The Thatcher illusion in humans and monkeys

Primates possess the remarkable ability to differentiate faces of group members and to extract relevant information about the individual directly from the face. Recognition of conspecific faces is achieved by means of holistic processing, i.e. the processing of the face as an unparsed, perceptual whole, rather than as the collection of independent features (part-based processing). The most striking example of holistic processing is the Thatcher illusion. Local changes in facial features are hardly noticeable when the whole face is inverted (rotated 180°), but strikingly grotesque when the face is upright. This effect can be explained by a lack of processing capabilities for locally rotated facial features when the face is turned upside down. Recently, a Thatcher illusion was described in the macaque monkey analogous to that known from human investigations. Using a habituation paradigm combined with eye tracking, we address the critical follow-up questions raised in the aforementioned study to show the Thatcher illusion as a function of the observer''s species (humans and macaques), the stimulus'' species (humans and macaques) and the level of perceptual expertise (novice, expert).     

FINE STRUCTURAL STUDIES ON THE INTERPHASE AND DIVIDING APICAL CELLS OF SPHACELARIA TRIBULOIDES (PHAEOPHYTA)1

The apical cells of Sphacelaria tribuloides Menegh. are larger than other thallus cells, contain more organelles and appear polarized. Their tip portion, where they grow, contains a well developed Golgi apparatus, abundant endoplasmic reticulum (ER) membranes, mitochondria, chloroplasts and a large number of small vacuoles. It seems likely that a continuous flow of membranous material from the ER membranes to the dictyosomes and from the latter to the plasmalemma of the extending tip portion takes place. In contrast, the basal pole possesses fewer organelles and is occupied mainly by large-sized, sometimes central vacuoles. The apical cells undergo two distinct types of highly asymmetrical differential divisions giving rise to cells of the thallus and hair initials. During the early stages of mitosis the nuclear envelope remains intact, except for fenestrated poles. Microtubules pass through the fenestrae into the nucleoplasm. During meta-phase, a typical chromosome plate is organized. The sites of attachment of spindle microtubules to the chromosomes are structurally different from the rest of the chromosomes. At late anaphase, the nuclear envelope breaks down completely. During telophase, a new membrane encloses the chromosomes which are decondensed and the nucleoli are reorganized. Cytokinesis proceeds long after mitosis at a stage in which the nuclei have increased in size and have moved farther apart. A membranous furrow develops centripetally, without the participation of microtubules. However, microtubules traverse the thin cytoplasmic strands which, in both interphase and cytokinetic cells, meander among the vacuoles of the basal pole of the cell and the internuclear space. Dictyosomes appear to be involved in the subsequent wall deposition.     

Constraints on flowering phenology in a phryganic (East Mediterranean shrub) community

The phenological pattern of flowering at the community level was studied in a Greek phryganic ecosystem near Athens for 4 consecutive years. Flowering is strongly seasonal: 80% of the insect-pollinated flora, which consists of 133 species, blooms between February and June. There is a variably expressed secondary flowering period in autumn. The pollinating fauna follows a strongly correlated pattern of abundance. Two types of plants were distinguished: pauciflorous species bearing <10 flowers that are large compared to the plant body, and multiflorous species with many small flowers. Pauciflorous species flower in the winter half of the year, while multiflorous species flower mainly in the summer half. The mean flower life spans are 9 and 3 days, respectively. The duration of flowering (DF) for each species is 55 days on average, which is long compared to other communities. The DF shows year-to-year variations, concomitant with the vicissitudes of the climate. The start of flowering of a species is statistically correlated with the temperature in the previous month, not with rainfall; its end date of flowering only partly compensates for the time gained or lost. DF is maximal in winter. The average flower life span of species flowering at any given date varies strongly and independently of the average DF. We tested the hypothesis that flowering phenology is set by phylogenetic and life form constraints. This could not be corroborated for phylogeny, evidently because of the overriding influence of the mediterranean climate, and probably also for biogeographical reasons. In contrast, life forms and multiflorous and pauciflorous species show strong differences. Many (51) of the species are therophytes; we tested the hypothesis that because of their annual habit they would be more dependent on pollination than perennials. Thus we anticipated that therophytic species would be differentiated from perennials in their flowering phenologies. This is not corroborated. We therefore conclude that the seed bank plays a role that is analogous to that of a perennial plant body.     

