RESUMEN
The expression of the early genes c-fos and c-jun were studied by blot hybridization in the central nervous system of the edible snail at the consolidation stage of a conditioned defensive reflex, with the aim of investigating genomic activity in neurons during learning. The c-fos gene was shown to be present in the Helix central nervous system, and its expression was shown to increase significantly during learning. Superinduction of the c-fos gene was observed in the presence of cycloheximide, a protein synthesis inhibitor. Corasol also induced this gene. Thus, induction of the c-fos gene in Helix can be induced by agents which induce it in higher vertebrates. This suggests that expression of the c-fos gene in Helix and in higher vertebrates is regulated by closely related mechanisms. Expression of the c-jun gene was insignificant, and definitive conclusions with regard to the role of this gene in learning cannot be drawn.
Asunto(s)
Condicionamiento Clásico/fisiología , Genes Inmediatos-Precoces/genética , Genes Inmediatos-Precoces/fisiología , Caracoles Helix/fisiología , Animales , Química Encefálica/efectos de los fármacos , Química Encefálica/fisiología , Cicloheximida/farmacología , Electrochoque , Alimentos , Expresión Génica/efectos de los fármacos , Expresión Génica/fisiología , Genes fos , Genes jun , Hibridación in Situ , Plasticidad Neuronal/efectos de los fármacos , Plasticidad Neuronal/fisiología , Inhibidores de la Síntesis de la Proteína/farmacología , Quinina/farmacología , ARN/biosíntesisRESUMEN
A considerable increase in the RNA amount in the course of learning was revealed in the Heix mollusk. The same chemicals were found to induce expression of the c-fos both in higher vertebrated and in the snail thus suggesting similar mechanisms of the regulation. The c-jun in the Helix CNS seems to take no part in the learning process.
Asunto(s)
Condicionamiento Clásico/fisiología , Reacción de Fuga/fisiología , Caracoles Helix/fisiología , Animales , Conducta Alimentaria/fisiología , Regulación de la Expresión Génica/genética , Regulación de la Expresión Génica/fisiología , Genes fos/genética , Genes fos/fisiología , Genes jun/genética , Genes jun/fisiología , Caracoles Helix/genética , Hibridación de Ácido Nucleico , ARN/análisis , ARN/genéticaRESUMEN
An increase of PKA activity in the cytoplasmic membrane and nuclei of the CNS conditioned snails was shown. We also found that c-fos as present in the Helix CNS, and its expression is enhanced during learning. A translocation of the PKA catalytic subunit into the nuclei and an activation of the c-fos expression might underlie the long-term plasticity in Helix.
Asunto(s)
Caracoles Helix/fisiología , Plasticidad Neuronal/fisiología , Animales , Núcleo Celular/enzimología , Sistema Nervioso Central/fisiología , Condicionamiento Psicológico/fisiología , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Citoplasma/enzimología , Expresión Génica , Genes fos , Caracoles Helix/genética , Aprendizaje/fisiología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Sistemas de Mensajero Secundario/fisiologíaRESUMEN
Estradiol receptors are discovered in nuclei, cytoplasm and plasmatic membranes of the target cells. Estradiol activates the transmembrane polyphosphoinositide system: it stimulates the protein kinase C translocation from cytosol to cell membranes, the membrane protein phosphorylation being elevated. Transmembrane adenylate cyclase system is also activated. The cAMP system stimulation by estradiol is mediated by protein kinase C, phosphorylating a protein of adenylate cyclase complex. Estradiol causes protein kinases A translocation into the cell nuclei and enhances the protein kinase NII activity. The role of protein phosphorylation, activated by steroid hormones, in the transcription and protein synthesis regulation, is discussed.
Asunto(s)
Hormonas/fisiología , Sistemas de Mensajero Secundario/fisiología , Adenilil Ciclasas/metabolismo , Animales , Membrana Celular/fisiología , Estradiol/metabolismo , Femenino , Fosfatidilinositoles/metabolismo , Fosforilación , Proteínas Quinasas/metabolismo , Receptores de Superficie Celular/fisiología , Receptores de Estradiol/fisiologíaRESUMEN
Stimulation of rat mammary tumour growth by estradiol is due to the activation of the adenylate cyclase system and cAMP-dependent protein kinases. A single administration of estradiol to ovariectomized rats causes a rise in the cAMP-dependent protein kinase activity in cell nuclei within the first 4-6 hours after injection. This effect is probably due to the translocation of enzymes into nuclei and an increase of their synthesis. The high level of the cAMP-dependent protein kinase activity in cell nuclei was observed in actively growing intact mammary tumours, in contrast to regressing ones in ovariectomized animals. This phenomenon can be accounted for by the decrease in the content of a thermostable protein inhibitor of cAMP-dependent protein kinases rather than by the high level of cAMP.
