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Biomedical subjects

Y Miyasaka

Publications and source records attributed to Y Miyasaka.

At least 19 recordsLinked to original sources
PubMed1998

A canine model of intracranial arteriovenous shunt with acute cerebral venous hypertension.

Increased pressure of draining veins in intracranial arteriovenous fistula is considered an important cause of clinical symptoms. To investigate hemodynamic changes in intracranial arteriovenous fistula with cerebral venous hypertension, we developed a new canine model of this condition. A lingual artery-superior sagittal sinus (SSS) shunt was constructed using a section of the femoral artery as an interposed graft; immediately after which, monitoring of SSS pressure (SSSP) and regional cerebral blood flow (rCBF) was started. The baseline SSSP was 4.1 +/- 3.7 mmHg. After shunt opening, it increased slightly but not significantly. When the SSS was occluded with a clip with the shunt closed, SSSP rose to 20.3 +/- 9.0 mmHg (p < 0.01). Finally, on shunt opening, with the SSS caudal (downstream) to it occluded, the SSSP increased to 59.5 +/- 22.9 mmHg (p < 0.01, multiple analysis of variance, contrast). The frontal lobe rCBF decreased as the cerebral perfusion pressure (CPP) (mean blood pressure minus SSSP) fell. However, cerebral vascular resistance decreased significantly and proportionately to the reduced CPP (r = 0.66, p < 0.0001). In conclusion, when an intracranial arteriovenous shunt was present, venous outflow obstruction was shown to be necessary for cerebral venous hypertension to occur. In acute venous hypertension, decreases in rCBF occurred, but the autoregulatory vasodilating response was also active.

Animals↗
PubMed1997

The efficacy of bypass surgery for the patients with hemorrhagic moyamoya disease.

The efficacy of bypass surgery for the patients with hemorrhagic Moyamoya disease were studied by multi-center retrospective questionnaire study. The rebleeding rate was 28.3% (39/138 patients) in conservative treatment group and 19.1% (29/152 patients) in bypass surgery group with no significant statistical difference. It is still difficult to clarify the efficacy of bypass surgery for prevention of hemorrhagic attack.

Adolescent↗
PubMed1997

Successful treatment of a patient with Graves' disease on hemodialysis complicated by antithyroid drug-induced granulocytopenia and angina pectoris.

We report here a patient with recurrent Graves' disease on hemodialysis. She also suffered from angina pectoris, which was probably a manifestation of Graves' disease due to the increased oxygen demands in the presence of fixed coronary lesions. Although antithyroid drugs induced mild granulocytopenia, propylthiouracil (PTU) or methimazole (MMI) was not discontinued during the administration of granulocyte colony-stimulating factor (G-CSF). The patient received sodium iodine-131 therapy, and became euthyroid with no chest pain. To our knowledge, this is the first case that illustrated the usefulness of G-CSF for antithyroid drug-induced granulocytopenia prior to thyroid ablation for Graves' disease complicated with chronic renal failure and angina pectoris.

Agranulocytosis↗
PubMed1997

Mass effect caused by clinically unruptured cerebral arteriovenous malformations.

OBJECTIVE: It is generally considered that mass effect caused by arteriovenous malformations (AVMs) is evidence of ruptures. In the present study, the incidence of mass effect in clinically unruptured AVMs was evaluated, and the underlying causative factors and pathophysiological mechanisms were studied. METHODS: Twenty-seven patients with clinically unruptured supratentorial pial AVMs were examined. The majority were suffering from epilepsy, and frontal lobe involvement was revealed in approximately half of the patients. Angiographic studies, computed tomographic scans, and magnetic resonance images were obtained for all patients. Twenty-one patients underwent removal of AVMs. In 10 of the surgically treated patients, intraoperative vascular pressure measurements were obtained before removal of the AVMs. RESULTS: Mass effect was detected in 12 (44%) of the 27 patients. Cortical sulci obliteration (eight patients) and lateral ventricle displacement (seven patients) were frequently noted. The volume of AVMs was significantly larger in patients with mass effect than in those without mass effect (P < 0.001). Large dilated venous sacs or ectatic veins were observed to be associated with mass effect (P < 0.001). In only one patient was gross displacement related to a surrounding massive brain edema. Draining vein pressure in patients with mass effect was significantly elevated as compared to the average value in patients without mass effect (22 +/- 5 versus 12 +/- 3 mm Hg) (P < 0.01). CONCLUSION: The present study suggests that mass effect is not infrequent in clinically unruptured AVMs. Furthermore, multiple causative factors were detected, including the large size of AVMs, marked draining vein dilatation, and brain edema around the AVMs. Findings also indicated that a pathophysiologically high pressure in the venous drainage system may contribute to mass effect.

Adolescent↗
PubMed1997

Hemolysis, elevated liver enzymes, and low platelets syndrome associated with primary anti-phospholipid antibody syndrome.

