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David R Nelson

Publications and source records attributed to David R Nelson.

At least 55 records · Page 3Linked to original sources
PubMed2004

Gel shift analysis of the empA promoter region in Vibrio anguillarum.

BACKGROUND: The induction of metalloprotease encoded by empA in Vibrio anguillarum occurs at high cell density in salmon intestinal mucus. Previously we have shown that there are significant differences in empA expression in two strains of V. anguillarum, M93Sm and NB10. It is hypothesized that differences in empA regulation are due to differences in binding of regulatory elements. RESULTS: Two strains of V. anguillarum, M93Sm and NB10, were examined and compared for the presence of DNA regulatory proteins that bind to and control the empA promoter region. Gel mobility shift assays, using a digoxigenin (DIG)-labeled oligomer containing a lux box-like element and the promoter for empA, were done to demonstrate the presence of a DNA-binding protein. Protein extracts from NB10 cells incubated in Luria Bertani broth + 2% NaCl (LB20), nine salts solution + 200 microg/ml mucus (NSSM), 3M (marine minimal medium), or NSS resulted in a gel mobility shift. No gel mobility shift was seen when protein extracts from either LB20- or NSSM-grown M93Sm cells were mixed with the DIG-labeled empA oligomer. The azocasein assay detected protease activity in all incubation conditions for NB10 culture supernatants. In contrast, protease activity was detected in M93Sm culture supernatants only when incubated in NSSM. Since the luxR homologue in V. anguillarum, vanT, has been cloned, sequenced, and shown to be required for protease activity, we wanted to determine if vanT mutants of NB10 exhibit the same gel shift observed in the wild-type. Site-directed mutagenesis was used to create vanT mutants in V. anguillarum M93Sm and NB10 to test whether VanT is involved with the gel mobility shift. Both vanT mutants, M02 and NB02, did not produce protease activity in any conditions. However, protein extracts from NB02 incubated in each condition still exhibited a gel shift when mixed with the DIG-labeled empA oligomer. CONCLUSIONS: The data demonstrate that protein extracts of V. anguillarum NB10 cells contain a protein that binds to a 50 bp oligomer containing the empA promoter-lux box-like region. NB10 cells express empA during stationary phase in all growth conditions. The DNA binding protein is not present in M93Sm extracts. M93Sm cells express protease activity only when incubated at high cell density in fish gastrointestinal mucus. The gel shift observed with NB10 cells is not due to VanT binding. The data also suggest that the DNA binding protein is responsible for the less restrictive expression of empA in NB10 compared to M93Sm.

Bacterial Proteins↗
PubMed2004

Curvature-induced defect unbinding in toroidal geometries.

Toroidal templates such as vesicles with hexatic bond orientational order are discussed. The total energy including disclination charges is explicitly computed for hexatic order embedded in a toroidal geometry. Related results apply for tilt or nematic order on the torus in the one Frank constant approximation. Although there is no topological necessity for defects in the ground state, we find that excess disclination defects are nevertheless energetically favored for fat torii or moderate vesicle sizes. Some experimental consequences are discussed.

Journal Article↗
PubMed2004

Keratin 8 and 18 hyperphosphorylation is a marker of progression of human liver disease.

Keratin 8 and 18 (K8/18) phosphorylation plays a significant and site-specific role in regulating keratin filament organization, association with binding proteins, and modulation of cell cycle progression. Keratin hyperphosphorylation correlates with exposure to a variety of stresses in cultured cells and in mouse models of liver, pancreatic, and gallbladder injury, and it is found in association with mouse and human Mallory bodies. We asked whether K8/18 phosphorylation correlates with human liver disease progression by analyzing liver explants and biopsies of patients with chronic noncirrhotic hepatitis C virus (HCV) or cirrhosis. We also examined the effect of HCV therapy with interleukin-10 on keratin phosphorylation. Using site-specific antiphosphokeratin antibodies we found keratin hyperphosphorylation on most K8/18 sites in all cirrhotic liver explants tested and in most liver biopsies from patients with chronic HCV infection. Immunofluorescence staining of precirrhotic HCV livers showed focal keratin hyperphosphorylation and limited reorganization of keratin filament networks. In cirrhotic livers, keratin hyperphosphorylation occurred preferentially in hepatic nodule cells adjacent to bridging fibrosis and associated with increased stress kinase activation and apoptosis. Histological and serological improvement after interleukin-10 therapy was accompanied by normalization of keratin hyperphosphorylation on some sites in 7 of 10 patients. In conclusion, site-specific keratin phosphorylation in liver disease is a progression marker when increased and a likely regression marker when decreased.

