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Biomedical subjects

L Wu

Publications and source records attributed to L Wu.

At least 109 records · Page 6Linked to original sources
PubMed2001

Metabolic characterization of spinocerebellar ataxia type 6.

BACKGROUND: Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative disorder characterized by slowly progressive ataxia and dysarthria. The mutational basis is an expanded CAG repeat sequence within the coding regions of the CACNL1A4 gene. Basic clinical, neuroimaging, and pathological, and epidemiological features have been described in the literature. However, the metabolic features of SCA6 have not been elucidated. OBJECTIVE: To investigate the metabolic features of SCA6. PATIENTS AND METHODS: Seven patients with SCA6 and 7 healthy individuals underwent positron emission tomography using fluorodeoxyglucose F 18. RESULTS: Cerebral glucose utilization in the 7 patients with SCA6 was characterized by significant hypometabolism in widespread structures, including cortical regions and basal ganglia, as well as the cerebellar hemispheres and brainstem. CONCLUSIONS: The results of the multiple-regional brain hypometabolism suggest that brain dysfunction associated with SCA6 may not be limited to the cerebellum and inferior olive, as previously suggested by the results of other pathologic studies.

Adult↗
PubMed2001

Molecular and cellular mediators of interleukin-1-dependent acute inflammatory arthritis.

OBJECTIVE: To examine the molecular and cellular mechanisms in a model of acute inflammatory monarticular arthritis induced by methylated bovine serum albumin (mBSA) and interleukin-1 (IL-1). METHODS: Mice were injected intraarticularly with mBSA on day 0 and subcutaneously with recombinant human IL-1beta on days 0-2. At day 7, knee joints were removed and assessed histologically. Flow cytometry and RNase protection were used to analyze IL-1-dependent events. RESULTS: C57BL/6 (B6), 129/Sv, and (B6 x 129/ Sv)F1 hybrid mice, all H-2b strains, were susceptible to mBSA/IL-1-induced arthritis, whereas C3H/HeJ (H-2k) mice were not. B6 mice lacking T and B cells (RAG1-/-) or major histocompatibility complex (MHC) class II antigens (MHCII-/-), and B6 mice treated with a CD4+ T cell-depleting monoclonal antibody, were resistant to disease. In contrast, B cell-deficient (muMT/ muMT) mice developed arthritis at an incidence and severity similar to that of controls. RelB-deficient (RelB-/-) bone marrow chimeric mice had arthritis that was significantly reduced in incidence and severity. In B6 mice, flow cytometry demonstrated an IL-1-dependent leukocyte infiltration into the synovial compartment and RNase protection assays revealed induction of messenger RNA (mRNA) for the chemokines monocyte chemoattractant protein 1, macrophage inhibitory protein 2 (MIP-2), RANTES, MIP-1alpha, and MIP-1beta, in vivo and in vitro. CONCLUSION: Arthritis induced by mBSA/IL-1 is strain specific and dependent on CD4+ T lymphocytes and at least partially on RelB, but not on B lymphocytes or antibody. IL-1 contributes to leukocyte recruitment to the synovium and directly induces chemokine mRNA production by synovial cells. This model of acute monarticular arthritis is particularly suitable for further investigations into cell-mediated immunity in arthritis and the role of IL-1.

Acute Disease↗
PubMed2001

Differential expression of chemokine receptors on peripheral blood, synovial fluid, and synovial tissue monocytes/macrophages in rheumatoid arthritis.

