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Biomedical subjects

W Qian

Publications and source records attributed to W Qian.

At least 109 records · Page 6Linked to original sources
PubMed1995

[A study on antimicrobial resistance of coagulase negative staphylococci].

One hundred and eight strains of coagulase negative staphylococci (CNS) isolated from different clinical specimens (sputum, urine, blood, various catheters etc.) were classified into 9 species of CNS with biochemical technique. Staphylococcus epidermidis and staphylococcus saprophyticus accounted for the majority (66%). Drug susceptibility tests revealed that they were highly resistant to penicillin, oxacillin, erythromycin, chloramphenicol, compound sulfamethoxazole, tetracycline, cephazolin and ++ceftazidim but relatively sensitive to vancomycin, amikacin, gentamicin and rifapen. The MIC of oxacillin ranged from 0.125 mg/L to 128 mg/L. The MIC90 was 64 mg/L. It is suggested that vancomycin is the therapy of first choice in methicillin resistant CNS infection.

Anti-Bacterial Agents↗
PubMed1994

Tree-structured non-linear filter and wavelet transform for microcalcification segmentation in digital mammography.

A novel algorithm was developed for computer aided diagnosis of microcalcification clusters in digital mammography. The method includes: (a) tree-structured central weighted median filters with variable shape windowing to suppress image noise but preserve image details; (b) a quasi range dispersion edge detector to increase edge contrast and definition; and (c) tree-structured wavelets for calcification segmentation. The preliminary evaluation of the method on nine mammograms showed that 100% sensitivity can be achieved at the expense of four false positive clusters per image. Research is ongoing for further optimization of the algorithm to reduce the number of false alarms and establish its clinical value.

Algorithms↗
PubMed1994

The application of fractal analysis to mammographic tissue classification.

As a first step in determining the efficacy of using computers to assist in diagnosis of medical images, an investigation has been conducted which utilizes the patterns, or textures, in the images. To be of value, any computer scheme must be able to recognize and differentiate the various patterns. An obvious example of this in mammography is the recognition of tumorous tissue and non-malignant abnormal tissue from normal parenchymal tissue. We have developed a pattern recognition technique which uses features derived from the fractal nature of the image. Further, we are able to develop mathematical models which can be used to differentiate and classify the many tissue types. Based on a limited number of cases of digitized mammograms, our computer algorithms have been able to distinguish tumorous from healthy tissue and to distinguish among various parenchymal tissue patterns. These preliminary results indicate that discrimination based on the fractal nature of images may well represent a viable approach to utilizing computers to assist in diagnosis.

Breast Neoplasms↗
PubMed1994

Vibrational analysis of glutathione.

Infrared and Raman spectra have been obtained of crystalline glutathione and its deuterated derivative and interpreted by normal mode analysis. The force field consisted of our empirical force fields for the peptide group and NH3+ and CO2- end groups, plus our ab initio force fields for the CH2SH and CH2COOH moieties. Observed bands are reproduced with an average error of 5 cm-1, demonstrating that the vibrational spectrum of such a complex molecule can be understood in great depth.

Amino Acid Sequence↗
PubMed1994

Wavelet compression and segmentation of digital mammograms.

An initial evaluation of Haar wavelets is presented in this study for the compression of mammographic images. Fifteen mammograms with 105 microns/pixel resolution and varying dynamic range (10 and 12 bits per pixel) containing clustered microcalcifications were compressed with two different rates. The quality and content of the compressed reconstructed images was evaluated by an expert mammographer. The visualization of the cluster was on the average good but degraded with increasing compression because of the discontinuities introduced by these types of wavelets as the compression rate increases. However, the artifacts in the decoded images were seen as totally artificial and were not misinterpreted by the radiologist as calcifications. The classification of the parenchymal densities did not change significantly but the morphology of the calcifications was increasingly distorted as the compression rate increased leading to lower estimates of the suspiciousness of the cluster and higher uncertainties in the diagnosis. The uncompressed and two sets of compressed images were also processed by a wavelet method to extract the calcifications. Despite the fact that the segmentation algorithm generated several false-positive signals in highly compressed images, all true clusters were successfully segmented indicating that the compression process preserved the features of interest. Our preliminary results indicated that wavelets could be used to achieve high compression rates of mammographic images without losing small details such as microcalcification clusters as well as detect the calcifications from either the uncompressed or compressed reconstructed data. Further research and application of multiresolution analysis to digital mammography is continuing.

Algorithms↗
PubMed1994

Spatial distribution of back scattering in the nuclear area of the non-cataractous human lens.

The spatial distribution of back scattering from a vertical cross-section of the nuclear area in non-cataractous human lens was investigated. The cross-section was centred on the pupil. There is no significant difference in average nuclear back scattering between sides. The distribution of back scattering along an axis perpendicular to the anatomical axis can be modelled as a second-order polynomial. It is believed that the increase of back scattering in the central region corresponds to the peak protein concentration in the centre of the nucleus. This information was obtained by imaging back scattering with Scheimpflug photography. The back scattering was measured photometrically in a 3 x 10 matrix of measuring areas within the lens nucleus. Each measuring area was 0.20 x 0.20 mm in size. It is anticipated that the established model will allow detection of nuclear cataract with high sensitivity, especially in early stages.

