Trypanosoma cruzi: The effects of zinc supplementation in the immune response during the course of experimental disease

Zinc is an essential nutritional component required for normal development and maintenance of immune functions. The possible effects of zinc in upregulating the host immune response during the acute and chronic phases of experimental Chagas’ disease were evaluated. In young, infected and Zn-supplemented animals, higher concentrations of IFN-γ and NO were observed. During the chronic phase, decreased concentrations of NO and IFN-γ were found for older infected animals that received Zn supplementation. For young animals, hearts from Zn-supplemented groups displayed reduced inflammatory infiltrate, heart weight and number of amastigote burdens. For older, infected and Zn-supplemented animals amastigote nests were absent with reduced inflammatory cell infiltrate. This study identifies a potentially novel therapeutic approach that could control the parasite load during acute phase of disease, consequently preventing the deleterious, parasite-elicited responses observed during chronic phase.     

The Vesicular Acetylcholine Transporter Is Required for Neuromuscular Development and Function

The vesicular acetylcholine (ACh) transporter (VAChT) mediates ACh storage by synaptic vesicles. However, the VAChT-independent release of ACh is believed to be important during development. Here we generated VAChT knockout mice and tested the physiological relevance of the VAChT-independent release of ACh. Homozygous VAChT knockout mice died shortly after birth, indicating that VAChT-mediated storage of ACh is essential for life. Indeed, synaptosomes obtained from brains of homozygous knockouts were incapable of releasing ACh in response to depolarization. Surprisingly, electrophysiological recordings at the skeletal-neuromuscular junction show that VAChT knockout mice present spontaneous miniature end-plate potentials with reduced amplitude and frequency, which are likely the result of a passive transport of ACh into synaptic vesicles. Interestingly, VAChT knockouts exhibit substantial increases in amounts of choline acetyltransferase, high-affinity choline transporter, and ACh. However, the development of the neuromuscular junction in these mice is severely affected. Mutant VAChT mice show increases in motoneuron and nerve terminal numbers. End plates are large, nerves exhibit abnormal sprouting, and muscle is necrotic. The abnormalities are similar to those of mice that cannot synthesize ACh due to a lack of choline acetyltransferase. Our results indicate that VAChT is essential to the normal development of motor neurons and the release of ACh.Cholinergic neurotransmission has key functions in life, as it regulates several central and peripheral nervous system outputs. Acetylcholine (ACh) is synthesized in the cytoplasm by the enzyme choline acetyltransferase (ChAT) (16). Choline supplied by the high-affinity choline transporter (CHT1) is required to maintain ACh synthesis (52). A lack of ChAT (4, 35) or the high-affinity choline transporter (21) in genetically modified mice is incompatible with life. ACh plays an important role in wiring the neuromuscular junction (NMJ) during development (38, 43). Embryonic synthesis of ACh is fundamental for the development of proper nerve-muscle patterning at the mammalian NMJ, as ChAT-null mice present aberrant nicotinic ACh receptor (nAChR) localization and increased motoneuron (MN) survival, axonal sprouting, and branching (4, 35).The vesicular ACh transporter (VAChT) exchanges cytoplasmic ACh for two vesicular protons (37, 41). Previously reported electrophysiological studies showed that quantal size is decreased by vesamicol, an inhibitor of VAChT, but only in nerve terminals that have been electrically stimulated (19, 59, 60, 63). VAChT overexpression in developing Xenopus MNs increases both the size and frequency of miniature-end-plate currents (54). In Caenorhabditis elegans, mutations in VAChT affect behavior (65). Moreover, a decrease in VAChT expression has functional consequences for mammals, as mutant mice with a 70% reduction in the expression levels of this transporter (VAChT knockdown [KD^HOM] mice) are myasthenic and have cognitive deficits (47). Hence, vesicular transport activity is rate limiting for neurotransmission “in vivo” (18, 47).Exocytosis of synaptic vesicle contents is the predominant mechanism for the regulated secretion of neurotransmitters (55). However, alternative mechanisms of secretion have been proposed (20, 56, 61). Quantal ACh release, comparable to that seen in developing nerve terminals, has been detected in myocytes and fibroblasts in culture, which presumably do not express VAChT (14, 24). More recently, it was found that the correct targeting of Drosophila photoreceptor axons is disrupted in flies with null mutations in ChAT (64). Remarkably, the inactivation of VAChT did not produce the same result (64). The result suggests that the release of ACh during development is not dependent on VAChT, perhaps because it is nonvesicular or because vesicular storage can occur without VAChT.To test if the VAChT-independent secretion of ACh has any physiological role in the mammalian nervous system, we generated a mouse line in which the VAChT gene is deleted. These mice lack the stimulated release of ACh from synaptosomes, die after birth, and show several alterations in neuromuscular wiring consistent with a severe decrease in the cholinergic input to muscles during development. These experiments indicate that VAChT has an important role in maintaining activity-dependent ACh release that supports life and the correct patterning of innervation at the NMJ.     

