Alpha-Synuclein Aggregation Mechanism in the Presence of Nanomaterials.

Parkinson's disease (PD) is characterized by the toxic oligomeric and fibrillar phases formed by monomeric alpha-synuclein (α-syn). Certain nanoparticles have been demonstrated to promote protein aggregation, while other nanomaterials have been found to prevent the process. In the current work, we use nuclear magnetic resonance spectroscopy in conjunction with isothermal titration calorimetry to investigate the cause and mechanism of these opposing effects at the amino acid protein level. The interaction of α-syn with two types of nanomaterials was considered: citrate-capped gold nanoparticles (AuNPs) and graphene oxide (GO). In the presence of AuNPs, α-syn aggregation is accelerated, whereas in the presence of GO, aggregation is prevented. The study indicates that GO sequesters the NAC region of α-syn monomers through electrostatic and hydrophobic interactions, leading to a reduced elongation rate, and AuNPs leave the NAC region exposed while binding the N-terminus, leading to higher aggregation. The protein's inclination toward quicker aggregation is explained by the binding of the N-terminus of α-syn with the gold nanoparticles. Conversely, a comparatively stronger interaction with GO causes the nucleation and growth phases to be postponed and inhibits intermolecular interactions. Our finding offers novel experimental insights at the residue level regarding the aggregation of α-syn in the presence of various nanomaterials and creates new opportunities for the development of suitably functionalized nanomaterial-based therapeutic reagents against Parkinson's and other neurodegenerative diseases.

Expedited liver transplantation as first-line therapy for severe alcohol hepatitis: ELFSAH; deferring corticosteroids in the sickest subset of patients.

BACKGROUND & AIMS: Severe alcohol-associated hepatitis (SAH) represents a lethal subset of alcohol-associated liver disease. Although corticosteroids are recommended by guidelines, their efficacy and safety remain questionable and so liver transplantation (LT) has been increasingly utilized. The timing and indication of corticosteroid use, specifically in patients being considered for LT requires further clarification. METHODS: A retrospective analysis was conducted on 256 patients with SAH between 2018 and 2022 at a single US center. RESULTS: Twenty of these patients underwent LT. Of the 256 patients, 38% had what we termed "catastrophic" SAH, defined as a MELD-Na ≥35 and/or discriminant function (DF) ≥100, which carried a mortality of 90% without LT. Compared with 100 matched controls, patients undergoing LT exhibited a one-year survival rate of 100% versus 35% (p < .0005). LT provided an absolute risk reduction of 65%, with a number needed to treat of 1.5. Steroid utilization in the entire cohort was 19% with 60% developing severe complications. Patients administered steroids were younger with lower MELD and DF scores. Only 10% of those prescribed steroids derived a favorable response. Sustained alcohol use post-LT was 20%. CONCLUSIONS: We propose ELFSAH: Expedited LT as First Line Therapy for SAH; challenging the current paradigm with recommendations to defer steroids in patients with "catastrophic" SAH (defined as: MELD-Na ≥35 and/or DF ≥100). Patients should be seen urgently by hepatology, transplant surgery, psychiatry and social work. Patients without an absolute contraindication should be referred for LT as first-line therapy during their index admission.

A novel scoring system to predict survival in cirrhotic patients undergoing isolated lung transplantation: The PENS-CEPT score.

Cirrhosis is usually regarded as a contraindication to isolated lung transplantation (ILT). We sought to determine which patients with cirrhosis could safely undergo ILT. Based on a retrospective analysis of patients with cirrhosis who underwent ILT at our center between 2007 and 2020, we developed an exclusionary algorithm (PENS-CEPT: Pittsburgh ExclusioN Score in Cirrhotics Evaluated for Pulmonary Transplant) to help determine which patients can undergo ILT with minimal incurred risk from their underlying liver disease. The score utilizes a combination of readily available clinical data and the presence (or absence) of spontaneous portosystemic shunts on preoperative cross-sectional imaging. Sixteen patients underwent ILT with a diagnosis of cirrhosis: nine with cystic fibrosis. On univariate analysis, only our model was able to predict 1 year survival. Of the nine patients that would have been approved using our model, there was only one short term death. Of the seven patients that would have been rejected by the model, all but one died within the first year with six dying of complications from liver failure. We are proposing a simple score utilizing routine clinical parameters and pre-operative imaging to determine the safety of ILT in cirrhotic patients. Further studies are required to validate this scoring system with the goal of safely increasing the opportunity for cirrhotic patients who would otherwise be rejected for ILT.

