Ionization and fragmentation of C60 by highly charged, high-energy xenon ions.
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Journal Article↗
Biomedical subjects
S Cheng
Publications and source records attributed to S Cheng.
Expression and function of HLA-DQ8 (DQA1*0301/DQB1*0302) genes in transgenic mice.
Transgenic mice expressing HLA-DQA1*0301 and HLA-DQB1*0302 genes (DQ8) were produced. The transgenes were then transferred into mouse (Ab degrees) class II negative mice: the only class II molecules expressed in these animals were therefore coded by the HLA-DQ8 genes. Good expression of HLA-DQ molecules was found. Both CD4+ T cells and DQ8-specific T-cell receptor V beta expressing cells were positively selected in these mice. The HLA-DQ8 molecules expressed in these animals can present various foreign and self antigens and induce T-cell proliferation in vitro. These mice will be invaluable in future studies of the structure and function of HLA-DQ8 genes.
Animals↗
Effects of dietary polyunsaturated fat on ethanol-induced Ito cell activation.
Ito cells, vitamin A-storing perisinusoidal cells, are believed to undergo myofibroblastic transformation in liver fibrogenesis. Our previous studies have shown that a diet high in polyunsaturated fat was key for induction of experimental alcoholic liver fibrosis. To investigate the cellular basis for this fibrogenic effect of a high-fat diet, we analyzed the content of vitamin A and cellular retinol binding protein (CRBP), the steady-state mRNA levels of procollagen-alpha1(I), transforming growth factor-beta1 (TGF-beta1), interleukin-6 (IL-6), and smooth muscle alpha-actin (alpha-SM) in freshly isolated Ito cells from rats given isocaloric amounts of ethanol and a low- or high-fat diet. After 10 wk, the Ito cell content of retinyl palmitate was severely reduced in both the high- and low-fat diet-ethanol-fed animals to 13-17% of those measured in respective pair-fed controls. On the other hand, the content of CRBP was reduced in the high-fat-ethanol rats but not in the low-fat-ethanol group. The cells from the high-fat-ethanol but not low-fat ethanol rats showed an 18-fold increase in procollagen-alpha1(I) mRNA at 17 wk, which was accompanied by 2.8- and 2.3-fold enhancement of TGF-beta1 and alpha-SM transcripts. IL-6 mRNA was not detected in the cells from any groups. These results demonstrate 1) myofibroblastic activation of Ito cells is evident in rats given a high-fat diet and ethanol but not in the low-fat-ethanol animals; 2) vitamin A depletion of Ito cells is the early and general effect of chronic ethanol intake but does not necessarily predict subsequent myofibroblastic activation; 3) reduced CRBP level is more closely associated with the subsequent cellular activation seen under the high-fat-ethanol regimen; and 4) IL-6 is not expressed in vivo by Ito cells from either normal livers or livers with alcoholic liver fibrosis.
Animals↗
Inhaled nitric oxide injures the pulmonary surfactant system of lambs in vivo.
Nitric oxide (.NO) is a free radical, and as such may damage the pulmonary surfactant system. To determine the potential toxicity of .NO in vivo, we exposed 35 newborn lambs to 0, 20, 80 or 200 ppm .NO in either 21 or 60% O2 for 6 h. At the end of the exposure, lambs had normal values of arterial Po2, Pco2, and pH; total protein concentration in the bronchoalveolar lavage was also at normal levels. There were no differences in the surface properties of surfactant among the air or 60% O2 groups. Pulmonary surfactant samples, isolated from the bronchoalveolar lavage of lambs breathing air or 20 ppm .NO and reconstituted at a lipid concentration of 3 mg/ml, reached a low minimum surface tension (Tmin < 3 mN/m) in a pulsating bubble surfactometer. On the other hand, abnormal surface properties were observed in 36 and 60% of surfactant samples isolated from lungs of lambs that breathed 80 or 200 ppm .NO, respectively. These findings were confirmed using a captive bubble surfactometer. Surfactant protein A, isolated from the lungs of lambs that breathed 200 ppm .NO, exhibited decreased ability to aggregate lipids in vitro. These data are consistent with injury to the surfactant apoproteins during inhalation of either 80 or 200 ppm .NO for 6 h.
Administration, Inhalation↗
Role of the palmitoylation of surfactant-associated protein C in surfactant film formation and stability.
