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Biomedical subjects

Y Weng

Publications and source records attributed to Y Weng.

At least 91 records · Page 5Linked to original sources

[Radionuclide scintigraphy in etiologic diagnosis of gastrointestinal bleeding in children].

OBJECTIVE: To assess the role of radionuclide scintigraphy in etiologic diagnosis of gastrointestinal bleeding in children, especially in detecting the cases of Meckel's diverticulum or double intestine. METHODS: 99mTc-pertechnetate abdominal scintigraphy was undertaken in 26 children with history of gastrointestinal bleeding. Additional 99mTc-RBC scintigraphy was performed in 12 cases who gave a negative 99mTc-pertechnetate scintigraphy as they had the signs of active bleeding. The final diagnosis of all cases was proved by surgery and pathology or endoscopy. RESULTS: In detecting Meckel's diverticulum and double intestine, the sensitivity, specificity and accuracy of 99mTc-Pertechnetate scintigraphy were 85. 7% (12/14), 91.7% (11/12) and 88.5% (23/26) respectively. CONCLUSION: Radionuclide scintigraphy may be the first procedure to explore the etiology in the lower digestive tract.

Child↗

[Primary multiple malignant schwannoma of the heart--a rarity].

The case is presented of a 51-year-old woman with increased of nightly dyspnea. An echocardiographic examination shows two intracardiac tumors. Histological features demonstrate an malignant schwannoma. The diagnosis was verified by immunohistological proof of S-100 protein in tumor cells.

Echocardiography↗

Using aortic allograft material to treat mycotic aneurysms of the thoracic aorta.

BACKGROUND: Although mycotic aneurysms are rare in this age of antibiotics, they nevertheless represent life-threatening lesions of the aortic wall because of their high incidence of rupture and significantly high rate of recurrence. METHODS: Between March 1988 and August 1994, cryopreserved allograft material was used to treat 8 patients (mean age, 62.5 years; range, 47 to 80 years) with mycotic aneurysms of the thoracic aorta at our institution. Two patients had emergency operations; the other operations in 6 patients were elective. The aneurysms were located at the previous cannulation site of the aorta (n = 1) or at the donor/recipient aortic anastomosis (n = 1) in the patients who had heart transplantation, in the ascending aorta in 3 patients with aortic valve endocarditis, in the aortic arch in 2, and in the descending aorta in 1. The operative technique consisted of excision of the mycotic aneurysm followed by allograft patch reconstruction in 5 patients, an allograft composite graft replacement of the ascending aorta in 2 patients with endocarditis, and combined aortic allograft root replacement and allograft patch reconstruction of the ascending aorta in 1 patient. RESULTS: The underlying infections of the aorta were treated successfully in 6 patients. One heart transplant recipient had reoperation because of recurrent mycotic aneurysm after allograft patch reconstruction at the donor/recipient anastomosis. There was one early death involving a patient with Salmonella sp sepsis. CONCLUSIONS: The use of aortic allograft material for repairing mycotic aortic aneurysms is a promising and effective operative concept for managing thoracic aortic infections.

Aged↗

Heart transplantation: a single-center experience.

BACKGROUND: The success of heart transplantation led to the extension of the criteria for both recipients and donors. The aim of the study was to evaluate the experience with this therapeutic approach for end-stage heart failure at a single center. METHODS: Between April 1986 and January 1996, 1,413 patients were accepted as candidates for heart transplantation. Ventricular assist devices were used as a bridge to transplantation in 173 patients (biventricular assist device in 141 patients and left ventricular assist device in 32 patients). The longest duration of support was 572 days (average, 46 days). RESULTS: Of the 1,413 patients, 891 underwent heart transplantation (65 children/adolescents and 826 adults; 522 (36%) patients died awaiting a donor heart. The average time spent on the waiting list was 107 days. The average recipient age was 44 years, and the age of donors was extended up to 69 years. Eighty-three patients with ventricular assist devices (48%) subsequently underwent heart transplantation. Twenty-five patients (2.7%) underwent retransplantation. The 30-day mortality rate was 14%, and the overall actual survival at 1, 5, and 10 years was 80%, 59%, and 50%, respectively. Ninety-four percent of patients were in New York Heart Association functional class I or II at 1 year, and 44% returned to work after transplantation. CONCLUSIONS: Despite the broadening of the selection criteria for both recipients and donors, heart transplantation remains an effective treatment for end-stage heart failure. Nevertheless, this therapeutic approach is severely limited by a considerable disparity between the need and availability of donor organs.

