Identification of novel adrenomedullin in mammals: a potent cardiovascular and renal regulator

We have identified cDNA encoding a new member of the adrenomedullin (AM) family, AM2, for the first time in mammals (mouse, rat and human). The predicted precursor carried mature AM2 in the C-terminus, which had an intramolecular ring formed by an S-S bond and a possibly amidated C-terminus. Phylogenetic analyses clustered AM2 and AM into two distinct but closely related groups. Similarity of exon-intron structure and synteny of neighboring genes showed that mammalian AM2 is an ortholog of pufferfish AM2 and a paralog of mammalian AM. AM2 mRNA was expressed in submaxillary gland, kidney, stomach, ovary, lymphoid tissues and pancreas of mice, but not in adrenal and testis. Intravenous injection of synthetic mature AM2 decreased arterial pressure more potently than AM, and induced antidiuresis and antinatriuresis in mice. These results show that at least two peptides, AM and AM2, comprise an adrenomedullin family in mammals, and that AM2 may play pivotal roles in cardiovascular and body fluid regulation.     

Contribution of comparative fish studies to general endocrinology: structure and function of some osmoregulatory hormones

Fish endocrinologists are commonly motivated to pursue their research driven by their own interests in these aquatic animals. However, the data obtained in fish studies not only satisfy their own interests but often contribute more generally to the studies of other vertebrates, including mammals. The life of fishes is characterized by the aquatic habitat, which demands many physiological adjustments distinct from the terrestrial life. Among them, body fluid regulation is of particular importance as the body fluids are exposed to media of varying salinities only across the thin respiratory epithelia of the gills. Endocrine systems play pivotal roles in the homeostatic control of body fluid balance. Judging from the habitat-dependent control mechanisms, some osmoregulatory hormones of fish should have undergone functional and molecular evolution during the ecological transition to the terrestrial life. In fact, water-regulating hormones such as vasopressin are essential for survival on the land, whereas ion-regulating hormones such as natriuretic peptides, guanylins and adrenomedullins are diversified and exhibit more critical functions in aquatic species. In this short review, we introduce some examples illustrating how comparative fish studies contribute to general endocrinology by taking advantage of such differences between fishes and tetrapods. In a functional context, fish studies often afford a deeper understanding of the essential actions of a hormone across vertebrate taxa. Using the natriuretic peptide family as an example, we suggest that more functional studies on fishes will bring similar rewards of understanding. At the molecular level, recent establishment of genome databases in fishes and mammals brings clues to the evolutionary history of hormone molecules via a comparative genomic approach. Because of the functional and molecular diversification of ion-regulating hormones in fishes, this approach sometimes leads to the discovery of new hormones in tetrapods as exemplified by adrenomedullin 2.     

Influence of weather conditions on the flight of migrating black storks

This study tested the potential influence of meteorological parameters (temperature, humidity, wind direction, thermal convection) on different migration characteristics (namely flight speed, altitude and direction and daily distance) in 16 black storks (Ciconia nigra). The birds were tracked by satellite during their entire autumnal and spring migration, from 1998 to 2006. Our data reveal that during their 27-day-long migration between Europe and Africa (mean distance of 4100 km), the periods of maximum flight activity corresponded to periods of maximum thermal energy, underlining the importance of atmospheric thermal convection in the migratory flight of the black stork. In some cases, tailwind was recorded at the same altitude and position as the birds, and was associated with a significant rise in flight speed, but wind often produced a side azimuth along the birds'' migratory route. Whatever the season, the distance travelled daily was on average shorter in Europe than in Africa, with values of 200 and 270 km d⁻¹, respectively. The fastest instantaneous flight speeds of up to 112 km h⁻¹ were also observed above Africa. This observation confirms the hypothesis of thermal-dependant flight behaviour, and also reveals differences in flight costs between Europe and Africa. Furthermore, differences in food availability, a crucial factor for black storks during their flight between Europe and Africa, may also contribute to the above-mentioned shift in daily flight speeds.     

