Anatomo-topographic and histo-cytological study of dromedary's spleen in Algeria.

BACKGROUND: Twenty-five spleens of adult, healthy dromedary of the local breed from the region of El Oued, Algeria, were collected at the slaughterhouse in order to carry out research to determine the macroscopic and microscopic structure of spleen in this species, macroscopic study revealed that the spleen has a rectangular shape with a triangular section, rounded edges, a little bit striated, its surface is smooth in which the aspect of the capsule and the parietal surface is shiny and smooth, the morphometric study was carried out after classifying the sampled spleen in five groups according to the animal's body weight which increases with age. MATERIALS AND METHODS: Our study revealed that the groups show a different value of mass which declines towards a drop of the index, also the indexes of length and width are following a decreasing order. RESULTS: The histological study revealed that the zone occupied by stroma did not exceed 26.81% of the total components of the capsule which is composed essentially of connective tissue and an inner layer of smooth muscle cells. Vascular and avascular trabeculae extend from the capsule. The immunohistochemistry study made it possible to visualise T lymphocytes of the splenic parenchyma using monoclonal antibodies where a statistical study was carried out to determine the composition of the various compartments of this organ. The localisation of immunocompetent cells in the splenic parenchyma has been elucidated with antibodies specific for T lymphocytes. CONCLUSIONS: The red pulp occupied a maximum area of the spleen with an average of 68.1% composed of sinusoids venous, the cords extend between the sinuses and the interlobular zone contain many cells: macrophages, plasma cells, red blood cells, white blood cells and platelets.

Transmission of infection to liver transplant recipients from donors with infective endocarditis: lessons learned.

Donors not meeting standard criteria, such as those with bacteremia, are now being used in response to the increasing need for organs for transplantation. Recommended strategies to prevent the occurrence of donor-derived bacteremia include the use of directed antibiotic prophylaxis. However, this approach does not eliminate the risk of infection transmission. Similarly, the management of organ recipients from donors with infective endocarditis (IE) remains uncharacterized. We report 2 cases of donor-derived bacterial infections in liver transplant recipients despite pathogen-specific antibiotic prophylaxis. In both instances, the donors had documented IE treated with appropriate antimicrobial therapy and clearance of bacteremia. Recipients had very distinctive clinical outcomes likely related to pathogen virulence and the extent of donor infection. Persistent infection in the transplanted liver should be suspected in organ recipients of a liver from donors with IE, despite the absence of bacteremia at the time of death and organ procurement. For eradication, recipients may require prolonged pathogen-directed antimicrobial therapy, such as is used for endovascular infections. Prompt recognition of donors with IE, appropriate notification, and prolonged antibiotic prophylaxis are key to reducing the risk of such donor-derived infections.

Group 1 LEA proteins, an ancestral plant protein group, are also present in other eukaryotes, and in the archeae and bacteria domains.

Water is an essential element for living organisms, such that various responses have evolved to withstand water deficit in all living species. The study of these responses in plants has had particular relevance given the negative impact of water scarcity on agriculture. Among the molecules highly associated with plant responses to water limitation are the so-called late embryogenesis abundant (LEA) proteins. These proteins are ubiquitous in the plant kingdom and accumulate during the late phase of embryogenesis and in vegetative tissues in response to water deficit. To know about the evolution of these proteins, we have studied the distribution of group 1 LEA proteins, a set that has also been found beyond the plant kingdom, in Bacillus subtilis and Artemia franciscana. Here, we report the presence of group 1 LEA proteins in green algae (Chlorophyita and Streptophyta), suggesting that these group of proteins emerged before plant land colonization. By sequence analysis of public genomic databases, we also show that 34 prokaryote genomes encode group 1 LEA-like proteins; two of them belong to Archaea domain and 32 to bacterial phyla. Most of these microbes live in soil-associated habitats suggesting horizontal transfer from plants to bacteria; however, our phylogenetic analysis points to convergent evolution. Furthermore, we present data showing that bacterial group 1 LEA proteins are able to prevent enzyme inactivation upon freeze-thaw treatments in vitro, suggesting that they have analogous functions to plant LEA proteins. Overall, data in this work indicate that LEA1 proteins' properties might be relevant to cope with water deficit in different organisms.

