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Biomedical subjects

G X Xu

Publications and source records attributed to G X Xu.

13 recordsLinked to original sources
PubMed2004

cDNA cloning and genomic structure of the duck (Anas platyrhynchos) MHC class I gene.

In order to provide data for studies on disease resistance, duck MHC class I cDNA (Anpl-MHC I) was cloned from a duck cDNA library and the genome structure was investigated. Anpl-MHC I genes encoded 344-355 amino acids. The genomic organization is composed of eight exons and seven introns. Based on the genetic distance, Anpl-MHC I cDNA from six individuals can be classified into four lineages (from Anpl-UAA to Anpl-UDA). A total of 28 amino acid positions in the peptide-binding domain (PBD) showed high scores by Wu-kabat index analysis. The Anpl-MHC amino acid sequence displayed seven critical HLA-A2amino acids that bind with antigen polypeptides, and have an 83.6-88.5% amino acid homology with each lineage, a 55.2-64.6% amino-acid homology with chicken MHC class I (B-FIV21, B-FIV2, Rfp-Y), and a 40.3-42.8% homology with mammalian MHC class I. Nested PCR detected that Anpl-MHC I can be expressed in the brain, heart, kidney, intestines and bursa. Compared with the human HLA-A2 tertiary structure of the PBD, Anpl-MHC I had an insertion or deletion variation in four domains (A-D). The phlyogenetic tree appears to branch in an order consistent with accepted evolutionary pathways.

Amino Acid Sequence↗
PubMed2001

Variable dimensionality from mononuclear and trinuclear to one and two dimensions: a series of copper(II) compounds with 4,4'-dipyridine dioxide.

Reaction of 4,4'-dipyridine dioxide (dpdo) and CuCl(2).6H(2)O in aqueous solution gave an adduct [Cu(H(2)O)(6)]Cl(2).2dpdo.2H(2)O 1, which has a hydrogen-bonded three-dimensional network. While substituting CuCl(2).6H(2)O with Cu(ClO(4))(2).6H(2)O, three pseudopolymorphs, namely, [Cu(dpdo)(6)][ClO(4)](2) 2, [Cu(3)(dpdo)(8)(H(2)O)(6)][ClO(4)](6).2dpdo.6H(2)O 3, and [Cu(dpdo)(H(2)O)(4)][ClO(4)](2).2dpdo 4, were isolated. 2 consists of a mononuclear copper coordinated with six terminal dpdo ligands. Adjacent mononuclear units are overlapped through pi-pi stacking of pyridine rings to give a 2D sheet with a triangular channel. 3 forms a trinuclear cluster bridged by two dpdo molecules. The solvate and terminal dpdo molecules are interwoven through hydrogen bonding and pi-pi stacking to lead to a rectangular channel with a dimensionality of 12.98 A x 13.44 A. 4 has a one-dimensional chain structure bridged by dpdo. Two solvate dpdo ligands link these chains through hydrogen bonding to generate two sets of three-dimensional networks which are interwoven through a common conjunctive point [Cu(H(2)O)(4)](2+), yielding a three-dimensional open framework with triangular channels. ClO(4)(-) anions are included within these channels in 2-4 through weak C-H...O hydrogen bonding. The introduction of the second spacer, 4,4'-bipyridine, generated a 2D architecture [Cu(dpdo)(4,4'-bipy)][ClO(4)](2).2H(2)O.dpdo 5, which is constructed by 4,4'-bipy and 4,4'-dpdo simultaneously, exhibiting a large channel with approximate dimensionality 11.1 A x 12.6 A, in which solvate 4,4'-dpdo ligand and perchlorate anions are accommodated.

Journal Article↗
PubMed2001

Distinguishing malignant from normal oral tissues using FTIR fiber-optic techniques.

Oral tissue samples were studied using mid-IR fiber-optic attenuated total reflectance spectroscopy and other spectral techniques. The 1745 cm(-1) band, which is assigned to the ester group (C==O) vibration of triglycerides, is a reliable marker that is present in normal tissues but absent or a weak band in malignant oral tissues. Other bands such as C--H stretching bands and the amide bands are also helpful in distinguishing malignant tissues from normal tissues. Subtraction spectra confirmed the above conclusion. In addition, Raman spectroscopic measurements were in agreement with the results observed from FTIR spectra.

Biomarkers, Tumor↗
PubMed2000

A phase I trial of a recombinant vaccinia virus expressing prostate-specific antigen in advanced prostate cancer.

