"the various forms of vitamin D are secosteroids, i.e., steroids in which one of the bonds in the steroid rings is broken. The structural difference between vitamin D and vitamin D is the side chain of D contains a double bond between carbons 22 and 23, and a methyl group on carbon 24. The active vitamin D metabolite calcitriol mediates its biological effects by binding to the vitamin D receptor (VDR), which is principally located in the nuclei of target cells. The binding of calcitriol to the VDR allows the VDR to act as a transcription factor that modulates the"
"Retinal Retinal is also known as retinaldehyde. It was originally called retinene, and renamed after it was discovered to be vitamin A aldehyde. Retinal is one of the many forms of vitamin A (the number of which varies from species to species). Retinal is a polyene chromophore, bound to proteins called opsins, and is the chemical basis of animal vision. Retinal allows certain microorganisms to convert light into metabolic energy. Vertebrate animals ingest retinal directly from meat, or they produce retinal from carotenoids, either from one of two carotenes (α-carotene, β-carotene) or from β-cryptoxanthin, a type of xanthophyll. These carotenoids"
"retinal, and retinoic acid. It is most well known for retinol’s imperative role in ensuring normal vision in mammals however retinoic acid is important in altering the expression of genes through nuclear receptors. The precursors for vitamin A are beta-carotenes which get converted to vitamin A, predominantly in the liver. Cats rely on preformed vitamin A in the diet as they are unable to carry out the conversion of beta-carotenes to vitamin A. Vitamin A recommendations are 6668 IU/kg for a feline in a growing or reproductive state and 3332 IU/kg for adult maintenance. A maximum vitamin A intake of"
"must be obtained from plants or other photosynthetic organisms. No other carotenoids can be converted by animals to retinal, and some carnivores cannot convert any carotenoids at all. The other main forms of vitamin A, retinol, and a partially active form, retinoic acid, may both be produced from retinal. Invertebrates such as insects and squid use hydroxylated forms of retinal in their visual systems, which derive from conversion from other xanthophylls. Living organisms produce retinal (RAL) by irreversible oxidative cleavage of carotenoids. For example, catalyzed by a beta-carotene 15,15'-monooxygenase or a beta-carotene 15,15'-dioxygenase. Just as carotenoids are the precursors of"
"other mammals. The carotenes α-carotene and γ-carotene, due to their single retinyl group (β-ionone ring), also have some vitamin A activity (though less than β-carotene), as does the xanthophyll carotenoid β-cryptoxanthin. All other carotenoids, including lycopene, have no beta-ring and thus no vitamin A activity (although they may have antioxidant activity and thus biological activity in other ways). Animal species differ greatly in their ability to convert retinyl (beta-ionone) containing carotenoids to retinals. Carnivores in general are poor converters of dietary ionone-containing carotenoids. Pure carnivores such as ferrets lack β-carotene 15,15'-monooxygenase and cannot convert any carotenoids to retinals at all"
"Retinoic acid Retinoic acid is a metabolite of vitamin A (retinol) that mediates the functions of vitamin A required for growth and development. Retinoic acid is required in chordate animals, which includes all higher animals from fish to humans. During early embryonic development, 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. The key role of retinoic acid in embryonic"
"Retinene The Retinenes (Retinene and Retinene) are chemical derivatives of the dietary supplement vitamin A (see retinol) formed through oxidation reactions. Retinene is better known as retinaldehyde or simply retinal and is fundamental in the transduction of light into visual signals in the photoreceptor level of the retina (known as the visual cycle). Retinene is more formally known as dehydroretinaldehyde. The energy of impinging photons will convert retinaldehyde from an 11-cis isomer into an all-trans form. In the retina, this conversion induces a conformational change in the surrounding opsin protein pigment, leading to signaling through the G protein transducin. Retinaldehyde"
"RBP1 Retinol binding protein 1, cellular, also known as RBP1, is a protein that in humans is encoded by the ""RBP1"" gene. RBP1 is the carrier protein involved in the transport of retinol (vitamin A alcohol) from the liver storage site to peripheral tissue. Vitamin A is a fat-soluble vitamin necessary for growth, reproduction, differentiation of epithelial tissues, and vision. The gene harbors four exons encoding 24, 59, 33, and 16 amino acid residues, respectively. The second intervening sequence alone occupies 19 kb of the 21 kb of the gene. Cellular retinol-binding protein-1 (CRBP-1) contributes to the maintenance of the"
