RESUMO
We have examined how herbimycin affects the survival and neuritogenesis of avian sympathetic neurons. Herbimycin promoted sympathetic neuron survival and neuritogenesis. At higher concentrations (> or = 100 ng/ml), herbimycin still enhanced neuron survival but blocked neuritogenesis. Addition of herbimycin (10-30 ng/ml) to neurons cultured in the presence of NGF or retinal conditioned medium altered neuronal morphology, with an increase in the number of neurites. Addition of NGF during hypoxia rescued 52% of the neurons compared to 14% survival in control conditions. Herbimycin alone rescued about 50% of the neurons. In the presence of NGF and 100 ng/ml herbimycin, 81% of the neurons survived hypoxia. Our results show that herbimycin promotes survival of chick sympathetic neurons and potentiates the effects of NGF.
Assuntos
Fibras Adrenérgicas/efeitos dos fármacos , Fibras Adrenérgicas/fisiologia , Quinonas/farmacologia , Animais , Benzoquinonas , Morte Celular/efeitos dos fármacos , Morte Celular/fisiologia , Hipóxia Celular/efeitos dos fármacos , Hipóxia Celular/fisiologia , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Células Cultivadas , Embrião de Galinha , Lactamas Macrocíclicas , Neuritos/efeitos dos fármacos , Neuritos/fisiologia , Rifabutina/análogos & derivadosRESUMO
The standard slipped-strand mispairing (SSM) model for the formation of variable number tandem repeats (VNTRs) proposes that a few tandem repeats, produced by chance mutations, provide the "raw material" for VNTR expansion. However, this model is unlikely to explain the formation of VNTRs with long motifs (e.g., minisatellites), because the likelihood of a tandem repeat forming by chance decreases rapidly as the length of the repeat motif increases. Phylogenetic reconstruction of the birth of a mitochondrial (mt) DNA minisatellite in guppies suggests that VNTRs with long motifs can form as a consequence of SSM at noncontiguous repeats. VNTRs formed in this manner have motifs longer than the noncontiguous repeat originally formed by chance and are flanked by one unit of the original, noncontiguous repeat. SSM at noncontiguous repeats can therefore explain the birth of VNTRs with long motifs and the "imperfect" or "short direct" repeats frequently observed adjacent to both mtDNA and nuclear VNTRs.
Assuntos
Pareamento Incorreto de Bases/genética , Repetições Minissatélites/genética , Mitocôndrias/genética , Modelos Genéticos , Poecilia/genética , Animais , Sequência de Bases , DNA Mitocondrial/análise , DNA Mitocondrial/genética , Genética Populacional , Dados de Sequência Molecular , Mutação , Filogenia , Análise de Sequência de DNA , Trinidad e TobagoRESUMO
The standard slipped-strand mispairing (SSM) model for the formation of variable number tandem repeats (VNTRs) proposes that a few tandem repeats, produced by chance mutations, provide the "raw material" for VNTR expansion. However, this model is unlikely to explain the formation of VNTRs with long motifs (e.g., minisatellites), because the likelihood of a tandem repeat forming by chance decreases rapidly as the length of the repeat motif increases. Phylogenetic reconstruction of the birth of a mitochondrial (mt) DNA minisatellite in guppies suggests that VNTRs with long motifs can form as a consequence of SSM at noncontiguous repeats. VNTRs formed in this manner have motifs longer than the noncontiguous repeat originally formed by chance and are flanked by one unit of the original, noncontiguous repeat. SSM at noncontiguous repeats can therefore explain the birth of VNTRs with long motifs and the "imperfect" or "short direct" repeats frequently observed adjacent to both mtDNA and nuclear VNTRs.
Assuntos
Animais , Research Support, Non-U.S. Gov't , Pareamento Incorreto de Bases/genética , Sequência de Bases , DNA Mitocondrial/análise , DNA Mitocondrial/genética , Genética Populacional , Repetições Minissatélites/genética , Mitocôndrias/genética , Modelos Genéticos , Dados de Sequência Molecular , Mutação , Filogenia , Poecilia/genética , Análise de Sequência de DNA , Trinidad e TobagoRESUMO
Multivoxel magnetic resonance (MR) spectroscopy and novel data analysis techniques were developed to obtain high-quality phosphorus-31 metabolite images from the human brain and to overlay each metabolite distribution directly onto corresponding hydrogen-1 MR images. The P-31 MR spectroscopic data were acquired by means of three-dimensional chemical shift imaging (phase encoding in three spatial dimensions) on a 1.5-T clinical instrument equipped with a specially designed quadrature P-31 birdcage coil constructed in the authors' laboratory. Axial, sagittal, and coronal metabolite images based on the area for any one of five peak regions (phosphodiester; phosphocreatine; gamma, alpha, and beta adenosine triphosphate) were generated from 8 X 8 X 8 or 12 X 12 X 8 CSI arrays with voxel sizes of 27 cm3 and 12 cm3, respectively. The positions of these images were aligned with anatomic features by means of the voxel-shifting capability of the Fourier transform. Direct overlays of these metabolite images on corresponding proton images demonstrated excellent correlation with anatomy, factors indicating the utility of this technique for viewing P-31 metabolite levels in all areas of the brain simultaneously.