Search PubMed⌕ Search

Biomedical subjects

Y Miyasaka

Publications and source records attributed to Y Miyasaka.

At least 73 records · Page 4Linked to original sources
PubMed1995

The effects of a carotid-jugular fistula on cerebral blood flow in the cat: an experimental study in the chronic period.

The purpose of the present study was to investigate the effects of feline carotid-jugular fistula (Spetzler's model) on cerebral blood flow at 8 weeks after creation of the fistula. Using laser-Doppler flowmetry, cortical cerebral blood flow (CBF) on the fistula side was measured in 10 cats, Occlusion of the fistula showed no cortical CBF changes in 6 animals, but transient increases in 4. CO2 reactivity in the closed fistula was preserved. No neurological or histological abnormalities were recognized. These findings suggested that cerebral hemodynamic changes due to Spetzler's CJ fistula model are minimal even in the chronic period after fistulization. Therefore, creation of another experimental arterio-venous fistula model is mandatory for the investigation of hemodynamic changes following resection of a cerebral arteriovenous malformation.

Animals↗
PubMed1995

Basic fibroblast growth factor increases regional cerebral blood flow and reduces infarct size after experimental ischemia in a rat model.

BACKGROUND AND PURPOSE: The aim of this study was to ascertain whether basic fibroblast growth factors (bFGF) caused reduction in size of cerebral infarcts in Sprague-Dawley rats with experimental ischemia. METHODS: In the first experiment we induced permanent occlusion of the left middle cerebral artery (MCA). Within 5 minutes after MCA occlusion, we infused bFGF (100 ng in 0.1 mL of saline) in the bFGF-treated group (n = 14) and 0.1 mL of saline alone in the control group (n = 7) into the common carotid artery ipsilateral to MCA occlusion. We harvested the brains 24 hours after MCA occlusion and determined infarct size planimetrically as a percentage of hemisphere size. In the second experiment cerebral blood flow (CBF) was continuously measured for 120 minutes after MCA occlusion in the bFGF-treated group (n = 9) and in the control group (n = 8) with the use of laser-Doppler flowmetry. RESULTS: Infarct size in the bFGF-treated group decreased significantly in comparison with that in the control group (repeated-measures ANOVA, P < .0001). CBF in the transitional areas between the MCA and the anterior cerebral artery significantly increased in the bFGF-treated group in comparison with that in the control group (repeated-measures ANOVA, P < .005). An approximate 58% decrease in infarct size and a 40% increase in regional CBF were seen on bFGF treatment. CONCLUSIONS: The present study suggested that intracarotid administration of bFGF (100 ng) can reduce infarct size after MCA occlusion. It was speculated that the increased CBF in the penumbral areas of MCA may contribute to contraction of infarct size.

Animals↗
PubMed1995

Theory of osteogenesis behavior based on calcium diffusion theory.

Osteogenesis is completed by the nucleation mechanism on crystal nuclei formation and growth after amorphous calcium phosphate accretion to collagen fibers. For nuclei formation, it is necessary to have preliminary ionic diffusion such as that of Ca2+ and PO4(3-) ions to this part. Therefore, promotion of ionic diffusion to this part is the first essential condition for osteogenesis. We have considered this phenomenon as the nucleation mechanism accompanied by preliminary diffusion behavior and shown the optimum mechanical condition on promoting this ionic diffusion. Furthermore, we noticed callus by callotasis as the typical example which fits this mechanical condition and investigated its histology. However, necking occurs at the site of callus sandwiched by cortical bones due to tensile stress, three axial tensile stress in radial and tangential directions, in addition to the tensile stress occurs at the netsection of the callus due to the constraint of cortical bones. Therefore, the size of pore along the collagen lamination and hole zone becomes large under this mechanical condition and ionic diffusion such as Ca2+, PO4(3-) is liable to occur at this part. By solving the partial differential equation of the stress-induced diffusion, diffusive particles are shown to concentrate at the high three axial tensile stress region. Therefore, a high concentrated region of Ca, PO4 is achieved and selective osteogenesis due to hydroxyapatite nucleation is considered to progress in this region. Histological investigation of the callus of rabbit showed that mineralization occurs at this site and supports the theory of stress-induced diffusion on osteogenesis behavior.

