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Biomedical subjects

M C Poon

Publications and source records attributed to M C Poon.

At least 109 records · Page 6Linked to original sources
PubMed1982

Platelet factor four and protamine sulfate neutralization of heparin fractionated according to anionic charge density.

The role of heparin structure in neutralization by the neutralizing substances (NS) platelet factor 4 (PF4) and protamine sulfate (PS) was investigated using a thrombin clotting assay and a series of more homogeneous heparin fractions varying systematically in charge density (Z). For a given heparin, plotting inverse clotting times measured without NS, and in the presence of PF4 or PS, vs heparin concentration yielded approximately parallel straight lines displaced horizontally according to the amount of NS. Potencies of heparin fractions in the absence of NS, or in the presence of PF4 of PS, depended almost identically upon Z2. Small but significant quantitative differences in potency among equivalent fractions from different heparins showed both PF4 and PS had a slight preference for the least active subfraction of decolorized heparins, but for the most active subfraction of undecolorized heparins. Neutralization of heparin by PF4 and PS probably proceeds by similar mechanisms, but the details of structure outside the antithrombin III-binding oligosaccharide of heparin may enter in differently.

Animals↗
PubMed1982

Heterogeneity in the composition of commercial heparins: comparison of anticoagulant activities and biochemical compositions of anionic density-fractionated heparins.

In this study the nature of compositional heterogeneity in commercial heparins was investigated. Five hog-mucosal (HM) and one beef-lung (BL) heparin were subjected to partition fraction in a two-phase system of 1-butanol containing hexadecylpyridinium chloride/aqueous NaCl, a system which fractionates heterogeneous heparins larger than 10,000 daltons according to anionic density. The heparins differed markedly in purity as determined by both the galactosamine content of the unfractionated preparations and the amount of uronate extracted at lower NaCl concentrations in the fractionation scheme. All fractions afforded linear plots of the logarithm of clotting time vs heparins concentration in the APTT assay with human plasma, thereby permitting measurement of concentration--independent specific activities. Equivalent fractions from different HM heparins had similar compositions, and with the exception of an unbleached sample, had equivalent specific APTT anticoagulant activities. These latter were linearly related to the square of anionic density. In contrast, the BL heparin behaved quite differently. Its most abundant fractions were extracted at higher NaCl concentrations than was the case for HM heparins, little systematic variation in anionic density was observed, and its fractions had much lower specific activities than equivalent HM fractions.

Animals↗
PubMed1982

Severe Fletcher factor (plasma prekallikrein) deficiency with partial deficiency of Hageman factor (factor XII): report of a case with observation on in vivo and in vitro leukocyte chemotaxis.

A case of cross-reacting material-negative Fletcher trait with additional partial deficiency of Hageman factor (HF, Factor XII) is described. Although the patient presented with a recent history of frequent epistaxis, he had no other personal or family history of a tendency toward bleeding or infection. Similar to other cases of Fletcher trait, his plasma showed a markedly prolonged partial thromboplastin time which could be corrected by prolonged incubation with the surface-activator kaolin. Surface-induced fibrinolysis, amidolysis of alpha-N-benzoyl-proline-L-phenylalanine-L-arginine-p-nitroanilide, and cold-promoted enhancement of factor VII activity, reactions requiring the presence in the plasma of fletcher factor (prekallikrein), in addition to Hageman factor and Fitzgerald factor (high-molecular weight kininogen), were also defective. In vivo chemotaxis of polymorphonuclear leukocytes and monocytes (Rebuck's skin window technique) in response to skin abrasions was defective, but was normal when diphtheria-tetanus toxoid was also applied. In vitro leukocyte chemotaxis (Boyden chamber technique) in response to normal or patient's own serum activated with zymosan was normal. Together with previous observations that kallikrein generated chemotactic activity, possibly via activation of C5, the present observations suggest that prekallikrein activation may be important for in vivo leukocyte chemotactic response to skin abrasion. The inheritance of Fletcher trait in this patient is unclear.l Although the father was an apparent heterozygote, the mother was completely normal for Fletcher factor procoagulant activity and antigen. The mild Hageman factor deficiency in the patient did not contribute significantly to the plasma defects described and was likely inherited from the father who had a low HF procoagulant activity.