IGF-dependent dynamic modulation of a protease cleavage site in the intrinsically disordered linker domain of human IGFBP2.

Functional regulation via conformational dynamics is well known in structured proteins but less well characterized in intrinsically disordered proteins and their complexes. Using NMR spectroscopy, we have identified a dynamic regulatory mechanism in the human insulin-like growth factor (IGF) system involving the central, intrinsically disordered linker domain of human IGF-binding protein-2 (hIGFBP2). The bioavailability of IGFs is regulated by the proteolysis of IGF-binding proteins. In the case of hIGFBP2, the linker domain (L-hIGFBP2) retains its intrinsic disorder upon binding IGF-1, but its dynamics are significantly altered, both in the IGF binding region and distantly located protease cleavage sites. The increase in flexibility of the linker domain upon IGF-1 binding may explain the IGF-dependent modulation of proteolysis of IGFBP2 in this domain. As IGF homeostasis is important for cell growth and function, and its dysregulation is a key contributor to several cancers, our findings open up new avenues for the design of IGFBP analogs inhibiting IGF-dependent tumors.

Characterization of hepatic steatosis using controlled attenuation parameter and MRI-derived proton density fat fraction in living donor liver transplantation.

BACKGROUND: The increasingly favorable outcomes of live donor liver transplant warrant development of screening techniques to expand current donor pool. Transient elastography (TE) with controlled attenuation parameter (CAP) is accessible and has promising diagnostic performance in non-obese individuals. Here, we demonstrate its utility in grading donor steatosis for risk assessment in living liver donors (LLD). STUDY DESIGN: In a prospective study of LLD and recipients, accuracy was determined using MRI-derived proton density fat fraction (PDFF) as reference. RESULTS: One hundred and one LLD underwent TE, 95 of whom had available PDFF. Median CAP and MRI-PDFF were 233 dB/m (206-270) and 2.9% (2.3-4.0), respectively. A CAP threshold of 270 dB/m captured all steatosis which was present in 13 (13%) LLD (AUROC .942, 100% sensitivity and 83% specificity). Performance further improved when excluding obese LLD and limiting analysis to M-probe (AUROC .971 and .974, respectively, with 87% specificity). There was no difference in CAP and MRI-PDFF between LLD and nondonors (P = .26 and .21, respectively). Early allograft dysfunction was observed in one recipient (CAP 316, PDFF 9.5%), zero underwent retransplant, and one died from sepsis. CONCLUSION: The specific role of CAP in living liver donation warrants further study, beginning with its use as screening tool across peripheral clinics.

The closing survival gap after liver transplantation for hepatocellular carcinoma in the United States.

