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Y C Wu

Publications and source records attributed to Y C Wu.

At least 127 records · Page 7Linked to original sources
PubMed1995

Pharmacological evaluation of N-methyl-actinodaphnine, a new vascular alpha-adrenoceptor antagonist, isolated from Illigera luzonensis.

The pharmacological activity of N-methyl-actinodaphnine, isolated from Illigera luzonensis, was determined by functional and binding experiments with peripheral tissues. In a functional study, N-methyl-actinodaphnine was a simple competitive antagonist of contractions elicited by phenylephrine (pA2 = 7.11) in rat thoracic aorta; it also competitively antagonised the clonidine-induced inhibition of the twitch response of rat vas deferens (pA2 = 5.01). In addition, [3H]inositol monophosphate formation caused by noradrenaline (3 microM) in rat isolated thoracic aorta was concentration dependently inhibited by N-methyl-actinodaphnine (1 and 10 microM); however, it had no effect on cyclic AMP and cyclic GMP contents. Additionally, N-methyl-actinodaphnine had extremely low affinity for thromboxane receptors, prostaglandin receptors, Ca2+ channels, muscarinic receptors, histamine receptors, beta-adrenoceptors, neurokinin and leukotriene receptors in vitro. However, N-methyl-actinodaphnine also possessed 5-hydroxytryptamine (5-HT) receptor blocking activity. Its potency for blocking 5-HT receptors was about 14 times less than that for blocking alpha 1-adrenoceptors. In binding experiments, N-methyl-actinodaphnine displaced biphasically the binding of 0.2 nM [3H]prazosin to cultured A10 cells. The selectivity for alpha 1-adrenoceptor subtypes was also investigated in rat vas deferens and spleens. The contractile response in rat vas deferens to noradrenaline was competitively inhibited by N-methyl-actinodaphnine with a pA2 value of 6.58; N-methyl-actinodaphnine also competitively antagonized the phenylephrine-induced contraction in rat spleen with a pA2 value of 7.38. These results indicate that N-methyl-actinodaphnine is a selective alpha 1-adrenoceptor antagonist. Furthermore, it is more selective for the alpha 1B- than for the alpha 1A-adrenoceptor subtype.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1995

Reliable determination of furosine in human serum and dialysate proteins by high-performance liquid chromatography.

Furosine, formed by hydrolysis of 1-deoxy-fructosyl-lysine (fructose-lysine), is a product of the Amadori rearrangement of glucose and epsilon-NH2-lysine. Fructose-lysine can react further with tissue and circulating proteins to produce advanced glycation end-products (AGEs). Peritoneal dialysate used in the treatment of patients with end-stage renal failure contains high concentrations of glucose which may lead to intraperitoneal formation of AGEs. To quantitate the kinetics of formation and peritoneal clearance of glycated peritoneal dialysate proteins, we developed an effective approach to the measurement of furosine in clinical samples of serum and peritoneal dialysate.

Borohydrides↗
PubMed1995

Teleradiology/telepathology requirements and implementation.

Teleradiology and telepathology form an integral part of the telemedicine concept. Teleradiology is becoming a mature technology because of advances in imaging technology, database design and communications infrastructure and capabilities. Telepathology has also made significant progress but more development is needed in the definition of required images, database design and standards. While the requirements of most clinical applications of teleradiology are well established, telemammography still presents some impediments. Technical difficulties in telemammography are presented in terms of the lack of a clinically accepted digital imaging system and large data volume required per image. Another important aspect in tele-imaging is the database question. Workstations constitute a window into database. Comprehensive database development is the most difficult and expensive technology for tele-imaging and operational features of such systems are discussed. Finally, we explore current examples of the use of telepathology and teleradiology in the global telemedicine context.

Computer Communication Networks↗
PubMed1995

Detection of lung nodules in digital chest radiographs using artificial neural networks: a pilot study.

