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Biomedical subjects

Y N Wu

Publications and source records attributed to Y N Wu.

At least 19 recordsLinked to original sources
PubMed2006

Accuracy of direct digital radiography in the study of the root canal type.

OBJECTIVES: To determine the accuracy of direct digital radiography (DDR) in the study of the root canal type. A sub aim was to assess intraexaminer and interexaminer agreement for this feature using DDR system. METHODS: 100 recently extracted permanent maxillary first premolars from Chinese population were used. Standardized periapical DDR images were taken from a buccolingual and mesiodistal direction. Then the specimens were accessed, injected with dye, demineralized, dehydrated and finally were cleared. The DDR images were evaluated based on the root canal type by two independent trained post-graduate students (examiner A and B) twice at an interval of 2 weeks. The cleared teeth were examined under 5 x magnification using a dental operating microscope by another experienced endodontist, and the data of root canal type were collected. RESULTS: The Kappa values for the agreement between the examiner A and the clearing technique were 0.3793 and 0.329, between the examiner B and the clearing technique were 0.2481 and 0.2184. While the Kappa values between the two observations of each examiner were 0.7704 and 0.7725, between the two examiners they were 0.537 and 0.4793, respectively. CONCLUSIONS: The intraexaminer agreement was good, and the interexaminer agreement was moderate, but the agreement between either DDR examiner and the clearing technique was poor, indicating the limited value of DDR alone when studying root canal type.

Adolescent↗
PubMed2001

[An association analysis of apolipoprotein E genotypes with Alzheimer's disease in Chinese population].

OBJECTIVE: To analyse the association of apolipoprotein E genotypes with Alzheimer's disease in Chinese population. METHODS: Using PCR and restriction enzyme digestion, we have analyzed ApoE allele frequency of Alzheimer's disease (AD) patients and healthy controls. RESULTS: Among the 56 cases of AD, the frequency of ApoE epsilon 2, ApoE epsilon 3, ApoE epsilon 4 are 3 (2.7%), 84 (75.0%), 25 (22.3%) respectively, while in the 67 controls they are 9 (6.7%), 115 (85.8%), 10 (7.5%) respectively. The frequencies of the two groups have significant difference (P < 0.01) and the frequency of ApoE epsilon 4 allele is higher in AD than that in the health controls and the statistical treatment suggest that there is significant difference (chi 2 = 10.99, P < 0.01, OR = 3.59, 95% CI = 1.54-8.41). The frequency of the ApoE epsilon 3 is lower in AD than that in the health controls and the difference is also statistically significant(P < 0.05). CONCLUSIONS: Our results are consistent with previous work in that proving the ApoE epsilon 4 allele is one of the risk factors of AD. The results also provide a support for the protection effect of ApoE epsilon 3 allele in developing AD.

Aged↗
PubMed2001

[A retrospective investigation of shoulder function after RND].

OBJECTIVE: This study was designed to investigate shoulder syndrome and its influence on daily life and employment, and to seek scientific rational standard for evaluating shoulder syndrome. METHODS: Retrospective investigation of shoulder function were carried out in 50 cases after RND through objective evaluation and subjective examination. RESULTS: 68% cases complained obvious handicap in their daily life and work, impaired shoulder function after RND can be seen in almost every case. CONCLUSION: RND can cause variable degree of disability in the shoulder which influences patients quality of life directly,self evaluation and abducting arm beyond 90 degrees are good standards for evaluating shoulder syndrome.

English Abstract↗
PubMed1999

Presynaptic inhibition preferentially reduces in NMDA receptor-mediated component of transmission in rat midbrain dopamine neurons.

