bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of oviductal fluid and heparin on fertility and characteristics of porcine spermatozoa
Authors: Kim Nam-Hyung , Day Billy N. , Lim Joon-Gyo , Lee Hoon Taek , Chung Kil Saeng
Published: September 2008

The objective of this study was to determine the effects of oviductal fluid and heparin on sperm penetration and the characteristics of spermatozoa. The addition of oviductal fluid and heparin to the fertilisation medium decreased sperm penetration and the mean number of spermatozoa in penetrated eggs. The number of spermatozoa firmly bound to zona pellucida was also decreased in the presence of oviductal fluid and heparin. Chlortetracycline (CTC) fluorescence patterns were used to determine the incidence of capacitation and the acrosome reaction. The proportion of capacitated and acrosome-free spermatozoa increased when spermatozoa were exposed for 1.5 and 3 h to oviductal fluid and heparin. In contrast heparin alone did not increase the number of capacitated spermatozoa at these time points. These results suggest that factor(s) in oviductal secretions reduce polyspermic fertilisation and the number of spermatozoa that will penetrate porcine oocytes. The reduction of polyspermic penetration by oviductal secretions may be due to a reduced number of spermatozoa in the fertilisation medium with an intact acrosome.
Intermediate filament proteins immunologically related to cytokeratins in the oocyte of the fishCyprinus carpio
Authors: Mencarelli Caterina , Cotelli Franco
Published: September 2008

We have used monoclonal antibodies specific for different sets of human cytokeratins and the anti-IFA (Intermediate Filament Antigen) antibody to investigate the expression of intermediate filament proteins in the mature oocyte of the teleostCyprinus carpio. Several polypeptides have been identified, showing molecular weights ranging from 43 to 65kDa. Two-dimensional analysis of the immunoreactive species revealed the presence of at least six major protein spots and a series of minor components, grouped in quite a narrow pI range from 5.52 to 6.28. The general complexity of the carp oocyte cytokeratin-related cytoskeleton appears to be higher than those described for oocytes of other vertebrate species.
The behaviour of mitotic nuclei after transplantation to early meiotic ooplasts or mitotic cytoplasts
Authors: Kubelka Michal , Moor Robert M.
Published: September 2008

This study evaluates the ability of the cytoplasm to determine the nature of the division cycle (meiotic or mitotic) in nuclei obtained from mitotically dividing cells. Using mouse oocytes in different stages of development two types of cytoplasm were prepared: firstly, early meiotic ooplasts were obtained by enucleation of non-matured, prophase-stage oocytes; secondly, mitotic cytoplasts were prepared by enucleation and activation of metaphase II (Mll)-stage oocytes. These two types of cytoplasts were then used in fusion experiments, in which mouse primitive type A spermatogonia (prospermatogonia) or mouse fibroblasts were used as a source of donor nuclei. While the fusion of prospermatogonia with mitotic cytoplasts resulted, as expected, in normal premature chromosome condensation (PCC) and subsequent pronuclear formation (58.1%), the majority of hybrids obtained by fusion of prospermatogonia with early meiotic ooplasts (40.3%) displayed unique morphology consisting of two sets of chromosomes organised in two spindle centres connected by microtubules. Each set of chromosomes contained the haploid (1n) number of chromosomes as revealed by chromosome analyses. The same morphology was observed also in 44.2% of hybrids in which the differentiated nuclei of fibroblasts were used as a source of donor mitotic nuclei. In both cases the hybrids were blocked at this stage with high activity of maturation promoting factor (MPF), resistant to any kind of activation and not able to undergo further development. These results suggest that the early meiotic ooplasm was able to induce the initiation of a meiosis-like reducing division in mitotic nuclei originating both from the germline cells and from more differentiated somatic cells.
The response of mouse oocytes injected with sea urchin spermatozoa
Authors: Wakayama T. , Uehara T. , Hayashi Y. , Yanagimachi R.
Published: September 2008

Sea urchin spermatozoa were injected into mature mouse oocytes to determine whether they can activate mouse oocytes and, if so, how they behave within the oocyte cytoplasm of such a distant species. While injection of a single spermatozoon into each oocyte did not activate any of the oocytes, injection of 10 spermatozoa activated about 20%. Within the cytoplasm of unactivated oocytes, sperm heads commonly transformed into chromosome-like structures. When a single spermatozoon was injected, and oocytes were then activated by Sr2+, about 30% of the activated oocytes had both female (mouse) and male (sea urchin) pronuclei when examined 8 h after sperm injection. These results indicated that sperm-borne oocyte activating factor(s) and the cytoplasmic factors controlling the development of the sperm pronucleus are not strictly species-specific.
Sperm head decondensation, pronuclear formation, cleavage and embryonic development following intracytoplasmic injection of mitochondria-damaged sperm in mammals
Authors: Ahmadi Ali , Ng Soon-Chye
Published: September 2008

