Biomedical subjects

J D Chen

Publications and source records attributed to J D Chen.

At least 55 records · Page 3Linked to original sources

PubMed2000

Cisapride provides symptomatic relief in functional dyspepsia associated with gastric myoelectrical abnormality.

OBJECTIVE: We evaluated the effects of cisapride (10 mg t.d.s. and 20 mg b.d.) on gastrointestinal symptoms and gastric myoelectrical activity in patients with functional dyspepsia. Myoelectrical activity was measured by electrogastrography. METHODS: Patients with functional dyspepsia, defined as discomfort in the epigastrium, a negative endoscopy, and clinical symptoms of dyspepsia, were enrolled. A total of 38 patients participated in the study (23 female; 15 male; 24-72 years of age). Screening electrogastrography identified those with a normal electrogastrogram (14 subjects) and those with an abnormal electrogastrogram (24 patients). Patients were randomly assigned to 2 weeks of placebo or 2 weeks of cisapride (10 mg t.d.s.); both groups then received 2 weeks of cisapride (20 mg b.d.). Electrogastrograms were repeated at the end of each 2-week treatment period. RESULTS: Cisapride 10 mg t.d.s. significantly improved symptoms in all patients. An additional 2 weeks of treatment with cisapride 20 mg b.d. led to continued improvement in symptoms in all patients, with significant improvement in the group with abnormal baseline electrogastrograms. Cisapride significantly improved postprandial bloating and discomfort in patients with abnormal baseline electrogastrograms. Cisapride also significantly improved postprandial gastric myoelectrical activity as measured by electrogastrography in patients with abnormal baseline electrogastrograms. CONCLUSION: Cisapride provides symptomatic relief and improves gastric myoelectrical abnormalities in patients with functional dyspepsia.

Adult↗

PubMed2000

Effects of caffeine on gastrointestinal myoelectric activity and colonic spike activity in dogs.

BACKGROUND: Caffeine is known to produce various effects on the gastrointestinal tract. Few studies have, however, investigated the effects of caffeine on gastrointestinal myoelectric activity under physiologic conditions. The aims of this study were to investigate the effects of caffeine on colonic motility (spike activity) and gastric and jejunal slow waves in conscious dogs. METHODS: The study was performed in eight healthy female hound dogs (15-20 kg) in which one pair of electrodes was implanted on the serosa of the stomach, one pair on the proximal jejunum, and another pair on the ascending colon. The protocol consisted of a 60-min recording as base line and a 90-min recording after intravenous injection of saline, a low dose of caffeine (125 mg), or a high dose of caffeine (250 mg). RESULTS: In the colon there was a significant increase in the number of spike bursts per minute after the injection of both the low (6.69+/-1.27 versus 8.22+/-1.31, P < 0.05) and the high dose (4.38+/-1.23 versus 6.92+/-0.98, P < 0.05) of caffeine. The increase in the total energy of spikes per minute after the injection of the high dose of caffeine was significantly higher than that after the low dose of caffeine (41.2+/-14.6 versus 133.4+/-39.2, P < 0.05). The characteristics of the gastric and jejunal slow waves were, however, not affected by caffeine. CONCLUSION: Caffeine increases spike activity in the colon, and its effect may be dose-dependent. Gastric and jejunal slow waves are not affected by caffeine.

Animals↗

PubMed2000

Time-frequency analysis of heart rate variability using short-time fourier analysis.

This study was done to introduce new parameters derived by time frequency analysis of heart rate variability data. Four simulation experiments were carried out to compare the short-time Fourier transform (STFT) analysis method to the traditional overall spectral analysis method. Sinusoidal signals were generated with identical total power in the high-frequency band, but varying time-frequency and time-amplitude information. The STFT method was also applied to heart rate variability data from the stages of normal human sleep. Data analysis included computation of the power in the high-frequency band by overall spectral analysis. The instability coefficients (ICs) of the frequency and power in the high-frequency band were derived by STFT analysis. The ICs derived by the STFT method were able to describe time-frequency and time-amplitude variations in sinusoidal signals which contained identical total power in a specified frequency range. The ICs of the frequency and power were able to differentiate variations in vagal activity between the stages of human sleep and waking. The ICs represent new parameters derived by the STFT method, and allow the detection and quantification of short-lasting time-frequency and time-amplitude variations that remain obscured by overall spectral analysis.

