Folic acid assay

Cells of Streptococcus fecalis (ATCC-8043) were grown in the AOAC folic acid assay medium [Lepper, Official and Tentative Methods of the Association of... 

It is important that the density of the cell culture used for folic acid assays is not more than 1 x 10 cells/mL. At higher densities, nutrients may become limiting which could result in decreased responsiveness to folic acid. During early starvation-induced development, responsiveness to folic acid declines rapidly (3). 

Folic acid assay on dextrimaltose (no. 2) was made through the courtesy of Dr. Warren M. Cox, Jr., Mead Johnson and Company. Using S. laelia R. the folic acid content was found to be 0.056 y per gram. 

MTX interferes with the growth of cancer cells by inhibiting the metabolism of folic acid. Drug efficacy was evaluated in vitro by MTT assay, as described above, and by Trypan Blue exclusion. Trypan Blue is a non-vital dye excluded by viable cells, but selectively staining dead cells. According to Figure 13.7, higher suppression of cell... 

Patients sustain convulsions and neurological deterioration. The urine contains low levels of the metabolites of serotonin, norepinephrine and dopamine. The reductase also plays a role in the maintenance of tetrahydrofolate levels in brain, and some patients have had low folate levels in the serum and CNS. Treatment has been attempted with tryptophan and carbidopa to improve serotonin homeostasis and with folinic acid to replete diminished stores of reduced folic acid. This therapy is sometimes effective. Diagnosis involves assay of DHPR in skin fibroblasts or amniotic cells. Phenylalanine hydroxylase activity is normal. 

J. M. Cooperman, Microbiological assay of folic acid activity in serum and whole blood. In Methods in Enzymology, XVIII, Part B (eds. D. G. McCormick and... 

The chemistry, metabolism, and clinical importance of folic acid have been the subject of many excellent reviews (A7, Gil, H14, H20, Rl). Folic acid deficiency leads to a macrocytic anemia and leucopenia. These symptoms are due to inadequate synthesis of nucleic acid. The synthesis of purine bases and of thymine, required for nucleic acid synthesis, is impaired in folic acid deficiency. Detection of folic acid activity in biologic fluids and tissues is of the utmost importance it distinguishes between the various anemias, e.g., those due to vitamin Bi2 or folic acid deficiency. Because morphology of the abnormal red cell does not help in diagnosing vitamin deficiency, one must rely on assay methods for differential diagnosis. Treatment of pernicious anemia with folic acid has led to subacute combined degeneration of the spinal cord despite... 

Chemical methods for folic acid detection are not useful for unfractionated biologic materials (H16). Reduction of folic acid in acid yields a methylpteridine and N-(p-aminobenzoyl) glutamic acid. The latter is estimated by a method for aromatic amines (B33). Another assay method of historical interest is the growth of chicks as a measure of the folic acid content of crude biological mixtures. 

Nearly all microbiologic assays for folic acid activity have used Streptococcus faecalis and Lactobacillus casei. Earlier it appeared that these organisms could not detect folic acid deficiency in man (C2, L8) for example, in one study using S. faecalis there was no detectable activity in the fasting serum of humans (C3). Administration of a loading dose of folic acid with subsequent assay by S. faecalis (G9) has served as a workable means of determining folic acid deficiency (C6), a technique having definite drawbacks (G10). 

A microbiologic assay for folic acid activity in human serum was devised (B12). It agrees with the clinical folic acid status (W4). 

Because of the multiplicity of folic acid factors reported in whole blood (Ul), the microbiologic assay for folic acid in whole blood and serum was regarded as valueless (C2, L8, W9) results based on S. faecalis methods (C2, C3) did not contradict this view. Streptococcus faecalis is inferior to L. casei in its utilization of the PGA polyglutamates... 

A modification of the above serum folic assay method was recently described (W4). The investigators confirmed the validity of this technique as a practical means of differentiating patients with folic acid from vitamin B12 megaloblastic anemias. Another modification of this method was also described (C4). These investigators reduced the over-all sensitivity by high serum dilutions and thus made the assay, as they used it, valueless as a diagnostic tool. 

