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Biomedical subjects

Y Weng

Publications and source records attributed to Y Weng.

At least 37 records · Page 2Linked to original sources

Patent ductus arteriosus in very low birthweight infants: complications of pharmacological and surgical treatment.

AIMS: To evaluate complications of surgical and pharmacological treatment of symptomatic patent ductus arteriosus (PDA) in very low birthweight (VLBW) infants. PATIENTS AND METHODS: Of 931 VLBW infants consecutively admitted 1987-1998, a significant PDA prompted first-choice treatment by indomethacin in 101 infants, and surgery in 55 infants. PDA closed or became asymptomatic after indomethacin in 64 patients (63%), while 34 went on to surgery. PDA closure was achieved in all 61 infants after ligation and in 26 of 28 infants after clipping. RESULTS: Transient renal impairment after indomethacin treatment was recorded in 40 of 101 infants (40%), compared to renal impairment in 9 of 55 infants (16%) undergoing surgery without prior indomethacin. No differences in necrotizing enterocolitis and intracranial hemorrhage rates were seen. Air leak occurred in 6 of 89 infants after surgery, two of which had fatal tension pneumothorax. Intraoperative hemorrhage requiring emergency transfusion occurred in 2 infants, wound infection occurred in 2 infants and phrenic palsy in one infant. Based on an intention-to-treat analysis, the overall fatality rates were 16 of 101 (16%) for indomethacin and 14 of 55 (25%) for surgery. CONCLUSIONS: Despite the short-comings inherent to retrospective analyses, we propose that surgery should be reserved for infants not responding to pharmacological PDA closure.

Birth Weight↗

[Relationship between epidemiology of HIV-1 infection and HIV-1 subtypes in Fujian province].

OBJECTIVE: To explore the relationship of AIDS epidemic and HIV-1 subtype in Fujian province of China based on molecular findings. METHODS: HIV-1 infected persons and patient with AIDS (HIV/AIDS) were identified by AIDS surveillance project in the province. AIDS epidemic situation was estimated by related data collected from the HIV/AIDS cases. HIV-1 C2-V3 region amplified from the PBMC DNA of HIV/AIDS cases was analysed by nucleotide sequencing to identified HIV-1 subtype. RESULTS: One hundred and eighty-eight cases of HIV/AIDS were found from 1987 to the end of 2000. Among 59 AIDS cases, 53 had died. HIV infection through heterosexual contacts took up 65.4%, including 44.1% of them infected abroad. Out of them, 83.1% were infected in Southeast Asia. Thirty-nine point nine percentage of the total HIV(+) were infected in China, while 9.0% were infected through blood transmission. Sequence analysis from 41 specimens showed that there were 4 kinds of HIV-1 subtypes, including A, B, C and E. Subtype E took up 75.6% (31/41), all infected by heterosexual contacts; subtype B taking up 17.1% (7/41) with most of them infected through blood transmission; subtype A and C were seen only 1 and 2 cases respectively. Gene divergence of innergroup of subtypes E was 12.245% +/- 3.894%, while subtype B was 10.762% +/- 2.707%. The high divergence of subtype E could be attributed to the region and time of infection. CONCLUSION: HIV prevalent rate has been increasing in Fujian with major transmission route of heterosexual contact. The dominant strain of HIV-1 was subtype E.

Acquired Immunodeficiency Syndrome↗

Ethanol alters angiotensin II stimulated mitogen activated protein kinase in hepatocytes: agonist selectivity and ethanol metabolic independence.

Angiotensin II activated mitogen-activated protein kinase (MAPK) (p42 and p44) in rat hepatocytes exposed to ethanol and the relevance of ethanol metabolism on this activation was investigated. Hepatocytes, isolated from rat liver, were treated with or without ethanol for 24 h. Angiotensin II, vasopressin, insulin, serum and epinephrine significantly increased hepatocyte MAPK activity. Platelet activating factor (PAF), tumor necrosis factor-alpha (TNF-alpha), and insulin-like growth factor-1 (IGF-1) had little effect on MAPK activation. Interestingly, among the above agonists, which activated hepatocyte MAPK, ethanol exposure potentiated only angiotensin II and epinephrine-stimulated MAPK. Thus, potentiation of MAPK by ethanol exhibited agonist selectivity. In contrast to several other cells, there was prevalence of p42 over p44 MAPK band in hepatocytes. Angiotensin II treatment caused a rapid activation (peak 5 min) of MAPK followed by a decrease to basal levels in 30 min. Exposure with 100 mM ethanol potentiated the angiotensin II stimulated MAPK activity. This potentiation was partially blocked by pertussis toxin suggesting it to be a G-protein-dependent event. Treatment of the hepatocytes with pyrazole (an inhibitor of ethanol metabolism) or acetaldehyde (an ethanol metabolite) had no effect on potentiation. Thus, ethanol potentiation of hepatocyte MAPK is agonist-selective and independent of ethanol metabolism.

