926 research outputs found
Agrobacterium-mediated transformation of the terpenoid indole alkaloid-producing plant species Tabernaemontana pandacaqui
Plants of the Apocynaceae family produce a
wide range of terpenoid indole alkaloids (TIAs) which
have important pharmaceutical applications. Studies of the
molecular mechanisms controlling TIA biosynthesis may
eventually provide possibilities to improve product yield
by genetic modification of plants or cell cultures. However, these studies suffer from the lack of transformation/regeneration protocols for Apocynaceae plants. We
chose to study the feasibility of Agrobacterium tumefaciens-mediated transformation of Tabernaemontana pandacaqui, because of the availability of an efficient regeneration procedure for this member of the Apocynaceae family. A procedure to produce transgenic T. pandacaqui
plants was established, albeit with low efficiency. Transgenic expression was demonstrated of an intron-containing β-glucuronidase reporter gene and of a gene coding for
the TIA biosynthetic enzyme strictosidine synthase from
Catharanthus roseus, another Apocynaceae species.info:eu-repo/semantics/publishedVersio
Agrobacterium-mediated transformation of the terpenoid indole alkaloid-producing plant species Tabernaemontana pandacaqui
Plants of the Apocynaceae family produce a
wide range of terpenoid indole alkaloids (TIAs) which
have important pharmaceutical applications. Studies of the
molecular mechanisms controlling TIA biosynthesis may
eventually provide possibilities to improve product yield
by genetic modification of plants or cell cultures. However, these studies suffer from the lack of transformation/regeneration protocols for Apocynaceae plants. We
chose to study the feasibility of Agrobacterium tumefaciens-mediated transformation of Tabernaemontana pandacaqui, because of the availability of an efficient regeneration procedure for this member of the Apocynaceae family. A procedure to produce transgenic T. pandacaqui
plants was established, albeit with low efficiency. Transgenic expression was demonstrated of an intron-containing β-glucuronidase reporter gene and of a gene coding for
the TIA biosynthetic enzyme strictosidine synthase from
Catharanthus roseus, another Apocynaceae species.info:eu-repo/semantics/publishedVersio
GEM operation in double-phase xenon
http://www.sciencedirect.com/science/article/B6TJM-4T7F5JF-5/2/897502f8049abd8c2dd3dffc3821f0f
A model of the reflection distribution in the vacuum ultra violet region
A reflection model with three components, a specular spike, a specular lobe
and a diffuse lobe is discussed. This model was successfully applied to
describe reflection of xenon scintillation light (175 nm) by PTFE and other
fluoropolymers and can be used for Monte Carlo simulation and analysis of
scintillation detectors. The measured data favors a Trowbridge-Reitz
distribution function of ellipsoidal micro-surfaces. The intensity of the
coherent reflection increases with increasing angle of incidence, as expected,
since the surface appears smoother at grazing angles. The total reflectance
obtained for PTFE is about 70% for VUV light at normal incidence in vacuum and
estimated to be up to 100% in contact with liquid xenon
Temperature evaluation in ex-vivo bovine bones submitted to drilling processes
A necrose óssea induzida durante o processo de furação é um fenómeno frequente que contribui
para problemas pós-operatórios. O calor de fricção gerado pelo contato entre a broca e a
parede do furo é inevitável. No entanto, a utilização de técnicas avançadas para a obtenção do
registo térmico durante a furação óssea é importante para a garantia da qualidade durante a
furação. O objetivo deste estudo é apresentar dois métodos experimentais diferentes para
analisar as condições de furação que geram as temperaturas mais baixas, evitando a
ocorrência da necrose óssea. Foram utilizados ossos de bovino ex-vivo para simular o processo
de furação considerando os efeitos do diâmetro da broca, velocidade de rotação e velocidade
de avanço. Foram realizados diferentes testes experimentais para avaliar a sua repetibilidade.
