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Biomedical subjects

D Wei

Publications and source records attributed to D Wei.

At least 55 records · Page 3Linked to original sources
PubMed1999

A low-distortion filter method to reject muscle noise in multi-lead electrocardiogram systems.

This paper proposes a low-distortion filter method for rejection of muscle noise in multilead electrocardiogram (ECG) systems. This approach combines low-pass filtering with a modified version of source consistency filtering. The low-pass filtering splits the raw ECG signal into a muscle-noise-free part and a muscle-noise-overlapping part. The modified source consistency filtering then extracts the signal components from the muscle-noise-overlapping part. The extracted signal components are restored to the muscle-noise-free part as the output. The performance of our method was verified with simulated and clinically recorded ECG signals. The simulated ECG signals were created from computer simulation using three-dimensional, realistically shaped heart and torso models. The ideal signals are superimposed with white noise to simulate muscle noise and with a low frequency sine wave to simulate baseline drift. For verification, our method was compared with Butterworth low-pass filters. The results show that our method can effectively reduce muscle noise with less distortion of the QRS wave than conventional low-pass filters.

Artifacts↗
PubMed1999

[Cellular immune function influence on postoperative patients with hepatocellular carcinoma and the clinical effect of TILs treatment].

OBJECTIVE: To investigate the cellular immune function influence on postoperative patients with hepatocellular carcinoma (HCC) and clinical effect of TILs, rIL-2 and cyclophosphamide treatment. METHODS: Eight postoperative HCC patients were treated with TILs, rIL-2 and cyclophosphamide. Six patients were infused from the hepatic artery, and the other 2 infused from the portal vein. RESULTS: The IL-2 NK activity, Tsubsets, CD4(+)/CD8(+) level in the peripheral blood of all patients increased and the IL-6, TNF level of most patients decreased (P > 0.05, P < 0.01). For 6 - 18 month follow-up after management, 6 patients with radical tumor resection showed no recurrence. One patient having palliative resection showed no remnant tumor enlargement. One patient with increased TNF level for 8 IU died from hepatic failure 8 months after chemotherapy. CONCLUSIONS: The TILs, rIL-2 and cyclophosphamide treatment of postoperative HCC patients is effective in improving antitumorgenic immune function, preventing tumor recurrence, and restraining remnant tumor growth.

Adult↗
PubMed1999

The association of Ala54Thr variant of intestinal fatty acid binding protein gene with general and regional adipose tissue depots.

OBJECTIVE: To ascertain the relationship between the Ala54Thr variation of FABP2 gene and general as well as regional adipose tissue depots. SUBJECTS: 165 subjects, in which 86 were subjects with normal glucose tolerance (NGT) [age 54.45+/-9.80, male/female 1.05, body mass index (BMI) 26.48+/-4.01] and 79 were subjects with non-insulin-dependent diabetes mellitus (NIDDM) (age 55.86+/-10.00, male/female 1.08, BMI 26.75+/-3.30). DESIGN AND MEASUREMENTS: An association study of FABP2-Ala54Thr variation detected by PCR/HhaI digestion with general and regional adipose tissue depots determined by BMI and magnetic resonance imaging [abdominal subcutaneous and visceral adipose tissue area (SA and VA) and femoral subcutaneous adipose tissue area (FA)]. RESULTS: The geneotype and allele frequencies of FABP2-Ala54Thr variation in Chinese were quite close to the frequencies in American Caucasians and Pima Indians reported in the literature. Significant difference in genotype frequency distribution was observed between FA subgroups comparisons (FA > or = 75 cm2 versus FA < 75 cm2) in NIDDM subjects (X2 = 11.460, P = 0.003), with significantly increased in Thr54-carrier [Thr54 (+)] genotype frequency and Thr54 allele frequency in NIDDM subject with FA < 75 cm2 (odd ratio for genotype was 4.62, X2 = 10.112, P = 0.001; and for allele = 2.36, X2 = 5.379, P = 0.020). The FA in NIDDM-Thr54 (+) subgroup was significantly lower than that in subjects with NIDDM-Thr54 (-) subgroup (61.19+/-21.51 cm2 versus 75.36+/-31.70 cm2, P = 0.021). Stepwise regression analysis revealed that FABP2-Thr54 genotype variation was an independent factor contributing to the variation of FA in NIDDM (P = 0.003). CONCLUSION: FABP2 is associated with regional adipose tissue depot. The decreased femoral subcutaneous adipose tissue depot in NIDDM subjects is related to FABP2-Thr54 variant.

