Disposition of the Highly Fat Distributed Compound 1-(4-Methoxyphenyl)-4-(2,2,4,6,7-Pentamethyl -2,3-Dihydro-1-Benzofuran-5-yl)Piperazine (TAK-357) in Rats and Dogs.

The non-clinical pharmacokinetics (PK) of TAK-357, a highly lipophilic (clogP>6) potential agent for the amelioration of Alzheimer's disease, was investigated in rats and dogs. A long half-life (t1/2) in plasma was observed in animals and a low total body clearance with high distribution volume was consistent with the long t1/2. The absorption, distribution, metabolism and excretion (ADME) studies using radiolabeled TAK-357 revealed that the total radioactivity was highly distributed to the adipose tissues and sustained with high concentration for over 4 weeks after oral administration. The metabolite analysis also revealed that the main component in the plasma and adipose tissues was unchanged TAK-357. The major elimination route of absorbed TAK-357 was suggested to be by metabolism. An ADME study indicated that the adipose tissue is the main depot of remaining TAK-357 in the body and slow release from the adipose tissues contributes to the long t1/2. The PK of highly lipophilic compounds have a tendency to be affected by body weight changes especially changes in the adipose tissues. Therefore, it is considered that the relationship between the plasma levels of TAK-357 and the body weight should be evaluated carefully during the clinical trials.

Efficient two-step photocarrier generation in bias-controlled InAs/GaAs quantum dot superlattice intermediate-band solar cells.

We studied the effects of the internal electric field on two-step photocarrier generation in InAs/GaAs quantum dot superlattice (QDSL) intermediate-band solar cells (IBSCs). The external quantum efficiency of QDSL-IBSCs was measured as a function of the internal electric field intensity, and compared with theoretical calculations accounting for interband and intersubband photoexcitations. The extra photocurrent caused by the two-step photoexcitation was maximal for a reversely biased electric field, while the current generated by the interband photoexcitation increased monotonically with increasing electric field intensity. The internal electric field in solar cells separated photogenerated electrons and holes in the superlattice (SL) miniband that played the role of an intermediate band, and the electron lifetime was extended to the microsecond scale, which improved the intersubband transition strength, therefore increasing the two-step photocurrent. There was a trade-off relation between the carrier separation enhancing the two-step photoexcitation and the electric-field-induced carrier escape from QDSLs. These results validate that long-lifetime electrons are key to maximising the two-step photocarrier generation in QDSL-IBSCs.

Pharmacokinetics of TAK-475, a Squalene Synthase Inhibitor, in Rats and Dogs.

The pharmacokinetics of TAK-475 (lapaquistat acetate), a squalene synthase inhibitor, was investigated in rats and dogs. After oral administration of (14)C-labeled TAK-475 ([(14)C]TAK-475) to rats and dogs at a dose of 10 mg/kg, the bioavailability (BA) was relatively low at 3.5 and 8.2%, respectively. The main component of the radioactivity in the plasma was M-I, which has a comparable pharmacological activity to TAK-475 in vitro. The radioactivity in the portal plasma after intraduodenal administration of [(14)C]TAK-475 to portal vein-cannulated rat was also mainly M-I, suggesting that most of the TAK-475 was hydrolyzed to M-I during the permeable process in the intestine. The concentrations of M-I in the liver, the main organ of cholesterol biosynthesis, were much higher than those in the plasma after oral administration of [(14)C]TAK-475 to rats. The main elimination route of the radioactivity was fecal excretion after oral administration of [(14)C]TAK-475 to rats and dogs, and the absorbed radioactivity was mainly excreted via the bile as M-I in rats. M-I excreted into the bile was partially subjected to enterohepatic circulation. These results suggest that although the BA values of TAK-475 are low, M-I can exert compensatory pharmacological effects in the animals. These pharmacokinetic characteristics in animals were also confirmed in the clinical studies. The evaluation of M-I disposition is important for the pharmacokinetics, pharmacodynamics and toxicity of TAK-475 in animals and humans.

Pharmacokinetics and Urinary Excretion Mechanism of Orteronel (TAK-700), A Novel 17,20-Lyase Inhibitor, in Animals.

