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Biomedical subjects

M Yu

Publications and source records attributed to M Yu.

At least 109 records · Page 6Linked to original sources
PubMed2000

Exercise-induced changes in expression and activity of proteins involved in insulin signal transduction in skeletal muscle: differential effects on insulin-receptor substrates 1 and 2.

Level of physical activity is linked to improved glucose homeostasis. We determined whether exercise alters the expression and/or activity of proteins involved in insulin-signal transduction in skeletal muscle. Wistar rats swam 6 h per day for 1 or 5 days. Epitrochlearis muscles were excised 16 h after the last exercise bout, and were incubated with or without insulin (120 nM). Insulin-stimulated glucose transport increased 30% and 50% after 1 and 5 days of exercise, respectively. Glycogen content increased 2- and 4-fold after 1 and 5 days of exercise, with no change in glycogen synthase expression. Protein expression of the glucose transporter GLUT4 and the insulin receptor increased 2-fold after 1 day, with no further change after 5 days of exercise. Insulin-stimulated receptor tyrosine phosphorylation increased 2-fold after 5 days of exercise. Insulin-stimulated tyrosine phosphorylation of insulin-receptor substrate (IRS) 1 and associated phosphatidylinositol (PI) 3-kinase activity increased 2.5- and 3. 5-fold after 1 and 5 days of exercise, despite reduced (50%) IRS-1 protein content after 5 days of exercise. After 1 day of exercise, IRS-2 protein expression increased 2.6-fold and basal and insulin-stimulated IRS-2 associated PI 3-kinase activity increased 2. 8-fold and 9-fold, respectively. In contrast to IRS-1, IRS-2 expression and associated PI 3-kinase activity normalized to sedentary levels after 5 days of exercise. Insulin-stimulated Akt phosphorylation increased 5-fold after 5 days of exercise. In conclusion, increased insulin-stimulated glucose transport after exercise is not limited to increased GLUT4 expression. Exercise leads to increased expression and function of several proteins involved in insulin-signal transduction. Furthermore, the differential response of IRS-1 and IRS-2 to exercise suggests that these molecules have specialized, rather than redundant, roles in insulin signaling in skeletal muscle.

Animals↗
PubMed2000

Genomic imbalance in rat mammary gland carcinomas induced by 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine.

2-Amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), a compound found in cooked meat, is a mammary gland carcinogen in female Sprague-Dawley rats. PhIP-induced rat mammary gland carcinomas were examined for mutations in several genes (exons) known to regulate cell growth and apoptosis, including p53 (4-8), p21(Waf1) (coding region), Apc (14, 15), B-catenin (3), E-cadherin (9,13,15), Bcl-x (coding region), Bax (3), IGFIIR (28), and TGFBIIR (3). DNA from 30 carcinomas was examined by single-strand conformation polymorphism analysis, but no mutations were detected in these genes or gene regions. DNA from carcinomas and matching normal tissue were further screened for allelic imbalance by using a polymerase chain reaction-based approach with primers to known microsatellite regions located throughout the rat genome. Of 53 markers examined, 12 revealed allelic imbalance. Microsatellite instability (MSI) was detected at two markers, one on chromosome 4 and one on chromosome 6. Sixty-five percent and 96% of all carcinomas examined (N=23) showed MSI at these loci on chromosomes 4 and 6, respectively, supporting the notion that MSI plays a role in PhIP-induced mammary carcinogenesis. Loss of heterozygosity (LOH), an indication of a possible tumor suppressor gene, was observed at 10 markers distributed on chromosomes 3, 10, 11, 14, and X. The frequency of LOH at these markers was 75-94%, supporting that the regions of allelic imbalance were largely similar for the PhIP-induced carcinomas examined in this study. When PhIP-induced carcinomas from rats placed on high-fat and low-fat diet were compared, no unique regions of allelic imbalance or statistical differences in the frequency of allelic imbalance were observed. Therefore, the high-fat diet, known to be a promoter of PhIP-induced rat mammary carcinogenesis, did not appear to influence allelic imbalance in the carcinomas. Interestingly, 7,12-dimethylbenz[a]-anthracene-induced mammary carcinomas did not show allelic imbalance at 11 of the 12 loci that showed allelic imbalance in PhIP-induced carcinomas. These findings suggest that distinct chemical carcinogens induce different patterns of allelic imbalance during rat mammary carcinogenesis. Since several of the known genes involved in carcinogenesis did not harbor mutations in PhIP-induced carcinomas, further studies are needed to clarify the critical genes involved in PhIP-induced mammary carcinogenesis and to determine whether regions of LOH harbor potentially novel tumor suppressor genes involved in this disease.

