Biomedical subjects

M S Cheang

Publications and source records attributed to M S Cheang.

28 records · Page 2Linked to original sources

PubMed1989

A reassessment of the bleeding time: association of age, hematocrit, platelet function, von Willebrand factor, and bleeding time thromboxane B2 with the length of the bleeding time.

In order to provide an overview of the relative contribution of platelet, von Willebrand factor, and other abnormalities to patients with clinical bleeding difficulties, we performed a retrospective survey of coagulation studies on 569 individuals referred to the University of Manitoba coagulation laboratory because they, or a closely related family member, showed clinical evidence of a bleeding disorder. There was a highly significant (p less than 0.001) negative correlation between the bleeding time and each of the following parameters: the platelet count; the hematocrit; the percent aggregation to collagen, epinephrine, ADP, and arachidonic acid; and the logarithm of von Willebrand factor antigen and a measure of its activity (ristocetin cofactor). A significant and independent inverse relationship between the length of the bleeding time and the extent of platelet adhesion to glass beads, patient age, and prothrombin consumption were also observed. Multivariate analysis of the ability of all parameters to predict the bleeding time showed an r2 of only 0.33. Bleeding time thromboxane B2, in a second smaller study of 70 patients, showed a negative correlation with the length of the bleeding time (p = 0.0001), and, when used together with the above parameters, significantly enhanced the ability to predict the length of the bleeding time (r2 = 0.55). Defects in platelet function, as measured in vitro, and significant enough to have an effect on the bleeding time, occurred with greater frequency than defects in von Willebrand factor in the Manitoba patients evaluated.

Adolescent↗

PubMed1988

Increased nausea and vomiting induced by naloxone in patients receiving cancer chemotherapy.

To evaluate the role of endogenous opiates in chemo-therapy-induced nausea and vomiting, the narcotic-antagonist naloxone was administered to six pediatric patients receiving cancer chemotherapy. Naloxone was administered by continuous intravenous (i.v.) infusion after randomized, double-blind controlled assignment at a dose of 0, 10 or 40 micrograms/kg/h for 12 h. Each patient was studied for four consecutive and identical courses of chemotherapy (eight courses for each naloxone dose or 24 courses in all). A dose-related increase in nausea (nausea score 2.5 +/- 2.24, 3.83 +/- 2.73, and 5.75 +/- 2.86/12 h, p = 0.003), vomiting (emetic events 6.0 +/- 7.50, 8.08 +/- 6.71, and 10.3 +/- 8.91/12 h, p = 0.035), and patient aversion (course preference rank 1.5 +/- 0.45, 2.83 +/- 1.17, and 3.25 +/- 0.42/4 courses, p = 0.014) was observed. The infusion of naloxone in the absence of chemotherapy was without effect. These results support a role for endogenous opiates in regulating chemotherapy-induced nausea and vomiting, and further suggest that narcotic agents may be effective antiemetics in this setting.

Adolescent↗

PubMed1988

The relationship of brachiocephalic vessel atheroma to transient ischemia of the brain and retina.

The relationships between transient cerebral and retinal ischemic symptoms and brachiocephalic angiographic findings were studied in 464 patients. The arterial abnormalities were more often bilateral than the symptoms suggested. Normal angiographic appearances were common, although abnormal arteries in patients without related symptoms were also common. When stenosis of the carotid system was 75 per cent or more, there was a strong correlation with symptoms.

Adult↗

PubMed1987

1-Desamino-8-D-arginine vasopressin (desmopressin) decreases operative blood loss in patients having Harrington rod spinal fusion surgery. A randomized, double-blinded, controlled trial.