We used patch pipettes to record whole-cell currents from single dopamine neurons in slices of rat midbrain. Pharmacological methods were used to isolate EPSCs evoked by focal electrical stimulation. Baclofen was significantly more potent for inhibiting NMDA receptor-mediated EPSCs (IC50=0.24 microM) compared with inhibition of EPSCs mediated by AMPA receptors (IC50=1.72 microM). The increased potency of baclofen for inhibiting the NMDA component persisted in superfusate that contained zero Mg2+ and when postsynaptic K+ conductances were reduced by Cs+ and QX-314. Effects of baclofen on EPSCs were blocked by the GABA(B) receptor antagonist CGP-35348. Adenosine was 20 fold more potent for reducing the NMDA component of transmission (IC50=31 microM) compared with inhibition of AMPA receptor-mediated EPSCs (IC50=654 microM). Effects of adenosine on EPSCs were blocked by the A1 receptor antagonist DPCPX. Both baclofen and adenosine significantly increased the ratio of EPSCs in paired-pulse studies, suggesting presynaptic sites of action. Although adenosine (1 mM) did not reduce currents evoked by exogenous NMDA (10 microM), baclofen (1 microM) reduced NMDA currents by 29%. Neither baclofen nor adenosine altered currents evoked by exogenous AMPA (1 microM). We conclude that adenosine acts at presynaptic A1 receptors to cause a preferential reduction in the NMDA component of synaptic transmission. In contrast, baclofen preferentially reduces NMDA EPSCs by acting at both pre- and postsynaptic GABA(B) receptors. By regulating NMDA receptor function, A1 and GABA(B) receptors may play important roles in regulating the excitability of dopamine neurons.

Adenosine↗
PubMed1997

[Clinical study on the recovery of sensory function in tissue flaps repairing the defect of oral and maxillofacial region]

The recovery of sensibility in 29 cases non-neurolorized tissue flaps and 4 cases neurolorized flaps have been studied clinically. The results showed that:the sensory function started to return from 3 months after operation and recovered gradually.Pain sensibility recovered first,followed by tactile,thermal and two-point discrimination sensibility.The recovery usually occured from edge to centre of the flap 2-3 years after operation,about 65.5% nonneurolorized flaps obtained good recovery of sensibility.The recovery rate of pain,tactile,thermal and two-point discrimination sensibililty was 64.7%,64.7%,53.0% and 23.5% respectively.Flaps recovered better than myocutaneous flaps.The recovery of sensibility of the neurolorized flaps occurred early and quickly.All 4 cases obtained excellent sensory recovery including two-point discrimination sensibility.The results suggest that:the sensory function of tissue flaps come from not only surrounding,but also deep tissue,any factor that can cause decrease of quality and quantity of regenerated nerve endings will inhibit flap from recovering its sensory function.

Journal Article↗
PubMed1997

Modeling schizophrenic behavior using general mixture components.

This article proposes a novel and general mixture component model, the features of which include a hierarchical structure with random effects, mixture components characterized by ANOVA-like linear regressions, and mixing mechanisms governed by logistic regressions. The model was developed as a consequence of attending to long-standing psychological theory about schizophrenic behavior. Scientifically revealing results are obtained by fitting the model to a data set concerning nonschizophrenic and schizophrenic eye-tracking behavior under different conditions. Included are descriptions of the algorithms for model fitting, specifically the ECM/SECM algorithms for large sample modal inference, and the Gibbs sampler for simulating the posterior distribution. For guidance on model comparison and selection, we use posterior predictive check distributions to obtain posterior predictive p-values for likelihood ratio statistics, which do not have asymptotic chi 2 reference distributions. These posterior predictive p-values suggest that all the mixture components in our model are necessary. The final model is selected using a combination of scientific parsimony, the posterior predictive p-values, and the posterior distributions of relevant parameters.

Algorithms↗
PubMed1996

Molecular determinants in the plasma clearance and tissue distribution of ribonucleases of the ribonuclease A superfamily.

