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Biomedical subjects

Q Zhou

Publications and source records attributed to Q Zhou.

At least 235 records · Page 13Linked to original sources
PubMed1998

Stereo capture: local rematching driven by binocularly attended 3-D configuration rather than retinal images.

Previous explanations for stereo capture were mainly based on the low-level perceptual processing of binocular stereopsis which usually shows that one pair of retinal images corresponds to only one 3-D perceptual configuration. Stereo capture, however, may encounter multiple perceptual configurations due to the matching ambiguity of wallpaper elements that may not be solved merely by bottom-up processing of the retinal stimuli. The present study suggests that binocular attention plays an important role in stereo capture by way of selecting and enhancing a perceptual configuration that is often ambiguous without attention involved. Stereo capture results from wallpaper's local rematching driven by binocularly attended 3-D configuration rather than retinal images.

Attention↗
PubMed1998

Accuracy of repeated blood sampling in rats: a new technique applied in pharmacokinetic/pharmacodynamic studies of the interaction between warfarin and co-enzyme Q10.

In the past, combined pharmacokinetic/pharmacodynamic (PK/PD) modeling studies of oral anticoagulants in rats have been hampered by the technical problems of blood sampling. In the present study, a semi-micromethod of preparing serial plasma samples for accurate assessment of the prothrombin times (PT) and clotting factor VII activity (CFA) in rats is proposed. The method consists of orbital bleeding, blood sample weighing, gravity calculation and buffer volume adjustment. No significant differences of CFA (percentage normal) were found between citrate-diluted and undiluted plasma. This technique was employed to examine the possibility of PK/PD interaction between warfarin and Co-enzyme Q10 (CoQ10). Rats were given a single oral dose (1.5 mg/kg) of warfarin either alone or on day 4 of an 8-day oral dosing regimen of 10 mg/kg CoQ10 daily. Serial plasma and serum samples, which were subjected to respectively measurements of the anticoagulant effects and concentrations of warfarin and its main metabolites, were obtained over a 96-h period following warfarin administration. All rats survived the whole experiment and maintained a stable condition except for a marked hematocrit decrease. CoQ10 significantly augmented warfarin metabolism but showed little effect on the absorption of warfarin. CoQ10 alone had no apparent effect on either the PT or CFA. The concomitant administration of CoQ10 and warfarin does not significantly affect the anticoagulant effect of warfarin. In conclusion, the proposed serial orbital bleeding technique in rats to prepare an accurate citrate-diluted plasma for PT and CFA measurement is rapid and reliable.

Animals↗
PubMed1998

Cyclins and breast cancer.

Cyclins are regulatory subunits for cyclin dependent kinases in the coordination of the cell cycle. Cyclins can also serve non-cell cycle functions, such as the transactivation of estrogen receptor by cyclin D. Evidence for the participation of the G1 cyclins D and E in breast cancer is summarized, including transgenic and knockout mice, transfections, and expression patterns in cohort studies. Overexpression of cyclin D has been reported in ductal carcinoma in situ (DCIS), and similar overexpression of cyclin E is suggested. Strategies to reduce cyclin expression are discussed as potential prevention efforts.

Animals↗
PubMed1998

Regulation of the stability of heat-stable antigen mRNA by interplay between two novel cis elements in the 3' untranslated region.

The heat-stable antigen (HSA) is a costimulatory molecule for T-cell activation. Its expression is strictly regulated during lymphocyte development and differentiation. Recent studies using HSA-transgenic mice have demonstrated that this regulated expression is critical for normal development of T and B lymphocytes. However, the mechanisms that control the expression of HSA are largely unknown. HSA mRNA is comprised of a 0.23-kb open reading frame and a 1.5-kb 3' untranslated region (3'UTR). The function of the long 3'UTR has not been addressed. Here we investigate the role of the 3'UTR of HSA mRNA. We show that a 160-bp element, located in the region of nucleotides 1465 to 1625 in the 3'UTR of HSA mRNA, promotes RNA degradation and that this effect is neutralized by a 43-bp fragment approximately 1 kb upstream of the negative cis element. Both positive and negative cis elements in the HSA mRNA are distinct from other sequences that are known to modulate mRNA stability. These results provide direct evidence that the interplay between two novel cis elements in the 3'UTR of HSA mRNA determines cell surface HSA expression by modulating its RNA stability.