Adipose Tissue↗
PubMed1998

Acute iboga alkaloid effects on extracellular serotonin (5-HT) levels in nucleus accumbens and striatum in rats.

The iboga alkaloid, ibogaine, its metabolite, noribogaine, and the congener, 18-methoxycoronaridine (18-MC) have all been claimed to have anti-addictive properties in animal models, but the mechanisms underlying these effects are unclear. Ibogaine and noribogaine were shown to have affinity for the serotonin transporter, and inhibition of serotonin reuptake has been proposed to be involved in their anti-addictive actions. It is not known yet if 18-MC also has this property. In vivo microdialysis and HPLC (microbore) were used to determine acute changes in extracellular serotonin levels in nucleus accumbens (NAC) and striatum (STR) after both i.p. (40 mg/kg for all drugs) and i.v. (1-10 mg/kg for ibogaine and noribogaine) drug administration in awake freely moving female Sprague-Dawley rats (250-275 g). After i.p. administration, ibogaine, noribogaine and 18-MC had very different effects on extracellular serotonin levels in both NAC and STR: ibogaine elicited large increases (up to 25-fold in NAC and 10- fold in STR), noribogaine produced moderate increases (up to 8-fold in NAC and 5-fold in STR), and 18-MC had no effect in either brain region. These and other data suggest that (1) the serotonergic system may not be an essential factor in the anti-addictive actions of these drugs; (2) ibogaine (or an unidentified metabolite) may release serotonin as well as inhibit its reuptake; (3) stimulation of the ascending serotonergic system may mediate ibogaine's hallucinogenic effect; and (4) 18-MC probably has no affinity for the serotonin transporter, and is unlikely to be a hallucinogen.

Animals↗
PubMed1998

Monitoring metal ion flux in reactions of metallothionein and drug-modified metallothionein by electrospray mass spectrometry.

The capabilities of electrospray ionization mass spectrometry are demonstrated for monitoring the flux of metal ions out of and into the metalloprotein rabbit liver metallothionein and, in one example, chlorambucil-alkylated metallothionein. Metal ion transfers may be followed as the reactions proceed in situ to provide kinetic information. More uniquely to this technique, metal ion stoichiometries may be determined for reaction intermediates and products. Partners used in these studies include EDTA, carbonic anhydrase, a zinc-bound hexamer of insulin, and the core domain of bacteriophage T4 gene 32 protein, a binding protein for single-stranded DNA.

Alkylation↗
PubMed1998

Possible mechanism of ECG features in patients with idiopathic ventricular fibrillation studied by heart model and computer simulation.