OBJECTIVE: Since it is likely that monocytes utilize chemokines to migrate to the rheumatoid arthritis (RA) joint, we investigated the expression of C-C chemokine receptors (CCR) 1-6 and C-X-C receptor 3 (CXCR3) in the peripheral blood (PB), synovial fluid (SF), and synovial tissue of patients with RA as well as in the PB of normal subjects. METHODS: We compared chemokine receptor expression on CD14+ monocytes from normal PB, RA PB, and RA SF using 2-color flow cytometry. Correlations with patient clinical data were determined. Chemokine and receptor expression were investigated in RA synovial tissue by immunohistochemistry and 2-color immunofluorescence to identify CD68+ macrophages. RESULTS: Most normal PB monocytes expressed CCR1 (87%) and CCR2 (84%), but not CCRs 3, 4, 5, or 6 or CXCR3. RA PB monocytes expressed CCR1 (56%) and CCR2 (76%), with significantly more expressing CCR3 (18%), CCR4 (38%), and CCR5 (17%) compared with normal PB monocytes. Significantly fewer SF monocytes from RA patients expressed CCR1 (17%), CCR2 (24%), and CCR4 (6%) while significantly more expressed CCR3 (35%) and CCR5 (47%) compared with RA and normal PB monocytes; CCR6 and CXCR3 were rarely detected. Clinically, the erythrocyte sedimentation rate was inversely correlated with the expression of CCR1 and CCR4 by RA PB, and CCR5 expression by RA SF was correlated with the SF white blood cell count. CCR1-, CCR2-, and CCR5-immunoreactive cells were found in RA synovial tissue and colocalized with CD68+ macrophages. RA synovial tissue RANTES (regulated upon activation, normally T cell expressed and secreted chemokine)- and monocyte chemoattractant protein 1-immunoreactive cells colocalized with CCR1 and CCR2, respectively, on serial sections. Macrophage inflammatory protein 1alpha (MIP-1alpha) was principally restricted to vascular endothelium, and MIP-1beta+ macrophages were found throughout the sections. CONCLUSION: Monocytes mainly express CCR1 and CCR2 in normal and RA PB, CCR3 and CCR5 in RA PB and RA SF, and CCR4 in RA PB. The differential expression of chemokine receptors suggests that certain receptors aid in monocyte recruitment from the circulation while others are important in monocyte retention in the joint.

Adult↗
PubMed2001

Selective lymphocyte chemokine receptor expression in the rheumatoid joint.

OBJECTIVE: In patients with rheumatoid arthritis (RA), chemokines and their receptors are important for lymphocyte trafficking into the inflamed joint. This study was undertaken to characterize the expression of chemokine receptors CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CXCR3, and CX3CR1 in normal (NL) peripheral blood (PB), RA PB, and RA synovial fluid (SF). METHODS: Using flow cytometry, immunohistochemistry, and 2-color immunofluorescence, we defined the expression of chemokine receptors on CD3+ T lymphocytes in RA synovial tissue (ST), RA SF, RA PB, and NL PB. RESULTS: The percentage of CD3+ lymphocytes expressing CCR2, CCR4, CCR5, and CX3CR1 was significantly elevated in RA PB compared with that in NL PB, while the percentage of CD3+ lymphocytes expressing CCR5 was significantly enhanced in RA SF compared with that in NL and RA PB. In contrast, similar percentages of CD3+ lymphocytes in NL PB, RA PB, and RA SF expressed CCR6 and CXCR3. Immunohistochemistry of RA ST showed lymphocyte expression of CCR4, and 2-color immunofluorescence staining revealed RA ST CD3+ lymphocytes intensely immunoreactive for CXCR3, suggesting that these 2 receptors may be particularly important for CD3+ lymphocyte trafficking to the inflamed joint. In comparisons of chemokine receptor expression on naive (CD45RA+) and memory (CD45RO+) CD3+ lymphocytes, there were greater percentages of memory CD3+/CD4+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD4+ lymphocytes in RA PB and RA SF, and greater percentages of memory CD3+/CD8+ lymphocytes expressing CCR4, CCR5, and CXCR3 than naive CD3+/CD8+ lymphocytes in RA SF, suggesting receptor up-regulation upon lymphocyte activation. In contrast, percentages of CD3+/CD8+ memory lymphocytes expressing CX3CR1 were significantly less than percentages of naive CD3+/CD8+ lymphocytes in RA PB, suggesting that this receptor may be down-regulated upon lymphocyte activation. A major difference between the RA PB and NL PB groups was significantly more CCR4+ memory leukocytes and memory CCR5+/ CD3+/CD8+ lymphocytes in RA PB than NL PB, further suggesting that these receptors may be particularly important for lymphocyte homing to the RA joint. CONCLUSION: These results identify CCR4, CCR5, CXCR3, and CX3CR1 as critical chemokine receptors in RA.

Arthritis, Rheumatoid↗
PubMed2001

Antigenic load and peripheral chimeric levels in entire and partial liver allograft recipients.

