Temperature effects on very slow desorption of native chlorobenzenes from sediment to water

The temperature dependence of the kinetics of very slow desorption of eight chlorobenzenes was studied in laboratory batch experiments on a field-contaminated sediment from Lake Ketelmeer, The Netherlands. The observed rate constants for very slow desorption averaged (1.5 +/- 0.4) x 10(-4)/h at 10 degrees C, (2.9 +/- 1.0) x 10(-4)/h at 20 degrees C, (5.8 +/- 2.4) x 10(-4)/h at 35 degrees C, and (6.4 +/- 3.0) x 10(-4)/h at 45 degrees C over all eight compounds. Activation energies for desorption to water were close to the enthalpy for dissolution of the pure solid in water. The activation energies ranged from 18 to 53 kJ/mol with an average of 36 +/- 11 kJ/mol. These values confirm earlier reported activation energies for very slow desorption to water. They are much less than values for activation energies for desorption to the gas phase. That difference can be explained in terms of rate limiting desorption from carbonaceous adsorption sites.     

T-cell synapse formation depends on antigen recognition but not CD3 interaction: studies with TCR:ζ, a candidate transgene for TCR gene therapy

T-cell receptors (TCRs) can be genetically modified to improve gene-engineered T-cell responses, a strategy considered critical for the success of clinical TCR gene therapy to treat cancers. TCR:ζ, which is a heterodimer of TCRα and β chains each coupled to complete human CD3ζ, overcomes issues of mis-pairing with endogenous TCR chains, shows high surface expression and mediates antigen-specific T-cell functions in vitro. In the current study, we further characterized TCR:ζ in gene-engineered T cells and assessed whether this receptor is able to interact with surface molecules and drive correct synapse formation in Jurkat T cells. The results showed that TCR:ζ mediates the formation of synaptic areas with antigen-positive target cells, interacts closely with CD8α and MHC class I (MHCI), and co-localizes with CD28, CD45 and lipid rafts, similar to WT TCR. TCR:ζ did not closely associate with endogenous CD3ε, despite its co-presence in immune synapses, and TCR:ζ showed enhanced synaptic accumulation in T cells negative for surface-expressed TCR molecules. Notably, synaptic TCR:ζ demonstrated lowered densities when compared with TCR in dual TCR T cells, a phenomenon that was related to both extracellular and intracellular CD3ζ domains present in the TCR:ζ molecule and responsible for enlarged synapse areas.     

Campylobacter jejuni-induced acute transverse myelitis

STUDY DESIGN: Case report. SETTING: University Hospital of Antwerp, tertiary referral hospital of the University of Antwerp, Edegem, Belgium. CASE REPORT: Campylobacter jejuni infection is related to various syndromes in which the peripheral nervous system is involved. An immune response is triggered through molecular mimicry between gangliosides of the peripheral nervous system and lipo-oligosaccharides of C. jejuni. We report a case of a previously healthy 17-year-old girl, who developed clinical manifestations of acute transverse myelitis (ATM) 7 days after a culture-proven C. jejuni enteritis. High titres of serum IgG antibodies to the ganglioside GM1 were found in the acute phase of disease, which decreased with clinical recovery. These antibodies cross-reacted with C. jejuni lipo-oligosaccharides, indicating that C. jejuni infections may induce ATM. CONCLUSIONS: Only a few cases of C. jejuni infection associated with demyelination of the central nervous system or spinal cord have been described. Physicians should be aware that C. jejuni might be another cause of transverse myelitis.     

Wheat bran affects the site of fermentation of resistant starch and luminal indexes related to colon cancer risk: a study in pigs

BACKGROUND: Recent studies suggest that resistant starch (effective in producing butyrate and lowering possibly toxic ammonia) is rapidly fermented in the proximal colon; the distal colon especially would, however, benefit from these properties of resistant starch. AIMS: To determine whether wheat bran (a rich source of insoluble non-starch polysaccharides), known to hasten gastrointestinal transit, could carry resistant starch through to the distal colon and thus shift its site of fermentation. METHODS: Twenty four pigs were fed four human type diets: a control diet, or control diet supplemented with resistant starch, wheat bran, or both. Intestinal contents and faeces were collected after two weeks. RESULTS: Without wheat bran, resistant starch was rapidly fermented in the caecum and proximal colon. Supplementation with wheat bran inhibited the caecal fermentation of resistant starch, resulting in an almost twofold increase (from 12.9 (2.5) to 20.5 (2.1) g/day, p<0.05) in resistant starch being fermented between the proximal colon and faeces. This resulted in higher butyrate (133%, p<0.05) and lower ammonia (81%, p<0.05) concentrations in the distal colonic regions. CONCLUSIONS: Wheat bran can shift the fermentation of resistant starch further distally, thereby improving the luminal conditions in the distal colonic regions where tumours most commonly occur. Therefore, the combined consumption of resistant starch and insoluble non-starch polysaccharides may contribute to the dietary modulation of colon cancer risk.     

Effects of dietary calcium and phosphate on the intestinal interactions between calcium, phosphate, fatty acids, and bile acids.

