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Biomedical subjects

C H Chang

Publications and source records attributed to C H Chang.

At least 163 records · Page 9Linked to original sources
PubMed1998

Osteoinduction using bone morphogenic protein in irradiated tissue.

OBJECTIVE: To prove the efficacy of bone morphogenic protein as an osteoinductive agent in irradiated tissue. DESIGN: Prospective randomized controlled trial designed to test the effectiveness of recombinant bone morphogenic protein 2 (rBMP-2) combined with solid hydroxyapatite disks in an irradiated tissue bed. SUBJECTS: Eighteen adult, male, white New Zealand rabbits weighing 3.0 to 3.5 kg. INTERVENTION: The rabbits were randomly divided, with 9 receiving radiation treatment and 9 receiving no radiation treatment. Each animal underwent implantation of 2 hydroxyapatite disks onto the snout at 9 weeks following radiation treatment. One disk was impregnated with rBMP-2 and the other with buffer only. The animals were killed at 3, 6, or 20 weeks after implantation for analysis. RESULTS: Histological analysis demonstrated that rBMP-2 was equally effective as an osteoinductive agent in the irradiated and nonirradiated tissue. We also found significantly increased new bone formation in the rBMP-2 group vs the buffer group. CONCLUSIONS: This study supports the potential clinical utility of rBMP-2 and solid hydroxyapatite in irradiated tissue beds. These findings have interesting implications for patients with head and neck cancer who have undergone radiation therapy and need bony reconstruction.

Animals↗
PubMed1998

Preparation and characterization of heparin-containing SBS-g-DMAEMA copolymer membrane.

The grafting of dimethyl amino ethyl methacrylate (DMAEMA) onto styrene-butadiene-styrene triblock copolymer (SBS) membrane was subsequently conducted by UV-radiation induced graft copolymerization without degassing to obtain the SBS-g-DMAEMA copolymer membrane. The substituted amino groups on the SBS-g-DMAEMA graft copolymer membrane were quaternized with iodomethane, and then the membrane was treated with heparin to prepare the heparin-containing SBS-g-DMAEMA copolymer membrane (SBS-g-DMAEMA-HEP). The graft copolymer membrane (SBS-g-DMAEMA) and the heparin-containing SBS-g-DMAEMA copolymer membrane (SBS-g-DMAEMA-HEP) were characterized by FTIR spectroscopy. The heparin content was determined by toluidine blue heparin assay. Contact angle, water content, and protein adsorption of fibrinogen and albumin experiments were also performed to evaluate the effect of graft amount and heparin content on the biocompatibility of SBS-g-DMAEMA and SBS-g-DMAEMA-HEP graft copolymer membranes. By using Kaelble's equation, the surface tension of SBS-g-DMAEMA and SBS-g-DMAEMA-HEP were determined. It was found that with increasing grafting amount and the heparin content, the surface tension and water content of SBS-g-DMAEMA membrane increased, whereas the contact angle decreased. The amount of the adsorption of albumin and fibrinogen decreased with increasing graft amount and heparin content. However, there was a minimum for adsorption of proteins in the SBS-g-DMAEMA and SBS-g-DMAEMA-HEP membranes.

Biocompatible Materials↗
PubMed1998

Solvation studies of DMP323 and A76928 bound to HIV protease: analysis of water sites using grand canonical Monte Carlo simulations.

We examine the water solvation of the complex of the inhibitors DMP323 and A76928 bound to HIV-1 protease through grand canonical Monte Carlo simulations, and demonstrate the ability of this method to reproduce crystal waters and effectively predict water positions not seen in the DMP323 or A76928 structures. The simulation method is useful for identifying structurally important waters that may not be resolved in the crystal structures. It can also be used to identify water positions around a putative drug candidate docked into a binding pocket. Knowledge of these water positions may be useful in designing drugs to utilize them as bridging groups or displace them in the binding pocket. In addition, the method should be useful in finding water sites in homology models of enzymes for which crystal structures are unavailable.

Alcohols↗
PubMed1998

Unexpected binding mode of tick anticoagulant peptide complexed to bovine factor Xa.

