Biomedical subjects

W Tang

Publications and source records attributed to W Tang.

At least 109 records · Page 6Linked to original sources

PubMed2000

The accuracy and precision performance of four videokeratoscopes in measuring test surfaces.

In this study we evaluated the accuracy and precision of three placido-disk videokeratoscopes (the Keratron, Medmont and TMS) and one videokeratoscope that uses the raster-stereogrammetry technique (PAR-CTS) in elevation topography with six test surfaces. The test surfaces were a sphere, an asphere, a multicurve, and three bicurve surfaces. Each instrument performed well on certain test surfaces, but none of the instruments excelled on all of the surfaces. The results showed high accuracy of the Keratron and Medmont instruments in measuring the sphere, asphere, and multicurve surfaces, but not the bicurve surfaces. The precision of the Keratron and Medmont instruments were high. The TMS and PAR-CTS instruments showed poorer accuracy than the Keratron and Medmont instruments for the multicurve test surface but showed better performance for the bicurve surfaces. The PAR-CTS had the poorest performance in precision of the four instruments. The use of the Noryl spherical test surface instead of polymethyl methacrylate (PMMA) resulted in small differences in the accuracy performance of the placido-disk videokeratoscopes only.

Cornea↗

PubMed2000

K(ATP) channel activation reduces the severity of postresuscitation myocardial dysfunction.

Postresuscitation myocardial dysfunction has been recognized as a leading cause of the high postresuscitation mortality rate. We investigated the effects of ischemic preconditioning and activation of ATP-sensitive K(+) (K(ATP)) channels on postresuscitation myocardial function. Ventricular fibrillation (VF) was induced in 25 Sprague-Dawley rats. Cardiopulmonary resuscitation (CPR), including mechanical ventilation and precordial compression, was initiated after 4 min of untreated VF. Defibrillation was attempted after 6 min of CPR. The animals were randomized to five groups treated with 1) ischemic preconditioning, 2) K(ATP) channel opener, 3) ischemic preconditioning with K(ATP) channel blocker administered 1 min after VF, 4) K(ATP) channel blocker administered 45 min before induction of ischemic preconditioning, and 5) placebo. Postresuscitation myocardial function, as measured by the rate of left ventricular pressure increase at 40 mmHg, the rate of left ventricular decline, cardiac index, and duration of survival, was significantly improved in both preconditioned and K(ATP) channel opener-treated animals. K(ATP) channel blocker administered 45 min before induction of ischemic preconditioning completely abolished the myocardial protective effects of preconditioning. We conclude that ischemic preconditioning significantly improved post-CPR myocardial function and survival. These results also provide evidence that the myocardial protective effects of ischemic preconditioning are mediated by K(ATP) channel activation.

Adenosine Triphosphate↗

PubMed2000

Atrial function during cardiac arrest caused by ventricular fibrillation.

OBJECTIVES: To report observations on preserved regular atrial electrical and mechanical systole during ventricular fibrillation (VF) and to quantitate blood flow generated by atrial contractions in this setting. METHODS: In 10 rats, right atrial pressure pulses were continuously recorded before and for an interval of 8 min after inducing VF. In 3 isolated, perfused rat hearts, epicardial right atrial electrograms were recorded after inducing VF. In 15 pigs, transesophageal echo-Doppler measurements were obtained with pulsed and color-Doppler visualization of flow across the mitral valve after onset of VF. RESULTS: In each rat, regular right atrial pressure pulses were documented during VF. These persisted over an average interval of 7.5 min. In isolated, perfused hearts, right atrial contractions were accompanied by regular atrial depolarizations. In pigs, regular atrial contractions generated atrial stroke volumes of approximately 12 mL, or 25% of prearrest values during the first minute after onset of VF, but those declined to approximately 6 mL after 10 min of untreated cardiac arrest. Blood flow from the left atrium into the left ventricle failed to advance significantly into the systemic circuit. During atrial diastole, we observed reversal of flow into the left atrium. CONCLUSIONS: Atrial contractions are preserved during the initial 8 min or more after cardiac arrest due to VF. Substantial forward flow into the left ventricle failed to advance through the outflow tract but regurgitated into the atrium during atrial diastole.

Animals↗

PubMed2000

Comparisons between sublingual and gastric tonometry during hemorrhagic shock.

