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Biomedical subjects

R Wang

Publications and source records attributed to R Wang.

At least 217 records · Page 12Linked to original sources
PubMed2000

Optical coherence microscopy. A technology for rapid, in vivo, non-destructive visualization of plants and plant cells.

We describe the development and utilization of a new imaging technology for plant biology, optical coherence microscopy (OCM), which allows true in vivo visualization of plants and plant cells. This novel technology allows the direct, in situ (e.g. plants in soil), three-dimensional visualization of cells and events in shoot tissues without causing damage. With OCM we can image cells or groups of cells that are up to 1 mm deep in living tissues, resolving structures less than 5 microm in size, with a typical collection time of 5 to 6 min. OCM measures the inherent light-scattering properties of biological tissues and cells. These optical properties vary and provide endogenous developmental markers. Singly scattered photons from small (e.g. 5 x 5 x 10 microm) volume elements (voxels) are collected, assembled, and quantitatively false-colored to form a three-dimensional image. These images can be cropped or sliced in any plane. Adjusting the colors and opacities assigned to voxels allows us to enhance different features within the tissues and cells. We show that light-scattering properties are the greatest in regions of the Arabidopsis shoot undergoing developmental processes. In large cells, high light scattering is produced from nuclei, intermediate light scatter is produced from cytoplasm, and little if any light scattering originates from the vacuole and cell wall. OCM allows the rapid, repetitive, non-destructive collection of quantitative data about inherent properties of cells, so it provides a means of continuously monitoring plants and plant cells during development and in response to exogenous stimuli.

Microscopy↗
PubMed2000

Genomic analysis of a nutrient response in Arabidopsis reveals diverse expression patterns and novel metabolic and potential regulatory genes induced by nitrate.

Microarray and RNA gel blot analyses were performed to identify Arabidopsis genes that responded to nitrate at both low (250 microM) and high (5 to 10 mM) nitrate concentrations. Genes involved directly or indirectly with nitrite reduction were the most highly induced by nitrate. Most of the known nitrate-regulated genes (including those encoding nitrate reductase, the nitrate transporter NRT1, and glutamate synthase) appeared in the 40 most strongly nitrate-induced genes/clones on at least one of the microarrays of the 5524 genes/clones investigated. Novel nitrate-induced genes were also found, including those encoding (1) possible regulatory proteins, including an MYB transcription factor, a calcium antiporter, and putative protein kinases; (2) metabolic enzymes, including transaldolase and transketolase of the nonoxidative pentose pathway, malate dehydrogenase, asparagine synthetase, and histidine decarboxylase; and (3) proteins with unknown functions, including nonsymbiotic hemoglobin, a senescence-associated protein, and two methyltransferases. The primary pattern of induction observed for many of these genes was a transient increase in mRNA at low nitrate concentrations and a sustained increase when treated with high nitrate concentrations. Other patterns of induction observed included transient inductions after both low and high nitrate treatments and sustained or increasing amounts of mRNA after either treatment. Two genes, AMT1;1 encoding an ammonium transporter and ANR1 encoding a MADS-box factor, were repressed by nitrate. These findings indicate that nitrate induces not just one but many diverse responses at the mRNA level in Arabidopsis.

Amino Acid Motifs↗
PubMed2000

Familial British dementia: expression and metabolism of BRI.

Vidal et al. (1999. Nature 399: 776-778) discovered that the underlying genetic lesion in familial British dementia (FBD) is a T-A transversion at the termination codon of a membrane protein, termed BRI. The mutation creates an arginine codon; translational read-through generates a novel protein, termed BRI-L, that is extended by 11 amino acids at the carboxyl-terminus. BRI-L is the precursor of the ABri peptide, a component of amyloid deposits in FBD brain. We demonstrate that both BRI and its mutant counterpart are constitutively processed by furin, resulting in the secretion of carboxyl-terminal peptide derivatives that correspond to all, or part of, ABri. Notably, elevated levels of peptides are generated from the mutant BRI precursor, suggesting that subtle conformational alterations at the carboxyl-terminus may influence furin-mediated processing. We have examined BRI/BRI-L processing by other members of the prohormone convertase (PC) family (PACE4, LPC, PC 5/6) and found that these enzymes also process BRI, albeit inefficiently. Moreover, BRI-L processing by the other PC members is severely compromised. Finally, our electron microscopic studies reveal that synthetic ABri peptides assemble into insoluble beta-pleated fibrils. Collectively, our results support the view that enhanced furin-mediated processing of mutant BRI generates amyloidogenic peptides that initiate the pathogenesis of FBD.

