Positive emotional induction interferes with the reconsolidation of negative autobiographical memories, in women only.

After reactivation, a previously consolidated memory can enter into a labile state followed by a re-stabilization process defined as reconsolidation. The aim of this study was to explore whether an existing negative autobiographical memory can be modified by using a non-invasive interference (audiovisual positive preparation) after reactivation and to determine if this effect could be dependent on the reconsolidation process. We found that the presentation of a positive inductor after a negative autobiographical memory reactivation may lead to a change in the emotional information of the original trace and that such effect can be mediated by the reconsolidation process. The modification of the memory has been shown in women only. These results suggest that a positive audiovisual induction may play a potential role in psychotherapeutic techniques for the modification of dysfunctional autobiographical memories.

Effects produced by different types of laser in cornea of Guinea pigs: Identification of a laser capable of producing superficial lesions without leaving scars.

PURPOSE: Climatic droplets keratopathy (CDK) is closely associated with superficial corneal erosions and lack of protective mechanisms against the harmful effects of ultraviolet radiation (UVR) during a prolonged period of time. One of the difficulties in studying the pathogenic mechanisms involved in this human disease is the lack of an experimental animal model. In this paper, a study is conducted on the effects of 4 types of lasers at various powers and time conditions on the normal guinea pig corneas in order to select only one laser condition that reversibly injures the epithelium and superficial stroma, without leaving scarring. METHODS: Damage was induced in the cornea of Guinea pigs using different powers and exposure times of 4 types of laser: argon, CO2, diode and Nd-Yag, and any injuries were evaluated by biomicroscopy (BM) and optical microscopy. Corneas from other normal animals were exposed to argon laser (350 mW, 0.3s, 50 µm of diameter), and the induced alterations were studied at different times using BM, optical coherence tomography (OCT) and transmission electron microscopy (TEM). RESULTS: Only argon laser at 350 mW, 0.3s, 50 µm of diameter produced epithelium and superficial stroma lesions. Some leukomas were observed by BM, and they disappeared by day 15. Corneal thickness measured by OCT decreased in the eyes treated with argon laser during the first week. Using TEM, different ultra structural alterations in corneal epithelium and stroma were observed during the early days, which disappeared by day 15. CONCLUSIONS: It was possible to develop reproducible corneal epithelium and anterior stroma injuries using Argon laser at 350 mW, 0.3s, 50 µm of diameter. In vivo and in vitro studies showed that injured corneas with these laser conditions did not leave irreversible microscopic or ultra structural alterations. This protocol of corneal erosion combined with exposure to UVR and partial deficiency of ascorbate in the diets of the animals for an extended period of time has been used in order to try to develop an experimental model of CDK.

Estudio del polimorfismo del gen de TNF-α, de dicha citocina, y de MCP-1 en pacientes con queratopatía climática esferoidea / Studies of TNF-α gene polymorphism, TNF-α and MCP-1 cytokines in patients with spheroidal climatic keratopathy

Objetivo. Investigar polimorfismo de nucleótidos únicos (SNP) en la posición -308 (G/A) del gen TNF-α y la participación de las citocinas TNF-α y MCP-1 en pacientes con queratopatía climática esferoidea (QCE) y en controles sanos. Materiales y métodos. Participaron 15 pacientes con QCE y 15 individuos sanos del departamento El Cuy, Provincia de Río Negro. Todos ellos, luego de firmar el consentimiento informado, recibieron un examen oftalmológico completo y se recolectaron muestras de sangre y lágrima para realizar diferentes estudios. EL ADN genómico fue obtenido de sangre de todos los individuos mediante el método de salting out y posteriormente amplificado y estudiado mediante reacción en cadena de la polimerasa (PCR) con el sistema de amplificación refractaria a la mutación (ARMS). También se investigaron concentraciones de algunas citocinas proinflamatorias en lágrimas y en sobrenadante de cultivo de células epiteliales corneales humanas (CECH) tratadas o no con radiación ultravioleta B (RUV-B). Resultados. Los resultados de SNP en la posición -308 (G/A) del gen TNF-α (frecuencia alélica y genotípica) indicaron ausencia de diferencias significativas entre pacientes y controles sanos. Fenotípicamente ambos grupos de individuos serían bajos o intermedios productores in vitro de la citocina TNF-α. Sin embargo en las lágrimas de pacientes con QCE se detectaron concentraciones significativamente superiores de TNF-α, IL-1ß y MCP-1 (citocinas proinflamatorias) que en lágrimas de individuos controles sanos (p<0,0001) En la periferia y limbo de la córnea las células dendríticas (CD) incrementaron significativamente con el progreso de la enfermedad (p<0,05). La contribución del epitelio corneal en el proceso inflamatorio fue investigada utilizando CECH expuestas o no a 10 mJ/cm2 de RUV-B. A pesar de la presencia de gelatinasas, IL-6 e IL-8 en sobrenadantes de cultivos obtenidos a las 48 horas (datos no mostrados) no observamos niveles detectables de TNF-α, IL-1ß ni MCP-1. Conclusión. Este trabajo aporta nuevos datos para aumentar los conocimientos sobre los mecanismos inmunológicos involucrados en la etiopatogenia y progresión de la QCE. Demostramos que las citocinas proinflamatorias MCP-1 y TNF-α están significativamente elevadas en lágrimas de individuos con QCE, como se observó previamente con IL-1ß. MCP-1 sería la responsable del aumento de CD en córnea periférica y limbo de estos pacientes a medida de que la enfermedad avanza. El hallazgo de que estas citocinas no pudieron ser detectadas en cultivos de CECH estresadas con RUV-B implica que otras células son las responsables de su producción o que además de RUV-B otros factores son necesarios para iniciar esta cascada de eventos que se observan en esta hipersensibilidad corneal humana(AU)

