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Biomedical subjects

S Yabuki

Publications and source records attributed to S Yabuki.

At least 19 recordsLinked to original sources
PubMed1998

Acute effects of nucleus pulposus on blood flow and endoneurial fluid pressure in rat dorsal root ganglia.

STUDY DESIGN: An experimental study to elucidate the initial factors in the pathogenesis of lumbar pain caused by disc herniation. OBJECTIVE: To evaluate the effects of autologous nucleus pulposus on blood flow and endoneurial fluid pressure in dorsal root ganglia. SUMMARY OF BACKGROUND DATA: Human sciatica is known to be associated with compression of lumbar nerve roots and dorsal root ganglia by herniated intervertebral discs. Recently, it has been shown that application of nucleus pulposus to nerve roots induces injury and pain-related behavior in experimental animals. In this study, the authors hypothesized that nucleus pulposus applied to a nerve root would cause increased intraneural edema and reduced blood flow in the corresponding dorsal root ganglia. Studies in peripheral nerves have shown that these initial pathophysiologic disturbances initiate complex events that exacerbate nerve injury and cause pain. METHODS: A total of 29 adult female Sprague-Dawley rats weighing 200 to 250 g had their left L5 nerve roots and associated dorsal root ganglia exposed. Autologous nucleus pulposus was harvested from the tail and applied to the L5 nerve root just proximally to the dorsal root ganglia (nucleus pulposus group). For control, the same volume of muscle was harvested from the surgical area in the back and applied similarly to the neural tissue (control group). Blood flow was continuously monitored using a laser Doppler flow probe for 3 hours (n = 10) or 4 hours (n = 8) in animals with indwelling cannulas for measurement of systemic arterial pressure. Endoneurial fluid pressures were recorded with a servonull micropipette system using glass micropipettes with tip diameters of 4 microns. Endoneurial fluid pressure in the dorsal root ganglia was measured before and 3 hours after application of nucleus pulposus (n = 7) or muscle (n = 4). After measurement of blood flow and endoneurial fluid pressure, the nerve root and dorsal root ganglia were processed for histology and evaluated by light microscope. RESULTS: Blood flow in the nucleus pulposus group was reduced by 10% to 20% from the initial value after 3 to 4 hours. This reduction was statistically significant compared with that of the control group (P < 0.01). Endoneurial fluid pressure was initially 2.6 +/- 1.2 cm H2O in the nucleus pulposus group, and 2.1 +/- 0.6 cm H2O in the control group. Three hours after application, endoneurial fluid pressure was 7.5 +/- 4.6 in the nucleus pulposus group (P > 0.05), and 2.0 +/- 0.8 in the control group (P > 0.05). Edema was the principal pathologic finding seen consistently in the nerve roots and in many of the associated dorsal root ganglia from animals treated with nucleus pulposus. CONCLUSION: Application of nucleus pulposus to nerve root increased endoneurial fluid pressure and decreased blood flow in the dorsal root ganglia. This study's acute observations in the dorsal root ganglia may thus help to explain why disc herniations without compression of neural tissue are sometimes painful because similar pathologic findings are observed after only nucleus pulposus application to the nerve root. The authors further suggest that exposure of nerve roots to nucleus pulposus may establish a "compartment syndrome" in the dorsal root ganglia.

Animals↗
PubMed1998

Effects of lidocaine on nucleus pulposus-induced nerve root injury. A neurophysiologic and histologic study of the pig cauda equina.

