602 research outputs found
Genes and translocations involved in POF
No full textChanges at a single autosomal locus and many X-linked loci have been implicated in women with gonadal dysgenesis [premature ovarian failure (POF) with deficits in ovarian follicles]. For the chromosome 3 locus, a forkhead transcription factor gene (FOXL2) has been identified, in which lesions result in decreased follicles by haploinsufficiency. In contrast, sporadic X; autosomal translocations are distributed at many points on the X, but concentrate in a critical region on Xq. The association of the breakpoints with genes involved in ovarian function is thus far weak (in four analyzed cases) and has not been related to pathology in other POF patients. While many more translocations can be analyzed in detail as the human genome sequence is refined, it remains possible that translocations like X monosomy (Turner syndrome) lead to POF not by interrupting specific genes important in ovarian development, but by causing aberrations in pairing or X-inactivation during folliculogenesis. It is noted that the critical region has unusual features, neighboring the X-inactivation center and including an 18 Mb region of very low recombination. These suggest that chromosome dynamics in the region may be sensitive to structural changes, and when modified by translocations might provoke apoptosis at meiotic checkpoints. Choices among models for the etiology of POF should be feasible based on studies of ovarian follicle development and attrition in mouse models. Studies would prominently include gene expression profiling of developmental-specific pathways in nascent ovaries with controlled levels of Fox12 and interacting proteins, or with defined changes in the X chromosome. Published 2002 Wiley-Liss, Inc
The Assessment of Landsat-8 OLI Atmospheric Correction Algorithms for Inland Waters
No full textThe OLI (Operational Land Imager) sensor on Landsat-8 has the potential to meet the requirements of remote sensing of water color. However, the optical properties of inland waters are more complex than those of oceanic waters, and inland atmospheric correction presents additional challenges. We examined the performance of atmospheric correction (AC) methods for remote sensing over three highly turbid or hypereutrophic inland waters in China: Lake Hongze, Lake Chaohu, and Lake Taihu. Four water-AC algorithms (SWIR (Short Wave Infrared), EXP (Exponential Extrapolation), DSF (Dark Spectrum Fitting), and MUMM (Management Unit Mathematics Models)) and three land-AC algorithms (FLAASH (Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes), 6SV (a version of Second Simulation of the Satellite Signal in the Solar Spectrum), and QUAC (Quick Atmospheric Correction)) were assessed using Landsat-8 OLI data and concurrent in situ data. The results showed that the EXP (and DSF) together with 6SV algorithms provided the best estimates of the remote sensing reflectance (Rrs) and band ratios in water-AC algorithms and land-AC algorithms, respectively. AC algorithms showed a discriminating accuracy for different water types (turbid waters, in-water algae waters, and floating bloom waters). For turbid waters, EXP gave the best Rrs in visible bands. For the in-water algae and floating bloom waters, however, all water-algorithms failed due to an inappropriate aerosol model and non-zero reflectance at 1609 nm. The results of the study show the improvements that can be achieved considering SWIR bands and using band ratios, and the need for further development of AC algorithms for complex aquatic and atmospheric conditions, typical of inland waters
High bone mass from mutation of low-density lipoprotein receptor-related protein 6 (LRP6)
