PubMed Health⌕ Search

Biomedical subjects

J Deng

Publications and source records attributed to J Deng.

At least 73 records · Page 4Linked to original sources
PubMed2000

Validation of a Monte Carlo dose calculation tool for radiotherapy treatment planning.

A new EGS4/PRESTA Monte Carlo user code, MCDOSE, has been developed as a routine dose calculation tool for radiotherapy treatment planning. It is suitable for both conventional and intensity modulated radiation therapy. Two important features of MCDOSE are the inclusion of beam modifiers in the patient simulation and the implementation of several variance reduction techniques. Before this tool can be used reliably for clinical dose calculation, it must be properly validated. The validation for beam modifiers has been performed by comparing the dose distributions calculated by MCDOSE and the well-benchmarked EGS4 user codes BEAM and DOSXYZ. Various beam modifiers were simulated. Good agreement in the dose distributions was observed. The differences in electron cutout factors between the results of MCDOSE and measurements were within 2%. The accuracy of MCDOSE with various variance reduction techniques was tested by comparing the dose distributions in different inhomogeneous phantoms with those calculated by DOSXYZ without variance reduction. The agreement was within 1.0%. Our results demonstrate that MCDOSE is accurate and efficient for routine dose calculation in radiotherapy treatment planning, with or without beam modifiers.

Bone and Bones↗
PubMed2000

Photon beam characterization and modelling for Monte Carlo treatment planning.

Photon beams of 4, 6 and 15 MV from Varian Clinac 2100C and 2300C/D accelerators were simulated using the EGS4/BEAM code system. The accelerators were modelled as a combination of component modules (CMs) consisting of a target, primary collimator, exit window, flattening filter, monitor chamber, secondary collimator, ring collimator, photon jaws and protection window. A full phase space file was scored directly above the upper photon jaws and analysed using beam data processing software, BEAMDP, to derive the beam characteristics, such as planar fluence, angular distribution, energy spectrum and the fractional contributions of each individual CM. A multiple-source model has been further developed to reconstruct the original phase space. Separate sources were created with accurate source intensity, energy, fluence and angular distributions for the target, primary collimator and flattening filter. Good agreement (within 2%) between the Monte Carlo calculations with the source model and those with the original phase space was achieved in the dose distributions for field sizes of 4 cm x 4 cm to 40 cm x 40 cm at source surface distances (SSDs) of 80-120 cm. The dose distributions in lung and bone heterogeneous phantoms have also been found to be in good agreement (within 2%) for 4, 6 and 15 MV photon beams for various field sizes between the Monte Carlo calculations with the source model and those with the original phase space.

Models, Theoretical↗
PubMed2000

Energy- and intensity-modulated electron beams for radiotherapy.

This work investigates the feasibility of optimizing energy- and intensity-modulated electron beams for radiation therapy. A multileaf collimator (MLC) specially designed for modulated electron radiotherapy (MERT) was investigated both experimentally and by Monte Carlo simulations. An inverse-planning system based on Monte Carlo dose calculations was developed to optimize electron beam energy and intensity to achieve dose conformity for target volumes near the surface. The results showed that an MLC with 5 mm leaf widths could produce complex field shapes for MERT. Electron intra- and inter-leaf leakage had negligible effects on the dose distributions delivered with the MLC, even at shallow depths. Focused leaf ends reduced the electron scattering contributions to the dose compared with straight leaf ends. As anticipated, moving the MLC position toward the patient surface reduced the penumbra significantly. There were significant differences in the beamlet distributions calculated by an analytic 3-D pencil beam algorithm and the Monte Carlo method. The Monte Carlo calculated beamlet distributions were essential to the accuracy of the MERT dose distribution in cases involving large air gaps, oblique incidence and heterogeneous treatment targets (at the tissue-bone and bone-lung interfaces). To demonstrate the potential of MERT for target dose coverage and normal tissue sparing for treatment of superficial targets, treatment plans for a hypothetical treatment were compared using photon beams and MERT.

Algorithms↗
PubMed2000

Monte Carlo verification of IMRT dose distributions from a commercial treatment planning optimization system.

