Biomedical subjects

Yuichi Murayama

Publications and source records attributed to Yuichi Murayama.

29 records · Page 2Linked to original sources

PubMed2004

Intraaneurysmal flow visualization by using phase-contrast magnetic resonance imaging: feasibility study based on a geometrically realistic in vitro aneurysm model.

OBJECT: The aim of this study was to evaluate the feasibility of complex intraaneurysmal flow visualization with the currently available phase-contrast magnetic resonance (MR) imaging modality. METHODS: A geometrically realistic in vitro aneurysm model, in which detailed flow velocity analysis had already been conducted using laser Doppler velocimetry was used for this in vitro hemodynamic simulation, so that the results of phase-contrast velocity measurements could be compared with the previous reliable results. On a 1.5-tesla unit, three orthogonal components of velocity were obtained using a standard two-dimensional fast low-angle shot flow quantification sequence. Three-dimensional (3D) intraaneurysmal flow structures recorded during one cardiac cycle were depicted in one midsagittal and three axial cross-sectional planes with the aid of gray scale phase-contrast velocity maps. Isovelocity contour maps and secondary flow vectors were also created based on the phase-contrast velocity maps by using MATLAB software. The isovelocity contours in those three axial sections could demonstrate the shapes of inward and outward flow areas and their alternation over one cardiac cycle. The secondary flow vectors demonstrated twin vortices within the outward flow area adjacent to the boundary layer of inward and outward flow in all axial planes. CONCLUSIONS: The phase-contrast MR imaging method was able to depict the complex 3D intraaneurysmal flow structures in the in vitro aneurysm model. Detailed 3D intraaneurysmal flow information will be obtainable in vivo after improvements are made in spatial resolution, which is expected in the near future. The capability to visualize intraaneurysmal flow structures directly with the use of noninvasive MR imaging technology will have a positive impact on future clinical practice.

Hemodynamics↗

PubMed2004

Treatment of unruptured aneurysms with GDCs: clinical experience with 247 aneurysms.

BACKGROUND AND PURPOSE: The GDC system is a valuable therapeutic alternative to surgical treatment of intracranial aneurysms. We present our clinical experience with the GDC technique used to treat unruptured cerebral aneurysms. METHODS: This is a retrospective review of 217 patients with 247 unruptured intracranial aneurysms who underwent embolization with GDCs between August 1991 and June 2000. One hundred sixty-seven of the 217 were female patients. Patient age ranged from 13 to 83 years. In 118 patients, the aneurysms were found when unrelated non-neurologic conditions indicated angiography, CT angiography, or MR angiography (group 1). Fifty-one patients with mass effect symptoms comprised group 2, 12 patients with aneurysms associated with arteriovenous malformations or tumors of the brain comprised group 3, 17 patients with unruptured aneurysms treated during the chronic phase of subarachnoid hemorrhage (SAH) comprised group 4, and 19 patients treated during the acute phase of SAH due to another ruptured aneurysm comprised group 5. RESULTS: Angiographic results revealed complete occlusion in 138 of 247 aneurysms (55.9%), neck remnants in 92 (37.2%), and incomplete occlusion in three (1.2%). GDC embolization was attempted unsuccessfully in 14 aneurysms (5.7%). Of the 198 patients without acute SAH (groups 1-4), 186 (93.9%) of 198 remained neurologically unchanged. Eleven of the 217 patients (5.1%) experienced neurologic deterioration caused by immediate procedural complications. One patient died (0.5%) as a result of aneurysmal rupture during embolization. For asymptomatic patients and those treated after the chronic period of SAH, the mean hospitalization stay was 2.9 days. CONCLUSION: GDC technology constitutes safe treatment for unruptured aneurysms, with successful anatomic and clinical results and low complication rates achieved.

Adolescent↗

PubMed2003

Matrix and bioabsorbable polymeric coils accelerate healing of intracranial aneurysms: long-term experimental study.

