Pharmacokinetics of a once-daily tacrolimus formulation in first nations and caucasian liver transplant recipients.

Patient ethnicity may influence the pharmacokinetics (PK) of tacrolimus. Because the Canadian First Nations (FN) constitute a large and increasing segment of the liver transplant population, we undertook to determine whether PK differences exist for a once-daily, extended release formulation of tacrolimus (Advagraf) in FN compared to Caucasian (CAUC) liver transplant recipients. Following achievement of a steady state with Advagraf, blood samples were drawn at 0, 1, 2, 4, 6, 8 and 24 hours for whole blood tacrolimus levels by commercial immunoassay and CYP3A4 and CYP3A5 allele analyses were performed by polymerase chain reactions. Nineteen subjects participated in the study (7 FN and 12 CAUC). The FN cohort had significantly higher AUC (214 ± 48 versus 168 ± 25, P < 0.05), Cmax (16.7 ± 4.4 ng/ml versus 11.3 ± 1.7 ng/ml, P < 0.05), Cmin (6.1 ± 1.0 ng/ml versus 4.7 ± 0.5 ng/ml, P < 0.05) and shorter Tmax (1.6 ± 0.2 hours versus 2.8 ± 0.3 hours, P < 0.05) values than CAUCs. CYP3A4 genotypes were C/C in both cohorts, while the CYP3A5 *1/*3 allele was present in 2/5 FN and 0/9 CAUC. The results of this study indicate that once-daily, extended release Advagraf results in higher blood tacrolimus levels and shorter times to Cmax in FN compared to CAUC liver transplant recipients.

Spontaneous Flares of Chronic Hepatitis B Virus in Hepatitis Be Antigen Negative Carriers Who Subsequently Clear Hepatitis B Surface Antigen.

BACKGROUND: Acute exacerbations of chronic hepatitis B virus (HBV) infections can occur in HBV-infected, hepatitis e antigen (HBeAg)-negative patients in the absence of recent withdrawal of antiviral or immunosuppressive therapies. Whether these spontaneous "flares" predict subsequent loss of hepatitis B surface antigen (HBsAg) has yet to be determined. OBJECTIVES: To document the percent of patients who experience spontaneous HBV flares and severity of the flares in chronic HBeAg-negative carriers. METHODS: A retrospective review of an HBV database identified and followed HBeAg-negative patients for biochemical evidence of flares (ALT > 5× normal) and subsequent HBsAg status. Patients that subsequently cleared HBsAg were matched 1:1 with those who remained HBsAg positive. RESULTS: Of 1299 HBeAg-negative patients followed for 10.2 ± 6.1 years, 88 (6.8%) developed spontaneous HBV flares. Flares occurred in 14/115 (12.2%) patients who subsequently cleared HBsAg and 4/111 (3.6%) matched patients who remained HBsAg positive (p = 0.025). The severity of flares was similar in the two study cohorts. Following multivariate analyses, only low HBV-DNA levels at baseline identified patients likely to subsequently clear HBsAg. CONCLUSIONS: Although more common in patients who subsequently clear HBsAg, spontaneous HBV flares do not predict subsequent HBsAg clearance.

Concomitant nonalcoholic fatty liver disease does not alter the activity, severity or course of primary biliary cholangitis.

BACKGROUND & AIMS: The impact of nonalcoholic fatty liver disease (NAFLD) on the natural history of primary biliary cholangitis (PBC) has yet to be described. The aim of this study was to document the activity, severity and progression of PBC in patients with concomitant NAFLD and compare the findings to those with PBC alone. METHODS: Disease activity was assessed by serum liver enzyme levels; severity, by Fib-4 scores and percent of patients with APRI >1.5; and progression, by changes in Fib-4 and prevalence of APRI >1.5 during follow-up. RESULTS: The study populations consisted of 168 PBC alone and 68 PBC/NAFLD patients. The mean ages and gender distributions of the two cohorts were similar. At presentation, PBC alone patients had greater disease activity (higher serum ALP and GGT values, P = .003 and 0.01, respectively) and advanced disease (higher Fib-4 (P = .04) scores) than PBC/NAFLD patients. Although the prevalence of APRI >1.5 was also higher in PBC alone (11.1%) vs PBC/NAFLD (4.7%) patients, the difference was not significant (P = .16). During mean follow-up of 6.7 ± 5.5 (PBC alone) and 6.4 ± 4.4 (PBC/NAFLD) years (ranges: 0.5-21 years) annual increases in Fib-4 and prevalence of ≥ APRI 1.5 were greater in PBC alone patients but the differences did not reach statistical significance. CONCLUSIONS: The results of this retrospective, single centre study suggest that the activity, severity and progression of PBC are not adversely affected by concomitant NAFLD.