Animals↗
PubMed2000

Alterations in cardiac function and gene expression during autoimmune myocarditis in mice.

Although myocarditis has been implicated in the pathogenesis of heart failure, a definitive relationship between myocardial inflammation, cardiac dysfunction, and changes in myocyte gene expression has not been established. In this study, we examined the hypothesis that myocardial inflammation and replacement fibrosis following an autoimmune response can progress to cardiac dysfunction and may result in progression to the heart failure phenotype. SWXJ mice were immunized with cardiac myosin on day 0 and day 7, in order to induce an autoimmune response to the myosin protein. Cardiac catheterization via the right carotid artery was performed on days 14, 21, 28, 35, and 42, using a 1.4F Millar transducer-tipped catheter. Hearts were weighed, and cross-sections were cut and stained with either haematoxylin and eosin or Masson's trichrome, in order to identify areas of inflammation and/or fibrosis. Myocardial gene expression was determined by Northern blot analysis. In mice with histological evidence of myocarditis, the heart weight/body weight ratio increased beginning on day 14, and cardiac function decreased beginning on day 21. Myocardial inflammation was accompanied by significant fibrosis beginning on day 21. Quantitation of mRNA showed expression of ventricular atrial naturietic factor, as well as a decrease in myosin heavy chain alpha, beginning on day 21. These data demonstrate that autoimmune inflammation of the heart results in significant cardiac dysfunction, leading to phenotypic alterations similar to those demonstrated in human heart failure and animal models of heart failure.

Animals↗
PubMed2000

Metabolism of [123I]epidepride may affect brain dopamine D2 receptor imaging with single-photon emission tomography.

Iodine-123 labelled epidepride is a novel radiopharmaceutical for the study of cerebral dopamine D2 receptors using single-photon emission tomography (SPET). A lipophilic labelled metabolite of [123I]epidepride which may enter the brain and hamper the quantitation of receptors has been observed in human plasma. In the present study, gradient high-performance liquid chromatography (HPLC) was used to investigate the plasma concentration of the lipophilic labelled metabolite and its correlation to SPET imaging of striatal dopamine D2 receptors. A linear regression fit showed a negative correlation between the amount of the lipophilic labelled metabolite and the striatum to cerebellum ratio (n=16, R=-0.58, P<0.02), suggesting that plasma metabolite analysis is essential when imaging dopamine D2 receptors with SPET using [123I]epidepride.

Adult↗
PubMed2000

Near-tetraploid minimally differentiated acute myeloid leukemia with extensive erythrophagocytosis by leukemic blasts.

Numerical change of chromosomes is common in acute myeloid leukemia (AML). However, a chromosome number as high as near-tetraploidy is very rare, especially in minimally differentiated AML (AML-M0). Erythrophagocytosis by reactive or malignant histiocytes is common in malignant hematological diseases; however, erythrophagocytosis by leukemic blasts is also very rare, especially in AML-M0. We report here the first case of AML-M0 with both of these unique characteristics: a near-tetraploid karyotype and erythrophagocytosis by leukemic blasts.

Acute Disease↗
PubMed2000

Cell cycle G2 arrest induced by HIV-1 Vpr in fission yeast (Schizosaccharomyces pombe) is independent of cell death and early genes in the DNA damage checkpoint.

