Altered plasma membrane phospholipid organization in Plasmodium falciparum-infected human erythrocytes

The intraerythrocytic development of the malaria parasite is accompanied by distinct morphological and biochemical changes in the host cell membrane, yet little is known about development-related alterations in the transbilayer organization of membrane phospholipids in parasitized cells. This question was examined in human red cells infected with Plasmodium falciparum. Normal red cells were infected with strain FCR3 or with clonal derivatives that either produce (K+) or do not produce (K-) knobby protuberances on the infected red cells. Parasitized cells were harvested at various stages of parasite development, and the bilayer orientation of red cell membrane phospholipids was determined chemically using 2,4,6-trinitrobenzene sulphonic acid (TNBS) or enzymatically using bee venom phospholipase A2 (PLA2) and sphingomyelinase C (SMC). We found that parasite development was accompanied by distinct alterations in the red cell membrane transbilayer distribution of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS). Increases in the exoplasmic membrane leaflet exposure of PE and PS were larger in the late-stage parasitized cells than in the early-stage parasitized cells. Similar results were obtained for PE membrane distribution using either chemical (TNBS) or enzymatic (PLA2 plus SMC) methods, although changes in PS distribution were observed only with TNBS. Uninfected cohort cells derived from mixed populations of infected and uninfected cells exhibited normal patterns of membrane phospholipid organization. The observed alterations in P falciparum-infected red cell membrane phospholipid distribution, which is independent of the presence or absence of knobby protuberances, might be associated with the drastic changes in cell membrane permeability and susceptibility to early hemolysis observed in the late stages of parasite development.     

Long-term experience with etanercept in the treatment of rheumatoid arthritis in elderly and younger patients: patient-reported outcomes from multiple controlled and open-label extension studies

BACKGROUND: The impact of long-term therapy for rheumatoid arthritis (RA) in elderly (> or = 65 years of age) and younger (< 65 years of age) patients, especially on patient-reported outcomes, has not been well studied. We evaluated patient-reported outcomes in elderly patients treated with etanercept, in contrast to outcomes in younger patients, using data from multiple controlled and open-label extension studies of patients with early RA (ERA; < or = 3 years) and late RA (LRA; disease-modifying antirheumatic drug [DMARD]-refractory RA). METHODS: This post hoc analysis included adult patients with RA enrolled in controlled, double-blind studies (up to 2 years) and subsequent open-label extension studies (up to 4 years). Patients were evaluated according to age at baseline of the original study. Patients may have received etanercept, placebo or methotrexate during the blinded treatment phases, but all patients had been receiving etanercept 25 mg twice weekly for at least 4 years. Both ERA and LRA extension studies are ongoing. Patient-reported outcome assessments included improvement in Health Assessment Questionnaire-Disability Index (HAQ-DI), proportions of patients achieving an improvement in HAQ-DI > or = 0.22 points, patients exhibiting worsening of HAQ-DI and patients achieving an HAQ-DI score of 0. RESULTS: Elderly patients, with either ERA or LRA, had significantly worse baseline mean HAQ-DI scores than younger patients (p < 0.05, Student's t-test) in most studies, indicating greater disability. Improvement in HAQ-DI was greatest during the first 3 months after starting etanercept treatment in the controlled phase and appeared to be sustained over 3-6 months in patients with early or DMARD-refractory RA. Across the various controlled trials, mean improvements from baseline in HAQ-DI ranged from 0.39 to 0.92 points in elderly patients and from 0.57 to 1.00 points in younger patients. Patients with ERA and LRA, regardless of age group, maintained their improvement in HAQ-DI throughout the open-label extension trials for up to a total of 6 years of etanercept therapy. Change from baseline in HAQ-DI was moderately correlated with 28-joint Disease Activity Score within each age group across the multiple trials. CONCLUSION: Both elderly and younger patients with RA treated with etanercept exhibited similar and rapid improvements in functional status during controlled studies, and these improvements were sustained during open-label extension trials.     

Dopamine D4 receptor signaling in the rat paraventricular hypothalamic nucleus: Evidence of natural coupling involving immediate early gene induction and mitogen activated protein kinase phosphorylation

The dopamine D4 receptor has been investigated for its potential role in several CNS disorders, notably schizophrenia and more recently, erectile dysfunction. Whereas studies have investigated dopamine D4 receptor-mediated signaling in vitro, there have been few, if any, attempts to identify dopamine D4 receptor signal transduction pathways in vivo. In the present studies, the selective dopamine D4 agonist PD168077 induces c-Fos expression and extracellular signal regulated kinase (ERK) phosphorylation in the hypothalamic paraventricular nucleus (PVN), a site known to regulate proerectile activity. The selective dopamine D4 receptor antagonist A-381393 blocked both c-Fos expression and ERK1/2 phosphorylation produced by PD168077. In addition, PD168077-induced ERK1/2 phosphorylation was prevented by SL327, an inhibitor of ERK1/2 phosphorylation. Interestingly, treatment with A-381393 alone significantly reduced the amount of Fos immunoreactivity as compared to basal expression observed in vehicle-treated controls. Dopamine D4 receptor and c-Fos coexpression in the PVN was observed using double immunohistochemical labeling, suggesting that PD168077-induced signaling may result from direct dopamine D4 receptor activation. Our results demonstrate functional dopamine D4 receptor expression and natural coupling in the PVN linked to signal transduction pathways that include immediate early gene and MAP kinase activation. Further, the ability of the selective dopamine D4 antagonist A-381393 alone to reduce c-Fos expression below control levels may imply the presence of a tonic dopamine D4 receptor activation under basal conditions in vivo. These findings provide additional evidence that the PVN may be a site of dopamine D4 receptor-mediated proerectile activity.     