A 28-year-old woman with a history of a spontaneous abortion developed thrombocytopenia, Coombs-negative hemolytic anemia, and liver dysfunction at the sixteenth week of pregnancy. These findings were compatible with hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome (hemolysis, elevated liver enzymes, and low platelet counts). Moreover, serum anti-phospholipid antibodies were positive, suggesting the association of anti-phospholipid antibody syndrome. An artificial abortion, anti-coagulation therapy, and plasma exchange were performed concomitantly with corticosteroid therapy. She responded to the therapy, a remission was obtained. Anti-phospholipid antibodies may play a role in the pathogenesis of HELLP syndrome.

Abortion, Induced↗
PubMed1997

[New combination therapy with FTM [5-FU, pirarubicin (THP) and MMC] for treatment of inoperable advanced gastric cancer].

Clinical usefulness of a new combination FTM therapy consisting of 5-FU, Pirarubicin (THP) and MMC for the treatment of advanced gastric cancers was investigated. 5-FU, THP or MMC was administered at a dose of 600 mg/m2 on day 1, 8, 22 and 29, 30 mg/m2 on days 1 and 22, and 10 mg/m2 on day one only of each course, respectively. Eighteen patients with inoperable advanced gastric cancer were treated with FTM. All drugs were investigated by intravenously by one shot. The tumor response rate was 50% [9 of 18 showed PR]. The survival rate was higher in responders than in nonresponders (18.1% vs 11.1%) (p < 0.05). Side effects in the gastrointestinal tract were minimal. Cardiotoxicity and nephrotoxicity were not detected, but myelosuppression was prominent in most cases. G-CSF was given in sixteen patients (88%), and platelet transfusion was performed in two patients (11%). New combination FTM therapy is an effective treatment regimen even for advanced inoperable gastric cancer.

Adult↗
PubMed1996

A source of haemorrhage in adult patients with moyamoya disease: the significance of tributaries from the choroidal artery.

This study concerns 19 patients over 16 years of age with Moyamoya disease. Ten cases of intracranial haemorrhage, as the initial haemorrhagic event in patients aged from 21 to 55 (haemorrhagic group) and 9 cases of ischaemic events in 18- to 53-year-old patients (ischaemic group) were included. All haemorrhages were associated with intraventricular haemorrhages (IVH); and all but one case of thalamic haemorrhage were thought to be primary IVH (2 cases of small paraventricular haemorrhage; 2 of small haemorrhages in the splenium; 5 with no intracerebral haematoma). In the 9 patients of the ischaemic group, there were 2 cases of transient ischaemic attacks and 7 of cerebral infarction. Angiographic evaluations demonstrated that the abnormal basal vessel formation and the collateral supplies from the external carotid arteries were poorly developed in both groups. In contrast, the collateral circulation via the choroidal and posterior pericallosal arteries was well demonstrated. Furthermore, marked enlargement of the choroidal arteries and the medullary arteries derived from them was seen more frequently in the haemorrhagic group. These findings suggested that the haemodynamic load in the vessels supplying the walls of the posterior parts of the ventricles and the periventricular region was increased, especially in the haemorrhagic group. Those vessels were considered to be important sites of IVH in adult patients with Moyamoya disease.

Adult↗
PubMed1996

Stump pressure as a guide to the safety of permanent occlusion of the internal carotid artery.

Does the absolute value of the stump pressure (post-occlusion back pressure) become a useful index of a good collateral circulation? The authors continuously monitored the mean arterial pressure before, during and after 20-minute balloon test occlusion in 24 patients. The stump pressure was then compared with the results of 99mTc-hexa-methyl propyleneamine (99mTc-HMPAO) single photon emission computed tomography (SPECT) performed after 20 minutes of test occlusion. Patients who failed to tolerate even brief periods of carotid occlusion and showed asymmetric decreases in cerebral blood flow (CBF) on SPECT were divided into high and moderate risk groups. Those with no significant change in CBF on the occluded side formed the minimum risk group. Mean stump pressure was over 50 mmHg in three of a total of 13 patients in the high and moderate risk groups, and below 50 mmHg in two of the 11 patients in the minimum risk group. The ratios of the initial mean stump pressure to the pre-occlusion mean arterial pressure (%) and of the final mean stump pressure at the end of occlusion to the post-opening mean arterial pressure (%) did not exceed 58% in any patient in the high and moderate risk groups, and were at least 60% in all patients of the minimum risk group. Maintenance of a mean stump pressure of 60% or more of the mean systemic pressure during test occlusion may be a more useful index of a good collateral circulation than the absolute value of mean stump pressure.

Adult↗
PubMed1996

Effects of nilvadipine (a dihydropyridine-type calcium entry blocker) on cerebral blood flow in acute experimental brain ischemia in rats.

