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Biomedical subjects

A Yeung

Publications and source records attributed to A Yeung.

At least 19 recordsLinked to original sources
PubMed2002

Screening for major depression in Asian-Americans: a comparison of the Beck and the Chinese Depression Inventory.

OBJECTIVE: This study compares the effectiveness of the Chinese version of the Beck Depression Inventory (CBDI) and the Chinese Depression Inventory (CDI) in screening for depression among Chinese Americans. METHOD: Five hundred and three Chinese-Americans in primary care were administered the CBDI and the CDI for depression screening. The results were compared with standard semistructured interview. RESULTS: With empirically determined cutoff scores of the CBDI (> or =13) and the CDI (>/=16), both instruments have good sensitivity (0.78) and excellent specificity (0.91 and 0.93, respectively). The correlation between the total scores of the two instruments was high (0.785, P < 0.01). The areas under the Receiver Operating Characteristic (ROC) curve of the CBDI and the CDI were 0.94 and 0.95, respectively, and were not significantly different. CONCLUSION: When administered by interviewers, the CBDI and the CDI have comparable effectiveness. Low participation among Chinese-Americans with self-report measures limits both scales as efficient depression screening instruments.

Asian↗
PubMed2001

Photoangioplasty with local motexafin lutetium delivery reduces macrophages in a rabbit post-balloon injury model.

OBJECTIVE: Motexafin lutetium (Lu-Tex, Antrin Injection) is a photosensitizer that selectively accumulates in atheromatous plaque where it can be activated by far-red light. The localization and retention of intra-arterially administered Lu-Tex and its efficacy following activation by endovascularly delivered light (photoangioplasty) was evaluated. METHODS: Bilateral iliac artery lesions were induced in 17 rabbits by balloon denudation, followed by a high cholesterol diet. Lu-Tex distribution within the atheroma was examined (n=8) following local injection. Fluorescence spectral imaging and chemical extraction techniques were used to measure Lu-Tex levels within the atheroma and adjacent normal tissue. Photoactivation was performed 15 min following Lu-Tex administration (180 J/cm fiber at 200 mW/cm fiber). Two weeks post photoangioplasty, vessels were harvested and hematoxylin and eosin (H&E) and RAM11 (macrophages) staining was performed. RESULTS: Local delivery of Lu-Tex achieved immediate high concentrations within plaque (mean 40x control iliac atheroma). Mean percent plaque area in the treated segments was significantly lower than in the non-treated contralateral lesions (73 vs. 82%, P<0.01). No medial damage was observed. Quantitative analysis using RAM11 positive cells revealed significant reduction of macrophages in treated lesions in both the intima (5 vs. 22%, P<0.01) and in media (8 vs. 23%, P<0.01) compared to untreated contralateral segments. CONCLUSIONS: Local delivery provides high levels of Lu-Tex selectively within atheroma. Photoactivation results in a significant decrease in macrophage and a small decrease in atheroma burden without damage to the normal vessel wall.

Angioplasty, Balloon↗
PubMed2001

SMART: The microstent's ability to limit restenosis trial.

In this randomized, prospective, multicenter trial (n = 661) of patients with de novo or restenotic coronary lesions, 330 patients received the MicroStent(R) II (MSII), and 331 received the Palmaz-Schatz (PS) stent. The short-term procedural success rates were 94.4% and 95.7%, respectively (P = 0.47). The 30-day cumulative incidence of major adverse events [death, myocardial infarction, CVA, target lesion revascularization (TLR)] was 6.4% for the MSII and 4.5% for the PS stent (P = 0.31). The in-stent binary restenosis rate at 6 months was 25.2% for the MSII and 22.1% for the PS stent (P = 0.636). Using Kaplan-Meier estimates, the incidence of clinically driven TLR was 8.9% for the MSII and 9.2% for the PS stent at 180 days; at 270 days, it was 12.8% and 12.1%, respectively (P = 0.83). MSII and the PS stents were comparable with respect to short-term procedural success, complications, and late clinical and angiographic restenosis.

Aged↗
PubMed2001

Acute and 6-month clinical and angiographic outcome after implantation of the ACS Duet stent for single-vessel coronary artery disease: final results of the European and US ACS Multi-link Duet Registry.

