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Biomedical subjects

C Lu

Publications and source records attributed to C Lu.

At least 73 records · Page 4Linked to original sources
PubMed2001

[Spectrophotometric determination of nitrite ion with acridine red based on the nitrosation reaction].

A new spectrophotometric method for the determination of nitrite ion was studied. The method is based on the nitrosation reaction of acridine red with nitrite ion in hydrochloric acid medium. The decolorization of acridine red by the reaction with nitrite was used to spectrophotometric determination at 525 nm. The optimum experimental conditions have been confirmed and 6 mol.L-1 hydrochloric acid is 1.5 mL; 5 x 10(-4) mol.L-1 acridine red is 2.0 mL, the reaction time is 20 min. On the selected conditions, Beer's law is obeyed and the linear range for the determination is 0.025-0.5 microgram.mL-1 NO2-.28 coexistent ions were examined and no serious interference for most of ions was observed. The method has been applied to determine nitrite ion in four water samples with satisfactory results. The relative standard deviation was less than 2.6% for 5 measurements in each water sample. A preliminary relation mechanism is supposed.

Hydrochloric Acid↗
PubMed2000

Laser flash photolysis evidence for styryl radical cation cyclization in the SET-induced photorearrangement of a p-methoxy-substituted 2-phenylallyl phosphite.

The SET-induced photorearrangement of dimethyl 2-(4-methoxyphenyl)allyl phosphite, 9 (UV light, uranium glass filter, 9,10-dicyanoanthracene (DCA), biphenyl), gives phosphonate 12 in 83% isolated yield. Laser flash irradiation at 355 nm of oxygen saturated solutions of phosphite 9 containing DCA and biphenyl generates the transient UV spectrum of the biphenyl radical cation that is quenched by electron transfer from phosphite 9 (k(q) = 8.9 x 10(9) M(-1) s(-1) at 20 degrees C) to form the 4-methoxystyryl cation 10. The UV spectrum of 10 decays by a measured first-order rate constant of 8.0 x 10(6) s(-1), presumably to generate the cyclic distonic radical cation 11. Intermediate 10 was further characterized by measurement of the second-order rate constants for its reaction with azide, chloride, and bromide ions and with the neutral nucleophile trimethyl phosphite. This study provides the first spectroscopic evidence regarding the proposed mechanism (Schemes 1 and 2) for the SET-induced photorearrangements of dimethyl 2-arylallyl phosphites to the corresponding 2-arylallylphosphonates. Moreover, absolute rate constants for the intramolecular trapping of alkene radical cations have seldom been measured. The removal of the electron from the styryl moiety of phosphite 9, rather than from phosphorus, and the detectability of 10 arise from the stabilizing effect of the 4-methoxy substituent. These results, however, do not allow conclusions to be made concerning the site of removal of an electron in the SET-induced photorearrangement of dimethyl 2-phenylallyl phosphite 1 to phosphonate 6.

Allyl Compounds↗
PubMed2000

The top of the inserted-like domain of the integrin lymphocyte function-associated antigen-1 beta subunit contacts the alpha subunit beta -propeller domain near beta-sheet 3.

We find that monoclonal antibody YTA-1 recognizes an epitope formed by a combination of the integrin alpha(L) and beta(2) subunits of LFA-1. Using human/mouse chimeras of the alpha(L) and beta(2) subunits, we determined that YTA-1 binds to the predicted inserted (I)-like domain of the beta(2) subunit and the predicted beta-propeller domain of the alpha(L) subunit. Substitution into mouse LFA-1 of human residues Ser(302) and Arg(303) of the beta(2) subunit and Pro(78), Thr(79), Asp(80), Ile(365), and Asn(367) of the alpha(L) subunit is sufficient to completely reconstitute YTA-1 reactivity. Antibodies that bind to epitopes that are nearby in models of the I-like and beta-propeller domains compete with YTA-1 monoclonal antibody for binding. The predicted beta-propeller domain of integrin alpha subunits contains seven beta-sheets arranged like blades of a propeller around a pseudosymmetry axis. The antigenic residues cluster on the bottom of this domain in the 1-2 loop of blade 2, and on the side of the domain in beta-strand 4 of blade 3. The I domain is inserted between these blades on the top of the beta-propeller domain. The antigenic residues in the beta subunit localize to the top of the I-like domain near the putative Mg(2+) ion binding site. Thus, the I-like domain contacts the bottom or side of the beta-propeller domain near beta-sheets 2 and 3. YTA-1 preferentially reacts with activated LFA-1 and is a function-blocking antibody, suggesting that conformational movements occur near the interface it defines between the LFA-1 alpha and beta subunits.