Angiotensin II↗

A secreted and LIF-mediated stromal cell-derived activity that promotes ex vivo expansion of human hematopoietic stem cells.

The development of culture systems that facilitate ex vivo maintenance and expansion of transplantable hematopoietic stem cells (HSCs) is vital to stem cell research. Establishment of such culture systems will have significant impact on ex vivo manipulation and expansion of transplantable stem cells in clinical applications such as gene therapy, tumor cell purging, and stem cell transplantation. We have recently developed a stromal-based culture system that facilitates ex vivo expansion of transplantable human HSCs. In this stromal-based culture system, 2 major contributors to the ex vivo stem cell expansion are the addition of leukemia inhibitory factor (LIF) and the AC6.21 stromal cells. Because the action of LIF is indirect and mediated by stromal cells, we hypothesized that LIF binds to the LIF receptor on AC6.21 stromal cells, leading to up-regulated production of stem cell expansion promoting factor (SCEPF) and/or down-regulated production of stem cell expansion inhibitory factor (SCEIF). Here we demonstrate a secreted SCEPF activity in the conditioned media of LIF-treated AC6.21 stromal cell cultures (SCM-LIF). The magnitude of ex vivo stem cell expansion depends on the concentration of the secreted SCEPF activity in the SCM-LIF. Furthermore, we have ruled out the contribution of 6 known early-acting cytokines, including interleukin-3, interleukin-6, granulocyte macrophage colony-stimulating factor, stem cell factor, flt3 ligand, and thrombopoietin, to this SCEPF activity. Although further studies are required to characterize this secreted SCEPF activity and to determine whether this secreted SCEPF activity is mediated by a single factor or by multiple growth factors, our results demonstrate that stromal cells are not required for this secreted SCEPF activity to facilitate ex vivo stem cell expansion. (Blood. 2000;95:1957-1966)

Animals↗

Influence of growth factors on tissue-engineered pediatric elastic cartilage.

OBJECTIVE: To investigate the influence of growth factors on tissue-engineered pediatric human elastic cartilage relative to potential clinical application. DESIGN: Controlled study. SUBJECTS: Eleven children ranging in age from 5 to 15 years provided auricular elastic cartilage specimens measuring approximately 1 x 1 x 0.2 cm and weighing approximately 100 mg. INTERVENTIONS: Three million chondrocytes were plated into 4 groups of Ham F-12 culture medium: group 1, Ham F-12 culture medium only; no growth factors (control group); group 2, Ham F-12 culture medium and basic fibroblast growth factor; group 3, Ham F-12 culture medium and transforming growth actor beta; and group 4, Ham F-12 culture medium and a combination of both growth factors. At 3 weeks, the cells were harvested and mixed with a copolymer gel of polyethylene glycol and polypropylene oxide (Pluronic F-127). The cell solution was injected subcutaneously into athymic mice. The constructs were harvested at up to 22 weeks of in vivo culture and histologically analyzed. RESULTS: The average number of cells generated in vitro was as follows: group 1, 12 million; group 2, 40 million; group 3, 7 million; and group 4, 35 million. Group 2 in vivo gross specimens were the largest and heaviest. Histologically, the control group and the basic fibroblast growth factor group (groups 1 and 2) exhibited characteristics compatible with normal auricular cartilage; groups 3 and 4 demonstrated cellular disorganization and moderate to severe fibrous tissue infiltration. CONCLUSIONS: Basic fibroblast growth factor demonstrates the greatest positive influence on the in vitro and in vivo growth of engineered pediatric human auricular cartilage. The results suggest that basic fibroblast growth factor has the potential for clinical application in which a goal will be to generate a large volume of tissue-engineered cartilage from a small donor specimen in a short period of time and of a quality similar to native human elastic cartilage.

