Search PubMed⌕ Search

Biomedical subjects

K Muramatsu

Publications and source records attributed to K Muramatsu.

At least 19 recordsLinked to original sources
PubMed2007

Use of the AO hook-plate for treatment of unstable fractures of the distal clavicle.

INTRODUCTION: We used a new internal fixative implant, the AO clavicle hook-plate, for treatment of unstable fractures of the distal clavicle. This study describes the operative procedure and the clinical results obtained, as well as discussion of the advantages and problems encountered. PATIENTS AND METHODS: Fifteen consecutive patients with unstable fractures of the distal clavicle (Neer type II) were treated using AO clavicle hook-plates. The average age of patients was 47 years and there were 13 males and 2 females. The mean follow-up period was 15.5 months. Plain radiographs of clavicles were used to assess bony union. Functional recovery of the shoulder joint was assessed using the Constant-Murley scoring system. RESULTS: All fractures eventually achieved solid bony union within 4 months after surgery. Thirteen patients (87%) showed hook migration into the acromion. Clinical results were excellent with a mean Constant-Murley score of 89 points at final follow-up. CONCLUSION: AO clavicle hook-plates are useful fixative implants for unstable fractures of the distal clavicle. Static fixation was achieved and physiotherapy can be started immediately after surgery. Early removal of the implant is recommended however because hooks inserted under the acromion migrated into the bone in most cases.

Adult↗
PubMed2007

Low-grade central osteosarcoma mimicking fibrous dysplasia: a report of two cases.

Low-grade central osteosarcoma is an unusual variant of conventional osteosarcoma. We present here two rare cases of low-grade central osteosarcoma resembling fibrous dysplasia. A 24-year-old woman diagnosed as fibrous dysplasia was treated with intra-lesional excision and curettage of the tumor but tumor recurred at 4 months after surgery. Distal femoral en-bloc resection was performed followed by arthroplasty with mega-prosthesis of the knee. A 57-year-old man diagnosed as central osteosarcoma was treated with wide excision of the tumor, followed by reconstruction with the vascularized fibula graft combined with an autogenous irradiated bone graft. Because of the difficulty in distinguishing low-grade central osteosarcoma from a benign lesion, open biopsy is needed to obtain a large tumor sample. Careful clinical and pathological evaluation is required to obtain a definite diagnosis. The treatment of low-grade central osteosarcoma is en-block resection with wide surgical margins.

Adult↗
PubMed2004

Active magnetic compensation composed of shielding panels.

Magnetically shielded rooms (MSRs) with materials of high permeability and active shield systems have been used to shield magnetic noise for biomagnetic measurements up to now. However, these techniques have various disadvantages. Therefore, we have developed a new shielding system composed of shielding panels using an active compensation technique. In this study, we evaluated the shielding performance of several unit panels attached together. Numerical and experimental approaches indicated that the shielding factor of a cubic model composed of 24 panels was 17 for uniform fields, and 7 for disturbances due to car movement. Furthermore, the compensation space is larger than that of an ordinary active system using large coils rather than panels. Moreover, the new active compensation system has the important advantage that panels of any shape can be assembled for occasional use because the unit panels are small and light.

Electromagnetic Fields↗
PubMed2004

Femoral reconstruction by single, folded or double free vascularised fibular grafts.

We reviewed 17 patients for a mean of 25 months period after free vascularised fibular transfer to reconstruct massive bone defect or recalcitrant nonunion of the femur. There were 11 cases of posttraumatic nonunion and six patients had a large bony defect following resection of bone tumour. Ten patients underwent double or folded and seven patients underwent single vascularised fibula graft transfer. Mean bony defect of the femur was 6.5 cm and mean length of grafted fibula was 15 cm. Revision surgery due to postoperative vascular complications was required in five cases. Twenty-three out of 24 (96%) vascularised fibulas were transferred successfully. The resultant outcome was successful in 15 out of 16 (94%) patients with confirmed bone union. Stress fracture occurred in three inlay fibula grafts. Hypertrophic change of the fibula graft was significantly noted in inlay grafts as compared to onlay grafts. All patients could walk without brace at a mean of 11 months postoperatively. Donor-site morbidity was minimum. Vascularised fibula grafting is a reliable and safe reconstructive procedure for massive femur defects. Folded or double fibula grafts cannot prevent stress fractures and the key point is to rigidly stabilise the femur in an anatomically aligned position.

Adolescent↗
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↗