Biological Methylation

Greenberg, David M.

doi:10.1002/9780470122709.ch8

Cited by 9 publications

(3 citation statements)

References 132 publications

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“…If both the methyl and the homocysteine moieties of methionine, rather than the homocysteine portion alone, are involved in methionine toxicity, glycine would appear to serve some function in relation to methyl me tabolism more effectively than serine. Studies of COi production from the methyl groups of methionine (37) and choline (36) which indicate that methionine methyl groups are converted to CO2 more rapidly than choline methyl groups, do not support the idea that the methyl group of methionine is metabolized via choline (38,39 (33), in which S-adenosylmethionine and glycine react to yield S-adenosylhomocysteine and sarcosine, with the latter being rapidly converted to COZ (40,41), should be examined in relation to the beneficial effect of glycine in methionine toxicity. The importance of the in creased cysteine and sulfur loads also remains to be investigated.…”

Section: Discussionmentioning

confidence: 99%

Glutamate Neurotransmission in the Cerebellar Interposed Nuclei: Involvement in Classically Conditioned Eyeblinks and Neuronal Activity

Aksenov

Serdyukova

Bloedel

et al. 2005

Journal of Neurophysiology

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The cerebellar interposed nuclei (IN) are critical components of a neural network that controls the expression of classically conditioned eyeblinks. The IN receive 2 major inputs: the massive, gamma-aminobutyric acid (GABA)-mediated input from the Purkinje cells of the cerebellar cortex and the relatively weaker, glutamate-mediated input from collaterals of mossy and climbing fiber cerebellar afferent systems. To elucidate the role of IN glutamate neurotransmission in conditioned response (CR) expression, effects of blocking fast glutamatergic neurotransmission in the IN with gamma-d-glutamylglycine (DGG) on the expression of conditioned eyeblinks and on cerebellar nuclear neuronal activity were examined. Surprisingly, blocking fast glutamate receptors in the IN did not abolish CRs. DGG decreased CR incidence and slightly increased CR latency. In contrast, identical amounts of DGG applied to the cerebellar cortex abolished CRs. Similar to the behavioral effects, DGG had unexpectedly mild effects on IN neurons. At the population level, the baseline firing frequency of IN cells was not affected. After DGG injections, the incidence of excitatory modulation of cell activity in the interstimulus interval decreased but was not abolished. A combined block of fast glutamate and GABA(A) neurotransmission using a mixture of DGG and picrotoxin dramatically reduced CR incidence, increased the firing frequency of all cell types, and virtually abolished all modulation of neuronal activity. These results indicate that fast glutamate neurotransmission in the IN plays only an accessory role both in the expression of behavioral CRs and in the generation of associated neuronal activity in the IN.

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Section: Discussionmentioning

confidence: 99%

Glutamate Neurotransmission in the Cerebellar Interposed Nuclei: Involvement in Classically Conditioned Eyeblinks and Neuronal Activity

Aksenov

Serdyukova

Bloedel

et al. 2005

Journal of Neurophysiology

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“…Moreover, individual AA can directly affect fat synthesis. The most studied AA is Met, which through the one carbon (C) cycle, transfers its methyl group to phosphatidylcholine [52]. Phosphatidylcholine is part of very low-density lipoproteins that transport long-chain fatty acids from the liver to the peripheral tissues in ruminants, including the mammary gland.…”

Section: Animal Performancementioning

confidence: 99%

Effects of Amount and Profile of Amino Acids Supply on Lactation Performance, Mammary Gland Metabolism, and Nitrogen Efficiency in Holstein Dairy Cows

Danes

Paula²,

Parys

et al. 2023

Animals

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To evaluate the effects of amount and profile of amino acid (AA) on milk protein yield (MPY), mammary metabolism, and efficiency of nitrogen use (ENU), ten cows were used in 5 × 5 replicated Latin squares and fed a positive control (16.1% crude protein-CP) or two lower CP diets (14.6 and 13.2%) with or without essential AA (EAA) infusion. The EAA solutions provided predicted limiting EAA in each treatment and were continuously infused into the abomasum of the cows. Milk production and MPY were not affected by treatment (mean 35.4 kg/d and 1.03 kg/d, respectively). Efficiency of nitrogen utilization was increased as dietary CP decreased but was not affected by EAA infusion (p < 0.01). Energy-corrected milk production was increased by EAA infusion into 13.2% CP, but not into 14.6% CP diet (p = 0.09), reaching the positive control value. Infusions increased mammary affinity for non-infused EAA (Ile, Phe, Thr, and Trp), allowing the same MPY despite lower arterial concentrations of these AA. Higher arterial concentrations of infused EAA did not increase their mammary uptake and MPY (p = 0.40; p = 0.85). Mammary metabolism did not fully explain changes in N efficiency, suggesting that it might be driven by less extramammary catabolism as AA supply was reduced.

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“…Ya en 1947 se hablaba de metilación, 20 pero sólo en 1963 Greenberg fue el primero en mencionar su trascendencia a varios niveles biológicos, 21 la HomCis fue detectada en sistemas biológicos hacia 1955 22 y Bartosinski B. en 1964 determinaba la biosíntesis del grupo metilo de la MET. 23 En 1951 en hígados de ratas se encontró la importancia de este órgano en el metabolismo de la Biología, patobiología y bioclínica de la homocisteína en la especie humana HomCis 24 y en 1952 comenzó a determinarse la existencia y biosíntesis de la MET en la bacteria E. coli.…”

Section: Historiaunclassified

Biología, patobiología y bioclínica de la homocisteína eh la especie humana

García¹

2010

Repert. Med. Cir.

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La homocistinuria fue descrita en 19a2 en niños con dificultades de aprendizaje y en 19a9 McCully informó la evidencia en autopsias de trombosis arterial eztensa y aterosclerosis en niños con elevadas concentraciones de homocisteína plasmática y homocistinuria. La homocisteína, un aminoácido de azufre, es un metabolito intermedio de la metionina, y sobre la base de estos hallazgos bioquímicos, ellos propusieron que la homocisteína plasmática elevada puede causar lesión neural y enfermedad vascular aterosclerótica. Hoy se considera un factor de riesgo independiente para esta última. La hiperhomocistinemia leve es bastante prevalente en la población general. Puede deberse a defectos genéticos en las enzimas que participan en el metabolismo de la homocisteína, carencias nutricionales de vitaminas y cofactores, ciertos medicamentos, ingesta rica en metionina o enfermedad renal. La alta concentración puede reducirse con folato, y es así que la suplementación vitamínica ha sido propuesta en individuos con hiperhomocistinemia con el fin de reducir su riesgo de enfermedad cardiovascular. En este artículo hacemos una revisión de la biología, la patobiología y la bioclínica del metabolismo de la homocisteína.

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Biological Methylation

Cited by 9 publications

References 132 publications

Glutamate Neurotransmission in the Cerebellar Interposed Nuclei: Involvement in Classically Conditioned Eyeblinks and Neuronal Activity

Glutamate Neurotransmission in the Cerebellar Interposed Nuclei: Involvement in Classically Conditioned Eyeblinks and Neuronal Activity

Effects of Amount and Profile of Amino Acids Supply on Lactation Performance, Mammary Gland Metabolism, and Nitrogen Efficiency in Holstein Dairy Cows

Biología, patobiología y bioclínica de la homocisteína eh la especie humana

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