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71.
72.
O'Rourke SM Carter C Carter L Christensen SN Jones MP Nash B Price MH Turnbull DW Garner AR Hamill DR Osterberg VR Lyczak R Madison EE Nguyen MH Sandberg NA Sedghi N Willis JH Yochem J Johnson EA Bowerman B 《PloS one》2011,6(3):e16644
To study essential maternal gene requirements in the early C. elegans embryo, we have screened for temperature-sensitive, embryonic lethal mutations in an effort to bypass essential zygotic requirements for such genes during larval and adult germline development. With conditional alleles, multiple essential requirements can be examined by shifting at different times from the permissive temperature of 15°C to the restrictive temperature of 26°C. Here we describe 24 conditional mutations that affect 13 different loci and report the identity of the gene mutations responsible for the conditional lethality in 22 of the mutants. All but four are mis-sense mutations, with two mutations affecting splice sites, another creating an in-frame deletion, and one creating a premature stop codon. Almost all of the mis-sense mutations affect residues conserved in orthologs, and thus may be useful for engineering conditional mutations in other organisms. We find that 62% of the mutants display additional phenotypes when shifted to the restrictive temperature as L1 larvae, in addition to causing embryonic lethality after L4 upshifts. Remarkably, we also found that 13 out of the 24 mutations appear to be fast-acting, making them particularly useful for careful dissection of multiple essential requirements. Our findings highlight the value of C. elegans for identifying useful temperature-sensitive mutations in essential genes, and provide new insights into the requirements for some of the affected loci. 相似文献
73.
Bernat Soria Sergio Navas Abdelkrim Hmadcha Owen P. Hamill 《The Journal of membrane biology》2013,246(3):215-230
Cell-attached and inside-out patch clamp recording was used to compare the functional expression of membrane ion channels in mouse and human embryonic stem cells (ESCs). Both ESCs express mechanosensitive Ca2+ permeant cation channels (MscCa) and large conductance (200 pS) Ca2+-sensitive K+ (BKCa2+) channels but with markedly different patch densities. MscCa is expressed at higher density in mESCs compared with hESCs (70 % vs. 3 % of patches), whereas the BKCa2+ channel is more highly expressed in hESCs compared with mESCs (~50 % vs. 1 % of patches). ESCs of both species express a smaller conductance (25 pS) nonselective cation channel that is activated upon inside-out patch formation but is neither mechanosensitive nor strictly Ca2+-dependent. The finding that mouse and human ESCs express different channels that sense membrane tension and intracellular [Ca2+] may contribute to their different patterns of growth and differentiation in response to mechanical and chemical cues. 相似文献
74.
75.
Natasha L. Heather José G. B. Derraik John Beca Paul L. Hofman Rangi Dansey James Hamill Wayne S. Cutfield 《PloS one》2013,8(12)
Objective
To assess the association of the Glasgow Coma Scale (GCS) with radiological evidence of head injury (the Abbreviated Injury Scale for the head region, AIS-HR) in young children hospitalized with traumatic head injury (THI), and the predictive value of GCS and AIS-HR scores for long-term impairment.Methods
Our study involved a 10-year retrospective review of a database encompassing all patients admitted to Starship Children’s Hospital (Auckland, New Zealand, 2000–2010) with THI.Results
We studied 619 children aged <5 years at the time of THI, with long-term outcome data available for 161 subjects. Both GCS and AIS-HR scores were predictive of length of intensive care unit and hospital stay (all p<0.001). GCS was correlated with AIS-HR (ρ=-0.46; p<0.001), although mild GCS scores (13–15) commonly under-estimated the severity of radiological injury: 42% of children with mild GCS scores had serious–critical THI (AIS-HR 3–5). Increasingly severe GCS or AIS-HR scores were both associated with a greater likelihood of long-term impairment (neurological disability, residual problems, and educational support). However, long-term impairment was also relatively common in children with mild GCS scores paired with structural THI more severe than a simple linear skull fracture.Conclusion
Severe GCS scores will identify most cases of severe radiological injury in early childhood, and are good predictors of poor long-term outcome. However, young children admitted to hospital with structural THI and mild GCS scores have an appreciable risk of long-term disability, and also warrant long-term follow-up. 相似文献76.
77.
