Biomedical subjects

H I Chen

Publications and source records attributed to H I Chen.

At least 19 recordsLinked to original sources

PubMed1995

The WW domain of Yes-associated protein binds a proline-rich ligand that differs from the consensus established for Src homology 3-binding modules.

The WW domain has previously been described as a motif of 38 semiconserved residues found in seemingly unrelated proteins, such as dystrophin, Yes-associated protein (YAP), and two transcriptional regulators, Rsp-5 and FE65. The molecular function of the WW domain has been unknown until this time. Using a functional screen of a cDNA expression library, we have identified two putative ligands of the WW domain of YAP, which we named WBP-1 and WBP-2. Peptide sequence comparison between the two partial clones revealed a homologous region consisting of a proline-rich domain followed by a tyrosine residue (with the shared sequence PPPPY), which we shall call the PY motif. Binding assays and site-specific mutagenesis have shown that the PY motif binds with relatively high affinity and specificity to the WW domain of YAP, with the preliminary consensus XPPXY being critical for binding. Herein, we have implicated the WW domain with a role in mediating protein-protein interactions, as a variant of the paradigm set by Src homology 3 domains and their proline-rich ligands.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Characterization of a novel protein-binding module--the WW domain.

We have identified, characterized and cloned human, mouse and chicken cDNA of a novel protein that binds to the Src homology domain 3 (SH3) of the Yes proto-oncogene product. We subsequently named it YAP for Yes-associated protein. Analysis of the YAP sequence revealed a protein module that was found in various structural, regulatory and signaling molecules. Because one of the prominent features of this sequence motif is the presence of two conserved tryptophans (W), we named it the WW domain. Using a functional screen of a cDNA expression library, we have identified two putative ligands of the WW domain of YAP which we named WBP-1 and WBP-2. Peptide sequence comparison between the two partial clones revealed a homologous proline-rich region. Binding assays and site-specific mutagenesis have shown that the proline-rich motif binds with relatively high affinity and specificity to the WW domain of YAP, with a preliminary consensus that is different from the SH3-binding PXXP motif. This suggests that the WW domain has a role in mediating protein-protein interactions via proline-rich regions, similar but distinct from Src homology 3 (SH3) domains. Based on this finding, we hypothesize that additional protein modules exist and that they could be isolated using proline-rich peptides as functional probes.

Adaptor Proteins, Signal Transducing↗

PubMed1995

Measurement of nitric oxide release in the isolated perfused rat lung.

In this study we have continuously measured real-time production of nitric oxide (NO) in the isolated, perfused rat lung by using an NO monitor (model NO-501, Inter Medical Co., Nagoya, Japan) with an NO-selective resin microsensor. A stable NO response was obtained when the sensor was placed in the pulmonary artery or the pulmonary vein; in contrast, the tracings obtained from the lung periphery were unstable. Furthermore, the NO release was higher when the isolated lungs were perfused with physiological salt solution rather than whole blood perfusion. Changes in NO production were also monitored in acute hypoxia and reoxygenation. Pretreatment with endotoxin (10 mg/kg) potentiated the NO release observed, and this effect of endotoxin was further potentiated by arginine (1 x 10(-4) M) and acetylcholine (1 x 10(-5) M) and countered by the NO synthase inhibitor, L-NG-nitro-arginine methyl ester (L-NAME; 1 x 10(-3) M).

Animals↗

PubMed1995

Effects of exercise training and deconditioning on platelet function in men.