Animals↗
PubMed1998

[Ultrasonographic rating score in evaluation of pathological severity and timing of operation for acute cholecystitis].

A rating score of ultrasonography to evaluate the pathological severity and timing of operative intervention of acute cholecystitis was designed. The ultrasonic rating score consisted of 7 items with were sensitive and specific in diagnosis of acute cholecystitis, accorded with the findings during operation. Emergency cholecystomies performed on patients with score < or = 10, 11-18 and > 18 points were 1/30, 4/42 and 7/13 respectively, followed by definite procedures. The results suggest that the ultrasonographic rating score is an useful approach in ultrasound diagnoses and timing of operation for acute cholecystitis.

Acute Disease↗
PubMed1998

[Clinical significance of pulmonary valvular resistance in children determined by color Doppler echocardiography].

Pulmonary valvular resistance (PVR) of 40 children with pulmonary valvular stenosis was determined by color Doppler echocardiography before and after percutaneous balloon pulmonary valvuloplasty as well as during their follow-up. The correlation coefficient of PVR between Doppler method and catheterization method was 0.85 ( P <0.01) and the correlation coefficient between PVR determined by former method and pulmonary valvular area determined by the latter was -0.80 ( P <0.01). This study indicates that color Doppler echocardiography can take the place of catheterization to determine PVR in assessing the severity of pulmonary valvular stenosis in children.

Adolescent↗
PubMed1998

[The value of color Doppler ultrasonography in diagnosing aneurysm].

Using Doppler ultrasound, we detected 59 patients with aneurysm, 54 cases were confirmed by angiography or operation or both. Among them, 33 cases (63%) showed true aneurysm, 18 cases (33%) pseudoaneurysm, and 2 cases (4%) superficial congenital arterio-venous aneurysm. Eight cases were associated with dissected stripping. One case was falsely diagnosed by ultrasonography. The diagnostic accuracy was 98%. The results suggest that color Doppler ultrasonography is useful in detecting aneurysm.

Adult↗
PubMed1998

[Slot blot analysis of metastasis suppression gene nm23 expression in human lung cancer].

To investigate the role of metastasis suppression gene (nm23) in the development and progression of human lung cancer, the mRNA expressions of nm23-H1 and nm23-H2 genes in a series of pulmonary tissues collected at various sites and with different properties were studied with slot blot hybridization. According to the observations on the normal pulmonary tissues, benign lesions, para- and non-cancer tissues, primary cancer and metastatic lymph nodes, there was a tendency of mRNA expression reduction of nm23-H1 and nm23-H2 genes. Among them, nm23-H2 mRNA expressions in lung cancer tissues were significantly decreased when compared with normal pulmonary tissues (P < 0.05), and nm23-H1 and nm23-H2 gene expressions in metastatic lymph nodes were both reduced, compared with those in normal pulmonary tissues (P < 0.05). There was no significant correlation between nm23 gene expression and lymph node metastasis in lung cancer. The results implied that reduction of nm23 gene expression might be associated with the development of lung cancer, but no evidence of metastasis suppression by nm23 gene was revealed in this study.

Adenocarcinoma↗
PubMed1998

[Northern blot analysis of nm23 gene expression in human lung cancer].