To evaluate the effect of 1-desamino-8-D-arginine vasopressin (desmopressin) on blood loss in surgery, we conducted a randomized, double-blind trial of the drug in 35 patients with normal hemostatic function who were having spinal fusion with Harrington rod instrumentation. Seventeen patients were designated to receive 10 micrograms/m2 of desmopressin, and 18, to receive a placebo. Preoperative testing showed that desmopressin increased factor VIII coagulant activity, von Willebrand antigen concentrations, glass bead platelet retention, and prothrombin consumption and decreased the partial thromboplastin and bleeding times (p less than or equal to 0.0003). During surgery, desmopressin reduced blood loss by 32.5% (547 mL; 95% confidence interval [CI], 19 to 1075; p = 0.015) and reduced the need for concentrated erythrocyte transfusions by 25.6% (0.86 units; 95% CI, 0.08 to 1.65; p = 0.022). After surgery, desmopressin reduced the duration of treatment with analgesic agents by 13.1% (34.0 hours; 95% CI, -5.2 to 72.7; p = 0.105), presumably by decreasing bleeding in the surgical wound. When adjusted for the origin of the scoliosis by two-way analysis of variance, this effect was even more evident (p = 0.014). Multiple regression analysis showed that the best three predictors of blood loss in surgery and transfusion requirements were the bleeding time, glass bead platelet retention, and the use of desmopressin.

Adolescent↗

PubMed1986

Comparison of adriamycin uptake in chick embryo heart and liver cells an murine L5178Y lymphoblasts in vitro: role of drug uptake in cardiotoxicity.

The mechanism of uptake of Adriamycin was investigated in chick embryo heart and liver cells and in murine L5178Y lymphoblasts in vitro. Drug uptake at 4 degrees C for 15 s due to rapid association accounted for a cell:medium distribution ratio of 104 +/- 14 (SE) in heart cells, 10.2 +/- 1.3 in liver cells, and 10.3 +/- 1.5 in L5178Y lymphoblasts. On thin-layer chromatographic analysis, 98% of the radioactivity migrated with the mobility of intact drug, suggesting that drug metabolism was negligible for at least 30 min in both heart and tumor cells. A time course of drug uptake was somewhat different in heart cells compared to that noted for liver or L5178Y cells. The steady state for drug uptake was reached more promptly in heart cells; apparent equilibrium was observed at 6 min in heart cells, at approximately 20 min in L5178Y lymphoblasts, but was not attained by 25 min in liver cells. Temperature dependence of drug uptake also differed in the three cell types; drug uptake was most temperature sensitive in L5178Y cells, intermediate in liver cells, and least temperature dependent in heart cells. Separation of heart, liver, and leukemic cells into membrane and cytosol fractions demonstrated that, at 1 and 30 min, more than 75% of the drug was associated with the membrane fraction. Trichloroacetic acid extraction of cell constituents revealed that, at 1 min, the acid-soluble fraction amounted to 32 +/- 2% of radioactivity in heart cells and 37 +/- 2% in L5178Y cells. Ethanol extraction of these cells demonstrated that, at 1 min, ethanol-soluble components accounted for 49 +/- 2% of radioactivity in heart cells and 27 +/- 2% in leukemic cells. The finding of a large component of rapid association together with evidence of prompt drug binding to cellular constituents made evaluation of unidirectional drug influx impractical. Accordingly, an investigation was undertaken of Adriamycin efflux from chick embryo heart and liver cells and L5178Y lymphoblasts, after the cells had been loaded with drug for various time intervals. In all three cell types, efflux was rapid down to a plateau level, representing nonexchangeable drug. As the period of time for loading cells was increased, there was a progressive rise in the level of nonexchangeable drug. Equilibration of the nonexchangeable pool occurred more rapidly in heart cells than in either liver or leukemic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1985

Absent factor VIII response to synthetic vasopressin analogue (DDAVP) in nephrogenic diabetes insipidus.

To study the effect of 1-deamino-8D-arginine vasopressin (DDAVP) on the factor VIII response in nephrogenic diabetes insipidus (NDI), 0.30 microgram/kg DDAVP was given to 2 unrelated NDI patients, 3 obligate carriers, and 20 controls. Factor VIII coagulant activity (FVIIIC) and factor VIII related antigen (FVIIIR:Ag) responses were absent in both NDI patients and were decreased by approximately 50% in the carriers by comparison with controls. These results show that the vasopressin receptor defect in NDI is not confined to the kidney but is equally expressed in other tissues including the vascular endothelium and hepatic sinusoids, the respective sites of FVIIIR:Ag and FVIIIC production. A decreased factor VIII response may help in identifying carriers in families at risk.

Adolescent↗

PubMed1984

Shortening of bleeding time by 1-deamino-8-D-arginine vasopressin in various bleeding disorders.

