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Biomedical subjects

J Wu

Publications and source records attributed to J Wu.

At least 469 records · Page 26Linked to original sources
PubMed2000

SU6656, a selective src family kinase inhibitor, used to probe growth factor signaling.

The use of small-molecule inhibitors to study molecular components of cellular signal transduction pathways provides a means of analysis complementary to currently used techniques, such as antisense, dominant-negative (interfering) mutants and constitutively activated mutants. We have identified and characterized a small-molecule inhibitor, SU6656, which exhibits selectivity for Src and other members of the Src family. A related inhibitor, SU6657, inhibits many kinases, including Src and the platelet-derived growth factor (PDGF) receptor. The use of SU6656 confirmed our previous findings that Src family kinases are required for both Myc induction and DNA synthesis in response to PDGF stimulation of NIH 3T3 fibroblasts. By comparing PDGF-stimulated tyrosine phosphorylation events in untreated and SU6656-treated cells, we found that some substrates (for example, c-Cbl, and protein kinase C delta) were Src family substrates whereas others (for example, phospholipase C-gamma) were not. One protein, the adaptor Shc, was a substrate for both Src family kinases (on tyrosines 239 and 240) and a distinct tyrosine kinase (on tyrosine 317, which is perhaps phosphorylated by the PDGF receptor itself). Microinjection experiments demonstrated that a Shc molecule carrying mutations of tyrosines 239 and 240, in conjunction with an SH2 domain mutation, interfered with PDGF-stimulated DNA synthesis. Deletion of the phosphotyrosine-binding domain also inhibited synthesis. These inhibitions were overcome by heterologous expression of Myc, supporting the hypothesis that Shc functions in the Src pathway. SU6656 should prove a useful additional tool for further dissecting the role of Src kinases in this and other signal transduction pathways.

3T3 Cells↗
PubMed2000

Normal development, wound healing, and adenovirus susceptibility in beta5-deficient mice.

Integrins have been shown to play important roles in embryonic development, wound healing, metastasis, and other biological processes. alphavbeta5 is a receptor for RGD-containing extracellular matrix proteins that has been suggested to be important in cutaneous wound healing and adenovirus infection. To examine the in vivo function of this receptor, we have generated mice lacking beta5 expression, using homologous recombination in embryonic stem cells. Mice homozygous for a null mutation of the beta5 subunit gene develop, grow, and reproduce normally. Keratinocytes harvested from beta5(-/-) mice demonstrate impaired migration on and adhesion to the alphavbeta5 ligand, vitronectin. However, the rate of healing of cutaneous wounds is not different in beta5(-/-) and beta5(+/+) mice. Furthermore, keratinocytes and airway epithelial cells obtained from null mice show adenovirus infection efficiency equal to that from wild-type mice. These data suggest that alphavbeta5 is not essential for normal development, reproduction, adenovirus infection, or the healing of cutaneous wounds.

Adenoviridae↗
PubMed2000

Ability of insulin to modulate hepatic glucose production in aging rats is impaired by fat accumulation.

Increased total fat mass (FM) and visceral fat (VF) may account in part for age-associated decrease in hepatic insulin action. This study determined whether preventing the changes in body fat distribution abolished this defect throughout aging. We studied the F(1) hybrid of Brown Norway-Fischer 344 rats (n = 29), which we assigned to caloric restriction (CR) or fed ad libitum (AL). CR (55% of the calories consumed by AL) was initiated and used at 2 mo to prevent age-dependent increases in FM and VF. AL rats were studied at 2, 8, and 20 mo; CR rats were studied at 8 and 20 mo. VF and FM remained unchanged throughout aging in CR rats. AL-fed rats at 8 and 20 mo had over fourfold higher FM and VF compared with both CR groups. Insulin clamp studies (3 mU. kg(-1). min(-1) with somatostatin) were performed to assess hepatic insulin sensitivity. Prevention of fat accretion resulted in a marked improvement in insulin action in the suppression of hepatic glucose production (HGP) (6.3 +/- 0.3 and 7.2 +/- 1.2 mg. kg(-1). min(-1) in 8- and 20-mo CR rats vs. 8.3 +/- 0.5 and 10.8 +/- 0.9 mg. kg(-1). min(-1) in 8- and 20-mo AL rats, respectively). The rate of gluconeogenesis (by enrichment of hepatic uridine diphosphate glucose and phosphoenolpyruvate pools by [(14)C]lactate) was unchanged in all groups. The improvement in hepatic insulin action in the CR group was mostly due to effective suppression of glycogenolysis (4.4 +/- 0.3 and 4.9 +/- 0.3 mg. kg(-1). min(-1) in 8- and 20-mo CR rats vs. 5.8 +/- 0.6 and 8.2 +/- 1.0 mg. kg(-1). min(-1) in 8- and 20-mo AL rats, respectively). The results demonstrated the preservation of hepatic insulin action in aging CR rats. Therefore, body fat and its distribution are major determinants of age-associated hepatic insulin resistance.

