RESUMEN

OBJECTIVES: The use of thio-urethane oligomers has been shown to significantly improve the mechanical properties of resin cements (RCs). The aim of this study was to use thio-urethane-modified RC to potentially reinforce the porcelain-RC structure and to improve the bond strength to zirconia and lithium disilicate. METHODS: Six oligomers were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP, P) or trimethylol-tris-3-mercaptopropionate (TMP, T) - with di-functional isocyanates - 1,6-Hexanediol-diissocyante (HDDI) (aliphatic, AL) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic, AR) or Dicyclohexylmethane 4,4'-Diisocyanate (HMDI) (cyclic, CC). Thio-urethanes (20 wt%) were added to a BisGMA/UDMA/TEGDMA organic matrix. Filler was introduced at 60 wt%. The microshear bond strength (µSBS), Weibull modulus (m), and failure pattern of RCs bonded to zirconia (ZR) and lithium disilicate (LD) ceramics was evaluated. Biaxial flexural test and fractographic analysis of porcelain discs bonded to RCs were also performed. The biaxial flexural strength (σbf) and m were calculated in the tensile surfaces of porcelain and RC structures (Z = 0 and Z = -t2, respectively). RESULTS: The µSBS was improved with RCs formulated with oligomers P_AL or T_AL bonded to LD and P_AL, P_AR or T_CC bonded to zirconia in comparison to controls. Mixed failures predominated in all groups. σbf had superior values at Z = 0 with RCs formulated with oligomers P_AL, P_AR, T_AL, or T_CC in comparison to control; σbf increased with all RCs composed by thio-urethanes at Z = -t2. Fractographic analysis revealed all fracture origins at Z = 0. CONCLUSION: The use of specific thio-urethane oligomers as components of RCs increased both the biaxial flexural strength of the porcelain-RC structure and the µSBS to LD and ZR. CLINICAL SIGNIFICANCE: The current investigation suggests that it is possible to reinforce the porcelain-RC pair and obtain higher bond strength to LD and ZR with RCs formulated with selected types of thio-urethane oligomers.

Asunto(s)

Cerámica/química , Porcelana Dental/química , Cementos de Resina/química , Resistencia a la Tracción , Uretano/química , Circonio/química , Ácido 3-Mercaptopropiónico/análogos & derivados , Bisfenol A Glicidil Metacrilato , Recubrimiento Dental Adhesivo , Materiales Dentales , Módulo de Elasticidad , Glicoles , Ensayo de Materiales , Fenómenos Mecánicos , Metacrilatos/química , Polietilenglicoles , Polimerizacion , Ácidos Polimetacrílicos , Glicoles de Propileno , Estrés Mecánico , Propiedades de Superficie

RESUMEN

Flavonoids are polyphenols that help the maintenance of health, aiding the prevention of diseases. In this work, CdTe QDs coated with 3-mercaptopropionic acid (3MPA), with an average size of 2.7nm, were used as photoluminescence probe for flavonoids in different conditions. The interaction between 14 flavonoids and QDs was evaluated in aqueous dispersions in the absence and in the presence of cetyltrimethylammonium bromide (CTAB). To establish a relationship between photoluminescence quenching and the concentration of flavonoids, the Stern-Volmer model was used. In the absence of CTAB, the linear ranges for quercetin, morin and rutin were from 5.0×10-6molL-1 to 6.0×10-5molL-1 and from 1.0×10-5molL-1 to 6.0×10-4molL-1 for kaempferol. The sensibility of the Stern-Volmer curves (Ks) indicated that quercetin interacts more strongly with the probe: Ks quercetin>Ks kaempferol>Ks rutin>Ks morin. The conjugation extension in the 3 rings, and the acidic hydroxyl groups (positions 3'and 4') in the B-ring enhanced the interaction with 3MPA-CdTe QDs. The other flavonoids do not interact with the probe at 10-5molL-1 level. In CTAB organized dispersions, Ks 3-hydroxyflavone>Ks 7-hydroxyflavone>Ks flavona>Ks rutin in the range from 1.0×10-6molL-1 to 1.2×10-5molL-1 for flavones and of 1.0×10-6molL-1 to 1.0×10-5molL-1 for rutin. Dynamic light scattering, conductometric measurements and microenvironment polarity studies were employed to elucidate the QDs-flavonoids interaction in systems containing CTAB. The quenching can be attributed to the preferential solubility of hydrophobic flavonoid in the palisade layer of the CTAB aggregates adsorbed on the surface of the 3MPA CdTe QDs.

