Responses of antioxidants and lipid peroxidation in mussels to oxidative damage exposure.

1. The aim of this work was to evaluate the relationships between free radical scavengers and lipid peroxidation in the common mussel Mytilus edulis. 2. Mussels were exposed to compounds known for their ability to produce free radicals (carbon tetrachloride, CCl4) and reactive oxygen species via redox cycling (menadione) and the effects on digestive gland, gills and remaining tissues were studied. 3. Lipid peroxidation parameters and the status of free radical scavengers (glutathione, vitamins A, E and C) were affected more by exposure to menadione than to CCl4. 4. The observed changes in the free radical scavengers content are indicative of a role in detoxication of damaging reactive species.     

Impact of human activities on the reproduction of Hooded Vultures Necrosyrtes monachus in Burkina Faso

During the last decades, the critically endangered Hooded Vulture Necrosyrtes monachus has strongly declined across its African range. Although direct persecution has been suggested as a major cause of this decline, little is known about the impact of humans on reproductive output in West Africa. We studied the impact of human activities on the reproductive output of Hooded Vultures in the Garango area of Burkina Faso. Twenty and 56 nesting attempts were monitored, respectively, during the breeding season in 2013/14 and 2014/15, to determine reproductive success and identify causes of nest failure. Annual breeding success varied between 0.68 and 0.71 chicks fledged per breeding pair per year and productivity was assessed at 0.57 chicks fledged per territorial pair in 2014/15. The main threats imposed by humans were poaching of eggs, chicks and collection of nest materials, leading to 20% (13 out of 64 breeding attempts) of nest failures over the two years. An additional important reason for nest failure was the pruning and (partial) cutting of nest trees. Despite this high level of human interference, we found that Hooded Vulture nest success increased with proximity to human settlements, probably because breeding vultures benefit from protection by people against persecution and disturbance.     

Evidence for "twisted plane" undulations in golden hamster sperm tails

Motile spermatozoa from the golden hamster have been arrested by rapid freezing and then fixed with glutaraldehyde at low temperature after substitution with ethylene glycol. As far as can be judged, the flagellar waveforms thus stabilized are similar to those seen in living sperm; in contrast, fixation in glutaraldehyde, without prior freezing, induces agonal changes in flagellar conformation. The characteristics waveform after freeze substitution contains three bends. Approx. half of these flagella are entirely planar. The rest are three dimensional, with the third bend displaced in a regular way from the plane containing the proximal two bends. From the geometry of these flagella, it is concluded that the plane of action of a given bending cycle undergoes a clockwise twist (from a forward viewpoint) as the cycle is succeeded by new bending cycles. This "twisted plane" undulation is quite different from helical movement. The twisting seems to occur abruptly, between cycles, as if each bending cycle has a preferred plane of action. The mechanism underlying the twisting is uncertain. However, on the basis of the angular displacements between the preferred planes, and the findings from electron microscopy, the following idea is presented as a working hypothesis: that, if the most proximal plane of bending is topographically determined by peripheral doublet 1, then successive distal planes of action are influenced predominantly by doublets 2, 3, etc., in clockwise sequence. The merits and weaknesses of this hypothesis are discussed.     

Characterization of cross-bridge elasticity and kinetics of cross-bridge cycling during force development in single smooth muscle cells

Force development in smooth muscle, as in skeletal muscle, is believed to reflect recruitment of force-generating myosin cross-bridges. However, little is known about the events underlying cross-bridge recruitment as the muscle cell approaches peak isometric force and then enters a period of tension maintenance. In the present studies on single smooth muscle cells isolated from the toad (Bufo marinus) stomach muscularis, active muscle stiffness, calculated from the force response to small sinusoidal length changes (0.5% cell length, 250 Hz), was utilized to estimate the relative number of attached cross-bridges. By comparing stiffness during initial force development to stiffness during force redevelopment immediately after a quick release imposed at peak force, we propose that the instantaneous active stiffness of the cell reflects both a linearly elastic cross-bridge element having 1.5 times the compliance of the cross-bridge in frog skeletal muscle and a series elastic component having an exponential length-force relationship. At the onset of force development, the ratio of stiffness to force was 2.5 times greater than at peak isometric force. These data suggest that, upon activation, cross-bridges attach in at least two states (i.e., low-force-producing and high-force-producing) and redistribute to a steady state distribution at peak isometric force. The possibility that the cross-bridge cycling rate was modulated with time was also investigated by analyzing the time course of tension recovery to small, rapid step length changes (0.5% cell length in 2.5 ms) imposed during initial force development, at peak force, and after 15 s of tension maintenance. The rate of tension recovery slowed continuously throughout force development following activation and slowed further as force was maintained. Our results suggest that the kinetics of force production in smooth muscle may involve a redistribution of cross-bridge populations between two attached states and that the average cycling rate of these cross-bridges becomes slower with time during contraction.     

Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications

Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of individuals representing 54 species of frogs, two species of salamanders, a caecilian, and a lungfish. Eight of these sites were present in all species examined, and two were found in all but one species. Alignment of these conserved restriction sites revealed, among anuran 28S rRNA genes, five regions of major length variation that correspond to four of 12 previously identified divergent domains of this gene. One of the divergent domains (DD8) consists of two regions of length variation separated by a short segment that is conserved at least throughout tetrapods. Most of the insertions, deletions, and restriction-site variations identified in the 28S gene will require sequence-level analysis for a detailed reconstruction of their history. However, an insertion in DD9 that is coextensive with frogs in the suborder Neobatrachia, a BstEII site that is limited to representatives of two leptodactylid subfamilies, and a deletion in DD10 that is found only in three ranoid genera are probably synapomorphies.      

Comparative tests of ectoparasite species richness in seabirds

Background  

The diversity of parasites attacking a host varies substantially among different host species. Understanding the factors that explain these patterns of parasite diversity is critical to identifying the ecological principles underlying biodiversity. Seabirds (Charadriiformes, Pelecaniformes and Procellariiformes) and their ectoparasitic lice (Insecta: Phthiraptera) are ideal model groups in which to study correlates of parasite species richness. We evaluated the relative importance of morphological (body size, body weight, wingspan, bill length), life-history (longevity, clutch size), ecological (population size, geographical range) and behavioural (diving versus non-diving) variables as predictors of louse diversity on 413 seabird hosts species. Diversity was measured at the level of louse suborder, genus, and species, and uneven sampling of hosts was controlled for using literature citations as a proxy for sampling effort.     

Polymorphism and differential selection for the sexes.

Various genetic models with different fitnesses for the sexes are investigated. Only a limited set of fitness values will result in a stable polymorphism, and the rate of approach to these equilibrium frequencies is extremely slow. These results indicate that there are problems associated with the interpretation of some human genetic traits by such models.     

Contribution to the thermodynamics of protein folding from the reduction in water-accessible nonpolar surface area

Protein folding and the transfer of hydrocarbons from a dilute aqueous solution to the pure liquid phase are thermodynamically similar in that both processes remove nonpolar surface from water and both are accompanied by anomalously large negative heat capacity changes. On the basis of a limited set of published surface areas, we previously proposed that heat capacity changes (delta C degrees p) for the transfer of hydrocarbons from water to the pure liquid phase and for the folding of globular proteins exhibit the same proportionality to the reduction in water-accessible nonpolar surface area (delta Anp) [Spolar, R.S., Ha, J.H., & Record, M.T., Jr. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 8382-8385]. The consequence of this proposal is that the experimental delta C degrees p for protein folding can be used to obtain estimates of delta Anp and of the contribution to the stability of the folded state from removal of a nonpolar surface from water. In this paper, a rigorous molecular surface area algorithm [Richmond, T.J. (1984) J. Mol. Biol. 178, 63-89] is applied to obtain self-consistent values of the water-accessible nonpolar surface areas of the native and completely denatured states of the entire set of globular proteins for which both crystal structures and delta C degrees p of folding have been determined and for the set of liquid and liquefiable hydrocarbons for which delta C degrees p of transfer are known. Both processes (hydrocarbon transfer and protein folding) exhibit the same direct proportionality between delta C degrees p and delta Anp. We conclude that the large negative heat capacity changes observed in protein folding and other self-assembly processes involving proteins provide a quantitative measure of the reduction in the water-accessible nonpolar surface area and of the contribution of the hydrophobic effect to the stability of the native state and to protein assembly.     

Opercular regeneration in Pomatoceros lamarckii Quatrefages (Polychaeta: Serpulidae). Differentiation of the operculum and deposition of the calcareous opercular plate

Following opercular amputation, stages in opercular regeneration in Pomatoceros lamarckii have been described by light, transmission and scanning electron microscopy. Two to three days after amputation, the rudimentary opercular filament is invested with a delicate cuticle composed of an outer filamentous layer and an inner thicker component composed of orthogonally-arranged layers of small fibril bundles. The opercular plate is uncalcified and composed of two major components, an outer, thin, electron-dense layer and an inner, thicker component which structurally resembles that of the opercular filament cuticle. Between five and eight days, opercular plate calcification is initiated as needle-like crystallites. The structural organization of the organic components of the opercular plate show changes which are related to the onset of calcification. From 13–17 days, the opercular plate becomes heavily calcified and is composed of highly-ordered, prism-like crystals. X-ray diffraction shows these crystals to be aragonite. The structure of the cuticle remains unchanged except that the orthogonally-arranged fibril bundles aggregate into thicker fibres. Amino acid analysis of the regenerated cuticle and organic components of the opercular plate show that they differ from one another and from the normal cuticle and opercular plate. During opercular regeneration, the differentiation of the cuticle and opercular plate-secreting cells are described and the mechanisms of cuticle and calcareous opercular plate secretion are discussed.