Recently, tritiated folic acid became available, making possible a nonmicrobiological method for studying the metabolism of folic acid. It obviates the toxic effects of folic acid antagonists on microbial assay organisms. This technique was used to follow the uptake, metabolism, and excretory products of folic acid (A4, J2, J3). 

G12. Girdwood, R. H., Microbiological methods of assay in clinical medicine with particular reference to the investigation of deficiency of vitamin B12 and folic acid. Scot. Med. J. 5, 10-22 (1960). 

Recently, Choy et al. also reported that LDHs are an efficient drug reservoir for folate derivatives [187]. Folic acid derivatives, folinic acid and methotrexate (MTX), have been successfully hybridized with Mg/Al LDHs by ion-exchange reactions. Cellular uptake tests with the MTX-LDH hybrids were carried out in the fibroblast (human tendon) and osteosarcoma (SaOS-2) cell lines by in vitro assay. They found that the LDH not only plays a role as a biocompatible delivery matrix for drugs but also facilitates a significant increase in the delivery efficiency. 

Drug/Lab test interactions Methotrexate, pyrimethamine, and most antibiotics invalidate folic acid and vitamin Bi2diagnostic microbiological blood assays. 

Some commonly used detectors are UV (at 280 nm), ELD, ED and microbiological assay of collected fractions. UV presents a low sensitivity, but all folate derivatives respond to this detection. ELD is used even if some compounds, like folic acid, do not fluoresce. Therefore, a postcolumn derivatization, involving hypochlorite to cleave folic acid, di- and tetra-hydrofolic acid oxidatively to fluorescence pterins [571], has been introduced. Eewer reports on the use of LC-MS for folate detection are available in the literature [578-580]. 

Deficiencies of folic acid and vitamin B1 are relatively common. Whenever macrocytic anemia is present, evaluation of these two vitamins is necessary 10 determine the cause of the condition, The standard method of measuring folic acid has been the microbiological assay (Bailey et al.. 19821. which can be used to measure folic acid in serum, blood, tissues, and foods. Improved high performance liquid chromatography (HPLC) methods have... 

The use of ELISA is broad and it finds applications in many biological laboratories over the last 30 years many tests have been developed and vahdated in different domains such as clinical diagnostics, pharmaceutical research, industrial control or food and feed analytics for instance. Our work has been to redesign the standard ELISA test to fit in a microfluidic system with disposable electrochemical chips. Many applications are foreseen since the biochemical reagents are directly amenable from a conventional microtitre plate to our microfluidic system. For instance, in the last 5 years, we have reported previous works with this concept of microchannel ELISA for the detection of thromboembolic event marker (D-Dimer) [4], hormones (TSH) [18], or vitamin (folic acid) [24], It is expected that similar technical developments in the future may broaden the use of electroanalytical chemistry in the field of clinical tests as has been the case for glucose monitoring. This work also contributes to the novel analytical trend to reduce the volume and time consumption in analytical labs using lab-on-a-chip devices. Not only can an electrophoretic-driven system benefit from the miniaturisation but also affinity assays and in particularly immunoassays with electrochemical detection. 

Folic Acid (folate). Chemically, folic acid is a pteryl-glutamic acid. The several forms that occur in nature depend on the numbers of glutamic acid units and methyl groups in the molecules. Because of its usual low concentration, folic acid is generally determined in food materials by the microbiological assay with lactobacillus casei and measured turbidimetrically or titrimetrically. Deficiency of this vitamin could result in... 

Examination of the bone marrow, although important, will only confirm that the hemopoiesis is megaloblastic. A deficiency of folic acid will also cause a megaloblastic anemia and it is not possible to identify the cause on the basis of morphology. A serum assay of both vitamins will usually indicate which is responsible. If the patient is vitamin B12 deficient, the next step is to carry out a vitamin B12 absorption test to confirm that the deficiency is due to a lack of intrinsic factor. Preferably this should not be done until the patient s vitamin B12 and hemoglobin levels have returned to normal, since the gastric and intestinal cells are also affected by a lack of vitamin B12 aborption may be less than optimal if it is attempted too early. Patients with pernicious anemia also have a histamine-fast achlorhydria and gastric atrophy. The disease appears to have an autoimmune basis and antibodies to intrinsic factor can be demonstrated in the serum of more than half of affected patients. 

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