Changes In Apparent Size Research Articles

Developmental changes in expression of a 60-kDa somatostatin receptor immunoreactivity in the rat brain.

The neuropeptide somatostatin (SRIF) exerts several important physiological actions in the adult CNS through interactions with membrane-bound receptors. SRIF expression is developmentally regulated and this regulation is most apparent in the cerebellum, where SRIF immunoreactivity is expressed at early postnatal ages and then disappears toward adulthood. The transitory nature of SRIF expression at a time of major changes in cerebellum suggests that this peptide may have a role in cerebellar development. To further investigate the role of the SRIF transmitter system during development, we have examined the levels of expression of SRIF receptors in the developing rat brain by immunoblotting using antiserum selective for a 60-kDa brain SRIF receptor. In whole rat brain, SRIF receptor immunoreactivity first appears at embryonic day 13 (E13), is elevated at E16, increases at birth, peaks at early postnatal ages, and then gradually declines with age. No apparent changes in size of the receptor occur with age. No consistent changes in levels of SRIF receptor immunoreactivity are detected from early postnatal ages to adulthood in the hippocampus, cerebral cortex, and striatum, but levels gradually decline in the hypothalamus. In contrast, SRIF receptor immunoreactivity is expressed transiently in cerebellum. SRIF receptor immunoreactivity is detectable in cerebellum at E16, increases in levels at birth, is apparent from postnatal day 3 to postnatal day 8, and then disappears. The transitory nature of SRIF receptor expression in cerebellum is unique and parallels the expression of SRIF immunoreactivity in this brain region. These findings support the hypothesis that SRIF has a role in cerebellar development.

Simulation of small-angle X-ray scattering behaviour of activated carbon fibres adsorbing water

Small-angle X-ray scattering (SAXS) measurements have been carried out in order to investigate the size of micropores in activated carbon fibres (ACF) and the apparent change in size for different relative humidities. The scattering intensity at smaller angles and the gyration radius Rg increase at first with increasing relative humidity and then decrease. To interpret this anomalous behaviour, a simulation study has been carried out by considering the change in the effective sizes of micropores and carbon grains caused by adsorption of water. The observed behaviour of the SAXS intensity and the Rg value can be explained by the increase in the effective grain-size due to the adsorption of water molecules around the carbon grains in ACF.

Looking into the water with a facet eye.

The apparent velocity and apparent size of objects approaching an animal strongly depend on their size, their position within the visual field and on the path along which they move. It also makes a considerable difference whether both the animal and the objects are in air, or whether the animal looks from one medium into the other, as is the case in animals that live at the water surface. To systematically investigate this situation we calculated apparent velocity and size in the midsagittal plane of approaching objects of flat horizontal, rodlike vertical and spherical shape. We confine our investigation to object movements along straight horizontal and vertical paths and consider the situation for eyes with and without acute zones. The apparent velocity of an approaching object is low in the far field and increases rapidly close to the eye in both air and water. Along horizontal paths and close to the animal it is higher in water than in air. Along vertical paths and close to the animal it is higher in air than in water. Both relationships are exaggerated when there is an acute zone for vertical resolution along the animal's horizon. Boundary curves are calculated along which an approaching object is seen by a linearly increasing number of receptors. The change of apparent size is characterized by the density of these lines. Below the water surface the change of apparent size is similar to that of the apparent velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

Manipulating stereopsis and vergence in an outdoor setting: Moon, sky and horizon

A simple stimulus generator has been constructed that permits a small illuminated target to be seen with variable inter-ocular disparity, when superimposed upon the binocular view of an outdoor landscape. This device was applied to several questions involving perception of size, distance and orientation, with the following results: 1. (1) when the apparent distance to an “artificial moon”, as perceived through stereopsis, is decreased by about 50-fold (from near horizon to about 60 m), its apparent size is reduced by only a miniscule amount (8% on average); hence, the moon illusion is probably not due to compensation—conscious or subconscious—for its apparent distance. 2. (2) those changes in apparent size known as convergence micropsia vary as a function of the visual surround; for a vergence change of 1 deg, greater perceived change in size of a small target arises when a landscape is seen nearby than with empty sky as surround. 3. (3) when a target is shown somewhat above the horizon against an empty sky, it must be viewed with divergence of the visual axes (image positions for “hyper-infinite” distance), in order to be perceived as vertically above objects on the skyline; this effect implies a strong backward tilt to the apparent vertical and probably reflects an attempt to “null out” the perceptual consequences of the convergence that typically occurs during downward saccades.