Biomarkers↗
PubMed2004

An immunomodulatory role for CD4(+)CD25(+) regulatory T lymphocytes in hepatitis C virus infection.

The CD4(+)CD25(+) regulatory T lymphocytes have been implicated in suppressing T cell immune responses. Our aim was to characterize the frequency, phenotype, function, and specificity of CD4(+)CD25(+) T cells in hepatitis C virus (HCV) infection. Peripheral CD4(+)CD25(+) cells from recovered (n = 15), chronic infected (n = 30), and normal control (n = 15) subjects were analyzed ex vivo for quantitation, phenotype, and effect on HCV-specific interferon gamma production and proliferation. CD4(+)CD25(+) specificity was determined by intracellular cytokine staining for interleukin 10 (IL-10). A higher proportion of CD4(+)CD25(+) were found in chronic infection (mean, 3.02%) when compared with recovered (1.64%, P = .001) and normal controls (2.27%, P = .02). CD4(+)CD25(+) cells display CD45RO(high), CD45RA(low), CD28(high), CD62L(high), and CD95(high) phenotype. HCV-specific interferon gamma activity was enhanced in peripheral blood mononuclear cells depleted of CD4(+)CD25(+) and suppressed in peripheral blood mononuclear cells enriched with CD4(+)CD25(+). Depletion of CD4(+)CD25(+) cells also enhanced HCV-specific CD4(+) and CD8(+) T cell proliferation. Cytokine analysis suggested CD4(+)CD25(+) cells secrete transforming growth factor beta (TGF-beta(1)) and IL-10. The inhibitory role for TGF-beta(1) was confirmed by anti-TGF-beta(1). Transwell studies showed CD4(+)CD25(+) mediated suppression to be dose dependent and requiring cell contact. CD4(+)CD25(+) cells showed HCV-specificity through IL-10 production, with a frequency ranging from 1.9% to 5.3%. A positive correlation was detected between CD4(+)CD25(+) T cell frequency and HCV RNA titer, whereas an inverse relation was found with liver inflammatory activity. In conclusion, CD4(+)CD25(+) T lymphocytes constitute a highly differentiated population and appear to play a role in viral persistence by suppressing HCV-specific T cell responses in a cell-cell contact manner.

Antibodies↗
PubMed2004

Sustained viral response to interferon and ribavirin in liver transplant recipients with recurrent hepatitis C.

Recurrent hepatitis C infection is an important cause of progressive fibrosis, cirrhosis, and graft loss following orthotopic liver transplantation. Treatment for posttransplant recurrence of hepatitis C with interferon-based therapy is difficult but results in loss of detectable virus in up to 30% of patients. However, the durability of viral clearance and the associated histologic response in this setting is unknown. The aim of this study was to determine whether viral loss in response to antiviral therapy is durable and associated with improvement in liver histology. All liver transplant recipients who received interferon-based treatment for recurrent hepatitis C virus (HCV) at the University of Florida from 1991 to 2002 were included in this study. Patients who lost detectable HCV after treatment with interferon alone or in combination with ribavirin were followed to assess the durability of viral response and its impact on liver histology. One hundred nineteen transplant recipients were treated with interferon or combination therapy. Twenty-nine (20 men, 9 women; mean age, 54 yrs [range, 42-74 yrs]) lost detectable HCV RNA and remained virus negative for at least 6 months after discontinuing therapy (sustained viral response[SVR]). The mean follow-up after discontinuing therapy was 24.7 months (range, 6-70 mos). Our study cohort included one patient with SVR following interferon monotherapy and 28 patients with SVR following combination therapy with interferon plus ribavirin. All patients remained HCV RNA negative (assessed by polymerase chain reaction or branched-DNA assay) during follow-up of up to 5 years. Liver histology assessed 2 years after treatment showed less inflammation compared with before treatment in 50% and showed no change in 38%. By 3 to 5 years post-treatment (n = 15 recipients), inflammation was reduced in 60% and remained unchanged in 33%. Fibrosis stage at 2 years improved by > or = 1 stage in 27 %, remained unchanged in 38 %, and worsened in 35% despite viral clearance. At 3 to 5 years, the fibrosis stage had improved in 67%, remained unchanged in 13%, and worsened in 20%. Both grade of inflammation and fibrosis stage improved by 3 to 5 years posttreatment compared with baseline histology (p < 0.05). In conclusion, loss of HCV after treatment of recurrent chronic hepatitis C with interferon and ribavirin is durable, and the durability of the SVR is associated with improvement in hepatic inflammation and regression of fibrosis.

