Studies on lung surfactant replacement in respiratory distress syndrome. Rapid film formation from binary mixed liposomes

Binary mixed liposomes were prepared from dipalmitoylphosphatidylcholine (DPPC) and a minor compound, e.g., egg phosphatidylglycerol (PG) at a ratio of 9:1. Using different preparative techniques, large unilamellar vesicles (LUV), small unilamellar vesicles (SUV) or multilamellar vesicles (MLV) were obtained and were studied with an electron microscope for morphology, with a Wilhelmy balance for spreading and surface tension lowering potential, and in the surfactant-depleted isolated rat lung for their ability to restore expiratory lung capacity. Only the simultaneous investigation of phospholipids by negative staining and thin sectioning allows unequivocal classification of liposomes. The surface-active structures prepared with the technique of Bangham et al. (Bangham, A.D., Hill, M.W. and Miller, N.G.A. (1974) in Methods in Membrane Biology (Korn, E., ed.), Vol. 1, pp. 1-68, Plenum Press, New York) at room temperature are LUV. LUV containing DPPC:PG at a ratio of 9:1 rapidly spread to a film with high surface tension lowering potential. Within 5 min after injection into the subphase they rise to the surface and form a film at the air/liquid interface able to lower the surface tension to less than 1 mN/m at compression. SUV of the same chemical composition, however, are immediately surface-active only when spread directly onto the surface. MLV exhibit poor surface activity. LUV or pure DPPC, applied onto the surface, are weakly surface active within 5 min. DPPC vesicles injected into the subphase at 37 degrees C do not adsorb to any film with surface tension lowering potential in this time. The minor compounds PE, PI, PS, PA, lysoPC enable DPPC to form surface-active films after application on saline at 37 degrees C. Removal of surfactant decreases the expiratory lung capacity of the isolated rat lung from 49.7 to 12.4% at 4 cmH2O. After substitution with natural surfactant, the expiratory lung capacity is twice that of the washed lung (25.9%), but the original distensibility of the native lung is not restituted. The effect of LUV containing DPPC:PG at a ratio of 9:1 is also remarkable (21.2%).

Membrane traffic in Dictyostelium discoideum: plasma membrane glycoconjugates internalized and recycled during fluid phase pinocytosis enter the Golgi complex

Plasma membrane glycoconjugates, enzymatically labelled with [3H]galactose, were used as an autoradiographic membrane marker for a morphometric analysis of membrane traffic during fluid phase pinocytosis in the amoeba, Dictyostelium discoideum. The fraction of grains associated with the plasma membrane decreased exponentially from 99% for cells fixed directly after labelling on the cell surface, to a steady-state value of 45% after about 1 h of pinocytotic activity. The complementary fraction of grains was observed on vacuolar membranes. Only after a lag of about 20 min, a small but significant fraction (3%) of the total grains, was found in the region of the Golgi membranes. During two subsequent doublings of cell number, over a period of 24 h, label was lost into the medium at a constant rate of 1% per h. The cell bound label remained fully membrane bound over the entire period. The beta(1-4) linkage was not noticeably modified, as judged by its susceptibility to hydrolytic release by beta-galactosidase. An analysis by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) showed an identical labelling pattern for total membrane fractions when prepared directly after labelling or after 24 h of membrane flow.

Disappearance and reformation of the nuclear lamina structure during specific stages of meiosis in oocytes

The nuclear lamina is a rigid, proteinaceous layer underlying the inner nuclear membrane of eucaryotic cells. It is present in somatic cell nuclei, disappears during mitosis, and is absent from male meiotic cells. We have investigated the disappearance and reformation of the nuclear lamina during meiosis in oocytes, using immunofluorescence and electron microscopy. We find that the status of the nuclear lamina during meiosis of oocytes differs from the reversible depolymerization seen in mitosis in two respects. First, the lamina disappears during meiotic prophase without affecting the structure of the nuclear membranes or the nuclear pores. Second, the proteins of the dissociated lamina are undetectable by immunological methods in pachytene oocytes, whereas they persist in the cytoplasm during mitosis.

