bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of stem cell factor in somatic–germ cell interactions during prenatal oogenesis
Authors: De Felici Massimo , Di Carlo Anna , Pesce Maurizio
Published: September 2008

During embryogenesis germ cells originate from primordial germ cells (PGCs). The development of mammalian PGCs involves a number of complex events (formation and segregation of PGC precursors, PGC migration and proliferation) which lead to the differentiation of oocytes or prospermatogonia (for a review see De Feliciet al., 1992). During recent years developments in methods for isolation, purification and culture of mouse PGCs have led to significant progress in the understanding of molecular mechanisms of migration, proliferation and differentiation of these cells (for reviews see De Felici, 1994; and De Felici & Pesce, 1994a). In this paper we describe the key role played by stem cell factor (SCF) in PGC development and early folliculogenesis.
Isolation of viable egg cells of rape (Brassica napus L.)
Authors: Katoh Norio , Lörz Horst , Kranz Erhard
Published: September 2008

The isolation of viable egg cells of rape (Brassica napus L.) has been achieved from microdissected ovules. The non-gametic cells of the embryo sac, synergids and central cells have also been isolated. Their morphology corresponded to that of these cells in situ, making a discrimination from isolated sporophytic cells possible. Two hours after isolation the egg cells were still viable. Viable egg cells have been reproducibly isolated with afrequency of 25% per dissected ovule.
Stage-specific requirement of phosphate for development of rat 1-cell embryos in a chemically defined medium
Authors: Miyoshi Kazuchika , Niwa Koji
Published: September 2008

Rat 1-cell embryos, recovered from naturally mated females, were cultured in a chemically defined medium (mR1ECM). When examined after 24, 56, 64 and 80h of culture, embryos developed to the 2-cell (100%), 4-cell (93%), 4-cell to 8-cell (97%) and ≥8-cell (95%) stages, respectively. When 0.4 M phosphate (NaH2PO4) was added to the medium after 0, 24, 56 and 64 h of culture, percentages (0–67%) of embryos that developed to the blastocyst stage after 115h of culture were lower than that (86%) in the medium without phosphate. However, addition of phosphate after 80h of culture accelerated blastocyst formation; a significantly higher percentage (94%) of blastocysts was obtained after 110 h of culture in this medium compared with when phosphate was not added (67%). When phosphate was added to the medium after 64h, almost all (97%) 8-cell embryos developed to the blastocyst stage by 100h of culture but development of 4-cell to 7-cell embryos was inhibited (22–63%). Acceleration of blastocyst formation was caused by addition of phosphate rather than by the exchange of the medium. The stimulatory effect of phosphate on embryo development was observed at concentrations of 0.1–1.2mM. The mean numbers of cells (54.5–60.9 cells) in blastocysts examined after 115 h of culture were increased by the addition of 0.4–1.6mM phosphate at 80 h as compared with blastocysts from cultures without phosphate (46.6 cells).
Calcium- and meiotic-spindle-independent activation of pig oocytes by the inhibition of staurosporine-sensitive protein kinases
Authors: Wang Weihua , Sun Qingyuan , Hosoe Misa , Shioya Yasuo
Published: September 2008

The dependence of pig oocyte activation (both nuclear activation and cortical granule exocytosis) induced by staurosporine on intracellular Ca2+rise and spindle assembly was studied. Nuclear activation was evaluated by pronuclear (PN) formation, cleavage and their developmental ability, and cortical granule (CG) exocytosis was assessed by electron microscopy and laser confocal microscopy of oocytes labelled with fluorescein isothiocyanate-peanut agglutinin. Exposure of pig oocytes of 0.3 and 3μM protein kinase inhibitor staurosporine for 30 min resulted in the nuclear activation in 71.8% and 85.7% of the oocytes, respectively. The pronuclei in activated oocytes contained several compact nucleoli. When the cleaved 2-cell oocytes were further culturedin vitro, 93.5% developed beyond the 4-cell stage, and 12.9% developed to the morula stage after 4 days of culture. Of the oocytes treated with 3μM staurosporine, 62.5% and 9.4% released their CGs partially and completely, respectively. The nuclear activation induced by staurosporine was overcome by the prior treatment of oocytes with okadaic acid, resulting in only 33.3% of the oocytes undergoing nuclear activation. However, when oocytes were exposed first to 1,2-bis(O-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (acetoxymethanal ester), a cell permeate calcium chelator, or Colcemid, a meiotic spindle disrupter, and then to staurosporine, nuclear activation was observed in 74.2% and 82.3% of the oocytes, espectively. These data were the same as those in oocytes treated only with staurosporine (85.7%). The present study indicates that pig oocytes can be activated by the inhibition of staurosporine-sensitive protein kinase(s), and that this activation is dependent upon mitogen-activated protein kinase but independent of the intracellular Ca2+rise and spindle integrity.
Microinjection of anti-α-tubulin antibody (DM1A) inhibits progesterone-induced meiotic maturation and deranges the microtubule array in follicle-enclosed oocytes of the frog,Rana pipiens
Authors: Lessman Charles A. , Wang Tao , Gard David L. , Woods Catherine W.
Published: September 2008

