RESUMO
The morphology and fine structure of the ocelli of Triatoma infestans have been analyzed by means of light and electron microscopy. The two dorsal ocelli of this species are located behind the compound eyes, looking dorsally and frontally. Externally, the ocelli are marked by the corneal lenses virtually spherical in form and limited internally by a cuticular apodeme. The lens focuses the incoming rays beyond the retina. A single layer of corneagen cells lies below the cuticular lens. The corneagen cells and photoreceptors are arranged in a cup-like fashion beneath the cuticular lens. A distal retinal zone comprises the rhabdoms, which are laterally connected in an hexagonal meshwork. A middle retinal zone comprises the receptor cell segment free of rhabdom, and a proximal zone their axons. In the middle zone, the oviform nuclei and spheroids are located. Screening pigment granules are present within the retinal cell. Spherical mitochondria are homogeneously distributed in the cytoplasm of the cell body. In the axonal zone, mitochondria are found in the peripheral region. Axons from receptor cells extend into the ocellar neuropile at the base of the ocelli, to synapse with second order neurons. The large axons of second order neurons are bundled by glial cells. The ocellar plexus exhibits a high diversity of synaptic unions (i.e. axo-dendritic, axo-axonic, dendro-axonic, and dendro-dendritic).
Assuntos
Olho/ultraestrutura , Triatoma/ultraestrutura , Animais , Olho/citologia , Masculino , Microscopia Eletrônica , Microscopia Eletrônica de Varredura , Retina/citologia , Retina/ultraestrutura , Sinapses/ultraestrutura , Triatoma/anatomia & histologia , Triatoma/citologiaRESUMO
Simple eyes or ocelli coexist with compound eyes in many adult insects. The change in the morphology of the ocelli along the five larval instars of Triatoma infestans was studied by light and scanning electron microscopy. Our analysis showed that the development of the ocelli of these bugs occurs gradually along the larval life. The photoreceptor layer is present from the second-instar onwards. The cornea appears first at the imaginal stage and grows up to the 18-20th day after the last ecdysis, associated to an increase in the retinal mass. Findings are discussed in a comparative fashion and in relation to the functionality of the ocellar system in T. infestans.
Assuntos
Olho/crescimento & desenvolvimento , Insetos Vetores/crescimento & desenvolvimento , Triatoma/crescimento & desenvolvimento , Animais , Olho/ultraestrutura , Microscopia EletrônicaRESUMO
The simple eyes (ocelli) of recently emerged adult Triatoma infestans exhibit a narrow elongated "pupil", surrounded by a ring of brown-reddish pigment, the "iris". This pupil does not respond to changes in the illumination, but varies in size after the imaginal ecdysis. This change corresponds, internally, with the growth of the corneal lens and the associated retina up to an age of about 20 days. This has not been previously observed in an insect. The use of this characteristic for recognising young adults of this species is suggested.
Assuntos
Envelhecimento/fisiologia , Iluminação , Pupila/fisiologia , Triatoma/fisiologia , Animais , Feminino , Insetos Vetores/fisiologia , MasculinoRESUMO
The projections of mechanosensory hairs located on the dorsal and lateral head of the adult haematophagous bug Triatoma infestans were analyzed by means of cobalt filling. Axons run into the anterior and posterior tegumentary nerve and project through the brain to the ventral nerve cord. The fibres are small in diameter and run as a fascicle. Some branches run into suboesophageal and prothoracic centres; others run as far as to the mesothoracic ganglion. These sensory projections resemble that of wind-sensitive head hairs of the locust. The functional role of this sensory system in this species is discussed.
Assuntos
Axônios/ultraestrutura , Encéfalo/ultraestrutura , Mecanorreceptores/ultraestrutura , Triatoma/ultraestrutura , Animais , Axônios/fisiologia , Encéfalo/fisiologia , Cobalto , Mecanorreceptores/fisiologia , Microscopia Eletrônica de Varredura , Triatoma/anatomia & histologiaRESUMO
In addition to compound eyes, most adult insects posses two or three simple eyes, the ocelli. The function of these photoreceptors remains elusive in most cases. Triatomine bugs posses two well-developed ocelli, located in a latero-dorsal position, behind the compound eyes. We tested the role of the ocelli in the phototactic behaviour of Triatoma infestans, by measuring the time spent by adult males in the dark half of an experimental arena, which had the other half illuminated. The occlusion of the ocelli or the compound eyes alone had little effect on the phototactic response of the bugs. Only those insects which had both their ocelli and compound eyes occluded showed a significant reduction in their negative response to light. The ability of the ocelli of T. infestans to mediate the phototactic response by themselves (i.e., not through the modulation of compound eyes sensitivity) constitutes the first report on this function in insects.
RESUMO
The anatomy of the adult nervous system of the haematophagous bug Triatoma infestans has been studied by means of dissections and histology. The central nervous system comprises three nervous masses: the brain+suboesophageal ganglion, the prothoracic ganglion, and the posterior fused ganglion (meso+metathoracic+abdominal ganglia). The form of the brain is determined by the tubular head and the highly developed muscles of the pharyngeal pump. The prothoracic ganglion is located near the posternum, the posterior ganglionic mass near the mesosternum. A significative variation of the branching pattern of abdominal nerves is reported. The innervations of mouth parts, salivary glands, muscles, retrocerebral complex, spiracles, rectum, reproductive organs, alary muscles, and peripheral nerves are described.
Assuntos
Sistema Nervoso/anatomia & histologia , Triatoma/anatomia & histologia , AnimaisRESUMO
The teaching of neurology as an entity within the concept of teaching in medicine is analized through the following questions: what are we teaching? To whom are we teaching? and why are we teaching? The first question concerns the pedagogical, sociological and psychological patterns used to elaborate locally-arranged goals for the creation of criteria and conduct. The second establishes the relationship between the influence of the technical-industrial adult generation on the present university generation and the reappraisal of human values through new pedagogic techniques. The third establishes the supply and demand process of assistant teaching and research physicians; it also dwells on the influence of the residency programmes and research trends, and their repercussion on the methodology of the medical curriculum.
Assuntos
Educação Médica , Neurologia/educação , Argentina , Currículo , Educação Médica/tendências , Estudantes de MedicinaRESUMO
Programmed teaching of neurologic semiology, charted in agreement to subsequent learning in clinical neurology, is conceived. The basis of the pedagogic system consists of respecting the systems that bind physiologically among themselves. The goal is the creation of areas of comprehension, dramatizing common functions and signology. To know "all" is of less validity than to posses an engram prepared by key information. The anatomic physiology memory, previous to the course and the weekly partial evaluation, is considered useful. The problematic of the competitive test is analyzed and its negative and positive criterions are exposed. Anatomy, physiology, semiology and clinical neurology spun together are estimated to favor pedagogic goals redundantly.