Effects of delay sequence in a delay discounting task.

Delay discounting refers to the decrease in subjective value of a reward as the delay until its receipt increases. In the present study we assessed the effects of the sequence of delay blocks (increasing or decreasing) on discounting and the data systematicity using a titrating procedure with human participants. All participants completed the delay discounting task in both an increasing and decreasing sequence of delays. Delays ranged from one day to ten years. We found steeper discounting when the delays were presented in an increasing sequence compared with when they were presented in a decreasing sequence. We also found steeper discounting when participants completed the increasing sequence condition first. Our results agree with other findings reported in the literature and suggest that delay discounting may be affected by prior and subsequent experience.

Antimicrobial, antioxidant activity and phytochemical prospection of Eugenia involucrata DC. leaf extracts.

The species Eugenia involucrata DC. is a plant native to Brazil and is traditionally used for intestinal problems, however, little research has documented about its biological potential and phytochemical profile. Thus, the objective of this study was to carry out preliminary phytochemical prospecting, antimicrobial and antioxidant potential of E. involucrata extracts. Using the E. involucrata leaves, aqueous and organic extracts were obtained using the following solvents (ethanol, methanol, hexane, acetone, dichloromethane and ethyl acetate). The phytochemical prospecting detected the presence of saponins, steroids, flavonoids and tannins in the extracts. Ethanolic and methanolic extracts presented antimicrobial activity for most of the bacterial strains tested, as well as for yeast Candida albicans, with concentrations between 3.12 and 50 mg/mL. The ethanolic and metanolic extract presented high free radical sequestration potential (>90%). The methanol extract showed an IC50 value statistically equal to that found for the commercial antioxidant BHT (p <0.05). The crude extracts obtained with ethanol and methanol were the most promising. These results suggest that methanolic, ethanolic and aqueous extracts are a promising source of natural bioactive.

Companion's effects upon resistance to change.

In order to investigate the effects of a companion's presence on resistance to change, five rats were trained under a multiple schedule comprised of components with high versus low rate of water reinforcement. After response rates became stable, water was given to the subjects prior to the experimental sessions, and these were conducted both in the absence and in the presence of a companion, which also could be responding or merely present. Results showed that the companion's presence increased resistance to satiation, mainly during the component with the higher reinforcement rate. These results suggest that the effect of the companion's presence may interact with reinforcement rate in determining response rate and resistance to satiation.

Antimicrobial, antioxidant activity and phytochemical prospection of Eugenia involucrata DC. leaf extracts

Abstract The species Eugenia involucrata DC. is a plant native to Brazil and is traditionally used for intestinal problems, however, little research has documented about its biological potential and phytochemical profile. Thus, the objective of this study was to carry out preliminary phytochemical prospecting, antimicrobial and antioxidant potential of E. involucrata extracts. Using the E. involucrata leaves, aqueous and organic extracts were obtained using the following solvents (ethanol, methanol, hexane, acetone, dichloromethane and ethyl acetate). The phytochemical prospecting detected the presence of saponins, steroids, flavonoids and tannins in the extracts. Ethanolic and methanolic extracts presented antimicrobial activity for most of the bacterial strains tested, as well as for yeast Candida albicans, with concentrations between 3.12 and 50 mg/mL. The ethanolic and metanolic extract presented high free radical sequestration potential (>90%). The methanol extract showed an IC50 value statistically equal to that found for the commercial antioxidant BHT (p 0.05). The crude extracts obtained with ethanol and methanol were the most promising. These results suggest that methanolic, ethanolic and aqueous extracts are a promising source of natural bioactive.

Resumo A espécie Eugenia involucrata DC. é uma planta nativa do Brasil e tradicionalmente utilizada para problemas intestinais, porém, poucas pesquisas documentam sobre seu potencial biológico e perfil fitoquímico. Assim, o objetivo deste trabalho foi realizar uma prospecção fitoquímica preliminar, o potencial antimicrobiano e antioxidante dos extratos de E. involucrata. A partir das folhas de E. involucrata, foram obtidos extratos aquosos e orgânicos com os seguintes solventes (etanol, metanol, hexano, acetona, diclorometano e acetato de etila). A prospecção fitoquímica detectou a presença de saponinas, esteroides, flavonóides e taninos nos extratos. Os extratos etanólico e metanólico apresentaram atividade antimicrobiana para a maioria das cepas bacterianas testadas, assim como para a levedura Candida albicans, com concentrações entre 3,12 e 50 mg/mL. Os extratos etanólico e metanólico apresentaram alto potencial de sequestro de radicais livres (> 90%). O extrato metanólico apresentou IC50 estatisticamente igual ao encontrado para o antioxidante comercial BHT (p 0,05). Os extratos brutos obtidos com etanol e metanol foram os mais promissores. Esses resultados sugerem que os extratos metanólico, etanólico e aquoso são uma fonte promissora de bioativos naturais.

