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Biomedical subjects

P M Yuen

Publications and source records attributed to P M Yuen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Dextran sedimentation in a semi-closed system for the clinical banking of umbilical cord blood.

BACKGROUND: The results of current processing procedures for reducing volume and recovering HPCs from umbilical cord blood (UCB) before cryopreservation vary. STUDY DESIGN AND METHODS: Dextran was added to bags containing UCB, followed by sedimentation for 30 minutes. The processed UCB was then frozen. RBCs, nucleated cells, MNCs, CD34+ cells, CFUs and long-term culture-initiating cells (LTC-ICs), viability, and sterility were evaluated. Fractionations in ficoll-hypaque and hydroxyethyl starch (HES) were also run in parallel for comparison. RESULTS: The nucleated cell (NC) recovery and RBC depletion were 86.1 percent and 94.3 percent, respectively (n = 50). Sedimentation with dextran also enabled the recovery of 80.7 percent MNCs and 82.6 percent CD34+ cells (n = 30). Postsedimentation samples displayed no impairment of CFU growth (n = 42, 108.7% CFU-C, 104.6% CFU-GEMM, 107% CFU-GM, and 95.7% BFU-E). Long-term cultures on five paired samples before and after sedimentation generated similar numbers of CFU-C each week (p = 0.88). Limiting dilution analysis of 12 paired pre/postsedimentation samples showed comparable median proportions of LTC-ICs (1/6494 vs. 1/5236; p = 0.18). The cell viability of 24 samples of thawed UCB after sedimentation was 90.3 percent (77.5-96%) and the recovery of CFU-C, CFU-GEMM, CFU-GM, and BFU-E of 11 postsedimentation samples was 93.4 percent, 84.9 percent, 92.3 percent, and 83.4 percent, respectively. NC recovery was significantly higher after treatment with dextran than with ficoll-hypaque (n = 30; 88.5% vs. 29.1%; p<0.005) and HES treatment (n = 21; 88.5% vs. 76.4%; p = 0.004). However, MNCs, CD34+ cells, CFUs, LTC-ICs, and RBCs were comparable. Two cycles of dextran sedimentation recovered 93.9 percent of NCs with cell viability of 98.6 percent (96.5-100%), whereas 11.7 percent of RBCs were retained (n = 20). The final yield volume was 33.5 (28-41) mL. CONCLUSION: In a semi-closed system, dextran sedimentation enabled volume reduction of UCB without significant quantitative and qualitative losses of HPCs.

Blood Banks↗
PubMed2001

Preclinical ex vivo expansion of cord blood hematopoietic stem and progenitor cells: duration of culture; the media, serum supplements, and growth factors used; and engraftment in NOD/SCID mice.

BACKGROUND: Ex vivo expansion of cord blood (CB) hematopoietic stem and progenitor cells increases cell dose and may reduce the severity and duration of neutropenia and thrombocytopenia after transplantation. This study's purpose was to establish a clinically applicable culture system by investigating the use of cytokines, serum-free media, and autologous plasma for the expansion of CB cells and the engraftment of expanded product in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. STUDY DESIGN AND METHODS: Enriched CB CD34+ cells were cultured in four media (Iscove's modified Dulbecco's medium with FCS, Gibco; X-Vivo-10, BioWhittaker; QBSF-60, Quality Biological; and StemSpan SFEM, Stem Cell Technologies) with four cytokine combinations (thrombopoietin [TPO], SCF, Flt-3 ligand [FL] with and without G-CSF, and/or IL-6). The effect of autologous CB plasma was also investigated. The read-out measures were evaluated on Days 8 and 12. After expansion at the optimized condition, cultured cells were transplanted into sublethally irradiated NOD/SCID mice. The engraftment of human CD45+ cells and subsets in the bone marrow, spleen, and peripheral blood was determined. RESULTS: QBSF-60 or StemSpan SFEM supported high yields of early progenitors (CD34+ cells, <or= 64.8-fold; CD34+CD38- cells, 330-fold; CFU-granulocyte erythroid macrophage megakaryocyte [GEMM], 248-fold) and CFUs of the myeloid (CFU-GM, 407-fold) and erythroid (BFU/CFU-E, 144-fold) lineages. The expansion of the megakaryocytic lineage was consistently higher in X-Vivo-10 (CFU-megakaryocyte, 684-fold). Autologous plasma promoted colony formation but reduced CD34+ cells and CFU-GEMM. The addition of G-CSF or IL-6 improved cell yields; G-CSF was more effective for committed progenitors. Expansion products from cultures in QBSF-60 with the cytokines engrafted and differentiated into the myeloid and lymphoid lineages in NOD/SCID mice. CONCLUSION: The data supported the strategy of expansion. The optimized condition may be applicable to clinical expansion for the abrogation or reduction of posttransplant cytopenia.

