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Biomedical subjects

R C Chen

Publications and source records attributed to R C Chen.

At least 55 records · Page 3Linked to original sources
PubMed1993

Effects of territrem-B on cholinergic responses of snail neuron.

Effects of territrem-B (TRB), a mycotoxin isolated from a rice culture of Aspergillus terreus, on the central neuron of the snail Achatina fulica were studied electrophysiologically. Territrem-B potentiated the acetylcholine (ACh) induced current of the neuron, while it had no effect on GABA or L-glutamate elicited currents. TRB and neostigmine increased the peak amplitude of the response elicited by the first perfusion of ACh and depressed the increase in current produced by a second perfusion. TRB and neostigmine showed different dose-dependent effects on ACh responses. The results suggested that TRB is a good tool for studying the physiological role of AChE in central neurons.

Acetylcholine↗
PubMed1993

Risk factors on the occurrence of response fluctuations and dyskinesias in Parkinson's disease.

We studied the risk factors that influence the occurrence of response fluctuations and dyskinesias in 194 patients with Parkinson's disease (PD). These factors included age at onset, disease severity at levodopa initiation, duration of illness prior to levodopa therapy and the daily dose of levodopa at the end of study. The first three were fixed covariates and the last one was time-dependent. Patients with age onset before 50 years showed a higher risk of developing response fluctuations (RF) and dyskinesias in univariate analysis. We estimated the combined effects of these covariates through multivariate analysis and found that the age at onset was the sole factor related to the incidence of both complications. Additionally, it was the only variable that could enter the predictive model of stepwise regression. Our observation suggested that age at onset determined the occurrence of RF and dyskinesias. Patients with younger age at onset had higher risk of developing these adverse effects.

Adult↗
PubMed1993

Activity of triciribine and triciribine-5'-monophosphate against human immunodeficiency virus types 1 and 2.

Triciribine (TCN) and its 5'-monophosphate (TCN-P) are novel tricyclic compounds with known antitumor activity; TCN-P is currently in phase II human clinical trials. We now report that these compounds have potent and selective activity against HIV-1 and HIV-2. Using a syncytial plaque assay, TCN and TCN-P were active against HIV-1 at 0.01-0.02 microM and had differential selectivities of 2250 and 1900, respectively, compared to 1850 for AZT. In contrast, TCN and TCN-P had minimal selectivity against human cytomegalovirus (50 and 27, respectively). TCN and TCN-P markedly inhibited HIV-1-induced p24 core antigen production, reverse transcriptase, and infectious virus production in a dose-dependent manner using HIV-1 acutely infected CEM-SS, H9, and persistently infected H9IIIB and U1 cells. In acutely infected PBL cells, TCN and TCN-P inhibited reverse transcriptase and infectious virus production but not p24 core antigen production. Using a microtiter XTT assay, TCN and TCN-P were active against a panel of HIV-1 and HIV-2 strains at IC50 values ranging from 0.02 to 0.46 microM. Evaluation of matched pairs of predrug and postdrug therapy HIV-1 isolates established that AZT-resistant and TIBO-resistant variants of HIV-1 were sensitive to TCN or TCN-P. Furthermore, unlike AZT and other fraudulent nucleosides, neither TCN, TCN-P, nor TCN-TP inhibited the viral reverse transcriptase. Thus, even though triciribine is a nucleoside chemically, it does not act biologically by classic nucleoside modalities but rather by a unique mechanism yet to be elucidated.

Acenaphthenes↗
PubMed1993

A randomized controlled trial on the treatment for acute partial ischemic stroke with acupuncture.

