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Biomedical subjects

L Ouyang

Publications and source records attributed to L Ouyang.

12 recordsLinked to original sources
PubMed2004

Growth of compound single- and multi-walled carbon nanotubes.

Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are complement to each other in many of their physical properties. We report the synthesis of carbon nanotube cables-a form of compound single- and multi-walled carbon nanotubes which could have the superior properties of both the SWCNTs and MWCNTs. This compound form of carbon nanotubes consists of a bundle of SWCNTs formed into a MWCNT, and the diameter of the inner most shell of the MWCNT ranges from a few to tens nanometers. The growth of these compound carbon nanotubes cannot be explained readily via existing modes of carbon nanotube growth, but promises a new way for improving and controlling the physical properties of either single- or multi-walled carbon nanotubes.

Journal Article↗
PubMed2000

[Diagnostic efficacy of glutamic acid decarboxylase antibody and islet cell antibody in type I diabetes mellitus].

OBJECTIVE: To investigate the diagnostic efficacy of glutamic acid decarboxylase antibody (GAD65-Ab) and islet cell antibody (ICA) in type I diabetes mellitus. METHODS: 104 cases of type I diabetes mellitus and 102 normal controls were recruited, GAD65-Ab was determined with radioligand assay and ICA with ELISA. The diagnostic efficacy of GAD65-Ab and ICA was analysed by receiver-operating characteristic (ROC) curve with sensitivity, specificity and curve area. RESULTS: (1) The optimal cut-off point of GAD65-Ab was at 0.30, while that of ICA was at 0.45. The area under the curve of GAD65-Ab and ICA were 0.835 and 0.715 respectively. Compared with 0.5, the area under curve of GAD65-Ab and ICA was higher (P < 0.0001). The area under curve of GAD65-Ab was higher than that of ICA(P < 0.01). (2) In type I diabetes mellitus patients, the positivity of GAD65-Ab was not correlated to the age of onset and duration of the disease, while the positivity of ICA was correlated to the age of onset and duration. CONCLUSION: Type I diabetes mellitus can be diagnosed with GAD65-Ab and ICA. The diagnostic efficacy of GAD65-Ab is higher than that of ICA. In patients of type I diabetes mellitus with adult-onset and duration more than one year, the diagnostic efficacy of GAD65-Ab is higher than that of ICA, while in patients of type I diabetes mellitus with adolescent-onset and duration less than one year, the diagnostic efficacy of ICA is higher than that of GAD65-Ab.

Adolescent↗
PubMed1999

A packaging cell line for lentivirus vectors.

Lentivirus vectors can transduce dividing and nondividing cells. Using three-plasmid transient transfections, high-titer (>10(9) IU/ml) recombinant lentivirus vectors pseudotyped with vesicular stomatitis virus G (VSV-G) protein can be generated (T. Kafri et al., Nat. Genet. 17:314-317, 1997; H. Miyoshi et al., Proc. Natl. Acad. Sci. USA 94:10319-10323, 1997; L. Naldini et al., Science 272:263-267, 1996). The recombinant lentiviruses can efficiently infect brain, liver, muscle, and retinal tissue in vivo. Furthermore, the transduced tissues demonstrated long-term expression of reporter genes in immunocompetent rodents. We now report the generation of a tetracycline-inducible VSV-G pseudotyped lentivirus packaging cell line which can generate virus particles at titers greater than 10(6) IU/ml for at least 3 to 4 days. The vector produced by the inducible cell line can be concentrated to titers of 10(9) IU/ml and can efficiently transduce nondividing cells in vitro and in vivo. The availability of a lentivirus packaging cell line will significantly facilitate the production of high-titer lentivirus vectors for gene therapy and study of human immunodeficiency virus biology.

Animals↗
PubMed1999

Diagnostic role of antibodies to glutamic acid decarboxylase in latent autoimmune diabetes mellitus in adults.

OBJECTIVE: To investigate the diagnostic role of antibodies to glutamic acid decarboxylase (GAD65-Ab) in latent autoimmune diabetes of adults (LADA) and the frequency of GAD-Ab in Chinese patients initially diagnosed as non-insulin-dependent diabetes mellitus (NIDDM). METHODS: Forty-five control subjects and 195 consecutive inpatients initially classified as NIDDM with > or = 35 years of age at onset and nonketotic history for > 6 months after diagnosis, were recruited. In vitro transcripted and translated recombinant human 35S-GAD65 was used in radioligand assay of GAD-Ab. RESULTS: The overall prevalence of GAD65-Ab was 14.8% (29/195) in NIDDM patients and 2.2% (1/45) in control subjects, respectively. Of the 29 GAD65-Ab positive patients, 17 (58.6%) were insulin-deficient while 12 (41.4%) were non-insulin-deficient. The prevalence of GAD65-Ab in NIDDM group with age of < 40 years at diabetes onset, ketotic history, body mass index (BMI) < 21 kg/m2, were significantly higher than that of corresponding control diabetic subgroups (2.5, 4.1 and 3.2 times, respectively). The sex, duration, symptoms of polyphagia, polydipsia, polyuria and weight loss at onset of the disease were not related to the prevalence of GAD65-Ab positivity. CONCLUSIONS: In China, patients initially diagnosed as NIDDM may in many cases suffer from LADA. Testing by GAD65-Ab may be of assistance to identifying LADA at the earliest stage of disease.

