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Search Results: 1 - 10 of 10056 matches for " Mijailovsky Sergio "
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Epicuticular lipids induce aggregation in Chagas disease vectors
Alicia Figueiras, Juan R Girotti, Sergio J Mijailovsky, M Patricia Juárez
Parasites & Vectors , 2009, DOI: 10.1186/1756-3305-2-8
Abstract: We analyzed the response of T. infestans fifth instar nymphs after exposure to different amounts either of total epicuticular lipid extracts or individual lipid fractions. Assays were performed in a circular arena, employing a binary choice test with filter papers acting as aggregation attractive sites; papers were either impregnated with a hexane-extract of the total lipids, or lipid fraction; or with the solvent. Insects were significantly aggregated around papers impregnated with the epicuticular lipid extracts. Among the lipid fractions separately tested, only the free fatty acid fraction promoted significant bug aggregation. We also investigated the response to different amounts of selected fatty acid components of this fraction; receptiveness varied with the fatty acid chain length. No response was elicited by hexadecanoic acid (C16:0), the major fatty acid component. Octadecanoic acid (C18:0) showed a significant assembling effect in the concentration range tested (0.1 to 2 insect equivalents). The very long chain hexacosanoic acid (C26:0) was significantly attractant at low doses (≤ 1 equivalent), although a repellent effect was observed at higher doses.The detection of contact aggregation pheromones has practical application in Chagas disease vector control. These data may be used to help design new tools against triatomine bugs.The lipid layer on the insect cuticle comprises a complex mixture of hydrocarbons, free and esterified fatty acids and fatty alcohols, and smaller amounts of other oxygenated components [1,2]. Their role protecting insects from water loss and hence preventing lethal desiccation is widely recognized [3-5]. They are also the first barrier against chemical or biological contact insecticides [6,7]. Growing evidence has been gathered for more than 30 years on the role of hydrocarbons in chemical communication in many insect species [8]. However, relatively few reports are available on the participation of oxygenated cuticular lipid compo
Cuticular hydrocarbons of Chagas disease vectors in Mexico
Juárez, M Patricia;Carlson, David A;Salazar Schettino, Paz María;Mijailovsky, Sergio;Rojas, Gloria;
Memórias do Instituto Oswaldo Cruz , 2002, DOI: 10.1590/S0074-02762002000600012
Abstract: capillary gas-liquid chromatography was used to analyse the cuticular hydrocarbons of three triatomine species, triatoma dimidiata, t. barberi and dipetalogaster maxima, domestic vectors of chagas disease in mexico. mixtures of saturated hydrocarbons of straight and methyl-branched chains were characteristic of the three species, but quantitatively different. major methylbranched components mostly corresponded to different saturated isomers of monomethyl, dimethyl and trimethyl branched hydrocarbons ranging from 29 to 39 carbon backbones. sex-dependant, quantitative differences in certain hydrocarbons were apparent in t. dimidiata.
Cuticular hydrocarbons of Chagas disease vectors in Mexico
Juárez M Patricia,Carlson David A,Salazar Schettino Paz María,Mijailovsky Sergio
Memórias do Instituto Oswaldo Cruz , 2002,
Abstract: Capillary gas-liquid chromatography was used to analyse the cuticular hydrocarbons of three triatomine species, Triatoma dimidiata, T. barberi and Dipetalogaster maxima, domestic vectors of Chagas disease in Mexico. Mixtures of saturated hydrocarbons of straight and methyl-branched chains were characteristic of the three species, but quantitatively different. Major methylbranched components mostly corresponded to different saturated isomers of monomethyl, dimethyl and trimethyl branched hydrocarbons ranging from 29 to 39 carbon backbones. Sex-dependant, quantitative differences in certain hydrocarbons were apparent in T. dimidiata.
Control of Pyrethroid-Resistant Chagas Disease Vectors with Entomopathogenic Fungi
Nicolás Pedrini,Sergio J. Mijailovsky,Juan R. Girotti,Raúl Stariolo,Rubén M. Cardozo,Alberto Gentile,M. Patricia Juárez
PLOS Neglected Tropical Diseases , 2009, DOI: 10.1371/journal.pntd.0000434