The purpose of this work was to use Monte Carlo simulations to verify the accuracy of the dose distributions from a commercial treatment planning optimization system (Corvus, Nomos Corp., Sewickley, PA) for intensity-modulated radiotherapy (IMRT). A Monte Carlo treatment planning system has been implemented clinically to improve and verify the accuracy of radiotherapy dose calculations. Further modifications to the system were made to compute the dose in a patient for multiple fixed-gantry IMRT fields. The dose distributions in the experimental phantoms and in the patients were calculated and used to verify the optimized treatment plans generated by the Corvus system. The Monte Carlo calculated IMRT dose distributions agreed with the measurements to within 2% of the maximum dose for all the beam energies and field sizes for both the homogeneous and heterogeneous phantoms. The dose distributions predicted by the Corvus system, which employs a finite-size pencil beam (FSPB) algorithm, agreed with the Monte Carlo simulations and measurements to within 4% in a cylindrical water phantom with various hypothetical target shapes. Discrepancies of more than 5% (relative to the prescribed target dose) in the target region and over 20% in the critical structures were found in some IMRT patient calculations. The FSPB algorithm as implemented in the Corvus system is adequate for homogeneous phantoms (such as prostate) but may result in significant under or over-estimation of the dose in some cases involving heterogeneities such as the air-tissue, lung-tissue and tissue-bone interfaces.

Computer Simulation↗
PubMed2000

Induction of cell cornification and enhanced squamous-cell marker SPRR1 gene expression by phorbol ester are regulated by different signaling pathways in human conducting airway epithelial cells.

Phorbol ester is a strong inducer for both cell cornification and squamous-cell marker SPRR1 gene expression in conducting airway epithelial cells. However, the signaling pathways involved in the regulation of both events have not been completely elucidated. The current study focuses on the common and divergent pathways involved in the induction of these two activities by phorbol-13-myristate-12-acetate (PMA). Using a protein kinase (PK) C inhibitor, bisindolylmaleimide I, PMA-induced cell cornification and SPRR1 gene expression were abolished. Further, a PKC activator, indolactam V, induced cell cornification in the absence of PMA treatment. These results suggest a PKC-dependent signaling pathway for both gene induction and enhanced cell cornification by PMA. However, a mitogen-activated protein kinase-specific inhibitor, PD98059, could only block the gene induction event but failed to prevent cell cornification induced by PMA. These results suggest that diverse signaling pathways after PKC activation by PMA are involved in the regulation of these two events.

Biomarkers↗
PubMed2000

Activation of signal transducer and activator of transcription-3 during proliferative phases of 3T3-L1 adipogenesis.

Signal transducer and activator of transcription-3 (STAT3) is abundantly expressed in preadipocytes and adipocytes, but little is known about its activation status or functional role during adipogenesis. In this report we investigate STAT3 activation in 3T3-L1 preadipocytes before and after differentiation into adipocytes. STAT3 was highly tyrosine phosphorylated and bound to DNA in proliferating preadipocytes, but not in growth-arrested preadipocytes or adipocytes. In growth-arrested confluent preadipocytes, induction of differentiation with methylisobutylxanthine, dexamethasone, and high dose insulin led to a delayed, but prolonged (3-day), increase in STAT3 tyrosine phosphorylation. This increase in STAT3 phosphorylation coincided temporally with postconfluent preadipocyte mitotic clonal expansion. Insulin and methylisobutylxanthine alone, but not dexamethasone, induced STAT3 tyrosine phosphorylation in postconfluent cells. Diminution of endogenous STAT3 expression by antisense morpholino oligonucleotides significantly decreased preconfluent preadipocyte proliferation. Collectively, these findings suggest a regulatory role for STAT3 during the proliferative phases of adipogenesis.

1-Methyl-3-isobutylxanthine↗
PubMed2000

[Improved liposome encapsulated hemoglobin by electret technology and its influence on the blood rheologic behavior in vitro].

To study the influence of different electret properties of Liposome Encapsulated Hemoglobin(LEH) on the blood rheologic behavior in vitro, four kinds of LEH have been prepared. Their electret properties have been determined by using Thermally Stimulated Depolarization Current(TSDC). The results show that 4# LEH, whose Ta is 12 degrees C and Ia is -5.6 x 10(-9) A, has the best electret property, furthermore, the results of the thrombus formation in vitro also show that the addition of 4# LEH induces the lightest thrombus figuration in vitro. It is obvious that the rational improvement of the electret property of LEH can meliorate the surface charge of blood and effectively inhibit the formation of thrombus.

