A fine-grained, up to 3-m-thick tephra bed in southwestern Saskatchewan, herein named Duncairn tephra (Dt), is derived from an early Pleistocene eruption in the Jemez Mountains volcanic field of New Mexico, requiring a trajectory of northward tephra dispersal of ~1500 km. An unusually low CaO content in its glass shards denies a source in the closer Yellowstone and Heise volcanic fields, whereas a Pleistocene tephra bed (LSMt) in the La Sal Mountains of Utah has a very similar glass chemistry to that of the Dt, supporting a more southerly source. Comprehensive characterization of these two distal tephra beds along with samples collected near the Valles caldera in New Mexico, including grain size, mineral assemblage, major- and trace-element composition of glass and minerals, paleomagnetism, and fission-track dating, justify this correlation. Two glass populations each exist in the Dt and LSMt. The proximal correlative of Dt1 is the plinian Tsankawi Pumice and co-ignimbritic ash of the first ignimbrite (Qbt1g) of the 1.24 Ma Tshirege Member of the Bandelier Tuff. The correlative of Dt2 and LSMt is the co-ignimbritic ash of Qbt2. Mixing of Dt1 and Dt2 probably occurred during northward transport in a jet stream.

Bovine cumulus-enclosed oocytes, initially cultured up to diakinesis (8h of initial culture) or metaphase I (12h of initial culture), were subsequently co-cultured for 6 h in contact with pig membrana granulosa (PMG) cells and then assayed for histone H1 and MAP kinase activities. In addition, the phosphorylation state of ERK 1,2 proteins was determined by Western blotting. The alterations in nuclear envelope breakdown, meiotic spindle formation and the patterns of chromosome condensation were analysed by immunofluorescence and transmission electron microscopy. The diakinesis-stage oocytes (initially cultured for 8h) already possessed high histone H1 kinase and MAP kinase activities that were correlated with condensed and partially individualised chromosomes. The ERK 1 and most ERK 2 proteins were partly phosphorylated. Following the 6h co-culture of these oocytes with PMG a rapid decrease in MAP kinase activity and a slower decrease in histone H1 kinase occurred, as well as ERK 1 and ERK 2 dephosphorylation. Both kinase activities and ERK 1,2 phosphorylation were fully restored following the release of the oocytes from co-culture and a subsequent culture in the absence of PMG. Moreover, the clumped bivalents were reindividualised and 56% of these oocytes reached metaphase II after 20 h of culture without PMG. The metaphase I oocytes, initially cultured for 12 h, displayed a fusiform meiotic spindle and a metaphase array of chromosomal bivalents, accompanied by high levels of both histone H1 and MAP kinase activity. Co-culture of MI oocytes with PMG abolished the activity of both kinases and caused the dephosphorylation of ERK 1 and ERK 2. Furthermore, the spindle microtubules were depolymerised and the chromosomal bivalents clumped into a single mass. Neither of the protein kinase activities nor the meiotic spindle were restored following subsequent culture in the absence of PMG for up to 20 h. These observations indicate that under in vitro conditions membrana granulosa cells can cause a prompt decrease in histone H1 and MAP kinase activities, and metaphase I oocytes. While these events are fully reversible in late diakinesis oocytes, metaphase I oocytes did not complete maturation after release from co-culture.

The NASA Discovery mission EPOXI, utilizing the Deep Impact flyby spacecraft, comprises two phases: EPOCh (Extrasolar Planet Observation and Characterization) and DIXI (Deep Impact eXtended Investigation). With EPOCh, we use the 30-cm high resolution visible imager to obtain ultraprecise photometric light curves of known transiting planet systems. We will analyze these data for evidence of additional planets, via transit timing variations or transits; for planetary moons or rings; for detection of secondary eclipses and the constraint of geometric planetary albedos; and for refinement of the system parameters. Over a period of four months, EPOCh observed four known transiting planet systems, with each system observed continuously for several weeks. Here we present an overview of EPOCh, including the spacecraft and science goals, and preliminary photometry results.

EPOXI (EPOCh + DIXI) is a NASA Discovery Program Mission of Opportunity using the Deep Impact flyby spacecraft. The EPOCh (Extrasolar Planet Observation and Characterization) Science Investigation will gather photometric time series of known transiting exoplanet systems from January through August 2008. Here we describe the steps in the photometric extraction of the time series and present preliminary results of the first four EPOCh targets.

In this study a specific inhibitor of cyclin-dependent kinases (cdks), butyrolactone I (BL I), was used for activation of pig and cattle metaphase II (MII) oocytes. BL I at a concentration of 100 μM was able to induce activation of both pig and cattle MII oocytes in a manner dependent on exposure time; however, precise timing of BL I exposure was required for the best activation results. The optimum activation rates were obtained when cattle MII oocytes were treated for 5 h with BL I and subsequently for 3-11 h in control medium, and pig MII oocytes for 8 h in BL I and then for 8-16 h in control medium; the percentage of activated oocytes after such treatment varied between 55% and 74% and between 53% and 81% for cattle and pig oocytes, respectively. Shorter exposures to BL I led to re-entry of the oocytes to the metaphase state in 35-50% of oocytes, the remaining oocytes forming a pronuclear stage; longer exposure to BL I led to increased numbers of oocytes being abnormal or degenerated. The behaviour of histone H1 kinase and mitogen activated protein (MAP) kinase, also measured during the experiment, reflected the morphological changes in the oocytes: both were inactivated after BL I treatment, though the inactivation of histone H1 kinase occurred 2 h ahead of that of MAP kinase. However, in the oocytes treated for a shorter time with BL I, with the reoccurrence of condensed chromatin in proportion of the oocytes cultured in control medium after BL I treatment, both kinases became reactivated. Taken together, these results suggest the possibility of using BL I for activation and cloning experiments in both species.

Temporal and spatial distribution of the sites of DNA replication were examined in 1-cell mouse embryos. Embryos were labelled with bromodeoxyuridine (BrdU) at hourly intervals after fertilisation, and the incorporation of BrdU was examined by laser-scanning confocal microscopy following immunostaining with an anti-BrdU antibody. DNA replication first started uniformly in both the male and female pronuclei in the intranuclear region and then was observed in the peripheral regions of nucleus and nucleolus. These changes, however, occurred asynchronously in that the female pronucleus required a longer time to complete replication in the intranuclear region but not in the peripheral regions. Inhibiting transcription with α-amanitin had no effect on the temporal and spatial patterns of DNA replication. Treatment of the embryos with trapoxin, a specific inhibitor of histone deacetylase, accelerated the completion of replication in the peripheral regions but not in the intranuclear region. These results suggest that DNA replication is temporally and spatially regulated in the 1-cell embryos and that acetylation of histones, but not transcription, is involved in the regulation of DNA replication.