Imprecision of high-sensitivity cardiac troponin assays at the female 99th-percentile

BACKGROUND

An analytical benchmark for high-sensitivity cardiac troponin (hs-cTn) assays is to achieve a coefficient of variation (CV) of ≤ 10.0 % at the 99th percentile upper reference limit (URL) used for the diagnosis of myocardial infarction. Few prospective multicenter studies have evaluated assay imprecision and none have determined precision at the female URL which is lower than the male URL for all cardiac troponin assays.

METHODS

Human serum and plasma matrix samples were constructed to yield hs-cTn concentrations near the female URLs for the Abbott, Beckman, Roche, and Siemens hs-cTn assays. These materials were sent (on dry ice) to 35 Canadian hospital laboratories (n = 64 instruments evaluated) participating in a larger clinical trial, with instructions for storage, handling, and monthly testing over one year. The mean concentration, standard deviation, and CV for each instrument type and an overall pooled CV for each manufacturer were calculated.

RESULTS

The CVs for all individual instruments and overall were ≤ 10.0 % for two manufacturers (Abbott CVpooled = 6.3 % and Beckman CVpooled = 7.0 %). One of four Siemens Atellica instruments yielded a CV > 10.0 % (CVpooled = 7.7 %), whereas 15 of 41 Roche instruments yielded CVs > 10.0 % at the female URL of 9 ng/L used worldwide (6 cobas e411, 1 cobas e601, 4 cobas e602, and 4 cobas e801) (CVpooled = 11.7 %). Four Roche instruments also yielded CVs > 10.0 % near the female URL of 14 ng/L used in the United States (CVpooled = 8.5 %).

CONCLUSIONS

The number of instruments achieving a CV ≤ 10.0 % at the female 99th-percentile URL varies by manufacturer and by instrument. Monitoring assay precision at the female URL is necessary for some assays to ensure optimal use of this threshold in clinical practice.

Guidance for use of neurofilament light chain as a cerebrospinal fluid and blood biomarker in multiple sclerosis management

Neurofilament light chain (NfL) is a long-awaited blood biomarker that can provide clinically useful information about prognosis and therapeutic efficacy in multiple sclerosis (MS). There is now substantial evidence for this biomarker to be used alongside magnetic resonance imaging (MRI) and clinical measures of disease progression as a decision-making tool for the management of patients with MS. Serum NfL (sNfL) has certain advantages over traditional measures of MS disease progression such as MRI because it is relatively noninvasive, inexpensive, and can be repeated frequently to monitor activity and treatment efficacy. sNfL levels can be monitored regularly in patients with MS to determine change from baseline and predict subclinical disease activity, relapse risk, and the development of gadolinium-enhancing (Gd+) lesions. sNfL does not replace MRI, which provides information related to spatial localisation and lesion stage. Laboratory platforms are starting to be made available for clinical application of sNfL in several countries. Further work is needed to resolve issues around comparisons across testing platforms (absolute values) and normalisation (reference ranges) in order to guide interpretation of the results.

Cross-sectional Characterization of SARS-CoV-2 Antibody Levels and Decay Rates Following Infection of Unvaccinated Elderly Individuals

Background

SARS-CoV-2 infections have disproportionally burdened elderly populations with excessive mortality. While several contributing factors exists, questions remain about the quality and duration of humoral antibody-mediated responses resulting from infections in unvaccinated elderly individuals.

Methods

Residual serum/plasma samples were collected from individuals undergoing routine SARS-CoV-2 polymerase chain reaction testing in a community laboratory in Canada. The samples were collected in 2020, before vaccines became available. IgG, IgA, and IgM antibodies against SARS-CoV-2 nucleocapsid, trimeric spike, and its receptor-binding domain were quantified via a high-throughput chemiluminescent enzyme-linked immunosorbent assay. Neutralization efficiency was also quantified through a surrogate high-throughput protein-based neutralization assay.

Results

This study analyzed SARS-CoV-2 antibody levels in a large cross-sectional cohort (N = 739), enriched for elderly individuals (median age, 82 years; 75% >65 years old), where 72% of samples tested positive for SARS-CoV-2 by polymerase chain reaction. The age group ≥90 years had higher levels of antibodies than that <65 years. Neutralization efficiency showed an age-dependent trend, where older persons had higher levels of neutralizing antibodies. Antibodies targeting the nucleocapsid had the fastest decline. IgG antibodies targeting the receptor-binding domain remained stable over time, potentially explaining the lack of neutralization decay observed in this cohort.

Conclusions

Despite older individuals having the highest levels of antibodies postinfection, they are the cohort in which antibody decay was the fastest. Until a better understanding of correlates of protection is acquired, along with the protective role of nonneutralizing antibodies, booster vaccinations remain important in this demographic.

High or increasing serum NfL is predictive of impending multiple sclerosis relapses

BACKGROUND

One-off serum levels of neurofilament light chain (sNfL) is an established predictor of emerging disease activity in multiple sclerosis (MS). However, the importance of longitudinal increases in sNfL is yet to be enumerated, an important consideration as this test is translated for serial monitoring. Glial Fibrillary Acidic Protein (sGFAP) is another biomarker of predictive interest. Our objective was to assess the association between longitudinal changes sNfL and prediction of future relapses, as well as a possible role for sGFAP.

METHODS

Participants with active MS were prospectively monitored for one year as part of a clinical trial testing mesenchymal stem cells. Visits every three months or less included clinical assessments, MRI scans and serum draws. sNfL and sGFAP concentrations were quantified with Single Molecule Array immunoassay. We used Kaplan-Meier estimates and Anderson-Gill Cox regression models with and without adjustment for age, sex, disease subtype, disease duration and expanded disability status score (EDSS) to estimate the rate of relapse predicted by baseline and longitudinal changes in biomarker.

RESULTS

58 Canadian and Italian participants with MS were enrolled in this study. Higher baseline sNfL was future relapse (Log-rank p = 0.0068), MRI lesions (p=0.0096), composite-relapse associated worsening (p=0.01) and progression independent of relapse activity (p=0.0096). Conversely, baseline sGFAP was only weakly associated with MRI lesions (0.044). Cross-sectional analyses of baseline sNfL revealed that a two-fold difference in baseline sNfL, e.g. from 10 to 20 pg/mL, was associated with a 2.3-fold increased risk of relapse during follow-up (95% confidence interval 1.65-3.17). Longitudinally, a two-fold increase in sNfL level from the first measurement was associated with an additional 1.46 times increased risk of relapse (1.07-2.00). The impact of longitudinal increases in sNfL on the risk of relapse were most pronounced for patients with lower baseline values of sNfL (<10 pg/mL: HR = 1.54, 1.06-2.24). These associations remained significant after adjustment for potential confounders.

