Spontaneous fibrinolysis in whole human plasma. Identification of tissue activator-related protein as the major plasminogen activator causing spontaneous activity in vitro

Spontaneous fibrinolysis of plasma clots was studied by following the lysis of the clots formed in 125I-fibrinogen-supplemented citrated plasma. Lysis of the clots invariably follows sigmoidal kinetics with S50 (the time required for 50% clot lysis) ranging from 3.5 to 4.7 days in 8 samples of pooled blood bank plasma and in the majority of apparently healthy donor plasmas. The spontaneous lysis of factor XII-deficient and prekallikrein-deficient plasmas was found to be similar to that of normal plasma. Addition of ellagic acid or antibodies against kallikrein or urokinase to normal pooled plasma did not alter significantly its rate of spontaneous lysis. On the other hand the addition of antibody against tissue activator (t-PA) inhibited over 80% of the spontaneous fibrinolysis in a 7-day incubation period at 37 degrees C, and the clot visually persisted for more than a month. Therefore, the factor XII-dependent components and prourokinase/urokinase system do not contribute significantly in whole plasma fibrinolysis in vitro, while the t-PA-related protein appears to be the major plasminogen activator responsible for initiating spontaneous fibrinolysis in whole plasma. Exogenous addition of increasing amounts of purified HeLa cell t-PA to normal pooled plasma in the ng/ml range cause progressively faster clot lysis. By extrapolation, normal pooled plasma is found to contain endogenous tissue activator in an amount functionally equivalent to 2 ng/ml of purified 60-kDa t-PA. The molecular nature of the t-PA-related proteins in plasma was studied by zymographic and immunological methods. The major t-PA-related protein in plasma was found to have a molecular mass of 100 kDa as determined by zymography. By incubating purified HeLa 60-kDa t-PA with a t-PA-depleted plasma, the 100-kDa component can be generated in plasma, suggesting that the latter is formed as a result of the binding of 60-kDa t-PA to a binding protein in plasma.     

Intra-individual length heterogeneity of Rana esculenta mitochondrial DNA

Mitochondrial DNA extracted from Rana esculenta oocytes appears heterogeneous in size. The length of these molecules varies continuously from 18,700 bp to 19,700 bp. Each animal is heteroplasmic and can be characterized by the range of the variation (400-700 bp) and the extreme sizes of the various molecules it carries. The variable region of the genome has been localized between the coding region and the replication origin area.     

Further results on the survival of a gene represented in a founder population

This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982).     

Purification of smooth-muscle myosin free of calmodulin and myosin light-chain kinase. Susceptibility to oxidation.

Smooth-muscle myosin purified as described by Persechini & Hartshorne [(1983) Biochemistry 22, 470-476] contains trace amounts of calmodulin and myosin light-chain kinase, which can be removed by Ca2+-dependent hydrophobic-interaction chromatography followed by calmodulin-Sepharose affinity chromatography. The resultant column-purified myosin exhibits properties similar to those of the non-purified myosin, e.g. actin activation of the Mg2+-ATPase requires Ca2+/calmodulin-dependent phosphorylation of the two 20 kDa light chains. However, unlike the non-purified myosin, the column-purified myosin undergoes a time-dependent transition to a form which no longer requires phosphorylation for actin activation of the myosin Mg2+-ATPase. This transition is identified as a time-dependent change in conformation of the column-purified myosin from a 10 S to 6 S form and is caused by slow oxidation of the column-purified myosin, since it could be prevented by storage under N2 and reversed by 5 mM-dithiothreitol.     

Capillary growth and diffusion distances in muscle

1. Tissue capillarity in muscle was modelled as square-ordered arrays with capillary-to-fiber ratios (C/F) from 0.5 to 'infinity'. 2. C/F up to two had marked effects on diffusion distances, but C/F above had only slight effects on average distances and almost no effect on maximal distances. 3. Capillary growth during normal maturation results in C/F around two. Thus, capillary growth in adult muscle may not be an adaptive mechanism for reducing diffusion distances.     

Fluorescence technique for comparative studies of substrate-binding subsites in serine proteinases. Application to subtilisins.

A fluorescence technique for comparative studies of substrate-binding subsites in serine proteinases is described. It consists of: selective labelling of the corresponding subsites with a fluorescent group by using N alpha-dansyl(5-dimethylaminonaphthalene-1-sulphonyl)ated peptide chloromethanes containing different numbers of amino acid residues, and probing the immediate environment of the subsites by quenching experiments using ionic and neutral quenchers. Intramolecular distances between the subsites and particular chromophores can be also determined. The technique is of general applicability to all serine proteinases. The above mentioned approach was applied to two proteinases: subtilisin Novo and mesentericopeptidase. It was concluded that the substrate-binding site of mesentericopeptidase is considerably more polar than that of subtilisin Novo. Intramolecular distances between the labelled subsites and tryptophan residues in the two proteinases were determined.