Experimental studies on the function of the cortical cytoplasmic zone of the preprophase microtubule band

Summary Centrifugation of young seedlings ofTriticum durum andTriticum aestivum for 8–10 hours at 1,500–2,000 x g causes a serious disorder of the spatial organelle relationships in the interphase as well as the preprophase and mitotic subsidiary cell mother cells (SMCs). The nucleus, most organelles and cytoplasm are displaced to the centrifugal end of the cell, while the vacuoles lie at the other end. However, after centrifugation, the preprophase microtubule bands (PMBs) are nucleated and remain at the expected position close to the guard cell mother cells (GMCs). In some elongated SMCs the PMBs become completely separated from the nucleus. The mitotic spindle exhibits variable orientation and is usually formed at some distance from the PMB cortical zone.Cytokinesis in SMCs is spatially highly disturbed and the cell plate shows a variety of unpredictable dispositions, which seem to be determined by: 1. the position of the preprophase-prophase nucleus and the orientation of the mitotic spindle as well as their spatial relationships to the PMB cortical zone, and 2. the space available for cell plate growth. Many of the daughter cells exhibit a highly variable shape and size in different planes. Usually one edge of the cell plate partly or totally joins the anticlinal parent wall adjacent to the PMB cortical zone.In some SMCs ofZea mays andTriticum aestivum, the junction regions of the periclinal walls with the anticlinal ones, lined by the PMB cortical zone in normal SMCs, are detectably thickened after the arrest of mitosis and the prevention of interphase microtubule formation by a prolonged colchicine treatment. In a small number of protodermal cells of the same plants, participating in the development of stomatal complexes, irregular wall bodies or incomplete wall sheets were formed at wall regions lined by the PMB cortical zone.The presented observations are in line with the following hypotheses: 1. the PMB cortical zone interacts with the growing edges of the cell plate attracting it to fuse with the underlying parent wall when the latter approaches the former at a critical distance, and 2. in SMCs particular regions of the PMB cortical zone and/or the adjacent plasmalemma promote the local wall deposition in the absence of microtubules.     

Secondary structure of mouse and rabbit α- and β-globin mRNAs: Differential accessibility of α and β initiator AUG codons towards nucleases

The nucleotide sequence from the 5′ terminus inward of one third of mouse α- and β^maj-globin messenger RNAs has been established. In addition, using 5′ ³²P end-labeled mRNAs as substrates and S1 and T1 nucleases as probes for single-stranded regions, the secondary structures of mouse and rabbit α- and β-globin mRNAs have been analyzed. Our results indicate that the AUG initiator codon in both mouse and rabbit β-globin mRNA is quite susceptible to cleavage with S1 and T1 nucleases, suggesting that it resides in a single-stranded exposed region. In contrast, the initiator AUG in the α-globin mRNA of both species is inaccessible to cleavage, indicating that it is either buried by tertiary structure or is base-paired. Since the rate of initiation of protein synthesis with β-globin mRNA in rabbit reticulocyte is 30–40% faster than for α-globin mRNA, these results imply a possible correlation between the differential rates of initiation with these two mRNAs and the accessibility of the respective AUG initiator codons.     

Histochemical studies on the oil-bodies ofMarchantia paleacea bert

Summary Correlated light and electron microscope histochemistry was performed on the oil bodies (OB) ofMarchantia paleacea. It was revealed that they contain significant quantities of material positive to PAS and periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) reactions. Ag deposits were localized on the matrix surrounding the globules and on the distinct one close to the inner face of the OB membrane. In addition, the lipophilic globules were peripherally impregnated with staining product. Polysaccharidic material appears to be elaborated in dictyosomes and then advanced into the OB by their vesicles.The OB show a lipophilic character and are intensely stained with Sudan black B, with an aqueous solution of osmium tetroxide and with the Nadi reaction as modified byDavid andCarde (1964).The performance of mercury bromophenol blue, aniline blue black, coomassie brilliant blue R and acid fuchsin stainings showed that the OB do not contain structurally detectable proteins. Besides, a positive reaction of the inner OB was obtained in fresh tissue with a variety of tests sensitive to phenolic or other aromatic ring compounds. On the contrary, the epidermal and scale OB containing small globules are obviously stained only with Gibbs' reagent. The colours obtained with the above reactions, were almost the same,i.e. brown with a red shade, except for the blue one of the Gibbs' reagent.The presented observations favour the conclusion that the OB matrix does not contain proteins, but substances polysaccharidic in nature. Phenolic and possibly other aromatic compounds appear to be present at least in inner OB.     

The interaction of Rh(II) and Rh(III) with DNA

The interaction of Rh2(II)(acetate)4, cis-[Rh(III)(en)2Cl2] Cl (en = ethylenediamine) and [Rh(III) (NH3)5Cl]Cl2 with calf thymus DNA has been studied at various r values [formula; see text] and interaction times. Electronic spectra, melting and cooling curves and sedimentation data indicate no interaction of the acetate complex with DNA, except in the case of a high r value and long interaction time. The other two complexes have been found to interact with the phosphate groups, thus stabilizing the macromolecule.     

