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Biomedical subjects

Y Horikawa

Publications and source records attributed to Y Horikawa.

At least 19 recordsLinked to original sources
PubMed1992

2-(Carboxycyclopropyl)glycines: binding, neurotoxicity and induction of intracellular free Ca2+ increase.

The excitatory actions of the eight stereoisomers of 2-(carboxycyclopropyl)glycine (CCG), conformationally rigid glutamate analogues, were analyzed for the glutamate receptor subtypes by means of binding assays with rat brain membranes. All CCG isomers inhibited the binding of [3H]3-(2-carboxypiperazine-4-yl)propyl-1-phosphonic acid ([3H]CPP) to N-methyl-D-aspartate (NMDA) receptors. The (2S,3R,4S) isomer (L-CCG-IV) was the most potent agonist for the NMDA receptor and its binding potency was 17- and 790-fold higher than that of L-glutamate and NMDA, respectively. The (2S,3S,4R) isomer (L-CCG-III) showed a potent inhibitory activity for [3H]D-aspartate uptake. Further, L-CCG-IV caused a marked increase of intracellular free Ca2+ concentration [( Ca2+]i) and potent neurotoxicity in the single rat cerebral cortical neurons in vitro, and both were blocked effectively by the NMDA antagonists. Significant correlations were observed between neurotoxicity and the increase of [Ca2+]i and [3H]CPP binding affinity to the NMDA receptor.

Amino Acids, Dicarboxylic↗
PubMed1992

Influence of CRT workstation on observer's performance.

The effects of the operability of the prototype CRT workstation and room illumination upon observer's performance were studied. In the experiment of reading CT images as a routine daily work at the CRT workstation, the average time required to analyse one CT image under a room illuminance of 100 lux was longer than that on the film viewbox. Prolongation occurred due mainly to the longer time required to retrieve and to arrange images as observers desired, and the limitation to the number of images simultaneously displayed on two CRT monitors. In the ROC studies to detect small pulmonary nodules on CRT images of computed radiography with imaging plate, illuminance around 170 lux showed the best result and a statistically significant difference (P less than 0.05) as compared with that of 480 lux. In addition to the radiologist's visual performance, room illumination must also be taken into consideration as it influences the observer's performance and diagnostic efficiency.

Computer Systems↗
PubMed1992

Ischemic optic neuropathy in a female carrier with Fabry's disease.

We report ocular findings of a patient with anterior ischemic optic neuropathy (AION) and cilioretinal artery occlusion in a female carrier of Fabry's disease. Fluorescein angiography revealed delayed filling of the upper and temporal part of peripapillary choroidal vessels and capillaries of the right optic disk and late filling of the cilioretinal artery. CT scanning was performed several times in early stages and demonstrated thickening of the intraorbital optic nerve due to ischemic edema. About 5 months later, the fellow eye showed optic disk edema, an early sign of AION, and was treated by systemic corticosteroid and urokinase whereby AION did not progress.

Adult↗
PubMed1992

Preparation and pharmacological evaluation of 4-(1,4-benzoquinon-2-yl)-4-phenylbutanamides as potential cerebral protective agents.

A new series of 4-(1,4-benzoquinon-2-yl)-4-phenylbutanamides (2) were synthesized for evaluation of their pharmacological activities. All these compounds synthesized showed significant antilipidperoxidation (ALP) activities with brain homogenate in rats and some of them possessed a protective effect against hypobaric hypoxia in mice. Especially, a thiomorpholine derivative (2l, SUN-4757) showed a wide efficacy spectrum to a variety of experimental screening assays designed for cerebral protective agents, and it had a high LD50 value.

Animals↗
PubMed1992

Reversal of alpha-methyltyrosine-induced hypoactivity by 6-(R)-5,6,7,8-tetrahydro-L-erythrobiopterin (R-THBP) in mice.

