Descripción: Some strains of Bacillus sphaericus are entomopathogenic to mosquito larvae, which transmit diseases, such as filariasis and malaria, affecting millions of people worldwide. This species is unable to use hexoses and pentoses as unique carbon sources, which was proposed to be due to the lack of glycolytic enzymes, such as 6-phosphofructokinase (PFK). In this study, PFK activity was detected and the pfk gene was cloned and sequenced. Furthermore, this gene was shown to be present in strains belonging to all the homology groups of this heterogeneous species, in which PFK activity was also detected. A careful sequence analysis revealed the conservation of different catalytic and regulatory residues, as well as the enzyme's phylogenetic affiliation with the family of allosteric ATP-PFK enzymes.

Descripción: Fil:Tigier, H.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Background: Detailed analysis of the dynamic interactions among biological, environmental, social, and economic factors that favour the spread of certain diseases is extremely useful for designing effective control strategies. Diseases like tuberculosis that kills somebody every 15 seconds in the world, require methods that take into account the disease dynamics to design truly efficient control and surveillance strategies. The usual and well established statistical approaches provide insights into the cause-effect relationships that favour disease transmission but they only estimate risk areas, spatial or temporal trends. Here we introduce a novel approach that allows figuring out the dynamical behaviour of the disease spreading. This information can subsequently be used to validate mathematical models of the dissemination process from which the underlying mechanisms that are responsible for this spreading could be inferred. Methodology/Principal Findings: The method presented here is based on the analysis of the spread of tuberculosis in a Brazilian endemic city during five consecutive years. The detailed analysis of the spatio-temporal correlation of the yearly geo-referenced data, using different characteristic times of the disease evolution, allowed us to trace the temporal path of the aetiological agent, to locate the sources of infection, and to characterize the dynamics of disease spreading. Consequently, the method also allowed for the identification of socio-economic factors that influence the process. Conclusions/Significance: The information obtained can contribute to more effective budget allocation, drug distribution and recruitment of human skilled resources, as well as guiding the design of vaccination programs. We propose that this novel strategy can also be applied to the evaluation of other diseases as well as other social processes. © 2010 Zorzenon dos Santos et al.

Descripción: A number of natural and synthetic substances are used in the treatment of immunological disorders. The immunosuppressive drugs are widely utilized in clinical treatments of autoimmune disorders, in the prevention of transplant rejection as well as in non-autoimmune diseases such as allergy. The design of immunosuppressive therapies is based on the control of the exacerbated immune response. The pathophysiologic mean of this concept is to modulate the action of mononuclear cells, being T cells the main targets. Immunosuppressive agents have different molecular targets, and an important drawback in their use is that they also inhibit the normal immune system response. Depending on their mode of action, immunosuppressive drugs can be classified in four different groups: antinflammatory drugs of the corticosteroid family, inhibitors of the calcineurin pathway, cytototoxic or antiproliferative drugs and specific antibodies. In this article, we focus on the molecular action of immunosuppressive drugs such as steroids, cyclosporine, tacrolimus, azathioprine, cyclophosphamide, sirolimus, mycophenolate mofetil, leflunomide and specific antibodies, providing data to characterize and improve the use of these agents.

Descripción: The deposition of fibrillar structures (amyloids) is characteristic of pathological conditions including Alzheimer's and Parkinson's diseases. The detection of protein deposits and the evaluation of their kinetics of aggregation are generally based on fluorescent probes such as thioflavin T and Congo red. In a search for improved fluorescence tools for studying amyloid formation, we explored the ability of N-arylaminonaphthalene sulfonate (NAS) derivatives to act as noncovalent probes of α-synuclein (AS) fibrillation, a process linked to Parkinson's disease and other neurodegenerative disorders. The compounds bound to fibrillar AS with micromolar Kds, and exhibited fluorescence enhancement, hyperchromism, and high anisotropy. We conclude that the probes experience a hydrophobic environment and/or restricted motion in a polar region. Time- and spectrally resolved emission intensity and anisotropy provided further information regarding structural features of the protein and the dynamics of solvent relaxation. The steady-state and time-resolved parameters changed during the course of aggregation. Compared with thioflavin T, NAS derivatives constitute more sensitive and versatile probes for AS aggregation, and in the case of bis-NAS detect oligomeric as well as fibrillar species. They can function in convenient, continuous assays, thereby providing useful tools for studying the mechanisms of amyloid formation and for high-throughput screening of factors inhibiting and/or reversing protein aggregation in neurodegenerative diseases. © 2008 by the Biophysical Society.

