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51.
52.
Keith L. McDougall Jake M. Alexander Sylvia Haider Aníbal Pauchard Neville G. Walsh Christoph Kueffer 《Diversity & distributions》2011,17(1):103-111
Aim We use data from 13 mountain regions and surrounding lowland areas to identify (1) the origins, traits and cultural uses of alien plant species that establish in mountains, (2) the alien species that are most likely to be a threat and (3) how managers might use this information to prevent further invasions. Location Australia, Canada, Chile, India, New Zealand, South Africa, Spain, Switzerland, USA. Methods Lists of alien species were compiled for mountains and their surrounding or nearby lowlands. Principal co‐ordinates analysis was performed on a matrix of similarities created using presence/absence data for alien species. The significance of differences between means for (1) similarity metrics of lowland and mountain groups and (2) species traits of lowland and mountain alien floras was determined using t‐tests. In seven of the 13 mountain regions, lists of alien species undergoing management were compiled. The significance of differences between proportions of traits for species requiring and not requiring management input was determined with chi‐square tests. Results We found that the proximal lowland alien flora is the main determinant of a mountain region’s alien species composition. The highest similarities between mountain floras were in the Americas/Pacific Region. The majority of alien species commonly found in mountains have agricultural origins and are of little concern to land managers. Woody species and those used for ornamental purposes will often pose the greatest threat. Main conclusions Given the documented potential threat of alien species invading mountains, we advise natural resource managers to take preventive measures against the risk of alien plant invasion in mountains. A strategy for prevention should extend to the surrounding lowland areas and in particular regulate the introduction of species that are already of management concern in other mountains as well as climatically pre‐adapted alien mountain plants. These may well become more problematic than the majority of alien plants currently in mountains. 相似文献
53.
Haider MA Olander JE Arnold RF Marous DR McLamb AJ Thompson KC Woodruff WR Haugh JM 《Biomechanics and modeling in mechanobiology》2011,10(6):915-924
A phenomenological mixture model is presented for interactions between biosynthesis of extracellular matrix (ECM) constituents
and ECM linking in a scaffold seeded with chondrocytes. A system of three ordinary differential equations for average apparent
densities of unlinked ECM, linked ECM and scaffold is developed along with associated initial conditions for scaffold material
properties. Equations for unlinked ECM synthesis and ECM linking include an inhibitory mechanism where associated rates decrease
as unlinked ECM concentration in the interstitial fluid increases. Linking rates are proposed to depend on average porosity
in the evolving tissue construct. The resulting initial value problem contains nine independent parameters that account for
scaffold biomaterial properties and interacting mechanisms in the engineered system. Effects of parameter variations on model
variables are analyzed relative to a baseline case with emphasis on the evolution of solid phase apparent density, which is
often correlated with the compressive elastic modulus of the tissue construct. The new model provides an additional quantitative
framework for assessing and optimizing the design of engineered cell-scaffold systems and guiding strategies for articular
cartilage tissue engineering. 相似文献
54.
Jelcick AS Yuan Y Leehy BD Cox LC Silveira AC Qiu F Schenk S Sachs AJ Morrison MA Nystuen AM DeAngelis MM Haider NB 《PloS one》2011,6(7):e21858
Variation in genetic background can significantly influence the phenotypic outcome of both disease and non-disease associated traits. Additionally, differences in temporal and strain specific gene expression can also contribute to phenotypes in the mammalian retina. This is the first report of microarray based cross-strain analysis of gene expression in the retina investigating genetic background effects. Microarray analyses were performed on retinas from the following mouse strains: C57BL6/J, AKR/J, CAST/EiJ, and NOD.NON-H2(-nb1) at embryonic day 18.5 (E18.5) and postnatal day 30.5 (P30.5). Over 3000 differentially expressed genes were identified between strains and developmental stages. Differential gene expression was confirmed by qRT-PCR, Western blot, and immunohistochemistry. Three major gene networks were identified that function to regulate retinal or photoreceptor development, visual perception, cellular transport, and signal transduction. Many of the genes in these networks are implicated in retinal diseases such as bradyopsia, night-blindness, and cone-rod dystrophy. Our analysis revealed strain specific variations in cone photoreceptor cell patterning and retinal function. This study highlights the substantial impact of genetic background on both development and function of the retina and the level of gene expression differences tolerated for normal retinal function. These strain specific genetic variations may also be present in other tissues. In addition, this study will provide valuable insight for the development of more accurate models for human retinal diseases. 相似文献
55.
