The hydrolytic deamination of cytosine and 5-methylcytosine residues in DNA appears to contribute significantly to the appearance of spontaneous mutations in microorganisms and in human disease. In the present work, we examined the mechanism of cytosine deamination and the response of the uncatalyzed reaction to changing temperature. The positively charged 1,3-dimethylcytosinium ion was hydrolyzed at a rate similar to the rate of acid-catalyzed hydrolysis of 1-methylcytosine, for which it furnishes a satisfactory kinetic model and a probable mechanism. In agreement with earlier reports, uncatalyzed deamination was found to proceed at very similar rates for cytosine, 1-methylcytosine, cytidine, and cytidine 5′-phosphate, and also for cytosine residues in single-stranded DNA generated from a phagemid, in which we sequenced an insert representing the gene of the HIV-1 protease. Arrhenius plots for the uncatalyzed deamination of cytosine were linear over the temperature range from 90°C to 200°C and indicated a heat of activation (ΔH ‡ ) of 23.4 ± 0.5 kcal/mol at pH 7. Recent evidence indicates that the surface of the earth has been cool enough to support life for more than 4 billion years and that life has been present for almost as long. If the temperature at Earth's surface is assumed to have followed Newton's law of cooling, declining exponentially from 100°C to 25°C during that period, then half of the cytosine-deaminating events per unit biomass would have taken place during the first 0.2 billion years, and <99.4% would have occurred during the first 2 billion years. spontaneous mutation | heat mutagenesis | cytosine deamination | HIV-1 protease I n the absence of enzymes, most biological reactions take place so slowly that they can be followed conveniently only at elevated temperatures (1). Among those reactions are several that may result in spontaneous mutation, notably the hydrolytic deamination of cytosine and 5-methylcytosine, which generate uracil and thymine, respectively. These deamination reactions have been shown to account for many of the single-site mutations that lead to inherited diseases in humans (2) and for the marked bias of spontaneous mutation toward increased AT content in microorganisms (3, 4). Rates of mutation have long been known to increase with increasing temperature, a phenomenon that Drake has termed "heat mutagenesis" (5).There is widespread (6-8), if not universal (9), agreement that life originated when the earth was warmer-perhaps much warmer-than it is today. A recent isotopic analysis of carbon inclusions in zircons from the Jack Hills in Western Australia indicates that life may have emerged as early as 4.1 billion years ago (10), shortly after water first appeared at the surface in liquid form (11). Several present-day organisms thrive at temperatures near the boiling point of water. Thus, Ignisphera aggregans (12) and Pyrococcus horikoshii (13) exhibit optimal growth temperature of 92°and 98°C, respectively, whereas another organism isolated from a hydrothermal vent has be...

Growing evidence indicates that drugs of abuse gain control over the individual by usurping glutamate-linked mechanisms of neuroplasticity in reward-related brain regions. Accordingly, we have shown that glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) activity in the amygdala is required for the positive reinforcing effects of alcohol, which underlie the initial stages of addiction. It is unknown, however, if enhanced AMPAR activity in the amygdala facilitates alcohol self-administration, which is a kernel premise of glutamate hypotheses of addiction. Here we show that low-dose alcohol (0.6 g/kg/30-min) self-administration increases phosphorylation (activation) of AMPAR subtype GluA1 S831 (pGluA1 S831) in the central amygdala (CeA), basolateral amygdala, and nucleus accumbens core (AcbC) of selectively bred alcohol-preferring P-rats as compared to behavior-matched (non-drug) sucrose controls. The functional role of enhanced AMPAR activity was assessed via site-specific infusion of the AMPAR positive modulator, aniracetam, in the CeA and AcbC prior to alcohol self-administration. Intra-CeA aniracetam increased alcohol- but not sucrose-reinforced responding, and was ineffective following intra-AcbC infusion. Since GluA1 S831 is a Ca2+/calmodulin-dependent protein kinase II (CaMKII) substrate, we sought to determine if AMPAR regulation of enhanced alcohol self-administration is dependent on CaMKII activity. Intra-CeA infusion of the cell-permeable CaMKII peptide inhibitor m-AIP dose-dependently reduced alcohol self-administration. A sub-threshold dose of m-AIP also blocked the aniracetam-induced escalation of alcohol self-administration, demonstrating that AMPAR-mediated potentiation of alcohol reinforcement requires CaMKII activity in the amygdala. Enhanced activity of plasticity-linked AMPAR-CaMKII signaling in the amygdala may promote escalated alcohol use via increased positive reinforcement during the initial stages of addiction.

When compared to patients with typically progressive ALS, patients with reversals differed in their demographics, disease characteristics, and treatments. While some of these patients may have had a rare antibody-mediated ALS mimicker, such as atypical myasthenia gravis, details of their exams, EMGs and family histories argue that this was unlikely. Instead, our data suggest that ALS reversals warrant evaluation for mechanisms of disease resistance and that treatments associated with multiple ALS reversals deserve further study.

No abstract

ALSUntangled reviews alternative and off-label treatments for people with ALS. Here we review light therapy. We show that it has theoretically plausible mechanisms, three flawed pre-clinical data, studies, and one incompletely documented case report supporting its use. We explain why further studies are needed to determine whether any specific light therapy protocol can help people with ALS.