Vitamin C | EPFL Graph Search

Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical "serum" ingredient to treat melasma (dark pigment spots) and wrinkles on the face. It is used to prevent and treat scurvy. Vitamin C is an essential nutrient involved in the repair of tissue, the formation of collagen, and the enzymatic production of certain neurotransmitters. It is required for the functioning of several enzymes and is important for immune system function. It also functions as an antioxidant. Most animals are able to synthesize their own vitamin C. However, apes (including humans) and monkeys (but not all primates), most bats, some rodents, and certain other animals must acquire it from dietary sources. There is some evidence that regular use of supplements may reduc

A method for the reliable and reproducible precipitation of phase pure high Ca/Si ratio (>1.5) synthetic calcium silicate hydrates (C-S-H)

Paul Bowen, Maya Nicole Harris, Karen Scrivener, Grace Simpson

Various methods have been developed to synthesize C-S-H; however, these methods have only allowed for the successful production of pure-phase C-S-H with Ca:Si of 1.5 or less. Attempts to form higher Ca:Si ratios by these methods gives C-S-H (Ca:Si 1.5 or less) in the presence of Ca(OH)(2). This paper focuses on a reliable method to produce single-phase C-S-H with Ca:Si molar ratios between 1 and 2. Reactant concentrations, temperature, pH, and mixing conditions are carefully controlled to ensure homogeneous precipitation of C-S-H. Guidelines on collection, drying, storage, and handling are also described.

PERGAMON-ELSEVIER SCIENCE LTD2022

Study of the influence of over-the-counter vitamin supplement intake on urine fluorescence to optimize cancer detection by fluorescence cystoscopy

Carla Martoccia, Hubert van den Bergh, Georges Wagnières, Matthieu Zellweger

Fluorescence cystoscopy (FC) efficiently enhances the detection and improves the therapeutic management of early bladder cancer. During an FC, about 150 ml of water is needed to inflate the bladder. The water is quickly diluted by urine which can be fluorescent. If this bladder washout fluid (BWF) becomes fluorescent, the FC images are frequently degraded. Unfortunately, it is unclear which elements of the diet may contribute to this background fluorescence. We propose to start this exploration with over-the-counter (OTC) vitamin supplements. To this end, we measured excitation-emission matrices of urine samples and the kinetics of modifications of urine fluorescence obtained from nine healthy volunteers before, during, and after intake of a commercially available OTC vitamin supplement. The pharmacokinetics shows that the BWF fluorescence values reach a maximum 8 to 10 h after vitamin intake. They decrease in the half-day that follows and reach values close to baseline similar to 1 day afterward. Based on these results, we conclude that, in order to avoid degradations of fluorescence images, it is likely best that the intake of OTC vitamin supplements be avoided during the week preceding an FC. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

Spie-Soc Photo-Optical Instrumentation Engineers2015

Functional characterization of a vitamin B12-dependent methylmalonyl pathway in Mycobacterium tuberculosis: implications for propionate metabolism during growth on fatty acids

John McKinney

Mycobacterium tuberculosis is predicted to subsist on alternative carbon sources during persistence within the human host. Catabolism of odd- and branched-chain fatty acids, branched-chain amino acids, and cholesterol generates propionyl-coenzyme A (CoA) as a terminal, three-carbon (C(3)) product. Propionate constitutes a key precursor in lipid biosynthesis but is toxic if accumulated, potentially implicating its metabolism in M. tuberculosis pathogenesis. In addition to the well-characterized methylcitrate cycle, the M. tuberculosis genome contains a complete methylmalonyl pathway, including a mutAB-encoded methylmalonyl-CoA mutase (MCM) that requires a vitamin B(12)-derived cofactor for activity. Here, we demonstrate the ability of M. tuberculosis to utilize propionate as the sole carbon source in the absence of a functional methylcitrate cycle, provided that vitamin B(12) is supplied exogenously. We show that this ability is dependent on mutAB and, furthermore, that an active methylmalonyl pathway allows the bypass of the glyoxylate cycle during growth on propionate in vitro. Importantly, although the glyoxylate and methylcitrate cycles supported robust growth of M. tuberculosis on the C(17) fatty acid heptadecanoate, growth on valerate (C(5)) was significantly enhanced through vitamin B(12) supplementation. Moreover, both wild-type and methylcitrate cycle mutant strains grew on B(12)-supplemented valerate in the presence of 3-nitropropionate, an inhibitor of the glyoxylate cycle enzyme isocitrate lyase, indicating an anaplerotic role for the methylmalonyl pathway. The demonstrated functionality of MCM reinforces the potential relevance of vitamin B(12) to mycobacterial pathogenesis and suggests that vitamin B(12) availability in vivo might resolve the paradoxical dispensability of the methylcitrate cycle for the growth and persistence of M. tuberculosis in mice.

2008

Functional characterization of a vitamin B12-dependent methylmalonyl pathway in Mycobacterium tuberculosis: implications for propionate metabolism during growth on fatty acids

John McKinney

2008