Adipose Tissue↗
PubMed2000

Association of phosphatidylinositol 3-kinase with the insulin receptor: compartmentation in rat liver.

Phosphatidylinositol 3-kinase (PI 3-kinase) plays an important role in a variety of hormone and growth factor-mediated intracellular signaling cascades and has been implicated in the regulation of a number of metabolic effects of insulin, including glucose transport and glycogen synthase activation. In the present study we have examined 1) the association of PI 3-kinase with the insulin receptor kinase (IRK) in rat liver and 2) the subcellular distribution of PI 3-kinase-IRK interaction. Insulin treatment promoted a rapid and pronounced recruitment of PI 3-kinase to IRKs located at the plasma membrane, whereas no increase in association with endosomal IRKs was observed. In contrast to IRS-1-associated PI 3-kinase activity, association of PI 3-kinase with the plasma membrane IRK did not augment the specific activity of the lipid kinase. With use of the selective PI 3-kinase inhibitor wortmannin, our data suggest that the cell surface IRK beta-subunit is not a substrate for the serine kinase activity of PI 3-kinase. The functional significance for the insulin-stimulated selective recruitment of PI 3-kinase to cell surface IRKs remains to be elucidated.

Androstadienes↗
PubMed2000

Vitronectin adsorption to chrysotile asbestos increases fiber phagocytosis and toxicity for mesothelial cells.

Biological modification of asbestos fibers can alter their interaction with target cells. We have shown that vitronectin (VN), a major adhesive protein in serum, adsorbs to crocidolite asbestos and increases fiber phagocytosis by mesothelial cells via integrins. Because chrysotile asbestos differs significantly from crocidolite in charge and shape, we asked whether VN would also adsorb to chrysotile asbestos and increase its toxicity for mesothelial cells. We found that VN, either from purified solutions or from serum, adsorbed to chrysotile but at a lower amount per surface area than to crocidolite. Nevertheless, VN coating increased the phagocytosis of chrysotile as well as of crocidolite asbestos. VN coating of both chrysotile and crocidolite, but not of glass beads, increased intracellular oxidation and apoptosis of mesothelial cells. The additional apoptosis could be blocked by integrin-ligand blockade with arginine-glycine-aspartic acid peptides, confirming a role for integrins in the fiber-induced toxicity. We conclude that VN increases the phagocytosis of chrysotile as well as of crocidolite asbestos and that phagocytosis is important in fiber-induced toxicity for mesothelial cells.

Adsorption↗
PubMed2000

Hyperthermic spreading depressions in the immature rat hippocampal slice.

Febrile seizures are the most common seizure type in children (6 mo to 5 yr). The pathophysiology of febrile seizures is unknown. Current genetic studies show that some febrile seizures result from channelopathies. We have performed electrophysiological experiments in in vitro hippocampal slices to test a novel hypothesis that a disordered regulation of ionic homeostasis underlies the genesis of febrile seizures. In transverse hippocampal CA1 slices from 104 rats, temperature increase from 34 degrees to 40 degrees C produced a series of spreading depressions (SDs), called hyperthermic SDs. The hyperthermic SDs were age-dependent, occurring in only 1/17 8-16 day-old animals, 44/49 17-60 day-old animals, and 11/20 rats older than than 60 days. The hyperthermic SDs usually occurred on the rising phase of the temperature. The mean temperature to trigger a first hyperthermic SD was 38.8 +/- 1.3 degrees C (mean +/- SD, n = 44). The hyperthermic SDs induced a reversible loss of evoked synaptic potentials and a dramatic decrease of input resistance. Neuronal and field epileptiform bursting occurred in the early phases of the hyperthermic SD. During hyperthermic SDs, pyramidal cell membrane potential depolarized by 38.3 +/- 4.9 mV (n = 20), extracellular field shifted negative 18.5 +/- 3.9 mV (n = 44), and extracellular K(+) rose reversibly to 43.8 +/- 10.9 mM (n = 6). Similar SDs could be evoked by ouabain or transient hypoxia with normal temperature. Tetrodotoxin could block initial epileptiform bursting, without blocking SDs. Hyperthermia-induced SDs should be investigated as possible contributing factors to febrile seizures.