The possible contribution of localized conduction delay and abnormal action potentials to ventricular fibrillation (VF) was studied by applying an anisotropic cardiac computer model to clinical cases of the Brugada-type electrocardiogram (ECG), which shows right bundle branch block (RBBB), a normal QT interval, ST-segment elevation, and late r' in leads V1 and V2. The anisotropic heart model was composed of 50,000 discrete units with a spatial resolution of 1.5 mm and was mounted in a human torso model. The longitudinal/transverse conduction velocity ratio was 3:1. For the normal ECG, a conduction velocity of 0.75 m/s was required. In the abnormal area of the right anterior epicardial wall, the conduction velocity was set at 0.2 m/s, with decreasing action potential amplitude and 10% prolonged action potential duration. The ECG features of ST-segment elevation and Brugada-type right bundle branch block pattern were simulated. The action potential duration was able to change dynamically with coupling interval of stimulation, with a ratio of 9% for normal ventricular muscle and 50% for Purkinje fibers. Five successive stimuli were applied to the left lateral epicardium 300 ms after the first sinus excitation, and sustained VF was induced with the transmural conduction delay at the right anterior ventricle as a block increasing the vulnerability. At the initiation of VF, reentry circuits were shown around the border zone of the right epicardium and were very heterogeneous around the conduction delayed area and septal area. In an area with the characteristics of nontransmural conduction delay, sustained VF was prevented, and the pattern of transient right bundle branch block appeared on the simulated ECG and body surface potential maps. The late r' wave was calculated in the precordial leads and right anterior site on the body surface potential maps. These results suggest that increased multipolarity in the border zone between the Purkinje fibers and delayed conduction area in the right ventricle might play an important role as a functional block for the persistence of VF.

Action Potentials↗
PubMed1998

A simulation study of Torsade de Pointes with M cells.

Recent studies have reported the relation between Torsade de Pointes (TdP) and midmyocardial (M) cell function associated with long QT syndrome. To investigate this relation, we conducted a simulation study with a three-dimensional (3D) heart model incorporating M cells in the anterolateral areas of the model. Parameters of premature cycle-length dependent shortening of action potential duration (APD) and conduction velocity for the M cells were adjusted to induce tachyarrhythmias of TdP type. Under a basic pacing cycle length of 1,000 msec at the sinus node, four successive premature beats of 160-ms interval were generated 300 ms after the first sinus pacing. Setting lower conduction velocity and longer APD to M cells induced sustained TdP-like tachyarrhythmia resembling ECG findings. TdP could not be induced without the presence of M cells. This study suggests that TdP might be caused by reentry around M cells and dispersive refractory areas due to prolonged APD and slow conduction velocity.

Action Potentials↗
PubMed1998

Refashioned short bowel segments for the construction of catheterizable channels (the Monti procedure): early clinical experience.

PURPOSE: We report the early results of a new surgical procedure to construct a catheterizable stoma from a small segment of bowel according to the Monti technique. MATERIALS AND METHODS: Since November 1996, 4 male and 4 female patients with a mean age of 14 years have undergone the Monti procedure in association with other reconstructive efforts. Indications included the unavailability of appendix because of concomitant ACE Malone appendicocecostomy in 2 patients, atretic appendixes in 3, previous appendectomy in 2 and technical difficulties during appendix isolation in 1. In no patient was small bowel used instead of a suitable appendix. Other simultaneous surgical procedures included bladder augmentation in 4 patients in whom the bowel tube and patch for augmentation were created with the same mesenteric pedicle (ileum in 3 and sigmoid colon in 1). RESULTS: Followup ranged from 3 to 11 months (mean 7). No patient has had difficulty with catheterization or any other problems related to the stoma. In 2 patients stomal leakage required additional procedures and pharmacological manipulation. CONCLUSIONS: The appendiceal Mitrofanoff procedure remains the technique of choice for the construction of catheterizable continent stomas. In the absence of a suitable appendix a catheterizable bowel conduit based on the Monti technique appears to be the best alternative in our early experience. The short segment of bowel required for conduit construction, excellent blood supply throughout its length, and the possibility of developing the tube and bowel patch for simultaneous augmentation from the same pedicle are some of the clear advantages of this technique.

Adolescent↗
PubMed1998

[Cytokines release related to cardiopulmonary bypass in patients with prosthetic valve replacement].