The objective of this study was to investigate the influence of sperm mitochondrial destruction on sperm head decondensation, male pronuclear formation, cleavage and embryonic development. In the study two models were used:heterologous (hamster ICSI assay: human sperm injected into a hamster oocyte) for evaluation of sperm head decondensation and pronuclear formation, and homologous (mouse model) for the study of fertilisation and development. Destruction of mitochondria of the sperm was achieved by exposure to cyanide, a respiratory poison. Rhodamine 123 was used to evaluate the functional integrity of mitochondria. Sperm head decondensation was found to be not statistically significantly affected by mitochondrial damage (p= 0.8), with 62.8% and 67.9% condensa tion in the experimental and control groups respectively. Male pronucleus formation was seen in 40.2% and 44.4% of the injected oocytes in the experimental and control groups respectively. In the mouse experiments 45.5% and 49.7% of the injected oocytes were fertilised in the mitochondria-damaged and live-intact sperm groups respectively(p = 0.53)Development to blastocyst was achieved in 53.5% and 59.4% of the experimental and control groups respectively; the difference was not significant (p= 0.71). Inner cell mass (ICM) cell number were 15.7 ± 4.02 and 43.1 ± 11.3 respectively in the mitochondria damaged group; the equivalent numbers were 14.12±4.12 and 39.3 ± 12.6 in the control group. However, the differences in ICM and total cell counts between these two groups were not significant. Of the blastocysts transferred to pseudopregnant mice, 51.3% (20/36) implanted and 33.4% (12/36) developed to live fetuses in the mitochondria-damaged group. These rates were 60.5% (23/38) and 39.5% (15/38) in the control group. In conclusion, this study shows that functional integrity of thesperm mitochondria is not necessary in the process of fertilisation and development when the sperm is deposited into the ooplasm. Fertilisation and development can be achieved by injection of sperm at the very early stage of necrosis in which only the mitochondria have been destroyed and the rest of the cell including the plasma membrane is still intact.
Oocyte maturation in rabbits: effects of calmodulin inhibitors
Authors: Henry Michael A. , Rawlins Richard G. , Radwanska Ewa , Fahy Mary M.
Published: September 2008

Oocyte maturation in mammals follows a highly conserved pattern of release from arrest through to the extrusion of the first polar body and formation of the second metaphase spindle. Oscillations in cytoplasmic calcium concentration precede the events of maturation in many species. These calcium ions interact with and activate calcium-binding proteins, including calmodulin, within the cell. Thus, it was of interest to us to examine whether calcium acted through calmodulin in the initial stages of maturation in rabbit oocytes or whether calmodulin was required for continuation through metaphase I on to metaphase II. Using the calmodulin inhibitor W-7 we found a significant (p< 0.05) decrease in the percentage of oocytes that underwent germinal vesicle breakdown. Calmidazolium did not prevent germinal vesicle breakdown; however, it caused a significant (p< 0.05) decrease in the proportion of oocytes with fully elaborated spindles and taxol-induced cytoplasmic asters. Both inhibitors caused a significant (p< 0.05) reduction in the proportion of oocytes that extruded their first polar bodies. The kinase inhibitor 6-DMAP caused a significant reduction in the proportion of oocytes with spindles and condensed chromatin, indicating the necessity for phosphorylation events in the resumption of meiosis. In rabbit oocytes calmodulin may play a role in the release from prophase arrest, and it is necessary for spindle preservation and continuation through metaphase I to metaphase II. The varying effects of the two inhibitor stems from their different binding sites on the calmodulin molecule thus causing a differential effect on its downstream effectors.
Caprine blastocyst formation following intracytoplasmic sperm injection and defined culture
Authors: Keskintepe L. , Morton P.C. , Smith S.E. , Tucker M.J. , Simplicio A.A. , Brackett B.G.
Published: September 2008

Experiments were undertaken to develop intracytoplasmic sperm injection (ICSI) to produce caprine embryos out of the normal breeding season. Oocytes were obtained from 2–6 mm ovarian follicles at slaughter. Selected oocytes with two to four layers of cumulus cells were incubated in 1 ml of H-TCM 199 supplemented with 10 μg each of oFSH and bLH (NHPP, NIDDK, NICHD, USDA) and 20% fetal bovine serum (FBS) in a thermos (38.5°C) for 4.5 h during transportation. Then, oocytes were transferred into 75 μl of freshly prepared maturation medium under paraffin oil and a mixture of 5% O2, 5% CO2 and 90% N2. Approximately 26 h after recovery oocytes were denuded by incubation with hyaluronidase (100 IU/ml) and pipetting and held at 38.5°C for 90 min. Spermatozoa frozen in egg yolk extender were thawed in a 37°C water bath for 15s. Motile fractions were selected by swim-up, then incubated for 90 mm in TALP with 10 μg heparin/ml. Each oocyte was positioned with its first polar body at 6 or 12 o'clock by a holding pipette. Sperm (1 μl) were added to 10 μl medium containing 10% polyvinylpyrrolidone. A sperm cell was aspirated into a pipette, and then injected head-first into the cytoplasm of an oocyte maintained in H-TCM 199 + 20% FBS at 37°C. Injected oocytes were transferred to HM and, after 90 min, cultured in 50 μl of BSA-free synthetic oviduct fluid plus polyvinyl alcohol, citrate and non-essential amino acids. Results demonstrate that caprine blastocysts can be produced outside the breeding season by the use of frozen-thawed semen and injection of sperm cells with broken tails into ova followed by culture in defined medium.
Effect of inhibitors of DNA replication on early zebrafish embryos: evidence for coordinate activation of multiple intrinsic cell-cycle checkpoints at the mid-blastula transition
Authors: Ikegami Richard , Rivera-Bennetts Alma K. , Brooker Deborah L. , Yager Thomas D.
Published: September 2008

