OPEN FILE.PDF

OWN WORKS:

MOUNTAIN ACCIDENTS DISAPPEARANCES
IN THE MOUNTAINS
ORIENTATION DISORDERS
BIOMETEOLOGY
CHRONOBIOLOGY
IN VITRO
CYTOLOGY ANTIPSYCHOSIS
COAGULOLOGY IN APOLEXIOLOGY FIBRINOLYSIS
SCHEDULE (from 2000)
DOCUMENT 1

PUBLICATIONS:
Cytodiagnostics of cerebrospinal fluid
DOCUMENT 1
DOCUMENT 2

DOPAMINE

The role of dopamine in the central nervous system 1991.
Review paper for the first degree of specialization in neurology.
From the Neurological Department of the Mining Medical Center in Katowice.
Head of the Department: Assoc. Dr. Hab. n. med. Zofia Kazibutowska

Dopamine /DA/ is a catecholamine produced in the body from L-tyrosine, an amino acid that is also a substrate of thyroid hormones. The direct precursor of DA is dihydroxyphenylalanine /DOPA/, and the enzyme enabling the biochemical reaction of DA formation is DOPA decarboxylase. In physiological conditions, DA is a substrate for other catecholamines: noradrenaline and adrenaline. The catabolism of the above-mentioned catecholamines leads to the formation of their methyl derivatives and vanillinmandelic and homovanillic acids detectable in urine. In a 24-hour urine collection under physiological conditions, 2-12 mg of vanillylmandelic acid is found. Catecholamines metabolites determined in urine and plasma are mostly derived from amines synthesized by chromaffin cells of the adrenal medulla. These cells are effectors of the sympathetic nervous system activated in the stress response. Acute failure of this system, as well as other pathophysiological conditions complicated by shock, have led to the use of catecholamines, including DA, as rapid and effective pressor agents maintaining blood pressure.
In the body of a healthy person, the content of total DA determined in plasma ranges from 7.7-27.0 nmol/l, and the free DA fraction from 0.78-3.8 nmol/l. In urine, the amount of unmetabolized DA is 1900 nmol per day. Due to the short half-life of DA - 1.75 min., in cases of its deficit in the central nervous system, pure DA preparations are not used, but its precursor L-DOPA, most often in complex preparations. The role of DA in the central nervous system results from its distribution in the brain. DA as a neurotransmitter is an active substance in the network of neurons ascending from the midbrain to higher levels of the brain. The cell bodies of these neurons are located in the melanin-rich zona compacta substantiae nigrae. The axons leaving from here are directed to several systems. Groups of neurons in the substantia nigra are designated with the symbols A.8-A10 and A12. A8 denotes a group of DA-ergic cells originating from the field adjacent to the red nucleus. A9 are neurons of the lateral part of the substantia nigra, whose axons go to the striatum. A10 is a group of neurons located in the ventral part of the tectum, constituting a connection between the midbrain and the prefrontal region and forming the mesolimbic system /8/. The functions of the DA-ergic system are related to the activities of most neurotransmitters present in the brain and are subject to a number of modulations. It has been found that the activity of neurons of groups A9 and A10 is modulated by neurotensin, substance P and dynorphin, and some DA-ergic cells simultaneously synthesize cholecystokinin. The sensitivity of the DA-ergic system to the effects of opioids has also been demonstrated. A9 and A10 neurons show identical responses to enkephalins, but differentiated responses to morphine and beta-endorphin. Alpha and gamma-endorphin, on the other hand, show opposite effects on the DA-ergic system /6,12/. From a biological point of view, the role of the DA-ergic pathways on the prefrontal area is extremely important. It was taken into account that the neurotransmitter used in the neocortex is acetylcholine. DA deficiency may also be responsible for the loss of higher nervous functions, dependent on the efficient functioning of this brain region. Recently, the possibility of increasing DA metabolism in the prefrontal area was discovered using a substance antagonistic to benzodiazepines: FG/7142-methyl-beta-carbolin -3-carboxamide. Its effect is nullified by prior administration of benzodiazepines /8/. The effector of DA action in the central nervous system are its two types of receptors: D1 and D2. Their stimulation is associated with a change in the level of adenylate cyclase in the effector cell membrane. Synapses with D1 and D2 receptors differ in location, and selected markers are used to determine them. For the D1 receptor, the antagonist is flupenthixol, and the agonist is the factor SKF-38393. D1 receptors are present in the neurons of the striatum, and their damage is caused by kainic acid, which simultaneously destroys the descending path from the striatum to the substantia nigra /3,6/.The antagonist of D2 receptors is spiperone, and the agonist is N-propylnorapomorphine. Both types of receptors also have common antagonists: butyrophenone and ergot alkaloids, with butyrophenone being a weak antagonist for D1 receptors. D2 receptors have been found on the synaptic endings of cortico-striatal neurons and in the pituitary gland. Damage to D2 receptors occurs in parkinsonism, when the loss of DA-ergic neurons of the nucleus caudatus manifests itself as a hypertonic-hypokinetic syndrome with tremors, and in the case of damage to the nucleus subthalamicus - myoclonus, athetotic, torsional and ballistic movements. This syndrome is also a common complication of neuroleptics and even after discontinuation of their use, it may remain a permanent loss. DA secretion in the substantia nigra is closely associated with the activity of the nucleus caudatus and enables the maintenance of a balance between the activity of alpha and gamma motor neurons. Damage to this structure is manifested by increased activity of alpha neurons and muscle stiffness. Diseases associated with hypofunction of DA-ergic pathways require the substitution of this catecholamine. In parkinsonism, anticholinergic agents are additionally used to reduce the accompanying hyperactivity of the cholinergic system. Blockade of muscarinic receptors with parasympatholytic substances reduces the symptoms of primary and secondary parkinsonism. Increasing the level of endogenous DA is also possible indirectly – by reducing the activity of monoamine oxidases (MAO). There are 2 types of these enzymes that cause the breakdown of catecholamines. MAO-A found in the lungs and MAO-B found in the liver, kidneys, brain and platelets. DA is a substrate of both types of MAO, and the MAO-B inhibitor deprenyl/Jumex/ used in parkinsonism allows for a reduction of its dose in combination with L-DOPA. Correcting the disturbed neurohormonal balance in the striatum is also possible through neurosurgical intervention, e.g. destruction of the globus pallidus and ventral thalamic nuclei, or implantation of