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Biomedical subjects

M H Wu

Publications and source records attributed to M H Wu.

At least 73 records · Page 4Linked to original sources

Control of idiopathic ventricular fibrillation by implantable cardioverter-defibrillator in a child who survived sudden death.

Idiopathic ventricular fibrillation (VF) is extremely rare in children who have not previously undergone cardiac surgery. Patients resuscitated from idiopathic VF remain at risk for recurrence. The use of an implantable cardioverter-defibrillator (ICD) effectively prevents such recurrences. We report the case of a 12-year-old girl who had a history of recurrent syncope and had survived an episode of VF. Serial studies after prolonged but successful resuscitation, including echocardiography, an electrocardiogram (ECG), and coronary angiography failed to reveal abnormal cardiac structures responsible for VF. No abnormal conduction pathways or abnormal early or late after depolarization were found on electrophysiologic study. The ST segments of the 12-lead ECG remained normal after procainamide challenge. The patient underwent ICD implantation 2 weeks after admission and syncope did not recur during a follow-up of 14 months. This report emphasizes that idiopathic VF may be responsible for syncope in children. ICD therapy prevents the recurrence of idiopathic VF and the associated risk of sudden death.

Child↗

Comparison of the BACTEC MGIT 960 with Löwenstein-Jensen medium for recovery of mycobacteria from clinical specimens.

SETTING: Taiwan Provincial Chronic Disease Control Bureau. OBJECTIVE: To evaluate the rate of recovery and the mean time to detection (TTD) of mycobacteria in clinical specimens with two culture systems, the BACTEC MGIT 960 and Löwenstein-Jensen (LJ) medium. DESIGN: We studied 365 specimens, collected from 166 patients. Specimens were processed with standard N-acetyl-L-cysteine (NALC)-NaOH method, then inoculated onto BACTEC MGIT 960 and onto LJ slants. RESULTS: A total of 124 mycobacterial isolates (114 Mycobacterium tuberculosis and 10 non-tuberculous mycobacteria) were detected. The recovery rates were 94% (117/124) with BACTEC MGIT 960 and 75.8% (94/124) with LJ. The rates of contamination for each of the systems were 5.5% with BACTEC MGIT 960 and 4.1% with LJ. The TTDs for mycobacteria were 10.7 days with BACTEC MGIT 960 and 30.6 days with LJ. Excluding the non-tuberculous mycobacteria, the TTDs for M. tuberculosis were 11.1 days with BACTEC MGIT 960 and 30.7 days with LJ. The difference in TTD between smear-positive and smear-negative specimens for either mycobacteria (10.0 vs 12.6 days; P = 0.06) or M. tuberculosis (10.1 vs 12.7 days; P = 0.06) with BACTEC MGIT 960 was not statistically significant. CONCLUSION: The BACTEC MGIT 960 system can expedite the recovery of mycobacteria in culture. Combined with conventional solid medium, it also increases the overall recovery of mycobacteria in culture.

Acetylcysteine↗

Outcomes of transcatheter valvotomy in patients with pulmonary atresia and intact ventricular septum.

