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Biomedical subjects

D Sun

Publications and source records attributed to D Sun.

At least 253 records · Page 14Linked to original sources
PubMed1997

Full length cDNA of rat RT1.DMa and RT1.DMb and expression of RT1.DM genes in dendritic and Langerhans cells.

MHC encoded DM heterodimers and classical MHC class II complexes meet in an endosomal/lysosomal compartment where DM heterodimers support peptide loading of MHC class II. Studies on peptide loading of rat class II and on peptide persistence in cells of the dendritic lineage prompted us to establish full length cDNA clones coding for the subunits alpha and beta of rat DM molecules as well as a mAb directed against the luminal moiety of the beta subunit. Here we describe the establishment of the first full length cDNA clones of rat RT1.DMa and RT1.DMb. The mode of expression of RT1.DM at the transcript level in bone marrow culture-derived dendritic cells, in Langerhans cells and in a number of additional accessory cells is reported. The beta protein was identified in detergent lysates of RT1.DM expressing cells by Western blot analysis using a newly established monoclonal antibody directed against the luminal part of RT1.DMbeta.

Amino Acid Sequence↗
PubMed1997

[Electron microscopy of elastic system fibers in the rat mandibular joint].

We study the Elastic System Fibers (ESFs) in the rat mandibular joint using light microscope and image analyzer system and Electron Microscope. The results showed that the ESFs in the articular disc and capsule were more than in the articular cartilage. In addition, microfibrils and elaunin were the principal ESFs in all the articular components. The microfibrils in the articular surfaces ran at nearly right angle to the collagen fibers. The ESFs beneath the articular surfaces and the other articular components showed no specific directivity. ESFs construct an extensive fibers network in the disc and the capsule.

Animals↗
PubMed1997

[A study of RBC relaxation process by use of resistivity method].

In this paper, the relaxation process of RBC in the suspending medium of medium viscosity was studied with the Erythrocyte Rheometer(Electric Resistive method) developed by ourselves. On the basis of Fricke-Velick conductive theory of RBC suspension, the experimental results were discussed. The results demonstrate that delta R/R0-t curve can really reflect the deformability of RBCs and the viscoelasty of RBCs after their deformation.

Animals↗
PubMed1997

[Simulation of a decoupling generalized predictive control algorithm for temperature-humidity system].

A decoupling generalized predictive control algorithm was presented in this paper. This algorithm was proposed to control the temperature-humidity system of a practical air-conditioning environmental chamber. By introducing absolute humidity as an intermediate variable, temperature and humidity of the system can be decoupled. Then the two decoupled systems are controlled by generalized predictive control (GPC) algorithm at different sample rates. Many simulation experiments demonstrated the effectiveness of the algorithm. Besides, decoupling of temperature and humidity will be extremely helpful to the application of GPC on the real system. This is also the effective method to control the temperature and humidity system.

Air Conditioning↗
PubMed1997

Identification of a phylogenetically conserved Sug1 CAD family member that is differentially expressed in the mouse nervous system.

We have isolated a cDNA clone from mouse, m56, that encodes a member of the Conserved ATPase-containing Domain (CAD) protein family. Sequence analysis revealed that m56 is identical to mouse mSug1/FZA-B and shares high homology with human Trip1, moth 18-56, and yeast Sug1. When examined, Sug1-like CAD proteins appear to function in the regulation of the 26S proteasome, as well as associate with members of the steroid/thyroid receptor superfamily and other transcriptional activators. m56 can complement the lethal phenotype of loss of SUG1 in yeast. We have examined the tissue distribution of m56 using Northern and Western blots, in addition to immunocytochemistry and in situ hybridization. While m56 was expressed in all tissues and cells examined, several classes of neurons, most notably in the hippocampus, olfactory bulb, and cerebellum, displayed elevated levels of m56 mRNA and protein. We also examined distribution of RNA polymerase II and 26S proteasome subunit 4 (S4) within the mouse brain by in situ hybridization. While all three genes had similar patterns of expression, there were significant differences among them. In moths, the expression of the Sug1 homolog 18-56 is dramatically up-regulated during programmed cell death. In addition, it has been previously demonstrated that the proteasome plays an essential role in the regulation of apoptosis in mammals. We examined the expression of m56 in mouse during natural and induced cell death in a variety of tissues and found no significant changes in expression. Taken together, the data presented here suggest that while m56 is a highly conserved gene that presumably plays essential but complex roles in basal and developmental processes, it may not represent a rate-limiting step in these processes.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1997

Bayesian design for dose-response curves with penalized risk.

