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Biomedical subjects

P C Lu

Publications and source records attributed to P C Lu.

At least 19 recordsLinked to original sources
PubMed2002

Computer-assisted automatic peak recognition and result evaluation for analysis of chlorinated hydrocarbons in environmental samples.

A data manipulation method has been developed for automatic peak recognition and result evaluation in the analysis of organic chlorinated hydrocarbons with dual-column gas chromatography. Based on the retention times of two internal standards, pentachlorotoluene and decachlorobiphenyl, the retention times of chlorinated hydrocarbons can be calibrated automatically and accurately. It is very convenient to identify the peaks by comparing the retention times of samples with the calibrated retention times calculated from the relative retention indices of standards. Meanwhile, with a suggested two-step evaluation method the evaluation coefficients and the suitable quantitative results of each component can be automatically achieved for practical samples in an analytical system using two columns with different polarities and two internal standards.

Automation↗
PubMed2001

A reevaluation and discussion on the threshold limit for hemolysis in a turbulent shear flow.

One major factor of red blood cell damage induced by artificial heart valves is the magnitude of turbulent shear stresses in the flow field. An often-cited threshold for hemolysis is 400 N/m(2) (Sallam and Hwang, Biorheology 21 (1984) 783). This value, however, was measured with a one-component laser Doppler anemometer and was not calculated from the major principal Reynolds shear stress, therefore underestimating the threshold. This study performed flow field measurements under similar conditions, using a two-component laser Doppler anemometer and determining major principal Reynolds shear stress, to reevaluate the hemolytic threshold as 800 N/m(2) with an exposure time of 1 ms. The Kolmogorov length scales, approximately 9 microm, are capable of inflicting direct damage to the red blood cells. These results will serve as a more accurate reference in future heart valve design and testing.

Blood Flow Velocity↗
PubMed2001

Posterior corneal surface changes after refractive surgery.

OBJECTIVE: To determine the frequency of changes in posterior corneal surface after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). DESIGN: Nonrandomized, comparative trial. PARTICIPANTS: Ninety-five eyes (71 patients) that underwent PRK (n = 45) or LASIK (n = 50). CONTROLS: Twenty nonsurgery eyes were used to validate the method of analysis of the posterior corneal curvature (PCC). Seventy nonsurgery eyes were used for comparisons. METHODS: Float, apex-fixed best fit corneal curvature (ABC), and posterior elevation difference were evaluated in 20 elevation topography maps at 6 zone diameters (3-7 and 10 mm) and at two time points. Corneal elevation maps before and after PRK or LASIK were analyzed by the ABC and float methods and compared with a nonsurgery group. MAIN OUTCOME MEASURES: Posterior corneal curvature change (mm) was classified as flattening, steepening, or no change. RESULTS: Flattening of more than 0.12 mm was found in 22.2% of eyes (n = 10) in the PRK group, a change of +/-0.12 mm was found in 53.3% of eyes (n = 24), and steepening of more than 0.12 mm was found in 24.4% of eyes (n = 11) using the float method and in 28.9% of eyes (n = 13), 35.6% of eyes (n = 16), and 35.6% eyes (n = 16), respectively, using the ABC method. In the LASIK group, the float method registered flattening in 20% of eyes (n = 10), no change in 52% of eyes (n = 26), and steepening in 28% of eyes (n = 14), whereas the ABC method registered flattening in 30% of eyes (n = 15), no change in 40% of eyes (n = 20), and steepening in 30% of eyes (n = 15). The nonsurgery group showed a similar change in PCC at two different time points similar to that of the PRK and the LASIK groups. CONCLUSIONS: The differences observed in the PCC after PRK or LASIK were not statistically significantly different from those observed over time in the nonsurgery control group.

Adult↗
PubMed2000

Turbulence characteristics downstream of bileaflet aortic valve prostheses.

This study was focused on a series of in vitro tests on the turbulent flow characteristics of three bileaflet aortic valves: St. Jude Medical (SJM), CarboMedics (CM), and Edwards Tekna (modified Duromedics, DM). The flow fields of the valves were measured in a pulsatile flow model with a laser-Doppler anemometer (LDA) at the aortic sinus area downstream of the valves. The heart rate was set at 70 beats per minute, the cardiac output was maintained at 5 liters per minute, and the aortic pressure wave forms were kept within the physiological range. Cycle-resolved analysis was applied to obtain turbulence data, including mean velocity, Reynolds stresses, autocorrelation coefficients, energy spectral density functions, and turbulence scales. The Reynolds shear stresses of all three valves induced only minor damage to red blood cells, but directly damaged the platelets, increasing the possibility of thrombosis. The smallest turbulence length scale, which offers a more reliable estimate of the effects of turbulence on blood cell damage, was three times the size of red blood cells and five times the size of platelets. This suggests that there is more direct interaction with the blood cells, thus causing more damage.

