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Retinoic Acid
Retinoic acid (used simplified here for all-''trans''-retinoic acid) is a metabolite of vitamin A1 (all-''trans''-retinol) that mediates the functions of vitamin A1 required for growth and development. All-''trans''-retinoic acid is required in chordate animals, which includes all higher animals from fish to humans. During early embryonic development, all-''trans''-retinoic acid generated in a specific region of the embryo helps determine position along the embryonic anterior/posterior axis by serving as an intercellular signaling molecule that guides development of the posterior portion of the embryo. It acts through Hox genes, which ultimately control anterior/posterior patterning in early developmental stages. All-''trans''-retinoic acid (ATRA) is the major occurring retinoic acid, while isomers like 13-''cis''- and 9-''cis''-retinoic acid are also present in much lower levels. The key role of all-''trans''-retinoic acid in embryonic development mediates the high teratogeni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinol
Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xerophthalmia. In regions where deficiency is common, a single large dose is recommended to those at high risk twice a year. It is also used to reduce the risk of complications in measles patients. It is taken by mouth or by injection into a muscle. Retinol at normal doses is well tolerated. High doses may cause enlargement of the liver, dry skin, and hypervitaminosis A. High doses during pregnancy may harm the fetus. The body converts retinol to retinal and retinoic acid, through which it acts. Dietary sources include fish, dairy products, and meat. Retinol was discovered in 1909, isolated in 1931, and first made in 1947. It is on the World Health Organization's List of Essential Medicines. Retinol is available as a generic medication an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transgenic Mice
A genetically modified mouse or genetically engineered mouse model (GEMM) is a mouse (''Mus musculus'') that has had its genome altered through the use of genetic engineering techniques. Genetically modified mice are commonly used for research or as animal models of human diseases, and are also used for research on genes. Together with patient-derived xenografts (PDXs), GEMMs are the most common ''in vivo'' models in cancer research. Both approaches are considered complementary and may be used to recapitulate different aspects of disease. GEMMs are also of great interest for drug development, as they facilitate target validation and the study of response, resistance, toxicity and pharmacodynamics. History In 1974 Beatrice Mintz and Rudolf Jaenisch created the first genetically modified animal by inserting a DNA virus into an early-stage mouse embryo and showing that the inserted genes were present in every cell. However, the mice did not pass the transgene to their offspring, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypogonadism
Hypogonadism means diminished functional activity of the gonads—the testes or the ovaries—that may result in diminished production of sex hormones. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen (e.g., estradiol) as hypoestrogenism. These are responsible for the observed signs and symptoms in both males and females. Hypogonadism, commonly referred to by the symptom "low testosterone" or "Low T", can also decrease other hormones secreted by the gonads including progesterone, DHEA, anti-Müllerian hormone, activin, and inhibin. Sperm development (spermatogenesis) and release of the egg from the ovaries (ovulation) may be impaired by hypogonadism, which, depending on the degree of severity, may result in partial or complete infertility. In January 2020, the American College of Physicians issued clinical guidelines for testosterone treatment in adult men with age-related low levels of testosterone. The guidelines are supported ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xerophthalmia
Xerophthalmia (from Ancient Greek "xērós" (ξηρός) meaning "dry" and "ophthalmos" (οφθαλμός) meaning "eye") is a medical condition in which the eye fails to produce tears. It may be caused by vitamin A deficiency, which is sometimes used to describe that condition, although there may be other causes. Xerophthalmia caused by a severe vitamin A deficiency is described by pathologic dryness of the conjunctiva and cornea. The conjunctiva becomes dry, thick and wrinkled. The first symptom is poor vision at night. If untreated, xerophthalmia can lead to dry eye syndrome, corneal ulceration, and ultimately to blindness as a result of corneal and retinal damage. Xerophthalmia usually implies a destructive dryness of the conjunctival epithelium due to dietary vitamin A deficiency—a rare condition in developed countries, but still causing much damage in developing countries. Other forms of dry eye are associated with aging, poor lid closure, scarring from a previous in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome P450
Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compounds, as well as for hormone synthesis and breakdown. In 1963, Estabrook, Cooper, and Rosenthal described the role of CYP as a catalyst in steroid hormone synthesis and drug metabolism. In plants, these proteins are important for the biosynthesis of defensive compounds, fatty acids, and hormones. CYP enzymes have been identified in all kingdoms of life: animals, plants, fungi, protists, bacteria, and archaea, as well as in viruses. However, they are not omnipresent; for example, they have not been found in ''Escherichia coli''. , more than 300,000 distinct CYP proteins are known. CYPs are, in general, the terminal oxidase enzymes in electron transfer chains, broadly categorized as P450-containing systems. The term "P450" is deriv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alcohol Dehydrogenase
