Differential Viral Dynamics by Sex and Body Mass Index During Acute SARS-CoV-2 Infection: Results from a Longitudinal Cohort Study

BACKGROUND

There is evidence of an association of severe COVID-19 outcomes with increased body mass index (BMI) and male sex. However, few studies have examined the interaction between sex and BMI on SARS-CoV-2 viral dynamics.

METHODS

Participants conducted RT-PCR testing every 24-48 hours over a 15-day period. Sex and BMI were self-reported, and Ct values from E-gene were used to quantify viral load. Three distinct outcomes were examined using mixed effects generalized linear models, linear models, and logistic models, respectively: all Ct values (Model 1); nadir Ct value (model 2); and strongly detectable infection (at least one Ct value ≤28 during their infection) (Model 3). An interaction term between BMI and sex was included, and inverse logit transformations were applied to quantify the differences by BMI and sex using marginal predictions.

RESULTS

In total, 7,988 participants enrolled in this study, and 439 participants (Model 1) and 309 (Model 2 and 3) were eligible for these analyses. Among males, increasing BMI was associated with lower Ct values in a dose-response fashion. For participants with BMIs greater than 29, males had significantly lower Ct values and nadir Ct values than females. In total, 67.8% of males and 55.3% of females recorded a strongly detectable infection; increasing proportions of men had Ct values <28 with BMIs of 35 and 40.

CONCLUSIONS

We observed sex-based dimorphism in relation to BMI and COVID-19 viral load. Further investigation is needed to determine the cause, clinical impact, and transmission implications of this sex-differential effect of BMI on viral load.

Performance of Rapid Antigen Tests to Detect Symptomatic and Asymptomatic SARS-CoV-2 Infection : A Prospective Cohort Study

BACKGROUND

The performance of rapid antigen tests (Ag-RDTs) for screening asymptomatic and symptomatic persons for SARS-CoV-2 is not well established.

OBJECTIVE

To evaluate the performance of Ag-RDTs for detection of SARS-CoV-2 among symptomatic and asymptomatic participants.

DESIGN

This prospective cohort study enrolled participants between October 2021 and January 2022. Participants completed Ag-RDTs and reverse transcriptase polymerase chain reaction (RT-PCR) testing for SARS-CoV-2 every 48 hours for 15 days.

SETTING

Participants were enrolled digitally throughout the mainland United States. They self-collected anterior nasal swabs for Ag-RDTs and RT-PCR testing. Nasal swabs for RT-PCR were shipped to a central laboratory, whereas Ag-RDTs were done at home.

PARTICIPANTS

Of 7361 participants in the study, 5353 who were asymptomatic and negative for SARS-CoV-2 on study day 1 were eligible. In total, 154 participants had at least 1 positive RT-PCR result.

MEASUREMENTS

The sensitivity of Ag-RDTs was measured on the basis of testing once (same-day), twice (after 48 hours), and thrice (after a total of 96 hours). The analysis was repeated for different days past index PCR positivity (DPIPPs) to approximate real-world scenarios where testing initiation may not always coincide with DPIPP 0. Results were stratified by symptom status.

RESULTS

Among 154 participants who tested positive for SARS-CoV-2, 97 were asymptomatic and 57 had symptoms at infection onset. Serial testing with Ag-RDTs twice 48 hours apart resulted in an aggregated sensitivity of 93.4% (95% CI, 90.4% to 95.9%) among symptomatic participants on DPIPPs 0 to 6. When singleton positive results were excluded, the aggregated sensitivity on DPIPPs 0 to 6 for 2-time serial testing among asymptomatic participants was lower at 62.7% (CI, 57.0% to 70.5%), but it improved to 79.0% (CI, 70.1% to 87.4%) with testing 3 times at 48-hour intervals.

LIMITATION

Participants tested every 48 hours; therefore, these data cannot support conclusions about serial testing intervals shorter than 48 hours.

CONCLUSION

The performance of Ag-RDTs was optimized when asymptomatic participants tested 3 times at 48-hour intervals and when symptomatic participants tested 2 times separated by 48 hours.

PRIMARY FUNDING SOURCE

National Institutes of Health RADx Tech program.

Design and implementation of a digital site-less clinical study of serial rapid antigen testing to identify asymptomatic SARS-CoV-2 infection

Background

Rapid antigen detection tests (Ag-RDT) for SARS-CoV-2 with emergency use authorization generally include a condition of authorization to evaluate the test's performance in asymptomatic individuals when used serially. We aim to describe a novel study design that was used to generate regulatory-quality data to evaluate the serial use of Ag-RDT in detecting SARS-CoV-2 virus among asymptomatic individuals.

Methods

This prospective cohort study used a siteless, digital approach to assess longitudinal performance of Ag-RDT. Individuals over 2 years old from across the USA with no reported COVID-19 symptoms in the 14 days prior to study enrollment were eligible to enroll in this study. Participants throughout the mainland USA were enrolled through a digital platform between October 18, 2021 and February 15, 2022. Participants were asked to test using Ag-RDT and molecular comparators every 48 hours for 15 days. Enrollment demographics, geographic distribution, and SARS-CoV-2 infection rates are reported.

Key Results

A total of 7361 participants enrolled in the study, and 492 participants tested positive for SARS-CoV-2, including 154 who were asymptomatic and tested negative to start the study. This exceeded the initial enrollment goals of 60 positive participants. We enrolled participants from 44 US states, and geographic distribution of participants shifted in accordance with the changing COVID-19 prevalence nationwide.

Conclusions

The digital site-less approach employed in the "Test Us At Home" study enabled rapid, efficient, and rigorous evaluation of rapid diagnostics for COVID-19 and can be adapted across research disciplines to optimize study enrollment and accessibility.

Performance of Rapid Antigen Tests to Detect Symptomatic and Asymptomatic SARS-CoV-2 Infection

Background

Performance of rapid antigen tests for SARS-CoV-2 (Ag-RDT) varies over the course of an infection, and their performance in screening for SARS-CoV-2 is not well established. We aimed to evaluate performance of Ag-RDT for detection of SARS-CoV-2 for symptomatic and asymptomatic participants.

Methods

Participants >2 years old across the United States enrolled in the study between October 2021 and February 2022. Participants completed Ag-RDT and molecular testing (RT-PCR) for SARS-CoV-2 every 48 hours for 15 days. This analysis was limited to participants who were asymptomatic and tested negative on their first day of study participation. Onset of infection was defined as the day of first positive RT-PCR result. Sensitivity of Ag-RDT was measured based on testing once, twice (after 48-hours), and thrice (after 96 hours). Analysis was repeated for different Days Post Index PCR Positivity (DPIPP) and stratified based on symptom-status.

Results

In total, 5,609 of 7,361 participants were eligible for this analysis. Among 154 participants who tested positive for SARS-CoV-2, 97 were asymptomatic and 57 had symptoms at infection onset. Serial testing with Ag-RDT twice 48-hours apart resulted in an aggregated sensitivity of 93.4% (95% CI: 89.1-96.1%) among symptomatic participants on DPIPP 0-6. Excluding singleton positives, aggregated sensitivity on DPIPP 0-6 for two-time serial-testing among asymptomatic participants was lower at 62.7% (54.7-70.0%) but improved to 79.0% (71.0-85.3%) with testing three times at 48-hour intervals.

Discussion

Performance of Ag-RDT was optimized when asymptomatic participants tested three-times at 48-hour intervals and when symptomatic participants tested two-times separated by 48-hours.

Finding a Needle in a Haystack: Design and Implementation of a Digital Site-less Clinical Study of Serial Rapid Antigen Testing to Identify Asymptomatic SARS-CoV-2 Infection

Background

Rapid antigen tests (Ag-RDT) for SARS-CoV-2 with Emergency Use Authorization generally include a condition of authorization to evaluate the test's performance in asymptomatic individuals when used serially.

Objective

To describe a novel study design to generate regulatory-quality data to evaluate serial use of Ag-RDT in detecting SARS-CoV-2 virus among asymptomatic individuals.

Design

Prospective cohort study using a decentralized approach. Participants were asked to test using Ag-RDT and molecular comparators every 48 hours for 15 days.

