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Biomedical subjects

C H Chen

Publications and source records attributed to C H Chen.

At least 343 records · Page 19Linked to original sources
PubMed1997

Effects of pimobendan and its active metabolite, UD-CG 212 Cl, on Ca2+-activated K+ channels in vascular smooth-muscle cells.

The aim of this study was to clarify the mechanisms of activation of Ca2+-dependent K+ (K(Ca)) channels by pimobendan, a new cardiotonic and vasodilator agent with phosphodiesterase inhibition properties, and its main metabolite, UD-CG 212 Cl, in vascular smooth-muscle cells from porcine coronary arteries. Both pimobendan and UD-CG 212 Cl induced relaxation of porcine coronary artery strips. However, in the presence of 100 microM Rp-cAMPS (Rp diastereomer of adenosine cyclic 3',5'-phosphorothioate), a membrane-permeable antagonist of cAMP, the effects of pimobendan decreased significantly. Application of 1 microM pimobendan activated K(Ca) channels in cell-attached patches, and this increase in activity was suppressed by 100 nM H-89 (N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide), a cAMP-dependent protein-kinase inhibitor. Pimobendan was ineffective in altering the activity of K(Ca) channels in inside-out patches. In contrast, UD-CG 212 Cl, at a concentration of 1 microM, activated K(Ca) channels not only in cell-attached patches but also in inside-out patches. Application of 100 nM H-89 also inhibited UD-CG 212 Cl-induced K(Ca) channels activity but to a lesser degree than that induced by pimobendan in cell-attached patches. In conclusion, there are two mechanisms of activation of K(Ca) channels by pimobendan and UD-CG 212 Cl. Activation by pimobendan occurs primary through the cAMP pathway, whereas UD-CG 212 Cl activates K(Ca) channels directly as well as through the cyclic AMP pathway.

Animals↗
PubMed1997

Lack of allelic association between 102T/C polymorphism of serotonin receptor type 2A gene and schizophrenia in Chinese.

Recent studies have reported an association between a 102T/C polymorphism of serotonin receptor type 2A gene (5-HT2A) and schizophrenia. In addition, an association was detected between a 102T/C polymorphism of the 5-HT2A receptor gene and drug response to clozapine in the treatment of schizophrenic patients. These studies suggest an important role of the 5-HT2A gene in schizophrenia. To study the possible involvement of the 5-HT2A gene in the pathogenesis of schizophrenia, a case-control association study was carried out in a Chinese population from Taiwan. No significant differences of genotype distributions, allele frequencies and homozygosity were detected between schizophrenic patients (n = 177) and nonpsychiatric controls (n = 98). When subjects were divided into subgroups according to sex, still no differences of allele frequencies or genotype distributions were noted between patients and controls. Our data do not support an allelic association between the 102T/C polymorphism of the 5-HT2A receptor gene and schizophrenia in Chinese population.

Alleles↗
PubMed1997

Case report: successful palliative treatment with intraperitoneal OK-432 injection for epithelioid haemangioendothelioma presenting with intractable ascites.

Epithelioid haemangioendothelioma is an unusual type of endothelium-derived vascular tumour of borderline malignancy, which has high variability in clinical presentations, depending on the primary site of involvement. We report on a 20-year-old woman who presented with progressive abdominal fullness for 6 months. Multiple lung and liver nodules with pleural effusion and profuse ascites were found. The diagnosis of epithelioid haemangioendothelioma was made after wedge biopsy of the liver. The ascites was intractable and refractory to strong diuretic therapy and repeated paracentesis. Therefore, six courses of intraperitoneal injection of OK-432 were administered. The ascites subsided to a minimal amount after treatment and the patient remained symptom-free for approximately 8 months. The ascites recurred later and another three courses of intraperitoneal injection of OK-432 were administered. The ascites disappeared again. The patient has remained symptom-free since the end of the second period of treatment.

Adult↗
PubMed1997

Influence of reference electrodes, stimulation characteristics and task paradigms on auditory P50.