STUDY OBJECTIVES: To compare sublingual tissue PCO(2), a disarmingly simple and noninvasive measurement of the severity of perfusion failure, with gastric tonometric PCO(2) during hemorrhagic shock in five male domestic pigs weighing between 35 and 40 kg. DESIGN: Prospective animal study. SETTING: Animal laboratory in a research institution. PARTICIPANTS: Domestic pigs. INTERVENTIONS: Hemorrhagic shock was induced by a modification of the Wigger's method. BP was maintained at 50 mm Hg for 120 min followed by reinfusion of shed blood at a rate of 100 mL/min with the aid of an infusion pump. MEASUREMENTS AND RESULTS: During bleeding, the mean arterial pressure decreased from an average of 127 to 42 mm Hg, and cardiac output decreased from 7.7 to 2.4 L/min. Arterial blood lactate concentration concurrently increased from 1.2 to 13.9 mmol/L. Sublingual PCO(2) (PslCO(2)) increased from 59 to 105 mm Hg, and gastric PCO(2) increased from 61 to 111 mm Hg. The correlation between time-coincident sublingual and gastric measurements of PCO(2) was r = 0.91 (p<0.0001). Bland-Altman analyses demonstrated a close correspondence between the two measurements. The reinfusion of shed blood promptly reversed the hemodynamic abnormalities and reestablished gastric and PslCO(2) to near baseline values. This contrasted with a delayed reversal of lactic acidosis. CONCLUSIONS: Under experimental conditions of hemorrhagic shock, sublingual capnometry yielded measurements that were interchangeable with those of gastric tonometry.

Animals↗

PubMed2000

Cytochrome P450 3A4-mediated interaction of diclofenac and quinidine.

The metabolism of diclofenac to its 5-hydroxylated derivative in humans is catalyzed by cytochrome P450 (CYP)3A4. We report herein that in vitro this biotransformation pathway is stimulated by quinidine. When diclofenac was incubated with human liver microsomes in the presence of quinidine, the formation of 5-hydroxydiclofenac increased approximately 6-fold relative to controls. Similar phenomena were observed with diastereoisomers of quinidine, including quinine and the threo epimers, which produced an enhancement in the formation of 5-hydroxydiclofenac in the order of 6- to 9-fold. This stimulation of diclofenac metabolism was diminished when human liver microsomes were pretreated with a monoclonal inhibitory antibody against CYP3A4. In contrast, neither cytochrome b(5) nor CYP oxidoreductase appeared to mediate the stimulation of diclofenac metabolism by quinidine, suggesting that the effect of quinidine is mediated through CYP3A4 protein. Further kinetic analyses indicated that V(max) values for the conversion of diclofenac to its 5-hydroxy derivative increased 4.5-fold from 13.2 to 57.6 nmol/min/nmol of CYP with little change in K(m) (71-56 microM) over a quinidine concentration range of 0 to 30 microM. Conversely, the metabolism of quinidine was not affected by the presence of diclofenac; the K(m) value estimated for the formation of 3-hydroxyquinidine was approximately 1.5 microM, similar to the quinidine concentration required to produce 50% of the maximum stimulatory effect on diclofenac metabolism. It appears that the enhancement of diclofenac metabolism does not interfere with quinidine's access to the ferriheme-oxygen complex, implicating the presence of both compounds in the active site of CYP3A4 at the same time. Finally, a approximately 4-fold increase in 5-hydroxydiclofenac formation was observed in human hepatocyte suspensions containing diclofenac and quinidine, demonstrating that this type of drug-drug interaction occurs in intact cells.

Cytochrome P-450 CYP3A↗

PubMed2000

Sublingual PCO2.

Explore the source record for details and available documents.

Animals↗

PubMed2000

[Consideration for ecological planning in mining areas].

On the basis of summarizing the status and trend of domestic and overseas ecological planning research, the necessity and significance of ecological planning research in mining areas were analyzed and its characteristics, research objectives, contents and methods were discussed. It is pointed out that establishing the theory and methodology of ecological planning in mining area is not only the requirement of their sustainable development, but also the requirement of active participation and cooperation of the researchers from different disciplines.

Conservation of Natural Resources↗

PubMed2000

Lymphangiogenesis in tumor tissues and 5'-Nase, Flt-4, Flk-1 expressions.

