RESUMEN
A soluble fraction from human frontal cortex with molecular weight less than 10 kD was tested for the presence of endogenous substances capable of modulating the [3H]-QNB binding to crude P1 + P2 fractions from the same region. The soluble fraction was able to decrease [3H]-QNB binding in a dose-response manner with an IC50 of about 30 micrograms/ml. The effect appeared to be noncompetitive in nature, since Bmax but not Kd was significantly affected; however, in some specimens a biphasic profile, with an initial inhibition of 88-90% of [3H]-QNB binding and 50-60% ulterior binding recuperation was also found. The modulator appeared to have a molecular weight less than 10,000 Daltons and was heat and trypsin resistant. These results point out the existence of an endogenous factor, which could be heterogeneous in regard to its molecular nature or to its action sites.
Asunto(s)
Lóbulo Frontal/química , Agonistas Muscarínicos/aislamiento & purificación , Antagonistas Muscarínicos/aislamiento & purificación , Proteínas del Tejido Nervioso/efectos de los fármacos , Neurotransmisores/aislamiento & purificación , Receptores Muscarínicos/efectos de los fármacos , Adolescente , Adulto , Unión Competitiva , Fibras Colinérgicas/fisiología , Relación Dosis-Respuesta a Droga , Humanos , Masculino , Microsomas/química , Peso Molecular , Agonistas Muscarínicos/metabolismo , Antagonistas Muscarínicos/metabolismo , Proteínas del Tejido Nervioso/aislamiento & purificación , Neurotransmisores/metabolismo , Desnaturalización Proteica , Quinuclidinil Bencilato/metabolismo , Receptores Muscarínicos/aislamiento & purificación , SolubilidadRESUMEN
A novel class of steroidal A/B ring isoxazoles have been prepared by two independent reaction schemes using 3 beta,17 beta-diacetoxyandrost-5-ene (1) and 3 beta,17 beta-diacetoxyandrost-4-en-6-one (4) as synthetic precursors. The key common intermediate in these syntheses, 3 beta,17 beta-diacetoxyandrost-4-eno[6,5,4-c,d] isoxazole (3), was prepared by synthetic methods described in both schemes. Further chemical modification of 3 yielded 3 beta,17 beta-dihydroxyandrost-4-eno[6,5,4-c,d] isoxazole (6), androst-3,17-dione-4-eno[6,5,4-c,d] isoxazole (7), and 17 beta-hydroxyandrost-3-one-4-eno[6,5,4-c,d] isoxazole (9). Human placental estrogen synthase (aromatase) bioassays were conducted to obtain the following IC50 values resulting from a 50% reduction of enzymatic activity: 6, 120.5 microM; 7, 1.889 microM. 9, 18.57 microM.
Asunto(s)
Inhibidores de la Aromatasa , Inhibidores Enzimáticos/síntesis química , Isoxazoles/síntesis química , Inhibidores Enzimáticos/farmacología , Humanos , Isoxazoles/farmacología , Espectroscopía de Resonancia MagnéticaRESUMEN
Despite extensive research efforts to identify unique molecular alterations in breast cancer, to date, no characteristic has emerged that correlates exclusively with malignancy. Recently, it has been shown that the multiprotein DNA replication complex (synthesome) from breast cancer cells has a significantly decreased replication fidelity compared to that of nonmalignant breast cells. Proliferating cell nuclear antigen (PCNA) functions in DNA replication and DNA repair and is a component of the synthesome. Using two-dimensional PAGE analysis, we have identified a novel form of PCNA in malignant breast cells. This unique form is not the result of a genetic alteration, as demonstrated by DNA sequence analysis of the PCNA gene from malignant and nonmalignant breast cells. This novel form is most likely the result of an alteration in the post-translational modification of PCNA in malignant breast cells. These findings are significant in that it is now possible to link changes in the fidelity of DNA replication with a specific alteration of a component of the DNA synthetic apparatus of breast cancer cells. The novel form of PCNA may prove to be a new signature for malignant breast cells.