.15-mm thickness (Dk/L measured by polarograph including boundary layer effect). After 24-h PMMA lens wear, TSCM showed no superficial epithelial cells but only exposed, underlying wing cells. The cornea with experimental A showed partial superficial epithelial desquamation. With experimental B wear, slight superficial epithelial cell swelling and desquamation were observed on the surface of the cornea. No changes were observed for the eye with experimental C and control. The observed severity of desquamation of superficial epithelial cells was dependent on the oxygen transmissibility (Dk/L) of RGP lenses worn. All in vivo findings were confirmed by SEM observations. Based on the results of this study, we conclude that (a) although Dk/L = 56 lens B shows no residual overnight corneal swelling, surface damage is still produced; (b) Dk/L = 64 lens C is best for epithelium showing the same corneal images as control; and (c) TSCM is a good way to evaluate the contact lens safety and efficacy in vivo at the cellular level noninvasively.

Animals↗

PubMed1992

Fatigue sensation and surface electromyogram during sustained shoulder flexion with spontaneous alternations of working arm.

Sustained contractions were compared between with (AW) and without (NAW) spontaneous alternations of working arm to investigate the fatigue level at which the contraction is felt to be stopped. Subjects maintained an upper limb in the horizontally flexed position at 5%, 10%, 15% and 20% of maximum voluntary contraction strength (MVC). Contractions were continued until they felt exhausted or 45min. had passed. Fatigue level was evaluated with 4 levels of fatigue sensations and surface electromyogram (EMG) of the deltoid. Mean amplitude (AEMG) and relative power in 8-40Hz (RPLF) of EMG were calculated. The following results were obtained. Fatigue level was lower in AW than in NAW for the same amount of work done by one arm. As AEMG often decreased with time, fatigue was estimated by relating AEMG to RPLF. At 20% MVC in AW the alternation interval decreased and the muscle fatigued with repeated contractions though the fatigue level was not severe. Contraction was felt to be stopped when the first fatigue sensation occurred. But it was not necessary to stop the contraction until considerable tiredness or apparent pain occurred.

Adult↗

PubMed1992

A quantitative method for LDH, MDH and albumin levels in tears with ocular surface toxicity scored by Draize criteria in rabbit eyes.

We have established a quantitative method for evaluation of ocular surface lesions on the basis of lactate dehydrogenase (LDH) activity, malate dehydrogenase (MDH) activity, and albumin levels in rabbit tears. Lesions were produced with solutions of 0.005-0.02% benzalkonium chloride (BAK), 0.01-0.03% chlorhexidine digluconate (CHX), and 0.01-0.03% polyhexamethylene biguanide hydrochloride (PHMB), all of which are widely used in topical ophthalmic preparations. Two drops of test solution were instilled 15 times into rabbit eyes at 5 minute intervals. Sixty minutes after 0.02% BAK instillation, tear LDH activity increased from 1,840 U/L (without instillation) to 26,100 U/L, and concomitantly tear albumin levels rose from 0.11 mg/mL (without instillation) to 9.48 mg/mL. Instillation of 0.03% CHX and 0.03% PHMB caused smaller increases in LDH and MDH activity and albumin tear levels. LDH activity and albumin levels in tears were significantly correlated with the degree of total ocular surface lesions in both cornea and conjunctiva as observed by slit lamp biomicroscopy quantified using a modified Draize score. Based on the results of this study, we believe that LDH activity and albumin level in tears can be used as objective indicators for the quantitative evaluation of ocular surface lesions on both cornea and conjunctiva following application of topical ophthalmic preparations containing cytotoxic preservatives in animals and man.

Albumins↗

PubMed1992

Tear lactate dehydrogenase levels. A new method to assess effects of contact lens wear in man.

Lactate dehydrogenase (LDH) activity in tears was measured in 202 myopic rigid gas permeable (RGP) and 79 hydrogel human contact lens wearers and 48 normal controls by noninvasive microcapillary sampling. The oxygen permeabilities (Dk) of five selected RGP contact lenses ranged between 0 and 230 x 10(-11) (cm2/s) ml O2/ml mm Hg), and the water content (WC) of the hydrogel lenses was 38, 72, and 80%. When normal diurnal variation of tear LDH activity and tear sample volume (0.3-0.6 microliters) were carefully controlled, the tear LDH activity of RGP lens wearers in daily and extended wear correlated as an inverse function of Dk/L, with the highest enzyme activity observed in wearers of polymethylmethacrylate daily wear lenses (347.4 U/L). The tear LDH activity in Menicon EX (Dk 108) lens wearers was higher in the extended wear (192.7 U/L) than in the daily wear group (161.9 U/L). There was no significant difference in tear LDH activity between the Menicon SF-P (Dk 230) extended wear group (132.0 U/L) and controls (133.5 U/L). In the hydrogel lens daily wear group, tear LDH activity of Experimental 72 (WC 72%) and Experimental 80 (WC 80%) was higher than that of hydroxyethylmethacrylate (HEMA) despite having high Dk value. Experimental 80 extended wearers showed lower LDH activity in tears sampled between 0.3 and 0.6 microliters than that of HEMA wearers. These results suggest that sequential measurement of LDH levels in tears may offer a new and unique method for the assessment of the physiologic effects of contact lens wear on the ocular surface, and provide a new clinical paradigm for the interaction of the contact lens with the cornea.

Adolescent↗

PubMed1989

Sex differences in static muscular endurance.

The relationship between the force level of sustained isometric contraction and the time until two indices of muscular fatigue was compared for the right elbow flexors between 6 young women and 6 men. The strength of the maximal voluntary contraction (MVC) measured at the wrist with the elbow at right angle was significantly greater in men (267 +/- 35 N) than in women (163 +/- 23 N). Endurance tasks were performed at randomly assigned contraction levels of 5, 10, 15, 20, 30, 40, and 50% MVC. The relative force (F% MVC) or the absolute force (F N) versus the endurance time or the time of pain ("itai") appearance (T min) curves were fitted to the following equation: log T = a + b.log (F--k). The most fitted equations were determined for each individual and each sex group by the value in the coefficient of determination. When comparing the curves in terms of the relative force, the endurance time and pain appearance time were longer in women than in men, particularly at lower contraction levels. In terms of the absolute force, however, they were longer in men than in women, particularly at stronger contractions. At lower contraction levels, less than 70 N, some women were similar to some men in fatigability.

Adult↗

PubMed1987