Setting

Participants throughout the mainland United States were enrolled through a digital platform between October 18, 2021 and February 15, 2022. Ag-RDTs were completed at home, and molecular comparators were shipped to a central laboratory.

Participants

Individuals over 2 years old from across the U.S. with no reported COVID-19 symptoms in the 14 days prior to study enrollment were eligible to enroll in this study.

Measurements

Enrollment demographics, geographic distribution, and SARS-CoV-2 infection rates are reported.

Key Results

A total of 7,361 participants enrolled in the study, and 492 participants tested positive for SARS-CoV-2, including 154 who were asymptomatic and tested negative to start the study. This exceeded the initial enrollment goals of 60 positive participants. We enrolled participants from 44 U.S. states, and geographic distribution of participants shifted in accordance with the changing COVID-19 prevalence nationwide.

Limitations

New, complex workflows required significant operational and data team support. Conclusions: The digital site-less approach employed in the 'Test Us At Home' study enabled rapid, efficient, and rigorous evaluation of rapid diagnostics for COVID-19, and can be adapted across research disciplines to optimize study enrollment and accessibility.

Utility of Whole Blood Real-Time PCR Testing for the Diagnosis of Early Lyme Disease

OBJECTIVES

Whole blood real-time polymerase chain reaction (WB-RTPCR) detection of Borrelia burgdorferi is not currently recommended for diagnosing Lyme disease. This study aims to elucidate the utility of WB-RTPCR as a diagnostic aid for early Lyme disease (ELD), defined as either positive PCR or positive immunoglobulin M with negative immunoglobulin G immunoblot.

METHODS

A retrospective analysis was performed on 33,199 blood specimens evaluated concurrently by WB-RTPCR and antibody-capture serology (ACEIA) methods (group A). Fifty-six pairs of specimens from a separate data set were retrospectively identified and analyzed at initial and follow-up time points to monitor for seroconversion (group B). Also, a separate data set of 2,526 specimens concurrently assessed by molecular and modified two-tiered enzyme-linked immunosorbent assay serology methods was analyzed (group C).

RESULTS

Group A yielded 1,379 specimens consistent with ELD when tested by ACEIA and WB-RTPCR. In total, 131 (9.5% of positive results) were identified by WB-RTPCR, with negative serology. Group C identified 358 samples compatible with ELD, with 31 (8.7% of positive results) identified by RTPCR alone.

CONCLUSIONS

When used concurrently with serologic testing, WB-RTPCR testing increases diagnostic sensitivity in cases of ELD.

A Comparison of Lyme Serological Testing Platforms with a Panel of Clinically Characterized Samples from Various Stages of Lyme Disease

Background

In 2019, the CDC updated serology testing guidelines for Lyme disease diagnosis to include alternative modified two-tiered testing that replaces the western blots of standard testing with an additional ELISA. Antibody-capture serological assays have also been used as an aid for Lyme diagnosis. A panel of clinically characterized samples from the CDC was tested to compare modified two-tiered testing to the standard two-tiered algorithm and an antibody capture immunoassay.

Methods

A CDC panel of 92 samples comprised a range of samples including early Lyme, Lyme neuroborreliosis, Lyme arthritis, infections by other pathogens, and healthy controls. The panel was tested on a standard two-tiered platform by the CDC, the ZEUS Borrelia Test System for modified two-tiered testing, and a lab-developed antibody-capture serological assay. Sensitivity and specificity results from each assay were compared to determine significance.

Results

The antibody-capture assay demonstrated increased sensitivity but decreased specificity compared to the modified and standard two-tiered platforms. There was no statistical difference found between the modified and standard two-tiered platforms.

Conclusions

Improved sensitivity of antibody-capture when testing early Lyme disease samples is offset by decreased specificity, especially with syphilis-positive samples. Modified two-tiered testing is similar to standard two-tiered methods while also being more scalable and simpler to interpret.

Association between liver and chronic kidney disease on hemoglobin A1c concentrations

INTRODUCTION

HbA1c is the gold standard for measuring long-range glycemic control in patients with type-2 diabetes mellitus. Conditions such as CKD or LD can lead to spurious HbA1c test results. There is conflicting literature about the relationship between HbA1c, LD, and CKD.

METHODS

Results for HbA1c concentrations were retrieved from 2015- to 2019. We evaluated over 2,500 test results with LD and 20,000 results with CKD compared to over 21,000 test results without LD, iron deficiency anemia, or CKD. Patients were classified as having LD if they had high ALT and AST concentrations. If they have abnormal serum creatinine and BUN or low eGFR based on age-based reference ranges for CKD. Kruskal-Wallis statistical analyses method was used to test whether the two samples followed the same distribution and significance. Results The median HbA1c concentration was 5.8% (40 mmol/l) among LD classified patients in both males and females vs. 5.4% (36 mmol/l) (P<0.001) for females and 5.6% (38 mmol/l) (P<0.001) for males without LD. A significant difference in median HbA1c concentrations were also observed between CKD samples (female: 5.7% (39 mmol/l), male: 6.0% (42 mmol/l)) and non-CKD samples (female: 5.4% (36 mmol/l), male: 5.6% (38 mmol/l)) (P<0.001). Depending on the population's CKD stage, median concentrations of % HbA1c are increased from stage-1 through stage-4 and fell in Stage-5. Conclusion Patients with high AST and ALT concentrations or CKD can have increased HbA1c concentrations compared to normal patients. When using HbA1c concentrations to monitor diabetes, healthcare professionals should consider LD or CKD status before making any therapeutic decisions.

Clinical variables associated with indeterminate QuantiFERON®-TB Gold assay results: role of pre-incubation delay

SETTING

The QuantiFERON^®-TB Gold (QFT) assay is an interferon-gamma release assay used for the clinical diagnosis of latent tuberculous infection. Relatively high rates of indeterminate results are a significant downside of the test.

OBJECTIVE

To evaluate clinical variables associated with lower QFT-indeterminate rates after reducing pre-incubation delay.

DESIGN

In 2016, a new protocol of on-site incubation of QFT samples, followed by analysis at the outside laboratory, was implemented, resulting in much shorter pre-incubation delay of the samples. We retrospectively identified 3583 patients who underwent QFT before and after implementation of the new protocol. Patient records were scrutinized and QFT results were evaluated with respect to associated clinical conditions.

RESULTS

The patients were analyzed by dividing them into two cohorts based on maximum pre-incubation time (standard vs. immediate). Monthly indeterminate results dropped from 12.7% ± 0.02 in the standard cohort to 5.5% ± 0.03 in the immediate cohort (P < 0.001). A significant reduction in relative indeterminate rates was found in the immediate cohort patients with immunocompromised state, autoimmune conditions, liver disease and hypoalbuminemia. No difference was identified in patients with malignancies and renal failure.

CONCLUSION

Limiting the pre-incubation time to 1 h maximum significantly improved QFT performance, especially in patients from certain clinical categories.

Comparison of Point-of-Care Activated Clotting Time Methods in Different Clinical Settings in a Large Academic Medical Center

OBJECTIVES

This study is a comparative analysis of measured activated clotting time (ACT) values by use of 5 different point-of-care (POC) ACT methods spanning the range detected during different clinical procedures at our institution.

METHODS

We determined the correlation, imprecision, and differences in measured ACT values with use of 4 POC ACT methods compared with a reference ACT method in 41 venous whole blood samples collected from 25 adult patients undergoing interventional procedures. The POC ACT methods evaluated included the i-STAT with kaolin activator in prewarm mode, i-STAT with Celite activator in prewarm and nonprewarm modes, ACTPlus, and HMSPlus, which was designated the reference method. Each venous whole blood patient sample was tested in duplicate on each POC ACT test system (total n = 410 ACT measurements). Analyses of imprecision and differences in measured ACT values were stratified by moderate (100-299 s) and high (≥300 s) ACT ranges.

RESULTS

In this study population, measured ACT values ranged from 100-835 s with use of the HMSPlus. All methods demonstrated good correlation (r ≥ 0.95) in ACT values compared to the reference method. Imprecision varied by method with ranges of 1.7%-2.7% CV in the moderate ACT range and 2.5%-4.8% CV in the high ACT range. ACTPlus and i-STAT-Celite-prewarm methods exhibited proportional differences in measured ACT values whereas the i-STAT-Celite-nonprewarm and i-STAT-kaolin-prewarm demonstrated constant differences in measured ACT values compared to HMSPlus.

