Biomedical subjects

X Z Tang

Publications and source records attributed to X Z Tang.

8 recordsLinked to original sources

PubMed2005

Constrained resonance in magnetic self-organization.

In a linear driven problem with integral constraints, resonant phenomena can still persist but occur away from the fundamental frequencies of the unconstrained linear system. The frequency and the mode structure of the constrained resonances are found to be the intrinsic properties of the undriven and unconstrained linear systems. This is shown with a Taylor-relaxed magnetized plasma in a torus that conserves the net toroidal flux. The constrained resonance leads to a number of modifications to the standard paradigm of Taylor relaxation in a toroidal plasma.

Journal Article↗

PubMed2005

Force-free magnetic relaxation in driven plasmas.

Taylor relaxation in a driven plasma with normal magnetic field intercepting the boundary is described by the Jensen-Chu theory, which predicts infinite energy and helicity barriers that constrain the accessible relaxed states to system scale. For a partially relaxed force-free (j=kB) plasma where k is a field line constant, nonlinearity regularizes the Jensen-Chu singularities and new branches of relaxed state become accessible, such as the flipped spheromak and other high k states.

Journal Article↗

PubMed1995

Preclinical analysis of intraperitoneal administration of 111In-labeled human tumor reactive monoclonal IgM AC6C3-2B12.

An IgM lambda human tumor cell-reactive monoclonal antibody was developed that reacts with cells of ovarian cancer, colorectal cancer, breast cancer, and certain other malignancies. The monoclonal antibody AC6C3-2B12, which was obtained from a recent recloning, was purified from tissue culture supernatants and analyzed by high-performance liquid chromatography and sodium dodecyl sulfate-PAGE. An animal model was developed in which human tumors grew either as solid peritoneal metastases or as s.c. nodules utilizing the human colorectal carcinoma cell line SW620. The biodistribution of 111In-labeled IgM conjugate was studied after i.v. or i.p. administration in nude mice bearing an s.c. xenograft or peritoneal tumor lumps of a human colorectal carcinoma (SW620). IgM administered i.v. cleared rapidly from blood and was deposited mainly in the liver [50% injected dose/g (ID)/g)], pancreas (20% ID/g), and kidney (10% ID/g) at 24 h. Tumor deposition was low (< or = 1.0% ID/g) in the s.c. tumor xenograft. In contrast, high tumor targeting (29% ID/g) was found in peritoneal tumor lumps after i.p. administration of 111In-labeled IgM. The biological half-life of IgM in the tumor was 100 h. Long peritoneal residence time (t 1/2 = 67 h) and low liver uptake (7% ID/g) were observed after i.p. administration. Blood activity was < 1% of the injected activity. Tumor:normal organ ratios were high (range, 2-290) from 2 to 144 h after i.p. administration. Whole body autoradiograms at 24 h after i.p. 111In-labeled IgM administration confirmed the biodistribution results. In normal beagle dogs, 75% of the i.p.-administered 111In-IgM decayed in the peritoneal cavity. The majority of the remaining radioactivity was taken up by mediastinal lymph nodes. Biological half-life in both locations was approximately 137 h. The i.p. administration of intact, specific radiolabeled IgM provides prolonged retention of radioactivity in tumor, low normal tissue uptake, a long peritoneal residence time, and very limited spillover of IgM into the circulation. This approach offers a promising new method for the diagnosis and treatment of certain patients with peritoneal carcinomatosis.

Animals↗

PubMed1995

Liver toxicity induced by combined external-beam irradiation and radioimmunoglobulin therapy.

High-dose radiation therapy for liver metastases of gastrointestinal malignancies might be improved by combining external-beam irradiation and radioimmunoglobulin therapy. We studied the liver toxicity of the proposed combination in healthy beagle dogs. A total dose of 30 Gy to the whole liver, delivered in 2-Gy fractions over 3 weeks, resulted in mild, temporary veno-occlusive disease (VOD) in three of three dogs. Reversible bone marrow damage was noted after two intravenous injections of 18.5 MBq of yttrium-90-labeled monoclonal antibody ZCE025 per kg body weight in three of three dogs. Administrations of the antibody were separated by 1 week. Three dogs treated by irradiation of the liver with radioimmunoglobulin therapy added during the last 2 weeks of the irradiation showed signs of radiation hepatitis (VOD) starting around 35 days after treatment. One dog had a complete recovery, and two dogs were euthanized in a stage of terminal liver failure around day 90 after treatment. Temporary bone marrow damage was observed after the combined treatment, similar to the bone marrow damage observed after radioimmunoglobulin therapy alone. Earlier studies in the same dog model showed that bone marrow is the dose-limiting organ if radioimmunoglobulin therapy is used alone. The addition of irradiation of the liver to radioimmunoglobulin therapy changes the dose-limiting organ from bone marrow to liver. The radiation hepatitis observed in dogs is very similar to that observed in humans and is reflected in early platelet consumption in the irradiated liver plus late elevations of liver enzymes and VOD in central hepatic veins on histological analysis. Future applications of combined liver irradiation and radioimmunoglobulin therapy in humans should use radioimmunoglobulin therapy agents which show minimal uptake by normal liver.

