PubMed Health⌕ Search

Biomedical subjects

J G Zhu

Publications and source records attributed to J G Zhu.

At least 19 recordsLinked to original sources
PubMed2006

Magnetic bistability and controllable reversal of asymmetric ferromagnetic nanorings.

Magnetization reversals through the formation of a vortex state and the rotation of an onion state are two processes with comparable probabilities for symmetric magnetic nanorings with a radius of about 50 nanometers. This magnetic bistability is the manifestation of the competition between the exchange energy and the magnetostatic energy in nanomagnets. The relative probability of the two processes in symmetric nanorings is dictated by the ring geometry and cannot be altered after fabrication. In this work, we report a novel type of nanorings--asymmetric nanorings. By tuning the asymmetry, we can control the fraction of the vortex formation process from about 40% to nearly 100% by utilizing the direction of the external magnetic field. The observed results have been accounted for by the dependence of the domain-wall energy on the local cross-section area for which we have provided theoretical calculations.

Journal Article↗
PubMed2006

Phytotoxicity of lanthanum in rice in haplic acrisols and cambisols.

Growth and physiological responses of rice to lanthanum were studied to elucidate the function of lanthanum in plants and its critical concentration relative to environmental safety. Shoot La content increased with the increasing added La concentrations. When shoot La content exceeded a toxic value, plant growth and chlorophyll a/b decreased and peroxidase (POD) activity, cell membrane permeability, and content of proline in the leaf increased. Leaf chlorophyll a/b and POD activity might provide useful criteria for early diagnoses of phytotoxicity of soil contaminated by La. In the present study, the critical concentration of La for rice relative to environmental safety was suggested to be 42.03 mg kg(-1) in red soil and 83.33 mg kg(-1) in paddy soil.

Cell Membrane Permeability↗
PubMed2003

Nitrate distribution and denitrification in the saturated zone of paddy field under rice/wheat rotation.

Nitrate concentration in well water collected from the wells near farm houses was investigated in the Taihu Lake basin (TBL) of China. Nitrate-N content of the well water ranged from 0.1 to 23 mgNl(-1), and 41% exceeded the criteria (10 mg Nl(-1)). It was found that the difference in well conditions, especially the depth of the well, was the main cause of the difference in the nitrate concentration of well water, i.e. it was higher in shallow well and lower in deeper well. A recommendation was made for local farmers to drill wells deeper than 10 m in order to reduce the risk of high ingestion of nitrate-N in their drinking water. Nitrate distribution and denitrification in the saturated zone of a paddy field under rice/wheat rotation in the TBL were studied. Porous pipes were installed in triplicate at depths of 1.5, 2.0, 2.5, 3.5 and 5 m respectively to collect the soil solution samples. Results showed that nitrate was the predominant N form in soil solution of saturated zone, and it increased from 1.5 to 2.5 m depth, and decreased from 2.5 to 5 m depth. N2O captured in the soil solution was very high comparing with N2O content in air. N2O content was positively correlated with nitrate concentrations in the soil profile. These results indicate that nitrate leached into saturated zone was mainly transformed via denitrification processes. Comparing the sum of inorganic nitrogen with the total nitrogen in soil solution samples collected from those wells at the field, some soluble organic nitrogen was found about 1-2 mg N l(-1) in average.

Biotransformation↗
PubMed2001

[Cloning and expression of human anti-colonic cancer single-chain Fv fragment].

We report a new strategy for the generation of human anticolon cancer monoclonal antibodies based on the molecular cloning and expression of immunoglobulin variable region cDNAs derived from peripheral blood mononuclear cells (PBMC) that were transformed by EBV. The immortalized B cells secreting tumor-specific antibodies were identified by HRT-18 cell ELISA and cloned by limiting dilution. Heavy- and light-chain VH-CH1 (gamma) and V kappa-C kappa cDNAs were rescued from ELISA-positive cells wells by RT-PCR. VH and V kappa were amplified by 2nd PCR and linked them together by 3rd PCR assembly with the use of a (Gly4Ser)3 linker. The ScFv cDNAs were then cloned into the fUSE 5 vector and displayed on phage. Phage clones were selected on HRT-18 cells and normal human PBMC. ELISA tested phage clones randomly picked after each panning step. > 80% of the clones showed a strong ELISA reaction, demonstrating the effectiveness of the panning procedure for selecting anticolon cancer antibodies. This approach offers an effective method by combining in vitro immunization, B-cell expansion for enrichment of specific B-lymphocytes, PCR gene cloning and phage display to make high-affinity human anticolon cancer monoclonal antibody molecules.

Antibodies, Monoclonal↗
PubMed2001

[Studies on the sex difference in proteins between male and female adult worm of Schistosoma japonicum].