Aged↗
PubMed1994

[Investigation of drug release in vitro from mitoxantrone-nanospheres].

We observed the rules of drug release in vitro from a liver targeting preparation-mitoxantrone polybutylcyanoacrylate nanospheres freeze-drying injection by dynamic penetration system and spectrophotometry. The results showed that the drug release of this nanospheres preparation accorded with the two phases kinetics rules in vitro. In the process of drug release, there were two phases. The first phase was a quick release phase, the quantity of released drug within 4 hours being more than 40%, t1/2 alpha = 1.40h. The second phase was a slow release phase, t1/2 beta = 169.02h. The rules of drug release accord with the normal rules of drug use. The preparation may be clinically used.

Drug Carriers↗
PubMed1994

[Clinical study of erythromycin action on gallbladder motility in patients with non-ulcer dyspepsia].

Thirty-two patients of non-ulcer dyspepsia (NUD) with gallbladder hypokinesia treated by oral erythromycin administration 0.125g three times daily for two weeks. Before and after oral erythromycin administration, gallbladder volumes were determined by ultrasound, and plasma motilin concentration were determined by radioimmunoassay. The results showed that before and after oral erythromycin administration, maximal percentage emptying of gallbladder were 48.24 +/- 8.30ml vs 69.74 +/- 10.78ml (P < 0.01), plasma motilin were 361.28 +/- 87.92ng/L vs 394.97 +/- 134.27ng/L (P > 0.05). It is indicated that erythromycin could reduce fasting and postprandial residual gallbladder volumes and increases maximal percentage emptying of gallbladder. It suggests that erythromycin might have an agonist action on the motilin receptor as an agonist action on the motilin receptor as an exogenously administrated motilin.

Adult↗
PubMed1993

EPR studies of singlet oxygen (1O2) and free radicals (O2.-, .OH, HB.-) generated during photosensitization of hypocrellin B.

Hypocrellin B(HB), a peryloquinone derivative, is one of the main photosensitive agents, hypocrellin. This pigment, in combination with phototherapy, has been used in human medicine to cure various skin diseases. The photochemistry (Type I and II) of HB has been studied using spin-trapping and spin-counteraction techniques. The results show that the active oxygen (1O2, O2.-, .OH) mechanism of HB photosensitization can be converted into nonoxygen free radical (HB.-) mechanism completely when oxygen is exhausted in the experimental system. Under anaerobic conditions, HB only undergoes Type I reaction, generating nonoxygen free radical (HB.-).

Electron Spin Resonance Spectroscopy↗
PubMed1993

Macrophage prostaglandin E2 and oxidative responses to endotoxin during immunosuppression associated with anaesthesia and transfusion.

The widespread use of blood transfusion in major surgical procedures has led to concern about the immunosuppressive effect of transfusion on patients with underlying malignancy. Transfusion may also suppress the host response to infection. The cellular mechanisms of transfusion-associated immunosuppression may involve macrophage prostaglandin E2 (PGE2) in modulating the host response to cancer and infection. We previously observed that the transfusion of blood increased PGE2 production by unstimulated macrophages. To investigate this PGE2 associated immunosuppression, we studied the effect of transfusion of rats using a physiological stimulus of macrophage PGE2 production, bacterial endotoxin. In the same macrophages, we analysed intracellular oxidative activity. Both allogeneic and syngeneic blood transfusion were associated with increased PGE2 release by macrophages. This stimulation of PGE2 increased with duration of storage of blood. A similar effect of serum indicated that a humoral factor was involved. Endotoxin (50 ng/ml-500 micrograms/ml) stimulated PGE2 production in all transfused subjects. The lowest endotoxin concentration gave proportionately the greatest stimulation. Oxidative activity was down-regulated in macrophages of transfused rats, supporting an immunosuppressive role of PGE2 within the macrophage. An effect of surgery on the oxidative response was also detected.

Anesthesia↗
PubMed1993

A common lens nuclear area in Scheimpflug photographs.

Scheimpflug photography has been proven to be a useful method for documentation of opacification of the lens nucleus. In the present study, a common lens nuclear area (CNA) is established for photometry of nuclear cataract on Scheimpflug photographs. Using the established method, one measurement for one photograph, and one photograph for each subject is enough for the photometry of nuclear density. Further, this method allows detection of a 10% change in nuclear density between two occasions with a group of at least 7 subjects, and for independent groups with at least 95 subjects in each group (alpha = 0.05, beta = 0.10). It is anticipated that the CNA will provide a useful tool for quantitative determination of nuclear cataract.

Aged↗
PubMed1993

Evaluation of gray scale steps on Scheimpflug photographs.