The results of transcatheter valvotomy in pulmonary atresia with intact ventricular septum (PA-IVS) patients are presented with an attempt to identify the predictive factors for pulmonary valvotomy alone as definitive treatment. Between June 1995 and December 1997, 14 PA-IVS neonates with tripartite right ventricle underwent an attempted pulmonary valvotomy. For perforation of the pulmonary valve, a guidewire was used in 4, and a radiofrequency guidewire in 10 patients. Two outcome groups were identified. Group I included those in whom transcatheter treatment achieved a definitive success; group II patients required surgery despite an initial successful valvotomy. The attempt failed in 3 patients, 1 of whom had pericardial effusion. Perforation of the pulmonary valve was achieved in 11 patients: 2 with a guidewire and 9 with a radiofrequency guidewire. A subsequent balloon valvuloplasty was performed in these 11 patients. After valvuloplasty, mean right ventricular pressure decreased from 124 +/- 24 to 60 +/- 15 mm Hg (p <0.01). One died of heart failure and infection 10 days later, despite successful weaning from prostaglandin E1. Group I patients (n = 6) were treated with transcatheter valvotomy alone. Group II patients (n = 4) required right ventricular outflow patch. Significant differences between the 2 groups (group I vs II) were identified in tricuspid valve Z value (0.52 +/- 0.37 vs -1.25 +/- 0.48, p <0.05), pulmonary valve Z value (-3.47 +/- 0.59 vs -5.43 +/- 0.94, p <0.05), and ratio of right-to-left ventricular area on the apical 4-chamber view (0.73 +/- 0.06 vs 0.49 +/- 0.03, p <0.05). There were no significant differences in hemodynamic characteristics between the 2 groups. After a follow-up period ranging from 7 to 35 months (mean 18 +/- 10.3), the most recent echocardiograms in the 10 patients showed a mean pressure gradient across the pulmonary valve of 17 +/- 15 mm Hg. All 10 patients had an oxygen saturation of >92%. Transcatheter valvotomy using a radiofrequency guidewire is a safe and effective treatment in selected patients with PA-IVS. Transcatheter valvotomy can be a definitive treatment in PA-IVS patients with a tricuspid valve Z value > or = -0.1, pulmonary valve Z value > or = -4.1 and ratio of right-to-left ventricular area > or = 0.65.

Catheterization↗

Activated neutrophils induce hyperpermeability and phosphorylation of adherens junction proteins in coronary venular endothelial cells.

The endothelial adherens junction is formed by complexes of transmembrane adhesive proteins, of which beta-catenin is known to connect the junctional protein vascular endothelial (VE)-cadherin to the cytoskeleton and to play a signaling role in the regulation of junction-cytoskeleton interaction. In this study, we investigated the effect of neutrophil activation on endothelial monolayer integrity and on beta-catenin and VE-cadherin modification. Treatment of cultured bovine coronary endothelial monolayers with C5a-activated neutrophils resulted in an increase in permeability as measured by albumin clearance across the monolayer. Furthermore, large scale intercellular gap formation was observed in coincidence with the hyperpermeability response. Immunofluorescence analysis showed that beta-catenin and VE-cadherin staining changed from a uniform distribution along the membrane of control cells to a diffuse pattern for both proteins and finger-like projections for beta-catenin in neutrophil-exposed monolayers. Correlatively, there was an increase in actin stress fiber formation in treated cells. Finally, beta-catenin and VE-cadherin from neutrophil-treated endothelial cells showed a significant increase in tyrosine phosphorylation. Our results are the first to link neutrophil-mediated changes in adherens junctions with intercellular gap formation and hyperpermeability in microvascular endothelial cells. These data suggest that neutrophils may regulate endothelial barrier function through a process conferring conformational changes to beta-catenin and VE-cadherin.

Animals↗

Role of O6-alkylguanine-DNA alkyltransferase in protecting against cyclophosphamide-induced toxicity and mutagenicity.