Asunto(s)

Ácido 3-Mercaptopropiónico/química , Compuestos de Cadmio/química , Compuestos de Cetrimonio/química , Flavonoides/química , Puntos Cuánticos/química , Telurio/química , Agua/química , Cetrimonio , Luminiscencia , Micelas , Tamaño de la Partícula , Pirenos/química , Soluciones , Tensoactivos/química

RESUMEN

OBJECTIVE: To evaluate the ability of thio-urethane oligomers to improve the properties of restorative composite resins. METHODS: Oligomers were synthesized by combining 1,6-hexanediol-diissocyante (aliphatic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 0-20 wt% to BisGMA-TEGDMA (70-30 wt%). Silanated inorganic fillers were added (70 wt%). Materials were photoactivated at 800 mW/cm(2) filtered to 320-500 nm. Near-IR was used to follow degree of methacrylate conversion (DC). Mechanical properties were evaluated in three-point bending with 2 mm × 2 mm × 25 mm bars for flexural strength/modulus and toughness (FS/E, and T) according to ISO 4049, and 2 mm × 5 mm × 25 mm notched specimens for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Results were analyzed with ANOVA/Tukey's test (α=5%). RESULTS: Significant increase in DC was observed in thio-urethane-containing materials especially for the group with 20 wt% of aliphatic version. Materials composed by oligomers also promoted higher FS, E, and KIC in comparison to controls irrespective of thio-urethane type. A significant increase in toughness was detected by ANOVA, but not distinguished in the groups. The PS was significantly reduced by the presence of thio-urethane for almost all groups. CONCLUSIONS: The use of thio-urethane oligomer to compose methacrylate-based restorative composite promote increase in DC, FS, E and KIC while significant reduces PS. SIGNIFICANCE: A simple additive was shown to reduce stress while increasing convrersion and mechanical properties, mainly fracture toughness. This has he potential of increasing the service life of dental composites, without changing current operatory procedures.

Asunto(s)

Resinas Compuestas/síntesis química , Uretano/química , Ácido 3-Mercaptopropiónico/análogos & derivados , Ácido 3-Mercaptopropiónico/química , Compuestos de Anilina/química , Bisfenol A Glicidil Metacrilato/química , Hidroxitolueno Butilado/química , Módulo de Elasticidad , Isocianatos/química , Ensayo de Materiales , Metacrilatos/química , Polietilenglicoles/química , Polimerizacion , Ácidos Polimetacrílicos/química , Glicoles de Propileno/química , Silanos/química , Estrés Mecánico

RESUMEN

Thio-urethanes were synthesized by combining 1,6-hexanediol-diissocyante (aliphatic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 10-30 phr to BisGMA-UDMA-TEGDMA (5:3:2, BUT). 25 wt% silanated inorganic fillers were added. Commercial cement (Relyx Veneer, 3M-ESPE) was also evaluated with 10-20 phr of aromatic oligomer. Near-IR was used to follow methacrylate conversion (DC) and rate of polymerization (Rpmax). Mechanical properties were evaluated in three-point bending (ISO 4049) for flexural strength/modulus (FS/FM, and toughness), and notched specimens (ASTM Standard E399-90) for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Volumetric shrinkage (VS, %) was measured with the bonded disk technique. Results were analyzed with ANOVA/Tukey's test (α=5%). In general terms, for BUT cements, conversion and mechanical properties in flexure increased for selected groups with the addition of thio-urethane oligomers. The aromatic versions resulted in greater FS/FM than aliphatic. Fracture toughness increased by two-fold in the experimental groups (from 1.17 ± 0.36 MPam(1/2) to around 3.23 ± 0.22 MPam(1/2)). Rpmax decreased with the addition of thio-urethanes, though the vitrification point was not statistically different from the control. VS and PS decreased with both oligomers. For the commercial cement, 20 phr of oligomer increased DC, vitrification, reduced Rpmax and also significantly increased KIC, and reduced PS and FM. Thio-urethane oligomers were shown to favorably modify conventional dimethacrylate networks. Significant reductions in polymerization stress were achieved at the same time conversion and fracture toughness increased.

Asunto(s)

Curación por Luz de Adhesivos Dentales , Cementos de Resina/química , Uretano/química , Ácido 3-Mercaptopropiónico/análogos & derivados , Ácido 3-Mercaptopropiónico/química , Bisfenol A Glicidil Metacrilato/química , Módulo de Elasticidad , Glicoles/química , Isocianatos/química , Ensayo de Materiales , Metacrilatos/química , Polietilenglicoles/química , Polimerizacion , Ácidos Polimetacrílicos/química , Poliuretanos/química , Glicoles de Propileno/química , Cementos de Resina/síntesis química , Espectroscopía Infrarroja Corta , Propiedades de Superficie , Resistencia a la Tracción

RESUMEN

A new chemiluminescence (CL) flow method for persulfate determination was developed based on luminol oxidation by in-line generated radicals. Reactive oxygen species (ROS) generated by CdTe quantum dots (QDs) under a low energetic radiation (visible light emitted by LEDs) promoted the decomposition of persulfate ion (S2O8(2-)) into sulfate radical (SO4(∙-)), leading to subsequent radical chain reactions that yield the emission of light. Due to the inherent radical short lifetimes and the transient behavior of CL phenomena an automated multi-pumping flow system (MPFS) was proposed to improve sample manipulation and reaction zone implementation ensuring reproducible analysis time and high sampling rate. The developed approach allowed up to 60 determinations per hour and determine S2O8(2-) concentrations between 0.1 and 1 mmol with good linearity (R=0.9999). The method has shown good repeatability with relative standard deviations below 2.5% (n=3) for different persulfate concentrations (0.1 and 0.625 mmol L(-1)). Limits of detection (3σ) and quantification (10σ) were 2.7 and 9.1 µmol L(-1), respectively. The MPFS system was applied to persulfate determination in bench scale UV/S2O8(2-) drug degradation processes of model samples showing good versatility and providing real time information on the persulfate consumption in photo-chemical degradation methodologies.