We address the developmental activation, in the zebrafish embryo, of intrinsic cell-cycle checkpoints which monitor the DNA replication process and progression through the cell cycle. Eukaryotic DNA replication is probably carried out by a multiprotein complex containing numerous enzymes and accessory factors that act in concert to effect processive DNA synthesis (Applegren, N.et al.(1995)J. Cell. Biochem.59, 91–107). We have exposed early zebrafish embryos to three chemical agents which are predicted to specifically inhibit the DNA polymerase α, topoisomerase I and topoisomerase II components of the DNA replication complex. We present four findings: (1) Before mid-blastula transition (MBT) an inhibition of DNA synthesis does not block cells from attempting to proceed through mitosis, implying the lack of functional checkpoints. (2) After MBT, the embryo displays two distinct modes of intrinsic checkpoint operation. One mode is a rapid and complete stop of cell division, and the other is an ‘adaptive’ response in which the cell cycle continues to operate, perhaps in a ‘repair’ mode, to generate daughter nuclei with few visible defects. (3) The embryo does not display a maximal capability for the ‘adaptive’ response until several hours after MBT, which is consistent with a slow rranscriptional control mechanism for checkpoint activation. (4) The slow activation of checkpoints at MBT provides a window of time during which inhibitors of DNA synthesis will induce cytogenetic lesions without killing the embryo. This could be useful in the design of a deletion-mutagenesis strategy.
Fate of microinjected sperm components in the mouse oocyte and embryo
Authors: Cummins James M. , Wakayama Teruhiko , Yanagimachi Ryuzo
Published: September 2008

Intact mouse sperm or mouse sperm tails alone, labelled with MitoTracker Green FM® fluorochrome, were injected into mouse oocytes and the cells cultured in vitro for up to 5 days. The dye stained midpiece mitochondria, the sperm tail coarse fibres and the sperm perforatorium. Intact sperm (or tails injected with separated heads) induced normal embryonic development. The mitochondria could be identified in embryos up to the 4-cell stage, remaining associated with the sperm tail. They largely disappeared by the 8-cell stage, when only a minority of embryos (6/43) could be found with small patches of mitochondria. Axonemal elements could be identified coiled up in single external blastomeres as late as day 5 blastocysts. By contrast, mitochondria as well as tail components could be identified up to 5 days after injection of sperm tails alone into non-activated oocytes and also in embryos that arrested development before the 8-cell stage. We conclude that disappearance of the labelled sperm mitochondria in normally cleaving embryos is not due to fading or inactivation of the fluorochrome marker, but is rather an event specifically tied to cell cycle activities around the second cell division.
Expression of Fas–Fas ligand system associated with atresia in murine ovary
Authors: Ping Xu Ji , Li Xiang , Mori Etsuko , Sato Eimei , Saito Shigeru , Guo Mao Wu , Mori Tsuneatsu
Published: September 2008

We detected that Fas receptor (Fas) was expressed at transcriptional levels in oocytes/eggs and some granulosa cells of murine ovary, whereas, Fas ligand (FasL) was found to be strongly expressed in granulosa cells by means ofin situhybridisation. These results were supported by an indirect immunofluorescence (IIF) test with anti-Fas monoclonal antibody (mAb)/FasL Ab. The lysates from granulosa cells were precipitated by anti-FasL Ab, exhibiting a specific band at 40 kDa. When zona pellucida (ZP)-free eggs were incubated with granulosa cellsin vitro, apoptosis (DNA fragmentation) was induced in the eggs, as detected by the terminal deoxynucleotide transferase mediated dUTP-nick end labelling (TUNEL) method. To examine whether FasL-bearing cells can induce apoptosis in eggs expressing Fas through molecular interaction between FasL and Fas, we employed a baculovirus expression system to generate FasL on the surface ofSpodoptera frugiperda(Sf9) cells. The co-incubation of eggs withAutographa californicanuclear polyhedrosis virus (AcNPV) and FasL transfected Sf9 (Sf9–FasL) cellsin vitrowas performed and resulted in the induction of apoptosis in eggs as detected by the TUNEL method. Apoptosis was absent in eggs co-incubated with AcNPV-1393 transfected Sf9 (Sf9−1393) cells. Thus, ovarian atresia was suggested to be induced by molecular interaction between FasL on granulosa cells and Fas on oocytes/eggs during oogenesis.
Activation of the metaphase checkpoint and an apoptosis programme in the early zebrafish embryo, by treatment with the spindle-destabilising agent nocodazole
Authors: Ikegami Richard , Zhang Jianshe , Rivera-Bennetts Alma K. , Yager Thomas D.
Published: September 2008

We have studied the developmental activation of the metaphase checkpoint, and the consequences of activating this checkpoint, in the zebrafish embryo. (1) Treatment with nocodazole (a microtubule destabiliser) before mid-blastula transition (MBT) produces complete destruction of all nuclei in the deep cell layer of the embryo. In contrast, nocodazole treatment after MBT efficiently produces metaphase arrest in this cell layer. Thus, the metaphase checkpoint becomes activated at MBT. (2) Although a metaphase arrest is induced by nocodazole, it is not induced by paclitaxel (a microtubule stabiliser). Thus the metaphase checkpoint appears to sense a destabilisation, but not a stabilisation, of spindle microtubules. (3) Metaphase-arrested cells (in nocodazole) can be driven into the next interphase by adding the Ca2+-specific ionophore A23187. Thus, a Ca2+-signalling pathway lies downstream of, or parallel to, the metaphase checkpoint. (4) After mid-gastrula stage, treatment with nocodazole produces DNA fragmentation in all three cell layers. In the enveloping epithelial monolayer (EVL), this is associated with a classical apoptotic phenotype. In the deep layer, it is associated with an unusual, highly condensed nuclear state that is entered directly from metaphase arrest. Thus, after the mid-gastrula stage, the embryo responds to nocodazle by undergoing apoptosis. (5) Nocodazole-induced apoptosis in the deep cell layer can be blocked by the caspase-1,4,5 inhibitors Ac-YVAD-CHO and Ac-YVAD-CMK. This suggests that a homologue of theC. elegans ced-9—ced-4—ced-3pathway is involved in control over apoptosis in the early zebrafish embryo.
Distribution of cortical granules in bovine oocytes classified by cumulus complex
Authors: Hosoe M. , shioya Y.
Published: September 2008