CONCLUSIONS

ACT values correlate well between POC methods. Imprecision and difference profiles vary by method; notably, imprecision exceeds systematic differences in the high ACT range and contributes to intermethod differences that are limitations worthy of consideration when contemplating a change in ACT methods.

Performance of rapid SOFIA Influenza A+B test compared to Luminex x-TAG respiratory viral panel assay in the diagnosis of influenza A, B, and subtype H3

Influenza is an acute respiratory illness caused by influenza A or B viruses that occur in outbreaks, mainly during the winter season. Rapid laboratory diagnosis of influenza can help guide the clinical management of suspected patients effectively. Clinical sensitivities and specificities of the rapid influenza diagnostic tests have varied considerably in the literature. Most of these studies are evaluated using previously frozen or stored specimens that had previously tested positive. This study compares the performance of the rapid SOFIA Influenza A+B test to nucleic acid multiplex test x-TAG respiratory viral panel (RVP) assay in freshly collected nasal aspirates and measured simultaneously by both assays. Retrospective data from 1649 nasal aspirates (September 2014 to May 2015) collected from adults as well as from children tested simultaneously by both rapid SOFIA Influenza A+B FIA immunofluorescence (Quidel, San Diego, CA) and qualitative nucleic acid multiplex RVP assay X-TAG Luminex technology (Luminex, Austin, Texas, USA) were analyzed. Concordance, and analytical sensitivity and specificity were evaluated for influenza A, subtypes H1 and H3, and influenza B. Prevalence for influenza A by RVP was 15%, for subtype H3 it was 11.2%, and for influenza B, 2.9%. None of the aspirates were positive for influenza A subtype H1. SOFIA Influenza rapid test demonstrated good specificity and low sensitivity compared with a nucleic acid test for influenza A, subtype H3, and for influenza B. SOFIA Influenza A + B test performed well in providing a rapid diagnosis, however, confirmatory molecular testing is recommended for negative test results. Re-evaluation of test performance should be periodically carried out during outbreaks with the emergence and circulation of new influenza strains.

Utilization of assay performance characteristics to estimate hemoglobin A1c result reliability

BACKGROUND

Allowable total error (TE(a)) goals for hemoglobin (Hb) A(1c) require minimal assay imprecision and bias and implementation of a robust QC monitoring program. Here, we compare the combined influence on the risk of reporting unreliable results of TE(a) goals, a routine QC practice, and assay performance characteristics of 6 Hb A(1c) instruments across 4 academic medical centers.

METHODS

The CLSI protocols EP-5 and EP-9 were applied to investigate Hb A(1c) result imprecision and bias on the Variant II Turbo and Variant II (Bio-Rad), G8 (Tosoh), Capillarys 2 Flex Piercing (Sebia), COBAS Integra 800 (Roche), and DCA Vantage (Siemens). Patient-weighted σ values and the risk of reporting unreliable Hb A(1c) results were determined for each assay at TE(a) specifications of 5%, 6%, and 7%.

RESULTS

A large range of patient-weighted σ values spanning 0.5 orders of magnitude at a 6% TE(a) was observed. Although imprecision for all instruments was <3%, bias impacted the majority of the σ changes observed. Estimates for reporting unreliable results varied almost 500-fold based on analytical performance alone.

CONCLUSIONS

Considerable differences in the probability of reporting unreliable Hb A(1c) results between different NGSP (formerly the National Glycohemoglobin Standardization Program)-certified platforms were observed. At a 6% TE(a), our study indicates all but the Capillarys 2 Flex Piercing requires that the maximum affordable QC be run. Risk estimates for individual laboratories' Hb A(1c) methods can be used to assess QC practices and residual risk of an unreliable Hb A(1c) result.

Protective effects of quercetin during influenza virus-induced oxidative stress

Oxidative stress was found to have a role in many viral diseases including AIDS, hepatitis and influenza. In the present study the pathology of influenza viral infection in the lungs, which may lead to oxidative stress, was investigated and an attempt was made to study the efficacy of anti-oxidants as therapeutic agents. Adult male mice of Swiss albino type were infected with influenza virus (A/Hong Kong/8/68) and studied for the antioxidant status in the lungs by evaluating the lung enzymatic anti-oxidant system including superoxide dismutase and catalase. Superoxide radical generation, which might increase by the activated alveolar macrophages, was estimated by nitroblue-tetrazolium reduction assay. We have also estimated lipid peroxidation levels in lung through thiobarbutiric acid reactive substances assay. We also examined the ability of flavonoid quercetin in protecting from influenza virus-induced oxidative stress. The influenza-infected group showed decreased levels of superoxide dismutase and catalase; however, anti-oxidant supplemented groups showed these activities to be the same as in the control group. The lipid peroxide levels were increased in virus-infected mice. Administration of quercetin lowered the lipid peroxide levels significantly. Formazan positive cells were increased by 80% in the virus-infected group and supplementation with quercetin reduced their number to 44%.

Reducing analytical variation between point-of-care and laboratory HbA1c testing

BACKGROUND

Point-of-care (POC) HbA1c testing allows for timely treatment changes, improved glycemic control, and patient and provider satisfaction. Substantial variation between POC and laboratory HbA1c results has been reported. At our university hospital diabetes clinic, we observed significant negative bias in HbA1c with the DCA Vantage (Siemens Healthcare Diagnostics, Tarrytown, NY, USA) compared with the Tosoh G8 HPLC laboratory analyzer (Tosoh Bioscience, San Francisco, CA, USA). This led us to systematically analyze the bias with the goal of recalibrating the DCA to minimize bias.

METHODS

We analyzed 45 patient samples, with HbA1c ranging between 5% and 10.8%, concurrently on two DCA analyzers and on the Tosoh G8 machine. The bias for each sample was the difference between the value on the DCA and the Tosoh G8 analyzer. Based on regression equations derived from the data, a correction factor for each DCA analyzer was calculated. The analyzers were recalibrated and retested for bias.

RESULTS

At baseline, the mean bias (range) was -0.5229 (+0.1 to -1.3) for Analyzer 1 and -0.5348 (0.0 to -1.6) for Analyzer 2. After recalibration, the mean bias (range) was 0.000 (+0.6 to -0.6) and 0.0003 (+0.5 to -0.5) for Analyzers 1 and 2, respectively, and the systematic negative bias seen prior to the calibration was almost eliminated.

CONCLUSIONS

We recommend periodic recalibration of POC analyzers to eliminate systematic unidirectional bias and to harmonize results between the POC and central laboratory analyzers within a healthcare system. Calibration may need to be repeated with any change in the reagent lot.

Rapid liquid chromatography/tandem mass spectrometer (LCMS) method for clozapine and its metabolite N-desmethyl clozapine (norclozapine) in human serum

Clozapine is indicated for the treatment of schizophrenia and related psychotic disorders. Several methods have been developed for monitoring Clozapine levels; however, they possess limited specificity and are often laborious. This study describes a simple liquid chromatography/tandem mass spectrometer (LCMS) method in human serum. The ion transitions monitored were m/z 327, 270, 296 for Clozapine, m/z 313, 192, 227 for Norclozapine and m/z 328, 271 for Loxapine. The assay is linear (25-1000 ng/ml) and showed a good correlation (r=0.98) within the analytical range of 79-1210 ng/ml in human serum. This assay is highly specific and sensitive for the simultaneous measurements of Clozapine and Norclozapine. The simplification of this assay makes it ideal for high throughput analyses of the patient samples in a routine clinical laboratory staffed with general medical technologists.

Analytical validation of an HPLC assay for urinary albumin

BACKGROUND

Microalbuminuria is the earliest clinical finding for renal disease. Diabetic individuals often produce modified forms of albumin, perhaps due to impaired lysosomal processing, that are undetectable by common immunoassays but accurately measured by HPLC.

METHODS

We evaluated the performance of a commercially available, FDA-approved HPLC assay (AusAm Biotechnologies, NY) and compare results to our immunoturbidimetric assay (ITA, Beckman-Coulter, CA) using random urine specimens from 32 nondiabetic and 60 type 1 and 2 diabetic subjects.