Microinjection of anti-α-tubulin (Dm1A) inhibited progesterone-induced meiotic maturation in large follicle-enclosed oocytes of the frog,Rana pipiens. DM1A (46nl; 10mg/ml) injection significantly increased the ED50value for progesterone as determined by germinal vesicle dissolution (GVD) bioassay. By contrast, low doses of microinjected DM1A (46nl; 2.5mg/ml), anti-actin (clone KJ43A), anti-cytokeratin (C-11), anti-intermediate filament antibody (IFA), generic IgG (46 nl; 20 mg/ml) or sodium azide (46 nl; 1 mg/ml), an antibody preservative, were without inhibitory effect in this bioassay. Microinjected, affinity-purified DM1A (46n1; 7.5mg/ml) was also inhibitory, but preabsorption with pure tubulin prior to injection significantly reduced the inhibitory effect. DM1A injection had no effect on centrifugation-induced germinal vesicle migration (GVM). Previous work indicated that drugs (e.g. demecolcine and nocodazole), which destabilise microtubules, enhance both centrifugation-induced GVM and progesterone-induced GVD inRanaoocytes. Taking these results together, it is suggested that DM1A injection may have differential effects on microtubules in this cell. Thus, while the majority of microtubules were apparentl depolymerised by DM1A (46nl; 10mg/ml) injection, a small subpopulation appeared to be stabilised as bundles. Confocal immunofluorescence microscopy of follicle-enclosed oocytes after DM1A injection revealed a major loss of microtubules throughout the cell however, apparent sparse bundles of nucrotubules arranged in an approximately 600 μm shell were associated with the injectate region 24h post-injection. By contrast, control follicle-enclosed oocytes topically labelled with DM1A post-fixation had extensive microtubule arrays similar to those previously reported inXenopusoocytes. Intracellular recording after DM1A injection and progesterone treatment yielded an intermediate membrane potential (Vm= −31.8mV) compared with control (immature) DMIA-injected cells (Vm= −44.7 mV) or potassium balanced salt solution (KBS)-injected cells matured with progesterone (Vm= −13.9mV). These results suggest that DM1A injection does not completely inhibit electrophysiological changes initiated by progesterone. Working hypotheses are proposed that suggest a role for microtubules in the action of progesterone which normally lifts the prophase I block in theRanafollicle-enclosed oocyte.
Induction of DNA replication in germinal vesicles and in nuclei formed in maturing mouse oocytes by 6-DMAP treatment
Authors: Fulka J. , First N.L. , Lee C. , Fulka J. , Moor R.M.
Published: September 2008

Immature mouse oocytes (germinal vesicle stage, GV), oocytes at different stages during maturation (prometaphase to anaphase I) and matured oocytes (metaphase II arrested) were cultured in 6-dimethylaminopurine (6-DMAP)-supplemented medium also containing bromodeoxyuridine for the assessment of DNA replication in these cells. Immature oocytes remained arrested at the GV stage and DNA replication was never detected in them. On the other hand, oocytes at the prometaphase to anaphase-telophase I stages responded to 6-DMAP treatment by forming nuclei which synthesised DNA. Mature (metaphase II) oocytes did not respond to 6-DMAP and their chromatin remained condensed. DNA synthesis could even be induced in GV-staged oocytes, but only when they were fused to freshly activated oocytes and incubated in 6-DMAP-supplemented medium.
Fertilisation competence of bovine normally matured or aged oocytes derived from different antral follicles: morphology, protein synthesis, H1 and MBP kinase activity
Authors: Pavlok Antonín , Kaláb Petr , Bobák Petr
Published: September 2008

We have investigated the fertilisation competence, protein synthesis, histone H1 kinase and myelin basic protein (MBP) kinase activities in three categories of bovine oocytes (derived from three size categories of follicles: M–medium, 2.5–5.0 mm; S–small, 1.5–2.5 mm; T – tiny, 1.0–1.5mm). In contrast to more or less normal meiotic maturation (85.6%) and fertilisation (70.8%) of M oocytes cultured for 24h, the fertilisation of M oocytes cultured for 40h was associated with increased rates of retarded male pronuclear development and retention of the second polar body. The S and T oocytes cultured for 24h or 40h were mostly arrested at defective late diakinesis - metaphase I (77.5–100%) stage. After fertilisation of S and T oocytes cultured for 24h no polar body was extruded and formation of one, three or four female pronuclei, together with mostly normal male pronuclei, was observed. The fertilisation of S and T oocytes after 40h culture resulted in a higher number of female and a decreased number of male pronuclei. A major change in the pattern of protein synthesis was associated with the resumption of meiosis. There were no significant differences in the profile of protein synthesis between oocyte categories in all groups either matured or fertilised. The H1 kinase activity reached comparable increased levels in oocytes of all categories matured for 24h and decreased during the 40h culture, most significantly in M oocytes. The MBP kinase activity was at approximately the same high level in all categories of oocytes after 24h of culture and remained stable until 40h. The fertilisation after 24h of culture resulted, in M oocytes, in low levels of both H1 and MBP kinase activities; in S oocytes, only H1 kinase was completely inactivated while MBP kinase activity decreased to some extent; in T oocytes, both H1 and MBP kinase activity decreased. Fertilisation of all oocyte categories after 40h culture resulted in complete inactivation of both these kinases to their basal levels.
Glycine and methionine transport by bovine embryos
Authors: Guyader-Joly Catherine , Khatchadourian Chaqué , Ménézo Yves
Published: September 2008

