PubMed Health⌕ Search

Biomedical subjects

I Chin-Yee

Publications and source records attributed to I Chin-Yee.

At least 19 recordsLinked to original sources
PubMed2005

A retrospective study evaluating single-unit red blood cell transfusions in reducing allogeneic blood exposure.

Although guidelines recommend the use of single-unit red blood cell (RBC) transfusions to minimize allogeneic blood exposure, clinical practice remains dominated by two-unit transfusions. This study assesses the potential impact of a single-unit transfusion policy on reducing RBC utilization. We performed a retrospective analysis of adult patients admitted to a tertiary care hospital who received one or two RBC units. In subjects transfused two units, the effect of one unit was estimated by dividing the change in haemoglobin by 2. The proportion of patients reaching a haemoglobin threshold of 70, 75, 80, 85 and 90 g L(-1) with a single RBC unit was estimated. Of 302 included patients, only 65 received a one-unit transfusion. Based on thresholds of > or = 90, > or = 80 and > or = 70 g L(-1), a single-unit transfusion would be sufficient in 42.0% (RRR = 0.54), 79.6% (RRR = 0.23) and 98.0% (RRR = 0.02) of cases, respectively. This corresponds to 0.21, 0.57 and 0.82 mean RBC units saved per patient. In the orthopaedic subpopulation, the mean RBC units saved are 0.53, 0.88 and 1.00 for the same haemoglobin targets. Adopting a policy of transfusing RBC in single-unit aliquots could significantly improve RBC utilization and decrease patient exposure to allogeneic blood.

Erythrocyte Transfusion↗
PubMed2005

Consenting to blood: what do patients remember?

We sought to characterize the consent process for transfusion and determine its impact on patients' knowledge and level of comfort with receiving blood. We identified all adult patients who had received blood transfusion at a tertiary care centre over 3 months. Patients who were discharged each received a survey that assessed their (1) recall of the consent process, (2) recall of information conveyed, (3) assessment of the discussion's understandability and (4) perceived knowledge of as well as comfort level with transfusion as a result of the discussion. Overall, 80% of respondents recalled discussing and signing an informed consent. Information was mostly conveyed by attending physicians (35%) and consent obtained in the patient's hospital room (38%) or the preadmission clinic (19%). Although the majority recalled the consent process, many did not recall the discussion of specific transfusion risks or alternatives to donor blood (88%). Although the majority felt the discussion was at least somewhat understandable (77%), only 35% felt better informed and more comfortable with accepting blood. Despite implementation of written informed consent for transfusion, patients' recollection and understanding of risks and alternatives remain poor. This suggests the need for improving risk communication.

Adolescent↗
PubMed2001

Inactivation of p53 sensitizes U87MG glioma cells to 1,3-bis(2-chloroethyl)-1-nitrosourea.

We examined the effect of p53 inactivation on the response of U87MG glioma cells to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). These studies were motivated by three observations: (a) some human astrocytomas are sensitive to BCNU and some are resistant; (b) chemosensitive astrocytomas are more likely to be found in young adults whose tumors are more likely to harbor a p53 mutation; and (c) mouse astrocytes lacking the p53 gene are more sensitive to BCNU than wild-type cells. Here, we observed that p53 inactivation by transfection with pCMV-E6 sensitized U87MG cells to BCNU. Compared with control U87MG-neo cells with intact p53 function, the clonogenic survival of U87MG-E6 cells exposed to BCNU was reduced significantly. In U87MG-E6 cells, sensitization to BCNU was associated with failure of p21(WAF1) induction, transient cell cycle arrest in S phase, accumulation of polyploid cells, and significant cell death. In contrast, resistance to BCNU in U87MG-neo cells was associated with up-regulation of p53, prolonged induction of p21(WAF1), sustained cell cycle arrest in S phase, and enhancement of DNA repair. U87MG cells with disrupted p53 function were less able to repair BCNU-induced DNA damage and survive this chemotherapeutic insult. The question arises of whether p53 dysfunction might be a chemosensitizing genetic alteration in human astrocytic gliomas.

Antineoplastic Agents, Alkylating↗
PubMed2000

Quality assurance of progenitor cell content of apheresis products: a comparison of clonogenic assays and CD34+ enumeration. The Canadian Apheresis Group and Canadian Bone Marrow.