Orteronel is newly identified as a selective 17,20-lyase inhibitor for an agent for castration resistant prostate cancer. The absorption and disposition of [(14)C]orteronel were investigated in rats and monkeys. Orteronel was extensively excreted into rat and monkey urine in an unchanged form after oral administration. The unbound based renal clearances in rats and monkeys were greater than the respective glomerular filtration rates (GFR), suggesting that urinary tubular secretion plays an important role in the renal excretion of orteronel. Therefore, the uptake of [(14)C]orteronel was investigated using rat kidney slices to estimate the contribution of carrier-mediated transport on the urinary tubular secretion. The uptake study using rat kidney slices suggested that the transport of orteronel from the blood circulation to the kidney was mediated by a digoxin sensitive transport system represented by Oatp4c1 and non-saturable components. Furthermore, the saturable component accounted for a limited fraction of the total renal uptake by rat kidney slices. These results suggested that non-saturable uptake mainly contributed to the renal excretion of orteronel in rats.

Characterization of Transporters in the Hepatic Uptake of TAK-475 M-I, a Squalene Synthase Inhibitor, in Rats and Humans.

TAK-475 (lapaquistat acetate) is a squalene synthase inhibitor and M-I is a pharmacologically active metabolite of TAK-475. Preclinical pharmacokinetic studies have demonstrated that most of the dosed TAK-475 was hydrolyzed to M-I during the absorption process and the concentrations of M-I in the liver, the main organ of cholesterol biosynthesis, were much higher than those in the plasma after oral administration to rats. In the present study, the mechanism of the hepatic uptake of M-I was investigated.The uptake studies of (14)C-labeled M-I into rat and human hepatocytes indicated that the uptakes of M-I were concentrative, temperature-dependent and saturable in both species with Km values of 4.7 and 2.8 µmol/L, respectively. M-I uptake was also inhibited by cyclosporin A, an inhibitor for hepatic uptake transporters including organic anion transporting polypeptide (OATP). In the human hepatocytes, M-I uptake was hardly inhibited by estrone 3-sulfate as an inhibitor for OATP1B1, and most of the M-I uptake was Na(+)-independent. Uptake studies using human transporter-expressing cells revealed the saturable uptake of M-I for OATP1B3 with a Km of 2.13 µmol/L. No obvious uptake of M-I was observed in the OATP1B1-expressing cells.These results indicated that M-I was taken up into hepatocytes via transporters in both rats and humans. OATP1B3 would be mainly involved in the hepatic uptake of M-I in humans. These findings suggested that hepatic uptake transporters might contribute to the liver-selective inhibition of cholesterol synthesis by TAK-475. This is the first to clarify a carrier-mediated hepatic uptake mechanism for squalene synthase inhibitors.

Potent neuropeptide Y Y1 receptor antagonist, 1229U91: blockade of neuropeptide Y-induced and physiological food intake.

Neuropeptide Y (NPY) is thought to increase food intake through the action of Y1 (-like) receptors in the hypothalamus. To confirm the involvement of Y1 receptors in feeding behavior, selective and potent antagonists for Y1 receptors are required. In the present study, we showed that a peptide, 1229U91 [(Ile,Glu,Pro,Dpr,Tyr,Arg,Leu,Arg, Tyr-NH2)2 cyclic (2,4'),(2',4)-diamide], is a potent and selective antagonist for Y1 receptors. 1229U91 displaced [125I]peptide YY (PYY) binding to membranes of human neuroblastoma-derived SK-N-MC cells that predominantly express Y1 receptors with a K1 value 0.10 nM and inhibited the NPY-induced increase in intracellular calcium levels(IC50 = 0.27 nM). In contrast, the K1 values for [125I]PYY binding to Y2 receptors in membranes of human neuroblastoma-derived SK-N-BE2 cells and rat hypothalamus were 700 nM and more than 1 microM, respectively. Although [125I]PYY could not detect Y1 receptors in the rat hypothalamic membranes, [125I]1229U91 revealed binding sites with a high affinity (Kd = 18 pM), indicating the presence of Y1 receptors in the hypothalamus. Intracerebroventricular injection of 1229U91 (30 micrograms) into male Sprague-Dawley rats completely inhibited NPY (5 micrograms)-induced food intake without any other behavioral change. Furthermore, intracerebroventricular injection of 1229U91 significantly suppressed physiological feeding behavior after overnight fasting. These results indicate that Y1 receptors in the rat hypothalamus mediate NPY-induced food intake, and that physiological feeding behavior after overnight fasting may be largely regulated by NPY via Y1 receptors. 1229U91 may be useful for further elucidating the pathophysiological roles of NPY in feeding behavior.

