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1.
Tuba Topal Zhenzhen Fan Laura Y. Deng Paul H. Krebsbach Cheri X. Deng 《Advanced Biosystems》2019,3(10)
Mechanical forces play important roles in human embryonic stem cell (hESC) differentiation. To investigate the impact of dynamic mechanical forces on neural induction of hESCs, this study employs acoustic tweezing cytometry (ATC) to apply cyclic forces/strains to hESCs by actuating integrin‐bound microbubbles using ultrasound pulses. Accelerated neural induction of hESCs is demonstrated as the result of combined action of ATC and neural induction medium (NIM). Specifically, application of ATC for 30 min followed by culture in NIM upregulates neuroecdoderm markers Pax6 and Sox1 as early as 6 h after ATC, and induces neural tube‐like rosette formation at 48 h after ATC. In contrast, no changes are observed in hESCs cultured in NIM without ATC treatment. In the absence of NIM, ATC application decreases Oct4, but does not increase Pax6 and Sox1 expression, nor does it induce neural rossette formation. The effects of ATC are abolished by inhibition of FAK, myosin activity, and RhoA/ROCK signaling. Taken together, the results reveal a synergistic action of ATC and NIM as an integrated mechanobiology mechanism that requires both integrin‐targeted cyclic forces and chemical factors for accelerated neural induction of hESCs. 相似文献
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Cheri A. Budzynski Rosemary Strasser Verner P. Bingman 《Ethology : formerly Zeitschrift fur Tierpsychologie》1998,104(2):111-118
There is debate over whether homing pigeons, Columba livia, use olfactory information as part of their navigational map. Antagonists of the theory argue that homing deficits noted in anosmic pigeons may be due to a non-specific impairment in general information processing. In Experiment I, we present data from a modest investigation describing the typical navigational deficits that occur following zinc sulphate-mediated anosmia. Our results are consistent with previous experiments that noted impairments in homing performance from unfamiliar locations of anosmic pigeons. Experiment II is a critical experiment that involved a spatial working memory paradigm; this paradigm consisted of testing zinc sulphate-treated birds in a forced-choice alternation task in a T-maze. This experiment allowed us to determine whether anosmic pigeons were impaired in memory performance, a robust measure of general information processing. There were no differences between the last day of training and a subsequent-test day when pigeons received an intranasal injection of zinc sulphate. This experiment suggests that zinc sulphate anosmia does not impair general information processing, supporting the hypothesis that homing pigeons use olfactory cues when homing from unfamiliar locations. 相似文献
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Cheri Gratto‐Trevor Susan M. Haig Mark P. Miller Thomas D. Mullins Sidney Maddock Erin Roche Predensa Moore 《Journal of Field Ornithology》2016,87(1):29-41
Most of the known wintering areas of Piping Plovers (Charadrius melodus) are along the Atlantic and Gulf coasts of the United States and into Mexico, and in the Caribbean. However, 1066 threatened/endangered Piping Plovers were recently found wintering in The Bahamas, an area not previously known to be important for the species. Although representing about 27% of the birds counted during the 2011 International Piping Plover Winter Census, the location of their breeding site(s) was unknown. Thus, our objectives were to determine the location(s) of their breeding site(s) using molecular markers and by tracking banded individuals, identify spring and fall staging sites, and examine site fidelity and survival. We captured and color‐banded 57 birds in January and February 2010 in The Bahamas. Blood samples were also collected for genetic evaluation of the likely subspecies wintering in The Bahamas. Band re‐sightings and DNA analysis revealed that at least 95% of the Piping Plovers wintering in The Bahamas originated on the Atlantic coast of the United States and Canada. Re‐sightings of birds banded in The Bahamas spanned the breeding distribution of the species along the Atlantic coast from Newfoundland to North Carolina. Site fidelity to breeding and wintering sites was high (88–100%). Spring and fall staging sites were located along the Atlantic coast of the United States, with marked birds concentrating in the Carolinas. Our estimate of true survival for the marked birds was 0.71 (95% CI: 0.61–0.80). Our results indicate that more than one third of the Piping Plover population that breeds along the Atlantic coast winters in The Bahamas. By determining the importance of The Bahamas to the Atlantic subspecies of Piping Plovers, future conservation efforts for these populations can be better focused on where they are most needed. 相似文献
