Experimental thrombosis model induced by laser beam. Application of aspirin and an extract of Ginkgo biloba: EGb 761

Effect of Ginkgo biloba extract (GbE-761) on the survival of fasciocutaneous flaps in rats

Cutaneous and fasciocutaneous flaps are used widely in the surgical reconstruction of various body segments, especially to cover exposed vital tissues. Partial or total necrosis of these flaps, secondary to insufficient tissue irrigation, is one possible complication. Therefore, investigations into antiplatelet aggregation, vasodilation and antioxidant properties are highly significant. The aim of the present study was to analyse the effect of GbE 761 on the survival of fasciocutaneous flaps in rats. For that purpose, GbE 761 was administered to 30 rats after the creation of 10 × 3 cm dorsal flaps on each animal. The rats were divided into three equal groups. GbE 761 was administered to Group A, starting immediately after surgery; Group B received it 24 h after the flap was cut; and Group C (controls) received 0.9% NaCl solution. The average area of necrosis was 29.53% in Group A, 26.25% in Group B and 46.12% in Group C. The difference between Groups B and C was statistically significant (p = 0.026). These initial findings suggest that GbE 761 administered on day 1 after surgery reduces the percentage of necrosis in fasciocutaneous flaps, relative to not giving GbE at all.

Ginkgo biloba and risk of cancer: secondary analysis of the Ginkgo Evaluation of Memory (GEM) Study

PURPOSE

Evidence from in vitro and in vivo studies suggests that Ginkgo biloba has cancer chemopreventive properties, but epidemiological evidence is sparse. We analyzed cancer as a secondary endpoint in the Ginkgo Evaluation of Memory (GEM) Study, the largest randomized, double-blind, placebo-controlled clinical trial of Ginkgo supplementation to date.

METHODS

A total of 3069 GEM participants 75+ years of age were randomized to twice-daily doses of either 120 mg Ginkgo extract (EGb 761) or placebo and followed for a median 6.1 years. We identified hospitalizations for invasive cancer by reviewing hospital admission and discharge records for all reported hospitalizations over follow-up. Using an intention-to-treat approach, we compared the risk of cancer hospitalization between participants assigned to treatment and those assigned to placebo.

RESULTS

During the intervention, there were 148 cancer hospitalizations in the placebo group and 162 in the EGb 761 group (Hazard ratio (HR), 1.09; 95% confidence interval (CI), 0.87-1.36; p = 0.46). Among the site-specific cancers analyzed, we observed an increased risk of breast (HR, 2.15; 95%CI, 0.97-4.80; p = 0.06) and colorectal (HR, 1.62; 95%CI, 0.92-2.87; p = 0.10) cancer, and a reduced risk of prostate cancer (HR, 0.71; 95%CI, 0.43-1.17; p = 0.18).

CONCLUSIONS

Overall, these results do not support the hypothesis that regular use of Ginkgo biloba reduces the risk of cancer.

The effect of Ginkgo biloba extract (EGb 761) on hepatic sinusoidal endothelial cells and hepatic microcirculation in CCl4 rats

It has been shown that Ginkgo biloba Extract (EGb 761) increases peripheral and cerebral blood flow and microcirculation and improves myocardial ischemia reperfusion injury. This study was designed to investigate the effect of EGb 761 on hepatic endothelial cells and hepatic microcirculation. Sixty male Wister rats were divided into normal, carbon tetrachloride (CCl4) and EGb groups, and were given normal saline, CCl4 and CCl4 plus EGb 761, respectively, for 10 weeks. Samples were taken from the medial lobe of the rat livers ten weeks later. Hepatic sinusoidal endothelial cells and other parameters of hepatic microcirculation were observed under transmission electron microscopy (TEM). The amount of malondialdehyde (MDA), endothelin (ET-1), platelet-activating factor (PAF) and nitric oxide (NO) in liver tissue was determined by spectrophotometry and radioimmunoassay, respectively. Compared with the CCl4 group, aggregation of blood cell or micro thrombosis in hepatic sinusoids, deposition of collagen in hepatic sinusoids and space of Disse, injury of endothelial cells and capillization of hepatic sinusoid was significantly reduced in the EGb group. The amount of MDA, ET-1 and PAF was markedly reduced in the EGb group than in the CCl4 group, while no significant difference in the amount of NO was observed between the two groups. The results demonstrate that EGb 761 has protective effect on hepatic endothelial cells and hepatic microcirculation in rats with chronic liver injury induced by CCl4. The mechanisms may involve its inhibition on ET-1, PAF and lipid peroxidation.

