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The rapidly evolving stem cell field puts much stress on developing educational resources. The ISSCR Education Committee has created a flexible stem cell syllabus rooted in core concepts to facilitate stem cell literacy. The free syllabus will be updated regularly to maintain accuracy and relevance.

Restoring the health of urban streams has many of the characteristics of a wicked problem. Addressing a wicked problem requires managers, academics, practitioners, and community members to make negotiated tradeoffs and compromises to satisfy the values and perspectives of diverse stakeholders involved in setting restoration project goals and objectives. We conducted a gap analysis on 11 urban stream restoration projects to identify disconnections, underperformance issues, and missing processes in the project structures used to develop restoration project goals and objectives. We examined the gap analysis results to investigate whether managers appropriately identified problem statements and met stated objectives. Projects that aimed to restore overall stream health commonly fell short for various reasons, including limited stakeholder and community input and buy-in, revealing potential limitations in the breadth of objectives, values, and stakeholder perspectives and knowledge types. Projects that emphasized integrating community values and diverse knowledge types tended to meet the expected outcomes of restoring stream processes through incremental solutions. Managers implementing more holistic solutions and values-driven approaches are more likely to consider diverse viewpoints from a variety of community local institutions. Based on these and other results, we propose a conceptual framework that integrates diverse perspectives and knowledge to enhance social and ecological outcomes of urban stream restoration. The framework also emphasizes the importance of setting objectives that support incremental solutions to foster more realistic expectations amongst stakeholders.

Over 100 years of studies in Drosophila melanogaster and related species in the genus Drosophila have facilitated key discoveries in genetics, genomics, and evolution. While high-quality genome assemblies exist for several species in this group, they only encompass a small fraction of the genus. Recent advances in long-read sequencing allow high-quality genome assemblies for tens or even hundreds of species to be efficiently generated. Here, we utilize Oxford Nanopore sequencing to build an open community resource of genome assemblies for 101 lines of 93 drosophilid species encompassing 14 species groups and 35 sub-groups. The genomes are highly contiguous and complete, with an average contig N50 of 10.5 Mb and greater than 97% BUSCO completeness in 97/101 assemblies. We show that Nanopore-based assemblies are highly accurate in coding regions, particularly with respect to coding insertions and deletions. These assemblies, along with a detailed laboratory protocol and assembly pipelines, are released as a public resource and will serve as a starting point for addressing broad questions of genetics, ecology, and evolution at the scale of hundreds of species.

Over 100 years of studies in Drosophila melanogaster and related species in the genus Drosophila have facilitated key discoveries in genetics, genomics, and evolution. While high-quality genome assemblies exist for several species in this group, they only encompass a small fraction of the genus. Recent advances in long-read sequencing allow high-quality genome assemblies for tens or even hundreds of species to be efficiently generated. Here, we utilize Oxford Nanopore sequencing to build an open community resource of genome assemblies for 101 lines of 93 drosophilid species encompassing 14 species groups and 35 sub-groups. The genomes are highly contiguous and complete, with an average contig N50 of 10.5 Mb and greater than 97% BUSCO completeness in 97/101 assemblies. We show that Nanopore-based assemblies are highly accurate in coding regions, particularly with respect to coding insertions and deletions. These assemblies, along with a detailed laboratory protocol and assembly pipelines, are released as a public resource and will serve as a starting point for addressing broad questions of genetics, ecology, and evolution at the scale of hundreds of species.

Accurate and comprehensive characterization of genetic variation is essential for deciphering the genetic basis of diseases and other phenotypes. A vast amount of genetic variation stems from large-scale sequence changes arising from the duplication, deletion, inversion, and translocation of sequences. In the past 10 years, high-throughput short reads have greatly expanded our ability to assay sequence variation due to single nucleotide polymorphisms. However, a recent de novo assembly of a second Drosophila melanogaster reference genome has revealed that short read genotyping methods miss hundreds of structural variants, including those affecting phenotypes. While genomes assembled using high-coverage long reads can achieve high levels of contiguity and completeness, concerns about cost, errors, and low yield have limited widespread adoption of such sequencing approaches. Here we resequenced the reference strain of D. melanogaster (ISO1) on a single Oxford Nanopore MinION flow cell run for 24 hr. Using only reads longer than 1 kb or with at least 30x coverage, we assembled a highly contiguous de novo genome. The addition of inexpensive paired reads and subsequent scaffolding using an optical map technology achieved an assembly with completeness and contiguity comparable to the D. melanogaster reference assembly. Comparison of our assembly to the reference assembly of ISO1 uncovered a number of structural variants (SVs), including novel LTR transposable element insertions and duplications affecting genes with developmental, behavioral, and metabolic functions. Collectively, these SVs provide a snapshot of the dynamics of genome evolution. Furthermore, our assembly and comparison to the D. melanogaster reference genome demonstrates that high-quality de novo assembly of reference genomes and comprehensive variant discovery using such assemblies are now possible by a single lab for under $1,000 (USD).