Circulating Levels of Interleukin 1-Receptor Antagonist and Risk of Cardiovascular Disease: Meta-Analysis of Six Population-Based Cohorts.

OBJECTIVE: Interleukin (IL)-1ß represents a key cytokine in the development of cardiovascular disease (CVD). IL-1ß is counter-regulated by IL-1 receptor antagonist (IL-1RA), an endogenous inhibitor. This study aimed to identify population-based studies on circulating IL-1RA and incident CVD in a systematic review, estimate the association between IL-1RA and incident CVD in a meta-analysis, and to test whether the association between IL-1RA and incident CVD is explained by other inflammation-related biomarkers in the MONICA/KORA Augsburg case-cohort study (Multinational Monitoring of Trends and Determinants in Cardiovascular Disease/Cooperative Health Research in the Region of Augsburg). APPROACH AND RESULTS: We performed a systematic literature search and identified 5 cohort studies on IL-1RA and incident CVD in addition to the MONICA/KORA Augsburg case-cohort study for a meta-analysis based on a total of 1855 CVD cases and 18 745 noncases with follow-up times between 5 and 16 years. The pooled standardized hazard ratio (95% confidence interval) for incident CVD was 1.11 (1.06-1.17) after adjustment for age, sex, anthropometric, metabolic, and lifestyle factors (P<0.0001). There was no heterogeneity in effect sizes (I2=0%; P=0.88). More detailed analyses in the MONICA/KORA study showed that the excess risk for CVD was attenuated by ≥10% after additional separate adjustment for serum levels of high-sensitivity C-reactive protein, IL-6, myeloperoxidase, soluble E-selectin, or soluble intercellular adhesion molecule-1. CONCLUSIONS: Serum IL-1RA levels were positively associated with risk of CVD after adjustment for multiple confounders in a meta-analysis of 6 population-based cohorts. This association may at least partially reflect a response to triggers inducing subclinical inflammation, oxidative stress, and endothelial activation.

Predicting Pre-transplant Abstinence in Patients with Alcohol-Induced Liver Disease.

BACKGROUND: Some patients with alcohol-induced liver failure will succumb to their disease prior to demonstrating compliance with the six months abstinence rule for liver transplantation. PURPOSE: The purpose of this study was to determine whether a patient's self-reported, longest period of abstinence predicts subsequent abstinence. METHODS: Adult patients (n=63) with alcohol-induced liver disease were asked to recall their longest period of abstinence prior to their initial hepatology visit. Compliance with instructions to remain abstinent was then documented. RESULTS: Nineteen patients (30%) achieved abstinence and 44 (70%) relapsed within six months of seeing their hepatologist. Relapses were more common in patients who self-reported previous periods of abstinence exceeding six months (19/44, 43%) compared with 2/19 (11%) in those with periods of less than six months (p=0.01). Serum albumin levels were lower in relapsers but other tests of liver function (bilirubin level and international ratio of prothrombin time) and predictors of post-transplant recidivism did not associate with relapses. On multivariate analysis, self-reported abstinence (OR: 0.11, 95% CI: 0.02-0.57, p=0.008) and serum albumin levels (regression coefficient 0.113, p=0.02) predicted relapses. CONCLUSIONS: A self-reported period of abstinence in excess of six months was associated with an increased risk of subsequent relapse following a hepatologist's instructions to remain abstinent. These counter-intuitive findings should be confirmed by larger, prospective studies.