This paper considers some Bayesian design problems in quantal response analysis. An experimenter must choose a set of dose levels and number of independent observations to take at these levels, subject to a total sample size, in order to estimate some characteristic phi, e.g., ED50, of a tolerance distribution F theta, where theta is the vector of unknown parameters. It is shown for the logistic model that the sampling variability of the posterior variance of phi is such that the predicted posterior variance alone is an undesirable criterion for design selection. A family of penalty functions is introduced that penalizes any excess in the posterior variance over the expected or predicted variance and protects against unexpected outcomes. The goal is to find a design that avoids experimental results with little information, at the expense of a small sacrifice in the Bayes risk. Numerical results indicate that the chance of an extreme posterior variance can be reduced by sacrificing a small amount of posterior risk.

Animals↗
PubMed1997

Mitochondrial tRNA(Leu(UUR)) gene mutation diabetes mellitus in Chinese.

OBJECTIVE: To ascertain the prevalence and clinical features of mitochondrial tRNALeu(UUR) gene nucleotide (nt) 3243 A-->G mutation diabetes mellitus in Chinese and to establish the approaches for genetic diagnosis of this subtype of diabetes during routine daily clinical practice. METHODS: Mitochondrial nt 3243 A-->G mutation was screened among 207 unrelated non-insulin-dependent diabetes mellitus (NIDDM) patients by using polymerase chain reaction (PCR)/Apa I restriction endonuclease digestion. Samples with positive result were confirmed by DNA sequence analysis. Genetic and clinical analysis were carried out in family members of the proband with positive genetic diagnosis. RESULTS: Positive results were found in two subjects during screening of unrelated NIDDM patients, which account for 2.4%-11.1% of NIDDM subjects with uncommon clinical features (with early age-of-onset, with low body-mass-index and on insulin therapy) or with positive family history of diabetes consistent with or unable to exclude from maternal inheritance. Genetic diagnosis was positive in 10 out of 25 family members in the pedigrees of these two probands. CONCLUSIONS: Mitochondrial tRNALeu(UUR) gene nt 3242 A-->G mutation should be considered in diabetic patients with the above-mentioned clinical features. The genetic diagnosis in daily clinical practice can be performed with allele specific priming amplification, or PCR/Hae III or Apa I digestion which are technically simple to perform and diagnostically easy to define.

Adolescent↗
PubMed1997

[Genetic analysis of familial hypertension].

In order to study the genetic mode of familial hepertension, 63 pedigreses, including 140 nuclear pedigrees, of familial hypertension were investigated by means of pedigreed analysis and segregative analysis. Pedigreed analysis revealed that there is an evident phenomenon of vertical transmission in familial hypertension. It is hypothesed that there is a segregative ratio of dominant inheritance in A x U and A x A marital types, which is supported by segregative analysis. The data obtained suggest that the familial hypertension is an autosomal dominant hereditary disease. It is suggested that the genetic modes of familial hypertension could be different according to the different marital types of the patients. This finding suggests that the disease has a genetic heterogeneity. The research results will provide the reference evidence for the prevention, treatment and diagnosis of familial hypertension.

Adolescent↗
PubMed1997

[Follow-up studies on hepatitis G infection in plasma donors with positive antibody against hepatitis C].

Antibodies against hepatitis G (anti-HGV) and HGV RNA were detected for frozen stored sera collected from 102 plasma donors and those subjects with positive anti-HGV and HGV RNA were followed-up for three years to study prevalence of HGV infection in them and their end-results. Anti-HGV was detected by enzyme immunoassay (EIA) with embedded antigen of synthetic peptide derived from different function regions of HGV. HGV RNA was detected by reverse transcription polymerase chain reaction (RT-PCR) with primers derived from NS3 region of HGV. Results showed that 19.61 percent (20/102) and 17.65 percent (18/102) of the plasma donors were positive for HGV RNA and anti-HGV, respectively, and 24.51 percent of them were infected with HGV (either positive for anti-HGV or HGV RNA), while only 0.94 percent (1/106) positive in the controls. It suggests that plasma donation is an important risk factor for HGV infection. Negative conversion rates of HGV RNA and anti-HGV during three-year follow-up were only 35.00 and 11.11 percent, respectively (7/20 and 2/18), which indicated a tendency of chronic carriage status in HGV infection.

