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Biomedical subjects

Wei Sun

Publications and source records attributed to Wei Sun.

At least 163 records · Page 9Linked to original sources
PubMed2003

A mechanistic study of danazol dissolution in ionic surfactant solutions.

This study examined the dissolution mechanism of the neutral drug danazol into solutions of the ionic surfactant sodium dodecyl sulfate (SDS). The effect of counterion concentration on drug dissolution was also studied by controlling the solution ionic strength (IS). The laminar flow apparatus of Shah and Nelson was chosen to measure in vitro dissolution rates for its simulation of physiological hydrodynamics. A mathematical model was developed to test the proposed mechanism for dissolution. Transport of the dissolved drug away from the tablet surface is the slow step in the process. Two major physicochemical properties, drug solubility in surfactant solutions and the effective diffusion coefficients used in the model, were measured in separate experiments for use in the transport model. Pulsed field proton nuclear magnetic resonance spectroscopy ((1)H NMR) was used to measure the drug diffusion coefficient. Actual drug dissolution rates were determined by multiplying the measured effluent drug concentration in the aqueous medium by its flow rate. The assumption of a transport-controlled dissolution rate was tested by plotting the measured dissolution rates as a function of medium flow rate in a log-log plot. A slope of 1/3 is predicted by the model and slopes of 0.26 to 0.32 were found experimentally, suggesting that the transport controlled mechanism is accurate. The model-predicted dissolution rates were compared with the experimental data. For SDS solutions without IS control, the model calculated data are 20-35% lower than the experimental results, whereas with IS control, the error is only 0.4-4%. We believe that there is significant electrostatic interaction between micelles in processes with low IS or poor IS control. In that situation, the nuclear magnetic resonance (NMR)-measured drug diffusivity would not be its actual value in the dissolution process.

Algorithms↗
PubMed2003

Histiocytic sarcoma involving the central nervous system: clinical, immunohistochemical, and molecular genetic studies of a case with review of the literature.

Histiocytic sarcoma (HS) is a rare disease, and there has been much confusion concerning the diagnostic criteria for this entity. Since immunohistochemical and cytogenetic techniques have become more universally available, many cases initially diagnosed as histiocytic sarcoma have been reclassified as other diseases. We describe a case of HS that presented as a single mass lesion in left occipital lobe. At autopsy the tumor also involved the meninges as a thick exudate. Histologic examination showed numerous large pleomorphic malignant cells with areas of necrosis, numerous neutrophils, and phagocytosis by tumor cells. Immunohistochemically, the tumor cells stained positively with antibodies directed against most histiocytic markers and did not stain with antibodies directed against myeloid markers, dendritic markers, CD30, ALK1, or other lymphoid markers. Molecular cytogenetic analysis showed no rearrangement [i.e. t(2;5) translocation or other variant] by fluorescence in situ hybridization. The T-cell receptor-gamma chain by multiplex polymerase chain reaction showed a polyclonal pattern. No heavy or light chain gene rearrangements were found. To our knowledge, this is the first reported autopsy case of this rare entity primarily involving the brain and meninges.

Adolescent↗
PubMed2003

Biaxial mechanical response of bioprosthetic heart valve biomaterials to high in-plane shear.

Utilization of novel biologically-derived biomaterials in bioprosthetic heart valves (BHV) requires robust constitutive models to predict the mechanical behavior under generalized loading states. Thus, it is necessary to perform rigorous experimentation involving all functional deformations to obtain both the form and material constants of a strain-energy density function. In this study, we generated a comprehensive experimental biaxial mechanical dataset that included high in-plane shear stresses using glutaraldehyde treated bovine pericardium (GLBP) as the representative BHV biomaterial. Compared to our previous study (Sacks, JBME, v.121, pp. 551-555, 1999), GLBP demonstrated a substantially different response under high shear strains. This finding was underscored by the inability of the standard Fung model, applied successfully in our previous GLBP study, to fit the high-shear data. To develop an appropriate constitutive model, we utilized an interpolation technique for the pseudo-elastic response to guide modification of the final model form. An eight parameter modified Fung model utilizing additional quartic terms was developed, which fitted the complete dataset well. Model parameters were also constrained to satisfy physical plausibility of the strain energy function. The results of this study underscore the limited predictive ability of current soft tissue models, and the need to collect experimental data for soft tissue simulations over the complete functional range.

Animals↗
PubMed2003

Tricuspid valve detachment in closure of congenital ventricular septal defect.