RESULTS

The HPLC assay was linear to 963 mg/l with a limit of detection of 6.1 mg/l. Within-run and between-run precision was <2% and 7-10%, respectively. Unpreserved urine was stable for at least 3 days at room temperature and 10 days at 4 degrees C. In both diabetic and nondiabetic subjects urinary albumin concentrations were higher by HPLC than by ITA, and many more diabetic and nondiabetic individuals were classified as microalbuminuric by HPLC than by ITA. The HPLC assay showed acceptable performance; however, because urinary albumin concentrations are higher in apparently healthy nondiabetic as well as diabetic subjects, different cutpoints will be necessary to accurately differentiate microalbuminuria.

CONCLUSIONS

Prospective studies are necessary to determine whether the HPLC assay can effectively detect microalbuminuria earlier than current assays without a concomitant increase in the false positive rate.

Accuracy evaluation of a new glucometer with automated hematocrit measurement and correction

BACKGROUND

Blood glucose meters are widely used in point of care testing, however, many studies have shown inaccuracies in the glucose measurement due to a number of factors. The present study evaluated the accuracy of a new glucometer capable of simultaneous measurement of patient's hematocrit with algorithmic adjustment of glucose result. This meter was compared with a reference method and 2 other existing meters widely used in the market.

METHODS

Venous whole blood samples from healthy volunteers were pooled and reconstituted to produce 5 different hematocrit (30-60%) concentrations. Each hematocrit specimen was spiked to produce 4 different glucose (50-500 mg/dl) concentrations.

RESULTS

Hematocrit measured by the new meter correlated well with the reference method. Mean percentage error differences, compared to the reference method, showed obvious differences between existing meters across the wide hematocrit range at various glucose concentrations. The new meter showed a steady and consistent glucose concentrations compared to the reference method.

CONCLUSION

The new glucometer, which simultaneously measures hematocrit and performs automated correction for the hematocrit effect, provides a glucose result with improved accuracy. Its measurement of hematocrit from the same blood sample will eliminate the need for additional collection of blood or measurement using another method.

Novel mutation method for increased cellulase production

AIM

Isolation of cellulase producing fungi and increasing cellulase production using novel mutations.

METHODS AND RESULTS

Cellulase-producing fungi were isolated from different soil samples using enriched Mandels cellulose agar, which is a selective media and seven different fungi were selected in the screening programme. These organisms were tested for cellulase production and two potent strains were identified. Two methods of mutations for strain improvement were employed to these strains. (1) Germinating fungal spore suspension was treated with 0.1 and 0.2 mg ml(-1) of 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), ethidium bromide (EtBr) and u.v. for 30 min and 1 h duration and plated on selective media with and with out amphotericin B. (2) Mutagens (EtBr and MNNG) were incorporated in the selective media in sublethal concentration (5 microg ml(-1)) along with antifungal antibiotic (amphotericin B 2 microg ml(-1)). Second method yielded maximum cellulase-producing mutants, which are also stable for cellulase production and are more potent than the mutants obtained by the first method.

CONCLUSIONS

Mutations using sublethal concentrations of mutagen for a prolonged period of growth has yielded mutants, which can produce more cellulase.

SIGNIFICANCE AND IMPACT OF THE STUDY

This new method could be applied to obtain potent fungal mutants for more enzymes production.

Gadolinium magnetic resonance contrast agents produce analytic interference in multiple serum assays

Gadolinium magnetic resonance contrast agents are known to interfere with some clinical chemistry tests, particularly colorimetric assays for serum calcium. We studied the effects of 4 agents, gadodiamide, gadoversetamide, gadopentetate dimeglumine, and gadoteridol, for interference with multiple serum assays. Gadodiamide and gadoversetamide produced clinically significant negative interference with colorimetric assays for serum angiotensin-converting enzyme, calcium, and zinc. These agents produced clinically significant positive interference in magnesium and total iron binding capacity assays and both positive and negative interference in iron assays. Gadopentetate dimeglumine produced a negative interference with iron assays, and gadopentetate dimeglumine and gadoteridol produced negative interference with a colorimetric zinc assay. Caution should be exercised when using colorimetric assays for angiotensin-converting enzyme, calcium, iron, magnesium, total iron binding capacity, and zinc in serum samples from patients who have recently received magnetic resonance contrast agents. In general, gadodiamide and gadoversetamide are more likely to produce a clinically significant interference than gadopentetate dimeglumine and gadoteridol. Likewise, certain analytic methods are more prone to interference, while others not affected.

Active site blockade of factor VIIa alters its intracellular distribution

Factor VIIa binding to tissue factor on cell surfaces not only triggers the coagulation cascade but also induces various intracellular responses that may contribute to many pathophysiological processes. Active site-inhibited factor VIIa, similar to factor VIIa, binds to tissue factor on cell surfaces and subsequently gets internalized and degraded. At present, it is unknown whether factor VIIa and active site-inhibited factor VIIa undergo a similar intracellular processing. The data presented herein show that although a fraction of both the internalized factor VIIa and active site-inhibited factor VIIa recycle back to the cell surface, the amount of active site-inhibited factor VIIa recycled back to the cell surface was substantially higher than that of factor VIIa. Furthermore, internalized factor VIIa and not active site-inhibited factor VIIa associates with nuclear fractions. Factor VIIa associated with the nuclear fraction was intact and functionally active. In contrast to factor VIIa, tissue factor is not found in the nuclear fraction. Additional studies show that the internalized factor VIIa specifically associates with cytoskeletal proteins, actin, and tubulin. In summary, the present data reveal that despite the common pathway of tissue factor-mediated processing, considerable differences exist in the trafficking of factor VIIa and active site-inhibited factor VIIa in fibroblasts.

Tissue factor-mediated endocytosis, recycling, and degradation of factor VIIa by a clathrin-independent mechanism not requiring the cytoplasmic domain of tissue factor

Endocytosis and recycling of coagulation factor VIIa (VIIa) bound to tissue factor (TF) was investigated in baby hamster kidney (BHK) cells stably transfected with TF or TF derivatives. Cell surface expression of TF on BHK cells was required for VIIa internalization and degradation. Approximately 50% of cell surface-bound VIIa was internalized in one hour, and a majority of the internalized VIIa was degraded soon thereafter. Similar rates of VIIa internalization and degradation were obtained with BHK cells transfected with a cytoplasmic domain-deleted TF variant or with a substitution of serine for cysteine at amino acid residue 245 (C245S). Endocytosis of VIIa bound to TF was an active process. Acidification of the cytosol, known to inhibit the internalization via clathrin-coated pits, did not affect the internalization of VIIa. Furthermore, receptor-associated protein, known to block binding of all established ligands to members of the low-density lipoprotein receptor family, was without an effect on the internalization of VIIa. Addition of tissue factor pathway inhibitor/factor Xa complex did not affect the internalization rate significantly. A substantial portion (20% to 25%) of internalized VIIa was recycled back to the cell surface as an intact and functional protein. Although the recycled VIIa constitutes to only approximately 10% of available cell surface TF/VIIa sites, it accounts for 65% of the maximal activation of factor X by the cell surface TF/VIIa. In summary, the present data provide evidence that TF-dependent internalization of VIIa in kidney cells occurs through a clathrin-independent mechanism and does not require the cytoplasmic domain of TF.

