Search PubMed⌕ Search

Biomedical subjects

K Muramatsu

Publications and source records attributed to K Muramatsu.

At least 19 recordsLinked to original sources
PubMed2001

Postoperative magnetic resonance imaging of lumbar disc herniation: comparison of microendoscopic discectomy and Love's method.

STUDY DESIGN: We performed a study to compare the magnetic resonance imaging findings up to 24 weeks after microendoscopic discectomy or surgery using Love's method in patients with lumbar disc herniation. OBJECTIVES: The objective was to determine whether or not microendoscopic discectomy was minimally invasive with respect to the nerve roots, cauda equina, and paravertebral muscles by comparing the postoperative magnetic resonance imaging findings in patients treated by microendoscopic discectomy and the conventional Love's method. SUMMARY OF BACKGROUND DATA: We introduced microendoscopic discectomy as a minimally invasive surgical procedure for lumbar disc herniation in September 1998 and have obtained good results. Microendoscopic discectomy is superior to the conventional Love's method in that it reduces postoperative pain, shortens the duration of hospitalization, and allows earlier resumption of normal activities. However, the effect of microendoscopic discectomy on the nerves and paravertebral muscles has not been evaluated objectively. METHODS: Enhancement of the nerve roots and paravertebral muscles, as well as the configuration of the cauda equina at the level of herniation, was assessed on axial magnetic resonance images obtained with contrast enhancement using gadolinium-diethylenetriamine penta-acetic acid before surgery and 1, 4, 8, 12, and 24 weeks after surgery in 25 patients who underwent microendoscopic discectomy and 15 patients who were treated using Love's method. RESULTS: Increased enhancement of the nerve roots was seen in 50.0% of the microendoscopic discectomy group and 46.2% of the Love group at 1 week after surgery. Enhancement of the paravertebral muscles at the surgical site tended to persist for longer in the microendoscopic discectomy group than in the Love group. However, muscle enhancement was widespread in some patients from the Love group. Abnormalities of the cauda equina attributed to surgical invasion were seen in 12.5% of the microscopic discectomy group and 15.4% of the Love group at 1 week after surgery. CONCLUSIONS: Microendoscopic discectomy had an effect on the nerve roots and cauda equina that was comparable with that of Love's method. The magnetic resonance images of the route of entry failed to show that microendoscopic discectomy is appreciably less invasive with respect to the paravertebral muscles.

Adult↗
PubMed2001

Vascular complication in free tissue transfer to the leg.

The lower-extremity free flap has a high incidence of vascular complication. A retrospective study of 70 free flap transplants in 70 patients (1987-2000) was conducted to investigate factors leading to vascular complication and free flap failure. The overall success rate was 92% (64 of 70 flaps); the incidence of vascular complications was 22% (16 of 70 flaps). Among 16 complicated flaps, 7 were transferred in severely crushed legs, and 4 were in multioperated legs attributable to chronic osteomyelitis. Venous thrombosis occurred in 12 flaps (86%). The success rate of the patients operated on at Yamaguchi University Hospital was higher (96%) than at other hospitals tested. The key factors contributing to improved outcome in free tissue transplantation in the leg were careful preoperative planning for highly traumatized legs and proper selection of the recipient vein and of the hospital at which immediate reexploration can be performed for vascular complicated flaps.

Adolescent↗
PubMed2001

Optical imaging reveals cation--Cl(-) cotransporter-mediated transient rapid decrease in intracellular Cl(-) concentration induced by oxygen--glucose deprivation in rat neocortical slices.

