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At least 343 records · Page 19Linked to original sources
PubMed1986

Effects of GABAergic drugs in vivo on high-affinity choline uptake in vitro in mouse hippocampal synaptosomes.

The effects of several gamma-aminobutyric acid (GABA)-ergic drugs on sodium-dependent high-affinity choline uptake (HACU) were investigated in the hippocampus. HACU was measured in vitro after in vivo administration of the drug to mice. HACU was inhibited by those drugs that enhance GABA transmission. The convulsant 3-mercaptopropionic acid, which decreases GABA levels, stimulated HACU. From these results and previous findings, it appears that GABA mediates a tonic inhibitory effect on the septal-hippocampal cholinergic system.

3-Mercaptopropionic Acid↗
PubMed1989

Mechanisms of action of new antiepileptic drugs.

Our understanding of how new antiepileptic drugs work mirrors what we know about how currently marketed antiepileptic compounds exert their action--that information is scarce and elusive. The mechanism of action of antiepileptic drugs is nevertheless inextricably linked to epileptogenesis itself, and investigations of several promising new compounds are underway to establish the levels at which these drugs act. Compounds act on synapses and membranes as well as affecting receptors, neurotransmitters, and peptides. The most extensive data are available on drugs that inhibit the action of GABA or its receptors, including new benzodiazepine-like agents and barbituric-acid derivatives. The few drugs that act by inhibiting the effects of excitatory amino acids are reviewed. Finally, the maximal electroshock test is an empirical method to determine the antiepileptic properties of a drug; several agents under development have been effective in this screening technique.

Acetamides↗
PubMed1993

Effects of various esters of trans-4-guanidinomethylcyclohexanecarboxylic acid, trypsin inhibitors, on the growth of Bacillus subtilis.

Various aromatic esters of trans-4-guanidinomethylcyclohexanecarboxylic acid (GMCHA), trypsin inhibitors, strongly inhibited the growth of Bacillus subtilis 558 and their effects were markedly affected by the species of substitution on the phenyl nucleus of the GMCHA phenyl esters. 4-tert-Butylphenyl ester of GMCHA (GMCHA-OPhtBu), a representative of various GMCHA esters, dose-dependently inhibited the growth of B. subtilis and DNA, RNA and protein syntheses in the cells. The growth inhibition was preceded by suppressive effect of GMCHA-OPhtBu on DNA synthesis. These results suggested the possible involvement of a trypsin-like proteinase in DNA synthesis. A trypsin-like proteinase was partially purified from B. subtilis 558 by DEAE-cellulose column chromatography, ammonium sulfate fractionation and successive chromatographies on Sephadex G-200, phenyl-Sepharose CL-4B, L-arginine-Sepharose 4B and Sephadex G-200 columns. The properties were compared with those of proteinase In, which momentarily appears just before the onset of DNA synthesis and seems to participate in the initiation of DNA replication, and which was purified from E. coli K-12 IAM 1264. The properties of the proteinase from B. subtilis 558 were similar to proteinase In, however, the molecular mass (110000) was different from that of the latter (66000). Various GMCHA esters strongly inhibited the proteinase activity and the order of the effects was closely correlated with that on the cell growth. The proteinase was tentatively called subtilis proteinase In.

Amino Acid Sequence↗
PubMed1981

Preferential stimulation by aurintricarboxylic acid of DNA-dependent RNA polymerase II activity in isolated larval nuclei of Artemia salina.

Aurintricarboxylic acid was found to stimulate preferentially RNA polymerase II activity in isolated nuclei of Artemia salina larvae. Studies on the in vitro transcription of a homologous chromatin indicate that this dye induces changes in the chromatin so as to enhance its template capacity for free RNA polymerase. Both free RNA polymerases I and II are equally sensitive to this dye in the absence of chromatin template. RNA polymerase II, however, becomes highly resistant to aurintricarboxylic acid when it is actively transcribing the chromatin template, whereas RNA polymerase I remains extremely sensitive even in the transcription complex. Therefore, in isolated nuclei, a preferential stimulation of alpha-amanitin-sensitive, but not-resistant RNA synthesis by aurintricarboxylic acid can be observed.

Animals↗
PubMed1986

Laser microprobe mass analysis (LAMMA) to verify the aluminon staining of bone.