Action Potentials↗
PubMed2000

Outcome of pediatric thromboembolic disease: a report from the Canadian Childhood Thrombophilia Registry.

The outcome for children with deep vein thrombosis (DVT) and pulmonary embolism (PE) is unknown. An understanding of morbidity and mortality of DVT/PE is crucial to the development of rational treatment protocols. The Canadian Childhood Thrombophilia Registry has followed 405 children aged 1 mo to 18 y with DVT/PE for a mean of 2.86 y (range, 2 wk to 6 y) to assess outcome. The all-cause mortality was 65 of 405 children (16%). Mortality directly attributable to DVT/PE occurred in nine children (2.2%), all of whom had central venous line-associated thrombosis. Morbidity was substantial, with 33 children (8.1%) having recurrent thrombosis, and 50 children (12.4%) having postphlebitic syndrome. Recurrent thrombosis and postphlebitic syndrome were more common in older children, although deaths occurred equally in all age groups. The incidence of recurrent thrombosis and postphlebitic syndrome are likely underestimated because of difficulties in diagnosis, especially in younger children. The significant mortality and morbidity found in our study supports the need for international multicenter randomized clinical trials to determine optimal prophylactic and therapeutic treatment for children with DVT/PE.

Adolescent↗
PubMed2000

Selenium supplementation of children in a selenium-deficient area in China: blood selenium levels and glutathione peroxidase activities.

Keshan disease is a cardiomyopathy restricted to the endemic areas of China and seen in residents having an extremely low selenium (Se) status. Prophylactic administration of sodium selenite has been shown to decrease significantly the incidence of acute and subacute cases. The aim offthe study was to assess the relative bioavailability of selenite versus organic Se-yeast in a Se-deficient area in China with a randomized double-blind double-dummy design. Healthy children (n=30) between 14 and 16 yr of age were randomized into three equal groups receiving either 200 microg/d selenite Se or 200 microg/d Se-yeast or placebo for 12 wk. Blood was drawn at baseline, 4, 8, and 12 wk and 4 wk postsupplementation. The plasma Se concentration (mean +/- SD) was 0.16+/-0.03 micromol/L at baseline. Selenite and Se-yeast supplementation increased plasma Se to plateau values, 1.0+/-0.2 and 1.3+/-0.2 micromol/L, respectively. In red cells, Se-yeast increased the selenium level sixfold and selenite threefold compared to placebo. The relative bioavailability of Se-yeast versus selenite measured as glutathione peroxidase (GSHPx) activity was similar in plasma, red blood cells, and platelets. GSHPx activity reached maximal levels in plasma and platelets of 300% and 200%, respectively, after 8 wk compared to the placebo group, but continued to increase in red cells for 16 wk. Our study showed that although both forms of Se were equally effective in raising GSHPx activity, Se-yeast provided a longer lasting body pool of Se. Se-yeast may be a better alternative to selenite in the prophylaxis of Keshan disease with respect to building up of body stores.

Adolescent↗
PubMed2000

Microcalorimetric study of Escherichia coli growth inhibited by the selenomorpholine complexes.

The inhibitory or antibiotic action of four kinds of the selenomorpholine complex on a strain of Escherichia coli was studied by microcalorimetry. Differences in their capacities to inhibit the metabolism of this bacterium were observed. The extent and duration of the inhibitory effect on the metabolism as judged from the rate constant, k, and the half-inhibitory concentration, IC50, varied with the different drugs. The rate constant (k) of Escherichia coli (in the log phase) in the presence of the drugs decreased with increasing concentrations of the drugs (C). The relationship of k and C is nearly linear for (1) selenomorpholine and (2) selenomorpholine hydrochloride, but for (3) N,N'-methylene bisselenomorpholine and (4) N-dodecyl selenomorpholine, it is not linear. The experimental results reveal that the sequence of antibiotic activity of selenomorpholines is (3) and (4) > (1) > (2).

Calorimetry↗
PubMed2000

No evidence of Helicobacter pylori sequences in pancreatic juices of patients affected by chronic pancreatitis.