In brain slices from young (postnatal day (P) 10--15) rat somatosensory cortex, real-time neuronal intracellular Cl(-) concentration ([Cl(-)](i)) recordings were made by an optical technique measuring 6-methoxy-N-ethlquinolinium iodide (MEQ) fluorescence. Oxygen--glucose deprivation (in vitro model of ischemia) induced a long-lasting [Cl(-)](i) increase preceded by a rapid, transient [Cl(-)](i) decrease that could not be inhibited by blockers of Cl(-) pumps, Cl(-) channels, or Cl(-) antiporters, but was sensitive to cation-Cl(-) cotransporter inhibitors (bumetanide and furosemide). Use of low external Na(+) or high external K(+) revealed that the Na(+),K(+)-2Cl(-) cotransporter was inhibited by bumetanide and furosemide, whereas the K(+)-Cl(-) cotransporter was preferentially inhibited by furosemide under our experimental conditions. With a reduced inward driving force for Na(+) (reducing Na(+),K(+)-2Cl(-) cotransport), the transient [Cl(-)](i) decrease was only rarely induced by oxygen-glucose deprivation. In contrast, with a reduced outward driving force for K(+) (reducing K(+)-Cl(-) cotransport), the transient [Cl(-)](i) decrease still occurred. These results suggest that the transient [Cl(-)](i) decrease was primarily mediated by a rapid inhibition of the inwardly directed Na(+),K(+)-2Cl(-) cotransporter. Reverse transcriptase-polymerase chain reaction (RT-PCR) experiments suggested that the isoform involved is NKCC1. We hypothesize that the initial rapid Cl(-) efflux might effectively delay the irreversible Cl(-) influx that mediates neuronal injury.

Animals↗
PubMed2001

In vitro evaluation of the heparin-coated Gyro C1E3 blood pump.

The blood-contacting surface, mainly composed of polycarbonate, of the Gyro C1E3 pump was modified using plasma glow discharge to introduce a carboxyl functional group, coated with a base layer of polyethyleneimine as a linker, and coupled with heparin by multi-ionic binding to enhance blood compatibility. A relative surface content of 3.7% sulfur, which demonstrated heparin immobilization on the polycarbonate substrate, was observed on x-ray photoelectron spectroscopy, and a initial bioactivity of approximately 88.5 +/- 7.3 mIU/cm2 was obtained by the chromogenic method for antifactor Xa assay. Furthermore, in vitro observation of platelet and fibrin adherence using bovine blood under dynamic flow conditions for 6 h revealed that the multi-ionically heparinized Gyro C1E3 had significantly stronger antithrombogenecity than the noncoated original type which was evaluated as a good hemocompatible blood pump for clinical use. Not only the Gyro C1E3 but also the ionically heparin-coated Gyro pump are expected to be thromboresistant in clinical use.

Blood Coagulation↗
PubMed2001

The effect of heat-treated human bone morphogenetic protein on clinical implantation.

For the clinical usage of human-derived bones, it is necessary to treat bones to reduce the risk of contamination by microorganisms. Bone morphogenetic protein is vulnerable to chemicals, but shows resistance to thermal heat to 70 degrees C in a short time. In this experiment, crude human bone morphogenetic protein was extracted from heat-treated bones at 60 degrees C for 10 hours and from nonheated bones. Sodium dodecyl sulfate polyacrylamide gel electrophoresis for these specimens was done. Gelatin capsules containing 5 mg of crude human bone morphogenetic protein extracted from heated and nonheated bones were implanted into thigh muscle pouches of five mice. At 20 days after implantation, the heterotopic bone formation was compared by evaluating the radiographic and histologic analyses. The sodium dodecyl sulfate polyacrylamide gel electrophoresis pattern of the human bone morphogenetic proteins showed five main bands (16, 22, 28, 35, and 67 kDa) that were almost identical. Heterotopic bone formation observed on the radiograph was induced by crude human bone morphogenetic protein from heated bones in a manner similar to that used for nonheated bones. The results from this study show that heat-treated bone preserves osteoinduction.

Animals↗
PubMed2001

Monitoring of nonlinear respiratory elastance using a multiple linear regression analysis.