The most common methods used for evaluation of the haematopoietic stem cell content of peripheral blood apheresis products are the colony forming cell assay and the enumeration of CD34+ cells by flow cytometry. The Canadian Apheresis Group and the Canadian Bone Marrow Transplant Group established a multicentre study to compare the reproducibility of colony forming cell assays and CD34+ enumeration by flow cytometry in six transplant centres routinely performing haematopoietic stem cell apheresis. Over a 5-month period in 1996, 31 fresh apheresis samples were shipped by overnight courier for testing at six centres to perform CD34+ enumeration by flow cytometry and clonogenic assays. The mean coefficient of variation and range for the following assays were: cell count 36% (2.6-148%), CFU-GM 82% (46-123%), CD34+ absolute/kg 60% (14-174%) and CD34+ per cent 42% (12-84%). The wide variation in cell count in this pilot study highlights the difficulties related to provision of samples for quality assessment programmes. Results showed poor interinstitutional reproducibility even among selected samples with similar cell counts for both CFC and CD34+ assays demonstrating the need for development and implementation of an interinstitutional quality assurance programme for haematopoietic stem cell assessment. Provision of a reliable source of testing material will be a necessary next step.

Antigens, CD34↗
PubMed1998

Single platform flow cytometric absolute CD34+ cell counts based on the ISHAGE guidelines. International Society of Hematotherapy and Graft Engineering.

In concert with the International Society of Hematotherapy and Graft Engineering (ISHAGE), we previously described a set of guidelines for detection of CD34+ cells based on a four-parameter flow cytometry method (CD45 FITC/CD34 PE staining, side and forward angle light scatter). With this procedure, an absolute CD34+ count is generated by incorporating the leukocyte count from an automated hematology analyser (two-platform method). In the present study, we modified the basic ISHAGE method with the addition of a known number of Flow-Count fluorospheres. To reduce errors inherent to sample washing/centrifugation, we implemented ammonium chloride lyse, no-wash no-fix sample processing. These modifications convert the basic protocol into a single-platform method to determine the absolute CD34 count directly from a flow cytometer and form the basis of the Stem-Kit from Coulter/Immunotech. A total of 72 samples of peripheral blood, apheresis packs, and cord blood were analysed and compared using the ISHAGE protocol with or without the addition of fluorescent microspheres. Comparison of methods showed a high correlation coefficient (r=0.99), with no statistically significant difference or bias between methods (P > 0.05). Linearity of the absolute counting method generated an R2 value of 1.00 over the range of 0-250/microl. Precision of the absolute counting method measured at three concentrations of CD34+-stabilised KG1 a cells (Stem-Trol, COULTER) generated a coefficient of variation (C.V.) ranging from 4% to 9.9%. In a further modification of the single-platform method, the viability dye 7-amino actinomycin D was included and demonstrated that both viable and nonviable CD34+ cells could be identified and quantitated. Together, these modifications combine the accuracy and sensitivity of the original ISHAGE method with the ability to produce an absolute count of viable CD34+ cells. It is the accurate determination of this value that is most clinically relevant in the transplant setting. These modifications may improve the interlaboratory reproducibility of CD34 determinations due to the reduction in sample handling and calculation of results.

Antigens, CD34↗
PubMed1998

Supernatant from stored red cells activates neutrophils.

Bioreactive substances including cytokines and lipids accumulate during storage of red blood cells (RBCs) but their clinical importance is uncertain. The goal of this study was to evaluate the effect of stored RBC supernatant on neutrophil activity in vitro. Packed RBCs (PRBCs) were collected and divided into two aliguots, one leukodepleted and the other nonleukodepleted. Plasma supernatant from PRBCs were collected on days 1, 8, 15, 29 and 35 and its effect on neutrophil expression of CD11b, CD16 and oxidative burst was measured by flow cytometry. Levels of tumour necrosis factor alpha (TNF alpha) and interleukin-8 (IL8) were also measured. The supernatant from PRBC units stored for greater than 15 days activated and primed neutrophils as evidenced by an increase CD11b and CD16 expression and oxidative burst. The greatest effect was seen in the oldest concentrates (35-day-old) (P < 0.008). Leukodepletion abrogated the effects of stored supernatant on CD11b and CD16 expression (P < 0.02) but did not reduce priming of the neutrophil oxidative burst (P > 0.1). Very low levels of IL8 and TNF alpha were detected in stored supernatants. Stored PRBC supernatant contains substances which directly enhance neutrophil expression of adhesion protein CD11b, CD16 and prime neutrophil oxidative burst. The exceedingly low level of IL8 and TNF alpha found in this study suggests that other factors may play a more important role in neutrophil priming and activation.

Biomarkers↗
PubMed1997

Quality assurance of stem cell enumeration by flow cytometry. Canadian QASE Study Group.