The similarities and differences among members of the RNase A superfamily provide an ideal opportunity to examine the molecular basis for differences in their pharmacokinetics and biodistribution. Plasma clearances in BALB/c mice are similar among the five RNases studied: human pancreatic RNase, angiogenin, eosinophil-derived neurotoxin, onconase, and bovine seminal RNase. The average clearance is 0.13 ml/min or 60% of the glomerular filtration rate (measured by [14C]inulin clearance during continuous infusion from an i.p. implanted osmotic pump). Angiogenin has a higher volume of distribution and plasma-to-muscle transport rate than the other RNases, suggestive of binding to endothelial cells. Organ distribution differs dramatically among these RNases. The RNase most toxic to tumor cells, onconase, exhibits the longest retention in the kidneys: at 180 min, 50% of the injected dose is found in the kidneys, whereas only 1% or less of the other RNases is retained in the kidneys. Slower elimination of onconase from the kidneys may be due to a higher degree of binding in the kidney or a resistance to proteolytic degradation. To elucidate the molecular determinants involved in tissue uptake, we examined the biodistribution of recombinant onconase and two onconasepancreatic RNase chimeric proteins. The tissue retention property of onconase appears to be located in at least two regions, one of which is in the NH2-terminal 9-amino acid alpha-helix. The NH2-terminal pyroglutamate of onconase, a residue essential for ribonucleolytic activity and cytotoxicity, does not play a role in kidney retention.

Animals↗
PubMed1996

Inhibition of HIV-1 production and selective degradation of viral RNA by an amphibian ribonuclease.

Ribonucleases appear to have physiologic roles in host defense against cancer, viruses, and other parasites. Previously it was shown that select ribonucleases added to cells concurrently with virions blocked human immunodeficiency virus, type I (HIV-1) infection of H9 cells. We now report that a ribonuclease homologous to RNase A, named onconase, inhibits virus replication in chronically HIV-1-infected human cells without killing the virally infected cell. Examining the mechanism of this inhibition shows that onconase enters the infected cells and degrades HIV-1 RNA without degrading ribosomal RNA or the three different cellular messenger RNAs analyzed. The homologous human pancreatic RNase lacks anti-viral activity. Comparing recombinant forms of onconase and a onconase-human RNase chimera shows that the N-terminal 9 amino acids and the pyroglutamyl residue of onconase are required for full anti-viral activity. Thus extracellular ribonucleases can enter cells, metabolize select RNAs, and inhibit HIV virion production within viable replicating cells.

Antiviral Agents↗
PubMed1996

Three- versus four-week administration of benzathine penicillin G: effects on incidence of streptococcal infections and recurrences of rheumatic fever.

OBJECTIVE: To investigate the effects of 3-week versus 4-week administration of benzathine penicillin G (BPG) on the incidence of Group A streptococcal infections and the recurrences of rheumatic fever (RF). STUDY DESIGN: We started, in 1979, randomly allocating all patients with RF to a 3-week or 4-week BPG prophylaxis program. They were examined at the RF clinic, every 3 to 6 months, and at any time they did not feel well. During 1979 to 1989, throat cultures and sera for antistreptolysin O and streptozyme titers were obtained at each clinic visit. Chest radiographs, electrocardiogram, color Doppler echocardiograms, and acute phase reactants were obtained. SUBJECTS: Two hundred forty-nine patients fulfilled the revised Jones criteria and were followed until December 1991: 124 in the 3-week and 125 in the 4-week program. Their age, sex, weight, percentage with history of RF, severity of cardiac involvement, follow-up duration, and compliance to program were comparable. Eight hundred eighty throat cultures were collected in the 3-week program and 770 were collected in the 4-week program. Six hundred sixteen and 627 sera were determined in each program for antistreptolysin O, and 582 and 592 sera for streptozyme titers. RESULTS: True streptococcal infections occurred in both programs: 39 infections in the 3-week program, and 59 infections in the 4-week program (7.5 vs 12.7 per 100 patient-years). Four infections with no antibody response occurred in the 3-week program, and three such infections in the 4-week program. Nine RF recurrences occurred in 8 patients in the 3-week program, and 16 recurrences in 16 patients in the 4-week program. Prophylaxis failure occurred in 2 of 124 patients in the 3-week program, and in 10 of 125 patients in the 4-week program (0.25 vs 1.29 per 100 patient-years). The overall recurrences/infections rate in each program was comparable, 13.6% vs 15.5%, but the recurrences/ infections rate due to prophylaxis failure was higher in the 4-week program than in the 3-week program, 3.0% versus 9.7%. CONCLUSIONS: This 12-year prospective and controlled study documented that streptococcal infections and RF recurrences occurred more often in the 4-week program than in the 3-week program. The risk of prophylaxis failure was fivefold greater in the 4-week program than in the 3-week program.

