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Biomedical subjects

M Yoshiura

Publications and source records attributed to M Yoshiura.

14 recordsLinked to original sources
PubMed1992

Uric acid as biochemical marker for retinal and optic nerve damage after occlusion and reperfusion of common carotid and vertebral arteries in rat.

Transient retinal and optic nerve ischemia lasting for 20 minutes was produced in Wistar rats by clipping bilateral common carotid arteries and coagulating both vertebral arteries by heat. The uric acid level in the retina and optic nerve were determined by high performance liquid chromatography with electrochemical detection just before induction of ischemia, 20 minutes after induction of ischemia, and after resolution of ischemia. Uric acid content in the optic nerve (28.0 +/- 4.5 ng/mg protein) was about 5 times higher than that in the retina (5.7 +/- 0.8 ng/mg protein) in the control experiment. Ischemia lasting for 20 minutes caused a 2.7-fold increase of uric acid in the optic nerve and a 1.8-fold increase in the retina. Following reperfusion of the blood flow by unclipping of the common carotid arteries, the uric acid level decreased to the control level in both the retina and optic nerve 30 minutes after unclipping, which was followed by 3.1- and 1.6-fold increases in uric acid in the retina and the optic nerve, respectively, at 60 minutes after unclipping. Although ischemia alone causes tissue damage, there is some clinical evidence that greater injury can occur after oxygen is reintroduced to ischemic tissue. Our results indicate that the retina is more likely to be damaged by reperfusion than the optic nerve.

Animals↗
PubMed1989

Allopurinol inhibits uric acid accumulation in the rat brain following focal cerebral ischemia.

Uric acid (UA) in the rat brain was measured by HPLC with an electrochemical detector following focal ischemia. At 24 h after the operation, the UA level in the ischemic center was 105.47 +/- 8.39 nmol/g tissue, whereas it was 8.36 +/- 1.86 in the sham-operated group. Allopurinol, xanthine oxidase inhibitor, almost completely inhibited this UA accumulation. These data demonstrate that the UA increase in the ischemic brain is due to the xanthine oxidase reaction.

Allopurinol↗
PubMed1989

[Changes in xanthine and uric acid in rat brain after middle cerebral artery occlusion].

Xanthine and uric acid, products of purine metabolism, were measured by reversed-phase high-performance liquid chromatography (HPLC) with electrochemical detection in rat forebrain following focal cerebral ischemia. Focal cerebral ischemia was induced in the rat by permanent occlusion of the left middle cerebral artery (MCA). Sprague-Dawley rats were anesthetized with halothane inhalation and left MCA was occluded via trans-retro-orbital approach. Normal and sham-operated rats were used as control animals. The animals were decapitated 2 (MCA = 5, Sham = 5), 4 (MCA = 7, Sham = 6), 8 (MCA = 5, Sham = 5), and 16 (MCA = 6, Sham = 6) hours or 1 (MCA = 5, Sham = 5), 2 (MCA = 6, Sham = 6), 7 (MCA = 7, Sham = 6), 14 (MCA = 6, Sham = 5), and 28 (MCA = 7, Sham = 5) days after the operation. The brains were removed and divided into right and left hemisphere. Each hemisphere was homogenized and centrifuged. The supernates were filtered with membrane filter. An aliquot of the filtrate was used for measurement of xanthine and uric acid in both of the ischemic and contralateral hemisphere by a HPLC system. In the normal group, xanthine and uric acid in the brain was 12.4 +/- 0.4 and 2.2 +/- 0.1 nmol/g tissue (mean +/- SEM), respectively. In the ischemic hemisphere, xanthine increased up to 57.7 +/- 5.2 nmol/g tissue 2 hours after MCA occlusion and reached a maximum value of 59.42 +/- 4.91 nmol/g tissue 4 hours following the induction of ischemia. Xanthine level was still high 8 hours after ischemia and then rapidly decreased to the normal value at day 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Xanthine and uric acid levels in rat brain following focal ischemia.

Changes of the xanthine and uric acid (UA) levels in rat forebrain following focal cerebral ischemia were studied by reversed-phase HPLC with electrochemical detection. Focal ischemia was induced by occluding the left middle cerebral artery in the rat. The xanthine level in the normal group was 11.50 nmol/g tissue. In the ischemic group, the xanthine concentration in the ischemic hemisphere progressively increased after occlusion and reached a maximum value of 59.42 nmol/g tissue 4 h after operation. The UA level in the normal group was 2.20 nmol/g tissue, whereas in the ischemic group the UA concentration in the ischemic hemisphere gradually increased after occlusion, reaching a value of 38.53 nmol/g tissue 24 h after ischemia. The concentration of UA remained elevated in the ischemic hemisphere until 48 h after occlusion, and reached a maximum value of 38.98 nmol/g tissue. The xanthine and UA levels in the contralateral hemisphere remained unchanged. The xanthine and UA concentrations in the sham-operated group did not show a significant increase after operation. The time course of xanthine and UA levels suggests that in ischemic forebrain UA is formed from xanthine as a product of purine metabolism.