Insulin secretion in liver transplant recipients following conversion to a prolonged release tacrolimus formulation.

Background: Post liver transplant diabetes mellitus (PLTDM) occurs in 10-40% of liver transplant recipients and is associated with increased morbidity and mortality. An important cause of PLTDM is tacrolimus induced, concentration-dependent, inhibition of insulin secretion. Objective: To determine if a newly licenced formulation of tacrolimus (Envarsus-PA), which achieves peak tacrolimus concentrations 20-30% lower than other tacrolimus formulations has less of an inhibitory effect on insulin secretion. Methods: Homeostatic model assessment (HOMA) for insulin secretion (HOMA-S) values and c-peptide levels were determined in 19 adult liver transplant recipients while being maintained on immediate- or slow-release tacrolimus formulations and repeated a minimum of 30 days following conversion to Envarsus-PA. Results: Insulin secretion was unchanged following conversion to Envarsus-PA (HOMA-S pre-conversion: 154 ± 133 vs. 129 ± 75, post-conversion [p = 0.32], and c-peptide levels; 1059 ± 602 and 934 ± 463 respectively, p = 0.42). Fasting blood glucose (FBG) and hemoglobin A1c (HbA1c) levels were also unchanged (FBG 5.7 ± 0.8 pre-conversion vs. 5.6 ± 0.7 post-conversion; p = 0.36 and HbA1c 4.9±1.2 pre-conversion versus 5.5±0.2 post-conversion, p = 0.34). Conclusions: Envarsus-PA had no significant effect on insulin secretion or glucose homeostasis beyond that associated with other tacrolimus formulations in adult liver transplant recipients.

Spongiform encephalopathy in transgenic mice expressing a point mutation in the ß2-α2 loop of the prion protein.

Transmissible spongiform encephalopathies are fatal neurodegenerative diseases attributed to misfolding of the cellular prion protein, PrP(C), into a ß-sheet-rich, aggregated isoform, PrP(Sc). We previously found that expression of mouse PrP with the two amino acid substitutions S170N and N174T, which result in high structural order of the ß2-α2 loop in the NMR structure at pH 4.5 and 20°C, caused transmissible de novo prion disease in transgenic mice. Here we report that expression of mouse PrP with the single-residue substitution D167S, which also results in a structurally well ordered ß2-α2 loop at 20°C, elicits spontaneous PrP aggregation in vivo. Transgenic mice expressing PrP(D167S) developed a progressive encephalopathy characterized by abundant PrP plaque formation, spongiform change, and gliosis. These results add to the evidence that the ß2-α2 loop has an important role in intermolecular interactions, including that it may be a key determinant of prion protein aggregation.

Post-transplant diabetes mellitus in Canadian liver and renal transplant recipients.

BACKGROUND: Post-transplant diabetes mellitus (PTDM) occurs in 10%-40% of liver and renal transplant recipients. Whether the risk factors for PTDM in liver and renal transplant recipients are similar and whether Indigenous Canadians, who have a high underlying prevalence of diabetes mellitus (DM), are at increased risk of developing PTDM have yet to be determined. OBJECTIVE: To describe and compare those variables associated with PTDM in adult Canadian liver and renal transplant recipients. METHODS: A retrospective chart review of adult liver and renal transplant recipients attending four transplant follow-up clinics in three Canadian provinces was undertaken. RESULTS: De novo PTDM was diagnosed in 184/905 (20.3%) liver and 179/390 (45.9%) renal transplant recipients. Older age, higher pre-transplant BMI, underlying immune-mediated liver disease, lower trough tacrolimus levels and longer duration of follow-up were independently associated with PTDM in liver transplant recipients and non-Caucasian race, higher pre-transplant BMI, and incidence of organ rejection in renal transplant recipients. Compared with Caucasians, Indigenous Canadians who had undergone renal transplantation had a significantly increased prevalence of PTDM (56.5% versus 40.0%, p = 0.035). The prevalence of PTDM in liver transplant recipients was similar in Indigenous Canadians and Caucasians (27.9% versus 20.1%, p = 0.215). CONCLUSIONS: The variables associated with PTDM differ in liver and renal transplant recipients. Compared with Caucasians, Indigenous Canadians undergoing renal transplantation are at increased risk of developing PTDM.

