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1.
Ethan R. Block Michael A. Tolino Jennifer S. Lozano Kira L. Lathrop Rebecca S. Sullenberger Abigail R. Mazie Jes K. Klarlund 《Molecular biology of the cell》2010,21(13):2172-2181
The ability of epithelia to migrate and cover wounds is essential to maintaining their functions as physical barriers. Wounding induces many cues that may affect the transition to motility, including the immediate mechanical perturbation, release of material from broken cells, new interactions with adjacent extracellular matrix, and breakdown of physical separation of ligands from their receptors. Depending on the exact nature of wounds, some cues may be present only transiently or insignificantly. In many epithelia, activation of the epidermal growth factor receptor (EGFR) is a central event in induction of motility, and we find that its continuous activation is required for progression of healing of wounds in sheets of corneal epithelial cells. Here, we examine the hypothesis that edges, which are universally and continuously present in wounds, are a cue. Using a novel culture model we find that their presence is sufficient to cause activation of the EGFR and increased motility of cells in the absence of other cues. Edges that are bordered by agarose do not induce activation of the EGFR, indicating that activation is not due to loss of any specific type of cell–cell interaction but rather due to loss of physical constraints. 相似文献
2.
We have compared regeneration proficiency for cultured explants from different tissues of different ecotypes ofArabidopsis thaliana. Proficiency varies widely with both tissue and ecotype, and is highest when the flux of light during regeneration is low. Analysis of F1 hybrids suggests that high proficiency is dominant to low proficiency. 相似文献
3.
Ethan P. White 《Ecology letters》2004,7(4):329-336
The species–time relationship (STR) is a macroecological pattern describing the increase in the observed species richness with the length of time censused. Understanding STRs is important for understanding the ecological processes underlying temporal turnover and species richness. However, accurate characterization of the STR has been hampered by the influence of sampling. I analysed STRs for 521 breeding bird survey communities. I used a model of sampling effects to demonstrate that the increase in richness was not due exclusively to sampling. I estimated the time scale at which ecological processes became dominant over sampling effects using a two‐phase model combining a sampling phase and either a power function or logarithmic ecological phase. These two‐phase models performed significantly better than sampling alone and better than simple power and logarithmic functions. Most community dynamics were dominated by ecological processes over scales <5 years. This technique provides an example of a rigorous, quantitative approach to separating sampling from ecological processes. 相似文献
4.
Haskell Andrew; Nadel Ethan R.; Stachenfeld Nina S.; Nagashima Kei; Mack Gary W. 《Journal of applied physiology》1997,83(2):407-413
Haskell, Andrew, Ethan R. Nadel, Nina S. Stachenfeld, KeiNagashima, and Gary W. Mack. Transcapillary escape rate of albuminin humans during exercise-induced hypervolemia. J. Appl. Physiol. 83(2): 407-413, 1997.To test thehypotheses that plasma volume (PV) expansion 24 h after intenseexercise is associated with reduced transcapillary escape rate ofalbumin (TERalb) and that localchanges in transcapillary forces in the previously active tissues favorretention of protein in the vascular space, we measured PV,TERalb, plasma colloid osmoticpressure (COPp), interstitialfluid hydrostatic pressure (Pi), and colloid osmotic pressure in legmuscle and skin and capillary filtration coefficient (CFC) in the armand leg in seven men and women before and 24 h after intense uprightcycle ergometer exercise. Exercise expanded PV by 6.4% at 24 h (43.9 ± 0.8 to 46.8 ± 1.2 ml/kg, P < 0.05) and decreased total protein concentration (6.5 ± 0.1 to6.3 ± 0.1 g/dl, P < 0.05) andCOPp (26.1 ± 0.8 to 24.3 ± 0.9 mmHg, P < 0.05), although plasmaalbumin concentration was unchanged. TERalb tended to decline (8.4 ± 0.5 to 6.5 ± 0.7%/h, P = 0.11) and was correlated with the increase in PV(r = 0.69,P < 0.05). CFC increased in the leg(3.2 ± 0.2 to 4.3 ± 0.5 µl · 100 g1 · min1 · mmHg1,P < 0.05), and Pi showed a trend toincrease in the leg muscle (2.8 ± 0.7 to 3.8 ± 0.3 mmHg, P = 0.08). These datademonstrate that TERalb isassociated with PV regulation and that local transcapillary forcesin the leg muscle may favor retention of albumin in the vascular spaceafter exercise. 相似文献
5.
