Redundancy and recombination in the Echinococcus AgB multigene family: is there any similarity with protozoan contingency genes?

Numerous genetic variants of the Echinococcus antigen B (AgB) are encountered within a single metacestode. This could be a reflection of gene redundancy or the result of a somatic hypermutation process. We evaluate the complexity of the AgB multigene family by characterizing the upstream promoter regions of the 4 already known genes (EgAgB1-EgAgB4) and evaluating their redundancy in the genome of 3 Echinococcus species (E. granulosus, E. ortleppi and E. multilocularis) using PCR-based approaches. We have ascertained that the number of AgB gene copies is quite variable, both within and between species. The most repetitive gene seems to be AgB3, of which there are more than 110 copies in E. ortleppi. For E. granulosus, we have cloned and characterized 10 distinct upstream promoter regions of AgB3 from a single metacestode. Our sequences suggest that AgB1 and AgB3 are involved in gene conversion. These results are discussed in light of the role of gene redundancy and recombination in parasite evasion mechanisms of host immunity, which at present are known for protozoan organisms, but virtually unknown for multicellular parasites.

Morphological Diversity and the Roles of Contingency, Chance and Determinism in African Cichlid Radiations

Background: Deterministic evolution, phylogenetic contingency and evolutionary chance each can influence patterns of morphological diversification during adaptive radiation. In comparative studies of replicate radiations, convergence in a common morphospace implicates determinism, whereas non-convergence suggests the importance of contingency or chance. Methodology/Principal Findings: The endemic cichlid fish assemblages of the three African great lakes have evolved similar sets of ecomorphs but show evidence of non-convergence when compared in a common morphospace, suggesting the importance of contingency and/or chance. We then analyzed the morphological diversity of each assemblage independently and compared their axes of diversification in the unconstrained global morphospace. We find that despite differences in phylogenetic composition, invasion history, and ecological setting, the three assemblages are diversifying along parallel axes through morphospace and have nearly identical variance-covariance structures among morphological elements. Conclusions/Significance: By demonstrating that replicate adaptive radiations are diverging along parallel axes, we have shown that non-convergence in the common morphospace is associated with convergence in the global morphospace. Applying these complimentary analyses to future comparative studies will improve our understanding of the relationship between morphological convergence and non-convergence, and the roles of contingency, chance and determinism in driving morphological diversification.

Probabilistic contingency learning with limbic or prefrontal damage

AB A fundamental capacity of the human brain is to learn relations (contingencies) between environmental stimuli and the consequences of their occurrence. Some contingencies are probabilistic; that is, they predict an event in some situations but not in all. Animal studies suggest that damage to limbic structures or the prefrontal cortex may disturb probabilistic learning. The authors studied the learning of probabilistic contingencies in amnesic patients with limbic lesions, patients with prefrontal cortex damage, and healthy controls. Across 120 trials, participants learned contingent relations between spatial sequences and a button press. Amnesic patients had learning comparable to that of control subjects but failed to indicate what they had learned. Across the last 60 trials, amnesic patients and control subjects learned to avoid a noncontingent choice better than frontal patients. These results indicate that probabilistic learning does not depend on the brain structures supporting declarative memory.

Age differences in instability, contingency, and level of self-esteem across the life span

We investigated age differences in instability, contingency, and level of self-esteem from age 13 to 72 years, using data from 1386 individuals who participated in a diary study over 25 days. Instability and contingency of self-esteem decreased from adolescence to old age, whereas level of self-esteem increased. Big Five personality traits predicted the level, but not the slope, of the trajectories of self-esteem characteristics. Age differences in self-esteem characteristics did not merely reflect age differences in instability and level of positive and negative affect. Finally, self-esteem characteristics showed a stable pattern of interrelations across the life span. Overall, the findings suggest that people’s self-esteem tends to become better adjusted—i.e., more stable, less contingent, and higher—across the life course.

Intrahepatic gas at postmortem computed tomography: forensic experience as a potential guide for in vivo trauma imaging

BACKGROUND: Until August 2004 there were 106 forensic cases examined with postmortem multislice computed tomography (MSCT) and magnetic resonance (MR) imaging before traditional autopsy within the Virtopsy project. Intrahepatic gas (IHG) was a frequent finding in postmortem MSCT examinations. The aim of this study was to investigate its cause and significance. METHODS: There were 84 virtopsy cases retrospectively investigated concerning the occurrence, location, and volume of IHG in postmortem MSCT imaging (1.25 mm collimation, 1.25 mm thickness). We assessed and noted the occurrence of intestinal distention, putrefaction, and systemic gas embolisms and the cause of death, possible open trauma, possible artificial respiration, and the postmortem interval. We investigated the relations between the findings using the contingency table (chi2 test) and the comparison of the postmortem intervals in both groups was performed using the t test in 79 nonputrefied corpses. RESULTS: IHG was found in 47 cases (59.5%). In five of the cases, the IHG was caused or influenced by putrefaction. Gas distribution within the liver of the remaining 42 cases was as follows: hepatic arteries in 21 cases, hepatic veins in 35 cases, and portal vein branches in 13 cases; among which combinations also occurred in 20 cases. The presence of IHG was strongly related to open trauma with systemic gas. Pulmonary barotrauma as occurring under artificial respiration or in drowning also caused IHG. Putrefaction did not seem to influence the occurrence of IHG until macroscopic signs of putrefaction were noticeable. CONCLUSIONS: IHG is a frequent finding in traumatic causes of death and requires a systemic gas embolism. Exceptions are putrefied or burned corpses. Common clinical causes such as necrotic bowel diseases appear rarely as a cause of IHG in our forensic case material.

Effects of genetic and environmental factors on chronic lower airway disease in horses

BACKGROUND: Environment and genetics influence the manifestation of recurrent airway obstruction (RAO), but the associations of specific factors with mild, moderate, and severe clinical signs are unknown. HYPOTHESIS: We hypothesized that sire, feed, bedding, time outdoors, sex, and age are associated with clinical manifestations of mild, moderate, and severe lower airway disease. ANIMALS: Direct offspring of 2 RAO-affected Warmblood stallions (F1S1, n = 172; F1S2, n = 135); maternal half-siblings of F1S1 (mHSS1, n = 66); and an age-matched, randomly chosen control group (CG, n = 33). METHODS: A standardized questionnaire was used to assess potential risk factors and to establish a horse owner assessed respiratory signs index (HOARSI 1-4, from healthy to severe) according to clinical signs of lower airway disease. RESULTS: More F1S1 and F1S2 horses showed moderate to severe clinical signs (HOARSI 3 and HOARSI 4 combined, 29.6 and 27.3%, respectively) compared with CG and mHSS1 horses (9.1 and 6.2%, respectively; contingency table overall test, P < .001). Sire, hay feeding, and age (in decreasing order of strength) were associated with more severe clinical signs (higher HOARSI), more frequent coughing, and nasal discharge. CONCLUSIONS AND CLINICAL RELEVANCE: There is a genetic predisposition and lesser but also marked effects of hay feeding and age on the manifestation of moderate to severe clinical signs, most markedly on coughing frequency. In contrast, mild clinical signs were not associated with sire or hay feeding in our populations.