The study of influence of the fractionated and acute ionizing radiation on plants revealed that it is able to induce genomic instability. The hypothesis that transcription rate of several evolutionary conserved DNA re...The study of influence of the fractionated and acute ionizing radiation on plants revealed that it is able to induce genomic instability. The hypothesis that transcription rate of several evolutionary conserved DNA repair genes AtKu 70, AtRAD51 and AtRadl, which keeps genome stability in cells of model plant Arabidopsis thaliana, changes differently depending on dose and mode of ionizing radiation exposure had been tested. Gel electrophoresis-based reverse transcription polymerase chain reaction （RT-PCR） method was used for quantifying mRNA transcription levels. The data demonstrated that mode and dose of irradiation affect transcription rate of the genes AtKuTO, AtRAD51 and AtRadI. The fractionated and acute X-ray irradiation may result in adaptive response through the induction of key DNA double-strand break （DSB） repair genes AtKu70 and AtRAD51, as well as in genome instability through transcriptional activation of error-prone AtRadl-mediated DNA DSB repair combined with decreased expression of AtRAD51. In plants at doses within the range of 3-9 Gy, an adaptive influence is prevailed, but at doses of 12-21 Gy an error-prone repair of double-strand DNA damage is activated. Fractionation of dose has a significant effect on the transcription of the genes AtKuTO, AtRAD51 and AtRadl only at doses of 15 Gy and 21 Gy. Acute dose of 15 Gy activates error-prone AtRadl-mediated DSB repair and repressed both AtRAD51-dependent and AtKu70-dependent repair pathways, while fractionated irradiation at the same total dose induces more accurate homologous recombination and canonical non-homologous end joining of the DNA strands. In case of A. thaliana exposed to X-rays at dose 21 Gy, the situation is going reversed because of strong induction of the all three genome caretaker genes in leaves of acutely irradiated plants in contrast to the plants under fractionated exposure.展开更多
In this study, we developed a highly sensitive dual-mode imaging system using gold nanoparticles （GNPs） conjugated to various fluorophores in solid phantoms. The system consists of fluorescence-lifetime imaging micr...In this study, we developed a highly sensitive dual-mode imaging system using gold nanoparticles （GNPs） conjugated to various fluorophores in solid phantoms. The system consists of fluorescence-lifetime imaging microscopy （FLIM） for surface imaging, diffusion reflection （DR） for deep-tissue imaging （up to 1 cm）, and metal-enhanced fluorescence （MEF）. We detected quenching in the fluorescent intensity （FI） for the conjugation of both gold nanospheres （GNS） and gold nanorods （GNRs） to Fluorescein, which has an excitation peak at a wavelength shorter than the surface plasmon resonance （SPR） of both types of GNPs. Enhanced FI was detected in conjugation to Rhodamine B （RhB） and Sulforhodamine B （SRB）, both with excitation peaks in the SPR regions of the GNPs. The enhanced FI was detected both in solution and in solid phantoms by the FLIM measurements. DR measurements detected the presence of GNRs within the solid phantoms by recording the dropped rates of light scattering in wavelengths corresponding to the absorption spectra of the GNRs. With the inclusion of MEF, this promising dual-mode imaging technique enables efficient and sensitive molecular and functional imaging.展开更多
In this paper,a focusing approach is presented to widen the use of efficient monostatic imaging algorithms for azimuth-invariant bistatic synthetic aperture radar(SAR) data.The bistatic range history is modeled by a p...In this paper,a focusing approach is presented to widen the use of efficient monostatic imaging algorithms for azimuth-invariant bistatic synthetic aperture radar(SAR) data.The bistatic range history is modeled by a polynomial of azimuth time.Using this model,an analytic form of the signal spectrum in the 2D frequency domain is derived,and a simple single-valued relation between the transmitter and receive ranges is established.In this way,a lot of monostatic image formation algorithms can be extended for the bistatic SAR data,and a bistatic chirp scaling algorithm is developed as an application of the new approach.This algorithm can be used to process the azimuth-invariant bistatic configuration where the transmitter and receiver platforms are moving on parallel tracks with the same velocity.In addition,some simulation results are given to demonstrate the validity of the proposed approach.展开更多
