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Biomedical subjects

W C Feng

Publications and source records attributed to W C Feng.

At least 19 recordsLinked to original sources
PubMed2001

Dysfunctional elimination syndrome in children without obvious spinal cord diseases.

Elimination dysfunction is a functional disease that encompasses the urinary and GI tracts. Because the presentation is varied and ED is a disease of exclusion, a thorough history and physical examination are mandatory. Noninvasive management that includes the "fundamental four" and continuous engagement and encouragement of the patient and family are the pillars of treatment. For patients who are refractory to this approach, new research in children-directed biofeedback research shows promise.

Biofeedback, Psychology↗
PubMed2001

Influence of virus strain, challenge dose, and time of therapy initiation on the in vivo influenza inhibitory effects of RWJ-270201.

The influenza virus neuraminidase inhibitor RWJ-270201 (cyclopentane carboxylic acid, 3-[cis-1-(acetylamino)-2-ethylbutyl]-4[(aminoiminomethyl)amino]-2-hydroxy-[cis, 2S, 3R, 4R]) was significantly inhibitory to an infection in mice induced by influenza A/NWS/33 (H1N1) virus when oral gavage (p.o.) treatment with 10 mg/kg per day was delayed at least 60 h after virus exposure. Treatment was 5 mg/kg twice daily for 5 days. Viral challenge doses of influenza A/Shangdong/09/93 (H3N2) virus ranging from the LD(70) to the LD(100) did not affect the marked antiviral efficacy of 12.5 mg/kg of RWJ-270201 administered p.o. twice daily for 5 days beginning 4 h pre-virus exposure; infection by an approximate 2 LD(100) dose (10(8) cell culture infectious doses/ml) was only weakly inhibited by the same treatment as seen by significant increase in mean day to death. Murine infections induced by influenza A/Bayern/57/93 (H1N1) and B/Lee/40 viruses were significantly inhibited by 100, 10, and 1 mg/kg per day of RWJ-270201 using the above treatment regimen; influenza A/PR/8/34 (H1N1) virus infections in mice were only moderately inhibited, the antiviral effects using this virus being lessening of arterial oxygen decline, reduced lung consolidation, and inhibition of lung virus titers primarily at the higher dosages.

Acids, Carbocyclic↗
PubMed2000

Interactive medical data on demand: a high-performance imaged-based approach across heterogeneous environments.

Medical data in image format continues to increase in both size and complexity. We have integrated advanced techniques in visualization, networked computing, and interface design to improve methods for accessing medical data comprising high-resolution images for reconstructions into three-dimensional volumetric representations. We present two approaches to handle the range of low to high-end client platforms, support visualization functionality, and provide the ability to manipulate very large data over heterogeneous computing and networking environments. We present examples of its use for clinical, research, and educational purposes and discuss future extensions.

Computer Communication Networks↗
PubMed1997

Nineteen-millimeter aortic St. Jude Medical heart valve prosthesis: up to sixteen years' follow-up.

UNLABELLED: BACKGROUND; Prosthetic valve replacement in a small aortic root without annulus enlargement raises concern about its long-term benefits. METHODS: Between July 1979 and June 1994, 104 (18%) of 593 patients underwent aortic valve replacement using the 19-mm St. Jude Medical heart valve prosthesis. There were 93 women and 11 men, with a mean age of 66.2 +/- 10.6 years. Forty-four patients (42%) were 70 or more years old. The mean body surface area was 1.61 +/- 0.16 m2 (range, 1.2 to 2.1 m2). Forty-nine patients (47%) underwent concomitant procedures; 23 patients (22%) required coronary artery bypass grafts and 25 patients (24%), mitral valve replacement. Ninety-eight patients (94%) presented in New York Heart Association class III and IV. RESULTS: The operative mortality was 7.6% (8 patients). Follow-up was 100% with a mean of 5.48 +/- 3.73 years (range, 1 to 16 years) and a total of 708 patient-years. There were 18 late deaths, with a mortality of 2.5% patient-years. The incidence of thromboembolism was 0.4% patient-years (3 patients) and anticoagulant-related morbidity was 0.85% patient-years (6 patients). Long-term survival in the two groups with a body surface area of less than 1.7 m2 and 1.7 m2 or more was not statistically different (p = 0.30). The univariate analysis with body surface area as a predictor of mortality showed that a larger body surface area had no effect on the long-term mortality (chi2 p value = 0.36). Survival for 5 and 10 years with the 95% confidence interval was 80.6% +/- 8.3% and 61.6% +/- 15%. Freedom from thromboembolism was 96.3% +/- 4.2% and anticoagulant-related hemorrhage was 91.8% +/- 6.8% at the end of 16 years. Cox proportional hazards model, with time-dependent covariates, showed that events of thromboembolism, anticoagulant-related hemorrhage, and myocardial infarction during follow-up increased the risk of late death (risk ratio, 9.5, 10.3, and 32.8, respectively). The age at operation was an independent risk factor, with decreased survival with age 70 or more years (p = 0.0002). However, body surface area (p = 0.97) and concomitant cardiac procedures (p = 0.86) were not statistically significant predictors of death. CONCLUSIONS: The long-term performance of the 19-mm St. Jude Medical heart valve prosthesis in the small aortic root is satisfactory irrespective of the body surface area, and it is a viable alternative for such patients.

