Significantly Decreased Mortality in a Large Cohort of Coronavirus Disease 2019 (COVID-19) Patients Transfused Early with Convalescent Plasma Containing High-Titer Anti-Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike Protein IgG

Coronavirus disease 2019 (COVID-19) convalescent plasma has emerged as a promising therapy and has been granted Emergency Use Authorization by the US Food and Drug Administration for hospitalized COVID-19 patients. We recently reported results from interim analysis of a propensity score-matched study suggesting that early treatment of COVID-19 patients with convalescent plasma containing high-titer anti-spike protein receptor binding domain (RBD) IgG significantly decreases mortality. We herein present results from a 60-day follow-up of a cohort of 351 transfused hospitalized patients. Prospective determination of enzyme-linked immunosorbent assay anti-RBD IgG titer facilitated selection and transfusion of the highest titer units available. Retrospective analysis by the Ortho VITROS IgG assay revealed a median signal/cutoff ratio of 24.0 for transfused units, a value far exceeding the recent US Food and Drug Administration-required cutoff of 12.0 for designation of high-titer convalescent plasma. With respect to altering mortality, our analysis identified an optimal window of 44 hours after hospitalization for transfusing COVID-19 patients with high-titer convalescent plasma. In the aggregate, the analysis confirms and extends our previous preliminary finding that transfusion of COVID-19 patients soon after hospitalization with high-titer anti-spike protein RBD IgG present in convalescent plasma significantly reduces mortality.

Convalescent plasma anti-SARS-CoV-2 spike protein ectodomain and receptor-binding domain IgG correlate with virus neutralization

The newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) highlights the urgent need for assays that detect protective levels of neutralizing antibodies. We studied the relationship among anti-spike ectodomain (anti-ECD), anti-receptor-binding domain (anti-RBD) IgG titers, and SARS-CoV-2 virus neutralization (VN) titers generated by 2 in vitro assays using convalescent plasma samples from 68 patients with COVID-19. We report a strong positive correlation between both plasma anti-RBD and anti-ECD IgG titers and in vitro VN titers. The probability of a VN titer of ≥160, the FDA-recommended level for convalescent plasma used for COVID-19 treatment, was ≥80% when anti-RBD or anti-ECD titers were ≥1:1350. Of all donors, 37% lacked VN titers of ≥160. Dyspnea, hospitalization, and disease severity were significantly associated with higher VN titer. Frequent donation of convalescent plasma did not significantly decrease VN or IgG titers. Analysis of 2814 asymptomatic adults found 73 individuals with anti-ECD IgG titers of ≥1:50 and strong positive correlation with anti-RBD and VN titers. Fourteen of these individuals had VN titers of ≥1:160, and all of them had anti-RBD titers of ≥1:1350. We conclude that anti-RBD or anti-ECD IgG titers can serve as a surrogate for VN titers to identify suitable plasma donors. Plasma anti-RBD or anti-ECD titers of ≥1:1350 may provide critical information about protection against COVID-19 disease.

Treatment of Coronavirus Disease 2019 Patients with Convalescent Plasma Reveals a Signal of Significantly Decreased Mortality

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, has spread globally, and proven treatments are limited. Transfusion of convalescent plasma collected from donors who have recovered from COVID-19 is among many approaches being studied as potentially efficacious therapy. We are conducting a prospective, propensity score-matched study assessing the efficacy of COVID-19 convalescent plasma transfusion versus standard of care as treatment for severe and/or critical COVID-19. We present herein the results of an interim analysis of 316 patients enrolled at Houston Methodist hospitals from March 28 to July 6, 2020. Of the 316 transfused patients, 136 met a 28-day outcome and were matched to 251 non-transfused control COVID-19 patients. Matching criteria included age, sex, body mass index, comorbidities, and baseline ventilation requirement 48 hours from admission, and in a second matching analysis, ventilation status at day 0. Variability in the timing of transfusion relative to admission and titer of antibodies of plasma transfused allowed for analysis in specific matched cohorts. The analysis showed a significant reduction (P = 0.047) in mortality within 28 days, specifically in patients transfused within 72 hours of admission with plasma with an anti-spike protein receptor binding domain titer of ≥1:1350. These data suggest that treatment of COVID-19 with high anti-receptor binding domain IgG titer convalescent plasma is efficacious in early-disease patients.

