ANTINEOPLASTIC ACTIVITY OF CULTURED BLUE-GREEN ALGAE (CYANOPHYTA)1

A large-scale screening program was initiated to evaluate laboratory-cultured blue-green algae (cyanobacteria) as a source of novel antineoplastic agents. Approximately 1000 cyanophyte strains from diverse habitats were cultured to provide extracts for testing. The screening program identified the families Scytonemataceae and Stigonemataceae as prolific producers of novel cytotoxic compounds. Rates of rediscovery of known compounds were relatively low.     

Temporal and spatial distribution of type XII collagen in high cell density culture of periosteal-derived cells.

Periosteal-derived cells of young chicks have been reported to possess the potential to undergo terminal differentiation into osteogenic or chondrogenic phenotypes under high cell density culture conditions. In this culture, the temporal and spatial distribution of type XII collagen was immunocytochemically assessed using a monoclonal antibody. These high-density plated cells first formed a multilayer of fibroblast-like cells, in which type I and XII collagen were evenly distributed throughout the full thickness of the culture. With time, the top portion of the culture differentiated into bone tissue, while cells below this top layer differentiated into hypertrophic chondrocytes. In this transition, type XII collagen was temporally and spatially colocalized primarily with type I collagen: the top portion of bone layer was positive for both type I and XII collagens, whereas their staining intensity in the bottom portion decreased with time in culture. Using this antibody, type XII collagen was also found in developing embryonic chick tibiotarsus. These observations, taken together, suggest that type XII collagen production is a characteristic property of bone-forming cells.     

The cytoplasmic tail dileucine motif LL572 determines the glycosylation pattern of membrane-type 1 matrix metalloproteinase

Membrane-type 1 matrix metalloproteinase (MT1-MMP; MMP-14) drives fundamental physiological and pathological processes, due to its ability to process a broad spectrum of substrates. Because subtle changes in its activity can produce profound physiological effects, MT1-MMP is tightly regulated. Currently, many aspects of this regulation remain to be elucidated. It has recently been discovered that O-linked glycosylation defines the substrate spectrum of MT1-MMP. We hypothesized that a mutual interdependency exists between MT1-MMP trafficking and glycosylation. Lectin precipitation, metabolic labeling, enzymatic deglycosylation, and site-directed mutagenesis studies demonstrate that the LL(572) motif in the cytoplasmic tail of MT1-MMP influences the composition of the complex O-linked carbohydrates attached to the hinge region of the protein. This influence appears to be independent from major effects on cell surface trafficking. MT1-MMP undergoes extensive processing after its synthesis. The origins and the molecular characters of its multiple forms are incompletely understood. Here, we develop and present a model for the sequential, post-translational processing of MT1-MMP that defines stages in the post-synthetic pathway pursued by the protein.     

Vector competence of Coquillettidia linealis (Skuse) (Diptera: Culicidae) for Ross River and Barmah Forest viruses

Abstract Coquillettidia linealis is a severe pest on some of the Moreton Bay islands in Queensland, Australia, but little is known of its breeding habitats and biology. Because of its high abundance and its association with Ross River (RR) and Barmah Forest (BF) viruses by field isolation, its vector competence was evaluated in the laboratory by feeding dilutions of both viruses in blood. For RR, Cq. linealis was of comparable efficiency to Ochlerotatus vigilax (Skuse), recognised as being a major vector. Results were as follows for Cq. linealis and Oc. vigilax , respectively: dose to infect 50%, 10^2.2 and <10^1.7 CCID₅₀/mosquito; 88% and 90% disseminated infection at 4 days postinfection; transmission at 4 days with rates of 68−92% and 25−60%. For BF dose to infect 50%, 10^2.7 and 10^2.0; disseminated infection rates on first transmission day (day 6), 40% and 70%; transmission rates of 8−16% and 0−10%. As a capillary-tube method was used rather than suckling mice to demonstrate transmission, transmission rates may be underestimates. This, the first study of the vector competence of Cq. linealis in Australia, demonstrates that this species deserves control on the southern Moreton Bay islands.     

Differential effects of elicitors on the viability of rice suspension cells

We have compared the effects of two elicitors of defense-related processes on rice (Oryza sativa L.) suspension cells. Both chitosan and salicylic acid induced the accumulation of extracellular chitinase, thickening of the cell wall, and a variety of cytological changes in treated cells. Chitosan also induced the production of a brown pigment and cell death. Both of these effects depended on the availability of reactive oxygen species, because the damage was greatly reduced by either catalase or free-radical scavengers. Pretreating cells with salicylic acid also protected them from the cytotoxic effects of chitosan. This type of induced tolerance persisted when salicylic acid was removed and was not simply due to the release of extracellular substances, because salicylic acid-treated cells did not protect untreated cells from chitosan-induced death. Salicylic acid also stimulated the production of a 10-kilodalton subtilisin inhibitor that was not produced by chitosan-treated cells. Most of these changes are associated with the hypersensitive response of many plant species, including monocotyledons, and may serve as an in vitro model for investigating the biochemistry of some diseases.     

Nitrogen‐mediated effects of elevated CO2 on intra‐aggregate soil pore structure

Soil pore structure has a strong influence on water retention, and is itself influenced by plant and microbial dynamics such as root proliferation and microbial exudation. Although increased nitrogen (N) availability and elevated atmospheric CO₂ concentrations (eCO₂) often have interacting effects on root and microbial dynamics, it is unclear whether these biotic effects can translate into altered soil pore structure and water retention. This study was based on a long‐term experiment (7 yr at the time of sampling) in which a C₄ pasture grass (Paspalum notatum) was grown on a sandy loam soil while provided factorial additions of N and CO₂. Through an analysis of soil aggregate fractal properties supported by 3D microtomographic imagery, we found that N fertilization induced an increase in intra‐aggregate porosity and a simultaneous shift toward greater accumulation of pore space in larger aggregates. These effects were enhanced by eCO₂ and yielded an increase in water retention at pressure potentials near the wilting point of plants. However, eCO₂ alone induced changes in the opposite direction, with larger aggregates containing less pore space than under control conditions, and water retention decreasing accordingly. Results on biotic factors further suggested that organic matter gains or losses induced the observed structural changes. Based on our results, we postulate that the pore structure of many mineral soils could undergo N‐dependent changes as atmospheric CO₂ concentrations rise, having global‐scale implications for water balance, carbon storage, and related rhizosphere functions.