Distinctive properties of plaque-type dura mater graft-associated Creutzfeldt-Jakob disease in cell-protein misfolding cyclic amplification.

There are two distinct subtypes of dura mater graft-associated Creutzfeldt-Jakob disease (dCJD) with methionine homozygosity at codon 129 of the PRNP gene. The majority of cases is represented by a non-plaque-type (np-dCJD) resembling sporadic CJD (sCJD)-MM1 or -MV1, while the minority by a plaque-type (p-dCJD). p-dCJD shows distinctive phenotypic features, namely numerous kuru plaques and an abnormal isoform of prion protein (PrP(Sc)) intermediate in size between types 1 and 2. Transmission studies have shown that the unusual phenotypic features of p-dCJD are linked to the V2 prion strain that is associated with sCJD subtypes VV2 or -MV2. In this study, we applied protein misfolding cyclic amplification (PMCA) using recombinant human prion protein as a substrate and demonstrated that p-dCJD prions show amplification features that are distinct from those of np-dCJD. Although no amplification of np-dCJD prions was observed with either 129 M or 129 V substrate, p-dCJD prions were drastically amplified with the 129 V substrates, despite the PRNP codon 129 incompatibility between seed and substrate. Moreover, by using a type 2 PrP(Sc)-specific antibody not recognizing PrP(Sc) in p-dCJD, we found that type 2 products are generated de novo from p-dCJD prions during PMCA with the 129 V substrates. These findings suggest that our cell-PMCA is a useful tool for easily and rapidly identifying acquired CJD associated with the transmission of the V2 CJD strain to codon 129 methionine homozygotes, based on the preference for the 129 V substrate and the type of the amplified products.

Efficient propagation of variant Creutzfeldt-Jakob disease prion protein using the cell-protein misfolding cyclic amplification technique with samples containing plasma and heparin.

BACKGROUND: To prevent the iatrogenic spread of variant Creutzfeldt-Jakob disease (vCJD) between humans via blood products or transfusion, highly sensitive in vitro screening tests are necessary. Protein misfolding cyclic amplification (PMCA) is one such candidate test. However, plasma has been reported to inhibit the PMCA reaction. Therefore, we investigated the cell-PMCA conditions that permit vCJD prion amplification in the presence of plasma. STUDY DESIGN AND METHODS: Cell-PMCA of vCJD samples was performed by adding various final concentrations of pooled plasma, citrate-phosphate-dextrose (CPD), albumin, globulin, or pooled plasma treated with ion exchangers. After heparin and plasma concentrations were optimized, multiround cell-PMCA was performed. RESULTS: When 1% to 50% of pooled plasma was added to heparinized cell-PMCA, amplification efficiency showed a double-peaked profile at less than 1% and 40% final plasma concentrations, indicating that plasma contains not only PMCA inhibitors but also promoters. Intravenous globulin did not inhibit cell-PMCA, but the protein G-bound fraction did. CPD, albumin-depleted plasma, and the unbound fraction of anion-exchange chromatography inhibited cell-PMCA, but albumin and the unbound fraction of the cation-exchange chromatography did not. The detection limit of abnormal prion protein in multiround cell-PMCA, when maintaining the final plasma concentration at 40% at each round, was 10(-10) dilutions of a vCJD brain specimen. CONCLUSION: We have established a novel cell-PMCA format in the presence of plasma without any pretreatment, where vCJD prion protein was amplified at comparable levels to that found without plasma. Our data suggest the feasibility of cell-PMCA as a practical blood test for vCJD prions.

Molecular barriers to zoonotic transmission of prions.

The risks posed to human health by individual animal prion diseases cannot be determined a priori and are difficult to address empirically. The fundamental event in prion disease pathogenesis is thought to be the seeded conversion of normal prion protein to its pathologic isoform. We used a rapid molecular conversion assay (protein misfolding cyclic amplification) to test whether brain homogenates from specimens of classical bovine spongiform encephalopathy (BSE), atypical BSE (H-type BSE and L-type BSE), classical scrapie, atypical scrapie, and chronic wasting disease can convert normal human prion protein to the abnormal disease-associated form. None of the tested prion isolates from diseased animals were as efficient as classical BSE in converting human prion protein. However, in the case of chronic wasting disease, there was no absolute barrier to conversion of the human prion protein.

