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Biomedical subjects

W Taki

Publications and source records attributed to W Taki.

At least 127 records · Page 7Linked to original sources
PubMed1985

Histologic changes in rat brain tissue caused by neodymium-yttrium aluminum garnet laser irradiation. II. Cerebellum.

Histologic changes after neodymium-yttrium aluminum garnet laser irradiation were evaluated in the rat cerebellum. Irradiation of 60 W (corresponds to 45.2 W/mm2) to the posterior fossa was dangerous even in adult rats, although this value was safe for the rat cerebral hemisphere as previously reported. The histologic changes caused by neodymium-yttrium aluminum garnet laser irradiation were similar to those caused by thermal energies. To the adult rat cerebellum, 45 W (35.2 W/mm2) can safely be applied. For the further use of the neodymium-yttrium aluminum garnet laser in neurosurgery, our findings should be taken into consideration.

Animals↗
PubMed1985

[Brain stem auditory evoked potentials for assessment of isolated fourth ventricle in three patients].

Isolated fourth ventricle is an untoward but interesting complication caused by the shunt procedure, which has been recognized since the introduction of CT scanning. Auditory brain stem evoked potentials (BAEPs) were recorded in a patient with isolated fourth ventricle for assessment of brain stem function. Case 1. A 9-year-old boy. He had undergone repair of the lumbosacral meningocele at birth, followed by shunting procedures, including repeated shunt revision, for hydrocephalus which subsequently developed. CT scanning on admission revealed typical findings of isolated fourth ventricle, while neurological examination disclosed no abnormalities. BAEPs on admission revealed normal waves both in amplitude and latency. This patient has been doing well without further shunting procedures. Case 2. A 17-year-old male was admitted with complaints of headache, diplopia, nystagmus and ataxic gait. He had a history of operation for radical removal of cerebellar astrocytoma and lateral ventriculo-peritoneal shunt at 9 years of age. CT scanning on admission revealed a typical isolated fourth ventricle, and fourth ventricle-peritoneal shunt was performed. Postoperative serial BAEPs revealed gradual improvement of brain-stem function. Clinically he has been symptom-free thereafter except for slight nystagmus. Case 3. A 2-year-old female suffering from hydrocephalus developed after neonatal intraventricular hemorrhage and ventriculitis. After repeated revision of a lateral ventriculo-peritoneal shunt, she was admitted in semicoma with vomiting and opisthotonic posture. CT study revealed an isolated fourth ventricle and preoperative BAEPs showed marked abnormalities. Although fourth ventricle-peritoneal shunt was performed, no remarkable change in BAEPs was obtained, and neurological deficit of considerable degree persisted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

New small-caliber antithrombotic vascular prosthesis: experimental study.

Vascular prostheses with the inner diameter smaller than 1 mm were implanted to the common carotid artery of rats, and their patency was examined. Four types of tubes were prepared for this purpose in Experiment 1: polyethylene (PE), poly-(acrylic acid)-grafted polyethylene (PE-AA), polyacrylamide-grafted polyethylene (PE-AAm), and poly(vinyl alcohol) (PVA) tubes. Comparative studies made using nonsuture anastomosis revealed that the PE-AAm and PVA tubes were antithrombotic, although disconnection was noted at the anastomotic sites within 1 week and 1 month, respectively. Thereafter in Experiment 2, the PVA tubes were implanted to the common carotid artery of 20 rats using conventional anastomosis. Neither anticoagulants nor fibrinolytic agents were used in both series of experiments. Patency of the PVA tubes was 80% after 1 week and 70% after 1 month. In patent cases after 1 month, the luminal surfaces of the prostheses and the host arteries were examined using scanning electron microscopy. The lumen of the arteries and anastomotic sites was covered with endothelial cells, while the lumen of the PVA tubes was free from thrombi and there was no neointima formation. So far, there has been reported no manmade material that has completely antithrombotic property in vivo. However, our studies disclosed that PVA is antithrombotic and one of the most promising materials for the inner surface of small vascular prostheses.

Acrylic Resins↗
PubMed1984

STA-MCA anastomosis in patients with skull base tumours involving the internal carotid artery--haemodynamic assessment by ultrasonic Doppler flowmeter.

The role of superficial temporal artery--middle cerebral artery (STA-MCA) anastomosis was investigated with an ultrasonic Doppler flowmeter in 3 patients with sphenoid ridge meningiomas and one with a parasellar malignant teratoma, all of which involved the intracranial internal carotid artery. The intraoperative Doppler flow study revealed a remarkable increase in flow volume of the STA after trial occlusion of the middle cerebral artery in one case and permanent occlusion in two cases. These results substantiate the effectiveness of STA-MCA anastomosis. We also discuss surgical and other contrivances for obtaining sufficient blood supply from this bypass to prevent cerebral ischaemia in the acute phase after elective or accidental occlusion of a major cerebral artery. This is the first report of STA-MCA anastomosis in cases with brain tumour.

Carotid Artery Diseases↗
PubMed1984

Extent of thermal penetration of Nd-YAG laser--histological considerations.

The extent of thermal penetration of Nd-YAG laser was studied histologically. The material was obtained from seven cases of various types of intracranial and extracranial tumours and normal temporal muscle obtained at operation. After irradiation of the tumour surface with the laser, the tumours were removed and depth and width of pathological changes caused by heat were studied. Histologically, materials consisted of a vaporized surface, carbonized, vesicular, necrotic, oedematous layer and surrounding intact brain tumour tissue. There was a direct relationship between the thermal effect and the irradiated thermal energy (watt x exposure time x pulse number). The results showed that the thermal effect was limited to a depth of 6 to 10 mm from the irradiated surface when irradiated 4 times at the power of 90 watts for 2 seconds.