As glycine is one of the most concentrated amino acids in the female genital tract, we investigated its uptake by bovine in vitro matured/in vitro fertilised blastocysts in the presence of increasing concentrations of radiolabelled glycine. We also determined methionine uptake by in vitro and in vivo produced embryos. In our study, the hypothesis of more than one site of enzyme activity for glycine substrate was not validated. We determined a Vmax of 23.4fmol/min per embryo and a Km value of 13.3μM. No significant difference was observed either between in vivo and in vitro derived embryos or between grade 1 and grade 2 embryos for methionine uptake. The methionine and glycine uptake of a day 7 bovine was similar to that of a day 4 mouse blastocyst. This is rather low if we consider the relative cell numbers.
The behaviour of mitochondria and cell integration during somatic hybridisation of sister blastomeres of the 2-cell mouse embryo
Authors: Sekirina G.G. , Bogoliubova N.A. , Antonova N.V. , Dyban A.P.
Published: September 2008

The capacity of sister blastomeres of mouse embryos for induced fusion changed during the 2-cell stage. It was at low level (24%) at the early 2-cell stage, increased and reached 98.5% at the middle 2-cell stage and fell sharply to 31% at the late 2-cell stage. At the time corresponding to the G2/Mphase of the cell cycle the blastomeres fused in only 8% of cases. Vital staining of 2-cell embryos by rhodamine 123 showed that the mitochondria were dispersed throughout the cytoplasm with a ringlike (around the nucleus) or spot-like (over the metaphase plate) concentration in the centre of each blastomere. At the periphery of blastomeres the mitochondrial content was low. The behaviour of the mitochondria reflected the subsequent events of structural and functional integration of the sister blastomeres under induced fusion: a discernible boundary between partners during 30 min after electrofusion or 1 h after fusion with polyethylene glycol; movement of the two ‘rings’ to the centre of the blastomere fusion products (BFP) to form one large bright ‘spot’ over the common metaphase plate; mitochondria outlining the shape of the spindle and connection between sister blastomeres until completion of the first mitosis of BFP The data obtained suggest that fusion of the blastomeres does not lead to extensive changes in the hybrid cytoplasm and integration of nuclear material is taking place only at metaphase stage Cytogenetic examination of BFP at the 2-cell stage confirmed reconstruction of the tetraploid embryos and found that sister blastomeres of such embryos could asynchronously enter the next cleavage division similarly to normal diploid 2-cell embryos.
Chromosomes of mouse primary spermatocytes undergo meiotic divisions after incorporation into homologous immature oocytes
Authors: Ogura Atsuo , Wakayama Teruhiko , Suzuki Osamu , Shin Tae-Young , Matsuda Junichiro , Kobayashi Yoshiro
Published: September 2008

The primary spermatocytes used were male germ cells at prophase I. The present study was undertaken to see whether bivalent chromosomes of mouse primary spermatocytes can undergo meiotic divisions within maturing oocytes and participate in subsequent embryonic development. Primary spermatocytes (pachytene to diplotene) freshly collected from the testes of mature males were electrofused with immature oocytes shortly before or after germinal vesicle breakdown. After culture in MEM-α medium for 15 h, most (> 90%) of the oocytes containing spermatocyte chromosomes underwent maturation and arrested at metaphase II (Mil). Among 23 Mil oocytes examined, 17 (74%) had one group of chromosomes and one polar body, indicating that male chromosomes had intermingled with those of the females and completed the first meiotic division. Chromosome analyses of these Mil oocytes demonstrated their diploidy. The metaphase chromosomes were transferred to enucleated Mil oocytes freshly recovered from superovulated mice. After artificial activation, the reconstructed Mil oocytes resumed meiosis and developed to the morula/blastocyst stage. However, no pups were born following embryo transfer into recipient females. These findings indicate that the chromosomes of primary spermatocytes undergo meiotic divisions in maturing oocytes and participate in the formation of diploid embryos.
Transformation of sperm nuclei into metaphase chromosomes in maturing pig oocytes penetratedin vitro
Authors: Wang Wei-Hua , Niwa Koji
Published: September 2008

Cumulus-free pig oocytes at the germinal vesicle (GV) stage were incubated in modified Brackett & Oliphant's medium with 5% fetal calf serum and 5mM caffeine with or without cryopreserved, ejaculated spermatozoa. When oocytes were transferred into modified tissue culture medium (TCM- 199B at pH 7.4) supplemented with 1OIU/ml eCG, 1OIU/ml hCG and 1 μg/ml oestradiol-17p after 8h of incubation with spermatozoa and cultured for 0–48 h, 86–99% of oocytes were penetrated. Most (95–100%) oocytes penetrated 0–16 h after transfer had decondensed sperm chromatin. However, 24 h after transfer 47% and 33% of penetrated oocytes contained recondensed sperm chromatin and sperm metaphase chromosomes, respectively. The proportion of penetrated oocytes containing sperm metaphase chromosomes increased after 36–48 h of transfer (51–65%). The transformation of sperm nuclei to metaphase chromosomes was obtained in 75% and 79% of anaphase I (AI) to telophase I (TI) and metaphase II (Mil) oocytes, respectively, but only in 38% of metaphase I (MI) oocytes. Moreover, such transformation was observed only in 1 of 30 oocytes at the stages of GV breakdown to prometaphase I and none of 69 oocytes at the GV stage. The transformation of sperm nuclei into metaphase chromosomes was completely inhibited in oocytes penetrated by eight or more spermatozoa. Well-developed male and female pronuclei were observed in only 3 (4%) of 77 oocytes penetrated 48 h after transfer. The proportion of oocytes reaching Mil was greatly inhibited by sperm penetration; only 18% of penetrated oocytes, but 87% of non-inseminated oocytes, reached Mil by 48 h after transfer. None of the oocytes penetrated by seven or more spermatozoa reached MIL Most (75%) oocytes were inhibited from the transition from MI to Mil even though they were cultured for 48 h. The present results indicate that: (1) the cytoplasm of maturing oocytes possesses an activity for transforming sperm nuclei into metaphase chromosomes, (2) immature pig oocytes penetrated by spermatozoa can undergo meiotic maturation to MI, and (3) the transition of such oocytes from MI to Mil is inhibited, suggesting that an activity of mitogen-activated protein kinase may be retarded.
Use of chemically defined system for the direct comparison of inner cell mass and trophectoderm distribution in murine, porcine and bovine embryos
Authors: Fuente Rabindranath de la , Allan King W.
Published: September 2008