Animals↗
PubMed1994

Anomaly of venous system in congenital occipital dermal sinus.

We report two cases of congenital occipital dermal sinus in which elongation of the vein of Galen, elevation of the straight sinus, division of the superior sagittal sinus, elevation of the confluence of sinuses, elevation of transverse sinus and narrowing of the torcular angle were observed in the venous phase of cerebral angiography. Enhanced computed tomography (CT) revealed enlargement of the supracerebellar cistern, elevation of the straight sinus and of the confluence of sinuses, but no evidence of intracranial lesions. In order to study the relationship between anomalies in the dural venous sinuses and congenital occipital dermal sinus, we examined both cases from an embryological viewpoint.

Arteriovenous Malformations↗
PubMed1994

The effects of a carotid-jugular fistula on cerebral blood flow in the cat: an experimental study in the acute period.

The purpose of the present study is to investigate the effects of feline carotid-jugular (CJ) fistula (Spetzler's model) on cerebral blood flow (CBF) in the acute period after creation of the fistula. Using laser-Doppler flowmetry, cortical CBF was measured on the fistula side of 11 cats. Temporary occlusion and opening of the fistula led to an immediate increase and decrease, respectively, in cortical CBF. However, CBF returned to baseline within 1 minute, on average. CO2 reactivity in the closed fistula was preserved. It is suggested that cerebral hemodynamic changes due to Spetzler's CJ fistula model are minimal in the acute period after fistulization.

Acute Disease↗
PubMed1994

Draining vein pressure increases and hemorrhage in patients with arteriovenous malformation.

BACKGROUND: Recent radiological studies have shown that arteriovenous malformations with impaired venous drainage may be susceptible to hemorrhage. To evaluate this hypothesis using a hemodynamic approach, we measured intravascular pressure during surgery in three patients with arteriovenous malformation. SUMMARY OF REPORT: In three patients we measured intravascular pressures in the draining venous system and the feeding arteries simultaneously before removal of arteriovenous malformations with marked segmental stenotic or occlusive draining veins and evidence of hemorrhage. The draining vein pressures at prestenotic (or preocclusive) sites in the three patients were 38, 25, and 40 mm Hg, respectively, all significantly above the normal cortical venous pressure, whereas pressure measurements in poststenotic sites and the sagittal sinus pressure in the venous drainage system approached normal values. The feeding artery pressures in the patients were lower than normal cortical artery pressure because of the arteriovenous shunt. CONCLUSIONS: Intraoperative vascular pressure measurements support the hypothesis that arteriovenous malformations with impaired venous drainage may be associated with a local increase in venous pressure and thus may be susceptible to hemorrhage.

Adolescent↗
PubMed1994

Aneurysmography for visualizing large aneurysms.

We report a case of a large cavernous sinus aneurysm, in which conventional angiography did not clearly demonstrate the exact form and the position of the neck. Superselective angiography performed with the catheter tip in the lumen of the aneurysm and with the internal carotid artery occluded just proximal to its neck is a new technique that demonstrates the morphological details of an entire aneurysm. With the use of cineangiography, the exact volume of the aneurysm was defined. The valuable aneurysmographic information obtained was useful in achieving occlusion of the aneurysm, while preserving the parent artery.

Carotid Artery, Internal↗
PubMed1994

Dural arteriovenous malformation involving the inferior petrosal sinus--case report.

A 59-year-old male presented with a dural arteriovenous malformation involving the inferior petrosal sinus manifesting as false-localizing ocular symptoms. Occlusion between the right inferior petrosal sinus and the right jugular bulb caused an unusual retrograde venous outflow from the inferior petrosal sinus to the cavernous sinus, thought to have been responsible for the chemosis, abducens nerve paresis, and orbital bruit. He was treated successfully with transarterial embolization and radiotherapy.

Cerebral Angiography↗
PubMed1994

Cerebral bacterial aneurysm and indications for cerebral angiography in infective endocarditis.

Six infective endocarditis patients who developed cerebral bacterial aneurysm were reviewed to clarify the indications and timing for cerebral angiography to achieve early detection of unruptured aneurysms. All cerebral bacterial aneurysms were confirmed either angiographically or at autopsy. All patients were treated conservatively. Four patients died due to ruptured aneurysm. Four of the six patients showed the signs and symptoms of cerebral and/or systemic embolism, followed by rupture or detection of cerebral bacterial aneurysm. Prodromal signs and symptoms of embolism in patients with infective endocarditis should be considered as indicators for cerebral angiography to detect cerebral bacterial aneurysms before rupture.

