Ocean Acidification and Increased Temperature Have Both Positive and Negative Effects on Early Ontogenetic Traits of a Rocky Shore Keystone Predator Species

The combined effect of ocean acidification and warming is expected to have significant effects on several traits of marine organisms. The gastropod Concholepas concholepas is a rocky shore keystone predator characteristic of the south-eastern Pacific coast of South America and an important natural resource exploited by small-scale artisanal fishermen along the coast of Chile and Peru. In this study, we used small juveniles of C. concholepas collected from the rocky intertidal habitats of southern Chile (39°S) to evaluate under laboratory conditions the potential consequences of projected near-future levels of ocean acidification and warming for important early ontogenetic traits. The individuals were exposed long-term (5.8 months) to contrasting pCO₂ (ca. 500 and 1400 μatm) and temperature (15 and 19°C) levels. After this period we compared body growth traits, dislodgement resistance, predator-escape response, self-righting and metabolic rates. With respect to these traits there was no evidence of a synergistic interaction between pCO₂ and temperature. Shell growth was negatively affected by high pCO₂ levels only at 15°C. High pCO₂ levels also had a negative effect on the predator-escape response. Conversely, dislodgement resistance and self-righting were positively affected by high pCO₂ levels at both temperatures. High tenacity and fast self-righting would reduce predation risk in nature and might compensate for the negative effects of high pCO₂ levels on other important defensive traits such as shell size and escape behaviour. We conclude that climate change might produce in C. concholepas positive and negative effects in physiology and behaviour. In fact, some of the behavioural responses might be a consequence of physiological effects, such as changes in chemosensory capacity (e.g. predator-escape response) or secretion of adhesive mucous (e.g. dislodgement resistance). Moreover, we conclude that positive behavioural responses may assist in the adaptation to negative physiological impacts, and that this may also be the case for other benthic organisms.     

Distribution of isoaccepting tRNAs and codons for proline and glycine in collagenous and noncollagenous chicken tissues

The relation between codon usage and tRNA content for proline and glycine, the major constituents of collagen, was studied in two tissues: the magnum of laying hen oviduct and the leg tendons of chick embryo where collagen is produced. Although the relative contents of tRNA(GCCGly) and tRNA(IGGPro) in tendons, as compared to magnum indicate a specialization of the tRNA population for collagen synthesis, the distribution of the preponderant codons in collagen mRNA is correlated but at a lesser extent to that of their cognate tRNAs.     

Relative content of isoaccepting tRNAs for glycine and proline in avian tendon cells with different rates of procollagen synthesis

The relative amounts of iso-tRNAsGly and iso-tRNAsPro existing in chick embryo tendon are indicative of a specialization of the tRNA population for collagen synthesis. These amounts are not modified (i) in primary avian tendon (PAT) cells in culture for which the procollagen production varies from about 10% of total protein synthesis to 60% and (ii) in tendons from immature chicks, which show a 3-fold decrease of procollagen production with increasing age. The characteristic tRNA pattern was not maintained in cells which had lost the ability to make high levels of collagen as observed in the cases of: (i) PAT cells reaching confluency; (ii) virus-transformed PAT cells and (iii) tendon from adult chick. Our data are consistent with the idea that tendon tRNA specialization for collagen synthesis is a differentiation feature independent of the expression level of the collagenic function but related to its maintenance.     

Cerebral and ocular abnormalities with anterior pituitary insufficiency of familial nature

Three families presenting one or several cases of brain or ophthalmic abnormalities and an hypopituitarism at least by one of the members have been observed. In the first family, the mother and one of her sons present bilateral choroidoretineal coloboma with amblyopia; one of these two suffers as well from panhypopituitarism. In the second family two premature twins, a brother and his sister, present a syndrome with hypophyseal dwarfism and ophthalmic abnormalities, consisting in the boy's case in an peripapillary depigmentation with no visible sight trouble whereas girl's is showing an extreme microphthalmia with major mental retardation. In the third family two 2nd degree cousins present a panhypopituitarism but only one of the two reveals through neuroradiological investigations corpus callosum and septum lucidum agenesia. The karyotype is normal in all the cases. An hereditary mechanism appears clearly in the first family. It is possible in the second, probable in the third one.     

Fluorescence polarization of polypeptides having a fluorescent endgroup

The polarization of fluorescence of a chromophore chemically bound on the NH₂ end of a poly(L -benzyl glutamate) molecule has been studied as a function of temperature, viscosity, and solvent. The relaxation times depend on both the overall rotation of the helix and the local rotation of the endgroup. In m–cresol the endgroup is rigidly bound and the rotational diffusion constant of the molecule is in good agreement with the values obtained by Kerr effect and dielectric relaxation. In other helicogenic solvents (DMF, DCE, etc.) the local rotation is nearly free. In m-cresol-DMF mixtures a sharp decrease of the polarization around a composition of 40% DMF can be interpreted as a change in the freedom of rotation of the endgroup. No discontinuity in the optical rotation is observed in the solvent mixture. The question of how a rapidly rotating endgroup could show an extrinsic Cotton effect as observed by Bloutand Yamaoka for the system Acridine Orange–PBLG in chloroform is then raised. Polarization of fluorescence measurements on this system show a nearly complete freedom of rotation of the dye and OH D measurements show no detectable Cotton effect in the dye absorption band.     

Dynamics of single-stranded DNA in polyacrylamide gels during pulsed field gel electrophoresis. A birefringence study

The study of the orientation of single-stranded DNA in polyacrylamide gels in denaturing conditions has been undertaken by electric birefringence in order to determine the mechanism involved in the electrophoretic transport. The presence of an overshoot in the birefringence signal, when applying the electric field, and the study of the influences of the electric field and of the gel concentration on the dynamics show that a mechanism of reptation with elongation of the molecule occurs in polyacrylamide gels with low T values. Therefore it is suggested that the use of pulsed fields in sequencing electrophoresis is possible and can lead to a large increase of the length of the fragments that can be sequenced in one single run.     

