IL-2-independent activation and proliferation in human T cells induced by CD28.

Although the role of CD28 in T cell costimulation is firmly established, the mechanisms by which it exerts its costimulatory actions are less clear. In many circumstances it is difficult to distinguish the effects of CD28 from subsequent actions of cytokines, such as IL-2, on T cell proliferation. Here, we report a model of CD28 costimulation using PMA plus the natural ligand CD80 that resulted in very limited stimulation of IL-2, as evidenced by both cytokine production and IL-2 promoter stimulation. Promoter assays revealed CD28-dependent effects on both NF-kappaB and AP-1, but not on NF-AT or the intact IL-2 promoter. In addition, T cell proliferation was completely resistant to the actions of the immunosuppressant cyclosporin A (CsA). Moreover T cell proliferation was unaffected by the addition of blocking Abs to both IL-2 and the IL-2 receptor, demonstrating that this form of costimulation by CD28 was independent of IL-2. We also investigated the effects of stimulating T cell blasts with CD80 alone and found that there was a limited requirement for IL-2 in this system. We conclude that CD28 costimulation can cause substantial T cell proliferation in the absence of IL-2, which is driven by a soluble factor independent of NF-AT transactivation.     

Misunderstanding of Front-Of-Package Nutrition Information on US Food Products

Front-of-package nutrition symbols (FOPs) are presumably readily noticeable and require minimal prior nutrition knowledge to use. Although there is evidence to support this notion, few studies have focused on Facts Up Front type symbols which are used in the US. Participants with varying levels of prior knowledge were asked to view two products and decide which was more healthful. FOPs on packages were manipulated so that one product was more healthful, allowing us to assess accuracy. Attention to nutrition information was assessed via eye tracking to determine what if any FOP information was used to make their decisions. Results showed that accuracy was below chance on half of the comparisons despite consulting FOPs. Negative correlations between attention to calories, fat, and sodium and accuracy indicated that consumers over-relied on these nutrients. Although relatively little attention was allocated to fiber and sugar, associations between attention and accuracy were positive. Attention to vitamin D showed no association to accuracy, indicating confusion surrounding what constitutes a meaningful change across products. Greater nutrition knowledge was associated with greater accuracy, even when less attention was paid. Individuals, particularly those with less knowledge, are misled by calorie, sodium, and fat information on FOPs.     

Diversity and biomass accumulation in cultured phototrophic biofilms

In the present study, biomass development and changes in community composition of phototrophic biofilms grown under different controlled ambient conditions (light, temperature and flow) were examined. Source communities were taken from a wastewater treatment plant and used to inoculate growth surfaces in a semi-continuous-flow microcosm. We recorded biofilm growth curves in cultures over a period of 30 days across 12 experiments. Biovolume of phototrophs and community composition for taxonomic shifts were also obtained using light and electron microscopy. Species richness in the cultured biofilms was greatly reduced with respect to the natural samples, and diversity decreased even further during biofilm development. Diadesmis confervacea, Phormidium spp., Scenedesmus spp. and Synechocystis spp. were identified as key taxa in the microcosm. While a significant positive effect of irradiance on biofilm growth could be identified, impacts of temperature and flow rate on biofilm development and diversity were less evident. We discuss the hypothesis that biofilm development could have been subject to multistability, i.e. the existence of several possible stable biofilm configurations for the same set of environmental parameters; small variations in the species composition might have been sufficient to switch between these different configurations and thus have contributed to overwriting the original effects of temperature and flow velocity.     

Transport of free polymannose-type oligosaccharides from the endoplasmic reticulum into the cytosol is inhibited by mannosides and requires a thapsigargin-sensitive calcium store