BACKGROUND AND PURPOSE: Acceleration of intra-aneurysmal clot organization and fibrosis may be a solution to preventing aneurysm recanalization after endovascular treatment. The purpose of this study was to evaluate the short-term efficacy and long-term safety of the new Matrix coil system. METHODS: Matrix coils consist of thin platinum coils covered with a bioabsorbable, polymeric material (polyglycolic acid/lactide). Fifty-two experimental aneurysms were created in 26 swine. All of the aneurysms were tightly packed with Matrix or Guglielmi detachable coils (GDC). Comparative angiographic and histopathologic data were analyzed at 2 weeks (n=14), 3 months (n=6), and 6 months (n=6) after embolization. RESULTS: Three aneurysms treated with GDC ruptured despite tight packing. No recanalization or rupturing was observed in the aneurysms embolized with Matrix coils. At 14 days after embolization, the aneurysms treated with Matrix coils exhibited a more extensive area of organized thrombus when compared with the aneurysms treated with GDC (87% versus 75%, P=0.008, n=11). At 3 months, both Matrix and GDC-treated aneurysms demonstrated complete clot organization. Neck tissue thickness was higher in Matrix-treated aneurysms at 14 days and 3 months, but not at 6 months. No untoward parent artery stenosis was observed in aneurysms treated with Matrix during follow-up. The angiographic cross-sectional area of the Matrix-treated aneurysms was smaller than those treated with GDC at the 3 months. CONCLUSIONS: Matrix accelerated aneurysm fibrosis and neointima formation without parent artery stenosis. The Matrix system might prevent aneurysmal recanalization after endovascular treatment of cerebral aneurysms.

Absorbable Implants↗

PubMed2003

In vitro measurement of fluid-induced wall shear stress in unruptured cerebral aneurysms harboring blebs.

BACKGROUND AND PURPOSE: Little attention has been focused on the role of fluid-induced wall shear stress in fully developed cerebral aneurysms. The purpose of this study is to evaluate the alternation and distribution of wall shear stress over 1 cardiac cycle in patients' aneurysms. METHODS: A middle cerebral artery aneurysm and a basilar tip aneurysm with localized outpouching (blebs) in their domes were selected for this study. With the use of a stereo lithography machine, geometrically realistic aneurysm models were created on the basis of 3-dimensional CT angiograms. In vitro shearing velocity measurement was conducted with the use of laser-Doppler velocimetry at multiple points on the aneurysmal wall to calculate the value of wall shear stress. The wall shear stress was documented at multiple points in the aneurysm inflow zone, dome, and outflow zone. RESULTS: Distribution of wall shear stress was not uniform in the aneurysm walls, and particular regions were exposed to relatively high wall shear stress. The wall shear stress changed dynamically throughout 1 cardiac cycle at the point where a high value of wall shear stress was noted. The blebs of both aneurysms were exposed to high wall shear stress. Unlike previous reports in which an ideal spherical aneurysm model was used, the aneurysm inflow zone was not exposed to high shear stress. CONCLUSIONS: In vitro aneurysm models based on the patients' angiograms allowed us to conduct a more realistic evaluation of wall shear stress in the aneurysms harboring blebs. These results provide us with further indications of the correlation of wall shear stress with the natural history of cerebral aneurysms.

Angiography↗

PubMed2003

Guglielmi detachable coil embolization of cerebral aneurysms: 11 years' experience.

OBJECT: The authors report on their 11 years' experience with embolization of cerebral aneurysms using Guglielmi Detachable Coil (GDC) technology and on the attendant anatomical and clinical outcomes. METHODS: Since December 1990, 818 patients harboring 916 aneurysms were treated with GDC embolization at University of California at Los Angeles Medical Center. For comparative purposes, the patients were divided into two groups: Group A included their initial 5 years' experience with 230 patients harboring 251 aneurysms and Group B included the later 6 years' experience with 588 patients harboring 665 aneurysms. Angiographically demonstrated complete occlusion was achieved in 55% of aneurysms and a neck remnant was displayed in 35.4% of lesions. Incomplete embolization was performed in 3.5% of aneurysms, and in 5% occlusion was attempted unsuccessfully. A comparison between the two groups revealed a higher complete embolization rate in patients in Group B compared with that in Group A patients (56.8 and 50.2%, respectively). The overall morbidity/mortality rate was 9.4%. Angiographic follow ups were obtained in 53.4% of cases of aneurysms, and recanalization was exhibited in 26.1% of aneurysms in Group A and 17.2% of those in Group B. The overall recanalization rate was 20.9%. Note that recanalization was related to the size of the dome and neck of the aneurysm. Overall incidence of delayed aneurysm rupture was 1.6%, a rate that improved in the past 5 years to 0.5%. Ten of 12 delayed ruptures occurred in large or giant aneurysms. CONCLUSIONS: The clinical and postembolization outcomes in patients treated with the GDC system have improved in the past 5 years. Aneurysm recanalization, however, is still a major limitation of current GDC therapy. Follow-up angiography is mandatory after GDC embolization of cerebral aneurysms. Further technical and device improvements are mandatory to overcome current GDC limitations.