Degrees of relatedness of T-even type E. coli phages using different or the same receptors and topology of serologically cross-reacting sites

The relatedness of a series of T-even like phages which use the Escherichia coli outer membrane protein OmpA as a receptor, and the classical phages T2, T4 and T6 has been investigated. Immunoelectron microscopy and the pattern of phage resistance in bacterial mutants revealed that: (i) phages of this morphology do not necessarily cross-react serologically; (ii) phages using different receptors may bind heterologous IgG everywhere except to the tip (comprising approximately 10% of one fiber polypeptide) of the long tail fibers; (iii) cross-reacting OmpA-specific phages may bind heterologous IgG only to the tip of these fibers: (iv) OmpA-specific phages not cross-reacting at the tip of the tail fibers use different receptor sites on the protein. Absence of cross-reactivity appears to reflect high degrees of dissimilarity. A DNA probe consisting of genes encoding the two most distal tail fiber proteins of T4 detected homologies only in DNA from phages serologically cross-reacting at this fiber. Even under conditions of low stringency, allowing the formation of stable hybrids with almost 30% base mismatch, no such homologies could be found in serologically unrelated phages. Thus, in the collection of phages examined, there are sets of very similar and very dissimilar tail fiber genes and even of such gene segments.

Studies of the persorption of large particles from radio-labelled cation exchangers

Experiments were carried out in pigs to ascertain to what extent the cation exchangers Ujolyt and Campanyl used in the prevention of urinary stones undergo persorption and appear in the urine. We used two preparations of different grain size and detected them by labelling with 35S. A maximum of 0.5% or 5 X 10(-3) of the dose was found as persorbed particles at 51 h, chiefly in the muscles. The number of persorbed particles from the fine-grained preparation was considerably greater than that from the coarse-grained product. The urine contained the smallest proportion of particles, less than 2 X 10(-5) of the dose. In view of these results there is no reason to believe that solid particles persorbed during treatment with ion exchange resins can act as crystallization centres for stone formation, and it is equally unlikely that ion exchangers have to reach the urine before they can exert their effect.

The disappearance of the nuclear lamina during spermatogenesis: an electron microscopic and immunofluorescence study

The nuclear lamina is a proteinaceous layer lying directly beneath the inner nuclear membrane in somatic cells. Here we demonstrate by indirect immunofluorescence and electron microscopy that the lamina is completely absent from the nuclei of spermatocytes and spermatids of the chicken. The absence of a lamina in these cells can also be demonstrated in isolated nuclei lacking the two nuclear membranes. Implications of this finding for possible functions of the nuclear lamina are discussed.

C-reactive protein in juvenile chronic arthritis: an indicator of disease activity and possibly amyloidosis

C-reactive protein (CRP) was found to be particularly high early in the course of those cases of juvenile chronic arthritis (JCA) with a systemic onset, the mean level being 12 mg/dl (120 mg/l). It was also raised in cases with a polyarticular onset, mean level 6 mg/dl, while in cases with a pauciarticular onset it was associated with only a modest increase up to 1.5 mg/dl (15 mg/l). At the onset of disease there was a good correlation with the erythrocyte sedimentation rate (ESR). Regression of systemic disease was associated with a steady fall in C-reactive protein, but those patients who developed amyloidosis within 5 years from onset had persistently high values until cytotoxic therapy was introduced. Patients who developed amyloidosis later tended to have high CRP levels in the months or even years before diagnosis. In a few patients with polyarthritis the CRP appeared to reflect severe disease more closely than their relatively low ESR.

Lactose carrier protein of Escherichia coli. Reconstitution of galactoside binding and countertransport

A procedure for the reconstitution of the lactose carrier protein, a galactoside:proton symporter in Escherichia coli, is described. Starting from cytoplasmic membranes derived from carrier-overproducing strains, essentially all proteins including 89% of the carrier are solubilized by a mixture of dodecyl/tetradecyl polyoxyethylene (n = 9.5) ether and dodecyl O-beta-D-maltoside. In the micellar state the carrier binds substrates with reduced affinity. Addition of E. coli phospholipids and removal of detergents by a hydrophobic column yields small vesicles (50-60-nm diameter). In these vesicles, about 70% of the carrier is recovered and reconstituted carrier is identical to native carrier in terms of substrate binding. After fusion of the small vesicles into larger vesicles (1-5 micrometers), rapid countertransport of galactosides is demonstrated. Attempts to show active galactoside transport by the imposition of artificial electrical potential or pH gradients were unsuccessful, most likely because the reconstituted vesicles are in fact highly permeable to protons.

