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Biomedical subjects

D C Chung

Publications and source records attributed to D C Chung.

At least 55 records · Page 3Linked to original sources
PubMed1990

Correlation between integrated evoked EMG and respiratory function following atracurium administration in unanaesthetized humans.

In six healthy volunteers, integrated evoked electromyography (IEEMG) measured in response to ulnar nerve stimulation was correlated with respiratory function-tidal volume (VT), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), maximum negative inspiratory pressure (NIP), hand grip (HG) and head-lift during steady-state infusion of subparalytic doses of atracurium. Studies were carried out at train-of-four T4/T1 = 0.2 and T4/T1 = 0.6. When T4/T1 = 0.2, all subjects had difficulty with swallowing and phonation, none could sustain any head-lift and HG was 26 per cent of control. However, VT was normal, FVC was 80 per cent, FEV1 was 82 per cent, and NIP was 50 per cent of control. AT T4/T1 = 0.6, all assessments of peripheral strength were normal, and all respiratory measurements were not significantly different from control, except for NIP which was 73 per cent of control (P less than 0.05). We conclude that an IEEMG of 0.6, recorded from the hypothenar muscles, in unanaesthetized subjects is consistent with near normal respiratory function.

Adult↗
PubMed1990

Heymann antigen GP330 demonstrates affinity for fibronectin, laminin, and type I collagen and mediates rat proximal tubule epithelial cell adherence to such matrices in vitro.

We have utilized monoclonal antibodies directed against glycoproteins on the surface of proximal tubule epithelial cells (PTEC) to study their interaction with matrix components. PTEC exposed to monoclonal antibodies directed against a 330-kDa cell surface glycoprotein exhibited a significant epitope-specific inhibition of attachment and proliferation on type I collagen-, fibronectin-, laminin-, and gelatin-coated tissue culture surfaces. This effect was not due to antibody toxicity since such cells did not exhibit metabolic dysfunction in suspension cultures and the inhibition could be reversed upon removal of the antibody from the cell surface. Furthermore, detergent-solubilized gp330 demonstrated specific affinity for fibronectin, laminin, and type I collagen which was not inhibited by Arg-Gly-Asp-containing peptides. A monoclonal antibody directed against the receptor epitope was capable of promoting PTEC adherence and growth when such an antibody was immobilized on cell culture dishes. Although gp330 acted as a receptor for matrix proteins in primary cultures of freshly isolated PTEC, this effect was not demonstrable in established cultures. These results suggest that freshly isolated PTEC depend on gp330 for their attachment to matrix molecules while in vitro-adapted PTEC rely on other receptors activated by culture conditions. The affinity of gp330 for matrix molecules may be of pathogenic relevance in the persistence of gp330-containing immune complexes formed in the glomerular capillary wall in experimental membranous nephropathy (Heymann nephritis).

Animals↗
PubMed1989

Seroepidemiology of hepatitis B virus, hepatitis D virus, and human immunodeficiency virus infections among parenteral drug abusers in southern Taiwan.

A total of 390 parenteral drug abusers (PDAs) at the Kaohsiung Municipal Narcotics Abstention Institute were examined for markers of hepatitis B virus (HBV), hepatitis D virus (HDV), and human immunodeficiency virus (HIV). All sera were tested for hepatitis B surface antigen (HBsAg), surface antibody (anti-HBs), and core antibody (anti-HBc) by radioimmunoassay (RIA) and for antibody to HIV (anti-HIV) by enzyme-linked immunosorbent assay (ELISA). Hepatitis B e antigen (HBeAg) and antibody to HDV (anti-HDV) were also tested for HBsAg-positive serum samples. Although the HBsAg-positive rate (22.1%) among PDAs was similar to that of the general population in southern Taiwan, the HBV infection rate (99.2%) and the anti-HDV-positive rate (78.5%) among HBsAg-positive subjects were significantly higher than those of the general population in southern Taiwan (P less than 0.0001). None of the PDAs studied were positive for anti-HIV. The levels of serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) among PDAs were significantly higher than those of the general population in southern Taiwan (P less than 0.0001). The more frequent the institutionalisation, the higher the infection rates with HBV and HDV and elevated levels of SGOT and SGPT. Horizontal transmission through parenteral drug abuse may be considered a possible reason for the significantly higher rates of HBV and HDV among parenteral drug abusers.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Impedance to transesophageal atrial pacing: significance regarding power sources.

