[Effects of plasminogen and streptokinase on the vital functions of nervous tissue cells in culture]

In the protein-deficient media plasminogen stimulated the vital functions of cells and in concentrations 10(-7)-10(-10) M it protected cells of sympathetic ganglia, neocortex and continues cell lines under damaging actions of H2O2 (0.0001 M), NH4CI (0.01 M) and cooling. Streptokinase essentially influenced the mode of damaging effect of ATP(0.001 M). Even a short-term exposition (20 min) of PC12 cells with both proteins (each in the concentration 10(-9) M) led to sharp alterations in intracellular ATP- or Ca(2+)-activated proteolysis. In some cases plasminogen and streptokinase provided acceleration of cultured tissue maturation, improvement of cell adhesion, high survival rate, the increase in quantity and length of processes and their arborisation. Electronic microscopy established the character of structural rearrangements of nervous tissue cells (neurons, astrocytes, oligodendrocytes), reflecting the protective action of plasminogen and streptokinase. In the presence of plasminogen and especially streptokinase, the total number of cultured glioma C6 and neuroblastoma IMR-32 cells, the intracellular contents of protein, RNA and DNA increased several-fold. Addition of plasminogen promoted formation of processes by neuroblastoma cells, this suggests initiation of differentiation of cellular elements. In cultures of sensitive and sympathetic ganglia streptokinase increased proliferation of Schwann cells. These proteins did not cause transformation of PC12 enterochromaffine cells to neurons, though plasminogen facilitated it. Plasminogen addition to cell cultures did not increase fibrinolytic activity of the culture medium in the culture medium, and streptokinase did not lose its plasminogen-activating capacity.

Structural diversity of streptokinase and activation of human plasminogen

The beta domain of streptokinase is required for plasminogen activation and contains a region of sequence diversity associated with infection and disease in group A streptococci. We report that mutagenesis of this polymorphic region does not alter plasminogen activation, which suggests an alternative function for this molecular motif in streptococcal disease.

[The effect of streptokinase on the development of rat cerebral cortex cells in vitro]

The aim of this study was to determine the effect of streptokinase (SK) on the ultrastructure of cellular elements in the cerebral cortex of newborn rats in vitro. Three series of cell cultures grown on DMEM were used, including those grown on the medium enriched with 15% fetal calf serum (control 1), cultures transferred to the depleted medium containing only 0.5% of this serum (control 2), and the experimental cultures, to which SK (2000 IU/ml) was added. Addition of SK to the medium prevented a reduction of the viability of mature (14 days) dissociated neocortical cell culture from 1-2-day-old rats, induced by a transfer of the culture to a blood serum protein-deficient medium. In a 7-day culture SK potentiated the decrease in the cell viability. In organotypical cultures, with the use of electron microscopy, it was found that SK in concentration used prevented the development of destructive changes in astrocytes, oligodendrocytes, and neurons of explants, induced by a deficit in serum proteins. The neurons contained numerous mitochondria, some of which had only a few cristae. Signs of destruction were observed only in neuronal nuclei. After exposure to SK for 48 hours an activation of oligodendrocytes (containing numerous myelin bodies) was noted which was accompanied by astrocyte disintegration (with hyperchromatic nuclei in the remaining cells). The neurons were resistant to SK exposure.

[Structure-functional change in streptokinase exposed to ultrasound]

To optimize conditions of acousto-enzymatic thrombolysis the influence of low-frequency ultrasound on the isolated preparation of streptokinase was investigated. The ultrasound treatment with intensity 26 W/cm2 at 37 degrees C within 5-10 minutes was not accompanied by changes of structure-functional properties of the streptokinase molecule. Increase of ultrasound-processing time (10-60 minutes) resulted in non-covalent hydrophobic aggregation of some part of the protein. In contrast to native protein ultrasound modified streptokinase is readily degraded by plasmin with formation of polypeptide fragments with molecular weights ranged from 43 up to 14 kD. The processes of aggregation and increased proteolytic degradation resulted in lower efficiency of plasmin autoactivation under the action of sounded streptokinase.

