Folates
Mostrando 25-36 de 70 artigos, teses e dissertações.
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25. Transport characteristics of folates in cerebrospinal fluid; a study utilizing doubly labeled 5-methyltetrahydrofolate and 5-formyltetrahydrofolate
Serum disappearance curves in dogs after the intravenous injection of radioactive methotrexate, 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, and folic acid followed first-order kinetics with half-disappearance times ranging from 1.3 to 9 hr respectively. Equilibration of spinal fluid tritium levels with those in serum was rapid (3.0 hr) for both of th
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26. The occurrence of folic acid (pteroyl-L-monoglutamic acid) in human blood serum after small oral doses
Human serum folates analysed by bioautography after oral doses of 0·5 mg folic acid (pteroyl-L-monoglutamic acid) show folic acid to be present.
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27. Hepatic and serum folates in patients fasting and after oral folic acid
The hepatic folate in non-anaemic hospital patients was found to correlate poorly with the fasting serum folate. The rise in methylfolate in the systemic circulation following the absorption of folic acid was directly related to the folate content of the liver.
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28. Microbiological assay on microtitre plates of folate in serum and red cells.
AIMS: To develop a simple microbiological assay for serum and red cell folates on 96-well microtitre plates, suitable for use in routine clinical diagnosis. METHODS: Use of a chloramphenicol resistant organism (NCIB 10463) saved time by avoiding aseptic precautions. Use of plate sealers facilitated mixing. Evaluation of assay performance included estimations
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29. Purification and properties of serine hydroxymethyltransferase from Sulfolobus solfataricus.
Serine hydroxymethyltransferase (SHMT) catalyzes the reversible cleavage of serine to glycine with the transfer of the one-carbon group to tetrahydrofolate to form 5,10-methylenetetrahydrofolate. No SHMT has been purified from a nonmethanogenic Archaea strain, in part because this group of organisms uses modified folates as the one-carbon acceptor. These mod
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30. In vitro activities of and mechanisms of resistance to antifol antimalarial drugs.
Certain drugs that interfere with folate metabolism (sulfones, sulfonamides, and inhibitors of dihydrofolate reductase) play an important role in the chemotherapy and prophylaxis of malaria. The activities and mechanisms of action of these drugs are regarded as similar in most respects to their activities against procaryotic microorganisms. Believed incapabl
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31. Purification of folate binding factor in normal umbilical cord serum.
Human umbilical cord serum was found to contain both free folate and folate complexed to a high-molecular weight factor. The complexed folate was bound to a very high affinity binder and was present in concentrations equivalent to as much as 60 ng of 5-methyltetrahydrofolic acid per ml of serum. Acidification of the serum caused disassociation of the folate-
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32. Stable transfectants of human MCF-7 breast cancer cells with increased levels of the human folate receptor exhibit an increased sensitivity to antifolates.
A major problem in cancer therapy is tumor drug resistance such as is found with antifolates (e.g., methotrexate [MTX]). We are specifically interested in the role of the human folate receptor (hFR) in MTX resistance. To investigate whether transfection of hFR results in increased MTX uptake and increased drug sensitivity, human mammary carcinoma (MCF-7) cel
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33. Effect of methotrexate on intracellular folate pools in purified myeloid precursor cells from normal human bone marrow.
We investigated the effects of the antifolate methotrexate on intracellular folate pools of human myeloid precursor cells (MPCs). Immature MPCs, representing 3.2% of the original marrow population, were selected from normal human bone marrow by immune rosetting. The intracellular folate pools were labeled by incubation with 5 X 10(-8) M [3H]5-formyl-FH4 and
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34. Significance of subnormal red-cell folate in thalassaemia.
Subnormal red-cell folate values were encountered in 20 of 63 thalassaemic subjects in a population with a low incidence of megaloblastosis. The abnormality was not associated with haematological changes of megaloblastosis and could not be explained on the basis of incomplete liberation of intra-erythrocytic folates, serum conjugase deficiency of vitamin B12
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35. Receptor-mediated folate accumulation is regulated by the cellular folate content.
Cultured monkey kidney cells are shown to possess a cell-surface receptor that binds 5-methyltetrahydro[3',5',7,9-3H4]folic acid (5-methyltetrahydro[3H]folic acid) with high affinity (Kd = 3 nM at 4 degrees C). The cell-surface binding capacity for [3H]folic acid or [3H]methotrexate is equivalent to that for 5-methyltetrahydro[3H]folate, but the Kd values ar
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36. Folate synthesis in plants: The p-aminobenzoate branch is initiated by a bifunctional PabA-PabB protein that is targeted to plastids
It is not known how plants synthesize the p-aminobenzoate (PABA) moiety of folates. In Escherichia coli, PABA is made from chorismate in two steps. First, the PabA and PabB proteins interact to catalyze transfer of the amide nitrogen of glutamine to chorismate, forming 4-amino-4-deoxychorismate (ADC). The PabC protein then mediates elimination of pyruvate an
National Academy of Sciences.