The aim of the study was to determine the safety and efficacy of the second-generation ACS Multi-Link Duet coronary stent system for the treatment of single, symptomatic, de novo, native coronary artery lesions. Between February and June 1998, 427 patients (69.3% male, 51.5% class 3 or 4 angina, 20.1% diabetic, 43.6% hyperlipidemia) were included at 38 centers in this prospective observational study. All patients received ticlopidine 500 mg/day for 1 month and aspirin > or =100 mg/day. The Duet stent was available in 8, 18, and 28 mm length and 3.0, 3.5, and 4.0 mm diameter. After adequate predilatation, stents were successfully implanted, at up to 16 atm, in 99.3% of patients. Mean vessel diameter by core laboratory quantitative coronary angiography was 3.0 +/- 0.53 mm and postprocedural minimum luminal diameter was 2.79 +/- 0.43 mm (12% +/- 9.3% diameter stenosis). At 30 days, 96.7% of patients were event-free and at 6 months 88.1% remained free of major adverse cardiac events. The restenosis rate was 18.1%. The ACS Duet stent was safely implanted in >99% of target lesions by a diverse group of international investigators. With late outcomes at least comparable to the best published results, this stent platform provides safe and effective percutaneous treatment of obstructive coronary artery disease. Cathet Cardiovasc Intervent 2001;54:25-33.

Aged↗
PubMed2001

Amplification of mutator cells in a population as a result of horizontal transfer.

Mutator cells that lack the mismatch repair system (MMR(-)) occur at rates of 10(-5) or less in laboratory populations started from wild-type cells. We show that after selection for recombinants in an interspecies mating between Salmonella enterica serovar Typhimurium and Escherichia coli, the percentage of MMR(-) cells rises to several percent of the recombinant population, and after a second successive mating and selection, greater than 95% of the recombinants are MMR(-). Coupling a single cross and selection with either mutagenesis or selection for spontaneous mutants also results in a dramatic increase in MMR(-) cells. We discuss how horizontal transfer can result in mutator strains during adaptive evolution.

Base Pair Mismatch↗
PubMed2000

The consequences of growth of a mutator strain of Escherichia coli as measured by loss of function among multiple gene targets and loss of fitness.

We have examined the composition of members of mutator populations of Escherichia coli by employing an extensive set of phenotypic screens that allow us to monitor the function of >700 genes, constituting approximately 15% of the genome. We looked at mismatch repair deficient cells after repeated cycles of single colony isolation on rich medium to generate lineages that are forced through severe bottlenecks, and compared the results to those for wild-type strains. The mutator lineages continued to accumulate mutations rapidly with each increasing cycle of colony isolation. By the end of the 40th cycle, after approximately 1000 generations, most of the lineages had reduced colony size, 4% had died out, 55% had auxotrophic requirements (increasing to 80% after 60 cycles), and 70% had defects in at least one sugar or catabolic pathway. In addition, 33% had a defect in cell motility, and 26% were either temperature-sensitive or cold-sensitive lethals. On the other hand, only 3% of the wild-type lineages had detectable mutations of any type after 40 cycles. By the 60th cycle, the typical mutator cell carried 4-5 inactive genes among the 15% of the genome being monitored, indicating that the average cell carried at least 24-30 inactivated genes distributed throughout the genome. Remarkably, 30% of the lineages had lost the ability to utilize xylose as a carbon source. DNA sequencing revealed that most of the Xyl(-) mutants had a frameshift in a run of eight G's (GGGGGGGG) in the xylB gene, either adding or deleting one -G-. Further analysis indicated that rendering E. coli deficient in mismatch repair unmasks hypermutable sites in certain genes or intergenic regions. Growth curves and competition tests on lineages that passed through 90 cycles of single colony isolation showed that all lineages suffered reduced fitness. We discuss these results in terms of the value of mutators in cellular evolution.

Adaptation, Biological↗
PubMed1999

Emulsification through Area Contraction.

Emulsification requiring very little input energy can be induced at an oil-water interface that is initially in a state of equilibrium. The process involves destabilization, through contraction, of local interfacial regions. For emulsification to occur, it is necessary for the interfacial structure to have no resistance to surface shearing. Such a mechanism of emulsification may have important implications for the approach to solving emulsion problems in the petroleum industry. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Direct selection for mutators in Escherichia coli.

