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Biomedical subjects

L S Yu

Publications and source records attributed to L S Yu.

At least 19 recordsLinked to original sources
PubMed2006

Response to chemotherapy in patients with lung metastases: how many nodules should be measured?

OBJECTIVE: With the introduction of cross-sectional imaging methods the number of lesions per patient that can be evaluated is frequently large and most oncologists and study protocols use only one lesion or a few 'representative' lesions to evaluate chemotherapy response. Intra-patient response variability can therefore affect evaluation reproducibility. This study evaluates intra-individual variation in response to chemotherapy in patients with multiple lung metastases. METHODS: We prospectively studied chest CT images of patients with solid tumors and pulmonary metastases under systemic chemotherapy being evaluated for tumor response. The response of 566 pulmonary nodules in 41 evaluations was determined by both WHO and RECIST criteria in order to determine intra-individual tumor response variation. RESULTS: There was almost perfect agreement between the WHO and the RECIST criteria for the evaluation of tumor response. High intra-individual variability of tumor response was observed in a significant proportion of the evaluations. A new nodule was the main criterion for determination of disease progression. A mean of 35% of the total number of nodules of a patient have a response evaluation different from that calculated with all the nodules together. CONCLUSIONS: Intra-individual variation in tumor response of pulmonary metastases is elevated in some patients. Selecting any or some nodules for response evaluation could significantly influence therapeutic response perception.

Adolescent↗
PubMed2006

Zolmitriptan uptake by human intestinal epithelial Caco-2 cells.

The oral uptake of zolmitriptan, a novel and highly selectively 5-HT 1B/1D receptor agonist, was evaluated in the human epithelial cell line caco-2 that possesses intestinal enterocyte-like properties when cultured in vitro. The study demonstrated that zolmitriptan uptake significantly depended upon the extracelluar temperature and pH in the Caco-2 cell. The zolmitriptan uptake at 39 degrees C was 2.1 fold as that at 23 degrees C and the zolmitriptan uptake at pH 8.0 was 2.7 fold as that at pH 6.0. The uptake rates of zolmitriptan on both sides increased with increasing zolmitriptan concentration from 0.1 to 10 mmol x L(-1), and it shows concave concentration-dependency at high concentration. The uptake rates of zolmitriptan on the basolateral side (BL) were 3-7 times higher than that on the apical side (AP). Verapamil, nimodipine, nifedipine, flunarizine, amiloride and sumatriptan significantly increased the uptake rates of zolmitriptan on the apical sides. Propafenone significantly inhibited the uptake rate of zolmitriptan on both sides. Propranolol and aspirin have no significant effect. The results indicated that the zolmitriptan uptake in Caco-2 cells was temperature, pH and concentration dependent, and was partially counteracted by the action of an outwardly directed efflux pump, presumably p-glycoprotein. Absorption interactions should be considered when P-gp substrates or inhibitors, Na+ -H+ exchange inhibitors, P-gp ATPase agonists or inhibitors are co-administered with zomitriptan in clinical practice.

Absorption↗
PubMed2003

Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes.

The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.

Journal Article↗
PubMed2002

[The human alpha(2A)-AR gene and the genotype of site -1296 and the susceptibility to motion sickness].

The gene sequences of alpha(2A)-adrenergic receptor(alpha(2A)-AR) in 39 Chinese and 1 Englishman showed 13 differences of g or c insertion or deletion in its regulation region, coding region and 3' untranslated region, compared with that reported in GenBank. The gene sequences from all the samples respectively were identical except for 2 single nucleotide polymorphisms, including the sequence of sense and antisense strand sequenced. It was found that: (1) the frequency of gg genotype in Chinese and Japanese, who are high susceptible to motion sickness, were 5.8 and 7.8 fold higher than that in Englishmen; (2) g allele frequencies in Chinese and Japanese were higher than latter ( P 0.01 ); (3) gg genotype frequency in population susceptible to motion sickness was 1.6 fold higher than that in population unsusceptible to motion sickness, and g allele frequency was higher than latter ( P 0.01 ). All the populations were in Hardy-Weinberg equilibrium. The results suggested that gg genotype and g allele at site -1296 in alpha(2A)-AR gene could associate with the susceptibility to motion sickness.