BACKGROUND: The course of chronic pancreatitis is often unpredictable and many factors are likely to be involved in the progression of the disease. In physiological condition, pancreatic juice exerts significant antibacterial activity, which is impaired in patients with chronic pancreatitis. AIM: Hypothesizing that Helicobacter pylori could, in these conditions, lead to an ascending infection, we aimed to assess the presence of H. pylori sequences in pancreatic juices of patients with chronic pancreatitis. METHODS: 40 patients (mean age 52+/-3 yr) with alcoholic chronic pancreatitis and H. pylori infection were examined. Pancreatic juices were collected during endoscopic retrograde cholangiopancreatography. Using polymerase chain reaction (PCR) with two primers homologous to a portion of urease-C gene, H. pylori DNA was detected. Gastric biopsies, microscopically positive to H. pylori were used as positive controls. RESULTS: All gastric biopsies produced H. pylori-specific DNA products. Conversely, no H. pylori urease-C gene sequences have been detected in any of the pancreatic juices. CONCLUSION: Our data suggest that the impaired antibacterial activity of pancreatic juices in patients affected by chronic pancreatitis does not have a permissive role for a superimposing H. pylori infection in the pancreas. The possibility that Helicobacter species other than pylori may be involved in a superimposing infection requires further investigation.

Chronic Disease↗
PubMed2000

Formation of a facial hematoma during endodontic therapy.

BACKGROUND: Sodium hypochlorite, or NaOCl, is one of the most commonly used irrigating solutions in endodontic practice. Its clinically proven antibacterial, solvent and lubricating properties make it a very appealing choice as an intracanal medicament. CASE DESCRIPTION: The authors present a case of facial hematoma formation after an inadvertent injection of NaOCl into the periapical tissues. The NaOCl solution caused extensive tissue destruction. Management of the condition required the hospitalization, intravenous antibiotic therapy and multiple intraoral surgical incisions to facilitate drainage. CLINICAL IMPLICATIONS: Use of NaOCl must be confined to the root canal system. This report reviews this intracanal medicament's potential toxicity and emphasizes the need for clinicians to remain cognizant of possible problems while using the solution.

Cellulitis↗
PubMed2000

RAS-Mediated radiation resistance is not linked to MAP kinase activation in two bladder carcinoma cell lines.

The expression of activated RAS oncogenes has been shown to increase radioresistance in a number of cell lines. The pathways by which RAS leads to radioresistance, however, are unknown. RAS activates several signal transduction pathways, with the RAF-MAP2K-MAP kinase pathway perhaps the best studied. MAP kinase has also been shown to be activated by radiation through this pathway. Given the important role of MAP kinase in multiple signaling events, we asked if radioresistance induced by RAS was mediated through the activation of MAPK. Cells of two human bladder carcinoma cell lines were used, one with a mutated oncogenic HRAS (T24) and other with a wild-type HRAS (RT4). The surviving fraction after exposure to 2 Gy of radiation (SF2) for the T24 cell lines was found to be 0.62, whereas that for RT4 cells was 0.40. Treatment with the farnesyl transferase inhibitor (FTI) L744,832, which inhibits RAS processing and activity, decreased the SF2 of T24 cells to 0.29, whereas the SF2 of RT4 cells remained unchanged after FTI treatment, thus demonstrating the importance of RAS activation to the radiosensitivity of cells with mutated RAS. MAP kinase activation was found to be constitutive and dependent on RAS in T24 cells, while it was inducible by radiation and was independent of RAS in RT4 cells. Treatment of both cell lines with the MAP2K inhibitor PD98059 inhibited MAPK activation; however, inhibiting MAPK activation had no effect on radiation survival of T24 or RT4 cells. These data indicate that MAPK activation does not contribute to RAS-induced radioresistance in this system.

Cell Survival↗
PubMed2000

NFkappaB activation, TNF-alpha expression, and apoptosis in the AIDS-Dementia-Complex.

The role of NFkappaB activation and its relationship to inflammatory mediators and apoptosis in the HIV-infected brain have remained uncertain. The cellular and regional distribution of NFkappaB, TNF-alpha, and apoptosis was examined in the frontal cortex (FC), deep white matter (DWM) and the basal ganglia (BG) of 17 patients with ADC. Nuclear staining for NFkappaB was localized predominantly to perivascular microglia/macrophages in the BG and DWM and correlated with ADC severity. Correlations were further found with HLA-DR, iNOS, TNF-alpha, and gp41 expression in these regions. The number of TUNEL-positive cells, particularly in the BG, correlated with ADC stage. Logistic regression analysis further showed a significant relationship between the likelihood of TUNEL staining in the BG and worsening cognitive impairment.