To examine cytokines release related to cardiopulmonary bypass(CPB), the anthers investigated the possible differences in cytokines responses between patients undergoing prosthetic valve replacement (study group, n = 10) and those receiving closure of patent ductus arteriosus or pericardiectomy(control group, n = 9). Venous levels of interleukin-2 (IL-2), soluble interleukin-2 receptor (sIL-2R), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interleukin-10 (IL-10) were measured at multiple time points before, during and after operation. As compared with pre-operative values, IL-2 levels in both groups decreased significantly (P < 0.05), and the levels of sIL-2R, IL-6, TNF-alpha, and IL-10 in both groups increased significantly at multiple time points post-operative (P < 0.01). All the values of cytokines returned to pre-operative levels at 7th post-operative day. Although there were no pre-operative differences in these cytokines between the two groups (P > 0.05), the post-operative changes of cytokines in study group was more obvious than that in control group (P < 0.01). In study group IL-10 rose to a peak value of around 620 pg/ml at the end of CPB while IL-6 and TNF-alpha levels reached their peak values of around 88 pg/ml and 52 pg/ml respectively at 1st post-operative day. IL-10 has been reported as an antiinflammatory cytokine. The preceding IL-10 peak value, as compared with the peak values of IL-6 and TNF-alpha, could be associated with the interplay and regulation of cytokine network. On the other hand, in control group the levels of IL-6, TNF-alpha, and IL-10 reached their peak values at 1st post-operative day simultaneously. The values were 34 pg/ml, 36 pg/ml, and 162 pg/ml respectively. This result suggests that besides surgical stress mediated cytokines production or suppression, CPB itself also results in obvious changes of cytokine metabolism. However further studies are needed to elucidate the underlying mechanisms and clinical value of post-operative cytokines production or suppression related to CPB in patients with prosthetic valve replacement.

Adult↗
PubMed1998

[Effects of endogenous TGF-beta during wound healing].

OBJECTIVE: To study the application of exogenous TGF-beta to excision, incision and burn wounds accelerating wound healing. METHODS: The expression of endogenous TGF-beta during burn wound healing was observed by mRNA dot blot hybridization and immunohistochemistry, respectively. RESULTS: Thermal injury could induce TGF-beta gene expression in cutaneous wounds. Expression level of TGF-beta mRNA increased over time to reach a peak around day 5 postburn, and declined at day 10 after thermal injury. Immunohistochemistry evidences indicated spatially and temporally that TGF-beta peptide mainly distributed at hair follicles and migrating epidermis at early and middle stages of repair process, and stronger immunoreactivity from days 5 to 10 after wound, which was directly proportional to epidermal cell migration and dermal fibroblast proliferation. CONCLUSION: The expression models of TGF-beta protein and gene suggests that TGF-beta play a critical role in regulation of repair process. Whether the inhibition of expression and overexpression of TGF-beta is correlated to imparied repair and scar formation remains to be studied.

Animals↗
PubMed1997

Structure of the carboxy-terminal fragment of the apo-biotin carboxyl carrier subunit of Escherichia coli acetyl-CoA carboxylase.

The biotin carboxyl carrier protein (BCCP) is a subunit of acetyl-CoA carboxylase, a biotin-dependent enzyme that catalyzes the first committed step of fatty acid biosynthesis. In its functional cycle the biotin carboxyl carrier protein engages in heterologous protein-protein interactions with three distinct partners, depending on its state of posttranslational modification. Apo-BCCP interacts specifically with the biotin holoenzyme synthetase, BirA, which results in the posttranslational attachment of biotin to an essential lysine residue on BCCP. Holo-BCCP then interacts with the biotin carboxylase subunit, which leads to the addition of the carboxylate group of bicarbonate to biotin. Finally, the carboxybiotinylated form of BCCP interacts with transcarboxylase in the conversion of acetyl-CoA to malonyl-CoA. The determinants of protein-protein interaction specificity in this system are unknown. One hypothesis is that posttranslational modification of BCCP may result in conformational changes that regulate specific protein-protein interactions. To test this hypothesis, we have determined the NMR solution structure of the unbiotinylated form of an 87 residue C-terminal domain fragment of BCCP (apoBCCP87) from Escherichia coli acetyl-CoA carboxylase and compared this structure with the high-resolution structure of the biotinylated form that was recently solved by X-ray crystallographic techniques. Although the overall folding of the two proteins is highly similar, small structural differences are apparent for residues of the biotin-binding loop that may be important for mediating specific protein-protein interactions.