Sublocalization of an Ataxia-Telangiectasia Gene Distal to D11S384 by Ancestral Haplotyping In Costa Rican Families 总被引:8,自引:4,他引:4
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Nancy Uhrhammer Ethan Lange Oscar Porras Arash Naeim Xiaoguang Chen Sepideh Sheikhavandi Sujata Chiplunkar Lan Yang Sugandha Dandekar Teresa Liang Nima Patel Sharon Teraoka Nitin Udar Nidia Calvo Patrick Concannon Kenneth Lange Richard A. Gatti 《American journal of human genetics》1995,57(1):103-111
In an effort to localize a gene for ataxia-telangiectasia (A-T), we have genotyped 27 affected Costa Rican families, with 13 markers, in the chromosome 11q22-23 region. Significant linkage disequilibrium was detected for 9/13 markers between D11S1816 and D11S1391. Recombination events observed in these pedigrees places A-T between D11S1819 and D11S1960. One ancestral haplotype is common to 24/54 affected chromosomes and roughly two-thirds of the families. Inferred (ancestral) recombination events involving this common haplotype in earlier generations suggest that A-T is distal to D11S384 and proximal to D11S1960. Several other common haplotypes were identified, consistent with multiple mutations in a single gene. When considered together with all other evidence, this study further sublocalizes the major A-T locus to ≈200 kb, between markers S384 and S535. 相似文献
6.
We have investigated primary and secondary responses of mouse splenic T cells to strong mixed lymphocyte stimulating antigens controlled by theMls locus using MHC-identical mixtures of cells. Our studies show that strong primaryMls-locus specific responses involve recognition of self I-A antigens, since BUdR and light suicide or F1 into parent radiation bone-marrow chimeras both demonstrate a preference of unprimed F1 T cells to respond to Mis-locus antigens associated with one parent's MHC antigens. Furthermore, conventional anti-I-A antisera and monoclonal anti-I-A antibody both inhibitMls-locus responses in an MHC-specific manner. Finally, as is typical of T cells responding to I-A antigens or to nominal antigens associated with self I-A,Mlslocus responses are mediated by Lyt-1+, 2– cells. One striking finding in these studies was the very high frequency of cells capable of responding to Mls-locus antigens, the highest being 1/300 splenic T cells. This plus evidence for recruitment during primaryMls-locus responses may account for reports of a lack ofI-A restriction in secondary anti-Mls locus responses to strong Mls-locus antigens, a finding with which we concur. The possibility that these secondary responses between noncongenic strains of mice may be directed at other genetic loci is also discussed. These experiments leave open the question of the biological role of theMls-locus and of the very large number of T cells reactive to it.Abbreviations used in this paper MHC
Major histocompatibility complex
- MIg
Mouse immunoglobulin
- MLC
Mixed lymphocyte culture
- TCGF
T-cell growth factor 相似文献
7.
Ethan Akin 《Mathematical biosciences》1980,50(3-4):239-250
In the dynamics of an evolutionary game an equilibrium in which all strategy types occur is called an interior equilibrium. Interior equilibria fail to exist only when there is domination among the strategy types. 相似文献
8.