"a requirement for local conversion of retinol to retinoic acid, as administered retinoic acid does not reach some critical tissues unless given in high amounts. Thus, if animals are fed only retinoic acid but no vitamin A (retinol or retinal), they suffer none of the growth-stunting or epithelial-damaging effects of lack of vitamin A (including no xerophthalmia—dryness of the cornea). They do suffer retina degeneration and blindness, due to retinal (retinaldehyde) deficiency. In addition, vitamin A-deprived but retinoic acid-supplemented male rats exhibit hypogonadism and infertility due to lack of local retinoic acid synthesis in the testis; similar treatment of female"
"enzyme. It's important for their skin for the same reason as Linoleic acid and can be found in ingredients such as animal fat. Vitamin A is a crucial nutritional component in the maintenance of feline skin and coat health. In addition to its many other functions, vitamin A plays an important role in the keratinization of the skin, hair and nails along with assisting in the development of various epithelial tissues throughout the body. The cells making up the epithelial tissues of the skin, respiratory and gastrointestinal tracts rely on vitamin A to successfully complete the process of mitosis in"
"cannot synthesize vitamin A from plant beta-carotene, and therefore must be supplemented with retinol from meat. A deficiency in vitamin A will result in a poor coat, with hair loss, with scaly and thickened skin. However an excess of vitamin A, called hypervitaminosis A, can result from over feeding cod liver oil, and large amounts of liver. Signs of hypervitaminosis A are overly sensitive skin, and neck pain causing the cat to be unwilling to groom its self, resulting in a poor coat. Supplementing vitamin A with retinol to a deficient cat, and feeding a balanced diet to a cat"
"Leafy greens are an excellent source of magnesium. Deficiency or excess intake of many vitamins can affect the brain contributing to developmental and degenerative diseases. Vitamin A is an essential nutrient for mammals which takes form in either retinol or the provitamin beta-Carotene. It helps regulation of cell division, cell function, genetic regulation, helps enhance the immune system, and is required for brain function, chemical balance, growth and development of the central nervous system and vision. In an experiment by Chongqing Medical University pregnant rats were either plentiful in vitamin A or were of a vitamin A deficiency (VAD) due"
"only for plant-eating mammals that possess the enzyme to make retinal from carotenoids that contain beta-ionone (some carnivores lack this enzyme). In species other than mammals, certain xanthophylls may be converted to hydroxylated retinal-analogues that function directly in vision. For example, with the exception of certain flies, most insects use the xanthophyll derived R-isomer of 3-hydroxyretinal for visual activities, which means that β-cryptoxanthin and other xanthophylls (such as lutein and zeaxanthin) may function as forms of visual ""vitamin A"" for them, while carotenes (such as beta carotene) do not. The xanthophyll cycle involves the enzymatic removal of epoxy groups from"
"in animals. Vitamin D is produced by ultraviolet irradiation of ergosterol found in many fungi. The vitamin D content in mushrooms and ""Cladina arbuscula"", a lichen, increase with exposure to ultraviolet light. This process is emulated by industrial ultraviolet lamps, concentrating vitamin D levels to higher levels. The United States Department of Agriculture reports D and D content combined in one value. Manufactured foods fortified with Vitamin D include some fruit juices and fruit juice drinks, meal replacement energy bars, soy protein-based beverages, certain cheese and cheese products, flour products, infant formulas, many breakfast cereals, and milk. In 2016 in"
"because its metabolite retinoic acid, plays an important role as a signal molecule in the development of several tisues and organs. Its natural precursor, β-carotene, is considered safe, whereas the consumption of animal liver can lead to malformation, as the liver stores lipophile vitamins, including retinol. Isotretinoin (13-cis-retinoic-acid; brand name Roaccutane), vitamine A analog, which is often used to treat severe acne, is such a strong teratogen that just a single dose taken by a pregnant woman (even transdermally) may result in serious birth defects. Because of this effect, most countries have systems in place to ensure that it is"
"also forms a part of bacteriorhodopsin, a light-induced proton pump found in some archaea. Experimentally, it is possible to replace 11-cis retinaldehyde by perfusing retinal tissue preparations with retinaldehyde derivatives. Selective modification of the retinaldehyde structure, particularly the density of electrons in the π-orbitals, can lead to insights into the interaction between the retinaldehyde moiety and the surrounding pigment protein. ""The names of all these molecules have recently been changed ... vitamin A is now retinol, retinene is retinal; there is also retinoic acid""—George Wald (1967). Retinene The Retinenes (Retinene and Retinene) are chemical derivatives of the dietary supplement vitamin"
"of vitamin D) to cholecalciferol (inactive form of vitamin D) following exposure to UV light from the sun. Cholecalciferol is then converted to calcidiol in the liver before further hydroxylated to calcitriol, the active form of vitamin D, in the kidney. However, the conversion of provitamin D to cholecalciferol is significantly lower in dogs than other mammals, and is not sufficient to maintain an adequate vitamin D status. Thus, dogs depend on dietary sources of vitamin D to meet their nutrient requirement. In the diet, there are two forms of vitamin D – cholecalciferol (vitamin D) from mainly animal sources,"