Asian People↗
PubMed2001

Immunomagnetic separation methods for the isolation of Campylobacter jejuni from ground poultry meats.

Campylobacter jejuni is now recognized as a leading foodborne pathogen, for which poultry products constitute the main transmission route. Two alternative immunomagnetic beads (IMB) were tested for direct detection of C. jejuni ATCC 35918 in artificially inoculated ground poultry meats and culture suspension. Polyclonal anti-Campylobacter antibodies were used to coat tosylactivated Dynabeads. The same antibodies conjugated with biotin were used to label streptavidin-coated beads. After these beads were incubated with inoculated poultry slurry or culture suspension, Campylobacter-bead complexes were separated from other components with a magnet. The capture efficiency was tested by plating bead-captured cells and unbound cells in the supernatant onto Karmali agar. The effects of different coating procedures, incubation time (60, 90, 120 min), numbers of immunomagnetic beads (10(6) to 10(7)/ml) and innoculum levels (10(3) to 10(7) CFU/g or ml) were determined. Without pre-enrichment, this approach could detect 10(4) CFU/g of ground poultry meats. These methods represent a new approach to extracting, concentrating and isolating Campylobacter spp. directly from foods.

Campylobacter jejuni↗
PubMed2001

Ground simulation of the G-excess illusion.

Objective. To observe the subjects' perception of orientation following certain head movements or change of simulator cab attitude in hypergravity (HG), and assess the feasibility of simulating G-excess illusion on the ground by a centrifuge-like Spatial Disorientation (SD) simulator. Method. 1.6 G force field was generated by planetary rotation of the simulator. Perception of orientation of the cab were collected from twelve male pilots' report following their heads pitch movements in pitch plane or cab attitude changes in roll plane under 1.6 G. Result. While making a pitch-up head movement, the pilots experienced a 63.8 degrees +/- 48.3 degrees pitch-up attitude change of the cab in pitch plane, and when the cab was tilted left 20 degrees, pilots experienced a tilt-left perception of 48.6 degrees +/- 39.4 degrees in roll plane. Conclusion. Although there's strong Coriolis effects onboard the SD simulator under 1.6 G, most pilots experienced the G-excess illusion. It demonstrated that it was feasible to use the centrifuge-like device to generate this kind of illusion on the ground.

Adult↗
PubMed2000

Obliquely oriented superior accessory fissure of the lower lobe of the lung: CT evaluation of the normal appearance and effect on the distribution of parenchymal and pleural opacities.

PURPOSE: To review computed tomographic (CT) and radiographic features of an oblique superior accessory fissure in the lower lobe of the lung. MATERIALS AND METHODS: CT scans in 34 patients with a prospectively identified accessory fissure of the lower lobe were reviewed and correlated with chest radiographs (31 patients). The fissure and its relationship to segmental bronchovascular structures were evaluated on transverse scans. Three-dimensional (3D) shaded surface display (SSD) reconstructions were obtained from spiral volume data (six patients). RESULTS: Thirty-four patients had 36 accessory fissures (26 right, 10 left). Four of the 36 accessory fissures were manifested by a normal fissure line; two, by slight thickening or minimal linear atelectasis; 16, by thicker linear or subsegmental atelectasis; two, by contiguous tumor infiltration; one, by adjacent consolidation; and 11, by intrafissural extension of pleural fluid. Analysis of bronchovascular structures revealed that this fissure was the superior accessory fissure. The 3D SSD reconstructions demonstrated an oblique orientation. On frontal radiographs, presence of this fissure correlated with a curvilinear band of atelectasis coursing inferomedially and obliquely from its intersection with the lateral aspect of the major fissure toward the infrahilar region on the right and the heart border on the left. Chest radiographs also showed intrafissural extension of pleural fluid. CONCLUSION: A superior accessory fissure of the lower lobe, more common on the right than on the left, can be identified at transverse CT. Contrary to previous descriptions, it may be oblique, as findings on transverse images suggest and 3D SSD reconstructions confirm. Its presence correlates with characteristic patterns of atelectasis and pleural fluid collection on conventional radiographs.