Orthotopic partial liver transplantation (PLT) models were developed in rats to explore the unique role of the liver in transplant tolerance. In PVG rats, syngeneic PLT established that surgical reduction to one-third of the liver and orthotopic transplantation permitted survival. Allogeneic PLT in the PVG to DA liver-tolerant model, both 50% and 33%, did not affect the tolerogeneic property of the liver, with all PLT recipients surviving indefinitely. Blood samples taken at various time points for detection of donor cells using flow cytometry showed a steady increase in donor cell chimerism in both PLT and whole liver transplantation (WLT) recipients that persisted throughout the 3-month observation period. At each time point, the level of donor cell chimerism in PLT was higher than that in WLT. We conclude that transplantation of one-third of the liver is compatible with survival in rats. Reduction of antigenic load by means of hepatectomy does not affect the tolerogenic effect of the liver in the PVG to DA LT model because of the remarkable regeneration capability of the liver. Peripheral chimeric levels increase progressively after WLT, suggesting that this is an ongoing immunological phenomenon. The earlier and increased chimerism after PLT may be associated with liver regeneration.

Animals↗
PubMed2001

RecQ helicases and topoisomerases: components of a conserved complex for the regulation of genetic recombination.

Maintenance of genomic stability relies on the efficient and accurate execution of DNA repair pathways, and is essential for cell viability and the prevention of cancer. Mutation of genes encoding RecQ helicases or topoisomerases gives rise to genomic instability through excessive recombination. Here, we review the recent biochemical and genetic evidence to indicate that these two classes of protein act in concert in a conserved pathway to maintain genomic stability by preventing inappropriate recombination.

Animals↗
PubMed2001

Troglitazone selectively inhibits glyoxalase I gene expression.

AIMS/HYPOTHESIS: The hyperglycaemia associated with diabetes causes excessive production of cytotoxic methylglyoxal, an alpha-oxo-aldehyde. The glyoxalase system, composed of glyoxalase I and glyoxalase II, with glutathione (GSH) as the cofactor, plays an important role in the detoxification of alpha-oxo-aldehydes. We tested the hypothesis that troglitazone, an insulin-sensitizing drug previously used in the treatment of Type II (non-insulin-dependent) diabetes mellitus, up-regulates the glyoxalase system either by increasing phase 2 enzyme activities and thereby increasing cellular GSH, or, by inducing glyoxalase enzyme activities. METHODS: Human astroglial cells, rat hepatocytes and cardiac myocytes were cultured and exposed to either troglitazone, or tertiary-butylhydroquinone (tBHQ, a phase 2 enzyme inducer). Glutathione content, advanced glycation end products (AGEs) and enzyme (glyoxalase I, glyoxalase II as well as the phase 2 enzymes, glutathione S-transferase and thioredoxin reductase) activities were determined. Glyoxalase I mRNA was also measured. RESULTS: Troglitazone had no effect on cellular GSH nor phase 2 enzyme activities but significantly reduced the activities of glyoxalase I and II; this inhibitory effect was concentration-dependent and time-dependent and was associated with reduced mRNA contents and increased AGEs formation. Rosiglitazone had no effect on glyoxalase I gene expression. tBHQ, a classic phase 2 enzyme inducer, had no effect on the glyoxalase system but did increase glutathione contents and the activities of glutathione S-transferase and thioredoxin reductase. CONCLUSION/INTERPRETATION: Our study shows that troglitazone is a selective inhibitor of the glyoxalase system. This inhibition of the glyoxalase system could contribute to troglitazone's hepatotoxic action which has previously been reported in a small percentage of individuals.

Animals↗
PubMed2001

Radiobiological effects of a low-energy ion beam on wheat.

The radiobiological effects of a low-energy nitrogen ion (N+) beam on wheat were studied, particularly with regard to the induction of chromosome aberrations. The results demonstrated that the three test varieties showed different sensitivities to ion implantation, and a higher dose of ion implantation had a marked effect on the germination and survival rate of the seeds exposed. The germination rate and survival rate curve basically followed a similar trend in the same variety. Cytological analysis indicated that ion beams were effective in producing chromosome aberrations. The frequencies of mitotic or meiotic cells with chromosome aberrations increased linearly with increasing doses. The aberration types included, for example, acentric fragments, chromosome deletions, lagging chromosomes, chromosome bridges and micronuclei. In the root tip cells, aberrations chiefly consisted of acentric fragments and deletions. Chromosome bridges and lagging chromosomes were the main aberration phenomena observed in the pollen mother cells. The highest frequencies of root tip cells and pollen mother cells with chromosome aberrations were 15.2% and 39.8%, respectively. Changes in morphology and mutant were also observed in the plants derived from exposed seeds.