DA-rich tissue into the patient's nucleus caudatus. At the same time, it should be remembered that the globus pallidus is the oldest phylogenetically structure of the striatum and performs an inhibitory function in the circle of excitations running between the thalamus, striatum, and cerebral cortex. Deficiency of gamma-aminobutyric acid and acetylcholine impairs its functions and is the cause of hypotonic-hyperkinetic syndrome with choreic movements and tics. In the context of the role of DA in the central nervous system, the relationships described above should be located within the nigrostriatal system. The DA-ergic pathways of the mesolimbic system terminate in the nucleus accumbens and the tuberculum olfactorium, i.e.D2 receptors have been found at the synaptic endings of cortico-striatal neurons and in the pituitary gland. Damage to D2 receptors occurs in parkinsonism, when the loss of DA-ergic neurons of the nucleus caudatus manifests itself as a hypertonic-hypokinetic syndrome with tremors, and in the case of damage to the nucleus subthalamicus - myoclonus, athetotic, torsional and ballistic movements. This syndrome is also a common complication of the use of neuroleptics and even after discontinuation of their use, it may remain a permanent loss. DA secretion in the substantia nigra is closely related to the activity of the nucleus caudatus and allows for maintaining a balance between the activity of alpha and gamma motor neurons. Damage to this structure manifests itself in increased activity of alpha neurons and muscle stiffness. Diseases associated with hypofunction of DA-ergic pathways require substitution of this catecholamine. In parkinsonism, anticholinergic agents are additionally used to reduce the accompanying hyperactivity of the cholinergic system. Blockade of muscarinic receptors with parasympatholytic substances reduces the symptoms of primary and secondary parkinsonism. Increasing the level of endogenous DA is also possible indirectly - by reducing the activity of monoamine oxidases /MAO/. There are 2 types of these enzymes that cause the breakdown of catecholamines. MAO-A found in the lungs and MAO-B found in the liver, kidneys, brain and platelets. DA is a substrate of both types of MAO, and the MAO-B inhibitor deprenyl /Jumex/ used in parkinsonism allows for a reduction of its dose in combination with L-DOPA. Correcting the disturbed neurohormonal balance in the striatum is also possible through neurosurgical intervention, e.g. destruction of the globus pallidus and ventral thalamic nuclei, or implantation of DA-rich tissue into the patient's nucleus caudatus. At the same time, it should be remembered that the globus pallidus is the oldest phylogenetically structure of the striatum and performs an inhibitory function in the circle of excitations running between the thalamus, striatum, and cerebral cortex. Deficiency of gamma-aminobutyric acid and acetylcholine impairs its functions and is the cause of hypotonic-hyperkinetic syndrome with choreic movements and tics. In the context of the role of DA in the central nervous system, the relationships described above should be located within the nigrostriatal system. DA-ergic pathways of the mesolimbiotic system ending in the nucleus accumbens and tuberculum olfactorium, i.e.D2 receptors have been found at the synaptic endings of cortico-striatal neurons and in the pituitary gland. Damage to D2 receptors occurs in parkinsonism, when the loss of DA-ergic neurons of the nucleus caudatus manifests itself as a hypertonic-hypokinetic syndrome with tremors, and in the case of damage to the nucleus subthalamicus - myoclonus, athetotic, torsional and ballistic movements. This syndrome is also a common complication of the use of neuroleptics and even after discontinuation of their use, it may remain a permanent loss. DA secretion in the substantia nigra is closely related to the activity of the nucleus caudatus and allows for maintaining a balance between the activity of alpha and gamma motor neurons. Damage to this structure manifests itself in increased activity of alpha neurons and muscle stiffness. Diseases associated with hypofunction of DA-ergic pathways require substitution of this catecholamine. In parkinsonism, anticholinergic agents are additionally used to reduce the accompanying hyperactivity of the cholinergic system. Blockade of muscarinic receptors with parasympatholytic substances reduces the symptoms of primary and secondary parkinsonism. Increasing the level of endogenous DA is also possible indirectly - by reducing the activity of monoamine oxidases /MAO/. There are 2 types of these enzymes that cause the breakdown of catecholamines. MAO-A found in the lungs and MAO-B found in the liver, kidneys, brain and platelets. DA is a substrate of both types of MAO, and the MAO-B inhibitor deprenyl /Jumex/ used in parkinsonism allows for a reduction of its dose in combination with L-DOPA. Correcting the disturbed neurohormonal balance in the striatum is also possible through neurosurgical intervention, e.g. destruction of the globus pallidus and ventral thalamic nuclei, or implantation of DA-rich tissue into the patient's nucleus caudatus. At the same time, it should be remembered that the globus pallidus is the oldest phylogenetically structure of the striatum and performs an inhibitory function in the circle of excitations running between the thalamus, striatum, and cerebral cortex. Deficiency of gamma-aminobutyric acid and acetylcholine impairs its functions and is the cause of hypotonic-hyperkinetic syndrome with choreic movements and tics. In the context of the role of DA in the central nervous system, the relationships described above should be located within the nigrostriatal system. DA-ergic pathways of the mesolimbiotic system ending in the nucleus accumbens and tuberculum olfactorium, i.e.DA secretion in the substantia nigra is closely associated with the activity of the nucleus caudatus and enables the maintenance of a balance between the activity of alpha and gamma motor neurons. Damage to this structure is manifested by increased activity of alpha neurons and muscle stiffness. Diseases associated with hypofunction of DA-ergic pathways require the substitution of this catecholamine. In parkinsonism, anticholinergic agents are additionally used to reduce the accompanying hyperactivity of the cholinergic system. Blockade of muscarinic receptors with parasympatholytic substances reduces the symptoms of primary and secondary parkinsonism. Increasing the level of endogenous DA is also possible indirectly – by reducing the activity of monoamine oxidases (MAO). There are 2 types of these enzymes that cause the breakdown of catecholamines. MAO-A found in the lungs and MAO-B found in the liver, kidneys, brain and platelets. DA is a substrate of both types of MAO, and the MAO-B inhibitor deprenyl/Jumex/ used