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Biomedical subjects

F Y Lau

Publications and source records attributed to F Y Lau.

At least 19 recordsLinked to original sources
PubMed2002

Antiproliferative activity of the extract of Gleditsia sinensis fruit on human solid tumour cell lines.

BACKGROUND: The fruit extract of Gleditsia sinensis Lam. (GSE) is a traditional herbal medicine that is saponin-rich. However, its activity on solid tumour cell lines has never been demonstrated. METHODS: The activity of GSE was demonstrated in four cancer cell lines (breast cancer MCF-7, MDA-MB231, hepatoblastoma HepG2 and oesophageal squamous carcinoma cell line SLMT-1) using MTT assay, anchorage-independent clonogenicity assay, DNA laddering and in situ cell death detection. RESULTS: The mean MTT(50) (the mean concentration of GSE to reduce MTT activity by 50%) ranged from 16 to 20 microg/ml of GSE. An anchorage-independent clonogenicity assay showed that all of the four solid tumour cell lines gradually lost their regeneration potential after treatment with GSE, DNA fragmentation and TUNEL analysis demonstrated that the action of GSE is both dose- and time course-dependent. CONCLUSIONS: Our results suggest that GSE has a cytotoxic activity and can induce apoptosis in human solid tumour cell lines.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Transfusion of peripheral blood stem cells from donor homozygous for a shared HLA-haplotype: avoiding fatal transfusion-associated graft-versus-host disease while preserving anti-leukemic effect.

BACKGROUND: Fatal transfusion-associated graft-versus-host disease was observed in immunocompetent patients transfused with blood from donors homozygous for a shared haplotype with the recipient (the P-F1 barrier). We tested whether it was possible to carry out successful transplantation in a patient with relapsed acute myeloid leukemia, using peripheral blood stem cells from his HLA-homozygous brother (HLA A2, B46, DRB1 901) who shared a haplotype with the patient (HLA A2, B46,75, DRB1 901,12). METHODS: A CD34 positively selected cell fraction (5.46x 10(6) CD34 cells/kg) was infused first, followed by subsequent infusion of graded doses of donor T cells (total 7.25x10(7) T cells/kg). Nonmyeloablative chemotherapy with idarubicin and cytarabine was given during the transplantation to reduce the leukemic burden and facilitate engraftment. Polymerase chain reaction with the VNTR primers, D1S80, was used to detect engraftment. RESULTS: Complete remission (>300days) and successful donor engraftment (90%) were achieved. CONCLUSIONS: Peripheral blood stem cells transplantation from a donor with a homozygous shared haplotype is possible with a minimal preparative regimen.

Acute Disease↗
PubMed2001

To err is human nature. Can transfusion errors due to human factors ever be eliminated?

BACKGROUND: Fatal hemolytic transfusion reaction due to ABO incompatibility occurs mainly as a result of clerical errors. Blood sample drawn from the wrong patient and labeled as another patient's specimen will not be detected by the blood bank unless there is a previous ABO grouping result. METHODS: In Hong Kong, we had designed a transfusion wristband system--portable barcode scanner system to detect such clerical errors. The system was well accepted by the house staff and had prevented two BO mismatched transfusion. Other current system of patient's identification may have similar results, but the wristband system has the advantages of being simple, inexpensive and easy to implement. The Hong Kong Government is planning to replace the personal identity card for all citizens with an electronic smart card by 2003. If the new card contains the person's detailed red cell phenotypes in digital code, then the phenotypes of all blood donors and admitted patients will be readily available. It is feasible to issue phenotype-matched blood to patients without any need of pre-transfusion testing, therefore eliminating mismatched transfusions for most patients. RESULTS: Our pilot study of 474 patients showed that the system was safe and up to 98% of admitted patients could be transfused without delays. CONCLUSIONS: Patients with rare phenotypes, visitors or illegal immigrants may still need pre-transfusion antibody screen, but if most patients can be issued blood units without testings, the potential savings in health care amount to US$14 million/year.