The role of catalytic cleft and exosite residues of factor VIIa for complex formation with tissue factor pathway inhibitor

The extrinsic coagulation pathway is initiated by the binding of plasma factor VIIa (VIIa) to the cell surface receptor tissue factor (TF). Formation of the TF-VIIa complex results in allosteric activation of VIIa as well as the creation of an extended macromolecular substrate binding exosite that greatly enhances proteolytic activation of substrate factor X. The catalytic function of the TF-VIIa complex is regulated by a specific Kunitz-type inhibitor, tissue factor pathway inhibitor (TFPI). TFPI inhibition of the TF-VIIa complex was enhanced by the presence of Xa. This study investigates the relative contribution of catalytic cleft and exosite residues in VIIa for inhibitory complex formation with TFPI. VIIa protease domain residues Q176, T239 and E296 are involved in the formation of stable inhibitor complex with free TFPI. Kinetic analysis further demonstrated a predominant role of the S2' subsite residue Q176 for the initial complex formation with TFPI. In contrast, no significant reductions in inhibition by TFPI-Xa were found for each of the mutants in complex with phospholipid reconstituted TF. However, reduced rates of inhibition of the VIIa Gla-domain (R36) and Q176 mutant by TFPI-Xa were evident when TF was solubilized by detergent micelles. These data demonstrate docking of the TFPI-Xa complex with the macromolecular substrate exosite and the catalytic cleft, in particular the S2' subsite. The masking of the mutational effect by the presence of phospholipid shows a critical importance of Xa Gla-domain interactions in stabilizing the quaternary TF-VIIa-Xa-TFPI complex.

Factor VIIIa-induced gene expression: potential implications in pathophysiology

Binding of factor VIIa (VIIa) to tissue factor (TF) triggers the coagulation cascade. Several studies indicate a possible role for TF-VIIa in other cellular functions, in addition to coagulation, under pathophysiological conditions. Recent studies suggest that TF-VIIa mediates cell signaling by two distinct mechanisms, TF cytoplasmic domain-dependent and TF-VIIa protease activity-dependent. In this review, we focus upon TF-VIIa protease-induced gene expression and how the altered gene expression could potentially affect various cellular processes.

Stability of prothrombin time and activated partial thromboplastin time tests under different storage conditions

Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are common laboratory tests that are useful in the diagnosis of coagulation disorders and monitoring anticoagulant therapy. Recent expansions in the outreach laboratory services at our institution prompted us to investigate the shipping limitations for some tests, including PT and aPTT. Although we followed NCCLS guidelines for the collection of blood specimens, we observed falsely elevated PT and aPTT values due to the different storage conditions. The objective of this study is to determine the effect of conditions and duration of storage on PT and aPTT tests using plasma and whole blood samples, respectively. For this study, 36 plasma samples with normal and prolonged PT and aPTT were exposed to different storage conditions. Blood was centrifuged immediately and plasma was stored at room temperature (RT), refrigerated at 4 degrees C, or frozen at -20 degrees C. The samples were analyzed at 0 h and repeated at 6, 12 and 24 h under various conditions. Although statistically significant differences were observed for plasma samples for normal PT tests after 12 h at refrigerated and frozen storage conditions, the differences would not change the clinical interpretation of the results. On the other hand, samples stored refrigerated or at RT showed significant differences for aPTT at 24 h. These differences would change clinical interpretation, especially for samples with normal or near normal aPTT times. Interestingly, aPTT was significantly higher for samples stored frozen when compared to refrigerated and RT conditions at 6 h. Similar patterns were also observed on ten whole blood samples with normal PT and aPTT values. In conclusion, either plasma or whole blood samples can be accepted for PT testing up to 24 h and for aPTT testing up to 12 h only, when transported either at RT or at 4 degrees C.

Symptomatic human rotavirus subgroups, serotypes & electropherotypes in Hyderabad, India

A total of 352 stool specimens obtained from children under 2 yr of age with acute diarrhoea, between January 1998 and March 1999, were screened for the presence of rotavirus by RNA-PAGE. Symptomatic human rotaviruses were detected in 57 of 352 (16.19%) specimens by RNA-PAGE. These 57 samples were tested for rotavirus double stranded RNA pattern and among these, 46 samples were tested for subgroup and serotype specificities. Among the 46 strains tested, 29 strains were found to be subgroup II and remaining 17 strains were subgroup I, indicating that subgroup II strains are more predominant than subgroup I strains. Subgroup I and II strains were circulating concurrently throughout the study period. Seventeen strains with 'short' RNA pattern and subgroup I specificity could not be assigned as serotype 2 strains as they exhibited cross-reactivity to MAbs specific for more than one serotype. Of the 29 subgroup II strains with 'long' RNA pattern, 16 (55.17%) were serotype 1, 8 (27.58%) were serotype 4. Five (17.24%) showed dual reactivity to serotypes 1 and 3. Our results indicated that serotype 1 and G2-like strains are predominant in Hyderabad. None of the virus strains showed an unusual RNA pattern.

Induction of tissue factor expression in whole blood: lack of evidence for the presence of tissue factor expression in granulocytes

The present investigation was undertaken to explore the effect of platelets, tumor necrosis factor (TNF) and phorbel ester [phorbol 12-myristate 13-acetate (PMA)] on lipopolysaccharide (LPS)-induced tissue factor (TF) activity and TF antigen by using Western blot and ELISA-techniques. LPS was found to induce correlating levels of TF antigen and the activity in monocytes. TNF and PMA, when used alone, failed to induce TF activity and the antigen in monocytes, but enhanced the LPS-induced TF activity and the antigen by 2 to 3-fold. Addition of platelet rich plasma to isolated blood cells enhanced the LPS-induced TF activity but not the antigen levels in monocytes. In contrast to whole platelets, platelet lysates enhanced both LPS-induced TF activity and the antigen. Granulocytes isolated from heparinized plasma incubated for 2 or 24 h with LPS alone or together with PMA, failed to generate TF antigen or the activity. Although granulocyte preparations isolated from whole blood that was incubated for 24 h with LPS and PMA apparently possessed a significant amount of TF activity and the antigen, this could be accounted for by trace levels of contaminating monocytes. Upregulation of LPS-induced TF activity but not the antigen by platelets in the presence of granulocytes suggests that the increased TF activity could be the result of PS enrichment of monocytes by fusion or platelets with activated monocytes.

Factor VIIa and thrombin induce the expression of Cyr61 and connective tissue growth factor, extracellular matrix signaling proteins that could act as possible downstream mediators in factor VIIa x tissue factor-induced signal transduction

Extracellular interactions of plasma clotting factor VIIa (FVIIa) with tissue factor (TF) on cell surfaces trigger the intracellular signaling events. At present, it is unclear how these signals influence phenotype. To elucidate this, we have used cDNA microarray technology to examine changes in transcriptional program in human fibroblasts in response to exposure to FVIIa. cDNA microarrays revealed that FVIIa binding to TF up-regulated the expression of Cyr61 and CTGF (connective tissue growth factor), the genes that encode extracellular matrix signaling proteins Cyr61 and CTGF, respectively. Northern blot analysis confirmed that FVIIa binding to TF markedly increased the expression of Cyr61 and CTGF in a time- and dose-dependent manner. FVIIa catalytic activity is required for the gene induction. In addition to FVIIa, thrombin also induced the expression of Cyr61 and CTGF. Hirudin abolished the thrombin-induced expression of these mRNAs but not the FVIIa-induced expression. FVIIa-induced expression of Cyr61 appears not to involve the currently known protease-activated receptors (PARs), whereas thrombin-induced expression involves the activation of PAR1 and possibly an additional PAR. Various intracellular signaling pathway inhibitors exhibited different inhibitory pattern on FVIIa and thrombin-induced up-regulation of Cyr61. Cyr61 and CTGF could act as downstream mediators of FVIIa x TF in affecting various biological processes.

Active site-blocked activated factor VII as an effective antithrombotic agent: mechanism of action

The tissue factor (TF) coagulation pathway is initiated when circulating factor (F)VII(a) encounters TF, a cell surface glycoprotein, as a result of vascular injury or pathological perturbation. TF-induced coagulation plays a primary role in hemostasis and also in the pathogenesis of various thrombotic disorders. Recent studies suggest that activation of the TF-pathway may also contribute to other pathophysiological processes by altering intracellular responses, either directly or via activated factor X (FXa) and thrombin generation. Therefore, suppression of the aberrant expression of TF/FVIIa on cell surfaces not only prevents thrombotic disorders but may also provide other protective effects. Recent ex-vivo and in-vivo experiments document the effectiveness of active site-blocked activated factor VII (FVIIai) in inhibiting TF-mediated injury. It is generally believed that FVIIai exerts its effects by limiting the formation of functional TF/FVIIa complexes by directly competing with plasma FVII(a) for limited available TF sites on cell surfaces. Although such competition can explain the effectiveness of FVIIai immediately after administration, it is not clear how it exerts its prolonged effects. In this manuscript, we summarize the use of FVIIai as an antithrombotic agent in various model systems and discuss potential mechanisms by which FVIIai may exert protective effects.

