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Abstract: Glycine is an amino acid neurotransmitter that is involved in both inhibitory and excitatory neurochemical transmission in the central nervous system. The role of glycine in excitatory neurotransmission is related to its coagonist action at glutamatergic N-methyl-d-aspartate receptors. The glycine levels in the synaptic cleft rise many times higher during synaptic activation assuring that glycine spills over into the extrasynaptic space. Another possible origin of extrasynaptic glycine is the efflux of glycine occurring from astrocytes associated with glutamatergic synapses. The release of glycine from neuronal or glial origins exhibits several differences compared to that of biogenic amines or other amino acid neurotransmitters. These differences appear in an external Ca2+- and temperature-dependent manner, conferring unique characteristics on glycine as a neurotransmitter. Glycine transporter type-1 at synapses may exhibit neural and glial forms and plays a role in controlling synaptic glycine levels and the spill over rate of glycine from the synaptic cleft into the extrasynaptic biophase. Non-synaptic glycine transporter type-1 regulates extrasynaptic glycine concentrations, either increasing or decreasing them depending on the reverse or normal mode operation of the carrier molecule. While we can, at best, only estimate synaptic glycine levels at rest and during synaptic activation, glycine concentrations are readily measurable via brain microdialysis technique applied in the extrasynaptic space. The non-synaptic N-methyl-d-aspartate receptor may obtain glycine for activation following its spill over from highly active synapses or from its release mediated by the reverse operation of non-synaptic glycine transporter-1. The sensitivity of non-synaptic N-methyl-d-aspartate receptors to glutamate and glycine is many times higher than that of synaptic N-methyl-d-aspartate receptors making the former type of receptor the primary target for drug action. Synaptic and non-synaptic N-methyl-d-aspartate receptors mediate different neural functions, many of which are not clearly defined at present. Non-synaptic glycine transporter-1 and its blockade by inhibitory drugs may be important in drug therapy interventions, such as for reducing negative symptoms of schizophrenia. [Copyright &y& Elsevier]

Abstract: Chicken posterior eyecup lined by the retina were prepared, loaded with [3H]glycine and superfused in order to determine its release in various experimental conditions. Electrical field stimulation of the retina evoked [3H]glycine release with a voltage- and frequency-dependent manner and this release may be originated from glycinergic amacrine cell processes of the inner plexiform layer of the retina. Glycine released from an abundance of different amacrine cells may modulate retinal circuitry by activation of inhibitory glycine receptors and by acting as a coagonist on N-methyl-d-aspartate receptors on AII amacrine cells and retinal ganglion cells. The latter effect of glycine may be modulated by glycine transporter type-1. Cells with glycine transporter type-1 immunopositive staining were visualized in the inner nuclear layer and dens immunolabeling was also detected throughout the inner plexiform layer of chicken retina. Glycine and the substrate-type glycine transporter type-1 inhibitor sarcosine increased [3H]glycine release from glycinergic amacrine cells and/or glial cells by extrusion of glycine from cytoplasmic pools by homo- and heteroexchange mechanisms. Deprivation of oxygen and glucose from the buffer used for superfusion evoked a marked increase in [3H]glycine efflux, an effect probably due to reverse mode operation of glycine transporter type-1. The non-transportable glycine transporter type-1 inhibitors NFPS and Org-24461, which did not alter [3H]glycine efflux from isolated chicken retina by themselves in normoxic condition, inhibited oxygen and glucose deprivation-induced [3H]glycine release. It is concluded that reduction of the N-methyl-d-aspartate receptor coagonist glycine concentrations in hypoxic conditions by glycine transporter type-1 inhibitors may decrease N-methyl-d-aspartate receptor-mediated neuronal toxicity and cell death in retinal tissue. [Copyright &y& Elsevier]