We have constructed strains that allow a direct selection for mutators of Escherichia coli on a single plate medium. The plate selection is based on using two different markers whose reversion is enhanced by a given mutator. Plates containing limiting amounts of each respective nutrient allow the growth of ghost colonies or microcolonies that give rise to full-size colonies only if a reversion event occurs. Because two successive mutational events are required, mutator cells are favored to generate full-size colonies. Reversion of a third marker allows direct visualization of the mutator phenotype by the large number of blue papillae in the full-size colonies. We also describe plate selections involving three successive nutrient markers followed by a fourth papillation step. Different frameshift or base substitution mutations are used to select for mismatch-repair-defective strains (mutHLS and uvrD). We can detect and monitor mutator cells arising spontaneously, at frequencies lower than 10(-5) in the population. Also, we can measure a mutator cascade, in which one type of mutator (mutT) generates a second mutator (mutHLS) that then allows stepwise frameshift mutations. We discuss the relevance of mutators arising on a single medium as a result of cells overcoming successive growth barriers to the development and progression of cancerous tumors, some of which are mutator cell lines.

2-Aminopurine↗
PubMed1999

General practice spirometry in North Staffordshire.

Spirometry is suggested, in North American and European guidelines, to be the most important measurement of lung function for the management of patients with chronic obstructive pulmonary disease (COPD). The aim of this study was to determine attitudes to and utilization of spirometry in general practices within North Staffordshire. All 95 practices in North Staffordshire were surveyed by telephone, using a standard proforma. Eighty-four practices (48 fundholding) containing 224 general practitioners (GPs) and serving 472,420 patients, agreed to take part. The survey was completed by practice nurses on 63 occasions, GPs on 14 and practice managers on seven. Eighteen practices possessed a spirometer, although eight did not use it. The measurements were performed by doctors in five of the practices, nurses in two and by both in three. Only two users had received formal training in the performance and interpretation of spirometry. Of the three practices using pneumotachograph spirometers, none knew how often the machine should be calibrated. Spirometry was used by five practices for diagnosis (although only four used it to determine forced expiratory volume in one second (FEV1)), three for monitoring and only one for bronchodilator reversibility testing. Although 44 (52%) practices thought that, ideally, spirometry should be available in the practice, only 10 of the 18 who had spirometers were currently providing this facility. Furthermore, the poor training puts into question the validity of some of the results obtained. Open access to hospital spirometry is one method of addressing these problems, and 73 (87%) practices, including 16 who already owned a spirometer, said that they would use such a service.

Data Collection↗
PubMed1998

Does Equilibrium Interfacial Tension Depend on Method of Measurement?

In the presence of surfactants, the equilibrium interfacial tension (IFT) between two immiscible fluids can be very dependent on the particular technique used for measurement. This is because the partitioning of surfactants between the two bulk phases and the interface, which ultimately determines IFT, depends on geometric factors such as the volume fractions and specific interfacial areas (i.e., interfacial areas per unit volume) of the two fluids. In this work, the effect of surfactant partitioning on equilibrium IFT is demonstrated both theoretically and experimentally. A novel technique which enables direct measurement of IFT at macroemulsion droplet surfaces, with direct application to emulsion research, is demonstrated. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Caco-2 cell ferritin formation predicts nonradiolabeled food iron availability in an in vitro digestion/Caco-2 cell culture model.

We have adapted an in vitro digestion/Caco-2 cell model to assess Fe availability from foods, by using ferritin formation by Caco-2 cells as an indicator of Fe uptake. Ferritin formation by Caco-2 cells occurs in response to Fe uptake at concentrations of available Fe greater than that of the culture media to which the cells have been adapted. This methodology circumvents the need for using radioactive Fe and thus eliminates the costs and controversies associated with food radiolabeling. To validate this method, we measured ferritin formation in Caco-2 cells exposed to digests containing Fe of relatively high and low availability. Our objective was to determine if ferritin formation would be proportional to Fe uptake and sufficiently sensitive to be an indicator of Fe availability from food digests. Our model uses established in vitro digestion techniques coupled with uptake of Fe by Caco-2 cell monolayers. Measurement of cell ferritin was done by a commercially available RIA. Higher ferritin formation was observed in cells exposed to digests containing FeSO4 plus ascorbic acid vs, digests containing FeSO4 plus citric acid. Additional comparisons of Fe availability from digests of beef, fish, corn and green beans yielded results that demonstrate higher Fe availability (i.e., greater ferritin formation) from beef and fish digests than from digests of corn and green beans. Overall, the results document the promotional effects of ascorbic acid and animal tissue on Fe uptake as measured indirectly by ferritin formation. The results of this study indicate that ferritin formation by Caco-2 cell monolayers is highly sensitive and accurately measures food Fe availability in this in vitro system.

Caco-2 Cells↗
PubMed1998

The excised preauricular sinus in 14 years of experience: is there a problem?