From January 1991 through December 2001, 600 patients underwent closure of a perimembranous ventricular septal defect through a right atrial approach at our institution. In 122 of these patients, the operation included temporary detachment of a tricuspid valve septal leaflet from the annulus to allow complete visualization of a perimembranous ventricular septal defect The mean age of the patients at surgery was 4.6 years in those who underwent leaflet detachment and 4.7 years in the 478 patients who did not (P > 0.05). Preoperatively, all patients were in sinus rhythm. Echocardiography showed trivial tricuspid regurgitation in 21 of the patients undergoing detachment and in 39 of the non-detachment patients. There was no difference in bypass time or aortic cross-clamp time between the 2 groups. Postoperatively, 3 patients in the non-detachment group had heart block; all other patients were in sinus rhythm. Echocardiograms on the 7th postoperative day showed small residual ventricular septal defects in none of the patients who underwent valve detachment and in 10 of the non-detachment patients; mild tricuspid regurgitation was present in 12 non-detachment patients only; and trivial tricuspid regurgitation was present in 19 patients who underwent valve detachment and in 29 who did not. There was no hospital death in either group. Long-term follow-up showed no progression of tricuspid regurgitation or tricuspid stenosis. All patients remained in sinus rhythm. This study suggests that tricuspid valve detachment is a safe, effective technique that improves exposure for ventricular septal defect repair and does not adversely affect valve competence.

Cardiac Surgical Procedures↗
PubMed2003

Postinfectious encephalitis (21 cases appended).

OBJECTIVE: To report 21 cases of postinfectious encephatitis according to ICD-NA, postinfectious/parainfectious encephalitis is an independent disease. METHODS: Using the uniform criteria provided by The Council of State and Territorial Epidemiologists (CSTE) and Centers for Disease Control and Prevention (CDC), we diagnosed postinfectious encephalitis among patients admitted to The First Hospital of Harbin Medical University and analyzed the characteristics of these cases. RESULTS: All the patients had histories of preceding infection, and most of them suffered from mental and conscious disorders. Adrenocortical hormone was effective. CONCLUSIONS: Postinfectious encephalitis is an independent disease. According to this article, about 10% patients with encephalitis admitted to our hospital are postinfectious.

Adolescent↗
PubMed2003

[Expression of cyclooxygenase-2 mRNA and identification of its spliceriant in human myometrium obtained from women in labor].

OBJECTIVE: To investigate the expression of cyclooxygenase-2 (COX-2) in human lower segments of myometrium obtained from women in labor and those not in labor and identify the splice variant of COX-2. METHODS: Reverse transcriptase-polymerase chain reaction (RT-PCR) was used for investigating the expression of COX-2. According to the sequence of rat COX-2 splice variant, the primers were designed and synthesized, then the splice variant of COX-2 in human myometrium from woman in labor was identified, cloned into vector and sequenced. RESULTS: The results showed that (1) The Expression of COX-2 mRNA was lower in human myometrium obtained from women who were not in labor than those in labor. (2) A new band of COX-2 was obtained in myometrium from a woman in labor. The fragment includes an unspliced intron, which locates between exons 7 and 8. CONCLUSION: COX-2 gene is not only expressed highly in human myometrium from women in labor, but also produced splicing variant by alternative splicing.

Adult↗
PubMed2003

Clinical diagnostic approach to severe acute respiratory syndrome: an institution's experience.

OBJECTIVE: To analyze diagnostic approach to severe acute respiratory syndrome (SARS) according to the diagnostic criteria issued by the Ministry of Health of China (MHC). METHODS: The clinical data and the diagnostic results of 108 cases of SARS were retrospectively reviewed according to the MHC criteria. RESULTS: There were 55 men and 53 women, with a median age of 34.5 years (range, 12 - 78 years). The interval between their first visit and clinical diagnosis was 3 days (range, 0 - 14 days). The diagnosis was made at the first visit in 7 (6.5%, 7/108) cases with a history of exposure to SARS patients and infiltrates on chest radiograph. Eighty-nine (82.4%) and 12 (11.1%) patients were categorized as probable cases and suspected cases respectively at their first visit and a clinical diagnosis of SARS was made subsequently. The interval between first visit and reaching the final diagnosis was 1 - 3 days in 72 (66.7%) cases and 4 days in 29 (26.9%) cases. The final diagnosis was made in 0 - 14 days (median, 2 days) for those (n = 59, 54.6%) with a history of close contact with SARS patients and 2 - 8 days (median, 3 days) for those (n = 49, 45.4%) living in Beijing but without such a history (P = 0.03). The chest radiograph was interpreted as unremarkable in 26 (24.1%) cases at their first visit, and the diagnosis was made in 4 days (range 2 - 8 days), which was significantly longer compared with other cases (P < 0.001). In patients without a history of close contact with SARS patients, all the five criteria were met after combination antibiotic therapy had failed. CONCLUSIONS: A chest radiograph without infiltrates at the early stage of SARS is an important factor responsible for delayed diagnosis. In patients without a history of close contact with SARS cases, antibiotic effect was a major factor influencing doctors' diagnosis.