文摘The study of influence of the fractionated and acute ionizing radiation on plants revealed that it is able to induce genomic instability. The hypothesis that transcription rate of several evolutionary conserved DNA repair genes AtKu 70, AtRAD51 and AtRadl, which keeps genome stability in cells of model plant Arabidopsis thaliana, changes differently depending on dose and mode of ionizing radiation exposure had been tested. Gel electrophoresis-based reverse transcription polymerase chain reaction （RT-PCR） method was used for quantifying mRNA transcription levels. The data demonstrated that mode and dose of irradiation affect transcription rate of the genes AtKuTO, AtRAD51 and AtRadI. The fractionated and acute X-ray irradiation may result in adaptive response through the induction of key DNA double-strand break （DSB） repair genes AtKu70 and AtRAD51, as well as in genome instability through transcriptional activation of error-prone AtRadl-mediated DNA DSB repair combined with decreased expression of AtRAD51. In plants at doses within the range of 3-9 Gy, an adaptive influence is prevailed, but at doses of 12-21 Gy an error-prone repair of double-strand DNA damage is activated. Fractionation of dose has a significant effect on the transcription of the genes AtKuTO, AtRAD51 and AtRadl only at doses of 15 Gy and 21 Gy. Acute dose of 15 Gy activates error-prone AtRadl-mediated DSB repair and repressed both AtRAD51-dependent and AtKu70-dependent repair pathways, while fractionated irradiation at the same total dose induces more accurate homologous recombination and canonical non-homologous end joining of the DNA strands. In case of A. thaliana exposed to X-rays at dose 21 Gy, the situation is going reversed because of strong induction of the all three genome caretaker genes in leaves of acutely irradiated plants in contrast to the plants under fractionated exposure.
文摘In this study, we developed a highly sensitive dual-mode imaging system using gold nanoparticles （GNPs） conjugated to various fluorophores in solid phantoms. The system consists of fluorescence-lifetime imaging microscopy （FLIM） for surface imaging, diffusion reflection （DR） for deep-tissue imaging （up to 1 cm）, and metal-enhanced fluorescence （MEF）. We detected quenching in the fluorescent intensity （FI） for the conjugation of both gold nanospheres （GNS） and gold nanorods （GNRs） to Fluorescein, which has an excitation peak at a wavelength shorter than the surface plasmon resonance （SPR） of both types of GNPs. Enhanced FI was detected in conjugation to Rhodamine B （RhB） and Sulforhodamine B （SRB）, both with excitation peaks in the SPR regions of the GNPs. The enhanced FI was detected both in solution and in solid phantoms by the FLIM measurements. DR measurements detected the presence of GNRs within the solid phantoms by recording the dropped rates of light scattering in wavelengths corresponding to the absorption spectra of the GNRs. With the inclusion of MEF, this promising dual-mode imaging technique enables efficient and sensitive molecular and functional imaging.
基金the National High Technology Research and Development Program (863) of China(No. 2008AA12Z108)
文摘In this paper,a focusing approach is presented to widen the use of efficient monostatic imaging algorithms for azimuth-invariant bistatic synthetic aperture radar(SAR) data.The bistatic range history is modeled by a polynomial of azimuth time.Using this model,an analytic form of the signal spectrum in the 2D frequency domain is derived,and a simple single-valued relation between the transmitter and receive ranges is established.In this way,a lot of monostatic image formation algorithms can be extended for the bistatic SAR data,and a bistatic chirp scaling algorithm is developed as an application of the new approach.This algorithm can be used to process the azimuth-invariant bistatic configuration where the transmitter and receiver platforms are moving on parallel tracks with the same velocity.In addition,some simulation results are given to demonstrate the validity of the proposed approach.