The current protocols for generation of induced pluripotent stem (iPS) cells involve genome integrating viral vectors which may induce tumorgenesis. The aim of this study was to develop and optimize a non-viral method without genetic manipulation for reprogramming of skeletal myoblasts (SMs) using small molecules.
Methods and Results
SMs from young male Oct3/4-GFP+ transgenic mouse were treated with DNA methyltransferase (DNMT) inhibitor, RG108. Two weeks later, GFP+ colonies of SM derived iPS cells (SiPS) expressing GFP and with morphological similarity of mouse embryonic stem (ESCs) were formed and propagated in vitro. SiPS were positive for alkaline phosphatase activity, expressed SSEA1, displayed ES cell specific pluripotency markers and formed teratoma in nude mice. Optimization of culture conditions for embryoid body (EBs) formation yielded spontaneously contracting EBs having morphological, molecular, and ultra-structural similarities with cardiomyocytes and expressed early and late cardiac markers. miR profiling showed abrogation of let-7 family and upregulation of ESCs specific miR-290-295 cluster thus indicating that SiPS were similar to ESCs in miR profile. Four weeks after transplantation into the immunocompetent mice model of acute myocardial infarction (n = 12 per group), extensive myogenesis was observed in SiPS transplanted hearts as compared to DMEM controls (n = 6 per group). A significant reduction in fibrosis and improvement in global heart function in the hearts transplanted with SiPS derived cardiac progenitor cells were observed.Conclusions
Reprogramming of SMs by DNMT inhibitor is a simple, reproducible and efficient technique more likely to generate transgene integration-free iPS cells. Cardiac progenitors derived from iPS cells propagated extensively in the infarcted myocardium without tumorgenesis and improved cardiac function. 相似文献56.
Functional analysis of a structural model of the ATP-binding site of the KATP channel Kir6.2 subunit 下载免费PDF全文
ATP-sensitive potassium (KATP) channels couple cell metabolism to electrical activity by regulating K+ flux across the plasma membrane. Channel closure is mediated by ATP, which binds to the pore-forming subunit (Kir6.2). Here we use homology modelling and ligand docking to construct a model of the Kir6.2 tetramer and identify the ATP-binding site. The model is consistent with a large amount of functional data and was further tested by mutagenesis. Ligand binding occurs at the interface between two subunits. The phosphate tail of ATP interacts with R201 and K185 in the C-terminus of one subunit, and with R50 in the N-terminus of another; the N6 atom of the adenine ring interacts with E179 and R301 in the same subunit. Mutation of residues lining the binding pocket reduced ATP-dependent channel inhibition. The model also suggests that interactions between the C-terminus of one subunit and the 'slide helix' of the adjacent subunit may be involved in ATP-dependent gating. Consistent with a role in gating, mutations in the slide helix bias the intrinsic channel conformation towards the open state. 相似文献
57.
Haider MZ Habeeb Y Al-Nakkas E Al-Anzi H Zaki M Al-Tawari A Al-Bloushi M 《Journal of biomedical science》2005,12(5):815-818
Summary Idiopathic generalized epilepsies (IGEs) are the most common types of epilepsy in childhood and adolescence. A variety of
data suggest that IGEs have a predominant genetic etiology. Recently, a number of gene mutations have been found to be associated
with various types of epilepsy in mainly the Caucasian populations. The objective of this study was to investigate the association
of three different candidate genes with IGE in Kuwaiti Arab children. This study includes 123 Kuwaiti patients with a confirmed
diagnosis of epilepsy. Most of the patients have had a diagnostic EEG with generalized spike-wave discharges (GSWs). All patients
were evaluated by using a validated seizure questionnaire. The clinical type of epilepsy was determined by a trained neurologist/pediatrician.
The study also include 100 controls, the control subjects were children which did not have any history of neurological disorders.
Blood samples were collected from all patients and control subjects after taking informed consent. DNA was isolated and analyzed
by molecular methods. A FokI polymorphism in neuronal nicotinic acetylcholine receptor alpha-4 subunit (CHRNA4) gene was detected by PCR-RFLP method.
