Oxidation of a cysteine-derived nucleophilic reagent by dimethyl sulfoxide in the amino acid derivative reactivity assay

The amino acid derivative reactivity assay (ADRA), which is an in chemico alternative to the use of animals in testing for skin sensitization potential, offers significant advantages over the direct peptide reactivity assay (DPRA) in that it utilizes nucleophilic reagents that are sensitive enough to be used with test chemical solutions prepared to concentrations of 1 mm, which is one-hundredth that of DPRA. ADRA testing of hydrophobic or other poorly soluble compounds requires that they be dissolved in a solvent consisting of dimethyl sulfoxide (DMSO) and acetonitrile. DMSO is known to promote dimerization by oxidizing thiols, which then form disulfide bonds. We investigated the extent to which DMSO oxidizes the cysteine-derived nucleophilic reagents used in both DPRA and ADRA and found that oxidation of both N-(2-(1-naphthyl)acetyl)-l-cysteine (NAC) and cysteine peptide increases as the concentration of DMSO increases, thereby lowering the concentration of the nucleophilic reagent. We also found that use of a solvent consisting of 5% DMSO in acetonitrile consistently lowered NAC concentrations by about 0.4 μm relative to the use of solvents containing no DMSO. We also tested nine sensitizers and four nonsensitizers having different sensitization potencies to compare NAC depletion with and without 5% DMSO and found that reactivity was about the same with either solvent. Based on the above, we conclude that the use of a solvent containing 5% DMSO has no effect on the accuracy of ADRA test results. We plan to review and propose revisions to OECD Test Guideline 442C based on the above investigation.

Efficient production of saikosaponins in Bupleurum falcatum root fragments combined with signal transducers

An efficient system to produce saikosaponins (saikosaponin-a and -d) in Bupleurum falcatum adventitious root fragments combined with signal transducers was developed. The roots are heterogeneous in terms of size and shape and sometimes form aggregates during cultivation. When the roots were cut to lengths of about 5 mm using a scalpel and cultivated, the root fragments did not form the aggregates, and root growth and saikosaponin production were not inhibited. After screening various signal transducers, it was clear that methyl jasmonate (MeJA) markedly promoted saikosaponin production. By comparing the effect of MeJA and related substances on saikosaponin production, we conclude that both the pentenyl and carboxylmethyl group of MeJA play an important role in the promotion of saikosaponin production. Addition of both 100 microM MeJA and 20 mM CaCl2 to the medium stimulated the content of saikosaponin in the root, with levels reaching 31.7 mg/g-dry root for 15 days of cultivation. A large amount of root fragments were prepared using a blender and cultivated (23 g-dry root/l) with 400 microM MeJA and 20 mM CaCl2, resulting in a high concentration of saikosaponins (747.3 mg/l).

Enhanced production of saikosaponins by root culture of Bupleurum falcatum L. using two-step control of sugar concentration

 The effect of sugar concentration on the production of saikosaponins was investigated using a root culture of Bupleurum falcatum L. The formation of the lateral roots, which were induced in the presence of indolebutyric acid, was suppressed as the sugar concentration was increased. After the lateral root tips had emerged from the inoculated roots, however, high concentrations of sugar showed no inhibitory effect on the development of the lateral roots. A two-step culture, with 1% sucrose at the beginning of the culture and addition of 6% sucrose at 14 days, when lateral roots have emerged, greatly improved the productivity, affording 0.8 g/l of saikosaponin-a and -d.

Comparative studies of carbohydrate-binding proteins from Xenopus laevis skin and eggs. Sugar-binding specificities and affinity purification

Salt and detergent extracts of acetone-dried powder of Xenopus laevis skin and eggs were fractionated on sugar-Sepharose columns, to which lactose, melibiose, galactose, rhamnose and mannose had been covalently linked, by successive elution with chelating reagent and specific sugars, resulting in separation of the different Ca2(+)-dependent and Ca2(+)-independent carbohydrate-binding proteins. The skin of X. laevis contains a salt-extractable Ca2(+)-dependent lactose-binding lectin of 30 kilodalton (kDa) and the eggs a similar lectin of 43 kDa, but they both lack Ca2(+)-dependent galactose-binding lectins. The 30 kDa lactose-binding lectin which agglutinates human A erythrocytes was isolated by successive affinity chromatography on two linked sugar-Sepharose columns, i.e., a galactose-Sepharose-lactose-Sepharose (GL) column system. Since the 30 kDa lectin was not recovered in the Ca2(+)-dependent lactose-binding protein fraction from the GL column system under the dithiothreitol (DDT)-free conditions, it was concluded that the lectin requires the presence of DTT and calcium for binding to the lactose-Sepharose column.

The importance of bile in reflux oesophagitis and the success in its prevention by surgical means

A study was instituted using the Rhesus monkeyan animal which has been found to resemble man both in respect of the anatomy of the gastrooesophageal region and of the secretion of hydrochloric acid from the stomach—as a model.