Regional Specification of the Xenopus Lateral Plate Mesoderm

@font-face { font-family: Times ; }@font-face { font-family: Cambria ; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: Times New Roman ; }div.Section1 { page: Section1; } Successful patterning of the embryo, from establishing the three primary axes to the regional specification of tissue progenitors is essential to generating a viable embryo. The three germ layers in the early embryo undergo patterning through slightly different mechanisms. The tissue of interest to this study is the lateral plate mesoderm (LPM), which will give rise to the lineages of the cardiovascular system and is essential for regional specification of adjacent germ layers. However, little is known about how the LPM itself undergoes regional specification and attains its intitial patterning after gastrulation. Here, I will demonstrate that a complex pattern of gene expression exists across the entire LPM shortly after gastrulation, much earlier than previously recognized. Furthermore, I will use molecular techniques to elucidate the signalling factors involved in the early patterning and regional specification the LPM. I hypothesize that both the retinoic acid (RA) and Fibroblast Growth Factor (FGF) signalling pathways are involved in the LPM regional specification in the neurula stage embryo. Through the use of exogenous modulators of the RA pathway, I will show that RA signalling is essential for patterning the anterior-dorsal and middle LPM domains. Secondly, by addition of a synthetic FGF receptor inhibitor I will demonstrate that FGF signalling is essential for establishing the anterior-ventral and posterior domains of the LPM and functions antagonistically to the RA pathway. I will also show that altering the activity of either of these two signalling pathways affects the specification of the early cardiovascular progenitors, particularly the cardiac and endothelial lineages. Finally I will provide preliminary evidence that one of the early LPM marker genes, Hand1, is necessary for normal cardiovascular development and thus provide a link between the early LPM pattern and later organogenesis. A thorough understanding of the mechanisms behind specifying embryonic lineages is of vital importance for basic biological knowledge, as well as for providing a basis for the emerging field of regenerative medicine, whereby researchers are attempting to generate organ progenitors in vivo to be used for cell therapies

Predictors of the Use of Respite Services by Caregivers of Alzheimer\u27s Patients: Racial and Generational Differences

This research applies one prominent model of service utilization (the Andersen- Newman Model) to better understand the way in which family care givers utilize respite services when caring for older relatives. Specifically, this research examines racial (black and white) and generational (spouse and adult-child) differences between caregivers of Alzheimer\u27s patients and the volume and type of respite services used. The sample (N= 359) is drawn from six Northeast Ohio programs in a consortium that uses a personal computer-based information system to collect intake, assessment, service use, and program satisfaction data from respite clients. Racial differences are found in client attrition and turnover. Results also show adult-child caregivers are the greatest users of day care. These generational differences persist despite the similarities in patient and caregiver need. Fee subsidy and relationship strain between the caregiver and elder predict the amount of service used. Findings suggest that practitioners need to take into account racial and generational factors in addition to traditional patient and caregiver needs when formulating care plans

Fgf is required to regulate anterior-posterior patterning in the Xenopus lateral plate mesoderm

Given that the lateral plate mesoderm (LPM) gives rise to the cardiovascular system, identifying the cascade of signalling events that subdivides the LPM into distinct regions during development is an important question. Retinoic acid (RA) is known to be necessary for establishing the expression boundaries of important transcription factors that demarcate distinct regions along the anterior posterior axis of the LPM. Here, we demonstrate that fibroblast growth factor (Fgf) signalling is also necessary for regulating the expression domains of the same transcription factors (nkx2.5, foxf1, hand1 and sall3) by restricting the RA responsive LPM domains. When Fgf signalling is inhibited in neurula stage embryos, the more posterior LPM expression domains are lost, while the more anterior domains are extended further posterior. The domain changes are maintained throughout development as Fgf inhibition results in similar domain changes in late stage embryos. We also demonstrate that Fgf signalling is necessary for both the initiation of heart specification, and for maintaining heart specification until overt differentiation occurs. Fgf signalling is also necessary to restrict vascular patterning and create a vascular free domain in the posterior end of the LPM that correlates with the expression of hand1. Finally, we show cross talk between the RA and Fgf signalling pathways in the patterning of the LPM. We suggest that this tissue wide patterning event, active during the neurula stage, is an initial step in regional specification of the LPM, and this process is an essential early event in LPM patterning. © 2011 Elsevier Ireland Ltd