Demonstration of Borna disease virus RNA in peripheral blood mononuclear cells derived from Japanese patients with chronic fatigue syndrome.

CFS, a recently named heterogeneous disorder, is an illness of unknown etiology. The association of CFS with viral infections has been suggested. A common association between CFS and several viruses examined has not been confirmed. Here, we centered on the possible link between CFS and BDV infection. By nested RT-PCR followed by hybridization, BDV RNA was demonstrated as a clear signal in PBMCs in 3 out of 25 CFS patients. The amplified cDNA fragments were cloned and sequenced. A total of 16 clones were studied. Intra-patients divergencies of the p24 were 2-9%, 3-20%, and 3-11% in the deduced amino acids. Inter-patient divergencies among the 16 clones were 3-24%. Antibodies to recombinant BDV p24 protein were detected in 6 CFS patients including one carrying BDV RNA. Overall, these gave the prevalence of 32% (8/25) in Japanese CFS patients, suggesting that Japanese CFS is highly associated with active infection of BDV, or a related agent.

Bcl-2 protein expression and gut neurohormonal polypeptide/amine production in colorectal carcinomas and tumor-neighboring mucosa, which closely correlate to the occurrence of tumor.

To clarify whether advanced colorectal carcinomas and tumor-neighboring mucosa simultaneously produce both Bcl-2 protein and gut neurohormonal polypeptides and/or amines, and the interrelationship of these phenomenon, we studied retrospective analysis of Bcl-2 protein production and neuroendocrine characteristics in 52 cases of advanced colorectal carcinoma and surrounding mucosa. All of the tumor-neighboring mucosa presented hyperplasia. The rates of enhanced immunoreactivity of the tumor-neighboring mucosa and of positive immunoreactivity of the carcinomas against human Bcl-2 protein and against human vasoactive intestinal polypeptide, pancreatic polypeptide and somatostatin were 78.8% and 94.2%, 82.7% and 59.6%, 78.8% and 67.3%, and 88.5% and 84.6% respectively. Double immunostaining for Bcl-2 protein and each peptide hormone revealed simultaneous expression. In contrast, that of tumor-neighboring mucosa and carcinomas to serotonin and chromogranin-A and to argyrophilia were 11.5% and 1.9%, 32.7% and 17.3%, and 26.9% and 21.2%, respectively. We concluded that tumor-neighboring crypt cells displayed not only hyperplasia but also neuroendocrine characteristics and that enhanced Bcl-2 protein immunoreactivity correlated with tumor occurrence in the wall of the colorectum. The production of Bcl-2 protein by tumor cells and tumor-neighboring crypt cells indicates that the bcl-2 protooncogene may act not only as an inhibitor of apoptosis but also as an inducer of neuroendocrine differentiation from the latent characteristics of the endodermal stem cell.

Saphenous vein graft to the distal vertebral artery between C-1 and C-2 using a lateral-anterior approach. Technical note.

The authors present a modified surgical procedure for extracranial vertebral artery reconstruction. The use of the proposed technique results in access to the V3 segment of the vertebral artery between the C-1 and C-2 vertebrae through the retrojugular space without requiring bone rongeuring. A saphenous vein bypass graft was placed between the common carotid artery and the V3 segment of the vertebral artery in three patients with bilateral occlusive lesions of the proximal vertebral arteries.

Video-assisted parathyroidectomy.

