Search PubMed⌕ Search

Biomedical subjects

S Konno

Publications and source records attributed to S Konno.

At least 91 records · Page 5Linked 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

Increased resistance to acute compression injury in chronically compressed spinal nerve roots. An experimental study.

STUDY DESIGN: Nerve conduction velocity was studied in the dog cauda equina subjected to chronic and, 1 week later, additional acute compression. OBJECTIVES: To model the situation of spinal stenosis by first inducing a controlled, chronic compression injury and then to add compression at various pressure levels to the already compressed cauda equina. SUMMARY OF BACKGROUND DATA: Previous models on nerve root and cauda equina compression have analyzed the effects of compression only on noninjured nerves. Clinically, the nerves that are compressed in spinal stenosis already are exposed to chronic compression. METHODS: The cauda equine in the lumbar spine of 10 dogs was first compressed by inflating a plastic balloon, which was placed in the spinal canal, to 10 mm Hg with a viscous substance or leaving it noninflated for control. After 1 week, a second plastic balloon, which was welded together with the first balloon, which had been located in the spinal canal for 1 week, was inflated to 50 or 100 mm Hg for 2 hours with 1.5 hour of recovery, and changes in the nerve conduction velocity were analyzed. Before inflation, baseline data, reflecting the effects of the chronic compression per se, were obtained. RESULTS: After 1 week, the nerve conduction velocity was significantly lower in the compressed cauda equina than in the control series, as an effect of the chronic compression. Additional compression demonstrated that the chronically compressed cauda equina was less susceptible to the compression-induced effects at 100 mm Hg compression. CONCLUSIONS: The data of the present study indicate that chronically compressed nerve roots acquire a tolerance to acute compression, which may indicate that there has been adaptation processes present in the compressed nerve tissue.

Acute Disease↗
PubMed1996

Cytokine concentrations in sputum of asthmatic patients.

To examine whether levels of inflammatory cytokines and eosinophil cationic protein (ECP) in the sputum reflect the severity of bronchial asthma, we measured their levels in the sputum of symptomatic and asymptomatic asthmatics. Interleukin (IL)-1 beta, IL-5, IL-6, IL-8, RANTES, tumor necrosis factor-alpha and ECP concentrations in the sputum of symptomatic patients were significantly higher than in asymptomatic subjects. These findings suggest that these inflammatory cytokines are involved in the exacerbation of asthma.

Adult↗
PubMed1996

Retinal blood flow increases following short-term aspirin usage in type I diabetics with no or minimal retinopathy.

In a double-masked, randomized, placebo-controlled, two-period crossover study, we measured the effect of aspirin on retinal blood flow in 8 type I diabetic patients, 5 with no observable retinopathy, and 3 with 1-10 observable microaneurysms and no other signs of retinopathy. Each patient ingested 1 capsule/day of either aspirin (650 mg) or placebo for 14 days. Following a 1-month washout period, the treatment was reversed. The bidirectional laser Doppler technique and monochromatic photography were used to measure the blood flow rate in a major temporal retinal artery in 1 eye of each patient at baseline and on the 14th day of each treatment period. Retinal blood flow increased following aspirin in 7 of the 8 patients. Using a standard crossover analysis we found a mean aspirin-placebo treatment difference of 21 +/- 17% (mean +/- 95% CI), which was statistically significant (p = 0.03). Retinal blood flow increased following aspirin by 44 +/- 10% (mean +/- SEM) in the 5 patients with no retinopathy (p = 0.04), but only by 8 +/- 10% (n.s.) in the 3 patients with minimal retinopathy.

Adult↗
PubMed1996

Retinal blood flow changes in type I diabetes. A long-term follow-up study.

PURPOSE: The authors previously reported that blood speeds in the retinal arteries were significantly lower in patients with type I diabetes than in controls without diabetes. The purpose of this long-term, follow-up study was to characterize the natural course of changes in blood speed and blood flow in these patients. METHODS: Twenty-four patients were followed up with serial annual measurements of the blood flow in a temporal retinal artery using the bidirectional laser Doppler technique and monochromatic photography. The follow-up period ranged from 2 to 6 years (mean, 3.8 years). Using standardized color fundus photography and fluorescein angiography, a retinopathy score was generated for each eye studied. Linear regression analysis was used to compute the slope of the change in retinal blood flow for each patient during the follow-up period. RESULTS: Retinal blood flow slopes were negative in 15 patients and positive in 9 patients. Multiple linear regression analysis showed that the retinal blood flow slopes were significantly related to the retinal blood flow measured at entry to the study and to the median duration of diabetes during the follow-up period (R2 = 0.56; P = 0.0002). There was a positive correlation between the retinal blood flow slopes and the median retinopathy score during the follow-up period (P = 0.47; P = 0.02). CONCLUSIONS: As duration of diabetes becomes longer and retinopathy becomes more severe, there is a transition from negative to positive retinal blood flow slopes. This bimodal relationship between the change in retinal blood flow and the duration of diabetes reflects the complex pathologic alterations that occur in the diabetic retina.

