Limitations and mechanisms influencing the migratory performance of soaring birds

Migration is costly in terms of time, energy and safety. Optimal migration theory suggests that individual migratory birds will choose between these three costs depending on their motivation and available resources. To test hypotheses about use of migratory strategies by large soaring birds, we used GPS telemetry to track 18 adult, 13 sub‐adult and 15 juvenile Golden Eagles Aquila chrysaetos in eastern North America. Each age‐class had potentially different motivations during migration. During spring, the migratory performance (defined here as the directness of migratory flight) of adults was higher than that of any other age‐classes. Adults also departed earlier and spent less time migrating. Together, these patterns suggest that adults were primarily time‐limited and the other two age‐classes were energy‐limited. However, adults that migrated the longest distances during spring also appeared to take advantage of energy‐conservation strategies such as decreasing their compensation for wind drift. During autumn, birds of all age‐classes were primarily energy‐minimizers; they increased the length of stopovers, flew less direct routes and migrated at a slower pace than during spring. Nonetheless, birds that departed later in autumn flew more directly, indicating that time limitations may have affected their decision‐making. During both seasons, juveniles had the lowest performance, sub‐adults intermediate performance and adults the highest performance. Our results show age‐ and seasonal variation in time and energy‐minimization strategies that are not necessarily exclusive of one another. Beyond time and energy, a complex suite of factors, including weather, experience and navigation ability, influences migratory performance and decision‐making.     

Individual variation in orientation promotes a 3000‐km latitudinal change in wintering grounds in a long‐distance migratory raptor

Migrating juvenile birds rely on endogenous information in choosing the direction in which to fly, but such input may be overridden by social interactions with experienced individuals. We tagged seven juvenile Short‐toed Eagles Circaetus gallicus with GPS transmitters in southern Italy. This trans‐Saharan migrant flies mainly by soaring and is therefore not well adapted to performing long water crossings. Five of the seven tagged juveniles used the longer but apparently safer route towards the Strait of Gibraltar, and two migrated along a southerly trajectory and subsequently spent the winter in Sicily, apparently forced to do so by the 150‐km‐wide Sicily Channel. One of these individuals took the longer route the following autumn. These results, combined with long‐term (15 years) visual field observations involving thousands of individuals, suggest that inexperienced Short‐toed Eagles may learn their migratory routes from experienced adults, whereas some of them migrate south in response to an innate orientation instinct. Transport costs, inherited information and geography apparently interact, forcing some Short‐toed Eagles to winter 3000 km to the north of the majority of their conspecifics.     

Characterization of a ligand-gated cation channel based on an inositol receptor in the silkworm,Bombyx mori

Insect herbivores recognize non-volatile compounds in plants to direct their feeding behavior. Gustatory receptors (Gr) appear to be required for nutrient recognition by gustatory organs in the mouthparts of insects. Gr10 is expressed in Bombyx mori (BmGr10) mouthparts such as maxillary galea, maxillary palp, and labrum. BmGr10 is predicted to function in sugar recognition; however, the precise biochemical function remains obscure. Larvae of B. mori are monophagous feeders able to find and feed on mulberry leaves. Soluble mulberry leaf extract contains sucrose, glucose, fructose, and myo-inositol. In this study, we identified BmGr10 as an inositol receptor using electrophysiological analysis with the Xenopus oocyte expression system and Ca²⁺ imaging techniques using mammalian cells. These results demonstrated that Xenopus oocytes or HEK293T cells expressing BmGr10 specifically respond to myo-inositol and epi-inositol but do not respond to any mono-, di-, or tri-saccharides or to some sugar alcohols. These inositols caused Ca²⁺ and Na⁺ influxes into the cytoplasm independently of a G protein-mediated signaling cascade, indicating that BmGr10 is a ligand-gated cation channel. Overall, BmGr10 plays an important role in the myo-inositol recognition required for B. mori larval feeding behavior.     