A recombinant vaccinia virus encoding human prostate-specific antigen (rV-PSA) was administered as three consecutive monthly doses to 33 men with rising PSA levels after radical prostatectomy, radiation therapy, both, or metastatic disease at presentation. Dose levels were 2.65 x 10(6), 2.65 x 10(7), and 2.65 x 10(8) plaque forming units. Ten patients who received the highest dose also received 250 microg/m2 granulocyte-macrophage colony-stimulating factor (GM-CSF) as an immunostimulatory adjunct. No patient experienced any virus-related effects beyond grade I cutaneous toxicity. Pustule formation and/or erythema occurred after the first dose in all 27 men who received > or =2.65 x 10(7) plaque forming units. GM-CSF administration was associated with fevers and myalgias of grade 2 or lower in 9 of 10 patients. PSA levels in 14 of 33 men treated with rV-PSA with or without GM-CSF were stable for at least 6 months after primary immunization. Nine patients remained stable for 11-25 months; six of these remain progression free with stable PSA levels. Immunological studies demonstrated a specific T-cell response to PSA-3, a 9-mer peptide derived from PSA. rV-PSA is safe and can elicit clinical and immune responses, and certain patients remain without evidence of clinical progression for up to 21 months or longer.

Adult↗
PubMed1997

Mechanisms of food effects of structurally related antiarrhythmic drugs, disopyramide and bidisomide in the rat.

PURPOSE: To determine whether the rat is a good animal model for the food effects observed with bidisomide but not with the structurally similar antiarrhythmic drug, disopyramide in man and to explore a reason for the differences in the food effects of these compounds. METHODS: The following effects on the absorption of bidisomide and/or disopyramide were examined in the rat: Food effects, gastrointestinal transit time under fasting and nonfasting conditions, pH effects, hypertonic solution effect of NaCl and glucose, bile effects, permeability, inhibitory effects by Gly, Gly-Gly, Gly-Pro, glucose and mannitol and drug binding to food. RESULTS: Remarkable food effects were observed with bidisomide but not with disopyramide. There was no difference in the GI transit time with and without food. The pH effect with and without food was similar. Effect of salt concentrations on bidisomide and disopyramide was similar. There was no bile effect on absorption of both compounds. Binding of bidisomide and disopyramide to food was similarly low. The apparent permeability of bidisomide was much lower than disopyramide especially in the ileum and its absorption was more inhibited by Gly, Gly-Gly and Gly-Pro. CONCLUSIONS: In the rat, as previously seen in humans, the food effect was observed with bidisomide but not with disopyramide. This difference was in part due to both lower intestinal permeability of bidisomide compared to disopyramide and greater inhibition of absorption by the amino acid, Gly and the dipeptides, Gly-Gly and Gly-Pro.

Animals↗
PubMed1995

Mutagens from heated Chinese and U.S. cooking oils.

BACKGROUND: The lung cancer incidence in Chinese women is among the highest in the world, but tobacco smoking accounts for only a minority of the cancers. Epidemiologic investigations of lung cancer among Chinese women have implicated exposure to indoor air pollution from wok cooking, where the volatile emissions from unrefined cooking oils are mutagenic. PURPOSE: This study was conducted to identify and quantify the potentially mutagenic substances emitted from a variety of cooking oils heated to the temperatures typically used in wok cooking. METHODS: Several cooking oils and fatty acids were heated in a wok to boiling, at temperatures (for the cooking oils) that ranged from 240 degrees C to 280 degrees C (typical cooking temperatures in Shanghai, China). The oils tested were unrefined Chinese rapeseed, refined U.S. rapeseed (known as canola), Chinese soybean, and Chinese peanut in addition to linolenic, linoleic, and erucic fatty acids. Condensates of the emissions were collected and tested in the Salmonella mutation assay (using Salmonella typhimurium tester strains TA98 and TA104). Volatile decomposition products also were subjected to gas chromatography and mass spectroscopy. Aldehydes were detected using high-performance liquid chromatography and UV spectroscopy. RESULTS: 1,3-Butadiene, benzene, acrolein, formaldehyde, and other related compounds were qualitatively and quantitatively detected, with emissions tending to be highest for unrefined Chinese rapeseed oil and lowest for peanut oil. The emission of 1,3-butadiene and benzene was approximately 22-fold and 12-fold higher, respectively, from heated unrefined Chinese rapeseed oil than from heated peanut oil. Lowering the cooking temperatures or adding an antioxidant, such as butylated hydroxyanisole, before cooking decreased the amount of these volatile emissions. Among the individual fatty acids tested, heated linolenic acid produced the greatest quantities of 1,3-butadiene, benzene, and acrolein. Separately, the mutagenicity of individual volatile emission condensates was correlated with linolenic acid content (r = .83; P = .0004). Condensates from heated linolenic acid, but not linoleic or erucic acid, were highly mutagenic. CONCLUSIONS: These studies, combined with experimental and epidemiologic findings, suggest that high-temperature wok cooking with unrefined Chinese rapeseed oil may increase lung cancer risk. This study indicates methods that may reduce that risk. IMPLICATIONS: The common use of wok cooking in China might be an important but controllable risk factor in the etiology of lung cancer. In the United States, where cooking oils are usually refined for purity, additional studies should be conducted to further quantify the potential risks of such methods of cooking.