The effectiveness of acupuncture in acute stroke remains largely untested and unproved. A randomized, controlled trial was carried out to study the feasibility of acupuncture in combination with conventional supportive treatment for acute stroke patients. A total of 30 patients, aged 46-74, with the onset of symptoms within 36 h were enrolled into the study after appropriate screening. All patients gave informed consent. Basing on the same supportive treatment, patients were randomly assigned to a treatment with or without acupuncture. The procedure and acupoint selection were discussed and decided through several meetings of a group of senior acupuncture doctors in Taiwan. Acupuncture was applied 3 times/week for 4 weeks. During the study period, there were no problems in conducting this trial in terms of patient availability and acceptance, and physician cooperation. A significantly better neurologic outcome was observed in the acupuncture group on day 28 and day 90. The improvement in neurologic status was greatest in patients with a poor neurologic score at baseline. There were no important side effects except for one episode of dizziness related to acupuncture treatment. The data and results of this study will be used as a guideline for planning a full-scale clinical trial, e.g. sample size calculation, method of randomization with stratification of prognostic factors, choosing acupuncture points and technique of acupuncture.

Acupuncture Points↗
PubMed1992

Subclavian steal phenomenon: a correlation between duplex sonographic and angiographic findings.

Correlation of duplex sonography, angiography of the vertebral artery, and the degree of subclavian or innominate stenosis was carried out in ten patients with the subclavian steal phenomenon. Four successive stages of Doppler waveform were identified by duplex sonography. Three angiographic patterns of decreasing severity, permanent reversal, to-and-fro motion and delayed opacification, were found. Permanent reversal angiograms corresponded to complete reversal or late transient Doppler waveforms. To-and-fro motion and delayed opacification angiograms did not necessarily have a corresponding Doppler pattern. The different stages of subclavian steal phenomenon on duplex sonography correlated significantly with the degree of subclavian or innominate stenosis. Stenosis of at least 60% was found to produce abnormal vertebral artery Doppler sonography, except in one patient. Duplex sonography is considered to be a sensitive and convenient method for detecting abnormal vertebral artery haemodynamics and the subclavian steal phenomenon, but some other factors may be important in producing the Doppler waveforms.

Adult↗
PubMed1992

Effect of cavity depth on stresses in a restored tooth.

Restorative procedures commonly replace lost tooth structure, but redistribution of functional stresses after treatment is not fully understood. Many restorative methods are dictated by the integrity of the remaining tooth structure, because sparse tooth structure can lead to fracture. It is essential to prevent fractures by having a clear concept of the designs for cavity preparations, and to anticipate the stresses of mastication on the remaining tooth structure. Knowledge of various internal parameters of cavity designs would facilitate selection of the appropriate cavity preparation for a specific clinical situation. Three cavity designs and restorations were examined in this study for stresses using the finite element technique. After placement of restorative materials, the dentin experienced a dramatic change in stress gradient immediately below the pulpal wall, and this response was magnified in deeper cavity preparations. Enamel also exhibited major alterations in the stress gradient in all three designs of cavity preparations. The combination of the changes can cause cracks in the remaining tooth structure, leading to cusp fracture immediately adjacent to the deepest portion of the cavity.

Alveolar Process↗
PubMed1992

Is asymptomatic bronchial hyperresponsiveness an indication of potential asthma? A two-year follow-up of young students with bronchial hyperresponsiveness.

