PubMed Health⌕ Search

Biomedical subjects

M C Poon

Publications and source records attributed to M C Poon.

124 records · Page 7Linked to original sources
PubMed1979

Pseudochloroma: extramedullary hematopoietic nodules in chronic myelogenous leukemia.

Five patients with chronic myelogenous leukemia had multiple hemorrhagic soft tissue lesions at the time of diagnosis. Histologic examination of tissue removed by biopsy and at autopsy revealed extramedullary hematopoietic nodules with associated hemorrhage and necrosis. No evidence of either blastic transformation or systemic bleeding diathesis was found. Pseudochloroma is a treatable although potentially fatal complication of uncontrolled chronic myelogenous leukemia and should not be confused with myeloblastomas occurring with blastic transformation. Early recognition of the syndrome, prompt treatment with intensive chemotherapy, and radiation therapy of intracranial lesions seem to provide effective control of this complication and reversion to a status that is responsive to conventional treatment of chronic myelogenous leukemia.

Adult↗
PubMed1978

Human plasma prekallikrein (Fletcher factor) clotting activity and antigen in health and disease.

Human plasma prekallikrein (Fletcher factor) clotting activity and antigen levels have been examined in various clinical conditions. Prekallikrein antigen was measured by a newly developed, specific, and sensitive radioimmunoassay. The assay had no demonstrable cross-reactivity with human urinary kallikrein nor, in the species tested, animal plasma prekallikrein. This assay was able to measure plasma kallikrein after its biological functions had been inactivated by plasma inhibitors. Normal human pooled plasma contained approximately 50 microgram/ml prekallikrein. Quantitative measurement of plasma prekallikrein was possible for concentrations as low as 0.3% of that of normal pooled plasma. A good correlation (correlation coefficient = 0.71) existed between titers of plasma prekallikrein measured by Fletcher factor clotting assays and radioimmunoassays among 40 normal subjects. Both prekallikrein clotting activity and antigen were significantly reduced in plasmas of patients with advanced hepatic cirrhosis or DIC. Prekallikrein activity and antigen were mildly decreased in plasmas or serums of patients with chronic renal failure and nephrotic syndrome but were normal in those of patients under treatment with warfarin or suffering from SLE, rheumatoid arthritis, sarcoidosis, or HANE. Human cord serum contained a lower titer of prekallikrein antigen than adult serum. Strenuous physical exercise did not significantly change plasma prekallikrein levels.

Animals↗
PubMed1977

Techniques for demonstration of the specificity of circulating anticoagulants against antihemophilic factor (factor VIII), with studies of two cases possibly related to diphenylhydantoin therapy.

Circulating anticoagulants against antihemophilic factor (AHF, factor VIII) sometimes seem to inactivate other clotting factors as well. Measurements of the concentration of clotting factors in highly diluted plasma, or after neutralization of the anticoagulant with purified AHF, have demonstrated the specific nature of the anticoagulant in a patient under treatment with diphenylhydantoin. A second case in a patient treated with this agent, and with penicillin, an agent previously associated with the evolution of circulating anticoagulants, is also described.

Adult↗
PubMed1976

Immunologic evidence that the properties of human antihemophilic factor (factor VIII) are attributes of a single molecular species.

Preparations of human plasma rich in antihemophilic factor (AHF, factor VIII) correct the coagulative defect of classic hemophilic plasma, form precipitates with specific heterologous antiserum, and support aggregation of platelets by ristacetin and retention of platelets by columns of glass beads. Whether these various properties can all be attributed to a single molecular species is disputed. Antiserums were prepared in rabbits to partially purified AHF and to high molecular weight (MW) and low MW fragments separated by gel filtration through columns of agarose in the presence of 0.25 M calcium chloride. Antiserums to AHF and to its high or low MW fragments all inactivated procoagulant AHF in plasma or in preparations of AHF. In contrast, antiserums to AHF and its low MW fragment inactivated procoagulant AHF in the low MW fragment, while that against the high MW fragment lacked this property. Thus, the low MW fragment appeared to have some antigenic sites not present or accessible to the antiserum against the high MW fragment. In agreement with this, the low MW fragment did not block antiserum against the high MW fragment as tested by the capacity of this antiserum to inactivate functional AHF in plasma. These immunologic studies support the view that the various properties of preparations of human AHF are attributes of a single molecular species.

Absorption↗
PubMed1976

Evidence that functional subunits of antihemophilic factor (Factor VIII) are linked by noncovalent bonds.