in parkinsonism allows for a reduction of its dose in combination with L-DOPA. Correcting the disturbed neurohormonal balance in the striatum is also possible through neurosurgical intervention, e.g. destruction of the globus pallidus and ventral thalamic nuclei, or implantation of DA-rich tissue into the patient's nucleus caudatus. At the same time, it should be remembered that the globus pallidus is the oldest phylogenetically structure of the striatum and performs an inhibitory function in the circle of excitations running between the thalamus, striatum, and cerebral cortex. Deficiency of gamma-aminobutyric acid and acetylcholine impairs its functions and is the cause of hypotonic-hyperkinetic syndrome with choreic movements and tics. In the context of the role of DA in the central nervous system, the relationships described above should be located within the nigrostriatal system. The DA-ergic pathways of the mesolimbic system terminate in the nucleus accumbens and the tuberculum olfactorium, i.e.DA secretion in the substantia nigra is closely associated with the activity of the nucleus caudatus and enables the maintenance of a balance between the activity of alpha and gamma motor neurons. Damage to this structure is manifested by increased activity of alpha neurons and muscle stiffness. Diseases associated with hypofunction of DA-ergic pathways require the substitution of this catecholamine. In parkinsonism, anticholinergic agents are additionally used to reduce the accompanying hyperactivity of the cholinergic system. Blockade of muscarinic receptors with parasympatholytic substances reduces the symptoms of primary and secondary parkinsonism. Increasing the level of endogenous DA is also possible indirectly – by reducing the activity of monoamine oxidases (MAO). There are 2 types of these enzymes that cause the breakdown of catecholamines. MAO-A found in the lungs and MAO-B found in the liver, kidneys, brain and platelets. DA is a substrate of both types of MAO, and the MAO-B inhibitor deprenyl/Jumex/ used in parkinsonism allows for a reduction of its dose in combination with L-DOPA. Correcting the disturbed neurohormonal balance in the striatum is also possible through neurosurgical intervention, e.g. destruction of the globus pallidus and ventral thalamic nuclei, or implantation of DA-rich tissue into the patient's nucleus caudatus. At the same time, it should be remembered that the globus pallidus is the oldest phylogenetically structure of the striatum and performs an inhibitory function in the circle of excitations running between the thalamus, striatum, and cerebral cortex. Deficiency of gamma-aminobutyric acid and acetylcholine impairs its functions and is the cause of hypotonic-hyperkinetic syndrome with choreic movements and tics. In the context of the role of DA in the central nervous system, the relationships described above should be located within the nigrostriatal system. The DA-ergic pathways of the mesolimbic system terminate in the nucleus accumbens and the tuberculum olfactorium, i.e.Correcting the disturbed neurohormonal balance in the striatum is also possible through neurosurgical intervention, e.g. destruction of the globus pallidus and ventral thalamic nuclei, or implantation of DA-rich tissue into the patient's nucleus caudatus. At the same time, it should be remembered that the globus pallidus is the oldest phylogenetically structure of the striatum and performs an inhibitory function in the circle of excitations running between the thalamus, striatum, and cerebral cortex. Deficiency of gamma-aminobutyric acid and acetylcholine impairs its functions and is the cause of hypotonic-hyperkinetic syndrome with choreic movements and tics. In the context of the role of DA in the central nervous system, the relationships described above should be located within the nigrostriatal system. DA-ergic pathways of the mesolimbiotic system ending in the nucleus accumbens and tuberculum olfactorium, i.e.Correcting the disturbed neurohormonal balance in the striatum is also possible through neurosurgical intervention, e.g. destruction of the globus pallidus and ventral thalamic nuclei, or implantation of DA-rich tissue into the patient's nucleus caudatus. At the same time, it should be remembered that the globus pallidus is the oldest phylogenetically structure of the striatum and performs an inhibitory function in the circle of excitations running between the thalamus, striatum, and cerebral cortex. Deficiency of gamma-aminobutyric acid and acetylcholine impairs its functions and is the cause of hypotonic-hyperkinetic syndrome with choreic movements and tics. In the context of the role of DA in the central nervous system, the relationships described above should be located within the nigrostriatal system. DA-ergic pathways of the mesolimbiotic system ending in the nucleus accumbens and tuberculum olfactorium, i.e.
in the anterior part of the substantia perforata anterior are associated with the sphere of emotions, drive and motivation. Brain function disorders caused by DA hyperactivity in the mesolimbic system are the assumption of the dopamine theory of schizophrenia and imply the use of neuroleptics in split-brain psychoses. These issues are deepened by recent research on DA secretion in the diencephalon. In the hypothalamus and pituitary gland, these neurons are an integral part of hormonal axes operating on the principle of negative feedback, e.g. as a factor inhibiting the secretion of prolactin and as regulators of the secretion of gonadotropic and mammotropic hormones. It has been noted that causing changes in the secretion of mammotropic hormones and the effect of DA, e.g. after the use of neuroleptics, may result in the occurrence of morphological changes in the male breast. The role of DA in the pineal gland, which produces this catecholamine even after its denervation, is unclear /13/. The mechanisms of DA action in the central nervous system are very complex and are subject to the influence of many endogenous substances and interfering interactions. It is possible to influence individual pathways and receptors as well as the entire system, e.g. depolarization of the DA system with muscimol / GABA-A receptor agonist /, or hyperpolarization of the system with baclofen / GABA-B receptor agonist /. Recently, great hopes have been associated with bromocriptine, which as an agonist of DA receptors in the hypothalamus can effectively inhibit galactorrhea. Previous studies of the DA system have enabled great progress in the treatment of diseases of the central nervous system, including Parkinson's disease and psychoses, and further studies create new opportunities for many patients to be cured. When planning further work in the field of neurobiochemistry, attention is drawn to the risk of causing irreversible changes - it is necessary to predict and prevent them.