Adaptor Proteins, Signal Transducing↗
PubMed2000

An empirical model of gamma-secretase activity.

gamma-Secretase catalyzes the cleavage at the carboxyl terminus of A beta to release it from the APP. While gamma-secretase is a major therapeutic drug target for the treatment of Alzheimer's disease (AD), it appears to be an unusual proteolytic activity, and, to date, no protease responsible for this activity has been identified. Based on studies of APP transmembrane domain (TMD) mutants, it is apparent that there are multiple pharmacologically distinct gamma-secretase activities that are spatially restricted and that presenilins (PS) regulate cleavage by gamma-secretases in a protease independent fashion. Based on these studies, we propose a multiprotease model for gamma-secretase activity and predict that the gamma-secretases are likely to be closely related proteases.

Amino Acid Sequence↗
PubMed2000

A Monte Carlo calculation of dosimetric parameters of 90Sr/90Y and 192Ir SS sources for intravascular brachytherapy.

The AAPM TG-60 report has proposed various dose calculation parameters for intravascular brachytherapy (IVBT). These parameters include the dose rate constant (or the dose rate at a reference position for a beta-particle emitting source), the radial dose function, and the anisotropy function. In this work, we have used a modified EGS4 Monte Carlo system to calculate these parameters for the two most commonly used IVBT sources (the beta-particle emitting 90Sr/90Y source and the photon emitting 192Ir SS source). To ensure the calculation accuracy, the present calculation was compared with several measurements and calculations reported by other authors. Excellent agreement was found for the results with the photon source. For beta-particle source calculation, the present results for a variety of point sources agree very well with a previous work. The presently calculated radial dose functions for the 90Sr/90Y source are consistent with those of a published work for intermediate radial distances. The dose uniformity in the axial direction was also studied. The contributions of bremsstrahlung photons to total doses for the 90Sr/90Y beta source, and the influence of ignoring electron transport on calculated doses for the 192Ir SS photon source are discussed.

Brachytherapy↗
PubMed2000

Three different vasoactive responses of rat tail artery to nicotine.

The vasoactive effects of nicotine on isolated rat tail artery tissues were studied. Nicotine transiently contracted rat tail artery tissues (EC50, 55.6 +/- 2 microM) in an extracellular Ca2+ dependent and endothelium-independent fashion. The blockade of alpha1-adrenoceptors, but not alpha2-adrenoceptors or P2X purinoceptors, inhibited the nicotine-induced contraction by 38 +/- 7% (p < 0.05). Nicotine (1 mM) depolarized membrane by 13 +/- 3 mV, but did not affect L-type Ca2+ channel currents, of the isolated rat tail artery smooth muscle cells. The phenylephrine-precontracted tail artery tissues were relaxed by nicotine (EC50, 0.90 +/- 0.31 mM), which was significantly inhibited after the blockade of nicotinic receptors. Simultaneous removal of phenylephrine and nicotine, after a complete relaxation of the phenylephrine-precontracted tail artery strips was achieved by nicotine at accumulated concentrations (> or =10 mM), triggered a Ca2+-dependent rebound long-lasting vasoconstriction (n = 20). This rebound contraction was abolished in the absence of calcium or in the presence of tetracaine in the bath solution. Pretreatment of vascular tissues with a nicotinic receptor antagonist did not affect the nicotine-induced vasoconstriction or nicotine withdrawal induced rebound contraction. The elucidation of the triphasic vascular effects of nicotine and the underlying mechanisms is important for a better understanding of the complex vascular actions of nicotine.

Animals↗
PubMed2000

Altered L-type Ca(2+) channel currents in vascular smooth muscle cells from experimental diabetic rats.

Vascular complications of diabetes are associated with abnormal Ca(2+) handling by vascular smooth muscle cells (SMCs) in which the alteration in L-type voltage-dependent Ca(2+) channel (VDCC) currents may play an important role. In the present study, the characteristics of L-type VDCC currents in tail artery SMCs from streptozotocin-induced diabetic rats were examined. The densities, but not the voltage dependence, of L-type VDCC currents were reduced as diabetes progressed from 1 wk to 3 mo. The inhibitory effect of dibutyryl-cAMP on L-type VDCC currents was greater in diabetic SMCs than in age-matched control cells (P < 0.01). Both the stimulatory effect of BAY K 8644 and the inhibitory effect of nifedipine on L-type VDCC currents were significantly enhanced in diabetic cells. The diabetes-related abnormalities in L-type VDCC currents were mimicked by culturing SMCs with a high concentration of glucose. Our results suggest that the properties of L-type VDCC in diabetic vascular SMCs were significantly altered, partially related to the increased L-type VDCC sensitivity to cAMP and hyperglycemia.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2000

Na(+)/H(+) exchange inhibition-induced cardioprotection in dogs: effects on neutrophils versus cardiomyocytes.