Adolescent↗
PubMed1994

Venous ischemia caused by dural arteriovenous malformation. Case report.

A case is presented of tentorial dural arteriovenous malformation (AVM) associated with visual hallucinations and quadrant hemianopsia. Computerized tomography (CT) and magnetic resonance imaging showed an ischemic region, mainly affecting the white matter of the right occipital lobe, that was defined as an area of increased blood volume on dynamic CT scans and as a decrease in cerebral blood flow on N-isopropyl-p-123I-iodoamphetamine single-photon emission CT scans. Angiography demonstrated venous congestion, probably because the retrograde arterial inflow from the dural AVM into the corticomedullary vein was direct and not via the sinuses. The symptoms and radiological findings improved immediately after endovascular treatment. The origin of these symptoms was fully evaluated and confirmed to be a reversible ischemic change caused by disturbance of the volume of venous return over an extensive area.

Aged↗
PubMed1994

The mechanical behavior and morphological structure of callus in experimental callotasis.

Experimental callotasis was made in rabbit femurs. In order to compare mechanical behaviors and morphological structure of callus in callotasis, mechanical tests and histological examination were performed. Twenty Japanese white male rabbits were used. The right femurs were osteotomized at the level of the midshaft with a rotary cutter and fixed with a mini-model external fixator. After a 5-day waiting period, bone lengthening was started at the rate of 0.25 mm two times a day. Animals were divided into four groups. Group 1 and Group 2 were continual distraction group, Group 3 and Group 4 discontinued distraction group. The viscoelastic property was demonstrated in continual distraction group irrespective of distraction period, we thought the central undifferentiated connective tissue in callus was mainly responsible for the mechanical behavior. On the other hand, in discontinued distraction group, viscoelastic property shifted to elastic property corresponding to the rest period, we thought this change of mechanical behavior was histologically owing to the replacement of undifferentiated connective tissue by cartilage and the partial union of bone in callus.

Animals↗
PubMed1994

[Venous angioma coexisting with other types of cerebrovascular malformations].

The authors report 3 cases in which, in addition to venous angioma, other types of vascular malformations coexisted. They discussed the pathological significance of this coexistence, and the treatment to be given in these conditions. Case 1: A 38-year-old man was admitted to the hospital because of progressive headaches of 3 days' duration. X-ray CT revealed a large hematoma in the left cerebellar hemisphere. Vertebral angiogram showed a caput medusae in the venous phase, which is a typical picture of venous angioma. The hematoma was surgically removed and careful inspection of the cavity wall was made. A thick vein and many thin walled dilated venules draining to the vein were observed in the cavity wall. These abnormal vessels were completely removed. Because of reaccumulation of the hematoma and massive edema of the hemisphere, reoperation was performed. On removing a part of the cerebellar hemisphere, a small mass of vascular network was found and removed together with the hematoma. Histologically, the first specimen was a typical venous angioma, and the second one was a arteriovenous malformation. Case 2: A girl 9 years of age was admitted because of headache and left sided ataxia. CT and MRI revealed a multi staged hematoma in the left cerebellar hemisphere. Vertebral angiography, however, failed to demonstrate any kind of vascular malformations. The hematoma was removed with its wall. The histological appearance was compatible with venous angioma. 4 years later she bled again, and reoperation was performed. Histological examination this time revealed a cavernous angioma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Completely thrombosed large aneurysm of the distal middle cerebral artery: a case report].

A 19 year old male was admitted for evaluation after a seizure. Physical and neurological examination was normal. CT demonstrated an enlarged, high density mass in the right parietal lobe. MRI showed a homogeneous high intensity T1 weighted mass, surrounded by a low intensity T2 weighted rim in the right parietal lobe. Angiography did not show any abnormal findings. A diagnosis of cavernous angioma with primary bleeding in the subcortical region of the right parietal lobe was made after radiological examination. Histological examination showed a completely thrombosed aneurysm. The mechanism of the complete thrombosis and the growth of this large aneurysm and the shortcomings of radiological examination are discussed.

