Endogenous synthesis

Alcoholism leads to fat accumulation in the liver, hyperlipidemia, and ultimately cirrhosis. The exact mechanism of action of ethanol in the long term is stiU uncertain. Ethanol consumption over a long period leads to the accumulation of fatty acids in the liver that are derived from endogenous synthesis rather than from increased mobilization from adipose tissue. There is no impairment of hepatic synthesis of protein after ethanol ingestion. Oxidation of ethanol by alcohol dehydrogenase leads to excess production of NADH. 

Tocotrienols present in rice bran inhibit the liver microsomal enzyme HMGCoA reductase (Qureshi and Qureshi, 1992), the key enzyme involved in the endogenous synthesis of cholesterol, and this helps to lower the circulating cholesterol. Inhibition of another enzyme, ACAT (Acyl coenzyme A acyl transferase), by y-oryzanol results in lowered LDL-C synthesis and enrichment... 

The building block molecules may have been synthesized in the atmosphere, the hydrosphere or on the lithosphere of the young Earth from species such as CO, CO2, CH4, H2O, N2 and NH3 (endogenous synthesis). 

Miller S. L. (2000). The Endogenous Synthesis of Organic Compounds in The Molecular Origins of Life, Editor BrackA. CUP (2000). 

The GP made a provisional diagnosis of osteomalacia and prescribed vitamin D supplements. Vitamin D measurements are not performed routinely, but the assumption is that a low result would have been obtained on the blood sample. Most of the vitamin D necessary to maintain normal calcium homeostasis is derived from endogenous synthesis by reactions in the skin (which require UV radiation from sunlight), liver and kidney. The cultural habits of Mrs Al-Ameri required her to dress in a burqah and niqab whenever she left the home, meaning that very little of her skin was exposed to daylight. 

Dopamine-mimetics. Administration of the precursor L-dopa promotes endogenous synthesis of dopamine (indication parkinsonian syndrome,... 

Cholesterol can be derived from two sources—food or endogenous synthesis from ace-tyl-CoA. A substantial percentage of endogenous cholesterol synthesis takes place in the liver. Some cholesterol is required for the synthesis of bile acids (see p. 314). In addition, it serves as a building block for cell membranes (see p. 216), or can be esterified with fatty acids and stored in lipid droplets. The rest is released together into the blood in the form of lipoprotein complexes (VLDLs) and supplies other tissues. The liver also contributes to the cholesterol metabolism by taking up from the blood and breaking down lipoproteins that contain cholesterol and cholesterol esters (HDLs, IDLs, LDLs see p.278). 

The requirement for vitamins in humans and other animals is the result of mutations in the enzymes involved in biosynthetic coenzymes. As intermediates of coenzyme biosynthesis are available in suf cient amounts in the diet of heterotrophic animals (see p. 112), the lack of endogenous synthesis did not have unfavorable effects for them. Microorganisms and plants whose nutrition is mainly autotrophic have to produce all of these compounds themselves in order to survive. 

Most authors use a mixture of the same composition as the test mixture for the incubation control, except for omission of UDP-sugar. As outlined above, complete suppression of endogenous synthesis is preferred by the present authors for determination of enzyme activities. 

Admitting that endogenous synthesis in the control mixtures is negligible or can be adequately suppressed, the difference in response of test and control samples toward the final detection system (Section 4) should be such that it is exclusively due to the bile pigment conjugate synthesized in the test incubation mixture. The latter requirement depends, to some extent, on the final assay procedure adopted (Section 4). 

F]-FLT is not or only marginally incorporated into DNA (<2%) and therefore not a direct measure of proliferation [122]. In vitro studies indicated that [ F]-FLT uptake is closely related to thymidine kinase 1 (TK1) activity and respective protein levels [117,118]. p F]-FLT is therefore considered to reflect TK1 activity and hence, S-phase fraction rather than DNA synthesis. Although being a poor substrate for type 1 equilibrative nucleoside transporters (ENT), cellular uptake of [ F]-FLT is further facilitated by redistribution of nucleoside transporters to the cellular membrane after inhibition of endogenous synthesis of thymidylate (TMP) de novo synthesis of TMP) [125]. However, the detailed uptake mechanism of [ F]-FLT is yet unknown and the influence of membrane transporters and various nucleoside metabolizing enzymes remains to be determined. 

Compared with the surprising variety of biochemical compounds that can be readily synthesized in Miller-type one-pot simulation experiments, the suite of organics produced under the conditions proposed by Wachtershauser is quite limited. However, the impressive demonstration that the FeS/H2S combination can reduce nitrogen to ammonia shows that considerable attention should be given to the reducing power of pyrite formation. Primordial life may have not been autotrophic, but should we hesitate to accept the idea that the primitive soup was formed from both extraterrestrial sources and endogenous synthesis in which pyrite production played a role After all, a spicy, thick bouillon is always tastier than a bland, diluted broth. 

The endogenous synthesis of organic compounds. In The Molecular Origin of Life, ed. A. Brack. Cambridge University Press. 

Carnitine, L-3-hydroxy-4-(trimethylammonium)butyrate, is a water-soluble, tri-methylammonium derivative of y-amino-jS-hydroxybutyric acid, which is formed from trimethyllysine via y-butyrobetaine [40]. About 75% of carnitine is obtained from dietary intake of meat, fish, and dairy products containing proteins with trimethyllysine residues. Under normal conditions, endogenous synthesis from lysine and methionine plays a minor role, but can be stimulated by a diet low in carnitine. Carnitine is not further metabolized and is excreted in urine and bile as free carnitine or as conjugated carnitine esters [1, 41, 42]. Adequate intracellular levels of carnitine are therefore maintained by mechanisms that modulate dietary intake, endogenous synthesis, reabsorption, and cellular uptake. 

Numerous studies have pointed to an important role for cholesterol during proliferation and progression of cancer (e.g., ref. 612-615). Rapidly dividing cancer cells have two major routes to fulfill their need for cholesterol to form new cell membrane endogenous synthesis of cholesterol and/or receptor-mediated uptake of exogenous LDL particle-associated cholesterol and cholesterol esters (ref. 612,613,615). Each LDL particle contains a cholesterol ester core surrounded by a polar shell of phospholipids (primarily phosphoglycerides), free cholesterol, and apolipoprotein B (ref. 616-618). Once bound to its cell surface receptor, LDL is internalized by receptor-mediated endocytosis and degraded in lysosomes, and the subsequently released cholesterol may be used for membrane synthesis by the tumor (ref. 619). 

Very little is certain on organic matter formation in the atmosphere or in the ocean of the primitive Earth as a result of lightning, volcanism, or other energy sources. Since no preserved geological records exist from the concerned era, there is no certainty about the reactor conditions (physical parameters kind, concentration and/or fluxes of reagents). The endogenous synthesis of... 

Incorporation of bromodeoxyuridine is enhanced by incubating in the presence of fluorodeoxyuridine (to block endogenous synthesis of thymidine — 11.8.2) and access of the antibody to the fixed cells is ensured by partial denaturation or brief nuclease treatment (Goncharoff et al., 1986). After development of the peroxidase reaction cells can be counterstained, for example, with neutral red. 

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