Adolescent↗
PubMed1996

Pharmacological characterization of inward current evoked by N-methyl-D-aspartate in dopamine neurons in the rat brain slice.

In midbrain dopamine neurons in vitro, N-methyl-D-aspartate (NMDA) evokes oscillation of membrane potential and burst firing which are dependent on a ouabain-sensitive sodium pump. In the present study, we investigated the ionic dependence and pharmacological modulation of NMDA-mediated currents which might be important in burst firing. By use of patch pipettes to record membrane currents in whole-cell voltage clamps, we found that NMDA (10 microM) evoked inward currents that were significantly reduced in a low extracellular concentration of Na+ (25 mM), but not when extracellular Ca+2 was decreased from 2.5 to 0.5 mM. The current-voltage relationship for subtracted NMDA currents showed a prominent region of negative slope conductance which was absent when the slice was perfused with solution containing zero Mg++. 7-Chlorokynurenic acid, an antagonist at the nonstrychnine-sensitive glycine binding site, produced a concentration-dependent reduction in amplitude of excitatory postsynaptic currents mediated by NMDA receptors (IC50 = 15 +/- 3 microM). NMDA-activated currents were blocked by phencyclidine (IC50 = 130 +/- 65 nM), dizocilpine maleate (MK-801) (1 microM) and ketamine (100 microM), but not by amantadine (1 mM). Spermine (100 microM), a polyamine which reportedly modulates NMDA currents in other neurons, presynaptically inhibited excitatory postsynaptic currents mediated by NMDA receptors but had no effect on the currents mediated by NMDA. We conclude that the most important factors for NMDA-induced burst firing are the relatively large Na+ influx through NMDA-gated channels and the strong voltage-dependent block of conductance by Mg++.

Animals↗
PubMed1995

Presynaptic inhibition of gamma-aminobutyric acidB-mediated synaptic current by adenosine recorded in vitro in midbrain dopamine neurons.

Adenosine receptor antagonists such as caffeine cause dopamine-dependent behavioral arousal and hyperlocomotion in rodents. In the present study, we used the whole-cell recording technique in the rat brain slice to investigate effects of adenosine on dopamine neurons and their synaptic inputs in the substantia nigra zona compacta and ventral tegmental area. Adenosine was most potent for inhibiting the amplitude of the inhibitory postsynaptic current (IPSC) mediated by gamma-aminobutyric acid (GABA)B receptors (EC50 = 47 +/- 3 microM) compared with inhibition of the GABAA-mediated IPSC (117 +/- 51 microM) and the excitatory amino acid-mediated excitatory postsynaptic current (119 +/- 36 microM). Adenosine failed to inhibit current evoked by exogenous GABA or baclofen, suggesting that adenosine acted presynaptically to reduce GABA release from nerve terminals. Adenosine inhibited the GABAB-mediated IPSC by acting at the adenosine A1 receptor, because its effect was blocked by the selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (100 nM), as well as by the methylxanthines caffeine (1 mM) and theophylline (300 microM). The rank-order of potency of adenosine agonists [N6-cyclohexyladenosine > R-(-)-N6-(2-phenylisopropyl)-adenosine = N6- cyclohexyladenosine > 5'-N-ethylcarboxamidoadenosine > 2-chloroadenosine] also was consistent with activation of the adenosine A1 receptor, whereas the selective adenosine A2A agonist CGS 21680 [2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido adenosine] had no effect on the GABAB IPSC. None of the adenosine agonists or antagonists affected holding current or membrane conductance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1994

RNase inhibition of human immunodeficiency virus infection of H9 cells.