China↗
PubMed1992

Genotoxicity of heated cooking oil vapors.

Epidemiological studies of lung cancer in Chinese women indicated that factors other than cigarette smoking are related to lung cancer risk. A case-control study suggested that indoor air pollution, particularly from cooking oil emissions, may be involved. Condensates of volatile emissions from rapeseed and soybean cooking oils were prepared and found to be genotoxic in short-term tests including the Salmonella mutation assay, SV50 forward-mutation assay, and sister-chromatid exchange assay, as well as the micronucleus assay in mouse bone marrow. In contrast, condensates from rapeseed oil with butylated hydroxyanisole or hydrogenated rapeseed oil were not mutagenic, implicating oxidation products as the cause for mutagenicity. Peanut oil and lard condensates were not mutagenic in any assay. The association of exposure to Chinese rapeseed cooking-oil emissions and lung-cancer risk may be related to the mutagenic component of these condensates.

Air Pollution, Indoor↗
PubMed1990

Adenosine triphosphate liposomes: encapsulation and distribution studies.

Four methods for encapsulating adenosine triphosphate (ATP) in liposomes were evaluated. Optimum entrapment required emulsifying ATP with the lipids used to form the liposome membrane in a high-speed homogenizer followed by evaporating the organic solvent with vigorous stirring. Under these optimum conditions ATP entrapment was 38.9%; i.e., the dosage form contained 38.9 g of ATP per 100 g of lipid. The distribution of positively charged liposomes loaded with ATP was studied in dogs with experimentally induced myocardial infarction. Intravenous injection of positively charged ATP liposomes caused accumulation of ATP in myocardial infarct tissue. Myocardial infarct tissue has reduced blood flow; since positively charged liposomes accumulated in infarct tissue, liposomes may be a drug delivery system for this disease state.

Adenosine Triphosphate↗
PubMed1989

[Studies on the preparation of adenosine triphosphate (ATP) liposomes].

In this paper, a method--improved emulsification vesicles (IEV) was proposed for the preparation of adenosine triphosphate (ATP) liposome. The ATP entrapment ratio reached 38.9% (w/w), which was much greater than that reported in the literature. Thus, IEV is an excellent method which has never been presented. Together with ultrafiltration for removing unentrapped drugs and radiation sterilization, these methods are most meaningful for the production of liposomes in large scale.

Adenosine Triphosphate↗
PubMed1988

Metabolic changes in women using a long-acting monthly oral contraceptive and return of ovulation on discontinuation.

Metabolic changes were investigated in two groups of women using oral contraceptives for 5 to 16 years. Blood samples were taken during the last cycle of oral contraceptive use and three months post-treatment. One group had used a monthly oral contraceptive (MOC, 3mg quinestrol and 10mg 16-methylene chlormadinone acetate) and the second group a daily oral contraceptive (DOC, 35 micrograms ethynylestradiol and 0.625 mg norethisterone). During treatment there were increases in serum total cholesterol and triglycerides but not HDL-C, in plasma total cortisol but not in renin activity, angiotensin II or urinary free cortisol excretion, in hemoglobin and some coagulation factors but not Factor X or antithrombin III, platelet function or fibrinolysis. The area under the blood glucose concentration-time curve, but not that for serum insulin, was slightly increased and there was no change in fasting blood sugar concentrations. All metabolic parameters, except plasma cortisol, which had shown an increase on treatment, had decreased to control levels within 3 months. Ovulation returned promptly in all women, the mean time being 70 days for Group MOC and 44 days for Group DOC. Thus, in spite of the long duration of use of the oral contraceptives, metabolic changes were minor.

Adult↗
PubMed1987

[Bone marrow necrosis and malignant tumors].

Twelve patients with bone marrow necrosis were diagnosed in our hospital during the past thirteen years. All were related to malignant tumors. Bone marrow metastatic carcinoma was diagnosed in 5, suspicious metastatic carcinoma in 3, acute leukemia in 2, chronic granulocytic leukemia in 1 and malignant histiocytosis in 1. In case 1, the necrosis was secondary to gastric cancer metastasis into the bone marrow and complicated by microangiopathic hemolytic anemia; in case 3, bone marrow necrosis was the initial manifestation and a diagnosis of acute lymphocytic leukemia was finally confirmed; in case 4 of acute monocytic leukemia, bone marrow necrosis followed intramedullary chemotherapy and in case 5, marrow necrosis was secondary to chronic granulocytic leukemia. These four manifestations mentioned above have not been reported yet at home. Three cases examined by systemic 99mTe bone scan suggest that 99mTe bone scan be useful in the diagnosis of marrow necrosis. In this paper, the causes, diagnosis, treatment, prognosis and pathogenesis are discussed.

Adult↗