Descripción: Xanthan is the major exopolysaccharide secreted by Xanthomonas spp. Despite its diverse roles in bacterial pathogenesis of plants, little is known about the real implication of this molecule in Xanthomonas pathogenesis. In this study we show that in contrast to Xanthomonas campestris pv campestris strain 8004 (wild type), the xanthan minus mutant (strain 8397) and the mutant strain 8396, which is producing truncated xanthan, fail to cause disease in both Nicotiana benthamiana and Arabidopsis (Arabidopsis thaliana) plants. In contrast to wild type, 8397 and 8396 strains induce callose deposition in N. benthamiana and Arabidopsis plants. Interestingly, treatment with xanthan but not truncated xanthan, suppresses the accumulation of callose and enhances the susceptibility of both N. benthamiana and Arabidopsis plants to 8397 and 8396 mutant strains. Finally, in concordance, we also show that treatment with an inhibitor of callose deposition previous to infection induces susceptibility to 8397 and 8396 strains. Thus, xanthan suppression effect on callose deposition seems to be important for Xanthomonas infectivity. © 2006 American Society of Plant Biologists.

Descripción: The life cycle of Ascocotyle (Leighia) hadra n. sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei, collected from Los Ranchos stream, near Mercedes city, Buenos Aires Province, Argentina. Metacercariae were found encysted in the liver and mesentery of experimentally and naturally infected fishes Cnesterodon decemmaculatus and Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Ascocotyle (Leighia) mcintoshi Price 1936 as described by Leigh, 1974, differing in behavior and morphology of cercarial, metacercarial and adult stages.

Descripción: The Chagas disease or Tripanosomiasis Americana affects between 16 and 18 million people in endemic areas. This disease affects the beating rate of infected patients' cardiomyocytes. At the Molecular Biology of Chagas Disease Laboratory in Argentina the effect of isolated patient's serum antibodies is studied over rat cardiomyocyte cultures. In this work an image processing application to measure the beating rate of this culture over video sequences is presented. This work is organized as follows. Firstly, a preliminary analysis of the problem is introduced, isolating the main characteristics of the problem. Secondly, a Monte Carlo experiment is designed and used to evaluate the robustness and validity of the algorithm. Finally, an algorithm of order O(T(N log N + N)) for tracking cardiomyocyte membranes is presented, where T is the number of frames and N is the maximum area of the membrane. Its performance is compared against the standard beating rate measure method. © Springer-Verlag Berlin Heidelberg 2005.

Descripción: Glucocorticoids are potent regulators of the innate immune response, and alteration in this inhibitory feedback has detrimental consequences for the neural tissue. This study profiled and investigated functionally candidate genes mediating this switch between cell survival and death during an acute inflammatory reaction subsequent to the absence of glucocorticoid signaling. Oligonucleotide microarray analysis revealed that following lipopolysaccharide (LPS) intracerebral administration at striatum level, more modulated genes presented transcription impairment than exacerbation upon glucocorticoid receptor blockage. Among impaired genes we identified ceruloplasmin (Cp), which plays a key role in iron metabolism and is implicated in a neurodegenative disease. Microglial and endothelial induction of Cp is a natural neuroprotective mechanism during inflammation, because Cp-deficient mice exhibited increased iron accumulation and demyelination when exposed to LPS and neurovascular reactivity to pneumococcal meningitis. This study has identified genes that can play a critical role in programming the innate immune response, helping to clarify the mechanisms leading to protection or damage during inflammatory conditions in the CNS. © 2007 Glezer et al.