OBJECTIVE: To investigate lymphangiogenesis in tumor tissues and 5'-Nase, Flt-4, Flk-1 expressions. METHODS: 5'-Nase and Aplase expressions and the morphology of lymphatics in gastric carcinoma tissues were observed with enzyme histochemistry. Flt-4 and Flk-1 expression in gastric carcinoma and sarcoma tissues was studied by immunohistochemistry. CNE-2z cells were implanted into the subdermal layer of nude mice and hyaluronic acid was injected at the same sites. After 4 or 5 weeks, nasopharyngeal carcinoma (NPC) xenograft tissues were cut for immunohistochemistry and enzyme histochemistry, and lymphangiogenesis, 5'-Nase, Alpase, Flt-4 and Flk-1 expression in NPC tissues was studied. Hyaluronic acid contents in sera of the patients with NPC and mice with NPC xenografts were measured by radioimmunoassay. RESULTS: There were a lot of lymphatics and solid strip-like tissues in gastric carcinoma and NPC xenograft treated with hyaluronic acid. The total number of lymphatics (26.9 +/- 14.2/HP) increased significantly in gastric carcinoma tissues. Flt-4 and Flk-1 positive expression was found in gastric carcinoma, sarcoma tissues and NPC xenograft. Most of the vessels with positive Flt-4 were lymphatics. Flk-1 expression was only found in the walls of blood vessels. Hyaluronic acid content (363.52 +/- 98.15 ng/ml) in sera of patients with NPC was higher than that of the patients with chronic nasopharyngeal inflammation (306.29 +/- 27.15 ng/ml), with a significant difference (P = 0.039). The hyaluronic acid content in sera of nude mice with NPC (2120.59 +/- 490.22 ng/ml) was markedly higher than that in normal mice (1588.99 +/- 502.12 ng/ml), with a significant difference between them (P = 0.007). CONCLUSION: There are a lot of lymph capillaries with positive 5'-Nase in gastric carcinoma and NPC xenograft treated with hyaluronic acid. Flt-4 positive expression is shown in gastric carcinoma, sarcoma tissues and NPC xenografts. The results suggest there is lymphangiogenesis in these malignant tumor tissues. Hyaluronic acid contents in sera of patients with NPC and nude mice with NPC increase, which may promote the formation of lymphatics.

5'-Nucleotidase↗

PubMed2000

[Non-cirrhotic portal hypertension associated with autoimmune disease].

OBJECTIVE: To summarize the cases of non-cirrhotic portal hypertension associated with autoimmune disease, review the literature and introduce the clinical and pathological features of the syndrome. METHODS: Six female patients treated, between 1983 and 1998 had no history of hepatitis. Variceal bleeding occurred in 5 patients. One patient received sclerotherapy and operation was performed in 3 patients for variceal bleeding. Four patients were subjected to liver biopsy. RESULTS: Liver dysfunction of these patients remained normal and variceal bleeding didn't reccur after therapy. Liver biopsy showed nodular regenerative hyperplasia without fibrous septa. CONCLUSIONS: Non-cirrhotic portal hypertension associated with autoimmune disease is a rare syndrome, characterized by significant portal hypertension as well as histological evidence that cirrhosis is absent. Prevention and treatment of variceal bleeding is very important.

Adult↗

PubMed2000

[Staple in pericardial devascularization of upper GI bleeding due to portal hypertension: application and therapeutic effect].

OBJECTIVE: To investigate the therapeutic effect of staple in pericardial devascularization on upper GI bleeding due to portal hypertension. METHODS: From July, 1997 to July, 2000, 30 portal hypertensive patients were treated by using pericardial devascularization plus partial resection of lower part of the esophagus with staple (CDH25). The eliminating rate of varicose veins of the lower part of the esophagus and the stenosis rate of anastomosis were evaluated. The therapeutic effect of pericardial devascularization without lower part esophageal resection in 28 patient with upper GI bleeding due to portal hypertension was taken as control. RESULTS: All the patients were followed up for 23 months. There was no death due to the operation. All patients in the study group had no upper GI rebleeding during the 23-month follow-up. The rebleeding rate in the control group was 18% (5/28) (P < 0.05 vs. Study group). The varicose veins eliminating rate was 100% in the study group and 53.6% (15/28) in the control group (P < 0.01); the stenosis rate of anastomosis was 6.7% (2/30) in the study group. CONCLUSION: The therapeutic effect of pericardial devascularization could be improved by the use of staple with shorter operative time.

Adult↗

PubMed2000

[Detection of bacterial DNA in blood with three pairs of primers].