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979-2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE

Accurate and comprehensive characterization of genetic variation is essential for deciphering the genetic basis of diseases and other phenotypes. A vast amount of genetic variation stems from large-scale sequence changes arising from the duplication, deletion, inversion, and translocation of sequences. In the past 10 years, high-throughput short reads have greatly expanded our ability to assay sequence variation due to single nucleotide polymorphisms. However, a recent de novo assembly of a second Drosophila melanogaster reference genome has revealed that short read genotyping methods miss hundreds of structural variants, including those affecting phenotypes. While genomes assembled using high-coverage long reads can achieve high levels of contiguity and completeness, concerns about cost, errors, and low yield have limited widespread adoption of such sequencing approaches. Here we resequenced the reference strain of D. melanogaster (ISO1) on a single Oxford Nanopore MinION flow cell run for 24 hr. Using only reads longer than 1 kb or with at least 30x coverage, we assembled a highly contiguous de novo genome. The addition of inexpensive paired reads and subsequent scaffolding using an optical map technology achieved an assembly with completeness and contiguity comparable to the D. melanogaster reference assembly. Comparison of our assembly to the reference assembly of ISO1 uncovered a number of structural variants (SVs), including novel LTR transposable element insertions and duplications affecting genes with developmental, behavioral, and metabolic functions. Collectively, these SVs provide a snapshot of the dynamics of genome evolution. Furthermore, our assembly and comparison to the D. melanogaster reference genome demonstrates that high-quality de novo assembly of reference genomes and comprehensive variant discovery using such assemblies are now possible by a single lab for under $1,000 (USD).

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979-2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979-2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.

We report annual snow accumulation rates from 1959 to 2004 along a 250 km segment of the Expéditions Glaciologiques Internationales au Groenland (EGIG) line across central Greenland using Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) radar layers and high resolution neutron-probe (NP) density profiles. ASIRAS-NP-derived accumulation rates are not statistically different (95 % confidence interval) from in situ EGIG accumulation measurements from 1985 to 2004. ASIRAS-NP-derived accumulation increases by 20 % below 3000 m elevation, and increases by 13 % above 3000 m elevation for the period 1995 to 2004 compared to 1985 to 1994. Three Regional Climate Models (PolarMM5, RACMO2.3, MAR) underestimate snow accumulation below 3000 m by 16–20 % compared to ASIRAS-NP from 1985 to 2004. We test radar-derived accumulation rates sensitivity to density using modeled density profiles in place of NP densities. ASIRAS radar layers combined with Herron and Langway (1980) model density profiles (ASIRAS-HL) produce accumulation rates within 3.5 % of ASIRAS-NP estimates in the dry snow region. We suggest using Herron and Langway (1980) density profiles to calibrate radar layers detected in dry snow regions of ice sheets lacking detailed in situ density measurements, such as those observed by the Operation IceBridge campaign.

We report annual snow accumulation rates from 1959 to 2004 along a 250 km segment of the Expéditions Glaciologiques Internationales au Groenland (EGIG) line across central Greenland using Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) radar layers and high resolution neutron-probe (NP) density profiles. ASIRAS-NP-derived accumulation rates are not statistically different (95 % confidence interval) from in situ EGIG accumulation measurements from 1985 to 2004. ASIRAS-NP-derived accumulation increases by 20 % below 3000 m elevation, and increases by 13 % above 3000 m elevation for the period 1995 to 2004 compared to 1985 to 1994. Three Regional Climate Models (PolarMM5, RACMO2.3, MAR) underestimate snow accumulation below 3000 m by 16–20 % compared to ASIRAS-NP from 1985 to 2004. We test radar-derived accumulation rates sensitivity to density using modeled density profiles in place of NP densities. ASIRAS radar layers combined with Herron and Langway (1980) model density profiles (ASIRAS-HL) produce accumulation rates within 3.5 % of ASIRAS-NP estimates in the dry snow region. We suggest using Herron and Langway (1980) density profiles to calibrate radar layers detected in dry snow regions of ice sheets lacking detailed in situ density measurements, such as those observed by the Operation IceBridge campaign.

We have derived digital elevation models (DEMs) over the western part of the Devon Ice Cap in Nunavut, Canada, using "swath processing" of interferometric data collected by Cryosat between February 2011 and January 2012. With the standard ESA (European Space Agency) SARIn (synthetic aperture radar interferometry) level 2 (L2) data product, the interferometric mode is used to map the cross-track position and elevation of the "point-of-closest-approach" (POCA) in sloping glacial terrain. However, in this work we explore the extent to which the phase of the returns in the intermediate L1b product can also be used to map the heights of time-delayed footprints beyond the POCA. We show that there is a range of average cross-track slopes (~ 0.5 to ~ 2°) for which the returns will be dominated by those beneath the satellite in the main beam of the antenna so that the resulting interferometric phase allows mapping of heights in the delayed range window beyond the POCA. In this way a swath of elevation data is mapped, allowing the creation of DEMs from a sequence of L1b SARIn Cryosat data takes. Comparison of the Devon results with airborne scanning laser data showed a mean difference of order 1 m with a standard deviation of about 1 m. The limitations of swath processing, which generates almost 2 orders of magnitude more data than traditional radar altimetry, are explored through simulation, and the strengths and weaknesses of the technique are discussed.