The purpose of the present study was to examine the effect of nilvadipine (a dihydropyridine-type calcium entry blocker) on the cerebral circulation, experimental models of cerebral ischemia were used to measure abrupt changes in the cortical cerebral blood flow (CBF) at the 'penumbra' (the boundary region between the anterior cerebral artery (ACA) and the middle cerebral artery (MCA)). Left middle cerebral artery occlusion (MCAO) was performed in Sprague--Dawley rats, and then 8 or 16 micrograms kg-1 of nilvadipine was administered to two groups of the rats. The former group was referred to as the 8-MCAO(+) group (n = 8), and the latter group, the 16-MCAO(+) group (n = 8). To a control group (n = 8), only the solvent of nilvadipine was administered. After the administration in each group, CBF and the mean arterial blood pressure (MAP) were continuously measured for 60 min. The MAP in both the 8-MCAO(+) and 16-MCAO(+) groups was significantly lower than in the control group for 25 min after nilvadipine administration (Wilcoxon 2 sample test, p < 0.05). Also, the CBF in the 16-MCAO(+) group was significantly lower (about 20%) for 55 minutes than that in the control group. On the other hand, the CBF in the 8-MCAO(+) group three minutes after nilvadipine administration was not significantly lower than in the control group (Wilcoxon 2 sample test). Our findings confirmed that nilvadipine (8 micrograms kg-1) maintained CBF while lowering the blood pressure in the experimental model of acute cerebral ischemia.

Animals↗
PubMed1996

Impaired autoregulation in an experimental model of chronic cerebral hypoperfusion in rats.

BACKGROUND AND PURPOSE: To verify the hypothesis that impaired autoregulation may contribute to cerebral swelling or hemorrhage after a sudden recovery of perfusion pressure, we studied the chronic effects of cerebral hypoperfusion on the autoregulatory responses of the pial arterioles in situ. METHODS: Eight to 12 weeks after a carotid-jugular fistula was created in rats, experiments were performed under alpha-chloralose and urethane anesthesia. Regional cerebral blood flow (rCBF) was determined by the hydrogen clearance method, and carotid pressure was measured. Using a closed cranial window, we determined the autoregulatory responses of the arterioles (30 to 50 microns) to both hypertension induced by norepinephrine and sudden fistula closure at various mean arterial pressures (MAPs). RESULTS: rCBF on the fistula side was reduced by 27%. Carotid pressure was significantly lower than normal but was immediately increased by fistula closure. The pial arterioles showed marked elongation and enlargement. During induced hypertension, the arterioles in the fistula group started to dilate at an MAP lower than that of the control group (130 versus 180 mm Hg, respectively). The arterioles constricted when the fistula was occluded at normal MAP. However, when the fistula was occluded at an MAP higher than 130 mm Hg, the vessels dilated. CONCLUSIONS: It was demonstrated that (1) chronic hypoperfusion induced impairment of the upper limit of autoregulation and (2) sudden fistula closure under hypertensive conditions caused vasodilation of the arterioles. These findings suggest that rapid restoration of perfusion pressure is possibly followed by a pressure breakthrough phenomenon in a chronically hypoperfused cerebrovasculature.

Animals↗
PubMed1996

Dural-pial arteriovenous malformation with unusual venous drainage.

A 41-year-old female presented with an uncommon mixed dural-pial arteriovenous malformation (AVM) with unusual venous drainage. Angiography at the initial operation for massive intracerebral hematoma in the parietal lobe showed no vascular malformations. Follow-up angiography 3 years later revealed a mixed dural-pial AVM at the previous surgical site. Unexpectedly, the venous drainage from the AVM was not into the patent superior sagittal sinus, but was retrograde into the contralateral cortical veins in the occipital lobe. No skull fracture or sinus thrombosis was demonstrated. The AVM was resected successfully without neurological deterioration. The pial portion of the lesion may have been a congenital anomaly, and the dural portion acquired. The development of a dural AVM at an earlier surgical site is uncommon, and may indicate the possible pathogenesis of acquired dural AVMs unrelated to sinus occlusion or accidental trauma. Furthermore, there are various possible patterns of venous drainage in vascular malformations.

Adult↗
PubMed1996

Improvement of erythroid toxicity by lentinan and erythropoietin in mice treated with chemotherapeutic agents.

Lentinan, an antitumor polysaccharide, has been assessed for its potential in vivo to augment erythroid progenitor cells and protect them from the cytotoxic effects of antitumor chemotherapeutics. Lentinan augmented the level of burst-forming units-erythroid (BFU-E) and accelerated the recovery of the reduced number of BFU-E in mice treated with 5-fluorouracil (5-FU); lentinan did not influence red blood cell counts or colony-forming unit-erythroid (CFU-E) numbers in the femoral marrow. A significant decrease in stem cell inhibitory factor (SCIF) activities in bone marrow and an increase in colony-forming unit-spleen (CFU-S) formation were observed in the lentinan-treated mice. The mechanism of augmented BFU-E formation may be partly due to augmented production of stem cells, giving rise to both CFU-GM and BFU-E. Furthermore, when lentinan administration was followed by administration of erythropoietin (Epo) in 5-FU-treated mice, increases in femoral marrow and splenic CFU-E formation and augmentation of reticulocyte counts were observed beyond the level observed in mice treated with Epo alone. These results suggest that lentinan may augment the effects of Epo on erythropoiesis in the course of anemia and the decreased erythropoiesis in cancer patients receiving chemotherapy.

Animals↗
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↗