The structure of recombinant tick anticoagulant peptide (rTAP) complexed to bovine factor Xa at 3.0 A resolution reveals the structural basis for the specificity and the high affinity of rTAP. Three N-terminal residues, Tyr501, Asn502 and Arg503, play a critical role in the complex formation as suggested by earlier mutagenic studies and the ornithodorin-thrombin complex. Unexpectedly, the side-chain of Tyr501 is located in the S1 pocket, although factor Xa favors arginine as a P1 residue. Arg503 is located at the aryl binding pocket and forms a salt-bridge with Glu97 of factor Xa. The autolysis loop, which is disordered in the uninhibited factor Xa structure, is involved in the formation of the complex as a part of the secondary binding site. The C-terminal helix of rTAP interacts with factor Xa as a secondary binding determinant. The N-terminal residues of rTAP reorganize during the formation of the factor Xa-rTAP complex from the conformation found in the solution into an extended conformation. The presence of the secondary binding site confirms the proposed two-step kinetic mechanism based on the results of a mutagenesis study.

Animals↗
PubMed1998

Video-assisted thoracoscopic surgery for spontaneous hemopneumothorax.

We operated on 403 patients with spontaneous pneumothorax between 1992 and 1996. Among these cases, 11 (2.7%) were spontaneous hemopneumothorax. The patients were all men, with ages ranging from 19 to 28 years (mean 23.8 years). The amount of blood drainage ranged from 650 to 2300 ml. Video-assisted thoracoscopic surgery was performed on these patients within 1 day after admission. The sources of bleeding were in the parietal and visceral pleurae of ruptured bullae (n = 6), the parietal pleura (n = 4), or the visceral pleura (n = 1). During operation, the ruptured bullae can be managed by an endoscopic linear stapler for a bullectomy, and the bleeding parietal pleura of the torn adhesion can be coagulated directly. Postoperative recovery of the 11 patients was uneventful, and they were discharged 4 to 10 days after the operation. No recurrence of spontaneous hemopneumothorax or any other complications occurred during follow-up. Thus spontaneous hemopneumothorax can be readily managed by cauterizing a bleeding site where appropriate, excising the apicocystic disease, and pleurodesis. As a minimally invasive method, video-assisted thoracoscopic surgery may be considered an initial treatment procedure in patients with spontaneous hemopneumothorax.

Adult↗
PubMed1998

Surgical closure of atrial septal defect. Minimally invasive cardiac surgery or median sternotomy?

BACKGROUND: Closure of ostium secundum atrial septal defect (ASD) vis median sternotomy (MS) is a simple procedure for most cardiac surgeons. Minimally invasive cardiac surgery (MICS) has recently been applied in the management of intracardiac lesions. METHODS: We report our experience in surgical closure of isolated ASD via MICS in 60 patients and via MS in 58 patients. There was no difference between these two groups in gender, age, body weight, ratio of systemic to pulmonary blood flow, and pulmonary arterial pressure. RESULTS: The duration of cardiopulmonary bypass was significantly longer in the MICS group than in the MS group [27 to 126 min (42 +/- 12) and 14 to 158 min (27 +/- 11), respectively; (p < 0.001]. However, the length of incision, incidence of temporary pacemaker wire insertion rate, duration of endotracheal intubation, timing of oral intake, postoperative day drainage amount, incidence of parenteral analgesic injection, postoperative length of stay, and return to normal activity interval were significant shorter and lower in patients of the MICS group than in those of the MS group. All the patients recovered rapidly from the surgery. Follow-up was complete in all patients, with no late complications and no residual shunt. CONCLUSION: Our results suggest that MICS is a good option for surgical closure of ASD.

Adolescent↗
PubMed1998

Cerebral blood flow velocity and vasomotor reactivity before and after shunting surgery in patients with normal pressure hydrocephalus.