Luminal free fatty acids and bile acids may damage the colonic epithelium and stimulate proliferation, which may increase the risk of colon cancer. It has been suggested that only soluble calcium ions (Ca2+) precipitate fatty acids and bile acids, thus reducing their lytic activity. Consequently, precipitation of luminal Ca2+ by dietary phosphate should inhibit these effects. To evaluate the proposed antagonistic effects of dietary calcium and phosphate, we studied the intestinal interactions between calcium, phosphate, fatty acids, and bile acids in rats fed purified diets that differed only in the concentrations of calcium and phosphate. Increased dietary calcium drastically decreased the solubility of fatty acids in the ileum, colon, and faeces, as well as the solubility of bile acids in the colon and faeces. Although dietary calcium strongly increased the total faecal fatty acid concentration and hardly affected the total faecal bile acid concentration, the fatty acid and bile acid concentrations in faecal water were drastically decreased by dietary calcium. Consequently, the lytic activity of faecal water was decreased. Dietary phosphate did not interfere with these intestinal effects of calcium. These results indicate that dietary phosphate does not inhibit the protective effects of dietary calcium on luminal solubility and the lytic activity of fatty and bile acids.     

Influence of long contact times on sediment sorption kinetics of spiked chlorinated compounds

The desorption kinetics of hexachlorobenzene (HCB) and 2,4,4'-trichlororbiphenyl (PCB 28) spiked to a field sediment were studied using a gas-purge technique. A contact time of up to 1,461 d was used to assess long-term changes in desorption kinetics. Purge-induced desorption experiments lasted from 300 to more than 4,000 h. Fast-, slow-, and very-slow-desorbing fractions could be distinguished. The desorption patterns changed with contact time from mainly fast- and slow-desorbing fractions toward the domination of slow- and very-slow-desorbing fractions. The desorption pattern for HCB after a contact time of 1,461 d became comparable to previously reported desorption patterns observed for in situ contaminants. An additional spike of HCB, PCB 28, 2,4,6-trichlorobiphenyl, and 2,2',4,5'-tetrachlorobiphenyl applied to the sediment purged for more than 4,000 h showed that very slow sites were accessible for these compounds within a few hours. Only very small fast-desorbing fractions could be detected after a contact time of just 48 h. These results indicate that domination of very slow desorption is caused not only by long contact times but, perhaps, also by the accessibility of specific sites within the sediment matrix.     

Influence of desorption and contact time on sediment-water distribution of spiked polychlorinated biphenyls and polycyclic aromatic hydrocarbons: relation with in situ distribution

The long-term sediment-water distribution of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), spiked to Lake Ketelmeer (The Netherlands) sediment, was studied using a gas-purge technique. Contact times varied from 2 to 1,461 d for the PCBs and from 5 to 100 d for the PAHs. Purge-induced desorption experiments lasted 300 to > 4,000 h. The initial distribution coefficients that were observed during the first part of the experiment were close to literature values for distribution after short contact times. The distribution coefficients increased during the purge-induced desorption experiments. The final distribution coefficients that were observed during the last part of the experiment were one to two orders of magnitude higher than the initial values and were close to distribution coefficients reported earlier for in situ PCBs and PAHs present in a field-contaminated sediment for years to decades. The change in distribution coefficients during a gas-purge experiment may resemble the long-term change in a field sediment. Final distribution coefficients seem to be a more relevant measure for the distribution coefficients of hydrophobic organic chemicals in aged field sediments than values obtained after short contact times.     

Dietary fructo-oligosaccharides in healthy adults do not negatively affect faecal cytotoxicity: a randomised, double-blind, placebo-controlled crossover trial

Fructo-oligosaccharides (FOS) are widely used in commercial food products. Most studies on FOS concern the health benefits, but some negative effects were recently reported concerning the faecal cytotoxicity and excretion of mucin-type oligosaccharides in combination with a Ca-restricted diet. The present study was performed to investigate whether these effects of FOS are observed in adults consuming a regular diet unrestricted in Ca. The study was a randomised, double-blind, placebo-controlled crossover trial, involving eleven healthy adults, who consumed 25-30 g FOS or maltodextrin (control) in a random order for 2 weeks in addition to their regular diet. Stools were collected for analysis of pH and SCFA (as markers of fermentation), for the assessment of faecal water cytotoxicity, and for the analysis of alkaline phosphatase activity (as a marker of epithelial cell turnover) and O-linked oligosaccharides (to estimate the excretion of mucin-type oligosaccharides). FOS consumption significantly altered bacterial fermentation (increased percentage of acetate, decreased percentage of butyrate) and tended to decrease stool pH. Furthermore, FOS consumption resulted in a significantly higher stool frequency and in significantly more complaints of flatulence. No significant differences between the control and FOS period were observed in the mean cytotoxicity of faecal water (37.5 (SEM 6.9)% v. 18.5 (SEM 6.9)%; P=0.084), in mean alkaline phosphatase activity (27.7 (SEM 2.9) v. 24.6 (SEM 3.2) U/g dry faeces; P=0.496) or in the mean excretion of mucin-type oligosaccharides (49.9 (sem 4.0) v. 53.5 (SEM 4.3) mg/g dry faeces; P=0.553). We conclude that dietary FOS in a dose up to 25-30 g/d altered the bacterial fermentation pattern but did not affect faecal cytotoxicity or the faecal concentration of mucin-type oligosaccharides in human adults consuming a regular diet.