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Ziyuan Ouyang - One of the best experts on this subject based on the ideXlab platform.
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platinum group elements of the Meishan permian triassic boundary section evidence for flood basaltic volcanism
Chemical Geology, 2007Co-Authors: Yangting Lin, Wenjie Shen, Liewen Xie, Ziyuan OuyangAbstract:Abstract Permian–Triassic boundary sections record the most severe mass extinction event in geological history. However, there is a long-standing controversy of whether bolide impact and/or basaltic flood volcanism triggered the mass extinction. Platinum-group elements (PGEs) are enriched in most extraterrestrial materials, but highly depleted in the terrestrial crust materials. We analyzed Ir, Ru, Rh, Pt and Pd in a set of samples from the global stratotype section and point (GSSP) of the Permian–Triassic boundary at Meishan, China, using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) and nickel sulfide fire assay (NiS-FA) combined with Te coprecipitation. The samples have no Ir anomaly (5–53 pg/g), and their PGE patterns normalized to chondrites are highly fractionated with Ir/Pd ratios of 0.02–0.03 × CI, distinct from most extraterrestrial materials. In contrast, these patterns are closely parallel to those of the Siberian and probably EMeishan flood basalts, suggestive of possible sources of PGEs from the basalts. The abundances of PGEs increase in order of the pyrite lamina on the top of bed 24, bed 25 and bed 26, and then decrease to bed 28, probably indicative of a maximum eruption of the flood basalts during deposition of bed 26. The new data favor massive volcanism, rather than extraterrestrial impact, as a major cause of the Permian–Triassic boundary mass extinction.
Yangting Lin - One of the best experts on this subject based on the ideXlab platform.
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analysis of platinum group elements in drill core samples from the Meishan permian triassic boundary section china
Chinese Journal of Geochemistry, 2014Co-Authors: Yangting LinAbstract:There is a long-standing controversy of what triggered the extinction at the Permian-Triassic boundary, the most severe mass extinction in the geologic record, including flood basaltic volcanism and/or bolide impact hypothesis. In order to clarify various pieces of evidence for the mass extinction event at the Permian-Triassic boundary, some researchers from some laboratories throughout the world have made a comprehensive study on a group of samples from the Meishan area of China. Some fresh core samples from the Permian-Triassic boundary in the Meishan area were analyzed in this study. The results showed that there is no Ir anomaly. Moreover, the PGEs patterns of those samples show obvious differentiation characteristics, that is different from the case encountered in meteorites. So no evidence supports the hypothesis of extraterrestrial impact. In contrast, the PGEs patterns are similar to those of Siberian and EMeishan basalts, which indicates that those PGEs are derived mainly from the basalts, lending a support to the correlation between mass extinction at the Permian-Triassic boundary and flood basaltic volcanism. This study has also confirmed the results for samples from section C prior to the analysis of the samples.
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platinum group elements of the Meishan permian triassic boundary section evidence for flood basaltic volcanism
Chemical Geology, 2007Co-Authors: Yangting Lin, Wenjie Shen, Liewen Xie, Ziyuan OuyangAbstract:Abstract Permian–Triassic boundary sections record the most severe mass extinction event in geological history. However, there is a long-standing controversy of whether bolide impact and/or basaltic flood volcanism triggered the mass extinction. Platinum-group elements (PGEs) are enriched in most extraterrestrial materials, but highly depleted in the terrestrial crust materials. We analyzed Ir, Ru, Rh, Pt and Pd in a set of samples from the global stratotype section and point (GSSP) of the Permian–Triassic boundary at Meishan, China, using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) and nickel sulfide fire assay (NiS-FA) combined with Te coprecipitation. The samples have no Ir anomaly (5–53 pg/g), and their PGE patterns normalized to chondrites are highly fractionated with Ir/Pd ratios of 0.02–0.03 × CI, distinct from most extraterrestrial materials. In contrast, these patterns are closely parallel to those of the Siberian and probably EMeishan flood basalts, suggestive of possible sources of PGEs from the basalts. The abundances of PGEs increase in order of the pyrite lamina on the top of bed 24, bed 25 and bed 26, and then decrease to bed 28, probably indicative of a maximum eruption of the flood basalts during deposition of bed 26. The new data favor massive volcanism, rather than extraterrestrial impact, as a major cause of the Permian–Triassic boundary mass extinction.
Stephen P. Ford - One of the best experts on this subject based on the ideXlab platform.