3,5-Diaryl-4,5-dihydroisoxazoles were synthesized and evaluated as monoamine oxidase (MAO) enzyme inhibitors and iron chelators. All compounds exhibited selective inhibitory activity towards the B isoform of MAO in the nanomolar concentration range. The best performing compound was preliminarily evaluated for its ability to bind iron II and III cations, indicating that neither iron II nor iron III is coordinated. The best compounds racemic mixtures were separated and single enantiomers inhibitory activity evaluated. Furthermore, none of the synthesised compounds exhibited activity towards MAO A. Overall, these data support our hypothesis that 3,5-diaryl-4,5-dihydroisoxazoles are promising scaffolds for the design of neuroprotective agents. [ABSTRACT FROM AUTHOR]

Cyclohexyliden- and 2-methylcyclohexyliden-hydrazo-4-arylthiazoles were synthesized and tested as antifungal agents. All compounds exhibited minimal inhibitory concentration (MIC) values comparable with those of fluconazole (FLC). Moreover, some compounds showed fungicidal activity at low concentration. Worth noting five out of nine compounds were active towardsCandida albicans25 FLC resistant isolated from clinical specimens. The cellular toxicity was evaluated and none of the compounds is toxic at the MIC. On the basis of our data we can conclude that these derivatives are promising agents for the treatment of resistantC. albicans. [ABSTRACT FROM PUBLISHER]

Completely different fluorescence behaviour of cavitands based on a same calix[4]resorcinarene compound was observed. While the fluorescence intensity of the parent compound, tetramethyl-cavitand ( 1) slowly faded as a result of UV-light exposure, the emission of the three-level cavitand with pyridazine moieties at the upper rim ( 5a) was enhanced by the excitation in the UV-region. The structure of fluorescence emission (characterized by excitation-emission matrices) and the absorption of 5a remained unaltered. The analysis of fluorescence decay curves reveals the presence of two separated components assigned to two individual emitting species. The measured significant increase of the average lifetime and quantum yield is the consequence of the UV-light induced transition between the different states of 5a. These observations can be explained by the structural difference between 5a and 1. As a counterpart of the naked cavitand ( 1) with methyl substituents at the upper rim only, 5a has three additional moieties benzene, triazole and pyridazine levels. Computational studies proved the existence of two conformational isomers of 5a. Upon ultraviolet light excitation a 'dark' to 'light' conformational transition occurs between the two isomers. This hypothesis was confirmed by anisotropy decay measurements. [ABSTRACT FROM AUTHOR]

Rat posterior eyecups containing the retina were prepared, loaded with [H]glycine and superfused in order to determine its release originated from glycinergic amacrine cells and/or glial cells. Deprivation of oxygen and glucose from the Krebs-bicarbonate buffer used for superfusion evoked a marked increase of [H]glycine release, an effect that was found to be external Ca-independent. Whereas oxygen and glucose deprivation increased [H]glycine release, its uptake was reduced suggesting that energy deficiency shifts glycine transporter type-1 operation from normal to reverse mode. The increased release of [H]glycine evoked by oxygen and glucose deprivation was suspended by addition of the non-competitive glycine transporter type-1 inhibitor NFPS and the competitive inhibitor ACPPB further suggesting the involvement of this transporter in the mediation of [H]glycine release. Oxygen and glucose deprivation also evoked [H]glutamate release from rat retina and the concomitantly occurring release of the NMDA receptor agonist glutamate and the coagonist glycine makes NMDA receptor pathological overstimulation possible in hypoxic conditions. [H]Glutamate release was suspended by addition of the excitatory amino acid transporter inhibitor TBOA. Sarcosine, a substrate inhibitor of glycine transporter type-1, also increased [H]glycine release probably by heteroexchange shifting transporter operation into reverse mode. This effect of sarcosine was also external Ca-independent and could be suspended by NFPS. Energy deficiency in retina induced by ouabain, an inhibitor of the Na-K-dependent ATPase, and by rotenone, a mitochondrial complex I inhibitor added with the glycolytic inhibitor 2-deoxy- d-glucose, led to increase of retinal [H]glycine efflux. These effects of ouabain and rotenone/2-deoxy- d-glucose could also be blocked by NFPS pointed to the preferential reverse mode operation of glycine transporter type-1 as a consequence of impaired cellular energy homeostasis. Immunohistochemical studies revealed that glycine transporter type-1, of which reverse mode operation assures [H]glycine release, is expressed in amacrine cells in the inner nuclear and plexiform layers of the retina and also in Müller macroglia cells. We conclude that disruption of the balanced normal/reverse mode operation of glycine transporter type-1 is likely a significant factor contributing to neurotoxic processes of the retina. The possibility to inhibit glycine transporter type-1 mediated glycine efflux by drugs more potently than glycine uptake might offer some therapeutic potential for the treatment of various neurodegenerative disorders of the retina. [ABSTRACT FROM AUTHOR]