Functional roles of streptokinase C-terminal flexible peptide in active site formation and substrate recognition in plasminogen activation

The bacterial protein streptokinase (SK) activates human plasminogen (Pg) into the fibrinolytic protease plasmin (Pm). Roughly 40 residues from the SK C-terminal domain are mobile in the crystal structure of SK complexed with the catalytic domain of Pm, and the functions of this C-tail remain elusive. To better define its roles in Pg activation, we constructed and characterized three C-terminal truncation mutants containing SK residues 1-378, 1-386, and 1-401, respectively. They exhibit gradually reduced amidolytic activity and Pg-activator activity, as well as marginally decreased binding affinity toward Pg, as more of the C-terminus is deleted. As compared with full-length SK, the shortest construct, SK(1-378), exhibits an 80% decrease in amidolytic activity (k(cat)/K(M)), an 80% decrease in Pg-activator activity, and a 30% increase in the dissociation constant toward the Pg catalytic domain. The C-terminal truncation mutations did not attenuate the resistance of the SK-Pm complex to alpha(2)-antiplasmin. Attempts at using a purified C-tail peptide to rescue the activity loss of the truncation mutants failed, suggesting that the integrity of the SK C-terminal peptide is important for the full function of SK.

Localization of plasminogen in the extracellular matrix of hamster eggs: exogenous activation by streptokinase

The plasminogen activator (PA)/plasminogen/plasmin proteolytic system has begun to be taken into account in the fertilization process. In this study, we demonstrated the presence of plasminogen in the extracellular matrix (ECM) of hamster oocytes by indirect immunofluorescence and immunoperoxidase assays using human anti-plasminogen. Plasminogen appeared first on the zona pellucida (ZP) of ovarian oocytes and later on the plasma membrane (PM) of oviducal eggs. This would suggest that oviducal oocytes modulate the expression of plasminogen binding sites on the PM. Human plasminogen as well as that of other species, known to be activated by streptokinase (SK), is rapidly converted to a plasmin-SK complex. We demonstrated the rapid formation of a SK-plasminogen complex that yields plasmin in the blood plasma of hamsters. Both the in vivo and in vitro SK treatment of eggs from superovulated female hamsters caused a decreased in the ZP dissolution time (ZPdt), probably either due to the proteolytic effect of plasmin or due to the SK-Plasminogen. Extracellular proteolysis assays carried out on agar-casein plates confirmed the proteolytic activity of SK-incubated eggs; the controls, on the contrary, failed to display a halo. These studies show that (1) superovulated hamster eggs contain plasminogen in their ECM, (2) oviducal eggs exhibit plasminogen on their PMs, indicating the presence of their corresponding binding sites, (3) in hamsters, SK, a non-enzymatic exogenous protein would be capable of activating ECM plasminogen to plasmin, and (4) the complex SK-plasminogen and/or the plasmin are capable of changing the ZPdt with alpha-chymotrypsin.

Studies about the mechanism of internalization by mammary epithelial cells of Escherichia coli isolated from persistent bovine mastitis

The purpose of this study was to investigate the interaction between Escherichia coli and primary mammary epithelial cell cultures derived from cows with persistent intramammary infection (IMI). Two strains of E. coli, isolated from the milk of two different cows suffering from persistent E. coli IMI were tested for adhesion to and invasion of three primary mammary epithelial cell cultures derived from mammary biopsies of the two infected cows. Intracellular E. coli were detected during five days post infection in vitro. Both strains of E. coli adhered to and invaded monolayers of all three primary mammary epithelial cell cultures. One strain adhered less but invaded more than the other. Comparison with other mammary pathogens indicated that E. coli invaded the cells less efficiently than Staphylococcus aureus, about as efficiently as Streptococcus dysgalactiae and more efficiently than Streptococcus uberis. The mechanism of E. coli invasion was studied using the cytoskeleton disrupting agents colchicine and cytochalasin D. These compounds inhibited the invasion of E. coli. Invasion of E. coli could also be inhibited by the phosphokinase inhibitors genistein and staurosporin in a dose-dependent fashion. Phorbol-myristyl-acetate (PMA) had no effect on the invasion of E. coli. Histology of mammary tissue revealed chronic inflammatory changes in quarters that were persistently infected by E. coli. Intracellular bacteria were not detected in mammary tissue sections. Polymerase chain reaction (PCR) analysis suggested that the two strains of E. coli lacked genes encoding for bundle-forming pili (bfpA), intimin (eae) and translocated intimin receptor (tir), which are characteristic for enteropathogenic E. coli (EPEC).