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Abstract We have empirically tested limits of the magnitude of multiple time steps in molecular dynamics simulations of aqueous systems, and the extent to which these offer a means to shorten computation time. Three different steps were employed, δ0t for calculation of “bonded” forces, δ1t for calculations of short-range (< 6 Å) non-bonded forces, and δ2t for long-range (< 10 Å) non-bonded forces. Each longer step was a multiple of the shortest one. The leap-frog integration algorithm was used with SHAKE for restraint of all bond lengths and water molecules. For a system of SPC water molecules, calculation of short-range non-bonded forces could be done with a time step δ1t = 10 fs, without appreciable change of the average temperature and energy, radial distribution function or diffusion coefficient. These properties were found to be insensitive to the inclusion of long-range non-bonded forces. A multiple-step protocol with δ0t = 2, δ1t = 4 and δ2t = 16 fs has been compared with a single-step procedure with δt 2 fs for small polypeptides in water. The exploration of conformation space, with crossing of low energy barriers, was tested with the glycine dipeptide and was found to proceed at similar rates. Mean, hysteresis and statistical error of the free energy for changing alanine to α-amino butyric acid in the dipeptide, calculated by the slow-growth method, proved independent of the cutoff distance or exact protocol, within 1 kJ/mol. In conclusion, we recommend, instead of use of a single time step of 2 fs at a 10 Å cutoff, use of a time step δt = 4 fs for short-range nonbonded forces and a time step δ2t = 16 fs for long-range nonbonded forces for a 60% reduction of computation time. 相似文献
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Han YW Ikegami A Rajanna C Kawsar HI Zhou Y Li M Sojar HT Genco RJ Kuramitsu HK Deng CX 《Journal of bacteriology》2005,187(15):5330-5340
Fusobacterium nucleatum is a gram-negative anaerobe that is prevalent in periodontal disease and infections of different parts of the body. The organism has remarkable adherence properties, binding to partners ranging from eukaryotic and prokaryotic cells to extracellular macromolecules. Understanding its adherence is important for understanding the pathogenesis of F. nucleatum. In this study, a novel adhesin, FadA (Fusobacterium adhesin A), was demonstrated to bind to the surface proteins of the oral mucosal KB cells. FadA is composed of 129 amino acid (aa) residues, including an 18-aa signal peptide, with calculated molecular masses of 13.6 kDa for the intact form and 12.6 kDa for the secreted form. It is highly conserved among F. nucleatum, Fusobacterium periodonticum, and Fusobacterium simiae, the three most closely related oral species, but is absent in the nonoral species, including Fusobacterium gonidiaformans, Fusobacterium mortiferum, Fusobacterium naviforme, Fusobacterium russii, and Fusobacterium ulcerans. In addition to FadA, F. nucleatum ATCC 25586 and ATCC 49256 also encode two paralogues, FN1529 and FNV2159, each sharing 31% identity with FadA. A double-crossover fadA deletion mutant, F. nucleatum 12230-US1, was constructed by utilizing a novel sonoporation procedure. The mutant had a slightly slower growth rate, yet its binding to KB and Chinese hamster ovarian cells was reduced by 70 to 80% compared to that of the wild type, indicating that FadA plays an important role in fusobacterial colonization in the host. Furthermore, due to its uniqueness to oral Fusobacterium species, fadA may be used as a marker to detect orally related fusobacteria. F. nucleatum isolated from other parts of the body may originate from the oral cavity. 相似文献
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Anwesha Sanyal Andy J. Chen Ernesto S. Nakayasu Cheri S. Lazar Erica A. Zbornik Carolyn A. Worby Antonius Koller Seema Mattoo 《The Journal of biological chemistry》2015,290(13):8482-8499
