Changes in platelet aggregation and fibrinolytic activity of blood in healthy persons during the 23-day physical cycle]

The blood of 100 health humans aged 18 to 40 years was analysed. The aggregation of platelets and blood fibrinolytic activity were shown to change within 23-day physical cycle according to Swoboda and Fliess. In the negative phase the platelets count, their aggregation, desaggregation process and blood fibrinolytic activity were higher than in the positive one. No substantial differences in platelets aggregation and blood fibrinolytic activity were found during the positive and negative phases of the emotional or intellectual cycles.     

An ethanol extract of Ramulus mori improves blood circulation by inhibiting platelet aggregation

Inappropriate platelet aggregation can cause blood coagulation and thrombosis. In this study, the effect of an ethanol extract of Ramulus mori (ERM) on blood circulation was investigated. The antithrombotic activity of ERM on rat carotid arterial thrombosis was evaluated in vivo, and the effect of ERM on platelet aggregation and blood coagulation time was evaluated ex vivo. To evaluate the safety of ERM, its cytotoxicity to platelets and its effect on tail bleeding time were assessed; ERM was not toxic to rat platelets and did not prolong bleeding time. Moreover, administering ERM to rats had a significant preventive effect on carotid arterial thrombosis in vivo, and significantly inhibited adenosine diphosphate- and collagen-induced platelet aggregation ex vivo, whereas it did not prolong coagulation periods, such as prothrombin time and activated partial thromboplastin time. The results suggest that ERM is effective in improving blood circulation via antiplatelet activity rather than anticoagulation activity.     

Prostacyclin-like activity in rat vascular tissues. Fast, long-lasting inhibition by treatment with lysine acetylsalicylate.

Both arterial and venous tissues obtained from normal rats released prostacyclin (PGI2)-like activity, as marked by its potent inhibitory effect on platelet aggregation. Intraperitoneal or intravenous administration of a single dose of a soluble lysine salt of acetylsalicyclic acid (L-ASA, 1-400 mg/kg) resulted in abolition or substantial reduction of prostacyclin-like activity released from rat vasculature. The inhibitory effect of L-ASA was evident one minute after its i.v. administration to the animals, persisted for at least 24 hours and was still detectable (in venous tissues only) 168 hours later. Venous tissues were inhibited by doses of L-ASA as low as 1 mg/kg, whereas arterial tissues were not inhibited by doses of LA-ASA lower than 10 mg/kg. This difference may possibly be related to the lower prostacyclin-like activity shown by rat venous tissues compared to arterial ones. It is suggested that L-ASA or part of its molecule may bind to and inhibit cyclo-oxygenase in the blood vessel wall in a manner similar to the acetylation of platelt cyclo-oxygenase.     

Prostacyclin-like activity in rat vascular tissues. fast, long-lasting inhibition by treatment with lysine acetylsalicylate

Both arterial and venous tissues obtained from normal rats released prostacyclin (PGI₂)-like activity, as marked by its potent inhibitory effect on platelet aggregation. Intraperitoneal or intravenous administration of a single dose of a soluble lysine salt of acetylsalicylic acid (L-ASA, 1–400 mg/kg) resulted in abolition or substantial reduction of prostacyclin-like activity released from rat vasculature. The inhibitory effect of L-ASA was evident one minute after its i.v. administration to the animals, persisted for at least 24 hours and was still detectable (in venous tissues only) 168 hours later. Venous tissues were inhibited by doses of L-ASA as low as 1 mg/kg, whereas arterial tissues were not inhibited by doses of L-ASA lower than 10 mg/kg. This difference may possibly be related to the lower prostacyclin-like activity shown by rat venous tissues compared to arterial ones.It is suggested that L-ASA or part of its molecule may bind to and inhibit cyclo-oxygenase in the blood vessel wall in a manner similar to the acetylation of platelet cyclo-oxygenase.     

The action of interferon and reaferon on the functional activity of human thrombocytes

The functional activity of thrombocytes (aggregation, endo- and exocytosis) and erythrocytes (aggregation) in healthy persons given a course of interferon or reaferon treatment has been studied. The results obtained in this study indicate that these preparations produce a modulating effect on the functions of thrombocytes and erythrocytes of donors having shown abnormal functional activity of these blood cells prior to the course of treatment.     

