Nlrp2, a Maternal Effect Gene Required for Early Embryonic Development in the Mouse

Maternal effect genes encode proteins that are produced during oogenesis and play an essential role during early embryogenesis. Genetic ablation of such genes in oocytes can result in female subfertility or infertility. Here we report a newly identified maternal effect gene, Nlrp2, which plays a role in early embryogenesis in the mouse. Nlrp2 mRNAs and their proteins (∼118 KDa) are expressed in oocytes and granulosa cells during folliculogenesis. The transcripts show a striking decline in early preimplantation embryos before zygotic genome activation, but the proteins remain present through to the blastocyst stage. Immunogold electron microscopy revealed that the NLRP2 protein is located in the cytoplasm, nucleus and close to nuclear pores in the oocytes, as well as in the surrounding granulosa cells. Using RNA interference, we knocked down Nlrp2 transcription specifically in mouse germinal vesicle oocytes. The knockdown oocytes could progress through the metaphase of meiosis I and emit the first polar body. However, the development of parthenogenetic embryos derived from Nlrp2 knockdown oocytes mainly blocked at the 2-cell stage. The maternal depletion of Nlrp2 in zygotes led to early embryonic arrest. In addition, overexpression of Nlrp2 in zygotes appears to lead to normal development, but increases blastomere apoptosis in blastocysts. These results provide the first evidence that Nlrp2 is a member of the mammalian maternal effect genes and required for early embryonic development in the mouse

Increasing Access to Surgical Services in Sub-Saharan Africa: Priorities for National and International Agencies Recommended by the Bellagio Essential Surgery Group

In this Policy Forum, the Bellagio Essential Surgery Group, which was formed to advocate for increased access to surgery in Africa, recommends four priority areas for national and international agencies to target in order to address the surgical burden of disease in sub-Saharan Africa

New understandings and exploration discovery of Paleogene reservoirs of Kunbei fault terrace belt, Qaidam Basin, NW China

The sedimentary facies distribution, sedimentary reservoir characteristics and main control factors of Paleogene Lulehe Formation and Lower Xiaganchaigou Formation were examined by studying on the Paleogene reservoir properties of Kunbei fault terrace belt in western Qaidam Basin, combined with well logging and seismic data. Because of the source control by Kunlun Mountains, the Lower Xiaganchaigou Formation developed braided river delta−lake sedimentary systems, mainly braided river delta front sediments, and the sand bodies distribution is SW-NE; the Lower Lulehe Formation mainly developed braided river delta plain, and braided river delta front mainly developed in the Upper Lulehe Formation. The reservoir physical properties of the braided river delta front in Lower Xiaganchaigou Formation are better, with favorable conditions of high-quality reservoirs. Tight reservoirs in Lulehe Formation have sweet spots. The oil and gas distribution of Lulehe Formation in Kunbei fault terrace belt is controlled by the content of argillaceous matrix. The new understandings of sedimentary reservoirs in Kunbei fault terrace belt play an important guiding role in oil and gas exploration of the area. Oil and gas exploration in the Qie 6, Qie 12 and Qie 16 structures achieves success, with almost one hundred million tons of proven geological reserves. Key words: Qaidam Basin, Kunbei fault terrace belt, Paleogene, sedimentary facies, reservoir characteristics, new area exploratio

Strike-slip superimposed Qaidam Basin and its control on oil and gas accumulation, NW China

Based on detailed field survey in the western Qaidam Basin, combined with petroleum exploration practices in recent years, this study suggests that the Qaidam Basin is a strike-slip superimposed basin jointly controlled by the left-lateral strike-slip Altyn Tagh and East Kunlun faults. The Altyn Tagh fault acts as the major controlling boundary, while the East Kunlun fault only controls the local evolution of the southern edge of the basin. To the east, the northern Qaidam-Qilian Shan thrust-fold belt passively accommodates the northeastward displacement along the Altyn Tagh fault through NE-SW directed shortening. In the India-Asia collision background, the left-lateral strike-slip faulting along the Altyn Tagh fault initiated from the early Eocene, forcing the Qaidam Basin to move northeastward, causing the thrust and slip deformation of the NW-SE faults in northern Qaidam margin-Qilian Mountain area, and the deposition of the Cenozoic since the Paleogene Lulehe Formation. During the Paleogene, the northern Qaidam Basin developed coarse-grained sediments like that in a foreland basin, forming poor quality source rocks; while the southwestern Qaidam Basin was an extensional sag basin where good quality source rocks deposited. By the early Miocene, left-lateral faulting along the Kunlun fault became active, leading to the formation of a series of en-echelon faults (e.g. the Kunbei fault, the Arlar fault and the Hongliuquan fault). These faults gradually migrated northward, their kinematics changing from left-lateral strike-slip motion to NE-SW transpression. Strike-slip-related structures controlled by those faults (e.g. the Yingxiongling structure) are ideal places for oil and gas accumulation from Paleogene source rocks. To sum up, the Qaidam Basin is a strike-slip superimposed basin jointly controlled by the left-lateral strike-slip Altyn Tagh and East Kunlun faults. The temporal and spatial superimposition of these two strike-slip faults during the Cenozoic controlled the evolution of the basin as well as the oil and gas accumulation. Key words: Qaidam Basin, East Kunlun fault, Altyn Tagh fault, strike-slip superimposed basin, control on oil and gas accumulatio

