Resumen Rhinella schneideri (o Bufo paracnemis), conocido popularmente en Brasil como sapo cururu, también se encuentra en otros países de América del Sur. Los efectos cardiovasculares de este veneno son ampliamente conocidos y recientemente se demostró que es capaz de afectar la unión neuromuscular en la preparación aislada de aves y ratones. En este trabajo, utilizamos microscopía electrónica de transmisión para investigar la ultraestructura de la terminación nerviosa motora y pliegues de unión postsináptica de preparaciones de nervio frénico-hemidiafragma incubadas durante 5 o 60 min con el extracto metanólico de R. schneideri (50 μg/mL). Además, se examinó el estado de los receptores de acetilcolina (AChR) mediante la ubicación de inmunofluorescencia de TRITC-α-bungarotoxina en la membrana de la placa terminal. Los resultados muestran que 5 min de incubación con el extracto de secreción de glándula disminuyeron significativamente (32 %) el número de vesículas sinápticas en el terminal del nervio motor, pero no disminuyeron la densidad electrónica en la parte superior de los pliegues de unión donde se concentran los receptores nicotínicos. Sin embargo, 60 min de incubación condujeron a una recarga significativa de los terminales nerviosos en las vesículas sinápticas, mientras que la inmunorreactividad del AChR no fue tan marcada como en el control y después de 5 min de incubación. Las fibras musculares estaban bien conservadas, pero los axones motores intramusculares no. Los hallazgos corroboraron los datos farmacológicos ya que la disminución en el número de vesículas sinápticas (5 min) seguida de recuperación (60 min) está de acuerdo con el aumento transitorio de la frecuencia de MEPPs, lo que significa una mayor liberación de neurotransmisores. Estos datos apoyan el modo de acción presináptico predominante de R. schneideri, pero no excluyen la posibilidad de una acción postsináptica secundaria dependiendo del tiempo en que la preparación esté expuesta al veneno.

Abstract Rhinella schneideri (or Bufo paracnemis), popularly known in Brazil as cururu toad, is also found in other countries in South America. The cardiovascular effects of this poison are largely known and recently was shown that it is capable to affect the neuromuscular junction on avian and mice isolated preparation. In this work, we used transmission electron microscopy to investigate the ultrastructure of the motor nerve terminal and postsynaptic junctional folds of phrenic nerve-hemidiaphragm preparations incubated for either 5 or 60 min with the methanolic extract of R. schneideri (50 µg/mL). In addition, the status of the acetylcholine receptors (AChR) was examined by TRITC-α-bungarotoxin immunofluorescence location at the endplate membrane. The results show that 5 min of incubation with the gland secretion extract significantly decreased (32 %) the number of synaptic vesicles into the motor nerve terminal, but did not decrease the electron density on the top of the junctional folds where nicotinic receptors are concentrated; however, 60 min of incubation led to significant nerve terminal reloading in synaptic vesicles whereas the AChR immunoreactivity was not as marked as in control and after 5 min incubation. Muscle fibers were well-preserved but intramuscular motor axons were not. The findings corroborated pharmacological data since the decrease in the number of synaptic vesicles (5 min) followed by recovery (60 min) is in accordance with the transient increase of MEPPs frequency meaning increased neurotransmitter release. These data support the predominant presynaptic mode of action of the R. schneideri, but do not exclude the possibility of a secondary postsynaptic action depending on the time the preparation is exposed to poison. Rev. Biol. Trop. 66(3): 1290-1297. Epub 2018 September 01.

The spermatogenesis of Piaractus mesopotamicus was investigated under light and transmission electron microscopy. The specimens were captured from their natural environment (Rio Miranda and Rio Aquidauana, Pantanal Matogrossense, Brazil) during April and September. The results were compared with the spermatogenic data of specimens under captivity condition. In both conditions, P. mesopotamicus presented the typical spermatogenesis pattern of the teleost fishes, showing no significative differences. The spermatozoon was classified as type I, which has a globular head without acrosome, a short middle piece and a long tail constituted only by the flagellum. This type of spermatozoon is considered the basic type in fishes.

A imunossupressão observada em micoses sistêmicas pode estar relacionada a danos nos órgãos linfóides primários. Assim, nosso laboratório tem estudado uma possível ação do Paracoccidioides brasiliensis sobre o timo de camundongos. Neste estudo, analisamos o timo de camundongos susceptíveis e resistentes ao fungo utilizando cepas de alta e baixa virulência. Todos os grupos apresentaram atrofia tímica, perda de delimitação corticomedular e aumento da taxa de apoptose. Entretanto, as alterações foram mais precoces e pronunciadas em camundongos inoculados com a cepa virulenta do fungo, sugerindo que a virulência fúngica pode estar diretamente ligada à atrofia tímica e indução de imunossupressão.

The immunosuppression observed in systemic mycosis can be related to primary lymphoid organs damage. Thus, our laboratory has studied the effects of the Paracoccidioides brasiliensis infection on the thymus of mice. Here, thymuses of susceptible and resistant mice were evaluated after inoculation with highly and slightly virulent isolates of the fungus. All groups presented thymic atrophy, loss of corticomedullary delimitation and increase of apoptotic index. However, mice inoculated with high virulent strain showed earlier and stronger alterations suggesting that thymic atrophy can be directly related to the fungal virulence and to the immunosuppression.