CONCLUSION

We enumerate the risk of relapse associated with dynamic changes in sNfL. Both baseline and longitudinal change in sNfL may help identify patients who would benefit from early treatment optimisation.

TRIAL REGISTRATIONS

Canada:NCT02239393, Italy:NCT01854957&EudraCT, 2011-001295-19 CLASSIFICATION OF EVIDENCE: This study provides class 1 evidence that high baseline and longitudinal increases in sNfL are predictive of impending relapses in patients with active MS.

Relative Ratios of Human Seasonal Coronavirus Antibodies Predict the Efficiency of Cross-Neutralization of SARS-CoV-2 Spike Binding to ACE2

BACKGROUND

Antibodies raised against human seasonal coronaviruses (sCoVs), which are responsible for the common cold, are known to cross-react with SARS-CoV-2 antigens. This prompts questions about their protective role against SARS-CoV-2 infections and COVID-19 severity. However, the relationship between sCoVs exposure and SARS-CoV-2 correlates of protection are not clearly identified.

METHODS

We performed a cross-sectional analysis of cross-reactivity and cross-neutralization to SARS-CoV-2 antigens (S-RBD, S-trimer, N) using pre-pandemic sera from four different groups: pediatrics and adolescents, individuals 21 to 70 years of age, older than 70 years of age, and individuals living with HCV or HIV. Data was then further analysed using machine learning to identify predictive patterns of neutralization based on sCoVs serology.

FINDINGS

Antibody cross-reactivity to SARS-CoV-2 antigens varied between 1.6% and 15.3% depending on the cohort and the isotype-antigen pair analyzed. We also show a range of neutralizing activity (0-45%) with median inhibition ranging from 17.6 % to 23.3 % in serum that interferes with SARS-CoV-2 spike attachment to ACE2 independently of age group. While the abundance of sCoV antibodies did not directly correlate with neutralization, we show that neutralizing activity is rather dependent on relative ratios of IgGs in sera directed to all four sCoV spike proteins. More specifically, we identified antibodies to NL63 and OC43 as being the most important predictors of neutralization.

INTERPRETATION

Our data support the concept that exposure to sCoVs triggers antibody responses that influence the efficiency of SARS-CoV-2 spike binding to ACE2, which may potentially impact COVID-19 disease severity through other latent variables.

FUNDING

This study was supported by a grant by the CIHR (VR2 -172722) and by a grant supplement by the CITF, and by a NRC Collaborative R&D Initiative Grant (PR031-1).

An international multi-center serum protein electrophoresis accuracy and M-protein isotyping study. Part I: factors impacting limit of quantitation of serum protein electrophoresis

Background Serum protein electrophoresis (SPEP) is used to quantify the serum monoclonal component or M-protein, for diagnosis and monitoring of monoclonal gammopathies. Significant imprecision and inaccuracy pose challenges in reporting small M-proteins. Using therapeutic monoclonal antibody-spiked sera and a pooled beta-migrating M-protein, we aimed to assess SPEP limitations and variability across 16 laboratories in three continents. Methods Sera with normal, hypo- or hypergammaglobulinemia were spiked with daratumumab, Dara (cathodal migrating), or elotuzumab, Elo (central-gamma migrating), with concentrations from 0.125 to 10 g/L (n = 62) along with a beta-migrating sample (n = 9). Provided with total protein (reverse biuret, Siemens), laboratories blindly analyzed samples according to their SPEP and immunofixation (IFE) or immunosubtraction (ISUB) standard operating procedures. Sixteen laboratories reported the perpendicular drop (PD) method of gating the M-protein, while 10 used tangent skimming (TS). A mean percent recovery range of 80%-120% was set as acceptable. The inter-laboratory %CV was calculated. Results Gamma globulin background, migration pattern and concentration all affect the precision and accuracy of quantifying M-proteins by SPEP. As the background increases, imprecision increases and accuracy decreases leading to overestimation of M-protein quantitation especially evident in hypergamma samples, and more prominent with PD. Cathodal migrating M-proteins were associated with less imprecision and higher accuracy compared to central-gamma migrating M-proteins, which is attributed to the increased gamma background contribution in M-proteins migrating in the middle of the gamma fraction. There is greater imprecision and loss of accuracy at lower M-protein concentrations. Conclusions This study suggests that quantifying exceedingly low concentrations of M-proteins, although possible, may not yield adequate accuracy and precision between laboratories.

An international multi-center serum protein electrophoresis accuracy and M-protein isotyping study. Part II: limit of detection and follow-up of patients with small M-proteins

Background Electrophoretic methods to detect, characterize and quantify M-proteins play an important role in the management of patients with monoclonal gammopathies (MGs). Significant uncertainty in the quantification and limit of detection (LOD) is documented when M-proteins are <10 g/L. Using spiked sera, we aimed to assess the variability in intact M-protein quantification and LOD across 16 laboratories. Methods Sera with normal, hypo- or hyper-gammaglobulinemia were spiked with daratumumab or elotuzumab, with concentrations from 0.125 to 10 g/L (n = 62) along with a beta-migrating sample (n = 9). Laboratories blindly analyzed samples according to their serum protein electrophoresis (SPEP)/isotyping standard operating procedures. LOD and intra-laboratory percent coefficient of variation (%CV) were calculated and further specified with regard to the method (gel/capillary electrophoresis [CZE]), gating strategy (perpendicular drop [PD]/tangent skimming [TS]), isotyping (immunofixation/immunosubtraction [ISUB]) and manufacturer (Helena/Sebia). Results All M-proteins ≥1 g/L were detected by SPEP. With isotyping the LOD was moderately more sensitive than with SPEP. The intensity of polyclonal background had the biggest negative impact on LOD. Independent of the method used, the intra-laboratory imprecision of M-protein quantification was small (mean CV = 5.0%). Low M-protein concentration and high polyclonal background had the strongest negative impact on intra-laboratory precision. All laboratories were able to follow trend of M-protein concentrations down to 1 g/L. Conclusions In this study, we describe a large variation in the reported LOD for both SPEP and isotyping; overall LOD is most affected by the polyclonal immunoglobulin background. Satisfactory intra-laboratory precision was demonstrated. This indicates that the quantification of small M-proteins to monitor patients over time is appropriate, when subsequent testing is performed within the same laboratory.

