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PubMed1952

[Right-handedness].

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Functional Laterality↗
PubMed1995

Morphologic cerebral asymmetries and handedness. The pars triangularis and planum temporale.

OBJECTIVE: To explore the relationship between morphologic cerebral asymmetries of the pars triangularis (PTr) and the planum temporale (PT) measured on three-dimensional, gradient-echo, magnetic resonance imaging scans of healthy right- and left-handed subjects. DESIGN: (Blinded) comparison of healthy right- and left-handed subjects who underwent magnetic resonance imaging. SETTING: The Seimens 1-T Magnetom (Seimens, Iselin, NH) at the University of Florida Health Science Center, Gainesville. SUBJECTS: Healthy right-handed (n = 8) and left-handed (n = 8) subjects matched for age, sex, and educational level. MAIN OUTCOME MEASURES: (1) Average length of the PTr (anterior ascending and anterior descending rami), (2) average length of the PT, (3) asymmetry quotients ([left-right]/[(left+right) (0.5)]) of the PTr and PT, and (4) combined asymmetry quotients of the PTr and PT. RESULTS: There was a significant leftward asymmetry of the PTr and PT in the right-handed subjects, but there was no significant asymmetry in the left-handed subjects. When the combined asymmetry quotient of the PTr and PT was calculated, the right-handed subjects had a leftward asymmetry (87.5% [n = 7]) or left was equal to right (12.5% [n = 1]), and the left-handed subjects had a leftward asymmetry (62.5% [n = 5]), left was equal to right (12.5% [n = 1]), or a rightward asymmetry (25% [n = 2]). In the left-handed subjects, writing posture seemed to predict these combined asymmetry quotients, ie, left-handed subjects using an inverted writing posture had a leftward asymmetry and left-handed subjects using a non-inverted writing posture had a rightward asymmetry of the perisylvian speech-language regions. CONCLUSIONS: On three-dimensional, gradient-echo, magnetic resonance imaging scans, we found a significant leftward asymmetry of the PTr and PT. When the groups were divided into right- and left-handed subjects, the former had a significant leftward asymmetry of the PTr and PT, while the latter did not. Measurements of the PTr and PT appear to be important indexes of the known functional asymmetries of the perisylvian speech-language regions.

Adult↗
PubMed2000

Designing a Helical Polymer that Reverses its Handedness at a Selected, Continuously Variable, Temperature We would like to thank R. L. B. Selinger for helpful discussions. The Office of Naval Research supported the work at both the Polytechnic University and the Naval Research Laboratory. The work at the Polytechnic University was also supported by the Chemistry and Polymers Programs of the National Science Foundation and by the Petroleum Research Fund administered by the American Chemical Society. We are grateful to Professor Krzysztof Matyjaszewski of Carnegie-Mellon University for a discussion that led to the development of this work.

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Journal Article↗
PubMed1991

Bacterial motility: handedness and symmetry.

Many bacteria swim by rotating thin helical filaments that extend into the external medium, as with common bacteria, or run beneath the outer membrane, as with spirochetes. Each filament is driven at its base by a motor that turns alternately clockwise and counterclockwise. The motor-filament complex is called a flagellum. Other kinds of bacteria glide, but their organelles of locomotion are not known. Since bacteria are microscopic and live in an aqueous environment, they swim at low Reynolds' number; cyclic motion works (e.g. rotation of a helix) but reciprocal motion does not (e.g. stroking of a singly hinged oar). By measuring concentrations of certain chemicals as they move through their environment, making temporal comparisons and modulating the direction of flagellar rotation, bacteria accumulate in regions that they find more favourable. Studies of bacterial chemotaxis are highly advanced, particularly for the peritrichously flagellated species Escherichia coli. A great deal is known about chemoreception, receptor-flagellar coupling and adaptation. Recently it has been found that E. coli can aggregate in response to signals generated by the cells themselves. Complex patterns form with remarkable symmetries.

Bacterial Physiological Phenomena↗
PubMed2004

On rotation, torsion, lateralization, and handedness of the embryonic heart loop: new insights from a simulation model for the heart loop of chick embryos.

The internal organs of vertebrates show specific anatomical left-right asymmetries. The embryonic heart is the first organ to develop such asymmetries during a process called dextro-looping. Thereby the initially straight heart tube curves toward its original ventral side and the resulting bend becomes displaced toward the right side of the embryo. Abnormal displacement of the heart loop toward the left is rare and is called levo-looping. Descriptive studies have shown that the lateralization of the heart loop is driven by rotation around its dorsal mesocardium. However, nothing was known on the modes of this process. To gain insight into this subject, different modes of rotation were tested in a simulation model for the looping chick embryo heart. The morphological phenotypes obtained in this model were compared with normal and mirror-imaged embryonic hearts. The following observations were made. One, rotation of the heart loop around its dorsal mesocardium has two consequences: first, lateral displacement of its bending portion either toward the right (D-loop) or left (L-loop) side of the embryo, and second, torsion of the cardiac bend into a helical structure that is wound either clockwise (right-handed helix) or counterclockwise (left-handed helix). The normal loop presents as a D-loop with left-handed helical winding and its mirror image presents as an L-loop with right-handed helical winding. This conflicts with the use to define D-loops as right- and L-loops as left-handed structures. Two, dextro-looping might be driven almost exclusively by rightward rotation of the arterial pole of the loop. It becomes complemented by leftward rotation of the venous pole during the subsequent phase of looping. An inverse mode of rotation might drive levo-looping. Three, the two different helical configurations of heart loops both can occur as right-sided, median, or left-sided positional variants. When viewed from the front, all right-sided variants appear as D-loops and all left-sided variants appear as L-loops at the end of dextro- or levo-looping. Their true asymmetric phenotypes become fully apparent only after simulation of the subsequent phase of looping. The terms D- and L-loop obviously do not fully define the chirality of heart loops. The chirality of their helical configuration should be defined, too. The implications of these data with respect to molecular and experimental data are discussed.

Animals↗