Blood Donors↗
PubMed1996

Efficacy of antitat gene therapy in the presence of high multiplicity infection and inflammatory cytokines.

Because human immunodeficiency virus type 1 (HIV-1) infection is characterized by a large number of viral replication cycles and rapid cell turnover in vivo, successful gene therapy requires an approach effective under these conditions. The antitat gene has been proposed for gene therapy because it effectively blocks Tat function and the replication of HIV-1. However, neither antitat nor any other antiviral gene has been shown to inhibit HIV in the presence of high viral load and inflammatory cytokines, a condition closer to the in vivo situation. We show that cells transduced with antitat retrovirus vector are resistant to high multiplicity of HIV infection. In the presence of inflammatory cytokines, including interleukin-1 and tumor necrosis factor, both known to activate viral gene expression independently of Tat, antitat suppressed virus replication. HIV-1 inhibition was observed when cell were treated with a mixture of inflammatory cytokines able to induce acquired immunodeficiency syndrome (AIDS) Kaposi's sarcoma cell growth. These molecules have been shown to be increased in HIV-1-infected individuals, and it is suggested they play a role in the pathogenesis of AIDS. Our results suggest that antitat is effective under conditions present in vivo and therefore a primary candidate for HIV-1 gene therapy.

CD4-Positive T-Lymphocytes↗
PubMed1996

Disruption of 12/15-lipoxygenase expression in peritoneal macrophages. Enhanced utilization of the 5-lipoxygenase pathway and diminished oxidation of low density lipoprotein.

Previously, we isolated the murine "leukocyte-type" 12-lipoxygenase (L-12LO) cDNA from RNA of peritoneal-elicited cells that consisted predominantly of leukocytes (Chen, X.-S., Kurre, U., Jenkins, N. A., Copeland, N. G., and Funk, C. D. (1994) J. Biol. Chem. 269, 13979-13987). By in situ hybridization we show that the L-12LO gene is expressed abundantly in a subset of peritoneal macrophages but not in elicited leukocytes, alveolar macrophages, or bone marrow-derived macrophages. L-12LO is highly related to human and rabbit 15-lipoxygenases, enzymes that have been implicated in the maturation process of red blood cells, and the oxidative modification of low density lipoproteins that is implicated in atherogenesis. Accordingly, these enzymes have been referred to as 12/15-lipoxygenases. We have inactivated the L-12LO gene in mice using homologous recombination in embryonic stem cells. Macrophage expression of L-12LO was abolished in homozygous deficient mice as was formation of 12-hydroxyeicosatetraenoic acid (12-HETE). In zymosan-stimulated cells, there was significant diversion of metabolism to the 5-lipoxygenase products leukotriene C4 and 5-HETE and in A23187-treated cells to 5-HETE only. The enhanced formation of 5-lipoxygenase metabolites was not due to compensatory changes of 5-lipoxygenase or 5-lipoxygenase activating protein but rather an apparent substrate diversion. L-12LO-deficient mice have no obvious abnormalities in reticulocyte or mature red blood cells, which suggest that in mice this pathway is not functionally important for erythrocytic development. Indices for oxidation of low density lipoprotein (measured as either thiobarbituric acid-reactive substances or the oxidant stress marker isoprostane 8-epi-prostaglandin F2alpha) were identical in incubations with unstimulated wild-type and L-12LO-deficient macrophages, but the zymosan-induced increase observed with wild-type macrophages was abolished in L-12LO-deficient cells. Thus, 12/15-lipoxygenase-deficient mice will be useful for the study of interaction between lipoxygenase pathways and determination of the in vivo role of 12/15-lipoxygenase-catalyzed oxidation of LDL in atherogenesis.

5-Lipoxygenase-Activating Proteins↗
PubMed1996

Structural distortions induced by integration host factor (IHF) at the H' site of phage lambda probed by (+)-CC-1065, pluramycin, and KMnO4 and by DNA cyclization studies.