Survey of renin and aldosterone testing practices by Ontario laboratories - Providing insight into best practices

Objectives

Testing for renin and aldosterone in clinical laboratories is complicated by pre-analytical considerations such as the posture for blood collection and susceptibility to cryoactivation of renin. From an analytical perspective, there are both renin activity and renin mass or concentration assays available. There can also be variability in result reporting practices and the aldosterone-renin ratio (ARR) cut-off applied to screen for primary aldosteronism (PA). The Institute for Quality Management in Healthcare (IQMH) Centre for Proficiency Testing surveyed laboratories on their handling of renin and aldosterone testing to better understand current practices.

Design and methods

An online survey was prepared and sent to 134 Canadian laboratories enrolled in endocrinology proficiency testing with IQMH.

Results

One hundred twenty Ontario laboratories submitted responses. While only six (5%) laboratories perform testing for both renin and aldosterone, 108 (90%) collect and process specimens to be tested by reference laboratories. The survey revealed considerable variation in practices including the recommended state of patients prior to sample collection (for example, regarding medications or salt intake), the patient posture specifications for sample collection, the precautions taken against cryoactivation of renin, the choice of renin activity or mass assay, and the ARR cut-off used. The available literature on these factors was then reviewed.

Conclusions

Although there is no standardized procedure for specimen collection, analysis, or result reporting for renin or aldosterone testing, we have attempted to summarize the available literature to develop evidence-based recommendations. Where laboratory practice differs from peers and/or recommended protocols, laboratories should review their practices.

Serum Neurofilament Light Chain Measurement in MS: Hurdles to Clinical Translation

Measurement of serum neurofilament light chain concentration (sNfL) promises to become a convenient, cost effective and meaningful adjunct for multiple sclerosis (MS) prognostication as well as monitoring disease activity in response to treatment. Despite the remarkable progress and an ever-increasing literature supporting the potential role of sNfL in MS over the last 5 years, a number of hurdles remain before this test can be integrated into routine clinical practice. In this review we highlight these hurdles, broadly classified by concerns relating to clinical validity and analytical validity. After setting out an aspirational roadmap as to how many of these issues can be overcome, we conclude by sharing our vision of the current and future role of sNfL assays in MS clinical practice.

Effective interventions to improve the quality of critically high point-of-care glucose meter results

Objectives

Point-of-care testing (POCT) is testing performed outside the traditional laboratory, often at the patient bedside. In hospital settings, blood glucose is the most common POCT. Staff performing POCT are not usually laboratory trained; they are clinical staff with a primary focus on treating patients. Clinical staff find POCT quality assurance (QA) practices burdensome and are often non-compliant. In hospitals within EORLA (Eastern Ontario Regional Laboratories Association), all critically high POCT glucose results must be repeated prior to acting, according to policy. Compliance with this policy is audited regularly.

Design

and methods: All POCT glucose tests performed in participating sites between January and June 2018 and June and December 2019 were audited for compliance with the critical repeat policy. The discordant repeat rate was also determined for each audit period. Between January and May 2019, there were interventions aimed at improving compliance with the repeat policy.

Results

Compliance with the critical repeat policy increased from 30 to 57% in 2019 compared to 2018, following nursing education and implementation of notifications on the glucose meters themselves. The rate of discordant repeat results (>20% different from initial) also improved at most sites in 2019 compared to 2018. Nurses cited insufficient cleaning of patient hands prior to initial testing as the primary reason for discordant repeats.

Conclusions

Operator compliance with POCT QA policies is an ongoing challenge requiring continual audit, feedback and education. A strong POCT multi-disciplinary committee with supports from senior and clinical leadership in an organization are key to improving compliance.

•

Compliance with the policy requiring repeat of all critically high POCT glucose results is audited as a quality indicator.

•

Audits demonstrated a high rate of non-compliance with the critical repeat policy by clinical staff performing POCT.

•

Approximately 25% of critically high glucose results repeated were discordant (>20% different from the initial result)

•

Implementation of meter notifications and nursing education led to significant improvements in compliance at most sites.

Does N-Terminal Pro-B-Type Natriuretic Peptide Improve the Risk Stratification of Emergency Department Patients With Syncope?

BACKGROUND

Studies have reported that natriuretic peptides provide prognostic information for emergency department (ED) syncope.

OBJECTIVE

To evaluate whether adding N-terminal pro-B-type natriuretic peptide (NT-proBNP) to the Canadian Syncope Risk Score (CSRS) improves prediction of 30-day serious adverse events (SAEs).

DESIGN

Prospective cohort study.

SETTING

6 EDs in 2 Canadian provinces.

PARTICIPANTS

1452 adult ED patients with syncope.

INTERVENTION

Serum NT-proBNP was measured locally at 1 site and batch processed at a central laboratory from other sites. The concentrations were not available to treating physicians or for adjudication of outcomes.

MEASUREMENTS

An adjudicated composite outcome of 30-day SAEs, including death and cardiac (arrhythmic and nonarrhythmic) and noncardiac events.

RESULTS

Of 1452 patients enrolled, 152 (10.5% [95% CI, 9.0% to 12.1%]) had 30-day SAEs, 57 (3.9%) of which were identified after the index ED disposition. Serum NT-proBNP concentrations were significantly higher among patients with SAEs than those without them (median, 626.5 ng/L vs. 81 ng/L; P < 0.001). Adding NT-proBNP values to the CSRS did not significantly improve prognostication (c-statistic, 0.89 and 0.90; P = 0.12 for difference), regardless of SAE subgroup or whether the SAE was identified after the index ED visit. The net reclassification index shows that NT-proBNP would have correctly reclassified 3% of patients with SAEs at the expense of incorrectly reclassifying 2% of patients without SAEs.

LIMITATIONS

Our study was powered to detect a 3% difference in the area under the curve. The heterogeneity of outcomes and robust baseline discrimination by the CSRS will make improvements challenging.

CONCLUSION

Although serum NT-proBNP concentrations were generally much higher among ED patients with syncope who had a 30-day SAE, this blood test added little new information to the CSRS. Routine use of NT-proBNP for ED syncope prognostication is not recommended.

PRIMARY FUNDING SOURCE

Physicians' Services Incorporated Foundation, Canadian Institutes of Health Research, and The Ottawa Hospital Academic Medical Organization.

