Androgen regulation of neuromuscular junction structure and function in a sexually dimorphic muscle of the frogXenopus laevis

Intraspecific variation can have important consequences for the structure and function of ecological communities, and serves to link community ecology to evolutionary processes. Differences between the sexes are an overwhelmingly common form of intraspecific variation, but its community-level consequences have never been experimentally investigated. Here, we manipulate the sex ratio of a sexually dimorphic predacious newt in aquatic mesocosms, then track their impact on prey communities. Female and male newts preferentially forage in the benthic and pelagic zones, respectively, causing corresponding reductions in prey abundances in those habitats. Sex ratio differences also explained a large proportion (33%) of differences in the composition of entire pond communities. Ultimately, we demonstrate the impact of known patterns of sexual dimorphism in a predator on its prey, uncovering overlooked links between evolutionary adaptation and the structure of contemporary communities. Given the extreme prevalence of sexual dimorphism, we argue that the independent evolution of the sexes will often have important consequences for ecological communities.

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Gastroesophageal Junction: Structure and Function as Assessed by Using MR Imaging

Radiology ◽

10.1148/radiol.10092340 ◽

2010 ◽

Vol 257 (1) ◽

pp. 115-124 ◽

Cited By ~ 44

Author(s):

Jelena Curcic ◽

Mark Fox ◽

Elad Kaufman ◽

Zsofia Forras-Kaufman ◽

Geoffrey S. Hebbard ◽

...

Keyword(s):

Mr Imaging ◽

Gastroesophageal Junction ◽

Structure And Function ◽

And Function ◽

Junction Structure

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Effects of cytochalasin D on occluding junctions of intestinal absorptive cells: further evidence that the cytoskeleton may influence paracellular permeability and junctional charge selectivity.

The Journal of Cell Biology ◽

10.1083/jcb.102.6.2125 ◽

1986 ◽

Vol 102 (6) ◽

pp. 2125-2136 ◽

Cited By ~ 301

Author(s):

J L Madara ◽

D Barenberg ◽

S Carlson

Keyword(s):

Electron Microscopy ◽

Freeze Fracture ◽

Structure And Function ◽

Cytochalasin D ◽

Absorptive Cell ◽

Absorptive Cells ◽

Charge Selectivity ◽

Occluding Junctions ◽

And Function ◽

Junction Structure

Intestinal absorptive cells may modulate both the structure and function of occluding junctions by a cytoskeleton dependent mechanism (Madara, J. L., 1983, J. Cell Biol., 97:125-136). To further examine the putative relationship between absorptive cell occluding junctions and the cytoskeleton, we assessed the effects of cytochalasin D (CD) on occluding junction function and structure in guinea pig ileum using ultrastructural and Ussing chamber techniques. Maximal decrements in transepithelial resistance and junctional charge selectivity were obtained with 10 micrograms/ml CD and the dose-response curves for these two functional parameters were highly similar. Analysis of simultaneous flux studies of sodium and the nonabsorbable extracellular tracer mannitol suggested that CD opened a transjunctional shunt and that this shunt could fully account for the increase in sodium permeability and thus the decrease in resistance. Structural studies including electron microscopy of detergent-extracted cytoskeletal preparations revealed that 10 micrograms/ml CD produced condensation of filamentous elements of the peri-junctional contractile ring and that this was associated with brush border contraction as assessed by scanning electron microscopy. Quantitative freeze-fracture studies revealed marked aberrations in absorptive cell occluding junction structure including diminished strand number, reduced strand-strand cross-linking, and failure of strands to impede the movement of intramembrane particles across them. In aggregate these studies show that CD-induced perturbation of the absorptive cell cytoskeleton results in production of a transepithelial shunt which is fully explained by a defect in the transjunctional pathway. Furthermore, substantial structural abnormalities in occluding junction structure accompany this response. Lastly, the abnormalities in occluding junction structure and function coincide with structural changes in and contraction of the peri-junctional actin-myosin ring. These data suggest that a functionally relevant association may exist between the cytoskeleton and the occluding junction of absorptive cells. We speculate that such an association may serve as a mechanism by which absorptive cells regulate paracellular transport.

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