Descripción: Xanthan is an industrially important exopolysaccharide produced by the phytopathogenic, gram-negative bacterium Xanthomonas campestris pv. campestris. It is composed of polymerized pentasaccharide repeating malts which are assembled by the sequential addition of glucose-1-phosphate, glucose, mannose, glucuronic acid, and mannose on a polyprenol phosphate carrier (L. Ielpi, R. O. Couso, and M. A. Dankert, J. Bacteriol. 175:2490- 2500, 1993). A cluster of 12 genes in a region designated xpsI or gum has been suggested to encode proteins involved in the synthesis and polymerization of the lipid intermediate. However, no experimental evidence supporting this suggestion has been published. In this work, from the biochemical analysis of a defined set of X. campestris gum mutants, we report experimental data for assigning functions to the products of the gum genes. We also show that the first step in the assembly of the lipid-linked intermediate is severely affected by the combination of certain gum and non- gum mutations. In addition, we provide evidence that the C-terminal domain of the gumD gene product is sufficient for its glucosyl-1-phosphate transferase activity. Finally, we found that alterations in the later stages of xanthan biosynthesis reduce the aggressiveness of X. campestris against the plant.

Descripción: This study reports on the standardization of an enzyme-linked immunosorbent assay (ELISA) for detecting specific antibodies anti-Trypanosoma cruzi in naturally infected dogs. Sera from 182 mongrel dogs of all ages residing in four rural villages in Santiago del Estera, Argentina, were collected in November 1994 and preserved in buffered neutral glycerin. All sera were tested by indirect hemagglutination test (IHAT), indirect immunofluorescence test (IFAT), and ELISA using the flagellar fraction of T. cruzi as antigen. Dog sera from an area without vectorial transmission were used to calculate ELISA specificity and cut-off value. Eighty-six percent of sera had concordant results for all tests. All sera reactive for IHAT and IFAT were also reactive for ELISA, except in one case. Sera tested by ELISA when diluted 1 : 200 allowed a clearer division between non-reactive and reactive sera than when 1 : 100 with greater agreement among serologic techniques. The specificity of ELISA was 96.2%. Among 34 adult dogs with a positive xenodiagnosis, sensitivity was 94% both for ELISA and IFAT. ELISA is the first choice for screening purposes and one of the pair of techniques recommended for diagnostic studies in dog populations.

Descripción: 1. 1. A family investigation was performed in eleven cases of Porphyria Cutanea Tarda (PCT). 2. 2. By using clinical findings, quantitative measurements and thin layer chromatography (TLC) of urinary porphyrins, overt and subclinical PCT patients have been identified. 3. 3. In the overt type, skin manifestations are present, excretion of urinary porphyrins is increased and the TLC pattern of porphyrins in urine is characteristic for PCT. 4. 4. In the subclinical type, patients have no clinical symptoms, excretion of porphyrins in urine might be normal or enhanced and TLC pattern of urinary porphyrins is typical for PCT. 5. 5. By applying these criteria a clear distinction between hereditary and non-hereditary PCT was possible. 6. 6. Among the 11 families studied, in four families where PCT was hereditary, four members have the overt type and ten relatives the subclinical type. 7. 7. In seven families where PCT was non-hereditary only the propositus has overt PCT and not a single relative showed any clinical or biochemical abnormality. © 1980.

Descripción: Phytophthora sojae causes root and stem rot, one of the most important diseases of soybean worldwide. Genetic diversity of 32 Phytophthora sojae isolates of different geographic origin from Argentina was evaluated with RAPD markers. The isolates were collected from diseased soybean plants and soil samples from Santa Fe, Buenos Aires, Córdoba and Entre Ríos provinces, in the Pampeana Region. DNA was amplified with 20 decanucleotides primers. Seven primers amplified 49 fragments, of which 35 were polymorphic, indicating high variability. RAPD analysis detected intraspecific variability even among isolates of the same geographic origin. © 2007 by The Mycological Society of America.

