432 research outputs found
Acceleration of Amphibian Forelimb Regeneration By Polypeptide Growth Factors
Growth factors are potentially important modulators of epimorphic regeneration. This study examined effects of intraperitoneal administration of selected growth factors on limb regeneration of adult newts, Notophthalmus viridescens. These agents stimulated regeneration, producing overlapping but nonidentical effects. Fibroblast growth factor-2 (FGF-2) and insulin-like growth factor I (IGF-I) stimulated bud emergence (8.3 ± 0.6 and 8.3 ± 0.7 days, respectively, vs 11.4 ± 1.1 days for controls). Progression to the cone stage was enhanced by both FGF-2 and transforming growth factor beta 5 ( TGF-~ 5) ; 14.6 ± 0.5 and 15.4 ± 0.4 days with FGF-2 and TGF-~5 , respectively, vs 16.5 ± 0.5 days in controls. Insulin accelerated attainment of the palette stage, 17.0 ± 0.7 days vs 19.0 ± 0.4 days for controls. No treatments affected attaining the digital stage; means between 22.4 and 23.4 days. Histological analysis revealed changes consistent with gross observations. In addition, regenerates from newts treated with FGF-2, TGF-~5. and insulin displayed signs of greater (or earlier) histogenesis than did control animals. These results are consistent with the notion that FGF-2, TGF-~5. and possibly lGF-I stimulate proliferation of blastema cells and that insulin, FGF-2, and TGF-~5 promote differentiation and histogenesis during forelimb regeneration. In conclusion, these results demonstrate that several polypeptide growth factors positively affect the progress of forelimb regeneration, that different growth factors influence the same or similar events of epimorphic regeneration, and that diverse growth factors have nonidentical effects on regeneration
Preparation and Characterizations of Chitosan/Citral Nanoemulsions and their Antimicrobial Activity
Background and Objective: The antimicrobial activity of essential oils has been long recognized, however, they easily evaporate and/or decompose during preparation, owing to direct exposure to heat, pressure and light. The current study deals with the formulation and characterization of bio-based oil in water nanoemulsions and their antimicrobial activity against plant pathogens.Material and Methods: Citral oil and low molecular weight chitosan were used for preparation of nanoemulsions in the presence of sodium tripolyphosphate. Nanoemulsions were prepared by adding dropwise citral at different ratios into an aqueous solution containing chitosan, sodium tripolyphosphate and surfactant with continuous stirring and then ultrasonication. The success of formulation was conïŹrmed by dynamic light scattering and scanning electron microscopy techniques. Physical stability and viscosity were investigated in details. The antimicrobial activity was evaluated against Erwinia carotovora, Aspergillus niger and Rhizopus stolonifer. Results and Conclusion: The nanoemulsions had a polydispersity index ranged from 0.508 to 0.614 and particle size from 27 to 1283 nm. The highest antimicrobial activity was observed with F1 formulation (EC50 = 23, 278 and 221 mg L-1, against Erwinia carotovora, Aspergillus niger and Rhizopus stolonifer, respectively). Based on the antimicrobial activity, the prepared chitosan/citral nanoemulsions can be a cost-effective way to protect crops from microbial pathogens. Because such formulations contain bioactive products, the development of resistant pathogens can be delayed.Conflict of Interest: The authors declare no conflict of interest.
