ABSTRACT
The taxonomic location of the Onychophora has been controversial because of their phenotypic and genotypic characteristics, related to both annelids and arthropods. We analyzed the ultrastructure of the neurons and their synapses in the cephalic ganglion of a poorly known invertebrate, the velvet worm Peripatus sedgwicki, from the mountainous region of El Valle, Mérida, Venezuela. Cephalic ganglia were dissected, fixed and processed for transmission electron microscopy. The animal has a high degree of neurobiological development, as evidenced by the presence of asymmetric (excitatory) and symmetric (inhibitory) synapses, as well as the existence of glial cell processes in a wide neuropile zone. The postsynaptic terminals were seen to contain subsynaptic cisterns formed by membranes of smooth endoplasmic reticulum beneath the postsynaptic density, whereas the presynaptic terminal showed numerous electron transparent synaptic vesicles. From the neurophylogenetic perspectives, the ultrastructural characteristics of the central nervous tissue of the Onychophora show important evolutionary acquirements, such as the presence of both excitatory and inhibitory synapses, indicating functional synaptic transmission, and the appearance of mature glial cells.
Subject(s)
Animals , Male , Female , Ganglia/ultrastructure , Invertebrates/ultrastructure , Neurons/ultrastructure , Synapses/ultrastructure , Invertebrates/classification , Microscopy, Electron, Transmission , VenezuelaABSTRACT
Se estudian las relaciones hosedador-parasito entre los amastigotes de Leishmania sp. y los macrofagos dermicos presentes en las lesiones de la trompa de hamsteres inoculados meses antes. Se supone la secrecion de un material denso a traves de la bolsa flagelar de los amastigotes. Dicho material es producido por los parasitos tan pronto quedan evueltos o limitados por la membrana de la vacuola parasitofora, formada poco despues de un breve periodo durante el cual los parasitos estaban libres en el citoplasma histiocito. Se sugiere que en dependencia de la rapidez con la cual dicho material sea segregado, se decide la proteccion de los parasitos contra las enzimas lisosomales de la celula hospedadora. Se dicute la veracidad de esta hipotesis a la luz de otras evidencias suposiciones elaboradas por otros investigadores