Resumo As bexigas natatorias do Hoplerythrinus unitaenitus (jeju), eritrinídeo de respiração aérea facultativa e do Osteoglossum bicirrhosum (aruanã), osteoglossídeo de respiração aquática, foram comparadas morfológica e histoquimicamente. No jeju, a bexiga tem função respiratória, enquanto no aruanã é um órgão hidrostático. Ambos são fisóstomos e a bexiga natatória é dividida em duas câmaras, cujas paredes são constituídas por três túnicas. Existem características morfológicas próprias de cada espécie, particularmente em relação à túnica interna: no jeju forma pregas aumentando assim a sua superfície; apresenta rico plexo capilar sub-epitelial e coxins musculares laterais. Os testes histoquímicos mostram que a bexiga natatória do jeju, contém mucopolissacárides, substâncias redutoras, lípides, colesterol e compostos afins: calciferol, íons férricos e proteínas. Há também fibras elásticas as quais estão em maior quantidade na porção anterior da câmara posterior. Com exceção das fibras elásticas, esses componentes localizam-se preferencialmente, no epitélio, lâmina própria e junto aos vasos sangüíneos, principalmente próximo aos coxins musculares. No aruanã, os testes para estas substâncias foram negativos, exceto alguns que se mostraram discretamente positivos no epitélio e a presença de fibras elásticas. Supõe-se que estes compostos químicos presentes no jeju tenham importância funcional na respiração desempenhada pela bexiga natatória.

Summary Morphological and histochemical comparisons were made between the swim-bladders of Hoplerythrinus unitaenitus (the "jeju"), a facultatively air breathing eritrinid fish, and Osteoglossum bicirrhosum (the "aruanã"), an osteoglossid fish which is restricted to aquatic respiration. In the "jeju", the swim-bladder has a respiratory function, while in the "aruanã" it is an hydrostatic organ. Both are physostomes, and the swim-bladder is divided into two chambers whose walls are made up of three enveloping membranes or mantles. There are morphological characteristics peculiar to each species, especially in the form of the mantles. In the "jeju" the mantle forms folds, which increase the surface area. The mantle also has a rich plexus of sub-epithelial capillaries and lateral muscular pads in this species. The histochemical tests show that the swim-bladder of the "jeju" contains mucopolysaccharides, reducing substances, lipids, cholesterol and the related compounds: calciferol, ferric ions, and proteins. There are also elastic fibers which are present in greater quantity in the anterior portion of the posterior chamber. With the exception of the elastic fibers, these components are usually located in the epithelium, the stripe itself, and near the blood vessels, especially near the muscular pads. In the "arunã" the tests for these substances were negative, except for a few which were discretely positive in the epithelium and in the presence of elastic fibers. It is suggested that the compounds found in the "jeju" have a function in the respiration carried out by the swim-bladder.

Resumo Os ovócitos de peixes teleósteos em fase pré-vitelogênica apresentam numerosos nucléolos localizados perifericamente no núcleo. Existem evidências morfológicas da passagem do material destes nucléolos para o citoplasma onde se associa a mitocôndrios e se dispersa, mantendo sempre a associação. Este material pode ser detectado no ovocito mesmo após o início da deposição de vitelo possivelmente vindo a constituir o plasma germinativo.

Summary The teleostean ovocytes in phase pre-vitelogenic show numerous nucleoli In the nucleus periphery. Morphological evidences indicate that the nucleolar material is transfered to the cytoplasm whese it associate with mitochondria. Later this dense material of nucleolar origin disperse in the cytoplasm always associated to the mitochondria. This material can be detected even after the yolk deposition and may constitute the ovocyte germ plasm.

Resumo O presente trabalho refere-se às diferenças infra-estruturais entre a bexiga natatória do jeju (teleósteo de respiração aérea facultativa) e do aruanã (teleósteo de respiração exclusivamente aquática ou branquial). Histologicamente, em ambos os casos, a parede da bexiga natatória se mostrou constituída por um epitélio, limitando a luz, com uma lâmina própria de tecido conjuntivo muito rico em colágeno, seguida de uma camada de musculatura lisa e uma adventícia. Os resultados sugerem que a adaptação à função respiratória na bexiga natatória do jeju refletem-se na diminuição da espessura da cobertura epitelial da câmara posterior, na presença desse epitélio de possíveis substâncias surfactantes que são eliminadas para a luz e na grande vascularização subepitelial.

Summary The present paper demonstrates the ultrastructural differences between the swimbladder of two teleostean fishes with different breathing behavior the jeju a facultative air breathing fish) and the aruanã (exclusively water breathing). Histologically both swimbladders are very similar. Their walls consist of an epithelium, its lamina propria, the muscular sheaths and the adventícia The results suggest that the respiratory adaptations of the jeju swimbladder are characterized by a decreased height of the epithelium in the posterior chamber, the presence of surfactants in the lumen and increased subepithelial vascularization.