The mammalian blastocyst comprises an inner cell mass (ICM) and a trophectoderm cell layer. In this study the allocation of blastomeres to either cell lineage was compared between murine, porcine and bovine blastocysts. Chemical permeation of trophectoderm cells by the Ca2+ionophore A23187 in combination with DNA-specific fluorochromes resulted in the differential staining of trophectoderm and ICM. Confocal microscopy confirmed the exclusive permeation of trophectoderm and the internal localisation of intact ICM cells in bovine blastocysts. Overall, differential cell counts were obtained in approximately 85% of the embryos assessed. Mean (±SEM) total cell numbers were 72.2 ± 3.1 and 93.1±5 forin vivoderived murine (n= 41) and porcine (n= 21) expanded blastocysts, respectively. Corresponding ICM cell number counts revealed ICM/total cell number ratios of 0.27 and 0.21, respectively. Comparison ofin vivo(n= 20) andin vitroderived bovine embryos on day 8 (n= 29) or day 9 (n= 29) revealed a total cell number of 195.25±9.9, 166.14±9.9 and 105±6.7 at the expanded blastocyst stage with corresponding ICM/total cell ratios of 0.27, 0.23 and 0.23, respectively. While total cell numbers differed significantly among the three groups of bovine embryos (p<0.05), the ICM/total cell ratio did not. These results indicate that a similar proportion of cells is allocated to the ICM among blastocysts of genetically divergent species.
Inositol triphosphate receptors in sea urchin sperm
Authors: Zapata Otilia , Ralston James , Beltraán Carmen , Parys Jan B. , Chen Ji Long , Longo Frank J. , Darszon Alberto
Published: September 2008

Inositol 1,4,5-triphosphate (Ins(1,4,5)P3) is a second messenger that regulates Ca2+channels in many important cell signalling pathways. In sea urchin sperm the outer investment of the egg triggers the acrosome reaction (AR) that involves Ins(1,4,5)P3production and the opening of two Ca2+channels. Here we have sought to identify a high-affinity Ins(1,4,5)P3receptor inStrongylocentrotus purpuratussperm. An Ins(1,4,5)P3binding component was affinity-purified 12-fold from sperm extracts. It displayed similar characteristics to the Ins(1,4,5)P3receptor from other sources: pH-dependent high affinity for Ins(1,4,5)3(KD=261 nM), a τ1/2of association and dissociation of 50 and 40s, respectively, specificity (IC)50>5μMfor Ins (1)P1, Ins(1,4)P2and Ins(1,3,4,5 P4), and pharmacological sensitivity 10 and 100μ heparin/ml inhibited 75% and 100% binding respectively). An antibody against the carboxy-terminal of the type I Ins(1,4,5)P3receptor of somatic cells recognised a Plasma membrane component in the sperm head and less intensely in the flagella. This antibody also recongnised a 240 kDa band from isolated head plasma membranes, and weakly in flagellar membrane. This IP3receptor-like protein may mediate the sustained uptake of Ca2+through the second Ca2+chanel opened during the AR.
Blastocoele formation and cell allocation to the inner cell mass and trophectoderm in haploid and diploid pig parthenotes developingin vitro
Authors: Kim Nam-Hyung , Uhm Sang Jun , Ju Jin Young , Lee Hoon Taek , Chung Kil Saeng
Published: September 2008

The objective of this study was to determine developmental pattern and cell allocation to the inner cell mass and trophectoderm in haploid and diploid embryos following parthenogenetic activation.In vitromatured porcine oocytes were activated by ethanol treatment and cultured in the presence or absence of cytochalasin B for 5h. The oocytes were then cultured in the NCSU23 for 9 days. The combined treatment with cytochalasin B following ethanol treatment did not increase (p>0.1) the incidence of activation. The incidence of development to the blastocyst stage was higher (p<0.05) in the combined treatments of ethanol and cytochalasin B as compared with ethanol treatment alone. The percentage of oocytes with two female pronuclei was higher (p< 0.01) in oocytes treated with cytochalasin B than that in ethanol treatment alone. Treatment with both ethanol and cytochalasin B increased (p<0.01) the incidence of diploid chromosome spread over just the ethanol treatment alone. The average numbers of total cells and inner cell mass were significantly reduced (p<0.05) in the ethanol treatment alone as compared with the combined cytochalasin B and ethanol treatment. These results suggested that the ploidy may affect blastocoele formation and cell allocation to inner cell mass and trophectoderm in the pig.
Spectral element modeling of spontaneous earthquake rupture on rate and state faults: Effect of velocity‐strengthening friction at shallow depths
Authors: Kaneko Y. , Lapusta N. , Ampuero J.‐P.
Published: September 2008