Adult↗
PubMed1994

[A case of acute cervical spinal epidural hematoma caused by extradural arterio-venous malformation].

The authors report a rare case of acute cervical epidural hematoma caused by the hemorrhage from extradural arterio-venous malformation. The patient was a 74-year-old Japanese man with a past history of total gastrectomy after being diagnosed as having gastric cancer 12 years before. Six hours prior to admission, the patient had experienced a sudden episode of severe nuchal pain radiating to both scapular areas, followed by rapid development of left-side Brown-Sequard Syndrome below the C4 cord level, and urinary incontinence. Plain cervical X-ray films did not show any destructive lesion suggesting a metastatic tumor. T1 and T2 weighted images of MRI demonstrated a high intensity mass lesion, suggesting an acute epidural hematoma, extending from C3 to C6 and compressing severely the left side spinal cord posteriorly. Twelve hours after the onset of symptoms, emergency laminectomy from C3 to C6 was performed and a fresh epidural clot with small vascular tissue was totally removed. Histological examination of the small vascular tissue in the hematoma revealed arterio-venous malformation. The postoperative recovery of the patient was dramatic. He regained full muscle strength and there was complete disappearance of sensory deficits 2 weeks after the operation. Although acute spinal epidural hematoma caused by extradural arterio-venous malformation is a rare clinical entity, MRI is the most helpful diagnostic tool for this condition. It should be stressed that accurate neuroradiological diagnosis and prompt surgical decompression of the spinal cord are essential to obtain an excellent surgical outcome.

Acute Disease↗
PubMed1994

[Bronchial carcinoid tumor with multiple brain metastasis].

Carcinoid tumor is regarded as a tumor with low grade malignancy, mostly originating from the gastrointestinal tract with little danger of metastasis. The authors encountered a very rare case of bronchial carcinoid tumor that had multiple metastasis to the intracranial space. The characteristics of radiological and hormonal examinations of this tumor are reported and discussed. The patient was a 73-year-old woman who gradually developed unsteadiness in walking and somnolence in daytime one month prior to admission. Those symptoms were aggravated and she began to vomit. On admission, neurological examination showed slight ataxia of left upper and lower extremities and dominant truncal ataxia. Chemical and hormonal examinations of blood and urine showed, gastrin was 230 pg/ml (37-172), ACTH was 67 pg/ml (< 60), serotonin was 565 ng/ml (53-200), and urinary 5-HIAA was 9.9 mg/day (0.8-4.8). Tumor markers (CEA, AFP, HGG, NSE) were all negative. Radiological examinations (chest X-P, CT scan) of her lung demonstrated a 3 x 3 cm tumor mass adjacent to the hilum of the left lower lobe. CT-scan of the head demonstrated cystic tumor in the vermis of the cerebellum (3 x 3 cm), the right posterior parietal lobe and the right temporal lobe. The wall of each tumor was enhanced by contrast medium. T1 weighted MRI demonstrated the walls of cystic tumors as iso intensity and the contents as low and high intensity with niveau formation. Little edema was recognized around the tumors. The wall of each cystic tumor was enhanced by Gd-DTPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

An unruptured arteriovenous malformation with edema.

We report a case of unruptured arteriovenous malformation in which an extensive zone of increased signal intensity in the brain parenchyma adjacent to the nidus is demonstrated on T2-weighted MR. This area of perilesional hyperintense signal exerts a compressive effect, suggesting that it represents perilesional edema.

Brain Edema↗
PubMed1993

Correlation between intravascular pressure and risk of hemorrhage due to arteriovenous malformations.

The correlation between intraoperative pressure levels measured in the feeding arteries and in the draining veins, and the risk of hemorrhage from arteriovenous malformations (AVMs) is discussed. Feeding artery pressure (FAP) was significantly higher in AVMs with hemorrhage (57 +/- 11 mmHg) than in AVMs without hemorrhage (38 +/- 4), and draining vein pressure (DVP) in the former (24 +/- 5) was significantly higher than that in the latter (13 +/- 5). FAP and DVP were inversely related to the number of draining veins and size of the AVMs. The present study suggests that a high FAP and a high DVP may contribute to the development of hemorrhage from AVMs, and supports previous reports that small AVMs and AVMs with only one draining vein are susceptible to hemorrhage.

Blood Pressure↗