PubMed Health⌕ Search

Biomedical subjects

Zhe Chen

Publications and source records attributed to Zhe Chen.

At least 19 recordsLinked to original sources
PubMed2026

Synthetic community derived from the root core microbes of a desert shrub Caragana korshinskii enhances wheat drought tolerance.

BACKGROUND: Drought, intensified by climate change, poses a mounting threat to global food security by severely constraining crop productivity. While microbial inoculants offer promise for drought tolerance, their poor adaptability remains insufficient for extremely water-deficient environments. Desert plants host unique drought-adapted microbiomes that remain largely unexplored for agricultural applications. RESULTS: Here, we investigated the microbial community of the desert shrub Caragana korshinskii and identified a core set of drought-responsive strains. A synthetic microbial community (SynCom) derived from these strains significantly improved wheat growth under drought stress. Metagenomic analyses revealed that microbial functions related to biofilm formation, quorum sensing, and carbon metabolism were enriched, with Pseudomonas identified as a key functional taxon. Guided by inter-strain interactions in biofilm assembly, we streamlined the consortium into a five-member synthetic community, where quorum-sensing signals promoted community-wide biofilm formation. Community biofilm production improved strain colonization and conferred greater drought tolerance compared to monocultures. In plants, mechanistic investigations indicated that the simplified SynCom inoculation universally upregulated MAPK and jasmonic acid signaling pathways. Furthermore, carbohydrate metabolic pathways such as starch and sucrose metabolism were specifically activated, suggesting a multi-level mechanism underlying SynCom-mediated drought tolerance. CONCLUSIONS: These findings demonstrate that SynCom constructed on the endophytic flora of desert plants can significantly enhance crop drought tolerance. Our work highlights the pivotal role of community biofilm synthesis in facilitating root colonization and activating a multidimensional drought tolerance network in plants. This study not only gives an ecological perspective on desert microbiome adaptations but also offers a strategic framework for developing effective microbial inoculants for arid-region agriculture. Video Abstract.

Caragana↗
PubMed2007

[Construction of a therapeutic effect evaluation system for patients with primary liver cancer based on syndrome differentiation in traditional Chinese medicine].

OBJECTIVE: To construct a system of therapeutic effect evaluation for patients with primary liver cancer according to the theory of syndrome differentiation in traditional Chinese medicine (TCM), and to examine its reliability. METHODS: Analytic hierarchy process and 100 mm surveyor's rod method were applied to obtain bottom layer and top level syndromes, which were used to construct the method of therapeutic effect evaluation, and its reliability was verified in clinical practice by comparing with some evaluation criteria in Western medicine, such as cancer severity scale; Karnofsky performance scale; Child-Pugh classification, cancer staging classification, and quality of life scale, etc. RESULTS: A system of therapeutic effect evaluation was constructed, and it could reflect the progress of tumor, changes of hepatic function and constitution. The evaluation scores acquired from the system were highly associated with the quality of life of the patients. CONCLUSION: The system of therapeutic effect evaluation can reflect the severity of disease and the characteristics of TCM treatment.

Carcinoma, Hepatocellular↗
PubMed2006

Limitations of silicon diodes for clinical electron dosimetry.

This work investigates the relevance of several factors affecting the response of silicon diode dosemeters in depth-dose scans of electron beams. These factors are electron energy, instantaneous dose rate, dose per pulse, photon/electron dose ratio and electron scattering angle (directional response). Data from the literature and our own experiments indicate that the impact of these factors may be up to +/-15%. Thus, the different factors would have to cancel out perfectly at all depths in order to produce true depth-dose curves. There are reports of good agreement between depth-doses measured with diodes and ionisation chambers. However, our measurements with a Scantronix electron field detector (EFD) diode and with a plane-parallel ionisation chamber show discrepancies both in the build-up and in the low-dose regions, with a ratio up to 1.4. Moreover, the absolute sensitivity of two diodes of the same EFD model was found to differ by a factor of 3, and this ratio was not constant but changed with depth between 5 and 15% in the low-dose regions of some clinical electron beams. Owing to these inhomogeneities among diodes even of the same model, corrections for each factor would have to be diode-specific and beam-specific. All these corrections would have to be determined using parallel plane chambers, as recommended by AAPM TG-25, which would be unrealistic in clinical practice. Our conclusion is that in general diodes are not reliable in the measurement of depth-dose curves of clinical electron beams.