Amino Acid Sequence↗
PubMed2000

Folding and function of I domain-deleted Mac-1 and lymphocyte function-associated antigen-1.

In those integrins that contain it, the I domain is a major ligand recognition site. The I domain is inserted between beta-sheets 2 and 3 of the predicted beta-propeller domain of the integrin alpha subunit. We deleted the I domain from the integrin alpha(M) and alpha(L) subunits to give I-less Mac-1 and lymphocyte function-associated antigen-1 (LFA-1), respectively. The I-less alpha(M) and alpha(L) subunits were expressed in association with the wild-type beta(2) subunit on the surface of transfected cells and bound to all the monoclonal antibodies mapped to the putative beta-propeller and C-terminal regions of the alpha(M) and alpha(L) subunits, suggesting that the folding of these domains is independent of the I domain. I-less Mac-1 bound to the ligands iC3b and factor X, but this binding was reduced compared with wild-type Mac-1. In contrast, I-less Mac-1 did not bind to fibrinogen or denatured bovine serum albumin. Binding to iC3b and factor X by I-less Mac-1 was inhibited by the function-blocking antibody CBRM1/32, which binds to the beta-propeller domain of the alpha(M) subunit. I-less LFA-1 did not bind its ligands intercellular adhesion molecule-1 and -3. Thus, the I domain is not essential for the folding, heterodimer formation, and surface expression of Mac-1 and LFA-1 and is required for binding to some ligands, but not others.

Animals↗
PubMed2000

Reaction of reducing hydroxyl radical adducts of pyrimidine nucleotides with riboflavin and flavin adenine dinucleotide (FAD) via electron transfer: a pulse radiolysis study.

Using the techniques of pulse radiolysis with time-resolved spectrophotometric detection, it has been demonstrated that the interaction of reducing OH radical adducts of dCMP, TMP and UMP with riboflavin (RF) and flavin adenine dinucleotide (FAD) does proceed via an electron transfer reaction. From buildup kinetics of radical species, the rate constants of electron transfer from reducing OH adducts of pyrimidines to RF and FAD have been determined, respectively. It could be deduced that RF and FAD would reduce the probability of repair of the damaged DNA in the presence of enzymes and antioxidants, accordingly RF and FAD might have a radiosensitization effect on DNA damage.

DNA↗
PubMed2000

Caspase-mediated degradation of AMPA receptor subunits: a mechanism for preventing excitotoxic necrosis and ensuring apoptosis.

Activation of ionotropic glutamate receptors of the AMPA and NMDA subtypes likely contributes to neuronal injury and death in various neurodegenerative disorders. Excitotoxicity can manifest as either apoptosis or necrosis, but the mechanisms that determine the mode of cell death are not known. We now report that levels of AMPA receptor subunits GluR-1 and GluR-4 are rapidly decreased in cultured rat hippocampal neurons undergoing apoptosis in response to withdrawal of trophic support (WTS), whereas levels of NMDA receptor subunits NR1, NR2A, and NR2B are unchanged. Exposure of isolated synaptosomal membranes to "apoptotic" cytosolic extracts resulted in rapid degradation of AMPA receptor subunits. Treatment of cells and synaptosomal membranes with the caspase inhibitors prevented degradation of AMPA receptor subunits, demonstrating a requirement for caspases in the process. Calcium responses to AMPA receptor activation were reduced after withdrawal of trophic support and enhanced after treatment with caspase inhibitors. Vulnerability of neurons to excitotoxic necrosis was decreased after withdrawal of trophic support and potentiated by treatment with caspase inhibitors. Our data indicate that caspase-mediated degradation of AMPA receptor subunits occurs during early periods of cell stress and may serve to ensure apoptosis by preventing excitotoxic necrosis.

Amino Acid Chloromethyl Ketones↗
PubMed2000

GM1 enhances the association of neuron-specific MAP2 with actin in MAP2-transfected 3T3 cells.

