Regulation of dorsal fate in the neuraxis by Wnt-1 and Wnt-3a

Members of the Wnt family of signaling molecules are expressed differentially along the dorsal–ventral axis of the developing neural tube. Thus we asked whether Wnt factors are involved in patterning of the nervous system along this axis. We show that Wnt-1 and Wnt-3a, both of which are expressed in the dorsal portion of the neural tube, could synergize with the neural inducers noggin and chordin in Xenopus animal explants to generate the most dorsal neural structure, the neural crest, as determined by the expression of Krox-20, AP-2, and slug. Overexpression of Wnt-1 or Wnt-3a in the neuroectoderm of whole embryos led to a dramatic increase of slug and Krox-20-expressing cells, but the hindbrain expression of Krox-20 remained unaffected. Enlargement in the neural crest population could occur even when cell proliferation was inhibited. Wnt-5A and Wnt-8, neither of which is expressed in the dorsal neuroectoderm, failed to induce neural crest markers. Overexpression of glycogen synthase kinase 3, known to antagonize Wnt signaling, blocked the neural-crest-inducing activity of Wnt-3a in animal explants and inhibited neural crest formation in whole embryos. We suggest that Wnt-1 and Wnt-3a have a role in patterning the neural tube along its dorsoventral axis and function in the differentiation of the neural crest.

Neural fate of seen and unseen faces in visuospatial neglect: A combined event-related functional MRI and event-related potential study

To compare neural activity produced by visual events that escape or reach conscious awareness, we used event-related MRI and evoked potentials in a patient who had neglect and extinction after focal right parietal damage, but intact visual fields. This neurological disorder entails a loss of awareness for stimuli in the field contralateral to a brain lesion when stimuli are simultaneously presented on the ipsilateral side, even though early visual areas may be intact, and single contralateral stimuli may still be perceived. Functional MRI and event-related potential study were performed during a task where faces or shapes appeared in the right, left, or both fields. Unilateral stimuli produced normal responses in V1 and extrastriate areas. In bilateral events, left faces that were not perceived still activated right V1 and inferior temporal cortex and evoked nonsignificantly reduced N1 potentials, with preserved face-specific negative potentials at 170 ms. When left faces were perceived, the same stimuli produced greater activity in a distributed network of areas including right V1 and cuneus, bilateral fusiform gyri, and left parietal cortex. Also, effective connectivity between visual, parietal, and frontal areas increased during perception of faces. These results suggest that activity can occur in V1 and ventral temporal cortex without awareness, whereas coupling with dorsal parietal and frontal areas may be critical for such activity to afford conscious perception.

Effect Of DNA-dependent protein kinase on the molecular fate of the rAAV2 genome in skeletal muscle

We report here that the DNA-dependent protein kinase (DNA-PK) affects the molecular fate of the recombinant adeno-associated virus (rAAV) genome in skeletal muscle. rAAV-human α1-antitrypsin (rAAV-hAAT) vectors were delivered by intramuscular injection to either C57BL/6 (DNA-PKcs+) or C57BL/6-SCID [severe combined immunodeficient (SCID), DNA-PKcs−] mice. In both strains, high levels of transgene expression were sustained for up to 1 year after a single injection. Southern blot analysis showed that rAAV genomes persisted as linear episomes for more than 1 year in SCID mice, whereas only circular episomal forms were observed in the C57BL/6 strain. These results indicate that DNA-PK is involved in the formation of circular rAAV episomes.

neuralized is essential for a subset of Notch pathway-dependent cell fate decisions during Drosophila eye development

neuralized (neur) is a neurogenic mutant of Drosophila in which many signaling events mediated by the Notch (N) receptor are disrupted. Here, we analyze the role of neur during eye development. Neur is required in a cell-autonomous fashion to restrict R8 and other photoreceptor fates and is involved in lateral inhibition of interommatidial bristles but is not required for induction of the cone cell fate. The latter contrasts with the absolute requirement for Suppressor of Hairless and the Enhancer of split-Complex for cone cell induction. Using gain-of-function experiments, we further demonstrate that ectopic wild-type and truncated Neur proteins can interfere with multiple N-controlled aspects of eye development, including both neur-dependent and neur-independent processes.