Proteins associated with untransformed estrogen receptor in vitro. Perturbation of hydrophobic interactions induces alterations in quaternary structure and exposure of the DNA-binding site.

Estrogen receptors from calf uteri have been analyzed by high-performance size-exclusion chromatography, chromatofocusing, and DNA affinity chromatography using conditions designed to evaluate the relative contribution of hydrophobic interactions between the steroid-binding subunit and other receptor-associated proteins. The single large (untransformed) species of soluble estrogen-receptor consistently (n = 9) found in calf uteri displayed a rapid change in Stokes radius from 8.0 to 3.5 nm upon exposure to elevated ionic strengths (0.4 M KCl). However, equilibration of the estrogen-receptor complex into urea (up to 6 M) did not dissociate the untransformed receptor into the 3.5-nm receptor form (subunit) observed in hypertonic (0.4 M KCl) buffers. Exposure to 6 M urea did result in conversion of the untransformed receptor (8.0 nm) to a 6.0-6.5-nm receptor form not previously observed in either hypotonic or hypertonic buffers. In the presence of both 6 M urea and 0.4 M KCl, the untransformed estrogen-receptor complex was converted to a smaller receptor form intermediate in apparent size (4.5-5.0 nm) to that observed in 6 M urea or 0.4 M KCl alone. The formation of this 4.5-5.0-nm receptor form was partially estrogen dependent as determined by parallel analyses of unliganded receptor in urea/KCl buffer. The urea-induced change in apparent size (8 nm to 6.0-6.5 nm) at low ionic strength was accompanied by little or no detectable change in net surface charge as determined by chromatofocusing but a complete exposure of the DNA-binding site as evidenced by nearly quantitative interaction with DNA-agarose.(ABSTRACT TRUNCATED AT 250 WORDS)

Degradation without apparent change in size of molybdate-stabilized nonactivated glucocorticoid-receptor complexes in rat thymus cytosol.

We have investigated the stability of the [3H]dexamethasone 21-mesylate-labeled nonactivated glucocorticoid-receptor complex in rat thymus cytosol containing 20 mM sodium molybdate. Cytosol complexes were analyzed under nondenaturing conditions by gel filtration chromatography in the presence of molybdate and under denaturing conditions by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. When analyzed under nondenaturing conditions, complexes from fresh cytosol and from cytosol left for 2 h at 3 degrees C eluted from gel filtration as a single peak of radioactivity with a Stokes radius of approximately 7.7 nm, suggesting that no proteolysis of the complexes had occurred in either cytosol. When analyzed under denaturing conditions, however, whereas the fresh cytosol gave a receptor band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis at Mr approximately 90,000 (corresponding to the intact complex), the cytosol that had been left for 2 h at 3 degrees C gave only a fragment (Mr approximately 50,000). This fragment, just as the intact complex, could be thermally activated to a DNA-binding form. Proteolysis of the receptor could be blocked by preparing the cytosol in the presence of EGTA, leupeptin, or a heat-stable factor present in the cytosol of rat liver and WEHI-7 mouse thymoma cells. From these results we conclude: (i) 20 mM molybdate does not protect the nonactivated glucocorticoid-receptor complex present in rat thymus cytosol against proteolysis under conditions which are commonly used for cell-free labeling of the receptor, and (ii) the demonstration of a Stokes radius of approximately 8 nm for the nonactivated glucocorticoid-receptor complex is not sufficient to indicate that the receptor complex is present in its intact form.

Stimulus location in egocentric space as a determinant of apparent visual size

Four separate groups of subjects were presented with vertically oriented visual stimuli which moved toward and away from them over a distance of 1-50 ft. There were two such stimuli, a tall one and a short one. The stimuli were viewed in well-articulated settings. Groups 1 and 2 observed them in an open field, and Groups 3 and 4 viewed them in a well-lit corridor. Both stimuli rested just above the ground plane. The tall one extended overhead, whereas the top of the short one was well below eye level. Groups 1 and 3 observed the moving targets from a standing position and reported on any changes in apparent size. Groups 2 and 4 viewed the short target only, both when standing and seated. When subjects were seated, the top of the small stimulus extended above them. It was found that, regardless of the setting (i.e., outdoors or in a corridor), an overhead stimulus was seen to shrink as it moved away from and grow as it approached the subject. Just the opposite occurred when the upper edge of the target was below eye level.

Slow posttranslational modification of a neurofilament protein.

