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Biomedical subjects

M Jägerstad

Publications and source records attributed to M Jägerstad.

At least 73 records · Page 4Linked to original sources
PubMed1976

Reduction of folate levels in the rat: Difference in depletion between the central and the peripheral nervous system.

1. Rats were deprived of dietary folate for 12 and 9.5 months in two experiments; one with and one without succinylsulfathiazole added to the diet. Folate levels decreased faster in the former experiment and the final blood values were lower. Tissue folate was examined in the latter experiment only. 2. The animals were repeatedly examined with neurological tests and compared with a control group supplemented with folic acid. Every test proved normal. Measurement of motor nerve conduction velocities after 12 months in the experiment where succinylsulfathiazole was given revealed lower velocities in the non-supplemented group. There was no difference between the groups in the experiment without succinylsulfathiazole. 3. In the latter experiment brain folate was reduced by only 16% in the non-supplemented animals compared with the controls, whereas whole blood folate fell by 60%, liver folate by 50% and sciatic nerve folate by 59%. 4. The central nervous system is resistant to systemic folate depletion, whereas the peripheral nerves are depleted to the same degree as the extra-neural tissues.

Animal Nutritional Physiological Phenomena↗
PubMed1976

Portal and peripheral plasma folates after ingestion of folic acid.

Folic acid in amounts of 2 mumol (0.88 mg) was given by mouth to four patients who had undergone portal vein catheterization. All had normal liver function. The increase in folates in plasma obtained from portal and peripheral veins was followed for three hours with the use of L. casei and S. faecalis as test organisms. The results lend support to the assumption that the liver is the main site of methylation of folic acid when given in physiological amounts.

Adult↗
PubMed1976

The hydrolysis and absorption of conjugated folates in man.

After ingestion of synthetic PteGlu3 in physiological doses, the folate forms were studied in plasma obtained from human vena portae blood. Plasma conjugase was inhibited by rapid heat-denaturation. The folate forms were assayed with L. casei and S. faecalis and identified by thin-layer chromatography (biautography). Mono- and diglutamic folate was demonstrated in the portal plasma, indicating that intestinal hydrolysis precedes the absorption of conjugated folates. The pteroylpolyglutamate hydrolase activity in the human gastrointestinal tract was investigated. The activity was demonstrated in gastric juice, pancreatic juice, and intestinal mucosa. The highest activity was found in the pancreatic juice with a pH-optimum of 4.5. In gastric juice the pH-optimum for the enzyme was 3 and the activity half of that found in pancreatic juice. However, in view of the volumes of these fluids produced every day, the activity at physiological pH might be enough to hydrolyse the daily intake of conjugated folates in amounts of about 500 mug.

Biological Assay↗
PubMedDate not supplied

Formation of heterocyclic amines using model systems.

Initially, modeling was used to identify the mutagenic heterocyclic amines and their precursors. Major precursors have been shown to be single amino acids or amino acids together with creatine or creatinine. There is also evidence that Maillard reactions are involved since heating sugar and amino acids together with creatine or creatinine has been shown to produce several of the mutagenic heterocyclic amines, especially the aminoimidazoazaarenes (AIA compounds), e.g., IQ, MeIQ, MeIQx, DiMeIQx and PhIP. Due to a low yield in the model systems, the mechanisms behind the formation of the mutagenic heterocyclic amines are still unclear and need further substantiation. The fact that some AIA compounds are also produced in the absence of sugar casts some doubts on an obligatory participation of the Maillard reaction; alternative routes might exist. Further work using isotopically labeled precursors needs to be done and so far such work has only been performed for PhiP. The formation of mutagenic heterocyclic amines is dependent on time, temperature, pH, concentration of the precursors, type of amino acid, and the presence of certain divalent ions. Water may have an impact both as a temperature regulator and as a solvent medium for the reactants.

Amines↗
PubMedDate not supplied

Formation of 2-amino-3,7,8-trimethylimidazo [4,5-f]quinoxaline, a new mutagen, by heating a mixture of creatinine, glucose and glycine.

When a mixture of creatinine, glycine and glucose was heated for 2 h at 128 degrees C in diethylene glycol containing 14% water, two mutagens were formed. One of them, responsible for 90% of the mutagenicity, has already been identified as 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). The other mutagen was purified and characterized. The UV absorption, mass and NMR spectra suggested that this mutagen was 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx). Comparison of the spectral properties of the compound obtained from the heated model mixture with those of synthetic material confirmed this structure. 7,8-DiMeIQx is a newly identified compound which, at a dose of 1 microgram, induced 163 000 and 9900 revertants of Salmonella typhimurium TA98 and TA100, respectively, with S9 mix.

Chemical Phenomena↗