Animals↗
PubMed2001

Liver iron estimation in beta-thalassaemia: comparison of MRI biochemical assay and histological grading.

AIMS: The aims of the study were to compare the efficacy of magnetic resonance imaging (MRI), biochemical assay and histological grading in estimating liver iron content, and to evaluate the value of liver to muscle signal intensity ratio (L/M ratio) on spin-echo T1-weighted images in this role. MATERIALS AND METHODS: Thirty-nine homozygous beta-thalassaemics had their L/M ratio measured on MRI, followed by ultrasound-guided liver biopsies with histological grading of iron storage and biochemical quantification of liver iron concentration (LIC-b) using atomic absorption spectrophotometry. RESULTS: A significant difference in L/M ratios between the four grades of iron storage on histology was observed (P < 0.001). The coefficient of correlation was -0.67 between L/M ratio and LIC-b ranging from 2 to 21.6 mg/g dry weight. Specific values of L/M ratio reliably reflected liver iron content at clinically important levels. A L/M ratio of < 0.6 has 86% sensitivity and 100% specificity in the prediction of grade 3 or 4 iron storage histologically and 81% sensitivity and 81% specificity in predicting LIC-b > 15 mg/g. A L/M ratio of > 0.8 predicts a histological iron storage grading of 0 or 1 with a 100% sensitivity and 74% specificity. CONCLUSION: L/M ratio on MRI is of value as a non-invasive alternative to repeated liver biopsies for estimating liver iron content at clinically important thresholds.

Adolescent↗
PubMed2001

A multicentre randomized controlled trial of oral misoprostol and i.m. syntometrine in the management of the third stage of labour.

Postpartum haemorrhage accounts for nearly 28% of maternal mortality in developing countries. Syntometrine is an effective and commonly used oxytocic in preventing postpartum haemorrhage, but it requires a controlled storage environment and i.m. administration. Misoprostol is an orally active uterotonic agent. A total of 2058 patients having a singleton pregnancy, low risk for postpartum haemorrhage and vaginal delivery were randomized to receive either 1 ml syntometrine or 600 microgram misoprostol for the management of the third stage of labour. There were no significant differences between the two groups in the mean blood loss, the incidence of postpartum haemorrhage and the fall in haemoglobin concentration. The need for additional oxytocic injection was significantly higher in the misoprostol group [relative risk (RR) 1.62, 95% confidence interval (CI) 1.34-1.96], but that of manual removal of placenta was reduced (RR 0.29, 95% CI 0.09-0.87). Shivering and transient pyrexia were more common in the misoprostol group. Oral misoprostol might be used in the management of the third stage, especially in situations where the use of syntometrine is contraindicated and facilities for storage and parenteral administration of oxytocics are limited.

Administration, Oral↗
PubMed2001

Clearance of TT virus after allogeneic bone marrow transplantation.

A 10-year-old girl with thalassemia underwent bone marrow transplantation. Before transplantation, she had persistent TT virus (TTV) DNAemia for at least 18 months. Interestingly, the viral DNAemia was cleared soon after transplant and remained undetectable at the latest follow-up at 28 months. The early clearance of TTV that had occurred before engraftment or initiation of any antiviral therapy, together with the absence of TTV DNA from the results of the liver biopsy performed before transplantation, led us to hypothesize that the hematologic compartment could have been the site for viral persistence. Thus, the conditioning regimen may have depleted the hemic cells and the hematologically compartmentalized TTV. The potential of hemic tropism of TTV and its role in hematologic diseases need to be considered.

Biopsy↗
PubMed2001

Relationship between birthweight and repeated courses of antenatal corticosteroids.