Colonization history of Galapagos giant tortoises: Insights from mitogenomes support the progression rule

Galapagos giant tortoises (Chelonoidis spp.) are a group of large, long-lived reptiles that includes 14 species, 11 of which are extant and threatened by human activities and introductions of non-native species. Here, we evaluated the phylogenetic relationships of all extant and two extinct species (Chelonoidis abingdonii from the island of Pinta and Chelonoidis niger from the island of Floreana) using Bayesian and maximum likelihood analysis of complete or nearly complete mitochondrial genomes. We also provide an updated phylogeographic scenario of their colonization of the Galapagos Islands using chrono-phylogenetic and biogeographic approaches. The resulting phylogenetic trees show three major groups of species: one from the southern, central, and western Galapagos Islands; the second from the northwestern islands; and the third group from the northern, central, and eastern Galapagos Islands. The time-calibrated phylogenetic and ancestral area reconstructions generally align with the geologic ages of the islands. The divergence of the Galapagos giant tortoises from their South American ancestor likely occurred in the upper Miocene. Their diversification on the Galapagos adheres to the island progression rule, starting in the Pleistocene with the dispersal of the ancestral form from the two oldest islands (San Cristóbal and Española) to Santa Cruz, Santiago, and Pinta, followed by multiple colonizations from different sources within the archipelago. Our work provides an example of how to reconstruct the history of endangered taxa in spite of extinctions and human-mediated dispersal events and provides a framework for evaluating the contribution of colonization and in situ speciation to the diversity of other Galapagos lineages.     

Molecular phylogeny and historical biogeography of the Anatolian lizard Apathya (Squamata,Lacertidae)

Apathya is a lacertid genus occurring mainly in south-east Turkey and its adjacent regions (part of Iran and Iraq). So far two morphological species have been attributed to the genus; A. cappadocica (with five subspecies, A. c. cappadocica, A. c. muhtari, A. c. schmidtlerorum, A. c. urmiana and A. c. wolteri) and A. yassujica. The first species occupies most of the genus’ distribution range, while A. yassujica is endemic of the Zagros Mountains. Here, we explored Apathya’s taxonomy and investigated the evolutionary history of the species by employing phylogenetic and phylogeographic approaches and using both mitochondrial (mtDNA) and nuclear markers. The phylogenetic relationships and the genetic distances retrieved, revealed that Apathya is a highly variable genus, which parallels its high morphological variation. Such levels of morphological and genetic differentiation often exceed those between species of other Lacertini genera that are already treated as full species, suggesting the necessity for a taxonomic revision of Apathya. The phylogeographical scenario emerging from the genetic data suggests that the present distribution of the genus was determined by a combination of dispersal and vicariance events between Anatolia and Southwest Asia dating back to the Miocene and continuing up to the Pleistocene. Key geological events for the understanding of the phylogeography of the genus are the movement of the Arabian plate that led to the configuration of Middle East (orogenesis of the mountain ranges of Turkey and Iran) and the formation of Anatolian Diagonal.     

Influence of inlet boundary conditions on the local haemodynamics of intracranial aneurysms

Haemodynamics is believed to play an important role in the initiation, growth and rupture of intracranial aneurysms. In this context, computational haemodynamics has been extensively used in an effort to establish correlations between flow variables and clinical outcome. It is common practice in the application of Dirichlet boundary conditions at domain inlets to specify transient velocities as either a flat (plug) profile or a spatially developed profile based on Womersley's analytical solution. This paper provides comparative haemodynamics measures for three typical cerebral aneurysms.

Three dimentional rotational angiography images of aneurysms at three common locations, viz. basilar artery tip, internal carotid artery and middle cerebral artery were obtained. The computational tools being developed in the European project @neurIST were used to reconstruct the fluid domains and solve the unsteady Navier–Stokes equations, using in turn Womersley and plug-flow inlet velocity profiles. The effects of these assumptions were analysed and compared in terms of relevant haemodynamic variables within the aneurismal sac. For the aneurysm at the basilar tip geometries with different extensions of the afferent vasculature were considered to study the plausibility of a fully-developed axial flow at the inlet boundaries.

The study shows that assumptions made on the velocity profile while specifying inlet boundary conditions have little influence on the local haemodynamics in the aneurysm, provided that a sufficient extension of the afferent vasculature is considered and that geometry is the primary determinant of the flow field within the aneurismal sac. For real geometries the Womersley profile is at best an unnecessary over-complication, and may even be worse than the plug profile in some anatomical locations (e.g. basilar confluence).