Neurotoxicity after hematopoietic stem cell transplant in multiple sclerosis

OBJECTIVE

Accelerated brain volume loss has been noted following immunoablative autologous hematopoietic stem cell transplantation (IAHSCT) for multiple sclerosis. As with other MS treatments, this is often interpreted as 'pseudoatrophy', related to reduced inflammation. Treatment-related neurotoxicity may be contributory. We sought objective evidence of post-IAHSCT toxicity by quantifying levels of Neurofilament Light Chain (sNfL) and Glial Fibrillary Acidic Protein (sGFAP) before and after treatment as markers of neuroaxonal and glial cell damage.

METHODS

Sera were collected from 22 MS patients pre- and post-IAHSCT at 3, 6, 9, and 12 months along with 28 noninflammatory controls. sNfL and sGFAP quantification was performed using the SiMoA single-molecule assay.

RESULTS

Pre-IAHSCT levels of sNfL and sGFAP were elevated in MS patients compared with controls (geometric mean sNfL 21.8 vs. 6.4 pg/mL, sGFAP 107.4 vs. 50.7 pg/mL, P = 0.0001 for both). Three months after IAHSCT, levels of sNfL and sGFAP increased from baseline by 32.1% and 74.8%, respectively (P = 0.0029 and 0.0004). sNfL increases correlated with total busulfan dose (P = 0.034), EDSS score worsening at 6 months (P = 0.041), and MRI grey matter volume loss at 6 months (P = 0.0023). Subsequent NfL levels reduced to less than baseline (12-month geometric mean 11.3 pg/mL P = 0.0001) but were still higher than controls (P = 0.0001). sGFAP levels reduced more slowly but at 12 months were approaching baseline levels (130.7 pg/mL).

INTERPRETATION

There is direct evidence of transient CNS toxicity immediately after IAHSCT which may be chemotherapy mediated and contributes to transient increases in MRI atrophy.

Comparisons between umbilical cord biomarkers for newborn hypoxic-ischemic encephalopathy

Background: Cord blood umbilical artery (Ua) pH, base deficit (BD), and pH eucapnic Blickstein/Green-50 may mislead clinicians to identify newborns at risk for hypoxic-ischemic encephalopathy. Neonatal eucapnic pH (pH euc-n Racinet-54) may be a comprehensive alternative. The goal of the study is to compare the predictive performance of these four biomarkers for the combined primary outcome of hypoxic-ischemic encephalopathy/death.Methods: This retrospective cohort study includes newborns ≥35 weeks gestational age. Receiver operating characteristics curves analysis was performed for Ua cord pH, BD, pH euc-n Racinet-54, and pH eucapnic Blickstein/Green-50 for the global cohort and for two subgroups of newborns with Ua cord pH ≤ 7.15. Cutoff values were derived for all four markers.Results: From the original cohort of 61,037 newborns born between 1 January 2007 and 31 December 2016, we excluded cases with major congenital malformations and missing/incomplete data. The global cohort includes 51,286 newborns and 60 newborns afflicted with hypoxic-ischemic encephalopathy (HIE)/death. The area under the curves (AUC) derived from the global cohort were comparable between Ua cord pH (0.95; 95%CI = 0.94-0.95), BD (0.93; 95%CI = 0.93-0.93), pH euc-n Racinet-54 (0.93; 95% CI = 0.93-0.93), and lower for pH Blickstein/Green-50 (0.78; 95% CI = 0.77-0.78) (p < .05). Within newborn with severe acidemia (pH ≤ 7.00) and moderate acidemia (7.00 ≤ pH ≤ 7.15), pH euc-n Racinet-54 had the largest AUC and best positive likelihood ratios especially for sensitivity ≥ 0.80 to minimize false negative cases.Conclusion: In this large retrospective study, predictive performance for Ua cord pH, BD, and pH euc-n Racinet-54 are comparable when applied to the global group. For newborns with Ua cord pH ≤ 7.00 and Ua cord 7.00 ≤ pH ≤ 7.15, pH euc-n Racinet-54 appears better to identify those with HIE/death, especially when the target is sensitivity > 80%. Prospective studies will confirm if pH euc-n Racinet-54 is a better alternative to Ua cord pH and BD to evaluate newborn acid-base physiology.

Laboratory assessment of multiple myeloma

Laboratory testing plays an essential role in the diagnosis and management of patients with multiple myeloma. A variety of chemistry and molecular assays are routinely used to monitor patient progress, response to treatment and relapse. Here, we have reviewed current literature and core guidelines on the details of laboratory testing in myeloma-related investigations. This includes the use and value of protein electrophoresis, serum free light chain and cytogenetic testing. Furthermore, we discuss other traditional chemistry assays essential to myeloma investigation, and potential interferences that may arise due to the disease nature of myeloma, that is, the presence of a monoclonal immunoglobulin. Finally, we discuss the importance of communication in protein electrophoresis results, where laboratorians are required to relate clinically relevant myeloma-relevant information to the ordering physician on the background of a complex pattern of serum or urine proteins. Laboratory testing in myeloma-related investigation relies on several traditional chemistry assays. However, we anticipate new tests and technologies to become available in the future with improved analytical sensitivity, as well as improved clinical sensitivity in identifying patients who are at high risk of progression to multiple myeloma.

Ethnic dependent differences in diagnostic accuracy of glycated hemoglobin (HbA1c) in Canadian adults

AIM

Previous studies have shown varying sensitivity and specificity of hemoglobin A1c (HbA1c) to identify diabetes and prediabetes, compared to 2-h oral glucose tolerance testing (OGTT) and fasting plasma glucose (FPG), in different ethnic groups. Within the Canadian population, the ability of HbA1c to identify prediabetes and diabetes in First Nations, Métis and Inuit, East and South Asian ethnic groups has yet to be determined.

METHODS

We collected demographic, lifestyle information, biochemical results of glycemic status (FPG, OGTT, and HbA1c) from an ethnically diverse Canadian population sample, which included a purposeful sampling of First Nations, Métis, Inuit, South Asian and East Asian participants.

RESULTS

Sensitivity and specificity using Canadian Diabetes Association (CDA) recommended cut-points varied between ethnic groups, with greater variability for identification of prediabetes than diabetes. Dysglycemia (prediabetes and diabetes) was identified with a sensitivity and specificity ranging from 47.1% to 87.5%, respectively in Caucasians to 24.1% and 88.8% in Inuit. Optimal HbA1c ethnic-specific cut-points for dysglycemia and diabetes were determined by receiver operating characteristic (ROC) curve analysis.