Radiologists can fail to detect up to 30% of pulmonary nodules in chest radiographs. A back-propagation neural network was used to detect lung nodules in digital chest radiographs to assist radiologists in the diagnosis of lung cancer. Regions of interest (ROIs) that contained nodules and normal tissues in the lung were selected from digitized chest radiographs by a previously developed computer-aided diagnosis (CAD) scheme. Different preprocessing techniques were used to produce input data to the neural network. The performance of the neural network was evaluated by receiver operating characteristic (ROC) analysis. We found that subsampling of original 64- x 64-pixel ROIs to smaller 8- x 8-pixel ROIs provides the optimal preprocessing for the neural network to distinguish ROIs containing nodules from false-positive ROIs containing normal regions. The neural network was able to detect obvious nodules very well with an Az value (area under ROC curve) of 0.93, but was unable to detect subtle nodules. However, with a training method that uses different orientations of the original ROIs, we were able to improve the performance of the neural network to detect subtle nodules. Artificial neural networks have the potential to serve as a useful classifier to help to eliminate the false-positive detections of the CAD scheme.

False Positive Reactions↗
PubMed1995

Constituents and cytotoxic principles of Nothapodytes foetida.

A new naturally occurring alkaloid, acetylcamptothecin, together with 17 known compounds, (+)-1-hydroxypinoresinol, omega-hydroxypropioguaiacone, p-hydroxybenzaldehyde, scopoletin, uracil, thymine, sitosterol, sitosteryl-beta-D-glucoside, 3 beta-hydroxy-stigmast-5-en-7-one, stigmast-5-en-3 beta,7 alpha-diol, 6 beta-hydroxystigmast-4-en-3-one, sitost-4-en-3-one, linoleic acid, trigonelline, camptothecin, 9-O-methoxycamptothecin and pumiloside were isolated and characterized from the stem of Nothapodytes foetida. Among them, scopoletin, camptothecin, 9-O-methoxycamptothecin and O-acetylcamptothecin showed significant cytotoxic activity.

Antineoplastic Agents, Phytogenic↗
PubMed1995

Influence of dialysis modality on plasma and tissue concentrations of pentosidine in patients with end-stage renal disease.

Plasma and tissue concentrations of pentose-derived glycation end-products ("pentosidine") are elevated in diabetic patients with normal renal function and in both diabetic and nondiabetic patients with end-stage renal disease. To determine the influence of dialysis modality and other clinical variables on the accumulation of pentosidine, we used high-performance liquid chromatography to measure this advanced glycation end-product in plasma, skin, and peritoneal samples obtained from 65 hemodialysis and 45 peritoneal dialysis patients. Plasma pentosidine levels were significantly lower in peritoneal dialysis patients. Concentrations of pentosidine in skin were similar in the two groups. In contrast, peritoneal concentrations of pentosidine were significantly higher in the patients maintained on peritoneal dialysis. Our results demonstrate that dialysis modality influences the plasma and tissue distribution of pentosidine. Compared with hemodialysis, peritoneal dialysis is associated with lower levels of this glycation end-product in plasma, but with higher levels in the peritoneum. The mechanisms accounting for lower circulating levels of pentosidine in peritoneal dialysis patients remain to be determined. Higher levels in peritoneal tissues may reflect chronic exposure to the high concentrations of glucose in peritoneal dialysate.

Arginine↗
PubMed1995

Classification of microcalcifications in radiographs of pathologic specimens for the diagnosis of breast cancer.

RATIONALE AND OBJECTIVES: Early detection of breast cancer depends on accurate classification of microcalcifications. We have developed a computer vision system that has the potential to classify microcalcifications objectively and consistently to aid radiologists in diagnosing breast cancer. METHODS: A convolution neural network (CNN) was used to classify benign and malignant microcalcifications in radiographs of pathologic specimens. Digital images were acquired by digitizing radiographs at a high resolution of 21 microns x 21 microns. RESULTS: Eighty regions of interest selected from digitized radiographs of pathologic specimens were used for training and testing of the neural network system. The CNN achieved an Az value (area under the receiver operating characteristic curve) of 0.90 in classifying clusters of microcalcifications associated with benign and malignant processes. CONCLUSION: Classification of microcalcifications in pathologic specimens for diagnosis of breast cancer was achieved at a high level in our computer vision system, which consists of high-resolution digitization of mammograms and a CNN.

Breast Neoplasms↗
PubMed1995

Bioactive constitutents from the stems of Annona montana.