The present study was conducted to examine distributional changes of cortical granules(CGs)during meitotic maturation and fetilisation in vitro and the developmental ability in bovine oocytes classified by cumulus cells. The oocytes were classified by the morphology if their cumulus cell layers as follows: class A, compact and thick; class B, compact but thin; class C, naked; and class D, expanded. some of the oocytes were stained with Lens curinalis agglutinin(LCA) before and after maturation in vitro and after insemination, and then stained with orcein to observe their nuclear stages. The others were left in culture. Distributional patterns of the CGs were classified into four types: type I, CGs distributed in clusters; type II, CGs dispersed and partly clustered; type III, all CGs dispersed; and type IV, no CGs Most of the oocytes before culture showed a type I pattern, but this decreased after maturation culture, whereas type III increased in class A. The oocytes of class B showed similar changes while the oocytes of class C did not. In class C, many oocytes showed type I after culture indicating that cytoplasmic maturation was not completed. IN class D, 80.4% of the oocytes exhibited types III before maturation culture, indicating that their cytoplasmic maturation was different from classes A–C. and about 70% of the class D oocytes were at the unclear stage of germinal vesicle breakdown(GVBD) before culture. The developmental rates to blastocysts in classes A–D were 28.7%, 23.1%, 0.5% and 3.4% respectively.
Orographic cirrus in the global climate model ECHAM5
Authors: Joos H. , Spichtinger P. , Lohmann U. , Gayet J.‐F. , Minikin A.
Published: September 2008

A comparison of satellite data with simulations from global circulation models shows that there is a lack of cirrus cloud amount in large‐scale models above and in the lee of mountains. The formation of orographic cirrus clouds due to gravity waves is usually not parameterized in large‐scale models. To improve the simulation of such orographically excited cirrus clouds a coupling of the gravity wave dynamics and the cloud microphysics has been implemented in the climate model European Centre/Hamburg 5 (ECHAM5). As homogeneous freezing of solution droplets strongly depends on the vertical velocity, an increased vertical velocity due to gravity wave activity in the upper troposphere leads to the formation of cirrus clouds with higher ice crystal number densities. A comparison of the new parameterization with measurements shows a better agreement with observations.
Equivalent vadose zone steady state flow: An assessment of its capability to predict transport in a realistic combined vadose zone–groundwater flow system
Authors: Russo David , Fiori Aldo
Published: September 2008

The applicability of an equivalent steady state vadose zone flow model to a realistic transient three‐dimensional, heterogeneous, combined vadose zone–groundwater flow system was tested here. Two cases pertinent to semiarid regions and the presence (or absence) of an irrigated crop were analyzed and are presented in detail using the hydraulic properties from the Bet Dagan trench. In addition, the case of a more humid region characterized by additional summer precipitation and soils of different textures was analyzed and is discussed briefly. Results of the analyses suggested that when the water table is located at sufficiently large distance from the soil surface, the vadose zone can be divided conceptually into two distinct zones: a highly transient, near‐surface zone and a deeper, quasi steady state zone. Under these conditions, an equivalent steady state influx, obtained by averaging the cumulative flux of the net applied water over the relevant time period, may provide a relatively good approximation of the cumulative water flux that crossed the water table. As for solute transport, in all cases examined, the trajectories of the centroid of the solute plume and the mean and the standard deviation of the solute breakthrough curves at a given horizontal control plane, CP (expressed as functions of the cumulative flux crossing the pertinent horizontal CP), associated with the transient flows were in relatively good agreement with their counterparts associated with the equivalent steady state flows, particularly under noncropped conditions and when the soil texture is coarser. The main finding of this study is that for the case in which the water table is located at sufficiently large distance from the soil surface, equivalent steady state vadose zone flow may reconstruct the “true” solute BTC (or the solute travel time PDF) at a horizontal CP located in the vicinity of the water table depth. The latter finding applies to heterogeneous soils of different textures and to different atmospheric forcing conditions at the soil surface and in the presence (or absence) of vegetation and despite the fact that features of the transport unique to vadose zone transient flow (induced by the temporal fluctuations in the water table depth) cannot be reproduced by the equivalent steady state vadose zone flow.
Rapid drawdown in slopes and embankments
Authors: Pinyol Núria M. , Alonso Eduardo E. , Olivella Sebastià
Published: September 2008