Molecular Architecture of Early Dissemination and Massive Second Wave of the SARS-CoV-2 Virus in a Major Metropolitan Area

We sequenced the genomes of 5,085 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strains causing two coronavirus disease 2019 (COVID-19) disease waves in metropolitan Houston, TX, an ethnically diverse region with 7 million residents. The genomes were from viruses recovered in the earliest recognized phase of the pandemic in Houston and from viruses recovered in an ongoing massive second wave of infections. The virus was originally introduced into Houston many times independently. Virtually all strains in the second wave have a Gly614 amino acid replacement in the spike protein, a polymorphism that has been linked to increased transmission and infectivity. Patients infected with the Gly614 variant strains had significantly higher virus loads in the nasopharynx on initial diagnosis. We found little evidence of a significant relationship between virus genotype and altered virulence, stressing the linkage between disease severity, underlying medical conditions, and host genetics. Some regions of the spike protein-the primary target of global vaccine efforts-are replete with amino acid replacements, perhaps indicating the action of selection. We exploited the genomic data to generate defined single amino acid replacements in the receptor binding domain of spike protein that, importantly, produced decreased recognition by the neutralizing monoclonal antibody CR3022. Our report represents the first analysis of the molecular architecture of SARS-CoV-2 in two infection waves in a major metropolitan region. The findings will help us to understand the origin, composition, and trajectory of future infection waves and the potential effect of the host immune response and therapeutic maneuvers on SARS-CoV-2 evolution.IMPORTANCE There is concern about second and subsequent waves of COVID-19 caused by the SARS-CoV-2 coronavirus occurring in communities globally that had an initial disease wave. Metropolitan Houston, TX, with a population of 7 million, is experiencing a massive second disease wave that began in late May 2020. To understand SARS-CoV-2 molecular population genomic architecture and evolution and the relationship between virus genotypes and patient features, we sequenced the genomes of 5,085 SARS-CoV-2 strains from these two waves. Our report provides the first molecular characterization of SARS-CoV-2 strains causing two distinct COVID-19 disease waves.

Molecular Architecture of Early Dissemination and Massive Second Wave of the SARS-CoV-2 Virus in a Major Metropolitan Area

We sequenced the genomes of 5,085 SARS-CoV-2 strains causing two COVID-19 disease waves in metropolitan Houston, Texas, an ethnically diverse region with seven million residents. The genomes were from viruses recovered in the earliest recognized phase of the pandemic in Houston, and an ongoing massive second wave of infections. The virus was originally introduced into Houston many times independently. Virtually all strains in the second wave have a Gly614 amino acid replacement in the spike protein, a polymorphism that has been linked to increased transmission and infectivity. Patients infected with the Gly614 variant strains had significantly higher virus loads in the nasopharynx on initial diagnosis. We found little evidence of a significant relationship between virus genotypes and altered virulence, stressing the linkage between disease severity, underlying medical conditions, and host genetics. Some regions of the spike protein - the primary target of global vaccine efforts - are replete with amino acid replacements, perhaps indicating the action of selection. We exploited the genomic data to generate defined single amino acid replacements in the receptor binding domain of spike protein that, importantly, produced decreased recognition by the neutralizing monoclonal antibody CR30022. Our study is the first analysis of the molecular architecture of SARS-CoV-2 in two infection waves in a major metropolitan region. The findings will help us to understand the origin, composition, and trajectory of future infection waves, and the potential effect of the host immune response and therapeutic maneuvers on SARS-CoV-2 evolution.

Treatment of Coronavirus Disease 2019 (COVID-19) Patients with Convalescent Plasma

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, has spread globally, and no proven treatments are available. Convalescent plasma therapy has been used with varying degrees of success to treat severe microbial infections for >100 years. Patients (n = 25) with severe and/or life-threatening COVID-19 disease were enrolled at the Houston Methodist hospitals from March 28, 2020, to April 14, 2020. Patients were transfused with convalescent plasma, obtained from donors with confirmed severe acute respiratory syndrome coronavirus 2 infection who had recovered. The primary study outcome was safety, and the secondary outcome was clinical status at day 14 after transfusion. Clinical improvement was assessed on the basis of a modified World Health Organization six-point ordinal scale and laboratory parameters. Viral genome sequencing was performed on donor and recipient strains. At day 7 after transfusion with convalescent plasma, nine patients had at least a one-point improvement in clinical scale, and seven of those were discharged. By day 14 after transfusion, 19 (76%) patients had at least a one-point improvement in clinical status, and 11 were discharged. No adverse events as a result of plasma transfusion were observed. Whole genome sequencing data did not identify a strain genotype-disease severity correlation. The data indicate that administration of convalescent plasma is a safe treatment option for those with severe COVID-19 disease.