Evolutionarily conserved proteins MnmE and GidA catalyze the formation of two methyluridine derivatives at tRNA wobble positions

The wobble uridine of certain bacterial and mitochondrial tRNAs is modified, at position 5, through an unknown reaction pathway that utilizes the evolutionarily conserved MnmE and GidA proteins. The resulting modification (a methyluridine derivative) plays a critical role in decoding NNG/A codons and reading frame maintenance during mRNA translation. The lack of this tRNA modification produces a pleiotropic phenotype in bacteria and has been associated with mitochondrial encephalomyopathies in humans. In this work, we use in vitro and in vivo approaches to characterize the enzymatic pathway controlled by the Escherichia coli MnmE•GidA complex. Surprisingly, this complex catalyzes two different GTP- and FAD-dependent reactions, which produce 5-aminomethyluridine and 5-carboxymethylamino-methyluridine using ammonium and glycine, respectively, as substrates. In both reactions, methylene-tetrahydrofolate is the most probable source to form the C5-methylene moiety, whereas NADH is dispensable in vitro unless FAD levels are limiting. Our results allow us to reformulate the bacterial MnmE•GidA dependent pathway and propose a novel mechanism for the modification reactions performed by the MnmE and GidA family proteins.     

Antiplasmodial benzophenones from the trunk latex of Moronobea coccinea (Clusiaceae)

In an effort to find antimalarial drugs, a systematic in vitro evaluation on a chloroquine-resistant strain of Plasmodium falciparum (FcB1) was undertaken on sixty plant extracts collected in French Guiana. The methanol extract obtained from the latex of Moronobea coccinea exhibited a strong antiplasmodial activity (95% at 10 μg/ml). The phytochemical investigation of this extract led to the isolation of eleven polycyclic polyprenylated acylphloroglucinols (PPAPs), from which eight showed potent antiplasmodial activity with IC50 ranged from 3.3 μM to 37.2 μM.     

Low-temperature effect on enzyme activities involved in sucrose–starch partitioning in salt-stressed and salt-acclimated cotyledons of quinoa (Chenopodium quinoa Willd.) seedlings

The effect of low temperature on growth, sucrose–starch partitioning and related enzymes in salt-stressed and salt-acclimated cotyledons of quinoa (Chenopodium quinoa Willd.) was studied. The growth of cotyledons and growing axes in seedlings grown at 25/20 °C (light/dark) and shifted to 5/5 °C was lower than in those only growing at 25/20 °C (unstressed). However, there were no significant differences between low-temperature control and salt-treated seedlings. The higher activities of sucrose phosphate synthase (SPS, EC 2.4.1.14) and soluble acid invertase (acid INV, EC 3.2.1.25) were observed in salt-stressed cotyledons; however, the highest acid INV activity was observed in unstressed cotyledons. ADP-glucose pyrophosphorylase (ADP-GPPase, EC 2.7.7.27) was higher in unstressed cotyledons than in stressed ones. However, between 0 and 4 days the highest value was observed in salt-stressed cotyledons. The lowest value of ADP-GPPase was observed in salt-acclimated cotyledons. Low temperature also affected sucrose synthase (SuSy, EC 2.4.1.13) activity in salt-treated cotyledons. Sucrose and glucose were higher in salt-stressed cotyledons, but fructose was essentially higher in low-temperature control. Starch was higher in low-temperature control; however, the highest content was observed at 0 day in salt-acclimated cotyledons. Results demonstrated that low temperature induces different responses on sucrose–starch partitioning in salt-stressed and salt-acclimated cotyledons. Data also suggest that in salt-treated cotyledons source–sink relations (SSR) are changed in order to supply soluble sugars and proline for the osmotic adjustment. Relationships between starch formation and SuSy activity are also discussed.     