Adult↗

PubMed2000

Noninvasive feature-based detection of delayed gastric emptying in humans using neural networks.

Radioscintigraphy is currently the gold standard for gastric emptying test which involves radiation exposure and is considerably expensive. We present a feature-based detection approach using neural networks for the noninvasive diagnosis of delayed gastric emptying from the cutaneous electrogastrogram (EGG). Simultaneous recordings of the EGG and scintigraphic gastric emptying test were made in 152 patients with symptoms suggestive of delayed gastric emptying. Spectral analyses were performed to derive EGG parameters which were used as the input of the neural network. The result of scintigraphic gastric emptying was used as the gold standard for the training and testing of the neural network. A correct classification of 85% (a specificity of 89% and a sensitivity of 82%) was achieved using the proposed method.

Adolescent↗

PubMed2000

Enhanced postprandial gastric myoelectrical activity after moderate-intensity exercise.

OBJECTIVE: The aim of this study was to investigate the change of postprandial gastric myoelectrical activity and its relation with vagal activity after exercise. METHODS: Nine subjects were studied in two sessions. In the control session, gastric myoelectrical activity was recorded using electrogastrography (EGG) for 30 min in the fasting state and 60 min after a test meal. In the exercise session, after the baseline recording of both the EGG and electrocardiogram (ECG), the subject was put on a cycle ergometer for exercise until reaching 50% of the maximum age-predicted heart rate for 10 min. The test meal was then given and the recording was resumed for 60 more minutes. Spectral analyses were performed on both the EGG and the heart rate variability derived from the ECG. RESULTS: The postprandial increment of the dominant power (p<0.05) and the percentage of the 2-4 cpm slow waves (p = 0.01) were significantly higher with exercise. The standard deviation of the postprandial dominant frequency was significantly decreased (more stable slow waves) with exercise (p<0.04). While cardiac vagal activity was significantly decreased after the meal, exercise did not significantly affect the postprandial change. CONCLUSIONS: Gastric slow waves become more regular, more stable, and of higher amplitude after exercise, and this enhancement is probably not mediated via the vagal pathway.

Eating↗

PubMed2000

Entrainment of intestinal slow waves with electrical stimulation using intraluminal electrodes.

The aim of this study was to investigate whether the intestinal stimulation would be feasible using a less invasive method: intraluminal electrodes. The study was performed in nine healthy hound dogs (15-26 kg). Four pairs of electrodes were implanted on the serosa of the jejunum at an interval of 5 cm with the most proximal pair 35 cm beyond the pylorus. An intestinal fistula was made 20 cm beyond the pylorus. Simultaneous recordings of intestinal myoelectrical activity were made for 2 h in the fasting state from both intraluminal and serosal electrodes. Various pacing parameters were tested. The frequency of the intestinal slow wave recorded from the intraluminal electrodes was identical to that from the serosal electrodes (18.78+/-0.3 cpm vs 18.75+/-0.3 cpm, r=0.99, p <0.001), and so was the percentage of normal 17-22 cycles/ min waves (95.83+/-3.9% vs 98.16+/-1.33%, r=0.96, p<0.01). A complete entrainment of the intestinal slow wave was achieved in every dog with electrical stimulation using intraluminal ring electrodes. The effective pacing parameters were pulse width of 70 ms, amplitude of 4 mA and frequency of 1.1 IF (intrinsic frequency). The time required for the entrainment of the intestinal slow wave with intraluminal pacing was 25.0+/-2.1 s. The maximum driven frequency was found to be 1.43+/-0.01 IF. The results reveal that intraluminal pacing is an effective and efficient method for the entrainment of intestinal slow waves. It may become a potential approach for the treatment of intestinal motor disorders associated with myoelectrical abnormalities.

Animals↗

PubMed2000

Human Slug is a repressor that localizes to sites of active transcription.