ERS-24, a Mammalian v-SNARE Implicated in Vesicle Traffic between the ER and the Golgi

We report the identification and characterization of ERS-24 (Endoplasmic Reticulum SNARE of 24 kD), a new mammalian v-SNARE implicated in vesicular transport between the ER and the Golgi. ERS24 is incorporated into 20S docking and fusion particles and disassembles from this complex in an ATP-dependent manner. ERS-24 has significant sequence homology to Sec22p, a v-SNARE in Saccharomyces cerevisiae required for transport between the ER and the Golgi. ERS-24 is localized to the ER and to the Golgi, and it is enriched in transport vesicles associated with these organelles.Newly formed transport vesicles have to be selectively targeted to their correct destinations, implying the existence of a set of compartment-specific proteins acting as unique receptor–ligand pairs. Such proteins have now been identified (Söllner et al., 1993a ; Rothman, 1994): one partner efficiently packaged into vesicles, termed a v-SNARE,¹ and the other mainly localized to the target compartment, a t-SNARE. Cognate pairs of v- and t-SNAREs, capable of binding each other specifically, have been identified for the ER–Golgi transport step (Lian and Ferro-Novick, 1993; Søgaard et al., 1994), the Golgi–plasma membrane transport step (Aalto et al., 1993; Protopopov et al., 1993; Brennwald et al., 1994) in Saccharomyces cerevisiae, and regulated exocytosis in neuronal synapses (Söllner et al., 1993a ; for reviews see Scheller, 1995; Südhof, 1995). Additional components, like p115, rab proteins, and sec1 proteins, appear to regulate vesicle docking by controlling the assembly of SNARE complexes (Søgaard et al., 1994; Lian et al., 1994; Sapperstein et al., 1996; Hata et al., 1993; Pevsner et al., 1994).In contrast with vesicle docking, which requires compartment-specific components, the fusion of the two lipid bilayers uses a more general machinery derived, at least in part, from the cytosol (Rothman, 1994), which includes an ATPase, the N-ethylmaleimide–sensitive fusion protein (NSF) (Block et al., 1988; Malhotra et al., 1988), and soluble NSF attachment proteins (SNAPs) (Clary et al., 1990; Clary and Rothman, 1990; Whiteheart et al., 1993). Only the assembled v–t-SNARE complex provides high affinity sites for the consecutive binding of three SNAPs (Söllner et al., 1993b ; Hayashi et al., 1995) and NSF. When NSF is inactivated in vivo, v–t-SNARE complexes accumulate, confirming that NSF is needed for fusion after stable docking (Søgaard et al., 1994).The complex of SNAREs, SNAPs, and NSF can be isolated from detergent extracts of cellular membranes in the presence of ATPγS, or in the presence of ATP but in the absence of Mg²⁺, and sediments at ∼20 Svedberg (20S particle) (Wilson et al., 1992). In the presence of MgATP, the ATPase of NSF disassembles the v–t-SNARE complex and also releases SNAPs. It seems likely that this step somehow initiates fusion.To better understand vesicle flow patterns within cells, it is clearly of interest to identify new SNARE proteins. Presently, the most complete inventory is in yeast, but immunolocalization is difficult in yeast compared with animal cells, and many steps in protein transport have been reconstituted in animal extracts (Rothman, 1992) that have not yet been developed in yeast. Therefore, it is important to create an inventory of SNARE proteins in animal cells. The most unambiguous and direct method for isolating new SNAREs is to exploit their ability to assemble together with SNAPs and NSF into 20S particles and to disassemble into subunits when NSF hydrolyzes ATP. Similar approaches have already been successfully used to isolate new SNAREs implicated in ER to Golgi (Søgaard et al., 1994) and intra-Golgi transport (Nagahama et al., 1996), in addition to the original discovery of SNAREs in the context of neurotransmission (Söllner et al., 1993a ).Using this method, we now report the isolation and detailed characterization of ERS-24 (Endoplasmic Reticulum SNARE of 24 kD), a new mammalian v-SNARE that is localized to the ER and Golgi. ERS-24 is found in transport vesicles associated with the transitional areas of the ER and with the rims of Golgi cisternae, suggesting a role for ERS-24 in vesicular transport between these two compartments.     

Changements de l'epithélium médian des bourgeons palatins de souris au stade de préfusion

Résumé Avant d'entrer en contact, les surfaces de fusion des processus palatins subissent des modifications. Certaines cellules épithéliales superficielles deviennent turgescentes, alors que d'autres conservent un aspect dense et aplati, elles se lysent et éclatent. Des noyaux semblables à ceux des assises profondes se retrouvent en surface, paraissant migrer vers le bourgeon antagoniste. Des projections filamenteuses apparaissent, quelques unes établissant un contact avec l'épithélium opposé, d'autres restant seulement sous forme d'expansion. Ces observations sont concordantes en microscopie photonique et en microscopie électronique à balayage.

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Modification of the medial epithelium of the palatal shelves of mice at the prefusion stage. A light and scanning electron microscopy study

Summary The fusion surfaces of the palatal processes are modified before coming into contact. Several superficial epithelial cells become hypertrophied, undergo lysis and burst, whereas others remain flattened and densely stained. Nuclei, similar to those localized in deeper layers are found on the surface and seem to migrate towards the opposite process. Filamentous projections appear and some establish a linkage with the opposite epithelium, whereas others expand freely from the surface. Light microscope observations agree with scanning electron microscopy findings.