Splenic rupture after surgical fixation of rib fractures with video-assisted thoracoscopic surgery: A case report.

INTRODUCTION: Recently, the utilization of surgical stabilization of rib fractures (SSRF) with video-assisted thoracoscopic surgery (VATS) has been increasing owing to its effectiveness. The present report describes the case of a patient who underwent SSRF with VATS and subsequently developed a splenic rupture that was speculated to be related to intrathoracic manipulation during surgery. PRESENTATION OF CASE: A 62-year-old male patient sustained injuries from a fallen festival car over his thoracoabdominal zone and was diagnosed with bilateral multiple rib fractures and burst fractures of the twelfth thoracic and first lumbar vertebrae. The patient underwent SSRF with VATS. Following surgery, the patient went into hemorrhagic shock due to a splenic rupture, necessitating an emergency open splenectomy. DISCUSSION: Despite no initial detection of splenic injury on contrast-enhanced CT, it is possible that a slight splenic injury existed at the time of the initial diagnosis. Moreover, during surgery, additional external forces may have been applied to the spleen due to positional changes, such as shifting to the lateral position or retracting the diaphragm using forceps; these manipulations could have potentially caused a slight splenic injury, possibly leading to splenic rupture. CONCLUSION: When performing SSRF through VATS, it is important to recognize that manipulation and traction of the diaphragm could potentially cause splenic rupture, even if a slight force is applied. Therefore, the diaphragm should be evaluated without traction and manipulation whenever possible.

Relationship between 2nd-generation angiotensin receptor blockers and the risk of hypotension in COVID-19 patients admitted to hospital.

It has not yet been established whether angiotensin II receptor blockers (ARB), statins, and multiple drugs affect the severity of COVID-19. Therefore, we herein performed an observational study on the effects of 1st- and 2nd-generation ARB, statins, and multiple drugs, on COVID-19 in patients admitted to 15 Japanese medical facilities. The results obtained showed that ARB, statins, and multiple drugs were not associated with the primary outcome (odds ratio: 1.040, 95% confidence interval: 0.688-0.571; 0.696, 0.439-1.103; 1.056, 0.941-1.185, respectively), each component of the primary outcome (in-hospital death, ventilator support, extracorporeal membrane oxygenation support, and admission to the intensive care unit), or the secondary outcomes (oxygen administration, disturbed consciousness, and hypotension, defined as systolic blood pressure ≤90 mmHg). ARB were divided into 1st- and 2nd-generations based on their approval for use (before 2000 and after 2001), with the former consisting of losartan, candesartan, and valsartan, and the latter of telmisartan, olmesartan, irbesartan, and azilsartan. The difference of ARB generation was not associated with the primary outcome (odds ratio with 2nd-generation ARB relative to 1st-generation ARB: 1.257, 95% confidence interval: 0.613-2.574). The odd ratio for a hypotension as one of the secondary outcomes with 2nd-generation ARB was 1.754 (95% confidence interval: 1.745-1.763) relative to 1st-generation ARB. These results suggest that patients taking 2nd-generation ARB may be at a higher risk of hypotension than those taking 1st-generation ARB and also that careful observations are needed. Further studies are continuously needed to support decisions to adjust medications for co-morbidities.

Beat-to-Beat Estimation of Peripheral Arterial Stiffness From Local PWV for Quantitative Evaluation of Sympathetic Nervous System Activity.

OBJECTIVE: Sympathetic nervous system activity (SNSA) can rapidly modulate arterial stiffness, thus making it an important biomarker for SNSA evaluation. Pulse wave velocity (PWV) is a well-known quantitative indicator of arterial stiffness, but its functional responsivity to SNSA has not been elucidated. This paper reports a method to estimate rapid changes in peripheral arterial stiffness induced by SNSA using local PWV (LPWV) and to further quantify SNSA based on the estimated stiffness. METHODS: LPWV was measured from the artery near the wrist to the artery near the forefinger using a biodegradable piezoelectric sensor and a photoplethysmography sensor in an electrocutaneous stimulus experiment in which pain evokes the SNSA. The relationship between LPWV, simultaneously measured peripheral arterial stiffness index, and self-reported pain intensity was quantified. RESULTS: The stiffness estimated by LPWV alone and the stiffness estimated by LPWV and arterial pressure both approximate the peripheral arterial stiffness index (R2 = 0.9775 and 0.9719). Pain intensity can be quantitatively evaluated in a sigmoidal relationship by either the estimated stiffness based on LPWV alone (r = 0.8594) or the estimated stiffness based on LPWV and arterial pressure (r = 0.9738). CONCLUSION: Our results demonstrated the validity of LPWV in the quantitative evaluation of SNSA and the optionality of blood pressure correction depending on application scenarios. SIGNIFICANCE: This study advances the understanding of sympathetic innervation of peripheral arteries through the sympathetic responsivity of LPWV and contributes a quantitative biomarker for SNSA evaluation.

