Recovery after mass extinction: evolutionary assembly in large-scale biosphere dynamics

Biotic recoveries following mass extinctions are characterized by a process in which whole ecologies are reconstructed from low-diversity systems, often characterized by opportunistic groups. The recovery process provides an unexpected window to ecosystem dynamics. In many aspects, recovery is very similar to ecological succession, but important differences are also apparently linked to the innovative patterns of niche construction observed in the fossil record. In this paper, we analyse the similarities and differences between ecological succession and evolutionary recovery to provide a preliminary ecological theory of recoveries. A simple evolutionary model with three trophic levels is presented, and its properties (closely resembling those observed in the fossil record) are compared with characteristic patterns of ecological response to disturbances in continuous models of three-level ecosystems.     

The non-LTR retrotransposons in Ciona intestinalis: new insights into the evolution of chordate genomes

Background  

Non-long terminal repeat (non-LTR) retrotransposons have contributed to shaping the structure and function of genomes. In silico and experimental approaches have been used to identify the non-LTR elements of the urochordate Ciona intestinalis. Knowledge of the types and abundance of non-LTR elements in urochordates is a key step in understanding their contribution to the structure and function of vertebrate genomes.     

Human urinary and renal alpha-L-fucosidases. A comparative study

1. Enzymatic forms of alpha-L-fucosidase from human renal tissue and urine were investigated. 2. In renal tissue two different isoenzymatic patterns were obtained by chromatofocusing of either directly soluble or detergent solubilized extracts. 3. On the other hand the urinary isoenzymatic pattern is similar to that obtained for the renal soluble extract.     

Effects of Rewarding and Unrewarding Experiences on the Response to Host-induced Plant Odors of the Generalist Parasitoid <Emphasis Type="BoldItalic">Cotesia marginiventris</Emphasis> (Hymenoptera: Braconidae)

Associative learning is known to modify foraging behavior in numerous parasitic wasps. This is in agreement with optimal foraging theory, which predicts that the wasps will adapt their responses to specific cues in accordance with the rewards they receive while perceiving these cues. Indeed, the generalist parasitoid Cotesia marginiventris shows increased attraction to a specific plant odor after perceiving this odor during contact with hosts. This positive associative learning is common among many parasitoids, but little is known about the effects of unrewarding host searching events on the attractiveness of odors. To study this, preferences of female C. marginiventris for herbivore-induced odors of three plant species were tested in a six-arm olfactometer after the wasps perceived one of these odors either i) without contacting any caterpillars, ii) while contacting the host caterpillar Spodoptera littoralis, or iii) while contacting the non-host caterpillar Pieris rapae. The results confirm the effects of positive associative learning, but showed no changes in innate responses to the host-induced odors after “negative” experiences. Hence, a positive association is made during an encounter with hosts, but unsuccessful host-foraging experiences do not necessarily lead to avoidance learning in this generalist parasitoid.     

Minimal model of self-replicating nanocells: a physically embodied information-free scenario

The building of minimal self-reproducing systems with a physical embodiment (generically called protocells) is a great challenge, with implications for both theory and applied sciences. Although the classical view of a living protocell assumes that it includes information-carrying molecules as an essential ingredient, a dividing cell-like structure can be built from a metabolism-container coupled system only. An example of such a system, modelled with dissipative particle dynamics, is presented here. This article demonstrates how a simple coupling between a precursor molecule and surfactant molecules forming micelles can experience a growth-division cycle in a predictable manner, and analyses the influence of crucial parameters on this replication cycle. Implications of these results for origins of cellular life and living technology are outlined.     

Analysis of planarian Adh3 supports an intron-rich architecture and tissue-specific expression for the urbilaterian ancestral form

The alcohol dehydrogenase class 3 enzyme (ADH3) is the presumed ancestral form of the medium-chain dehydrogenase-reductase ADH family. This enzyme has been involved in formaldehyde and nitric oxide metabolism of a variety of deuterostomes and ecdysozoan protostomes. We have now characterized the structure and expression of the Adh3 gene in the lophotrochozoan Schmidtea mediterranea, a freshwater planarian. The planarian gene expands over 8.7 kb and is organized into 7 exons. The 1340 bp long Adh3cDNA contains a 1137 bp open reading frame corresponding to a deduced protein of 379 amino acids. The protein sequence is consistent with that expected for a typical class III enzyme. Twenty out of the twenty-two amino acid positions associated with enzymatic roles are strictly preserved, which suggests that the enzymatic capabilities have been conserved. In situ hybridization experiments show that Adh3 is expressed along the intestine of S. mediterranea specimens. This is consistent with the pattern observed in invertebrates and in contrast with the widespread expression of vertebrate Adh3. The comparative study across bilateria, which now includes a lophotrochozoan representative, further supports the idea that the urbilaterian Adh3 ancestor showed an intron-rich architecture and tissue-specific expression, and strengthens the view that widespread expression of Adh3 was a vertebrate innovation.     