To clarify the nature of auditory P50, middle latency auditory evoked potentials were recorded by using different conditions of reference electrodes (linked earlobes, LE; balanced non-cephalic, BN), stimulation characteristics (tone burst, human voice) and tasks (counting, simple reaction) in 10 right-handed males (aged 21-36 years). EEG was recorded from Fz, Cz, Pz, C3, C4, T3 and T4 according to the 10-20 system. Two groups of electrode sites were made for the statistical analysis: a midline group, Fz, Cz and Pz, and a lateral group, T3, C3, Cz, C4 and T4. The results were that the P50 amplitudes with BN electrodes were significantly higher than those with LE in both groups (midline, P < 0.01; lateral, P < 0.01); the P50 amplitudes by voice stimulation were significantly higher than those by tone stimulation in the lateral group (P < 0.05), and the P50 latencies under a simple reaction paradigm were significantly shorter than those under a counting task in both groups (midline, P < 0.05; lateral, P < 0.05). These results suggest that various factors including motor response affect the P50 amplitudes and latencies.

Acoustic Stimulation↗
PubMed1997

Negative correlation of reaction times and the auditory P50 in a Go, No-Go paradigm.

We investigated the relationship between reaction times in a Go, No-Go paradigm and various components of the auditory event-related potentials. The P50 latencies in the Go trials were significantly earlier than those in the No-Go trials. The N200 and P300 were positively associated with the reaction times. However, the P50 latencies showed negative correlation with the reaction times, and the negative correlation at F3 was the largest. Referring to source studies on P50, it is suggested that the activation of either the ascending activating system or the left premotor area through that system might affect the speed of reaction.

Adult↗
PubMed1997

A study of verbal and spatial information processing using event-related potentials and positron emission tomography.

The activated cerebral regions and the timing of information processing in the hemispheres was investigated using event-related potentials (ERP) and regional cerebral blood flow (rCBF) as the neurophysiological indicators. Seven men and one woman (age 19-27 years) were asked to categorize two-syllable Japanese nouns (verbal condition) and to judge the difference between pairs of rectangles (spatial condition), both tests presented on a monochrome display. In the electroencephalogram (EEG) session, EEG were recorded from 16 electrode sites, with linked earlobe electrodes as reference. In the positron emission tomography (PET) session, rCBF were measured by the 15O-labeled H2O bolus injection method. Regions of interest were the frontal, temporal, parietal, occipital and central lobes, and the entire cerebral hemispheres. When the subtracted voltages of the ERP in homologous scalp sites were compared for the verbal and spatial conditions, the significant differences were at F7.F8 and T5.T6 (the 10-20 system). The latencies of the differences at T5.T6 were around 200, 250 and 320 ms. A significant difference in rCBF between the verbal and spatial conditions was found only in the temporal region. It was concluded that early processing of information, that is, registration and simple recognition, may be performed mainly in the left temporal lobe for verbal information and in the right for spatial information.

Adult↗
PubMed1997

Peptide YY and the Y2 agonist PYY-(13-36) inhibit neurons of the dorsal motor nucleus of the vagus.

Peptide YY (PYY) is released by endocrine cells in the ileum in response to the presence of fatty acids in the intestinal lumen. Circulating PYY suppresses vagally mediated digestive functions as a consequence of direct action on neurons in the dorsal medulla. Recent evidence from our laboratory suggests that this PYY-mediated inhibition of digestion occurs because of peptide action at the Y2-type receptor in the dorsal medullary region encompassing vago-vagal reflex circuitry. The present study describes the effects of PYY and the specific Y2 agonist peptide PYY-(13-36) on neurons of the dorsal motor nucleus of the vagus (DMN) in both the 1) intact in vivo and 2) in vitro brain stem slice preparation. Our results show that 50% of DMN neurons recorded under in vivo or in vitro conditions, including synaptic blockade, are inhibited by the application of PYY or PYY-(13-36). Approximately 45% are not affected, and only approximately 5% are activated. These results suggest that one of the principal means by which PYY suppresses digestive functions is by the direct inhibition of cholinergic vagal efferent neurons of the DMN via action at a Y2 receptor.

Animals↗
PubMed1997

Inhibitory effects of hypercholesterolemia and ox-LDL on angiogenesis-like endothelial growth in rabbit aortic explants. Essential role of basic fibroblast growth factor.