Adolescent↗

Genetic and biochemical characterization of mutations in the ATPase and helicase regions of the Upf1 protein.

mRNA degradation is an important control point in the regulation of gene expression and has been linked to the process of translation. One clear example of this linkage is the nonsense-mediated mRNA decay pathway, in which nonsense mutations in a gene can reduce the abundance of the mRNA transcribed from that gene. For the yeast Saccharomyces cerevisiae, the Upf1 protein (Upf1p), which contains a cysteine- and histidine-rich region and nucleoside triphosphate hydrolysis and helicase motifs, was shown to be a trans-acting factor in this decay pathway. Biochemical analysis of the wild-type Upf1p demonstrates that it has RNA-dependent ATPase, RNA helicase, and RNA binding activities. A UPF1 gene disruption results in stabilization of nonsense-containing mRNAs, leading to the production of enough functional product to overcome an auxotrophy resulting from a nonsense mutation. A genetic and biochemical study of the UPF1 gene was undertaken in order to understand the mechanism of Upf1p function in the nonsense-mediated mRNA decay pathway. Our analysis suggests that Upf1p is a multifunctional protein with separable activities that can affect mRNA turnover and nonsense suppression. Mutations in the conserved helicase motifs of Upf1p that inactivate its mRNA decay function while not allowing suppression of leu2-2 and tyr7-1 nonsense alleles have been identified. In particular, one mutation located in the ATP binding and hydrolysis motif of Upf1p that changed the aspartic and glutamic acid residues to alanine residues (DE572AA) lacked ATPase and helicase activities, and the mutant formed a Upf1p:RNA complex in the absence of ATP; surprisingly, however, the Upf1p:RNA complex dissociated as a consequence of ATP binding. This result suggests that ATP binding, independent of its hydrolysis, can modulate Upf1p:RNA complex formation for this mutant protein. The role of the RNA binding activity of Upf1p in modulating nonsense suppression is discussed.

Adenosine Triphosphatases↗

Identification and characterization of mutations in the UPF1 gene that affect nonsense suppression and the formation of the Upf protein complex but not mRNA turnover.

To understand the relationship between translation and mRNA decay, we have been studying how premature translation termination accelerates the degradation of mRNAs. In the yeast Saccharomyces cerevisiae, the Upf1 protein (Upf1p), which contains a cysteine- and histidine-rich region and nucleoside triphosphate hydrolysis and helicase motifs, was shown to be a trans-acting factor in this decay pathway. A UPF1 gene disruption results in the stabilization of nonsense-containing mRNAs and leads to a nonsense suppression phenotype. Biochemical analysis of the wild-type Upf1p demonstrated that it has RNA-dependent ATPase, RNA helicase, and RNA binding activities. In the work described in the accompanying paper (Y. Weng, K. Czaplinski, and S. W. Peltz, Mol. Cell. Biol. 16:5477-5490, 1996) mutations in the helicase region of Upf1p that inactivated its mRNA decay function but prevented suppression of leu2-2 and tyr7-1 nonsense alleles are identified. On the basis of these results, we suggested that Upf1p is a multifunctional protein involved in modulating mRNA decay and translation termination at nonsense codons. If this is true, we predict that UPF1 mutations with the converse phenotype should be identified. In this report, we describe the identification and biochemical characterization of mutations in the amino-terminal cysteine- and histidine-rich region of Upf1p that have normal nonsense-mediated mRNA decay activities but are able to suppress leu2-2 and tyr7-1 nonsense alleles. Biochemical characterization of these mutant proteins demonstrated that they have altered RNA binding properties. Furthermore, using the two-hybrid system, we characterized the Upf1p-Upf2p interactions and demonstrated that Upf2p interacts with Upf3p. Mutations in the cysteine- and histidine-rich region of Upf1p abolish Upf1p-Upf2p interaction. On the basis of these results, the role of the Upf complex in nonsense-mediated mRNA decay and nonsense suppression is discussed.

Amino Acid Sequence↗

Correction of complete atrioventricular septal defects with the double-patch technique and cleft closure.