We develop a spectral element method (SEM) for simulating dynamic rupture on rate and state faults and use it to study how the rupture is affected by a shallow fault region of steady state velocity‐strengthening friction. Our comparison of the developed SEM and a spectral boundary integral method (BIM) for an antiplane (two‐dimensional) test problem shows that for the finest resolution that we use, the two methods produce virtually identical solutions, with negligible differences in rupture arrival times and peak slip velocities (less than 0.05% of their absolute values). The convergence with grid reduction of the developed SEM is comparable to that of BIM. We also use the test problem to compare numerical resolution required for different state evolution laws and for linear slip‐weakening friction. Using our three‐dimensional implementation of the methodology, we find that a shallow velocity‐strengthening fault region can significantly alter dynamic rupture and ground motion. The velocity‐strengthening region suppresses supershear propagation at the free surface occurring in the absence of such region, which could explain the lack of universally observed supershear rupture near the free surface. In addition, the velocity‐strengthening region promotes faster falloff of slip velocity behind the rupture front and decreases final slip throughout the entire fault, causing a smaller average stress drop. The slip decrease is largest in the shallow parts of the fault, resulting in a depth profile of slip qualitatively consistent with observations of shallow coseismic slip deficit. The shallow velocity‐strengthening region also reduces the amplification of strong ground motion due to a low‐velocity bulk structure.
Variations in the oceanic vertical carbon isotope gradient and their implications for the Paleocene‐Eocene biological pump
Authors: Hilting Anna K. , Kump Lee R. , Bralower Timothy J.
Published: September 2008

Variations in the efficiency of the biological pumping of carbon from the surface to the deep ocean have been invoked to explain changes in atmospheric pCO2 and thus climate on a variety of timescales. We compiled published Paleocene and Eocene foraminiferal carbon isotope data and adjusted them to a uniform timescale to investigate changes in the biological pump in the early Cenozoic. Eight basinal time series were binned into 0.01 Ma increments and five water column depth horizons. The carbon isotope data reveal remarkably coherent trends in surface, thermocline, and deep water carbon isotope values through the Paleocene and Eocene. These data were used to drive a three‐box ocean carbon isotope model to estimate long‐term relationships among changes in atmospheric pCO2, organic and inorganic carbon burial, and biological pumping. Our model results provide evidence for two different modes of organic carbon cycling. During the Paleocene and earliest Eocene, atmospheric pCO2 drawdown was driven externally by terrestrial organic carbon burial. After the earliest Eocene, variations in atmospheric pCO2 resulting from imbalances in organic carbon cycling appear to have been driven by variations in the biological pump. A temporary decline in biological pump efficiency at ∼50 Ma may have led to increased atmospheric pCO2, increased weathering and nutrient delivery to the oceans, and enhanced organic carbon burial. Thus, a biological‐pump‐driven increase in atmospheric pCO2 created a counterintuitive inverse relationship between organic carbon burial and atmospheric pCO2, with no indication of the burial event in the surface water carbon isotope record.
Carbonatite and silicate melt metasomatism of the mantle surrounding the Hawaiian plume: Evidence from volatiles, trace elements, and radiogenic isotopes in rejuvenated‐stage lavas from Niihau, Hawaii
Authors: Dixon Jacqueline , Clague David A. , Cousens Brian , Monsalve Maria Luisa , Uhl Jessika
Published: September 2008

We present new volatile, trace element, and radiogenic isotopic compositions for rejuvenated‐stage lavas erupted on Niihau and its submarine northwest flank. Niihau rejuvenated‐stage Kiekie Basalt lavas are mildly alkalic and are isotopically similar to, though shifted to higher 87Sr/86Sr and lower 206Pb/204Pb than, rejuvenated‐stage lavas erupted on other islands and marginal seafloor settings. Kiekie lavas display trace element heterogeneity greater than that of other rejuvenated‐stage lavas, with enrichments in Ba, Sr, and light‐rare earth elements resulting in high and highly variable Ba/Th and Sr/Ce. The high Ba/Th lavas are among the least silica‐undersaturated of the rejuvenated‐stage suite, implying that the greatest enrichments are associated with the largest extents of melting. Kiekie lavas also have high and variable H2O/Ce and Cl/La, up to 620 and 39, respectively. We model the trace element concentrations of most rejuvenated‐stage lavas by small degrees (∼1% to 9%) of melting of depleted peridotite recently metasomatized by a few percent of an enriched incipient melt (0.5% melting) of the Hawaiian plume. Kiekie lavas are best explained by 4% to 13% partial melting of a peridotite source metasomatized by up to 0.2% carbonatite, similar in composition to oceanic carbonatites from the Canary and Cape Verde Islands, with lower proportion of incipient melt than that for other rejuvenated‐stage lavas. Primary H2O and Cl of the carbonatite component must be high, but variability in the volatile data may be caused by heterogeneity in the carbonatite composition and/or interaction with seawater. Our model is consistent with predictions based on carbonated eclogite and peridotite melting experiments in which (1) carbonated eclogite and peridotite within the Hawaiian plume are the first to melt during plume ascent; (2) carbonatite melt metasomatizes plume and surrounding depleted peridotite; (3) as the plume rises, silica‐undersaturated silicate melts are also produced and contribute to the metasomatic signature. The metasomatic component is best preserved at the margins of the plume, where low extents of melting of the metasomatized depleted mantle surrounding the plume are sampled during flexural uplift. Formation of carbonatite melts may provide a mechanism to transfer plume He to the margins of the plume.
Aqueous depletion of Mg from olivine surfaces enhanced by ion irradiation
Authors: Cantando E. D. , Dukes C. A. , Loeffler M. J. , Baragiola R. A.
Published: September 2008

