Control of retinoic acid receptor expression in mouse melanoma cells by cyclic AMP.

Retinoic acid receptor (RAR) alpha and gamma mRNAs were constitutively expressed in B16 melanoma cells with or without retinoic acid (RA) treatment. RAR beta mRNA, however, was significantly expressed only after exposure to RA. Induction of RAR beta by RA occurred within 1 h and was not inhibited by cycloheximide (i.e., did not require new protein synthesis). All three RAR mRNA levels were dramatically decreased with 8-bromo-cyclic AMP treatment and could not be rescued by addition of RA. Analysis of RAR gamma revealed that this decrease occurred within 1 h of exposure to 8-bromo-cyclic AMP and was not blocked by simultaneous treatment with cycloheximide. The stability of RAR gamma mRNA was not altered by cyclic AMP treatment. Nuclear extracts from 8-bromo-cyclic AMP-treated cells showed a large decrease in protein binding to a retinoic acid response element (RARE) oligonucleotide compared to control cells. This correlated with a marked reduction of RA-stimulated RARE-reporter gene activity in transfected cells which were treated with cyclic AMP. Pretreatment of B16 cells with cyclic AMP prior to RA addition dramatically reduced induction of PKC alpha, an early marker of RA-induced cell differentiation. Thus, cyclic AMP can antagonize the action of RA most likely via its ability to inhibit RAR expression.

Correlation of retinoid binding affinity to retinoic acid receptor alpha with retinoid inhibition of growth of estrogen receptor-positive MCF-7 mammary carcinoma cells.

Both anchorage-dependent growth and anchorage-independent growth of the estrogen receptor-positive mammary carcinoma cell line MCF-7 are inhibited by all-trans-retinoic acid. This cell line has nuclear retinoic acid receptors (RARs) alpha and gamma. The natural retinoids all-trans-retinoic acid and 9-cis-retinoic acid and a series of 12 conformationally restricted retinoids, which showed a range of binding selectivities for these receptors and had either agonist or antagonist activity for gene transcriptional activation by the RARs, were evaluated for their abilities to inhibit anchorage-dependent (adherent) and anchorage-independent (clonal) growth of MCF-7 cells. Correlation analyses were performed to relate growth inhibition by these retinoids with their binding affinity to RAR alpha or RAR gamma. Inhibition of anchorage-dependent growth in culture after 7 days of retinoid treatment correlated with binding to RAR alpha (n = 14; P < or = 0.001) and not to RAR gamma (n = 14; P > 0.1). Both the RAR alpha-selective retinoid agonists and the two RAR antagonists that were evaluated inhibited adherent cell growth. The RAR gamma-selective agonists had very low growth inhibitory activity (< 10%) at concentrations as high as 12.5 microM. These results suggest that RAR alpha is the retinoid receptor involved in the inhibition of adherent cell growth by retinoids and that transcriptional activation by this receptor on a RAR response element does not appear to be required for this process to occur. For this series of retinoids, inhibition of anchorage-independent growth after 21 days of retinoid treatment only correlated (n = 12; P < or = 0.005) with binding affinity to RAR alpha for the retinoid agonists, although the RAR gamma-selective retinoids displayed weak activity. The RAR antagonists were very poor inhibitors of growth. These results suggest that activation of gene transcription by RAR alpha appears to be required for inhibition of anchorage-independent growth by retinoids in this estrogen receptor-positive mammary carcinoma cell line.

Identification of structurally altered estrogen receptors in human breast cancer by site-directed monoclonal antibodies.

We have developed and characterized site-directed monoclonal (MAb) and polyclonal antibodies to a specific domain in the N-terminal A/B region in order to assess estrogen receptor (ER) structural integrity in human breast tumor samples. The antibodies (Abs) reacted specifically with the native (undenatured) ER from various species. The synthetic peptides competed effectively for ER binding to the Abs, suggesting site-specificity. The Abs recognized the activated (4S) and transformed (5S) but not the unactivated, untransformed, molybdate-stabilized (8S) ER, suggesting that the epitope is inaccessible in the 8S form. Some of these Abs reacted with ER bound to its responsive elements, as determined by gel mobility shift assay. To evaluate the structural integrity of ER in breast cancer, we have utilized a) ligand binding analysis for the hormone binding domain; b) site-directed MAb to the DNA-binding domain; and c) site-directed MAb to the N-terminal transactivation domain. Analysis of ER from 29 human breast tumors revealed that 10 out of 29 tumors (35%) contained ER with intact hormone-, DNA-, and N-terminal domains. Thirteen out of 29 tumors (approximately 45%) contained ER with intact hormone binding and N-terminal domains but were defective only in the DNA-binding domain. Three out of 29 tumors (approximately 10%) contained ER defective only in the N-terminal domain. Another subgroup of tumors (3/29; approximately 10%) had ER with normal hormone binding domain but were defective in both the DNA-binding and the N-terminal activation domains.(ABSTRACT TRUNCATED AT 250 WORDS)

Vitamin A metabolism in the human intestinal Caco-2 cell line.