"Carotenoid oxygenase Carotenoid oxygenases are a family of enzymes involved in the cleavage of carotenoids to produce, for example, retinol, commonly known as vitamin A. This family includes an enzyme known as RPE65 which is abundantly expressed in the retinal pigment epithelium where it catalyzed the formation of 11-cis-retinol from all-trans-retinyl esters. Carotenoids such as beta-carotene, lycopene, lutein and beta-cryptoxanthine are produced in plants and certain bacteria, algae and fungi, where they function as accessory photosynthetic pigments and as scavengers of oxygen radicals for photoprotection. They are also essential dietary nutrients in animals. Carotenoid oxygenases cleave a variety of carotenoids"
"of Retinol, a dietary form of Vitamin A, and for their fins used to make shark fin soup. Some species of sharks also were valued for their hides from which a very tough and durable leather could be made. From 1947 through 1949 Springer worked for Shark Industries, Inc. as Asst. Production Manager. The company, bought out by the Borden Milk Co. in 1949, ceased operations shortly after as Vitamin A was first synthesized in 1947 while at the same time the most sought after shark species were being ""fished out"" in waters near the company's shark liver processing plant"
"light emitted by the moon during the night. It can be extrapolated that the high ratio of rods to cones present in modern human eyes was retained even after the shift from nocturnal back to diurnal. Vitamin A is necessary for proper functioning of the human eye. The photopigment rhodopsin found in human rod cells is composed of retinal, a form of vitamin A, bound to an opsin protein. Upon the absorption of light rhodopsin was decomposed into retinal and opsin through bleaching. Retinal could then have one of two fates: it could recombine with opsin to reform rhodopsin or"
"kidney and liver are contributors to the use of vitamin A in the body of the majority of species while the cats liver does not produce the enzyme Beta-carotene 15,15'-monooxygenase which converts the beta-carotene into retinol (vitamin A). To summarize: cats do not have high levels of this enzyme leading to the cleavage and oxidation of carotenoids not taking place. Vitamin D3 is a dietary requirement for cats as they lack the ability to synthesize vitamin D3 from sunlight. Cats obtain high levels of the enzyme 7-dehydrocholestrol delta 7 reductase which causes immediate conversion of vitamin D3 from sunlight to"
"from their diets. Carotenes contribute to photosynthesis by transmitting the light energy they absorb to chlorophyll. They also protect plant tissues by helping to absorb the energy from singlet oxygen, an excited form of the oxygen molecule O which is formed during photosynthesis. β-Carotene is composed of two retinyl groups, and is broken down in the mucosa of the human small intestine by β-carotene 15,15'-monooxygenase to retinal, a form of vitamin A. β-Carotene can be stored in the liver and body fat and converted to retinal as needed, thus making it a form of vitamin A for humans and some"
"an electron acceptor in photosystem I during photosynthesis. For this reason, vitamin K is found in large quantities in the photosynthetic tissues of plants (green leaves, and dark green leafy vegetables such as romaine lettuce, kale, and spinach), but it occurs in far smaller quantities in other plant tissues (roots, fruits, etc.). Iceberg lettuce contains relatively little. The function of phylloquinone in plants appears to have no resemblance to its later metabolic and biochemical function (as ""vitamin K"") in animals, where it performs a completely different biochemical reaction. Vitamin K (in animals) is involved in the carboxylation of certain glutamate"
"has been passed from unicellular to multicellular organisms including Homo sapiens. This vitamin was most likely selected by evolution for sensing light because retinal causes a shift in photoreceptor absorbance to the visible light range. This shift in absorbance is especially important for life on Earth because it generally matches the peak irradiance of sunlight on its surface. A second reason why retinal evolved to be vital for human vision is because it undergoes a large conformational change when exposed to light. This conformational change is believed to make it easier for the photoreceptor protein to distinguish between its silent"
"be obtained from the diet. The term is conditional both on the circumstances and on the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for anthropoid primates, humans, guinea pigs and bats, but not for other mammals. Vitamin D is not an essential nutrient for people who get sufficient exposure to ultraviolet light, either from the sun or an artificial source, as then they synthesize vitamin D in skin. Humans require thirteen vitamins in their diet, most of which are actually groups of related molecules, ""vitamers"", (e.g. vitamin E includes tocopherols and tocotrienols, vitamin K includes vitamin"