We have derived digital elevation models (DEMs) over the western part of the Devon Ice Cap in Nunavut, Canada, using "swath processing" of interferometric data collected by Cryosat between February 2011 and January 2012. With the standard ESA (European Space Agency) SARIn (synthetic aperture radar interferometry) level 2 (L2) data product, the interferometric mode is used to map the cross-track position and elevation of the "point-of-closest-approach" (POCA) in sloping glacial terrain. However, in this work we explore the extent to which the phase of the returns in the intermediate L1b product can also be used to map the heights of time-delayed footprints beyond the POCA. We show that there is a range of average cross-track slopes (~ 0.5 to ~ 2°) for which the returns will be dominated by those beneath the satellite in the main beam of the antenna so that the resulting interferometric phase allows mapping of heights in the delayed range window beyond the POCA. In this way a swath of elevation data is mapped, allowing the creation of DEMs from a sequence of L1b SARIn Cryosat data takes. Comparison of the Devon results with airborne scanning laser data showed a mean difference of order 1 m with a standard deviation of about 1 m. The limitations of swath processing, which generates almost 2 orders of magnitude more data than traditional radar altimetry, are explored through simulation, and the strengths and weaknesses of the technique are discussed.

Oocytes are stockpiled with proteins and mRNA that are required to drive the initial mitotic divisions of embryogenesis. But are there proteins specific to meiosis whose levels must be decreased to begin embryogenesis properly? The Drosophila protein Cortex (Cort) is a female, meiosis-specific activator of the Anaphase Promoting Complex/Cyclosome (APC/C), an E3 ubiquitin ligase. We performed immunoprecipitation of Cortex followed by mass spectrometry, and identified the Polo kinase inhibitor Matrimony (Mtrm) as a potential interactor with Cort. In vitro binding assays showed Mtrm and Cort can bind directly. We found Mtrm protein levels to be reduced dramatically during the oocyte-to-embryo transition, and this downregulation did not take place in cort mutant eggs, consistent with Mtrm being a substrate of APC[superscript Cort]. We showed that Mtrm is subject to APC[superscript Cort]-mediated proteasomal degradation and have identified a putative APC/C recognition motif in Mtrm that when mutated partially stabilized the protein in the embryo. Furthermore, overexpression of Mtrm in the early embryo caused aberrant nuclear divisions and developmental defects, and these were enhanced by decreasing levels of active Polo. These data indicate APC[superscript Cort] ubiquitylates Mtrm at the oocyte-to-embryo transition, thus preventing excessive inhibition of Polo kinase activity due to Mtrm's presence.

We show first results of a combined ground based and airborne validation campaign for CryoSat-2 synthetic aperture interferometric radar altimeter (SIRAL) measurements over Austfonna, Svalbard. A decade time series of glacier facies for this ice cap interpreted from 800 MHz ground-penetrating radar data clearly show there to be considerable variation within the firn pack, which needs to be captured by CryoSat-2 if we are to correctly interpret the satellite observed surface changes. The ground based radar data were obtained with a CRESIS Ku-band FMCW radar. The radar was operated to cover the frequency band of the CryoSat-2 SIRAL and the airborne version, Airborne Synthetic Aperture and Interferometric Radar Altimeter System (ASIRAS) carried by the Danish geophysics plane. Simultaneous profiles were obtained within half a day of each other with all three radars during the spring calibration/validation campaign on the Austfonna ice cap, Svalbard. The profiles, totaling approximately 200 km, span an elevation change of 400 m from the summit down to the ablation area, and cover a range of glacier facies and surface snow conditions. The ground based KU-band radar, which clearly images the near surface layering, was supported by manual snow depth sounding, 800 MHz radar, snow pits, firn cores, and borehole videos, all of which are used to validate interpretation of the CryoSat-2 data.

The intimate synapsis of homologous chromosome pairs (homologs) by synaptonemal complexes (SCs) is an essential feature of meiosis. In many organisms, synapsis and homologous recombination are interdependent: recombination promotes SC formation and SCs are required for crossing-over. Moreover, several studies indicate that initiation of SC assembly occurs at sites where crossovers will subsequently form. However, recent analyses in budding yeast and fruit fly imply a special role for centromeres in the initiation of SC formation. In addition, in budding yeast, persistent SC-dependent centromere-association facilitates the disjunction of chromosomes that have failed to become connected by crossovers. Here, we examine the interplay between SCs, recombination, and centromeres in a mammal. In mouse spermatocytes, centromeres do not serve as SC initiation sites and are invariably the last regions to synapse. However, centromeres are refractory to de-synapsis during diplonema and remain associated by short SC fragments. Since SC-dependent centromere association is lost before diakinesis, a direct role in homolog segregation seems unlikely. However, post-SC disassembly, we find evidence of inter-centromeric connections that could play a more direct role in promoting homolog biorientation and disjunction. A second class of persistent SC fragments is shown to be crossover-dependent. Super-resolution structured-illumination microscopy (SIM) reveals that these structures initially connect separate homolog axes and progressively diminish as chiasmata form. Thus, DNA crossing-over (which occurs during pachynema) and axis remodeling appear to be temporally distinct aspects of chiasma formation. SIM analysis of the synapsis and crossover-defective mutant Sycp1⁻/⁻ implies that SCs prevent unregulated fusion of homolog axes. We propose that SC fragments retained during diplonema stabilize nascent bivalents and help orchestrate local chromosome reorganization that promotes centromere