Purpose. To investigate Single Nucleotide Polymorphism (SNP) at -308 position (G/A) of TNF-α gen and involving of TNF-α and MCP-1 cytokines in Climatic Droplet Keratopathy (CDK) patients and healthy controls. Materials and methods. Fifteen patients with CDK and fifteen healthy controls from departamento El Cuy, province of Rio Negro were involved in this study. After informed consent was obtained from all participants, they had a complete eye examination and then tear and blood samples were collected to perform different assays. DNA was obtained from blood of all individuals using the method of "salting out" and then amplified and studied performing the polymerase chain reaction (PCR) with Amplification-refractory Mutation System (ARMS). Furthermore, some cytokines concentrations were measured in tears and supernatants from human corneal epithelial cells (HCEs) exposed or not to UVR-B radiation. Results. Analysis from SNP at position -308 (G/A) of TNF-α gen (allelic and genotypic frequency) showed no significant differences between patients and healthy controls. Phenotypically both groups of individuals would be low or intermediate in vitro producers of TNF-α cytokine. However, in tears from CDK's patients we detected significantly higher concentrations of TNF-α, IL-1ß and MCP-1 (pro-inflammatory cytokines) than in healthy control subjects tears (p<0.0001). At the corneal peripheral / limbus area, dendritic cells (DCs) increased significantly with the progression of the disease (p<0.05). The corneal epithelium contribution to the inflammatory process was investigated using HCEs exposed or not to 10 mJ/cm2 of UV radiation­B (UVR-B). Despite the presence of gelatinases, IL-6 and IL-8 in culture supernatants obtained after 48 hours (data not shown), detectable levels of TNF-α, IL-1ß and MCP-1 were not detected. Conclusion. This study provides new insights to increase our knowledge about the immunological mechanisms involved in the etiopathogenesis and progression of CDK. We showed that pro-inflammatory cytokines MCP-1 y TNF-α were significantly increased in tears from CDK's patients, as previously described with IL-1ß. MCP-1 would be responsible for the increasing of DCs on the corneal peripheral / limbus area of these subjects as the disease progresses. The fact that these cytokines could not be detected in cultures of HCEs stressed with UVR-B implies that other cells are responsible for their production or, in addition to UVR-B, other factors are necessary to initiate the cascade of events observed in this human corneal hypersensitivity. (AU)

Effect of divalent metal ions on the activity and stability of Beta-galactosidase isolated from Kluyveromyces lactis

Este estudo demonstra como a Beta-galactosidase pode ser desativada e reativada usando EDTA e íons metálicos divalentes. A enzima foi desativada após 20 minutos na presença de EDTA. Desativação máxima para a menor concentração de EDTA (10-3 mol.L-1) ocorreu na presença do tampão Tris-HCl. A enzima recuperou 50% de sua atividade inicial após 10 minutos na presença de Mg2+ em concentrações superiores a 0,1mmol.L-1.Concentrações de 10-4 e 10-3 mol.L-1 de Mn2+ e Co2+ foram suficientes para reativar a enzima em 300% comparado ao controle de íons Mn2+ e aproximadamente 100% para íons Co2+. A enzima perdeu gradualmente a sua atividade quando a concentração foi de 10-2 mol.L-1. Ni2+ e Zn2+ foram incapazes de restabelecer a atividade catalítica. Km app e Vmax app foram 1,95 ± 0,05 mmol.L-1 e 5,40 ± 0,86 x 10-2 mmol.min-1.mg-1. A temperatura e pH ótimos foram 34ºC e 7,5. A meia vida da holoenzima foi de 17,5 min a 30ºC e para a apoenzima foi de 11,0 min a 30ºC. Quanto à variação de pH, a apoenzima provou ser mais sensível que a holoenzima.