"human retina, its function is unknown. In the mouse, it photo-entrains the retina and cornea at least ex vivo. These pineal opsins, found in the Actinopterygii (ray-finned fish) apparently arose as a result of gene duplication from Rh1 (rhodopsin). These opsins appear to serve functions similar to those of pinopsin found in birds and reptiles. Opsin proteins covalently bind to a vitamin A-based retinaldehyde chromophore through a Schiff base linkage to a lysine residue in the seventh transmembrane alpha helix. In vertebrates, the chromophore is either 11-""cis""-retinal (A1) or 11-""cis""-3,4-didehydroretinal (A2) and is found in the retinal binding pocket of"
"week. Tanning beds emitting 2–6% UVB radiation have a similar effect, though tanning is inadvisable. Vitamin D comes in two forms. Cholecalciferol (vitamin D) is synthesized in the skin after exposure to the sun or consumed from food, usually from animal sources. Ergocalciferol (vitamin D) is derived from ergosterol from UV-exposed mushrooms or yeast and is suitable for vegans. When produced industrially as supplements, vitamin D is typically derived from lanolin in sheep's wool. However, both provitamins and vitamins D and D have been discovered in spp. (especially ) and these edible lichen are harvested in the wild for producing"
"calcification of arteries and other soft tissues. Chemically, the vitamin K family comprises 2-methyl-1,4-naphthoquinone (3-) derivatives. Vitamin K includes two natural vitamers: vitamin K and vitamin K. Vitamin K, in turn, consists of a number of related chemical subtypes, with differing lengths of carbon side chains made of isoprenoid groups of atoms. Vitamin K, also known as phylloquinone, is made by plants, and is found in highest amounts in green leafy vegetables because it is directly involved in photosynthesis. It may be thought of as the plant form of vitamin K. It is active as a vitamin in animals and"
"differentiative state of endometrial cells through the regulation of bioavailability of retinol. On the converse, loss of CRBP-1 is associated with development of endometrial cancer. RBP1 Retinol binding protein 1, cellular, also known as RBP1, is a protein that in humans is encoded by the ""RBP1"" gene. RBP1 is the carrier protein involved in the transport of retinol (vitamin A alcohol) from the liver storage site to peripheral tissue. Vitamin A is a fat-soluble vitamin necessary for growth, reproduction, differentiation of epithelial tissues, and vision. The gene harbors four exons encoding 24, 59, 33, and 16 amino acid residues, respectively."
"Rose hip seed oil Rose hip seed oil is a pressed seed oil, extracted from the seeds of the wild rose bush (""Rosa moschata"" or ""Rosa rubiginosa"") in the southern Andes. Rosehip seed oil can also be extracted from ""Rosa canina"", which grows in many regions of the world including South Africa and Europe. The oil contains provitamin A (mostly beta-Carotene). It has been wrongly said to contain retinol (vitamin A) which is a vitamin solely made by animals from provitamin A. It does however contain levels (up to .357 ml/L) of tretinoin or all-trans retinoic acid, a vitamin A"
"(resulting in carotenes not being a form of vitamin A for this species); while cats can convert a trace of β-carotene to retinol, although the amount is totally insufficient for meeting their daily retinol needs. Chemically, carotenes are polyunsaturated hydrocarbons containing 40 carbon atoms per molecule, variable numbers of hydrogen atoms, and no other elements. Some carotenes are terminated by hydrocarbon rings, on one or both ends of the molecule. All are coloured to the human eye, due to extensive systems of conjugated double bonds. Structurally carotenes are tetraterpenes, meaning that they are synthesized biochemically from four 10-carbon terpene units,"
"with hair loss. Other signs include corneal opacity, lenticular cataracts, hemorrhagic adrenals, fatty degeneration of the kidney and liver, and inflammation of the mucous membrane of the gastrointestinal tract. Post-mortem studies in rhesus monkeys fed a riboflavin-deficient diet revealed about one-third the normal amount of riboflavin was present in the liver, which is the main storage organ for riboflavin in mammals. Riboflavin deficiency in birds results in low egg hatch rates. As a chemical compound, riboflavin is a yellow-orange solid substance with poor solubility in water compared to other B vitamins. Visually, it imparts color to vitamin supplements (and bright"
"have been called retinylidene proteins. Opsins are prototypical G protein-coupled receptors (GPCRs). Bovine rhodopsin, the opsin of the rod cells of cattle, was the first GPCR to have its X-ray structure determined. Bovine rhodopsin contains 348 amino acid residues. The retinal chromophore binds at Lys. Although mammals use retinal exclusively as the opsin chromophore, other groups of animals additionally use four chromophores closely related to retinal. These are 3,4-didehydroretinal, (3""R"")-3-hydroxyretinal, (3""S"")-3-hydroxyretinal, and (4""R"")-4-hydroxyretinal. Many fish and amphibians use 3,4-didehydroretinal, also called dehydroretinal. With the exception of the dipteran suborder Cyclorrhapha, the so-called higher flies, all insects examined use the (""R"")-enantiomer"