Linkage of the gene controlling the synthesis of the fourth component of complement to the major histocompatibility complex of the guinea pig 总被引:1,自引:1,他引:0
C4-deficient (C4D) guinea pigs are lacking in C4 synthesis, a condition that appears to be caused by a structural gene defect. This defect is inherited as a simple autosomal recessive trait. We have demonstrated linkage between C4D and the major histocompatibility complex of the guinea pig (GPLA). Inbred C4D and inbred strain 13 guinea pigs appear to have the same GPLA haplotype. The use of these two strains should provide an animal model for reconstitution studies of C4 synthesis and for studied exploring the possible role of C4 in cellular and humoral immune responses.Abbreviations used in this paper are C4D
deficiency of the fourth component of complement
- MHC
major histocompatibility complex
- GPLA
major histocompatibility complex of the guinea pig
- MLC
mixed lymphocyte culture 相似文献
9.
Samantha Swank Ethan Elazegui Sophia Janidlo Thomas J. Sanger Michael A. Bell Yoel E. Stuart 《Ecology and evolution》2022,12(7)
Loss and reduction in paired appendages are common in vertebrate evolution. How often does such convergent evolution depend on similar developmental and genetic pathways? For example, many populations of the threespine stickleback and ninespine stickleback (Gasterosteidae) have independently evolved pelvic reduction, usually based on independent mutations that caused reduced Pitx1 expression. Reduced Pitx1 expression has also been implicated in pelvic reduction in manatees. Thus, hindlimb reduction stemming from reduced Pitx1 expression has arisen independently in groups that diverged tens to hundreds of millions of years ago, suggesting a potential for repeated use of Pitx1 across vertebrates. Notably, hindlimb reduction based on the reduction in Pitx1 expression produces left‐larger directional asymmetry in the vestiges. We used this phenotypic signature as a genetic proxy, testing for hindlimb directional asymmetry in six genera of squamate reptiles that independently evolved hindlimb reduction and for which genetic and developmental tools are not yet developed: Agamodon anguliceps, Bachia intermedia, Chalcides sepsoides, Indotyphlops braminus, Ophisaurus attenuatuas and O. ventralis, and Teius teyou. Significant asymmetry occurred in one taxon, Chalcides sepsoides, whose left‐side pelvis and femur vestiges were 18% and 64% larger than right‐side vestiges, respectively, suggesting modification in Pitx1 expression in that species. However, there was either right‐larger asymmetry or no directional asymmetry in the other five taxa, suggesting multiple developmental genetic pathways to hindlimb reduction in squamates and the vertebrates more generally. 相似文献
10.
Peptide YY (PYY) and ghrelin (GHR) may modulate one another's actions within the hypothalamus. Peripheral infusion of PYY in humans acutely suppresses circulating concentrations of GHR. Whether an association between PYY and GHR exists in the peripheral circulation of humans over 24 h is unknown. The purpose of this study was to determine if circulating concentrations of PYY and GHR were significantly associated over 24 h in humans. Participants (n = 13) were normal weight, moderately active, women ages 18–24 yr. Blood samples were obtained q10 min for 24 h and assayed using RIA for total PYY and total GHR hourly from 0800 to 1000 h and 2000 to 0800 h and q20 min from 1000 to 2000 h. Dietary intake during the 24 h procedure was comprised of 55% carbohydrates, 30% fat, and 15% protein (three meals and a snack). Statistical analyses included linear mixed-effects modeling to test whether PYY predicted GHR concentrations over 24 h. Participants weighed 57.0 ± 1.5 kg and had 26.1 ± 1.5% body fat (15.0 ± 1.1 kg), 42.1 ± 1.1 kg fat free mass, a BMI of 21.3 ± 0.5 kg/m2 and RMR of 1072 ± 28 kcal/24 h. Visually, PYY and GHR exhibited an inverse association over nearly the entire 24 h period. Statistically, circulating concentrations of 24 h PYY predicted 24 h GHR (ghrelin = 1860.51–2.14*PYY; p = 0.04). Circulating concentrations of PYY are inversely associated with GHR over 24 h. These data provide evidence that PYY may contribute to the modulation of the secretion of GHR in normal weight, premenopausal women over a 24 h period and supports similar inferences from experimental studies in animals and humans. 相似文献