Hypercholesterolemic (HC) rabbits exhibit suppressed compensatory vascular growth after restriction of arterial supply. However, neovascularization is commonly found in atheromas containing inflammatory cells. We used an in vitro model to determine the effects of hypercholesterolemia on angiogenesis in the absence or presence of inflammatory cells. HC rabbit aortic explants (1 mm2) with or without (n = 90 each) lesion-forming inflammatory cells were cultured in a collagen matrix with serum-free medium. Explant-derived endothelial cell growth was organized into capillary-like microtubes (CLM) that could be videomicroscopically quantified. CLM growth from lesion-free HC explants was significantly reduced to 13 +/- 4% of the value in explants (n = 90) from normocholesterolemic (NC, n = 15) rabbits (P < .001). In contrast, in lesion-containing HC explants, the matrix was invaded by foam cells, and CLM growth was not inhibited. Immunoassayable basic fibroblast growth factor (bFGF, in pg/mL) in the culture medium was significantly lower in lesion-free HC (< 5) than NC explants (11 +/- 2, P < .01) or HC explants with lesions (14 +/- 3). In addition, CLM growth was reduced in NC explants incubated with oxidized LDL (ox-LDL, 50-100 micrograms/mL). Exogenous bFGF (10 ng/mL) reversed the inhibitory effects of hypercholesterolemia and ox-LDL, whereas bFGF-neutralizing antibody (10 micrograms/mL) abolished CLM growth in all groups. In cultured rabbit aortic endothelial cells, ox-LDL reduced DNA synthesis, but this inhibition was reversed by bFGF. We conclude that hypercholesterolemia and ox-LDL inhibit angiogenesis like endothelial growth because of a suppressed availability of endogenous bFGF. Retained responsiveness to exogenous bFGF suggests that inducing bFGF expression at targeted sites may improve collateral growth in hyperlipidemic arterial disease.

Animals↗
PubMed1997

Foreign body aspiration into the lower airway in Chinese adults.

OBJECTIVES: Foreign body aspiration into the lower airway in adults is uncommon. We designed this study to investigate the clinical presentations, precipitating factors, management choice, and complications of foreign body aspiration in Chinese adults. PATIENTS AND METHODS: We analyzed 43 consecutive adult patients with foreign body aspiration between February 1980 and December 1995 from the medical record registry and cross index system of a tertiary medical center. RESULTS: The most common symptoms are chronic cough, hemoptsis, fever, and dyspnea. Only three patients (7%) presented with choking. Chest radiograph demonstrated the foreign body in nine cases (21%). The most common foreign body was bone fragments (21/43, 49%). Lodgment is more common in the right, especially the right intermediate bronchus and basal bronchus. Three patients were also diagnosed as having lung cancers. Precipitating factors include CNS dysfunction, facial trauma, intubation, dental procedure, and underlying pulmonary diseases. Flexible fiberoptic bronchoscopy removed the foreign body in 25 cases (58%) during the first attempt and 32 cases (74%) in total. Complications include obstructive pneumonitis (including one case of actinomycosis infection), atelectasis, bronchiectasis, lung abscess, and lung torsion (two cases). CONCLUSION: The nature of foreign body in Chinese adults was different from the Western adults. The initial clues to foreign body aspiration in adults are usually obscure or indirect. We suggest flexible fiberoptic bronchoscopy as the first-line approach. Follow-up bronchoscopy and chest radiograph are recommended to detect chronic complications or coexisting lung cancer.

Adult↗
PubMed1997

Involvement of nitric oxide and N-methyl-D-aspartate in acute hypoxic altitude convulsion in mice.

BACKGROUND: Altitude convulsion is a rather specific form of experimental convulsion which is induced by acute exposure to a hypobaric hypoxic condition. Several neurotransmitters have been shown to be involved in the mechanisms of altitude convulsions. However, their roles and interaction were not clear. HYPOTHESIS: The novel neurotransmitter nitric oxide (NO) may be involved in the mechanisms of altitude convulsion through its neuronal signalling roles in relation to the NMDA receptor. METHODS: There were 177 mice intraperitoneally administrated (i.p.) with several drugs. The altitude convulsion threshold (ACT) was used as an index to evaluate the acute hypoxic tolerance. RESULTS: NO synthesis precursor, L-arginine (20, 40, 200, 800 mg/kg), resulted in a dose-dependent decrease in the ACT in mice, while the NO synthase (NOS) inhibitor, NG-nitro-L-arginine-methyl ester (L-NAME, 1.25, 2.50, 5.00 mg/kg, i.p.) increased the ACT. Pretreatment with L-NAME (5.0 mg/kg) prior to L-arginine (200 mg/kg) administration prevented the effect of decreasing ACT caused by L-arginine. Similarly, N-methyl-D-aspartate (NMDA, 2.5, 10.0, 20.0 mg/kg, i.p.) yielded a decrease in the ACT in mice and this decrease in hypoxic tolerance caused by NMDA can be prevented by pretreatment with either NMDA receptor antagonist 2-amino-5-phosphovalerate (AP-5, 20.0 mg/kg, i.p.) or NOS inhibitor L-NAME (5.0 mg/kg, i.p.). CONCLUSIONS: These findings suggest an important signalling role for nitric oxide and NMDA in the development of altitude convulsion and further support the hypothesized relationship between NMDA-receptor mediated neurotoxicity and nitric oxide.