The purpose of this study was to evaluate pre- and post-shunting haemodynamic changes and their correlation with the clinical results in normal pressure hydrocephalus (NPH). Accordingly, eleven demented patients with clinical signs suggestive of NPH received examinations of cerebral blood flow velocity (BFV) and vasomotor reactivity (VMR) by transcranial Doppler sonography with carbogen testing before and after shunt treatment. Computerized tomography (CT), clinical assessment and neuropsychological grading were performed prior to and at 3 months following surgery. A control group consisting of 10 patients was included to establish baseline data. The pre-operative CBF studies in the anterior cerebral artery (ACA) and the middle cerebral artery (MCA) revealed the NPH patients did not have significant decreases of BFVs, but had significant decreases of carbogen VMR (P < 0.05). After shunting, there were no significant changes of the BFVs as compared with the pre-shunting data. The post-shunting VMR of the ACA was significantly higher than the pre-shunting one (p < 0.05), but there was no variation in that of the MCA. Both the values of post-shunting VMR in ACA and the post-shunting increase in VMR in MCA of the 7 shunt-responsive patients who improved mentally and in other symptoms were significantly higher than those of patients without improvement (p < 0.05). In addition, the five patients with gait improvement showed significantly higher values of post-shunting VMR of ACA and the post-shunting increase of VMR for both ACA and MCA when compared with those patients without gait improvement (p < 0.05, respectively). Our study supports the view that patients with NPH had various degrees of impaired VMR in both the ACA and the MCA, but showed insignificant reduction in BFVs, indicating a compensatory mechanism of CBF over time to accommodate the subnormal state of cerebral perfusion pressure. Shunt placement would improve the VMR in responsive patients. Postoperatively, an increase of VMR tends to accompany improvement of the functional state: that in the MCA alone is associated with symptomatic improvement in mental function and that increase in VMR in both the ACA and the MCA with improvement in gait, respectively.

Adult↗
PubMed1998

Minimally invasive cardiac surgical techniques in the closure of ventricular septal defect: an alternative approach.

BACKGROUND: Minimally invasive cardiac surgical techniques recently have been applied in the management of a variety of intracardiac lesions. METHODS: Fourteen patients (6 boys and 8 girls; age, 8.9 +/- 5.5 years; body weight, 29.0 +/- 13.5 kg) were operated on using minimally invasive cardiac surgical techniques for the closure of a ventricular septal defect (subarterial in 11 patients and perimembranous in 3 patients). The operations were performed through a left anterior minithoracotomy and were guided by video-assisted endoscopic techniques under femorofemoral cardiopulmonary bypass. The myocardium was protected by continuous coronary perfusion with hypothermic fibrillatory arrest. The right ventricular outflow tract was entered after pericardiotomy was performed. RESULTS: Closure of the defect (directly in 4 patients and by patch in 10 patients) was performed successfully in all patients. A right ventricular outflow tract obstruction and ruptured sinus of Valsalva aneurysm also were repaired in 1 patient each. The duration of cardiopulmonary bypass was 41 +/- 10 minutes (range, 28 to 100 minutes) and the total operative time was 2.2 +/- 0.8 hours (range, 1.3 to 3.5 hours). All the patients recovered rapidly from their operation and had an uneventful postoperative course. Follow-up (mean, 6.2 months; range, 6 to 9 months) was complete in all patients. There were no late deaths. Transthoracic echocardiographic examination showed no residual shunt and no aortic regurgitation in all patients. CONCLUSIONS: Our experience demonstrates that minimally invasive cardiac surgical techniques are technically feasible and an alternative option for the repair of a ventricular septal defect.

Cardiac Surgical Procedures↗
PubMed1998

Minimal access surgical techniques in coronary artery bypass grafting for triple-vessel disease.

BACKGROUND: Minimal access surgical techniques in coronary artery bypass grafting have been used mainly in the management of single-vessel disease. METHODS: Fifteen patients, 11 men and 4 women with a mean age of 64.1 years (range, 35.7 to 78.0 years), underwent operation for triple-vessel disease using minimal access techniques. The procedures were performed through a limited left parasternal thoracotomy using femorofemoral extracorporeal circulation. The myocardium was protected by the antegrade infusion of cold blood cardioplegic solution while the aorta was cross-clamped. RESULTS: Under direct vision, the left saphenous vein grafts were connected sequentially to the diagonal branch, obtuse marginal branch, and posterior descending branch, and the left internal thoracic artery graft was anastomosed to the left anterior descending artery in each patient. The mean aortic cross-clamp time was 86 +/- 17 minutes (range, 67 to 125 minutes). The mean duration of extracorporeal circulation was 112 +/- 22 minutes (range, 82 to 162 minutes). The postoperative course was uneventful in all patients. Follow-up was complete in all patients at a mean of 7.4 months (range, 6.0 to 8.5 months), and there were no late deaths or angina. Coronary angiography in 8 patients showed patent grafts. CONCLUSIONS: Our experience demonstrates that minimal access surgical techniques in coronary artery bypass grafting are technically feasible and may be an alternative approach in the surgical revascularization of triple-vessel disease.