Adult↗
PubMed1997

St. Jude Medical cardiac valves in small aortic roots: follow-up to sixteen years.

Prosthetic aortic valve replacement in the small aortic root raises concerns of its long-term effects. Between 1978 and 1994, 270 patients received only small aortic prostheses (< or = 21 mm). There were 117 men (43.3%) and 153 women (56.7%) with a mean age of 64.3 +/- 11.6 years (range 19 to 87 years). The body surface areas ranged from 1.2 to 2.26 m2 (mean 1.71 +/- 0.27 m2). Ninety-one percent of patients had New York Heart Association class III or IV symptoms and 33% underwent concomitant coronary artery bypass grafting. The operative mortality rate was 3.3% (9 deaths) and follow-up (100%) extended from 1 to 16 years (mean 6.2 +/- 3.9 years) with cumulative survival of 1676 patient-years. There were 55 late deaths (3.28% per patient-year). The linearized rates of morbidity reported as percent per patient-year were as follows: structural failure, 0%; paravalvular leak, 0.12%; prosthetic endocarditis, 0.24%; anticoagulant-related morbidity, 1.24%; and thromboembolism, 1.10%. In 89% of the survivors New York Heart Association functional performance had improved to class II or I. The actuarial survival with 95% confidence intervals at 5, 10, and 16 years was 86.9% (82.5%, 91.3%), 68.6% (60.6%, 76.6%), and 53.6% (36.6%, 70.6%), respectively. Freedom from late valve-related events (95% confidence intervals) at 10 and 16 years was as follows: thromboembolism, 91.2% (86.6%, 95.8%) and 78.3% (62.6%, 94%); anticoagulant-related morbidity, 89.1% (83.8%, 94.4%) and 81.0% (65.1%, 96.9%); and prosthetic endocarditis, 98.8% (97.5%, 100%) and 98.8% (97.5%, 100%), respectively. Multivariate analysis revealed age at operation, myocardial infarction, and endocarditis affected the long-term survival. The risk of sudden death irrespective of body surface area and valve size was not statistically different. Thus the long-term performance of the St. Jude Medical valve in small aortic roots is satisfactory.

Adult↗
PubMed1995

Stroke during coronary artery bypass grafting using hypothermic versus normothermic perfusion.

Does the abandonment of hypothermic perfusion during cardiopulmonary bypass compromise cerebral protection and thus lead to a higher incidence of stroke? From 1987 to June 1993, 2,585 consecutive patients underwent myocardial revascularization using warm-body (perfusion at 37 degrees C), cold-heart (cold cardioplegic arrest) surgical technique and were followed for new overt neurologic deficits. Perfusion pressure was maintained between 50 and 70 mm Hg, and hematocrit was kept around 20%. There were 25 operative deaths (1%) in this normothermic group, and new neurologic deficits developed after operation in 25 patients (1%). These results were compared retrospectively with those in 1,605 patients who underwent myocardial revascularization between 1980 and 1986 with moderate hypothermic (25 degrees to 30 degrees C) perfusion, the same surgical team, and similar operative techniques. The normothermic group included more elderly patients, more patients with left ventricular dysfunction and unstable angina, and more frequent use of an internal mammary artery conduit. Neurologic complication rates were 1% and 1.3% for the normothermic and hypothermic perfusion groups, respectively. Risk factors for stroke that were identified included age greater than 70 years, severity of aortic arch atherosclerosis, and severe hypotension in the perioperative period. Thus, in a large clinical series, the incidence of overt neurologic injuries was found to be no higher with normothermic perfusion than with hypothermic perfusion.

Aged↗
PubMed1994

Analyses of beta-thalassemia mutant DNA interactions with erythroid Krüppel-like factor (EKLF), an erythroid cell-specific transcription factor.

