Upstream thrombus growth impairs downstream thrombogenesis in non-anticoagulated blood: effect of procoagulant artery subendothelium and non-procoagulant collagen

In the present experiments we have investigated the influence of wall shear rate and axial position on platelet and fibrin deposition which results when flowing human non-anticoagulated blood is exposed to either non-procoagulant fibrillar collagen (human type III) or procoagulant subendothelium (rabbit aorta). Platelet adhesion, thrombus volume and fibrin deposition were morphometrically evaluated at axial positions of 1 and 13 mm following perfusions for 5 min at shear rates of 100, 650 and 2,600 s-1. An axially-dependent decrease of platelet adhesion (34-57%, p less than 0.01-0.05) and thrombus volume (57-80%, p less than 0.05) was observed on collagen at all shear rates. On subendothelium, an axially-dependent decrease was observed for platelet adhesion only at 100 s-1 (29%; p less than 0.01) and for thrombus volume at shear rates of 650 s-1 and above (49-58%, p less than 0.01). Deposition of fibrin on subendothelium was axially decreased (16-42%, p less than 0.05) at all shear rates, while no significant axial differences were seen on collagen. However, substantially more fibrin was deposited on the subendothelium (p less than 0.05), and the upstream platelet adhesion and thrombus volume were lower than on collagen (p less than 0.05) at 100 s-1 and 650 s-1. The axially-dependent phenomena on the two surfaces are consistent with the concept of rapid-growing upstream thrombi which deplete the blood layer streaming adjacent ot the surface of platelets, leading to decreased platelet deposition further downstream.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dependence of blood clot lysis on the mode of transport of urokinase into the clot--a magnetic resonance imaging study in vitro

Magnetic resonance imaging was employed to study the dependence of clot lysing patterns on two different modes of transport of urokinase into whole blood clots. In one group of clots (nonperfused clots, n1 = 10), access of urokinase to the fibrin network was possible by diffusion only, whereas in the other group (perfused clots, n2 = 10) bulk flow of plasma containing urokinase was instituted through occlusive clots by a pressure difference of 3.7 kPa (37 cm H2O) across 3 cm long clots with a diameter of 4 mm. It was determined separately that this pressure difference resulted in a volume flow rate of 5.05 +/- 2.4 x 10(-2) ml/min through occlusive clots. Perfused clots diminished in size significantly in comparison to nonperfused ones already after 20 min (p less than 0.005). Linear regression analysis of two-dimensional clot sizes measured by MRI showed that the rate of lysis was more than 50-times faster in the perfused group in comparison to the nonperfused group. It was concluded that penetration of the thrombolytic agent into clots by perfusion is much more effective than by diffusion. Our results might have some implications for understanding the differences in lysis of arterial and venous thrombi.     

Cerebral hemorrhagic risk of aspirin or heparin therapy with thrombolytic treatment in rabbits

We studied the incidence of cerebral hemorrhage in an animal model of embolic stroke to determine the safety of aspirin, heparin, and tissue plasminogen activator therapies. We occluded the middle cerebral arteries of rabbits with labeled blood clots and administered either tissue plasminogen activator, heparin, aspirin, tissue plasminogen activator plus aspirin, tissue plasminogen activator plus heparin, or saline at various times after stroke. Compared to saline controls, both the aspirin-only and the tissue plasminogen activator-plus-aspirin groups had a significantly higher incidence of cerebral hemorrhage, whereas the heparin and tissue plasminogen activator combination groups did not. We conclude that aspirin antiplatelet therapy alone may increase the risk of hemorrhagic infarction, whereas heparin or tissue plasminogen activator therapy appears to be relatively safe.     

Cytologic criteria for the formation of a risk group in Barrett esophagus]

Oncologic screenings of the populations in the areas with increased incidence of esophageal cancer have revealed Barrett's ulcer in 1 percent of the examinees. Endoscopic and cytologic characteristics of this condition are presented. Precancer changes--severe dysplasia--are most frequent in male Kazakhs (14.1 percent) aged 50 to 59 (14.7 percent). Subjects with Barrett's ulcer developing severe dysplasia, as evidenced by cytograms, should be included in the group of subjects at risk for carcinoma of the lower third of the esophagus and cardia.     

Experience with a metered-dose inhaler with a spacer in the pediatric emergency department

Studies of adults suggest that metered-dose inhalers with spacers are as effective as hand-held nebulizers for bronchodilator delivery. We studied 13 children with acute asthma. They received two puffs every 2 minutes from metered-dose inhalers with spacers (range, 4 to 14 puffs) titrated until improvement stopped. Peak expiratory flow increased 34% for metered-dose inhalers with spacers after the first 2 puffs and increased 87% for metered-dose inhalers with spacers after dose titration. After titration, respiratory rate decreased by 12%, heart rate increased by 2%, and breath sounds improved in 92% of the patients. We concluded that the metered-dose inhalers with spacers are an effective device for the treatment of asthma in the pediatric emergency department and that the use of metered-dose inhalers with spacers with titration can achieve significant bronchodilation in the treatment of patients with acute asthma.     

Dental and periodontal disturbances due to magnesium deficit

Experimental results in female rats with marginal magnesium deficiency a and clinical results in over 100 female tetanic patients suggest the deleterious influence of magnesium on oro-facial tissues.     

Early alterations of rat intestinal diamine oxidase activity by azoxymethane,an intestinal carcinogen

Some mutagenic hydrazino compounds are also diamine oxidase inhibitors. Therefore, this interrelationship was studied for the intestinal carcinogen azoxymethane.In vitro, azoxymethane was a very weak inhibitor of rat intestinal diamine oxidase activity.In vivo, after subcutaneous injection of a single dose of azoxymethane, diamine oxidase activity was increased in the duodenum but was mainly inhibited in the colon. Intestinal diamine oxidase activity may then be influenced by regulatory processes induced by azoxymethane rather than by a direct effect.Supported by a grant of the Deutsche Forschungsgemeinschaft Ku 464/2-2.