HIV-1 Vpr induces cell cycle G2 arrest, morphological changes and cell death in human and fission yeast cells. The cellular targets for G2 arrest were expected to be the inhibitory phosphorylation sites of Cdc2, as G2 arrest correlates with hyperphosphorylation and decreased activity of Cdc2 in both human and fission yeast cells. In this study, we present direct evidence of genetic suppression of Vpr-induced G2 arrest by cdc2 mutations. Mutations in cdc2 (cdc2-1w and cdc2-3w) reduce the ability of Vpr to induce G2 arrest. A strain with a mutation changing the Tyr15 of Cdc2 to the non-phosphorylated Phe (Y15F) eliminated Vpr-induced G2 arrest indicating that Tyr15 of Cdc2 is the sole target for induction of G2 arrest by Vpr. Although the G2 arrest induced by DNA damage also proceeds through phosphorylation of Tyr15, the rad1, rad3, rad9 and rad17 mutations, which eliminate the G2 checkpoint for DNA damage, did not block the G2 arrest induced by Vpr. Furthermore, Vpr expression did not alter sensitivity of these rad mutants to UV radiation. Thus, the pathways for the induction of G2 arrest by DNA damage and Vpr are not identical. Interestingly, Vpr still induces cell death and morphological changes in the Y15F Cdc2 strain indicating that G2 arrest is not required for morphological changes and cell death. This conclusion was further supported by the observation that mutations in Vpr, which have lost their ability to induce G2 arrest, retained the ability to kill cells.

CDC2 Protein Kinase↗
PubMed2000

Efficient gene transfer to hematopoietic progenitor cells using SV40-derived vectors.

We used recombinant SV40 (rSV40)-derived vectors to deliver transgenes to human and simian hematopoietic progenitor cells in culture, and in vivo after transduction ex vivo. rSV40 are highly efficient vectors that are made in very high titers. They infect almost all cells, whether resting or dividing. Two rSV40s were used: SV(HBS), carrying hepatitis B surface antigen as a marker; and SV(Aw) carrying IN#33, a single chain Fv antibody against HIV-1 integrase. CD34+ cells derived from human fetal bone marrow (HFBM) and rhesus macaque bone marrow were transduced once with SV(HBS) without selection. On average 60% of colonies derived from transduced CD34+ cells carried and expressed HBsAg, as assessed by PCR and immunochemistry. Transgene carriage persisted following differentiation of transduced rhesus CD34+ cells into T lymphocytes. In an effort to increase the percentage of gene-marked cells, three sequential treatments of CD34+ cells were done using SV(Aw), without selection. Two weeks later, >95% of colonies expressed IN#33. Unselected SV(Aw)-transduced CD34+ cells from HFBM were transplanted into sublethally irradiated SCID mice. Bone marrow harvested 3 months later showed that >50% of bone marrow cells expressed IN#33. This is comparable with the percentage of human cells in these animals' bone marrow as judged by immunostaining for human CD45. The stability and longevity of transduction in this setting suggests that rSV40 vectors integrate into the cellular genome. This possibility was supported by finding that PCR of genomic DNA using primer pairs with one cellular and one viral primer yielded PCR products only in transduced, but not control, cells. These PCR products hybridized with an SV40 DNA fragment. Thus, rSV40 vectors transduce normal human and primate bone marrow progenitor cells effectively without selection, and maintain transgene expression in vivo following reimplantation. Such high efficiency transduction may be useful in treating diseases of CD34+ cells and their derivatives.

Animals↗
PubMed2000

Ordering three microsatellites on porcine chromosome 12 by single sperm typing.

Three microsatellite loci on porcine chromosome 12 were ordered by single sperm typing to expand the limited genetic map of this region. Individual sperm cells from a Chinese indigenous Qingping boar triply heterozygous at SW874, SW1350 and SW1553 were amplified using PEP and heminesting primer design at each locus. Analysis of the sperm typing data by the SPERM.FOR program showed that the most likely order was SW1553-SW1350-SW874.

Animals↗
PubMed2000

Screening tests of disseminated intravascular coagulation: guidelines for rapid and specific laboratory diagnosis.