CONCLUSIONS

Our sample showed broad differences in the ability of HbA1c to identify dysglycemia or diabetes in different ethnic groups. Optimal cut-points for dysglycemia or diabetes in all ethnic groups were substantially lower than CDA recommendations. Utilization of HbA1c as the sole biochemical diagnostic marker may produce varying degrees of false negative results depending on the ethnicity of screened individuals. Further research is necessary to identify and validate optimal ethnic specific cut-points used for diabetic screening in the Canadian population.

The Risk of Acute Rejection Following Kidney Transplant by 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D Status: A Prospective Cohort Study

Background:

Prediction of acute kidney transplant rejection remains imperfect despite several known risk factors. There is an increasing appreciation of the potential importance of the vitamin D pathway in immunological disease and transplantation.

Objective:

The purpose of this study was to determine the association of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D with acute rejection.

Design:

This was a prospective cohort study.

Setting:

Three academic adult kidney transplant programs in Ontario, Canada, were chosen.

Patients:

All consecutive adult patients at the 3 institutions who received a solitary kidney transplant, were able to provide written informed consent, and planned to be followed at the same center post-operatively were included.

Measurements:

Serum concentration of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were measured at baseline, 3, and 6 months post-transplantation. Acute rejection was classified using Banff criteria.

Methods:

The co-primary outcome was the association between 25-hydroxyvitamin D or 1,25-dihydroxyvitamin D and time to first occurrence of biopsy-proven acute rejection (BPAR) within the first year after kidney transplantation. Cox proportional hazards models were fitted taking into account the time-varying nature of serum concentrations of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D.

Results:

From 556 screened patients, data on 327 kidney transplant recipients are included. First BPAR occurred in 54 (16.5%) patients. In adjusted Cox proportional hazards models, the serum concentration of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D was not associated with acute renal transplant rejection (hazard ratio 1.00; 95% [confidence interval] CI, 0.87-1.14, per 10 nmol/L increase, and hazard ratio 0.97; 95% CI, 0.84-1.12, per 10 pmol/L increase, respectively).

Limitations:

Given the observational design, we cannot rule out the possibility of residual confounding that limited our ability to detect a clinically significant effect of vitamin D metabolites on acute rejection.

Conclusions:

A low serum concentration of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D is not associated with an increased risk of acute kidney transplant rejection following kidney transplantation.

Origin of surface canting within Fe3O4 nanoparticles

The nature of near-surface spin canting within Fe3O4 nanoparticles is highly debated. Here we develop a neutron scattering asymmetry analysis which quantifies the canting angle to between 23° and 42° at 1.2 T. Simultaneously, an energy-balance model is presented which reproduces the experimentally observed evolution of shell thickness and canting angle between 10 and 300 K. The model is based on the concept of Td site reorientation and indicates that surface canting involves competition between magnetocrystalline, dipolar, exchange, and Zeeman energies.

Prediction of clinical outcomes using B-type natriuretic peptides in the general population: a systematic review

The use of B-type natriuretic peptides to predict outcomes in general populations has been investigated in a number of primary studies. A previous systematic review considering natriuretic peptides in cardiovascular disease included a subgroup of general population studies, which suggested an association with a number of clinical outcomes. We electronically searched Medline, Embase, AMED, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and CINAHL for English-language articles published between 1989 and mid-2012. We utilized trained reviewers and standardized forms to screen articles for inclusion and extract data from included articles. All included studies (n = 7) were summarized in narrative and tabular form. A general population was defined as one that was randomly selected from a community setting where no specific inclusion or exclusion criteria were specified. The seven included studies all used FDA approved assays for NT-proBNP. The range of clinical outcomes and heterogeneity did not allow for meta-analysis. The hazard ratios for predicting outcomes in the included studies ranged from 1.0 to 4.1 (all p values <0.05). The discrimination statistics reported in four studies all demonstrated statistically significant improvements in predicting outcomes. NT-proBNP is associated with heart failure, all-cause and cardiovascular mortality, and other combined cardiovascular events in a general unselected population. The discrimination statistics suggest modest improvements in risk stratification. No prospective studies exist to demonstrate the clinical utility of using B-type natriuretic peptides to predict clinical outcomes in a general population.

Performance of BNP and NT-proBNP for diagnosis of heart failure in primary care patients: a systematic review

National and international guidelines have been published recommending the use of natriuretic peptides as an aid to the diagnosis of heart failure (HF) in acute settings; however, few specific recommendations exist for governing the use of these peptides in primary care populations. To summarize the available data relevant to the diagnosis of HF in primary care patient population, we systematically reviewed the literature to identify original articles that investigated the diagnostic accuracy of B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) in primary care settings. The search yielded 25,864 articles in total: 12 investigating BNP and 20 investigating NT-proBNP were relevant to our objective and included in the review. QUADAS-2 and GRADE were used to assess the quality of the included articles. Diagnostic data were pooled based on three cutpoints: lowest and optimal, as chosen by study authors, and manufacturers' suggested. The effect of various determinants (e.g., age, gender, BMI, and renal function) on diagnostic performance was also investigated. Pooled sensitivity and specificity of BNP and NT-proBNP using the lowest [0.85 (sensitivity) and 0.54 (specificity)], optimal (0.80 and 0.61), and manufacturers' (0.74 and 0.67) cutpoints showed good performance for diagnosing HF. Similar performance was seen for NT-proBNP: lowest (0.90 and 0.50), optimal (0.86 and 0.58), and manufacturers' (0.82 and 0.58) cutpoints. Overall, we rated the strength of evidence as high because further studies will be unlikely to change the estimates diagnostic performance.

Preliminary study of faecal cortisol and corticosterone as an index of acute cortisol secretion in the koala (Phascolarctos cinereus)

BACKGROUND

Stress can play a role in disease incidence in all species via immunosuppression and has been implicated as a contributing factor in significant infectious diseases of koalas. Faecal cortisol measurement may represent a non-invasive methodology for quantifying stress in koalas.

METHODS

We used an ACTH (adrenocorticotropic hormone) stimulation test (10 IU) to induce sustained secretion of cortisol, which was measured in serum samples from four koalas and subsequently it was attempted to locate a corresponding elevation in either cortisol or corticosterone measurements within the faeces.

RESULTS

Although ACTH administration resulted in an elevation of serum cortisol for at least 4 h post injection, it was not possible to identify a corresponding peak in corticosterone or cortisol concentrations in extracts from the faeces, consistent with the known gut transit time of the koala.

CONCLUSION

Faecal cortisol and corticosterone metabolites may not be reliable indices of acute changes in cortisol secretion in the koala and studies that attempt to use faecal cortisol as an index of stress will need to be interpreted with caution.

