L-arginine plasma concentrations in hypercholesterolaemia.
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Arginine↗
Biomedical subjects
F L Pasini
Publications and source records attributed to F L Pasini.
Pharmacodynamics of ticlopidine in man in relation to plasma and blood cell concentration.
In 6 normal volunteers given single oral doses of 250,500 and 1000 mg ticlopidine (T), the peak plasma level of unchanged drug was reached after about 2 h. There was no correlation between the plasma T level and its inhibitory effect on platelet function, expressed as % inhibition of ADP-induced aggregation. By means of HPLC and GC/MS significant concentrations of T were demonstrated in washed red cells, platelets and neutrophils, with a marked difference in the time course of the appearance of cell-associated drug. The time course of platelet-associated T very accurately fitted that of the antiaggregatory activity. After subacute oral administration (250 mg b.d. for 7 days), the maximum effect on platelet function was observed after 3 to 4 days, when a significant concentration of platelet-associated T had been reached. The pharmacological effect persisted as long as drug was detectable in platelet. An in vitro study strongly suggested that the antiaggregating effect was retained by treated washed platelets but not by treated plasma. It is suggested that the platelet compartment represents the pharmacological target of T via a specific uptake system.
Adult↗
Hemodynamic and hemorheologic effects of i.v. Dilevalol in hypertensive patients.
The authors evaluated the effect of Dilevalol infusion on blood pressure, heart rate, central hemodynamics, and rheologic parameters in hospitalized inpatients affected with mild or moderate hypertension. After a dose-finding phase and a washout period of one week, 10 patients aged fifty to seventy-two-years (median 61.5) were given either a single dose of Dilevalol 60 mg or placebo, and seven days later they underwent the other treatment, according to a single-blind, crossover design. Central hemodynamic measurements were performed by means of M-mode echocardiography, and hemorheologic parameters were evaluated by means of strain-gauge plethysmography. The maximal increase in lower extremity flow at rest had been obtained with the infusion of 60 mg Dilevalol during dose-finding, and so this dose was chosen for the second part of the study. The infusion of Dilevalol significantly increased rest flow and decreased blood viscosity, but the changes in central, parameters were not considered clinically relevant, although statistically significant. Blood pressure decreased without significant changes in heart rate. Thus, the acute administration of Dilevalol reduced blood pressure, without affecting heart rate and central hemodynamics, confirming the vasodilating effect of the drug. A significant improvement was also shown on blood viscosity in these hypertensive patients.
Blood Viscosity↗
Defibrotide inhibits Ca2+ dependent neutrophil activation: implications for its pharmacological activity in vascular disorders.
Defibrotide (DEF) is a polydeoxyribonucleotide agent provided with profibrinolytic and antithrombotic properties. Moreover, an antiischemic, cardioprotective effect of the drug has recently been demonstrated in experimental animals. Increasing evidence exists of the important role played by neutrophils in the development of tissue damage during chronic and acute ischemia and in the early phases of reperfusion. In order to evaluate whether the overall cytoprotective effect of DEF could be based, at least in part, on a neutrophil-involving mechanism, the authors studied the in vitro effects of the drug on human neutrophil activation triggered by several specific stimuli. The drug dose-dependently (10-100 microM) inhibited enzyme release, superoxide anion generation, and chemiluminescence induced in neutrophils by the chemoattractant oligopeptide fMLP and by the divalent cation ionophores A23187 and ionomycin. The increase of extracellular calcium concentration from 0.5 to 2.0 mM antagonized the inhibitory effect of DEF. The use of the fluorescent probe Fura 2/AM led them to show that DEF is able to reduce the cytosolic free calcium increase following specific stimulation by affecting extracellular calcium entrance. Such a behavior resembles that of calcium-antagonistic drugs, thus suggesting that DEF works, at least in part, similarly to calcium entry blockers. Such an activity on cell calcium translocation could represent the underlying molecular mechanism of cytoprotection. Finally, the inhibitory action on neutrophil functions may play a role in tissue protection during ischemic injury.
Calcium↗
Differential effect of adenosine on DNA synthesis in lymphoid and myeloid cell lines.
In this report, the effects of adenosine on the promyelocytic cell line HL-60 and on T-lymphocytic clones are compared. According to previous reports, adenosine induces a dose-dependent inhibition of DNA synthesis in T-lymphocytes. Conversely, adenosine dose-dependently enhances DNA synthesis in HL-60 cells, as documented with [3H]thymidine uptake studies and flow cytometric cell-cycle analysis. Unlike its effect on lymphocytes, the adenosine effect on HL-60 cells does not seem to be mediated by receptor binding, but it appears to be correlated with an intracellular mechanism following active uptake. Despite the different effects exerted by adenosine on lymphocytes and myeloid cells, a purinergic pathway appears to be more generally involved in the regulation of some phases of cell growth.