STUDY DESIGN: Application of autologous nucleus pulposus on nerve roots and treatment with local application of lidocaine in the pig. OBJECTIVES: Studies of the effects of lidocaine on nucleus pulposus-exposed nerve roots. SUMMARY OF BACKGROUND DATA: Nerve root infiltration may improve radicular symptoms beyond the pharmacologic duration of local anesthetics, but the mechanisms for this effect are not known. METHODS: Nucleus pulposus was harvested from a lumbar disc and placed onto the sacrococcygeal cauda equina in pigs. In Series 1, early lidocaine treatment of nucleus pulposus-induced nerve root injury, pigs received 2% lidocaine (n = 5) or saline (n = 5) before and after surgery. Nerve conduction velocity and histologic appearance were studied after 3 days. In Series 2, delayed lidocaine treatment of nucleus pulposus-induced nerve root injury, after 7 days 2% lidocaine was administered epidurally to nucleus pulposus-exposed (n = 4) and -nonexposed (n = 4) nerve roots. Nerve conduction velocity, muscle action potentials, and histologic appearance were assessed. RESULTS: In Series 1, early treatment with lidocaine limited the reduction in nerve conduction velocity. The epidural inflammation was less in lidocaine treated animals. In Series 2, nerve conduction velocity was lower in nucleus pulposus-exposed animals than in nonexposed animals. The initial reduction of nerve conduction velocity and muscle action potential was similar between the groups, but the recovery of muscle action potential was slower and less complete in nucleus pulposus-exposed nerve roots. There was minimal histologic nerve injury in both series and in both protocols. CONCLUSIONS: Early treatment with lidocaine may reduce nucleus pulposus-induced nerve root injury. Lidocaine induced a delayed recovery in nerve roots exposed to nucleus pulposus. Further studies are needed to clarify the therapeutic effects of nerve root infiltration and the pathophysiology of nucleus pulposus-induced nerve root injury.

Anesthetics, Local↗
PubMed1998

High-throughput flow-injection analysis of glucose and glutamate in food and biological samples by using enzyme/polyion complex-bilayer membrane-based electrodes as the detectors.

The concentration of glucose was determined by a combination of flow injection analysis (FIA) with amperometric enzyme sensor detection. The enzyme sensor was prepared by immobilizing glucose oxidase on an electrode coated with a polyion complex layer consisting of poly-L-lysine and poly(4-styrenesulfonate). The inner, polyion complex layer was useful for preventing electrochemical interferents (e.g., L-ascorbic acid, uric acid and acetaminophen) from reaching the electrode surface, which was effective for reducing the interferential responses upon the injections of biological and food samples. The sensor-based system could be used for the determination of glucose from 10 microM to 3 mM with the sampling rate of 180 h-1, and was stable for more than 2 months. An FIA system for determining L-glutamic acid (3 microM-0.5 mM) was also prepared by using an enzyme electrode based on a glutamate oxidase/polyion complex-bilayer as the detector.

Biosensing Techniques↗
PubMed1998

[Creutzfeldt-Jakob disease associated with ocular dipping--a case report].

We presented a case of Creutzfeldt-Jakob disease (CJD) associated with ocular dipping (OD). A 65-year-old woman was hospitalized with two months history of progressive ataxia and mental deterioration. On admission, she was bed-ridden and stuporous with rigidity of the four limbs. Her both eyes were noted to deviate downward slowly from midpossition, taking 1 to 3 seconds to reach the nadir and rapidly returned to midpossition. It was felt that these abnormal eye movements are compatible with OD. Findings of EOG were compatible with that of typical OD. Electroencephalogram obtained a few months later revealed periodic synchronous discharge. Magnetic resonance imaging of the brain which had demonstrated mild cerebral atrophy in the beginning subsequently revealed full-brown cerebral atrophy. Hence, she was diagnosed of having CJD. There has been no report of CJD associated with OD. The OD was observed to last as long as 110 days. When the above described abnormal eye movements were noted, there was no signs indicative of brain stem dysfunction present. Therefore, we feel that the present case suggest that a diffuse cerebral dysfunction involving the cerebral cortex and basal ganglia may underlie in the development of OD.

Aged↗
PubMed1998

[Recovery from out-of-hospital cardiac arrest after mild hypothermia: report of two cases].

We report two patients with out-of-hospital cardiac arrest who recovered after hypothermia therapy. A 25-year-old man and a 16-year-old boy were transferred to our hospital after cardiopulmonary arrest due to idiopathic ventricular fibrillation and hypertrophic cardiomyopathy, respectively. We carried out hypothermia therapy using cooling blankets, and the patients were maintained at 32-33 degrees C for 96 and 36 h, respectively. After slow rewarming, they regained consciousness and recovered. During hypothermia, hypokalemia and arrhythmia occurred. Their arrest times (no spontaneous circulation and no CPR) were 10 min and 8 min, and CPR times (no spontaneous circulation while CPR was being performed) were 24 min and 20 min, respectively. In cases where the duration of ischemia is prolonged, the prognosis is expected to be poor. Therefore, we believe that hypothermia therapy is beneficial for such patients.

