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Comparative Anatomy and Physiology of the Mammalian Eye
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The cornea is responsible for approximately 70% of the refractive power of the eye. It is able to transmit light because of the regular arrangement of its stromal collagen, its avascular nature, and because of its state of relative deturgesence. These properties result in some unique requirements. Since it is avascular, the cornea obtains its oxygen primarily from the tear film and its glucose from the aqueous humor.2,6 Some oxygenation also occurs from the aqueous humor.2 The majority of the glucose is consumed by the epithelium and endothelium and is metabolized predominantly by the hexose monophosphate shunt pathway.2 In addition to metabolizing glucose, the corneal epithelium also stores glucose in the form of glycogen.2
Concept of Nutrition
Published in Anil Gupta, Biochemical Parameters and the Nutritional Status of Children, 2020
Monosaccharides as hexoses—namely fructose, glucose, galactose, and mannose—represent the major source of energy for the body, whereas, pentoses—namely ribose and deoxyribose—are involved in the synthesis of nucleic acids, as pentoses have poor nutritional and caloric values. Hexoses constitute a major proportion of the daily diet. Disaccharides, such as sucrose, maltose, and lactose, and polysaccharides like starch and glycogen are macromolecules and are hydrolyzed in the lumen of alimentary canal into monosaccharides.
Host Defense I: Non-specific Immunity
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
During engulfment, pseudopodia actively reach out to enclose particles. The movement of the cell membrane requires reorganization of the cytoskeleton (microtubules and microfilaments) and is energy-dependent. The cell membrane completely surrounds the particles and fuses forming an intact outer membrane and a phagocytic vesicle (phagosome) in the cytoplasm (Figure 10–6). Following ingestion, a number of changes in cellular metabolism occur. O2 consumption and lactic acid production increase. Glucose metabolism increases, especially the hexose monophosphate shunt, rising from 1% to 10% of total glucose expenditure. Membrane lipid synthesis increases, and cyclic AMP is concentrated in phagosomes.
Developments in reading frame restoring therapy approaches for Duchenne muscular dystrophy
Published in Expert Opinion on Biological Therapy, 2021
Anne-Fleur E. Schneider, Annemieke Aartsma-Rus
It has also been shown feasible to increase muscle delivery of AONs by formulating them in hexose solutions [60,61] or glycine solutions [62]. This increase was observed for both PMOs and 2OMePS AONs for hexose and, the effect was shown to be related to the metabolic state of the mdx muscle, which due to active and continuous muscle regeneration has a very high demand for nutrients. The increased uptake was not observed in wild type mice [61]. While DMD patients show some hypertrophy at the earliest stages of their disease, the regenerative capacity of human muscle is unfortunately much less than that of the mdx mouse model. As such, most likely the uptake benefit will be much less in humans than mice. For the glycine formulation, only PMOs were used. Here uptake is facilitated by the facts that glycine increases regeneration in mdx mice [62], and that PMOs rely on active regeneration for uptake [63].
High alcohol-producing Klebsiella pneumoniae causes fatty liver disease through 2,3-butanediol fermentation pathway in vivo
Published in Gut Microbes, 2021
Nan-Nan Li, Wei Li, Jun-Xia Feng, Bing Du, Rui Zhang, Shu-Heng Du, Shi-Yu Liu, Guan-Hua Xue, Chao Yan, Jing-Hua Cui, Han-Qing Zhao, Yan-Ling Feng, Lin Gan, Qun Zhang, Wei-Wei Zhang, Di Liu, Chen Chen, Jing Yuan
The genes encoding all of the enzymes of the Embden-Meyerhof-Parnas pathway (EMP), hexose monophosphoric acid pathway (HMP), Entner-Doudoroff (ED) pathway, and Tricarboxylic acid cycle (TCA) pathway were present in K. pneumoniae W14 and TH1. Analyses of the genome sequences revealed the determinants of hexose-metabolizing enzymes such as invertase, levansucrase, glucokinase, glucose-6-phosphate isomerase, and glucose-fructose oxidoreductase. These enzymes would enable K. pneumoniae to use sucrose, fructose, and glucose (as well as probably glycerol, mannose, raffinose, and sorbitol), then, convert acetyl-coA to acetaldehyde using MhpF and AdhE, and finally, produce alcohol through alcohol dehydrogenases (ADHs). More than 12 highly specific ADHs could catalyze the conversion of acetaldehyde to ethanol. Furthermore, most of these ORFs were also found to be actively transcribed in association with ethanol production by K. pneumoniae W14 and TH1. These results strongly suggested that the rapid production and high yield of ethanol could probably be attributed to the presence of 12 ADHs and pyruvate decarboxylase (GL003732 and GL001278, thiamine pyrophosphate protein TPP-binding domain protein [EC:4.1.1.74]), an enzyme not frequently observed in bacteria.
Standardizing and increasing the utility of lipidomics: a look to the next decade
Published in Expert Review of Proteomics, 2020
Yuqin Wang, Eylan Yutuc, William J Griffiths
Excellent methods for the GC-MS profiling of bile acids were developed in the 1970’s and 1980’s and since these halcyon days the field has possibly regressed at the Alter of simplicity [133–135]. As GC-MS is not generally suitable for analysis of conjugated bile acids sample preparation is paramount involving, separation of different conjugation types followed by hydrolysis, derivatization and ultimately GC-MS analysis [133,134]. The separation methods make extensive use of ion-exchange chromatography for group fractionation, this still has value for modern day bile acid profiling using LC-MS/MS [102]. A lipidomic study of bile acids is challenging based on the huge range of polarity and solubilities extending from almost water insoluble lithocholic acid (stone bile acid) to highly water soluble taurocholic acid sulfate, and the huge number of different forms of conjugation i.e. at C24 a free acid, glycine or taurine amidate or a glucuronic acid ester, and at ring hydroxy groups esters with sulfuric acid or acetals with glucose, glucuronic acid or N-acetyl glucosamine [86]. Note, it is unlikely that the exact hexose sugar, will be identified by LC-MS methods. Additionally, hydroxylation can be at almost any carbon when the activities of the gut microflora and the enterohepatic system are considered. The picture is further complicated when C27 and nor bile acids are considered. Never-the-less there are currently excellent methods for bile acid analysis if it is accepted that they are not fully comprehensive [136–140].