Prion proteins with different conformations accumulate in Gerstmann-Sträussler-Scheinker disease caused by A117V and F198S mutations.

Gerstmann-Sträussler-Scheinker disease (GSS) is characterized by the accumulation of proteinase K (PK)-resistant prion protein fragments (PrP(sc)) of approximately 7 to 15 kd in the brain. Purified GSS amyloid is composed primarily of approximately 7-kd PrP peptides, whose N terminus corresponds to residues W(81) and G(88) to G(90) in patients with the A117V mutation and to residue W(81) in patients with the F198S mutation. The aim of this study was to characterize PrP in brain extracts, microsomal preparations, and purified fractions from A117V patients and to determine the N terminus of PrP(sc) species in both GSS A117V and F198S. In all GSS A117V patients, the approximately 7-kd PrP(sc) fragment isolated from nondigested and PK-digested samples had the major N terminus at residue G(88) and G(90), respectively. Conversely, in all patients with GSS F198S, an approximately 8-kd PrP(sc) fragment was isolated having the major N terminus start at residue G(74). It is possible that a further degradation of this fragment generates the amyloid subunit starting at W(81). The finding that patients with GSS A117V and F198S accumulate PrP(sc) fragments of different size and N-terminal sequence, suggests that these mutations generate two distinct PrP conformers.

Extensive arachnoid ossification with associated syringomyelia presenting as thoracic myelopathy. Case report and review of the literature.

The authors present the case of progressive thoracic myelopathy caused by the extensive ossification of the arachnoid membrane and associated intramedullary syrinx. Based on their findings and results of the literature search, they describe a pathological basis for this rare condition, discuss its incidence and symptomatology, and suggest a simple classification for various types of the arachnoid ossification. They also discuss the magnetic resonance imaging features of arachnoid ossification and associated spinal cord changes. The particular value of plain computerized tomography, which is highly sensitive in revealing intraspinal calcifications and ossifications, in the diagnostic evaluation of patients with a clinical picture of progressive myelopathy is emphasized.

Misleading hepatitis C serology following administration of intravenous immunoglobulin.

Intravenous immunoglobulin (IVIG) is a blood derivative that is being evaluated for the prevention and treatment of numerous disorders. Recent studies have suggested beneficial effects from the prophylactic administration of IVIG to very-low-birth-weight neonates. A disadvantage of such therapy is misleading infectious disease serologic assays following administration of IVIG. The authors report a recent case in their neonatal intensive care unit of a 24-week gestational age girl with a misleading positive hepatitis C serology reaction following IVIG administration.

Familial protein S deficiency is associated with recurrent thrombosis.

Recent studies have demonstrated that protein C deficiency is associated with recurrent familial thrombosis. In plasma, activated protein C functions as an anticoagulant. This anticoagulant response requires a vitamin K-dependent plasma protein cofactor, referred to as protein S. Since the anticoagulant activity of activated protein C is dependent on protein S, we hypothesized that patients lacking functional protein S might have associated thrombotic disease. Two related individuals with otherwise normal coagulation tests are described whose plasma is not effectively anticoagulated with activated protein C. Addition of purified human protein S to their plasma restores a normal anticoagulant response to activated protein C. We have developed a rapid one-stage clotting assay for protein S to quantitate the level of protein S in their plasma. Plasma is depleted of protein S by immunoadsorption with immobilized antiprotein S antibodies. The resultant plasma responds poorly to activated protein C, but is effectively anticoagulated in a dose-dependent fashion upon addition of purified protein S or small quantities of plasma. The affected individuals possess less than 5% protein S activity. Using Laurell rockets, protein S antigen was detected in the plasma but was at reduced levels of 13 and 18% in the two individuals. When the barium eluate of the patient plasma was chromatographed on quaternary aminoethyl Sephadex, a single peak of protein S antigen devoid of protein S anticoagulant cofactor activity was detected early in the chromatogram. In contrast, the barium eluate from normal donors separated into two peaks, one emerging early and also devoid of anticoagulant cofactor, and the second peak with anticoagulant activity emerging later. The first peak of protein S antigen, from both the normal donor and the patient, chromatographed in the region of the complement component C4-binding protein-protein S complex. These studies suggest that protein S deficiency may result in recurrent thrombotic disease.

Determination of functional levels of protein C, an antithrombotic protein, using thrombin-thrombomodulin complex.

Protein C is a vitamin K-dependent plasma protein. Activated protein C is a potent anticoagulant and enhances blood clot lysis. We have developed a functional assay for protein C in human plasma. The measurement of protein C is accomplished by the addition of thrombomodulin, an endothelial-cell-associated cofactor for protein C activation, and thrombin in a 1:1 molar complex. The activated protein C formed in the plasma is immunoadsorbed with goat anti-human protein C IgG-agarose. The immunoadsorbed activated protein C retains the ability to hydrolyze chromogenic substrates, and after unbound plasma proteins are removed by washing, the bound activated protein C is quantitated by incubation with the substrate H-D-phe-pip-arg-p-nitroanilide (S-2238). Normal individuals have functional protein C levels of 3.9-5.9 micrograms/ml, with a mean value of 4.8 micrograms/ml. Individuals undergoing warfarin anticoagulation and patients with advanced liver diseases have decreased levels, as do certain patients with evidence of intravascular clotting. Functional protein C levels correlate well with immunologic levels of the protein in the patient groups studied. Heparin enhances the rate of activated protein C inhibition, as monitored by recovery of activated protein C by immunoadsorption. A patient with recurrent venous thrombosis and abnormal functional protein C activity, but normal levels of antigen, has been identified.