Transesophageal stimulation is an expeditious method of atrial pacing. Using pulse widths of 10 msec results in reduction of current requirement to values that are usually less than 15 mA. An unknown variable in transesophageal atrial pacing has been impedance. In this study, we investigated the impedance to transesophageal atrial pacing in ten patients using a stimulator with a 63 V power source capable of delivering constant current to 20 mA against an impedance of 2,000 ohms. A bipolar electrode was used to deliver stimuli with a current of 15 mA. Voltage across a known resistance and current were measured on an oscilloscope and the impedance was calculated. Pacing thresholds were also performed and ranged from 6.2 to 16.5 mA (mean 9.4 +/- 2.9 mA, SD). Impedance varied between 720 and 2,670 ohms (mean 1,750 +/- 540 ohms). The stimulator used to measure impedance in man and two other commercially available stimulators were bench tested against known resistances of 500 to 2,000 ohms. The other stimulators with power sources of 12.5 and 15 V had attenuation of the delivered current at resistances of between 1,000 and 2,000 ohms. Thus, this study has demonstrated that transesophageal atrial pacing incurs impedances two to five times greater than incurred with intracardiac pacing leads. Therefore stimulators with high power sources are required to deliver the programmed current against these impedances.

Atrial Function↗
PubMed1989

[A study on the prevalence and risk factors of muscular fibrotic contracture in Jia-Dong Township, Pingtung County, Taiwan].

In order to examine the prevalence and risk factors of muscular fibrotic contracture (MFC) among school children in Jia-Dong Township, Pingtung County, a prevalence survey combined case-control study was carried out from January to April, 1988. All the school children aged from 6 to 19 years old were first screened at schools and then referred to the Provincial Pingtung Hospital for confirmatory diagnosis based on the non-invasion criteria. A total of 83 MFC cases were identified including 79 gluteal fibrotic contracture (GFC) patients, 3 deltoid fibrotic contracture (DFC) patients, and 1 affected both GFC and DFC. The prevalence was significantly higher in males (17.3 per 1,000) than in females (10.5 per 1,000). The prevalence was found to increase with age after 6 years of age, peaked at the age group of 13-15 years, and decline thereafter. Most MFC cases clustered in both Wen-Fon and Yuan-Wen villages locate in the southern coast of Taiwan Island. Among 83 MFC patients, 65 were further interviewed to obtain information on the risk factors of MFC. A total of 65 healthy classmates one-to-one matched with MFC cases on aged, sex, and living villages were selected as the control group which was also interviewed. The case-control study showed a positive association between the frequency of injection and the MFC in a dose-response relationship. The injection site also correlated with the development of the GFC and DFC. It was reasoned that the injection might be the most important risk factor of MFC. Follow-up study of 65 operated MFC cases indicated a high percentage (89.2%) of hyperscar formation in the incision region.

Adolescent↗
PubMed1988

Seroepidemiological studies on hepatitis B and D viruses infection among five ethnic groups in southern Taiwan.

In order to compare the prevalence of hepatitis B virus (HBV) and hepatitis D virus (HDV) infection among five ethnic groups in Pingtung County of southern Taiwan, a total of 240 serum samples were collected from September to October, 1985, from the following five ethnic groups: Taiwanese, Hakka, Mainland Chinese, aboriginal Paiwanese, and aboriginal Rukaiese. Ages of subjects ranged from 5 to 69 years. All sera were tested for hepatitis B surface antigen (HBsAg), surface antibody (anti-HBs), and core antibody (anti-HBc) by radioimmunoassay (RIA). Hepatitis B e antigen (HBeAg) and antibody to hepatitis D antigen (anti-HDV) were also tested for those with HBsAg-positive sera. Results showed that 44.1% of all sera examined were negative for HBsAG but positive for both anti-HBs and anti-HBc; additionally, 24.6% were negative for both HBsAg and anti-HBs but positive for anti-HBc. Only 134 serum samples showed negative results for HBV markers, indicating an HBV infection rate of 88.8%. The anti-HDV positive rate was estimated to be 2.7% among HBsAg-positive subjects. The HBsAg-positive rates among Rukaiese, Paiwanese, Hakka, Taiwanese, and Mainland Chinese were 25.8, 22.5, 16.7, 12.9, and 10.0%, respectively; while the prevalence rates of HBV infection among the above five groups were 94.2, 94.6, 85.4, 87.5, and 82.5%, respectively. Differences in the HBsAg-positive rate and HBV infection rate among these ethnic groups were statistically significant. We conclude that people living in Pingtung County are more frequently infected with HBV when compared with inhabitants in northern Taiwan.