Acute Disease↗
PubMed1997

Presumptive identification of streptococci by pyrrolidonyl-beta-naphthylamide (PYR) test.

BACKGROUND: Group A streptococci and enterococci can be differentiated from other streptococci on the basis of their ability to cleave L-pyrrolidonyl-beta-naphthylamide. METHODS: In the present study, the L-pyrrolidonyl-beta-naphthylamide (PYR) test, pigment medium and bile esculin medium have been used to presumptively identify the streptococci. In total, 114 strains of group A streptococci, 350 strains of non-group A streptococci, 202 strains of enterococci and 197 strains of non-enterococci have been tested. RESULTS: The results of the present investigation show that sensitivities of different test methods are: PYR broth, 99.08%; Murex PYR, 98.48%; bacitracin, 95%; bacitracin and sulfamethoxazole/trimethoprim (SXT), 95%; pigment medium, 99.23%; bile esculin medium, 99.26%. Additionally, specificities of various tests are: PYR broth and Murex PYR, 99.82%; bacitracin, 90.90%; bacitracin and SXT, 98.87%; pigment medium and bile esculin medium, 100%, respectively. CONCLUSIONS: PYR test has been observed to be very easy to use and may hence be considered as a rapid, reliable and cost-effective method for presumptive identification of group A streptococci and enterococci in the clinical laboratory.

Enterococcus↗
PubMed1997

Atherosclerosis as a microvascular disease: impaired angiogenesis mediated by suppressed basic fibroblast growth factor expression.

We present evidence that hypercholesterolemia and oxidized low-density lipoprotein (ox-LDL) impair endothelial cell growth by suppressing basic fibroblast growth factor (bFGF) expression. Background studies show that diet-induced hypercholesterolemia in rabbits impairs hyperplastic lumen-expanding remodeling of the carotid artery in response to a chronic flow load. Hypercholesterolemia also markedly impairs compensatory macrovascular and microvascular growth in rabbit ears with surgical restriction of arterial supply. In an in vitro model of angiogenesis, arterial explants cultured in a three-dimensional collagen gel exhibited organized endothelial cell growth with formation of capillary-like microtubes (CLM). CLM growth was sensitive to inhibition by neutralizing antibodies against bFGF. With explants excised from both the aorta of hypercholesterolemic rabbits and from coronary arteries of patients with coronary arteriosclerosis, CLM growth and release of immunoassayable bFGF to the culture medium were suppressed. Growth suppression was reversed partially by exogenous bFGF. In control explants, ox-LDL produced a suppression of CLM growth that could be reversed by exogenous bFGF. In endothelial cells in culture, ox-LDL suppressed bFGF expression and DNA synthesis in a dose-dependent manner. We conclude that atherosclerosis is associated with impaired bFGF-dependent endothelial cell growth manifested by impaired adaptive growth responses of large arteries and microvessels.

Animals↗
PubMed1997

Apolipoprotein B gene polymorphisms in Taiwanese ischemic stroke patients.

We analyzed the AluI restriction fragment length polymorphism (RFLP) of the apolipoprotein B (apoB) gene to determine the association between AluI allelic distribution and the occurrence of ischemic stroke in Taiwan. A total of 44 healthy volunteers and 159 ischemic stroke patients were included in the study. The allele frequency of AluI was very similar in the two groups, 0.87 in the patient group and 0.89 in the control group, for the major allele A-. The distribution of A-/A-, A-/A+, and A+/A+ genotypes of the patients was not significantly different from that of the controls. Among ischemic stroke patients, the A+ allele of the AluI restriction site was significantly associated with elevated apoB levels. The results of this study suggest that the presence of the rare AluI RFLP may contribute to an elevated plasma apoB level, which is a known risk factor for ischemic stroke.