The past and the future fate of the universe and the formation of structure in it

The history and the ultimate future fate of the universe as a whole depend on how much the expansion of the universe is decelerated by its own mass. In particular, whether the expansion of the universe will ever come to a halt can be determined from the past expansion. However, the mass density in the universe does not only govern the expansion history and the curvature of space, but in parallel also regulates the growth of hierarchical structure, including the collapse of material into the dense, virialized regions that we identify with galaxies. Hence, the formation of galaxies and their clustered distribution in space depend not only on the detailed physics of how stars are formed but also on the overall structure of the universe. Recent observational efforts, fueled by new large, ground-based telescopes and the Hubble Space Telescope, combined with theoretical progress, have brought us to the verge of determining the expansion history of the universe and space curvature from direct observation and to linking this to the formation history of galaxies.

Using ubiquitin to follow the metabolic fate of a protein.

We describe a method that can be used to produce equimolar amounts of two or more specific proteins in a cell. In this approach, termed the ubiquitin/protein/reference (UPR) technique, a reference protein and a protein of interest are synthesized as a polyprotein separated by a ubiquitin moiety. This tripartite fusion is cleaved, cotranslationally or nearly so, by ubiquitin-specific processing proteases after the last residue of ubiquitin, producing equimolar amounts of the protein of interest and the reference protein bearing a C-terminal ubiquitin moiety. In applications such as pulse-chase analysis, the UPR technique can compensate for the scatter of immunoprecipitation yields, sample volumes, and other sources of sample-to-sample variation. In particular, this method allows a direct comparison of proteins' metabolic stabilities from the pulse data alone. We used UPR to examine the N-end rule (a relation between the in vivo half-life of a protein and the identity of its N-terminal residue) in L cells, a mouse cell line. The increased accuracy afforded by the UPR technique underscores insufficiency of the current "half-life" terminology, because in vivo degradation of many proteins deviates from first-order kinetics. We consider this problem and discuss other applications of UPR.

Cell fate determination in the vertebrate retina.

In the vertebrate central nervous system, the retina has been a useful model for studies of cell fate determination. Recent results from studies conducted in vitro and in vivo suggest a model of retinal development in which both the progenitor cells and the environment change over time. The model is based upon the notion that the mitotic cells within the retina change in their response properties, or "competence", during development. These changes presage the ordered appearance of distinct cell types during development and appear to be necessary for the production of the distinct cell types. As the response properties of the cells change, so too do the environmental signals that the cells encounter. Together, intrinsic properties and extrinsic cues direct the choice of cell fate.

Fate of biological control introductions: monitoring an Australian fungal pathogen of grasshoppers in North America.

In North America there are two generally recognized pathotypes (pathotypes 1 and 2) of the fungus Entomophaga grylli which show host-preferential infection of grasshopper subfamilies. Pathotype 3, discovered in Australia, has a broader grasshopper host range and was considered to be a good biocontrol agent. Between 1989 and 1991 pathotype 3 was introduced at two field sites in North Dakota. Since resting spores are morphologically indistinguishable among pathotypes, we used pathotype-specific DNA probes to confirm pathotype identification in E. grylli-infected grasshoppers collected at the release sites in 1992, 1993, and 1994. In 1992, up to 23% of E. grylli-infected grasshoppers of the subfamilies Melanoplinae, Oedipodinae, and Gomphocerinae were infected by pathotype 3, with no infections > 1 km from the release sites. In 1993, pathotype 3 infections declined to 1.7%. In 1994 grasshopper populations were low and no pathotype 3 infections were found. The frequency of pathotype 3 infection has declined to levels where its long-term survival in North America is questionable. Analyses of biocontrol releases are critical to evaluating the environmental risks associated with these ecological manipulations, and molecular probes are powerful tools for monitoring biocontrol releases.

Fate of a redundant gamma-globin gene in the atelid clade of New World monkeys: implications concerning fetal globin gene expression.