The effects of peripheral administration of 6-(R)-5,6,7,8-tetrahydro-L-erythrobiopterin dihydrochloride (R-THBP), a natural cofactor for tyrosine and tryptophan hydroxylases, were investigated in mice treated with a competitive inhibitor of tyrosine hydroxylase, alpha-methyltyrosine (alpha-MT). A subcutaneous dose of 250 mg/kg of alpha-MT decreased markedly both ambulatory activity and cerebral contents of norepinephrine, dopamine and their metabolites in mice. An intraperitoneal dose of 100 mg/kg of R-THBP, which did not alter ambulatory activities in normal mice, improved the hypoactivity in alpha-MT-treated mice. Moreover, R-THBP at intraperitoneal doses of 60 and 100 mg/kg inhibited the impairment of cerebral catecholamine metabolism induced by alpha-MT in mice. We suggest that the reversal of the alpha-MT effects by R-THBP might be due to reactivation of tyrosine hydroxylase in the central nervous system.

Animals↗
PubMed1992

[Combined therapy with prostaglandin E1 ointment and lumbar sympathetic ganglion block on intractable skin ulcers accompanied by Bürger's disease].

For the 2 patients with intractable skin ulcers and pain accompanied by thromboangiitis obliterans (Bürger's disease), we applied combined therapy with lumbar sympathetic block, continuous epidural block and prostaglandin E1 ointment. Prostaglandin E1 (PGE1) was prepared as a topical ointment by mixing with Plastibase (polyethylene resin, 5%, liquid paraffin, 95%) at a concentration of 10 micrograms.g-1. The ointment was kept in a refrigerator until use. Following debridement and washing of the surface of ulcers as required, the ointment was applied evenly onto the surrounding and over the surface of each ulcer 2 times daily after sterilization. With this therapy the ulcers were cured completely in 10 days after the start of treatment. No side effect was observed both locally and systemically. Although the combined therapy we used with prostaglandin E1 ointment was a noninvasive method, a remarkable shortening of the period of treatment was achieved.

Aged↗
PubMed1991

[Stereotactic irradiation using a linear accelerator with helmet-type shell].

A new method is proposed for external stereotactic and three-dimensional irradiation for a small target in the skull. In this method, we use a special long tube collimator, helmet-type shell (guiding rods are attached to the shell using the CT-stereotactic apparatus) and 10 MV linear accelerator. The patient's head is fixed conservatively by the helmet-type shell. In the phantom experiment, the 90% isodose area was 10 mm in diameter, and the error between the geometrical center of the target and the irradiated center was 2 mm.

Brain Neoplasms↗
PubMed1991

[Arterial embolization therapy for metastatic bone and soft-tissue tumors with microcatheter and microcoils].

Transcatheter arterial embolization therapy was performed in fifteen patients with hypervascular metastatic bone and soft-tissue tumors (7 from renal carcinoma, 5 from hepatocellular carcinoma, and one each from breast, thyroid, and cholangiocarcinoma). Sites of metastasis were spine (7), pelvis (5), skull (2), paraspine (2), chest wall (1), and thigh (1). Five patients had not responded to previous radiation therapy and hyperthermia. Embolization of feeding arteries was performed superselectively with long tapered catheters or coaxial microcatheters. Emulsion of Lipiodol and anticancer agent, polyvinyl alcohol sponge, gelatin sponge, and microcoils were used as embolic materials in various combinations. Relief of pain was experienced in 14 of 15 patients. Two patients were operated following embolization with minimal blood loss. Change in tumor size was evaluated by CT or MRI in ten patients. Reduction of tumor size were more than 50% in five patients, from 25% to 50% in two, and no change in three patients. Especially, patients embolized with microcatheter and microcoils showed excellent long-term results. No serious complications were seen. In conclusion, superselective arterial embolization therapy with coaxial microcatheter and microcoils was proved to be an useful treatment for hypervascular metastatic bone and soft-tissue tumors.

Adult↗
PubMed1991

Noise effects on spike propagation in the stochastic Hodgkin-Huxley models.

Effects of membrane current noise on spike propagation along a nerve fiber are studied. Additive current noise and channel noise are considered by using stochastic versions of the Hodgkin-Huxley model. The results of computer simulation show that the membrane noise causes considerable variation of the propagation time of a spike (thus changes in interspike intervals) for a small unmyelinated fiber of radius 0.1 approximately 1 micron.