To determine the possibility that asymptomatic bronchial hyperresponsiveness (BHR) develops into symptomatic asthma, a two-year follow-up study was conducted in 81 students (48 male, 33 female; 11 to 17 years) who were found to have BHR in a 3,067 population survey (BHR group). Eighty-eight age-matched students (48 male, 40 female) with normal bronchial responsiveness served as control subjects. Daily symptom cards were recorded. Peak expiratory flow rate was measured for 24 h when symptoms occurred. Histamine inhalation tests were performed at the beginning of the study and at the end of the first and the second year. In the BHR group, 58 students remained bronchial hyperresponsive at the end of follow-up. Nine of 31 students with initially diagnosed bronchial asthma had their symptoms relieved entirely, but ten asymptomatic students developed asthma. The incidence of newly diagnosed asthma (12.5 percent in the BHR group or 20 percent in the asymptomatic BHR group) and the total percentage of diagnosed asthma (39.5 percent) in the BHR group were significantly higher than those (2.27 percent, 2.27 percent) in the control group. FVC and FEV1 showed no significant difference between two groups. PD20 FEV1 values in newly diagnosed asthmatics were significantly lower than those in asymptomatic students both at the beginning (3.05 +/- 1.56 mumol vs 6.14 +/- 1.60 mumol, p < 0.05) or the end (3.47 +/- 1.73 mumol vs 6.55 +/- 1.51 mumol, p < 0.05). The percentage of early respiratory illness was significantly higher in those with newly diagnosed asthma (80 percent) than in asymptomatic students (22.3 percent), but atopic index and the percentage of parental asthma showed no difference between two groups. In nine asthmatics whose symptoms were relieved entirely in the two-year follow-up, PD20 FEV1 was undetectable within the cumulative dose of 7.8 mumol of histamine in three students and rose from 4.58 +/- 1.85 mumol to 7.62 +/- 1.02 mumol in the remaining six. The higher the BHR, the more likely the students developed asthma. About 45 percent of asymptomatic students with PD20 < or = 3.2 mumol developed asthma in the following two years and 80 percent of them had a history of early respiratory illness, suggesting that they may have subclinical or potential asthma.

Adolescent↗
PubMed1992

[Facial or nasal mask pressure support ventilation in managing acute exacerbation of chronic respiratory failure in chronic obstructive pulmonary diseases].

11 COPD patients (age: 65 +/- 9 Yrs) with acute exacerbation of chronic respiratory failure (PaCO2 11.3 +/- 1.1kPa) were treated with mask pressure support ventilation, another 10 similar patients (age: 68 +/- 12 Yrs) served as control. BiPAP ventilator was used with the following modifications: (1) Non-rebreathing valve set-in proximal to mask; (2) 5 LPM oxygen flow delivered into mask to reduce the dead space effect. Mask ventilation was given 2-3 hours every time and 1-2 time daily for 7 days. Synchrony and airway patency were specially monitored. The results suggested that mask ventilation could reduce PaCO2, improve PaO2, relieve dyspnea and decrease the possibility of intubation.

Aged↗
PubMed1992

[Takayasu's arteritis: a study by vascular sonography with special emphasis on carotid duplex].

Takayasu's arteritis (TA) is a chronic inflammatory disease mainly affecting young females involving the great vessels; the aorta and its major branches. Diagnosis and delineation of patterns of involvement used to depend on intra-arterial angiography in the past. With the advent of high resolution duplex ultrasonographic technique, TA can be non-invasively inspected in the vasculitis phase. Based on our ultrasound study of cervical and lower extremity vessels, 6 patients were proved to have TA by angiography. Some characteristic carotid imaging findings can be identified at the sonographic probe detectable regions, i.e., (1) The inflammatory changes of TA mainly involved the proximal parts of 3 major cervical branches from the aortic arch, but the distal parts of them and the internal carotid arteries are relatively spared. (2) The inflammatory plaques of TA are relatively homogeneous in appearance, concentric in deposition and a long extent of involvement. Differential diagnosis between TA and atherosclerotic changes can be made by the preferential sites, echogenic properties, length of involvement and manner of proliferation. Regular follow-up by ultrasonography in 2 patients showed that response to treatment and disease progression could be easily monitored.

Adult↗
PubMed1992

Clinical manifestations of bronchogenic carcinoma.

A retrospective clinical study was carried out on 227 pathologically proven cases of bronchogenic carcinoma from eastern Taiwan, between October 1986 and March 1990. The ratio of males to females was low (2.15:1). The most common cell type was adenocarcinoma (39.2%), with squamous cell carcinoma (36.1%) being the second most common. Adenocarcinoma contributed to 51.4% of the bronchogenic carcinoma in women and 33.5% in men. History of cigarette smoking was strongly associated with squamous cell carcinoma and small cell carcinoma. The most common symptom was a cough (69%). The majority of small cell carcinoma and squamous cell carcinoma appeared to be of the central type in location while most adenocarcinoma appeared to be of the peripheral type. Bronchoscopic examination was the most valuable method for confirming the diagnosis of bronchogenic carcinoma. Most patients presented late and only 19 cases (8.4%) underwent surgery. Aborigines have a lower risk of developing bronchogenic carcinoma. The clinical manifestations of bronchogenic carcinoma in eastern Taiwan are similar to those found in Taiwan as a whole.