Dose-Response Relationship, Radiation↗
PubMed2006

A gradient feature weighted Minimax algorithm for registration of multiple portal images to 3DCT volumes in prostate radiotherapy.

PURPOSE: To develop an accurate, fast, and robust algorithm for registering portal and computed tomographic (CT) images for radiotherapy using a combination of sparse and dense field data that complement each other. METHODS AND MATERIALS: Gradient Feature Weighted Minimax (GFW Minimax) method was developed to register multiple portal images to three-dimensional CT images. Its performance was compared with that of three others: Minimax, Mutual Information, and Gilhuijs' method. Phantom and prostate cancer patient images were used. Effects of registration errors on tumor control probability (TCP) and normal tissue complication probability (NTCP) were investigated as a relative measure. RESULTS: Registration of four portals to CTs resulted in 30% lower error when compared with registration with two portals. Computation time increased by nearly 50%. GFW Minimax performed the best, followed by Gilhuijs' method, the Minimax method, and Mutual Information. CONCLUSIONS: Using four portals instead of two lowered the registration error. Reduced fields of view images with full feature sets gave similar results in shorter times as full fields of view images. In clinical situations where soft tissue targets are of importance, GFW Minimax algorithm was significantly more accurate and robust. With registration errors lower than 1 mm, margins may be scaled down to 4 mm without adversely affecting TCP and NTCP.

Algorithms↗
PubMed2006

Evaluation of the EDR-2 film for relative dosimetry of high-energy photon and electron beams.

A sensitometric study of Kodak XV and EDR-2 radiographic films (Eastman Kodak Company, Rochester, NY) was performed using photons ranging from 75 kV to 18 MV and electrons ranging from 6 to 20 MeV. To investigate the applicability of the EDR-2 film for clinical radiation dosimetry, percentage depth-doses, profiles and distributions in open and dynamically wedged fields were measured using film and compared with data from a linear diode. Moreover, conventional quality assurance dose parameters were measured, including open-field dose profiles to determine flatness and symmetry of photon and electron beams. Finally, film was employed to validate dose distributions produced by complex computerised treatment planning techniques. Our conclusion is that the EDR-2 film is an effective tool for relative dosimetry of photon and electron beams.

Dose-Response Relationship, Radiation↗
PubMed2006

When does visual attention select all features of a distractor?

What happens after visual attention is allocated to an object? Although many theories of attention assume that all of its features are selected and processed, there has been little direct evidence that an irrelevant feature dimension of an attended nontarget is processed. In 5 experiments presented here, the authors used a singleton paradigm to investigate the effect of attention on nontarget objects. Participants made a speeded feature discrimination of a target for which the response was either compatible or incompatible with an irrelevant feature dimension of a distractor. The results show that the irrelevant distractor features were processed to the point that they interfered with the response to the target. The response compatibility effect was observed even when the location of the target or the distractor was invariant, although it was much weaker when both locations were invariant. These results demonstrate that in many circumstances, an attended distractor is completely selected and fully processed, and the complete processing of distractors depends on a number of factors, many of which are related to the strength of attention to the distractor.

Attention↗
PubMed2006

Potential impact of prostate edema on the dosimetry of permanent seed implants using the new 131Cs (model CS-1) seeds.

Our aim in this work was to study the potential dosimetric effect of prostate edema on the accuracy of conventional pre- and post-implant dosimetry for prostate seed implants using the newly introduced 131Cs seed, whose radioactive decay half-life (approximately 9.7 days) is directly comparable to the average edema resolution half-life (approximately 10 days) observed previously by Waterman et al. for 125I implants [Int. J. Radiat. Oncol. Biol. Phys. 41, 1069-1077 (1998)]. A systematic calculation of the relative dosimetry effect of prostate edema on the 131Cs implant was performed by using an analytic solution obtained previously [Int. J. Radiat. Oncol. Biol. Phys. 47, 1405-1419 (2000)]. It was found that conventional preimplant dosimetry always overestimates the true delivered dose as it ignores the temporary increase of the interseed distance caused by edema. The overestimation for 131Cs implants ranged from 1.2% (for a small edema with a magnitude of 10% and a half-life of 2 days) to approximately 45% (for larger degree edema with a magnitude of 100% and a half-life of 25 days). The magnitude of pre- and post-implant dosimetry error for 131Cs implants was found to be similar to that of 103Pd implants for typical edema characteristics (magnitude < 100%, and half-life <25 days); both of which are worse compared to 125I implants. The preimplant dosimetry error for 131Cs implants cannot be compensated effectively without knowing the edema characteristics before the seed implantation. On the other hand, the error resulted from a conventional post-implant dosimetry can be minimized (to within +/-6%) for 131Cs implants if the post-implant dosimetry is performed at 10+/-2 days post seed implantation. This "optimum" post-implant dosimetry time is shorter than those determined previously for the 103Pd and 125I implants at 16+/-4 days and 6+/-1 weeks, respectively.