Study of platelet behavior in vivo after endothelial stimulation with laser irradiation using fluorescence intravital videomicroscopy and PEGylated liposome staining

Platelets contain an array of potent proinflammatory mediators, and therefore they are regarded as mediator and effector cells in inflammation. Knowing the role of platelets during these processes is crucial and the analysis of their behavior in situ and the associated mechanisms is consequently particularly important. However, conventional in vitro staining techniques induce modification of the characteristics of platelets. This study aimed to evaluate platelet behavior in vivo after endothelial stimulation (without endothelial denudation or exposure of basal lamina and/or collagen) with an argon laser, using video intravital microscopy in combination with a new an innovative platelet staining technique based on polyethyleneglycol (PEG) liposomes. The study was performed on skin by using a dorsal skin-fold chamber implanted in golden hamsters. Platelets were stained by 5,6-CF-encapsulated PEGylated liposomes injected intravenously. The skin microcirculation was observed with an intravital microscope (using x25, x40, and x80 magnifications) fitted with a xenon light source, an epifluorescence assembly, and an ultra-high sensitivity video camera for fluorescence imaging. Platelet activation without endothelial denudation or exposure of basal lamina and/or collagen was obtained with an argon laser emitting at 514.5 nm with the following parameters: 20 mW, 300 ms, 120 J/cm(2). The 80-microm laser beam was focused on a vessel and its position was controlled with the microscope. Thanks to the spatial resolution of the intravital microscopic imaging system, the platelets were seen rolling individually on the endothelium. After laser stimulation, platelets were activated and three phases were observed: recruitment, adhesion and detachment. The observation of these three phases was time dependent and the kinetics of the process were quantified. The recruitment reached a maximum after 90 +/- 20 s. The adhesion phase lasted for 110 +/- 25 s. At last, detachment of all platelets was observed. This detachment started 200 +/- 20 s after irradiation and was completed in less than 2 min. This study confirms that laser irradiation used with optimal parameters can induce platelet activation without thrombus formation. Platelets can adhere only transiently on stimulated endothelium. This phenomenon may therefore represent a defense mechanism, by which platelets would accumulate in the vicinity of an injury, making them available for immediate response. At last, this study has clearly demonstrated the advantages of our new and innovative platelet staining method using PEGylated liposomes, which are (i) in situ labeling, (ii) use of a hydrophilic marker located in an aqueous compartment within the platelet, and (iii) labeling of platelets allowing observation during the whole experiment.

Ginkgo biloba for the prevention and treatment of cardiovascular disease: a review of the literature

Results from clinical trials demonstrate that standardized leaf extracts of Ginkgo biloba (SGB extract) reduce the symptoms of age-associated memory impairment and dementia, including Alzheimer's disease, and may be of benefit in treating intermittent claudication. In addition, preliminary results suggest that SGB extract may be useful in preventing and treating cardiovascular disease (CVD). particularly ischemic cardiac syndrome. Since many patients with cardiovascular disease are already taking anticoagulants and antiplatelet drugs, self-medication with SGB extract is not recommended without the advice of their physician. Although SGB extracts look promising for preventing and treating CVD, well-controlled clinical trials are needed before clinical recommendations can be made.

Adverse effects of unconventional therapies in the elderly: A systematic review of the recent literature

Unconventional therapies are increasingly popular, not least in populations of elderly individuals. This review summarizes the evidence regarding the risk unconventional therapies may entail for the elderly. Computerized literature searches were performed to locate all reports with original data on this topic. Most of the evidence found was anecdotal by nature and thus has obvious limitations. The results show that elderly patients can suffer harm from unconventional therapies. Herbal treatments are associated most frequently with adverse events. They can cause both direct toxicity and unwanted herb-drug interactions. Acupuncture, spinal manipulation and even massage therapy have also been implicated. Indirect risks exist if unconventional therapies are employed as a substitute for conventional treatments. It is concluded that unconventional therapies are not risk-free for elderly patients. All parties involved ought to be educated with a view of minimizing this risk, and more research is needed to increase our understanding of this area.

Inhibition of type 4 phosphodiesterase by rolipram and Ginkgo biloba extract (EGb 761) decreases agonist-induced rises in internal calcium in human endothelial cells