Adenocarcinoma↗
PubMed1991

Trauma, especially of the submandibular glands, causes release of epidermal growth factor into bloodstream in mice.

Submandibular glands in mice were traumatized by handling and then removed. Immunoreactive epidermal growth factor (EGF) in serum increased after 5 min and continued to increase, reaching at 1 h a peak of 50-fold normal in males and twice normal in females. If after traumatization the glands were repositioned with their blood supply intact, maximal increase of serum EGF at 1 h was 190-fold control values in males and 2-fold in females. In male mice, incision of abdominal wall skin led to a 15-fold increase of EGF in the serum; this rise was absent 3 days after sialoadenoectomy. After traumatization, repositioned submandibular glands lost 80% of their EGF; after the abdominal wall incision, only 30%. Following removal of submandibular glands, decrease of EGF level in serum was very slow: to 60% of the initial value after 3 days and to 40% after 10 days. By the HPLC characteristics, immunoreactive EGF in control serum and at its peak were indistinguishable. Urinary excretion of EGF was significantly elevated only when its serum level was 190-fold normal. We conclude that traumatized submandibular glands discharge into circulation a large part of their stored EGF. A similar but much less pronounced process takes place after abdominal skin incision. The presence of EGF in serum after its slow decline in sialoadenoectomized mice shows that a fraction of circulating EGF may recirculate prolonging its apparent half-life.

Animals↗
PubMed1991

The syndrome of ophthalmoplegia, ataxia and areflexia (Fisher's syndrome): clinical analysis of 9 cases.

From January 1976 through December 1988, 9 patients with clinical manifestations of the syndrome of ophthalmoplegia, ataxia and areflexia were diagnosed at National Taiwan University Hospital. Among them, 2 patients experienced recurrent attacks. A total of 12 attacks were recorded. Preceding symptoms of upper respiratory tract infection were noted in 9 out of 12 attacks. A spectrum of neuro-ophthalmological manifestations was observed. Most of these findings were probably secondary to central nervous system involvement. An elevation of protein level without pleocytosis was found in CSF examination of 6 attacks. Electrodiagnostic studies suggested large myelinated sensory fibers involvement as the major finding in 5 patients. A benign course in all 9 patients was noted. Special attention to nosological position and unusual features are also discussed.

Adolescent↗
PubMed1991

Abbreviated rating score for Parkinson's disease.

A total of 240 patients of Parkinson's disease (PD) were studied (125 male, 115 female). The age of onset was 60.0 +/- 9.9 years(Y) (mean +/- S.D.) (range 30-87). A 0-4 rating score was applied on each of 6 major symptoms: i.e. tremor, rigidity, bradykinesia, gait, activities of daily living and fluctuation with maximum score of 24. According to the Hoehn and Yahr's stages, there were 44 cases in stage I, 141 in stage II, 31 in stage III, 19 in stage IV and 5 in stage V. Fluctuation in symptoms occurred in 42.9%, dyskinesia in 7.1%, psychosis in 9.6%, depression in 4.6%, and dementia in 2.9%. The mean duration of PD was 4.9 +/- 4.5 Y with 40% 5 years or longer. Significantly longer duration of PD was seen in the patients suffering from fluctuation (6.7 +/- 4.7 Y), dyskinesia (10.7 +/- 6.7 Y) and psychosis (9.4 +/- 6.5 Y). The mean duration of L-dopa treatment was 4.1 +/- 3.4 Y. The patients showing fluctuation (6.2 +/- 4.0 Y) or dyskinesia (7.6 +/- 4.7 Y) had significantly longer duration of L-dopa treatment. The mean daily dose of L-dopa was 370 +/- 203 mg. The patients with fluctuation (430 +/- 187 mg) or dyskinesia (545 +/- 265 mg) received significantly higher dose of L-dopa. Dementia tended to occur in the patients having later age of onset of PD (71.2 +/- 11.2 Y). The symptom score was significantly worse in those with fluctuation, dyskinesia, psychosis and dementia. It was well correlated with the Hoehn and Yahr's staging system.

