Assessment of Socially Acceptable Body Sizes by University Students

RAND, COLLEEN SW, JAQUELYN L RESNICK, ROBERTA S SELDMAN. Assessment of socially acceptable body sizes by university students. The objective of this study was to determine if more than one body size (the ideal) is considered socially acceptable. Two hundred undergraduates rated ideal male and female sizes, all socially acceptable male and female sizes, and their own current and desired sizes. Stimuli were arrays of nine outline drawings illustrating extremely thin to very fat male and female sizes. Most students considered three of nine sizes socially acceptable. There was high consensus on the sizes considered ideal. Although nearly three-quarters of women and half of men desired to be a different size, most considered their current size socially acceptable for other people. The results clearly demonstrate the existence of a range of socially acceptable male and female body sizes. The current size of most students was within this range. Exclusive focus on ideal body size distorts understanding of both other-size and own-size evaluations.     

Eye-Hand Coordination during Visuomotor Adaptation with Different Rotation Angles: Effects of Terminal Visual Feedback

This study examined adaptive changes of eye-hand coordination during a visuomotor rotation task under the use of terminal visual feedback. Young adults made reaching movements to targets on a digitizer while looking at targets on a monitor where the rotated feedback (a cursor) of hand movements appeared after each movement. Three rotation angles (30°, 75° and 150°) were examined in three groups in order to vary the task difficulty. The results showed that the 30° group gradually reduced direction errors of reaching with practice and adapted well to the visuomotor rotation. The 75° group made large direction errors of reaching, and the 150° group applied a 180° reversal shift from early practice. The 75°and 150° groups, however, overcompensated the respective rotations at the end of practice. Despite these group differences in adaptive changes of reaching, all groups gradually adapted gaze directions prior to reaching from the target area to the areas related to the final positions of reaching during the course of practice. The adaptive changes of both hand and eye movements in all groups mainly reflected adjustments of movement directions based on explicit knowledge of the applied rotation acquired through practice. Only the 30° group showed small implicit adaptation in both effectors. The results suggest that by adapting gaze directions from the target to the final position of reaching based on explicit knowledge of the visuomotor rotation, the oculomotor system supports the limb-motor system to make precise preplanned adjustments of reaching directions during learning of visuomotor rotation under terminal visual feedback.     

A Wireless EEG Recording Method for Rat Use inside the Water Maze

With the continued miniaturisation of portable embedded systems, wireless EEG recording techniques are becoming increasingly prevalent in animal behavioural research. However, in spite of their versatility and portability, they have seldom been used inside water-maze tasks designed for rats. As such, a novel 3D printed implant and waterproof connector is presented, which can facilitate wireless water-maze EEG recordings in freely-moving rats, using a commercial wireless recording system (W32; Multichannel Systems). As well as waterproofing the wireless system, battery, and electrode connector, the implant serves to reduce movement-related artefacts by redistributing movement-related forces away from the electrode connector. This implant/connector was able to successfully record high-quality LFP in the hippocampo-striatal brain regions of rats as they undertook a procedural-learning variant of the double-H water-maze task. Notably, there were no significant performance deficits through its use when compared with a control group across a number of metrics including number of errors and speed of task completion. Taken together, this method can expand the range of measurements that are currently possible in this diverse area of behavioural neuroscience, whilst paving the way for integration with more complex behaviours.     

Lysolecithin-cholesterol interaction. A spin-resonance and electron-micrographic study.

Another publication (rand, R. P., Pangborn, W., Purdon, A. D., and Tinker, D. O.(1975) Can. j. Biochem. 53, 189-195) has established that lysolecithin and cholesterol interact to form an equimolar complex. We have investigated this complex using the techniques of electron spin resonance (e.s.r) and electronmicroscopy. By varying the cholesterol concentration with lysolecithin in both thin films and dispersions studied by these techniques, we have observed the interaction between lysolecithin and equimolar complex below 50 mol % cholesterol, and between crystalline cholesterol and equimolar complex above 50 mol % cholesterol. We have observed an interesting alteration in morphology by electron microscopy, and an isotropic to anisotropic spectral change using 3-dosylcholestane and 12-doxylstearic acid spin-labelled probes when the cholesterol concentration is increased from 20 to 33 mol %. The equimolar complex is stable in the presence of crystalline cholesterol, and exhibits no phase changes in the physiological temperature range. Implications for membrane structure are discussed.     

Tilted hydrocarbon chains of dipalmitoyl lecithin become perpendicular to the bilayer before melting.