We describe functional tests and molecular modeling of erythroid Krüppel-like factor (EKLF) interactions with its DNA binding site. EKLF, a zinc finger-containing, erythroid-specific transcription factor, binds and transactivates from the CACCC element, an evolutionarily conserved DNA sequence present within a large number of erythroid-specific promoters and enhancers. This DNA binding element is the site of naturally occurring point mutations that give rise to beta-thalassemia. We have directly tested whether CAC site point mutations (including two of the beta-thalassemia mutants) affect EKLF transactivation and DNA binding function. In vivo analyses demonstrate that EKLF is unable to transactivate a reporter plasmid that contains these mutations. In vitro analyses reveal a 40-100-fold decrease in binding affinity for these sites that accounts for the in vivo observations. The homology between the three EKLF and Zif268 zinc fingers and their conserved sequence-specific contacts to their target site allowed us to formulate a molecular model of the EKLF/CAC site complex, based primarily on energy minimization/refinement of the Zif268/DNA co-crystal structure. These models suggest that both specific and nonspecific hydrogen bonding play a critical role in the ability of EKLF to prefer binding to its cognate site. Analysis of sequence-specific contacts by EKLF to its target site within the beta-globin promoter verified the residues predicted to be important by the functional and modeling data. Together these results demonstrate that EKLF displays a strong discriminatory ability among potential DNA target sites consistent with the beta-thalassemia data. They also suggest that lack of EKLF binding to these sites may play a determining role in its phenotype, and they strengthen the evidence in favor of EKLF's proposed role in erythroid-specific transcriptional activation through the CACCC elements.

Amino Acid Sequence↗
PubMed1994

Modeling a conformationally sensitive region of the membrane sector of the fungal plasma membrane proton pump.

A molecular model for transmembrane segments 1 and 2 from the fungal proton pumping ATPase has been developed, and this structure is predicted to form a helical hairpin loop structure in the membrane. This region was selected because it is highly conformationally active and is believed to be an important site of action for clinically important therapeutics in related animal cell enzymes. The hairpin loop is predicted to form an asymmetric tightly packed structure that is stabilized by an N-cap between D140 and V142, by hydrogen bonding between residues in the turn region and the helices, and by pi-pi interactions between closely apposed aromatic residues. A short four-residue S-shaped turn is stabilized by hydrogen bonding but is predicted to be conformationally heterogeneous. The principal effect of mutations within the hairpin head region is to destabilize the local close packing of side groups which disrupts the pattern of hydrogen bonding in and around the turn region. Depending on the mutation, this causes either a localized or a more global distortion of the primary structure in the hairpin region. These altered structures may explain the effects of mutations in transmembrane segments 1 and 2 on ATP hydrolysis, sensitivity to vanadate, and electrogenic proton transport. The conformational sensitivity of the hairpin structure around the S-turn may also account for the effects of SCH28080 and possibly ouabain in blocking ATPase function in related animal cell enzymes. Finally, the model of transmembrane segments 1 and 2 serves as a template to position transmembrane segments 3 and 8. This model provides a new view of the H(+)-ATPase that promotes novel structure/function experimentation and could serve as the basis for a more detailed model of the membrane sector of this enzyme.

Amino Acid Sequence↗
PubMed1994

Neurological complications during myocardial revascularization using warm-body, cold-heart surgery.

Does the use of warm-body perfusion in elderly patients with severe cerebrovascular disease lead to a higher incidence of stroke, due to hypotension secondary to low systemic vascular resistance? Two thousand, three hundred eighty-three (2,383) consecutive myocardial revascularizations were performed (1987-1992) using warm-body (perfusion 37 degrees C), cold-heart surgery (cold cardioplegic arrest). The perfusion pressure was maintained between 50-70 torr; hematocrit was kept around 20%. Prospective data during hospitalization revealed 23 operative deaths (1%), and 24 patients (1%) who developed new neurological signs after surgery. The latter formed three groups: Group I consisted of six patients with severe neurological deficits, who never regained consciousness and died after support systems withdrawal. Group II included 14 patients with postoperative clinical evidence of focal cerebral infarction (9 had hemiplegia, 2 had visual disturbance, and 3 showed alteration of memory), all of whom had residual defects at discharge; Group III was composed of four patients with minor neurological deficits after surgery (hemiparesis, gait disturbance, mental changes) which had cleared up by discharge. These data were compared retrospectively with 1605 patients (1980-1986) undergoing myocardial revascularization with moderate (25-30 degrees C) hypothermia and the same surgical team and operative techniques. Both groups had similar preoperative demographics except the warm group included more elderly patients, higher numbers with unstable angina and poor ejection fraction, and more frequent use of a mammary artery conduit. Neurological complications were 1% and 1.3% for the normothermic and hypothermic perfusion groups respectively. Incremental risk factors of stroke remain: age over 70 years, diffuse atherosclerosis of the aorta, carotid occlusive disease, and severe hypotension during perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Perioperative paraplegia and multiorgan failure from heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia and thrombosis syndrome is a rare but devastating complication. We report a patient with heparin-induced thrombocytopenia in whom heparin-induced thrombocytopenia and thrombosis syndrome developed after a cardiac operation, complicated by acute thrombosis of the aorta followed by renal failure, paralysis, and ischemic necrosis of the lower extremities. The literature suggests aspirin, dipyridamole, and iloprost as effective prophylactic agents for perioperative heparin-induced thrombocytopenia and thrombosis syndrome. This unfortunate complication underscores the importance of close platelet count monitoring in all preoperative patients undergoing prolonged heparin therapy.