OBJECTIVE: To explore the sex difference in proteins between male and female adult worm of Schistosoma japonicum. METHODS: Two-electrophoresis was used to analyse the difference of protein between the male and female adult worm of S. japonicum (Chinese strain). RESULTS: Two-dimensional electrophoresis analysis revealed that at the site of 43 kDa and an isoelectric point (pI) of 5.60-5.90 the male worm exhibited a band carrying a number of spots and dots, being longer and wider than that exhibited by the female worm. The female worm exhibited 7 specific dots. CONCLUSION: The sex differences in proteins between male and female adult worms of S. japonicum are significant.

Animals↗
PubMed2000

[Study of monoclonal anti-idiotype antibody that bears the internal image of nasopharyngeal carcinoma associated antigen].

We prepared anti-idiotypic monoclonal antibodies (Ab2) against FC2 and HNL5 that recognized as nasopharyngeal cancer (NPC) associated antigens. These Ab2, which designated as 2H4 and 5D3, could inhibit the binding of FC2 or HNL5 to NPC cell lines. The anti-sera from the immunized mice that contained anti-anti-idiotype antibodies (Ab3) could compete with FC2 or HNL5 for binding with NPC cell by a competitive inhibition assay. When 2H4 or 5D3 immunized mice coupled with keyhole limpet hemocyanin(KLH), positive and specific delayed-type hypersensitivity (DTH) reaction occurred after the mice were stimulated by NPC cells. The proliferative response of the splenocytes was significantly higher in experimental groups than that in control groups. Therefore, it is suggested that the anti-idiotypic antibodies (Ab2) 2H4 and 5D3 are the Ab2 beta bearing the internal image of the epitope of NPC associated antigen, that either 2H4 or 5D3 expressing three dimensional shapes which resemble the structure of natural antigens can induce humoral and cellular immune response.

Animals↗
PubMed1998

An efficient method for small field treatment dose calculation for stereotactic radiosurgery using a LINAC.

The normal procedure for a physician-physicist team designing a treatment plan for multiarc stereotactic radiosurgery is the trial-and-error approach of changing the collimator size and the location of the isocenter of radiation and viewing the isodose curves on two-dimensional computed tomography (CT) or magnetic resonance imaging (MRI) image planes. Automatic optimization procedures have also been used to optimize beam weight or beam size. However, either process is very time consuming. To improve the speed of the dose calculation, a random sampling method has been proposed. Unfortunately, the sampled values of an objective function are different from one sample to another. Such a sampling method cannot be used in automatic optimization because the next move in an optimization process is based on the current and past objective function values. To this end, an adaptive method based on the size of the collimators is proposed and used to determine a small volume in the shape of a hollow sphere for which the dose is calculated. With an appropriate choice of an adaptive hollow sphere, the objective function calculated based on such a hollow sphere is the same as that calculated with the traditional three-dimensional (3-D) cube matrix. However, with the new adaptive method, the speed of calculating a dose can be improved by a factor of 4 to a factor of 100. Because of the improvement in the speed of calculating a treatment dose, the new adaptive hollow sphere method for calculating a treatment dose can be used routinely in designing a treatment plan.

Automation↗
PubMed1996

[Studies on preparation and characteristics of cisplatin chitosan microspheres].

In this paper, the preparation, drug content, size and size distribution, appearance and morphology, release characteristics in vitro and degradation characteristics of cisplatin chitosan microspheres (CDDP-DAC-MS) were studied. CDDP-DAC-MS were prepared by emulsion-crosslink technique. The CDDP-DAC-MS was shown to have rough spherical surface under scanning electron microscopy. The average diameter of the microspheres was 74.80 microns and CDDP content was 20.83% +/- 0.36%. CDDP-DAC-MS swelled slightly in saline after 1 h. Within the test period, the release of CDDP from CDDP-DAC-MS in saline solution could be described by first-order equation. The microspheres were sterilized by 60Co radiation. After 28 d of hepatic artery embolization with CDDP-DAC-MS in dogs, pathological photomicrograph showed that CDDP-DAC-MS could still be observed.

Animals↗
PubMed1995

Treatment planning optimization for multiple arcs stereotactic radiosurgery using a linear accelerator.

