Domestic and peridomestic transmission of American cutaneous leishmaniasis: changing epidemiological patterns present new control opportunities

Predictions that deforestation would reduce American cutaneous leishmaniasis incidence have proved incorrect. Presentations at a recent international workshop, instead, demonstrated frequent domestication of transmission throughout Latin America. While posing new threats, this process also increases the effectiveness of vector control in and around houses. New approaches for sand fly control and effective targeting of resources are reviewed.     

Detection of aflatoxin-contaminated grain by three granivorous bird species

Supplemental feeding of game species and the use of backyard feeders to attract avian wildlife are common practices throughout the United States. However, these activities may expose wildlife to aflatoxins. We tested the hypothesis that wild birds would avoid consuming aflatoxin-contaminated feed. Individual northern bobwhites (Colinus virginianus), white-winged doves (Zenaida asiatica), and green jays (Cyanocorax yncas) were presented with feeders that had four compartments, which contained milo that was contaminated with aflatoxin levels of 0, 100, 500, and 1,000 microg/kg, respectively. Feed remaining was weighed at 6, 12, 18, 24, 36, 48, 60, and 72 hr after the initiation of the trial. White-winged doves and northern bobwhites did not avoid contaminated feed. However, green jays selected against aflatoxin-tainted grain. Because white-winged doves and northern bobwhites did not avoid contaminated feed, the risk of exposure to this potentially hazardous toxin exists for these species.     

Chiral aggregates and asymmetric induction of the reduction of prochiral ketones

The aim of this work was to establish structure-reactivity relationships between chiral aggregates (micelles, vesicles, and "pseudo-micelles" of amphiphilic dendrimers) and asymmetric induction. In water, micelles or vesicles formed with sugar-headed surfactants gave less than 10% ee in the reduction of prochiral ketones by NaBH(4), in contrast with dendrimers bearing the same types of sugar moieties, which gave more than 50% ee under the same reaction conditions. Moreover, in the presence of neoglycodendrimers in THF we have been able to improve reduction of prochiral ketones to give very high stereoselectivity, near 100% in many cases. Comparison of these results suggests that to improve high stereoselectivity it is necessary to work with rigid, well-organized colloidal objects. Copyright 2000 Wiley-Liss, Inc.     

Mice expressing the alpha(1B)-adrenergic receptor induces a synucleinopathy with excessive tyrosine nitration but decreased phosphorylation

We had previously reported that systemic overexpression of the alpha(1B)-adrenergic receptor (AR) in a transgenic mouse induced a neurodegenerative disease that resembled the parkinsonian-like syndrome called multiple system atrophy (MSA). We now report that our mouse model has cytoplasmic inclusion bodies that colocalize with oligodendrocytes and neurons, are positive for alpha-synuclein and ubiquitin, and therefore may be classified as a synucleinopathy. Alpha-synuclein monomers as well as multimers were present in brain extracts from both normal and transgenic mice. However, similar to human MSA and other synucleinopathies, transgenic mice showed an increase in abnormal aggregated forms of alpha-synuclein, which also increased its nitrated content with age. However, the same extracts displayed decreased phosphorylation of alpha-synuclein. Other traits particular to MSA such as Purkinje cell loss in the cerebellum and degeneration of the intermediolateral cell columns of the spinal cord also exist in our mouse model but differences still exist between them. Interestingly, long-term therapy with the alpha(1)-AR antagonist, terazosin, resulted in protection against the symptomatic as well as the neurodegeneration and alpha-synuclein inclusion body formation, suggesting that signaling of the alpha(1B)-AR is the cause of the pathology. We conclude that overexpression of the alpha(1B)-AR can cause a synucleinopathy similar to other parkinsonian syndromes.     