Assessment of Ureters at Dangerous Locations in Lateral Lumbar Interbody Fusion.

INTRODUCTION: This study aimed to investigate the ureteral running position from the viewpoint of the spine, and to identify the spinal level and left-right difference in the ureter at a dangerous location of ureteral injury during surgery. METHODS: This retrospective study included 100 consecutive patients (39 males and 61 females; average age, 70.4 years). Preoperative contrast-enhanced computerized tomography (CT) scans obtained in the supine position for patients who underwent lateral lumbar interbody fusion (LLIF) were analyzed. The ureter location was divided into four regions on the axial CT images based on the lumbar disk levels as follows: A (ventral-medial), B (ventral-lateral), C (dorsal-medial), and D (dorsal-lateral). The C region surrounded by the vertebral body and the psoas muscle was assumed to have the highest probability of ureteral injury. We examined the characteristics of the ureteral position at each disc level. RESULTS: In the upper lumbar spine, the ureter was outside the lateral dorsoventral axis from the contact point of the psoas muscle, while in the lower lumbar spine, it was inside the axis. The ureters located in the C region increased significantly in the lower lumbar disk levels (L1-L2 and L2-L3: 0%; L3-L4: 5.5%; L4-L5: 14.8%; L5-S: 31.5%). Comparing the left and right sides, especially at L4-L5, the ureter in the C region was observed in 21% of all ureters on the left side and in 9% on the right side. With respect to gender differences, the ureters present in the C region were significantly more common in women at lumbar disk levels L3-L4, L4-L5, and L5-S. CONCLUSIONS: The ureters in the C region were common on the left side and at lower lumbar disk levels. To avoid ureteral injury, it is necessary to confirm the location of the ureter by using preoperative images and performing LLIF carefully.

Deduction of the evaluation limit and termination timing of multi-round protein misfolding cyclic amplification from a titration curve.

In this study, the efficacy of disinfectants in reducing the partially protease-resistant isoform of prion protein was evaluated by a multi-round protein misfolding cyclic amplification (PMCA) technique. Hamster brains infected with scrapie-derived strain 263K were homogenized, treated under inactivating or mock conditions, and subjected to multi-round PMCA. Four sets of serial 10-fold dilutions of mock-treated samples were analyzed. Although considerable variability was observed in the signal patterns, between the second and sixth rounds the number of the PMCA round correlated in a linear fashion with the mean dilution factor of mock-treated, infected brains, corresponding to a log reduction factor (LRF) of 3.8-7.3 log. No signals were observed in the PMCA products amplified from normal hamster brain homogenates. The mean numbers of rounds at the first appearance of the signal for 1 M and 2 M NaOH-treated samples were 4.33 and 4, respectively. Using the linear regression line as the titration curve, the LRFs of these disinfectants were found to be 6.1 and 5.8 log, respectively; these values were not significantly different. The mean number of rounds for the alkaline cleaner and sodium dodecyl sulfate were 9 and 10.33, respectively, and were outside the range of both the linear regression line and evaluation limit. The disinfectants were considered very effective because their LRFs were ≥7.3 log. These estimations were concordant with previous bioassay-based reports. Thus, the evaluation limit seems to be valuable in some applications of multi-round PMCA, such as disinfectant assessment and process validation.

Pressure-based Detection of Heart and Respiratory Rates from Human Body Surface using a Biodegradable Piezoelectric Sensor.