Onconase and bovine seminal RNase, two members of the RNase A superfamily, inhibit human immunodeficiency virus type 1 replication in H9 leukemia cells 90-99.9% over a 4-day incubation at concentrations not toxic to uninfected H9 cells. Two other members of the same protein family, bovine pancreatic RNase A and human eosinophil-derived neurotoxin, have no detectable antiviral activity, demonstrating a strikingly selective antiviral activity among homologous ribonucleases. The antiviral RNases do not appear to affect viral particles directly but inhibit replication in host cell cultures. Onconase, already in clinical trials for cancer therapy, and bovine seminal RNase have potential as antiviral therapeutics.

Animals↗
PubMed1994

Control of cationic amino acid transport and retroviral receptor functions in a membrane protein family.

A partial cDNA sequence indicated that the T lymphocyte early-activation gene (Tea) encodes a protein related to the dual-function ecotropic retrovirus receptor/cationic amino acid transporter (ecoR/CAT1), and RNA blots suggested highest Tea expression in T lymphocytes and liver (MacLeod, C.L., Finley, K., Kakuda, D. Kozad, C.A., and Wilkinson, M.F. (1990) Mol. Cell. Biol. 7, 3663-3674). The sequence of full-length Tea cDNA from liver (3683 bases) predicts a 657-amino-acid protein (CAT2 alpha) with 12-14 transmembrane domains. A long (515 base) region with six initiation codons and termination codons precedes the translation start codon. The liver Tea cDNA is identical to Tea cDNA from T lymphocytes (encoding CAT2 beta) with the exception of an apparent alternatively spliced sequence encoding a hydrophilic loop of 43 amino acids. The liver-specific sequence contains unique consensus sites for phosphorylation by cyclic AMP-dependent protein kinase and by protein kinase C. Injection of Xenopus oocytes with CAT2 alpha or CAT2 beta messenger RNA resulted in expression of Na(+)-independent cationic amino acid transport that was detected by current measurements under voltage-clamp. Although the amino acid sequences of the isoforms differ in only 21 of 43 residues with the majority of substitutions being conservative, the apparent affinity of CAT2 beta for arginine uptake was 70-fold higher than the CAT2 alpha isoform (Km 38 microM versus 2.7 mM). Neither isoform functioned as a receptor for ecotropic or amphotropic murine retroviruses. However, CAT1-CAT2 chimeric proteins that contain the first three putative extracellular loops of ecoR/CAT1 functioned as ecotropic receptors despite a diminished capacity to bind the viral envelope glycoprotein. The chimeric proteins also functioned as basic amino acid transporters with substrate affinities corresponding to the CAT2 isoform constituting the carboxyl-terminal portion. These results demonstrate that domains of these transporters can function in chimeric combinations to control viral receptor and transport functions.

Amino Acid Sequence↗
PubMed1994

Long-term outcome of patients with rheumatic fever receiving benzathine penicillin G prophylaxis every three weeks versus every four weeks.

OBJECTIVE: To compare the efficacy of injections of 1.2 million units of benzathine penicillin G given every 3 weeks versus every 4 weeks for secondary prevention of rheumatic fever, based on the long-term outcome of patients receiving such prophylaxis. METHODS: A total of 249 consecutive patients with rheumatic fever, randomly assigned to either a 3-week or a 4-week regimen, were examined every 3 to 6 months, and followed for 794 and 775 patient-years, respectively. RESULTS: Compliance with each regimen was comparable: 83 (66.9%) of 124 patients in the 3-week group versus 92 (73.6%) of 125 patients in the 4-week group stayed in the program (p > 0.05). Streptococcal infections occurred less frequently in those receiving the 3-week regimen: 7.5 versus 12.6 per 100 patient-years (p < 0.01). Prophylaxis failed in 2 patients receiving the 3-week regimen and in 10 receiving the 4-week regimen (0.25 and 1.29 per 100 patient-years respectively; p = 0.015). Serum penicillin levels were adequate (> or = 0.02 micrograms/ml) in 100 (56%) of 179 samples obtained 21 days after penicillin injection in the 3-week regimen, and in 51 (33%) of 155 samples obtained 28 days after injection in the 4-week regimen (p < 0.01). Of 71 patients with mitral regurgitation in the 3-week regimen, 47 (66%) no longer had the murmur; of 87 patients in the 4-week regimen, 40 (46%) no longer had the murmur (p < 0.05). CONCLUSIONS: This 12-year controlled study indicates that the outcome of patients with rheumatic fever is better with a 3-week than with a 4-week penicillin prophylaxis regimen. Greater emphasis and more widespread use of the 3-week regimen should be recommended.

