Hisayo Okamoto

Localization of arachidonate 12-lipoxygenase in canine brain tissues.

Abstract: The cytosol fraction from a thoroughly imgated canine cerebrum was subjected to immunoaffinity chromatography using a monoclonal antibody against porcine leukocyte 12‐lipoxygenase. Arachidonate 12‐lipoxygenase eluted from the column with some retardation. The enzyme, with a specific activity of 9 nmol/min/mg of protein, converted arachidonic acid to 12(S)‐hydroperoxy‐5,8,10,14‐eicosatet‐raenoic acid. The enzyme was active not only with arachidonic acid, but also with linoleic and α‐linolenic acids. In contrast, 12‐lipoxygenase of canine platelets was almost inactive with linoleic and α‐linolenic acids, and the platelet enzyme was also distinguished from the cerebral enzyme in terms of reactivity with the anti‐12‐lipoxygenase antibody. 12‐Lipoxygenase activity was also detected in the cytosol fractions of other parts of canine brain: basal ganglia, hippocampus, cerebellum, olfactory bulb, and medulla oblongata.

Effects of thromboxane synthetase inhibitor (RS-5186) on experimentally-induced cerebral vasospasm.

RS-5186, which inhibits thromboxane A2 (TXA2) synthetase activity, ameliorated delayed cerebral vasospasm in a canine two-hemorrhage model. Subarachnoid hemorrhage was induced in 15 dogs, which were divided into two groups. In the RS-5186-treated group (9 dogs), 50 mg kg-1 of RS-5186 was administered twice a day for seven days. The remaining six dogs without administration of RS-5186 were used as a control group. In the RS-5186-treated group, the angiographic diameter of the basilar artery on Day 7 after subarachnoid hemorrhage was constricted to 60.9% +/- 11.6% (n = 9, mean +/- SD) of that on Day 0, before subarachnoid hemorrhage. The corresponding value was 42.8% +/- 6.1% (n = 6) in the control group. There was a statistically significant difference between these percentages. In the RS-5186-treated group, plasma thromboxane B2 level on Day 7 was 144.3 +/- 28.1 pg ml-1 (n = 4), which was lower than the 815.5 +/- 162.0 pg ml-1 (n = 4) in the control group (p < 0.0005). The plasma 6-keto-prostaglandin F1 alpha level on Day 7 was 180.5 +/- 66.5 pg ml-1 (n = 4) in the RS-5186-treated group, and higher than 107.3 +/- 12.4 pg ml-1 (n = 4) in the control group (p = 0.0734). Thus, administration of RS-5186 reduced TXA2 plasma level and had a beneficial effect on angiographically-detected delayed vasospasm.

Endothelium is required for 12-hydroperoxyeicosatetraenoic acid-induced vasoconstriction

The pharmacological effects of 12-hydroperoxyeicosatetraenoic acid (12-HPETE) were examined using isolated canine basilar artery segments and isometric tension recording. 12-HPETE produced transient contraction of the artery segment while arachidonic acid or 12-hydroxyeicosatetraenoic acid (12-HETE) had a much lower potency. 12-HPETE-induced contraction which showed a requirement of a functional endothelium and a rapid insensitivity to re-administered 12-HPETE, was completely inhibited by the potassium channel blocker, glibenclamide. Other hydroperoxides did cross-desensitize the 12-HPETE-induced contraction, however, arachidonic acid or 12-HETE did not affect markedly. Here, we present that 12-HPETE is involved in the regulation of vascular tension via its effects on the endothelium.

Relationship of hypotension and cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage

Abstract Objectives: Changes in systemic arterial blood pressure and the degree of cerebral vasospasm were investigated in 125 patients with aneurysmal subarachnoid hemorrhage. Methods: Systemic arterial blood pressure was measured every 2 hours in each patient for a period of more than 2 weeks, and a fall in systemic blood pressure (FBP) was defined as a decrease of >40 mmHg of systolic blood pressure between two consecutive measurements. Results: A total of 91 FBPs occurred in 52 (41.6%) of 125 patients despite specific post-operative management to prevent hypovolemia. Five (5.5%) of the 91 FBPs occurred just before the onset of symptomatic vasospasm. Symptomatic vasospasm was observed in 36 (69.2%) of 52 patients with FBP and in 32 (43.8%) of 73 patients without FBP (p<0.01, chi-squared test). A hypodense area on computed tomographic scans in association with cerebral vasospasm was observed in 25 (48.1%) of 52 patients with FBP and in 21 (28.8%) of 73 patients without FBP (p<0.05). Discussion: We conclude that FBP might result from delayed cerebral vasospasm and/or brain dysfunction owing to subarachnoid hemorrhage itself.

A case of ruptured aneurysm associated with spinal arteriovenous malformation presenting with hematomyelia: case report.