BACKGROUND: Controversy continues to surround determining which is the most beneficial method of complete atrioventricular septal defect repair, eg, one- versus two-patch repair, closure of mitral cleft, and the necessity of annuloplasty. METHODS: Between January 1988 and November 1995, 120 patients with complete atrioventricular septal defect underwent total correction at the German Heart Institute Berlin. Sixty-nine of the patients were infants and 51 were children or adolescents. Eleven patients had previously undergone pulmonary artery banding. One hundred three patients had Down's syndrome. In all 120 patients complete atrioventricular septal defect repair was performed using the two-patch technique. The mitral cleft was closed with interrupted sutures in 119 cases. RESULTS: Thirty-four patients required aggressive treatment of postoperative pulmonary hypertensive crises (including nitric oxide inhalation). There were 12 hospital deaths (10%). Mortality was highest in patients with persistently high postoperative pulmonary arterial pressure (pulmonary artery pressure/systemic artery pressure > 0.6) (7 of 17 patients died; 41%). Associated atrioventricular valve anomalies, especially dysplastic valve tissue and severe preoperative cardiopulmonary instability necessitating catecholamine support and artificial ventilation, represented other risk factors. There were six late deaths (5%); cumulative mortality was 15%. Four patients suffered a complete heart block and sick sinus node syndrome necessitating pacemaker implantation 1 to 6 months after operation. During the follow-up period (3 to 80 months after operation), 7 patients (6.8% of survivors) were successfully reoperated on after significant mitral valve incompetence due to an open "cleft" (suture failure) developed. CONCLUSIONS: Correcting complete atrioventricular septal defect using the two-patch technique, routine cleft closure, and atrial septal incision led to a low incidence of residual mitral valve incompetence. Mortality was primarily influenced by severe cardiopulmonary instability and additional atrioventricular valve anomalies preoperatively and the persistence of high pulmonary arterial hypertension postoperatively.

Administration, Inhalation↗

Extracorporeal membrane oxygenation as a bridge to cardiac transplantation in children.

The feasibility and efficacy of extracorporeal membrane oxygenation (ECMO) as a bridge to cardiac transplantation was examined in 6 pediatric patients who suffered irreversible myocardial failure after undergoing surgery for congenital heart defects. The mean time of ECMO support was 260.5 h, range 101-402 h. Three patients underwent transplantation, 2 of whom are long-term survivors. Progressive hypotension as a result of capillary leak syndrome precluded further ECMO support in the other 3 patients. Overall, 2 of the 6 patients survived. Major complications were encountered in 4 patients including bleeding in 2, a seizure in 1, and renal failure in 3, 2 of whom recovered renal function after transplantation. Infection did not occur in any of the 6 patients. Exchanging ECMO components was performed with no difficulties; these exchanges included a centrifugal pump once for 3 patients and a membrane oxygenator once for 2 patients. Our results indicate that ECMO can safely keep critically ill pediatric transplant candidates alive for more than 1 week with a low incidence of multiple organ failure.

Adolescent↗

Mycotic aortic aneurysms after orthotopic heart transplantation: a three-case report and review of the literature.

Mycotic aortic aneurysm is a rare yet life-threatening complication after orthotopic heart transplantation. This article reviews three cases of mycotic aortic aneurysm in heart transplant recipients developing in the first year after heart transplantation. Excision of the aneurysm and in situ reconstruction of the ascending aorta were performed with a patch of glutaraldehyde-fixed pericardium or cryopreserved aortic allograft material as a patch or conduit replacement. These cases show that early diagnosis by computed tomographic scanning, surgical treatment, high-dose parenteral antibiotics, and close follow-up are essential for successful treatment.

Adult↗

Freehand subcoronary aortic valve and aortic root replacement with cryopreserved homografts: intermediate term results.

