Left-right Asymmetry (left-right + asymmetry)

Distribution by Scientific Domains


Selected Abstracts


Left-right asymmetry in gut development: what happens next?

BIOESSAYS, Issue 10 2009
Sally F Burn
The gastrointestinal tract is an asymmetrically patterned organ system. The signals which initiate left-right asymmetry in the developing embryo have been extensively studied, but the downstream steps required to confer asymmetric morphogenesis on the gut organ primordia are less well understood. In this paper we outline key findings on the tissue mechanics underlying gut asymmetry, across a range of species, and use these to synthesise a conserved model for asymmetric gut morphogenesis. We also discuss the importance of correct establishment of left-right asymmetry for gut development and the consequences of perturbations in this process. [source]


A mutation in the zebrafish Na,K-ATPase subunit atp1a1a.1 provides genetic evidence that the sodium potassium pump contributes to left-right asymmetry downstream or in parallel to nodal flow

DEVELOPMENTAL DYNAMICS, Issue 7 2006
Elin Ellertsdottir
Abstract While there is a good conceptual framework of dorsoventral and anterioposterior axes formation in most vertebrate groups, understanding of left-right axis initiation is fragmentary. Diverse mechanisms have been implied to contribute to the earliest steps of left-right asymmetry, including small molecule signals, gap junctional communication, membrane potential, and directional flow of extracellular liquid generated by monocilia in the node region. Here we demonstrate that a mutation in the zebrafish Na,K-ATPase subunit atp1a1a causes left-right defects including isomerism of internal organs at the anatomical level. The normally left-sided Nodal signal spaw as well as its inhibitor lefty are expressed bilaterally, while pitx2 may appear random or bilateral. Monocilia movement and fluid circulation in Kupffer's vesicle are normal in atp1a1am883 mutant embryos. Therefore, the Na,K-ATPase is required downstream or in parallel to monocilia function during initiation of left-right asymmetry in zebrafish. Developmental Dynamics 235:1794,1808, 2006. © 2006 Wiley-Liss, Inc. [source]


Hippocampal volume and asymmetry in mild cognitive impairment and Alzheimer's disease: Meta-analyses of MRI studies

HIPPOCAMPUS, Issue 11 2009
Feng Shi
Abstract Numerous studies have reported a smaller hippocampal volume in Alzheimer's disease (AD) patients than in aging controls. However, in mild cognitive impairment (MCI), the results are inconsistent. Moreover, the left-right asymmetry of the hippocampus receives less research attention. In this article, meta-analyses are designed to determine the extent of hippocampal atrophy in MCI and AD, and to evaluate the asymmetry pattern of the hippocampal volume in control, MCI, and AD groups. From 14 studies including 365 MCI patients and 382 controls, significant atrophy is found in both the left [Effect size (ES), 0.92; 95% confidence interval (CI), 0.72,1.11] and right (ES, 0.78; 95% CI, 0.57,0.98) hippocampus, which is lower than that in AD (ES, 1.60, 95% CI, 1.37,1.84, in left; ES, 1.52, 95% CI, 1.31,1.72, in right). Comparing with aging controls, the average volume reduction weighted by sample size is 12.9% and 11.1% in left and right hippocampus in MCI, and 24.2% and 23.1% in left and right hippocampus in AD, respectively. The findings show a bilateral hippocampal volume loss in MCI and the extent of atrophy is less than that in AD. By comparing the left and right hippocampal volume, a consistent left-less-than-right asymmetry pattern is found, but with different extents in control (ES, 0.39), MCI (ES, 0.56), and AD (ES, 0.30) group. © 2009 Wiley-Liss, Inc. [source]


Bilateral asymmetry in the limb bones of the chimpanzee (Pan troglodytes),

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2005
L.A. Sarringhaus
Abstract There is much debate in behavioral primatology on the existence of population-level handedness in chimpanzees. The presence or absence of functional laterality in great apes may shed light on the origins of human handedness and on the evolution of cerebral asymmetry. The plasticity of long bone diaphyses in response to mechanical loading allows the functional interpretation of differences in cross-sectional geometric. While left-right asymmetry in upper limb diaphyseal morphology is a known property in human populations, it remains relatively unexplored in apes. We studied bilateral asymmetry in 64 skeletons of wild-caught chimpanzee using the humerus, second metacarpal, and femur. The total subperiosteal area (TA) of the diaphyses was measured at 40% of maximum humeral length and at the midshaft of the metacarpals and femora using external silicone molds. Overall, the TA values of the left humeri were significantly greater than the right, indicating directional asymmetry. This effect was even greater when the magnitude of difference in TA between each pair of humeri was compared. The right second metacarpals showed a tendency toward greater area than did the left, but this did not reach statistical significance. The lack of asymmetry in the femur serves as a lower limb control, and suggests that the upper limb results are not a product of fluctuating asymmetry. These findings imply behavioral laterality in upper limb function in chimpanzees, and suggest a complementary relationship between precision and power. Am J Phys Anthropol 2005., © 2005 Wiley-Liss, Inc. [source]


Left-right asymmetry in gut development: what happens next?

BIOESSAYS, Issue 10 2009
Sally F Burn
The gastrointestinal tract is an asymmetrically patterned organ system. The signals which initiate left-right asymmetry in the developing embryo have been extensively studied, but the downstream steps required to confer asymmetric morphogenesis on the gut organ primordia are less well understood. In this paper we outline key findings on the tissue mechanics underlying gut asymmetry, across a range of species, and use these to synthesise a conserved model for asymmetric gut morphogenesis. We also discuss the importance of correct establishment of left-right asymmetry for gut development and the consequences of perturbations in this process. [source]