Diagnosis of acute megakaryoblastic leukemia by flow cytometry and immunoalkaline phosphatase techniques. Utilization of new monoclonal antibodies.

This report demonstrates a case of acute megakaryoblastic leukemia evolving in a patient with idiopathic myelofibrosis with myeloid metaplasia. A presumptive diagnosis was made by cytochemical stains, alpha-naphthyl acetate esterase, and alpha-naphthyl butyrate esterase. The diagnosis was established by electron microscopic platelet peroxidase studies of the peripheral blood blast cells and supported by flow cytometry and immunoalkaline phosphatase studies. Specific monoclonal antibodies directed against platelet glycoproteins Ib (6D1) and IIb/IIIa (10E5), which have not been described frequently in analyzing leukemia, were used for flow cytometry and direct immunoalkaline phosphatase technique. Cytogenetic studies demonstrated a deletion of the long arm of chromosome 6 with breakpoints at bands q15 and q23, and ring chromosome 6 (p25, q27). The diagnosis of megakaryoblastic leukemia requires accurate cytochemical stains, platelet peroxidase by electron microscopic examination, and studies employing specific monoclonal antibodies directed against platelets and megakaryoblasts. The exact origin of the circulating megakaryoblasts in these cases is not known and needs additional investigation.

Fibronectin concentration in plasma of patients with breast cancer, colon cancer, and acute leukemia.

Plasma fibronectin was measured in patients with breast cancer, colon cancer, and acute leukemia. In the patients with solid tumors, mean levels were significantly elevated above the mean level of age- and sex-matched normals whether the disease was thought to be metastatic or not (P less than 0.001). It did not make a difference whether the determinations were done prior to or during chemotherapy. Fibronectin was measured serially in eight hospitalized patients with leukemia during intensive induction chemotherapy. Normal concentrations were found prior to therapy. However, fibronectin concentration fell on the day following chemotherapy in nine of 12 episodes (P less than 0.05), and during sepsis in 13 of 13 episodes (P less than 0.001). Thus, the concentration was influenced by at least two factors: recent chemotherapy and sepsis. Because fibronectin concentration is sensitive to clinical events other than the status of the malignancy, it seems unsuitable as a tumor marker, at least as a single isolated measurement.

Observations of colloidal gold labelled platelet microtubules: high voltage electron microscopy and low voltage-high resolution scanning electron microscopy.

18 nm colloidal gold-antitubulin and 4 nm colloidal gold-antitubulin were used to label microtubules in adherent, fully spread platelets. Both sizes of marker effectively labelled microtubules in the partially extracted platelets. However only the 4 nm gold penetrated the dense microfilament matrix of the inner filamentous zone so that portions of microtubules within this cytoskeletal zone could be tracked. The gold marker could be visualized well with 1 MeV high voltage transmission EM and with 5 kV or greater secondary imaging or 20 kV backscattered imaging of carbon only coated samples. 1 kV secondary imaging permitted high resolution imaging of the surface of tubules and the microfilaments with their respective associated material. Individual gold-antibody complexes were difficult to identify by shape alone due to the tendency of the antibody coats to blend together when in very close approximation and due to the presence of other molecules or molecular aggregates similar in size to the gold-antibody labels. Microtubules were seen to wind in and out of the inner and outer filamentous zones as they encircled the granulomere. Some tubules were seen to "dead end" at the peripheral web. Numerous smaller microtubule loops were present principally in the outer filamentous zone and tubules could be followed as they went from the outer filamentous zone through the inner filamentous zone and into the granulomere.

Action of thrombin on surface glycoproteins of human platelets.

We labeled surface glycoproteins of human platelets by the neuraminidase-galactose oxidase/borotritiide and the periodate/borotritiide methods. When labeled platelets were treated with 1-nM thrombin, a minor glycoprotein weighing 68,000-85,000-d was lost from the surface, and a soluble glycoprotein weighing 57,000-68,000-d was found in the supernatant. Treatment of platelets with ADP, collagen, or the calcium ionophore A23187 did not cause loss of the 68,000-85,000-d glycoprotein from platelet surfaces or appearance of the 57,000-68,000-d glycoprotein in the supernatant. However, trace amounts of the intact 68,000-85,000-d glycoprotein were found in the supernatants of platelets that were not treated with thrombin. The numerous effects of thrombin on platelets could be initiated by cleavage and release the thrombin-sensitive glycoprotein.