COVID-19 infection in liver transplant recipients: Clinical features and outcomes from a Canadian multicentre cohort.

BACKGROUND: Prior studies have assessed risk factors and clinical outcomes in liver transplant (LT) recipients infected with COVID-19 globally; however, there is a paucity of Canadian data. Our multicentre study aims to examine the characteristics and clinical outcomes of LT patients with COVID-19 infection in Canada. METHODS: Adult LT recipients with reverse transcription-polymerase chain reaction (RT-PCR) confirmed COVID-19, from Canadian tertiary care centres between March 2020 and June 2021 were included. RESULTS: A total of 49 patients with a history of LT and COVID-19 infection were identified. Twenty-nine patients (59%) were male, median time from LT was 66 months (IQR 1-128), and median age was 59 years (IQR 52-65). At COVID-19 diagnosis, the median alanine transaminase (ALT) was 37 U/L (IQR 21-41), aspartate aminotransferase (AST) U/L was 34 (IQR 20-37), alkaline phosphatase (ALP) U/L was 156 (IQR 88-156), total bilirubin was 11 µmol/L (IQR 7-14), and international normalized ratio (INR) was 1.1 (IQR 1.0-1.1). The majority of patients (86%) were on tacrolimus (monotherapy or combined with mycophenolate mofetil); median tacrolimus level at COVID-19 diagnosis was 5.3 µg/L (IQR 4.0-8.1). Immunosuppression was modified in eight (16%) patients post-infection. Eighteen patients (37%) required hospitalization, and three (6%) required intensive care unit (ICU) admission and mechanical ventilation. Four patients (8%) died from complications related to COVID-19 infection. On univariate analysis, neither age, sex, comorbidities, nor duration post-transplant were associated with risk of hospitalization or ICU admission. CONCLUSIONS: LT recipients with COVID-19 have high rates of hospitalization but fortunately have low rates of ICU admission and mortality in this national registry.

A universal method for detection of amyloidogenic misfolded proteins.

Diseases associated with the misfolding of endogenous proteins, such as Alzheimer's disease and type II diabetes, are becoming increasingly prevalent. The pathophysiology of these diseases is not totally understood, but mounting evidence suggests that the misfolded protein aggregates themselves may be toxic to cells and serve as key mediators of cell death. As such, an assay that can detect aggregates in a sensitive and selective fashion could provide the basis for early detection of disease, before cellular damage occurs. Here we report the evolution of a reagent that can selectively capture diverse misfolded proteins by interacting with a common supramolecular feature of protein aggregates. By coupling this enrichment tool with protein specific immunoassays, diverse misfolded proteins and sub-femtomole amounts of oligomeric aggregates can be detected in complex biological matrices. We anticipate that this near-universal approach for quantitative misfolded protein detection will become a useful research tool for better understanding amyloidogenic protein pathology as well as serve as the basis for early detection of misfolded protein diseases.

Resistance of bovine spongiform encephalopathy (BSE) prions to inactivation.

Distinct prion strains often exhibit different incubation periods and patterns of neuropathological lesions. Strain characteristics are generally retained upon intraspecies transmission, but may change on transmission to another species. We investigated the inactivation of two related prions strains: BSE prions from cattle and mouse-passaged BSE prions, termed 301V. Inactivation was manipulated by exposure to sodium dodecyl sulfate (SDS), variations in pH, and different temperatures. Infectivity was measured using transgenic mouse lines that are highly susceptible to either BSE or 301V prions. Bioassays demonstrated that BSE prions are up to 1,000-fold more resistant to inactivation than 301V prions while Western immunoblotting showed that short acidic SDS treatments reduced protease-resistant PrP(Sc) from BSE prions and 301V prions at similar rates. Our findings argue that despite being derived from BSE prions, mouse 301V prions are not necessarily a reliable model for cattle BSE prions. Extending these comparisons to human sporadic Creutzfeldt-Jakob disease and hamster Sc237 prions, we found that BSE prions were 10- and 10(6)-fold more resistant to inactivation, respectively. Our studies contend that any prion inactivation procedures must be validated by bioassay against the prion strain for which they are intended to be used.