Pathogenic mechanism of acute post-streptococcal glomerulonephritis

Considerable knowledge has been accumulated regarding the characteristics of acute post-streptococcal glomerulonephritis (APSGN), and many attempts have been made to identify a streptococcal factor or factors responsible for triggering this disease. However, the pathogenic mechanism behind APSGN remains largely unknown. As glomerular deposition of C3 is generally demonstrated before that of IgG in the disease process, it is likely that the inflammatory response is initiated by renal deposition of a streptococcal product, rather than by deposition of antibodies or pre-formed immune complexes. During recent years, a number of streptococcal products have been suggested to be involved in the pathogenic process. In this review, possible roles of these factors are discussed in the context of the clinical and renal findings most often demonstrated in patients with APSGN. Streptokinase was observed to be required in order to induce signs of APSGN in mice, and a number of findings suggest that the initiation of the disease may occur as a result of renal binding by certain nephritis-associated variants of this protein. However, additional factors may be required for the development of the disease.

Effect of fibrin-fibrinogen degradation products on human basilar artery preparations

Experiments were performed to determine the effects of fibrin-fibrinogen degradation products on the human basilar artery in vivo. Citrated plasma and streptokinase were incubated at 37 degrees C to produce a preparation of fibrinogen degradation products. Aliquots of the incubate were obtained at 90 minutes, 48 hours, and 1 and 2 weeks after preparation, and were separated into fractions of different molecular weight (MWt), using an ultrafiltration technique. Each fraction was tested at each of the above times for contractile activity and possible interaction with a threshold concentration of 5-hydroxytryptamine (5-HT) on the human basilar artery. Contractile activity was initially confined to the 90-minute aliquot fraction MWt greater than 100,000, but as the incubation proceeded, such activity was also seen in the lower MWt fraction less than 100,000 greater than 10,000 at all time intervals. This activity was never seen in the fraction MWt less than 10,000 at any time. Enhancement of the 5-HT response was initially confined to the higher molecular weight fractions, but after 48-hour incubation all fractions showed this activity. It is suggested that products of fibrin-fibrinogen degradation may be involved directly or indirectly in influencing the pathophysiological mechanism(s) responsible for cerebral arterial spasm following subarachnoid hemorrhage.

Kinetics of plasma coagulation and lysis I: Basic kinetic model for time course of coagulation-lysis systems and its potential application to clinical studies

The time courses of coagulation and coagulation-lysis were spectrophotometrically monitored after the addition of thrombin or thrombin-streptokinase to plasma, diluted 1:5 with normal saline, obtained from normal and presumably abnormal subjects. The kinetics of clotting, after an initial lag period of 0.5-1.5 min, demonstrated essentially first-order dependence on the amount of fibrinogen available to form the clot, and the asymptotic absorbance was independent of thrombin concentration. The rate of clotting was a function of added thrombin, and the ratios of the rate constants at 2.5 and 1.25 units of thrombin/ml of undiluted plasma were 1.65 +/- 0.03 SEM. At early times, the coagulation-lysis curve with thrombin-streptokinase could be superimposed on the clotting curve with thrombin alone for a given plasma with minor compensation for variable lag times. Subsequently, the curves diverged; lysis was monitored by the decrease in absorbance of the coagulation-lysis system. The rate of fibrinolysis increased with streptokinase concentration and was a function of the extent of lysis, and it permitted the description of the kinetics of lysis by a pseudoautocatalytic mechanism where the bimolecular rate constant appears proportional to streptokinase concentration. Ranges of clotting and lytic parameters for the plasma of normal subjects are given, and their potential use in diagnosing abnormalities is described.