Adaptive evolution in GroEL from distantly related endosymbiotic bacteria of insects.

Many symbioses between bacteria and insects resulted from ancient infections followed by strict vertical transmission within host lineages. The strong bottlenecks under which this transmission occurs promote the neutral fixation of slightly deleterious mutations by genetic drift. As predicted by Muller's ratchet, this fixation will drive endosymbiotic bacteria through an irreversible dynamics of fitness loss. The chaperonin GroEL has been proposed as a compensatory mechanism whereby endosymbiotic bacteria of aphids persist. Here, we show that endosymbiotic bacteria of insects from two phylogenetically very distant bacterial phyla have fixed amino acid substitutions by positive selection in functionally important GroEL regions involved in either GroES/peptide binding or in the en bloc movement of the GroEL apical domain. These results, together with the high levels of constitutive expression of GroEL in these endosymbionts, provide valuable insights into the evolution of a molecular mechanism responsible for the maintenance of the symbiotic lifestyle.

Evidence for positive selection in the capsid protein-coding region of the foot-and-mouth disease virus (FMDV) subjected to experimental passage regimens.

We present sequence data from two genomic regions of foot-and-mouth disease virus (FMDV) subjected to several experimental passage regimens. Maximum-likelihood estimates of the nonsynonymous-to-synonymous rate ratio parameter (d(N)/d(S)) suggested the action of positive selection on some antigenic sites of the FMDV capsid during some experimental passages. These antigenic sites showed an accumulation of convergent amino acid replacements during massive serial cytolytic passages and also in persistent infections of FMDV in cell culture. This accumulation was most significant at the antigenic site A (the G-H loop of capsid VP1), which includes an Arg-Gly-Asp (RGD) cellular recognition motif. Our analyses also identified a subregion of VP3, part of the fivefold axis of FMDV particles, that also appeared to be subjected to positive selection of amino acid replacements. From these results, we can conclude that under the restrictive conditions imposed either by the presence of the monoclonal antibodies, by the persistent infections, or by the competition processes established between different variants of the viral population, amino acid replacement in some capsid-coding regions can be positively selected toward an increase of those mutants with a higher capability to infect the cell.

Detecting changes in the functional constraints of paralogous genes.

We describe a new procedure to determine whether regional alterations in the evolutionary constraints imposed on paralogous proteins have occurred. We used as models the A and B (alternatively called alpha and beta) subunits of V/F/A-ATPases, originated by a gene duplication more than 3 billion years ago. Changes associated to three major splits (eubacteria versus Archaea-eukaryotes; Archaea versus eukaryotes; and among free-living bacteria and symbiotic mitochondria) were studied. Only in the first case, when we compared eubacterial or mitochondrial F-ATPases versus eukaryotic vacuolar V-ATPases or archaeal A-ATPases, constraint changes were observed. Modifications in the degree of regional constraining were not detected for the other two types of comparisons (V-ATPases versus A-ATPases and within F-ATPases, respectively). When the rates of evolution of the two subunits were compared, it was found that F-ATPases regulatory subunits evolved faster than catalytic subunits, but the opposite was true for A- and V-ATPases. Our results suggest that, even for universal and essential proteins, selective constraints may be occasionally altered. On the other hand, in some cases no changes were detected after periods of more than 2.2 billion years.

The foot-and-mouth disease RNA virus as a model in experimental phylogenetics.

Phylogenetic reconstruction methods are subject to two types of limitations: our knowledge about the true history of organisms and the gross simplification implied in the numerical simulation models of the relationships between them. In such a situation, experimental phylogenetics provides a way to assess the accuracy of the phylogenetic reconstruction methods. Nonetheless, this capacity is only feasible for organisms in which replication and mutation rates are high enough to provide valuable data. On the other hand, experimental phylogenetics also provides insights on the main evolutionary processes acting on viral variability under different population dynamics. Our study with the foot-and-mouth disease virus (FMDV) strongly suggests that the phylogenetic reconstruction methods can infer erroneous phylogenies due to nucleotide convergences between isolates belonging to different experimental lineages. We also point out that the diverse evolutionary mechanisms acting in different experimental dynamics generate alterations and change the frequencies of genetic variants, which can lead to the misinterpretation of the real evolutionary history.