Adolescent↗
PubMed1998

[A case of measles encephaloneuropathy in a pregnant women].

We reported a patient with measles encephaloneuropathy. A 26-year-old woman in her 15th week of gestation became febrile and developed cutaneous eruption typical of measles on July 1 1997. Five days after appearance of the rash, fetal death was identified and the fetus was removed. Following the operation, she became comatous. Neurological examination revealed neck stiffness, flaccid paralysis of the four limbs, and decreased sweating in the lower limbs. CSF protein was 143 mg/dl with cell count of 1365/mm3. Myelin basic protein in CSF was positive. High titers of antimeasles antibodies were found in the serum and the cerebrospinal fluid. EEG revealed a predominance of slow waves. In MRI obtained earlier in her illness, high signal intensity areas were noted to spread in the brain stem and external capsule on T2-weighted images. However, T1-weighted image was unremarkable. Serial electrophysiological studies suggested demyelination of the motor nerves. With combination of methylprednisolone and immunoglobulin therapy, she made a remarkable recovery without any neurologic sequelae. We believe that the measles encephalitis in our patient is predominantly demyelinating due to an immunologic reaction in a pathophysiological aspect. We should pay attention to coincident poly-radiculoneuropathy in the early stage of measles encephalopathy.

Adult↗
PubMed1997

The effects of normal, frozen, and hyaluronidase-digested nucleus pulposus on nerve root structure and function.

STUDY DESIGN: Autologous nucleus pulposus was modified and applied to the cauda equina in pigs. Histology and neurophysiology were assessed after 7 days. OBJECTIVES: To assess if alterations of the nucleus pulposus would change the degree and distribution of the nerve injury induced by autologous nucleus pulposus. SUMMARY OF BACKGROUND DATA: It was reported recently that nucleus pulposus may induce structural and functional changes in nerve roots after epidural application. The basic mechanisms causing these changes are not fully understood. METHODS: Nucleus pulposus was harvested from lumbar discs and submitted to either of three treatments; 37 C for 24 hours (n = 5), -20 C for 24 hours (n = 5), or digestion by hyaluronidase for 24 hours (n = 6). In two additional pigs, nucleus pulposus was applied just after harvest as a control to verify previous observations. After 7 days, nerve conduction velocity was recorded, and specimens were processed for blinded light microscopic assessment. RESULTS: When nucleus pulposus was applied just after harvest, or when it had been kept at 37 C or digested by hyaluronidase for 24 hours, there was a significant reduction in nerve conduction velocity similar to previous observations. When nucleus pulposus had been kept at -20 C for 24 hours, however, there was no reduction in conduction velocity. There were no apparent differences between the groups at the histologic assessment. Staining of the nucleus pulposus showed that the cells in the nucleus pulposus exposed to -20 C were lysed, whereas the cells in the nucleus pulposus treated by the two other methods were mainly unaffected. CONCLUSIONS: Because freezing of the nucleus pulposus probably kills the cells but does not affect other components, one may assume that the biologic effects induced by the nucleus pulposus may be related to its cell population.

Animals↗
PubMed1997

Voltammetric enzyme sensor for urea using mercaptohydroquinone-modified gold electrode as the base transducer.

A voltammetric urea-sensing electrode was prepared by combining a lipid-attached urease layer with a 2,5-dihydroxythiophenol-modified gold electrode. A self-assembled monolayer of dihydroxythiophenol was prepared on the gold surface by soaking the electrode into an ethanolic solution containing the modifier. A layer of the lipid-attached enzyme and that of acetyl cellulose overcoat were successively made on the dihydroxythiophenol-modified electrode by applying a dip-coating procedure. The addition of urea in a test solution (10 mM phosphate buffer, pH 7.0) brought about an increase of pH near the urease layer. The pH shift accompanied a negative shift of the anodic peak, which corresponded to the electro-oxidation of dihydroxyphenol moiety to form quinone, on the linear sweep voltammograms for the urease/dihydroxythiophenol electrode. The concentration of urea (0.2-5 mM) could be determined by measuring the electrode current at -0.05 V versus Ag/AgCl from the voltammogram. The electrode was applied to the determination of urea in human urine; the measurement of electrode current at such a low potential provided the urea determination without any electrochemical interference from L-ascorbic acid and uric acid.

