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C M Maragos

Publications and source records attributed to C M Maragos.

21 records · Page 2Linked to original sources
PubMed1990

Quantitative estimates of N-nitrosotrimethylurea formation in the porcine stomach.

Gastric formation of N-nitrosotrimethylurea (NTMU) was quantified by repeated sampling of the gastric contents of full-sized fistulated pigs after the addition of 250 mumol trimethylurea (TMU) and 25-125 mumol nitrite. Maximum gastric nitrite concentration was 100-500 microM based on the gastric volume and amount of added nitrite, which is within the range reported in human gastric contents. The total amount of NTMU formed over time was quantified by estimating both the NTMU concentration and gastric volume using multiple additions of polyethylene glycol. Administration of 25 mumol of nitrite resulted in the formation of 320 nmol of NTMU. The total amount of NTMU formed was linearly related to nitrite dose. Conversion of nitrite to NTMU was of the order of 1-3%. Potassium thiocyanate (200-2000 mumol) had no effect on NTMU formation when given immediately preceding 75 mumol nitrite. Ascorbic acid at 225 and 341 mumol (0.66 and 1.0 of the recommended dietary allowance) inhibited nitrosation of TMU by an average of 54 and 84%. A pig with an average gastric pH of 1.9 formed 4.5-fold more NTMU than did a second pig at pH 4.8. These results suggest that low micromolar amounts of N-nitrosoureas can be formed in the normal stomach when nitrite is consumed in amounts to which humans are commonly exposed.

Animals↗
PubMedDate not supplied

Quantitation and stability of fumonisins B1 and B2 in milk.

The well-documented presence of fumonisin mycotoxins B1 and B2 (FB1 and FB2) in corn raises the possibility that these toxins are carried over into the milk of animals fed with contaminated feed. The presence of FB1 and FB2 in milk has not been assessed because of the lack of sensitive analytical techniques for this matrix. Two methods, liquid chromatography (LC) and enzyme-linked immunosorbent assay (ELISA), were adapted for the analysis of milk. The ELISA, produced commercially for screening corn, required no sample preparation and was reproducible but was of low sensitivity [concentration that inhibits color development by 50% (IC50), 1200-1600 ng FB1/mL]. The more sensitive LC method involves serial extraction of milk with methanol-acetone and strong anion exchange followed by derivatization with naphthalene-2,3-dicarboxaldehyde. Recoveries of 50 ng FB1 and FB2/mL from unpasteurized and unhomogenized milk were 84 and 83%, respectively (limit of detection, 5 ng/mL). Recoveries of FB1 from whole homogenized milk (76%) were slightly lower. Heating milk for 30 min at 62 degrees C, to mimic pasteurization, did not significantly reduce FB1 or FB2 recovery, nor did storing milk for 11 days at 4 degrees C. The LC method was applied to 165 samples of milk, only 1 of which was positive. This finding suggests that exposure of humans to FB1 and FB2 from milk is low.

Animal Feed↗