Adult↗
PubMed1998

Regulation of erythroid Krüppel-like factor (EKLF) transcriptional activity by phosphorylation of a protein kinase casein kinase II site within its interaction domain.

Erythroid Krüppel-like factor (EKLF) is a red cell-specific activator whose presence is crucial for establishing high levels of adult beta-globin expression in definitive cells during erythroid ontogeny. However, its simple presence within the erythroid lineage is not sufficient to activate the beta-globin promoter. One explanation that may account for this is that post-translational modification of EKLF differs within erythroid cell populations and regulates its activity. We have therefore addressed whether phosphorylation plays a role in modulating EKLF action. First, in vivo analyses implicate serine/threonine kinases as important players in the terminal differentiation of MEL cells, and demonstrate that EKLF is phosphorylated at serine and threonine residues within its transactivation region. Second, directed disruption of a protein kinase casein kinase (CK) II site, located within the EKLF interaction domain, abolishes EKLF transactivation and in vivo competition activity. Third, in vitro assays demonstrate that CKIIalpha interacts with EKLF, and that the EKLF interaction domain is phosphorylated by CKII only at Thr-41; however, the CKII-site mutant is not phosphorylated. Finally, the transactivation capability of EKLF is augmented by co-transfection of CKIIalpha. We conclude that EKLF is a phosphoprotein whose ability to transcriptionally activate an adjacent promoter is critically dependent on the phosphorylation status of a specific site located within the EKLF interaction domain, and that serine/threonine kinases play an important role in this process.

Amino Acid Sequence↗
PubMed1998

Transcriptional factors for specific globin genes.

Correct temporal control of the beta-like globin cluster is generated in part by the binding of tissue-restricted transcriptional regulators to their cognate sites. Erythroid Krüppel-like Factor (EKLF) is one of these red cell-specific activators that is particularly important for switching on adult beta-globin gene expression. However, its simple presence is not sufficient to activate the beta-globin promoter, as primitive erythroid cells and a number of erythroid cell lines express EKLF yet do not express adult beta-globin. One explanation that may account for these observations is that post-translational modification of EKLF differs within these cell populations. To address this issue, we are investigating whether phosphorylation plays a role in modulating EKLF activity. In vitro and in vivo approaches have been used to demonstrate that EKLF is a phosphoprotein whose ability to bind DNA and transcriptionally activate an adjacent promoter is critically dependent on its phosphorylation status. Of particular interest is a casein kinase II site within the EKLF minimal transactivation domain.

Adult↗
PubMed1996

GABP mediates insulin-increased prolactin gene transcription.

The insulin-response element from the prolactin gene is identical to the Ets-binding site, and dominant-negative Ets protein inhibits insulin-increased prolactin gene expression. Immunoblotting identified the Ets-related transcription factor GABP in nuclear extracts from GH cells. Expression of GABP alpha and GABP beta 1 squelches insulin-increased prolactin gene expression. GABP alpha and GABP beta 1 bind the insulin-response element of the prolactin promoter, and anti-GABP alpha and anti-GABP beta 1 antibodies supershift a species seen with nuclear extracts from GH cells. GABP alpha immunoprecipitated from insulin-treated, 32P-labeled GH cells was phosphorylated 3-fold more than GABP alpha from control cells. There was no increase in phosphorylation of GABP beta in response to insulin. Mitogen-activated protein (MAP) kinase activity is increased 10-fold in insulin-treated GH4 cells. MAP kinase immunoprecipitated from control cells does not phosphorylate GABP alpha while MAP kinase immunoprecipitated from insulin-treated cells shows substantial phosphorylation of GABP alpha. These studies suggest that GABP mediates insulin-increased transcription of the prolactin gene. GABP may be regulated by MAP kinase phosphorylation.

Base Sequence↗
PubMed1995

A consensus insulin response element is activated by an Ets-related transcription factor.