Nuclear spin coherence in a quantum wire

We have observed millisecond-long coherent evolution of nuclear spins in a quantum wire at 1.2 K. Local, all-electrical manipulation of nuclear spins is achieved by dynamic nuclear polarization in the breakdown regime of the Integer Quantum Hall Effect combined with pulsed Nuclear Magnetic Resonance. The excitation thresholds for the breakdown are significantly smaller than what would be expected for our sample and the direction of the nuclear polarization can be controlled by the voltage bias. As a four-level spin system, the device is equivalent to two qubits.Comment: 5 pages, 5 figure

MRI of "diffusion" in the human brain: New results using a modified CE-FAST sequence.

“Diffusion-weighted” MRI in the normal human brain and in a patient with a cerebral metastasis is demonstrated. The method employed was a modified CE-FAST sequence with imaging times of only 6-10 s using a conventional 1.5-T whole-body MRI system (Siemens Magnetom). As with previous phantom and animal studies, the use of strong gradients together with macroscopic motions in vivo causes unavoidable artifacts in diffusion-weighted images of the human brain. While these artifacts are shown to be considerably reduced by averaging of 8-16 images, the resulting diffusion contrast is compromised by unknown signal losses due to motion

Dynamical elastic bodies in Newtonian gravity

Well-posedness for the initial value problem for a self-gravitating elastic body with free boundary in Newtonian gravity is proved. In the material frame, the Euler-Lagrange equation becomes, assuming suitable constitutive properties for the elastic material, a fully non-linear elliptic-hyperbolic system with boundary conditions of Neumann type. For systems of this type, the initial data must satisfy compatibility conditions in order to achieve regular solutions. Given a relaxed reference configuration and a sufficiently small Newton's constant, a neigborhood of initial data satisfying the compatibility conditions is constructed

Existence of axially symmetric static solutions of the Einstein-Vlasov system

We prove the existence of static, asymptotically flat non-vacuum spacetimes with axial symmetry where the matter is modeled as a collisionless gas. The axially symmetric solutions of the resulting Einstein-Vlasov system are obtained via the implicit function theorem by perturbing off a suitable spherically symmetric steady state of the Vlasov-Poisson system.Comment: 32 page

Ongoing methane discharge at well site 22/4b (North Sea)and discovery of a spiral vortex bubble plume motion