Chemical DNA damage activates p21 WAF1/CIP1-dependent intra-S checkpoint

When cells progressing in G₁ phase are irradiated with UV light, two damage checkpoint pathways are activated: CHK1-Cdc25A and p53-p21^WAF1/CIP1, both targeting Cdk2 but the latter inducing long lasting inactivation. In similarly irradiated S phase cells, however, p21^WAF1/CIP1-dependent checkpoint is largely inactive. We report here that p21-dependent checkpoint can effectively be activated and induce a prolonged S phase arrest with similarly extended inactivation of Cdk2 by association of p21 if mid-S phase cells are damaged with a base-modifying agent instead of UV light, indicating that the poor utilization of p21-dependent checkpoint is not an innate property of S phase cells.     

Alkaline DNA fragmentation,DNA disentanglement evaluated viscosimetrically and sister chromatid exchanges,after treatment in vivo with nitrofurantoin

Nitrofurantoin was not positive as a carcinogen in long term assays. In vitro it was positive in some short term tests and negative in others. We have examined Nitrofurantoin for its capability of inducing DNA damage in vivo. With the alkaline elution technique, Nitrofurantoin appeared clearly positive in all the tissues examined (liver, kidney, lung, spleen and bone marrow). In the liver we also observed some cross-linking effect. In bone marrow cells Nitrofurantoin was also clearly positive in terms of sister chromatid exchanges (SCEs) induction. DNA damage in vivo was also examined with a viscosimetric method, more sensitive than alkaline elution. With this method the results were essentially negative, suggesting that the two methods detect different types of damage. In view of its positivity in many organs and in two short term tests in vivo, the carcinogenic potential of Nitrofurantoin should be reconsidered.     

Schistosoma mansoni: reactivity with infected human sera and monoclonal antibody characterization of a glycoprotein in different developmental stages

Cercarial glycoproteins of Schistosoma mansoni were purified by concanavalin A affinity chromatography. The purified fraction consisted of at least 15 polypeptides when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sera of infected humans specifically immunoprecipitated all of these polypeptides. These purified glycoproteins were used as antigen for preparing monoclonal antibodies. One of these monoclonal antibodies immunoprecipitated cercarial polypeptides that were identical to polypeptides immunoprecipitated with sera of infected humans as analyzed by two-dimensional gel electrophoresis. Direct binding assays with ¹²⁵I-labeled monoclonal antibody showed that proteins sharing antigenic determinants recognized by this monoclonal antibody were present not only in cercariae (the source of the immunogen) but also in adult male and female worms and in eggs. The protein molecules expressing these antigenic determinants were glycosylated in each of the developmental stages of the larvae, but differed with respect to molecular weight. These findings indicate a role for this monoclonal antibody in serodiagnosis and immunoprophylaxis.     

Mutagenicity testing in mammalian cells: I. Derivation of a chinese hamster ovary cell line heterozygous for the adenine phosphoribosyltransferase and thymidine kinase loci

As a first step in the development of a multiple-marker, mammalian cell mutagenesis assay system, we have isolated a Chinese hamster ovary (CHO) cell line that is heterozygous for both the adenine phosphoribosyltransferase (aprt) and thymidine kinase (tk) loci. Presumptive aprt^+/? heterozygotes with intermediate levels of APRT activity were selected from unmutagenized CHO cell populations on the basis of resistance to low concentrations of the adenine analog, 8-azaadenine. A functional aprt^+/? heterozygote with ～50% wild-type APRT activity was subsequently used to derive sublines that were also heterozygous for the tk locus. Biochemical and genetic characterization of one such subline, CHO-AT3-2, indicated that it was indeed heterozygous at both the aprt and tk loci. CHO-AT3-2 cells permitted single-step selection of mutants resistant to 8-azaadenine or 5-fluorodeoxyuridine, allowing quantitation and direct comparison of mutation induction at the autosomal aprt or tk loci, as well as in the gene involved in ouabain resistance or at the X-linked, hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus. Significant dose-dependent increases in mutation frequency were observed for all 4 genetic markers after treatment of CHO-AT3-2 cells with ethyl methanesulfonate.