Determination of Chlormequat and Mepiquat in Foods by Liquid Chromatography/Mass Spectrometry or Liquid Chromatography/Tandem Mass Spectrometry: Interlaboratory Study

Interlaboratory validation studies have been performed on 2 methods for the determination of chlormequat (CLQ) and mepiquat (MPQ). Both methods used identical extraction procedures and stable isotope internal standardization but differed in the use of liquid chromatography/mass spectrometry (LC/MS) or LC/tandem mass spectrometry (LC/MS/MS) for the determination, the amount of internal standard used, and the expected limit of detection. After addition of deuterated internal standards, CLQ and MPQ were extracted with methanol–water and determined by LC/MS or LC/MS/MS with positive electrospray ionization. Eight European laboratories participated in the LC/MS method study, analyzing mushroom, pear, wheat flour, and fruit puree with residues of CLQ in the range 0.040–1.19 mg/kg and of MPQ in the range 0.041–0.39 mg/kg. For CLQ, the Horwitz ratio (HoRat) values for individual test materials/levels were in the range 0.85–1.13 with amean of 1.00, showing good method performance. For MPQ, the Ho values for mushroom, pear (both levels), and wheat flour were in the range 0.83–0.94, again indicating good method performance. For the determination of MPQ in infant food (fruit puree) at 0.041 mg/kg, the Ho was 1.7 when a value of 0 reported by one participant was excluded. In the LC/MS/MS study, in which 11 laboratories participated, a separate sample set was analyzed with residues of CLQ in the range 0.007–1.03 mg/kg and of MPQ in the range 0.008–0.72 mg/kg. Ho values for CLQ were in the range 0.27–1.36 and for MPQ in the range 0.51–2.10, all corresponding to acceptable method performance.

Stimulated murine peritoneal macrophages in suspension and cell culture: enzyme determinations by biochemical and histochemical means

Peritoneal exudate cells of mice were studied up to 4 days after i.p. injection of thioglycollate broth medium by means of conventional enzyme determinations and quantitative histochemical measurements of individual cells. Cells from the peritoneal cavity were either investigated immediately after harvesting or after culturing periods of up to six days for enzymic activities of aminopeptidase, esterase, lactate dehydrogenase and beta-galactosidase. A fairly good correlation exists between biochemical determinations of aminopeptidase and esterase activity and the mean of histochemical data. Following a sharp increase in the number of cells after stimulation, aminopeptidase, esterase and lactate dehydrogenase activities per cell were found to be increased. Moreover, the cells taken three or five days after simulation synthesized large amounts of aminopeptidase and esterase as shown by culturing experiments. This capacity of the cells was subsequently lost in cells harvested seven days after stimulation but beta-galactosidase increased and lactae dehydrogenase was more readily released into culture supernatants. The increase in aminopeptidase and esterase was dependent on protein synthesis since it was abolished by cycloheximide. Thioglycollate broth medium provokes immigration of cells into the peritoneal cavity where cells apparently differentiate by increasing their aminopeptidase and esterase concentrations, and by raising their intracellular catabolism rates, which leads eventually to the decay of the cells. The different enzymic phenotypes and the large heterogeneity at any time point after stimulation presumably also reflect different functional properties during the inflammatory process.

Toxin-specific ultrastructural alterations of the mouse liver after burn injuries and the possibility of a specific antitoxic therapy

Electron-microscopic studies in mice revealed similar and comparable mitochondrial alterations of the liver cells 5-7 days after either a sublethal controlled burn injury or an i.p. injection of an equivalent dose of a burn toxin. Electron microscopy 5 days after i.p. application of different amounts of the burn toxin in rats showed that the extent of the liver alterations correlates directly to the applied dose (occurrence of: cristolysis--intramitochondrial vacuolization--total vacuolar changes of mitochondria(. Controls with the non-toxic/"native" compound isolated from normal skin or excision of a skin piece identical in size to the sublethal burn showed no ultrastructural changes in the liver of mice or rats. In a 2nd series of experiments the therapeutic effect of an antitoxic IgG raised in sheep was tested. The first 3 days after a standard burn or an i.p. injection of 15 mg burn toxin mice obtained 10 mg of the antitoxic IgG (2x/day). Controls injected with the "native" compound or excised as described were treated in the same way. The results showed a specific complete immunological protection from mitochondrial alterations by either the toxin or the burn injury. These results suggest the possibility of an antitoxic IgG-therapy in severe burns.