ABSTRACT
Despite that many image encryption systems based on chaotic or hyperchaotic systems have been proposed to protect different kinds of information, it has been crucial to achieve as much security as possible in such systems. In this sense, we numerically implement a known image encryption system with some variants, making special emphasis when two operations are considered in the scrambling stage. The variants of such an encryption system are based on some hyperchaotic systems, which generated some substitution boxes and the keys of the system. With the aim to have a more complete evaluation, some internal stages of the image encryption scheme have been evaluated by using common statistical tests, and also the scaling behavior of the encrypted images has been calculated by means of a two-dimensional detrended fluctuation analysis (2D-DFA). Our results show that the image encryption systems that include two operations or transformations in the scrambling stage present a better performance than those encryption systems that consider just one operation. In fact, the 2D-DFA approach was more sensitive than some common statistical tests to determine more clearly the impact of multiple operations in the scrambling process, confirming that this scaling method can be used as a perceptual security metric, and it may contribute to having better image encryption systems.
ABSTRACT
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Subject(s)
Humans , Terminology as Topic , Periodicals as Topic/standards , Abbreviations as TopicABSTRACT
Leishmania are protozoan parasites that infect macrophages and their survival is partially achieved through inhibition of the cellular oxidative burst by parasite lipophosphoglycan (LPG). PKCalpha is the predominant PKC isoenzyme required for macrophage oxidative burst, yet it is not known if different susceptibility of BALB/c and C57BL/6 mice to Leishmania mexicana could be related to PKCalpha. We analysed the effect of L. mexicana promastigotes and parasite LPG on expression of PKCalpha and on its activity in macrophages of both mouse strains. Our data show that expression of the isoenzyme was not altered either by LPG or by L. mexicana promastigotes. Yet LPG exerted opposing effects on PKCalpha activity of macrophages between both strains: in susceptible BALB/c cells, it inhibited PKCalpha activity, whereas in the more resistant strain it augmented enzymatic activity 2.8 times. In addition, LPG inhibited oxidative burst only in susceptible BALB/c macrophages and the degree of inhibition correlated with parasite survival. Promastigotes also inhibited PKCalpha activity and oxidative burst in macrophages of BALB/c mice, whereas in C57BL/6, they enhanced PKCalpha activity and oxidative burst inhibition was less severe. Our data indicate that control of PKCalpha-induced oxidative burst by L. mexicana LPG relates with its success to infect murine macrophages.
Subject(s)
Glycosphingolipids/metabolism , Leishmania mexicana/pathogenicity , Macrophages/immunology , Macrophages/parasitology , Protein Kinase C-alpha/antagonists & inhibitors , Protein Kinase C-alpha/biosynthesis , Respiratory Burst , Animals , Disease Susceptibility/immunology , Gene Expression Profiling , Leishmaniasis, Diffuse Cutaneous/immunology , Leishmaniasis, Diffuse Cutaneous/parasitology , Male , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Survival AnalysisABSTRACT
Protein A is associated in a covalent way to the Staphylococcus aureus wall and is exposed in the bacterial surface. Its increasing use as an immunochemical reagent is due to its great affinity for immunoglobulins of multiple animal species. In this work we are presenting a method for the semiquantitative determination of bacterial surface protein A, describing the content of this protein in three certified strains and 15 new S. aureus isolations. Protein A titers were determined by a microassay as the inverse of dilutions of standardized bacterial suspensions that caused agglutination at the end point in ram erythrocytes, sensitized with anti-erythrocyte serum. Using certified strains, protein A+ (Cowan I) and protein A-(Wood 46), reproducibility of the method was assured and the relative hemagglutinating potence of new isolations was determined showing it was constant and typical of the strain. Titrations fluctuated from non detectable to a maximum of 256. Using the described method, protein A in S. aureus isolations can be quantitated to analyze its distribution and obtain new producing strains from this protein.