Functional magnetic nanoparticle assemblies: formation, collective behavior, and future directions

This Perspective describes recent progress in the development of functional magnetic nanoparticle assemblies. After describing the formation of two- and three-dimensional particle arrays in terms of the size-dependent driving forces, we focus on magnetic nanoparticle arrays. We discuss how the self-organized structure can modify the magnetic behavior, relative to that of isolated particles. We highlight an important development, described in this issue of ACS Nano by Kostiainen and co-workers, who have demonstrated not only the novel aqueous self-assembly of magnetic particles but also controlled and reversible disassembly. Finally, we explore two inter-related future directions for self-assembly of magnetic nanoparticles: the formation of more complex, hierarchical structures and the integration of self-assembly with fabrication techniques for electronic devices.

Pre-analytic and analytic sources of variations in thiopurine methyltransferase activity measurement in patients prescribed thiopurine-based drugs: A systematic review

OBJECTIVES

Low thiopurine S-methyltransferase (TPMT) enzyme activity is associated with increased thiopurine drug toxicity, particularly myelotoxicity. Pre-analytic and analytic variables for TPMT genotype and phenotype (enzyme activity) testing were reviewed.

DESIGN AND METHODS

A systematic literature review was performed, and diagnostic laboratories were surveyed.

RESULTS

Thirty-five studies reported relevant data for pre-analytic variables (patient age, gender, race, hematocrit, co-morbidity, co-administered drugs and specimen stability) and thirty-three for analytic variables (accuracy, reproducibility). TPMT is stable in blood when stored for up to 7 days at room temperature, and 3 months at -30°C. Pre-analytic patient variables do not affect TPMT activity. Fifteen drugs studied to date exerted no clinically significant effects in vivo. Enzymatic assay is the preferred technique. Radiochemical and HPLC techniques had intra- and inter-assay coefficients of variation (CVs) below 10%.

CONCLUSION

TPMT is a stable enzyme, and its assay is not affected by age, gender, race or co-morbidity.

Assessment of thiopurine S-methyltransferase activity in patients prescribed thiopurines: a systematic review

BACKGROUND

The evidence for testing thiopurine S-methyltransferase (TPMT) enzymatic activity or genotype before starting therapy with thiopurine-based drugs is unclear.

PURPOSE

To examine the sensitivity and specificity of TPMT genotyping for TPMT enzymatic activity, reducing harm from thiopurine by pretesting, and the association of thiopurine toxicity with TPMT status in adults and children with chronic inflammatory diseases.

DATA SOURCES

MEDLINE, EMBASE, the Cochrane Library, and Ovid HealthSTAR (from inception to December 2010) and BIOSIS and Genetics Abstracts (to May 2009).

STUDY SELECTION

Two reviewers screened records and identified relevant studies in English.

DATA EXTRACTION

Data on patient characteristics, outcomes, and risk for bias were extracted by one reviewer and independently identified by another.

DATA SYNTHESIS

54 observational studies and 1 randomized, controlled trial were included. Insufficient evidence addressed the effectiveness of pretesting. Genotyping sensitivity to identify patients with low and intermediate TPMT enzymatic activity ranged from 70.33% to 86.15% (lower-bound 95% CI, 54.52% to 70.88%; upper-bound CI, 78.50% to 96.33%). Sparse data precluded estimation of genotype sensitivity to identify patients with low to absent enzymatic activity. Genotyping specificity approached 100%. Compared with noncarriers, heterozygous and homozygous genotypes were both associated with leukopenia (odds ratios, 4.29 [CI, 2.67 to 6.89] and 20.84 [CI, 3.42 to 126.89], respectively). Compared with intermediate or normal activity, low TPMT enzymatic activity was significantly associated with myelotoxicity and leukopenia.

LIMITATION

Available evidence was not rigorous and was underpowered to detect a difference in outcomes.

CONCLUSION

Insufficient evidence addresses the effectiveness of TPMT pretesting in patients with chronic inflammatory diseases. Estimates of the sensitivity of genotyping are imprecise. Evidence confirms the known associations of leukopenia or myelotoxicity with reduced TPMT activity or variant genotype.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality.

Assessment of thiopurine methyltransferase activity in patients prescribed azathioprine or other thiopurine-based drugs

OBJECTIVES

To examine whether pretreatment determination of thiopurine methyltransferase (TPMT) enzymatic activity (phenotyping) or TPMT genotype, to guide thiopurine therapy in chronic autoimmune disease patients, reduces treatment harms. Other objectives included assessing: preanalytic, analytic, and postanalytic requirements for TPMT testing; diagnostic accuracy of TPMT genotyping versus phenotyping; association of thiopurine toxicity with TPMT genotypic or phenotypic status; and costs of testing, care, and treating drug-associated complications.

DATA SOURCES

MEDLINE®, EMBASE®, and Healthstar were searched from inception to May 2010; the Cochrane Library® to October 2009; and BIOSIS®, Genetics Abstracts, and EconLit™ to May 2009, for English language records.

REVIEW METHODS

A reviewer screened records, and a second reviewer verified exclusions and subsequent selection of relevant studies. Studies in patients with leukemia and organ transplant were excluded. Additionally, laboratories that provide TPMT analytical services were surveyed to assess means of TPMT testing in practice. Where possible, risk of bias was assessed using standard criteria. Meta-analyses estimated diagnostic sensitivity, and specificity; and odds ratios of associations.

RESULTS

1790 titles or abstracts, and 538 full text records were screened. 114 observational studies and one RCT were included. Majority of studies were rated fair quality, except for diagnostic studies with 37 percent of studies rated poor. In general, there were few patients who were homozygous (or compound heterozygous) for TPMT variant alleles in the included studies limiting applicability. There is insufficient evidence examining effectiveness of pretesting in terms of reduction in clinical adverse events. Sufficient preanalytical data were available regarding preferred specimen collection, stability and storage conditions for TPMT testing. There was no clinically significant effect of age, gender, various coadministered drugs, or most morbidities (with the exception of renal failure and dialysis). TPMT phenotyping methods had coefficients of variation generally below 10 percent. TPMT genotyping reproducibility is generally between 95-100 percent. The sensitivity of genotyping to identify patients with low or intermediate TPMT enzymatic activity is imprecise, ranging from 70.70 to 82.10 percent (95 percent CI, lower bound range 37.90 to 54.00 percent; upper bound range 84.60 to 96.90 percent). Sensitivity of homozygous TPMT genotype to correctly identify patients with low to absent enzymatic activity was 87.10 percent (95 percent CI 44.30 to 98.30 percent). Genotyping specificity approached 100 percent. Leukopenia was significantly associated with low and intermediate enzymatic activity (low activity OR 80.00, 95 percent CI 11.5 to 559; and intermediate activity OR 2.96, 95 percent CI 1.18 to 7.42), and homozygous and heterozygous TPMT variant allele genotype (OR 18.60, 95 percent CI 4.12 to 83.60; and 4.62, 95 percent CI 2.34 to 9.16, respectively). In general, TPMT phenotyping costs less than genotyping, although estimates across studies are quite heterogeneous.