Blood Viscosity↗
PubMed2000

Body size and prostate cancer: a population-based case-control study in China.

We conducted a population-based case-control study in China to investigate whether body size plays a role in prostate cancer etiology and whether it can explain the rapid increase in prostate cancer incidence rates in China. A total of 238 cases newly diagnosed with primary prostate cancer in Shanghai, China, during 1993-1995 were included in the study. Four hundred and seventy-one healthy control subjects were randomly selected from among residents of Shanghai and frequency-matched to cases on the basis of age. In-person interviews were conducted to elicit information on height, weight history, and other lifestyle factors. Waist and hip circumferences were measured at interview. Odds ratios (ORs) were used to measure the association between prostate cancer and anthropometric variables including height, weight, body mass index (BMI), waist, hip, and right upper arm circumferences, and waist-to-hip ratio (WHR; an indicator of abdominal adiposity). High levels of WHR were related to an excess risk, with men in the highest quartile (WHR > 0.92) having an almost 3-fold risk (OR, 2.71; 95% CI = 1.66-4.41; Ptrend = 0.0001) compared with men in the lowest quartile (WHR < 0.86). In contrast, men in the highest quartile of hip circumference (>97.4 cm) had a reduced risk (OR, 0.46; 95% CI = 0.29-0.74; Ptrend = 0.0002) relative to men in the lowest quartile (<86 cm). No association was found for height, usual adult weight, or preadult and usual adult BMI. Our results suggest that even in a very lean population (average BMI = 21.9), abdominal adiposity may be associated with an increased risk of clinical prostate cancer, pointing to a role of hormones in prostate cancer etiology. Additional research is needed to confirm these findings in prospective studies, especially in Western populations where abdominal obesity is much more common, and to clarify the underlying hormonal mechanisms involved.

Abdomen↗
PubMed2000

Buprenorphine given after surgery does not alter renal ischemia/reperfusion injury.

BACKGROUND AND PURPOSE: Potential drugs for human acute renal failure are often tested in an animal model of renal ischemia/reperfusion injury. Analgesics are often not given after surgery because of concerns that they would alter renal function. Therefore, we tested whether postoperative analgesia would alter animal health or affect the degree of renal injury. METHODS: Mice were subjected to either 32 or 37 minutes of renal ischemia, given two or six doses of buprenorphine or vehicle at 12-hour intervals, and followed for 72 hours. In some animals, we measured body temperature and physical activity by use of telemetry. RESULTS: Animals treated with buprenorphine recovered more rapidly from surgery based on postoperative activity, and had a small but not significant tendency for faster restoration of normal body temperature. Animals treated with buprenorphine had less weight loss after 37 minutes of ischemia. Buprenorphine given after surgery did not influence the degree of renal injury after ischemia/reperfusion. CONCLUSIONS: Buprenorphine should be given after renal ischemia-reperfusion surgery because administration of the proper analgesic improved animal health without interfering with the renal ischemia/reperfusion model. Analgesic treatment at the time of the operation and 12 hours after was sufficient. Buprenorphine may reduce the post-surgical stress response, and thus potentially improve the specificity of testing for drugs that reduce or treat renal injury.

Analgesics, Opioid↗
PubMed2000

[Evaluation of red cell mean corpuscular volume and simple tube red cell osmotic fragility quantitative test in detection of thalassemia].

OBJECTIVE: To evaluate and compare the detection efficiency of red cell mean corpuscular volume(MCV) test against simple tube red cell osmotic fragility quantitative test(STROFQT) in diagnosis of thalassemia. METHODS: 1978 subjects (989 couples) were detected by both MCV test and STROFQT, 158 samples from subjects were tested by alpha,beta-thalassemia DNA polymerase chain reaction(PCR) and serum ferritin test. RESULTS: The positive rate (9.0%), sensitivity (98.9%) of MCV test were higher than those of STROFQT (8.1%, 88.6%) (P < 0.05). The specificity of MCV test showed no statistic significance compared with that of STROFQT (P > 0.05). CONCLUSION: Both MCV test and STROFQT served as helpful approaches in detection of thalassemia, MCV test shows better diagnostic efficiency for screening than STROFQT.