Partially purified human antihemophilic factor (AHF, factor VIII), when treated with high concentrations of salt, has been shown to dissociate into two components: one, of relatively low molecular weight, possesses procoagulant activity, and the other, of higher molecular weight, forms precipitates with heterologous antiserum against AHF and supports ristocetin-induced platelet aggregation. The ease of separation suggests that the two components in the native state might be held together by noncovalent bonds. Earlier observations do not exclude the possibility that the subunits may be covalently bonded in nature but might be severed by plasma proteolytic enzymes during laboratory manipulation. The issue was examined by preparing partially purified AHF from fresh human plasma in the presence of protease inhibitors, including benzamidine, soybean trypsin inhibitor, epsilon-aminocaproic acid, heparin, and hirudin. Under these conditons, gel filtration in the presence of 0.25 M calcium chloride and 0.001 M benzamidine resulted in its separation into two components, having properties identical to those separated in the absence of these protease inhibitors. The inhibitor mixture blocked generation and action of streptokinase- and kaolin-activated plasmin from plasma, and protected both plasma AHF and partially purified AHF from the action of thrombin. Surface-induced activation of PTA (factor XI) was partially inhibited, and that of Christmas factor (factor IX) was completely inhibited. This observation provides further evidence that in the native state the high- and low-molecular-weight components of preparations of antihemophilic factor are held together by noncovalent bonds.

Benzamidines↗
PubMed1975

Glutamic-pyruvic transaminase activity related to red blood cell age.

Red blood cell glutamic-pyruvic transaminase (GPT) phenotypes and catalytic activities were studied in normal subjects and in patients with various hemolytic syndromes associated with reticulocytosis. To assess the effect of cell age of GPT activity, young cells were separated from older cells by centrifugation, and the catalytic activities were compared. In normal blood, there was a progressive fall in GPT activity from the top layer (younger cells) to the bottom layer (older cells), with a mean ratio of 1.90 plus or minus 0.42. Similarly, in the blood of patients with reticulocytosis, the enzyme activity of the reticulocyte-rich layer was higher than that of the layer containing older cells (mean ratio 1.94 plus or minus 0.95).

Alanine Transaminase↗
PubMed1975

Heterogeneity of human circulating anticoagulants against antihemophilic factor (factor VIII).

The heterogeneity of human circulating anticoagulants against antihemophilic factor (AHF, factor VIII) observed in seven patients, both with and without classic hemophilia, was investigated by neutralization of their activity with antiserums directed to whole IgG and to lambda and kappa light chains. All seven anticoagulants were immunoglobulins. Six appeared to contain both kinds of light chains, although the dual light chain composition of two of these could be demonstrated only at high concentration of antiserum. In one circulating anticoagulant, light chain specificity could not be demonstrated with small amounts of antiserum, and with larger amounts, only lambda light chain specificity was revealed. Whether or not this circulating anticoagulant really contained a single light chain type could not be ascertained with our technique. The evidence presented suggested that circulating anticoagulant antibodies against AHF are polyclonal in nature.

Absorption↗
PubMed1973

Immunofluorescent staining of lung biopsy in fibrosing alveolitis.

There is a group of lung diseases, as yet of unknown cause, which are characterized by a pathologic picture of alveolar wall fibrosis with an intra-alveolar exudate containing large cells. A case is reported with this clinicopathological picture in which immunofluorescent studies of the biopsied lung tissue revealed no tissue-bound immunoglobulins, complement component (beta(1) C) or fibrinogen. The literature on the immunofluorescent studies of biopsied lung tissue in this group of lung diseases is reviewed. The reports are scant and varied, making it impossible to conclude that autoallergic mechanisms are solely responsible as the pathogenetic mechanism in this group of lung diseases.

Biopsy↗
PubMedDate not supplied

Quantitation of ABO mixed-cell populations by a peroxidase-anti-peroxidase immunoenzyme method.

The peroxidase-anti-peroxidase immunoenzyme method was applied to red blood cell ghosts for the detection of ABO mixed-red blood cell populations. Red blood cell ghosts produced by acid-glycine lysis eliminated previous problems due to distorted red blood cell and hemoglobin-associated peroxidase activity. Anti-A,B was used to discriminate between various mixtures of test cells in group O cells. The positive-stained minor population of test cells stained dark brown following application of the peroxidase-anti-peroxidase method and the nonreactive group O cells were counterstained light blue with Coomassie brilliant blue which facilitated quantitation. The expected and observed numbers of positive-stained cells per 1000 cells were not significantly different as computed by X2. As low as a 0.5 percent minor population in an ABO red blood cell mixture could be accurately quantitated by this method.

ABO Blood-Group System↗