AIDS Dementia Complex↗
PubMed2000

The proteasome controls the expression of a proliferation-associated nuclear antigen Ki-67.

The proteasome is a protease complex responsible for rapid, selective, and irreversible removal of regulatory proteins, as well as many other cellular proteins. In this study, we have demonstrated that a proliferation-associated nuclear protein Ki-67 depended on the proteasome for its rapid degradation. A proteasome-specific inhibitor lactacystin augmented Ki-67 protein levels in pancreatic cancer BxPC-3 cells while repressed the level of steady-state Ki-67 mRNA. Inhibition of the proteasome also led to accumulation of two CDK inhibitors p27(kip1) and p21(cip1) in the BxPC-3 cells. Failed reduction of Ki-67 protein and enhanced levels of the two CDK inhibitors are likely contributing factors for the suppressed BxPC-3 proliferation after proteasome inhibition.

Acetylcysteine↗
PubMed2000

Hemostatic parameters and platelet activation marker expression in cyanotic and acyanotic pediatric patients undergoing cardiac surgery in the presence of tranexamic acid.

We have investigated hemostatic parameters including platelet activation in 56 pediatric patients with or without cyanosis undergoing cardiopulmonary bypass (CPB) and cardiac surgery to repair congenital defects. Patients were participants in a study assessing the effects of tranexamic acid on surgery-related blood loss. Parameters monitored included blood loss, prothrombin F1.2, thrombin-antithrombin complexes, t-PA, PAI-1, plasminogen, fibrin D-dimer, and plasma factor XIII. Additionally, flow cytometry monitored platelet degranulation (P-selectin or CD63), as well as surface-bound fibrinogen, von Willebrand factor and factor XIIIa. Cyanotic patients had evidence of supranormal coagulation activation as both fibrin D-dimer and PAI-1 levels were elevated prior to surgery. While the extent of expression of P-selectin or CD63 was not informative, platelet-associated factor XIIIa was elevated in cyanotic patients at baseline. In both patient groups, CPB altered platelet activation state and coagulation status irrespective of the use of tranexamic acid.

Antifibrinolytic Agents↗
PubMed2000

Analysis of temperature-modulated high-performance liquid chromatography as a tool for detection of single nucleotide polymorphism.

OBJECTIVE: To establish and evaluate temperature-modulated high-performance liquid chromatography(TmHPLC) as a rapid and efficient technique of detecting single nucleotide polymorphism(SNP). METHODS: Several TmHPLC parameters, such as the eluting gradient ranges and column temperatures used for analysing the amplicons have been studied. The size of DNA fragments suitable for analysis of SNP was studied. Also the sensitivity of the TmHPLC was evaluated. RESULTS: The suitable chromatographic condition of TmHPLC was found out. The elution peaks of dNTP and primers could be separated from those of polymerase chain reaction products of the genomic DNA. The heterozygotes of SNP from the sequenced DNA fragment with 178bp, 269bp and 272bp could be distinguished from the homozygotes of SNP clearly. CONCLUSION: The authors have established and evaluated the TmHPLC method, which is an efficient, sensitive and rapid method for screening out SNP in the DNA fragments of larger size.

Chromatography, High Pressure Liquid↗
PubMed2000

[Genetic polymorphisms of eight STR loci in a Chinese Han population].

OBJECTIVE: To understand the allele structure and genetic polymorphism at eight STR loci in Chinese Han population and construct a preliminary database. METHODS: EDTA-blood specimens were collected from the unrelated individuals in Chengdu, China. The DNA samples were extracted with Chelex method and were amplified by PCR technique. The PCR products were analyzed by the PAG horizontal electrophoresis with discontinuous buffer system and by the approach of the automated fluorescence detection. RESULTS: Five STR loci consist of simple repeat motifs, while three STR loci contain complex repeat structures. The STR polymorphisms at all of the eight loci have been observed in Chinese Han population. According to the obtained data, the combined exclusion probability and the combined discrimination power for these STR markers in Chinese population are 0.9978 and 0.999 999 992, respectively. CONCLUSION: The obtained data are beneficial to understanding the population genetics of the eight STR loci in Chinese Han population. For forensic genetics, the obtained data can be used to calculate the probabilities dealing with the paternity test and the individual identification.

China↗