Effects of cadmium,copper, and zinc on growth and thiol content of aquatic hyphomycetes

The effects of cadmium, copper, and zinc on the growth of ten strains ofaquatic hyphomycetes were investigated. On a solid medium, Cd and Cu reducedradial growth of most strains by 50% at concentrations between150–400 µM; in a liquid medium, the strains were more sensitive.The inhibitory effects of zinc were much less severe. Two isolates(Articulospora tetracladia and Tetracladium marchalianum) from a copper-minestream were more resistant against copper than conspecific strains from anon-polluted stream. Heliscus lugdunensis and Varicosporium elodeaeresponded to Cd exposure, but not to Cu or Zn exposure, by increasedsynthesis of SH-containing compounds. Glutathione levels showed a unimodalresponse to increasing Cd and Zn exposure. With copper, glutathionedecreased at intermediate levels of contamination. In the presence of Cd, H. lugdunensis synthesized several unknown sulfur-rich substances that wereabsent or produced at reduced rates in control cultures.     

Anaerobic electron acceptor chemotaxis in Shewanella putrefaciens.

Shewanella putrefaciens MR-1 can grow either aerobically or anaerobically at the expense of many different electron acceptors and is often found in abundance at redox interfaces in nature. Such redox interfaces are often characterized by very strong gradients of electron acceptors resulting from rapid microbial metabolism. The coincidence of S. putrefaciens abundance with environmental gradients prompted an examination of the ability of MR-1 to sense and respond to electron acceptor gradients in the laboratory. In these experiments, taxis to the majority of the electron acceptors that S. putrefaciens utilizes for anaerobic growth was seen. All anaerobic electron acceptor taxis was eliminated by the presence of oxygen, nitrate, nitrite, elemental sulfur, or dimethyl sulfoxide, even though taxis to the latter was very weak and nitrate and nitrite respiration was normal in the presence of dimethyl sulfoxide. Studies with respiratory mutants of MR-1 revealed that several electron acceptors that could not be used for anaerobic growth nevertheless elicited normal anaerobic taxis. Mutant M56, which was unable to respire nitrite, showed normal taxis to nitrite, as well as the inhibition of taxis to other electron acceptors by nitrite. These results indicate that electron acceptor taxis in S. putrefaciens does not conform to the paradigm established for Escherichia coli and several other bacteria. Carbon chemo-taxis was also unusual in this organism: of all carbon compounds tested, the only positive response observed was to formate under anaerobic conditions.     

Superoxide dismutase mimetic activity of a cyclic tetrameric Schiff base N-coordinated Cu(II) complex

A pulse radiolytic study using the cyclic tetrameric Schiff base N-coordinated copper complex Cu(TAAB)²⁺ has been performed. The reaction of the Cu(TAAB)²⁺ complex with superoxide revealed pseudo first-order characteristics with the rate constant of k ₂ = (2.9 ± 0.5) × 10⁸ mol^–1 s^–1 dm³. The complex survive presence of competing serum albumin in physiological concentrations. The complex stability constant K = 1.15 × 10¹⁸ (log K = 18.06) is two orders of magnitude higher than that of Cu(II)-serum albumin (log K = 16.2). Transient changes of the stability during the oxidation/reduction process and in the presence of 600 /mol l^–1 albumin did not affect significantly either the electronic absorption of the complex or its catalytic activity.     

Junction formation in aggregated embryonal carcinoma cells

Under the action of supplemental calcium, H6 mouse embryonal carcinoma cell aggregates undergo compaction, a morphological phenomenon similar to mouse embryonic compaction. Formation of various types of cell junctions, especially gap junctions, is associated with compaction of the embryo and we sought to analyze the pattern of junction formation during aggregation and compaction of H6 cells. At 24 hr of aggregation, gap junctions were abundant in both uncompacted and compacted aggregates but quantitative analysis of freeze fracture replicas of these junctions showed a 20-fold increase in the size of the largest gap junctions in compacted aggregates. Such a difference in size could even be detected at 12 hr of aggregation. Tight junctions were not normally formed in 12 hr aggregates but initial stages of tight junction formation could be noticed in 12 hr compacted aggregates. More definitive tight junctions and desmosomes were evident only after 48 hr of aggregation. Thus we have observed that both uncompacted and compacted aggregates can form gap junctions at similar frequencies, suggesting that cell flattening, which contributes to the compacted morphology, is not a requisite for gap junctions. Likewise, generation of the compacted morphology seems to be independent of gap junction formation. This supports the idea that compaction in embryonal carcinoma cells results from calcium-induced cell flattening, probably through the mobilization of cytoskeletal elements. Calcium-dependent features of H6 cell aggregation and compaction enables the independent analysis of separate steps in compaction.     