Triammonium aurin tricarboxylate (aluminon) has been used to localize aluminum in 2 micron sections of undecalcified, methyl methacrylate embedded bone obtained from patients with terminal chronic renal failure. Aluminum appeared in four cases as bright red lines at the mineralized-bone boundary. In two cases, however, purplish lines were found and one patient showed red as well as purplish lines. Laser microprobe mass analysis (LAMMA) identified aluminum at the location of the red lines and both aluminum and iron at the purplish lines. Furthermore, both iron and aluminum were found in histiocytic bone marrow cells, which showed brownish aluminon staining. It appears that when aluminum and iron occur together, aluminon staining may yield aberrant results. This study shows that LAMMA can be used for the identification of elements sought by histochemical methods and thus permits the evaluation of their staining effects.

Aluminum↗
PubMed2001

Gamma-aminobutyric acid type B receptors with specific heterodimer composition and postsynaptic actions in hippocampal neurons are targets of anticonvulsant gabapentin action.

Gamma-aminobutyric acid (GABA) activates two qualitatively different inhibitory mechanisms through ionotropic GABA(A) multisubunit chloride channel receptors and metabotropic GABA(B) G protein-coupled receptors. Evidence suggests that pharmacologically distinct GABA(B) receptor subtypes mediate presynaptic inhibition of neurotransmitter release by reducing Ca2+ conductance, and postsynaptic inhibition of neuronal excitability by activating inwardly rectifying K+ (Kir) conductance. However, the cloning of GABA(B) gb1 and gb2 receptor genes and identification of the functional GABA(B) gb1-gb2 receptor heterodimer have so far failed to substantiate the existence of pharmacologically distinct receptor subtypes. The anticonvulsant, antihyperalgesic, and anxiolytic agent gabapentin (Neurontin) is a 3-alkylated GABA analog with an unknown mechanism of action. Here we report that gabapentin is an agonist at the GABA(B) gb1a-gb2 heterodimer coupled to Kir 3.1/3.2 inwardly rectifying K+ channels in Xenopus laevis oocytes. Gabapentin was practically inactive at the human gb1b-gb2 heterodimer, a novel human gb1c-gb2 heterodimer and did not block GABA agonism at these heterodimer subtypes. Gabapentin was not an agonist at recombinant GABA(A) receptors as well. In CA1 pyramidal neurons of rat hippocampal slices, gabapentin activated postsynaptic K+ currents, probably via the gb1a-gb2 heterodimer coupled to inward rectifiers, but did not presynaptically depress monosynaptic GABA(A) inhibitory postsynaptic currents. Gabapentin is the first GABA(B) receptor subtype-selective agonist identified providing proof of pharmacologically and physiologically distinct receptor subtypes. This selective agonism of postsynaptic GABA(B) receptor subtypes by gabapentin in hippocampal neurons may be its key therapeutic advantage as an anticonvulsant.

Acetates↗
PubMed2003

Gabapentin therapy for amyotrophic lateral sclerosis: lack of improvement in neuronal integrity shown by MR spectroscopy.

BACKGROUND AND PURPOSE: Proton MR spectroscopy has revealed impaired neuronal integrity in the motor cortex of patients with amyotrophic lateral sclerosis (ALS). We hypothesized that the N-acetylaspartate (NAA)-creatine (Cr) ratios in the motor cortex and adjacent brain could reflect the therapeutic effectiveness of gabapentin (GBP) treatment in ALS. METHODS: Eight patients with ALS underwent MR spectroscopy before and 26.5 days +/- 8.8 after starting GBP. In 10 patients with ALS who were not treated with GBP, paired spectra were obtained 21.4 days +/- 7.2 apart. Fourteen healthy subjects underwent a single MR spectroscopic examination. The NAA/Cr ratio was measured in the precentral gyrus, the postcentral gyrus, the superior parietal lobule, the supplementary motor area, and the premotor cortex. RESULTS: The NAA/Cr ratio was decreased in the precentral and postcentral gyri of patients with ALS compared with healthy controls. In those with ALS, the change in the NAA/Cr ratio was not different between treated patients and untreated patients in any of the regions studied. CONCLUSION: No improvement in neuronal integrity was detected in motor and nonmotor cerebral regions after GBP treatment. This result agrees with that of prior investigations showing the equivocal clinical effectiveness of GBP for ALS and supports the validity of the NAA/Cr ratio as a surrogate of therapeutic effectiveness.

Acetates↗
PubMed1989

[The use of "aluminal" stain in dermatology and venereology. I. Indication of protein fractions after disc electrophoresis].