THROMBOLIC STROKE Fibrinolysis in physiological conditions and in patients with thrombotic stroke Review paper for the 2nd degree of specialization in neurology Department of Neurology, Upper Silesian Medical Center, Katowice 1998 Head of specialization Krystyna Stolarzewicz-Zając, MD – neurology specialist Reviewer: Danuta Ryglewicz, MD – neurology specialist








Blood coagulation and fibrinolysis constitute a common coagulological process. Fibrinolysis is a natural consequence of hemostasis. Physiologically, the activation of the coagulation and fibrinolysis system is initiated on one of two tracks: intrinsic, when collagen is exposed in the damaged vessel wall, or extrinsic, when tissue thromboplastin is released from damaged tissue. The coagulation and fibrinolysis system is represented by biochemical components contained in dispersed structures, mainly within the vessels (plasma, thrombocytes, endothelium). These components often occur as inactive precursors, e.g. as zymogens (inactive enzymes) and in the form of activated factors. In addition to components considered essential in this process, e.g. coagulation factors and plasminogen, there is a rich group of coagulation and fibrinolysis modulators. Modulators act as activators or inhibitors of the process, and some of them, under specific conditions, perform both of these functions. Both the states of excess or deficiency of essential components of coagulation and fibrinolysis and the action of modulators, underlie the thrombotic changes encountered in cerebral infarction caused by arterial thrombosis (infarctus ischemicus cerebri propter thrombosim arteriae) /iicpta/. Originally, HEMOSTASIS is the result of the interaction of the vessel wall, platelets and plasma coagulation factors. Adhesion and aggregation of morphological blood elements through the activation of adenosine diphosphate (ADP) in platelets activates their secretion. Platelets secrete numerous coagulation mediators, including: serotonin, adrenaline, betathromboglobulin, platelet factor 3, antiheparin platelet factor 4. Platelet aggregation is reversible until thrombin is activated. The intrinsic pathway of coagulation proceeds according to the stages of factor activation: prekallikrein (Fletcher factor) with high molecular weight kininogen lead to the formation of kallikrein, factor XII (Hageman), XI (PTA – plasma thromboplastin antecedent), IX (Christmas) obtain active forms successively, factor VIII (AHF – antihemophilic factor) with calcium ions and phospholipid interact with factor X (Stuart-Prower), active factor X together with factor V (proaccelerin), phospholipid and calcium ions interact with factor II (prothrombin) to form thrombin, active thrombin acts multidirectionally: on factor I (fibrinogen) which later cleaves fibrinopeptides A and B; on factor XIII (FSF – fibrin stabilizing factor), activating it; on factors V and VIII and on platelets stimulating their aggregation and secretion, finally fibrinogen is transformed into soluble fibrin monomers (FM), and then they polymerize and stabilize the insoluble fibrin clot under the influence of FSF and calcium ions; finally, clot retraction occurs in the presence of platelets. Activation of factor X is a convergent moment for the extrinsic and intrinsic coagulation pathways.The extrinsic pathway is initiated by tissue factor (tissue thromboplastin) and factor VII (proconvertin). Activated factor VII (convertin) acts on factor X. The production of prothrombinase is already a common stage of hemostasis for both activation pathways. A large group of factors, some of which simultaneously act as fibrinolysis inhibitors, plasma protease inhibitors, and some as acute phase proteins – inhibit the coagulation process. These include: antithrombin III (AT III), which is an important cofactor of the anticoagulant effect of heparin, because AT III accelerates its effect 3-fold. AT III forms irreversible complexes with thrombin, factor Xa, and also acts on active factors: VII, IX, X, XI, XII. AT III is an alpha-2-globulin synthesized in the liver. Of particular importance for the structural unity of its molecule is proline at position 407. protein C, which is a hepatic enzyme of plasma dependent on vitamin K, activated by thrombin in the presence of thrombomodulin and calcium ions. It inactivates active factors V and VIII in the presence of phospholipid. protein S, which acts as a cofactor of active protein C (ACP). Its participation is essential in the antithrombotic function of APC. The antithrombotic effect of the protein C and protein S complex does not occur when the protein C inhibitor is active or the factor V Leiden mutant is present. heparin cofactor II is a glycoprotein produced in the liver and acts faster in the presence of heparin and dermatan sulfate, catalyzing thrombin to an inactive form. C1 esterase inhibitor inhibits the functions of active factors XI and XII. TFPI (tissue factor pathway inhibitor) inhibits the formation of the tissue factor complex, active factor VII and X, forming an irreversible complex with the first two. Plasma protease inhibitors are a large group of modulators of coagulation and fibrinolysis. They include, among others, coagulation inhibitors: alpha-2-macroglobulin inhibiting prothrombin and alpha-1-antitrypsin inhibiting prothrombin and active factor XI. These inhibitors and alpha-1-antiplasmin in the case of their overactivity can cause hypercoagulation, because then they become inhibitors of fibrinolysis. Alpha-2-macroglobulin is a glycoprotein synthesized in the liver. This inhibitor inhibits serine, cysteine, aspartate proteases, collagenases, plasminogen activators. It is an acute phase protein. Complexes that alpha-2-macroglobulin forms with enzymes are eliminated from the circulation through hepatocyte surface receptors. For FIBRINOLYSIS, the key inactive factor is plasminogen. This zymogen is a betaglobulin, which as a glycoprotein contains 2% sugars and a single polypeptide chain with a known sequence of 791 amino acids. Its molecular weight is 92 kD, the average concentration in human plasma is 20.3 mg/dl. The main site of its synthesis is the liver and probably eosinophilic granulocytes of the bone marrow. A significant part of the systemic pool of plasminogen lies in the extravascular area,and its active form – plasmin requires proteolysis of plasminogen. Then, 2 peptide bonds in the chain are broken. Lys-plasmin with a molecular weight of 83 kD is created with a heavy chain A and a light chain B, which contains the active center. Plasmin is a non-specific proteolytic enzyme that digests numerous proteins, including fibrin and fibrinogen. Plasmin also digests, for example, casein, beta-lactoglobulin, complement