Adolescent↗
PubMed1988

Spectral analysis of ventilation in elderly subjects awake and asleep.

We studied the periodicities of ventilation in elderly subjects using digital comb filtering. Two groups of subjects were studied, those with and without sleep apnea. Measurements were made in wakefulness, stage 1-2 sleep, and where possible in stage 3-4 sleep. For each of the digital filters we calculated the average power of the oscillatory output. To compare subject groups we first specifically determined the average power in the filter with the maximum output. The mean of this measurement was greater in elderly subjects with apnea compared with those without apnea, both during wakefulness and stage 1-2 sleep. In both groups of subjects the cycle time of the major ventilatory oscillations was on the order of 40-60 s. There was no difference in this cycle time between the two groups of subjects in wakefulness or stage 1-2 sleep. Thus, whereas similar oscillatory processes occur in subjects with and without apnea, it is the magnitude of the oscillation that differs between the two groups. These conclusions are supported by analysis of the output of individual filters of the digital comb filter. In both groups, stage 1-2 sleep produced significantly increased oscillations in ventilation. Both in wakefulness and stage 1-2 sleep, significantly greater periodicities occurred in the apneic compared with the nonapneic group. In the few subjects who had sufficient data in stage 3-4 sleep for spectral analysis, ventilatory oscillations were virtually absent in this state. Our data suggest that subjects who develop apnea during sleep have an increased propensity for periodic breathing even while awake.

Aged↗
PubMed1988

Changes in compartmental ventilation in association with eye movements during REM sleep.

The effect of phasic eye movement activity on ventilation during rapid-eye-movement (REM) sleep was studied in seven healthy young adults by use of the respiratory inductive plethysmograph. Mean ventilation (VE) and ventilatory components during REM sleep were not significantly different from that seen in either stages 1-2 or 3-4 sleep. The percent of rib cage contribution to ventilation in REM sleep, 29.3 +/- 5.1%, was reduced compared with 54.4 +/- 5.8% in stage 1-2 and 52.2 +/- 4.3% in stage 3-4 sleep (P less than 0.005). When one separated breaths by the degree of associated phasic eye movement activity, it became apparent that breathing during REM sleep is very heterogeneous. Increasing eye movement activity was associated with inhibition of ventilation with a reduction in VE from 5.1 +/- 0.3 to 3.8 +/- 0.3 l/min. Tidal volume and frequency both fell, whereas inspiratory duration was unchanged. Compartmental ventilation was also affected, with the fall in the rib cage contribution from 37.8 +/- 6.4 to 15.3 +/- 5.6%. Chest wall and abdominal movement became more asynchronous as phasic-eye-movement activity increased and frank paradoxical breathing was seen.

Adult↗
PubMed1988

Lewis lung carcinoma variants with differing metastatic specificities adhere preferentially to different defined extracellular matrix molecules.

Differential cell adhesion has been proposed to play a role in organ-specific tumor metastasis. To further explore this hypothesis, we have employed a Lewis lung carcinoma cell line and 2 variants that differ in their ability to metastasize to lung and liver. The three cell lines were tested for their ability to adhere to defined extracellular matrix components that had been previously adsorbed to nylon membranes. Our results demonstrate that the parental cell line adheres preferentially to fibronectin relative to all other adhesion molecules tested. The lung colonizing variant, M27, adheres well to fibronectin and also to type V collagen but adheres poorly to laminin, to types I and VI collagen or to heparan sulfate. In contrast, the liver colonizing H59 cell line was highly adherent to laminin as well as to fibronectin but did not adhere to heparan sulfate or to any of the collagen types tested. These results demonstrate that three related cell lines with differing metastatic specificities have marked differences in their abilities to bind to defined matrix molecules. Such differences may play a role in the preferential localization to specific organ beds in vivo.

Animals↗
PubMed1987

Termination of spontaneous atrial flutter by transesophageal pacing.