Acetyl-CoA Carboxylase↗
PubMed1997

Human tyrosyl-tRNA synthetase shares amino acid sequence homology with a putative cytokine.

To test the hypothesis that tRNATyr recognition differs between bacterial and human tyrosyl-tRNA synthetases, we sequenced several clones identified as human tyrosyl-tRNA synthetase cDNAs by the Human Genome Project. We found that human tyrosyl-tRNA synthetase is composed of three domains: 1) an amino-terminal Rossmann fold domain that is responsible for formation of the activated E.Tyr-AMP intermediate and is conserved among bacteria, archeae, and eukaryotes; 2) a tRNA anticodon recognition domain that has not been conserved between bacteria and eukaryotes; and 3) a carboxyl-terminal domain that is unique to the human tyrosyl-tRNA synthetase and whose primary structure is 49% identical to the putative human cytokine endothelial monocyte-activating protein II, 50% identical to the carboxyl-terminal domain of methionyl-tRNA synthetase from Caenorhabditis elegans, and 43% identical to the carboxyl-terminal domain of Arc1p from Saccharomyces cerevisiae. The first two domains of the human tyrosyl-tRNA synthetase are 52, 36, and 16% identical to tyrosyl-tRNA synthetases from S. cerevisiae, Methanococcus jannaschii, and Bacillus stearothermophilus, respectively. Nine of fifteen amino acids known to be involved in the formation of the tyrosyl-adenylate complex in B. stearothermophilus are conserved across all of the organisms, whereas amino acids involved in the recognition of tRNATyr are not conserved. Kinetic analyses of recombinant human and B. stearothermophilus tyrosyl-tRNA synthetases expressed in Escherichia coli indicate that human tyrosyl-tRNA synthetase aminoacylates human but not B. stearothermophilus tRNATyr, and vice versa, supporting the original hypothesis. It is proposed that like endothelial monocyte-activating protein II and the carboxyl-terminal domain of Arc1p, the carboxyl-terminal domain of human tyrosyl-tRNA synthetase evolved from gene duplication of the carboxyl-terminal domain of methionyl-tRNA synthetase and may direct tRNA to the active site of the enzyme.

Amino Acid Sequence↗
PubMed1997

Relationship between adduct formation, rates of excision repair and the cytotoxic and mutagenic effects of structurally-related polycyclic aromatic carcinogens.

The cytotoxic and mutagenic effect of 1-nitrosopyrene (1-NOP) and N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) were compared with that of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) as a function of the initial frequency of adducts formed in the DNA of repair-proficient diploid human fibroblasts and the fraction remaining at the time the cells replicate their DNA. The principal adducts of all three agents involve guanine. The initial level of BPDE-, 1-NOP-, or N-AcO-AAF-induced adducts per 10(6) nucleotides required to lower the survival of these cells to 37% of the control was 8, 25, and 50, respectively. The frequency of mutants per 10(6) clonable cells induced at those levels of initial adduct formation was 160, 80, and 40, respectively. We determined the rate of excision repair of these adducts from the overall genome, from the individual strands of the hypoxanthine phosphoribosyltransferase (HPRT) gene, and in the case of 1-NOP and BPDE, at the level of individual nucleotides in the nontranscribed strand of exon 3 of that gene, a region where mutations induced by those agents are particularly frequent. 1-NOP-induced adducts were excised from the overall genome and from the individual strands of HPRT at a rate 2-3 times faster than BPDE-induced adducts. The average rate of repair of 1-NOP-induced adducts in exon 3 was also 2-3 times faster than the average rate of repair of BPDE-induced adducts. However, at particular nucleotides 1-NOP-induced adducts were repaired much faster, or slower, or in some cases at a rate equal to that of BPDE-induced adducts. Excision repair of N-AcO-AAF-induced adducts (i.e., deacetylated aminofluorene residues) was significantly slower than that of BPDE- or 1-NOP-induced adducts, and was not strand-specific. In an in vitro assay, BPDE adducts were four times more effective in blocking transcription than were 1-NOP or N-AcO-AAF-induced adducts. We conclude that the cytotoxic and mutagenic effect of these carcinogens reflect a complex interplay of adduct conformation, ability of adducts to block replication and transcription, and variation in the rate of excision repair, even at the nucleotide level.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1997

High relaxivity linear Gd(DTPA)-polymer conjugates: the role of hydrophobic interactions.