Relationship between Anti-Spike Protein Antibody Titers and SARS-CoV-2 In Vitro Virus Neutralization in Convalescent Plasma

Newly emerged pathogens such as SARS-CoV-2 highlight the urgent need for assays that detect levels of neutralizing antibodies that may be protective. We studied the relationship between anti-spike ectodomain (ECD) and anti-receptor binding domain (RBD) IgG titers, and SARS-CoV-2 virus neutralization (VN) titers generated by two different in vitro assays using convalescent plasma samples obtained from 68 COVID-19 patients, including 13 who donated plasma multiple times. Only 23% (16/68) of donors had been hospitalized. We also studied 16 samples from subjects found to have anti-spike protein IgG during surveillance screening of asymptomatic individuals. We report a strong positive correlation between both plasma anti-RBD and anti-ECD IgG titers, and in vitro VN titer. Anti-RBD plasma IgG correlated slightly better than anti-ECD IgG titer with VN titer. The probability of a VN titer ≥160 was 80% or greater with anti-RBD or anti-ECD titers of ≥1:1350. Thirty-seven percent (25/68) of convalescent plasma donors lacked VN titers ≥160, the FDA-recommended level for convalescent plasma used for COVID-19 treatment. Dyspnea, hospitalization, and disease severity were significantly associated with higher VN titer. Frequent donation of convalescent plasma did not significantly decrease either VN or IgG titers. Analysis of 2,814 asymptomatic adults found 27 individuals with anti-RBD or anti-ECD IgG titers of ≥1:1350, and evidence of VN ≥1:160. Taken together, we conclude that anti-RBD or anti-ECD IgG titers can serve as a surrogate for VN titers to identify suitable plasma donors. Plasma anti-RBD or anti-ECD titer of ≥1:1350 may provide critical information about protection against COVID-19 disease.

Treatment of COVID-19 Patients with Convalescent Plasma in Houston, Texas

BACKGROUND

COVID-19 disease, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread globally, and no proven treatments are available. Convalescent plasma therapy has been used with varying degrees of success to treat severe microbial infections for more than 100 years.

METHODS

Patients (n=25) with severe and/or life-threatening COVID-19 disease were enrolled at the Houston Methodist hospitals from March 28 to April 14, 2020. Patients were transfused with convalescent plasma obtained from donors with confirmed SARS-CoV-2 infection and had been symptom free for 14 days. The primary study outcome was safety, and the secondary outcome was clinical status at day 14 post-transfusion. Clinical improvement was assessed based on a modified World Health Organization 6-point ordinal scale and laboratory parameters. Viral genome sequencing was performed on donor and recipient strains.

RESULTS

At baseline, all patients were receiving supportive care, including anti-inflammatory and anti-viral treatments, and all patients were on oxygen support. At day 7 post-transfusion with convalescent plasma, nine patients had at least a 1-point improvement in clinical scale, and seven of those were discharged. By day 14 post-transfusion, 19 (76%) patients had at least a 1-point improvement in clinical status and 11 were discharged. No adverse events as a result of plasma transfusion were observed. The whole genome sequencing data did not identify a strain genotype-disease severity correlation.

CONCLUSIONS

The data indicate that administration of convalescent plasma is a safe treatment option for those with severe COVID-19 disease. Randomized, controlled trials are needed to determine its efficacy.

A Simulation Course Focusing on Forensic Evidence Collection Improves Pediatric Knowledge and Standardizes Curriculum for Child Abuse

OBJECTIVES

Our hypothesis was that pediatric residents and medical students who participated in a structured forensic evidence collection course would have improved knowledge of prepubertal evidence collection practices and pubertal genital anatomy.