Biosensing Techniques↗
PubMed1996

Incision of the anulus fibrosus induces nerve root morphologic, vascular, and functional changes. An experimental study.

STUDY DESIGN: The effects on nerve root structure, vasculature, and function after incision of the adjacent disc was studied in a dog model. OBJECTIVES: To see if only incision of the disc per se is sufficient for inducing similar changes. SUMMARY OF BACKGROUND DATA: It is well known that nucleus pulposus will induce nerve root structural and functional changes in experimental situations. In these previous studies, relatively large amounts of nucleus pulposus were applied. METHODS: The left L7 nerve root was exposed and mobilized in 10 dogs. In five dogs, the adjacent L6-L7 disc was incised, and in five other dogs, the disc was not incised. After 7 days, nerve conduction velocity was recorded, and specimens were obtained for histologic evaluation. RESULTS: The nerve conduction velocity was significantly lower in the incision group (13 +/- 14 m/sec) compared with the nonincision group (73 +/- 5 m/sec). Structural changes of the axons were more pronounced in the incision group, however, the degree and distribution was too limited to fully account for the neurophysiologic reactions observed. There aims were obvious signs of capillary stasis with an increased number and diameter of the intraneural capillaries in the incision group. CONCLUSIONS: The present study indicated that incision of the anulus fibrosus is sufficient to induce significant morphologic and functional changes and that vascular mechanisms may be of importance for the observed changes. These experimental data suggest that leakage of nucleus pulposus material from anular tears, with injury to adjacent nerve roots, might be one pathophysiologic mechanism in patients with low back pain and sciatica but with no radiologic or surgical evidence of disc herniation.

Animals↗
PubMed1996

Back muscle injury after posterior lumbar spine surgery. Topographic evaluation of intramuscular pressure and blood flow in the porcine back muscle during surgery.

STUDY DESIGN: Intramuscular pressure and blood flow of the back muscles were evaluated topographically during posterior lumbar spine surgery. The topographic damage of the back muscle after surgery was studied. OBJECTIVE: To investigate the relationship between intramuscular pressure or blood flow during posterior lumbar surgery and the back muscle injury after surgery. SUMMARY OF BACKGROUND DATA: Latrogenic back muscle injury in an animal and human model has been reported previously. Changes of intramuscular pressure and blood flow during surgery might be related to the muscle injury. No previous study on this issue has been published. METHODS: The contact pressure between the retractor blade and muscle tissue was monitored in 10 pigs during posterior surgery of the lumbar spine. On one side, intramuscular pressure at 5, 10, and 20 mm lateral to the retractor and on the other side blood flow of the back muscle at 5 and 20 mm during surgery were measured. Histologic changes of the back muscle at 5, 10, and 20 mm to the midline were evaluated 3 hours after surgery. RESULTS: The contact pressure decreased exponentially with time. Intramuscular pressure 5 mm lateral to the retractor was 114 +/- 31 mm Hg and was significantly higher than at 10 mm and 20 mm. Blood flow markedly decreased during surgery and recovered incompletely after releasing the retractor at 5 mm and 20 mm lateral to the retractor. Blood flow at 5 mm was significantly lower than at 20 mm throughout surgery. The muscle damage 3 hours after surgery was more severe near the retractor blade. CONCLUSIONS: The back muscles were exposed to pathophysiologic condition by a retractor during posterior lumbar spine surgery. External compression by a retractor increases intramuscular pressure to levels that impede local muscle blood flow. The muscle degeneration after surgery could be explained by direct mechanical damage and by the increased intramuscular pressure of muscle tissue by the retractor.

Animals↗
PubMed1996

Positions of dorsal root ganglia in the cervical spine. An anatomic and clinical study.

