RESUMEN
The evolutionary origins of the protistan phylum, Myxozoa, have long been questioned. Although these obligate parasites are like protozoans in many features, several aspects of their ontogeny and morphology have implied a closer relationship to metazoan lineages. Phylogenetic analyses of 18S ribosomal RNA sequences from myxozoans and other eukaryotes, with the use of parsimony, distance, and maximum-likelihood methods, support the hypothesis that myxozoans are closely related to the bilateral animals. These results suggest that the Myxozoa, long considered an assemblage of protozoans, should be considered a metazoan phylum.
Asunto(s)
Eucariontes/clasificación , Parásitos/clasificación , ARN Ribosómico 18S/genética , Animales , Secuencia de Bases , Evolución Biológica , Eucariontes/genética , Funciones de Verosimilitud , Datos de Secuencia Molecular , Parásitos/genética , Filogenia , Probabilidad , ARN Protozoario/genéticaRESUMEN
A method is described for the rapid preparation of lung cell fractions enriched in type II alveolar pneumocytes. Isolated perfused rabbit lungs are exposed to Fe3O4 by tracheal lavage, which permits pulmonary alveolar macrophages to phagocytize the particles. Alveolar epithelial cells are then selectively freed from the basement membrane matrix by critical placement of collagenase and elastase. Detached cells are harvested either by repeated tracheal lavage or by mincing the lobes and filtering freed cells through a series of nylon mesh sieves. Iron oxide-containing macrophages are then removed from the harvested cells by a strong magnetic field. A final sizing of the macrophage-depleted suspension yields a preparation enriched in alveolar type II cells. Eight million viable cells (95% type II) were obtained per rabbit lung when harvested by lavage, while 32 x 10(6) (88% type II) cells were obtained from minced lungs. These values for cell yield and relative purity are comparable to previously described separation methods that depend upon differences in cell density or size. A major advantage of the magnetic separation procedure is the substantially shortened preparation time, typically 2 hr instead of 4. The viability (90-95%), oxygen consumption (88 nmol/10(6) cells/hr), and incorporation of [14C]acetate and [14C]choline (0.44 and 0.115 nmol/10(6) cells/hr, respectively) indicate that these cells will be suitable for pharmacologic and toxicologic investigation.
Asunto(s)
Separación Celular/métodos , Macrófagos/citología , Magnetismo , Óxidos , Alveolos Pulmonares/citología , Animales , Supervivencia Celular , Centrifugación , Óxido Ferrosoférrico , Hierro , Metabolismo de los Lípidos , Macrófagos/fisiología , Masculino , Consumo de Oxígeno , Fagocitosis , ConejosRESUMEN
Rabbit glomeruli and tubules were obtained by retrograde perfusion of magnetite into the lower aorta as previously described for the isolation of rat glomeruli. In addition, an alternative method of separating rabbit glomerular and tubular basement membranes from a single renal cortex preparation was developed. These preparations, which represent the Triton X-100-insoluble material, were extracted in sequence with deoxycholate, dodecyl sulfate in the presence and absence of 2-mercaptoethanol at 8 degrees C and again in the latter at 100 degrees C. The polypeptides solubilized at each step of this sequence were characterized by electrophoresis. The final extract consisted almost exclusively of red-staining, presumably collagenous bands, while the earlier extracts consisted of blue-staining, presumably noncollagenous bands. No significant differences were found between the glomerular and tubular basement membrane extracts.
Asunto(s)
Membrana Basal/análisis , Glomérulos Renales/análisis , Túbulos Renales/análisis , Animales , Membrana Basal/ultraestructura , Colágeno/análisis , Detergentes , Electroforesis en Gel de Poliacrilamida , Glomérulos Renales/irrigación sanguínea , Glomérulos Renales/ultraestructura , Túbulos Renales/ultraestructura , Métodos , Péptidos/análisis , Conejos , Solubilidad , Coloración y EtiquetadoRESUMEN
Intravenous administration of the electron-opaque tracer ferritin resulted in substantial elevation of serum histamine levels in both the Munich--Wistar and Wistar-Furth strains of albino rats. Lewis rats were unaffected. Similarly, infusion of the non-protein tracer dextran was followed by greatly elevated serum histamine concentrations in Munich-Wistar and Lewis, but not in Wistar-Furth, rats. In sharp contrast with these results were those obtained using the tracer polyvinylpyrrolidone (PVP). PVP infusion caused no elevation of serum histamine levels in any of the rat strains studied. Caution in the use of such tracers is thus advised, since serum histamine concentration affects vascular permeability. Careful matching of ultrastructural tracer and strain of experimental animal is prerequisite in permeability studies.