@misc{petitte_liu_yang_2004, title={Avian pluripotent stem cells}, volume={121}, ISSN={["1872-6356"]}, url={http://europepmc.org/abstract/med/15296979}, DOI={10.1016/j.mod.2004.05.003}, abstractNote={Pluripotent embryonic stem cells are undifferentiated cells capable of proliferation and self-renewal and have the capacity to differentiate into all somatic cell types and the germ line. They provide an in vitro model of early embryonic differentiation and are a useful means for targeted manipulation of the genome. Pluripotent stem cells in the chick have been derived from stage X blastoderms and 5.5 day gonadal primordial germ cells (PGCs). Blastoderm-derived embryonic stem cells (ESCs) have the capacity for in vitro differentiation into embryoid bodies and derivatives of the three primary germ layers. When grafted onto the chorioallantoic membrane, the ESCs formed a variety of differentiated cell types and attempted to organize into complex structures. In addition, when injected into the unincubated stage X blastoderm, the ESCs can be found in numerous somatic tissues and the germ line. The potential give rise to somatic and germ line chimeras is highly dependent upon the culture conditions and decreases with passage. Likewise, PGC-derived embryonic germ cells (EGCs) can give rise to simple embryoid bodies and can undergo some differentiation in vitro. Interestingly, chicken EG cells contribute to somatic lineages when injected into the stage X blastoderm, but only germ line chimeras have resulted from EGCs injected into the vasculature of the stage 16 embryo. To date, no lines of transgenic chickens have been generated using ESCs or EGCs. Nevertheless, progress towards the culture of avian pluripotent stem cells has been significant. In the future, the answers to fundamental questions regarding segregation of the avian germ line and the molecular basis of pluripotency should foster the full use of avian pluripotent stem cells.}, number={9}, journal={MECHANISMS OF DEVELOPMENT}, author={Petitte, JN and Liu, G and Yang, Z}, year={2004}, month={Sep}, pages={1159–1168} }
 @article{nobles_yarian_liu_guenther_agris_2002, title={Highly conserved modified nucleosides influence Mg2+-dependent tRNA folding}, volume={30}, ISSN={["0305-1048"]}, DOI={10.1093/nar/gkf595}, abstractNote={Transfer RNA structure involves complex folding interactions of the TPsiC domain with the D domain. However, the role of the highly conserved nucleoside modifications in the TPsiC domain, rT54, Psi55 and m5C49, in tertiary folding is not understood. To determine whether these modified nucleosides have a role in tRNA folding, the association of variously modified yeast tRNA(Phe) T-half molecules (nucleosides 40-72) with the corresponding unmodified D-half molecule (nucleosides 1-30) was detected and quantified using a native polyacrylamide gel mobility shift assay. Mg2+ was required for formation and maintenance of all complexes. The modified T-half folding interactions with the D-half resulted in K(d)s (rT54 = 6 +/- 2, m5C49 = 11 +/- 2, Psi55 = 14 +/- 5, and rT54,Psi55 = 11 +/- 3 microM) significantly lower than that of the unmodified T-half (40 +/- 10 microM). However, the global folds of the unmodified and modified complexes were comparable to each other and to that of an unmodified yeast tRNA(Phe) and native yeast tRNA(Phe), as determined by lead cleavage patterns at U17 and nucleoside substitutions disrupting the Levitt base pair. Thus, conserved modifications of tRNA's TPsiC domain enhanced the affinity between the two half-molecules without altering the global conformation indicating an enhanced stability to the complex and/or an altered folding pathway.}, number={21}, journal={NUCLEIC ACIDS RESEARCH}, author={Nobles, KN and Yarian, CS and Liu, G and Guenther, RH and Agris, PF}, year={2002}, month={Nov}, pages={4751–4760} }
 @article{liu_janowitz_kamykowski_2001, title={Influence of environmental nutrient conditions on Gymnodinium breve (Dinophyceae) population dynamics: a numerical study}, volume={213}, ISSN={["1616-1599"]}, DOI={10.3354/meps213013}, abstractNote={A model of Gymnodinium breve population dynamics modified from Liu et al. (2001; Mar Ecol Prog Ser 210:101-124) is used to investigate the influence of various nutrient conditions on the population increase of an alongshore population filament of G. breve cells as it moves onshore across a continental shelf. The environmental conditions in the model are derived from measure- ments or theory applicable to bloom development on the west Florida shelf. The simulations indicate that the potential nutrient input patterns here represented by nitrogen sources on the shelf, i.e., off- shore, mid-shelf and coastal upwellings, a Trichodesmium-released surface nitrogen source associ- ated with multi-nutrient ocean fertilization by air-borne dust input, and a coastal surface plume are all eligible to trigger and/or support a G. breve bloom. However, the occurrence, timing, location, duration, and intensity of the bloom are determined by nitrogen concentration, input location, and temporal availability. Some nitrogen support at the offshore initiation stage of population growth may induce earlier bloom development, but without additional nitrogen input in coastal regions, the bloom may not fully develop. As long as the nitrogen is available continuously from offshore through coastal regions, a G. breve population can develop into a fish-killing intensity (1 to 2.5 × 10 5 cells l -1 ) in a month or so from a background concentration of <1000 cells l -1 with a maximum growth rate of ~0.16 doublings d -1 . An explosive growth stage is not present for the total population in the simula- tions in which fish-killing cell concentrations are developed in 30 d. However the illusion of explosive growth may be created by the first appearance of a high G. breve population density at the surface late in bloom development. In some cases, daily averaged surface concentration can increase by a factor of 10 in 2 d and increase from a background level of 500 cells l -1 to bloom levels of 10 4 cells l -1 in 8 d due primarily to surface accumulation resulting from appropriately directed swimming behav- ior. This numerical investigation further demonstrates that the vertical migration of G. breve can play a critical role not only in the efficient utilization of natural resources, but also in the population dis- tribution.}, journal={MARINE ECOLOGY PROGRESS SERIES}, author={Liu, G and Janowitz, GS and Kamykowski, D}, year={2001}, pages={13–37} }