NEUROPEPTIDE Y RECEPTORS FROM CALF BRAIN: EFFECT OF CRUDE CONUS VENOM PREPARATIONS ON [H]NPY BINDING

NPY receptors are identified in calf frontal cortex and hippocampus membrane preparations by binding of N-[propionyl-³H] neuropeptide Y. Saturation and competition binding data with PYY, NPY-(18–36) and NPY itself fit with a single class of sites: for the radioligand K_D = 1.4 ± 0.5 nM, B_max = 434 ± 180 fmol/mg protein in frontal cortex, K_D = 0.7 ± 0.2 nM, B_max = 267 ± 50 fmol/mg protein in hippocampus. Competition curves of the Y₁-subtype selective agonist [Leu³¹, Pro³⁴]NPY are biphasic in both membrane preparations: high affinity sites (i.e. Y₁-subtype) amount to 80% in frontal cortex and 23% in hippocampus. The remaining sites are of the Y₂-subtype. Out of 23 Conus venom preparations, 17 inhibit the binding of [³H]NPY in both membrane preparations, but only two of them (from Conus aulicus and C. pennaceus) do so with high potency (ic₅₀ < 5 μg protein/ml). Only one venom preparation (from C. mercator) had weak discriminatory properties (ic₅₀Y₂/ic₅₀Y₁ = 6). Venom from C. anemone increased the [³H]NPY binding 5-fold and with an ic₅₀ of 15–18 μg protein/ml. This binding occurred to the venom itself and was unrelated to the NPY receptors since it was equally potent when displaced by [Leu³¹, Pro³⁴]NPY, NPY-(18–36), PYY and NPY. Copyright © 1996 Elsevier Science Ltd     

Bryozoaires des milieux récifaux miocèes du sillon sud-rifain au Maroc

Moissette, P. & Saint Martin, J_:P. 1995 11 30 Bryozoaires des milieux récifaux miocenes du sillon sud-rifain au Maroc. [Bryozoans from Miocene reef environments in the South-Rifian corridor of Morocco. In late Miocene coral reefs from the Fes area (Northern Morocco), bryozoans are the best-represented group. An inventory of the bryozoan fauna (59 species) was taken on two reefs with different organization and palaeogeographical situation in a late Miocene seaway between the Atlantic and the Mediterranean. A study of the bryozoans and their zoarial forms allows an improved reconstruction of reefal environments and available habitats. Membraniporiforrn (encrusting) colonies largely predominate, whereas celleporiforms (nodular colonies) are more rare. Rigid erect (vinculariiform, adeoniform, and reteporiform) and rigid articulated zoarial types (cellariiform and catenicelliform) are fairly well represented. At depths of about 10 m and on the reef front encrusting bryozoans were well developed in cryptic habitats on living coral substrates. Erect species lived in cavities provided by the coral framework, and plants offered flexible substrates for the attachment of epiphytal forms. □Bryozoa, coral reefs, Morocco, Messininn, pulueoecology. Dans les récifs coralliens du Miocène supérieur de la région de Fes (Maroc septentrional), les bryozoaires constituent, parrni les organismes conservés, le groupe le mieux représenté. Un recensement de la fame de bryozoaires (59 espèces) a été effectué dans deux récifs d'organisation et de situation paléogéographique différentes, dans un secteur de communication entre Atlantique et Méditerranée au MiocéFne supérieur. L'étude des bryozoaires et de leurs formes zoariales permet de proposer une meilleure reconstitution de I'environnement récifal et des habitats disponibles. Les colonies membraniporiformes (encrobtantes) predominent largement, alors que les cellepori-formes (colonies noduleuses) sont beaucoup plus rares. Les types zoariaux érigés rigides (vincula-riiforme, adéoniforme et rétéporiforme) et érigés articulés (cellariiforme et catenicelliforme) sont assez bien représentés. A des profondeurs denviron 10 m et dans la partie antérieure des constructions récifales, les bryozoaires encroûtants étaient bien développés dans des habitats cryptiques sur substrats coralliens vivants. Des formes dressées vivaient dans les cavités ménagées par le bâti corallien et des supports végétaux permettaient également la fixation de formes épiphytes. □Bryozouires, récifs coralliens, Muroc, Messinien, puléoécologie.     