BACKGROUND Spinal cord arteriovenous malformation (AVM) associated with spinal aneurysm is not particularly rare, but cases presenting with hematomyelia are relatively rare compared to those with subarachnoid hemorrhage (SAH). We report a rare case of successfully treated spinal AVM associated with ruptured aneurysm presenting with hematomyelia. CASE DESCRIPTION A 52-year-old male was admitted to our hospital with sudden onset of tetraplegia, respiratory disturbance, and superficial sensory disturbance. Computed tomography revealed hematomyelia at the level of C3-4. Gadolinium-enhanced magnetic resonance imaging showed small, enhanced lesions. Angiography revealed an intradural perimedullary arteriovenous malformation associated with two aneurysms on the feeding arteries. Administration of high-dose methylprednisolone gradually ameliorated his symptoms. Direct surgical obliteration was performed on the 30th day after the onset. The bilateral C3 cervical radicular arteries and the nidus were coagulated. Angiography performed after surgery showed neither the aneurysms nor the nidus. He was discharged with only mild weakness in the left upper extremity and mild left hypesthesia 3 months after surgery, and was fully independent. CONCLUSION We report a case of hematomyelia caused by ruptured aneurysm associated with spinal arteriovenous malformation that was successfully treated with surgical obliteration.

Huge lobar intracerebral hemorrhage by glioblastoma multiforme

A 66-year-old man was presented with a huge right temporo-parietal lobar hemorrhage caused by a glioblastoma multiforme, which enlarged rapidly after evacuation of the hematoma. He became semicomatose and subsequent head computed tomography (CT) showed a huge right temporoparietal subcortical hemorrhage with uncal herniation (Fig. 1a). Emergency evacuation of the hematoma was performed. Two months after surgery, follow-up CT demonstrated giant right temporo-parietal lesion which revealed ring-like enhancement with contrast medium (Fig. 1b). Pathological analysis revealed a glioblastoma multiforme with obvious ‘‘pseudopalisading’’ form (Fig. 2). The incidence of intracranial hemorrhage due to a brain tumor has been reported to be 0.9–11% [1, 2]. Hemorrhagic intracranial neoplasmas were of various types, including metastatic tumor, pituitary adenoma, glioma, and so on. Wakai et al. reported the incidence of hemorrhage from brain tumors [2]. In their series, seven of 17 patients aged 14 or under died of massive hemorrhage from tumor and none of the patients 15 or older died. This report illustrates the importance of diagnosis of an unusual huge fatal hemorrhagic glioblastoma.

Role of 12-HPETE in the Pathogenesis of Cerebral Vasospasm

Delayed cerebral vasospasm occurring between the 4th day and the 14th day after subarachnoid hemorrhage (SAH) affects the patient outcome seriously. Its occurrence correlates to the presence and the amount of subarachnoid clot. It is different from ordinary constriction of vessel, since the cerebral vasospasm is delayed onset and long lasting contraction of the vessel which also involves histological changes. Although almost all substances which existed in blood clot had been investigated as candidates caused delayed vasospasm, no substance by itself had been accepted as a cause. Watanabe et al.1 and Shimizu et al.2 reported that 12-hydroxyeicosatetraenoic acid (12-HETE) was detected in subarachnoid clot using the canine SAH model, and 5–1 ipoxygenase pathway of arterial wall with vasospasm was much activated compared with the control vessel. Moreover, 12-hydroperoxyeicosatetraenoic acid (12-HPETE) injected into canine major cistern was produced delayed onset and long lasting vasospasm comparable to the canine SAH model. The injected 12-HPETE into the canine major cistern was decreased rapidly and disappeared from cerebrospinal fluid (CSF) at 6 hours after its injection3. It was interesting and curious that the vasospasm occurred after 12-HPETE disappeared from CSF. The present study was aimed to clarify the trace of injected 12-HPETE into canine major cistern.

Localization of arachidonate 12-lipoxygenase in canine brain tissues

The cytosol fraction from a thoroughly irrigated canine cerebrum was subjected to immunoaffinity chromatography using a monoclonal antibody against porcine leukocyte 12-lipoxygenase. Arachidonate 12-lipoxygenase eluted from the column with some retardation. The enzyme, with a specific activity of 9 nmol/min/mg of protein, converted arachidonic acid to 12(S)-hydroperoxy-5,8,10,14-eicosatetraenoic acid. The enzyme was active not only with arachidonic acid, but also with linoleic and alpha-linolenic acids. In contrast, 12-lipoxygenase of canine platelets was almost inactive with linoleic and alpha-linolenic acids, and the platelet enzyme was also distinguished from the cerebral enzyme in terms of reactivity with the anti-12-lipoxygenase antibody. 12-Lipoxygenase activity was also detected in the cytosol fractions of other parts of canine brain: basal ganglia, hippocampus, cerebellum, olfactory bulb, and medulla oblongata.