Numerous studies have examined the effect of Na(+)/H(+) exchanger (NHE) inhibition on the myocardium; however, the effect of NHE-1 inhibition on neutrophil function has not been adequately examined. An in vivo canine model of myocardial ischemia-reperfusion injury in which 60 min of left anterior descending coronary artery occlusion followed by 3 h of reperfusion was used to examine the effect of NHE-1 inhibition on infarct size (IS) and neutrophil function. BIIB-513, a selective inhibitor of NHE-1, was infused before ischemia. IS was expressed as a percentage of area at risk (IS/AAR). NHE-1 inhibition significantly reduced IS/AAR and reduced neutrophil accumulation in the ischemic myocardium. NHE-1 inhibition attenuated both phorbol 12-myristate 13-acetate- and platelet-activating factor-induced neutrophil respiratory burst but not CD18 upregulation. Furthermore, NHE-1 inhibition directly protected cardiomyocytes against metabolic inhibition-induced lactate dehydrogenase release and hypercontracture. This study provides evidence that the cardioprotection induced by NHE-1 inhibition is likely due to specific protection of cardiomyocytes and attenuation of neutrophil activity.

Animals↗
PubMed2000

Amiodarone induces apoptosis of human and rat alveolar epithelial cells in vitro.

The antiarrhythmic amiodarone (AM) and its metabolite desethylamiodarone (Des) are known to cause AM-induced pulmonary toxicity, but the mechanisms underlying this disorder remain unclear. We hypothesized that AM might cause AM-induced pulmonary toxicity in part through the induction of apoptosis or necrosis in alveolar epithelial cells (AECs). Two models of type II pneumocytes, the human AEC-derived A549 cell line and primary AECs isolated from adult Wistar rats, were incubated with AM or Des for 20 h. Apoptotic cells were determined by morphological assessment of nuclear fragmentation with propidium iodide on ethanol-fixed cells. Necrotic cells were quantitated by loss of dye exclusion. Both AM and Des caused dose-dependent necrosis starting at 2.5 and 0.1 microg/ml, respectively, in primary rat AECs and at 10 and 5 microg/ml in subconfluent A549 cells (P < 0.05 and P < 0.01, respectively). AM and Des also induced dose-dependent apoptosis beginning at 2.5 microg/ml in the primary AECs (P < 0.05 for both compounds) and at 10 and 5 microg/ml, respectively, in the A549 cell line (P < 0.01). The two compounds also caused significant net cell loss (up to 80% over 20 h of incubation) by either cell type at drug concentrations near or below the therapeutic serum concentration for AM. The cell loss was not due to detachment but was blocked by the broad-spectrum caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone. Furthermore, the angiotensin-converting enzyme inhibitor captopril (500 ng/ml) and the angiotensin-receptor antagonist saralasin (50 microg/ml) significantly inhibited both the induction of apoptosis and net cell loss in response to AM. These results are consistent with recent work from this laboratory demonstrating potent inhibition of apoptosis in human AECs by captopril (Uhal BD, Gidea C, Bargout R, Bifero A, Ibarra-Sunga O, Papp M, Flynn K, and Filippatos G. Am J Physiol Lung Cell Mol Physiol 275: L1013-L1017, 1998). They also suggested that the accumulation of AM and/or its primary metabolite Des in lung tissue may induce cytotoxicity of AECs that might be inhibitable by angiotensin-converting enzyme inhibitors or other antagonists of the renin-angiotensin system.

Adenocarcinoma↗
PubMed2000

Abrogation of bleomycin-induced epithelial apoptosis and lung fibrosis by captopril or by a caspase inhibitor.

