Molecular evidences that Heterotermes tenuis should be a species complex

Dissertação de mestrado em Investigação Biomédica, apresentada à Faculdade de Medicina da Universidade de CoimbraA epilepsia é uma patologia crónica caracterizada por ataques epiléticos espontâneos. Esta patologia afeta cerca de 65 milhões de pessoas no mundo inteiro, de todas as idades e ambos os géneros. Pensa-se que a génese e/ou propagação dos ataques epiléticos tem origem na hiperexcitabilidade neuronal. No sistema nervoso central, o balanço entre a atividade excitatória e inibitória é maioritariamente mediada pelo glutamato, um neurotransmissor excitatório, e pelo ácido gama-aminobutírico (GABA), um neurotransmissor inibitório. O GABA atua, em parte, através da ativação de recetores de GABA do tipo A (GABAAR), os quais são, na sua grande parte, constituídos por duas subunidades α, duas β e uma subunidade γ2. Os GABAARs apresentam uma grande mobilidade na membrana, podendo deslocar-se entre as regiões sinápticas e extra-sinápticas. A acumulação dos GABAARs nas sinapses inibitórias é regulada pela proteína scaffold gefirina, a qual desempenha um papel importante no controlo da neurotransmissão GABAérgica rápida. A expressão superficial dos recetores GABAA é também influenciada pela taxa de internalização, a qual ocorre em regiões extra-sinápticas, assim como por mecanismos de regulação intracelular que determinam a taxa de reciclagem. Ataques epiléticos simples ou recorrentes provocam uma desregulação das sinapses GABAérgicas a diferentes níveis. Porém, os mecanismos moleculares responsáveis por esta desregulação ainda não estão completamente estudados. Resultados obtidos por imunohistoquímica sugerem que o aumento do número de axónios e de terminais GABAérgicos observados na epilepsia do lobo temporal, tanto em humanos como em modelos animais, pode estar relacionado com o sprouting de neurónios GABAérgicos. No entanto, a possibilidade deste efeito ser devido a um aumento da produção de GABA ou de marcadores relacionados não foi descartada. Foi também sugerido que alterações na população de GABAARs pós-sinápticos podem contribuir para a redução da atividade inibitória do GABA em neurónios principais durante o status epilepticus (SE). Efectivamente, no status epilepticus foi demonstrada uma perda rápida de GABAARs sinápticos que contém subunidades β e γ, enquanto que GABAARs extra-sinápticos que contém subunidades α e δ não sofrem alterações. Estas alterações na expressão superficial dos GABAAR estão correlacionadas com o decréscimo nas mIPSCs observadas após a indução de SE. Porém, os mecanismos responsáveis pela alteração na expressão superficial dos GABAARs no SE não estão ainda bem esclarecidos. O objetivo principal deste trabalho foi o estudo das alterações pós-sinápticas induzidas pelo SE ao nível das sinapses GABAérgicas. Para este propósito, implementámos um sistema in vitro simples que consiste em culturas de neurónios de hipocampo que foram expostos transitoriamente a uma solução desprovida de Mg2+ (SE). Observámos que o SE aumenta os níveis de [Ca2+]i através de um mecanismo dependente da ativação de recetores N-metil-D-aspartato (NMDA). Imagiologia de cálcio em células individuais, usando Fluo-4, permitiu observar diferentes padrões de variação de [Ca2+]i em função do período de exposição ao SE. Usando o mesmo modelo, verificámos um aumento da internalização de GABAARs, acompanhada por um decréscimo da fosforilação da subunidade β3 e uma clivagem da gefirina. Estes resultados indicam que a estabilidade sináptica dos GABAARs é comprometida pelo SE, durante e depois da crise. Mostrámos também que o 8 SE provoca uma redução na taxa de reciclagem dos recetores GABAAR. No conjunto, os nossos resultados demonstram que o SE provoca diversas alterações na sinapse GABAérgica, nomeadamente no tráfego dos recetores e na modulação do seu destino pós-endocitose, acompanhado por uma destabilização da homeostasia do cálcio. Esta dissertação oferece as bases para uma nova linha de investigação tendo por objetivo o estudo dos danos provocados pelo SE em neurónios de hipocampo. Uma melhor compreensão destes mecanismos moleculares pode permitir identificar novos alvos terapêuticos para o tratamento do SE e novas estratégias para prevenir o desenvolvimento de epilepsia crónica.Epilepsy is a chronic condition characterized by recurrent unprovoked seizures. The disease affects approximately 65 million people worldwide, from all ages and both genders. It is thought that neuronal hyper-excitability is one of the main permissive factors for the genesis and/or propagation of epileptic seizures. In the Central Nervous System (CNS) the balance between excitation and inhibition is mostly regulated by the excitatory neurotransmitter glutamate and the inhibitory γ-aminobutyric acid (GABA), respectively. The neurotransmitter GABA acts, in part, through activation of GABAA receptors (GABAAR), which are mostly composed of 2α-, 2β-, and 1γ2-subunits, and the accumulation of these receptors at inhibitory synapses is regulated by the scaffold protein gephyrin. GABAAR present a dynamic mobility between synaptic and extrasynaptic localization, and modulation of the interaction between GABAAR and gephyrin plays an important role in the control of fast GABAergic signalling strength. Total surface expression of GABAAR is controlled by their internalization at extrasynaptic sites, in addition to post-internalization sorting mechanisms which determine the rate of recycling. Single and recurrent seizures lead to a dysregulation of GABAergic synapses at different levels, but the mechanisms involved are still not fully understood. Sprouting of GABAergic neurons may account for the observed persistence or increase in labelling of GABAergic axons and terminals in human temporal lobe epilepsy and related animal models. However, the possible contribution from an increased expression of GABA or related markers in other neurons was not ruled out. Alterations in the population of postsynaptic GABAAR were also suggested to partly contribute to the reduction of GABA-mediated inhibition of principal neurons in status epilepticus (SE). SE was shown to trigger a rapid loss of synaptic GABAAR containing β and γ subunits, while extrasynaptic receptors containing α and δ subunits remain unaffected. These alterations in the surface expression of the receptors directly link the decrease in the miniature inhibitory post-synaptic currents observed after induction of SE with the selective internalization of synaptic GABAAR containing β and γ subunits. However, the mechanisms underlying the effects of SE on the surface expression of GABAAR is not fully elucidated. The main objective of this work was to further investigate the SE-induced post-synaptic alterations in GABAergic synapses. For this purpose we implemented a simple in vitro system consisting in cultured hippocampal neurons, which were exposed transiently to a solution lacking Mg2+ (status epilepticus; SE). We observed that SE increases the [Ca2+]i by a mechanism dependent on the activation of N-methyl-D-aspartate receptors. However, single cell calcium imaging with Fluo-4 showed different patterns of [Ca2+]i, which were also determined by the duration of the SE period. Using the same experimental approach we found an enhanced internalization of GABAARs which was accompanied by a decrease in the phosphorylation of the β3 subunit and a cleavage of gephyrin. Together, these results indicate that GABAAR synaptic stability is compromised during and after SE, and additional experiments showed a reduction in the rate of receptor recycling in hippocampal neurons subjected to SE. Our results demonstrate that SE evokes short- and long-term alterations in GABAergic synapses, namely in receptor trafficking and in their post-endocytotic sorting, accompanied by a disruption of calcium homeostasis. This work sets the basis 10 for further studies on the mechanisms underlying the SE-evoked alterations in hippocampal neurons. A better understanding of these mechanisms may provide new targets for the therapy of SE and strategies for preventing the development of chronic epileps

