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Biomedical subjects

Y Sakurai

Publications and source records attributed to Y Sakurai.

At least 361 records · Page 20Linked to original sources
PubMed1992

Surface-modulated skin layers of thermal responsive hydrogels as on-off switches: II. Drug permeation.

'On-off' regulation of drug permeation through membranes in response to external temperature change has already been achieved using thermosensitive copolymers of N-isopropyl acrylamide (IPAAm) with butyl methacrylate (BMA). Increasing temperature induced formation of a dehydrated polymeric surface skin layer that stopped drug permeation. In this study, to control 'on-off' permeability of a drug, the polymer surface shrinking process was regulated by changing the length of alkyl side chain of the copolymer methacrylate component. Permeation experiments with indomethacin were performed in response to stepwise temperature changes between 20 and 30 degrees C with copolymers of IPAAm with BMA, hexyl methacrylate (HMA), and lauryl methacrylate (LMA). Burst permeation was found at the initial stage of the second 'on' period for both poly(IPAAm-co-HMA) and poly(IPAAm-co-LMA). These results suggest that drug diffuses during 'off' periods to change the concentration profile in the polymer gel. Polymer surface skin formation maintains a localized high water content inside the polymer gel even if drug permeation stops. The length of the alkyl side chain is an important parameter to control 'on-off' permeability of drug.

Acrylic Resins↗
PubMed1992

Japanese crossed Wernicke's aphasia.

A right-handed Japanese man with no personal or family history of left-handedness developed severe Wernicke's aphasia, a mild constructional disorder, and slight left hemiparesis. MRI revealed infarction in the territory of the righ middle cerebral artery, including areas homologous to Broca's and Wernicke's areas. The cerebral blood flow in these areas remained diminished even after language activation. The most likely explanation is that language production occurred in the left Broca's area, while language comprehension occurred in the right Wernicke's area (a dissociated aphasia).

Aphasia, Wernicke↗
PubMed1992

Aneurysms arising from the proximal (A1) segment of the anterior cerebral artery. A study of 38 cases.

This study reviews aneurysms of the proximal segment (A1) of the anterior cerebral artery in 38 patients (23 men and 15 women) and their surgical, angiographic, and clinical management. Thirty-seven aneurysms were saccular and one was fusiform. The incidence of A1 aneurysms among a total of 4295 aneurysm cases treated was 0.88%. Multiple aneurysms occurred in 17 patients (44.7%) of the 38 cases; in 10 (58.8%), there was bleeding from the A1 aneurysm. The aneurysms were classified into five categories according to the mode of origin of the aneurysm in relation to the A1 segment: in 21 cases, aneurysms originated from the junction of the A1 segment and a perforating artery; in eight, from the A1 segment directly; in six, from the proximal end of the A1 fenestration; and in two, from the junction of the A1 segment and the cortical branch. One patient had a fusiform aneurysm. Computerized tomography (CT) of these aneurysms revealed bleeding extending to the septum pellucidum similar to that of anterior communicating artery aneurysms. When performing radical surgery it is very important to recognize the characteristics of A1 aneurysms, including multiplicity, a high incidence of vascular anomalies (especially A1 fenestration), and their similarity to anterior communicating artery aneurysms on CT.

Adult↗
PubMed1992

Cerebral blood flow and metabolism following superficial temporal artery to superior cerebellar artery bypass for vertebrobasilar occlusive disease.

In order to clarify the effectiveness of extracranial-intracranial bypass operations in patients with vertebrobasilar occlusive disease, the authors used positron emission tomography to investigate the cerebral blood flow (CBF) and metabolism of eight patients undergoing superficial temporal artery (STA)-superior cerebellar artery (SCA) bypass procedures. In the preoperative studies, CBF in the region of the posterior fossa was low and the oxygen extraction fraction (OEF) was high, the so-called "misery perfusion syndrome." Such changes were evident in both the posterior circulation and the anterior circulation regions. Postoperatively, there was a significant increase in CBF, a significant decrease in the OEF not only in the region of posterior circulation but also over the entire brain, and a disappearance of the uncoupling between CBF and oxygen metabolism. The STA-SCA bypass procedure is effective in improving CBF and metabolism in patients with vertebrobasilar occlusive disease.

Arterial Occlusive Diseases↗
PubMed1992

[Naming difficulties seen in a case of alexia with agraphia caused by a left postero-inferior temporal lesion].

A 71-year-old right-handed man presented writing and reading difficulties as well as naming difficulties. Neuropsychological examinations revealed mild fluent type aphasia accompanied by alexia and agraphia predominantly affecting kanji and also severe naming difficulties. Brain MRI showed cerebral subcortical hemorrhage extending from the anterior one-third of the left temporal lobe to the temporo-occipital junction involving the fusiform gyrus. The analysis of the several reported cases with severe alexia with agraphia for kanji including ours revealed a close correlation between the severity of kanji writing disturbances and that of naming difficulties. It was also shown that cases with severe naming difficulties had lesion extending anteriorly to the anterior middle temporal gyrus or medially to the parahippocampal gyrus, suggesting that the disconnection between the parahippocampal gyrus and other cortices including the temporal lobe was essential for production of naming difficulties.

