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91.
Mary Jane West-Eberhard has suggested that plasticity may be of primary importance in promoting evolutionary innovation and
diversification. Here, we explore the possibility that the diversification of phytophagous insects may have occurred through
such a process, using examples from nymphalid butterflies. We discuss the ways in which host plant range is connected to plasticity
and present our interpretation of how West-Eberhard’s scenario may result in speciation driven by plasticity in host utilization.
We then review some of the evidence that diversity of plant utilization has driven the diversification of phytophagous insects
and finally discuss whether this suggests a role for plasticity-driven speciation. We find a close conceptual connection between
our theory that the diversification of phytophagous insects has been driven by oscillations in host range, and our personal
interpretation of the most efficient way in which West-Eberhard’s theory could account for plasticity-driven speciation. A
major unresolved issue is the extent to which a wide host plant range is due to adaptive plasticity with dedicated modules
of genetic machinery for utilizing different plants. 相似文献
92.
Elisabetta Catalani Silvia Tomassini Massimo Dal Monte Luigi Bosco Giovanni Casini 《Cell and tissue research》2009,336(3):423-438
Fibroblast growth factors (FGFs) exert basic functions both during embryonic development and in the adult. The expression
of FGFs and their receptors has been reported in mammalian retinas, although information on the organization of the FGF system
is still incomplete. Here, we report a detailed double-label immunohistochemical investigation of the localization patterns
of FGF1 and its receptors FGFR1 and FGFR2 in adult and early postnatal mouse retinas. In adult retinas, FGF1 is localized
to ganglion cells, horizontal cells, and photoreceptor inner and outer segments. FGFR1 is found in ganglion cells and Müller
cells, whereas FGFR2 is primarily located in ganglion cells, the nuclei of Müller cells, and glycine-containing amacrine cells.
During postnatal development, the patterns of FGF1, FGFR1, and FGFR2 immunostaining are similar to those in the adult, although
transient FGF1-expressing cells have been detected in the proximal inner nuclear layer before eye opening. These patterns
are consistent with a major involvement of FGF1, FGFR1, and FGFR2 in ganglion cell maturation (during development) and survival
(in the adult). Moreover, FGF1 may affect amacrine cell development, whereas Müller cells appear to be regulated via both
FGFR1 and FGFR2 throughout postnatal life. In immature retinas, large numbers of amacrine cells, including those containing
calbindin and glycine, display both FGF1 and FGFR2 immunoreactivities in their nuclei, suggesting an action of FGF1 on FGFR2
leading to the maturation of these amacrine cells during a restricted period of postnatal development.
This work was supported by funding from the Italian Ministry of Education. 相似文献
93.
Chemosensory neurons in the olfactory epithelium (OE) project axonal processes to the olfactory bulb (OB) of the brain. During
embryonic stages, on their trajectory to the OB, the outgrowing axons traverse the so-called cribriform mesenchyme, which
is located between the OE and the OB. The molecular cues guiding these axons through the cribriform mesenchyme are largely
unknown. To identify molecules influencing the axonal trajectory in the murine cribriform mesenchyme, we performed microarray
analyses focusing on extracellular matrix (ECM) proteins present in this tissue. Thereby, the ECM protein Reelin turned out
to be an interesting candidate. Reelin was found to be expressed by numerous cells in the cribriform mesenchyme during the
embryonic stages when the first axons navigate from the OE to the OB. These cells were closely associated with olfactory axons
and apparently lack glial and neuronal markers. In the mesenchyme underlying the OE, localization of the Reelin protein was
not confined to the Reelin-expressing cells, but it was also observed to be widely distributed in the ECM—most prominently
in regions traversed by olfactory axons. Importantly, these axons were found to be endowed with the Reelin receptor very-low-density
lipoprotein receptor (VLDLR). Finally, Reelin expression was also detectable in neuronal cells of the OB, which are contacted
by VLDLR-positive olfactory axons. In summary, the results of the present study suggest that a Reelin/VLDLR signaling pathway
might contribute to the formation of olfactory projections to the OB and the establishment of initial contacts between the
incoming axons and neurons in the OB.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Funding: This work was supported by the Deutsche Forschungsgemeinschaft. 相似文献
94.
95.