Three structurally related acid amides, N-trans-feruloyltyramine (1), N-p-coumaroyltyramine (2), and N-trans-caffeoyltyramine (3), one lignan, (-)-syringaresinol (4), one aromatic aldehyde, syringaldehyde (5), and two steroids, beta-sitosterol and beta-sitosterol-beta-D-glucoside were isolated from the stem parts of Annona montana (Annonaceae). N-trans-Caffeoyltyramine (3) is a new natural compound. These compounds and their acetate derivatives were subjected to the antiplatelet aggregation and cytotoxicity bioassay where some of them showed significant activities.

Animals↗
PubMed1995

The calcium-activated potassium channels of turtle hair cells.

A major factor determining the electrical resonant frequency of turtle cochlear hair cells is the time course of the Ca-activated K current (Art, J. J., and R. Fettiplace. 1987. Journal of Physiology. 385:207-242). We have examined the notion that this time course is dictated by the K channel kinetics by recording single Ca-activated K channels in inside-out patches from isolated cells. A hair cell's resonant frequency was estimated from its known correlation with the dimensions of the hair bundle. All cells possess BK channels with a similar unit conductance of approximately 320 pS but with different mean open times of 0.25-12 ms. The time constant of relaxation of the average single-channel current at -50 mV in 4 microM Ca varied between cells from 0.4 to 13 ms and was correlated with the hair bundle height. The magnitude and voltage dependence of the time constant agree with the expected behavior of the macroscopic K(Ca) current, whose speed may thus be limited by the channel kinetics. All BK channels had similar sensitivities to Ca which produced half-maximal activation for a concentration of approximately 2 microM at +50 mV and 12 microM at -50 mV. We estimate from the voltage dependence of the whole-cell K(Ca) current that the BK channels may be fully activated at -35 mV by a rise in intracellular Ca to 50 microM. BK channels were occasionally observed to switch between slow and fast gating modes which raises the possibility that the range of kinetics of BK channels observed in different hair cells reflects a common channel protein whose kinetics are regulated by an unidentified intracellular factor. Membrane patches also contained 30 pS SK channels which were approximately 5 times more Ca-sensitive than BK channels at -50 mV. The SK channels may underlie the inhibitory synaptic potential produced in hair cells by efferent stimulation.

Animals↗
PubMed1995

Management of primary chest wall tuberculosis.

Primary tuberculosis of the chest wall is rare and its clinical presentation may resemble pyogenic abscess or tumour. The diagnosis is difficult, since smears or cultures of aspirate frequently fail to show tubercle bacilli. Seven cases of primary chest-wall tuberculosis treated between 1973 and 1992 are described. All presented with a progressively enlarging mass. The diagnosis was based on bacteriologic and histologic findings, but definitive diagnosis was obtained before treatment in only two cases. Satisfactory results were obtained with surgical debridement and specific chemotherapy in six cases and with chemotherapy alone in one case. From this limited experience, we suggest that primary chest-wall tuberculosis should initially be treated with a combination regimen of antituberculous chemotherapy, which should take more than 9 months. If the lesion progressively enlarges or secondary infection occurs, however, adequate surgical debridement is also required.

Abscess↗
PubMed1995

Primary uncommon malignant tumors of the esophagus: an analysis of 30 cases.