Adult↗
PubMed2000

[Spectrum of mycotic keratitis in China].

OBJECTIVE: To investigate the spectrum of mycotic keratitis in China. METHODS: We scraped and evaluated 615 mycotic keratitis in microbiology laboratories of Zhengzhou (central China), Shijiazhuang (north China) and Guangzhou (south China) in the twenty-two years between Jan. 1, 1975 and Jun. 30, 1997. RESULTS: Organisms of 18 genuses and 615 species isolated from corneal ulcers were found. Fusarium species were isolated the most frequently (65.0% in Zhengzhou, 33.3% in Shijiazhuang and 39.2% in Guangzhou), followed by Aspergillus (20.5% in Zhengzhou, 21.7% in Shijiazhuang, 30.7% in Guangzhou), Penicillium (3.6% in Zhengzhou, 11.6% in Shijiazhuang) and Curvularis (13.1% in Guangzhou). Between Jan. 1, 1975 and Dec. 31, 1986, Aspergillus species were most commonly isolated in Guangzhou (48.5%), followed by Fusarium (27.7%) and Penicillium (14.27%). CONCLUSIONS: Just as different regions of the world are characterized by specific endemic infections, the predominating organisms in corneal fungal infections also vary throughout the world. These regional differences in causative organisms in mycotic keratitis are clinically important because they influence the initial and more definite therapy. This study shows that Fusarium species are the most common organisms of mycotic keratitis in China.

Aspergillus↗
PubMed2000

[Polymorphism of ACE gene and its relationship with serum ACE activity in the Hans in Chengdu region].

This study was aimed at the angiotensin converting enzyme (ACE) gene insertion/deletion(I/D) polymorphism distribution in Chinese and its relationship with serum ACE activity(SACE). SACE activity and ACE gene polymorphism in 90 healthy persons in Chengdu region were investigated using a spectrophotometric assay and the PCR technique, respectively. The results showed that, in the Hans, DD genotype of ACE gene was 18%, DI genotype 44%, and II genotype 38%. Allele frequencies were 0.40 for the D allele and 0.60 for the I allele. There were significant relationships between ACE I/D polymorphism and SACE activity. The results suggest that ACE genotype distribution be different between races, that II genotype and I allele be more frequent in Chinese, and that SACE activity be under the influence of a genetic polymorphism of ACE in Chinese.

Adult↗
PubMed2000

[The changes of serum angiotensin converting enzyme activity in Type 2 diabetes and its vascular complications].

This investigation was made with reference to the changes of serum angiotensin converting enzyme (SACE) activity in type 2 diabetes and its vascular complications. SACE activity was studied in 127 type 2 diabetic patients and 90 healthy persons by using a spectrophotometric assay. The results showed SACE activity was obviously higher in diabetic patients (459.51 +/- 175.85 U) than in healthy persons (321.14 +/- 121.27 U); SACE activity was significantly higher in type 2 diabetic patients with diabetic nephropathy (548.27 +/- 166.60 U) than in patients without diabetic nephropathy (383.2 +/- 139.00 U), but there was no difference between patients with microalbuminuria and macroalbuminuria; no statistical difference was detected in SACE activity between diabetic patients with diabetic retinopathy (465.64 +/- 178.93 U) and without retinopathy (449.07 +/- 170.04 U); SACE activity was not associated with the course of diabetes, blood pressure, blood lipid and blood glucose. These data suggest that raised SACE activity might only play a role in the initiation of type 2 diabetes and diabetic nephropathy, but not relate to the progress of diabetic nephropathy, the onset of diabetic retinopathy and hypertension.

Aged↗
PubMed2000

Detection of glutamate and gamma-aminobutyric acid in vitreous of patients with proliferative diabetic retinopathy.

PURPOSE: To study the levels of glutamate and gamma-aminobutyric acid (GABA) in vitreous of patients with proliferative diabetic retinopathy (PDR) and to investigate their roles in retinal ischemia. METHOD: Vitreous samples were collected from 25 patients (27 eyes) with PDR and 14 patients (14 eyes) with idiopathic macular hole. Glutamate and GABA detection were performed by high-performance liquid chromatography (HPLC). RESULTS: Patients with PDR had significantly higher concentrations of glutamate and GABA than the control group. The glutamate level has a significantly positive correlation with GABA level. CONCLUSION: Detection of glutamate and GABA in vitreous provides biochemical support for the mechanism and treatment of ischemic retinal damage in patients with PDR.