Asunto(s)

Ácido 3-Mercaptopropiónico/efectos de la radiación , Compuestos de Cadmio/efectos de la radiación , Luminol/química , Compuestos de Potasio/efectos de la radiación , Puntos Cuánticos/efectos de la radiación , Especies Reactivas de Oxígeno/química , Sulfatos/efectos de la radiación , Telurio/efectos de la radiación , Ácido 3-Mercaptopropiónico/química , Compuestos de Cadmio/química , Luz , Nanopartículas/química , Oxidación-Reducción , Compuestos de Potasio/química , Puntos Cuánticos/química , Sulfatos/química , Telurio/química

RESUMEN

This study aims at modifying dual-cure composite cements by adding thio-urethane oligomers to improve mechanical properties, especially fracture toughness, and reduce polymerization stress. Thiol-functionalized oligomers were synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene with trimethylol-tris-3-mercaptopropionate, at 1:2 isocyanate:thiol. Oligomer was added at 0, 10 or 20 wt% to BisGMA-UDMA-TEGDMA (5:3:2, with 25 wt% silanated inorganic fillers) or to one commercial composite cement (Relyx Ultimate, 3M Espe). Near-IR was used to measure methacrylate conversion after photoactivation (700 mW/cm(2) × 60s) and after 72 h. Flexural strength and modulus, toughness, and fracture toughness were evaluated in three-point bending. Polymerization stress was measured with the Bioman. The microtensile bond strength of an indirect composite and a glass ceramic to dentin was also evaluated. Results were analyzed with analysis of variance and Tukey's test (α = 0.05). For BisGMA-UDMA-TEGDMA cements, conversion values were not affected by the addition of thio-urethanes. Flexural strength/modulus increased significantly for both oligomer concentrations, with a 3-fold increase in toughness at 20 wt%. Fracture toughness increased over 2-fold for the thio-urethane modified groups. Contraction stress was reduced by 40% to 50% with the addition of thio-urethanes. The addition of thio-urethane to the commercial cement led to similar flexural strength, toughness, and conversion at 72h compared to the control. Flexural modulus decreased for the 20 wt% group, due to the dilution of the overall filler volume, which also led to decreased stress. However, fracture toughness increased by up to 50%. The microtensile bond strength increased for the experimental composite cement with 20 wt% thio-urethane bonding for both an indirect composite and a glass ceramic. Novel dual-cured composite cements containing thio-urethanes showed increased toughness, fracture toughness and bond strength to dentin while demonstrating reduced contraction stress. All of these benefits are derived without compromising the methacrylate conversion of the resin component. The modification does not require changing the operatory technique.

Asunto(s)

Resinas Compuestas/química , Cementos de Resina/química , Compuestos de Azufre/química , Uretano/química , Ácido 3-Mercaptopropiónico/química , Peróxido de Benzoílo/química , Bisfenol A Glicidil Metacrilato/química , Cerámica/química , Recubrimiento Dental Adhesivo , Dentina/ultraestructura , Módulo de Elasticidad , Humanos , Isocianatos/química , Curación por Luz de Adhesivos Dentales/métodos , Ensayo de Materiales , Metacrilatos/química , Docilidad , Polietilenglicoles/química , Polimerizacion , Ácidos Polimetacrílicos/química , Poliuretanos/química , Auto-Curación de Resinas Dentales/métodos , Silanos/química , Estrés Mecánico , Propiedades de Superficie , Resistencia a la Tracción , para-Aminobenzoatos/química

RESUMEN

The N-methyl-D-aspartate receptor (NMDAR) is involved in synaptic plasticity, learning, memory, and neurological diseases like epilepsy and it is the major mediator of excitotoxicity. Functional NMDARs in the mature brain are heteromeric complexes composed of different subunits: GluN1 and GluN2. There are four different GluN2 subunits (A-D) and each of them critically determines the pharmacological and electrophysiological properties of NMDARs. GluN1 is ubiquitously expressed in the central nervous system while the highest GluN2A expression is in the hippocampus. Adenosine, an endogenous anticonvulsant, is a neuromodulator with a critical role in the regulation of neuronal activity, mediating its effect on specific receptors, among which adenosine A1 receptor is highly expressed in the hippocampus. In the present work hippocampal GluN2A expression after the convulsant drug 3-mercaptopropionic acid (MP) induced seizures and the effect of cyclopentyladenosine (CPA) given alone or prior to MP (CPA + MP) in an acute or repetitive experimental model was studied. CPA administered to rats for one or 4 days increases seizure threshold induced by MP. After one administration of MP, no significant difference in GluN2A expression was observed in CPA and CPA + MP by Western blot, although immunohistochemistry revealed an increase in CA2/3 area. However, repetitive MP administration during 4 days showed a significant increase of GluN2A expression, and the repetitive administration of CPA 30 min prior to MP caused a significant decrease of GluN2A expression with respect to MP treatment, returning to control levels. These results show that GluN2A subunit is involved in repetitive MP-induced seizures, while CPA administration displays a protective effect against it.