Laboratory experiments demonstrate that olivine irradiated with keV ions and exposed to water exhibits up to a 60% reduction from the original near‐surface concentration of magnesium, as measured by X‐ray photoelectron spectroscopy. The depth of this depletion layer is measured to be ∼15 nm. Irradiations were performed with 4 keV ions at fluences from 1014–1019 ions cm–2 and water immersion times ranging from 3 s to more than 100 h in neutral (pH = 6.8), high‐purity water. The depletion of Mg depends strongly on ion fluence but weakly on immersion time after 3 min, when it saturates. Remarkably, ion irradiation enhances the rate of surface depletion of Mg from olivine by a factor of 26,000. This effect must be considered when assessing the surface composition of samples exposed to simulated space weathering in the laboratory and during the handling and analysis of irradiated extraterrestrial specimens acquired via sample return missions.
Selective role of calcineurin in haematopoiesis and lymphopoiesis
Authors: Gallo Elena M , Ho Lena , Winslow Monte M , Staton Tracy L , Crabtree Gerald R
Published: September 2008

The calcineurin/NFAT (nuclear factor of activated T‐cells) signalling pathway is essential for many aspects of vertebrate development and is the target of the widely used immunosuppressive drugs FK506 and cyclosporine A. The basis for the therapeutic specificity of these drugs has remained unclear, as calcineurin is expressed ubiquitously. By inactivating calcineurin during haematopoietic development, we found that although this signalling pathway has an important, non‐redundant role in the regulation of lymphocyte developmental checkpoints, it is not essential for the development of blood myeloid lineages. These studies have shown that the specificity of calcineurin inhibitors arises from the selective use of calcineurin at distinct developmental stages. The requirement for calcineurin/NFAT in the development of the adaptive but not of the innate immune system is consistent with the idea that the evolutionary appearance of this pathway was involved in the emergence of vertebrates.
Central Obesity as a Precursor to the Metabolic Syndrome in the AusDiab Study and Mauritius
Authors: Cameron Adrian J. , Boyko Edward J. , Sicree Richard A. , Zimmet Paul Z. , Söderberg Stefan , Alberti K. George M.M. , Tuomilehto Jaakko , Chitson Pierrot , Shaw Jonathan E.
Published: September 2008

Evidence from epidemiologic studies that central obesity precedes future metabolic change and does not occur concurrently with the appearance of the blood pressure, glucose, and lipid abnormalities that characterize the metabolic syndrome (MetS) has been lacking. Longitudinal surveys were conducted in Mauritius in 1987, 1992, and 1998, and in Australia in 2000 and 2005 (AusDiab). This analysis included men and women (aged ≥25 years) in three cohorts: AusDiab 2000–2005 (n = 5,039), Mauritius 1987–1992 (n = 2,849), and Mauritius 1987–1998 (n = 1,999). MetS components included waist circumference, systolic blood pressure, fasting and 2‐h postload plasma glucose, high‐density lipoprotein (HDL) cholesterol, triglycerides, and homeostasis model assessment of insulin sensitivity (HOMA‐S) (representing insulin sensitivity). Linear regression was used to determine which baseline components predicted deterioration in other MetS components over 5 years in AusDiab and 5 and 11 years in Mauritius, adjusted for age, sex, and ethnic group. Baseline waist circumference predicted deterioration (P < 0.01) in four of the other six MetS variables tested in AusDiab, five of six in Mauritius 1987–1992, and four of six in Mauritius 1987–1998. In contrast, an increase in waist circumference between baseline and follow‐up was only predicted by insulin sensitivity (HOMA‐S) at baseline, and only in one of the three cohorts. These results suggest that central obesity plays a central role in the development of the MetS and appears to precede the appearance of the other MetS components.
Mechanisms of neuronal death in disease: defining the models and the players
Authors: Ribe Elena M. , Serrano-Saiz Esther , Akpan Nsikan , Troy Carol M.
Published: September 2008

Dysregulation of life and death at the cellular level leads to a variety of diseases. In the nervous system, aberrant neuronal death is an outstanding feature of neurodegenerative diseases. Since the discovery of the caspase family of proteases, much effort has been made to determine how caspases function in disease, including neurodegenerative diseases. Although many papers have been published examining caspases in neuronal death and disease, the pathways have not been fully clarified. In the present review, we examine the potential players in the death pathways, the current tools for examining these players and the models for studying neurological disease. Alzheimer's disease, the most common neurodegenerative disorder, and cerebral ischaemia, the most common cause of neurological death, are used to illustrate our current understanding of death signalling in neurodegenerative diseases. A better understanding of the neuronal death pathways would provide targets for the development of therapeutic interventions for these diseases.
Reading Trajectories of Children With Language Difficulties From Preschool Through Fifth Grade
Authors: Skibbe Lori E. , Grimm Kevin J. , Stanton-Chapman Tina L. , Justice Laura M. , Pence Khara L. , Bowles Ryan P.
Published: September 2008

Purpose

The current work examined which theory of reading development, thecumulative reading trajectoryor thecompensatory trajectory of development,most accurately represents the reading trajectories of children with language difficulties (LD) relative to their peers with typical language (TL) skills. Specifically, initial levels of reading skills, overall rate of growth, and patterns of growth were examined.