Chromatic VEP assessment of human macular pigment: comparison with minimum motion and minimum flicker profiles

To assess the effects of macular pigment optical density (MPOD) on isoluminant stimuli and to quantify MPOD electrophysiologically, MPOD distribution profiles were obtained in normal subjects using minimum motion and minimum flicker photometry. Isoluminance of VEP stimuli was determined using minimum flicker and tritan confusion lines were determined using a minimum distinct border criterion. Onset-offset and reversal VEPs to isoluminant red/green, blue/green, and subject-specific tritan gratings of different diameters were recorded from the same 14 subjects tested psychophysically. VEPs were additionally recorded to annular gratings. Chromatic VEP selectivity was assessed by Fourier analysis and as an index; onset negativity/(onset negativity + onset positivity). Peak MPOD varied between 0.2-0.8. Chromatic onset VEPs to all isoluminant 3-deg fields were predominantly negative. Larger blue/green and tritan stimuli elicited VEPs with additional positive, achromatic components; for 9-deg gratings, peak MPOD showed negative correlation with the power of the VEP fundamental (r = -0.70) and with the selectivity index (r = -0.83). Annular gratings elicited chromatic-specific B/G VEPs but only when isoluminance was determined for the annulus. Chromatic selectivity loss in VEPs to large B/G or Tritan gratings can be used to estimate subject-specific MPOD. An important implication is that isoluminant Tritan stimuli with short-wavelength components must be restricted in size in order to optimize koniocellular selectivity.     

The effect of serum on monocyte tissue factor generation

Human monocytes generate the procoagulant tissue factor (MTF) following exposure to a variety of immune stimuli in vitro. The generation of MTF is modified by T cells, lymphokines, and immunoregulatory lipoproteins, and recent studies have shown that MTF can be activated in an immune- specific manner following exposure to antigen. We have examined the role of serum factors in the regulation of MTF generation. Low concentrations (less than 1%) of heat-inactivated normal human serum greatly enhanced MTF generation in cultures of normal peripheral blood mononuclear cells. The stimulatory effect was observed in cultures of both unstimulated cells and cells exposed to bacterial lipopolysaccharide. Stimulation was not observed at high serum concentrations (greater than 10%) and could not be explained by endotoxin contamination or activation of the assay system. Stimulatory activity was present in plasma and BaSO4-adsorbed plasma as well as autologous and allogeneic serum, was not abolished by removal of serum lipoproteins, and did not require the presence of T cells for its expression. Sera from 28 different normal volunteers were screened for stimulatory activity and demonstrated a wide variation in potency. These results suggest that a potent factor is present in sera that enhances the expression of MTF activity in vitro. This factor is distinct from previously described lipoprotein regulators and may play a role in the initiation of coagulation in both normal hemostasis and pathologic states.     

Inflammatory central nervous system involvement in rheumatoid arthritis

We describe a patient with seropositive rheumatoid arthritis who developed pachymeningitis resulting in optic atrophy. Clinical, histopathologic, and radiologic findings in 18 additional cases of inflammatory CNS disease associated with rheumatoid arthritis are reviewed. The three characteristic neuropathologic findings were rheumatoid nodules, pachymeningitis or leptomeningitis, and vasculitis. In most cases, more than one of these histopathologic processes were found. The typical host was middle-aged with long-standing severe nodular disease. However, contrary to previous reports, CNS disease occurred in a significant number of patients without active synovitis and extracranial vasculitis and nodules. Although no correlation between specific neurologic symptoms and neuropathology was noted, patients with CNS nodules tended to be asymptomatic more often than patients with vasculitis or meningitis. CSF analysis and computed axial tomography were helpful diagnostic tools, but diagnosis was ultimately made only by directed biopsy or at autopsy. Treatment with surgical decompression and/or corticosteroids has proved beneficial in several cases. Inflammatory CNS involvement in rheumatoid arthritis should be considered in any patient with neurologic symptoms in whom infectious and malignant processes are ruled out. An aggressive, invasive approach for diagnostic biopsies seems warranted.     

A new approach to dominant lethal testing

Male weanling rats were given triethylenemelamine (TEM) at 0.025, 0.050, or 0.075 mg/kg and male adult rats were given TEM at 0.050 mg/kg, all by gavage 5 days/week for 10 weeks. At the end of the treatment period, the animals were immediately cohoused with two females each during Week 1 and with two other females during Week 2. The females were sacrificed 14 days from the midweek of cohousing, and the numbers of corpora lutea and live and dead implantations were counted. Statistical analyses of the number of dead implantations per pregnant female and of the number of females with one or more dead implantations or with two or more dead implantations indicated significant increases in all indexes for the adults and a more variable response on the part of the weanlings. The results from this study indicate that there is no loss of pertinent information by employing this approach except that of stage sensitivity. It reduces the amount of data usually required and assesses the more significant dominant lethal effect, that of postimplantation loss.