Species Composition of Termites (Isoptera) in Different Cerrado Vegetation Physiognomies

Little is known about the termite fauna of the different vegetation physiognomies in the Cerrado biome. It is suggested that the species compositions in grassland and savanna areas are closely related to each other, and quite distinct from those of forests. This study compared the species composition from five different physiognomies of Cerrado, and tested the hypothesis that the termite faunas of savannas and grasslands form a distinct group from that of forests. The study was conducted in the Parque Estadual da Serra de Jaraguá, state of Goiás, Brazil. Termites were sampled from two physiognomies of savanna, one natural grassland, one pasture, and one gallery forest. A transect with 10 parcels of 5x2 m was established in each physiognomy. The relative abundance was inferred by the number of encounters, termites were classified in feeding guilds, and the dissimilarity in the species composition between the physiognomies was calculated. A total of 219 encounters, of 42 species of two families were recorded. The most abundant feeding guilds were the humivores (98) and xylophages (55). The physiognomies with the largest number of species were rupestrian cerrado (23 species) and cerrado sensu stricto (21). The physiognomies had a similar species composition (less than 55% dissimilarity), mainly the natural open areas. The hypothesis of a distinct fauna of termites in forest vegetation was refuted. The termite fauna of gallery forest is very different from that of pasture, but most species also occur in natural open areas. The impact of pasture on the diversity and composition of termites seems to be significant, but the impact is even greater on the proportion of the feeding guilds, reducing the proportion of xylophages and intermediates

Key to the soldiers of Angularitermes Emerson with a new species from Brazilian Amazonia (Isoptera: Termitidae: Nasutitermitinae)