STUDY DESIGN: The authors investigated the positions of dorsal root ganglia and the relation of the location to symptoms and to the effects of nerve root infiltration in the cervical spine anatomically and clinically. OBJECTIVES: To clarify normal variation of positions of dorsal root ganglia and the relation of the location of dorsal root ganglia to symptoms and to the effects of nerve root infiltration. SUMMARY OF BACKGROUND DATA: The dorsal root ganglia of the spinal nerve has attracted much attention as an important structure in the mechanisms of radicular symptoms in the lumbar spine. Although the position of the dorsal root ganglia in the lumbar spine has been classified recently, there are few reports regarding the dorsal root ganglia in the cervical spine. METHODS: The positions of dorsal root ganglia were divided into two types: proximally situated and distally situated. The positions of dorsal root ganglia in the anatomic and clinical cases were compared. The relation of the positions of dorsal root ganglia to symptoms and to the clinical effects of nerve root infiltration were analyzed. RESULTS: There was no statistically significant difference in positions of dorsal root ganglia in C6 nerve roots between anatomic and clinical cases. In addition, there was no relation between symptoms and the positions of dorsal root ganglia in clinical cases. However, there was a significant difference in positions of dorsal root ganglia in C7 nerve roots between anatomic and clinical cases. Nerve root infiltration was significantly more effective in the distally situated type of dorsal root ganglia. CONCLUSIONS: This study defined the normal variation of the positions of dorsal root ganglia. The results strongly suggest that some attention should be paid to the position of dorsal root ganglia in the diagnosis and treatment of cervical radiculopathy.

Adult↗
PubMed1996

Location of the non-heme iron center on the alpha subunit of photoreactive nitrile hydratase from Rhodococcus sp. N-771.

Nitrile hydratase (NHase) from Rhodococcus sp. N-771, which possesses a non-heme iron center binding nitric oxide (NO), is activated by light irradiation. To localize the iron center in the protein, we quantified Fe atoms and performed FTIR measurements of the isolated alpha and beta subunits. The native NHase and the isolated alpha subunit contained about 1.0 and 0.8 mol Fe per mol protein, respectively, whereas the beta subunit contained only a trace of Fe. An NO stretching band was observed at 1852 cm-1 in the FTIR spectrum of the alpha subunit, but not in that of the beta subunit. Upon light irradiation of the alpha subunit, the affinity of the Fe atom decreased and the NO band disappeared from the FTIR spectrum. These observations indicate that the non-heme iron center, which is responsible for the photoreaction, is present in the alpha subunit.

Amino Acid Sequence↗
PubMed1996

Safety and feasibility of continuous monitoring of coronary flow velocity in acute myocardial infarction by Doppler guide wire.

We investigated the safety and limitations of the Doppler guide wire for continuous monitoring of coronary flow velocity outside the catheterization laboratory in 17 patients with acute myocardial infarction. After direct angioplasty, patients were taken to the coronary care unit with the Doppler guide wire positioned within the artery. Flow velocity was continuously monitored. Heparin was titrated to an active clotting time > 200 seconds. Clinical outcome and angiographic analyses were evaluated. Flow velocity monitoring was conducted with an 88.2% success rate and lasted for 16 +/- 5 hours. Monitoring failed in 2 of the 4 right coronary artery cases. Small amounts of thrombus were seen to adhere to the Doppler guide wire at the end of monitoring. No complications were related to the procedure. No deterioration of angiographic findings was observed. This preliminary study confirmed the safety of the Doppler guide wire for continuous monitoring of coronary flow in patients with acute myocardial infarction.

Aged↗
PubMed1996

Distal coronary flow velocity immediately after direct angioplasty for acute myocardial infarction.

To evaluate coronary flow dynamics after direct angioplasty and to define the determinants of flow-velocity variables in the infarct artery, we measured coronary flow velocity in 36 infarct arteries and 64 normal coronary arteries by using a Doppler guide wire. Flow-velocity variables in the infarct arteries did not return to normal even after successful direct angioplasty, and phasic coronary flow in infarct arteries varied considerably. Normal phasic flow was calculated as the ratio of diastolic to systolic flow ratio (DSVR) of greater than or equal to mean DSVR - 1 SD in normal coronary arteries. Infarct-related arteries were divided into two groups: normal DSVR (n = 28) and low DSVR (n = 8). Reduced diastolic peak velocity with a relative preservation of systolic velocity contributed to a low DSVR flow. Angiographic slow flow and late recanalization were significantly related to low DSVR flow. Thus the extent of disturbed microcirculation can be evaluated by assessing phasic flow after direct angioplasty for acute infarction.