The rapid drawdown condition arises when submerged slopes experience a rapid reduction of the external water level. Classical procedures developed to determine the flow regime within the slope and the resulting stability conditions are reviewed in the paper. They are grouped in two classes: the “stress‐based” undrained approach, recommended for impervious materials, and the flow approach, which is specified for rigid pervious materials (typically a granular soil). Field conditions often depart significantly from these simplified cases and involve materials of different permeability and compressibility arranged in a complex geometry. The drawdown problem is presented in the paper as a fully coupled flow‐deformation problem for saturated/unsaturated conditions. Some fundamental concepts are first discussed in a qualitative manner and, later, explored in more detail in synthetic examples, solved under different hypotheses, including the classical approaches. Some design rules, which include a few fundamental parameters for the drawdown problem, have also been solved in a rigorous manner to illustrate the limitations of simplified procedures. A significant portion of the paper is devoted to the discussion of a comprehensive case history. In Shira, earth dam pore pressures were recorded at different points inside the embankment during a controlled drawdown. Predictions of four calculation procedures (instantaneous drawdown, pure flow, coupled flow‐elastic, and coupled flow‐elastoplastic, all of them for saturated/unsaturated conditions) are compared with measured pressure records. Only the coupled analysis provides a consistent and reasonable solution. The role of the different soil properties in explaining the phenomena taking place during drawdown is finally discussed.
High‐resolution surveys along the hot spot–affected Galápagos Spreading Center: 1. Distribution of hydrothermal activity
Authors: Baker Edward T. , Haymon Rachel M. , Resing Joseph A. , White Scott M. , Walker Sharon L. , Macdonald Ken C. , Nakamura Ko‐ichi
Published: September 2008

The spatial density of hydrothermal activity along most mid‐ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005–2006 we tested the effect of thickened crust on hydrothermal activity using high‐resolution mapping of plumes overlying the hot spot–affected Galápagos Spreading Center from 95° to 89°42′W (∼560 km of ridge crest). Plume mapping discovered only two active, high‐temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence (ph), the fraction of ridge crest overlain by significant plumes, was 0.11 ± 0.014, about half that expected for a non–hot spot mid‐ocean ridge with a similar magmatic budget. Plume distributions on the Galápagos Spreading Center were uncorrelated with abrupt variations in the depth of the along‐axis melt lens, so these variations are apparently not controlled by hydrothermal cooling differences. We also found no statistical difference (for a significance level of 0.05) in plume incidence between where the seismically imaged melt lens is shallow (2 ± 0.56 km, ph = 0.108 ± 0.045) and where it is deep (3.4 ± 0.7 km, ph = 0.121 ± 0.015). The Galápagos Spreading Center thus joins mid‐ocean ridges near the Iceland (Reykjanes Ridge), St. Paul‐Amsterdam (South East Indian Ridge), and Ascension (Mid‐Atlantic Ridge) hot spots as locations of anomalously scarce high‐temperature venting. This scarcity implies that convective cooling along hot spot–affected ridge sections occurs primarily by undetected diffuse flow or is permanently or episodically reduced compared to normal mid‐ocean ridges.
High‐resolution surveys along the hot spot–affected Galápagos Spreading Center: 2. Influence of magma supply on volcanic morphology
Authors: White Scott M. , Meyer Jason D. , Haymon Rachel M. , Macdonald Ken C. , Baker Edward T. , Resing Joseph A.
Published: September 2008

The Galápagos Spreading Center (GSC) at 89°–95°W exhibits large gradients in magma supply at a relatively constant intermediate spreading rate, making this area an ideal natural laboratory to study the effects of magma supply on volcanism at seafloor spreading ridges. Prior work shows that the GSC develops from axial valley to shallow axial rise and a shallow magma sill, much like a typical fast spreading ridge, as the contribution of the hot spot increases. The volcanic morphology varies with magma supply in a predictable manner that we divide into three terrains based on the characteristic style of volcanic emplacement and edifice construction within each terrain. The volcanic cone terrain comprises most of the GSC and is characterized by prominent volcanic cones within a >1 km wide and >100 m deep axial graben. Approaching the area of maximum mantle plume influence at 91°W, the GSC axis lies along an elevated axial rise split by a <1 km wide and <100 m deep axial graben, and the style of volcanism shifts to axial volcanic ridge terrain characterized by axis‐elongate, low‐relief ridges of pillow lava. The lava channel terrain comprises only one segment on either side of the maximum magma supply at 91°W, where sheet lava flows and lava channels are relatively widespread. A general lengthening of seafloor fissures with increasing magma supply suggests a greater tendency toward linear source eruptions, in agreement with the volcanic observations. These results suggest that magma supply rather than magma chamber depth or rate of tectonic extension is the primary influence on lava morphology, hence eruptive processes, at seafloor spreading ridges in general. In both the axial volcanic ridge and lava channel terrains, a single prominent volcanic cone exists within each volcanic segment, suggesting a segment‐centered magma focusing.
Subsurface imaging of vegetation, climate, and root‐zone moisture interactions
Authors: Jayawickreme Dushmantha H. , Van Dam Remke L. , Hyndman David W.
Published: September 2008

Changes in global climate and land use affect important processes from evapotranspiration and groundwater recharge to carbon storage and biochemical cycling. Near surface soil moisture is pivotal to understand the consequences of these changes. However, the dynamic interactions between vegetation and soil moisture remain largely unresolved because it is difficult to monitor and quantify subsurface hydrologic fluxes at relevant scales. Here we use electrical resistivity to monitor the influence of climate and vegetation on root‐zone moisture, bridging the gap between remotely‐sensed and in‐situ point measurements. Our research quantifies large seasonal differences in root‐zone moisture dynamics for a forest–grassland ecotone. We found large differences in effective rooting depth and moisture distributions for the two vegetation types. Our results highlight the likely impacts of land transformations on groundwater recharge, streamflow, and land‐atmosphere exchanges.
Horizontal subduction and truncation of the Cocos Plate beneath central Mexico
Authors: Pérez‐Campos Xyoli , Kim YoungHee , Husker Allen , Davis Paul M. , Clayton Robert W. , Iglesias Arturo , Pacheco Javier F. , Singh Shri K. , Manea Vlad Constantin , Gurnis Michael
Published: September 2008

