Mapping the navigational knowledge of individually foraging ants,Myrmecia croslandi

Ants are efficient navigators, guided by path integration and visual landmarks. Path integration is the primary strategy in landmark-poor habitats, but landmarks are readily used when available. The landmark panorama provides reliable information about heading direction, routes and specific location. Visual memories for guidance are often acquired along routes or near to significant places. Over what area can such locally acquired memories provide information for reaching a place? This question is unusually approachable in the solitary foraging Australian jack jumper ant, since individual foragers typically travel to one or two nest-specific foraging trees. We find that within 10 m from the nest, ants both with and without home vector information available from path integration return directly to the nest from all compass directions, after briefly scanning the panorama. By reconstructing panoramic views within the successful homing range, we show that in the open woodland habitat of these ants, snapshot memories acquired close to the nest provide sufficient navigational information to determine nest-directed heading direction over a surprisingly large area, including areas that animals may have not visited previously.     

Fine genetic mapping of the proximal part of mouse Chromosome 2 excludes Pax-8 as a candidate gene for Danforth's short tail (Sd)

Danforth's short tail (Sd) is a semidominant mutation of the mouse with effects on the skeleton and the urogenital system. In view of its phenotype and its position in the proximal part of Chromosome (Chr) 2, three genes qualified as possible candidates: Pax-8, a paired box-containing gene; Midkine (Mdk), a retinoic acid-responsive gene; and a new locus (Etl-4) identified by enhancer trapping with a lacZ reporter gene which showed expression in the notochord, the mesonephric mesenchyme, and the apical ectodermal ridge. Three different backcrosses involving all three genes in different combinations were set up and analyzed. From our results we conclude that Sd, Etl-4, Pax-8, and Mdk are independent loci, with Etl-4 being the closest genetic marker (1.1±1.4 cM) to the Danforth's short tail (Sd) gene.     

Monitoring individual development of isolated wheat zygotes: a novel approach to study early embryogenesis

Summary A culture method has been established by which development of isolated wheat (Triticum aestivum L.) zygotes can be monitored individually until formation of multicellular structures. As was shown recently, these isolated zygotes have a high capacity to form differentiated embryos and normal plants, and thus constitute a suitable object to study early embryogenesis. After being isolated within 6 h after pollination (hap), zygotes were immobilized in an agarose droplet directly on a microscopic chamber slide, which allows for both subsequent development through co-culture with feeder aggregates, as well as detailed observation and photographic documentation of individiual behavior. Shortly after fertilization, the wheat zygote, like the unfertilized egg cell, is characterized by one conspicuous nucleolus. Typically, a second and a third nucleolus appeared between 5 and 8.5 hap. Between 7 and 15 hap, we observed nucleolar vacuolation indicating enhanced ribosomal activity. Continuous cell expansion with slight cell elongation was detected until around 15 hap, followed by a period of transitory reduction in cell volume which roughly corresponded with mitosis. Mitotic prophase of a zygote could easily be detected by the disappearance of all nucleoli within a few minutes. The division plane was generally established perpendicular to the formerly established cell elongation axis. At cytokinesis, which was completed by 19 hap in 90% of the individuals observed, 2 or 3 nucleoli were detected again per daughter cell. The first cell division, including the establishment of a cleavage furrow with intercellular spaces, was completed in all cases within 23 hap. Since this result is in accordance with what is known from earlier studies based upon fixed material, and since the zygotes subsequently continue embryogenesis, in vitro development is assumed to be analogous to that in planta. This experimental system constitutes a valuable experimental tool for further detailed research, both at the cellular and at the molecular level.Abbreviations hap hours after pollination - NOR nucleolus-organizing region     

Membrane composition of jetted lipid vesicles: a Raman spectroscopy study

Microfluidic jetting is a promising method to produce giant unilamellar phospholipid vesicles for mimicking living cells in biomedical studies. We have investigated the chemical composition of membranes of vesicles prepared using this approach by means of Raman scattering spectroscopy. The membranes of all jetted vesicles are found to contain residuals of the organic solvent decane used in the preparation of the initial planar membrane. The decane inclusions are randomly distributed over the vesicle surface area and vary in thickness from a few to several tens of nanometers. Our findings point out that the membrane properties of jetted vesicles may differ considerably from those of vesicles prepared by other methods and from those of living cells. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Calcium dysregulation in Alzheimer's disease