Snail/Slug family proteins have been identified in diverse species of both vertebrates and invertebrates. The proteins contain four to six zinc fingers and function as DNA-binding transcriptional regulators. Various members of the family have been demonstrated to regulate cell movement, neural cell fate, left-right asymmetry, cell cycle, and apoptosis. However, the molecular mechanisms of how these regulators function and the target genes involved are largely unknown. In this report, we demonstrate that human Slug (hSlug) is a repressor and modulates both activator-dependent and basal transcription. The repression depends on the C-terminal DNA-binding zinc fingers and on a separable repression domain located in the N terminus. This domain may recruit histone deacetylases to modify the chromatin and effect repression. Protein localization study demonstrates that hSlug is present in discrete foci in the nucleus. This subnuclear pattern does not colocalize with the PML foci or the coiled bodies. Instead, the hSlug foci overlap extensively with areas of the SC-35 staining, some of which have been suggested to be sites of active splicing or transcription. These results lead us to postulate that hSlug localizes to target promoters, where activation occurs, to repress basal and activator-mediated transcription.

Base Sequence↗

PubMed2000

Sequestration and inhibition of Daxx-mediated transcriptional repression by PML.

PML fuses with retinoic acid receptor alpha (RARalpha) in the t(15;17) translocation that causes acute promyelocytic leukemia (APL). In addition to localizing diffusely throughout the nucleoplasm, PML mainly resides in discrete nuclear structures known as PML oncogenic domains (PODs), which are disrupted in APL and spinocellular ataxia cells. We isolated the Fas-binding protein Daxx as a PML-interacting protein in a yeast two-hybrid screen. Biochemical and immunofluorescence analyses reveal that Daxx is a nuclear protein that interacts and colocalizes with PML in the PODs. Reporter gene assay shows that Daxx drastically represses basal transcription, likely by recruiting histone deacetylases. PML, but not its oncogenic fusion PML-RARalpha, inhibits the repressor function of Daxx. In addition, SUMO-1 modification of PML is required for sequestration of Daxx to the PODs and for efficient inhibition of Daxx-mediated transcriptional repression. Consistently, Daxx is found at condensed chromatin in cells that lack PML. These data suggest that Daxx is a novel nuclear protein bearing transcriptional repressor activity that may be regulated by interaction with PML.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Spatio-temporal nonlinear modeling of gastric myoelectrical activity.

The accomplishment of a complete digestive process of human stomach is regulated by a spatio-temporally-coordinated electric pattern called gastric myoelectrical activity (GMA). The normal patterns of GMA present temporal evolution from endogenous rhythmic oscillation to bursting of spikes associated with contractions, and also ordered spatial propagation of the oscillating waves. The abnormal patterns of GMA have been observed in temporal dysrhythmia, such as tachygastria, bradygastria and arrhythmia, and in spatial propagation failure, such as retrograde propagation and uncoupling. Different GMA patterns are associated with different gastric symptoms and there exist some nonlinear mechanisms to govern the formation and dynamic evolution of these patterns. However, these mechanisms are so complex that few of them are known by medical observations. The aim of this study is to explore these mechanisms by spatio-temporal modeling of GMA. The single-cell model simulating the formation process of slow waves and spikes, the multi-cell model simulating the propagation process of GMA and the extracellular model simulating the formation of bipolar recordings are presented.

Computer Simulation↗

PubMed1999

Disruption of normal gastric myoelectric functioning by sleep.

STUDY OBJECTIVES: The aim of this study was to assess the effects of sleep on gastric myoelectric activity as measured by electrogastrography in healthy individuals. The goal was to elucidate the role of central influences in the regulation of normal gastric functioning. DESIGN: Electrograstrogram (EGG) was recorded during polysomnographically monitored waking and sleep. SETTING: Sleep laboratory. PARTICIPANTS: 17 healthy volunteers. MEASUREMENTS AND RESULTS: EGG parameters were computed for 20-minute segments of pre-sleep waking, stage 2 sleep, stage 4 sleep, and REM sleep using both overall and running spectral analysis of EGG data. The dominant power decreased significantly from waking (31.4 +/- 1.4 dB) to all sleep stages (23.1 +/- 1.5 dB during stage 2; 24.7 +/- 1.4 dB during stage 4; 24.3 +/- 1.3 dB during REM sleep). The percentage of 2-4cpm activity decreased significantly during NREM sleep (64.6 +/- 7.6% during stage 2 sleep; 57.5 +/- 5.5% during stage 4 sleep) compared to its waking value (90.8 +/- 3.2%), but not compared to REM sleep (74.1 +/- 5.4%). The instability coefficient of the dominant frequency increased significantly from waking (0.19 +/- 0.03) to all sleep stages (0.36 +/- 0.05 during stage 2 sleep; 0.47 +/- 0.05 during stage 4; 0.34 +/- 0.05 during REM sleep). No significant differences between the sleep stages were found for any measure. CONCLUSIONS: Sleep is associated with increases in gastric dysrhythmia and instability of the gastric slow wave frequency when compared to waking. These findings suggest that the intrinsic electrical activity of the stomach is significantly influenced by central nervous system mechanisms, and support the notion of a brain-gut axis.