BACKGROUND: Socio-economic inequalities among different racial/ethnic groups have increased in many high-income countries. It is unclear, however, whether increasing socio-economic inequalities are associated with increasing differences in survival in liver transplant (LT) recipients. METHODS: Adults undergoing first time LT for hepatocellular carcinoma (HCC) between 2002 and 2017 recorded in the Scientific Registry of Transplant Recipients (SRTR) were included and grouped into three cohorts. Patient survival and graft survival stratified by race/ethnicity were compared among the cohorts using unadjusted and adjusted analyses. RESULTS: White/Caucasians comprised the largest group (n=9,006, 64.9%), followed by Hispanic/Latinos (n=2,018, 14.5%), Black/African Americans (n=1,379, 9.9%), Asians (n=1,265, 9.1%) and other ethnic/racial groups (n=188, 1.3%). Compared to Cohort I (2002-2007), the 5-year survival of Cohort III (2012-2017) increased by 18% for Black/African Americans, by 13% for Whites/Caucasians, by 10% for Hispanic/Latinos, by 9% for patients of other racial/ethnic groups and by 8% for Asians (All P values<0.05). Despite Black/African Americans experienced the highest survival improvement, their overall outcomes remained significantly lower than other ethnic∕racial groups (adjusted HR for death=1.20; 95%CI 1.05-1.36; P=0.005; adjusted HR for graft loss=1.21; 95%CI 1.08-1.37; P=0.002). CONCLUSION: The survival gap between Black/African Americans and other ethnic/racial groups undergoing LT for HCC has significantly decreased over time. However, Black/African Americans continue to have the lowest survival among all racial/ethnic groups.

Idiopathic pneumatosis intestinalis secondary to lactulose use in patients with cirrhosis.

BACKGROUND AND AIM: Few case reports exist that link lactulose use with pneumatosis intestinalis in cirrhotics. This study investigates the relationship between lactulose use and idiopathic pneumatosis intestinalis in a cohort of cirrhotic patients. METHODS: This case series considers several notable cases of patients with idiopathic pneumatosis intestinalis and concurrent lactulose use. Idiopathic pneumatosis intestinalis was defined as pneumatosis intestinalis with no identifiable etiology. A cohort of 119 patients with cirrhosis and pneumatosis intestinalis were identified in a tertiary care setting, via chart review by a multidisciplinary team. Eleven of these patients were found to have idiopathic pneumatosis intestinalis. Nine of these patients were being treated with lactulose. RESULTS: Six out of 9 patients with idiopathic pneumatosis intestinalis that were being treated with lactulose saw resolution of pneumatosis intestinalis following discontinuation of treatment. CONCLUSIONS: The etiology of idiopathic pneumatosis intestinalis is likely multifactorial, but lactulose might play a preventable role in its formation.

Hernia Management in Cirrhosis: Risk Assessment, Operative Approach, and Perioperative Care.

BACKGROUND: The rising incidence of liver disease has complicated the management of common surgical pathologies. Hernias, in particular, are problematic given the shortage of high-quality data and differing expert opinions. We aim to provide a narrative review of hernia management in cirrhosis as a first step toward developing evidence-based recommendations for the care of these patients. MATERIALS AND METHODS: A literature review using separate search strings was conducted for PubMed and Cochrane Central Register of Controlled Trials databases. Review articles, conference abstracts, randomized clinical trials, and observational studies were included. Articles without a focus on patients with end-stage liver disease were excluded. Manuscripts were selected based on relevance to perioperative risk assessment, medical optimization, surgical decision-making, and considerations of hernia repair in patients with cirrhosis. RESULTS: The existing literature is varied with regard to focus and quality of data. Of the 4516 articles identified, 51 full-text articles were selected for review. In general, there is evidence to suggest that individuals with compensated cirrhosis may successfully undergo and benefit from hernia repair. Patients at high risk for decompensated cirrhosis may be best served by nonoperative management. CONCLUSIONS: Carefully selected patients with cirrhosis may proceed with herniorrhaphy. A multidisciplinary approach is essential to provide high-quality care and improve outcomes.

Incidence of Recurrent NASH-Related Allograft Cirrhosis.

BACKGROUND: Cirrhosis secondary to nonalcoholic steatohepatitis (NASH) is projected to become the leading indication for liver transplantation (LT) in the USA in the next decade. The long-term implications of post-LT NASH, specifically on the development of allograft cirrhosis, are not well known. METHODS: A retrospective cohort of patients at a single large center undergoing LT for NASH from 2000 to 2015 was identified using a prospectively collected database. A total of 226 patients undergoing LT for NASH were identified. Mean follow-up for the cohort was 7 years. Seventy-five percent of patients underwent at least one liver biopsy post-LT. RESULTS: Eighty-one patients (36%) developed recurrence of biopsy-proven NASH. Fifteen patients developed bridging fibrosis but only four patients (1.8%) progressed to recurrent NASH cirrhosis at a mean of 9 years post-LT. Body mass index at the time of LT was statistically higher in the NASH allograft cirrhosis group. Recurrent disease was less common and less severe in those transplanted with black donors. All four patients with recurrent NASH cirrhosis developed evidence of portal hypertension, but all remained alive at follow-up. CONCLUSION: Although recurrent NASH following LT is common, the development of allograft cirrhosis is rare. These findings are useful when counseling patients and important to consider during their post-LT care.

