Detecting sudden changes in dynamic rotation displays.

Four experiments and controls were run in order to determine the ability of the visual system to detect slight changes in three-dimensional (3D) rotating stimuli in comparison to two-dimensional (2D) controls. A small number of observers (between 5 and 8) viewed computerized displays of pixel-defined transparent rotating spheres or circular patches of pixels drifting linearly in opposite directions. Halfway through the circuit of rotation a letter was briefly displayed and the rotation continued with some change introduced.

Ternus effect: two processes or differential activation? Comments on Odic and Pratt's 2008 paper.

Using a bistable apparent-motion display, Odic and Pratt (2008, Perception 37 1790-1804) have recently presented data that they interpret as being inconsistent with what they call "the two-process theory". Instead, they argue, their data can be explained by the differential-activation theory along with a process they identify as "temporal summation of contrast". It is argued here that Odic and Pratt misinterpreted the two-process distinction and used a display that was too unusual to be adequately addressed by it.

SpTie1/2 is expressed in coelomocytes, axial organ and embryos of the sea urchin Strongylocentrotus purpuratus, and is an orthologue of vertebrate Tie1 and Tie2.

A full length cDNA sequence expressed in coelomocytes shows significant sequence match to vertebrate Tie1 and Tie2/TEK. Vertebrate Tie2/TEK is the receptor for the angiopoietins and plays an important role in angiogenesis and hematopoiesis, whereas Tie1 regulates the activity of Tie2. The deduced sequence of the SpTie1/2 protein has a similar order and organization of domains to the homologous vertebrate proteins including a highly conserved receptor tyrosine kinase domain in the cytoplasmic tail.

Orientation anisotropy in the Ternus phenomenon.

The Ternus display is an ambiguous, multi-element, apparent-movement animation which can be perceived in two alternative organizations. One of these involves the simultaneous movement of several elements and is called group movement. The other involves the movement of one element only and is called element movement.

Spatial correspondence and relation correspondence: grouping factors that influence perception of the Ternus display.

We cite two different perceptual-correspondence principles whose emphasis can help to disambiguate the otherwise ambiguous Ternus display in apparent movement (a display that can alternately be seen in one of two possible configurations). One of these principles is spatial correspondence, which emphasizes the maintenance of similar stimulus elements in given locations over time. The other principle is relation correspondence, which emphasizes the maintenance of the inter-organization of stimulus elements across frames.

Metal-dependent repression of siderophore and biofilm formation in Actinomyces naeslundii.

Actinomyces naeslundii is a pioneer of the oral cavity and forms a biofilm on the tooth's surface. Most bacteria require iron for survival and in pathogenic bacteria iron availability regulates virulence gene expression. Metal-dependent repressors control gene expression involved in metal transport and uptake including siderophores.

The evolution of explanations of a perceptual phenomenon: a case history using the Ternus effect.

The Ternus effect involves a multi-element stimulus that can lead to either of two different percepts of apparent movement depending upon a variety of stimulus conditions. Since Ternus's 1926 discussion of this phenomenon, many researchers have attempted to explain it. We examine the history of explanations of the Ternus effect and show that they have evolved to contemporary theoretical positions that are very similar to Ternus's own ideas.

Factors influencing the ability to detect motion reversals in rotation simulations.

Five experiments probed the conditions under which observers fail to report instantaneous reversals in the direction of motion of pixels that define the rotation of a transparent sphere or plane. Our results showed that the extent to which rotation reversals were not reported depended upon whether observers used strict or lax criteria to make their judgments, the degree of perspective present in the rotation simulations, and the percentage of pixels that actually reversed direction. Furthermore, we found failures to report rotation reversals both with stimuli whose pixels were confined to smooth surfaces and scattered within volumes.

Effects on face recognition of spatial-frequency information contained in inspection and test stimuli.

Researchers often assume a critical band of spatial frequencies is required for face recognition. Also, many studies have not measured the contrast required for recognition. On Day 1, observers viewed high-pass-filtered (HP), low-pass-filtered (LP), or unfiltered (UF) faces.

Do variables that affect similar bistable apparent-movement displays result in similar changes in perception?

Two bistable apparent-movement displays (i.e. ones that generate two qualitatively different kinds of movement percepts under different conditions) were compared.

Cell swelling increases intracellular calcium in Necturus erythrocytes.

This study examined the role of Ca(2+) in regulatory volume decrease by Necturus erythrocytes. Hypotonic shock (50% tonicity) stimulated an increase in cytosolic free Ca(2+), detected using epi-fluorescence microscopy and the fluorescent Ca(2+) indicator fluo-4-AM (10 microM). A similar increase in fluorescence did not occur under isosmotic conditions, unless cells were exposed to the Ca(2+) ionophore A23187 (0.

Buildup and decay of a three-dimensional rotational aftereffect obtained with a three-dimensional figure.

Gaps in past literature have raised questions regarding the kinds of stimuli that can lead to three-dimensional (3-D) rotation aftereffects. Further, the characteristics of the buildup and decay of such aftereffects are not clear. In the present experiments, rotation aftereffects were generated by projections of cube-like stimuli whose dynamic perspective motions gave rise to the perception of rotation in unambiguous directions; test stimuli consisted of similar cubes whose rotation directions were ambiguous.

Rotifers: exquisite metazoans.

Rotifers comprise a modestly sized phylum (≈1,850 species) of tiny (ca. 50-2,000 μm), bilaterally symmetrical, eutelic metazoans, traditionally grouped within the pseudocoelomates or Aschelminthes. These saccate to cylindrically shaped protostomes possess three prominent regions (corona, trunk, foot).