No full textWnt/β-catenin signaling is important for skeletal development and health. Eleven heterozygous gain-of-function missense mutations within the first β-propeller of low-density lipoprotein receptor-related protein 5 (LRP5) are known to cause the autosomal dominant disorder called high bone mass (HBM). In 2019, different heterozygous LRP6 missense mutations were identified in two American families with the HBM phenotype but including absent lateral maxillary and mandibular incisors. We report a 19-year-old Argentinian man referred for “osteopetrosis” and nine years of generalized, medium-intensity bone pain and arthralgias of both knees. His jaw and nasal bridge were broad and several teeth were missing. Routine biochemical testing, including of mineral homeostasis, was normal. Urinary deoxypyridinoline and serum CTX were slightly increased. Radiographic skeletal survey showed diffusely increased radiodensity. DXA revealed substantially elevated BMD Z-scores. Digital orthopantomography confirmed agenesis of his maxillary and mandibular lateral incisors and his second left superior premolar. Cranial magnetic resonance imaging showed diffuse thickening of the calvarium and skull base, dilation of the sheath of the optic nerves containing increased fluid and associated with subtle stenosis of the optic canal, and narrow internal auditory canals. Mutation analyses identified a heterozygous indel mutation in exon 4 of LRP6 involving a single nucleotide change and 6-nucleotide deletion (c.678T > Adel679-684, p.His226Gln-del227-228ProPhe) leading to a missense change and 2-amino acid deletion that would compromise the first β-propeller of LRP6. Experience to date indicates LRP6 HBM is indistinguishable from LRP5 HBM without mutation analysis, although in LRP6 HBM absence of adult lateral incisors may prove to be a unique feature.Fil: Brance, María Lorena. Reumatología y Enfermedades Óseas; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Médicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Brun, Lucas Ricardo Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Médicas; ArgentinaFil: Cóccaro, Nicolás M.. Sanatorio Británico; ArgentinaFil: Aravena, Andrés. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Ósea; ArgentinaFil: Duan, Shenghui. Shriners Hospitals for Children; Estados UnidosFil: Mumm, Steven. Shriners Hospitals for Children; Estados Unidos. Washington University in St. Louis; Estados UnidosFil: Whyte, Michael P.. Shriners Hospitals for Children; Estados Unidos. Washington University in St. Louis; Estados Unido
MEASURING LIPOPROTEIN KINETICS IN ZEBRAFISH TO CHARACTERIZE NEW REGULATORS OF LIPOPROTEIN METABOLISM
No full textLipids are critical for life and require lipoproteins to navigate the aqueous environment of the blood. However, high levels of apolipoprotein B (APOB) containing lipoproteins (B-lps) have been linked to increased cardiovascular disease (CVD) risk. While standard methods for assessing CVD risk focus on lipoprotein levels, understanding the reasons behind elevated B-lp levels can require a closer look at B-lp kinetics. Presently, B-lp turnover studies require the use of radio-labeled isotopes and computational modeling.
Genetic studies continue to identify new genes affecting B-lps, often without mechanistic insight, including the asialoglycoprotein receptor 1 (ASGR1) gene. Human mutations in ASGR1 lower LDL and disproportionally reduce the risk for CVD. To understand how ASGR1 affects B-lps, I identified the zebrafish ortholog asgr1a. Surprisingly, asgr1a mutant adults for two CRISPR-induced alleles exhibited reduced steatosis when fed a Western diet and secreted the excess cholesterol in their feces while not showing any changes in B-lp numbers or sizes.
This led me to suspect that asgr1a might affect B-lp kinetics. Additionally, the lab had identified and characterized mutations in mttpc655 and pla2g12bsa659 that impaired the triglyceride loading of B-lps, resulting in smaller B-lps. Intriguingly, these mutants did not present with impacts on the vasculature or steatosis.
To study lipoprotein turnover in zebrafish, I developed LipoTimer, a fusion protein reporter of the photoconvertible fluorophore Dendra2 to the endogenous locus of apoBb.1, the APOB ortholog of zebrafish. UV light exposure shifts the emission spectrum of Dendra2 from green to red, allowing us to follow red-state ApoB-Dendra2 labeled B-lps. Using the LipoTimer, we discovered that mttpc655 and pla2g12bsa659 mutant larvae have significantly shorter B-lp half-life of whole-body and circulating B-lps. Adapting the LipoTimer assay for juvenile zebrafish, I found that a high-cholesterol diet slows down the B-lps turnover, likely through saturation of lipoprotein lipase.