Asunto(s)

Adenosina/análogos & derivados , Hipocampo/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Receptores de N-Metil-D-Aspartato/metabolismo , Convulsiones/tratamiento farmacológico , Convulsiones/metabolismo , Ácido 3-Mercaptopropiónico , Adenosina/administración & dosificación , Adenosina/farmacología , Adenosina/uso terapéutico , Animales , Hipocampo/efectos de los fármacos , Hipocampo/patología , Immunoblotting , Inmunohistoquímica , Masculino , Fármacos Neuroprotectores/farmacología , Propidio/metabolismo , Ratas , Ratas Wistar

RESUMEN

3MPA-CdTe QDs in aqueous dispersion was used as a fluorescent probe for the determination of lapachol, a natural naphthoquinone found in plants of the Bignoniaceae family genus Tabebuia. Working QDs dispersions (4.5×10(-8) mol L(-1) of QDs) was prepared in aqueous media containing Tris-HCl buffer pH 7.4 and methanol (10% in volume). The excitation was made at 380 nm with signal measurement at 540 nm. To establish a relationship between fluorescence (corrected to inner filter effect) and concentration of lapachol, a Stern-Volmer model was used. The linear range obtained was from 1.0×10(-5) to 1.0×10(-4) mol L(-1). The limit of detection (x(b)-3s(b)) was 8.0×10(-6) mol L(-1). The 3MPA-CdTe QDs probe was tested in the determination of lapachol in urine, previously cleansed in an acrylic polymer. The average recovery was satisfactory.

Asunto(s)

Ácido 3-Mercaptopropiónico/química , Compuestos de Cadmio/química , Colorantes Fluorescentes/química , Naftoquinonas/química , Puntos Cuánticos , Telurio/química , Absorción , Humanos , Naftoquinonas/análisis , Naftoquinonas/orina , Espectrometría de Fluorescencia

RESUMEN

INTRODUCTION: Metallo-ß-lactamase (MBL) has been reported all over the world. METHODS: The inhibitory effect of mercaptopropionic acid (MPA) on bacterial growth was evaluated by comparison between disk diffusion and broth dilution methodology with determination of the minimum inhibitory concentration (MIC) for multidrug-resistant Acinetobacter baumanni strains. RESULTS: MPA significantly inhibited growth of the strains. CONCLUSIONS: The use of MPA can affect the results in phenotypic methods of MBL detection.

Asunto(s)

Ácido 3-Mercaptopropiónico/farmacología , Acinetobacter baumannii/efectos de los fármacos , Farmacorresistencia Bacteriana Múltiple , Inhibidores Enzimáticos/farmacología , beta-Lactamasas/efectos de los fármacos , Acinetobacter baumannii/enzimología , Acinetobacter baumannii/crecimiento & desarrollo , Pruebas de Sensibilidad Microbiana/métodos , beta-Lactamasas/biosíntesis

RESUMEN

Inhibitory mechanism of cerebellum epileptic activity can be involved depending on the intensity and frequency of seizure convulsions. N-methyl-D-aspartate receptors (NMDARs) play key roles in excitatory synaptic transmission and have been implicated in neurological disorders: in cerebellum, they have specific characteristics. NMDARs are heteromeric complexes, and the expression of functional receptors in mammalian cells requires the subunit NR1 (essential) and one NR2 subtype of the four isoforms: NR2A-NR2D. In mature Purkinje cells, the combination of NR1 with NR2B subunits forms functional NMDARs; NR2B subunit may be altered in exocitotoxic events. Cyclopentyladenosine (CPA), an adenosine analogue, administered to rats, for one or more days, increases seizure threshold induced by the convulsant drug 3-mercaptopropionic acid (MP). In this study, we focused on the expression of NR2B in cerebellum after repetitive seizures induced by MP and the effect of adenosine analogue CPA administered alone or previous to MP (CPA + MP). A significant decrease in NR2B in the whole cerebellum was observed after MP and CPA administration with a tendency to recover to normal values in the combined treatment of CPA administered 30 min before MP by Western blot assay. In immunohistochemical studies, NR2B expression was observed and analysed in Purkinje cells. NR2B expression was decreased after MP (55%) and CPA (12%) administration, and CPA injected 30 min before MP led to 28% reduction in Purkinje cells. These results could be related to Purkinje cell damage or alternatively to avoid the excitotoxic effect. Results recorded after CPA + MP treatment seemed involved in decreasing the convulsant MP effect.