A missense mutation (Ser248Phe) in CHRNA4 gene was analyzed by PCR-RFLP using HpaII. A C121W mutation in sodium-channel beta-1 subunit (SCN1B) gene was screened by a PCR-RFLP method using HinPI. A 2-bp deletion in Cystatin B gene was detected by PCR-RFLP using XcmI. The incidence of three FokI polymorphism genotypes in Kuwaiti IGE patients was 1,1 (85%), 1,2 (14%) and 2,2 (1%) respectively. The missense mutation
Ser248Phe of CHRNA4 gene was not detected at all in Kuwaiti IGE patients. The C387G transversion resulting in C121W change
in third exon of the SCN1B gene was detected in 3/123 patients (2%). The patients carrying this mutation also exhibited febrile
seizures. The incidence of 2 bp deletion in the cystatin B gene was found to be 4% (5/123 IGE patients). The data obtained
from molecular analysis show a lack of association between three candidate genes and clinical expression of IGE in Kuwaiti
Arab children. This is completely different from the findings reported from Caucasian populations of France, Australia and
USA in which case a strong association has been reported between IGE and these genes.
To whom corresspondence should be addressed. Tel: +965-5319486; Fax: +965-5338940; E-mail: haider@hsc.edu.kw 相似文献
58.
59.
The shear flow dynamics of reversible red cell aggregates in dense suspensions were investigated by ultrasound scattering, to study the shear disruption processes of Rayleigh clusters and examine the effective mean field approximation used in microrheological models. In a first section, a rheo-acoustical model, in the Rayleigh scattering regime, is proposed to describe the shear stress dependence of the low frequency scattered power in relation to structural parameters. The fractal scattering regime characterizing the anisotropic scattering from flocs of size larger than the ultrasound wavelength is further discussed. In the second section, we report flow-dependent changes in the low-frequency scattering coefficient in a plane-plane flow geometry to analyze the shear disruption processes of hardened or deformable red cell aggregates in neutral dextran polymer solution. Rheo-acoustical experiments are examined on the basis of the rheo-acoustical model and the effective medium approximation. The ability of ultrasound scattering technique to determine the critical disaggregation shear stress and to give quantitative information on particle surface adhesive energy is analyzed. Lastly, the shear-thinning behavior of weakly aggregated hardened or deformable red cells is described. 相似文献
60.
Memory impairment is a major problem afflicting mankind. The association between memory functions and neurotransmitter functions is of great interest for understanding brain function. Serotonergic pathways play an important role in the modulation of memory functions but the importance of its receptor types and subtypes on memory functions is still unclear. Activation and blockade of various serotonin (5-HT) receptors has been reported to alter cognitive processes and 5-HT receptor antagonism could be beneficial in the treatment of cognitive diseases. The role of 5-HT on memory functions is complicated. Among the 5-HT receptors subtypes, 5-HT(1A) receptors are of special interest because these receptors are present in the brain areas involved in learning and memory functions such as hippocampus and cortex. The present study was therefore designed to investigate the effect of activation and blockade of somatodendritic and/or postsynaptic 5-HT(1A) receptor on learning and memory functions in rats using modified version of water maze. In this study, 8-OH-DPAT (8-hydroxy-2-(di-N-propylamino) tetralin) at 0.3?mg/kg significantly enhanced learning acquisition (LA), short-term memory (STM) and long term memory (LTM) of rats pre-injected with saline suggesting that the activation of pre-synaptic 5-HT(1A) receptors by its agonist enhanced the memory functions of rats. Conversely, rats injected with 8-OH-DPAT at 1.0?mg/kg exhibited impaired LA and STM and had no effect on LTM. It was also shown in this study that blockade of 5-HT(1A) receptors by spiperone enhanced LA, had no effect on STM but impaired the LTM, which showed that the blockade of 5-HT(1A) receptors by its antagonist exerts different effect on different types of memory. This study suggests that 5-HT(1A) receptor could be used as a significant pharmacological target for the treatment of CNS diseases. Unraveling the role of serotonin in cognition and memory disorders could provide better therapy and it may lead to new insights in our understandings of learning and memory. 相似文献