Linear IgA Bullous Dermatosis Preceding the Diagnosis of Primary Sclerosing Cholangitis and Ulcerative Colitis: A Case Report.

Linear IgA bullous dermatosis (LABD) is a rare autoimmune blistering disorder seen in the pediatric and adult populations that is often linked to a medication, infection, or underlying gastrointestinal, hepatobiliary, or autoimmune disease. In this study, we describe the case of a 23-year-old white man whose presentation and diagnosis of LABD ultimately led to the discovery of underlying primary sclerosing cholangitis (PSC) and ulcerative colitis (UC). His dermatitis resolved with topical steroids and dapsone, and he is undergoing systemic treatment for his UC and PSC. This exceptional case further validates the association between LABD with UC, strengthens that with PSC, and underscores the importance of alerting clinicians to consider conducting a systemic workup in addition to thorough medication history on making the diagnosis of LABD.

Extracorporeal cellular therapy (ELAD) in severe alcoholic hepatitis: A multinational, prospective, controlled, randomized trial.

Severe alcoholic hepatitis (sAH) is associated with a poor prognosis. There is no proven effective treatment for sAH, which is why early transplantation has been increasingly discussed. Hepatoblastoma-derived C3A cells express anti-inflammatory proteins and growth factors and were tested in an extracorporeal cellular therapy (ELAD) study to establish their effect on survival for subjects with sAH. Adults with sAH, bilirubin ≥8 mg/dL, Maddrey's discriminant function ≥ 32, and Model for End-Stage Liver Disease (MELD) score ≤ 35 were randomized to receive standard of care (SOC) only or 3-5 days of continuous ELAD treatment plus SOC. After a minimum follow-up of 91 days, overall survival (OS) was assessed by using a Kaplan-Meier survival analysis. A total of 203 subjects were enrolled (96 ELAD and 107 SOC) at 40 sites worldwide. Comparison of baseline characteristics showed no significant differences between groups and within subgroups. There was no significant difference in serious adverse events between the 2 groups. In an analysis of the intent-to-treat population, there was no difference in OS (51.0% versus 49.5%). The study failed its primary and secondary end point in a population with sAH and with a MELD ranging from 18 to 35 and no upper age limit. In the prespecified analysis of subjects with MELD < 28 (n = 120), ELAD was associated with a trend toward higher OS at 91 days (68.6% versus 53.6%; P = .08). Regression analysis identified high creatinine and international normalized ratio, but not bilirubin, as the MELD components predicting negative outcomes with ELAD. A new trial investigating a potential benefit of ELAD in younger subjects with sufficient renal function and less severe coagulopathy has been initiated. Liver Transplantation 24 380-393 2018 AASLD.

Prospective Study of the Impact of Liver Biopsy Core Size on Specimen Adequacy and Procedural Complications.

