Cultured lung cells: effects of isotopic dilution and some undefined stimulation on the incorporation of radiolabeled palmitate and choline into phosphatidyl choline (lecithin)

Using radiolabels, we studied the effect of certain experimental conditions on the incorporation of choline and palmitate into phosphatidyl choline (lecithin) of cloned type II rat lung cells. When the label was changed from methyl-3H to 1,2-14C the incorporation of choline was reduced to 1/3; in contrast, when the label was moved from 1-14C to 9,10-3H, the incorporation of free palmitate was more than doubled. Removal of choline from the culture medium caused trebling of choline incorporation and appreciable decrease in palmitate uptake, indicating respectively an expected effect of increased choline label concentration in the absence of carrier, and a marked dependence of palmitate on choline incorporation. Removal of fetal calf serum produced more than 2/3 decrease in palmitate incorporation (instead of an expected increase because of palmitate isotope concentration), whereas choline uptake was not affected, meaning respectively that either serum hormones or serum lipids, or both simultaneously, are important for palmitate but not for choline incorporation. This is only the beginning of a host of studies required to clarify the role of fetal calf serum constituents onto lecithin biosynthesis in cultured lung cells and finally gain a full appreciation of the biosynthetic pathways of phosphatidyl choline (“surfactant”) in type II cells of alveolar epithelium.

Cultured lung cells: interplay effects of beta-mimetics, prostaglandins and corticosteroids in the biosynthesis of dipalmitoyl lecithin

Cell lines derived from type II lung cells were used to study interplays of substances affecting incorporation of labeled precursors [1(-14)C]palmitate and [methyl-3H]choline into phosphatidyl choline. Ethanol stimulated markedly biosynthesis of dipalmitoyl phosphatidyl choline in cloned rabbit lung cells; the stimulating action of ethanol was reduced very much by cortisol and less by ritodrine. In the presence of 0.1 microM isoproterenol, two prostaglandins, E2 and F2alpha, caused marked depressions in the incorporation of both precursors by cell line A 549 derived from human lung adenocarcinoma. One concluded that among the agents studied, ethanol and cortisol are potent antagonists, and so were also the prostaglandins and isoproterenol.

Effects of prostaglandins E2 and F2alpha on lecithin biosynthesis by cultured lung cells

Transformed cells from human lung carcinoma (Line A549), resembling type II pneumocytes, were cultured in monolayer at 37 degrees C and incubated for five hours with 3H-choline and 14C-palmitate in the presence of various concentrations of prostaglandins (PGS) E2 and F2alpha. In the control (no PG) the level of % palmitate incorporation was 13.5 x as high as that of choline, after taking isotope dilution into account. Between the concentrations studied, 0.1 and 10 muM, both prostaglandins stimulated markedly the incorporation of both precursors, though choline up to 3 x better than palmitate. This was indicated by a change in the palmitate/choline incorporation ratio from 13.5 to as low as 4.2. At the lowest PG concentration, 0.1 muM, PGE2 was much more effective than PGF2alpha in stimulating the incorporation of both precursors.

Ultrastructure of in vitro type 2 epithelial cell cysts derived from adult rabbit lung cells

Fragments of adult rabbit lung, composed chiefly of terminal airway obtained by a trypsin digestion technique were maintained on collagen-coated cellulose sponges in Ham's F12 medium. Cell-sponge associations were examined with light microscopy, scanning and transmission electron microscopy over a period from 6 to 28 days. After an initial 24- to 48-hour period of cell migration from the airway fragment, sponge matrices became lined with cells suggestive of alveolar macrophages. After one week in culture, cysts appeared to be composed entirely of type 2 epithelial cells. These were characterized by a microvillous apical border and an elaborate junctional complex. The lumen of these cysts contained both myelin-like lamellar configurations and tubular myelin structures such as have been described from pulmonary washings. Consistent with the age of the sponge cultures, one or more cyst types described as young, middle and late could be found simultaneously. Middle aged cysts showed signs of active secretion into the lumen. Late cysts showed changes in the epithelium comprising the cyst wall suggestive of a cell type intermediate between type 1 and type 2 epithelial cells.