The elastic pressure/volume (P/V) curve obtained by the multiple linear regression (MLR) technique using a new model, was compared with the quasi-static P/V points obtained by the rapid airway occlusion technique. Seven infants were studied during mechanical ventilation using a pressure controlled mode. The resistive pressure was subtracted from airway opening pressure, thus determining the elastance related pressure, which was then plotted against the volume to make an MLR-elastance curve. Quasi-static P/V curves of the rapid occlusion technique were constructed by plotting the different inspiratory and expiratory volumes against the corresponding values of the quasi-static airway pressure. The calculated MLR-elastance curves closely fit the experimental quasi-static P/V points obtained by the occlusion technique. There were, however, some discrepancies due to the viscoelastic behaviour of the respiratory system. Although slightly altered by these discrepancies, the multiple linear regression-elastance curves did fit the observed quasi-static pressure/volume characteristics for use in clinical practice. The multiple linear regression technique may prove to be clinically useful by continuous monitoring of respiratory system mechanics during mechanical ventilation.

Airway Resistance↗
PubMed2001

Renin-angiotensin system is involved in the mechanism of increased serum asymmetric dimethylarginine in essential hypertension.

Endothelium-dependent/nitric oxide (NO)-mediated vasodilation is impaired in hypertensive individuals. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO synthase, is synthesized by many types of cells including vascular endothelial cells. The serum level of ADMA is elevated in patients with essential hypertension, but the mechanism for this increase is unknown. Therefore, the present study examined whether the renin-angiotensin system (RAS) is involved. Patients with essential hypertension [systolic blood pressure (BP) > 160 mmHg and/or diastolic BP > 95 mmHg] were randomized to an angiotensin-converting enzyme (ACE) inhibitor treatment group (perindopril, 4mg/day for 4 weeks, n = 7), an angiotensin II type 1 (AT1) receptor antagonist treatment group (losartan, 50 mg/day for 4 weeks, n = 7) or a beta-blocker treatment group (bisoprolol, 5 mg/day for 4 weeks, n = 7). Before and after the treatment, BP, serum concentration of ADMA and plasma concentration of von Willebrand factor (vWF, a biological marker of endothelial injury) were measured. Perindopril, losartan and bisoprolol decreased BP to a similar extent, and either perindopril or losartan, but not bisoprolol, significantly decreased serum ADMA and plasma vWF. These findings suggest that the RAS may contribute to the mechanism of increased serum ADMA as well as to the endothelial injury observed in hypertensive patients. The vasculoprotective actions of ACE inhibitors or AT1 receptor antagonists may be explained at least in part by amelioration of the endothelial injury through a decrease in the serum ADMA concentration.

Adrenergic beta-Antagonists↗
PubMed2001

[A case of hookworm infestation with dissociation values between FDP-E and FDP-D dimer].

We previously reported a five-year-old girl showing bleeding tendency and transient morphological and functional platelet abnormalities probably due to a hookworm, Necator Americanus, infestation. In this report, we describe the rarely accelerated fibrinogenolysis and/or fibrinolysis in this patient whose value of fibrinogen and/or fibrin degradation products(FDP) determined with an FDP-E assay was much higher than that determined with a D-dimer assay. Namely, on day-1 and day-13 of hospitalization, her D-dimer values were only 10 to 20% of the prospected values from FDP-E values. We speculated this phenomenon was induced by circulating protease(-like) agent(s) produced by hookworm, because the only slightly participation of plasmin and/or granulocyte elastase was evaluated by the determination of enzyme-inhibitor complexes. And the other possibility of fibrinogen degradation by blast- or tumor-associated protease was excluded by the clinical manifestations and primary disorders. In conclusion, we report a very rare case with the accelerated fibrinogenolysis and/or fibrinolysis in a patient with the hookworm infestation. We are interested in the mechanism that manifested the patient's bleeding tendency accompanied with morphological and functional platelet abnormalities.

Child, Preschool↗
PubMed2001

Characteristic features of the acetabular labrum in healthy children.

Radial magnetic resonance images of the acetabular labrum were obtained on 40 hips of healthy children. There were no right-left or male-female differences. In children aged 11 years or younger, the labrum on the antero-superior weightbearing portion was triangular in shape, and there was an insular-shaped or linear high-intensity area inside; on the mid-superior portion, the labrum appeared as a regular triangular, low-intensity area; and on the postero-superior portion, it was flat. In children aged 12 and 13 years, the shape of the labrum in each portion was similar to that of the younger children, but the high signal intensity area on the antero-superior portion appeared less frequently. The size of the labrum relative to the femoral head was greater in younger children.