Adult↗
PubMed2004

Tobacco use before and after liver transplantation: a single center survey and implications for clinical practice and research.

Compared to alcohol use, and despite its potential health implications, tobacco use among candidates and recipients of orthotopic liver transplantation (OLT) has not been the focus of much attention. The purpose of the present study is to examine lifetime pre- and post-OLT prevalence rates of tobacco use, relapse rates after OLT, and comorbid use of alcohol and tobacco. Structured interviews were conducted to examine retrospective accounts of lifetime tobacco use in 202 OLT recipients. Sixty percent of OLT recipients reported a lifetime history of smoking, with 15% reporting smoking post-OLT. Of smokers who quit before OLT, 20% reported relapse to smoking post-OLT. Finally, 54% reported using both tobacco and alcohol pre-OLT. In light of these prevalence data and known health risks associated with tobacco use, there is an urgent need to examine the relationship between tobacco use and OLT outcomes. Furthermore, assessment of tobacco use and the provision of treatment for nicotine dependence should be a routine part of OLT candidacy evaluations and follow-up, based on general medical risk factors and potential relevancy to patient and graft survival.

Aged↗
PubMed2004

One-year protocol liver biopsy can stratify fibrosis progression in liver transplant recipients with recurrent hepatitis C infection.

Determinants of progression to cirrhosis in hepatitis C virus (HCV) infection have been well described in the immunocompetent population but remain poorly defined in liver transplant (LT) recipients. This cohort study determines the factors contributing to the development of fibrosis and its rate of progression in the allograft. Predictive factors analyzed include: demographics, host and donor factors, surgery-related variables (cold and warm ischemia time), rejection episodes, cytomegalovirus infection (CMV), and immunosuppression. Over 12 years, 842 adult LTs were performed at our institution; 358 for the indication of HCV. A total of 264 patients underwent protocol liver biopsies at month 4 and yearly after LT. Using the modified Knodell system of Ishak for staging fibrosis, the median fibrosis progression rate was .8 units/year (P < .001). Rapid fibrosis progression (> .8 units/year) was best identified by liver histology performed at 1 year. Donor age > 55 years was associated with rapid fibrosis progression and development of cirrhosis (P < .001). In contrast, donor age < 35 years was associated with slower progression of fibrosis (P = .003). Risk factors for graft loss due to recurrent HCV included recipient age > 35 years (P = .01), donor age > 55 years (P = .005), and use of female donor allografts (P = .03). In conclusion, fibrosis progression in HCV-infected LT recipients occurs at a rate of .8 units/year. Increased donor age has a major impact on disease progression, graft failure, and patient survival. A liver biopsy performed at 1 year posttransplant can help identify those patients more likely to develop progressive disease and may allow better targeting of antiviral therapy.

Adult↗
PubMed2004

Structural studies of the manganese stabilizing subunit in photosystem II.