ABO Blood-Group System↗
PubMed2001

Successful engraftment in two adult patients with severe aplastic anemia using nonmyeloablative conditioning followed by unrelated HLA-mismatched cord blood transplantation.

Umbilical cord blood as an alternative source of hematopoietic stem cells and nonmyeloablative conditioning are very exciting new developments in transplantation. We report here mixed chimerism in two adult patients with severe aplastic anaemia using nonmyeloablative conditioning and two-antigen mismatched cord blood transplantation resulting in satisfactory clinical response. Our results suggest that such transplant is possible with minimal toxicity.

Adolescent↗
PubMed2001

Provision of phenotype-matched blood units: no need for pre-transfusion antibody screening.

BACKGROUND AND OBJECTIVES: The Hong Kong government is planning to introduce an electronic smart identity card for all seven million citizens in 2003. If the smart card contains the full red cell phenotype/genotype of the individual, it may be possible to transfuse phenotype-matched blood units without pre-transfusion antibody screening. We conducted a feasibility study. DESIGN AND METHODS: Red cell phenotype was determined for 407 donor blood units and 493 patients for whom an antibody screen had been ordered. The computer program selected phenotype-matched blood from the donor stock for the patients according to actual transfusion request. For patients with a positive antibody screen, full crossmatching was carried out with the computer-selected phenotype units. The frequencies of the various red cell phenotypes in the population were calculated from Red Cross data of antigen frequencies. The probabilities of finding at least one unit of phenotype-matched blood from a 300-unit hospital stock and a 4,000-unit Red Cross stock were determined for each phenotype. Cost analysis was performed. RESULTS: Ninety-two out of 493 patients received a total of 395 blood units. The required number of phenotype-matched blood units could be found for 92 patients using a 300-unit pool and for all patients using a 4,000-unit pool. We calculated that phenotype-matched blood could be provided for more than 98% of patients without antibody screening. The total cost of the project is US$ 98 million with potential savings of US$ 14 million per year. INTERPRETATION AND CONCLUSIONS: It is feasible and cost-effective to transfuse patients with phenotype-matched blood without antibody screening using a smart card system.

Blood Group Antigens↗
PubMed2000

Improvement in transfusion safety using a specially designed transfusion wristband.

Fatal haemolytic transfusion reaction due to ABO incompatibility occurs mainly as a result of clerical error. A blood sample drawn from the wrong patient and labelled as another patient's will not be detected by the blood bank unless there is a previous ABO grouping result. We report here the detection of such clerical error by the use of a specially designed transfusion wristband. The wristband has the following special features: (i) once attached, it cannot be removed except by cutting; (ii) it has a pocket containing a transfusion label; (iii) a unique transfusion barcode is printed on each transfusion label and the corresponding wristband simultaneously by computer technology; (iv) a transfusion label removed from the wristband after attachment to the patient has a characteristic tear-mark distinguishing it from one removed prior to attachment. The blood bank only accepted those specimens bearing the tear-marked transfusion labels. All blood units for this patient were labelled with this unique transfusion code together with the patient's details. The nurses counter-checked the transfusion code on the blood units against the transfusion code on the patient's transfusion wristband prior to transfusion. If the blood sample for compatibility testing was drawn from the 'wrong' patient, the intended patient either did not carry a wristband or the transfusion codes did not match at all. Pretransfusion compatibility tests were performed on 2189 patient samples using this procedure. It was well accepted by both ward and blood bank staff. Two potential mismatched transfusions were avoided. These two clerical errors would not have been detected because neither patient had previous ABO grouping results.

Blood Banks↗
PubMed1998

Comparison of late results of balloon valvotomy in mitral stenosis with versus without mitral regurgitation.