Aged↗
PubMed1992

[Benefits of totally implanted central venous access in patients with cancer].

A totally implanted system for improved central venous access has been investigated during 44 procedures in 38 patients (37 with cancer and one with cerebral infarction). Most of them lacked peripheral venous sites, and ten per cent of the patients had a prior chronic external central venous catheter. This system is implanted using local anesthesia and consists of a port connected to a central venous catheter threaded through the subclavian vein into the superior vena cava. The system was used mainly for intermittent administration. Injections and infusions of virtually all classes of antineoplastic drugs or antibiotics (81%), blood components (26%), hyperosmolar total parenteral nutrition (47%), and intravenous solutions (53%) were administered through the system. Twenty-one patients died with the system still functioning. Ten of the systems were eventually removed, either after completion of therapy (1) or because of a complication (9). In another 13 cases the devices were working at the completion of the study. Infections accounted for nine per cent of port complications. Four systems became occluded and two of them were replaced. Overall patient acceptance was excellent. This system can be assigned to an appropriate setting that facilitates management of the cancer patient.

Adolescent↗
PubMed1992

[A case of acute subdural hematoma in the posterior fossa with idiopathic thrombocytopenic purpura].

Intracranial bleeding is one of fatal complications in idiopathic thrombocytopenic purpura although its reported incidence is low. A case of spontaneous acute subdural hematoma complicated with idiopathic thrombocytopenic purpura was reported. He was hospitalized complaining of sudden onset of headache and nasal bleeding without neurological deficit. CT scan revealed subdural hematoma in the posterior fossa especially below the tentorium cerebelli. Further hematological examination proved very low platelet count (1,000/mm3) and antiplatelet antibody in confirmation of a diagnosis of idiopathic thrombocytopenic purpura. As his neurological status was good, he was treated medically. His symptoms and platelet count improved gradually with corticosteroid therapy. Reviewing the literature, acute subdural hematoma with idiopathic thrombocytopenic purpura was quite rare and only three cases reported.

Acute Disease↗
PubMed1991

Toxicity and antitumor activity against solid tumors of micelle-forming polymeric anticancer drug and its extremely long circulation in blood.

Toxicity and in vivo antitumor activity against five solid tumors (C 26, C 38, M 5076, MKN-45, MX-1) of Adriamycin (ADR)-conjugated poly(ethylene glycol)-poly(aspartic acid) block copolymer (PEG-P[Asp(ADR)]) were evaluated, and its pharmacokinetic behavior in blood and biodistribution by i.v. injection were obtained. PEG-P[Asp(ADR)] was revealed to express higher antitumor activity than ADR against all the examined tumors except MKN-45. Especially against C 26, PEG-P[Asp(ADR)] expressed critical suppression of tumor growth and considerably prolonged life span of the treated mice. PEG-P[Asp(ADR)] was observed in blood at much higher concentrations with a longer half-life than ADR after the i.v. injection. PEG-P[Asp(ADR)] was known to form a micellar structure with a diameter of approximately 50 nm and a narrow distribution in phosphate-buffered saline. Therefore, the stabilized circulation of ADR residue in blood by binding to the block copolymer was considered to result from the micellar structure which possesses the hydrated outer shell composed of the poly(ethylene glycol) chains.

Animals↗
PubMed1991

Effects of YM264, a novel PAF antagonist, on puromycin aminonucleoside-induced nephropathy in the rat.

We investigated the effects of YM264, WEB2086, methylprednisolone and ticlopidine on puromycin-induced nephropathy in the rat. Puromycin produces marked proteinuria, hypercholesterolemia, and hypoalbuminemia. The structurally differing PAF antagonists YM264 and WEB2086 inhibited proteinuria and improved hypercholesterolemia and hypoalbuminemia. Methylprednisolone also exhibited a beneficial effect on these variables. However, ticlopidine, a platelet inhibitor, showed no inhibitory effect on nephropathy. These results indicate that PAF may play a major role in puromycin-induced nephropathy in the rat, and that PAF antagonists may prove of therapeutic value in the treatment of nephropathy in humans.

Animals↗
PubMed1991

Specific cleavages of arginyl peptide bonds at basic amino acid pairs by a serine proteinase from the microsomal membranes of rat liver.

The specificity of action of a serine proteinase from the microsomal membranes of rat liver was investigated at pH 7.5 and 37 degrees C using various peptides as substrates. HPLC analyses of the peptides produced followed by their amino acid analyses have revealed that the enzyme is a unique endopeptidase specifically cleaving arginyl peptide bonds at paired basic amino acid residues. Thus, the enzyme is suggested to be a kind of processing proteinase involved in the conversion of proproteins to their mature forms. Indeed, the enzyme cleaved specifically the NH2-terminal 20-residue peptide of proalbumin at the Arg-Arg sequence.

Amino Acid Sequence↗
PubMed1991

Treatment of proximal vertebral artery stenosis. Vertebral to subclavian transposition.