Asunto(s)

Ácido 3-Mercaptopropiónico/farmacología , Adenosina/análogos & derivados , Convulsivantes/farmacología , Células de Purkinje/efectos de los fármacos , Células de Purkinje/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Convulsiones/inducido químicamente , Animales , Masculino , Ratones , Células de Purkinje/citología , Ratas , Ratas Wistar , Convulsiones/metabolismo

RESUMEN

Previous evidence has shown that chronic 3-mercaptopropionic acid (MP) administration induced brain P-glycoprotein (P-gp) overexpression altering target site accumulation of phenytoin. The aim of the present work was to assess the involvement of P-glycoprotein in carbamazepine and phenobarbital hippocampal pharmacokinetics in an experimental model of epilepsy, induced by repetitive MP administration. Seizures were induced in Wistar rats by injection of MP (45 mg kg(-1), i.p.) during 10 days. Control rats (C) were injected with saline solution. In order to monitor extracellular brain antiepileptic levels, a concentric probe was inserted into the hippocampus. Animals were administered with carbamazepine (10 mg kg(-1), i.v.) or phenobarbital (20 mg kg(-1), i.v.) 30 min after intraperitoneal administration of vehicle or nimodipine (2 mg kg(-1)), a well known P-glycoprotein inhibitor. No differences were found in hippocampal concentrations of carbamazepine comparing all groups. In vehicle pre-treated rats, hippocampal phenobarbital concentrations were lower in MP (maximal concentration, C(max): 6.0+/-0.6 microg ml(-1), p<0.05) than in C animals (C(max): 9.4+/-0.9 microg ml(-1)). Control rats pre-treated with nimodipine showed similar results (C(max): 10.7+/-0.6 microg ml(-1)) than those pre-treated with vehicle. Nimodipine pre-treatment in MP rats enhanced hippocampal phenobarbital concentrations (C(max): 10.2+/-1.0 microg ml(-1), p<0.05) as compared with vehicle pre-treatment. Results of our work suggest that P-glycoprotein (P-gp) overexpression by repetitive seizures induced by MP administration does not modify brain bioavailability of carbamazepine. Conversely, hippocampal levels of phenobarbital are reduced in MP rats with regard to non-epileptic rats, suggesting a potential role of P-gp overexpression in pharmacoresistance to phenobarbital.

Asunto(s)

Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Anticonvulsivantes/farmacocinética , Carbamazepina/farmacocinética , Hipocampo/metabolismo , Fenobarbital/farmacocinética , Convulsiones/tratamiento farmacológico , Ácido 3-Mercaptopropiónico , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/antagonistas & inhibidores , Análisis de Varianza , Animales , Modelos Animales de Enfermedad , Epilepsia/inducido químicamente , Epilepsia/tratamiento farmacológico , Hipocampo/efectos de los fármacos , Masculino , Microdiálisis , Nimodipina/farmacología , Ratas , Ratas Wistar , Convulsiones/inducido químicamente , Tiempo

RESUMEN

NMDA receptor is involved in synaptic plasticity, learning, memory and neurological diseases like epilepsia and it is the major mediator of excitotoxicity. NR2B-containing NMDA receptors may be playing a crucial role in epileptic disorders. In the present study the effect of the convulsant drug 3-mercaptopropionic acid (MP) repetitive administration (4-7 days) on the hippocampal NR2B subunit was studied. A significant decrease in NR2B in the whole hippocampus was observed after MP4 with a tendency to recover to normal values in MP7 by western blot assay. Immunohistochemical studies showed a decrease in several CA1 and CA2/3 strata (21-73%). MP7 showed a reversion of the drop observed at 4 days in stratum oriens, pyramidal cell layer in CA1, CA2/3 and CA1 stratum radiatum. A significant fall in the lacunosum molecular layer of both areas and stratum radiatum of CA2/3 was observed. The immunostaining in MP4 showed a decrease in the granulare layer from dentate gyrus (20%), in hillus (71%) and subicullum (63%) as compared with control and these decreases were similar at MP7 values. Results showed decreases in NR2B subunit expression in different areas following repeated MP-induce seizures, suggesting that NR2B expression is altered depending on the diverse hippocampal input and output signals of each region that could be differently involved in modulating MP-induced hyperactivity.

Asunto(s)

Hipocampo/metabolismo , Receptores de N-Metil-D-Aspartato/biosíntesis , Convulsiones/metabolismo , Ácido 3-Mercaptopropiónico , Animales , Convulsivantes , Inmunohistoquímica , Masculino , Subunidades de Proteína/biosíntesis , Ratas , Ratas Wistar , Convulsiones/inducido químicamente

RESUMEN

Angiotensin-converting enzyme (kininase II [ACE]) inhibitors are capable of potentiating bradykinin (BK) effects by enhancing the actions of bradykinin on B(2) receptors independent of blocking its inactivation. To investigate further the importance of ACE kininase activity on BK-induced vasodilation, we investigated the effect of inhibiting ACE, as well as other kininases, on both BK metabolism and vasodilator effect in preparations that exhibit increased ACE activity. Mesenteric arterial beds obtained from 1-kidney, 1-clip hypertensive rats presented augmented ACE and angiotensin I converting activities compared with normotensive rats. The isolated and perfused mesenteric beds were exposed to BK for 15 minutes in the absence or in the presence of kininase inhibitors; then, the perfusate was collected for analysis of the products of BK metabolism by high-performance liquid chromatography. BK was metabolized to the fragments BK(1-8), BK(1-7), and BK(1-5), and the recovery of intact BK was reduced by 47% in the hypertensive group. Recovery of BK was increased in both groups in the presence of a kininase I inhibitor and in the hypertensive group by neutral endopeptidase 24.11 inhibitor; however, ACE inhibition did not affect BK metabolism in both groups. In contrast, only the ACE inhibitor potentiated the vasodilator effect of BK in a mesenteric bed preconstricted with phenylephrine; the increase in BK effect, nevertheless, was not greater in arteries from hypertensive rats that presented an increased ACE activity when compared with those in the normotensive group. These data demonstrated that ACE inhibitor-induced potentiation of BK vasodilator effects is not related to their actions on BK degradation.