Acetabulum↗
PubMed2000

Nitric oxide synthase activity and inhibition after neonatal hypoxia ischemia in the mouse brain.

Despite the emergence of therapies for hypoxic-ischemic injury to the mature nervous system, there have been no proven efficacious therapies for the developing nervous system. Recent studies have shown that pharmacological blockade of neuronal nitric oxide synthase (nNOS) activity can ameliorate damage after ischemia in the mature rodent. We have previously shown that elimination of nNOS neurons, either by targeted disruption of the gene or by pharmacological depletion with intraparenchymal quisqualate, can decrease injury after hypoxia-ischemia. Using a simpler pharmacological approach, we studied the efficacy of a systemically administered NOS inhibitor, 7-nitroindazole, a relatively selective inhibitor of nNOS activity. Using multiple doses and concentrations administered after the insult, we found that there was only a trend for protection with higher doses of the drug. A significant decrease in NOS activity was seen at 18 h and 5 days in the cortex, and at 2 h and 18 h in the hippocampus after the hypoxia-ischemia. nNOS expression decreased and remained depressed for at least 18 h after the insult. When nNOS expression was normalized to MAP2 expression, a decrease was seen at 18 h in the cortex and at 2 and 18 h in the hippocampus. These data suggest that further inhibition of NOS activity at early timepoints may not provide substantial benefit. At 5 days after the insult, however, NOS activity and normalized nNOS expression returned to baseline or higher in the hippocampus, the region showing the most damage. These data suggest that delayed administration of nNOS inhibitor after hypoxic-ischemic injury might be beneficial.

Animals↗
PubMed2000

Role of conventional and vascularized bone grafts in scaphoid nonunion with avascular necrosis: A canine experimental study.

The effectiveness of vascularized and conventional bone grafts in the treatment of carpal fracture nonunion with avascular necrosis was evaluated in 12 adult dogs. The proximal third of the radiocarpal bone was removed bilaterally and frozen in liquid nitrogen. Its replacement, leaving a 4-mm gap, simulated a scaphoid fracture nonunion with avascular necrosis. A dorsal radius inlay graft was placed across the gap. The graft was nonvascularized, or conventional on one side, and vascularized with a reverse-flow arteriovenous pedicle on the other. Following a healing period, quantitative assessment of bone blood flow, fracture healing, and bone remodeling was conducted. Seventy-three percent of the vascularized grafts and none of the conventional grafts healed. At 6 weeks, bone blood flow in the proximal pole was significantly higher on the side of the vascularized graft. Quantitative histomorphometry of the avascular proximal segment demonstrated significantly higher levels of fluorochrome-labeled osteoid- and osteoblast-covered trabecular surfaces on the vascularized graft side. These experimental data support the potential clinical application of pedicled reverse-flow vascularized grafts in the treatment of carpal fracture nonunions with avascular necrosis, including proximal pole scaphoid nonunions.

Animals↗
PubMed2000

Evolution of brain injury after transient middle cerebral artery occlusion in neonatal rats.

