Inhibitory effects of excitatory amino acids on pyramidal cells of the in vitro turtle medial cortex

1992 ◽  
Vol 92 (1) ◽  
Author(s):  
Ra�lE. Russo ◽  
JulioC. Velluti
Keyword(s):  
Amino Acids ◽  
Excitatory Amino Acids ◽  
Pyramidal Cells ◽  
Inhibitory Effects ◽  
Medial Cortex

scholarly journals Fusion of the N-terminal 119 amino acids with the RelA-CTD renders its growth inhibitory effects (p)ppGpp-dependent

2021 ◽  
Author(s):  
Jayashree Pohnerkar ◽  
Krishma Tailor ◽  
Prarthi Sagar ◽  
Keyur Dave
Keyword(s):  
Amino Acids ◽  
Feedback Regulation ◽  
Inhibitory Effects ◽  
E Coli ◽  
Growth Inhibitory ◽  
In The Wild ◽  
Regulatory Aspect ◽  
And Function

The guanosine nucleotide derivatives ppGpp and pppGpp are central to the remarkable capacity of bacteria to adapt to fluctuating environment and metabolic perturbations. These alarmones are synthesized by two proteins, RelA and SpoT in E. coli and the activities of each of the two enzymes are highly regulated for homeostatic control of (p)ppGpp levels in the cell. Although the domain structure and function of RelA are well defined, the findings of this study unfold the regulatory aspect of RelA that is possibly relevant in vivo. We uncover here the importance of the N-terminal 1-119 amino acids of the enzymatically compromised (p)ppGpp hydrolytic domain (HD) of monofunctional RelA for the (p)ppGpp mediated regulation of RelA-CTD function. We find that even moderate level expression of RelA appreciably reduces growth when the basal levels of (p)ppGpp in the cells are higher than in the wild type, an effect independent of its ability to synthesize (p)ppGpp. This is evidenced by the growth inhibitory effects of oversynthesis of the RelA-CTD in the relA+ strain but not in relA null mutant, suggesting the requirement of the functional RelA protein for basal level synthesis of (p)ppGpp, accordingly corroborated by the restoration of the growth inhibitory effects of the RelA-CTD expression in the relA1 spoT202 mutant. The N-terminal 119 amino acids of RelA fused in-frame with the RelA-CTD, both from 406-744 amino acids (including TGS) and from 454-744 amino acids (sans TGS) caused growth inhibition only in spoT1 and spoT202 relA1 mutants, uncovering the hitherto unrealized (p)ppGpp-dependent regulation of RelA-CTD function. An incremental rise in the (p)ppGpp levels is proposed to progressively modulate the interaction of RelA-CTD with the ribosomes, with possible implications in the feedback regulation of the N-terminal (p)ppGpp synthesis function, a proposal that best explains the nonlinear relationship between (p)ppGpp synthesis and increased ratio of RelA:ribosomes, both in vitro as well as in vivo.

Excitatory amino acids: new tools for old stories or Pharmacological subtypes of glutamate receptors: electrophysiological studies

1991 ◽  
Vol 69 (7) ◽  
pp. 1123-1128 ◽  
Author(s):  
David Lodge ◽  
Martyn G. Jones ◽  
Andrew J. Palmer
Keyword(s):  
Amino Acids ◽  
Glutamate Receptors ◽  
Binding Sites ◽  
Excitatory Amino Acids ◽  
Channel Blocking ◽  
Electrophysiological Studies ◽  
Spinal Neurones ◽  
Potent Antagonist

Although the N-methyl-D-aspartate (NMDA) subtype of L-glutamate receptor is well characterized, the significance of non-NMDA glutamate-sensitive binding sites is not well documented. In this study, a new tricyclic quinoxalinedione (NBQX) and an arthropod toxin (philanthotoxin) were shown to block responses of spinal neurones in vivo to kainate, quisqualate, and AMPA in parallel but had little effect on responses to NMDA. Philanthotoxin appeared to be a use-dependent antagonist consistent with a channel-blocking mode of action. On cortical wedges in vitro, however, NBQX proved to be a more potent antagonist of AMPA and quisqualate than of kainate (pA2 values of 7.1, 7.0, and 5.6, respectively) with no effect at 10 μM on responses to NMDA. These studies provide evidence that on cortical neurones, but not on spinal neurones, AMPA and kainate depolarize by pharmacologically different mechanisms.Key words: glutamate receptors, quinoxalinediones, philanthotoxin, AMPA, kainate.

Release of excitatory amino acids “In vitro” by free radicals

1988 ◽  
Vol 20 ◽  
pp. 295
Author(s):  
D.E. Pellegrini-Giampietro ◽  
G. Cherici ◽  
V. Carlà ◽  
F. Moroni
Keyword(s):  
Amino Acids ◽  
Free Radicals ◽  
Excitatory Amino Acids

Effect of Excitatory Amino Acids on Rat Hypothalamic Somatostatin Secretion In Vitro

Peptides ◽  
1997 ◽  
Vol 18 (7) ◽  
pp. 1039-1043 ◽  
Author(s):  
Pierre Joanny ◽  
Jean Steinberg ◽  
Charles Oliver ◽  
Michel Grino
Keyword(s):  
Amino Acids ◽  
Excitatory Amino Acids ◽  
Somatostatin Secretion

scholarly journals The sites of hydrolysis of dipeptides containing leucine and glycine by rat jejunum in vitro

1969 ◽  
Vol 114 (4) ◽  
pp. 855-861 ◽  
Author(s):  
E. B. Fern ◽  
R. C. Hider ◽  
D. R. London
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
The Other ◽  
Peptidase Activity ◽  
Rat Jejunum ◽  
Effective Inhibitor ◽  
Inhibitory Effects ◽  
Molar Basis ◽  
Hydrolysis Of

1. The effect of peptides containing leucine and glycine on accumulation of leucine and glycine by everted jejunal rings was studied. 2. It was shown that, on a molar basis, leucyl-leucine is a more effective inhibitor of uptake of [14C]leucine than is either leucylglycine or glycyl-leucine. These latter dipeptides behave alike. 3. The concentration of the dipeptides and their constituent amino acids in both the incubation medium and the tissue has been followed in these experiments by amino acid analysis. No leucine-containing peptides were observed in the tissue. 4. The inhibitory effects of the mixed dipeptides are altered by pH changes in an analogous way to the alterations in peptidase activity. 5. The experimental results indicate that leucine-containing peptides are hydrolysed before the transport step. 6. Glycylglycine, on the other hand, has only a small effect on the accumulation of glycine, although large amounts of the peptide accumulate unchanged in the tissue. This suggests that glycylglycine is taken up by a different mechanism to that for the leucine dipeptides.

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