Culture characteristics of cells derived from type II pneumocyte enriched fractions from rabbit and rat

Type II cell enriched fractions were isolated from rabbit and rat lungs using density gradient centrifugation. Cultures established from these fractions contained predominantly cells similar in most morphological respects to type II pneumocytes. These were in continuous replicating culture for 1 year and still exhibited contact inhibition. Membrane-bound structures reminiscent of, but no longer strictly identical to, type II cell lamellar cytosomes were seen in cells from these long-term cultures although their numbers were reduced in comparison to lamellar bodies in freshly isolated cells. Mitochondrial numbers and sizes, determined morphometrically, were reduced after culture in comparison to freshly isolated type II cells and those in situ. Phosphatidylcholine was synthesized by these cells and released into the extracellular medium. Application of laser activated electronic sizing data, confirmed by direct micrometry, demonstrated a significant increase in cell size as a function of culture. This sizing data, after prior confirmation by electron microscopy, was used as an aid in identifying type II cells and macrophages in dispersion, especially with those cells derived from rabbit lungs.

Studies of in vitro infection by Trypanosoma cruzi. I. Ultrastructural studies on the invasion of macrophages and L-cells

The interactions of Trypanosoma cruzi with L-cells, and with normal and activated macrophages in vitro were studied by ultrastructural techniques. T. cruzi actively invades cultured L-cells and uniformly destroys them. Normal macrophages could control a 1:1 (parasite to host cell) infection, but were destroyed by a 10:1 infection. BCG-activated macrophages, however, controlled a 10:1 infection but not one at a ratio of 100:1. It appears that parasites that survive within host cells do so outside cytoplasmic vacuoles, whereas when they are relegated to host cell phagosomes they are destroyed. Culture forms of T. cruzi have several means of access into host cells. Marcrophages are better able to survive infection than are non-phagocytic cells. Finally, it is suggested that control of an experimental infection in vitro is dependent upon numbers of parasites to macrophages as well as the state of the macrophages.

Sites of cytoplasmic ribonucleoprotein-filament assembly in relation to helical body formation in axenic trophozoites of Entamoeba histolytica

Axenic trophozoites of Entamoeba histolytica showed increased logarithmic growth but absence of "chromatoid" material (stacked helical arrays of ribonucleoprotein [RNP]) when grown in an all-liquid monophasic culture. Organisms grown in a liquid overlay on a semisolid slant (biphasic medium) showed slow logarithmic growth and the presence of chromatoid material. Chromatoid material accumulated in the rapidly growing trophozoites from monophasic culture during treatment with the Vinca alkaloid, vinblastine. Many of the glycogen-free regions of vinblastine-treated trophozoites as well as, to a lesser degree, of normal cells grown in monophasic and biphasic cultures, contained free ribosomes and randomly oriented 60 A filaments. As ribonucleoprotein assumed the packed helical configuration, areas consisting of parallel, packed filaments could be detected adjacent to and continuous with the ordered RNP arrays. This arrangement could be visualized most frequently in vinblastine-treated trophozoites grown in monophasic cultures. Depending on the tilt of the section with respect to the longitudinal axis of individual helices, 60 A filamentous material could be demonstrated associated with the RNP helices. Localization of ribonucleoprotein precursors was followed by means of high resolution radioautography with uridine-(3)H and cytidine-(3)H. With a short (30-min) pulse, label could be visualized only over the glycogen-free areas containing free ribosomes and filaments. With 60-min pulses, label could also be seen over the packed helical arrays. With 30-min pulses followed by a 60-min cold chase, label was seen chiefly over RNP helices. It is postulated that the areas containing ribosomes and filaments represent sites of assembly of the RNP helices possibly on a filament protein column. The possibility that the final helical configuration may be due to a property of this protein is suggested.