Chromosome Aberrations↗
PubMed2001

Synthesis of 2-(2,3-dimethoxyphenyl)-4-(aminomethyl)imidazole analogues and their binding affinities for dopamine D(2) and D(3) receptors.

A series of 2-(2,3-dimethoxyphenyl)-4-(aminomethyl)imidazole derivatives was prepared and their affinity for dopamine D(2) and D(3) receptors was measured using in vitro binding assays. Several oxadiazole analogues were also prepared and tested for their affinity for dopamine D(2) and D(3) receptors. The results of receptor binding studies indicated that the incorporation of an imidazole moiety between the phenyl ring and the basic nitrogen did not significantly increase the selectivity for dopamine D(3) receptors, whereas the incorporation of an oxadiazole at the same region resulted in a total loss of affinity for both dopamine receptor subtype binding sites. The most selective compound in this series is 2-(5-bromo-2,3-dimethoxyphenyl)-4-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolinomethyl)imidazole (5i), which has a D(3) receptor affinity of 21nM and a 7-fold selectivity for D(3) versus D(2) receptors. The binding affinity for sigma(1) and sigma(2) receptors was also measured, and the results showed that several analogues were selective sigma(1) receptor ligands.

Animals↗
PubMed2001

[[(18)F]N-(4'-fluorobenzyl)-4-(3-bromophenyl) acetamide for imaging the sigma receptor status of tumors: comparison with [(18)F]FDG, and [(125)I]IUDR.

A series of biodistribution studies were conducted with the radiotracer, [(18)F]N-(4'-fluorobenzyl)-4-(3-bromophenyl)acetamide, [(18)F]1 in nude mice bearing tumor xenografts of the mouse mammary adenocarcinoma, line 66. This radiotracer has a high affinity for both sigma(1) and sigma(2) receptors. In vivo studies were also conducted in order to assess the effect of blocking sigma(1) receptors on tumor uptake and the tumor:background ratio of this radiotracer. The results of these studies revealed that blocking the sigma(1) receptor so that only the sigma(2) receptors are labeled in vivo, results in a higher tumor:background ratio with only a small reduction in the tumor uptake of the radiotracer relative to the no-carrier-added (i.e., nonselective) conditions. Comparative in vivo studies were also conducted with the anatomic and metabolic imaging agent, [(18)F]FDG, and a radiolabeled DNA precursor, [(125)I]IUdR. Both of these radiolabeled compounds represent classes of agents that have been proposed for imaging the proliferative status of solid tumors. The results of these studies indicated that a sigma(2)-selective imaging agent may be, 1) a better anatomic imaging agent for breast cancer than [(18)F]FDG, and 2) a better functional imaging agent than the radiolabeled DNA precursors, [(123/124)I]IUdR and [(11)C]thymidine, for measuring the proliferative status of breast tumors with PET and SPECT. However, additional studies will be needed to compare sigma(2)-selective imaging agents with [(18)F]FLT in order to determine which is the more appropriate imaging agent for measuring the proliferative status of breast tumors with PET.

Acetamides↗
PubMed2001

Differentiation and quantitation of isomeric dipeptides by low-energy dissociation of copper(II)-bound complexes.

Application of the kinetic method based on the dissociation of transition metal centered cluster ions is extended from chiral analysis (Tao, W. A.; Zhang, D.; Nikolaev, E. N.; Cooks, R. G. J. Am. Chem. Soc. 2000, 122, 10598) to quantitative analysis of isomeric mixtures, including those with Leu/Ile substitutions. Copper(II)-bound complexes of pairs of peptide isomers are generated by electrospray ionization mass spectrometry and the trimeric complex [CuII(ref)2(A) - H]+ (analyte A, a mixture of isomeric peptides; reference compound ref, usually a peptide) is caused to undergo collisional dissociation. Competitive loss of the neutral reference compound or the neutral analyte yields two ionic products and the ratio of rates of the two competitive dissociations, viz. the product ion branching ratio R is shown to depend strongly on the regiochemistry of the analyte in the precursor [CuII(A)(ref)2 - H]+ complex ion. Calibration curves are constructed by relating the branching ratio measured by the kinetic method, to the isomeric composition of the mixture to allow rapid quantitative isomer analysis.

Amino Acids↗
PubMed2001

Myc requires distinct E2F activities to induce S phase and apoptosis.

