Triggering and persistence of trail-laying in foragers of the ant Lasius niger

In the ant Lasius niger, the ability to ingest their own desired volume is the key criterion that rules the recruiting behaviour of scouts. This volume acts as a threshold triggering the trail-laying response of foragers. In this paper, we show that this desired volume is specific to each individual and is kept constant over successive trips to a food source. This individual specificity contrasts with the variability of all individual desired volumes within the colony. In this study, it is also shown that, among L. niger foragers, 14% never participate in the formation of the chemical pathway and never lay a trail over successive trips. Among the others foragers, interindividual differences in the persistence of trail-laying behaviour over successive trips are observed but do not rely on an individual specialisation, in which some ants would lay a trail more frequently and persistently than other scouts. We discuss how an individual in the foraging behaviour can play an essential role in the regulation of food retrieval dynamics.     

Comparative analysis of cloned larval and adult globin cDNA sequences of Xenopus laevis

cDNA clones complementary to 9 S poly(A)⁺ RNA from erythroblasts of anemic larvae and adults of Xenopus laevis have been prepared. Clones, containing at least 400 bp of cDNA, have been analyzed by cross-hybridization and restriction mapping. They were found to comprise four unrelated main groups of sequences (two larval and two adult) and each main group contained two related subgroups. Partial sequence analysis and comparison of restriction data to previously published maps allowed the four main groups to be identified as α- or β-globin sequences. The sequence divergence between the subgroups was determined by melting curves of homo- and heteroduplexes. We found that the larval sequences have diverged twice as far as the adult ones. To account for this result, different hypotheses on globin gene evolution are proposed.     

Trace Fossils from the Brioverian (Ediacaran–Fortunian) in Brittany (NW France)

The Ediacaran–Fortunian ichnofauna from Central Brittany (NW France) is revised for the first time since the pioneering work by Lebesconte at the end of the 19th century. The study is based on fossils from the type-localities of the historical Brioverian taxa Montfortia (traces from Montfort-sur-Meu) and Neantia (wrinkle surfaces from Néant-sur-Yvel), and on two new outcrops from Saint-Gonlay. The ichnofossil assemblage includes Helminthoidichnites tenuis, Helminthopsis tenuis, Gordia marina, Palaeophycus tubularis, ?Neonereites uniserialis, and ?Spirodesmos archimedeus. Locally, the grazing traces are associated with wrinkle surfaces considered as microbially induced sedimentary structures (MISS). The sedimentological characteristics of these deposits correspond to a shelf marine environment. Both U-Pb datings on detrital zircon and ichnostratigraphic criteria tend toward an Ediacaran age of the fossiliferous deposits, but we cannot exclude the possibility of a Fortunian age at the present state of knowledge.     

Differential effects of monensin on the plant secretory pathway

The sodium ionophore monensin was used as an inhibitor of Golgifunction to study the secretory event in suspension-culturedsycamore cells. The morphological changes induced by monensinwere recorded. Concurrent studies of the disturbance causedby the drug were carried out by biochemical, cytochemical andimmunocytochemical techniques. Monensin induced accumulationof smooth and coated vesicles in the vicinity of the Golgi apparatus,swelling of Golgi cisternae and also provoked the formationof extracytoplasmic pockets between the plasma membrane andthe cell wall. Cytochemical tests for polysaccharides and immunolocalizationof secreted pectins, recognized by the monoclonal antibody JIM7, were performed, and the results indicated that the biosynthesisand/or processing machinery of polysaccharides was affectedby the drug. In contrast, immunolocalization of glycoproteins,recognized by the monoclonal antibodies JIM 84 and JIM 13 demonstratedthat the accumulation of vesicles in the cytoplasm were Golgiderived, and that the secretion of glycoproteins was not drasticallyaffected by monensin. Fluorography of radiolabelled proteinsdemonstrated that in this system the secretion of proteins wasnot qualitatively changed by monensin. The implications of theseresults are discussed in the light of the current hypotheseson the effects of monensin on the secretory pathway. Key words: Golgi apparatus, immunocytochemistry, monensin, secretion     

The PTK7 and ROR2 Protein Receptors Interact in the Vertebrate WNT/Planar Cell Polarity (PCP) Pathway

The non-canonical WNT/planar cell polarity (WNT/PCP) pathway plays important roles in morphogenetic processes in vertebrates. Among WNT/PCP components, protein tyrosine kinase 7 (PTK7) is a tyrosine kinase receptor with poorly defined functions lacking catalytic activity. Here we show that PTK7 associates with receptor tyrosine kinase-like orphan receptor 2 (ROR2) to form a heterodimeric complex in mammalian cells. We demonstrate that PTK7 and ROR2 physically and functionally interact with the non-canonical WNT5A ligand, leading to JNK activation and cell movements. In the Xenopus embryo, Ptk7 functionally interacts with Ror2 to regulate protocadherin papc expression and morphogenesis. Furthermore, we show that Ptk7 is required for papc activation induced by Wnt5a. Interestingly, we find that Wnt5a stimulates the release of the tagged Ptk7 intracellular domain, which can translocate into the nucleus and activate papc expression. This study reveals novel molecular mechanisms of action of PTK7 in non-canonical WNT/PCP signaling that may promote cell and tissue movements.     

Awareness of Memory Deficits in Early Stage Huntington's Disease

Patients with Huntington''s disease (HD) are often described as unaware of their motor symptoms, their behavioral disorders or their cognitive deficits, including memory. Nevertheless, because patients with Parkinson''s disease (PD) remain aware of their memory deficits despite striatal dysfunction, we hypothesize that early stage HD patients in whom degeneration predominates in the striatum can accurately judge their own memory disorders whereas more advanced patients cannot. In order to test our hypothesis, we compared subjective questionnaires of memory deficits (in HD patients and in their proxies) and objective measures of memory dysfunction in patients. Forty-six patients with manifest HD attending the out-patient department of the French National Reference Center for HD and thirty-three proxies were enrolled. We found that HD patients at an early stage of the disease (Stage 1) were more accurate than their proxies at evaluating their own memory deficits, independently from their depression level. The proxies were more influenced by patients'' functional decline rather than by patients'' memory deficits. Patients with moderate disease (Stage 2) misestimated their memory deficits compared to their proxies, whose judgment was nonetheless influenced by the severity of both functional decline and depression. Contrasting subjective memory ratings from the patients and their objective memory performance, we demonstrate that although HD patients are often reported to be unaware of their neurological, cognitive and behavioral symptoms, it is not the case for memory deficits at an early stage. Loss of awareness of memory deficits in HD is associated with the severity of the disease in terms of CAG repeats, functional decline, motor dysfunction and cognitive impairment, including memory deficits and executive dysfunction.     

The multifaceted roles of Eph/ephrin signaling in breast cancer

Eph receptors and their membrane-bound ligands are intimately involved in the control of morphogenic processes during embryonic development and adult tissue homeostasis. By their ability to orchestrate cell migration, pattern formation and tissue integrity they are also prone to be involved in carcinogenic growth. In this review we concentrate on their involvement in the normal and carcinogenic development of the breast. In this context we summarize their multi-faceted functions as tumor suppressors, tumor promoters, angiogenic inducers and regulators of stem cell homeostasis.