The effects of Gingko biloba extract EGb 761 on 5 isolated, vascular, cyclic nucleotide phosphodiesterase (PDE) isoforms were evaluated. EGb 761 preferentially inhibited PDE4 (IC(50)=25.1 mg/L), the isoform that is mainly present in endothelial cells, in a competitive manner (K:(i)=12.5 mg/L). Because changes in cyclic nucleotide levels may affect intracellular calcium ([Ca(2+)](i)) levels in endothelial cells, we examined the effects of EGb 761 on both resting [Ca(2+)](i) levels and agonist-induced rises in [Ca(2+)](i) in single human umbilical vein endothelial cells (HUVECs) in culture. The effects of EGb 761 were compared with those of rolipram, a selective PDE4 inhibitor that increases cellular cAMP levels, and the cAMP analogue dibutyryl cAMP (db-cAMP). EGb 761 (20 and 100 mg/L), rolipram (50 micromol/L), and db-cAMP (100 micromol/L) significantly inhibited histamine-, ATP-, and thrombin-induced [Ca(2+)](i) increases in HUVECs without modifying resting [Ca(2+)](i) levels. Similar results were obtained by using a Ca(2+)-free bath solution. EGb 761 (100 mg/L), but not rolipram (50 micromol/L) or db-cAMP (100 micromol/L), also inhibited Ca(2+) influx into cells having thapsigargin-depleted internal Ca(2+) stores and bathed in a Ca(2+)-free external solution. Our results are consistent with an inhibition of PDE activity that causes a reduction of agonist-induced increases in [Ca(2+)](i) in HUVECs, mainly by inhibition of Ca(2+) mobilization from internal stores. It thus may be that the cardiovascular effects of EGb 761 involve inhibition of PDE4 activity and subsequent modification of Ca(2+) signaling in endothelial cells.

Antiplatelet and antithrombotic effects of a combination of ticlopidine and ginkgo biloba ext (EGb 761)

The antiplatelet and antithrombotic effects of the oral combination treatment of ticlopidine and Ginkgo biloba extract (EGb 761) were studied in normal and thrombosis-induced rats. The ex vivo inhibitory effect on ADP-induced platelet aggregation of a small dose of ticlopidine (50 mg/kg/day) in combination with EGb 761 (40 mg/kg/day) was comparable to a larger dose of only ticlopidine (200 mg/kg/day). Bleeding time was also prolonged by 150%. Thrombus weight was also consistently decreased by a combination of ticlopidine and EGb 761 in an arterio-venous shunt model at two doses of ticlopidine (50 mg/kg) plus EGb 761 (20 mg/kg) and ticlopidine (50 mg/kg) plus EGb 761 (40 mg/kg). A combinatory treatment in acute thrombosis model in mice also showed a higher recovery than a single treatment.

Combination of two doses of acetyl salicylic acid: experimental study of arterial thrombosis

The antithrombotic effect of high dose acetylsalicylic acid is well known, and recently, in vitro studies hinted the potent thrombotic effect of ultra-low dose of acetylsalicylic acid (<1mg/day) showing a significant decrease in bleeding time. In this study, we investigated the effect of a combination between a high and an ultra-low dosage (100 mg/kg+ 10(-30) mg/kg) on an arterial thrombosis induced by a laser beam. We used an intravital microscopic technique, allowing to evaluate (anti)-thromboembolic events at previously determined locations of microvasculature. Thrombus formation was induced by argon-laser shot. The instrumental test setup was completed with a video system, to select mesenteric arterioles with the same diameter (between 15 and 25 microm). The changes in platelet aggregability were determined by Cardinal and Flower method, and the concentration of acetylsalicylic acid in the plasma was measured by high pressure liquid chromatography. Antithrombotic effect of high dose (100 mg/kg) acetylsalicylic acid was confirmed in all results obtained. Asa injected at ultra-low dose (10(-30) mg/kg) had a potent thrombotic properties and decreased significantly the bleeding time. The subcutaneous administration of the combination of the two doses permitted to come back to the control values, and the bleeding time was shortened compared to control group.

A Comparison of Heparin and New Anticoagulants for Cardiopulmonary Bypass Surgery

Heparin is still the major anticoagulant of choice during CPB, but it may cause thrombocytopenia and severe bleeding in patients. In light of these complications, the devel opment of new anticoagulant drugs seemed to be necessary for these patients. Many experimental studies focused on r-hirudin, which presented a less hemorrhagic effect than heparin. How ever, neither antagonist has been shown to reverse this effect.

Action of neurotransmitters: acetylcholine, serotonin, and adrenaline in an experimental arterial thrombosis induced by oxygen free radicals

It is well known that high stress and particularly an enhancement of plasma catecholamines and myocardial infarction have a close relation. In addition, adrenaline is presented as a prothrombogenic agent in vivo. The role of the other agents such as serotonin or acetylcholine, in the development of arterial thrombosis is somewhat uncertain, although, the role of each of them is often considered at the level of vascular regulation only. Therefore, the present study was designed to investigate the effects of three neurotransmitters on experimental arterial thrombosis model induced by generation of free radicals. The results demonstrate that intravenously injection of adrenaline or serotonin (1 ng/kg) stimulated arterial thrombosis formation, whereas injection of high dose of acetylcholine (5 mg/kg) slackened the thrombosis formation.