METHODS

The course curriculum included a forensic evidence collection video created by the sexual assault nurse examiner directors. After watching the video, the participants simulated forensic evidence collection using forensic evidence collection kits and chain of evidence protocols in a hybrid simulation setting under the supervision of a pediatric sexual assault nurse examiner. The participants completed a multiple-choice test and a fill-in-the-blank anatomical diagram test before and after the course.

RESULTS

Of an eligible 48 participants, 42 completed the course; therefore, our participant response rate was 87.5%. There was significant improvement in knowledge, with an average pretest score of 62% ± 20% and the average posttest score of 86% ± 9% (P < 0.001). Qualitative evaluations were overwhelmingly positive, with consistent scoring of 6/6 in a 6-point agree scale. Learning themes, which emerged from open-ended questions on the evaluations, included knowledge gained on evidence collection processes (n = 26), how to appropriately interact with abused patients (n = 8), hands-on nature of the experience and the benefits of walking through the examination (n = 7), and pubertal genital anatomy knowledge (n = 3). Participants suggested that more instruction on anatomy would be helpful.

CONCLUSIONS

We found that pediatric residents' and medical students' knowledge of pediatric sexual abuse may be improved with a short simulation course focusing on forensic evidence collection.

The Prevalence and Role of Hemoglobin Variants in Biometric Screening of a Multiethnic Population: One Large Health System's Experience

OBJECTIVES

To characterize and quantitate hemoglobin (Hb) variants discovered during biometric hemoglobin A1c (HbA1c) analyses in a large multiethnic population with a focus on the effect of variants on testing method and results.

METHODS

In total, 13,913 individuals had their HbA1c measured via ion-exchange high-performance liquid chromatography. Samples that had a variant Hb detected or HbF fraction more than 25% underwent variant Hb characterization and confirmation by gel electrophoresis. RBC indices were also evaluated for possible concomitant thalassemia.

RESULTS

Of the 13,913 individuals evaluated, 524 (3.77%) had an Hb variant. The prevalence of each variant was as follows: HbS trait (n = 396, 2.85%), HbSS disease (n = 4, 0.03%), HbC trait (n = 85, 0.61%), HbCC disease (n = 2, 0.01%), HbSC disease (n = 5, 0.04%), HbE trait (n = 18, 0.13%), HbD or G trait (n = 9, 0.06%), HbS β-thalassemia + disease (n = 1, 0.01%), hereditary persistence of HbF (n = 2, 0.01%), and HbMontgomery trait (n = 1, 0.01%). Concomitant α-thalassemia was detected in 20 (3.82%) of the 524 individuals with an Hb variant.

CONCLUSIONS

This study represents one of the largest epidemiologic investigations into the prevalence of Hb variants in a North American metropolitan, multiethnic workforce and their dependents and reinforces the importance of method selection in populations with Hb variants.

The Presence of Anti-HLA Donor-Specific Antibodies in Lung Allograft Recipients Does Not Correlate With C4d Immunofluorescence in Transbronchial Biopsy Specimens

Context.—C4d immunofluorescence (IF) is a surrogate for development of donor-specific antibodies (DSAs) against human leukocyte antigen (HLA) class I and II antigens in kidney and heart biopsy specimens for monitoring of antibody-mediated (humoral) allograft rejection (AMR). Use of C4d IF in monitoring of lung allografts has shown conflicting results.

Objective.—To determine if C4d IF can be used as a reliable marker for AMR and if it correlates with the presence of DSAs and histologic findings on biopsy.

Design.—All transbronchial biopsies in lung allograft recipients, performed at our institution in a 3-year period, were reviewed. A cohort of 92 patients with 110 corresponding biopsies met the inclusion criteria of (1) having a resulted DSA within 2 weeks of biopsy and (2) having C4d immunofluorescence studies performed and confirmed.

Results.—Twenty-nine patients (31.5%) were positive for DSAs and 63 patients (68.5%) did not develop DSAs. Positive C4d capillary IF was seen in 18 of 110 total biopsy specimens (16.4%). Eight of these biopsy samples were from patients positive for DSAs and 10 were from patients negative for DSAs. The correlation coefficient between the presence of DSAs and C4d IF was 0.1628 (P = .09).