We show first results of a combined ground based and airborne validation campaign for CryoSat-2 synthetic aperture interferometric radar altimeter (SIRAL) measurements over Austfonna, Svalbard. A decade time series of glacier facies for this ice cap interpreted from 800 MHz ground-penetrating radar data clearly show there to be considerable variation within the firn pack, which needs to be captured by CryoSat-2 if we are to correctly interpret the satellite observed surface changes. The ground based radar data were obtained with a CRESIS Ku-band FMCW radar. The radar was operated to cover the frequency band of the CryoSat-2 SIRAL and the airborne version, Airborne Synthetic Aperture and Interferometric Radar Altimeter System (ASIRAS) carried by the Danish geophysics plane. Simultaneous profiles were obtained within half a day of each other with all three radars during the spring calibration/validation campaign on the Austfonna ice cap, Svalbard. The profiles, totaling approximately 200 km, span an elevation change of 400 m from the summit down to the ablation area, and cover a range of glacier facies and surface snow conditions. The ground based KU-band radar, which clearly images the near surface layering, was supported by manual snow depth sounding, 800 MHz radar, snow pits, firn cores, and borehole videos, all of which are used to validate interpretation of the CryoSat-2 data.

When Drosophila melanogaster embryos initiate zygotic transcription around mitotic cycle 10, the dose-sensitive expression of specialized genes on the X chromosome triggers a sex-determination cascade that, among other things, compensates for differences in sex chromosome dose by hypertranscribing the single X chromosome in males. However, there is an approximately 1 hour delay between the onset of zygotic transcription and the establishment of canonical dosage compensation near the end of mitotic cycle 14. During this time, zygotic transcription drives segmentation, cellularization, and other important developmental events. Since many of the genes involved in these processes are on the X chromosome, we wondered whether they are transcribed at higher levels in females and whether this might lead to sex-specific early embryonic patterning. To investigate this possibility, we developed methods to precisely stage, sex, and characterize the transcriptomes of individual embryos. We measured genome-wide mRNA abundance in male and female embryos at eight timepoints, spanning mitotic cycle 10 through late cycle 14, using polymorphisms between parental lines to distinguish maternal and zygotic transcription. We found limited sex-specific zygotic transcription, with a weak tendency for genes on the X to be expressed at higher levels in females. However, transcripts derived from the single X chromosome in males were more abundant that those derived from either X chromosome in females, demonstrating that there is widespread dosage compensation prior to the activation of the canonical MSL-mediated dosage compensation system. Crucially, this new system of early zygotic dosage compensation results in nearly identical transcript levels for key X-linked developmental regulators, including giant (gt), brinker (brk), buttonhead (btd), and short gastrulation (sog), in male and female embryos.

As genetic issues play a growing role in health practice and public policy, new knowledge in this field will continue to have significant implications for individuals and society. Written to communicate sound and modern science in an accessible way for professionals and students with various levels of scientific background, this thoroughly revised edition of The Human Genome contributes to creating a genetically literate research and clinical population. With case studies and introductory vignettes which illustrate a wide range of perspectives on complex topics in genetics and updated material on the latest research on disease-specific topics, this book serves as a valuable resource for students and working professionals alike. Includes topical material on forensics, disease studies, and the human genome project to engage non-specialist students Full, 4-color illustration program enhances and reinforces key concepts and themes Uniform organization of chapters includes interest boxes that focus on human health and disease, chapter-opening case studies, and concept statements to engage non-specialist readers

As genetic issues play a growing role in health practice and public policy, new knowledge in this field will continue to have significant implications for individuals and society. Written to communicate sound and modern science in an accessible way for professionals and students with various levels of scientific background, this thoroughly revised edition of The Human Genome contributes to creating a genetically literate research and clinical population. With case studies and introductory vignettes which illustrate a wide range of perspectives on complex topics in genetics and updated material on the latest research on disease-specific topics, this book serves as a valuable resource for students and working professionals alike. Includes topical material on forensics, disease studies, and the human genome project to engage non-specialist students Full, 4-color illustration program enhances and reinforces key concepts and themes Uniform organization of chapters includes interest boxes that focus on human health and disease, chapter-opening case studies, and concept statements to engage non-specialist readers