The Impact of Applying ISO Standards Systems on Improving the Quality of the Performance in Higher Educational Institutions in Egypt
Applying ISO 21001:2018 standard ensures that universities have a competitive advantage as well as the achievement of their objectives. This study aims to identify the impact of implementing ISO 21001: 2018 management systems standards on the performance quality of higher education institutions. The study investigates the reasons why private higher education institutions seek ISO standards certificates in general and the specifications of management systems for educational institutions in particular. The study applied a set of statistical testing methods on paired samples as well as independent samples to ensure quality assurance. The study also proposes the required prerequisites that should be considered. The study investigated a hypothesis stating that "there are no statistically significant differences before and after applying the ISO 21001:2018 management systems specification for educational institutions in improving the quality of performance in higher education institutions" which was rejected by conducting an experiment in Future University in Egypt and accepting the alternative hypothesis. The study confirmed the impact of quality which was previously investigated by prior research that has been discussed in this study. The study further presented the need to apply quality based on determined criteria which were not considered in prior studies. Moreover, the study proposed the impact of ISO standards in educational institutions in general and in Egypt in specific. This recommendation is proved by this study to enhance the quality level in educational institutions
Methylene tetrahydrofolate reductase, transforming growth factor-ÎČ1 and lymphotoxin-α genes polymorphisms and susceptibility to rheumatoid arthritis
AbstractBackgroundRheumatoid arthritis is a widely prevalent autoimmune disorder with suggested genetic predisposition.ObjectivesThe aim of this study is to detect the pattern of genetic polymorphism of methylene tetrahydrofolate reductase (MTHFR C677 T and A1298 C), transforming growth factor-ÎČ1 (TGF-ÎČ1 T869 C) and lymphotoxin-α (LT-α A252G) in patients having rheumatoid arthritis and correlate these patterns to disease activity and serum levels of tumor necrosis factor-alpha (TNF-α), B-Cell Activating Factor (BAFF), and osteopontin.MethodsA total of 194 subjects, 90 controls and 104 patients with rheumatoid arthritis were genotyped for MTHFR C677 T and A1298 C, TGF-ÎČ1 T869 C and LT-α A252G polymorphisms using a methodology based on PCR-RFLP. Also serum levels of TNF-α, osteopontin and BAFF were measured by ELISA kits.ResultsThe CT genotype and T allele of MTHFR C677 T and GG genotype and G allele of LT-α A252G are associated with the risk of RA and with higher levels of the pro-inflammatory cytokine, TNF-α in patients with rheumatoid arthritis.ConclusionOur findings suggest that there is association between MTHFR C677 T and LT-α A252G genes polymorphisms and increased risk of RA in this sample of Egyptian population
Polimorfismos dos genes metilenotetrahidrofolato redutase, fator de crescimento transformador ÎČ1 e linfotoxinaâα e susceptibilidade Ă artrite reumatoide
ResumoAntecedentesA artrite reumatoide Ă© uma doença autoimune amplamente prevalente com sugerida predisposição genĂ©tica.ObjetivosDetectar o padrĂŁo de polimorfismo dos genes metilenotetrahidrofolato redutase (MTHFR C677T e A1298C), fator de crescimento transformador ÎČ1 (TGFâÎČ1 T869C) e linfotoxinaâα (LTâα A252G) em pacientes com artrite reumatoide e correlacionar esses padrĂ”es com a atividade da doença e os nĂveis sĂ©ricos de fator de necrose tumoral alfa (TNFâα), fator ativador de linfĂłcitos B (BAFF) e osteopontina.MĂ©todosForam genotipados 194 indivĂduos â 90 controles e 104 com artrite reumatoide â Ă procura de polimorfismos dos genes MTHFR C677T e A1298C, TGFâÎČ1 T869C e LTâα A252G com uma metodologia baseada na PCRâRFLP. Mensuraramâse tambĂ©m os nĂveis sĂ©ricos de TNFâα, osteopontina e BAFF com kits de Elisa.ResultadosO genĂłtipo CT e o alelo T do MTHFR C677T e o genĂłtipo GG e alelo G do LTâα A252G estĂŁo associados ao risco de AR e a nĂveis mais elevados da citocina prĂłâinflamatĂłria TNFâα em pacientes com artrite reumatoide.ConclusĂŁoOs achados do presente estudo sugerem que hĂĄ associação entre os polimorfismos dos genes MTHFR C677T e LTâα A252G e um risco aumentado de AR nessa amostra da população egĂpcia.AbstractBackgroundRheumatoid arthritis is a widely prevalent autoimmune disorder with suggested genetic predisposition.ObjectivesThe aim of this study is to detect the pattern of genetic polymorphism of methylene tetrahydrofolate reductase (MTHFR C677T and A1298C), transforming growth factorâÎČ1 (TGFâÎČ1 T869C) and lymphotoxinâα (LTâα A252G) in patients having rheumatoid arthritis and correlate these patterns to disease activity and serum levels of tumor necrosis factorâalpha (TNFâα), BâCell Activating Factor (BAFF), and osteopontin.MethodsA total of 194 subjects, 90 controls and 104 patients with rheumatoid arthritis were genotyped for MTHFR C677T and A1298C, TGFâÎČ1 T869C and LTâα A252G polymorphisms using a methodology based on PCRâRFLP. Also serum levels of TNFâα, osteopontin and BAFF were measured by ELISA kits.ResultsThe CT genotype and T allele of MTHFR C677T and GG genotype and G allele of LTâα A252G are associated with the risk of RA and with higher levels of the proâinflammatory cytokine, TNFâα in patients with rheumatoid arthritis.ConclusionOur findings suggest that there is association between MTHFR C677T and LTâα A252G genes polymorphisms and increased risk of RA in this sample of Egyptian population
Measuring the brightness temperature distribution of extragalactic radio sources with space VLBI
We have used VSOP space very long baseline interferometry observations to
measure the brightness temperature distribution of a well-defined sub-set of
the Pearson-Readhead sample of extragalactic radio sources. VLBI which is
restricted to Earth-diameter baselines is not generally sensitive to emitting
regions with brightness temperatures greater than approximately K,
coincidentally close to theoretical estimates of brightness temperature limits,
K. We find that a significant proportion of our sample have
brightness temperatures greater than K; many have unresolved
components on the longest baselines, and some remain completely unresolved.