Conclusions.—A significant proportion of DSA-positive patients had negative C4d IF results and frequently have no histologic changes on biopsy specimens. DSA-negative patients can be positive for C4d and may show the same histologic changes as reported for DSA-positive patients. Diagnosis of AMR in lung may require a collaborative approach combining clinical data, DSA status, and histology.

Detection of the JAK2(V617F) mutation in myeloproliferative disorders by melting curve analysis using the LightCycler system

CONTEXT

A specific mutation, JAK2(V617F), was recently recognized as having diagnostic value for myeloproliferative disorders. No practical assay is currently available for routine use in a clinical laboratory.

OBJECTIVE

We report the development of a real-time polymerase chain reaction melting curve analysis assay that is appropriate for molecular diagnostics testing.

DESIGN

Specific primers and fluorescence resonance energy transfer probes were designed, and patients with a previously diagnosed myeloproliferative disorder, de novo acute myeloid leukemia, or reactive condition were selected. The DNA was extracted from fresh and archived peripheral blood and bone marrow specimens, and real-time polymerase chain reaction melting curve analysis was performed on the LightCycler platform (Roche Applied Science, Indianapolis, Ind).

RESULTS

The JAK2 region was successfully amplified, and wild-type amplicons were reproducibly discriminated from JAK2(V617F) amplicons. Titration studies using homozygous wild-type and mutant cell lines showed the relative areas under a melting curve were proportional to allele proportion, and the assay reliably detected one mutant in 20 total cells. JAK2(V617F) was identified in patients previously diagnosed with a myeloproliferative disorder or acute myeloid leukemia transformed from myeloproliferative disorder, whereas a wild-type genotype was identified in patients with reactive conditions or de novo acute myeloid leukemia.

CONCLUSIONS

These findings demonstrate the suitability of this assay for identifying JAK2(V617F) in a clinical laboratory setting. Furthermore, the semiquantitative detection of JAK2(V617F) in archived specimens provides a new tool for studying the prognostic significance of this mutation.

Herbal remedies: effects on clinical laboratory tests

CONTEXT

Complementary and alternative medicine (herbal medicines) can affect laboratory test results by several mechanisms.

OBJECTIVE

In this review, published reports on effects of herbal remedies on abnormal laboratory test results are summarized and commented on.

DATA SOURCES

All published reports between 1980 and 2005 with the key words herbal remedies or alternative medicine and clinical laboratory test, clinical chemistry test, or drug-herb interaction were searched through Medline. The authors' own publications were also included. Important results were then synthesized.

DATA SYNTHESIS

Falsely elevated or falsely lowered digoxin levels may be encountered in a patient taking digoxin and the Chinese medicine Chan Su or Dan Shen, owing to direct interference of a component of Chinese medicine with the antibody used in an immunoassay. St John's wort, a popular herbal antidepressant, increases clearance of many drugs, and abnormally low cyclosporine, digoxin, theophylline, or protease inhibitor concentrations may be observed in a patient taking any of these drugs in combination with St John's wort. Abnormal laboratory results may also be encountered owing to altered pathophysiology. Kava-kava, chaparral, and germander cause liver toxicity, and elevated alanine aminotransferase, aspartate aminotransferase, and bilirubin concentrations may be observed in a healthy individual taking such herbal products. An herbal product may be contaminated with a Western drug, and an unexpected drug level (such as phenytoin in a patient who never took phenytoin but took a Chinese herb) may confuse the laboratory staff and the clinician.

CONCLUSIONS

Use of alternative medicines may significantly alter laboratory results, and communication among pathologists, clinical laboratory scientists, and physicians providing care to the patient is important in interpreting these results.

SWOT Analysis for Molecular Diagnostics: Strengths, Weaknesses, Opportunities, and Threats

Daniel Farkas, PhD, and David Bernard, MD, PhD, discuss strengths, weaknesses, opportunities, and threats associated with molecular diagnostics.

Management of drug-induced hyperthermia

PURPOSE OF REVIEW

To review the current literature describing drug-induced hyperthermia and its treatment. Specifically, five syndromes will be discussed: malignant hyperthermia, neuroleptic malignant syndrome, anticholinergic poisoning, sympathomimetic poisoning, and serotonin syndrome.

RECENT FINDINGS

The most recent findings in the literature are the recognition of previously undescribed drugs or drug combinations that have lead to hyperthermia. Recent literature also attests to the potential morbidity and mortality of drug-induced hyperthermia.