Adult↗
PubMed1990

Bronchial hyperresponsiveness in young students of southern China: relation to respiratory symptoms, diagnosed asthma, and risk factors.

A cross sectional study was carried out to determine the prevalence of bronchial hyperresponsiveness and asthma in 3067 students aged 11-17 years in an urban and a rural area of Guangzhou (Canton), China. The methods used included a self administered questionnaire, a histamine bronchial provocation test, and allergen skinprick tests. Bronchial hyperresponsiveness was defined as a 20% fall in FEV1 and peak expiratory flow at a provoking dose of histamine (PD20) less than 7.8 mumol on two occasions four weeks apart. The response rate was 98.0% and 99.2% in the two areas. The prevalence of bronchial hyperresponsiveness was 4.1% and of diagnosed asthma 2.4% in the total population. There were no significant differences in prevalence between the urban and the rural area or between boys and girls. The 11-12 year group had a higher prevalence of bronchial hyperresponsiveness (7.6%) than the older groups. Of the 125 with bronchial hyperresponsiveness, 12.0% were defined as having severe or moderate (PD20 less than 0.8 mumol), 26% mild (0.9-3.2 mumol), and 62% slight bronchial hyperresponsiveness (3.3-7.8 mumol). The severity of bronchial hyperresponsiveness was closely related to diagnosed asthma, wheezing, and cough, though half the students with bronchial hyperresponsiveness were symptom free. The most common allergens were house dust and house dust mite in the city, and hay dust, pollen, and feathers in the rural area. The odds ratios for having respectively slight, mild or moderate, and severe bronchial hyperresponsiveness were 5.9, 21.0, and 30.4 for atopy; 1.9, 1.9, and 7.3 for early respiratory infection; and 3.1, 2.5, and 5.6 for a history of parental asthma.

Adolescent↗
PubMed1989

Distribution of thalamic nociceptive neurons activated from the tail of the rat.

The purpose of the present study was to map systematically in the thalamus the distribution of neurons processing nociceptive information from the tail of the rat. Pentobarbital-anesthetized and gallamine-paralyzed rats were used. Glass microelectrodes were used to record extracellularly from thalamic neurons. Noxious radiant heat stimuli were applied to the tail with a tail-flick apparatus, and the recorded neurons were localized with horseradish peroxidase deposits or by marking electrodes left in situ. A number of 121 neurons were tested of which 45 responded. Of these, 13 were located in the ventrobasal complex (VB), 17 were located in the central lateral nucleus and the parafascicular nucleus of the intralaminar nuclei (ILN). The rest of the responding neurons were located in the posterior group, the reticular thalamic nucleus, and the zona incerta. The nucleus submedius was not examined specifically. It is concluded that the VB and the ILN are two of the most important thalamic nuclei for processing nociceptive information from the tail of the rat.

Action Potentials↗
PubMed1989

Neurological complications of sarcoidosis.

The medical records of 285 patients at Royal Prince Alfred Hospital with a definite diagnosis of sarcoidosis over the period 1973-87 were reviewed. Fourteen (4.9%) had involvement of the nervous system, in 8 of whom the neurological manifestations were the presenting feature of the disease. The age range of neurosarcoidosis was 22 to 79 years and there was a female preponderance (10:4). Neurological complications (some patients experienced more than one complication) were facial nerve palsy (4), myopathy (3), aseptic meningitis (3), deafness/vertigo (2), hydrocephalus (2), hypopituitarism (2) and peripheral neuropathy (1). Most patients received corticosteroid therapy. Two patients required neurosurgical management for hydrocephalus and 1 for pituitary sarcoid. The frequency and type of neurological complications in this Australian study are similar to those reported from the Northern Hemisphere.

Adolescent↗