Adenosine↗
Selective 1H-NMR relaxation investigations of membrane-bound drugs in vitro. 3. Calcium-entry blockers and adenosine.
Selective proton relaxation rates (SPRR) were measured for selected protons of nimodipine or diltiazem in the presence of neutrophils, allowing detection of binding to the cell membrane. Fast exchange exchange of drug molecules between bound and free environments was shown to be the main factor determining the enhancement of SPRR, whereas viscosity effects could be neglected. The SPRR enhancement was almost completely cancelled out by the presence of adenosine as a cosolute in a dose-dependent fashion, leading to the suggestion that the endogenous mediator 'adenosine' affects binding of calcium-entry blockers to the neutrophil surface.
Adenosine↗
Adenosine blocks calcium entry in activated neutrophils and binds to flunarizine-sensitive calcium channels.
Adenosine is able to prevent Ca+(+) influx into activated neutrophils as detected by the specific fluorescent indicator Quin 2. Such an effect is shown in a similar fashion by the calcium entry blocker flunarizine. The binding interaction between flunarizine and the neutrophil membrane as well as the flunarizine-adenosine antagonism are shown by the 1H-NMR technique, thus supporting evidence of a competition between the agents at the same or a nearby site on the cell membrane.
Adenosine↗
In vivo and in vitro evidence of an adenosine-mediated mechanism of calcium entry blocker activities.
Drugs such as dipyridamole (200 micrograms/kg/min), an adenosine uptake inhibitor, and theophylline (300 micrograms/kg/min), an adenosine receptor antagonist, respectively increased and decreased postischemic hyperemia in normal subjects, as well as in POAD patients. Moreover, dipyridamole pretreatment was able to antagonize the reduction of peak flow induced by nifedipine, and the potentiating effect of flunarizine on postischemic hyperemia was affected significantly by theophylline, thus suggesting a possible interference of calcium entry blocker drugs with the endogenous adenosine system. In a cellular model (polymorphonuclear leukocytes--PMN) the inhibitory effect of calcium entry blockers on stimulated functions (degranulation and free radical production) was highly antagonized by theophylline. Finally, a 1H-NMR spectroscopy study showed a binding interaction between adenosine and flunarizine on the cell membrane. An adenosine-receptor coupling to the calcium entry blocker channels is suggested.
Adenosine↗
Allopurinol prevents ischaemia-dependent haemorheological changes.
Pre-treatment with allopurinol is able markedly to attenuate the deterioration in blood viscosity (BV) and whole blood filterability (WBF) that occurs after ischaemia during exercise. It also reduces the exercise-induced increase in serum oxidase activity, although this action is slightly less effective in peripheral obliterative arterial disease (POAD) patients. Conversely, allopurinol is completely ineffective in modifying haemorheological parameters in vitro, and it does not affect superoxide anion generation or enzyme release from neutrophils stimulated in vitro with formyl-methionyl-leucyl-phenylalanine (FMLP). It is suggested that allopurinol may attenuate changes in BV and WBF by affecting xanthine-oxidase-dependent free radical formation in tissues.
Aged↗
Effect of defibrotide on polymorphonuclear leukocytes: modulation of calcium entry and availability.
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Biological Availability↗
Conformation and dynamics of the chemotactic peptide formyl-L-methionyl-L-leucyl-L-phenylalanine in solution.
Several conformational and dynamic features of the chemotactic peptide formyl-L-methionyl-L-leucyl-L-phenylalanine in solution have been delineated by investigations of NMR and IR spectroscopic parameters. Both 1D and 2D NMR experiments have been performed for detection of scalar and dipolar proton-proton connectivities, whereas 13C and 1H relaxation parameters have been interpreted in terms of molecular dynamics. The main conformation appeared to be unfolded with the three hydrophobic side chains extending in divergent directions with respect to the backbone. The existence of relatively weak intermolecular hydrogen bonds was demonstrated, involving the formamide end group, with increase in the hydrophobicity of the external surface.
Magnetic Resonance Spectroscopy↗
Hemorheological factors in the pathophysiology of acute and chronic cerebrovascular disease.