NO对家兔Oddi括约肌肌电活动和血压的影响

应用３２只家兔观察一氧氮对Ｏｄｄｉ括约肌肌电和血压的影响。静脉注射ＮＯ合酶抑制剂Ｎ＾Ｇ－硝基－Ｌ－精氨酸,可见ＳＯ肌电振幅增大和血压升高,Ｌ－ＮＮＡ所致的肌电活动增强可Ｌ－精氨酸反转。     

Changes in the guanylate cyclase activity of human thrombocytes during ADP-inducible aggregation]

Activity of guanylate cyclase (GC) and its capacity for sodium nitroprusside (SNP) activation were determined in platelets with different state of aggregation. The development of ADP-induced reversible aggregation was accompanied by a decrease in the basal GC activity and by an increase in the SNP activation of GC. It was shown that elevation of GC sensitivity to SNP during the aggregation might be due to the decrease in the state of enzyme blood deficiency. Preincubation of platelets with SNP before ADP adding markedly diminished or even prevented aggregation, depending on SNP concentration. GC parameters in platelets with prevented aggregation were just the same as in control. It is suggested that the regulatory role of cGMP system in platelet aggregation may be seen in the increase in GC sensitivity to endogenous activator, presumably to NO.     

Method for collecting rat thrombocytes and determining their aggregation

Three different methods of blood collection from rats are studied and compared, namely decapitation, catheterization of the carotid artery and puncture of the heart left ventricle. The latter method is preferable in studies of platelet aggregation. The method for isolation of washed platelets from rat blood is described in detail. The platelets stored for several hours at 20 degrees C did not lose the ability for aggregating under exposure to low concentrations of ADP. The curves of aggregation of washed and plasma platelets are provided. To study the rate of aggregation, a model is offered based on the approximation of the aggregation curves by the exponential A = A0exp (-alpha t). Such an approach made it possible to treat the data objectively and to reveal the features of platelet functional activity, particularly in arterial hypertension.     

Characterization of the salivary apyrase activity of three rodent flea species

1. Salivary gland lysates of the adult female fleas Oropsylla bacchi, Orchopea howardi and Xenopsylla cheopis hydrolyse ATP and ADP, but not AMP, thus characterizing the existence of a salivary apyrase activity. 2. In all species Mg++ or Ca++ function as activators, and a pH optimum between 7 and 8 is observed. 3. Salivary gland lysates of male fleas contain significantly smaller amounts of the enzyme activity than do those of female fleas. 4. Immediately following a blood meal, apyrase activity and protein content of female X. cheopis salivary glands are 2-3-fold less than that of unfed fleas, indicating that salivary apyrase activity is secreted during feeding. 5. It is suggested that, as in other arthropods, salivary apyrase may facilitate blood location and blood feeding by preventing ADP-induced platelet aggregation at the site of the bite.     

Platelet - vessel wall interaction: role of blood clotting

Vascular damage initiates not only the adhesion and aggregation of blood platelets but also coagulation, which is of mixed (intrinsic and extrinsic) origin. Evidence is presented that thrombin, generated as a result of the injury, is a prerequisite for platelet aggregation. Platelets, after activation, in their turn promote coagulation. Prostaglandin I2 (PGI2 or prostacyclin) inhibits coagulation induced by damaged vascular tissue. This effect of PGI2 is mediated by the inhibition of platelets in their participation in the generation of factor Xa and thrombin. Dietary cod liver oil, by changing plasma coagulability, decreases the procoagulation activity of vessel walls, and arterial thrombosis. Another fish oil with similar effects on plasma coagulability and some other haemostatic parameters does not modify vessel wall-induced clotting, nor does it significantly lower arterial thrombosis tendency; this indicates the physiological relevance of vessel wall-induced clotting in arterial thrombus formation. Some evidence is also given for the importance of vessel wall-induced clotting in primary haemostasis.     

Inheritance of very low serum dopamine-beta-hydroxylase activity.