Animals↗
PubMed1991

Effects of atrial natriuretic peptide on ischemic brain edema in rats evaluated by proton magnetic resonance method.

We examined the effect of atrial natriuretic peptide on cerebral edema in 96 rats. Forty-four rats were given 30 (n = 11), 120 (n = 26), or 150 (n = 7) micrograms/kg of the peptide intravenously over 24 hours after occlusion of the left middle cerebral artery to induce cerebral ischemia. We then measured the brain water content, the brain sodium and potassium contents, the in vitro proton nuclear magnetic resonance longitudinal (T1) and transverse (T2) relaxation times, and the area of the edematous regions. Compared with saline treatment (n = 39), peptide treatment decreased the brain water content in a dose-dependent manner and decreased the brain sodium content significantly (p less than 0.05). Peptide treatment also suppressed the lengthening of both T1 and T2 in edematous tissue (p less than 0.05 and p less than 0.01, respectively) and reduced the area of the edematous regions observed by magnetic resonance imaging (p less than 0.01). Atrial natriuretic peptide appears to have a pharmacological effect on ischemic brain edema, possibly by suppressing the elevation of water content through regulation of electrolyte transport in the brain.

Animals↗
PubMed1991

Induction of kinetic cell death and its underlying mechanisms.

Using a modified Langendorff system, we established an experimental model of kinetic cell death in the rat heart. After calcium (5.5 mM) was loaded for 20 min and 10(-7) mol isoproterenol was then delivered to the perfusion medium, the hearts developed tonic contracture. Histological examination of the myocardium revealed widespread kinetic cell death. Stimulation of alpha-adrenoceptors with phenylephrine did not induce kinetic cell death, even after calcium loading. In our kinetic cell death model in the rat, the outflow of creatine phosphokinase into the perfusion medium was increased after isoproterenol application, with a peak occurring at 45 min. The peak transient increase in the intracellular calcium ion concentration (the Ca-transient) was measured using Fura2/AM, and was found to be augmented by increasing the calcium concentration of the perfusion medium. These results suggest that in the presence of an increased intracellular calcium concentration, even slight stimulation of beta-adrenoceptors can easily induce myocardial injury.

Animals↗
PubMed1991

[An evaluation of cerebral blood flow and metabolism of reconstructive vascular surgery using positron emission tomography--a report of 4 cases].

Changes in cerebral hemodynamics due to reconstructive cerebral vascular surgery were evaluated using positron emission tomography (PET). Three minor stroke cases and 1 TIA case, brought on by main trunk stenosis, were included. STA-MCA anastomoses was performed in two of the cases and carotid endarterectomy was performed in the remaining two cases. CBF, CBV, OEF, CMRO2 and CBF/CBV were investigated using PET with the ROIs fixed in both normal and stenosis areas. On the two cases of STA - MCA anastomosis, clear hemodynamic improvement was not demonstrated. On the two carotid endarterectomy cases, the hemodynamic factors showed improvement.

Aged↗
PubMed1991

[The application of in vivo diffusion weighted magnetic resonance imaging to intracranial disorders].

We have developed a magnetic resonance (MR) spin echo method to obtain diffusion weighted imaging using motion-probing gradient (MPG) pulses in one or three orthogonal directions before and after a 180 degree pulse. Phantom models containing water and acetone, normal volunteers and patients with brain tumors, brain edema and infarction were examined. Experimental models of brain edema including triethyltin intoxication and cold injuries were also examined in Wistar rats. MRI was performed at a 1.0-T clinical machine or a 4.7-T experimental machine using spin echo pulse sequences with or without additional MPGs on one or three orthogonal axes. The one direction method was useful to define diffusion anisotropy of myelinated axonal fibers in white matter. Faster diffusion was detected in the white matter parallel to the direction of MPGs. On the other hand, slower diffusion was detected perpendicular to the direction of MPGs because the myelin sheath restricted water diffusion. The three orthogonal gradients method was useful to demonstrate the difference in the diffusion coefficients in various diseases due to its larger total gradient strength. The clear distinction between the cytotoxic edema, which revealed slower diffusion, and the vasogenic edema, which revealed faster diffusion, was demonstrated in the experimental models using diffusion weighted image. In the clinical cases, faster diffusion was demonstrated in the brain tumor and perifocal vasogenic edema, which was in agreement with the results in the experimental models of rats. Brain tumors such as low grade astrocytoma with microcysts and perifocal vasogenic edema have very wide extracellular space.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effects of atrial natriuretic peptide on brain oedema: the change of water, sodium, and potassium contents in the brain.