Adolescent↗
PubMed2003

Prevention of pancreaticojejunal anastomotic leakage after pancreaticoduodenectomy with separate internal drainage of bile and pancreatic fluid.

OBJECTIVE: To introduce a new reconstructional procedure to decrease the complications after pancreaticoduodenectomy. METHODS: Separate internal drainage of bile and pancreatic fluid in pancreaticoduodenectomy was performed in 256 patients. The digestive tract was reconstructed with Child method, with invaginated pancreaticojejunostomy using a long silastic tube to drain pancreatic fluid internally, an end-to-side choledochojejunostomy and an end-to-side duodenojejunostomy or gastrojejunostomy. Gastrostomy drainage was also performed. RESULTS: No complications of pancreatic leakage were found. CONCLUSION: The separate internal drainage of bile and pancreatic fluid plays an important role in preventing pancreaticojejunal anastomotic leakage.

Adult↗
PubMed2003

Effect of nitric oxide synthase inhibitor on proteoglycan metabolism in repaired articular cartilage in rabbits.

OBJECTIVE: To study the effect of nitric oxide synthase inhibitor, S-methyl thiocarbamate (SMT), on proteoglycan metabolism in repaired articular cartilage in rabbits. METHODS: Twenty-four male New Zealand white rabbits, aged 8 months and weighing 2.5 kg+/-0.2 kg, were used in this study. Cartilage defects in full thickness were created on the intercondylar articular surface of bilateral femurs of all the rabbits. Then the rabbits were randomly divided into 3 groups (n=8 in each group). The defects in one group were filled with fibrin glue impregnated with recombinant human bone morphogenetic protein-2 (rhBMP-2, BMP group), in one group with fibrin glue impregnated with rhBMP-2 and hypodermic injection with SMT (SMT group) and in the other group with nothing (control group). All the animals were killed at one year postoperatively. The tissue sections were stained with safranine O-fast green and analyzed by Quantiment 500 system to determine the content of glycosaminoglycan through measuring the percentage of safranine O-stained area, the thickness of cartilages and the mean gray scale (average stain intensity). Radiolabelled sodium sulphate (Na(2)(35)SO(4)) was used to assess the proteoglycan synthesis. RESULTS: At one year postoperatively, the percentage of safranine O-stained area, the mean gray scale and the cartilage thickness of the repaired tissues in SMT group were significantly higher than those of BMP group (P<0.01) and the control group (P<0.05). Result of incorporation of Na(2)(35)SO(4) showed that the proteoglycan synthesis in SMT group was higher than those of BMP group and the control group (P<0.01). CONCLUSIONS: SMT, a nitric oxide synthase inhibitor, can significantly increase the content of glycosaminoglycan and proteoglycan synthesis, and computer-based image analysis is a reliable method for evaluating proteoglycan metabolism.

Analysis of Variance↗
PubMed2003

[The study of autonomic nervous activities in patients with obstructive sleep apnea syndrome].

OBJECTIVE: To explore the nocturnal variation of autonomic nervous system (ANS) in patients with obstructive sleep apnea syndrome (OSAS) and the transformation after surgery. METHOD: Sixty-one subjects with OSAS were recruited to undergo 7-hour nocturnal polysomnography(PSG) in sleep lab. Sixteen subjects with OSAS were performed PSG before and after UPPP. Sixteen subjects without OSAS were included as controls. Power spectrum analysis of heart rate variability (HRV) was performed in each subject. RESULT: The nocturnal of ANS activities were abnormal in patients with OSAS, especially the enhancement of sympathetic nervous activity. It increased gradually along with aggravating condition. The activities of sympathetic and vagus nerve were decreased significantly. CONCLUSION: There are abnormal ANS activities in patients with OSAS. Effective treatment of OSAS by surgery will significantly reduce the parameters of ANS, and redress the abnormality of heart rate and blood pressure.

Adult↗
PubMed2002

Retinal precursor cells express functional ionotropic glutamate and GABA receptors.