Brachytherapy↗
PubMed2006

Automated 2D-3D registration of a radiograph and a cone beam CT using line-segment enhancement.

The objective of this study was to develop a fully automated two-dimensional (2D)-three-dimensional (3D) registration framework to quantify setup deviations in prostate radiation therapy from cone beam CT (CBCT) data and a single AP radiograph. A kilovoltage CBCT image and kilovoltage AP radiograph of an anthropomorphic phantom of the pelvis were acquired at 14 accurately known positions. The shifts in the phantom position were subsequently estimated by registering digitally reconstructed radiographs (DRRs) from the 3D CBCT scan to the AP radiographs through the correlation of enhanced linear image features mainly representing bony ridges. Linear features were enhanced by filtering the images with "sticks," short line segments which are varied in orientation to achieve the maximum projection value at every pixel in the image. The mean (and standard deviations) of the absolute errors in estimating translations along the three orthogonal axes in millimeters were 0.134 (0.096) AP(out-of-plane), 0.021 (0.023) ML and 0.020 (0.020) SI. The corresponding errors for rotations in degrees were 0.011 (0.009) AP, 0.029 (0.016) ML (out-of-plane), and 0.030 (0.028) SI (out-of-plane). Preliminary results with megavoltage patient data have also been reported. The results suggest that it may be possible to enhance anatomic features that are common to DRRs from a CBCT image and a single AP radiography of the pelvis for use in a completely automated and accurate 2D-3D registration framework for setup verification in prostate radiotherapy. This technique is theoretically applicable to other rigid bony structures such as the cranial vault or skull base and piecewise rigid structures such as the spine.

Algorithms↗
PubMed2006

Application of Gafchromic film in the dosimetry of an intravascular brachytherapy source.

The methodology of brachytherapy source dosimetry with Gafchromic MD 55-2 film (ISP Technologies, Inc.) is examined with an emphasis on the nonlinearity of the optical density-dose relation within the dynamic dose range, the radial distance-dependent measurement uncertainty, and the format of data presentation. The specific source chosen for this study was a Checkmate (Cordis Corporation) intravascular brachytherapy system. The two-dimensional dose distribution around the source was characterized by a comprehensive analysis of measurement uncertainties. A comparative analysis of the dosimetric data from the vendor and from the scientific literature showed a substantial consistency of the information available for the Checkmate source. Our two-dimensional dosimetric data for the Checkmate source trains is presented in the form of measured along and away dose tables.

Blood Vessels↗
PubMed2006

Morphological and pathologic changes of experimental chronic atrophic gastritis (CAG) and the regulating mechanism of protein expression in rats.