CONCLUSIONS

There is insufficient direct evidence regarding the effectiveness of pretesting of TPMT status in patients with chronic autoimmune diseases. Indirect evidence confirms strong association of leukopenia with lower levels of TPMT activity and carrier genotype already established in the literature.

Correlation of a multi-cytokine panel with clinical disease activity in patients with rheumatoid arthritis

OBJECTIVE

Explore the potential use of a cytokine panel as biochemical markers of disease activity in rheumatoid arthritis (RA) patients.

DESIGN AND METHODS

57 adult RA patients were assessed using five validated clinical disease activity tools: Health Assessment Questionnaire (HAQ), standard 28-joint Disease Activity Score (DAS28), DAS28 using C-reactive protein (DAS28-CRP), Clinical Disease Activity Index (CDAI), and Simple Disease Activity Index (SDAI). Plasma cytokine levels (IL-2, IL-4, IL-6, IL-8, IL-10, VEGF, IFN-γ, TNF-α, IL1α, IL1β, MCP1, and EGF) were measured in 47 of the 57 patients and correlated with clinical indicators.

RESULTS

We found significant correlations between plasma levels of IL-6 and all clinical measures of disease activity; Spearman coefficients (p values) were: HAQ: 0.347(0.017); DAS28: 0.409(0.005); DAS-CRP: 0.378(0.011); CDAI: 0.312(0.033); SDAI: 0.310(0.039); ESR: 0.448(0.002); and CRP: 0.513(0.001). IFN-γ also correlated with DAS-CRP: 0.309(0.039) and SDAI: 0.301(0.044). Furthermore, the levels of IL-6 and IFN-γ increased significantly with worsening disease, as defined by the European League Against Rheumatism (EULAR) classification of disease activity.

CONCLUSION

A significant correlation between plasma levels of IL-6 and clinical disease activity in patients with RA suggests a future role of IL6 as a disease activity marker.

Core-shell magnetic morphology of structurally uniform magnetite nanoparticles

A new development in small-angle neutron scattering with polarization analysis allows us to directly extract the average spatial distributions of magnetic moments and their correlations with three-dimensional directional sensitivity in any magnetic field. Applied to a collection of spherical magnetite nanoparticles 9.0 nm in diameter, this enhanced method reveals uniformly canted, magnetically active shells in a nominally saturating field of 1.2 T. The shell thickness depends on temperature, and it disappears altogether when the external field is removed, confirming that these canted nanoparticle shells are magnetic, rather than structural, in origin.

Calcium-sensing receptor mutations and denaturing high performance liquid chromatography

The calcium-sensing receptor (CASR), a plasma membrane G-protein-coupled receptor, is expressed in parathyroid gland and kidney, and controls systemic calcium homeostasis. Inactivating CASR mutations are associated with familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism, and activating mutations cause autosomal dominant hypocalcemia (ADH). CASR mutation identification plays an important role in the clinical management of mineral metabolism disorders. We describe here a high-throughput method using screening with denaturing high performance liquid chromatography (DHPLC) to initially interrogate 12 amplicons covering translated exons and exon/intron boundaries, followed by sequencing of any amplicon with a modified melting curve relative to wild type, and direct sequencing of a 13th amplicon encoding the COOH-terminal tail to distinguish causative mutations from three common missense single nucleotide polymorphisms. A blinded analysis of 32 positive controls representing mutations throughout the CASR sequence, as well as 22 negative controls, yielded a concordance rate of 100%. We report eight novel and five recurrent FHH mutations, along with six novel and two recurrent ADH mutations. Thus, DHPLC provides a rapid and effective means to screen for CASR mutations.

Minimally invasive biomarkers for detection and staging of colorectal cancer

Colorectal cancer (CRC) is the third most prevalent cancer, with approximately one million cases estimated world wide in 2006, resulting in more than 500,000 deaths. Approximately 40% of colorectal cancers are diagnosed with localized disease, which have approximately a 90% five-year survival rate. However, the prognosis worsens with advancing stage, and only 5% of patients diagnosed with distant metastases survive 5 years. Therefore, the need for early detection is clear. Currently, guaiac-based fecal-occult blood testing (gFOBT) in large population-based trials has been shown to reduce CRC-related mortality, but the sensitivity for detecting early disease is low. DNA-based fecal screening appears to have the potential to significantly increase sensitivity without decreasing specificity. This review will focus primarily on newer molecular-based biomarkers and their utility in screening large populations for CRC, predicting treatment efficacy and providing prognostic information related to survival and disease progression.

Inhibition of MEK or cdc2 kinase parthenogenetically activates mouse eggs and yields the same phenotypes as Mos(-/-) parthenogenotes

Mammalian eggs are arrested in metaphase II of meiosis until fertilization. Arrest is maintained by cytostatic factor (CSF) activity, which is dependent on the MOS-MEK-MAPK pathway. Inhibition of MEK1/2 with a specific inhibitor, U0126, parthenogenetically activated mouse eggs, producing phenotypes similar to Mos(-/-) parthenogenotes (premature, unequal cleavages and large polar bodies). U0126 inactivated MAPK in eggs within 1 h, in contrast to the 5 h required after fertilization, while the time course of MPF inactivation was similar in U0126-activated and fertilized eggs. We also found that inactivation of MPF by the cdc2 kinase inhibitor roscovitine induced parthenogenetic activation. Inactivation of MPF by roscovitine resulted in the subsequent inactivation of MAPK with a time course similar to that following fertilization. Notably, roscovitine also produced some Mos(-/-)-like phenotypes, indistinguishable from U0126 parthenogenotes. Simultaneous inhibition of both MPF and MAPK in eggs treated with roscovitine and U0126 produced a very high proportion of eggs with the more severe phenotype. These findings confirm that MEK is a required component of CSF in mammalian eggs and imply that the sequential inactivation of MPF followed by MAPK inactivation is required for normal spindle function and polar body emission.

