RESUMEN
The mammalian interleukin-1 beta-converting enzyme (ICE) has sequence similarity to the C. elegans cell death gene ced-3. We show here that overexpression of the murine ICE (mICE) gene or of the C. elegans ced-3 gene causes Rat-1 cells to undergo programmed cell death. Point mutations in a region homologous between mICE and CED-3 eliminate the ability of mICE and ced-3 to cause cell death. The cell death caused by mICE can be suppressed by overexpression of the crmA gene, a specific inhibitor of ICE, as well as by bcl-2, a mammalian oncogene that can act to prevent programmed cell death. Our results suggest that ICE may function during mammalian development to cause programmed cell death.
Asunto(s)
Apoptosis , Metaloendopeptidasas/fisiología , Proteínas Virales , Animales , Secuencia de Bases , Caspasa 1 , Línea Celular , Cartilla de ADN/química , Técnicas In Vitro , Metaloendopeptidasas/antagonistas & inhibidores , Ratones , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Proteínas Proto-Oncogénicas/farmacología , Proteínas Proto-Oncogénicas c-bcl-2 , Ratas , Proteínas Recombinantes de Fusión/metabolismo , Serpinas/metabolismoRESUMEN
Multipotent neural cell lines were generated via retrovirus-mediated v-myc transfer into murine cerebellar progenitor cells. When transplanted back into the cerebellum of newborn mice, these cells integrated into the cerebellum in a nontumorigenic, cytoarchitecturally appropriate manner. Cells from the same clonal line differentiated into neurons or glia in a manner appropriate to their site of engraftment. Engrafted cells, identified by lacZ expression and PCR-mediated detection of a unique sequence arrangement, could be identified in animals up to 22 months postengraftment. Electron microscopic and immunohistochemical analysis demonstrated that some engrafted cells were similar to host neurons and glia. Some transplant-derived neurons received appropriate synapses and formed normal intercellular contacts. These data indicate that generating immortalized cell lines for repair of, or transport of genes into, the CNS may be feasible. Such lines may also provide a model for commitment and differentiation of cerebellar progenitor cells.
Asunto(s)
Trasplante de Tejido Encefálico/fisiología , Cerebelo/trasplante , Neuronas/trasplante , Envejecimiento , Animales , Biomarcadores , Diferenciación Celular , Línea Celular , Cerebelo/citología , Cerebelo/crecimiento & desarrollo , Técnicas de Cultivo/métodos , Genes myc , Ratones , Ratones Endogámicos , Microscopía Electrónica , Neuronas/citología , Neuronas/ultraestructura , Transfección , beta-Galactosidasa/genética , beta-Galactosidasa/metabolismoRESUMEN
Brainstem trigeminal vascular convergence (TVC) neurons receive an excitatory, nociceptive input from cranial blood vessels as well as the facial skin or cornea. In the present study, a population of cat TVC neurons was electrophysiologically identified and then intracellularly labelled with horseradish peroxidase. One TVC neuron from lamin IV and one from lamina V were processed for electron microscopy. Both cells have extensive axon terminal fields within trigeminal nucleus interpolaris as well as lamina IV and V of trigeminal nucleus caudalis. Analysis of thin sections showed that the soma and dendrites of the TVC neurons are contacted by synaptic terminals of various types. Both cells have myelinated axons and collaterals that give rise to unmyelinated preterminal processes. Within nucleus caudalis, terminals of the TVC cells contain round synaptic vesicles that synapse primarily with dendrites and spines.
Asunto(s)
Vasos Sanguíneos/inervación , Encéfalo/irrigación sanguínea , Nervio Trigémino/ultraestructura , Animales , Encéfalo/ultraestructura , Gatos , Circulación Cerebrovascular , Peroxidasa de Rábano SilvestreRESUMEN
Methanogens catalyze the hydrogen-dependent eight-electron reduction of carbon dioxide to methane. Two of the key catalysts in the eight-electron reduction pathway are the nickel-containing enzymes F420-reducing hydrogenase and methyl reductase. In the present study, the structures of these archaebacterial enzymes from Methanobacterium thermoautotrophicum delta H have been determined by electron microscopy. By negative stain techniques, F420 hydrogenase was found to be a ring structure with a diameter of 15.7 nm and an inner channel 4 nm in diameter. Shadow-casting experiments demonstrated that the rings were 8.5 nm deep, indicating a holoenzyme molecular weight of 8.0 X 10(5). Methyl reductase appeared to be an oligomeric complex of dimensions 8.5 by 9 by 11 nm, with a central stain-penetrating region. The morphology and known subunit composition suggest a model in which the subunits are arranged as an eclipsed pair of open trimers. Methyl reductase was also found in the form of larger aggregates and in paracrystalline arrays derived from highly concentrated solutions. The extremely large size of F420 hydrogenase and the methyl reductase supramolecular assemblies may have relevance in vivo in the construction of multiprotein arrays that function in methane biogenesis.