Aged↗
PubMed1997

A hypertension control program in Yu-Chi, Taiwan: preliminary results.

The purpose of this study was to evaluate the feasibility and effectiveness of a community approach to hypertension control in both high risk and general populations in an agricultural district with limited medical and community resources. It was conducted in Yu-Chi district of Nan-Tou county in central Taiwan from 1993 to 1994. The study included blood pressure screening, follow-up, health education, village-based campaigns, and program evaluation after 6 months of intervention. Two villages each were randomly assigned to intervention and control groups. Intervention comprised visits by trained volunteers to measure blood pressure and body weight, and education related to hypertension. All residents 40 years of age and older were enrolled. A total of 471 residents from the intervention villages and 426 residents from the control villages completed the study. Overall, for the intervention and control groups, the knowledge and behavior related to hypertension improved significantly 6 months after the baseline survey. The improvement was greater in the subgroup of hypertensives in the intervention group than in the controls. The educational intervention also significantly improved the status of awareness, treatment, and the control of hypertension, and reduced blood pressure in the hypertensive subjects. We conclude that a hypertension control program that relies solely on limited community resources is feasible and effective.

Adult↗
PubMed1997

[Reasons of failure in blocking mother-infant transmission of HBV by using vaccine and related strategies].

We have detected the serum marker of HBV of 32 mothers whose HBsAg present positive and their children whom were given Hepatitis B vaccine immunization throughout duration of their mothers' pregnancy, altogether making up 66 cases. In 3 of these 32 families, Hepatitis B vaccine failed to block transmission between mother and infant. Direct nucleotide sequence analysis of HBV were carried out in 7 HBsAg positive infected persons. To confirm the possibility of HBV transmission between mother and infant on molecular level, we used PCR technique and DNA sequencing method. The reasons of which HBV vaccine failed in blocking transmission were discussed at the point of views of virus variation. Besides, we make and emphasized discussion on how to tighten up the measurement of controlling the course of infection and protecting susceptible population.

DNA, Viral↗
PubMed1997

Sequential changes of esophageal motility after endoscopic injection sclerotherapy or variceal ligation for esophageal variceal bleeding: a scintigraphic study.

OBJECTIVE: Endoscopic injection sclerotherapy and variceal ligation are two popular endoscopic methods used to treat esophageal variceal hemorrhage. These two methods have not been compared with regard to esophageal dysfunction after treatment. This is a prospective investigation of esophageal dysmotility after endoscopic injection sclerotherapy and variceal ligation. METHODS: Sequential changes of esophageal motility after endoscopic injection sclerotherapy (n = 25) and variceal ligation (n = 25) were investigated in 50 cirrhotic patients with recent variceal bleeding. Another 22 cirrhotics without esophageal varices were included as controls. Radionuclide esophageal transit tests were performed before initial endoscopic treatment, and 1 and 3 months after variceal eradication. RESULTS: The baseline esophageal transit time was longer in both the sclerotherapy (n = 25, 7.8 +/- 1.4 s) and ligation groups (n = 25, 8.2 +/- 1.8 s) than in controls (n = 22, 6.7 +/- 0.7 s, p < 0.005). The transit time was longer in patients with large varices than in those with small varices (8.3 +/- 1.7 vs. 7.2 +/- 0.7 s, p < 0.05). In the sclerotherapy group, the transit time was prolonged 1 month after variceal eradication, compared with its pretreatment state (n = 20, 7.6 +/- 1.5 vs. 10.0 +/- 2.2 s, p < 0.0001) but was shortened at 3 months compared with 1 month after variceal eradication (n = 12, 10.7 +/- 1.5 vs. 8.6 +/- 2.2 s, p < 0.05). Multiple regression analysis showed that the number of treatment sessions required to eradicate varices was the only significant factor associated with prolonged transit time (p < 0.05). In the ligation group, the transit time changed little at 1 month or 3 months after variceal eradication. CONCLUSIONS: Impairment of esophageal motility can be significant with endoscopic injection sclerotherapy but is reversible. However, endoscopic variceal ligation exerts no significant impact on esophageal motility.

Esophageal and Gastric Varices↗