Mechanisms of factor VIIa‐catalyzed activation of factor VIII

Summary. Background: Factor (F)VIIa, complexed with tissue factor (TF), is a primary trigger of blood coagulation, and has extremely restricted substrate specificity. The complex catalyzes limited proteolysis of FVIII, but these mechanisms are poorly understood. Objectives: In the present study, we investigated the precise mechanisms of FVIIa/TF‐catalyzed FVIII activation. Results: FVIII activity increased ～4‐fold within 30 s in the presence of FVIIa/TF, and then decreased to initial levels within 20 min. FVIIa (0.1 nm ), at concentrations present physiologically in plasma, activated FVIII in the presence of TF, and this activation was more rapid than that induced by thrombin. The heavy chain (HCh) of FVIII was proteolyzed at Arg⁷⁴⁰ and Arg³⁷² more rapidly by FVIIa/TF than by thrombin, consistent with the enhanced activation of FVIII. Cleavage at Arg³³⁶ was evident at ～1 min, whilst little cleavage of the light chain (LCh) was observed. Cleavage of the HCh by FVIIa/TF was governed by the presence of the LCh. FVIII bound to Glu‐Gly‐Arg‐active‐site‐modified FVIIa (K_d, ～0.8 nm ) with a higher affinity for the HCh than for the LCh (K_d, 5.9 and 18.9 nm ). Binding to the A2 domain was particularly evident. Von Willebrand factor (VWF) modestly inhibited FVIIa/TF‐catalyzed FVIII activation, in keeping with the concept that VWF could moderate FVIIa/TF‐mediated reactions. Conclusions: The results demonstrated that this activation mechanism was distinct from those mediated by thrombin, and indicated that FVIIa/TF functions through a ‘priming’ mechanism for the activation of FVIII in the initiation phase of coagulation.     

High-grade Cerebral Arteriovenous Malformation Treated with Targeted Embolization of a Ruptured Site: Wall Enhancement of an Intranidal Aneurysm as a Sign of Ruptured Site

Partial targeted embolization of the ruptured site of cerebral arteriovenous malformations (AVMs) is considered effective to prevent rebleeding. The site of rupture is usually determined by morphological features, such as an intranidal aneurysm or a venous varix; however, the site can be difficult to identify in high-grade AVM with complicated angioarchitecture. The authors present a case of a 36-year-old woman with high-grade AVM presented with repeated hemorrhage. Cerebral angiography showed intranidal aneurysm, which was considered the ruptured site. The T₁-weighted imaging with gadolinium enhancement demonstrated linear enhancement along the outer surface of the thickened wall of the intranidal aneurysm, which could be supplementary information to identify the ruptured site. Obliteration of the intranidal aneurysm was successfully achieved by emergent targeted embolization using N-butyl cyanoacrylate. The patient recovered and regained an independent status. The patient underwent volume-staged radiosurgery and experienced no further hemorrhage during the 26 months follow-up. Targeted embolization of the ruptured site is considered effective to prevent rebleeding in high-grade cerebral AVMs. Wall enhancement of the intranidal aneurysm, in addition to the structural characteristics, could be helpful in identifying the site of rupture embedded in the complicated angioarchitecture.     

A genome‐wide association study of venous thromboembolism identifies risk variants in chromosomes 1q24.2 and 9q

Summary. Objectives: To identify venous thromboembolism (VTE) disease‐susceptibility genes. Patients and methods: We performed in silico genome wide association scan (GWAS) analyses using genotype data imputed to approximately 2.5 million single‐nucleotide polymorphisms (SNPs) from adults with objectively‐diagnosed VTE (n = 1503), and controls frequency matched on age and gender (n = 1459; discovery population). Single‐nucleotide polymorphisms exceeding genome‐wide significance were replicated in a separate population (VTE cases, n = 1407; controls, n = 1418). Genes associated with VTE were re‐sequenced. Results: Seven SNPs exceeded genome‐wide significance (P < 5 × 10^?8): four on chromosome 1q24.2 (F5 rs6025 [factor V Leiden], BLZF1 rs7538157, NME7 rs16861990 and SLC19A2 rs2038024) and three on chromosome 9q34.2 (ABO rs2519093 [ABO intron 1], rs495828, rs8176719 [ABO blood type O allele]). The replication study confirmed a significant association of F5, NME7 and ABO with VTE. However, F5 was the main signal on 1q24.2 as only ABO SNPs remained significantly associated with VTE after adjusting for F5 rs6025. This 1q24.2 region was shown to be inherited as a haplotype block. ABO re‐sequencing identified 15 novel single nucleotide variations (SNV) in ABO intron 6 and the ABO 3′ UTR that were strongly associated with VTE (P < 10^?4) and belonged to three distinct linkage disequilibrium (LD) blocks; none were in LD with ABO rs8176719 or rs2519093. Our sample size provided 80% power to detect odds ratios (ORs) = 2.0 and 1.51 for minor allele frequencies = 0.05 and 0.5, respectively (α = 1 × 10^?8; 1% VTE prevalence). Conclusions: Apart from F5 rs6025, ABO rs8176719, rs2519093 and F2 rs1799963, additional common and high VTE‐risk SNPs among whites are unlikely.     