A new method for staining the electrophoregrams is described. After disk electrophoresis the gels are treated in a solution with 0.01-0.02% of aluminol stain, 0.0027-0.0108% of iron chloride (III), and 7% of acetic acid. The method has been employed in examinations of solid basalioma soluble proteins; the transferrin zone fraction has been virtually undetectable on the electrophoregram of this basalioma.

Aurintricarboxylic Acid↗
PubMed1986

GABAergic regulation of enkephalin in rat striatum: alterations in Met5-enkephalin level, precursor content and preproenkephalin messenger RNA abundance.

The influence of chronic activation of gamma-aminobutyric acid (GABA) system on Met5-enkephalin (ME) biosynthesis was investigated in male rats. Activation of GABA system was achieved by raising the brain GABA concentration with aminooxyacetic acid (AOAA) or gabaculine which inhibits GABA-transaminase the enzyme responsible for the catabolism of GABA. After a regimen of repeated administration of AOAA (80 mg/kg/day for 8 days), the GABA concentration in the striatum could be maintained 2-fold greater than control value. AOAA decreased the ME levels in the striatum in a dose (20, 40 and 80 mg/kg)- and time (1-, 2-, 4- and 8-day treatment(s)-dependent fashion. Gabaculine also decreased the ME level in the striatum. Changes in ME level were not observed in other brain regions such as hypothalamus, hippocampus, frontal cortex and medulla/pons. In order to understand the mechanism involved in the decrease in ME level, the biosynthesis of ME was assessed. The preproenkephalin messenger RNA abundance was quantitated by RNA-complementary DNA hybridization technique; the total RNA was isolated, dot-blotted and hybridized with a nick-translated complementary DNA probe from rat brain. Administration of AOAA (80 mg/kg/day) for 8 days increased the preproenkephalin messenger RNA abundance whereas 1-, 2- or 4-day treatments did not alter the levels significantly. A similar trend of response was observed in the cryptic ME level which is indicative of the precursor content. The results suggest that chronic activation of the GABA system induces a sustained release of ME; in order to replenish the depletion, the biosynthesis of ME is augmented.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminooxyacetic Acid↗
PubMed1978

Effects of cicloxilic acid on secretory function of the liver. II. Effect on biliary secretion of bile acids, cholesterol and lecithin in anesthetised bileduct-cannulated rat.

cis-2-Hydroxy-2-phenyl-cyclohexanecarboxilic acid (cicloxilic acid) increases the output of bile acids and decreases that of cholesterol both in normal and in sodium taurocholate-infused rats; the biliary output of lecithin remains unchanged in normal animals but is increased in taurocholate-treated animals. The increased output of bile acids is interpreted as true stimulation of the bile-forming function of the liver, an activity supposedly mediated by stimulation of the metabolism of cholesterol to bile acids, independent of the drug's hydrocholeretic properties. The changes in the relative molar concentrations of the three micelle-forming bile constituents, namely bile acids, cholesterol, and lecithin, induced by cicloxilic acid lead to an appreciable lowering of the lithogenic index, thus suggesting that the drug may have antilithogenic activity.

Animals↗
PubMedDate not supplied

The preventative effect of the antifibrinolytic agents, epsilon-aminocaproic acid and tranexamic acid, on stress ulcer formation in rats.

The effect of the antifibrinolytic agents, epsilon-aminocaproic acid (EACA) and tranexamic acid (t-AMCHA), on acute gastric ulcers induced by cold restraint stress in rats was studied. Intravenous administration of 500 mg/Kg of EACA and t-AMCHA before exposure to stress significantly reduced the severity of gastric bleeding and ulcer formation (P less than 0.01). These agents did not affect gastric acid secretion in pylorus-ligated rats. The results indicate that antifibrinolytic agents may be beneficial in the prevention of stress ulcers in man and support the concept that local gastric fibrinolysis may play a role in the pathogenesis of stress ulcers.

Aminocaproates↗
PubMed1994

Emerging perspectives on the mechanism of action of gabapentin.

Significant advances have been made in understanding the molecular and cellular mechanisms underlying seizure disorders and the actions of antiepileptic drugs. Agents with new mechanisms of action or enhanced activity via known mechanisms might provide improved seizure control or more selective therapy for specific epilepsies. Gabapentin is a new antiepileptic drug that is structurally similar to the neurotransmitter GABA and the endogenous amino acid L-leucine. The mechanism of action of gabapentin is not fully understood, but its distinct profile of anticonvulsant activity in animal seizure models and its lack of activity at many drug binding sites associated with other antiepileptic drugs indicate that its mechanism of action is novel.

Acetates↗