Platelets play an important role in the pathogenesis of cardiovascular disease. It has also been noticed that regular exercise can reduce the risk of cardiovascular disease. This is the first study to demonstrate that endurance exercise training may suppress platelet adhesiveness and aggregation and that deconditioning may reverse the training effects. Healthy male sedentary subjects were randomly divided into control and training groups. The trained men were trained on a bicycle ergometer at about 60% of maximal oxygen consumption for 30 minutes per day, 5 days per week for 8 weeks, then deconditioned for 12 weeks. During the experimental period, blood samples of the trained subjects were collected before and immediately after a progressive exercise test every 4 weeks. The same experiments were applied to the controls at the beginning of this study and 8 weeks thereafter. A tapered parallel-plate chamber was used to assess platelet adhesiveness. Platelet aggregation induced by ADP was evaluated by the percentage of reduction in single platelet count. Our results showed that (1) platelet adhesiveness and aggregability were increased by short-term strenuous exercise in both control and trained groups, but the enhancement of platelet aggregability was decreased after exercise training in the trained subjects; (2) at rest and immediately after strenuous exercise, platelet adhesiveness and aggregability were decreased by training, whereas they were unchanged in the control group; and (3) deconditioning reversed the training effects on resting and postexercise platelet adhesiveness and aggregability back to the pretraining state. These results suggest that platelet adhesiveness and aggregability may be depressed by exercise training but be reversed back to the pretraining state after deconditioning.

Blood Platelets↗

PubMed1994

The sympathetic efferent innervation of the cutaneous and muscle veins in cats. A comparative study using retrograde localization with horseradish peroxidase.

Previous studies using electrical stimulation, tension recording and fluorescence histochemical methods indicate that variations in the sympathoadrenergic innervation exist in regional veins of the limb. In the present experiment, we used horseradish peroxidase (HRP) as a retrograde tracer to localize and quantitate the sympathetic innervations to the saphenous, femoral and muscle veins in the cat. The animal was anesthetized with pentobarbital. In three groups of cats, a segment of saphenous (n = 8), femoral (n = 8) and muscle (n = 10) vein was isolated. HRP was applied on the outer vein wall for 3-4 h to allow uptake into the nerve endings. The paravertebral sympathetic chain on the same side of HRP application was dissected after the animal was killed and fixed 60 h following the application of tracer. HRP-labeled neurons were counted in each sympathetic ganglion from L1 to S1. The average number of neurons (mean +/- SE) were 913 +/- 99, 732 +/- 70 and 234 +/- 32, respectively, for saphenous, femoral and muscle vein. There was no statistical difference between the saphenous and femoral vein (P > 0.1). The muscle vein was far less innervated (P < 0.001). When the surface area (mm2) of the vein segment for HRP application was taken into account, the neurons per mm2 were 44.1 +/- 4.8 for saphenous vein, 24.6 +/- 1.8 for femoral vein and 10.2 +/- 1.3 for muscle vein. The neuron density was significantly different among the three groups (P < 0.01). In a single ganglion, the distribution of HRP-neurons appeared to be scattering in pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Evaluation of left ventricular functional status using thermodynamic indices.

Conventional methods to assess cardiac contractility have been focused on the mechanical properties of the myocardium. Many of these have suffered from theoretical and practical drawbacks. In this study, we have attempted to evaluate the left ventricular contractile status using the thermodynamic principle and compared these indices with the conventional index (dP/dt). A total of 8 mongrel dogs were anesthetized and artificially ventilated. A Millar catheter with high-fidelity multiple sensors was inserted into the aorta to record the simultaneous changes in aortic flow and pressure waves. Cardiac inotropy was increased by graded doses (2-32 micrograms/kg/min) of dobutamine. Angiotensin injection (100-300 micrograms) to achieve a blood pressure elevation of 30 mmHg was employed for afterload augmentation. Preload was increased by rapid infusion of 6% dextran solution (20 ml/kg). Several thermodynamic parameters were calculated at steady state during the control period and after drug interventions. These included power-averaged rate of power density generation (ARPD), peak ejection rate of change of power (PREP), energy-averaged power density (APD) and frequency-normalized ARPD (FARPD). PREP and APD were unchanged by afterload increment while FARPD, ARPD and dP/dt decreased significantly with an increase in afterload, ARPD was highly sensitive to an increased preload (p < 0.001), and PREP was also changed significantly by an increase in preload. dP/dt was boarderlinely affected by Dextran infusion (p = 0.05), and APD was independent of preload (P > 0.05). Inotropic stimulation increased ARPD, PREP, APD, FARPD and dP/dt by 139.0 +/- 48.0%, 98.0 +/- 51.4%, 74.0 +/- 49.7%, 60.0 +/- 30.4% and 44.6 +/- 10.4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1992

Cholinergic agonists and interleukin 1 regulate processing and secretion of the Alzheimer beta/A4 amyloid protein precursor.