The congenital preauricular sinus is usually asymptomatic. However, if recurrent infection occurs, complete surgical excision of the sinus is required. If the sinus tracts are not entirely removed, recurrence is likely to follow. A retrospective study of the surgical results at The Hospital for Sick Children in Toronto, Ontario, was completed. One-hundred sixty-five primary preauricular excision procedures, performed in 146 patients between the years 1982 and 1996, were reviewed. All clinical, operative, and postoperative data were gathered. Patient outcome and epidemiologic issues were addressed. The overall recurrence rate of this series was 9.09 percent (15 of 165 sinuses). For the group of patients with active infection present at surgery, the recurrence rate was 15.79 percent, and when no infection was present, recurrence rate was 8.22 percent (p value = 0.32, odds ratio = 2.09). Moreover, in patients who underwent surgical drainage of an abscess before the procedure, 16.7 percent of the sinuses recurred, whereas in the patients who did not have an abscess, only 8.16 percent recurred (p value = 0.25, odds ratio = 2.25). In the group of patients in whom auricular cartilage was not excised from the base of the tract, 18.52 percent of the sinuses recurred; when cartilage was excised, the recurrence rate was 4.5 percent (p value = 0.006). A very high recurrence rate of 21.95 percent was found in the group of patients in whom no modality was used to demonstrate the sinus tract at surgery. A high recurrence rate of 10.87 percent was found in the group for whom probing with a cannula was used to identify the tract (p value = 0.17); a low recurrence rate of 2 percent was found in a group with dye injection only (p value = 0.015). In those patients in whom sinus probing and dye injection were used simultaneously, there were no recurrences (0 percent, p value < 0.05). In conclusion, a patient with an actively infected preauricular sinus or one with a previous abscess may have a tendency to experience a higher recurrence rate after excisional surgery. Excising a cartilage piece at the base of the tract and demonstrating the sinus with dye injection or with dye injection and probing at the time of surgery will reduce recurrence rates. In conclusion, we advise the excision of cartilage in the base of the tract as well as the use of methylene blue injection and probing of the sinus at surgery.

Adolescent↗
PubMed1998

Efficacy of transabdominal ultrasound examination in the diagnosis of early pregnancy complications in an emergency department.

OBJECTIVE: To assess the value of ultrasound in an emergency department in the diagnosis of early pregnancy complications, the efficacy of a study protocol in identifying ectopic pregnancies, and the agreement on ultrasound findings among emergency department staff and gynaecologists. METHODS: All women presenting with early pregnancy complications had a transabdominal ultrasound scan performed by the attending doctor and checked by a senior doctor. The ultrasound findings were classified as normal intrauterine pregnancy (IUP), probable abnormal pregnancy, definite ectopic pregnancy, no definite IUP, and other. Women with clinical and ultrasound findings compatible with threatened abortion were referred to a gynaecologist, or were admitted if findings suggested abnormal or ectopic pregnancy, or if a definite IUP could not be confirmed on ultrasound scan. For patients who were admitted or referred, a transvaginal ultrasound scan was performed by the attending gynaecologist. The findings of the gynaecologist were used as the gold standard. RESULTS: 151 cases were enrolled during a four month study period. Ultrasound findings in the emergency department included definite IUP in 95 (63%), probable abnormal IUP in 20 (13%), no definite IUP in 23 (21%), and other findings in four (3%). For evaluating the presence or absence of IUP, sensitivity of the initial scan was 82% (95% confidence interval 76% to 88%) and specificity 92% (88% to 96%). Agreement between junior and senior emergency department doctors on their ultrasound findings was 81% (75% to 87%) and between emergency department senior staff and gynecologists 85% (79% to 91%). The diagnoses made in the emergency department were thought to be compatible with the final assessments by gynaecologist in 72% (65% to 79%). Using either no definite IUP or other findings as a positive screening test for ectopic pregnancy, the sensitivity, specificity, positive predictive value, and negative predictive value were 80% (74% to 86%), 78% (71% to 85%), 12% (7% to 17%), and 99% (97% to 100%), respectively. CONCLUSIONS: Transabdominal ultrasound performed in the emergency department is useful in screening for early pregnancy complications. Ectopic pregnancy should be suspected when no IUP is found on preliminary scanning.

