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Biomedical subjects

W Guo

Publications and source records attributed to W Guo.

At least 55 records · Page 3Linked to original sources
PubMed2001

Characterization of mice with a combined suppression of I(to) and I(K,slow).

Cardiac-specific expression of a truncated Kv1.1 polypeptide (Kv1DN) attenuates the slow inactivating outward K(+) current (I(K,slow)), increases action potential duration (APD) and Q-T intervals, and induces spontaneous ventricular arrhythmias. Expression of the pore mutant of Kv4.2 (Kv4DN) eliminates the fast component of the transient outward current (I(to)) and prolongs APDs and Q-T intervals markedly; however, no arrhythmias are seen in Kv4DN mice, suggesting that APD and Q-T prolongation are not per se proarrhythmic. To test this hypothesis, the Kv1DN and Kv4DN lines were crossbred to produce animals (Kv1/Kv4DN) expressing both transgenes in an identical genetic background. Whole cell voltage-clamp recordings from left ventricular apex cells confirmed that in Kv1/Kv4DN left ventricular apex cells, both components (fast and slow) of I(to) and the 4-aminopyridine-sensitive component of I(K,slow) are eliminated, resulting in marked APD prolongation compared with wild-type, Kv1DN, or Kv4DN cells. Telemetric electrocardiogram monitoring (n = 10 mice/group) revealed a significant prolongation of Q-Tc and P-R intervals in Kv1/Kv4DN animals compared with Kv1DN or Kv4DN animals. Spontaneous arrhythmias were observed mainly in Kv1DN mice. Thus the attenuation of fast I(to) in addition to I(K,slow) in Kv1/Kv4DN mice causes significant prolongation of APD and Q-T intervals and attenuation of spontaneous arrhythmias.

4-Aminopyridine↗
PubMed2001

Functional expression of a GFP-tagged Kv1.5 alpha-subunit in mouse ventricle.

The experiments here were undertaken to determine the feasibility of increasing the cell surface expression of voltage-gated ion channels in cardiac cells in vivo and to explore the functional consequences of ectopic channel expression. Transgenic mice expressing a green fluorescent protein (GFP)-tagged, voltage-gated K+ (Kv) channel alpha-subunit, Kv1.5-GFP, driven by the cardiac-specific alpha-MHC promoter, were generated. In recent studies, Kv1.5 has been shown to encode the micromolar 4-aminopyridine (4-AP)-sensitive delayed rectifier K+ current (I(K,slow)) in mouse myocardium. Unexpectedly, Kv1.5-GFP expression is heterogeneous in the ventricles of these animals. Although no electrocardiographic abnormalities were evident, expression of Kv1.5-GFP results in marked decreases in action potential durations in GFP-positive ventricular myocytes. In voltage-clamp recordings from GFP-positive ventricular myocytes, peak outward K+ currents are significantly higher, and their waveforms are distinct from those recorded from wild-type cells. Pharmacological experiments revealed a selective increase in a micromolar 4-AP-sensitive current, similar to the 4-AP-sensitive component of I(K,slow) in wild-type cells. The inactivation rate of the "overexpressed" current, however, is significantly slower than the Kv1.5-encoded component of I(K,slow) in wild-type cells, suggesting differences in association with accessory subunits and/or posttranslational processing.

Action Potentials↗
PubMed2001

Determination of lomefloxacin, an antibacterial drug, in pharmaceutical preparations based on its polarographic catalytic wave in the presence of 2-iodoacetamide.

In a 0.125 mol/L phosphate (pH 6.6)/2.5 x 10(-4) mol/L 2-iodoacetamide solution, lomefloxacin yields a response of a polarographic catalytic current. The second-order derivative peak current of the catalytic wave of lomefloxacin is proportional to its concentration in the range of 1.0 x 10(-8)-1.0 x 10(-6) mol/L (r = 0.998). The sensitivity of the catalytic wave is 25-times higher than that of the corresponding reduction wave for 5.0 x 10(-7) mol/L lomefloxacin. The proposed method was applied to the determination of lomefloxacin in pharmaceutical preparations. The polarographic reduction wave is ascribed to a one-electron reduction of the C=C bond of lomefloxacin zwitterion accompanied by an acid-base equilibrium. The catalytic wave should be caused by regeneration of the lomefloxacin molecule at electrode surface due to the one-electron reduction product being further oxidized by electroreductive intermediate products of 2-iodoacetamide.

