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Biomedical subjects

Y Sakurai

Publications and source records attributed to Y Sakurai.

At least 19 recordsLinked to original sources
PubMed1992

Auditory working and reference memory can be tested in a single situation of stimuli for the rat.

The comparison of working and reference memory is one of the most valuable research angles for revealing the precise neural mechanisms of memory. The present study introduces a method to test both auditory working and reference memory during a short period in the rat. The apparatus and stimuli are identical for both memory tasks. High and low tones, between which lies a 5-s interval, are continuously presented. The task for working memory is a continuous nonmatching-to-sample. The rat makes go and no-go responses to indicate whether the current tone is the same as (match) or different from (nonmatch) the preceding tone. The task for reference memory is a continuous discrimination. The rat makes go responses on high-tone trials and no-go responses on low-tone trials. With alternate training in these tasks, the rat comes to perform well in both tasks. The rat can only know which task is employed in a given session from its own response-reward contingency during the early trials of each session.

Animals↗
PubMed1992

Suppressive effect of acupuncture on delayed type hypersensitivity to trinitrochlorobenzene and involvement of opiate receptors.

We reported previously that electroacupuncture (Acu) at an acu-point equivalent to GV-4 in mice either enhanced or suppressed the delayed type hypersensitivity (DTH) to 2,4,6-trinitrochlorobenzene (TNCB, picryl chloride) depending on the time of treatment. We report here the suppression of the efferent phase of DTH to TNCB by Acu in mice. In 7- to 9-week-old male BALB/c, C57BL/6 and ddY mice, significant suppression of the DTH was observed when Acu had been applied once per day for three consecutive days before TNCB challenge. When Acu had been applied a single, significant suppression also occurred. Application to another point (at a middle area of the femoral muscle) failed to suppress the DTH to TNCB. This Acu-evoked DTH suppression was blocked dose-relatedly by pretreatment of systemic naloxone hydrochloride, indicating that opioid receptor-mediated mechanisms are involved in this immune response.

Animals↗
PubMed1992

Comparison of constant infusion and flooding dose techniques to measure muscle protein synthesis rate in dogs.

The exact relationship between the constant infusion and flooding dose techniques for measuring fractional muscle protein synthesis (FMPS) rates was determined in anesthetized dogs during the postabsorptive period, using different isotopes of leucine as tracers. First, [1,2-13C]- and [U-14C]leucine were given simultaneously by prime-constant infusion for 5 h to establish that both isotopes gave comparable FMPS rate values. The tracers gave almost identical FMPS rates and the values obtained after 3 and 5 h were not different. Next, the constant infusion and flooding dose methods were compared in the same animal by first measuring FMPS rate with a prime-constant infusion of [U-14C]leucine, then with a flooding dose of 376 mumol/kg [1,2-13C]leucine. The flooding dose method gave FMPS rates that were markedly greater than the constant infusion values. Finally, the effect of a 376 mumol/kg leucine flooding dose on FMPS rate was assessed using the prime-constant infusion of [U-14C]lysine. The large dose of leucine decreased FMPS rate by approximately 50% because acid-soluble muscle lysine (precursor) specific activity increased while the rate of incorporation of labeled lysine into protein decreased. These results indicate that the flooding dose method gives FMPS rates that are markedly greater than those obtained with the constant infusion method and that the latter method is not valid when a large dose of leucine is given.

Animals↗
PubMed1992

Kanji word reading process analysed by positron emission tomography.

Positron emission tomography, involving the H2(15)O injection technique, was used to study changes in regional cerebral blood flow during Japanese kanji word reading. Three-times intrasubject averaging analysis revealed that the main cortical responses occurred in the bilateral (left-side dominant) posterior inferior temporal area for visual input. We believe the left posterior inferior temporal area processes highly complex morphological features of kanji. For language output, left-side dominant activation of the posterior inferior frontal gyrus and the basal ganglia was found.

Adult↗
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↗