Adolescent↗
PubMed1994

Retinoic acid disrupts the Golgi apparatus and increases the cytosolic routing of specific protein toxins.

All-trans retinoic acid can specifically increase receptor mediated intoxication of ricin A chain immunotoxins more than 10,000 times, whereas fluid phase endocytosis of ricin A chain alone or ricin A chain immunotoxins was not influenced by retinoic acid. The immunotoxin activation by retinoic acid does not require RNA or protein synthesis and is not a consequence of increased receptor binding of the immunotoxin. Vitamin D3 and thyroid hormone T3, that activate retinoic acid receptor (RAR) cognates, forming heterodimers with retinoid X receptor (RXR), do not affect the potency of immunotoxins. Among other retinoids tested, 13-cis retinoic acid, which binds neither RAR nor RXR, also increases the potency of the ricin A chain immunotoxin. Therefore, retinoic acid receptor activation does not appear to be necessary for immunotoxin activity. Retinoic acid potentiation of immunotoxins is prevented by brefeldin A (BFA) indicating that in the presence of retinoic acid, the immunotoxin is efficiently routed through the Golgi apparatus en route to the cytoplasm. Directly examining cells with a monoclonal antibody (Mab) against mannosidase II, a Golgi apparatus marker enzyme, demonstrates that the Golgi apparatus changes upon treatment with retinoic acid from a perinuclear network to a diffuse aggregate. Within 60 min after removal of retinoic acid the cell reassembles the perinuclear Golgi network indistinguishable with that of normal control cells. C6-NBD-ceramide, a vital stain for the Golgi apparatus, shows that retinoic acid prevents the fluorescent staining of the Golgi apparatus and eliminates fluorescence of C6-NBD-ceramide prestained Golgi apparatus. Electron microscopy of retinoic acid-treated cells demonstrates the specific absence of any normal looking Golgi apparatus and a perinuclear vacuolar structure very similar to that seen in monensin-treated cells. This vacuolization disappears after removal of the retinoic acid and a perinuclear Golgi stacking reappears. These results indicate that retinoic acid alters intracellular routing, probably through the Golgi apparatus, potentiating immunotoxin activity indepedently of new gene expression. Retinoic acid appears to be a new reagent to manipulate the Golgi apparatus and intracellular traffic. As retinoic acid and immunotoxins are both in clinical trials for cancer therapy, their combined activity in vivo would be interesting to examine.

4-Chloro-7-nitrobenzofurazan↗
PubMed1994

Detection of varicella-zoster virus DNA in air samples from hospital rooms.

Varicella-zoster virus (VZV) is a highly contagious infectious agent that causes outbreaks in institutional settings. Transmission of VZV is felt to occur following direct contact with an infected individual and by aerosol spread. To document the aerosolization of VZV, a polymerase chain reaction (PCR) assay was used to detect VZV DNA in air samples obtained from hospital rooms of patients with active VZV infection. VZV DNA was detected in 64 (82%) of 78 air samples from rooms housing patients with active varicella and 9(70%) of 13 samples from rooms of patients with herpes zoster. VZV was detected 1.2-5.5 m from patients' beds and for 1-6 days following onset of rash. On some occasions, VZV DNA could be detected outside the hospital isolation rooms housing patients. This PCR-based method allows the detection and semiquantitation of VZV aerosolization and can be a useful tool for monitoring efforts to control VZV aerosols in the environment.

Adolescent↗