Alkylating Agents↗
PubMed2001

Cloning and expression of hamster telomerase catalytic subunit cDNA.

Topical application of 7,12-dimethylbenz(alpha)-anthracene induces tumors in the hamster cheek pouch. Telomerase activity is increased in the cancer tissues if compared to normal adjacent tissues in both human and hamster oral cancer. In order to achieve a probe and to investigate the putative role of telomerase in oral carcinogenesis using the hamster cheek pouch model, we have cloned the cDNA encoding the hamster telomerase catalytic subunit (hamTERT). The hamster TERT cDNA encoded 1128 amino acids and shared 64% amino acid identity with human TERT and 80% with murine TERT. As noted with human TERT which express several alternatively spliced mRNAs, we have also detected one alternatively spliced hamTERT mRNA in hamster cancer cells. Transient transfection of hamTERT cDNA in a retroviral expression vector reconstituted telomerase activity in the telomerase negative human lung fibroblast IMR90 cells.

Alternative Splicing↗
PubMed2001

c-Myc and Sp1/3 are required for transactivation of hamster telomerase catalytic subunit gene promoter.

The hamster and human TERT promoters share common critical protein binding sites, such as the GC-box or E-box, which is known to be a binding site for Sp1/Sp3 transcriptional factors and c-Myc, respectively. Our previous data demonstrated that Sp1/Sp3 synergistically transactivate the hamster TERT (hamTERT) promoter. In this study, we determined the role of c-Myc in the regulation of hamTERT, and analyzed the relative significance of GC-boxes and the E-box for transcriptional activation of hamster TERT. Wild-type, mutated E-box or mutated GC-box hamTERT core promoter reporter was introduced into 293T cells in combination with murine or human Myc expression vectors. The promoter activity was determined using the luciferase assay, and the transfection efficiency was normalized with CAT activity. The electrophoretic mobility shift assay (EMSA) was done to prove the nuclear protein binding activity of the GC-box (region II) or E-box. Overexpression of murine or human Myc transactivated hamTERT core promoter activity. Inversion mutation in the E-box or substitution mutation in the GC-boxes abrogated endogenous or Myc induced hamTERT transactivation. Region II is the single most important Sp1/3 binding site in transcriptional activation, and multiple combined mutations in the GC-boxes abolished the hamTERT promoter activity. These results indicate that c-Myc and Sp1/3 are the major regulatory determinants of the hamTERT transcriptional activation. The mechanism of TERT gene activation during immortalization and carcinogenesis may be conserved among species.

Animals↗
PubMed2001

Lateral difference in reaction times to lateralized auditory stimuli.

Evidence suggests that Reaction time (RT) is affected by human behaviour in that stimuli are processed and conducted faster and more accurately when they are presented directly to the specialised hemisphere and responded to more quickly when stimulus and response are mediated by the same hemisphere. The purpose of the current study was to investigate the effect of laterality using one parameter-reaction time (RT) on ipsilateral reactions to monuaural latralized stimuli. Twenty-four undergraduate polytechnic students and 10 representative level Rugby players participated in the study by reacting unilaterally to single and choice RT using simple and complicated sensor motor reactions (SMR). Results Shorter reaction times by the dominant hand while testing simple and complicated audio SMR, without reference to sex and sport skills results have been explained in terms of specialisation of left hemisphere in different aspects of information processes mechanisms, geared towards programming of the movement.

Acoustic Stimulation↗
PubMed2001

[Preliminary studies of microsatellite markers OarAE101 and BM1329 in five sheep breeds].

