Benign TdT-positive cells in pediatric and adult lymph nodes: a potential diagnostic pitfall

Benign TdT-positive cells have been documented in a variety of non-hematopoietic tissues. Scant data are however available on their presence in non-neoplastic lymph nodes. This study is aimed to: (i) characterize the presence/distribution of benign TdT-positive cells in pediatric and adult reactive lymph nodes; (ii) define the phenotype and nature of such elements. This retrospective study considered 141 reactive lymph nodes from pediatric and adult patients without history of neoplastic disease. TdT-positive cells were characterized by immunohistochemical and morphometric analyses and their presence was correlated with the clinical-pathological features. The nature of TdT-positive cells was investigated by: (i) double immunostaining for early lymphoid cell markers; and (ii) assessment of TdT expression in fetal lymph nodes. Sparse TdT-positive cells were documented in all pediatric cases and in most (76%) adult lymph nodes. TdT-positive cell density was higher in children than adults (15.9/mm2 versus 8.6/mm2; P<.05). TdT positivity did not correlate with any clinical and histological parameter and double immunostaining disclosed a phenotype compatible with early lymphoid precursors (positivity for CD34, CD10 and variable expression of CD7). A very high TdT-positive cell density (802.4/mm2) was reported in all fetal lymph nodes. In conclusion, TdT-positive cells are a common finding in pediatric and adult lymph nodes. The interstitial distribution and low number of such cells allows for the differential diagnosis with precursor lymphoid neoplasms. The high density in fetal lymph nodes and the phenotype of such cells suggest their belonging to an immature lymphoid subset gradually decreasing with age

Murine terminal deoxynucleotidyl transferase: cellular distribution and response to cortisone

The mouse thymus contains two forms of terminal deoxynucleotidyl transferase (TdT) which are distinguishable by the salt concentration necessary to elute them from a phosphocellulose column, by their distrubtion among the thymocyte subpopulations, and by their sensitivity to cortisone treatment. In the whole thymus the later eluting peak (peak II) is the predominant one with about 3-10% of the total activity appearing in peak I. Both peak I and peak II activities are most sensitively assayed by the polymerization of dGMP onto an oligo(dA) primer. The minor population of thymocytes which is less dense and cortisone-resistant contains a higher specific activity of peak I TdT. The majority of TdT activity is, however, found in the major population of thymocytes which occurs in the center region of a bovine serum albumin gradient and is cortisone-sensitive. A very low level of an activity indistinguishable from peak II TdT activity is also detected in the mouse bone marrow. Other tissues, such as spleen, liver, heart, and brain lack detectable amounts of TdT activity

Enhancing Terminal Deoxynucleotidyl Transferase Activity on Substrates with 3' Terminal Structures for Enzymatic De Novo DNA Synthesis.

Enzymatic oligonucleotide synthesis methods based on the template-independent polymerase terminal deoxynucleotidyl transferase (TdT) promise to enable the de novo synthesis of long oligonucleotides under mild, aqueous conditions. Intermediates with a 3' terminal structure (hairpins) will inevitably arise during synthesis, but TdT has poor activity on these structured substrates, limiting its usefulness for oligonucleotide synthesis. Here, we described two parallel efforts to improve the activity of TdT on hairpins: (1) optimization of the concentrations of the divalent cation cofactors and (2) engineering TdT for enhanced thermostability, enabling reactions at elevated temperatures. By combining both of these improvements, we obtained a ~10-fold increase in the elongation rate of a guanine-cytosine hairpin

TarTar: A Timed Automata Repair Tool

We present TarTar, an automatic repair analysis tool that, given a timed diagnostic trace (TDT) obtained during the model checking of a timed automaton model, suggests possible syntactic repairs of the analyzed model. The suggested repairs include modified values for clock bounds in location invariants and transition guards, adding or removing clock resets, etc. The proposed repairs are guaranteed to eliminate executability of the given TDT, while preserving the overall functional behavior of the system. We give insights into the design and architecture of TarTar, and show that it can successfully repair 69% of the seeded errors in system models taken from a diverse suite of case studies.Comment: 15 pages, 7 figure

Aeroelastic model helicopter rotor testing in the Langley TDT

Wind-tunnel testing of a properly scaled aeroelastic model helicopter rotor is considered a necessary phase in the design development of new or existing rotor systems. For this reason, extensive testing of aeroelastically scaled model rotors is done in the Transonic Dynamics Tunnel (TDT) located at the NASA Langley Research Center. A unique capability of this facility, which enables proper dynamic scaling, is the use of Freon as a test medium. A description of the TDT and a discussion of the benefits of using Freon as a test medium are presented. A description of the model test bed used, the Aeroelastic Rotor Experimental System (ARES), is also provided and examples of recent rotor tests are cited to illustrate the advantages and capabilities of aeroelastic model rotor testing in the TDT. The importance of proper dynamic scaling in identifying and solving rotorcraft aeroelastic problems, and the importance of aeroelastic testing of model rotor systems in the design of advanced rotor systems are demonstrated