Cyclophosphamide is used to treat a wide range of human malignancies. However, it is also a known carcinogen associated with induction of therapy-related leukemia and bladder cancer. The DNA repair protein, O6-alkylguanine-DNA alkyltransferase (AGT), protects cells from the toxic and mutagenic effects of O6-alkylating agents. We report here the contribution of AGT in protecting against the toxic and mutagenic effects of cyclophosphamide. CHO cells transduced with wild-type human AGT (CHO(AGT)) and pcDNA3 (CHOpcDNA3) were treated with activated cyclophosphamide derivatives, 4-hydroperoxycyclophosphamide (4-HC), 4-hydroperoxydidechlorocyclophosphamide (4-HDC), a progenitor of acrolein, and phosphoramide mustard (PM). The results show that CHO(AGT) is 7- or 20-fold less sensitive to the toxic effects of 30 microM 4-HC or 300 microM 4-HDC, respectively, than CHOpcDNA3 cells as measured by cell survival using a colony-forming assay. CHO(AGT) cells treated with 20 microM 4-HC or 200 microM 4-HDC produced 4- or 7-fold lower mutation frequency as measured at the HPRT locus than CHOpcDNA3 cells treated with the same dose of drugs. At 30 microM acrolein, the cell survival for CHO(AGT) was 30% compared with 18.7% for CHOpcDNA3. The mutation frequency of acrolein at the same dose was 57 mutants/10(6) cells in CHOpcDNA3 compared with no mutants in CHO(AGT). In contrast, CHO(AGT) and CHOpcDNA3 cells treated with PM had similar survival curves and exhibited no difference in mutation frequency. The present study demonstrates that AGT plays an important role in protecting against the toxic and mutagenic effect of cyclophosphamide and suggests that acrolein, not PM, is responsible for generating the toxic and mutagenic lesion(s) protected by the AGT protein.

Alkyl and Aryl Transferases↗

Balloon dilatation for critical pulmonary stenosis.

This study was conducted to investigate the outcome of balloon valvuloplasty for critical pulmonary stenosis in young infants. During a 6.2-year period between January 1992 and February 1998, 34 infants with critical pulmonary stenosis, aged 1 to 58 days (16.8+/-16.6 days), underwent attempted balloon valvuloplasty in this institution. The procedure was accomplished in 28 patients, but failed in six. Surgical pulmonary valvotomy was performed in the six patients with one mortality. Immediately following valvuloplasty, the mean right ventricular systolic pressure decreased from 109.2+/-28.6 to 55.1+/-23.6 mm Hg in the 28 patients (P<0.01). The mean pressure gradient decreased from 85.6+/-29.4 to 26+/-21.4 mm Hg (P<0.01). However, one who had a severely hypoplastic right ventricle requiring prolonged prostaglandin E1 infusion after valvuloplasty underwent a right ventricular outflow tract patch. After a follow-up period ranging from 2 months to 6.4 years (30.5+/-19.1 months), one patient developed recurrent pulmonary stenosis and underwent a repeated balloon valvuloplasty. Of the 27 patients (79%) with a definitive success of balloon valvuloplasty, the mean pressure gradient estimated with Doppler echocardiography at most recent follow-up was 15.2+/-6.8 mm Hg. Therefore, balloon valvuloplasty is the procedure-of-choice for critical pulmonary stenosis. Surgery should be reserved for those with unsuccessful balloon valvuloplasty.

Arrhythmias, Cardiac↗

Regression of ductus arteriosus aneurysm in a neonate demonstrated by three-dimensional computed tomography.

We present a case of ductus arteriosus aneurysm in a neonate in whom the diagnosis was made by echocardiography, three-dimensional surface rendering computed tomography (CT) and was subsequently confirmed by angiography. Regression of aneurysm after indomethacin treatment was clearly demonstrated in a follow-up CT scan. To our knowledge, this is the first report of ductus arteriosus aneurysm and its regression detected by 3D surface rendering CT.

Aneurysm↗

Aberrant left brachiocephalic vein: CT imaging findings and embryologic correlation.

Computed tomography was utilized to evaluate aberrant left brachiocephalic vein (ALBCV), an infrequently discussed congenital vascular anomaly among Chinese people. Associated vascular variation and possible embryonic correlation are discussed. Since 1990, a total of 14 cases of ALBCV have been reported in patients receiving CT scan of chest, and was mainly an incidental diagnosis. One case was confirmed angiographically and two others were confirmed by magnetic resonance imaging. Emphasis was placed on the entry of the azygos vein into the superior vena cava (SVC), the length of the SVC, and the presence of other cardiovascular abnormalities. Of the 14 cases of ALBCV, the level of azygos vein entry was higher than the origin of the SVC in 7 cases: 4 were approximately the same level and 3 were lower. The average length of the SVC was approximately 5. 6 cm shorter than that of the general population, which is approximately 7.0 cm. Three cases had associated vascular anomaly. Most cases of ALBCV had azygos vein drainage level higher than or equal to the origin of the SVC. Right-sided aorta is one of the causes giving rise to the ALBCV during embryonic development. The CT scan remains a definitive diagnostic modality for ALBCV.