R28 retinal progenitor cells offer the potential to replace damaged neurons; however, their ability to differentiate into the appropriate phenotype may depend on whether they express glutamatergic and GABAergic receptors. Whole-cell recordings and immunocytochemistry were used to identify glutamatergic and GABAergic receptors on proliferating R28 cells. R28 cells lacked voltage-gated channels; however, they produced inward currents when non-NMDA, NMDA, GABAa and GABAb receptor agonists were perfused onto the cells. R28 cells were immunoreactive to GluR1, 2 and 3, NMDA and GABAa receptors consistent with electrophysiological results. These results indicate that R28 progenitor cells express glutamatergic and GABAergic receptors capable of influencing their fate and function when grafted into retina or elsewhere in the nervous system.

Animals↗
PubMed2002

Requirement of Ca2+ and CaMKII for Stat1 Ser-727 phosphorylation in response to IFN-gamma.

In response to IFN-gamma, the latent cytoplasmic protein signal transducers and activators of transcription 1 (Stat1) becomes phosphorylated on Y701, dimerizes, and accumulates in the nucleus to activate transcription of IFN-gamma-responsive genes. For maximal gene activation, S727 in the transcription activation domain of Stat1 also is inducibly phosphorylated by IFN-gamma. We previously purified a group of nuclear proteins that interact specifically with the Stat1 transcription activation domain. In this report, we identified one of them as the multifunctional Ca(2+)/calmodulin-dependent kinase (CaMK) II. We demonstrate that IFN-gamma mobilizes a Ca(2+) flux in cells and activates CaMKII. CaMKII can interact directly with Stat1 and phosphorylate Stat1 on S727 in vitro. Inhibition of Ca(2+) flux or CaMKII results in a lack of S727 phosphorylation and Stat1-dependent gene activation, suggesting in vivo phosphorylation of Stat1 S727 by CaMKII. Thus two different cellular signaling events, IFN-gamma receptor occupation and Ca(2+) flux, are required for Stat1 to achieve maximal transcriptional activation through regulation of phosphorylation.

3T3 Cells↗
PubMed2002

Glycogen synthase kinase-3beta is complexed with tau protein in brain microtubules.

In Alzheimer's disease, microtubule-associated protein tau is hyperphosphorylated by an unknown mechanism and is aggregated into paired helical filaments. Hyperphosphorylation causes loss of tau function, microtubule instability, and neurodegeneration. Glycogen synthase kinase-3beta (GSK3beta) has been implicated in the phosphorylation of tau in normal and Alzheimer's disease brain. The molecular mechanism of GSK3beta-tau interaction has not been clarified. In this study, we find that when microtubules are disassembled, microtubule-associated GSK3beta dissociates from microtubules. From a gel filtration column, the dissociated GSK3beta elutes as an approximately 400-kDa complex. When fractions containing the approximately 400-kDa complex are chromatographed through an anti-GSK3beta immunoaffinity column, tau co-elutes with GSK3beta. From fractions containing the approximately 400-kDa complex, both tau and GSK3beta co-immunoprecipitate with each other. GSK3beta binds to nonphosphorylated tau, and the GSK3beta-binding region is located within the N-terminal projection domain of tau. In vitro, GSK3beta associates with microtubules only in the presence of tau. From brain extract, approximately 6-fold more GSK3beta co-immunoprecipitates with tau than GSK3alpha. These data indicate that, in brain, GSK3beta is bound to tau within a approximately 400-kDa microtubule-associated complex, and GSK3beta associates with microtubules via tau.

Alzheimer Disease↗
PubMed2002

[Long-term effect of nitric oxide synthase inhibitor on repair of articular cartilage defects repairing].

OBJECTIVE: To discuss the long-term effect of inducible nitric oxide synthase inhibitor S-methylisothiourea (SMT) on repair of articular cartilage defects. METHODS: Twenty-four adult New Zealand White rabbits with full-thickness defects of cartilage created in the trochlear groove of their bilateral femurs were divided into three groups randomly, 8 in each group: (1) control group in which nothing was filled into the defects; (2) BMP group in which the defects were filled with collagen fibrin gel impregnated with recombinant human bone morphogenic protein (rhBMP); and (3) SMT group in which the defects were filled with collagen fibrin gel impregnated with rhBMP and hypodermic injection of SMT (5 mg .(-1) 12 h(-1)) was given. The animals were killed one year later. The gross appearance of the defects was assessed. The amount of released NO and the activity of NOS were examined by chemical colorimetry. The distribution of collagen was examined by immunohistochemistry. The proteoglycan synthesis and cell activity was assessed by incorporation of radiolabelled sodium sulphate Na(2)(35)SO(4) and bromodeoxyuridine. RESULTS: One year after the defects in SMT group showed greater improvement in margin integration, cellular morphology, and architecture within defect than those in BMP group and control group (P < 0.01). Immunohistochemistry showed that there was less type-I collagen and more type-II collagen in SMT group than in the other two groups. Radiolabelled sodium sulphate (Na(2)(35)SO(4)) incorporation test showed that the proteoglycan synthesis in defects was higher in SMT group than in the other two groups (P < 0.01). BrdU incorporation test showed cells in repaired tissue with remarkable proliferous activity. CONCLUSION: iNOS inhibitor SMT significantly improves the quality of repair of defected cartilage and delays its degradation.