By adapting LipoTimer for tissue-specific B-lp turnover and adult animal studies, we may uncover the effects of asgr1a on lipoprotein kinetics. LipoTimer’s potential to directly measure B-lp half-life in diverse conditions, mutants, and drug studies makes it a valuable tool for understanding lipoprotein turnover
Survey of plant density tolerance in U.S. maize germplasm
No full textGlobal demand for cereal crops like maize is rising at a rapid pace as the world population expands beyond 7 billion people. To meet these needs, productivity (i.e. grain yield) per unit area must be increased. A survey of U.S. maize germplasm was conducted to identify sources of favorable alleles for plant density tolerance and better understanding the genetics involved. Hybrids created using a genetically diverse set of inbreds representing parentage of key heterotic sub-groups were evaluated at plant densities ranging from 19,000 plants per acre (ppA) to 54,000 ppA. Five categories of traits were hypothesized to be associated with plant density tolerance: photosynthetic capability, growth responses, source-sink relationship, general stress tolerance, and plant architecture. Fifty phenotypic traits from these five categories were evaluated in three environments that differed for levels of moisture availability. The relationship between plant density and grain yield was assessed for each hybrid, with a wide range of responses observed. Five hybrids showed substantial tolerance to plant densities ≥47,000 ppA based on grain yield. Phenotypic trait correlations revealed a subset of traits associated with grain yield. Further analysis provided insight into relationships among traits that ultimately influence grain yield. All 5 categories of traits were found to have an association with grain yield directly and indirectly. Analysis of environments with differing moisture levels suggested that the 5 top-performing hybrids at high plant density have exceptional capacity for light utilization and translation of that energy into kernel mass. Estimates of heritability for grain yield at high plant densities were found to be similar to those at other plant densities, therefore requiring no alteration with breeding strategies used for new and improved maize lines. Results of this work will be used to create plant materials for further characterization of the trait through QTL mapping and candidate gene approaches.Item withdrawn by Mark Zulauf ([email protected]) on 2012-07-17T19:25:55Z
Item was in collections:
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Original Data
Group with Access Administrator
Release Date: 2014-09-18 16:27:16 UTC
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemItem marked as restricted to the 'Administrator' Group (id=1) by Seth Robbins ([email protected]) on 2012-09-18T21:27:24Z
Item is restricted until 2014-09-18T21:27:16ZLimited Restriction Lifted for Item 34813 on 2014-09-18T10:00:47Z
MEASURING LIPOPROTEIN KINETICS IN ZEBRAFISH TO CHARACTERIZE NEW REGULATORS OF LIPOPROTEIN METABOLISM
No full textLipids are critical for life and require lipoproteins to navigate the aqueous environment of the blood. However, high levels of apolipoprotein B (APOB) containing lipoproteins (B-lps) have been linked to increased cardiovascular disease (CVD) risk. While standard methods for assessing CVD risk focus on lipoprotein levels, understanding the reasons behind elevated B-lp levels can require a closer look at B-lp kinetics. Presently, B-lp turnover studies require the use of radio-labeled isotopes and computational modeling.
Genetic studies continue to identify new genes affecting B-lps, often without mechanistic insight, including the asialoglycoprotein receptor 1 (ASGR1) gene. Human mutations in ASGR1 lower LDL and disproportionally reduce the risk for CVD. To understand how ASGR1 affects B-lps, I identified the zebrafish ortholog asgr1a. Surprisingly, asgr1a mutant adults for two CRISPR-induced alleles exhibited reduced steatosis when fed a Western diet and secreted the excess cholesterol in their feces while not showing any changes in B-lp numbers or sizes.
This led me to suspect that asgr1a might affect B-lp kinetics. Additionally, the lab had identified and characterized mutations in mttpc655 and pla2g12bsa659 that impaired the triglyceride loading of B-lps, resulting in smaller B-lps. Intriguingly, these mutants did not present with impacts on the vasculature or steatosis.
To study lipoprotein turnover in zebrafish, I developed LipoTimer, a fusion protein reporter of the photoconvertible fluorophore Dendra2 to the endogenous locus of apoBb.1, the APOB ortholog of zebrafish. UV light exposure shifts the emission spectrum of Dendra2 from green to red, allowing us to follow red-state ApoB-Dendra2 labeled B-lps. Using the LipoTimer, we discovered that mttpc655 and pla2g12bsa659 mutant larvae have significantly shorter B-lp half-life of whole-body and circulating B-lps. Adapting the LipoTimer assay for juvenile zebrafish, I found that a high-cholesterol diet slows down the B-lps turnover, likely through saturation of lipoprotein lipase.