Highlights • Mega ebullition of biogenic methane from an abandoned offshore gas well, North Sea. • Evidence for midwater bubble plume intrusion, fallback, and short-circuiting of the plume. • Effective trapping of seabed released methane underneath the thermocline. • First observation of a spiral vortex methane plume and marginal turbulences. • Megaplumes appear less efficient in terms of vertical methane transport than previously thought. Abstract First direct evidence for ongoing gas seepage activity on the abandoned well site 22/4b (Northern North Sea, 57°55′ N, 01°38′ E) and discovery of neighboring seepage activity is provided from observations since 2005. A manned submersible dive in 2006 discovered several extraordinary intense seepage sites within a 60 m wide and 20 m deep crater cut into the flat 96 m deep seafloor. Capture and (isotope) chemical analyses of the gas bubbles near the seafloor revealed in situ concentrations of methane between 88 and 90%Vol. with δ13C–CH4 values around −74‰ VPDB, indicating a biogenic origin. Bulk methane concentrations throughout the water column were assessed by 120 Niskin water samples showing up to 400.000 nM CH4 in the crater at depth. In contrast, concentrations above the thermocline were orders of magnitude lower, with a median value of 20 nM. A dye tracer injection into the gas seeps revealed upwelling bubble and water motion with gas plume rise velocities up to ∼1 ms−1 (determined near the seabed). However, the dissolved dye did not pass the thermocline, but returned down to the seabed. Measurements of direct bubble-mediated atmospheric flux revealed low values of 0.7 ± 0.3 kty−1, much less than current state-of-the-art bubble dissolution models would predict for such a strong and upwelling in situ gas bubble flux at shallow water depths (i.e. ∼100 m). Acoustic multibeam water column imaging data indicate a pronounced 200 m lateral intrusion at the thermocline together with high methane concentration at this layer. A partly downward-orientated bubble plume motion is also visible in the acoustic data with potential short-circuiting in accordance to the dye experiment. This observation could partly explain the observed trapping of most of the released gas below the well-established thermocline in the North Sea. Moreover, 3D analyses of the multibeam water column data reveal that the upwelling plume transforms into a spiral expanding vortex while rising through the water column. Such a spiral vortex motion has never been reported before for marine gas seepage and might represent an important process with strong implication on plume dynamics, dissolution behavior, gas escape to the atmosphere, and is considered very important for respective modeling approaches

Understanding early organogenesis using a simplified in situ hybridization protocol in Xenopus

Organogenesis is the study of how organs are specified and then acquire their specific shape and functions during development. The Xenopuslaevis embryo is very useful for studying organogenesis because their large size makes them very suitable for identifying organs at the earliest steps in organogenesis. At this time, the primary method used for identifying a specific organ or primordium is whole mount in situ hybridization with labeled antisense RNA probes specific to a gene that is expressed in the organ of interest. In addition, it is relatively easy to manipulate genes or signaling pathways in Xenopus and in situ hybridization allows one to then assay for changes in the presence or morphology of a target organ. Whole mount in situ hybridization is a multi-day protocol with many steps involved. Here we provide a simplified protocol with reduced numbers of steps and reagents used that works well for routine assays. In situ hybridization robots have greatly facilitated the process and we detail how and when we utilize that technology in the process. Once an in situ hybridization is complete, capturing the best image of the result can be frustrating. We provide advice on how to optimize imaging of in situ hybridization results. Although the protocol describes assessing organogenesis in Xenopus laevis, the same basic protocol can almost certainly be adapted to Xenopus tropicalis and other model systems

Retinoic acid is a key regulatory switch determining the difference between lung and thyroid fates in Xenopus laevis

<p>Abstract</p> <p>Background</p> <p>The lung and thyroid are derived from the anterior endoderm. Retinoic acid and Fgf signalling are known to be essential for development of the lung in mouse but little is known on how the lung and thyroid are specified in <it>Xenopus</it>.</p> <p>Results</p> <p>If either retinoic acid or Fgf signalling is inhibited, there is no differentiation of the lung as assayed by expression of <it>sftpb</it>. There is no change in expression of thyroid gland markers when retinoic acid signalling is blocked after gastrulation and when Fgf signalling is inhibited there is a short window of time where <it>pax2 </it>expression is inhibited but expression of other markers is unaffected. If exogenous retinoic acid is given to the embryo between embryonic stages 20 and 26, the presumptive thyroid expresses <it>sftpb </it>and <it>sftpc</it>, specific markers of lung differentiation and expression of key thyroid transcription factors is lost. When the presumptive thyroid is transplanted into the posterior embryo, it also expresses <it>sftpb</it>, although <it>pax2 </it>expression is not blocked.</p> <p>Conclusions</p> <p>After gastrulation, retinoic acid is required for lung but not thyroid differentiation in <it>Xenopus </it>while Fgf signalling is needed for lung but only for early expression of <it>pax2 </it>in the thyroid. Exposure to retinoic acid can cause the presumptive thyroid to switch to a lung developmental program.</p