Extracellular ATP activates a P2 receptor in necturus erythrocytes during hypotonic swelling.

We recently reported that ATP is released from Necturus erythrocytes via a conductive pathway during hypotonic swelling and that extracellular ATP potentiates regulatory volume decrease (RVD). This study was designed to determine whether extracellular ATP exerts its effect via a purinoceptor. This was accomplished using three different experimental approaches: 1) hemolysis studies to examine osmotic fragility, 2) a Coulter counter to assess RVD, and 3) the whole-cell patch-clamp technique to measure membrane currents.

Aberrant S(RN)1 Reaction of 4-Aminophenol with alpha,p-Dinitrocumene: EPR Observation of Intermediates.

The tert-butoxide-induced substitution of alpha,p-dinitrocumene by 4-aminophenol unexpectedly afforded the N-coupled product, 2-(4-hydroxyanilino)-2-(4-nitrophenyl)propane. EPR observations revealed arylaminyl radical intermediates as well as coupled anion radicals, hence the normal S(RN)1 process may compete with an alternative nonchain reaction pathway.

Discrimination of rotation from linear motion: influence of interference gratings and dichoptic viewing.

Observers viewed a screen on which a number of patches containing horizontally moving pixels were presented. Target patches consisted of pixels whose motion simulated the rotation of a cylinder around its Y-axis; distractors, of pixels whose motion was linear. The task was to assess whether a display contained a target patch.

Motion capture of stationary lines by apparently moving terminators.

Several studies and observations of a new form of motion capture are reported: frames containing identical rows of evenly spaced vertical lines are alternated in a standard apparent-motion paradigm. However, one vertical line in the first frame has short horizontal 'terminators' attached; the terminators are shifted to a different line in the second frame. Alternation that includes an unpatterned, nonzero interstimulus interval results in perceived motion of a vertical line along with the terminators.

Extracellular ATP stimulates volume decrease in Necturus red blood cells.

This study examined whether extracellular ATP stimulates regulatory volume decrease (RVD) in Necturus maculosus (mudpuppy) red blood cells (RBCs). The hemolytic index (a measure of osmotic fragility) decreased with extracellular ATP (50 microM). In contrast, the ATP scavenger hexokinase (2.

Background spatial frequency influences perception of luminance-based apparent movement.

Apparent movement occurs when stimulus figures are presented at different spatial locations at different times. In the present studies, the periodicity of the background upon which stimuli were presented was manipulated. Subjects viewed a bistable movement display presented on a background consisting of a variable-frequency grating.

Protein kinase C and regulatory volume decrease in mudpuppy red blood cells.

This study examined whether protein kinase C (PKC) stimulates K+ efflux during regulatory volume decrease (RVD) in Necturus maculosus (mudpuppy) red blood cells (RBCs). The limit of osmotic fragility increased with the general protein kinase inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7, 10 micrometer), but not with the cyclic nucleotide-dependent kinase antagonists N-(2'-guanidinoethyl)-5-isoquinolinesulfonamide (HA-1004, 10 micrometer) and N-2-(methylamino)ethyl-5-isoquinoline-sulfonamide (H-8, 5 micrometer). Consistent with these results, osmotic fragility also increased with the PKC antagonists bisindolylmaleimide I (GF-109203X or bis I, 100 nm), bisindolylmaleimide II (bis II, 100 nm), and chelerythrine (10 micrometer).

5-Lipoxygenase metabolites of arachidonic acid regulate volume decrease by mudpuppy red blood cells.

We examined whether metabolites of arachidonic acid (AA) regulate K+ efflux during regulatory volume decrease (RVD) by mudpuppy red blood cells (RBCs). Volume regulation was inhibited by the phospholipase A2 antagonists mepacrine (10 microM) and ONO-RS-082 (10 microM); the inhibitory effect of ONO-RS-082 was reversed by gramicidin (5 microM). Eicosatetraynoic acid (ETYA, 100 microM), a general antagonist of AA metabolism, also blocked RVD.

The detection of stimuli rotating in depth amid linear motion and rotation distractors.

In three experiments, observers watched displays consisting of two or more areas that contained unidirectionally moving pixels. In half of the displays, one area of pixels contained movement that corresponded to the projection of the front surface of a rotating cylinder. The total duration of the displays and the number of stimulus areas per display were varied.

The role of background in mediating apparent movement.

The spatial structure of the background upon which figures engage in apparent movement has been a neglected variable in research. In this pilot study, the presence of a sine-wave-grating as background had a strong influence on the quality of apparent movement that was perceived by 3 observers.

Potassium conductance activated during regulatory volume decrease by mudpuppy red blood cells.

The cellular basis of regulatory volume decrease (RVD) by mudpuppy (Necturus maculosus) red blood cells (RBCs) was examined. Volume regulation was inhibited by replacing extracellular Na+ with K+. In contrast, addition of gramicidin (5 microM) to the extracellular medium enhanced RVD.

A comparison of varieties of "second-order" motion.

Bistable apparent-movement displays were created using four different kinds of "second-order" stimuli in which figures were defined by binocular disparity, spatial phase shifts of periodic luminance distributions, relative motion, and texture-element orientation differences. For each display, characteristics of the local structure of the figures, backgrounds, or both were varied. For each experimental condition, the type of apparent movement seen as a function of interstimulus interval was measured, and it was found that the relationship between perceived apparent movement and interstimulus interval differed across the types of displays viewed.