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Biomedical subjects

S Yabuki

Publications and source records attributed to S Yabuki.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1995

A model for acute, chronic, and delayed graded compression of the dog cauda equina. Presentation of the gross, microscopic, and vascular anatomy of the dog cauda equina and accuracy in pressure transmission of the compression model.

STUDY DESIGN: A new model for controlled, graded compression of the dog cauda equina was developed using the dog lumbar spine. The model was defined regarding macroscopic, microscopic, and vascular anatomy and regarding accuracy in pressure transmission. OBJECTIVES: The study was performed to develop a model for controlled, graded compression that would allow for acute, chronic, and delayed compression. SUMMARY OF BACKGROUND DATA: There has been an increasing interest for the reactions of the spinal nerve roots to mechanical deformation. The previously used models have had limitations regarding the duration and the onset of the compression and possibilities for a controlled variation of the compression pressure on chronically compressed nerve roots. METHODS: Macroscopic examination, light microscopy, and ink injection of the vasculature was used to assess the anatomic characteristics of the nerve tissue and the vasculature of the cauda equina in the dog lower lumbar spine. The relation between known pressures in the compression balloon used to compress the cauda equina and the pressure in the central thecal sac was assessed by measuring the pressure in an artificial thecal sac with a pressure transducer. RESULTS. The neural and vascular anatomy was found to have a close resemblance to the human cauda equina. The pressure in the thecal sac was within 5% of the pressure in the compression balloon at various pressures between 0-200 mm Hg. CONCLUSION: The presented model provides a good pressure transmission to the dog cauda equina, which has an anatomy that closely resembles the human cauda equina. The model may be well suited for physiologic studies of cauda equina compression. A double-balloon system may provide unique opportunities to induce chronic compression and delayed compression, i.e., additional compression after a certain time of chronic compression to resemble the changes in pressure that are characteristic for neurogenic claudication.

Animals↗
PubMed1995

A model for acute, chronic, and delayed graded compression of the dog cauda equina. Neurophysiologic and histologic changes induced by acute, graded compression.

STUDY DESIGN: The results of acute compression on nerve function and morphology were analyzed in a recently developed model for graded cauda equina compression in the dog. OBJECTIVES: The model was developed to better mimic the clinical situation of cauda equina compression in association with spinal canal stenosis. SUMMARY OF BACKGROUND DATA: The compression of the cauda equina has been induced by metal clips, plastic bands, constrictors, and inflatable balloons. No model has used the intact spinal canal and induced compression by increasing the pressure per se in the canal. METHODS: An inflatable balloon with a diameter exceeding the diameter of the spinal canal was placed under the lamina of the L7 vertebra in the dog. The balloon was inflated to various pressures, and muscle action potential area and nerve conduction velocity were monitored during 2 hours of compression and 1.5 hours of recovery. Nerve root specimens were processed for light microscopic examination. RESULTS: There was a progressive reduction of muscle action potential area and nerve conduction velocity that was proportional to the applied pressure. Histologic evaluation revealed no nerve fiber damage but a slight intraneural edema after compression at 200 mg Hg. CONCLUSIONS: The presented model may provide reproducible results regarding neurophysiologic and morphologic effects after acute, graded compression of the dog cauda equina. Two additional conclusions can be made from this study. First, the area measurement of the MAP is probably well suited for recordings and analyses of changes in muscle action potentials. Second, the specific onset rate of this study, in relation to previous studies, indicates that there is a threshold for the compression onset rate for inducing additional nerve injury located in the interval 0.1-0.8 seconds. The results from the present study provides important baseline data for the continued studies on chronic and intermittent compression with the compression model.

Action Potentials↗
PubMed1995

Nerve root infiltration and sympathetic block. An experimental study of intraradicular blood flow.

