Assessment of papain-induced lung injury in isolated lungs by measurements of aerosol deposition and mixing.

Aerosol bolus inspirations were used to assess lung injury in 15 isolated dog lungs exposed to low (0-375 units) or high doses (600-1,200 units) of papain. Effective air space size (EAD) was determined from aerosol deposition during a 5-s breath hold. Convective mixing was assessed by the spreading of the expired bolus with respect to expired volume, quantified by a coefficient of dispersion (CD) equal to the square root of the difference in the variances of the expired and inspired boluses divided by the volumetric penetration of the bolus. After exposure, CD measured with deeply penetrating boluses increased by an average of 2.5% in the low-exposure group (P greater than 0.05) and 28.0% in the high-exposure group (P less than 0.0001). CD measured with shallowly penetrating boluses decreased by 4.3% (P less than 0.0001) in the low-exposure group and increased by an average of 18.3% in the high-exposure group (P less than 0.05). Papain exposure caused EAD to increase in some lungs and decrease in others. For deep bolus penetrations, EAD changed by an average of -0.8% in the low-exposure group (P greater than 0.05) and +21.1% in the high-exposure group (P greater than 0.05). Both EAD and CD appeared to be sensitive to lung injury. However, changes in EAD were less consistent than those in CD, possibly due to changes caused by lung injury in the regional distribution of inspired aerosol.     

Inhibition of platelet phosphatidylinositol synthetase by an analog of CDP-diacylglycerol

Unpublished portions of the synthesis of a phosphinate-phosphonate diether analog of CDPdiacylglycerol are reported. The liponucleotide analog was found to be a very powerful inhibitor of platelet PI synthetase; kinetic data suggest a competitive inhibition mechanism. The structural specificity of CDPdiacylglycerol for liponucleotide-mediated biosynthetic reactions is discussed.     

Electron microscopic evidence of circular molecules in 9-S globin mRNA from rabbit reticulocytes

9S globin mRNA prepared by the proteinase K method from polysomes of rabbit reticulocytes consists of 40% circular molecules as revealed by electron microscopy, if spreading of the molecules is performed from a solution of 50% formamide, 0.5 M NaCl, 25 mM Tris, 10 mM EDTA, pH 8, after 16 h incubation at 42 °C. We assume a noncovalent nature of the circularization because of the fact that a total transformation into the well known linear form occurs if strong denaturing conditions for spreading were used. The biological significance of the circular globin mRNA molecules is unknown.     

Site of inhibitory action of CRE 9-41 on ACTH release from isolated rat pituitary cells

The corticotropin-releasing factor (CRF) analog CRF 9-41 inhibits CRF, but not forskolin or dibutyryl cyclic AMP, stimulated release of ACTH from isolated pituitary cells. CRF 9-41 also blocks CRF-stimulated accumulation of cyclic AMP in a parallel dose dependent fashion. CRF 9-41 has no effect on basal ACTH release or cAMP levels. This substantiates that the analog acts as a direct CRF antagonist and that the site of this inhibition is most likely at the level of binding of CRF to its receptor on the corticotrope. Various substances, including most prominently glucocorticoids, inhibit release of ACTH from the pituitary. In an effort to develop another class of inhibitors, Rivier et al recently synthesized analogs of corticotropin releasing factor (CRF). One among these, alpha-helical ovine CRF 9-41 blunts adrenalectomy and stress induced ACTH release in non-anesthetized rats. At micromolar concentrations, CRF 9-41, shifts rightward the dose response of isolated pituitary cells to ovine CRF. Thus, the authors suggested that CRF 9-41 acts as a competitive antagonist to CRF-induced ACTH secretion. CRF appears to act through stimulation of adenylate cyclase. To determine the potential site of action of CRF 9-41 in the activation sequence for adenylate cyclase, we studied its effects on pituitary cyclic AMP formation and ACTH secretion from dispersed anterior pituitary cells derived from normal adult rats, as well as, its interaction with cyclic nucleotide agonists.     

Purification and Properties of Rubrophilin: A Novel Brain Specific Membrane Polypeptide

Rubrophilin, a unique brain specific polypeptide, was purified to apparent homogeneity from microsomal fractions of bovine brains. The peptide stains pink with Coomassie Brilliant Blue R-250 (C.I. No. 42660) under specific conditions, has an apparent Mr of 53,000, and is acidic with an apparent pI of 4.9. The purification involves initial solubilization of delipidated microsomes in sodium dodecyl sulfate, followed by ammonium sulfate fractionation, reversed ammonium sulfate gradient elution from diatomaceous earth, gel filtration on polyacrylamide (Biogel P-200), gradient elution chromatography from hydroxylapatite, and reverse-phase chromatography from phenyl-Sepharose. A yield of about 5 mg of rubrophilin was obtained from 9 g of microsomal proteins. Amino acid analysis shows that rubrophilin contains only nine amino acids with residues/mol as follows: alanine (102), glutamic acid (97), lysine (65), proline (55), aspartic acid (48), glycine (44), serine (37), threonine (35), and valine (10). Cysteine, methionine, tryptophan, tyrosine, isoleucine, phenylalanine, histidine, and arginine could not be detected. Relative rubrophilin content of vertebrate brains was as follows: mammals greater than birds greater than reptiles greater than fishes. It is present in mouse retina and human neuroblastoma cell cultures but could not be detected in octopus optic lobe or in cultured C-6 rat glioma cells.