OBJECTIVE: To study the pathologic change and molecular regulation in cell proliferation and apoptosis of gastric mucosa in rats with chronic atrophic gastritis (CAG), and evaluate the possible mechanisms. METHODS: Rats were administered with 60% alcohol or 2% salicylate sodium, 20 mmol/L deoxycholate sodium and 0.1% ammonia water to establish chronic atrophic gastritis (CAG) models. The gastric specimens were prepared for microscopic view with hematoxylin and eosin (H-E) and alcian blue (A-B) stain. The number of infiltrated inflammatory cells, the thickness of the mucosa gland layer (microm) and the number of gastric glands were calculated. The damage of barrier in mucosa with erosion or ulceration, and the thickness of mucin were examined by scanned electron microscope (SEM). The levels of PGE(2), EGF (epiderminal growth factor) and gastrin in the serum were measured with radioimmunoassay or ELISA method. The immunohistochemistry method was used to observe the number of G cells, the expression of protein of EGFR (EGF receptor), C-erbB-2, p53, p16 and bcl-2 in gastric tissue. RESULTS: Under SEM observation, the gastric mucosa was diffused erosion or ulceration and the thickness of mucin was decreased. Compared with normal rats, the grade of inflammatory cell infiltration in CAG rats was elevated, whereas the thickness and number of gastric gland were significantly lower (P<0.05). Compared with normal level of (0.61+/-0.28) microg/L, EGF in CAG (2.24+/-0.83) microg/L was significantly higher (P<0.05). The levels of PGE(2) and gastrin in serum were significantly lower in CAG rats than that in normal rats (P<0.05). Immunohistochemistry detection showed that the number of G cell in antrum was lower in CAG group (P<0.05). Immuno-stain showed EGFR protein expression in the basal and bilateral membrane, and the cytoplasma in atrophic gastric gland, while negative expression was observed in normal gastric epithelial cells. Positive staining of p53 and p16 protein was localized in the nucleus of epithelial cells. The former was higher positively expressed in atrophic gland, while the later was higher positively stained in normal gastric tissue. bcl-2 protein was positively stained in the cytoplasma in atrophic gastric gland, while very weakly stained in normal gastric tissue. CONCLUSION: The pathological findings in gastric gland accorded with the Houston diagnostic criteria of antrum-predominant CAG. CAG in rats was related with the damage of barrier in gastric mucosa and the misbalance of cell proliferation and apoptosis. There was high protein expression of oncogene, while inhibitor of suppressor gene in CAG rats indicated high trend of carcinogenesis.

Animals↗
PubMed2006

Reinstating object-based attention under positional certainty: the importance of subjective parsing.

Previous studies have shown that interference from flanking distractors can be modulated by the object organization of the scene. The experiments reported here test for object-based attention under conditions of positional certainty, which allow a narrow focus of attention to the target. Prior research has suggested that object-based attention does not arise in these circumstances, but the experiments presented here show that object-based attention can still appear if previous experience with the stimuli leads participants to interpret the stimulus pattern as two separate objects. Two control experiments demonstrate that the appearance of object-based attention is not due simply to a widening of the focus of spatial attention. The presence of object-based attention in such a focused-attention task argues against Shomstein and Yantis's (2002) proposed explanation of object-based attention based on priority in the order of visual search.

Attention↗
PubMed2006

[Study on the growth of orbital volume in individuals at different ages by computed tomography].

OBJECTIVE: To study the growth aspects of orbital volume and to establish the normal value of orbital volume by computed tomography (CT). METHODS: One hundred and twenty three individuals without eye diseases (64 males, 59 females) were divided into 5 groups according to the age. Orbital volume and length of horizontal transverse axis and anterior-posterior axis of the eye were measured at different levels in original or reconstructive CT images. The relationship between orbital volume and age, gender and eyeball volume was analyzed. RESULTS: There was no difference between the left and right orbital volume in all age groups. Orbital volume grew rapidly before 20 years of old. Mean orbital volume in males aged 17 and females aged 13 was 23.54 and 21.75 ml, respectively, which reached 95% of the adult orbital volume. In normal adult, orbital volume in the male was larger than that of the female. The mean orbital volume of adult male and female was (25.04 +/- 2.37) ml and (22.89 +/- 2.67) ml, respectively. A strong linear correlation was presented between the age and orbital volume (P < 0.05). The difference of orbital volume between the male and female was statistically non-significant before 14 years old (P = 0.315). The growth of eyeball volume was consistent with that of the orbital volume, the ratio of eyeball/orbit volume was decreased with age from 0.40 to 0.26. CONCLUSIONS: There is no difference between the right and left orbital volume. Orbital volume is correlated with age and gender. Orbital volume grows rapidly before 20 years of old and still grows slowly after 40 years old.

Adolescent↗
PubMed2006

[Progress on research and application of traditional Chinese medicine in intervention treatment of primary liver carcinoma].

Status of research and application of traditional Chinese medicine (TCM) in intervention treatment of primary liver carcinoma in the latest three years was reviewed in this paper. The effects of TCM combining interventional therapy mainly embodied in three aspects: the anti-tumor action, the effects for treatment of embolism syndrome and the effects for preventing and treating recurrence and metastasis. And the keystone in further researches was also pointed out, it should be focused on anti-angiogenesis of tumor by TCM for better preventive and therapeutic effects on post-intervention recurrence and metastasis.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

Stochastic correlative firing for figure-ground segregation.