As genetic issues play a growing role in health practice and public policy, new knowledge in this field will continue to have significant implications for individuals and society. Written to communicate sound and modern science in an accessible way for professionals and students with various levels of scientific background, this thoroughly revised edition of The Human Genome contributes to creating a genetically literate research and clinical population. With case studies and introductory vignettes which illustrate a wide range of perspectives on complex topics in genetics and updated material on the latest research on disease-specific topics, this book serves as a valuable resource for students and working professionals alike. Includes topical material on forensics, disease studies, and the human genome project to engage non-specialist students Full, 4-color illustration program enhances and reinforces key concepts and themes Uniform organization of chapters includes interest boxes that focus on human health and disease, chapter-opening case studies, and concept statements to engage non-specialist readers

Interferometric Radar Altimeters (IRA's) use dual receive antennas to overcome one of the spatial limitations of pulse-limited altimeters. In a conventional IRA measurement, the range and across-track direction of a scatterer are determined using the phase difference between the antennas. We demonstrate a method of determining multiple elevation points across a swath orthogonal to the instrument ground track in regions of steep terrain, such as ice-sheet margins. We use data from an airborne IRA (a prototype of the CryoSat-2 instrument), and compare the results to simultaneous Airborne Laser Scanner (ALS) observations. This application results in a 75-fold increase in measurement density compared to conventional radar altimetry. Along a ∼2.5 km ground track, the RMS departure between the IRA- and ALS-derived measurements was 1.67 m. Based on our result, although our approach is limited to areas of relatively steep slope, a 25- to 75-fold increase in elevation measurements could be achieved in coastal regions of Antarctica and Greenland with similar processing of CryoSat-2 data.

Heterochromatin contains many repetitive DNA elements and few protein-encoding genes, yet it is essential for chromosome organization and inheritance. Here, we show that Drosophila that lack the Su(var)3-9 H3K9 methyltransferase display significantly elevated frequencies of spontaneous DNA damage in heterochromatin, in both somatic and germ-line cells. Accumulated DNA damage in these mutants correlates with chromosomal defects, such as translocations and loss of heterozygosity. DNA repair and mitotic checkpoints are also activated in mutant animals and are required for their viability. Similar effects of lower magnitude were observed in animals that lack the RNA interference pathway component Dcr2. These results suggest that the H3K9 methylation and RNAi pathways ensure heterochromatin stability.

Interferometric Radar Altimeters (IRA's) use dual receive antennas to overcome one of the spatial limitations of pulse-limited altimeters. In a conventional IRA measurement, the range and across-track direction of a scatterer are determined using the phase difference between the antennas. We demonstrate a method of determining multiple elevation points across a swath orthogonal to the instrument ground track in regions of steep terrain, such as ice-sheet margins. We use data from an airborne IRA (a prototype of the CryoSat-2 instrument), and compare the results to simultaneous Airborne Laser Scanner (ALS) observations. This application results in a 75-fold increase in measurement density compared to conventional radar altimetry. Along a ∼2.5 km ground track, the RMS departure between the IRA- and ALS-derived measurements was 1.67 m. Based on our result, although our approach is limited to areas of relatively steep slope, a 25- to 75-fold increase in elevation measurements could be achieved in coastal regions of Antarctica and Greenland with similar processing of CryoSat-2 data.

Crossover recombination and the formation of chiasmata normally ensure the proper segregation of homologous chromosomes during the first meiotic division. zhp-3, the Caenorhabditis elegans ortholog of the budding yeast ZIP3 gene, is required for crossover recombination. We show that ZHP-3 protein localization is highly dynamic. At a key transition point in meiotic prophase, the protein shifts from along the length of the synaptonemal complex (SC) to an asymmetric localization on the SC and eventually becomes restricted to foci that mark crossover recombination events. A zhp-3::gfp transgene partially complements a null mutation and reveals a separation of function; although the fusion protein can promote nearly wild-type levels of recombination, aneuploidy among the progeny is high, indicating defects in meiotic chromosome segregation. The structure of bivalents is perturbed in this mutant, suggesting that the chromosome segregation defect results from an inability to properly remodel chromosomes in response to crossovers. smo-1 mutants exhibit phenotypes similar to zhp-3::gfp mutants at higher temperatures, and smo-1; zhp-3::gfp double mutants exhibit more severe meiotic defects than either single mutant, consistent with a role for SUMO in the process of SC disassembly and bivalent differentiation. We propose that coordination of crossover recombination with SC disassembly and bivalent formation reflects a conserved role of Zip3/ZHP-3 in coupling recombination with SC morphogenesis.