Adult↗
PubMed1998

One-stage sternal stenting with homograft bone after cardiac operation in pediatric patients.

Low cardiac output after open heart operations in neonates and infants carries a high mortality. Delayed sternal closure may be life-saving but may prolong hospital stay and increase costs. To circumvent these issues, we shaped homograft bone and interposed it between the sternal edges to allow primary wound closure in 2 pediatric patients. Midterm results are satisfactory.

Bone Transplantation↗
PubMed1998

Video-assisted minimal access in excision of left atrial myxoma.

BACKGROUND: Minimal access surgery with video-assisted endoscopy has been applied to the correction of intracardiac lesions. We report our experience using this technique in surgical excision of left atrial myxoma in 3 patients. METHODS: From November 1995 to March 1997, 3 female patients, ages 45 to 80 years (mean, 62.7 years), received emergency operations for excision of left atrial myxoma. These operations were performed through a right anterior submammary minithoracotomy or right parasternal incision with the assistance of endoscopy during femoro-femoral cardiopulmonary bypass. The myocardium was protected by continuous coronary perfusion with fibrillatory arrest or cardioplegic arrest with aortic cross-clamping. RESULTS: All the tumors were excised completely through the right atrial approach. The bypass time was 92 to 148 minutes (mean, 111 minutes). The operation time was 3.2 to 4.4 hours (mean, 3.7 hours). There were no hospital deaths. Follow-up, which ranged from 6 to 19 months (mean, 10.5 months), was complete in all patients. Transthoracic echocardiographic examination showed good ventricular function without any residual tumors. Patients were found to be in New York Heart Association functional class I or II. They were satisfied with the good cosmetic healing of the incision. CONCLUSIONS: Our experience demonstrates that minimal access surgery is a technically feasible, safe, and effective procedure in surgical excision of left atrial myxoma.

Aged↗
PubMed1998

In vitro cytotoxicity of IgG antibodies on vascular endothelial cells from patients with endemic peripheral vascular disease in Taiwan.

A unique peripheral vascular disorder called 'blackfoot disease' is endemic in a limited area on the south-west coast of Taiwan. Clinically, the signs and symptoms of blackfoot disease (BFD) are similar to those of arteriosclerosis and Buerger's disease. A destruction of vascular endothelial cells (ECs) takes place at an early stage in the affected limbs. Currently, the cause of BFD is believed to be artesian drinking water containing a high concentration of arsenic and/or humic substances, although the mechanism of EC destruction is not entirely understood. The purpose of the present study was to examine the factors related to EC damage in BFD. Thus, we investigated the effects of purified IgG collected from patients with BFD (BFD-IgG) and from normal controls (N-IgG) on cultured EC. We found that: (1) EC binding activity of BFD-IgG was significantly higher than that of N-IgG; (2) BFD-IgG, at a concentration higher than 100 microg/ml but not N-IgG, induced concentration-dependent EC cytotoxicity; (3) BFD-IgG at a concentration of 100 microg/ml stimulated neither the release of von Willebrand factor nor the expression of intercellular adhesion molecule-1 by EC. Fluorescent video microscopic examination revealed an increase in transcapillary and interstitial diffusion of nailfold capillary loops in clinically normal fingers of BFD patients. These findings strongly suggested that immunological mechanisms played a significant role in the pathogenesis of BFD. We propose that only persons who produce the IgG anti-endothelial cell antibody are potential victims of BFD.

Antibodies, Anti-Idiotypic↗
PubMed1998

A possible role for protein kinase C in CO2/H+-induced c-fos mRNA expression in PC12 cells.