Segregation of sensory inputs into separate objects is a central aspect of perception and arises in all sensory modalities. The figure-ground segregation problem requires identifying an object of interest in a complex scene, in many cases given binaural auditory or binocular visual observations. The computations required for visual and auditory figure-ground segregation share many common features and can be cast within a unified framework. Sensory perception can be viewed as a problem of optimizing information transmission. Here we suggest a stochastic correlative firing mechanism and an associative learning rule for figure-ground segregation in several classic sensory perception tasks, including the cocktail party problem in binaural hearing, binocular fusion of stereo images, and Gestalt grouping in motion perception.

Acoustic Stimulation↗
PubMed2005

Structure of the p115RhoGEF rgRGS domain-Galpha13/i1 chimera complex suggests convergent evolution of a GTPase activator.

p115RhoGEF, a guanine nucleotide exchange factor (GEF) for Rho GTPase, is also a GTPase-activating protein (GAP) for G12 and G13 heterotrimeric Galpha subunits. The GAP function of p115RhoGEF resides within the N-terminal region of p115RhoGEF (the rgRGS domain), which includes a module that is structurally similar to RGS (regulators of G-protein signaling) domains. We present here the crystal structure of the rgRGS domain of p115RhoGEF in complex with a chimera of Galpha13 and Galphai1. Two distinct surfaces of rgRGS interact with Galpha. The N-terminal betaN-alphaN hairpin of rgRGS, rather than its RGS module, forms intimate contacts with the catalytic site of Galpha. The interface between the RGS module of rgRGS and Galpha is similar to that of a Galpha-effector complex, suggesting a role for the rgRGS domain in the stimulation of the GEF activity of p115RhoGEF by Galpha13.

Amino Acid Motifs↗
PubMed2005

Selective attention and the perception of an attended nontarget object.

Although many theories of attention assume that attending to an object results in the processing of all its feature dimensions, there has been no direct evidence that the irrelevant dimensions of an attended nontarget object are encoded. This article explores factors that modulate such processing. In 6 experiments, participants made a speeded response to a probe preceded by a prime that varied in 2 dimensions. Their reaction times to the probe were influenced by the response compatibility between the relevant and irrelevant dimensions of the prime. Furthermore, the effect was observed only when attention was directed to a nonlocation object feature and when participants' reaction times were relatively long. These results suggest that the effect of attention on a nontarget object is more complex than was previously understood.

Attention↗
PubMed2005

Dose rate dependence of the relative biological effectiveness of 103Pd for continuous low dose rate irradiation of BA1112 rhabdomyosarcoma cells in vitro relative to acute exposures.

PURPOSE: To measure the relative biological effectiveness (RBE) of continuous low dose rate irradiation (CLDRI) using 103Pd sources relative to acute high dose rate irradiations (AHDRI) from a 250 kVp x-ray beam and an x-ray beam having an equivalent mono-energetic photon energy equal to the average energy of the 103Pd source for BA1112 rhabdomyosarcoma cells. MATERIALS AND METHODS: A customized 103Pd irradiator was built to provide CLDRI using 103Pd at different dose rates relevant to clinical interstitial brachytherapy to BA1112 rhabdomyosarcoma cells growing in exponential phase in culture. A special x-ray beam that simulates the photon energies emitted by the 103Pd source was also developed to provide acute high dose rate irradiation at those energies. Cell survival curves from different irradiation conditions were measured. The RBE with respect to AHDRI using standard 250 kVp x-rays was determined from the doses required to achieve a cell surviving faction of 0.01. RESULTS: For acute irradiation, the RBE of the x-rays simulating (103)Pd was 1.24 relative to 250 kVp x-rays. A profound dose rate effect was observed at low dose rates in the range of 6.8 - 14.4 cGy/h that are typical of permanent interstitial brachytherapy. At cell-surviving fraction of 0.01, the RBE of CLDRI at 6.8 and 14.4 cGy/h using 103Pd sources was reduced by a factor of 3 and 2, respectively, relative to the acute exposure. This observation is in good agreement with recent in vivo tumor cure studies performed on BA1112 tumor. CONCLUSION: The relative biological effectiveness of the photons emitted by 103Pd depends on both the linear energy transfer (LET) of the low energy photons and the dose rate of the irradiation. The higher LET of 103Pd photons is biologically more effective in killing BA1112 tumor cells compared to conventional 250 kVp x-rays when both are delivered at the same dose rate. But the gain in RBE that results from the higher LET can be quickly negated by the reduced dose rate of the irradiation.

Animals↗