Evidence for a partial redundancy of the fibronectin-binding proteins for the transfer of mycoloyl residues onto the cell wall arabinogalactan termini of Mycobacterium tuberculosis

Mycobacterium tuberculosis produces a series of major secreted proteins, the fibronectin-binding proteins (Fbps), also known as the antigen 85 complex, that are believed to play an essential role in the pathogenesis of tuberculosis through their mycoloyltransferase activity required for maintaining the integrity of the bacterial cell envelope. Four different fbp genes are found in the genome of M. tuberculosis, but the reason for the existence of these Fbps sharing the same substrate specificity in vitro in mycobacteria is unknown. We have shown previously that, in the heterologous host, Corynebacterium glutamicum, FbpA, FbpB and FbpC can all add mycoloyl residues to the cell wall arabinogalactan and that, in M. tuberculosis, the cell wall mycoloylation decreases by 40% when fbpC is knocked out. To investigate whether the remaining 60% mycoloylation came from the activity of FbpA and/or FbpB, fbpA- and fbpB-inactivated mutant strains were biochemically characterized and compared with the previously studied fbpC-disrupted mutant. Unexpectedly, both mutants produced normally mycoloylated cell walls. Overproduction of FbpA, FbpB or FbpC, but not FbpD, in the fbpC-inactivated mutant strain of M. tuberculosis restored both the cell wall-linked mycolate defect and the outer cell envelope permeability barrier property. These results are consistent with all three enzymes being involved in cell wall mycoloylation and FbpC playing a more critical role than the others or, alternatively, FbpC is able to compensate for FbpA and FbpB in ways that these enzymes cannot compensate for FbpC, pointing to a partial redundancy of Fbps. In sharp contrast, FbpD does not appear to be an active mycoloyltransferase enzyme, as it cannot complement the fbpC-inactivated mutant. Most importantly, application of Smith degradation to the cell walls of transformants demonstrated that the multiple Fbp enzymes are redundant rather than specific for the various arabinogalactan mycoloylation regions. Neither FbpA nor FbpB attaches mycoloyl residues to specific sites but, like FbpC, each enzyme transfers mycoloyl residues onto the four sites present in the arabinogalactan non-reducing end hexaarabinosides.     

Effect of Cecropin B and a Synthetic Analogue on Propagation of Fish Viruses In Vitro

Abstract Cecropins and other natural antimicrobial peptides are widely distributed in animals from insects to mammals. These proteins have been shown to be major constituents of the innate immune systems of animals for nonspecific defense of the host against various bacteria and parasites. Therefore, exploitation of this natural innate defense system may lead to the development of effective methods for protecting fish from invasion by microbial pathogens. Recently, we have demonstrated that the introduction of cecropin transgenes into Japanese medaka (Oryzias latipes) conferred resistance to infection by fish bacterial pathogens. Aside from a few reports documenting the antiviral effect of antimicrobial peptides including cecropins against mammalian viruses, there is no evidence for the effect of these peptides against fish viruses. In this article we present results of in vitro characterization of native cecropin B and a synthetic analogue, CF17, against several important fish viral pathogens—namely, infectious hematopoietic necrosis virus (IHNV), viral hemorrhagic septicemia virus (VHSV), snakehead rhabdovirus (SHRV), and infectious pancreatic necrosis virus (IPNV). Upon coincubation of these peptides and viruses, the viral titers yielded in fish cells were reduced from several fold to 104-fold. Direct disruption of the viral envelope and disintegration of the viral capsids may be involved in the inhibition of viral replication by the peptides. Results of our studies demonstrate the potential of manipulating antimicrobial peptide genes by transgenesis to combat viral infection in fish.     