Cytochemical changes in the developmental process of Nostoc sphaeroides (cyanobacterium) 总被引:1,自引:0,他引:1
There are several apparent developmental stages in the life cycle of Nostoc sphaeroides Kützing, an edible cyanobacterium found mainly in paddy fields in central China. The cytochemical changes in developmental
stages such as hormogonia, aseriate stage, filamentous stage and colony in N. sphaeroides were examined using fluorescent staining and colorimetric methods. The staining of acidic and sulfated polysaccharides increased
with development when hormogonia were used as the starting point. Acidic polysaccharides (AP) were most abundant at the aseriate
stage and then decreased, while the sulfated polysaccharides (SP) were highest at the colony stage. Quantitatively, along
the developmental process from hormogonia to colony, total carbohydrates first increased, then became stable, and then reached
their highest level at the colony stage, while reducing sugars were highest at the hormogonia stage and then decreased sharply
once development began. SP were not detectable in the hot water soluble polysaccharides (HWSP), and hormogonia had the lowest
content of AP, while old colonies had the highest. The AP content of the aseriate stage, filamentous stage and young colony
stage were very similar. The evolutionary relationships reflected in the developmental stages of N. sphaeroides are discussed. 相似文献
96.
Essential role for the Pak4 protein kinase in extraembryonic tissue development and vessel formation
Yanmei Tian Liang Lei Marta Cammarano Tanya Nekrasova Audrey Minden 《Mechanisms of development》2009,126(8-9):710-720
Pak4 is a member of the group B family of Pak serine/threonine kinases, originally identified as an effector protein for the Rho GTPase Cdc42. Pak4 knockout mice are embryonic lethal and do not survive past embryonic day 11.5. Previous work on Pak4 knockout mice has focused on studying the phenotype of the embryo. Abnormalities in the extraembryonic tissue, however, are common causes of early embryonic death in knockout mice. Extraembryonic tissue associated with the Pak4-null embryos was therefore examined. Abnormalities in both yolk sacs and placentas resulted when Pak4 was deleted. These included a lack of vasculature throughout the extraembryonic tissue, as well as an abnormally formed labyrinthine layer of the placenta. Interestingly, epiblast-specific deletion of Pak4 using a conditional knockout system, did not rescue the embryonic lethality. In fact, it did not even rescue the extraembryonic tissue defects. Our results suggest that the extraembryonic tissue abnormalities are secondary to defects that occur in response to epiblast abnormalities. More detailed analysis suggests that abnormalities in vasculature throughout the extraembryonic tissue and the epiblast may contribute to the death of the Pak4-null embryos. 相似文献
97.
Arnon D. Jurberg Tiana Gonçalves Tatiane A. Costa Ana Carolina A. de Mattos Bernardo M. Pascarelli Pedro Paulo A. de Manso Marcelo Ribeiro-Alves Marcelo Pelajo-Machado José M. Peralta Paulo Marcos Z. Coelho Henrique L. Lenzi 《Development genes and evolution》2009,219(5):219-234
Schistosomiasis is a water-borne parasitic illness caused by neoophoran trematodes of the genus Schistosoma. Using classical histological techniques and whole-mount preparations, the present work describes the embryonic development
of Schistosoma mansoni eggs in the murine host and compares it with eggs maintained under in vitro conditions. Two pre-embryonic stages occur inside
the female worm: the prezygotic stage is characterized by the release of mature oocytes from the female ovary until its fertilization.
The zygotic stage encompasses the migration of the zygote through the ootype, where the eggshell is formed, to the uterus.
Fully formed eggs are laid still undeveloped, without having suffered any cleavage. In the outside environment, eight embryonic
stages can be defined: stage 1 refers to early cleavages and the beginning of yolk fusion. Stage 2 represents late cleavage,
with the formation of a stereoblastula and the onset of outer envelope differentiation. Stage 3 is defined by the elongation
of the embryonic primordium and the onset of inner envelope formation. At stage 4, the first organ primordia arise. During
stages 5 to 7, tissue and organ differentiation occurs (neural mass, epidermis, terebratorium, musculature, and miracidial
glands). Stage 7 is characterized by the nuclear condensation of neurons of the central neural mass. Stage 8 refers to the
fully formed larva, presenting muscular contraction, cilia, and flame-cell beating. This staging system was compared to a
previous classification and could underlie further studies on egg histoproteomics (morphological localizome). The differentiation
of embryonic structures and their probable roles in granulomatogenesis are discussed herein.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
98.
Mike Friedrich Revaz Nozadze Qiang Gan Vladimir Ermolayev Gregory S. Harms 《Biochemical and biophysical research communications》2009,390(3):722-8
Single-molecule detection and tracking is important for observing biomolecule interactions in the microenvironment. Here we report selective plane illumination microscopy (SPIM) with single-molecule detection in living organisms, which enables fast imaging and single-molecule tracking and optical penetration beyond 300 μm. We detected single nanocrystals in Drosophila larvae and zebrafish embryo. We also report our first tracking of single quantum dots during zebrafish development, which displays a transition from flow to confined motion prior to the blastula stage. The new SPIM setup represents a new technique, which enables fast single-molecule imaging and tracking in living systems. 相似文献
99.
100.