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conceptus competition for uterine space different strategies exhibited by the Meishan and yorkshire pig
Journal of Animal Science, 2002Co-Authors: Kimberly A Vonnahme, M E Wilson, Stephen P. FordAbstract:Our laboratory has demonstrated that Yorkshire placentae increase in size and surface area during the final third of gestation. In contrast, Meishan placental size remains constant during late gestation, but the density of blood vessels at the placental-endometrial interface increases markedly. Preliminary observations from our laboratory suggest that if one of two adjacent Meishan fetuses dies, the placenta of the remaining Meishan conceptus fails to increase its length of implantation or its placental weight or surface area. In contrast, if one of two adjacent Yorkshire fetuses dies, the adjacent conceptus accelerates its placental growth. The objective of this experiment was to document that Yorkshire, but not Meishan, conceptuses accelerate placental growth when adjacent fetuses are experimentally destroyed on d 40 of gestation. Straightbred Meishan (n = 5) and Yorkshire (n = 5) females were laparotomized and one uterine horn was randomly assigned to receive fetal crushing (treated horn); the other uterine horn served as a within-animal control. In the treated horn, every other fetus was then crushed through the uterine wall and the animals were allowed to recover. On d 111, animals were killed, uteri were recovered, and fetal weight, crown-rump length (CRL), placental weight, implantation site length, and placental surface area were recorded. Although there were no statistically significant differences in fetal weight or CRL observed between treated or control horns of females of either breed, there was a tendency for the fetuses in the treated uterine horn to be longer and heavier in both breeds. There were no differences in placental weight, placental surface area, or implantation site length between conceptuses in Meishan treated and control horns, which averaged 173.8+/-6.4 g, 1,162.7+/-35.9 cm2, and 19.0+/-0.4 cm, respectively. In contrast, placental weight, placental surface area, and implantation site length were increased (P < 0.05) in Yorkshire treated horns compared to Yorkshire control horns (306.1+/-26.0 g, 1,835+/-93.9 cm2, and 33.4+/-1.5 cm vs 253.7+/-13.4 g, 1,474.3+/-50.4 cm2, and 27.2+/-0.8 cm; respectively). These data confirm that Yorkshire conceptuses, but not Meishan conceptuses, accelerate placental growth when adjacent littermates perish as late as d 40 of gestation. These data indicate that differences exist in the strategies employed by Meishan and Yorkshire conceptuses in the competition for nutrients during gestation.
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Development of Meishan and Yorkshire littermate conceptuses in either a Meishan or Yorkshire uterine environment to day 90 of gestation and to term.
Biology of reproduction, 1998Co-Authors: Matthew E. Wilson, Nina J. Biensen, Curtis R. Youngs, Stephen P. FordAbstract:To investigate the impacts of uterine type and conceptus genotype on development through late gestation, Meishan and Yorkshire embryos were co-transferred into the uteri of either Meishan or Yorkshire recipients that were subsequently slaughtered on Day 90 of gestation. At slaughter, regardless of conceptus genotype, fetuses and placentae were markedly smaller when recovered from Meishan than from Yorkshire recipients. Whereas Meishan and Yorkshire fetuses recovered from Meishan uteri were similar in weight, Meishan fetuses were markedly lighter than littermate Yorkshire fetuses when recovered from Yorkshire uteri. Because of the marked differences between fetal weights observed in Yorkshire recipients on Day 90 of gestation, Meishan and Yorkshire embryos were co-transferred to Yorkshire recipients that were allowed to farrow. Surprisingly, Meishan and Yorkshire fetuses cogestated in Yorkshire recipients were born at similar weights, whereas Meishan placentae were markedly smaller. The weight of Meishan placentae were similar on Day 90 and at term, whereas the weight of Yorkshire placentae were markedly larger (-70%) at term than on Day 90. The constant weight of Meishan placentae from Day 90 to farrowing appears to result from an ability to increase their vascularity during this interval. In contrast, Yorkshire placentae may be forced to increase their weight to keep pace with fetal growth during this period. Because uterine capacity sets the upper limit on litter size, the decreased endometrial surface area required per conceptus in the Meishan pig seems to explain its greater potential for increased litter size.
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A Decreased Placental Size and Increased Vascular Density Results in Increased Prolificacy in the Meishan Pig
1997Co-Authors: Matthew E. Wilson, Stephen P. Ford, Nina J. BiensenAbstract:and Implications The Chinese Meishan pig farrows 3 to 5 more pigs per litter than U.S. pig breeds. When Meishan and Yorkshire embryos are co-transferred to a Yorkshire recipient, Meishan fetuses and placentae are smaller than Yorkshire fetuses and placentae through day 90 of gestation. At farrowing, Meishan placentae are still smaller than Yorkshire placentae; however, Meishan fetuses are born at the same weight as their Yorkshire littermates. This tremendous growth of the Meishan fetus between day 90 and term is the result of an increased vascularization of the Meishan placenta. In this experiment we investigated the time course of placental vascular development of Meishan and Yorkshire conceptuses during late gestation. Our results demonstrate that Yorkshire fetuses increase the potential for nutrient extraction from the maternal blood by increasing the size of their placentae; however, Meishan fetuses achieve the same end by increasing the density of placental blood vessels while maintaining a constant placental size. The increased vascular density of the Meishan placenta then allows the conceptus to occupy less space in the uterus, allowing more fetuses to survive to term.