Os resultados identificaram o diâmetro da broca como o parâmetro mais crítico na indução de
temperaturas mais elevadas durante a furação óssea.This research was supported by the Portuguese Foundation of Science and Technology under the research project UID/EMS/50022/2013. The third author acknowledges the funding of Project NORTE-01-0145-FEDER-000022-SciTech -Science and Technology for Competitive and Sustainable Industries, co-financed by Programa Operacional Regional do Norte (NORTE2020), through Fundo Europeu de Desenvolvimento Regional (FEDER).info:eu-repo/semantics/publishedVersio
A promoter region that controls basal and elicitor-inducible expression levels of the NADPH: cytochrome P450 reductase gene (Cpr) from Catharanthus roseus binds nuclear factor GT-1
NADPH:cytochrome P450 reductase (CPR) is
essential for the activation of cytochrome P450 enzymes,
which are involved in a wide variety of metabolic
pathways in plants, including those related to defence
responses. In the subtropical plant Catharanthus roseus
several cytochrome P450 enzymes operate in the biosynthesis of defence-related terpenoid indole alkaloids
(TIAs). In agreement with the importance of CPR in
defence, Cpr mRNA levels in C. roseus were found to be
enhanced by fungal elicitor preparations that also induce
TIA biosynthesis and P450 gene expression. Here we
describe the isolation of a C. roseus genomic DNA clone
covering the 5¢ part of the Cpr gene and 1.6-kb of upstream sequences. Mapping of the transcription start site
showed the untranslated leader sequence is approximately 280 bp long. To study the control of gene expression by the Cpr promoter, transcriptional fusions
between Cpr promoter fragments and the gusA reporter
gene were generated and their expression was analyzed
in stably transformed tobacco plants. The Cpr promoter
fragment extending from )1510 to )8, with respect to
the ATG start codon, conferred basal and elicitor-inducible expression on the gusA reporter gene, strongly
indicating that the Cpr gene of C. roseus is indeed controlled by this promoter region. Progressive deletion
from the 5¢ end of the promoter to position )632 had little e ect on gusA expression. However, deletion to
position )366 resulted in a complete loss of basal activity and largely eliminated elicitor-induced expression,
indicating that the region from )632 to )366 contains
the main transcription-enhancing cis-regulatory sequences. Electrophoretic mobility shift assays with tobacco nuclear extracts showed that binding sites for
nuclear factor GT-1 are redundant in the Cpr promoter,
but absent from the downstream part of the leader sequence. The presence of strong GT-1 binding sites in the
main enhancer region ()632 to )366), is suggestive of a
functional role for this factor in basal expression and
elicitor responsiveness of the Cpr promoter.info:eu-repo/semantics/publishedVersio
A promoter region that controls basal and elicitor-inducible expression levels of the NADPH: cytochrome P450 reductase gene (Cpr) from Catharanthus roseus binds nuclear factor GT-1
NADPH:cytochrome P450 reductase (CPR) is
essential for the activation of cytochrome P450 enzymes,
which are involved in a wide variety of metabolic
pathways in plants, including those related to defence
responses. In the subtropical plant Catharanthus roseus
several cytochrome P450 enzymes operate in the biosynthesis of defence-related terpenoid indole alkaloids
(TIAs). In agreement with the importance of CPR in
defence, Cpr mRNA levels in C. roseus were found to be
enhanced by fungal elicitor preparations that also induce
TIA biosynthesis and P450 gene expression. Here we
describe the isolation of a C. roseus genomic DNA clone
covering the 5¢ part of the Cpr gene and 1.6-kb of upstream sequences. Mapping of the transcription start site
showed the untranslated leader sequence is approximately 280 bp long. To study the control of gene expression by the Cpr promoter, transcriptional fusions
between Cpr promoter fragments and the gusA reporter
gene were generated and their expression was analyzed
in stably transformed tobacco plants. The Cpr promoter
fragment extending from )1510 to )8, with respect to
the ATG start codon, conferred basal and elicitor-inducible expression on the gusA reporter gene, strongly
indicating that the Cpr gene of C. roseus is indeed controlled by this promoter region. Progressive deletion
from the 5¢ end of the promoter to position )632 had little e ect on gusA expression. However, deletion to
position )366 resulted in a complete loss of basal activity and largely eliminated elicitor-induced expression,
indicating that the region from )632 to )366 contains
the main transcription-enhancing cis-regulatory sequences. Electrophoretic mobility shift assays with tobacco nuclear extracts showed that binding sites for
nuclear factor GT-1 are redundant in the Cpr promoter,
but absent from the downstream part of the leader sequence. The presence of strong GT-1 binding sites in the
main enhancer region ()632 to )366), is suggestive of a
functional role for this factor in basal expression and
elicitor responsiveness of the Cpr promoter.info:eu-repo/semantics/publishedVersio
Perspectives for Positron Emission Tomography with RPCs
In this study we address the feasibility and main properties of a positron
emission tomograph (PET) based on RPCs. The concept, making use of the
converter-plate principle, takes advantage of the intrinsic layered structure
of RPCs and its simple and economic construction. The extremely good time and
position resolutions of RPCs also allow the TOF-PET imaging technique to be
considered. Monte-Carlo simulations, supported by experimental data, are
presented and the main advantages and drawbacks for applications of potential
interest are discussed.Comment: Presented at "RPC2001-VI Workshop on Resistive Plate Chambers and
Related Detectors", Coimbra, Portugal, 26-27 November 2001 (5 pages
Detection of Scintillation Light of Liquid Xenon with a LAAPD
First observation of liquid xenon scintillation due to alpha-particles and
gamma-rays with a large area avalanche photodiode immersed in the liquid is
reported. An energy resolution of 10% (FWHM) and a coincidence time resolution
of less then 1 ns (FWHM) were measured with 5.5 MeV alpha-particles and 511 keV
gamma-rays, respectively. The quantum efficiency of the photodiode for xenon
scintillation light (wavelength 178 nm) is estimated to be ~100%.Comment: 11 pages, 9 figures, to be published in Nuclear Instruments and
Method
A survey of energy loss calculations for heavy ions between 1 and 100 keV
The original Lindhard-Scharff-Schi{\o}tt (LSS) theory and the more recent
Tilinin theory for calculating the nuclear and electronic stopping powers of
slow heavy ions are compared with predictions from the SRIM code by Ziegler.
While little discrepancies are present for the nuclear contribution to the
energy loss, large differences are found in the electronic one. When full ion
recoil cascade simulations are tested against the elastic neutron scattering
data available in the literature, it can be concluded that the LSS theory is
the more accurate.Comment: Presented at the 10th International Symposium on Radiation Physics,
17-22 September, 2006, Coimbra, Portugal; style corrections, small change to
fig.
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