Animals↗
PubMed2002

Litigation cells: their incidence and classification in gynecologic smears.

"Litigation cells" are defined as benign cells which may mimic dysplasia or cancer and might be used by plaintiffs' witnesses to imply that the cytotechnologist or pathologist "missed" cells of dysplasia or cancer. We reviewed 180 cervical smears from 166 patients who had hysterectomy for benign leiomyomas. All smears were performed within 12 months prior to hysterectomy. None of the uteri contained dysplasia or cancer on histologic examination. 90.6% of smears reviewed had at least one cell or cell group with atypia mimicking dysplasia or cancer. These "litigation cells" were classified as follows: parabasal cells, metaplastic squamous cells, degenerated endocervical cells, reactive endocervical cells, endometrial cells, neutrophils, histiocytes, and air-dried cells. Diseases mimicked by these cells included squamous cell carcinoma, high-grade squamous intraepithelial lesion, low-grade squamous intraepithelial lesion, adenocarcinoma, and glandular dysplasia. These "litigation cells" can be correctly classified by experienced cytotechnologists and cytopathologists and recognized as benign. We recommend that in all cases of alleged malpractice against cytotechnologists and/or pathologists the smears should be reviewed by a panel of individuals trained and experienced in cytopathology. The smears should be reviewed without knowledge of the clinical outcome and in an environment that simulates the normal screening practice.

Female↗
PubMed2002

Recent development on computer aided tissue engineering--a review.

The utilization of computer-aided technologies in tissue engineering has evolved in the development of a new field of computer-aided tissue engineering (CATE). This article reviews recent development and application of enabling computer technology, imaging technology, computer-aided design and computer-aided manufacturing (CAD and CAM), and rapid prototyping (RP) technology in tissue engineering, particularly, in computer-aided tissue anatomical modeling, three-dimensional (3-D) anatomy visualization and 3-D reconstruction, CAD-based anatomical modeling, computer-aided tissue classification, computer-aided tissue implantation and prototype modeling assisted surgical planning and reconstruction.

Animals↗
PubMed2002

E-cadherin expression in urothelial carcinoma in situ, superficial papillary transitional cell carcinoma, and invasive transitional cell carcinoma.

Flat urothelial carcinoma in situ (CIS) is a precursor of invasive transitional cell carcinoma (TCC). High-grade TCCs frequently are accompanied by CIS in surrounding urothelium. In contrast, superficial, noninvasive papillary TCCs are often low grade and generally are unaccompanied by CIS. E-cadherin (E-CD) is a member of a family of transmembrane glycoproteins involved in intercellular adhesion. Loss or decreased expression of E-CD has been linked to the invasive phenotype of a wide variety of human neoplasms, including bladder tumors. The objective of this study was to compare the expression of E-CD in high-grade urothelial dysplasia (HD)/CIS, superficial papillary TCC, benign urothelium, and invasive TCC. Staining for E-CD was performed in formalin-fixed, paraffin-embedded sections using a Ventana NexES immunostainer (Tuscon, AZ). Percentage and intensity of cell membrane staining for E-CD was calculated for the 4 groups using the quantitative Automatic Cellular Imaging System (ChromaVision, San Juan Capistrano, CA). The results were as follows: The CIS group (n = 23) had percentage and intensity (92.8%, 120.0 U) of E-CD expression similar to the superficial noninvasive papillary TCC group (n = 16, 97.8%, 123.0 U) and the benign urothelium group (n = 17, 87.9%, 104.6 U), but it had statistically significant higher percentage and intensity than the invasive TCC group (n = 15, 45.4%, and 39.2 U, P <.05). Our data indicate that CIS and superficial, noninvasive papillary TCCs strongly express E-CD. In contrast, loss of E-CD expression is associated with the invasive TCC phenotype. Only when TCCs become invasive does E-CD expression decrease in directly proportion to the depth of invasion.

Cadherins↗