The synthesis and subsequent modification of neurofilament (NF) polypeptides has been examined in pulse-chase experiments, using cultured chick spinal cord neurons. Fluorography of the [35S]methionine-labeled cytoskeletal proteins, after separation by two-dimensional gel electrophoresis, revealed that (a) the mid-size chicken NF protein, NF-M160, is synthesized as a smaller and more basic precursor, NF-M130; (b) beginning approximately 8 h after translation, NF-M130 slowly and continuously becomes larger and more acidic, attaining the size and charge of NF-M160 16 or more h later, and undergoing no further change in mobility for many days thereafter; and (c) in contrast, the low molecular weight NF protein, NF-L, is synthesized as such, and undergoes no subsequent change in apparent size or charge. Additional experiments provided evidence that the conversion of NF-M130 to NF-M160 is due, at least in part, to phosphorylation: (a) Incubation of similar cultures in 32PO4 resulted in incorporation into NF-M160 and transitional forms, but not into NF-M130. (b) An antiserum to NF-M160 was found by immunoblot analysis to bind strongly to untreated NF-M160, but poorly to phosphatase-treated NF-M160, and not at all to NF-M130. It has already been demonstrated (Bennett, G. S., S. J. Tapscott, C. DiLullo, and H. Holtzer, 1984, Brain Res., 304:291-302) that this anti-NF-M160 fails to stain the soma of motor neurons in sections of chick spinal cord, but detects an increasing gradient of immunoreactivity in the proximal axons. These results, together with the known kinetics of axoplasmic transport of NF, suggest that the mid-size chicken NF protein is synthesized as NF-M130 and is extensively modified, at least in part by phosphorylation, to become NF-M160 during transport along proximal neurites. Once maximally modified, NF-M160 undergoes no further net change during transport along distal neurites.

Reliability, sex difference, and Honi phenomenon in a distorted room.

Test-retest reliability and sex differences when viewed in a distorted room were investigated. The presence of the Honi phenomenon, which is less change in apparent size of a spouse than of a stranger, was examined. A reliability coefficient was obtained by testing 27 college men twice. Judgments of size from 25 of the men and 25 women who viewed black disc targets and also from 10 women viewing husbands' and strangers' photographs were compared. The reliability was high, .87. Sex difference was significant. Women's larger reading was interpreted as a more meaningful or valuable perception of things than men's. The Honi phenomenon does not exist.

The perception of lead vehicle movement in darkness

Three experimental studies are described on the detection of longitudinal lead-vehicle movement in darkness. Experiment I, performed in the laboratory, isolated the relative horizontal angular motion of the lead-vehicle's taillights as a cue to the detection of relative longitudinal movement. Movement thresholds were determined as a function of initial headway, exposure duration, direction of the movement, and the presence of a background. All these factors except the last had significant effects on the movement threshold. Experiment II, also a laboratory-experiment, isolated changes in apparent size or brightness of the taillights as a cue. Movement thresholds were again found to be a function of the variables investigated in Experiment I. However, thresholds now were much higher than under the isolated angular cue. It was therefore concluded that the relative horizontal angular motion of the lead-vehicle's taillights is the priminent cue in the detection of relative vehicle motion in depth. Experiment III substantiated this conclusion by confirming the parametric outcomes of Experiment I under realistic night-driving conditions. The practical relevance of the estimates made from the data of two important temporal parameters in car following, viz. time until collision and free time after detection.

Brain Scans, Dexamethasone Therapy, and Brain Tumors

Eight men with primary or metastatic brain tumors were examined with brain scans before and after the administration of dexamethasone. All patients demonstrated some improvement in their clinical neurologic status during therapy, and two patients had a dramatic response. Seven of the eight patients examined showed a decrease in the apparent size of the original lesion on recent brain scan while receiving dexamethasone. Comparison of immediate scans obtained 15 to 20 minutes following the administration of sodium pertechnetate Tc 99m with those obtained two or three hours later suggests that the change in apparent size of the original lesion results from decrease in peritumor edema.

Size-tuned mechanisms: Correlation of data on detection and apparent size

Detection thresholds were obtained for uniformly illuminated and non-uniformly illuminated (disk-annulus) stimuli. Then, the stimuli were presented at threshold and observers attempted to discriminate between uniform and non-uniform stimuli, and also made judgments of the apparent size of each stimulus. The uniform and non-uniform stimuli were not discriminated. Changes in apparent size were correlated with changes in detection thresholds. These findings support a multiple size-tuned mechanism interpretation.

Apparent size and duration of a movement after-effect.

Four experiments were performed to study the relationship between Emmert's law and the duration of the movement after-effect (MAE). The duration of the MAE increased with increased distance of the test field; this result was shown to be produced by the correlative change in apparent size of the after image. The effect did not occur when cues for distance judgments were reduced. Reducing the duration of the MAE suppressed the variation in its duration at varying distances of the test field. Some implications for the mechanism of the MAE are discussed.