BACKGROUND AND AIMS OF THE STUDY: The traditional method of aortic valve replacement with a homograft has been free-hand insertion in the subcoronary position. Recently, total root replacement has become increasingly popular. We present our experiences with both methods in this study. MATERIAL AND METHODS: Between January 1, 1987 and March 31, 1996, 208 patients underwent homograft replacement of the aortic valve (free-hand subcoronary technique, n = 147 and root replacement, n = 61). The age of the patients ranged between 1.5 and 78 years with a mean age of 41 years. There were 55 females and 153 males. Ninety-four patients had infected aortic root (with 47 ring abscesses) and 114 patients had sterile aortic roots. In these series, patients with small aortic root, complicated endocarditis, dilated aortic annulus and aneurysm received aortic root replacement. RESULTS: The hospital mortality of patients with non-infected and infected roots was 2.6% and 8.5% respectively making an overall hospital mortality of 5.2%. In patients with free-hand subcoronary valve implantation (AVR) and root replacement (ARR) techniques the hospital mortality was 3.4% and 9.8% respectively. The major risk factor for death was New York Heart Association functional class IV with sepsis. Eight years patient survival in patients with AVR and ARR was 95% +/- 2% and 86% +/- 4% respectively. Freedom from structural deterioration in patients with AVR and ARR was 96.5% +/- 2% and 98% +/- 3% whereas freedom from reoperation was identical 94% +/- 2% and 93% +/- 4% respectively. However, the incidence of reoperation in patients under 40 years of age, particularly in children (< 16 years of age) during the eight years' follow up was 27%. The rate of recurrent endocarditis was 3.6% in ARR patients and development of postoperative pseudoaneurysm formation occurred in 1.4% of AVR patients with endocarditis. CONCLUSION: In conclusion, ARR technique provides low rate of reoperation in the early postoperative period. Cryopreserved homografts in the subcoronary position in adult patients < 40 years of age showed excellent medium term durability and hemodynamic performance providing evidence that long term outcome with a meticulous subcoronary implantation technique is comparable to that with the ARR technique.

Adolescent↗

[Adults with congenital heart defects--clinical spectrum and surgical management].

Two hundred adults who underwent surgery for congenital heart disease at our institution within a four year period were the basis for this report. Clinical data was obtained, i.e. demographic details, past medical history, physical findings, EKGs, echocardiograms, catheterization and angiography material as well as the New York Heart Association (NYHA) class. Intraoperative findings, perioperative management, complications and morbidity and mortality were assessed. After discharge the patients were followed on an outpatient basis. Again the clinical findings, laboratory results and NYHA class were recorded. Age ranged from 16 to 75 years (mean = 38). There were 114 females and 86 males. 178 patients had primary surgical correction, 18 were reoperated after prior correction and 4 underwent palliation. Eighty-three percent of the patients were symptomatic preoperatively. Seventeen percent were diagnosed per chance, for example by a preemployment physical examination, without a prior history of heart disease. The patients were grouped according to related diagnoses (Table 1). Among the 130 patients with left to right shunts, 112 had an atrial septal defect, 7 a ventricular septal defect, 5 a persistent ductus arteriosus, and 6 partial anomalous pulmonary venous return. Atrial flutter or fibrillation occurred in approximately 10% of all patients with atrial septal defects. It was terminated either by rapid overdrive pacing or DC cardioversion. Postoperatively the patients with pulmonary hypertension were monitored invasively with arterial lines and thermodilution catheters. Therapy consisted of alkalization, hyperventilation and sedation. There was only one postoperative death in this patient group due to marked pulmonary hypertension (1/130 = 0.8%). Nineteen adults had obstruction to right or left ventricular outflow. Surgery included valvotomy, infundibulectomy and valve replacement by homograft or mechanical valve. One patient with multiple previous surgeries expired due to bleeding (3%). Thirteen patients had coarctation. All of them were hypertensive, some on medication. Surgery consisted of aortic patchplasty or interposition of a graft. There was no mortality. Perioperative antihypertensive therapy was necessary in most patients and consisted of nifedipin, nitroprussid or propanolol intravenously. Upon follow up 11 patients became normotensive, 8 of these without the need for medication. Fifteen cyanotic patients underwent 11 corrective and 4 shunt procedures (3 with tricuspid atresia, 10 with Tetralogy of Fallot and 2 with complex cyanotic heart disease. Three died due to low cardiac output or dysrhythmias (20%). The survivors improved their clinical status markedly. Seven adults with Ebstein's disease had valve reconstruction and/or ASD closure. Five had recurrent supraventricular tachycardia, 2 paradoxical emboli with neurological symptoms and 4 out of 7 had decreased exercise tolerance. One patient died postoperatively because of dysrhythmias (14%). Sixteen patients had a variety of defects, i.e. status post Rastelli operation and conduit obstruction, status post Tetralogy of Fallot with pulmonary valvar disease, corrected transposition with left AV valve insufficiency, congenital mitral valve disease and double aortic arch, no deaths. The overall operative mortality was 6/200 = 3%. the late mortality was 4/200 = 2%. The morbidity included 7 reoperations due to bleeding. Five patients needed short-term hemodialysis. One patient developed hemiplegia and two patients had permanent decrease of their left ventricular function. The mean length of follow up was 21 months. The clinical status improved from a NYHA class mean of 2.1 +/- 0.9 to 1.2 +/- 0.45 (p < 0.001). In Germany significant numbers of adults with operated and unoperated congenital heart disease do exist. Detection of these patients can be difficult due to inconspicuous murmurs or stable clinical status.