Adolescent↗

Internal support of tissue-engineered cartilage.

BACKGROUND: Auricles previously created by tissue engineering in nude mice used a biodegradable internal scaffold to maintain the desired shape of an ear. However, the biodegradable scaffold incited a compromising inflammatory response in subsequent experiments in immunocompetent animals. OBJECTIVE: To test the hypothesis that tissue-engineered autologous cartilage can be bioincorporated with a nonreactive, permanent endoskeletal scaffold. MATERIALS AND METHODS: Auricular elastic cartilage was harvested from Yorkshire swine. The chondrocytes were isolated and suspended into a hydrogel (Pluronic F-127) at a cell concentration of 5 x 10(7) cells/mL. Nonbiodegradable endoskeletal scaffolds were formed with 1 of 5 polymers: (1) high-density polyethylene, (2) soft acrylic, (3) polymethylmethacrylate, (4) extrapurified Silastic, and (5) conventional Silastic. Three groups were studied: (1) a control group using only the 5 polymers, (2) the 5 polymers enveloped by Pluronic F-127 only, and (3) the implants coated with Pluronic F-127 seeded with chondrocytes. All constructs were implanted subdermally; implants containing cells were implanted into the same animal from which the cells had been islolated. The implants were harvested after 8 weeks of in vivo culture and histologically analyzed. RESULTS: Only implants coated by hydrogel plus cells generated healthy new cartilage. With 3 polymers (high-density polyethylene, acrylic, and extrapurified Silastic), the coverage was nearly complete by elastic cartilage, with minimal fibrocartilage and minimal to no inflammatory reaction. The Food and Drug Administration-approved conventional Silastic implants resulted in fragments of fibrous tissue mixed with elastic cartilage plus evidence of chronic inflammation. The polymethylmethacrylate implant was intermediate in the amount of cartilage formed and degree of inflammation. CONCLUSIONS: This pilot technique combining tissue-engineered autologous elastic cartilage with a permanent biocompatible endoskeleton demonstrated success in limiting the inflammatory response to the scaffold, especially to high-density polyethylene, acrylic, and extrapurified Silastic. This model facilitates the potential to generate tissue of intricate shape, such as the human ear, by internal support. Arch Otolaryngol Head Neck Surg. 2000;126:1448-1452

Animals↗

[Artificial heart in terminal stage of dilated cardiomyopathy in childhood].

In children with dilated cardiomyopathy the disease may progress so rapidly that they die during the waiting period before a suitable donor organ is found. Fifteen children of 4 months to 15 years of age had been in congestive heart failure with multiorgan failure due to dilated cardiomyopathy, where intensive medical treatment had failed. After resuscitation, a miniaturized pulsatile ventricular assist device for the mechanical replacement of heart function was implanted. The biventricular assist device ("Berlin Heart") consists of two extracorporeal pneumatically driven polyurethane blood pumps, with a multi-layer flexible membrane that separates a blood and an air chamber. Four silicon cannulae connect the blood pumps to the patient. A three-leaflet valve prevents blood reflux. The pumps are driven by a pulsatile electropneumatic system. In 12 of the 15 children the bridging to transplantation was successful with a support time of 1 to 98 days (mean 24 days). Nine of them were extubated and mobilized while assisted. Three children died during the support time due to hemorrhage, sepsis, and pulmonary failure. In addition, there was one infarction of the arteria cerebri media. To date seven of the transplanted children are in good condition on follow-up. The beneficial effects of ventricular assist device use are well known in adult patients and with special devices it can be transferred to infants and children in whom longer need for support is anticipated. Even in small infants it is an effective method for bridging to cardiac transplantation.

Adolescent↗

Pseudoaneurysm of the outflow graft in a patient with Novacor N100 LVAD system.

Six months after implantation of a wearable Novacor N100 left ventricular assist device, a 47-year-old patient developed a swelling that overlay the body of sternum. Computed tomographic scan of the chest revealed a pseudoaneurysm of the Novacor outflow graft. The patient was taken back to surgery and the diagnosis was confirmed at operation. Repair was performed by direct sutures via right anterolateral thoracotomy, under deep hypothermia and low flow technique. The postoperative course was uneventful.