Descripción: 1. 1. The present work undertakes a comparative study on the hexachlorobenzene (HCB) porphyria induction in female rats of Wistar and CHBBTHOM strains. The purpose was to characterize the CHBBTHOM strain with respect to the haem metabolic pathway, its regulatory mechanisms and its response to foreign drugs. 2. 2. After 7 weeks of treatment it was observed that the hepatic porphyrins increased 140 times, ALA-synthase 4 times and PCL was 73% inhibited in the Wistar strain. 3. 3. On the other hand the animals of CHBBTHOM strain showed lesser alteration on these parameters; hepatic porphyrins increased only 3-fold, ALA-synthase 1.7-fold and PCL was only 22% inhibited. 4. 4. Total iron liver content was nearly equal in both strains of rats. 5. 5. The results obtained would indicate that the lower susceptibility of the CHBBTHOM strain to acquire porphyria does not seem to be due to either: (1) congenital alterations of any parameters of the haem metabolic pathway, since the behaviour of normal animals from both strains was similar; or (2) a lower hepatic iron content in such animals. 6. 6. These findings would suggest that the differential response to HCB to this strain would be looked for in another metabolic pathway, such as that involved in the metabolization process of the toxic. © 1989.

Descripción: Plants have evolved sophisticated mechanisms to sense and respond to pathogen attacks. Resistance against necrotrophic pathogens generally requires the activation of the jasmonic acid (JA) signaling pathway, whereas the salicylic acid (SA) signaling pathway is mainly activated against biotrophic pathogens. SA can antagonize JA signaling and vice versa. Here, we report that the necrotrophic pathogen Botrytis cinerea exploits this antagonism as a strategy to cause disease development. We show that B. cinerea produces an exopolysaccharide, which acts as an elicitor of the SA pathway. In turn, the SA pathway antagonizes the JA signaling pathway, thereby allowing the fungus to develop its disease in tomato (Solanum lycopersicum). SA-promoted disease development occurs through Nonexpressed Pathogen Related1. We also show that the JA signaling pathway required for tomato resistance against B. cinerea is mediated by the systemin elicitor. These data highlight a new strategy used by B. cinerea to overcome the plant's defense system and to spread within the host. © 2011 American Society of Plant Biologists. All rights reserved.

Descripción: Aims: To establish a reliable and rapid protocol to simultaneously obtain high quality DNA from an infected host plant and the infecting pathogen. To develop an accurate and sensitive low-cost assay for the quantification and in planta monitoring of Phytophthora infestans growth.Methods and Results: In this study, we describe a SYBR Green-based quantitative real-time PCR (qPCR) method for the quantification of P. infestans. The method is based on a simultaneous plant-pathogen DNA purification followed by a qPCR in which the relative quantification of pathogen and plant DNA is performed. Besides assuring an accurate quantification, the use of a plant gene provides a reliable indicator of sample quality, allowing the exclusion of inappropriate samples. By applying this methodology, we were able to detect P. infestans in potato leaf and tuber tissue before the first symptoms of the disease were observed and to monitor the in planta growth of the pathogen for 6 days.Conclusions: This is a reliable low-cost assay that provides rapid, accurate and sensitive quantification of the late blight pathogen, allowing the in planta monitoring of P. infestans growth.Significance and Impact of the Study: The quantitative nature of the assay described in this study may be useful in plant breeding programmes and basic research. The method is appropriate for the comparison of cultivars with different, and even subtle, degrees of pathogen resistance and in the screening of new anti-oomycete compounds. The method can be easily adapted to tomato and the model plant Nicotiana benthamiana. © No claim to Argentinean Government works. Letters in Applied Microbiology 51, 603-610 © 2010 The Society for Applied Microbiology.