Influence of training background on jumping height

The aim of this study was to compare the pattern of force production and center of mass kinematics in maximal vertical jump performance between power athletes, recreational bodybuilders, and physically active subjects. Twenty-seven healthy male subjects (age: 24.5 +/- 4.3 years, height: 178.7 +/- 15.2 cm, and weight: 81.9 +/- 12.7 kg) with distinct training backgrounds were divided into 3 groups: power track athletes (PT, n = 10) with international experience, recreational bodybuilders (BB, n = 7) with at least 2 years of training experience, and physically active subjects (PA, n = 10). Subjects performed a 1 repetition maximum (1RM) leg press test and 5 countermovement jumps with no instructions regarding jumping technique. The power-trained group jumped significantly higher (p < 0.05) than the BB and PA groups (0.40 +/- 0.05, 0.31 +/- 0.04, and 0.30 +/- 0.05, respectively). The difference in jumping height was not produced by higher rates of force development (RFD) and shorter center of mass (CM) displacement. Instead, the PT group had greater CM excursion (p < 0.05) than the other groups. The PT and BB groups had a high correlation between jumping height and 1RM test (r = 0.93 and r = 0.89, p < 0.05, respectively). In conclusion, maximum strength seems to be important for jumping height, but RFD does not seem relevant to achieve maximum jumping heights. High RFD jumps should be performed during training only when sport skills have a time constraint for force application.     

Intermittent exercise as a conditioning activity to induce postactivation potentiation

Postactivation potentiation (PAP) is defined as a short-term increase in voluntary muscle activation following a previous conditioning activity (CA). Controversy about PAP is mostly attributed to the characteristics of the CA and the training status of the subjects. While some studies have found that PAP can be induced by series of 5-10 second maximal voluntary isometric contractions or near maximal dynamic contractions (e.g., 3-5 repetition maximum), others have failed to do so. On the other hand, some studies suggest that intermittent contractions can also induce PAP. However, even though PAP was observed, its duration was not taken into account, leaving ground for further investigations. The purpose of this study was threefold: (a) to verify if PAP can progressively enhance performance of voluntary actions throughout a set of intermittent contractions; (b) to verify PAP duration when induced by an intermittent contractions protocol; and (c) to verify if PAP effects were reproducible in different sessions when induced by intermittent contractions. Ten physically active men, not engaged in strength training, underwent 5 randomized experimental sessions, during which they performed a set of 10 unilateral knee extensions (KE) (1 every 30 seconds) at 60 degrees x s(-1) in an isokinetic dynamometer. Peak torque was evaluated over the 10 unilateral KE and at the randomized intervals of 4, 6, 8, 10, and 12 minutes post CA. Peak torque was potentiated 1.3 (+/-0.79) N x m per unilateral KE, and the potentiation effect persisted for 12 minutes after the last contraction. These findings were reproduced in all 5 experimental sessions. Thus, intermittent conditioning activities seem to be an effective way to produce PAP. However, these activities should be tested in a more real world situation to verify the applicability as a warm-up routine.     

Transition metal complexes bearing atropisomeric saturated NHC ligands

From achiral imidazolinium salts, chiral transition metal complexes containing an N-heterocyclic carbene (NHC) ligand were prepared (metal = palladium, copper, silver, gold, rhodium). Axial chirality in these complexes results from the formation of the metal-carbene bond leading to the restriction of rotation of dissymmetric N-aryl substituents about the C–N bond. When these complexes exhibited a sufficient configurational stability, a resolution by chiral high-performance liquid chromatography (HPLC) on preparative scale enabled isolation of enantiomers with excellent enantiopurities (>99% ee) and good yields. A study of the enantiomerization barriers revealed the effect of the backbone nature as well as the type of transition metal on its values. Nevertheless, the evaluation of palladium-based complexes in asymmetric intramolecular α-arylation of amides demonstrated that the ability to induce an enantioselectivity cannot be correlated to the configurational stability of the precatalysts.