OBJECTIVE: To develop a stable and sensitive method to detect gut-derived bacterial DNA present in the blood. METHODS: Blood culture and PCR were performed simultaneously when temperature of patients (n = 23) was higher than 38.5 degrees C after laparotomy. PCR was performed after DNA extraction, target genes being beta-lactosidase gene of Escherichia coli(E. coli), glutamine synthase gene of Bacteroides Fragilitas, and 16SrRNA gene of most pathogenic bacteria. DNA of standard strains of E. coli and Bacteroides Fragilitas served as positive controls, blank control as negative controls, and healthy volunteers (n = 20) served as normal controls. We performed PCR twice with part of the samples (n = 20) in order to test the repetition of this method. RESULTS: The repetition rate of PCR was 95%. Three of blood cultures were positive (13.0%, 3/23), the corresponding positive ratio of PCR was 43.5% (10/23) which was higher than that of the blood culture (P = 0.016). CONCLUSION: PCR is more sensitive than blood culture in detection of bacteremia.

Bacterial Translocation↗

PubMed2000

[Surgical treatment of rectal villous adenomas: report of 49 cases].

OBJECTIVE: To evaluate surgical treatment of rectal villous adenomas. METHODS: Forty-nine cases of rectal villous adenomas treated with different surgical procedures were reviewed. Twenty (40.8%) of 49 patients had Mason's operation, eleven(22.4%) had Dixon's operation, eighteen (36.8%) had transanal excision and other procedures. RESULTS: Seventeen(34.7%) of 49 were villous adenomas containing invasive carcinoma. The rates of recurrence and complication of Mason's operation were 0% and 10% (2/20), Dixon's operation were both 18% (2/11), other procedures were 33.3% (6/18) and 16.7% (3/18). CONCLUSION: Mason's operation for most cases of villous adenomas at mid and low rectum can be a safe and effective method of treatment.

Adenoma, Villous↗

PubMed2000

[A clinical study on coincidence with hyperthyroidism and thyroid carcinoma].

OBJECTIVE: A retrospective study has been carried out to evaluate the prevalence of coincidence with hyperthyroidism and thyroid carcinoma. METHODS: 394 patients underwent surgery for hyperthyroidism and 245 patients suffered from thyroid cancer were chosen for the study in our hospital from January 1983 to June 1998. RESULTS: Thyroid cancer and hyperthyroidism coincided in 12 patients. The incidence of thyroid cancer was 3.0% (12/394) in hyperthyroidism, and the incidence of hyperthyroidism was 4.9% in thyroid cancer. There were 7 female and 5 male, with a diffuse goiter (n = 3), a diffuse goiter with a cold nodule (n = 3), multinodular goiter (n = 6). Among the 12 patients, 7 patients had an occult thyroid cancer with a diameter of 1 cm or less, most of them with papillary carcinoma, less frequently had metastases, 4 patients had thyroid cancer with a diameter of 3 cm or more, and 3 patients had metastases. CONCLUSIONS: The prevalence of coincidence with thyroid cancer and hyperthyroidism is more than that of thyroid cancer in population. Diagnostics for exclusion of thyroid cancer is required carefully even in the presence of hyperthyroidism.

Female↗

PubMed2000

[Prediction of peritoneal fluid pancreatic amylase to histopathological change and prognosis of acute experimental necrotic pancreatitis of monkey].

OBJECTIVE: To observe the significance of peritoneal fluid pancreatic amylase in predicting the degree of histopathological change and prognosis of acute necrotic pancreatitis (ANP) of monkey. METHODS: Injection of the mixture of bile and trypsin into the pancreatic duct set up ANP monkey model. RESULTS: The severity of ANP depended on the injection rate and volume, in correlation to the peritoneal fluid pancreatic amylase (PF Amylase) in the early stage of ANP. With the rate (3-13 ml/min) and volume (0.1-1.0 ml/kg) of injection increase, the PF Amylase in the early stage of the ANP significantly went up. Meanwhile, the survival time was negatively correlated to the PF Amylase in the early stage (0.5 hour) of ANP (t = -9.06 InX + 129.85, r = -0.88, P < 0.01). CONCLUSIONS: The PF Amylase in the early stage of ANP can effectively predict the severity of ANP and prognosis.

Amylases↗

PubMed1999

Characterization of the human diacylglycerol kinase epsilon gene and its assessment as a candidate for inherited retinitis pigmentosa.