SUMMARY

Although the recognition of causative agents is increasing, the treatment of drug-induced hyperthermia remains unchanged and continues to be primarily supportive.

Hormone sensitive lipase mRNA in both monocyte and macrophage forms of the human THP-1 cell line

The identity of the neutral cholesteryl ester hydrolase (CEH) in human monocyte/macrophages is uncertain. Prior studies indicate that hormone sensitive lipase (HSL) is a major CEH in mouse macrophages, and that HSL mRNA is present in human THP-1 monocytes. In the present study, HSL mRNA expression was examined in THP-1 cells as a function of differentiation status and cholesterol enrichment. By RT-PCR with primer pairs that span exon boundaries, HSL mRNA was demonstrated in THP-1 monocytes and phorbol-ester differentiated THP-1 macrophages. cDNA identities were confirmed by sequencing. By Northern blotting, with HSL cDNA as probe, THP-1 monocytes were found to contain HSL mRNA of approximately 3 and 3.9 kb. In THP-1 macrophages, the 3 kb mRNA was greatly diminished, while the level of the 3.9 kb mRNA was maintained. mRNA of approximately 3 and 3.9 kb are those expected of the 86-kDa (adipocyte) and 117-kDa (testicular) HSL isoforms, respectively. The presence of the testicular isoform mRNA was confirmed in THP-1 cells by amplification and sequencing of an isoform-specific cDNA. Additionally, Northern-blot comparisons showed that the 3 and 3.9 kb mRNA in THP-1 comigrated with the HSL mRNA in 3T3-L1 adipocytes and rat testis, respectively. The level of the 3.9 kb mRNA did not vary greatly with cholesterol enrichment. Thus, the HSL gene is transcribed in THP-1 cells both before and after differentiation into macrophages; after differentiation, the predominant mRNA is that for the 117-kDa isoform. This isoform is a CEH, and may mediate some CE turnover in THP-1 cells.

FGF receptor availability regulates skeletal myogenesis

Fibroblast growth factors (FGFs) and their receptors are critical participants in embryonic development, including the genesis of skeletal, cardiac, and smooth muscle. FGF signaling is mediated through interactions between multiple FGF ligands and transmembrane tyrosine kinase receptors, resulting in activation of a number of signal transduction pathways. Skeletal myocytes express FGF ligands and receptors in a coordinated fashion, suggesting that these molecules participate in autocrine signaling in the myocyte. Endogenously produced FGF has been shown to inhibit myogenesis, but the role of FGF receptor availability in directing myocyte proliferation and differentiation has not been established. To determine the contribution of receptor availability to the regulation of myogenesis, receptor availability was either increased by expressing a full-length FGF receptor-1 or decreased by expressing a truncated FGF receptor-1 in cultured skeletal myocytes. Constitutive expression of a full-length FGF receptor-1 increased myocyte proliferation and delayed differentiation. Conversely, a reduction in functional FGF receptor signaling by expression of a truncated FGF receptor-1 decreased proliferation and enhanced differentiation of myocytes. These data demonstrate that FGF receptor availability plays a critical regulatory role in skeletal myogenesis.

Is oral albuterol effective for acute cough in non-asthmatic children?

Fifty-nine non-asthmatic children with acute cough were randomized to receive oral albuterol or placebo for 7 d. There was a similar, rapid rate of resolution of acute cough for the two groups, but more shaking or trembling in those treated with albuterol (5/30 vs 0/29; p = 0.05). In ambulatory children with acute cough who have no history of asthma and a normal chest examination, oral albuterol does not reduce the frequency or duration of cough.

Cholesteryl ester hydrolysis in J774 macrophages occurs in the cytoplasm and lysosomes

