The flocculation of bacteria using cationic synthetic flocculants and chitosan

Summary Bacteria are flocculated with high molecular weight cationic synthetic flocculants and chitosan. High charge density polymers are the most effective of the synthetic flocculants. Only chitosan is effective in flocculating the E. coli and B. subtilis cultures in complex broth. The difference in effectiveness between the synthetic flocculants and chitosan for flocculating E. coli, B. subtilis and Z. mobilis may be attributed to hydrogen bonding between the polysaccharide flocculant and cell surface polymers in addition to electrostatic interactions, and, in complex media, complexation of synthetic polymers with anionic polyelectrolytes.     

Rb+ influxes differentiate between growth arrest of cells by different agents

The effect of cell cycle on Rb+ (K+) fluxes was studied in NIH 3T3 mouse fibroblasts. Serum starvation or isoleucine deprivation resulted in cell arrest at an early G1/G0 phase, accompanied by a marked decrease in both ouabain-sensitive and ouabain-resistant Rb+ influx. On the other hand, cells arrested at late G1/G0 phase by hydroxyurea treatment have high ouabain-sensitive and ouabain-resistant Rb+ influx. Butyric acid treatment resulted in cell arrest at an early G1/G0 phase, but in contrast to serum or isoleucine starvation did not decrease Rb+ influxes. It is thus shown that quiescent cells may have Rb+ influx rates as high as that of logarithmically growing cells. The results are consistent with the hypothesis that an increased ion permeability of the cell is initiated at a critical stage in G1/G0 phase, and that butyric acid may arrest the cell beyond that stage.     

Potentiation by the lithium ion of morphogenetic responses to a Xenopus inducing factor

We have cultured explants of Xenopus blastular animal cap tissue from embryos that had received an earlier treatment with LiCl and from their untreated siblings, in various concentrations of XTC-cell-derived mesoderm-inducing factor (XTC-MIF, Smith, 1987; Smith et al. 1988). The pretreatment with lithium that we used transforms later morphogenesis in the whole embryo to give radialized body forms with anterior/dorsal levels of structure grossly over-represented. In addition, animal caps from 'Li+' embryos were allowed to develop without exposure to in vitro MIF (Li+ controls) and compared with normal uninduced control explants, and explants were made from normal early blastulae but given various initial treatments with LiCl in culture. The results confirm that the lithium ion itself will not induce mesoderm in competent, animal cap tissue of Xenopus. It does, however, enhance the responsiveness of this tissue to XTC-MIF, in a way that parallels its recently reported effect in the case of another mesoderm inducer of different character, bFGF (Slack et al. 1988). The effects observed are sufficient to imply that the altered body pattern that follows lithium treatment, in whole embryos, could be caused by modulation of the responses to an unaltered pattern of in situ inductive stimuli. We also observe evidence that appreciable inductive signals reach animal pole tissue beyond the limits of mesoderm formation in normal development. Relatively low concentrations of MIF prevent the development of an epidermis-specific marker in dissociated blastular animal cap cells (Symes et al. 1988). When such experiments are repeated in relation to the lithium pretreatment of embryos, such treatment is seen to have sensitized the cell population, so that the MIF concentration range that assures complete suppression of the marker is reduced. The results are discussed in relation to induction considered as pattern formation.     

Simulation of nitrogen assimilation by heterotrophic soil microbial biomass

Assimilation of N by heterotrophic soil microbial biomass is associated with decomposition of organic matter in the soil. The form of N assimilated can be either low molecular weight organic N released from the breakdown of organic matter (direct assimilation), or NH⁺₄ and NO⁻₃ from the soil inorganic N pool, into which mineralized organic N is released (mineralization immobilization turnover). The kinetics of C and N turnover in soil is quantifiable by means of computer simulation models. NCSOIL was constructed to represent the two assimilation schemes. The rate of N assimilation depends on the rate of C assimilation and microbial C/N ratio, thereby rendering it independent of the assimilation scheme. However, if any of the N forms is labeled, a different amount of labeled N assimilation will be simulated by the different schemes. Experimental data on inorganic N and ¹⁵N and on organic ¹⁵N dynamics in soils incubated with ¹⁵N added as NH⁺₄ or organic N were compared with data simulated by different model schemes. Direct assimilation could not account for the amount of ¹⁵N assimilated in any of the experimental treatments. The best fit of the model to experimental data was obtained for the mineralization immobilization turnover scheme when both NH⁺₄ and NO⁻₃ were assimilated, in proportion to their concentration in the soil.     

Observations on the effect of radiotherapy,followed by injection of pig lymph node cells,in reducing the number of pulmonary tumors induced by intravenous injection of tumor cells into isogenic mice

Summary Pulmonary tumors were produced in A. strain mice by intravenous injection of A. strain mammary carcinoma cells. The mesenteric lymph nodes of pigs were immunized by implantation of fragments from the same tumors into the pig mesentery.Tumor-immune pig lymph node cells when injected IV 7 days after tumor cells did not reduce the number of tumors, counted on day 14. However, when preceded by 200 rad thoracic irradiation on day 3 (which increased the number of pig cells settling in the lungs) tumor-immune cells given IV reduced the number of tumors compared with the effect of irradiation alone, or in combination with nonimmune pig cells.When tumor-immune pig cells were injected IP on day 7 (following thoracic irradiation on day 3), no antitumor effect was observed. Thus immediate pig cell/tumor cell contact is important in order to obtain an antitumor effect.Pig cells immunized against a human bladder carcinoma did not reduce pulmonary tumor formation by one of the mouse tumors.     

Nuclear components responsible for the retention of steroid--receptor complexes, especially from the standpoint of the specifcity of hormonal responses.

1. By covalently linking nuclear components from hormone-sensitive cells to Sepharose 2B, it is possible to investigate the interaction between nuclear components and cytoplasmic receptor-steroid complexes by affinity chromatography. 2. Many factors are implicated in the specifity of nuclear-cytoplasmic interactions, including the nature of the nuclear components, the presence of the cytoplasmic receptor protein and the provision of the appropriate steroid ligand. 3. Two distinct sets of binding sites are present in nuclear extracts immobilized to Sepharose 2B, namely a small number of specific high-affinity sites and a larger number of non-specific low affinity-sites. 4. Considerable evidence supports the importance of the high-affinity binding sites in the manifestation of hormonal specificity in different tissues. Although the study has centred largely on androgenresponsive systems, the findings are germane to cytoplasmic-nuclear interactions in general. 5. The high-affinity or acceptor sites in nuclear extracts reside in the basic but non-histone protein fraction. 6. Hormonal specificity is seemingly maintained by both the cytoplasmic and nuclear components, and the results are discussed in the context of the mechanism of action of steroid hormones.