components, ACTH, glucagon, somatotropin, angiotensin, mucoproteins, coagulation factors II, V, IX, XII. Physiological fibrinolysis is a secondary fibrinolysis that leads to the disintegration of insoluble fibrin (stabilized fibrin polymer) under the influence of plasmin. In contrast to secondary fibrinolysis, primary fibrinolysis is a pathology that can cause some hemorrhages. In primary fibrinolysis, the lytic action of plasmin is revealed against fibrinogen or forms of soluble fibrin – before the formation of a hemostatic plug. Secondary fibrinolysis lasts 48-72 hours and leads to the return of normal flow after transient hemostasis and vessel damage. As a result of secondary fibrinolysis, early fibrin degradation products (350-2000 kD) are formed, followed by late ones, the smallest of which (240 kD) are D-dimers. D-dimers are DDE fragments linked by gamma-gamma bonds between D fragments, resistant to plasmin action. Plasminogen activators in the intrinsic pathway are: kallikrein, activated factor XII and plasma activator – urokinase (urokinase plasminogen activator) /u-PA/. Plasminogen activator in the extrinsic pathway is tissue type plasminogen activator (t-PA/). U-PA is contained in urine and plasma as a zymogen. It is synthesized in the form of a single-chain glycoprotein (scu-PA -single chain urokinase plasminogen activator) with a molecular mass of 54 kD, which is converted in plasma into an active 2-chain form under the influence of plasmin. Only the tcu-PA (twice chain urokinase plasminogen activator) form complexes with PAI-1. T-PA is a 67 kD serine protease present in plasma at a concentration of about 70 pM. It is released from the vascular endothelium under the influence of various stimuli, e.g. exercise, hypoxia, some drugs. It is present in 1- and 2-chain forms. Both forms retain the ability to form complexes with inhibitors. It shows significant daily fluctuations in level, as well as dependence on sex and age. There is experimental evidence that a fragment of the laminin chain (Lam A2091-2108) may be a proactivator of t-PA. Laminin is a large glycoprotein non-collagen component of the basement membrane. It is probably contained in elastic fibers, as shown in studies on sheep by Kittelberger R. et al., 1989. It has binding sites for various components of the extracellular matrix and numerous biological functions. It was found that its 19-amino acid fragment obtained from the E8 region of the carboxyl section of the A chain with the sequence:Cys-Ser-Arg-Ala-Arg-Lys-Glu-Ala-Ala-Ser-Ile-Lys-Val-Ala-Val-Ser-Ala-Asp-Arg-NH2 designated as Lam A2091-2108 peptide ( PA 22-2 ) is a potential activator of plasminogen via t-PA. The profibrinolytic effect is also caused by FM fibrin monomer molecules associated with the coagulation cascade, which are stimulators of t-PA. A similar effect is caused by fibrinogen and fibrin degradation products ( tFDP ), which inhibit the hemostatic functions of thrombocytes. Exogenous activators of fibrinolysis of bacterial origin are strepto- and staphylokinase. Fibrinolysis is increased by: catecholamines (exertion, emotion), fever, electroconvulsive therapy, hypoxia, acetylcholine, histamine, nicotinic acid. Secondary fibrinolysis is modulated by inhibitors, of which the 2 most important biologically in humans due to their potency are: alpha-2-antiplasmin and plasminogen activator inhibitor type 1 (PAI-1). Excessive action of fibrinolysis inhibitors can cause hypercoagulation. Alpha-2-antiplasmin is a glycoprotein with a molecular weight of 68 kD synthesized in the liver. It was discovered in 1975 and described in 1982 by Miles et al. and in 1983 by Stormorken et al. It is an inhibitor of plasmin, plasminogen, kallikrein, alpha-chymotrypsin, trypsin, thrombin, active factors X and XI and XII and urokinase. In plasma it occurs in an active, proteolytically modified form and in the form of stable equimolar complexes primarily with plasmin (PAP). Complexes containing alpha-2-antiplasmin are removed from the circulation by the surface receptor SR2 of the hepatocyte cell membrane. Liver damage, e.g. its cirrhosis, causes a decrease in the level of alpha-2-antiplasmin. Its level also decreases in DIC (disseminated intravascular coagulopathy). Alpha-2-antiplasmin immediately inactivates free plasmin formed in plasma, with which it forms a stoichiometric complex in a 1:1 ratio. Initially, the reaction is reversible. A necessary condition for rapid interaction of alpha-2-antiplasmin with plasmin is a free active center and lysine-binding sites in plasmin. Active factor XIII in the presence of calcium ions attaches alpha-2-antiplasmin to fibrin via cross-links. Plasminogen has a lower affinity for alpha-2-antiplasmin, which also reacts with it via lysine-binding sites. The concentration of alpha-2-antiplasmin in plasma – about 1 µmol is lower than the average concentration of plasminogen – 1.5 – 2 µmol. Therefore, in the case of intensive activation of fibrinolysis and conversion of all plasminogen to plasmin, alpha-2-antiplasmin is the first line of defense, but it is not sufficient to prevent plasminemia, which threatens the digestion of fibrinogen and other plasma proteins. The physiological role of alpha-2-antiplasmin is limited to inactivating free plasmin and plasminogen in plasma, which are not associated with the clot.Severe bleeding accompanying congenital deficiency of alpha-2-antiplasmin in homozygotes with this defect proves the importance of this inhibitor for hemostasis. In contrast to alpha-2-antiplasmin, which in physiological conditions protects against the lytic state associated with plasminemia, another inhibitor of fibrinolysis - PAI is considered a strong prothrombotic factor. Currently, 3 types of PAI are distinguished. PAI-1 with a molecular mass of 54 kD has a single-chain structure, and its concentration in plasma is about 1/10 nM. The carrier of PAI-1 in plasma is vitronectin. In addition to plasma PAI-1, there is about a 5-fold larger pool of it in blood platelets. PAI-1 belongs to acute-phase proteins (Zawilska K.,1995). It has an inhibitory effect on t-PA and u-PA, forming stable complexes with them. PAI-2 with a molecular weight of 60 kD is present in detectable concentrations only during pregnancy. It most likely comes from the placenta, is produced in endothelium, megakaryocytes, smooth muscle cell cultures and hepatoma cells. Protein C inhibitor is considered PAI-3. PAI-3 is bound by activated protein C (APC), which results in an increase in circulating t-PA levels, secondarily activation of plasmin and increased fibrinolysis. Modulating functions in the fibrinolysis system are also demonstrated by: C1 esterase inhibitor, which is an inhibitor of