Despite the loss of CryoSat, ESAs first Earthopportunity mission, during its launch sequence in Oct2005 ESA have been fortunate enough to have acquired,processed to Level 1b and analysed a significant amountof campaign data from ESAs demonstration AirborneSAR/Interferometric Radar Altimeter System (ASIRAS)designed to have similar functionality to CryoSatsSynthetic Interferometric Radar Altimeter (SIRAL).This data acquisition took place for the original purposeof validating CryoSat retrievals.Our initial analyses of the level 1b data have revealedsome very interesting results both over land and sea icetest sites from respective campaigns conducted in theArctic during the land-ice spring/autumn campaigns of2004 and for sea-ice in the Bay of Bothnia duringMarch 2005. Since a further ASIRAS campaign in theArctic is guaranteed for April/May 2006 we look at howthis data can be exploited in view of future ESA Earthobservation radar altimeter missions. Verification of theASIRAS data with coincident laser altimeter and in-situdata collected at test sites is also presented.The paper also provides a review of key space and airborne radar altimeters dating from 1957 including thoseusing the synthetic aperture radar (SAR) technique asapplied to radar altimeters leading to the development ofCryoSat.

The centromere/kinetochore complex plays an essential role in cell and organismal viability by ensuring chromosome movements during mitosis and meiosis. The kinetochore also mediates the spindle attachment checkpoint (SAC), which delays anaphase initiation until all chromosomes have achieved bipolar attachment of kinetochores to the mitotic spindle. CENP-A proteins are centromere-specific chromatin components that provide both a structural and a functional foundation for kinetochore formation. Here we show that cells in Drosophila embryos homozygous for null mutations in CENP-A (CID) display an early mitotic delay. This mitotic delay is not suppressed by inactivation of the DNA damage checkpoint and is unlikely to be the result of DNA damage. Surprisingly, mutation of the SAC component BUBR1 partially suppresses this mitotic delay. Furthermore, cid mutants retain an intact SAC response to spindle disruption despite the inability of many kinetochore proteins, including SAC components, to target to kinetochores. We propose that SAC components are able to monitor spindle assembly and inhibit cell cycle progression in the absence of sustained kinetochore localization.

Despite the loss of CryoSat, ESAs first Earthopportunity mission, during its launch sequence in Oct2005 ESA have been fortunate enough to have acquired,processed to Level 1b and analysed a significant amountof campaign data from ESAs demonstration AirborneSAR/Interferometric Radar Altimeter System (ASIRAS)designed to have similar functionality to CryoSatsSynthetic Interferometric Radar Altimeter (SIRAL).This data acquisition took place for the original purposeof validating CryoSat retrievals.Our initial analyses of the level 1b data have revealedsome very interesting results both over land and sea icetest sites from respective campaigns conducted in theArctic during the land-ice spring/autumn campaigns of2004 and for sea-ice in the Bay of Bothnia duringMarch 2005. Since a further ASIRAS campaign in theArctic is guaranteed for April/May 2006 we look at howthis data can be exploited in view of future ESA Earthobservation radar altimeter missions. Verification of theASIRAS data with coincident laser altimeter and in-situdata collected at test sites is also presented.The paper also provides a review of key space and airborne radar altimeters dating from 1957 including thoseusing the synthetic aperture radar (SAR) technique asapplied to radar altimeters leading to the development ofCryoSat.

STAT5 is a member of the signal transducers and activation of transcription (STAT) family of latent transcription factors activated in a variety of cytokine signaling pathways. We introduced alanine substitution mutations in highly conserved regions of murine STAT5A and studied the mutants for dimerization, DNA binding, transactivation, and dominant negative effects on erythropoietin-induced STAT5-dependent transcriptional activation. The mutations included two near the amino-terminus (W255KR-->AAA and R290QQ-->AAA), two in the DNA-binding domain (E437E-->AA and V466VV-->AAA), and a carboxy-terminal truncation of STAT5A (STAT5A/triangle up53C) analogous to a naturally occurring isoform of rat STAT5B. All of the STAT mutant proteins were tyrosine phosphorylated by JAK2 and heterodimerized with STAT5B except for the WKR mutant, suggesting an important role for this region in STAT5 for stabilizing dimerization. The WKR, EE, and VVV mutants had no detectable DNA-binding activity, and the WKR and VVV mutants, but not EE, were defective in transcriptional induction. The VVV mutant had a moderate dominant negative effect on erythropoietin-induced STAT5 transcriptional activation, which was likely due to the formation of heterodimers that are defective in DNA binding. Interestingly, the WKR mutant had a potent dominant negative effect, comparable to the transactivation domain deletion mutant, triangle up53C. Stable expression of either the WKR or triangle up53C STAT5 mutants in the murine myeloid cytokine-dependent cell line 32D inhibited both interleukin-3-dependent proliferation and granulocyte colony-stimulating factor (G-CSF)-dependent differentiation, without induction of apoptosis. Expression of these mutants in primary murine bone marrow inhibited G-CSF-dependent granulocyte colony formation in vitro. These results demonstrate that mutations in distinct regions of STAT5 exert dominant negative effects on cytokine signaling, likely through different mechan