A retrospective study was conducted in a university teaching hospital to review the association between birthweight and the number of courses of antenatal corticosteroids received in 236 singleton pregnancies. Those pregnancies complicated with pregnancy-induced hypertension, preeclampsia, diabetes mellitus and intrauterine growth restriction were excluded. The results showed that the birthweight ratio (calculated as the baby's birthweight divided by the median birthweight for that gestational age) was negatively correlated with the number of courses of corticosteroids received. Further, exposure to four or more courses of antenatal corticosteroids was associated with a significant reduction in birthweight ratio and a three-fold increase in the risk of being small-for-dates compared to those exposed to one to three courses.

Birth Weight↗
PubMed2001

Pyometra. What is its clinical significance?

OBJECTIVE: To evaluate the clinical outcomes of pyometra. STUDY DESIGN: Retrospective study conducted between 1993 and 1999 in two regional hospitals. RESULTS: Pyometra represented 0.038% of gynecologic admissions. Of the 27 women with pyometra, 6 (22.2%) cases were associated with malignancy, 1 (3.7%) was associated with genital tract abnormality, and 20 (74.1%) were idiopathic. Patients with idiopathic pyometra tended to be older and had a higher incidence of concurrent medical conditions. Five (18.5%) women experienced spontaneous perforation of pyometra. A preoperative diagnosis was correctly made in 17 of 22 (77.3%) patients without spontaneous perforation. Most women were treated with dilatation of the cervix and drainage. Nine women (33.3%) had persistent or recurrent pyometra; three of them were asymptomatic. CONCLUSION: Pyometra is an uncommon condition, but the incidence of associated malignancy is considerable, and the risk of spontaneous perforation is higher than previously thought. Dilatation and drainage is the treatment of choice, and regular monitoring after initial treatment is warranted to detect persistent and recurrent disease.

Adult↗
PubMed2000

Complications of laparoscopic surgery for benign ovarian cysts.

STUDY OBJECTIVE: To assess complications of laparoscopic surgery in the management of ovarian cysts. DESIGN: Prospective observational study (Canadian Task Force classification II-2). SETTING: University-affiliated hospital. PATIENTS: Consecutive patients (513) undergoing laparoscopic surgery for ovarian cysts not suspected to be malignant. INTERVENTION: Laparoscopic surgery. MEASUREMENTS AND MAIN RESULTS: A total of 587 ovarian cysts were removed from 513 women. Conversion to laparotomy was necessary in five cases (<1%). Mean +/- SD cyst diameter was 5.5+/-2.9 cm, with endometriomas (44. 5%) and dermoids (24.3%) being the two most common pathologies; 6.6% were functional. Mean +/- SD operating time was 69+/-31 minutes, and hospital stay and postoperative convalescence was 2.6+/-1.5 and 14.3 +/-9.6 days, respectively. The overall complication rate was 13.3%. Major complications occurred in three patients (0.6%): one small bowel injury and two ureter injuries. Cannula site complications were five inferior epigastric vessel injuries and four incisional hernias at the 10-mm lateral port site. CONCLUSION: Laparoscopic ovarian surgery was associated with 13.3% complications, with 0.6% being major. Careful patient selection and proper surgical training are critical to ensure safe performance of laparoscopy.

Adult↗
PubMed2000

The role of outpatient diagnostic hysteroscopy in identifying anatomic pathology and histopathology in the endometrial cavity.

STUDY OBJECTIVE: To evaluate the role of outpatient diagnostic hysteroscopy. DESIGN: Retrospective review (Canadian Task Force classification II-2). SETTING: University teaching hospital-based outpatient clinic. PATIENTS: One thousand six hundred women, 67.3% premenopausal and 32.7% postmenopausal. INTERVENTION: Diagnostic hysteroscopy without premedication or anesthesia; endometrial sampling or hysteroscopy-guided biopsy was performed when appropriate. MEASUREMENTS AND MAIN RESULTS: Outpatient hysteroscopy was successfully performed in 1468 women (91.8%). Eleven women (0. 7%) developed vasovagal response during the procedure, 18 required hospital admission because of pain or hemorrhage, and 2 were suspected of having uterine perforation. All recovered spontaneously without intervention. Intrauterine anatomic pathology was diagnosed in 17.0%; the overall frequency of myomas and endometrial polyps was 12.3% and 7.1%, respectively. The sensitivity and positive predictive value of hysteroscopy without biopsy in diagnosing endometrial carcinoma were only 58.8% and 20.8%, respectively. Of 1112 women with hysteroscopic impression of normal or atrophic endometrium, 10 (0.9%) had endometrial hyperplasia on biopsy. CONCLUSION: Hysteroscopy without biopsy carries low sensitivity and positive predictive value in the diagnosis of endometrial carcinoma and hyperplasia. In our opinion the predictive value of a negative hysteroscopy is inadequate, and endometrial biopsy should be performed during hysteroscopy for accurate diagnosis of endometrial histopathology.