The ganglioside GM1 is a glycosphingolipid which enhances process formation of several neuronal lines and potentiates some growth factor-mediated responses. Previously we have shown that 24 h exposure of Neuro 2a cells to GM1 mobilized the neuron-specific microtubule-associated protein, MAP2, away from microtubule-rich areas to areas of neurite sprouting where MAP2 was more closely associated with the subcortical actin network. To examine the role of GM1 in fostering the shift of the association of MAP2 from tubulin to actin, NIH 3T3 cells were co-transfected with pHook-1, which expresses a surface antigen, and a construct expressing MAP2. Transfected cells were selected with magnetic beads coated with a hapten that binds to the expressed surface antigen and treated with 150 microg/ml GM1 for 18-24 h. Actin and MAP2 or tubulin and MAP2 were immunolocalized and examined with confocal microscopy. MAP2 was found throughout the cytoplasm as well as associated with actin filaments. As observed previously with Neuro 2a, GM1 treatment of transfected fibroblasts redistributed the MAP2 away from direct association with microtubules to peripheral areas where the association of MAP2 with actin was enhanced. GM1 did not induce neurite-like processes in MAP2-transfected cells. Treatment with cytochalasin B, which is reported to result in process formation, also did not induce neurite-like processes. These studies suggest that GM1's ability to mobilize MAP2 and promote its association with actin is not restricted to neurons.

3T3 Cells↗
PubMed2000

Enoximone echocardiography for predicting recovery of left ventricular dysfunction after revascularization : a novel test for detecting myocardial viability.

BACKGROUND: The possibility that enoximone, a nonglycoside, noncatechol, positive inotropic agent, in combination with 2-dimensional echocardiography may predict recovery of myocardial dysfunction after revascularization has not been yet evaluated. METHODS AND RESULTS: Forty-five patients with chronic coronary artery disease and left ventricular dysfunction underwent dobutamine (DE, 5 to 10 microg. kg(-1). min(-1)) and enoximone (EE, 1.5 mg/kg, over 10 minutes) echocardiography. Myocardial wall motion was scored from 1 (normal) to 4 (dyskinesia): an asynergic segment was considered to have contractile enhancement when the score decreased by >/=1 grade. Of 478 asynergic segments, 216 (45%) exhibited functional recovery after revascularization. Dobutamine- and enoximone-induced contractile enhancement was observed in 41% and 46% of segments, respectively. Compared with DE, EE had higher sensitivity (88% versus 79%, P<0.01) and negative predictive value (90% versus 84%, P<0.05) in predicting functional recovery. The specificity (89% versus 90%) and positive predictive value (87% for both EE and DE) were similar. Concordant interpretation of EE and DE findings was found in 85% (406 of 478) of affected segments. Prerevascularization coronary angiography showed that stenosis severity of vessels supplying areas which only improved with enoximone was significantly greater (89.9%) than that of vessels (77.7%) supplying areas that responded to both agents (P<0.02). Both dobutamine and enoximone increased heart rate (16% and 10%, respectively), whereas enoximone did not cause changes in systolic blood pressure that increased by 14% with dobutamine. CONCLUSIONS: Enoximone echocardiography provides a novel and reliable approach for the prediction of functional recovery after revascularization. Compared with dobutamine echocardiography, the test yields higher sensitivity and induces lesser hemodynamic alterations.

Adult↗
PubMed2000

[Analysis of complication in the spinal pedicle screw internal fixation].

In 1990-1998, five hundred and twenty patients treated with spinal pedicle screw internal fixation were analyzed. The main operative complication was screw misplacement(7.1%), and others such as screw bend and extra-long screw were less seen. The postoperative complications included screw breakage (13.3%) and backache(14.2%). Recently, by making use of RF screw system and X-ray monitor, the complications were significantly decreased.

Adolescent↗
PubMed2000

Photosynthetic CO(2) assimilation, chlorophyll fluorescence and photoinhibition as affected by nitrogen deficiency in maize plants.

Effects of nitrogen deficiency on photosynthetic CO(2) assimilation, PSII photochemistry and photoinhibition were investigated in maize plants grown under natural illumination. Nitrogen-deficient plants had a significantly smaller CO(2) assimilatory capacity, but they showed little changes in the maximal efficiency of PSII photochemistry, the rate of Q(A) reduction and the heterogeneity of PSII reaction centers, suggesting that nitrogen deficiency had little effects on PSII primary photochemistry and photoinhibition even under natural illumination. However, modifications in PSII photochemistry under the steady state of photosynthesis induced by nitrogen deficiency were observed. This is reflected in decreases in the quantum yield of PSII electron transport, the efficiency of excitation energy capture by open PSII reaction centers, and the photochemical quenching coefficient and an increase in the non-photochemical quenching coefficient. These results suggest that modifications of PSII photochemistry under the steady state of photosynthesis may be a mechanism to downregulate photosynthetic electron transport so that production of ATP and NADPH would be in equilibrium with the decreased demand in the Calvin cycle in nitrogen-deficient plants. On the other hand, the nitrogen-deficient plants still exhibited increased susceptibility to photoinhibition when exposed to very high irradiance, although nitrogen deficiency induced no photoinhibition under natural illumination. Our results suggest that such increased susceptibility to photoinhibition was associated with the increased accumulation of inactivated PSII reaction centers, the decreased capacity of non-photochemical quenching, and the increased fraction of the reduction state of Q(A).