Angiotensin-converting enzyme is involved in apoptosis of alveolar epithelial cells (Wang R, Zagariya A, Ang E, Ibarra-Sunga O, and Uhal BD. Am J Physiol Lung Cell Mol Physiol 277: L1245-L1250, 1999). This study tested the ability of the angiotensin-converting enzyme inhibitor captopril or the caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (ZVAD-fmk) to block alveolar epithelial cell apoptosis and lung fibrosis in vivo in response to bleomycin (Bleo). Male Wistar rats received 8 U/kg of Bleo (bleomycin sulfate) or vehicle intratracheally. Subgroups of Bleo-treated rats received captopril, ZVAD-fmk, or vehicle alone. Lung collagen was assessed by picrosirius red or hydroxyproline assay at 1, 7, and 14 days post-Bleo, and apoptosis was detected by in situ end labeling (ISEL). Bleo increased alveolar septal and peribronchial collagen by 100 and 133%, respectively (both P < 0.01), by day 14 but not earlier. In contrast, ISEL was increased in alveolar and airway cells at all time points. Captopril or ZVAD-fmk inhibited collagen accumulation by 91 and 85%, respectively (P < 0. 01). Both agents also inhibited ISEL in alveoli by 99 and 81% and in airways by 67 and 63%, respectively. These data suggest that the efficacy of captopril to inhibit experimental lung fibrogenesis is related to inhibition of apoptosis. They also demonstrate the antifibrotic potential of a caspase inhibitor.

Amino Acid Chloromethyl Ketones↗
PubMed2000

Passive and iontophoretic delivery of three diclofenac salts across various skin types.

The in vitro permeation of three diclofenac salts--diclofenac sodium (DFS), diclofenac potassium (DFP) and diclofenac diethylammonium (DFD)-across skin by both passive and iontophoretic transport were investigated. Various skin types were used as the barriers to elucidate the mechanism controlling transdermal delivery of diclofenac salts. The importance of the intercellular (paracellular) route for both DFS and DFP in passive permeation was elucidated. The transfollicular route constitutes an important permeation pathway for DFS but not for DFP. The route and mechanism for transdermal iontophoresis of DFD across the skin was somewhat different to that of the other salts. Hair follicles may be a more important pathway for DFD than for DFS and DFP under iontophoresis, while the intercellular lipid pathway showed the opposite result. Combination of iontophoresis and a penetration enhancer, cardamom oil, did not show a synergistic effect on diclofenac salt permeation. The results of this investigation suggest that the transdermal mechanism and the route of diclofenac salt uptake via passive and iontophoretic transport can be affected by their counterions.

Animals↗
PubMed2000

Triple-staining to identify apoptosis of hepatic cells in situ.

To identify apoptosis of nonparenchymal cells in fibrotic livers, we established a triple staining method which combined immunohistochemistry for cell markers and Masson staining for collagen as well as terminal deoxynucleotidyl transferase UTP nick end labeling (TUNEL). Five microm formalin fixed, paraffin-embedded liver sections were prepared for staining. Firstly, TUNEL staining was carried out to detect apoptosis of liver cells. Then, the sections were subjected to immunohistochemistry for alpha-smooth muscle actin (alpha -SMA) or KP-1 to identify hepatic stellate cells or Kupffer cells. Finally, Masson staining was performed to show the relationship between apoptosis and collagens. In addition, we optimized different conditions of fixation, digestion and color development which may affect the results.

Animals↗
PubMed2000

[A molecular cytogenetic study on chromosome anomalies of chronic myeloid leukemia].

OBJECTIVE: To study the bcr/abl fusion gene in chronic myeloid leukemia (CML) cases with Philadelphia chromosome(Ph) negative, and variant Ph translocations and other chromosome anomalies. METHODS: The status of bcr/abl fusion gene in 8 kinds of chromosome anomalies was tested with dual-color fluorescence in situ hybridization (D-FISH) technique. RESULTS: The positive hybridization was demonstrated in 3 cases of variant Ph CML and other 7 cases of standard Ph, respectively. In 2 cases of Ph-negative CML, one case that had karyotype such as 46,XY,t(9;18) showed positive hybridization, the other case with 46,XY,inv(2) showed negative result. CONCLUSION: The result demonstrates that D-FISH technique is reliable for detecting bcr/abl fusion gene. The existence of negative bcr/abl fusion gene CML implies that some other initial events inducing CML might have occurred in such cases.

Adult↗
PubMed2000

Quantification of Alzheimer amyloid beta peptides ending at residues 40 and 42 by novel ELISA systems.