Water-soluble isoindoloquinoxalin (IIQ) imines and the corresponding acetates were conveniently prepared from the key intermediates 2-(2′-aminophenyl)-2 H -isoindole-1-carbonitriles obtained by a Strecker reaction between substituted 1,2-dicarbaldehydes and 1,2-phenylenediamines. Both series were screened by the National Cancer Institute (Bethesda, MD) and showed potent antiproliferative activity against a panel of 60 human tumor cell lines. Several of the novel compounds showed GI 50 values at a nanomolar level on the majority of the tested cell lines. Among IIQ derivatives, methoxy substituents at positions 3 and 8 or/and 9 were especially effective in impairing cell cycle progression and inducing apoptosis in cancer cells. These effects were associated to IIQ-mediated impairment of tubulin polymerization at pharmacologically significant concentrations of tested compounds. In addition, impaired DNA topoisomerase I functions and perturbation in telomere architecture were observed in cells exposed to micromolar concentrations of IIQ derivatives. The above results suggest that IIQ derivatives exhibit multi-target cytotoxic activities. [ABSTRACT FROM AUTHOR]

The HIV-1 Reverse Transcriptase (RT) is a validated and deeply explored biological target for the treatment of AIDS. However, only drugs targeting the RT-associated DNA polymerase (DP) function have been approved for clinical use. We designed and synthesised a new generation of HIV-1 RT inhibitors, based on the (3Z)-3-(2-[4-(aryl)-1,3-thiazol-2-yl]hydrazin-1-ylidene)-2,3-dihydro- 1H -indol-2-one scaffold. These compounds are active towards both RT-associated functions, DNA polymerase and ribonuclease H. The structure, biological activity and mode of action of the new derivatives have been investigated. In particular, the nature of the aromatic group in the position 4 of the thiazole ring plays a key role in the modulation of the activity towards the two RT-associated functions. [ABSTRACT FROM AUTHOR]

Resveratrol is a polyphenol found in grapes and red wine, showing well-characterized anti-inflammatory and antiproliferative activities. In order to exceed resveratrol׳s biological effects and to reveal the structural determinants of the molecule׳s activity, numerous derivatives were synthesized recently. Most of these resveratrol analogs vary from the original molecule in the number, position or identity of the phenolic functional groups. Investigation of the analogs provided important data regarding structure–activity relationship of the molecule. With the exception of cis- and trans-resveratrol and the reduced form dihydroresveratrol, little is known about the molecular effects of the stilbene backbone. In the present study we investigated the anti-inflammatory properties of a new, triple-bond resveratrol analog, 3,4′,5-trihydroxy-diphenylacetylene (TDPA) on lipopolysaccharide-stimulated RAW macrophages. We found that the analog had weaker antioxidant activity and stronger inhibitory effect on nuclear factor-kappaB activation, and on cyclooxygenase-2, tumor necrosis factor α and interleukin-6 production. It also prevented lipopolysaccharide-induced depolarization of the mitochondrial membrane. In contrast to resveratrol, TDPA increased the phosphorylation of c-Jun N-terminal and p38 mitogen activated protein kinases. In summary, we identified a novel compound with better anti-inflammatory properties than resveratrol. Our results contributed to a better understanding of the structural determinants of resveratrol׳s biological activities. [ABSTRACT FROM AUTHOR]