Animals↗

PubMed1994

Morphometric measurement of collagen in liver tissue with posthepatitis liver cirrhosis portal hypertension.

A correct estimation of the collagen content in cirrhosis liver tissue and analysis of its relation to the degree of liver function injury are important to the clinician in the establishment of the diagnosis in the liver diseases. The author has performed the morphometric measurement of collagen with liver tissue pathological section by using TJTY-300 image analysis system. It was found that the cirrhotic liver tissue's collagen area and collagen average grey degree were notably higher than those in normal men (P < 0.05), average optical density was markedly lower than that in normal men (P < 0.05), integral optical density had no significant difference (P > 0.05) between patients and normal controls, but the integral optical density in cirrhotic liver was 1.21 times that of normal men. It suggests that the collagen content in cirrhotic liver tissue increased obviously, the average density of the increased collagen was lower than that in the normal liver tissue and the density of increased collagen was not homogeneous. Comparison between normal controls and patients with different Child-Pugh liver function grades in liver tissue collagen parameters revealed that the cirrhotic liver's collagen content can, to different degree, directly reflect the function status of cirrhotic liver.

Adult↗

PubMed1988

Mitochondrial DNA polymorphism in Chinese.

Human mitochondrial DNA (mtDNA) restriction endonuclease fragment patterns were analyzed using placenta DNA isolated from 273 individuals representing four different nationalities, the Han, the Uygur, the Kazakh and the Hui populations. Thirty-eight fragment patterns (morphs) were observed with the enzyme ApaI, BamHI, EcoRI, HindIII, HinfI, HhaI, HapII, KpnI, Mbol, PstI, PvuII, SacI, ScaL and XhoI. Fourteen new morphs, including some only existing in individual racial and national populations were observed, which indicates that there is a significant difference in the distribution of mtDNA morphs among various national and racial populations. By comparison with the mtDNA sequences in primate species, some mtDNA ancestral morphs were found to be retained in Oriental population today. This result provided indirect evidence that Asia may be one of the human original sources. Genetic distances among four national populations computed and employed in construction of an average linkage tree suggested that the Uygur and the Kazakh populations combined to form a branch at first, then the Han and the Hui came together to form another one, and at last, these two branches converged into a stem. Again, it was found that the internal variation within the Uygur and the Kazakh populations was greater than that within the Han and the Hui populations. These results showed a relationship among the four different national populations in China based on the molecular level.

China↗

PubMed1984

The binding of insulin-like growth factor II to the erythroleukemia cell line K562.

The erythroleukemia cell line K562 was previously shown to have specific binding sites for insulin but not for insulin-like growth factor I (IGF-I). In this study the presence of specific receptors for insulin-like growth factor II (IGF-II) is established. Scatchard analysis of the competition curve for IGF-II disclosed a non-cooperative binding kinetic with a calculated affinity constant 2.4 X 10(8) M-1 and a receptor number of 4.8 X 10(4) sites/cell. IGF-I displayed 10% crossreactivity over the IGF-II receptor but insulin did not crossreact at all. Instead insulin, present in high concentrations, enhanced the binding of IGF-II. The presence of IGF II but not IGF-I receptors makes the K562 cell line suitable for studying properties of the type-2 receptor.

Binding Sites↗

PubMed1983

Characterization of insulin binding to the erythroleukemia cell line K 562.

The K 562 is a transformed human erythroid stemcell and is used as a target cell for NK-T-cells. In this study the presence of insulin receptors in K 562 is established. The best binding and negative cooperativity was found in the two Hepes containing buffers whereas no cooperativity was obtained in the Krebs-Ringer buffer. The calculated affinity constants and receptor number per cell varied according to the buffer. Preincubation with insulin caused a down-regulation of the insulin binding capacity. 10 ng/ml caused a lowering of the affinity, with an unchanged number of receptors. 100 ng/ml caused a decrease in receptor number with unchanged affinity. These results were found in both Hepes and Krebs-Ringer phosphate buffer. IGF-I shows cross-reactivity with the insulin receptor, with a potency of 12 and 100 times less than insulin in Krebs-Ringer phosphate buffer and G-buffer respectively. However, no specific IGF-I receptors were found. The presence of receptors on K 562 cells suggests a biological role for insulin. The different results in the different buffers, indicate that a buffer containing Hepes and/or Tris, is required to expose negative cooperativity and make the receptors more accessible to insulin.

Binding, Competitive↗