BACKGROUND: Uncommon malignant tumors of the esophagus are defined as any histological type of malignant esophageal tumors other than the typical squamous cell carcinoma. Their biological characteristics remain obscure because of their rarity. Thus, this is a retrospective review of patients here with uncommon esophageal cancers in an attempt to evaluate their prognostic factors and proper therapeutic modalities. METHODS: Among 1,674 patients with esophageal cancers, only 30 (1.8%) with uncommon esophageal cancers were collected between 1977 and 1992. The clinical parameters for evaluation consisted of age, sex, histological type, location, staging and a variety of therapeutic management techniques and their results. RESULTS: Histologically, there were 10 adenocarcinomas, 7 small cell carcinomas, 6 adenosquamous carcinomas, 3 carcinosarcomas, 1 mucoepidermoid carcinoma, 1 adenoid cystic carcinoma, 1 fibrosarcoma, and 1 basal cell carcinoma. The mean age was 65.8 years, ranging from 46 to 85 years. Upon admission to hospital, the most common clinical symptoms included dysphagia, body weight loss and substernal pain. The tumor staging, according to TNM classification was evaluated as follows: Stage I: 13.3%, Stage II: 46.7%, Stage III: 16.9%, Stage IV: 23.3%. The middle third thoracic esophagus was the most common location of tumor occurrence. Overall one-year, two-year, and five-year survival rates were 39.3%, 21.4%, and 10.7% respectively. These results were as poor as those of squamous cell carcinoma. However, the patients with Stage I and Stage II tumors (mean, 23.8 months) had significantly better survivals than those with Stage III and Stage IV (mean, 3.9 months). Furthermore, if the tumor was resectable, the patients undergoing esophagectomy had much better one-year and two-year survival rates than those without esophagectomy (p < 0.01). In addition, patients with small cell carcinoma seemed to have worse treatment outcome than those with other histological types of tumors. CONCLUSIONS: These results suggested that key factors contributing to prognosis included tumor staging as well as respectability. Thus, it is recommended that, with early detection and diagnosis, esophagectomy might be the treatment-of-choice in managing these uncommon esophageal malignancies. Adjuvant therapy including irradiation and chemotherapy may be helpful, particular for small cell carcinoma.

Aged↗
PubMed1994

Reduction of false positives in computerized detection of lung nodules in chest radiographs using artificial neural networks, discriminant analysis, and a rule-based scheme.

A computer-aided diagnosis (CAD) scheme is being developed to identify image regions considered suspicious for lung nodules in chest radiographs to assist radiologists in making correct diagnoses. Automated classifiers--an artificial neural network, discriminant analysis, and a rule-based scheme--are used to reduce the number of false-positive detections of the CAD scheme. The CAD scheme first detects nodule candidates from chest radiographs based on a difference image technique. Nine image features characterizing nodules are extracted automatically for each of the nodule candidates. The extracted image features are then used as input data to the classifiers for distinguishing actual nodules from the false-positive detections. The performances of the classifiers are evaluated by receiver-operating characteristic analysis. On the basis of the database of 30 normal and 30 abnormal chest images, the neural network achieves an AZ value (area under the receiver-operating-characteristic curve) of 0.79 in detecting lung nodules, as tested by the round-robin method. The neural network, after being trained with a training database, is able to eliminate more than 83% of the false-positive detections reported by the CAD scheme. Moreover, the combination of the trained neural network and a rule-based scheme eliminates 96% of the false-positive detections of the CAD scheme.

Diagnosis, Computer-Assisted↗
PubMed1994

Removing the assumption of conditional independence from Bayesian decision models by using artificial neural networks: some practical techniques and a case study.

The article describes how artificial neural networks with special designs can be applied to approximate a subjective Bayesian decision model without the assumption of conditional independence. New techniques are proposed to resolve some of the practical difficulties during the processes of problem structuring, knowledge elicitation, quantitative modeling, and model interpretation. A Bayesian model considering the conditional dependencies to predict a teenager's marijuana use was constructed by experts using these techniques, and compared to another conventional Bayesian model which assumed conditional independence. The new approach without the assumption of conditional independence had predictive power (r = 0.7) in the test of linearity compared to the conventional approach (r = 0.58) on a data set (n = 129). Its receiver operating characteristic curve dominated the alternative approach within the range (true positive fraction > 0.7) that we were interested in. The interpretations of the possible conditional dependencies provided by the artificial neural network after the training process were consistent with the expert's descriptions.

Adolescent↗
PubMed1994

(-)-Discretamine, a selective alpha 1D-adrenoceptor antagonist, isolated from Fissistigma glaucescens.