Activation of protein kinase C by phorbol esters is known to accelerate the processing and secretion of the beta/A4 amyloid protein precursor. We have now examined various first messengers that increase protein kinase C activity of target cells for their ability to affect beta/A4 amyloid protein precursor metabolism. Acetylcholine and interleukin 1, which are altered in Alzheimer disease, were shown to increase processing of the beta/A4 amyloid protein precursor via the secretory cleavage pathway. Cholinergic agonists stimulated secretion in human glioma and neuroblastoma cells as well as in PC12 cells transfected with the M1 receptor, while interleukin 1 stimulated secretion in human endothelial and glioma cells.

Acetylcholine↗

PubMed1992

Increase of plasma neuropeptide Y-like immunoreactivity following chronic hypoxia in the rat.

In an attempt to understand the changes of circulating neuropeptide Y (NPY) during hypoxia, the plasma level of NPY was investigated by radioimmunoassay. Exposure of rats to hypobaric hypoxia at an altitude of 18,000 ft for 4 weeks causes an increase of pulmonary pressure and an elevation of plasma NPY-like immunoreactivity (NPY-LI). However, the systemic blood pressure was not elevated by this chronic hypoxia. Also, plasma noradrenaline (NA) estimated by chromatographic analysis (HPLC-ECD) was not markedly raised. Failure of bretylium and guanethidine, sympathetic neuron blockers, in reducing the plasma NPY-LI level of these rats ruled out the participation of adrenergic nervous terminals. Adrenal medulla seems responsible for this elevation of plasma NPY-LI because this magnitude disappeared in adrenalectomized rats. These data suggest that chronic hypoxia induced an elevation of circulating NPY from the adrenal gland of rats.

Adrenal Glands↗

PubMed1992

Antigen-specific tachycardia and hypotension in rodents.

Tachycardia and hypotension, two cardiovascular responses to anaphylaxis, were specifically induced by antigen in mice and rats, respectively. Intravenous injection of poly (Glu60Ala30Tyr10) (GAT) elicited tachycardia within 30-40 sec in GAT-primed B6 mice. Moreover, a minute amount of GAT (0.2 micrograms) was enough to sensitize the mice to subsequent GAT-induced tachycardia. Challenging doses ranging from 100 ng to 500 micrograms. could elicit tachycardia. The kinetics of tachycardia induction was different from that of antibody production or delayed-type hypersensitivity. Tachycardia was induced from day 6 after immunization, while delayed-type hypersensitivity developed as early as day 4, and anti-GAT antibodies were undetectable on day 6 and would not reach a maximum until day 8. Specific antigen-induced hypotension was also observed in rats. Furthermore, cardiovascular changes in both species could be passively transferred by heat-treated (56 degrees C, 30 min) sera from immunized animals. These benchmarks of antigen-induced cardiovascular changes in mice or rats could be used as models to study the immune control of cardiovascular changes in anaphylactic responses.

Amino Acid Sequence↗

PubMed1992

The contribution of alpha-adrenoceptors to neurally-mediated contractions of the rabbit urethral smooth muscle.