Adult↗
PubMed1997

Effect of Shear on the Strength of Polymer-Induced Flocs

Micromechanics was used to show that the rupture strength of polymer-induced flocs varied with the hydrodynamic conditions at which the flocs were formed. A maximum floc strength at an intermediate shear rate was observed. The overall performance of the polymeric flocculants, as determined by two independent methods, showed that the conditions for optimal flocculation did not coincide with those for maximum floc strength. The amount of flocculation was explained in terms of the competing effects of the particle collision frequency and the destructive hydrodynamic forces. The contributing forces to the floc strength are, however, more likely to be densification of the floc by shear and the weakening of reattachment strengths. The evidence presented here may be useful for explaining flocculation data that depart from the constant yield stress theory. Thus, the notion of the floc strength varying with shear rate may offer an alternative to multilevel floc structure models in the description of flocculation kinetics. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Coronary AVE micro stents: serial quantitative angiography and histology in a canine model.

The AVE Micro Stent (AVE Inc., Santa Rosa, CA) is composed of helically welded 3 mm long, zigzag crowns with stent lengths from 6 to 39 mm and diameters from 2.5 to 4.5 mm. Quantitative coronary angiography and histologic analyses of acute and chronic implantation were obtained in 52 stented coronary segments of 18 dogs. Three hearts with 8 stented coronary segments were harvested after 24 hr, 3 hearts with 9 stented segments were harvested after 2 weeks, 6 hearts with 15 stented segments were harvested at 8 weeks, and 6 hearts with 20 stented segments were harvested at 24 weeks post-deployment. There were no procedural complications, deaths, or acute vessel closures. The average lumen diameter of the stented segment was largest at 2 weeks (3.3 +/- 0.3 mm). The smallest average diameters were observed at 8 weeks after the stent deployment (2.7 +/- 0.4, P < 0.05) with an increase again at 24 weeks (2.9 +/- 0.6). The pre-explant percent of stenosis was <30% in all animals. Histologically, a peak of inflammation was visible at 2 weeks; however, the extent of luminal narrowing reached its peak at 8 weeks and the lumen dimension increased somewhat at 24 weeks. The degree of intimal thickening remained relatively constant throughout the different time points (<200 microm). Overall, these data suggest that constrictive remodeling within the stented segment occurs at 8 weeks in this animal model. The later increase of the stented segment dimensions as well as higher net gain at 24 weeks compared to 8 weeks after deployment suggests that this constriction is a transitory phenomenon.

Angioplasty, Balloon, Coronary↗
PubMed1996

Resistive-load detection in healthy school-aged children.

The ability to detect changes in respiratory resistance, which may be important in acute and chronic adaptations to airways obstruction, has not been measured previously in children. Two methods were used to measure the resistive-load detection thresholds (the added resistance that produced a "just noticeable difference" in perception) in a group of 38 healthy children and adolescents aged 7-16 years. Total respiratory system resistance (Rrs), as measured by forced oscillation, was used as an index of each child's intrinsic baseline (pre-test) resistance. To determine thresholds a computer program added various percentages of baseline resistance according to response (first method) and then in random order (second method). Thresholds by at least one of the two methods were detectable in 32 of the children (84%), and failure to detect a threshold was less common in older than in young children. Thresholds obtained by each method were significantly related to one another (r = 0.54, P < 0.05). Baseline resistance accounted for a marginally significant proportion of the variation in thresholds as assessed by the tracking method (R2 = 0.12, P < 0.10) and a large proportion of the variation in thresholds as assessed by the random method (R2 = 0.66, P < 0.0001). Thresholds expressed in terms of percent of baseline resistance were found to have mean values of 100.4-105.0%, regardless of gender or age. Results from a comparison group of adults (n = 10) indicated lower threshold by both procedures (mean values, 71.90-76.50%). We conclude that perceptual thresholds for added resistive loads are determined, in part, by growth-related changes in intrinsic resistance.

Adolescent↗
PubMed1996

Conceptual and methodologic issues in quantifying perceptual accuracy in childhood asthma.

Delineated methodologic issues in the study of symptom perception in childhood asthma. A review of past and recent psychophysiological and clinical studies of both adults and children presents the methodologic and analytic approaches that have been applied to quantify perceptual accuracy. Peak expiratory flow rate, forced expiratory volume in the first second, and force expiratory flow can serve as objective measures of asthma. A visual analog scale, a numerical guess, and a categorical description as subjective measures all have clear strengths and weaknesses. Correlational analysis of subjective-objective data, arithmetic differences between subjective guess and objective value, and an error grid categorization can each be applied to calculate an accuracy index on an individual subject. Illustrative examples reveal that the same data lead to different indices depending on the method chosen. Empirical research is needed to standardize various methodologic approaches. Given the increasing prevalence, severity, and morbidity of pediatric asthma, the study of symptom perception may be a critical component in our understanding of asthma management, and will likely lead to useful clinical interventions.

Adolescent↗