Adult↗
PubMed1996

[Role of the vitreous in central retinal vein occlusion].

To investigate the role of the vitreous in eyes with central retinal vein occlusion, especially in relation to neovascularization and macular edema, we conducted a retrospective chart review of the vitreous condition of 150 patients (150 eyes) with central retinal vein occlusion. Based on fluorescein angiography findings and color photographs, eyes with central retinal vein occlusion were classified as ischemic or nonischemic. In ischemic cases, retinal or optic disc neovascularization, or both, developed in eight (57%) of 14 eyes without complete posterior vitreous detachment at the final examination. The prevalence of neovascularization was significantly higher than in eyes with complete posterior vitreous detachment (0%, 0/43) at the final examination (p < 0.01). In nonischemic cases, the prevalence of no posterior vitreous detachment or partial posterior vitreous detachment with vitreomacular adhesion was significantly higher in eyes with macular edema (76%, 28/37) than in eyes without it (23%, 13/56) at the final examination (p < 0.01). Complete posterior vitreous detachment may protect against retinal or optic disc neovascularization in eyes with severe central retinal vein occlusion. Vitreomacular adhesion may cause persistent macular edema in eyes with mild central retinal vein occlusion.

Adult↗
PubMed1996

[Endothelin-1 levels in sputum and plasma of asthmatic patient after allergen provocation].

Recently, endothelin-1 (ET-1) has a potent of contractive effect to bronchial smooth muscle, and it suggests that ET-1 contributes to pathophysiology of bronchial asthma. To study the role of endothelin-1 (ET-1) in allergic asthma, we measured ET concentration in plasma and in sputum of nine allergic subjects following allergen provocation by using sandwich-enzyme immunoassay (EIA). ET-1 concentration in plasma were higher during IAR (2.31 +/- 0.24 pg/ml) (0.05 < p < 0.1) and LAR (2.55 +/- 0.27 pg/ml) (0.05 < p < 0.1) than prechallenge value (1.99 +/- 0.23 pg/ml) but there was no significant difference. On the other hand ET-1 concentration in sputum were significantly higher during IAR (14.75 +/- 2.77 pg/ml) (p < 0.05) and LAR (18.51 +/- 4.57 pg/ml) (p < 0.05) than prechallenge values (4.29 +/- 2.55 pg/ml). Thus these results suggest that ET-1 play a role of allergic bronchoconstraction (IAR and LAR) after allergen challenge.

Adolescent↗
PubMed1996

Differential diagnosis of macular breaks by microperimetry using the scanning laser ophthalmoscope.

To improve the differential diagnosis of macular breaks by microperimetry using the scanning laser ophthalmoscope (SLO), we studied 50 consecutive breaks detected by biomicroscopy and indirect ophthalmoscopy. The full-thickness macular break was easily diagnosed using only biomicroscopy and indirect ophthalmoscopy because the macular break had a cuff in 22 of the eyes. SLO microperimetry also showed an absolute scotoma within the macular break and a relative scotoma on the cuff in these 22 eyes. However, in the other 28 eyes it was impossible to distinguish between the full-thickness macular breaks and pseudo-macular breaks or lamellar macular breaks using only biomicroscopy and indirect ophthalmoscopy because of the absence of a cuff. However, SLO microperimetry differentiated full-thickness macular breaks from pseudomacular breaks or lamellar macular breaks in these 28 eyes. SLO microperimetry is indispensable for determining the prognosis of and the surgical indication requirements for idiopathic macular breaks.

Diagnosis, Differential↗
PubMed1996

Effects of OP-1206 (prostaglandin E1) on nerve-conduction velocity in the dog cauda equina subjected to acute experimental compression.

The effect of OP-1206, a prostaglandin E1 derivative, on cauda equina function was analyzed in a model for acute cauda equina compression in the dog. An inflatable balloon was placed under the lamina of the seventh lumbar vertebra in the dog and muscle action potential area (MAP area) and nerve-conduction velocity (NCV) were monitored during 2 h of compression and 1.5 h of recovery. OP-1206 was infused systemically at three concentrations. Only the highest concentration (30 ng/kg/min) of OP-1206 could prevent the reduction in NCV. However, this concentration had no similar effect on the MAP area. The data suggest the potential therapeutic use of prostaglandin E1 analogues for the future treatment of intermittent claudication.

Action Potentials↗
PubMed1996

Optic nerve head circulation after topical calcium channel blocker.

