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Medium Design for Cell Culture Processing
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Thymidine and hypoxanthine are commonly used as pyrimidine and purine sources in contemporary media. They are readily linked to a ribose 5-phosphate in the cell to become inosine monophosphate (IMP) and TMP. IMP enters the synthetic pathway to make AMP and GMP, which are further phosphorylated into ATP and GTP. TMP is converted to UMP and CMP. If hypoxanthine is not available in the medium, de novo synthesis is the primary source and must be sufficiently active to sustain cell growth since the salvage pathway only recycles the base “salvaged” from nucleic acid degradation, but does not generate the nucleosides needed for proliferation. In de novo synthesis, the four nitrogen atoms in each purine ring are derived from glutamine, aspartate, and glycine, while obtaining carbons requires CO2, formate, glycine, and folic acid. The de novo synthesis of pyrimidine similarly requires glutamine, aspartic acid, and CO2. One can see that without a sufficient supply of hypoxanthine, many precursors will be needed for nucleoside biosynthesis.
Contributions of Recombinant Microbes and Their Potential
Published in Yoshikatsu Murooka, Tadayuki Imanaka, Recombinant Microbes for Industrial and Agricultural Applications, 2020
Arnold L. Demain, Akira Kimura, Atsuhiko Shinmyo
Recombinant DNA techniques are making their way into the amino acid production area. Escherichia coli strains have been constructed with plasmids bearing amino acid biosynthetic opérons. Plasmid transformation has been accomplished in Corynebacterium, Brevibacterium, and Serratia, so that recombinant DNA technology is now used to improve these commercial amino acid-producing strains. In the area of flavor nucleotides, genetic engineering of the inosine monophosphate dehydrogenase gene in a B. subtilis strain, which was producing 7 g/L guanosine and 19 g/L inosine, changed production to 20 g/L guanosine and 5 g/L inosine [84].
Alterations in Cellular Enzyme Activity, Antioxidants, Adenylates, and Stress Proteins
Published in Alan G. Heath, Water Pollution and Fish Physiology, 2018
ATP is the most variable component of the adenylate pool. In fish it decreases during muscular exercise (Schulte and Hochachka, 1990) and hypoxia (see Chapter 2), and different temperatures can result in significant changes (Walesby and Johnston, 1980; Kindle and Whitmore, 1986). For the most part, ADP and AMP change comparatively little with these kinds of alterations in activity or environment. With decreases in ATP, one might expect a rise in AMP, but this does not necessarily occur because it can be converted to inosine monophosphate (IMP).
Investigation of the embryo-toxicity of the antiviral drug “Ribavirin” in Wistar rats during different gestation periods
Published in Egyptian Journal of Basic and Applied Sciences, 2023
Mohamed Magdy, Abd El Wahab El Ghareeb, Taha M. A. Eldebss, Heba Ali Abd El Rahman
The quantity of ribavirin that has passed through the placenta is changed to ribavirin-5-phosphate inside the fetus’s cells, which impacts the performance of Inosine monophosphate dehydrogenase (IMPDH) that is involved in the production of nitrogenous base guanosine monophosphate. So ribavirin impacts the transcription of DNA within the fetus [23] . In addition, ribavirin impacts active cells, which shows why ribavirin is teratogenic to the fetus; since the cells are constantly and perpetually dividing, this implies that they must generate new genetic information, so inhibiting DNA synthesis as a result of action on IMPDH, cumulative impact manifested as teratogens in distinct fetal areas [22]. This outcome is compatible with Salman et al. [43] when they investigated the effects of ribavirin at various dosages of 10, 20, and 50 mg/kg on rat fetuses and their skeletons.
Assembly of nucleobases into rings and cages via metal ions
Published in Journal of Coordination Chemistry, 2022
Bernhard Lippert, Pablo J. Sanz Miguel
Cyclic dinuclear purine complexes involve either combinations of N1 and N6 metal binding sites (adenine), or combinations of N7 and X6 with guanine/hypoxanthine (X = O) or adenine (X = NH−) [46]. The first one is comparable to that of deprotonated C. All options can be realized in head-tail or head-head fashion, and charges of the nucleobases (anionic; neutral in normal or rare tautomeric form) are a function of pH. Depending on the existence or absence of bonds between the two metals, either two fused five-ring chelates or a folded eight-membered ring are present in the first case, whereas two fused six-ring chelates or a continuous ten-membered ring are present in the second case (Scheme 5). Typical examples include a diplatinum(II) complex of 9EtA (N1,N6; head-tail; no M–M bond; eight-ring) [47], a dirhenium(II) complex of 9EtA (N1,N6; head-head; fused five-rings) [48], or a Cu(II) complex of inosine monophosphate, IMP (N7,O6; head-tail; no M-M bond; ten-ring) [49]. This latter compound displays a variation of the N7,O6 binding mode in that in addition Cu ions bind to the N1 sites of the deprotonated hypoxanthine ligands. Similar variations occur also in N1,N6 bridged 9MeA [50] or in N1,N6 bridged 8-aza-9-methyladenine complexes [51] with metal entities bonded in monofunctional ways to N7 positions of the two purine ligands. Interestingly, the tetracarboxylate complex of dirhodium(II) reacts with d(GpG) and d(pGpG) dinucleotides with substitution of two carboxylate bridges and formation of two head-head N7,O6 chelates of the two guanine bases [52].
Substrate metabolism during exercise: Sexual dimorphism and women’s specificities
Published in European Journal of Sport Science, 2022
Nathalie Boisseau, Laurie Isacco
Adenosine triphosphate (ATP), adenosine diphosphate (ADP) and phosphocreatine (PCr) concentrations at rest and after an acute and intense bout of exercise do not seem to be different between sexes (Esbjornsson, Sylven, Holm, & Jansson, 1993). Resting muscle glycogen concentrations are associated more with dietary CHO availability and training level than with body composition sexual dimorphism (Areta & Hopkins, 2018). During a Wingate-type exercise (30s of maximal exercise on a cycle ergometer), glycogen sparing seems to be more important in women, but only in type I muscle fibres. Three hypotheses have been proposed to explain this observation. First, during an acute exercise of supramaximal intensity, catecholamine production might be lower in women than men (Gratas-Delamarche, Le Cam, Delamarche, Monnier, & Koubi, 1994). Second, some enzymatic activities, such as phosphorylase, phosphofructokinase (PFK-1), and lactate dehydrogenase (LDH), might be lower in women (Esbjornsson et al., 1993). Third, the surface of type I muscle fibres is generally higher in women than men (Esbjornsson et al., 1993). Unlike in men, training (endurance and sprint) does not seem to influence catecholamine production in women during a Wingate-type exercise (Jacob et al., 2002). However, the recovery of the maximum strength might be faster in women. This could be explained by lower absolute anaerobic power and/or better ATP recovery via inosine monophosphate re-amination (Esbjornsson-Liljedahl, Bodin, & Jansson, 2002).