BACKGROUND AND PURPOSE: Stroke in preterm and term babies is common and results in significant morbidity. The vulnerability and pathophysiological mechanisms of neonatal cerebral ischemia-reperfusion may differ from those in the mature cerebral nervous system because of the immaturity of many receptor systems and differences in metabolism in neonatal brain. This study details the neuropathological sequelae of reperfusion-induced brain injury after transient middle cerebral artery (MCA) occlusion in the postnatal day 7 (P7) rat. METHODS: P7 rats were subjected to 3 hours of MCA occlusion followed by reperfusion or sham surgery. Diffusion-weighted MRI was performed during MCA occlusion, and maps of the apparent diffusion coefficient (ADC) were constructed. Contrast-enhanced MRI was performed in a subset of animals before and 20 minutes after reperfusion. Triphenyltetrazolium chloride (TTC) staining of the brain was performed 24 hours after reperfusion. Immunohistochemistry to identify astrocytes (glial fibrillary acidic protein), reactive microglia (ED-1), and neurons (microtubule-associated protein 2) and cresyl violet staining were done 4, 8, 24, and 72 hours after reperfusion. RESULTS: On contrast-enhanced MRI, nearly complete disruption of cerebral blood flow was evident in the vascular territory of the MCA during occlusion. Partial restoration of blood flow occurred after removal of the suture. A significant decrease of the ADC, indicative of early cytotoxic edema, occurred in anatomic regions with a disrupted blood supply. The decline in ADC was associated with TTC- and cresyl violet-determined brain injury in these regions 24 hours later. The ischemic core was rapidly infiltrated with reactive microglia and was surrounded by reactive astroglia. CONCLUSIONS: In P7 rats, transient MCA occlusion causes acute cytotoxic edema and severe unilateral brain injury. The presence of a prominent inflammatory response suggests that both the ischemic episode and the reperfusion contribute to the neuropathological outcome.

Animals↗
PubMed2000

Electron spin resonance studies of dipalmitoylphosphatidylcholine liposomes containing soybean-derived sterylglucoside.

The effects of soybean-derived sterylglucoside (SG) on the fluidity of liposomal membrane composed of dipalmitoylphosphatidylcholine (DPPC) were investigated compared with those of soybean-derived sterol (SS) and cholesterol (Ch) using an electron spin resonance spectrometer. Three kinds of liposomes were prepared in the molar ratio of DPPC/X=7/4, where X is SS, Ch or SG. The fluidity close to the polar head groups increased with an increase of temperature in the DPPC membrane containing SS, Ch and SG in the range 35 to 45 degrees C. Those near the hydrophobic end changed with an increase in temperature in liposomes containing SS, Ch and SG, which had a fluidizing effect on the DPPC membrane below the transition temperature (Tm, 41.9 degrees C) and a condensing effect over the Tm. The fluidizing effects of these compounds around 37 degrees C near the polar head group and the hydrophobic end increased in the following order: Ch < SG < or = SS and SS < Ch < SG, respectively. SG increased the fluidity of liposomal membrane dramatically above the Tm (35.4 degrees C). These results suggest that the high fluidity close to the hydrophobic end of the liposomal membranes around 37 degrees C, the decrease of Tm, and the sigmoidal nature of fluidity vs. temperature are important factors in the effectiveness of liposomes containing SG as a carrier of drugs.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2000

Portal systemic encephalopathy presenting with dressing and constructional apraxia.

We report a case with portal systemic encephalopathy who presented with dressing and constructional apraxia and subtle weakness of the left hand. We initially suspected a cerebrovascular attack in the right cerebral hemisphere, but brain T1-weighted magnetic resonance (MR) imaging revealed high intensity in the basal ganglia and hyperammonemia was detected. We performed abdominal MR angiography, which visualized an intrahepatic portal systemic shunt. Cerebral blood flow, measured by xenon-enhanced computed tomography, was decreased in the bilateral, but more dominantly right-sided, parietal watershed regions. We speculate that these boundary territories might be susceptible to damage by toxic metabolites of hepatic encephalopathy.

Aged↗
PubMed2000

Restoration of prehension with the double free muscle technique following complete avulsion of the brachial plexus. Indications and long-term results.