Journal Article↗
PubMed2000

Lens opacifications detected by slitlamp biomicroscopy are associated with exposure to organic nitrate explosives.

CONTEXT: Unusual cataracts (flecks) have been reported to occur at very low levels of trinitrotoluene exposure, but prevalence estimates vary widely. Cataracts have not been reported among workers in the United States exposed to organic nitrate explosives. OBJECTIVES: To determine the prevalence of unusual cataracts in a population of workers in the United States exposed to organic nitrate explosives, to determine whether associations exist with reported cataract risk factors, and to determine if other eye effects (eg, retinal hemorrhage) are associated with exposure. DESIGN: Cohort prevalence study. SETTING: A university-based ophthalmologic clinic. SUBJECTS: Sixty-one workers from an explosives plant comprised the exposed group. The comparison group consisted of 56 workers using chemicals other than organic nitrate explosives. OUTCOME MEASURES: The primary outcome measure was opacifications (flecks) of the crystalline lens, graded clinically on a scale of 0 to 4 +. Additional measures included visual acuity, applanation tonometry, and clinical evaluation using standard examination techniques. RESULTS: Sixty-three percent of the workers had anterior cortical lens opacifications in a pattern of peripheral flecks. Exposed subjects were 18 times more likely to exhibit changes than those not exposed, a statistically significant association (95% confidence interval [CI], 5.0-65.0; P<.001). A statistically significant association with the duration of exposure was also found. CONCLUSIONS: Asymptomatic, low-grade cataracts (flecks) were identified in 63% of the workers exposed to pentolite. No other eye effects were found to be associated with exposure. Cataracts were not associated with other known risk factors, but were associated with the duration of exposure. Biomicroscopy is widely available and useful for detecting changes in the asymptomatic stages.

Adult↗
PubMed2000

Pesticide exposure of children in an agricultural community: evidence of household proximity to farmland and take home exposure pathways.

Children's exposure to organophosphorus (OP) pesticides in an agricultural community in central Washington State was determined. Spot urine and hand wipe samples were collected from 109 children 9 months to 6 years of age, as were house dust samples, and wipe samples from various surfaces. Children were categorized based on parental occupation (agricultural vs nonagricultural) and on household proximity to pesticide-treated orchards. Median house dust concentrations of dimethyl OP pesticides in homes of agricultural families were seven times higher than those of reference families (1. 92 vs 0.27 microg/g; P<0.001). Median pesticide metabolite concentrations in agricultural children were five times higher than those in reference children (0.05 vs 0.01 microg/ml; P=0.09). Median pesticide concentrations in housedust (P=0.01) and metabolite concentrations in urine (P=0.01) from agricultural families were significantly higher in the children living near treated orchards (within 200 ft or 60 m) than those living more distant. Ten of 61 agricultural children had detectable OP pesticide levles on their hands, whereas none of the reference children had detectable levels. These findings indicate that children living with parents who work with agricultural pesticides, or who live in proximity to pesticide-treated farmland, have higher exposures than do other children living in the same community

Agriculture↗
PubMed2000

Open-loop and closed-loop optokinetic nystagmus (OKN) in myasthenia gravis and nonmyasthenic subjects.

Optokinetic nystagmus (OKN) eye movements of myasthenia gravis (MG) and nonmyasthenic ocular palsies, and normal subjects were examined under closed-loop and open-loop conditions. The open-loop OKN condition was achieved by adding the signal of eye-movement velocity of OKN to the computer-generated signal controlling the stimulus grating moving. The OKN was recorded by means of electromagnetic search scleral coil technique. In MG patients, the open-loop gains of OKN increased significantly after the intramuscular injection of an acetylcholinesterase inhibitor, neostigmine, while the closed-loop OKN gains were not significantly changed. Both the closed-loop and open-loop OKN gains of normal subjects and nonmyasthenic patients were not increased for the administration of neostigmine. The experimental results indicated that the open-loop OKN gain could be sensitive to reflect the changes of the function of neuromuscular junction in MG patients.

Adolescent↗
PubMed2000

Saliva biomonitoring of atrazine exposure among herbicide applicators.

