RESUMO
Antiserum raised against purified Trypanosoma cruzi proteasomes was used to isolate two cDNA clones, tcpr29 and tcpr29B, and the corresponding genomic sequence, termed tcpr29A. Both cDNAs and the gene contain a 798-bp ORF, coding for a 266-amino acid protein, with a predicted molecular mass of 29 kDa. Sequence comparisons show that the protein encoded by tcpr29 belongs to the alpha6 subfamily of proteasome subunits. Southern analysis indicated that tcpr29 subunit is encoded by a single-copy gene which maps to chromosome 20 of the CL Brener clone. Allelic variants were found in other T. cruzi isolates, suggesting heterozygosity for the gene in some and homozygosity in other strains. A spliced-leader addition site was identified 123 bp upstream from the start codon, generating a stable 1.5-kb transcript. Western analysis revealed that tcpr29A is constitutively expressed during the life cycle of the parasite.
Assuntos
Cisteína Endopeptidases/genética , Genes de Protozoários , Complexos Multienzimáticos/genética , Fases de Leitura Aberta , Trypanosoma cruzi/genética , Regiões 5' não Traduzidas/genética , Adenosina Trifosfatases/genética , Sequência de Aminoácidos , Animais , Arabidopsis/genética , Sequência de Bases , Clonagem Molecular , Cisteína Endopeptidases/química , DNA Complementar , Dictyostelium/genética , Drosophila melanogaster/genética , Humanos , Dados de Sequência Molecular , Peso Molecular , Complexos Multienzimáticos/química , Complexo de Endopeptidases do Proteassoma , Subunidades Proteicas , Ratos , Proteínas Recombinantes/química , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido Nucleico , Trypanosoma cruzi/enzimologiaRESUMO
Two pigeons, with previous exposure to concurrent schedules, were submitted to 29 sessions of 8 hours each with concurrent variable-interval variable-interval schedules in which reinforcement parameters changed from session to session. In the first nine sessions reinforcement durations were equal in both schedules while reinforcement frequencies varied; in Sessions 10 through 18, both frequency and duration of reinforcement were varied; in Sessions 19 through 29, only reinforcement duration was varied. Results with this different procedure confirm previous findings that behavior is more sensitive to changes in reinforcement frequency than to reinforcement magnitude.
RESUMO
Five pigeons were exposed to different pairs of concurrent variable-interval, variable-interval schedules on nine experimental conditions of 30 sessions each. For every session, the parameters of the generalized matching equation were computed for the first five, six, seven, eight, and nine experimental conditions. The exponent a, both for response and time distribution, tended to decrease with increases in number of experimental conditions and to increase with number of sessions per condition, but values of k (bias) varied unsystematically. When the subjects were exposed to five new pairs of schedules, with 55 sessions per condition, the findings were confirmed. Data from the literature on the generalized matching law suggest that the variability of exponent values may be explained in part by the use of naive or experienced subjects in different investigations and by the variability in number of experimental conditions and in number of sessions per condition.