Adult↗

PubMed1999

SMRTe, a silencing mediator for retinoid and thyroid hormone receptors-extended isoform that is more related to the nuclear receptor corepressor.

SMRT (silencing mediator for retinoid and thyroid hormone receptors) and N-CoR (nuclear receptor copressor) mediate transcriptional repression of important regulators that are involved in many signaling pathways. SMRT and N-CoR are related proteins that form complexes with mSin3A/B and histone deacetylases to induce local chromatin condensation and transcriptional repression. However, SMRT is substantially smaller than N-CoR, lacking an N-terminal domain of approximately 1,000 aa that are present in N-CoR. Here, we report the identification of SMRT-extended (SMRTe), which contains an N-terminal sequence that shows striking similarity with N-CoR. As in N-CoR, this SMRTe-N-terminal domain also represses basal transcription. We find that SMRTe expression is regulated during cell cycle progression and SMRTe transcripts are present in many embryonic tissues. These data redefine a structurally and functionally more related nuclear receptor corepressor family and suggest an additional role for SMRTe in the regulation of cycle-specific gene expression in diverse signaling pathways.

Amino Acid Sequence↗

PubMed1999

Blind separation of multichannel electrogastrograms using independent component analysis based on a neural network.

The electrogastrogram (EGG) is an abdominal surface measurement of gastric myo-electrical activity which regulates gastric contractions. It is of great clinical importance to record and analyse multichannel EGGs, which provide more information on the propagation and co-ordination of gastric contractions. EGGs are, however, contaminated by myo-electric interference from other organs and artefacts such as motion and respiration. The aim of the study is to separate the gastric signal from noisy multichannel EGGs without any information on the interference, using independent component analysis. A neural-network model is proposed, and corresponding unsupervised learning algorithms are developed to achieve the separation. The performance of the proposed method is investigated using artificial data simulating real EGG signals. Experimental EGG data are obtained from humans and dogs. The processed results of both simulated and real EGG data show the following: first, the proposed method is able to separate normal gastric slow waves from respiratory artefacts and random noises. It is also able to extract gastric slow waves, even when the EGG is contaminated by severe respiratory and ECG artefacts. Secondly, when the stomach contains various gastric electric signals with different frequencies, the proposed method is able to separate these different signals, as illustrated by simulations. These data suggest that the proposed method can be used to separate gastric slow waves, respiratory and motion artefacts, and intestinal myo-electric interference that are mixed in the EGG. It can also be used to detect gastric slow-wave uncoupling, during which the stomach has multiple gastric signals with different frequencies. It is believed that the proposed method may also be applicable to other biomedical signals.

Adult↗

PubMed1999

Postprandial response of jejunal slow waves and mediation via cholinergic mechanism.

