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At least 595 records · Page 33Linked to original sources

Studies on human platelets stored at 20-22 degrees C without agitation.

Human blood platelets in ACD plasma were stored in sterile plastic bags for 24-96 h at the ambient temperature without agitation. No spontaneous aggregation nor bacterial contamination were noted. A progressive loss of the following parameters was seen: platelet count; ADP-, thrombin-, collagen-, and epinephrine-induced platelet aggregation; platelet factor 3 activity; reversible response to the osmotic shock; volumetric constants; amount of UV-absorbant material; 14C-5-hydroxytryptamine and 3H-adenosine uptake and release; platelet population pattern and glycogen synthesis activity. The platelet aggregation and release, the osmotic shock test, and the platelet population pattern appear to better illustrate the early changes during platelet storage and to account for the 25-42% of recirculation of 24 h stored platelets administered into thrombocytopenic patients. As stated by Murphy and Gaardner, platelets stored at 20-22 degrees C with or without agitation, although having failed to retain total functional and biochemical capacities, paradoxically seem to recuperate in vivo as shown by survival data and hemostatic effects.

Adenosine↗

Anatomy of the ciliary body and cyclocryotherapy.

Anatomical measurements were carried out on the ciliary body, and its relationship to the structures of the chamber angle and the corneal limbus was examined in order to find the best application site for the cryoprobe in cyclocryotherapy. According to our results and to the experiences of other authors, the following procedure will make cyclocryotherapy most effective: a cryoprobe of normal tip diameter (2.5 mm) should be placed with its anterior edge 1.5 mm posterior to the limbus superiorly and 1.0 mm nasally, temporally, and inferiorly. The temperature at the tip should be around -70 degrees C, and the time of application about 60 s. Marked individual differences in the thickness of the pars plicata and the ciliary muscle may affect the results in some patients despite standardized treatment.

Adult↗

Experimental investigations on the penetration into the eyeball of iron administered intraorbitally.

In order to elucidate the still controversial question whether iron foreign bodies located in the orbit can produce siderosis bulbi, the authors studied the concentration of iron in the aqueous of rabbits in which the metal was placed outside the eyeball, close to the exposed sclera. It was found that iron penetrates into the eye, its concentration in the aqueous increasing with the lapse of time. It was also found that this concentration was distinctly higher in animals which had received higher amounts of iron.

Animals↗

Experimental investigations on the effect of desferrioxamine on the aqueous level of iron administered intraorbitally.

Rabbits with an iron foreign body in the orbit were given transconjunctival injections of desferrioxamine every 4th day. It was found that after 12 months the level of iron in the aqueous of their eyes was distinctly lower than in another group, which received no medication. Under the conditions of the experiment, desferrioxamine distinctly prevented extrabulbar iron from penetrating into the eyeball.

Animals↗

Cavernous hemangioma of the iris.

A case of cavernous hemangioma of the iris is reported which could be diagnosed without histopathological examination on the basis of clinical observations, particularly of the characteristic changes occurring in fluorescein angiography. The importance of fluorescein angiography in the differential diagnosis of angioma of the iris is stressed.

Fluorescein Angiography↗

Long-term observations of patients with acute retinal pigment epitheliitis.

Because of some authors presumptions that acute retinal pigment epitheliitis is not a distinct clinical entity but the early stage of other fundus diseases, the results of long-term observations of 5 patients with this disease are reported. The results of 6- to 7-year observations of these patients have shown that in none of them the fundus lesions developed into other retinal diseases. This indicates that acute retinal pigment epitheliitis is a distinct clinical entity.

Adult↗

Modulation of tissue factor expression by rapamycin and FK-506 in lipopolysaccharide-stimulated human mononuclear cells and serum-stimulated aortic smooth muscle cells.

Inflammation is a key pathogenic component of atherosclerosis; it also promotes thrombosis, a process underlying acute coronary events and stroke. Cells present in atherosclerotic plaque show abnormal tissue factor (TF) expression. Macrolides, in addition to their antimicrobial properties, have antiinflammatory effects that might help prevent atherothrombosis. The aim of this study was to determine the effect of an immunosuppressant macrolide, rapamycin (Sirolimus), on the expression of TF and its inhibitor (TFPI) by monocytic cells (human blood mononuclear and THP-1 cells) and human aortic smooth muscle cells, in comparison with FK-506 and azithromycin. In monocytic cells, rapamycin and FK-506 inhibited LPS-induced TF activity, antigen and mRNA expression through a transcriptional mechanism involving NF-kappaB. In smooth muscle cells, rapamycin and azithromycin had no effect on serum-induced TF expression, while FK-506 increased serum-induced TF protein and mRNA expression. TFPI levels in the culture supernatants of serum-stimulated smooth muscle cells were not modified by any of the three macrolides. Rapamycin slightly inhibits TFPI induction by LPS in monocytic cells. In addition to its recently established efficacy in the prevention of stent restenosis, the inhibitory effect of rapamycin on the TF pathway might have interesting therapeutic implications.

