Plasmalogens protect unsaturated lipids against UV-induced oxidation in monolayer

Oxidative stress results from the attack by free radicals of several cellular targets (proteins, DNA and lipids). The cell equilibrium is a direct consequence of the pro-/antioxidant balance. In order to understand the physiological processes involved in oxidative stress, we followed oxidation of unsaturated lipids using a biomimetic system: Langmuir monolayers. The oxidation mode chosen was UV-irradiation and the lipid model was a polyunsaturated phospholipid: 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC). The monomolecular film technique was used to measure membrane rheology before and after UV-irradiation. We showed that the UV-irradiation of a DLPC monomolecular film led to a molecular area and surface elasticity modulus decrease that attests to the apparition of new molecular species at the air-water interface. The antioxidant effect of a synthetic plasmalogen (1-O-(1'-(Z)-hexadecenyl)-2-O-oleoyl-sn-glycero-3-phosphocholine or P(PLM)OPE) was tested on the oxidation of DLPC. Indeed, for about 25% mol P(PLM)OPE in mixed DLPC/P(PLM)OPE monolayers, a complete inhibition of the molecular area and the surface elasticity modulus decreases was observed in our experimental conditions. Lower P(PLM)OPE quantities delayed but did not prevent the DLPC oxidation in mixed monolayers.     

M142.2 (cut-6), a novel Caenorhabditis elegans matrix gene important for dauer body shape

The cuticle of the nematode Caenorhabditis elegans is a collagenous extracellular matrix which forms the exoskeleton and defines the shape of the worm. We have characterized the C. elegans gene M142.2, and we show that this is a developmentally regulated gene important for cuticle structure. Transgenic worms expressing M142.2 promoter fused to green fluorescent protein showed that M142.2 is expressed in late embryos and L2d predauers, in the hypodermal cells which synthesize the cuticle. The same temporal pattern was seen by RT-PCR using RNA purified from specific developmental stages. A recombinant fragment of M142.2 was expressed in Escherichia coli and used to raise an antiserum. Immunohistochemistry using the antiserum localized M142.2 to the periphery of the alae of L1 and dauers, forming two longitudinal ribbons over the hypodermal cells. Loss-of-function of M142.2 by RNAi resulted in a novel phenotype: dumpy dauers which lacked alae. M142.2 therefore plays a major role in the assembly of the alae and the morphology of the dauer cuticle; because of its similarity to the other cut genes of the cuticle, we have named the gene cut-6.     

Fear and stress reactions in two species of duck and their hybrid

Susceptibility to fear and stress has often been studied in birds using selection experiments. Crosses between different species of the same genus have also been used to study the type of transmission observed for "fixed action patterns." In this experiment we used a cross between two species (male muscovy and female pekin ducks) to study the genetic transmission of various characteristics of fear reactions and adrenal activity. Males of the three genetic types (two parental species and the hybrid) were submitted to tonic immobility and fear of man tests. Blood was collected for corticosterone assay before and after physiological stress or injection of 5 microg/kg of immediate synacthen (ACTH agonist). The muscovy duck showed lower levels of fear reactions than the pekin duck in the majority of behavioral tests (six of eight). Corticosterone levels were also nearly always the lowest in muscovy ducks (five of six). Generally speaking, the muscovy duck appeared to be less fearful and less susceptible to stress than the pekin duck. The mule duck was similar to one parent, midway between the two, or showed heterosis for fear of man at 10 weeks of age (more fearful than the two parents). Corticosterone levels were midway between the two parents in the mule duck with only one exception, i.e., where the pekin duck was dominant. The existence of heterosis for fear is surprising, as this character is classically considered to be submitted to stabilizing selection. The transmission of corticosterone levels and other fear characteristics is, however, compatible with stabilizing selection. The results are discussed in terms of adaptability.     

Tumor-derived exosomes are a source of shared tumor rejection antigens for CTL cross-priming

The initiation of T-cell-mediated antitumor immune responses requires the uptake and processing of tumor antigens by dendritic cells and their presentation on MHC-I molecules. Here we show in a human in vitro model system that exosomes, a population of small membrane vesicles secreted by living tumor cells, contain and transfer tumor antigens to dendritic cells. After mouse tumor exosome uptake, dendritic cells induce potent CD8+ T-cell-dependent antitumor effects on syngeneic and allogeneic established mouse tumors. Therefore, exosomes represent a novel source of tumor-rejection antigens for T-cell cross priming, relevant for immunointerventions.     