t-PA, kallikrein and factor XII. In addition, kallikrein and factor XII are inhibited by alpha-2-antiplasmin and AT III, and kallikrein additionally by alpha-2-macroglobulin and alpha-1-antitrypsin. It is assumed that ischemic stroke occurs in about 80% on the background of a clot (thrombus) of the artery or (much less frequently) - vein and in 20% on the background of an embolism (embolism) of the artery. Iicpta is a co-result of slowing down blood flow, disorders of its composition and damage to the endothelium at the site of the clot formation. Arterial thrombus is formed mainly from platelets, fibrin and erythrocytes and is a substrate for fibrinolysis. In the pathomechanism of the clot, a weakened vasomotor activity is observed, sometimes on the basis of arteriosclerosis and the dominance of thrombogenic blood factors over fibrinolytic factors. These phenomena are a derivative of fluctuations in platelet aggregation, t-PA level, cortisol secretion and sympathetic impulsation. The rhythm of these fluctuations shows circadian periodicity and favors the occurrence of thrombotic strokes during sleep and in the morning hours. Jovicic B. et al.,1991, studying the circadian dynamics of platelet adhesion and fibrinolytic activity in patients with ischemic stroke (21 men aged 51-65 years) found that circadian changes in platelet adhesion and fibrinolytic activity are constant but their degree of oscillation and its phase differ in comparison with these parameters in healthy individuals. Observations by Muller JE, 1989, indicate a higher frequency of cerebral strokes in the morning hours, but at the same time a more significant dependence on the cycle of circadian activity than a direct relationship with the time of day.The thrombotic etiology of stroke is the result of a disturbance in the coagulological balance of the organism, manifested by the dominance of the coagulation process over fibrinolysis. In physiological conditions, both of these processes remain in dynamic equilibrium. Thrombogenesis in thrombosis is hemostasis occurring in the wrong place and subject to incorrect regulation. The clot undergoes uncontrolled growth and impaired dissolution. The cause of thrombosis are prothrombotic phenomena: thrombophilia and hypercoagulability occurring in the endothelium, platelets and involving coagulation and fibrinolysis factors together with their regulators. Thrombophilia means inherited disorders of coagulation and fibrinolysis that favor the occurrence of thromboembolic episodes, and hypercoagulability also includes acquired predispositions to thrombosis. The participation of fibrinolysis inhibitor components, especially PAI-1, in the thrombotic mechanism of stroke is emphasized (Han XM et al., 1990, Han XM, 1991, Guan KJ et al., 1993). These authors demonstrated, among others, using chromogenic factors methods, an increased level of PAI in patients after ischemic stroke, leading to decreased fibrinolysis and increased risk of thrombosis. A highly thrombogenic effect in the etiopathogenesis of atherosclerosis is exerted by an increased level of apolipoprotein a (apoa) contained in lipoprotein A (Lp a). The structural similarity of apoa to the components of fibrinolysis (especially plasminogen) determines its competitiveness in the fibrinolysis process. In addition, apoa, by binding to endothelial cells, increases the secretion of PAI-1. Glueck CJ et al.,1995, showed in 87 patients, after an average of 1 year from stroke, the presence of risk factors for stroke: hypofibrinolysis, increased Lp a level, dyslipidemia. These changes were accompanied significantly more often than in the control group by increased PAI activity and increased t-PA antigen level. The autosomal dominant type of inheritance for apoa determines the genetic predisposition of people with hyperapolipoproteinemia a to impaired fibrinolytic functions. Apart from atherosclerosis, numerous diseases of different etiology but with partially convergent pathogenesis exert a prothrombotic effect. In diabetes, one of the causes of impaired fibrinolysis is the abnormal interaction of plasminogen with its activators and fibrin due to non-enzymatic glycosylation of these proteins. Infections are often accompanied by venous thrombosis: thrombophlebitis – thrombophlebitis of superficial veins and phlebothrombosis – deep vein thrombosis. Neoplasms may be accompanied by paraneoplastic syndromes with thrombosis. Hypercoagulation may occur in some types of liver and kidney failure, collagenoses, sleep apnea syndrome (OSA). Common hematological disorders that have a prothrombotic effect include platelet diseases, e.g. essential thrombocythemia and post-splenectomy thrombocytosis, in which the existence of “sticky” platelets that promote thrombosis is presumed. Hypercoagulation associated with increased hematocrit is caused by some erythrocyte diseases, i.e.true and symptomatic polycythemia, sickle cell anemia, paroxysmal nocturnal hemoglobinuria. In most of the above-mentioned diseases, symptomatic coagulopathy occurs. A large group of primary coagulopathy, i.e. disorders related a priori to the pathology of coagulation and fibrinolysis factors, is rich in thrombotic symptomatology. They often manifest themselves in the form of venous thrombosis, where the contributing factor is slower blood flow than in arteries. There are no unequivocal studies confirming either exclusively venous or exclusively arterial thrombosis. Thrombophilic deficiencies of coagulation inhibitors more often promote venous thrombosis, and their intraarterial manifestation is usually a secondary phenomenon. An example may be a type of metabolic thrombophilia on the basis of hyperhomocysteinemia with frequent thrombotic symptomatology. Hypercoagulability is associated with an increased level of coagulation factors, which may be promoted by a thrombogenic diet. Cipolli PL et al., 1991, using animal material, demonstrated a statistically significant increase in the activity of some coagulation factors (V, X), prothrombotic parameters of the thromboelastogram, with a thrombogenic diet. Hyperfibrinogenemia has been confirmed as a risk factor for vascular diseases – including ischemic stroke, as reported by Catto AJ and Grant PJ, 1995, who also indicated the role of other factors (VII, VIII von Willebrand), whose role in the etiology of thrombotic stroke is discussed alongside the significance of an increased level of factor II and PCCs (prothrombin complex concentrates). In turn, in dysfibrinogenemia, a type of fibrin is formed from abnormal fibrinogen, which is usually insensitive to fibrinolysis. Increased coagulability is indicated by an excess of FM fibrin monomers in plasma, e.g. in sepsis, multi-organ trauma, postoperative condition or in preeclampsia up to 2% of fibrin may be present in this form. FM is a subclinical indicator of a high risk of thrombosis. Hereditary, mostly autosomal dominant cases of thrombophilia concern deficiencies of some coagulation inhibitors such as: AT III, protein C, protein S, heparin cofactor II, which are of significant importance in diagnosing a clot. These thrombophilias can be of 2 types in heterozygotes depending on the quantitative or qualitative nature of the deficiency and type III in homozygotes with AT III deficiency. Their penetration is low, reaching several % of the entire population (e.g. up to 0.05% for AT III alone) and is more frequent in people under 45 years of age. Hereditary AT III deficiency of Utah type is associated with the replacement of proline at position 407 with leucine, which changes the geometry of the AT III molecule and affects the rate of its elimination from the circulation. In the geometric variant of the Hamilton type, tyrosine occurs instead of alanine at position 382 and such AT III, while remaining a substrate for serine proteases, does not have inhibitory properties.Acquired hypercoagulability due to impaired synthesis of AT III occurs in some liver diseases, loss of AT III – in nephrotic syndrome, and AT III deficiency is also found after treatment with L-asparaginase or DDAVP (desaminoarginine vasopressin) and in venous stasis. The level of free AT III or in complexes with thrombin (TAT) is assessed in the laboratory. The level of free protein S decreases in women taking oral contraceptives. Studies of proteins C and S, as well as APC modified with the addition of deficient factor V allow the determination of some pathologies of factor V (e.g. V Leiden mutation), VIII and the identification of the cause of fibrinolytic insufficiency caused by the insufficiency of these proteins. An acquired decrease in the level of protein C should be expected in some liver function disorders, nephrotic syndrome, DIC, treatment with oral anticoagulants, acute leukemia, diabetes. Congenital protein C deficiency in children often leads to thrombosis, and deficiencies of all coagulation inhibitors together with heparin cofactor II in people under 45 years of age are responsible for several percent of causes of thrombosis. Components of the antiphospholipid syndrome (aCL – anticardiolipin antibody, Las – lupus anticoagulants) have an inactivating effect on the activity of proteins C, S and AT III, hence the indication for their determination. In addition, aCL and Las may accompany SLE and are considered risk factors for ischemic stroke in people under 50 years of age. ACL may increase PAI activity in stroke patients. Hart RG and Kanter MC, 1991, found that in recent stroke up to 7% of cerebral infarctions associated with coagulopathy are noted. Some fibrinolytic disorders are also associated with thrombophilia. It is caused by quantitative and qualitative autosomal dominant plasminogen disorders, which occur, for example, in 2% of Japanese people. Thrombophilia also affects some activators and inhibitors of fibrinolysis, such as t-PA, prekallikrein, and changes in coagulation factors directly related to fibrinolysis, such as dysfibrinogenemia or factor XII disorders. Recently, more attention has been paid to the examination of t-PA concentration in stroke. There are conflicting reports on the correlation of its level with the coexistence of ischemic stroke. Some report an increase in its level at the beginning of the stroke, and then a decrease. Kempter B. et al., 1995, in 2 patients 3-6 months after stroke, using provocation of hemostasis disorders by limiting venous flow for 5 min, showed a weaker increase in t-PA and FbDP in patients compared to the control group. Others observe a constant trend of increasing t-PA levels in ischemic stroke, e.g. Margaglione M. et al., 1994, in a group of over 100 stroke patients showed increased levels of t-PA and PAI-1 compared to the control group. Many authors also report a decreased level of t-PA as a risk factor for thrombosis and a positive correlation of its decrease with increased levels of triglycerides, VLDL,insulin and BMI and blood pressure values. The most important indicators of fibrinolysis activation include:  fibrinogen degradation products (FgDP) containing fibrinopeptide A and an examination of the concentration of N-terminal Bbeta peptides. An increase in Bbeta 1-42 indicates fibrinogenolysis. The presence of this peptide together with Bbeta 1-118 are symptoms of primary fibrinolysis.  fibrin degradation products (FbDP) and Bbeta 15-42 peptide indicate the activation of secondary fibrinolysis. A diagnostic role similar to FbDP is played by the determination of D-dimers, in which an increase of up to 60,000 ng/ml is found in DIC in the course of alcoholic liver cirrhosis, in hepatitis, in tumors, in sepsis, in multi-organ damage, and up to 19,000 ng/ml was detected in phlebothrombosis. Increased D-dimer values ​​are also typical for pulmonary embolism and generalized atherosclerosis. The normal D-dimer level does not exceed 500 ug/l in people under 70 years of age and increases with age without showing any dependence on gender.  fibrinogen and fibrin degradation products (tFDP) determined together have a less specific meaning, although at the same time they are a more accessible method. TFDP inhibits the action of thrombin on fibrinogen, the generation of plasma thromboplastin, FM polymerization and platelet adhesion, aggregation and viscous transformation. PAI-1 activity and antigen concentration find significant application in the diagnosis of thrombotic conditions of cerebral strokes. The usefulness of this indicator is confirmed by experimental studies. As it results from the experimental work of Sawa H. et al., 1994, damage to the carotid arteries increases the PAI-1 level, and as a result reduces fibrinolytic activity and may initiate or exacerbate thrombosis. There are also non-standardized methods for determining the complexes of t-PA with PAI-1, u-PA with PAI-1 and PAI-2. When determining PAI-1, attention is paid to its significant daily fluctuations, differences dependent on sex and age, exercise and the fact that it belongs to acute phase proteins. It has been shown that with normal and increased RR, angiotensin II increases the level of PAI-1 in plasma. Increased PAI activity has been found in sepsis and septic shock, in malignant tumors, after surgery, in pregnancy in preeclampsia, in myocardial infarction and recurrent myocardial infarction, in deep vein thrombosis and stroke. In assessing the risk of coronary artery disease, the value of determining the level of PAI-1 antigen is greater than its activity. There