Photosystem II (PSII) is the plant photosynthetic reaction center that carries out the light driven oxidation of water. The water splitting reactions are catalyzed at a tetranuclear manganese cluster. The manganese stabilizing protein (MSP) of PSII stabilizes the manganese cluster and accelerates the rate of oxygen evolution. MSP can be removed from PSII, with an accompanying decrease in activity. Either an Escherichia coli expressed version of MSP or native, plant MSP can be rebound to the PSII reaction center; MSP reconstitution reverses the deleterious effects associated with MSP removal. We have employed Fourier transform infrared (FTIR) spectroscopy and solution small angle x-ray scattering (SAXS) techniques to investigate the structure of MSP in solution and to define the structural changes that occur before and after reconstitution to PSII. FTIR and SAXS are complementary, because FTIR spectroscopy detects changes in MSP secondary structure and SAXS detects changes in MSP size/shape. From the SAXS data, we conclude that the size/shape and domain structure of MSP do not change when MSP binds to PSII. From FTIR data acquired before and after reconstitution, we conclude that the reconstitution-induced increase in beta-sheet content, which was previously reported, persists after MSP is removed from the PSII reaction center. However, the secondary structural change in MSP is metastable after removal from PSII, which indicates that this form of MSP is not the lowest energy conformation in solution.

Energy Transfer↗
PubMed2004

Stabilized beta-catenin promotes hepatocyte proliferation and inhibits TNFalpha-induced apoptosis.

The human hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. The mechanisms of liver cell oncogenic transformation are still unknown. The beta-catenin mutations are identified in up to 30% of HCC and 80% of hepatoblastoma, suggesting a potential role of beta-catenin in the pathogenesis of liver cancers. To define the biological role of the stabilized beta-catenin in liver cell growth and transformation, we examined the effect of mutant beta-catenin on an immortalized murine hepatocyte cell line, AML12. A cell line that stably expresses mutant beta-catenin was established. The cell proliferation, apoptosis, and cell transformation of this cell line were characterized. Our data indicate that the stabilized beta-catenin enhances hepatocyte proliferation, suppresses TNFalpha/Act D-induced cell apoptosis, and causes weak anchorage-independent cell growth. The stabilized beta-catenin-containing cells did not develop tumor in immune-deficient mice. The target genes, c-myc and cyclin D1, were activated by beta-catenin in the hepatocytes. Our study suggests that mutant beta-catenin can promote cell proliferation and cell survival ability, but the stabilized beta-catenin alone is insufficient for completely oncogenic transformation.

Animals↗
PubMed2004

Comparison of cytochrome P450 (CYP) genes from the mouse and human genomes, including nomenclature recommendations for genes, pseudogenes and alternative-splice variants.

OBJECTIVES: Completion of both the mouse and human genome sequences in the private and public sectors has prompted comparison between the two species at multiple levels. This review summarizes the cytochrome P450 (CYP) gene superfamily. For the first time, we have the ability to compare complete sets of CYP genes from two mammals. Use of the mouse as a model mammal, and as a surrogate for human biology, assumes reasonable similarity between the two. It is therefore of interest to catalog the genetic similarities and differences, and to clarify the limits of extrapolation from mouse to human. METHODS: Data-mining methods have been used to find all the mouse and human CYP sequences; this includes 102 putatively functional genes and 88 pseudogenes in the mouse, and 57 putatively functional genes and 58 pseudogenes in the human. Comparison is made between all these genes, especially the seven main CYP gene clusters. RESULTS AND CONCLUSIONS: The seven CYP clusters are greatly expanded in the mouse with 72 functional genes versus only 27 in the human, while many pseudogenes are present; presumably this phenomenon will be seen in many other gene superfamily clusters. Complete identification of all pseudogene sequences is likely to be clinically important, because some of these highly similar exons can interfere with PCR-based genotyping assays. A naming procedure for each of four categories of CYP pseudogenes is proposed, and we encourage various gene nomenclature committees to consider seriously the adoption and application of this pseudogene nomenclature system.

Alternative Splicing↗
PubMed2004

Severe protein C deficiency predicts early death in severe sepsis.