Adult↗
PubMed1999

Production of listeriolysin O by Listeria monocytogenes (Scott A) under heat-shock conditions.

Early stationary phase cells of Listeria monocytogenes (Scott A) were examined to determine the effect of heat-shock on the production of listeriolysin O (LLO) during and after resuscitation at 37 degrees C. Cells were subjected to a heat-shock at 48 degrees C for 1 h. Intracellular and extracellular proteins of the heat-shocked cells were assayed for LLO using a microtiter plate hemolysis assay and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Our results showed that significant amounts of LLO are synthesized under heat-shock conditions that are not detected in the extracellular medium by a functional assay. This situation is evident by the absence of hemolytic activity immediately after heat-shock, and may be due to either a lack of excretion or inactivation of the LLO at 48 degrees C once outside the cell. By studying the intracellular and extracellular proteins using SDS-PAGE and immunoblots of the heat-shocked cells, we substantiated an absence of excretion as an operating mechanism. Heat-shocked cells resumed LLO production within 2-4 h of resuscitation at 37 degrees C, achieving an activity level 2-fold higher compared to the controls and 4-fold higher compared to cells immediately after heat-shock. Most likely, the LLO excreted must have been from LLO accumulated in the cells during heat-shock.

Bacterial Toxins↗
PubMed1997

Attitudes towards mental illness: testing the contact hypothesis among Chinese student nurses in Hong Kong.

This study investigated whether previous contact with mental illness affected the attitudes to mental illness (AMI) of general student nurses in Hong Kong-the contact hypothesis. We employed a quasi-experimental design. We compared the attitudes to mental illness of students who had previous contact with mental illness through having taken a psychiatric secondment with those who had not taken a psychiatric secondment. Also, we compared the AMI of: students who had taken other courses related to mental illness with those who had not; those who had a family history of mental illness with those who had not; and those who lived with a mentally ill relative with those who did not. We found that previous contact with mental illness had no significant effect on the attitudes to mental illness of the students. In other words our findings do not support the contact hypothesis. Our sample expressed positive general attitudes to mental illness when presented with general issues about mental illness. However, their attitudes were less positive when presented with specific issues about mental illness that might impinge upon their daily lives. We discuss the implications of these findings for mental health nursing practice, education and research.

Adolescent↗
PubMed1997

The psychophysiological assessment method for pilot's professional reliability.

BACKGROUND: Previous research has shown that a pilot's professional reliability depends on two relative factors: the pilot's functional state and the demands of task workload. The Psychophysiological Reserve Capacity (PRC) is defined as a pilot's ability to accomplish additive tasks without reducing the performance of the primary task (flight task). HYPOTHESIS: We hypothesized that the PRC was a mirror of the pilot's functional state. The purpose of this study was to probe the psychophysiological method for evaluating a pilot's professional reliability on a simulator. METHODS: The PRC Comprehensive Evaluating System (PRCCES) which was used in the experiment included four subsystems: a) quantitative evaluation system for pilot's performance on simulator; b) secondary task display and quantitative estimating system; c) multiphysiological data monitoring and statistical system; and d) comprehensive evaluation system for pilot PRC. Two studies were performed. In study one, 63 healthy and 13 hospitalized pilots participated. Each pilot performed a double 180 degrees circuit flight program with and without secondary task (three digit operation). The operator performance, score of secondary task and cost of physiological effort were measured and compared by PRCCES in the two conditions. Then, each pilot's flight skill in training was subjectively scored by instructor pilot ratings. In study two, 7 healthy pilots volunteered to take part in the experiment on the effects of sleep deprivation on pilot's PRC. Each participant had PRC tested pre- and post-8 h sleep deprivation. RESULTS: The results show that the PRC values of a healthy pilot was positively correlated with abilities of flexibility, operating and correcting deviation, attention distribution, and accuracy of instrument flight in the air (r = 0.27-0.40, p < 0.05), and negatively correlated with emotional anxiety in flight (r = -0.40, p < 0.05). The values of PRC in healthy pilots (0.61 +/- 0.17) were significantly higher than that of hospitalized pilots (0.43 +/- 0.15) (p < 0.05). The PRC value after 8 h sleep loss (0.50 +/- 0.17) was significantly lower than those before sleep loss (0.70 +/- 0.15) (p < 0.05). CONCLUSION: We conclude that a pilot's PRC, which was closely related to flight ability and functional state, could partly represent the pilot's professional reliability. It is worthwhile to further research using a pilot's PRC as a predictor of mental workload in aircraft design.