Adult↗

PubMed2003

Three-dimensional blood flow analysis in a wide-necked internal carotid artery-ophthalmic artery aneurysm.

OBJECT: The aim of this study was to evaluate axial and secondary flow structures in a wide-necked internal carotid artery-ophthalmic artery aneurysm, one of the most common locations for endovascular coil placement. METHODS: A clear acrylic aneurysm model was manufactured from a three-dimensional computerized tomography angiogram. Intraaneurysm blood flow analysis was conducted using an acrylic aneurysm model together with laser Doppler velocimetry and particle imaging velocimetry. The maximal axial blood flow velocities in the inflow and outflow zones at the aneurysm orifice were noted at the peak systolic phase, measuring 46.8 and 24.9% of that in the parent artery, respectively. The mean size of the inflow zone during one cardiac cycle was 44.3 +/- 9.8% (range 35.6-58.7%) the size of the axial section at the aneurysm orifice. In the lower and upper planes of the aneurysm dome, the mean size of inward and outward flow areas were 43.3 +/- 6.7% and 43.8 +/- 6.8% the size of the axial cross-sectional plane, respectively. The axial flow velocity structures were dynamically altered throughout the cardiac cycle, particularly at the aneurysm orifice. The fastest secondary flow at the opening was also noted at the peak systolic and early diastolic phases. Axial blood flow velocity was slower in the upper axial plane of the aneurysm dome than in the lower one. Conversely, the secondary flow component was faster in the upper plane. CONCLUSIONS: The side-wall aneurysm in this study did not demonstrate a simple flow pattern as was previously seen in ideally shaped experimental aneurysms in vitro and in vivo. The flow patterns of inflow and outflow zones were very difficult to predict based on the limited flow information provided on standard digital subtraction angiography, even in an aneurysm with a relatively simple dome shape.

Aneurysm↗

PubMed2003

Combined endovascular treatment for both intracranial aneurysm and symptomatic vasospasm.

BACKGROUND AND PURPOSE: The best strategy for treatment of subarachnoid hemorrhage due to ruptured cerebral aneurysm is obliteration of the aneurysm as soon as possible. Early surgery is desirable if the patient does not develop severe vasospasm or is clinically stable. However, if the patient has already developed severe vasospasm on admission, surgery may carry the risk of increasing the severity. We evaluated the safety and effectiveness of combined Guglielmi detachable coil (GDC) embolization and angioplasty in a single session for the treatment of ruptured aneurysms associated with symptomatic vasospasm. METHODS: From January 1992 to January 2001, 12 consecutive patients with ruptured aneurysms associated with symptomatic vasospasm were treated. Patients were classified as Hunt and Hess grade 2 (n = 1), 3 (n = 6), 4 (n = 4), or 5 (n = 1) and Fisher CT group 2 (n = 1), 3 (n = 10), or 4 (n = 1). They underwent GDC aneurysm occlusion and balloon angioplasty (n = 6), intraarterial papaverine infusion (n = 2), or both (n = 4) in a single session. In nine patients, aneurysm coil occlusion was performed first. RESULTS: Complete GDC occlusion was achieved in eight patients, a small neck remnant persisted in three, and embolization was incomplete in one patient. In all patients, angiographic improvement of vasospasm was obtained. In one patient, a thromboembolic complication occurred and was treated with urokinase. Clinical outcomes at discharge were good recovery in six, moderate disability in two, severe disability in three, or death in one. CONCLUSION: Endovascular treatment can be the first therapeutic option for ruptured aneurysms associated with severe vasospasm on admission. It offers some advantages over surgery in this setting, but these are balanced by the risk of thromboembolism.

Adult↗

PubMed2002

Variation of variable number of tandem repeat sequences in the 3'-untranslated region of primate dopamine transporter genes that affects reporter gene expression.