A parathyroid tumor is not larger than other tumors, so minimally invasive surgery has long been a major focus of parathyroid surgeons. Improving endoscopic instruments has facilitated the recent changes in approaches to parathyroid surgery. Endoscopic parathyroidectomy is developed in a totally closed space with CO2 gas insufflation. This method has a risk of complications, such as extensive emphysema or hypercarbia. Minimally invasive video-assisted parathyroidectomy (MIVAP) has greater safety, low cost, easy procedure and flexibility in changing the working space including conversion to open method when compared with endoscopic parathyroidectomy. MIVAP can be performed with only a 1-1.5-cm small incision on the neck. MIVAP is indicated in the patient with parathyroid adenoma or renal hyperplasia that is defined preoperatively using ultrasonography and 99mTc-methoxyisobutylisonitrile (MIBI) scan. Furthermore, the radio-guided technique using nuclear navigation after preoperative administered MIBI is being developed. This method is so useful during MIVAP that we combined MIVAP and radio-guided surgery to develop minimally invasive radio-guided and video-assisted parathyroidectomy (MIRVAP). After injection of 600 MBq of MIBI, intraoperative nuclear mapping was performed using a hand-held gamma probe. Then we expected to find swollen parathyroid tumor at surgery when radioactivity at a level relatively higher than background was found. Following this mapping result, MIVAP was started and succeeded. The radio-guided technique is also indicated for open parathyroidectomy (radio-guided open parathyroidectomy, RGOP) in multiglandular disease (MGD) when it was not possible to identify those lesions completely, for instance in asymmetric hyperplasia, such as multiple endocrine neoplasia (MEN) 1. In conclusion, MIVAP is beneficial for minimal invasiveness and cosmesis. Furthermore, radio-guided parathyroidectomy (MIRVAP and RGOP) is more useful and feasible. Improvement of endoscopic instruments and modification of the dose of MIBI administered might facilitate treating more cases by MIRVAP instead of RGOP.

Pre- and postoperative bone metabolism of primary hyperparathyroidism.

UNLABELLED: Primary hyperparathyroidism (PHPT) is a well-known indicator of severe bone loss. However, the recovery process of bone mineral density after surgery in PHPT patients is not sufficiently clear. We examined postoperative bone metabolism in 24 PHPT patients. PATIENTS AND METHODS: Subjects were 24 patients with PHPT upon whom we performed parathyroidectomy in the Department of Surgery II, Fukushima Medical University. Mean age was 54.2 years and the male-to-female ratio was 10:14; mean time of follow-up was 27.3 months. Patients were divided histopathologically into 16 adenomas and eight hyperplasias, and classified by heredity into seven familial (six, MEN 1; one, MEN 2) and 17 sporadic types. Bone mineral density was measured by dual energy X-ray absorptometry (DXA) and digital image processing (DIP). Age-matched values of these parameters were obtained. Serum bone metabolic parameters; ionized calcium (CaF), phosphorus, intact PTH (iPTH), c-PTH, ALP, osteocalcin (OC) and PTHrP were measured. RESULTS: PHPT patient preoperative bone mineral densities were significantly lower than those of healthy controls. Those by DIP method were lower than those by DXA. High CaF, iPTH, OC and ALP levels were indicated before surgery, but all parameters immediately became normal. Longitudinal bone mineral density changes of asymptomatic cases increased more than those of patients with renal stone and/or ostitis fibrosa. In adenoma cases, tumor weights were significantly inversely, which correlated with preoperative DIP bone density measurements. CONCLUSION: Preoperative PHPT patients showed decreased bone density; bone loss in symptomatic cases was especially prominent compared to asymptomatic cases. Most PHPT patients had not completed the BMD recovery after surgery, so even asymptomatic and mild PHPT patients should undergo parathyroidectomy to minimize irreversible bone loss.

Establishment of the transformants expressing human cytochrome P450 subtypes in HepG2, and their applications on drug metabolism and toxicology.

Transformants with stable expression of a series of human cytochrome P450 (CYP) subtypes in the human hepatic cell line, HepG2, were established. These transformants are designated Hepc/1A1.4, Hepc/1A2.9, Hepc/2A6L.14, Hepc/2B6.68, Hepc/2C8.46, Hepc/2C9.1, Hepc/2C19.12, Hepc/2D6.39, Hepc/2E1.3-8 and Hepc/3A4.2-30, which stably expressed human CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4, respectively. The expression of the CYP subtypes in the transformants was confirmed by both determination of enzyme activities and the reverse transcriptase polymerase chain reaction (RT-PCR) procedure. The apparent K(m) values of the expressed CYP subtypes for their specific substrates were close to those of human liver microsomes. In addition to their CYP activities, these transformants retained glucuronide- and sulfate-conjugating activities. Furthermore, the activities of CYP2C9, CYP2D6 and CYP3A4 were inhibited by their specific inhibitors. The cytotoxicity of acetaminophen (APAP), cyclophosphamide (CPA) and benz[a]anthracene (BA) were analyzed by CYP-expressing transformants. The cytotoxicity depended on the expression of CYP subtypes and increased in a dose-dependent manner. These results show the metabolic activation of APAP, CPA and BA by the specific CYP subtypes expressed in the transformants and demonstrate the usefulness of these transformants for in vitro metabolic and toxicological studies in human liver.