Adolescent↗

Clinical and experimental demonstration of complete healing of porous Dacron patch grafts used for closure of the arteriotomy after carotid endarterectomy.

A clinical porous Dacron patch graft used for closure after carotid endarterectomy was explanted 24 hr postmortem during autopsy. There had been no TIAs or stroke postoperatively, and the cause of death was congestive heart failure. The graft had been implanted for 25 months. The specimen had a very clean surface, was completely incorporated by full-wall tissue ingrowth, and the flow surface was covered with well-organized neointima containing endothelial cells and smooth muscle cells, as confirmed by immunological studies. For comparison, animal experiments were performed. In both the clinical and experimental specimens the carotid patches were patent without neointimal compromise of the lumen, and their healing patterns were similar, with endothelium on the flow surface.

Aged↗

Accelerated healing of Dacron grafts seeded by preclotting with autologous bone marrow blood.

> Studies have suggested that bone marrow-derived cells in the circulation may have the capacity and potential to endothelialize and heal vascular graft surfaces. We have investigated whether accelerated endothelialization could be achieved for Dacron grafts seeded by preclotting with bone marrow blood (BMB). Five 8 mm x 6 cm Dacron grafts seeded and preclotted with BMB and four controls preclotted with peripheral blood were implanted in the descending thoracic aorta (DTA) of mongrel dogs for 2 and 4 weeks. Two additional BMB DTA grafts were studied for 3 months. Five pairs of BMB and control grafts (4 mm x 6 cm) were bilaterally implanted into the carotids of dogs for 1 week and five pairs for 4 weeks. All grafts remained patent. BMB seeding/preclotting was a simple, effective method to accelerate early graft endothelialization without increasing thrombogenicity. Further studies are needed before clinical application can be recommended.

Animals↗

Morphology and histology of human and canine internal thoracic arteries.

BACKGROUND: We evaluated human and canine internal thoracic arteries (ITAs) to determine whether the latter is valid for studies relevant to clinical use. METHODS: We studied 19 human ITAs obtained from 1 female and 14 male victims of recent fatal accidents who had no evidence of cardiovascular disease (mean age = 39+/-19 years; range = 15 to 79 years), and ITAs of 21 randomly-selected mongrel dogs of both sexes, weighing 18-40 kg (average = 24.3+/-5.7 kg). Specimens were fixed in formalin at a controlled pressure of 120 mm Hg, before extensive assessment that included intimal thickening, condition of the internal elastic lamina, and number of medial elastic lamellae and vasa vasorum. RESULTS: The canine morphology and histology were similar to the human ITAs, but there was no intimal hyperplasia, and the media and adventitia were thinner (ITAs of humans older than 40 years had significant increases in medial thickness, as well as in overall length). Morphologically and histologically, the left and right canine ITAs were almost completely the same. CONCLUSIONS: Canine ITAs are valid for bilateral comparative studies and are a useful tissue source and model for clinically-relevant experimental studies.

Adolescent↗

Genetic tracing of arterial graft flow surface endothelialization in allogeneic marrow transplanted dogs.

In order to trace genetically the source of fallout endothelialization on arterial grafts, six beagle dogs with successful autologous bone marrow transplantation received composite tandem aortic grafts with an isolated, totally impervious Dacron graft and a porous Dacron graft for 12 weeks. For impervious segments, five of 12 fresh tissue samples were Factor VIII/von Willebrand factor + (FVIII/vWF) and seven had faint or negative signals; three of the FVIII/vWF + samples had alpha-actin + smooth muscle cells. Polymerase chain reaction (PCR) study showed eight had a pure donor DNA genotype and four had donor/host mixed, with the donor predominant. Of 12 AgNO3-stained samples, 11 showed pure donor type and one had donor/host mixed, with the donor predominant. For porous segments, all 12 fresh samples had positive flow surface FVIII/vWF and alpha-actin cells. PCR showed all these samples and all 12 AgNO3-stained samples had donor/host mixed type, but the host pattern was predominant. Porous graft healing appears to involve both cellular fallout and tissue ingrowth, and bone-marrow-derived cells may be a source for fallout.