Asunto(s)

Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Bradiquinina/farmacología , Hipertensión/fisiopatología , Arterias Mesentéricas/enzimología , Peptidil-Dipeptidasa A/metabolismo , Vasodilatadores/farmacología , Ácido 3-Mercaptopropiónico/análogos & derivados , Ácido 3-Mercaptopropiónico/farmacología , Animales , Presión Sanguínea , Bradiquinina/metabolismo , Sinergismo Farmacológico , Inhibidores Enzimáticos/farmacología , Glicopéptidos/farmacología , Hipertensión/enzimología , Técnicas In Vitro , Lisina Carboxipeptidasa/antagonistas & inhibidores , Masculino , Arterias Mesentéricas/efectos de los fármacos , Arterias Mesentéricas/fisiopatología , Metaloendopeptidasas/antagonistas & inhibidores , Neprilisina/antagonistas & inhibidores , Fragmentos de Péptidos/metabolismo , Inhibidores de Proteasas/farmacología , Ratas , Ratas Wistar , Vasodilatación/efectos de los fármacos , Vasodilatadores/metabolismo

RESUMEN

Metabotropic glutamate receptors (mGluR) play a role in synaptic transmission, neuronal modulation and plasticity but their action in epileptic activity is still controversial. On the other hand adenosine acts as a neuromodulator with endogenous anticonvulsive properties. Since cerebellum from epileptic patients has shown neuronal damage, sometimes associated with Purkinje cells loss, we have explored the effect of repetitive seizures on two types of mGluR in the cerebellum. Seizures were induced by the convulsant drug 3-mercaptopropionic acid (MP) and the effect of the adenosine analogue cyclopentyladenosine (CPA) alone or before MP administration (CPA+MP) were also evaluated. The expression of the receptors subtypes 2/3 (mGluR2/3) and 4a (mGluR4a) was assessed by immunocitochemistry. Granular cell layer was labeled with mGluR2/3 antibody and increased immunoreactivity was observed after MP (60%), CPA (53%) and CPA + MP (85%) treatments. Control cerebellum slices showed mGluR4a reactivity around Purkinje cells, while MP, CPA and CPA+MP treatment decreased this immunostaining. Repetitive administration of MP and CPA induces an increased cerebellar mGluR2/3 and a decreased mGluR4a immunostaining, suggesting a distinct participation of both receptors that may be related to the type of cell involved. A protective action and /or an apoptotic effect may not be discarded. CPA repetitive administration although increase seizure latency, cannot prevent seizure activity.

Asunto(s)

Ácido 3-Mercaptopropiónico/metabolismo , Adenosina , Cerebelo/metabolismo , Convulsivantes/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Ácido 3-Mercaptopropiónico/administración & dosificación , Adenosina/administración & dosificación , Adenosina/análogos & derivados , Adenosina/metabolismo , Animales , Cerebelo/citología , Convulsivantes/administración & dosificación , Humanos , Inmunohistoquímica , Masculino , Ratas , Ratas Wistar , Receptores de Glutamato Metabotrópico/genética

RESUMEN

The present work was undertaken to examine the central pharmacokinetics of phenytoin (PHT) in an experimental model of epilepsy, induced by administration of 3-mercaptopropionic acid (MP), and possible participation of P-glycoprotein in this model of epilepsy. Repeated seizures were induced in male Wistar rats by injection of 3-MP (45 mg kg(-1), i.p.) during 10 days. Control rats (C) were injected with saline solution. In order to monitor extracellular PHT levels, either a shunt microdialysis probe or a concentric probe was inserted into carotid artery or hippocampus, respectively. All animals were administered with PHT (30 mg kg(-1), i.v.) 30 min after intraperitoneal administration of vehicle (V) or nimodipine (NIMO, 2 mg kg(-1)). No differences were found in PHT plasma levels comparing all experimental groups. In pre-treated rats with V, hippocampal PHT concentrations were lower in MP (maximal concentration, C(max): 2.7+/-0.3 microg ml(-1), p<0.05 versus C rats) than in C animals (C(max): 5.3+/-0.9 microg ml(-1)). Control rats pre-treated with NIMO showed similar results (C(max): 4.5+/-0.8 microg ml(-1)) than those pre-treated with V. NIMO pre-treatment of MP rats showed higher PHT concentrations (C(max): 6.8+/-1.0 microg ml(-1), p<0.05) when compared with V pre-treated MP group. Our results indicate that central pharmacokinetics of PHT is altered in MP epileptic rats. The effect of NIMO on hippocampal concentrations of PHT suggests that P-glycoprotein has a role in reduced central bioavailability of PHT in our epileptic refractory model.