Aortic Valve↗
PubMed1999

Immunolocalization and gene expression of matrilysin during corneal wound healing.

PURPOSE: To investigate the protein level of matrilysin and stromelysin-1 and the gene expression of matrilysin in rat corneas after excimer keratectomy using immunofluorescence staining, reverse transcriptase-polymerase Chain Reaction (RT-PCR), and in situ hybridization. METHODS: Rat corneas were treated with 3-mm excimer laser keratectomy (193-nm ArF). Unwounded corneas served as controls. Confocal microscopy was used to immunolocalize matrilysin protein at 6 hours, 1 day, 3 days, 1 week, 4 weeks, and 8 weeks after surgery. RT-PCR was performed to analyze matrilysin mRNA in unwounded controls and in 3-day wounded corneas. In situ hybridization was performed to localize matrilysin mRNA. RESULTS: Matrilysin was immunolocalized to the epithelial layers of unwounded and wounded corneas, predominantly to the leading edge at 6 hours and 1 day after wounding and to the epithelial layer at 3 to 7 days after surgery. Stromelysin-1 was expressed in the deep stromal layer in the first 3 days after wounding and in the area of newly synthesized stromal matrix 1 week after surgery. Upregulation of matrilysin expression 3 days after wounding was confirmed by RT-PCR. In situ hybridization revealed that the gene expression of matrilysin in rat corneas was upregulated during the migration phase (6 hours, 1 day) and that matrilysin mRNA was predominantly localized to the basal cell layers during the subsequent cell proliferation phase (7 and 14 days). CONCLUSIONS: Basal epithelial cells express matrilysin during the migration proliferation phase of corneal wound healing after excimer keratectomy.

Animals↗
PubMed1998

Immunoconfocal localization of gelatinase B expressed by migrating intrastromal epithelial cells after deep annular excimer keratectomy.

PURPOSE: Intrastromal epithelial migration occurs following deep excimer annular keratectomy. Our purpose is to determine the localization of gelatinase B expression and its relationship to migrating intrastromal epithelial cells following deep annular excimer keratectomy. METHODS: Rabbit corneas were treated with deep annular ablation and harvested 3, 5, 7 and 14 days following surgery. Histological examination was performed. Confocal microscopy was used to determine the time and the pattern of gelatinase B expression. This was compared to AE-5, vimentin, and alpha-smooth muscle actin immunolocalization. RESULTS: Histologic examination revealed islands of epithelial cells within the corneal stroma after deep annular excimer ablation, whereas eyes treated with superficial annular keratectomy did not show intrastromal epithelial migration. Immunoconfocal microscopy using monoclonal anti-matrix metalloproteinase-9 (MMP-9) antibody demonstrated the presence of gelatinase B at the outer borders of the intrastromal epithelial islands following deep annular excimer keratectomy. CONCLUSION: Gelatinase B may be involved in the process of intrastromal epithelial migration following deep annular excimer keratectomy.

Actins↗
PubMed1997

Flavobacterium indologenes keratitis.

Flavobacterium indologenes has recently been implicated in nosocomial or opportunistic infection. It has been isolated from lids, conjunctiva, and lacrimal system, and is resistant to most antibiotics. No previous cases of F. indologenes corneal ulcer have been reported in the literature. The natural habitat of Flavobacteria is soil, water, plants, and foodstuffs. In the hospital environment, these bacteria exist in water systems and on wet surfaces. They are not part of the normal ocular flora.

Administration, Topical↗
PubMed1996

Computer-assisted peak recognition for polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in environmental samples.

A software has been developed for the peak recognition of 136 polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) after high resolution gas chromatography coupled with mass spectrometry (HRGC/HRMS). Based on the retention times of (13)C labelled 2,3,7,8-substituted PCDD/F internal standards, the retention times of all PCDD and PCDF can be calibrated automatically and accurately. Therefore, it is very convenient to identify the peaks by comparing the retention of samples and the calibrated retention times of their chromatograms. Hence, this approach is very significant because it is impossible to obtain always a standard chromatogram and PCDD/F analysis are very expensive and time consuming. The calibration results can be transferred to Excel for calculation. The approach is a first step to store costly and environmentally relevant data for future application.

Journal Article↗
PubMed1991

[Experimental studies on immunostimulatory effects of the Isatis indigotica polysaccharide].