A field study was conducted in which saliva samples were collected from a cohort of herbicide applicators during the pre-emergent spray season in Ohio in 1996. Atrazine concentrations were detected in human saliva samples using an enzyme-linked immunosorbent assay (ELISA) method. Trend due to atrazine exposure and subsequent elimination in the body were evidenced by the temporal pattern of decreasing atrazine concentrations in saliva over time. Median salivary concentrations of atrazine on non-spray days were significantly lower than on spray days for each sampling time (Mann-Whitney U-Wilcoxon rank sum test, P < 0.01). Within spray days, median salivary atrazine concentrations were significantly higher on days atrazine was sprayed than on days herbicides other than atrazine were sprayed for each sampling time (Mann-Whitney U-Wilcoxon rank sum test, P = 0.02 for 4 6 p.m. samples, P = 0.04 for bedtime samples, P = 0.03 for next-morning samples). Median salivary atrazine concentrations on days atrazine was sprayed were higher than the median concentration for the corresponding sampling time on non-spray days and on days when other herbicides were sprayed. Salivary concentration of atrazine is a plausible indicator of those days in which atrazine spraying was likely to have occurred. Salivary concentrations of atrazine not only reflect exposures resulting from spraying atrazine, but also exposures from other field activities where applicators may come in contact with atrazine. The results of this study confirmed data from animal experiments that atrazine is able to cross the cell membranes of salivary glands, and can be measured in human saliva with high sensitivity. The sampling method itself is convenient and easy to use in the field, with a high compliance rate, and analytical procedures are rapid and inexpensive. It is, therefore, concluded that saliva sampling of atrazine exposure among herbicide applicators is a feasible biomonitoring method.

Adult↗
PubMed2000

Reengineering a database for clinical trials management: lessons for system architects.

This paper describes the process of enhancing Trial/DB, a database system for clinical studies management. The system's enhancements have been driven by the need to maximize the effectiveness of developer personnel in supporting numerous and diverse users, of study designers in setting up new studies, and of administrators in managing ongoing studies. Trial/DB was originally designed to work over a local area network within a single institution, and basic architectural changes were necessary to make it work over the Internet efficiently as well as securely. Further, as its use spread to diverse communities of users, changes were made to let the processes of study design and project management adapt to the working styles of the principal investigators and administrators for each study. The lessons learned in the process should prove instructive for system architects as well as managers of electronic patient record systems.

Clinical Trials as Topic↗
PubMed2000

Effect of freezing on the activity of catalase in apple flesh tissue.

Catalase (CAT, EC 1.11.1.6) activity was measured in flesh tissue of six apple cultivars (Malus domestica Borkh. cvs. Braeburn, Gala, Jonagold, McIntosh, Red Delicious, and Spartan). Activity of CAT was determined for fresh and frozen tissue of the same fruit. Freezing resulted in reductions of 50 to 90% in CAT activity compared with the activity measured in crude extracts from fresh tissues. The rate of freezing had an impact on the level of reduction of CAT activity, with slower freezing procedures leading to greater losses in activity. Six additives to the extraction buffer were tested to evaluate their potential to reduce the inactivation of CAT from frozen tissue, but only EDTA and Tween 20 showed any benefit. However, EDTA and Tween 20 provided only partial recovery in CAT activity. In contrast, crude extracts prepared from fresh tissue showed no appreciable loss in CAT activity after frozen storage for two weeks at -80 degrees C. Gel electrophoresis and immunological analysis indicated that the loss in CAT activity from tissue freezing could be attributed to loss of both the tetrameric CAT enzyme structure and total CAT protein. The implications of using freezing to preserve apple tissue samples prior to catalase activity analysis is discussed.

Catalase↗
PubMed2000

Canine distemper virus causes apoptosis of Vero cells.

Apoptosis of Vero cells infected with two canine distemper virus (CDV) vaccine strains was detected using TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick end-labelling (TUNEL), flow cytometric analysis, agarose gel electrophoresis and electron microscopy (EM). By TUNEL, apoptotic cells were found in CDV-Onderstepoort (CDV-Ond)-infected cells. DNA fragments isolated from infected cells were separated by agarose gel electrophoresis and a 'ladder' pattern appeared. EM observations demonstrated that the cells undergoing cytopathic effect (CPE) possessed morphological characteristics of apoptotic cells. Flow cytometric analysis indicated that CDV could induce apoptosis of Vero cells, but the percentages of the apoptotic cells were correlated with the CPE types. The strain showing the cell-rounding type of CPE produced a much higher percentage of apoptotic cells than CDV-Ond with the syncytium type of CPE (P < 0.01). It was concluded that CDV vaccine strains could induce apoptosis of Vero cells and the apoptosis was virus strain-dependent and cell-dependent. The mechanism remains to be studied.

Animals↗