The enumeration of CD34+ cells by flow cytometry is commonly employed to assess progenitor/stem cell numbers in peripheral blood, cord blood, and apheresis products used for peripheral blood stem cell transplantation (PBSCT). Until recently, the enumeration of CD34+ cells has evolved in the absence of any procedural guidelines or quality assurance programs. We established a voluntary quality assurance for stem cell enumeration (QASE) program for Canadian laboratories involved in PBSCT. The goals of this study were 1) to survey current flow cytometric procedures for CD34 enumeration; 2) to evaluate inter-institutional reproducibility of currently employed assays; and 3) to evaluate the impact of adoption of a common method on inter-laboratory variability. Fourteen to nineteen laboratories participated in this program by enumerating CD34+ cells in shared cord blood samples. The survey showed a wide variation in flow cytometric methodology which in part contributed to the wide range in results obtained between different centres. Major differences in methodology included the number of events counted, use of isotype control and gating strategy. Participation in this program and adoption of a common methodology increased level of agreement for any given result although this trend did not reach statistical significance (P = 0.13). The results of this survey emphasize the need for a quality assurance program for stem cell enumeration by flow cytometry.

Antigens, CD34↗
PubMed1997

The red cell storage lesion and its implication for transfusion.

Storage of red blood cells in preservative medium is associated with metabolic, biochemical and molecular changes to erythrocytes collectively referred to as the "storage lesion." In addition to corpuscular injury, bioreactive substances including cytokines and lipids accumulate in the medium during storage. We review evidence for those storage related changes and potential clinical implications for red blood cell transfusion.

Blood Preservation↗
PubMed1996

Comparison of two methods to detect P-glycoprotein in patients with chronic lymphocytic leukaemia.

P-glycoprotein (Pgp) is a transmembrane protein associated with multiple drug resistance. Pgp can be detected by several monoclonal antibodies or its activity inferred by measuring drug uptake. We compared two methods for quantitating Pgp in 32 patients with chronic lymphocytic leukaemia. The monoclonal antibody 4E3, which recognizes an external epitope of Pgp, was detected by flow cytometry. Intracellular daunorubicin (DNR) accumulation was measured by flow cytometry in the presence (treated) and absence (control) of cyclosporin, an agent known to inhibit Pgp. Correlation between the degree of positivity on the drug uptake assay and Pgp detected by monoclonal antibody 4E3 was poor (r = 0.06). No association with previous drug exposure or lymphocyte doubling time and Pgp positivity was found in this series of patients. Poor correlation between assays might reflect a lack of sensitivity of the DNR uptake assay. Drug accumulation may be influenced by other cellular efflux pumps unrelated to Pgp, making the DNR assay non-specific.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

The ISHAGE guidelines for CD34+ cell determination by flow cytometry. International Society of Hematotherapy and Graft Engineering.

The increased use of Peripheral Blood Stem Cells (PBSC) to reconstitute hematopoiesis in autotransplant and, more recently, allotransplant settings has not been associated with a consensus means to quality control the PBSC product. Since the small population of cells that bear the CD34 antigen are thought to be responsible for multilineage engraftment, graft assessment by flow cytometric quantitation of CD34+ cells should provide a rapid, reliable, and reproducible assay. Unfortunately, although a number of flow cytometric assays for CD34 enumeration have been described, the lack of a standardized method has led to the generation of widely divergent data. Furthermore, none of these assays has been validated as to interlaboratory reproducibility and suitability for widespread clinical application. In early 1995, the International Society of Hematotherapy and Graft Engineering (ISHAGE) established a Stem Cell Enumeration Committee, the mandate of which was to validate a simple, rapid, and sensitive flow cytometric method to quantitate CD34+ cells in peripheral blood and apheresis products. We also sought to establish its utility on a variety of flow cytometers in clinical laboratories and its reproducibility between transplant centers. Here, we describe the four-parameter flow methodology adopted by ISHAGE for validation in a multicenter study in North America.

Antigens, CD34↗
PubMed1996

Use of cytokines in clozapine-induced agranulocytosis.

OBJECTIVE: To report and review the use of cytokines for the treatment of clozapine-induced neutropenia. METHOD: Case report and review of literature. RESULTS: Cytokines, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF), appear to shorten the duration of clozapine-induced neutropenia. CONCLUSIONS: G-CSF or GM-CSF therapy should be considered in patients with profound neutropenia of prolonged duration (high-risk neutropenia).

Adult↗
PubMed1995

Flaxseed: a potential treatment for lupus nephritis.