Adult↗
PubMed1993

Five-tube most-probable-number method using the Fung-Yu tube for enumeration of Listeria monocytogenes in restructured meat products during refrigerated storage.

The survival of Listeria monocytogenes in cooked, chopped hams stored at 5 degrees C for 5 weeks was studied. Slices of chopped ham (25 g) were inoculated with a three-strain mixture of L. monocytogenes (LM 101M, LM 103M, and Scott A) at levels of < or = 350 cfu/25 g and packaged in Stomacher bags. Prior to inoculation, L. monocytogenes cells were subjected to either heat-injury (56 degrees C, 30 min) or freeze-injury (-18 degrees C, 14 days). The organisms were detected by a five-tube most-probable-number (MPN) technique using the motility enrichment Fung-Yu tube, and the direct plating method. After storage at 5 degrees C for 1 week, there was a one log10 reduction in counts. Thereafter, Listeria recovered and heat- and freeze-injured cells grew to 10(7) and 10(8) within 5 weeks, respectively. Similar results were obtained from both methods. However, direct plating could not recover L. monocytogenes at low levels (< or = 100/25 g), whereas MPN counts were obtained at these low levels. The pH (6.22 +/- 0.10) of the chopped hams remained constant throughout the study. These results indicated that low numbers of L. monocytogenes surviving sublethal heat- or freeze-injury could initiate growth after recovery in chopped hams. The five-tube MPN method using the Fung-Yu tube was effective in enumerating both low and high levels of L. monocytogenes in food.

Animals↗
PubMed1992

Electronystagmographic features in some peripheral and central vestibular disorders: application of multiple discriminant analysis of electronystagmographic parameters.

In routine clinical electronystagmographic (ENG) tests (postrotatory, optokinetic, caloric and tracking tests), eye movement signals were analyzed and a multiple discriminant analysis was carried out with the aid of a microcomputer. Six parameters were selected and, based on these, two functions for discriminating between peripheral and central disorders were established. Discrimination between 35 patients with peripheral lesions and 15 patients with central lesions was made with a correct classification rate of 97.1 and 86.7%, respectively. These rates are significantly higher than that of any single ENG test analysis. Our results indicate that the clinical application of ENG can be improved by searching for more sensitive ENG parameters and adopting the comprehensive analysis approach.

Adult↗
PubMed1991

Concept of a soft, compressible artificial ventricle under evaluation.

This study was designed to compare the relative merits of soft and rigid artificial ventricles. A cascade mock circulation was used to measure cardiac output under different circumstances. The data show that these soft air driven ventricles show a Starling's-like response over a wider range of filling pressures than identical, but rigid, ventricles. Compression of soft ventricles by high intrathoracic pressures was simulated in vitro. Air pressures up to +20 mm Hg did not seriously affect soft ventricles. Cardiac tamponade was simulated by compressing the ventricle in a closed fluid compartment. Tamponade became severe when volume reduction of the ventricle rose to 60 ml. Hemolysis caused by soft and rigid ventricles was tested in a blood bag set-up and was 48-82% higher in the rigid ventricle, depending on the driving conditions. Possibly, this could be explained by the authors' finding that rigid ventricles showed a 20% higher intraventricular dP/dtmax value than soft ventricles. Soft ventricles were implanted in three calves as a total artificial heart (TAH). Implantation without quick connectors was easy because the surgeon could easily fold and compress the ventricles. No physiological complications of softness were observed. Blood damage in the animals was low (less than 5 mg/dl). The authors conclude that soft ventricles show distinct surgical and functional advantages over rigid ventricles.