Based on analysis of data from a trans‐Mexico temporary broadband seismic network centered on Mexico City, we report that the subducting Cocos Plate beneath central Mexico is horizontal, and tectonically underplates the base of the crust for a distance of 250 km from the trench. It is decoupled from the crust by a very thin low viscosity zone. The plate plunges into the mantle near Mexico City but is truncated at a depth of 500 km, probably due to an E‐W propagating tear in the Cocos slab. Unlike the shallow slab subduction in Peru and Chile, there is active volcanism along the Trans Mexican Volcanic Belt (TMVB) that lies much further inland than regions to either side where subduction dip is not horizontal. Geodynamical modeling indicates that a thin weak layer such as imaged by the seismic experiment can explain the flat subduction geometry.
Illumination of the plasmasphere by terrestrial very low frequency transmitters: Model validation
Authors: Starks M. J. , Quinn R. A. , Ginet G. P. , Albert J. M. , Sales G. S. , Reinisch B. W. , Song P.
Published: September 2008

A composite model of wave propagation from terrestrial very low frequency (VLF) transmitters has been constructed to estimate the wave normal angles and fields of whistler mode waves in the plasmasphere. The model combines a simulation of the fields in the Earth‐ionosphere waveguide, ionospheric absorption estimates, and geomagnetic field and plasma density models with fully three‐dimensional ray tracing that includes refraction, focusing, and resonant damping. The outputs of this model are consistent with those of several previous, simpler simulations, some of which have underlying component models in common. A comparison of the model outputs to wavefield data from five satellites shows that away from the magnetic equator, all of the models systematically overestimate the median field strength in the plasmasphere owing to terrestrial VLF transmitters by about 20 dB at night and at least 10 dB during the day. In addition, wavefield estimates at L < 1.5 in the equatorial region appear to be about 15 dB too low, although measured fields there are extremely variable. Consideration of the models' similarities and differences indicates that this discrepancy originates in or below the ionosphere, where important physics (as yet not conclusively identified) is not being modeled. Adjustment of the low‐altitude field estimates downward by constant factors brings the model outputs into closer agreement with satellite observations. It is concluded that past and future use of these widely employed trans‐ionospheric VLF propagation models should be reevaluated.
Global distribution and seasonal concentration change of methyl iodide in the atmosphere
Authors: Yokouchi Yoko , Osada Kazuo , Wada Makoto , Hasebe Fumio , Agama Mario , Murakami Ryuichi , Mukai Hitoshi , Nojiri Yukihiro , Inuzuka Yoko , Toom‐Sauntry Desiree , Fraser Paul
Published: September 2008

We investigated seasonal variations in atmospheric CH3I at high, middle, and low latitudes in both hemispheres: at Alert (82.5°N, 62.5°W), over the northern and western Pacific Ocean (shipboard measurements); Cape Ochiishi (43.2°N, 145.5°E); Tsukuba (36.0°N, 140.1°E); Happo Ridge (36.7°N, 137.8°E); Hateruma Island (24.1°N, 123.8°E); San Cristobal Island (1.0°S, 89.4°W); Cape Grim (40.4°S, 144.6°E); and Syowa Station in Antarctica (68.5°S, 41.3°E) throughout 2004 and over an extended period of years at some sites. The highest median CH3I concentration was observed at San Cristobal Island, on the equator in the eastern Pacific, although no concentration elevation was found on or near the equator over the western Pacific. The lowest concentration was found in the Arctic and Antarctica, where they showed very similar seasonal variations that were clearly inversely correlated with variations in incident solar radiation. In the marine boundary air at midlatitude, the CH3I concentration was well correlated with surface seawater temperature (SST). Global atmospheric CH3I in wintertime was rather uniformly distributed (around 0.5 ppt) at middle and high latitudes.
Spatial distribution of Bacteria and Archaea and amoA gene copy numbers throughout the water column of the Eastern Mediterranean Sea
Authors: De Corte Daniele , Yokokawa Taichi , Varela Marta M , Agogué Hélène , Herndl Gerhard J
Published: September 2008

Until recently, ammonia oxidation, a key process in the global nitrogen cycle, was thought to be mediated exclusively by a few bacterial groups. It has been shown now, that also Crenarchaeota are capable to perform this initial nitrification step. The abundance of ammonia oxidizing Bacteria and Archaea was determined using the bacterial and archaeal ammonia monooxygenase-α subunit (amoA) gene as functional markers in a quantitative PCR approach and related to the abundance of Bacteria and Archaea in the Eastern Mediterranean Sea. Archaeal amoA copy numbers decreased from 4000–5000 copies ml−1 seawater from the 200–500 m depth layer to 20 copies ml−1 at 1000 m depth. β-Proteobacterial amoA genes were below the detection limit in all the samples. The archaeal amoA copy numbers were correlated with NO2− concentrations, suggesting that ammonia-oxidizing Archaea may play a significant role in the nitrification in the mesopelagic waters of the Eastern Mediterranean Sea. In the bathypelagic waters, however, archaeal amoA gene abundance was rather low although Crenarchaeota were abundant, indicating that Crenarchaeota might largely lack the amoA gene in these deep waters. Terminal restriction fragment length polymorphism analysis of the archaeal community revealed a distinct clustering with the mesopelagic community distinctly different from the archaeal communities of both, the surface waters and the 3000–4000 m layers. Hence, the archaeal community in the Eastern Mediterranean Sea appears to be highly stratified despite the absence of major temperature and density gradients between the meso- and bathypelagic waters of the Mediterranean Sea.
Telomere Length Is Associated With Obesity Parameters but With a Gender Difference
Authors: Nordfjäll Katarina , Eliasson Mats , Stegmayr Birgitta , Melander Olle , Nilsson Peter , Roos Göran
Published: September 2008