Aneurysm, False↗

Tricuspid valve dysfunction and surgery after orthotopic cardiac transplantation.

OBJECTIVE: The study examines the prevalence of tricuspid regurgitation and biopsy-induced flail tricuspid leaflets after orthotopic heart transplantation and evaluates the results of the tricuspid valve surgery. METHODS: By a computerized search of the databases 647 of 889 patients who survived heart transplantation for more than 30 days were identified for this study. The primary tool for rejection monitoring in our institution is the daily observation of intramyocardial ECG (IMEG) based on day-by-day changes of the maximal QRS complex amplitude. Endomyocardial biopsy with 45-cm-long sheath bioptome was performed only in doubtful IMEG and echocardiographic data and at times of annual routine heart catheterization. Tricuspid regurgitation was diagnosed clinically and by echocardiography as mild, moderate and severe. Eleven patients received prosthetic valve replacements (four bioprostheses and seven mechanical valves) and six patients underwent valve reconstruction. The choice of xenograft valve was dictated by the condition of renal function. Patient survival and incidence of tricuspid regurgitation and freedom from operation for severe tricuspid regurgitation were analyzed with Kaplan-Meier method. RESULTS: The prevalence of tricuspid regurgitation was 20.1%. Mild and moderate tricuspid regurgitation was seen in 14.5 and 3.1% of the patients, respectively, who were responsive to medical therapy and remained clinically stable in NYHA class I-II. Severe tricuspid regurgitation was seen in 16 (2.5%) patients who presented signs of an acute right heart dysfunction. Tricuspid valve pathology at operation revealed biopsy-induced rupture of the Chordae tendineae at various valve segments mostly the anterior and posterior leaflets. There was one hospital death (<30 day) and five late deaths due to infection, arrhythmia and trauma and no procedural-related or directly cardiac related death. Ten patients (62.5%) are alive at a mean follow-up time of 29.9 months (range 4-81 months) and nine survivors are in NYHA class I-II and one in class III. CONCLUSIONS: Severe tricuspid regurgitation in transplanted hearts is associated mainly with biopsy-induced injury or endocarditis. Other regimes of rejection monitoring may help to eliminate this complication. Apart from our preference of valve repair, the choice of valve substitute may be influenced by the presence or the prospect of chronic renal failure. Heart transplant patients can safely undergo valve surgery with acceptable mortality, low morbidity and excellent intermediate-term clinical results. Mild to moderate functional tricuspid regurgitation is responsive to medical therapy and non-progressive and occur in 17.6% of orthotopic transplanted hearts without having a detrimental effect on the right ventricular performance.

Aged↗

Medium-term results of heart transplantation using older donor organs.

BACKGROUND: Donor heart shortage has necessitated the expansion of the donor pool by the use of older hearts. PATIENTS AND METHODS: In a 13-year period, 1,070 heart transplants were performed in 1,035 adults at the German Heart Institute Berlin. We divided the patients into 3 groups: Group I, donor age <35 years (n = 524); Group II, donor age 35 to 50 years (n = 379); Group III, donor age >50 years (n = 167). We analyzed post-operative mortality (up to 30 days), cumulative survival rates, cardiac dependent morbidity, and changes in the left/right ventricular ejection fraction as well as freedom from cytomegalovirus infection and freedom from acute rejection episodes grade >/= 2 (International Society for Heart and Lung Transplantation). We also calculated the rate of cardiac interventions per patient in the groups. RESULTS: Recipients in Group III were significantly older, compared with Groups I and II. The post-operative mortality was 16.8% in Group I, 29.8% in Group II, and 23.4% in Group III. The differences were significant (p = 0. 00001) between Group I and Group II. The long-term cumulative survival rates were significantly better in Group I when compared with Groups II and III (p < 0.00001, p = 0.014), but it did not differ between Groups II and III (p = 0.18). However, cardiac morbidity in Groups I and II was significantly lower when compared with Group III (p = 0.0009, p = 0.037). Mean left and right ventricular ejection fraction was >55% and did not significantly change in groups for up to 10 years. Freedom from cytomegalovirus infection was not significantly different between Groups II and III (p = 0.09). Significantly fewer percutaneous transluminal coronary angioplasties were performed in Group I, but comparable numbers were carried out in Groups II and III (p = 0.53). For retransplantation a similar situation occurred. CONCLUSION: We did not find significant differences in the mid-term follow-up between patients who received hearts from 35- to 50-year-old donors and from those who had received hearts from donors >50 years, despite increased cardiac morbidity in Group III. Close monitoring of the coronary situation after heart transplantation and expanded indications for revascularization in Group III makes heart transplantation with older hearts a suitable option to save the lives of patients in end-stage heart failure.