Establishment of a human hepatocyte line (OUMS-29) having CYP 1A1 and 1A2 activities from fetal liver tissue by transfection of SV40 LT.

Immortalized human hepatocytes that can retain functions of drug-metabolizing enzymes would be useful for medical and pharmacological studies and for constructing an artificial liver. The aim of this study was to establish immortalized human hepatocyte lines having differentiated liver-specific functions. pSVneo deoxyribonucleic acid, which contains large and small T genes in the early region of simian virus 40, was introduced into hepatocytes that had been obtained from the liver of a 21-wk-old fetus. Neomycin-resistant immortalized colonies were cloned and expanded to mass cultures to examine hepatic functions. Cells were cultured in a chemically defined serum-free medium, ASF104, which contains no peptides other than recombinant human transferrin and insulin. As a result, an immortal human hepatocyte cell line (OUMS-29) having liver-specific functions was established from one of the 13 clones. Expression of CYP 1A1 and 1A2 messenger ribonucleic acid by the cells was induced by treatment with benz[a]pyrene, 3-methylcholanthrene, and benz[a]anthracene. OUMS-29 cells had both the polycyclic aromatic hydrocarbon receptor (AhR) and AhR nuclear translocator. Consequently 7-ethoxyresorufin deethylase activity of the cells was induced time- and dose-dependently by these polycyclic aromatic hydrocarbons. This cell line is expected to be instrumental as an alternative method in animal experiments for studying hepatocarcinogenesis, drug metabolisms of liver cells, and hepatic toxicology.

Impaired left ventricular diastolic filling occurs in diabetic patients without atherosclerotic coronary artery disease.

Using left ventriculography, left ventricular diastolic function was studied in 24 diabetic patients who had angina pectoris without atherosclerotic large-vessel coronary artery diseases (group A, 14 patients with exercise-induced ischemic ST-T changes as seen during electrocardiogram; group B, 10 patients without such changes). In groups A and B, the global peak filling rate was significantly less than that in control patients without diabetes or cardiac diseases. The ratio of the global time to the peak filling rate to the diastolic time was higher in both groups A and B than in the control groups. However, the total of time differences, defined as the sum of the time differences between global time to the peak filling rate and each of the three regional time to the peak filling rate, was greater in group A than in either group B or the control patients. Total time difference was similar in group B and the controls. Left ventricular diastolic filling was impaired in diabetic patients without large-vessel coronary artery disease. Impaired diastolic filling was present regionally in patients with ischemic ST-T change but globally in those without such change.

Menaquinone (vitamin K2)-6 production by mutants of Flavobacterium meningosepticum.

Flavobacterium meningosepticum IFO 12535, a menaquinone (MK) producer, was mutagenized to improve productivity. A mutant, which was resistant to 1-hydroxy-2-naphthoate (HNA), was found to produce MK more abundantly: 34 mg/liter of culture broth and 5.5 mg/g of dry cells. The mutant was less sensitive to inhibition by HNA on MK biosynthesis than the wild-type strain. MK was isolated from cells of the mutant and identified as MK-6 based on its physicochemical characteristics. Mutants, which were given each KCN resistance, aromatic amino acid auxotrophy and no carotenoid productivity, did not show further increase of productivity.

Detection of turkey rhinotracheitis virus from chickens with swollen head syndrome by reverse transcriptase-polymerase chain reaction (RT-PCR).

We developed a sensitive and specific method, reverse transcriptase-polymerase chain reaction (RT-PCR) method, for detection of turkey rhinotracheitis virus (TRTV). Two sets of primers were designed from F protein gene sequence of TRTV 3B strain. Sensitivity of detection by nested PCR with the primers corresponded to 0.4 TCID50. Applying this method to a field case of swollen head syndrome (SHS), TRTV could be detected directly from chicken trachea and turbinates. It was identified that this method was very useful to examine the relation of TRTV and SHS.