The transport of free polymannose-type oligosaccharides from the lumen of the endoplasmic reticulum into the cytosol has been recently demonstrated (Moore,S.E.H., et al., 1995, EMBO J., 14, 6034-6042), but at present little is known of the characteristics of this process. Here, it is shown that inhibition of the transport of endogenously synthesized metabolically radiolabeled free oligosaccharides out of the endoplasmic reticulum into the cytosol of permeabilized HepG2 cells occurs when assays are conducted in the presence of mannose (IC50, 4.9 mM), or its derivatives modified at the first carbon (C1) of the sugar ring; alpha-methyl mannoside (IC50, 2.0 mM), mannoheptulose (IC50, 1.6 mM), and alpha-benzyl mannoside (IC50, 0.8 mM), whereas other monosaccharides (50 mM), differing from mannose at position; C2 (glucose), C3 (altrose), C4 (talose), C5 (l-rhamnose), and C6 (mannoheptose), have little effect. N-Acetylglucosamine does not inhibit oligosaccharide transport and, furthermore, although mannobioses and a mannotriose inhibit free oligosaccharide transport, di-N-acetylchitobiose is without effect. It is also shown that if the transport assay buffer is either depleted of calcium ions, or supplemented with the Ca2+/Mg2+ATPase inhibitor, thapsigargin, or with calcium ionophores, free oligosaccharide transport out of the endoplasmic reticulum is inhibited. These results demonstrate that the terminal nonreducing mannosyl residues of free polymannose-type oligosaccharides and not their N-acetylglucosamine-containing reducing termini, play an important role in the interaction of the free oligosaccharide with the transport machinery, and that this transport process requires the presence of calcium sequestered in the lumen of the endoplasmic reticulum.      

Uptake of l-Phenylalanine in Synchronous Chlorella fusca. Characterization of the Uptake System

Phenylalanine uptake in Chlorella fusca was measured, using the membrane filter technique. The cells were synchronized, and harvested at specific points of the life cycle. Experiments with autospores showed that the uptake followed saturation kinetics, with a K_m= 5 μM. V_max, was 0.1 nmol/min × 10⁷ cells. The optimum temperature for the uptake was 40°C, and the activation energy was 1700 J/mol. The uptake showed a high specificity towards l -phenylalanine; presence of the unlabelled stereoisomer did not inhibit the uptake. Uptake of l -phenylalanine was inhibited in the presence of other analogues or other amino acids, but only if they were present in concentrations considerably higher than that of L-phenylalanine. Variations in the ratio of Na4⁺ to K⁺ in the external solution during uptake experiments did not have any influence upon the uptake rate of l -phenylalanine. The cells were able to take up the amino acid against a concentration gradient. At pool maximum the ratio between internal and external amino acid concentration was 1000/1. 2,4-Dinitro-phenol inhibited the uptake completely. Exchange between internal and external l -phenylalanine could not be demonstrated. The K_m value did not change during the life cycle of the cells. The uptake rate reached a maximum at the end of the light period, and fell to a minimum just before sporulation started. It is concluded that Chlorella fusca cells have a highly specific, active uptake system for l -phenylalanine. The system is constitutive, independent on the K or Na concentration, and the mechanism of uptake does not change during the life cycle of the cells.     

Effect of light and temperature on biomass, photosynthesis and capsular polysaccharides in cultured phototrophic biofilms

Phototrophic biofilms seem to be suitable candidates for tertiary wastewater treatment due to their high uptake capacity for nutrients and other pollutants, also taking into account the time and cost savings derived from easy procedures for biomass harvesting. Biomass accrual, structure, and physiology of biofilms affect the efficiency of nutrient removal by its microbial community. Here, we construct a biofilm consisting of a cyanobacterium Synechocystis sp. and the green alga Chlorococcum sp. and determine the effect of combined variations of irradiance and temperature on the biofilm structure and function. The two species were isolated from phototrophic biofilms naturally developing in an Italian wastewater treatment plant and grown in a microcosm designed for biofilm investigations. Phototrophic biomass accumulation, percent species composition, photosynthetic response and the amount and composition of capsular polysaccharides (CPS), including anionic residues, are reported. The results showed that biofilm development required relatively moderate irradiances (60 μmol photons m⁻² s⁻¹) below which development was arrested. Both light and temperature had a strong effect on the composition of each species to the biofilm. The CPS compositions also changed with temperature, light and species composition. The CPS of the green-algal-dominated biofilm had the higher uronic acid content indicating a potential to exploit green algae in the treatment of waste contaminated with heavy metals. Given the knowledge of the response of certain species to light and temperature combinations, it may be possible to construct biofilms of known species and CPS composition to use them for specific applications.