OBJECTIVE: To study the clinician's ordering pattern in the diagnosis of disseminated intravascular coagulation (DIC) and to analyze the utility of selected tests by assessing their sensitivity, specificity, and overall efficiency. DESIGN: Retrospective, nonrandomized, clinical study. SETTING: University hospital intensive care units. PATIENTS: A total of 82 inpatients treated in our intensive care units were identified from the hospital computer system as having been tested for DIC in a 3-month period. INTERVENTION: Screening tests for DIC were ordered for the suspected patients. MEASUREMENTS AND MAIN RESULTS: Prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen/fibrin degradation products (FDP), and fibrinogen were used most frequently as DIC diagnostic tests. The FDP and D-dimer combination (n = 39) had the highest diagnostic efficiency of 95%, with sensitivity being 91% and specificity 94%. This is followed by FDP (n = 71), efficiency 87%, sensitivity 100%, and specificity 67%; PT/PTT and FDP combination (n = 71), efficiency 86%, sensitivity 91%, and specificity 71%; and D-dimer (n = 44), efficiency 80%, sensitivity 91%, and specificity 68%. The rest of the commonly used tests, such as PT, PTT, thrombin time, platelet count, fibrinogen, and the presence of schistocytes (n = 80), had individually either low specificity or low sensitivity and, therefore, low efficiency scores (57%, 57%, 70%, 67%, 65%, and 51%, respectively). CONCLUSIONS: The D-dimer and FDP tests offered the best test panel in the diagnosis of DIC. We propose the use of D-dimer, FDP, and antithrombin as the DIC diagnostic test panel, with D-dimer and FDP providing a rapid and specific diagnosis, antithrombin providing insight to the severity and prognosis, and FDP (rapid and less expensive than D-dimer) to follow-up the progress of the condition once the diagnosis is established.

Disseminated Intravascular Coagulation↗
PubMed2000

Effects of methamphetamine on trauma patients: a cause of severe metabolic acidosis?

OBJECTIVE: Presentation of a trauma patient with severe unexplained metabolic acidosis, possibly attributable to the vasoconstrictive properties of smokable "crystal" methamphetamine. In addition, a review of trauma registry data was undertaken to determine the effects of methamphetamine on trauma patients. DESIGN: Case report and retrospective case-control study. SETTING: Urban tertiary teaching hospital. PATIENTS: Two controls were obtained for each case controlling for age, Injury Severity Score, and mechanism of injury. Patients > or =16 yrs of age with a urine toxicology screen positive for methamphetamine were included. MEASUREMENTS AND MAIN RESULTS: Data were obtained from the trauma registry for the period of January 1994 to June 1995. Trauma patients using methamphetamine had a significantly lower blood alcohol level compared with the control group. Otherwise, there were no significant differences detected in vital signs, laboratory values, procedures, treatment, or outcome between the two groups. Details regarding one patient who presented with severe life-threatening acidosis are presented. CONCLUSIONS: Trauma patients with recent use of smokable methamphetamine may present with severe acidosis requiring urgent attention and treatment. This acidosis may exaggerate the severity of the actual injury. However, urine testing for methamphetamine does not identify patients who may harbor this acidosis.

Acidosis↗
PubMed2000

The exceptionally large genome of Hendra virus: support for creation of a new genus within the family Paramyxoviridae.

An outbreak of acute respiratory disease in Hendra, a suburb of Brisbane, Australia, in September 1994 resulted in the deaths of 14 racing horses and a horse trainer. The causative agent was a new member of the family Paramyxoviridae. The virus was originally called Equine morbillivirus but was renamed Hendra virus (HeV) when molecular characterization highlighted differences between it and members of the genus Morbillivirus. Less than 5 years later, the closely related Nipah virus (NiV) emerged in Malaysia, spread rapidly through the pig population, and caused the deaths of over 100 people. We report the characterization of the HeV L gene and protein, the genome termini, and gene boundary sequences, thus completing the HeV genome sequence. In the highly conserved region of the L protein, the HeV sequence GDNE differs from the GDNQ found in almost all other nonsegmented negative-strand (NNS) RNA viruses. HeV has an absolutely conserved intergenic trinucleotide sequence, 3'-GAA-5', and highly conserved transcription initiation and termination sequences similar to those of respiroviruses and morbilliviruses. The large genome size (18,234 nucleotides), the unique complementary genome terminal sequences of HeV, and the limited homology with other members of the Paramyxoviridae suggest that HeV, together with NiV, should be classified in a new genus in this family. The large genome of HeV also fills a gap in the spectrum of genome sizes observed with NNS RNA virus genomes. As such, it provides a further piece in the puzzle of NNS RNA virus evolution.