Anti-Bacterial Agents↗

Association of the Toll-like receptor 4 gene Asp299Gly polymorphism with acute coronary events.

OBJECTIVE: Atherosclerosis is a chronic inflammatory disease of the blood vessels. Toll-like receptor 4 (TLR4) is a transmembrane receptor that is involved in mediating inflammatory responses to bacterial endotoxin and other ligands. The aim of this study was to search for an association between a common functional polymorphism of TLR4--Asp299Gly--and acute coronary syndrome. METHODS AND RESULTS: We conducted a case-control study of 183 patients with acute coronary syndromes and 216 controls. We screened the TLR4 gene for the Asp299Gly polymorphism using a 5' fluorogenic assay. The 299Gly allele was associated with a decreased risk of acute coronary events independently of standard coronary risk factors. The adjusted odds ratio associated with this allele was 0.41 (95% CI, 0.18 to 0.95; P=0.037). In controls, TLR4 heterozygosity was also associated with a significant decrease in plasma fibrinogen and soluble vascular cellular adhesion molecule-1 levels (P<0.01). CONCLUSIONS: These results, which must be confirmed by a prospective longitudinal study, provide evidence of an association between the Asp299Gly polymorphism of the human TLR4 receptor and acute coronary syndromes. They confirm the previously reported involvement of TLR4 in carotid and femoral artery atherosclerosis.

Acute Disease↗

Folic acid deficiency enhances oral contraceptive-induced platelet hyperactivity.

In previous studies conducted in female rats and in women, oral contraceptives (OC) were found to induce a platelet hyperactivity that was related to an oxidative stress. Because cases of megaloblastic anemia have been reported to occur in women taking OC, these treatments are suspected of depleting folate stores. In the study presented herein, which was conducted in rats, we sought to determine the influence of dietary folic acid deficiency (FD) on the thrombogenicity of OC. Animals were fed for 6 weeks with either a folic acid-deficient diet (250 micrograms/kg folic acid) or a control diet (750 micrograms/kg). One-half of the animals in each group were treated with OC (ethinyl estradiol plus lynestrenol). FD and OC individually potentiated platelet aggregation in response to thrombin and ADP and the release and metabolism of arachidonic acid, in particular, the biosynthesis of thromboxane. These platelet activities were further enhanced in animals given both the folic acid-deficient diet and the OC treatment. In addition, FD enhanced the pro-oxidant state in OC-treated rats characterized by (1) a fall in platelet and plasma n-3 fatty acids, (2) an increase in plasma lipid peroxidation products such as conjugated dienes, lipid peroxides, and thiobarbituric reactive substances, (3) a rise in ex vivo erythrocyte susceptibility to free radicals. Moreover, we found that OC treatment led to a reduction of plasma and erythrocyte folate concentrations associated with a moderate hyperhomocysteinemia. Under our experimental conditions, we did not find significant synergistic effects between OC and FD. We propose that, although the untoward effects associated with the OC treatment may not primarily be dependent on FD, the folic acid deficiency magnified OC-induced oxidative stress, which resulted in platelet hyperactivity by elevating the pro-oxidant homocysteine plasma concentration. Despite the limitations of this animal model, the data of the present study suggest that in addition to cigarette smoking, inadequate folic acid intake might predispose those taking OC to vascular thrombosis.

Animals↗

Effect of advanced glycation end product-modified albumin on tissue factor expression by monocytes. Role of oxidant stress and protein tyrosine kinase activation.

Diabetes is associated with a hypercoagulable state that contributes to macrovascular complications, including cardiovascular events. The glycation reaction, a consequence of chronic hyperglycemia, has also been implicated in the pathogenesis of diabetic complications. Glycated proteins have receptors on monocytes and generate reactive oxygen species that can regulate the expression of a number of genes. As abnormal monocyte expression of tissue factor (TF), the main initiator of the coagulation cascade, is responsible for thrombosis in a number of clinical settings, we studied the effect of glycated albumin on monocyte TF expression. Mononuclear cells were incubated with glycated albumin for 24 hours, and monocyte TF activity was measured with a plasma recalcification time assay; TF antigen was measured by ELISA and TF mRNA by RT-PCR. Glycated albumin induced blood monocyte expression of the procoagulant protein TF at the mRNA level. Oxidative stress appeared to be involved in this effect, as the antioxidant N-acetylcysteine diminished TF mRNA accumulation in stimulated monocytes. Hydroxyl radicals, which may be generated inside cells from H2O2 via the Fenton reaction, also appeared to be involved in this effect, as hydroxyl radical scavengers downregulated TF activity and antigen levels (but not TF mRNA). Finally, the involvement of activated protein tyrosine kinase in the transmission of the signal from the membrane to the nucleus was suggested by the inhibitory effect of herbimycin A. These results point to a new mechanism for the hypercoagulability often described in diabetic patients and suggest that antioxidants or protein tyrosine kinase inhibitors might be of therapeutic value in this setting.

Acetylcysteine↗

Polymorphisms of the tissue factor pathway inhibitor (TFPI) gene in patients with acute coronary syndromes and in healthy subjects : impact of the V264M substitution on plasma levels of TFPI.