Animals↗

Electrophysiological profile after inward rectifier K channel blockade by barium in isolated rabbit hearts. Altered repolarization and unmasked decremental conduction property.

AIMS: The aims of this study were to define the changes of cardiac conduction properties after selective IK1 blockade in isolated hearts. METHODS AND RESULTS: Intracardiac recording and stimulation in Langendorff-perfused rabbit hearts were used to define cardiac conduction properties after Ba2+, a well known IK1 blocker. Ba2+ prolonged the corrected QT interval and decreased, or even abolished, the amplitude of the T wave. The conduction time through the sinoatrial (SA interval), the atrioventricular node (AH interval) and His-Purkinje system (HV interval) were not significantly changed. However, at higher atrial pacing rates the HV interval was lengthened by Ba2+ in a frequency-dependent manner. The recovery curve of the His-Purkinje system (the relationship of H2V2 to V1H2) was changed by Ba2+ to a prematurity-dependent pattern (AV nodal behaviour). Such a response was neither observed with 4-aminopyridine (Ito blocker) nor with d-sotalol (IK blocker). The atrial and ventricular refractory periods as well as the relative refractoriness (measured by the difference between relative refractory period and the absolute refractory period) of the ventricular tissue were increased by Ba2+. CONCLUSION: The electrophysiological profile of selective IK1 block in isolated hearts revealed altered repolarization of cardiac tissue. The decremental conduction properties, which are normally present in the atrioventricular node (with a paucity of IK1), were unmasked by IK1 block in the His-Purkinje system. The T wave, particularly its amplitude, is more closely related to IK1 than to Ito.

Animals↗

Acute poisoning with a herbicide containing imazapyr (Arsenal): a report of six cases.

BACKGROUND: Acute pesticide poisoning is a major cause of morbidity and mortality in Taiwan and herbicides are most frequently implicated. Imazapyr [2-(4-isopropyl-4-methyl-5-oxo-2 imidazoline-2-yl)nicotinic acid] is a new herbicide, recently registered in Taiwan under the tradename "Arsenal" (Imazapyr 23.1%, Cyanamid Taiwan Corporation, Taipei). Imazapyr is also marketed as Assault, Chopper, Contain, and Pivot. To the best of our knowledge, there is no information in the literature concerning acute toxicity in humans after ingestion of herbicides containing this compound. METHOD: Six cases of acute poisoning with Arsenal occurred during the period 1993-1997 in a single hospital. Emergency room records and medical charts were reviewed. RESULTS: Of 6 cases, 5 were suicide attempts and 1 was an act of violence inflicted on a child. Three of the 6 patients (50%) presented with severe symptoms, including impairment of consciousness and respiratory distress requiring intubation. Other presentations included metabolic acidosis (2), hypotension (2), leukocytosis (3), fever (2), mild elevation of hepatic transaminase and creatinine (2), unconjugated hyperbilirubinemia (2), oral ulceration (2), pharyngolaryngitis (2), and chemical burns of the cornea (1). All cases had copious vomiting after ingestion of Arsenal. No mortality occurred. CONCLUSION: According to our observations, it appeared the toxic syndrome that results from a large quantity (> 100 mL) of Arsenal herbicide ingestion consists of hypotension, pulmonary dysfunction, oral mucosal and gastrointestinal irritation, and transient liver and renal dysfunction. However, the existence of a dose-response relationship, with increasing amounts of ingestion resulting in more severe symptoms, needs further observation and studies that include a larger series.