Integration Host Factor (IHF) is a sequence-specific DNA-bending protein that is proposed to interact with DNA primarily through the minor groove. We have used various chemical probes [(+)-CC-1065, a minor-groove-specific agent that alkylates N3 of adenine and traps bends into the minor groove; pluramycin, a minor-major-groove threading intercalator that alkylates N7 of guanine; KMnO4, which reacts more strongly with bases in denatured DNA] to gain more information on the interaction of IHF with the H' site of phage lambda. In addition to the 13-bp core consensus recognition element present at all IHF binding sites, the H' site also has an upstream AT-rich element that increases the affinity of IHF for this site. Our results reveal new details of IHF-DNA interaction at this site. Results with (+)-CC-1065 modification suggest that IHF interacts with the adenines on the 3'-side of the AT-rich element and likely induces a minor-groove bend in its vicinity, which in turn stabilizes the interaction. Pluramycin modification experiments suggest the presence of both short- and long-range structural perturbations (possible DNA unwinding events) on either side of the IHF contact region. Although IHF is known to induce a large bend in DNA at the H' site, no separation of base pairs was detected when the bent DNA was probed with KMnO4. DNA cyclization studies indicate a large magnitude (approximately 180 degrees) for the IHF-induced bend at the H' site, consistent with > 140 degrees bend estimated by gel electrophoresis methods. These studies suggest that IHF-induced DNA bending is accompanied by the introduction of a DNA node, DNA unwinding, and/or by some other DNA distortion. An enhanced binding and stability of IHF was observed on small circular DNA.

Adenine↗
PubMed1996

Production of tumor necrosis factor-alpha as a result of glia-T-cell interaction correlates with the pathogenic activity of myelin basic protein-reactive T cells in experimental autoimmune encephalomyelitis.

Tumor necrosis factor-alpha (TNF-alpha) has attracted the greatest attention as a major factor in experimental autoimmune encephalomyelitis (EAE) pathogenesis. We compared rats undergoing EAE with manipulated but healthy animals by examining TNF-alpha gene expression in cells recovered from the brain. We used reverse transcriptase-polymerase chain reaction (RT-PCR) as a sensitive assay for detection and Northern blot hybridization as a reliable quantitative assay of TNF-alpha mRNA. TNF-alpha gene expression was consistently detected in rats immunized with myelin basic protein (MBP) emulsified in complete Freund adjuvant (CFA), but not in rats immunized with MBP emulsified in incomplete Freund adjuvant (IFA), which does not induce EAE. Similarly, brain-derived cells from rats injected with cloned encephalitogenic T cells contained increased amounts of TNF-alpha mRNA compared with rats injected with nonencephalitogenic T cell clones similar in antigen specificity and in vitro lymphokine-producing capacity. Considering that the differing pathogenic capacity of MBP-reactive T cells might result from differing patterns of interaction with glia, we examined the impact of T-cell-glia interaction in vitro on cytokine gene expression in both cell types. Glial components were efficient in inducing TNF-alpha expression in T cells; T cells and T-cell-derived cytokines could elicit expression of several lymphokine genes in glial cells. Comparison of RT-PCR and blot hybridization assays, however, suggested that cytokine expression was much more efficient, on a per cell basis, in T cells than in glia. TNF-alpha was shown to have direct cytotoxic effect on glial cells, which was greatly enhanced by small amounts of interferon-gamma (IFN-gamma).

Animals↗
PubMed1996

Phosphorylation of the high molecular weight neurofilament protein (NF-H) by Cdk5 and p35.

The high molecular weight neurofilament protein (NF-H) is highly phosphorylated in the axon. The phosphorylation sites have been identified as KSP (Lys-Ser-Pro) repeats in the tail domain of NF-H. These KSP sequences are present more than 50 times in the NF-H tail, and most of these sites are normally phosphorylated in vivo. These KSP sites can be further divided into two separate consensus sequences, KSPXK and KSPXY (where Y is not K). The extensive phosphorylation of NF-H has been proposed to play a critical role in the determination of axonal diameter. Recent studies have shown that Cdk5, a kinase related to the cell cycle-dependent kinase Cdc2, is expressed in the brain and associates with the cytoskeleton. In vitro phosphorylation studies have shown that Cdk5 in conjunction with its activator, p35, is able to phosphorylate histone H1, dephosphorylated NF-H, as well as a synthetic peptide with the repetitive KSP motif. We have cloned the cDNAs for rat Cdk5 and p35 by reverse transcription-polymerase chain reaction and cDNA library screening and studied the phosphorylation of NF-H both in vivo and in vitro. By transient transfection assays, we have shown that NF-H can only be extensively phosphorylated in the presence of both Cdk5 and p35. This phosphorylation can be inhibited by a Cdk5-dominant negative mutant, an observation which further supports that Cdk5 is a kinase that is able to phosphorylate NF-H. By immunoprecipitating Cdk5 and p35 from the transfected cells, we have been able to show that the KSPXK repeats are the preferred phosphorylation sites for Cdk5, while the KSPXY repeats are not directly phosphorylated by Cdk5 and p35.