A vapor generator for transonic flow visualization

A vapor generator was developed for use in the NASA Langley Transonic Dynamics Tunnel (TDT). Propylene glycol was used as the vapor material. The vapor generator system was evaluated in a laboratory setting and then used in the TDT as part of a laser light sheet flow visualization system. The vapor generator provided satisfactory seeding of the air flow with visible condensate particles, smoke, for tests ranging from low subsonic through transonic speeds for tunnel total pressures from atmospheric pressure down to less than 0.1 atmospheric pressure

The Impact of Agricultural Technology in Sub-Saharan Africa: A Synthesis of Symposium Findings

The Symposium on the Impact of Technology on Agricultural Transformation in Sub-Saharan Africa funded by AID/AFR/ARTS and AID/RD/EID under the Michigan State University Food Security Cooperative Agreements, was held in Washington, D.C., Oct. 14-16, 1992. A primary purpose of the symposium was to present evidence which would either confirm or contradict the perception that the accomplishments of TDT were insufficient to justify continued funding. A secondary objective was to consider the adequacy of available analytical tools for impact assessment. The rate of return (ROR) is the most commonly used valuative measure of investments in technology development and transfer. Examined as a group, the estimated RORs support the proposition that African agricultural research has had people-level impacts, and that these impacts are large enough to justify the level of investment that led to the impacts. An important part of the impact assessment story is the analysis of factors that had a positive or negative effect on the impact of TDT. Five major factors emerged from the studies presented and comments by symposium participants: agroclimatic conditions, civil unrest, research system performance, policy, and markets. Progress has been made in moving forward with the process of TDT, in spite of adverse conditions. This progress includes enhancing the capabilities of national, regional and international institutions to generate new techniques, pushing forward the technology frontier, transferring technology, and increasing productivity both in farm production and post-harvest activities. Activities such as structural adjustment, improvements in agricultural and macroeconomic policy, greater reliance on democracy and capitalism, investments in infrastructure, and a greater willingness to work with the private sector have increased the potential for TDT to have significant impact. Given the importance of raising productivity in agriculture as a step towards agricultural transformation, continued investment in agricultural TDT is merited. The evidence of impact achieved from previous investments shows that those investments have paid off. Coupled with the evidence of beneficial changes in the macroeconomic policy environment in many countries, this provides the basis for expecting that future investments will pay off. What is perhaps unique about the symposium is the movement towards a commodity sector perspective as the next logical step toward including more demand-side considerations in the TDT agenda.International Development, Research and Development/Tech Change/Emerging Technologies, Downloads July 2008 - June 2009: 18,

Wind-Tunnel Survey of an Oscillating Flow Field for Application to Model Helicopter Rotor Testing

A survey was conducted of the flow field produced by the Airstream Oscillator System (AOS) in the Langley Transonic Dynamics Tunnel (TDT). The magnitude of a simulated gust field was measured at 15 locations in the plane of a typical model helicopter rotor when tested in the TDT using the Aeroelastic Rotor Experimental System (ARES) model. These measurements were made over a range of tunnel dynamic pressures typical of those used for an ARES test. The data indicate that the gust field produced by the AOS is non-uniform across the tunnel test section, but should be sufficient to excite a model rotor

Efficacy of Electrical Stimulation Intervention in Treating Adults with Dysphagia: A Systematic Review

Purpose: Dysphagia is a term used for a swallowing disorder resulting from problems with the oral cavity, pharynx, esophagus, or gastroesophageal junction. Dysphagia can have significant impacts on an individual’s quality of life and statistics suggest that nearly 15 million adults in the United States present with swallowing disorders. Common medical complications associated with dysphagia are malnutrition, dehydration, aspiration pneumonia, and even death. Traditional dysphagia treatment (TDT) for adults currently consists of diet modification, compensatory strategies involving postural adjustments, and swallowing exercises to strengthen musculature. The objective of this systematic review is to determine whether electrical stimulation (ES) improves swallowing function in adults with dysphagia. Methodology: Four indexed databases were searched to obtain studies pertaining to the use of ES in dysphagia treatment and its success. Application of inclusionary and exclusionary criteria narrowed the results and relevant studies were selected for this systematic review. Studies were also hand-selected and appraised for validity to ensure minimal bias. Results: Results of the selected studies revealed varying statistically significant effects of ES as a treatment for adults with dysphagia. However, many studies suggest ES is most effective in producing positive outcomes when coupled with TDT. Conclusion: The results of the systematic review suggest efficacy of ES is highest when it is used in conjunction with TDT. Studies with statistically significant results reported on only a minor improvement with ES. None of the studies reported negative outcomes related to ES. Additional research is needed to determine overall efficacy of ES as an evidence-based intervention for adults with dysphagia resulting from various etiologies.https://scholarworks.uvm.edu/csdms/1005/thumbnail.jp