Asunto(s)

Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/efectos de los fármacos , Resistencia a Medicamentos/efectos de los fármacos , Epilepsia/tratamiento farmacológico , Hipocampo/efectos de los fármacos , Nimodipina/farmacología , Fenitoína/agonistas , Ácido 3-Mercaptopropiónico , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Animales , Anticonvulsivantes/agonistas , Anticonvulsivantes/farmacocinética , Bloqueadores de los Canales de Calcio/farmacología , Bloqueadores de los Canales de Calcio/uso terapéutico , Convulsivantes , Modelos Animales de Enfermedad , Resistencia a Medicamentos/fisiología , Epilepsia/inducido químicamente , Epilepsia/metabolismo , Líquido Extracelular/efectos de los fármacos , Líquido Extracelular/metabolismo , Hipocampo/metabolismo , Hipocampo/fisiopatología , Masculino , Microdiálisis , Nimodipina/uso terapéutico , Fenitoína/farmacocinética , Ratas , Ratas Wistar

RESUMEN

Astrocytes are very sensitive to alterations in the brain environment and respond showing a phenomenon known as astroglial reaction. S100beta is an astroglial derived neurotrophic factor, seems to be involved in neuroplasticity. The aim of this work was to study the astrocytic response in rat hippocampus and cerebral cortex after repetitive seizures induced by 3-mercaptopropionic acid (MP) administration. Immunocytochemical studies were performed to analyze GFAP and S100beta expression. Both studied areas showed hypertrophied astrocytes with enlarged processes and increased soma size. Astrocyte hyperplasia was observed only in the cerebral cortex. A significant decrease in the astrocytic S100beta immunostaining occurs after MP treatment. These results indicate that MP administration induces an astroglial reaction with reduced intracellular S100beta level. The observed reduction in astroglial S100beta could be related to the release of this factor to the extracellular space, where it may produce neurotrophic or deleterious effects accordingly to the concentration achieved. The mechanism of this remains to be elucidated.

Asunto(s)

Astrocitos/metabolismo , Corteza Cerebral/metabolismo , Epilepsia/metabolismo , Proteína Ácida Fibrilar de la Glía/metabolismo , Hipocampo/metabolismo , Proteínas S100/metabolismo , Ácido 3-Mercaptopropiónico , Animales , Astrocitos/patología , Corteza Cerebral/patología , Convulsivantes , Epilepsia/inducido químicamente , Epilepsia/patología , Hipocampo/patología , Masculino , Ratas , Ratas Wistar

RESUMEN

1. Failure of anticonvulsive drugs to prevent seizures is a common complication of epilepsy treatment known as drug-refractory epilepsy but their causes are not well understood. It is hypothesized that the multidrug resistance P-glycoprotein (Pgp-170), the product of the MDR-1 gene that is normally expressed in several excretory tissues including the blood brain barrier, may be participating in the refractory epilepsy. 2. Using two monoclonal antibodies against Pgp-170, we investigated the expression and cellular distribution of this protein in the rat brain during experimentally induced epilepsy. Repeated seizures were induced in male Wistar rats by daily administration of 3-mercaptopropionic acid (MP) 45 mg/kg i.p. for either 4 days (MP-4) or 7 days (MP-7). Control rats received an equivalent volume of vehicle. One day after the last injection, rats were sacrificed and brains were processed for immunohistochemistry for Pgp-170. As it was previously described, Pgp-170 immunostaining was observed in some brain capillary endothelial cells of animals from control group. 3. Increased Pgp-170 immunoreactivity was detected in MP-treated animals. Besides the Pgp-170 expressed in blood vessels, neuronal, and glial immunostaining was detected in hippocampus, striatum, and cerebral cortex of MP-treated rats. Pgp-170 immunolabeled neurons and glial cells were observed in a nonhomogeneous distribution. MP-4 animals presented a very prominent Pgp-170 immunostaining in the capillary endothelium, surrounding astrocytes and some neighboring neurons while MP-7 group showed increased neuronal labeling. 4. Our results demonstrate a selective increase in Pgp-170 immunoreactivity in the brain capillary endothelial cells, astrocytes, and neurons during repetitive MP-induced seizures. 5. The role for this Pgp-170 overexpression in endothelium and astrocytes as a clearance mechanism in the refractory epilepsy, and the consequences of neuronal Pgp-170 expression remain to be disclosed.

Asunto(s)

Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/efectos de los fármacos , Encéfalo/efectos de los fármacos , Resistencia a Múltiples Medicamentos/genética , Epilepsia/genética , Neuroglía/efectos de los fármacos , Neuronas/efectos de los fármacos , Ácido 3-Mercaptopropiónico/farmacología , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Animales , Anticonvulsivantes/farmacología , Barrera Hematoencefálica/efectos de los fármacos , Barrera Hematoencefálica/fisiología , Encéfalo/metabolismo , Encéfalo/fisiopatología , Convulsivantes/farmacología , Modelos Animales de Enfermedad , Células Endoteliales/efectos de los fármacos , Células Endoteliales/metabolismo , Epilepsia/tratamiento farmacológico , Epilepsia/metabolismo , Inmunohistoquímica , Masculino , Neuroglía/metabolismo , Neuronas/metabolismo , Ratas , Ratas Wistar , Convulsiones/inducido químicamente , Convulsiones/tratamiento farmacológico , Convulsiones/genética

RESUMEN

3 alpha-Hydroxy-6,19-oxidopregn-4-ene-20-one (4) was prepared in seven steps from pregnanolone acetate. At 0.1 microM concentration 4 significantly increased GABA induced (36)Cl(-) influx in hamster cerebral cortex synaptoneurosomes while at 20 mg/kg it decreased the percentage of hamsters showing seizures induced by 3-mercaptopropionic acid.

