Transformation of MMC-E epithelial cells by acute 3611-MSV: inhibition of collagen synthesis and induction of novel polypeptides

Mouse embryo epithelial cells MMC-E were transformed by novel fibrosarcoma-inducing murine sarcoma virus 3611-MSV. The cells were analyzed for the production and deposition of pericellular glycoproteins by immunofluorescence and by radioactive metabolic and cell surface labeling techniques followed by analysis in polyacrylamide gels and fluorography. The pericellular fibronectin matrix was lost, but unlike in virus-transformed fibroblastic cells, the production of fibronectin was not affected. The major differences detected were decrease in collagen production and initiation of synthesis of two major glycoproteins with Mr 58,000 and 60,000. Cell surface carbohydrate labeling indicated that after 3611-MSV transformation the cells expressed Mr 100,000 and 68,000 polypeptides. The present and previous results show that viral transformation of epithelial cells induces different transformed phenotypes that are associated with distinct alterations in pericellular glycoproteins.     

Inhibition of modulation of thymus-leukemia antigens by concanavalin A.

When incubated at 37 °C in medium containing antibodies specific for thymus-leukemia (TL) antigens, viable cells bearing these antigens become resistant to the cytolytic effects of guinea pig complement, a process termed antigenic modulation. Antibody-induced membrane redistribution of the TL antigens, detected by indirect immunofluorescence, occurs with a similar pace. When high concentrations of concanavalin A (Con A) were included with antibodies in the incubation medium, TL antigenic modulation as well as antigen patching and capping were markedly inhibited, similar to effects of Con A on membrane immunoglobulin redistribution with murine spleen cells. Colchicine antagonized the inhibition by Con A suggesting the involvement of microtubules. In parallel experiments high concentrations of Con A failed to alter the quantity of TL antigen expression or its rate of change with time during incubation in cognate antisera. These results support the hypotheses that (a) generalized alterations in membrane receptor mobility may be induced by ligand binding to the cell membrane, and (b) under certain conditions stable interactions occur between normally independent cell surface antigens.     

Role of β-carotene in the reaction centres of Photosystems I and II of spinach chloroplasts prepared in non-polar solvents

Spinach chloroplasts have been prepared nonaqueously using non-polar solvents (n-hexane, CCl₄, n-heptane) and the β-carotene content extracted in a controlled manner. This procedure is reproducible and does not result in large structural or spectral changes of the chloroplasts. The organisation of the chlorophyll-proteins is unaltered, as fragmentation with digitonin results in the appearance of the same fractions as found previously for aqueously-prepared chloroplasts, including the pink zone containing cytochromes f and b₆ in the ratio 1:2. The chloroplasts possess both Photosystem I activity (P-700 photo-bleaching, and NADP⁺ photoreduction) and Photosystem II activity (parabenzoquinone reduction with Mn²⁺ as electron donor, and chlorophyll fluorescence induction). Use of moderate intensity red illumination has allowed a study of the role of β-carotene in photochemistry separate from its roles in energy transfer and photoprotection.Removal of the fraction of β-carotene closely associated with the Photo-system I reaction centre caused the rate of NADP⁺ photoreduction to fall to a low, but significantly non-zero level. Thus, in the complete absence of β-carotene, photochemistry can still be observed, however the specific association of β-carotene with the reaction centre is required for maximal rates. We propose that β-carotene bound at the reaction centre decreases the rate of transfer of excitation energy away from the reaction centre, and increases the rate of photochemistry. It is possible that this occurs via formation of an exciplex between ground state β-carotene and chlorophyll in the first excited state.     

Integration of mammalian, microbial and drosophila procedures for evaluating chemical mutagens.

cis-Platinum(II)diamminodichloride (PDD), an anti-tumor agent, induced auxotrophic mutations in Escherichia coli, some of which were reverted to prototrophy by exposure to PDD, 2-aminopurine (2-AP), and N-methyl-N′-nitro-N-nitroguanidine (NTG), but not ICR derivatives. Similarly, various 2-AP-, NTG-, and ultraviolet light-induced auxotrophs were reverted to prototrophy by PDD. Some PDD-induced auxotrophs carried nonsense mutations and others could be phenotypically suppressed by growth with streptomycin. Although these findings suggest that PDD promotes base substitutions, this mutagen may also cause base subtractions because (like NTG)it induced, at reduced frequency, reversion to prototrophy of certain ICR-induced auxotrophs. Isomeric trans-platinum(II)diamminodichloride, which lacks anti-tumor activity, was an ineffective mutagen. Near-optimal conditions for PDD-induced mutagenesis entailed prolonged cultivation with low levels of mutagen where the frequency of forward mutation to auxotrophy was 10⁻³ and that of a selected trp isolate to prototrophy was 10⁻².     

Sterile host yeasts (SHY): a eukaryotic system of biological containment for recombinant DNA experiments.

A system of biological containment for recombinant DNA experiments in Saccharomyces cerevisiae (Brewer's/Baker's yeast) is described. The principle of containment is sterility: the haploid host strains all contain a mating-type-non-specific sterile mutation. The hosts also contain four auxotrophic mutations suitable for selection for the various kinds of vectors used. All vectors are derivatives of pBR322 which can be selected and maintained in both yeast and Escherichia coli. The system has recently been certified at the HV2 level by the National Institutes of Health.     

The C1B domains of novel PKCε and PKCη have a higher membrane binding affinity than those of the also novel PKCδ and PKCθ

The C1 domains of novel PKCs mediate the diacylglycerol-dependent translocation of these enzymes. The four different C1B domains of novel PKCs (δ, ε, θ and η) were studied, together with different lipid mixtures containing acidic phospholipids and diacylglycerol or phorbol ester. The results show that either in the presence or in the absence of diacylglycerol, C1Bε and C1Bη exhibit a substantially higher propensity to bind to vesicles containing negatively charged phospholipids than C1Bδ and C1Bθ. The observed differences between the C1B domains of novel PKCs (in two groups of two each) were also evident in RBL-2H3 cells and it was found that, as with model membranes, in which C1Bε and C1Bη could be translocated to membranes by the addition of a soluble phosphatidic acid without diacylglycerol or phorbol ester, C1Bδ and C1Bθ were not translocated when soluble phosphatidic acid was added, and diacylglycerol was required to achieve a detectable binding to cell membranes. It is concluded that two different subfamilies of novel PKCs can be established with respect to their propensity to bind to the cell membrane and that these peculiarities in recognizing lipids may explain why these isoenzymes are specialized in responding to different triggering signals and bind to different cell membranes.     

~（60）Co－γ射线诱变柠檬酸产生菌黑曲霉Co9－6的研究

本试验采用￣（６０）Ｃｏ－γ射线对柠檬酸产生菌黑曲霉Ｃｏ９－６进行辐射,经两次处理后选育出Ｌ１２１７和Ｌ８０１两株优良柠檬酸产生菌。中试结果表明菌株Ｌ１２１７较Ｌ８０１更优：产酸率较菌株Ｃｏ９－６提高１７．６％、发酵周期缩短１３．４％、对糖转化率提高１３．３％。