Sex and differentiation: population genetic divergence and sexual dimorphism in Mexican goodeid fish 总被引:1,自引:0,他引:1
Ritchie MG Hamill RM Graves JA Magurran AE Webb SA Macías Garcia C 《Journal of evolutionary biology》2007,20(5):2048-2055
Genetic differentiation arises due to the interaction between natural and sexual selection, migration and genetic drift. A potential role of sexual selection in speciation has received much interest, although comparative studies are inconsistent in finding supporting evidence. A poorly tested prediction is that species subject to a higher intensity of sexual selection should show greater genetic differentiation amongst populations because females from these populations should be more choosy in mate choice. The Goodeinae is a group of endemic Mexican fishes in which female choice has driven some species to be morphologically sexually dimorphic, whereas others are relatively monomorphic. Here, we measured population divergence, using microsatellite loci, within four goodeid species which show contrasting levels of sexual dimorphism. We found higher levels of differentiation between populations of the more dimorphic species, implying less gene flow between populations. We also found evidence of higher levels of genetic differences between the sexes within populations of the dimorphic species, consistent with greater dispersal in males. Adjusted for geographic distance, the mean F(ST) for the dimorphic species is 0.25 compared with 0.16 for the less dimorphic species. We conclude that population differentiation is accelerated in more sexually dimorphic species, and that comparative phylogeography may provide a more powerful approach to detecting processes, such as an influence of sexual selection on differentiation, than broad-scale comparative studies. 相似文献
78.
Background
Clinically, plantar fasciitis (PF) is believed to be a result and/or prolonged by overpronation and excessive loading, but there is little biomechanical data to support this assertion. The purpose of this study was to determine the differences between healthy individuals and those with PF in (1) rearfoot motion, (2) medial forefoot motion, (3) first metatarsal phalangeal joint (FMPJ) motion, and (4) ground reaction forces (GRF).Methods
We recruited healthy (n=22) and chronic PF individuals (n=22, symptomatic over three months) of similar age, height, weight, and foot shape (p>0.05). Retro-reflective skin markers were fixed according to a multi-segment foot and shank model. Ground reaction forces and three dimensional kinematics of the shank, rearfoot, medial forefoot, and hallux segment were captured as individuals walked at 1.35 ms−1.Results
Despite similarities in foot anthropometrics, when compared to healthy individuals, individuals with PF exhibited significantly (p<0.05) (1) greater total rearfoot eversion, (2) greater forefoot plantar flexion at initial contact, (3) greater total sagittal plane forefoot motion, (4) greater maximum FMPJ dorsiflexion, and (5) decreased vertical GRF during propulsion.Conclusion
These data suggest that compared to healthy individuals, individuals with PF exhibit significant differences in foot kinematics and kinetics. Consistent with the theoretical injury mechanisms of PF, we found these individuals to have greater total rearfoot eversion and peak FMPJ dorsiflexion, which may put undue loads on the plantar fascia. Meanwhile, increased medial forefoot plantar flexion at initial contact and decreased propulsive GRF are suggestive of compensatory responses, perhaps to manage pain. 相似文献79.
Wen-Hao Hsu Cara L. Lewis Gail M. Monaghan Elliot Saltzman Joseph Hamill Kenneth G. Holt 《Journal of biomechanics》2014
The purpose of the present study was to determine the effects of orthoses designed to support the forefoot and rearfoot on the kinematics and kinetics of the lower extremity joints during walking. Fifteen participants volunteered for this study. Kinematic and kinetic variables during overground walking were compared with the participants wearing sandals without orthoses or sandals with orthoses. Orthoses increased knee internal abduction moment during late stance and knee abduction angular impulse, and reduced the medial ground reaction force during late stance, adduction free moment, forefoot eversion angle, ankle inversion moment and angular impulse, hip adduction angle, hip abduction moment, and hip external rotation moment and angular impulse (p<0.05). Orthoses decreased the torsional forces on the lower extremity and reduced the loading at the hip during walking. These findings combined with our previous studies and those of others suggest that forefoot abnormalities are critically important in influencing lower extremity kinematics and kinetics, and may underlie some non-traumatic lower extremity injuries. 相似文献
80.
Austin J Rice Frances JD Alvarez Amy L Davidson Heather W Pinkett 《Channels (Austin, Tex.)》2014,8(4):327-333
In order to shuttle substrates across the lipid bilayer, membrane proteins undergo a series of conformation changes that are influenced by protein structure, ligands, and the lipid environment. To test the effect of lipid on conformation change of the ABC transporter MolBC, EPR studies were conducted in lipids and detergents of variable composition. In both a detergent and lipid environment, MolBC underwent the same general conformation changes as detected by site-directed EPR spectroscopy. However, differences in activity and the details of the EPR analysis indicate conformational rigidity that is dependent on the lipid environment. From these observations, we conclude that native-like lipid mixtures provide the transporter with greater activity and conformational flexibility as well as technical advantages such as reconstitution efficiency and protein stability. 相似文献