OBJECTIVE: To explore the relationship between measures of baseline disease severity and survival time in patients with severe sepsis. DATA SOURCE: A retrospective evaluation of the placebo group from a large placebo-controlled phase III clinical trial (PROWESS) comprising a total of 840 patients with severe sepsis from 164 medical centers. DATA EXTRACTION AND SYNTHESIS: Data collected included baseline demographics and disease severity measurements, baseline protein C and interleukin-6 levels, 28-day and in-hospital survival rates, and cause of death to 28 days. The survival curve for the placebo patients can be divided into three segments during which the rate of death seemed to be different: the rapid alpha phase (day 0 to day 5), the beta phase (day 6 through day 15), and the gamma phase (day 16 to day 28). The risk of death during each phase was statistically significantly different. More patients died of refractory shock during the alpha phase than in the beta and gamma phases, whereas more patients died of respiratory failure during the beta and gamma phases than during the alpha phase. Multiple organ failure was a frequent cause of death during all phases. Protein C levels at the start of each time interval were highly predictive of outcome within that phase, with continued protein C deficiency being associated with mortality. Patients who died during either the alpha or beta phases had higher interleukin-6 levels at baseline than those who died later or who eventually survived. CONCLUSIONS: The rate and cause of death for patients with severe sepsis differs during the 28-day postdiagnosis period. Severe protein C deficiency (<40% of the level of protein C in pooled normal human plasma) and high interleukin-6 levels were associated with early death that resulted predominantly from refractory shock and multiple organ dysfunction.

Cause of Death↗
PubMed2004

Effect of factor V Leiden polymorphism in severe sepsis and on treatment with recombinant human activated protein C.

OBJECTIVE: Coagulation activation is part of the acute innate host response to infection that, when uncontrolled, may contribute to organ dysfunction and death. Activated protein C limits excessive coagulation activation by inactivating factors Va and VIIIa. The factor V Leiden mutation (R506Q), a prothrombotic gene polymorphism, disrupts the activity of this natural anticoagulant by rendering factor Va partially resistant to inactivation by activated protein C. Previous findings in the mouse factor V Leiden endotoxemia model and in patients with severe sepsis suggest that factor V Leiden constitutes a rare example of a balanced gene polymorphism that may provide a survival advantage for heterozygous carriers with severe sepsis. We sought to confirm that carriers of this prothrombotic factor V Leiden mutation do not have an increased risk of developing severe sepsis and that carriers with severe sepsis derive similar treatment benefit from recombinant human activated protein C (drotrecogin alfa [activated]) as non-factor V Leiden carriers. DESIGN: Prospective collection of factor V Leiden status from two clinical studies of severe sepsis (PROWESS and ENHANCE). SETTING: : A total of 447 clinical sites across 25 countries. PATIENTS: A total of 3894 adult patients with severe sepsis. INTERVENTION: Either 24 microg x kg x hr drotrecogin alfa (activated) (n = 3063) or placebo (n = 800) for 96 hrs or no exposure to the study drug (n = 31). MAIN RESULTS: The effect of the factor V Leiden carrier status in severe sepsis in the PROWESS study has been previously reported. The combined data on factor V Leiden status from 3894 adult patients with severe sepsis from the PROWESS and ENHANCE (a single-arm, open-label study of drotrecogin alfa [activated]) studies are reported here. At study entry, 3.9% of patients (150/3894) presenting with severe sepsis were heterozygous carriers. No homozygous factor V Leiden carriers were identified. The proportion of factor V Leiden carriers in patients with severe sepsis differs slightly from that predicted (allelic frequency of 2.5%) by the Hardy-Weinberg equation for the general white population (p =.05). There was no significant difference in baseline disease severity (Acute Physiology and Chronic Health Evaluation II score or number of organ dysfunctions) between heterozygous carriers and non-Leiden carriers. There was no significant difference in serious bleeding or thrombotic event rates with drotrecogin alfa (activated) treatment between heterozygous carriers and non-Leiden carriers. The 28-day mortality rates for heterozygous carriers and non-Leiden carriers with drotrecogin alfa (activated) treatment were 20.3% and 24.9%, respectively (risk ratio, 0.82; 95% confidence interval, 0.57-1.17). CONCLUSIONS: : Compared with non-Leiden carriers, factor V Leiden heterozygous carriers may have a slightly decreased risk of developing severe sepsis from infection, do not seem to have increased mortality in severe sepsis, and derive similar benefit and risk profiles from drotrecogin alfa (activated) treatment. Therefore, factor V Leiden carriers should not be excluded from this new sepsis therapy.

Anti-Infective Agents↗
PubMed2004

Leukocyte and endothelial cell interactions in sepsis: relevance of the protein C pathway.