1. The nature of the nerve-mediated contractions in the urethral smooth muscle from the rabbit was studied in vitro. Field stimulation caused smaller contractile responses than in the detrusor of the rabbit. 2. There was no significant difference in response to field stimulation or exogenous agents acting on adrenoceptors between longitudinal and circular strips from the rabbit urethra. Histological studies showed that the urethral muscle is arranged in three layers, which run circularly and longitudinally. 3. Atropine had very little effect on the response to field stimulation, phentolamine almost abolished the contractile response to nerve stimulation and sometimes unmasked a relaxation. 4. The alpha 1-adrenoceptor blocking agent, prazosin, blocked both the contractile response to the alpha 1-receptor agonist phenylephrine and that to intrinsic nerve stimulation, with similar potencies. The alpha 2-blocking agent yohimbine shifted the dose-response curve of the contractile response to the alpha 2-agonist, clonidine, in a dose-dependent manner, 10(-7) M causing a 10 fold shift. This concentration had no effect on the response to intrinsic nerve stimulation, suggesting that alpha 2-receptors are not involved in the response. Higher concentrations of yohimbine caused a suppression of the nerve-evoked response which is assumed to be non-specific. 5. Noradrenaline, phenylephrine, and clonidine caused dose-dependent contractile responses in the rabbit urethral strips. The contractions induced by clonidine developed more slowly than those induced by noradrenaline and phenylephrine. 6. These results demonstrate that the rabbit urethral smooth muscle contains both alpha 1- and alpha 2-adrenoceptors, and the nerve-mediated contraction of the rabbit urethra is adrenergic in nature and mediated mainly via alpha 1-adrenoceptors.

Animals↗

PubMed1992

Bronchial responsiveness in an area of air pollution resulting from wire reclamation.

Spirometric data from 86 primary school children living in an area of air pollution resulting from wire reclamation incineration were analysed and compared with 92 non-exposed schoolchildren. There were lower values for forced vital capacity and forced expiratory volume and thus a higher incidence of pulmonary function abnormalities in the children in the polluted area than those in a non-polluted area. There was no significant difference in the prevalence of respiratory symptoms between these two areas when surveyed by a questionnaire. Twenty eight schoolchildren from a non-polluted area and 26 children from the polluted area, who were said to have no respiratory symptoms and for whom consent forms were obtained, were recruited for a bronchial responsiveness test. Nine (35%) of 26 children in the polluted area were responders (less than 50 U) and only one of the control subjects was a responder. The mean (SD) log cumulative dose producing a 35% decrease in respiratory conductance and the minimum cumulative dose required to decrease respiratory conductance from the baseline in the children of the polluted area were significantly lower than that of the control subjects (1.32 (0.37) log units and 1.26 (0.44) log units, respectively, compared with 1.70 (0.10) log unit for both measurements in non-exposed children). These results indicate that air pollution resulting from wire reclamation can produce a detrimental effect on both pulmonary function and bronchial responsiveness in primary schoolchildren who are continually exposed to air pollutants from the time of their birth.

Air Pollutants↗

PubMed1992

Air embolism-induced lung injury in isolated rat lungs.

Pulmonary air embolism causes physical obstruction of microvasculature and leads to permeability changes, release of mediators, and injury to lung tissue. In this study we employed an isolated perfused rat lung model to investigate the primary and secondary effects produced by infusion of air into the pulmonary artery. Infusion of various doses of air (0.10-0.25 ml) over a 1-min period produced a dose-dependent increase in pulmonary arterial pressure and lung weight gain. In contrast, when a constant air dose was administered over various periods of time (0.25 ml over 0.5-8.0 min), the pulmonary arterial pressure rose to the same extent regardless of the infusion rate, whereas the lung weight gain increased proportionately with the rate of infusion. Total vascular resistance rose from 1.41 +/- 0.04 to 5.04 +/- 0.09 mmHg.ml-1.min in rats given 0.25 ml air over 1 min (n = 14, P less than 0.001), with greater than or equal to 90% of this increase occurring in the arterial segments. Both thromboxane B2 and endothelin concentrations also increased in the perfusate, suggesting their involvement in this increased resistance. Furthermore the pulmonary filtration coefficient increased from 0.21 +/- 0.05 to 1.28 +/- 0.26 g.min-1.cmH2O-1.100 g (n = 8, P less than 0.001), and the protein concentration in lung lavage fluid also rose, indicating lung injury. Leukocyte counts in the perfusate were unaffected by embolization, but chemiluminescent activity was increased, indicating a possible role for activated leukocytes in lung injury induced by air emboli.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Terbutaline acts at multiple sites to inhibit bronchoconstriction induced by dry air in canine peripheral airways.