Oculomotor effects upon binocular rivalry.

Binocular rivalry was generated by projecting dissimilar Julesz-type patterns to each eye. The minimum angular width of the patterns needed to observe rivalry was measured at four retinal eccentricities for two simulated viewing distances: 200 and 20 cm. The angular width needed to just detect rivalry was up to 50% greater for the 20 cm viewing distance as compared with the threshold width measured at 200 cm. This increased tolerance for rivalry for near fixation was inversely proportional to the change in apparent size. The results suggest that the lateral geniculate nucleus is the site of size-scaling or “zooming”.

Apparent modifiability of receptive fields during accommodation and convergence and a model for size constancy

The size of Ricco's summation area can be altered by changing accommodation and convergence (A-C). For foveal stimuli of fixed retinal size, the change in Ricco's area is approximately the same as the change in apparent size induced by the A-C factors. As distance from the foveola increases, the A-C effect becomes smaller. However, size constancy is also rapidly lost outside the fovea. Therefore, the changes in Ricco's area and size constancy seem to be correlated for at least two parameters, namely A-C factors and retinal position. Assuming that the Ricco area reflects receptive field size, the effects of retinal position and A-C factors on the Ricco area suggest a model for size constancy.

The Effect of Oculomotor Adjustments on Apparent Size

An object of fixed angular size looks smaller when the eyes are adjusted for near vision than when they are adjusted for far vision. This fact was reported first by Wheatstone, the inventor of the stereoscope.1 Wheatstone's qualitative observations were confirmed by several later investigators,2 and quantitative studies of the phenomenon have been made by Adams, Frank, Hermans, and Swenson.3 The research lXeported below deals mainly with two questions to which the previous investigators have not given clear answers. The first is whether the changes in apparent size are related to changes in apparent distance in the manner postulated by several current theories of 'size-constancy.'4 The second is which of the oculomotor adjustments, or possibly which combination of adjustments, controls the changes in apparent size. The principal oculomotor adjustments that are made in response to a change in viewing distance are (1) changes in the angle of convergence of the visual axes, (2) changes in the power of the lens (accommodation), and (3) changes in the diameter of the pupil. Convergence and accommodation are so linked that a change in one produces a change in the other, and a change in either is usually accompanied by a change in the diameter of the pupil.

Apparent Movement of Simple Figures in the Ganzfeld

If autokinetic movement under conditions of darkness results from an inadequate visual framework, then similar movement of a figure in an illuminated uniform visual field should occur. The apparatus used to investigate this hypothesis has been described in detail (1). 0, using his right eye alone, looked into an illuminated sphere and was presented with a uniform field containing an 8 cm. circular figure at a distance of 1 m. Intensity and chromaticity of the figure were independently varied by changing the illumination of an adjoining sphere. 15 graduate students observed a series of situations in which differences between figure and field were systematically varied. 0 described each simation during 3-min. periods of stirnulacion, followed by 2-min. rest periods. Each experimental session lasted 90 min. Spontaneous autokinetic movement of the figure was reported by 11 0s in about 40% of the situations in each series. There was a predominance of movement to che right which may have resulted from the use of the right eye alone. The frequency of reports of movement was not dependent upon the kind of difference between figure and field, i.e., chromatic differences or intensity difference~. An amoeba-like movement of the figure was often produced by chromatic differences alone. Forward movement and pulsation was sometimes produced by large intensity differences. The occasional disappearance of the figure was always preceded by its movement. When the intensity of the figure was gradually changed, about 70% of the time all 0s reported movement of the figure and the fog-like field in opposite directions. Thus, with increasing intensity differences, the figure moved forward and the fog receded, while with decreasing intensity differences, the figure receded and the fog moved forward. Under these conditions, movement was sometimes experienced without any change in apparent distance. However, even when a change in apparent distance was reported, there was no systematic change in apparent size. REFERENCE 1. COHEN, W. Spatial and textural characteristics of the Ganzfeld. Amer. J. Psychol., 1957, 70, 403-410.

Real and Apparent Changes in Size of Marine Animal Populations during the Australian Fisheries Investigations

Real and Apparent Changes in Size of Marine Animal Populations during the Australian Fisheries Investigations

Demonstration of Pupillary, Accommodative, and Consensual Reflexes Through Changes in Apparent Size of a Pinhole

Demonstration of Pupillary, Accommodative, and Consensual Reflexes Through Changes in Apparent Size of a Pinhole