Adult↗
PubMed2000

Incidence, risk factors and outcome of varicella-zoster virus infection in children after haematopoietic stem cell transplantation.

We report a retrospective analysis of VZV infection after haematopoietic stem cell transplantation (HSCT) in children. Thirty-three (30%) of the total 109 children who were transplanted during a 7 year period developed post-transplant VZV infection. Twenty-four of these 33 (73%) children had VZV infection within 1 year following HSCT. The cumulative incidences of post-transplant VZV infection at 1 and 5 years were 26% and 45%, respectively. The positive and negative predictive values of pretransplant VZV serology in recipients on the development of HZ following HSCT were 39% and 88%, respectively. Pretransplant VZV seropositivity in recipients was the only risk factor for post-transplant herpes zoster (HZ) infection on multivariate analysis. All patients responded to acyclovir. The median duration of VZV infection was 5 days. Three (11%) and one (3%) children with HZ developed visceral dissemination and post-herpetic neuralgia, respectively. No mortality was directly attributed to VZV infection. VZV infection remains a major cause of morbidity in children after HSCT. Further studies are warranted to evaluate the potential use of VZV vaccine in these children. Bone Marrow Transplantation (2000) 25, 167-172.

Acyclovir↗
PubMed2000

Early iron reduction programme for thalassaemia patients after bone marrow transplantation.

Thirty thalassaemia patients received iron reduction starting at around 3 months post transplant. Sixteen received desferrioxamine and nine had phlebotomy, five patients had desferrioxamine followed by phlebotomy. The desferrioxamine group had higher serum ferritin levels at the start of iron reduction as compared to the phlebotomy group (5292 vs 2453 microg/l, P EQ 0.001). After 444 and 407 days of iron reduction, serum ferritins at cessation of iron reduction in both groups was similar (665 vs 588 microg/l). The rate of decline of serum ferritin in both groups was similar. There was no graft rejection during the programme. Early institution of iron reduction in ex-thalassaemia is safe.

Adolescent↗
PubMed2000

Single vs twice daily G-CSF dose for peripheral blood stem cells harvest in normal donors and children with non-malignant diseases.

The optimal dose and schedule of G-CSF for mobilization of peripheral blood stem cells (PBSC) is not well defined. G-CSF mobilization was performed in a group of healthy donors and paediatric patients for autologous back-up before receiving allogeneic stem cell transplant. Seventeen consecutive subjects who received G-CSF at 5 microg/kg/dose twice daily (group A) were compared with a historical control group of 25 subjects who received a single daily dose of 10 microg/kg/day G-CSF (group B). Double blood volume apheresis for PBSC collection was started on day 5. G-CSF was continued and apheresis repeated until the targeted CD34+ cell dose was achieved. Both groups were comparable for sex, age, body weight and reason for PBSC collection. Over two-thirds of the subjects in both groups were less than 16 years of age. The G-CSF priming and apheresis were well tolerated. When the first day apheresis products were analyzed, group A resulted in significantly higher yield of total nucleated cells (5.91 vs 3.92 x 108/kg, P = 0. 013), mononuclear cells (5.73 vs 3.92 x 108/kg, P = 0.017), CD34+ cells (2.80 vs 1.69 x 106/kg, P = 0.049) and colony-forming units (107 vs 54 x 104/kg, P = 0.010) as compared with group B. We conclude that the two dose schedule is more efficient in mobilizing PBSC in normal donors and children with non-malignant diseases. This approach may reduce the number of aphereses required and thus reduce the transplant cost.

Adolescent↗
PubMed2000

Umbilical cord blood transplantation for Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI).