Control of crater morphology on flow path direction of Soufriere-type pyroclastic flows

We present a model of fountain collapse for small-scale (Soufrière-type) explosive eruptions that relates the asymmetry of a volcanic crater (e.g., the presence of crater notches) with the emplacement direction of pyroclastic flows. Analysis of two-dimensional simulations of compressible fluids emanating from asymmetric nozzles shows that under sonic to supersonic conditions, the streamline of a jet can become tilted. The inclination of the streamline increases with greater slant angle of the nozzle and with increasing exit pressure. Using the two-dimensional simulations as analogues to volcanic eruptions, we propose that pyroclastic ejecta within the inner core of an erupting jet column can become asymmetrically focused before collapsing at fountain heights of a few hundred meters above the crater exit. The ensuing pyroclastic flows associated with fountain collapse thus become directional in character with flow orientation controlled by crater geometry and eruption exit pressure. The model applies to volcanoes with vertical conduits and crater to vent geometries that act as effective sonic to supersonic jet nozzles. We propose that the 1984 eruption of Mayon volcano fits this model. In the second phase of this eruption a prominent crater notch imparted a southeastward tilt to the basal gas thrust region of the eruption column. In turn, this led to the discharge of pyroclastic flows onto the southeast flank of the volcano. Copyright 1999 by the American Geophysical Union

Bedrock gas reservoirs in Dongping area of Qaidam Basin, NW China

The geological characteristics of bedrock gas reservoirs and the reason for the enrichment and high production of gas in the Dongping area of the Qaidam Basin are studied based on logging data, image log data, core observation, thin section analysis, reservoir microscopic study and cap rock condition evaluation. The main lithology of the bedrock reservoirs in the Dongping area is granite and granite gneiss. The reservoir space mainly consists of fractures, dissolution pores and micro-pores, among which massive matrix micro-pores and dissolution pores are the key factors for the high and stable gas production in the study area. Due to the Tertiary salty environment, the fractures and pores 0 to 18 meters from the bedrock top are filled with gypsum and calcite, forming good “top-sealing” cap rock, this special reservoir-cap rock combination in wide distribution results in the high production of these gas reservoirs. There are two types of gas reservoirs: one is fracture-pore reservoirs at the top of the bedrock, mainly distributed 20−50 m below the “top sealing” cap rock, strongly controlled by tectonic background, and high and stable in gas production; the other is fractured reservoirs inside the bedrock, large in gas-bearing depth, great gas-bearing differences, abrupt change in lateral direction, and high but not stable in production. Key words: bedrock gas reservoir, reservoir space, matrix pore, saline environment, Dongping area, Qaidam Basi

Integrated geophysical studies on the distribution of Quaternary biogenic gases in the Qaidam Basin, NW China

Quaternary biogenic gas fields in the Sanhu area of the Qaidam Basin are characterized by gentle structures, shallow burial, weak compaction, high porosity and great bulk thickness, which determine their unique geophysical anomalies, such as the locally low gravity, micro-magnetic high frequency anomaly, seismic event push-down and attribute anomaly. An integrated geophysical processing and interpretation scheme is put forward for shallow biogenic gas prediction in this area. Amplitude preservation is performed for 1:100000 gravity data and the processing results are correlated with known gas distributions and aeromagnetic results, remote sensing and seismic hydrocarbon detection. This study shows that the residual gravity low anomaly has a good correlation with the gas field and, as an important feature of the biogenic gas field, the amplitude of residual gravity low anomaly is directly proportional to the measure of gas reservoir. Based on the residual gravity low anomaly and other exploration data, the distribution of gas reservoirs in the Sanhu area is characterized by vertical overlapping, lateral zoning and local enrichment. Residual gravity anomaly, in combination with regional geologic data, reveals three favorable zones, one fairly favorable zone (low gas production zone), five possibly favorable zones and four favorable targets. Key words: Qaidam Basin, Sanhu area, Quaternary, biogenic gas, gravity, magnetic, seismic, geophysical integration, exploration directio