-Mutations of the gene encoding tissue factor pathway inhibitor (TFPI), an inhibitor of TF-induced activation of the coagulation cascade, were screened for in 130 patients and 142 healthy controls to determine whether these variants contribute to acute coronary syndromes or modify plasma TFPI levels. The following 3 new polymorphisms were identified: 384T-->C in exon IV, which does not change the corresponding amino acid (tyrosine 57); -33C-->T in intron 7 (the T/T, C/T, and C/C genotypes were found in approximately 50%, 40%, and 10% of subjects in both groups); and 874G-->A in exon IX (GTG-->ATG), which predicts a valine to methionine change (V264M) in the carboxy-terminus tail of TFPI. The V264M polymorphism was found in 9.2% of the cases and 4.9% of the controls; the associated odds ratio (OR) for acute coronary syndromes was 2.0 (95% confidence interval [CI], 0.7 to 5.1). The OR increased to 3.6 (95% CI, 0.8 to 15.7) and 3.2 (95% CI, 0.9 to 11.8) in nonsmokers and patients without other risk factors, respectively. The possible link between the V264M polymorphism and coronary heart disease was checked in a large case-control study of myocardial infarction (Etude Cas-Témoins de l'Infarctus du Myocarde [the ECTIM Study]). The results showed no link between the V264M polymorphism and coronary syndromes. Interestingly, however, 5 patients heterozygous for the V264M polymorphism had significantly lower plasma TFPI levels than did 13 patients with the most common genotype. Although our present results do not support an association between TFPI polymorphisms and acute coronary syndromes, the possibility that 1 of them, especially the exon IX polymorphism, is associated with subtypes of myocardial infarction or to evolutive particularities that were not assessed in this study, cannot be excluded and is currently being evaluated.

Acute Disease↗

Vascular endothelial growth factor production by fibroblasts in response to factor VIIa binding to tissue factor involves thrombin and factor Xa.

Tissue factor (TF) assembled with activated factor VII (FVIIa) initiates the coagulation cascade. We recently showed that TF was essential for FVIIa-induced vascular endothelial growth factor (VEGF) production by human fibroblasts. We investigated whether this production resulted from TF activation by its binding to FVIIa or from the production of clotting factors activated downstream. Incubation of fibroblasts with a plasma-derived FVIIa concentrate induced the generation of activated factor X (FXa) and thrombin and the secretion of VEGF, which was inhibited by hirudin and FXa inhibitors. By contrast, the addition of recombinant FVIIa to fibroblasts did not induce VEGF secretion unless factor X was present. Moreover, thrombin and FXa induced VEGF secretion and VEGF mRNA accumulation, which were blocked by hirudin and FXa inhibitors, respectively. The effect of thrombin was mediated by its specific receptor, protease-activated receptor-1; in contrast, the effect of FXa did not appear to involve effector cell protease receptor-1, because it was not affected by an anti-effector cell protease receptor-1 antibody. An increase in intracellular calcium with the calcium ionophore A23187 or intracellular calcium chelation by BAPTA-AM had no effect on either basal or FXa-induced VEGF secretion, suggesting that the calcium signaling pathway was not sufficient to induce VEGF secretion. Finally, FVIIa, by itself, had no effect on mitogen-activated protein (MAP) kinase activation, contrary to thrombin and FXa, which activate the p44/p42 MAP kinase pathway, as shown by the blocking effect of PD 98059 and by Western blotting of activated MAP kinases. These findings indicate that FVIIa protease induction of VEGF expression is mediated by thrombin and FXa generated in response to FVIIa binding to TF-expressing fibroblasts; they also exclude a direct signaling involving MAP kinase activation via the intracellular domain of TF when expressed by these cells.

Antithrombins↗

Mechanism of paradoxic pulse in bronchial asthma.

To elucidate the mechanism of paradoxic pulse in severe bronchial asthma, we performed hemodynamic studies and measured esophageal pressure in nine patients who had status asthmaticus and clinical paradoxic pulse. Two-dimensional echocardiography allowed simultaneous assessment of cyclic changes in right- and left-heart size throughout the respiratory cycle. Esophageal pressure varied from a markedly negative level during inspiration (-24.4 +/- 6.5 cm H2O) to a positive level during expiration (7.6 +/- 6.0 cm H2O). Competition between right- and left-heart chambers for pericardial space during inspiration was suggested by the reduced left ventricular cross-sectional area at end-systole (-24%, p less than 0.01) and end-diastole (-32%, p less than 0.01), the leftward septal shift, and the increased right ventricular internal diameter at end-systole (42%, p less than 0.01) and end-diastole (40%, p less than 0.001). Competition for filling, however, could not entirely account for the paradoxic pulse, for systemic and pulmonary pulse pressures were almost (within one cardiac cycle) in phase: both were minimal at inspiration and maximal at expiration. The increase in impedance to right ventricular ejection is another major factor reducing left ventricular preload at inspiration. This reduction in preload was shown to be the predominant mechanism for the decrease in left ventricular stroke output at inspiration.

Adult↗