Stage-specific antigens reacting with monoclonal antibodies against contact site A, a cell-surface glycoprotein of Dictyostelium discoideum

Monoclonal antibodies against a glycoprotein presumably involved in adhesion of aggregating Dictyostelium discoideum cells have been used for labeling of the antigen at the cell surface. The antigen is distributed over the whole surface of the cells, apparently in form of small clusters. The antigen appears concomitantly with the acquisition of EDTA-stable adhesiveness typical of aggregation competent cells. In contrast, discoidin I, a lectin whose accumulation during development parallels EDTA-stable adhesiveness in another strain (NC-4), is present in nearly the same amounts of growth phase and aggregating cells of AX2-214, the strain used by use. Thus, no correlation exists in this strain between the expression of discoidin I and the development of cell adhesiveness. The 80 kilodalton glycoprotein typical of aggregation competent cells has been purified by affinity chromatography on a monoclonal antibody column. The purified antigen absorbs adhesion-blocking Fab from rabbits. Another antigen strongly reacting with the same monoclonal antibodies has an apparent molecular weight of 106 000 and is not detectable before slugs are formed.

Nitrosated urea pesticide metabolites and other nitrosamides. Activity in clastogenicity and SCE assays, and aberration kinetics in Chinese hamster V79-E cells

The nitrosoureas 1-methyl-1-nitroso-3-phenylurea, 1-ethyl-1-nitroso-3-phenylurea, 1-methyl-1-nitroso-3-(p-fluorophenyl)urea, 1-methyl-1-nitroso-3-(p-chlorophenyl)urea, and 1-methyl-1-nitroso-3-(p-bromophenyl)urea, as well as their non-nitrosated parent compounds, were checked for induction of chromosomal aberrations and sister-chromatid exchanges in V79-E cells without metabolic activation in vitro. For comparison, methylnitrosourea, ethylnitrosourea and nitrosocarbaryl were included in this study. Whereas the non-nitrosated agents were inactive, the nitroso derivatives were potent clastogens and inducers of SCEs. Clastogenicity parallels SCE induction, but the latter assay is about 10 times more sensitive (based on concentration of substance) than the clastogenicity assay. The dependence of aberration frequency on sampling time, which was studied for 5 nitroso compounds, revealed striking differences. As demonstrated by differential chromatid staining, the lag phase until maximal aberration rates may cover more than 2 cell cycles. Preventive oncological aspects of these nitrosamides and the mechanism of aberration kinetics are discussed.

Mechanism of phagocytosis in Dictyostelium discoideum: phagocytosis is mediated by different recognition sites as disclosed by mutants with altered phagocytotic properties

The recognition step in the phagocytotic process of the unicellular amoeba dictyostelium discoideum was examined by analysis of mutants defective in phagocytosis, Reliable and simple assays were developed to measure endocytotic uptake. For pinocytosis, FITC-dextran was found to be a suitable fluid-phase marker; FITC-bacteria, latex beads, and erythrocytes were used as phagocytotic substrates. Ingested material was isolated in one step by centrifuging through highly viscous poly(ethyleneglycol) solutions and was analyzed optically. A selection procedure for isolating mutants defective in phagocytosis was devised using tungsten beads as particulate prey. Nonphagocytosing cells were isolated on the basis of their lower density. Three mutant strains were found exhibiting a clear-cut phenotype directly related to the phagocytotic event. In contrast to the situation in wild-type cells, uptake of E. coli B/r by mutant cells is specifically and competitively inhibited by glucose. Mutant amoeba phagocytose latex beads normally but not protein-coated latex, nonglucosylated bacteria, or erythrocytes. Cohesive properties of mutant cells are altered: they do not form EDTA-sensitive aggregates, and adhesiveness to glass or plastic surfaces is greatly reduced. Based upon these findings, a model for recognition in phagocytosis is proposed: (a) A lectin-type receptor specifically mediates binding of particles containing terminal glucose (E. coli B/r). (b) A second class of "nonspecific" receptors mediate binding of a variety of particles by hydrophobic interaction. Nonspecific binding is affected by mutation in such a way that only strongly hydrophobic (latex) but not more hydrophilic particles (e.g., protein-coated latex, bacteria, erythrocytes) can be phagocytosed by mutant amoebae.