Exclusion of known protease-activated receptors in factor VIIa-induced signal transduction

The protease activity is mandatory for intracellular activities induced by coagulation factor VIIa (FVIIa), and in this way it resembles signal transduction induced by thrombin and trypsin caused by specific, proteolytic cleavage of protease activated receptors (PARs). The mechanism for FVIIa-induced signal transduction is, however, not known although a mechanism involving PAR cleavage has been deduced from studies of cytosolic Ca2+ release and p44/p42 mitogen activated protein kinase (MAPK) activation. In the present work we have examined the possibilities that i) FVIIa-induced signal transduction involves the activation of one of the four known PARs, or ii) exposure of cells to FVIIa releases a soluble ligand that is responsible for MAPK activation. For this purpose, we evaluated the effects of FVIIa, thrombin, FXa, trypsin and PAR agonist peptides on the Ca2+ release and MAPK activation in tissue factor-(TF) transfected baby hamster kidney (BHK[+TF]) cells and Madin-Darby canine kidney (MDCK) cells. FVIIa induced a significant MAPK signal in BHK(+TF) cells and in MDCK-I and -II cells whereas no MAPK activation was observed with thrombin, FXa or PAR agonist peptides. Thrombin, trypsin, PAR-1 and PAR-2 agonist peptides induced a prominent Ca2+ response in both cell types. In contrast the cells did not respond with a detectable Ca2+ signal when treated with FVIIa. These results suggest that the intracellular activity induced by FVIIa is distinctly different from that induced by trypsin, thrombin and FXa not involving any of the known PARs. Conditioned medium from BHK(+TF) cells treated with FVIIa failed to induce a MAPK response in untreated BHK(+TF) cells when FVIIa was removed by immunoadsorption from the medium prior to its transfer to the untreated BHK(+TF) cells. Although it is not possible entirely to exclude a transient response close to the cell surface, the data suggest that the intracellular response was not induced by an autocrine release of a soluble mediator to the medium.

Reversible regulation of tissue factor-induced coagulation by glycosyl phosphatidylinositol-anchored tissue factor pathway inhibitor

Endothelial and tumor cells synthesize tissue factor pathway inhibitor (TFPI-1), which regulates tissue factor (TF) function by TF. VIIa. Xa. TFPI-1 quaternary complex formation (where VIIa and Xa are coagulation factors) and by translocation of these complexes into glycosphingolipid-rich microdomains of the cell membrane. Recombinant TFPI-1 added exogenously to cells is targeted to a degradation pathway. This study analyzes whether quaternary complex formation with endogenous TFPI-1 results also in internalization and degradation. We demonstrate that endogenous TFPI-1 and recombinant TFPI-1 differ in their distribution on the cell surface. Recombinant TFPI-1 is found in phospholipid- and glycosphingolipid-rich membrane domains, whereas endogenous TFPI-1 preferentially localizes to glycosphingolipid-rich microdomains. On quaternary complex formation, endogenous TFPI-1 remains protease sensitive and accessible for antibodies on intact cells, demonstrating that it is not appreciably internalized. Rather, regulation of TF by TFPI-1 is restored within 12 hours, consistent with dissociation of quaternary complexes on the cell surface. Endogenous TFPI-1 can be released from the cell surface by phospholipase treatment, indicating that TFPI-1 either is a glycosyl phosphatidylinositol (GPI)-anchored protein or binds to a GPI-linked receptor. We demonstrate that expression of a recombinant GPI-anchored form of TFPI-1 targets TF. VIIa complexes to glycosphingolipid-rich membrane fractions. Thus, GPI anchoring of TFPI-1 is sufficient for regulation of TF. VIIa complex function by a pathway of reversible inhibition rather than internalization and degradation.

Suppression of transcription factor Egr-1 by curcumin

The transcription factor early growth response-1 gene product (Egr-1) is a member of the family of immediate early response genes and regulates a number of pathophysiologically relevant genes in vasculature that are involved in growth, differentiation, immune response, wound healing, and blood clotting. In the present study, we investigated the effect of curcumin, a natural plant phenolic compound known to exhibit anticarcinogenic, antioxidant, and antiinflammatory properties, on Egr-1 expression in endothelial cells and fibroblasts. Gel mobility shift assays showed that pretreatment of endothelial cells and fibroblasts with curcumin suppressed phorbol 12-myristate 13-acetate and serum-induced Egr-1 binding activity to the consensus Egr-1 binding site and also to the Egr-1 binding site present in the promoter of tissue factor gene. Western blot analysis revealed that curcumin inhibited phorbol 12-myristate 13-acetate-induced de novo synthesis of Egr-1 protein in endothelial cells. Suppression of Egr-1 protein expression in curcumin-treated cells stemmed from the suppression of Egr-1 mRNA. Northern blot analysis showed that curcumin inhibited serum and phorbol 12-myristate 13-acetate induced expression of tissue factor and urokinase-type plasminogen activator receptor mRNA in fibroblasts. Cumulatively, the data show that curcumin suppresses the induction of transcription factor Egr-1 and thereby modulates the expression of Egr-1-regulated genes in endothelial cells and fibroblasts.

Discordant expression of tissue factor and its activity in polarized epithelial cells. Asymmetry in anionic phospholipid availability as a possible explanation

Recent studies have shown a discrepancy between the level of tissue factor (TF) expression and the level of TF procoagulant activity on the apical and basolateral surface domains of polarized epithelial cells. The present investigation was performed to elucidate possible reasons for the discordant expression of TF and its activity on the surface of polarized epithelial cells using a human intestinal epithelial cell line, Caco-2 and Madin-Darby canine kidney epithelial cells, type II (MDCK-II). Functional activity of coagulation factor VIIa (VIIa) in complex with TF was 6- to 7-fold higher on the apical than the basolateral surface in polarized Caco-2 cells. In contrast, no significant difference was found in the formation of TF/VIIa complexes between the apical and basolateral surface. Confocal microscopy of Caco-2 cells showed TF expression on both the apical and the basolateral surface domains. Studies with MDCK-II cells showed that the specific functional activity of TF expressed on the apical cell surface was 5-fold higher than on the basolateral surface. To test whether differential expression of TF pathway inhibitor (TFPI) on the apical and basolateral surface could account for differences in TF/VIIa functional activity, we measured cell-surface-bound TFPI activity in Caco-2 cells. Small but similar amounts of TFPI were found on both surfaces. Further, addition of inhibitory anti-TFPI antibodies induced a similar enhancement of TF/VIIa activity on both surface domains. Because the availability of anionic phospholipids on the outer leaflet of the cell membrane could regulate TF/VIIa functional activity, we measured the distribution of anionic phospholipids on the apical and basolateral surface by annexin V binding and thrombin generation. The results showed that the anionic phospholipid content on the basolateral surface, compared with the apical surface, was 3- to 4-fold lower. Mild acid treatment of polarized Caco-2 cells, which markedly increased the anionic phospholipid content on the basolateral surface membrane, increased the TF/VIIa activity on the basolateral surface without affecting the number of TF/VIIa complexes formed on the surface. Overall, our data suggest that an uneven expression of TF/VIIa activity between the apical and basolateral surface of polarized epithelial cells is caused by differences in anionic phospholipid content between the two surface domains and not from a polar distribution of TFPI.

Factor VIIa-induced p44/42 mitogen-activated protein kinase activation requires the proteolytic activity of factor VIIa and is independent of the tissue factor cytoplasmic domain

Signal transduction induced by activated factor VII (FVIIa) was studied with baby hamster kidney (BHK) cells transfected with human tissue factor (TF). FVIIa induced phosphorylation of p44/42 mitogen-activated protein kinase (MAPK) in cells expressing TF, BHK(+TF), but not in wild-type BHK(-TF) cells. BHK(+TF) cells responded to FVIIa in a dose-dependent manner, with detectable phosphorylation above 10-20 nM FVIIa. BHK cells transfected with a cytoplasmic domain-deleted version of TF, (des248-263)TF, or a C245S substitution variant of TF also supported FVIIa-induced MAPK activation. Experiments with active site-inhibited FVIIa, thrombin, factor Xa, and hirudin confirmed that the catalytic activity of FVIIa was mandatory for p44/42 MAPK activation. Furthermore, a high concentration of FVIIa in complex with soluble TF induced p44/42 MAPK phosphorylation in BHK(-TF) cells. These data suggest that TF was not directly involved in FVIIa-induced p44/42 MAPK phosphorylation but rather served to localize the action of FVIIa to the cell surface, potentially to cleave a cell surface receptor. Desensitization experiments with sequential addition of proteases suggested that the p44/42 MAPK response induced by FVIIa was distinctly different from the thrombin response, possibly involving a novel member of the protease-activated receptor family.