Aged↗
PubMed1996

Thermotropic phase behavior and stability of monosialoganglioside micelles in aqueous solution.

The thermotropic phase behavior of monosialoganglioside in a dilute aqueous dispersion at pH 6.8 was measured by using synchrotron radiation small-angle x-ray scattering and was analyzed by a shell-modeling method. Previous calorimetric studies on ganglioside systems have shown quite different thermotropic behaviors from other biological lipid systems, however, the details have still been ambiguous. Because of high statistical data and a shell-modeling analysis, we could elucidate the internal structural change of monosialoganglioside micelle induced by the elevation of temperature from 6 to 60 degrees C, that is, the shrinkage of the hydrophilic region and the slight expansion of the hydrophobic region occurring simultaneously, accompanying the elongation of the axial ratios of the ellipsoidal micelles. The model structures obtained explain the changes in the experimental scattering curves, the distance distribution functions, and the gyration radii. In addition we have also found an evident thermal hysteresis in the scattering curves and in the structural parameters. The present result suggests that the thickness of the hydrophilic region, namely, the conformation of oligosaccharide chains, is sensitive to a change of temperature.

Biophysical Phenomena↗
PubMed1996

Assessment of atrioventricular nodal electrophysiological characteristics after radiofrequency catheter ablation of the slow pathway in atrioventricular nodal reentrant tachycardia--3-month follow up.

Radiofrequency catheter ablation of the slow pathway is commonly used to treat atrioventricular (AV) nodal reentrant tachycardia. However, there has been little study of the follow-up assessment of AV nodal physiology. We compared AV nodal electrophysiological characteristics before, immediately after, and again 3 months after successful catheter ablation in 17 patients (mean age 50 +/- 16 years). Sinus cycle length, Wenckebach cycle length, A-H interval at a paced cycle length of 600 ms, effective refractory period and functional refractory period of the fast pathway were significantly changed immediately after catheter ablation, but had recovered 3 months after the procedure. There were no significant differences between the electrophysiological parameters immediately after catheter ablation and those 3 months after the procedure under the intravenous injection of atropine sulfate. We conclude that, due to changes in autonomic nervous tone, AV nodal electrophysiological characteristics are influenced immediately after catheter ablation of the slow pathway in AV nodal reentrant tachycardia.

Adult↗
PubMed1996

Effect of radiofrequency catheter ablation of the slow pathway on the atrioventricular node.

Although the effective refractory period (ERP) of the fast pathway is reported to be shortened after radiofrequency catheter ablation of the slow pathway in atrioventricular nodal reentrant tachycardia (AVNRT), whether the atrioventricular (AV) nodal physiology maintains the same condition over the long term is controversial. To assess the AV nodal physiology after catheter ablation of the slow pathway in AVNRT, the A-H interval and ERP of the fast pathway were measured before, immediately after and 3 months after catheter ablation in 12 patients. We compared these factors in 12 patients with left concealed accessory bypass tract to clarify the mechanism of the electrophysiological change in the AV node. Both the A-H interval and ERP of the fast pathway were significantly shortened from 111 +/- 18 to 96 +/- 17 ms and 365 +/- 68 to 261 +/- 52 ms immediately after catheter ablation (p < 0.01), and recovered to 128 +/- 44 and 372 +/- 80 ms 3 months after catheter ablation. There were no significant differences in the A-H interval of the fast pathway between the period immediately after and 3 months after catheter ablation following administration of atropine sulfate (99 +/- 52). There were no significant differences in the ERP of the fast pathway between the period immediately after and 3 months after catheter ablation following administration of atropine sulfate (248 +/- 33 ms). On the contrary, there were no significant changes in the A-H interval and ERP of the AV node at these two times in patients with Wolff-Parkinson-White (WPW) syndrome. The change in characteristics of AV nodal physiology was observed only immediately after catheter ablation in AVNRT, but not in WPW syndrome. The change in electrophysiology immediately after catheter ablation was similar to that following administration of atropine sulfate in AVNRT 3 months after catheter ablation. These findings suggest that catheter ablation does not cause a permanent change in AV nodal physiology and that the location of the ablated site plays an important role in AV nodal physiology.

Adult↗