Cardiovascular disease (CVD) and obesity have been coupled to short telomere length in peripheral blood. The biological background to this observation is not obvious from the literature. In this study we have analyzed a large set of known risk factors for CVD in relation to telomere length in blood cells on a merged cohort of 989 individuals recruited in the Malmö Diet and Cancer Cohort (MDCC) and the Northern Sweden MONICA project. We found a significant or borderline association between obesity parameters and telomere length in women after age and center adjustments (BMI: r = −0.106, P = 0.021, weight: r = −0.087, P = 0.060, waist circumference: r = −0.099, P = 0.032, hip circumference: r = −0.128, P = 0.005). In men, a positive borderline correlation to high‐density lipoprotein (HDL) (r = 0.111, P = 0.053) and a negative correlation to 2‐h post‐oral glucose‐tolerance test (OGTT) was observed (r = −0.202, P = 0.045). In neither group any association was found between telomere length and cholesterol, serum triglycerides, serum low‐density lipoprotein, plasma insulin, blood pressure, pulse pressure, or smoking habits. Our data indicate that telomere length is associated with an “obesity‐phenotype” but only in women.
Circulating Leptin and Stress‐induced Cardiovascular Activity in Humans
Authors: Brydon Lena , O'Donnell Katie , Wright Caroline E. , Wawrzyniak Andrew J. , Wardle Jane , Steptoe Andrew
Published: September 2008

Obesity is associated with an elevated risk of hypertension and cardiovascular disease. The adipocyte hormone leptin, which stimulates energy expenditure in animals by activating the sympathetic nervous system (SNS), is believed to play a role in this association. However, evidence in humans remains sparse. We investigated the relationship between circulating leptin and cardiovascular and inflammatory responses to acute psychological stress in humans. Participants were 32 men and 62 women aged 18–25 years. Cardiovascular activity was assessed using impedance cardiography at baseline, during acute laboratory stress, and during a 45‐min recovery period. Plasma cytokines were measured in blood drawn at baseline and 45‐min poststress. In women only, baseline plasma leptin was significantly associated with stress‐induced changes in heart rate (β = 0.53, P = 0.006), heart rate variability (HRV) (β = −0.44, P = 0.015), and cardiac preejection period (PEP) (β = −0.51, P = 0.004), independent of age, adiposity, and smoking. Women's plasma leptin levels also correlated with stress‐induced elevations in the proinflammatory cytokine interleukin‐6 (IL‐6) (β = 0.35, P = 0.042). Circulating leptin is an independent predictor of sympathetic cardiovascular activity, parasympathetic withdrawal, and inflammatory responses to stress in women. Because cardiovascular and inflammatory stress responses are predictive of future cardiovascular disease, leptin may be a mechanism mediating the adverse effects of stress and obesity on women's cardiovascular health.
Long‐term Effects of Large‐volume Liposuction on Metabolic Risk Factors for Coronary Heart Disease
Authors: Mohammed B. Selma , Cohen Samuel , Reeds Dominic , Young V. Leroy , Klein Samuel
Published: September 2008

Abdominal obesity is associated with metabolic risk factors for coronary heart disease (CHD). Although we previously found that using liposuction surgery to remove abdominal subcutaneous adipose tissue (SAT) did not result in metabolic benefits, it is possible that postoperative inflammation masked the beneficial effects. Therefore, this study provides a long‐term evaluation of a cohort of subjects from our original study. Body composition and metabolic risk factors for CHD, including oral glucose tolerance, insulin resistance, plasma lipid profile, and blood pressure were evaluated in seven obese (39 ± 2 kg/m2) women before and at 10, 27, and 84–208 weeks after large‐volume liposuction. Liposuction surgery removed 9.4 ± 1.8 kg of body fat (16 ± 2% of total fat mass; 6.1 ± 1.4 kg decrease in body weight), primarily from abdominal SAT; body composition and weight remained the same from 10 through 84–208 weeks. Metabolic endpoints (oral glucose tolerance, homeostasis model assessment of insulin resistance, blood pressure and plasma triglyceride (TG), high‐density lipoprotein (HDL)‐cholesterol, and low‐density lipoprotein (LDL)‐cholesterol concentrations) obtained at 10 through 208 weeks were not different from baseline and did not change over time. These data demonstrate that removal of a large amount of abdominal SAT by using liposuction does not improve CHD metabolic risk factors associated with abdominal obesity, despite a long‐term reduction in body fat.
Conformational changes and flexibility in T-cell receptor recognition of peptide–MHC complexes
Authors: Armstrong Kathryn M. , Piepenbrink Kurt H. , Baker Brian M.
Published: September 2008

