A constitutively activated chimeric cytokine receptor confers factor- independent growth in hematopoietic cell lines

The high-affinity receptor for granulocyte-macrophage colony- stimulating factor (GMR) comprises at least 2 distinct subunits, alpha and beta common (beta c), whereas the normal erythropoietin receptor (nEpoR) comprises only one known subunit. An arginine to cysteine (R129C) mutation of the extracytoplasmic domain of the murine EpoR leads to Epo-independent growth in transduced cells (cEpoR). To investigate the proliferative functions of the cytoplasmic regions of each GMR subunit separately and the potential of the R129C EpoR mutation to induce factor-independent growth through heterologous receptor regions, we constructed four hybrid receptors: the extracellular region of either murine nEpoR or cEpoR linked to the transmembrane and cytoplasmic regions of either the human GMR alpha or beta c subunit (nE alpha, nE beta, cE alpha, and cE beta). We then expressed them in an interleukin-3-dependent murine cell line, Ba/F3. Expression of nE beta led to Epo-dependent growth, whereas expression of cE beta conferred factor-independent growth. Surprisingly, expression of cE alpha also resulted in factor-independent cell growth, whereas nE alpha did not respond to Epo. Furthermore, the functional hybrid receptors showed Epo-dependent (nE beta) or constitutive (cE alpha and cE beta) tyrosine phosphorylation of the cytoplasmic kinases JAK1 and JAK2. We reasoned that the proliferative signal of cE alpha was transduced either through the alpha tail itself or through an accessory protein such as the endogenous murine beta common subunit (mu beta c). To distinguish these possibilities, the chimeric receptor cE alpha was expressed in the interleukin-2-dependent murine cell line, CTLL-2, that does not express mu beta c. cE alpha did not induce cell growth in CTLL-2; however, when mu beta c was coexpressed with cE alpha in CTLL-2, factor-independent growth was reconstituted. In conclusion, the cytoplasmic domain of the GMR alpha subunit requires a beta chain for transduction of a proliferative signal. Furthermore, the R129C EpoR mutation can constitutively activate heterologous receptors to mediate factor-independent proliferation.     

RESPIRATORY MECHANICS AND SURFACTANT IN THE ACUTE RESPIRATORY DISTRESS SYNDROME

1. Although abnormalities in pulmonary surfactant were initially implicated in the pathogenesis of the acute respiratory distress syndrome (AROS) 30 years ago, most subsequent research has focused on mediators of the parenchymal acute lung injury (ALI) and the associated increase in alveolocapillary permeability . 2. Surfactant is essential for normal breathing and the severity of ALI correlates with surfactant dysfunction and abnormalities in surfactant composition; however, no relationship has been shown with respiratory system compliance. In neonates and most animal models, respiratory system compliance will directly reflect the elastic properties of the lung. However, the greater vertical height of the chest wall in adults, in combination with the increase in lung density due to ALI, results in dependent collapse of alveoli. Because simple, global measurement of compliance is strongly influenced by the volume of aerated lung, alternative measures of respiratory mechanics may reflect surfactant dysfunction . 3. Using a dynamic, volume-dependent model of respiratory mechanics to indirectly reflect this heterogeneous inflation, we have found direct relationships with surfactant composition in patients with ARDS. A failure of surfactant to increase surface tension in large alveoli may also explain why lung overdistension occurs at relatively low pressures. Furthermore, surfactant dysfunction will exaggerate heterogeneous lung inflation, augmenting regional overinflation, and is essential for ALI secondary to repetitive opening and closing of alveoli during tidal ventilation . 4. Ventilation-induced ALI has also been shown to result in massive increases in pro-inflammatory cytokines within the lung. Because ALI itself fails to compartmentalize cytokines, with spillover into the systemic circulation resulting in distant organ dysfunction, surfactant dysfunction may have widespread implications .     

A qualitative study to identify community structures for management of severe malaria: a basis for introducing rectal artesunate in the under five years children in Nakonde District of Zambia

Background  

Malaria is a serious illness among children aged 5 years and below in Zambia, which carries with it many adverse effects including anemia and high parasites exposure that lead to infant and childhood mortality. Due to poor accessibility to modern health facilities, malaria is normally managed at home using indigenous and cosmopolitan medicines. In view of problems and implications associated with management of severe malaria at home, rectal artesunate is being proposed as a first aid drug to slow down multiplication of parasites in children before accessing appropriate treatment.     