Asunto(s)
Estradiol/farmacología , Neoplasias Mamarias Experimentales/metabolismo , Proteínas Quinasas/metabolismo , Células Tumorales Cultivadas/efectos de los fármacos , Adenilil Ciclasas/metabolismo , Animales , Activación Enzimática , Estabilidad de Enzimas , Femenino , Calor , Inhibidores de Proteínas Quinasas , Ratas , Ratas EndogámicasAsunto(s)
Adenilil Ciclasas/metabolismo , Estradiol/farmacología , Neoplasias Hormono-Dependientes/fisiopatología , Proteína Quinasa C/fisiología , Animales , Membrana Celular/enzimología , Activación Enzimática , Femenino , Neoplasias Hormono-Dependientes/enzimología , Ovariectomía , Ratas , Ratas Endogámicas , Células Tumorales CultivadasRESUMEN
The mechanisms of stimulating effect of estradiol on the growth of hormone-dependent mammary tumours in experimental animals were studied. Estradiol receptors were detected in plasmatic membranes of estradiol-dependent tumour cells. Estradiol-independence of tumours was found to be a result of the impairment of the estradiol receptors in the plasmatic membranes, intracellular receptors, or of their ability to interact with the chromatin of the target cells. It was shown that the interaction of receptors of plasmatic membranes of hormone-dependent tumour cells with estradiol results in activation of the membrane adenylate cyclase and in a short-term rise of a cAMP content. A treatment of the hormone-dependent tumours with ovarian hormones brings about an increase in the activity of the cAMP-dependent protein kinases in cell nuclei, which points to their translocation from cytosol. Under effect of estradiol the phosphorylation of nuclear proteins at the serine, threonine and tyrosine residues increases.
Asunto(s)
Estradiol/metabolismo , Neoplasias Mamarias Experimentales/metabolismo , Neoplasias Hormono-Dependientes/metabolismo , Receptores de Estradiol/metabolismo , Receptores de Estrógenos/metabolismo , Animales , AMP Cíclico/metabolismo , Femenino , Ratones , Ovariectomía , Proteínas Quinasas/metabolismo , Ratas , Ratas Endogámicas , Receptores de Estradiol/análisisRESUMEN
Early effects of estradiol on the adenylate cyclase system in target tissues were investigated. The proliferative processes in the estradiol-dependent mammary tumours and uterus of the rat were arrested by ovariectomy. Subsequent hormonal treatment resulted in adenylate cyclase activation and the increase of the cAMP level in these tissues, probably to be connected with the initiation of the cell growth. These events were followed by a decrease of the cAMP content necessary for active proliferation of tumour cells. cAMP phosphodiesterase is not responsible for the increase in the cyclic nucleotide content, but provides for its further hydrolysis. The stimulation of the adenylate cyclase system at early steps of estradiol action is typical both for normal and transformed estradiol-dependent tissues.
Asunto(s)
Adenilil Ciclasas/metabolismo , Estradiol/farmacología , Neoplasias Mamarias Experimentales/enzimología , 3',5'-AMP Cíclico Fosfodiesterasas/metabolismo , 9,10-Dimetil-1,2-benzantraceno , Animales , División Celular/efectos de los fármacos , AMP Cíclico/metabolismo , Activación Enzimática/efectos de los fármacos , Femenino , Neoplasias Mamarias Experimentales/inducido químicamente , Neoplasias Mamarias Experimentales/patología , Ratas , Ratas Endogámicas , Útero/enzimologíaRESUMEN
These data demonstrate that actinomycin D inhibits only 75-80% of DNA synthesis in cells of E. coli treated by lysozyme and ethyl enediaminetetraacetate. The residual synthesis is not the result of untemplated polymerization of dNTP. The DNA synthesis in spheroplasts does not correlate with replication of chromosomal DNA of E. coli catalyzed by DNA polymerase III sensitive to sulfhydryl blocking agents. N-ethylmaleimide does not inhibit this synthesis. No ATP stimulation of DNA synthesis is observed. The enzyme(s) responsible for DNA synthesis on endogenous template is (are) concentrated in interphase (D-fraction) as revealed by high speed centrifugation of spheroplasts lysate and they are absent in the chromosomal DNA fraction. dTTP 4-(N-2-chloroethyl-N-mehylamino) benzylamide suppresses completely the insensitive to actinomycin D action DNA synthesis and practically does not act on the sensitive one. It is suggested, that the DNA synthesis stable to the action of the antibiotic is catalyzed by RNA dependent DNA polymerase.