Two microsatellite markers OarAE101 and BM1329 which were closely linked to the fecundity gene FecB in Booroola sheep were analysed for polymorphisms in Small Tail Han sheep, Hu sheep, Charollais sheep, Ujumqin sheep, Dorset sheep, F1 (Dorset x Small Tail Han sheep). The number of alleles for OarAE101 was 5 or 4 in five sheep breeds. The number of alleles for BM1329 was all 4 in five sheep breeds. The polymorphic information contents for OarAE101/BM1329 in Small Tail Han sheep, Hu sheep, Charollais sheep, Ujumquin sheep, Dorset sheep, F1(Dorset x Small Tail Han sheep) were 0.57/0.54, 0.62/0.67, 0.61/0.59, 0.62/0.66, 0.56/0.67, 0.62/0.68, respectively. Least squares mean of litter size for OarAE101 107 bp/113 bp was significantly higher than those for OarAE101 109 bp/109 bp and 107 bp/111 bp (P < 0.05) in Small Tail Han sheep. Least squares means for litter size were not significantly different among other OarAE101 genotypes. The allele 107 bp of OarAE101 had a significant positive correlation with litter size in Small Tail Han sheep, both alleles 109 bp and 111 bp of OarAE101 had a significant negative correlation with litter size in Small Tail Han sheep. Least squares mean of litter size for BM1329 146 bp/158 bp was significantly higher than those for other BM1329 genotypes (P < 0.05) in Small Tail Han sheep. Least squares means for litter size were not obviously different among other BM1329 genotypes. The allele 146 bp of BM1329 had a significant positive correlation with litter size in Small Tail Han sheep, the allele 148 bp of BM1329 had a significant negative correlation with litter size in Small Tail Han sheep.

Alleles↗
PubMed2001

Correlation between the expression of cyclin A protein and p53 activity in oral squamous cell carcinomas.

Cyclins and wild-type p53 protein are prime cell cycle regulators and may be involved in tumorigenesis. Cyclin A is a late S cyclin and its abnormalities have been reported in several cancers, including oral squamous cell carcinomas. To explore whether aberrant G1/S in p53 mutant tumours leads to increased cyclin A protein in oral squamous cell carcinomas (OSCC), a total of 39 samples were evaluated for the expression of cyclin A and p53 protein by an immunohistochemical method using a labelled polymer assay. These samples comprised two hyperkeratotic and three oral premalignant lesions (two moderate and one severe dysplastic lesions), and 27 OSCC, together with seven healthy controls. The results demonstrated that the cyclin A protein was localized and highly expressed in the nuclei of the tumour cells. Although there was no correlation between cyclin A detection and the local lymph node involvement, a positive correlation was noted between the positivity of cyclin A and p53 protein (p <0.05). The results suggested that cyclin A may contribute to the progression of oral cancer and correlated to some degree with that of the p53 gene activity.

Carcinoma, Squamous Cell↗
PubMed2001

[Diagnosis and management of endoleak after endovascular repair of abdominal aortic aneurysm].

OBJECTIVE: To determine the diagnosis and management of endoleak after endovascular repair of abdominal aortic aneurysm (AAA). METHODS: We analysed retrospectively the data of 37 cases of infrarenal AAA treated by endovascular repair and investigated the reasons, managements, results and prognosis of endoleaks. RESULTS: Of 13 patients with endoleak at stent-graft deployment, 6 developed type I endoleak, 3 type II endoleak, 2 type III endoleak, 1 type IV endoleak, and 1 unknown reason. Type I and III endoleaks disappeared after management with additional techniques. The primary endoleak rate was 13.5%(5/37). Three sealed endoleak, 2 persistent endoleaks and 2 secondary endoleaks were found during follow up. The late endoleak rate was 10.8% (4/37). CONCLUSIONS: Endoleak is a chief complication after endovascular repair of infrarenal AAA. The influencing factors for endoleak include neck morphology, distance, angulation, calcification, stent-graft selection and side branching arteries. Additional procedure and follow up are very important. Techniques to find endoleak include CTA, Duplex and MRA after operation. Endoleak with enlarged aneurysm should be treated actively.

