Uptake and intracellular distribution of lanthanum

The present investigation of the cellular distribution of lanthanum was undertaken in order to control the validity of the "Lanthanum method" used for the study of the cell calcium compartments. The presence of lanthanum was evaluated in the isolated guinea-pig heart and its subcellular fractions perfused with a lanthanum-containing Tyrode solution. Lanthanum was determined by instrumental neutron activation analysis. Under the adopted experimental conditions (30-min incubation in the presence of 12.5 microM lanthanum), lanthanum is carried across the cell membrane and is taken up by subcellular organelles. These results confirm the limited validity of investigations based on of the "Lanthanum method".     

Experimental muscular amebiasis in hamsters as a biological model.

Trophozoites of Entamoeba histolytica maintained in vitro in Pavlova's medium were inoculated by deep intramuscular injection into the proximal left hindleg of hamsters. Thioglycollate medium was utilized as a successful vehicle to induce the infection. The invasion of the muscular tissue by the vegetative forms caused the formation of abscesses with great destruction of muscular fibers. The lesions were limited to the muscular tissue of the femoral area. The number of trophozoites, the medium of thioglycollate as a vehicle, the volume of the inoculum and the trauma caused by the needle were important elements in the evolution of the muscular amebic abscesses. A limited trial of the amebicidal activity of metronidazole utilizing the amebic intramuscular infection was also performed.     

Trypanosoma cruzi: ultrastructural, cytochemical and freeze-fracture studies of protein uptake.

Epimastigotes and trypomastigotes of Trypanosoma cruzi, obtained from liquid cultures, have vesicles and multivesicular structures in their cytoplasm. Horseradish peroxidase (HRP) was used as a tracer to study the uptake of protein by these two forms. In epimastogotes HRP is ingested by a process of pinocytosis which occurs through the cytostome. Trypomastigotes do not have a cytostome, and pinocytosis occurs through the flagellar pocket region. The pinocytotic vesicles can fuse with each other to form large multivesicular structures that are more abundant in epimastigotes than in trypomastigotes. The cell membrane as well as the membranes of the pinocytotic vesicles and the large multivesicular structure have carbohydrates, as detected by the periodic acid-thiosemicarbazide-silver proteinate technique. Intramembranous particles were observed by using the freeze-fracture technique. The cell membrane has many particles, whereas the membranes of the vesicles and multivesicular structure have few or no particles.     

Trypanosoma cruzi high infectivity in vitro is related to cardiac lesions during long-term infection in Beagle dogs

Trypanosoma cruzi is a hemoflagelate parasite associated with heart dysfunctions causing serious problems in Central and South America. Beagle dogs develop the symptoms of Chagas disease in humans, and could be an important experimental model for better understanding the immunopathogenic mechanisms involved in the chagasic infection. In the present study we investigated the relation among biological factors inherent to the parasite (trypomastigote polymorphism and in vitro infectivity) and immunoglobulin production, inflammation, and fibrosis in the heart of Beagle dogs infected with either T. cruzi Y or Berenice-78 strains. In vitro infectivity of Vero cells as well as the extension of cardiac lesions in infected Beagle was higher for Y strain when compared to Berenice-78 strain. These data suggested that in vitro infectivity assays may correlate with pathogenicity in vivo. In fact, animals infected with Y strain, which shows prevalence of slender forms and high infectivity in vitro, presented cardiomegaly, inflammation, and fibrosis in heart area. Concerning the immunoglobulin production, no statistically significant difference was observed for IgA, IgM or IgG levels among T. cruzi infected animals. However, IgA together IgM levels have shown to be a good marker for the acute phase of Chagas disease.     

Synthesis and trypanocidal activity of ent-kaurane glycosides

Novel ent-kaurane glucosides were synthezised by a Koenigs-Knorr reaction between C17 and C19 alcohols derived from kaurenoic acid and 2,3,4,6-tetra-O-acetyl-glucopyranosyl bromide, followed by the hydrolysis of the acetates. Main products were assayed in vitro and in vivo against blood trypomastigote forms of Trypanosoma cruzi, the aetiological agent of Chagas' disease (American trypanosomiasis). The results allowed to establish structure-activity relationships among these derivatives, as well as pointed out the C19-methylester-C17-O-glucoside as a potential trypanocidal agent, whose trypanocidal profile was shown to be comparable to those of gentian violet and benznidazole.     