[Penetration of cefotaxime into human cerebrospinal fluid].

The penetration of cefotaxime (CTX) into the cerebrospinal fluid (CSF) was monitored to evaluate the prophylactic efficacy of the drug against post-craniotomy infections. Doses ranged from 1 to 2 g were administered to patients with subarachnoid hemorrhage due to the rupture of cerebral aneurysm, traumatic cerebral contusion, or subdural edema accompanied by intracerebral hemorrhage, by intravenous drip infusion over a period of 30 or 60 minutes. CTX readily entered the CSF with concentrations exceeding MICs against the major pathogens occurring after craniotomy. CTX proved to be effective in the prevention of post-craniotomy infections in noninflammatory situations, especially after surgery in the case of cerebral traumas or subarachnoid hemorrhage.

[A study of cefoperazone levels in the cerebrospinal fluid of patients with hydrocephalus].

Eleven neurosurgical patients without intracranial infection were given 4 g cefoperazone (CPZ) intravenously for 30 minutes. Ventricular drainage was performed in 10 cases, and 1 case with cisternal drainage. Eight of 11 cases showed moderate to severe ventricular dilatation. Serum and ventricular cerebrospinal fluid (CSF) concentrations of CPZ were measured for 8 hours after injection. Average peak serum concentration of CPZ was 476 micrograms/ml and the half-life was 150 minutes. Patients with obstructive hydrocephalus showed relative good penetration of CPZ in CSF (2.74 approximately 5.29 micrograms/ml). Especially, those who had severe dilatation of ventricles demonstrated sequential increased concentration (5.48 approximately 6.25 micrograms/ml at 8 hours). In poor risk patient and intracerebral hemorrhage with ventricular hemorrhage cases, who had normal range of CSF cell counts and protein, CPZ level was low, less than 2 micrograms/ml. In cases with severe subarachnoid hemorrhage, sufficient concentration (11 micrograms/ml) of CPZ was observed in cisternal CSF. The CPZ concentrations in CSF after 4 g administration did not seem to exceed comparing to 2 g dosing.

[Etiology of water and electrolyte metabolism imbalance following the rupture of cerebral aneurysms--with special reference to preoperative condition].

One hundred fourteen patients with ruptured cerebral aneurysms were reviewed in regard to the incidence and etiological factors of preoperative disturbances of water and electrolyte metabolism. Patients with inadequate salt intake, evidence of renal disease, cardiac failure or excessive diuretic therapy were excluded. Twenty-five (21.9%) patients developed water and electrolyte disturbances. Hyponatremia (less than 130 mEq/l) occurred in 18 (15.8%) of 114 patients. The majority of those patients with hyponatremia showed laboratory findings and/or clinical features suggesting the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). The mean interval between the last subarachnoid hemorrhage (SAH) and the development of hyponatremia was 13.5 days (range 6 to 26 days). No patients developed hypernatremia (more than 155 mEq/l). Preoperative diabetes insipidus (DI) occurred in 7 (6.1%) of 114 patients. The mean interval between the last SAH and the onset of DI was 26.5 days (range 15 to 35 days). When compared with the onset of hyponatremia following SAH, the development of DI was significantly delayed. The present study showed that the following five types of patients significantly related to the development of preoperative water and electrolyte disturbances after SAH due to cerebral aneurysms. The patients with ruptured aneurysms of anterior communicating, anterior cerebral artery or internal carotid artery. The patients in grade III, IV according to Hunt & Hess. The patients with high density in the basal subarachnoid space on the CT scan. The patients with a small hematoma in the region of the basal frontal interhemispheric fissure in cases with aneurysms of the anterior communicating or anterior cerebral artery.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cerebral vasospasm following subarachnoid hemorrhage in arteriovenous malformation].

Cerebral vasospasm after SAH from AVMs is rare. Only few reports have been made. Vasospasm was confirmed in 4 out of 13 patients with SAH from AVMs at the Sagamihara National Hospital in the past 5 years. The incidence of vasospasm following rupture of AVM is higher than those in previous reports ranging between 8 and 12 percent. This high incidence (31%) might be attributable to the timing from the last SAH attack until angiography. The existence of massive subarachnoid blood clots around the arteries of the circle of Willis is the most important factor causing vasospasm after SAH from AVMs.