Dexamethasone is known to have an inhibitory effect on IL-1 production. To determine the mechanism(s) of this inhibition, adherent human blood monocytes were stimulated with Escherichia coli lipopolysaccharide (LPS) (10 sg/ml) in the presence of dexamethasone. Nuclear transcription run-off assays showed that LPS induced IL-1IB gene transcription two-to fourfold and that this induction was unaffected by dexamethasone exposure (10-5 M). The lack of dexamethasone's transcriptional effects was further supported by the absence of any significant change in IL-I1f mRNA accumulation between LPS-stimulated monocytes exposed or unexposed to dexamethasone, as determined by Northern blot analysis.Posttranscriptionally, dexamethasone was found to have multiple effects: slight prolongation of IL-1jf mRNA half-life, moderate inhibition of translation of the IHAlfl precursor, and profound inhibition of the release of IL-igi into the extracellular fluid.The data indicate that IL-1fi is first translated as the 33,000-D pro-IL-1ft protein, the predominant intracellular form, and the processed to a 17,500-D IL-i1f protein before or during extracellular transport. The major inhibitory effects of dexamethasone appear to be directed at the translational and posttranslational steps involved in these events.
Transmembrane electrical and pH gradients have been measured across human erythrocytes and peripheral blood lymphocytes using equilibrium distributions of radioactively labelled lipophilic ions, and of weak acids and weak bases, respectively. The distributions of methylamine, trimethylamine, acetic acid and trimethylacetic acid give calculated transmembrane pH gradients (pHe-pHi) for erythrocytes of between 0.14-0.21 for extracellular pH values of 7.28-7.16. The distributions of trimethylacetic acid. DMO and trimethylamine were determined for lymphocytes, establishing upper and lower limits of the calculated pH gradient over the external pH range of 6.7 to 7.7. Tritiated triphenylmethyl phosphonium ion (TPMP) and 14C-thiocyanate ion (SCN) equilibrium distributions were measured in order to calculate transmembrane electrical potentials, using tetraphenylboron as a catalyst to facilitate TPMP equilibrium. Transmembrane potentials of -7 to -10 mV were calculated from SCN and TPMP, respectively for red cells, and -35 to -52 mV respectively, in the case of lymphocytes. Distributions of TPMP and potassium ions were determined in the presence of valinomycin over a wide range of extracellular potassium concentrations for red cells and the calculated Nernst potentials for TPMP compared to the calculated potential using the Goldman equation for chloride and potassium ions. Distributions of TPMP, SCN and potassium ions were also determined for lymphocyte suspensions as a function of extracellular potassium and the calculated Nernst potentials for TPMP and SCN compared to the calculated potassium diffusion potential.
Bronchoalveolar lavage has emerged as a useful technique for the study of pulmonary interstitial disorders. Several types of information are provided by the evaluation of lavage fluid. First, the identification of cellular constituents helps to separate inflammatory processes in which lymphocytes predominate (for example, sarcoidosis, hypersensitivity pneumonitis, and berylliosis) from those in which neutrophils or macrophages predominate (for example, idiopathic pulmonary fibrosis and histiocytosis X). Second, the cells removed during lavage can be studied for their immune properties and function; tested with specific antigens, in diseases such as berylliosis and hypersensitivity pneumonitis; and examined for the presence of unique surface antigens with monoclonal antibodies (for example, histiocytosis X). Third, in conjunction with scanning electron microscopy and electron probe analysis, lavage makes possible the identification of inorganic particles in alveolar macrophages of patients with pneumoconiotic lung disease. Finally, although lavage is still an investigative procedure for most pulmonary disorders, it has an established role in the diagnosis of opportunistic infections in the immunocompromised patient.
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