Blood Coagulation↗
PubMed1982

Inflammatory fibrous histiocytoma: an important variant of malignant fibrous histiocytoma highly responsive to chemotherapy.

Inflammatory fibrous histiocytoma is a recently recognized variant of malignant fibrous histiocytoma. Patients managed with surgical excision or radiation therapy usually have had multiple recurrences, often with metastases. The disease is insidious but ultimately fatal. Four consecutive patients were treated with inflammatory fibrous histiocytoma with alkylating agents with or without anthracyclines and produced prolonged and sustained remissions. Inflammatory fibrous histiocytoma may be another highly chemotherapeutically responsive tumor that deserves active case identification for aggressive curative therapy.

Adolescent↗
PubMed1981

Nonimmune interaction of leukocytes with platelets and megakaryocytes.

Platelet-leukocyte interaction was observed in an asymptomatic woman. After incubation in the patient's EDTA-plasma, autologous and allogeneic platelets adhered to the surfaces of neutrophils, monocytes, macrophages and, rarely, eosinophils. Monocytes, macrophages, and occasionally neutrophils phagocytosed platelets. Degranulation of peroxidase-positive lysosomes into the platelet-containing phagosome was demonstrated ultrastructurally. Bone marrow studies indicated that bands and earlier neutrophilic precursors did not participate in the reaction, and that neutrophils adhered to, and were rarely engulfed by megakaryocytes. Sequential exposure of the patient's EDTA-plasma to platelets and leukocytes indicated that a nondialyzable factor(s) was first absorbed by platelets which then interacted with leukocytes. The reaction proceeded best in the presence of EDTA at 21 degrees C, and was inhibited or dissociated by divalent cations or at 37 degrees C. Metabolic integrity of both platelets and leukocytes was also essential for the reaction since each was inhibited by formalin fixation and partially inhibited by the metabolic inhibitor 2-deoxyglucose. Formalin-treated platelets continued to absorb the plasma factor(s). The plasma and the cell fractions were inactivated by periodate and nonspecific protease. Treatment of the platelets with trypsin or the leukocytes with neuraminidase diminished the interaction by 50%. The reaction was also interfered with by concanavalin A. Immunofluorescent and immunoabsorption studies failed to identify an immune component of this interaction. These findings indicate that the plasma factor(s) and the cell surface receptors are nonimmune glycoconjugates and consequently differ from previously documented cases of platelet-leukocyte interaction.

Absorption↗
PubMed1981

Hemoglobin A1 in the diagnosis of chemical diabetes mellitus.

HbA1 was determined in 16 subjects with normal oral glucose tolerance test (OGTT), in 8 subjects with normal fasting plasma glucose (FPG) but with abnormal OGTT (chemical diabetes mellitus) and in 25 subjects with overt diabetes mellitus. The HbA1 values were 7.53 +/- 0.1%, 8.37 +/- 0.17% and 11.92 +/- 0.42% (+/- SEM), respectively. The HbA1 values of subjects with chemical diabetes mellitus were significantly higher (p less than 0.0025) than those of subjects with normal OGTT. Thus, the determination of HbA1 may prove to be useful to substantiate a significantly abnormal glucose tolerance (chemical diabetes mellitus).

Diabetes Mellitus↗
PubMed1981

Quantitation of plasma warfarin concentrations by high performance liquid chormatography.

A rapid, sensitive, and specific high performance liquid chromatographic (HPLC) method for the quantitative analysis of warfarin in plasma is described. The method involves an extraction from acidified plasma, removal of basic substances, and reextraction into ether. The method is sensitive (0.06-9.0 microgram/ml) and precise (coefficient of variation less than 2%) and makes use of a Bondapak C-18 column. Several methods have been reported for the analysis of warfarin; each has some disadvantage in terms of specificity, sensitivity, reproducibility, or convenience. A fluorometric method (1) was rapid, but in our hands was neither precise nor sensitive and yielded values consistently higher than the proposed method. An HPLC method (2) that incorporated a Permaphase column and dioxane as the mobile phase did not perform at all with a Bondapak C-18 column. Gas-liquid chromatography involved derivatization (3), which did not afford reproducibility in our laboratory. Two other published HPLC methods (4,5) showed interference from diazepam. The method described in this paper is specific, accurate, and convenient. It has sufficient sensitivity to measure low warfarin levels, is linear to 9 microgram/ml, and is free of interference by common drugs. The clinical utility of this method is illustrated with three case reports.

