The pepsinogen releasing effect of Helicobacter pylori lipopolysaccharide

Background. Helicobacter pylori lipopolysaccharide (LPS) affects pepsinogen release by a nontoxic mechanism. We hypothesized that this effect was characteristic of the organism and related to the clinical status of the strain. Materials and methods. LPS was isolated from 11 H. pylori strains whose pathogenic profile was known and four other nongastric bacteria. The effects of luminal LPS on guinea pig gastric mucosal pepsinogen release was evaluated using the Ussing chamber technique. CCK‐8 (10^?9M) was used as a positive control. Results. H. pylori LPS dose‐dependently stimulated pepsinogen release with a maximal stimulation at 250 µg/ml (~4500%; p < .001 vs. control). LPS from other Helicobacter or Campylobacter species had no effect on pepsinogen release. ANOVA demonstrated significant differences in the efficacies of pepsinogen release between the 11 clinical H. pylori strains (p < .0001) despite the fact that they were all cagA⁺ and 90% had the cytotoxic vacA subtype s1. Physical and chemical disruption of the LPS suggested that both the structure and the carbohydrate composition of this molecule may play a critical role in pepsinogen release. Polymyxin B partly (p < .03) inhibited and dephosphorylation completely inhibited (p = .0002) LPS‐stimulated pepsinogen release. Conclusion. Pepsinogen release is an innate property of all cagA⁺H. pylori LPS. The structure of the molecule and composition of side‐chains are important in this response which appears to be partially lipid A driven.     

The uptake of carbon dioxide by plant roots

Summary The uptake of C¹⁴O₂ by the roots of intact tomato plants from solution containing Na₂C¹⁴O₃ was studied at different light intensities as well as in darkness.Where plants had previously been starved for CO₂ for 12 hours, a higher rate of C¹⁴ uptake was observed than with plants which had been transferred directly from the soil to the radioactive solution.In general, the C¹⁴ content of the roots was slightly higher than that of the shoots. At light intensities under the compensation point and in darkness the C¹⁴ content of the shoots relative to the roots decreased. This was accompanied by release of C¹⁴O₂ during respiration, indicating that the absorbed C¹⁴ was readily translocated upwards and released as C¹⁴O₂ under these conditions. At light intensities above the compensation point no C¹⁴O₂ was released.