Adult↗

Sequence of the V. parahaemolyticus gene for cytoplasmic N, N'-diacetylchitobiase and homology with related enzymes.

The nucleotide sequence of the gene encoding the cytoplasmic N, N'-diacetylchitobiase [EC 3.2.1.14] from Vibrio parahaemolyticus (ATCC #27969) has been determined. The deduced peptide sequence of this unusual beta-hexosaminidase surprisingly shows minimum evolutionary relationship to two other reported N, N'-diacetylchitobiases from vibrios, except in highly conserved regions which are also homologous to lysosomal beta-hexosaminidases from eukaryotes including humans. In contrast, the two other beta-hexosaminidases from vibrios with reported sequences are much more closely related to each other. This novel 85 kDa cytoplasmic glycosyl hydrolase with restricted specificity participates in the high level utilization of chitin-derived 2-deoxy-2-acetamido-D-glucose (GlcNAc) by vibrios as one of two parallel pathways for the metabolism of N,N'-diacetylchitobiose [Bassler, B.L., Yu, C., Lee, Y.C., and Roseman, S. (1991) J. Biol. Chem. 266, 24276-24286]. These pathways use chitin-binding proteins for the adherence of the bacterial chitinase to the substrate, and an extracellular chitinase and a periplasmic chitodextrinase to produce N,N'-diacetylchitobiose. The V. parahaemolyticus cytoplasmic N,N'-diacetyl-chitobiase reported herein appears to be a unique protein, lacking a signal sequence, and genetically distant from other known chitinoclastic beta-N,N'-diacetyl-hexosaminidases. This is consistent with its limited substrate specificity to small GlcNAc terminated oligosaccharides and its cytoplasmic rather than periplasmic localization.

Amino Acid Sequence↗

Usefulness of intravenous propofol anesthesia for radiofrequency catheter ablation in patients with tachyarrhythmias: infeasibility for pediatric patients with ectopic atrial tachycardia.

General anesthesia is sometimes required during radiofrequency catheter ablation (RFCA) of various tachyarrhythmias because of an anticipated prolonged procedure and the need to ensure stability during critical ablation. In this study, we examine the feasibility of using propofol anesthesia for RFCA procedure. There were 150 patients (78 male, 72 female; mean age 30 years, range 4-96 years) in the study. Electrophysiologic study was performed before and during propofol infusion in the initial 20 patients and was performed only during propofol infusion in the remaining 130 patients. In the initial 20 patients, propofol infusion increased the sinus rate and facilitated AV nodal conduction. The accessory pathway effective refractory period, as well as the sinus node recovery time, atrial effective refractory period, and ventricular effective refractory period were not significantly changed. There were 152 tachyarrhythmias in 150 patients (24 atrial flutter, 31 AV nodal reentrant tachycardia, 68 AV reciprocating tachycardia, 12 ventricular tachycardia, and 17 atrial tachycardia). Most (148/152) tachycardias remained inducible after anesthesia and RFCA was performed uneventfully. However, in four of the seven pediatric patients with ectopic atrial tachycardia, the tachycardia terminated after propofol infusion and could not be induced by isoproterenol infusion. Consequently, RFCA could not be performed. Intravenous propofol anesthesia is feasible during RFCA for most tachyarrhythmias except for ectopic atrial tachycardia in children.

Adolescent↗

A variant of long QT syndrome manifested as fetal tachycardia and associated with ventricular septal defect.

Two patients with a novel variant of long QT syndrome are described. The clinical course was characterised by an in utero onset of ventricular tachycardia and atrioventricular block (at 26 and 30 weeks' gestational age, respectively), and an association with a ventricular septal defect. Studies of both patients' families identified relatives with prolonged QT interval, syncope, or sudden death. One patient died of intractable ventricular tachycardia at 4 days old. The other received beta blocker treatment and a pacemaker. She died suddenly at the age of 10 months. The unique association with ventricular septal defect and the malignant clinical course warrants further molecular diagnosis of this novel variant of long QT syndrome.

Female↗