The maintenance of endoplasmic reticulum (ER) homeostasis is a critical aspect of determining cell fate and requires a properly functioning unfolded protein response (UPR). We have discovered a previously unknown role of a post-translational modification termed adenylylation/AMPylation in regulating signal transduction events during UPR induction. A family of enzymes, defined by the presence of a Fic (filamentation induced by cAMP) domain, catalyzes this adenylylation reaction. The human genome encodes a single Fic protein, called HYPE (Huntingtin yeast interacting protein E), with adenylyltransferase activity but unknown physiological target(s). Here, we demonstrate that HYPE localizes to the lumen of the endoplasmic reticulum via its hydrophobic N terminus and adenylylates the ER molecular chaperone, BiP, at Ser-365 and Thr-366. BiP functions as a sentinel for protein misfolding and maintains ER homeostasis. We found that adenylylation enhances BiP''s ATPase activity, which is required for refolding misfolded proteins while coping with ER stress. Accordingly, HYPE expression levels increase upon stress. Furthermore, siRNA-mediated knockdown of HYPE prevents the induction of an unfolded protein response. Thus, we identify HYPE as a new UPR regulator and provide the first functional data for Fic-mediated adenylylation in mammalian signaling. 相似文献
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Kari O. Raivio Cheri S. Lazar Michael A. Becker 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,678(1):58-64
During the growth cycle of normal fibroblasts and of fibroblasts deficient in glucose-6-phosphate dehydrogenase activity, the concentration of 5-phosphoribosyl-1-pyrophosphate and of Pi, as well as the activity of 5-phosphoribosyl-1-pyrophosphate synthetase, decreased to stable values in confluent cultures. A high degree of correlation (0.89 and 0.91 for two normal and 0.69 for one glucose-6-phosphate dehydrogenase-deficient cell strain, respectively) was shown between intracellular Pi and 5-phosphoribosyl-1-pyrophosphate concentrations under varying culture and incubation conditions. 5-phosphoribosyl-1-pyrophosphate concentrations were elevated in normal fibroblasts incubated with methylene blue only if intracellular Pi levels were high. Neither methylene blue nor 6-aminonicotinamide, singly, affected intracellular Pi concentrations. However, when normal cells were pretreated with 6-aminonicotinamide and then with methylene blue, intracellular Pi decreased, 5-phosphoribosyl-1-pyrophosphate was depleted, and its rate of generation decreased. Under similar conditions, glucose-6-phosphate dehydrogenase-deficient fibroblasts maintained unaltered Pi levels, and 5-phosphoribosyl-1-pyrophosphate concentration and generation were slightly increased. The decrease in intracellular Pi in normal cells after the combined treatment was commensurate with an accumulation of 6-phosphogluconate, which did not take place in mutant cells. The changes in 5-phosphoribosyl-1-pyrophosphate synthesis, whether due to the stage of growth or various experimental manipulations, were always concordant with changes in intracellular Pi level. The regulatory role of Pi is consistent with the known enzymic properties of 5-phosphoribosyl-1-pyrophosphate synthetase. 相似文献
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Sorrells TR Kuritzky LY Kauhanen PG Fitzgerald K Sturgis SJ Chen J Dijamco CA Basurto KN Gordon DM 《PloS one》2011,6(4):e18717
The invasive Argentine ant (Linepithema humile) is established worldwide and displaces native ant species. In northern California, however, the native winter ant (Prenolepis imparis) persists in invaded areas. We found that in aggressive interactions between the two species, P. imparis employs a potent defensive secretion. Field observations were conducted at P. imparis nest sites both in the presence and absence of L. humile. These observations suggested and laboratory assays confirmed that P. imparis workers are more likely to secrete when outnumbered by L. humile. Workers of P. imparis were also more likely to secrete near their nest entrances than when foraging on trees. One-on-one laboratory trials showed that the P. imparis secretion is highly lethal to L. humile, causing 79% mortality. The nonpolar fraction of the secretion was chemically analyzed with gas chromatography/mass spectrometry, and found to be composed of long-chain and cyclic hydrocarbons. Chemical analysis of dissected P. imparis workers showed that the nonpolar fraction is derived from the Dufour's gland. Based on these conclusions, we hypothesize that this chemical defense may help P. imparis to resist displacement by L. humile. 相似文献