We examined the effect of the beta 2-agonist terbutaline on dry airflow-induced bronchoconstriction (AIB) in the canine lung periphery. Using a wedged bronchoscope technique, collateral resistance (Rcs) and airway wall temperature (Taw) were measured before and after a 2-min exposure to dry air. When sublobar segments were challenged with dry air, Taw fell during challenge (p less than 0.001), and Rcs increased 5 min postchallenge (p less than 0.01). Pretreatment with terbutaline (100 micrograms/kg) reduced the fall induced by dry-air challenge in Taw by 37% and the subsequent rise in Rcs by 87%. Terbutaline significantly reduced the concentrations of thromboxane B2 (TxB2) and prostaglandin D2 (PGD2), and decreased the concentration of epithelial cells recovered in bronchoalveolar lavage fluid 5 min postchallenge. In addition, terbutaline attenuated histamine- and PGD2-induced constriction. Finally, peripheral lung sensitivity (as assessed by delta Rcs/delta Taw) to challenge after treatment with terbutaline was significantly less than that calculated for untreated control animals (p less than 0.05). These data are consistent with the idea that terbutaline attenuates AIB by (1) facilitating replacement of water lost during exposure to dry air, (2) inhibiting mediator production and release from osmosensitive cells, and (3) reducing smooth muscle responsiveness.

Airway Resistance↗

PubMed1992

Effects of acute exercise on the biosynthesis of eicosanoids in rats.

We conducted this study to evaluate the effects of different intensities of acute exercise on the regulation of endogenous eicosanoid levels in male Wistar rats. The animals were divided into 4 groups; i.e.: control, mild exercise, moderate exercise and severe exercise. Immediately after exercise, animals were sacrificed. Plasma prostacyclin (PGI2) level and PGI2 release from two vessel segments (i.e., thoracic aorta and inferior vena cava) were determined by a specific 6-keto-PGF1 alpha (125I) radioimmunoassay. Urine thromboxane was determined by a specific 11-dehydro-TXB2 (125I) radioimmunoassay and normalized by urine creatinine. Although both plasma PGI2 and urine thromboxane tended to be elevated by severe exercise, only the increase in thromboxane was statistically significant (p < 0.05). In addition, PGI2 release from both vessels were not affected by different intensities of acute exercise. We also observed that aortic PGI2 release was greater than their corresponding veins in each group. We therefore conclude that only severe acute exercise, rather than mild or moderate exercise, may affect prostacyclin-thromboxane balance in rats.

Animals↗

PubMed1992

Vasodilator and oxidant scavenger in the neurogenic pulmonary edema induced by cerebral compression.

In vagotomized rats, cerebral compression (CC) produced marked increase in arterial pressure and pulmonary hemorrhagic edema (PHE). We studied the effects of a vasodilator and an oxidant scavenger to delineate the role of hemodynamic and permeability factors in this type of neurogenic PHE. Infusion of sodium nitroprusside at a dose of 5 micrograms/kg/min significantly reduced the CC-induced pressor response by 14% and the lung edema by 41%. A dose of 10 micrograms/kg/min blocked the pressor response by 51%, and completely prevented the lung injury. Dimethylthiourea (DMTU), a potent scavenger for oxidants such as hydroxyl radical and hydrogen peroxide, in doses of 300 and 600 mg/kg was pretreated 15 min before CC. Although DMTU was shown to block the permeability lung damage caused by phorbol myristate acetate (a neutrophil activator), this agent did not exert any effect on the CC-induced pressor response and lung injury. The data indicate that granulocyte-mediated oxidants such as hydroxyl radical and hydrogen peroxide do not appear to be involved in this type of neurogenic lung pathology. The results support the concept that PHE induced by intracranial hypertension is initiated by hemodynamic changes in the systemic and pulmonary circulation. Hydrostatic effect plays a major role in this type of neurogenic lung pathology.

Animals↗

PubMed1991

Vascular factors in isovolumic systemic and pulmonary circuit.