A necessary feature of the immune system, TCR (T-cell receptor) cross-reactivity has been implicated in numerous autoimmune pathologies and is an underlying cause of transplant rejection. Early studies of the interactions of αβ TCRs (T-cell receptors) with their peptide–MHC ligands suggested that conformational plasticity in the TCR CDR (complementarity determining region) loops is a dominant contributor to T-cell cross-reactivity. Since these initial studies, the database of TCRs whose structures have been solved both bound and free is now large enough to permit general conclusions to be drawn about the extent of TCR plasticity and the types and locations of motion that occur. In the present paper, we review the conformational differences between free and bound TCRs, quantifying the structural changes that occur and discussing their possible roles in specificity and cross-reactivity. We show that, rather than undergoing major structural alterations or ‘folding’ upon binding, the majority of TCR CDR loops shift by relatively small amounts. The structural changes that do occur are dominated by hinge-bending motions, with loop remodelling usually occurring near loop apexes. As predicted from previous studies, the largest changes are in the hypervariable CDR3α and CDR3β loops, although in some cases the germline-encoded CDR1α and CDR2α loops shift in magnitudes that approximate those of the CDR3 loops. Intriguingly, the smallest shifts are in the germline-encoded loops of the β-chain, consistent with recent suggestions that the TCR β domain may drive ligand recognition.
Verbal Working Memory and Story Retelling in School-Age Children With Autism
Authors: Gabig Cheryl Smith
Published: September 2008

Purpose

This study examined verbal working memory and language ability in 15 school-age children with autism using 3 verbal working memory tasks and 1 story recall task.

Method

Three measures of verbal working memory—nonword repetition, memory for digits span, and sentence imitation—were given to children with autism and age-matched controls. Verbal working memory measures were chosen to reflect increasing levels of cognitive–linguistic complexity. Story retelling was measured using
The
Renfrew Bus Story
(J. Cowley & C. Glasgow, 1994) and was scored for the percentage of propositions recalled and the average utterance length.

Results

A profile of verbal working memory deficits was seen in children with autism, with poorer performance on more complex verbal memory tasks. Performance on the 3 verbal memory tasks was independent of articulation ability. For the group with autism, receptive vocabulary was associated with sentence imitation and story recall but not with nonword repetition or digits span. Sentence imitation was related to story recall, but the relationship disappeared when the effect of vocabulary was removed.

Conclusions

Vocabulary and language processing demands affect the performance of children with autism on tasks of verbal memory and story retelling. Results are viewed within a
connectionist
framework of verbal working memory
.
The Effect of Classroom Amplification on the Signal-to-Noise Ratio in Classrooms While Class Is in Session
Authors: Larsen Jeffery B. , Blair James C.
Published: September 2008

Purpose

The purpose of this study was to measure the signal-to-noise ratios in classrooms while class was in session and students were interacting with the teacher and each other.

Method

Measurements of noise and reverberation were collected for 5 different classrooms in 3 different schools while class was in session. Activities taking place during the measurements were recorded to compare with sound level measures. The use of infrared classroom amplification was compared with no amplification.

Results/Conclusion

The results revealed that when classroom amplification was used, students heard the teacher’s voice at a level that was an average of 13 dB above the noise floor as compared to an average of +2 dB above the noise floor without amplification.
Quantitative scanning near-field microwave microscopy for thin film dielectric constant measurement
Authors: Karbassi A. , Ruf D. , Bettermann A. D. , Paulson C. A. , van der Weide Daniel W. , Tanbakuchi H. , Stancliff R.
Published: September 2008

We combine a scanning near-field microwave microscope with an atomic force microscope for use in localized thin film dielectric constant measurement, and demonstrate the capabilities of our system through simultaneous surface topography and microwave reflection measurements on a variety of thin films grown on low resistivity silicon substrates. Reflection measurements clearly discriminate the interface between ∼38nm silicon nitride and dioxide thin films at 1.788GHz. Finite element simulation was used to extract the dielectric constants showing the dielectric sensitivity to be Δεr=0.1 at εr=6.2, for the case of silicon nitride. These results illustrate the capability of our instrument for quantitative dielectric constant measurement at microwave frequencies.
Broken symmetry in laterally coupled InAs/GaAs quantum dots molecule
Authors: Baira M. , Sfaxi L. , Bouzaiene L. , Maaref H. , Chauvin N. , Bru-Chevallier C.
Published: September 2008

Laterally coupled quantum dot (QD) structures (artificial molecules) are investigated using one layer composed of InAs islands grown by molecular beam epitaxy. We have elaborated, at different InAs growth rates, a series of samples. Those elaborated at lower InAs growth rate present a weak and inhomogeneous QD density. The atomic force microscopy images show that the QDs are gathered by pair having a variable interdot separation. This is what enables us to study the lateral coupling. At 10 K, microphotoluminescence (micro-PL) measurements (realized on a design of 0.2 μm diameters) present either one, two, or four peaks. To understand the origin of these peaks, we have calculated the excitonic transitions of a system of two identical laterally coupled QDs according to the distance that separates them. The results of this model do not explain PL spectra. Then, we have considered a system of two QDs having slightly different sizes (asymmetric system). We have shown that when the interdot distance is ranging between 20 and 28 nm, the presence of four optically active excitonic transitions is in good agreement with the experience. For interdot distances lower than 18 nm, the calculation shows that the four excitonic states become a mixture of equiprobable states of two completely decoupled QDs. Two among these states are symmetric and then optically bright, while the two others are asymmetric and optically dark. In this case, the result is comparable to the one obtained with a system having identical QDs.