Adolescent↗

Phacoemulsification and posterior chamber intraocular lens implantation.

OBJECTIVE: The study was designed to evaluate the therapeutic effects of phacoemulsification and PMMA posterior chamber intraocular lens implantation. METHODS: The surgery was performed on 74 eyes of 67 patients with senile, complicated and congenital cataracts. RESULTS: Post-operatively, the visual acuities with spherical correction or without correction were 0.5 or better in 80.5% at one week and with correction, in 97.6% at three months. The mean astigmatism was 1.90 +/- 1.15 D at one week and 0.93 +/- 0.55 D at three months which were respectively less than that in the control group with a 10-12 mm large incision (P < 0.001), but almost the same as that in the control group with a small incision and manual nucleus division technique (P > 0.05). The main complications were iris bite in 6 eyes, capsular rupture in 2 eyes and aseptic hypopyon in one eye. The selection of cases, surgical techniques and management of intraoperative complications were discussed. CONCLUSION: These results suggest that phacoemulsification be applied extensively. However, that it has more complications and risk must be emphasized for a beginner.

Adult↗

Characterization of the VHL tumor suppressor gene product: localization, complex formation, and the effect of natural inactivating mutations.

The human VHL tumor suppressor gene has been implicated in the inherited disorder von Hippel-Lindau disease and in sporadic renal carcinoma. The homologous rat gene encodes a 185-amino acid protein that is 88% sequence identical to the aligned 213-amino acid human VHL gene product. When expressed in COS-7 cells, both the human and the rat VHL proteins showed predominant nuclear, nuclear and cytosolic, or predominant cytosolic VHL staining by immunofluorescence. A complicated pattern of cellular proteins was seen that could be specifically coimmunoprecipitated with the introduced VHL protein. A complex containing VHL and proteins of apparent molecular masses 16 and 9 kDa was the most consistently observed. Certain naturally occurring VHL missense mutations demonstrated either complete or partial loss of the p16-p9 complex. Thus, the VHL tumor suppressor gene product is a nuclear protein, perhaps capable of specifically translocating between the nucleus and the cytosol. It is likely that VHL executes its functions via formation of specific multiprotein complexes. Identification of these VHL-associated proteins will likely clarify the physiology of this tumor suppressor gene.

Amino Acid Sequence↗

Prolonged open sternotomy after pediatric open heart operation: experience with 113 patients.

Between April 1990 and November 1993, 1,252 open heart operations were performed in infants and children with congenital heart defects. Prolonged open sternotomy was used in 113 patients (9%) in 10 surgical categories. Thirty-six of these children (32%) were infants and 43 (38%) were newborns. Twenty-four patients (21%) had undergone operation previously; 3 newborns had been treated with extracorporeal membrane oxygenation before the operation. The patients were grouped according to indications for prolonged open sternotomy as follows: group I, 31 patients with squeezed (large) heart syndrome (1 death); group II, 14 patients with hemodynamic instability after sternal approximation (2 deaths/14.2%); group III, 35 patients with low output state after bypass (17 deaths/48.5%); group IV, 21 patients with extracorporeal circulatory assist devices (15 deaths/71.4%); group V, 3 patients with severe arrhythmias (no deaths); and group VI, 9 patients with atypical tamponade that necessitated reopening the sternum in the intensive care unit (6 deaths/66.6%). Overall mortality was 36.2% (41 patients). Four group IV patients were weaned successfully from extracorporeal membrane oxygenation and heart transplantation was performed successfully on two others. All but one of the deaths occurred before delayed sternal closure. After hemodynamic stabilization was achieved, the sternum was closed in all 72 surviving patients with absorbable sutures (in 86% within the first 6 days after operation). In 50 patients (69% of survivors) pericardial substitution with a polytetrafluoroethylene membrane was performed. One newborn with mediastinal infection after extracorporeal membrane oxygenation was treated successfully with retrosternal drain and suction lavage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