The celA gene, encoding a glycosyl hydrolase family 3 beta-glucosidase in Azospirillum irakense, is required for optimal growth on cellobiosides

The CelA beta-glucosidase of Azospirillum irakense, belonging to glycosyl hydrolase family 3 (GHF3), preferentially hydrolyzes cellobiose and releases glucose units from the C(3), C(4), and C(5) oligosaccharides. The growth of a DeltacelA mutant on these cellobiosides was affected. In A. irakense, the GHF3 beta-glucosidases appear to be functional alternatives for the GHF1 beta-glucosidases in the assimilation of beta-glucosides by other bacteria.     

Effects of exogenous ammonia or free amino acids on proteolytic activity and protein breakdown products in Streptococcus bovis,Prevotella albensis,and Butyrivibrio fibrisolvens

We studied in details the ammonia or free amino acids (AA) effects on proteolytic activity of three ruminal bacteria: enzymatic activities and protein breakdown products were measured at the end of the exponential growth phase. In Streptococcus bovis the simultaneous uptake of ammonia and probably small peptides induced a decline in total proteolytic activity as a result of changes in endopeptidasic activities. With free AA, the tendency for the endopeptidasic activities to specialise was more evident and the total proteolytic activity decreased too. In Prevotella albensis, the inhibition of proteolysis with free AA was linked to the disappearance of free endopeptidases, to the specialization of cell-associated endopeptidases and to the decrease in exopeptidases. The decrease of proteolysis in P. albensis when ammonia was added was more difficult to interpret. With ammonia or AA Butyrivibro fibrisolvens developed a distinct behavior of those expressed by the other species: the increase of the total proteolytic activity could be explained by a better balance of the endopeptidases expressed. It then clearly appeared that the expression of the proteolytic activities are linked to the nature and/or to the quantity of the nitrogen source. This leads each species to adopt its own nutritional strategy in order to adapt to the environmental conditions of the ruminal ecosystem. Received: 2 July 2001 / Accepted: 28 September 2001     

Maxi K+ channel mediates regulatory volume decrease response in a human bronchial epithelial cell line

The cell regulatory volume decrease (RVD) response triggered by hypotonic solutions is mainly achieved by the coordinated activity of Cl- and K+ channels. We now describe the molecular nature of the K(+) channels involved in the RVD response of the human bronchial epithelial (HBE) cell line 16HBE14o-. These cells, under isotonic conditions, present a K+ current consistent with the activity of maxi K+ channels, confirmed by RT-PCR and Western blot. Single-channel and whole cell maxi K+ currents were readily and reversibly activated following the exposure of HBE cells to a 28% hypotonic solution. Both maxi K+ current activation and RVD response showed calcium dependency, inhibition by TEA, Ba2+, iberiotoxin, and the cationic channel blocker Gd3+ but were insensitive to clofilium, clotrimazole, and apamin. The presence of the recently cloned swelling-activated, Gd3+-sensitive cation channels (TRPV4, also known as OTRPC4, TRP12, or VR-OAC) was detected by RT-PCR in HBE cells. This channel, TRPV4, which senses changes in volume, might provide the pathway for Ca2+ influx under hypotonic solutions and, consequently, for the activation of maxi K+ channels.     

Typology of activity bouts and effect of fearfulness on behaviour in meat-type chickens

Increased physical exercise is known to prevent leg problems in meat-type chickens. Our aims were to study in detail the organisation of general and locomotor activity, to determine how physical exercise could be promoted and to investigate the effects of tonic immobility (TI) duration on spontaneous activity. Chicks were allocated to two groups according to their TI duration at 3 and 20 days (fearful birds, HF, n=11; non-fearful birds, LF, n=14). The behaviour patterns expressed by awake birds were recorded as 'activity bouts'. Activity bouts were then classified into five classes according to the most long-lasting activity in the bout. The behaviour patterns were similar in both groups. The FORAGING class contained long-lasting bouts with high levels of locomotor activity which decreased considerably with age, when bouts of EATING and DRINKING classes became more and more numerous. Bouts in the PREENING and NONE classes contained low activity. In conclusion, the level of activity in home pens was poorly related to TI. Categorisation of bouts into five classes is valuable to understand the general organisation of activity in chickens. The FORAGING class included bouts with high levels of locomotion and it could thus be used as a general indicator of activity.