RESUMO
Upregulation of the proto-oncoprotein Myc, a basic, helix-loop-helix, leucin zipper domain transcription factor has profound consequences on cell proliferation, cell growth and apoptosis. Cell cultures of somatic c-myc-/- rat fibroblasts show extremely prolonged doubling times of 52 h. Using time-lapse microscopy, we show here that individual c-myc-/- cells proceeded within approximately 24 h through the cell cycle as fast as c-myc+/+ cells. However, c-myc-/- cells were highly sensitive to contact inhibition and readily arrested in the cell cycle already at low density. Activation of conditional MycER overcame cell cycle arrest in c-myc-/- cells and led to continuous proliferation at the expense of increased apoptosis at high cell density. Conditional expression of Mad1, a Myc antagonist, represses proliferation of different cell types including U2OS cells. In analogy to the effect of Myc, this occurs mainly by reducing the probability of cells remaining in the cycle. Our data demonstrate that the Myc/Max/Mad network does not regulate the duration of the cell cycle, but the decision of cells to enter or exit the cell cycle.
Assuntos
Ciclo Celular , Proteínas de Ligação a DNA/metabolismo , Fosfoproteínas/metabolismo , Proteínas Proto-Oncogênicas c-myc/metabolismo , Proteínas Repressoras/metabolismo , Fatores de Transcrição , Animais , Apoptose/genética , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Fatores de Transcrição de Zíper de Leucina Básica , Contagem de Células , Proteínas de Ciclo Celular , Divisão Celular , Linhagem Celular , Células Cultivadas , Inibição de Contato/genética , Proteínas de Ligação a DNA/genética , Deleção de Genes , Regulação da Expressão Gênica , Microscopia de Vídeo , Proteínas Nucleares , Fosfoproteínas/genética , Proteínas Proto-Oncogênicas c-myc/genética , Ratos , Proteínas Repressoras/genética , Fatores de TempoRESUMO
Genetic surveys of parthenogenetic vertebrate populations have demonstrated a common pattern of relatively high degrees of clonal variation and the coexistence of numerous clones. In striking contrast, the Phoxinus eos/Phoxinus neogaeus/hybrid gynogen complex of cyprinid fishes exhibits no clonal variation within a northern Minnesota drainage characterized by successional beaver ponds. Gynogens were sampled from three habitats in each of four different pond types in a single drainage in Voyageurs National Park, Minnesota. The abundance of gynogens relative to sexual dace varied with pond type, being least common in deep upland ponds and most common in shallow, collapsed, lowland ponds (13.4% and 48.6%, respectively). Simple-sequence multilocus DNA fingerprinting of 464 individual gynogens detected one, and only one, clone. DNA fingerprints, generated sequentially by using three oligonucleotide probes, (CAC)5, (GACA)4, and the Jeffreys' 33.15 probe, all revealed the same unprecedented lack of variation. The extreme lack of clonal diversity in these gynogens across a range of habitat types does not fit the general pattern of high clonal diversity found within populations of other vertebrate parthenogens.
Assuntos
Cyprinidae/genética , Variação Genética , Animais , Sequência de Bases , Cyprinidae/fisiologia , Impressões Digitais de DNA , Demografia , Água Doce , Minnesota , Dados de Sequência Molecular , Mosaicismo , Sondas de Oligonucleotídeos , Partenogênese , Ploidias , Densidade Demográfica , Especificidade da EspécieRESUMO
A total of 201 patients and their relatives in a hospital in Copenhagen participated in a structured interview investigation about their knowledge of the long-term effects of alcohol and their attitudes to restrictions. The majority approved of an upper limit for alcohol consumption within the recommended limits but a total of approximately 1/3 preferred a higher limit. Only 28% realised that there was a difference in how much alcohol women and men can tolerate. The majority, but far from all of the participants knew that alcohol could damage the liver and brain but few knew of damage to other organs. A total of 64% had a positive attitude to prohibition of alcohol consumption in places of employment in Denmark. It is suggested that information about alcohol should be concentrated in the form of simple clear messages.
Assuntos
Consumo de Bebidas Alcoólicas , Alcoolismo , Conhecimentos, Atitudes e Prática em Saúde , Adolescente , Adulto , Idoso , Atitude Frente a Saúde , Dinamarca , Etanol/efeitos adversos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores SocioeconômicosRESUMO
Development and implementation of local and regional plans to control nonpoint sources of pollution from agricultural land are major mandates of section 208 of Public Law 92-500. Many planners tend to equate erosion control as measured by the universal soil loss equation with improvements in water quality. Others implement channel management practices which degrade rather than improve water quality and thereby decrease the effectiveness of other efforts to control nonpoint sources. Planners rarely recognize the importance of the land-water interface in regulating water quality in agricultural watersheds. More effective planning can result from the development of "best management systems" which incorporate theory from all relevant disciplines.