Animals↗
PubMed1987

Electrochemically treated glassy carbon electrode for amperometric detection in high-performance liquid chromatography.

The application of an electrochemically pre-treated glassy carbon electrode for the amperometric detection of electroactive components, such as tyrosine and oxipurinol, in biological samples was studied in order to demonstrate the usefulness of a pre-anodized electrode in high-performance liquid chromatography. The electrochemical pre-treatment was carried out in 0.2 M phosphate buffer (potassium dihydrogenphosphate-potassium hydroxide, pH 6.5) at 1900 mV vs. Ag/AgCl for 2 min. The pre-anodized electrode response for the oxidation of lactic acid and pyruvic acid was also studied. The electrochemical treatment enhanced and stabilized the electrode response to the oxidation of tyrosine and both acids.

Chromatography, High Pressure Liquid↗
PubMed1986

Postmortem changes in uric acid and ascorbic acid in human cerebral cortex tissues excised after cardiac death.

There has been no report on the determination of uric acid (UA) in human brain and heart tissues. UA and ascorbic acid (AA) in human cerebral cortex and heart tissues excised after cardiac death have been studied by reversed-phase high-performance liquid chromatography (HPLC) with electrochemical detection (ECD). It has been found that the levels of AA and UA in the human cerebral cortex tissues tend to decrease and increase, respectively, after cardiac death as a function of time between death and forensic operation. In addition, it has been found that there is no special relationship between UA levels in human heart tissues and time after cardiac death, also that the UA levels in the heart are high as compared with those in human cerebral cortex tissues. We have emphasized that the HPLC-ECD method is useful in determining UA and AA in mammalian tissues by one-time chromatography to gain a better understanding of the relationship between disease and serum urate level.

Ascorbic Acid↗
PubMed1986

Changes of uric acid level in rat brain after focal ischemia.

Changes of uric acid level in rat cerebral hemisphere after left middle cerebral artery (MCA) occlusion were studied by reversed-phase HPLC with electrochemical detection. Uric acid level in the normal group was 2.98 nmol/g tissue. Uric acid concentration of the left hemisphere in the left MCA-occluded group progressively increased after occlusion, and reached a maximum value of 67.26 nmol/g tissue 24 h after ischemia. Uric acid levels in the right hemisphere remained unchanged. Uric acid concentration of the left hemisphere in sham-operated group was 9.29 nmol/g tissue 24 h after the operation.

Animals↗
PubMed1986

Liquid chromatographic determination of uric acid and ascorbic acid in rat retinae after ophthalmic artery and optic nerve ligation.

Change of urate and ascorbate levels in retinae of rat left eyes after ophthalmic artery and optic nerve ligation was studied by reversed-phase high-performance liquid chromatography with electrochemical detection. The right eyes were used for sham operation. We found that uric acid levels in the retinae of the left eyes increased as a function of time after the operation, whereas those of the right eyes remained unchanged. In addition, we found that ascorbic acid levels in the retinae of the rat eyes decreased after the operation.

Animals↗
PubMed1984

Postmortem changes of uric acid in various rat tissues: determination of uric acid by reversed-phase high-performance liquid chromatography with electrochemical detection.

As a function of time after decapitation, postmortem changes of uric acid in various rat tissues have been studied by reversed-phase high-performance liquid chromatography with electrochemical detection. The chromatographic examination revealed that uric acid in rat tissues such as brain, liver, musculus rectus abdominis, and femoral muscle tends to increase after decapitation as a function of time between the sacrifice and homogenization in a 2.0% metaphosphoric acid solution.

Animals↗
PubMed1984

Simultaneous determination of uric and ascorbic acids in human serum by reversed-phase high-performance liquid chromatography with electrochemical detection.

A rapid, easy, and accurate method for the determination of uric acid and ascorbic acid in human serum by reversed-phase high-performance liquid chromatography with electrochemical detection has been developed. Human serum (0.5 ml) was mixed with 1.5 ml of an aqueous solution containing 2.0% metaphosphoric acid and the mixture was centrifuged at 3000g for 30 min. The supernatant was passed through a membrane filter to remove the particulate matter. Ten microliters of the filtrate was injected into the chromatographic system employed in this study. Complete separation of uric acid and ascorbic acid was achieved in about 2 min. The assay limit for quantitation was about 10 pg for uric acid and ascorbic acid under the present chromatographic conditions. The analytical recoveries of uric acid and ascorbic acid in human serum samples were found to be almost 100%.

Ascorbic Acid↗