OBJECTIVE: An American Association for the Study of Liver Diseases (AASLD) consensus document stressed the importance of obtaining sufficient liver biopsy specimens to minimize sampling errors. Many centers continue to use smaller-diameter core systems to minimize perceived complication risks. The objective of this study was to assess the impact of core gauge (18- vs 16-gauge) on specimen adequacy and procedural complications. SUBJECTS AND METHODS: One hundred fifty patients referred for liver biopsy were randomized to undergo 16- or 18-gauge ultrasound (US)-guided core biopsy. Hemorrhage was qualitatively evaluated, and pain was assessed using a 10-point rating scale. The length and number of portal tracts per specimen were assessed. On the basis of the AASLD guidelines, specimen adequacy was defined as 11 or more portal tracts. Differences in pathology metrics and pain scoring were assessed using chi-square and linear regression models. RESULTS: No significant hemorrhage occurred in either group, and there was no difference in postbiopsy pain scores. The mean specimen length obtained with 16-gauge needles was less than that obtained with 18-gauge needles (1.7 vs 1.9 cm, p = 0.03). The mean number of portal tracts obtained with 16-gauge biopsies was greater than obtained with 18-gauge systems (14 vs 13, p = 0.03); 85% of 16-gauge biopsy specimens and 80% of 18-gauge biopsy specimens were adequate on the basis of the AASLD criteria, although this difference was not statistically significant. CONCLUSION: US-guided 18- and 16-gauge core biopsies are similarly safe. A large percentage of 18- or 16-gauge specimens are inadequate when AASLD quality control adequacy thresholds are applied, and specimen adequacy is not significantly affected by biopsy gauge.

Stratification of risk of death in severe acute alcoholic hepatitis using a panel of adipokines and cytokines.

BACKGROUND: Dysregulated adipose tissue metabolism has been implicated in the pathogenesis of alcoholic liver disease in murine models. We aimed to characterize serum markers of adipose tissue metabolism and inflammation in patients with severe acute alcoholic hepatitis (AAH) and determine their utility to predict survival in severe AAH. METHODS: A prospective, case-control study design was used. Seventy-six patients hospitalized with severe AAH and 25 ambulatory patients with alcoholic cirrhosis as controls were included. Serum samples were collected for biochemical analyses. Patients were followed for 180 days after enrollment to determine the survival. RESULTS: AAH patients exhibited higher serum glycerol and free fatty acid levels, suggesting enhanced adipose tissue triglyceride hydrolysis. Patients with AAH demonstrated a distinct serum lipidomic profile compared with alcoholic cirrhosis but not in systemic and adipose-specific insulin resistance. AAH patients had higher serum resistin and plasmin activation inhibitor-1 levels, while serum leptin was decreased. Serum levels of the prolipolytic cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL-8, and IL-15 were significantly higher in AAH patients. Only 53% of AAH patients survived 180 days after admission, while all cirrhotic patients were alive at the end of the study period. Among patients with severe AAH, white blood cell count, hemoglobin, resistin, IL-6 and TNF-α were associated with 180-day survival, and all 5 markers demonstrated accuracy by area under receiver-operator curve analysis. Serum IL-6 levels ≥38.66 pg/ml most precisely identified deaths in severe AAH. Patients with IL-6 ≥ 38.66 pg/ml had significantly decreased mean survival compared to those with lower levels. CONCLUSIONS: AAH patients demonstrate evidence of increased adipose tissue lipolysis and altered serum lipidomic profile compared with alcoholic cirrhosis patients. IL-6 may be a useful biomarker to risk stratify severe AAH patients at the highest risk of mortality.

Safety and technical success of percutaneous left main coronary artery stenting.

OBJECTIVE: Critical stenosis of left main coronary artery (LMCA) has always remained a challenge for interventional cardiologists. Conventionally Coronary Artery Bypass Grafting (CABG) is done for these patients but recently Percutaneous Coronary Intervention (PCI) is also being tried more frequently, but data of PCI is scarce in this regard. Our objective was to determine the safety and technical success rate of percutaneous left main coronary artery stenting. METHODS: This was 12 month follow up study conducted at Pakistan Institute of Medical Sciences (PIMS), Islamabad from 11(th) Jan 2012 to 11(th) Jan 2013. All symptomatic patients who underwent coronary angiogram at PIMS and were found to have either isolated LMCA disease or coexisting osteal Left Anterior Descending (LAD) artery disease were potentially eligible for the study. Patients who had previous surgical treatment for coronary artery disease and those with renal dysfunction requiring dialysis were excluded. Patients were counselled in detail regarding the pros and cons of PCI versus CABG.Those who opted for PCI were included in the study. All these patients were treated with percutaneous left main coronary artery stenting with or without osteal LAD stenting. RESULTS: Seventy two patients had LMCA disease during angiogram. Fifteen patients opted for CABG. Four patients did not meet the inclusion criteria, whereas 53 patients were finally enrolled. Mean age of patients were 55.45±10.275 years. Twenty nine patients were with acute coronary syndrome and 22 presented with unstable angina.PCI with stenting was technically successful in all patients. One patient died three months after PCI, there was no other mortality. CONCLUSION: Our study showed that Percutaneous Coronary Intervention (PCI) to LMS has good technical success rate; the safety of the procedure is also acceptable.