Method

Children were classified according to whether or not they exhibited LD at 54 months of age (LDn= 145; TLn= 653), using data from the National Institute of Child Health and Human Development’s Early Child Care Research Network (see NICHD, 1993). A latent shape growth curve model was used to model reading skills at 4 time points from preschool through fifth grade.

Results

In comparison to children with TL, children with LD showed lower reading skills in preschool, but their overall reading growth was faster. All children developed the skills associated with reading more rapidly at earlier ages compared to later ages. Children with LD continued to exhibit reading skills that were substantially lower than those of children with TL during fifth grade.

Conclusion

Results supported the compensatory trajectory of development. Speech-language pathologists are encouraged to adopt evidence-based practices in order to boost reading outcomes for children with LD beginning in preschool.
Developing Treatment for Adolescents Who Stutter: A Phase I Trial of the Camperdown Program
Authors: Hearne Anna , Packman Ann , Onslow Mark , O’Brian Sue
Published: September 2008

Purpose

To investigate in detail how adolescents who stutter perform during treatment, with the aim of informing treatment development for this age group.

Method

The Camperdown Program was conducted with 3 adolescents who stutter. Their performance during treatment was recorded in detail, and outcome measures were collected before treatment and on 5 occasions after treatment.

Results

One participant responded extremely well to treatment, with percentage of syllables stuttered (%SS) scores at 12 months follow-up around 1%. In addition, his speech naturalness was within normal limits. Another participant withdrew from treatment during maintenance, yet he still approximately halved his pretreatment %SS scores and was also sounding natural after treatment. This participant was satisfied with his treatment outcome. A third participant did not reach maintenance and did not benefit from the treatment.

Conclusion

The adolescent who succeeded in treatment presented with a high level of self-confidence and maturity. When examining the factors that seemed to impact on treatment outcome, an underlying theme of decreased parent influence and increased peer influence and self-direction was detected. These are fundamental during the journey through adolescence from childhood to adulthood. Future directions in developing treatments for adolescents are discussed.
Integrating American Indian/Alaska Native Culture Into Shared Storybook Intervention
Authors: Inglebret Ella , Jones Carla , Pavel D. Michael
Published: September 2008

Purpose

The purpose of this clinical exchange is to provide information for speech-language pathologists (SLPs) so they will be able to provide culturally responsive intervention for young children of American Indian and Alaska Native heritage. The focus is on a particular strategy–the integration of culturally based stories into shared storybook intervention.

Method

The use of culturally based stories is presented as it relates to sociocultural theory and the expressed priority of Native peoples to revitalize their cultural teaching and learning practices, inclusive of storytelling. Strategies are presented that SLPs can follow in preparing for the use of culturally based stories, as well as in ensuring that the stories that are selected for use are authentic and appropriate for the children involved. The strategies discussed represent the collaborative efforts of Native and non-Native professionals to link a review of pertinent scholarly literature with ancestral knowledge that is derived from tribal elders and tradition bearers of the Southern Puget Salish peoples. The article concludes by illustrating the application of these strategies to a program involving young children of culturally and linguistically diverse backgrounds.

Conclusion

SLPs can integrate culturally based stories into their language and literacy intervention to encourage American Indian and Alaska Native children.
The Use of Conversational Repairs by African American Preschoolers
Authors: Stockman Ida J. , Karasinski Laura , Guillory Barbara
Published: September 2008

Purpose

This study aimed to describe the types and frequency of conversational repairs used by African American (AA) children in relationship to their geographic locations and levels of performance on commonly used speech-language measures.

Method

The strategies used to initiate repairs and respond to repair requests were identified in audiovisual records of spontaneous speech sampled from 120 Head Start students in Michigan (n= 69) and Louisiana (n= 51) at 3 years of age. The 30–40-min samples were elicited with common stimuli and activities while the children interacted with an adult examiner.

Results

All participants initiated repairs and responded to examiner requests for conversational repairs. Some repair strategies were observed more often than others. The frequency, but not the types, of some of the strategies used varied significantly with participant location and level of speech-language performance.

Conclusion

AA children used the same types of conversational repair strategies that have been observed among young speakers of Standard English varieties.

Clinical Implication

Use of conversational repairs should be included among the pragmatic behaviors expected for 3-year-old AA children.
Understanding geospatial interests by visualizing map interaction behavior
Authors: Aoidh Eoin Mac , Bertolotto Michela , Wilson David C.
Published: September 2008

Much information can be derived about users’ geospatial information requirements based on how they interact with a geospatial system. Our research focuses on the analysis of mouse movements and map navigation operations as a proxy to implicitly determine users’ interests. Visualization provides an effective way of investigating how these interactions can provide an insight into users’ preferences and task at hand. This article describes GIViz (Geospatial Interactions Visualizer), a visualization tool that enables system designers to analyze user interface behavior with a geospatial data set. Behavior traits identified can be exploited to improve map personalization engines. In particular, this article discusses the visualization of user interface behavior to gain a better understanding of the correlation between users’ actions, the interaction strategy employed for approaching a particular type of task and users’ interests.
A temporal focus + context visualization model for handling valid-time spatial information
Authors: Carvalho Alexandre , De Sousa A. Augusto , Ribeiro Cristina , Costa Emília
Published: September 2008

