Monoclonal antibodies against alpha toxin of Clostridium perfringens

Ten distinct monoclonal antibodies (MAbs) against alpha toxin of Clostridium perfringens were produced by the fusion of SP2/O with spleen cells of mice immunized with alpha toxoid, and alpha toxin mixed with or without ethylenediamine-tetraacetate (EDTA). The antibody activity was evaluated by antigen-binding activity in an enzyme linked immunosorbent assay (ELISA), by phospholipase C (PLC)-neutralizing activity using both egg yolk lecithin and p-nitrophenylphosphoryl-choline (PNPPC) hydrolysis reactions and by anti-lethal activity in mice. Since the toxin-neutralizing activities of each MAb were not parallel, it has been suggested that the three biological activities may not be located in the same site in the toxin molecule. This report also describes the development of a simple purification of the toxin by affinity chromatography and a sensitive immunoassay for quantitation of the toxin using the monoclonal antibody.     

Germination in spores of Dryopteris filix-mas: Regulation of rhizoid elongation as a second phytochrome-mediated response

Spore germination in Dryopteris filix-mas occurs via a cascade of cellular responses, and chlorophyll formation, mitosis or rhizoid elongation are commonly used as parameters to determine spore germination. Detailed investigations of these parameters led to the hypothesis that they are regulated by different, independent phytochrome-mediated responses. This concept could be confirmed, as is described in this paper which demonstrates that perception of light via phytochrome occurs within two different phases separated in time. Presence of the far-red absorbing phytochrome form, P_fr, for 36 h, induces chlorophyll formation and the first unequal cell division, by which a rhizoid initial and a protonemal initial are formed (first phytochrome-mediated response). However, rhizoid elongation requires a second period of P_fr, presence (second phytochrome-mediated response). There is a clear temporal distinction between the first and the second phytochrome-mediated response with respect to the coupling of P_fr to the transduction chain; P_fr is unable to induce rhizoid growth until 60 h after the start of the first red irradiation. The effectivity of P_fr for inducing the second response shows an optimum at ca 96 h after the beginning of the presence of P_fr; thereafter, it declines slowly. The fluence-response relationship and the presence of red/far-red reversibility demonstrate that rhizoid elongation is a low-fluence response mediated by phytochrome and is independent of the first phytochrome response.     

Comparison of axonemal proteins from two kinds of Tetrahymena. I. Different characteristics of dyneins in heat stability

Tetrahymena thermophila could still swim after incubation of the cell body at 40°C for 30 min, whereas Tetrahymena pyriformis did not show any motility after the treatment. Turbidity measurements revealed that axonemes of T. pyriformis lost ATP-dependent sliding activity by the heat treatment, whereas those of T. thermophilia still had the activity under the same conditions. In connection with this difference in susceptibility to high temperature, the biochemical characteristics of dyneins were compared between the two species of Tetrahymena. Axonemal dyneins from the two species had significant vanadate-sensitive ATPase activity even after the heat treatment. Native gel electrophoresis and the following two-dimensional electrophoresis showed that the outer arm dynein of T. thermophilia is more stable in maintaining native configuration than that of T. pyriformis against the heat treatment, although both treated dyneins keep three (α, β and γ) subunits. Analysis by peptide mapping demonstrated that β- and γ-subunits of the outer arm dynein are considerably different in amino acid sequences between the two species. These results imply that dynein of T. thermophilia changed their amino acid sequences and biochemical characteristics to adapt to high temperature.     

Molecular genetics of Thiobacillus ferrooxidans.

Thiobacillus ferrooxidans is a gram-negative, highly acidophilic (pH 1.5 to 2.0), autotrophic bacterium that obtains its energy through the oxidation of ferrous iron or reduced inorganic sulfur compounds. It is usually dominant in the mixed bacterial populations that are used industrially for the extraction of metals such as copper and uranium from their ores. More recently, these bacterial consortia have been used for the biooxidation of refractory gold-bearing arsenopyrite ores prior to the recovery of gold by cyanidation. The commercial use of T. ferrooxidans has led to an increasing interest in the genetics and molecular biology of the bacterium. Initial investigations were aimed at determining whether the unique physiology and specialized habitat of T. ferrooxidans had been accompanied by a high degree of genetic drift from other gram-negative bacteria. Early genetic studies were comparative in nature and concerned the isolation of genes such as nifHDK, glnA, and recA, which are widespread among bacteria. From a molecular biology viewpoint, T. ferrooxidans appears to be a typical member of the proteobacteria. In most instances, cloned gene promoters and protein products have been functional in Escherichia coli. Although T. ferrooxidans has proved difficult to transform with DNA, research on indigenous plasmids and the isolation of the T. ferrooxidans merA gene have resulted in the development of a low-efficiency electroporation system for one strain of T. ferrooxidans. The most recent studies have focused on the molecular genetics of the pathways associated with nitrogen metabolism, carbon dioxide fixation, and components of the energy-producing mechanisms.     

Phytochrome-mediated phototropism inAdiantum cuneatum young leaves

Phototropism of youngAdiantum fern leaves is induced by red light as well as blue light. The red light response is mediated by phytochrome. This is the first evidence of phytochrome action in diploid fern tissue. The blue light response is mainly mediated not by phytochrome, but probably by a blue light-absorbing pigment as in the case of almost all plants and fungi. The red light-induced phototropism becomes detectable within 2 hr after the onset of unilateral light. The highest bending rate is about 10 degrees/hr, which occurs between 3–5 hr after the induction of the tropic response. The bending region is about 6–8 mm from the highest point of the coiled crozier where the growth rate becomes slow.     

Pressurized gas transport in two Japanese alder species in relation to their natural habitats

Oxygen uptake measurements have shown that pressurized gas transport, resulting from the physical effect of thermo-osmosis of gases, improves oxygen supply to the roots of the seedlings in two alder speciesAlnus japonica (Thunb.) Steud. andAlnus hirsuta (Spach) Rupr., which are both native in Japan. When gas transport conditions were established by irradiation of the tree stems the internal aeration was increased to a level nearly equal to the oxygen demand of the root system in leafless seedlings ofA. hirsuta, but was higher inA. japonica so that excess oxygen was excreted into the environment. An increase of superoxide dismutase (SOD) activity, which protects plants from toxic oxygen radicals and post-anoxic injury, has been observed in root tissues ofA. japonica when the seedlings were flooded for 3 days. The increase of SOD activity, in concert with high gas transport rates, may enable this tree species to grow in wet sites characterized by low oxygen partial pressure in the soil and by varying water tables. A less effective gas transport, flood-induced reduction of SOD activity in root tissues, and reduced height growth in waterlogged soil may be responsible for the fact thatA. hirsuta is unable to inhabit wettland sites.     

Oral administration of antigen does not influence the proliferation and IFN-γ production of responsive CD8+ T cells but enables to establish T cell clones with different lymphokine production profile.

Feeding of a whole casein diet, which abolished the α_s1-casein-specific proliferation and IFN-γ productivity of CD⁴⁺ T cells, did not affect the proliferative response of CD8⁺ T cells with regard to the antigen dose response, cell dose response, kinetics of the proliferation and epitope specificity, as well as IFN-γ production. To assess the characteristics of the CD8⁺ T cells, we established α_s1-casein-specific CD8⁺ T cell clones from both casein-fed and control mice. The established clones produced different amount of IFN-γ and IL-10, and one clone derived from the casein-fed mice produced a remarkable amount of IL-10. The clones from casein-fed mice produced considerable amounts of TGF-β, while those from control mice produced only small amounts. The possible role of CD8⁺ T cells in oral tolerance is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.