GIPC participates in G protein signaling downstream of insulin-like growth factor 1 receptor

Several recent studies have demonstrated that insulin-like growth factor (IGF)-1-induced mitogen-activated protein kinase (MAP kinase) activation is abolished by pertussis toxin, suggesting that trimeric G proteins of the G(i) class are novel cellular targets of the IGF-1 signaling pathway. We report here that the intracellular domain of the Xenopus IGF-1 receptor is capable of binding to the Xenopus homolog of mammalian GIPC, a PDZ domain-containing protein previously identified as a binding partner of G(i)-specific GAP (RGS-GAIP). Binding of xGIPC to xIGF-1 receptor is independent of the kinase activity of the receptor and appears to require the PDZ domain of xGIPC. Injection of two C-terminal truncation mutants that retained the PDZ domain blocked IGF-1-induced Xenopus MAP kinase activation and oocyte maturation. While full-length xGIPC injection did not significantly alter insulin response, it greatly enhanced human RGS-GAIP in stimulating the insulin response in frog oocytes. This represents the first demonstration that GIPC x RGS-GAIP complex acts positively in IGF-1 receptor signal transduction.

Regulation of Xenopus oocyte meiosis arrest by G protein betagamma subunits

BACKGROUND

Progesterone induces the resumption of meiosis (maturation) in Xenopus oocytes through a nongenomic mechanism involving inhibition of an oocyte adenylyl cyclase and reduction of intracellular cAMP. However, progesterone action in Xenopus oocytes is not blocked by pertussis toxin, and this finding indicates that the inhibition of the oocyte adenylyl cyclase is not mediated by the alpha subunits of classical G(i)-type G proteins.

RESULTS

To investigate the possibility that G protein betagamma subunits, rather than alpha subunits, play a key role in regulating oocyte maturation, we have employed two structurally distinct G protein betagamma scavengers (G(t)alpha and betaARK-C(CAAX)) to sequester free Gbetagamma dimers. We demonstrated that the injection of mRNA encoding either of these Gbetagamma scavengers induced oocyte maturation. The Gbetagamma scavengers bound an endogenous, membrane-associated Gbeta subunit, indistinguishable from Xenopus Gbeta1 derived from mRNA injection. The injection of Xenopus Gbeta1 mRNA, together with bovine Ggamma2 mRNA, elevated oocyte cAMP levels and inhibited progesterone-induced oocyte maturation.

CONCLUSION

An endogenous G protein betagamma dimer, likely including Xenopus Gbeta1, is responsible for maintaining oocyte meiosis arrest. Resumption of meiosis is induced by Gbetagamma scavengers in vitro or, naturally, by progesterone via a mechanism that suppresses the release of Gbetagamma.

The classical progesterone receptor mediates Xenopus oocyte maturation through a nongenomic mechanism

Xenopus laevis oocytes are physiologically arrested at G(2) of meiosis I. Resumption of meiosis, or oocyte maturation, is triggered by progesterone. Progesterone-induced Xenopus oocyte maturation is mediated via an extranuclear receptor and is independent of gene transcription. The identity of this extranuclear oocyte progesterone receptor (PR), however, has remained a longstanding problem. We have isolated the amphibian homologue of human PR from a Xenopus oocyte cDNA library. The cloned Xenopus progesterone receptor (xPR) functioned in heterologous cells as a progesterone-regulated transcription activator. However, endogenous xPR was excluded from the oocyte nucleus and instead appeared to be a cytosolic protein not associated with any membrane structures. Injection of xPR mRNA into Xenopus oocytes accelerated the progesterone-induced oocyte maturation and reduced the required concentrations of progesterone. In enucleated oocytes, xPR accelerated the progesterone-induced mitogen-activated protein kinase activation. These data suggest that xPR is the long sought after Xenopus oocyte receptor responsible for progesterone-induced oocyte maturation.

Xenopus laevis TRK-fused gene (TFG) is an SH3 domain binding protein highly expressed in the cement gland

TRK-fused gene (TFG) was originally identified in humans as the N-terminus of an oncogenic fusion protein TRK-T3, associated with papillary thyroid carcinoma. An amino-terminal coiled coil domain of TFG is responsible for mediating oligomerization of the TRK-T3 oncoprotein, resulting in constitutive activation of the TRK protein tyrosine kinase and oncogenesis. We have cloned the Xenopus laevis homologue of TFG and demonstrated that xTFG was highly expressed in the cement gland of tailbud embryos. Overexpression of xTFG2-136 (including the coiled coil domain) in early embryos, via mRNA microinjection as well as transgenic expression using the recently described restriction enzyme mediated integration (REMI) transgenesis, did not alter embryonic development or development of a functional cement gland, despite clear evidence that xTFG2-136 strongly interacted with endogenous xTFG. Finally, we have identified a potential SH3 binding motif in xTFG (and in TFG) and have demonstrated that xTFG selectively interacted with SH3 domains of Src, PLCgamma, and the p85 phosphatidylinositol 3-kinase subunit.

Perianal recurrence in colonic cancer

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Sphingomyelin metabolism in rat liver after chronic dietary replacement of choline by N-aminodeanol

Sphingomyelin (SM) is a structural element of cell membranes and lipoproteins, and participates in signal transduction. To determine whether a choline analog (N-amino-N,N-dimethylaminoethanol, N-aminodeanol, NADe) can be substituted for choline in the SM of liver, rats (male, Sprague-Dawley-derived) were fed a diet that was low in choline and methionine, and contained 35.5 mmol of NADe/kg. After 18 months, liver plasma membranes and microsomes contained 48.9 +/- 3.6 and 93.6 +/- 6.9 nmol/mg protein of phosphatidyl-NADe, respectively, and 3.2 +/- 0.2 and 3.5 +/- 0.1 nmol/mg protein of ceramide phospho-NADe. The SM content of microsomes from NADe-fed rats was about one-third lower than for the control, and phosphatidylcholine (PC) was reduced by < 10%; there was also a small decrease in PC, but not SM, in plasma membranes. In vitro assays of enzymes involved in SM metabolism found no change in PC:ceramide cholinephosphotransferase, but the NADe-fed animals had higher phosphatidylethanolamine:ceramide ethanolaminephosphotransferase activity, greater incorporation of methyl groups from [methyl-3H]-S-adenosyl methionine into SM, and a lower neutral sphingomyelinase activity. These results show that NADe-fed rats from considerable amounts of ceramide phospho- and phosphatidyl-NADe; however, liver plasma membranes retain relatively normal levels of PC and SM, perhaps due to increases in the de novo pathway for SM synthesis and decreases in SM turnover.