Spatiotemporal databases provide effective means to represent, manage and query information evolving over time. However, the visualization of record sets that result from spatiotemporal queries through traditional visualization techniques can be of difficult interpretation or may lack the ability to meaningfully display several instants at the same time. We propose a Temporal Focus + Context visualization model to overcome issues from such techniques resorting to concepts from Information Visualization. In this model, Focus + Context is applied to time rather than, as more typically, to attributes or space, and allows large amounts of data from distinct periods of time and from several record sets to be compressed onto one. Underlying the proposed visualization technique is the calculation of a temporal degree of interest (TDOI) for each record driven by specific analysis, exploration or presentation goals and based on the record valid time attribute, as well as on user-defined temporal visualization requirements. In the mapping stage of the visualization pipeline, the TDOI for a record is used to control graphical properties, such as transparency and color. More complex rendering properties, such as sketch drawing edges or other non-photorealistic enhancement techniques, can also be used to convey the temporal aspects of data, replacing the original graphical features of the record data. By enhancing or dimming the representation of a data item, according to the corresponding degree of interest, it is possible to meaningfully compress information about distinct temporal states of data onto the same visualization display. The model has been applied to several test scenarios and proved appropriate and useful for a wide range of domains that require the display, exploration and analysis of spatial information discretely evolving over time.
Invited Article: Deep Impact instrument calibration
Authors: Klaasen Kenneth P. , A’Hearn Michael F. , Baca Michael , Delamere Alan , Desnoyer Mark , Farnham Tony , Groussin Olivier , Hampton Donald , Ipatov Sergei , Li Jianyang , Lisse Carey , Mastrodemos Nickolaos , McLaughlin Stephanie , Sunshine Jessica , Thomas Peter , Wellnitz Dennis
Published: September 2008

Calibration of NASA’s Deep Impact spacecraft instruments allows reliable scientific interpretation of the images and spectra returned from comet Tempel 1. Calibrations of the four onboard remote sensing imaging instruments have been performed in the areas of geometric calibration, spatial resolution, spectral resolution, and radiometric response. Error sources such as noise (random, coherent, encoding, data compression), detector readout artifacts, scattered light, and radiation interactions have been quantified. The point spread functions (PSFs) of the medium resolution instrument and its twin impactor targeting sensor are near the theoretical minimum [∼1.7pixels full width at half maximum (FWHM)]. However, the high resolution instrument camera was found to be out of focus with a PSF FWHM of ∼9pixels. The charge coupled device (CCD) read noise is ∼1 DN. Electrical cross-talk between the CCD detector quadrants is correctable to <2 DN. The IR spectrometer response nonlinearity is correctable to ∼1%. Spectrometer read noise is ∼2 DN. The variation in zero-exposure signal level with time and spectrometer temperature is not fully characterized; currently corrections are good to ∼10 DN at best. Wavelength mapping onto the detector is known within 1pixel; spectral lines have a FWHM of ∼2pixels. About 1% of the IR detector pixels behave badly and remain uncalibrated. The spectrometer exhibits a faint ghost image from reflection off a beamsplitter. Instrument absolute radiometric calibration accuracies were determined generally to <10% using star imaging. Flat-field calibration reduces pixel-to-pixel response differences to ∼0.5% for the cameras and <2% for the spectrometer. A standard calibration image processing pipeline is used to produce archival image files for analysis by researchers.
Exciton diffusion and energy transfer in organic solar cells based on dicyanovinyl-terthiophene
Authors: Holzhey A. , Uhrich C. , Brier E. , Reinhold E. , Bäuerle P. , Leo K. , Hoffmann M.
Published: September 2008

We discuss exciton transport and energy transfer in organic solar cells based on dicyanovinyl-terthiophene (DCV3T). Time-resolved surface luminescence quenching experiments on double layers of DCV3T and zinc-phthalocyanine as luminescence quencher are analyzed in the framework of a three-level luminescence model with an initially absorbing state of short lifetime that relaxes to a longer living emitting state. Luminescence quenching of the emitting state is assigned to Förster-type energy transfer with an apparent Förster radius of 2.1 nm, which is in accordance with the Förster radius obtained from the spectral overlap integral. A diffusion based analysis for the emitting state yields a diffusion length of Le=6.9 nm. The short living initial state is quenched by diffusion of the excitons to the interface with a diffusion length of La=5.3 nm. External quantum efficiency measurements of the photocurrent in a corresponding organic solar cell structure evaluated with a two-level diffusion model give a diffusion length of LEQE=6.0 nm, whereas a two-level model for stationary luminescence quenching yields a diffusion length of Lcw=12 nm. This suggests that only one type of the excitons contributes to the photocurrent.
Influence of the (111) twinning on the formation of diamond cubic/diamond hexagonal heterostructures in Cu-catalyzed Si nanowires
Authors: Arbiol Jordi , Fontcuberta i Morral Anna , Estradé Sònia , Peiró Francesca , Kalache Billel , Roca i Cabarrocas Pere , Morante Joan Ramon
Published: September 2008

The occurrence of heterostructures of cubic silicon/hexagonal silicon as disks defined along the nanowire ⟨111⟩ growth direction is reviewed in detail for Si nanowires obtained using Cu as catalyst. Detailed measurements on the structural properties of both semiconductor phases and their interface are presented. We observe that during growth, lamellar twinning on the cubic phase along the ⟨111⟩ direction is generated. Consecutive presence of twins along the ⟨111⟩ growth direction was found to be correlated with the origin of the local formation of the hexagonal Si segments along the nanowires, which define quantum wells of hexagonal Si diamond. Finally, we evaluate and comment on the consequences of the twins and wurtzite in the final electronic properties of the wires with the help of the predicted energy band diagram.