Amino Acid Sequence↗
PubMed1996

A member of the phylogenetically conserved CAD family of transcriptional regulators is dramatically up-regulated during the programmed cell death of skeletal muscle in the tobacco hawkmoth Manduca sexta.

The intersegmental muscles (ISMs) of the tobacco hawkmoth Manduca sexta participate in the emergence behavior of the adult moth at the end of metamorphosis and then die during the subsequent 30-hr period. The trigger for this death is a decline in the circulating titer of the insect molting hormone 20-hydroxyecdysone (20-HE). Previous work has demonstrated that the ability of the ISMs to die is dependent on new gene expression. Using a differential hybridization cloning strategy, a cDNA library made from the ISMs committed to die was screened, and four up-regulated clones were isolated. One clone, 18-56, was selected for this study. Northern and Western analysis demonstrated that while clone 18-56 was expressed in all tissues examined and during every stage of ISM development, there was a dramatic increase in expression at both mRNA and protein levels when the ISMs became committed to die. If ISM death was delayed by an injection of 20-HE on the day proceeding adult emergence, 18-56 expression remained at basal levels. Immunocytochemistry demonstrated that 18-56 protein was located predominantly in nuclei prior to the commitment of the ISMs to die and then accumulated to high levels in cytoplasm at the time of cell death. DNA sequence analysis revealed that 18-56 protein shares 74% identity with yeast SUG1 and 92% with human Trip1, both of which are members of the conserved CAD (Conserved ATPase-containing Domain) family of putative transcriptional regulators. To verify that these genes shared functional as well as sequence homology, Manduca clone 18-56 was transformed into a yeast mutant for SUG1 function. Manduca 18-56 was able to both complement the lethal SUG1 phenotype and to suppress the transcriptional activity of a SUG1 mutation in yeast. Taken together, these data support the hypothesis that members of the phylogenetically conserved CAD family participate in important basal and developmental processes.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1996

Detection of anticentromere antibodies using recombinant human CENP-A protein.

OBJECTIVE: To evaluate CENP-A reactivity with anticentromere antibodies (ACA) using recombinant protein (rCENP-A). METHODS: Human CENP-A antigen was overexpressed in insect cells using the baculovirus system. We tested for ACA activity against the full-length recombinant polypeptide by immunoblot and by enzyme-linked immunosorbent assay (ELISA). RESULTS: Of the ACA+ sera studied (n = 38), 95% were positive when tested against the rCENP-A in the ELISA system. Of the ACA- sera (n = 100), only 2% gave false-positive results in the assay. There was good correlation between the recombinant and bona fide antigens in assaying for ACA reactivity. CONCLUSION: CENP-A is a significant ACA target. The availability of the rCENP-A assay is a valuable adjunct to the previously described rCENP-B assay in analyses of the clinical significance of ACA.

Animals↗
PubMed1996

Agents that target telomerase and telomeres.

Telomeres are guanine-rich regions that are located at the ends of chromosomes and are essential for preventing aberrant recombination and protecting against exonucleolytic DNA degradation. Telomeres are maintained by telomerase, an RNA-dependent DNA polymerase. Because telomerase is known to be expressed in tumor cells, which concurrently have short telomeres, and not in most somatic cells, which usually have long telomeres, telomerase and telomere structures have been recently proposed as attractive targets for the discovery of new anticancer agents. The most exciting current strategies are aimed at specifically designing new drugs that target telomerase or telomeres and new models have been formulated to study the biological effects of inhibitors of telomerase and telomeres both in vitro and in vivo.

Animals↗