Transesophageal atrial pacing using the constant-rate technique was performed in 26 patients presenting with spontaneous atrial flutter (atrial cycle length between 180 and 270 ms). All but one patient had been treated with one or more antiarrhythmic agents (digoxin, quinidine, procainamide, propranolol, verapamil, diltiazem, and propafenone) within the previous 12 hours. Transesophageal atrial pacing at cycle lengths between 80 and 180 ms was successful in terminating atrial flutter in 22 patients: immediate reversion to sinus rhythm in 16, following transient sinus pause in one, following a brief period of atrial fibrillation in three, and following longer periods of atrial fibrillation in another two. No post-conversion ventricular arrhythmia and no other complications were observed. All patients experienced only a mild burning discomfort during the procedure. It is concluded that atrial pacing via the esophagus is a safe and noninvasive technique of terminating spontaneous atrial flutter. The effectiveness of this technique is comparable to endocardial or epicardial atrial pacing.

Adolescent↗
PubMed1986

The quick-mount pipeline connector: failure of a "fail-safe" device.

This report describes the absence of gas flow despite the apparent proper mounting of a Canadian Liquid Air nitrous oxide quick-mount connector to its wall outlet. A similar but potentially more dangerous malfunction can occur with oxygen quick-mount connectors. The nature and cause of this defect are examined.

Anesthesiology↗
PubMed1986

Improved transesophageal recording and stimulation utilizing a new quadripolar lead configuration.

Transesophageal pacing and recording are valuable techniques in the diagnosis and treatment of patients with arrhythmias. Bipolar pacing with bipolar catheters has been effective, but recording from the same electrodes is not possible during and immediately following pacing. We utilized a fine no. 4 French quadripolar catheter in 21 subjects to stimulate the atrium and record atrial electrical activity simultaneously. Pacing characteristics were equivalent to previously used bipolar catheters and recording was markedly enhanced. Bipolar atrial electrograms could be recorded either during pacing or at the first atrial depolarization following pacing in all patients. Thus, this quadripolar pacing lead improves the diagnostic value of studies involving transesophageal atrial pacing and recording.

Arrhythmias, Cardiac↗
PubMed1986

Importance of breath size in calibrating the respiratory inductive plethysmograph.

The usual method of calibrating the respiratory inductive plethysmograph (RIP) is to have the subject breathe over a rather narrow volume range, either resting tidal volume or into a bag containing a fixed larger volume, in both the standing and supine positions. During a previous study in our laboratory using the RIP to quantify ventilation during sleep in young and elderly adults, we began to observe that the accuracy of the RIP measurements could be improved if we calibrated using a wider range of tidal volumes which encompassed the smaller breath sizes we were measuring during sleep. We therefore decided to investigate whether the size of the breaths used for calibrating the RIP was indeed important in improving the accuracy of the device. Eight healthy, nonsmoking young adult men participated in the study. Three sets of calibration factors for the RIP were determined based on low (300 to 500 ml), normal (500 to 800 ml) and high tidal volume (over 800 ml) breaths. Each of these sets of calibration factors were then used to validate three different sets of supine tidal volumes (low, normal, high). For all volumes tested, the RIP values most closely approximated the spirometric volumes when the calibration breaths and validation breaths were of the same size.

Adult↗
PubMed1985

Ventilatory and arousal patterns during sleep in normal young and elderly subjects.

Since elderly subjects have lower chemosensitivity, we postulated that ventilation might be more state dependent in the elderly. To address this we investigated the changes in ventilation, measured by respiratory inductive plethysmography, with sleep in 12 healthy young (19-29 yr) and 13 elderly (greater than 65 yr) subjects. Ventilation was measured in representative periods in each sleep state. These data showed that there is no difference between the elderly and the young either in mean ventilation or in the variability of ventilation awake or in the different states of sleep. In both groups ventilation was variable in stage 1-2 sleep and least variable in stage 3-4 sleep. The variability in stage 1-2 sleep was due to periodic breathing (cycle time approximately 45 s) in both age groups. Although within a sleep state no differences were observed, over the night of study the elderly behaved differently from the young. Apneas occurred more frequently in the elderly, and 5 of 13 elderly met the criteria for sleep apnea syndrome compared with 1 of 12 young subjects. Apneas tended to occur predominantly in stage 1-2 sleep and seem to be an exaggeration of the periodicity that is typical of this state. Four of the elderly with apnea remained in this stage of sleep throughout the night of study. The apneic episodes usually terminated with an electroencephalogram arousal that occurred prior to or simultaneously with the onset of ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