STUDY DESIGN: The nerve root of L7 was exposed, and a clamp was applied to simulate radiculopathy. Intraradicular blood flow was measured at the takeoff point of the nerve root and at the distal to the dorsal root ganglion before and after nerve root infiltration with 2% lidocaine or physiological saline solution (control group), or sympathetic ganglion block with 2% lidocaine. OBJECTIVES: To investigate one of the mechanisms of the therapeutic effect of nerve root infiltration by assessing changes in intraradicular blood flow. SUMMARY OF BACKGROUND DATA: Increased intraradicular blood flow was noted both proximal and distal to the clamp after nerve root infiltration or sympathetic ganglion block with 2% lidocaine. No increase was seen after nerve root infiltration with saline solution. Macroscopic and microscopic examination showed that dye after nerve root infiltration did not spread beyond the clamped region to the proximal site. METHODS: Intraradicular blood flow was measured with a tissue blood flowmeter using the electrolytic hydrogen clearance method before and after nerve root infiltration with 2% lidocaine or physiologic saline solution (control group), or sympathetic ganglion block with 2% lidocaine. RESULTS: Increased intraradicular blood flow was noted both proximal and distal to the clamp after nerve root infiltration or sympathetic ganglion block with 2% lidocaine. No increase was seen after nerve root infiltration with saline solution. CONCLUSIONS: An increase in intraradicular blood flow is related to one of the mechanisms of the therapeutic effect of nerve root infiltration. This effect may be mediated by the sympathetic nervous system.

Animals↗
PubMed1995

Modifications to a carbon paste glucose-sensing enzyme electrode and a reduction in the electrochemical interference from L-ascorbate.

A glucose-sensing enzyme electrode was prepared by incorporating polyethylene glycol-modified glucose oxidase, horseradish peroxidase and 1,1'-dimethylferrocene into a carbon paste. The modification of glucose oxidase with polyethylene glycol was effective for increasing the enzyme activity in the carbon paste owing to the enhanced affinity of the polyethylene glycolmodified enzyme for the hydrophobic carbon paste matrix. In contrast, however, the enzyme activity of the polymer-modified peroxidase was lower than the unmodified peroxidase in the carbon paste matrix because of a severe loss of the enzyme activity during the modification with polyethylene glycol. Hence, the enzyme pair of polyethylene glycol-modified glucose oxidase and unmodified peroxidase was used for preparing the enzyme electrode. The reductive current response of the electrode to glucose was recorded at -0.2 V vs. Ag/AgCl. After the addition of glucose (100 microM), the current increased immediately and reached a plateau (delta = -0.12 microA) within 30 s. The current response was linear up to a glucose concentration of 500 microM and the detection limit was 20 microM (S/N = 5). Interference from ascorbate was very small: the current response to 1 mM glucose (-1.1 microA) was slightly reduced to -0.9 microA when 1 mM ascorbate was added to the glucose-containing solution. In biological and food samples, the concentration of ascorbate is generally quite low compared with the glucose concentration. The interference from ascorbate could actually be ignored for the purpose of determining glucose in soft drinks.

Ascorbic Acid↗
PubMed1995

[HTLV-I-associated neuropathy].

A 70-year-old man was admitted to our hospital because of a 15-year history of walking difficulty, disturbance of sensation in the palm for 2 years and hand tremor for 6 months. On admission, the scapulohumeral muscles showed fasciculation and atrophy. There was action tremor in the upper limb, and the proximal lower limb showed atrophy and weakness. Standing and walking were impossible. Deep tendon reflexes were decreased in lower limbs. Pathologic reflexes were not found. There was distal dominant sensory disturbance, and urination was difficult. Needle EMG showed a neurogenic pattern in 4 all limbs. MCV and F-latency were delayed. SCV in the median nerve and the amplitude in the sural nerve were decreased. Biopsy of the sural nerve revealed both axonal change and demyelination. Biopsy of the quadriceps femoris muscle showed neurogenic change with helper T-cell infiltration. Anti-HTLV-I antibody and ATL-like cells in both blood and CSF were positive. There were HTLV-I provirus DNA with a polyclonal pattern and the type of HLA as HAM. The HTLV-I infection was of the HAM type. As the present patient showed mainly neuropathy without pyramidal signs, was not considered to have HAM.

Aged↗