Conclusive evidence was provided that gamma 1, the upstream of the two linked simian gamma-globin loci (5'-gamma 1-gamma 2-3'), is a pseudogene in a major group of New World monkeys. Sequence analysis of PCR-amplified genomic fragments of predicted sizes revealed that all extant genera of the platyrrhine family Atelidae [Lagothrix (woolly monkeys), Brachyteles (woolly spider monkeys), Ateles (spider monkeys), and Alouatta (howler monkeys)] share a large deletion that removed most of exon 2, all of intron 2 and exon 3, and much of the 3' flanking sequence of gamma 1. The fact that two functional gamma-globin genes were not present in early ancestors of the Atelidae (and that gamma 1 was the dispensible gene) suggests that for much or even all of their evolution, platyrrhines have had gamma 2 as the primary fetally expressed gamma-globin gene, in contrast to catarrhines (e.g., humans and chimpanzees) that have gamma 1 as the primary fetally expressed gamma-globin gene. Results from promoter sequences further suggest that all three platyrrhine families (Atelidae, Cebidae, and Pitheciidae) have gamma 2 rather than gamma 1 as their primary fetally expressed gamma-globin gene. The implications of this suggestion were explored in terms of how gene redundancy, regulatory mutations, and distance of each gamma-globin gene from the locus control region were possibly involved in the acquisition and maintenance of fetal, rather than embryonic, expression.

How I Learned to Stop Worrying and Love the Bits: Archival Motivation in the Digital Age

Why do people become archivists? Historically (and anecdotally) it was a deep love of musty, old records that drew people to the profession. While there have been many other motivating forces that inspired would-be archivists, it is most often that one hears of people seeking jobs in archives for love of “the stuff,” as evidenced in Kate Thiemer’s blog post, Honest tips for wannabe archivists (2012). As a result of the continually advancing presence of digitized and born digital archival collections, the physical nature of archival “stuff” is changing. While there remains the physical imprint of digital information on floppy disks, CDs, DVDs, hard drives, and old computers; the aspects of these physical artifacts might not evoke the same visceral pull to the profession as musty, raspy, paper-based documents. In light of this shift in physical presentation of information, we are faced with the question: how does love of archival “stuff” translate to work in digital archives? What is and/or will be the pull to become a digital archivist? To answer these questions, we will perform a survey-based study where we will invite archivists who work with both traditional and digital archival material to answer questions related to the aspects of their work that inspired or motivated them to join the profession. What motivates people to become archivists? What aspects of digital archives do or can potentially motivate people to seek out a career as an archivist? What, if any, motivational factors for becoming a traditional archivist are the same as those for becoming a digital archivist? What, if any, motivational factors for becoming a traditional archivist are different from those for becoming a digital archivist? By answering these questions, we hope to expand the archival discussion on what it means to be an archivist in the digital age. What compelling intrinsic, evidential, or informational values are present in digital archival content that will draw professionals to the field? Are there other values inherent in digital content that are currently unexplored? In our poster, we will present our discussion of the topic, our survey design, and results we have at the time of the Institute. Thiemer, K. (2012). Honest tips for wannabe archivists. Archivesnext blog. Retrieved from http://www.archivesnext.com/?p=2849

Fate and Transport of Naproxen in a Sandy Aquifer Material: Saturated Column Studies and Model Evaluation

Naproxen-C14H14O3 is a nonsteroidal anti-inflammatory drug which has been found at detectable concentrations in wastewater, surface water, and groundwater. Naproxen is relatively hydrophilic and is in anionic form at pH between 6 and 8. In this study, column experiments were performed using an unconsolidated aquifer material from an area near Barcelona (Spain) to assess transport and reaction mechanisms of Naproxen in the aquifer matrix under different pore water fluxes. Results were evaluated using HYDRUS-1D, which was used to estimate transport parameters. Batch sorption isotherms for Naproxen conformed with the linear model with a sorption coefficient of 0.42 (cm3 g−1), suggesting a low sorption affinity. Naproxen breakthrough curves (BTCs) measured in soil columns under steady-state, saturated water flow conditions displayed similar behavior, with no apparent hysteresis in sorption or dependence of retardation (R, 3.85-4.24) on pore water velocities. Soil sorption did not show any significant decrease for increasing flow rates, as observed from Naproxen recovery in the effluent. Sorption parameters estimated by the model suggest that Naproxen has a low sorption affinity to aquifer matrix. Most sorption of Naproxen occurred on the instantaneous sorption sites, with the kinetic sorption sites representing only about 10 to 40% of total sorption.