| 1. |
- Gonda, A., et al.
(författare)
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Predation- and competition-mediated brain plasticity in Rana temporaria tadpoles
- 2010
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 23:11, s. 2300-2308
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Tidskriftsartikel (refereegranskat)abstract
- An increasing number of studies have demonstrated phenotypic plasticity in brain size and architecture in response to environmental variation. However, our knowledge on how brain architecture is affected by commonplace ecological interactions is rudimentary. For example, while intraspecific competition and risk of predation are known to induce adaptive plastic modifications in morphology and behaviour in a wide variety of organisms, their effects on brain development have not been studied. We studied experimentally the influence of density and predation risk on brain development in common frog (Rana temporaria) tadpoles. Tadpoles grown at low density and under predation risk developed smaller brains than tadpoles at the other treatment combinations. Further, at high densities, tadpoles developed larger optic tecta and smaller medulla oblongata than those grown at low densities. These results demonstrate that ecological interactions - like intraspecific competition and predation risk - can have strong effects on brain development in lower vertebrates.
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| 2. |
- Trokovic, N., et al.
(författare)
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Brain plasticity over the metamorphic boundary : carry-over effect of larval environment on froglet brain development
- 2011
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 24:6, s. 1380-1385
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Tidskriftsartikel (refereegranskat)abstract
- Brain development shows high plasticity in response to environmental heterogeneity. However, it is unknown how environmental variation during development may affect brain architecture across life history switch points in species with complex life cycles. Previously, we showed that predation and competition affect brain development in common frog (Rana temporaria) tadpoles. Here, we studied whether larval environment had carry-over effects in brains of metamorphs. Tadpoles grown at high density had large optic tecta at metamorphosis, whereas tadpoles grown under predation risk had small diencephala. We found that larval density had a carry-over effect on froglet optic tectum size, whereas the effect of larval predation risk had vanished by metamorphosis. We discuss the possibility that the observed changes may be adaptive, reflecting the needs of an organism in given environmental and developmental contexts.
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| 3. |
- Trokovic, N., et al.
(författare)
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Exosomal secretion of death bullets: a new way of apoptotic escape?
- 2012
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Ingår i: American Journal of Physiology-Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 303:8
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Tidskriftsartikel (refereegranskat)abstract
- Trokovic N, Pollanen R, Porola P, Stegaev V, Hetzel U, Tivesten A, Engdahl C, Carlsten H, Forsblad-D'Elia H, Fagman JB, Lagerquist M, Konttinen YT. Exosomal secretion of death bullets: a new way of apoptotic escape? Am J Physiol Endocrinol Metab 303: E1015-E1024, 2012. First published August 12, 2012; doi: 10.1152/ajpendo.00139.2012.-Ovariectomy/estrogen deficiency causes selective apoptosis of the serous epithelial cells of the submandibular glands (SMG) in female mice. Because such apoptosis does not occur in healthy, estrogen-deficient male mice, it was hypothesized that dihydrotestosterone (DHT) protects epithelial SMG cells against apoptosis. The antiapoptotic effect of DHT on human epithelial HSG cells exposed to tumor necrosis factor-alpha and cycloheximide was studied. Correspondingly, the proapoptotic effect of androgen deficiency was studied in orchiectomized (ORX) androgen-knockout (ARKO) and wild-type (WT) mice. The health state of the SMG cells was studied with Alcian blue-periodic acid Schiff (AB-PAS) and amylase staining and transmission electron microscopy (TEM). The eventual protective antiapoptotic effect of dehydroepiandrosterone (DHEA) treatment was tested in this model. Apoptosis was assessed using immunohistochemisty of cleaved effector caspase-3 and its activator caspase-8 and the TUNEL assay. To test for the bioavailability, intracrine metabolism and sex steroid effects of DHEA, cystein-rich secretory protein-3 (CRISP-3), and leucine-isoleucine-valine transport system 1 (LIV-1) were used as androgen-and estrogen-regulated biomarkers, respectively. DHT protected HSG cells against induced apoptosis. In mice, androgen deficiency resulted in extensive activation of apoptotic caspase-8/3 cascade in serous epithelial cells. However, in salivary glands, active caspases were not translocated to nuclei but secreted to salivary ducts in exosome-like particles, which are associated with weak AB-PAS and amylase staining of the androgen-deprived cells and reduced number of intracellular secretory granules. DHEA treatment suppressed induction of proapoptotic caspases and almost normalized mucins and amylase and ultramophology of the serous epithelial cells in WT ORX but not ARKO ORX mice. According to the CRISP-3 and LIV-1 markers, DHEA probably exerted its effects via intracrine conversion to DHT.
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