In this study, it was demonstrated that Beta-galactosidase can be deactivated and reactivated with EDTA and divalent metal ions. The enzyme was deactivated after 20 minutes in EDTA solution. Maximal deactivation at the lowest EDTA concentration (10-3 mol.L-1) occurred in the presence of Tris-HCl buffer (pH 7.0). The enzyme recovered 50% of its initial activity after 10 minutes at Mg2+concentrations higher than 0.1 mmol.L-1. Experimental concentrations of 0.1 mmol.L-1 Mn2+ and 1.0 mmol.L-1 Co2+ were sufficient to reactivate the enzyme to around 300% of the control activity for the Mn2+ ion and nearly 100% for the Co2+ ion. The enzyme gradually lost its activity when the Co2+ concentration was 10-2 mol.L-1. Ni2+ and Zn2+ were unable to restore the catalytic activity. Km app and Vmax app were 1.95 ± 0.05 mmol.L-1 and 5.40 ± 0.86x10-2 mmol.min-1.mg-1, with o-NPG as substrate. Optimal temperature and pH were 34oC and 7.5. The half-life (t1/2) at 30ºC was 17.5 min for the holoenzyme and 11.0 min for the apoenzyme. With respect to pH variation, the apoenzyme proved to be more sensitive than the holoenzyme.

Production of beta-galactosidase by Trichoderma reesei FTKO-39 in wheat bran: partial purification of two isozymes.

Trichoderma reesei FTKO-39 grown at 35 degrees C for 5 d on wheat bran supplemented with MgCl2 and lactose as the carbon source produced two isozymes of beta-galactosidase: BGT I and BGT II. These isozymes were partially purified on a DEAE-Trisacryl column. Both BGT I and BGT II fractions exhibited optimum activity at 65 degrees C, but the pH optima were 4.0 and 6.5, respectively. The isozymes also showed similar thermal stability. However, BGT I was more stable than BGT II in a pH range of 3.0-10.0. At least two different beta-galactosidases are produced by T. reesei, as revealed by the two bands seen on a 6% polyacrylamide gel stained for activity.

Xylanases from fungi: properties and industrial applications.

Xylan is the principal type of hemicellulose. It is a linear polymer of beta-D-xylopyranosyl units linked by (1-4) glycosidic bonds. In nature, the polysaccharide backbone may be added to 4-O-methyl-alpha-D-glucuronopyranosyl units, acetyl groups, alpha-L-arabinofuranosyl, etc., in variable proportions. An enzymatic complex is responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-beta-xylanase and beta-xylosidase. These enzymes are produced by fungi, bacteria, yeast, marine algae, protozoans, snails, crustaceans, insect, seeds, etc., but the principal commercial source is filamentous fungi. Recently, there has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production. This review describes some properties of xylan and its metabolism, as well as the biochemical properties of xylanases and their commercial applications.

Controlled hydrolysis of cheese whey proteins using trypsin and alpha-chymotrypsin.

This study examined the production of protein hydrolysates with controlled composition from cheese whey proteins. Cheese whey was characterized and several hydrolysis experiments were made using whey proteins and purified beta-lactoglobulin, as substrates, and trypsin and alpha-chymotrypsin, as catalysts, at two temperatures and several enzyme concentrations. Maximum degrees of hydrolysis obtained experimentally were compared to the theoretical values and peptide compositions were calculated. For trypsin, 100% of yield was achieved; for alpha-chymotrypsin, hydrolysis seemed to be dependent on the oligopeptide size. The results showed that the two proteases could hydrolyze beta-lactoglobulin. Trypsin and alpha-chymotrypsin were stable at 40 degrees C, but a sharp decrease in the protease activity was observed at 55 degrees C.

Inhibitory effect of propolis and bee venom on the mutagenicity of some direct- and indirect-acting mutagens.

The antimutagenic effect of ethanolic extract of propolis (EEP) and honeybee (Apis mellifera) venom, both collected in the State of São Paulo, Brazil, was assessed by the Salmonella/microsome assay upon direct- and indirect-acting mutagens. EEP had inhibitory effect (in an ascending order) on the mutagenicity power of daunomycin (TA102), benzo(a)pyrene (TA100), and aflatoxin B(1)(TA98) and the venom acted against the mutagenicity of 4-nitro-o-phenylenediamine (TA98) and daunomycin (TA102). Teratogenesis Carcinog. Mutagen. 19:403-413, 1999.