Regulation of tissue factor pathway inhibitor expression in smooth muscle cells

Tissue factor pathway inhibitor (TFPI) is the primary physiological inhibitor that regulates tissue factor-induced blood coagulation. TFPI is thought to be synthesized, in vivo, primarily by microvascular endothelial cells. Little is known about how TFPI is regulated under pathophysiological conditions. In this study, we determined mechanisms by which TFPI expression is regulated by human pulmonary artery smooth muscle cells (PASMC), because these cells contribute to remodeling of the pulmonary vasculature in disease. PASMC in culture constitutively synthesize and secrete TFPI. Exposure of PASMC to phorbol myristate acetate, lipopolysaccharide, tumor necrosis factor alpha, thrombin, interleukin-1, and transforming growth factor-beta had no significant effect on expression of TFPI by PASMC. By contrast, treatment of PASMC with serum and basic fibroblast growth factor (bFGF)/heparin markedly upregulated the expression of TFPI activity and antigen. On Western blot analysis, a protein consistent with full-length TFPI (42 kD) was identified in the conditioned media of PASMC, and the levels of the protein were much higher in the conditioned media of serum and bFGF/heparin-treated cells. Northern blot analysis showed that PASMC constitutively express TFPI mRNA, and treatment of cells with serum and bFGF/heparin had a minimal effect on the steady-state levels of TFPI mRNA. Nuclear run-on analysis did not show a significant increase in the transcriptional rate of TFPI gene in PASMC treated with serum or bFGF/heparin. Cycloheximide, but not actinomycin-D, treatment inhibited the serum and bFGF/heparin-induced increase in TFPI activity in PASMC. In conclusion, our data demonstrate that PASMC constitutively synthesize and secrete TFPI and serum or bFGF upregulate its expression, suggesting that growth factors that can stimulate the vessel wall in vivo might locally regulate TFPI expression. Our study also suggests that control of TFPI expression by serum or bFGF occurs via translational rather than transcriptional regulation.

Effect of dexamethasone on lymphocyte subpopulations in premature infants with bronchopulmonary dysplasia

OBJECTIVE

This study was designed to determine the effect of dexamethasone treatment on peripheral blood lymphocyte counts and subpopulations in premature infants with bronchopulmonary dysplasia (BPD).

STUDY DESIGN

Peripheral blood lymphocyte subpopulations in 12 premature infants with BPD were analyzed before treatment with a 6-week course of dexamethasone (day 0), on days 3 and 10 of treatment, and 2 weeks after discontinuing dexamethasone therapy (day 56). Lymphocyte immunophenotypes were determined using direct two-color immunofluorescent staining followed by flow cytometry.

RESULTS

The percentage of lymphocytes was significantly lower on days 3 (17.55 +/- 2.55) and 10 (20 +/- 11.8) of dexamethasone therapy compared with before (30.36 +/- 6.41) or after treatment. The percentage of T cells was significantly lower on days 3 and 10 of dexamethasone therapy (mean +/- SEM; 58.09 +/- 1.93 and 60.09 +/- 2.47, respectively) compared with before (67.09 +/- 4.24) or after treatment. The absolute number of T cells was significantly lower on day 10 of therapy. The percentage of CD4+ cells was significantly lower on days 3 (38.91 +/- 2.49) and 10 (40.45 +/- 2.24) of therapy, and this decrease persisted after dexamethasone was stopped (36.73 +/- 3.41). The absolute number of CD4 cells was significantly lower on day 10 (1328 +/- 216) of therapy and reached a nadir on day 56 (1143 +/- 106). Similarly, the CD4/CD8 ratio was also significantly lower on days 3 and 10 of treatment (1.56 +/- 0.18 and 1.64 +/- 0.14, respectively) and reached a nadir on day 56 (1.04 +/- 0.13).

CONCLUSION

Dexamethasone significantly reduced the percentage and absolute number of lymphocytes, T cells, and CD4 cells, as well as the CD4/CD8 ratio. A reduction in CD4 cells and in the CD4/CD8 ratio persisted 2 weeks after dexamethasone therapy was stopped. In contrast, the absolute number of B cells increased transiently, and CD8 cells were unaffected by dexamethasone. This alteration in lymphocyte subpopulations may help account for the clinically beneficial anti-inflammatory effect of dexamethasone in the treatment of BPD complicated by respiratory failure. The dexamethasone-induced decrease in CD4 cells may also increase the susceptibility of these infants to infection.

Development of a urinary free cortisol assay using solid-phase extraction-capillary electrophoresis

In clinical practice, the measurement of urinary free cortisol (UFC) provides the most sensitive and specific diagnostic information for excess adrenal production of cortisol. The existing methodologies (RIA and HPLC) are time consuming, costly, involve tedious extractions, derivatizations and problems with non-specific interactions with cortisol metabolites in urine. In the present study, we describe the development of an SPE-CE method for the rapid analysis of UFC. UFC was concentrated using SPE C18 cartridges (3M Empore) under a vacuum and eluted with acetonitrile-SDS. The use of 10% acetone to wash cartridges before final elution with acetonitrile-SDS showed significant improvements in the free cortisol recovery. The complete extraction was accomplished in 10-15 min with a recovery of 89-94%. CE analysis was done on a Beckman P/ACE 5010 with detection at 254 nm using a neutral capillary. Detection limits of free cortisol in urine was improved to 10 microg/l with SPE compared to 500 microg/l without SPE. No interferences either from BSA or other urinary cortisol metabolites affected the free cortisol determinations. The results showed the feasibility of a rapid UFC detection with improved sample handling capacity.

Resveratrol, a polyphenolic compound found in wine, inhibits tissue factor expression in vascular cells : A possible mechanism for the cardiovascular benefits associated with moderate consumption of wine

A number of studies suggest that moderate consumption of red wine may be more effective than other alcoholic beverages in decreasing the risk of coronary heart disease mortality. The phytochemical resveratrol found in wine, derived from grapes, has been thought to be responsible for cardiovascular benefits associated with wine consumption because it was shown to have antioxidant and antiplatelet activities. In the present investigation, we examined the effect of resveratrol on induction of tissue factor (TF) expression in vascular cells that were exposed to pathophysiological stimuli. The data presented herein show that resveratrol, in a dose-dependent manner, inhibited the expression of TF in endothelial cells stimulated with a variety of agonists, including interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNFalpha) and lipopolysaccharide (LPS). A similar inhibition of TF induction was also seen in LPS stimulated monocytes that were pretreated with resveratrol before their stimulation with LPS. In addition, resveratrol was shown to inhibit the LPS-induced expression of TNFalpha mRNA in endothelial cells and of TNFalpha and IL-1beta mRNA in monocytes. Nuclear run-on analysis in endothelial cells showed that resveratrol inhibited TF expression at the level of transcription. However, resveratrol did not significantly alter the binding of the transcription factors c-Fos/c-Jun and c-Rel/p65, the transcription factors required for the induction of TF promoter in both endothelial cells and monocytes. Similarly, resveratrol had no significant effect on the binding of NF-kappaB in endothelial cells stimulated with IL-1beta, TNFalpha, and LPS. Overall, our data show that resveratrol could effectively suppress the aberrant expression of TF and cytokines in vascular cells, but it requires further investigation to understand how resveratrol exerts its inhibitory effect.