Severe Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI) is usually fatal by early adulthood. Bone marrow transplantation is the only form of definitive enzyme replacement therapy available. A 5-year-old boy with Maroteaux-Lamy syndrome has successful recovery of bone marrow and enzymatic functions after umbilical cord blood transplant from his unaffected HLA-identical brother. Busulphan (16 mg/kg) and cyclophosphamide (200 mg/kg) were used as preparative chemotherapy with short methotrexate and long cyclosporin as prophylaxis against graft-versus-host disease (GVHD). A total of 6.08 x 10(7)/kg nucleated cells and 2.92 x 10(5)/kg CD34+ cells were transplanted with neutrophil engraftment achieved on day 26. There was no evidence of acute and chronic GVHD. Fifteen months after transplant, a normal level of N-acetylgalactosamine-4-sulphatase activity was achieved despite mixed chimerism. There was clinical improvement of hepatosplenomegaly, facial and skin features, joint mobility and resolution of suppurative middle ear effusion. He returned to school and continued to perform well in academic studies. We report here the first successful umbilical cord blood transplant as treatment of Maroteaux-Lamy syndrome.

Adult↗
PubMed2000

Expression of interleukin (IL) 1 type I and type II receptors in megakaryocytic cells and enhancing effects of IL-1beta on megakaryocytopoiesis and NF-E2 expression.

Megakaryocytopoiesis is regulated by thrombopoietin (TPO) and cytokines such as interleukin 3 (IL-3), IL-6 and IL-11. This study investigated the in vitro effects of IL-1beta on megakaryocytopoiesis and the expression of IL-1 type I and type II receptors (IL-1 RI and RII) on mega-karyocytic cell lines and primary cells. Our results demonstrated that IL-1beta alone or in combination with TPO induced megakaryocyte colony forming units (CFU-MK) from murine and human haematopoietic cells. Using reverse-transcription polymerase chain reaction (RT-PCR) and Southern hybridization techniques, the mRNA of IL-1beta, IL-1 RI, IL-1 RII and the transcription factor NF-E2 were detected in CD61+ CD41+ cells cultured from cord blood and four megakaryocytic cell lines, Meg-01, DAMI, CHRF-288-11 and M-07e. The expression of IL-1 RI and RII proteins was confirmed by flow cytometry and immunofluorescence staining. In Meg-01 cells, the expression of NF-E2 was increased at both mRNA and protein levels after treatment with IL-1beta for 4 h. This study demonstrated for the first time the presence of IL-1 receptors on megakaryocytic cells and the induction of NF-E2 by IL-1beta. The mitogenic effect of IL-1beta on this lineage could be mediated through IL-1 receptors and the activation of NF-E2.

Analysis of Variance↗
PubMed2000

A randomised double-blind placebo-controlled trial of transcervical intrauterine local anaesthesia in outpatient hysteroscopy.

OBJECTIVE: To assess whether transcervical intrauterine instillation of local anaesthetic agent reduces pain during diagnostic outpatient hysteroscopy and endometrial biopsy. DESIGN: Prospective, randomised, double blind, placebo-controlled trial. SETTING: Outpatient hysteroscopy clinic in a university teaching hospital. POPULATION: Ninety women undergoing outpatient diagnostic hysteroscopy with or without endometrial biopsy. METHODS: Transcervical intrauterine instillation of 5 mL of 2% lignocaine into the uterine cavity before performing the procedure. MAIN OUTCOME MEASURES: Evaluation of pain at different stages of the procedure using a visual analogue scale and changes in blood pressure and heart rate. RESULTS: The use of local anaesthetic did not alleviate pain experienced during hysteroscopy and endometrial biopsy. It did not prevent the occurrence of vaso-vagal reactions; however the incidence of these was low. CONCLUSIONS: Transcervical instillation of local anaesthesia neither reduced pain nor prevented vaso-vagal reaction during hysteroscopy and endometrial biopsy.

Administration, Topical↗
PubMed2000

Small bowel herniation through subumbilical port site following laparoscopic surgery at the time of reversal of anesthesia.

Incisional hernias through laparoscopic trocar sites are unusual complications of laparoscopy. Two cases of small bowel herniation at subumbilical port site occurred at the time of withdrawal of the trocar sheath at the end of the laparoscopic procedure are reported. The herniations were precipitated by the coughing movements of the patients as a result of too early reversal of the general anesthesia. Awareness of the complication, precaution at time of sheath withdrawal and a well-timed reversal of the general anesthesia are important in avoiding such a complication.

Adult↗