Background Expert guidelines recommend low-risk women to consume a daily multivitamin supplement containing 400 µg of folic acid (FA) to prevent the occurrence of neural tube defects. This study assessed the knowledge, attitude and practice of physicians regarding FA recommendations, status and health outcomes during pregnancy since physicians play an essential role in promoting appropriate FA intake. Methods A cross-sectional survey of a sample of physicians practicing in the National Capital Region was self-administered in 2018-2019. Results Approximately 70% of physicians were not familiar with the most recent guidelines and 55% of them most often recommend a 1000 µg-FA supplement. A high level of willingness to recommend a supplement containing 400 µg-FA was reported by almost all physicians. Conclusion While most physicians would not feel comfortable recommending a supplement that is not in line with the most recent evidence-based guidelines, educational programs targeted to physicians are needed to improve their knowledge, attitude and practice.

The influences of dietary deficiencies of folic acid or zinc on rotaviral disease infant mice were studied. Preliminary studies indicated that bovine and simian rotaviruses, but not porcine rotavirus, caused diarrhea in infant mice. Bovine and porcine rotaviruses were not, however, sufficiently infectious to replace murine rotavirus in studies utilizing the murine model. It was also determined that murine rotavirus purified by a cesium chloride gradient was highly infectious and useful for subsequent studies on nutritional influences of rotaviral disease. In dietary studies, female Swiss Webster mice were fed diets containing deficient, moderately deficient, or adequate levels of folic acid or zinc. The quantity of s[specific nutrient added to the tow diets were 0, 0.125, and 0.50 ug of folic acid per gram of diet, and 4, 12, and 60 ug of zinc per gram of diet. The infants from these mice were orally inoculated with approximately 100 ID of purified murine rotavirus with sterile diluent as a control. Uninfected infants from dams fed the lowest folic acid diet gained weight at a significantly reduced rate compared with the two groups fed the higher dietary folic acid levels. Infants from the same low folic acid group had significantly less folate levels in their livers which indicated that a deficiency was achieved. A moderate enhancement of rotaviral disease was seen in these folic acid-deprived infants as determined by their decreased ability to gain weight, increased incidences of diarrhea, and an increased number which exhibited high rotaviral antigen titers in their intestines. Serum rotaviral antibody titers were below detectable levels in a significant number of animals fed the lowest folic acid diet. Zinc deficiency in the infant mice was evidenced by significantly reduced thymus weight, inability to gain body weight, lower zinc concentration in whole infant mice, alopecia and presence of skin rashes. The zinc deficiency produced in this study did not significantly affect weight gained by the infants, presence of diarrhea, titers of virus recovered from the intestine, rotaviral specific antibody in sera, rotaviral specific antibody in milk, ratio of intestine wieght to whole mouse weight, and serum sodium levels. Since zinc deficiency did not alter the rotaviral diesease, studies with athymic nude mice were done. After per os rotaviral exposure none of the athymic mice, while all of the mice with thumuses, had serum antibodies specific to rotavirus, demonstrating that elicitation of rotaviral specific antibodies was T-cell dependent.

Folate degradation in micronutrient fortified corn masa and tortillas was evaluated using masa prepared from either nixtamalized corn flour or fresh nixtamal. A laboratory evaluation of the effects of pH, iron, and holding time at elevated temperature on folate loss in corn flour masa failed to show significant differences in any variable-treatment combination. An additional study was conducted at a commercial tortilla mill in Guadalajara, Mexico using masa prepared from fresh nixtamal. Commercial nixtamal was fortified with one of two different micronutrient premixes, containing iron, zinc, riboflavin, thiamin, niacin and either unencapsulated or lipid-encapsulated folic acid. A batch of each fortified masa and an unfortified control batch were prepared on each of two consecutive days. Folate loss in prepared masa increased with prebake masa holding time for both premixes. Encapsulated folic acid showed a significantly lower percent loss from theoretical, indicating a protective effect from the lipid coating. No significant differences in folate levels were found between prebake masa and baked tortillas. Holding baked tortillas for up to 12 hours also had no effect on folate levels. Results indicate that added folic acid is degraded during the grinding process, as well as during pre-bake holding of masa. Native folate showed no significant loss.