Antimicrobial, antioxidant activity and phytochemical prospection of Eugenia involucrata DC. leaf extracts / Atividade antimicrobiana, antioxidante e prospecção fitoquímica dos extratos das folhas de Eugenia involucrata DC

Abstract The species Eugenia involucrata DC. is a plant native to Brazil and is traditionally used for intestinal problems, however, little research has documented about its biological potential and phytochemical profile. Thus, the objective of this study was to carry out preliminary phytochemical prospecting, antimicrobial and antioxidant potential of E. involucrata extracts. Using the E. involucrata leaves, aqueous and organic extracts were obtained using the following solvents (ethanol, methanol, hexane, acetone, dichloromethane and ethyl acetate). The phytochemical prospecting detected the presence of saponins, steroids, flavonoids and tannins in the extracts. Ethanolic and methanolic extracts presented antimicrobial activity for most of the bacterial strains tested, as well as for yeast Candida albicans, with concentrations between 3.12 and 50 mg/mL. The ethanolic and metanolic extract presented high free radical sequestration potential (>90%). The methanol extract showed an IC50 value statistically equal to that found for the commercial antioxidant BHT (p <0.05). The crude extracts obtained with ethanol and methanol were the most promising. These results suggest that methanolic, ethanolic and aqueous extracts are a promising source of natural bioactive.

Resumo A espécie Eugenia involucrata DC. é uma planta nativa do Brasil e tradicionalmente utilizada para problemas intestinais, porém, poucas pesquisas documentam sobre seu potencial biológico e perfil fitoquímico. Assim, o objetivo deste trabalho foi realizar uma prospecção fitoquímica preliminar, o potencial antimicrobiano e antioxidante dos extratos de E. involucrata. A partir das folhas de E. involucrata, foram obtidos extratos aquosos e orgânicos com os seguintes solventes (etanol, metanol, hexano, acetona, diclorometano e acetato de etila). A prospecção fitoquímica detectou a presença de saponinas, esteroides, flavonóides e taninos nos extratos. Os extratos etanólico e metanólico apresentaram atividade antimicrobiana para a maioria das cepas bacterianas testadas, assim como para a levedura Candida albicans, com concentrações entre 3,12 e 50 mg/mL. Os extratos etanólico e metanólico apresentaram alto potencial de sequestro de radicais livres (> 90%). O extrato metanólico apresentou IC50 estatisticamente igual ao encontrado para o antioxidante comercial BHT (p <0,05). Os extratos brutos obtidos com etanol e metanol foram os mais promissores. Esses resultados sugerem que os extratos metanólico, etanólico e aquoso são uma fonte promissora de bioativos naturais.

Learned helplessness: effects of response requirement and interval between treatment and testing.

Three experiments investigated learned helplessness in rats manipulating response requirements, shock duration, and intervals between treatment and testing. In Experiment 1, rats previously exposed to uncontrollable or no shocks were tested under one of four different contingencies of negative reinforcement: FR 1 or FR 2 escape contingency for running, and FR1 escape contingency for jumping (differing for the maximum shock duration of 10s or 30s). The results showed that the uncontrollable shocks produced a clear operant learning deficit (learned helplessness effect) only when the animals were tested under the jumping FR 1 escape contingency with 10-s max shock duration. Experiment 2 isolated of the effects of uncontrollability from shock exposure per se and showed that the escape deficit observed using the FR 1 escape jumping response (10-s shock duration) was produced by the uncontrollability of shock. Experiment 3 showed that using the FR 1 jumping escape contingency in the test, the learned helplessness effect was observed one, 14 or 28 days after treatment. These results suggest that running may not be an appropriate test for learned helplessness, and that many diverging results found in the literature might be accounted for by the confounding effects of respondent and operant contingencies present when running is required of rats.