A method for the calibration of gray scale density in a Scheimpflug photograph was established. Based on the result of statistical analysis, it was found that variability in the film emulsion was insignificant if the measuring area > or = 0.01 mm2. Each lens image should be calibrated with the reference gray scale in the same photograph. Photometric readings of the lens image was converted to gray scale levels. This conversion can be obtained from fitting photometric readings of the gray scale as a function of gray scale steps with a third order polynomial. Adopting this calibration procedure, 95% of estimated nuclear densities are within +/- 3-5% of the real value.

Analysis of Variance↗
PubMed1992

Vibrational studies of the disulfide group in proteins. Part V. Correlation of SS stretch frequencies with the CCSS dihedral angle in known protein disulfide bridges.

Normal mode calculations have been done on 92 disulfide bridges in 25 known protein structures in order to correlate the SS stretch frequency with the CCSS dihedral angle. It is possible to classify the frequencies into four major categories, which provide a more detailed classification scheme than previously proposed from dialkyl disulfide correlations.

Disulfides↗
PubMed1992

Vibrational studies of the disulfide group in proteins. VI. General correlations of SS and CS stretch frequencies with disulfide bridge geometry.

Normal mode calculations have been done on a range of disulfide bridge conformations in order to determine how the SS stretch and CS stretch frequencies depend on structure. In addition to varying the C alpha C beta SS and NC alpha C beta S dihedral angles, we have varied the phi, psi of the adjoining peptide groups since we have shown that these also influence the above frequencies. In order to obtain structural information from the observed frequencies, we have done a study of the conformational states found in 92 disulfide bridges in 25 known protein structures. This permits making a statistically based correlation between CS stretch frequencies and the possible contributing conformers.

Disulfides↗
PubMed1992

Repetitive, episodic hypoxia causes diurnal elevation of blood pressure in rats.

An association between chronic high blood pressure and obstructive sleep apnea has been described. We hypothesized that repetitive episodic hypoxia patterned after the hypoxia seen in sleep apnea could contribute to diurnal elevation of blood pressure. Using 12-second infusions of nitrogen into daytime sleeping chambers, four groups of male rats (250-375 g) were subjected to intermittent hypoxia (3-5% nadir ambient oxygen) every 30 seconds, 7 hours per day for up to 35 days. In one group, blood pressure was measured weekly by the tail-cuff method in conscious animals during 5 weeks of episodic hypoxia. In the other three groups, blood pressure was measured in conscious animals via femoral artery catheters at baseline and after 20, 30, or 35 days of exposure. Additional groups served as controls: two sham groups housed in identical "hypoxia" chambers received compressed air instead of nitrogen (35 days) while two other groups remained unhandled in their usual cages (35 days). Both groups challenged with 35 days episodic hypoxia showed significant increases in blood pressure compared with controls: the tail-cuff rats showed a 21 mm Hg increase in systolic pressure (p less than 0.05) and the intra-arterially measured rats a 13.7 mm Hg increase in mean arterial pressure (p less than 0.05). The 30-day exposed rats also showed a 5.7 mm Hg increase in mean pressure over baseline (p less than 0.05). Blood pressure did not change significantly from baseline in the control groups. Left ventricle-to-body weight ratio was higher in both 35-day exposed groups than in unhandled or sham controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A double-blind trial of nocturnal supplemental oxygen for sleep desaturation in patients with chronic obstructive pulmonary disease and a daytime PaO2 above 60 mm Hg.

The efficacy of nasal oxygen during sleep was evaluated in patients with COPD, episodic rapid eye movement sleep desaturation, and a daytime PaO2 greater than 60 mm Hg. The double-blind, randomized 3-yr trial used nasal oxygen versus room air in two groups of nocturnal sleep desaturating subjects. The setting was the outpatient chest clinic of a Veterans Affairs Medical Center. There were 51 patients with moderate to severe COPD, daytime PaO2 greater than or equal to 60 mm Hg: 38 with proven REM sleep desaturation and 13 without desaturation. Nocturnal oxygen at 3 L/min was delivered by concentrator to 19 desaturating subjects, and room air at 3 L/min was delivered by defective concentrator to the remaining 19 desaturating subjects. There was no gas therapy for the 13 nondesaturating subjects. The nocturnal desaturator group who received supplemental oxygen during sleep over 36 months showed a significant downward trend in pulmonary artery pressure (-3.7 mm Hg) compared with desaturating patients treated with room air (+3.9 mm Hg). Nonvascular parameters of hypoxia, such as hemoglobin and red blood cell mass, did not differ between the sham- and oxygen-treated groups. Mortality was decidedly higher in the desaturating patients compared with non-desaturating subjects, but there was no significant difference between oxygen- and sham-treated desaturating subjects. We conclude that nasal supplemental oxygen used during sleep to reverse episodic desaturation in COPD patients whose daytime PaO2 is above 60 mm Hg has a beneficial effect in reducing pulmonary artery pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Double-Blind Method↗