Polygalacturonase inhibiting protein in plant cell walls

Polygalacturonase inhibiting protein (PGIP) is localized in plant cell walls and plays an important role both in pectic substance metabolism and in prevention of the penetration of phytopathogenic microorganisms. Apparently, PGIP is responsible for the specificity of cell--cell interactions during pollination or inoculation by fungi nonpathogenic for the particular plant. PGIPs from different plants share a basic common structure. They are rather thermostable glycoproteins enriched with leucine and contain about 20% carbohydrates; the molecular weight varies between 37-54 kD. The synthesis of PGIP is encoded by one gene, and its expression is stimulated by injury and fungal infection. The resistance of plant tissues to infection frequently correlates with PGIP expression and with inhibiting action on fungal PG. Thus, PGIP is believed to be useful for gene engineering to obtain transgenic plants resistant to fungal infection or retaining commercial value during storage.     

HEAVY METAL–INDUCED OXIDATIVE STRESS IN ALGAE1

Heavy metals, depending on their oxidation states, can be highly reactive and, as a consequence, toxic to most organisms. They are produced by an expanding variety of anthropogenic sources suggesting an increasingly important role for this form of pollution. The toxic effect of heavy metals appears to be related to production of reactive oxygen species (ROS) and the resulting unbalanced cellular redox status. Algae respond to heavy metals by induction of several antioxidants, including diverse enzymes such as superoxide dismutase, catalase, glutathione peroxidase and ascorbate peroxidase, and the synthesis of low molecular weight compounds such as carotenoids and glutathione. At high, or acute, levels of metal pollutants, damage to algal cells occurs because ROS levels exceed the capacity of the cell to cope. At lower, or chronic, levels algae accumulate heavy metals and can pass them on to organisms of other trophic levels such as mollusks, crustaceans, and fishes. We review here the evidence linking metal accumulation, cellular toxicity, and the generation of ROS in aquatic environments.     

In murine AIDS, B cells are early targets of defective virus and are required for efficient infection and expression of defective virus in T cells and macrophages.

Previous studies showed that B cells and CD4+ T cells are required for induction of a murine retrovirus-induced immunodeficiency syndrome, murine AIDS. Using B6 mice deficient in mature B cells as a result of a knockout of the transmembrane exon of the immunoglobulin M gene, we found that spleen and other tissues from murine AIDS virus-infected mice did not express the defective virus (BM5def) required for induction of disease, even though helper viruses were readily detectable and BM5def proviral DNA was present. This indicates that the B-lineage cells are the primary targets for infection and expression of the defective virus and that in the absence of mature B cells, there is inefficient infection of T cells and macrophages.     

The ferric iron-binding protein of pathogenic Neisseria spp. functions as a periplasmic transport protein in iron acquisition from human transferrin

The ferric iron-binding protein (Fbp) expressed by pathogenic Neisseria spp. has been proposed to play a central role in the high-affinity acquisition of iron from human transferrin. The results of this investigation provide evidence that Fbp participates in this process as a functional analogue of a Gram-negative periplasmic-binding protein component, which operates as a part of a general active transport process for the receptor-mediated, high-affinity transport of iron from human transferrin. Known properties of Fbp are correlated with those of other well-characterized periplasmic-binding proteins, including structural features and the reversible binding of ligand. Predictive of a periplasmic-binding protein, which functions in the high-affinity acquisition of iron, is that Fbp is a transient participant in the process of iron acquisition from human transferrin. Evidence for this is demonstrated by results of pulse–chase experiments. Taken together, the data described here and elsewhere suggest that pathogenic Neisseria spp. use a periplasmic-binding protein-mediated active transport mechanism for the acquisition of iron from human transferrin.     

Variations in expression of xenotropic murine leukemia virus genomes in lymphoid tissues of NZB mice.

Lymphocytes from Thy, Sp, LN, and BM and NZB mice were tested for expression of X-MuLV genomes as cell surface gp70 (XenCSA) or infectious virus. The results demonstrate major dissociations for these parameters of X-MuLV expression in different lymphoid compartments and suggest that factors involved in T lymphocyte differentiation modify the levels of expression in these two modes.     

A Simple and Automatic Leaflet Movement-monitoring System

A simple and automatic leaflet movement-monitoring system using phototransistors is described for Albizzia julibrissin.     

Murine plasma cells secreting more than one class of immunoglobulin heavy chain. III. Immunoglobulin production by established cultures and cloned lines of SAMM 368.

SAMM 368, a plasmacytoma which produces IgA-kappa and IgG2b-kappa was established in vitro from primary explants or after animal passage. The 9 lines that were established produced both paraproteins. The production of both immunoglobulins by single cells was demonstrated by immunofluorescent staining and cloning. Continuous culture of 3 parent lines for 18 months and 11 cloned lines for periods from 5 to 7 months demonstrated that double production is a stable characteristic of this plasmacytoma. Two single paraprotein-producing varients (IgG2b or IgA) were derived when cells were cultured in the presence of Fungizone. Chromosomal analysis of SAMM 368 indicates that this double producing tumor has a modal number similar to those observed in myelomas producing a single immunoglobulin class.