The effect of palmitoylation of pulmonary surfactant-associated protein C (SP-C) on the surface activity of phospholipid mixtures of dipalmitoylphosphatidylcholine and phosphatidylglycerol was studied. Phospholipids reconstituted with palmitoylated or depalmitoylated bovine SP-C were examined at neutral and acidic pH using a captive bubble surfactometer. At low pH, effective lipid adsorption and near zero surface tensions upon compression were obtained even with protein-free samples. At physiological pH, only SP-C-containing samples achieved such properties. Lipid adsorption was decreased by prior SP-C depalmitoylation. Bubbles with palmitoylated SP-C were more mechanically stable and required less compression to reach low surface tensions. Subphase depletion experiments showed that dynamically cycled surface layers containing palmitoylated SP-C maintained their surface activity after subphase lipid depletion. In contrast, surface activity was rapidly lost where depalmitoylated SP-C or SP-B was included. Our results indicate that although SP-C palmitoylation has little effect on its ability to enhance lipid adsorption and surface tension reduction, it greatly enhances lipid respreading and film stability and is therefore important for surfactant function.
1,2-Dipalmitoylphosphatidylcholine↗
[C-myc activation by translocation in human primary non-small cell lung cancer].
OBJECTIVE: Lung cancer is one of the most common human neoplasms. The carcinogenesis and development of lung cancer are related to activation and inactivation of many oncogenes and tumor-suppressor genes. We reported c-myc activation by translocation in SV40T-transformed human bronchial epithelial cells and lung cancer cell line before. In order to confirm that c-myc translocation exists in human primary non-small cell lung cancer, we continued our studies in 12 primary human lung cancers. METHODS: We applied major fluorescence in situ hybridization (FISH) in combination with immunohistochemistry. RESULTS: c-myc translocation was detected in two cases of the 12 primary lung cancers. Overexpression of c-myc was detected in the two cases by means of immunohistochemistry. CONCLUSION: These results suggest that c-myc can be activated by translocation in human primary lung cancer.
Adenocarcinoma↗
[Detection of rpoB gene mutation in Mycobacterium tuberculosis by PCR "cold" SSCP].
OBJECTIVE: To evaluate the applicability of detection of rpoB gene mutation in M. tuberculosis susceptibility testing. METHODS: 87 M. tuberculosis isolates and 22 sputum specimens from patients with active pulmonary tuberculosis were detected by PCR-SSCP. RESULTS: The sensitivity of PCR for rpoB gene amplification was 100 pg DNA and 5000 organisms. The rpoB gene could be detected in the all isolates tested. In comparison with conventional susceptibility testing methods, the sensitivity and specificity of PCR-"cold" SSCP analysis for detecting rifampin resistance in 87 M. tuberculosis isolates was 89.6% and 100%, respectively. Among 22 smear- and culture-positive sputum specimens, only 1 (4.5%) was positive by PCR, however, 6 (27.3%) of them were positive by nested-PCR. The "cold" SSCP results of these 6 specimens were corresponding to that of the susceptibility testing. CONCLUSIONS: The PCR-"cold" SSCP described here can easily and rapidly detect rifampin resistance of M. tuberculosis. After increasing the primer specificity and amplification sensitivity, the technique might be used for detection of M. tuberculosis rifampin resistance in clinical specimen directly.
Antibiotics, Antitubercular↗
[Relationship between INH-resistance and katG mutation in M. tuberculosis].
OBJECTIVE: To investigate the molecular mechanism of INH-resistance and the relationship between INH-resistance and KatG mutations. METHODS: Use the primers designed from the 5' end of the KatG gene to amplify 282bp fragments from INH-susceptible and -resistant M. tuberculosis isolates. Single strand conformation polymorphism (SSCP) for their PCR products were analysed. RESULTS: No katG gene sequence deletion was observed, mutations were detected in 17 of 30 INH-resistant strains and no gene perturbations were shown in 16 INH-susceptible isolates. CONCLUSION: The results suggested that mutation in katG gene was one of the most important INH-resistant mechanisms in M. tuberculosis.
Antitubercular Agents↗
[beta-Amyloid protein and Alzheimer's disease].
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Alzheimer Disease↗
Structural predictions for the ligand-binding region of glycoprotein hormone receptors and the nature of hormone-receptor interactions.
BACKGROUND: Glycoprotein hormones influence the development and function of the ovary, testis and thyroid by binding to specific high-affinity receptors. The extracellular domains of these receptors are members of the leucine-rich repeat (LRR) protein superfamily and are responsible for the high-affinity binding. The crystal structure of a glycoprotein hormone, namely human choriogonadotropin (hCG), is known, but neither the receptor structure, mode of hormone binding, nor mechanism for activation, have been established. RESULTS: Despite very low sequence similarity between exon-demarcated LRRs in the receptors and the LRRs of porcine ribonuclease inhibitor (RI), the secondary structures for the two repeat sets are found to be alike Constraints on curvature and beta-barrel geometry from the sequence pattern for repeated beta alpha units suggest that the receptors contain three-dimensional structures similar to that of RI. With the RI crystal structure as a template, models were constructed for exons 2-8 of the receptors. The model for this portion of the choriogonadotropin receptor is complementary in shape and electrostatic characteristics to the surface of hCG at an identified focus of hormone-receptor interaction. CONCLUSIONS: The predicted models for the structures and mode of hormone binding of the glycoprotein hormone receptors are to a large extent consistent with currently available biochemical and mutational data. Repeated sequences in beta-barrel proteins are shown to have general implications for constraints on structure. Averaging techniques used here to recognize the structural motif in these receptors should also apply to other proteins with repeated sequences.
