RESUMO
Leishmania sp. protozoa are introduced into a mammalian skin by a sandfly vector, whereupon they encounter increased temperature and toxic oxidants generated during phagocytosis. We studied the effects of 37 degrees C "heat shock" or sublethal menadione, which generates superoxide and hydrogen peroxide, on Leishmania chagasi virulence. Both heat and menadione caused parasites to become more resistant to H(2)O(2)-mediated toxicity. Peroxide resistance was also induced as promastigotes developed in culture from logarithmic to their virulent stationary phase form. Peroxide resistance was not associated with an increase in reduced thiols (trypanothione and glutathione) or increased activity of ornithine decarboxylase, which is rate-limiting in trypanothione synthesis. Membrane lipophosphoglycan increased in size as parasites developed to stationary phase but not after environmental exposures. Instead, parasites underwent a heat shock response upon exposure to heat or sublethal menadione, detected by increased levels of HSP70. Transfection of promastigotes with L. chagasi HSP70 caused a heat-inducible increase in resistance to peroxide, implying it is involved in antioxidant defense. We conclude that leishmania have redundant mechanisms for resisting toxic oxidants. Some are induced during developmental change and others are induced in response to environmental stress.
Assuntos
Peróxido de Hidrogênio/toxicidade , Leishmania infantum/efeitos dos fármacos , Animais , Antioxidantes/farmacologia , Glicoesfingolipídeos/metabolismo , Proteínas de Choque Térmico HSP70/biossíntese , Leishmania infantum/metabolismo , Ornitina Descarboxilase/biossíntese , Estresse Oxidativo , Compostos de Sulfidrila/metabolismoAssuntos
Veia Porta/diagnóstico por imagem , Trombose/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Idoso , Angiografia/métodos , Neoplasias do Sistema Biliar/diagnóstico por imagem , Feminino , Humanos , Aumento da Imagem/métodos , Fígado/diagnóstico por imagem , Neoplasias Hepáticas/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X/métodos , Varizes/diagnóstico por imagemRESUMO
We present an unusual case of a granulocytic sarcoma (chloroma) of the sacrum which predated the initial clinical manifestation of acute myelogenous leukemia. Although granulocytic sarcomas occur in up to 9.1% of cases of acute myelogenous leukemia they usually present concurrently with the leukemic presentation. Although granulocytic sarcomas can involve several different organ systems, bone is the most common site.
Assuntos
Leucemia Mieloide/diagnóstico , Sacro , Neoplasias da Coluna Vertebral/diagnóstico , Feminino , Humanos , Leucemia Mieloide Aguda/diagnóstico , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios XAssuntos
Adenocarcinoma/diagnóstico por imagem , Neoplasias Pancreáticas/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Adenocarcinoma/patologia , Idoso , Angiografia/métodos , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Neoplasias Pancreáticas/patologiaRESUMO
The hydrophobic photoaffinity label 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine was used to label Sendai virus proteins during fusion with cardiolipin and phosphatidylserine liposomes. Preferential labeling of the viral fusion protein during the initial stages of fusion demonstrated that this protein interacts with the hydrophobic core of the target membrane as an initiating event of virus-liposome fusion. Labeling showed time, temperature, and pH dependence consistent with earlier fluorescent measurements of fusion kinetics. The present method provides conclusive evidence supporting the hypothesis that hydrophobic interaction of the fusion protein with the target bilayer is an initial event in the fusion mechanism of viral membranes.
Assuntos
Lipossomos/metabolismo , Fusão de Membrana , Vírus da Parainfluenza 1 Humana/fisiologia , Proteínas Virais de Fusão/metabolismo , Marcadores de Afinidade , Animais , Azirinas , Cardiolipinas/metabolismo , Embrião de Galinha , Concentração de Íons de Hidrogênio , Fosfatidilserinas/metabolismo , Contagem de Cintilação , TemperaturaRESUMO
Bacteriophage lambda attaches to Gram-negative bacteria using the outer membrane protein LamB as its receptor. Subsequently, DNA is injected by the bacteriophage into the host cell for replication and expression. The mechanism of DNA injection, however, is poorly understood. In order to begin to characterize DNA injection, a quantitative kinetic assay to detect injection into reconstituted LamB liposomes is described. The technique involves monitoring the increase in fluorescence of liposome-encapsulated ethidium bromide, which occurs as DNA enters the aqueous compartment of the vesicles. The data indicate that injection is several times faster than indicated by earlier studies and is complete within 1 min. Such assays which allow direct observation of this process are necessary first steps toward a mechanistic understanding.