Perceptual Alternations in Stereokinesis

Perception ◽  
1988 ◽  
Vol 17 (1) ◽  
pp. 31-34 ◽  
Author(s):  
Giorgio Vallortigara ◽  
Paola Bressan ◽  
Marco Bertamini
Keyword(s):  
Frontal Plane ◽  
Circular Disc ◽  
Frontoparallel Plane ◽  
Circular Trajectory ◽  
Size Change ◽  
Prolonged Observation ◽  
Stimulation Of

When a flat ellipse is slowly rotated in the frontoparallel plane, two different 3-D percepts can be obtained: (i) a rigid circular disc tilting back and forth in 3-D space, and (ii) an elongated egg, slanted into 3-D space, whose end parts seem to be located at different distances from the observer and describe a circular trajectory with respect to the frontal plane. Under prolonged observation, the two 3-D percepts alternate in time, separated by brief intervals in which either the rotation of a rigid flat ellipse in the frontal plane or an amoeba-like distortion of a 2-D shape can be perceived. An experiment is reported in which the sequence of perceptual alternations was investigated. Results show that the 3-D disc is mostly preceded by impressions of elastic amoeba-like deformations, whereas the 3-D egg is mostly preceded by the percept of a rotating flat ellipse. Direct transitions from egg to disc are not as frequent as transitions from disc to egg. Results are discussed in relation to Braunstein and Andersen's hypothesis that phenomena of this sort might result from the stimulation of automatic mechanisms for perceiving size change (changing—size neural channels).

Multiple 3-D Interpretations in a Classic Stereokinetic Effect

Perception ◽  
1986 ◽  
Vol 15 (4) ◽  
pp. 405-408 ◽  
Author(s):  
Paola Bressan ◽  
Giorgio Vallortigara
Keyword(s):  
Prolonged Exposure ◽  
Frontal Plane ◽  
Circular Disc ◽  
Frontoparallel Plane ◽  
Circular Trajectory ◽  
Axis Ratio ◽  
Stereokinetic Effect ◽  
Flat Pattern

It is known that a flat ellipse rotating in the frontoparallel plane sooner or later appears as a rigid circular disc tilting in 3-D space. An experiment is reported in which prolonged exposure to the same flat pattern produces a second previously unnoticed 3-D percept: an elongated egg slanted in 3-D space, which points towards the observer and the end parts of which describe a circular trajectory in the frontal plane. It is shown that the achievement of this alternative percept is not affected by the particular shape of the ellipse, although the time needed to reach it increases with an ellipse with a 2:3 axis ratio.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

Gap junctions in the prothoracic glands of the tobacco hornworm, Manduca sexta

1992 ◽  
Vol 50 (1) ◽  
pp. 706-707
Author(s):  
Ji-da Dai ◽  
M. Joseph Costello ◽  
Lawrence I. Gilbert
Keyword(s):  
Gap Junctions ◽  
Small Molecules ◽  
Manduca Sexta ◽  
Freeze Fracture ◽  
Cell Communication ◽  
Cellular Level ◽  
Thin Sections ◽  
Prothoracic Glands ◽  
Polyhydroxylated Steroids ◽  
Stimulation Of

Insect molting and metamorphosis are elicited by a class of polyhydroxylated steroids, ecdysteroids, that originate in the prothoracic glands (PGs). Prothoracicotropic hormone stimulation of steroidogenesis by the PGs at the cellular level involves both calcium and cAMP. Cell-to-cell communication mediated by gap junctions may play a key role in regulating signal transduction by controlling the transmission of small molecules and ions between adjacent cells. This is the first report of gap junctions in the PGs, the evidence obtained by means of SEM, thin sections and freeze-fracture replicas.

Activator protein-1 is necessary for angiotensin-II stimulation of human adrenocorticotropin receptor gene transcription

2001 ◽  
Vol 268 (6) ◽  
pp. 1802-1810
Author(s):  
Danielle Naville ◽  
Estelle Bordet ◽  
Marie-Claude Berthelon ◽  
Philippe Durand ◽  
Martine Begeot
Keyword(s):  
Angiotensin Ii ◽  
Gene Transcription ◽  
Receptor Gene ◽  
Activator Protein 1 ◽  
Activator Protein ◽  
Stimulation Of
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