This study investigates the relationship between respiration and autonomic nervous system (ANS) activity and proposes a parallel detection method that can simultaneously extract the heart rate (HR) and respiration rate (RR) from different pulse waves measured using a novel biodegradable piezoelectric sensor. The synchronous changes in heart rate variability and respiration reveal the interaction between respiration and the cardiovascular system and their interconnection with ANS activity. Following this principle, respiration was extracted from the HR calculated beat-by-beat from pulse waves. Pulse waves were measured using multiple biodegradable piezoelectric sensors each attached to the human body surface. The Valsalva maneuver experiment was conducted on seven healthy young adults, and the extracted respiratory wave was compared with a reference respiratory wave measured simultaneously. The experimental results are consistent with the observations from reference waves, where R2 = 0.9506, p < 0.001 for the extracted RR and the reference RR, thus demonstrating the detection capability under different respiratory statuses.

Open anastomosis of extracardiac conduit for total cavopulmonary connection decreases post-operative pleural effusion.

OBJECTIVE: The goal of this study was to see whether the open anastomosis technique using vacuum-assisted venous drainage at the time of the Fontan procedure was associated with decreased post-operative pleural effusion. METHODS: We analysed a subgroup of patients with a functional single ventricle who underwent non-fenestrated total cavopulmonary connection completion with the insertion of an extracardiac conduit as the sole or predominant procedure conducted by a single surgeon at a single institute, using either an open or closed anastomosis technique. RESULTS: Median age and weight were 2.3 years, with a range from 1.3 to 27.6 years and 11.4 kilograms, with a range from 9.7 to 43 kilograms, respectively. The open anastomosis technique was associated with a shorter bypass run (p = 0.015), decreased surgical duration (p = 0.032), fewer pleural effusion days (p = 0.049), and lesser pleural effusion (p = 0.013) than closed anastomosis. Correlation analysis demonstrated a significant relationship between the amount of pleural effusion and surgical duration (correlation efficient, 0.535; p = 0.033). A logistic regression model showed that the open technique was associated with a 20-fold increase in the likelihood of having a total chest tube discharge of less than 300 millilitres (p = 0.027). CONCLUSIONS: The open anastomosis technique shortens operative duration and bypass run, which in turn might contribute to decreased pleural effusion soon after the modified Fontan procedure.

Two distinct prions in fatal familial insomnia and its sporadic form.

Fatal familial insomnia is a genetic prion disease, which is associated with the aspartic acid to asparagine substitution at codon 178 of the prion protein gene. Although the hallmark pathological feature is thalamic and olivary degeneration, there is a patient with an atypical fatal familial insomnia without the hallmark feature. The cause of the pathological variability is unclear. We analysed a Japanese fatal familial insomnia kindred and compared one atypical clinicopathological fatal familial insomnia phenotype case and typical fatal familial insomnia phenotype cases with transmission studies using multiple lines of knock-in mice and with protein misfolding cyclic amplification. We also analysed the transmissibility and the amplification properties of sporadic fatal insomnia. Transmission studies revealed that the typical fatal familial insomnia with thalamic and olivary degeneration showed successful transmission only using knock-in mice expressing human-mouse chimeric prion protein gene. The atypical fatal familial insomnia with spongiform changes showed successful transmission only using knock-in mice expressing bank vole prion protein gene. Two sporadic fatal insomnia cases with thalamic and olivary degeneration showed the same transmissibility as the typical fatal familial insomnia phenotype. Interestingly, one sporadic fatal insomnia case with thalamic/olivary degeneration and spongiform changes showed transmissibility of both the typical and atypical fatal familial insomnia phenotypes. Protein misfolding cyclic amplification could amplify both typical fatal familial insomnia cases and sporadic fatal insomnia cases but not the atypical fatal familial insomnia phenotype or other sporadic Creutzfeldt-Jakob disease subtypes. In addition to clinical findings and neuropathological features, the transmission properties and the amplification properties were different between the typical and atypical fatal familial insomnia phenotypes. It is suggested that two distinct prions were associated with the diversity in the fatal familial insomnia phenotype, and these two prions could also be detected in sporadic fatal insomnia.

Combination chemotherapy of S-1 and low-dose twice-weekly cisplatin for advanced and recurrent gastric cancer in an outpatient setting: a retrospective study.