Previous work has shown that the Myc transcription factor induces transcription of the E2F1, E2F2, and E2F3 genes. Using primary mouse embryo fibroblasts deleted for individual E2F genes, we now show that Myc-induced S phase and apoptosis requires distinct E2F activities. The ability of Myc to induce S phase is impaired in the absence of either E2F2 or E2F3 but not E2F1 or E2F4. In contrast, the ability of Myc to induce apoptosis is markedly reduced in cells deleted for E2F1 but not E2F2 or E2F3. From this data, we propose that the induction of specific E2F activities is an essential component in the Myc pathways that control cell proliferation and cell fate decisions.

Adenoviridae↗
PubMed2001

Spectrophotometric determination of polyacrylamide in waters containing dissolved organic matter.

Using polyacrylamide (PAM) to reduce soil erosion in irrigated land has increased rapidly in recent years. A simple and reliable method to measure the PAM concentration in waters containing dissolved organic matter (DOM) is of great importance in assessing the fate and efficiency of PAM application. In this research, an analytical method to determine the PAM concentration of waters with correction for DOM interference was developed and tested. The method is based on a combination of determining the total concentration of amide groups by the N-bromination method (NBM) and determining the DOM content spectrophotometrically. The total concentration of amide groups of both PAM and DOM was determined by NBM at 570 nm. The DOM moiety, which is proportional to DOM concentration, was determined by spectrophotometry using a UV 254-nm wavelength. The actual PAM concentration of a water sample (soil extract containing PAM in this study) was obtained from NBM readings subtracted by the interferential DOM contribution using a correction curve. Analysis of PAM in two soil-water samples showed that the recoveries ranged from 94 to 100.3% for the 2 mg/L PAM sample and from 98.4 to 101.4% for the 10 mg/L PAM sample with various DOM concentrations. The coefficients of variation were <6% in all cases.

Acrylic Resins↗
PubMed2001

SPTLC1 is mutated in hereditary sensory neuropathy, type 1.

Hereditary sensory neuropathy type 1 (HSN1, MIM 162400; ref. 1) genetically maps to human chromosome 9q22 (refs. 2-4). We report here that the gene encoding a subunit of serine palmitoyltransferase is located within the HSN1 locus, expressed in dorsal root ganglia (DRG) and mutated in HSN1.

Acyltransferases↗
PubMed2001

A point mutation in CD28 distinguishes proliferative signals from survival signals.

Upon interaction with its ligand, B7, CD28 becomes phosphorylated on tyrosines. One tyrosine in particular (Y170 in mouse CD28, Y173 in human CD28) has received much attention. This is because it permits CD28 to recruit SH2-containing signaling molecules, including phosphoinositide 3 kinase, Grb2 and Gads. Using mice we employed a transgenic approach to express a tyrosine-->phenylalanine mutant form of CD28 that uncouples these SH2-mediated interactions from CD28. The CD28 mutant is unable to up-regulate expression of the prosurvival protein Bcl-xL, rendering the T cells more susceptible to radiation-induced death. Nonetheless, this mutated form of CD28 still prevents the induction of anergy and promotes T cell proliferation, interleukin 2 secretion and B cell help. Thus, we describe a single point mutation within the CD28 cytoplasmic domain that uncouples signals required for proliferation and survival.

Animals↗
PubMed2001

A photic visual cycle of rhodopsin regeneration is dependent on Rgr.

During visual excitation, rhodopsin undergoes photoactivation and bleaches to opsin and all-trans-retinal. To regenerate rhodopsin and maintain normal visual sensitivity, the all-trans isomer must be metabolized and reisomerized to produce the chromophore 11-cis-retinal in biochemical steps that constitute the visual cycle and involve the retinal pigment epithelium (RPE; refs. 3-8). A key step in the visual cycle is isomerization of an all-trans retinoid to 11-cis-retinol in the RPE (refs. 9-11). It could be that the retinochrome-like opsins, peropsin, or the retinal G protein-coupled receptor (RGR) opsin12-16 are isomerases in the RPE. In contrast to visual pigments, RGR is bound predominantly to endogenous all-trans-retinal, and irradiation of RGR in vitro results in stereospecific conversion of the bound all-trans isomer to 11-cis-retinal. Here we show that RGR is involved in the formation of 11-cis-retinal in mice and functions in a light-dependent pathway of the rod visual cycle. Mutations in the human gene encoding RGR are associated with retinitis pigmentosa.

Animals↗