1. The selectivity of (-)-discretamine for alpha 1-adrenoceptor subtypes was investigated by use of functional and binding studies in rat vas deferens, spleen and aorta, and in cultured DDT1MF-2 and A10 cells. 2. In prostatic portions of rat vas deferens, the competitive antagonists (-)-discretamine, 5-methylurapidil (5-MU) and prazosin inhibited contractions to noradrenaline (NA) with pA2 values of 6.21, 8.71 and 9.27, respectively. The irreversible antagonist, chloroethylclonidine (CEC, 100 microM) failed to affect contractions to NA while nifedipine (1 microM) blocked them almost completely. 3. In rat spleen, the competitive antagonists (-)-discretamine, 5-MU and prazosin inhibited contractions to phenylephrine with pA2 values of 6.44, 7.19 and 9.45, respectively. CEC (100 microM) significantly reduced the maximum contraction to phenylephrine while nifedipine (1 microM) did not affect it. 4. In rat aorta, the competitive antagonists (-)-discretamine, 5-MU and prazosin inhibited contractions to NA with pA2 values of 7.60, 8.00 and 9.40, respectively. CEC also antagonized the contractions to NA in a competitive manner with a pA2 value of 6.10. 5. The specific binding of [3H]-prazosin to DDT1MF-2 and A10 cells was concentration-dependent and saturated at 3-5 nM with KD values of 0.24 +/- 0.02 and 0.20 +/- 0.02 nM, respectively. (-)-Discretamine,5-MU, CEC and prazosin inhibited specific [3H]-prazosin binding to DDTIMF-2 and AlO cells in a concentration-dependent manner with ICso values of 390.8 +/- 20.6, 43.6 +/- 3.9, 200.0 +/- 30.0 and 0.8 +/- 0.1 nM, respectively in DDTIMF-2 cells, and 25.0 +/- 3.2, 8.6 +/- 1.4, 1000.0 +/- 30.8 and 0.52 +/- 0.03 nM, respectively in AlO cells.6. Pretreatment of Al0 cells with CEC (10 MicroM) for 30 min and then washed out thoroughly, reduced specific [3H]-prazosin binding by 30%. The CEC-insensitive [3H]-prazosin binding was inhibited by(-)-discretamine with an IC50 value of 7.0 +/- 0.3 nM.7. 5-MU (100 nM), CEC (1 MicroM) and prazosin (10 nM) markedly inhibited NA (3 MicroM)-induced [3H]-inositol monophosphate formation in DDTIMF-2 and A1O cells, while (-)-discretamine (100 nM)inhibited NA-induced [3H]-inositol monophosphate formation only in AlO cells.8. In conclusion, (-)-discretamine is a selective alpha lD-adrenoceptor antagonist in vascular smooth muscle.Its selectivity among various al-adrenoceptor subtypes is alpha 1A: alpha1B: alpha1D =0.04:0.07:1.0.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1994

Pharmacological characteristics of liriodenine, isolated from Fissistigma glaucescens, a novel muscarinic receptor antagonist in guinea-pigs.

1. The pharmacological activities of liriodenine, isolated from Fissistigma glaucescens, were determined in isolated trachea, ileum and cardiac tissues of guinea-pigs. 2. Liriodenine was found to be a muscarinic receptor antagonist in guinea-pig trachea as revealed by its competitive antagonism of carbachol (pA2 = 6.22 +/- 0.08)-induced smooth muscle contraction. It was slightly more potent than methoctramine (pA2 = 5.92 +/- 0.05), but was less potent than atropine (pA2 = 8.93 +/- 0.07), pirenzepine (pA2 = 7.02 +/- 0.09) and 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, pA2 = 8.72 +/- 0.07). 3. Liriodenine was also a muscarinic antagonist in guinea-pig ileum (pA2 = 6.36 +/- 0.10) with a pA2 value that closely resembled that obtained in the trachea. 4. Liriodenine was 10 fold less potent in atrial preparations (left atria, pA2 = 5.24 +/- 0.04; right atria, pA2 = 5.35 +/- 0.09 and 5.28 +/- 0.07 for inotropic and chronotropic effects, respectively) than in smooth muscle preparations. 5. High concentration of liriodenine (300 microM) partially depressed the contractions induced by U-46619, histamine, prostaglandin F2 alpha, neurokinin A, leukotriene C4 and high K+ in the guinea-pig trachea. The inhibitions were characterized by a rightward shift in the concentration-response curves with suppression of their maximal contraction. 6. High concentration of liriodenine (300 microM) did not affect U-46619- or neurokinin A-induced tracheal contraction in the presence of nifedipine (1 microM) or in Ca(2+)-free (containing 0.2 mM EGTA) medium. 7. Neither cyclic AMP nor cyclic GMP content of guinea-pig trachealis was changed by liriodenine (30-300 microM). 8. It is concluded that liriodenine is a selective muscarinic receptor antagonist in isolated trachea, ileum and cardiac tissues of guinea-pigs. It is more potent in smooth muscle than in cardiac preparations. It also acts as a blocker of voltage-dependent Ca2+ channels at a high concentration (300 microM).