Adult↗
PubMed1983

Krypton-81m single photon emission tomography and the collateral circulation in carotid occlusion: the role of the circle of Willis and leptomeningeal anastomosis.

Cerebral perfusion images were investigated in patients with carotid artery occlusion, using single photon emission computed tomography with the infusion of krypton-81m into the internal, common carotid and vertebral arteries. The contribution of the circle of Willis and cerebral cortical anastomoses to the maintenance of adequate blood supply into the involved hemisphere was analysed. It was concluded that the cerebral perfusion image is superior to angiography in evaluating collateral circulation, and in the case of carotid occlusion, the circle of Willis is important in preventing infarction in the territory of the perforating arteries, while the cerebral cortex mainly receives its blood supply through the cortical leptomeningeal anastomoses, illustrating the major role of the leptomeningeal anastomosis as a collateral channel.

Adult↗
PubMed1983

Superimposition of Krypton-81m single photon emission CT and X-ray CT images for cerebral blood flow evaluation.

Selective arteriographic infusion of krypton-81m was used to obtain cerebral single photon emission computed tomograms. These were then superimposed on X-ray computed tomograms to assess topographically the perfusion of the entire brain. This method enhances the detecting capability for abnormal perfusion areas and has been used in 21 patients with various brain diseases.

Carotid Artery Thrombosis↗
PubMed1983

Intra-arterial ACNU therapy for malignant brain tumors. Experimental studies and preliminary clinical results.

The authors examined the growth rate of mouse 203 glioma cells in vitro and found it to be markedly inhibited after exposure to ACNU for 5 minutes at a drug concentration of 100 micrograms/ml. Rats that had undergone intracranial implantation of T1 neurogenic tumor were treated by 5 mg/kg of ACNU administered either intravenously or intra-arterially. The median survival times for the control animals and the animals undergoing intravenous or intracarotid administration of ACNU were 23, 29, and 46 days, respectively. The difference in survival time between the intravenous and intracarotid administration groups was statistically significant (p less than 0.01) when examined by the Cox-Mantel test. In a clinical trial, 17 patients with glioblastoma were treated by ACNU, eight intravenously and nine by the intra-arterial route. The drug was given in doses of 2 to 3 mg/kg at least twice before and twice after a course of postoperative radiotherapy. Intra-arterial administration was performed over a period of 5 minutes under local anesthesia. The median postoperative survival time for the patients in the intra-arterial group was 12.5 months, compared with 9.0 months for those in the intravenous group. The survival rate for the intra-arterial group was slightly higher, although statistically not significant, probably because the number of cases was small. The degree of thrombocytopenia due to ACNU tended to be less marked in the intra-arterially treated patients. The theoretical advantages of the intra-arterial administration of ACNU are discussed.

Adult↗
PubMed1982

Management of spontaneous carotid-cavernous fistulae.

Fifteen cases of spontaneous carotid-cavernous fistulae, including 4 patients with spontaneous cure and 8 treated with electrothrombosis, are reviewed. Careful angiographic observation will verify closure of the fistula. Aggravation of visual and/or ocular symptoms can also develop with spontaneous carotid-cavernous fistulae. Recurrence of symptoms and development of collaterals were noted, especially after carotid ligation or embolization of the external carotid artery. Electrothrombosis successfully closed the fistulae in 7 patients. The internal carotid artery was occluded in 1 patient who had a preoperative carotid stenosis at the cervical level. The ability to differentiate angiographically between single and multiple fistulae provides a new possibility that spontaneous carotid-cavernous fistulae can be treated with detachable balloon catheters.

Adult↗
PubMed1982

The Nd:YAG laser in neurological surgery.

The Nd:YAG laser has been applied in microneuro-surgery and has been found to be quite effective in removing had and hemorrhagic tumors such as meningiomas, tumors of the deep skull base, or tumors deep in the ventricle. Another indication for the use of the Nd:YAG laser is to open the thick sellar floor in transsphenoidal operations.

Adenoma↗
PubMed1981

Blood compatibility of hydrophilic polymers.

Blood compatibility has been studied for hydrophilic polymers such as poly(vinyl alcohol) (PVA), its derivative, and polyethylene grafted with water-soluble monomers. The surfaces in contact with electrolyte solutions have been characterized by measuring the zeta potentials. The study of plasma protein adsorption on these polymers has revealed that bovine serum albumin as well as bovine serum fibrinogen adsorbs to a lesser extent as the hydrophilicity of the polymers increases. Platelet deposition and fibrin formation, examined using platelet-rich plasma, have been found to take place less significantly on PVA as well as sodium acrylate- and acrylamide-grafted polyethylene than on nongrafted and acrylic acid-grafted polyethylene. Ex vivo experiments with canine whole blood have shown that formation of thrombus on PVA is less than on siliconized glass but increases upon heat treatment which reduces the hydrophilicity. When PVA tubes of about 1 mm diameter are anastomosed to the carotid artery of rat, the patency rate is found to depend strongly on the anastomotic technique. From the results on the zeta potential and the experiments in vitro and ex vivo it can be concluded that the material having a surface from which solvated, neutral chains are extended into the outer aqueous phase may exhibit excellent resistance to thrombus formation.

Adsorption↗