Two-photon fluorescence microscopy (2PFM) has become a powerful technique for bioimaging in non-invasive cancer diagnosis and also investigating the mechanization and original of a variety of diseases by tracking various biological processes. Because the fluorescence emission by two photon absorbing (2PA) is directly proportional to the square of the intensity of excitation light, this intrinsic property of 2PA provides 2PFM great advantages over traditional one-photon fluorescence microscopy (1PFM), including high 3D spatial localization, less photodamage and interference from biological tissue because of using longer wavelength excitation (700-1300 nm). However, most 2PA probes are hydrophobic and their photostabilities are questionable, severely limiting their biological and medical applications. In addition, probes with significant specificity for certain organelles for tracking cellular processes or metal ions for monitoring neural transmission are somewhat rare. Moreover, it is also very significant to deliver the probes to specific disease sites for early cancer diagnosis. In order to increase the water solubility of probes, polyethylene glycol (PEG) was introduced to a fluorene-based 2PA probe LT1 for lysosomal 2PFM cell imaging. The 2PFM bioimaging application of the novel two-photon absorbing fluorene derivative LT1, selective for the lysosomes of HCT 116 cancer cells is described in Chapter II. Linear and nonlinear photophysical and photochemical properties of the probe were investigated to evaluate the potential of the probe for 2PFM lysosomal imaging. After the investigation of the cytotoxicity of this new probe, colocalization studies of the probe with commercial lysosomal probe Lysotracker Red in HCT 116 cells were conducted. A high colocalization coefficient (0.96) was achieved and demonstrated the specific localization of the probe in lysosomes. A figure of merit, F[subscript M], was introduced by which all fluorescent probes for 2PFM can be compared. LT1 was demonstrated to have a number of properties that far exceed those of commercial lysotracker probes, including much higher 2PA cross sections, good fluorescence quantum yield, and, importantly, high photostability, all resulting in a superior figure of merit. Consequently, 2PFM was used to demonstrate lysosomal tracking with LT1. In addition to lysosomes, it is also very significant to investigate the physiological roles of free metal ions in biological processes, especially Zn²⁺, because Zn²⁺ normally serves either as the catalytic elements in enzymatic activity centers or as structural elements in enzymes and transcription factors. However, biocompatible and effective Zn²⁺ probes for 2PFM bioimaging are infrequent. In Chapter III, 2PFM bioimaging with a hydrophilic 2PA Zn²⁺ sensing fluorescent probe, bis(1,2,3-triazolyl)fluorene derivative, is described. 2PFM bioimaging of the probe in living HeLa cancer cells was demonstrated. The results revealed a significant fluorescence increase upon introduction of Zn²⁺ into the cancer cells, and a reversible Zn²⁺ binding to the probe was also demonstrated, providing a robust probe for two-photon fluorescence zinc ion sensing. Early cancer diagnosis is another critical application for 2PFM, but there are still huge challenges for this new technique in clinical areas. Most 2PA probes with large two-photon absorbing cross sections and fluorescence quantum efficiency are synthetically more accessible in hydrophobic forms. In order to increase the efficiency of the probes and minimize the effect of the probe on the human body, delivery of the probe specifically to cancer sites is desired. The synthesis and characterization of narrow dispersity organically modified silica nanoparticles (SiNPs), diameter ~30 nm, entrapping a hydrophobic two-photon absorbing fluorenyl dye, are reported in Chapter IV. The surface of the SiNPs was functionalized with folic acid to specifically deliver the probe to folate receptor (FR) over-expressing HeLa cells, making these folate 2PA dye-doped SiNPs potential candidates as probes for two-photon fluorescence microscopy (2PFM) bioimaging. In vitro studies using FR over-expressing HeLa cells demonstrated specific cellular uptake of the functionalized nanoparticles. However, when the concentration of the dye in SiNPs increased for higher signal output, the fluorescence quantum efficiency of a probe normally decreases because of self-quenching. In Chapter V, a near-infrared (NIR) emitting probe is reported to overcome this limitation through both aggregate-enhanced fluorescence emission and aggregate enhanced two-photon absorption. The dye was encapsulated in SiNPs and the surface of the nanoparticles was functionalized with PEG followed by a folic acid derivative to specifically target folate receptors. NIR emission is important for deep tissue imaging. In vitro studies using HeLa cells that upregulate folate receptors indicated specific cellular uptake of the folic acid functionalized SiNP nanoprobe. Meanwhile, the probe was also investigated for live animal imaging by employing mice bearing HeLa tumors for in vivo studies. Ex vivo 2PFM tumor imaging was then conducted to achieve high quality 3D thick tissue tumor images.

No description available.

The enzymatic interconversion of serine to glycine and N5, N10-methylene tetrahydrofolate to N5 -methyl tetrahydrofolate have been studied in a cell-free system derived from bovine brain. A partial purification of serine transhydroxymethylase and N5, N10 -methylene tetrahydrofolate reductase has been achieved by ammonium sulfate fractionation, protamine sulfate fraction, and by various column chromatography procedures. The two enzymes studied catalyze sequentially the reductive transfer of the hydroxymethyl group of serine to the N5 position of tetrahydrofolate forming N5 -methyl tetrahydrofolate. The products of these reactions were assayed by the incorporation of C14 from a one-carbon precursor i.e., L-beta-(C14)-serine, or N5 -methyl (C14) tetrahydrofolate. The partial purified serine transhydroxymethylase exhibited an absorption peak at 415 mμ due to the bound pyridoxal-5-phosphate and had a maximum pH optimum at 7.6. N5, N10 -methylene tetrahydrofolate reductase is a flavoprotein with a maximum pH optimum at 6.5 and an absorption peak at 405 mμ.

No description available.