The postprandial characteristics of jejunal myoelectrical activity and its mediation via cholinergic nerves were investigated in this study. Four pairs of bipolar electrodes were implanted on the serosa of the proximal jejunum of nine female hound dogs (14-22 kg). In the control session, the recording of jejunal myoelectrical activity was made for 30 min in the fasting state and for 90 min after a solid meal (0.45 kg, 838 kcal). The study session followed the same protocol except that a bolus of 0.25 mg/kg atropine was injected intravenously 30 min after the meal. Computerized spectral analysis was performed to calculate the frequency, power, and percentage of 17-22 cycles/min (cpm) slow waves. A special artificial neural network program was applied to compute the spike bursts superimposed on slow waves. All data were expressed as mean +/- SE. The postprandial frequency of the jejunal slow waves was significantly increased from 18.42 +/- 0.28 cpm in the fasting state to 18.95 +/- 0.22, 19.28 +/-0.23, and 19.28 +/- 0.22 cpm during the first, second, and third 30-min periods after the meal (all P < 0.03 in comparison with the fasting state). The percentage of the slow waves superimposed with spike bursts was increased from 19.33 +/- 3.90% at fasting state to 35.16 +/-2.76%, 32.87 +/- 4.06%, and 34.88 +/- 3.51% during the first, second, and third 30-min periods after the meal (all P < 0.03 in comparison with fasting state). Atropine abolished the postprandial increases in the frequency of slow waves and the number of spike bursts. No significant postprandial changes in the power and the percentage of 17-22 cpm slow waves were observed. In conclusion, the postprandial response of the jejunal slow waves after a solid meal presents as an increase of the frequency of slow waves and the number of the spike bursts which can be abolished by atropine, and the postprandial response of the jejunal slow waves is a neural reflex dominantly mediated via vagal cholinergic nerves.

Animals↗

PubMed1999

Effects of electroacupuncture on gastric migrating myoelectrical complex in dogs.

The aim-of this study was to investigate the characteristics of the gastric slow wave during different phases of the migrating myoelectrical complex (MMC) and the effect of electroacupuncture on the MMC. The experiment was performed in eight hound dogs implanted with one pair of bipolar serosal electrodes 2 cm proximal to the pylorus. Gastric myoelectrical activity was recorded for three complete cycles of the MMC in two sessions, one with electroacupuncture at points ST36 and PC6 and the other at sham points. The acupuncture was performed for 30 min in phase I of the second cycle of the MMC. Spectral analysis was performed to compute the frequency and power (amplitude) of the gastric slow wave, whereas blind visual analysis was applied to compute the appearance of spike potentials and the length of each phase of the MMC. It was found that there was a significant difference in the frequency and power of the gastric slow wave during different phases of the MMC (P < 0.05). Phase I was characterized with the highest frequency and lowest power of the gastric slow wave, whereas phase III exhibited the highest power in the slow wave. It was also found that in comparison with the sham points, electroacupuncture at the acupoints increased the number of spike bursts. This increase was not significant during the MMC cycle with electroacupuncture (34.4+/-4.1 vs 27.5+/-2.5%, P > 0.05) but became significant during the cycle after electroacupuncture (39.8+/-3.3% vs 27.5+/-2.5%, P < 0.0005). Similarly, during the MMC cycle after electroacupuncture at the acupoints, there was a significant decrease in the length of phase I (14.8+/-2.2 vs 46.9+/-6.1 min, P < 0.003) and a significant increase in the length of phase II (75.6+/-9.9 vs 30.6+/-4.1 min, P < 0.003) and phase III (25.8+/-0.6 vs 22.1+/-0.7 min, P < 0.003). A similar increase was observed during the MMC cycle with electroacupuncture but was not statistically significant. In conclusion, the gastric slow wave has the highest power during phase III of the MMC, indicating that the antral contraction is characterized not only by the appearance of spikes, but also by the increased power of the slow wave. Electroacupuncture at acupoints of ST36 and PC6 enhances the gastric MMC by reducing the length of phase I and increasing the length of phases II and III.

Acupuncture Points↗

PubMed1999

Postprandial changes of sympathovagal balance measured by heart rate variability.

The aim of this study was to investigate the sympathovagal balance after meals by measuring the spectral analysis of heart rate variability (HRV). Nine healthy volunteers were enrolled in this study. The electrocardiogram (ECG) was recorded for 30 min in a fasting state and 60 min after a 500-kcal test meal. The HRV was derived from the ECG and was measured by power spectral analysis using fast-Fourier transform algorithm. It reveals two dominant spectral components. The low-frequency (LF) band reflects primarily sympathetic activity with some parasympathetic input. The high-frequency (HF) band is a reflection of parasympathetic (vagal) activity. The LF-to-HF ratio is considered a marker of sympathovagal balance. It was found that the postprandial LF-to-HF ratio, compared with the fasting state, was significantly increased at both the first 30 min (2.50 +/- 0.49 vs 1.78 +/- 0.33, P < 0.05) and the second 30 min (2.68 +/- 0.55 vs 1.78 +/- 0.33, P < 0.05). The postprandial HF diminished significantly at both the first (16.0 +/- 0.5 vs 21.8 +/- 4.2, P < 0.05) and the second (13.8 +/- 9.5 vs 21.8 +/- 4.2, P < 0.05) 30-min period. In conclusion, the postprandial sympathovagal ratio shows a sustained elevation lasting 1 hr, mainly attributed to diminished vagal activity.