To evaluate the effect of 1-deamino-8-D-arginine vasopressin (DDAVP) in various bleeding disorders, 10 micrograms/m2 DDAVP was administered to subjects with von Willebrand disease (13), platelet function defects (12), von Willebrand disease and platelet defects together (8), or isolated prolongation of the bleeding time (5). DDAVP shortened the bleeding time similarly in all patient groups. Shortening of the bleeding time was also observed in 2 patients with aspirin-induced platelet defects and in 2 normal subjects. DDAVP administration was associated with falls in the platelet count, mean platelet volume, and partial thromboplastin time, and rises in platelet adhesion, factor VIII coagulant activity, factor VIII related antigen, and von Willebrand factor activity. The basal bleeding time was the only predictor of the magnitude of the bleeding-time correction. Normal haemostatis was achieved with DDAVP plus epsilon-aminocaproic acid and no blood product support during operations in 18 patients with bleeding disorders.

Adolescent↗

PubMed1984

Improved hemophilia A carrier detection by DDAVP stimulation of factor VIII.

We studied the differential increase in FVIIIc and FVIII R:Ag after the intravenous infusion of 0.30 micrograms/kg DDAVP in 20 obligate hemophilia A carriers and in 20 female controls. FVIIIc increased in carriers (59.5 +/- 23.1 to 137.5 +/- 45.9) and in controls (98.0 +/- 20.7 to 259.9 +/- 57.4) (P less than 0.001), but the magnitude of the FVIIIc increase in carriers was less than that in controls by 51.9% (P less than 0.001). FVIII R:Ag increased comparably in carriers (105.2 +/- 30.4 to 171.9 +/- 25.4) and controls (92.1 +/- 33.0 to 165.2 +/- 20.6). Using the post-DDAVP instead of the standard FVIIIc/FVIII R:Ag ratio, hemophilia carrier detection was increased from 85% (with 10% false positive and 20% false negative assignments) to 95% (with 5% false positive and 5% false negative assignments). Toxicity associated with DDAVP infusion correlated linearly with doses greater than 10.5 +/- 1.3 micrograms/m2 (P less than 0.02) and with total doses greater than 17.0 +/- 4.5 micrograms (P less than 0.02). The use of DDAVP improves carrier detection in factor VIII-deficient hemophilia.

Adolescent↗

PubMedDate not supplied

How Baby-Friendly are Manitoba hospitals? The Provincial Infant Feeding Study. Breastfeeding Promotion Steering Committee of Manitoba.

The Breastfeeding Promotion Steering Committee of Manitoba conducted the cross-sectional Provincial Infant Feeding Study in 1996 to examine: correlation between breastfeeding policies and actual practices in Manitoba hospitals; compliance with Baby-Friendly Hospital Initiative (BFHI) criteria; and associations between hospital practices and two-week breastfeeding duration. Three separate surveys obtained information from: administrators concerning hospital policy; nursing staff concerning hospital practices; and all women giving birth in a five-week period, concerning breastfeeding rates and maternal perceptions of hospital practices. The results highlighted the need for policy and practice changes to comply with BFHI criteria. 92% initiated breastfeeding, and 84% were breastfeeding at two weeks postpartum. Independent predictors of weaning included: in-hospital supplementation (adjusted RR = 2.1, 95% CI 1.02-4.36, p = 0.04); temporarily interrupting breastfeeding while in hospital (adjusted RR = 4.9, 95% CI 2.7-8.9, p = 0.0001); no previous breastfeeding experience (adjusted RR = 2.5, 95% CI 1.4-4.4, p = 0.002); and Grade 12 or less maternal education.

Adult↗

PubMedDate not supplied

MSAFP levels in aboriginal Canadian women.

Maternal serum alpha-fetoprotein (MSAFP) levels in 529 non-diabetic aboriginal Canadian women were compared with levels in 13,285 non-diabetic non-aboriginal women. A woman was considered to be aboriginal if she was listed on the Indian Register of Canada. After controlling for the gestational age on the date at which the sample was drawn and maternal weight, MSAFP levels appeared to be approximately 4 to 5% higher in aboriginal women. The possible implications of this finding on an MSAFP screening program are discussed.

Adult↗