For vascular reconstruction in cases of atherosclerotic stenosis at the origin of the vertebral artery, we use vertebral to subclavian artery transposition. We discuss the advantages and effectiveness of such treatment based on a study of 32 cases. We have experienced neither surgical mortality nor morbidity and the outcome at the time of discharge has been favourable. Follow-up revealed no deaths, however, three cases exhibited symptoms of cerebral ischaemia. One had a supratentorial completed stroke, and the other two hat TIA or RIND, but without any notable lesion in the angiograms. There were no cases of cerebral infarction of the posterior fossa. We believe that this method should be the first choice for treatment of cases without lesions of the subclavian artery for the following reasons: serious operative complications have not been encountered, surgical invasion is minimal, temporary occlusion of the common carotid artery is unnecessary, the operation can be done by occluding only the vertebral artery, and unlike various bypass operations, anastomosis is required at only one location and is consequently technically uncomplicated. Following anastomosis the cerebral blood pathway is physiological.

Adult↗
PubMed1991

Acute revascularization for progressing stroke.

The effectiveness of acute stage vascular reconstruction in cases of progressing stroke is reported. The clinical material consists of 28 cases of progressing stroke in the anterior circulation upon which vascular reconstruction was performed. Following admission, brain protective substances (500 ml mannitol, 500 mg vitamin E, 500 mg phenytoin) and dextran, were administered to the patients, and induced hypertension was also performed. Changes in symptoms were then observed and vascular reconstruction was carried out in cases where symptoms progressed. The vascular lesion was on the internal carotid artery in 8 cases and on the middle cerebral artery in 20 cases. Complete disappearance of neurological symptoms was obtained in 12 cases, whereas only mild neurological symptoms remained but a return to normal social life was possible in 11 other cases. Symptoms remained in three cases and there were two fatalities. In a long-term follow-up study, there were no cases of aggravation of symptoms due to ischaemic stroke. Moreover, the reconstruction was judged as effective on the basis of cerebral blood flow and metabolism. We concluded that acute vascular reconstruction for progressing stroke under the administration of brain protective substances is effective in preventing the progression of neurological symptoms.

Adult↗
PubMed1991

Early CT features of ruptured cerebral aneurysms of the posterior cranial fossa.

This report describes our retrospective evaluation of CT features of the acute phase in 34 cases of ruptured cerebral aneurysms of the posterior cranial fossa. The results are as follows. 1. Examination of cisternal haematoma distribution revealed that SAH had extended to the supra- and infratentorial cisterns in 28 cases (82%). There were only 6 cases (18%) in which SAH was confined to the posterior cranial fossa only but even when there was subarachnoid haematoma in both the supra- and infratentorial cisterns, thick haematomas were seen at the periphery of the brain stem. In cases of vertebral artery-posterior inferior cerebellar artery aneurysms (VA-PICA AN), haematomas in the ambient cistern were thicker on the aneurysm side. In addition, in cases of basilar artery-bifurcation (BA-Bifurcation AN) and basilar artery-superior cerebelli artery aneurysms (BA-SCA AN), there were many thick, high-density haematomas in the interpeduncular cistern. 2. The rate of intracerebral haemorrhage was extremely low (1 patient). 3. The rate of intraventricular haemorrhage was high, and these haemorrhages demonstrated a reflux pattern. 4. The rate of hydrocephalus was high (76.5%) in comparison with that noted in association with SAH due to the rupture of anterior circulation aneurysms.

Adult↗
PubMed1991

Limitation of temporary vascular occlusion during aneurysm surgery. Study by intraoperative monitoring of cortical blood flow.

The limitations of temporary vascular occlusion during aneurysm surgery as evidenced by the postoperative ischemic symptoms in relation to cerebral blood flow were studied. Six of the 39 cases had postoperative ischemic neurological deficit. When residual cerebral blood flow was below 15 mL/min/100 g, transient symptoms were seen when temporary clipping was for 10-20 minutes. When more than 20 minutes of clipping was required, irreversible deficits were found. Correlations between residual cerebral blood flow, duration of temporary clipping, and postoperative ischemic symptoms were found. The monitoring of cortical cerebral blood flow is an effective means for determining the limits of temporary vascular occlusion.

Adult↗
PubMed1991

Novel cerebroprotective agents with central nervous system stimulating activity. 1. Synthesis and pharmacology of 1-amino-7-hydroxyindan derivatives.

To develop a novel cerebroprotective agent with central nervous system (CNS) stimulating activity, a series of 1-amino-7-hydroxyindan derivatives was synthesized, and their effects on the survival time of mice under hypoxic conditions were tested. CNS-stimulating activity was also evaluated by examining the promotional effect on the recovery from cerebral concussion induced coma in mice. Several compounds prolonged the survival time of mice in hypoxic conditions at a dose of 30 mg/kg (sc or ip) and 100 mg/kg (po). They also exhibited the promotional effects on recovery from coma at a dose of 100 mg/kg po. The three most potent compounds in both tests, 1-amino-7-hydroxy-6-(1-methylpropyl)indan, 1-amino-7-hydroxy-4, 6-dimethyl-2-phenylindan, and 1-amino-7-hydroxy-2,2,4,6-tetramethylindan were selected for further investigations. Structure-activity relationships were also discussed.

Animals↗