Congenital facial palsy and emotion processing: The case of Moebius syndrome

According to the Darwinian perspective, facial expressions of emotions evolved to quickly communicate emotional states and would serve adaptive functions that promote social interactions. Embodied cognition theories suggest that we understand others' emotions by reproducing the perceived expression in our own facial musculature (facial mimicry) and the mere observation of a facial expression can evoke the corresponding emotion in the perceivers. Consequently, the inability to form facial expressions would affect the experience of emotional understanding. In this review, we aimed at providing account on the link between the lack of emotion production and the mechanisms of emotion processing. We address this issue by taking into account Moebius syndrome, a rare neurological disorder that primarily affects the muscles controlling facial expressions. Individuals with Moebius syndrome are born with facial paralysis and inability to form facial expressions. This makes them the ideal population to study whether facial mimicry is necessary for emotion understanding. Here, we discuss behavioral ambiguous/mixed results on emotion recognition deficits in Moebius syndrome suggesting the need to investigate further aspects of emotional processing such as the physiological responses associated with the emotional experience during developmental age.     

Paleoclimatic constraints on the CO2 atmospheric retention factor

Once CO₂ is emitted into the atmosphere, it is gradually absorbed by natural carbon sinks. Its airborne fraction changes as a function of time depending on the sequestering performance of the sinks, in particular on their characteristic times, as reproduced by carbon cycle models. It is accepted that even after a time of the order of several thousands of years the atmospheric concentration will not return to its original value prior to the CO₂ injection. The fraction of the injected CO₂ amount that remains in the atmosphere for many thousands of years is measured by the atmospheric retention factor (ARF). The knowledge of this parameter is of great importance to accurately project both CO₂ concentration and temperature changes in the next decades and centuries. However, current ARF estimates span a broad range from ~10 to ~30 %, clustering on average around ~20 %. Here we employ two new approaches that allow us to constrain the ARF value. The first method is based on the paleoclimatic information about the coupling between CO₂ and temperature changes during the last glacial-to-interglacial transition. The second approach takes advantage of the CO₂ concentration changes, that are detectable in the paleoclimatic records of the last centuries, in response to comet-induced periodic cooling episodes. We find ARF estimates of 18 and 23 %, respectively, from the two approaches. The present results confirm that the ARF is likely to be around 20 %, in agreement with pre-existing estimates.     

An alternative approach to evaluating the intraspecific genetic variability of parasites

Analysis of DNA polymorphisms provides important information for the molecular characterization of parasite strains and clones. Because we still know little about the genomes of parasites, such analysis has to rely on methods applicable to any eukaryotic genome, such as DNA fingerprinting with multilocal minisatellite probes and the polymerase chain reaction (PCR)-based random amplified polymorphic DNA technique (RAPD). However, DNA fingerprinting is cumbersome and needs large amounts of parasite DNA, and RAPD can exhibit low reproducibility and spurious bands, both of which appear to be related to the low stringency of the PCR procedure. Riva Oliveira, Andréa Macedo, Egler Chiari and Sérgio Pena here evaluate the applicability to parasites of a technique described two years ago called simple sequence repeat-anchored PCR amplification (SSR-PCR), in which a single primer is needed [the (CA)(8)RY primer] and highstringency conditions are applied.     

Macroreticulate buffers: a novel approach to pH control in living systems.

It is possible to control the pH of growing living systems in vitro by adding, to the growth media, macroreticulate buffers, i.e. amphoteric resins made with buffering and titrant groups simultaneously affixed to the matrix. Such beads possess a very precise isoelectric point (pI) and are able to maintain the solutions' pH close to their pI values for extended growth periods. These pearls are made of a neutral polyacrylamide backbone containing up to 200 mM grafted weak acrylamido acids and bases. It is possible to produce such buffers with any desired pH value in the pH 2.5-11 scale. An example is given of conditioning the pH of endive plants grown hydroponically.     

miR‐181a/b control the assembly of visual circuitry by regulating retinal axon specification and growth

Connectivity and function of neuronal circuitry require the correct specification and growth of axons and dendrites. Here, we identify the microRNAs miR‐181a and miR‐181b as key regulators of retinal axon specification and growth. Loss of miR‐181a/b in medaka fish (Oryzias latipes) failed to consolidate amacrine cell processes into axons and delayed the growth of retinal ganglion cell (RGC) axons. These alterations were accompanied by defects in visual connectivity and function. We demonstrated that miR‐181a/b exert these actions through negative modulation of MAPK/ERK signaling that in turn leads to RhoA reduction and proper neuritogenesis in both amacrine cells and RGCs via local cytoskeletal rearrangement. Our results identify a new pathway for axon specification and growth unraveling a crucial role of miR‐181a/b in the proper establishment of visual system connectivity and function. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 75: 1252–1267, 2015