Assessing toxicity of Lake Diefenbaker (Saskatchewan,Canada) sediments using algal and nematode bioassays

Lake Diefenbaker, on the South Saskatchewan River, Saskatchewan, Canada, receives, on average, 90% of its inflow from snowmelt and rainfall in the Rocky Mountains. The inflowing rivers also receive irrigation return flows and municipal and industrial effluents which may result in the contamination of lake sediments. The sediments were assessed by nematode and algal bioassays.The toxicity of five chemical fractions of the sediment was determined using the nematode Panagrellus redivivus as the test organisms. The results suggest that the sediment chemical fractions frequently inhibit growth and maturation, while lethality was observed at 4 of 12 sites.Samples from 3 of these sites were further evaluated using conventional elutriate Algal Fractionation Bioassays (AFB) with both natural Lake Diefenbaker phytoplankton and a mixed laboratory grown algal culture. The natural phytoplankton showed inhibition at sediment: water ratios of 10: 1; whereas the algal cultures showed both enhancement and inhibition. Evidently, the sediments are frequently toxic to the species tested except for the algal culture. The AFB assesses the mitigative and synergistic effects of contaminants and nutrients and being a conventional elutriate, is more realistic and potentially more acceptable than the chemical fractionation/nematode bioassay technique which essentially considers potential trace organic contaminant effects.     

Effect of culture media and growth phase on the morphology of lactobacilli and on their ability to adhere to epithelial cells

Previous studies have demonstrated that the ability of lactobacilli to attach to and colonize uroepithelial surfaces is an important characteristic that enhances interference against uropathogenic bacteria. This adherence capacity was found to vary amongst lactobacillus strains and with the type of growth medium used to culture the organisms. The present study was undertaken to examine further the effect of culture media and growth phase on lactobacillus adherence to uroepithelial cells in vitro. In addition, a freeze substitution technique was developed to examine the morphology of strainsLactobacillus casei ssrhamnosus RC-17,L. casei GR-1, andL. acidophilus T-13 in relation to growth conditions and adhesion. A growth curve was plotted for strain GR-1, and adherence was found to be lowest for bacteria in early log phase (39 bacteria per uroepithelial cell) and highest in stationary phase (59 bacteria per uroepithelial cell). Strains RC-17 and GR-1 attached in high numbers to uroepithelial cells, whereas T-13 was poorly adherent. The latter formed a long, relatively dense, fibrous capsule after growth in brain heart infusion yeast extract agar, unlike strains GR-1 and RC-17, which formed a short, tightly bound, electron-dense capsule which surrounded the cells in a radial fashion. Growth of RC-17 in batch cultures of human urine, with and without addition of carbohydrates, resulted in formation of an irregular, fibrous extracellular matrix. These experiments illustrate that growth phase and culture conditions affect the extracellular structure of lactobacilli and also affect the adherence capacity of these bacteria. Structural changes mediated by availability of nutrients may partly explain why lactobacilli vary between species and between hosts in their colonization of the urogenital tract.     

Regulation of the CD2 alternate pathway of T cell activation by CD3. Evidence for heterologous desensitization

Normal resting T cells were stimulated through the alternate CD2 pathway. A CD3 mAb VIT3 completely blocked their proliferative response. The time interval for 50% inhibition lasted for 24 h after the onset of CD2 stimulation. Mitogen-activated cloned long term cultured T cells could also be stimulated via CD2. This proliferative response was again inhibitable by VIT3, indicating that CD3 regulates the CD2 pathway not only in resting cells, but also in lymphocytes actively involved in an Ir. T cells were further loaded with Quin2 and their free cytoplasmic Ca2+ levels were monitored in response to CD3 and CD2 stimulation. Antibodies directed against both surface R triggered a rapid elevation of Ca2+ levels. Both responses were abrogated when the cells had been treated overnight with VIT3. The free cytoplasmic Ca2+ levels of VIT3-pretreated cells, however, were not higher than those of control cells. These results point to a functional interaction between CD3 and CD2 possibly at the level of signal transducing proteins. Finally, cholera toxin was found to inhibit the Ca2+ response in Jurkat T cells. Both the CD3 and CD2 stimulation were sensitive to cholera toxin, indicating that a GTP-binding protein may be involved in signal transduction for both surface structures.     

Quantitation of antibody uptake on A group erythrocytes using immunoautoradiography and monoclonal IgM anti-A

The number of antibody molecules on individual erythrocytes was counted in A1, A2, A3 B and A group individuals using immunoautoradiography (IAR) and monoclonal IgM anti-A1. Quantitation was also done for A group pregnant women. The number of antibody molecules on different red cells of an individual varied widely. Gross variations were also noted in cells of different individuals from one and the same group. The mean values of the uptake of the number of antibody molecules showed the following range A1 greater than A2 greater than Ax greater than A3B. When compared to the average for total A1 adults, red cells of pregnant women and newborn infants showed a 10.7% and 19.7% reduction respectively, in antibody uptake. The mean number of antibody molecules per A1 adult red cells was 5.6 +/- 3 X 10(4), while A2 had 0.85 +/- 0.35 X 10(4) molecules, thus showing a significant quantitative variation.     

Kinetics of activation antigen expression by in vitro-stimulated human T lymphocytes

In this study a panel of monoclonal antibodies was used to investigate the kinetics of the appearance of activation-linked surface determinants as well as cytoplasmic and nuclear determinants in human T cells following lectin stimulation. Well known activation markers, such as Ia/DR, transferrin receptor, IL-2 receptor, T10, and gp24, were compared and investigated together with the T13 structure, recently found in this laboratory. T13, not demonstrable on resting T cells, could be seen within 24 hr after lectin stimulation. Kinetics of the appearance were similar to IL-2 receptor and transferrin receptor expression. Ia/DR synthesis was investigated separately for each polypeptide and the cytoplasmic invariant gamma-chain expression could be demonstrated for the first time with a gamma-chain-specific monoclonal antibody VIC-Y1. Moreover, gamma-chain synthesis seems to precede alpha- and beta-chain occurrence in human T cells. In addition, data from quantitative studies on antigenic densities are presented.