These observations begin to bridge the gap between the extended jets seen with
ground-based VLBI and the microarcsecond structures inferred from intraday
variability, evidenced here by the discovery of a relationship between intraday
variability and VSOP-measured brightness temperature, likely due to the effects
of relativistic beaming. Also, lower limits on jet Lorentz factors, estimated
from space VLBI observations, are starting to challenge numerical simulations
that predict low Lorentz factor jets.Comment: 4 pages + 1 figure, ApJ letters, accepte
The Pearson-Readhead Survey of Compact Extragalactic Radio Sources From Space. II. Analysis of Source Properties
We have performed a multi-dimensional correlation analysis on the observed
properties of a statistically complete core-selected sample of compact
radio-loud active galactic nuclei, based on data from the VLBI Space Observing
Programme (Paper I) and previously published studies. Our sample is drawn from
the well-studied Pearson-Readhead (PR) survey, and is ideally suited for
investigating the general effects of relativistic beaming in compact radio
sources. In addition to confirming many previously known correlations, we have
discovered several new trends that lend additional support to the beaming
model. These trends suggest that the most highly beamed sources in
core-selected samples tend to have a) high optical polarizations; b) large
pc/kpc-scale jet misalignments; c) prominent VLBI core components; d)
one-sided, core, or halo radio morphology on kiloparsec scales; e) narrow
emission line equivalent widths; and f) a strong tendency for intraday
variability at radio wavelengths. We have used higher resolution space and
ground-based VLBI maps to confirm the bi-modality of the jet misalignment
distribution for the PR survey, and find that the sources with aligned parsec-
and kiloparsec-scale jets generally have arcsecond-scale radio emission on both
sides of the core. The aligned sources also have broader emission line widths.
We find evidence that the BL Lacertae objects in the PR survey are all highly
beamed, and have very similar properties to the high-optically polarized
quasars, with the exception of smaller redshifts. A cluster analysis on our
data shows that after partialing out the effects of redshift, the luminosities
of our sample objects in various wave bands are generally well-correlated with
each other, but not with other source properties.Comment: 21 pages, 10 figures. Accepted for publication in the Astrophysical
Journal. Part I can be found at astro-ph/010227
Discovery of the Galaxy Proximity Effect and Implications for Measurements of the Ionizing Background Radiation at Low Redshifts
We present an analysis of galaxy and QSO absorption line pairs toward 24 QSOs
at redshifts between z~0.2 and 1 in an effort to establish the relationship
between galaxies and absorption lines in physical proximity to QSOs. We
demonstrate the existence of a galaxy proximity effect, in that galaxies in the
vicinities of QSOs do not show the same incidence and extent of gaseous
envelopes as galaxies far from QSOs. We show that the galaxy proximity effect
exists to galaxy-QSO velocity separations of ~ 3000 km/s, much larger than the
size of a typical cluster (~ 1000 km/s), i.e. it is more comparable to the
scale of the sphere of influence of QSO ionizing radiation rather than the
scale of galaxy-QSO clustering. This indicates that the QSO ionizing radiation
rather than some dynamical effect from the cluster environment is responsible
for the galaxy proximity effect. We combine previous findings that (1) many or
most Lya absorption lines arise in extended galaxy envelopes, and (2) galaxies
cluster around QSOs to show that the magnitude of the Lya forest proximity
effect is underestimated. Consequently, determinations of the UV ionizing
background intensity using the proximity effect are likely overestimated. We
use the galaxy-QSO cross-correlation function measured from our data to
estimate the magnitude of this overestimate and find that it could be as high
as a factor of 20 at z<1. This can have strong implications for models of the
origin and evolution of the ionizing background, and may indicate that QSOs
produce sufficient ionizing flux at all redshifts to account for the entire
background radiation field.Comment: 26 pages, 3 figures, to appear in ApJ, October 20, 200
Electrical transport between epitaxial manganites and carbon nanotubes
The possibility of performing spintronics at the molecular level may be
realized in devices that combine fully spin polarized oxides such as manganites
with carbon nanotubes. However, it is not clear whether electrical transport
between such different material systems is viable. Here we show that the room
temperature conductance of manganite-nanotube-manganite devices is only half
the value recorded in similar palladium-nanotube-palladium devices.
Interestingly, the former shows a pseudogap in the conductivity below the
relatively high temperature of 200 K. Our results suggest the possibility of
new spintronics heterostructures that exploit fully spin polarized sources and
drains
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