Amino Acid Sequence↗
Differentiation-dependent up-regulation of the human papillomavirus E7 gene reactivates cellular DNA replication in suprabasal differentiated keratinocytes.
mRNA transcription, DNA amplification, and progeny production of human papillomaviruses (HPVs) are closely linked to squamous epithelial differentiation in patient papillomas. Because suprabasal, differentiated keratinocytes have exited the cell cycle for days or weeks and because viral DNA synthesis requires the host DNA replication machinery, HPVs must have a mechanism to reactivate the essential host genes. In this study, we show via acute recombinant retrovirus infection that an intact E7 gene of either high-risk or of low-risk HPV genotypes, under the control of its respective native enhancer-promoter, induced proliferating cell nuclear antigen (PCNAs) expression in the suprabasal cells of epithelial raft cultures of primary human foreskin keratinocytes (PHK). The cellular differentiation program was unaltered by the viral oncoprotein; it was essential for high HPV promoter activity. Furthermore, extensive host chromosomal DNA replication took place in differentiated cells of HPV-18 E7-expressing raft cultures and of patient laryngeal papillomas caused by HPV-6. These results indicate that the main function of the E7 protein is to reactivate host DNA replication machinery to support viral replication in differentiated, noncycling cells.
Base Sequence↗
Access to peptide regions of a surface mucin (MUC1) is reduced by sialic acids.
Mucinous glycoproteins are present on the surfaces of tumor cells. Knowledge of which parts of the mucin molecule are accessible targets for cells of the immune system is important in the development of successful therapeutic approaches. One breast (ZR-75-1), two colon (Colo 205 and SW1116), and three pancreas (Capan-2, HPAF and SW1990) cancer cell lines were examined. The reactivities of antibodies HMFG-2, specific for the tripeptide (DTR) in the 20 amino acid tandem repeat of MUC1, and SM-3 (PDTRP) were greatly enhanced by pre-treating cells with an inhibitor of O-glycosylation, benzyl-alpha-N-acetylgalactosamide. However, desialylation of cell surfaces with neuraminidase or pre-treatment with an inhibitor of carbohydrate processing, monensin, also greatly enhanced the reactivities of HMFG-2, SM-3 and HMFG-1 (PDTR). Thus, sialic acids on termini of neighboring oligosaccharides significantly limit access to the peptide region recognized by antibodies HMFG-1/2 and SM-3.
Amino Acid Sequence↗
Concept and progress in the development of RGD-containing peptide pharmaceuticals.
The cell adhesion domain, arginine-glycine-aspartic acid (RGD), has been incorporated into synthetic peptides to perform either of two modes of drug action, antagonist or agonist. Short, conformationally constrained peptides have been developed as antagonists for the platelet membrane glycoprotein complex, the integrin alpha IIb beta 3, using cell-based and integrin-based assays. In combination with a comparative molecular modeling study, these results have helped identify common conformational elements in the pharmacophore of this class of molecules. Peptides are presented that are highly potent, integrin specific, and that possess reduced pharmacological side effects. Also presented is the development of a peptide that modifies, noncovalently, the surfaces of a wide variety of synthetic materials used in medical implants. The agonist activity of [corrected] this molecule is evident from its ability to stimulate cell attachment on these surfaces. This is shown to translate into an in vivo activity of faster and more complete tissue integration, and a reduction in foreign body response.
Amino Acid Sequence↗
Estimation of structural and geometrical properties of cortical bone by computerized tomography in 78-year-old women.
The structural and geometrical properties of the tibia shaft were investigated at two sections by means of computerized tomography (CT) in 78-year-old women with high (n = 19) and low (n = 17) calcaneal bone mineral density (BMD, g/cm3) previously measured by 125I-photon absorption. The high BMD group had a 20-21% higher tibial BMD and 9-12% higher bone cross-sectional area than was observed in the low BMD group. The distribution of bone mass indicated that the low BMD group had lost bone mainly from the endosteal surface, especially in the anterior part of the tibia. However, both groups had a similar basic pattern of mass distribution at the measured sections. The high BMD group had higher moments of inertia at the upper section than the low BMD group. The differences between the groups were more pronounced when only the high density areas were included. At the lower section, the differences between the groups also appeared significant at the high density levels. There were no group differences in the area moments of inertia. The results suggest that the true distribution of bone mass should be taken into account in determining the moments of inertia. In the tibia, determination of the cross-sectional mass distribution of bone combined with BMD should have a better discriminatory capability than BMD only in studying bone strength and fracture risk.