Asunto(s)

Pregnanolona/análogos & derivados , Pregnanolona/síntesis química , Pregnanolona/farmacología , Receptores de GABA-A/efectos de los fármacos , Ácido 3-Mercaptopropiónico/antagonistas & inhibidores , Ácido 3-Mercaptopropiónico/farmacología , Animales , Corteza Cerebral/citología , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Convulsivantes/farmacología , Cricetinae , Indicadores y Reactivos , Convulsiones/inducido químicamente , Convulsiones/prevención & control , Estereoisomerismo , Relación Estructura-Actividad , Sinaptosomas/efectos de los fármacos , Sinaptosomas/metabolismo

RESUMEN

GABA is the principal neurotransmitter of the mammalian circadian system, and its activity is subject to diurnal and circadian variations, with maximal values in hypothalamic turnover, content and binding during the night. In this study we have examined rhythms in the proconvulsant effect of inhibition of glutamate decarboxylase (GAD) in hamsters (Mesocricetus auratus) as well as the anticonvulsant effect of androsterone, a neurosteroid that positively modulates the GABA(A) receptor. Administration of 10-60 mg/Kg of 3-mercaptopropionic acid (3-MPA, a GAD inhibitor) induced convulsions that were analyzed by an ad-hoc severity scale, with a lower sensitivity threshold at 24:00 h. Moreover, the latency for first and maximal convulsive response times was significantly lower at night. A similar temporal profile (maximal effect at midnight) was found for picrotoxin-induced seizures. Androsterone (40 mg/Kg) completely inhibited 3-MPA-induced tonic/clonic seizures at 12:00 h, while it had a partial inhibitory effect at 24:00 h. These results support the importance of temporal regulation of GABAergic modulation in the central nervous system.

Asunto(s)

Ácido 3-Mercaptopropiónico/toxicidad , Androsterona/farmacología , Anticonvulsivantes/farmacología , Ritmo Circadiano/fisiología , Convulsivantes/toxicidad , Animales , Conducta Animal/efectos de los fármacos , Cricetinae , Inhibidores Enzimáticos/farmacología , Epilepsia Tónico-Clónica/inducido químicamente , Antagonistas del GABA/farmacología , Antagonistas de Receptores de GABA-A , Glutamato Descarboxilasa/antagonistas & inhibidores , Masculino , Mesocricetus , Picrotoxina/farmacología

RESUMEN

The administration of convulsant drugs has proven a powerful tool to study experimental epilepsy. We have already reported that the administration of convulsant 3-mercaptopropionic acid (mp) at 150 mg/kg enhances binding affinity of muscarinic antagonist [3H]quinuclidinyl benzilate ([3H]QNB) to certain rat CNS membranes during seizure and postseizure without affecting site number. Results obtained with a 100-mg/kg dose of mp have shown reversible increases in [3H]QNB binding to cerebellum and hippocampus, whereas a delayed response has been found in striatum. Neither a subconvulsant dose nor in vitro addition modifies binding. In order to evaluate preseizure, seizure as well as early (30 min) and late (24 h) postseizure stages, we employed a 50 mg/kg dose and tested [3H]QNB binding to CNS membranes. Changes in binding were as follows (in %): in cerebellum, +37, +86, and +40 at preseizure, seizure and early postseizure stages, respectively, but there was a decrease at late postseizure; in hippocampus, +27 at pre- and seizure stages, but a decrease at early and late postseizure. No changes were found in striatum or cerebral cortex membranes at any stage studied. Saturation curves analysed by Scatchard plots indicated that changes in [3H]QNB binding to cerebellar membranes are attributable to an increase in ligand affinity at seizure, followed by a decrease in binding site number at postseizure. A similar profile was observed for hippocampus except that the decrease in binding site number, though lower than at postseizure, was already evident at seizure stage. Results confirm a region-specific response to the convulsant and transient changes provide an example of neuronal plasticity.

Asunto(s)

Ácido 3-Mercaptopropiónico/farmacología , Encéfalo/metabolismo , Quinuclidinil Bencilato/farmacocinética , Receptores Muscarínicos/metabolismo , Animales , Membrana Celular/metabolismo , Cerebelo/metabolismo , Corteza Cerebral/metabolismo , Convulsivantes/farmacología , Cuerpo Estriado/metabolismo , Hipocampo/metabolismo , Cinética , Ligandos , Masculino , Ensayo de Unión Radioligante , Ratas , Ratas Wistar , Receptores Muscarínicos/efectos de los fármacos , Convulsiones/inducido químicamente , Convulsiones/metabolismo , Tritio