Abstract: We used isolated chicken retina to induce spreading depression by the glutamate receptor agonist N-methyl-d-aspartate. The N-methyl-d-aspartate-induced latency time of spreading depression was extended by the glycineB binding site competitive antagonist 7-chlorokynurenic acid. Addition of the glycine transporter type-1 inhibitors NFPS and Org-24461 reversed the inhibitory effect of 7-chlorokynurenic acid on N-methyl-d-aspartate-evoked spreading depression. The glycine uptake inhibitory activity of Org-24461, NFPS, and some newly synthesized analogs of NFPS was determined in CHO cells stably expressing human glycine transporter type-1b isoform. Compounds, which failed to inhibit glycine transporter type-1, also did not have effect on retinal spreading depression. These experiments indicate that the spreading depression model in chicken retina is a useful in vitro test to determine activity of glycine transporter type-1 inhibitors. In addition, our data serve further evidence for the role of glycine transporter type-1 in retinal neurotransmission and light processing. [Copyright &y& Elsevier]

3-Acetyl-2,5-diaryl-2,3-dihydro-1,3,4-oxadiazoles were designed, synthesized, and tested as inhibitors against human monoamine oxidase (MAO) A and B isoforms. Several compounds, obtained as racemates, were identified as selective MAO-B inhibitors. The enantiomers of some derivatives were separated by enantioselective HPLC and tested. The R-enantiomers always showed the highest activity. Docking study and molecular dynamic simulations demonstrated the putative binding mode. We conclude that these 1,3,4-oxadiazoles derivatives are promising reversible and selective MAO-B inhibitors. [ABSTRACT FROM AUTHOR]

The most dominant hypotheses for the pathogenesis of schizophrenia have focused primarily upon hyperfunctional dopaminergic and hypofunctional glutamatergic neurotransmission in the central nervous system. The therapeutic efficacy of all atypical antipsychotics is explained in part by antagonism of the dopaminergic neurotransmission, mainly by blockade of D dopamine receptors. N-methyl- d-aspartate (NMDA) receptor hypofunction in schizophrenia can be reversed by glycine transporter type-1 (GlyT-1) inhibitors, which regulate glycine concentrations at the vicinity of NMDA receptors. Combined drug administration with D dopamine receptor blockade and activation of hypofunctional NMDA receptors may be needed for a more effective treatment of positive and negative symptoms and the accompanied cognitive deficit in schizophrenia. To investigate this type of combined drug administration, rats were treated with the atypical antipsychotic risperidone together with the GlyT-1 inhibitor Org-24461. Brain microdialysis was applied in the striatum of conscious rats and determinations of extracellular dopamine, DOPAC, HVA, glycine, glutamate, and serine concentrations were carried out using HPLC/electrochemistry. Risperidone increased extracellular concentrations of dopamine but failed to influence those of glycine or glutamate measured in microdialysis samples. Org-24461 injection reduced extracellular dopamine concentrations and elevated extracellular glycine levels but the concentrations of serine and glutamate were not changed. When risperidone and Org-24461 were added in combination, a decrease in extracellular dopamine concentrations was accompanied with sustained elevation of extracellular glycine levels. Interestingly, the extracellular concentrations of glutamate were also enhanced. Our data indicate that coadministration of an antipsychotic with a GlyT-1 inhibitor may normalize hypofunctional NMDA receptor-mediated glutamatergic neurotransmission with reduced dopaminergic side effects characteristic for antipsychotic medication. [ABSTRACT FROM AUTHOR]