BACKGROUND: We have reported the efficacy and safety of S-1 combined with low-dose consecutive cisplatin therapy for advanced and recurrent gastric cancer, but the regimen was difficult because daily cisplatin administration was necessary. We have already confirmed that cisplatin of 6 mg/m2 twice-weekly maintained the same protein-bound Pt concentration as that of 3 mg/m2 of cisplatin daily. In the present study, the efficacy and safety of a combination of S-1 and low-dose twice-weekly cisplatin were investigated. PATIENTS AND METHODS: The participants were 32 patients treated at our hospital, and all were admitted for the first 2 weeks of therapy. S-1 at 80 mg/m2 daily was administered orally in two divided doses. Cisplatin at 6 mg/m2 was administered by intravenous drip infusion over 30 minutes on 2 days each week, day 1 and day 4. Each treatment cycle consisted of 4 weeks of drug administration followed by a 2-week drug-free period (6 weeks in total). RESULTS: A total of 146 cycles were administered, with a median of three cycles (range: 1-24) per patient. The results were rated as a complete response in 1 case, partial response in 24 cases and stable disease in 5 cases. The response rate was 78.1% (25/32) and the median survival time was 12.0 months (95% confidence interval (CI) 8.9-15.1 months). The response rate did not differ between previously treated and untreated patients. The one-year survival rate was 48.2% (95% CI 30.3-66.0%). The major adverse reactions were myelosuppression and gastrointestinal symptoms. The total incidence of grade 3 or greater adverse reactions was 15.6% (5/32). CONCLUSION: The combination of S-1 and low-dose twice-weekly cisplatin therapy appears to be highly efficacious and safe and shows promise as a useful treatment strategy, even in outpatient clinics.

A survey on infection control in emergency departments in Japan.

AIM: Infection control in the emergency department is important for hospital risk management; however, few clinical guidelines have been established. This study aimed to determine whether hospitals in Japan have infection control manuals, and investigate the contents of manuals, consulting systems, and isolation facilities for emergency departments. METHODS: A total of 517 hospitals certified as educational institutions for board-certified acute care physicians in Japan were requested between March and May 2015 to provide a written evaluation of the infection control in the emergency department. RESULTS: A total of 51 of 303 (16.8%) hospitals had no manuals regarding infection control in the emergency department. Among 250 hospitals having emergency department manuals, 115 (46.0%) did not include contents regarding disinfection and sterilization for imaging examination rooms, and only 44 (17.6%) had criteria for contacting the emergency medical service when patients are suspected of, or diagnosed with, communicable diseases. Of the 303 hospitals, 277 (91.4%) prepared specific manuals for the 2009 pandemic influenza. Of the 303 hospitals, 80 (26.4%) did not prepare manuals for the Ebola virus disease outbreak in West Africa in 2014. Furthermore, 92 (30.4%) of the 303 hospitals did not have any negative-pressure isolation rooms. CONCLUSIONS: Practices and guidelines necessary for infection control in the emergency department were not sufficiently covered in the hospitals studied. Education, information sharing, and a checklist for preparing manuals are needed to establish better infection control systems in emergency departments.

Simultaneous observation of superficial cortical and intracerebral microvessels in vivo during reperfusion after transient forebrain ischemia in rats using synchrotron radiation.

Using a newly developed angiography system that combines monochromatic synchrotron radiation (MSR) as an X-ray source with a high-definition camera or video system, we observed superficial cortical and intracerebral microvessels simultaneously in vivo during reperfusion after transient forebrain ischemia. Transient brain ischemia was induced by 10-min four-vessel occlusion in rats under general anesthesia. Angiographic images were then sequentially obtained at 3 frames/s. The detector features a 7-microm equivalent pixel size projected onto the input area and a 7 mmx7 mm input field. Changes in the cerebral microvessels were observed before and 1, 5, 10, 15, 20 and 30 min after transient cerebral ischemia using the MSR angiography system. The calibers of the internal carotid artery (ICA), middle cerebral artery (MCA), and striate artery (SA) significantly increased 1 min after reperfusion, while the pial arteriole (PA) caliber significantly decreased (76% of base line). The MCA, PA and SA were significantly dilated 5 and 10 min after reperfusion. Although the caliber of the ICA significantly decreased after 30 min reperfusion compared with the basal value, the calibers of the other three vessels remained larger than the basal values throughout the experiment. Early venous filling was observed at 5 and 10 min after reperfusion. The MSR angiography system is useful for investigating morphological changes in both cortical and central branches of cerebral vessels in rats during reperfusion after cerebral ischemia.

Efficacy of isoproterenol for treating amlodipine overdose resulting in bradycardia.