The Psychological and Financial Impact of Long-distance Travel for Liver Transplantation.

BACKGROUND: Patients who travel long distances to undergo liver transplantation have limited opportunities to develop confidence in their new healthcare providers and experience fewer support visits from family and friends at the transplant site. The objectives of this study were to document the psychological and financial impact of having to travel long distances for liver transplantation in adult liver disease patients. METHODS: This was a single-center, prospective study that used a 7-question survey, including Likert scales, patient recall, and administrative databases. RESULTS: Ninety-six adult outpatient liver transplant recipients (59% males; mean age, 43.1 ± 2.1 y) participated in the survey. Approximately 70% (more so among males and higher educated patients) felt that they had sufficient time to develop confidence in their new healthcare providers and 87% felt that confidence in their local healthcare providers had not been diminished by undergoing the procedure elsewhere. Forty-four percent of patients felt that their overall liver transplant experience had been compromised by more limited opportunities for support visits, a perception that was twice as common in females. Median out-of-pocket expenses were under $5000, and inflation corrected costs to third-party payers have been stable for the past 20 y. CONCLUSIONS: The principal psychological impact of travelling long distances for liver transplantation relates to the consequences of fewer support visits. Confidence in the new and local healthcare teams is not compromised by such travel in most patients. Out-of-pocket expenses are under $5000, and transplant costs to third-party payers have remained stable over the past 20 y.

Epidemiology, clinical treatment patterns, and survival of hepatocellular carcinoma in Manitoba.

Background: Hepatocellular carcinoma (HCC) has a very poor survival rate, especially for those who do not receive a potentially curative therapy. Methods: Treatment details were collected for 320 HCC patients diagnosed in Manitoba between January 2011 and December 2015. Patients had a mean age of 67.3 years, and 71.6% were men. Of these patients, 67 (20.9%) received curative treatment, 36 (11.3%) received non-curative treatment, and 217 (67.8%) received supportive care only; 71.3% of patients had liver cirrhosis. Alcoholic cirrhosis was the most common etiology of chronic liver disease (22.2%). Results: Those who received curative treatment had a significantly lower incidence of portal vein thrombosis and multinodular disease than those in other groups. Patients who received supportive care only had a higher incidence of ascites. We found no difference in the distribution of cirrhosis or portal hypertension among the treatment groups. The 2- and 5-year overall survival rates for the whole cohort were 27% and 14%, respectively. No significant change was found in 2-year survival for patients diagnosed in each year from 2011 to 2015 (p = 0.250). Also, we found no significant change in proportion of treatment given to patients over the same period (p = 0.432). Conclusion: The poor survival rate of HCC patients in Manitoba could potentially be improved by maximizing the use of local therapy and by implementing multidisciplinary-based case discussion. Efforts should also be directed toward early management of infective, alcoholic, and non-alcoholic steatohepatitis, which will, we hope, lead to a reduction in the incidence of HCC.

Trafficking of prion proteins through a caveolae-mediated endosomal pathway.

To understand the posttranslational conversion of the cellular prion protein (PrPC) to its pathologic conformation, it is important to define the intracellular trafficking pathway of PrPC within the endomembrane system. We studied the localization and internalization of PrPC in CHO cells using cryoimmunogold electron microscopy. At steady state, PrPC was enriched in caveolae both at the TGN and plasma membrane and in interconnecting chains of endocytic caveolae. Protein A-gold particles bound specifically to PrPC on live cells. These complexes were delivered via caveolae to the pericentriolar region and via nonclassical, caveolae-containing early endocytic structures to late endosomes/lysosomes, thereby bypassing the internalization pathway mediated by clathrin-coated vesicles. Endocytosed PrPC-containing caveolae were not directed to the ER and Golgi complex. Uptake of caveolae and degradation of PrPC was slow and sensitive to filipin. This caveolae-dependent endocytic pathway was not observed for several other glycosylphosphatidyl inositol (GPI)-anchored proteins. We propose that this nonclassical endocytic pathway is likely to determine the subcellular location of PrPC conversion.

