Eye height scaling of absolute size in immersive and nonimmersive displays.

Eye-height (EH) scaling of absolute height was investigated in three experiments. In Experiment 1, standing observers viewed cubes in an immersive virtual environment. Observers' center of projection was placed at actual EH and at 0.7 times actual EH. Observers' size judgments revealed that the EH manipulation was 76.8% effective. In Experiment 2, seated observers viewed the same cubes on an interactive desktop display; however, no effect of EH was found in response to the simulated EH manipulation. Experiment 3 tested standing observers in the immersive environment with the field of view reduced to match that of the desktop. Comparable to Experiment 1, the effect of EH was 77%. These results suggest that EH scaling is not generally used when people view an interactive desktop display because the altitude of the center of projection is indeterminate. EH scaling is spontaneously evoked, however, in immersive environments.

Seeing big things: overestimation of heights is greater for real objects than for objects in pictures.

In six experiments we demonstrate that the vertical-horizontal illusion that is evoked when viewing photographs and line drawings is relatively small, whereas the magnitude of this illusion when large objects are viewed is at least twice as great. Furthermore, we show that the illusion is due more to vertical overestimation than horizontal underestimation. The lack of a difference in vertical overestimation between pictures and line drawings suggests that vertical overestimation in pictures depends solely on the perceived physical size of the projection on the picture surface, rather than on what is apparent about an object's represented size. The vertical-horizontal illusion is influenced by perceived physical size. It is greater when viewing large objects than small pictures of these same objects, even when visual angles are equated.

In vitro and in vivo evidence for actin association of the naphthylphthalamic acid-binding protein from zucchini hypocotyls.

The N-1-naphthylphthalamic acid (NPA)-binding protein is part of the auxin efflux carrier, the protein complex that controls polar auxin transport in plant tissues. This study tested the hypothesis that the NPA-binding protein (NBP) is associated with the actin cytoskeleton in vitro and that an intact actin cytoskeleton is required for polar auxin transport in vivo. Cytoskeletal polymerization was altered in extracts of zucchini hypocotyls with reagents that stabilized either the polymeric or monomeric forms of actin or tubulin. Phalloidin treatment altered actin polymerization, as demonstrated by immunoblot analyses following native and denaturing electrophoresis. Phalloidin increased both filamentous actin (F-actin) and NPA-binding activity, while cytochalasin D and Tris decreased both F-actin and NPA-binding activity in cytoskeletal pellets. The microtubule stabilizing drug taxol increased pelletable tubulin, but did not alter either the amount of pelletable actin or NPA-binding activity. Treatment of etiolated zucchini hypocotyls with cytochalasin D decreased the amount of auxin transport and its regulation by NPA. These experimental results are consistent with an in vitro actin cytoskeletal association of the NPA-binding protein and with the requirement of an intact actin cytoskeleton for maximal polar auxin transport in vivo.

Cytoplasmic Orientation of the Naphthylphthalamic Acid-Binding Protein in Zucchini Plasma Membrane Vesicles.

Polar transport of the plant hormone auxin is blocked by substances such as N-1-naphthylphthalamic acid (NPA), which inhibit auxin efflux and block polar auxin transport. To understand how auxin transport is regulated in vivo, it is necessary to discern whether auxin transport inhibitors act at the intra- or extracellular side of the plasma membrane. Populations of predominantly in-side-in plasma membrane vesicles were subjected to treatments that reverse the orientation. These treatments, which included osmotic shock, cycles of freezing and thawing, and incubation with 0.05% Brij-58, all increased NPA-binding activity and the accessibility of the binding protein to protease digestion. Marker activities for inside-out vesicles also increased, indicating that these treatments act by altering the membrane orientation. Finally, binding data were analyzed by multiple analyses and indicated that neither the affinity nor abundance of binding sites changed. Kinetic analyses indicated that the change in NPA-binding activity by Brij-58 treatment was due to an increase in the initial rates of both association and dissociation of this ligand. These experiments indicated that the NPA-binding site is on the cytoplasmic face of the plasma membrane in zucchini (Cucurbita pepo L. cv Burpee Fordhook).

Globin genes in Polynesians have many rearrangements including a recently described gamma gamma gamma gamma/.

Rearrangements involving genes of the alpha- and beta-globin loci were frequently detected in DNA from Polynesians. A founder effect and genetic drift occurring 2,000-3,000 years ago as Polynesians migrated eastward across the Pacific is proposed as the likely mechanism for these genetic changes that include deletions or additions of alpha-, gamma-, and zeta-globin genes and an unusual restriction fragment length polymorphism (RFLP) associated with the zeta gene. Preliminary data show different frequencies for gene rearrangements between island groups. Further study of these differences should provide additional information on the prehistory of Polynesians.

Influence of alpha thalassaemia on haematological parameters in Polynesian patients.

DNA mapping of the alpha globin gene cluster in cord blood from Polynesians has shown an increased frequency of alpha thalassaemia and triplicated alpha genes. Reduced levels of haemoglobin, mean corpuscular haemoglobin or mean corpuscular volume in these neonates may indicate alpha thalassaemia. Recognition of this will avoid unnecessary haematological investigations and iron supplementation.