Human alpha- to zeta-thrombin cleavage occurs with neutrophil cathepsin G or chymotrypsin while fibrinogen clotting activity is retained

Human neutrophil cathepsin G or bovine chymotrypsin proteolytically cleaved human alpha-thrombin at the B-chain Trp148-Thr149 bond generating a new form, zeta-thrombin. While incubation of alpha-thrombin with cathepsin G at pH 7.4 and 37 degrees C resulted in a partial loss of fibrinogen clotting activity, 86 +/- 13% of the clotting activity and 99 +/- 16% of the active sites titratable with p-nitrophenyl p-guanidinobenzoate were retained upon controlled passage of alpha-thrombin through chymotrypsin-Sepharose 4B at pH 6.2 or 7.4 and 24 degrees C (n = 15). Kinetic parameters for H-D-hexahydrotyrosyl-Ala-Arg p-nitroanilide were Km = 1.52 +/- 0.60 vs 1.32 +/- 0.18 microM and kcat = 51.9 +/- 2.9 vs 35.8 +/- 6.4 s-1 with alpha-thrombin vs chymotrypsin-prepared zeta-thrombin (n = 4 vs 3), respectively (I = 0.15 M, pH 7.4, and 24 degrees C). Some 95% of the clotting activity was lost when zeta-thrombin was passed through trypsin-Sepharose 4B under conditions for converting alpha- to nonclotting beta- and subsequently gamma-thrombin. The resulting gamma-like thrombins eluted bimodally with 260 and 310 mM NaCl when applied to Amberlite CG-50 resin [cross-linked poly(methylacrylic acid)] developed with a linear salt gradient in 50 mM Tris at pH 7.4 and 24 degrees C. These elution peaks correspond to 240, 330, and 350 mM NaCl for gamma-, alpha-, and zeta-thrombin, respectfully, implying that the anion-binding exosite is partially destroyed in gamma-like thrombins but is intact in zeta-thrombin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors restricting maximal preservation of neuronal glycogen after perfusion fixation with dimethyl sulfoxide and iodoacetic acid in Bouin's solution. Histochemical observations in the brain of the Netherlands dwarf rabbit

Thirty seconds after an initial intracardial epinephrine injection, deeply anesthetized animals are perfused consecutively with saline, Bouin's and 100% ethanol solutions, each containing 1% or 5% DMSO (Me2SO) and 0.01 M iodoacetic acid. In the Netherlands dwarf rabbit and the guinea pig, a maximal preservation of dimedone PAS-stainable, saliva-digestible glycogen is achieved, without signs of polarization of glycogen, in many neuronal and neuroglial cells occupying either brain stem nuclei or occasionally narrow perivascular zones. Tentatively, these results are ascribed to a combined effect of (a) the alleged capacity of DMSO to accelerate fixation and to suppress activation of adenylate cyclase and (b) the rapid action of Bouin's solution so that the glycogen particles become instantaneously enclosed in situ in a skeleton of coagulated proteinaceous elements. The paradoxical over-all reduction in preservation of neuronal and astrocytic glycogen may be associated either with a demonstrable loss of the fixative into the peripheral vasculature, because of contrary actions of DMSO and epinephrine, or with a transvascular passage of epinephrine resulting in neuronal glycogenolysis where the blood-brain barrier is absent or affected by DMSO. Other defects are the occurrence of myriad pericapillary foci of inadequate tissue preservation, rare petechial hemorrhages, post mortem fat emboli, and ubiquitous Buscaino plaques. Despite these adverse results preventing utilization of this technique in systematic histochemical investigations on neuronal glycogen, remarkable qualitative characteristics such as the neurons' capacity to store glycogen throughout their perikarya have been revealed.     

Antithrombin reactions with alpha- and gamma-thrombins.

Human alpha-thrombin with high clotting activity and its proteolyzed derivative gamma-thrombin with virtually no clotting activity reacted in an essentially identical manner with antithrombin. The two enzyme forms bound proflavin with similar constants and showed identical behavior with small substrates. No significant differences were found for the antithrombin reactions (measured by proflavin displacement or active site titration) with respect to kinetics, extent of reaction, or effect of added heparin. The enzyme--antithrombin complexes could not be dissociated with sodium dodecyl sulfate (NaDodSO4) but the NaDodSO4-denatured complexes were dissociated by hydroxylamine treatment. The gamma-thrombin-antithrombin complex has an approximate molecular weight of 75 000 by disc gel electrophoresis as compared with 100 000 for the alpha-complex, consistent with the polypeptide structures of the two proteins. The gamma-thrombin--antithrombin complex did not inhibit clotting catalyzed by alpha-thrombin. In addition, fibrinogen did not affect the reaction of gamma-thrombin with antithrombin or antithrombin--heparin. Thus, the antithrombin and antithrombin--heparin reactions do not involve the fibrinogen recognition sites which are destroyed by proteolytic conversion of alpha-thrombin to the noncoagulant gamma form.     

Specificity and distribution of antigenic determinants on the polyoma virus capsid and nature of the reaction of immunoglobulin G antibody with the capsid surface.

Antisera to the LP and SP34 strains of polyoma virus have been prepared and their reactions with purified virions studied by double diffusion in agar and direct assay of antibody binding. One or more common antigenic determinants appear on the capsids of both strains. The form of this determinant varies slightly on each of the strains tested. The SP34 strain also carries its own strain-specific antigenic determinant. Both strains of virus were able to bind 150 anti-LP IgG³ molecules per virion and 50 anti-SP IgG molecules per virion. The slow rate of dissociation of bound IgG antibody (k_dissociation = 2 × 10⁻⁶ s⁻¹), and the rapid rate of antibody binding (k_dissociation = 2 × 10⁷m⁻¹ s⁻¹), suggest that IgG antibody is bound to the capsid surface through two antigen-antibody bonds. 50 anti-SP IgG molecules per capsid, divalently bound, completely inhibit the binding of 150 anti-LP IgG molecules, and vice versa. Consideration of the symmetry and molecular dimensions of the IgG molecule and the polyoma virus capsid leads to a model of the divalent interaction of IgG antibody with the common antigenic determinant(s). In this model, one species of antibody binds divalently to opposed subunits of a hexamer morphological unit. The other species of antibody binds divalently to the subunits on either side of the point of tangency of any two morphological units.     

Interaction of phenytoin and primidone.

The ratio of derived phenobarbitone to unmetabolized primidone in the serum was significantly higher in 50 epileptic patients on a combination of primidone and phenytoin than in 12 patients on primidone alone, though the dose and serum levels of primidone were similar in the two groups. Out of 253 patients attending a seizure clinic 47% were taking a combination of these two anticonvulsants. The effect of phenytoin on the metabolism of primidone may have clinical implications in view of the frequency of their combined use.     

A new mutation in MT-ND1 m.3928G>C p.V208L causes Leigh disease with infantile spasms

New mutations in mitochondrial DNA encoded genes of complex I are rarely reported. An infant developed Leigh disease with infantile spasms. Complex I enzyme activity was deficient and response to increasing coenzyme Q concentrations was reduced. Complex I assembly was intact. A new mutation in MT-ND1 m.3928G>C p.V208L, affecting a conserved amino acid in a critical domain, part of the coenzyme Q binding pocket, was present at high heteroplasmy. The unaffected mother did not carry measurable mutant mitochondrial DNA, but concern remained for gonadal mosaicism. Prenatal testing was possible for a subsequent sibling. The ND1 p.V208L mutation causes Leigh disease.