Adult↗

Surgical treatment of active infective aortic valve endocarditis with associated periannular abscess--11 year results.

AIMS: The aim of the study was to evaluate the long-term results of allograft and prosthetic valve replacement in the treatment of infective aortic valve endocarditis with periannular abscess. METHODS: Between March 1988 and March 1996, 65 patients underwent surgery for active aortic valve endocarditis and paravalvular abscess. The indications for surgery were congestive heart failure, systemic emboli and atrioventricular block III. The pre-operative evaluation was performed with transoesophageal echocardiography. Aortic valve replacement was performed with allografts in 47 cases, with mechanical valves in 15, and bioprosthetic valves in three cases. All patients with total ventricular-aortic dehiscence and prosthetic valve endocarditis were treated with allografts. RESULTS: The 30-day mortality rate was 23.5% in the prosthetic group, when compared with 8.5% in the patients treated with allografts. The rate of recurrent valve infections during the 11-year follow-up period was 27.1% in the prosthetic group and 3.2% in the allograft group. The actuarial 11-year survival rate was 82.1% in the allograft group and 64.7% in the prosthetic group. CONCLUSION: Aortic allografts are an effective treatment for infective aortic valve endocarditis with associated periannular abscess. The operative mortality and recurrent infection rates are lower than in the prosthetic group, resulting in a significantly higher survival rate. Diagnosis and surgical management of these cases should be based on pre-operative transoesophageal echocardiography.

Abscess↗

The correction of congenital heart defects with less invasive approaches.

BACKGROUND: The minimally and less invasive approaches for the surgical treatment of different heart diseases are rapidly increasing because of their cosmetic and recovery-related advantages. Presented here are the results of less invasive surgery in 51 patients with congenital heart defects. METHODS: From June 1996 to January 1999, we used less invasive techniques for the correction of congenital heart defects in 51 patients. In 32 patients, we performed right anterolateral thoracotomy (6-13 cm), and on the other 19 patients, we used the partial inferior sternotomy (4-7 cm). The ascending aorta and the caval veins were cannulated in all patients. RESULTS: The following congenital heart defects were corrected: ostium secundum atrial septal defect (n = 35), sinus venosus atrial septal defect with partial anomalous pulmonary venous connection (n = 7), ventricular septal defect (n = 7), tetralogy of Fallot (n = 1), and cor triatriatum sinistrum (n = 1). The average age of the patients was 15 years old ranging from 2 months to 48 years and the average weight 39.6 kg (range 3.8-86 kg). The patients were removed from artificial respiratory support on average 8 hours (range 1-48 hours) after surgery and left the hospital after 7 days (range 2-10 days). In 16 patients, blood transfusions were required, an average 5.7 ml/kg BW (range 1.45-19.75 ml/kg BW). The postoperative course was uneventful in all patients. Follow-up (range 3-33 months, mean 17.5 months) was complete with no late deaths or residual defects. CONCLUSION: The right anterolateral thoracotomy and the partial inferior sternotomy provide a safe approach for the correction of certain congenital heart defects. These techniques enable operative correction without any additional risks being incurred and can be performed with standard instruments and cannulation. Additional approaches for extracorporeal circulation are unnecessary.

Adolescent↗

Engineering autogenous cartilage in the shape of a helix using an injectable hydrogel scaffold.