Abstract: Background Triatoma infestans-mediated transmission of Tripanosoma cruzi, the causative agent of Chagas disease, remains as a major health issue in southern South America. Key factors of T. infestans prevalence in specific areas of the geographic Gran Chaco region—which extends through northern Argentina, Bolivia, and Paraguay—are both recurrent reinfestations after insecticide spraying and emerging pyrethroid-resistance over the past ten years. Among alternative control tools, the pathogenicity of entomopathogenic fungi against triatomines is already known; furthermore, these fungi have the ability to fully degrade hydrocarbons from T. infestans cuticle and to utilize them as fuel and for incorporation into cellular components. Methodology and Findings Here we provide evidence of resistance-related cuticle differences; capillary gas chromatography coupled to mass spectrometry analyses revealed that pyrethroid-resistant bugs have significantly larger amounts of surface hydrocarbons, peaking 56.2±6.4% higher than susceptible specimens. Also, a thicker cuticle was detected by scanning electron microscopy (32.1±5.9 μm and 17.8±5.4 μm for pyrethroid-resistant and pyrethroid-susceptible, respectively). In laboratory bioassays, we showed that the virulence of the entomopathogenic fungi Beauveria bassiana against T. infestans was significantly enhanced after fungal adaptation to grow on a medium containing insect-like hydrocarbons as the carbon source, regardless of bug susceptibility to pyrethroids. We designed an attraction-infection trap based on manipulating T. infestans behavior in order to facilitate close contact with B. bassiana. Field assays performed in rural village houses infested with pyrethroid-resistant insects showed 52.4% bug mortality. Using available mathematical models, we predicted that further fungal applications could eventually halt infection transmission. Conclusions This low cost, low tech, ecologically friendly methodology could help in controlling the spread of pyrethroid-resistant bugs.
Biological Control of the Chagas Disease Vector Triatoma infestans with the Entomopathogenic Fungus Beauveria bassiana Combined with an Aggregation Cue: Field, Laboratory and Mathematical Modeling Assessment
Lucas Forlani?,Nicolás Pedrini?,Juan R. Girotti?,Sergio J. Mijailovsky,Rubén M. Cardozo?,Alberto G. Gentile?,Carlos M. Hernández-Suárez?,Jorge E. Rabinovich?,M. Patricia Juárez
PLOS Neglected Tropical Diseases , 2015, DOI: 10.1371/journal.pntd.0003778
Abstract: Background Current Chagas disease vector control strategies, based on chemical insecticide spraying, are growingly threatened by the emergence of pyrethroid-resistant Triatoma infestans populations in the Gran Chaco region of South America. Methodology and findings We have already shown that the entomopathogenic fungus Beauveria bassiana has the ability to breach the insect cuticle and is effective both against pyrethroid-susceptible and pyrethroid-resistant T. infestans, in laboratory as well as field assays. It is also known that T. infestans cuticle lipids play a major role as contact aggregation pheromones. We estimated the effectiveness of pheromone-based infection boxes containing B. bassiana spores to kill indoor bugs, and its effect on the vector population dynamics. Laboratory assays were performed to estimate the effect of fungal infection on female reproductive parameters. The effect of insect exuviae as an aggregation signal in the performance of the infection boxes was estimated both in the laboratory and in the field. We developed a stage-specific matrix model of T. infestans to describe the fungal infection effects on insect population dynamics, and to analyze the performance of the biopesticide device in vector biological control. Conclusions The pheromone-containing infective box is a promising new tool against indoor populations of this Chagas disease vector, with the number of boxes per house being the main driver of the reduction of the total domestic bug population. This ecologically safe approach is the first proven alternative to chemical insecticides in the control of T. infestans. The advantageous reduction in vector population by delayed-action fungal biopesticides in a contained environment is here shown supported by mathematical modeling.
Desirability of a standard notation for fisheries assessment  [PDF]
Sergio Ragonese, Sergio Vitale
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.48057