A Surgical Case of Frontal Lobe Epilepsy Due to Focal Cortical Dysplasia Accompanied by Olfactory Nerve Enlargement: Case Report

A 45-year-old man came to our clinic due to refractory general tonic seizure and an attack of unintended yelling. Magnetic resonance imaging (MRI) demonstrated mild cortical hyperintensity on fluid attenuated inversion recovery (FLAIR) image in the left basal frontal area. Enlargement of the left olfactory nerve was also detected below the affected gyrus. Subtotal resection of the MRI-visible epileptogenic lesion was performed without any neurological deficit. The final pathological diagnosis was focal cortical dysplasia (FCD) type IIa. Seizures and yelling attacks subsided after surgery. Extracerebral abnormalities, including cranial nerve enlargement, are common in patients with hemimegalencephaly. However, such abnormalities are rare with FCD.     

Enhancement of acetaminophen cytotoxicity in selenium-binding protein-overexpressed COS-1 cells

The role of selenium-binding protein (SeBP), which has a high ability to associate with acetaminophen (AAP), on the cytotoxicity of AAP was studied. To clarify this issue, we examined the cytotoxic effect of AAP using COS cells stably expressing SeBP. Expression of SeBP enhanced the susceptibility of the cells to AAP-induced cytotoxicity. Several clones of SeBP-expressed COS cells were obtained, and they exhibited different degrees of susceptibility toward AAP. It was found that there is an inverse correlation between the expression level and the cell viability (r=-0.872). On the other hand, no increase in toxicity was observed in the SeBP-expressed cells treated with N-acetyl-p-quinone imine (NAPQI), which is an active metabolite of AAP. These results show that SeBP is an important factor in AAP hepatotoxicity. Moreover, our data suggest that the toxic mechanism of AAP differs from that of NAPQI.     

Bladder smooth muscle cell phenotypic changes and implication of expression of contractile proteins (especially caldesmon) in rats after partial outlet obstruction

BACKGROUND: The purpose of the present study was to investigate morphological changes in bladder smooth muscle of rats with partial outlet obstruction. We investigated smooth muscle cell phenotypic changes and implication of synthetic phenotype in contractility decrease and bladder compliance after bladder outlet obstruction. METHODS: Partial bladder outlet obstruction was introduced in female rats. Bladder were removed at 1, 3, 6, 10 and 20 weeks after the obstruction. Temporal pattern of changes in bladder mass, light microscopic pathogenesis and phenotypic expression of the bladder smooth muscle cells in the electron micrographs were investigated. Expression of contractile protein was also investigated by the immunoblotting method. RESULTS: Marked increase in bladder mass with marked thickening of smooth muscle layer was observed at 1 week after obstruction. The ratio of myocytes exhibiting contractile and synthetic phenotypes was almost constant until 6 weeks after the obstruction, but thereafter, synthetic phenotypes gradually increased and the ratio (synthetic/contractile phenotype) was 1.5-fold at 20 weeks after the obstruction. Caldesmon was most markedly expressed after the obstruction among contractile proteins examined by the immunoblotting method. CONCLUSION: Phenotypic changes were confirmed in bladder smooth muscle, and the decrease of the ratio of contractile phenotype was observed after long-term obstruction of the bladder outlet. Among the contractile proteins in the bladder smooth muscle cell, caldesmon was considered a reliable marker for predicting the pathogenetic conditions of the bladder.     

Multiple biopsies of normal‐looking urothelium in patients with superficial bladder cancer: Are they necessary?

BACKGROUND: The objective of the study presented here was to assess the usefulness and indications of multiple biopsies of normal-appearing urothelium in patients with superficial bladder cancer. METHODS: Between December 1996 and December 2002, multiple biopsies of normal-appearing bladder mucosa were performed in 100 patients with superficial bladder transitional cell carcinoma. Biopsy specimens were taken from seven different sites in females and nine different sites in males. RESULTS: In eight of 100 patients, bladder cancers were detected in the biopsy specimens. Three cases were Ta and five were Tis. All of the five patients with carcinoma in situ (CIS) in their biopsy specimens had multiple papillary broad-base tumors and positive urinary cytology. The detection ratio of CIS in patients with these findings was 17.9% (5/28). No concomitant CIS was detected in the 72 patients who had a solitary tumor, pedunculated tumor(s), or negative urinary cytology. CONCLUSION: Multiple mucosal biopsies of normal-appearing urothelium are not necessary for all patients with superficial bladder cancer. They are, however, necessary for patients with multiple papillary broad-base tumors and positive urinary cytology.