A series of studies were conducted to evaluate effects of lactation, exercise, and anti-folate drugs on folate status in the horse, and the bioavailability of supplement and feed folate in the horse. In the first study, mares and foals had adequate plasma folate, RBC folate, and plasma homocysteine concentrations during 6 mo of lactation and growth. Therefore, mares and foals maintained on quality grass/legume pastures and offered a pasture supplement did not require additional folate supplementation to maintain folate status during lactation and growth. In the second study, 25 mg of oral folic acid (FA) supplemented 5 times/wk to 11 mature horses engaged in routine submaximal exercise did not improve folate status, submaximal athletic performance, or combat the increase in oxidative stress during the 12 wk supplementation period compared to 11 horses not given supplemental folate. The common practice of supplementing horses with oral FA in vitamin supplements appears to be of little benefit to horses engaged in routine submaximal exercise. In the third study, daily oral administration of pyrimethamine (PYR) and sulfadiazine (SDZ) for 9 wk followed by 6 wk of coadministration of either Peptidoglycan or FA was associated with a decline in folate status resulting in moderate hyperhomocysteinemia, but not clinical signs of anemia. Peptidoglycan as a source of formylated folate and FA were not effective in improving folate status in horses coadministered PYR and SDZ, two anti-folate drugs commonly administered in equine veterinary practice. The last study assessed the bioavailability of oral and i.v. 5-methyltetrahydrofolate (5-mTHF), 5-formyltetrahydrofolate (5-fTHF), or FA, and the bioavailability of folate from concentrates fed to horses. The minimum efficiency of absorption for supplemental FA was 11 %. The low bioavailability of FA indicates a need for further research on the potential benefits of alternative sources of folate, including 5-fTHF, on increasing folate status in the horse. / Ph. D.

The effects of dietary folic acid supplementation on serum folate status, conceptus development and reproductive performance in gilts and sows was investigated in a series of experiments. The specific objectives of the study were to: 1) to study the serum folates profile following rapid consumption of a single meal containing different levels of supplemental folic acid; 2) to study the effects of maternal folic acid supplementation on conceptus survival, growth and development prior to mid-gestation in gilts and sows; and 3) to study the effects of multiple levels of dietary folic acid supplementation on sow reproductive performance over four successive parities. In the first experiment (Chapter III), gilts fed a single, rapidly consumed meal, had a rapid increase in serum folates concentration during the first hour postprandial. Within eight hours after feeding, serum folates in the gilts had returned to near prefeeding levels. The results also suggest that supplementing the diet with increasing levels of folic acid over a range of 0 to 4 ppm results in more rapid postprandial uptake and elimination of folic acid from general circulation. In the second experiment (Chapter IV), supplementing the diet of first parity and third parity breeding sows with 2 ppm folic acid had no effect on litter size at day 45 of gestation. However, several measurements associated with placental and fetal growth were increased with folic acid supplementation. Results of a fifth parity trial with four levels of supplemental folic acid were variable and inconclusive. The implications of increased placental and fetal growth up to day 45 of gestation in the first and third parity sows is discussed. In the third experiment (Chapter V), a decline in serum folate concentration in pregnant sows from mating to mid- to late gestation was clearly demonstrated. Supplementing the sow's diet with folic acid over a range of 0 to 4 ppm resulted in a linear increase in serum folate concentration at mating, during gestation and at weaning. However, under the conditions of this experiment, folic acid supplementation had no significant effect on sow reproductive performance. / Ph. D.

Folate deficiency, a prevalent vitamin deficiency in America, can stem from environmental and/or genetic causes. The most common inborn error of folate metabolism is deficiency of methylenetetrahydrofolate reductase (MTHFR), which catalyzes the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. Severe MTHFR deficiency results in hyperhomocysteinemia and homocystinuria; patients present with developmental delay, and various neurological and vascular disorders. This thesis describes three mutations identified in the MTHFR locus in patients with severe deficiency: 1025T→C (M→T), 1027T→G (W→G), and 1768G→A (E→K). Genotype-phenotype correlations are described, along with biochemical characterization of three mutations (983A→G (N→S), 1025T→C, 1027T→G). All three mutations exert their effect by decreasing Vmax without changing the enzyme's affinity for its substrate, 5-methyltetrahydrofolate. The 983A→G variant also conferred decreased affinity for FAD, a cofactor. / The more common and mild deficiency observed in the general healthy population is probably due in part to insufficient dietary intake of folate. Folate deficiency has been associated with increased risk for colon cancer. In a pilot study presented here, the impact of altered folate intake on tumor multiplicity in the Min mouse, a model for multiple intestinal neoplasia, was assessed. Folate deficient diets did not produce a consistent change in tumor numbers. However, a linear correlation between S-adenosylmethionine and S-adenosylhomocysteine content of preneoplastic tissue and tumor multiplicity was identified. / This thesis contributes to our understanding of the impact of genetic- and/or dietary-induced folate deficiency on cellular and organismal functions.