Extracellular adenine nucleotides inhibit the release of major monocyte recruiters by human monocyte-derived dendritic cells

Extracellular ATP is known to affect the maturation of monocyte-derived dendritic cells mainly by regulation of cytokines and costimulatory molecules. The present study describes the inhibition of MCP-1 (CCL2) and MIP-1alpha (CCL3) release by human monocyte-derived dendritic cells in response to adenine nucleotides. Our pharmacological data support the involvement of P2Y11 and P2Y1 purinergic receptors in the downregulation of these major monocyte recruiters. Migration assays have demonstrated that supernatants of dendritic cells treated with adenine nucleotides or anti-MCP-1/MIP-1alpha blocking antibodies display a strongly reduced capacity to attract monocytes and immature dendritic cells.     

Determining body fuels of wintering mallards

Measuring body lipids and proteins of wild animals such as mallards is essential to determine the impact of the environment on their body condition. A major difficulty, however, is that biochemical analysis of carcass is tedious and therefore cannot be applied at a large scale. The main objective of this study was therefore to find out if simple measurements can be used as indices of total body lipids and proteins. Four classes of lipid and protein indices, derived on a 'source' group, were defined according to their complexity and condition of application (field or laboratory). Accuracy of the indices was evaluated on an independent group, of which the body composition calculated from indices was compared to carcass analysis. In live birds, body mass was an accurate and convenient predictor for both lipid and protein masses. If carcasses are available, extensive analysis provides a higher accuracy for body lipids only. This can be simply obtained through multiple regressions using abdominal fat mass and/or dry body mass.     

Nocturnal predation of king penguins by giant petrels on the Crozet Islands

Dietary segregation of sympatric seabirds in the Southern Ocean is partly linked to differences in their foraging techniques. We have investigated the activity of giant petrels (Macronectes spp.) in a king penguin (Aptenodytes patagonicus) colony day and night during the austral winter of 2001 on the Crozet Islands. Using an automatic identification system and an infrared video camera, we followed 15 petrels tagged with micro transponders. Our data show that giant petrels predate king penguin chicks during the night. The activity of giant petrels is even slightly higher during nighttime than during the day. In addition, our data show a higher nocturnal activity by northern giant petrels (M. halli) than by southern giant petrels (M. giganteus). These unexpected results raise questions concerning visual adaptations to nocturnal foraging in giant petrels and their potential impact on the sleep, vigilance and crèching behavior of penguin chicks.     

Time/depth usage of Adélie penguins: an approach based on dive angles

Data on the swim speed, dive depth and feeding rates of three Adélie penguins (Pygoscelis adeliae) foraging in summer 1998/1999 in Adélie Land, Antarctica were collected using dorsally-mounted loggers, in tandem with oesophageal temperature sensors. Swim speed could be integrated, together with the rate of change of depth, to determine dive and return-to-surface angles. Overall, birds increased rates of change of depth during commuting phases so that dive angles were steeper in dives terminating at greater depths. Angles of descent and ascent during feeding dives were greater than during non-feeding dives. Variation in the descent angle over time of particular dives was generally less than 10°, but the angles of the ascent phases varied more widely. The importance of selecting the optimum descent and ascent angles with respect to prey exploitation, oxygen stores and time gained in the feeding area over the course of a dive by diving at a steeper angle is discussed.     

Design,synthesis and anti-malarial activities of synthetic analogs of biselyngbyolide B,a Ca2+ pump inhibitor from marine cyanobacteria

Biselyngbyaside, an 18-membered macrolide glycoside from marine cyanobacteria, and its derivatives are known to be sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA) inhibitors. Recently, a SERCA orthologue of the malaria parasite, PfATP6, has attracted attention as a malarial drug target. To provide a novel drug lead, we designed new synthetic analogs of biselyngbyolide B, the aglycone of biselyngbyaside, based on the co-crystal structure of SERCA with biselyngbyolide B, and synthesized them using the established synthetic route for biselyngbyolide B. Their biological activities against malarial parasites were evaluated.