Recently we have found that hypercapnia induces nuclear protein (FOS) expression in the brainstem chemosensitive neurons, including catecholamine-containing cells. In the present studies we examined the role of protein kinase C (PKC) pathway in CO2-induced c-fos expression. Because of the complexity of the CNS system, experiments were performed in pheochromocytoma cells (PC12 cells). These cells originate from neuronal crest and express catecholaminergic traits. We depleted PKC from PC12 cells by prolonged (48 h) exposure to high concentration of phorbol 12-myristate, 13-acetate (PMA, 100 nM), and then determined the expression of: (1) c-fos mRNA by Northern blot (2) PKC isoforms, tyrosine phosphorylated and unphosphorylated MAP (mitogen activated protein) kinases by Western blot. Depletion of PKC abolished the effect of CO2 on c-fos mRNA expression, inhibited MAP kinases tyrosine phosphorylation and suppressed the expression of PKC(alpha) and PKC(zeta). These results suggest that MAP kinases, PKC(alpha) and/or PKC(beta) might be involved in CO2-induced c-fos mRNA expression.

Animals↗
PubMed1998

Transmission blocks for lower neck and inguinal lymph node radiotherapy.

We evaluate techniques for radiotherapy to low neck and inguinal lymph nodes. Partial transmission blocks (PTBs) simplify treatment planning, daily setup, and improve reproducibility and dose homogeneity. PTBs minimize the risk for dose misadministration to critical organs. Disadvantages include doses that are potentially lower to the medial cervical lymphatics and higher to the femur. PTBs can surmount common treatment planning problems.

Groin↗
PubMed1998

Totally minimally invasive cardiac surgery for coronary artery disease.

OBJECTIVE: We report our experience using minimally invasive techniques both to perform coronary artery bypass and harvesting of saphenous vein grafts in 25 patients with left main or triple vessels disease. METHODS: From March 1997 to June 1997, 25 patients received elective coronary artery bypass grafting using minimally invasive surgical techniques for left main or triple vessels disease. Saphenous vein grafts were harvested using minimally invasive techniques under direct vision. The coronary artery bypass grafting was performed through a limited left anterior parasternal minithoracotomy under femoro-femoral or aorto-atrial cardiopulmonary bypass. The myocardium was protected by antegrade infusion of cold blood cardioplegic solution while the aorta was cross-clamped. RESULTS: Three to four distal anastomoses were performed with the saphenous vein graft and the left internal thoracic arterial graft. The aortic cross-clamp time was 60-135 min. The duration of cardiopulmonary bypass was 89-172 min. The postoperative course was uneventful for all patients. All patients were found to be in New York Heart Association functional class I or II on follow-up from 3-7 months after surgery. CONCLUSIONS: Minimally invasive coronary artery surgery is technically feasible and can be performed in left main or triple vessel disease safely and effectively for complete revascularization.

Cardiopulmonary Bypass↗
PubMed1998

Minimally invasive cardiac surgery for intracardiac congenital lesions.

OBJECTIVE: Minimally invasive cardiac surgery has recently been applied to the correction of intracardiac lesions. This report reviews our experience of minimally invasive cardiac surgery in 119 patients with intracardiac congenital lesions. METHODS: From October 1995 to April 1997, 119 patients (48 male and 71 female, aged 0.9-65 years old, 18.5+/-17.8) received elective minimally invasive cardiac surgery at Chang Gung Memorial Hospital, Taipei, Taiwan for repair of atrial septal defect (96 patients) or ventricular septal defect (23 patients). The operations were performed through right submammary incision (ASD) or left parasternal minithoracotomy (VSD), under femoro-femoral or femoro-atrial cardiopulmonary bypass with fibrillatory arrest. RESULTS: All of the defects were repaired successfully. The bypass time was 25-125 min (46+/-18). The operation time was 1.5-5.2 h (2.8+/-0.8). The postoperative course was uneventful in all patients. Follow-up (1.0-18.2 months, mean 7.3) was complete, with no late deaths or residual shunt. All patients were found to be in NYHA functional class I or II. CONCLUSION: Our experience demonstrate that minimally invasive cardiac surgery is a technically feasible, safe, and effective procedure in surgical correction of selective simple intracardiac congenital lesions, yielding good short-term results.

Adolescent↗