By adapting LipoTimer for tissue-specific B-lp turnover and adult animal studies, we may uncover the effects of asgr1a on lipoprotein kinetics. LipoTimer’s potential to directly measure B-lp half-life in diverse conditions, mutants, and drug studies makes it a valuable tool for understanding lipoprotein turnover
Effects of Reinforcement Surface Morphology on Toughening of Brittle-Matrix Composites
No full textThe mechanical properties of brittle-matrix composites critically depend upon the nature of the
reinforcement/matrix interface. Recent theoretical and experimental work has shown that the
morphology of the reinforcement surface can play a dominant role in determining the toughening
behavior in these materials. In this work, the role of reinforcement surface roughness is
examined both analytically and experimentally. Measurements of the debonding and frictional
sliding of rough fibers in glass matrices, obtained using a modified fiber pullout technique, show
a significant dependence on fiber surface roughness. The effects of surface roughness are
explored further by measuring systematic changes in the fiber sliding behavior with controlled
fiber coatings. The available analytical models of rough fiber sliding are examined to interpret
the experimental results
Computer simulation to guide choice of breeding strategies for maker-aided multiple trait integration in maize
No full textWith the rapid rate of adoption by farmers worldwide of crop varieties containing multiple value-added traits, mainly genetically modified traits, as many as 15 to 20 transgenic events may be offered in new maize hybrids by 2030 (Que et al. 2010; Fraley 2012). Multiple Trait Integration (MTI) is designed to integrate the specific transgenic events conferring the value-added trait phenotypes into the elite genetic package represented by the target hybrid, regaining the performance attributes of the target hybrid along with reliable expression of the value-added traits. From a breeding standpoint, MTI involves four steps: Single Event Introgression, Event Pyramiding, Trait Fixation, and Version Testing. We considered the breeding process to introgress 15 transgenic events into a target maize hybrid, incorporating 8 into the female parent and 7 into the male parent, to design a comprehensive and efficient approach to MTI overall.
Focusing on the first step, Single Event Introgression which is conducted in parallel streams to convert a given recurrent parent for individual events, the primary breeding goal is to minimize residual non-recurrent parent germplasm remaining from the trait donor, especially in the chromosomal proximity to the event (i.e. linkage drag). Setting a defined lower limit of 96.66% recurrent parent (RP) germplasm recovery (i.e. ≤ 120 cM non-recurrent parent germplasm), conversion for 15 events requires the final selections in Single Event Introgression to have < 8 cM total amount of non-recurrent parent germplasm across the genome with ~ 1 cM non-recurrent parent germplasm in the 20 cM region flanking the event. Using computer simulation, we sought to identify optimal breeding strategies for Single Event Introgression in terms of selection scheme, required population size, and selection intensity. In addition, strategies for choice of donor parent to facilitate conversion efficiency and quality were evaluated. Selection schemes classified as three-stage, modified two-stage, and combined selection conducted from BC1 through BC3, BC4, or BC5 were compared using a moderate constant population size. Criteria for evaluating efficiency included amount of total residual non-recurrent parent germplasm, amount of non-recurrent parent germplasm remaining in the chromosomal region flanking the event in the finished conversion, total number of marker data points required, total population size across generations, and total number of generations. One selection scheme successfully met the defined goals for this breeding step. It involved five generations of marker-aided backcrossing, with BC1 through BC3 selected for the event of interest and minimal linkage drag at population size of 600, and BC4 and BC5 selected for the event of interest and recovery of the RP germplasm across the genome at population size of 400; selection intensity was set at 0.01 for all generations. Furthermore, two essential criteria for choosing an optimal donor parent for a given RP were established: introgression history showing reduction of linkage drag to ~ 1 cM in the 20 cM region flanking the event and genetic similarity between the RP and potential donor parents. Computer simulation demonstrated that a ‘quality’ single event conversion can be accomplished earlier than BC5 given a donor parent with modest levels of genetic similarity. This study lays the groundwork for a comprehensive approach to MTI by providing appropriate starting materials with which to proceed with Event Pyramiding and Trait Fixation.