Amino Acid Sequence↗
PubMed2000

HuD RNA recognition motifs play distinct roles in the formation of a stable complex with AU-rich RNA.

Human neuron-specific RNA-binding protein HuD belongs to the family of Hu proteins and consists of two N-terminal RNA recognition motifs (RRM1 and -2), a hinge region, and a C-terminal RRM (RRM3). Hu proteins can bind to AU-rich elements in the 3' untranslated regions of unstable mRNAs, causing the stabilization of certain transcripts. We have studied the interaction between HuD and prototype mRNA instability elements of the sequence UU(AUUU)(n)AUU using equilibrium methods and real-time kinetics (surface plasmon resonance using a BIACORE). We show that a single molecule of HuD requires at least three AUUU repeats to bind tightly to the RNA. Deletion of RRM1 reduced the K(d) by 2 orders of magnitude and caused a decrease in the association rate and a strong increase in the dissociation rate of the RNA-protein complex, as expected when a critical RNA-binding domain is removed. In contrast, deletion of either RRM2 or -3, which only moderately reduced the affinity, caused marked increases in the association and dissociation rates. The slower binding and stabilization of the complex observed in the presence of all three RRMs suggest that a change in the tertiary structure occurs during binding. The individual RRMs bind poorly to the RNA (RRM1 binds with micromolar affinity, while the affinities of RRM2 and -3 are in the millimolar range). However, the combination of RRM1 and either RRM2 or RRM3 in the context of the protein allows binding with a nanomolar affinity. Thus, the three RRMs appear to cooperate not only to increase the affinity of the interaction but also to stabilize the formed complex. Kinetic effects, similar to those described here, could play a role in RNA binding by many multi-RRM proteins and may influence the competition between proteins for RNA-binding sites and the ability of RNA-bound proteins to be transported intracellularly.

3' Untranslated Regions↗
PubMed2000

Calibration of HCV working reagents for NAT assays against the HCV international standard. The Collaborative Study Group.

BACKGROUND AND OBJECTIVES: Five HCV RNA reference reagents, the Paul Ehrlich Institut (PEI) reference 75, the National Institute for Biological Standards and Control (NIBSC) reagent 96/586, the Central Laboratory of the Netherlands Red Cross Blood Transfusion Service (CLB) Pelispy HCV RNA run control S2001, the Istituto Superiore di Sanità (ISS) reagent 0498 and the CBER panel member No. 1, were calibrated against the WHO International Standard, 96/790. MATERIALS AND METHODS: The reference materials were calibrated in a collaborative study organised by NIBSC. Nineteen laboratories, using a range of qualitative and quantitative assays returned results. RESULTS: The concentrations of the reagents were: 25,000 IU/ml for the PEI material, 710 IU/ml for the NIBSC material 96/586, 1,000 IU/ml for the CLB material, 1,700 IU/ml for the ISS material 0498 and 250 IU/ml for the CBER panel member No. 1. CONCLUSIONS: The calibration of these five reference reagents for HCV RNA nucleic acid amplification technology (NAT) assays enables them to be used for standardisation and validation of assays. Such calibrants are essential for meeting the requirements of the European Medicinal Evaluation Agency (EMEA) for the testing of plasma pools and donations for HCV RNA for the release of blood products and the PEI requirements for the release testing of erythrocyte and thrombocyte concentrates.

Calibration↗
PubMed2000

Immobilization of Notch ligand, Delta-1, is required for induction of notch signaling.