Balloon mitral valvotomy (BMV) is safe and effective in patients with mitral stenosis (MS) and coexisting mild mitral regurgitation (MR). Influence of preexisting MR on late outcome of BMV is under evaluation. We included 77 patients without MR and 72 with MR in this study, and compared their immediate and late results in a mean follow-up of 33 +/- 24 months after BMV. Patients with coexisting MR were older and more frequently had significant valvular calcium and atrial fibrillation than patients without MR. After BMV, mitral valve gradient decreased, and cardiac output and mitral valve area by planimetry increased significantly (all p = 0.0001) in both groups. There was no difference in values of mitral valve gradient and cardiac output after BMV between the groups. Mitral valve area was significantly smaller in patients with preexisting MR. During follow-up, there were 11 patients (14%) in the group without MR and 24 (33%) in the group with MR developed cardiac events (p = 0.006). Cumulative event-free survival was 90% at the second year, 87% at the fourth year, and 69% at the sixth year, respectively, in the group without MR versus 78%, 62%, and 37%, respectively, in the group with MR (p = 0.0014). Cox regression showed that preexisting MR was a significant predictor for late cardiac events with a threefold increased hazard risk (p = 0.0025), but age, valvular calcium, echocardiographic score, and cardiac rhythm also played a culpable role. We conclude that preexisting MR is an important risk factor for poor, late outcome of BMV.

Adolescent↗
PubMed1998

Lack of structural rearrangement in c-kit and stem cell factor genes in Hong Kong Chinese patients with myelodysplastic syndromes or acute myeloid leukaemia.

Stem cell factor is a haemopoietic growth factor that interacts with the c-kit-encoded transmembrane tyrosine kinase receptor during signal transduction in haemopoietic progenitor stem cells. We have screened 127 Chinese patients with myelodysplastic syndromes or acute myeloid leukaemia for structural rearrangements in the stem cell factor and c-kit genes using Southern blot analysis. No structural rearrangements were detected in any of the bone marrow samples that were tested. It seems that structural rearrangements in the stem cell factor and c-kit genes are rare in Hong Kong patients who have a haematological malignancy.

Journal Article↗
PubMed1997

Low frequency of c-kit expression and detection of an aberrant Kit message among Hong Kong Chinese myelogenous leukaemia patients.

The c-kit proto-oncogene encodes a transmembrane tyrosine kinase receptor. It is expressed by the primitive CD34 positive haemopoietic stem cells and interacts with the Kit ligand for signal transduction. It was reported to be expressed in over 80% of acute myelogenous leukaemia (AML) patients in North America and Japan. We analyzed 20 AML patients for c-kit expression using either Northern blot analysis or flow cytometry with the YB5.B8 anti-c-kit antibodies. Only 6 out of 20 AML patients expressed the c-kit mRNA or protein product. However, a previously unreported abnormal sized 1.7-1.9 kb transcript was detected in the blast cells of 1 AML patient, 1 acute mixed lineage leukaemia patient and 1 chronic myelogenous leukaemia (CML) patient in myeloblastic transformation. Our data suggested that in most Hong Kong Chinese AML patients, leukaemia transformation may have occurred at a c-kit negative stage. Alternatively, the abnormal sized c-kit transcript that was detected in some Chinese myeloid leukaemia patients may represent an aberrant c-kit receptor that plays an important role in leukaemogenesis.

Blotting, Southern↗
PubMed1997

A novel prognostic scoring system to predict late outcome after percutaneous balloon valvotomy in patients with severe mitral stenosis.

We developed a prognostic scoring system to predict the outcome of follow-up after balloon mitral valvotomy. The system incorporates seven variables before valvotomy: age, New York Heart Association class, fluoroscopic calcification, echocardiographic score, cardiac rhythm, mitral regurgitation, and mitral valve area. Each variable was coded with either 0 or 1 and a total score was between 0 and 7. The study included 150 patients with a mean follow-up of 33 +/- 24 months. In patients with scores of 0-1, 2-3, 4-5, and 6-7, the estimated cardiac event-free survival rate was 97%, 94%, 86%, and 68%, respectively, at 1 year; 95%, 88%, 74%, and 47%, respectively, at 3 years; and 92%, 82%, 61%, and 30%, respectively, 5 years after valvotomy (p = 0.0001). The hazard risk ratio for cardiac events was 1.7 times greater for every step up of the score (p = 0.0001). Our scoring system provides a simple but effective method to predict late outcome of balloon mitral valvotomy.

Catheterization↗