Human diacylglycerol kinase epsilon (hDGK epsilon) displays high selectivity for arachidonate-containing substrates and may be essential in the termination of signals transmitted through arachidonoyl-diacylglycerol and/or the synthesis of phospholipids with defined fatty acid composition. We herein report the genomic structure, chromosomal mapping, and mutation screening of hDGK epsilon gene. hDGK epsilon gene contains at least 12 exons spanning approximately 30 kb of genomic sequence and was mapped to chromosome 17q22 by fluorescence in situ hybridization. A search for disease gene linkage revealed that a locus for autosomal dominant retinitis pigmentosa (adRP) known as RP17 resided in that region, and Northern blot analysis showed that hDGK epsilon was expressed in human retina. The hDGK epsilon gene was then localized to one of the YAC clones containing a STS marker for the RP17 locus by YAC contig mapping. Direct sequencing following PCR amplification of two affected DNA samples from that type of adRP patients, however, did not reveal any mutation in hDGK epsilon exons.

Cell Line↗

PubMed1999

The inwardly rectifying K(+) channel subunit GIRK1 rescues the GIRK2 weaver phenotype.

The weaver (wv) gene has been identified as a glycine to serine substitution at residue 156 in the H5 region of inwardly rectifying K(+) channel, GIRK2. The mutation is permissive for the expression of homotetrameric channels that are nonselective for cations and G-protein-independent. Coexpression of GIRK2wv with GIRK1, GIRK2, or GIRK3 in Xenopus oocytes along with expression of subunit combinations linked as dimers and tetramers was used to investigate the effects of the pore mutation on channel selectivity and gating as a function of relative subunit position and number within a heterotetrameric complex. GIRK1 formed functional, K(+) selective channels with GIRK2 and GIRK3. Coexpression of GIRK2wv with GIRK1 gave rise to a component of K(+)-selective, G-protein-dependent current. Currents resulting from coexpression of GIRK2wv with GIRK2 or GIRK3 were weaver-like. Current from dimers of GIRK1-GIRK2wv, GIRK2-GIRK2wv, and GIRK3-GIRK2wv was phenotypically similar to that obtained from coexpression of monomers. Linked tetramers containing GIRK1 and GIRK2wv in an alternating array gave rise to wild-type, K(+)-selective currents. When two mutant subunits were arranged adjacently in a tetramer, currents were weaver-like. These results support the hypothesis that in specific channel stoichiometries, GIRK1 rescues the weaver phenotype and suggests a basis for the selective neuronal vulnerability that is observed in the weaver mouse.

Amino Acid Substitution↗

PubMed1999

A GC-rich sequence within the 5' untranslated region of human basonuclin mRNA inhibits its translation.

By the method of RNase protection, the 5' ends of the basonuclin mRNA were mapped to four sites distributed over 400 bases of the genomic sequence, a result implying four different basonuclin transcripts within the cell. Despite the heterogeneity at the 5' end, all four basonuclin mRNA shared the same translation initiation codon. However, only two transcripts contained, in their 5' untranslated region (UTR), a GC-rich sequence of approx. 180 bases. The ability of this GC-rich sequence to form a large and stable secondary structure was suggested by experimental results from primer extension, RNase resistance, and computer analysis of the sequence. In vitro study showed that translation of basonuclin RNA containing this putative structure could not be initiated efficiently from the first two AUGs, whereas those that lacked it could.

5' Untranslated Regions↗

PubMed1999

p53 directly enhances rejoining of DNA double-strand breaks with cohesive ends in gamma-irradiated mouse fibroblasts.

The p53 gene regulates the cell cycle response to DNA damage, which may allow time for adequate DNA repair. We asked whether p53 could directly increase the repair of defined double-strand breaks (DSBs) by nonhomologous end-joining in gamma-irradiated mouse embryonic fibroblasts with differing p53 status. By using an episomal plasmid reactivation assay, we found that presence of wild-type p53 enhanced rejoining of DSBs with short complementary ends of single-stranded DNA. p53 appeared to be directly involved in this regulation, because rejoining enhancement was dependent on the presence of nonspecific DNA binding activity as mediated by the COOH-terminal domain and was independent of transactivating function. We hypothesize that tumor cells lacking p53 and normal cells with wild-type p53 may use different pathways for repair of radiation-induced DSBs.

3T3 Cells↗