Serum dopamine-beta-hydroxylas (DBH) activity was measured in blood samples obtained from 841 children ages 6-12, 277 adults subjects, and 114 relatives of children with serum DBH activity of less than 50 units. Approximately 4% of the children and 3% of the adult subjects tested had very low sweum DBH activity (50 units or less). Because these subjects appeared to make up a separate subgroup within the population and because of a striking familial aggregation of subjects with very low enzyme activity, serum DBH activity was measured in blood obtained from members of 22 families of probands with very low serum enzyme activity. The results of sibship and pedigree analyses of the data were compatible with autosomal recessive inheritance of very low serum DBH activity. Unaffected parents of probands had serum DBH activity intermediate between that found in affected individuals and in control population. No significant correlation of serum DBH activity with either systolic or diastolic blood pressure was found in this randomly selected population of children.     

Cyclic nucleotides and platelet aggregation. Effect of aggregating agents on the activity of cyclic nucleotide-metabolizing enzymes.

The activities of adenylate and guanylate cyclase and cyclic nucleotide 3':5'-phosphodiesterase were determined during the aggregation of human blood platelets with thrombin, ADP, arachidonic acid and epinephrine. The activity of guanylate cyclase is altered to a much larger degree than adenylate cyclase, while cyclic nucleotide phosphodiesterease activity remains unchanged. During the early phases of thrombin-and ADP-induced platelet aggregation a marked activation of the guanylate cyclase occurs whereas aggregation induced by arachidonic acid or epinephrine results in a rapid diminution of this activity. In all four cases, the adenylate cyclase activity is only slightly decreased when examined under identical conditions. Platelet aggregation induced by a wide variety of aggregating agents including collagen and platelet isoantibodies results in the "release" of only small amounts (1-3%) of guanylate cyclase and cyclic nucleotide phosphodiesterase and no adenylate cyclase. The guanylate cyclase and cyclic nucleotide phosphodiesterase activities are associated almost entirely with the soluble cytoplasmic fraction of the platelet, while the adenylate cyclase if found exclusively in a membrane bound form. ADP and epinephrine moderately inhibit guanylate and adenylate cyclase in subcellular preparations, while arachidonic and other unsaturated fatty acids moderately stimulate (2-4-fold) the former. It is concluded that (1) the activity of platelet guanylate cyclase during aggregation depends on the nature and mode of action of the inducing agent, (2) the activity of the membrnae adenylate cyclase during aggregation is independent of the aggregating agent and is associated with a reduction of activity and (3) cyclic nucleotide phosphodiesterase remains unchanged during the process of platelet aggregation and release. Furthermore, these observations suggest a role for unsaturated fatty acids in the control of intracellular cyclic GMP levels.     

Covalent complexes of albumin with serotonin, ketanserin and lysergic acid antagonize the activity of serotonin in human platelets

Covalent conjugates of bovine serum albumin (BSA) and 5-HT, ketanserin or d-lysergic acid were synthesized and characterized by polyacrylamide gel electrophoresis, whole blood clearance experiments in mice and aggregation studies with human platelets. Using the standard synthesis procedure, each mol of BSA bound 13.4 mol of [3H]5-HT. Derivatization did not cause significant protein aggregation as determined by electrophoresis. All three conjugates antagonized the ability of 5-HT to amplify aggregation caused by low concentrations of ADP. The antagonist activity of each conjugate was concentration dependent; 2.6 microM 5-HT-BSA completely inhibited the aggregation caused by 13 microM 5-HT. None of the BSA drug conjugates, including 5-HT-BSA, amplified platelet aggregation caused by ADP in the absence of 5-HT. Aggregation by ristocetin, collagen, epinephrine or ADP alone was not significantly affected by the conjugates. Whole blood elimination experiments in mice demonstrated that the three conjugates and underivatized BSA are equally stable in the circulation. These prototypic 5-HT drug-protein conjugates may be useful for probing 5-HT2 receptor-ligand interactions in human platelets.     