The human intestinal Caco-2 cell line, described as enterocyte-like in a number of studies, was examined for its ability to carry out the metabolism of vitamin A normally required in the absorptive process. Caco-2 cells contained cellular retinol-binding protein II, a protein which is abundant in human villus-associated enterocytes and may play an important role in the absorption of vitamin A. Microsomal preparations from Caco-2 cells contained retinal reductase, acyl-CoA-retinol acyltransferase (ARAT), and lecithin-retinol acyltransferase (LRAT) activities, which have previously been proposed to be involved in the metabolism of dietary vitamin A in the enterocyte. When intact Caco-2 cells were provided with beta-carotene, retinyl acetate, or retinol, synthesis of retinyl palmitoleate, oleate, palmitate, and small amounts of stearate resulted. However, exogenous retinyl palmitate or stearate was not used by Caco-2 cells as a source of retinol for ester synthesis. While there was a disproportionate synthesis of monoenoic fatty acid esters of retinol in Caco-2 cells compared to the retinyl esters typically found in human chylomicrons or the esters normally synthesized in rat intestine, the pattern was consistent with the substantial amount of unsaturated fatty acids, particularly 18:1 and 16:1, found in the sn-1 position of Caco-2 microsomal phosphatidylcholine, the fatty acyl donor for LRAT. Both ARAT and LRAT have been proposed to be responsible for retinyl ester synthesis in the enterocyte.(ABSTRACT TRUNCATED AT 250 WORDS)

Analise da aptidao do chagasico para o trabalho. / Analysis of the ability to work of patients with Chagas' disease

Os autores advertem inicialmente quanto a presenca de trabalhadores chagasicos nas empresas, caracterizando-os como doentes em sua maioria, com alteracoes minimas no coracao, nao detectadas em exames clinicos nao complementados por propedeuticas mais sofisticadas, mas que podem, no entanto, levar uma vida praticamente normal. Apresentam um estudo de 19 trabalhadores chagasicos, de uma industria siderurgica, por tempo de servico prestado antes e apos o diagnostico, licencas e acidentes do trabalho, circunstancias dos diagnosticos, condicoes na admissao, e tipos de lesao encontrados. Concluem que nao ha razao para temer-se o trabalhador chagasico em servico, desde que sob controle, pois a sua maioria podera levar uma vida praticamente normal. O afastamento do trabalho fica restrito aquela minoria que apresenta cardiopatia grave

Analise do absentismo em usina siderurgica. / Analysis of the absenteeism in steel metallurgy plants

Os autores abordam o absentismo em seus varios aspectos, apresentando dados estatisticos de uma empresa siderurgica no ano de 1980, que sao comparados com anos anteriores. Os periodos de afastamento, os dados percentuais com que cada doenca interfere nas ausencias, alem de outras formas de absentismo sao mostrados. Os afastamentos pelo INPS, destacando uma maior incidencia em empregados jovens e de menor tempo de servico sao estudados - esse dados coincidem com os de acidentes do trabalho, de maior prevalencia nos empregados com ate tres anos de casa. Destacam a complexidade da luta contra o absentismo ressaltando o aumento gradativo das faltas por acidentes que nao do trabalho, e a diminuicao constante dos classificados como transtornos mentais. Analisam e comentam, ao final, os dados coletados, resaltando a sua importancia no processo de tomada de decisoes que tem por finalidade a diminuicao de falhas ao trabalho

Contribuicao ao estudo das alteracoes auditivas e de ordem neuro-vegetativas atribuiveis ao ruido. / Auditive and autonomic changes induced by noise

Apos considerarem a nocividade do ruido sobre o aparelho auditivo e a saude psicossomatica, os autores fazem um estudo de dois grupos de individuos: os que trabalham em areas de ruido acima de 85 dB e, abaixo de 70 dB, respectivamente. A investigacao e dirigida para alteracoes do aparelho auditivo por trauma sonoro e disturbios de ordem neuro-vegetativa, considerando-se idade e tempo de exposicao ao agente agressivo. Os resultados indicam que as queixas de ordem neuro-vegetativa aparecem predominantemente, na faixa de 2 a 5 anos de funcao, no grupo de individuos que trabalham em area de ruido, e que, no grupo controle, tais queixas surgiram em individuos mais idosos. Ressaltam, comparativamente aos acidentes do trabalho com perda, que ha equivalencia de queixas e acidentes na faixa de 2 a 5 anos de servico. Foram encontrados 16 casos de surdez por trauma sonoro no grupo estudado e 5 no grupo controle, podendo estes ultimos ser relacionados a funcoes anteriores em ambientes ruidosos. Concluem que, alem de influencia negativa do ruido sobre a audicao, fato inconteste, e ele fator desencadeante de diversos sintomas de ordem neuro-vegetativa, chamando a atencao para uma possivel faixa de alarme, apos a qual os sintomas diminuem