Qian Xiao - One of the best experts on this subject based on the ideXlab platform.
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Genomic signatures reveal selection of characteristics within and between Meishan pig populations
Animal genetics, 2018Co-Authors: Hao Sun, Zhengwu Wang, Z. Zhang, Qian Xiao, S. Mawed, Xiangzhe Zhang, H. Yang, M. Zhu, M. XueAbstract:The Chinese Meishan pig breed is well known for its high prolificacy. Moreover, this breed can be divided into three types based on their body size: big Meishan, middle Meishan (MMS) and small Meishan (SMS) pigs. Few studies have reported on the genetic signatures of Meishan pigs, particularly on a genome-wide scale. Exploring for genetic signatures could be quite valuable for revealing the genetic architecture of phenotypic variation. Thus, we performed research in two parts based on the genome reducing and sequencing data of 143 Meishan pigs (74 MMS pigs, 69 SMS pigs). First, we detected the selection signatures among all Meishan pigs studied using the relative extended haplotype homozygosity test. Second, we detected the selection signatures between MMS and SMS pigs using the cross-population extended haplotype homozygosity and FST methods. A total of 111 398 SNPs were identified from the sequenced genomes. In the population analysis, the most significant genes were associated with the mental development (RGMA), reproduction (HDAC4, FOXL2) and lipid metabolism (ACACB). From the cross-population analysis, we detected genes related to body weight (SPDEF, PACSIN1) in both methods. We suggest that rs341373351, located within the PACSIN1 gene, might be the causal variant. This study may have achieved consistency between selection signatures and characteristics within and between Meishan pig populations. These findings can provide insight into investigating the molecular background of high prolificacy and body size in pig.
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transcriptome analysis revealed the embryo induced gene expression patterns in the endometrium from Meishan and yorkshire pigs
International Journal of Molecular Sciences, 2015Co-Authors: Jiangnan Huang, Ruize Liu, Qian XiaoAbstract:The expression patterns in Meishan- and Yorkshire-derived endometrium during early (gestational day 15) and mid-gestation (gestational days 26 and 50) were investigated, respectively. Totally, 689 and 1649 annotated genes were identified to be differentially expressed in Meishan and Yorkshire endometrium during the three gestational stages, respectively. Hierarchical clustering analysis identified that, of the annotated differentially expressed genes (DEGs), 73 DEGs were unique to Meishan endometrium, 536 DEGs were unique to Yorkshire endometrium, and 228 DEGs were common in Meishan and Yorkshire endometriums. Subsequently, DEGs in each of the three types of expression patterns were grouped into four distinct categories according to the similarities in their temporal expression patterns. The expression patterns identified from the microarray analysis were validated by quantitative RT-PCR. The functional enrichment analysis revealed that the common DEGs were enriched in pathways of steroid metabolic process and regulation of retinoic acid receptor signaling. These unique DEGs in Meishan endometrium were involved in cell cycle and adherens junction. The DEGs unique to Yorkshire endometrium were associated with regulation of Rho protein signal transduction, maternal placenta development and cell proliferation. This study revealed the different gene expression patterns or pathways related to the endometrium remodeling in Meishan and Yorkshire pigs, respectively. These unique DEGs in either Meishan or Yorkshire endometriums may contribute to the divergence of the endometrium environment in the two pig breeds.
Tung Yi Lee - One of the best experts on this subject based on the ideXlab platform.
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age of the eMeishan flood magmatism and relations to permian triassic boundary events
Earth and Planetary Science Letters, 2002Co-Authors: Sunlin Chung, Tung Yi LeeAbstract:The Permian^Triassic (P^T) mass extinction, the greatest biological mortality event in the Earth’s history, was probably caused by dramatic and global forcing mechanisms such as the Siberian flood volcanism. Here we present the first set of high-precision 40 Ar/ 39 Ar dating results of volcanic and intrusive rocks from the EMeishan Traps, South China, which define a main stage of the flood magmatism at V251^253 Ma and a subordinate precursory activity at V255 Ma. This time span is generally coeval with, or slightly older than, the age of the P^T boundary estimated by the ash beds in the Meishan stratotype section and the main eruption of the Siberian Traps. Our data reinforces the notion that the eruption of the EMeishan Traps, rather than eruption of the Siberian Traps, accounted for the formation of the P^T boundary ash beds in South China. The EMeishan flood magmatism, which occurred in the continental margin comprising thick marine limestone formations, moreover, may have triggered rapid release of large volumes of methane and carbon dioxide that could have been responsible for the global N 13 C excursion and associated environmental crisis leading to the mass extinction at the P^T boundary. fl 2002 Elsevier Science B.V. All rights reserved.