The transfer of genes encoding cytokines into tumor cells has emerged as a new strategy to increase in vivo host reactivity to a variety of tumors. Because gene transfer into tumor cells cannot be easily applied in the clinical setting, we have developed an experimental model of gene transfer into fibroblasts and examined the capacity of these engineered cells to elicit an antitumor immune response. Interleukin-12 (IL-12) is a heterodimeric cytokine with pleiotropic activities presenting strong antitumor and antimetastatic effects in murine models. A bicistronic retroviral vector was constructed that contained the cDNAs encoding both chains (p40 and p35) of murine IL-12 separated by an internal ribosomal entry site sequence. Syngeneic cutaneous fibroblasts obtained from newborn mice and transduced to secrete either IL-12 or IL-2 were injected subcutaneously with B16F0 or B16F1 melanoma cells. The time of tumor occurrence and overall survival of mice were significantly prolonged when B16F1 cells were coinjected with cytokine-producing fibroblasts compared with B16F1 alone or B16F1 together with unmanipulated fibroblasts. Systemic effects were seen in the mice injected with either IL-2- or IL-12-secreting fibroblasts, with the highest proliferation capability and interferon-gamma production observed in vitro from splenocytes from recipients of IL-2-secreting fibroblasts. Injection of IL-2-secreting fibroblasts or coinjection of IL-2- and IL-12-producing fibroblasts resulted in a significant increase of survival in the B16F0 model; in some cases, complete disease eradication was observed. These results suggest that cutaneous fibroblasts represent a target of choice for gene transfer and would be useful in the treatment of minimal residual disease in humans.

BACKGROUND: Mixed allogeneic hematopoietic chimerism has previously been reliably achieved and shown to induce tolerance to fully MHC-mismatched allografts in mice and monkeys. However, the establishment of hematopoietic chimerism has been difficult to achieve in the discordant pig-to-primate xenogeneic model. METHODS: To address this issue, two cynomolgus monkeys were conditioned by whole body irradiation (total dose 300 cGy) 6 and 5 days before the infusion of pig bone marrow (BM). Monkey anti-pig natural antibodies were immunoadsorbed by extracorporeal perfusion of monkey blood through a pig liver, immediately before the intravenous infusion of porcine BM (day 0). Cyclosporine was administered for 4 weeks and 15-deoxyspergualin for 2 weeks. One monkey received recombinant pig cytokines (stem cell factor and interleukin 3) for 2 weeks, whereas the other received only saline as a control. RESULTS: Both monkeys recovered from pancytopenia within 4 weeks of whole body irradiation. Anti-pig IgM and IgG antibodies were successfully depleted by the liver perfusion but returned to pretreatment levels within 12-14 days. Methylcellulose colony assays at days 180 and 300 revealed that about 2% of the myeloid progenitors in the BM of the cytokine-treated recipient were of pig origin, whereas no chimerism was detected in the BM of the untreated control monkey at similar times. The chimeric animal was less responsive by mixed lymphocyte reaction to pig-specific stimulators than the control monkey and significantly hyporesponsive when compared with a monkey that had rejected a porcine kidney transplant. CONCLUSION: To our knowledge, this is the first report of long-term survival of discordant xenogeneic BM in a primate recipient.

STAT5 is a member of the signal transducers and activation of transcription (STAT) family of latent transcription factors activated in a variety of cytokine signaling pathways. We introduced alanine substitution mutations in highly conserved regions of murine STAT5A and studied the mutants for dimerization, DNA binding, transactivation, and dominant negative effects on erythropoietin-induced STAT5-dependent transcriptional activation. The mutations included two near the amino-terminus (W255KR-->AAA and R290QQ-->AAA), two in the DNA-binding domain (E437E-->AA and V466VV-->AAA), and a carboxy-terminal truncation of STAT5A (STAT5A/triangle up53C) analogous to a naturally occurring isoform of rat STAT5B. All of the STAT mutant proteins were tyrosine phosphorylated by JAK2 and heterodimerized with STAT5B except for the WKR mutant, suggesting an important role for this region in STAT5 for stabilizing dimerization. The WKR, EE, and VVV mutants had no detectable DNA-binding activity, and the WKR and VVV mutants, but not EE, were defective in transcriptional induction. The VVV mutant had a moderate dominant negative effect on erythropoietin-induced STAT5 transcriptional activation, which was likely due to the formation of heterodimers that are defective in DNA binding. Interestingly, the WKR mutant had a potent dominant negative effect, comparable to the transactivation domain deletion mutant, triangle up53C. Stable expression of either the WKR or triangle up53C STAT5 mutants in the murine myeloid cytokine-dependent cell line 32D inhibited both interleukin-3-dependent proliferation and granulocyte colony-stimulating factor (G-CSF)-dependent differentiation, without induction of apoptosis. Expression of these mutants in primary murine bone marrow inhibited G-CSF-dependent granulocyte colony formation in vitro. These results demonstrate that mutations in distinct regions of STAT5 exert dominant negative effects on cytokine signaling, likely through different mechan

The intensity of discordant xenograft cellular rejection makes it unlikely that safe doses of immunosuppressive drugs will alone be sufficient to permit long-term survival. We have therefore concentrated our efforts on establishing tolerance to xenogeneic organs through lymphohematopoietic chimerism and the elimination of preformed natural antibodies (nAbs).

