Jan McDonagh

Detection of Malignant Tumors

Abstract A sensitive and specific blood test for cancer has long been sought. The water-suppressed proton nuclear magnetic resonance (NMR) spectrum of plasma is dominated by the resonances of plasma lipoprotein lipids. We measured the mean line widths of the methyl and methylene resonances, which were found to be correlated with the presence or absence of malignant tumors. Values for the average line width were lower in patients with cancer. We analyzed plasma from 331 people (normal controls, patients with malignant and benign tumors, patients without tumors, and pregnant patients); NMR analysis and measurement of line widths were blinded to diagnosis or patient group. The mean line width for 44 normal controls (±SD) was 39.5±1.6 Hz. For 81 patients with untreated cancer, demonstrated by biopsy, the line width was 29.9±2.5 Hz. Patients with malignant tumors were reliably distinguished from normal controls by this method (P<0.0001), and differed from patients with diseases that did not involve tumors (lin...

A Naturally Occurring Antibody That Inhibits Fibrin Polymerization

A 13-year-old girl with chronic aggressive hepatitis, postnecrotic cirrhosis, ulcerative colitis, and a coagulation defect acquired an antibody that specifically interfered with fibrin formation. We sought to characterize the antibody and determine the mechanism of its inhibitory activity. The patients purified fibrinogen was functionally normal; however, the antibody inhibited the self-assembly of fibrin and prolonged the clotting times of the patients plasma. This antibody, which belonged to the IgG class of immunoglobulins, acted early in the polymerization process to inhibit the association of fibrin monomers, as indicated by a prolonged lag time and a decreased slope in the polymerization curves. It did not inhibit fibrinopeptide cleavage or fibrin cross-linking. Affinity chromatography indicated that the antibody bound strongly to both fibrinogen and fibrin monomer.

Biosynthesis of Factor XIII A and B Subunits

Factor XIIIa (FXIIIa), the blood coagulation enzyme, functions as a transglutaminase to covalently stabilize fibrin clots by introducing γ-glutamyl-e-lysyl peptide bonds between fibrin molecules (for detailed reviews, see references 1 and 2). The FXIII proenzyme exists in two zymogenic forms.3 Extracellular or plasma FXIII is composed of two subunits, A(Mr =80,500)4 and B(M =76,500),5 associated non-covalently as a tetrameric complex, A2B2.6,7 Intracellular FXIII is a dimer of only A subunits, A2.6 The A chains in both zymogens are identical and contain the active center sulfhydryl group.7,8 Upon activation by thrombin in the presence of calciurn ions, both zymogens give rise to the same enzymatic activity, FXIIIa.8,9

Physical characterization of recombinant tissue plasminogen activator

Electron microscopic and physical-chemical properties of one- and two-chain tissue plasminogen activator (t-PA) were studied. The molecular weight of one-chain t-PA obtained by both sedimentation equilibrium and SDS-PAGE was estimated to be about 65,000, while both chains in the reduced two-chain form were in the range of 35,000-40,000. Sedimentation coefficients were identical for both forms of t-PA (S(0)20,w = 4.12). The two forms of t-PA were indistinguishable by electron microscopic analysis, which confirmed the sedimentation results, and showed that they were ellipsoidal and relatively compact. The major and minor axes were approx. 13 nm and approx. 10 nm and f/f0 was 1.36. The individual domains of t-PA are relatively small and are folded within the molecule, so that the overall appearance is globular.

Fibrinogen-Sepharose interaction with prothrombin, prethrombin 1, prethrombin 2 and thrombin

Binding of prothrombin, prethrombin 1, prethrombin 2 and thrombin to fibrinogen-Sepharose was studied. Thrombin and prethrombin 2 bound to fibrinogen-Sepharose, while prethrombin 1 and prothrombin did not. Bound thrombin and prethrombin 2 were recovered from the column by eluting with 0.1 M NaCl/0.05 M Tris-HCl buffer (pH 7.4). The affinity of thrombin and prethrombin 2 to fibrinogen-Sepharose depended on ionic strength and reached a maximum at 50 mm concentration. Prethrombin 2 interacts with fibrinogen as well as thrombin; and prothrombin fragment 1.2 is not important in the formation of this complex. Thus, prethrombin 2, which is a precursor of thrombin without measurable enzymatic activity and which lacks the single cleavage at Arg-322-Ile-323 present in thrombin, has the same or very similar structural conformation as thrombin and has the same macromolecular substrate recognition site. These results confirm the earlier results that active center is not necessary in fibrinogen-thrombin interaction.

Alteration of aliphatic lipid proton NMR linewidths by malignant tumors in guinea pigs

Water-suppressed proton nuclear magnetic resonance spectroscopy was used to observe plasma lipoprotein lipid methyl and methylene resonances from guinea pigs which had been injected with viable or heat-killed line 1 or line 10 tumor cells or sterile oil. It was shown that the widths of these resonances became significantly sharper as the number of tumor cells grew. Plasma from tumor-free control animals showed no change in the NMR linewidths. It is concluded that the changes observed reflect a specific host response to viable tumor cells, and in these models there is a reciprocal relationship between the number of viable tumor cells and the linewidths of plasma lipoprotein methyl and methylene resonances.