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8-Oxo-2'-deoxyguanosine
8-Oxo-2'-deoxyguanosine (8-oxo-dG) is an oxidized derivative of deoxyguanosine. 8-Oxo-dG is one of the major products of DNA oxidation. Concentrations of 8-oxo-dG within a cell are a measurement of oxidative stress. In DNA Steady-state levels of DNA damages represent the balance between formation and repair. Swenberg et al. measured average frequencies of steady state endogenous DNA damages in mammalian cells. The most frequent oxidative DNA damage normally present in DNA is 8-oxo-dG, occurring at an average frequency of 2,400 per cell. When 8-oxo-dG is induced by a DNA damaging agent it is rapidly repaired. For example, 8-oxo-dG was increased 10-fold in the livers of mice subjected to ionizing radiation, but the excess 8-oxo-dG was rapidly removed with a half-life of 11 minutes. As reviewed by Valavanidis et al. increased levels of 8-oxo-dG in a tissue can serve as a biomarker of oxidative stress. They also noted that increased levels of 8-oxo-dG are frequently found d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Oxidation
DNA oxidation is the process of oxidative damage of deoxyribonucleic acid. As described in detail by Burrows et al., 8-oxo-2'-deoxyguanosine (8-oxo-dG) is the most common oxidative lesion observed in duplex DNA because guanine has a lower one-electron reduction potential than the other nucleosides in DNA. The one electron reduction potentials of the nucleosides (in volts versus NHE) are guanine 1.29, adenine 1.42, cytosine 1.6 and thymine 1.7. About 1 in 40,000 guanines in the genome are present as 8-oxo-dG under normal conditions. This means that >30,000 8-oxo-dGs may exist at any given time in the genome of a human cell. Another product of DNA oxidation is 8-oxo-dA. 8-oxo-dA occurs at about 1/10 the frequency of 8-oxo-dG. The reduction potential of guanine may be reduced by as much as 50%, depending on the particular neighboring nucleosides stacked next to it within DNA. Excess DNA oxidation is linked to certain diseases and cancers, while normal levels of oxidized nucleot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deoxycholic Acid
Deoxycholic acid is a bile acid. Deoxycholic acid is one of the secondary bile acids, which are metabolic byproducts of intestinal bacteria. The two primary bile acids secreted by the liver are cholic acid and chenodeoxycholic acid. Bacteria metabolize chenodeoxycholic acid into the secondary bile acid lithocholic acid, and they metabolize cholic acid into deoxycholic acid. There are additional secondary bile acids, such as ursodeoxycholic acid. Deoxycholic acid is soluble in alcohol and acetic acid. When pure, it comes in a white to off-white crystalline powder form. Deoxycholic acid is available as a generic medication in the United States as of April 2021, sold under the brand name Kybella among others. Applications Deoxycholic acid has been used since its discovery in various fields of human medicine. In the human body deoxycholic acid is used in the emulsification of fats for absorption in the intestine. It has, in some countries (including Switzerland) been licensed as an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Base Excision Repair
Base excision repair (BER) is a cellular mechanism, studied in the fields of biochemistry and genetics, that repairs damaged DNA throughout the cell cycle. It is responsible primarily for removing small, non-helix-distorting base lesions from the genome. The related nucleotide excision repair pathway repairs bulky helix-distorting lesions. BER is important for removing damaged bases that could otherwise cause mutations by mispairing or lead to breaks in DNA during replication. BER is initiated by DNA glycosylases, which recognize and remove specific damaged or inappropriate bases, forming AP sites. These are then cleaved by an AP endonuclease. The resulting single-strand break can then be processed by either short-patch (where a single nucleotide is replaced) or long-patch BER (where 2–10 new nucleotides are synthesized). Lesions processed by BER Single bases in DNA can be chemically damaged by a variety of mechanisms, the most common ones being deamination, oxidation, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Damage Theory Of Aging
The DNA damage theory of aging proposes that aging is a consequence of unrepaired accumulation of naturally occurring DNA damage. Damage in this context is a DNA alteration that has an abnormal structure. Although both mitochondrial and nuclear DNA damage can contribute to aging, nuclear DNA is the main subject of this analysis. Nuclear DNA damage can contribute to aging either indirectly (by increasing apoptosis or cellular senescence) or directly (by increasing cell dysfunction). Several review articles have shown that deficient DNA repair, allowing greater accumulation of DNA damage, causes premature aging; and that increased DNA repair facilitates greater longevity. Mouse models of nucleotide-excision–repair syndromes reveal a striking correlation between the degree to which specific DNA repair pathways are compromised and the severity of accelerated aging, strongly suggesting a causal relationship. Human population studies show that single-nucleotide polymorphisms in D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deoxyguanosine
Deoxyguanosine is composed of the purine nucleobase guanine linked by its N9 nitrogen to the C1 carbon of deoxyribose. It is similar to guanosine, but with one hydroxyl group removed from the 2' position of the ribose sugar (making it deoxyribose). If a phosphate group is attached at the 5' position, it becomes deoxyguanosine monophosphate. Deoxyguanosine is one of the four deoxyribonucleosides that make up DNA. See also * 8-Oxo-2'-deoxyguanosine 8-Oxo-2'-deoxyguanosine (8-oxo-dG) is an oxidized derivative of deoxyguanosine. 8-Oxo-dG is one of the major products of DNA oxidation. Concentrations of 8-oxo-dG within a cell are a measurement of oxidative stress. In DNA Steady-state leve ... References Nucleosides Purines Hydroxymethyl compounds {{Biochemistry-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Demethylation