OBJECTIVE: To give an overview of leukocyte and endothelial cell interactions in sepsis and to explore the role of the protein C pathway in modulating the innate immune response via its anti-inflammatory properties. DATA SOURCE: Novel in vitro data and a MEDLINE search for the terms "activated protein C," "recombinant human activated protein C," "inflammation," "leukocyte adhesion," and "sepsis" were used, along with clinical trial databases from the PROWESS trial and a phase I human endotoxin trial evaluating recombinant human activated protein C (drotrecogin alfa [activated]). DATA EXTRACTION AND SYNTHESIS: The protein C pathway is positioned at the interface between the endothelium and the leukocyte response of the innate immune system. Activated protein C (APC) possesses profibrinolytic, anti-inflammatory, and anti-apoptotic properties, acting as an endothelial cell and microvascular modulator in opposition to thrombin and the proinflammatory cytokines. Distribution of the receptor for APC, endothelial protein C receptor, was detected on effector cells of the innate immune response. This suggests a further role for the protein C pathway in regulating inflammation. In neutrophils and eosinophils, an endothelial protein C receptor-mediated APC response leads to reduced migration in response to cytokine gradients. Endothelial protein C receptor may also suppress the apoptotic response in monocytes and enhance the expression of the adhesion integrin CD11b in granulocytes. The microvascular, anti-inflammatory influence of APC in sepsis is supported by suppression of endothelial cell adhesion molecules and the ability of APC to protect the endothelium from inflammatory insult. CONCLUSIONS: The coordinated effects of the protein C pathway on the endothelium and the leukocyte response of the innate immune system are supported by potential restriction of endothelial protein C receptor expression to cells of the innate immune system and by suppression of adhesion molecule expression on the endothelium by APC. Reduced neutrophil migration in response to cytokines is also mediated by endothelial protein C receptor. Further clinical studies will be needed to define the intrinsic role of the protein C pathway in coordinating the innate immune response in endothelium-based inflammation.

Animals↗
PubMed2004

Hospital mortality and resource use in subgroups of the Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) trial.

OBJECTIVE: To compare differences in hospital mortality and resource use in adult severe sepsis subjects randomized to receive drotrecogin alfa (activated) (DrotAA) or placebo in the PROWESS trial. DESIGN: Retrospective, cross-sectional, blinded follow-up of subjects enrolled in a previous randomized, controlled trial. SETTING: One hundred sixty-four tertiary care institutions in 11 countries. PARTICIPANTS: The 1,690 subjects with severe sepsis enrolled and treated with study drug in PROWESS, of whom 1,220 were alive at 28 days (the end of the original PROWESS follow-up). INTERVENTIONS: DrotAA (n = 850), 24 microg/kg/hr for 96 hrs, or placebo (n = 840). MEASUREMENTS AND MAIN RESULTS: New follow-up data through hospital discharge were merged with existing 28-day follow-up data. Hospital mortality was calculated for designated subgroups. Intensive care unit and hospital length of stay and Simplified Therapeutic Intervention Scoring System-28 (TISS-28) scores were calculated overall and in designated subgroups. Hospital discharge location was recorded. The 95% confidence interval of most subgroups contained the relative risk estimate for overall 28-day and hospital mortality. Median hospital length of stay and intensive care unit length of stay were similar in both treatment groups: 16 vs. 17 days (p = .22) and 9 vs. 9 days (p = .7) for placebo vs. DrotAA. No significant difference in TISS-28 scores was observed between treatment groups overall or in subgroups of disease severity. In subjects for whom discharge destination was reported, 42.8% of placebo subjects and 46.8% of DrotAA subjects (two thirds of survivors in each group) were discharged directly to home. CONCLUSIONS: Reduction in hospital mortality with DrotAA in most of the subgroups of PROWESS is consistent with the reduction in 28-day and hospital mortality observed in the overall PROWESS population. Additional survivors created with DrotAA treatment did not increase per-patient resource use or intensive care unit or hospital length of stay.

APACHE↗
PubMed2004

Sources of variability on the estimate of treatment effect in the PROWESS trial: implications for the design and conduct of future studies in severe sepsis.