Porto-Sinusoidal Vascular Disease in Congenital Erythropoietic Porphyria Needing Liver Transplantation.

Porphyria caused by inherited disorders in heme biosynthesis can lead to accumulation of porphyrins in various organs. Liver involvement due to porphyria mostly results in cholestasis leading to liver cirrhosis or hepatocellular carcinoma. Congenital erythropoietic porphyria (CEP), a rare porphyria due to deficiency of uroporphyrinogen III synthase, mostly results in cutaneous manifestations. There are reports of liver involvement including varying degree of fibrosis in patients with CEP. We report a unique case of a patient with CEP who developed porto-sinusoidal vascular disease with complications of portal hypertension that necessitated liver transplantation.

Liver surface nodularity and ascites are associated with mortality risk in acute alcohol-associated hepatitis.

BACKGROUND: Acute alcohol-associated hepatitis (AH) is associated with high mortality. CT-derived liver surface nodularity (LSN) is a robust prognostic biomarker in other chronic liver diseases. The aim of this study was to determine relationships between LSN, disease severity, and mortality in AH. METHODS: Adults hospitalized with AH from January 2016 to March 2020 were included if an abdominal CT was performed between 8 weeks prior to 72 h after hospitalization. LSN was measured using quantitative methods (Liver Surface Nodularity Software version 0.88, Birmingham, AL, USA). Cox proportional hazards models, logistic regression and AUROC analysis were used to examine relationships between LSN and 180-day transplant-free survival. RESULTS: Of 386 patients hospitalized with AH during the study period, 230 had CT scans performed, and 205 met inclusion criteria. Mean transplant-free survival was 127 days (95% CI 118-137). Within each cohort, patients were grouped into low [LSN-LOW, N = 109 (53.2%)] and high [LSN-HIGH, N = 96 (46.8%)] LSN strata based on an optimal cutoff of 2.86 derived from unadjusted ROC curves. Patients with high LSN had features of portal hypertension, which included encephalopathy [53 (55.2%) vs. 43 (39.4%), p = 0.017], ascites on CT [81 (84.4%) vs. 69 (63.3%), p = 0.001] and portosystemic shunts [78 (81.2%) vs. 69 (63.3%), p = 0.003]. High LSN, ascites and MELD were independently associated with lower likelihood of 180-day transplant-free survival, and inclusion of a score assigning 1 point each for high LSN or ascites on CT (AHRADS score) to MELD enhanced diagnostic accuracy of AUROC for 180-day survival compared to MELD alone [AUROC 0.782 (95% CI 0.719-0.845) vs. 0.735 (0.667-0.802), p = 0.023]. CONCLUSIONS: CT-derived factors that include LSN and ascites are radiographic biomarkers associated with 180-day transplant-free survival in alcohol-associated hepatitis.

Unleashing the potential of fNIRS with machine learning: classification of fine anatomical movements to empower future brain-computer interface.