We examined the effect of atrial natriuretic peptide (ANP) administration on cerebral oedema in rats. Intravenous ANP infusion with total dose of 120 micrograms/kg and 100 micrograms/kg suppressed the elevation of water and Na contents in left middle cerebral artery (MCA) occluded and cold injured brain tissue, indicating that ANP has a suppressive effect on cerebral oedema. Similar ANP infusion at a low dose of 1 microgram/kg/h for 6 h also resulted in observation of the anti-oedematous effect in both models, with no observable occurrence of the known systemic effects of ANP on systolic blood pressure (SBP), heart rate (HR), hematocrit, or serum electrolyte ion (Na+, K+, Cl-) concentrations. The results thus suggest that the anti-oedematous effect of ANP is attributable to water and Na content control by ANP specific to the damaged tissue, possibly through inhibition of sodium transport. Taken together with a recent study in which it was shown that ANP might inhibit sodium transport in cerebral microvessel, our results suggest that ANP suppresses the development of brain oedema by inhibiting sodium transport and the coupled water influx.

Animals↗
PubMed1990

Effects of atrial natriuretic peptide on ischaemic brain oedema evaluated by the proton magnetic resonance method.

The effect of atrial natriuretic peptide (ANP) on cerebral oedema in rats was examined by magnetic resonance (MR). After occlusion of the left middle cerebral artery (MCA) to induce cerebral ischaemia, rats received continuous infusion of ANP for 24 h at a total dose of 120 micrograms/kg or 150 micrograms/kg. Proton relaxation times (T1 and T2) of excised oedematous tissue were measured in vitro and the area of the oedematous region was determined in vivo by the use of magnetic resonance imaging (MRI). The administration of ANP was found to decrease the lengthening of both T1 and T2 in the oedematous tissues and shown by MRI to decrease the area of the oedematous region, compared with group receiving saline. The topographic observations in vivo suggest that ANP suppress the development of the oedematous region.

Animals↗
PubMed1990

Lewy bodies in the lower sacral parasympathetic neurons of a patient with Parkinson's disease.

Lewy bodies were observed incidentally in the neurons of the dorsal group of nucleus intermediolateralis of the 3rd sacral segment of the spinal cord in a 74-year-old male with Parkinson's disease. The findings indicate the degeneration of the preganglionic parasympathetic neurons innervating the internal anal sphincter. The correlation between the findings and the mechanism of constipation in this disease are discussed.

Aged↗
PubMed1990

Demyelination and remyelination in spinal cord lesions of human lymphotropic virus type I-associated myelopathy.

We describe postmortem findings in a patient with human T lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM). The patient developed the disease 8 years after blood transfusion and showed good response to corticosteroid treatment but died of cardiac failure. Histologically, chronic, mild meningoencephalomyelitis was noted predominantly involving the bilateral lateral and anterior columns of the middle to lower thoracic segments. The spinal cord lesions showed obvious loss of myelinated nerve fibers and fibrillary gliosis with minimal inflammatory cell infiltration. Electron microscopy of the lesion revealed disintegration of the myelin sheaths, regular separation of the minor dense line of the myelin sheaths, and completely demyelinated axons. In addition, remyelinated fibers with thin central myelin sheaths and disproportionately large axons were seen frequently. These findings indicate that primary demyelination and remyelination by oligodendrocytes occur in the spinal cord lesions of HAM.

Aged↗