Modulation of arterial baroreflex control of muscle sympathetic nerve activity by muscle metaboreflex in humans

We aimed to investigate the interaction [with respect to the regulation of muscle sympathetic nerve activity (MSNA) and blood pressure] between the arterial baroreflex and muscle metaboreflex in humans. In 10 healthy subjects who performed a 1-min sustained handgrip exercise at 50% maximal voluntary contraction followed by forearm occlusion, arterial baroreflex control of MSNA (burst incidence and strength and total activity) was evaluated by analyzing the relationship between beat-by-beat spontaneous variations in diastolic arterial blood pressure (DAP) and MSNA both during supine rest (control) and during postexercise muscle ischemia (PEMI). During PEMI (vs. control), 1) the linear relationship between burst incidence and DAP was shifted rightward with no alteration in sensitivity, 2) the linear relationship between burst strength and DAP was shifted rightward and upward with no change in sensitivity, and 3) the linear relationship between total activity and DAP was shifted to a higher blood pressure and its sensitivity was increased. The modification of the control of total activity that occurs in PEMI could be a consequence of alterations in the baroreflex control of both MSNA burst incidence and burst strength. These results suggest that the arterial baroreflex and muscle metaboreflex interact to control both the occurrence and strength of MSNA bursts.     

Blood lactate dehydrogenase activity in newborn children

Arterial and venous blood samples from babies' umbilical cord vessels before lung breath beginning were used to measure arterial-venous difference between lactate dehydrogenase activity, pH and oxygen blood saturation (sO2). Enzyme activity was 735.4 +/- 90.8 U/L in venous blood and 672.0 +/- 108.1 U/L in arterial one, pH 7.21 +/- 0.06 and 7.32 +/- 0.06, sO2 32.9 +/- 12.7 and 56.5 +/- 18.3%, respectively. Reverse correlation between enzyme activity, pH and sO2 was found.     

The efferent sympathetic activity of the rabbit renal nerve during local application of adrenaline to the carotid sinus]

Adrenalin solution (1:1000) administered at the carotid sinus, through excitation of the depressoric C-fibre system of the carotid nerve, induces a strong, lasting reflectoric decrease of arterial pressure with slowing heart rate, associated with an almost complete inhibition of the efferent sympathetic activity of the renal nerve. The efferent sympathetic activity, arterial blood pressure and heart rate, both at the onset and at the height of adrenalin action, show corresponding activity changes: the relative inhibition of the sympathetic nerve is strongest correlated with the depressoric blood-pressure effect, while the decrease of heart rate, related to the initial activity, is least pronounced.     

Cardiovascular adjustments to rhythmic handgrip exercise: relationship to electromyographic activity and post-exercise hyperemia

The purpose of this study was to examine the association among electromyographic (EMG) activity, recovery blood flow, and the magnitude of the autonomic adjustments to rhythmic exercise in humans. To accomplish this, 10 healthy subjects (aged 23-37 y) performed rhythmic handgrip exercise for 2 min at 5, 15, 25, 40, and 60% of maximal voluntary force. Heart rate and arterial blood pressure were measured at rest (control), during each level of exercise, and for 2 min following exercise (recovery). The rectified, filtered EMG activity of the exercising forearm was measured continuously during each level of exercise and was used as an index of the level of central command. Post-exercise hyperemia was calculated as the difference between the control and the average recovery (2 min) forearm blood flows (venous occlusion plethysmography) and was examined as a possible index of the stimulus for muscle chemoreflex activation. Heart rate, arterial pressure, forearm EMG activity, and post-exercise hyperemia all increased progressively with increasing exercise intensity. The magnitudes of the increases in heart rate and arterial pressure from control to exercise were directly related to both the level of EMG activity and the degree of post-exercise hyperemia across the five exercise intensities (delta heart rate vs EMG activity: r = 0.99; delta arterial pressure vs EMG activity: r = 0.99; delta heart rate vs hyperemia: r = 0.99; and delta arterial pressure vs hyperemia: r = 0.98; all p less than 0.01). Furthermore, the level of EMG activity was directly related (r = 0.99) to the corresponding degree of hyperemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Peptides as inhibitors of thrombin coagulation activity and of thrombocyte aggregation]