OBJECTIVE: To elucidate sources of variability in the estimate of treatment effects in a successful phase 3 trial in severe sepsis and to assess their implications on the design of future clinical trials. DESIGN: Retrospective evaluation of prospectively defined subgroups from a large phase 3, placebo-controlled clinical trial (PROWESS). SETTING: The study involved 164 medical centers. PATIENTS: Patients were 1,690 patients with severe sepsis. INTERVENTIONS: Drotrecogin alfa (activated) (Xigris) 24 microg/kg/hr for 96 hrs, or placebo. MEASUREMENTS AND MAIN RESULTS: All prospectively defined subgroups were examined to identify treatment effects that potentially differed across subgroup strata (assessed by Breslow-Day p < .10). Potential interactions were identified for subgroups defined by a) presence vs. absence of a significant protocol violation (p = .07); b) original vs. amended protocol (p = .08); and c) Acute Physiology and Chronic Health Evaluation (APACHE) II quartile at baseline (p = .09). No treatment benefit was observed in patients having a protocol violation, regardless of type. There appeared to be less treatment effect in patients enrolled under the original vs. amended protocol. The risk ratio exceeded 1.0 for patients in the lowest APACHE II score quartile. A highly significant correlation was observed between the sequence of enrollment at a site, the frequency of protocol violations, and the observed treatment effect. As enrollment increased, frequency of protocol violations decreased (p < .0001) and the treatment effect improved. The correlation between the sequence of enrollment and improvement in treatment effect remained even after removal of patients with protocol violations. Removal of the first block of patients at each site from the analysis reduced the extent of interaction by protocol version and APACHE II score. CONCLUSIONS: A learning curve appeared to be present within the PROWESS trial such that the ability to demonstrate efficacy improved with increasing site experience. This potential learning curve may have implications for design of future trials. Investigational sites may need to require a minimum level of protocol-specific experience to appropriately implement a given trial. This experience should be an important consideration in designing trials and analysis plans. Diligence by coordinating centers, site investigators, study coordinators, and sponsors is necessary to ensure that the protocol is executed as designed such that a treatment benefit, if present, will be evident.

APACHE↗
PubMed2004

Effects of drotrecogin alfa (activated) in human endotoxemia.

In a phase III clinical trial, drotrecogin alfa (activated) was shown to improve survival and promote faster improvement of cardiovascular and respiratory dysfunction in patients with severe sepsis. To further examine mechanisms involved in the action of this drug, a healthy human endotoxin model was used. Healthy volunteers (eight per group) received drotrecogin alfa (activated) or placebo intravenously for 8 h in a randomized, double-blind, controlled manner. After 2 h of study drug infusion, endotoxin (2 ng/kg) was infused and measurement of physiologic responses and biomarkers continued for 24 h. Consistent with results from severe sepsis clinical trials, drotrecogin alfa (activated) improved mean arterial pressure during the period of infusion after endotoxin exposure. In contrast to severe sepsis clinical trials using drotrecogin alfa (activated) but similar to another human endotoxin study, no significant antithrombotic, profibrinolytic, or anti-inflammatory effects were observed. These results suggest a novel role for drotrecogin alfa (activated) in the human endotoxin model.

Adolescent↗
PubMed2004

Comparative genomics of rice and Arabidopsis. Analysis of 727 cytochrome P450 genes and pseudogenes from a monocot and a dicot.

Data mining methods have been used to identify 356 Cyt P450 genes and 99 related pseudogenes in the rice (Oryza sativa) genome using sequence information available from both the indica and japonica strains. Because neither of these genomes is completely available, some genes have been identified in only one strain, and 28 genes remain incomplete. Comparison of these rice genes with the 246 P450 genes and 26 pseudogenes in the Arabidopsis genome has indicated that most of the known plant P450 families existed before the monocot-dicot divergence that occurred approximately 200 million years ago. Comparative analysis of P450s in the Pinus expressed sequence tag collections has identified P450 families that predated the separation of gymnosperms and flowering plants. Complete mapping of all available plant P450s onto the Deep Green consensus plant phylogeny highlights certain lineage-specific families maintained (CYP80 in Ranunculales) and lineage-specific families lost (CYP92 in Arabidopsis) in the course of evolution.

Arabidopsis↗