Alzheimer disease (AD) is the most common form of adult dementia. Its pathological hallmarks are synaptic degeneration, deposition of amyloid plaques and neurofibrillary tangles, leading to neuronal loss. A few hypotheses have been proposed to explain AD pathogenesis. The beta-amyloid (Abeta) and hyperphosphorylated tau hypotheses suggest that these proteins are the main players in AD development. Another hypothesis proposes that the dysregulation of calcium homeostasis may be a key factor in accelerating other pathological changes. Although Abeta and tau have been extensively studied, recently published data provide a growing body of evidence supporting the critical role of calcium signalling in AD. For example, presenilins, which are mutated in familial cases of AD, were demonstrated to form low conductance calcium channels in the ER and elevated cytosolic calcium concentration increases amyloid generation. Moreover, memantine, an antagonist of the NMDA-calcium channel receptor, has been found to have a beneficial effect for AD patients offering novel possibilities for a calcium signalling targeted therapy of AD. This review underscores the growing importance of calcium ions in AD development and focuses on the relevant aspects of calcium homeostasis.     

Influence of Interfacial Composition on in Vitro Digestibility of Emulsified Lipids: Potential Mechanism for Chitosan's Ability to Inhibit Fat Digestion

The objective of this study was to investigate the influence of interfacial composition and electrical charge on the in vitro digestion of emulsified fats by pancreatic lipase. An electrostatic layer-by-layer deposition technique was used to prepare corn oil-in-water emulsions (3 wt% oil) that contained droplets coated by (1) lecithin, (2) lecithin–chitosan, or (3) lecithin–chitosan–pectin. Pancreatic lipase (1.6 mg mL⁻¹) and/or bile extract (5.0 mg mL⁻¹) were added to each emulsion, and the particle charge, droplet aggregation, and free fatty acids released were measured. In the presence of bile extract, the amount of fatty acids released per unit amount of emulsion was much lower in the emulsions containing droplets coated by lecithin–chitosan (38 ± 16 μmol mL⁻¹) than those containing droplets coated by lecithin (250 ± 70 μmol mL⁻¹) or lecithin–chitosan–pectin (274 ± 80 μmol mL⁻¹). In addition, there was much more extensive droplet aggregation in the lecithin–chitosan emulsion than in the other two emulsions. We postulated that lipase activity was reduced in the lecithin–chitosan emulsion as a result of the formation of a relatively thick cationic layer around each droplet, as well as the formation of large flocs, which restricted the access of the pancreatic lipase to the lipids within the droplets. Our results also suggest that droplets initially coated by a lecithin–chitosan–pectin layer did not inhibit lipase activity, which may have been because the chitosan–pectin desorbed from the droplet surfaces thereby allowing the enzyme to reach the lipids; however, further work is needed to establish this. This information could be used to create food emulsions with low caloric level, or to optimize diets for individuals with lipid digestion problems.     

A classification of major natural habitats of Amazonian white-water river floodplains (várzeas)

Most countries sharing the Amazon basin have signed the Ramsar Convention on Wetlands of International Importance but still lack complete wetland inventories, classification systems, and management plans. Amazonian wetlands vary considerably with respect to hydrology, water and soil fertility, vegetation cover, diversity in plant and animal species and primary and secondary productivity. Here, we propose a classification system of major natural habitats of Amazonian white-water river floodplains (várzeas) based on hydrological, water and soil chemistry and biological parameters. The Amazonian várzea is one of the largest Amazonian wetlands. It is exceptionally rich in plant and animal species and plays important roles in landscape history, evolution, hydrology and biogeochemical cycles of the Amazon basin. Most of Amazonia??s rural population lives in or along the várzea, emphasizing the economic importance of its natural resources. Our classification indicates five major systems, which are subdivided into 10 main habitats and up to 40 functional (vegetation) units of which the most important mesohabitats are described. We understand this classification as a dynamic system, as it is open to the inclusion of future research attempts and habitats without affecting the entire classification system. Our classification may be used for scientific purposes, such as comparative studies on biomass, productivity, biogeochemical cycles and biodiversity. Also, because the classification builds on habitat types and/or vegetation and functional units already distinguished by the local population it may be especially useful in guiding intelligent use of várzea habitat for specific management activities, such as agriculture, animal husbandry, forestry, fisheries, and conservation.