Flaxseed is rich in alpha-linolenic acid (alpha-LA) which has anti-atherogenic properties, and lignans which are platelet activating factor (PAF)-receptor antagonists. These constituents of flaxseed, and its beneficial effects in the MRL/lpr lupus mouse prompted us to perform this dosing study in lupus nephritis patients. Nine patients were enrolled, eight of whom completed the study. After the baseline studies, patients were given 15, 30, and 45 g of flaxseed/day sequentially at four week intervals, followed by a five-week washout period. Compliance, disease activity, blood pressure, plasma lipids, rheology, PAF-induced platelet aggregation, renal function, and serum immunology were assessed. Flaxseed-sachet count and a significant increase of serum alpha-LA indicated good compliance for 15 and 30 g doses. Total and LDL cholesterol, and blood viscosity were significantly reduced with 30 g and to a lesser extent 45 g doses. PAF-induced platelet aggregation was inhibited by all doses. There was a significant decline in serum creatinine with 30 and 45 g, and a concomitant increase in creatinine clearance with increasing flaxseed dose. Proteinuria was reduced with 30 g and to a lesser extent with 45 g of flaxseed. Complement C3 was significantly elevated by all three doses. CD11b expression on neutrophils, a measure of C3bi receptors, was significantly reduced with the 30 g dose. In conclusion, 30 g flaxseed/day was well tolerated and conferred benefit in terms of renal function as well as inflammatory and atherogenic mechanisms important in the pathogenesis of lupus nephritis.

Adult↗
PubMed1994

Validation of a single point flow cytometric assay for determining P-glycoprotein activity in multidrug resistant cell lines.

P-glycoprotein, a transmembrane protein which acts as an energy dependent efflux pump, has been implicated as one mechanism of multidrug resistance (MDR) in human tumours. Commonly employed assays measure P-glycoprotein immunohistochemically or mdr1 messenger RNA. In this study we compared a single point flow cytometric assay for determining activity of P-glycoprotein with cellular expression of P-glycoprotein determined by Western blot. Five cell lines, with varying levels of multiple drug resistance, were incubated with daunorubicin (DNR) in the presence (treated) and absence (control) of cyclosporine or verapamil, agents known to inhibit the activity of P-glycoprotein. The treated cell lines, along with non-treated controls were examined for intracellular concentrations of DNR measured by fluorescence intensity using a flow cytometer. The ratio of fluorescence intensity expressed in the treated/control was used as an index of functional activity of P-glycoprotein. Functional activity of the P-glycoprotein as determined by flow cytometry correlates highly with cellular content of P-glycoprotein measured by western blot (correlation coefficients of r = 0.90-0.98 for the various cell line combinations). This method represents a rapid single point flow cytometric assay which may be suitable for screening clinical samples for P-glycoprotein activity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Abrogation of MRL/lpr lupus nephritis by dietary flaxseed.

A diet supplemented with flaxseed, rich in alpha-linolenic acid and plant lignans (the latter, potent platelet-activating factor receptor antagonists), was tested in a murine model of lupus nephritis. MRL/lpr female mice (n = 25) were fed 15% flaxseed diet for 14 weeks commencing at 10 weeks of age. As controls, 30 MRL/lpr mice received a standard rodent diet without flaxseed. Isotope-glomerular filtration rate (14C-inulin clearance) was measured at 9, 16, and 24 weeks of age. Proteinuria was assessed at 2-week intervals. Spleen lymphocyte proliferation, quantitated by DNA analysis, was evaluated using flow cytometry at 9, 13, 19, and 21 weeks of age. Mortality was recorded throughout the study. Glomerular filtration rate at 16 weeks was greater in flaxseed-fed mice (0.15 +/- 0.03 mL/min) compared with controls (0.06 +/- 0.04 mL/min; P = 0.01). The onset of proteinuria (Albustix, Ames Division, Miles Laboratories, Rexdale, Ontario, Canada; > or = 2+) was delayed by 4 weeks in the flax-treated mice. The percentage of flaxseed-fed mice with proteinuria was lower than the control mice up to 21 weeks of age (39% v 58%; P = 0.01). Spleen lymphocyte proliferation (percentage of cells in S-phase) at 13 weeks of age was significantly higher in the control group (22.9 +/- 5.0, P = 0.01) but not in the flaxseed group (17.2 +/- 4.9) compared with baseline (9 weeks of age) values (13.0 +/- 3.5). Mortality was lower in the flaxseed-fed mice versus the control mice (assessed by Mantel-Haenszel (log-rank) test; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