Effects of aplysiatoxin and debromoaplysiatoxin on growth and differentiation of normal human bronchial epithelial cells

The effects of aplysiatoxin and debromoaplysiatoxin on the clonal growth rate, cross-linked envelope formation and plasminogen activator secretion of normal human bronchial epithelial cells were studied. Neither compound was mitogenic over a wide range of concentrations (10^–13 to 10^–7M). Both aplysiatoxin and debromoaplysiatoxin inhibited clonal growth rate with 50% inhibitory concentrations of 3 × 10^–11M and 10^–10M, respectively. Both compounds induced the formation of cross-linked envelopes and increased plasminogen activator secretion with equal potency. These data are similar to those previously obtained with 12-0-tetradecanoylphorbol-13-acetate and teleocidin B and suggest that aplysiatoxin and debromoaplysiatoxin induce terminal squamous differentiation in normal human bronchial epithelial cells.Abbreviations TPA 12-0-tetradecanoylphorbol-13-acetate - NHBE Normal Human bronchial epithelial - ID₅₀ 50% inhibitory concentration (dose) - PA Plasminogen activator - CLE Cross-linked envelope - LHC Laboratory of Human Carcinogenesis     

The effects of diphosphonates on the growth and glycolysis of connective-tissue cells in culture.

1. The effects of two diphosphonates (compounds containing a P-C-P bond), disodium dichloromethanediphosphonate and disodium 1-hydroxyethane-1,1-diphosphonate, on the metabolism of cultured rat calvaria cells, rabbit ear cartilage cells and rat skin fibroblasts were investigated. 2. The diphosphonates had no effect on the growth of cartilage cells and on the exponential growth of the calvaria cells and the fibroblasts. However, dichloromethanediphosphonate stopped the growth of the calvaria cells and the fibroblasts after the beginning of confluence, whereas the untreated cells were still growing to a certain extent. This inhibition was dose-dependent. After the drug was withdrawn, the cells recovered slowly. 1-Hydroxyethane-1,1-diphosphonate had no detectable effect on the growth of any of the cell types studied. Both diphosphonates decreased the cloning efficiency of calvaria cells and fibroblasts. 3. The K+ content of cartilage, calvaria and skin cells was diminished only by the highest (0.25 mM) concentration of dichloromethanediphosphonate. 4. Radioactive dichloromethanediphosphonate and 1-hydroxyethane-1,1-diphosphonate were taken up linearly with time for at least 48 h by calvaria cells and fibroblasts. The diphosphonate concentration in the cells depended on its concentration in the medium. 5. Both diphosphonates, in a dose-dependent fashion, markedly inhibited glycolysis, dichloromethanediphosphonate being more effective than 1-hydroxyethane-1,1-diphosphonate, at drug doses that had no effect on cell growth or cellular K+ content. Calvaria cells were much more sensitive than cartilage cells. When cartilage cells were cultured in an N2 atmosphere, these effects on glucose and lactate metabolism disappeared. 6. As increased acid production appears to be associated with resorption of bone, this decrease in lactate may explain why diphosphonates are effective inhibitors of bone resorption in vivo.     

Regulation of the synthesis of lutropin-induced protein in rat testis Leydig cells

The mechanism of action of lutropin on the stimulation of the synthesis of a specific lutropin-induced protein in rat testis Leydig cells was investigated. Lutropin-induced protein has a mol.wt. of approx. 21000 and is detected by labelling the Leydig-cell proteins with [³⁵S]methionine, followed by separation by polyacrylamide-gel electrophoresis and radioautography of the dried gel. The incorporation of ³⁵S into lutropin-induced protein was used as an estimate for the synthesis of the protein. Incubation of Leydig cells with dibutyryl cyclic AMP or cholera toxin also resulted in the stimulation of synthesis of the protein. Synthesis of lutropin-induced protein, when maximally stimulated with 100ng of lutropin/ml, could not be stimulated further by addition of dibutyryl cyclic AMP. Addition of 3-isobutyl-1-methylxanthine, a phosphodiesterase inhibitor, further increased synthesis of the protein in the presence of a submaximal dose of lutropin (10ng/ml) but not in the absence of lutropin or with maximal amounts of lutropin (100 and 1000ng/ml). Actinomycin D prevented the effect of lutropin on the stimulation of lutropin-induced protein synthesis when added immediately or 1h after the start of the incubation, but not when added after 5–6h. This is interpreted as reflecting that, after induction of mRNA coding for lutropin-induced protein, lutropin had no influence on the synthesis of the protein in the presence of actinomycin D. Synthesis of the protein was also stimulated in vivo by injection of choriogonadotropin into rats 1 day after hypophysectomy, and the time course of this stimulation of lutropin-induced protein synthesis in vivo was similar to that obtained by incubating Leydig cells in vitro with lutropin. From these results it is concluded that stimulation of lutropin-induced protein synthesis by lutropin is most probably mediated by cyclic AMP and involves synthesis of mRNA.     

Distribution of cell surface lets protein in co-cultures of normal and transformed cells

When LETS protein positive and negative cells were co-cultured, the positive cells remained as positive and the negative cells remained as negative. Apparently the transformed cells do not secrete factors which are sufficient to influence the distribution of surface LETS protein on normal cells.