A change in the conformation of prions accompanies the emergence of a new prion strain.

To investigate the role of the pathogenic prion protein (PrP(Sc)) in controlling susceptibility to foreign prions, two Syrian hamster (SHa) prion strains, Sc237 and DY, were transmitted to transgenic mice expressing chimeric SHa/mouse PrP genes, Tg(MH2M). First passage of SHa(Sc237) prions exhibited prolonged incubation times, diagnostic of a species barrier. PrP(Sc) of the new MH2M(Sc237) strain possessed different structural properties from those of SHa(Sc237), as demonstrated by relative conformational stability measurements. This change was accompanied by a disease phenotype different from the SHa(Sc237) strain. Conversely, transmission of SHa(DY) prions to Tg(MH2M) mice showed no species barrier, and the MH2M(DY) strain retained the conformational and disease-specific properties of SHa(DY). These results suggest a causal relationship between species barriers, changes in PrP(Sc) conformation, and the emergence of new prion strains.

Factors associated with time to laparoscopic cholecystectomy for acute cholecystitis.

AIM: To determine patient and process of care factors associated with performance of timely laparoscopic cholecystectomy for acute cholecystitis. METHODS: A retrospective medical record review of 88 consecutive patients with acute cholecystitis was conducted. Data collected included demographic data, co-morbidities, symptoms and physical findings at presentation, laboratory and radiological investigations, length of stay, complications, and admission service (medical or surgical). Patients not undergoing cholecystectomy during this hospitalization were excluded from analysis. Hierarchical generalized linear models were constructed to assess the association of pre-operative diagnostic procedures, presenting signs, and admitting service with time to surgery. RESULTS: Seventy cases met inclusion and exclusion criteria, among which 12 were admitted to the medical service and 58 to the surgical service. Mean +/- SD time to surgery was 39.3 +/- 43 h, with 87% of operations performed within 72 h of hospital arrival. In the adjusted models, longer time to surgery was associated with number of diagnostic studies and endoscopic retrograde cholangio-pancreatography (ERCP, P = 0.01) as well with admission to medical service without adjustment for ERCP (P < 0.05). Patients undergoing both magnetic resonance cholangiopancreatography (MRCP) and computed tomography (CT) scans experienced the longest waits for surgery. Patients admitted to the surgical versus medical service underwent surgery earlier (30.4 +/- 34.9 vs 82.7 +/- 55.1 h, P < 0.01), had less post-operative complications (12% vs 58%, P < 0.01), and shorter length of stay (4.3 +/- 3.4 vs 8.1 +/- 5.2 d, P < 0.01). CONCLUSION: Admission to the medical service and performance of numerous diagnostic procedures, ERCP, or MRCP combined with CT scan were associated with longer time to surgery. Expeditious performance of ERCP and MRCP and admission of medically stable patients with suspected cholecystitis to the surgical service to speed up time to surgery should be considered.

Conformation of PrP(C) on the cell surface as probed by antibodies.

We have investigated the conformation of Syrian hamster PrP(C) on the surface of transfected CHO cells by performing cross-competition experiments between a set of nine monoclonal antibody fragments (Fab) directed to defined epitopes throughout the protein. No competition was observed between antibodies recognizing epitopes located within the unstructured N-terminal portion of PrP(C) and those recognizing epitopes located within the ordered C-terminal half of the molecule. However, competition was observed between antibodies recognizing overlapping epitopes and between antibodies recognizing epitopes lying adjacent to one another in the PrP sequence. Titrating the reactivity of each Fab against cell-surface PrP(C) revealed a clear heterogeneity in the accessibility of different specific epitopes. Fab D18, recognizing sequence incorporating the first alpha-helix of PrP(C), bound the largest fraction of the cell-surface PrP population. In contrast, Fab E123, binding an epitope at the extreme N terminus of PrP, and Fab 13A5, binding an epitope in the central region of PrP, were able to recognize fewer than half the number of PrP(C) molecules bound by Fab D18. The pattern of antibody reactivity we observed may, in part, result from N-terminal truncation of a proportion of PrP(C) molecules found at the cell surface. However, truncation cannot account for the marked disparity between exposure of the Fab D18 and 13A5 epitopes, which lie adjacent in the PrP sequence. The relative inaccessibility of the 13A5 epitope likely reflects either PrP(C)-PrP(C) interaction, interaction between PrP(C) and other constituents on the cell membrane, or the existence of PrP(C) subspecies with distinct conformations.

