DTYMK is an essential gene in mice and heterozygosity does not cause neural tube defects.

Regulation of nucleotide biosynthesis is necessary for maintaining cellular processes including DNA replication and repair. A key enzyme in this process is deoxythymidylate kinase (dTYMK), which catalyzes the initial step in the production of dTTP from dTMP. This gene constitutes the first merged step of dTTP synthesis from the de novo and salvage pathways which regulate dTMP biosynthesis. Decreased de novo dTMP biosynthesis causes dysregulated dTTP:dUTP pools, and leads to increased uracil in DNA and neural tube closure defect (NTD) development in mice. The goal of this research was to investigate if dTYMK, the downstream enzyme in dTTP production, is an essential gene in mice and if impairments in dTYMK play a causal role in development including NTD pathology in mice. Dtymk+/- C57BL/6J females were weaned onto either a control, excess folic acid, or folic acid deficient diet and timed breeding was performed after 8 weeks on diet. The offspring were analyzed for NTDs and other reproductive outcomes at embryonic day 12.5 (E12.5). Dtymk-/- mice were confirmed to be embryonic lethal before E12.5, and Dtymk+/- mice on all three experimental diets did not show the presence of open neural tube defects, spina bifida or exencephaly. However, the expression of dTYMK in Dtymk+/- mouse embryos was confirmed to be decreased by approximately 3-fold compared to Dtymk+/+ embryos. Although dTYMK was demonstrated to be an essential gene in mice and is required for the regulation of nucleotide pools in vitro, there was no evidence of increased risk of NTDs because of a reduction in expression of this enzyme during embryonic development. It is possible that a further reduction in expression may be required to see developmental anomalies in C57BL/6J mice.

The Role of Brain Barriers in Maintaining Brain Vitamin Levels.

It is increasingly recognized that tissue-specific nutrient deficiencies can exist in the absence of whole-body deficiency and that these deficiencies may result from disease or disease-related physiological processes. Brain and central nervous system tissues require adequate nutrient levels to function. Many nutrients are concentrated in the cerebrospinal fluid relative to the serum in healthy individuals, and other nutrients resist depletion in the presence of whole-body nutrient depletion. The endothelial, epithelial, and arachnoid brain barriers work in concert to selectively transport, concentrate, and maintain levels of the specific nutrients required by the brain while also blocking the passage of blood-borne toxins and pathogens to brain and central nervous system tissues. These barriers preserve nutrient levels within the brain and actively concentrate nutrients within the cerebrospinal fluid and brain. The roles of physical and energetic barriers, including the blood-brain and blood-nerve barriers, in maintaining brain nutrient levels in health and disease are discussed.

Extending viability of Lactobacillus plantarum and Lactobacillus johnsonii by microencapsulation in alginate microgels.

AIM: To investigate whether microencapsulation of Lactobacillus in alginate microbeads will lead to increased longevity during refrigerated storage or simulated digestion. MATERIALS AND METHODS: Microscopy was used to confirm that Lactobacillus plantarum ATCC BAA-793 and Lactobacillus johnsonii ATCC 33200 were immobilised within the microbeads and laser scattering analysis was used to determine the mean diameter of the microbeads. The number of viable cells were enumerated throughout refrigerated storage and simulated digestion experiments. RESULTS: Microencapsulation was shown to have differing effects on viability depending on the species, but led to extended viability during refrigerated storage and simulated digestion in L. johnsonii and L. plantarum respectively. CONCLUSION: Fermented functional foods contain microbes beneficial to human health. However, extended shelf storage and the harsh environment of the GI tract significantly reduces the number of viable microbes reaching the consumer. Microencapsulation allows beneficial microbes to reach the gut of the consumer in higher numbers, and thus confer greater health benefits.

Microencapsulation in Alginate and Chitosan Microgels to Enhance Viability of Bifidobacterium longum for Oral Delivery.

Probiotic microorganisms are incorporated into a wide variety of foods, supplements, and pharmaceuticals to promote human health and wellness. However, maintaining bacterial cell viability during storage and gastrointestinal transit remains a challenge. Encapsulation of bifidobacteria within food-grade hydrogel particles potentially mitigates their sensitivity to environmental stresses. In this study, Bifidobacterium longum subspecies and strains were encapsulated in core-shell microgels consisting of an alginate core and a microgel shell. Encapsulated obligate anaerobes Bifidobacterium longum subsp. infantis and Bifidobacterium longum subsp. longum exhibited differences in viability in a strain-dependent manner, without a discernable relationship to subspecies lineage. This includes viability under aerobic storage conditions and modeled gastrointestinal tract conditions. Coating alginate microgels with chitosan did not improve viability compared to cells encapsulated in alginate microgels alone, suggesting that modifying the surface charge alone does not enhance delivery. Thus hydrogel beads have great potential for improving the stability and efficacy of bifidobacterial probiotics in various nutritional interventions.