3 research outputs found
Reworking of old continental lithosphere: an important crustal evolution mechanism in orogenic belts, as evidenced by Triassic I-type granitoids in the East Kunlun orogen, Northern Tibetan Plateau
<p>There is a strong genetic relationship between the petrogenesis of I-type granitoids and the evolution of continental crust
in orogenic belts. This study of I-type granitoids in the East Kunlun orogen, Northern Tibetan Plateau, shows that reworking
of old continental lithosphere is an important key to this genetic relationship. The East Kunlun has numerous Triassic granitic
plutons that are related to subduction of the Palaeo-Tethyan ocean and terrane collision in the early Mesozoic. U–Pb analysis
of zircons from these Triassic granitoids indicates that the granitic magmatism lasted from 249 to 223 Ma. Based on elemental
and isotopic compositions and their petrogenesis, the magmatism can be divided into three groups. (1) Group 1 consists of
quartz diorites and granodiorites (241–249 Ma), which are metaluminous high-K calc-alkaline I-type granitoids and exhibit
typical subduction-related chemical characteristics. They were derived from lower crust mainly composed of Precambrian metabasaltic
basement rocks with different degrees of involvement of mantle material. (2) Group 2 consists of granitic porphyries and syenogranites
(231–238 Ma), which are high Rb/Sr, metaluminous to weakly peraluminous high-K alkali-calcic I-type granitoids, showing characteristics
of typical pure crustal-derived granitoids. They were derived from partial melting of a Mesoproterozoic metagreywacke source
in the lower crust. (3) Group 3 consists of porphyry granodiorites (<em>c</em>. 223 Ma), which are metaluminous high-K calc-alkaline I-type granitoids and exhibit the typical geochemical characteristics
of adakites (e.g. high La/Yb and Sr/Y ratios and low Y and Yb contents). Their high K<sub>2</sub>O and low Mg# with evolved Sr–Nd–Hf isotopic compositions indicate that they were most probably derived from thickened mafic
lower continental crust, which underwent partial melting induced by underplated hot mafic magma. Combining the present work
with previous studies, we propose that the subduction of the Palaeo-Tethyan ocean lasted from 278 to 241 Ma, and the collision
between the Bayan Har terrane and the East Kunlun occurred at 231–238 Ma, whereas the group 3 granitoids most probably formed
in a post-collisional setting. Overall, all the studied I-type granitoids were derived from partial melting of old continental
lower crust with minor addition of lithospheric mantle material; thus reworking of old continental lithosphere is an important
mechanism for the evolution of orogenic crust.
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DataSheet1_Wound healing mechanism of antimicrobial peptide cathelicidin-DM.pdf
Background and Purpose: Chronic wound infections and the development of antibiotic resistance are serious clinical problems that affect millions of people worldwide. Cathelicidin-DM, an antimicrobial peptide from Duttaphrynus melanostictus, has powerful antimicrobial activity and wound healing efficacy. So, it could be a potential candidate to address this problem. In this paper, we investigate the wound healing mechanism of cathelicidin-DM to establish a basis for preclinical studies of the drug.Experimental Approach: The effects of cathelicidin-DM on cell proliferation and migration, cytokines, and mitogen-activated protein kinase (MAPK) signaling pathways were examined. Then mice whole skin wound model was constructed to evaluate the wound healing activity of cathelicidin-DM, and further histological changes in the wounds were assessed by hematoxylin-eosin staining (H&E) and immunohistochemical assays.Key Results: Cathelicidin-DM promotes the proliferation of HaCaT, HSF, and HUVEC cells in a concentration-dependent manner and the migration of HSF, HUVEC, and RAW.264.7 cells. Moreover,cathelicidin-DM can involve in wound healing through activation of the MAPK signaling pathway by upregulating phosphorylation of ERK, JNK, and P38. However, cathelicidin-DM didn’t affect the secretion of IL-6 and TNF-α. At the animal level, cathelicidin-DM accelerated skin wound healing and early debridement in mice as well as promoted re-epithelialization and granulation tissue formation, α-SMA expression, and collagen I deposition in mice.Conclusion and Implications: Our data suggest that cathelicidin-DM can be engaged in the healing of infected and non-infected wounds through multiple pathways, providing a new strategy for the treatment of infected chronic wounds.</p
An Early Mesozoic transcontinental palaeoriver in South China: evidence from detrital zircon U–Pb geochronology and Hf isotopes
<p>Detrital zircon geochronology reveals that Late Triassic–Early Jurassic fluvial sandstones from the major basins of the South
China Craton have similar age patterns and define four populations at 2.6–2.4 Ga, 2.0–1.7 Ga, 850–700 Ma and 480–210 Ma. The
late Palaeoproterozoic group is predominant in all of the five samples, and yielded remarkable age peaks at <em>c</em>. 1.85 Ga. These zircons have ϵ<sub>Hf</sub>(t) values between −22.5 and +3.6, suggesting derivation from reworked Archaean crust and minor juvenile crustal additions
in the late Palaeoproterozoic. These characteristics differ from those of the Yangtze Block but correlate well with those
of samples from the eastern Cathaysia Block. Palaeocurrent analysis of the Early Mesozoic sandstones shows predominant west-
and NW-directed palaeoflows, supporting derivation of the sediments from the Cathaysia Block. The remarkable similarities
in provenance signatures and spatial changes of lithofacies of the Triassic–Jurassic around the South China Craton delineate
an east–west-trending sedimentary zone extending from Korea to West China. Accumulation of these sediments was probably related
to the development of an active continental margin produced by westward subduction of the Palaeo-Pacific Plate. A <em>c</em>. 2000 km long westerly draining transcontinental palaeoriver probably had existed in the Early Mesozoic and fed the basins
in Korea, South China and West China.
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