Alcohol dehydrogenases (ADH) () are a group of dehydrogenase enzymes that occur in many organisms and facilitate the interconversion between alcohols and aldehydes or ketones with the reduction of nicotinamide adenine dinucleotide (NAD+) to NADH. In humans and many other animals, they serve to break down alcohols that otherwise are toxic, and they also participate in generation of useful aldehyde, ketone, or alcohol groups during biosynthesis of various metabolites. In yeast, plants, and many bacteria, some alcohol dehydrogenases catalyze the opposite reaction as part of fermentation to ensure a constant supply of NAD+. Evolution Genetic evidence from comparisons of multiple organisms showed that a glutathione-dependent formaldehyde dehydrogenase, identical to a class III alcohol dehydrogenase (ADH-3/ADH5), is presumed to be the ancestral enzyme for the entire ADH family. Early on in evolution, an effective method for eliminating both endogenous and exogenous formaldehy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ALDH1A3
Aldehyde dehydrogenase 1 family, member A3, also known as ALDH1A3 or retinaldehyde dehydrogenase 3 (RALDH3), is an enzyme that in humans is encoded by the ''ALDH1A3'' gene, Function Aldehyde dehydrogenase isozymes are thought to play a major role in the detoxification of aldehydes generated by alcohol metabolism and lipid peroxidation. The enzyme encoded by this gene uses retinal as a substrate, either in a free or a cellular retinol-binding protein form. Cancer ALDH1A3 gene has been observed progressively downregulated in Human papillomavirus Human papillomavirus infection (HPV infection) is caused by a DNA virus from the '' Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and r ...-positive neoplastic keratinocytes derived from uterine cervical preneoplastic lesions at different levels of malignancy. For this reason, ALDH1A3 is likely to be associated with tum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ALDH1A2
Aldehyde dehydrogenase 1 family, member A2, also known as ALDH1A2 or retinaldehyde dehydrogenase 2 (RALDH2), is an enzyme that in humans is encoded by the ''ALDH1A2'' gene. This protein belongs to the aldehyde dehydrogenase family of proteins. The product of this gene is an enzyme that catalyzes the synthesis of retinoic acid (RA) from retinaldehyde. Retinoic acid, the active derivative of vitamin A (retinol Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xeroph ...), is a paracrine hormone signaling molecule that functions in developing and adult tissues. The studies of a similar mouse gene suggest that this enzyme and the cytochrome CYP26A1, concurrently establish local embryonic retinoic acid levels that facilitate posterior organ development and prevent spina bifida. Three transcript va ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ALDH1A1
Aldehyde dehydrogenase 1 family, member A1, also known as ALDH1A1 or retinaldehyde dehydrogenase 1 (RALDH1), is an enzyme that is encoded by the ''ALDH1A1'' gene. Function This protein belongs to the aldehyde dehydrogenases family of proteins. Aldehyde dehydrogenase is the second enzyme of the major oxidative pathway of alcohol metabolism. Two major liver isoforms of this enzyme, cytosolic and mitochondrial, can be distinguished by their electrophoretic mobilities, kinetic properties, and subcellular localizations; this gene encodes the main cytosolic isoform, which has a lower affinity for aldehydes than the mitochondrial enzyme. Most Caucasians have two major isozymes, while approximately 50% of East Asians have only the cytosolic isozyme, missing the mitochondrial isozyme. A remarkably higher frequency of acute alcohol intoxication among East Asians than among Caucasians could be related to the absence of the mitochondrial isozyme. Furthermore, mutations in this enzyme have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinaldehyde Dehydrogenase
In enzymology, a retinal dehydrogenase, also known as retinaldehyde dehydrogenase (RALDH), catalyzes the chemical reaction converting retinal to retinoic acid. This enzyme belongs to the family of oxidoreductases, specifically the class acting on aldehyde or oxo- donor groups with NAD+ or NADP+ as acceptor groups, the systematic name being retinal:NAD+ oxidoreductase. This enzyme participates in retinol metabolism. The general scheme for the reaction catalyzed by this enzyme is: retinal + NAD+ + H2O \rightleftharpoons retinoic acid + NADH + H+ Structure Retinal dehydrogenase is a tetramer of identical units, consisting of a dimer of dimers. Retinal dehydrogenase monomers are composed of three domains: a nucleotide-binding domain, a tetramerization domain, and a catalytic domain. The dimer can be pictured as an "X" with the dimers forming upper and lower halves that cross over each other. Interestingly, the nucleotide-binding domain of retinal dehydrogenase contains 5 instea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinol Dehydrogenase
In enzymology, a retinol dehydrogenase (RDH) () is an enzyme that catalyzes the chemical reaction :retinol + NAD+ \rightleftharpoons retinal + NADH + H+ Sometimes, in addition to or along with NAD+, NADP+ can act as a preferred cofactor in the reaction as well. The substrate of the enzyme can be all-''trans''- or -''cis''- retinol. There are at least over 20 different isolated enzymes with RDH activity to date. Thus, the two substrates of this enzyme are retinol and NAD+, whereas its 3 products are retinal, NADH (or NADPH in the case where NADP+ is a cofactor), and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is retinol:NAD+ oxidoreductase. Other names in common use include retinol (vitamin A1) dehydrogenase, MDR, microsomal retinol dehydrogenase, all-trans retinol dehydrogenase, retinal reductase, and retinene reductase. This enzyme pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regulation Of Gene Expression
Regulation of gene expression, or gene regulation, includes a wide range of mechanisms that are used by cells to increase or decrease the production of specific gene products (protein or RNA). Sophisticated programs of gene expression are widely observed in biology, for example to trigger developmental pathways, respond to environmental stimuli, or adapt to new food sources. Virtually any step of gene expression can be modulated, from transcriptional initiation, to RNA processing, and to the post-translational modification of a protein. Often, one gene regulator controls another, and so on, in a gene regulatory network. Gene regulation is essential for viruses, prokaryotes and eukaryotes as it increases the versatility and adaptability of an organism by allowing the cell to express protein when needed. Although as early as 1951, Barbara McClintock showed interaction between two genetic loci, Activator (''Ac'') and Dissociator (''Ds''), in the color formation of maize see ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