Adult↗
PubMed1980

Composite lymphoma: report of a unique case.

Composite lymphoma with more than one well demarcated non-Hodgkin's or Hodgkin's lymphoma in the same organ or mass is rare. Only 22 such cases, each with two lymphomas, have been reported. We describe a unique case in which there were three non-Hodgkin's lymphomas, according to the Rappaport's nomenclature, in the spleen and abdominal lymph nodes.

Abdominal Neoplasms↗
PubMed1980

Lymphoma simulating Crohn's colitis.

A patient with lymphomatous colitis whose disease mimicked Crohn's colitis has been presented. The diagnosis was not made despite multiple endoscopic biopsies. Lymphomatous colitis may produce a clinical and colonoscopic picture similar to Crohn's colitis.

Aged↗
PubMed1980

Plasma exchange in idiopathic thrombocytopenic purpura.

Two cases of adult-onset idiopathic thrombocytopenic purpura (ITP), refractory to conventional therapy, were treated. Because of recent successful reports of plasma exchange in ITP, this technique was performed on each patient. In both cases, the therapy was unsuccessful in controlling their disease, suggesting that in refractory adult-onset ITP, plasma exchange may not be an effective mode of therapy.

Adult↗
PubMed1979

Multiple myeloma masquerading as chromophobe adenoma.

A 62-year-old woman presenting with intracranial lesion eroding the sella with compression of optic chiasma was found to have plasmacytoma of the pituitary area. At the time of initial surgery, the patient had no biochemical, immunologic or marrow findings of multiple myeloma. The intracranial tumor was interpreted initially as chromophobe adenoma on light microscopy, but the diagnosis of plasmacytoma was established by electron microscopic examination of the tumor. The case illustrates the usefulness of electron microscopy as a diagnostic tool.

Adenoma, Chromophobe↗
PubMed1979

Giant platelet granules in a child with the Chediak-Higashi syndrome.

Previous ultrastructural investigation have not identified abnormal lysosomes in platelets obtained from humans or animals with the Chediak-Higashi Syndrome. We report here a patient whose megakaryocytes and platelets were found to contain giant granules when viewed by light and electron microscopy. The granules measured up to 1.5 micrometer in diameter, contained either homogeneous or heterogeneous material, were acid phosphatase positive, and were present in approximately 30% of bone marrow megakaryocytes and 5% of circulating platelets. A decrease was observed in serotonin containing dense granules, serotonin uptake and serotonin release as reported previously. Microtubules in platelets and megakaryocytes were intact and no other morphologic abnormalities were identified. No clinical evidence of bleeding was observed in this patient and platelet counts have been normal. The lack of giant platelet lysosomes in other reported cases of Chediak-Higashi Syndrome attests to significant heterogeneity in this disease with a spectrum of clinical and laboratory findings.

Adenosine Diphosphate↗
PubMed1979

Inflammatory fibrous histiocytoma: response to non-surgical therapy: a case report.

A case of inflammatory fibrous histiocytoma arising in soft tissue near the sacrum is presented. The patient's mode of presentation, clinical course, and tumor histology were typical of this disease. The tumor was inoperable, and radiotherapy combined with doxorubicin, cyclophosphamide, and intermediate-dose oral methotrexate produced a dramatic complete response lasting over 27 months. Favorable results with nonsurgical therapy have not previously been reported for this disease. The gratifying result obtained, although of relatively short duration to date, indicates that combined modality therapy may provide significant back-up to aggressive surgery. The use of these agents in an adjuvant setting merits study.

Adult↗