348 research outputs found

    β-Perfect Graphs

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    AbstractThe class ofβ-perfect graphs is introduced. We draw a number of parallels between these graphs and perfect graphs. We also introduce some special classes ofβ-perfect graphs. Finally, we show that the greedy algorithm can be used to colour a graphGwith no even chordless cycles using at most 2(χ(G)−1) colours

    On the structure of (pan, even hole)-free graphs

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    A hole is a chordless cycle with at least four vertices. A pan is a graph which consists of a hole and a single vertex with precisely one neighbor on the hole. An even hole is a hole with an even number of vertices. We prove that a (pan, even hole)-free graph can be decomposed by clique cutsets into essentially unit circular-arc graphs. This structure theorem is the basis of our O(nm)O(nm)-time certifying algorithm for recognizing (pan, even hole)-free graphs and for our O(n2.5+nm)O(n^{2.5}+nm)-time algorithm to optimally color them. Using this structure theorem, we show that the tree-width of a (pan, even hole)-free graph is at most 1.5 times the clique number minus 1, and thus the chromatic number is at most 1.5 times the clique number.Comment: Accepted to appear in the Journal of Graph Theor

    Increasing Cervical Cancer Screening in a Hispanic Migrant Farmworker Community through Faith-Based Clinical Outreach

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    Objective: Partnerships between academic medical centers and faith-based community organizations have been associated with increased screening rates in low-income minority women. We describe clinical outcomes of an outreach partnership between a cancer center and a faith-based outreach clinic offering gynecologic screening services in central Florida to increase cervical cancer screening adherence in a priority population of primarily Hispanic farmworker women. Methods: Data sources included a retrospective chart review. This descriptive study examined patterns of cervical cancer screening behavior among the patient population of the faith-based outreach clinic. Results: Findings suggest that among this group of patients, the demographic factors that predict adherence with cervical cancer screening recommendations are number of years having lived in the United States and marital status. Women residing in the United States for more than 5 years were significantly more adherent with cervical cancer screening recommendations compared with women who have resided in the United States for 5 years or less (p = .05), and married women were more likely to be adherent than unmarried women (p = .02). Conclusions: The partnership was successful in increasing cervical cancer screening adherence in this medically underserved population. When enabling barriers to screening adherence are removed through faith-based clinical outreach and engaged continuously for a number of years, uninsured, low-income Hispanic women are more likely to receive recommended preventive services

    A Protein Aggregation Based Test for Screening of the Agents Affecting Thermostability of Proteins

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    To search for agents affecting thermal stability of proteins, a test based on the registration of protein aggregation in the regime of heating with a constant rate was used. The initial parts of the dependences of the light scattering intensity (I) on temperature (T) were analyzed using the following empiric equation: I = Kagg(T−T0)2, where Kagg is the parameter characterizing the initial rate of aggregation and T0 is a temperature at which the initial increase in the light scattering intensity is registered. The aggregation data are interpreted in the frame of the model assuming the formation of the start aggregates at the initial stages of the aggregation process. Parameter T0 corresponds to the moment of the origination of the start aggregates. The applicability of the proposed approach was demonstrated on the examples of thermal aggregation of glycogen phosphorylase b from rabbit skeletal muscles and bovine liver glutamate dehydrogenase studied in the presence of agents of different chemical nature. The elaborated approach to the study of protein aggregation may be used for rapid identification of small molecules that interact with protein targets

    Forced expression of Lmx1b enhances differentiation of mouse ES cells into serotonergic neurons

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    The LIM homeodomain transcription factor Lmx1b is a key factor in the specification of the serotonergic neurotransmitter phenotype. Here, we explored the capacity of Lmx1b to direct differentiation of mouse embryonic stem (mES) cells into serotonergic neurons. mES cells stably expressing human Lmx1b were generated by lentiviral vector infection. Clones expressing Lmx1b at a low level showed increased neurogenesis and elevated production of neurons expressing serotonin, serotonin transporter, Tryptophan hydroxylase 2, and transcription factor Pet1, the landmarks of serotonergic differentiation. To explore the role of Lmx1b in the specification of the serotonin neurotransmission phenotype further, a conditional system making use of a floxed inducible vector targeted into the ROSA26 locus and a hormone-dependent Cre recombinase was engineered. This novel strategy was tested with the reporter gene encoding human placental alkaline phosphatase, and demonstrated its capacity to drive transgene expression in nestin+ neural progenitors and in Tuj1+ neurons. When it was applied to the inducible expression of human Lmx1b, it resulted in elevated expression of serotonergic markers. Treatment of neural precursors with the floor plate signal Sonic hedgehog further enhanced differentiation of Lmx1b-overexpressing neural progenitors into neurons expressing 5-HT, serotonin transporter, Tryptophan hydroxylase 2 and Pet1, when compared to Lmx1b-non expressing progenitors. Together, our results demonstrate the capacity of Lmx1b to specify a serotonin neurotransmitter phenotype when overexpressed in mESC-derived neural progenitors

    Thermal Denaturation and Aggregation of Myosin Subfragment 1 Isoforms with Different Essential Light Chains

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    We compared thermally induced denaturation and aggregation of two isoforms of the isolated myosin head (myosin subfragment 1, S1) containing different “essential” (or “alkali”) light chains, A1 or A2. We applied differential scanning calorimetry (DSC) to investigate the domain structure of these two S1 isoforms. For this purpose, a special calorimetric approach was developed to analyze the DSC profiles of irreversibly denaturing multidomain proteins. Using this approach, we revealed two calorimetric domains in the S1 molecule, the more thermostable domain denaturing in two steps. Comparing the DSC data with temperature dependences of intrinsic fluorescence parameters and S1 ATPase inactivation, we have identified these two calorimetric domains as motor domain and regulatory domain of the myosin head, the motor domain being more thermostable. Some difference between the two S1 isoforms was only revealed by DSC in thermal denaturation of the regulatory domain. We also applied dynamic light scattering (DLS) to analyze the aggregation of S1 isoforms induced by their thermal denaturation. We have found no appreciable difference between these S1 isoforms in their aggregation properties under ionic strength conditions close to those in the muscle fiber (in the presence of 100 mM KCl). Under these conditions kinetics of this process was independent of protein concentration, and the aggregation rate was limited by irreversible denaturation of the S1 motor domain
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