PURPOSE: Our purpose was to investigate the effects of the calcium channel blocker verapamil on intraocular pressure and blood circulation in the human optic nerve head. METHODS: The effects of three different concentrations of topical verapamil (0.063%, 0.125%, and 0.25%) on intraocular pressure and optic nerve head capillary blood speed were measured in 12 healthy normal subjects. In a randomized, double-masked design, each subject received one drop of either verapamil or placebo in one eye and the opposite treatment in the fellow eye. Anterior optic nerve circulation was assessed at baseline and 90 min after instillation of the drops using the laser Doppler technique. RESULTS: The intraocular pressure was significantly reduced compared with baseline in both verapamil- and placebo-treated eyes at each concentration. The reductions of intraocular pressure were greater in verapamil-treated eyes (12-17%) than in placebo-treated eyes (9-12%). No systemic effect on heart rate or blood pressure was detected after administration of topical verapamil. The capillary blood speed in the optic nerve head was increased in both verapamil- and placebo-treated eyes at each concentration, although the only statistically significant increases were with the 0.25% concentration. The mean +/- SEM increase compared with baseline at the 0.25% concentration was 10.4 +/- 3.6% in verapamil-treated eyes (p = 0.017), and 11.6 +/- 4.4% in placebo-treated eyes (p = 0.026). CONCLUSIONS: These results indicate that topical administration of verapamil lowers the intraocular pressure and increases the capillary blood speed in the optic nerve head in normal subjects. Changes measured in verapamil-treated eyes were also observed in placebo-treated eyes, indicating a crossover effect.

Administration, Topical↗
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

Intermittent cauda equina compression. An experimental study of the porcine cauda equina with analyses of nerve impulse conduction properties.

STUDY DESIGN: Neurophysiologic reactions of cauda equina nerve roots to intermittently applied compression were assessed for two different modes of compression using a porcine model. OBJECTIVE: To assess the neurophysiologic reactions of cauda equina nerve roots to intermittently applied compression. SUMMARY OF BACKGROUND DATA: A number of experimental studies have been presented recently regarding the reaction pattern of spinal nerve roots to compression. These studies have used a continuous pressure level. For studies of pathophysiologic mechanisms behind neurogenic claudication, however, it would be more relevant to study the effects of intermittently applied compression. METHODS: The cauda equina was exposed and compression was applied by two inflatable balloons. Two different modes of compression were used. Either the two balloons were inflated and deflated simultaneously (intermittent compression), or just the caudal balloon was inflated and deflated while the cranial balloon was kept continuously inflated (continuous/intermittent compression). The experimental series were: intermittent compression at 10 mm Hg (n = 5) and 50 mm Hg (n = 5), and continuous/intermittent compression at 10 mm Hg (n = 5) and 50 mm Hg (n = 5). For both modes of compression the pressure in the balloons with intermittent inflation was maintained for 10 minutes and deflated for 5 minutes. This procedure was repeated in 8 cycles for 2 hours. Muscle action potentials were recorded in the tail muscles. RESULTS: Compression at 10 mm Hg induced similar reductions of muscle action potentials for both compression modes. At 50 mm Hg, the effects were more pronounced at continuous/intermittent compression than at intermittent compression. The reduction of muscle action potentials was slightly more pronounced for 50 than for 10 mm Hg at intermittent compression. However, a statistically significant difference in the results was found only between 10 and 50 mm Hg at the continuous/intermittent compression mode. CONCLUSIONS: The established model allows investigation of the effects of intermittent cauda equina compression, which might be clinically more relevant than continuous compression regarding the pathophysiologic mechanisms behind neurogenic claudication.

Action Potentials↗
PubMed1995

A rapid transport route between the epidural space and the intraneural capillaries of the nerve roots.

STUDY DESIGN: The possibility of epidurally applied substances reaching the intraneural capillaries of the spinal nerve roots and cauda equina was assessed in the pig sacrococcygeal spine. METHODS: The presence of Evans blue-labelled albumin in intraneural capillaries after epidural application for 1, 10, or 30 minutes was studied with fluorescence microscopy. Ink angiography was used to determine whether there were any direct communicating vessels between the epidural vein plexus and the intraneural capillaries. RESULTS: Evans blue-labelled albumin was present in the intraneural capillaries 1 minute after epidural application. Microangiography demonstrated small venules that connected the epidural vein plexus and the intraneural capillaries. CONCLUSIONS: The results of this study demonstrated a rapid transport route between the epidural space and the intraneural capillaries. The results suggest that nucleus pulposus material, as well as epidurally applied substances, such as local anesthetic drugs or epidurally injected corticosteroids, may have a rapid, direct transport route to the axons of the spinal nerve roots. The demonstrated transport route also may be related to the mechanisms behind epidural anesthesia and spinal nerve root infiltration.

Albumins↗