Using stable isotopes to unravel the role of sea-ice in the methane cycle
; ; et al
Conference (2015, May 16)
Methane plays an important role in the Earth’s climate system. The atmospheric methane concentration has increased in concert with the industrialization, but since the mid 80’s the methane growth rate ... [more ▼]
Methane plays an important role in the Earth’s climate system. The atmospheric methane concentration has increased in concert with the industrialization, but since the mid 80’s the methane growth rate decreased to reach a near-zero level in 2000 and started to increase again from 2007 on. However, the underlying variations in sources and/or sinks that cause these variations are to date not well understood. To predict future climate, it is essential to unravel the processes controlling the methane cycle, especially in the Arctic regions, which are highly vulnerable to climate change and contain large methane reservoirs. Recently, an unexpected methane excess has been reported above Arctic sea-ice showing that sea-ice might play a significant role in the methane cycle. Nonetheless, the nature of the process leading to methane production in or nearby sea-ice has not yet been identified. We applied a new multi-proxy approach merging atmospheric chemistry, glaciology and biogeochemistry to understand and quantify the processes responsible for the methane excess above sea-ice. We performed methane isotope (d13C and dD) analyses on sea-ice samples, as well as geochemical measurements, to determine the possible pathways involved in methane production and removal in or nearby sea-ice. We will present results from sea-ice samples drilled above the shallow-shelf in Barrow (Alaska) from January to June 2009 as well as above deep Southern Ocean locations in 2013. It has long been thought that methane present in sea-water would oxidize in or under the sea ice, but our first stable isotope sea ice profiles show no significant oxidation pattern. On the other hand, we show that landfast sea ice from both the shallow-shelf of Barrow and our deeper Southern Ocean site is supersaturated in methane and that under specific conditions methane is likely formed in the ice. [less ▲]Detailed reference viewed: 35 (1 ULg)
In vitro oocyte IGF-I priming increases inner cell mass proliferation of in vitro-formed bovine blastocysts
; ; et al
in Theriogenology (2012), 78(3), 517-527
Studies addressing the effects of supraphysiological levels of IGF-1 on oocyte developmental competence are relevant for unravelling conditions resulting in high bioavailability of IGF-1, such as the ... [more ▼]
Studies addressing the effects of supraphysiological levels of IGF-1 on oocyte developmental competence are relevant for unravelling conditions resulting in high bioavailability of IGF-1, such as the polycystic ovary syndrome (PCOS). This study investigated the effects of supraphysiological levels of IGF-1 during in vivo folliculogenesis on the morula-blastocyst transition in bovine embryos. Compacted morulae were non-surgically collected and frozen for subsequent mRNA expression analysis (IGF1R, IGBP3, TP53, AKT1, SLC2A1, SLC2A3, and SLC2A8), or underwent confocalmicroscopy analysis for protein localization (IGF1R and TP53), or were cultured in vitro for 24 h. In vitro-formed blastocysts were subjected to differential cell staining. The mRNA expression of SLC2A8 was higher in morulae collected from cows treated with IGF-1. Both IGF1R and TP53 protein were present in the plasma membrane and cytoplasm. IGF-1 treatment did not affect protein localization of both IGF1R and TP53. In vitro-formed blastocysts derived from morulae recovered from IGF-1-treated cows displayed a higher number of cells in the inner cell mass (ICM). Total cell number (TCN) of in vitro-formed blastocysts was not affected. A higher mean ICM/TCN proportion was observed in in vitro-formed blastocysts derived from morulae collected from cows treated with IGF-1. The percentage of in vitro-formed blastocysts displaying a low ICM/TCN proportion was decreased by IGF-1 treatment. In vitro-formed blastocysts with a high ICM/TCN proportion were only detected in IGF-1 treated cows. Results show that even a short in vivo exposure of oocytes to a supraphysiological IGF-1 microenvironment can increase ICM cell proliferation in vitro during the morula to blastocyst transition [less ▲]Detailed reference viewed: 25 (6 ULg)
In vivo oocyte developmental competence is reduced in lean but not in obese superovulated dairy cows after intraovarian administration of IGF1.
; ; et al
in Reproduction (Cambridge, England) (2011), 142(1), 41-52
The present study investigated the role of IGF1 in lactating lean and non-lactating obese dairy cows by injecting 1 μg IGF1 into the ovaries prior to superovulation. This amount of IGF1 has been linked ... [more ▼]
The present study investigated the role of IGF1 in lactating lean and non-lactating obese dairy cows by injecting 1 μg IGF1 into the ovaries prior to superovulation. This amount of IGF1 has been linked with pregnancy loss in women with the polycystic ovary syndrome (PCOS) and was associated with impaired bovine oocyte competence in vitro. Transcript abundance and protein expression of selected genes involved in apoptosis, glucose metabolism, and the IGF system were analyzed. Plasma concentrations of IGF1 and leptin, and IGF1 in uterine luminal fluid (ULF), were also measured. IGF1 treatment decreased embryo viability in lean cows to the levels observed in obese cows. Obese cows were not affected by IGF1 treatment and showed elevated levels of IGF1 (in both plasma and ULF) and leptin. Blastocysts from lean cows treated with IGF1 showed a higher abundance of SLC2A1 and IGFBP3 transcripts. IGF1 treatment reduced protein expression of tumor protein 53 in blastocysts of lean cows, whereas the opposite was observed in obese cows. IGF1 in plasma and ULF was correlated only in the control groups. Blastocyst transcript abundance of IGF1 receptor and IGFBP3 correlated positively with IGF1 concentrations in both plasma and ULF in lean cows. The detrimental microenvironment created by IGF1 injection in lean cows and the lack of effect in obese cows resemble to a certain extent the situation observed in PCOS patients, where IGF1 bioavailability is increased in normal-weight women but reduced in obese women, suggesting that this bovine model could be useful for studying IGF1 involvement in PCOS. [less ▲]Detailed reference viewed: 24 (2 ULg)
Effects of intraovarian application of insulin-like growth factor-1 (IGF-1) on the superovulatory response of diary cattle.
; ; Beckers, Jean-François et al
in Reproduction in Domestic Animals (2009), 44(S1), 38Detailed reference viewed: 24 (2 ULg)
Purified FSH supplemented with defined amounts of LH for superovulation in dairy cattle .
; Beckers, Jean-François ; et al
in Theriogenology (1988, January), 29(1), 260Detailed reference viewed: 21 (2 ULg)