An identification key based on characters of the soldier caste is provided for species of Angularitermes. Soldiers of previously described species in the genus, A. clypeatus, A. nasutissimus, A. orestes, A. pinocchio and A. tiguassu, are illustrated along with a new species, Angularitermes coninasus, n. sp., that is described and illustrated from soldier and worker castes. Samples of the new species were collected from epigeal nests at the Brazilian Amazon rainforest. The soldier of A. coninasus, n. sp. is distinguished from its congeners by having a short conical frontal tube, much wider at its base.Fil: Carrijo, Tiago F.. Universidade de São Paulo; BrasilFil: Rocha, Mauricio M.. Universidade de São Paulo; BrasilFil: Cuezzo, Adriana Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto Superior de Entomología; ArgentinaFil: Cancello, Eliana M.. Universidade de São Paulo; Brasi

Termite diversity in the Abobral region of the Pantanal wetland complex, Brazil

This is the first termite survey using standard protocols in the Abobral region of the Pantanal complex of South America. Abobral, which is primarily composed of four physiognomies: 1) campo, annually flooded grassland; 2) capão, which are islands of semi-deciduous forests; 3) carandazal, annually flooded vegetation composed of a native palm; and 4) paratudal, annually flooded savanna vegetation. Ten species of termites were sampled in the capões, three in the grasslands, two in the paratudal and no species in the carandazal. The diversity of termites in the Abobral Pantanal is concentrated in the capões, which stay above water level during the flood season. In the others physiognomies of the Abobral, the termite fauna is poor. The species composition of termites of the Abobral Pantanal seems to be more related to the Cerrado and Chaco faunas than to the Amazonia and Atlantic Forest faunas

CISTACANTOS DE GIGANTORHYNCHUS ECHINODISCUS (ACANTHOCEPHALA, GIGANTORHYNCHIDAE), EN TERMITAS NEOTROPICALES (ISOPTERA, TERMITIDAE)

Specimens of Labiotermes emersoni (Araujo, 1954) and Orthognathotermes heberi Raw & Egler, 1985, were collected at Parque Nacional da Serra da Canastra, State of Minas Gerais, Brazil. Soldiers of the two species were suspected to carry larval acanthocephalan parasites due to different sizes and shape of their heads and because some specimens had a conspicuous, cylindrical, whitish 'body' in the hemocoel, around the digestive tract in the abdomen. The termites showed shape alteration and light pigmentation dystrophy of the heads induced by the larval acanthocephalans. These alterations were documented photographically and the cystacanths described. The encysted juveniles removed from the hemocoel of infected soldier termites and processed accordingly, were determined as Gigantorhynchus echinodiscus (Diesing, 1851). The proboscis had the typical cylindrical shape and the characteristic two distal circles of large hooks (6+12), covered with small, almost rootless spines, and a very short neck. This is the first record from Brazil of any species of termites infected with acanthocephalans of the genus Gigantorhynchus Hamann, 1892 and the first record of G. echinodiscus cystacanths infecting the intermediate host.Los especímenes de Labiotermes emersoni (Araujo, 1954) y Orthognathotermes heberi Raw & Egler, 1985, se colectaron en el Parque Nacional de Serra da Canastra, Estado de Minas Gerais, Brasil. Se sospechaba que soldados de las dos especies eran portadores de larvas de acantocéfalos parásitos debido a diferentes tamaños y formas de la cabeza, además de un “cuerpo” blanquecino, cilíndrico visible en el hemocele de algunos ejemplares, alrededor del tubo digestivo en el abdomen. Los termitas mostraron alteración de forma y leve distrofia de pigmentación en sus cabezas inducidas por los acantocéfalos larvales. Estas alteraciones se documentaron fotográficamente y se describen los cistacantos. Las formas juveniles enquistadas retiradas del hemocele de soldados infectados se identificaron como Gigantorhynchus echinodiscus (Diesing, 1851). Los probóscides tenían la típica forma cilíndrica y los característicos dos círculos distales de grandes ganchos (6+12), cubiertos de pequenas espinas, casi sin raíces y un cuello muy corto. Este es el primer registro de dos especies de termitas infectadas por acantocéfalos del género Gigantorhynchus Hamann, 1892 y el primero registro de cistacantos de G. echinodiscus infectando el hospedero intermediário

Overview of the Morphology of Neotropical Termite Workers: History and Practice

This contribution deals with the worker caste of the Neotropical termite fauna. It is a compilation of present knowledge about the morphology of pseudergates and workers, including the literature discussing the origin and evolution of this caste, the terminology used in the different taxonomic groups, and the techniques used to study these individuals, especially examination of the gut, mandibles, legs, and nota. In order to assist in identifying workers, it includes a key for the families that occur in the Neotropical Region and a characterization of workers of all families, especially the subfamilies of Termitidae, with descriptions and illustrations of diagnostic morphological features of genera. We point out advances and gaps in knowledge, as well as directions for future research