For molecular biology in mammals, DNA demethylation causes replacement of 5-methylcytosine (5mC) in a DNA sequence by cytosine (C) (see figure of 5mC and C). DNA demethylation can occur by an active process at the site of a 5mC in a DNA sequence or, in replicating cells, by preventing addition of methyl groups to DNA so that the replicated DNA will largely have cytosine in the DNA sequence (5mC will be diluted out). Methylated cytosine is frequently present in the linear DNA sequence where a cytosine is followed by a guanine in a 5' → 3' direction (a CpG site). In mammals, DNA methyltransferases (which add methyl groups to DNA bases) exhibit a strong sequence preference for cytosines at CpG sites. There appear to be more than 20 million CpG dinucleotides in the human genome (see genomic distribution). In mammals, on average, 70% to 80% of CpG cytosines are methylated, though the level of methylation varies with different tissues. Methylated cytosines often occur in groups ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epigenetics In Learning And Memory
While the cellular and molecular mechanisms of learning and memory have long been a central focus of neuroscience, it is only in recent years that attention has turned to the epigenetic mechanisms behind the dynamic changes in gene transcription responsible for memory formation and maintenance. Epigenetic gene regulation often involves the physical marking (chemical modification) of DNA or associated proteins to cause or allow long-lasting changes in gene activity. Epigenetic mechanisms such as DNA methylation and histone modifications (methylation, acetylation, and deacetylation) have been shown to play an important role in learning and memory. DNA Methylation DNA methylation involves the addition of a methyl group to a 5' cytosine residue. This usually occurs at cytosines that form part of a cytosine-guanine dinucleotide (CpG sites). Methylation can lead to activation or repression of gene transcription and is mediated through the activity of DNA methyltransferases (DNMTs). DNM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, it would be impossible for language, relationships, or personal identity to develop. Memory loss is usually described as forgetfulness or amnesia. Memory is often understood as an informational processing system with explicit and implicit functioning that is made up of a sensory processor, short-term (or working) memory, and long-term memory. This can be related to the neuron. The sensory processor allows information from the outside world to be sensed in the form of chemical and physical stimuli and attended to various levels of focus and intent. Working memory serves as an encoding and retrieval processor. Information in the form of stimuli is encoded in accordance with explicit or implicit functions by the working memory processor. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CpG Site
The CpG sites or CG sites are regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5' → 3' direction. CpG sites occur with high frequency in genomic regions called CpG islands (or CG islands). Cytosines in CpG dinucleotides can be methylated to form 5-methylcytosines. Enzymes that add a methyl group are called DNA methyltransferases. In mammals, 70% to 80% of CpG cytosines are methylated. Methylating the cytosine within a gene can change its expression, a mechanism that is part of a larger field of science studying gene regulation that is called epigenetics. Methylated cytosines often mutate to thymines. In humans, about 70% of promoters located near the transcription start site of a gene (proximal promoters) contain a CpG island. CpG characteristics Definition ''CpG'' is shorthand for ''5'—C—phosphate—G—3' '', that is, cytosine and guanine separated by only one phosphate group; phosphate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transversion
Transversion, in molecular biology, refers to a point mutation in DNA in which a single (two ring) purine ( A or G) is changed for a (one ring) pyrimidine ( T or C), or vice versa. A transversion can be spontaneous, or it can be caused by ionizing radiation or alkylating agents. It can only be reversed by a spontaneous reversion. Ratio of transitions to transversions Although there are two possible transversions but only one possible transition per base, transition mutations are more likely than transversions because substituting a single ring structure for another single ring structure is more likely than substituting a double ring for a single ring. Also, transitions are less likely to result in amino acid substitutions (due to wobble base pair), and are therefore more likely to persist as "silent substitutions" in populations as single nucleotide polymorphisms (SNPs). A transversion usually has a more pronounced effect than a transition because the third nucleotide codo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synaptic Plasticity
In neuroscience, synaptic plasticity is the ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity. Since memories are postulated to be represented by vastly interconnected neural circuits in the brain, synaptic plasticity is one of the important neurochemical foundations of learning and memory (''see Hebbian theory''). Plastic change often results from the alteration of the number of neurotransmitter receptors located on a synapse. There are several underlying mechanisms that cooperate to achieve synaptic plasticity, including changes in the quantity of neurotransmitters released into a synapse and changes in how effectively cells respond to those neurotransmitters. Synaptic plasticity in both excitatory and inhibitory synapses has been found to be dependent upon postsynaptic calcium release. Historical discoveries In 1973, Terje Lømo and Tim Bliss first described the now widely studied phenomenon of long-term pote ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Repair
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in tens of thousands of individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur, including double-strand breaks and DNA crosslinkages (interstrand crosslinks or ICLs). This can eventually lead to malignant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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