Insulin increases expression of somatostatin-chloramphenicol acetyltransferase (CAT) constructs 10-fold and thymidine kinase-CAT constructs 5-fold in GH4 cells. These responses are similar to our previously reported data on insulin-increased prolactin-CAT expression. They are also observed in HeLa cells and are thus not cell type specific. The evidence suggests that the insulin responsiveness of these genes is mediated by an Ets-related transcription factor. First, linker-scanning mutations and/or deletions of the prolactin, somatostatin, and thymidine kinase promoters suggest that their insulin responsiveness is mediated by the sequence CGGA. This sequence is identical with the response element of the Ets-related transcription factors. Second, CGGA-containing sequences placed at -88 in the delta MTV-CAT reporter plasmid conferred insulin responsiveness to the mammary tumor virus promoter. Third, expression of the DNA-binding domain of c-Ets-2, which acts by blocking effects mediated by Ets-related transcription factors, inhibits the response of these promoters to insulin. Finally, the Ets-related proteins Sap and Elk-1 bind to the prolactin, somatostatin, and thymidine kinase insulin-response elements. An Ets-like element was found in all insulin-sensitive promoters examined and may serve a similar function in those promoters.

Animals↗
PubMed1994

In vivo damage and recA-dependent repair of plasmid and chromosomal DNA in the radiation-resistant bacterium Deinococcus radiodurans.

Deinococcus radiodurans R1 and other members of this genus share extraordinary resistance to the lethal and mutagenic effects of ionizing radiation. We have recently identified a RecA homolog in strain R1 and have shown that mutation of the corresponding gene causes marked radiosensitivity. We show here that following high-level exposure to gamma irradiation (1.75 megarads, the dose required to yield 37% of CFU for plateau-phase wild-type R1), the wild-type strain repairs > 150 double-strand breaks per chromosome, whereas a recA-defective mutant (rec30) repairs very few or none. A heterologous Escherichia coli-D. radiodurans shuttle plasmid (pMD68) was constructed and found to be retained in surviving D. radiodurans R1 and rec30 following any radiation exposure up to the highest dose tested, 3 megarads. Plasmid repair was monitored in vivo following irradiation with 1.75 megarads in both R1/pMD68 and rec30/pMD68. Immediately after irradiation, plasmids from both strains contained numerous breaks and failed to transform E. coli. While irradiation with 1.75 megarads was lethal to rec30 cultures, a small amount of supercoiled plasmid was regenerated, but it lacked the ability to transform E. coli. In contrast, wild-type cultures showed a cell division arrest of about 10 h, followed by exponential growth. Supercoiled plasmid was regenerated at normal levels, and it readily transformed E. coli. These studies show that D. radiodurans retains a heterologous plasmid following irradiation and repairs it with the same high efficiency as its chromosomal DNA, while the repair defect in rec30 prevents repair of the plasmid. Taken together, the results of this study suggest that plasmid DNA damaged in vivo in D. radiodurans is repaired by recA-dependent mechanisms similar to those employed in the repair of chromosomal DNA.

Chromosomes, Bacterial↗
PubMed1993

Identification, sequencing, and targeted mutagenesis of a DNA polymerase gene required for the extreme radioresistance of Deinococcus radiodurans.

Deinococcus radiodurans and other species of the same genus share extreme resistance to ionizing radiation and many other agents that damage DNA. Two different DNA damage-sensitive strains generated by chemical mutagenesis were found to be defective in a gene that has extended DNA and protein sequence homology with polA of Escherichia coli. Both mutant strains lacked DNA polymerase, as measured in activity gels. Transformation of this gene from wild-type D. radiodurans restored to the mutants both polymerase activity and DNA damage resistance. A technique for targeted insertional mutagenesis in D. radiodurans is presented. This technique was employed to construct a pol mutant isogenic with the wild type (the first example of targeted mutagenesis in this eubacterial family). This insertional mutant lacked DNA polymerase activity and was even more sensitive to DNA damage than the mutants derived by chemical mutagenesis. In the case of ionizing radiation, the survival of the wild type after receiving 1 Mrad was 100% while survival of the insertional mutant extrapolated to 10(-24). These results demonstrate that the gene described here encodes a DNA polymerase and that defects in this pol gene cause a dramatic loss of resistance of D. radiodurans to DNA damage.

Amino Acid Sequence↗
PubMed1987

Space motion sickness preflight adaptation training: preliminary studies with prototype trainers.

Preflight training frequently has been proposed as a potential solution to the problem of space motion sickness. The paper considers successively the otolith reinterpretation, the concept for a preflight adaptation trainer and the research with the Miami University Seesaw, the Wright Patterson Air-Force Base Dynamic Environment Simulator and the Visually Coupled Airborne Systems Simulator prototype adaptation trainers.

Adaptation, Physiological↗