BACKGROUND: Recent interest in reconstruction of the upper limb following brachial plexus injuries has focused on the restoration of prehension following complete avulsion of the brachial plexus. METHODS: Double free muscle transfer was performed in patients who had complete avulsion of the brachial plexus. After initial exploration of the brachial plexus and (if possible) repair of the fifth cervical nerve root, the first free muscle, used to restore elbow flexion and finger extension, is transferred and reinnervated by the spinal accessory nerve. The second free muscle, transferred to restore finger flexion, is reinnervated by the fifth and sixth intercostal nerves. The motor branch of the triceps brachii is reinnervated by the third and fourth intercostal nerves to restore elbow extension. Hand sensibility is restored by suturing of the sensory rami of the intercostal nerves to the median nerve or the ulnar nerve component of the medial cord. Secondary reconstructive procedures, such as arthrodesis of the carpometacarpal joint of the thumb, shoulder arthrodesis, and tenolysis of the transferred muscle and the distal tendons, may be required to improve the functional outcome. RESULTS: The early results were evaluated in thirty-two patients who had had reconstruction with use of the double free muscle procedure. Twenty-six of these patients were followed for at least twenty-four months (mean duration, thirty-nine months) after the second free muscle transfer, and they were assessed with regard to the long-term outcome as well. Satisfactory (excellent or good) elbow flexion was restored in twenty-five (96 percent) of the twenty-six patients and satisfactory prehension (more than 30 degrees of total active motion of the fingers), in seventeen (65 percent). Fourteen patients (54 percent) could position the hand in space, negating simultaneous flexion of the elbow, while moving the fingers at least 30 degrees and could use the reconstructed hand for activities requiring the use of two hands, such as holding a bottle while opening a cap and lifting a heavy object. The results were analyzed to identify factors affecting the outcome. CONCLUSIONS: The double free muscle procedure can provide reliable and useful prehensile function for patients with complete avulsion of the brachial plexus.

Accessory Nerve↗
PubMed1999

Limb allotransplantation in rats: combined immunosuppression by FK-506 and 15-deoxyspergualin.

The immunosuppressive effect of combined therapy using FK-506 and 15-deoxyspergualin was investigated in rat limb allotransplantation. The right hindlimb of an inbred Dark Agouti rat (RT1a) was transplanted to a Lewis rat (RT1l) and observed for 120 days. Eighty-eight transplantations were performed. Rejection of the grafts was evaluated histologically as well as macroscopically. A pathologic grading system was used to rate the severity of rejection. Limb survival time in Lewis rats receiving FK-506 therapy for days was significantly prolonged by combined therapy with 15-deoxyspergualin. Histologic study showed practically no rejection in all the graft-composing tissues except the skin and bone marrow, in which there was rejection. These results suggest that tissues like bone, cartilage, and muscle may survive transplantation with short-term combination FK-506 and 15-deoxyspergualin therapy even after withdrawal of both agents.

Animals↗
PubMed1999

The relationship between the rigidity of the liposomal membrane and the absorption of insulin after nasal administration of liposomes modified with an enhancer containing insulin in rabbits.

The relationship between the rigidity of the liposomal membrane and the absorption of insulin after nasal administration of liposomes modified with an enhancer containing insulin was investigated for the nasal delivery of peptide drugs in rabbits. The rigid liposomal membrane makes liposomes stable, protecting insulin from enzymatic degradation. Soybean-derived sterol (SS) or its sterylglucoside (SG) was used as an enhancer. Dipalmitoylphosphatidylcholine (DPPC) liposomes modified with SG had increased fluidity of the hydrophobic group of the liposome bilayer compared with the liposomes modified with cholesterol (Ch) or SS, as shown by measurements of the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5,-hexatriene (DPH); however, the fluidity of the polar group of the liposome bilayer was decreased according to measurements of steady-state fluorescence anisotropy of dansylhexadecylamine (DSHA) at 37 degrees C. These findings suggest that the fluidity of the hydrophobic group of the liposome bilayer is responsible for the increase of liposomal leakage and instability of the liposomes. When insulin was administered nasally to rabbits as a solution, no hypoglycemic effect was observed. The administration of insulin contained in DPPC/SG (7/4, mole) liposomes with high fluidity caused a high glucose reduction of long duration (8 hr). DPPC/SS and DPPC/Ch (7/4) liposomes with low fluidity caused low glucose reductions. These results demonstrated that liposomes modified with SG can be useful as carriers of insulin administered nasally.

1,2-Dipalmitoylphosphatidylcholine↗