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- Bibikova, E. V., et al.
(author)
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Sarmatia-Volgo-Uralia junction zone: Isotopic-geochronologic characteristic of supracrustal rocks and granitoids
- 2009
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In: Stratigraphy and Geological Correlation. - 0869-5938. ; 17:6, s. 561-573
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Journal article (peer-reviewed)abstract
- The geochronologic (U-Pb isotopic system of zircons) and isotopic-geochemical (Sm-Nd isotopic system of the bulk rock) studies were performed along the profile extending from the eastern Sarmatia (in the west) to the Middle Volga megablock of Volgo-Uralia (in the east), i.e., across the entire junction zone for dating the integration of Sarmatia and Volgo-Uralia, representing two segments of the East European Craton. It is established that the examined rocks are characterized by the Paleoproterozoic Nd isotopic model age, which varies from 2.1 and 2.4 Ga, except for some samples indicating a similar age of the crust through the entire Sarmatia-Volgo-Uralia junction zone. The highly metamorphosed complexes of the granulite and amphibolite facies constituting the southwestern margin of Volgo-Uralia are Paleoproterozoic, not Archean, in age, contrary to previous views. Two Early Paleoproterozoic lithotectonic complexes are defined in Volgo-Uralia: South Volga metasedimentary and Tersa metasedimentary-volcanogenic. The obtained data confirm the asynchronous integration of individual segments into the East European Craton: the integration of Sarmatia and Volgo-Uralia approximately 2100-2000 Ma ago was followed by the conjunction of this newly-formed continent with Fennoscandia ca. 1800 Ma ago.
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- Popova, Svetlana N., et al.
(author)
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alpha 11 beta 1 integrin-dependent regulation of periodontal ligament function in the erupting mouse incisor
- 2007
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In: Molecular and Cellular Biology. - 0270-7306 .- 1098-5549. ; 27:12, s. 4306-4316
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Journal article (peer-reviewed)abstract
- The fibroblast integrin alpha 11 beta 1 is a key receptor for fibrillar collagens. To study the potential function of alpha 11. in vivo, we generated a null allele of the alpha 11 gene. Integrin alpha 1(-/-) mice are viable and fertile but display dwarfism with increased mortality, most probably due to severely defective incisors. Mutant incisors are characterized by disorganized periodontal ligaments, whereas molar ligaments appear normal. The primary defect in the incisor ligament leads to halted tooth eruption. alpha 11 beta 1-defective embryonic fibroblasts displayed severe defects in vitro, characterized by (i) greatly reduced cell adhesion and spreading on collagen 1, (ii) reduced ability to retract collagen lattices, and (iii) reduced cell proliferation. Analysis of matrix metalloproteinase in vitro and in vivo revealed disturbed MMP13 and MMP14 synthesis in alpha 11(-/-) cells. We show that alpha 11 beta 1 is the major receptor for collagen I on mouse embryonic fibroblasts and suggest that alpha 11 beta 1 integrin is specifically required on periodontal ligament fibroblasts for cell migration and collagen reorganization to help generate the forces needed for axial tooth movement. Our data show a unique role for alpha 11 beta 1 integrin during tooth eruption.
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