Lymphocyte depletion of donor bone marrow by counterflow centrifugal elutriation: results of a phase I clinical trial

We report here the results of a phase I clinical trial using counterflow centrifugal elutriation (CCE) for the removal of donor T lymphocytes before allogeneic bone marrow transplantation (BMT). Thirty- eight patients received lymphocyte-depleted allografts from HLA- identical, MLR-nonreactive sibling donors. The patients entered onto the study were either at high risk on the basis of age (median, 39 years) or disease status (acute leukemia in early relapse [ER], chronic myelogenous leukemia [CML] in accelerated phase [AP], or therapy resistant [RES] lymphoma). All patients received a standard lymphocyte dose of 1 x 10(6) morphologic lymphocytes per kilogram ideal body weight (BW) and were maintained on cyclosporine A (CsA) for 170 days after BMT. Prompt engraftment occurred in 37 of 38 patients with a median time to absolute neutrophil count (ANC) greater than 500/microL of 18 days. Although acute graft-v-host disease (GVHD; clinical stage I or greater) was observed in 45%, it was limited to the skin in all but five patients. Survival was related to disease status at the time of BMT. Among patients with acute leukemia in first or second remission, CML in chronic phase (CP) or lymphoma in partial remission (PR), 64% are currently alive, in contrast to 31% of patients with acute leukemia in third remission or early relapse, CML in second CP or AP, or RES lymphoma. Median follow-up for all patients was 351 days (range, 105 to 711 days). We conclude that this procedure is safe and warrants further evaluation in a randomized efficacy trial.     

Surfactant phosphatidylcholine composition during dexamethasone treatment in chronic lung disease

OBJECTIVES--To determine whether dexamethasone 'matures' the phosphatidylcholine (PC) composition of broncheoalveolar fluid in infants at high risk of neonatal chronic lung disease (CLD), either by increasing the proportion of dipalmitoylphosphatidylcholine (DPPC), expressed as a percentage of total PC (%DPPC), or by increasing the ratio of DPPC to palmitoyloleoylphosphatidylcholine (DPPC:POPC ratio). DESIGN--Double blind, placebo controlled. SETTING AND PATIENTS--Sixteen infants < 32 weeks' gestation, < 1250 g birth weight who were dependent on mechanical ventilation and requiring a fractional inspired oxygen of > 0.30 at 12 days of chronological age. INTERVENTION--Randomisation to receive a two week reducing course of dexamethasone base at an initial dose of 0.2 mg/kg three times a day, or equivalent volumes of normal saline, starting at 14 days. Eight infants were randomised into each group. Broncheoalveolar lavage was performed serially throughout the study period or until extubation. PC composition of the fluid was analysed by high performance liquid chromatography. OUTCOME MEASURES--The %DPPC and the DPPC:POPC ratios were calculated for individual infants for days -1 and 0 combined, days 1 and 3 combined, and days 5 and 7 combined. Analysis of covariance was used to analyse the results. RESULTS--The DPPC:POPC ratio was significantly less in the treated group than the placebo group on days 1 and 3, and not greater as the hypothesis stated. Three out of five infants treated with dexamethasone and for whom data were available showed a substantial rise in DPPC:POPC ratio on days 5/7, compared with the placebo group, but overall these changes were not statistically significant. CONCLUSIONS--The data do not support the hypothesis that dexamethasone's action in producing a clinical improvement within the first 72 hours of treatment for neonatal CLD is by the 'maturation' of pulmonary surfactant PC.     

PIC10 The Influence of Case Mix Bias on Costs of Hospitalisation for Lower Respiratory Tract Infection

OBJECTIVE: To compare costs of hospitalisation for lower respiratory tract infection (LRTI) in patients who received antibiotics before admission versus those who did not and in patients with and without underlying chronic obstructive airways disease (COAD).
METHODS: All hospitalisations were analysed in a population of 350,000 resident in Tayside during 1993–94. Three groups of patients were identified by primary discharge diagnosis in 1993–94 and previous admissions from 1980 to 1992: (1) acute exacerbation of COAD, (2) LRTI plus a secondary diagnosis of COAD or previous admission with COAD, and (3) LRTI but no secondary COAD or previous admission with COAD. Setting-specific costs were applied (e.g., general medicine, intensive care, geriatrics). Dispensed antibiotic prescribing in the 28 days before admission was identified from all community pharmacies. Non-parametric statistical tests were used.
RESULTS: Patients with COAD were more likely to have received antibiotics before admission: COAD (n = 893) 49%; COAD+LRTI (n = 316) 43%; LRTI only (n = 822) 33%. Odds ratio for COAD vs LRTI only 1.90 (95% CI 1.56 to 2.31); COAD+LRTI vs LRTI only 1.50 (95% CI 1.15 to 1.96). Patients who received antibiotics before admission had lower hospital costs than patients who did not. Median total costs per admission: COAD £1050 vs £1164 (p = 0.5); COAD+LRTI £1067 vs £1354 (p = 0.5); LRTI only £1220 vs £1500; (p = 0.009). Adjusted for community antibiotic prescribing, the hospital costs of patients with LRTI were significantly higher than those of patients with COAD (p = 0.001) but not those of patients with COAD+LRTI (p = 0.096).
CONCLUSION: Economic models of the potential impact of different community antibiotics on hospital LRTI costs will be subject to case mix bias unless they adjust for community antibiotic use and co-morbidity with COAD.