The worldwide increase of the publications concerning the assessment of marine renewable living resources is highlighting long-standing problems with symbols and annotations. Starting from the symbols presented within the classic fisheries masterpieces produced, mainly in the fifty of the last century, a first “Milestone” list was organised. Thereafter, the pertinent literature was (not exhaustively) browsed in order to integrate this Milestone list on the base of a set of decisional criteria. The present contribution consists in using the Latin letters as well established symbols for the corresponding parameters, leaving free to specific use (with few historical exceptions) the Greek letters in view to open a discussion among all the fisheries scientists and bodies in order to move towards a common language and better communication standards.

On the k–Lucas Numbers of Arithmetic Indexes  [PDF]
Sergio Falcon
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.310175
Abstract: In this paper, we study the k–Lucas numbers of arithmetic indexes of the form an+r , where n is a natural number and r is less than r. We prove a formula for the sum of these numbers and particularly the sums of the first k-Lucas numbers, and then for the even and the odd k-Lucas numbers. Later, we find the generating function of these numbers. Below we prove these same formulas for the alternated k-Lucas numbers. Then, we prove a relation between the k–Fibonacci numbers of indexes of the form 2rn and the k–Lucas numbers of indexes multiple of 4. Finally, we find a formula for the sum of the square of the k-Fibonacci even numbers by mean of the k–Lucas numbers.
A Quantistic Interpretation of the Relationship between the Earth-Core and the Atmosphere  [PDF]
Sergio Manzetti
Atmospheric and Climate Sciences (ACS) , 2014, DOI: 10.4236/acs.2014.44046

The atmospheric behaviour of air is largely governed by low and high pressure systems. However, the relationship between these systems is not linear, as winds, sea temperatures and solar intensity modulate their dynamics and reduce predictability. Several other factors are known to affect these atmospheric dynamics, such as solar cycles. Recent evidence shows however that the earth’s gravitational field can be quantized in terms of quantum numbers, as recently published in Nature. The implications of this relationship between gravity and quantum numbers give rise to the possible key role of a quantum behaviour of gravity in affecting the formation of high- and low-pressure systems. In this letter, the author suggests a relation between the recently observed quantized nature of gravity, the weight of air and the formation of Low and High pressure areas in the atmosphere. The theory is novel and can aid in the understanding of interplay between the earths core forces, the gravitational behaviour and the atmospheric dynamics. There are however several parts of this theory that need further development, and an initial expression of this putative relationship is introduced.

Relationships between Some k -Fibonacci Sequences  [PDF]
Sergio Falcon
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.515216
Abstract: In this paper, we will see that some -Fibonacci sequences are related to the classical Fibonacci sequence of such way that we can express the terms of a k -Fibonacci sequence in function of some terms of the classical Fibonacci sequence. And the formulas will apply to any sequence of a certain set of k' -Fibonacci sequences. Thus we find k -Fibonacci sequences relating to other k -Fibonacci sequences when σ'k is linearly dependent of \"\".
Causal Groupoid Symmetries  [PDF]
Sergio Pissanetzky
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.54059

Proposed here is a new framework for the analysis of complex systems as a non-explicitly programmed mathematical hierarchy of subsystems using only the fundamental principle of causality, the mathematics of groupoid symmetries, and a basic causal metric needed to support measurement in Physics. The complex system is described as a discrete set S of state variables. Causality is described by an acyclic partial order w on S, and is considered as a constraint on the set of allowed state transitions. Causal set (S, w) is the mathematical model of the system. The dynamics it describes is uncertain. Consequently, we focus on invariants, particularly group-theoretical block systems. The symmetry of S by itself is characterized by its symmetric group, which generates a trivial block system over S. The constraint of causality breaks this symmetry and degrades it to that of a groupoid, which may yield a non-trivial block system on S. In addition, partial order w determines a partial order for the blocks, and the set of blocks becomes a causal set with its own, smaller block system. Recursion yields a multilevel hierarchy of invariant blocks over S with the properties of a scale-free mathematical fractal. This is the invariant being sought. The finding hints at a deep connection between the principle of causality and a class of poorly understood phenomena characterized by the formation of hierarchies of patterns, such as emergence, selforganization, adaptation, intelligence, and semantics. The theory and a thought experiment are discussed and previous evidence is referenced. Several predictions in the human brain are confirmed with wide experimental bases. Applications are anticipated in many disciplines, including Biology, Neuroscience, Computation, Artificial Intelligence, and areas of Engineering such as system autonomy, robotics, systems integration, and image and voice recognition.

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