Mouse-adapted scrapie infection of SN56 cells: greater efficiency with microsome-associated versus purified PrP-res

The process by which transmissible spongiform encephalopathy agents, or prions, infect cells is unknown. We employed a new differentiable cell line (SN56) susceptible to infection with three mouse-adapted scrapie strains to gain insight into the cellular infection process. The effect of disease-associated PrP (PrP-res) association with microsomal membranes on infection efficiency was examined by comparing sustained PrP-res production in cells treated with either scrapie brain microsomes or purified, detergent-extracted PrP-res. When normalized for quantity of input PrP-res, scrapie brain microsomes induced dramatically enhanced persistent PrP-res formation compared to purified PrP-res. Infected SN56 cells released low levels of PrP-res into the culture supernatant, which also efficiently initiated infection in recipient cells. Interestingly, microsomes labeled with a fluorescent marker were internalized by SN56 cells in small vesicles, which were subsequently found in neuritic processes. When bound to culture wells to reduce internalization during the infection process, scrapie microsomes induced less long-term PrP-res production than suspended microsomes. Long-term differentiation of infected SN56 cells was accompanied by a decrease in PrP-res formation. Our observations provide evidence that infection of cells is aided by the association of PrP-res with membranes and/or other microsomal constituents.     

Coronary Microvascular Disease in Chronic Chagas Cardiomyopathy Including an Overview on History,Pathology, and Other Proposed Pathogenic Mechanisms

This review focuses on the short and bewildered history of Brazilian scientist Carlos Chagas''s discovery and subsequent developments, the anatomopathological features of chronic Chagas cardiomyopathy (CCC), an overview on the controversies surrounding theories concerning its pathogenesis, and studies that support the microvascular hypothesis to further explain the pathological features and clinical course of CCC. It is our belief that knowledge of this particular and remarkable cardiomyopathy will shed light not only on the microvascular involvement of its pathogenesis, but also on the pathogenetic processes of other cardiomyopathies, which will hopefully provide a better understanding of the various changes that may lead to an end-stage heart disease with similar features. This review is written to celebrate the 100th anniversary of the discovery of Chagas disease.     

Differences in sperm morphology in foam‐nesting leptodactyline frogs (Anura,Leptodactylidae)

Sperm morphology is diverse among vertebrates and is influenced by the reproductive strategies adopted by species. In anurans, sperm morphology is associated with reproductive modes and mating systems. Here, we describe the sperm morphology of 11 frog species in the genus Leptodactylus and that of Lithodytes lineatus and discuss the relationship between sperm morphology and species' mating systems. We observed two distinct sperm morphotypes among the leptodactyline species, which differed mostly in head morphology. Type I sperm had triangular head, discrete acrosome vesicle with posterior margin not clearly visible; type II sperm had elongated head, clear acrosomal vesicle with posterior margin clearly visible. These sperm types do not seem to be associated with phylogeny; instead, type II sperm was observed in all polyandrous species analysed and in species with evidences of polyandry. Moreover, sperm of all species presented tail with undulating membrane connected to the axial fibre. We suggest that differences in sperm morphology might be associated with sperm competition to what polyandrous species are subjected. However, natural history observations on polyandrous mating in some species presenting type II sperm and phylogenetic comparative studies are need to elucidate the role of mating systems in the evolution of sperm morphology in leptodactylines.     

<Emphasis Type="Italic">Pteris exigua</Emphasis> (Pteridaceae), a new endemic species from Tucumano-Boliviano forests in northwestern Argentina

Pteris exigua, an endemic species from the Tucumano-Boliviano forests, northwestern Argentina, is described and distinguished from similar species of Pteris that occur in this region.