The relationship of cholesteryl ester hydrolysis to the physical state of the cholesteryl ester in J774 murine macrophages was explored in cells induced to store cholesteryl esters either in anisotropic (ordered) inclusions or isotropic (liquid) inclusions. In contrast to other cell systems, the rate of cholesteryl ester hydrolysis was faster in cells containing anisotropic inclusions than in cells containing isotropic inclusions. Two contributing factors were identified. Kinetic analyses of the rates of hydrolysis are consistent with a substrate competition by co-deposited triglyceride in cells with isotropic inclusions. In addition, hydrolysis of cholesteryl esters in cells with anisotropic droplets is mediated by both cytoplasmic and lysosomal lipolytic enzymes, as shown by using the lysosomotropic agent, chloroquine, and an inhibitor of neutral cholesteryl ester hydrolase, umbelliferyl diethylphosphate. In cells containing anisotropic inclusions, hydrolysis was partially inhibited by incubation in media containing either chloroquine or umbelliferyl diethylphosphate. Together, chloroquine and umbelliferyl diethylphosphate completely inhibited hydrolysis. However, when cells containing isotropic inclusions were incubated with umbelliferyl diethylphosphate, cholesteryl ester hydrolysis was completely inhibited, but chloroquine had no effect. Transmission electron microscopy demonstrated a primarily lysosomal location for lipid droplets in cells with anisotropic droplets and both non-lysosomal and lysosomal populations of lipid droplets in cells with isotropic droplets. These results support the conclusion that there is a lysosomal component to the hydrolysis of stored cholesteryl esters in foam cells.

Monitoring heparin therapy: APTT results from partial- vs full-draw tubes

Results of the activated partial thromboplastin time (APTT) test can be influenced by biologic, preanalytic, and analytic variables. When a patient is being treated with unfractionated heparin, the correct interpretation of the APTT test result is essential. Laboratories should evaluate all variables influencing this result, particularly when determining the "therapeutic" range for heparin treatment. This study compared the APTT results assayed on specimens drawn into 2 different types of evacuated blood collection tubes. A statistically significant difference was seen in the results when the APTT was outside the reference interval, including results in the therapeutic range for unfractionated heparin. When the therapeutic range is determined by the laboratory, the evacuated blood collection tube system must be standardized.

Nighttime dosing assures postdistribution sampling for therapeutic drug monitoring of digoxin

To study the appropriateness of phlebotomy for digoxin therapeutic drug monitoring (TDM) in outpatients, we conducted a retrospective chart review, a computer search of all previous TDM testing, and a questionnaire of all outpatients (n = 86) who had serum digoxin determinations between April 10 and April 28, 1992 (585 tests). In patients who took digoxin at the same time daily (40 patients, 300 tests), 52% of tests were performed on inappropriate samples drawn within 6 h of the last dose. No patient who took digoxin after 1700 had inappropriate tests. Phlebotomy for serum digoxin determinations before distribution of digoxin is complete is a common problem in outpatients, leading to clinically uninterpretable test results. Postdistribution sampling can be assured by nighttime dosing, and this recommendation has been implemented at our hospital.

Nighttime dosing assures postdistribution sampling for therapeutic drug monitoring of digoxin

To study the appropriateness of phlebotomy for digoxin therapeutic drug monitoring (TDM) in outpatients, we conducted a retrospective chart review, a computer search of all previous TDM testing, and a questionnaire of all outpatients (n = 86) who had serum digoxin determinations between April 10 and April 28, 1992 (585 tests). In patients who took digoxin at the same time daily (40 patients, 300 tests), 52% of tests were performed on inappropriate samples drawn within 6 h of the last dose. No patient who took digoxin after 1700 had inappropriate tests. Phlebotomy for serum digoxin determinations before distribution of digoxin is complete is a common problem in outpatients, leading to clinically uninterpretable test results. Postdistribution sampling can be assured by nighttime dosing, and this recommendation has been implemented at our hospital.

cAMP stimulates cholesteryl ester clearance to high density lipoproteins in J7774 macrophages

The regulation by cAMP of cholesteryl ester hydrolysis and net depletion of cellular cholesteryl ester (cholesteryl ester clearance) in J774 murine macrophages was explored. Using Sandoz 58035 to selectively inhibit acyl CoA:cholesterol acyltransferase, we showed that the absolute rate of cholesteryl ester hydrolysis was stimulated 2-fold in J774 cells by the cAMP analogues 8-(4-chlorophenylthio)adenosine 3':5'-cyclic monophosphate and dibutyryl-cAMP. The rate of hydrolysis was also stimulated by prostaglandin E1, by cholera toxin, and by a mixture of forskolin and isobutylmethylxanthine, but was not affected by epinephrine or dibutyryl-cGMP. These data demonstrate that cholesteryl ester hydrolysis in J774 cells can be stimulated by cAMP-dependent protein kinase. Cholesteryl ester clearance from J774 cells was achieved upon incubation with high density lipoproteins (HDL) plus CPT-cAMP but not with HDL alone. HDL-mediated cholesteryl ester clearance was dependent on the concentration of both HDL and CPT-cAMP. The data suggest that the defect responsible for the lack of HDL-mediated cholesteryl ester clearance in J774 cells involves a failure to modulate cAMP levels.