Invertebrate bioturbation can reduce the clogging of sediment: an experimental study using infiltration sediment columns

1. Invertebrate bioturbation can strongly affect water‐sediment exchanges in aquatic ecosystems. The objective of this study was to quantify the influence of invertebrates on the physical characteristics of an infiltration system clogged with fine sediment. 2. Two taxa (chironomids and tubificids) with different bioturbation activities were studied in experimental slow infiltration columns filled with sand and gravel and clogged with a 2 cm layer of fine sediment at the surface. We measured the effects of each taxon separately and combined on hydraulic head, water mobility and sediment reworking. 3. The results showed that invertebrates could reduce sediment clogging and this effect was linked to the functional mode of bioturbation of each group. Tubificid worms dug networks of galleries in the fine sediment, creating pathways for water flow, which reduced the clogging of sediment. In contrast, the U‐shaped tubes of chironomids were restricted to the superficial layer of fine sediments and did not modify the hydraulic conductivity of experimental columns. The combination of invertebrates did not show any interactive effects between tubificids and chironomids. The occurrence of 80 tubificids in the combination was enough to maintain the same hydraulic conductivity that 160 worms did in monospecific treatment. 4. The invertebrates like tubificid worms can have a great benefit on functioning of clogged interfaces by maintaining high hydraulic conductivity, which contributes to increased water‐sediment exchanges and stimulates biogeochemical and microbial processes occurring in river sediments.     

Alternative sites for ecdysteroid production in insects

Summary

Several evidences have been obtained in various insect species demonstrating that, besides prothoracic glands and ovaries, other tissues could be alternative sites of moulting hormone production. After a detailed review on the various methods of investigation and criteria required to validate such observations, the nature of these sites, namely oenocytes, epidermis and testes, is discussed. Their possible involvement in moulting and/or reproduction is analyzed, giving the opportunity to put forward several new hypotheses. In particular, autocrine and paracrine secretions of ecdysteroids could play a role in localized developmental events, more difficult to control from endocrine glands possibly mitosis, meiosis, reprogramming, regeneration or early steps of embryogenesis).     

Bathysabellaria neocaledoniensis, a new genus and species of Sabellariidae (Annelida, Polychaeta) from bathyal zones off New Caledonia (Southwest Pacific Ocean)

A new genus and species of Sabellariidae is described from deep water off New Caledonia and compared with other sabellariids having four parathoracic segments.     

A Membrane Receptor Mechanism for Steroid Hormones Reinitiating Meiosis in Xenopus Laevis Oocytes*

There is a membrane progesterone receptor in Xenopus laevis oocytes that undergo meiosis under steroid exposure. Early responses include a decrease of leucine uptake, a decrease of adenylate cyclase and alkaline phosphatase activities, and a decrease of the phosphorylation of a specific p48 protein in the membrane. These results are compatible with a decrease of membrane fluidity brought about by the hormonal message. However the above-cited effects as well as the Ca₂₊-changes are not yet enough well understood to be able to precisely delineate their role in meiosis reinitiation.     

Of squeezers and skippers: factors determining the age at moult of immature African Penguins Spheniscus demersus in Namibia

We used banding and resighting records of 391 African Penguins Spheniscus demersus banded as chicks and later resighted during immature moult to explain the roles of date of fledging and age at moult in determining the season of moult and its timing within the season. Breeding was continuous, but immature moult occurred mainly during spring and summer. Age at immature moult extended over 11 months, from 12 to 23 months after hatching. Birds that fledged during summer and early autumn generally moulted during the next moult season (squeezers), whereas birds that fledged in late autumn, winter and spring skipped the next moult season to moult only the following season (skippers). There was a significant relationship between age at moult and moult date, with young birds moulting later in the season than older birds. The age at moult of immature birds appears to be constrained by minimum age, moult seasonality and plumage wear. Birds that fledged over nearly 2 years moult during one season. Counts of moulting immature African Penguins have not been used to estimate year-class strength and post-fledging survival owing to the wide range of ages at immature moult. Our results provide the means of assigning recruits to specific age groups.