OBJECTIVE: Previous successful efforts to tissue engineer cartilage for an auricle have used an immunocompromised nude mouse xenograft model. Subsequent efforts in an immunocompetent autogenous animal model have been less successful because of an inflammatory response directed against the foreign scaffold polymer used to provide an auricular shape. We studied an alternative polymer material and surgical technique to engineer autogenous cartilage in the shape of a human ear helix using injectable hydrogel scaffolding, Pluronic F-127 (polyethylene oxide and polypropylene oxide). SUBJECT: Yorkshire swine. MATERIAL AND METHODS: Fresh autogenous chondrocytes were suspended in a biodegradable, biocompatible co-polymer hydrogel, Pluronic F-127, at a concentration of 3 x 10(7) cells/mL. To support the contour of the implant, a skin fold channel in the shape of the helix of a human ear was created in the skin in three sites on the ventral surface of the animal. The cell-hydrogel suspension was injected through the skin fold channel. For controls, injections were made into identical channels using either cells alone or the Pluronic F-127 without cells. After 10 weeks, the specimens were excised and examined both grossly and histologically. RESULTS: Grossly, all implants retained a helical-like shape. Excised specimens possessed flexible characteristics consistent with elastic cartilage. The specimens could be folded and twisted and on release of mechanical pressure would instantly return to the original shape. Histological evaluation of the implants using H&E, Safranin O, trichrome blue, and Verhoeff's stains demonstrated findings consistent with mature elastic cartilage. Control injection of hydrogel alone demonstrated no evidence of cartilage formation and control injection of chondrocytes alone showed evidence only of disassociated elastic cartilage. CONCLUSION: Injection of autologous porcine auricular chondrocytes suspended in a biodegradable, biocompatible hydrogel of Pluronic F-127 resulted in the formation of cartilage tissue in the approximate size and shape of a human ear helix. This preliminary method extends the concept of auricular tissue engineering from an immunocompromised xenograft animal model to an immunocompetent autologous animal model.

Animals↗

Transthoracic pacing in a very low birth weight infant with congenital complete atrioventricular block.

We report our experience of pacemaker treatment in a premature infant of 830 g with congenital complete atrioventricular block due to maternal Sjögren's Syndrome. The infant was delivered by cesarean section at an estimated gestational age of 26 weeks because of fetal bradycardia, decreasing fetal movements, and hydrops. Immediate postnatal transesophageal ventricular pacing was not successful, whereas transthoracic pacing with self-adhesive patch electrodes adapted to body size resulted in an effective increase of the infant's heart rate until operative application of temporary epimyocardial pacing wires allowed external stimulation of the heart.

Adult↗

Structure-function studies of the self-assembly domain of the human immunodeficiency virus type 1 transmembrane protein gp41.

The coiled-coil region of the human immunodeficiency virus type 1 transmembrane protein (gp41) makes up the interior core of the six-helix bundle structure of the gp41 self-assembly domain. We extended our previous study of this domain (Y. Weng and C. D. Weiss, J. Virol. 72:9676-9682, 1998) by analyzing 23 additional mutants at positions that lie at the interface of the interior core and outer helices. We found nine new functional mutants. For most mutants, the activity could be explained by the ability of the modeled mutants to stabilize the six-helix bundle structure. The present study provides insights into the envelope glycoprotein fusion mechanism and information for rational drug and vaccine design.

Amino Acid Sequence↗

Performance tests of vacuum pumps in small and large dental facilities.

A study was conducted to compare and assess the performance of various vacuum pumps in small and large dental clinic operations. A four-chair dental clinic operation was set up at the laboratory to simulate a small dental clinic environment. The performance of two dry and two wet pumps was assessed in the laboratory via extensive performance data acquisition tests. Data were also collected in two small dental clinics of practising dentists. Large dental system performance tests were conducted at the Ellsworth Air Force Base and Minot Air Force Base dental clinics. At each clinic, data were collected with both the existent turbine pump and a rotary vane RAMVAC pump.

Data Collection↗

[Advances and perspectives in mechanical heart assist].

Mechanical circulatory support devices were first developed to permanently replace the failing heart. Today, however, the majority of these devices are used as a mechanical bridge in patients awaiting heart transplantation. With this indication, important information on using mechanical assist devices has been assembled. We present our experience, which has been gained since 1987 in the area of patient selection, post-implant patient care and device maintenance. More than 450 patients have since been implanted with assist devices at our institution. Mechanical circulatory support may not only lead to recovery from secondary organ failure, but also to myocardial remodeling and recovery of the heart function in some patients. Additionally we report our experience with a newly developed implantable axial flow pump and discuss the possibility and costs of permanent support in some patients.

Adult↗