OBJECTIVE: To investigate the role of nm23 gene expression in lung cancer. METHODS: Forty human lung cancer tissues and 19 non-cancerous pulmonary tissues were studied for their nm23-H1 and nm23-H2 mRNA expression with nonradioactive Northern blot hybridization. Correlation of nm23 mRNA expression with clinical features of lung cancer was analyzed. RESULTS: The mRNA expression of nm23-H2 gene in poorly differentiated squamous-cell carcinoma was significantly decreased compared to that in moderately differentiated squamous-cell carcinoma. The mRNA expression of nm23-H1 and nm23-H2 genes in small cell lung cancer was decreased compared to that in squamous-cell carcinoma. No significant difference in nm23 mRNA expression was observed in lung cancers with and without lymph node metastasis, nor was there significant difference in patients with lung cancers in different stages. CONCLUSION: The mRNA expression of nm23 gene is correlated with the degree of differentiation of lung cancer, but there is no evidence of metastasis suppression effect by nm23 gene.

Adenocarcinoma↗
PubMed1998

[Synthesis of several analogues of antifungal steroid alkaloids].

In order to search for new type antifungal drugs, seven analogues of antifungal alkaloids were synthesized, each through a reaction sequence of ten or eleven steps, using the commercially available steroid, 3 beta-acetoxy-5, 16-pregnadiene-20-one as the starting material. The preliminary antifungal tests in vitro showed that compounds 3a-c, and 5 were more effective than fluoconazole. Nineteen new compounds were synthesized in this work.

Alkaloids↗
PubMed1998

[FTIR microscope study on the change of membrane protein and lipids of erythrocyte damaged by free radicals].

The FTIR Microscope and Computer Aided Analysis were used to study not only the change of secondary structure of erythrocyte membrane protein attacked by the free radicals, but also the effect of oxygen centered free radicals on the membrane lipids in this paper. The results indicate that the content of alpha-helix in the secondary structure of protein clearly changed because of the attack of the free radicals. Damaged by free radicals in 30 minutes, the protein structure could not be restored after 3 hours. The number of the P=O (vp=0), C=O and C=C in the lipids of the membrane was changed. These changes were caused by the peroxidation of the oxygen centered free radicals.

Adult↗
PubMed1998

[Simultaneous determination of metronidazolum and vitamin B6 by the derivative spectrophotometry].

A new method for simultaneous determination of metronidazolum and vitamin B6 was established by the third derivative spectrophotometry in 0.1 mol/L HCl solution. The detection limits were 0.81 microg/mL for metronidazolum and 0.16 microg/mL for vitamin B6. The linear range of determination was 1.6-22.4 microg/mL for both metronidazolum and vitamin B6. This method has been applied to the determination of metronidazolum and vitamin B6 in tabellae metronidazoli compositae with satisfactory results. The coefficients of variation are below 2.26 and 2.65% and the recoveries are 93-102% and 99-101% for metronidazolum and vitamin 6, respectively.

Limit of Detection↗
PubMed1998

Microtubule contribution to the reflectance of the retinal nerve fiber layer.

PURPOSE: The reflectance of the retinal nerve fiber layer (RNFL) arises from cylindrical light scattering elements distributed throughout its thickness. To determine whether these elements include axonal microtubules, eyecup preparations of the toad Bufo marinus were treated with the microtubule depolymerizing agent colchicine. METHODS: Some eyecups were incubated for various times in different colchicine concentrations and then fixed and prepared for electron microscopy (EM). In other eyecups the reflectance of the RNFL at 440 nm was measured by means of imaging microreflectometry. After a period of baseline measurements, the bathing solution was changed either to one of identical composition (control experiments) or to one containing 10 mM colchicine. Measurements then continued for 2 to 3 hours. RESULTS: Quantitative EM showed that colchicine caused the density of axonal microtubules to decrease by approximately one third in 2 hours. Reflectometry showed, in control experiments, that the RNFL reflectance remained near baseline for the duration of an experiment. In contrast, after changing to colchicine solution, the RNFL reflectance declined to a level 37% to 55% below baseline. CONCLUSIONS: Microtubules made a major contribution to the 440-nm reflectance of the unmyelinated axons of the toad RNFL and could make a similar contribution to the reflectance of human RNFL.

Animals↗