Case: Amlodipine predominantly affects vascular smooth muscle cells. Amlodipine overdose usually presents with vasodilatory shock, accompanied by reflex tachycardia rather than bradycardia.An 81-year-old woman presented with impaired consciousness 8 h after ingesting 50 5-mg amlodipine tablets with suicidal intent. On admission, her blood pressure was 50/40 mmHg and her heart rate was 45 b.p.m. Serum amlodipine level was extremely high (474.4 ng/mL), causing refractory bradycardia. She remained hypotensive despite fluid resuscitation, and therefore was administered dopamine and norepinephrine. She was also administered glucagon and calcium gluconate, and underwent high-dose insulin euglycemic therapy. Outcome: Although her blood pressure improved, bradycardia progressively worsened and isoproterenol infusion was initiated, which resulted in an improvement in her heart rate. The patient discharged on day 14 without any complications. Conclusion: Isoproterenol is effective for treating bradycardia after amlodipine overdose.

Cerebral Protection During Mitral Valve Repair in a Patient With Moyamoya Syndrome.

In patients with moyamoya syndrome requiring heart surgery, the brain blood flow during the low perfusion state under cardiopulmonary bypass is a concern. We report on a successful mitral valve repair and tricuspid repair in a patient with moyamoya syndrome, performed using an integrated cerebral protection strategy with cerebral oxygen saturation monitoring, intraaortic balloon pumping, and cardiopulmonary bypass perfusion at a relatively high pressure. An integrated approach with a thorough discussion among cardiac surgeons, anesthesiologists, and perfusionists was invaluable to protect brain perfusion in a patient with moyamoya syndrome.

Biliopancreatic fistula caused by an intraductal papillary-mucinous tumor of the pancreas confirmed by biochemical analysis of mucin.

Intraductal papillary-mucinous tumor of the pancreas is occasionally accompanied by biliopancreatic fistula. However, it is difficult to show the inflow of mucin produced by the tumor into the common bile duct. To confirm the biliopancreatic fistula, the mucin-rich fraction was purified from the bile and stained with antimucin antibodies. Western blot analysis showed characteristic smear staining patterns for mucin molecules with three types of antimucin antibodies. Immunohistochemical analysis with the antibody showed significant signals of the cancer cells and the luminal content of the dilated pancreatic duct. These results showed that the bile contained an abundance of mucin, which was produced by the primary pancreatic tumor. In cases with intraductal papillary-mucinous tumor of the pancreas, biochemical analysis of mucin molecules in the bile can be of clinical use in consideration of pathological process of tumor progression.

High-level production of prourokinase-annexin V chimeras in the methylotrophic yeast Pichia pastoris.

Prourokinase (proUK)-annexin V chimeras expressed by the methylotrophic yeast Pichia pastoris in a synthetic medium as part of a system designed to yield a novel thrombolytic agent are degraded, as it is thought, by various yeast proteases present in the culture supernatant. Minimization of proteolysis was therefore investigated to increase the yield of intact proUK-annexin V. Protease inhibitor screening study indicated several proteases including at least serine protease like chymotrypsin were involved in the proteolysis. Addition of more than 10% of peptone or more than 0.2 mol l(-1) of arginine to the medium was effective in minimizing proteolysis in shake-flask culture. Culture condition of higher pH was also effective, however, induced a cell death. Cell improvement by increasing the methanol utilization ability yielded greater tolerance to high pH. As a result, the culture condition with highly concentrated peptone solution fed under controlled conditions of pH 8.0 was established, which greatly reduced proteolytic degradation in fed-batch fermentation. These optimal conditions, which enabled fibrinolytic activity to reach 7800 IU ml(-1), could easily be applied in industrial scale production.

Evaluating prion models based on comprehensive mutation data of mouse PrP.

The structural details of the essential entity of prion disease, fibril prion protein (PrP(Sc)), are still elusive despite the large body of evidence supporting the prion hypothesis. Five major working models of PrP(Sc) structure, which are not compatible with each other, have been proposed. However, no systematic evaluation has been performed on those models. We devised a method that combined systematic point mutation with threading on knowledge-based amino acid potentials. A comprehensive mutation experiment was performed on mouse prion protein, and the PrP(Sc) conversion efficiency of each mutant was examined. The models were evaluated based on the mutation data by using the threading method. Although the data turned out to be rather more consistent with the models that assumed a conversion of the N-terminal region of core PrP into a ß helix than with others, substantial modifications were also required to further improve the current model based on recent experimental results.