Polysaccharides extracted from the root of Isatis indigotica (IIP, 50 mg/kg.d, ipx8d) significantly increased the weight of spleen and number of white blood cell and lymphocyte in peripheral blood in normal ICR mice, and antagonized the immunosuppressive actions of hydrocortisone. There were marked potentiating effects on delayed hypersensitivity reaction induced by 2, 4-dinitrochlorobenzene in normal NIH mice treated with IIP as well as in immunodepressed mice induced by cyclophosphamide. By administration of IIP, the percentage of ANAE+ lymphocytes stained with acid alpha-naphthyl acetate esterase method were significantly increased in peripheral blood of normal ICR mice, and the decreases in number of ANAE+ lymphocytes in mice induced by hydrocortisone were prevented to a certain extent. But IIP could not enhance Con A-induced lymphocyte proliferation of C57BL mouse spleen cells in vitro measured with MTT colorimetric assay. In addition, the plaque forming cells in 5 x 10(6) splenocytes of NIH mice treated with IIP were higher than that of the control group (P less than 0.01). IIP could also elevate the clearance rate of intra-venous charcoal particles in normal mice, i.e., stimulated the phagocytic activity of macrophages. The result indicates that IIP is capable of increasing humoral and cellular immune functions and enhancing the functions of reticuloendothelial system, and might be a good immunopotentiator.

Adjuvants, Immunologic↗
PubMed1990

[Pharmacological localization of Horner's syndrome. Case report].

Horner's syndrome is derived from an interruption of the sympathetic pathway at any point along its course between the hypothalamus and the orbit. This pathway is generally considered to consist of three neurons. It had been suggested that the pupillary response to various pharmacologic agents will aid in localizing the lesioned neuron in the sympathetic pathway. We had the opportunity to observe a patient who developed Horner's syndrome as a consequence of pulmonary apex adenocarcinoma. Clinical, radiologic and pharmacologic studies are presented. The methods of pharmacologic localization are discussed.

Amphetamines↗
PubMed1983

A model investigation of the velocity and pressure spectra in vascular murmurs.

A physical model consisting of an axisymmetrical jet in a rigid plexiglass pipe was used to study the flow and pressure fluctuations downstream from an aortic stenosis. The fluctuating velocity components, u and v, at several locations in the steady liquid jet were measured using a laser Doppler anemometer system. Simultaneous wall pressure fluctuations were monitored by an array of nine miniature pressure transducers wall mounted in the axial direction. This paper presents the detailed measurements of mean velocity profiles, turbulent intensity distributions and RMS pressure fluctuations. The energy spectra obtained for the pressure fluctuations and the u and v velocity components are compared. Contrary to earlier works, we found that the differences between peak frequencies of the pressure spectra and the characteristic frequencies of the velocity spectra vary with positions downstream from the nozzle. These differences are discussed in light of pseudosound generation by the eddy structures in the stenotic flow field.

Aortic Valve Stenosis↗
PubMed1980

Physical characteristics of pulmonary artery stenosis murmurs in calves.

To better understnad the characteristics of cardiovascular murmurs and turbulent energy transmission, we made simultaneous measurements of pressure (sound) and velocity fluctuations in the vicinity of surgically produced stenoses in the pulmonary artery of calves. We did a spectral analysis of these data and found an identifiable break frequency at which the slopes of the pressure fluctuations changed. By use of these break frequencies and the corresponding blood jet velocity and vessel diameter measurements, Strouhal numbers were calculated. The jet velocity, Reynolds number, Strouhal number, and unsteadiness parameter values changed when the vessel was stenosed. When the power spectrum curves for the velocity fluctuations and the sound were compared, they tended to show a correlation between break frequencies. We speculate that this apparent correlation indicated a transfer from turbulent to acoustic energy.

Aging↗
PubMed1979

The theoretical basis of column chromatography in multicomponent separation.

Microparticulate packings (silica and chemically bonded silica) developed in our institute and produced in China have been evaluated by the method published previously with a column efficiency of 1,400 to 10,000 theoretical plates per 10 cm length for HPLC and 1,700 to 4,400 plates per 10 cm length for GC. By varying the surface area of silica and composition of the eluent, the linear relationship of capacity factor of various compounds and the high speed chromatograms of HPLC and HPGC have been given.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

The retention behaviour of conjugated bile acids in reversed phase high performance liquid chromatography.

The retention behaviour of conjugated bile acids has been studied in a reversed phase high performance liquid chromatographic (RP-HPLC) system by using the mixture of methanol and aqueous phosphate buffer as the mobile phase. The retentions of the conjugates in RP-HPLC have been found to be mainly controlled by the glycine and taurine groups. The selectivity between five different glycine and taurine conjugated bile acids is a constant in RP-HPLC. This selectivity has been used for peak identification in the practical separation of conjugated bile acids.

Bile↗