Manipulating PEPC levels in plants

This review examines the current understanding of the structural, functional and regulatory properties of C4 and C3 forms of higher plant phosphoenolpyruvate carboxylase. The emphasis is on the interactive metabolic and post-translational controls acting on the enzyme in the physiological context of C4 photosynthesis and the anaplerotic pathway. A brief overview is given concerning the recent developments of PEPC-based genetic engineering of C3 plants with the aim of improving photosynthetic performance in normal and limiting environmental conditions. So far, in spite of achieving a considerable increase in PEPC levels, more work needs to be done with respect to the correct dosage and location before that goal is reached. Some unpublished results on the transformation of maize with a sorghum C4 PEPC cDNA are also presented. They show that it is possible to increase photosynthetic PEPC levels in this C4 plant and that the modification in enzyme content has a pleiotropic physiological impact and, notably, an improved water use efficiency when water is limited.     

Recombinant antibodies against subcellular fractions used to track endogenous Golgi protein dynamics in vivo

Generation of specific antibodies against enriched subcellular fractions is a powerful strategy to identify and characterize cellular components. We show that recombinant antibodies can be selected in vitro by phage display against complex subcellular fractions, namely microtubule-binding proteins and Golgi stacks. This technique has allowed us to overcome many limitations of the classical animal-based approach and generate cell biology-compliant antibodies. In addition, we show that intracellular expression of GFP-tagged recombinant antibodies can reveal the dynamics of endogenous proteins in vivo . Endogenous Giantin is very static and outlines the Golgi in living cells. It accumulates neither onto Golgi-derived tubules upon Brefeldin A treatment before Golgi disappearance, nor onto de novo formed Golgi mini-stacks upon microtubule depolymerization, and remains instead on the 'old' pericentriolar Golgi. This suggests that, in contrast to other Golgi matrix proteins, endogenous Giantin is very stably associated with the Golgi and does not efficiently recycle to the ER. Altogether, we show that the antibody phage display technique represents an efficient alternative to rapidly generate versatile antibodies that represent new tools to study protein function.     

Recognition of the neural chemoattractant Netrin-1 by integrins alpha6beta4 and alpha3beta1 regulates epithelial cell adhesion and migration

Netrins, axon guidance cues in the CNS, have also been detected in epithelial tissues. In this study, using the embryonic pancreas as a model system, we show that Netrin-1 is expressed in a discrete population of epithelial cells, localizes to basal membranes, and specifically associates with elements of the extracellular matrix. We demonstrate that alpha6beta4 integrin mediates pancreatic epithelial cell adhesion to Netrin-1, whereas recruitment of alpha6beta4 and alpha3beta1 regulate the migration of CK19+/PDX1+ putative pancreatic progenitors on Netrin-1. These results provide evidence for the activation of epithelial cell adhesion and migration by a neural chemoattractant, and identify Netrin-1/integrin interactions as adhesive/guidance cues for epithelial cells.     

Beta 1-adrenergic receptor polymorphisms confer differential function and predisposition to heart failure

Catecholamines stimulate cardiac contractility through beta(1)-adrenergic receptors (beta(1)-ARs), which in humans are polymorphic at amino acid residue 389 (Arg/Gly). We used cardiac-targeted transgenesis in a mouse model to delineate mechanisms accounting for the association of Arg389 with human heart failure phenotypes. Hearts from young Arg389 mice had enhanced receptor function and contractility compared with Gly389 hearts. Older Arg389 mice displayed a phenotypic switch, with decreased beta-agonist signaling to adenylyl cyclase and decreased cardiac contractility compared with Gly 389 hearts. Arg389 hearts had abnormal expression of fetal and hypertrophy genes and calcium-cycling proteins, decreased adenylyl cyclase and G alpha(s) expression, and fibrosis with heart failure This phenotype was recapitulated in homozygous, end-stage, failing human hearts. In addition, hemodynamic responses to beta-receptor blockade were greater in Arg389 mice, and homozygosity for Arg389 was associated with improvement in ventricular function during carvedilol treatment in heart failure patients. Thus the human Arg389 variant predisposes to heart failure by instigating hyperactive signaling programs leading to depressed receptor coupling and ventricular dysfunction, and influences the therapeutic response to beta-receptor blockade.