PURPOSE: Multiarc stereotactic radiosurgery is a technique used to irradiate an intracranial tumor with minimal damage to the surrounding normal tissue. The purpose of this paper is to present a method for and the results from optimizing three dimensional (3D) treatment dose for multiarc stereotactic radiosurgery. METHODS AND MATERIALS: The normal procedure for a physician-physicist team designing a treatment plan for multiarc stereotactic radiosurgery is the trial-and-error approach of changing the collimator size and the isocenter of radiation by viewing the isodose curves on a two dimensional (2D) computed tomography (CT) or magnetic resonance imaging (MRI) image plane. Not only is this time consuming, but the resulting treatment plan is not optimal in most, if not all, cases. One reason for such nonconformal isodose curves is that the same collimator size is used for all arcs. However, it is very difficult to determine manually the different collimator sizes for different arcs. A derivative free optimization method is used to optimize the collimator size for each arc, as well as the 3D coordinates of the isocenter(s). RESULTS: One spherical and two ellipsoidal artificial tumors, and one actual tumor, were used to show the utilities of the optimization process. The 90% isodose curves resulting from optimization conform very well with the tumor; whereas the 90% isodose curves from the conventional method either do not envelop the entire tumor when the collimator size is too small, or a large volume of normal tissue is also irradiated by the 90% dose when the next larger collimator size is used. CONCLUSIONS: When the collimator size for each arc and the location of the isocenters(s) are optimized in a multiarc stereotactic surgery treatment plan, the 90% isodose curve conforms to the tumor much better than when the same collimator size is used for all arcs.

Algorithms↗
PubMed1995

Identification and partial sequence of a cDNA that is differentially expressed in human brain tumors.

Differential display technique was used to identify mRNAs that are differentially expressed in malignant versus benign brain tumors. Using this method, a novel 1.4-kb long cDNA (MM1) clone was isolated and sequenced. The nucleotide and the translated amino acid sequence of MM1 cDNA clone did not show significant homology to any known sequence in the Genebank. The expression of MM1 appears to be almost eightfold higher in glioblastomas compared to low grade astrocytomas and slightly higher in malignant meningiomas than in benign meningiomas. The size of mRNA from northern analysis appears to be 7 kb, which is much higher than the size of the isolated MM1 cDNA clone. Expression of MM1 was also seen in various cell lines derived from human tumors including glioblastomas. Whereas low level expression was seen in kidney, esophagus, liver, lymph node, ovary and testis, none of the other tissues from a total of 18 different human organs showed any MM1 expression.

Amino Acid Sequence↗
PubMed1995

[Studies on hepatic arterial embolization with cisplatin-chitosan-microspheres in dogs].

Cisplatin-chitosan-microspheres (CDDP-DAC-MS) was chosen as a model preparation. Pharmacokinetics, targeting and embolization effects and alteration of liver function were studied after hepatic arterial embolization in dogs with CDDP-DAC-MS, and the platinum content in plasma and liver was determined by flameless atomic absorption spectrophotometry (FAAS). The result of clinical trial was also reported. After the CDDP-DAC-MS and CDDP solution were respectively infused into hepatic artery of dogs through a 5F catheter, the plasma concentration of platinum and AUC of CDDP-DAC-MS group was lower than that of CDDP solution group, but the platinum content in hepatic tissue was 2.92 times as much as that when CDDP solution was given after 24 h. Angiograms revealed a remarkable decrease in the number of arterioles in liver, and histopathologic specimens showed nodular necrosis and hepatic cell degeneration in embolized region. The levels of GPT, GOT and ALP rose transiently after embolization and recovered to normal within 3 weeks. The clinical therapy in six liver cancer patients was successful. It would appear that CDDP-DAC-MS may be a good chemoembolization agent.

Animals↗
PubMed1991

Evidence suggesting that the ARS elements associated with silencers of the yeast mating-type locus HML do not function as chromosomal DNA replication origins.

The silent mating-type loci of Saccharomyces cerevisiae, HML and HMR, are flanked by transcriptional silencers that have ARS activity (i.e., they function as replication origins when in plasmids). To test whether these ARS elements are chromosomal origins, we mapped origins near HML (close to the left telomere of chromosome III). Our results indicate that the HML-associated ARS elements either do not function as chromosomal replication origins or do so at a frequency below our detection level, suggesting that replication from a silencer-associated origin in each S phase is not essential for the maintenance of transcriptional repression at HML. Our results also imply that the ability of a DNA fragment to function as an ARS element in a plasmid does not ensure its ability to function as an efficient chromosomal replication origin. Telomere proximity is not responsible for inactivating these ARS elements, because they are not detectably functional as chromosomal origins even in genetically modified strains in which they are far from the telomere.

Chromosome Mapping↗
PubMed1991

Androgen receptors in laryngeal carcinoma and their clinical significance.

Specific radioligand [3H] methyltestosterone incubation and dextran-coated charcoal absorption technique (DCC) were used to test cytosol androgen receptors (AR) of laryngeal carcinoma in 33 patients. In all specimens, high level AR ranged from 3 to 16.9 fmol/mg of cytosol protein (mean 10 +/- 3.9 fmol/mg), and dissociation constant was 1.7 x 10(-9) mole. Laryngeal carcinoma is considered a sex hormone-dependent tumor. High level of AR in laryngeal carcinoma may indicate a super-demand on androgen; when the content of AR increases the tumor proliferates perniciously. Antiandrogen endocrine therapy may be helpful in treating laryngeal carcinoma.

Adult↗