Predicting propulsive forces using distributed sensors in a compliant, high DOF, robotic fin.

Engineered robotic fins have adapted principles of propulsion from bony-finned fish, using spatially-varying compliance and complex kinematics to produce and control the fin's propulsive force through time. While methods of force production are well understood, few models exist to predict the propulsive forces of a compliant, high degree of freedom, robotic fin as it moves through fluid. Inspired by evidence that the bluegill sunfish (Lepomis macrochirus) has bending sensation in its pectoral fins, the objective of this study is to understand how sensors distributed within a compliant robotic fin can be used to estimate and predict the fin's propulsive force. A biorobotic model of a bluegill sunfish pectoral fin was instrumented with pressure and bending sensors at multiple locations. Experiments with the robotic fin were executed that varied the swimming gait, flapping frequency, stroke phase, and fin stiffness to understand the forces and sensory measures that occur during swimming. A convolution-based, multi-input-single-output (MISO) model was selected to model and study the relationships between sensory data and propulsive force. Subsets of sensory data were studied to determine which sensor modalities and sensor placement locations resulted in the best force predictions. The propulsive forces of the fin were accurately predicted using the linear MISO model on intrinsic sensory data. Bending sensation was more effective than pressure sensation for predicting propulsive forces, and the importance of bending sensation was consistent with several results in biology and engineering studies. It was important to have a spatial distribution of sensors and multiple sensory modalities in order to predict forces across large changes to dynamics. The relationship between propulsive forces and intrinsic sensory measures is complex, and good models should allow for temporal lags between forces and sensory data, changes to the model within a fin stroke, and changes to the model through gait transitions.

Atypical prion protein conformation in familial prion disease with PRNP P105T mutation.

Protease-resistant prion protein (PrP(Sc) ) is diagnostic of prion disease, yet its detection is frequently difficult. Here, we describe a patient with a PRNP P105T mutation and typical familial prion disease. Brain PrP(Sc) was undetectable by conventional Western blotting and barely detectable after phosphotungstate precipitation, where it displayed an atypical pattern suggestive of noncanonical conformation. Therefore, we used a novel misfolded protein assay (MPA) that detects PrP aggregates independently of their protease resistance. The MPA revealed the presence of aggregated PrP in similar amounts as in typical sporadic Creutzfeldt-Jakob disease. These findings suggest that measurements of PrP aggregation with the MPA may be potentially more sensitive than protease-based methodologies.

The octarepeat region of the prion protein is conformationally altered in PrP(Sc).

BACKGROUND: Prion diseases are fatal neurodegenerative disorders characterized by misfolding and aggregation of the normal prion protein PrP(C). Little is known about the details of the structural rearrangement of physiological PrP(C) into a still-elusive disease-associated conformation termed PrP(Sc). Increasing evidence suggests that the amino-terminal octapeptide sequences of PrP (huPrP, residues 59-89), though not essential, play a role in modulating prion replication and disease presentation. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report that trypsin digestion of PrP(Sc) from variant and sporadic human CJD results in a disease-specific trypsin-resistant PrP(Sc) fragment including amino acids approximately 49-231, thus preserving important epitopes such as the octapeptide domain for biochemical examination. Our immunodetection analyses reveal that several epitopes buried in this region of PrP(Sc) are exposed in PrP(C). CONCLUSIONS/SIGNIFICANCE: We conclude that the octapeptide region undergoes a previously unrecognized conformational transition in the formation of PrP(Sc). This phenomenon may be relevant to the mechanism by which the amino terminus of PrP(C) participates in PrP(Sc) conversion, and may also be exploited for diagnostic purposes.