Genetic polymorphism has been reported in the 3'-untranslated region (3'-UTR) of the human dopamine transporter (DAT) gene and the variable number of tandem repeat (VNTR) polymorphism has been proposed to be associated with normal personal traits or psychoneurological disorders. To assess the variation of this region in nonhuman primates, we amplified the VNTR regions by the polymerase chain reaction in several species of apes and monkeys, and determined their DNA sequences. The 3'-UTR of the chimpanzee DAT gene was also polymorphic and alleles with one or two unit(s) of a 40 bp sequence were found, while all gorillas and orangutans examined had only 2-repeat allele. Cynomolgus macaques and African green monkeys shared 11- or 12-repeat and 5-repeat alleles, respectively. By performing transient transfection assay, we found that most of the VNTR sequences of nonhuman primates exhibited higher activities on reporter gene assay as compared to those of human 9-, 10- and 11-repeat sequences.

3' Untranslated Regions↗

PubMed2002

Fusarenon-X induced apoptosis in HL-60 cells depends on caspase activation and cytochrome c release.

Fusarenon-X (FX), a trichothecene mycotoxin, is well known to be cytotoxic to mammalian cells. Our previous study revealed that FX induced apoptosis in mouse thymocytes both in vivo and in vitro. We investigated the mode of apoptosis induced by FX using HL-60 cell culture. When FX at a final concentration of 0.5 microg/ml was added, cell degradation was observed 5 h after exposure, and most of the cells had fallen into apoptosis 24 h after exposure. DNA fragmentation into 180-bp multimers was observed 5 h after exposure, and its dose-dependency was clear in the cells treated with 0.1 microg/ml and higher doses. The percentage of apoptotic cells (sub-G(0) population) increased dose- and time-dependently after exposure, when analyzed using flow cytometry. The activities of caspase-3, -8, and -9 were elevated within 2 h by exposure to FX. DNA fragmentation and an increase in the apoptotic population were abrogated by pre-treating the cells with broad-spectrum caspase inhibitors Z-VAD-fmk or Z-Asp-CH(2)-DCB. Cytochrome c release from mitochondria to cytoplasm was observed clearly, and this release occurred caspase-independently. These findings suggest that FX induces apoptosis in HL-60 cells by stimulating cytochrome c release followed by its downstream events including the activation of multiple caspases.

Apoptosis↗

PubMed2002

Cellular responses of bioabsorbable polymeric material and Guglielmi detachable coil in experimental aneurysms.

BACKGROUND AND PURPOSE: Acceleration of healing mechanisms is a promising approach to improve current limitations of endovascular aneurysm therapy with the use of platinum coils. We evaluated a new endovascular therapeutic, bioabsorbable polymeric material (BPM), which may promote cellular reaction in the aneurysms. METHODS: Four different concentrations of lactide/glycolic acid copolymer [poly(D-L-lactic-co-glycolic acid)] (PLGA), 85/15, 75/25, 65/35, and 50/50, were used as BPMs. Sixteen experimental aneurysms were created in 8 swine. Eight-millimeter-long spiral-shaped BPMs were surgically implanted in the aneurysms without tight packing (n=3 for each BPM). Guglielmi detachable coils (GDCs) were used as control (n=4). The animals were killed 14 days after embolization, and angiographic, histological, and immunohistochemical analyses were performed. RESULTS: Despite loose packing of aneurysms with BPMs, faster BPMs such as 50/50 or 65/35 PLGA demonstrated more mature collagen formation and fibrosis in the sac and neck of the aneurysm. One aneurysm treated with 65/35 PLGA, 1 treated with 75/25 PLGA, and all 3 treated with 85/15 PLGA showed a neck remnant on angiography. There was a linear relationship between collagen levels and polymer degradation properties (r=-0.9513). CONCLUSIONS: This preliminary animal study indicates that acceleration of aneurysm healing with the use of BPM is feasible. This concept can be applied to decrease and perhaps prevent aneurysmal recanalization after endovascular treatment of cerebral aneurysms.

Absorbable Implants↗

PubMed2002

Sequence comparison of the dopamine receptor D4 exon III repetitive region in several species of the order Carnivora.

It was previously demonstrated that the dog dopamine receptor D4 (DRD4) gene is polymorphic in terms of the repeat number and/or order of 39- and 12-bp sequences located in the third exon. To examine whether or not the repetitive region is present in other species of the order Carnivora, the homologous region of DRD4 genes were sequenced in the gray wolf, raccoon dog, Asiatic black bear, common raccoon and domestic cat. In the family Canidae, the wolf had an identical sequence to that of the dog 447b allele, and a repetitive sequence similar to the dog DRD4 was also recognized in the raccoon dog. On the other hand, no obvious repeated structure was observed in the sequences of the bear, raccoon and cat.

Amino Acid Sequence↗