Abstract: Single neuron firing rate was recorded from dorsal raphe nucleus of anesthetized rats. The firing rate of raphe neurons varied from 4 to 8 discharge per second before drug administration and this neuronal activity was decreased by L-701,324 (2mg/kg i.v. injection), a competitive antagonist of glycineB binding site of N-methyl-d-aspartate (NMDA) receptors. The glycine transporter type-1 (GlyT1) antagonists Org-24461 (10mg/kg i.v.) and NFPS (3mg/kg i.v.) reversed the inhibitory effect of L-701,324 on single neuron activity recorded from dorsal raphe nucleus of the rat. Org-24461 and NFPS both tended to increase the raphe neuronal firing rate also when given alone but their effect was not significant. This finding serves further evidence that glutamate released from axon terminals of the cortico-striatal projection neurons stimulates serotonergic neurons in the raphe nuclei and this effect is mediated at least in part by postsynaptic NMDA receptors. Thus, GlyT1 inhibitors are able to reverse the hypofunctional state of NMDA receptors, suggesting that these drugs may have beneficial therapeutic effects in neurological and psychiatric disorders characterized with impaired NMDA receptor-mediated transmission. [Copyright &y& Elsevier]

The in vitro and in vivo pharmacology of two glycine transporter-1 (GlyT1) inhibitors, N[3-(4′-fluorophenyl)-3-(4′-phenylphenoxy)-propyl]sarcosine (NFPS) and R,S-(+/−)N-methyl-N-[(4-trifluoromethyl)phenoxy]-3-phenyl-propylglycine (Org 24461), was studied. NFPS and Org 24461 inhibited the uptake of [3H]glycine in hippocampal synaptosomal preparation with IC50 values of 0.022 and 2.5 μM. Neither NFPS nor Org 24461 (0.1 μM) showed significant binding to α-1, α-2, and β-adrenoceptors, D1 and D2 dopamine receptors, and 5-HT1A and 5-HT2A serotonin receptors in membranes prepared from rat brain or to cloned 5-HT6 and 5-HT7 receptors. At 10 μM concentrations, binding affinity was measured for NFPS to 5-HT2A and 5-HT2C serotonin receptors and α-2 adrenoceptors and for NFPS and Org 24461 to 5-HT7 serotonin receptors. Glycine (0.1 mM) and sarcosine (5 mM) increased [3H]glycine efflux from superfused rat hippocampal slices preloaded with [3H]glycine. NFPS and Org 24461 (0.1 mM) did not influence [3H]glycine efflux, however, they inhibited glycine-induced [3H]glycine release. These findings indicate that NFPS and Org 24461 selectively inhibit glycine uptake without being substrates of the transporter protein. Several antipsychotic tests were used to characterize antipsychotic effects of NFPS and Org 24461 in vivo. These compounds did not alter apomorphine-induced climbing and stereotypy in a dose of 10 mg/kg po in mice and did not induce catalepsy in a dose of 10 mg/kg ip in rats. The ID50 values of NFPS were 21.4 mg/kg and higher than 30 mg/kg ip for inhibition of phencyclidine (PCP)- and d-amphetamine-induced hypermotility in mice and these values were 2.5 and 8.6 mg/kg ip for Org 24461. NFPS and Org 24461 did not exhibit anxiolytic effects in light–dark test in mice, in the meta-chlorophenylpiperazine (mCPP)-induced anxiety test (minimal effective dose or MED was higher than 3 mg/kg ip) and in the Vogel conflict drinking test in rats (MED was higher than 10 mg/kg ip). Both NFPS and Org 24461 (1–10 mg/kg ip) reversed PCP-induced changes in EEG power spectra in conscious rats. These data support the view that GlyT1 inhibitors may have potential importance in treatment of negative symptoms of schizophrenia. [Copyright &y& Elsevier]

The interrupted diazotization of 3-aminoindoles and 3-aminopyrroles, achieved by quenching with cold water immediately after addition of nitrite, leads to diazonium species with nitrate as counter ion. [ABSTRACT FROM AUTHOR]