Experiments were conducted in 12 pentobarbital-anesthetized dogs with sinus denervation and vagotomy. The chest was opened, and the heart was replaced by a roller pump with two perfusion lines. The systemic and pulmonary circulations (SC and PC) were perfused with a constant and adjustable flow (Q). Venous outflows were directly driven by pumps without passing through a reservoir. In each closed circuit, the total blood volume remained constant because inflow and outflow were simultaneously and equally altered. In both SC and PC, arterial pressure (Pa), i.e., systemic arterial and pulmonary arterial pressures (SAP and PAP), was a positive function of Q, and venous pressure (Pv), i.e., right atrial and left atrial pressures (RAP and LAP), was a negative function of Q. The first series of experiments involved three equal step reductions in Q from baseline to zero flow. The venous-to-arterial compliance ratio (Cv/Ca) was calculated from delta Pa/delta Pv and vascular resistance (VR) from (Pa - Pv)/Q. The values of Cv/Ca in SC increased from 9.3 +/- 0.4 to 14.5 +/- 1.1 and 21.9 +/- 1.4 (P less than 0.001) in the three-step Q reduction. VR in the SC was not significantly dependent on Q. In the PC, the Cv/Ca was approximately 2.0 and VR was 0.16 mmHg.ml-1.min.kg, both values being independent of Q. Multiple-step reduction in Q for regression equations was carried out in 8 of the 12 dogs. We found that only the SAP was a linear function of Q (ml.min-1.kg-1): SAP = 18.458 + 0.953Q.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Cyclooxygenase pathway mediates lung injury induced by phorbol and platelets.

The role of platelets in lung injury has not been well defined. In the present study of isolated perfused rat lungs, phorbol myristate acetate (PMA; 0.15 microgram/ml) or platelets (6.7 X 10(4)/ml) alone did not discernibly change the pulmonary arterial pressure (PAP) or lung weight (LW). However, the combination of platelets and PMA drastically increased the PAP and LW (delta PAP 26.2 +/- 1.0 mmHg, delta LW 2.7 +/- 0.4 g). delta PAP was positively correlated with the increase in thromboxane B2 produced by infusion of platelets and PMA (thromboxane B2 = 35.6 + 0.97 delta PAP, r = 0.67, P less than 0.01). The hypertension and edema formation induced by PMA and platelets were strongly attenuated by indomethacin, an inhibitor of platelet cyclooxygenase (delta PAP 5.6 +/- 2.0 mmHg, P less than 0.001; delta LW 0.0 +/- 0.1 g, P less than 0.001), and by imidazole, an inhibitor of thromboxane A2 synthase (PAP 8.0 +/- 2.5 mmHg, P less than 0.001; LW 0.0 +/- 0.3 g, P less than 0.01). Inactivation of platelet lipoxygenase with nordihydroguaiaretic acid mildly depressed pulmonary pressure but did not affect delta LW (delta PAP 18.9 +/- 1.6 mmHg, P less than 0.05; delta LW 3.1 +/- 0.3 g, P greater than 0.05). In vitro experiments showed that the capacity of platelets to release oxygen radicals was only 2.6% of that found for granulocytes. These results suggest that platelets may be activated by PMA to increase PAP and vascular permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Effects of air pollution resulting from wire reclamation incineration on pulmonary function in children.

This study evaluated the effect of long-term air pollution resulting from wire reclamation incineration on pulmonary function in children. General physical examination and the determination of spirometric parameters, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and forced mid-expiratory flow (FEF25-75%) were conducted in 400 primary school children between ages 9 and 11 years who reside in one control and three polluted areas. A survey using ATS-DLD-78-C questionnaire indicated that there were no significant differences in their demographic characteristics among children in the four areas under study. Those who had nonrespiratory diseases that might affect pulmonary function and those who failed to perform spirometric measurements were excluded from the study; therefore, 382 children were included in data analysis. The results revealed that (1) the mean values of FVC and FEV1 (expressed as percentage of predicted values calculated from Polgar's equations) in the polluted areas were significantly lower than the nonpolluted area (p less than 0.05), and (2) the incidence of pulmonary function abnormality in the polluted areas was greater than that of the nonpolluted area (p less than 0.05). The results indicated that air pollution produced by wire reclamation incineration can impair children's pulmonary function.

Air Pollution↗