A series of linear copolymers of DTPA-class Gd3+ conjugates, linked by alpha, omega-alkyldiamides with a varying number (n) of methylenes separating the amide function, were synthesized. Surprisingly, their relaxivities at all fields increased with increasing n. At MRI fields and 35 degrees C, the relaxivities of the n = 10 and n = 12 polymers were unexpectedly high, similar to those of rigid dendrimer-based Gd3+ chelates. The magnetic field dependence of solvent proton 1/T1 was measured for aqueous urea-free and urea-containing polymer solutions. The results for urea-free solutions imply an increase of rigidity (required for high relaxivities) with increasing n, arising from hydrophobic interactions of the methylene groups with solvent. This hypothesis is supported by a large decrease in the relaxivities upon addition of urea, which is known to weaken hydrophobic interactions. The relaxivities are also independent of polymer concentration, indicating that the hydrophobic interactions are intramolecular.

Contrast Media↗
PubMed1997

False-positive reduction technique for detection of masses on digital mammograms: global and local multiresolution texture analysis.

We investigated the application of multiresolution global and local texture features to reduce false-positive detection in a computerized mass detection program. One hundred and sixty-eight digitized mammograms were randomly and equally divided into training and test groups. From these mammograms, two datasets were formed. The first dataset (manual) contained four regions of interest (ROIs) selected manually from each of the mammograms. One of the four ROIs contained a biopsy-proven mass and the other three contained normal parenchyma, including dense, mixed dense/fatty, and fatty tissues. The second dataset (hybrid) contained the manually extracted mass ROIs, along with normal tissue ROIs extracted by an automated Density-Weighted Contrast Enhancement (DWCE) algorithm as false-positive detections. A wavelet transform was used to decompose an ROI into several scales. Global texture features were derived from the low-pass coefficients in the wavelet transformed images. Local texture features were calculated from the suspicious object and the peripheral subregions. Linear discriminant models using effective features selected from the global, local, or combined feature spaces were established to maximize the separation between masses and normal tissue. Receiver Operating Characteristic (ROC) analysis was conducted to evaluate the classifier performance. The classification accuracy using global features were comparable to that using local features. With both global and local features, the average area, Az, under the test ROC curve, reached 0.92 for the manual dataset and 0.96 for the hybrid dataset, demonstrating statistically significant improvement over those obtained with global or local features alone. The results indicated the effectiveness of the combined global and local features in the classification of masses and normal tissue for false-positive reduction.

Biophysical Phenomena↗
PubMed1997

[Experimental study of temporal expression of endogenous TGF alpha in partial thickness scalded wounds].

Investigating spatial and temporal expression and distribution of endogenous TGF alpha, and clarifying its role in burn wound healing. Immunohistochemical and mRNA dot blot hybridization approaches were adopted. Thermal injury can induce TGF alpha gene expression. The expression peaks at the time when repair cells migrate and proliferate most actively, and declines on near completion of epithelialization. Otherwise, the mRNA expression of EGF receptor manifests the same change as TGF alpha's. Immunohistochemical investigation indicates that TGF alpha is mainly distributed in the survived hair follicles and reepithelialized cell layers, and the immunoreactive staining is proportional to epidermal cell growth and migration. Thermal injury can induce endogenous TGF alpha and EGF receptor expression, which is well controlled and correlated with the migration and proliferation of keratinocytes. Endogenous TGF alpha plays a positive role in regulation of wound healing.

Animals↗