Adult↗

PubMed1999

Primary intrathoracic malignant fibrous histiocytoma and angiosarcoma.

Primary intrathoracic malignant fibrous histiocytoma and angiosarcoma are rare sarcomas constituting less than 0.2% of lung cancers. The typical imaging appearance is a large, well-circumscribed, non-cavitating, non-calcified, peripheral lung mass without hilar or mediastinal lymphadenopathy. Bronchoscopy and percutaneous needle aspiration are of limited value in differential diagnosis, and thoracotomy is warranted for definitive diagnosis.

Adult↗

PubMed1999

Gastric myoelectric activity in patients with end-stage liver disease.

BACKGROUND: Abnormalities of gastrointestinal motility and transit time have been reported in association with end-stage liver disease. Motility abnormalities could be routinely studied if a simple noninvasive test were available. The electrogastrogram is a cutaneous measure of gastric myoelectric activity and correlates well with serosal recordings of gastric myoelectric activity. The aim of this study was to evaluate gastric myoelectric activity in patients with end-stage liver disease. METHODS: Fourteen patients with end-stage liver disease had gastric myoelectric activity measured with the electrogastrogram. An electrogastrogram was considered abnormal when normal gastric slow waves were seen less than 70% of the time or there was no increase in the electrogastrogram amplitude after a meal. RESULTS: Abnormal electrogastrograms were present in 8 of 14 (57%) end-stage liver disease patients. CONCLUSIONS: Abnormal gastric myoelectric activity is common in end-stage liver disease.

Adult↗

PubMed1999

Impaired gastric slow waves induced by spatial disorientation and effect of domperidone.

OBJECTIVES: Our aims were to investigate the dominant frequency and regularity of gastric myoelectrical activity during motion sickness induced with the advanced spatial disorientation demonstrator (ASDD) and to evaluate the effect of domperidone on gastric myoelectrical activity and gastrointestinal symptoms during motion sickness. METHODS: Thirteen healthy volunteers participated in this study. This study was executed using the ASDD, which could duplicate several spatial disorientation phenomena in a safe, controlled environment. Each subject participated in two sessions and received oral administration of 10 mg domperidone before the study in one of the sessions. In each session, three 15-min EGG recordings were made before, during, and after rotation. The symptoms were scored by Graybiel's scale of motion sickness before and after rotation. All EGG data were subjected to computerized spectral analysis to obtain the percentage of normal 2-4 cycles/min (cpm) slow waves, percentage of tachygastria, EGG dominant frequency and power, and instability coefficient of the dominant frequency. RESULTS: We have found that the percentage of normal gastric slow wave was decreased (control session: 86.2 +/- 4.0% vs 70.0 +/- 5.4%, p < 0.01; domperidone session: 82.7 +/- 4.6% vs 69.8 +/- 5.6%, p < 0.03) and the percentage of tachygastria was increased (control session: 8.7 +/- 3.2% vs 17.8 +/- 5.6%, p < 0.01; domperidone session: 9.2 +/- 3.3% vs 18.1 +/- 3.5%, p < 0.01) after rotation in both sessions. The minute-by-minute variation of the gastric slow wave frequency was significantly increased during rotation in both sessions (control: 0.74 +/- 0.16 vs 1.35 +/- 0.19, p < 0.01; domperidone: 0.90 +/- 0.20 vs 1.47 +/- 0.17, p < 0.01). Domperidone did not prevent dysrhythmia or the symptoms of motion sickness. CONCLUSIONS: The percentage of normal gastric slow waves is decreased and the percentage of tachygastria is increased with spatial disorientation. Domperidone does not prevent gastric dysrhythmia or the symptoms of motion sickness induced with spatial disorientation.

Adult↗