Aortic Aneurysm, Abdominal↗
PubMed2001

Effect of all-trans retinoic acid and arsenic trioxide on tissue factor expression in acute promyelocytic leukemia cells.

OBJECTIVE: To study the effect of all-trans retinoic acid (ATRA) and arsenic troxide (As2O3) on tissue factor (TF) expression and procoagulant activity (PCA) of acute promyelocytic leukemia (APL) cells in vivo and in vitro. METHODS: PCA from freshly isolated APL blasts from APL patients treated with ATRA or As2O3 was detected using a one-stage clotting assay. TF antigen was detected by ELISA and TF mRNA by RT-PCR. The maturation sensitive (NB4) or resistant subclones (NB4-R1) of the promyelocytic NB4 cell line, as well as U937 cells infected with pMSCV-PML-RARa treated with or without ATRA or As2O3, were also examined. RESULTS: Both ATRA and As2O3 can down-regulate the TF antigen, its mRNA transcription and membrane PCA of APL cells in vivo and in vitro, in a time-dependent manner. The TF antigen level in PML-RARa + U937 cells was significantly higher than that in U937 cells infected with retrovirus vector. Both ATRA and As2O3 can also down-regulate the TF antigen in U937 cells transfected with or without PML-RARa. CONCLUSION: Tissue factor expression and PCA in APL cells may be down-regulated by ATRA and As2O3. By down-regulating TF expression, As2O3 might also be used to improve the DIC-related hemorrhage in APL. Our data indicate that elevated TF antigen in PML-RARa + U937 may be related to the fusion protein PML-RARa. The down-regulating effect of ATRA and As2O3 on TF expression in U937 cells might not involve this fusion protein.

Adolescent↗
PubMed2001

[Endovascular stent-grafting of descending thoracic aortic lesions].

OBJECTIVE: To discuss the feasibility of endoluminal stent-grafting for descending thoracic aortic lesions. METHODS: 12 patients underwent stent-grafting of the thoracic aorta with Talent (11 patients) and Vanguard (1) device. Endovascular technique was used in 12 patients with descending thoracic aortic aneurysms (5 patients), Stanford B dissections (6), and pseudoaneurysm (1). 13 straight stent-grafts were inserted through 18-24 F theaths via a femoral arteriotomy under local (2 patients) or general (10) anesthesia. RESULTS: The procedure was technically successful in all patients without aneurysm rupture, paraplegia, and organs or limbs ischemia. There were 3 early endoleaks. Follow-up showed that 4 of 5 aortic aneurysms were excluded completely and one endoleak was changed into persistent. Four entries of 6 patients with stanford B dissection were excluded and 2 early endoleaks were sealed during one month after operation. Four false lumen were filled completely and 2 false lumen were filled partly by thrombosis. CONCLUSION: Descending thoracic aortic stent-grafting is a safe, highly successful and feasible alternative to conventional surgery. The long-term result remains unclear, especially that of the endovascular repair of Stanford B dissection.

Adult↗
PubMed2001

[The preliminary study on change of serum enzyme level in crush syndrome rat].

OBJECTIVE: To study the changes of serum creatinine kinase(CK) and its cardiac-specific isoenzyme compound(CK-MB) levels in crush injury rats. METHODS: Crush injury was produced in SD rats, the serum levels of CK and CK-MB were studied by automated biochemical analyzer. RESULTS: The levels of plasma CK and CK-MB were much higher in crush injury rats than those of the control group. CONCLUSIONS: Cardiomyocyte injury may be induced in the early stage of crush injury rats.

Animals↗
PubMed2001

[The changes of tryptase activity in anaphylactic shock guinea-pigs].

OBJECTIVE: To investigate the changes of the activity of tryptase of sera, lungs and bronchial tubes in the guinea-pigs which suffered from hetero-serum anaphylactic shock. METHODS: Sera and tissues were collected from anaphylactic shock guinea-pigs, and the enzyme activity was tested colormetrically using special substrate, BAPNA. RESULTS: The activity of tryptase of sera, lungs and bronchial tubes increased significantly in Anaphylactic guinea-pigs compared with control group. CONCLUSION: The changes of tryptase activity are helpful to diagnose anaphylactic shock.