Animals↗
PubMed1991

In vitro hemodynamic analysis of flexible artificial ventricles.

An in vitro fluid dynamic study was performed to compare the hemodynamic characteristics of a rigid and a flexible total artificial heart. The artificial ventricles were incorporated into a mock circulatory system, and pressure signals within the ventricular chamber, proximal to the inflow valve and distal to the outflow valve, were obtained. The instantaneous flow rate through the inflow and outflow valves was measured with electromagnetic flow probes. Flow visualization studies performed on the flexible ventricle suggested a vortical motion within the chamber with a smooth washout of fluid in the next pumping phase, but flow disturbances were observed near the wall of the ventricle as well as near the outflow valve. The rate of pressure increase (dP/dt) was smaller in the flexible ventricle as compared with the rigid ventricle for comparable flows and heart rates. The results of the present study indicated that the flexible ventricle with polyurethane valves, having the advantage of ease of implantation and cost savings, can be a viable alternative as a bridge to transplant.

Heart, Artificial↗
PubMed1990

Loss of anticoagulant effect of heparin during circulation of human blood in vitro.

Device-induced thrombogenesis was studied in an in vitro model using human blood circulated through an artificial ventricle. A new constant pressure filtration technique was used to detect circulating microemboli, the activated partial thromboplastin time (APTT) test was used to monitor the blood for the presence of anticoagulant activity of heparin, and hemolysis was quantified by measuring the plasma free hemoglobin level. Circulation of blood through a 20-ml stroke volume pneumatically driven ventricle for 6-9 h resulted in a significant reduction of APTT, indicating the loss of the anticoagulant effect of heparin. Microemboli concentration was minimal until the APTT decreased below 125 s, at which time the microemboli concentration increased rapidly. This was presumed to be due to the formation of thrombi following a decrease in heparin activity. A significant increase in hemolysis was also noted when blood was pumped. None of these changes was noted in the nonpumped control blood. Spontaneous loss of heparin activity in blood circulated by a pneumatically driven pump may have clinical implications and may help understanding of the problems associated with device-induced thrombogenesis.

Adult↗
PubMed1990

Development of a new inflow valve for a 20cc semisoft ventricle: preliminary results.

We remodeled and tested our semisoft 20cc ventricle and made a new bileaflet flap inflow valve. Housings, bases, outflow valve, and a newly designed diaphragm were all made by vacuum forming and put together by radiofrequency welding or glue. In vitro, the ventricle produced a cardiac output of 2.5 to 3.0 L/min and showed reliable durability results. Hematological testing showed no important thrombogenicity of the new valve. Cardiac output was higher than expected for the volume of the ventricle, perhaps because of stretching or flow through. Animal experiments with the left ventricular assist device (LVAD) version was done at Ohio State University. Earlier in Utah, we did 20 cc total artificial heart (TAH) implantations and LVAD experiments in lambs and recently in calves with the 60cc TAH version. A soft ventricle is easy to implant and low in production costs.

Animals↗
PubMed1989

The return of elastomer valves.

This paper concerns the heart valves to be used mainly in artificial hearts. Most of our tricusp semilunar valves are made of polyurethane. These valves have functioned in artificial hearts for up to 62 days, and have been implanted in sheep for 1 year without evidence of thromboembolism. Our valves have a wide opening, using redundant leaflets that are "bistable." Accelerated testing by air jet provides 1,000 closures per second. Regurgitation is measured in an apparatus with the help of a competent valve. All polyurethanes change with age, but Silastic does not.

Animals↗