Differential scanning calorimetry studies of dipalmitoyl lecithin show two reversible transitions as the temperature is changed between 20 and 50 degrees C. A pretransition endotherm occurs at 35 degrees C prior to the main chain melting endotherm which occurs at 42 degrees C. X-ray diffraction studies show that below 33 degrees C the chains of the lecithin are fully extended, packed in a hexagonal crystalline lattice but tilted with respect to the plane of the bilayer. Between 35 and 42 degrees C the chains are similarly packed but oriented perpendicular to the bilayer plane. Above 44 degrees C the chains are "melted" or disordered. Monolayer studies of dipalmitoyl lecithin using continuous recording of pressure with molecular area reveal the existence of two solid condensed phases corresponding to these tilted and verticle chain structures. The tilted to perpendicular transition would account for the pretransition endotherm of the lipid; the crystalline to melted change corresponds to the larger transition observed at 42 degrees C.     

The effect of cholesterol on measured interaction and compressibility of dipalmitoylphosphatidylcholine bilayers

We have examined the phase diagram of dipalmitoylphosphatidylcholine (DPPC)--cholesterol-water mixtures at low cholesterol content, and report phase separation between 3 and 10 mol% cholesterol. The two lamellar phases at equilibrium in this region appear to be pure DPPC and 11 mol% cholesterol in DPPC. For these two lamellar phases, which are made up of alternating layers of water and bimolecular lipid leaflets, we have measured the forces of interaction between leaflets and the lateral pressure and compressibility of the leaflets. Both bilayers experience a strong repulsive force when forced together only a few ?ngstr?ms (1 A = 0.1 nm) closer than their maximum separation in excess water. However, the presence of 11 mol% cholesterol causes the bilayers to move apart of 35-A separation from the 19-A characteristic of pure DPPC in excess water. This swelling may result from a decrease in van der Waals attraction between bilayers or from an increase in bilayer repulsion. Differences in bilayer interaction can be a cause for phase separation. More importantly these differences can cause changes in the composition of regions of membranes approaching contact. At 11 mol%, cholesterol substantially increases the lateral compressibility of DPPC bilayers leading to higher lateral density fluctuations and potentially higher bilayer permeability.     

X-Ray Diffraction Study in Water of Lipids Extracted from Human Erythrocytes: The Position of Cholesterol in the Lipid Lamellae

Lipids, carefully extracted from fresh human erythrocytes, form liquid-crystalline structures in water. A phase diagram of this system was constructed, characterizing, by X-ray diffraction, the structures which form as a function of concentration of lipid and temperature. One extended range of concentration of the phase diagram, in which a single lamellar phase exists, permitted further analysis of the diffraction data. This phase consists of lipid layers of constant thickness separated by water layers of varying thickness according to the water content of the system. The distribution of the electron density is precisely analyzed and the amplitude of the reflections is, at all concentrations, proportional to the Fourier Transform of an isolated lipid layer. This shows that the lipid layer is filled with the hydro-carbon chains of the phospholipids and is covered on both sides by their hydrophilic groups. Cholesterol, present in high concentration in erythrocyte membranes, is located so that part of its steroid nucleus is between the polar groups of the phospholipid molecules while the rest of the molecule extends into the inner hydrocarbon layer.     

Mechanical Properties of the Red Cell Membrane: II. Viscoelastic Breakdown of the Membrane

A technique is described for measuring the stress required to rupture the red cell membrane. It requires a measure of the pressure and time to suck a cell into a micropipette. If a long tongue is pulled into a micropipette, the membrane spontaneously collapses on itself, as does a cylinder of fluid of length equal to its diameter, and a small refractile globule and a swollen red cell are produced. If the cells are hypotonically swollen enough, they cannot afford enough area for a long tongue to move into the pipette and when stressed for a time, hemolyse and disappear into the pipette. Calculation of membrane tension shows that the membrane can withstand a wide variety of tensions, up to a maximum of 20 dynes/cm for short periods of time, but even at much lower stresses the membrane eventually either ruptures, and the cell hemolyses, or relaxes; there does not appear to be a yield stress. This observation and the kinetics of the cell breakdown lead to a viscoelastic model of the cell membrane. The membrane substance has a Young's modulus of approximately 10⁶ to 10⁸ dynes/cm² and a viscosity of 10⁷ to 10¹⁰ poises. This confirms and extends the viscoelastic model proposed by Katchalsky et al. (3).