Anaphylaxis↗
PubMed2001

[Cloning and expression of D-arabitol dehydrogenase gene from Acetobacter suboxydans in Escherichia coli].

The partial genomic library of Acetobacter suboxydans was constructed using Yeast-E. coli shuttle plasmid YEp352 as vector. Two positive transformants, designated as DH5 alpha(pAD91) and DH5 alpha(pAD98), were obtained by screening the growth of transformants on the agar plate in which D-arabitol was used as the sole carbon source. The results of Southern blot and restriction endonuclease analysis showed that the two recombinants are identical. The insert is about 2.3 kb. Arabitol dehydrogenase activity assay indicated that the transformants could produce D-xylulose-forming D-arabitol dehydrogenase. Hence, the gene encoding D-arabitol dehydrogenase exists in the cloned DNA fragment.

Acetobacter↗
PubMed2001

[Expression of alpha-acetolactate decarboxylase gene from Bacillus subtilis in Brewer's yeast].

Yeast YIp-type expression recombinant plasmid(pCMA2-1) was constructed. The expression of alpha-acetolactate decarboxylase gene from Bacillus subtilis was controled by CUP1 promoter and its own terminator. The recombinant plasmid pCMA2-1 was introduced into the brewer's yeast PJ3-5. Transformants were selected using copper resistance as selected marker. The results of activity assay showed that PJ3-5 didn't produce alpha-acetolactate decarboxylase(ALDC), where as the activity of alpha-ALDC in transformants were induced by copper sulfate. The laboratory scale fermentation test confirmed that the total diacetyl concentration was reduced effectively by alpha-ALDC in transformant.

Bacillus subtilis↗
PubMed2001

[Synergetic protective effects of glial cell line-derived neurotrophic factor combined with neurotrophin-3 in F-actin on hair cell after noise trauma].

OBJECTIVE: To investigate if glial cell line-derived neurotrophic factor (GDNF) combined with neurotrophin-3 (NT-3) provides synergetic protection in filamentous actin (F-actin) on hair cell (HC) from acoustic trauma. METHODS: Guinea pigs were exposed to 4 kHz narrow band noise at 115 dB SPL for 4 h. Test group (n = 12) with a mixture of GDNF (100 ng/ml) and NT-3(2.5 micrograms/ml) or control group (n = 9) with artificial perilymph (AP) was delivered to the scala tympani via a mini-osmotic pump (0.5 microliter/h) for a total of 14 days. Auditory function was assessed by measuring thresholds of auditory brainstem responses (ABRs) elicited by clicks prior to surgery, 3 days after surgery (1 day before noise exposure) and 10 days following noise exposure (before animals were sacrificed), respectively. F-actin, labeled by rhodamine-phalloidin, was examined in the guinea pig cochlea using fluorescence microscopy for quantitative assessment of hair cell damage. RESULTS: There was a statistically significant increase the survival of out hair cell(P < 0.001, P < 0.01) and inner hair cell(P < 0.01, P < 0.01) and decrease in ABR threshold (P < 0.05, P < 0.01) in both the GDNF and NT-3 treated and untreated ear of animals. CONCLUSION: Our findings indicate that GDNF combined with NT-3 may effectively protect the inner ear from noise--induced hearing loss.

Actins↗
PubMed2000

Phase transition in the n > 2 honeycomb O(n) model

We determine the phase diagram of the O(n) loop model on the honeycomb lattice, in particular, in the range n>2, by means of a transfer-matrix method. We find that, contrary to the prevailing expectation, there is a line of critical points in the range between n = 2 and infinity. This phase transition, which belongs to the three-state Potts universality class, is unphysical in terms of the O(n) spin model, but falls inside the physical region of the n-component corner-cubic model. It can also be interpreted in terms of the ordering of a system of soft particles with hexagonal symmetry.

Journal Article↗