The hemorheologic changes in three groups of patients suffering from acute and chronic cerebrovascular diseases were studied. Firstly, a horizontal study on 57 patients with definite stroke and on 49 patients with TIA was made. Plasma viscosity, whole blood filtration rate, fibrinogen concentration and hematocrit were evaluated as markers of the rheological property of blood. Blood samples were drawn within 6 h from the onset of vascular syndrome. The findings were compared with values obtained in 112 as controls. At the same time, washed red cell filtration rate, together with lactoferrin, betaglucuronidase and beta-thromboglobulin plasma level were assayed. In both groups the onset of the vascular storm was associated with a marked increase of plasma fibrinogen and of blood and plasma viscosity and a significant decrease of whole blood filterability. Lactoferrin, betaglucuronidase and beta-thromboglobulin levels were also significantly increased. Following this, a longitudinal study was performed on 27 patients with definite stroke and 32 patients with TIA. The clinical regression of acute stroke was associated with the progressive reduction of rheological abnormalities. Finally, 81 patients with clinical diagnosis of cerebrovascular disease due to previous stroke or repeated TIA were studied together. An increase of blood viscosity, of fibrinogen concentration and of hematocrit and a decrease of blood filtration rate together with higher levels of beta-thromboglobulin were registered. These results confirm the existence of an association between CVD and hemorheological alterations and suggest more in depth research directed towards identifying the significance of these alterations in the pathogenesis of tissue ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
Acute Disease↗
Adenosine inhibits polymorphonuclear leukocyte in vitro activation: a possible role as an endogenous calcium entry blocker.
Adenosine is able to in vitro inhibit FMLP-dependent activation of polymorphonuclear leukocytes as evaluated by enzyme release, superoxide anion generation and chemiluminescence production. The inhibiting effect is more relevant when A23187 is employed as stimulating agent. In this case the effect is significantly reversed by increasing concentrations of extracellular calcium. Since A23187-dependent activation is strictly dependent on Ca++ influx into the cell, the hypothesis is suggested that adenosine could act by regulatory mechanisms involving membrane calcium transport.
Adenosine↗
Angioimmunoblastic lymphadenopathy with dysproteinemia complicated by Kaposi's sarcoma.
A case of clinically and morphologically typical angioimmunoblastic lymphadenopathy (AILD) in a 68-year-old man during a prolonged antibiotic treatment for urinary infection is presented. Lymph node biopsy at first showed findings suggestive of an exhaustion of the germinal center immunological activity (like those characterizing angiofollicular lymph any clear transition into malignant lymphoma. The course of the disease was characterized by the occurrence of opportunistic infections (toxoplasmosis, herpes zoster), and finally by the onset of a cutaneous Kaposi's sarcoma. The possible relation of AILD to Kaposi's sarcoma is discussed, and the main clinical and morphological data of the case of AILD (about 200) reported in the literature are reviewed.
Aged↗
Action of cinnarizine on the hyperviscosity of blood in patients with peripheral obliterative arterial disease.
Cinnarizine, a drug capable of improving blood flow, was studied for its action on blood viscosity and its main components in patients affected by peripheral obliterative arterial diseases (POAD). Both acute and chronic administration of the drug diminished the increased whole-blood viscosity in patients, without affecting plasma and serum viscosity, hematocrit, plasma fibrinogen concentration, and plasma osmolality. Since cinnarizine also led to a significant increase of peripheral muscular blood flow, it was hypothesized that this action may be due to an increased deformability of the red cells, and may play a considerable role in the therapeutic approach to POAD.
Arterial Occlusive Diseases↗
Inhibition by cinnarizine of the properdin-dependent activation of complement.
Cinnarizine (1-benzhydryl-4-cinnamylpiperazine dihydrochloride), a well-known antagonist of vasoactive agents, has previously been shown to inhibit the activation of complement at the level of the fourth component. Cinnarizine was now tested in a system of complement activation by the properdin-dependent alternative pathway. At the concentration of 7.10(-5) M the compound completely inhibited the hemolytic reaction, which is the consequence of human complement activation in the presence of inulin or zymosan. This in vitro effect of cinnarizine was abolished by the addition of 1 mM MgCl2. These findings extend the anticomplementary activity of cinnarizine to the properdin pathway and support its interaction with the magnesium-dependent steps of the activation sequence.
Animals↗
[Effects of diphtheria and tetanus toxins on liver regeneration in the rat].
The effects of diphtheria toxin and tetanus toxin on the regenerating rat liver were studied. The following parameters were used: liver regeneration percentage, mitotic index, protein content and serum complement C3 fraction level. Diphtheria toxin does not affect the liver regeneration, that what confirms the poor sensitivity of the rat to this toxin. Tetanus toxin inhibits the cellular division, while causes an increase in the cell protein content, resulting in hepatocyte hypertrophy. Both toxins cause a fall of the serum complement C3 fraction.
Animals↗
[Study of various aspects of humoral immunity in a group of patients affected by myocardial infarct].
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Adult↗