Animals↗
PubMed1994

Antimuscarinic action of liriodenine, isolated from Fissistigma glaucescens, in canine tracheal smooth muscle.

1. The antimuscarinic properties of liriodenine, isolated from Fissistigma glaucescens, were compared with methoctramine (cardioselective M2 antagonist) and 4-diphenylacetoxy-N-methylpiperidine (4-DAMP, smooth muscle selective M3 antagonist) by radioligand binding tests, functional tests and measurements of second messenger generation in canine cultured tracheal smooth muscle cells. 2. Liriodenine, pirenzepine, methoctramine and 4-DAMP displaced [3H]-N-methyl scopolamine ([3H]-NMS) binding in a concentration-dependent manner with Ki values of 2.2 +/- 0.4 x 10(-6), 3.3 +/- 0.7 x 10(-7), 8.9 +/- 2.3 x 10(-8) and 2.3 +/- 0.6 x 10(-9) M, respectively. The curves for competitive inhibition of [3H]-NMS with liriodenine, methoctramine and 4-DAMP were best fitted according to a two site model of binding, but pirenzepine was best fitted according to a model with one site. 3. Liriodenine and 4-DAMP displayed a high affinity for blocking tracheal contraction (pKB = 5.9 and 9.1, respectively) and inositol phosphate formation (pKB = 6.0 and 8.9, respectively), but a low affinity for antagonism of cyclic AMP inhibition (pKB = 4.7 and 7.8, respectively). 4. Methoctramine blocked cyclic AMP inhibition with a high affinity (pKB = 7.4), but it antagonized tracheal contraction and inositol phosphate formation with a low affinity (pKB = 6.1 and 6.0, respectively). 5. In conclusion, both M2 and M3 muscarinic receptor subtypes coexist in canine tracheal smooth muscle and are coupled to the inhibition of cyclic AMP formation and phosphoinositide breakdown, respectively. The antimuscarinic characteristics of liriodenine are similar to those of 4-DAMP. It may act as a selective M3 receptor antagonist in canine tracheal smooth muscle.

Adenylyl Cyclase Inhibitors↗
PubMed1994

Immunomodulation by levamisole in patients with recurrent aphthous ulcers or oral lichen planus.

The purpose of this study was to evaluate the effect of levamisole on the immune system of patients with recurrent aphthous ulcers (RAU) or oral lichen planus (OLP) in an open trial. Lymphocyte subsets, serum immunoglobulins, and circulating immune complexes (CIC) in patients with RAU or OLP and in normal control subjects were determined by an indirect immunofluorescence (IIF) technique with monoclonal anti-lymphocyte antibodies, by single radial immunodiffusion, and by precipitation with 3% polyethylene glycol, respectively. In addition, the anti-nuclear antibodies (ANA) and anti-basal cell antibodies (anti-BCA) in sera were detected by an IIF technique. We found a significant improvement in clinical symptoms and normalization of the decreased CD4/CD8 ratio in RAU patients after levamisole treatment. Moreover, the decreased CD4/CD8 ratio, which persisted until the remission stage in the untreated RAU patients, reverted to normal in the active late stage in the levamisole-treated patients. This reversion of aberrant cellular immunity in an earlier stage of the ulcer cycle may explain why RAU patients experience symptom improvement after levamisole treatment. Although RAU patients treated with levamisole for 1 to 3 or 4 months still had higher than normal levels of CIC and serum immunoglobulins, the levels of their IgA and IgM returned to normal values after 4 months of levamisole treatment. The serum ANA detected in 6 patients with RAU and 3 patients with erosive OLP disappeared after 1-22 months of levamisole treatment. The disappearance of serum anti-BCA was also observed in 50% of the anti-BCA-positive patients with erosive OLP after 3-13 months of levamisole treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