Next, we focused on the second and third steps in MTI: Event Pyramiding and Trait Fixation. Using computer simulation, we aimed to 1) identify an optimal breeding strategy for pyramiding of 8 events into the female RP (and 7 in the male RP), and 2) evaluate breeding strategies for Trait Fixation to create a ‘finished’ conversion of each RP homozygous for all events in an efficient and effective manner. Building on work by Ishii and Yonezawa (2007a), a symmetric crossing/selfing schedule for Event Pyramiding was devised for stacking 8/7 events in a target RP. Trait Fixation breeding strategies considered self-pollination and doubled haploidy approaches to achieve homozygosity as well as seed chipping and tissue sampling approaches to facilitate genotyping. With self-pollination approaches, 2 generations of selfing rather than 1 for Trait Fixation (i.e. ‘F2 enrichment’ as per Bonnett et al. (2005)) were utilized to eliminate bottlenecking due to extremely low frequencies of desired genotypes in the population. The efficiency indicators such as total number of population size across generations (NT), total number of marker data points (MDP), total number of generations (GEN), number of seeds sampled by seed chipping (NSC), and number of plants requiring tissue sampling (NTS), number of pollinations (NP) (i.e. selfing and crossing) were considered in comparisons of breeding strategies. A breeding strategy involving seed chipping and two-generation self-pollination approaches (SC+SELF) was determined to be the most efficient breeding strategy considering GEN and resource requirements such as MDP, NT, NSC, NTS, and NP. Doubled haploid may have limited utility in Trait Fixation for MTI under the defined breeding scenario. This outcome paves the way for optimizing the last step in the MTI process, Version Testing, which involves hybridization of female and male RP conversions to create versions of the converted hybrid for performance evaluation and commercial release.Item withdrawn by Mark Zulauf ([email protected]) on 2012-07-19T13:12:25Z
Item was in collections:
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Original Data
Group with Access Administrator
Release Date: 2014-09-18 16:27:16 UTC
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemItem marked as restricted to the 'Administrator' Group (id=1) by Seth Robbins ([email protected]) on 2012-09-18T21:27:31Z
Item is restricted until 2014-09-18T21:27:16ZLimited Restriction Lifted for Item 34838 on 2014-09-18T10:01:02Z
Interface Design in Brittle-Brittle Systems
No full textIn brittle matrix composites both ceramic, intermetallic, and cement-based, design of the fiber-matrix
interface is key to achieving high composite toughness. In this paper we explore first, a
method for accurately determining interfacial properties and second, the influence of physical
and chemical aspects of the fiber-matrix interface which influence fracture toughness of the
composite.
A modified fiber pullout technique has been developed which allows direct experimental
evaluation of the force-displacement relation for a crack bridging fiber. The technique allows
continuous, accurate measurement of stable, progressive debonding and frictional sliding.
Coupled with an appropriate analysis, the test provides a quantitative determination of
interfacial properties relevant to the toughening of brittle materials.
Among the parameters of influence in determining interfacial properties, and consequently,
composite toughness, are interface toughness, surface roughness, residual stress state, and
coefficient of friction. Each of these can be altered by use of coatings or surface modifications.
Examples of each will be reviewed in a variety of brittle systems
Lithuania's Taiwan policy: navigating the EU-China dynamic
No full textThe author examines what values and messages appeared in the press releases of Lithuania and the European Union in the period from January 1, 2019 to January 1, 2024 related to the one-China policy which is a one of the frameworks under which the of the European Union's Common Security and Defence Policy operates. In order to research the topic, the following research questions were asked: 1. To what extent do Lithuania and the European Union present coherent or divergent statements on Taiwan? 2. How did the EU address Lithuania's move within the framework of its relations with China?
In the empirical part of the work, qualitative content analysis was used and a coding table was created to sort the data. There were 103 press releases and official statements in the sample of this master thesis, of which 49 were press releases from Lithuanian and 54 from European Union agencies. As a result of the work, the tonality, main messages and values were dissected and analysed. The analysis also included the application of two small state theories (Long, 2005) (Nasra, 2011) and contexualising the statements through them
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