A task was undertaken to determine possible inadequacies if FAA design standards and guidelines set forth in the Helicopter Design Advisory Circular (AC 150/5390-2). This report is based upon the results of an analysis of helicopter mishaps which occurred within a 1 mile radius of various landing sites, including heliports, airports, and unimproved sites. NTSB and U.S. Army reports describing mishaps that occurred at or near a facility were used. The focus of the analysis was to determine the manner in which facility design may contribute to mishaps. Particular attention was given to issues concerning the size, obstruction clearance, and adequacy of facility protected airspace and operational areas. Mishap type and location, as well as the applicable design issues, were analyzed from the reports and are discussed. This study concludes that overall, the Heliport Design Advisory Circular provides very good guidelines for heliport design and is a valid instrument. Several areas for possible improvement within the document have been identified. Recommendations include areas addressing obstruction marking, facility maintenance, wind indicator location, and guidelines for operations at airports.

A torsional Kolsky bar (split-Hopkinson bar) was used to deform tubular specimens of AISI 1018 cold rolled steel and AISI 1020 hot rolled steel at a nominal strain of 10 to the 3th power per s. Shear bands were observed to form in both steels and the temperature of the material in the bands was measured by determining the infrared radiation emitted at the metal surface. For this purpose, a linear array of ten indium-antimonide detectors was used to determine temperature history at ten neighboring points lying across the projected path of the shear band. Results showed that shear bands in these low carbon steels are relatively wide, that the maximum temperature rise in the band is about 450 C and that the temperature distribution across the band is consistent with results based on an analysis performed by Shawki and Clifton. The two steels have very different work hardening rates and the strain at which localization is first observed is very different for the two steels: in the cold-rolled steel it occurs at about 15% strain, while in the hot-rolled the strain is nearer 100%. This result also is consistent with predictions based on the analysis.

The purpose of this investigation is to determine the effect of microstructure on the dynamic and quasi-static fracture initiation in a plain carbon steel. For this purpose experiments were conducted on an AISI 1020 steel with either of two microstructures, the first a normalized microstructure, and the second an isothermally transformed (at 550 C) ferritic-pearlitic microstructure. An important distinction between these microstructures is the resulting density and size of grain boundary carbides that are found to initiate cleavage cracks. The high rate fracture toughness testing method employed was developed only recently. Tests were conducted over the temperature range -130C to 65C. The fracture toughness tests were complemented by high rate and quasi-static plasticity tests to provide necessary data on the mechanical behavior of both microstructure over the same temperature range and over approximately the same range of strain rates. Results show that the isothermally transformed microstructure is both stronger and tougher than the normalized microstructure at temperatures below about 18C where cleavage occurs. This appears to be due to the reduction in density of grain boundary carbides. At temperatures above 18C the fracture mode is fibrous in both microstructures and the toughness of the two microstructures are comparable. The quasi-static strength of the isothermally transformed microstructure is higher but the strength at higher strain rates is a little lower at temperatures above 18C. (Author)

Results are presented of a series of experiments performed with two steels to investigate the dependence of flow stress on strain rate and its history. For this purpose quasi-static, dynamic and incremental strain rate tests were conducted on SAE 1020 hot-rolled steel and SAE 1018 cold-rolled steel at room temperature. It is shown that while the flow stress of both steels exhibits a significant strain rate sensitivity, the effect of strain rate history is relatively small in comparison with that generally found in fcc and hcp metals. A comparison is made with results of the work of other investigators. (Author)

A summary of the site development and equipment costs for the development of the complete facility at Kirtland Air Force Base, Albuquerque, New Mexico, is presented and operational requirements are discussed. The funding requirements presented in this volume are divided into two categories of Site Development and Laser Test System. The Site Development items defined in Volume I comprise the Military Construction Program for the facility; the Laser Test System items, defined in Volume II, comprise the RDT and E funding required for the facility. This document is Volume III of a three-volume final report covering the overall study conducted for the Air Force Weapons Laboratory to define the total cost and to specify design criteria for a Chemical Laser Test Facility. The design criteria for the architectural and engineering design of the facility are presented in Volume I and the design requirements for the Laser Test System are presented in Volume II.

The present study examines the effects of within-sequence repetitions for visually presented consonants under conditions of quiet and concurrent articulation (CA). In an immediate serial recall (ISR) procedure, participants wrote down the 6-consonants in the order of original presentation. CA reduced serial recall and abolished the phonological similarity effect.However, the effects of within-trial repetitions were broadly similar under quiet and CA.Specifically, adjacent repetitions facilitated recall of the repeated item, whereas spaced repetitions (separated by 3-intervening items) impaired recall accuracy for the repeated item(i.e. the Ranschburg effect). These data are the first to demonstrate the Ranschburg effect for visual-verbal stimuli under CA.