Descripción: 1. 1. Studies on porphyrin biosynthesis from exogenus ALA, at various time intervals as well as direct enzyme measurements (aminolevulimc acid dehydratase (ALA-D); porphobilinogenase (PBG ase) and deaminase were carried out in hemolysates of human erythrocytes from healthy controls and patients with lead poisoning (Pb), acute intermittent porphyria (AIP), porphyria cutanea tarda (PCT), erythropoietic protoporphyria (EPP), variegate porphyria (VP) and congenital erythropoietic porphyria (CEP). 2. 2. Inhibited ALA-D in Pb, reduced PBGase and deaminase in AIP, lower uroporphyrinogen decarboxylase in PCT, and diminished isomerase in CEP, were confirmed. In addition, ALA-D was found, reduced in AIP, unchanged in PCT and increased in EPP, VP and CEP. PBGase and deaminase were, on the other hand, increased in Pb and PCT, unchanged in VP and diminished in EPP and CEP. 3. 3. Total porphyrin biosynthesis is a function of time; compared to normals, is lower in CEP and AIP, but higher in PCT. 4. 4. The porphyrin profile changes along the time; uroporphyrin increases at longer intervals while that of coproporphyrin concomitantly diminished. A significance enhancement of octacarboxylic porphyrins was observed during the entire duration of the incubation in PCT hemolysates. In CEP the main porphyrin was always uroporphyrin I. 5. 5. Studies on both total porphyrins formed and their distribution were performed in hemolysates from cases of non-hereditary and hereditary PCT and AIP, before and after therapy. © 1980.

Descripción: In Optometry and in Audiology, the routine tests to prescribe correction lenses and headsets are respectively the visual acuity test (the first chart with letters was developed by Snellen in 1862) and conventional pure tone audiometry (the first audiometer with electrical current was devised by Hartmann in 1878). At present there are psychophysical non invasive tests that, besides evaluating visual and auditory performance globally and even in cases catalogued as normal according to routine tests, supply early information regarding diseases such as diabetes, hypertension, renal failure, cardiovascular problems, etc. Concerning Optometry, one of these tests is the achromatic luminance contrast sensitivity test (introduced by Schade in 1956). Concerning Audiology, one of these tests is high frequency pure tone audiometry (introduced a few decades ago) which yields information relative to pathologies affecting the basal cochlea and complements data resulting from conventional audiometry. These utilities of the contrast sensitivity test and of pure tone audiometry derive from the facts that Fourier components constitute the basis to synthesize stimuli present at the entrance of the visual and auditory systems; that these systems responses depend on frequencies and that the patient's psychophysical state affects frequency processing. The frequency of interest in the former test is the effective spatial frequency (inverse of the angle subtended at the eye by a cycle of a sinusoidal grating and measured in cycles/degree) and, in the latter, the temporal frequency (measured in cycles/sec). Both tests have similar duration and consist in determining the patient's threshold (corresponding to the inverse multiplicative of the contrast or to the inverse additive of the sound intensity level) for each harmonic stimulus present at the system entrance (sinusoidal grating or pure tone sound). In this article the frequencies, standard normality curves and abnormal threshold shifts inherent to the contrast sensitivity test (which for simplicity could be termed "visionmetry") and to pure tone audiometry (also termed auditory sensitivity test) are analyzed with the purpose of contributing to divulge their ability to supply early information associated to pathologies not solely related to the visual and auditory systems respectively. © 2008 American Institute of Physics.

Descripción: We previously demonstrated that extracellular bacterial DNA activates neutrophils through a CpG- and TLR9-independent mechanism. Biofilms are microbial communities enclosed in a polymeric matrix that play a critical role in the pathogenesis of many infectious diseases. Because extracellular DNA is a key component of biofilms of different bacterial species, the aim of this study was to determine whether it plays a role in the ability of biofilms to induce human neutrophil activation. We found that degradation of matrix extracellular DNA with DNase I markedly reduced the capacity of Pseudomonas aeruginosa biofilms to induce the release of the neutrophil proinflammatory cytokines IL-8 and IL-1β (>75%); reduced the upregulation of neutrophil activation markers CD18, CD11b, and CD66b (p < 0.001); reduced the number of bacteria phagocytosed per neutrophil contacting the biofilm; and reduced the production of neutrophil extracellular traps. Consistent with these findings, we found that biofilms formed by the lasI rhlI P. aeruginosa mutant strain, exhibiting a very low content of matrix extracellular DNA, displayed a lower capacity to stimulate the release of proinflammatory cytokines by neutrophils, which was not decreased further by DNase I treatment. Together, our findings support that matrix extracellular DNA is a major proinflammatory component of P. aeruginosa biofilms. Copyright © 2010 by The American Association of Immunologists, Inc.