Aorta, Abdominal↗
PubMed1993

Warm body, cold heart surgery. Clinical experience in 2817 patients.

Systemic hypothermia is used almost universally in cardiac surgery. Since 1987, 2817 patients have had normothermic cardiopulmonary bypass (NCPB, "warm body", bladder temperature 36 degrees C) with cold blood cardioplegic arrest ("cold heart", 8 degrees-14 degrees C) during open heart surgery. No patients were denied this technique regardless of age, condition or severity of surgery. Clinical Characteristics in Patients: Age range: 16-84 years, mean 66; male/female ratio 3:1; pump time (min) 24-183, mean 91; cross-clamp time (min) 15-148, mean 68; types of surgery: coronary artery bypass (n = 2214), valvular (n = 489) and miscellaneous (aneurysms, tumors, arrhythmias, congenital, etc) (n = 114). One thousand and sixty-nine (1069) patients had urgent coronary artery bypass grafting (CABG). The ejection fraction was less than 0.40 in 843 patients (30%). The thirty-day operative mortality for the entire group was 1.7% (48/2817 patients): CABG = 1% (23/2214 patients), valvular = 3% (15/489 patients) and miscellaneous 9% (10/114 patients). Postoperative complications were: perioperative myocardial infarction (34 patients) = 1.2%, postoperative bleeding requiring reexploration (37 patients) = 1.3%, stroke (27 patients) = 1%, and mediastinal infection (21 patients) = 0.7%. During NCPB (WARM) systemic vascular resistance was extremely low, cardiac output was high and it was easier to wean patients from the pump. No intraaortic balloon pump was used during this period. Pulmonary complications and coagulopathy were extremely rare. These results provide reassurance that NCPB (WARM) in combination with cold cardioplegic arrest provides excellent myocardial and total body protection during cardiac surgery and is particularly suitable for high-risk patients.

Aged↗
PubMed1993

Warm body, cold heart: myocardial revascularization in 2383 consecutive patients.

Systemic hypothermia is used almost universally in cardiac surgery. Since 1987, 2383 patients underwent normothermic cardiopulmonary bypass (NCPB, "warm body", bladder temperature 36 degrees C) with cold blood cardioplegic arrest ("cold heart", 8-14 degrees C) during myocardial revascularization. No patients were denied this technique regardless of age, condition or severity of surgery. Clinical characteristics in patients: Age range: 31-92 years, mean 66; male/female ratio 3:1; pump time (min): 23-228, mean 80; cross clamp time (min): 18-152, mean 60. One thousand, one hundred and sixty-one patients (49%) had urgent coronary artery bypass grafting (CABG). Ejection fraction was less than 0.4 in 843 patients (30%). Thirty-day operative mortality was 1% (23/2383 patients). Postoperative complications were: perioperative myocardial infarction (35 patients) = 1.5%; postoperative bleeding requiring reexploration (33 patients) = 1.4%; stroke (22 patients) = 0.9%; mediastinal infection (24 patients) = 1%; and renal insufficiency (25 patients) = 1%. During NCPB (warm), systemic vascular resistance was extremely low, cardiac output was high and it was easier to wean patients from the pump. No patient required the intraaortic balloon pump during peri- and post-operative periods. Pulmonary complications and coagulopathy were extremely rare. These results provide reassurance that NCPB (warm) in combination with cold cardioplegic arrest provides excellent myocardial and total body protection during myocardial revascularization and is particularly suitable for high-risk patients.

Aged↗
PubMed1992

Long-term results of St. Jude Medical valve in the tricuspid position.

Little is known of the St. Jude Medical heart valve's long-term clinical performance in the tricuspid position. Fourteen patients underwent tricuspid valve replacement between 1981 and 1984. Ages of the patients ranged from 32 to 81 years. Eight patients (68%) were in New York Heart Association class IV preoperatively. Twelve patients had other concomitant cardiac operations. One patient (8%) died within 30 days after operation, due to cerebrovascular accident. Postoperatively, all patients were anticoagulated with warfarin sodium and showed improvement in functional class. There were no mechanical valve failures or thromboses in patients on the anticoagulation regimen. Follow-up in all patients extended over 7 to 10 years with a mean of 8 years. There were six late deaths unrelated to valve function. The actuarial survival curve with these patients is 50% over 10 years. In conclusion, the St. Jude Medical valve is a good mechanical substitute in the tricuspid position, and we recommend its use when reconstruction is not possible and there is no contraindication for anticoagulation.

Adult↗