is a positive correlation between PAI-1 growth and BMI, hypertension, android obesity according to the WHR index, insulin, triglycerides, VLDL levels, and a negative correlation with HDL levels. It has been noted that antiplatelet treatment causes a decrease in PAI-1 levels in patients in secondary prevention after ischemic stroke with increased fibrinolysis indices such as: fibrinogen, AT III, TAT, t-PA antigen, PAP, D-dimers. In photometric studies of the PAI to t-PA activity ratio, a reciprocal increase was found in the period after the acute phase of stroke and an increase in t-PA at the beginning of stroke.Simultaneous monitoring of alpha-2-antiplasmin and PAI-1 activity, which are the main inhibitors of fibrinolysis, allows for a more in-depth analysis of the thrombotic process, although in a narrow range. Excluding or confirming the role of these fibrinolysis inhibitors and their mutual references provide a basis for the etiological interpretation of thrombogenesis in the disease under study. The classification by some researchers of increased PAI-1 activity as a risk factor for thromboembolic vascular diseases and a decrease in the level of alpha-2-antiplasmin in some hemorrhages of congenital origin confirms their role in hemostasis disorders. It is even proposed to include increased PAI-1 level among the symptoms of polymetabolic syndrome. In turn, the physiological role of alpha-2-antiplasmin constitutes its barrier to the development of a lytic state, i.e. excessive nonspecific proteolytic activity of free plasmin in plasma. The lytic state occurs after the depletion of alpha-2-antiplasmin reserves, when free plasmin non-specifically digests fibrinogen, proaccelerin, antihemophilic factor, among others. Based on diagnostic data, attempts are made to draw therapeutic conclusions, which result in experimental and clinical studies on the use of thrombolytic drugs in ischemic stroke. The aim is to neutralize fibrinolysis inhibitors and directly bind the drug to the clot and activate endogenous plasminogen. At the same time, the thrombin time is prolonged and the FDP level is increased. Among the fibrinolytic drugs of the first generation: streptokinase, urokinase and APSAC (acylated streptokinase complex with human lys-plasminogen), there is no preparation that does not pose a risk of a lytic state complication after therapeutic use. First-generation fibrinolytic drugs with relatively low affinity for fibrin also act on fibrinogen contained in plasma. Therefore, compared to second-generation fibrinolytic drugs (t-PA, scu-PA), they are less useful in the treatment of ischemic stroke. Urokinase, unlike streptokinase, does not have antigenic properties, which encourages its local intra-arterial use in ischemic stroke, but limited indications and inconclusive results do not make this method common, also in its application. There are, however, numerous works on the therapeutic use of t-PA in ischemic stroke. It shows high affinity for fibrin. This natural activator of fibrinolysis is inhibited in the body by PAI. Through the kringle-2 domain, t-PA enters into a complex with PAI, which is then taken up by hepatocytes. Also used is genetically engineered rt-PA (recombinant tissue plasminogen activator) from the gene of chromosome 8 responsible for the synthesis of human t-PA. It does not cause the formation of antibodies. Both t-PA and rt-PA are important when used immediately after a stroke – preferably within 1.5 hours.Later, the risk of bleeding complications increases significantly. Recommended doses are (according to various sources): 0.35-1.08 mg/kg; 0.6-0.95 mg/kg or 20-30 MIU rt-PA. T-PA seems to be a very valuable drug when used intravenously, but its use requires a lot of organizational effort and costs. Third-generation fibrinolytic drugs introduced into experimental studies are characterized by increased affinity to fibrin, prolonged duration of action and resistance to inhibitors, which in effect makes them more effective and causes fewer bleeding complications. These include:

• r-PA recombinant plasminogen activator, a 39 kD mutant not recognized by liver endothelial cell receptors,
• rt-PA-NTK – t-PA mutated in 3 places, 80 times more resistant to inactivation by PAI,
• r-staphylocoagulase (recombinant staphylokinase) forms stoichiometric 1:1 complexes with plasminogen generating plasmin. In the absence of fibrin, it is inhibited in plasma by alpha-2-antiplasmin, which prevents the lytic state. It is more effective than streptokinase,
• bat-PA (DSPA-alpha) – extract from vampire bat saliva, 200 times more selective for plasminogen than t-PA. There are many drugs with fibrinolytic activity under research, e.g. proteins constituting chimeras of t-PA and other proteins, fibrinolytic drugs conjugated with monoclonal antibodies directed against thrombus components, hirudin - thrombin inhibitor and other enzymes isolated from leech saliva, such as hemetin, destabilase and ancrod obtained from viper venom. Attention was also paid to the profibrinolytic activity of metformin. Traditional methods of stroke treatment used before the introduction of fibrinolytic treatment also show an effect on fibrinolysis. Tohgi H. et al., 1993, showed a reduction of PAI-1 level in patients after stroke with antiplatelet treatment (ticlopidine 0.2/d or acetylsalicylic acid 40 mg/d). The effectiveness of these drugs is also emphasized by Członkowska A., 1995.

FIBRINOLYSIS IN PHYSIOLOGICAL CONDITIONS AND IN PATIENTS WITH ISCHEMIC STROKE

Review of a review paper:

The paper by Sławomir Graff, MD, is a review paper. The author discusses in detail the processes of coagulation and fibrinolysis in physiological conditions and the disturbances of their mutual balance, which are the basis of thrombotic changes occurring in strokes. Apart from atherosclerosis, numerous diseases of different etiology have a prothrombotic effect. Hypercoagulability may occur in diabetes, neoplastic processes, liver and kidney failure, collagenoses, polycythemia, sickle cell anemia. The participation of hematological disorders in the etiopathogenesis of ischemic strokes is relatively rare, but such a possibility should always be considered, especially in cases of ischemic stroke in young people. Performing targeted tests in these cases allows for making a diagnosis and attempting targeted treatment. The author discusses the action of fibrinolytic drugs of the 1st, 2nd and 3rd generation.

The work is prepared carefully. The author discusses in detail the problems of fibrinolysis based on many literature items.
The work meets all the requirements for a review paper for the 2nd degree specialization in neurology.
Dr. med. Danuta Ryglewicz - neurology specialist