Inhibitors of neutral cholesteryl ester hydrolase

p-Nitrophenyl N-butyl, N-octyl, and N-dodecyl carbamates and a newly synthesized diethyl phosphate compound were studied as potential inhibitors of the cholesteryl ester hydrolases of Fu5AH rat hepatoma cells. Whole homogenates of Fu5AH cells were used as an enzyme source for the assay of cholesteryl ester hydrolase activity. All four compounds led to marked inhibition (70-80%) of neutral cholesteryl ester hydrolase activity (assayed at pH 7) at concentrations where the activity of acid cholesteryl ester hydrolase (assayed at pH 4) was unaffected. Cholesteryl ester hydrolysis was also evaluated in intact cultured cells induced to accumulate cholesteryl esters in cytoplasmic lipid droplets by exposure to cholesterol-rich phospholipid dispersions. Hydrolysis was then assessed during subsequent incubations in the presence of an inhibitor of cholesterol esterification. All compounds caused significant inhibition of cholesterol ester hydrolysis with the diethyl phosphate being the most effective. At a concentration that caused greater than 90% inhibition of the hydrolysis of cytoplasmic cholesteryl esters, the compound had only a minimal effect on lysosomal hydrolysis of cholesteryl esters. These results suggest that diethyl phosphates and N-alkylcarbamates may be of value in future studies on the substrate specificities, regulation, and physiological role(s) of cholesteryl ester hydrolases.

Potential problems in the use of commercial preparations of radiolabeled cholesterol

Through a series of biological and analytical procedures, we demonstrate that a compound purchased from a commercial supplier as [7-3H]cholesterol was not cholesterol. In mouse peritoneal macrophages, this compound was metabolized differently than other radiolabeled cholesterol preparations and was accumulated in the steryl ester pool. In contrast, Fu5AH rat hepatoma cells did not discriminate this compound from cholesterol. Further analysis of the anomalous [7-3H]cholesterol by TLC after cholesterol oxidase treatment and by HPLC indicated that this radiochemical was less polar than cholesterol standard and other radiolabeled cholesterol preparations tested. Mass spectrometry analysis disclosed that the chemical has a similar fragmentation pattern and the same molecular weight (386) as cholesterol.

Influence of high density lipoprotein on esterified cholesterol stores in macrophages and hepatoma cells

The ability of high density lipoproteins (HDL) to induce the clearance of cholesteryl esters from cultured cells has been explored. Studies using the J774 mouse macrophage cell line showed that these cells are not stimulated to clear esterified cholesterol upon exposure to HDL. This was observed over a wide range of HDL concentrations (10 to 1000 micrograms/ml HDL protein), and the lack of stimulation was not influenced by a number of factors relating to the preparation of the HDL, such as HDL subfraction, varying extents of lecithin:cholesterol acyltransferase modification, or heparin-Sepharose chromatography to remove particles containing apo E. Neither the method of loading the cells with esterified cholesterol nor the physical state of the lipid droplets affected the inability of HDL to elicit esterified cholesterol clearance. In the presence of the acyl CoA:cholesterol acyltransferase inhibitor, Sandoz 58-035, where a high level of intracellular free cholesterol was generated, efflux of only a small fraction of the excess free cholesterol to HDL was observed. J774 cells were able to clear esterified cholesterol efficiently in the presence of cholesterol-free apolipoprotein HDL/phospholipid particles, indicating that the cells have the capacity to clear esterified cholesterol. Fu5AH hepatoma cells and P388.D1 mouse macrophage cells also failed to clear esterified cholesterol in response to HDL. In contrast, mouse peritoneal macrophages cleared esterified cholesterol efficiently to HDL, indicating that there are fundamental differences between mouse peritoneal macrophages and the other cells types studied in regard to cholesterol metabolism as influenced by HDL.