BACKGROUND: The amyloid beta (Abeta) peptide is a key molecule in the pathogenesis of Alzheimer's disease. Reliable methods to detect and quantify soluble forms of this peptide in human biological fluids and in model systems, such as cell cultures and transgenic animals, are of great importance for further understanding the disease mechanisms. In this study, the application of new and highly specific ELISA systems for quantification of Abeta40 and Abeta42 (Abeta peptides ending at residues 40 or 42, respectively) in human cerebrospinal fluid (CSF) are presented. MATERIALS AND METHODS: Monoclonal antibodies WO-2, G2-10 and G2-11 were thoroughly characterized by (SPOT) epitope mapping and immunoprecipitation/mass spectrometry. We determined whether aggregation affected the binding capacities of the antibodies to synthetic peptides and whether components of the CSF affected the ability of the antibodies to bind synthetic Abeta1-40 and Abeta1-42 peptides. The stability of Abeta40 and Abeta42 in CSF during different temperature conditions was also studied to optimize sample handling from lumbar puncture to Abeta assay. RESULTS: The detection range for the ELISAs were 20-250 pM. The intra-assay variations were 2% and 3%, and the inter-assay variations were 2% and 10% for Abeta40 and Abeta42, respectively. The antibodies specifically detected the expected peptides with equal affinity for soluble and fibrillar forms of the peptide. The presence of CSF obstructed the recognition of synthetic peptides by the antibodies and the immunoreactivity of endogenous CSF Abeta decreased with increasing storage time and temperature. CONCLUSIONS: This study describes highly sensitive ELISAs with thoroughly characterized antibodies for quantification of Abeta40 and Abeta42, an important tool for the understanding of the pathogenesis of Alzheimer's disease. Our results pinpoint some of the difficulties associated with Abeta quantification and emphasize the importance of using a well-documented assay.

Albumins↗
PubMed2000

Tetraethylammonium-evoked oscillatory contractions of rat tail artery: a K-K model.

Spontaneously rhythmic contraction of peripheral blood vessels actively modulates the peripheral circulation and blood pressure. However, the underlying mechanisms for the complex rhythmic contraction patterns of various vascular tissues are not yet fully understood. In the present study, the tetraethylammonium (TEA)-induced spontaneously oscillatory contractions of isolated rat tail artery tissues were examined. It was found that TEA evoked arterial oscillatory contractions in a concentration-dependent, but endothelium-independent manner. The voltage-dependent K+ (Kv) channel specific blocker, 4-aminopyridine (4-AP), induced a sustained, but not oscillated, vascular contraction. The presence of 4-AP had no effect on the TEA-induced oscillatory contractions. The blockade of KCa channels with charybdotoxin or apamin did not affect the basal force of vascular tissues. Neither the TEA-induced oscillatory contraction was affected by these blockers. The opening of KATP channels by levcromakalim or their blockade by glybenclamide ceased or increased, respectively, the oscillation of TEA-induced contractions. The absence of Ca2+ or the presence of nifedipine in the bath solution completely abolished the effects of TEA. The inhibition of Ca2+-ATPase in the sarcoplasmic reticulum with micromolar concentrations of thapsigargin or cyclopiazonic acid either abolished or enhanced, respectively, the TEA-induced oscillatory contractions. Ryanodine did not affect the TEA-induced oscillatory contraction. In conclusion, the TEA-induced oscillatory contraction may be initiated by the blockade of the TEA-sensitive delayed rectifier K+ channels and maintained by the TEA-insensitive but ATP-sensitive K+ channels. This K-K model presents a novel mechanism for the depolarization-induced rhythmic contractions of small arteries.

Animals↗
PubMed2000

Effects of carbon tetrachloride-injured hepatocytes on hepatic stellate cell activation and salvianolic acid A preventive action in vitro.

OBJECTIVE: To investigate the effects of carbon tetrachloride (CCl(4))-injured hepatocyte on hepatic stellate cell (HSC) activation, the relation between lipid peroxidation and liver fibrosis, and the action mechanisms of salvianolic acid A (SA-A), one of water soluble components extracted from radix salvia miltiorrhizae, against HSC activation and liver fibrosis. METHODS: The hepatocytes were isolated from the normal rats, incubated with SA-A at different concentrations, respectively, and vitamin E severed as control. At the same time the cells were fumigated with CCl(4) for 24h, and ALT activities in the medium were measured. After the cell medium was changed and cultured for another 24h, the medium was collected as "hepatocyte conditioned medium" (HCM) and measured for malondiadehyde (MDA) content. Then HCM was incubated with primary cultured HSC for 48h, and HSC proliferation, type I collagen gene expression and protein production were observed. RESULTS: ALT activity and MDA content in the hepatocyte medium were increased remarkably after the cell was injured. HCM could obviously promote HSC proliferation, type I collagen mRNA expression and protein production. SA-A could markedly inhibit ALT activity and MDA content in hepatocytes, and decreased collagen gene expression and protein production. CONCLUSION: The secretion from the peroxidative injured hepatocyte could stimulate HSC activation, SA-A could decrease activation by alleviation of hepatocyte peroxidation.

Alanine Transaminase↗