Tissue factor pathway inhibitor in tetracycline-induced pleuritis in rabbits

Pleural fibrin deposition that promotes loculation and fibrosis after pleural injury is initiated by tissue factor (TF). In this study, we sought to determine if tissue factor pathway inhibitor (TFPI), an inhibitor of the TF-factor VIIa complex, was likewise expressed in tetracycline (TCN)-induced pleural injury and, if so, whether TFPI was locally elaborated. Pleural fluid TFPI activity approximated that of plasma by 24 h and doubled by 3 days after intrapleural TCN. By contrast, pleural fluid coagulation factors VII and V remained below plasma concentrations at these intervals. Immunohistochemical studies demonstrated TF, TFPI and fibrin localized in pleural and subpleural tissues and within intrapleural adhesions. TFPI activity and mRNA were also elaborated by rabbit pleural mesothelial cells and lung fibroblasts. TFPI is locally expressed and pleural fluid TFPI exceeds plasma levels during TCN-induced pleural injury. Resident cells as well as extravasation likely contribute to intrapleural TFPI. TFPI expression temporally and anatomically approximates that of TF and may limit TF-induced fibrin deposition in evolving TCN-induced pleuritis.

Tissue factor on cells

Tissue factor (TF), a cell surface glycoprotein, serves as the cellular receptor for either activated or non-activated factor VII [FVII(a)] and it is the formation of TF-FVII(a) complexes on cell surfaces which triggers the coagulation cascade in vivo. TF procoagulant functional expression on cell surfaces can be regulated by at least three distinct major mechanisms: (1) transcriptional regulation of TF gene expression; (2) cell membrane alterations in cells expressing TF; and (3) neutralization of TF-activated factor VII (FVIIa) activity by plasma inhibitors. The TF gene, which is not normally expressed in vascular cell types, can be induced by several pathophysiological stimuli, particularly those elaborated upon in inflammation and cancer. However, some of the stimuli elaborated in these pathological processes, e.g. basic fibroblast growth factor, suppress the induced expression of TF in endothelium. Not all TF molecules expressed on cell surfaces are functional even though they have the ability to bind to FVII(a). The availability of anionic phospholipids on cell membranes in the vicinity of TF and the spatial localization of TF within the cell membrane influence the functional activity of TF. Once TF-FVII(a) complexes are assembled on cell surfaces, at least two plasma inhibitors, TF pathway inhibitor and antithrombin III play an important role in regulating the TF-FVII(a) functional activity by inhibiting the activation of factor VII bound to TF and by inhibiting the catalytic activity of TF-FVIIa complexes. The availability of heparan sulphate proteoglycans with anticoagulant activity on cell surfaces plays an important role in enhancing the activity of the inhibitors. This manuscript summarizes the mechanisms by which TF functional expression on cells is regulated with a particular emphasis on the recent findings of the authors and their collaborators.

Interaction of activated factor VII and active site-inhibited activated factor VII with tissue factor

The coagulation cascade is initiated by binding of plasma activated or non-activated factor VII [FVII(a)] to cell surface tissue factor (TF). TF-induced coagulation plays a primary role not only in haemostasis but also in the pathogenesis of various thrombotic disorders. Recent studies with animal model systems showed that the administration of active site-inhibited FVIIa (FVIIai) blocked TF-FVIIa-induced fibrin and thrombus formation. These data suggest that FVIIai competes with plasma FVII(a) for a limited number of TF sites expressed on cells either constitutively or induced after the perturbation. To obtain insights into the mechanism(s) by which FVIIai is effective in inhibiting TF-FVIIa induced coagulation in vivo, we compared the interaction of FVIIai and FVIIa with TF using a variety of competition assays and direct binding assays. The TF-FVIIa amidolytic activity competition assay showed that FVIIai bound with a threefold higher affinity than that of FVIIa to TF relipidated in phosphatidylcholine (PC) vesicles, whereas no significant differences were found between FVIIa and FVIIai binding to TF if it had been relipidated in mixed phospholipid vesicles containing PC and phosphatidylserine (PS). When FVIIa and FVIIai binding to TF was analysed in a FXa generation assay, we found that FVIIai bound to TF in PCPS vesicles with two- to fivefold higher affinity than that of FVIIa, whereas the affinity of FVIIai for TF in PC vesicles was seven- to 10-fold higher than that of FVIIa. Direct binding analysis to TF, immobilized on a sensor chip or on a cell surface, showed a faster association and a slower dissociation of FVIIai to TF compared with that of FVIIa. Equilibrium binding to cell surface TF showed that the affinity of FVIIai was fivefold higher than that of FVIIa to non-functional TF, whereas both FVIIa and FVIIai bound functional TF with the same high affinity. The enhanced affinity of FVIIai to TF, particularly to non-functional TF, would make FVIIai a valuable reagent to block TF-induced coagulation before it is triggered by cell injury or a pathological stimuli.

Inhibition of tissue factor gene activation in cultured endothelial cells by curcumin. Suppression of activation of transcription factors Egr-1, AP-1, and NF-kappa B

Binding of plasma factor VII(a) to tissue factor (TF) initiates the coagulation cascade. In health, TF is not expressed in endothelial cells. However, endothelial cells express TF in response to lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF alpha), and other biological stimuli. TF expression by endothelial cells is implicated in thrombotic disorders in patients with a variety of clinical disorders. In the present study, we demonstrate that curcumin (diferulolylmethane), a known anticarcinogenic and anti-inflammatory agent, inhibited phorbol 12-myristate 13-acetate (PMA), LPS, TNF alpha, and thrombin-induced TF activity and TF gene transcription in human endothelial cells. The present data show that curcumin prevented the activation of c-Rel/p65, which is essential for TF gene activation in endothelial cells, by impairing the proteolytic degradation inhibitor protein, I kappa B alpha. The data also show that curcumin downregulated AP-1 binding activity. The present studies are the first to demonstrate that PMA, but not LPS, TNF alpha, and thrombin, induced Egr-1 binding to the second serum-responsive region (SRR-2) of TF promoter and that curcumin inhibited the PMA-induced Egr-1 binding to SRR-2. Overall, the data suggest that the anticarcinogenic and anti-inflammatory properties of curcumin may be related to its ability to inhibit cellular gene expression regulated by transcription factors NF-kappa B, AP-1, and Egr-1.

Binding of factor VIIa to tissue factor induces alterations in gene expression in human fibroblast cells: up-regulation of poly(A) polymerase

Tissue factor (TF) is the cellular receptor for an activated form of clotting factor VII (VIIa) and the binding of factor VII(a) to TF initiates the coagulation cascade. Sequence and structural patterns extracted from a global alignment of TF confers homology with interferon receptors of the cytokine receptor super family. Several recent studies suggested that TF could function as a genuine signal transducing receptor. However, it is unknown which biological function(s) of cells are altered upon the ligand, VIIa, binding to TF. In the present study, we examined the effect of VIIa binding to cell surface TF on cellular gene expression in fibroblasts. Differential mRNA display PCR technique was used to identify transcriptional changes in fibroblasts upon VIIa binding to TF. The display showed that VIIa binding to TF either up or down-regulated several mRNA species. The differential expression of one such transcript, VIIa-induced up-regulation, was confirmed by Northern blot analysis. Isolation of a full-length cDNA corresponding to the differentially expressed transcript revealed that VIIa-up-regulated gene was poly(A) polymerase. Northern blot analysis of various carcinomas and normal human tissues revealed an over expression of PAP in cancer tissues. Enhanced expression of PAP upon VIIa binding to tumor cell TF may potentially play an important role in tumor metastasis.

Mechanisms of activity of lupus anticoagulants

Lupus anticoagulants comprise a heterogenous group of circulating immunoglobulins that are associated with an increased risk of thrombosis. It was believed earlier that these antibodies were directed against anionic phospholipids. Recent findings, however, establish that the autoantibodies in lupus anticoagulants are not directed against "native" anionic phospholipids but rather to modified phospholipids, lipid-protein adducts, and certain phospholipid binding proteins. Despite a marked increase in the number of citations in recent years on laboratory and clinical manifestations of lupus anticoagulants, the pathogenetic mechanisms involved remain unknown. This review focuses on antigen specificities of autoantibodies in lupus anticoagulants and the mechanisms by which these antibodies contribute to an increased thrombotic risk in patients with lupus anticoagulant.