Absorptiometry, Photon↗
Elastic wave propagation in bone in vivo: methodology.
The purpose of this study was to investigate the usefulness of elastic wave propagation (EWP) in estimating the mechanical properties (elasticity) of human tibia. The test group was composed of 78-yr-old women assigned to high (n = 19) and low (n = 17) bone mineral density (BMD) groups as measured at the calcaneus by the 125I-photon absorption method. The EWP apparatus consisted of an impact-producing hammer with a force strain gauge and two accelerometers positioned on the bone. Results for nylon and acrylic were used to calibrate the apparatus. Polyvinyl chloride (PVC) solid rods and tubes of various diameters were used to evaluate the relationship between the elastic wave velocity and cross-sectional area. The density and the cross-sectional area of tibia were measured by the computerized tomographic (CT) method at the same intersection points as velocity recordings. The velocities in tibia of bending waves produced by the mechanical hammer were found to depend on the density, area moment of inertia, and density-dependent elastic constants of bone. It is important to account for the changes of these quantities along the bone. It is suggested that the velocity of elastic waves and various indices derived there from provide inexpensive ways of evaluating the elastic properties of bone.
Acceleration↗
Deficiency of vitamin E and selenium enhances calcium-independent phospholipase A2 activity in rat lung and liver.
Conditions promoting oxidative stress, which is implicated in many diseases, activate phospholipases A2, a family of enzymes central to phospholipid metabolism and signal transduction. Little is known about isozyme specificity with respect to this activation process. Accordingly, a dietary deficiency model known to induce oxidative stress was used to investigate phospholipase A2 isozyme activity in rat tissues. Long-Evans hooded rats were fed purified diets for 6 wk with or without the addition of vitamin E and selenium in a 2 x 2 factorial design. Phospholipase A2 activity was assessed in lung, liver, kidney and heart cytosol and microsomes in the presence (5 mmol/L CaCl2) or absence (5 mmol/L EGTA) of calcium with dipalmitoylphosphatidylcholine at pH 6.5. Lung phospholipase A2 activity was also assessed with 1-stearoyl-2-arachidonoylphosphatidylcholine as substrate at pH 8.5. Organ samples from rats deficient in both nutrients showed two- to tenfold higher calcium-independent phospholipase A2 activity in lung cytosol and microsomes, and in liver cytosol compared with samples from control and single nutrient-deficient rats. In contrast, the calcium-dependent activity was affected only slightly. The malondialdehyde concentration of the organs was measured and the pattern obtained mirrored that of enhanced phospholipase A2 activity for lung but not for liver. The enhanced phospholipase A2 activity in the lung cytosol and microsomes from rats deficient in both nutrients was partially blocked by p-bromophenacylbromide, further enhanced by dithiothreitol and unaffected by treatment with diisopropylfluorophosphate. These results suggest that deficiency of both vitamin E and selenium activates and/or induces unique calcium-independent forms of phospholipase A2 markedly in rat lung, and to a lesser extent in liver.
Animals↗
Template integrity is essential for PCR amplification of 20- to 30-kb sequences from genomic DNA.
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Base Sequence↗
Generation of entire human papillomavirus genomes by long PCR: frequency of errors produced during amplification.
Recently, several improvements of traditional PCR techniques have facilitated the amplification of significantly longer DNA target sequences. Here we report an improved method for amplification of entire human papillomavirus (HPV) genomes. Using rTth DNA polymerase, XL (Perkin-Elmer, Foster City CA), and the accompanying XL PCR buffer system, we have successfully amplified 8-kb genomes from approximately 10 copies of input reference strain HPV16 DNA. This long PCR (LPCR) method was subsequently used to amplify the entire HPV16 genome from clinical specimens. The fidelity with which the rTth DNA polymerase XL amplified target sequences under our chosen amplification conditions was estimated by partial sequencing of cloned LPCR products generated from cloned reference strain HPV16 genomes. A region spanning the HPV16 E6, E7, and part of the E1 open reading frames (ORFs) was sequenced in 29 clones. A total of 33 nucleotide substitutions were observed in the 23.5 kb sequenced. This corresponds to an error frequency of approximately one error per 700 bases. Finally, LPCR methods were used to amplify entire, novel HPV genomes from clinical specimens. LPCR primer pairs were designed for amplification of seven potentially novel HPV types. Amplicons of approximately 8 kb were generated from five of the seven HPV types targeted. One of the LPCR-generated novel genomes, CP141, was subsequently cloned and a partial sequence was determined.
Amino Acid Sequence↗