Diabetic Retinopathy↗
PubMed2000

[Study on the role of superoxide anion in promoting proliferation and transformation of rat liver oval cell line WB-E344].

OBJECTIVE: To study the role of superoxide anion (O2.-) in promoting proliferation and transformation of rat liver oval cell strain WB-F344. METHODS: WB-F344 cells cultured were stimulated directly by O2.- generated by interaction of xanthine with xanthine oxidase (X-XO). The effect of O2.- in promoting proliferation of WB cells was investigated by using MTT colorimetric analysis, 3H-Tdr incorporation liquid scintillation counter and 3H-Tdr incorporation autoradiography. WB cells initiated with N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) were promoted by stimulating continuously with O2.- of low concentration (X: 100 mumol/L, XO: 0.2 mU/ml). The transformation effect was tested by morphologic observation, karyotype analysis and anchorage-independent growth assay. RESULTS: Proliferation of WB cells was induced obviously by O2.- of low concentration for only one time. WB cells initiated with MNNG were transformed by action with O2.- of low concentration continuously for 15 d and typical morphologic character of transformed cells was observed. In karyotype analysis the cells chromosome number changed and the frequency of structure aberration raised dramatically. Also the transformed cells could form clone on self-solid culture medium. CONCLUSIONS: The biological effect of O2.- was related closely with its dose; The effects of low concentration in promoting proliferation and transformation of liver oval cells indicate its important role in hepatocarcinogenesis and antioxidation was able to provide a new clue in prevention and cure of hepatoma.

Animals↗
PubMed1999

Circadian rhythm of patched1 transcription in the pineal regulated by adrenergic stimulation and cAMP.

The tumor suppressor patched1 (PTC1), a product of the mammalian homologue of the Drosophila segment polarity gene patched, is a receptor for hedgehog (HH) and is crucial for embryonic development. Although little is known about the signal transduction pathways leading to the activation of ptc1, increased ptc1 transcription has always been associated with elevated HH activity and decreased activity of cAMP-dependent protein kinase A. Here, we demonstrate that in the mammalian pineal gland, ptc1 expression exhibits a dramatic diurnal rhythm with peak expression at midnight. ptc1 mRNA expression in the pineal is regulated by a clock mechanism mediated by the superior cervical ganglion. Most importantly, ptc1 transcription can be induced by agents activating the cAMP signal transduction pathway both in vivo and in vitro and appears to be independent of HH signaling.

Adenosine Triphosphatases↗
PubMed1999

Downregulation of DNA (cytosine-5-)methyltransferase is a late event in NGF-induced PC12 cell differentiation.

DNA methylation patterns are a critical component of the epigenetic machinery that controls the expression of genetic programs in vertebrates. DNA methyltransferase gene (dnmt1) encodes the enzyme catalyzing the methylation of DNA during replication. We tested the hypothesis that the expression of dnmt1 is regulated with the developmental state of neuronal cells. We show that DNA methyltransferase (Dnmt1) activity is sharply reduced 4 days after induction of differentiation of PC12 cells with NGF. Similarly, the adult brain expresses reduced levels of Dnmt1 activity. We propose that the level of Dnmt1 is downregulated to adjust the activity of the DNA methyltransferase to a different role in mature post-mitotic neurons. Both the abundance of dnmt1 mRNA as well as the Dnmt1 polypeptide are downregulated. Downregulation of dnmt1 parallels other indicators of withdrawal from the cell cycle such as induction of p21, and downregulation of the S phase maker PCNA (proliferating cell nuclear antigen). The temporal pattern of downregulation of dnmt1 in nerve growth factor (NGF)-induced PC12 cells is different from myotube differentiation where downregulation of DNA methyltransferase and demethylation is an early event and was proposed to play a causal role in differentiation. We propose that NGF differentiation of PC12 cells represents a different paradigm of involvement of DNA methylation in terminal differentiation.

Animals↗