In this study, we explore the potential of using functional near-infrared spectroscopy (fNIRS) signals in conjunction with modern machine-learning techniques to classify specific anatomical movements to increase the number of control commands for a possible fNIRS-based brain-computer interface (BCI) applications. The study focuses on novel individual finger-tapping, a well-known task in fNIRS and fMRI studies, but limited to left/right or few fingers. Twenty-four right-handed participants performed the individual finger-tapping task. Data were recorded by using sixteen sources and detectors placed over the motor cortex according to the 10-10 international system. The event's average oxygenated Δ HbO and deoxygenated Δ HbR hemoglobin data were utilized as features to assess the performance of diverse machine learning (ML) models in a challenging multi-class classification setting. These methods include LDA, QDA, MNLR, XGBoost, and RF. A new DL-based model named "Hemo-Net" has been proposed which consists of multiple parallel convolution layers with different filters to extract the features. This paper aims to explore the efficacy of using fNRIS along with ML/DL methods in a multi-class classification task. Complex models like RF, XGBoost, and Hemo-Net produce relatively higher test set accuracy when compared to LDA, MNLR, and QDA. Hemo-Net has depicted a superior performance achieving the highest test set accuracy of 76%, however, in this work, we do not aim at improving the accuracies of models rather we are interested in exploring if fNIRS has the neural signatures to help modern ML/DL methods in multi-class classification which can lead to applications like brain-computer interfaces. Multi-class classification of fine anatomical movements, such as individual finger movements, is difficult to classify with fNIRS data. Traditional ML models like MNLR and LDA show inferior performance compared to the ensemble-based methods of RF and XGBoost. DL-based method Hemo-Net outperforms all methods evaluated in this study and demonstrates a promising future for fNIRS-based BCI applications.

Evaluation of 1H NMR metabolic profiling using biofluid mixture design.

A strategy for evaluating the performance of quantitative spectral analysis tools in conditions that better approximate background variation in a metabonomics experiment is presented. Three different urine samples were mixed in known proportions according to a {3, 3} simplex lattice experimental design and analyzed in triplicate by 1D (1)H NMR spectroscopy. Fifty-four urinary metabolites were subsequently quantified from the sample spectra using two methods common in metabolic profiling studies: (1) targeted spectral fitting and (2) targeted spectral integration. Multivariate analysis using partial least-squares (PLS) regression showed the latent structure of the spectral set recapitulated the experimental mixture design. The goodness-of-prediction statistic (Q(2)) of each metabolite variable in a PLS model was calculated as a metric for the reliability of measurement, across the sample compositional space. Several metabolites were observed to have low Q(2) values, largely as a consequence of their spectral resonances having low s/n or strong overlap with other sample components. This strategy has the potential to allow evaluation of spectral features obtained from metabolic profiling platforms in the context of the compositional background found in real biological sample sets, which may be subject to considerable variation. We suggest that it be incorporated into metabolic profiling studies to improve the estimation of matrix effects that confound accurate metabolite measurement. This novel method provides a rational basis for exploiting information from several samples in an efficient manner and avoids the use of multiple spike-in authentic standards, which may be difficult to obtain.

Pilot-scale anaerobic co-digestion of municipal wastewater sludge with restaurant grease trap waste.

The maximum feasible loading rate of grease trap waste (GTW) to the municipal wastewater sludge (MWS) was investigated using two 1300 L pilot-scale (1200 L active volume) digesters under mesophilic conditions at a 20 day solids retention time. During the co-digestion, the test reactor received a mixture of GTW and MWS while the control reactor received only MWS. The test digester loading was increased incrementally to a maximum of 280% of the control digester COD loading. The highest feasible GTW loading was determined to be 23% and 58% in terms of its total 1.58 kg VS/(m(3) d) and 3.99 kg COD/(m(3) d) loadings, respectively. This test digester COD loading represented 240% of the control digester COD loading. At this loading, test digester biogas production was 67% greater than that of the control. During the test digester quasi steady state loading period when VS from GTW represented 19% of its total VS loading, the test digester COD and VS removal rates were 2.5 and 1.5 fold those of the control digester, respectively. The test digester biogas production declined markedly when the percentage of VS from GTW in its feed was increased to 30% of its total VS loading. Causes of the reduced biogas production were investigated and attributed to inhibition due to long chain fatty acid accumulation.