The analysis of literature and our own data of regulatory peptides influence on the blood coagulation system is presenting. Various natural and synthetic peptides inhibit the activity of thrombin and platelet aggregation. Direct specific inhibitors of thrombin are peptides developed on the base of D-Phe-Pro-Arg sequence. Strong specific inhibitors of the prothrombinase complex factor Xa were isolated from tissues and saliva of the blood-sucking organisms. These inhibitors decrease thrombin generation at the early stage of blood coagulation cascade Anticoagulating peptides from the tick Ornithodoros moubata tissue (TAP), the recombinant rTAP from the saliva glands of tick Ornithodoros savignyi and peptide with even greater anticoagulating activity from saliva glands of fly Glossina morsitans morsitans were isolated and characterised. For complete and reliable suppression of thrombus formation simultaneous administration of thrombin and platelet aggregation inhibitors is necessary. Main terminal stage of platelet aggregation is the interaction of receptor GP IIb/IIIa with adhesive fibrinogen sequence Arg-Pro-Asp (RGD). Peptides derived on the base of this sequence compete with fibrinogen in reaction with platelet receptors. A lot of corresponding peptidomimetics were synthesised, e.g. MK-852, RO-44 and particularly effective compound integrelin. Many direct platelet aggregation inhibitors were found in snake venoms. Recombinant peptide TAP mentioned above exerts both antithrombin and antiaggregation activity. Peptides and peptide mimetics of this type rapidly and irreversibly bound with receptor GP IIb/IIIa. They have short half life time in the blood plasma. Their preference in comparison with other drugs is particularly rapid and strong action. In our experiments it was demonstrated, that simple proline-containing peptides Pro-Gly, Trp-Pro, Pro-Gly-Pro (putative fragments of collagen and elastin) possesses significant antithrombotic and anticoagulant potential in vitro and in in vivo. Perhaps these peptides are members on intrinsic complex of haemostasis regulators.     

Effect of cervical sympathetic trunk transection on renal sympathetic nerve activity in rats

Stellate ganglion blockade (SGB) with a local anesthetic increases muscle sympathetic nerve activity in the tibial nerve in humans. However, whether this sympathetic excitation in the tibial nerve is due to a sympathetic blockade in the neck itself, or due to infiltration of a local anesthetic to adjacent nerves including the vagus nerve remains unknown. To rule out one mechanism, we examined the effects of cervical sympathetic trunk transection on renal sympathetic nerve activity (RSNA) in anesthetized rats. Seven rats were anesthetized with intraperitoneal urethane. RSNA together with arterial blood pressure and heart rate were recorded for 15 min before and 30 min after left cervical sympathetic trunk transection. The baroreceptor unloading RSNA obtained by decreasing arterial blood pressure with administration of sodium nitroprusside was also measured. Left cervical sympathetic trunk transection did not have any significant effects on RSNA, baroreceptor unloading RSNA, arterial blood pressure, and heart rate. These data suggest that there was no compensatory increase in RSNA when cervical sympathetic trunk was transected and that the increase in sympathetic nerve activity in the tibial nerve during SGB in humans may result from infiltration of a local anesthetic to adjacent nerves rather than a sympathetic blockade in the neck itself.     

Cervical preganglionic sympathetic nerve activity and chemoreflexes in the cat

The role of chemoreflexes originating from carotid body and central chemoreceptors in the regulation of cervical preganglionic sympathetic nerve (PSN) activity was studied in anesthetized and spontaneously breathing cats. PSN efferents which responded to hypoxia were selected for the study. The PSN activity, breath-by-breath inspiratory tidal volume, tracheal PO2 and PCO2, and arterial systemic blood pressure were recorded simultaneously. The responses of PSN efferents to transient changes in and steady-state levels of arterial PO2 and PCO2 and to graded bolus injections of intravenous sodium cyanide (50-100 micrograms), nicotine (50-100 micrograms), and dopamine hydrochloride (30-60 micrograms) were compared before and after bilateral section of carotid sinus nerves (CSN). CSN section raised the base-line PSN activity and practically eliminated the responses to brief pharmacological stimuli, but it did not eliminate the responses to transient changes in and steady-state levels of arterial PO2 and PCO2. However, CSN section diminished PSN responses and abolished ventilatory responses to hypoxia. Thus the PSN response to hypoxia was partly independent of peripheral chemoreflex and of respiratory drive. We conclude that carotid body chemoreflex elicits fast PSN responses and that a moderate decline in arterial PO2 causes an additional slow, direct excitation of sympathetic nervous system. The latter indicates O2 chemosensitivity of the system in the physiological range of arterial PO2. This O2-sensing property may allow sympathetic nervous system to initiate chemoreflex responses independent of the peripheral chemoreceptors.