Cell-cell interactions mediated by Notch and its ligands are known to effect many cell fate decisions in both invertebrates and vertebrates. However, the mechanisms involved in ligand induced Notch activation are unknown. Recently it was shown that, in at least some cases, endocytosis of the extracellular domain of Notch and ligand by the signaling cell is required for signal induction in the receptive cell. These results imply that soluble ligands (ligand extracellular domains) although capable of binding Notch would be unlikely to activate it. To test the potential activity of soluble Notch ligands, we generated monomeric and dimeric forms of the Notch ligand Delta-1 by fusing the extracellular domain to either a series of myc epitopes (Delta-1(ext-myc)) or to the Fc portion of human IgG-1 (Delta-1(ext-IgG)), respectively. Notch activation, assayed by inhibition of differentiation in C2 myoblasts and by HES1 transactivation in U20S cells, occurred when either Delta-1(ext-myc) or Delta-1(ext-IgG) were first immobilized on the plastic surface. However, Notch was not activated by either monomeric or dimeric ligand in solution (non-immobilized). Furthermore, both non-immobilized Delta-1(ext-myc) and Delta-1(ext-IgG) blocked the effect of immobilized Delta. These results indicate that Delta-1 extracellular domain must be immobilized to induce Notch activation in C2 or U20S cells and that non-immobilized Delta-1 extracellular domain is inhibitory to Notch function. These results imply that ligand stabilization may be essential for Notch activation.

Cell Communication↗
PubMed2000

Effect of long-term mild hypothermia therapy in patients with severe traumatic brain injury: 1-year follow-up review of 87 cases.

OBJECT: The goal of this study was to investigate the protective effects of long-term (3-14 days) mild hypothermia therapy (33-35 degrees C) on outcome in 87 patients with severe traumatic brain injury (TBI) (Glasgow Coma Scale score < or = 8). METHODS: In 43 patients assigned to a mild hypothermia group, body temperatures were cooled to 33 to 35 degrees C a mean of 15 hours after injury and kept at 33 to 35 degrees C for 3 to 14 days. Rewarming commenced when the individual patient's intracranial pressure (ICP) returned to the normal level. Body temperatures in 44 patients assigned to a normothermia group were maintained at 37 to 38 degrees C. Each patient's outcome was evaluated 1 year later by using the Glasgow Outcome Scale. One year after TBI, the mortality rate was 25.58% (11 of 43 patients) and the rate of favorable outcome (good recovery or moderate disability) was 46.51% (20 of 43 patients) in the mild hypothermia group. In the normothermia group, the mortality rate was 45.45% (20 of 44 patients) and the rate of favorable outcome was 27.27% (12 of 44 patients) (p < 0.05). Induced mild hypothermia also markedly reduced ICP (p < 0.01) and inhibited hyperglycemia (p < 0.05). The rates of complication were not significantly different between the two groups. CONCLUSIONS: The data produced by this study demonstrate that long-term mild hypothermia therapy significantly improves outcomes in patients with severe TBI.

Adult↗
PubMed2000

[Effects of hypoxic preconditioning on anoxic tolerance and IL-1 beta expression in cultured rat hippocampal neurons].

AIM: To study the effects of hypoxic-preconditioning on anoxia-tolerance and IL-1 beta expression in cultured rat hippocampal neurons after anoxia. METHODS: 12 day cultured hippocampal neurons in control and hypoxic-preconditioning group were exposed to anoxic environment(0.9 L/LN2 + 0.1 L/LCO2) for 2, 4, 8 and 12 h. The neurons were immunocytochemically stained using the anti-serum against rhIL-1 beta, The number of survival neurons and the mean optical density (OD) of IL-1 beta expression were investigated. RESULTS: The morphological changes and IL-1 beta expression induced by acute anoxia in hypoxic-preconditioning neurons were significantly less than those in control. The number of survival neurons was higher in the hypoxia-preconditioning group than that in control group after acute hypoxia. CONCLUSION: Hypoxia-preconditioning can induce the development of anoxia-tolerance in cultured hippocampal neurons. The decreased IL-1 beta in hippocampal neurons may be an adaptive reaction to acute anoxia.

Animals↗
PubMed2000

Structural implications for the design of molecular vaccines.

The major histocompatibility complex molecules bind and present short antigenic peptide fragments on the surface of antigen presenting cells to T-cell receptors. Recognition of peptide-MHC by cytotoxic T-cells initiates a cascade of signals to T-cells, which in turn destroy the antigen presenting cell. In the design of molecular vaccines for the treatment of diseases, an understanding of the 3-dimensional structure of MHC class I and is interaction with both peptide and T-cell receptor is an important prerequisite. In this review, we will discuss such crystal structures, as well as structures of glycopeptides and alternative T-cell antigens presented by MHC molecules.

Amino Acid Sequence↗